Patent GB-493854-A (GB)
Title: Traffic actuated control systems and apparatus
IPC: G08G1/08
Filed: 1937-04-15
Abstract: 493,854. Road signals for controlling traffic. AUTOMATIC SIGNAL CORPORA. TION. April 15, 1937, No. 10747. Convention date, April 15, 1936. [Class 118 (ii)] In a traffic control system for use at an intersection, the shift of the right of way is delayed by a period of time by the passage of a vehicle over a road pad or other detector in the street having the right of way, the period being successively decreased in accordance with the amount of waiting traffic in the cross street. The " go " period in a street comprises (1) an initial interval the length of which depends on the number of vehicles in the queue which has formed since the previous " go " period ; (2) a rest interval, during which the right of way remains until a call is entered from the cross street, or if a call has been entered since the last " go " period in that street, a memory device, which may be a locking relay, is actuated, which now becomes effective to terminate the interval; (3) a traffic timed interval during which each vehicle is allowed a period in which to cross the intersection, this period being decreased by each vehicle joining the queue on the cross street. If this interval is terminated due to the maximum timer or to the vehicle interval becoming less than a predetermined time, a return call for the right of way is entered operating the memory device which is effective in the rest interval (2) of the cross street. In order to time the initial interval on the N-S street, Fig. 3, a condenser KE, which has been charged negatively at the end of the previous " go " period and partly discharged by every vehicle joining the queue during the " stop " period, detector 51 operating relay E to charge and discharge condenser K1 from condenser KE, is now used to time the interval by being charged through the resistance R5 to remove the paralyzing bias from the valve AT causing relay B to operate which in turn actuates solenoid S stepping round a cam shaft with contacts C into position 2. The rest interval is only terminated when memory relay 17 has locked, actuating solenoid S. This will occur if detector 52 in E-W street has operated relay F during the E-W stop period. Otherwise the rest interval will continue until terminated either by a vehicle approaching on the E-W street or by the operation of a periodic call circuit if switch 69 is closed causing relay C to operate due to the reduction of negative bias on valve CT, the grid condenser KC being charged through resistance R8. In position 3 of the cam-shaft, the bias on valve AT is reduced due to the charging of condenser KE through resistance R4, the condenser being discharged by the passage of each vehicle over detector 51 in the N-S street. The grid of valve BT is connected to condenser KD which was charged at the end of the " go " period on the E-W street and has been partly discharged at every actuation of detector 52, and relay F, condenser K2 removing some charge upon each actuation. Relay B, which may be polarized, is dependent upon the current through valve A7 passing through coil b3, its operation being modified due to the opposing effect of the current in b2 through valve BT. If B operates before A then a return call is entered, E being operated, causing M to lock up. A maximum timer comprising resistance R2 condenser KC, valve CT and relay C is provided upon the operation of which a return call is also entered. In position 4, the N-S amber period, the timer comprises resistance R1, condenser KC and relay C. In positions 5-8 the operation of the apparatus occurs as in positions 1-4. In a modification, Fig. 4, gas-filled triodes are used in the timing circuits. The initial interval is timed by condenser KINS, tube YT and resistance RZ5, relay YR being operated upon tube YT breaking down. The condenser KINS, charged from potentiometer PZ7 through RZ15, is discharged by increments due to operation of E2 and condenser KZI before being used to time the initial interval. Operation of YR causes the stepping switch driving magnet OM to be energized, moving on the wiper on the contact banks. In the rest position condenser KY is charged through resistance RZ13, the grid of tube YT being connected to potentiometer PZ5. If switch Z69, the periodic call switch is closed, tube YT fires after an interval and is similarly affected if contact bm6 is made due to the actuation of detector 252 and relay FZ in releasing the holding circuit of relay BM during the time which has elapsed since the end of the last E-W " go " period. Otherwise the rest interval is prolonged until contact bm6 is made due to actuation of detector 252. In position 3, valve YT, condenser KV and resistance RZ17 comprise the normal vehicle timer, the condenser being discharged due to actuation of detector Z51. A variable vehicle timer is also used consisting of condenser KVV, charged through RZ4, and valve VVT. The grid of VVT is connected to condenser KGNS, which was charged negatively and partly discharged during the E-W stop period whenever relay FZ is actuated, connecting condenser KBNS to KGNS. If VVR operates, relay AM falls away and a return call is made, but if YR operates first, AM remains locked. The maximum timer comprising condenser KMX, resistance RZ2 and valve MXR also gives a return call when operated. If AR is de-energized, it is effective in position 6 to keep the E-W rest period to a minimum. In position 4, the amber period is timed through valve YT, condenser KY and resistance RZ1. A particular type of vehicle, e.g. fire engine may have the same effect as a number of vehicles, by the use of a special detector, Fig. 5, connected to the ordinary detector 251. The detector 292 may be only responsive to a high note and cause the armature 294 to oscillate, giving impulses across the contacts 298, the motion being damped by eddy currents.