| 摘要 |
610,931. Fluid-pressure brakes. WESTING- HOUSE BRAKE & SIGNAL CO., Ltd., PETER, L. H., and SIMMONS, A. W. April 10, 1946, No. 10988. [Class 103 (i)] In control valve apparatus comprising a first valve adapted when open to establish communication between a source of fluid pressure or vacuum and a receptacle, e.g. a brake cylinder, and a second independently-operated valve adapted when open to establish communication between the receptacle and atmosphere, communication is caused to be established between atmosphere and that side of the first valve leading to the receptacle when this valve is closed, and the receptacle is under these conditions isolated from atmosphere by means interposed in the pipe or passage leading from the valve to the receptacle. Leakage past the valve cannot, therefore, affect the pressure in the receptacle. As shown, the supply of compressed air to and its release from a brake cylinder 1 are controlled by electromagneticallyoperated application and holding valves 2 and 3, the circuits of which are controlled, e.g. as described in Specification 434,131, by a driver's valve (not shown) of the self-lapping type. The valve 2 comprises a member 5 which is normally seated to cut-off supply from a main reservoir pipe 6 to a pipe 7 communicating through a timing choke 20, a non-return valve 8 and a pressure-limiting valve device 9 with a pipe 10 provided with a safety valve 17. A second member 18, movable with the member 5, vents the pipe 7 to atmosphere through ports 19 when the member 5 is seated. The valve 3 has a winding 11, in series with the winding 4 of the valve 2, and a second winding 12, either of these windings being capable of holding the valve closed to cut off communication between an atmospheric outlet 14 and a brake cylinder exhaust pipe 13 provided with a timing choke 21. The valve device 9 comprises a valve member 15 operated by a piston 16 acted on by a spring 23 and the pressure in the pipe 10. When the driver's valve is operated, the windings 4, 11 and 12 are energized to unseat the member 5, seat the member 18 and close the valve 3. As soon as the brake cylinder pressure has risen to the required value, the windings 4 and 11 are de-energized by the action of the driver's valve and the member 5 is then seated to cut off the supply and the member 18 unseated to vent the pipe 7, reduction in the pressure in the cylinder 1 being prevented by the closing of the valve 8. The winding 12 remains energized to hold the valve 3 closed. The apparatus is stated to be particularly applicable to a tractor-trailer brake system in which a driver's valve, the self-lapping action of which is controlled by the pressure established in a tractor brake cylinder, is arranged to establish a corresponding pressure in the trailer brake cylinders. In this case, any leakage past the closed application valve for the tractor brake cylinder would cause the driver's valve to release pressure fluid from the tractor brake cylinder and also from the trailer brake cylinders, the application valves of which may not be subject to leakage. The non-return valve 8 may be replaced by a valve operated by the valve 2 so as to be opened when the member 5 is unseated and closed when the member 5 is seated. |
