A DRAIN VALVE

摘要

PCT No. PCT/GB97/01715 Sec. 371 Date Aug. 18, 1999 Sec. 102(e) Date Aug. 18, 1999 PCT Filed Jun. 24, 1997 PCT Pub. No. WO98/00324 PCT Pub. Date Jan. 8, 1998A drain valve of an air braking system for vehicles has a drainage piston, a main sump and auxiliary sump. Moisture passes from the main sump to the auxiliary sump in response to pressure at a signal port which closes off air supply through ports. A reduction in pressure at the signal port causes the ports to be reconnected and allows moisture to be expelled through the drainage outlet.