GB2380720A

GB2380720A - Vehicle hitch

Info

Publication number: GB2380720A
Application number: GB0124138A
Authority: GB
Inventors: Andrew Wayne Butt
Original assignee: BILL BENNETT ENGINEERING Ltd
Current assignee: BILL BENNETT ENGINEERING Ltd
Priority date: 2001-10-08
Filing date: 2001-10-08
Publication date: 2003-04-16
Anticipated expiration: 2021-10-08
Also published as: GB0124138D0; GB2380720B

Abstract

A vehicle pick-up hitch 2 comprises a mounting frame 4 and a draw bar 6, the mounting frame 4 and draw bar 6 forming links of a quadrilateral linkage 8 and being interconnected by other links 10, 12, 14, 16 of the quadrilateral linkage 8. Drive means, in the form of a double acting hydraulic ram 18, acts between the mounting frame 4 and the draw bar 6 to move the draw bar 6 along a path which is predetermined by the geometry of the quadrilateral linkage 8.

Description

VEHICLE HITCH This invention relates to a vehicle hitch and particularly although not exclusively relates to a pick-up hitch for a tractor.

BACKGROUND OF THE INVENTION It is well known that large construction and agricultural vehicles may be required to tow trailers, rollers or other trailed implements. The larger the trailer, the larger the trailer draw bar must be in order to resist the loads imposed on it during towing.

Consequently, the weight of the draw bar of a large trailer is such that it cannot be manouevered safely by hand.

Furthermore, the height of the hitch of a trailer draw bar from the ground varies greatly from one trailer to another. Consequently, vehicle hitches have been developed which drop down during a hitching operation and are raised to engage the trailer or implement draw bar. These hitches are collectively known as pick-up hitches. In the most usual arrangement found on an agricultural tractor, the tractor draw bar is hinged to the tractor at one end and is provided with a pin hitch or hook at the other end. The draw bar is pivoted up or down about the hinge by means of links connected to hydraulically actuated drop arms which form part of a three point linkage hydraulic lift. Such a lift is provided as standard equipment on many agricultural vehicles and some construction vehicles.

It is also known to make the draw bar of a pick-up hitch telescopic, so that it can be pulled out from the vehicle or can be powered in or out by means of a

Conventional pick-up hitches have the significant functional disadvantage that they rely on the drop arms of the tractor hydraulics to pivot the draw bar up or down. As a result, the links which extend from the draw bar to the drop arms obstruct the rear of the vehicle. In the case of an agricultural tractor, these links often limit the travel of the top link of the three point linkage hydraulic lift and are easily damaged. The present invention therefore seeks to provide a hitch which does not require links extending to the drop arms and leaves the rear of the vehicle unobstructed.

SUMMARY OF THE INVENTION According to the present invention, there is provided a vehicle hitch comprising a mounting frame and a draw bar, the mounting frame and draw bar forming links of a quadrilateral linkage and being interconnected by the other links of the quadrilateral linkage, drive means being provided which acts between the mounting frame and the draw bar to move the draw bar along a path which is predetermined by the geometry of the quadrilateral linkage.

The term"quadrilateral linkage"as used throughout this specification means a linkage comprising at least four links.

Preferably, the drive means comprises a linear drive device. Preferably, the linear drive device is double acting. Most preferably, the linear drive device comprises a hydraulic ram.

Preferably, the vehicle hitch comprises two laterally spaced apart quadrilateral linkages. Preferably, each of the said linkages includes a pair of the said other links, one link of each pair being longer than the other. The other links may comprise"drop links"which move in a substantially vertical plane (with the vehicle resting on level ground).

Preferably, at least a portion of the draw bar is retractable into the mounting frame by operation of the drive means. Preferably, the drive means is at least partially housed within the draw bar.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention and to show how the same may be carried into effect reference will now be made, by way of example, to the accompanying drawings, in which :- Figure 1 is a perspective view of a pick-up hitch in the open or lowered position; Figure 2 is a side view of the hitch of Figure 1; and Figure 3 is a side view of the pick-up hitch with the draw bar in the raised or closed position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Referring to Figures 1 and 2 of the drawings, the pickup hitch 2 comprises a mounting frame in the form of a channel shaped sub-frame 4. The sub-frame 4 is bolted to the rear underside of a vehicle. In the case of an agricultural tractor ! the sub-frame 4 is conveniently

bolted to the underside of the rear axle housing (not shown) and is centrally located between the rear wheels. A draw bar 6 is pivotably connected to the sub-frame 4 by means of two spaced apart parallel quadrilateral linkages 8a and 8b including four drop links 10,12, 14,16. A double acting hydraulic ram 18 is connected at one end to the sub-frame 4 and at the other end to the draw bar 6 by means of pinned connections 20,22.

In the illustrated embodiment, the draw bar 6 is provided with a hook 24, but any form of hitching arrangement, such as a pin hitch, could be used in place of the hook 24. Furthermore, the draw bar may be provided with replaceable ends, such that the hook 24 may be replaced with an alternative hitching arrangement at will. The end of the sub-frame 4 towards the rear of the tractor is provided with a locking plate 25 and a pair of interconnected pivoting lock catches 26 which can be moved from an engaged to a disengaged position by means of a conventional linkage such as a rod or cable arrangement (not shown) which is operable from the operator's station of the vehicle.

Corresponding locking projections 28 are fixed to the outer (hook) end 30 of the draw bar 6.

The quadrilateral linkage can be adapted to other particular applications, but in the illustrated embodiment, the links 10,12 located closer to the hook end 30 of the draw bar 6 are longer than the links 14, 16 located closer to the other end of the draw bar.

The respective pairs of links 10,12 and 14,16 are pivotably connected to sides of the sub-frame 4 by means of pinned connections which pass across the full width of the sub-frame 4, and are pivotably connected to the sides of draw bar 6 by means of further pinned

connections which pass through the full width of the draw bar 6. This arrangement provides additional strength, but it will be appreciated that the pivoting connection of the links to the draw bar 6 and sub-frame 4 may be made by any known arrangement and may for example comprise bolts which pass into threads formed in the draw bar 6 and/or sub-frame 4.

In normal operation of a vehicle to which is fitted a pick-up hitch in accordance with the present invention, the hitch assumes the raised or closed orientation shown in Figure 3. In this"transport"position, the draw bar 6 is housed substantially within the open interior of the channel shaped sub-frame 4 and is held in position by engagement of the lock catches 26 on the sub-frame 4 with the projections 28 formed on the draw bar 6. If the vehicle is to be hitched to a trailer, the vehicle operator releases the lock catches 26 from the projections 28 and extends the hydraulic ram 18, thereby pivoting the draw bar 6 away from the sub-frame 4 into the orientation illustrated in Figure 2.

It will be appreciated that by operation of the quadrilateral linkage, not only is the hook end 30 of the draw bar 6 pivoted downwards, but it is also pivoted away from the rear of the vehicle so that the operator is provided with increased visibility from the operator station during the hitching operation. The amount by which the hook end 30 of the draw bar 6 is lowered and swung away is adjusted by the operator in accordance with the relative height of a towing ring of a draw bar of the trailer or implement which is to be hitched. If desired, the design geometry of the hitch can be selected such that with the hook end 30 of the draw bar 6 in the lower most position, the hook 24 is driven slightly beneath ground level and can engage

towing eyes which have become partially buried in soft ground.

Once the tractor has been manouevered such that the hook 24 is located below the towing eye of the trailer or implement, the hydraulic ram is retracted, thereby swinging the hook end 30 of the draw bar 6 back and up towards the vehicle into the orientation shown in Figure 3. In this operation, the lock catches 26 re-engage the projections 28 and the hook 24 is brought into proximity with the locking plate 25, thereby preventing the towing eye of the trailer or implement from jumping off the hook whilst it is being towed.

As the draw bar and hydraulic ram 18 are situated within the sub-frame 4 when in the"transport" position, the pick-up hitch is extremely compact and the ground clearance of the vehicle is not limited unnecessarily. Furthermore, the hydraulic ram 18 and associated pipework is protected from damage.

The illustrated pick-up hitch is a self-contained subassembly and works independently, so that on an agricultural tractor, the three point linkage is unobstructed and unaffected by operation of the pick-up hitch. Also, by appropriate selection of components, a pick-up hitch in accordance with the present invention can be provided with a lifting capacity in excess of the lifting capacity of the three point linkage of the tractor.

In the illustrated embodiment, the pick-up hitch is powered by a double acting hydraulic ram. However, in certain circumstances a single acting hydraulic ram may be appropriate. In this application, the ram would be retracted under power, but would extend under the

weight of the draw bar and whatever was attached to the draw bar at the time. Furthermore, the single hydraulic ram could be replaced by more than one hydraulic ram or by one or more pneumatic rams, or by any power source which acts between the sub-frame 4 and the draw bar 6. One possible embodiment would include a single central quadrilateral linkage with hydraulic rams on both sides, although many different configuration are possible.

In an alternative embodiment, one end of the hydraulic ram may be pivotably connected to the draw bar 6 or to one or more of the drop links of the quadrilateral linkage and the opposite end of the hydraulic ram may be pivotably connected to some other part of the vehicle, such as the vehicle's chassis or a bracket connected to the vehicle. The pick-up hitch would operate in the same way as in the illustrated embodiment, because the hydraulic ram would still effectively be acting between the draw bar 6 and the sub-frame 4. However, the hitch would no longer be a completely self-contained sub-assembly.

A pick-up hitch in accordance with the present invention can be fitted to any part of a vehicle and could for example be fitted to the front of the vehicle or could even be adapted for fitting to a nonhorizontal surface at the rear of a vehicle with appropriate adjustment of the geometry of its components.

Claims

CLAIMS 1. A vehicle hitch comprising a mounting frame and a draw bar, the mounting frame and draw bar forming links of a quadrilateral linkage and being interconnected by the other links of the quadrilateral linkage, drive means being provided which acts between the mounting frame and the draw bar.
2. A vehicle hitch as claimed in claim 1, in which the drive means comprises a linear drive device.
3. A vehicle hitch as claimed in claim 2, in which the linear drive device is double acting.
4. A vehicle hitch as claimed in any one of the preceding claims in which the drive means comprises a hydraulic ram.
5. A vehicle hitch as claimed in any one of the preceding claims, comprising two spaced apart quadrilateral linkages, each linkage including a pair of the said other links, one link of each pair being longer than the other.
6. A vehicle hitch as claimed in any one of the preceding claims, in which at least a portion of the draw bar is retractable into the mounting frame by operation of the drive means.
7. A vehicle hitch as claimed in any one of the preceding claims in which the drive means is at least partially housed within the draw bar, when the drive means is retracted.

<Desc/Clms Page number 9>
8. A vehicle hitch as claimed in any one of the preceding claims in which the drive means is connected to the mounting frame and the draw bar.
9. A vehicle hitch as claimed in claim 8, in which the drive means is pivotably connected to the mounting frame and the draw bar.
10. A vehicle hitch substantially as described herein with reference to and as shown in the accompanying drawings.