Photocontrol device for grade mounted light fixture

A light fixture has a light-transparent cover at substantially grade level and a photocontrol device with a self-flushing outer surface for preventing accumulation of opaque material thereon. The light fixture is adapted to be positioned within a recess in the graded environment and includes a housing which encloses a lamp electrically connected to the photocontrol device. The self-flushing outer surface of the photocontrol device discourages the build-up of opaque material so that the photocontrol device can reliably detect changes in the ambient light conditions outside the light fixture and operate the lamp in response to the detected changes.

FIELD OF THE INVENTION 
The invention relates to a photocontrol device for controlling the lamp 
operation of a grade-mounted outdoor light fixture. Overlying the lamp is 
a cover substantially flush with the surrounding landscape, while the 
remainder of the light fixture is recessed below the landscape grade. A 
light-transmitting plug transmits ambient light to a photocontrol switch 
which turns the fixture lamp on and off in response to changes in the 
ambient light conditions. The upper surface of the plug is self-flushing 
to prevent accumulation of light-blocking materials thereon and is also 
substantially flush with the landscape grade. 
BACKGROUND OF THE INVENTION 
Grade-mounted light fixtures perform a variety of desirable functions, such 
as illuminating the facades and exteriors of buildings, creating aesthetic 
light and shadow effects in a range of architectural and landscape 
settings and providing safety and security lighting around commercial and 
industrial buildings. Such light fixtures are referred to as grade-mounted 
because, they are installed into recesses in the landscapes adjacent the 
buildings so that the uppermost surface of the light fixture, which is 
typically a transparent cover overlying the lamp, is generally flush with 
the landscape surface. It can be appreciated that such recessed light 
fixtures are ideal in environments in which lighting is desired without 
the unsightliness or disruptive lines of an above-grade light fixture. 
In view of their installation into recesses in the landscape, recessed 
light fixtures require special consideration in their design and 
construction. For example, the light fixture must be as water tight as 
possible to avoid the corrosive effect of soil, plants, concrete or other 
material having an appreciable moisture content. Protection against water 
penetration is all the more important since visual inspection of such 
recessed light fixtures usually necessitates withdrawal of the fixture 
from its recess, a time-consuming and labor-intensive task. Additionally, 
the very low profile of the recessed light fixtures makes it difficult to 
successfully adapt these fixtures with desirable modifications such as, 
for example, photosensitive devices which detect changes in the ambient 
light conditions and automatically activate and deactivate the lamp 
without the need for operator intervention. In fact, a number of 
commercially available photosensitive devices have proven to be 
impractical or unreliable in their application to the unique environment 
of recessed light fixtures. 
Conventional photosensitive devices generally comprise a switch having a 
light sensitive diode which generates electrical signals in response to 
the intensity of light incident upon its detecting means and a light 
transmitting channel or plug which channels outside light to the 
photosensitive switch. 
One commercially available button type photocontrol device has a sensor 
cell mounted on a rectangular plastic housing, an arrangement much like a 
dish on a table top. The sensor cell faces towards the sky, while the 
bottom of the box rests on the fixture housing. In another commercially 
available photosensitive device, the housing has an integral threaded, 
hollow stem which can be threaded directly into a threaded aperture of the 
fixture housing. A third type of commercially available photosensitive 
device has a cylindrical housing with a threaded hollow stem for 
engagement with the aperture of the fixture housing. 
However, as can be appreciated, these outer mounted photocontrol devices 
are ill suited for recessed light fixtures. The flat surface of the sensor 
cells which receive the ambient light can easily be blocked by dirt, dust, 
plant debris or other opaque materials which collect thereon. With the 
sensor cell partially or completely blocked by the accumulated materials, 
only a significantly reduced amount of ambient light passes through the 
sensor cell to fall onto and activate the photosensitive diode in the 
switch. Eventually, when the amount of ambient light falling through to 
the switch is beneath a preset threshold, the switch responds as if dark 
conditions prevail outside the light fixture and thus acts to turn on the 
lamp. As can be seen, such "false reading" by the photocontrol device can 
waste energy nd unnecessarily reduce the operating life of the lamp and 
the other light fixture components by turning on the lamp when diminished 
or dark light conditions do not, in fact, exist. 
Additionally, in recessed light fixture applications, it is desirable that 
the switch be beneath the exterior surface of the landscape grade so the 
smooth, grade level appearance of the fixture is maintained. In addition 
to marring the aesthetic appearance of the grade-mounted light fixture, 
these known photosensitive devices can interfere with pedestrians walking 
over the outer surface of the fixture or with lawn mowers or other 
landscape maintenance machines which pass over the light fixture. 
The interference problems caused by the excessive height of the known 
photocontrol devices can be reduced if the switch component of the 
photosensitive devices is disposed beneath the outer surface of the 
fixture while the light channeling plug is the sole component which 
projects above the outer surface of the light fixture. It is known to 
dispose the switch components of photosensitive devices within the housing 
of a light fixture while positioning the light collecting plug on the 
exterior of the housing. For example, see U.S. Pat. No. 3,264,466 to 
Bacon, Jr., U.S. Pat. No. 3,274,392 to Harling and U.S. Pat. No. 3,543,099 
to Turner. These patents are directed to photosensitive devices disposed 
within street lamps or other light fixtures positioned some distance above 
ground. However, while these patents disclose light collecting plugs which 
prevent, to some degree, the accumulation of dirt or other opaque material 
on their outer surface -- see, for example, the dome shaped collectors of 
Bacon and Turner and the conical light collector of Harling -- these 
patents offer little guidance to the successful adaptation of a 
photosensitive device to a grade mounted or recessed light fixture. For 
example, the conical light collector of Harling is angled so that a 
desirable amount of light rays are reflected by the reflective surface of 
the collector onto the underlying photosensitive cell. Thus, the height to 
which the conical collector projects above the light fixture housing is 
not a design constraint as it is with received light fixtures. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide an outdoor grade-mounted 
fixture having a photocontrol device which minimizes the accumulation of 
light-blocking materials on its light-transmitting plug while having its 
uppermost part at substantially grade level. 
It is a further object of the invention to provide a recessed lighting 
fixture having a photocontrol device which has a minimum height above 
grade level so as to minimize interference with pedestrians and landscape 
maintenance equipment. 
It is yet a further object of the invention to provide a photocontrol 
device for a recessed lighting fixture which is easily installed. 
It is yet an additional object of the invention to provide a photocontrol 
device for a recessed lighting fixture which can be sealed in a 
water-tight manner with the fixture without the need for extensive sealing 
hardware. 
It is yet another object of the invention to provide a photocontrol device 
for a recessed lighting fixture having a plug which is a single piece and 
which can be readily installed to the fixture. 
It is yet another object of the invention to provide a recessed lighting 
fixture in which the switch of the photocontrol device can be positioned 
beneath the outer surface of the light fixture. 
It is yet an additional object of the invention to provide a photocontrol 
device for a recessed lighting fixture which is not readily susceptible to 
breaking or bending when impacted by moving objects such as a shoe or 
landscape maintenance equipment. 
The foregoing objects are accomplished by a light fixture positionable in a 
recess in a graded environment, comprising a housing, located in the 
recess, having an outer top surface located substantially at grade level 
and including first and second apertures. A light-transparent lens is 
coupled to the housing in the first aperture. A lamp is mounted within the 
housing for directing light through the cover. A photocontrol device is 
operatively connected to the lamp for operating the lamp in response to 
changes in the ambient light conditions outside the light fixture. The 
photocontrol device includes a light-transparent member coupled to the 
housing in the second aperture, the member having an outer surface 
including self-flushing means for preventing accumulation of opaque 
material thereon, and a photosensitive switch coupled to the housing for 
receiving ambient light passing through the light-transparent member and 
having means for electrically connecting the switch to the lamp. 
Other objects, advantages and salient features of the present invention 
will become apparent from the following detailed description, which, taken 
in conjunction with the annexed drawings, discloses preferred embodiments 
of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Light fixture 10 in accordance with the invention is shown in FIGS. 1, 2 
and 3 in a graded landscape environment 12. Light fixture 10 includes a 
lamp housing 14 and a ballast housing 15 having an outer top surface 16. 
The fixture is mounted within a recess 17 of landscape environment 12 such 
that outer top surface 16 is substantially at the level of the surrounding 
top surface of landscape environment 12. 
As seen in FIGS. 1-3, housing 14 encloses the various components of light 
fixture 10 and has continuous, water-tight housing base 18 which forms a 
protective, water-tight barrier between the internal electrical components 
of light fixture 10 and the surrounding soil of landscape environment 12. 
A housing cover 16a is secured to housing base 18 by fasteners 20. The 
fasteners pass through apertures in cover 16a and threadedly engage 
internally threaded holes 22 of housing base 18. A gasket 24 is disposed 
between the under side of cover 16a and housing base 18 so that moisture 
cannot penetrate at the interface between the cover 16a and housing base 
18. 
Ballast housing 15 has a housing base 15a and a cover 15b. A gasket 15c 
seals cover 15b and housing base 15a. The ballast housing 15 is separately 
formed from lamp housing 14 and is coupled to housing 14 by fasteners. 
Cover 16a includes a first aperture 26 and a second aperture 28. A 
transparent lens 30 is sealingly disposed in first aperture 26 and is 
positioned to overlie a lamp 32 supported on the inside of housing 14. 
Light from lamp 32 is transmitted through transparent lens 30 to 
illuminate the outside environment. 
A photocontrol device 34 for operating lamp 32 in response to changes in 
the ambient light conditions includes a switch 36 disposed beneath cover 
16a and a plug 38 threadably received in second aperture 28. Wires 40 
connect photo-control device 34 and lamp 32 so that the lamp is 
electrically activated in response to changes in ambient light conditions 
detected by photocontrol device 34. A transformer 42 (partially shown in 
FIG. 3) supplies power to lamp 32 via wires 44. A cable connects 
transformer 42 to a power source (not shown). 
Housing 14 is advantageously constructed of fiberglass reinforced polyester 
composite. This material offers desirable strength and high resistance to 
corrosion, and is light weight for easy installation. Material of high 
strength is desirable, for example, so that outer surface 16 formed by 
cover 16a resists deformation when stepped on and so that housing base 18 
resists deformation from dirt or gravel compacted against it. Housing 14 
is advantageously designed to enclose the components of light fixture 10 
in as small a volume as possible so that light fixture 10 can be fitted in 
a wide variety of large and small recesses in a landscape environment 12. 
Transparent lens 30 is advantageously crowned or slightly convex to promote 
run off of water, dirt and other materials. The transparent lens 30 is 
advantageously constructed of borosilicate or tempered glass to resist 
exposure to weather elements, pedestrian traffic, landscape maintenance 
equipment and other impact and wear forces. Gasket 24, suitably 
constructed of water resistant material such as single piece molded 
silicone, is also disposed between transparent lens 30 and cover 16a to 
seal first aperture 26 against water penetration. 
Fasteners 20 are advantageously constructed of stainless steel to resist 
corrosion and are tamper resistant to prevent unauthorized access to light 
fixture 10. 
Switch 36 of photocontrol device 34 has an externally threaded stem 50 
which threadably engages second aperture 28. The core of stem 50 is 
transparent to permit light from plug 38 to enter switch 36. 
As best seen in FIG. 4, plug 38 is preferably constructed as a single unit 
of clear thermoplastic material and comprises a generally conical outer 
top surface 52 and an externally threaded post 54 threaded into second 
aperture 28. Second aperture 28 is defined in a generally cylindrical 
member 28a depending from cover 16a. An annular groove 56 having a 
diameter lightly larger than the diameter of post 54 receives an 0-ring 
58. The 0-ring compressed against outer surface 16 when plug 38 is 
threaded into second aperture 28, thereby providing a water tight seal 
between plug 38 and second aperture 28. Additional protection against 
water penetration through aperture 28 is provided by an arrangement 
comprising nut 60 and a second O-ring 62 disposed around stem 50. Nut 60 
is threadable along stem 50 to compress O-ring 62 against the bottom end 
of cylindrical member 28a. O-ring 62 forms a water tight seal when 
compressed. 
Outer surface 52 of plug 38 is self-flushing -- i.e., the surface is 
downwardly inclined so that dirt and debris tends to slide off the plug, 
especially when mixed with water. The self-flushing shape of outer surface 
52 minimizes the accumulation of dirt, debris and other opaque material 
which inevitably accumulates on recessed light fixtures. The accumulation 
of opaque material on the plug can so limit the ambient light reaching the 
underlying switch of the photocontrol device that the device wrongly 
"interprets" the lack of ambient light as indicative of dark light 
conditions outside the light fixture. The photocontrol device would then 
operate the lamp in an untimely manner. 
As best seen in FIG. 3, the height to which outer surface 52 projects above 
outer surface 16 is relatively small and preferably on the order of less 
than 1/2 inch. By comparison, several commercially available photocontrol 
devices adaptable to recessed light fixtures typically project more than 2 
inches above the light fixture. The reduced height of plug 38 minimizes 
interference with pedestrian traffic on light fixture 10 and minimizes the 
risk that plug 38 will be damaged by landscape maintenance equipment. 
Although outer surface 52 of plug 38 is conical, the surface can be of any 
self-flushing shape such as, for instance, a ramp or wedge shape. 
While various embodiments have been chosen to illustrate the invention, it 
will be understood by those skilled in the art that various changes and 
modifications can be made therein without departing from the scope of the 
invention as defined in the appended claims.