Patent GB-631378-A (GB)
Title: Improvements in brakes for trailer vehicles
IPC: B60T11/10
Filed: 1946-04-06
Abstract: 631,378. Fluid-pressure-operated brakes. LOW LOADING TRAILER CO., Ltd., and CLARKE, C. V. April 6, 1946, No. 10671. [Class 103 (i)] [Also in Group XXVIII] Trailer vehicle brake mechanism comprises a hydraulic pump or transmitter connected to the brake cylinders and actuated by the road wheels by means which are normally held inoperative against the action of biassing means by a control member adapted to be connected to a pedal on the tractor vehicle, the extent of movement of the control member determining the brake pressure as by controlling a pressure relief valve. The pedal may also directly operate the tractor brakes. The trailer brake pressure may be adjustable according to the load on the trailer. As shown, an arm 4 on a shaft 5 carries a follower 3 for engagement with a cam 2 on the axle of a trailer vehicle and a second arm 7 on the shaft is connected to the piston 14 of a hydraulic pump or transmitter which is rockably mounted by a rubber bush 14<SP>4</SP> within a reservoir 6 and connected by a pipe 15 to the brake cylinders. The piston carries inlet valves 14<SP>1</SP> and delivers past a cupwasher 14<SP>2</SP>. A disc 9 connected by a chain 8 to the arm 7 carries a cam 17 for varying the spring-loading 19 of a pressure relief valve 18. The disc 9 is normally held by a cable 12 connected to an arm 13 on the shaft 10 of the disc against the bias of a spring 11 and the piston return-spring 16, in a position in which the follower 3 is away from the cam 2 and the valve spring 19 is unloaded. Initial movement of the cable 12 to apply the brakes permits engagement of the follower 3 with the cam 2 to operate the pump and further movement loads the spring 19, the braking pressure being dependent upon the amount of movement of the cam 17 and thus of the cable 12. This cable is connected to a rod 21, Fig. 2, slidable in a casing 20 and adapted to be coupled to a link slidable in a casing 26 mounted on the tractor vehicle. The link is connected to a lever which is pivoted in casing 26 and is operated by a cable 32. In order that the amount of movement of the cable 12 and thus the trailer braking pressure for a given movement of the cable 32 may be varied, there may be two links connected at different points on the lever in casing 26 to either of which the rod 21 maybe coupled. Alternatively, a leverage device automatically variable by the load on the trailer may be provided. The cable 32 extends to a lever 35, Fig. 6, pivoted at 36 in a floating casing 34 and connected by a rod 39 to the tractor brake pedal F. The casing 34 is connected by a rod 41 to the tractor brakes. Cable 32 is normally tensioned by a spring 37 sufficiently to hold the trailer brake mechanism inoperative. Depression of the pedal moves the casing 34 bodily to apply the tractor brakes and rocks the arm 35 and moves the cable 32 relatively to the casing to an extent dependent upon the pedal pressure and the reaction in the rod 41. The trailer and tractor brake pressures are thus dependent upon the pedal pressure and on each other. In the event of breakaway of the trailer, the brakes mechanism thereof is rendered operative automatically by the springs 11, 16. Release of these brakes when the trailer is uncoupled can be effected by a hand lever 24, Fig. 2, pivoted to the casing 20 and engaging the rod 21. When the tractor brakes are hydraulically operated, the trailer brake may be applied with a pressure dependent upon the tractor brake pressure, by connecting the cable 32 to a plunger which is subject to the pressure in the master cylinder acting against a spring which normally holds the plunger in a position to hold the trailer brake mechanism inoperative.