US3085179A

US3085179A - Control means

Info

Publication number: US3085179A
Application number: US782907A
Authority: US
Inventors: William C Keeran
Original assignee: Vapor Corp
Current assignee: Vapor Corp
Priority date: 1958-12-24
Filing date: 1958-12-24
Publication date: 1963-04-09
Anticipated expiration: 1980-04-09

Description

W. C. KEERAN CONTROL MEANS April 9, 1963 Filed DeC. 24, 1958 Arroz/Jes@ W. C. KEERAN CONTROL MEANS April 9, 1963 Filed Dec. 24, 1958 3 Sheets-Sheet 2 INVENTOR WML/AM 6I K55/ZAM #Tram/5 s W. C. KE ERAN April 9, 1963 CONTROL MEANS 5 Sheets-Sheet 3 Filed`DeG. 24, 1958 INV ENTOR W/LL/A/v/ C. K55/ZAM United States Patent O 3,055,3l79 CNTRGL MEANS Wiiliam C. Keeran, Evanston, lili., assigner, by rnesne assignments, to Vapor Corporation, Chicago, Ill., a corporation otr' Delaware Filed Dec. 2d, 1953, Ser. No. '782,967 8 Ciaiins. ifi. 3l7--124) The present invention relates to control means, and more specifically to control means incorporating a light sensitive element for turning on and off, or otherwise, controlling sources of illumination.

Light control means have been extensively employed in connection with street lighting systems, advertising signs and the like. They also have application in connection with warning lights on radio and television towers, navigation beacons, and illumination of service stations, parking lots, factory areas, viaduct underpasses, outdoor telephone booths, et cetera. It would be desirable to provide light control means for automatically turning on street lights, flood lights, warning lights and advertising lights whenever illumination is needed at a selected predetermined degree of darkness regardless of the particular time of day, which control means will also automatically turn off or otherwise render ineffective the illumination when it is not needed. Such device or control means should be very sensitive so that a small change in light of the order of less than one half foot candle will cause operation of the device. In addition to being very sensitive, such device must have 'a long life and, furthermore, it should be capable of being replaced in a very simple manner. Moreover, should any portion thereof fail, it should fail with the light control switch thereof in closed position so as to supply the necessary illumination Whether needed or not. Such a device should have a very low power consumption, preferably less than one half watt exclusive of the load circuit controlled by the device. Additionally, `such a device should be capable of being adjusted so that the light level at which the control operates may be varied at will, but, once adjusted to some selected setting, it will operate uniformly thereafter. Although such a device must be very sensitive to light changes, it must be insensitive to momentary and extraneous sources of light such as lightning, automobile headlights and the like. Furthermore, since such control apparatus must be capable of being located in exposed places in a variety of atmospheres, it should be completely sealed against exposure to atmosphere and yet protected so that snow or dirt or the direct rays of the sun cannot adversely affect the light sensitive element of the device.

Accordingly, it is an object of the present invention to provide an improved control means incorporating all of the desirable characteristics enumerated above.

It is another object of the present invention to provide a new and improved illumination control means for automatically turning on illumination when needed in response to a particular level of ambient illumination and automatically turning off illumination when not needed.

It is another object of the present invention to provide an improved light control means which is simple and compact, which will give long years of service and yet which involves a disposable unit which can be replaced in a simple manner similar to replacing a light bulb or the like.

A still further object of the present invention resides in a light control means which employs no elec-tronic tubes or equivalent devices and yet which is sensitive to very small changes in illumination of the order of less than one half foot candle.

Another object of the present invention resides in the 3,85,l'i"ii Patented Apr. 9, 1963 ICC provision of a light control means which is affected solely by changes in illumination and which is unaffected by changes in ambient temperature such as are encountered in climates where the temperature may be very hot in one season of the year and very cold in another.

Further objects and advantages of the present invention will become apparent as the following description proceeds, and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specication.

For a better understanding of the present invention, reference may be had to the accompanying drawings in which:

FIG. 1 is a perspective view of a control unit embodying the present invention;

FIG. 2 is an enlarged elevational view, partly in section, of the control unit of FIG. l;

FIG. 3 is a greatly enlarged fragmentary View of a `small portion of FIG. 2 more clearly to illustrate the features of the present invention;

FIG. 4 is a fragmentary sectional view taken on line 4--4 of FIG. 2, assuming that FIG. 2 shows the complete structure;

FIG. 5 is an enlarged fragmentary sectional view taken on 'line 5 5 of FiG. 2, again assuming that FIG. 2 shows the complete structure;

FIG. 6 is a fragmentary sectional View taken along line 6-6 of FIG. 5, assuming that FIG. 5 shows the complete structure, and with a portion of the housing cut away;

FIG. 7 is a sectional view through the solenoid controlled switch embodied in the unit of FIG. l and generally comprises a reduced sectional view taken on line '7 7 of FIG. 5, assuming that FIG. 5 shows the complete structure;

FIG. 8 is a sectional view taken on line S- of FIG. 5, also assuming that FIG. 5 shows the complete structure;

FIG. 9 is 'a sectional view taken on line 9 9 of FIG. 2, assuming that FIG. 2 shows the complete structure;

FIG. d0 is a sectional view taken on line IQ--Itl of FIG. 2, assuming that FIG. 2 shows the complete structure;

FIG. 11 is a sectional view taken on line ill-11 of FIG. 5, assuming that FIG. 5 shows the complete structure;

FIG. l2 is a schematic circuit diagram showing the electrical circuit embodied in the particular modification of FIG. l; and

FIG. 13 is a circuit diagram similar to FIG. 12 illustrating another application of the present invention.

Brieily, the present invention comprises a small compact sealed housing having means to plug the same into an electric circuit to be controlled thereby, which housing includes a light sensitive element, current control means operated thereby, together with suitable time delay means, and which may or may not include a high current carrying switch in addition to the aforementioned current control means, depending upon the particular application. The time delay means also embodies temperature compensation means so as to make sure that the device operates the same regardless of the ambient temperature likely to be encountered. Relatively small changes in electrical current caused by the light sensitive element are utilized to operate the current control means directly without the requirement of any electronic tubes, transistors or the like. Additionally, except for switch contacts, no moving parts are involved. Novel sealing means are incorporated so that the entire device is sealed against the entrance of dirt, moisture or other foreign matter.

Referring now to the drawings, there is illustrated in G. l a light control means or a unit generally designated by the reference numeral 2t) which is very compact and which comprises a base 21 sealed to a tubular member 22 which forms part of a suitable housing within which is mounted a light sensitive element generally designated at 23. in order that illumination may reach the llight sensitive element 23, the upper part of the tubular housing 22 is enclosed by a transparent or translucent member or window 24 which is actually illustrated as a cup-shaped member hermetically sealed to the upper end of `the tubular member 22, as will be described in greater detail hereinafter, thereby to define with the base 2 the complete housing. For the purpose of controlling the effectiveness of the window provided by the transparent or translucent member 24 and, consequently, for controlling the light level at which the light sensitive element 23 is rendered effective, there is provided a light level control element or cap 25 in the form of an adjustable cup-shaped cover member which may be selectively adjusted to decrease or increase the quantity of ylight reaching lthe light sensitive element 23, as the case may be.

Aside from the housing referred to above which is de- I:lined by the

elements

2i, 22 and 24, the light control means of the present invention essentially comprises the light sensitive element 23, a time delay unit generally designated at 26, best shown in FIG. 12 of the drawings, and suitable current control means which may comprise a snap-acting switch 27' operated by the time delay unit 9 26. The switch 27 may be the sole means for controlling the electrical circuit, or, as illustrated in FIG. l2, a suitable electromagnetic switch generally designated at 28 may be provided, the energization of which is controlled by the switch 2'7.

In order that the light control means 2t) of the present invention may effectively comprise a throw away unit which can readily be replaced, a plurality of

prongs

29, 39 and 311 are associated with the base 2 which are arranged in the form of a conventional three-prong twist lock type electrical connector so that they may readily be inserted in a suitable socket well known in the art. It should be understood that other types of connection may also be employed. As was mentioned above, the iight control means or unit 20 may include a high cur rent switch 28 capable `of carrying very high currents for controlling illumination of the order of 3000- watts. However, 4for low current applications such switch may be dispensed with and a simple snap-acting switch 27 alone may be employed. In an arrangement for controlling very high currents where a high current switch 28 is incorporated, a unit built in accordance with the present invention was less than nine inches in ever-all height, and the tubular member 22 had an outer diameter of only one and three-quarters inches, while the base 21 had a diameter or lthree inches.

Considering now, iirst of all, the housing and sealed construction of the light control means of the present invention, the base 21 may comprise any suitable member such as a casting of aluminum or similar material, which casting has an enlarged annular iiange 2id and a central cylindrical portion 2lb of an outer diameter so as to snugly iit the inner diameter of the tubular member 22. The underside of the base 21, as best shown in FIG. l of the drawings, is provided with a recess on the underside thereof to receive a molded insulating member 33 which has the

contacts

29, 30 and 3ft suitably molded therein. The element 33` is essentially available on the market as a commercial element and meets certain specifications so as to fit standard sockets of the twist lock type. The portion 2lb of the base 2l, which also is illustrated as having a shallow recess on the top thereof opposite the recess accommodating the member 33, is provided with a plurality of openings 35 (FIG. 9) through which insulated

conductors

36, 37 and 33, best shown in FIG. 12 of the drawings, may extend for electrical connection with the terminals 29, 3d and 3l, respectively. As illustrated in the drawings, the

conductors

36 and 37, which `for `certain applications must carry relatively high currents, are substantially larger than the conductor 38, which is merely required to carry a relatively low control current.

To permit a sealed connection to be made between the base 21 and the tubular housing 22, the portion 2lb of the base 2l is provided with two spaced apart circumferential recesses 39 and 4d, respectively, the recess 39 being immediately adjacent the ilange portion 21a, while the recess titl is adjacent the top of the portion 2lb as viewed in FIG. 2 of the drawings. The recess lil is adapted to accommodate a sealing ring di which is preferably the well-known l(Zt-ring, while the recess 39 is ernployed to permit securing the base 2i to the tubular housing in a final assembly step. When all the parts are assembled and the electrical connections are made, the portion 2lb of the base 2l is telescoped into the lower end of the tubular member 22, a seal being provided by the sealing ring dit. The lower end of the tubular member 22 lis then deformed as indicated at 22a as by a rolling or peening operation whereby the portion 22a is `forced into the circumferential recess 3g, thus securing the tubular member 22 to the base 21 in sealed relationship therewith.

For the purpose of insuring a sealed arrangement at the upper end of the tubular member 22 which will prevent moisture or the like from entering the sealed housing provided with the present arrangement, the transparent or translucent cup-shaped member 24, which may be formed of glass or a suitable transparent or translucent plastic, is provided with a very small annular iiange 24a around the outside of the open end of the member 24. The member 22 is `furthermore provided with an annular deformation 22b slightly below the open upper end thereof which provides an annular `shoulder for supporting a ring 42 of L-shaped cross section, as clearly shown in FIGS. 2 and 3 of the drawings. A suitable sealing ring 43, preferably an 'O-ring, is disposed in the recess defined by the annular member or ring 42 of l.- shaped cross section. When the cup-shaped member 24 is seated on the O-ring as shown in FlG. 2 of the drawings, the upper end of the tubular member 22 is peened over as indicated at 22C as by a rolling operation or the like, which eifectively forces the rim including the tlange 24a of the cup-shaped member 2d into sealing engagement with the IO-ring d3, which O-ring is also forced into sealing engagement with the interior sur-face of the tubular member 22. There is thus provided in a very simple manner an hermetic seal at the upper end of the tubular member 22.

To provide means for adjusting the light control and thus control the eifectiveness of the window provided by the cup-shaped member 24, there is provided the adjustable light level control element or cap 2S which may be formed of aluminum or other suitable material. As illustrated, the transparent or translucent cup-shaped member 24 is provided with an opening 44 in the closed end thereof for receiving a hollow stud member t-a' which has the closed and sealed end thereof extending into the cup-shaped member 24?. This stud 15 is secured in sealed relationship with respect to the opening as by means of resilient washer or gasket members 46 and 47, one on either side of the wall defining the closed end of the cup-shaped member 24. A flange 45a is provided on the stud 4S and a washer 48 is pressed over the lower por tion of the stud 45 and suitably secured thereto as by welding so as to compress the washers 46 and d'7 against opposite sides of the end wall of the member 24. The interior of the hollow stud member iii is threaded as indicated at 49 to receive an adjusting screw 5t) secured to the inside of cap and disposed alon-g the longitudinal axis thereof. The cap 25 is somewhat conical in shape and is larger in diameter than the cup-shaped member 24. By suitable rotating the element 25, more or less of the cup-shaped member 24 is exposed, and consequently the window through which light is supplied to the light sensitive element 23 is selectively controlled. Preferably, the member 25 is knurled or roughened on the exterior surface as clearly Iindicated in FIG. 2 of the drawings to make for easy manual adjustment.

In order to make sure that the particular selective adjustment of the member 25 remains at whatever setting it is initially set, the sealing washer 46 is of such a diameter as to be slightly larger than the inner diameter of the adjustable member 25' as clearly indicated in FIG. 2 0f the drawings, thus providing a frictional drag. The member 46, therefore, performs two functions: rst, to seal the transparent member 2d against the entrance of moisture at the opening 44 and, second, to insure that the light control member 25 remains yfixed at any selected adjustment.

In View of the detailed .description included above, it will be appreciated that there has been provided a completely sealed housing for incorporating the light control means of the present invention. `liiurthermore, the sealed unit may be connected into any suitable electric circuit by a simple plugging operation as will be readily understood by those skilled in the art, thus permitting ready replacement.

Before considering how the elements of the light control device of the present invention are supported within the sealed housing heretofore described, the individual components of the device will first be considered in detail with reference to both the schematic diagram or FlG. l2 and the structural disclosures thereof. First of all, the light sensitive element 23 has been schematically designated in FIG. 12 as a photcconductive cell whose electrical conductance changes under illumination. Thus, FIG. 12 indicates that the light sensitive element is ef- -fectively a variable resistor. Although a photoconductive cell has `been found to be especially desirable as far as the present invention is concerned, other types of light sensitive elements may be employed. A light sensitive element of the photoconductive type generally ernploys a chemical element which lies in the border-land between conductors and insulators. As the light imposed Iupon the chemical element increases in intensity, the resistance thereof decreases, thus permitting more current to how through the light sensitive cell which is connected in a circuit across a suitable source of voltage. The particular chemical element employed for the light sensitive element 23 forms no part of the present invention, but it might comprise cadmium sulphide, cadmium selenide, lead sulphide or the like. Preferably and as will be described in greater detail hereinafter, the light sensitive element 23 is mounted below the bottom of the cup-shaped member 24 as shown in FIG. 2 of the drawings whereby direct rays of sunlight are prevented by the tubular member 22 from reaching the element 23 except through the window defined by the cup-shaped member 24. The adjustable cap member 25 provides a sort of sun shade, considering vertical mounting of the dev-ice which is desirable, and also the design is such that snow or dirt cannot accumulate to effectively close the window provided in the sealed housing.

i A light sensitive element such as 23 is a very fast aeting device and, to all intents and purposes, is almost instantaneously responsive to a change in illumination. It is desired in a light control apparatus that the gradual reduction in the level of illumination as it becomes dark in the evening will cause the device to turn on suitable lights, and when the level of illumination increases to a sufficient extent in the morning to turn off such lights. However, since the light control device of the present invention is likely to be exposed to extraneous momentary sources of light such as lightning, automobile headlights and the like, there is provided the time delay device 26 which prevents instantaneous operation of the switch means 27 in response to any change in illumination applied to the light sensitive element 23. In accordance with the present invention the time delay device 26 comprises two identical

bimetallic elements

50 and 51 having corresponding ends thereof secured to a suitable insulating support 52. This support is schematically illustrated in FIG. 12, but as shown in the other views of the drawings comprises an annular member suitably supported above the base 21 by a pair of spaced rods 53 disposed parallel with the longitudinal axis of tubular member 22, as best shown in FIGS. 2, 5, 6, 7 and 9 of the drawings. The bimetallic element 5ft has one end theref fastened to the support S2 as by screws 55. Suitable end support means 56 may be provided, one on either face of the bimetallic element 50. Similarly, the bimetallic element 5l, which is identical with the bimetallic element 5d, is secured to the support S2 as by fastening means such as -screws 57. A pair of support means 5S, similar to the support means 56, are disposed one on either side of the bimetallic element 5i. The other ends of the bimetallic elements 5f) and 5l not secured to the support 52 are free and, with equal heating, these bimetallic elements will be deflected in equal amounts in the same direction. In other words, the high expansion sides of the bimetallic elements Si) and S1 are similarly orientated so that upon an equal increase in temperature of the

bimetallic elements

50 and 51 they will be deflected equally toward the left as viewed in FIG. 12 of the drawings. This arrangement insures that changes in ambient temperature will have no effect on the operation of the switch 27 controlled by the time delay unit 26 or, in other words, the switch 27 is insensitive to ambient temperatu're.

Secured to the free end of the bimetallic element Sii is the current control means 27 illustrated as a snap switch which may be any one of the well-known switches operating with a snap action such as are variously sold as microswitches or the like. The particular snap-acting switch illustrated in FIGS. 5I 8 and 1l of the drawings is by way of example only and comprises an insulated base plate 6i? suitably secured as by rivets 61 to the free end of the bimetallic element Sil. The snap switch 27 further lincludes a pair of relatively

movable contacts

62 and 63, the Contact 62 being a stationary contact and the contact o3 being a movable contact. A suitable overcenter mechanism including the spring 64 will insure that the contacts 62 and are made and broken with a snap action. The switch 27 has been specifically illustrated as of the normally open type, but for certain applications as described hereinafter it might equally well comprise a normally closed type switch.

Secured to the `free end of the bimetallic element S1 is a suitable insulated switch operating member '70 which is preferably adjustably mounted for movement along its longitudinal axis in a Z-shaped bracket 72 riveted as indicated at 73 to the free end of bimetallic element Sil. The insulated actuating member 7o is preferably mounted on the end of an adjusting screw 7d threadedly mounted in a suitable opening in Z-shaped support 72. A suitable lock nut 75 is provided for locking adjust-ing screw 7d in any selected position. The insulating switch actuating member 7d is adapted upon movement of the free end of the bimetallic element 51 towa-rd the free end of bimetallic element 5h to actuate the snap switch 2.7.

It will be apparent from the above description that since the bimetallic elements Sil and 51 move together in response to ambient temperature changes, operation of the switch 27 could not be accomplished without additional means. To this end there is provided a heating element `or resistance heater '76 surrounding the bimetallic eleassalito V. d' ment l, which heating element is electrically connected in series with the light sensitive element 23. A suitable insulating layer 77 surrounding an intermediate portion of ybirnetallic element 5l, as best shown in FG. 5 of the rawings, insulates heater 76 from bimetallic element 5l. To permit ready electrical connection with resistance heater 76, a pair of

band terminals

78 and 79 are secured around the layer "I7 at either end of heating element 76'. As illustrated in the drawings, a suitable conductor 80' interconnects the light sensitive element 23 (FlG. 4) and the heating element terminal 78, While the other terminai 79 of the heating element is connected by a conductor Sl directly to the conductor 3S. The other terminal of the light sensitive element 23 is connected by a conductor 32 to the conductor 37. Conductor 3S is preferably connected to ground, while conductor 37 is preferably connected to one side of an alternating current source so that ll() volts of O-cycle current are normally connected across the serially arranged light sensitive element 23 and resistance heater 7d. During daylight hours the light falling on light sensitive element Z3 is such as to decrease its resistance sufficiently to cause a current to flow through the resistor or resistance heater 76. The light sensitive element 2-3 should be such as to be capable of continuously withstanding a maximum of about one half watt of electrical energy. The resistance of the heater element '76 must be such that regardless how low the resistance of the light sensitive element 23 Ibecomes due to high intensity of ambient light, the power dissipation in the light sensitive element 2,3 will never exceed one halt watt.

During daylight hours the current flowing in heater element 76 will cause bimetallic element 5l to be dellected toward bimetallic element 56 to acuate normally open snap-acting switch 2-7 to the closed position. Preferably, the circuit constants are such that when the light level on the light sensitive element 23 falls to less than a one half foot candle, and preferably of the order of a one quarter foot candle, the current flowing in heater element 76 will decrease to the point that bimetallic element 5l will deflect away from element Sti and cause the snap-acting switch Z7 to open the circuit at

contacts

62 and 63. For many applications the snap-acting switch 27 is capable of performing a direct switching operation on the illumination control circuit, and to this end the

contacts

62 and 63 may be connected directly in the lighting circuit to be controlled. lf this is the case then the switch 27 is a normally closed switch instead of the normally open switch `as illustrated. Thus, with the normally closed switch, as the light level increases, the resistance of the light sensitive element 23 decreases to permit suilicient current to ow through resistor 76 to heat bimetallic element 5l, with the result that the normally closed contacts of the switch 27, which would be required in such case, are opened. However, the present invention has been illustrated particularly for .use with a high current carrying switch such as 2S, and under these circumstances the switch 27 must have normally open contacts as illustrated. Under these conditions an alternating current power source indicated at 83 in FIG. l2 would be Connected between terminal 3) of unit Ztl and one terminal of a lighting load S4. The other terminal of the lighting load would be connected to terminal Z9. Also, terminal 3l would `be connected to the terminal of power source 83 to which the lighting load is connected.

Considering now the electromagnetic switch 28, it has been illustrated `as a mercury switch of the type shown in Lemp Patent No. 536,811. lt may, however, comprise the high current switching device disclosed and claimed in copending Brosseau and Keeran application Serial No. 782,823, tiled concurrently herewith and assigned to the same assignee as the instant application. Preferably this switch comprises a sealed envelope 85 shaped in the form of an inverted Y with a pair of hollow diverging legs 85a and 317i) connected to an upwardly extending and vertically disposed hollow leg 85e. A reciprocating magnetic plungto to er 86 is disposed in the leg tc, which plunger is connected to a bridging contact 87. As illustrated, the bridging contact is of U-shaped configuration with the lower end of plunger connected to the bight of the U, and the legs 57a and 87!) of the U extending into the hollow legs and h, respectively. "the hollow legs 35a and 85h of the sealed envelope 85 contain mercury indicated at 8S to a level slightly below the common connection with the upwardly directed leg 85e thus effectively delining two separate mercury pools. The bridging element 87, due to the action of gravity on it and the associated plunger 256, is normally disposed so that the legs 87a and 37b are disposed within the two mercury pools thus electrically interconnecting these mercury pools. Upward movement of the bridging contact d'7 will interrupt the circuit between these pools. The envelope S5 may be evacuated or may be iilled with a suitable inert atmosphere such as nitrogen or the like. Electrical terminals ta and 8% (FG. 7), extending into the hollow legs 35a and SSI), respectively, are sealed in the glass envelope 85 and provide the switch terminals to which electrical connections are made. As illustrated, the terminals 89a and 55% are connected to the

conductors

36 and 37, respectively, which conductors are in turn connected to the terminals 29 and Sti, respectively.

ln order to actuate the magnetic plunger 8d of high current carrying switch ZS within the sealed envelope S5, these is provided a solenoid winding 90 surrounding the leg 85C of the envelope S5. The plunger 86 and solenoid winding Siti effectively provide an electromagnet for actuating the mercury switch described above. Energization of the winding 9d will cause the circuit to be broken between bridging contact 37 and the mercury pools disposed in hollow legs 85a and Sb of sealed envelope 35.

To support the electromagnetically actuated high current carrying switch 28 within the small sealed housing described above, the annular support 5?; is relied upon. As illustrated, the solenoid winding 90 is mounted upon the support 52, with the leg 85e of the sealed envelope 85 extending through the central opening 91 in annular support SZ. As illustrated in FIG. 5 ofthe drawings, support 52 is provided with diametrically opposed notches 92 to accommodate the diverging legs 85a and iSb of the sealed envelope With this arrangement annular support 52, solenoid winding 9u, arm 85C of the sealed envelope SS and plunger Se are concentrically arranged.

'For the purpose of completing the electrical circuit and as illustrated in FIG. l2 of the drawings, one terminal of the solenoid winding 96 is connected by a conductor 95 with the switch contact 63, while the switch contact 62 is connected 'oy the conductor 38 to the grounded terminal 3l. The other terminal of the solenoid winding 9i) is connected by a conductor 97 to the conductor 82, which is connected to the power conductor 37 at the switch terminal The support 52; may be provided with suitable notches 9S to position the conductors Si), 82, 95 and 97 so as not to interfere with `the tubular member 22. t

In view of the detailed description included above, the operation of the light control means of the present invention will readily be understood by those skilled in the art. Where the lighting load involves relatively high currents, the circuit as shown in FIG. l2 will be employed. During normal daylight hours the current flowing through heating element '7o will be suiciently high due to the low resistance of the light sensitive element 23 as to cause the bimetallic element 5l to deflect and close the sna acting switch 26. rlhis will result in energization of the solenoid winding 9i?, with the result that the mercury switch is moved to deenergize the lighting load When the light level decreases to a predetermined level, for example, one half foot candle, the resistance of the light sensitive element 23 increases, thus increasing the impedance to current flow in the circuit including heater element '76 whereby bimetallic element 5l cools and deilects in a direction to permit switch 27 to open. Openaosaire ing of switch Z7 deenergizes the solenoid winding 90 to cause the electromagnetically actuated mercury switch 23 to close due to the action of gravity upon the plunger 86 and bridging contact 87.

For applications where only a relatively low current lighting load is to be employed, the solenoid operated switch 28 and the conductors 9S and 97 will be completely eliminated, and the switch 27, which now must be a normally closed switch, may be used directly to control the lighting circuit. Under these conditions, for the arrangement shown in FIG. 12 the `contact terminal 29 will be omitted and the power and load will be serially connected across

terminals

30 and 31.

There are applications of the present invention where it may be desirable to energize the lighting load when the light level falls to a predetermined value but to turn off the lighting load before daylight again arrives. For example, in the advertising field, the trafc after midnight or one oclock in the morning may be sufficiently low as not to justify keeping an advertising sign lighted. In the above mentioned Brosseau and Keeran application there is disclosed and claimed a control circuit in which a timing device is incorporated with a switching device. The present invention may also be associated with such a timing device and in FIG. 13 of the drawings there is illustrated an application of the present invention where it is desired to turn off the illumination at a predetermined selected time. `The corresponding parts of FIG. 13 are designated by the same reference numerals as in the preceding embodiment. As there illustrated, and in accordance with the disclosure of the Brosseau and Keeran application, there is added to the arrangement of FIG. l2 a mechanism or clock and ycam arrangement generally designated at 19t) which may comprise a conventional electric clock 101, which makes 1 r.p.m. in twenty-four hours. This clock is drivingly connected, preferably through a slip clutch 192, to a cam 103, which cam is adapted to control a normally open snap-acting switch 194 having a xed contact 105 and a movable contact 106. The switch is connected in series with the c oil 90 and the

terminals

30 and 31. Thus, the load circuit may be controlled by closing either the `contacts of the switch 27 or the contacts of the cam-actuated switch 104. Preferably, the cam 103 is designed to keep the switch 104 closed for a fixed period such, for example, as six hours, after which the switch is again opened. 'As illustrated, the cam 103 is provided with an indicator 16'7 which preferably is visible on the face of the clock 101. By setting the indicator 107 to the time of day at which the operator happens to be adjusting the mechanism 100, the cam 103 may be caused to close the circuit at midnight and open it when a fixed period of time has elapsed. The timer means 100 will thus energize lthe winding 90 of the mercury switch 28 at midnight, thus preventing the light sensitive element 23 from keeping the lights energized during that fixed period. Obviously, the cam 1153 can be designed to give any span other than a sixhour span, which has been chosen by way of example only. Furthermore, by providing the indicator 107, the operator, in setting it to whatever the time is when the device is set, which is possible by virtue of the slip clutch 102, will be assured of proper adjustment thereof. The arrangement of FIG. 13 is particularly useful for lighting arrangements such as advertising signs where there is no need to have light after a predetermined time, which might also be true of factory parking lots and the like.

From the above description it will be apparent that there has been provided a light control means which requires no electronic tubes, transistors or similar devices, and except for the employment f switch contacts involves no moving parts. In the event of failure of any of the components, such as the light sensitive cell, the device will fail safe in that illumination will be provided. The entire components of the device are embodied in a sealed unit which may be thrown away when defective and replaced by a new unit.

While there have been illustrated and described a particular embodiment of the present invention and applications thereof, it will lbe appreciated that numerous changes and modications will occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications as fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

v1. Switching apparatus, comprising a hermetically sealed housing having a 4window wall portion, a photocell mounted in one end of said housing and disposed to intercept at least a portion of the light entering said housing through said `window wall portion, said photolcell having an electrica-l characteristic which varies in accordance with the light impinging on said photocell, electromagnetic switching means comprising a set of relatively movable contacts mounted in said sealed housing between said photocell and the other end of said housing, a set of terminals extending through said housing and electrically connected to respective ones of said contacts, and means mounted within said housing responsive to said electrical characteristic of said photocell for selectively operating said switching means, said means responsive to said electrical characteristic comprising a bimetallic switch actuating member and a heater resistor for said bimetallic member, said resistor being serially connected with said photocell.

2. Switching apparatus, comprising a generally tubular, hermetically sealed housing having a window wall portion at one end thereof, a photocell mounted in said housing in proximity to said wall portion, a switch mounted in said housing between said photocell and the other end of said housing, means electrically connecting said switch to said photocell to cause said switch to be actuated in response to the level of light impinging on said photocell, a plurality of terminals extending through said other end of said housing, said terminals being electrically connected to said switch, and an opaque light adjusting means mounted at said one end of said housing for movement along the longitudinal axis of said housing for controlling the light transmitting effectiveness of said window wall portion selectively .to adjust the sensitivity of said apparatus` 3. Switching apparatus as set forth in claim 2 wherein said light adjusting means comprises a cup-shaped member threadedly connected to said housing.

4. A light responsive switching device comprising a current responsive electromagnetic mercury relay having an operating coil and a set of normally closed first contacts, a time delay switch including a set of second contacts and a bimetallic actuating member for closing said second contacts when the temperature of said member exceeds a predetermined value, a heating resistance for said actuating member, a photocell, means for serially connecting said resistance and said photocell across a source of voltage, and means for serially connecting said operating coil and said second contacts across a source of voltage so that said normally closed first contacts of said relay are opened and closed without delay in response to the respective closing and opening of said second contacts, said second contacts closing when the light impinging on said photocell is above a predetermined level for a period suiiicient to heat said resistance to actuate said member, and opening when the light impinging on said photocell is below a predetermined level for a period suflicient to permit said member to return to its unactuated position.

i5. The switching apparatus of claim 2 wherein means are provided to hold said light adjusting means in any predetermined selected position, which means also serves to seal said housing.

6. Light control means, comprising a base, electrical terminals projecting from said base, an electromagnetic switch supported above said base including an insulating support, time delay means depending yfrom said support including switch means, a light sensitive element mounted above said support, circuit means for connecting said terminals, said electromagnetic switch, said time delay means and said light sensitive element into an electric circuit whereby said switch is actuated in response to gradual changes in light level between predetermined limits, a housing cooperating with said. base for enclosing all of said elements except a portion of said base and terminals, said housing including a cup-shaped transparent wall portion at the upper end thereof secured to a tubular member in sealed relationship therewith to permit illumination to reach said element, and means for sealing said housing to said base.

7. The light control means of claim 6 wherein means comprising a circular opaque member adjustably positioned relative to said cup-shaped transparent member is CJI 1?; provided selectively to adjust the sensitivity of said light control means.

8. Switching apparatus as set forth in claim 2 wherein said light adjusting means comprises a member threadedly connected to said one end of said housing.

References Cited in the file of this patent UNITED STATES PATENTS 2,331,475 Johnson Oct. 12, 1943 2,631,247 Shaw Mar. 10, 1953 2,697,803 Eadie Dec. 2l, 1954 2,753,492 Jay July 3, 1956 2,755,392 Garnick July 17, 1956 2,898,525 Jacobs Aug. 4, 1959 2,900,520 Frank Aug. 18, 1959 FOREXGN PATENTS 159,650 Sweden July 16, 1957

Claims

1. SWITCHING APPARATUS, COMPRISING A HERMETICALLY SEALED HOUSING HAVING A WINDOW WALL PORTION, A PHOTOCELL MOUNTED IN ONE END OF SAID HOUSING AND DISPOSED TO INTERCEPT AT LEAST A PORTION OF THE LIGHT ENTERING SAID HOUSING THROUGH SAID WINDOW WALL PORTION, SAID PHOTOCELL HAVING AN ELECTRICAL CHARACTERISTIC WHICH VARIES IN ACCORDANCE WITH THE LIGHT IMPINGING ON SAID PHOTOCELL, ELECTROMAGNETIC SWITCHING MEANS COMPRISING A SET OF RELATIVELY MOVABLE CONTACTS MOUNTED IN SAID SEALED HOUSING BETWEEN SAID PHOTOCELL AND THE OTHER END OF SAID HOUSING, A SET OF TERMINALS EXTENDING THROUGH SAID HOUSING AND ELECTRICALLY CONNECTED TO RESPECTIVE ONES OF SAID CONTACTS, AND MEANS MOUNTED WITHIN SAID HOUSING RESPONSIVE TO SAID ELECTRICAL CHARACTERISTIC OF SAID PHOTOCELL FOR SELECTIVELY OPERATING SAID SWITCHING MEANS, SAID MEANS RESPONSIVE TO SAID ELECTRICAL CHARACTERISTIC COMPRISING A BIMETALLIC SWITCH ACTUATING MEMBER AND A HEATER RESISTOR FOR SAID BIMETALLIC MEMBER, SAID RESISTOR BEING SERIALLY CONNECTED WITH SAID PHOTOCELL.