Patent GB-602382-A (GB)
Title: Improvements in compressed air braking equipment for rail or other vehicles
IPC: B60T8/18
Filed: 1945-10-13
Abstract: 602,382. Fluid-pressure brakes. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. Oct. 13, 1945, No. 26824. Convention date, Nov. 8, 1944. [Class 103 (i)] In a compressed-air brake, means are provided for automatically varying the pressure established in the brake cylinder in accordance with the load on the vehicle, and comprise an additional volume chamber which communicates with the brake cylinder through valve mechanism controlled by the load on the vehicle and the pressure established in the chamber during brake application. As shown, the valve mechanism is arranged to be operated to open a connection between the brake cylinder and chamber by a force inversely proportional to the load on the vehicle acting in opposition to the pressure in the chamber. The brake cylinder 3 is in communication with a chamber 4, containing a spring-loaded piston 5, through a pipe 8, a passage 9, a one-way check-valve 10, a passage 11, a pipe 12, a valve chamber 13, a passage 15 controlled by a spring-loaded valve 14, a chamber 16 closed by a diaphragm 44, a pipe 17 and passages 18 and 19. A cylinder 22 is in communication with the brake cylinder through a passage 23 and ports 24 in the chamber 13, and contains a piston 25 which acts on the arm 26 of a lever 27 by means of a spring 28 and is loosely coupled thereto by a link 29. The arm 26 is pivotally connected at 30 to a slidable rod 31 having an adjustable foot 32. The apparatus is mounted on a chassis, bogie or truck-member of the vehicle so that the foot 32 is aligned with a relatively movable part, and the extent of movement of the rod 31 is thus governed by the deflection of the vehicle springs. The lever 27 is fulcrumed at 33 and has a second arm 34 pivoted to a cup 36 in which a plunger 38, secured to the diaphragm 44 and to the stem 43 of the valve 14, is freely slidable within limits imposed by a shoulder 39 and pin 40. A compression spring 41 is interposed between a flange 42 on the plunger and -a seating on the cup. The movements of the plunger and lever are restrained by springs 50 and 49 respectively, and a dashpot comprising a cylinder 46 containing a piston 45 connected to the plunger is provided to damp movements thereof due to vibrations and oscillations of the vehicle. When the brake is applied, the valve 14 is forced on to its seating and the piston 25 moved downwardly to compress the spring 28 and depress the lever arm 26 by an amount determined by the extent of movement of the rod 31 allowed by the vehicle spring deflection. This causes an upward movement of the lever arm 34 to compress the spring 41 and open the valve 14. Compressed-air then enters the chamber 4 via the passage 15, the chamber 16 and the pipe 17, and moves the piston 5 to the right against the action of its spring. Air continues to flow until the pressure in the chamber 4, and hence above the diaphragm 44, is sufficient to overcome the upward thrust of the spring 41, when the valve 14 will close and isolate the chamber 4 from the brake cylinder. When the pressure in the brake cylinder is relaxed, the chamber 4 exhausts through the valve 14 and a throttle 53 in a passage byepassing the valve 10, the effect of the throttle being to cushion the return movement of the piston 5. The housing 52 containing the valve 10 may be rotated to the position of Fig. 2 (not shown) to place the chamber 4 in direct communication with the brake cylinder should the automatic control become defective. The chamber 4 is provided with a safety valve comprising a housing 54 containing a spring- loaded plunger 55 which carries a valve member 57 controlling an exhaust passage 58. The housing and plunger are interconnected by diaphragms 59 and 60 which define chambers 61 and 62 in communication with the chamber 4 and brake cylinder respectively. If there is no pressure in the chamber 62, the valve will operate at some selected value of brake cylinder pressure determined by the strength of the spring 56. As pressure builds up in the chamber 4, and hence in the chamber 62, it will partly cancel the effect of the pressure in chamber 61, but, as the area of the diaphragm 60 is greater than that of the diaphragm 59, a greater force will be exerted on the plunger 55 and the valve will operate at a proportionally lower brake cylinder pressure. Specification 602,381 is referred to.