WO2001051309A1

WO2001051309A1 - The towing of vehicles

Info

Publication number: WO2001051309A1
Application number: PCT/GB2000/003940
Authority: WO
Inventors: D. Anthony Buckley; Richard Guy
Original assignee: The Automobile Association Limited
Priority date: 2000-01-14
Filing date: 2000-10-13
Publication date: 2001-07-19
Also published as: AU2000278050A1

Abstract

Repair vehicle including a stowable and deployable trailer, a trailer and a method of deploying a trailer. The repair vehicle may be driven to a repair site with the trailer stowed in the vehicle. When desired, the trailer is deployable by a deployment means. When deployed, the trailer is connected to the chassis of the repair vehicle by a means other than the deployment means.

Description

THE TOWING OF VEHICLES

This invention relates to the towing of vehicles and in particular the recovery from a road of a broken-down vehicle.

The towing of a broken-down vehicle has altered dramatically over the years. Initially tow ropes were the standard method which was later improved by use of a rigid tow bar. In such cases however the broken-down vehicle required a driver to steer the broken-down vehicle whilst it was being towed.

Later developments included the use of an A frame. This is a frame where the legs of the "A" were fitted to the bumper, or later the suspension, of the vehicle to be towed. At the point of the "A" a tow hitch is positioned to be fitted to a tow bar of a towing vehicle. An advantage of such a system is that a driver is not needed in the towed vehicle. A disadvantage is that the bodywork or suspension of the towed vehicle may be damaged.

Another arrangement which avoids the risk of damage to the towed vehicle is to support the front wheels of the broken-down vehicle on a trailer, often called a "car ambulance", which is pivotally attached to the towing vehicle in the usual way for a trailer. Such car ambulances work well in towing a broken-down vehicle. However, it is very inconvenient for a roadside patrol vehicle permanently to have to tow a trailer, especially as it is often the case that broken-down vehicles can be repaired quickly on the roadside and so there is no need for the trailer to remove the vehicle.

As a result a type of trailer known as "Stow and Tow" was developed.

This was a trailer which is carried in a disassembled form in the repair vehicle. Once the repair man realises that he cannot effect a quick roadside repair, he assembles the trailer and winches the front wheels of the broken down vehicle on to it, to tow the vehicle to a convenient repair centre. A problem with such Stow and Tow trailers, however is that their parts are heavy to manhandle during assembly, and then assembly is very time consuming; it >θften takes over one hour to complete the assembly of the trailer and to get the broken-down vehicle onto the trailer. During all that time, the occupants of the recovery vehicle and the repair man are exposed to the dangers of passing traffic.

A further form of recovery vehicle is one having a support for the front wheels of the vehicle to be recovered which is mounted on an arm pivotably connected to the bed or chassis of the recovery vehicle. In this case, when a vehicle is to be recovered, the arm is pivoted so the support rests on the floor, and the front wheels of the vehicle to be recovered are pulled onto the support. The arm is then pivoted to lift the front wheels of the vehicle to be recovered above the ground. In this case, the weight of the recovered vehicle must be borne by the rear axle of the recovery vehicle. Also, the weight of the recovered vehicle will give a moment of force about the rear axle of the recovery vehicle. Therefore, the recovery vehicle must be a heavy duty vehicle.

According to a first aspect of the invention there is provided a method in which a repair vehicle is able to drive to a repair site without any trailer, the trailer being accommodated in a stowed position on board the repair vehicle, and at the repair site means are provided to deploy a trailer out from the stowed position to a towing position behind the rear of the repair vehicle, and thereafter to couple a towing end of the trailer to the rear of the repair vehicle so that the towing forces are transmitted to the repair vehicle directly rather than via the said means, the coupling between the trailer and the repair vehicle allowing free movement of the trailer relative the repair vehicle so that it can follow the repair vehicle when towed. The advantages of such an arrangement are that the trailer is normally stowed within the repair vehicle and so, when driving to a repair site, the repair vehicle need not be hampered by the trailer. At the repair site, however, the trailer is already assembled and simply deployed from the rear of the vehicle. This can be achieved automatically, relatively quickly and need not involve any heavy lifting. Also by ensuring that the trailer is coupled to the vehicle directly for towing, all the large towing forces need not be accommodated by the means for deploying the trailer and so those means can as a result be made relatively light-weight and compact.

Once the trailer has been used and is no longer needed, it can be thereafter retracted into the vehicle to its stowed position.

According to a second aspect of the invention, a repair vehicle having a chassis and bodywork mounted on the chassis, comprises deployment and retraction means for a trailer mounted within the bodywork of the repair vehicle and attached to the chassis, the trailer carried by these extension and retraction means normally stowed by those means within the bodywork but movable by those means to the rear of the repair vehicle to a towing position and from that position to the stowed position, and coupling means for attaching a towing end of the trailer and the chassis so that towing forces are taken directly by the chassis of the repair vehicle.

The trailer for use in the invention can be of generally conventional construction and will be of the type designed to support the front wheels of a broken down vehicle. This will generally involve a main towing frame generally of "T" shape, which comprises a lengthwise member constituting the stem of the "T" which has a towing end at the base of the stem where it is coupled to the vehicle, and a transverse member constituting the cross-part of the "T" and joined to the end of the lengthwise member away from the towing end. The transverse member will have a pair of wheels at or near its ends and have means, such as wheel pans, on to which the front wheels of a broken down vehicle can rest for towing.

The wheels of the trailer can be mounted in a self steering manner so that the trailer can follow the towing vehicle around corners when the front wheels of a broken down vehicle are supported by the trailer. Suitable self steering arrangements are known.

It is not essential but may be desirable in some circumstances for the trailer to be stowed in a compacted condition width-wise. Thus when the trailer is in the towing position it may be desirable for it to be wider to accommodate the broken-down vehicle than the width available within the bodywork of the repair vehicle. As will be appreciated this will often depend upon the size of the repair vehicle.

If the trailer needs to be brought to a compacted condition for stowing, this can be achieved by giving the transverse member resiliency along its length, e.g. by providing parts which are capable of resiliently telescoping one into the other to reduce the width of the trailer. This resilience may be provided by a suitable gas strut. Cam means on the vehicle may be provided to reduce the width of the trailer as it enters the bodywork of the vehicle for stowing, the inherent resiliency causing the trailer to resume its full width as it is moved to its towing position. Alternatively, the parts may be slid together against the resilient bias by another force, for example by a cable attached to the parts around suitable pulleys or the like to pull the components in. To prevent changes in width during towing, it is preferred that the width of the trailer be fixed by manually or automatically operable locking means which are operated to lock the transverse member to its open position for towing and are released before the trailer is brought to the stowed position. Preferably, the transverse member is lockable in one of a number of different positions. The means for retracting and extending the trailer may comprise a unit, which forms a third aspect of the invention, that comprises frame means to be attached to a structural part of the vehicle, translation means movable along the frame in one direction, which is to be a fore and aft direction when the frame is mounted on the vehicle, coupling means for attaching a trailer to the translation means, and coupling means for fixing the towing end of the trailer directly to the structural part, such as the chassis of the vehicle, when the translation means reaches the limit of its travel corresponding to the towing position.

In order that the unit can remain relatively compact it is desirable that its overall length in the said one direction be roughly the same as the extent of movement of the translation means, which in turn is fixed by the extent of movement required between the stowed and towing positions of the trailer. Therefore, it is preferred not to use an hydraulic piston/cylinder arrangement which would require that overall length to be almost double that required in order to accommodate the piston/cylinder arrangement in its extended position. Instead it is preferred to use an arrangement such as a rack and pinion, or more preferably a rotatable screw and a trunnion which works along the screw as the latter is rotated. Such an arrangement can be relatively simple since a small electric motor and reduction gear can be used to operate the screw.

The trailer should be attached to the vehicle at its towing end by means of a universal pivot to allow the usual relative movement between the trailer and vehicle during towing. In addition a hole may be provided through this pivot and a pin provided which is passed through that hole to lock into engagement with means attached to the chassis of the vehicle when the translation means are in a fully extended position with the trailer in its towing position, e.g. manually or by means of a simple electronically operated solenoid. In this way, towing forces will then be directly passed via the pin to the chassis of the vehicle. This allows the unit itself to be relatively lightweight since it does not need to be strong enough in itself to take all of the towing forces.

An important advantage of such a compact and light-weight unit is that it can readily be fitted to existing vehicles, and accommodated within normal sized bodywork so that there remains sufficient space for the tools which need to be carried and room for passengers from the broken down vehicle during towing. Such vehicles are often referred to as double cab vehicles and examples are LDV Convoy 3.5T, Doublecab, Voltswagon T4 2.5 Tdi Doublecab and Ford Transit T150 Doublecab.

The trailer may have its own braking system. This can be achieved by the provision of a telescoping arrangement for the trailers such that braking of the vehicle causes compression of such parts of the trailer and the movement causing that compression is used to move and apply the brakes to the wheels of the trailer.

Such an arrangement can be improved according to the further feature of the invention by providing the wheels of the trailer with disc brakes and providing a hydraulic piston/cylinder unit associated with the telescoping arrangements on the trailer, the unit acting as a pump to pass hydraulic fluid to the disc brakes to activate them when the trailer compresses as a result of braking of the vehicle.

The deployment system is preferably connected to the chassis of the vehicle in such a way that there may be some relative movement between the deployment system and the chassis. Preferably the deployment system is pivotably mounted to the chassis, and preferably the amount of relative movement is limited. This arrangement is advantageous especially when the trailer is deployed on uneven or sloping ground as it prevents the deployment of the trailer raising the rear of the recovery vehicle. Alternatively, this can be achieved by suitable suspension of the recovery vehicle.

The invention will now be described by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows a plan view of a trailer;

Figure 2 shows a view of the mounting of a wheel to the base of the trailer;

Figure 3 shows a view of the coupling between the trailer and the chassis of a recovery vehicle;

Figure 4 shows a cross-sectional side view of a deployment means;

Figure 5 shows a side view of a wheel support used with the trailer of the present invention;

Figure 6 shows a front view of the wheel support of Figure 5; and

Figure 7 shows a detailed view of a ratchet mechanism for use with the wheel support of Figure 5 or 6.

As shown in plan view in Figure 1 , the trailer according to one example of the present invention is of a generally T-shape. The stem of the T-shape forms a towing member 1 that is retractable and fixable to the towing vehicle. The cross-member 2 of the T-shape includes a wheel 3 at either end, and pans 4 to receive the wheels of a broken down vehicle that is to be recovered.

The wheels 3 and pans 4 are each mounted to a member 5 that is mounted telescopically on the cross-member 2 of the trailer, allowing the relative distance between the wheels 3 and the relative distance between the pans 4 to be varied. This is advantageous as it allows the trailer to be used to recover vehicles of different widths. For vehicles of different widths, the space between the front wheels of the vehicle will be different. Therefore, by varying the width between the pans 4 of the trailer that support the wheels of the vehicle during recovery, different width vehicles may be recovered using the same trailer. Without this feature, it would be necessary to increase the width of the pans 4 to allow these to align with the wheels of the vehicle, therefore increasing the size and weight of the trailer. Further, as described below, the telescopic arrangement assists in the stowing of the trailer when not in use.

The wheel support 4 is shown in greater detail in Figures 5 and 6. The support 4 includes a generally flat base plate 4 that is slightly inclined to the horizontal. A front contact member 121 is pivotally mounted on a pivot 125 towards the front of the support, and a similar rear contact member 122 is pivotally mounted towards the rear of the support. Each of the front and rear contact members 121, 122 includes a tubular cross bar 126, 127 connected to the pivot 125 by bent arms. As shown best in Figure 5, when a wheel 124 is driven onto the base plate 120, the contact members 121, 122 are pivoted about the respective pivots 125 so the support bars 126, 127 contact the front and rear of the wheel 124 respectively.

As shown in detail in Figure 7, each pivot rod 125 is provided with a ratchet wheel 111, including a series of circumferential teeth 116, 117. A catch 112 is mounted pivotally about a pivot point 113, and includes a dent 115 to engage the teeth of the ratchet wheel 111. The catch 112 is biased by a spring 114 into engagement with the teeth 116, 117. In the example shown in Figure 7, the ratchet wheel 111, and therefore the pivot rod 125 and contact member (not shown in Figure 7) attached thereto, are able to freely rotate anti-clockwise (direction A as shown in Figure 7). In this case, the dent 115 on the catch 112 merely rides along the gently inclined surface 117 of the teeth. However, rotation in the opposite direction (direction B as shown in Figure 7) is prevented, since the dent 115 engages the sharp surface 116 of the teeth in this direction. Therefore, rotation of the ratchet wheel 111, and therefore pivoting of the contact member in one direction is prevented. To release the ratchet wheel 111, and allow movement of the contact member in the opposite direction, the catch 112 is pulled out of engagement of the teeth 116 of the ratchet wheel, against the bias of the spring 114, allowing rotation of the ratchet wheel 111 in either direction. It will be appreciated that the direction in which the ratchet wheel 111 is able to turn is dependent upon the orientation of the teeth, and the positioning of the catch 112.

In use, the front and rear contact members 121 , 122 are pivoted to a position below the base plate 120 of the support 4. A ramp 130 is hooked over the pivot 125 of the rear contact member 122 using a hook 131. The wheels 124 of the vehicle are then rolled onto the base plate 120. When the front of the vehicle has passed over the front contact member 121, this can be pivoted about the axis 125 until the cross bar 126 contacts the front of the wheel 124. The ratchet mechanism prevents the cross bar 126 moving away from contact with the wheel 124. In some cases, where the vehicle has a sufficiently high ground clearance, the front contact member 121 may be raised into position before the vehicle is rolled onto the support. The rear contact member 122 is similarly pivoted until the contact bar 127 is in contact with the rear of the wheel 124. Again, the ratchet mechanism ensures that the contact bar 127 remains in contact with the wheel 124. The ramp 130 may then be removed. A strap 123 is clamped to the rear cross bar 127, and passes over the top of the wheel 124 to the front of the support. The strap 123 is tightened, for example using a ratchet mechanism. This strap 123 helps hold the wheel 124 in place, and also pulls the rear contact member 122 into tighter contact with the wheel 124.

When the vehicle is to be removed, the strap 123 is removed and the catches 112 of the front and rear ratchet mechanisms are moved against the bias of the respective springs 114, disengaging the detents 115 from the teeth of the ratchet wheels 111. This allows the contact members 121, 122 to be pivoted away from the wheel 124, and allows the vehicle to be rolled off the support.

In an alternative embodiment, the front contact member 121 is freely pivotable between a first position lying on the base 120, and a second position in which the cross-member 126 is positioned to contact the first of a wheel 124. The rear contact member 122 is then rotated behind and into contact with the rear of the wheel 124 where it is locked in place by a ratchet mechanism 111. In this case, the wheel size 124 is still locked in place by the two contact members 121, 122.

Each wheel 3 is connected to the member 5 by a pivotal coupling 6 that enables the wheels 3 to self-steer. The longitudinal plane of the wheels 3 are angled inwardly at a small camber angle to help reduce wear of the tyres, and to assist with the self-centring of the wheels. Each wheel 3 is mounted on an axle that is supported by a first support 10 of the pivotal coupling 6. This is coupled to a second support 11, provided co-axially with the first support 10, and attached thereto by a king pin, allowing relative rotational movement between the first and second supports 10,11. The second support 11 is fixed to the member 5. The axis of the pivotal connection between the first and second support 10,11 is angled outwardly, such that the theoretical extension of the axis intersects the ground at a point to the inside the wheel 3. This arrangement is similar to the self-centring arrangement of vehicles, such as lorries. The abutting surfaces of the first and second supports 10,11 is angled. In this way, the relative rotation of the first and second supports 10,11 causes the second support 11 to be lifted away from the first support 10. The weight of the trailer and the vehicle supported by the trailer causes this lifting to be resisted, thereby encouraging the supports 10,11 to rotate back to their lowest position, in which the wheels 3 are centred. This lifting and reverting action is similar to that achieved with a rising butt hinge of a door.

A locking mechanism is provided on the hinge to stop the relative rotation of the supports 10,11. This is especially useful when the towing vehicle is reversing, in which case turning or steering of the wheels of the trailer is not desirable.

The towing member 1 is receivable through a bush 20 mounted on the chassis of the towing vehicle, and into a receiving housing 26 in the towing vehicle extending upwardly at an angle of about 15° to the horizontal. This angle is dependent on the length of the towing member 1 and the height of the towing vehicle.

The deployment mechanism is mounted to the chassis in such a way that it has a limited degree of freedom of movement. In particular, the receiving housing 26 is connected to the chassis by a pivot 50 at an intermediate position along the length of the housing, allowing rotation of the housing with respect to the chassis. A U-shaped bracket 52 is mounted on the housing 26 and the housing 26 is received within the bracket 52, thereby preventing lateral movement of the housing 26 with respect to the chassis. The housing 26 is also connected to the chassis by a resilient connection, for example a spring 51 to limit the degree of movement of the housing. The ability of the housing 26 to move is advantageous, especially when the recovery vehicle is on flat ground. The movement ensures that the wheels of the trailer will contact the ground, but will not cause the rear of the recovery vehicle to be lifted, as would otherwise be the case if the wheels of the trailer contact the ground at a height above the plane on which the wheels or the vehicle lie.

The receiving housing 26 includes a threaded rod 25. The end of the towing member 1 includes a plate 27 including an internally threaded hole 28 which receives the threaded rod 25. The threaded rod 25 is driven by a motor, typically a 12v motor. By rotating the threaded rod 25, the plate 27, and therefore the entire towing member 1, is driven along the threaded rod 25, thereby retracting or deploying the towing member 1 from the housing 26 depending on the direction of rotation of the threaded rod 25. The speed of rotation of the threaded rod 25, and the pitch of the threads, is selected such that towing member may be retracted or deployed within an acceptable time period, typically around 1 minute. Runners may be included to ease the deployment of the towing member 1.

A threaded system as described is preferred for the deployment of the trailer since this does not require any additional length. In particular, the length of the threaded rod 25 can be substantially the same length as the towing member 1 , and this will allow the complete retraction and deployment of the towing member 1. An automatic lubrication arrangement may advantageously be used. If systems such as hydraulic systems were used, this would require additional space, and in particular additional length, to accommodate the retraction and deployment means. However, other means may be used that fit into the available space for allowing the deployment and retraction of the towing member 1 , for example using a rack and pinion. In some cases, the vehicle may have sufficient room to accommodate a hydraulic or other system.

Especially in view of the compact size of the deployment means, this does not have sufficient strength to support the weight of the trailer and the vehicle being recovered. Therefore, according to the present invention, the trailer, once deployed, is attached to the vehicle by a means other than the deployment means. As shown best in Figure 3, the end of the towing member 1 is provided with a ring connector 30 within which a ball connector 31 having an axial opening 34 is provided. When the towing member 1 is fully deployed, this opening 34 will align with a though opening 35 in the bush 20. A pin (not shown) is provided through the opening 35 in the bush 20 and through the opening 34 in the ball connector 31, thereby securing the towing member 1 in place. As the ball connector 31 is able to rotate relative to the ring connector 30, some movement of the towing member 1 is possible, in particular pivotal movement relative to the vehicle to allow the trailer to follow the towing vehicle around bends, and to allow the trailer to be at a different angle to the towing vehicle when not on flat ground. When the trailer is fully deployed, the plate 27 contacts the rear of the bush 20 or the chassis of the vehicle. Therefore, when the trailer is pulled by the towing vehicle, the forces through the towing member 1 are coupled directly to the chassis of the vehicle, either by the coupling of the end of the towing member to the bush 20 via the pin, or through the contact between the plate 27 and the bush 20 or chassis of the vehicle or both, and not through the lightweight deployment means.

As best shown in Figure 3, the ring connector 30 is loosely mounted in the end of the towing member 1 , allowing some relative movement between the ring connector 30 and the towing member 1. A spring 32 biases the ring connector 30 towards an extended position from the towing member 1. The ring connector 30 is held captive within the towing member 1 , for example by the provision of a flange around the ring connector 30 that abuts against an inwardly turned flange of the end of the towing member 1. As also shown in Figure 3, the towing member 1 includes an elongate actuating member 33. When the trailer is being towed by a towing vehicle, the towing forces will be applied to the towing member 1 through the ring connector 30, thereby pulling the ring connector 30 outwardly from the towing member 1 into its extended position. When the towing vehicle slows down, the forces transmitted through the ring connector 30 and the towing member 1 will be reduced, causing the ring connector 30 to move against the bias of the spring 32 and into the towing member 1. As the ring connector 30 is moved into the towing member 1, the connector 30 will contact and move the actuating member 33. This movement of the actuating member 33 causes actuation of a braking system to brake the wheels 3 of the trailer. For example, this braking system may be a hydraulic braking system in which the movement of the actuating member 33 causes the release of hydraulic brake fluid from a source through pipes to cause the application of brakes, such as disk brakes, to each of the wheels 3. This ensures that when the recovery vehicle slows or brakes, the wheels 3 of the trailer are also braked, thereby ensuring that the trailer slows together with the recovery vehicle.

As described above, the cross-member of the T-shaped trailer includes telescoping sections to allow the width of the trailer to be varied as required. The cross-member includes a biasing means to bias the telescoping sections into an extended position. This allows the trailer to be easily extended in the width wise direction. One or more locking pins are provided to fix the telescopic sections in the desired position.

To further reduce the space required for the trailer when stowed, the trailer is stored in a position where the telescopic sections are contracted as far as possible. A system is provided to automatically contract the trailer as it is retracted into the recovery vehicle, and to automatically extend the trailer as it is deployed. In one example, this is achieved by providing a pin on the extension sections 5 and an inwardly directed track or guide on the chassis of the recovery vehicle. As the trailer is retracted into the vehicle, the pin engages and runs along the track or guide, causing the member 5 to be slid along the main cross-member 2 against the action of the bias means to reduce the width of the trailer as it is retracted. When the trailer is deployed, the pins again run along the tracks or guides to extend the width of the trailer.

Alternatively, a pulley may be provided on the cross-member 2, with cables attached to the extension sections 5 running around the pulley. When the trailer is partially retracted into the body of the recovery vehicle, the cables are pulled around the pulley, thereby causing the extension sections 5 to slide inwards along the cross member 2. In a preferred arrangement, a single cable runs around a first pulley on the cross-member 2, around a second pulley on one of the extension sections 5 and is connected to the other extension section 5. When the cable is pulled, this will pull the sections 5 towards each other.

The bias means in the cross-member may be in the form of gas struts or springs.

Lights may be provided on the trailer, and in this case the cabling may run through tubes to protect this.

Claims

1. A method in which a repair vehicle is able to drive to a repair site without any trailer, the trailer being accommodated in a stowed position on board the repair vehicle, and at the repair site means are provided to deploy a trailer out from the stowed position to a towing position behind the rear of the repair vehicle, and thereafter to couple a towing end of the trailer to the rear of the repair vehicle so that the towing forces are transmitted to the repair vehicle directly rather than via the said means, the coupling between the trailer and the repair vehicle allowing free movement of the trailer relative the repair vehicle so that it can follow the repair vehicle when towed.

2. A method according to Claim 1, in which the trailer is deployed automatically, relatively quickly and without the need for any heavy lifting.

3. A method according to Claim 1 or Claim 2, in which, after the trailer is no longer needed, it is retracted into the vehicle to its stowed position.

4. A repair vehicle having a chassis and bodywork mounted on the chassis, further comprising deployment and retraction means for a trailer mounted within the bodywork of the repair vehicle and attached to the chassis, the trailer carried by the deployment and retraction means normally stowed by those means within the bodywork but movable by those means to the rear of repair vehicle to a towing position and from that position to the stowed position, and coupling means for attaching a towing end of the trailer and the chassis so that towing forces are taken directly by the chassis to the repair vehicle.

5. A repair vehicle according to Claim 4, in which the trailer is of the type to support the front wheels of a broken down vehicle.

6. A repair vehicle according to Claim 5, in which the trailer has a main towing frame generally of "T" shape, which comprises a lengthwise member constituting the stem of the "T" which has a towing end at the base of the stem where it is coupled to the vehicle, and a transverse member constituting the cross-part of the "T" and joined to the end of the lengthwise member away from the towing end.

7. A repair vehicle according to Claim 6, in which the transverse member includes a pair of wheels at or near its ends and means, such as wheel pans, on to which the front wheels of a broken down vehicle can rest for towing.

8. A repair vehicle according to any one of Claims 4 to 7, in which the wheels of the trailer are mounted in a self steering manner so that the trailer can follow the towing vehicle around corners when the front wheels of a broken down vehicle are supported by the trailer.

9. A repair vehicle according to any one of Claims 4 to 8, in which the transverse member of the trailer has resiliency along its length allowing the trailer to be compacted widthwise for storage, and allowing variation in the width of the trailer to accommodate vehicles to be recovered of different width.

10. A repair vehicle according to Claim 9, in which the trailer includes parts which are capable of resiliently telescoping one into the other to reduce the width of the trailer.

11. A repair vehicle according to Claim 10, in which the vehicle includes means to reduce the width of the trailer as it enters the bodywork of the vehicle for stowing, the inherent resiliency causing the trailer to resume its full width as it is moved to its towing position.

12. A repair vehicle according to any one of Claims 8 to 11 , in which, to prevent changes in width during towing, a locking means is provided to lock the transverse member to its desired position for towing and are released before the trailer is brought to the stowed position.

13. A repair vehicle according to any one of Claims 4 to 12, in which the trailer is attached to the vehicle at its towing end by means of a universal pivot to allow the usual relative movement between the trailer and vehicle during towing.

14. A repair vehicle according to Claim 13, in which a hole is provided through this pivot and a pin provided which is passed through that hole to lock into engagement with means attached to the chassis of the vehicle when the translation means are in a fully extended position with the trailer in its towing position.

15. A repair vehicle according to Claim 14, in which the pin is provided through the hole by an electronically operated solenoid.

16. A repair vehicle according to any one of Claims 4 to 15, in which the trailer has its own braking system.

17. A repair vehicle according to Claim 16, in which the trailer includes a telescoping arrangement such that braking of the vehicle causes compression of such parts of the trailer and the movement causing that compression is used to move and apply the brakes to the wheels of the trailer.

18. A repair vehicle according to any one of claims 4 to 17, in which the deployment and retraction means is pivotally mounted to the vehicle.

19. A unit comprising frame means to be attached to a structural part of a repair vehicle, translation means movable along the frame in one direction, which is to be a fore and aft direction when the frame is mounted on the vehicle, coupling means for attaching a trailer to the translation means, and coupling means for fixing the towing end of the trailer directly to the structural part, such as the chassis of the vehicle, when the translation means reaches the limit of its travel corresponding to the towing position.

20. A unit according to Claim 19, in which the translation means comprises a rotatable screw and a trunnion which works along the screw as the latter is rotated, the trunnion being connected to the trailer for deploying and retracting the trailer from the towing vehicle.

21. A unit according to Claim 20, in which a small electric motor and reduction gear is provided to operate the screw.

22. A repair vehicle according to any one of Claims 4 to 18, including the unit of any one of Claims 19 to 21.

23. A repair vehicle according to any one of Claims 4 to 18 or 22, used in accordance with the method of any one of Claims 1 to 3.