Patent GB-972696-A (GB)
Title: Improvements relating to compressed fluid braking apparatus
Inventor: SIMMONS ARTHUR WILLIAM
IPC: B60T15/30
Filed: 1960-12-08
Abstract: 972,696. Fluid-pressure brakes. WESTING- HOUSE BRAKE & SIGNAL CO. Ltd. Nov. 29, 1961 [Dec. 8, 1960], No. 42228/60. Heading F2F. In a distributer valve for a compressed air braking system for rail vehicles wherein a diaphragm 14 is acted on by brake cylinder pressure in chamber 16 via connection BC, a diaphragm 15 is acted on by brake pipe pressure in chamber 20 via connection BP and by a control reservoir pressure on its underface via connection CR, and a quick-service volume 24 is adapted to be connected to the brake pipe on initial reduction of pressure therein by relative movement of follower assemblies 32, 37 of the two diaphragms, after which these assemblies move together to open an application valve 30, means is provided to prevent separation of the diaphragms during release of brake cylinder pressure until the latter has fallen below a predetermined value in relation to the brake pipe pressure. As shown, this means consists of a resilient seat formed by an annular plate 53 and a spring 52 which is stronger than a spring 35 for maintaining the assembly 32 on the seat in the fully released condition of the brake. Chamber 36 below the diaphragm 14 is connected to atmosphere via opening 19 and also with an exhaust passage 33 in the assembly 32 by way of a restriction 34 so that the brake cylinder is exhausted when the assembly 32 rests on the seat 53, the exhaust passage 33 being closed by the valve 30 when the assembly is raised to open the valve 30 to pressure from an auxiliary reservoir via passage 28, restriction 29 and connection AR. The assembly 37 of the diaphragm 15 comprises an opening 38 to enable the control reservoir to be charged from the brake pipe when the brake is released, also a stem 42 slidable within a valve closure member 46 which is urged downwardly by a spring 49 and is in turn slidable within a sleeve 41, the latter being received within a bore in a partition member of the housing for up and down sliding movement. Seals are provided for these sliding members. Sleeve 41 has an annular flange 44 provided with a valve seat for closing the opening 38, and also an opening 45 communicating with the quick-service volume 24. Closure member 46 has a seat 50 to engage the flange 44 for cutting off the volume 24 from the brake pipe and also a passageway 47 connecting the volume 24 via an aperture 43 in the sleeve 41 to atmosphere. This passageway is closable by closure member 48 on the stem 42. In operation, starting from, the released position shown, where volume 24 is connected to atmosphere, reduction of pressure in the brake pipe causes pressure in the control reservoir acting against spring 39 to lift the assembly 37, first closing the passageway 47, then lifting the closure member 46 to raise seat 50 communicating volume 24 with the brake pipe, and finally closes the opening 38. Thereafter the two diaphragms and their following assemblies move together to open the application valve 30, shutting off exhaust passage 33. If a graduated release is desired the subsequent rise in brake pipe pressure is effected slowly whereas brake cylinder pressure is reduced fairly rapidly after opening of the exhaust passage so that assembly 32 moves back to lap position. If, however, brake pipe pressure is increased rapidly the brake pipe pressure preponderates for a time and the assembly 32 is forced down beyond its rest position, compressing the spring 52 so as to prevent separation of the diaphragms and consequent premature exhausting of the quickservice volume 24 until the brake cylinder pressure has reduced to the desired level. A ball valve 26 and restriction 27 are provided for recharging the auxiliary reservoir from the brake pipe.