GB1174247A - Fluid Pressure Operated Braking Apparatus - Google Patents

Abstract

1,174,247. Fluid-pressure brakes. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd. 6 Dec., 1966 [21 Dec., 1965; 29 April, 1966; 18 May, 1966; 27 May, 1966; 8 July, 1966; 15 July, 1966; 20 July, 1966], Nos. 10038/69, 10039/69, 10040/69, 10041/69, 10042/69, 10043/69 and 10044/69. Divided out of 1,174,243. Heading F2F. In a fluid-pressure operated braking apparatus an electro-pneumatic conversion device 9, 14, 15 is provided for converting an electric current, the magnitude of which is variable to indicate a desired degree of braking, into an appropriate fluid-pressure and means for applying the fluid-pressure to a fluid-pressure-responsive braking means. In the diagrammatic arrangement as shown in Fig. 1 the braking apparatus employed on a railway vehicle is driven from an A.C. traction supply and this supply is made available, not only for traction purposes but also, for the operation of the braking apparatus. The alternating current is made available at input terminals 1 and 2 of the apparatus to a voltage stabilizing circuit 3 and thence to a variable ratio transformer 4 under the control of a brake control handle 7 and thence to a unitary power factor Boucherot circuit 5 to bridge rectifiers 8, 12, 13 on each of the coaches so that their D.C. outputs are connected to the operating coils of electropneumatic conversion devices 9, 14, 15 which operate to apply the brakes on each vehicle of the train. Fig. 2 shows an alternative circuit arrangement in which the brake control handle 7 controls a rheostat 22 fed by D.C. supply which acts to control a transductor 21 fed with an A.C. supply, the remainder of the circuit being as in Fig. 1. Fig. 3 shows the braking circuit of the vehicle incorporating a load measuring means 23 which permits measurement of the load on the vehicle by a pressure transducer from the air suspension 11 of a vehicle bogie, the signal being fed into a blending box 27 which controls an electro-pneumatic converter 7 to allow pneumatic pressure from a supply reservoir 4 to flow via the converter 7 and a relay valve 20 to the brake cylinders 14 of the vehicle. The reservoir 4 is charged to a predetermined value from the main reservoir train pipe 1 and train wires 2 and 3 apply to the blending box 27 an alternating current signal dependent upon the setting of the control means. A limiting valve 30 may be inserted in the line leading to the electro-pneumatic converter 7 to limit the maximum value of the supply pressure thereto. The limiting valve 30 is such that, for any degree of loading of the vehicle, the maximum value of the supply pressure is just in excess of that which is required for obtaining a maximum degree of operation of the breaking means under the condition of loading. In alternative embodiments (not shown) the conversion device includes a limiting valve having a fast blowdown facility and being able to provide wheel slip control. Where dynamic braking is provided in addition to a system such as described in any of the above embodiments the blending box 27 is provided with electrical circuit means responsive to an output signal derived from the dynamic braking part of the vehicle's equipment which is also responsive to the signal in the wires 2, 3. By this means the pneumatic braking is operated to make up the deficiency in the dynamic braking when necessary.