Fluid motor-pump unit

A reversible fluid motor-pump assembly for transferring power between first and second hydraulic fluid systems, comprising a housing having first high and low pressure ports coupled to said first hydraulic fluid system and second high and low pressure ports coupled to said second hydraulic fluid system;

• a first motor-pump unit for moving fluid from said first high pressure port to said first low pressure port, and a second motor-pump unit for pumping fluid from said second low pressure pump to said second high pressure port, said first and second motor-pump units each comprising a cylinder block disposed against rotation within said housing having a plurality of axially extending cylinders formed therein each receiving a reciprocal piston and including a cylinder block port for communication with the associated high and low pressure ports, a central rotatable shaft within said housing with said cylinders circumferentially arranged with respect thereto, means coupled between said shaft and said pistons for converting between rotational and reciprocal motion, a valve plate rotatable with the shaft in running alignment with said cylinder block and between the associated high and low pressure ports, said valve plate including valve ports for sequentially communicating said cylinder block ports respectively with the associated high and low pressure ports upon shaft rotation, and a pressure-balancing member within said housing in running alignment with said valve plate opposite said cylinder block, said member including a generally circular pattern of generally axially extending fluid passages aligned axially with respective ones of said cylinder block ports for communication with said cylinder block ports through said valve ports upon valve plate rotation for receiving fluid under pressure through said valve ports whereby the fluid pressure within each said passage corresponds with the fluid pressure at its associated cylinder block port regardless of the position of valve plate rotation, each of said passages of each of said first and second motor-pump units comprising a relatively small orifice passage for communicating with said valve ports, and a relatively enlarged cylinder, said relatively enlarged cylinders formed within said pressure-balancing member being radially staggered with respect to each other, radially inwardly staggered ones of said balancing member cylinders being formed to have a diameter relatively larger than radially outwardly staggered ones of said balancing members cylinders, and fluid sealing means for sealing said passages and for pressure-reacting against said housing for urging said balancing member axially toward said valve plate for dynamically pressure-balancing axial forces applied to said valve plate;
• and means for connecting said first motor-pump unit with said second motor-pump unit for power transfer therebetween whereby the one of said units coupled to the one of said first and second hydraulic fluid systems having the higher fluid pressure drivingly operates the other of said units.

A fluid motor-pump assembly for transferring power between fluid systems, comprising a housing having first high and low pressure ports and second high and low pressure ports for respective connection to first and second fluid systems;

• cylinder block means within said housing forming a pair of generally opposed sets of circumferentially arranged and axially extending cylinders, and forming first and second sets of cylinder block ports for respective communication with said first and second housing pressure ports;
• a plurality of piston assemblies each including a pair of back-to-back connected pistons reciprocally received respectively within a generally opposed pair of cylinders of said cylinder sets;
• a central axially extending rotatable shaft within said housing;
• means coupled between said shaft and said piston assemblies for converting between rotational and reciprocal motion;
• first and second valve plates on said shaft in running alignment with said cylinder block means generally between respectively said first set of cylinder block ports and said first housing pressure ports, and said second set of cylinder block ports and said second housing pressure ports, each of said valve plates including a pair of valve ports for sequentially communicating said cylinder block ports with the associated housing pressure ports upon shaft rotation;
• and first and second pressure-balancing members within said housing in running alignment respectively with said first and second valve plates opposite said cylinder block means, said pressure-balancing members each including a generally circular pattern of generally axially extending fluid passages aligned axially with respective ones of said cylinder block ports, each of said passages receiving fluid sealing means responsive to fluid pressure at the associated cylinder block port for urging said member axially against the associated valve plate for dynamically pressure-balancing axial forces applied to said associated valve plate regardless of rotational position thereof, said generally circular pattern of axially extending passages in each of said pressure-balancing members including a plurality of radially staggered passages with radially inwardly staggered ones of said passages having a diameter relatively larger than radially outwardly staggered ones of said passages.