US2246208A - Traffic signal apparatus - Google Patents

Description

' June 17, 1941. R. E. HOBBS I TRAFFI SIGNAL APPARATUS 7 Filed March 20, 1940 2 Sheets-Sheet 2 7/ ISnnentor Roberf E Ho66s Patented June 17, 1941 UNITED 'sTATEs PATENT '?o F cE; v

TRAFFIC SIGNAL APPARATUS Robert E. Hobbs, Detroit, Mich. i Application March 20, 1940-, Serial No. 325,075

4 Claims.

This invention relates to electrical traffic signals and particularly to automatic control apparatus for such signals.

An object of the invention is to provide a rotary circuit-controlling apparatus serving to relatively time periods of illumination of a set of coordinated trafiic signals, and further affording regulation of each such period independently.

Another object is to provide for periodically and automatically correcting any deviation from a proper setting of rotating parts of an electrical timing apparatus.

A further object is to effect said periodic automatic correction through a control which may be remote from the affected apparatus.

A further object is to subject a plurality of similar apparatuses, exercising timing control of corresponding sets of electrical signals, to a concurrent and periodic remote control to effect any such correction as may be required to maintain proper coordination of said apparatuses.

These and Various other objects the invention attains by the construction hereinafter described and illustrated in the accompanying drawings, wherein:

Fig. 1 is a side elevational view of the improved apparatus, together with a diagram of a traffic signal circuit. 1

Fig. 2 is a top plan view of said apparatus.

Fig. 3 is an end view of the apparatus.

Fig. 4 is a fragmentary view of the other end of the apparatus, drawn-to an increased scale.

Fig. 5 is a longitudinal vertical sectional view of an end portion of the apparatus taken on the line 55 of Fig. 2.

Fig. 6 is a cross section taken on the line 6-6 of Fig. 5.

Fig. 7 is a side view of a rotary cam for controlling the circuit of a green signal light.

Fig. 8 is a similar view of a control cam for an amber light.

Fig. 9 is a similar view of a control cam for a red light.

Fig. 10 is a cross section of the apparatus, taken on the line Ill-I0 of Fig. 5 and diagrammatically showing two electromagnets and their circuit.

Fig. 11 is a sectional detail of a yieldable contact button, the section being taken on the line |lll of Fig. 1.

In these views, the reference character I designates a base plate rigidly carrying a pair of standards 2 and 3 at its ends. Horizontally journaled in such standards is a shaft 4, adapted to be driven at a quite gradual speed from an elec tric or other motor 5, through a drive connection formed by any suitable train of reduction gears 6, 1, said motor and drive connection being such as to drive theshaft at a substantially uniform speed. Freely mounted on the shaft 4 is a sleeve 8 carrying three segmental cams 9, l0, and II, each comprising duplicate laterally adjoined parts independently secured on the sleeve by set-screws I 2. or the like. By relatively adjusting the duplicate parts rotatively,

the cam surface jointly formed thereby may be angularly'increased or reduced. During predetermined" fractions of each revolution of the camstheirperipheries engage yieldable contact buttons l3, one for each cam, such buttons having individual electrical connections I4 (see Fig. 1) to the green, amber, and red lights I5, [6, and I! of one or more traffic signals. The other terminals of said lights have a common electri- 7 cal connection l8 to one terminal of a current source I9 have its other terminal grounded. By providing also a ground connection 20 for the base plate I, an energizing circuit through any of the lights l5, l6, and I1 is completed when its corresponding contact button I3 is cam-ena As best appears in Fig. 11, each contact .button surmounts a shank 2i slidable vertically in an insulating bushing 22 inserted in the base, said shank being upwardly urged by a coiled spring 23 seatingv on suchbushing. A pin 24 on each shank limits its response to the corresponding spring.

A releasable drive from the shaft 4 to the sleeve 8' is established by a pair of clutch members 25 fixed respectively on one end of said sleeve and on the shaft, and normally held in driving engagement. by a coiled spring 26 compressed between the other end of the sleeve and an abutment 21 on. the shaft. For periodically declutching the shaft and sleeve, there is secured to the standard 2 an annular electro-magnet 28, coaxial with the-shaft and sleeve and coacting with a disk-shaped armature 29. fixed on the sleeve. .The securing means for the magnet may be of anysuitable type and, as illustrated, comprises a set of circumferentially spaced; brackets 30. Normally the spring 26 holds the sleeve'and armature predeterminedly spaced from the magnet 28, the spring being overcome whenthe magnet is energized. An anti-frictionv thrust bearing 3| comprising an annular set of balls 32 minimizes friction when the armature is attracted to the magnet, said balls projecting sufiiciently to take the thrust.

The purpose of periodically declutchin'g the shaft and. sleeve is to afford an angular correction on the position of the sleeve, in case such correction is necessary. The correcting means is an electro-magnet 33 coacting with an armature 34 fixed on the sleeve. As illustrated (see Fig. the magnet 33 is carried on the base I by a bracket 35, and the armature is rigidly secured by an arm 36 to the armature 29. The orbit of the armature 34 is such as to afford it the minimum required clearance in passing the magnet 33, said armature and the magnet poles being arcuately conformed to said orbit. Fig. 10 shows the two electro- magnets 28 and 33 as included in a common circuit 31 controlled by a switch 38, and further shows a provision for periodically closing the switch, consisting of a gradually rotating cam 39 driven by a motor 40 and having a tooth 4| acting on the switch once in a revolution.

To facilitate an initial accurate setting of the apparatus and permit any deviation from such setting to be readily observed, if desired, a pointer t2 projecting radially from one. end of the sleeve 3 travels in proximity to a dial 43 having suitable radial calibrations, as best. appears in Fig. 4.

In use, the described apparatus may control any desired number of the triple signals, I5, l6, and I1 in unison, as where it. is desired to simultaneously start or stop all traffic along a certain section of street or highway having signals. at various points. Signals in the next adjoining sections of such street or highway would in common practice be differently timed? so as to minimize traffic stops. Serious difficulty is experien'ced, in present practice, in maintaining proper coordination of the differently timed signals, with result that traffic is held up unduly at certain signals. Under ideal conditions, the change from red to green in a given section occurs as traflic moving at a reasonable rate, app-roaches such section. In the improved trafiic system which will incorporate the disclosed apparatus, one of thelatter willmaintain proper timing of the signals of each street or highway section, and the circuit shown in Fig. 10 may take effect on any desired number of such apparatuses to periodically correct any deviation from a correct coordination.

The automatic correction provision presupposes that any deviation from correct timing will be slight. This can be assured by effecting the correction at sufficiently frequent intervals. The master timing device 39 40, 4|, must, however, be strictly accurate to give reasonable value to the system. The switch-closing position of. the cam 39 must be reached atone of the regularly recurring time intervals when the armature 34' of each apparatus should be squarely above. its control magnet 33: If 'said' armature is about thirty degrees or less ahead of or. behind its proper place, the momentary 'energization of the magnet 33 will act throughthe. corresponding armature to establishthe correct position of the sleeve 8 and the cams, while the, magnet 28' maintains the sleeve de'clutchedfrom the shaft. The correction could be accomplished, through an'angle materially greater than thirty degrees, but in practice deviations are quite'unlikely to exceed fifteen degrees. It. is to be understood that the siz of the clutchfteeth has been. great- 1y exaggerated in the drawing for sake of clearness. In practice it will be desirable to employ a clutch having quite numerous and. small teeth so that closing of the clutch following deenergization of the two magnets will not disturb the angular relation of shaft and sleeve.

Employment of the described automatic correction device will permit a traffic control system, however extensive, to be properly coordinated at all times. As distinguished from present systems, the described system requires strictly ac curat-e uniformity of drive only as regards a single master control apparatus, avoiding the difficult and practically impossibl problem of maintaining constant strict uniformity in numerous control mechanisms each dominating a certain traflic section.

It will be understood, of course, that a single master controller may dominate only such apparatuses as operate at substantially the same speed. If a city or other district has systems of apparatuses differing as to the driving speed,

either several master controllers will be necessary, or a single controller must act upon. several switches closing same at periods suited to the different systems.

The invention is presented as including all such changes and modifications as come within th scope of the following claims.

What I claim is:

1. An automatic resetting device comprising coaxial, rotative driving and driven members, a pair of clutch members establishing a releasable drive connection between the driving and driven members, means yieldablymaintaining engagement of the clutch members, an armature substantially fixed upon and substantially coaxial with the driven member, electro-magnetic means disposed substantially symmetrically with respect to the axis of the driven member and effective on the driven member through said armature to release'the clutch, electro-magnetic means tending' to establish the driven member in a definite rotative position, when the clutch is released, and a circuit adopted to energize both of said electro-magnetic means.

2. An automatic resetting device, as set forth in claim 1, the first mentioned electro-magnetic means being an annular electro-magnet surrounding the driven member.

3. In, an automatic resetting means as set forth in claim 1, anti-friction means limiting movement of said armature toward the corresponding lectro-magnetic means and increasing the freedom of response of the driven member to electro-magnetic rotative actuation of the driven member.

4. In an automatic resetting device, a shaft, a sleeve, rotatively. mounted on the shaft, a clutch establishing a releasable drive connection fromthe shaft to one endv of the sleeve, a spring reacting between the shaft and the other endof. the sleeve toyieldably clos the clutch, an armature. mounted. substantially rigidly on the sleeve, an el'ectro-magnet effectiveon the sleeve through said armature to release the clutch, anti-friction means engaged by the armature upon its attraction toward the mag-net, and electro-magnetic means effective on the sleeve when the-clutch is released to establish the sleeve in. a predetermined rotative. position.

ROBERTE. HOBBS.

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