Patent GB-190722124-A (GB)
Title: Improvements relating to Fluid Pressure Brakes for Railway and like Vehicles.
Filed: 1907-10-07
Granted: 1908-04-23
Abstract: 22,124. Westinghouse Brake Co., [Westinghouse Air Brake Co.]. Oct. 7. Brakes ; sanding rails.-In fluidpressure brakes for railway vehicles, a double brake cylinder or two brake cylinders are employed, and one cylinder or the smaller part of the double cylinder, is used in service applications as a straight - air system with, in one arrangement, electrically-controlled valves, and both cylinders are used in automatic or emergency applications. Means are provided for reducing the brake-cylinder pressure as the speed decreases after emergency applications, and for automatically sanding the rails during emergency applications only. The double brake cylinder 14, Fig. 2, has two pistons, the smaller 34 of which moves in the stem 35 of the larger piston 33. In service applications, air passes from the compressed-air reservoir on each car along a pipe 11, through a valve 20 and pipe 12, and enters the smaller cylinder only through an opening 37 in the piston 33. The valve 20 is mounted on a piston 21, and is normally closed by a spring 23 as the fluid pressures on both sides are equalized through a small hole in the piston. A channel 25 leads from the upper side of the piston to a chamber containing a valve 27, which normally closes the passage 26 leading to the brake cylinder or to exhaust. When the valve 27 is opened by passing a current through the solenoid 9, the pressure at the top of the piston 21 falls, and the valve 20 is opened by the reservoir pressure, which then passes to the brake cylinder. The brakes are released by energizing a solenoid 10, which opens a valve 28 and connects the brake cylinder port 22 to atmosphere at 29. The continuous train-pipe 16 is provided with an ordinary Westinghouse quickacting triple valve 15, and when a reduction of train-pipe pressure occurs the reservoir pipe 13 is placed in communication with the port 32 leading to the larger piston 33, so that increased braking pressure is obtained. A blow-down valve 30 is in communication with the port 32 and serves to limit the brake-cylinder pressure. The valve 30 is kept seated by a spring 39 and a solenoid 18 which is energized by a current from a generator 19, Fig. 3, driven from the wheel axle. As the strength of the solenoid decreases with .the speed of the vehicle, the brake-cylinder pressure also decreases as the vehicle comes to rest. Instead of the valve 15, an electrically-controlled valve 58, Figs. 3 and 4, having a slide valve 41, may be used to control the supply of air from the auxiliary reservoir pipe 13 to the large brake cylinder pipe 32 in emergency applications. The valve 41 is carried by a piston 42 and is pushed to the right by a spring 45, the pressures on both sides of the piston being balanced by leakage. The outlet from the chamber 44 is normally closed by a valve 47, and a diaphragm 49 is provided with a pin which opens the valve 47 when the diaphragm is moved towards it. The diaphragm is secured to the armature of a solenoid 50, which is in circuit with leads 53, 54 running through the train and constantly supplied with current. The strength of the solenoid 50 is sufficient to hold the diaphragm armature against the action of a second solenoid 51, arranged in the circuit of the generator 19, and a spring 52. When the train divides or the circuit is broken by opening a switch 56, the solenoid 50 is de-energized and the valve 47 is lifted by the spring 52 so that the air in the chamber 44 is released and the piston 41 moves the slide valve to open the emergency brake-cylinder port 32 to the reservoir pipe 13. The valve 47 is closed by the brake-cylinder pressure acting on the diaphragm 49 ; but this is opposed, if the speed is great, by the action of the solenoid 51 which tends to keep the valve open. In another arrangement in which straight and automatic systems are used, the reservoir 5, Fig. 6, on each car communicates by a pipe 4 with the driver's valve 3, and feeds the automatic train-pipe 16 through the port 60. The straight-air train-pipe 2 is normally open to atmosphere through a cavity 73 in the valve and a port 61, and in service applications the air passes from the pipe 4 through a port in the drivers' valve to the train-pipe 2, and thence through a cavity 65 in a slide valve 64 and a passage 66 to the small brake cylinder. The valve 64 is carried by a piston 63 which communicates on one side with the trainpipe 16 and on the other side with the brake reservoir 5. When the train divides or an emergency valve is opened, the piston moves the valve 64 to the right, opens a port 68, leading to the large brake cylinder, to the reservoir 5, and closes the port 66. In the arrangement shown in Fig. 7, two separate brake cylinders are used, and the slide valve 64 is provided with an additional port 69 to allow air to pass to the service brake cylinder 35 as well as to the auxiliary cylinder 14 in emergency applications. The cylinder 14 is exhausted, to release the brakes, through a cavity 70 in the valve 64 which connects the port 68 to the exhaust port 71. A pipe 72 leading to a sanding-device is placed in the passage 68, so that the sanding-device is operated only during emergency applications of the brakes by the air passing from the reservoir to the emergency brake cylinder.