Patent GB-743155-A (GB)
Title: Improvements relating to driver's brake control devices for electro-pneumatically controlled fluid pressure braking apparatus
IPC: B60T8/20
Filed: 1953-09-15
Abstract: 743,155. Fluid-pressure brakes. WESTING- HOUSE BRAKE & SIGNAL CO., Ltd., and SIMMONS, A. W. Aug. 30, 1954 [Sept. 15, 1963], No. 25422/53. Class 103 (1). In order to prevent hunting of the contacts 5, a driver's brake control device for electropneumatically controlled fluid-pressure braking apparatus of the kind in which the adjustment of an operating handle to effect an application or release of the brakes causes the operation of electric contacts controlling the energizing circuit of electromagnetically operated valves for the adjustment of the pressure in a brake cylinder, due to the delay between the establishment of that pressure in the brake cylinder and in the chamber of the operating cylinder of the brake control device, the electric contacts are biased towards their lap position when they are displaced from the lap position. The brake control device comprises an operating handle 22 normally rotatable from the brake release position illustrated in an anti-clockwise direction to bring about an electro-pneumatic application of the brakes. Thus movement of the handle 22 in the direction of the arrow causes a shift 28, integral with arm 29, to be rotated also in an anti-clockwise direction. However, due to the opposition of spring 38 of the operating cylinder arrangement 1, the link 21 rocks about its pivot 23 rocking the contact arm 34, through the linkage 26, 21 and 19, in an anti-clockwise direction into its lap position wherein the moving contact 32 bridges the fixed contacts 31, 33 to complete an electrical circuit and energize the holding electromagnetically operated valves of the system to cut off the communication between the brake cylinder and the atmosphere. In this position, each spring- loaded plunger 9, 11 abuts its associated fixed abutment 8, 12 situated on each side of the fixed pivot 17 of the contact arm 34. Further movement of the operating handle in an anti-clockwise direction continues to rock link 21 about its pivot 23 and the contact arm 34 is further rotated into its application position until the contact arm spring-loaded plunger 11 is fully depressed and whilst moving contact 32 still bridges fixed contacts 31, 33, thus retaining the holding magnets energized, it also bridges other contacts (not shown) to energize electromagnetically-operated valves to admit air into the brake cylinders. Any further anti-clockwise movement of the operating handle 22 causes link 21 to be rocked about pivot 19a and forces plunger 39 to be withdrawn from the shank 4 of the piston 3 against the action of the spring 38. As compressed air is admitted to the brake cylinder, the pressure in chamber 2 of the operating cylinder 1 rises and forces piston 3 downwards, compressing spring 5, pushing plunger 39 downwards and causing link 21 to be rocked in a clockwise direction about pivot 25. This causes the contact arm 34 to move in a clockwise direction back to its lap position to break the energizing circuit to the valves and prevent flow of compressed air to the brake cylinder. By the time this pressure has built up in the operating chamber 2, the actual pressure in the brake cylinder may have risen above this pressure; however, the spring-loaded plunger 9 prevents the contact arm 34 from moving beyond its lap position to its release position illustrated. Similarly, when the vehicle brakes are applied and the contact arm 34 is in its lap position, it is possible to reduce the degree of braking without completely releasing the brakes by means of the action of the spring- loaded plunger 11. An alternative arrangement is described in which the plungers are replaced by a spring-loaded roller which is caused to ride up a cam or by a leaf-spring arrangement.