Hydraulic control valve having void control means

Claim 1

A HYDRAULIC CONTROL VALVE INCLUDING A BODY HAVING A BORE, A PAIR OF SERVICE PASSAGES LEADING FROM THE BORE, SEPARATE FLUID SUPPLY AND RETURN PASSAGES THAT CONNECT WITH THE BORE, AND A VALVE ELEMENT IN THE BORE SHIFTABLE IN OPPOSITE DIRECTIONS TO SELECTIVELY COMMUNICATE EITHER SERVICE PASSAGE WITH THE SUPPLY PASSAGE AND THE OTHER SERVICE PASSAGE WITH THE RETURN PASSAGE, CHARACTERIZED BY THE FOLLOWING: (A) THAT SAID SERVICE AND RETURN PASSAGES HAVE PORTIONS THEREOF ADJACENT TO ONE ANOTHER; (B) THAT THE BODY HAS A PAIR OF BYPASSES, ONE ASSOCIATED WITH EACH SERVICE PASSAGE, EACH BYPASS HAVING INNER AND OUTER ENDS THAT RESPECTIVELY OPEN TO ITS ASSOCIATED SERVICE AND RETURN PASSAGE PORTIONS TO AFFORD COMMUNICATION THEREBETWEEN; (C) THAT PRESSURE RESPONSIVE VALVE MECHANISMS IN THE BODY, ONE FOR EACH BYPASS, AND LOCATED, WHOLLY OUTSIDE ITS ASSOCIATED SERVICE PASSAGE, CONTROL FLUID FLOW THROUGH SAID BYPASSES, AND EACH OF SAID VALVE MECHANISMS COMPRISES, (1) A CYLINDER OPENING FORWARDLY TO THE ASSOCIATED RETURN PASSAGE PORTION AT A LOCATION OPPOSITE THE OUTER END OF ITS ASSOCIATED BYPASS AND SUBSTANTIALLY COAXIAL WITH THE LATTER, (2) A PLUNGER-LIKE REVERSE ACTING CHECK VALVE IN EACH CYLINDER, EXTENSIBLE FORWARDLY THEREFROM INTO THE RETURN PASSAGE TO A BYPASS CLOSING POSITION AT WHICH THE FRONT OF THE CHECK VALVE ENGAGES SAID OUTER END OF ITS ASSOCIATED BYPASS AND RECEIVES THE FORCES OF PRESSURE FLUID IN THE ASSOCIATED SERVICE PASSAGE THAT TEND TO UNSEAT THE CHECK VALVE, (3) PASSAGE MEANS COMMUNICATING THE SERVICE PASSAGES WITH THEIR RESPECTIVE CYLINDERS SO THAT PRESSURE FLUID FROM THE SERVICE PASSAGES CAN EXERT FORCE ON THE REAR OF THEIR RESPECTIVE CHECK VALVES TO NORMALLY HOLD THEM CLOSED, AND THROUGH WHICH PASSAGE MEANS FLUID IN THE CYLINDERS CAN BE EXHAUSTED TO THE SERVICE PASSAGES DURING OPENING OF THEIR RESPECTIVE VALVES, AND (4) A FORWARDLY FACING EXTERNAL SURFACE ON THE FROM PORTION OF EACH CHECK VALVE, UPON WHICH PRESSURE FLUID IN THE RETURN PASSAGE EXERTS FORCE TO EFFECT RETRACTION OF SAID FRONT PORTION OF THE CHECK VALVE TO OPEN ITS ASSOCIATED BYPASS WHENEVER THE PRESSURE OF SUCH RETURN FLUID EXCEEDS THAT OF FLUID IN ITS ASSOCIATED SERVICE PASSAGE, TO THUS PERMIT RETURN FLUID TO FLOW THROUGH ITS BYPASS TO THE ASSOCIATED SERVICE PASSAGE SUBSTANTIALLY UNRESTRICTED BY THE CHECK VALVE.