DECELERATION AND PRESSURE SENSITIVE PROPORTIONING VALVE

A proportioning valve assembly (10, 130) in a housing (12) is pressure responsive to control the flow of fluid to a wheel brake cylinder. The proportioning valve assembly (10, 130) includes a movable retainer (50) coupled with a differential piston (30) for movement therewith, a stationary retainer (70) mounted by the housing (12) and surrounding a second piston (80) having an enlarged diameter portion (88) that defines with an end (11, 16) of the housing (12) a chamber (90). The second piston (80) has a poppet (84) extending into an interior opening (54) of the movable retainer (50), the movable retainer (50) supporting a seal (56) disposed about the extension (82) of the second piston (80). The seal (56) is positioned for closing an opening (73) of the stationary retainer (70) through which the second piston (80) extends. The second piston (80) contains a poppet valve (99) which controls fluid flow through a passage (85) from one side of the second piston (80) to the other side, and the second piston (80) provides support for an inertia-sensitive object (110) which controls operation of the poppet valve (99). When the differential piston (30) and movable retainer (50) move in response to inlet fluid pressure and the seal (56) closes the opening (73) of the stationary retainer (70), fluid on both sides of the enlarged diameter portion (88) of the second piston (80) is isolated from the inlet fluid pressure, and resulting deceleration of the vehicle causes the inertiasensitive object (110) to move and close the poppet valve (99) to trap fluid pressure within the chamber (90) and prevent further movement of the second piston (80).