Coupling

#This invention relates to a coupling. The invention relates more particularly to a trailer coupling for transmitting traction force from a draughting vehicle to a trailer.

#According to the invention, there is provided a trailer coupling comprising at least one torque element which is resililently yieldable under torque, which is arranged to permit relative vertical movement between a draughting vehicle and a trailer, and which is further adapted to resist such relative movement to thereby damp the relative movement. The trailer coupling further comprises two attachment plates, one for attaching the coupling to the draughting vehicle and the other for attaching the coupling to a trailer. The attachment plates are spaced apart from each other with the torque element between them and the torque element is fast with one of the attachment plates and is operatively associated with the other attachment plate by means of a linkage.

#According to the invention, there is also provided a trailer coupling comprising four torque elements, at least one torque element being resiliently yieldable under torque, arranged to permit relative vertical movement between a draughting vehicle and a trailer, and adapted to resist such relative movement to thereby damp the relative movement. The trailer coupling also comprises two attachment plates. One pair of torque elements is fast with one of the attachment plates and the other pair of torque elements is fast with the other attachment plate. The trailer coupling further comprises a set of linkages for interconnecting the torque elements.

#The invention is now described with reference to the accompanying drawings, in which:

#FIG. 1 shows a three-dimensional view of one embodiment of a trailer coupling in accordance with the invention;

#FIG. 2 shows a sectional view on line II--II of FIG. 1;

#Referring to FIGS. 1 to 3 of the drawings, reference numeral 10 indicates one embodiment of the trailer coupling in general. It includes two attachment plates 12 and 14 having holes 16 and 18 through which fastening bolts may be passed for mounting the coupling.

#The coupling 10 further includes four torsion elements 20 and 22 fast with the attachment plate 12, and 24 and 26 fast with the attachment plate 14. The torsion elements 20 and 24 are interconnected by means of linkages 30, which the torsion elements 22 and 26 are interconnected by means of linkages 32.

#Referring to FIG. 2, there is shown a cross-sectional view of the torsion elements 24. The other torsion elements 20, 22 and 26 are identical. The torsion element 24 includes an outer steel tube 34 of square cross-section and a smaller bar 36 also of square cross-section which may be a tube as shown, or may be solid. The inner tube 36 is fitted within the outer tube 34 by means of four pads 38 of resilient material such a natural or synthetic rubber fitted in the corners of the outer tube 34 so that the inner tube 36 is held in position within the outer tube 34. When the inner tube 36 is turned within the outer tube 34, the resilient pads 38 are compressed, whereby torque is generated which resists arcuate movement which tends to urge the inner tube 36 to an at rest position within the outer tube 34 as shown in FIG. 2. The inner tube 36 is fast with the respective linkages 30 and 32 so that any movement of the inner tube 36 within the outer tube 34 is transmitted through the respective linkage 30, 32, and vice versa.