Patent GB-409376-A (GB)
Title: Improvements in or relating to traffic control signals
IPC: G08G1/08
Filed: 1932-10-31
Abstract: 409,376. Road-traffic control systems. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, RENSHAW, A. P. B., Brookwood, Alder Road, West Derby, and WRIGHT, D., 91, Hampstead Road, Elm Vale, all in Liverpool. Oct. 31, 1932, No. 30617. [Class 118 (ii).] A signalling system for controlling the trumc at an intersection of three roads is operated by the traffic through timing mechanism comprising a condenser adapted, when charged to the striking voltage of a neon lamp, to operate a solenoid which steps a cam shaft to effect a signal change. The system is such that : (1) when there is no traffic on any of the roads, right of way may either remain with the road which last had it or may be transferred to any predetermined one of the roads ; (2) right of way is given successively to the roads in an order which may be predetermined but so that the length of time one road retains the right of way is dependent upon the approach of vehicles in that road, or in either of the other roads ; (3) a road which does not require right of way cannot hold it to the disadvantage of one which does ; (4) a vehicle whose progress is prevented by a continuous stream of opposing traffic is required to wait only a predetermined time ; (5) the vehicles are given a time commensurate with their speed to pass the intersection. The vehicle actuated switches Phase A, Phase B, Phase C, respectively, may be as described in Specification 360,924 and the signals comprise red, RA, RB, RC, amber AA, AB, AC, and green lamps GA, GB, GC, Fig. 2, for roads A, B, C (not shown) respectively. The cam shaft which is stepped by a solenoid S, Fig. 1, has nine positions and controls twentytwo contacts, C1-C22, the contacts closed for each position being shown in the table, Fig. 3. The timing mechanism comprises a condenser QA, Fig. 1, adapted to be charged up over a resistance X1-X20, and a neon lamp FA in series with a relay A. Manually set switches C, INL, VHA, VHB, VHC, C.AMB, the contacts of which are connected to appropriate points in resistance X1-X20, control, respectively, the initiating time for each of the green signals, the time of the green signal on A, B, and C roads, and the time of each amber signal. Operation. Assuming the cam shaft is in position 2, contacts C2, C4, C8, C12, C13, C15, C19 are closed, relays G and K, Fig. 3, are energized and right of way is with road A, green lamp GA being lit over contacts k5, c8, Fig. 2, and the red lamps RB, RC, over l6, m6, respectively. Assuming there is no further traffic on road A and a vehicle approaches on road B, operation of the Phase B switch energizes a relay E, Fig. 1, which locks over contacts e1, l7, and operates a relay H, Fig. 3, over e3, C2, relay H locking over h1, C13. When the cam shaft was stepped to position 2 condenser QA, Fig. 1, began to charge up over the circuit C4, k3, switch VHA, and resistance X1 .... If there is still no traffic on road A when the condenser QA has charged to the striking voltage of lamp FA, relay A operates in series with the latter over contacts l4, e2, and at contacts a1 operates solenoid S to step the cam shaft to position 3, where the amber lamps AA, AB are lit over C22, g3, h3, and GA extinguished. Amber is now showing on road A, red and amber on road B, and red on road C. A charging circuit for condenser QA is made over the circuit C11, switch C.AMB and resistance X1, ... , and in due course relay A is energized to step the cam shaft to position 4. Here, a relay L, Fig. 3 is energized over C20, h2 ; it locks over C13, l1, at l5 lights the amber lamp GB and at l6 extinguishes the red lamp RB. The relays G, K, release at C12, the amber lamps are released at C22, and RA, RC are lit over k<6>, m<6>. Condenser QA now charges over contacts C16 and the common interval switch C.INL and in due course the cam shaft is rotated to position 5. The signals do not change, and condenser QA is charged over C4 and switch VHB. The stepping of the cam shaft to give right of way to road C and then to road A, should a vehicle approach on these roads when the preceding road having right of way has no traffic thereon, is similar, relays F, J, M for road C corresponding to D, G, K for road A, and E, H, L for road B. Should right of way be with road A, for example, and a vehicle operate the road switch in road C, there being no traffic on roads A and B, relay F operates, locks over f1, m7, and at f<2> completes the series circuit for lamp FA and relay A and the cam shaft is stepped to position 3 as before. Relay H has not operated however, and the amber lamp AB is not lit. After the amber period the cam shaft is stepped to position 4 where all the red lamps are lit and a rapid charging circuit for condenser QA made over k2, l2, m2 and low resistance YH. The cam shaft steps to position 5 and then to position 6 over the same operating circuit. Here red and amber is shown to road C and after the amber period timed by switch C.AMB the cam shaft steps to position 7 and then to 8 to give right of way to road C. When right of way is given to any road, for example A, the charging circuit for condenser QA is made over the appropriate switch VHAVHC. The discharge circuit through lamp FA and relay A is however not completed and right of way remains with this road unless traffic is waiting on one of the other roads, when relays E or F are operated. Should further vehicles approach on road A, a discharge circuit for the condenser is made over d2, k4, C15 at each actuation of the Phase A switch, the locking circuit of which is open at C17. Moreover these discharges are inversely proportional to the speeds of actuating vehicles, so that even with vehicles waiting on roads B and C, the right of way for road A is extended by an amount commensurate with the speeds of the vehicles thereon. Under these conditions a continuous stream of traffic on any road would extend right of way therefor indefinitely. To prevent this a maximum timer is provided comprising a condenser QB, neon lamp FB and relay B, Fig. 2. The condenser QB is charged over one of the maximum time switches MAX.A, MAX.B, MAX.C and resistance XB1- XB7, provided traffic is waiting on one of the other roads, and at the end of a predetermined time determined for each road by the setting of the corresponding maximum time switch, the lamp FB strikes and relay B energizes. At b1, relay B energises solenoid S to step the cam shaft and at contacts b2, b3 or b4 energizes the road relay of the road from which right of way has been removed so that right of way will eventually be returned thereto. The road relay of a road losing right of way is also energized if the road contacts thereof are operated during the following amber signal, over contacts C17. By operating one of the arterial switches ART.A, ART.B, ART.C which cause conditions similar to a waiting vehicle the right of way will be returned to the corresponding road when there is no traffic on any of the roads. The time of the three amber signals may be prolonged by the insertion of resistances YD, YE, YF in the charging circuit of condenser QA by means of contacts d4, e4, f4 respectively. The neon lamps are fed from rectified alternating current, and the various relays are shunted by small rectifiers that they may be operated by alternating current. Specification 351,703 also is referred to.