US 1788111 A
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D. D, KNOWLES STREET LIGHTING SYSTEM Filed Aug. 22, 1928 Jan. 6, 1931.
.l 9 e MJ 2 e \V e lv\ 4 g f A 5 w en \\\L 0e a@ w INVENTOR A De'weyD Know/es.
ATTORNEY Patented Jan.' A6, 1931 -UNrrED STAT-Es PATENT oi-r-"lca DEWEY n. inrowmss, or wlmnrsnuno, rENNsYLvmA, AssIeNoa fro wrsrmonousta marmo mmuc'runme conm, A oonromirrou or rENNsYLvANIA' saveur-LIGHTING srs'rmc R S S u D f Application led August 22, 1928. Serial No. 301,415.
My invention relates to control systems and particularly to circuit-controlling means em loying light-sensitive cells. .v
t is one of-the main objects of my inven` tion to provide a control system for power consuming circuits embodying light-sensitive cells to actuatethe control devices inaccord-I ance with major variations from light to darkness and vice versa, in which minor variations in light intensity shall be prevented from causing repeated energization and deenergization of the lighting units.
In practicing my invention, I provide an electromagnetic circuit controller for controlling the energiz'aton 'of one or more power-'- consuming devices, a light-sensitive cell for controlling an electro-magnetic relay and an auxiliary lighting unit, the ener izationof which is controlled directly by tie electro/- magnetic relay and secondarily by the lightsensitive cell.
In the single sheet of drawings,
Figure 1 is a schematic illustration, par-A tially in section, of circuits and apparatus embodying my invention; Fig. 2 is a diagram of light intensities which vary from darkness todaylight, and,
Fig. 3 is a diagramV showing the Variation in light intensities when changing from daylight to darkness.- v
Referring more particularly' to Fig. 1 of 1 the drawing, I have thereillustrated a supply circuit comprising conductors 11 and 12,
an electro-magnetic relay or contactor 13 em v bodying an actuating coil 14 and acore member 15 associated therewith and having secured thereto a contact-bridging member 16, A plurality of lower contact members 17 are engaged by the bridging member 16 when the coil 14 is deenergized. A pair of upper contact members 18 are engaged by the bridging member 16 when coil 14 is energized.` A plurality of lighting units 19, indicate generally only for the purpose of illustrating a power-consuming circuit, may be connected in parallel-circuit relation, relatively toeach other, and their energization is controlled by the contactor 13. However, I desire it to be understood that the circuit shown is illustrative only and that any auxiliary circuit,
branch circuit or controlled circuit may be substituted.
Means for controlling the actuation of the contacter 13 comprises a light-sensitive cell 21 which shown generally only, and may, for example, be a selenium cell. It is Well known that selenium has the property of having -a relatively high electrical resistance when not subjected to any light, such as daylight, while its Yresistance decreases very appreciably yift subjected to light of any appreciable intensity. The cell 21 is preferably mounted in a light-tight box 22 having an opening 23, therethrough, to permit daylight or other light to strike the cell 21 and cause it to` change its electrical resistance.
AAn auxiliarylight source is represented by a lamp 24: also-located within'the box 22 and so connected to the contactor 13 as to lbe energized lwhen the coil 14 is energized and to be deenergized when the bridging member 16 is in operative engagement with the contactmembers 17, at which time the lighting units 19 are energized. When 'a control system of this kind is used for streetslighting circuits, the cell 22 is to be subjected to daylight and to darkness in order to properly control the energization of the lighting units 19. It may happen, however, that the intensity of the light may rise to such value as to cause deenergization of the units 19 by reason of the decrease in the resistance of the cell-21 and the flow of current Vtherethrough and through the coil 14 of the contactor 13. If a momentary decrease in the light intensity should be so great as to cause theresistance of the cell 21 to increase to a relatively high value, the lights would again be energized and this might happen several times, thereby causing undesired operation of the system. v
Referring to Fig. 2 of the drawings, I have there illustrated a curve 25 of increasing major light variations, the intensity starting at zero, or at some very low value, as may be the case during the night, and increasing up to say 35 units of intensity, which value may be sufficiently high to ,cause the system to operate to deenergize the units 19. Thiswill be the case ifthe cell 21 is so constructed and 1 cell 21 will still be 35 units, Which value is suiiciently high to maintain the contactor in its operated position. Several minor variations are indicated by curves 25 and 26, the minimum values in no case falling below that necessary to maintain the energization of the coil 14.
`Referring'to Fig. 3 of the draWings,- I have there illustrated a curve of decreasing major intensity of light, such as may occur at nightfall. The broken-line curve 28 illustrates the intensity of the light reaching the cell 21, inasmuch as the auxiliary lamp 24 is still energized. Once the light intensity, as represented by curve 28, reaches a value of 28 foot candles, -the resistance becomes high enough to sufliciently decrease the current traversing it and the coil 14 to permit deenergization'of the coil 14 and consequent energization of the units 19.
As soon as the total light intensity reaching the cell 2 1 drops to a value of 28 foot candles, as indicated by the numeral 29, the auxiliary light source is extinguished, and the amount o light reaching the cell will be that shown in curve 27 to the-right of the vertical line eX- tending below the point 29.
It is, of course, obvious that the amount of illumination providedblyl the auxiliary light 24- may be varied wit in relatively Wide limits, but I have drawn curves 25 and 26 and 27 and 28 with a difference of 10 units of light intensity therebetween. Provided that the variations of the light intensity on the outside of the box 22 do not exceed 10. lihdt units, the system will operate as descri as the lighting unitsnhuwn have shown and described m above and, in case actual tests show that greater variations in light intensit will occur at daybreak or at nightfall, it 1s only necessary to provide a larger amount of auxiliary illumination.-
The device and s stem embodying my invention thus providd a relatively simple and easily operated control system which 1s elective to prevent repeated ene ization and deenergization of anycontrol ed circuit such to minor variations inthe light intensity.
While, for purposes of illustration only, I invention as apglied-to a lighting circuit, do not desire to limited t ereto, as it may obviously be used to control any workcircuit or secondary controlcircuit. For instance,tl1e circuit ImellnS 0 such limitations shall be placed thereon las are imposed by the prior art or are set forth in the appended claims.
I claim as my invention:
1. In a control system, in combination, an energy-translating device to be controlled, a circuit controller therefor, a light-sensitive cell forl controlling the energization of the circuit controller, a li ht source operatively associated with the cell, and means associated with the controller for energizing the light source when the energy-translating device is deenergilzed.
2. In a control system, the combination With acontrolled circuit, a circuit controller therefor, and a light-sensitivecell for controlling the energization ofi the circuit controller, of a lamp operatively associated with the cell and means for causing energization` of the lamp when the first named control cirvincluding a light-sensitive cell `subjected to' 'maior variations of light intensity, for contro ling the cnergization ofthe controlled system, of an auxiliary source of light operatively associated with the cell, and means for controlling the auxiliary light source to Vcounteract the effect of minor variations of light intensity on the cell. i
In a control system, the combination with a system to be controlled, and means, including a light-sensitive' cell subjected to varying light lntensity, for controlling the energization of the controlled system, of ratively associated with the cell for locally ecreasing the ntensityof light to which the cell is sub'ected when the variable light intensity has ecreased to a predetermined value. 4
'6. In a control system, the Acombination with a s slemto be controlled, a circuit controller t erefor and a light-sensitive cell subjected to a slow major -increase of light in-V tensity for controlling the o eration of the ycircuit controller, of an auxi iary source of l light' operatively associated with the cell, and
lso 4 means associated with the circuit controlled for suddenly increasing the local light intensity to which the cell is subjected when the light intensity has reached a redetermined value by reason of the slow major increase.
7. In a, control system, in combination, an
energy-translating device to be controlled, a.
circuit controller therefor, a photo-sensitive" device, subject to varying light intensity, for controlling the energization of said circuit controller, and regulating means operatively associated with said photo-sensitive device and responsive to the condition of said controller to abruptly-increase the state of excitation of said photo-sensitivey device when said translating device has been rendered inactive and to abru tly decrease the state of excitation of said photo-sensitive device When said translating device has been rendered active.`
8. In a control system, in combination, an energy-translating device to be controlled, a current-responsive circuit controller therefor, a photo-sensitive device, subject to varying light intensity, for controlling the energization of said circuit controller, and regulating means operatively associated with said photo-sensitive device and responsive to the condition of said controller to abruptly increase the current exciting-said .controller when said translating device has been rendered inactive and to abruptly decrease the current exciting said controller when 'said translating device has been rendered active. 9. In a control system, in combination, an energy-translating device to be controlled, a circuit controller therefor, a hoto-sensitive device, subject to varying light intensity, for controlling 4the energization of said circuit controller, and regulating means operatively associated with said photo-sensitive device and responsive to the condition of said controller to abruptly increase the state of energization of said controller when said translating device has been rendered inactive and to abruptly decrease the state of energizationof said controller when said translating-device has been rendered active.
n testimony whereof, I -have hereunto subscribed my name this 14th day-of August,
. DEWEY D.-VKNOWLES.