Patent GB-620865-A (GB)
Title: Improvements relating to valve devices for deceleration control apparatus for vehicles
IPC: B60T8/74
Filed: 1947-01-28
Abstract: 620,865. Fluidpressure - operated brakes. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. (Westinghouse Air Brake Co.). Jan. 28, 1947, No. 2588. [Class 103 (i)] In valve mechanism controlled by a vehicle-wheel slip detector of the rotary inertia type for reducing and restoring the pressure in a brake-operating cylinder, including a piston valve for venting the cylinder, this valve is controlled by an auxiliary valve operated by fluid pressure controlled in turn by the pilot valve of the wheel slip detector, whereby prompt operation of the piston valve is ensured, the arrangement being such that if during a brake application the pilot valve pipe where each is provided, should break or the pilot valve should remain open, the brake cylinder pressure, though at first reduced, is restored. The equipment shown is similar to that described in Specification 588,327 and comprises a wheel slip detector for each wheel axle of the two axle-trucks of a railway vehicle, the brakes for all the wheels being operated by a single cylinder supplied by a driver's valve of the self-lapping type. The vent valve mechanism is interposed in the pipe connections between the driver's valve and the brake cylinder and according to Fig. 2 is connected to the driver's valve, the brake cylinder and the pilot-valves of the several wheel slip detectors by pipes 36, 37 and 29 respectively. Pressure fluid supplied to the pipe 36 to apply the brakes flows (a) to the brake cylinder by passage 49, annular chamber 48 around the piston valve 44, post 52, chamber 53, passage 37a, pipe 37 ; (b) to the pilot valve of the wheel slip detector by choke 93, pipe 29 ; (c) by passage 92 to the chamber 83 on one side of a diaphragm 76, which operates through a valve stem 85 an auxiliary valve 75 ; (d) to the chamber 89 on the other side of diaphragm 76 from chamber 83 through non-return valve 94 and passage 90 ; (e) to the chamber 50 above the piston valve 44 through passage 36a and choke 51. When the cylinder pressure acting in passage 53a beneath valve 54 is sufficient to overcome spring 58, the valve 54 is opened to connect passages 53a, 73. The diaphragm chamber 89 communicates with a capacity chamber 38. When the brakes are applied, the parts thus assume the positions shown, apart from the valve 54. When in the event of wheel slip, the chambers 89, 83 are connected to atmosphere through the pipe 29 and the pilot valve, the pressure in chamber 83 falls more rapidly than that in chamber 89 which takes place through passages 90, 104, non-return valve 99, passage 105, choke 107, passage 82, choke 51, passage 36a, choke 93 and pipe 29. The diaphragm 76 is thus moved to the left against the action of the spring 87 to open the auxiliary valve 75, thus rapidly venting the chamber 50 through passage 82, this valve and chamber 83. The chamber 48 is vented less rapidly through valve 75 because of the choke 51 so that the piston 44 moves upwards against the spring 45 to unseat the valve 42, thus cutting off the brake cylinder passage 37a from chamber 48 and pipe 36 and connecting it to atmosphere by port 47. The piston 44 also opens the valve 67 to connect chamber 50 to the port 47. When the wheel slip ceases and the pipe 29 is closed, pressure equalizes in chambers 89, 83 so that valve 75 re-closes. The cylinder pressure acting on diaphragm 59 having fallen to a low value, the valve 54 is closed by the spring 58 so that the pressure in chamber 50 equalizes through choke 51 with that in chamber 48 sufficiently to effect the return of the piston valve 44, whereupon the brake cylinder pressure is restored by supply from the pipe 36. If the pipe 29 should break prior to the initiation of a brake application, the brakes normal application will be effected and the wheel slip detector will be inoperative, but if the pipe should break while the brakes are applied, the valve 75 and piston valve 44 will be operated to reduce the brake cylinder pressure, but in view of the relatively small volume of the chambers 89, 38, the pressure therein will reduce sufficiently relatively to that in chamber 83 to effect the reclosing of the valve 75 though the cylinder pressure may have fallen to atmospheric. The valve 54 also having closed, the piston valve 44 is then returned, and the brake cylinder pressure restored. The cylinder pressure is similarly restored if the pilot valve should "stick" open. If it is desired to dispense with the auxiliary valve device, an adaptor plate having a passage for connecting the passages 109, 92 may be substituted for the sections 30, 35. The cylinder pressure will not then be restored after a pressure reduction due to breaking of the pipe 29 or sticking open of the pilot valve. In a modification, the valves 54, 67 are omitted so that the piston valve 44 remains open to vent the brake cylinder only until the valve 75 closes consequent upon equalization of the pressure on opposite sides of the diaphragm 76. A modification is also shown for use with wheel slip detectors of the type in which an electric switch is actuated upon the occurrence of slip, instead of a pilot valve. In this case a passage corresponding to the pipe 29 leads to a magnet valve which is attached to the main body of the device and which when energized by the wheel slip detector opens the passage to atmosphere.