Submersible light fixture

A submersible light having an electrically nonconductive reflector and no other electrically conductive elements requiring grounding, a tough lens to withstand impacts from swimmers and features providing quick and easy serviceability. Because of these features, the light of the invention meets safety requirements allowing the light to be mounted less that 18 inches below the waterline, thereby allowing its placement in areas of pools that have been heretofore off limits to conventional lights. In addition, a cord holder about the external surface of the light's housing and twist lock base and housing with a radial O-ring seal provide for quick and easy disassembly and re-installation of the light.

FIELD OF THE INVENTION 
The present invention relates to an apparatus and method for illumination, 
and, more particularly, to the illumination of liquid containers, such as 
pools, spas and the like. 
BACKGROUND OF THE INVENTION 
Swimming pools and spas are well known and provide recreational and health 
benefits to many people across the United States. Swimming pools and spas 
typically have water circulation systems that include electrical devices 
such as pumps and heaters. Further, many pools and spas have submersible 
lights located under the waterline to illuminate the water at night, 
thereby making the pool or spa safe and aesthetically appealing to 
swimmers. 
Because of such electrical devices, swimming pools and spas are subject in 
most jurisdictions to restrictive codes intended to reduce the chance of 
accidental electric shock to swimmers. Typically, all conductive elements 
associated with a pool or spa, including submersible lights, are grounded 
in a conductive net. Additionally, a separately grounded electrical panel 
supplies power to electrical devices around the pool, such as 
transformers, pumps and lights. 
A conventional submersible pool light typically is mounted within a 
conductive niche that is integrally associated with the side of the pool 
and is electrically grounded to the pool grounding net. This niche has a 
dome-shaped housing featuring an opening that is generally aligned with 
the pool wall and an interior cavity that is sized to accept a pool light. 
The interior cavity of the niche extends underground away from the pool 
wall so that the pool light can be mounted flush with the wall of the 
pool. The rear of the niche has a port that provides a sealed opening for 
a power cord to extend from the light to the pool's electrical panel. The 
front of the light does not seal the niche from the pool water: instead, 
pool water is admitted into the niche to cool the light. 
The aforementioned conventional submersible pool light has a housing with 
an electric light bulb sealed therein, a lens located in front of the 
light bulb and a bezel around the lens to mount the light to the niche and 
cover the periphery of the niche for aesthetic purposes. This pool light 
typically has at least one electrically conductive element, such as a 
metal reflector mounted adjacent to the light bulb or a metal housing or 
other metal components. Accordingly, this pool light must be grounded to 
the pool's conductive net by a ground wire. The power cord of this light 
also contains a ground conductor leading to the pool's electrical panel. 
While pool lights of the previously described type are generally 
acceptable, under certain circumstances such lights can have certain 
drawbacks. In particular, the electrically conductive reflector of the 
light can radiate electrical energy into a pool or spa if a fault occurs 
elsewhere in the pool's electrical service. Normally, if the electrical 
service of the pool has been properly installed and maintained the effect 
of such a fault will be minimal. However, sometimes the electrical service 
is not properly installed or maintained. In such cases, a fault on the 
electrical service ground can cause electricity to radiate from the 
conductive reflector, housing or other metal components, into the pool, 
resulting in harm to swimmers. Because of this possibility, submersible 
lights are required to be installed at least 18 inches below the 
waterline, where radiation of electricity would cause less harm to 
swimmer. In particular, because a shock from the light would be 
concentrated in a location away from the waterline, the heart and head of 
a typical swimmer would be less likely to bear the brunt of the electric 
shock. 
There is another requirement that a pool light must satisfy for it to be 
mounted less than 18 inch below the waterline. This requirement mandates 
that the light withstand a predetermined impact so that accidental 
breakage of the light by a swimmer is less likely. Conventional pool 
lights have previously had glass lenses because of the high temperature of 
the light bulb, which must be sized to provide adequate light to the pool. 
Because glass lenses are relatively brittle, they have sometimes been 
unable to satisfy the aforementioned impact requirement. 
The aforementioned requirement for mounting a pool light less than 18 
inches below the waterline is of great concern because many pool and spa 
owners wish to install lights in the shallow end of the pool or in steps 
that are less than 18 inches below the waterline. Considering that pool 
walls often curve at depths of less than 18 inches to blend with the 
bottom surface and that light niches are intended for installation in flat 
wall surfaces, the typical pool therefore has limited locations for pool 
lights because they must be mounted in flat wall surfaces 18 inches below 
the waterline. Accordingly, the areas where conventional pool lights can 
be located are limited, thereby unduly restricting the illumination of the 
pool. 
This 18 inch depth requirement also gives rise to another concern, namely, 
efficient and aesthetic lighting of the pool. Generally speaking, a 
specific amount of light must be reflected from the pool light onto the 
walls and bottom of a pool to provide the illumination necessary for a 
safe and inviting pool. However, when a pool light illuminates a pool, it 
does so with some inefficiency because some of its light escapes directly 
from the pool by crossing the flat water-to-air boundary. Accordingly, if 
some of the light escapes from the pool without illuminating the sides or 
bottom, a higher power light is required to provide such a safe and 
inviting appearance for swimmers. This inefficient illumination results in 
higher electricity bills for the operator of the pool and increases the 
cost of the light, which has a higher power light bulb than would 
otherwise be needed. 
The light that escapes from a lit pool intersects the air-to-water boundary 
at an angle of incidence that is less than a reference angle known as the 
"critical angle." Both the angle of incidence and the critical angle are 
measured from the normal to the flat water-to-air boundary. For a 
water-to-air boundary, an angle of incidence of 48.5 degrees or more will 
cause total reflection of light back into the pool. Accordingly, pool 
lights mounted at the previously mentioned 18 inch depth tend to be 
inherently inefficient because some of their light will intersect the 
waterline at an angle of less than 48.5 degrees, thereby directly escaping 
without ever reflecting off of the pool's bottom or walls. 
Another submersible light has been developed in an effort to address the 
foregoing problems. While this light is generally effective in lighting 
pools, under some circumstances it may be subject to the same drawbacks 
discussed above. In particular, this light utilizes an electrically 
conductive metal reflector and a glass lens. The metal reflector requires 
a ground wire connected to the pool's conductive net, which increases the 
manufacturing cost of the light. Furthermore, under certain circumstances, 
such as an incorrect or damaged installation, there is a risk that the 
metal reflector could radiate electrical energy into the pool and harm 
swimmers. The glass lens of this light also could have difficulty 
satisfying the impact test for the light to be mounted less than 18 inches 
below the waterline. The pool light shown in the U.S. patent to 
Poppenheimer, U.S. Pat. No. 5,349,505, may have some of the 
characteristics described above, although applicants are not aware of any 
specific information regarding this light beyond what is shown in the 
patent. 
Another drawback of conventional submersible pool lights is the difficulty 
of servicing them. Periodically, a pool light must be removed from its 
niche to replace a burnt-out bulb or attend to other service or 
maintenance. Typically, conventional pool lights have a power cord long 
enough to extend from the niche to the sidewalk (commonly referred to in 
the pool industry as the "deck") next to the pool to allow the light to be 
brought above the waterline for servicing once it has been removed from 
the niche. Once brought out of the niche and onto the pool sidewalk, a 
conventional pool light is difficult to disassemble because it has many 
mechanical fasteners holding a bezel or face plate onto its housing. These 
fasteners must be removed with tools, which takes time and effort. These 
mechanical fasteners are required at least in part to provide a large 
force to hold a conventional axial seal between the faceplate and the 
housing. 
Finally, when the light is reassembled, it must be re-inserted into the 
niche. Such re-insertion is difficult because the long power cord must be 
located in the niche, which must accommodate the light as well. Although 
the power cord can be wrapped around the housing of the light (which is 
usually tapered), the light typically has nothing to hold the coiled cord. 
Accordingly, the cord can slide off the housing of the light and create an 
obstruction that blocks the insertion of the light into the niche. Such 
interference only makes the servicing of the many-fastener light more 
awkward, difficult and frustrating. 
It should, therefore, be appreciated that there is a need for a submersible 
light that has the following features: no conductive elements requiring 
grounding, a tough lens to withstand impacts from swimmers, and quick and 
easy serviceability. The present invention fulfills all of these needs. 
SUMMARY OF THE INVENTION 
The present invention provides a submersible light assembly that has the 
following features: no conductive elements requiring grounding, and a 
tough lens to withstand impacts from swimmers and quick and easy 
serviceability. Because of these features, the light of the invention 
meets safety requirements for the light to be mounted less than 18 inches 
below the waterline, thereby allowing its placement in areas of pools that 
have been heretofore off limits. In addition, a cord holder and a 
twist-lock base provide for quick and easy disassembly and re-installation 
of the light. 
The submersible light assembly includes an electrically nonconductive and 
hollow housing having a peripheral wall. A lens mount extends across an 
open front end of the peripheral wall and is connected thereto. A plastic 
lens is mounted in the lens mount. An end cap is releasably mounted in the 
peripheral wall at the rear end of the housing. A light source is located 
within the housing and has a socket and an electric light mounted in the 
socket. The electric light has an electrically nonconductive reflector 
positioned to direct light through the lens. A two wire electric cord is 
connected to the socket to deliver electric power thereto. The electric 
cord passes through the end wall of a niche and through the end cap of the 
housing. The housing, lens, lens mount, and end cap are all made of 
electrically nonconductive material. 
In a more detailed aspect of the invention, a transformer remotely located 
from the housing powers the electric light. The transformer has an 
isolated voltage input and voltage output. The voltage output of the 
transformer is coupled to the light socket to define a light circuit. The 
only conductive material of the light is that of the light circuit and the 
light. Therefore, no ground wire is needed on the submersible light so the 
light poses no danger of radiating electricity out into the pool. In other 
more detailed aspects of the invention, the light is of the type having a 
glass prismatic reflector, the lens of the light is made from clear 
polymeric material and the housing of the light is made from a glass 
filled polymeric material. 
A major advantage of the submersible light is that it contains no 
conductive material capable of radiating potentially dangerous electricity 
out into the pool. Therefore, the submersible light is safer than 
conventional pool lights and can be mounted less than 18 inches below the 
waterline in a myriad of locations within swimming pools or spas. 
In other aspects of the invention, a submersible light is provided that has 
a housing having a forward end, a rearward end, an external surface 
therebetween and a power cord. A front flange is located adjacent to the 
forward end of the housing and extends radially outwardly from the 
external surface of the housing. A rear flange is located adjacent to the 
rearward end of the housing and extends radially outwardly from the 
external surface of the housing. When the light is installed into the 
niche, the power cord can be advantageously wrapped around the housing and 
held between the front and rear flanges to secure the power cord for easy 
installation of the light. In other more detailed aspects of the 
invention, a cord catch is provided to more securely fasten the cord to 
the housing. In yet another detailed aspect, the cord extends from the 
housing at an angle to advantageously facilitate wrapping of the cord 
about the housing. 
In yet other aspects of the invention, a submersible light is provided that 
includes a housing having a forward end, a rearward end, and internal 
surface therebetween defining a chamber sized to enclose a light, an 
opening in the forward end of the housing and an opening in the rearward 
end of the housing. A lens is mounted across the forward opening of the 
housing to seal the chamber in the housing. A base is mounted across the 
rearward opening of the housing. The base has a twist lock configured to 
engage the housing to secure the base to the housing and hold a seal in a 
predetermined position radially between the base and the housing to 
prevent fluid from entering the chamber of the housing. Detentes and 
matching projections can be formed in the twist lock mechanism to lock the 
base to the housing so that the radial seal is located in a predetermined 
position between the housing and the base. 
One advantage associated with the twist lock feature described above is 
that it provides for the quick and easy disassembly of the submersible 
light. Such quick and easy action of the twist lock works in concert with 
the radial seal, which seals with less force than a conventional axial 
compression seal, thereby alleviating the need for the plurality of 
fasteners of conventional pool lights.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As shown in the exemplary drawings, the present invention is embodied in a 
submersible light, generally referred to by the reference numeral 10, for 
use within a niche 12 preferably mounted in the wall 14 of a swimming pool 
16. The light 10 has a tubular housing 18 enclosing a light bulb 20, a 
base 22 mounted to the rear of the housing 18, and a lens 24 mounted on 
the front of the housing 18. A decorative bezel 26 also is mounted to the 
front of the housing to removably hold a colored filter 28 over the lens 
24 of the light 10 for aesthetic purposes (FIGS. 1 and 2). The bezel 26 
defines a hole 30 sized to accept a mounting screw 32 that engages the 
niche 12 to hold the light 10 therein. A two-conductor power cord 34 
extends from the base 22 at the rear of the light 10, through the niche 12 
and to an isolation transformer 36 located in a junction box 38. The 
isolation transformer 36 has a primary winding 40 and a secondary winding 
42 that is isolated from the primary winding (FIG. 1A). The transformer 36 
steps down 110 volts A.C. to a low voltage (i.e., less than 15 volts A.C.) 
to power the light bulb 20. 
The niche 12, also commonly known as a wet-niche or a fixture housing, has 
standard characteristics that are well known in the pool products 
industry. Among these characteristics is a main opening 44 having an upper 
flange 46 defining a hole 48 sized to accept the bezel screw 32 to fasten 
the light to the niche 12. The niche 12 also has a lower flange 50 sized 
to clip into the bottom of the light's housing 18 to retain it in the 
niche 12. A common sealed port (not shown) located in the rear of the 
niche 12 accommodates the power cord 34 of the light 10. Niches of the 
type described above are available from the American Products, Inc. of 
Moorpark, Calif. Now the individual components of the preferred 
submersible light 10 will be discussed. 
The housing 18 of the submersible light 10 preferably has a generally 
cylindrical exterior surface 52 and a generally cylindrical interior 
surface 54 that defines a rear opening 56 and a front opening 58 (FIGS. 2, 
3 and 8). The interior surface 54 has a diameter sized to enclose a 
portion of the base 22 and the light bulb 20, as described below. The 
interior surface 54 of the housing 18 also features two opposed 
projections 60, one of which is longer (as measured along the 
circumference of the housing's interior surface 54) than the other. Each 
projection 60 has a forward facing notch 62. A flange 64 extends radially 
outwardly from the front opening 58 of the housing 18. Reinforcing fins 66 
extend between the front flange 64 and the exterior surface 52 of the 
light 10. The fins 66 are generally evenly distributed around the exterior 
surface 52 of the housing 18. A hole 68 is located on the top of the 
flange 64 to allow the bezel mounting screw 32 to pass therethrough to 
engage the niche 12. The lower portion of the front housing flange 64 has 
an angled retainer clip 70 sized to engage the lower flange 50 of the 
niche. A groove 72 is located concentrically around the front opening 58 
of the housing 18 to hold sealant therein to seal the lens 24 to the 
housing 18. Four holes 74 are evenly distributed around the front opening 
58 of the housing 18. Inside each of these openings 74 a tab 76 is mounted 
to engage barbed clips 78 projecting from the lens 24. Another set of 
holes 80 is located on the housing flange 64 to engage barbed clips 82 on 
the bezel 26. A retainer clip 83 on the bezel 26 snaps over the housing 
flange 64 to clip the bezel 26 to the housing 18. The holes 80 allow water 
to pass therethrough for cooling of the light 10. The rear opening 56 of 
the housing 18 mates with the base 22 of the light 10, which is 
hereinafter described. 
The base, otherwise known as an endcap, 22 of the preferred submersible 
light 10 has rear flange 84 and an exterior surface 86 defining a circular 
circumferential slot 88 and a two opposed, forwardly curving slots 90 for 
engagement with the housing 56 of the light 10 (FIGS. 2 and 3). The 
circular slot 88 is sized to accept an elastomeric O-ring 92 that provides 
a radial seal between the base 2 and the interior surface 54 of the 
housing 22. Each of the opposed curving slots 90 extends 180 degrees 
around the base 18 to a stop surface 93. Each curving slot 90 has an 
opening 94 keyed to the length of an associated one of the projections 60 
on the inside 54 of the housing 18 (FIG. 8). Such a keyed 
arrangement-ensures that the base 22 is inserted into the housing 18 in a 
correct orientation wherein a thermostat 104 mounted in the base 22 comes 
to rest in a position above the light bulb 20 and immediately adjacent to 
the housing's interior surface 54. The curved slots 90 include small 
projections 98 that are sized to engage the detentes 62 formed on the 
projections 60 within the housing (FIG. 5). These small projections 98 are 
located to engage the detentes 62 on the projection 60 when the base 22 
and housing 18 are in a position ensuring that the O-ring 92 is fully 
engaged radially between the interior surface 54 of the housing 18 and the 
circular slot 88 of the base 22. The power cord 34 projects from a water 
tight seal 100 in the base 22 at an angle to position the cord 34 in an 
orientation that facilitates the winding of the cord 34 around the 
external surface 52 of the housing 18 (FIG. 6 and 7). The base 22 also 
contains a socket 102 sized to accept the bulb 20. To avoid overheating of 
the light 10, the thermostat 104 turns the light bulb 20 off if the 
temperature inside the housing 18 exceeds 100 degrees centigrade. 
Together, the curved 180 degree slots 90 engage the projections 60 on the 
interior surface 54 of the housing 18 to allow the base 22 to easily twist 
on to the housing 18. One advantage associated with this twist lock 
feature described above is that it provides for the quick and easy 
disassembly of the preferred submersible light 10. Such quick and easy 
action of the twist lock works in concert with the radial seal 92, which 
seals with less force than a conventional axial compression seal, thereby 
alleviating the need for the plurality of fasteners of conventional pool 
lights. 
The notched cord catch 96 on the flange 84 of the base 22 enables the power 
cord 34 to be wrapped and held around the exterior surface 52 of the 
housing 18 between the flange 84 of the base 22 and the front flange 64 of 
the housing 18 (FIGS. 6 and 7). The power cord 34 is long to enable the 
light 10 to be removed from the niche 12 and brought above the waterline 
106 for service. The cooperating flanges 84 and 64 and the cord catch 96 
advantageously allow any excess power cord 34 to be neatly wrapped about 
the housing 18 during installation of the light 10 into the niche 12. 
Accordingly, the power cord 34 of the preferred light 10 does not 
interfere with the installation of the light 10 into the niche 12 after 
the light 10 has been removed for servicing. The materials used in the 
construction of the preferred light 10 will now be described. 
The housing 18 and the base 22 are both made of a non-electrically 
conductive, tough, heat resistant material. This material should be 
thermally conductive to allow the pool water to cool the light. Along 
these lines, a glass filled polymeric material is presently preferred. One 
material from which the housing can be made is VALOX brand polymeric 
material sold by the General Electric Corporation of Pittsfield, Mass., 
which is a 20% glass filled polyester material. The glass filling enables 
the base 22 and the housing 18 to dissipate heat from the light bulb 20 by 
conducting it to the pool water surrounding the light 10. Without such 
thermal conductivity, a conventional polymeric housing and base would 
probably melt from the heat given off by the light bulb 20. Accordingly, 
the preferred light 10 advantageously has a nonconductive housing 18 and 
base 22 that are heat resistant, thereby allowing for the use of a more 
powerful light bulb 20, which increases the amount of light diffused into 
the pool. 
The light bulb 20 is preferably a 12 volt A.C., 75 watt, type MR-16 bulb 
with a built-in glass prism reflector 108, although other low voltage 
light bulbs may be suitable. The prism reflector 108 diffuses light in a 
twenty degree frustoconical space 110 in front of the light bulb (FIG. 3). 
The lens 24 is sized and spaced from the light bulb 20 so that the 
boundary of this frustoconical space is generally aligned with the 
periphery 112 of the lens 24. This arrangement provides efficient 
diffusion of light into the pool. The lens has an inside surface 114 
defining dimples 116 preferably having a 0.04 inch radius. The components 
of the preferred light 10 can be made by the use of commonly known plastic 
molding techniques. 
The lens 24 is made from a tough, non-electrically conductive, transparent 
material such as grade 3103 MAKROLON brand polycarbonate material sold by 
Bayer Aktiengesellschaft of Leverkusen, Germany or other clear materials 
that are tough and heat resistant. This polycarbonate material is 
nonconductive and is tough enough to withstand the impact test required 
for lights that are mounted less than eighteen inches below the waterline 
of the pool. The lens 24 also is heat resistant and will not melt from the 
heat given off by the light bulb 20, which, as described above, is spaced 
from the lens 20 to allow maximum diffusion of light into the pool. The 
barbed clips 78 of the lens 24 extend rearwardly to engage the front 
flange 64 of the housing 18 (FIG. 2 and 3). These clips 78 are sized to 
pass through the holes 74 in the front flange 64 of the housing and engage 
the small tabs 76 mounted therein to hold the lens 24 to the housing 18. A 
tongue 118 is located concentrically about the periphery of the lens 24 
and is sized to mate with the groove 72 on the housing 18. Commonly 
available polyurethane sealant is placed between the tongue 118 of the 
lens 24 and the housing's groove to permanently mount the lens 24 to the 
housing 18. 
An important advantage associated with the preferred submersible light 10 
is that it contains no conductive material capable of radiating 
potentially dangerous electricity out into the pool. Therefore, the 
submersible light is safer than conventional pool lights and can be 
mounted less than 18 inches below the waterline in a myriad of locations 
within swimming pools or spas. 
It should be appreciated from the foregoing description that the preferred 
submersible light 10 has the following features: no conductive elements 
requiring grounding and a tough lens 24 to withstand impacts from swimmers 
and quick and easy serviceability. Because of these features, the 
preferred light 10 meets safety requirements allowing the light to be 
mounted less that 18 inches below the waterline, thereby allowing its 
placement in areas of pools that have been heretofore off limits. Further, 
because no electrically conductive elements in the light 10 require 
grounding, no ground wires are needed and, thus, the light can be powered 
by a two conductor power cord 34, thereby reducing the cost of the light. 
The cord catch 96 and twist lock base 22 and housing 18 engagement provide 
for quick and easy disassembly and re-installation of the light 10. 
While a particular form of the invention has been illustrated and 
described, it will be apparent that various modifications can be made 
without departing from the spirit and scope of the invention. Accordingly, 
it is not intended that the invention be limited, except as by the 
appended claims and equivalents thereof.