GB2122961A

GB2122961A - Trailer coupling for vehicles

Info

Publication number: GB2122961A
Application number: GB08304776A
Authority: GB
Inventors: Hans Riehle
Original assignee: ORIS METALLBAU KG RIEHLE H
Current assignee: ORIS METALLBAU KG RIEHLE H
Priority date: 1982-06-28
Filing date: 1983-02-21
Publication date: 1984-01-25
Also published as: FR2529140B1; GB2122961B; GB8304776D0; NL181568B; ZA833957B; DE3224014A1; FR2529140A1; DE3224014C2; BE895826A; DK60683D0; SE8300950D0; IT1164620B; NL181568C; DK60683A; SE455179B; CH657328A5; DK156165B; DK156165C; IT8347754A0; SE8300950L

Abstract

A trailer coupling for motor vehicles, has a removable ball neck 4 with a coupling ball (not shown), which is inserted from the rear and from below into a housing 1 and a tensioning system for keeping the ball neck 4 free from play is automatically triggered by the insertion operation. The tensioning system consists essentially of a spring-loaded lifter 8 or slide arranged in the ball neck, of articulated levers 14, 16 which are articulated on the ball neck 4 and on the lifter 8 and of a spring-loaded pivotable cam 20 which co-operates with the articulated levers 14, 16 and of a detent pin 28 on the housing which projects through a recess in the ball neck into a groove 30 on the lifter 8. The ball neck has studs 6 engageable in retaining grooves 3 in the housing. <IMAGE>

Description

SPECIFICATION Trailer coupling for vehicles The invention relates to a trailer coupling for vehicles, particularly but not exclusively for passenger cars, which includes a housing downwardly open when the coupling is in the installed condition, and a ball neck provided with a coupling ball which is insertable into the housing and detachably lockable thereto, the housing having an opening to the rear and upper part, wherein a retaining groove is provided on each side in the lower part of the housing for receiving a respective studs projecting laterally from the ball neck and a tensioning system arranged in the ball neck and having a pivotable cam and a ram adapted to be forced by the cam against the bias of a spring against the upper guide part of the housing so that the studs on the ball neck are locked in the respective retaining grooves.

With a trailer coupling of this type, which has proved successful in practice and which is known for the applicant company's earlier application, No. GB 80-13764 (German Offenlegungsschrift 30 00 824) clamping of the ball neck in the housing, after its insertion, is effected by a hand lever which engages on the swivel axle of the cam and with the aid of which the cam of the tensioning system is swivelled into a position in which the cam forces the ram against the housing and thus forces the studs or pegs on the ball neck firmly into their retaining grooves.

The invention seeks to provide a coupling in which the ball neck may be not only inserted into the housing and inadvertent clamping may be prevented, but on additional measures or actions are required to tighten the tensioning system.

According to the invention there is provided a trailer coupling for vehicles, which includes a housing downwardly open when the coupling is in the installed condition, and a ball neck provided with a coupling ball which is insertable into the housing and detachably lockable thereto, the housing having an opening to the rear and an upper guide part, wherein a retaining groove is provided on each side in the lower part of the housing for receiving a respective stud projecting laterally from the ball neck and a tensioning system arranged in the ball neck and having a pivotable cam and ram adapted to be forced by the cam against the bias of a spring against the upper guide part of the housing so that the studs on the ball neck are locked in the respective retaining grooves, the tensioning system being such that, when the ball neck is inserted into the housing the system moves automatically out of an untensioned or relaxed position into a position for securing the ball neck in the housing.

The advantage achieved by the invention is that insertion of the ball neck into the housing of the trailer coupling and clamping of the ball neck in the housing take place simultaneously, and the clamping operation itself does not necessitate any measures other than the mere insertion of the ball neck. Accordingly, a clamping operation is omitted. When the ball neck is inserted, then it is also clamped and the trailer coupling is ready for operation.

In an advantageous embodiment of the invention the tensioning system can comprise in addition to the cam two articulated levers which are interconnected and the first of which is linked to the lower end of the ram and the second of which is articulated, below the first lever, on the ball neck and in addition a guide roller is arranged at the point of inter-connection between the articulated levers and, when the tensioning system is relaxed, the guide roller rests in a locking recess of the cam, the cam being biassed in the tensioning direction by a spring a detent pin being provided on the housing which, upon insertion of the ball neck moves the ram upwards relative to the ball neck so that the guide roller on the articulated levers disengages from the locking recess of the cam and the cam is rotated by said spring, a rising cam face bringing the articulated levers, by way of the guide roller, into a substantially fully extended position in which the ram is rigidly supported on the housing.

In a preferred embodiment, when the tensioning system is in the tightened state, the guide roller lies generally at the same height or level as the swivel axis of the cam and, when the tensioning system is relaxed, the roller lies below and spaced from said axis. As a result of this, no torque is exerted on the cam when the tensioning system is tightened whereas, when the tensioning system is untensioned, a torque develops which is greater than the torque exerted on the cam by the spiral spring so that a tensioning system in a stable state is ensured.

In order to prevent the articulated levers from occupying an over extended position relative to one another when the tensioning system is tightened, suitably stops can be provided on the articulated levers, at their point of connection.

The detent pin on the housing can project through a recess in the ball neck into a longitudinal slot in the ram, the upper limiting face of the said slot coming into contact with the detent pin when the ball neck is inserted into the housing.

A spring-loaded locking pin may be provided on the ball neck which pin is engageable in a slot in the cam which lies on an arc about the swivel axis of the cam and which locked may restrict random pivotal movement of the cam in such a manner that the guide roller of the articulated levers be achieved.

To untension the tensioning system when the ball neck is removed from the housing, a hand wheel provided with markings to indicate whether the tensioning system is tightened or untensioned may be provided to enable the cam to be manually rotated.

An embodiement of the invention will now be described, by way of example with reference to the drawing in which: Figure 1 shows a longitudinal section through the housing of a trailer coupling and a ball neck, during the insertion operation and when a tensioning system is relaxed, and Figure 2 shows the object according to Figure 1 after the ball neck has been inserted and with the tensioning system having been tightened.

A housing 1, made of a forging or a casting, of a trailer coupling is in the installed position arranged below the rear bumper of a passenger car, in a cross member consisting of sheet steel pressings as shown in Figure 1, the said housing being fastened to the cross member by bolts. The housing is open in a downward direction and, for a great part of its overall height, in a rearward direction. A cylindrical guide surface 2 is provided in the upper closed part. Arranged in and on both sides of the lower part are bayonet-like retaining grooves 3 which extend substantially horizontally from the rear end of the housing and then run downwards.

The housing 1 serves to hold and support a removable ball neck 4 which is provided with a coupling ball (not shown). At its upper free end, the ball neck 4 has a round or ball shaped surface 5, the diameter of which is equal to that of the guide surface 2 in the housing 1. Studs or pegs 6 project laterally from the ball neck 4 and when the ball neck 4 has been inserted in the housing 1, engage in the retaining groove 3.

The trailer coupling has a tensioning system which comprises a lifter or ram 8 which is slidably mounted in a longitudinal bore 7 in the ball neck 4 and which is biassed downwards away from the end of the neck 4 having the surface 5 by a compression spring 9 supported on the ball neck 4. The upper end of the ram 8 has a frusto-conical extension 10 which, with the ball neck 4 inserted, engages in a countersunk recess 11 at the top of the housing 1 which is offset from the axis of the ram 8.An articulated lever 14 is linked by means of a pin 13 to the lower end of the ram 8 which projects into a downwardly open recess 12 in the ball neck 4, the said lever being pivotally connected by means of a pin 1 5 to a second articulated lever 1 6 which, lying in the central longitudinal axis of the ram 8, is pivotally mounted below the ram 8 by means of a pin 17 to the ball neck 4. Mounted at the point of connection, pin 1 5, between the two articulated levers 14, 1 6 is a guide roller 1 8 which co-operates with a cam 20 secured in the recess 12 so as to be rotatable about a swivel axle 19. The profile of the cam 20 has a locking recess 21 for the guide roller 1 8 and a rising cam face 22.A volute, spiral spring 23, is arranged next to the cam 20 and has one end secured to the swivel axle 1 9 and its other end to the neck 4 so as exert a torque on the cam 20 in the direction of arrow 24. A spring-loaded locking pin 25 arranged on the side of the ball neck 4 cooperates with an arcuate slot 26 which is formed in the cam 20 and lies on an arc about the swivel axle 1 9. On the other side of the ball neck 4, a hand wheel 27 by which the cam 20 can be pivoted manually when the locking pin 25 is withdrawn from the slot 26 connected to the swivel axle 1 9.

A detent pin 28 is attached to the leading side of the housing 1 and by means of a recess 29 extending between the ball-shaped surface 5 and the pegs 6, co-operates with a longitudinal groove 30 in the ram 8.

When the tensioning system is in the inoperative position shown in Figure 1 , the ball neck is inserted in the housing 1 from below and from the rear, pushed upwards and then lowered so that the pegs 6 can engage and lock in the retaining grooves 3. When the ball neck is so attached, the detent pin 28 passes through the recess 29 into the upper part of the groove 30 so that, when the ball neck is lowered into the retaining grooves 3, the ram 8 comes into contact with the detent pin 28 and is pushed upwards against the bias of the spring 9 relative to the ball neck 4. As a result of this movement, the articulated levers 14, 1 6 tend to move into an extended position and the guide roller 1 8 is moved out of the locking recess 21.The cam 20 can then be rotated by the hand wheel 27 to pivot clockwise in the direction of arrow 24 and the cam face 22, by way of the guide roller 18 and the articulated levers 14, 1 6, forces the ram 8 and its extension 10 upwards into the countersunk recess 11 in the housing. When the ball neck 4 is in this position, as shown in Figure 2, the tensioning system is completely tightened and the trailer coupling is ready for operation as the tensioning system is also secured because, during the rotary movement of the cam 20 in the direction of arrow 24, the slot 26 becomes positioned in such a manner that the locking pin 25 can move into the slot 26.

The pin 15, which connects the articulated levers 14, 16 to one another and which bears the guide roller 18, lies on the same level as the swivel axle 19 when the tensioning system is tightening so that no torque is exerted on the cam 20. The ram 8 is kept free from play since in the event of signs of wear the cam 20 continues to exert pressure with the rising cam face 22, with the aid of the spring 23. The maximum angle 32 which can be formed by the articulated levers 14, 1 6 relative to one another is limited by stops (not shown) on the levers 14, 16. The slot 26 in the cam 20 is dimensioned in such a manner that the cam can be moved only to such an extent that the guide roller 1 8 cannot move into the locking recess 21 and that adjustment of the articulated levers is possible only up to the angle 32.

To release the ball neck 4 from the housing 1, the locking pin 25 is withdrawn from the slot 26 to enable the hand wheel 27, which is provided with suitable markings to be rotated counter to the direction of arrow 24, so that the compression spring 9 in the ball neck 4 can urge the ram 8 downwards. As a result of downward movement of the filter 8, the articulated levers 14, 16 occupy an increasingly smaller angular position relative to one another and the guide roller 1 8 drops into the locking recess 21 on the cam 20. Thus, all the parts of the tensioning system occupy the position as seen in Figure 1 and the ball neck 4 can be released from the housing.

Since the hand wheel 27 is required merely for releasing the tension of the tensioning system, it can be arranged on the swivel axle so as to be detachable.

Claims

1. A trailer coupling for vehicles, which includes a housing downwardly open when the coupling is in the installed condition, and a ball neck provided with a coupling ball which is insertable into the housing and detachably lockable thereto, the housing having an opening to the rear and an upper guide part, wherein a retaining groove is provided on each side in the lower part of the housing for receiving a respective stud projecting laterally from the ball neck, and a tensioning system arranged in the ball neck and having a pivotable cam and a ram adapted to be forced by the cam against the bias of a spring against the upper guide part of the housing so that the studs on the ball neck are locked in the respective retaining grooves, the tensioning system being such that, when the ball neck is inserted into the housing, the system moves automatically out of an untensioned or relaxed position into a position for securing the ball neck in the housing.

2. A coupling according to Claim 1 , wherein the tensioning system comprises, in addition to the cam two articulated levers which are interconnected and the first of which is linked to the lower end of the ram and the second of which is articulated, below the first lever, on the ball neck, and in addition a guide roller is arranged at the point of inter-connection between the articulated levers and, when the tensioning system is relaxed, the guide roller rests in a locking recess of the cam, the cam being biassed in the tensioning direction by a spring, a detent pin being provided on the housing which, upon insertion of the all neck, moves the ram upwards relative to the ball neck so that the guide roller on the articulated levers disengages from the locking recess of the cam and the cam is rotated by said spring with a rising cam face bringing the articulated levers, by way of the guide roller, into a substantially fully extended position in which the ram is rigidly supported on the housing.

3. A coupling according to Claim 2, wherin when the tensioning system is in the tightened state, the guide roller lies generally at the same height or level as the swivel axis of the cam and, when the tensioning system is relaxed, the roller lies below and spaced from said axis.

4. A coupling according to Claim 2 or 3 wherein the articulated levers are provided with stops which prevent the articulated levers from moving into an over extended position.

5. A coupling according to any one of Claims 1 to 4, wherein the detent pin on the housing projects through a recess in the ball neck into a longitudinal slot into the ram, the upper limiting face of the said slot coming into contact with the detent pin when the ball neck is inserted into the housing.

6. A coupling according to any one of Claims 1 to 5, wherein a spring-loaded locking pin is provided on the ball neck which pin is engageable in a slot in the cam which lies on an arc about the swivel axis of the cam.

7. A coupling according to Claim 6, wherein when the locking pin is engaged, the slot restricts random pivotal movement of the cam in such a manner that the guide roller cannot engage in the locking recess nor can an over-entended position of the articulated levers relative to one another be achieved.

8. A coupling according to any one of Claims 1 to 7, wherein a handwheel provided with markings to indicate whether the tensioning system is tightened or relaxed is provided to enable the cam to be manually rotated.

9. A trailer coupling for a passenger vehicle substantially as described herein with reference to, and as illustrated in, Figures 1 and 2 of the accompanying drawings.