Patent GB-164041-A (GB)
Title: Improvements in and connected with brakes operated by fluid pressure
IPC: B60T15/18
Filed: 1919-11-29
Abstract: 164,041. Drolshammer, I. O. G. Nov. 29, 1919. Fluid pressure. - The brake cylinder supply and exhaust valve is controlled by the brake cylinder pressure acting against a spring, the loading of which is determined by the position of a piston subject to train-pipe or other controlling fluid-pressure or to electromagnetic action opposed to a second spring. The valve may have means for locally venting the train-pipe and for limiting the braking pressure according to the load. Cocks for applying the brakes from a car and for cutting out the brakes on a car may be provided. Figs. 1 and 3 shows the application to a compressedair two-chamber or differential system. The reservoir B and brake cylinder chamber C<2> is connected to the train-pipe E through the non-return valve V, the chamber C' being connected to the control valve D which also is connected to the train-pipe at e, E<2> through the normally open cocks H<1>, H<2>. The control valve comprises a spring f<2> abutting against the valve casing and a head X which contacts with a piston K subject to the trainpipe pressure in the pipe E<2>. A second spring f<1> is interposed between the head X and a piston slide valve s subject also to the pressure in the brake cylinder chamber C<1> by the connection g. A piston c on the rod d serves to counterbalance the brake-cylinder pressure transmitted by the spring f<1> to the pistons K, X. The parts are shown in Fig. 3 in the application position in which the chamber C' is open to the atmosphere by the passages b, grooves h, and port i. If the train-pipe pressure is increased, the pistons K, X compress the spring f<2> and the valve s is moved by the spring f<1> to cut off the grooves h and uncover the train-pipe port e so that air flows into the chamber C<1> until the pressure therein is sufficient to return the valve to the lap position. By grading the train-pipe pressure up or down the pressure in the chamber C' may be correspondingly varied. Leakage from the chamber C<1> is automatically compensated by the valve and as the train-pipe pressure reduction to effect braking may be small the pressure in the chamber C<2> and reservoir B will also be maintained sufficiently high against leakage for efficient braking. To accelerate the pressure reduction along the train-pipe, the space to the left of the piston K may be vented to a space R, Fig. 4, through a passage O in an application of the brakes; the volume of this space may correspond to the volume of air which would otherwise be returned to the train-pipe by the displacement of the piston. The space R is normally open to atmosphere by the port r. To limit the maximum braking pressure on a car, stops of varying thickness carried by an arm m may be interposed between a collar t on the valve-rod d and the valve casing. Further reduction of the trainpipe pressure beyond that which corresponds to the position of the valve d and head X defined by the stop thus does not affect the pressure in the chamber C<1>. The arm m can be automatically operated according to the load by the movement of the car body on the bearing springs. A cock with ports of different sizes may be interposed between the brake cylinder and the control valve, and be adjusted simultaneously with the stop so as to vary the rate of increase of the braking pressure as well as its maximum value. For applying the brake in emergency, from the car, the cock H<2>, Figs. 1 and 6, may be turned to connect the pipe E<2> to atmosphere past the spring-loaded valve V<2> which limits the pressure reduction. To cut out the brakes on a car, the cock H<1> is turned to close the train-pipe connection and to connect the ports u, y thereby allowing the air to escape from the cylinder and reservoir. For a single chamber brake the spring f<2> is disposed between the head X and the left-hand end of the casing and the train-pipe pressure acts against the piston c. If an auxiliary reservoir is used, it is connected at e but the brake cylinder may be supplied by the train-pipe alone which is then connected at e. The valve may also be adapted for systems in which the braking action is obtained by increasing the pressure on the control piston. A solenoid may be arranged to act upon the rod d to effect electric control of the valve with or without pneumatic control.