GB1135572A - Hydraulic devices for retarding of wheeled vehicles - Google Patents

Abstract

1,135,572. Track brakes. DOWTY MINING EQUIPMENT Ltd. 22 July, 1966 [30 July, 1965], No. 32684/65. Heading F2E. In a telescopic hydraulic retarder device for fixing adjacent a track including a piston 12, which is depressible by the wheels of a passing rail vehicle into a fixed cylinder 11 and forms a variable volume hydraulic chamber 14 therewith, and a pressure responsive valve 24 dis posed between said chamber and a lower pressure outlet 15, which valve re mains open when the pis ton is depressed by vehides running at low speeds but closes under the pressure differential developed across it when the piston is depressed by vehicles exceeding a predetermined speed whereupon flow takes place through a high pressure valve 31, said valve 24 comprises a valve housing formed by larger and smaller coaxial bores 17 and 18 in the piston walls and a movable annular valve member 24, which is urged to the open position shown by a spring 34 and has a flange 25 engageable with the smaller bore to close communication between the chamber 14 and fluid outlet 15. A high pressure piston relief valve 31 is contained by the annular valve member and is spring-urged with the latter against a stop 37. On depression of the piston by a vehicle wheel moving below a predetermined speed, flow from chamber 14 takes place past flange 25 and ports 23 to outlet 15. On depression of the piston by a vehicle wheel moving in excess of said predetermined speed, the pressure drop across the valve causes the flange 25 to move into the bore 18 to close off chamber 14 from the outlet. Further discharge of fluid may then take place through piston valve 31 which is lifted by fluid pressure.