Hydrostatic transmission system

A hydrostatic transmission system comprising a hydraulic circuit consisting of a high-pressure section and a low-pressure section, which together include a free-piston engine having at least two cylinders each having one engine piston to which is connected a pump piston, said engine piston being rigidly connected to said pump piston for the purpose of joint axial motion;

• at least one rotary motor or linear actuator adapted to be driven by the hydraulic fluid pressurized by said piston pumps;
• valve means for directing the hydraulic fluid to and from said motor or actuator;
• means for controlling the operation of said free-piston engine, said controlling means comprising a rotary distributor and a rotary, auxiliary hydraulic motor of the positive displacement type in the low-pressure section of the circuit, said auxiliary hydraulic motor being provided with transmission means for driving said rotary distributor at the number of revolutions governed by the frequency of said free-piston engine, said rotary distributor being provided with ports for alternately connecting each pump cylinder in turn to the high-pressure section and to the low-pressure section of the hydraulic circuit in such an order that each pump is connected to the high-pressure section during at least part of its pumping stroke from the stroke's beginning, and to the low pressure section during the entire length of its return stroke.