Patent GB-190326056-A (GB)
Title: Improvements in connection with Valves, Cylinders and Fittings for Vacuum Railway Brake Apparatus.
Inventor: GRESHAM JAMES
Filed: 1903-11-28
Granted: 1904-11-24
Abstract: 26,056. Gresham, J., Gresham, H. E., and Kiernan, G. Nov. 28. Brakes, vacuum. Comprises means for reducing the full initial effect of the brakes automatically and gradually to a predetermined degree, and means for increasing the flow of air into the train pipe during an emergency application. The graduation of the brake pressure may be effected by providing in a valve between the ends of the brake cylinder a restricted passage which gradually destroys the vacuum in the cylinder, or by fitting two brake cylinders to each set of brake rigging, and gradually eliminating the effect of one by the use in it of a perforated piston. Fig. 1 shows a ball valve which enables the air to be withdrawn from the top and bottom of the brake cylinder through the ports b, c respectively. The ball a is mounted in a cage d on the cover e, and is secured by a screw cap f. A lug g enters the boss hand holds the valve steady. Normally, the ball a is raised from its seat i and the valve disc k is pressed up to its seat q by the atmospheric pressure on the lower surface of the diaphragm m. When the air enters the train-pipe, it passes to the chamber 20 and port c, and leaks through the clearance between the tubular valve stem j and the valve seat i, and passes through the orifices l, m in the stem j to the chamber 19, and thence to the low-pressure side of the brake cylinder piston. The brake pressure is thus gradually reduced until the pressure in the chamber 19, together with the compression of the spring r, enables the ball a to fall on its seat i. In the modification shown in Fig. 2, the air entering the chambar 20 and port c also leaks through the port u to the closed chamber 18 beneath the diaphragm n, which gradually compresses the spring r, raises the valve k to its seat g, and causes the conical stem j to lift the ball a. Air then passes between the stem j and the seat i, and leaks through cuts in the face of the valve k into the chamber 19 and thence to the vacuous part of the brake cylinder. Fig. 4 shows a brake apparatus with the cylinders x, y connected to the train-pipe v and operating the common brake shaft 3. The air entering the cylinder y from the train-pipe v passes gradually through the aperture 4 in the piston z, and thus gradually destroys the vacuum above it, and reduces the braking effect. The cylinder x may be fitted with the ball valves described above, so as to reduce still further the braking effect. Fig. 5 shows the quick-acting emergency valve, which consists of a flat valve 11 attached to a diaphragm 25 and moving on the ribs 13 on a plug or pin 14, between which and the valve 11 the air passes slowly in an ordinary service application. If air enters the train-pipe 23 rapidly, the valve 11 is lifted from its seat, and the momentary reduction of the pressure in the chamber 24 lifts the flap valve 7, so that the external air rushes through the cone 5 and valve 11 to the pipe 16 leading to the brake cylinder. The valve 7, which is pivoted at 27 to the removable cover plate 8, may be locked by a hook 15 on a spindle 9 rotated by a handle. The dust is filtered or screened from the air by a sponge cloth or coarse canvas 28, which is secured to the cone by mounting it on a wire hoop 6, the ends of which are twisted or clinched together behind a stiffening-ring on the cone.