US2702896A

US2702896A - Traffic signal control

Info

Publication number: US2702896A
Application number: US208373A
Authority: US
Inventors: John J Alles
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-01-29
Filing date: 1951-01-29
Publication date: 1955-02-22
Anticipated expiration: 1972-02-22

Description

Feb. 22, 1955 J. J, ALLES 2,702,896

TRAFFIC SIGNAL CONTROL Filed Jan. 29, 1951 fi f f /a 2/ 20 /4 f fffa/vafy f l 60A/realm@ by@ 27 47 w@ Y /l 'q CTA/ren! fir/0N /i J5 js 22A .ik 23'\ l! n 27 l J 2g d, e/iq j (j 36 /8 1N VEN TOR. JoH/v .Z 4U 5 Bymff., am

United States Patent O TRAFFIC SIGNAL CONTROL John J. Alles, Wilkes-Barre, Pa.

Application January 29, 1951, Serial No. 208,373

3 Claims. (Cl. 340-40) This invention relates to traffic signal controls and particularly to an arrangement for varying the time cycle thereof in the control of highway traic.

In highway traic signal arrangements, switching means normally will be located at the various intersections for operating the trafiic signals at said intersections, these controllers generally being termed secondary control- 1ers. The secondary controllers have switch elements Afor the purpose of sequentially lighting the usual green, amber and red lights at the intersections, or whatever combination of ligh-ts might be employed.

lIn order to control sequentially the `ilow of traffic along a highway, -it is necessary to provide means Ito synchronize in a predetermined relationship, lthe various secondary controllers with a primary or central station. This is `accomplished Vnormally by means of pulses or current interruptions at predetermined times for the purpose of bringing all of the secondary controllers into a predetermined relationship or synchronism. `When it is desired to have a progressive flow of traffic along a highway, it is necessary that arrangements be made so that -the change in the main street green ligh-t, or 'a predetermined light change, occurs at progressive intervals along the highway, so that a car moving along the street will be able to move at a predetermined speed without stopping, the green light occuring at the correct time. `In such a control system, however, the cycle lshould be changed according to the demand or time of day `and this has not been satisfactorily solved in prior devices.

iIn the prior art, the frequency applied to a synchronous motor has been changed to vary the speed. This is not satisfactory because it permi-ts only a narrow range in `speed change because the torque of the motor falls off with increase of speed and the torque requirements of a traflic signal controller remains constant.

`One of the objects of this invention is to provide a simplified arrangement for varying the cycle length of the secondary controllers in a highway traffic signal control system.

In a preferred aspect of the invention, the switching `elements of the secondary -or local controllers can be operated by a synchronous or constant speed motor arrangement. The arrangement can include a small synchronous or similar motor driving the switch operating mechanism through a casing having a gear train therein. As will be explained in detail hereafter, the gear train within the casing may have an armature at the beginning of the gear train arranged so that the armature can be rotated relative to the casing so as to provide a differential speed reduction. The gear train is connected to the switch operating mechanism and the friction therein is such that when the casing itself is turned, the switch mechanism will be turned, the gears and casing rotating as a unit. The armature can be energized, when desired, by a coil arrangement fed lfrom a central station energizing means. When it is desired to change the cycle length, the armature can be driven in the direction of the rotation of the casing, only a small torque being required to overcome the friction in the gears. For example, the energy irnpressed can be supplied by means of a square wave source -of current, such as a commutator means or by suitable electronic circuits. llt has been found that using standard sine wave alternating current for varying the speed of the cycle extension motor will permit a relatively small change in speed to the cycle extension. lf a wave ydiffering from rthe sine wave fform, such as one more closely approaching a square wave as described hereafter,

2,702,896 Patented Feb. 22, 1955 a much greater variation in speed can be obtained and still maintain synchronism between the current supply source and the cycle extension motor. The failure of Ithe cycle extension gearing, or any part of the speed varying mechanism, will not prevent driving of the control switch by the cycle extension driving mechanism. Because of the fact that only the friction mustbe overcome, the power required for the speed variation purposes is a minimum which may become an important fact in a system having many controllers. The frequency can be controlled to produce the desired cycle length.

-In the drawings:

IFigure 1 illustra-tes a local or secondary station, schematically showing a traiic signal and the means controlled by the driving mechanism of the cycle extension mechanism of the present invention.

'Figure 2 is an enlarged view, partially in section, of the `driving mechanism.

lFigure 3 is a view looking in the direction 3-3 of Figure 2.

lFigure 4 is a diagrammatic representation of a square wave.

Fig. 5 is an enlarged sectional View of the gear train and casing in Fig. `2.

In Figure Il, one of the trac signal lights atan intersection is illustrated at 10 having -green light 11, amber light 12 and red light 13. It is to be understood that the amber can be omitted or that other combinations can be used. Cable 14 is illustrated connecting the lights with the local or second-ary controller shown diagrammatically at l15. The secondary controller may take various forms, such as -for example, one similar to that illustrated in Patent No. 2,236,297, with the exception of the dial drive. 'In such a control arrangement, a dial having switch operating contacts usually is employed to sequentially operate a solenoid rotating a cam shaft controlling Ithe circuits to the various lights. The solenoid has pulses fed thereto ywhen a change is to 'be made which operates a ratchet means for rotating the cam sha-ft. One of the cams and one of the switches on the dial is used yfor the purpose of locally synchronizing the cam shaft with the dial once each cycle such, for example, as described in said patent. The local synchronization can be accomplished in various manners and the secondary controller can take different forms. It is to be understood that various means can b e used to rotate lthe dial as to operate the switching circuits.

The dial or switch operating mechanism of secondary controller I1'5 can be driven by shaft 16 in any suitable manner. Shaft or loperator k16 can be journalled in a plate '17, said shaft extending into gear casing -18 and being connected with the train of gears 19 therein (Fig. 2). This train may, for example, be composed of gear `30 on shaft i16, gear '30 meshing with pinion 31, pinion 31 being carried on shaft `32 mounted on the casing 18. Gear 33 can turn with shaft 32 and be meshed with pinion 34, pinion 34 turning gear 35 which turns pinion 36. Gear 37 meshes with pinion 38 which is mounted on shaft 39. The friction between the gears and the parts carried to -the'casing 1f8 is such that the shaft will turn with the casing 18 when the gear train is inactivated. The gear ratio in said gear casing 18 is quite high, for example, 3600 to l. Casing -18 preferably has a reduced portion 20 connected with shaft 21. Shaft 21 is connected through gear train 19 in casing 18 with `a synchronous or constant speed motor 23. Synchronous motor 23 may be of any suitable type.

When motor 23 is energized by la source of local power 25, shaft 21 and casing 1-8 will be turned thereby. There is suicient friction in the gear train 19 so that shaft 16 will rotate with casing 18 so as to deliver the full torque of lthe motor 23. The inner end of the gear train connected to shaft 24 preferably is located in the reduced portion 20 of the -gear casing and has an armature 19' (Fig. 3) connected therewith.

Winding 26 is mounted on the laminated core structure 27. The core ends are suitably spaced and shaped so lthat the central aperture dened by its ends will surround or at least partially encircle the reduced portion `20 of the gear casing. The core and winding are arranged so that they can influence or rotate the armature connected to the gear train.

The winding 26 may be energized in various manners at `the desired frequency so as to produce the speed required of shaft 16 to drive the control dial or switch means. If the winding is unenergized, the gear train will turn with the casing because of friction therein, and shaft 16 in turn will rotate at the same speed as the casing and shaft 21.

Winding 26 can be fed with alternating square wave pulses by various means such being generated and controlled by a central station. One manner in which square waves can be supplied is illustrated schematically at 28 in Fig. 2. A source of direct current 29 feeds slip rings 30, said slip rings being suitably connected with

commutator segments

31, 31. Shaft 32 is driven by motor 33 to rotate the commutator segments. Brushes or collectors 34 feed the alternating square wave pulses through leads 35 to winding 25. The speed of motor 33 can be varied so as to control the `frequency and thus the speed of armature 19 within casing 20. The square wave pulse means can be located in the central station and thus the cycle length of the secondary controllers adjusted accordingly at the central station.

Various types of square wave generating devices may be used such as, for example, conventional electronic circuit arrangements. As an illustration only, the form of a square wave energy source is illustrated in Fig. 4. The shape of the square wave is such as to insure the armature in the casing staying in step therewith. The core and windings may be suitably arranged so as to be self-starting such as by the shaded pole elements 35 (Fig. 3). Other similar alternating wave `forms -of course can be used. One of the purposes of modifying the sine wave form is to keep the armature in step over a greater range of speed.

The armature 19 and winding 26 are connected and arranged to rotate in the direction which the casing tends to induce. Thus, the power required from winding 26 -is small because substantially all tha-t is necessary is to overcome the friction involved.

It is evident that the details of construction can be varied without departing from the spirit of the invention except as defined in the appended claims.

What is claimed is:

1. In a traic signal control arrangement, the combination including a signal control switch having connections with the lights to be controlled, a constant speed motor, a gear train connection and casing means holding said ygear train in which said gear train is rotatably mounted, said gear train having a driving shaft means, the friction between the gears of said gear train rotatably locking said shaft means and casing means to turn said shaft means with said casing means when the gear train is inactivated, said. gear train connection and driving means being connected between said motor and signal control switch, an armature connected to said gear train at a point spaced from said shaft means and operable to drive said gear train and shaft means independently of said driving means, reversing current means adjacent said armature for driving said gear train at a preselected speed, local synchronizing means connected to said signal control switch, and means remotely controlling the frequency of the reversing current so as to control the cycle length by varying the speed of said shaft means relative to said casing.

2. `In a signal control device having a signal control switch and a constant speed driving motor, the combination including a rotatable casing means, a gear train including a plurality of meshed gears rotatably mounted within said casing means and connected to a concentric rotatable shaft means extending exteriorly of said casing means rotatable relative to said casing means, the friction between the gears of said gear train rotatably locking said shaft means and casing means to turn said shaft means with said casing means when the gear train is inactivated, said constant speed motor being connected to one of said means, a driving connection connected to the other of said means, an armature connected to said gear train means at a point spaced from said shaft means driving said shaft means through said gear train means, and an armature energizing means adjacent said armature for energizing the same to rotate said shaft means relative to said casing means.

3. In a signal control device, having a signal control switch means, a const-ant speed motor means, the combination including a connection between said constant speed motor means and an operator for said control switch means, comprising a casing shell and a gear train rotatably mounted therein, said gear train having a plurality of meshed gears on substantially parallel shafts in said casing shell, at least some of said shafts being offset relative to the axis of the casing shell, said gear train being connected to a driving shaft connection rotatable relative to said casing when the gear train is activated and extending exteriorly of said shell on its axis, and connected to said operator, the friction between the gears of said gear train rotatably locking said driving shaft connection with said casing shell to turn said shaft connection with said casing shell when said gear train is inactivated, an electric motivating means including an armature connected to said gear train to rotate the driving shaft connection relative to said casing to reduce the speed at which a control switch means is driven by said shaft connection when said electric motivating means is driven, and means energizing said electric motivating means in a speed reducing direction, so as to reduce the drive speed of said control switch.

References Cited in the le of this patent UNITED STATES PATENTS 1,703,178 Sifton Feb. 26,1929 1,802,630 Cotal Apr. 28,1931 2,451,457 Shepherd Oct. 12,1948 2.459.429 Jeffers Jan. 18.1949