Feedback-type oil-hydraulic drive

Claim 1

AN ELECTROHYDRAULIC DRIVE FOR CONVERTING PULSED DIGITAL COMMAND DATA INTO HYDRAULIC POWER, COMPRISING HYDRAULIC PRESSURE FLUID SUPPLY MEANS, A HYDRAULIC ROTARY POWER MOTOR HAVING HYDRAULIC PRESSURE CONDUIT MEANS, AN ELECTRIC-PULSE OPERATED STEPPING MOTOR HAVING A ROTATABLE MEMBER, MEANS FOR CONNECTING SAID STEPPING MOTOR TO A SOURCE OF INCREMENTAL PULSE DATA, SAID STEPPING MOTOR BEING CAPABLE OF TRANSLATING SAID PULSE DATA INTO PREDETERMINED ANGULAR DISPLACEMENT OF SAID ROTATABLE MEMBER, A FLUID PRESSURE CONTROL DEVICE CONNECTING SAID SUPPLY MEANS WITH SAID PRESSURE CONDUIT MEANS, SAID CONTROL DEVICE HAVING TWO CONCENTRIC AND COAXIALLY ROTATABLE CONTROL STRUCTURES OF WHICH ONE IS JOINED WITH SAID MEMBER OF SAID STEPPING MOTOR TO ROTATE TOGETHER THEREWITH AND THE OTHER IS JOINED WITH SAID POWER MOTOR TO ROTATE TOGETHER THEREWITH, SAID TWO CONTROL STRUCTURES HAVING RESPECTIVE CONTACT SURFACES IN GLIDING ENGAGEMENT WITH EACH OTHER, EACH OF SAID TWO STRUCTURES HAVING CONDUIT MEANS FORMING PORTS LOCATED IN THE CONTACT SURFACE AND REGISTRABLE WITH THE PORTS OF THE OTHER STRUCTURE TO A VARIABLE DEGREE DEPENDING UPON THE DEPARTURE OF SAID TWO STRUCTURES FROM A GIVEN ANGULAR POSITION RELATIVE TO EACH OTHER, WHEREBY THE FLOW OF PRESSURE FLUID TO SAID POWER MOTOR IS METERED BY SAID STEPPING MOTOR TO OPERATE SAID POWER MOTOR AT THE ROTATING SPEED OF SAID PILOT MOTOR.