US2925583A

US2925583A - Control apparatus responsive to traffic density

Info

Publication number: US2925583A
Application number: US564949A
Authority: US
Inventors: Walter M Jeffers
Original assignee: Crouse Hinds Co
Current assignee: Crouse Hinds Co
Priority date: 1956-02-13
Filing date: 1956-02-13
Publication date: 1960-02-16
Anticipated expiration: 1977-02-16

Description

Feb.16,1960

Filed Feb. 13, 1956 w. M. JEFFERS 2,925,583

CONTROL APPARATUS RESPONSIVE TO TRAFFIC DENSITY 3 Sheets-Sheet l f \Er i ooooboo .F ET 2 67 6B 69 7o INVENTOR.

' V wazter M. Ja

HZ tam ey.

Feb. 1 6, 1960 w. M. JEFFERS 2,925,583

CONTROL APPARATUS RESPONSIVE TO TRAFFIC DENSITY Filed Feb. 13, 1956 s Sheets-Sheet 3 flE- IN VEN TOR.

BY Miter M. UE/fers United States Patent "CONTROL APPARATUS RESPONSIVE TO TRAFFIC DENSITY Walter M. Jelfers, Syracuse, N.Y., assignor to Cronse- Hinds Company, Syracuse, N.Y., a corporation of New York Application February 13, 1956, Serial No. 564,949

8 Claims. (Cl. 340-37) This invention has to do with vehicular trafiic signaling systems and relates more particularly to that type of .system wherein the signal control apparatus is varied in :timers for controlling the display of the trafiic signals .at the various intersections of the system, the timers being operated by variable speed motors, the speed of which is determined by the voltage impressed. upona circuit interconnecting all of the timers. v

The invention has as an object an arrangement inr corporated in such a system which functions to maintain the voltage on the interconnecting circuit inproportion to the density of traffic moving through the'signalized area.

The invention consists in the novel features and in the combinations and constructions hereinafter set forth and claimed.

In describing this invention, reference is had to the accompanying drawings in which like characters fdesignate corresponding parts in all the views.

In the drawings Figure 1 illustrates a series of highway intersections in a schematic diagram showing the arrangement of the apparatus embodied in the system.

Figure 2 is a schematic diagram of the master timer and a secondary timer.

Figure 3 is a schematic. wiring diagram showing a portion of the circuit arrangement of the apparatus for varying the voltage on the cycle control circuit. 7

' Eigure 4, when placed to the right of Figure 3, completes the circuit of the voltage control apparatus;

Referring to Figure 2 of the drawings, indicates the ,motor driven dialof the master controller, this dial being 1 provided with a pin or lobe 2 1 for 'engaging'thc movable contact 22 to move the same out of engagement with the fixed contact 23 once during each revolution of the dial 20. The dial 20 is rotated by a variable speed motor having a driving coil 24 and a brake coil 25. I

- Each secondary controller of the system has a contact dial 26 provided with a pin 27 for moving the movable contact 29 into engagement with the fixed contact 32. The dial 26 is also driven by a similar variable speed motor having a driving coil 34 and a brake coil 36. The

with the master controller once during each revolution of the dial 20.

The hot side 38 of the power line feeding the driving coil 24 is connected, through wire 39, to the movable contact 22. In resynchronizing systems of the general type herein disclosed,

thecontacts

22, 23, are normally engaged as shown, and the contact 23is connected through wire 40 to contact 29 which is normally out of engagement 'withcontact 32. .The contact 32 is connected 2,925,583 Patented Feb. 16, 1966 to one side of a relay coil 50, the opposite side of the coil being connected to a common return conductor 51.

The brake coil 36 normally has voltage applied to it from a wire 53 which also applies this voltage to the braking coil- 25 of the master timer. The opposite sides of the brake coil 25 and the driving coil 24 are connected to the common return 54. Wire 53 is connected to a fixed Contact 55 normally engaged by a movable contact 56 connected to the brake coil 36 through wire 57. The opposite side of the coil 36 is connected to the common return 51 through wire 58, movable contact 59, fixed contact 69. The voltage thus impressed on the coil 36 deter- -mines the braking effect of the coil and accordingly, the

speed at which the dial 26 rotates.

If a secondary timer is out of step with the master, the

contacts

29, 32, will be closed while the

contacts

22, 23, are closed and coil 50 will be energized, moving the contact 56 into engagement with a fixed contact 61 which is connected to the hot. side 38 of the supply. This trans fer applies line voltage to the braking coil 36 causing the dial 26 to stop and it will dwell until it is released by the opening of

contacts

22, 23, at the master timer. The

f circuit includes a limiting resistor 62 to reduce the current in the brake coil 36 so that the dial will not run backwards. The speed control wire 53 is also connected to a fixed contact 63 which, when relay 50 is energizedfis engaged by a movable contact 64 connected through a. resistor 65 to the common return wire 51. The purpose of this contact arrangement is to substitute the load of the resistor 65 in place of the coil 36 so that the removal of the brake coil from the control circuit will not vary the voltage in that circuit. Also contact 59 is moved into engagement with contact 66 to shift wire 58 from wire 51 to thelocal common 54.

If the secondary timer is in step with the master, the

contacts

22, 23, are opened at the same

instant contacts

29, 32, are closed, so that there is no dwell of the secondary timer. An arrangement of this general type is disclosed in Patent No. 1,929,378 to Carl H. Bissell, October 3, 1933. a

This invention has to do particularly with the arrangement for varying the voltage in the conductor 53 in pro- I wire 73 which extends to the common return54.

In like manner, detector 68 is connected through wire 74 to coil 75 of an associated relay, and detector 69 is connected to coil 76 of an associated relay, and detector 73 is connected to coil 77 of its associated relay. There may be any number of these detectors 67-70 employed to take a fair sampling of the traffic moving in the sig nalized area. Each of the

relays

71, 75, 76, 77, has a movable contact 78 normally engaged with a fixed contact 79 which is connected through wire 80, potentiometer 81, wire 82, variable resistor 83, resistor 84, to the plus side of a full wave rectifier 86, 87, supplied by a transformer 88 connected by wires 89, 96, to the

feed circuit

39, 54. The movable contact is connected through limiting resistor 92 to a variable condenser 93, the opposite side of which is connected through

wires

94, 95, to a con denser 96.

When the relays 7'1, 75, 76, 77, are deenergized and their contacts 78 are in engagement with the contacts 79, the condensers 93 are. charged through the adjustable potentiometer 81. When relay 71 is closed by its detector 67, contact 78 is moved'into engagement with contact 100. The charge on the condenser 93 is thus transferred through rwires ltl l, 102, movable contacts -103, .104,..of.manually.

operable switches

105, 106, wire 107-, to the. condenser 96.

w The condensers 93 are of relatively small capacity. The condenser '96 is of larger capacity and accumulates the charges transferred from the condensers 93 by actuation of the associated,

detector relays

71, 75, 76, 77', and this charge is transferred to the grid 110 of tube -.111. .The output of tube 111 iscompared with the .voltageon conductor 53 which is supplied from a variable. transformer 115, seevFigure 4, and the resultant of .the. voltage of the tube output and wire 53 is fed to :a..serv o amplifier 116 for the control of a motor 117. The tube 111 is supplied with plate power through the ,transformer 118 and rectifiers 119, 120, the output of V @which isfiIteredTbycondenser 121. The arrangement -.is such..that .if the grid 110 is at zero potential, high =.plate current flows givingva potential drop across resistor -12 lfthe grid 110 is madehighly negative, plate current:..stops and there is'no potential across resistor 124. aThesgrid-is normally biased so that there is no plate scurrent. .Actuations of the detectors 67- 7% decrease -Ihis.bias, allowing plate current. to flow and, as the '.charge on the condenser 9 6 is increased by successive r.-detector ;actuations, the potential across the resistor 12 4 51's, increased and accordingly, the voltage in conductor .12 is.increased. eczBias potential is supplied by the transformer 126 and '.rectifier,.1 27 and is filtered by the condenser 128. The .positive.- output is connected through

wires

129, 130, .-..tot the cathode 131 of tube 111. The negative output connects ,to the grid through conductor 134, resistor .135, .wire 136, resistor 137. The resistor 137 is provided to limit or prevent excessive grid current when sit has. positive bias.

..z-tive with.respect to the side connected to wire 95. 7 Each 7 actuation of a detector transfers a pulse of charging The resistor 138 is employed to' agive a definite maximum resistance. from the bottom of termines the voltage on the wire 53. Also, as previously prect relation to traflic density, the pointer 153 of trans-' former 'must be re-positioned accordingly. This is stated, the pointer 153 is moved by reversible motor 117 through the action of the servo amplifier 116 which, in turn, operates according to the function of the voltage of conductors and 53. The conductor 125 forms a.

portion of a loop circuit starting from the common return wire 5 through wire 1%, wire 129, the left portion of resistor 124, wire 125, pointer 158, wire 159, resistor 160, theleft'portion of resistor 161, wire162, pointer 163, wire 164,

resistors

165, 170, 17 1, voltage limiter 172, wire 173, to the common side 54. Two major potentials are injected into this 'circuitone is that across the resistor 124 broughtabout by detector actuation. The other is across resistor 165 proportional to the voltage in conductor 53. The circuit is arranged so that these two potentials oppose each other. If they are equal, no current flows through the loop. This condition prevails only when the voltage of conductor 53 is equal to the flow of traflic in the signalized'area.

If the voltage inconductor 53 does nothave the corefiected bylthe reversible motor 117 under the' control of the servo amplifier 116. The amplifier input is taken from the balancing loop or bridge circuitacross the coil 201 being connected to the common return 54. This transformer furnishes voltage to a

circuit

204, 205, including a rectifying tube 206. This circuit includes a filter'arrangement including the condensers 207 and '

resistors

208, 209. With this arrangement, a D.C. voltage is. supplied to the loop circuit through the

conductors

204, 205, and this voltage is in direct proportion to the ,voltage on the conductor 53. a The arrangementis' such that the voltage in the

circuit

204, 205, opposes the voltage" introduced in the loop circuit by plate current from tube 111 flowing through resistor 124. If these voltages are equal, no current flows through' the loop. The volt- 1 age in the loop circuit, modified by'the voltage in the acuriient, and resistor 141 smooths out these pulses so that the potentialacross the condenser 140 changes ;:;gradually.w The condenser 96 and theresistor 14-1 thus ;,ser.ve; t o filter out the pulsationsbefore' they can reach t the condenser 140. 'The resistor 'notonly couples .;.the grid to the cathode butalso serves as a discharge element for condenser and, by the same token,

v:{condenser 96.. This resistor is continuously removing the charge from these condensers. Actuations of the Qdetectors charge the condensers, and resistor 135 is c ontinuously discharging them. The voltage on the con- ,densers can not rise indefinitely, but will stop when the rat,e ofcharge and discharge are equal. Accordingly,

.. the potential across the condenser 140 is therefore proportional to traflic density.

? 1 ..;Eachfof the

detector relays

7l, 7s, 76, 77, when ..-energized, acts to increase the charge on the condenser .140. The operation of the relays can be independent or simultaneous since each relay circuit is complete in 'itself. .Continuous closure of one relay will not neu- .tralize the others because, it simply holds the small ca- ..pacitor 93 .across the condensers 96, 140, producing an effect of no importance. V V

As previously. stated,.the' voltage in conductor 53 is producedby' the variable transformer 115. .The winding 150..-ofr. the transformer is. connected to the hot'feed 39 =th'rough .wire 151'and to l the return 5l ,by wire 152. The movable pointer 153 is connected to wire 53. The

circuit

204, 205, appears across the limiter 172 which consists. of rectifiers 210, 211, thecharacteristic of which is such that they will notpass'current ofeny appreciable value unless there is a potential of one volt or more inf the" circuit. Above this value, they pass current that increases rapidly with rise in potential. The resistor absorbs the excess potential that is "blocked from the amplifier circuit by the limiter 172. The resistor 171 is employed only to, reduce the sensitivity of the limiter 172. i i

.. The'rnotor 117 could be operated by a polarized'relay with its coil connected in the bridge or loopcircuit," or

could be controlled by a magnetic amplifierof the proper design. However, when an A.C. servo amplifier is'emv rter to change the DC. to AC. This'rectifier combi- V ployed, as in this case, direct current. output acrossthe limiter 172 will not effect operation of the amplifier. The DC. must be converted to A.C., and

rectifiers

220, 221, 223 and 224 are used in abridge arrangement as'a connation is fed with about six volts AC; from the secondary of a transformer 225, through

wires

226, 227, and in- 1' cluding a resistor 228. The current from the transformer flows downwardly simultaneously through the two-rectiher arms during halfof the cycle. The current is blocked during the other half of the cycle. The rectifiers are matched so that there is no potential between the left and right junctions of the arms connected to the wires 230,

231, when the rectifienbri'clge is balanced. However, if there is a DC. potential fed through the-wires 230,231,

* from the loop circuit, the balance will be disturbed and an alternating component will be superimposed upon the i DQ, potential. The. wires 230'; 231, "are connected to also supplied with A.C. power from

supply

39, 54, through wires 236,237.

It w'illibe apparent that the polarity of this component will be dependent upon the direction of the bridge unbalance. 'In other words, the polarity in the wires 230, 231, which depends upon the direction of unbalance in the potential between the loop circuit depending on the output of tube 111 by detector actuation, and the potential in the

circuit

204, 205, which is proportional to the potential in wire 53.

The result of this unbalance is the rectifier bridge 220- 224 is a flow of alternating current through the coupling capacity 236 to the amplifier 116. Any frequency components higher than sixty cycles are attenuated by filter condenser 237. Accordingly, there is an AC. input to the amplifier 116 when the rectifier bridge is unbalanced I and the instant polarity of the A.C. current with respect to the instant polarity in the

A.C. supply circuit

236, 237, i is dependent upon the direction of bridge unbalance. This AC. is amplified by the servo amplifier in a conventional manner and applied to the servo motor 117 through wire 240.. This current drives the motor in one direction or the =other, causing the movable slider 153 of the auto transi former to rotate in such a direction as to rebalance the bridge. This results in a system of density control wherein the speedof the master and secondary timer dials 20, 26, operate continuously at a speed comparable to trafiic (density. p 4

It is desirable to provide for certain adjustments in the apparatus to more elfectively handle traflic condittions existing in a particular installation. For example, "it is desirable that the system should always operate on ithe shortest cycle that traffic in the area controlled by the system can follow. This gives the maximum speed of progression. As tratfic density increases, the cycle period of the trafiic signal increases, assuming that the vehicles ':are impeded by the density and can not reach a fast pro.- :gression of speed. High density at low speed should give :a longer cycle to the signals than the same density at high :speed and this arrangement handles traffic most efficiently.

It is therefore desirable to provide adjustments so that the trafiic cycle will be controlled in part by the speed of the :moving traffic. It is also desirable not to have the cycle period shifting or changing for a short or momentary increase in the density of traffic. It is also desirable to prov ide iior operation of the system at certain times on a fixed Ehasis rather than according to the density of trafiic. My

system provides for such adjustments.

, When the slider of the potentiometer 81 is positioned .at the top of the resistor, the condensers 93 charge only 5 :to the grid bias potential that is across the condenser 123 and resistor 138. The capacity of the condensers 93 is low enough so that the quantity of charge transferred for actuation is low. If the slider is positioned at the bottom of the resistor 81, the condensers 93 will charge to a value equal to the grid bias plus the potential across the resistor :81. This gives a high transfer per actuation. "tentiometer 81 therefore may be considered as a master weighting control for all detectors and the detectors can be weighted individually by adjusting the condensers 93. The circuit between the contacts 100 and wire 101 include 'a potentiometer 250 which serves to limit the dischargeof the condensers 93 to a safe value and which can be :adjusted so that the complete charge is transferred from.

The po- ;the condensers 93 only for the slowest moving cars.

The potentiometer 161 is employed to adjust the mini- :mum cycle. It is used for injecting an adjustable voltageinto the bridge loop circuit. A fixed potential across the potentiometer 161 is supplied by a transformer 252, rec '

Jtifier

253, 254, and a filter condenser 255. When the :slider of the potentiometer 161 is at the left end of the resistance, as shown in Figure 4, the operation of the bridge circuit is as previously described. If the slider is :moved toward the right, a potential is inserted and polariized to add to that developed in the resistor 124. In this 6 event, even though there is no traffic the servo amplifier receives a voltage and raises the potential on wire 53 'uhtil the voltage acrossthe resistor 124 equals that inserted or added by 161. This determines the minimum cycle that will be given; v

Provision is made for cancelling out temporarily any cycle increase completed by actuation of the detectors. This is accomplished lay pressing switch 106. removes the grid of tube 111 from the condensers 96, 140, and connects it to the negative bias supply through wire 260.

The maximum cycle period obtained is adjustable by the potentiometer 124 for automatic operation. If the slider of this potentiometer is set to the left end of the resistance, no current is delivered to the loop circuit and actuation does not increase the cycle. If the slider is set to the extreme right of the resistance, it delivers enough potential to wire 125 to give the system maximum cycle. This happens when the grid bias becomes zero. Push button switch 105 when pressed disconnects the grid of tube 111 from the condensers 96, 140, and it connects the grid to the cathode through wire 261 simulating maximum density. The potentiometer 124 can then be adjusted for the maximum cycle by observing the change in the voltage on conductor 53. In the manipulation of the switches .105, 106, the detector relay contacts 100 are disconnected from the condensers 96, 140, and the resistor 135. is disconnected from the condensers. i

For operating the system on fixed cycles, the two gang switch arrangement 158, 163 can be rotated to any one of five positions. When switch 158 is moved out of engagement with the contact of wire 125, the resistor 124 is removed from the bridge circuit. The switch 163 connects any one of the five

potentiometers

269, 270, 271, 272-, 273, to the wire 164. This injects an adjustable potential which must be balanced by the potential at resister 165 and the voltage on Wire 53 automatically assunaes the necessary value. The potentiometer 269 may :he set to give a cyclefor example, of fifty seconds; the

potentiometer 27 0 to give a cycle for sixty seconds, and so on. Accordingly, rotation of this gang switch provides any offlzpiurality ofidesired pre-set cycles.

During automatic operatiomit may be desirable to adjust for acertain unregistered density that must be exceeded before any cycleincrease occurs. This is accomplished by overbiasing the tube 111. The input to the bias rectifier 127 comes from the voltage divider 275 connected across the secondary of the transformer 126. The resistor 276 has such a value that when the slider of 275 is at the left end of the resistance, the bias is just enough to stop the flow of plate current. As the slider is moved to the right, the bias is more than enough to stop plate current. Then there must be a certain trafiic density before the bias will be reduced below the cut-oft value of the tube 111, ailowing plate current to flow and change the cycle. When this adjustment is made to increase the unregistered density, it is at the same time desirable to increase the master Weighting of traflic in order that the master trafdc density will give the maximum cycle. To avoid adjustment of the potentiometer 81, the potentiometer $3 is coupled mechanically to the slider of potentiometer 275, whereby when the slider 275 is moved to the right, the slider of 83 moves upwardly increasing the voltage across 81. This automatically gives the required 7 increase in weighting.

What I claim is:

1. Trafiic signal control apparatus responsive to traffic density comprising a master controller, a plurality of variable speed secondary controllers operable through repeated cycles for the control of tratfic signals, all of said controllers being connected .to a control circuit, a power supply for said control circuit including a voltage control means adjustable to increase and decrease the voltage on said control circuit, each of said controllers having means for operating the controller through said "a -speed d epende t ppon --the voltage 'on said lo q cuin'apl iralityof vehicle-actuated detectors disposed lto'befactuated" by traffic rnovirigunder the connot or said signals,"mean'soperable in'respons'e to actuationof said detectors to continuously adjust said voltage control irneans to maintain thevoltage on said control circuit ijin proportion'to'the'irequency of said detector actuation.

{2.1'lrafiic'control apparatus responsivetotrai'rlc density comprising 'aplurality of variable speed controllers operablev through repeated cycles for the control of traflic signals, all'jofsaid controllers being connected to a control circuit, means for energizing said control circuit, each bfsaidcontrqllers. having n eans for operating the' con- "troller through said' cycles ata speeddependent upon the .voltage on said control circuit, a condenser, a plurality V 'of'vehi'cle 'actuated detectors disposed to be actuated by i'traiiifimoving under' the control of said signals, means fior'c'onstantly discharging said condenser, means operable upon each actuationot each detector to increase the "charge on fsa'id condensen and means operable to conitinuou'sly adjust-the voltage on said control circuit in proportiomto the voltage across said condenser.

l'fTraffic control apparatus responsive to traiiic den- ;sity comprising a; plurality of variable speed controllers operable through repeatedcyclesfor the control of trafiic signals,all of said controllers being connected to a control circuit, means for energizing said control circuit, each at said'controllers having means for operating'the controller through said cycles at a speed dependent upon Tthe'volta'ge on said cotnrol circuit, a condenser, a plurality 'ofvehicle actuated detectors disposed to be actuated by name moving under the control of said signals, means for constantly dischargingsaid condenser, means operable upon each" actu'ationof each detector to increase the "chargeion said condenser, an electron amplifying tube 'liavirig'its inputconnected across said condenser, a voltage control means jconnected to the output of said tube and T'being operable to continuously-adjust the voltage on said controlcircuit in proportion to the voltage of the output of said tube.

4. Traffic control apparatus responsive to traffic density 'cornprising a plurality of variable speed controllers operable through repeated cycles for the control of traffic sig- "nalsgall of said cotnrollers being connected to a control circuitpmeans for energizing said control circuit, eachof said controllers having means for operating the 1' controller through said cycles at'a speed dependent upon "the voltagecn "said controlcircuit, a condenser, a pin- -rali ty of vehicle actuated detectors'disposed to be actuated j bytrafiic rnoving under the control of said signals, means for constantly-discharging said condenser, means operable upofe'ach'actuationbt each detector to increase the 1 e-'onsaictcohde ranelectron-amp fying.t hehev' ing its input circuit connected across saidlcgndensena power supply' for said icontrjol circuit includ ng '.a1 ;adjustable auto .transfiormer,,.a reversible niotor operatively connected to said transformer for adjusting the same ,to increase aridfdec'reaseIthejvoltage in said control circuit, a servo amplifierfor controlling said motor, a bridge pircuit including ,theoutput of .said tube connected to said amplifier, and a feed hackcircuit-from said control circuit to said bridge circuit.

'5. Apparatus as defined inclaim 4 vwherein the charge on said condenseris increasedbyeacn detector actuation inversely to the speed of the vehicle actuating the detector.

.6. Apparatusas definedin claim 4 andincludingmeans for adding a predetermined voltage to said bridge circuit.

7. Apparatus asdefined'in claim 4 and including means for increasing the biasQonsaid tube.

8. :Trafl'lc control. apparatus responsive to traflic density comprising, apluralityo'f variable speedcontrollers operable through. repeated trafiic cycles for the control pf tratiic signals, all of said controllers being connected'to a control circuit, ,meansforenergizing said control circuit,

each of said controllers having means foroperating the controller through; saidcyclesata speed; dependent upon the voltagejon said controlcircuit, a-condenser, a pluraiityof vehicleactuateddetectors disposedto be actuated ;by traffic niovingiiuudenthe contrclq said i nals an for continuously establishing a charge of-tpredeterjrninedi value on said condenser, said;detectors being operable upon eachwactuation thereof to vary said predetermined charge, amplifying means having its input circuit corp trolledby said condenser, a power supply-torsaidcontrel circuit including,'an, adjustable voltage control, a

' lreversiblemotorpperatively connected to said voltage .controllfor adjusting the same to increase and decrease the voltage in said control circuit, a servo amplifier for controlling said ,motor, ,a bridge circuit including ,the output ofsaid amplifier n eans connected to said; servo amplifier, and a feed backicircuit from said control circuit to said bridgecircuit.

ReEer nces-Citedin the file of this patent UNITED STATES. PATENTS 2,750,576 7 Beaubien- June12,19 5 6