Free-piston motor with hydraulic or pneumatic energy transmission

Apparatus for driving a member, such as a wheel, pulley, rod or similar member, comprising at least one rotary or linear motor which is coupled to said member and which is driven by a pressurized fluid, particularly a hydraulic motor or similar hydraulic apparatus, which on one side is in communication via a pipe with at least one accumulator for a pressurized fluid, particularly a liquid, and on the other side with an outlet leading to a reservoir for said liquid, and further comprising at least one free-piston unit consisting of a cylinder with at least one free piston which is slidable to-and-fro therein and which delimits a space within the cylinder in such a manner that on the expansion stroke of the piston, during which the latter is displaced in the other direction, the volume of the space is increased while on the compression stroke of the piston, during which the latter is displaced in the one direction, the volume of the space is reduced, while means are provided for the admission and discharge of a gas into and out of said space respectively, together with means for heating the gas compressed in said space by the compression stroke of the piston, the latter being connected to a member of general plunger-like shape which is adapted to slide to-and-fro inside at least one stationarily mounted chamber member, at least two parts of different diameters of the periphery of the plunger-shaped member making sliding fits with parts of the inside wall of the chamber member, while the plunger-shaped member has three substantially radial surfaces each of which delimits within the chamber member a substantially closed chamber whose capacity gradually varies as the piston makes its expansion and compression strokes, of which surfaces a first radial surface delimits a first or plunger chamber which is in communication with a source of pressurized fluid, and a second radial surface delimits a second or displacement chamber which is in communication via a nonreturn valve with the reservoir and is connected via a second nonreturn valve to the accumulator, so that during the stroke of the piston whereby the capacity of the second chamber is increased liquid is drawn out of the reservoir into this chamber and during the other, opposite stroke of the piston whereby the capacity of the second chamber is reduced this liquid is forced out of said chamber in order to load the accumulator, and the third radial surface has a smaller operative area than the first radial surface and delimits substantially inside the chamber member a third chamber, while its capacity increases and decreases respectively during the expansion and compression strokes of the piston, characterized in that the first or plunger-chamber is in communication with said source of pressurized fluid through an operable valve member so that by opening said valve member the piston makes it compression stroke and the third chamber is solely in open communication with said accumulator.