GB247535A - Improvements in or relating to fluid pressure brake apparatus for railway vehicles - Google Patents

Abstract

247,535. Hildebrand, W. Feb. 13, 1925, [Convention date]. Fluid-pressure.-In brake apparatus comprising an accelerator valve associated with each triple or equivalent control valve and adapted to vent the train-pipe to a chamber in an application of the brakes so as to prevent the air displaced by the piston of the control valve from being delivered into the train-pipe, means are provided for ensuring the movement of the accelerator valve to operative position before that of the control valve. According to Fig. 1, the apparatus comprises a control valve S and an accelerator valve B connected to the train-pipe at L. The accelerator valve has a short stroke and small frictional resistance so as to be sensitive and comprises a piston q subject on one side to train-pipe pressure and on the other side to that in the auxiliary reservoir H through the pipe e and actuating a pair of slides valves a, b<1>. The valve a is adapted to vent the train-pipe side of the piston q to the chamber U. The control valve S comprises the usual piston k subject to opposing train-pipe and auxiliary reservoir pressures and actuating main and subsidiary slide valves g, s<1> controlling the brake cylinder connection c and normally venting the chamber U to atmosphere by a restricted passage h<1> and a port m. The piston rod of the valve S carries a counter-piston v one face. of which is normally exposed to atmospheric pressure by way of pipe c<1>, valve b<1>, and port i. Upon a slight reduction of train-pipe pressure to effect an application of the brakes, the piston q and valves a, b<1> are immediately moved to close the exhaust port i and to open the pipe l<1>leading to the chamber U, but the movement of the control valve piston k is delayed by reason of the auxiliary reservoir pressure acting on the counterpiston v. The provision of the restricted passage h<1> prevents any considerable escape of air from the chamber U from taking place before closure of the port in by a valve. g. The counter-piston v and valve b<1> may be dispensed with and the smaller resistance to movement of the accelerator valve B compared with that of the control valve S be relied upon to ensure the movement of the one valve before that of the other. In this case, the resistance to movement of the accelerator valve may be further reduced by the substitution of a flap valve for the valve a. According to the Specification as open to inspection under Sect. 91 (3) (a), the invention may be applied to vacuum brakes. This subjectmatter does not appear in the Specification as accepted.