Vehicle recovery apparatus

Abstract

A trailer for vehicle recovery, has a towing coupling (12, fig 1), and a pair of pivotal limbs 30, each limb 30 having a platform 50 that slides on it from a position near the pivot 32 when the limb 3

Description

TECHNICAL FIELD The present disclosure relates to an apparatus and in particular to a trailer for performing roadside vehicle recovery. The apparatus comprises a drive assembly generally configured to adjust limbs of the trailer between a stowed state and a deployed state. BACKGROUND One form of apparatus for recovering a vehicle relates to a trailer comprising a coupling, which may be attached to a towing hitch of a recovery vehicle. A cross-member is mounted transversely on the coupling. The cross-member has wheels mounted at each end. Inboard of the wheels are a pair of platforms, which are adapted to support either the front or rear wheels of the vehicle being recovered. SUMMARY The present disclosure relates to an apparatus and in particular to a compact recovery trailer may be stowed within a normal recovery vehicle, for example a panel van. and may be rapidly deployed when needed and rapidly stored after use. Deploying and storing a recovery trailer can be cumbersome and time consuming, however, due for example to using bulky deployment equipment that may impede the recovery trailer's storage. One or more aspects of the present disclosure are directed to alleviating such difficulties. In accordance with a first aspect of the present disclosure, there is provided an apparatus for recovering a first vehicle, the apparatus comprising: a coupling with means for attachment to a second, towing vehicle, a pair of wheels attached to the coupling and a pair of platforms secured to the coupling, wherein the coupling has first and second portions, wherein the first and second portions are hinged together at adjacent ends, about an axis; wherein a first portion of the coupling has means for being secured to a towing hitch of the second vehicle, at an end thereof distal from the end hinged to the second portion; wherein the second portion of the coupling has a pair of limbs pivotally mounted adjacent an end thereof remote from the end hinged to the first portion, wherein the limbs are pivotal between a stowed state in which they are disposed parallel to the coupling, one on either side of the coupling and a deployed state in which they are disposed coaxially of one another on an axis transverse to the longitudinal axis of the coupling; wherein the platforms are mounted and configured to slide, one on each of the limbs, wherein the platforms are interconnected to the second portion of the coupling by a coupling means, so that when the limbs are in the stowed state, the platforms are slid inwardly towards the pivot connections of the limbs to the coupling and, when the limbs are in the deployed state, the platforms are slid outwardly towards the free ends of the arms; and wherein a self-steering wheel is mounted on each of the limbs, wherein the selfsteering wheels are disposed outboard of the platforms when the limbs are in the deployed state; and a drive assembly configured to adjust the limbs between the stowed and deployed states, wherein the drive assembly comprises: a rotary motor; a gearbox mechanically coupled to the rotary motor, wherein the gearbox comprises a plurality of pairs of gears in a gear train; a translation screw mechanically coupled to the gearbox, wherein the rotary motor, the gearbox and at least part of the translation screw are provided within a housing and are arranged along the longitudinal axis of the second portion, wherein the rotary motor and / or gearbox are secured to the second portion via one or more mounts; and a pair of connectors, each connector being mounted at one end to one of the limbs, the other end of each connector being mounted to the translation screw, so that actuation of the drive assembly in one direction will adjust the limbs from their stowed to their deployed states and actuation of the drive assembly in the opposite direction will adjust the limbs from their deployed to their stowed states. The translation screw may be mounted within the second portion via a support. The support may have an internal form factor that tapers towards the gearbox and / or comprises a bearing unit through which the translation screw passes. The rotary motor may be an electric motor optionally connectable to an external power source. The apparatus may comprise a detachable platform extension attached to each platform, optionally wherein the platform extension comprises a guard rail. Each of the pair of platforms and / or the detachable platform extension may have a width of at least 290mm, preferably at least 299mm, and a length of at least 185mm, preferably at least 195mm. The detachable platform extension may comprise side boxes each having a height of at least 50mm, a width of at least 30mm, and a depth of at least 3mm. A releasable locking means may be provided between the first and second portions of the coupling, to lock the coupling in the deployed state. A locking pin may engage through aligned apertures in the first and second portions of the coupling, to lock the coupling in the deployed state. A releasable means may be provided to lock the limbs in their deployed state relative to the second portion of the coupling, optionally wherein locking fasteners engage through aligned openings in the limbs and the second portion of the coupling. Means may be provided to assist and control relative movement between the first and second portions of the coupling as they are adjusted between their stowed and deployed states. One or more gas struts may act between the first and second portions of the coupling. The coupling means between the platforms and the second portion of the coupling may be alterable, to permit alteration of the lateral position of the platforms. A coupling means pivotally attached to each platform may be pivotally attached to a protrusion on the second portion of the coupling by means of a pin which engages through aligned openings in the coupling means and the protrusion, a plurality of openings being provided in the coupling means and / or the protrusion to permit adjustment of the coupling means. The self-steering wheels may be mounted on the platforms and / or are interconnected so that they will adopt the same steering angle. The self-steering wheels may be interconnected hydrostatically. The self-steering wheels may each have a steering lever which is attached to a double acting ram; a first chamber on the ram attached to one wheel being connected to a first chamber on the ram attached to the other wheel; and a second chamber on the ram attached said one wheel being connected to a second chamber on the ram attached to said other wheel, by hydraulic tubes, to form closed hydraulic circuits; so the movement of one wheel will be transmitted to the other wheel. Restrictors may be provided in the tubes to provide damping. An isolation valve may be provided in at least one hydraulic tube by which the position of the self-steering wheels may be locked. A means may be provided for pivotally mounting the apparatus in the second vehicle. Cylindrical protrusions may be provided for engagement of a bracket mounted within the second vehicle. A means may be provided for controlling movement of the apparatus between its stowed and deployed states. Said means for controlling movement of the apparatus may comprise a winch. A means may be provided for locking the apparatus in a stowed position, within the second vehicle. In accordance with a second aspect of the present disclosure, there is provided a vehicle comprising the apparatus of the first aspect. The optional features described in relation to the first aspect are also applicable to the second aspect where compatible. With the apparatus described above, when the limbs are in the deployed state the apparatus may be attached to the towing hitch of a second, towing (recovery) vehicle to allow a first to be towed. However, when not in use, the limbs of the apparatus with the platforms for supporting wheels and self-steering wheels attached thereto may be adjusted to a stowed state and the coupling may be folded about its hinge point, to form a compact assembly, which may easily be stowed in the back of the second vehicle. The provision of the drive assembly allows for rapid and automated deployment while maintaining the coupling's outward form factor such that storage of the apparatus is not impeded. The gearbox increases the torque output of the rotary motor thereby improving the durability of the drive assembly. A relatively high level of control over the speed and torque by which the limbs are adjusted between their stowed and deployed states may be realised by the provision of the gearbox and enhanced by the provision of plural pairs of gears in a gear train. Further advantages of the drive assembly will become apparent from the description below. According to an embodiment of the disclosure, a pivot structural support is preferably provided in the back of the second vehicle to which the free end of the first portion of the coupling may be pivotally attached. A winch may also be provided by which pivoting of one portion of the coupling relative to the other may be controlled. The winch may also be used to recover the first (e.g., broken down) vehicle and pull in onto the apparatus. According to another embodiment of the disclosure, a linkage mechanism connecting the platforms to the coupling may be adjustable to adjust the position of the platforms to match the track of the first vehicle (the vehicle being recovered). Furthermore, the selfsteering wheels are preferably secured to the platforms so that the track of the apparatus will also be adjusted with the platforms. The self-steering wheels may also be interconnected so that the steering angles of the two wheels are the same and to prevent the wheels from vibrating independently due to single wheel impacts, for example when one of the wheels is subjected to a discreet disturbance such as a pothole or kerb strike. The two wheels may be interconnected by a mechanical connection, such a connection would however have to be articulated to accommodate movement of the limbs and adjustable to accommodate variation in the track. According to another embodiment, the wheels are interconnected hydrostatically, each wheel having a steering limb which is connected to a double acting cylinder, the two cylinders being interconnected by means of flexible tube so that as one of the wheels pivots about its axis the movement is transmitted to the other wheel. The platforms may be sized, in terms of their inner length and inner width (corresponding to the length and width of a vehicle tyre respectively) so that relatively large vehicles, more generally vehicles having relatively wide tyre widths, can be pulled onto the apparatus and thereafter towed. A platform extension, which may comprise a ramp and / or guard rail, may additionally or alternatively be sized for the same purpose. While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that other embodiments, beyond the particular embodiments described, are possible as well. All modifications, equivalents, and alternative embodiments falling within the spirit and scope of the appended claims are covered as well. The above discussion is not intended to represent every example embodiment or every implementation within the scope of the current or future Claim sets. The Figures and Detailed Description that follow also exemplify various example embodiments. Various example embodiments may be more completely understood in consideration of the following Detailed Description in connection with the accompanying Drawings. BRIEF DESCRIPTION OF DRAWINGS One or more embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a plan view of an apparatus in accordance with the present disclosure, in its deployed configuration; Figure 2 shows a front view of the apparatus illustrated in Fig. 1, in its stored configuration; Figure 3 shows a perspective view of the apparatus in its stored configuration; Figure 4 is an illustration of components of a drive assembly, according to an example; Figure 5 is a photograph of a drive assembly, according to another example; Figure 6 shows a side elevation of the apparatus shown in Fig. 1, illustrating a first stage of deployment of the apparatus; Figure 7 shows a plan view of the apparatus shown in Fig. 1, illustrating a second stage of the deployment of the apparatus; and Figures 8A-C show plan views of a detachable platform extension, according to an example. DETAILED DESCRIPTION As illustrated in the drawings, an example apparatus 10 according to one embodiment has a coupling (that may otherwise be termed a drawing) 12. The coupling 12 is formed in two portions or sections, a forward (first) portion 14 and a rearward (second) portion 16. The forward and rearward portions 14, 16 are pivoted together about adjacent ends, by pivot fastener (e.g., a pivot pin) 18 so that the portions 14 and 16 may be disposed end to end, or the rearward portion 16 may be folded underneath the forward portion 14. The forward end of the forward portion 14 extends beyond the pivot fastener 18 and has openings or apertures therein, the openings aligning with corresponding openings in the rearward portion 16 when the forward and rearward portions 14 and 16 are disposed end to end, so that a locking fastener (e.g., a locking pin) 20 may be inserted through the openings, to lock the coupling in its extended position. A stop (not shown) is provided to prevent the forward and rearward portions 14 and 16 going past the position in which the openings are aligned. A pair of gas struts 22 are provided between the forward and rearward portions 14 and 16 of the coupling 12 to assist and control relative movement of the portions 14 and 16, as the coupling 12 is moved between its folded and extended states. A towing hitch, for example a ball joint cup 24 is secured to the forward end of the forward portion 14 of the coupling 12, for attachment to a towing hitch 100 of a recovery (second) vehicle. A pair of cylindrical protrusions (such as trunions) 26 are also provided adjacent the forward end of the forward portion 14 of coupling 12, one extending to each side thereof. A pair of limbs, which may also be referred to as arms, 30 are pivotally mounted to a structural support (e.g., a bracket) 31 secured to the rear end of the rearward portion 16 of the coupling 12. The limbs 30 are mounted by means of pivot fasteners (e.g., pivot pins) 32, for movement in the plane of the rearward portion 16 of the coupling 12. The limbs 30 extend beyond the pivot fasteners 32 and a pair of connectors or links 34 extend from the end of each limb 30 to a block 36 mounted for axial movement on a translation (or lead) screw 38. The apparatus comprises a drive assembly 39 comprising a rotary motor 40, a gearbox 41 and the translation screw 38. The rotary motor 40 is an electric motor in this example that in some cases may be connectable to an external power source. The gearbox 41 is mechanically coupled to the rotary motor 40 and the translation screw 38 so that rotary mechanical motion generated by the rotary motor 40 is converted into rotational motion of the translation screw 38. In this way, actuation of the drive assembly 39 causes the translation screw 38 to be rotated to move the block 36 linearly, causing the limbs 30 to pivot about the pivot fasteners 32, between a stowed state (or position) in which the limbs 30 are disposed parallel and in juxtaposed relationship to the rearward portion 14 of the coupling 12, as illustrated in Figs. 2 and 3; and a deployed state (or position) in which the limbs 30 extend transversely of the axis of the coupling 12, as illustrated in Fig. 1. The rotary motor 40, gearbox 41 and at least part of the translation screw 38 (sufficient to mechanically couple to the connectors 34) are provided (e.g., housed or installed) within the second portion 16 (e.g., provided within a cavity or recess defined by the second portion 16). In the deployed state, openings at the end of limb 30 are aligned with openings 42 in the structural support 31 so that securing fasteners (e.g., locking pins) 44 may be located through openings 42, to secure the limbs 30 in their deployed states. Fig. 4 is an illustration of certain components of a drive assembly 39 according to an example. Specifically, a gearbox 41 comprising a plurality of pairs of gears in a gear train 43a, 43b. There are two pairs in this example, although a greater number of gear trains may also be used. A first gear of the first pair of gears 43a is coupled to the rotary motor 40. The first gear of the first pair of gears 43a on the rotary motor side of the gearbox 41 may comprise a coupling specifically adapted to mate with an output shaft of the rotary motor 40. A first gear of the second pair of gears 43b is coupled to the translation screw 38. A second gear of the first pair of gears 43a is coupled to and provided on the same axis as a second gear of the second pair of gears 43b. The gearbox 41 is used to reduce the speed of the translation screw 38 relative to the speed of rotation of the rotary motor 40 while increasing torque, allowing the rotary motor 40 to apply the necessary toque to the translation screw 38 whilst being run from, e.g., a recovery vehicle's power supply (e.g. a 12V or 24V automotive battery). The translation screw 38 has a simplified form for brevity and, according to this example, is positioned substantially centrally within and along the longitudinal axis of the second portion 16. The rotary motor 40 and gearbox 41 may be secured to the second portion 16 by one or more mounts 46, such as by the same mount (that may afford a relatively simple installation) or respective mounts for the rotary motor 40 and gearbox 41 (that may improve vibrational dampening). As discussed further below the one or more mounts 46 may be configured to act as a sink to dissipate, to the second portion 16 and / or the local environment, heat and / or noise generated by the drive assembly 39 during use. A generally inline arrangement of the rotary motor 40, gearbox 41 and translation screw 38 with respect to the second portion 16 may improve their reliability 38 by minimising off-axis vibrations during use. To this end, the number of gear trains 43a, 43b and their respective positions may be set such that the rotary motor 40 is aligned with the longitudinal axis of the translation screw 38. In turn, the form factor of the drive assembly is compact, while access to the components of the drive assembly 39 from each side of the second portion 16 is facilitated. Fig. 5 is a photograph of a drive assembly 39 according to another example, wherein like reference signs refer to like components introduced above. The drive assembly is provided substantially within the second portion 16 and comprises the components described above. In this example the rotary (electric in this example) motor 40 is connectable to an external power source (not shown) and comprises means, such as a clutch, to adjust output speed / torque. The translation screw 38 is mounted within the second portion 16 via a support 47. The support 47 has an internal form factor configured to dissipate vibrations from the drive assembly 39 into the second portion 16 (e.g., by comprising a recess or cavity within which the translation screw 38 is located and that tapers towards the gearbox 41). The support 47 may irrespective of its internal form factor comprise a bearing unit or housing (not shown) through which the translation screw passes. A lubricant 48 may be applied where components of the drive assembly 39 abut or otherwise come into close contact with the one or mounts 46 to reduce friction. Returning to Figs. 1-3, a pair of platforms 50 has tubular mounting means 52, which locate and slide one on each of the limbs 30. The platforms 50, which also may be referred to as pans or wheel platforms, each define a platform for the wheels of the towed vehicle. Spring loaded adjustable chocks 54 are provided at the rearward end of the platforms 50, which will be depressed as the wheel of the vehicle is moved onto the platform 50 and will spring up to help retain the towed vehicle on the apparatus 10. Additional fastening means, for example straps or chains may also be provided for securing the towed vehicle. The platforms may be sized to support the towing of relatively large (e.g., modern) vehicles. Preferred dimensions in this respect are at least 290mm for the width, more preferably at least 299m, and at least 185mm for the depth / length, more preferably at least 195mm. Coupling means, such as links, 60 are pivotally connected between the platforms 50 and protrusions (projections) 62 on the structural support 31, the coupling means 60 causing the platforms 50 to slide outwardly on limbs 30 as the limbs are moved between their stored and deployed states and to slide inwardly on limbs 30 as the limbs 30 are moved between their deployed and stowed states. The coupling means 60 are secured to the protrusions 62 by means of locking pins 64 which engage through opening 66 in the ends of coupling means 60 and protrusions 62. Several openings 66 are provided in both the coupling means 60 and protrusions 62, by which the effective length of the coupling means 60 may be altered. The distance between the platforms 50 when the limbs 30 are in their deployed states, may thereby be adjusted to suit the track of the towed vehicle. A pair of self-steering wheels 70 are mounted one on each of the platforms 50, the selfsteering wheels 70 being mounted on the outside of the platforms 50, when the limbs 30 are in their deployed states. The self-steering wheels 70 are mounted on kingpins 72 which extend substantially vertically but are inclined at appropriate camber and castor angles to provide a self-steering effect. Steering levers 74 are provided on each of the self-steering wheels 70, the steering levers 74 being connected to double-acting cylinders or rams 76 mounted on the platforms 50. The cylinders 76 on either side of the apparatus 10 are interconnected by flexible hydraulic tubes (e.g., hoses) 78, the forward chamber of one cylinder 76 being connected to the forward chamber of the other cylinder 76 and the rearward chamber of one cylinder 76 being connected to the rearward chamber of the other cylinder 76. The connected chambers thereby form closed hydraulic circuits by which any steering movement of one wheel 70 will be transmitted to the opposite wheel 70. For example, when the left wheel 70 is steered to the left due to its self-steering properties, the volume of the forward chamber 84 on the left cylinder 76 decreases forcing fluid to be transferred to the forward chamber 84 on the right cylinder 76 causing the right wheel 70 to be steered to the left. This steering motion causes the volume of the rearward chamber 86 of the right cylinder 76 to decrease and forces fluid into the rearward chamber 86 of the left cylinder 76, which is consistent with the applied steering motion. This fluid transfer works in the opposite sense to steer both wheels 70 to the right. In this manner, the wheels 70 will remain in phase to minimise tyre scrub and steering shimmy, particularly when the apparatus 10 is subjected to any uneven forces, for example, when one wheel 70 is subject to discreet disturbance such as a pothole or kerb strike. Furthermore, interlinking of the wheels 70 in this manner will resist and damp out any unwanted motion of the wheels 70. The amount of steering damping can be varied by adjusting the sizes of the tubes 78 or fitting restrictors 82, to control the rate of flow of fluid. An isolation valve 80 may be provided between the cylinders 76, in order to lock the wheels 70 when, for example, reversing. The use of flexible tubes 78 as described above allows for movement of the wheels 70 between the deployed and stowed positions of the apparatus 10 and also permits adjustment of the track of the apparatus 10. In the stowed position, as illustrated in Fig. 2, the apparatus is disposed substantially vertically in the rear of the recovery vehicle, the cylindrical protrusions 26 on the forward portion 14 of the coupling 12 engaging a pivot bracket 90 - see Fig, 6 - which is mounted to the floor of the recovery vehicle. The stowed apparatus 10 may be locked in position in the recovery vehicle by, for example, means of the locking fastener 20 which may engage apertures in a suitable locking bracket 92 mounted within the recovery vehicle. As also shown in Fig. 6, a winch 94 may also be provided in the recovery vehicle, the winch cable 96 passing over pulley means 98 and being secured to the coupling 12 adjacent the interconnection of the forward and rearward portions 14, 16 thereof. To deploy the apparatus the locking fastener 20 is released from the bracket 92 within the recovery vehicle and the forward section 14 of the coupling 12 is permitted to pivot rearwardly about the cylindrical protrusions 26, movement thereof being controlled by the winch 94. As the forward portion 14 pivots rearwardly the rearward portion 16 of the coupling 12 pivots away from the forward portion 14 under the influence and control of the gas struts 22. When the platforms 50 and wheels 70 are clear of the recovery vehicle, as illustrated in Fig. 3, the locking pins 64 may be engaged through suitable openings 66 in the coupling means 60 and protrusions 62 on structural support 31, to provide an appropriate separation of the platforms 50 to match the track of the vehicle to be towed. The translation screw 38 may then be rotated by the rotary motor 40 and gearbox 41 to pivot limbs 30 outwardly, as illustrated in Fig. 7, until the limbs 30 extend transversely of the longitudinal axis of the coupling 12. Securing fasteners 44 are then located through the openings in the ends of limbs 30 and openings 42 in the structural support 31 to secure the limbs 30 in position. The forward portion 14 of coupling 12 is then lowered further by means of the winch 94 until the forward and rearward portions are brought to the fully deployed state, when the locking fastener 20 is located through the aligned openings therein. As the forward portion 14 of the coupling 12 is lowered, small rollers 58 at the rear of the platforms 50 will first engage the ground permitting the platforms 50 to move backwardly until the self-steering wheels 70 come into engagement with the ground. After the forward and rearward portions 14, 16 of the coupling 12 have been locked in the deployed state by the locking fastener 20, the front of the coupling 12 may then be lifted, either manually or by means of the winch 94, from the mounting bracket 90 and the ball joint cup 24 engaged with the towing hitch 100 of the recovery vehicle. A detachable platform extension may then be attached, using means known in the art, to the trailing edge of each of the platforms 50 and the winch 94 is used to draw the vehicle being recovered onto the platforms 50 and the vehicle is located and secured to the apparatus 10 using the adjustable wheel chocks 54 and restraining straps. An example is shown in Figs. 8A-C that show complementary (front and side) plan views of a platform extension 102 comprising, as an optional feature, a guard rail 104 in a closed (Fig. 8A) and an open (Figs. 8B and C) configuration. Preferred dimensions of the platform extension 102 in this regard dimensions in this regard are at least 290mm for the width, more preferably at least 299m, and at least 185mm for the depth / length, more preferably at least 195mm, and at least 50mm, at least 30mm, and at least 3mm for the height, width, and depth respectively for the side boxes 106. As discussed above, the separation distance between the platforms 50 when the limbs 30 are in their deployed states may be adjusted to suit the track of the towed vehicle. The towing of vehicles comprising relatively wide tyres (which may be a common characteristic of modern vehicles) may be further enabled and improved by a platform extension 102 attached to each of the platforms 50 and having a size that, according to the preferred dimensions, accommodates said tyres. The reverse procedure is used to stow the apparatus 10 after use. Various modifications may be made to the embodiments described above. For example, the locking fasteners 20, 44 used to secure the coupling 20 and limbs 30 in their deployed states may be replaced by any suitable, releasable latch means. 5 In a further embodiment the wheels of the apparatus 10 may be secured directly to the limbs 30, so that the track of the apparatus 10 is fixed or is adjustable independently of the platforms 50. Other embodiments are intentionally within the scope of the accompanying claims.

Claims

1. An apparatus for recovering a first vehicle, the apparatus comprising:a coupling with means for attachment to a second, towing vehicle, a pair of wheels attached to the coupling and a pair of platforms secured to the coupling,wherein the coupling has first and second portions, wherein the first and second portions are hinged together at adjacent ends, about an axis;wherein a first portion of the coupling has means for being secured to a towing hitch of the second vehicle, at an end thereof distal from the end hinged to the second portion;wherein the second portion of the coupling has a pair of limbs pivotally mounted adjacent an end thereof remote from the end hinged to the first portion, wherein the limbs are pivotal between a stowed state in which they are disposed parallel to the coupling, one on either side of the coupling and a deployed state in which they are disposed coaxially of one another on an axis transverse to the longitudinal axis of the coupling;wherein the platforms are mounted and configured to slide, one on each of the limbs,wherein the platforms are interconnected to the second portion of the coupling by a coupling means, so that when the limbs are in the stowed state, the platforms are slid inwardly towards the pivot connections of the limbs to the coupling and, when the limbs are in the deployed state, the platforms are slid outwardly towards the free ends of the arms; andwherein a self-steering wheel is mounted on each of the limbs, wherein the selfsteering wheels are disposed outboard of the platforms when the limbs are in the deployed state; anda drive assembly configured to adjust the limbs between the stowed and deployed states, wherein the drive assembly comprises:a rotary motor;a gearbox mechanically coupled to the rotary motor, wherein the gearbox comprises a plurality of pairs of gears in a gear train;a translation screw mechanically coupled to the gearbox, wherein the rotary motor, the gearbox and at least part of the translation screw are provided within a housing and are arranged along the longitudinal axis of the second portion, wherein the rotary motor and / or gearbox are secured to the second portion via one or more mounts; anda pair of connectors, each connector being mounted at one end to one of the limbs, the other end of each connector being mounted to the translation screw, sothat actuation of the drive assembly in one direction will adjust the limbs from their stowed to their deployed states and actuation of the drive assembly in the opposite direction will adjust the limbs from their deployed to their stowed states.

2. An apparatus according to any one of the preceding claims, wherein the translation screw is mounted within the second portion via a support, the support having an internal form factor that tapers towards the gearbox and / or comprising a bearing unit through which the translation screw passes.

3. An apparatus according to any preceding claim, wherein the rotary motor is an electric motor optionally connectable to an external power source.

4. An apparatus according to any preceding claim, comprising a detachable platform extension attached to each platform, optionally wherein the platform extension comprises a guard rail.

5. An apparatus according to claim 4, wherein each of the pair of platforms and / or the detachable platform extension has a width of at least 290mm, preferably at least 299mm, and a length of at least 185mm, preferably at least 195mm.

6. An apparatus according to claim 5, wherein the detachable platform extension comprises side boxes each having a height of at least 50mm, a width of at least 30mm, and a depth of at least 3mm.

7. An apparatus according to any preceding claim, wherein a releasable locking means is provided between the first and second portions of the coupling, to lock the coupling in the deployed state.

8. An apparatus according to claim 7, wherein a locking pin engages through aligned apertures in the first and second portions of the coupling, to lock the coupling in the deployed state.

9. An apparatus according to any one of the preceding claims, wherein a releasable means is provided to lock the limbs in their deployed state relative to the second portion of the coupling, optionally wherein locking fasteners engage through aligned openings in the limbs and the second portion of the coupling.

10. An apparatus according to any one of the preceding claims, wherein means are provided to assist and control relative movement between the first and second portions of the coupling as they are adjusted between their stowed and deployed states.

11. An apparatus according to claim 10, wherein one or more gas struts act between the first and second portions of the coupling.

12. An apparatus according to any one of the preceding claims, wherein the coupling means between the platforms and the second portion of the coupling are alterable, to permit alteration of the lateral position of the platforms.

13. An apparatus according to claim 12, wherein a coupling means pivotally attached to each platform is pivotally attached to a protrusion on the second portion of the coupling by means of a pin which engages through aligned openings in the coupling means and the protrusion, a plurality of openings being provided in the coupling means and / or the protrusion to permit adjustment of the coupling means.

14. An apparatus according to any one of the preceding claims, wherein the selfsteering wheels are mounted on the platforms and / or are interconnected so that they will adopt the same steering angle.

15. An apparatus according to claim 14, wherein the self-steering wheels are interconnected hydrostatically.

16. An apparatus according to claim 15, wherein the self-steering wheels each have a steering lever which is attached to a double acting ram; a first chamber on the ram attached to one wheel being connected to a first chamber on the ram attached to the other wheel; and a second chamber on the ram attached said one wheel being connected to a second chamber on the ram attached to said other wheel, by hydraulic tubes, to form closed hydraulic circuits; so the movement of one wheel will be transmitted to the other wheel.

17. An apparatus according to claim 16, wherein restrictors are provided in the tubes to provide damping.

18. An apparatus according to claim 16 or 17, wherein an isolation valve is provided in at least one hydraulic tube by which the position of the self-steering wheels may be locked.

19. An apparatus according to any one of the preceding claims, wherein a means is provided for pivotally mounting the apparatus in the second vehicle.

20. An apparatus according to claim 19, wherein cylindrical protrusions are provided for engagement of a bracket mounted within the second vehicle.

21. An apparatus according to any one of the preceding claims, wherein a means is provided for controlling movement of the apparatus between its stowed and deployed states.

22. An apparatus according to claim 21, wherein said means for controlling movement of the apparatus comprises a winch.

23. An apparatus according to any one of the preceding claims, wherein a means is provided for locking the apparatus in a stowed position, within the second vehicle.

24. A vehicle comprising the apparatus of any preceding claim.

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