Supply valve for dual circuit systems

In a supply valve, a housing defining a bore therewithin, said housing having an outlet and a pair of inlets communicating with said bore, a shuttle slidable in said bore in response to a pressure differential between said inlets to communicate one of said inlets to said outlet and close the other inlet when the pressure level at said one inlet is greater than the pressure level at the other inlet and sliding to close said one inlet and communicate said other inlet to said outlet when the pressure differential between said inlets reaches a predetermined level, said shuttle including a pair of fluid pressure responsive areas corresponding to each of said inlets, at least one of said pair of areas including one portion communicated to its corresponding inlet and an other portion communicated to the outlet when the corresponding inlet is closed, said other portion being communicated to said corresponding inlet when said corresponding inlet is communicated to said outlet, and orifice means for providing uninterrupted communication between said outlet and said other portion of said areas, said pressure differential operating on said one portion of one of said areas to initiate movement of said shuttle away from said one inlet, said pressure differential operating on both of said portions of said one area to complete the movement of said shuttle, to open said one inlet and to close said other inlet, said valve including resilient means biased to move said shuttle away from said other inlet, to open said other inlet and to close said one inlet when said pressure differential reaches a predetermined level, said bore being stepped to define a larger diameter portion and a pair of smaller diameter portions, one of said smaller portions corresponding to said one inlet and the other smaller portion corresponding to said other inlet, said larger diameter portion cooperating with said smaller diameter portions to define a pair of shoulders corresponding to each of said inlets, said shuttle including a pair of stems projecting from opposite ends of said shuttle, one of said stems defining said one portion of said one area, said shuttle and said stems cooperating to define a pair of annular end faces extending radially outward from said stems, one of said end faces defining said other portion of said one area, said shuttle also including an abutment engaging a corresponding abutment on said bore when said other inlet is closed.