Patent GB-679937-A (GB)
Title: Improvements in or relating to fluid actuated slide valves for double acting piston engines
IPC: F01L5/00
Filed: 1950-02-10
Abstract: 679,937. Engine valve-gear. FOLKIEN, F. Feb. 10, 1950, No. 3449/50. Classes 122(i) and 122(ii) A rodless slide valve for double-acting piston engines comprises a main slide valve d<SP>1</SP> having piston portions e<SP>1</SP>, e<SP>2</SP> of different diameters which are slidably mounted respectively within a first main actuating chamber A and a second main actuating chamber B, and an auxiliary slide valve d<SP>2</SP> associated with said main slide valve and moveable independently thereof, said actuating chambers being adapted to be connected to the working cylinder a of an engine in such manner that movement of the working piston b to the limit of its stroke in one direction permits elastic fluid from the working cylinder to pass to the second main actuating chamber to effect relative movement between the main and auxiliary slide valves to connect the second main actuating chamber to a main source of elastic fluid supply to cause continued movement of the main slide valve, said continued movement as the main slide valve approaches the limit of its stroke resulting in the connection of the second main actuating chamber to atmosphere to permit operation of the auxiliary slide valve to cut off the supply of pressure fluid to the second main actuating chamber; movement of the working piston to the limit of its stroke in the opposite direction permitting pressure fluid from the working cylinder to pass to said first main actuating chamber A to effect initial movement of the main and auxiliary slide valves in the opposite direction. The main valve d<SP>1</SP> is connected to the auxiliary valve d<SP>2</SP> through a bolt h engaging in a recess t. Steam is supplied through a port DE and is distributed to the upper end of the engine cylinder a through valve chamber r<SP>1</SP> and duct o<SP>1</SP> and to the lower end thereof through bore o, port o<SP>2</SP> and duct a<SP>2</SP>. The steam is exhausted through port DA. During its upward movement, the piston b passes o v e rand uncovers a passage 1 and steam from the cylinder flows through the passage and bores 7 into the upper valve actuating chamber A. The main valve moves downwards and when the collar e<SP>1</SP> passes over base 4a, line steam from the inlet flows through bores 4a, 7, to the first actuating chamber to assist the valve movement and to hold it in its lower position. Movement of the valve in the upward direction takes places when piston b passes over and uncovers a passage 2 through which steam flows through a chamber m<SP>2</SP> and bore 9 in the auxiliary valve to the second actuating chamber B. The main valve moves upwards and separates from the auxiliary valve thereby opening a bore 8 through which live steam from the inlet passes into chamber B to assist the valve movement. An actuating collar e<SP>2</SP> on the main valve then uncovers a bore 6a and steam passes from the cylinder to further assist the valve movement until a distributing collar f<SP>1</SP> uncovers a port p' and opens the upper end of the cylinder together with the chamber B to exhaust. The exhaust from chamber B is assisted by a duct 5 which then communicates with the exhaust port D A. Duct a<SP>2</SP>, being then open to live steam, has a duct 3 communicating with the auxiliary valve chamber C and the steam passing to the latter raises the auxiliary valve until it again abuts the main valve and holds it in its upper position. Condensate in the cylinder may be removed by a ram l which has grooves 10, 11 opening to atmosphere. The ram holds the valves in their upper position. Other embodiments are described in which the slide valve controls tandem and parallel cylinder compound engines.