Patent GB-1094552-A (GB)
Title: Traffic signal systems
Inventor: CASCIATO LEONARD
IPC: G08G1/081
Filed: 1965-09-13
Abstract: 1,094,552. Road traffic signals. T. A. M. HUTCHISON. Feb. 14, 1966 [Sept. 13, 1965], No. 39049/65. Heading G4Q. A traffic control system comprises a number of local controllers 12, of which one is shown in Fig. 1, and a master controller 10 including a digital computer 34 having at least one recorded signal programme, and channels 16 extending from each local controller to the master to indicate the current phase which is compared in the computer with the phase required by the programme. The programme varies with time of day, and one input to the computer is from a digital clock 36 (shown in detail in Fig. 8) which counts seconds after midnight or some other set time, and the computer provides output signals at the times required by the programme (which may differ for each local controller) to change the phase of the traffic signals. Vehicle detectors 14 provide a further input to the master controller 10 where they pass to a counter unit 32 (shown in detail in Fig. 7); this comprises a counter (246) and a neon lamp (250) in parallel, and a rotary switch (258 and 260) which is stepped one position by each input pulse. The state of the switch is read periodically (e.g. every 2 seconds) by the computer which subtracts the present value from the previous value to measure traffic volume. Different programmes may be selected according to time of day or measured traffic volume. The computer output circuit 28 (shown in detail in Fig. 5) responds to the time of occurrence of pulses to energize a " hold " relay (172) maintaining central control and an " actuate " relay (170) which can advance the local controller by up to three steps in one output cycle. The " hold " relay must be energized periodically or a drop-out control (218) causes control to revert to the local controllers. The monitor unit 20 (shown in detail in Fig. 4) converts the input on lines 16A-16C into a form suitable for an input to the computer and displays the current phase as a pattern of steady and pulsating lights. There are eight possible phases, not all of which need be used, corresponding to main road green and red, the two amber phases, and four phases wherein green is displayed on only one of the approach roads. Local controller.-When operating under local control a synchronous motor 42, Fig. 3, drives three dial cams 46, 48 and 50. Contacts 52 are closed by keys 51 on dial 46 and thereby energize a solenoid 58 which advances a camshaft one step; cams 82 then advance the signal lights 85 to the next phase and cams 84 alter the output on lines 16A-16C. At the end of each cycle cam 80 opens contacts 62 thereby de-energizing contacts 52 and preventing advance unless or until contacts 54 are closed by dial cam 48. In this way the cams and the dial cams are automatically synchronised once each cycle. When the " hold " solenoid 90 is energized the motor 42 is stopped by a brake 44a operated by solenoid 44 when contacts 56 are closed by dial cam 50, so that the dial cams are always stopped in the same position. The solenoid 58 can their be energized from the master controller via " actuate " relay 100. If switch 66 is turned to its other position, the phases are advanced by manual operation of switch 86.