A fluid operable brake control valve apparatus is provided which includes a brake cylinder valve for controlling the supply of fluid pressure into and out of a brake cylinder. The valve is operable by a main pressure responsive member moveable in response to changes in pressure when applied to a brake pipe. A quick service valve is operable in response to such a change tending to cause a brake application for connecting a quick service volume to the brake pipe to enhance the change at commencement of an application. An accelerated release valve device is operable in response to release of fluid pressure from the quick service volume to connect a charged accelerated release reservoir to the brake pipe to assist a change of pressure in the brake pipe causing such a release.
This invention relates to a valve assembly for a railway braking system, including a brake cylinder pressure-maintaining valve which, during brake application, takes air from the brake pipe and feeds it into the brake cylinder until it reaches minimum brake pressure. To avoid the need for an extra valve, the brake cylinder pressure-maintaining valve is used as a quick service bulb exhaust valve during brake release and member are provided to ensure that the brake cylinder pressure maintaining valve opens immediately on brake release. Once the brakes have been applied, pressure in the brake cylinder is maintained from the quick service bulb 59. Brake cylinder exhaust pressure taken from a point 124 after the brake cylinder exhaust valve 50, but before the brake cylinder exhaust choke 70, is directed to chamber G above the inshot and brake cylinder-maintaining valve diaphragm 131. Since the pressure in port 124 upstream of the brake cylinder exhaust choke 70 attains a pressure well within 10 p.s.i. of chamber H, the spring 67 in chamber G can open the brake cylinder maintaining valve 64. Thus, immediate opening of brake cylinder-maintaining valve 64 occurs when the bi-stable operator moves to the release position. Bulb pressure from QS bulb 59 is then able to flow via the BC maintaining choke 65 and fall with the fall of brake cylinder pressure in port 120.
