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Abstract

A control apparatus for a brake system having a housing with a first bore for retaining a spool valve and a second bore for retaining a selector valve. A cap separates the first bore into a first chamber and a second chamber. The first chamber has an inlet port connected to a source of fluid under pressure, a gear port for connected the source of fluid under pressure to a hydraulically operated device, a relief port connected to a reservoir and an outlet passage connected to a selector valve which communicates pressurized fluid through an outlet port to a brake booster. The second chamber is connected to the reservoir and the second bore. The a spool valve has a peripheral surface with first and second grooves separated by lands and an internal operational passage connecting the second groove to the outlet passage. A first return spring positions the spool valve in the first bore such that pressurized fluid is communicated to the hydraulically operated device by way of the inlet port, first groove and gear port. An actuating apparatus has an input piston that is located in the second chamber for receiving an input force of an operator, a plunger which extends through the cap to be partly located in the first and second chambers, a second return spring for urging the input piston toward a rest position and an actuation spring for connecting the input piston with the plunger. An input force moves the input piston in the second chamber to communicate an actuation force to the spool valve by way of the actuation spring and plunger to position the spool valve and restrict communication between the first groove and the gear port and divert operational pressurized fluid to the outlet passage to effect a brake application. The movement of the input piston within the second chamber is modified by communication of fluid therefrom to the selector valve to provide a smooth rate of actuation for the spool valve and to provide a back up source of operational pressurized fluid in the absence of the source of pressurized fluid.

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First Claim