Hydraulic torque amplifier, particularly for steering devices

A hydraulic torque amplifier for steering device or the like, comprising, housing means having interchangeable inlet and outlet ports, input and output shafts rotatably journaled in said housing in a coaxial and axially spaced relation, a planetary piston motor having an externally toothed gear connected to said output shaft and meshing internally toothed gear secured to said housing with movement relative to said housing being limited to orbital and nonrotational motions, the teeth of said gears meshing in sealing engagement to form expanding and contracting cells on opposite sides of the line of eccentricity between said gears, a bore in said housing, said housing having a set of passages with respective communication with said cells and forming a set of circumferentially arranged openings in said bore, and a rotary slide valve arrangement in said bore using said set of bore openings for directing pressurized fluid from said inlet port to said planetary piston motor and exhausting fluid from said motor to said outlet port, said slide valve arrangement having inner and outer sleeves connected respectively to said input and output shafts, said outer sleeve having two sets of alternately arranged commutating passages cooperable with said set of housing bore openings, said inner sleeve having communication with said inlet and outlet ports and being moveable in opposite directions relative to said outer sleeve to selectively connect said inlet and outlet ports to said commutating passages to effect a desired direction of rotation for said output shaft, neutral position spring means between said sleeves for closing said valve arrangement in the absence of torque being applied to said input shaft, and lost motion means between said input and output shaft for limiting relative rotational movement therebetween.