Our Ref 133900/73 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): Tidd Ross Todd Limited, Maui Street, Pukete, Hamilton, New Zealand Address for Service: James and Wells Intellectual Property Level 11, St George Centre, 60 Marcus Clarke Street Canberra ACT 2601, Australia Invention Title: An Articulated Pick and Carry Crane The following statement is a full description of this invention, including the best method for performing it known to us.
James & Wells ref: 133900/73 AN ARTICULATED PICK AND CARRY CRANE TECHNICAL FIELD The present invention relates to an articulated pick and carry crane, particularly an articulated pick and carry crane including a roll over protection structure. BACKGROUND ART There is an increasing focus on improving safety in the workplace. This is particularly true in relation to the operation of heavy vehicles such as trucks, tractors, and earthmoving machinery. Operators of such vehicles face a high risk of injury or even death in the event of an accident leading to the vehicle rolling. In response to this risk, standards have been established to ensure that structures for protection of vehicle operators in these circumstances meet minimum requirements. Reference to a roll over protection structure, or "ROPS" should be understood to mean an operator compartment structure configured to meet strength and energy absorption requirements set by regulatory agency standards - for example AS2292.2 / ISO 3471 at the time of filing the application. These requirements have been established to increase the likelihood that the operator of a vehicle will be protected in the event of the vehicle overturning or rolling over. While many vehicles may include framework which is intended to provide some form of protection in the event of a roll, this does not necessarily mean that this frame may be considered a roll over protection structure. At present, ROPS standard structures are not known to be implemented in vehicle mounted cranes. Traditionally, cranes are not susceptible to rolling over as the crane functionality is not used while the vehicle moves. The vehicle is effectively an inbuilt carrier unit, used to transport the crane between job sites with the boom of the crane in a retracted and fixed position. In order to increase stability while stationary, support structures such as outriggers may be deployed in order to widen the base. Indeed, in some known cranes, such as the AT-20 manufactured by TerexTM at the time of filing of the present application, the operator cab acts as a support structure for the crane boom. In order to do so, the frame of the cab must be sufficiently rigid to resist damage under load. This contrasts with the requirement in most standards relating to roll over protection structures, including Australian standards, that a degree of deformation is required in the event of a roll for the purpose of energy absorption. 2 James & Wells ref: 133900/73 However, the applicant has identified that cranes designed to pick up a load, and move with it (known as "pick and carry" cranes), may be vulnerable to rolling in the course of operation. Pick and carry cranes which are articulated may be particularly susceptible to rolling. Articulation of the crane enables a tighter turning circle, which is highly important in order for the crane to be maneuvered into position within relatively restricted areas. Further, articulation enables slewing of the boom to assist in placement of a load being carried by the boom. However, this articulated configuration has some disadvantages from a safety perspective. Firstly, the angle of the front and rear chassis assemblies relative to each other may be such that weight distribution is accentuated on one side in comparison with what would be experienced by a rigid chassis. This can cause the crane to be more prone to rolling in some orientations. This may be accentuated by the environment in which such cranes may be used. For example, in a mining context the crane may be used in areas in which the overburden (material covering the mineral of interest) is loose. This may provide an unstable base, where areas may give way when a load is applied, causing the crane to become unbalanced and potentially overturn. Additionally, mining roads and other areas within the mine in which vehicles operate are often susceptible to large potholes as the result of the materials used to form the roads, the volume of traffic, and the heavy weight of vehicles operating in such areas. These potholes present an additional overturning hazard. Secondly, this maneuverability may enable the crane to access locations other crane types cannot reach, let alone operate in. This could lead to the crane being used in a situation which the operator knows is not ideal, but does so regardless - considering it to be a practical solution. Further, while an articulated pick and carry crane is likely to be used when stationary, or at lower speeds on a work site (for example, less than four kph), it should ideally be capable of being driven on the open road at speeds of approximately 80 kph. While designed to have this capability, it cannot be escaped that the articulated body and associated steering system are primarily intended for operation at low speeds. As such, cranes of this configuration are generally more susceptible to accidents (and thus rolling) at high speeds than rigid body counterparts. As articulated pick and carry cranes generally have a relatively high ratio of weight to wheel base in order to achieve a desirable load capacity while minimizing size, making them more likely to overturn in the case of an accident. 3 James & Wells ref: 133900/73 Also, the camber of mining roads is generally greater than in public roads in order to shed water as quickly as possible. This is intended to reduce the hazard caused by water pooling on the road and penetrating the surface, causing rapid deterioration of the road. However, such a camber can exaggerate issues such as oversteering which articulated pick and carry cranes may already be susceptible to. There are a number of difficulties associated with the provision of a roll over protection structure in an articulated pick and carry crane. In particular, the operator's cab is preferably located on the front chassis assembly, primarily for maximising visibility, as is the crane boom assembly. It is important that the vision of the operator not be impaired. Visibility affects the ability of the operator to both accurately control the crane to perform the lifting and placing of loads, and also safely operate movement of the vehicle. Weight distribution between the front and rear is directly related to load capacity in an articulated pick and carry crane. Essentially, the heavier the front is relative to the rear, the lower the load capacity. The weight in the rear may be increased to compensate for this, but there are wider design implications in doing so. In particular, there are restrictions on vehicle curbweight if a vehicle is intended for use on public roads. Also, one of the attractive features of smaller pick and carry cranes is their ability to drive into a building or space with height restrictions, carrying a load into or out of the building. If a roll over protection structure were to extend into space which might otherwise be occupied by the crane boom, other aspects of the crane may be required to compensate for this. For example, the ride height may need to be adjusted, which would have implications for the suspension of the vehicle and/or ground clearance. As well as affecting the height of a pick and carry crane, and depending on the cab configuration, a roll over protection structure extending beyond the cab may also affect the range of movement which may be achieved by the crane boom - reducing its effectiveness. There are tight restrictions around the extent of damage which a roll over protection structure may experience before it must be replaced. As such, it is quite possible that the roll over protection structure may require replacement in the case of an incident where the remainder of the crane is readily able to be repaired. It is an object of the present invention to address at least one of the foregoing problems or at least to provide the public with a useful choice. All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The 4 James & Wells ref: 133900/73 discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in Australia or in any other country. Throughout this specification, the word "comprise", or variations thereof such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only. DISCLOSURE OF THE INVENTION According to one aspect of the present invention there is provided an articulated pick and carry crane, including: a chassis including a front chassis portion and a rear chassis portion; a pivot coupling connecting the front chassis portion and rear chassis portion; a crane boom associated with the front chassis portion; and an operator cab associated with the front chassis portion, characterised in that the articulated pick and carry crane includes a roll over protection structure associated with the front chassis portion. It should be appreciated that reference to the various components being associated with the chassis is intended to encompass embodiments in which the components are not attached directly to the chassis per se, but may, for example, be attached to a secondary frame and/or additional components which are in turn attached to the chassis. Further, it should be appreciated that reference to a crane boom may encompass the associated components used to perform the various functions of a crane - for example the lift cylinder or cylinders used to control the angle of the boom, and hoist for lifting and lowering of the load. In a preferred embodiment the roll over protection structure is made of medium tensile steel. One of the common requirements for ROPS certification is that the structure deforms to a 5 James & Wells ref: 133900/73 certain extent in response to loading. This medium tensile steel may assist in achieving the required energy absorption without fracture of the structure. In a preferred embodiment the operator cab includes an operator seat and passenger seat. In one embodiment, the operator seat may be positioned in front of the passenger seat. However, it should be appreciated that this is not intended to be limiting, and that other configurations are envisaged - for example side by side. According to another aspect of the present invention there is provided an articulated pick and carry crane, including: a chassis including a front chassis portion and a rear chassis portion; a pivot coupling connecting the front chassis portion and rear chassis portion; a crane boom associated with the front chassis portion; and an operator cab associated with the front chassis portion, the cab including an internal frame, characterised in that the internal frame forms a roll over protection structure. Reference to an internal frame should be understood to mean the structure to or around which exterior cladding such as panels, windows, or doors are attached. By providing the roll over protection structure as the internal frame, a number of advantages may be gained. Firstly, it may be highly important, particularly for safety reasons, that the vision of the operator be maintained - both while driving the crane and also during lifting and placement of a load. An external frame surrounding the operator cab, in particular one including vertical pillars, may create blind spots which act as a safety hazard to both the operator as well as other people or equipment in the vicinity of the crane By providing the roll over protection structure within the internal frame of the operator cab, the risk of reducing the operator's vision may be reduced Further, such an arrangement may reduce weight of the crane, and the front chassis portion in particular by eliminating the need for the framing otherwise required to provide shape to the cab. Essentially, the roll over protection structure may perform a dual function - both the intended measure of safety against rolling, and providing the structure enabling the cab to be enclosed for operator comfort and safety as well as aesthetic styling. 6 James & Wells ref: 133900/73 This reduced weight may also reduce the impact of the introduction of a roll over protection structure on the load capacity of the articulated pick and carry crane. As previously discussed, the heavier the front is relative to the rear, the lower the load capacity of the crane. There are design restrictions around simply making the rear heavier - particularly overall curbweight if the crane is to be used on public roads. By reducing the impact of the roll over protection structure on the weight of the crane, greater flexibility with regard to other attributes of the crane may be achieved. For example, if the curbweight of the articulated pick and carry crane is below the limit, the crane may include a counterweight of at least a portion of the weight balance. Such a counterweight may enable adjustment of the ratio of the weight of the front and rear portions of the crane to optimize for lifting capacity and stability on the road. As such, in a preferred embodiment the articulated pick and carry crane includes a counterweight configured to adjust the weight ratio of the front chassis portion to the rear chassis portion. Removing the need for an exterior roll over protection structure also assists in keeping the dimensions of the articulated pick and carry crane as compact as possible. This is particularly important in cranes intended to have access to buildings or other limited spaces. On a related note, such an internal roll over protection structure would be particularly useful in extending protection across both the passenger and operator zones of a cab having the configuration in which the passenger is seated behind the operator. An external roll over protection system located behind the cab as known in other applications may need to extend at an upwards angle to ensure that deflection would not encroach into the deflection limiting zone associated with the operator. Similarly, alternative configurations using external pillars to surround the cab may need to provide sufficient space between such an external roll over protection structure and the cab to ensure that deflection of the structure did not cause the cab itself to encroach into the deflection limiting zone. Such arrangements could create limitations in terms of the available space for movement of the crane boom, and also meeting desired a desired height. According to a further aspect of the present invention there is provided an articulated pick and carry crane, including: a chassis including a front chassis portion and a rear chassis portion; a pivot coupling connecting the front chassis portion and rear chassis portion; a crane boom associated with the front chassis portion; and 7 James & Wells ref: 133900/73 an operator cab associated with the front chassis portion, characterised in that the front chassis portion includes a releasably attached roll over protection structure. According to a further aspect of the present invention there is provided a method of manufacturing an articulated pick and carry crane, the crane including a chassis, the chassis including a front chassis portion and a rear chassis portion, a pivot coupling connecting the front chassis portion and rear chassis portion, a crane boom associated with the front chassis portion, an operator cab associated with the front chassis portion, and a roll over protection structure releasably attached to the front chassis portion, the method characterised by the step of: releasably attaching the roll over protection structure to the front chassis portion. By enabling the roll over protection structure to be releasably attached to the crane, the roll over protection structure may be manufactured as a single part, and used in either manufacture of a new crane, or repair of a damaged unit. In a preferred embodiment the roll over protection structure is a weldment. Reference to a weldment should be understood to mean an assembly of parts welded together. By forming the roll over protection structure as a weldment, it is envisaged that stress may be directly transferred between parts forming the roll over protection structure without requiring additional connection pieces. Also, separate connectors such as bolts may allow the parts to flex to a greater extent than welds under certain loading conditions - which may be undesirable for the purposes of meeting the requirements for roll over protection structure standards. Further, welding does not require punching or drilling of holes in the parts to enable assembly, which may affect the structural properties of the parts. As such, it is envisaged that forming the roll over protection structure as a weldment may result in a lower weight structure which is more easily capable of meeting the requirements of roll over protection structure standards. In the case of an accident involving a roll over event it is envisaged that, by virtue of the requirements for deflection, the roll over protection system may require replacement while the remainder of the crane may be readily repaired. Providing the ability to effectively swap roll over protection structures without cutting the crane or breaking of welds may reduce the complexity (and associated costs) in performing this repair work. In a preferred embodiment the roll over protection structure is releasably attached to the front chassis portion by way of a plurality of bolts. 8 James & Wells ref: 133900/73 Such an arrangement is considered to provide a low cost means for securely attaching and easily removing the roll over protection structure, which may be achieved using readily available parts and tools. It should be appreciated that reference to releasable attachment by way of bolts is not intended to be limiting, and that alternative releasable attachment means are envisaged. For example, releasable attachment may be achieved by way of twistlocks, pins, or a combination thereof. BRIEF DESCRIPTION OF THE DRAWINGS Further aspects of the present invention will become apparent from the ensuing description which is given by way of example only and with reference to the accompanying drawings in which: FIG. 1 is a side view and top view of an articulated pick and carry crane according to one aspect of the present invention; FIG. 2 is a series of perspective views of a front chassis portion of an articulated pick and carry crane including a roll over protection structure according to an aspect of the present invention. BEST MODES FOR CARRYING OUT THE INVENTION FIG. 1a and FIG. 1b illustrates an articulated pick and carry crane (generally indicated by arrow 1) in accordance with the present invention. The crane 1 includes a front chassis portion 2 and a rear chassis portion 3. The chassis portions 2 and 3 are connected by pivot couplings 4a and 4b which form an articulation point 5. Two hydraulic actuators (for example hydraulic actuator 6) on either side of the articulation point 5 are controlled to extend and retract, thus pivoting the portions 2 and 3 relative to each other in order to steer the crane 1. Control of the steering is achieved by translating steering wheel movement into a desired oil pressure in each hydraulic actuator corresponding to a particular angle of the portions 2 and 3 relative to each other. The front chassis portion 2 includes a base pivot mount 7, to which a telescoping boom 8 is coupled. The boom 8 is also coupled to a luffing actuator 9, which may be controlled to adjust the angle of the boom 8. A hoist system including a winch 10 controls the lowering and lifting of a load attachment point 11 (which typically includes a hook - not illustrated). 9 James & Wells ref: 133900/73 In a preferred embodiment the weight distribution between the front axle and rear axle may be substantially 42% front axle, 58% rear axle. The weighting towards the rear enables greater load capacity of the crane 1 than a more even distribution. However, it is envisaged that a counterweight (not illustrated) may be used to adjust the weight distribution to 46% front axle, 54% rear axle. In doing so, handling of the crane 1 at higher speeds may be improved. The front chassis portion 2 further includes an operator cab 12 in which the operator is seated in front of a passenger. The operator cab 12 includes an internal frame (not illustrated) to which the external panels, doors, and windows are mounted. FIG. 2a, FIG. 2b and FIG. 2c provide perspective views of the front chassis portion 2 of the articulated pick and carry crane 1 illustrated in FIG. 1a and FIG 1b, including a roll over protection structure 13, or ROPS formed as a weldment. In FIG. 2a, the ROPS 13 is shown as attached to the front chassis portion 2. It should be appreciated that the ROPS forms the internal frame alluded to with reference to FIG. 1a and FIG. 1 b, and that the panels, doors and windows shown in FIG. 1 may be attached thereto. FIG. 2b and FIG. 2c provide exploded views of the ROPS 13 relative to the front chassis portion 2. In FIG. 2b it may be seen that the ROPS 13 includes a recess 14 configured to fit over a corresponding section 15 on the front chassis portion, and bolts 16 inserted through into tapped holes 17 in the front chassis portion 2. The ROPS 13 further includes mounting brackets 18 configured to be received by recesses 19 in the front chassis portion 2 - as illustrated in FIG. 2c. Bolts 20 may be passed through the respective mounting brackets 18 and recesses 19 and secured with nuts 21. Bolts 16 and 20 releasably attach the ROPS 13 to the front chassis portion 2. It is envisaged that the ROPS 13 may be produced as a standard part (potentially including the running gear), ready to be attached to an articulated pick and carry crane either in the course of manufacture, or as a replacement for a damaged ROPS on an otherwise repairable crane. Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims. 10