US2045136A - Traffic actuated signal system - Google Patents

Description

June 23, 1936. H. A. HAUGH, JR. ET AL 2,045,136

TRAFFIC ACTUATED SIGNAL SYSTEM Filed March 10, 1928 5 Sheets-Shee t l A street .5 6t reet 6cm neq H. A. HAUGH, JR 1-: AL 2,045,136

TRAFFIC ACTUATED SIGNAL SYSTEM June 23, {1936.

3 Sheets-Sheet 2 Filed March lo, 1928 was June 23, 1936 H. A. HAUGH. JR, 'ET AL 2 045,1 6

TRAFFIC ACTUATED SIGNAL SYSTEM Filed March 10, 1928 5 Sheets-Sheet 3 HM A Haas/1J2. [Hans B 6:52 INVENTORS EUGENE 0 5mm A TTORNEYS.

Patente June 23, 1936 2,045,136 'rnarrro ao'rna'rnn SIGNAL SYSTEM Henry A. Haugh, .lr., Charles D. Geer, and Eugene D. Stirlen, New Haven, Conn., assignors to The Engineering and Research Corporation, New Haven, (John, a corporation of Connecticut I Application March 10, 1928, Serial No. 260,770

25 Claims. (Cl. 177-337) This invention relates to automatic traffic control systems, and more particularly to a selfregulating signal system for controlling vehicle traffic at intersections of very busy streets in congested down-town areas of cities.

One form of automatic control system to which this invention may be applied is set forth in British Patent No. 299,040 and relates to a tranic signal system in which the signal is operated through a controller by means of traffic moving in the street. In this system the trafiic is regulated at each intersection by vehicle-actuated means located near the intersection.

aforesaid Haugh application, Serial No. 227,490

have a common assignee. v

. One object of this invention is to provide apparatus which may be used in conjunction with an automatic tralfic control system such as that set forth, whereby the system shall be more fiexible in operation and shall have a wider range of application, and this object is accomplished by providing apparatus which shall function in response to the volume of trafiic moving on the highway at a distance from the intersection.

Another object of this invention is to provide a variable 'time limit relay mechanism which shall operate in conjunction with-automatic vehicle actuated systems now in use, to control the period of time which traffic shall wait on one cross street before the signal is taken away from continuous traflic to allow waiting vehicles on the intersecting street to proceed.

A further object of the invention is to provide variable time limit relays for use in highway traffic control systems of the character designated, the time limits of which shall be varied by vehicular traffic at a distance from the intersection, so that the signal for traffic to proceed shall be given through variable maximum periods of time, depending upon the volume and/or density of traliic in the highways.

A further object of the invention is to provide variable maximum time limit relays for traffic control systems of the character designated in which the maximum timeperiodat which the relays operate shall be in part a-function of the volume and/or density of trafiic on the streets leading to the intersection.

Other objects will be more manifest by reference to the following specification and drawings and as particularly set forth in the claims.

In the drawings Figure 1 is a diagrammatic view of a tramc signal system embodying our invention.

Figure 2 is a diagrammatic drawing of one embodiment of our invention showing in detail the electrical circuits and various components.

Figure 3 shows in diagram form a vehicle actuated means for completing an electrical circuit and subsequently breaking it as the wheel of a 7 car passes over it.

control system. An automatic trafiic control system embodying our invention comprises three parts: 1. Any automatic trafiic control system employing a relay or timer system to control the operation of the .signal means; 2. A variable time limit control device having a minimum and a maximum period which can be set arbitrarily for any predetermined time and arranged so that its time of operation will vary between these two set arbitrary periods in accordance with impulses received; 3. Tramc actuated means placed in the streets which pass through the intersection on which the signal means is used, but placed at a'distance from the intersection. In practice we contemplate placing these street devices in the streets at the intersections adjacent to the intersection on which the signal is placed.

While we have described above in general an improvement on an automatic tramc control system embodying our invention, and have shown that this invention is comprised of three main and interconnected parts, we now describe in detail one complete and specific system embodying our invention. In this specific and complete embodiment of our invention, we illustrate the device used in conjunction with an automatic traffic control system such as set forth in the British Patent No. 299,040 above referred to. We do not describe in detail all of the features of .the operation and construction of the system shown in the Brit'- ish patent referred to except in so far as to show its relation to this embodiment of our invention. The system shown in the British patentreferred to as one embodiment of our invention is capable of numerous methods of operation as described in the specification of the patent under the several connections and combinations of connections. and it is clear that our invention may be applied to any one or more of the British systems of operation, regardless of whether the trafilc actuated means shown in the British patent are connected or disconnected under any of the modes of operation so long as the maximum limit relays 28 and I3 in our application, or their equivalent in the British patent referred to, are a governing factor in the timing.

InFigure l, the elements I. 2, 3, 4, 5 and 8 represent the units of an automatic traffic control system to which our invention may be applied. I is a signal means, 2 is the controller, 3, 4, 5 and 8 are vehicle actuated means used to affect the operation of the controller. I, 8, 8 and III are vehicle actuated means located at a distance from the intersection and employed to control the operation of the variable time limit relays called for by our invention. The wiring will be fully explained by reference to the other figures.

Figure 3 shows a vehicle actuated means consisting of a ramp arm I! pivoted at I8, and supported by spring I9. When a wheel passes over the ramp arm it is depressed, pressing contacts I5 and I6 together closing the circuit in wires I I and I2. When the wheel has passed oil of the ramp am, spring I9 again raises the arm, allowing contacts I6 and I6 to separate and open the circuit in wires II and I2.

Figure 4 shows in further detail the method of wiring the vehicle actuated means together.

Figure 2 shows the wiring in further detail, and the construction and function of the variable time limit relays in diagram form. The variable time limit relays are designated in 58 and SI. They are constructed as follows: 28 is a solenoid. 2I is the solenoid, core, and is movable. 23 is a cylinder containing all and 22 is a piston containing a valve which will allow rapid downward motion, but a slow restricted upward motion. This construction is the same as in the usual oil dash pot" time limit relay known to the arts. When 28 is energized, the core 2| rises slowly against the resistance of the dash pot in the well-known manner. When 28 is de-energized the core drops back at once. Contacts 51 and 58 which are opened by rod 24 when core 2I has risen sufficiently to allow it to press against 42 are attached to an insulated block H, which is in turn attached to a movable rod 25. This movable rod 25 has ratchet teeth along its lower end as illustrated. Adjacent to the ratchet is a magnet 28 whose armature 21, rests against stop 31. Armature 21 is arranged so that when magnet 26 is energized, the ratchet teeth are engaged and the ratchet is lifted one tooth. Magnet 29 is connected so as to be energized wheneversolenoid20isenergized. Attached to armature 34 of magnet 29 is a magnet 28 and its armature.

38. Armature 34 is pivoted at", and is held against stop 38 by spring 35. When 29 is not energized armature 30 of magnet 28 is disengaged from the ratchet on arm 25. When magnet 29 is energized, armature 34 pulls over to the magnet, and the pivot 43 causes the lower end of the ar-' which is pivoted at the point 3i is kept against stop 44 by spring 36 and pawl or check 33 engages the teeth of theratchet while the point of armature 38 does not. By the construction of the check as illustrated, the ratchet can be raised, inasmuch as the check will not prevent upward motion. but the ratchet cannot fall. On the other hand. if magnet 28 is energized while magnet 29 is energized, the pointed end of armature 38 will move toward the ratchet, while the check 33 will 10 move away slightly. The construction as illus trated is such that energizing magnet 28 and then de-energizing it will lower the ratchet one tooth. When magnet 29 is energized," and magnet 28 is I not energized, if magnet 28 is energized it willlift 15 its armature 21 which will raise the ratchet one tooth. The check 33 will allow this to occur, but prevent the ratchet from falling back upon the-deenergizing of 26.

Thus it is clear that when 29 is energized, every 20 time the circuit to 28 is made and broken, the

,ratchet will rise one tooth, and every time the circuit to 28 is made and then broken, the ratchet will fall one tooth. Stops 38 and 48 are adjustable and represent the maximum that the ratchet 25 can rise or'fall.

In this time limit relay, the time at which contacts 51 and 58 are separated after energizing of solenoid 28 will depend upon the position of the arm bearing the contacts and the ratchet. If 30.

the arm is near or at stop 40 the period will be short-if the arm is near or at stop 39 the period will be long. The position of the arm will depend upon the relative number of impulses received by the two magnets 26 and 28. 35

Referring to Fig. 5, the following description illustrates our invention as applied to the automatic control system set forth in the British Patent No. 299,040 referred to, above. To more clearly explain the operation of this system we 40 will first describe it without considering the modifying action of our invention. To do this we will temporarily disregard ramps I, 8, 9, and I0, shown in Figure '1 and their effect on variable time limit relays 68 and 5|. We shall also assume that coil 5 28 will require 30 seconds, continuous energizing, before it breaks contacts 51 and 68.

Referring to Figures 2 and 5 of the drawings, the wiring diagram shows the connections arranged for the operation of the system when the 50 yellow light is visible from both streets in the absence of traffic on either street.

Case ISinqle vehicle approaching from A Street-Assume a vehicle approaches on A Street and actuates ramp 5, as shown in Figure l, clos- 5.3 ing the circuit between wires'8l and 82. This energizes coil I92 through wires 62 and 6|, coil I82 and wire 248, pulling up armature I9I, breaking the circuit between armature I 9| and contact I98 and closing the circuit between armature Hi 00 and contact I93. This allows current from a suitable source to flow through relay I26 by way of wires III, IIIl,2III and 2 thereby operating armatures I45 and I49. The contact of armature I45 with contact I48 causes current to continue 5 to flow through relay I28, by way of wires 2I2, contact I8I, armature I59, wires 228, 222 and 22I, thus holding relay I28 in the operated position after the passing of the wheel has permitted contacts I9I and I93 to separate. Armature I49 7 makes contact with I50, by way of wires 2", M8, armature I98, contact I99, wire 2I9, relay I34 and wire 228, armature I85 being already in contact with I81, thereby causing armature I" to break contact I18 and make contact I18. Current being ture I65 breaks from contact I61 thereby interinterrupted'between armature I11 and contact I19 de-energi'zes relay I33, which was energized through wires TM, 222, armature I11, contact I19, wire 221, wires I51, I58, contacts I63 and I62, wire 223 and wire 2I6. This causes armature I68 to break from contact I10 thereby preventing energization of relay I35 and action of the latter through armature I14 and contact I16 to light the green light on B Street and the red light on A Street. Armature I68 making contact with I69 causes current to flow through wire 224 and solenoid 20 and relay I30. Solenoid 20 and relay I30 thereupon begin to operate. If no other car 'approaches from A Street to connect wires 6| and 62 and thus separate contacts I90 and I9I shown in Fig. 5, relay I30 is continuously energized. 10 seconds after relay I30 is energized, armature I59 breaks from contacts I and I6I thereby stopping the flow of current by way of wires 2I0, armature I45, contact I46, wire 2I2,

contact I6I, contact I60, wire 2I3, contacts 51 and 58 and wire 2M, through relay I32 which permits armature I to break from contact I61 and make contact with I66 thereby de-energizing relay I34 and through wire 225 energizing relays 13 and I3I causing armature I" to break from contact I13 and make contact with I12, thereby extinguishing green light and red light 86 and lighting the yellow light 89. When relay I34 is de-energized, armature I11 breaks from contact I18 and makes contact with I19. Breaking contact I18 opens the holding circuit and releases the armature of relay I26, thus dropping it back to its normal unoperated position. Armature I11 making contact with I19 energizes relay I33. Two seconds after relay I33 is energized, armature I68 breaks from contact I69 thereby deenergizing solenoid 20 and relay I30 and makes contact I10. The de-energizing of solenoid 20 has no effect on the circuit inasmuch as it had not been energized continuously for 30 seconds. The release of relay I30 causes armature I59 to make contact with I60 and I6I thereby energizing relay I32, from wire 226 which, after 2 seconds, causes armature I65 to break from contact I66 thereby de-energizing solenoid 13 and relay I3I and make contact with I61. of solenoid 13 and relay I3I has no effect on the circuit, inasmuch as neither had been energized long enough to operate. A yellow light is now shown in both streets and the entire system hasreturned to its original condition.

Case II--Continuous tralfic on A Street with no trafllc on B Street.If in the preceding operation no cars had approached the intersection from BStreet, but vehicles had approached on A Street and actuatedv ramp 5 or 1 within 10 seconds of the previous actuation of either ramp,

thereby breaking the coil circuit of 10 second relay I30 at contacts I and I9I, shown in Fig. 5, then armature I59 would have maintained a continuous contact with I60 and I6I, thus preventing 10 second relay I30 from causing the circuit to operate as in Case I so as to extinguish green light 85 showing in A Street and red light 86 showing in B Street. This circuit provides in addition, that current flow through the coil of relay I26, armature I45 and contact I46 even after armature I11 has broken contact from I18. The purpose of this is brought out later. The 30 second time-limit relay 20 which was energized at the same time .that 10 second relay I30 was energized, breaks the circuit between contact 51 and contact 58 30 seconds after it is energized, thereby releasing the 2 second time limit relay I32. Arma The de-energizing rupting the current operating relay I34. Armature I1I breaks contact from I13 and makes contact with I12 thereby extinguishing green, light 85 showing in A Street and redlight 86 showing in B Street, and lighting the yellow light 80.

Armature I11 breaks from contact I18 but in this particular case does not interrupt the current operating relay I26 because of the fact that said current is supplied through contacts I59 and I 6I on relay I30 which are connected in parallel with contacts I11 and I18. The fact that relay I26 therefore remains energized, causes lights 85 and 86 to show after yellow light 89 has been lighted for 4'seconds, thus returning the right of way to A Street after giving pedestrians a 4 second period in which to cross A Street.

The actual operation of the circuit to produce this effect is as follows. Armature I11 connects with contact I 19, thereby energizing the 2 second time limit relay I 33 as before described. Two seconds after relay I33 is energized armature I68 breaks from contact I69 thereby opening the circuit to solenoid 20 and relay I30, through wire 224,

whereupon contact 51makes contact with 58 and energizes the 2 second relay I32. Two seconds after relay I32 is energized, armature I65 makes contact with I61, thereby energizing relay I34 whereupon armature I1I breaks from contact I12 thus extinguishing the yellow light and makes contactwith I13 thus lighting the A Street green light 85 and the B Street red light 06. This cycle-of operations repeats as long as vehicles operate either ramp in A Street within intervals of 10 seconds and none operate a ramp in B street. In the event that vehicles fail to operate either A Street rampwithin an interval of 10 seconds, the subsequent operation is as described in Case I.

Case III--One vehicle on A Street followed within 10 seconds by one vehicle on B Street.-

Under this condition, the circuit operates as in Case I with the following changes. When relay I34 is de-energized through the breaking of armature I65 from contact I61, armature I11 makes contact with I 19. A vehicle operates either ramp 4 or 6 in B Street which causes current to flow through the coil of relay I21. The contacts of ramps 4 and 6 as shown in the drawings, control relay I21 through wires 63 and 64 and relay I94 just as contacts in ramps 5 and 3 control relay I26, and they control relay I3I just as contacts in ramps 5 and 3 control relay I30. Relay I21 is now held in the operated position by current flowing through armature I41 and contact-I48,

contact I64 and armature I62, and wires 223 and 2I6. Armature I11 making contact with I19 energizes relay I 33 through wires I51, I58 contacts I63, and I62. Two seconds after relay I33 is energized, armature I68 makes contact with I10 thereby operating relay I35 through switch 206,

yellow light and to make contact with I16 thereby lighting the green light 83 on B Street and red light 84 on A Street. Thus the effect has been that the vehicle in A Street has retained the right of way for 10 seconds and at the end of this 10 second period, the signal has gone through the cautionary yellow period to an indication of right of way on B Street.

When relay I35 was energized I80- I gized aiterarmature I58 has made contact with I60 and I6I. When relay I32 was originally deenergized by the separation of armature I58 irom contact I60, as explained in Case I, armature I65 made contact with I66 thereby energizing time limit relays 13 and I3I. relay I 3| was energized, due to the fact that neither ramp in B Street had been operated by a second vehicle, which would have de-energized relay I3I, armature I62 breaks contact with I63 and I64 thereby de energizing relay I33 thus permitting armature I68 to break contact'Irom I 10 and make contact with I68. The breaking of the circuit between I68 and I10 de-energized relay I35, thus breaking contact between I14 and I16 thereby extinguishing green light 83 and red light 84 and making contact between I14 and I thus lighting the yellow light 88. Armature I80 breaks from contact I8I thereby de-ener gizing relay I21 by way of wires 230 and 23I, whereupon armature I41 breaks contact with I48. Armature I80 in making contact with I 82 energizes the 2 second relay I32 through contacts 51, 58, I60 and I58, on relays and I30. Two seconds after relay I32 is energized armature I65 makes contact I61 .and breaks from contact I66 thereby de-energizing time limit relays 13 and I3I. Inasmuch as relay 13 had not been energized for a suflicient .length of time to operate its armature, it has not acted to control the circuit. The de-energizing of relay I3I permits ar-' mature I62 to make contact with I63 and I64 thereby energizing. relay I33,'through contacts I18 and I18. Two seconds after relay I33 is energized, armature I68 breaks from I68 thereby deencrgizing relays 20 and I30 and makes contact with I10 so that relay I35 operates immediately when relay I21 is energized. The circuit has now completed its cycle and has returned to the condition at the beginning of Case I, and as shown in Fig. 2.

Case IV-Continuous traflic on A Street with one vehicle waiting on B Street-Under these conditions, the circuit operates as outlined in Case II until a vehicle operates one of the ramps in B Street. The opening of the circuit between contacts 51 and 58 which occurs 30 seconds after relay 20 isenergized, deenergizes relay I32 causing armature I65 to break from contact I61 and make contact with I66. Connecting armature I65 with contact I66 energizes relays 13 and 13I. Breaking the circuit between armature I65 and contact I61 de-energizes relay I 34 whereupon armatures HI and I11 fall back extinguishing the A Street green light 85 and the B Street red light 86 through breaking the circuit between armature Ill and contact I13. Armature I1I making contact with I12 lights the yellow light 89. Armature I11 breaking from contast I18 does not de-energize relay I26 because current for relay I26 is supplied through wire 225, armature I58 and contact I 6I, armature I45 and contact I46. In the meantime a vehicle has operated one of the ramps on B Street cnergizingrelay I21. Current to keep relay I21 energized after said vehicle has crossed the ramp flows through armature I41, contact I48, contact I64, and armature I62. Armature I52 now makes contact with contact I53. Armature I11 which made contact with Ten seconds aftercontact with I63.

contact I18 when relay I 34 was de-energised thereupon energized relay I33 through wires I51 and I58, contacts I63 and I62. Two seconds after relay I33 is energized armature I58 breaks from contact I68 thereby de-energizing relays 28 5 and I30. Armature I68, through making contact with contact I10, now energizes relay I35 through switch 206 and contacts'20l, 200, I53, and I52. Armature I14 now breaks from contact I15, thus extinguishing the yellow light, and makes contact with I16, thereby lighting the B Street green light 83 and the A Street red light 84. Armature I80 breaks from contact I 82 and makes contact with I8I thereby causing relay I32 to remain deenergized despite the closing of contact 51 with in contact 58. Armature I65 therefore remains in contact with I66 keeping relay 13 energized and also relay I 3i .energized, inasmuch as this case assumes that a second car does not pass over a B Street ramp. Hence 10 seconds after relay III was energized, armature I62 breaks from contact I63 and contact I64 thereby de-energizes relay I33. Armature I68, of relay I33, now breaks from contact I10 and makes contact with I88 thereby energizing relays 20 and I30. Relay I35 is now de-energized through the break between armature I68 and contact I10. Armature I14 now breaks from contact I16 thereby extinguishing the B Street green'light 83 and the A- Street red light 84. The yellow light 88 is now lighted through armature I14 and contact I15. Armature I80 at the same time breaks from contact I8I thereby de-energizing relay I 21 inasmuch as armature I62 is not now in contact with I64.

Armature I80 makes contact with contact I82 thereby energizing relay I32 through contacts 51, 58, I58, and I60. Two seconds after relay I32 is energized, armature I65 breaks from contact I66, thereby de-energizing relay 13 and relay I3I, and makes contact with I61, thereby energizing relay I34 through switch 205, contacts I88, I88, wires 2I8 and 2", contacts I50 and I48. Armature "I now breaks from contact I12 extinguishing the yellow light and makes contact with I13 again lighting the A Street green light 85 and the B Street red light 86. Armature I11 also breaks from contact I18 thereby insuring that relay I33 will remain de-energized even though wire I51 be in contact with wire I58 and armature I62 be in Armature I11 now makes contact with I18 thus paralleling armature I58 and contact I6I. The system has now returned to the condition in which it was when the single vehicle actuated the ramp in B Street. In this description we have shown how continuous trailic in A Street would be interrupted for a suiiicient period to allow a single vehicle from B Street to use the intersection, and how right of way would return immediately thereafter to A Street in which the continuous stream of traflic had 60 been interrupted.

Case V-C'ontinuous tramc in both streets.- Under these conditions the circuit operates asit did in Case II to transfer the right of way from A Street to B Street. But, continuous trafllc in B Street opens the contacts through which the current energizing relay I3I passes. Armature I62 therefore continues to make contact with I63 and I64. Relay I33 therefore remains energized until wire I51 breaks from wire I58 which will take place 30 seconds aiter relay 13 is energized. The energizing of relay 13 is caused in accordance with the description given in Case II. Wire I51 now breaking contact with I 58 de-energizes relay I33. Armature I68 breaks contact from I18 2,045,186 and makes contact with I69 thereby de-energizing relay I and energizing time limit relays 20 and I30. Armature I16 now breaks contact with I16, thereby extinguishingBStreet green go" signal 83 and A Street red light 84, and makes contact with I15 thereby lighting the yellow light. Armature I80 now breaks from contact I8I which action has no effect on the circuit inasmuch as this connection is also made by armature I62 and contact I56. Armature I80 makes contact with I82 thereby energizing relay I32. Two seconds after relay I32 is energized, armature I65 breaks from contact I66 thereby causing the de-energizing of relays 13 and I3I thereby causing wire I51 to make contact with I56 and makes contact with IE1 thereby energizing relay I3t through switch 205, contacts I99, I90, I and I49. Armature I1I now breaks from contact I12 extinguishing the yellow light and makes contact with I13 lighting the A Street green light 85 and the B Street red light 86. Armature I11 breaks from contact I19 thereby causing relay I33 to remain ole-energized even though wire I51 makes contact with M8 and armature I62 makes contact with I63. Armature I11 now makes contact with I18 and the circuit has returned to the condition in which it was at the beginning of this description.

It is apparent from the foregoing description that the relay 20 limits the length of time during which tralfic may flow continuouslyon A Street. As soon as the go signal is given to A Street, relay 20 is energized and if trafiic is continuous on A Street the go signal remains on A Street for 30 seconds. Then relay 20 operates so as to remove the go signal from A Street and give it to B Street. Simultaneously relay 20 is de-energized and relay 13 is energized. Relay 13 performs the same functions for B Street as relay 20 does for A Street.

Nevertheless the maximum period during which traffic may flow undisturbed is fixed and cannot be varied by the traffic. The purpose of our invention is to vary-this maximum period by electrical impulses caused by traffic operating vehicle actuated devices in the streets. The method of obtaining this variation and the value is set forth below.

While in the above description the application of our invention to one form of trafilc control systems has been set forth and one embodiment of our invention has been illustrated, it will be obvious to those skilled in the art that the in-- vention may take many forms and may be applied to many types of traflic control systems, and it is not intended to limit our invention to the particular form illustrated. It will be appreciated that numerous changes in construction and rearrangement of parts with respect to the construction of the timer,-of the time adjustment means, of the traffic responsive means, and in the mode of installation and point of application of these several means might be resorted to without departing from the spirit of the invention as defined by the claims.

A Street, vehicle actuated means 1 and 9 are connected in parallel by wires II and I2. Vehicle actuated means 8 and I0 are connected in parallel by wires I3 and I4. Variable time limit relay 50 functions to control the maximum period through which a continuous stream of traffic can hold the go signal on A Street. nected to magnet '26 in relay 50 and to magnet H in relay 5I. Street, solenoid 20 will immediately be energized Wires II and I2 are con-- When the go signal is given to A and functions as heretofore described. Magnet 29 will be energized simultaneously inasmuch as in our invention this magnet is connected in parallel with the solenoid. Also since B Street has the stop signal, solenoid 13 will be deenergized as heretofore described Since magnet 12 is in parallel with solenoid 13, it will also be de-energized. When the go signal is on A Street, ve=

hicles moving toward the intersection on A Street will pass over ramp 1-or ramp 9, and will send electrical impulses through wires II and I2 to variable time limit relays 50 and 5I. Impulses going into variable time limit relay 50 through wires II and I2 operate magnet 26 causing ratchet 25 to raise, and since A Street has the go signal, solenoid 20, and magnet 29 are energized, so that ,when magnet 26 causes the ratchet 25 to be raised, pawl 33 will prevent its return. Since ratchet 25 has been raised, rod 24 has to move through a greater distance than formerly before it separates contacts 51 and 58 and this allows solenoid 20 to be energized for a longer period than 30 seconds. Impulses going to variable time limit relay 5| through wires I I and I2 energize magnet I I Since B Street has the stop signal,

solenoid 13 and magnet 12 are de-energized, and

the ratchet will not operate, but remains in its minimum time position. Thus the true efiect of cars arriving on A Street during the period which it holds the go signal is to increase the length of, the maximum period for which A Street can hold the go.signal. Cars approaching on B Street pass over vehicle actuated means 8 and I0, and send electrical impulses through wires I3 and I4 to variable time limit relays 50 and 5|. Impulses going to relay 50 through wires I3 and I l energize magnet 26 causing ratchet to drop one tooth for each impulse. Impulses going to relay 5| through wires I3 and I4 energize magnet 10. Inasmuch as solenoid 13 and magnet 12 of time limit relay 5| are not energized, there is no effect producedin time limit relay 5|. Hence, when A Street has the go signal, cars approaching the intersection on A Street tend to lengthen the maximum period during which A Street can 7 hold the "go. signal, while cars approaching on A Street tend to shorten the period during which B Street can hold the go signal.

The result of this operation is as follows. Suppose both streets have a more or less continuous tramc flow, but, A Street has a fairly dense flow while B Street hasa sparse and scattered flow, and suppose the go" signal is on A Street. As the vehicles on A Street approach the intersec tion, magnet 26 willbe operated very frequently by the passage of the large number of vehicles over ramps 1 and 9. Vehicles approaching the intersection on B Street, will pass over ramps 8 or I0, energizing magnet 28 from time to time.

The vehicles will move forward intothe block and stop at A Street. Since there are many more somewhere near the maximum period. when A Street loses the'light, name on A Street will be in the least congested condition since it has been flowing freely, barring some other.conges- 7 name on B'Street will be condensed into a waiting block. when B Street traflic moves forward, any new cars arriving on B Street will tend to lengthen the B Street maximum period as determined by relay 13, while cars moving into the waiting block on A Street will tend to shorten the B Street go; period. Since there is not a dense flow on B Street the maximum period, as determined by relay I3, will be shortened so as to almost coincide with the minimum period as determined by relay l3! and B Street will lose the "go signal at, or shortly after, the expiration of theminimum period. It the trafiic on both streets becomes about equal, and is light in volume, streets A and B will alternately hold the go signal for equal minimum or nearly equal minimum periods, giving a frequent shifting oi the go signal back and forth between the streets. It trafllc becomes unbalanced between the two streets the maximum periods will lengthen out on the street having the heavier tramc flow. It traiflc on both streets increases to a degree of congestion, the

periods will lengthen on both streets, for cars moving on the "go street will increase its period, while on the stop" street, congestion will prevent cars coming into the block and thus prevent a decrease in the go street's time period. This is especially desirable for it is believed by some traflic engineers that where traflic is especially dense long go" periods are the most eflicient,'whereas in light traihc short go" periods are more desirable.

What we claim is:

1. In a traffic control system, a signal device for intersecting traflic lanes for indicating stop and go signals, vehicle actuated means located in the traillc lanes and at a distance from the intersection, a control mechanism connected to said vehicle-actuated means for regulating the display oi signals alternately to the trafllc lanes including automatic variable maximum time limit relay means for determining the maximum period of said displays, said relay means being actuated by the vehicle means in such a manner that traino moving in the traflic lanes shall vary the maximum period as determined by said maximum time limit relay means and during which a go? signal may be displayed to one 01 the lanes while trailic is accumulating in an intersecting lane.

2. In a tramc signal control system for intersecting tramc lanes, a signal device to be disposed at the intersection of the lanes, vehicle actuated means located in or adjacent to the trailic lanes near the intersection, other vehicle actuated means placed in or adjacent to the trailic lanes at a distance from the intersection; a control mechanism connected to said vehicle actuated means for operating the signal device to display "go" signals alternately to the said lanes in response to impulses received from both of the vehicle actuated means and including automatic variable time limit relay means which determine the maximum period of said displays, said relay means being operated by the vehicle actuated means in such a manner that tramc moving in the tramc lanes shall influence the period as determined by said maximum time limit relay tion in the path of the trafllc moving on A Street:

of way periods to each lane, means operable to limit the time of right of way in each lane and vehicle actuated means for varying the limiting point of the limiting means on the right of way period in response to changes in the diiierence between the number of cars traversingeach lane.

4. A traiilc control system to be disposed at the intersection of two vehicle lanes, and including signalling means for according and interrupting right of way indication to each lane, operating means for said signalling means, vehicle actuated means disposed in at least one of said lanes for controlling said operating means to cause said signalling means to indicate right of way to said lane, means forming a part of said operating means to limit the time period of right of way in each lane and other vehicle actuated means for varying the time period of said right of way limiting means in response to changes in the difference between the number of cars traversing each lane.

lane, means forming a part of said operating.

means to limit the time period of right of way in each lane and other vehicle actuated means in at least one lane and disposed'at a point further from the intersection than the first named vehicle actuating means, said last named means being operable during the right of way period of said lane to increase the time period of said right of way limiting means.

6. A traflic control system to be disposed at the intersection of two vehicle lanes, and including signalling means for according and interrupting right of way indication ,to each lane, operating means for said signalling means, vehicle actuated means disposed in at least one of said lanes for controlling said operating'means to cause said signalling means to indicate right of way to said lane, means forming a part of said operating means to limit the time period of right of way in each lane, and other vehicle actuated means in at least one lane and located at a point fur.- ther from the intersection than the first named vehicle actuating means, said last mentioned means being operable during the right of way period of the other lane to decrease the time period of said right oi way limiting means.

7. A trailic control system to be disposed at the intersection of two vehicle lanes, and including signalling means for according and interrupting right of way indication to each lane, operating means for said signalling means, vehicle actuated means disposed in at least one 01' said lanes for controlling said operating means to cause said signalling means to indicate right of way to said lane, means forming a part 0! said operating means to limit the time period of right of way in each lane and other vehicle actuated means in at least one lane and located at a point further from the intersection than the first named vehicle actuating means, said last named means being connected to said operating means to increase the time period of said right oi way limiting means during the right of way oi said lane and to decrease the time period of said right of way limiting means during right of way to the other lane.

8. A trafllc control system to be disposed at the intersection of a plurality of interfering traiiic each of said lanes, traflic actuated means disposed lanes, comprising "stop and go indicators in each of said lanes, traflic actuated means disposed in at least one of said lanes and connected to said indicators'to cause the display of a go signal in said lane upon actuation by an approaching vehicle, means associated therewith for retaining said go signal for a predetermined period of time, and means for varying said predetermined period of time in response to changes in the ratio that the number of cars traversing said last mentioned lane bears to the number of cars traversing an interfering lane.

9. A trailic control system to be disposed at the intersection of a plurality of interfering trailic lanes, comprising stop and"go indicators in in at least one of said lanes and connected to said indicators to cause the display of a go signal in said lane upon actuation by an approaching vehicle, means associated therewith for retaining said go signal for a predetermined minimum period of time, means for retaining said go signal beyond the predetermined minimum period of time upon the subsequent actuation of said first mentioned means, means for terminating the display of said go signal upon the elapse of a predetermined maximum period of time and means for varying the predetermined maximum period of time in response to changes in the difference between the number of cars traversing each of said lanes.

10. A traflic control system to be disposed at the intersection of a plurality of interfering traffic lanes, comprising stop and gov indicators in each of said lanes, traffic actuated means disposed in each of said lanes, means connected to said trafilc actuated means and said indicators for causing the display of a go signal in a lane upon operation of the traflic actuated means in said lane, means associated therewith for retaining said go" signal in saidlane for a predetermined minimum period of time, means for retaining said go signal in said lane beyond said predetermined minimum period of time upon the subsequent actuation of the trafiic actuated means disposed in said lane, means for terminating the display .of said "go signal upon the elapse of a predetermined maximum period of time, and additional trafiic actuated means disposed in each of said lanes for varying the length of the predetermined maximum-period of time in response to changes in the comparative density of traffic in said lanes. i

11. A traffic control system to be disposed at the intersection of two vehicle lanes including signalling means for according and interrupting right of way in each lane, trafiic actuated means in at least one of said lanes and connected to said signalling means for according right of way indication to said lane when actuated by an approaching vehicle, a minimum time control device associated therewith for retaining right of way in said lane for a predetermined period, means for retaining said right of way beyond said period upon r the subsequent actuation of said traific actuated 'means, a variable maximum time control device for interrupting said right of way, and other traffic actuated means for varying the period of operation of said variable maximum time control device. i

12. A traflic control system to be disposed at the intersection of two vehicle lanes including signalling means for according and interrupting right of way in each lane, traific actuated means in at least one of said lanes and connected to said signalling means for according right of way indication to said lane, a minimum time control device associated therewith for retaining right of way 1 maximum time control device.

13. A traffic control system to be disposed at the intersection of two vehicle lanes including signalling means for according and interrupting right of way in each lane, trafiic actuated means in one of said lanes and connected to said signalling means for according right of way indication to said lane, a minimum time control device associated therewith for retaining right of way in said lane for a predetermined period, means connected to said trafilc actuated means for retaining said right of way beyond said period upon the continued approach of. vehicles, a variable maximum time control device for interrupting said right of way after the'elapse of a predetermined period of time, and other trafiic control means located in the other of said trafiic lanes, said last named means being operable during the right of way of interfering traffic lanes, signalling means for according and interrupting right of way to each lane, timing mechanism connected thereto for causing the alternate display of said signalling means in each lane for predetermined periods of time, and means associated therewith for varying the predetermined periods of time in response to changes in thedifierence between the number of cars in each lane.

15. In combination with a traflic control system adapted to be disposed at the intersection of interfering traific lanes, signalling means for according and interrupting right of way to each lane, timing mechanism connected thereto for causing the alternate display of said signalling means in each lane for predetermined periods of time, and means for varying the predetermined periods of time in response to changes in the difference between the number of cars in each lane, said last named means including traffic actuated devices disposed in each lane for increasing the period of right of way accorded that lane when actuated during the period of rightof Way in said lane and for decreasing the period of right of way accorded an interfering lane when actuated during the period of right of way in said interfering lane.

16. A trafiic control system, to be disposed at the intersection of a plurality of trafilc lanes, comprising signalling means for alternately displaying stop and right of way indications in each lane, timing means connected thereto for controlling the period of right of way accorded switch mechanism after the elapse of a predctermined period of time, magnetically operated means for decreasing said predetermined period of time when energized, vehicle actuated devices disposed in a lane not having the right of way and connected to said magnetically operated means to energize it upon a vehicle actuating the vehicle actuated device in last said lane, other magnetically operated means for increasing said.

predetermined period of time when energized, and other vehicle actuated devices disposed in the trafiic lane having the period of right of way and connected to said last named magneticaily operated means to energize it upon the approach of a vehicle in said lane.

17. A trafiic control system to be disposed at the intersection of two traihc lanes and comprising signalling means adapted to accord and interrupt right of way to such lanes, trafilc responsive means associated with one of said lanes. a timer connected between said traflic responsive means and said signalling means and including means acting in response to trafllc actuation of said responsive means for according and maintaining right of way in said one lane between predetermined minimum and maximum periods, further trafiic responsive means in the second lane and means for reducing said maximum period in response to actuation of said further trafiic responsive means in the second lane when the first lane has the right of way.

18. A tramc control system to be disposed at the intersection of two traffic lanes and comprising signalling means adapted to accord and interrupt right of way to such lanes, traflic responsive means associated with one of said lanes, a timer connected between said 'tramc responsive means and said signalling means and including mechanism acting in response to actuation of said responsive means to accord and maintain right of way in said lane up to a predetermined maximum period of time, further trafllc responsive means in the second lane and means for reducing such maximum time period in response to operation of the further trafiic responsive means in the second lane when the first lane has the right of way.

19. A traflic control system to be disposed at the intersection of two tramc lanes and comprising signalling means adapted to accord and interrupt right of way to such lanes, traflic responsive means associated with each of said lanes, a timer connected between said controls and said signalling means and including means acting in response to actuation of said responsive means for according and maintaining such right of way alternately in each lane for a minimum period of time, means for increasing the period of right of way beyond said minimum period in response to operationof said traflic responsive means in the lane having'right of way, means for interrupting said right of way after a predetermined maximum period of time, and means for decreasing said maximum-period on the lane having the right of way in response to actuation of traiiic responsive means in the lane not havsivemeans in one of said lanes, timing means connected to the signalling means and traflic responsive means and including means operable upon actuation of the responsive means to accord right of wayto said lane up to a predetermined maximum period, and means operable in response to actuation at a remote intersection of interfering traflic lanes including one lane common to the first and second mentioned intersections to vary said maximum period. 21. A trafiic control system including at' one intersection of interfering traflic lanes signalling means for according and interrupting right of way in the lanes, trafilc actuated means in 'the lanes of said intersection, operating means con- 10 nected to said signalling means and traillc lectu- .ated means to cause said signalling means to transfer right of way back and forth between the lanes in response to actuations of said trafllc actuated means, timing means associated with said operating means to provide time limits for the period of right of way accorded to such lanes and traific responsive means located at a second intersection of trafilc lanes including one lane common to both mentioned intersections, and means associated with said timing means and connected to said trailic responsive means and operable by actuation of said traillc responsive means at said second intersection to vary the time limit of said timing means. 22. A traffic control system including at one intersection of interfering traific lanes signalling means for according and interrupting right of way in the lanes, trailic actuated means in the lanes of said intersection, operating means connected to said signalling means and trafllc actuated meansto cause said signalling means to transfer right of way back and forth between the lanes in response to actuations of said traflic actuated means, timing means associated with said operat- 3 ing means to provide time limits for the period of a right of way accorded to such lanes and including traflic responsive means located at adjacent intersections of. trafilc lanes, each including one lane common with the first mentioned intersection, and means associated with said timing means and connected to said trafllc responsive 'means and operable by actuation of said trafllc responsive means'at said adjacent intersection to vary the time limit of said timing means at' said first mentioned intersection.

23. A trafiic control system including at one intersection of interfering trafllc lanes signalling means for according and interrupting right of way in the lanes, trailic actuated means in the lanes of said intersection, operating means connected to said signalling means and trafllc actuated means to cause said signalling 'meansto transfer right of way back and forth between the lanes in response to actuations of said trailic actu- 5 ated means, timing means associated with said operating means to provide time limits for the period of right of way accorded to such lanes and including traflic responsive means located at ad- Jacent intersections of traili'c lanes, each including one lane common with the first mentioned intersection, and control means associated with said timing means and connected to said traflic responsive means and including means operable by actuation of said tramc responsive means at said adjacent intersections in each lane approaching said first mentioned intersection so as to tend to increase the time limit of such lane and decrease the time limit on other lanes.

24. A trafiic control system for an intersection of trailic lanes "comprising signal means for according and interrupting right 01' way in such lanes, a timer having an adjustable time setting and governing the operation of said signal means normally to accord right of way cyclically to each 7 of said lanes in succession tor time periods determined by such time setting, means for adjusting said time setting between certain limits to vary such right of way period between corresponding limits, traiilc responsive means in one of said lanes, and means connecting said adjusting means with said traffic responsive means to operate the former progressively to vary said setting away from one limit and toward the other upon successive actuations of the latter by trafiic.

25. A traflic control system for the intersection of interfering tramc lanes comprising signalling means adapted to accord and interrupt right oi way to such lanes, a timer connected to and governing the operation of said signalling means normally to accord right of way cyclically and alternately to each of said lanes for time periods predetermined by its time setting} trafic responsive means in each of said lanes for actuation by trafllc approaching the intersection, means forming a part of said timer and operating in response to successive actuations by traflic in a first of said lanes to progressively adjust the time 5 in a second of said lanes interfering with the first to progressively adjust the time setting of said timer to decrease such time period for right of way on said first lane from any time setting to which the timer has been adjusted by the increase adjusting means.

HENRY A. HAUGH,- JR. CHARLES D. GEER. EUGENE D; S'IIRLEN.

CERTIFICATE OF CORRECTION.

Patent "No. 2,045,136. June 23, 1956.

HENRY A. HAUGH, JR. ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 4, first column, line 4, for "lircuit" read circuit; page 5, first column, line 4, for ""go" signal" read light; same page and column, strike out the paragraph beginning with the word "While" comprising lines 49 to 65 inclusive, and insert the same after line, 33, page 6, first column; page 5, second column, line 6, after "described" insert a .period; and line 73, for "light" read "go" signal; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 22nd day of September, A. D. 1956.

Henry Van Arsdale (Seal) Acting Commissioner of Patents.

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