GB285804A - An arrangement for controlling an operation depending upon whether a device is in motion or stationary - Google Patents

Abstract

285,804. Associated Telephone & Telegraph Co., (Assignees of Hudd, A. E.). Feb. 21, 1927, [Convention date]. Fluid-pressure.-Apparatus for controlling an operation depending upon whether a device is stationary or in motion in which the operation takes place or not according to the relative position of two members comprises one member adapted to move only in a normal direction towards the surface of the device and provided with a second member interposed between the first member and the surface and incapable of being moved relatively to the first member solely by the pressure exerted thereon by the first member but if the surface is in motion the second member is moved relatively to the first member against a restoring force and is held in a position away from its normal position until the first member is withdrawn away from the surface. The apparatus illustrated forms part of an automatic train control system and is for the purpose of preventing the driver from releasing the brakes following an automatic brake application, before the train has stopped. A piston 4, 11 slidable in a fixed cylinder 10 mounted over one of the wheels W of the locomotive carries a member 5 having a spherical seating on the part 11 and held in the normal position shown in relation to the piston by a spring 8. The piston is held in the retracted position by a spring 18 abutting on the end 12 of the piston and that of a bolt 17 secured to the fixed collar 19. A pipe 2 is arranged to supply compressed air to the interior of the piston 4 by way of apertures 13. The pipe 2 also communicates with a piston 3 arranged to actuate contacts 7 of an electric switch, the operation of which permits of release of the brakes. Normally the pipe 2 is open to atmosphere by way of the orifice 28 in a valve device C. If the lever of this device is de. pressed a valve 29 is opened to admit pressure air to the pipe 2. As the spring 18 is weaker than the spring 6 of the piston 3, the piston 4 is first moved so as to bring the part 5 into contact with the wheel W which if the wheel is rotating is then deflected so that flutings 9 permit escape of the air from the piston 4 and pipe 2 so that the piston 3 is not actuated. If however on account of the wheel being stationary the member 5 is not so deflected, the pressure rises beneath the piston 3 sufficiently to overcome the spring 6 and the contacts 7 are operated. The device is also applicable to signalling systems in mines where for instance it is important to avoid the change of a signal while the elevator is moving.