GB901244A - Improvements in or relating to hydraulic actuating mechanism - Google Patents

Abstract

901,244. Fluid-pressure brakes. PLESSEY CO. Ltd. March 17, 1960 [May 12, 1959], No. 16183/59. Class 103 (1). [Also in Groups XXIV, XXIX and XXXI] Hydraulic actuating mechanism has a cylinder 5 with a main piston 2 connected to an auxiliary piston 4 which limits the forward stroke of piston 2, whereby piston 4 participates in any excess of return stroke of piston 2 beyond a predetermined length, and a non- return valve 12, 14 supplying liquid to take-up the space vacated by movement of piston 4 with piston 2 but preventing escape of liquid during reverse movement of piston 4. Counterclockwise rotation of lever 15 operates valve 19 to stop the flow of pressure fluid from port 16 to port 21 and connects port 16 to chamber 5 via port 17, the pressure moving piston 2 to the right to release a clutch which is completely released when piston 2 abuts piston 4, fluid displaced by piston 2 passes to port 21 via port 18. On clutch engagement, clutch springs move piston 2 to the left and on wear of the clutch linings, a stop ring 7 in piston bore 8 engages a circlip 10 on piston 4 to move piston 4 with piston 2 until the clutch is fully engaged. The engagement of pistons 2 and 4 pressurizes the liquid in chamber 11 which acts via line 22 to move a piston 23 in brake cylinder b to apply the brakes; on re-engagement of the clutch, brake release springs move piston 23 until shoulder 29 engages piston 25 which is held fixed by liquid behind it; a circlip 26 moves piston 25 with piston 23 in the brakeapplying direction when the brake linings have worn, fluid being admitted to behind piston 25 via non-return valve 28. A re-setting valve 37 enables liquid to be removed from behind piston 25 for re-setting purposes. Pressure created in chamber 5 on clutch release acts via line 31 on plunger 32 to set an engine throttle to an idle position which is adjustable by a screw head 34.