Patent GB-1387274-A (GB)
Title: Control mechanisms for overrun brakes
IPC: B60T7/20
Filed: 1971-11-19
Abstract: 1387274 Disabling trailer over-run brakes F G TAYLOR 5 Feb 1973 [19 Nov 1971] 53724/71 Heading F2E In a combination comprising a towing vehicle and a trailer including an over-run brake and disabling means for it there is provided, for bringing the disabling means into operation, a control mechanism including an operating member which in use is mounted on the towing vehicle, and a mechanical linkage for linking the operating member to the disabling means, which linkage is adapted to transmit to the disabling means movement of the operating member relative to the towing vehicle in at least one direction, and which linkage includes a releasable coupling whereby the operating member and a part of the linkage can remain on the towing vehicle and a further part of the linkage can remain on the trailer when the trailer and towing vehicle are separated. As shown in Fig. 1, when an operating member 25 is pulled in the direction of hook 29b, a three-armed disabling lever 21 carrying a stop element 20 is pivoted counter-clockwise so that eventually the stop element 20 lies in the path of a socket portion 17 carried at the forward end of a tow bar 18 slidable in a housing 14 secured to the chassis 10 of a trailer vehicle. Then, when the towing vehicle including framework 15 and ball portion 16 is reversed (i,e. moved leftwards), the tow bar 18 cannot be pushed backwards sufficiently far relative to housing 14 to pivot brake-applying lever 11 counter-clockwise; thus, the trailer brakes are not applied. On resumption of forward movement, however, a collar 31 on tow bar 18 contacts a third arm 32 on lever 21, thereby tilting lever 21 clockwise and thus moving stop element 20 out of the path of socket 17. Then, when the trailer advances on tow bar 18 during over-run, the brakes will be applied. In a modification, not illustrated by a drawing, the socket 17 is formed with a rearwardly-projecting ledge on which stop element 20 rests when in the operative position; the collar 31 and arm 32 are dispensed with because on forward movement the stop element 20 falls by gravity to its inoperative position. The stop element may alternatively engage the rearward end of the tow bar itself. In Figs. 2 to 4 a control lever 134 cranked in a plane perpendicular to the tow bar axis and pivoted at its mid-point is pulled so as to pivot counter-clockwise against the force of a spring 137 by means of an operating member 125 and cables 122, 123. In so doing, a lug 136 on the upper end of the control lever engages, and pivots counter-clockwise, a two-armed disabling lever 133, thus rendering this lever operative. Once the disabling means is operative, the operating member 125 may be released, whereupon spring 137 pivots the control lever 134, but not the disabling lever, back to its initial position. The cable 122 may be attached directly to the disabling lever 133, control lever 134 being dispensed with. Rods or other inextensible elements may be substituted for the cables. In either case the control means may include a spring (not performing the function of spring 137) through the intermediary of which force is transmitted from the operating member to the disabling means so that the latter may be set in a position with the spring stressed and biasing the disabling means towards its operative position, prior to rearward movement of the towbar. Then when the tow bar reaches an appropriate position on reversing, the disabling means would be moved automatically to its operative position.