Patent GB-1222181-A (GB)
Title: Control valve for compressed air brakes, more especially for rail vehicles
IPC: B60T17/18
Filed: 1969-01-01
Abstract: 1,222,181. Railway brake control valve. KNORR-BREMSE G.m.b.H. 1 Jan., 1969 [26 Jan., 1968], No. 75/69. Heading F2F. A control valve for compressed, air brakes, especially for rail vehicles, comprising a triple pressure member for indirectly or directly controlling the brake cylinder pressure and a maximum pressure limiter which limits the rise in pressure in the brake cylinder to an established maximum value, the limiter being in a connecting line between the storage tank and the inlet valve of the triple pressure member, is characterized in that the maximum pressure limiter is urged in the closing direction by the pressure in the connecting line between the inlet valve of the triple pressure member and the seat of the maximum pressure limiter. Before a storage tank 12 is filled with compressed air from the train pipe, (not illustrated) the maximum pressure limiter 1 is in the open position. The Figure shows it in the closed position, which is after the filling operation, (described below), has started. As the storage tank 12 is being filled, the air passes therefrom into a pressure chamber 11, through a minimum pressure limiter 4 and along lines 8<SP>1</SP> and 8 to a triple pressure member 5; it also passes between flange 34 and valve seat 47 of maximum pressure limiter 1, through pressure chamber 42, past control nozzle 9 and along line 8. When the compressed air pressure, which is able to act on the top of piston 18 through bores 43 and 44, exceeds the force of a spring 37, the maximum pressure limiter 1 closes. Storage tank pressure is now operative above inlet valve 6. If the train pipe pressure is lowered by operation of a driver's brake valve, a plunger 7 in the triple pressure member 5 is raised, opening inlet valve 6 against the spring pressure shown, and the storage tank pressure. Compressed air now flows from storage tank 12 via inlet valve 6, a pressure chamber 14 in triple pressure member 5, a pipe 16, and the pressure chamber 17 above valve diaphragm 3, and then directly or through the control of a relay valve to a brake cylinder 10. With the consequent lowering of pressure in pipe lines 8, the maximum pressure limiter 1 opens again. After a certain rise in pressure in pressure chamber 17, diaphragm 3 closes the minimum pressure limiter 4; thereafter the air flows via the maximum pressure limiter 1 and nozzle 9 to the triple pressure member 5, until the inlet valve 6 is balanced, and closes. The piston 18 of the maximum pressure limiter 1 moves in a cylinder ring 19 threaded at 20 into a fixed part of the housing 2 and making contact with the diaphragm 3. The piston 18 has a piston rod 24 sliding in an insert component 23 whose flange 48 is also screwed into the housing. The piston-rod 24 abuts a plunger 29 sliding in a bore 28 of the component 23, the plunger 29 ending in a flange 34 having a packing 30 which co-operates with the valve seat 47. The spring 37 acts upwards on the flange 34 through the agency of a cup-shaped member 35 and downwards against an adjusting nut 38 threaded on to the valve seat member 39.