Long-piston hydraulic machines

In a hydraulic machine having a plurality of pistons reciprocally mounted in respective cylinders formed in a cylinder block and positioned circumferentially at a first radial distance about the rotational axis of a drive element, each said piston having a body portion and a head end and each respective cylinder having a valve end and an open head portion beyond which said head end of each said piston extends at all times, and said pistons also having a stroke varying up to a predetermined maximum, the improvement comprising:

• a respective lubricating channel formed in the cylindrical wall of each said cylinder in said cylinder block;
• all of said lubricating channels being interconnected to form a continuous lubricating passageway in said cylinder block;
• and
• each said respective lubricating channel being substantially closed by the axial cylindrical body of each respective piston during the entire stroke of each said piston, thereby substantially closing said continuous lubricating passageway at all times so that the only source of lubricating fluid supplying said continuous lubricating passageway is a minimal flow of fluid between each said respective cylindrical wall of each said cylinder and said axial cylindrical body of each respective piston.