GB2069951A - Vehicle towing equipment - Google Patents

Abstract

A towing unit comprises a tractor (2) and a lifting assembly (4), which can pivot relatively to the tractor (2) about a horizontal transverse axis. Pivotal movement of the lifting assembly (4) relative to the tractor (2) about a vertical axis (20) is prevented by retaining means (18), which are releasable. The lifting assembly has lifting means (16) for raising one end of a vehicle to be towed. The force applied by the raised end of a vehicle is supported by ground-engaging wheels (14) of the lifting assembly (4) without significantly affecting the axle loads of the wheels (6) and (8) of the tractor (2). <IMAGE>

Description

SPECIFICATION Vehicle towing equipment This invention relates to a towing unit suitable for towing a vehicle.

When a motor vehicle is undrivable after an accident or a breakdown, and it is necessary to remove the vehicle to, for example, a repairer or a scrap yard, two possibilities are available. Either the vehicle can be loaded onto a trailer, or it can be towed, possibly with one end raised from the ground. The latter possibility is more frequently used, because a trailer which is strong enough to carry the weight of a car is likely to be expensive, and it is sometimes difficult to raise a damaged car onto a trailer.

However, the conventional pick-up truck used for towing suffers from the disadvantage that, when supporting the raised end of a vehicle, very high loads are supported by the rear axle. This is because the rear axle not only supports approximately half of the weight of the towed vehicle, but it may also support more than half of the weight of the pick-up truck, since the moment applied by the weight of the towed vehicle tends to lift the front end of the towing vehicle. Apart from being dangerous, this can often cause the rear axle load to exceed limits prescribed by legislation.

It is known to avoid this problem by supporting the car on a sub-assembly which is hitched to a towing vehicle at a location behind the rear wheels of the towing vehicle. This however, significantly increases the total length of the unit.

Furthermore, the towed vehicle is connected to the towing vehicle for pivotal movement about two separate vertical axes, i.e. about the pivotal connection of the sub-assembly to the towing vehicle and about the pivotal connection between the towed vehicle and the sub-assembly. This makes the unit difficult to manoeuvre, and almost impossible to drive in reverse.

According to the present invention there is provided a towing unit suitable for towing a vehicie, the unit comprising a tractor and a lifting assembly which is connected to the tractor for pivotal movement relative to the tractor about an axis which extends horizontally and transversely of the intended direction of travel of the unit, retaining means being provided for resisting pivotal movement of the lifting assembly relative to the tractor about a vertical axis, the lifting assembly comprising at least one ground engaging wheel and lifting means for attachment to a vehicle to be towed.

With a construction in accordance with the present invention, the weight of a vehicle supported by the unit is carried almost entirely by the lifting assembly, with no significant force being applied to the tractor. If the retaining means is releasable, the manoeuvrability of the unit can be increased, for example when working at low speeds in confined surroundings, such as often occurs when recovering a vehicle from, for example, a multi-storey car park. With the retaining means in its retaining position, the unit behaves like a close-coupled tractor and trailer, and it is desirable for the rear wheels of the tractor and the ground engaging wheels of the lifting assembly to be as close together as possible in order to avoid tyre scrub.

In a preferred construction, the tractor is a fourwheeled vehicle, and the pivotal connection between the tractor and the lifting assembly is positioned in front of the rear wheels of the tractor, with respect to the intended direction of travel of the unit. With this construction, any vertical force exerted by the lifting assembly on the tractor is distributed reasonably evenly between the front and rear axles of the tractor.

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which: Figure 1 is a side view of a towing unit; and Figure 2 is a plan view of the towing unit of Figure 1.

The unit shown in the Figures is suitable for recovering private vehicles and light vans which are undrivable as a resuit of accident damage or breakdown. It is, however, within the scope of the present invention to provide a larger and stronger unit for recovering heavy commercial vehicles.

The towing unit comprises a tractor 2 and a lifting assembly 4. The tractor 2 has front wheels 6 and rear wheels 8, and is provided with a sturdy pillar 10 to which the lifting assembly 4 is hitched.

The lifting assembly 4 itself comprises a rigid frame 12 provided with ground-engaging wheels 14 and lifting means 16. The frame 12 is made from welded steel members and is connected to the pillar 10 in a universally pivotable manner, for example by a conventional ball hitch. A releasable retaining means 1 8 is provided which, when in a retaining position, as illustrated in Figure 1, prevents pivoting movement of the lifting assembly 4 relative to the tractor 2 about a vertical axis 20. When the retaining means is released, the lifting assembly is free to swing about the axis 20. The retaining means comprises two parallel bars which are connected together rigidly and are mounted on the rear of the tractor 2 for pivotal movement about a transverse axis.In the retaining position shown in Figure 1, the two bars are disposed one on each side of the adjacent member of the frame 12, so trapping that member between them. In the released position, the two bars of the retaining means 1 8 lie flat against the rear panel of the tractor 2, thus releasing the frame 12.

The lifting means 1 6 comprises a boom 22 which is pivotally connected at one end to the frame 12 and carries at the other end a spacer beam 24 from which hang two chains 26. A hydraulic lifting jack 28 acts between the frame 12 and the boom 22 to raise and lower the boom 22. The jack 28 is preferably supplied with hydraulic fluid from a pump driven by the engine of the tractor 2.

In use of the unit illustrated in Figures 1 and 2, the unit is reversed into close proximity with whichever end of the vehicle is to be raised, and, with the boom 22 lowered, the chains 26 are secured to the vehicle, for example by wrapping them around the axle of the vehicle. The boom 22 is then raised by the jack 28 until the appropriate end of the vehicle is at the required height above the ground. In this position, the weight of the raised end of the vehicle exerts a moment on the lifting assembly 4, with the wheels 14 acting as fulcrum. This moment is exerted on the tractor 2 at the pillar 10, and applied at that point an upward force on the tractor 2. Since this force is exerted between the front wheels 6 and the rear wheels 8 of the tractor, it does not significantly affect the weight distribution of the tractor.

Furthermore, since the lever arm between the wheels 14 and the pillar 10 is significantly greater than that between the wheels 14 and the line of action of the force applied by the raised end of the vehicle, the force exerted at the pillar 10 is small compared to the weight of the raised end of the car. The weight of the raised end of the car is supported entirely by the wheels 14. Since the only additional weight supported by these wheels is that of the lifting assembly 4 itself, which can be of fairly light construction, the axle loads exerted on the wheels 14 are unlikely to be above legal limits.

In normal travel of the unit with the towed vehicle, the retaining means 18 will be in the position shown in Figure 1, so restraining pivotal movement of the lifting assembly 4 about the axis 20. The lifting assembly 4 can, however, float vertically by pivoting about a transverse axis 21 also passing through the ball hitch, so relieving the tractor 2 of any significant vertical forces. The beam 24 is pivotable relative to the boom 22, for example by means of a hook and eye connection.

Thus, when negotiating a turn, the towing unit as a whole will pivot relatively to the towed vehicle at the connection between the boom 22 and the beam 24.

If the manoeuvrability of the unit is to be increased, for example when the recovery is to be effected in a restricted space, the retaining means 1 8 can be released, in which case the lifting assembly may, for example, be able to swing relatively to the tractor 2 about an arc of at least 1800, and the clearance between the frame 12 and the rear end of the tractor 2 should be large enough to allow such movement.

With the retaining means in position, there will inevitably be some tyre scrub during turning of the towing unit. This can be minimised by making the longitudinal distance between the wheels 8 and 14 as small as possible, for example, less than 1 metre.

Claims (12)

1. A towing unit suitable for towing a vehicle, the unit comprising a tractor and a lifting assembly which is connected to the tractor for pivotal movement relative to the tractor about an axis which extends horizontally and transversely of the intended direction of travel of the unit, retaining means being provided for resisting pivotal movement of the lifting assembly relative to the tractor about a vertical axis, the lifting assembly comprising at least one ground engaging wheel and lifting means for attachment to a vehicle to be towed.

2. A towing unit as claimed in claim 1, in which the retaining means is releasable.

3. A towing unit as claimed in claim 2, in which the retaining means comprises a pair of bars which are pivotally connected to the tractor for movement between a retaining position in which the bars are disposed one on each side of a frame member of the lifting assembly to prevent lateral movement of the frame member, and a released position in which the bars are free of the frame member.

4. A towing unit as claimed in claim 2 or 3, in which, when the retaining means is released, the lifting assembly is pivotable about a vertical axis over an arc of at least 1800 relatively to the tractor.

5. A towing unit as claimed in any one of the preceding claims, in which the tractor is a wheeled vehicle.

6. A towing unit as claimed in claim 5, in which the pivotal connection between the lifting assembly and the tractor is disposed in a vertical plane which is ahead of the rear wheels of the tractor, with respect to the intended direction of travel of the unit.

7. A towing unit as claimed in claim 5 or 6, in which the or each ground engaging wheel of the lifting assembly is adjacent the rear wheels of the tractor.

8. A towing unit as claimed in claim 7, in which, when the unit is travelling straight ahead, the distance in the longitudinal direction between the rear wheels of the tractor and the or each groundengaging wheel of the lifting assembly is less than 1 metre.

9. A towing unit as claimed in any one of the preceding claims, in which the lifting assembly isr arranged so that a weight raised by the lifting assembly causes an upwardly directed force to be applied to the tractor at the pivotal connection between the lifting assembly and the tractor.

10. A towing unit as claimed in any one of the preceding claims, in which the lifting means comprises a boom pivotally connected to a frame of the lifting assembly, and a jack which acts between the frame and the boom to raise and lower the boom.

11. A towing unit as claimed in any one of the preceding claims, in which the jack is a hydraulic jack.

12. A towing unit substantially as described herein with reference to and as shown in the accompanying drawings.