Patent GB-190421973-A (GB)
Title: Improvements in Automatic Vacuum Brakes, for Railway Trains.
Inventor: CHURCHWARD GEORGE JACKSON
Filed: 1904-10-12
Granted: 1905-08-31
Abstract: 21,973. Churchward, G. J. Oct. 12. B r a k e s.-Relates to valves for obtaining quick action in vacuum brakes, and consists of a particular arrangement of valves by which quick action is obtained in moderated service applications as well as in full emergency applications. In addition to a valve K, Fig. 3, of known construction, for opening the train-pipe B and the brake cylinder L fully to the atmosphere in emergency applications, a valve A is provided which admits a limited quantity of air to the brake cylinder and to the trainpipe in service applications, the branch pipe B<1> by which the brake cylinder is exhausted being provided with a restricted passage or non- return valve for preventing the air admitted to the brake cylinder frnm entering the train - pipe in sufficient quantity to operate the existing emergency valve K. The valve A is constructed as shown in Fig. 1. It comprises a central chamber open to the train-pipe B, two chambers D<2>, E', open to the atmosphere, and a vacuum chamber H connected to the train-pipe by a passage through the spindle F of the valve, the end F<4> of this passage being restricted by a pin I, which is cut away at I<1> to enlarge the passage when the valve is operated. The spindle F is fixed to three diaphragms C, C', C' and carries two valves, one G which normally closes the brake cylinder connection D<1>, and another G<1> which normally cuts off the open air chamber E' from a small chamber which is formed under the diaphragm C' and is connected by holes F<5> to the passage through the valve spindle and thus by the hole F<3> to the trainpipe. A spring H<1> may be used to steady the valve. On the driver admitting a suitable amount of air to the train-pipe to make a service application, the difference of pressure on the two sides of the diaphragm C<2> causes the valves G, G<1> to open. Equalization of pressure then takes place in the chamber H through the enlarged opening F<4>, and the valves close again. A suitable construction for the valve K, Fig. 1, is shown in Fig. 2. It consists of two valves O, O<1> for connecting the open air chamber R to the brake cylinder and train-pipe respectively, and two diaphragms N, N<1>, all mounted on a spindle formed with a small passage P' for connecting the vacuum chamber with the train-pipe. In another arrangement, shown in Fig. 4, a single apparatus is arranged to give quick action both in service and in emergency applications. The valve 13 which controls admission to the train-pipe is, in this arrangement, formed with an extending boss 13<a>, which restricts the opening when the valve moves only a short distance as in service applications, but leaves a clear opening when the valve is moved its full distance as in emergency applications. The brakecylinder admission valve 12 is opened in each case- The spindle of the valve is connected to a single diaphragm 9, above which is a vacuum chamber 10 connected by a small passage 14 with the trainpipe. The chamber 10 also has an opening 15 to the atmosphere, normally closed by a valve 16, carried by a spindle 17 which projects into the chamber 10 and is partly cut away at 17<a>. A small spring 18 shorter than the spindle 17 is placed round it, and an additional steadying- spring 18<a> may also be used. In a service application, the main-valve spindle 11 moves a short distance and is checked by the spring 18. The vacuum in the chamber 10 is then quickly destroyed by the entrance of air through the aperture 15, and the valves are quickly closed again. In an emergency application, however, the spindle is moved with sufficient force to compress the spring 18 and to bring the full-sized part of the spindle 17 into the aperture 15, thus causing the equalization of pressure in the chamber 10 to take place less rapidly. In the branch from the train-pipe to the brake-cylinder pipe there is placed a non-return valve 20 with a restricted opening 21. A non- return valve may be used in place of the restricted passage from the train-pipe to the small vacuum chamber in the arrangements shown in Figs. 1 and 4. The valves may be so adjusted that the brakes can be applied by air admitted through the driver's valve only. The Provisional Specification describes an automatic valve which normally restricts the branch passage from the train-pipe to the brake cylinder but allows it to open more widely when the brake cylinders are being exhausted by the ejector. It consists of a spindle attached to a diaphragm which is controlled by a vacuum chamber having a variable-sized opening to the train-pipe.