Patent GB-315772-A (GB)
Title: Improvements relating to the automatic emergency control of locomotives, motor wagons and other machines by safety devices of the "dead man's button" type
IPC: B60L3/02
Filed: 1928-01-18
Abstract: 315,772. Hoff, W. Jan. 18, 1928. Fluid-pressure. - Automatic power control means of the kind in which a periodic movement on the part of the driver is required to prevent the power supply from being shut off is characterized by interrupter mechanism which is mechanically driven from the running gear of the locomotive and periodically breaks a subsidiary electric circuit which ensures that after a given time the main power circuit is broken, means being also provided whereby, whenever the subsidiary circuit is broken, the driver can complete it again and so prevent the impending interruption of the main circuit. In the construction shown in Fig. 3 a dead man handle or button D is normally kept depressed by the driver against the action of a spring so as to bridge contacts 12, 13, and complete a circuit from V to O through an electromagnet S, contacts 9, 10 bridged by the armature of a magnet Z, contact 8 and a drum M having an insulating segment 7. The circuit for the magnet Z is also completed through the contacts 10, 9, 8 and the drum M. The drum M is rotated from the running gear of the locomotive so that the segment 7 opens the circuit once in 1100 yards say. If at any time the driver releases the button D the circuit through the magnet S is broken and delay-action mechanism is brought into action whereby, after a predetermined time interval, the main power circuit is broken and a brake valve operated to apply the brakes. If the button is depressed again before the interval expires the magnet S is energized as before and the normal control is maintained. The action thus far described is not novel. According to the present invention, when the insulated segment 7 bears against the contact 8 the circuits through both magnets are broken and the armature of magnet Z is pulled off by its spring 11 so that even when the segment 7 has passed the contact 8 the magnet circuits are not re-made. If, however, the button D is now momentarily released the circuit for the magnet Z is completed through contacts 14, 15 and conductor 17, its armature is attracted and is held attracted while the button is depressed again to complete the original circuit. As soon as the armature bridges the contacts 9, 10 the circuit for the magnet S is closed as before and thus the main power circuit is not broken. A signal of any kind is given to the driver to let him know when he has to release the button D. Thus a lamp may be lit or extinguished, a bell may be rung, a buffer may be projected from the button, a rubber ball may be caused to fall on the driver's foot, or a weak electric shock may be given to the driver. The delay-action mechanism used in connection with the magnet S may be of the known kind shown in Fig. 2, in which the armature normally holds a continuously-rotating worm 1 out of contact with a worm-wheel 3, so that when the magnet is de-energized the worm engages and drives the wheel. The wheel is normally held by a spring in such a position that it has to make half a revolution before a cam acts on a rod 4 and allows a spring 5 to open the main power circuit at XY and the brake valve V. Several buttons may be arranged in parallel and controlling a magnet which operates two pairs of contacts similarly arranged to the contacts 12 - - 15 controlled by the single button D in Fig. 3. Two or more interrupting drums M may be provided, by the use of which any desired interval between the interruptions of the button circuit may be obtained. A delay-action device may be employed dependent on the interval between interruptions of a circuit by a rotating drum such as M. Apparatus on the line at special places, such as the approach to stations, may also be used to break or act on the button circuit so as to ensure the driver being at his post at these places. Fig. 6 shows a device which puts the button (not shown) out of action for a predetermined interval after a regulating handle of the locomotive is operated. The device is connected at 30 to a circuit in connection with the button, so that if 30 is connected to earth through the device the button is inoperative and need not be kept depressed. As shown, 30 is connected to earth through contacts 28, 29, bridged by the released armature of a magnet H, line 34 and contacts 36, 35 adapted to make contact with spaced conductor segments on a controller or other handle K. The magnet circuit can be completed either through line 33 and a rotating conductor segment 31 or through line 34 and the segments on the handle K. When the segment 31 momentarily makes contact with line 33 the magnet is energized, its armature is attracted and the circuit through the point 30 and contact 29, 28 is broken, so that the button must be depressed to keep the main circuit intact. The contacts 27, 26 are now bridged by the magnet armature and the magnet circuit is maintained through line 34 and the handle K. This is the position for normal running. If the controller handle is moved to a fresh position the magnet circuit is broken, the armature is released and bridges the contacts 29, 28, the button circuit is earthed or short-circuited and so the button is out of operation until the contact 31 next completes the magnet circuit. Two or more controlling handles may be arranged in series in the inductor 34 so that movement of any one of them puts the button out of action temporarily. Fig. 8 shows a device for use mainly in shunting whereby the button D can be released, after each reversal of the direction of motion of the locomotive, until a shaft 92, driven from the running gear has made a complete revolution. The shaft 92 is connected to earth and carries an arm 90 - which normally bears against and drives an insulated stop 91 fixed to a wheel 98 making contact with a conductor leading to the magnet S controlled by the button D. When the direction of motion of the locomotive is reversed, the shaft 92 is also driven reversely, the arm 90 makes contact with the ring 89, and the button D is shortcircuited until the arm 90 bears against the other side of the stop and is again thereby insulated from the ring.