Patent GB-432148-A (GB)
Title: Improvements in and relating to automatic traffic control systems
IPC: D03D51/00
Filed: 1934-07-09
Abstract: 432,148. Road systems for controlling traffic. OPEL, F. VON, 33, Bismarckstrasse, Charlottenburg, Berlin. July 9, 1934, No. 20108. Convention date, July 8, 1933. Addition to 415,852. [Class 118 (ii)] In the system described in the parent Specification in which the cycles of switching operations are subject to continuous variation in accordance with the ratio of traffic densities in two streets, the ratio at any moment is represented by the difference in potential on two condensers 16, 20 which are charged by impulses due to the detectors 1, 2 in the respective streets. This potential difference is applied to the grid of valve 37 over which condenser 50 is charged. When the charge is sufficient to break down a discharge tube 51, relay 52 makes a circuit for magnet 64 which steps a drum (not shown), controlling contacts as shown in Fig. 2. The charge on condenser 50 may alternatively be applied to the grid of a second valve, the anode current of which controls the operation of relay 52. The condensers 16, 20 are always associated with the same street and are not switched over so that they are always associated with the blocked and free streets respectively as are the counting devices in the parent Specification. Otherwise, the various features provided for in the parent Specification are applied in the present arrangement except that they are effected only by controlling the charging and discharging periods of condensers. Detailed operation. It is assumed that the green light has just come up in the street in which detector 2 is situated, the drum contacts shown by black lines in Fig. 2, column 2, being closed. Manually operated contacts 7, 62, 43 are also closed. Each vehicle passing detector 2 operates relay 11 which charges up condenser 20 over fixed resistance 21 and variable resistance 24, the value of successive charges decreasing logarithmically. Each vehicle passing detector 1 in the blocked street operates relay 5 to charge condenser 16 over resistance 17 in a similar manner. The contacts of 5, 11 are preferably of make-before-break type. The potential difference between the charges on the two condensers 16, 20, representing the ratio between the traffic densities in the blocked and free streets, is applied over 30<a>, 34<a> and 31<a> to the grid-filament circuit of valve 38 which controls the charging of condenser 50. When the charge is sufficient to break down the discharge tube 51, relay 52 pulls up and magnet 64 steps the drum (not shown), so that the drum contacts take up the position shown in Fig. 2, column 3, and the green lamp is replaced by yellow. During the green signal, the charging of condenser 50 is controlled by adjustable resistance 59 ; the charging of the " free " condenser 20 is more rapid than the blocked condenser 16 owing to the additional charging path over resistance 24 which is adjusted according to the distance of detector 2 from the crossing ; " free condenser 20 is continuously and slowly discharged over resistance 45 to remove from condenser 20 a charge corresponding to the vehicle passing detector 2 which will have passed the crossing. When the yellow lamp comes up, the grid of valve 38 is connected over 34b to potentiometer 42 which provides a predetermined bias independent of any vehicle control, and the charging circuit for condenser 50 is completed over 49<a> without any resistance so that the charging time is fixed and short. Relay 52 then pulls up to step the drum again, whereupon the contacts shown in column 4 are closed and the red lamp comes up. It will be seen that during the yellow period, condenser 20 retains the charge it had at the end of the green period, since the discharge circuit over resistance 45 is open ; condenser 16 also retains its charge, and both condensers receive extra charges during the yellow period. When the red period commences, condenser 16 receives charges over 17 and 25 in parallel from detector 1 which is now in the free street, it is discharged over resistance 46 to allow as previously explained, for vehicles passing over the crossing, and condenser 20 is charged up from the blocked street. The potential difference between condensers 20, 16 is now applied to the grid circuit of valve 38 and relay 52 ultimately pulls up to change red to yellow. Resistances 58, 59 in the charging circuit of condenser 50 are manually adjusted to allow for the normal density difference between the two streets. A period for dispersal of vehicles in a blocked street on becoming free may be provided by giving the green period two steps of the drum, the first step controlled by the number of waiting vehicles and the second by the density ratio in the normal manner.