Patent GB-776624-A (GB)
Title: Improvements in or relating to safety devices for railway vehicles
IPC: B60L3/02
Filed: 1955-02-03
Abstract: 776,624. Controlling rail vehicles. DEUTAWERKE VORM. DEUTSCHE TACHOMETERWERKE GES. Feb. 3, 1955 [Feb. 5, 1954], No. 3174/55. Class 79(5). [Also in Group XXXIV] A rail vehicle safety device of the kind requiring the continued or intermittent operation, by the driver of a vigilance key, the safety device becoming effective to give a visible or audible warning signal or to apply the brakes on such operation ceasing as on incapacity of the driver, comprises an integrating mechanism for storing electrical pulses obtained from a generator driven by a wheel axle, the integrated pulses representing a predetermined track distance, being applied to effect a warning signal and brake operation. The integrating mechanism may be mechanical such as a stepping switch or electrical such as a condenser. The impulses may be produced preferably on the closed circuit principle from an A.C. generator e.g. of a speed increasing device from a cam-operated electrical contact, or a magnetically operated contact, or from the A.C. current produced by a resistance conductor or rotating field system. In the case of the condenser, the potential thereacross may be applied to an electronic switching device such as a glow discharge device, or a thyratron, to render it conductive at a predetermined potential and effect a warning signal or brake application. The safety device may be combined with a time- or speed-responsive safety device, the impulses being fed e.g. to a synchroneous motor which only rotates when the impulse rate corresponds to the preselected speed of the motor, e.g. 20 km/hr., to operate a switch to render ineffective the time- or speed- or time and speed responsive safety device and render effective the distance responsive safety device. Common leads may be used to transmit the current from the speedometer generator to the speedometer indicator and to transmit the safety device impulses to the integrating mechanism. As shown in Fig. 3 the pulses are generated by a closure of a contact 4 intermittently operated by a cam 3 rotated through transmission gear 2 from the speedometer A.C. generator 1. The vigilance key is a reversible switch comprising a reversible brush contact 38a adapted as a deadcentre member actuated by a pedal 37 similar to the accelerator pedal of a motor vehicle, so that as the pedal is oscillated about its mean suspended position the contact 38a brushes over a fixed contact 38 and completes an energising circuit for the release magnet 36 of the stepping switch 31 thereby disengaging the stepping pawls 30 and then holding pawl 32 from the ratchet wheel 31, which, if it has been advanced at all render the action of the pawl 30 due to the energisation of the magnet winding 28 by impulses generated by the intermittent closure of contact 4, returns under spring control to its former position. The energisation of magnet coil 36 opens a delayed-action contact 25 which only closes after, say, 1 minute, and by correctly timed actuation of the vigilance key within this delay period, a start of the stepping switch 31 is permanently prevented. If, however, the pedal 37 is brought into one or other extreme end position and held there, due, e.g. to the incapacity of the operator, then by closing one of the contacts 26, 27, the contact 25 is bridged and the stepping coil 28 is immediately connected into circuit and the stepping switch set into motion by the impulses without regard to the position of the time switch 25 and after running through a certain stretch of track, the contacts 33, 34a are closed to operate the warning signal 34 followed later by the closing of contacts 33, 35a to operate the brake control mechanism 35. A warning lamp 42 in parallel with the stepping coil 28 lights up whenever the switch 31 is in motion. If the train is to be brought to a standstill immediately on the collapse of the driver, the contacts 26, 27 then bridge the contacts 33, 35a instead of contact 25.