GB1345472A - Device for connection to an agricultural tractor fitted with a three point hitch a semi-trailer or agricultural implement - Google Patents

Abstract

1345472 Hitch device LAMECANO-SOUDURE-REMOISE 12 Jan 1972 1421/72 Heading A1P A device, used for connecting a tractor fitted with a three-point hitch to a trailer, has a safety device which permits unhitching in event of tilting of the trailer., Hitching is carried out by raising hook 9 from a lowered position so that claw 9a is moved up until it is beneath tow-ring 31 Fig. 9. Lift arms 43 are actuated and they raise hook 9, which pivots about pin 10, until 9a engages ring 31. The faces 6a of coupling claws 6 contact coupling bar 9c as hook 9 moves upwards and the claws are pushed backwards and pivot about trunnions 5 on base plate 1. Claws 6 are tensioned by springs 13 so that they seat against bar 9c and thereby lock bar 9. Trailer ring 31 is trapped between 9a and stop 32, which is screwed to plate 1. When coupling has been carried out the lifting arms are lowered slightly to relieve the tension in chains 40 which link hook 9 to drawbar 38, which is itself linked via ties 42 to lift arms 43. Unhitching is performed by slightly raising arms 43 to free bar 9c from contact with claws 6, which are then disengaged by moving lever 18 to turn trunnions 5. The arms 43 are lowered whilst lever 18 is held in position. A system of automatic uncoupling works in the event of accidental tilting of the trailer. Stop 32 is movable round bolt 34 Fig. 9 when it is subjected to a certain torque which is adjustable by means of deformable but incompressible ring element 36. A safety device ensures that claws 6 are still locked in the event of failure of springs 13. Finger 26 is fixed to link 55 and lies behind claw 6 which cannot move forward (to the right in Fig. 1) and lever 18 is therefore non-operable. Before operating this lever hand grips 45 are used to draw rod 47 up sleeve 48 against spring 49 (not shown) and thereby lift link 55, and therefore finger 26, via link 52. During the hitching process cam 25 on bar 9c Fig. 3 lifts finger 26 in passing and compresses spring 49 (not shown), and after having passed the lock is automatically brought into action. Another device ensures secure locking of claws 6 in the event of failure of springs 13. For uncoupling to occur claws 6 must swing back and simultaneously hook 9 must rise. The latter is stopped from rising too far by placing an element between base plate 1 and hook 9. Cheeks 8 of base plate 1 are bored with holes so that hook 9 can be easily replaced by another type of hook. Trunnions 16 on base plate 1 may serve for fixing a support 57 intended to receive a rotating head 58 adjustable in height and connected by pin 59.