GB2493283A

GB2493283A - Overhead access platform

Info

Publication number: GB2493283A
Application number: GB1213295.7A
Authority: GB
Inventors: Alan Watt
Original assignee: Monkey Tower Ltd
Current assignee: Monkey Tower Ltd
Priority date: 2011-07-28
Filing date: 2012-07-26
Publication date: 2013-01-30
Anticipated expiration: 2032-07-26
Also published as: GB2493283B; GB201112994D0; GB2493283A9; GB201213295D0

Abstract

Overhead access platform comprises a wheeled base 10, an extendable mast 16 comprising at least two sections 17, 18 connected together for relative sliding movement, a lower section 17 of the mast being mounted on the base 10, a platform 26 attached to an upper section 18 and a counterweight 31 assembly. Each section may comprise a pair of rails 20, 22 with rungs 21, 23 therebetween, at least one of the rails of the lower section may be hollow to receive the counterweight 31 assembly. A flexible tension member 29 which may be a metal cable or chain, with a guide such as a pulley, interconnects the second section to the counterweight. The second section 18 of the mast is narrower than the first section 17, there may be at least one intermediate section being slidably arranged with respect to the existing sections, corresponding counterweight assemblies may be provided between the sections. The base may have outriggers 13. Releasable pawls, dogs, pins or rung locks 32 may be arranged between the sections. Struts (35, figure 6) may be provided between the base and the rails and rungs (37) may extend therebetween. The work platform may be provided with a handrail 27 and gate 28.

Description

OVERHEAD ACCESS PLATFORM

This invention relates to an overhead access platform including an extendable mast carrying a work platform.

Overhead access platforms are well known, for example from US4427093 or GB2432573, to allow a more safe working environment than can S be obtained from a ladder or a pair of steps, for instance for changing lamps or light fittings within a building, painting and other maintenance works. Typically, a wheeled base is provided with a fixed telescopic ladder, an upper section of which carries a work platform. The ladder is extended by means of a winch pulling on a cable which is arranged to raise the upper section and so lift the platform to the required height. Automatically-operating releasable pawls or dogs are disposed between the ladder sections, in order to lock the sections against relative sliding movement, once the platform has been raised.

In the case of the overhead access platforms of US3737007 and also GB406072, there is mentioned the use of counterweights to reduce the apparent weight of the lifting section and platform. The counterweights hang freely of the main assembly and in use of the platform those counterweights are liable to swing and so cause damage to the equipment or injury to personnel.

The provision of a manually-operated winch makes the platform relatively slow to deploy or stow, and adds to the overall cost of the apparatus. Further, there are additional costs associated with maintenance of the winch and its cabling systems including pulleys, connectors and so on. Safety requirements also dictate that the winch and cabling systems should be checked periodically.

It is a principal aim of the present invention to provide an overhead access platform which addresses the disadvantages mentioned above, and so which is relatively quick and easy to deploy at a required site, allowing the work platform to be raised to an appropriate height for the work to be undertaken.

According to this invention, there is provided an overhead access platform comprising a base, an extendable mast comprising at least two sections connected together for relative sliding movement along the length thereof, one section of the mast being mounted on the base to project upwardly therefrom and a work platform being attached to a second section of the mast, and a counterweight assembly for the second section including at least one flexible tension member interconnecting the second section to a counterweight arranged for rising and falling movement within the confines of the mast, corresponding to lowering and raising movement respectively of the second section.

The provision of the counterweight assembly significantly reduces the apparent weight of the work platform and the second section of the mast, supporting that platform. This makes it easier to raise and lower the work platform to the required height, allowing for the possibility of the platform being raised manually, acting directly on the work platform or the second section, without the need to employ a winch or other mechanised aid. An additional benefit of the counterweight assembly is that the accelerations and velocities of the platform and the second section are reduced should the platform slip or be accidentally released, reducing the risk of injury to an operator or of damage to the access platform. By arranging the counterweight within the confines of the mast, the likelihood of the counterweight striking some other object or someone in the vicinity of the access platform is greatly reduced, so enhancing safety in use.

Most preferably, each section of the mast is in the form of a ladder having a pair of rails with spaced rungs extending between the rails. This facilitates access to the work platform, when raised. At least one of the rails of the one (lower) section may be hollow so that the counterweight may be received in that rail, for rising and falling movement therewithin. In this way, protection is afforded to the rising and falling counterweight so obviating the likelihood of damage to the components of the access platform or of injury to an operator. Both rails of the lower section may be hollow so that counterweight assemblies may be provided on both sides of the mast, in order to give better counterbalancing for the parts of the access platform which are raised or lowered, and so reduce yet further the manual effort required for raising the The flexible tension member may comprise a metal cable or chain together with a guide such as a pulley arranged at the upper end of the hollow is rail, with one end of the cable or chain secured to the counterweight and the other end to the second (lifting) section of the mast.

In a preferred form of access platform of this invention, the second section of the mast is narrower than the one section, with the rails of the second section being slidably received between the rails of the one section but being slidably connected thereto. In a modification of this arrangement, there may be at least one intermediate section disposed between the one and second sections of the mast, the or each intermediate section being slidably arranged with respect to the one and second sections. The sections may be coupled together, for example by means of cables and pulleys, so as to ensure that during raising and lowering movement of the work platform, the second and intermediate sections perform simultaneous sliding movement with respect to the one (stationary) section. In this embodiment, essentially corresponding counterweight assemblies may be provided between the second section and the intermediate section or the one section, and between the intermediate section and the one section.

Conveniently, the base may be in the form of a wheeled trolley, which may be furnished with out-rigger supports to increase the stability of the work platform. The one section may be fixedly secured to the base so as to project vertically upwardly therefrom and releasable pawls, dogs, pins or rung-locks such as those described in US4299306 may be arranged between the sections to allow the releasable locking together of the sections with the work platform at a desired elevation, within the limits of relative sliding movement of the sections.

Rungs preferably extend between the rails of the two sections of the mast, to facilitate climbing of the mast to the platform. Struts may be provided between the base and the rails of the mast in order to triangulate the connection is of the mast to the base and increase the rigidity of the assembly of the base and mast. Further rungs may extend between the struts, so that the struts form a low level ladder to assist a user in reaching and then climbing the mast.

To enhance safety, the work platform may be provided with an encircling handrail or may have the provision to fit one. A gate may be arranged within that handrail to facilitate access to the work platform from the mast.

By way of example only, two specific embodiments of overhead access platform of this invention will now be described in detail, reference being made to the accompanying drawings, in which:-Figure 1 is an isometric view from the front and one side of the first embodiment of access platform, in a raised setting; Figure 2 is an isometric view similar to that of Figure 1 but from the rear and other side and with the work platform at an intermediate position; Figure 3 is an isometric view from the front and one side of the access platform, in a lowered setting with one side rail of the lower section partially cut away to show the counterweight assembly; Figure 4 is an isometric view similar to that of Figure 3 but from the rear and other side and with the out-riggers removed; Figure 5 is an isometric view similar to that of Figure 2 but from the front and one side and again with one side rail of the lower section partly cut away to show the counterweight assembly; Figure 6 is an isometric view from the rear and one side of the second embodiment of access platform, in a lowered setting; and Figure 7 is an isometric view from the front and other side of the access platform of Figure 6.

Is Referring to Figures 1 to 5 of the drawings, there is shown an overhead access platform comprising a wheeled base 10 including side members 11 supporting two pairs of wheels 12. Each wheel is provided with a locking arrangement (not shown) to restrain the rotation thereof and the wheels of at least one of the pairs thereof may be in the form of castors. Two out-riggers 13, each having a jack 14, are mounted to the side members 11 by bars 15 which telescope into the side members 11. The out-riggers 13 may be removed (as shown in Figure 4) when the platform is to be wheeled from place-to-place and though only two out-riggers are shown in Figures 1 and 2, similar out-riggers may be plugged into the other ends of the side members 11, further to increase stability.

A mast 16 comprises a lower section 17 secured to the wheeled base 10 and an upper section 18 slidably connected to the lower section 17. The lower section 17 extends vertically upwardly and is braced by members 19 to the base 10. That section 17 has a pair of hollow side rails 20 and rungs 21 extending between the side rails 20, the spacing of the rungs being such that the lower section may serve as a ladder. Similarly, the upper section 18 also has a pair of hollow side rails 22 together with rungs 23 extending between those side rails, again to serve as a ladder. The spacing between the side rails 22 of the upper section is such that the upper section is a sliding fit between the rails 20 of the lower section, but in front of the rungs 21 thereof. The outer face of each rail 22 of the upper section 18 has a groove 24 formed therealong and secured to the inner face of each rail 20 of lower section 17 is a pair of angle plates 34 one limb of each of which projects into the associated groove 24. In this way, the upper section 18 is constrained for sliding movement along the is length of the mast 16.

A work platform 26 is attached to the side rails 22 of the upper section 18, so as to project over the wheeled base 10. That work platform 26 has a handrail assembly 27 extending therearound but with a gate 28 pivoted to one side for inward swinging movement with respect to the work platform, to facilitate access to the work platform from the upper section 18. A lock (not shown) is provided for the gate, to secure that gate in the closed position shown in the drawings.

A counterweight assembly is provided for the upper section 18 and its work platform 26, substantially to balance the weight thereof. On each side of the mast, there is a cable 29 secured at one end 30 to the upper section 18 and at the other end to a metal counterweight 31 disposed within the hollow side rail of the lower section 17. The cable 29 passes over a pulley 35 provided within the side rail 20 at the upper end thereof and the counterweight is a loose fit within the rail so that it may freely rise and fall, corresponding to the movement of the upper section 18 with respect to the lower section 17. By providing sufficiently massive counterweights in each of the two side rails 20 of the lower section 17, it is possible to balance most of the weight of the upper section 18 and the work platform 26, so that a relatively small force need be applied to the upper section in order to raise that section and its work platform.

Conversely, a relatively small force is required to control the descent of the upper section 18 and the work platform 26.

At the lower end of the upper section 18, a pair of pawls are pivoted to the rails 20, the pawls being linked together by a control bar 33. The pawls will normally fall under gravity to rest on the adjacent rung 23 of the upper section 18. If the upper section is to be raised, the pawls 32 will pivot to pass each rung is 21 in turn of the lower section 17, but the pawls will prevent descent of the upper section by engaging the next rung of the lower section below the pawls.

The control bar 33 may be used to lift the pawls and free them from the rungs of the lower section, to allow descent of the upper section. An elastic tensioning cord 36 extends between the control bar 33 and a cleat 37 on a side rail 22 of the upper section so that when the upper section is to be lowered fully, the pawls may be rendered inoperative by tensioning the cord.

The wheeled base 10 is fitted with removable ballast weights 38 to give additional stability to the access platform, when in use.

Figures 6 and 7 show the second embodiment of access platform which is generally similar to the first embodiment and insofar as is possible, like reference numbers with those of the first embodiment indicate like parts. The second embodiment differs from the first in that the bracing members 19 are replaced by a pair of struts 35 extending between the wheeled base 36 and the side rails 20 of the mast 16. Rungs 37 extend between the struts 35 at a suitable spacing such that the struts and rungs form a step ladder to assist a user in reaching the mast 16 and then climbing the mast to gain entry to the platform 26.

In the embodiment of Figures 6 and 7, the struts 35 are on the opposite side of the mast from the platform 26, as compared to the first embodiment where the bracing members 19 are on the same side of the mast as the platform. As a consequence of this, and to ensure the entire assembly has sufficient stability when in use, the mast 20 is moved closer to the end of the base on the side thereof remote from the platform. This has the advantage that the platform may be used for example over a desk top so long as there is sufficient clearance beneath the desk to allow the relatively low height of the is base to be pushed beneath the desk until the mast 20 contacts the edge of the desk top. In the case of the first embodiment, movement of the base beneath a desk may be restricted by the presence of the bracing members 19.

In all other material respects, the second embodiment of overhead access platform shown in Figures 6 and 7 is essentially the same as that of the first embodiment, shown in Figures 1 to 5 and will not therefore be described again here.

It will be appreciated from the foregoing that access platforms of this invention are particularly suitable for use indoors or outdoors, such as for the servicing of light fittings or other overhead maintenance or installation operations. By virtue of the profile of the wheeled base 10 with the out-riggers 13 removed, the apparatus may easily be wheeled from place-to-place. The base itself may be pushed under a table or fitted into the keyhole of a desk or in the case of the second embodiment pushed under drawer units or other furniture on short legs, so as to give access for example to a light fitting over the surface of the table, desk or the like. As the counterweights substantially balance the work platform 26 and the second section 18, the work platform may easily and safely be raised to the required height once the wheeled base has been suitably positioned. When the work has been completed, the work platform may be safely lowered to allow the access platform to be wheeled away. -10-

Claims

<claim-text>CLAIMS1. An overhead access platform comprising a base, an extendable mast comprising at least two sections connected together for relative sliding movement along the length thereof, one section of the mast being mounted on the base to project upwardly therefrom and a work platform being attached to a S second section of the mast, and a counterweight assembly for the second section including at least one flexible tension member interconnecting the second section to a counterweight arranged for rising and falling movement within the confines of the mast, corresponding to lowering and raising movement respectively of the second section.</claim-text> <claim-text>2. An overhead access platform as claimed in claim 1, wherein each section of the mast is in the form of a ladder having a pair of rails with spaced rungs extending between the rails.</claim-text> <claim-text>3. An overhead access platform as claimed in claim 2, wherein at least one of the rails of said one section is hollow and the counterweight is received in that rail of the one section, for rising and falling movement therewithin.</claim-text> <claim-text>4. An overhead access platform as claimed in claim 3, wherein the flexible tension member passes over a guide arranged at the upper end of said one rail, one end of the flexible tension member being secured to the counterweight and the other end to the second section.</claim-text> <claim-text>5. An overhead access platform as claimed in claim 4, wherein the flexible tension member comprise a metal cable or a chain and the guide comprises a rotatable pulley for the cable or chain.</claim-text> <claim-text>6. An overhead access platform as claimed in any of claims 3 to 5, wherein both rails of said one section are hollow and each receives a respective counterweight on each side of the mast.</claim-text> <claim-text>7. An overhead access platform as claimed in any of claims 2 to 6, wherein said second section of the mast is narrower than said one section, the rails of the second section being slidably received between the rails of said one section.</claim-text> <claim-text>8. An overhead access platform as claimed in any of the preceding claims, wherein there is at least one intermediate section disposed between said one and second sections of the mast, the at least one intermediate section being slidably arranged with respect to the one and second sections.</claim-text> <claim-text>9. An overhead access platform as claimed in claim 8, wherein the second and at least one intermediate sections are coupled together for simultaneous sliding movement with respect to the one section.</claim-text> <claim-text>10. An overhead access platform as claimed in claim 8 or claim 9, wherein essentially corresponding counterweight assemblies are provided between the second section and the intermediate section, and between the intermediate section and the one section.</claim-text> <claim-text>11. An overhead access platform as claimed in any of the preceding claims, wherein the one section is fixedly secured to the base to project upwardly therefrom.</claim-text> <claim-text>12. An overhead access platform as claimed in claim 2 or any claim dependent thereon, wherein rungs extend between the rails of at least the second section.</claim-text> <claim-text>13. An overhead access platform as claimed in claim 12, wherein a pair of triangulation struts are provided between the base and the rails of the one section of the mast projecting upwardly from the base.</claim-text> <claim-text>14. An overhead access platform as claimed in claim 13, wherein rungs extend between the pair of triangulation struts whereby the struts serve as a ladder for climbing towards the second section of the mast.</claim-text> <claim-text>15. An overhead access platform as claimed in any of the preceding claims, wherein dogs or pawls are provided between the sections of the mast to allow releasable locking together of the sections at a desired elevation within the limits of relative sliding movement of the sections, to restrain descent of the 16. An overhead access platform as claimed in any of the preceding claims, wherein the base is in the form of a wheeled trolley.17. An overhead access platform as claimed in any of the preceding claims, wherein the base is provided with out-rigger supports to increase the stability of the work platform.18. An overhead access platform as claimed in any of the preceding claims, is wherein the work platform is provided with an encircling handrail assembly.19. An overhead access platform as claimed in claim 18, wherein the handrail assembly includes a gate which may be opened to facilitate access to the work platform from the mast.20. An overhead access platform as claimed in claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.</claim-text>