US3419726A - Outdoor lighting photocontrol having adjustable shade - Google Patents

Description

Dec. 31, 1968 J. c. OLSEN 3,419,726

OUTDOOR LIGHTING PHOTOCONTROL HAVING ADJUSTABLE SHADE Filed Aug. 10, 1965 INVENTOR. cfofm C. OZsefl 3 419,726 OUTDOOR LIGHTING PHOTOCONTROL HAVING ADJUSTABLE SHADE John C. Olsen, Racine, Wis., assignor to McGraw- Edison Company, Milwaukee, Wis., a corporation of Delaware Filed Aug. 10, 1965, Ser. No. 478,692 2 Claims. (Cl. 250237) ABSTRACT OF THE DISCLOSURE A photocontrol assembly for outdoor lighting fixtures including a generally opaque housing having a transparent window portion, a photocell within the housing having a light sensitive area facing the transparent window in the housing, and adjustable shade means between the interior surface of the housing and the photocell for adjusting the intensity of light falling on the photocell from the transparent window. The adjustable shade comprises an annular strip of pliable transparent material of progressively decreasing transparency rotatably movable within said housing to adjust the intensity of light reaching the photocell.

This invention relates to photocontrol devices and, more particularly, to new and improved means for shading the photocell in a photocontrol device.

Prior art photocontrols for outdoor luminaires generally include a photocell sensitive to ambient illumination for altering an electrical signal to a relay which controls a switch in the luminaires lamp energizing circuit. The photocell of such prior art devices is usually located behind a window in the photocontrol housing which is generally oriented so that direct sunlight does not fall on the photocell. After such photo controls have been assembled, it is the usual practice to calibrate the control by covering a portion of the photocell with an adjustable shade so that operation will occur at the desired level of ambient illumination. This method of adjustment is not entirely satisfactory because the entire photocell is not evenly illuminated which tends to cause excessive heating in the unshaded portion of the photocell.

It is an object of the invention to provide a photocontrol having a shade which allows even photocell illumination.

A further object of the invention is to provide a photocontrol shade which provides a high maximum to minimum light transmitting ratio and which is adjustable over a wide range of light levels.

These and other objects and advantages of the instant invention will become more apparent from the detailed description thereof, taken with the accompanying drawings in which:

FIG. 1 is a side elevational view showing an outdoor lighting fixture provided with a photocontrol according to the instant invention;

FIG. 2 is a side elevational view, partly in section, of a photocontrol according to the instant invention;

FIG. 3 is a side elevational view illustrating the shade of the photocontrol shown in FIG. 2;

FIG. 4 is a view taken olong lines 44 of FIG. 3;

FIG. 5 illustrates the photocell shade prior to its assembly in the photocontrol device; and

FIG. 6 shows an alternate embodiment of the invention.

Referring now to the drawings in greater detail, the luminaire 9 illustrated in FIG. 1 is shown to include a reflector 10 and a refractor 11 supported below a housing 12 which encloses circuit elements for energizing the lamp 13. The lamp circuitry is controlled in accordance United States Patent 0 3,419,726 Patented Dec. 31, 1968 with the level of ambient illumination by a photo control 14 mounted atop the luminaire housing 12.

The photocontrol is shown in FIG. 2 to include an inverted, generally cup-shaped housing 16 having a lower closure plate 17 suitably affixed thereto. It is the general practice for housing 16 to be opaque except for a window 18 on one side thereof.

The photocontrol 14 also includes a photocell 20 and an operating mechanism 21. The photocell 20 has a light sensitive area 19 positioned opposite the window 18 so that it will be exposed to the ambient light passing through said window. The details of the operating mechanism 21 are not shown but, as those skilled in the art will ap preciate, will generally include a relay operable by the photocell 20 to open and close an energizing circuit to the lamp 13 in accordanse with the level of the ambient illumination. A plurality of plug-in connectors 22 are secured to and extend from the closure plate 17 for mechanically annd electrically connecting the photocontrol 14 to the luminaire 9.

The level of ambient illumination falling on the light sensitive area 19 is also controlled by a shade or screen 23 positioned between the photocell 20 and the housing 18. More specifically, the screen 23 is shown in FIG. 5 initially to be in the form of a generally arcuate strip of pliable transparent material, such as plastic, upon which shading has been applied. In the illustrated embodiment, the shading consists of a plurality of small dots, spots or specks 24 which are substatnially uniformly distributed within incremental areas of said strip and which are progressively denser from a clear area 25 to a substantially opaque area 26. The specks 24 are applied to the screen 23 in any suitable manner, such as by silk screening.

After the specks have been applied to the screen 23, it is joined at its edges to form a generally annular member which substantially conforms to the inner surface of the housing 16. As seen in FIGS. 2, 3 and 4, the screen 23 is disposed between the photocell 20 and the inner surface of the housing 16 and in surrounding relation to the operating mechanism 21. This places the shade 23 in a position to intercept all straight line paths between the window 18 and. the light sensitive area 19 of the photocell 20. As a result, the shade 23 will screen a portion of the light passing through the window 18 and falling on the area 19 of the photocell 20. The amount of light transmitted by the shade 23 will depend upon which of its incremental areas is disposed in the operative position between the window 18 and the photocell 20.

It can be seen that in each incremental portion of the shade 23, the specks 24 are substantially equally spaced and this spacing decreases from the clear area 25 to the opaque area 26. This insures that regardless of which of the areas of the shade 23 is positioned between the window 18 and the photocell 20, the light will be substantially uniformly distributed over the sensitive area 19 of the photocell 20. In this manner, even illumination of the photocells sensitive area 19 is achieved thereby avoiding cell overheating.

As seen in FIG. 2, a small opening 28 is formed adjacent one side of the bottom closure plate 17 and below the transparent window 18 in the housing 16. When the cap 29 which normally closes the opening 28 is removed, the screen 23 may be rotated by inserting a sharp pick (not shown) into the opening 28. lln this manner, the desired area of the screen 23 may be moved between the window 18 and the photocell 20.

By adjusting the screen 23 relative to the photocell 20 and the window 18, a wide range of light transmission levels can be achieved. For example, when the clear portion 25 of the screen 23 is opposite the phottocell 20,

substantially all of the light falling in the screen 23 will pass through to the photocells sensitive area 19 allowing the operating mechanism 21 to operate at a relatively low level of ambient illumination. When the screen is rotated to the areas of more numerous dots and toward the substantially opaque portion 26, smaller amounts of light are transmitted through to the photocell 20 requiring a higher level of ambient illumination for operation of the mechanism 21.

While in the illustrated embodiment the screen 23 is shown to have dots or specks 24 applied thereto in increasing density from the clear area 25 to the substantially opaque area 26, those skilled in the art will appreciate that any type of pattern which will produce this effect will operate equally as well. For example, FIG. 6 shows an alternate embodiment of the invention wherein the screen 23' comprises a substatnially opaque number in which a plurality of openings have been formed therein. A relatively large opening 25', which at least has substantially the same area as the light sensitive area 19 of the photocell 20 provides a clear area in the screen 23'. In addition, a plurality of apertures 24' are provided and arranged so that they are equally spaced in each incremental area of the shade 23 and decrease substantially uniformly in size from the clear area 24 to the substantially opaque area 26', which has no openings.

While only a few embodiments of the invention have been shown and described, it is not intended to be limited thereby, but only by the scope of the appended claims.

I claim:

1. A photocontrol device for outdoor lighting fixtures comprising:

a housing having a inverted cup-shaped member with a top portion and a circular depending wall portion, said housing further including a lower closure plate for colsing the lower opening of said cup shaped member, and said housing being generally opaque with a transparent portion in said depend-- ing Wall portion;

a photocell positioned within said housing and having a light sensitive area facing said transparent housing portion; and

shade means having portions of progressively decreasing transparency and being mounted within said housing for selective movement of the progressively decreasing transparent portions thereof between the transparent portion of said housing and said photocell, said shade means being located in all of its positions of its selective movement to intercept substantially all straight line paths between said transparent housing portion and said light sensitive area so that the light transmitted through said transparent housing portion and through said shade means will be substantially uniformly distributed over the light sensitive area of said photocell, and said shade means being of an annular shape conforming loosely to the shape of the interior surface of said depending wall portion and movably retained vertically between said closure plate and the interior surface of said top portion so as to be rotatably adjustable within said housing to adjust the intensity of light falling on said light sensitive area.

2. The invention as defined in claim 1 in which said shade means comprises an annular strip of pliable transparent material.

References Cited UNITED STATES PATENTS 12/1934 Lyle 250-237 X 6/1941 Thomas 250-237 X US Cl. X.R. 250239

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