GB706235A - Improvements in or relating to braking means for railway wagons and the like adaptedto be controlled according to varying conditions of loading - Google Patents

Abstract

706,235. Fluid pressure railway brakes. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. March 31, 1952 [April 10, 1951], No. 8112/52. Class 103(1) A variable load braking apparatus for vacuum operated braking systems for railway vehicles comprises a variable leverage mechanism which, upon an increase in pressure in the train pipe, brings about a local admission of air to a brake operating cylinder at a pressure determined by the load carried by the vehicle. The valve mechanism comprises a casing 1 subdivided internally into three main compartments by resilient diaphragms 2 and 3 acting upon a lever 12 to control the operation of a spring controlled valve 10 which governs the entry of atmospheric air through port 11. Compartment 4 is in open communication with the train pipe through passage 5. Compartment 6 is in open communication with the upper chamber of the brake cylinder. Compartment 7 is in open communication through passage 8 with the lower chamber of the brake cylinder and also communicates through a non-return valve 9 with the train pipe compartment 4. Control lever 12 is provided with a fulcrum 13 mounted on a sliding member 14 engaging an arm 18 mounted on a short shaft 19 which extends through a packed gland in the wall of the casing 1. Damping arrangements prevent transient vibrations of the vehicle spring deflection from being transmitted to the mechanism for adjusting the fulcrum 13 so that this adjustment is controlled solely by the vehicle load. The shaft 19 is coupled to one end of a lever 22 by a screw threaded arm 23, the opposite end of the lever 22 being secured to a dashpot device 26 secured to the casing 1. One end of an arm 29 is pivotally mounted on a support 30 secured to a casing 1, the arm 29 being coupled at an intermediate point to a spring strut device 31. The opposite end of the arm 29 is pivotally connected to an adjustable head 32 arranged to rest on the bogie of the vehicle, a compression spring 33 being interposed between the head 32 and an abutment 34, secured to the body of the vehicle. By this means only sustained variations of load, affect the position of the fulcrum 13 along lever 12. A relief valve 43 is provided, which when opened establishes communication between the upper and lower brake cylinder chambers, thereby reducing the degree of brake application. The spring-loaded relief valve 43 controls communication between a compartment 44 connected by passage 45 with the passage 8 leading to the lower brake cylinder chamber and is operated through a flexible diaphragm separating compartments 6 and 44 by the lever 49 driven by a cam 57 fixed to a shaft 19, when a sustained variation of load takes place. Preferably the vehicle is provided with two brake cylinders; one for effecting braking in accordance with the tare weight, the other being provided with the invention to effect braking in accordance with the loading of the vehicle.