US2878423A - Traffic light switching arrangement - Google Patents

Description

March 17, 1959 E. J. a. KIPS EI'AL 2,878,423

TRAFFIC LIGHT swncame ARRANGEMENT Fil ed March 26. 1956 zsnBQzS-SnM 1 INVENTORS EDUARD J. E. KIPS 8. JAN W. DERKSEN av W, Zia-1M flt/ March 17, 1959 E, 5, mpg ETAL 2,878,423

TRAFFIC LIGHT SWITCHING ARRANGEMENT Filed March 26, 1956 2-Sheets-Sheet 2 mun "v" INVENTORS EDUARD J. E. KIPS & JAN W. DERKSEN United States Patent TRAFFIC LIGHT SWITCHING ARRANGEMENT Eduard Jan Egbert Kips, The Hague, and Jan Willem Derksen, Ouderkerk a./d. Amstel, Netherlands Application March 26, 1956, Serial No. 573,946

Claims priority, application Netherlands April 1, 1955 5 Claims. (Cl. 315-163) The present invention relates to a switching ararngement by means of which the light points belonging to a trafiic light or to a group of traffic lights may periodically be switched on and extinguished. Per traflic' light mostly three light points are used which respectively radiate a green, a yellow and a red light. For operating a trafilc light a mechanically driven controller and a relay are used as a. rule. Both the contacts and the driving mechanism of the controller, as well as the relay give rise to breakdowns in the long run which, when the trafiic is heavy, may cause great difficulties and even accidents.

The object of the invention is to provide a more reliable switching arrangement in which all of the above elements that may cause break-downs, can be dispensed with.

According to the invention this object is accomplished in that the periodical switching on and switching oi oi the light points belonging to the traific light or to the trafiic lights of a group is efiected by means of an uninterrupted series of pulses supplied to each of a number of discharge tubes connected in a closed circuit, which discharge tubes are adapted to be brought into a conductive condition by said pulses and which each upon reaching said condition render the preceding tube of the circuit nonconductive and prime the subsequent tube for ignition by the subsequent pulse.

According to the invention an electronic device connected with one of the discharge tubes is preferably provided per light point, which device under the influence of the change in the conductive condition of the relative tube generates an extinguishing and an ignition voltage which are passed to two of the light points respectively.

According to another feature of the invention a thyratron is preferably series-connected with each light point, which thyratron receives its ignition and extinguishing voltages from two of the said electronic devices respectively.

The invention is illustrated hereinafter with reference to the accompanying drawing. This drawing illustrates in the form of a block diagram a manner of applying this invention to a group of two traffic lights shown in Figure 1, Figure 2 showing one of the possible elaborations of said block diagram.

The apparatus in substance comprises a series of 42 discharge tubes to which every three seconds a pulse is supplied by a generator which, for example, may consist of a multivibrator.

The tubes shown in the block diagram of Figure l by the reference numerals 3, 6 30, 33, 36 97 117, 120 and 123 in accordance with the point of time of their ignition in each cycle, are interconnected in a cyclic excluding circuit arrangement in which only one tube at a time is made conductive, while as each tube becomes conductive the preceding tube automatically becomes non-conductive and the subsequent tube is automatically primed. Such circuit ararngements are known per so. As a rule they are constructed with gas filled tubes, the type of tube comprising the so-called cold cathode being the most suitable. However, thyratrons are also suitable, as will appearfrom the description of Figure 2.

The tubes 3, 6 etc., therefore, are successively ignited with intervals of three seconds, during which ignition a change of voltage manifests itself in the terminal k connected with the relative tube. Said changes in voltage are used to periodically light and extinguish. the light points of the group, six in number here, via electronic devices I and thyratrons T controlled thereby. The light points are combined in the conventional manner into groups of three points which radiate a red, yellow and green light respectively. They are designated by R, Y and G, respectively.

Each of the light points is series-connected with one of the thyratrons T T its ignition and extinguishing voltages from 1 the thyratron T receives its ignition and extinguishing voltages from 1 and T from 1 Each of the electronic devices I may be connected by means of a cord with each of the terminals k. Inv the case shown, in which I, is connected with the terminal of the tube 0, I with the terminal of the tube 33 and I with the terminal of the tube 36, the green light to the left will start burning when the tube 0 is ignited. After 33 seconds T is extinguished by I via I so that the green light is extinguished and at the same time T will be rendered conductive by 1 so that the yellow light to the left starts burning. Three seconds later again T is extinguished by 1 via l and T; is rendered conductive by I so that the yellowlight gives Way to the red light. until T is extinguished by 1 via 1 which takes place after a period of 90 (126-36) seconds. Each safe period, therefore, is followed 'by an unsafe period which is almost three times as long.

The same applies to the right hand traffic light.

By means of the cord connections it is possible to select the safe and unsafe" periods within. the limits of the time of the total cycle (here 126 seconds) at will. If desired, it is even possible to make two or more safe and as many unsafe periods fall within each cycle, by providing I I etc. with more than one cord and to connect said cord with terminals k, located in various places of the cycle.

It is also possible to operate two or more diflerent groups of traffic lights from one and the same closed circuit arrangement of discharge tubes irrespective of whether the periods of said groups are mutually equal or not, provided that the time of the cycle of each of said groups equals that of the closed circuit arrangement or a whole fraction thereof.

In all of these cases the desired periodical changes from red via yellow to green and conversely take place without any mechanically moved part, such as a controller or relay, being used.

Figure 2 shows an elaboration of the block diagram of Figure l, in which both for the tubes of the cyclic excluding circuit arrangement 0-123 and for the tubes of the switches I I and I thyratrons are used. The thyratrons of the excluding circuit arrangement are provided with two grids and in the extinguished condition they are primed because during the ignition of the preceding tube a positive biasing potential is applied to their own outer grid. Upon the next pulse, which arrives at the inner grid, the primed tube is ignited and the preceding tube is extinguished because the anodes of the tubes are interconnected by condensers. This last is also the case with the thyratrons of the switches I I and 1;, which are ignited respectively when the terminal k with which the relative control grid is connected receives a positive voltage pulse from the cathode of its thyratron.

As long as one of the thyratrons of the switches I remains ignited there is a positive biasing potential on The thyratron T receives This red light continues burning.

assesses the control .gridsoi1the1two,triodes of the'r'elative switch T, which triodes are connected in parallel and are fed by alternating current and the associated lamp of the traflic light is fed via a transformer. The use of a transformer here presentsthe, advantage that the traffic lightsmay be kept at a low voltage and the use of two parallelv tubes:renders it simple to cause the lamps of the traffic lighttto burnunder the entire, voltage (by day) or under halfthe voltage (in the evening and night).

Therthree second period chosen byway of example in theforegoing is entirely arbitrary and may be changed according torequirements which then naturally results in a proportional change in the duration of the total :cycle..

The adjustment of this durationmay be effected by remotescontrol, if. desired, e. g. by accommodating the pulse generator, PG, which must bra-controllable. then, in a station located at some distance from the trafiic light, or-theugroup of traflic lights. Also other groups of trafiic .lightsrmaythen be controlled fromsthe, same station.v

We claim:

1. A traffic light switching arrangement in which theacterized in that per light point an electronic device con nectedwith one of the discharge tubes is provided, whiclf under the influence of a change in the conductive con clition of the relative tube generates an extinguishing voltage and an ignition voltage which are passed to two of the light points respectively.

3. A switching arrangement according to claim 2, characterized in that the electronic devices consist of thyratrons the anodes of which are interconnected via condensers and the cathode voltages of which respectively control the ignition and the extinction of the. light points.

4. A switching arrangement according to claim-.2, characterized in that the light points are each 'fed by the secondary coil of a transformer, the primary coil 'ofjwhich is fed via one or two electron tubes. froma sourceof,

alternating current.

33. A switching arrangement accordingto claim 3, characterized in that the light points are each fed by the secondary coil of a transformer, the primary coil of which is fed viaone, or two electrontubesfroma source of alternating current.

References Cited in-the fileofthispatent UNITED STATESIPATENTS 2,325,764 Gall N Aug. 3, 1943 2,463,463 Izenour Mar. 1', 1949 2,608,674 Depp Aug. 23, 1952 2,696,572 Schmid Dec. 7, 1954 2,719,966 Schurr Oct. 4, 1955 2,765,426 Faulkner Oct. 2, 19561 OTHER REFERENCES The-Use of (301d Cathode Counting Tubes- ForThe Control of Resistance Welding by T. W. Brady, Electronic Engineering, February-1956, pages 71-74.

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