Patent GB-1352025-A (GB)
Title: Locking of trailer couplings
IPC: B60D1/06
Filed: 1971-05-01
Abstract: 1352025 Anti-theft devices for ball and socket couplings G BARNES 14 Feb 1972 [1 May 1971] 12588/71 Heading B7J [Also in Divisions E1-E2] A device, for locking a trailer coupling of the kind comprising a hitch head 10, defining a socket 11, and a plunger mechanism 12 movable by a handle 13, relative to the head 10 between a restricting position in which a plunger 16 of the mechanism restricts the socket 11, and a clear position in which the plunger 16 does not restrict the socket 11, whereby to permit a ball head (not shown) of a towing hitch to be inserted into or removed from the socket 11 in known manner, which device 20 comprises a hollow lever body A housing a rotatable keylock member J and a cam member C rotatable by the lock member J; an abutment member B to which the body A is connected by means of a link pin F engaging a slot 22 in the member B so as to shroud the member B; and bolt means E to secure the member B rigidly to a plunger mechanism 12 of the trailer coupling wherein the link pin F permits the body A to be moved with respect to the member B and wherein the cam member C is engageable with the abutment member B to restrict the movement of the body A with respect to the member B. The lower end 21 of the body A, Fig. 2, has a threaded pin G to engage in a recess 18 of the coupling hitch head 10. The lock member J includes a conventional cylinder lock rotatable in a cylindrical way having opposed detent slots in the upper part of the body A. The rear part 26 of the lock is slotted to receive a boss 27 of the cam member C which boss is pivotally retained in the slotted part 26 by a pin H. The cam member C which is shown in an unlocked position in Fig. 2, has a cam 28, a downward extension 29 and an extension 30 extending into a chamber 19 in the plunger mechanism 12 and biased by a spring D to urge the lock J outwardly. The extension 30 passes through an aperture in an extension 31 of the member B. The latter has an abutment surface 32 having a recess 33 receiving the extension 29. In the unlocked position shown in Fig. 2, the lower part 21 of the body can be moved outwardly about the pin from the recess 18 until clear of a projection 17 on the hitch head 10, whereafter the handle 13 can be raised to move the plunger 16 clear of the socket 11. During this pivotal movement of the body A the extensions 30 and 29 move further into the chamber 19 and the recess 32, respectively, and the member C pivots on the pin H. When the device is in the position shown in Fig. 2, a key may be inserted into the lock keyway 34 and given half a turn in a clockwise direction, Fig. 1, the cam 28 being swung to engage the surface 32 and by reaction to force the body A upwards relative to the abutment member B to cause the pin G, on the end 21 of the body A, to enter the recess 18. This causes the pin F to move upwards in the aperture 22. At the same time the extension 29 is swung upwards to occupy the space between the upper part of the extension 31 and the innermost wall of the body A to prevent the lower end 21 being swung outwards of the head, even if the pin G is removed or otherwise fails to engage the recess 18. Stops are provided on the member B to prevent the lock J being rotated more than half a turn.