GB316599A - Improvements in compressed air brakes - Google Patents

Abstract

316,599. Anderberg, A., and Anderberg, E. A. April 30, 1928. Fluid-pressure.-An accelerator for compressed air brakes comprises a movable control member actuated by train pipe pressure. and arranged in a chamber having a movable wall which is moved by means combined with the central member to increase the volume of the chamber in a certain proportion to the decrease thereof due to the movement of the control member caused by the fall of train pipe pressure. The stroke volume of the control member or triple valve piston 1, Fig. 2, is thus not returned to the train pipe but is eliminated by the movement of the movable wall or piston 9<a>. The invention also comprises an arrangement for accelerating the action of a two chamber compressed air brake so as quickly to advance the brake shoes to the wheels in which the function chamber is connected to the train pipe by a connection having a valve adapted to connect the function chamber with the atmosphere on a small train pipe pressure fall. The two chamber brake may be that described in Specification 275,401. The triple valve piston 1, Fig. 1, carries a head 5 and packing 6 which on movement of the piston to brake application position closes an opening in a spring-pressed sleeve valve 9 and moves the latter to cause ports 24, 25 to register and vent the interior of the slide valve to atmosphere. The space above the smaller piston 10 of a differential piston 10, 11 is thus also vented through a port 12 and ports 24, 25 and the differential piston moves upwards to raise by means of a head 19 a spring-pressed valve 17 sliding in the piston to open a port 16 and vent to atmosphere the space below the larger piston 11 and thus also the function chamber of the two chamber brake connected by pipe 14 to this space. The pressure in the train-pipe 4 acts on an annular surface between the pistons 10, 11 through a pipe 13. The valve 17 will be reclosed when the pressure in the function chamber of the two chamber brake has been reduced in proportion to the difference in size of the opposite faces of the piston 11. Release of the brakes causes the piston 1 and the sleeve valve 9 to rise and close ports 24, 25, the valve 9 is then stopped by a collar 23, and the valve 6 opens and admits train pipe pressure to the interior of valve 9 and the space above the piston 10 which is depressed and allows train pipe air to feed to the brake function chamber by feed grooves 21 from the pipe 13. In Fig. 2 the sleeve valve 9 is modified to form the movable wall or piston 9<a> having a stroke volume equal to or slightly greater than that of the piston 1. Different means are provided for permitting the stroke volume of the piston 9<a> to escape to the atmosphere., comprising a valve 26 connected to the piston 9<a>, which opens to the atmosphere by a channel 27 after the valve 6 is closed. An exchangeable nozzle 28 is provided at the end of the channel 27 to regulate the rapidity of escape of air. The valve 6 is connected by pin-and-slot to the piston 1 and is spring-pressed. A channel 29 connects the space below the piston 9<a> with the space above the piston 10. The differential piston 10, 11 is acted on by a return spring 30 which may be varied in dimension so that the differential piston may be set in action for different decreases in train pipe pressure. Equations are given for calculating the strength of this spring and the areas of the differential pistons. A cock V is provided, adapted to assume three positions : I (that shown) in which the apparatus operates as described above; II in which the brake is entirely out of action and III in which the device according to the invention is out of action and the triple valve acts as usual in connection with two-chamber brakes. The pipes a, b, 14<1> areconnected respectively to the auxiliary reservoir, the single-chamber cylinder and the function chamber of the two-chamber cylinder.