Dual circuit brake valve differential pressure control mechanism

Dual circuit brake valve comprising a housing having a pair of inlet ports and a pair of outlet ports, each of said outlet ports being associated with a corresponding one of said inlet ports, a pair of valve members for controlling communication between each inlet port and its corresponding outlet port, manual valve actuating means for controlling one of said valve members, said manual valve actuating means including a control actuating member slidably mounted in said housing and movable toward and away from a position operating said one valve member to initiate communication between one of said inlet ports and its corresponding outlet port, a relay actuating member slidably mounted in said housing and movable therein relative to said control actuating member to permit the latter to move away from the relay actuating membe during brake release, said relay actuating member being responsive to the pressure differential between said outlet ports for operating the other valve member in response to operation of the one valve member, said actuating members having corresponding facing ends, and reaction force transfer means carried by one of said actuating members for transferring a predetermined force to said relay actuating member upon operation of said manual valve actuating means, said reaction force transfer means including a spring retainer projecting from the facing end of said one actuating member toward the forcing end of the other actuating member, stop means carried by said spring retainer, a plunger slidably mounted in said spring retainer, and a spring yieldably urging said plunger toward engagement with said stop means and toward the facing end of the other actuating member for engagement therewith upon operation of said manual valve actuating means to effect a brake application to thereby transfer the force generated by said spring to the relay actuating member when the plunger is engaged with the forcing end of the other actuating member when a brake application is effected.