Radial piston hydraulic motor of variable cylinder capacity

A hydraulic motor, comprising:

• a housing;
• a shaft journaled in said housing and rotatable about an axis of rotation, said shaft being formed with an outer peripheral polygonal surface having angularly adjoining portions;
• means in said housing forming a plurality of radial cylinders angularly spaced around said shaft;
• respective drive pistons reciprocatable in said cylinders and having inner ends turned toward said shaft;
• a ring of circular outer periphery surrounding said shaft and interposed between said shaft and said inner ends, said inner ends bearing on said ring, said ring being formed with a central polygonal opening provided with an inner periphery having portions thereof complementary to said portions of said outer peripheral surface of said shaft, said ring being radially displaceable transverse to said axis of rotation, thereby varying an eccentricity of said outer periphery of said ring with respect to said shaft;
• piston means displaceable in said shaft and surrounded by said inner periphery of said opening for displacing said ring radially relative to said shaft to set said eccentricity and thereby vary a capacity of said cylinders;
• and
• controllable locking means releasably securing said ring to said shaft at an eccentricity set by said piston means and disengageable for resetting of said eccentricity, said controllable locking means including elastic means for automatically pressing the inner periphery of said opening against said outer peripheral surface of said shaft to prevent shifting of said ring upon pressure of said drive pistons thereagainst, and hydraulic means for relieving pressing of said inner periphery of said opening against said outer peripheral surface to enable displacement of said ring by said piston means.