GB411559A - Improvements relating to fluid pressure engines for operating railway or other vehicle doors or for similar purposes - Google Patents

Abstract

411,559. Door - operating engines. PETERS & CO., Ltd., G. D., and ARTHURTON, R. I. D., Windsor Works, Slough, Buckinghamshire. Dec. 19, 1932, No. 35986. [Class 65 (i).] In a fluid-pressure engine of the differential piston type, for operating vehicle doors or similar purposes, the pipe which supplies fluid under pressure to the larger pressure area of the piston arrangement also supplies a reservoir through a non-return valve so long as the pressure in the reservoir is less than the supply pressure, and the arrangement is such that when the engine is being driven in one direction by pressure fluid acting on the larger piston area the air displaced by the smaller piston area is compressed into the reservoir to provide a supply of fluid at relatively high pressure which acts on the smaller piston area to produce the return stroke of the engine when the larger piston area is placed to exhaust. The reservoir may be connected with the smaller piston area through a non-return valve, a separate small port being provided for the passage of air into the reservoir when compressed by the smaller piston area. The engine may have two pistons of different sizes, or a single trunk piston, the smaller pressure area in the latter case being constituted either by the end of the trunk or by the annulus between trunk and cylinder. The reservoir may be entirely separate from the cylinder, or may be formed by a continuation of the smaller cylinder separated therefrom by a diaphragm; it may also be formed integral with the cylinder as an annulus or jacket around the cylinder. Where a trunk piston is used the reservoir may be provided in the trunk. The doors are preferably driven through a sector gear engaging a rack on the rod connecting two pistons or, in the case of a trunk piston with the annulus forming the smaller piston area, on an extension of the trunk. The Figure shows an engine of the type having two pistons 14, 13 connected by a rack rod 24 engaging a sector gear 28 on a door shaft 30, with the reservoir 12 surrounding the cylinder. The air inlet pipe to the large end of the cylinder is connected through a non-return valve 10 with the reservoir 12, and the reservoir is connected with the small end of the cylinder through a non-return valve 11 and a small inlet passage 20.