Patent GB-314599-A (GB)
Title: Departure-time indicator for transport systems
IPC: B61L25/00
Filed: 1928-04-04
Abstract: 314,599. Bridge, E. K. April 4, 1928. Selective signalling apparatus; illuminated stencil and transparency indicators. - A device for indicating the times of departures of trains or other passenger vehicles from stations or other stopping places comprises clock-controlled means for indicating the number of minutes or other interval of time before the departure of the next train and manually-controlled electric impulsesending mechanism for setting the indicator on the departure of a train to indicate the interval of time before the departure of the next train. Means are also provided for obscuring or extinguishing the indications when at zero or being reset, and for correcting errors in the time indications. The indicators may be arranged singly or in groups, each group simultaneously indicating the departure times of a number of trains to different destinations. The indicators may comprise bands wound on end rollers, drums, or a clock dial with index hands. In the form shown, Figs. 1, 2, and 3, the indicators are constituted by drums 6, 7, having the units and tens of minutes marked thereon respectively, the units drum 6 being driven by ratchet and pawl mechanism 9, 10 under the control of an electromagnet 12. The drum 7 is driven from the drum 6 by any known form of transfer-mechanism, a cam 13 and spring-controlled pawl 14 being shown. The drums are enclosed in a casing 58 and a shutter D is interposed between the drums and apertures in the casing. The shutter is carried by arms 20 pivoted at 21 and connected by a link to the core 23 of an electromagnet 24 in an independent circuit. When the shutter is raised by excitation of the magnet 24 a pin 25 engages a shoulder 26 on a bell-crank lever 27 to hold it in the raised position. A pin 28 on the drum trips the lever 27 when the drum is returned to its zero position. The setting mechanism for sending impulses to change rapidly the indications to set the indicator to the interval of time before the next train departs is shown in Figs. 4 and 5, and comprises a rotatable pointer 33 movable anti-clockwise through any desired angle over a dial 34 and adapted to return under the action of a spring. The pointer carries a ratchet wheel 35 with which engages two pawls 36 carried by a ratchet disc 37 so that on anticlockwise rotation the disc 37 is rotated, backward movement being prevented by a detent 38. A spiral spring 39 connects the disc 37 to the hub of a toothed wheel 40 which is dragged around with the disc 37 until a stop 41 on the wheel engages a stop 42 on the disc. The wheel 40 through gearing 43, 44 drives a governor 45 and a make-and-break device 46 comprising contact strips 47 and brushes 48. An indented ring 59 is provided on the cover 60 and co-operates with justifying pawls 62. As an alternative the setting mechanism may comprise a fixed clock dial graduated in minutes by means of perforations into which plugs can be inserted at the departure times. Each plug acts as a stop for a projection on a ring or disc driven anti-clockwise by a spring motor or other means. In the wiring diagram, Fig. 6, is shown a clock-driven transmitter A, a group of three indicators B, B', B<2> with pilot or checking indicators C, C', C<2>, and a station clock F. The transmitter sends regular impulses through a relay 3 to control the main circuit 4 and send impulses to the three indicators. The magnet 24 operating the shutter D of each indicator is arranged in a circuit 16 having a supply 17, switch 18, and plug 19. The setting mechanism designated by E has its contact brushes 24 arranged in a circuit 29 with plugs 31, 32 whereby any one of the indicators may be adjusted. In operation the setting arm 33 is moved clockwise to the position of the minute hand at the time of departure of the last train and is then turned anticlockwise to the time of departure of the next train, whereupon the necessary number of impulses is transmitted to the indicator. The operator then temporarily closes the switch 18 to move the shutters and uncover the reading apertures. Push switches 51, 52 shunted across the relay 3 and setting mechanism E are provided for sending correcting impulses through the indicators. In a modification of the indicator the drums are replaced by graduated discs, the numerals of which are magnified by projection on to a. translucent screen. Means may be provided for extinguishing the illuminating means when the discs reach zero and for relighting the means when the indicator has been set, thus dispensing with the use of a shutter. Instead of plugs a selecting switch may be, used to connect up the desired indicator, the switch being held in set position against the action of a spring by a pawl-and-ratchet device. The ratchet wheel has a projection which in the neutral position of the selecting switch operates a spring switch to maintain the circuit sending the regular impulses to the indicator closed. When the projection is moved the spring switch opens the impulse circuit and bridges contacts in an auxiliary circuit including an electromagnet, contacts associated with the abutments 41, 42 of the setting mechanism, and a manually operable switch, the magnet serving to release the pawl to permit return of the selecting switch.