Patent GB-348696-A (GB)
IPC: B60T15/04
Filed: 1930-02-17
Abstract: 348,696. Fluid-pressure brakes. WESTINGHOUSE BRAKE & SAXBY SIGNAL CO., Ltd., 82, York Road, King's Cross, London.-(Assignees of Farmer, C. C. ; 7008, Thomas Boulevard, Pittsburg, U.S.A.) Feb. 17, 1930, No. 5232. Convention date, March 12, 1929. [Class 103 (i).] To prevent overcharging of a fluid-pressure brake system the direct supply of fluid from the main reservoir to the train-pipe when the drivers valve is in the release position is automatically cut off after an interval of time dependent upon the extent of the train-pipe pressure reduction effected in the preceding application of the brakes, charging being completed by the usual feed valve. The valve mechanism comprises a rotary disc valve 2 with a handle 4 controlling the usual equalizing piston 5 and train-pipe discharge valve 6, the chamber 9 connecting to the train-pipe 11 by passage 10 and the chamber 6a to the seat of the valve 2 by passage 8 and to the equalizing reservoir 7a by passage 7. In the service application position of the valve 2, during which the train-pipe is vented in the usual way by the valve 6, air is supplied from the main reservoir 27 through a feed valve 31, passage 32, the valve 2, passage 35, choke plug 36 to a passage 15 and from this passage to chambers 14, 16 on either side of a diaphragm 13 and to a timing reservoir 18. The fluid pressures on the diaphragm 13 being equalized the valve 20 is held closed by the spring 39. Air from the main reservoir 27 is supplied by passage 26 to the underside of a piston valve 23 and equalizes through a port 28 to the upper side of the valve and thus with the valve 20 closed the valve 23 is held seated. The lower central area of the valve 23 is at this time subject to feed valve pressure by the passages 30, 32 and the disc valve 2. When the valve 2 is turned to the release position, as shown, the passage 15 is connected to the exhaust passage 40. The fluid pressure above the diaphragm 13 is thus immediately released but the check valve 38 permits exhaust of the timing reservoir 18 only through the restricted port 44. The diaphragm 13 is thus raised and the valve 20 opened. The chamber 22 of the piston valve 23 is thus also vented by the passage 15 and this valve lifts permitting main reservoir air to flow to the train-pipe by the passages 30, 43, 10. When the pressure in the timing reservoir 18 and diaphragm chamber 16 falls sufficiently to permit the spring 39 to close the valve 20, the piston valve 23 seats to cut off the direct supply from the main reservoir to the brake pipe, and as soon as the pressure in the passage 30 falls to the value of the setting of the feed valve 31 air is supplied thereby to this passage and to the train-pipe past the check valve 33. Since air is supplied to the timing reservoir 18 only during the time that the trainpipe pressure is being reduced in making an application of the brakes it follows that the time during which the train-pipe is subsequently charged directly by the valve 23 is dependent upon the extent of the train-pipe pressure reduction.' To allow direct charging of the train-pipe independent of the control by the valve 20 and as long as the handle 4 is in the release position, a projection is provided on the valve handle 4 which can be slid into position when desired to open a valve 46 and thus to unseat the piston valve 23 by venting the chamber thereof by the passage 48. The choke plug 36 may be replaced by a piston arranged in the passage 35 and having a stem having sufficient clearance in the passage to provide the desired restriction.