GB898330A - A pneumatically-operated free piston engine - Google Patents

Abstract

898,330. Compressed air engines; engine valve gear. GEWERKSCHAFT EISENHUTTE WESTFALIA. Oct. 1, 1958 [Oct. 8, 1957], No. 31372/58. Classes 122 (2) and 122 (3). A pneumatically-operated free piston engine is arranged so that the working air is controlled by a freely-oscillating slide valve 34 which is guided in a bore within the piston 11 and disposed in the direction of oscillation of the latter the distribution of the working air taking place by way of duets provided in the interior of the piston. The piston is mounted in a cylinder 10 and is formed with a larger working piston 12 defining working chambers 14, 15 and two smaller pistons 16, 17 working in cushion chambers 18, 19. The slide valve 34 is mounted in an axial bore in the piston and is formed with an annular groove 35 which, depending upon the position of the valve, allows compressed air to flow to either of the working chambers 14, 15. In operation, with the valve in the position shown, air is fed through an inlet 20, annular chamber 21, ports 22, annular groove 23, ports 24 and annular chamber 25, into the working chamber 15, and air in the chamber 14 is exhausted through an axial bore 30, annular groove 32 and radial bores 33. The piston then moves and accelerates to a midway position until, at this point, air trapped in the cushion chamber 18 begins to retard its movement. The slide valve, due to its kinetic energy, continues to move at the same speed and thereby reverses its position, thus allowing the air to be admitted into the chamber 14; the valve is cushioned at each end of its stroke by rubber or like buffers 36. In order that the valve may be returned to the starting position shown irrespective of when the compressed air supply to the piston is shut off, an auxiliary differential piston 38 is mounted in a cylinder 40, 42 and is connected to the valve by a rod 46 and spring-release coupling 47, 49. At the commencement of a stroke with the valve in the position shown, air which is being fed to the chamber 15 is also fed to the larger end 39 of the auxiliary piston through a port 26 and restricted opening 43 thereby moving the auxiliary piston together with the valve until the latter reaches the end of its stroke; the stroke of the auxiliary piston is greater than the stroke of the valve and thus continues its movement until the spring-release coupling 47, 49 is disconnected. The valve is now free to move, during normal running, under the action of kinetic energy. When the air supply is discontinued, air which has been trapped between the inner side of the piston head 39 and the end of the cylinder 42 expands and moves the piston 38 until the spring-coupling re-engages with the valve and returns the latter to the position shown.