Patent GB-360471-A (GB)
Title: Improvements in traffic control systems
IPC: G08G1/085
Filed: 1930-08-06
Abstract: 360,471. Road signals for controlling traffic. JENNINGS, H. W. K., 51, Chancery Lane, London.-(Automatic Signal Corporation ; 205, Church Street, New Haven, Connecticut, U.S.A.) Aug. 6, 1930, No. 23542. [Class 118 (ii).] The closing of a pedestrian-operated control switch P, Fig. 7, energizes a relay 87 controlling a timing circuit which is opened and closed for predetermined periods to light signals in a desired sequence. The lighting of the signals is controlled by switches 56 .. 65 operated by cams 42, Fig. 6, mounted on a shaft 23 which is rotated by ratchet wheel 25, Fig. 4, rotated by a pawl 35 attached to a core 32 in an electromagnet 29. The timing circuit comprises a glow tube 84, a condenser 83, a relay 94, and one of the adjustable resistances 80, 103, 101, 102, which are switched in as the cams rotate, the arrangement being such that when the voltage across the condenser is built up to the critical voltage of the tube, a current flows momentarily from the condenser through the tube and relay 94, which then closes a circuit through the electromagnet 29 actuating the cams. The condenser 83 is discharged at the end of each movement of the cams, through a shunt resistance 100 by the closing of a switch 76 actuated by the arm 26 carrying the pawl 35. The switches 56 .. 65 each have contacts 52, 53, Fig. 6, carried on flexible strips 46, 47, the inner strips having projections 51 engaging the cams, each of which operate two pairs of contacts. The cams are so shaped that the switches are closed three times during each revolution of the cams. The lines A .. D, Fig. 5a, indicate when the ten switches 56 .. 65 are open and closed during the rotation of the five cams through one-third of a revolution. The dots and thick lines indicate that 'the switches are closed. In the normal position of the cams corresponding to the line D, the switches 56, 57 are closed, thus lighting yellow signals on, say, main and cross streets. When a pedestrian closes the switch P, a circuit is completed through the relay 87, which closes contacts 92, 93, completing the discharge circuit for the condenser 83 through the tube 84, with consequent rotation of the cams by the pawl 35 to a position corresponding to the line A. In this position, the switches 58, 59 are closed, thus lighting the red signals, and the switch 65 of the resistance 80 is opened and the switch 62 of the resistance 101 is closed. The resistance 101 is so adjusted that the time necessary for the condenser 83 to reach the critical voltage of the glow tube is, say, five seconds. The tube then flashes and the cams are moved forward another notch to the position corresponding to the line B. In this position, the lighting switches 56, 57 are open, and the lighting switches 58, 59 remain closed, while by the closing of switch 63 the condenser 83 is now charged through a resistance 102 adjusted to give, say, ten seconds before the condenser is discharged through the glow tube. The cams are then moved forward to the position corresponding to the line C, causing the yellow light on the cross street to reappear and switching a resistance 103 into the condenser circuit. This resistance may be set to allow five seconds before the condenser is discharged. The cams then move to the position corresponding to the line D, and the operations are twice repeated during the rotation of the cams through the other two-thirds of their revolution. The cams may be actuated by a number of pedestrian-operated switches connected in parallel. The relay 87 is maintained energized after operation of a switch P by a locking switch 90. The circuit through this switch is interrupted by a cam-operated switch 60 in the position of the cams corresponding to the line B.