Patent GB-320861-A (GB)
Title: Improvements in and relating to control devices for fluid pressure braking apparatus
IPC: B60T15/30
Filed: 1928-07-20
Abstract: 320,861. Tomlinson, A. V., (Westinghouse Air Brake Co.). July 20, 1928. Fluid-pressure.-In a control valve for fluid pressure brakes influenced by a control chamber at one side of an abutment, the pressure in the control chamber is automatically maintained at a predetermined value to prevent undesirable variation in pressure in this chamber from adversely affecting the operation of the valve. The pressure in the control chamber 24 connected to a constant pressure reservoir 2 is maintained constant by a spring pressed diaphragm 93. Fall of pressure in the train pipe 4, and a chamber 16, on brake application, allows the pressure in the chamber 24 to move the diaphragm system 12 - - 15, and valve 27 to close the chamber 20 to the exhaust port 28 and open it to the pipe 29 leading to the auxiliary reservoir 3. The increased pressure in the chamber 20 acts on the diaphragms to reclose the valve 27. Leakage from this chamber is re-established to maintain the pressure constant, by the reopening of the valve 27. Chambers 38, 31 are connected bv passages 21, 37 to the chamber 20 so that the pressure therein is the same. The rise of pressure in the chamber 31, consequent on the rise of pressure in the chamber 20 on brake application, acts on a piston 30 to move a slide valve 32 to close a chamber 33 and the brake cylinder passage 36 to the exhaust port 77 to open a valve 34 to admit pressure fluid from the auxiliary reservoir by the pipe 29 to the brake cylinder 1. The increased pressure of fluid in chamber 33 acts on the piston 30 to reclose the valve 34 and maintain a certain brake cylinder pressure. A slide valve 75 controlled by a spring-pressed diaphragm 39 is. adapted to cut off the chambers 31, 38 from the chamber 20 to limit the maximum service brake application. In the emergency position of the emergency valve 7 the chamber 41 behind this diaphragm is connected by a passage 42 and a port 97 to the chamber 48, the fluid pressure in which maintains the valve 75 open; otherwise the chamber 41 is connected to the exhaust port 92. The piston 44 of the emergency valve 7 is also moved by the reduction of train pipe pressure on service application until it abuts against a spring stop 78 and the auxiliary slide valve 47 is moved to register ports 80, 81 to vent the valve chamber 48 to an exhaust port 82 and thus prevents further movement of the valve. Also a cavity 83 connects ports 84. 68 in order to vent the_ train pipe through passages 17 and check valve 67 to the brake cylinder through check valve 86 and the passage 36. On emergency application the piston 44 moves to compress the spring stop 78 and uncovers a port 79 so that pressure fluid passes from the chamber 48 by a passage 51 to the quick action valve piston 49 which it moves and opens a vent valve 52 connecting the train pipe to an atmospheric port 87. The main valve 46 is then moved and by means of a cavity 88 connects passages 51, 71 and the valve 52 is held open until the pressure in the quick action chamber 72 blows down through a restricted port 89 in the piston 49. In the release position of the valve 46 the chambers 55, 57 of the emergency application valve 11 is connected by a cavity 90 with the service reservoir passage 29. In the emergency position a cavity 91 connects these chambers with an exhaust port 92 and the piston 54 of this valve moves to connect the reservoir 3 with passages 59, 36 and the brake cylinder. The reservoirs 2, 3 are charged through slide valves 8, 9 operated by bellows diaphragms 62 and diaphragm heads 61. In the release position of the valve 7 the chamber 48 is charged from the train pipe through passages 17, 68, and a check valve 69 and the quick action chamber 72 is charged through a passage 71.