Patent GB-355741-A (GB)
Title: Improvements in traffic control systems
IPC: G08G1/08
Filed: 1930-05-28
Abstract: 355,741. Road-traffic signals. AUTOMATIC SIGNAL CORPORATION, 205, Church Street, New Haven, Connecticut, U.S.A.- (Assignees of Biach, J. L. and Geer, C. D. ; 205, Church Street, New Haven, Connecticut, U.S.A.) May 28, 1930, No. 16464. Convention date, April 23. [Class 118 (ii).] In a traffic control system for use at a highway and a cross street wherein the signalling means is actuated, through timers, by vehicle actuated road means, the latter is provided in the cross street only and the system functions such that (1) in the absence of traffic on the cross street, right of way is normally shown on the highway; (2) a vehicle approaching on the cross street transfers right of way to the cross street immediately, only if right of way has been given to the highway for a predetermined period; (3) a vehicle which has passed a road ramp is protected against opposing traffic for a predetermined period of time sufficient to permit the vehicle to pass the intersection of traffic lanes; (4) if traffic on the cross street is continuous, right of way will, after a predetermined time, be transferred to the highway; (5) if a vehicle has right of way taken from it after it has actuated the ramp, the system will be left in such a condition that right of way will return to the delayed vehicle as soon as traffic conditions permit; (6) if there is no traffic on the cross road right of way is periodically transferred to the cross-road to allow pedestrians to cross the intersection ; (7) if one or more vehicles after passing the actuating means do not receive right of way immediately, they will be protected when they do receive it for an additional period of time to allow the vehicles to get started. Cam mechanism. The signalling lamps, green, yellow and red for A and B streets, A being the highway, are operated over contacts 56 .. 71, Fig. 9, actuated by cams mounted on a shaft 23, Fig. 5. Energization of a magnet 29 rotates anticlockwise members 26, pinned at 27, 28, the pawl 35 sliding over a tooth of the ratchet wheel 25 fixed to the cam shaft 23. Upon de-energization of the magnet 29, a spring 34 rotates the members 26 clockwise and the pawl 35 steps the shaft one tooth of the wheel 25. When magnet 29 energizes, the pin 27 immediately closes contacts 75, 76 and near the end of its anticlockwise travel closes contacts 83, 85 and 84, 86, the latter being opened before contacts 75, 76 when magnet 29 de-energizes. The wheel 25 has eighteen steps, six steps corresponding to a complete signal cycle, the six positions of each cam being shown at 72, Fig. 9, eight cams only being necessary when the number of signal cycles per revolution of the shaft 23 is odd. Operation. Normally with right of way on the highway (A street) the cams are in position F, contacts 56, 59 being closed to light the A street green and the B street red lamps. Contacts 65 are also closed causing a condenser 109 to charge up over resistance 105. Should a vehicle now approach on B street actuating the ramp therein to short the lines 10, 11, Fig. 9, a relay 114 is energized over lines 98, 113, 11, 10 and locks up over contacts 116, 117, 62 and line 119. Should right of way have been with A street sufficiently long for the condenser 109 to charge up to the critical voltage of a glow tube 110 the former will discharge through the tube 110 and relay 97 over contacts 111, 112. The relay 97 momentarily closes contacts 100, 101, the resultant momentary energization of magnet 29 advancing the cams to position A where the A and B street yellow lamps are lighted over contacts 57, 60. Contact 67 now energizes a condenser 126 over resistance 122 and after two seconds discharges through the tube 127 and relay 96. The latter at contacts 103, 104 energizes magnet 29 to step the cams to position B where the A street red and B street green lamps are lighted over contacts 58, 61. Contacts 69 now energize the condenser 126 over resistance 129 and after three seconds the tube 127 again operates relay 96 and magnet 29 to step the cams to position C. Here, contact 71 is closed and as relay 114, de-energized when the cams left B position, the condenser 126 now energizes over resistance 130 and contacts 131, 132, and after seven seconds (if no more cars approach on B street) tube 127 again actuates and magnet 29 steps cams to position D where both the A and B street yellow lamps are lighted. Condenser 126 now energizes over resistance 133 and contact 68 and after two seconds the cams are stepped to E position where the A street green and B street red lamps are lighted. Here, condenser 126 charges up over contact 70 and resistance 134 and after five seconds discharges to step the cams to position F, completing a signal cycle. When magnet 29 energizes, contacts 94, 95 corresponding with contacts 83, 85 and 84, 86 in Fig. 5, close, discharging the condensers 109, 126 over resistances 121, 128 respectively. If right of way is with B street, and more vehicles approach thereon before the end of the seven second period, timed in position C of the cams, relay 114 will operate momentarily at each actuation of the ramp, causing the condenser 126 partially to discharge through resistance 136 by way of contacts 132, 133, so that for each further vehicle on B street the timing mechanism in the C position is reset. Moreover, the time of actuation of the relay 114 is in each case commensurate with the speed of the vehicle, and as condenser 126 does not fully discharge at each actuation of contact 132, the amount of reset of the timer is commensurate with the speed of the actuating vehicle. To prevent continuous traffic on B street from holding right of way indefinitely, the condenser 109 is also energized in C position of cams, over resistance 137 and contact 64, causing, after twenty seconds, actuation of the tube 110 resulting in stepping of the cams to F position, to give right of way to A street. The difference in this case is that relay 114 is operated over contacts 138, 139 when relay 97 energizes ; it locks up momentarily over contact 93, 116, 117 and when the cams are stepped to D position is still held at contact 62. This ensures that right of way will return to B street again without an additional actuation of the B street ramp. The three second period in position B of the cams is that allowed for cars waiting on B street to get into motion. If there is no traffic on B street, right of way would normally remain indefinitely with A street. In cam position F, however, condenser 126 is energized over contact 66 and resistance 139<1>, and after two minutes right of way is transferred to B street to enable pedestrians to cross the intersection. Manual control. Opening of a switch 140 disconnects the timing mechanisms whereupon the magnet 29 may be operated to step the cams by depression of the pushbutton 141. Modifications. The signal colours may be altered by varying the cam contours. Thus the yellow may be replaced by a blank (no colour) or may be omitted when changing from red to green, or the red and yellow may be overlapped. The resistance 105 which times the period when right of way is with A street may be varied by manually rotating a stepping switch the contacts of which are connected to various points in the resistance 105. The vehicle actuated device may be a beam of light projected across the road and received upon a photo-electric cell, a passing vehicle causing the current to fluctuate, or it may comprise an electromagnetic device.