Patent GB-909937-A (GB)
IPC: G08G1/08
Abstract: 909,937. Road signals for controlling traffic. LABORATORY FOR ELECTRONICS Inc. Nov. 18, 1958 [Nov. 18, 1957], No. 37144/58. Class 118. In a traffic-actuated traffic control system having more than two interfering traffic lanes controlled by a parent controller according right-of-way to the lanes in succession, a minor controller responding to actuation by traffic in one lane interrupts the parent controller in its cycle and accords right-of-way to that lane to allow passage of minor traffic turning across the major stream and then returns control to the parent controller. Independent operation of the parent controller (Fig. 3), requires that the switches SW10, SW11 be closed. The operation of the parent controller, which is of the type described in U.S.A. Specification 2,156,138, is regulated by a ratchetdriven cam-shaft stepped on by a solenoid SR. The cam-switches C1-C18 and C20-C22 are closed as shown by the solid black markings on the shaft position chart. When operating as a vehicle-actuated controller, in position 6<SP>1</SP>, which is the phase A vehicle interval period, the vehicle interval timing condenser QA charges over cam contact C4 but each subsequent operation of the A road detector 401 operates a relay ER which at contact E2 tends to discharge the condenser QA. Thus the vehicle interval for phase A is extended so long as vehicles continue to arrive on road A. However, when a vehicle arrives on road B, detector 402 operates a relay DR and at contact D3 and cam contact C1 charges a maximum timing condenser QB. In the usual way either condenser QA or condenser QB will thus become fully charged, firing a respective gas-discharge tube FA or FB to operate a respective relay AR or BR. At either contact A1 or B1 the solenoid SR is momentarily energized and steps the cam-shaft to its next position 1<SP>1</SP>, where the phase A yellow or clearance interval is timed by condenser QA over cam contact C3. At the conclusion of this fixed period, the condenser QA flashes the tube FA and so operates the relay AR, to step the shaft, as before, to its position 2<SP>1</SP>. In positions 2<SP>1</SP>, 3<SP>1</SP> and 4<SP>1</SP> the phase B initial interval, extendible vehicle interval and yellow clearance interval respectively are similarly timed. In positions 51 and 6<SP>1</SP> the phase A initial interval and extendible vehicle interval respectively are timed. Closure of the recall switches PA and PB simulates phase A and phase B calls respectively and with both switches closed, the controller grants right-of-way to each phase alternately irrespective of vehicle actuation. If the phase A detector 401 is disconnected at point G and recall switch PA only is closed, then the controller will remain in phase A until a vehicle-initiated call is received from the phase B detector 402, when the cycle will continue, thus providing semi-actuated operation. The minor movement controller (Fig. 4) is connected to the parent controller circuit over lines 210-216, 218 and 219 (shown in both Fig. 3 and Fig. 4) and the switch SW11 is open, in order that the minor movement controller may interrupt the power supply of the parent controller and so stop that controller whilst the minor phase is in being. The minor movement controller is regulated by an eleven-position six-bank rotary switch stepped on by a drive magnet MM. The control of the phase B signal lights and of the phase A yellow signal light is retained by the parent controller. At rest, in position 1 of the rotary switch, a vehicle interval timing condenser 50 and a maximum timing condenser 49 charge up, but even when fully charged cannot cause their associated tubes 25, 35 to conduct, as the grids are biased off. A vehicle in a left-turn lane of road A will close detector 101 or 101<SP>1</SP> to operate a detector magnet MD, which locks over contact 88 and rotary switch contact C1. At contact 89 the tube grids are earthed, and when, say, the vehicle interval timing condenser 50 is fully charged, tube 25 will conduct on the next negative half-cycle applied from a low voltage A.C. source 21. Consequently, relay AS will operate, which at contact 94 momentarily energizes the drive magnet MM and at contacts 52 and 54 discharges the timing condensers 49 and 50, thus releasing the magnet MM and so stepping the rotary switch from the rest position 1 to position 2. In this position the wiper of bank A earths line 215 and thus operates relay DR (Fig. 3) to register a call in the parent controller for a phase B period (assuming the parent controller has been resting in the phase A vehicle interval position 6<SP>1</SP>). The rotary switch then steps as before to position 3 and waits, as the timing circuit is now connected via switch contact F3 and held open at contacts 96. When the major phase A is complete, the parent controller cam-shaft moves to position 1<SP>1</SP> for the clearance period and at contact C9 releases relay PG which closes contacts 96 to recommence the charging of the timing condensers 49, 50, and at contacts 71 registers a call with the parent controller for a further phase A period by earthing line 214 and so operating relay ER. The rotary switch then steps as before to position 4 and after the phase A major yellow clearance period, the parent controller cam-shaft moves to position 2<SP>1</SP>. The phase B period now follows in the parent controller, whose cam-shaft then moves to positions 3<SP>1</SP> and 4<SP>1</SP>. Cam contact C10 operates relay YB so that over rotary switch contact E4 and closed contacts 90 the grid circuits of the tubes 25, 35 are earthed and the rotary switch steps in due time to position 5. At contact E5 the switch timing circuits are held inoperative and the switch waits for the conclusion of the phase B yellow clearance period, when the parent camshaft moves to position 5<SP>1</SP>. Cam contact C10 then releases relay YB, contacts 90 therefore allowing the tube 25 to conduct so that the rotary switch steps to position 6. At open contact 105 the power circuit for the parent controller is broken and this therefore remains in position 5<SP>1</SP> until the minor A phase is completed in the rotary positions 6, 7, 8 and 9. In position 9 wiper A releases relay GR and contacts 73/74 close and allow the parent controller to resume operation and drive the camshaft to position 6<SP>1</SP>. The rotary switch returns rapidly through skip positions 10 and 11 to position 1 and rests again. If, however, a minor phase A call is received from detector 101, or 1011 during this time it is stored on relay MD, which locks over bank C, in order to initiate another minor phase. Synchronization of the two controls.-The minor phase A is inserted at the commencement of the major phase A period in whatever position the parent controller cam-shaft may be when a minor phase A call is received. If the camshaft is in position 4<SP>1</SP> (phase B clearance period) when the minor traffic call is initiated, then the rotary switch waits in position 1 until the camshaft steps to position 5<SP>1</SP>, when it goes through the sequence outlined above, inserting the phase A minor period at the commencement of the next phase A major period. If the parent controller cam-shaft is in position 5<SP>1</SP> or 6<SP>1</SP> (phase A major period) when a minor traffic detector 101 or 1011 is operated, the minor controller rotary switch steps to position 3 in order to initiate calls for phase A and phase B periods in the parent controller and waits until the end of the major phase A extendible vehicle interval, the cam-shaft then stepping to position 1<SP>1</SP> and the rotary switch to position 4. Here the switch waits for the completion of the major phase A and phase B periods, when the camshaft steps to position 4<SP>1</SP>. If the cam-shaft is in positions 1<SP>1</SP>, 2<SP>1</SP> or 31 (phase B period) when a minor traffic call is received, the rotary switch steps to position 4 without sending a call for phase B operation and waits until the phase B period is finished, when the cam-shaft steps to position 4<SP>1</SP>. In each of the latter cases, when the cam-shaft steps to position 51 the sequence continues as previously described. Modifications.-Provision is made for an inverted minor phase which will allow certain traffic at a suitable intersection to proceed at all times except when the minor phase A traffic has right-of-way. The inverted signals are the converse of the phase A minor signals and are operated in conjunction therewith. Provision is also made for inserting the phase A minor period without lengthening the overall time cycle. Switch SW11 (Fig. 3) is closed so that operation of the minor controller at no time interrupts the drive of the parent controller. Alternatively, by connecting line 218 to the minor controller and opening switch SW10, with switch SW11 closed, switch 149 open, and switch 146 closed, the minor phase is inserted within the phase A major initial period, but the parent cam-shaft will wait in position 6<SP>1</SP> until the minor phase is complete, before commencing the phase A major vehicle interval. Overlap, or filter, signals may be provided during the minor phase for non-interfering traffic.