GB1206713A - Improvements in or relating to devices responsive to change in their velocities - Google Patents

Abstract

1,206,713. Brake valves controlled by inertial masses. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd. 15 Jan., 1969 [19 Jan., 1968], No. 2929/68. Heading F2F. [Also in Division G1] A device responsive to a change in its velocity includes a support for a fluid-pressure control valve having a restricted fluid flow inlet port, an outlet port, and a throttling element movable with respect to a valve seat providing an exhaust port, to vary the fluid flow through it, and a pendulum suspended on the support to support the throttling element while moving it in accordance with the displacement of the pendulum from a reference position with respect to the support, so that in operation, when a fluid pressure is present at the inlet port, the fluid pressure at the outlet port depends on the degree of throttling of the valve seat, which is consequent on the degree of displacement of the pendulum when the support is subjected to a change of velocity in the pendulum's plane of vibration. As shown in Fig. 1, compressed air from an inlet (not shown) enters a passage 52 and flows therefrom through filter 54, chamber 55, and choke 43 to a chamber 46; chamber 46 communicates with passages in a valve block 48; valve block 48 ends in a valve seat 42 forming with a ball 41 an adjustable exhaust port. Chamber 46 also communicates with a relay chamber 62 on the right-hand side of a diaphragm 63 which carries a conduit 64 normally closed by the right-hand end of a valve member 71. Valve member 71 is normally urged on to a seat 73 by a spring 72 to prevent communication between inlet passage 52 and an outlet 53. The ball 41 is loosely located by a cup 40 secured to a flexible suspension 43 having at its lower end a pendulum bob 34 constrained by two adjustable springs 351, 352. Valve block 48 is adjusted during assembly so that when the device is at rest or moving at constant velocity in a straight line, sufficient air escapes at 42 to permit diaphragm 63 to remain undisplaced. In operation, when the velocity of the device in the direction of arrow 30 falls, pendulum bob 34 moves to the left against the force of spring 351, and ball 41 is moved closer to valve seat 42, so that pressure in chamber 46 builds up, the pressure increase being communicated through conduit 44 to chamber 62, so that the diaphragm 63 is forced to the left. This opens valve 71, 73, permitting compressed air from passage 52 to flow out at 53. This air may be passed to a cylinder serving to reduce the force of vehicle brakes being applied by spring pressure, so that the fall of velocity, or deceleration, is checked, whereupon the pendulum bob returns to its equilibrium position and the cycle is repeated. Diaphragm 63, valve 71, 73, and the connection between valve 71, 73 and inlet passage 52 may all be omitted; instead, chamber 46 may communicate directly with the outlet. Springs 351, 352 may be pre-adjusted so that at constant velocity some pressure, instead of zero pressure, is applied to outlet port 53, so that the device is responsive to an increase in velocity in the direction of arrow 30, as well as to a decrease, as described above. The embodiment of Fig. 2 is designed to respond when the deceleration rises to a preselected value, thus effecting a reduction of the braking force when this value is reached, and permitting re-application of the full braking force when the deceleration falls again (instead of responding over a continuous range, as Fig. 1 does). For this purpose, diaphragm 10 is a snapaction diaphragm, and only one spring 6 is provided. The spacing of exhaust-valve button 8 from its valve seat 9 is adjusted by a set-screw 18. Also, the loading provided by spring 6 may be adjusted by inserting through a hole in the set-screw 18 a probe which is set to produce on the pendulum bob 3 a force equivalent to that produced by the desired deceleration. The adjusting cap 7 is then screwed up until the force of spring 6 just overcomes the force due to the probe. A stop-screw 19 is adjusted and locked to prevent excessive movement of bob 3 to the left with consequent damage to button 8. The compressed air inlet communicates with space 13 and also, via choke 12, with space 11 on the right-hand side of diaphragm 10. This embodiment is useful where the same braking force is applied to each of a plurality of vehicles on a track. If this braking force is designed for the heaviest loaded vehicles, the force may decelerate less heavily-loaded vehicles too rapidly; the invention serves to produce a more uniform retardation rate for the plurality of vehicles.