WO2001090485A1

WO2001090485A1 - Thoroughfare marking removal

Info

Publication number: WO2001090485A1
Application number: PCT/GB2001/002357
Authority: WO
Inventors: Peter Briggs
Original assignee: Lineclean Limited
Priority date: 2000-05-25
Filing date: 2001-05-25
Publication date: 2001-11-29
Also published as: GB0112835D0; AU2001258641A1; EP1297223A1; GB2362671A

Abstract

A method of removing a thoroughfare marking (12) from a thoroughfare surface (14) involves creating a bond with the thoroughfare marking (12) that is greater than the bond between the thoroughfare marking (12) and the thoroughfare surface (14) to enable the thoroughfare marking (12) to be removed from the thoroughfare surface (14).

Description

Thoroughfare Marking Removal

This invention relates to the removal of markings that have been applied to thoroughfares such as roads, pavements, carriageways, public highways, aircraft runways, taxiways and aprons, parking lots, private car parks, docks, seaports, passageways, corridors and any other areas where markings are required to act as guides or warnings, as by lane markings, loading or waiting restrictions, road priorities, or other information., to those passing along the thoroughfares. Thoroughfare markings help thoroughfare users to maintain a correct path on the thoroughfare and to receive information from messages applied to the thoroughfare surface. More particularly, the invention relates to road markings.

Methods of applying road markings fall into three general groups and include the following:- applying liquid paint, as by spraying onto, or using a roller on, the thoroughfare surface; using an adhesive either by applying an adhesive layer followed by the application of a suitable marking material onto the adhesive layer to bond the marking material to the thoroughfare surface or by applying a pressure sensitive adhesive marking tape; or applying a thermoplastic material which has been heated to a viscous state to the road surface and which interacts with the surface so that the applied thermoplastic material when hardened is bonded to the underlying road surface. The thermoplastic material that is currently used in road markings in the United Kingdom is composed of a hydrocarbon resin, mineral oil, titanium oxide, an extender, aggregate and glass beads to impart a reflective effect.

Of all these methods, the last using a thermoplastic material is preferred because it produces the most securely bonded, hard wearing and long lasting marking that can be used with a much wider range of thoroughfare surfaces. Thus, to the best of applicant's knowledge, thermoplastic road markings have gained widespread acceptance, at least in the United Kingdom.

Thermoplastic road markings have highly resilient physical properties, are of low cost and have the ability of being easily manipulated when in a viscous state brought about by heating. The ease of manipulation is an important consideration when applying the road marking. Moreover, with those road surfaces that are made of concrete or asphalt that contain aggregate, which are the most commonly used, the resulting road surface contains superficial fine crevices which are dependent upon the size of aggregate used. Upon application, the viscous thermoplastic material seeps into and fills these superficial fine crevices. This seepage has the beneficial effect, when the material of the road marking is ultimately solidified, of the marking interacting with the road surface material to increase the strength of the bond between the marking and the road.

Whilst it will be appreciated from the foregoing that road markings are required to be as durable as possible, there are times when the existing markings need to be removed or hidden. Road markings have a finite service life that is primarily due to the erosion caused by the passage of vehicle tyres across them, which will eventually cause unacceptable wear. This service life is generally considerably less than that of the surfacing of the road on which the markings are laid, so that there is a regular programme for their replacement. Furthermore, there are also circumstances, irrespective of damage that can occur, as by a road accident for example, in which road markings need to be removed before they have reached the end of their serviceable lives. Such circumstances include redesigns of traffic flows at junctions and the redirection of traffic into temporary lanes during maintenance on major roads. Further, thick road markings such as thermoplastic markings may need to be removed before some road surface treatments can be applied. The current trend in the UK towards thinner road surfacing overlays is increasing the need for removal of road markings from highways before road surfacing overlay treatment commences. Unfortunately, thermoplastic markings are difficult to remove from concrete and asphalt road surfaces in an environmentally friendly manner.

In the UK, the traditional method of removing road markings is to burn them off the road surface, e.g. by the use of propane gas flame. However, the high temperatures required to burn off the road marking material from asphalt road surfaces can have a deleterious effect on the road surfacing on which the markings have been laid because it will harden the bituminous binder in the asphalt. Additionally, the use of large quantities of non-renewable propane gas energy at high temperatures is not environmentally friendly. Moreover, the noxious fumes of carbon monoxide and nitrogen oxide emitted by burning off have the consequential environmentally unacceptable inevitability of the noxious fumes escaping to cause damage to health and to life. For temporary situations, the road markings are masked with a black covering material such as tar which has the disadvantage that adhesion of the covering material to the marking can fail early. An extension of use of a covering material is in situations where the road marking needs renewal. One common method of preparing the underlying surface before application of the new road marking is simply to apply a dark, opaque layer over the existing worn-out road marking. This method has the important disadvantage of raising the overall height of the road marking relative to the road surface such that the extended height of the road marking may form a dam that inhibits water flow. Inadvertent use of this method may lead to the formation of dangerous large bodies of standing water on the surface of the road, and if applied to road markings near to the sides of a road, may prove to be incompatible with carefully designed drainage systems dependent on pre-determined patterns of surface water run-off.

"Burning off' to remove road markings is disclosed in:-

US 4,765,773 to Hopkins in which microwave generators are set to evaporate or volatilise the road marking to remove it from the road and the volatilised road marking fumes are passed through a filter before discharging them to atmosphere; and

US 3,915,771 to Gatzke in which temporary adhesive-backed road marking tape is decomposed by flame heating to a high temperature.

Heat is also used in other known methods of removing road markings but only by the application of heat to the road marking to a temperature at which the road marking material is "softened", i.e. not "burnt off and then the softened road marking removed by the application of other means, as can be appreciated from:-

GB 2,039,519 (US 4,584,044) to Nihon Sanko Kogyo discloses softening of a heat fusible road marking by means of solid-to-solid heat conduction using a sheet of fusing agent which is applied to the surface of the road marking and ignited to produce red-hot embers by combustion at a temperature that is higher than the melting point of the road marking material. The "softened" road marking is removed by means of a scraper such as a shovel; In DE-OLS 2,650,487 to Wirtgen, a road marking is heated with blue flame combustion gas or microwaves, if necessary to a blister formation, to reduce the bond with the road surface. The "softened" road marking is removed by means of a highspeed revolving steel brush; and US 4,863,309 to Corbin discloses infra-red heating of the asphalt surface of the roadway and the road marking to a temperature just below that at which the road marking will soften but not liquefy. The softened road marking is then selectively cooled to below 100°F to reduce its bond strength with the hot road asphalt surface and then the cooled road marking is peeled from the heated asphalt surface.

In other known methods with which the present invention is not concerned and which involve heat and multilayer road markings, heat is used to soften the material of the underlayer that bonds the road marking to the road surface to enable the road marking to be removed as follows :- GB 1,567,527 to Eigenmann discloses a multi-layer road marking tape and the use of a blade-like tool heated by a gas burner that is the inserted between an upper tape layer and a heat softenable underlayer to soften the underlayer and scrape the expensive upper tape layer from the less expensive underlayer for reuse;

GB 2,298,220 to Illinois Tool Works discloses road markings in the form of individual reflective elements that can be used for temporary road marking, a plurality of which are bonded to a road surface by curing a reactive adhesive. The individual road markings are removed for reuse by heat softening the bonding adhesive to enable the road markings to be pulled out of the road surface; and

EP 41,335 to Pacey discloses a pre-formed road marking tape having a thermosetting thermoplastic backing which is heated to bond the road marking tape to the surface and is softened by heating to remove the bonded road marking tape from the road surface.

Other known methods, which do not involve the use of heat but make use of multilayer temporary road mark tapes, with which the present invention is also not concerned are:- EP 304,405 to Snoline in which a temporary use road marking tape has an adhesive backing that enables the tape to be bonded to, and removed from, the road surface;

US 5,679,437 to Hackworth which discloses a temporary use laminated road marking tape that is provided with a pressure sensitive hot melt adhesive backing or a static cling vinyl film backing that enables the tape to be bonded to, and removed from, the road surface; and

WO 99/46447 to Trelleborg Industri that discloses removal of a temporary road marking tape of a particular composition when it is no longer required, by freezing the tape to a brittle state and disintegrating the tape to a powder form by brushing with a rotating steel brush and removing the disintegrated tape by suction.

All that remains are those known mechanical methods of removing road markings that are dirty, noisy, energy consuming and environmentally unfriendly. Such methods leave behind confusing traces of the marking and result in unsatisfactory removal of the marking to the level of the road surface of concrete or asphalt roads due to the seepage of the thermoplastic road marking into the fine crevices of the road surface. The remaining 'shadow' of road markings is a common sight on roads and can be confusing to road users, especially at night. Also, total removal of the marking often result in removal of road surface material to below the road surface level thereby causing unacceptable damage and have a deleterious effect on the road surface. These known mechanical methods are cutting, grinding scraping and brusbing_Λ

"Cutting" as disclosed in:- WO 98/42915 to Bartell Industries uses a floating head cutter mechanism that avoids producing ruts in the road surface and flat spots on the cutter heads;

EP 133,961 to Feichtner & Bossert uses a rotary cutter mechanism with a plurality of circular cutting blades; and

JP 10306407 to Osaki Kogyo uses a cutting machine having horizontally driven cutting blades that are adjustable in height to remove a surface layer of the road marking only. The removed surface layer is recovered, leaving a thin layer of road marking behind and the removed surface road marking material is mixed with a binder to form a new road marking material. "Grinding" as disclosed in:-

WO/9821412 to Bartell Industries that uses a grinding machine mounted on a carriage with a suspension therebetween enabling a grinder to follow the profile of the road surface; and in

US 5,605,381 to Schmoock that uses grinding wheels.

"Scraping" is used in:-

US 4,405,177 to Yamashita where a plurality of road marking removal scrapers are angularly spaced on a rotor for free rotation about their axes so that the rotation of the rotor causes the scraper tips to move in arcuate paths; and

"Brashing" is used in EP 284,600 to Famag-Fahrzeug which discloses a rotating cylinder carrying road marking removal brushes.

Softening of the road marking material to reduce the bond strength between the road marking and a concrete or asphalt surface road followed by a mechanical action such as scraping has a number of disadvantages. These disadvantages include leaving road marking material behind at least in the crevices and even on the road surface and the effectiveness of scraping is reduced further still if the road surface is uneven. This is a disadvantage of GB 2,039,519 (US 4,584,044) to Nihon Sanko Kogyo and of DE-OLS 2,650,487 to Wirtgen. Moreover, even though US 4,863,309 to Corbin does not use mechanical means to "peel away" the softened road marking which has been selectively and differentially cooled with respect to the heated asphalt road surface, the enormous amounts of non-recoverable energy used for infrared heating of the road surface and then cooling the softened marking with ice, cooling water or other coolant would be so prohibitively expensive as to disqualify the Corbin method for commercial use.

All known methods involving mechanical means with or without pre-softening of the road marking material do not, in themselves, commercially address the problem of residue marking material left on the road or the risk of, or actual damage to, the road surface, let alone the environmental problems of noise pollution, dirt and dust generation and the disposal or processing of waste products, noxious fumes and cost effective recycling of the removed road marking material.

Therefore, the main objects of the present invention are to provide methods of, and apparatus for, removing thoroughfare markings from thoroughfare surfaces, particularly road surfaces, which are efficient, reduce noise and pollution and do not damage the thoroughfare surface.

With a view to fulfilling these objects, and from one aspect, the present invention resides in a method of removing a thoroughfare marking made from a thermoplastic material by softening the thoroughfare marking sufficiently to create a bond with the softened thoroughfare marking, which bond becomes stronger than the bond already existing between the thoroughfare marking and the thoroughfare surface.

Expressed in another way, the invention resides in softening the thoroughfare marking material at least superficially with respect to the surface of the thoroughfare and creating a bond with the softened superficial region of the thoroughfare marking material that becomes stronger than the bond between the thoroughfare marking material and the thoroughfare surface to enable the thoroughfare marking material to be removed, at least substantially, from the thoroughfare surface.

From another aspect, the present invention resides in softening the thoroughfare marking until its exposed surface is viscous, and creating a bond with the exposed viscous surface of the thoroughfare marking material that becomes stronger than the bond between the thoroughfare marking material and the thoroughfare surface to enable the thoroughfare marking material to be removed, at least substantially, from the thoroughfare surface. ^

By creating a higher strength bond with the softened region of the thoroughfare marking, which bond becomes stronger than that which already exists between the thoroughfare marking and the thoroughfare surface, the invention provides a method of removing road markings that is quick to operate, allows work at slow traffic speeds, is efficient in removing at least the majority of visible road marking material, does not damage the underlying asphalt or concrete road surface and is sustainable in that there is the potential for the removed road marking material to be recycled.

The invention utilises a principle of relative bond strengths to effect removal of the thoroughfare marking from the thoroughfare surface that is disclosed in the specification of applicant's earlier patent application GB 0012814.0 entitled "Removal of Road Markings" filed 25 May 2000. The specification of GB 0012814.0 alludes to the difference in the bond strengths being dependent upon the constituents of the thermoplastic material marking and an underlying thoroughfare surface and softening the road marking to enable the creation of a relatively higher strength bond when the softened thermoplastic material hardens.

Thus, in accordance with a preferred feature of the invention the bond of relatively higher strength is created when the softened region of the road marking is allowed to harden.

The beauty of the invention is that the thoroughfare marking does not have to be, yet can be, softened throughout its thickness but only to the point at which the higher strength bond can be created. So softening of the superficial region or surface of the road marking can be sufficient to enable the creation of a higher strength bond.

Accordingly, when just the superficial region or surface of the road marking is softened, the amount or quantity of softening agent used and thus the effect on the environment can be minimised. For example, where the softening agent used is heat produced by a propane gas flame, the quantity of non-renewable energy expended, and thus green house gas emissions, are reduced. This is in contradistinction to GB 2,039,519 (US 4,584,044) to Nihon Sanko Kogyo, DE-OLS 2,650,487 to Wirtgen and US 4,863,309 to Corbin referred to above.

When heat is used as the softening agent, the softened thoroughfare marking is allowed to cool sufficiently to permit the thoroughfare marking material to harden to create the higher strength bond. Although heat is preferred, the softening agent could be a suitable chemical compound. In order to achieve consistent results, applicant has found in tests that the initially softened thoroughfare marking can be removed by pressing down a thermoplastic material against the softened thoroughfare marking, allowing the softened thoroughfare marking to cool to a temperature at which it is hardened to create the relatively higher strength bond with the said thermoplastic material and lifting the cooled thermoplastic material taking with it the bonded thoroughfare marking to remove the bonded thoroughfare marking from the underlying surface of the thoroughfare.

Whilst the tests carried out by the applicant used a thermoplastic material which was the same as that of the thoroughfare marking, similar thermoplastic materials may alternatively be used. Similar types of thermoplastic materials encompass similar thermoplastic binders mixed with contrasting types of aggregate_^ Moreover, applicant envisages the use of materials other than thermoplastics for use in creating the relatively higher strength bond, provided that such other materials will achieve an equivalent result. Put another way, it is critical that the thermoplastic material of the thoroughfare marking and the material for pressing down and lifting to effect removal are compatible, i.e. capable of forming a relatively high strength bond with each other that is sufficient to remove the thoroughfare marking from the underlying thoroughfare surface.

Applicant has found in the tests that the optimum temperature range to achieve the requisite softening of the exposed surface of the thoroughfare marking can be measured at the interface between the thoroughfare marking and the thoroughfare surface and is from 80°C to 82°C, which is below the melting point of the thoroughfare marking. Furthermore, in such tests applicant has found that the optimum cooling temperature at which the initially softened thoroughfare marking has hardened to the point at which the higher strength bond is created is about 40°C at the thoroughfare marking/thoroughfare surface interface. This is because although temperatures beyond 82°C will increase the adhesive qualities of the softened thoroughfare marking, higher temperatures will also increase the time taken to cool to the optimum cooling temperature, and this slows down the whole removal process. Obviously, increasing the temperature beyond the melting point of the thermoplastic material of the thoroughfare marking at which the thermoplastic marking material liquefies will destroy the integrity of the thermoplastic marking material leading to an inability to efficiently form bonds and remove the marking.

For ease and efficiency of application, the method preferably includes forming the thermoplastic material into a brick and retaining the brick in a holder to form an thoroughfare marking removal element, such as a block, leaving the exposed surface of the brick proud of the holder for pressing down against the softened thoroughfare marking.

Conveniently, the thermoplastic material of the brick is of the same family of thermoplastics as that of the thoroughfare marking itself, and is usually supplied as a powder for heating up to a viscous state before laying on a thoroughfare surface to cool and harden and produce a durable thoroughfare marking.

To form the thoroughfare marking removal block, powdered thermoplastic thoroughfare marking material is heated until fluid, poured into the holder which acts as a mould and allowed to cool and harden to form the brick. Prior to pouring, suitable retaining means may be inserted into the mould space of the holder, such as rods through holes in walls of the holder. After hardening, the top and two side walls of the holder can be removed leaving the bottom and two oppositely facing side walls held in position by retainers on exposed end regions of the rods. The retainers may be nuts that engage with complimentary threads on the rods.

With a view to improving adhesion, i.e. the bond strength of the brick with the softened surface of the thoroughfare marking when the thermoplastic material has cooled and hardened, the brick may be given a textured exposed surface, such as a linearly textured exposed surface, either by providing the top wall of the mould with a correspondingly textured surface or by the use of an abrading tool such as a rasp on the exposed surface of the hardened brick.

From yet another aspect, the present invention resides in a method of removing thermoplastic thoroughfare markings, including softening a thermoplastic thoroughfare marking by heating until its exposed surface is viscous, pressing down a brick of a thermoplastic material that is compatible with thermoplastic material of the thoroughfare marking and allowing the thermoplastic marking to cool sufficiently to form a bond between the marking and the brick and lift the thoroughfare marking with the brick.

The present invention also resides in apparatus for removing thermoplastic thoroughfare markings from a thoroughfare surface, for example made from asphalt, concrete, or asphalt concrete, said apparatus including a thoroughfare marking removal element incorporating a material that is compatible with the thermoplastic material of the marking, means for heating the marking to a temperature at which the exposed surface becomes viscous, means for pressing the compatible materials of the thoroughfare marking removal element down against the viscous surface of the marking until the marking has cooled and for lifting the element taking the cooled thoroughfare marking with it to remove the thoroughfare marking from the underlying thoroughfare surfaced

Preferably, the compatible material is the same thermoplastic material as that of the same family of thermoplastics as the thoroughfare marking and is in the form of a brick.

Obviously the lifting force required must be sufficient to overcome the relatively lower strength bond between the thoroughfare marking and the thoroughfare surface when the element is lifted and take with it the cooled thoroughfare marking.

Applicant also found in the tests, that heating to an optimum predetermined temperature consistent with rendering the exposed surface of the thoroughfare marking viscous can be ensured by sensing means which detects the predetermined temperature at the interface between the thoroughfare surface and the heated thoroughfare marking at which point the heating can be stopped, preferably in response to a signal from the sensing means. Cooling can then be allowed to take place of itself over a time period which is determined by the sensing means which in this case detects when the interface between the thoroughfare surface and the thoroughfare marking has cooled to a predetermined temperature consistent with forming the relatively higher strength bond •to enable the cooled thoroughfare marking to be taken with the element when the element is lifted.

The pressing down and lifting means for the marking removal element may be of any suitable kind consistent with efficient operation. For example for relatively small areas such as private car parks, the marking removal element may be supported on a frame for actuation by a lever in one direction to engage the viscous surface of the softened marking and the lever actuated in the opposite direction to lift the marking removal element with the cooled marking from the underlying thoroughfare surface.

For highways, continuous and efficient operation is required. In this case the pressing down and lifting means is advantageously constituted by an endless loop like a tank track for example. The track carries a multiplicity of marking removal elements and is revolved to press down each marking removal element region against the viscous surface of the softened thoroughfare marking successively when each element has turned around a front end of the track. As the track revolves, each marking removal element that has been pressed down remains pressed down for a sufficient period of time for the softened marking to cool to the predetermined temperature and harden such that as each successive marking removal element turns around the rear end of the track, that removal marking element is lifted and takes with it the cooled and hardened thoroughfare marking. Thus, time taken for the thoroughfare marking to cool to the predetermined temperature determines the speed of revolution of the track, as the time taken for each marking removal element to travel from the front to the rear end of the track is the time taken to cool. This coupled with the distance between the two ends of the track sets the speed of revolution of the track.

If the marking removal elements are carried by the track in closely adjacent relationship, the lifting action imparted by the revolution of the track will result in the cooled and hardened thoroughfare marking being peeled from the underlying surface, as disclosed in the specification of the applicant's aforementioned patent application. An advantage of having an endless loop like a tank track is that its revolving motion can be used to drive the thoroughfare marking removal apparatus along the thoroughfare surface without necessarily needing any other driving means.

In another embodiment the endless loop has a layer of thermoplastics material which replaces the blocks.

Hereinafter, for convenience, both the thermoplastic layered endless loop and the tank track will, be referred to as a track.

In order to guard against any of the thoroughfare surface material, primarily asphalt, being removed during removal of the thoroughfare marking, and thus damage, a force may be applied on opposite sides respectively of the road marking. The force may be applied by any appropriate means such as rollers, which may freely rotate or may be driven. The rollers, or other appropriate means, may be resiliently mounted as by springs.

The potential for recycling the removed thoroughfare marking material can be realised by grinding or milling the removed thoroughfare marking from the or each marking removal element. Alternatively, the material of the removed thoroughfare marking can be prised off the or each marking removal element by any appropriate tool such as a scraper blade which is passed along the plane of separation between the removed marking and the or each marking removal element. The tool may be heated to facilitate separation.

It is preferred that the marking removal blocks are secured in their holders by a method that allows quick removal of the block so that block replacement may be easily effected. One method identified is by incorporating two threaded bolts that run through the marking removal block and housing to be secured on the far side by threaded nuts.

Conveniently, the removal block holder may have features that allow the holder to be easily manipulated without interfering with the removal block. It is preferred that these features are integral with the removal block holder. Such features may include elongated projections extending laterally from the sides of the block holder, which Applicant has found useful for maintaining control over the height of the block holder, and hence the block, over the thoroughfare marking. Also, Applicant has found these features useful in controlling the attitude at which the block holder, and hence the block, meets or departs from the thoroughfare surface.

A further preferred feature is for the removal block to have a rough, e.g. corrugated surface when coming into contact with the softened thoroughfare marking. A rough surface increases the effective surface area with which the thoroughfare marking can effect a bond, and thus increases bond strength between the thoroughfare marking and the removal block. Applicant has found that by using a rotary profile cutter, the surface of the removal block after profiling may be corrugated in both the longitudinal and transverse direction of the removal block by the cutting action of the profiler and by the continuing motion of the removal block under the profiler.

As the ancillary equipment such as a removal block profiler and, for example suction devices, have substantial power requirements it is preferable for these features to be powered separately from the main drive motor for providing motive power for the removal block track.

As an adjunct to the Applicant identified need for the angle at which the removal blocks meet the thoroughfare markings and depart from the thoroughfare surface, means such as ramp-down and ramp-up guides are preferably provided to maintain accurately the optimum angle at which the removal block meets or departs from the thoroughfare surface. For example, Applicant has found that the angle at which the removal blocks depart from the thoroughfare surface, with the thoroughfare marking bonded to the removal blocks, is critical in maintaining the bond between the marking and the removal block sufficiently well for the marking to stay attached until the marking is ready for removing from the removal block. Ramp-up guides enable the removal blocks to be gently released from contact with the thoroughfare surface before travelling round the back wheel of the track. Furthermore, Applicant has found, through testing, that the optimum angle at which each removal block gently leaves contact with the ground is between 2°-5° measured from the ground. If the removal block is lifted from the thoroughfare surface abruptly with an angle much greater than 5°, such as when the removal block proceeds around a back wheel forming part of the apparatus directly from the thoroughfare surface without being first eased away from contact with the thoroughfare surface, then the thoroughfare marking tends to remain bonded with the thoroughfare surface. Additionally, if previous sections of the thoroughfare marking have already been lifted off the thoroughfare surface and are proceeding around the back wheel, then the thoroughfare marking previously bonded to a removal block but still on the thoroughfare surface is likely to remain attached to the thoroughfare surface until the tension in the thoroughfare marking strip created by the pull exerted by already removed thoroughfare marking will cause the thoroughfare marking suddenly to break or suddenly detach from the thoroughfare surface. Either outcome is undesirable as a thoroughfare marking strip which is broken means that the residual thoroughfare marking on the thoroughfare surface will require removal by re-running the removal apparatus over that section of thoroughfare, or will necessitate removal by some other means. Sudden detachment of the oroughfare marking from the thoroughfare surface is also undesirable due to the stresses that the sudden release of tension in the marking applies to the apparatus, as well as causing jerky, hesitant progress along the thoroughfare. Applicant has solved this problem by using the ramp-up guides to ease the thoroughfare marking off the thoroughfare surface first, while remaining bonded to the removal block.

A similar device to that of the ramp-up guide may be fitted to the front of the track, except that at the front, the track will be urged downwards to meet the thoroughfare marking at the optimal angle. Doing so will allow the optimum traction to be obtained from contact with the softened thoroughfare marking. As an alternative feature if insufficient traction is found, tractor weights may be added to the structure of the apparatus to increase the downwards force on the thoroughfare marking, and hence traction. It is envisaged that the ramp-up and ramp-down guides may be implemented as a series of rollers.

To facilitate the accurate placing of the track onto the ramping devices, a guide having a width substantially that of the track may be fitted alongside the track just before the ramping devices so that the track enters the ramping devices accurately. It is further envisaged that the guide and the ramping devices act upon the elongated removal block holder features, and that the guides themselves are tapered at their leading and trailing edges to accept smoothly the removal block holders.

According to a further embodiment of the invention, it is preferable that the leading edge of each thermoplastic brick be tapered so that each thermoplastic brick may be smoothly introduced to the thoroughfare marking.

In a further preferred feature, the gas burners heating the thoroughfare marking are encased v^thin a flame guard so that the ground on either side of the thoroughfare marking is not heated any more than is necessary, saving energy and possible damage to the thoroughfare surface. A further refinement is the provision of a shutter so that the amount of heat provided to the thoroughfare marking may be controlled continuously. Heating of the thoroughfare marking is required more on a cold day than on a warmer day with a higher ambient temperature. Thus, the shutter may prevent overheating of the thoroughfare marking. As a further preferred feature, a temperature sensor may be provided to measure the temperature of the thoroughfare marking after heating and before introduction with the removal block, so that the amount of heat applied to the thoroughfare marking may be moderated. It is further preferred that the temperature sensor is incorporated into a feedback system that automatically regulates the shutter on the flame guard, thus moderating the amount of heat that is applied to the thoroughfare marking. In this way, the optimum temperature for the softened thoroughfare marking to meet the removal block is maintained during operation of the apparatus without intervention by the operator.

Preferably, the temperature sensor may also moderate the speed of the track so that if the sensor detects that the thoroughfare marking is not being heated sufficiently, the speed may be decreased with the benefit of more heat being applied to the thoroughfare marking. The ability to control the track speed may be in the alternative to, or in addition to, the ability to control the flame guard shutter.

A further preferred feature is for the gas burner to have a small roller or wheel, that extends beyond the front of the burner assembly or flame guard, which runs along the thoroughfare, surface, indicating where the gas burner is applying heat to the thoroughfare. In this way, any misalignment between the gas burner and the thoroughfare marking may be easily identified, and adjustments can then be made to maintain proper alignment of the heat application and the thoroughfare marking.

In a further preferred feature, support rollers may be provided at the fore and aft end of the track to maintain a height differential between the lowermost point of the front sprocket wheel and the thoroughfare surface, and the lowermost point of the rear sprocket wheel and the thoroughfare surface. Maintaining a height differential will enable the ramping rollers to work as the ramping rollers will need to be able to raise the track from the thoroughfare surface to meet the rear sprocket wheel or lower the track from the front sprocket wheel to meet the thoroughfare surface.

In yet another preferred feature, levelling means such as at least one levelling wheel may be provided on one or both sides of the track to ensure stability of the track when in operation or on inclined or cambered surfaces. As an additional preferred feature, the levelling wheels may be individually extended or retracted so that they may maintain the track level with the ground in all circumstances. As a further feature of the levelling wheels, they may be used to raise the track completely out of contact with the ground so that, for instance during transportation or storage, the track or the whole apparatus is not worn or damaged unnecessarily. It is preferred that any levelling wheel be attached by a castor mount to permit the levelling wheel to be used when the track is following a curved thoroughfare marking.

From another aspect, the invention resides in softening of the thoroughfare marking by means of an endless heated wire mesh that envelops the track. The wire mesh is preferably heated electrically, and it comes into contact with the thoroughfare marking before the removal blocks do. By the time each removal block reaches a respective portion of the thoroughfare marking, the wire mesh has already softened the thoroughfare marking to the extent that the thoroughfare marking is ready for bonding with the removal blocks through the wire mesh.

Thus, through the application of heat to the thoroughfare marking by the heated wire mesh, the thoroughfare marking is softened sufficiently to enable the thoroughfare marking to create a bond with the removal blocks, which bond becomes stronger than the bond already existing between the thoroughfare marking and the thoroughfare surface.

After bonding between the softened thoroughfare marking and the removal blocks is achieved, each removal block - with a section of thoroughfare marking and wire mesh attached - is eased away from the thoroughfare surface before the wire mesh and the thoroughfare marking is separated from the removal blocks. A further step is that the thoroughfare marking is then removed from the wire mesh by brasbing or some other physical action. The removal blocks may then be re-profiled.

A further preferred feature of the above embodiment is to provide means for separating the removal block from the wire mesh and thoroughfare marking. One method of achieving this is to use a hot wire which is in contact with the whole width of the wire mesh. The position of the separation means is preferably after the track has left the ramp-up guide.

In another embodiment, the wire mesh is heated by gas burners mounted at the front of the track, before the wire mesh makes contact with the thoroughfare marking.

In a further embodiment each removal block has an individual wire mesh attached to the surface of the removal block that comes into contact with the thoroughfare marking. Each individual wire mesh may then be heated individually. As a further preferred feature, each individual wire mesh may be spring loaded to come into pressing contact with the thoroughfare surface. A further embodiment of the present invention has the track attached to a separate drive module such as a buggy. The buggy may preferably be powered so that the track may be left unpowered, in which case the track is able to rotate around the rollers solely due to the traction generated between the removal blocks and the thoroughfare markings. In another embodiment of the buggy attachment, both the track and the buggy are powered. The buggy may be used to start the track moving, and once enough traction has been established with the thoroughfare marking the track may be powered up and the buggy powered down. Alternatively, both the buggy and the track may be powered. The buggy may be used to carry ancillary equipment required by the track, such as power generators and hoppers/bins for storage of removed thoroughfare marking material. The buggy also acts as a stabiliser for the track. The buggy may be rigidly attached to the track. Alternatively, the buggy may be hingedly attached to the track so that the track may be pivoted or lifted in relation to the buggy.

Preferably, the buggy has three wheels, at least one of which may be driven. A differential may be used if two driven wheels are on the same axle. In order to allow the buggy to follow curved thoroughfare markings it is preferable that at least one wheel is steerable with respect to the buggy. Preferably, means are be provided for the track to be attached to the buggy in a manner to allow the track to follow the buggy around curved thoroughfare markings. Taking advantage of the fact that the chain has limited ability to curve in a plane orthogonal to the plane in which the links engage sprockets, the track has an ability to follow curved thoroughfare markings without requiring the whole apparatus to yaw significantly

As an alternative to actually steering the buggy, the buggy is statically attached to the track, and the steerable wheel is, or steerable wheels are, able to pivot, thereby allowing the buggy and track to follow a curved thoroughfare marking.

In a further alternative embodiment of the steerable buggy, the whole buggy is pivotally attached to the track, and when the steerable wheel is steered, or the steerable wheels are steered, the whole buggy is able to pivot relative to the track, urging the track to follow the turn of the buggy, and hence allows the track to follow a curved thoroughfare marking. Making the track length shorter will increase the ability of the track to be turned and thus, to follow curved thoroughfare markings. Moreover, shaping the thermoplastic bricks to allow adjacent bricks in the track to yaw from being in a straight line with respect to each other will allow the track better to follow curved thoroughfare markings.

In order to enable the track to follow the path of the thoroughfare marking the front sprocket wheel of the track may be attached to the frame of the track in a manner which allows the front sprocket wheel to pivot about an axis perpendicular to the thoroughfare surface, thus allowing the sprocket wheel and track to follow the thoroughfare marking.

Alternatively, the removal blocks may be mounted on a track that allows individual sideways translation of the blocks, i.e. lateral movement of the blocks relative to the track. This, coupled with a guide element which directs sideways movement of the blocks according to the curvature of the thoroughfare marking, enables the blocks to follow the curved thoroughfare marking.

The steering mechanism may be hydraulically actuated. Advantageously, the steering mechanism may respond to inputs from sensors mounted in front of the track that sense the position of the thoroughfare marking and sends steering commands to a steering system that allows autonomous following of the thoroughfare marking independent of the operator.

Alternatively, only one support linking is enough to provide leading steering input to the track from the buggy, such that when the track needs to be lifted off the thoroughfare, another support member attached to the buggy and the track enables lifting of the track.

Instead of using gas heating as a softening agent, a hot pliable material that is compatible with the thoroughfare marking and the removal blocks is applied to the thoroughfare marking to effect softening of the thoroughfare marking. The use of a hot pliable material softens the thoroughfare marking sufficiently to create a bond with the removal block, this bond then becoming stronger than the bond already existing between the thoroughfare marking and the thoroughfare surface. The removal block may then be removed from the thoroughfare surface, taking the thoroughfare marking with it in the process. The applied hot compatible material may then comprise part of the bond between the thoroughfare marking and the removal block itself.

As another alternative to heat softening, a chemical reactant or compound is to the thoroughfare marking to effect sufficient softening to create the requisite bond with the removal block. A first chemical reactant or compound may cause an exothermic reaction which softens the moroughfare marking due to the heat generated. Another chemical reactant or compound softens the thoroughfare marking by dissolving the thoroughfare marking by breaking down the bond structure present in the thoroughfare marking.

Thus, in this specification the term 'thermoplastic' material includes those materials that can be softened by agents other than heat.

The Applicant has found through experimentation that the best results for removal of the thoroughfare marking from the thoroughfare surface occur from heating the surface of the thoroughfare marking to a temperature from 60°C to 80°C, and lifting of the road marking from the thoroughfare surface at a temperature of no more than 40°C once the bond between the thoroughfare marking and the removal brick has formed.

Applicant has also found that through the expansion and contraction of the gap between adjacent removal blocks as the blocks proceed around the rear drive wheel, the thoroughfare marking bonded to adjacent removal blocks may form peaks above the joint between adjacent removal blocks, allowing that portion of the thoroughfare marking to be more easily removed.

In order to ensure that there is an adequate bond between the thoroughfare marking and the leading edge of each removal block, the respective sections of thoroughfare marking that make contact with the leading edge of each thermoplastic removal brick are heated to a higher temperature than that of the rest of the thoroughfare marking. Applicant has discovered that forming an adequate bond between the leading edge of each thermoplastic removal brick and the thoroughfare marking is important in ensuring that the portion of thoroughfare marking attached to each thermoplastic removal brick remains attached as the removal block is lifted from the ground and proceeds around the rear wheel.

Furthermore, selective heating of the thoroughfare marking to match the shape or configuration of the removal block enables the removal block to have less area in contact with the thoroughfare marking, and hence less heating of the thoroughfare marking will be required. As not all the thoroughfare marking requires heating to the same extent as the areas in contact with the thermoplastic removal bricks, the thermoplastic removal bricks may be shaped accordingly to reduce cost and weight.

In general, the smaller the contact area between the thermoplastic removal brick and the thoroughfare marking, the less heating of the thoroughfare marking will be required.

In a further embodiment, spaces are left between adjacent thermoplastic removal bricks on the track. An example of when this configuration of track is advantageous is when the road marking to be removed is discontinuous, and the thermoplastic removal bricks are spaced correspondingly.

Advantageously, hot air may be used to soften the road marking to the required extent for bonding with the thermoplastic removal bricks.

In yet another aspect, the invention resides in a method of removing thoroughfare markings which comprises using a gas burner to apply heat to the thoroughfare marking to soften the thoroughfare marking to a sufficient extent that a jet of compressed hot air may blow the softened thoroughfare marking onto a ramp, and then onto an endless loop made of a material compatible with the thoroughfare marking, so that the thoroughfare marking may bond with the track. At a later stage in the movement of the track the thoroughfare marking can then be removed from the track. Preferably, the jet of compressed hot air is directed onto the softened thoroughfare marking through a nozzle.

The invention also comprises a heated enclosure covering one or more of the following features: the gas burner, the hot air jet nozzle, the ramp and all or part of the track that is made of a material compatible with the thoroughfare marking.

The term compatible material refers to a material such as a thermoplastic material with which the softened thoroughfare marking may form a bond.

The invention also resides in a kit of parts for use in removing thoroughfare markings from a thoroughfare surface including any of the endless loops and marking removal elements defined hereinabove.

In a modification of any of the methods defined hereinabove a material, such as a thermoplastic material that is compatible with a thoroughfare marking material, is softened sufficiently to create a bond with the thoroughfare marking which bond becomes stronger than the bond already existing between the thoroughfare marking and the thoroughfare surface.

In order that the invention may be more readily understood, some embodiments in accordance therewith will now be described, by way of example, with reference to the accompanying drawings, in which:-

Figure 1 is a diagrammatic side elevation of one embodiment of apparatus for removing thoroughfare markings from a thoroughfare surface, constructed in accordance with the invention, and incorporating an actuating lever and a marking removal element;

Figures 2, 3, 4 and 5 are photographs taken of an embodiment of the invention using a modified removal element and showing another way of carrying out the invention;

Figure 6a is a diagrammatic side elevation of a second embodiment of apparatus incorporating an endless loop for use in removing thoroughfare markings from a thoroughfare surface and with a side of a housing forming part of the apparatus removed;

Figure 6b is a more detailed side view of an endless loop in the form of a tank track forming part of the apparatus of Figure 6a; Figure 7 is a diagrammatic isometric view of a third embodiment of apparatus incorporating an endless loop for use in removing thoroughfare markings from a thoroughfare surface;

Figure 8 is an isometric detail of one element of an endless loop incorporating one section of the loop, one thoroughfare marking removal element and also illustrating a part of a thoroughfare marking separating device; and

Figure 9 is a side elevation of one section of the endless loop of Figure 7 including a thoroughfare marking separation device.

Figure 10 is a perspective view of a second embodiment of a removal block and housing; Figure 11 is an end view of the apparatus as shown in Figure 10;

Figure 12 is a side view of the apparatus as shown in Figures 10 and 11;

Figure 13 shows a perspective detail of the corrugated surface of the thermoplastic brick and holder;

Figure 14 shows an end view of Figure 13; Figure 15 shows a side view of Figure 13 and 14;

Figure 16 is a perspective view showing another embodiment of the apparatus shown in Figures 7 to 9;

Figure 17 is a perspective detail of the front end of another embodiment of the apparatus as shown in Figures 7 to 9; Figure 18 is a schematic showing a side view of the embodiment of the apparatus as shown in Figure 10 to 17;

Figure 19 shows a schematic of another embodiment of the present invention using a heated wire mesh;

Figure 20 shows a perspective view of the apparatus of Figures 10 to 19 attached to a buggy;

Figure 21 shows a second perspective view of the apparatus of Figure 20;

Figure 22 shows in perspective the steering mechanism of Figures 20 and 21, shown without the profiler for reasons of clarity; Figure 23 shows in plan form a schematic of an alternative arrangement of steering for the apparatus as shown in Figures 20 to 22 when connected to a buggy;

Figure 24 shows in schematic form an embodiment of the apparatus in accordance with another aspect of the invention; Figure 25 is a detail of the thoroughfare marking heating feature of Figure 24;

Figure 26 is another view of the apparatus of Figure 16 from behind and to one side;

Figure 27 is a schematic detail of the front end of the apparatus as shown in Figure 18; Figure 28 is a plan view of the apparatus as shown in Figures 20 to 22;

Figure 29 is a perspective cut-away view of Figures 20 to 22 and 28, with part of the track removed for reasons of clarity;

Figure 30 is another view of the apparatus as shown in Figures 20 to 22, 28 and 29; Figure 31 is a side view of the apparatus as shown in Figures 20 to 22 and 28 to

30;

Figure 32 is an end view of the apparatus as shown in Figures 20 to 22 and 28 to 31;

Figure 33 is a perspective view of the apparatus as shown in Figures 20 to 22 and 28 to 32 in more detail- Figure 34 is a close-up view of part of the apparatus as shown in Figure 34;

Figure 35 is another perspective view of the apparatus as shown in Figures 20 to 22 and 28 to 34;

Figure 36 is another perspective view of the apparatus as shown in Figures 20 to 22 and 28 to 35;

Figure 37 is a plan view of the apparatus as shown in Figures 20 to 22 and 28 to 36;

Figure 38 is an end view of the apparatus as shown in Figures 20 to 22 and 28 to 37; and Figure 39 is a side elevation of the apparatus as shown in Figures 20 to 22 and

28 to 38. In the following description the same reference characters are used to designate the same or similar parts, and for convenience and conciseness, the generic word "thoroughfare" will be replaced by "road".

Referring to Figure 1 of the drawings, there is shown an apparatus which is generally indicated at 10 for removing a thermoplastic road marking 12 from a road surface 14 made from asphalt with which the thermoplastic road marking 12 forms a relatively low strength bond. The apparatus 10 includes a road marking removal element constituted by a block 16 having a holder 17 for a brick 18 of thermoplastic material which is compatible with, and in this case is the same as, the thermoplastic material of the road marking 12. The holder 17 is constituted by a steel plate which is fixed to the thermoplastic brick 18 nearer to the left-hand side, as illustrated, by four screws 20 of which two only are shown. Projecting from the steel plate 19 is an inverted U-shaped upright 21 that provides upper and lower end stops 22 and 23 for an actuating lever 24 formed by a steel bar for use in lifting and lowering the block 16 in a manner to be described.

Initially the marking removal block 16 will occupy a position (not illustrated) in which it lies on the road surface 14 adjacent the road marking 12. At this time, the road marking 12 is heated by a propane gas burner (not shown) to a temperature at which the exposed surface of the marking 12 becomes viscous. That is to say the exposed surface is softened sufficiently to enable the creation of a relatively high strength bond with the softened region of the road marking 12, which bond becomes stronger than that which already exists between the road marking 12 and the road surface 14.

To lift the block 16 from the position in which it lies on the road surface, the upper end 24a of the actuating lever is grasped and its free end 24b is engaged against an abutment 25. The lever end 24a is then raised in the direction of the arrow 26 from the resting position against the end stop 23 at a location intermediate the lever ends 24a and 24b until the lever abuts the end stop 22. Continued raising of the lever end 24a whilst engaged with the end stop 22 causes lifting of the block which is then swivelled to lie above the road marking 12. The lever end 24a is lowered to lower the block 16 and bring the thermoplastic brick 18 into engagement with the viscous surface of the road marking 12 which is the position shown in Figure 1. The combined weight of the block 16, upright 21 and lever 24 cause thermoplastic brick 18 to be pressed down against the viscous surface of the road marking for a sufficient time until the marking has cooled and hardened to form the higher strength bond with the thermoplastic brick 18. Then the lever 22 is actuated, as before, to lift the block initially with a tilting action which at this time takes the cooled road marking 12 with it to remove the marking from the underlying road surface 14 leaving nothing of the marking behind.

In Figures 2 to 5, the marking removal block 16 differs from that of Figure 1 in that the thermoplastics brick holder 17 is of U-shaped cross-section with the base of the U forming a bottom wall 17a and the arms of the U forming oppositely facing side walls 17b. Moreover, the thermoplastic brick 18 is retained in the holder by bolts 20 that extend between, and out of the holder 17 through holes in, the side walls 17b, where they are threaded and are held in the holder by nuts 20a. The threaded extensions provide leverage points at the sides of the holder 17 for lifting the marking removal block 16 with the road marking 12 to remove the marking 12 from the road surface 14. In this embodiment, the thermoplastic brick 18 is approximately 115mm long by 75 mm wide by 63 mm thick and it is the thickness of the brick 18 that corresponds to the width of the road marking 12. ^•

Preparation of the removal block of Figures 2 to 5 involves heating of powdered thermoplastic road marking material the same as that which has been used to form the road marking 12, until it is fluid, then pouring the fluid marking material into a rectangularly shaped steel mould having a bottom wall and four oppositely facing side walls. The threaded bolts 20 are inserted through the holes in two oppositely facing walls prior to the pouring of the fluid thermoplastic and held in position by screwing on the nuts 20a. After pouring, the mould is closed by a top wall to form the exposed surface of the thermoplastic brick 18. When the marking material has cooled and hardened, the top wall and the two side walls without the bolts are removed leaving the bottom wall 17a and side walls 17b forming the U-shaped, in cross-section, holder 17.

The road marking 12 on the asphalt road surface 14 of Figure 2 has been softened by the application of heat until the surface of the road marking is viscous, as described with reference to Figure 1. However, applicant has ascertained that 'the temperature of the road marking 12 prior to application of the road marking removal block 16 to the road marking and before the removal block 16 is lifted to remove the road marking 12 from the road surface 14 needs to be carefully controlled. Otherwise the creation of a higher strength bond that is sufficient to overcome the existing lower strength bond between the road marking 12 and the road surface 14 when^' the removal block is lifted will not be achieved and road marking material will be left behind. In the tests, this was achieved by sensing the temperature of the interface between the road marking and the underlying road surface by the use of a thermocouple.

More particularly Figures 2 to 5 illustrate the road marking removal process from the point at which the road marking has cooled and hardened to form the higher strength bond between the thermoplastic brick and the road marking.

Referring to Figure 2, this shows the road marking removal block 16 in a position in which it has been lifted with a tilting action by the engagement of a lever (not shown) with the leverage points at one side of the holder 17 together with the road marking 12a that has been bonded to the thermoplastic brick 18 away from the road surface 14 and before having been separated from the road marking 12b that was not bonded to the thermoplastic brick 18 and which remains on the road surface.

Figure 3 illustrates just how well the higher strength bond works because the bonded road marking 12a remains attached to the thermoplastic brick and in separating from the road marking 12b has lifted some of the marking 12b away from the road surface 12 as indicated by the reference 12c. This also demonsfrates the cohesiveness of the material of the road marking and this property is made use of in embodiments to be described.

The aftermath of the bonded road marking 12b being successfully removed without leaving any frace of the road marking 12b behind is shown in Figure 4. Figure 5 shows the underside of the road marking as attached to the thermoplastic brick, the salient feature being the extraneous material picked up by the road marking which, if not removed, would dramatically hinder the ability of the thermoplastic brick to perform the next removal operation successfully.

Whilst the embodiments of Figure 1 and Figures 2 to 5 could be used to remove thermoplastic road markings from small areas such as private car parks having a few markings, there is a need for a continuous method which is fast and efficient for removing road markings from public highways where the markings may stretch for many miles.

Such an apparatus is generally indicated at 30 in Figure 6a and comprises a housing 32 supporting a tank track like endless loop 33 extending around, and being entrained over, drive wheels 34, 35 and 36. The wheels 34, 35 and 36 are driven by any suitable means, such as a motor through appropriate gearing, in a manner known to those skilled in the art. The drive wheels 34, 35 and 36 revolve the track along a path defined by the position of the wheels in the direction indicated by arrow A. The track 33 is in the form of a chain (not shown) carrying a plurality of closely adjacently disposed blocks 16, each carrying a thermoplastic brick 18. If a particular brick 18 is damaged, or suffers excessive wear, the use of a multitude of discrete thermoplastic bricks 18 linked together rather than a continuous band of thermoplastic material, enables a particular brick to be quickly and cheaply replaced rather than having to replace a whole band.

At the front end region 31 of the housing 30, the housing carries a motorised wire cleaning brush 35 for use in cleaning the road marking 12 and road surface 14.

Cleaning of the surface of the road marking 12 in this way is done with a view to improving cohesion between the surface of the road marking 12 and the thermoplastic bricks 18.

Immediately after the wire brush 35 a gas flame heater 36 is mounted on the housing 32 for providing short duration high intensity heat to soften the road marking 12 in the manner as previously described. When the road marking is softened superficially by heating, the surface of the road marking becomes viscous, also as previously described. A second gas heater 37 is optionally provided for heating the thermoplastic bricks 18 of the removal blocks 16 instead of, or in addition to, the road marking 12 prior to meeting the road marking 12. However, applicant considers that this second heater is not critical to the success of this method of road marking removal, except in the case where only the removal blocks are heated.

As the apparatus 30 advances along the road surface 14 in the direction of the illustrated arrow C driven by the revolution of the track 33, each road marking removal block 16 on the track 33 will be successively pressed down against a corresponding section of the road marking 12 for a period of time that that block 16 takes to travel from the location Y of first impact with that road marking section to the location Z where that marking removal block 16 is lifted by the revolution of the track taking that bonded section 12a with it, as determined by the speed of revolution of the track. Optionally, means are provided for maintaining a downward force of the track throughout the length of the contact patch, although the weight of the apparatus 30 will normally provide sufficient pressure to effect bonding between the road marking and the removal blocks in a continuous manner.

As each marking removal block 16 proceeds towards the rear drive wheel 35, the bond interface between the removal block and the bonded road marking section 12a cools and road marking section 12a hardens to produce the high strength bond. Before each removal block in turn starts to lift as it travels around the rear drive wheel 35, the bond strength between the bonded road marking section 12a and that removal block 16 is greater than that between the corresponding section 12b of the road marking 12 and the underlying road surface 14. This action allows each bonded road marking sectionl2 continuously to peel off the underlying road surface and be carried round the rear wheel 35 while remaining bonded to each removal block 16 as illustrated in Figure 6b.

As the blocks 16 carrying the bonded road marking sections 12a are carried along the topside of the track path, between wheels 35 and 36, the material of the bonded road marking sections is removed from the blocks by a profile cutter 38. A motor 39 drives the profile cutter via a chain drive 39a. Alternatively the profile cutter may be powered off the same motor as that for the driving wheels 34 and 35. The profile cutter is adjusted so as to take off road markings in situ on the removal blocks 16 down to the original level of the removal blocks 16 so that each block 16 is ready to be softened again and pressed down against the next road marking section at the location N to form another high strength bond. Since the material of the thermoplastic bricks 18 of the removal blocks 16 is similar to or the same as the material of the road markings, removing the road markings down to the exact boundary between the road marking and the removal block is not critical. Even if any road marking is left on the block this will not materially affect the bonding ability of the thermoplastic bricks in the removal blocks. However, if the road marking was not removed the thickness of the thermoplastic bricks would increase and this would affect the ride height of the apparatus, as well as affect its balance;

The road marking material removed by the profile cutter 38 is carried away by suitable means for storage. Preferably, the material is recycled. If necessary, the material can be cleaned by a washing process prior to re-melting and/or may be purified after re- melting before it is used again. A silo 40 supported by a wheel 40a may be conveniently provided for storage of the removed material at the rear of the apparatus 30. Additionally, a vacuum cleaner 41 with a suction tube 41a is provided behind the silo 40 for collecting any road marking material that falls to the road surface 14 after re- profiling of the thermoplastic bricks 18. To this end, a powered or static brush 42 is provided underneath the silo to gather the fallen road marking material so that it is more easily picked up by the vacuum cleaner.

The thermoplastic bricks 18 of the road marking blocks 16 do not form strong bonds with the road surface 14 either with or in absence of road markings. This means that the apparatus 30 will be effective in removing intermittent road markings as opposed to continuous road markings without damaging the apparatus or the road surface.

The apparatus 30 may be constructed as a self-contained and/or self-propelled machine, or may be made as an accessory trailing a tractor engine. The apparatus of Figures 7 to 9 which is generally indicated at 50 and which is also for highway use incorporates several improvements and modifications as compared to the apparatus of Figures 6a and 6b. The apparatus 50 has a housing which has been omitted for clarity of illustration and a main frame 51 that supports the tank track 33 and sprocketed drive wheels 34 and 35 as well as other ancillary attachments to be described. Two longitudinally extending beams 52 (only one shown) form parts of the frame 51 and between them the drive wheels 34 and 35 are supported by respective shafts 34a, 35a in suitable bearings (not shown). Sub-frames 53 and 54 are supported from the main frame 51, with the subframe 53 mounting the main drive motor (not shown) for the drive wheels 34 and 35 and associated equipment and the sub-frame 54 (shown in dashed lines) supporting the profile cutter 38.

The tank track 33 has a chain 33a linking and supporting the multiple road marking removal blocks 16 and thermoplastic blocks 18 and extending along the underside of track 33. Air holes (not shown) may be provided in the thermoplastic bricks 18 to facilitate cooling of the bricks after they meet the heated road marking, thereby hastening the formation of a strong bond between the brick and the road marking. In Figure 9 the profile cutter 38 is shown removing the material of the bonded road marking 12b from the thermoplastic brick 18. The width of the track 33 is approximately 15 cm and the length of the track in plan view is approximately 200 cm. Each drive wheel, 34, 35 is approximately 60 cm in diameter and has fifty seven sprocket teeth (not shown) extending around its outer circumference and in engagement with the chain 33 a.

As shown in Figures 8 and 9, the holder 17 of each marking removal block 16 comprises an upper plate 17a that is fixed to the thermoplastic brick 18 and which is supported on a lower plate 17b by four tubular spring-assisted legs 17c (only three visible) which extend between the plates 17a and 17b. Each spring-assisted leg 17c has a telescopic locating pin 60 inside and concentric with a compression spring 61 (Figure 9). The two plates 17a and 17b project laterally beyond the thermoplastic brick 18 to provide lateral extensions 17d, at the four corners respectively of which are located the spring-assisted legs 17c so that the telescopic locating pins in the legs 17d can protrude above the surface of the plates 17a and 17b through respective apertures 62. The plates 17 and 17b with the spring-assisted legs 17c provide a resilient mounting to a respective link 33b (Figure 9) of the chain 33a. Such a resilient mounting assists the thermoplastic bricks 18 to follow the contour of the road surface 14 and facilitates application to the road marking 12 and formation of the high strength bond. As each marking removal block 16 block passes underneath thermoplastic brick profile cutter 38 the lower plate 17b of the holder 17 rests against a block support 63.

The rear drive wheel 35 is driven from the main drive motor mounted on the subframe 53 through an adjustable gear ratio drive mechanism that is generally indicated at 55 and is mounted on the main frame 51. The drive m tor through the drive wheel 35 provides the motive power for revolving the track 33 in the direction as indicated by arrow B. It is envisaged that gear ratios may be easily changed to accommodate different situations that require different torque/speed requirements, such as roads with a steep gradient.

In this embodiment, the pressurised gas burner 36, supplied by a portable propane gas bottle (not shown), is mounted on the main frame 51 and projects from the front end of the apparatus 50. The gas nozzles of the burner 36 are made by flow drilling the nozzle head and different burner heads can be fitted to vary the flame pattern and thermal distribution depending on the thickness, width and material composition of the road marking to be removed. Optionally, a sensor, (not shown) may be employed just before the burner nozzle that senses optical contrast changes between the road surface and the road markings, so that the gas burners only turn on fully when the road marking is beneath the gas nozzle. This 'intelligent' heat application helps reduce the possible risk damage to the road surface in between intermittent road markings, and also reduce energy expenditure.

Three castors are supported from the main frame 51 for a purpose to be described. Two casters that are the same in structure and in operation are mounted on the beams 52 on opposite sides respectively near the front of the frame 51. Only the caster 56 on the right hand side as illustrated of the main frame 51 is visible. The third castor is designated 57 and is mounted as by a strut 58 on the sub-frame 53 for the main drive motor.

An adjustable strut 59 carries the front caster 56 so that the height of the front end of the apparatus 50 can be raised or lowered according to circumstance. It is advantageous in some circumstances to operate the apparatus 50 in an inclined configuration, with the front end with drive wheel 34 lower than the rear end with drive wheel 35. The decision to use any given front running height is made depending on, amongst other factors, particular bonding and cooling characteristics of the materials used in the road markings, thickness of the road markings, wear of the thermoplastic bricks 18 and ambient environmental conditions such as temperature and moisture content. With a rising slope from the front end to the rear end of the apparatus 50, the action of the track 33 rising from the road surface has the effect of lifting the road marking from the road surface and not peeling the road marking off, as is the case when the track reaches rear drive wheel 35.

The front castors such as 56 are also steerable to enable the apparatus to follow and operate on curved road markings. Front castor steering is preferred over rear castor steering as the lateral forces needed to be generated to yaw the front end of the apparatus in operation are lower than the corresponding lateral forces at the rear of the apparatus. This is because the bonds between the road marking and the thermoplastic bricks 18 of the road marking removal blocks 16 have not yet hardened nearer to the front drive wheel 34 so the road marking is still relatively pliable and easier to manipulate than when the bonds have hardened.

Referring to Figures 10 to 12, there is shown a second embodiment of the removal block 16. Thermoplastic brick 18 is mounted in a metal brick holder 70, and in between two vertical side plates 71 integral with the base of the holder 70. Each holder 70 has three webs 72 that provide strength to the join between each vertical side plate 71 and the base of the holder 70. The thermoplastic brick 18 is securely located in the holder 70 and between the vertical side plates 71 by two threaded metal bolts 73 which pass through a first vertical side plate, the brick 18, and are secured after passing through the second vertical side plate by a metal nut at the far side. When a thermoplastic brick requires replacing, removal of the bolts 73 allows the used thermoplastic brick to be easily removed from the holder, and a new thermoplastic brick may be inserted and easily secured by replacing bolts 73.

At each side of the holder 70 are two metal guide strips 74 which extend laterally from the end of the webs 72 and are integral with the holder 70. Guide strips 74 provide a convenient means for each holder 70 to be manipulated. The chain 33a is attached to each lower plate 17b through only two of the four spring-assisted legs 17c, these two being the front two in the direction of travel of the chain when in use. The respective link of the chain 33a which is attached to the holder shown in Figures 10 to 12 is shown at 33b.

Figures 13 to 15 show the surfSce of the thermoplastic brick 18 as when in operation. The surface of the removal block 18 is corrugated both longitudinally 79a and laterally 79b. The longitudinal corrugations 79a are caused by the cutting edges of each arm of the profile cutter 38. The lateral corrugations are caused by the thermoplastic brick moving forwards in between each cut by an arm of the profile cutter. The corrugation of the surface of the thermoplastic brick 18 increases the effective surface area with which the thermoplastic brick may bond with the softened road marking, thus leading to a stronger bond compared to a smooth surfaced thermoplastic brick.

The profile cutter 38 is hydraulically driven and uses a separate power source from that which is used to power the track 33. Furthermore, a vacuum cutting removal system 84 (not shown) removes all the cuttings by suction and deposits the cuttings into twin cutting bins (also not shown). Two cutting bins are provided so that the re-profiling process can continue to remove excess road marking from the surface of the removal bricks even when one cutting bin is full by switching to the second cutting bin. In switching to the second cutting bin the first cutting bin may be emptied, and the road marking removal operation is not interrupted. The profile cutter 38 rotates at approximately 600 rpm and performs an 'uphill' cut on the track 33, that is to say that the horizontal tangential velocity of the cutting arms at the bottom of each revolution is in the opposite direction to that of the track 33. Now turning to Figure 16, there is shown another embodiment of the apparatus of Figures 10 to 15. Before track 33 reaches the rear wheel 35 it passes beneath a support roller 80. Around the same position the support roller 80 there are two guides 81, one of each side of the track 33, which ensure that the track is aligned properly as it passes between the guides 81. As can be seen in Figure 16, the leading and trailing ends of the guides are tapered so as to accept smoothly the guide strips 74 of each thermoplastic block holder 70 passing between. Just after the support roller 80 there is a ramp-up guide in the form of a line of inclined rollers 82 which are inclined relative to the ground at an angle of approximately 3° and perform the task of gently lifting the removal blocks from the ground before the removal blocks reach the wheel 35. The ramp-up rollers comprise a series of four rollers on each side, and the total length of the line of rollers 82 is approximately 30 centimetres. The vertical height through which the ramp-up rollers raise the track by the position of the last roller is approximately 15mm

Figure 17 shows a feature of the front end of another embodiment of the apparatus, which has a flame guard 86 mounted to the main frame 51 of the apparatus. Flame guard 86 has ventilation slots 88, and a shutter 87 which can selectively open and close, thus controlling the amount of heat that is applied to the adjacent portion of the road marking 12. The gas burner 36 is introduced into the flame guard through housing 89. A small wheel 83 is mounted on an extension that protrudes from the front of the flame guard 86. The wheel 83 is aligned with the burner nozzle (not shown) and it allows easy visualisation of where the burner flame will hit the road, and thus, whether adjustment is necessary to align the flame with the road marking 12. On a hot day the shutter is slightly closed so that less heat is transferred onto the road marking and road, thus preventing overheating of the road marking and possible damage to the road surface. A temperature sensor (not shown) is provided with the flame guard, and the sensor monitors the surface temperature of the road marking. The temperature sensor controls the shutter so that the correct surface temperature of the road marking is maintained, and thus the road marking reaches the removal blocks having been softened to the appropriate temperature. There is a backup provided for manually adjusting amount of opening of shutter. Figure 18 shows in schematic fashion the relative positions of the parts of the apparatus described in Figures 10 to 17. In Figure 18 a second support roller 85 is positioned at the forward end of the track. Around the same position as the forward support roller 85 are ramp-down guides (not shown), one on each side of the track which perform the reverse function as the ra np-up rollers, that is to say the ramp-down guides gently ease or persuade the thermoplastic blocks 18 of the track 33 into contact with the road marking. The ramp-down guides start having an effect on the removal blocks at around 15mm from the surface of the road marking. The leading edge of each thermoplastic brick 18 is rounded slightly so that smooth contact can be made with the road marking as the thermoplastic brick is applied to its top surface.

Figure 19 shows an alternative method for softening the road marking. A looping fine wire mesh 90 encompasses the track 33. The wire mesh 90 passes over four rollers, 91a to 9 Id, and the rollers are mounted onto the main frame 51. Roller 91a is spring loaded to press the wire mesh 90 down onto the road surface. Between points J and K the wire mesh is in contact with the road marking. Between points K and L the wire mesh is in contact with the thermoplastic blocks 18 as well as the road marking, whilst the road marking is still on the road surface. Between the points L and M the road marking 12 is bonded to the removal blocks 18 through the wire mesh 90, and the road marking has been lifted off the ground due to the action of ramp-up rollers 82 on the removal block housings 70. At point M there is a splitter 92 which separates the wire mesh from the removal blocks. The splitter in this embodiment is simply a heated wedge shaped with a knife edge, although other means such as a wire cutter, or a heated wire cutter, may be also used.

The wire mesh is electrically heated and from J to K heats the road marking to soften it sufficiently to adhere to a thermoplastic block 18 by the time the road marking makes contact with the removal blocks at K. Then bonding between the road marking and the thermoplastic blocks 18 occurs. By the time the road marking 12 reaches point L, the wire mesh and the road marking and the thermoplastic block are all lifted from the road surface by the ramp-up rollers 82. After point M the fine wire mesh is separated from the thermoplastic blocks 18, and the road marking 12d stays on the wire mesh 90. The road marking is then brushed off the wire mesh and collected for re-cycling at a cleaning station 93 positioned over part of the wire mesh loop, and the thermoplastic blocks 18 continue around the track for re-profiling at the profiler (not shown).

As an alternative, or in addition, to electrical heating of the wire mesh 90, a gas burner station may be provided at 94 for heating of the wire mesh before the wire mesh makes contact with the road marking.

Figures 20 and 21 show the apparatus of Figures 7 to 19 attached to a motorised buggy 100. The buggy comprises three wheels, a steerable front wheel 95, a powered rear wheel 96 and a freewheel 97. Alternatively, both rear wheels 96 and 97 may be powered through a differential (not shown). A combined motor and reduction gearbox 98 powers the rear wheel 96. In this embodiment the road marking removal track 33 is not powered, although provision is made so that the rear sprocket wheel 35 of apparatus 50 may be connected up to the motor 98 to enable the frack to be powered also. The buggy 100 comprises a sturdy ladder frame construction 99 of box section metal. A front cross member 101 and. rear cross member 102 connect the frame 99 of the buggy 100 to the frame 51 of the road marking removal apparatus 50. The front and rear cross members connect with the buggy frame through hinge joints 103 and 104 respectively, and at the other end are connected to frame 51 through static joints (not shown). Hinge Joints 103 and 104 allow the apparatus 50 and track 33 to be lifted off the ground in a pivoting motion, thus increasing ground clearance for transportation of the apparatus 50.

Levelling wheels (not shown) are attached to the main frame 51 on the side of the track opposite to the buggy and help to ensure that the track remains level with the ground surface. This is particularly of use when the road marking to be removed has been applied to a highly cambered surface or where there is the possibility, due to a slanting the road surface, that the track will not maintain a good contact with the road marking. The levelling wheels are castor mounted and are also mounted at the ends of vertical hydraulic cylinders so that they can be raised or lowered according to the level of the road surface. The levelling wheels also have a manual backup which allows manual adjustment to be made to the ride height of the apparatus. The ability to alter the height of the track relative to the road allows the track to be raised completely clear of the road during transporting, thus saving wear on the track 33 or other parts of the apparatus. When not in use, the levelling wheels are retracted so that they do not touch the ground and interfere with the road marking removal process.

Figure 22 shows a detail of the front wheel, in particular the steering mechanism for the front wheel 95. The axle for front wheel 95 is attached to a vertical member 106 which is in turn pivotally connected to the frame 99 of buggy 100. Vertical member 106 connects to frame 99 by a hinge 107, which allows front wheel 95 to turn in an arc about hinge 107, thus providing steering for the^" buggy and attached road marking removal apparatus 50. At the top end of vertical member 106 a horizontal steering crossbar 108 is attached at one end. The other end of horizontal steering crossbar 108 is attached to a second vertical member 109 by a hydraulic cylinder 110. Second vertical member 109 is fixedly joined to frame 99. Hydraulic cylinder 110 is pivotally attached at one end to second vertical member 109 by hinge 111 and pivotally attached at the other end to horizontal steering crossbar 108 by another hinge 112. By retraction and extension of a piston and cylinder device 110 front wheel 95 is turned about its pivot 107 and thus steering is effected.

In the alternative embodiment of steering mechanism shown in Figure 23, only the first cross member 101 is attached to the frack frame 51 during operational use. Cross member 101 is attached at one end to frame 51 by a removable pivot 113 so that the frame 51 may rotate about pivot 113 in a plane parallel to the cross member 101. The other end of cross member 101 is attached to the frame 99 of the buggy by a swivelling hinge 114 so that cross member 101 may rotate in a horizontal plane and incline in a vertical plane about 114 accordingly. When the steerable wheel 95 is turned, the frack will tend to follow the buggy. When the track is to be lifted off the ground, for instance when in transportation, removable pivot 113 is removed, and the cross member

101 is instead bolted to the frame 51 at points 115a and 115b. The second cross member

102 is then swung down and also bolted to frame 51 at points 116a and 116b. As second cross member 102 is attached to the buggy frame 99 by pivot 104, the pivoting action of both cross members 101 and 102 allow the track to be lifted off the ground. To support cross members 101 and 102 when they are bolted to frame 51, retainers 117 and 118 are fitted to frame 99. Retainer 118 also allows second cross member 102 to rest unconnected to frame 51 when not in use. Several methods for allowing the track to follow the path of the road marking are possible. For instance, by attaching the front sprocket wheel to the frame 51 in a manner which allows the sprocket wheel to pivot about an axis perpendicular to the ground, the sprocket wheel and track are enabled to follow the road marking. Alternatively, the thermoplastic blocks 18 may be mounted on a track which allows individual sideways translation of the block while mounted on the frack: this coupled with a guide element which is directed to move the blocks according to the curve of the road marking may also enable the track to following the road marking. As the track chain will allow a limited amount of bending in a plane orthogonal to the plane in which the sprockets are engaged, this may achieve yaw adjustment of the track. All these methods take advantage of the fact that, between the contact point of the softened road marking and the removal blocks and the pivot point 105, the road marking is pliable enough so that yawing of the track along the axis of the track and in a plane parallel to the ground can be accommodated by the still-hardening bond between the softened road marking and the removal blocks.

Figure 24 shows an alternative method and system for removal of road markings leaving the road surface free of any driver distractions caused by leftover road markings. The road marking first enters a preheat oven 120 containing gas burners 36. After the desired temperature has been reached, compressed air blowers 121 blast a stream of compressed hot air onto the softened road marking 12s, forcing the softened road marking onto a ramp 122. At the end of the ramp the road marking is then deposited onto a thermoplastic belt 33 which loops around rollers 123, 124, 125 and 126. The ramp 122 and the belt 33 are situated within a heated enclosure 119 (not shown in Figure 24 for reasons of clarity) so that the road marking does not have opportunity to harden before reaching the belt. As the road marking deposited onto belt 33 is still soft, the road marking will bond with the thermoplastic of the belt and be carried in the direction of arrow P. Near the top of the belt, after the road marking has reached roller 125, the belt is re-profiled by profile cutter 38 and the road markings bonded to the belt are excised by the profiler. Excess road marking material is deposited into road marking hopper 127 for re-use or re-cycling. After a section of road has progressed through the stage whereby the softened road marking is blasted from the surface, each respective section then passes beneath a second heating oven 128 where the road surface, and any road marking residue, is softened again. A rotary brush 42 is provided just behind the second oven so that any softened residue may be dislodged and brushed away from the area of ground where road marking formerly was. After brushing, a sand dispenser 129 dispenses a coating of sand onto the area of ground formerly occupied by the road marking, coating any remaining road marking with a layer of sand. The sand deposited is of a colour that matches the surrounding ground colour thus masking any remaining road marking and making it invisible to the road user. After the sand has been deposited, a sand compressor 130 compacts the sand coating in the road surface so that the sand is thoroughly embedded into any remaining road marking, and also into the superficial crevices of the road. Finally, a suction device 131 removes any excess sand that is not attached to the road or any remaining road marking. Of course, suction device 131 also removes any road marking that was dislodged by rotary brush 42.

Figure 25 shows the blasting action of the method and apparatus described above in Figure 26 in detail. Road marking 12 approaches the gas burners 36 in the pre-heater oven 120. When sufficiently softened, the softened road marking 12s is then urged onto the ramp 122 by a blast of hot compressed air 132, such that the road marking forms into lumps 12t. At the end of ramp 122, the road markings 12t are then deposited on the thermoplastic belt 33 ready for bonding with the belt, and the subsequent removal of the bonded road marking 12u from the belt by the profile cutter (not shown).

Figures 26 to 39 show other views and close-ups of the apparatus as already shown in previous views.

Although the invention has been described with reference to thermoplastic thoroughfare markings and thoroughfare surfaces containing aggregate, it will be appreciated that the present invention is applicable to thoroughfare markings, made of any suitable material applied to any other suitable surfaces such as floor coverings of hospital corridors.

Claims

1. A method of removing a thoroughfare marking from a thoroughfare surface, characterised in that a bond is created with the thoroughfare marking that is greater than the bond between the thoroughfare marking and the thoroughfare surface.

2. A method of removing a thoroughfare marking made from a thermoplastic material, said method being characterised by softening the thoroughfare marking sufficiently to create a bond with the softened thoroughfare marking, which bond becomes stronger than the bond already existing between the thoroughfare marking and the thoroughfare surface.

3. A method of softening a thoroughfare marking material, characterised by softening the thoroughfare marking material at least superficially with respect to the surface of the thoroughfare and by creating a bond with the softened superficial region of the thoroughfare marking material that becomes stronger than the bond between the thoroughfare marking material and the thoroughfare surface to enable the thoroughfare marking material to be removed, at least substantially, from the thoroughfare surface.

4. A method of softening a thoroughfare marking, characterised by softening the thoroughfare marking until its exposed surface is viscous and by creating a bond with the exposed viscous surface of the thoroughfare marking material that becomes stronger than the bond between the thoroughfare marking material and the thoroughfare surface to enable the moroughfare marking material to be removed, at least substantially, from the thoroughfare surface.

5. A method as claimed in any one of claims 1 to 4, characterised in that the bond of relatively higher strength is created when the softened thoroughfare marking hardens.

6. A method as claimed in any one of claims 1 to 5, characterised in that heat is used as a softening agent.

7. A method as claimed in any one of claims 1 to 5, characterised in that a suitable chemical reactant or chemical compound is the softening agent.

8. A method as claimed in any one of claims 1 to 7, characterised by pressing down a thermoplastic or other material that is compatible with that of thoroughfare marking against the thoroughfare marking.

9. A method as claimed in any one of claims 1 to 8, characterised by allowing the initially softened thoroughfare marking to harden to create the relatively higher strength bond with the said thermoplastic or other material.

10. A method as claimed in claim 9, characterised by lifting the hardened thermoplastic

. material taking with it the bonded thoroughfare marking to remove the bonded . thoroughfare marking from the underlying surface of the thoroughfare.

11. A method as claimed in claim 6 or any claim dependent thereon, characterised by allowing the softened thoroughfare marking to cool to a temperature at which it is hardened to create the relatively higher strength bond with the said thermoplastic or other material.

12. A method as claimed in claim 11, characterised the temperature at which the thoroughfare marking is removed from the thoroughfare surface is no greater than 40°C.

13. A method as claimed in claim 11 or claim 12, characterised by heating the thoroughfare marking to a temperature that when measured at surface of the thoroughfare marking is from about 60°C to 80°C and preferably about 70°C.

14. A method as claimed in any one of claims 11 to 13, characterised in that the temperature is below the melting point of the thoroughfare marking.

15. A method as claimed in claim 8 or any claim dependent thereon, characterised in that the thermoplastic or other compatible material is formed into a brick.

16. A method as claimed in claim 15, characterised by retaining the brick in a holder to form a thoroughfare marking removal element, such as a block, leaving the exposed surface of the brick proud of the holder for pressing down against the softened thoroughfare marking.

17. A method as claimed in claim 15 or claim 16, characterised in that the brick is provided with a roughened, or textured exposed surface.

18. A method as claimed in any one of claims 8 to 17, characterised in that the thermoplastic or other material that is compatible with that of thoroughfare marking is formed as or as part of an endless loop.

19. A method as claimed in any one of claims 1 to 18, characterised by applying a force on opposite sides respectively of the moroughfare marking during removal of the thoroughfare marking from the thoroughfare surface.

20. A modification of the method claimed in any one of claims 1 to 19, characterised in that a or the thermoplastic or other material that is compatible with the thoroughfare marking material is softened sufficiently to create a bond with the thoroughfare marking which bond becomes stronger than the bond already existing between the thoroughfare marking and the thoroughfare surface.

21. Apparatus for removing a thermoplastic thoroughfare marking from a thoroughfare surface, for example made from asphalt, concrete, or asphalt concrete, said apparatus including a thoroughfare marking removal element incorporating a material that is compatible with the thermoplastic material of the marking, means for softening the thoroughfare marking and means for pressing the compatible materials of the thoroughfare marking removal element against the softened thoroughfare marking to create a bond with the thoroughfare marking which bond becomes stronger than the bond already existing between the thoroughfare marking and the thoroughfare surface and for lifting and thereby removing the bonded thoroughfare marking material from the thoroughfare surface.

22. Apparatus as claimed in claim 21, characterised in that means are provided for heating either the thoroughfare marking or thoroughfare marking removal element to effect softening of the thoroughfare marking or thoroughfare marking removal element

23. Apparatus as claimed in claim 21 or 22, characterised in that the compatible material is the same thermoplastic material or of the same family of thermoplastics as the thoroughfare marking and is in the form of a brick.

24. Apparatus as claimed in claim 23, characterised in that the leading edge of the brick or each of a plurality of bricks is tapered.

25. Apparatus as claimed in any one of claims 19 to 24, characterised in that the pressing down and lifting means is constituted by an endless loop like a tank track for example.

26. Apparatus as claimed in claim 24, characterised in that the endless loop carries a multiplicity of marking removal bricks and is revolved to press down each marking brick against the thoroughfare marking.

27. Apparatus as claimed in claim 26, characterised in that the marking removal bricks are carried by the endless loop in closely adjacent or relatively widely spaced relationship.

28. Apparatus as claimed in any one of claims 19 to 27, characterised by means for applying a force to the thoroughfare surface on opposite sides respectively of the thoroughfare marking during removal of the thoroughfare marking from the thoroughfare surface.

29. Apparatus as claimed in claim 28, characterised in that the force applying means is a plurality of rollers.

30. Apparatus as claimed in any one of claims 21 to 29, characterised by means, such as ramp-down and ramp-up guides, for mamtaining an optimum angle at which the or each removal brick or the material that is compatible with the thermoplastic material of the thoroughfare marking meets or departs from the thoroughfare surface.

31. Apparatus as claimed in claim 30, characterised in that the optimum angle is from 2° to 5°.

32. Apparatus as claimed in claim 30 or claim 31, characterised in that the ramp-up. and ramp-down guides are a series of rollers.

33. Apparatus as claimed in any one of claims 30 to 32, characterised in that a guide having a width substantially the same as that of the frack is fitted alongside the endless loop just before the ramping devices to facilitate accurate placing of the track onto the ramping devices.

34. Apparatus as claimed in claim 22 or any claim dependent thereon, characterised in that a temperature sensor is provided to moderate the speed of revolution of the track.

35. Apparatus as claimed in any one of claims 21 to 34, characterised in that the softening of the thoroughfare marking is effected by means of an endless heated wire I mesh that embraces the track.

36. A modification of the apparatus as claimed in any one of claims 21 to 35, characterised in that the material that is compatible with the thermoplastic material of the marking is carried by an endless loop.

37. A kit of parts for use in removing a thoroughfare marking from a thoroughfare surface including any of the parts of the apparatus claimed in any one of claims 21 to 36. ^•

38. A method of removing a thoroughfare marking from a thoroughfare,* surface, substantially as hereinbefore described with reference to any one of Figures 1 to 39 of the accompanying drawings.

39. Apparatus for removing a thoroughfare marking from a thoroughfare surface substantially as hereinbefore described with reference to any one of Figures 1 to 39 of the accompanying drawings.