GB2165511A

GB2165511A - Trailer couplings

Info

Publication number: GB2165511A
Application number: GB08523189A
Authority: GB
Inventors: Rodney Brian Witter
Original assignee: Witter Ltd C P
Current assignee: Witter Ltd C P
Priority date: 1984-10-11
Filing date: 1985-09-19
Publication date: 1986-04-16
Also published as: GB8425727D0; GB8523189D0

Abstract

A towing coupling 10 for a trailer, caravan or the like comprises a coupling head 12 for the trailer attachable to a towing vehicle by a ball (not shown) engaged in a socket 16, wherein damping means are provided on the axis of rotation of the coupling ball. The damping means comprises upper and lower friction plates 40, 46 connected by a drive arm 42 to one end of drive link 56. The other end of the drive link 56 is connected to an arm 26 secured to the coupling head 12. The coupling ball (not shown) is fixed to a stem 20 rotatable in a housing 24. The damping means is said to damp pitching and snaking movements of the trailer. <IMAGE>

Description

SPECIFICATION Trailer and like couplings This invention relates to trailer and like couplings and, in particular, to couplings for coupling a trailer e.g.a boat-carrying trailer, caravan or the like to a towing vehicle.

There is a phenomenon known as snaking that can occur under certain conditions whereby a towed caravan or the like can oscillate about its longitudinal axis and hence relative to its towing vehicle. It is possibleforthese oscillations to increase until the stability of not only the caravan but its towing vehicle are affected.

The object of this invention is to provide a trailer coupling that can prevent or at least reduce the effect of said oscillations.

According to this invention there is provided a towing coupling for a trailer, caravan or the like comprising a coupling head for the trailer attachable to a towing vehicle by a ball and socket, wherein damping means are provided on the axis of rotation of the coupling ball.

Conventionally the ball is provided on the towing vehicle and the socket on a drawbar of or connected to the trailer, caravan or the like.

The damping means preferably comprises a drive link that is pivotally coupled to the drawbar at one end and to the ball coupling at the other end.

Coupling of the arm is preferably by means of ball and socket couplings. The drawbar may have an arm extending therefrom or connected thereto at or near the end remote from the towing vehicle, which arm has a ball end providing the first coupling pointfor the arm. The second coupling ball is preferably provided on a drive arm mounted on a stem of the main coupling ball of the towing vehicle. The main coupling ball is preferably rotatably held in a housing on the towing vehicle and damping is by means of friction between upper and lower surfaces of the housing and corresponding friction plates provided for each surface thereof. Preferably friction linings are provided between the respective surfaces.

There may also be provided means for increasing the damping such as by drawing the friction surfaces closertogethersay by tightening a lock-nut on an extension of the stem below the friction surfaces.

For engagement and disengagement of the trailer coupling a lifting handle may be provided on the couplind head and the drive arm/drive link coupling readily disconnectable say by means of a snap connection.

The coupling of the invention can reduce or even eliminate the disadvantageous oscillations referred to above in the following manner. Rotation of the drawbar causes the link arm to rotate which rotation in turn causes the main coupling ball to rotate.

However, rotation of the main coupling ball is resisted by friction between the respective surfaces of the ball/arm part and the ball housing of the towing vehicle.

Not only can oscillations about longitudinal axis of the trailer be damped but also pitching orvertical movements of the coupling will cause the drive arm to rotate and hence cause damping.

Advantages of the coupling of the present invention are that unlike previous couplings, the damping force can be provided at the optimum position, i.e.

on the axis of rotation of the coupling and vertically below the main coupling ball. Furthermore the coupling of the present invention may not affect the overrun braking mechanism of the trailer or caravan, since the connection is made to the coupling head and not to the "A" frame or drawbar of the caravan or trailer.

Another advantage of the present invention is that no assymetric loading is introduced to the trailer or caravan in the form of a rolling couple which might tend to cause turning over of the trailer or caravan.

Finally, the drive arm can be arranged so that horizontal, vertical and pitching movements of the trailer or caravan are damped.

This invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure lisa plan view of a towing coupling; Figure 2 is a side view of a towing coupling; Figure 3 is another plan view of the towing coupling showing movement of the drive arm; Figure 4 is a section on line AA of Figure 3; Figure 5 is a section on line BB of Figure 3; and Figure 6 is a view in the direction of arrow C of Figure 3.

Referring to the drawings, a towing coupling 10 comprises an elongate generally upturned U-section coupling head 12 attached to a trailer drawbar 14. At the end remote from the trailer, the coupling head is formed into a socket 16 to receive ball 18 rotatably mounted via its stem 20 in a ball housing 24 of a towing vehicle (not shown).

Near the trailer end of coupling head 12 is attached an arm 26 by means of bolts 28 through a plate 30 from which the arm 26 extends. The other end of the arm 26 is in the form of a ball 32.

Above the ball housing 24 and on the stem 20 of the ball 18 is an upper friction plate 40 from which extends drive arm 42 which also ends in the form of a ball 44. On the stem 20 below the ball housing 24 is another friction plate 46. Between the friction plates 40 and 46 and their respective faces of the housing 24 are friction linings 48. The friction plates 40 and 46 are secured on the stem 20 by means of a locking nut 50 and locking washer 52 on the end of the stem 20 which is approriately screw threaded.

Returning to the balls 32 and 44, these are connected by a drive link 56 having sockets 58 and 59 formed one at each end.

The trailer coupling 10 operates in the following fashion. As the coupling is rotated about ball 18 by movement of the trailer the link arm 56 is caused to rotate, for example to a position shown by dotted lines in Figure 3. The drive link 56 in turn causes the drive arm 42 to rotate but rotation of that arm is damped by the friction linings 48 between the respective friction surfaces. In this way vertical, horizontal and pitching movements of the trailer can all be damped.

The torque required to rotate the coupling can be increased by means of the locking nut 50 which can drawthefriction plates together against annular flange 61 near the top of the stem 20.

Finally, for manoeuvering the trailer to engage or disengage the coupling a handle 60 as shown in Figures 1 and 2 only is provided. The drive link 56 is arranged to be permanently attached to the arm 26 and a snap connection at the drive arm 42 for engagement or disengagement of the trailer.

Claims

1. A towing coupling for a trailer, caravan or the like comprising a coupling head forthetrailer attachable to a towing vehicle by a ball and socket, wherein damping means are provided on the axis of rotation of the coupling ball.

2. Atowing coupling as claimed in claim 1, wherein the ball is provided on the towing vehicle and the socket on a drawbar of or connected to the trailer, caravan or the like.

3. Atowing coupling as claimed in claim 2, wherein the damping means comprises a drive link that is pivotally coupled to the drawbar at one end and to the ball coupling at the other end.

4. A towing coupling as claimed in claim 1,2 or 3, wherein coupling of the arm is by means of ball and socket couplings.

5. Atowing coupling as claimed in claim 4, wherein the drawbar has an arm extending therefrom or connected thereto at or near the end remote from the towing vehicle, which arm has a ball end providing the first coupling point for the arm.

6. Atowing coupling claimed in claim 4 or 5, wherein the second coupling ball is provided on a drive arm mounted on a stem of the main coupling ball of the towing vehicle.

7. Atowing coupling as claimed in any one of claims 1 to 6, wherein the main coupling ball is rotatably held in a housing on the towing vehicle and damping is by means of friction between upper and lower surfaces of the housing corresponding friction plates provided for each surface thereof.

8. Atowing coupling as claimed in claim 7, wherein friction linings are provided between the respective surfaces of the housing.

9. A towing coupling as claimed in claim 7 or 8 also having means for increasing the damping.

10 Atowing coupling as claimed in claim 9, wherein damping increasing means comprises a lock-nut on an extension of the stem below the friction surfaces, whereby the friction surfaces are drawn closer together by tightening of the lock-nut.

11. A towing coupling as claimed in any one of claims 1 to 10, wherein for engagement and disen gagementofthetrailercoupling a lifting handle is provided on the coupling head and the drive arm/ drive link coupling is readily disconnectable.

12. Atowing coupling substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.