US3334330A

US3334330A - Multiple program traffic control systems

Info

Publication number: US3334330A
Application number: US513639A
Authority: US
Inventors: Garland E Fieser
Original assignee: EW Bliss Co Inc
Current assignee: EW Bliss Co Inc
Priority date: 1965-11-17
Filing date: 1965-11-17
Publication date: 1967-08-01
Anticipated expiration: 1984-08-01

Description

Allg- 1, 1967 G E. FIESER 3,334,330

MULTIPLE PROGRAM TRAFFIC CONTROL SYSTEMS Original Filed Feb. 26, 1957 4 s s t 1 CENTRAL 20 STATION 2| LOCAL 5 F l G. CONSTANT 46 45 $552 5 44 7 37 CYCLE LENGTH VARIABLE FREQUENCE GENERATOR CONTROL L l l l I g I INVENTOR GARLAND E. FIESER CHANNEL SELECTOR SWITCHES y 7- M F I (a. 6

Attorneys Aug. l, 1967 G. E. FIESER MUIJTIPIJE PROGRAM TRAFFIC CONTROL SYSTEMS Original Filed Feb. 26, 1957 4 Sheets-Sheet 2 l/VVENTUR GARLAND E FIESER BY 7% 8 Body Attorneys 06: E: w; mm: mm: 5.5m:

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mOhOE mDOZOmIuZ w Nw mw vfl W P [W 9 a s m s s 82 29 30. m8. 3 2 w mm .1 s e s a s Q mm? mm 2; 8 |v*V Aug. 1, 1967 G. E. FIESER 3,334,330

MULTIPLE PROGRAM TRAFFIC CONTROL SYSTEMS Original Filed Feb. 26, 1957 4 Sheets-Sheet 3 Attorneys 1967 G. E. FIESER' 3,334,330

MULTIPLE PROGRAM TRAFFIC CONTROL SYSTEMS Original Filed Feb. 26, 1957 4 Sheets-Sheet 4 Q5 48\ 595 \oos T 70 L K H6 X333 58 79 Q 72 Q /?7 4- T 1 38 37 f CONSTANT Ill 7 HS, SPEED '08 82 |o5s moron 82B \IO4S s 3 -IO3S II I95 IIQR 12s w REVERSIBLE E '11 S MOTOR I IIISS SYNCHRONOU M00 28\ w 28 60 w 26\ g) 67 I m FIG? T INVENTOR GARLAND E. FIESER 4 2 2 L2 20 2| 22 23 2 5 BY 7 8 Attorneys United States Patent 3,334,330 MULTIPLE PROGRAM TRAFFIC CONTROL SYSTEMS Garland E. Fieser, East Moline, Ill., assignor to E. W. Bliss Company, Canton, Ohio, a corporation of Delaware Continuation of abandoned application Ser. No. 366,438, May 11, 1964, which is a division of application Ser. No. 642,469, Feb. 26, 1957, now Patent No. 3,133,264, dated May 12, 1964. This application Nov. 17, 1965, Ser. No. 513,639

5 Claims. (Cl. 340-40) This application is a continuation of my copending application, Ser. No. 366,438, filed May 11, 1964, now abandoned, which is in turn a divisional application of my parent application, Ser. No. 642,469, filed Feb. 26, 1957, now United States Patent No. 3,133,264, issued May 12, 1964.

The invention relates to systems which control the flow of traffic across a number of intersections of traflic paths and which comprise a central station and a plurality of coordinated outlying local stations. The traific paths may be railroad tracks, highways, city streets, or foot paths. Traffic across these intersections is usually controlled by signals of some sort which give the right of way alternately to one and then the other intersecting path.

The invention, though not limited to autos moving on city streets, will be illustrated as applied to city streets on which traffic flows across successive intersections and is controlled by changing traffic signals. The signals, usually lights at a given intersection include at least a go signal, a stop signal and a caution signal. Usually the go signal is a green light, the stop signal is usually a red light, and the caution signal, indicating that the other signals are about to change, is usually an amber light.

Usually the amber signal follows the green signal, giving notice of an impending change of signals from green, allowing passage, to the red signal, forbidding passage. Sometimes amber also appears after a red signal before the green appears.

At each intersection apparatus referred to herein as a LOCAL STATION is provided which changes the position of switches at the proper time to cause the signals to appear according to a program.

More specifically the invention relates to such trafiic systems that are adapted to operate according to one of a considerable number of programs. The program to be used is selected from the central station. Under each program the local stations are so coordinated that traffic flows through an area controlled by the system with the least interruption.

It is obvious that in giving the green light to a car on one path, a car on the intersecting path has to stop for a red light. If we assume that at a given time twice as many cars go east and west than north and south, twice as much time might be given for the green on east and west than for north and south.

Usually one street is more important than the other; it is customary to refer to one street as the main street and the other as the cross street. The time that is required to allow traffic to flow first on the cross street, then on the main street, is referred to as a CYCLE. Looking down main street at the time when traffic on the main street has the go signal, the cycle will consist of the sum of 3,334,330 Patented Aug. 1, 1967 the time required to display the caution signal, the stop signal, and then to complete the period during which the go signal is displayed.

The cycle is divided between two periods. During the first period green, followed by amber is on the main street. During the second period green, followed by amber, is on the cross street. This division, expressed as a fraction of the cycle, is the SPLIT.

It will be apparent that under some conditions of highway surface or of visibility cars move faster or slower, and therefore better results are obtained by changing the total length of the cycle while keeping the split the same.

Since it takes time to stop a car and start it up from a stop, the ideal program will allow as many cars as possible to move at a uniform rate past successive intersections so that, looking along one path, one is green, the next red, the next green, so that traffic may flow at a uniform rate if the distances between streets are all the same length. If there are long and short blocks, it may be desirable to speed up, or to delay, the signal of the one intersection relative to the intersections that are considered typical.

The percentage of a cycle length by which the initiation of a cycle at one intersection is delayed or advanced relative to the initiation of a cycle at other intersections is called the OFFSET.

It thus appears that if the entire system is properly coordinated the cycle length at all intersections, and the split and the offset at each station, must be coordinated.

Experience has shown that any assumed preponderance of traffic in one direction will change during various periods of a day. It is obvious that there will be at least three traific conditionsmorning rush, normal day, and evening rush. Existing systems usually provide a central station that can change the operation of local stations to conform to any one of three programs. Each program represents a particular combination of cycle length, split, offset. Each local station has three dials and the selection of all dials No. 1 giving one program, dials No. 2 another program, and dials No. 3 a third. It follows that with most existing systems there can be no more than three programs, and in each program a particular combination of cycle, split, and offset are associated.

' In accordance with the present invention there is provided an improvement in a traflic control system for controlling a plurality of trafiic signal means, such as lights, which display go, caution and stop intervals to main street and cross street trafiic fiow at a tratfic flow intersection during each cycle of traflic flow signals. Signal timing and control means may be provided which are normally intermittently energized for timing and controlling the duration of the intervals displayed by each of the traffic signal means. Further, trafiic cycle length split determining means are provided for developing split determining signals representative of a desired traffic cycle length split of the intervals displayed by each of the trafiic signal means. In addition, a plurality of selectable split control means are provided which are associated with each traffic signal means with each of the split control switching means representative of a desired split. Split selecting means are associated with each trafiic signal means and are responsive to the split determining signals for selectively rendering the split control switching means active and inactive in accordance with the split determining signals. The plurality of split control switching means are normally continuously cycling through traffic signal cycles and are operative during each cycle through the selected active switching means to periodically connect the timing and control means with a source of energy.

In accordance with another aspect of the present invention, there is provided an improved trafiic control system of the type having: a master controller including a first device for providing cycle length determining signals and a second device for providing offset determining signals; and, a plurality of master controlled, local controllers for controlling traffic signal displays during each traffic signal cycle, each said local controller including a third device responsive to the cycle length determining signals for changing the duration of the cycle length of the traffic signal cycle of the local controller and a fourth device responsive to the offset determining signals for changing the offset relationship of the trafiic signal cycle of the local controller. More particularly, the improvement comprises: a device in the master controller independent of the first and second devices for providing split determining signals; and, a device in each local controller independent of the third and fourth devices and responsive to the split determining signals for changing the split of the traffic signal cycle of the local controller, whereby the split of the traffic signal cycle of the local controllers may be changed independently of changes in the cycle length and/ or offset relationship.

The primary object of the invention is to give greater flexibility to a traffic control system. It permits the cycle length to be varied by infinitesimal increments. Having selected the cycle length, the central station can select any one of four splits and any one of four offsets at each local station.

Where a traffic control system has such flexibility, and as new equipment is added as the city grows, difficulty may be experienced with back feedsthe closing of switches at one local station placing current on connecting channels that will actuate other local controllers in a manner not anticipated.

A second object of the invention therefore is to connect the central station to a selector at the local station in a manner that will cause a mechanical device at the station to run at a speed and in a manner determined by the central station. The central station does not transrnit any signals directly to the apparatus that controls the changing light pattern at an intersection. The mechanical device in the selector, using local current, will place current at the proper time on the apparatus controlling each signal light. Since the electrical system leading from the central station to the mechanical device in the selector and the electrical system controlled by the mechanical device that leads to the traffic lights have no common electrical elements, there can be no feed back.

Another object is to provide local controllers that will always give the same duration of the caution signal, regardless of what combination of other elements is used.

Experience has shown that the driver of a car gets used to a caution light at a given intersection having a certain duration. If this light stays on a longer or shorter time than the driver anticipates the driver gets confused. Hence, though the cycle length at a given local station varies, the time the amber is on should remain unchanged. In the three dial systems described, each of the three dials can be set for the same length amberbut if the cycle length is varied independent of other factors or if there is only one dial, this fixed length of amber is lost.

Another object of the invention is to synchronize the local stations in a manner that, if the line from the central station to the local stations should fail to function, each local station will continue to function as an independent unit.

In most existing systems the signal changes are brought about by the use of local current. To make sure the signals at adjacent intersections remain in step, all

the local controllers come to a stop at the end of a cycle and are started off on the next cycle by a synchronizing pulse received from the central station. Should the line connecting the central station with local stations be broken, all local controllers might come to a complete stop at the end of a cycle and trafiic over the entire city might be tied up. To avoid this, the invention synchronizes in such a manner that, should the synchronizing current fail, each local controller would continue to function as an independent, nonsychronized traffic controller.

Another object is to avoid transitional cycles of abnormal length. The cycle has been defined as the time that elapses from the time caution goes on for traffic in a given path and both the stop and go signal periods are completed. Normally these cycles are of the same length.

However, if the offset is changed during a cycle, that cycle obviously will be longer or shorterthis is called a transitional cycle. In existing systems, if the offset is changed, the local controller is thrown out of synchronism and must wait until the next sychronizing pulse may come.

To illustrate with an extreme case, the cycle at a given time may be 60 seconds. Let us assume further that there is a split into 20 seconds for the cross street, 40 seconds for the main street. If during the change of offset the local controller is brought out of synchronism, it may have to wait almost 60 seconds-let us assume it waits 50 seconds before it starts. Then, if that offset change came when the cross street had the right of way, we will have a transitional cycle of 110 seconds, divided by 20 seconds for main street and seconds for the cross street. Such a transitional cycle will confound traffic for quite some time thereafter.

The invention avoids this by dividing the extra time that goes into the transitional cycle over several cycles and always in proportion to the split being used.

The cycle length of a controller, momentarily out of step, is shortened or lengthened depending upon which will require the least time to get into step. The controller does not stop but rather runs on a slower or faster total cycle ratio and maintains the desired split even through this transition period.

Another object is to reduce the time required to change to a different offset by either lengthening or shortening the transitional cyclewhichever requires the least time to accomplish.

The invention contemplates selecting, at the central station, the cycle length by changing the speed of a mechanical device at the selector at each local station, and selecting which switches controlled by that device should determine the offset. To reduce the period of confusion in changing from one pattern of operation to another, the shift of the mechanical device to allow for a different offset should be made as rapidly as possible. To accomplish this a reversible motor is used to advance or to retard the switches relative to the shaft driven at a constant speed related to the length of the cycle.

FIGURE 1 indicates, diagrammatically, a system incorporating the invention;

FIGURE 2 is a plan view of a portion of the apparatus at each station in FIGURE 1 of the system drawn to a larger scale;

FIGURE 3 is a section taken along line 33 in FIG- URE 2;

FIGURE 4 is a section taken along line 44 in FIG- URE 2',

FIGURE 5 is a section taken along line 5-5 in FIG- URE 2;

FIGURE 6 shows diagrammatically the apparatus at the central station indicated at 1 in FIGURE 1;

FIGURE 7 is a wiring diagram;

FIGURE 8 is an exploded view showing a portion of a modified dial;

FIGURE 9 shows a typical relay; and,

FIGURE shows a modified form of some of the elements of FIGURE 1 when three trafiic paths intersect.

The invention will first be described as applied to the usual intersections of two pathsa main street and a cross street.

1 indicates the central station that controls the local stations both as to the length of the cycle, the split, the offset, and also their synchronization. The term local station includes all of the apparatus at a street intersection that is required to control the change of signals at that intersection.

At each local station there is a selector 2 shown in detail in FIGURE 2. Each selector is connected to the central station by six

channels

20, 21, 22, 23, 24, 25, not counting the common return. In the illustration the common return is not shown, the various units which are sometimes connected to a common return, being shown grounded.

Only two local selectors are shown in FIGURE 1 though it is understood that there may be a large number of selectors in the system.

Each selector controls a timing and control device generally indicated at 3 and also shown in part in FIGURE 8. In existing traffic signals systems such timing devices are referred to as dials. The timing device will be so referred to herein. Each dial permits adjustment of the cams shown relative to each other.

The dial controls the operation of a stepping switch 4. The selector and the dial determine when the traflic signals generally indicated at 5 are to be changed by the stepping switch. The traflic signals are here illustrated by three lights 50,- 51, 52 which may respectively show amber, green, and red on main street and three lights 53, 54, 55 that show amber, green and red respectively on the cross street.

The stepping switch 4 has a shaft 46 carrying eight cams. Cams 40-45 each control one of switches 40s45s. To facilitate associating each switch with the cam or relay actuating it, the switch carries the cam or relay number which controls it, followed by an s. As shown, the cams have raised portions, and when the follower of the switch is in contact with the raised portion, the switch is closed. Each of these switches connects line 8 supplying current to one of the traffic lights 5055 at a time determined by the shape and relative position of the raised portions of each of the particular cams 40-45. Cam 49 on shaft 46 controls switch 49s that places atappropriate times current from line 8 on line 76 leading to relay 70. Cam 59 on shaft 46 controls switch 59.9 used in keeping shaft 36 of dial 3 and shaft 46 in proper relationship.

The shaft 46 is moved by solenoid 48 that actuates ratchet wheel 47 on the shaft. While only six signals 50 55 are shown, it is obvious that by placing more cams in the stepping switch and more steps on ratchet 47 more signals can be controlled. Thus intersections of more than two streets requiring more than six trafiic lights may be controlled. It is also obvious that the traffic signals can be of any electrically controlled type and are not limited to street lights.

The dial 3 at each intersection does not run continuously but it does make one revolution during each cycle. The dial at any other intersection does the same. This dial runs at a fixed speed during the time all signal changes that are required to shift the right of way from one street to the other are made, then stops until the next shift of right of way is to be made.

The cycles at the various street intersections are set to start at fixed, related, intervals to permit the smooth flow of trafiic through successive street intersections. Should one dial lose or gain in travel relative to other dials, the flow of traflic would be adversely affected. Hence it is customary to provide for synchronizing the operation of all dials. Channel 21 leading from the central station to each local selector is used, in a manner to be described more fully, to synchronize all selectors. Each selector then sends out an impulse at the proper time to its dial.

The function of the dial shown in FIGURE 1 and generally indicated at 3 is to provide current at the proper time to actuate stepping solenoid 48 to move the shaft 46, and the cams carried by the shaft, one step at a time to change the signals at a particular intersection.

The dial 3 in FIGURE 1 is shown in the position when a cycle is approaching completion, traific is flowing on main street with a go signal, and when the apparatus is awaiting a signal from selector 2 to terminate the first part of the cycle.

The dial has a shaft 36 that can be driven by a motor 37 at a constant speed sufficiently fast to make a half revolution in less time than is required to complete the shortest split of the shortest cycle for which the apparatus is designed. The shaft 36 carries cams 3033 which respectively control switches 30s-33s.

While the dial 3 is shown diagrammatically with a cam 30 having several projections in fixed relation to each other, each of the

projections

74, 78, is shown in exploded view, FIGURE 8, as an arm mounted independently of the other arms on the shaft 36. Each arm carries a set screw that permits setting the arm in a particular relation to the dial disc 121 that is permanently fastened to the shaft 36 such as by a pin 123. In this way the positions of the projections can be varied to secure any desired length of the amber light period. It will be recalled when shaft 36 runs, it runs at a fixed speed and the angular positions of the

projections

74, 78, 80 determine when the ratchet 47 is to be actuated.

Motor 37 receives its current over line 38 that connects with switch 70s. In the position shown, with relay 70 deenergized, switch 70s connects with line 71 that leads to switch 33s which is shown as open. Accordingly, the shaft 36 is at rest. When current comes over line 58 from the selector 2 to line 71, it passes over switch 70s to line 38 and the motor 37 starts to turn shaft 36 in the direction of the arrow. Thus turns cam 33 and closes switch 33s that now provides current from L2 over

lines

79, 72 over switch 33s and line 71, switch 70s and line 38 to continue running motor 37 after current ceases to flow over 58. The shaft 36 therefore continues to revolve and a projection on cam 31 closes switch 31s and current now flows from line 8, line 79, switch 31s, line 73, to ratchet sole noid 48. This will turn shaft 46 one step and the cams carried thereby are usually set so that the switch 31s causes cam 40 to close switch 40s toturn on the amber signal on main street, while cam 41 opens switch 41s and thus turns off the green signal on main street.

As dial shaft 36 continues to revolve, a projection 74 on cam 30 closes switch 30s. This places current on ratchet motor 48 if switch 59s is already closed. Current then flows from L2 over line 8, switch 59s, line 75, switch 30s to ratchet motor 48 and shaft 46 moves another step.

The initial contact is made by cam 31, and the next contact by cam 30 if switch 59s is closed primarily to assure that stepping switch shaft 46 is iri a particular position when the selector places current on line 58 to start a new cycle.

No matter in what position shaft 46 is when the cam 31 closes switch 31s to terminate the first part of the cycle, solenoid 48 will move shaft 46 one step. If the shaft is in the position shown, that will move cam 59 to a position where cam 59 has closed switch 59s and as cam 30 sends out subsequent impulses by closing switch 31s, current will flow over switch 59s as described to switch 30s and on to ratchet solenoid 48.

However, if shaft 46 is not in the position shown, the

ratchet solenoid 48 will respond to cam 30 and switch 30s only until green is on main street and then cam 59 will open switch 59s. The shaft 46 now stops until the termination of the first part of the cycle starts when cam 31 will close switch 31s and again start shaft 46.

If at the start of a new cycle the shaft 46 is in proper position, cam 41 is holding switch 41s closed giving a green light 51 on main street and cam 45 holds switch 45a closed giving a red light 55 on the cross street. If ratchet solenoid 48 is actuated, the shaft 46 carries the cams to a position where cam 40 closes switch 40s energizing amber light 50 on the main street, cam 41 opens switch 41s turning off main street green signal 51. However, cam 45 still holds switch 45s closed, keeping the red signal 55 on the cross street. It will be noted that the length of the amber period is fixed by the relative position of

cams

30 and 31 and the constant speed of motor 37. When the shaft 46 has made the second step initiated by projection 74-, the projection on cam 49 closes switch 49s and places current from line 8 on line 76 that energizes relay 70 and draws switch 70s into contact with line 77. Current now flows over line 7?, switch 32s, line 77, switch 70s, line 38 to keep motor 37 running. However, when the shaft 36 has made half a turn cam 32 will open switch 32s whose follower is now in the cam notch and prevents any further flow of power over line 77 which will cut the current off line 38 and stop the motor 37. The main street now has a red signal, the cross street a green signal and these remain until the dial is started again.

To start the dial again, current must come over line 57. When this happens current fiows over

lines

57, 77, switch 70s, line 38 to motor 37 and the shaft 36 revolves again. The shaft 36 is turned enough to lift the follower of switch 32s out of the notch in cam 32 and current now flows from L2 over line 79, switch 32s and line 77 to mot-or 37 and keeps it running even though the current over line 57 ceases.

Projection 78 on cam 30 will now close contact 30s and cause ratchet solenoid 48 to step shaft 46 one step if cam 59 holds switch 59s closed. That will place amber on the cross street, turn off the green on the cross street, leave red on the main street.

After the lapse of time desired for the fixed amber period, projection 80 on cam 30 again closes switch 30s and this causes the shaft 46 to be moved one more step. This will place the green on the main street'and the red on the cross street. The shaft 36 now continues to run at a fixed speed until cam 33 again opens switch 33s. This stops motor 37. Thus, the single dial 3 will, each time it is started by current on either

line

57 or 58, turn through a half turn and in so doing will turn off the green on whichever street it is, turn on the amber on that street for a fixed time, then turn on the red light, while on the other street the red is held while the amber is on the first named street, then changes to green.

When this change from green to red and red to green on the two streets is accomplished, the dial stops and awaits another signal from the selector. In describing the operation of dial 3 and stepping switch 4 it was noted that current must periodically come from the selector 2 over

lines

57 or 58 if the apparatus is to continue in operation.

Summarizing, the function of dial 3 is to provide amber signals of fixed length before the green changes to red regardless of the length of the cycle or the split or offset. Thus, it is seen that the dial 3 may be defined as signal timing and control means which is normally intermittently energized for timing and controlling the duration of the intervals displayed by each of the traffic signal means.

The operation of the selector shown in FIGURE 2 will now be explained. Referring to FIGURE 2, and assuming that motor 114 is not energized but motor 60 is energized, it will be clear that motor 60 will turn shaft 62 through a gear system. The shaft carries two cams 63, 64-. As will be explained later, motor 60 is normally supplied with current from the central station over channel 20 in FIGURE 7, and the frequency of that current determines the speed of motor 60 and thus the length of time it takes for one cycle which is equal to one revolution of shaft 62. The function of these earns 63, 64 is to synchronize this selector 2 with all other selectors by assuring that at one point in the revolution of shaft 62 it Will be in a preset relationship to the shafts 62 of all other selectors 2 in the system. Referring to FIGURE 3 it will be seen that each cam is circular but has a step that permits the

spring arms

65, 66 to d p at the appropriate time. The contact 67 is open during almost the entire revolution, all except for the short period measured by angle 68. This angle is usually made 1% of one revolution of shaft 62.

Referring to FIGURE 7 it will be seen that during normal operation of the system, with current on channel 20, current will pass through fail-safe relay coil 26 which will draw switch 26s into contact with line 61. This provides current from channel 20 over switch 27s, line 61, switch 26s, line 69, to motor 60. During one percent of each revolution of shaft 62, contact 67 is closed and channel 21 is connected over contact 67 to relay coil 27 during that 1% of the revolution of shaft 62. Channel 21 carries a synchronizing current 98% of the time.

If the shaft 62 and cam 63 are in synchronism with the central station, the switch 67 will close during the 2% of the time there is no current on channel 21. Relay coil 27 will not be actuated and switch 27s will not open.

However, if shaft 62 gets out of synchronism and closes contact 67 while synchronizing current is on channel 21 the relay 27 will attract armature 27s and break the circuit to the motor 60 which will now stop until the current fiow in channel 21 again ceases at the end of the cycle. That allows relay 27 to permit armature 27s to re-establish current flow to motor 60. Thus, the shaft 62 is synchronized with similar shafts in all selectors in the system.

One of the features of the circuit is that if for some reason variable frequency channel 20 fails to function, relay 26 which is normally held closed will open, armature 26s will make contact between line 28 and motor 60. The motor 60 will then cease the selector to function independent of the central station and traffic signals will be changed even though on a program not coordinated with adjacent intersections.

The manner in which motor 60 actuates apparatus to place current on

lines

57 and 58 to initiate each split of the cycle will now be described. 91 indicates the carrier gear of a differential transmission, riding free on shaft 62 and rotatably supporting double gears each having toothed portions 33-94 meshed respectively with pinion 92 and gear 95. While gear 91 is held at rest by a gear 115, pinion 92 which is permanently fixed to shaft 62 through double gears 93-34 will turn pinion 95 riding free on shaft 62. Through interposed gearing this pinion 95 drives shaft 96 carrying split control switching means including at least four pairs of

cams

100, 101, 102, 103 for controlling contacts 100s, 101s, 102s and 103s (see FIGURES 2 and 7). With gear 91 at rest, the speeds of

shaft

62 and 96 are the same if the various gears between

shafts

62 and 96 are properly selected.

The drawing shows three additional split control switching means such as pairs of

cams

104, 105, 106 that may be used in the modified form of the invention to be described later.

The purpose of cams 101, 102, 103 is to close contacts which provide current on line 58 at a time depending on the split of the cycle desired, to initiate movement of dial 3 to terminate the first part of the cycle as previously defined.

The purpose of cams 100 is to close a contact 100s that places current on line 57 at the proper time to initiate movement of dial 3 to terminate the second part of the cycle.

These pairs of cams are similar in construction. FIG-

URES

2 and 4

show cams

100A, 100B, forming cam pair 100. Each cam can be adjusted by set screws 97 to any desired angular position on shaft 96. The cams of any pair are usually adjusted relative to each other so that angle 68B is about 18 degrees. Each cam has a drop and a

spring contact arm

65 or 66, that closes a contact between its

arms

65,66.

Each of the cam pairs 101, 102, 103 is set on shaft 96 at a different angular position relative to cam 100 and any one of the three cams can close a contact to place current on line 58 to initiate termination of the first portion of the cycle. Thus, cams 101 may be set to close contact 101s a half revolution before cam 100 closes contact 100s, would be a 50-50 split. Cam 102 may be set to close its contacts 102s, /3 of a revolution before cam 100 closes contact 100s, that will give a 33-67% split of whatever total cycle length is selected.

Each of these contacts 101s, 10263103.: can supply power, if current is supplied to the line containing the contact, to line 58 which feeds current over switch 70s in the position shown in FIGURE 7 to line 38 leading to motor 37 to keep it in operation through the first termination of the portion of the cycle. Which of cam pairs 101, 102, 103 is to determine the split is decided by the central station which controls relays that supply current to only one of the contacts controlled by the cam pairs.

Channel 25 leads to split selecting mean-s in the form of relay coil 11 which controls the position of two switches 11s. The relays in the selector controlled by lines to are generally similar, some, like relay 11 illustrated in FIGURE 9 control two switches, others only one switch. Referring to FIGURE 9, channel 25 leads to a grounded relay coil 11. The frame 124 which carries relay coil 11 also carries the screw 125. Separated by insulated discs are a number of elements including two flexible arms forming switches 11s. The frame 124 pivotally supports armature 126 that moves pillar 127. Pillar 127 moves switches 11s from their normal position. If current is on channel 25, current which otherwise goes to line 83 will be switches to line 85.

If neither

channels

24 or 25 carry current from the central station to the selectors, the switches 10s and 11s will be in the position shown in FIGURE 7 and current flows from L2 over line 81, switch 10s, line 82, switch 11s to line 83 and thence to line 58 at the instant when contact 103s is closed. This contact is closed by cam 103, as described, only for a short time during the revolution of shaft 96. At that instant, current flows over line 58 to switch 70s.

If current is placed on channel 25 at the central station, switches 11s are moved, and now, to start the termination of the first portion of the cycle current must flow over line 81, switch 10s, line 82, switch 11s, line 85, contact 102s, line 58, switch 70s, line 38 to motor 37. This differs from the previously described circuit only in that contact 102s is substituted for contact 103s. Therefore, cams 102 now determine the split and not cams 103. If current at the central station is placed on channel 24, split selecting means in the form of relay coil 10 will be energized and move switch 10s. To start the' termination of the first portion of the cycle current must now flow over 81, switch 10s, line 86, switch 101s, line 58, switch 70s, line 38. This will happen when cams 101, on shaft 96 in FIGURE 2 close contact 101s.

It has been shown that the selector has a normal split, governed by cams 103, but that by placing current at the central station on the proper channels, the split created by each selector will be determined by cams 101 or 102. All three sets of cams 101, 102, 103 can be set on shaft 96 so that each cam pair gives any desired split. Thus the selector will initiate the termination of the first portion of each cycle by placing current on line 58 at a time determined by whether channel 24 or channel 25, or neither, is energized.

As described, the current on line 58 initiates the operation of motor 37 and that causes the go signal on main street to be terminated, the caution signal to be held for a fixed time, and then the stop signal to be shown on main street while a go signal appears on the cross street. Motor 37, after turning shaft 36 through a set part of a revolution, stops.

Meanwhile shaft 96 continues to turn and in due course the cams place current on line 57.

This contact on the arms controlled by cams 100 is shown at 100.9 in FIGURE 7. This contact allows current from L2 to flow over line 110, line 111, contact 100s, line 57, switch 70s to line 38 and then to motor 37. Switch 70s was moved from the position shown in FIGURE 7 at the end of the first portion of the cycle. If the apparatus is in step, cam 32 will be advanced a half turn from the position shown in FIGURE 1. The short period during which contact 100s is closed is sufiicient to allow motor 37 to turn shaft 36 far enough to move cam 32 into position to close switch 32s. Current from L2 will now flow from L2 over line 79, switch 32s, line 77, switch 70s and line 38 to motor 37 continuing the motor in operation. As already described, the dial 3 will now actuate the stepping switch 4 as needed and change the lights 50-55 to transfer the flow of traffic from the cross street back to the main street. When the shaft 46 in stepping switch 4 has turned far enough to turn on the amber, then the red, cam 49 closes a circuit over line 76 that places current on relay coil 70 which moves switch 70s to break the circuit that has kept the motor 37 running. As previously explained, switch 70s is not connected withv line 57 until termination of the first portion of the cycle which shifts traffic from the main street to the cross street has been completed. Then, with relay 70 energized and the switch 70s moved into contact with line 77 the closing of switch 100s determines when the split is to come and places current on line 38 that starts the dial motor 37 to complete the second part of the cycle.

The offsets at a particular intersection are changed by placing current on motor 114 in the selector 2.

The selector is so designed that if the central station calls for a particular offset by placing current on one of the channels leading to the local station, that current will only reach motor 114 if the offset at which the selector is operating is other than that desired. As soon as the selector operates at the offset desired by the central station, the current is automatically taken off motor 114. Moreover, to reduce the time required for this adjustment, control means are provided whereby motor 114 will turn in whichever direction requires the least revolutions of motor 114.

The motor 114, through gearing, drives a shaft 98 which carries gear and also a plurality of selectable offset control switching means in the form of four

sets

116, 117, 118, 119 of paired cams 87-88 connected to each other by studs 109. Each pair of cams can be adjusted relative to other pairs angularly as desired on shaft 98. Each cam 87, see FIGURE 5, has a raised portion 108 extending over half a circumference for actuation of a corresponding single-pole, double-throw motor

direction control switch

116R, 117R, 118R and 119R. Cam 88 shown behind cam 87 in FIGURE 5, is a circular disc with only one notch at 107. Cam 88, in each cam pairs 116, 117, 118, 119 closes a switch that remains closed until the shaft 98 has moved the cam into a position where the notch 107 of the cam coincides with a follower on the switch in the position shown in FIGURE 5. These switches, in FIGURE 7, are referred to as 116s. 117s, 118s, 119s.

The other cam 87 in each cam pair closes one of switches 116R-11-9R to line 128 when the hump of the cam engages the follower and to line 129 in FIGURE 7 if the hump on the cam does not engage the follower. The motor 114 is of a type that will turn in one direction when current is placed on line 128 and in the reverse direction when placed on line 129.

The shaft 98 carries a gear 115 that engages the carrier gear 91. Thus, when motor 114 is supplied with energy, the shaft 96 is advanced or retarded relative to shaft 62 and thus the offset is changed. Current is now placed on line 57 by cam 100, not when contact 67 closes, but at a fixed angular offset therefrom.

At any one time current is in only one of the circuits containing switches 116s-119s. If there is no current in channel 23 or channel 22, then cam pair 119 determines the offset.

Referring to FIGURE 7, with switches 13s and 12s in the de-energized position shown, it will be seen that if switch 119s is closed current will flow over switch 119R.

This will place current on either line 128 or line 129 depending on the position of switch 119R, and start motor 114. When the motor has turned cam pair 119 to the position shown in FIGURE where the follower falls into notch 107 the switch 119s will open and the motor 114 stops.

As the motor 60 turns through cycle after cycle, the motor 114 stays at rest and the gear 115 holds the carrier gear 91 at rest in the position shown.

If the central station wants the offset to be determined by cam pair 118 rather than by cam pair 119, current is placed on channel 23 to energize offset selecting means in the form of coil 12 to move switches 12s. Current now flows from line 110, over switches 13s, 12s to switch 118s. When switch 118s is closed current flows to motor 114. Since cam pair 118 is angularly displaced from cam pair 119, switch 118s will be closed and current will flow to motor 114 to move shaft 98 and gear 115 to the position that gives the offset that corresponds to cam 118.

If the central station wants the offset to be determined by cam 117 current is placed on channel 22. This actuates relay coil 13 that moves switch 13s and current now flows from line 110, over switches 13s and 12s to switch 117s. In the manner described, this will cause drive means in the form of motor 114 to turn shaft 98 until the gear 115 has turned gear 91 to a position corresponding to a new offset.

If the central station wants the offset to be determined by cam 116, current is placed on both

channels

22 and 23. Current now flows from line 110, over switch 13s, switch 12s, to switch 116s and if that is closed, over switch 116R to either

lines

128 or 129.

It will be noted that changes of offset are accomplished by motor 114 entirely apart from synchronization which is controlled by

cams

65, 66 and motor 60.

Therefore, if when the motor 60 is being synchronized a change in offset is in progress, the actuation of motor 114 will merely cause the differential gear 91 to be moved in a manner to change the time when the cycle beginning and split is initiated by cams 100-103 carried by shaft 96. At the end of any cycle this change in length of the transitional cycle will be determined by the amount of travel of shaft 98 necessary to change the offset that is being completed.

The apparatus at each location that directs the flow of traffic, comprising traffic signals, stepping switch, dial and selector have been described. The central station 1, shown in outline in FIGURE 6, will now be described. A variable frequency generator 15 is supplied with current from lines L2 and L1. The frequency transmitted to

lines

16 and 17 may be changed by moving lever 18. Line 17 is connected to the outgoing channel 20 that leads to all local controllers at street intersections.

Lines

16 and 17 lead to a variable speed motor drive 19 that turns the cam 29 to make one revolution for every cycle of traffic signal change.

Current from L2 flows over switch 29s to channel 21 except when the notch on cam 29 briefly opens the switch 29s. That interruption of current on channel 21 is used to synchronize all the selectors in the system in the manner previously described.

L2 also supplies current to switches 22s, 23s, 24s, 25s.

Closing of either switch 22s or 23s, or both, changes the offset at the selectors by sending current over

channels

22 and 23.

Closing of switches 24s or 253, places current on

channels

24 or 25 that determine the split at each selector. While these switches 22s-25s are shown as hand actuated, it will be understood that they might be actuated by a programming device of any sort.

In view of the foregoing description of central station 1, it will be appreciated that the generator 15, together with the motor drive 19 and cam 29, serve with switches 24s, 25s and

channels

24 and 25 as traffic cycle length split determining means for developing split determining signals representative of a desired cycle length split of the intervals to be displayed by each of the traffic signal means, i.e., lights 50 through 55. Further, it will be appreciated that the generator 15, motor drive 19 and cam 29 serve with switches 22s and 23s and

channels

22 and 23 as offset determining means for developing offset determining signals representative of desired offsets.

The operation of the system will now be described.

A series of plans for handling traffic flow under various conditions such as morning rush, normal traffic, evening rush are first made. A decision is made how long the amber is to stay on and the

cams

30, 31 on the dial 3 are set so that one cam 31 will start the amber interval on the main street, the next earn 74 will start the green interval on the cross street and the red interval on the main street with a set lapse of time. The dial 3 runs always at a fixed rate and comes to a stop after the green has been shifted from one street to the other. The length of time the amber is on may be set differently for different intersections if desired.

The length of the cycle desired at any particular timethe same throughout the systemis now determined by moving lever 18 to change the frequency of the current sent out over channel 20 from the central station. This determines how fast motor 60 will turn

shafts

62 and 96 and the

cams

63, 64 and 100-104 carried by these shafts.

When

cams

63 and 64 close contact 67, should shaft 62 be out of synchronism, the synchronizing current flowing through channel 21 will open 27s, stopping motor 60 until the central station synchronizing switch 29s opens, allowing 27s to close again starting motor 60 and shaft 62 in step with the cam 29 and the shafts at other selectors. Depending on whether current is placed on channel 24, channel 25, or neither, the switch controlled by One of the cams 101-103 is activated. Each of these cams can be set to divide the cycle into different proportions for each street intersection and whenever that cam closes a circuit, the dial is started to display amber for a fixed time on one street and then green on the other street until the dial reaches the stop and until the dial is again released by the cam 100. Thus all the local controllers are synchronized, but they may operate at different splits of a cycle, a cycle that can be varied in length, but is common to all.

When current is placed on channel 22 or channel 23, or both, current is placed on lines controlled by cams 116 to 119. If the local selector is already operating at the offset desired, the switch controlled by the cam will be in the position shown in FIGURE 5 and no current will pass to motor 114.

If the offset called for is different than the one in use, the switch will transmit current to motor 114 which will turn the planetary system through gear 115, and this will move all the cams in shaft 96 forward or backward to secure the new offset desired.

When these adjustments have been made, the selector will place current on

line

57, 58 at the proper times. Each time current is placed on one of these lines the dial 3 is started up to place current at the proper times on ratchet solenoid 48. This steps shaft 46 along so that the traffic flow on the two intersecting streets will be according to the selected cycle, split and offset.

Itv will be seen that, in contrast to the usual traffic control systems in which the local controllers contain a plurality of dials, any one of which can be connected to circuits coming from a central station whereby current from the central station actuates' relays in the local controller, the actuation of the traffic lights 50 to 55 is controlled entirely by a mechanical deviceshaft 96 and the cams 100-103 carried thereon and shaft 98 and the cams 116-119 carried thereon in FIGURE 2located at the local intersection. The invention provides means whereby the central station 1 can control the cycle length, the split, and the offset by sending out current to select which of the cam pairs 100-103 shall function to control the split, and which of the cam pairs 116-119 shall function to move the shaft 96 relative to shaft 62 by placing current on motor 114 to change the offset.

As thus far described, the invention applies to the usual traffic intersection consisting of a main and a cross street. However, the invention is not limited thereto. By way of example, for a main street and two cross streets, FIGURE shows a stepping switch which may be used in conjunction with the device of FIGURE 2 and circuitry of FIGURE 7 which are shown as including contacts 104s, 105s, and 106s operated by three cam pairs 104, 105, 106 not utilized in the usual intersection of two traffic lanes. Cams 101, 102, 103 give a choice, as described, of splits between the main and one cross street, whether there are three or only two streets. If there are three streets, one of the three cams 101-103 initiates the termination of the first portion of the cycle and determines when the portion of the cycle to be applied to passage of traffic on the main street will be terminated. One of the cams 104-106 then determines how the remaining part of the cycle is to be split by terminating flow on the first cross street.

It will be noted in FIGURE 10, that cams 130-133 on shaft 136 correspond to cams -33 on shaft 36 in FIG- URE 1. As shown in FIGURE 7, during each cycle the closure of one of switches 101s, 102s, 103s feeds current over line 58, switch 70s to start motor 37. Cam 133 will close switch 33s and provide current over line 71 to keep motor 37 running for a third of a revolution. Then the second of the two notches in cam 133 will stop the motor.

When shaft 96 has turned far enough so that one of cams 104-106 closes a switch 104s-106s that is on a line supplied with current by the prevailing split selection, current will again flow o'ver line 58, switch 70s to start the motor 37. This carries the first cross street through amber to red and places the go signal on the second cross street.

Shaft 136 continues to revolve until cam 149, corresponding to cam 49, closes switch 49s placing current on line 76 that actuates relay 70 and moves switch 70s out of contact with line 71 and into contact with line 77. As described, motor 37 will continue until the notch in cam 132 opens switch 32s.

As the shaft 96 continues to revolve cam 100 will close switch 100s and place current on line 57 that will again start motor 37. This will terminate the third portion of the cycle and permits traffic to flow on the main street.

Thus, during one cycle, referring to FIGURE 1, current is supplied once in each cycle to line 57 and twice to line 58. FIGURE 10 shows modified

shafts

136 and 146 that are substituted for shafts 36 and 46 and a six step ratchet 147 substituted for ratchet 47 in FIGURE 1.

Cam 159 functions as cam 59 in FIGURE 1 to keep shaft 146 and shaft 136 in step. Cam 149 determines when the relay 70 is to be energized to prepare switch 70s for the last split of the cycle. Cams 140, 141, 142, corresponding to earns 40, 41, 42 previously described, control signals 50, 51, 52 that provide signals controlling flow of traffic on the main street: cams 143, 144, 145, control switches 43s, 44s, s and signals 53, 54, 55 on the first cross street. Cams 163, 164, 165 are duplicates of cams 143, 144, 145, but are set at a different angle 14 on shaft 146. They close switches 163s, 164s, 165s to control

signals

153, 154, 155. These signals, on the second cross street, function as signals 53, 54, 55 on the first cross street.-

While the invention has been illustrated as applied to the usual street pattern with traffic lights controlling the flow of cars, with signals consisting of green, amber and red, it will be understood by those familiar with the art that other types of traffic, other kinds of signals, other sequences of signals in a given path could readily be provided by the invention.

I claim:

1. In a traffic control system for controlling a plurality of traffic signal means each displaying go, caution and stop intervals to main street and cross street traffic flow at a traffic flow intersection during each cycle of traffic flow signals, signal timing and control means normally intermittently energized for timing and controlling the duration of said caution intervals displayed by each said signal means, traffic cycle length split determining means for developing split determining signals representative of a desired trafiic cycle length split of said intervals displayed by each said traflic signal means, a plurality of selectable split control switching means associated with each traffic signal means with each split control switching means representative of a desired split, split selecting means associated with each traffic signal means and responsive to said split determining signals for selectively rendering said split control switching means active and inactive in accordance with said split determining signals, and means continuously cycling said plurality of split control switching means throughout all traffic signal cycles so that during each traffic signal cycle said selected active switching means periodically connects said timing and control means with a source of energy.

2. In a traffic control system as set forth in claim 1, wherein said intermittently energized timing and control means includes constant speed driven make and break switches which complete one cycle with each traffic signal cycle and are prearranged to control and time said caution intervals so that the duration of said caution intervals remains constant with variations in traffic cycle length.

3. In a traffic control system as set forth in claim 1, including variable frequency developing means for developing a trafiic cycle length determining signal of a frequency related to a desired traffic signal cycle length, said cycling means being responsive to said traffic cycle length determining signal to drive said split control switching means in accordance with the frequency thereof whereby said trafiic signal cyclelength varies substantially inversely with variations in the frequency of said cycle length determining signal.

4. Traffic cycle length split control means for controlling the traffic cycle length split of traffic flow and comprising: means for developing split determining signals, a plurality of selectable split control switching means each representative of a desired split, split selecting means responsive to said split determining signals for selectively rendering said split control switching means active and inactive in accordance with said split determining signals, and means continuously cycling said plurality of split control switching means throughout all traffic cycles so that all split control switching means are actuated once each traffic cycle.

5. Traffic cycle length split control means for controlling the traffic cycle length split of traffic flow and comprising:

means for developing split determining signals;

a plurality of actuata'ble split control switching means each representative of a desired split and each having electrically active and inactive conditions;

split selecting means responsive to said split determining signals for selectively rendering said split conl5 l6 trol switching means electrically active and inactive control switching means are each actuated by a difin accordance with said split deter-mining signals; fefent 0116 Of Said a uat r m ans. a plurality of switch actuator means each for momen- References Cited tar ly actuating a different one of sa1d actuatahle 5 UNITED STATES PATENTS split control switching means during each trafiic sig- 2 657 375 10/1953 Paul 340 Cycle; 2,939,723 6/1961 Baker 34 .4

means continuously driving said plurality of switch actuator means throughout all traffic signal cycles, so NEIL READ, Examiner.

that during each traffic signal cycle all of said split 10 THOMAS B HABECKER, Examiner,

Claims

1. IN A TRAFFIC CONTROL SYSTEM FOR CONTROLLING A PLURALITY OF TRAFFIC SIGNAL MEANS EACH DISPLAYING GO, CAUTION AND STOP INTERVALS TO MAIN STREET AND CROSS STREET TRAFFIC FLOW AT A TRAFFIC FLOW INTERSECTION DURING EACH CYCLE OF TRAFFIC FLOW SIGNALS, SIGNAL TIMING AND CONTROL MEANS NORMALLY INTERMITTENTLY ENERGIZED FOR TIMING AND CONTROLLING THE DURATION OF SAID CAUTION INTERVALS DISPLAYED BY EACH SAID SIGNAL MEANS, TRAFFIC CYCLE LENGTH SPILT DETERMINING MEANS FOR DEVELOPING SPLIT DETERMINING SIGNALS REPRESENTATIVE OF A DESIRED TRAFFIC CYCLE LENGTH SPLIT OF SAID INTERVALS DISPLAYED BY EACH SAID TRAFFIC SIGNAL MEANS, A PLURALITY OF SELECTABLE SPLIT CONTROL SWITCHING MEANS ASSOCIATED WITH EACH TRAFFIC SIGNAL MEANS WITH EACH SPLIT CONTROL SWITCHING MEANS RESPRESENTATIVE OF A DESIRED SPLIT, SPLIT SELECTING MEANS ASSOCIATED WITH EACH TRAFFIC SIGNAL MEANS AND RESPONSIVE TO SAID SPLIT DETERMINING SIGNALS FOR SELECTIVELY RENDERING SAID SPLIT CONTROL SWITCHING MEANS ACTIVE AND INACTIVE IN ACCORDANCE WITH SAID SPLIT DETERMINING SIGNALS, AND MEANS CONTINUOUSLY CYCLING SAID PLURALITY OF SPLIT CONTROL SWITCHING MEANS THROUGHOUT ALL TRAFFIC SIGNAL CYCLES SO THAT DURING EACH TRAFFIC SIGNAL CYCLE AND SELECTED ACTIVE SWITCHING MEANS PERIODICALLY CONNECTS SAID TIMING AND CONTROL MEANS WITH A SOURCE OF ENERGY.