Positive displacement machines and methods of increasing load-carrying capacities thereof

A positive displacement machine comprising:

• a cylinder block adapted to be rotated about an axis of the positive displacement machine;
• a plurality of cylindrical bores defined in the cylinder block and surrounding the axis, each of the cylindrical bores having a bore wall and a port;
• a plurality of pistons reciprocably disposed within the cylindrical bores, each of the pistons defining a piston-cylinder lubrication interface with the bore wall of a corresponding one of the cylindrical bores and defining a displacement chamber within the cylindrical bore adjacent the port thereof;
• a working fluid located within the displacement chambers and within the piston-cylinder lubrication interfaces to provide a load-bearing function between the pistons and the bore walls of the cylinder bores;
• a circumferencially continuous radial step in a surface of each of the cylindrical bores between the piston-cylinder lubrication interface and the displacement chamber thereof that defines an end of the piston-cylinder lubrication interface, wherein distal ends of the pistons are located within the displacement chambers of the cylinder bores, do not pass the radial steps of the cylindrical bores, and do not enter the piston-cylinder lubrication interfaces as the pistons reciprocate within the cylindrical bores during operation of the positive displacement machine;
• and
• a plurality of circumferential grooves located within the piston-cylinder lubrication interfaces, at least one of the grooves being located on the bore wall of each of the cylindrical bores, the grooves having an opening facing the pistons and in fluidic communication with the piston-cylinder lubrication interfaces so as to contain a portion of the working fluid, wherein the grooves promote hydrostatic balancing of pressure of the working fluid within the piston-cylinder lubrication interfaces and increase a load-carrying capacity of the working fluid within the piston-cylinder lubrication interfaces during operation of the positive displacement machine.