Patent ID: 6769744
Filing Date: 2004-08-03
Classification: B60T,Y10T

Abstract:
A combined spring brake modulating relay valve comprising:a housing having a control port wherein the control port is adapted to receive a signal from a control valve, supply port separate from the control port wherein the supply port is directly connected to pressurized air from an associated reservoir, delivery port, exhaust port, and a chamber formed therein in selective communication with the supply port adapted to receive pressurized air from the associated reservoir as a result of the signal received by the control port for communication between the supply port and the delivery port, the delivery port adapted to communicate with associated spring brake chambers, and the exhaust port adapted to communicate with ambient; a valve member in the chamber normally biased to preclude communication between the supply and delivery ports and permit communication between the delivery port and the exhaust port; a first piston received in the housing and movable iii response to pressure from the control port; a second piston received in the housing and operatively associated with the first piston for selective movement relative to the first piston; primary and secondary ports communicating with opposite faces of the second piston and communicating with primary and secondary brake circuits so that when both brake circuits are operational, there is no impact on the second piston; and a first spring urging the first piston toward abutting engagement with the second piston under certain pressure conditions.