Patent GB-920405-A (GB)
Title: Brake control apparatus with means for selecting between direct and graduated release
IPC: B60T15/30
Filed: 1961-01-09
Abstract: 920,405. Fluid pressure brakes. WESTINGHOUSE AIR BRAKE CO. Jan. 9, 1961 [Jan. 20, 1960], No. 813/61. Class 103 (1). In a fluid-pressure braking apparatus for railway vehicles a service valve means 8 is controlled by brake pipe pressure and the pressure of fluid in a chamber 21, a selector valve means 10 is operable selectively to (a) a direct release position to establish a connection neutralizing the effect of pressure fluid in the chamber 21 acting in opposition to pressure fluid in a volume 19 and connect the volume 19 to an auxiliary reservoir 5, and (b) a graduated release position to disestablish such connections and connect the chamber 21 to the brake cylinder 7 such that when the selector valve means 10 is in the direct release position the service valve means 8 will assume its lap position when the pressure in the volume 19 reduces to substantially the existing reduced value of brake pipe pressure 4 and will be moved to and remain in the release position upon a subsequent increase in brake pipe pressure for effecting a complete release of the brakes provided such increase in brake pipe pressure exceeds a slight degree, such that with the selector valve means 10 in the graduated release position the service valve means 8 will assume its lap position whenever brake cylinder pressure corresponds substantially to the magnitude of the differential between the brake pipe pressure and the pressure in the volume 19 thereby permitting the brakes to be graduated off according to the degree of brake pipe pressure which is restored towards the valve of the pressure in the volume 19. As shown in the Figure, the brake controlling valve includes a service portion 2 and an interconnected emergency portion 3. Release position.-In the release position shown in which the slide valve 15, associated with the motor 12, 13, 14 of the service valve device 8, is biased by a helical spring 25 so that when the tandem-selector valve 10 is in its graduated release position the brake cylinder 7 is discharged to atmosphere via passages 45, 73, 74. Brake application.-When brake pipe pressure is reduced, the pressure in chamber 16 is reduced accordingly and the valve 15 is moved towards its service position, the passageway 65 is cut-off from chamber 17 to prevent backflow of pressure fluid from the volume 19 into the brake pipe 4 and to bottle-up pressure fluid in volume 19 at substantially the value of the normal charge of brake pipe pressure. The movement of valve 15 also closes passage 74 and cuts-off the brake cylinder 7 from exhaust and connection is made from auxiliary reservoir 5 via passage 47, check valve 79 to passage 75 and thence via cavity 73 to passage 45 leading to the brake cylinder 7 and to chamber 35 of a combined charging and quick service cut-off valve device 9. When selector valve 10 is operated to a direct release position by moving handle 43 clockwise a quarter of a turn, the passage 45 will be cut-off from chamber 21 and the latter will be vented via passageway 41 and vent port 44 so that the auxiliary reservoir will be connected via passageway 42 to passage 47 and thus to chamber 48 which is open via passage 83 to chamber 17, so that chamber 21 will remain constantly vented and volume 19 will constantly open to the auxiliary reservoir 5. A valve 50 controls venting of the emergency reservoir 6 which is always connected to a chamber 53 via branch passage 72. When the selector valve 10 is in the graduated release position, a valve 49 controls the venting of the volume 19 but not of the auxiliary reservoir 5. When the valve 50 is unseated the pressure fluid will be released not only from the emergency reservoir 6 but also from the auxiliary reservoir 5 via selector valve passageway 42, passage 47, cheek valve 71 and emergency reservoir passage 72. The pusher finger 60 is preferably shorter than the finger 59 so that upon a slight degree of upward movement of valve 49 by tilting a lever 54 the valve 49 will become unseated to vent volume 19 and upon a greater degree of upward movement the valve 50 will be unseated for venting the emergency reservoir 6. U.S.A. Specifications 2,031,213 and 2,841,448 are referred to.