Luminaire containment means for lamp rupturing

Containment means for a luminaire that captures hot particles created by the unlikely event of a pressurized lamp rupture is disclosed. In one embodiment, the containment means comprises a mesh interposed between the lamp and a refractor of the luminaire typically formed of an acrylic material. The mesh captures hot particles having a sufficient heat capacity and temperature to create excess heat damage to the refractor.

BACKGROUND OF TUE INVENTION 
This invention relates to a luminaire having means for containing hot 
particles of lamp components produced by the unlikely event of the lamp 
rupture. More particularly, this invention relates to a mesh interposed 
between a pressurized lamp and a refractor lens or globe of a flammable 
material of the luminaire for intercepting and capturing the hot particles 
that may be dislodged from the pressurized lamp under the unlikely rupture 
condition and which particles are of a sufficient temperature and heat 
capacity to cause excessive heat damage to the luminaire. 
As disclosed in U.S. patent application Ser. No. 047,813 filed May 8, 1987 
now abandoned of C. A. Willis assigned to the same assignee as the present 
invention, lamps under a pressurized condition, such as metal halide and 
tungsten-halogen lamps may experience a rupture condition. These 
pressurized lamps, and in particular, metal halide discharge lamps may 
experience the rupture condition which causes hot flying fragments to be 
dislodged from the lamp. Lamp failures which occur in such a manner are 
infrequent and although incidences of such failures are extremely minor, 
there is no practical way known at this time to completely eliminate the 
possibility of such failures. 
One way of minimizing such failures in continuously operating systems is to 
turn the lamps, in particular the metal halide lamps, off once a week for 
about 15 minutes. If this procedure is followed, those lamps approaching 
the end of their life will either probably fail to restart before reaching 
a point where a chance for a non-passive rupture failure begins to 
increase or the failure will occur due to the arc related to the metal 
halide lamp being unable to withstand the thermal stresses during warm-up 
and the arc will fail at a low, relatively non-destructive pressure. 
Replacing lamps at or before the end of their rated life will also 
decrease the possibility of non-passive rupture failures. Another way to 
minimize the possible hazards associated in the unlikely event of an arc 
tube rupturing, is to operate the lamp in a fixture designed to contain 
such a failure, such as a fixture comprising a refractor or lens made of a 
tempered safety glass. 
Glass enclosures such as tempered safety glass lenses while serving as 
means for containing a ruptured arc tube do not have the benefits of 
plastic materials. For example, plastic materials due to their weight and 
non-fracture characteristics avoid the hazards of having heavy chunks of 
borosilicate glass comprising a lens falling from luminaires that may be 
located in factories. Further, the light weight plastics, such as acrylic, 
may be more accurately molded to provide superior optical features 
relative to those yielded by glass. In the unlikely event of a 
catastrophic failure caused by the bursting of the arc tube of the metal 
halide lamp, it is possible for hot shards of a quartz arc tube to impinge 
or otherwise fall directly onto the acrylic or other flammable plastic 
lens or refractor which may result in burning hot plastic from the lens or 
refractor dripping down onto the environment located under the related 
luminaire. It is desired that means be provided within the luminaire to 
substantially reduce or even eliminate the related heat damage to the 
luminaire by capturing and containing any hot particles that have the 
potential to ignite the flammable lens or refractor of the luminaire. 
Accordingly, it is an object of the present invention to provide 
containment means for a luminaire which largely eliminates the risk of 
igniting the flammable plastic lens or refractors and its related 
secondary fire risks. 
SUMMARY OF THE INVENTION 
The present invention is directed to containment means for a luminaire that 
intercepts and captures hot particles projected from a pressurized lamp in 
the unlikely event of a lamp rupturing condition and which particles are 
of a sufficient temperature and heat capacity to cause excessive heat 
damage to the luminaire. 
In various embodiments, the luminaire comprises an upper housing, a 
pressurized lamp accommodated by the upper housing, a plastic or metal 
enclosure having refractor or lens attachment means, a refractor or lens 
connected to the attachment means, and a mesh assembly interposed between 
the pressurized lamp and the refractor or lens.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates a luminaire 10 related to one embodiment of the present 
invention. The luminaire 10 comprises an upper housing 12, a pressurized 
lamp such as a metal halide lamp 14 (shown in phantom) having an arc tube 
commonly formed of a quartz material and disposed therein and which is 
accommodated by the upper housing. The luminaire 10 has an enclosure 16 
formed of a reflective material which for the embodiment of FIG. 1 is 
commonly termed a reflector. Further, the enclosure 16 of FIG. 1 may have 
attachment means 18 comprising clamps 20 for attaching to a refractor or 
lens 22 for closing the bottom or exit area from which the light generated 
by the luminaire is transmitted. The refractor or lens 22 serves as a 
window or exit area for the transmitted light. For other embodiments, the 
bottom portion may be opened and devoid of a window member so that the 
light does not encounter any transmitting medium other than air while 
being transmitted from the exit or window area. For the embodiment shown 
in FIG. 1, a refractor 22 closes the bottom portion of the luminaire 10 
and is connected to attachment means 18. The luminaire 10 further 
comprises containment means 24 which is of particular importance to the 
present invention and is shown in FIG. 2. 
The containment means 24 is placed on and connected to the outer rim of the 
window 22 and is therefore interposed between the refractor 22 and the 
metal halide lamp 14. Alternatively, for embodiments in which the 
luminaires do not have their bottom portion closed by a window member so 
as to provide an opened window area, the containment means may be placed 
on and connected to the enclosure 16 so as to be interposed between the 
open portion of the enclosure and the pressurized lamp 14. 
In the various embodiments of the present invention, the containment means 
may be sealed to its supporting member and may be trimmed so as to conform 
to the shape of its supporting member. The containment means is preferably 
formed of a stainless steel material but may be of a material selected 
from the group consisting of steel, aluminum, brass, copper, and other 
high melting point metals or alloys. Further, a glass cloth, or other 
noncombustible insulated material may be selected for the containment 
means 24. Various other high melting point materials may be used so long 
as the mechanical integrity of the mesh is not damaged when subjected to 
particles of a ruptured lamp in a manner to be described. Further, in that 
in various embodiments the containment means 24 is interposed between the 
lamp 14 and window member 22, it is desired that optical characteristics 
of the selected material be taken into account with regard to reducing the 
effect of the containment means on the light output of the luminaire 10. 
The containment means 24 of the present invention in addition to the 
embodiment of FIG. 1 may find application in a wide range of 
non-industrial luminaires such as a globe type enclosure 30 shown in FIG. 
3 or a wall and ceiling mounting type 40 shown in FIG. 4. The shape of the 
luminaires 30 and 40 is not critical and each such luminaire has an 
enclosure or window member having a function similar to the reflector 16 
or refractor 22, respectively, discussed with regard to FIG. 1. The 
luminaire 30 has a window member in the shape of a globe 32 completely or 
partially encompassing the pressurized lamp 14 and controlling the light 
emitted therefrom. Similarly, luminaire 40 has a window member 42 having a 
rectangular form completely or partially encompassing the pressurized lamp 
14 and controlling the light emitted therefrom. In the luminaires 30 and 
40, the containment means 24 is interposed between the pressurized lamp 
14, accommodated by the upper housing of each luminaire, and globe 32 and 
the rectangular device 42 respectively. 
The window member be it a refractor, lens or globe related to the present 
invention is of a flammable or fusible plastic material selected from the 
group of transparent or translucent optical plastics consisting of 
polyolefins such as polymethylmethacrylate, polystyrene, polyethylene, and 
fluorocarbons, and other plastics such as cellulosics, polycarbonates, and 
polyesters. These optical devices may also be formed of thin films of 
organic material which may not ignite when subjected to particles of hot 
quartz, in a manner to be described, but may melt and allow hot quartz to 
drop below the confines of the related luminaire. 
As discussed in the "Background" section, the lamp 14 such as a metal 
halide lamp or possibly a tungstenhalogen type, may unlikely encounter a 
rupture or non-passive explosive condition. Under such unlikely 
conditions, the non-passive lamp may dislodge or project hot pieces of the 
quartz arc tube of the lamp 14 that, without the benefits of the present 
invention, may otherwise reach the lenses, refractors or globes of the 
embodiments of FIGS. 1, 2 and 3, and which being formed of a flammable or 
fusible plastic material such as acrylic may be ignited or damaged in an 
excess manner as discussed in the "Background" section. 
In my pursuit to find a solution to prevent the ignition or fusible damage 
to the luminaire, it was determined that while the rupturing of the arc 
tube may cause the projection of hot quartz particles of all size from 
that of microscopic dimensions to those of relatively large dimensions, 
only particles of certain dimensions and characteristics are the main 
contributors to the damage desired to be prevented. It was determined that 
such contributing particles are in excess of a particular size so as to 
have sufficient heat capacity and be of a sufficient temperature to start 
or ignite a fire of the flammable material on which these particles land. 
It was determined quartz particles of between about 1/4 inch square to 
about 1/2 inch square or greater projected from a typical arc tube having 
an operating temperature in excess of about 1100.degree. C., are of 
sufficient heat capacity and temperature to cause excessive heat or fire 
damage to the luminaire. Projected quartz particles of less than 1/4 inch 
square upon arriving at the lenses, refractor or globes, do not impart 
enough energy to start or ignite a fire of concern. 
Upon such determination, it was realized that if a containment means, in 
the form of a mesh having openings small enough to prevent passage of hot 
quartz particles having a heat capacity which is great enough to ignite 
the flammable device and yet such opening being large enough to yield 
adequate optical transmission, was interposed between the metal halide 
lamp 14 and the flammable device such as the refractor 22 of FIG. 1, the 
globe 32 of FIG. 2 or the window 42 of FIG. 3, then such a mesh would 
prevent the hot quartz particles having the discussed sufficient heat 
capacity and temperature from reaching the flammable device and thereby 
prevent the flammable device from encountering any burning conditions that 
may otherwise create fire damage. It was further realized that mesh 
openings of less, than 5/32 of an inch and preferably 1/4 of an inch or 
less measured in a diagonal manner, serve the desired purpose of the 
containment means. 
It should now be appreciated that the practice of the present invention 
provides containment means for a luminaire that intercepts and captures 
any hot particles large enough to cause a fire in an acrylic enclosure 
under the unlikely event of a pressurized lamp rupturing condition.