Radial hydraulic motors and pumps

Claim 1

A radial hydraulic motor or pump comprising a cylinder block having a plurality of cylinders relatively rotatable about a first axis, reciprocating members in said cylinders, and a rotor relatively rotatable about a second axis parallel to and spaced from the first axis, and having chordal internal faces on which the radially outward ends of the reciprocating members slidably and sealingly bear; characterized in that each of said reciprocating members is formed with a recess in the radially outer end thereof substantially equal but slightly less in area than the area of the associated cylinder and each of said cylinders is formed with an elongated recess at the radially inner periphery thereof substantially equal in area to the area of the cylinder in which the reciprocating member is positioned, and said rotor is formed with a plurality of recesses in the radially inner periphery thereof, first fluid port means are provided which extend through the reciprocating members to put said faces in fluid communication with said cylinders substantially at work fluid pressure and over areas whereby radial outward forces occasioned by hydraulic fluid in said cylinders during working strokes are borne hydraulically at least substantially entirely and substantially directly by said faces, with said recesses at the radially inner periphery of each cylinder functioning to create a balance of radially inward and radially outward forces on said cylinder caused by said work fluid during the working strokes, and second fluid port means are provided operative to put fluid into communication with said recesses in said rotor substantially at work fluid pressure, said recesses in said rotor having areas and being located such that said work fluid exerts, in use, a substantially equal and generally opposite force on said rotor to the radial outward forces acting on said faces occasioned by hydraulic fluid in said cylinders during at least a substantial part of working strokes.