GB274166A - Improvements in fluid pressure engines for operating railway carriage doors and for other purposes - Google Patents

Abstract

274,166. Rowntree, H. April 7, 1926. Checks; operating and controlling doors &c. by treadles, pneumatically and electrically. - A differential fluid-pressure engine for operating doors &c. comprises interconnected piston faces of different areas and a check valve or cushioning device carried by and movable in relation to the piston for controlling the pressure in the cylinder or part of the cylinder adjacent to the larger face. Fig. 1 shows a piston 8 provided with a large hollow rod 5 giving a difference of the areas subject to fluid pressure on the two sides. The head of the cylinder is provided with a liner 13 leading to a passage 14 connected with an opening 15 controlled by a plug 16 and connected to a pipe supplying pressure or exhaust. A similar outlet at the other end of the cylinder is controlled by a screw 19<1>. The hollow piston rod 5 contains a sliding member 10 pressed outwards by a spring and carrying a washer adapted to engage the liner 13. The ends of the cylinder are connected by piping to a three-way valve by which pressure fluid may be supplied to both ends, or to the right-hand end only, the left-hand end being open to exhaust. When pressure is supplied to both ends, the piston moves to the right under the influence of fluid entering by the passage 18<1> only, the passage through the liner 13 remaining closed until the spring 11 reaches its equilibrium position. The door connected to the hollow piston is opened, an adjustable cushioning being effected by the screw 19'. If the valve is rotated to open the left hand of the piston to exhaust, the piston moves rapidly to the left until the washer on the extension 10 closes the liner 13, after which the fluid escapes only through the passage 18<1>, with a cushioning effect. In a modification, the liner 13 may be replaced by a counter-sunk plug with a small hole controlled by a needle valve, while at the other end the fluid flows through a ball valve provided with speed plugs 89, 90, Fig. 8, which allow a greater flow in one direction, viz. through both plugs when the ball is lifted, than in the other and thus provide a cushion. The cushioning is effected in this manner at the end of each stroke in the apparatus shown in Fig. 8; the plunger 96 in the hollow piston rod, and is formed with a valve face which is pressed by the spring against the inner face of the hollow rod. During the exhaust stroke at the left-hand end, the rod moves rapidly until the plunger strikes the cylinder end and opens the valve, when the sudden outflow of compressed fluid within the rod cushions the end of the stroke. An electromagnetic valve may replace the handoperated valve by which the supply of fluid to the ends of the cylinder is controlled. Fig. 13 shows a further modification, in which two unequal pistons are connected, replacing the single piston with unequal faces. A check valve 127 is pressed on to its seat by a spring, and connected to an abutment within the hollow piston rod engaging the end of the rod in the right-hand positions of the pistons; the valve thus closes with a cushioning effect as the piston moves to the left.