Brake control valve

A control valve for a vehicle fluid pressure braking system includes a housing having an inlet port, an outlet port and a delivery port. A plunger is movable in the housing to control communication between the ports. The plunger is provided with a shoulder which carries a sealing member which engages with a seating area on the housing to provide a seal controlling communication between the aforementioned ports. The seal includes a circumferentially extending cavity on the housing in which the body portion of the seal is received. A pair of beads project from the body portion of the seal in opposite axial directions, so that when the seal is moved into engagement with the seating surface, one of the beads sealingly engages the sealing surface, and the axial direction forces generated thereby force the bead on the opposite side of the seal into sealing engagement with a sealing surface on the plunger. When the plunger is moved away from the seating surface, thereby abruptly reducing the pressure level around the plunger, high pressure air which is trapped in the groove receiving the body portion of the seal may escape by deflecting the bead away from the sealing surface on the plunger, thereby preventing the high pressure fluid from forcing the seal from the groove.