Differential flow hydraulic transmission

A hydraulic transmission comprising:

• a housing, an input shaft and output shaft journaled in the housing for rotation about a common axis of rotation, a pump rotor secured to the input shaft, a motor rotor adjacent the pump rotor, hinge means connecting the motor rotor to the output shaft for providing rotation of the motor rotor and output shaft as a unit about said common axis while allowing the motor rotor to tilt about a hinge axis extending perpendicular to said common axis, the rotor having opposing flat surfaces extending at an acute angle to each other, said surfaces being positioned by said hinge means at a variable angle to said common axis, a plurality of pump cylinders in a pump rotor, a plurality of motor cylinders in the housing, the cylinders extending parallel to said common axis and being arcuately spaced around said common axis, the motor rotor being positioned between one of the ends of the pump cylinder and one of the ends of the motor cylinders, pump and motor piston means slidable in each of the pump and motor cylinders respectively, the pump piston means being in sliding engagement with one of said motor rotor surfaces and the motor piston means being in sliding engagement with the other of said motor rotor surfaces, a rotary valve member positioned between one end of the pump rotor and the housing and rotatable about said common axis, the housing having a fluid passage extending from each motor cylinder opening adjacent one side of the valve member and the pump rotor having a fluid passage from each pump cylinder opening adjacent the opposite side of the rotary valve member, the valve member having a pair of fluid passages, each valve member passage connecting a group of pump cylinder passages to each other and to a group of motor cylinder passages, and means coupling the valve member and the output shaft for rotating the valve member relative to the housing and the pump cylinder in synchronism with rotation of the output shaft, relative rotation between the valve member and the housing switching the motor cylinder passages successively from one group of pump cylinders to the other, and relative rotation between the valve member and the pump rotor switching the pump cylinder passages successively from one group of motor cylinders to the other.