Hydraulic balancing system for rotary positive displacement fluid handling devices

Claim 1

IN A POSITIVE DISPLACEMENT FLUID HANDLING DEVICE: AN OUTER CASING MEMBER HAVING FIRST AND SECOND OPPOSITE END WALLS FORMING AN INTERNAL CHAMBER THEREIN AND THROUGH WHICH END WALLS AN AXIS OF ROTATION EXTENDS; AN INTERNAL MEMBER IN SAID CHAMBER; MEANS FOR PROVIDING RELATIVE ROTATION BETWEEN SAID INTERNAL MEMBER AND SAID CASING MEMBER; SAID INTERNAL MEMBER HAVING A PLURALITY OF CYLINDER BORES THEREIN; A PISTON IN EACH CYLINDER BORE CONSTRUCTED AND ARRANGED TO BE RECIPROCATED IN SAID BORE DURING RELATIVE ROTATION OF SAID INTERNAL AND OUTER CASING MEMBERS; SAID FIRST END WALL OF SAID CASING MEMBER AND THE ADJACENT END OF SAID INTERNAL MEMBER HAVING RESPECTIVE VALVING SURFACES WHICH ARE IN SLIDING SEALING ENGAGEMENT WITH EACH OTHER AND WHICH DEFINE AREAS OF HIGH AND LOW PRESSURE THAT ARE EXERTED AGAINST SAID END OF SAID INTERNAL MEMBER; SAID INTERNAL MEMBER HAVING A FLOW COMMUNICATING PORT FOR EACH CYLINDER BORE EXTENDING BETWEEN EACH BORE AND THE VALVING SURFACE OF SAID INTERNAL MEMBER; SAID SECOND END WALL OF SAID CASING MEMBER HAVING A COAXIALLY POSITIONED ABUTMENT SURFACE FACING SAID INTERNAL MEMBER; SAID INTERNAL MEMBER HAVING A COAXIALLY POSITIONED RECESS THEREIN FACING SAID ABUTMENT SURFACE; A BALANCE RING SEALINGLY ENGAGING THE SIDES OF SAID RECESS AND HAVING A SURFACE WITH ANNULAR GROOVES SLIDINGLY ENGAGING SAID ABUTMENT SURFACE, THE AREA OF SAID BALANCE RING DISPOSED BETWEEN SAID GROOVES BEING COMMUNICATED BY THROUGH PASSAGES WITH THE OPPOSITE FACE OF SAID BALANCE RING AND PROPORTIONED OF SLIGHTLY LESS AREA THAN THE AREA OF SAID BALANCE RING EXPOSED TO THE PRESSURE AT ITS OPPOSITE FACE TO EFFECT SLIGHT ENGAGEMENT FORCE BETWEEN SAID BALANCE RING AND ABUTMENT SURFACE; A PLURALITY OF INDIVIDUAL FLOW PASSAGES COMMUNICATING RESPECTIVE CYLINDER BORES WITH SAID RECESS; SAID INDIVIDUAL FLOW PASSAGES EACH HAVING A FLOW RESTRICTION DEFINED BY A SECTOR SHAPED CROSS-SECTION AND AN ELONGATED LENGTH LOCATED AT A RADIAL DISTANCE INWARDLY OF THE OUTER PERIPHERY OF THE WALL STRUCTURE DEFINING SAID RECESS FOR LIMITING FLOW THERETHROUGH FROM SAID RECESS TO ITS RESPECTIVE CYLINDER BORE WHEN ITS CYLINDER BORE IS COMMUNICATED TO LOW PRESSURE TO PROVIDE LAMINAR FLOW AT ALL TIMES THERETHROUGH.