GB671470A - Improvements in or relating to compressed air operated piston apparatus - Google Patents

Abstract

671,470. Operating railway points. STRUNK, G. March 27, 1950. [March 25, 1949] No. 8236/49. Class 104 (i). [Also in Groups XXVIII and XXIX] In a compressed air actuated single-stroke piston and cylinder assembly suitable for switching rail points wherein the stroke is effected by alternately venting chambers 5, 4, Fig. 1a, on either side of the piston 2 through ducts 10, 12 controlled by a valve 14 and ducts 11, 13 controlled by a valve 15, the chambers 5, 4 are connected symmetrically through further ducts 18, 19 to a flutter valve 16 which allows access of compressed air to vent ducts 11, 13 for the time being closed but denies it to the temporarily open vent ducts 10, 12 ; or conversely to open air exhaust to atmosphere for the valve-controlled pipe for the time being open and to close said exhaust to the valvecontrolled pipe for the time being closed. In operation and on opening say valve 15 the resulting air flow in the flutter valve housing 6 causes the valve 16 which may be of the ball spring-biassed disc or plunger type to seat in the position shown and thus allow access of pressure air to the chamber 5. On closing valve 15.and opening valve 14 the ball 16 assumes its opposite seat to allow air to flow to the chamber 4 to effect the return stroke. In a modification, the vent valves 14, 15 are replaced by a single vent port 26, Figs. 1a and 1b, controlled by a differential piston 42, 45 itself controlled by a single relief valve 49 which when opened releases pressure from below the piston 45 to allow a wedge 52 to hold an auxiliary valve 25 seated against an extension 22, or 23 of the ducts 10, 11 respectively and thereby exhausts one or other of them to the port 26 now uncovered by the piston 42. In a further modification, the chamber 5, Fig. 9, is first vented through a chamber 17 of a control cylinder 86 to the open valve 14, and the flutter valve 16 allows access of air to a chamber 17a to displace the control piston 8 and supply compressed air to the working chamber 4 and simultaneously connect the chamber 5 to a vent 9. The valves 14, 15 are controlled by a hand striking lever 61, Fig. 6, acting alternately on valve plungers 14a, 15a through an eccentric 65 and a rocking lever 66 mounted on the rod 68 of a piston 69 normally held in its right-hand position by a spring 71. The valve 15 can be opened only when the piston 69 is subjected to pressure in the chamber 4, and the lever 61 is in its neutral position thus allowing displacement of the piston rod 68 and lever 66 beyond a stop. In a further modification which corresponds with the construction described with reference to Figs. 1a, 1b, reversal takes place by compression and not by venting of one of the pipes leading to the working piston.