A brake pressure reducing valve assembly for a vehicle comprising:
- a valve body;
- first and second normally open valve means for controlling communication between respective associated inlet and outlet chambers;
- said first valve means comprising a first inlet chamber within said valve body connectable to a source of brake actuating fluid, a first outlet chamber within said valve body and connectable to a brake actuator, a first brake pressure responsive piston slidably mounted in said valve body separating said first inlet chamber from said first outlet chamber, a first valve seat on said first piston in said first inlet chamber, and a deceleration responsive first valve member movably mounted in said first inlet chamber and engageable with said first valve seat for maintaining said first valve means normally open when the deceleration of the vehicle is below a first threshold value and for engaging said first valve seat for closing said first valve means when the deceleration of the vehicle reaches a second threshold value, said first valve member being movable in said valve body in response to pressure in said first inlet chamber produced by said source of brake actuating fluid;
- and
- said second valve means comprising a second inlet chamber within said valve body and connectable to a source of brake actuating fluid, a second outlet chamber in said body and connectable to a brake actuator, a second brake pressure responsive piston slidably movable in said valve body separating said second inlet chamber from said second outlet chamber and movable in response to pressure in said second inlet chamber produced by said source of brake actuating fluid connected to said second inlet chamber, a second valve member between said second inlet and outlet chambers, a second valve seat on said second piston engageable with said second valve member for closing said normally open second valve means in the engaged positions, compression spring means in said valve body and operatively mounted between said first and second pistons for urging said pistons in a direction away from each other, so that said pistons are moved towards each other against the force of said compression spring means to affect closing of said first and second valve means, the force required to move said second piston towards said first piston against the force of said compression spring means in any position of said first piston is determined by the position of said first piston, and when said first piston moves in response to brake pressure in said first inlet chamber exceeding a predetermined value and the deceleration of the vehicle is below said first threshold value said first valve member and said first valve seat move with said first piston to maintain separation between said first valve member and said first valve seat until deceleration of the vehicle reaches said second threshold valve.