Hydraulic control valve with void control means

Claim 1

A SECTIONAL CONTROL VALVE OF THE TYPE COMPRISING AN INLET SECTION HAVING AN INLET CHAMBER INTO WHICH PRESSURE FLUID FROM A SOURCE THEREOF CAN BE INTRODUCED, A RETURN FLUID MANIFOLD COMMUNICATED WITH AN OUTLET, AND AT LEAST ONE CONTROL SECTION CONFINED BETWEEN THE INLET SECTION AND THE RETURN FLUID MANIFOLD, OF THE TYPE IN WHICH A SPOOL IS SLIDABLE TO EACH OF A PAIR OF OPERATING POSITIONS TO COMMUNICATE EITHER OF A PAIR OF OPERATING POSITIONS TO COMTROL SECTION WITH A SUPPLY PASSAGE THEREIN THAT CONNECTS WITH THE INLET CHAMBER, WHILE COMMUNICATING THE OTHER SERVICE PASSAGE WITH A RETURN PASSAGE IN THE CONTROL SECTION, SAID VALVE BEING CHARACTERIZED BY THE FOLLOWING: (A) THAT ALL OF THE RETURN PASSAGES ARE CONNECTED TO A COMMON EXHAUST HEADER HAVING ONE END COMMUNICATING WITH THE RETURN FLUID MANIFOLD AND WHICH EXTENDS THROUGH EACH CONTROL SECTION CROSSWISE OF THE SPOOL THEREIN; (B) THAT THE OTHER END OF THE EXHAUST HEADER IS COMMUNICABLE WITH THE INLET CHAMBER THROUGH A PRESSURE RELIEF VALVE WHICH NORMALLY BLOCKS COMMUNICATION BETWEEN TH EINLET CHAMBER AND SAID EXHAUST HEADER, BUT IS RESPONSIVE TO PRESSURE OF FLUID IN THE INLET CHAMBER IN EXCESS OF A PREDETERMINED VALUE OF OPEN AND PERMIT FLOW OF FLUID THEREFROM TO THE EXHAUST HEADER; AND