GB2087817A - Vehicle trailer hitch - Google Patents

Abstract

A vehicle trailer hitch includes a retaining member (21) pivoted to engage and retain a towing ball (13) in the coupling head (11) and a locking member (15), the members (15,21) having mutually co-operating cam surfaces such that the retaining member (21) is movable to release the ball (13) by sequential angular and linear movement of the locking member (15). Unauthorised use may be prevented by a padlock received in an eye (27). <IMAGE>

Description

SPECIFICATION Vehicle trailer hitch This invention relates to towing hitches for trailer vehicles and is particularly concerned with towing hitches of the ball and socket type.

Such hitches are well known and comprise a ball head attached to a towing vehicle and a co-operating socket attached to the drawbar of a tailer vehicle.

The ball head is of a generally standard size and shape but many different types of drawbar socket have been proposed.

It is desirable for the socket to incorporate a latch member operable from an open position, where free engagement of the ball head in the socket is permitted, to a 'closed' position where the ball head is retained in the socket. The latch member may, for example, engage the underside of the ball head in the 'closed' position.

A lifting handle is usuaily provided on the trailer vehicle drawbar for manouvering the trailer vehicle.

The lifting handle may be associated with the latch member so that one handed coupling of the trailer vehicle to the towing vehicle if possible. For safety's sake the latch member may be spring urged toward the 'closed' position. The socket may incorporate a safety device operable to prevent inadvertent movement of the latch member to the 'open' position.

Known socket couplings of the above type have several disadvantages. One type of socket coupling requires a very strong spring to hold the latching member in the closed position, the latching member being released by upward movement of the lifting handle. Such an arrangement requires considerable effort to move the latch member from the 'closed' position whilst holding the trailer drawbar against the upward pull on the lifting handle.

Another type of socket coupling incorporates the safety device external of the coupling. Since many trailer vehicles, especially caravans and camping trailers, lie unused for long periods in the open air without maintenance, such arrangements are subjectto sticking and seizure.

The present invention seeks to provide a socket coupling having a novel latching mechanism and associated safety device and which is arranged for low operational effort.

According to the invention there is provided:- a towing coupling for a trailer, the coupling having a socket for receiving the head of a towing ball and including a latching mechanism which in intended use is operable from an 'open' position, where free engagement of the ball head in the socket is permitted, to a 'closed' position, where the underside of the ball head is engaged to retain the head in the socket, characterised thereby that the latching mechanism includes a retaining member and a locking member having mutually co-operating cam surfaces, the retaining member being movable between the 'open' position and the 'closed' position by sequential linear and angular movement of the locking member.

Preferably the latching mechanism is resiliently biased toward the 'closed' position.

Other features of the invention are included in the following description of a preferred embodiment shown by way of example, on the accompanying drawings in which: Figure 1 is a somewhat diagrammatic transverse section through a socket coupling according to the invention and in the 'closed' position.

Figure 2 shows a transverse section of the socket of Figure 1 in the 'open' position.

Figure 3 is a view on the socket opening of the coupling when in the 'closed' position.

Figure 4 is a view on the socket opening of the coupling when in the 'open' position.

With reference to the accompanying drawings there is shown a coupling body 11 having a shank for attachment to the drawbar of a trailer vehicle and incorporating a recess 12 for receiving the towing ball head 13 (shown in chain-dot outline) of the towing vehicle.

A through bore 14 to the recess 12 supports a cylindrical pin 15, one end of which is attached to a lifting handle 16 of the coupling and the other end of which extends into the recess 12 and carries a cam head 17. A helical wire spring 18 is located about the pin 15 between the camhead 17 and the upper face of the recess 12.

That part of the recess 12 adjacent the nose of the body 11 is a part-spherical form for engagement with the towing ball head 13. A retaining member 21 is pivotable about a cross pin 22 and has a part spherical face 23 for engagement with a lower peripheral portion of the towing ball head 13. The member 21 effectively closes the ball head opening in the recess 12 to insertion or removal of the ball head 13.

The rear face of the retaining member 21 forms a cam profile for co-operation with the camhead 17 against which the member 21 is biased by a light hairpin spring 24.

The helical spring 18 biasses the cambead 17 both toward the mouth of the recess 12 and anticlockwise, when viewed into the recess, to engage in a notch 25 formed in the recess wall. A lug 26 on the coupling body 11 limits consequent rotation of the lifting handle 16.

The normal state of the mechanism is as shown in Figures 1 and 3. This corresponds to the 'closed' position where a towing ball head can neither enter into or be removed from the recess. For security an eye 27 is formed in the lifting handle 16 for co-operating with an eye of the lug 26 to receive a padlock.

Operation of the hitch is as follows: To open the socket for engagement with the towing head 13 the lifting handle 16 must be turned to free the camhead 17 from engagement with the notch 25. Upward movementofthe handle 16 againstthe helical spring 18 will allow the retaining member 21 to pivot under the action of the hairpin spring 24.

The towing ball and coupling may now be interengaged, the ball head pivoting the retaining member 21 to engage its underside.

On release of the lifting handle 16, the camhead 17 will move to re-engage the notch 25 and lock the retaining member 21 in position, so restraining the ball head. Should the ball head not be properly engaged by the retaining memberthe handle 16 will not return to the "closed" position. This will serve as an indication of incorrect or incomplete engagement of the ball head in the socket. Since neither the helical spring 18 northe hairpin spring 24 serve to transmit drawbar loads, they may be light enough to merely return the mechanism to the "closed" position, thus ensuring a low operational effort.

An advantage of the towing coupling will be clear from the illustrations of Figure 1 and Figure 2 in that the mechanism of the hitch is housed by coupling body and thus protected from adverse weather conditions.

Claims (8)

1. A towing coupling for a trailer, the coupling having a socket for receiving the head of a towing ball and including a latchinhg mechanism which in intended use is operable from an 'open' position, where free engagement of the ball head in the socket is permitted, to a 'closed' position, where the underside of the ball head is engaged to retain the head in the socket, characterised thereby that the latching mechanism includes a retaining member and a locking member having mutually co-operating cam surfaces, the resulting member being movable between the 'open' position and the 'closed' position by sequential linear and angular movement of the locking member.

2. A towing coupling according to Claim 1 characterised thereby that the latching mechanism is resliently biased toward the 'closed' position.

3. Atowing coupling according to Claim 1 or Claim 2 characterised thereby that the angular movement of the locking member is about the axis of linear movement.

4. Atowing coupling according to Claim 3 characterised thereby that the locking member is resiliently biased bya single helical spring.

5. A towing coupling according to Claim 3, characterised thereby that the retaining member is pivoted transversely to the axis of the locking member.

6. A towing coupling according to Claim 5, characterised thereby that the retaining member is spring biased against the locking member.

7. Atowing coupling according to Claim 5, or Claim 6, characterised thereby that the retaining member is engageable with at least a portion of the upper and lower peripheral halves of the towing ball head.

8. A towing coupling substantially as described herein and as illustrated by Figures 1 to 4, ofthe accompanying drawings.