Patent GB-1246297-A (GB)
Title: Improvements in or relating to fluid-pressure braking systems for vehicles
IPC: B60T13/38
Filed: 1968-12-20
Abstract: 1,246,297. Fluid-pressure release of spring-applied brakes. ROBERT BOSCH G.m.b.H. 20 Dec., 1968 [5 Jan., 1968], No. 60637/68. Heading F2F. In a known arrangement of a manual braking unit 27 for controlling the filling of the storage space 5 of a spring-loaded brake cylinder 1 where the actuating linkage 34 is provided with a pilot valve 38 in a relief line 20, the system also having a cut-out 7 (for the cylinder 1) which is released by the pilot valve 38, the manual braking unit 27 is assembled with at least one one-way valve 38 acting as the pilot valve, and a pressure-responsive shut-off valve unit 7 is provided as the cut-out between unit 27 and cylinder 1; the valve unit 7 also includes a closing member 18 which controls the relief line 20 in which the one-way valve 38 is located. In the charged, brake-off position, closing member 29 is out of contact with seat 31 but in contact with seat 30. Pressure from supply line 42 is thus communicated to the region below piston 32, to conduit 26, and past non-return valve 8 to working chamber 5 of brake cylinder 1; also from the region below valve 8 through clearance 13 (between extension pin 12 and radial wall 14), through bore 16 of shut-off piston 15, through passage 23 at the bottom of piston 15, through annular valve space 22, around valve seat 19, to pressure relief line 20, closed at 36. Part-braking position.-Cranked hand-lever 34 is moved slightly to the right, whereby cylindrical extension 35 is lifted off the end of pressure relief line 20 to permit communication with piston space 40 which communicates with the atmosphere. Annular valve space 22 is thereby vented, so spring 24 forces piston 15 downwards; piston 15 unseats non-return valve 8 by engaging the head of pin 12, and by the time valve-closing member 18 has reached seat 19, energy-storing spring 2 has moved slightly to the right to apply the brake (attached to piston-rod 4). With further slight movement of hand lever 34, closing member 29 reaches seat 31 to isolate the region below piston 32, and consequently the non-return valve 8, from the pressure supply. Thus, supply of compressed air to the working chamber 5 of brake cylinder 1 is shut off. Full braking position.-From the position just described, the hand lever 34 is moved fully to the right, whereupon extension 35, acting upwards on spring 33, raises piston 32 to lift seat 30 off closing member 29 (which, it will be remembered, is already in contact with seat 31. Working chamber 5 is thereby vented past open non-return valve 8, through conduit 26 and through piston space 40. Spring 2 thereupon operates the brake fully. With the parts of structure 7 in the position shown, and relief line 20 closed at 36 (brake-off position), if the supply pressure fails, the pressure above non-return valve 8, and in the conduit 26 connected to it, falls. Non-return valve 8 remains closed, and relief line 20 remains cut off, so working chamber 5 is not relieved, and the brake remains off. In the event of fracture of conduit 26 the situation is effectively the same as if the supply pressure fails, and the brake remains off. In the event of fracture of pressure relief line 20, piston 15 is first forced downwardly by its spring 24, so valve 8 is pulled open. Compressed air from conduit 26 now flows past open valve 8 and via bore 16 and passage 23 to the underside of piston 15, raising it again, and raising valve closing member 18 off its seat 19 again. This state continues until pressure in working chamber 5, in conduit 26 and in relief line 20 has been reduced sufficiently for spring 24 to force piston 15 down finally, whereupon member 18 seats on 19 to close line 20. Other similar valves 38 may be connected to reliefline 20. A separate source 50 of compressed air may be connected to relief line 20 to take care of possible fracture in conduit 26 or lack of supply pressure. The apparatus is intended for motor vehicles.