Patent ID: 8235680

Claim:
A radial cylinder hydraulic motor having continuously variable displacement capabilities and comprising: oscillating hydraulic cylinders which are driven to oscillate through an eccentric crankpin formed on the motor shaft and carrying a radially movable ring adapted to be shifted along the radial direction of the crankpin by actuation of opposed counteracting hydraulic cylinders housed within the crankpin; a hydraulic control circuit for controlling and adjusting the positions of said counteracting hydraulic cylinders in a continuous manner; an electronic control circuit adapted to control the hydraulic control circuit and process signals from at least one position sensor arranged to detect the positions of said oscillating cylinders; and a rotary joint for hydraulic conduits through which said counteracting hydraulic cylinders are controlled and adjusted; wherein the sensor comprises an angular position sensor placed close to the oscillation axis of at least one oscillating cylinder to measure, based upon changes in the signal, an angular position currently entered by the cylinder liner during the swing; wherein the rotary joint for hydraulic conduits comprises a respective annular groove formed in the inside diameter of a cover of the motor at a location close to a drive pin; wherein each annular groove is communicated hydraulically to a respective conduit and terminated at its pin end with a respective sealing bush which is set in the cover and engaged rotatively by said drive pin, being each formed with an annular groove which is communicated to the corresponding annular groove in the cover; and wherein the respective sealing bush comprises a side seal, and the drive pin comprises a radial communication hole in communication with the hydraulic feed conduits.