Dual brake valve with brake proportioning

Dual circuit brake valve having a pair of inlet ports, a pair of outlet ports, a pair of valve members in said housing, one of said valve members controlling communication between one of said inlet ports and a corresponding outlet port, the other valve member controlling communication between the other inlet port and its corresponding outlet port, manually actuated means for controlling one of said valve members, fluid pressure responsive relay means for operating the other valve member, passage means communicating the outlet port controlled by said one valve member with said fluid pressure responsive relay means for causing the latter to operate said other valve member in response to pressure changes at said outlet port controlled by said one valve member to thereby establish a corresponding pressure level at the outlet port controlled by the other valve member, and pressure proportioning means controlling communication through said passage means, said pressure proportioning means including a control port on said housing communicated with a signal pressure, said pressure proportioning means being responsive to said signal pressure to shift between a first condition permitting uninhibited communication through the passage means to communicate a pressure level to the relay means substantially equal to the fluid pressure level communicated to said outlet port controlled by the one valve member and a second condition wherein said pressure proportioning means proportions communication through said passage means to establish a fluid pressure level at said relay means which is a predetermined poroportion of the fluid pressure level communicated to said outlet port controlled by said one valve member.