APPAREIL D'ECLAIRAGE INVIOLABLE A SOURCE LUMINEUSE RADIOACTIVE

TAMPER-RESISTANT FIXTURE FOR SELF-LUMINOUS RADIOACTIVE LIGHT

Abrégé anglais

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TAMPER-RESISTANT FIXTURE FOR
SELF-LUMINOUS RADIOACTIVE LIGHT
ABSTRACT OF THE DISCLOSURE
A tamper-resistant fixture encloses a self-
luminous radioactive light in order to prevent removal of
the light. The fixture is secured to a mounting surface
using tamper-resistant screws and anchors and allows the
light to illuminate the immediate surroundings to mark an
exit route without the necessity of power.
SPECS/SAF1248.01

Revendications

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THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A tamper-resistant fixture for a self-luminous
radioactive light operable to be affixed to a
surface, said fixture comprising a rearwardly located
panel, means for attaching said self-luminous
radioactive light to said rearwardly located panel, a
plurality of side panels attached to said rearwardly
located panel about its perimeter, a forwardly
located panel attached to said side panels operable
to enclose said self-luminous radioactive light, and
tamper-resistant means to attach said front panel to
said surface.
2. A fixture as in claim 1 wherein said front panel is
transparent.
3. A fixture as in claim 2 wherein said front panel is
impact-resistant.
4. A fixture as in claim 3 wherein said front panel is
non-breakable.
5. A fixture as in claim 2 wherein said rear panel is
transparent.
6. A fixture as in claim 2 wherein the inside surfaces
of said side panels are reflective.
7. A fixture as in claim 2 wherein said tamper-
resistant means are tamper-resistant screws and
anchors.

Description

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TAMPER-RESISTANT FIXTURE FOR
SELF-LUMINOUS RADIOACTIVE LIGHT
INTRODUCTION
This invention relates to a lighting fixture
and, more particularly, to a lighting fixture which
restricts access to a self-luminous radioactive light
which is contained within the fixture which light is used
to mark an exit route for evacuation purposes under
emergency egress or blackout conditions.
BACKGROUND OF THE INVENTION
The use of self-luminous radioactive lights for
emergency purposes when external power is not available is
known. One company, for example, Safety Light Corporation
t of Bloomsburg, Pennsylvania, manufactures exit and other
emergency signs using such radioactive lights.
A self-luminous radioactive light is similar in
some respects to conventional low pressure gas discharge
fluorescent lights. A low pressure gas discharge light is
created by coating the inside surface of a long glass tube
with phosphors and injecting inert argon gas and a drop of
mercury. An electrode is placed at each end and the tube
is sealed. In operation, a current is applied to the
electrodes so that the temperature of the electrode
increases and so emits ions. A potential is applied
between the two electrodes and the resulting electric
field causes the emitted ions to drift through the tube.
The ions strike and excite atoms of argon gas which in
turn excite atoms of mercury. When the excited mercury
atoms fall back to their unexcited valence state, photons
are emitted which strike the inside surface of the tube

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and excite phosphors. The phosphors radiate light out of
the glass tube.
In comparison, a self-luminous radioactive light
is produced by coating the inside surface of a glass tube
with phosphors and injecting a radioactive gas into the
tube before the tube is sealed. As the radioactive gas
decays, particles are emitted which strike and excite the
phosphors on the inside of the glass tube. In turn, the
phosphors radiate light out of the glass tube.
A preferred radioactive gas is tritium (a
hydrogen isotope with two neutrons) which emits low energy
beta radiation. Tritium decays to form helium.
Self-luminous radioactive lights have been found
to be particularly useful in emergency lighting
applications where external power may be unavailable.
Because they function independently of electricity and
have lives typically as long as ten (10) to twenty (20)
years, said lights are an inexpensive and dependable
source of light in emergency situations. However, self-
luminous radioactive lights produce relatively small
amounts of light and they are typically used as
illumination for warning and directional signs.
An emerging use is to place such lights at low
heights along corridors to mark a pathway much in the way
that reflectors are used to mark highway lanes at night.
However, such installations can attract unwanted interest
and vandalism. Because the light is part of an emergency
system which must be continuously available and because it
is manufactured with radioactive material, it is important
to prevent the removal of such lights as far as possible.

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SUMMARY OF THE INVENTION
According to the invent:ion, there is provided a
tamper-resistant fixture for a self-luminous radioactive
light operable to be affixed to a surface, said fixture
comprising a rearwardly located panel, means for attaching
said self-luminous radioactive light to said rearwardly
located panel, a plurality of side panels attached to said
rearwardly located panel about its perimeter, a forwardly
located panel attached to said side panels operable to
enclose said self-luminous radioactive light, and tamper-
resistant means to attach said front panel to said
surface.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
An embodiment of the invention will now be
described, by way of example only, with the use of
drawings in which:
Figure 1 is a diagrammatic front view of the
fixture according to the invention in its flush-mount
configuration;
Figure 2 is a diagrammatic sectional view of the
apparatus of Figure 1 taken along II-II of Figure l;
Figure 3 is a diagrammatic front view of the
fixture according to the invention in its surface-mount
configuration; and
Figure 4 is a diagrammatic sectional view of the
apparatus of Figure 3 taken along IV-IV of Figure 3.

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DESCRIPTION OF SPECIFIC EMBODIMENT
Referring now to the drawings, a tamper-
resistant fixture for a self-lum:inous radioactive light
according to the invention is generally illustrated at 10
in Figures 1 and 2. This flush-mount fixture 10 comprises
a rear panel 11, a plurality of side panels 12 and a
forwardly located front panel 13. A strip of transparent,
high contact double face tape 17 is affixed to the inside
surface of rear panel 11. Screws 14 extend through holes
in a self-luminous radioactive light 20 and through rear
panel 11. Tamper-resistant screws 15 extend through front
panel 13. It is envisioned that the tamper-resistant
aspect of screws 15 will include heads requiring non-
standard screwdrivers. Anchors 16 are provided forsecuring the tamper-resistant screws 15.
A self-luminous radioactive light is illustrated
at 20. The light 20 is mounted within the fixture 10
which is then mounted to a first surface 21. A
longitudinal hole 22 is provided such that fixture 10 may
be mounted flush with surface 21.
Referring to Figures 3 and 4, the surface-mount
configuration of the invention is generally illustrated at
30. The surface-mount fixture 30 includes the flush-
mount fixture 10 and a surface-mount adaptor 31 which
includes a hole 32 therein. The surface-mount fixture 30
includes second anchors 33 in place of first anchors 16 as
used with the flush-mount embodiment earlier described.
The fixture 30 is mounted to a second surface
23.

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OPERATION
With reference to Figures 1 and 2, the self-
luminous radioactive light 20 is initially positioned in
the flush-mount fixture 10. The self-luminous
radioactive light 20 is attached to the rear panel 11
using high contact double face clear tape strip 17 and
mounting screws 14. Rear panel 11 is made of transparent
plexiglass in order that the radioactive warning label and
serial number on the back of radioactive light 20 may be
seen. Side panels 12 are arranged around and attached to
the perimeter of rear panel 11 such that a closed fixture
in the form of a box is made. The side panels 12 and the
rear panel 11 are chemically bonded together, conveniently
by a solvent weld. Side panels 12 are made opaque and
reflective to better direct and reflect light outward.
The front panel 13 is solvent welded to the side
panels 12 so as to enclose the self-luminous radioactive
light 20. Front panel 20 is made of a transparent high
impact, high density polycarbonate material, an example of
which is known as LEXAN (Trademark) to allow the light
from the self-luminous radioactive light 20 to cast
forward. It has been found that a 3/16 inch thickness for
25 front panel 20 is of satisfactory strength.
Flush-mount fixture 10 is attached to first
surface 21 by inserting the fixture 10 into hole 22, rear
panel 11 first, until front panel 13 abuts the top of
30 surface 21. Tamper-resistant screws 15 and first anchors
16 are used to secure the front panel 13 to the first
surface 21 in a flush mounted or recessed manner.
With reference now to Figures 3 and 4, the
surface-mount fixture 30 is attached to a second flat and
continuous surface 23 by inserting the fixture 10, rear

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panel 11 first, into longitlldinal hole 32 in surface-mount
adaptor 31 which is, in turn placed flush against the
second surface 23. Tamper-resistant screws 15 and second
anchors 33 are then used to secure fixture 10 to the
surface-mount adaptor 31 in a flush mounted or recessed
manner and the surface-mount adaptor 31 to the second
surface 23 in a surface mounted manner.
While a specific embodiment of the tamper-
resistant fixture according to the invention has been
described, many modifications will readily occur to those
skilled in the art to which the invention relates and,
accordingly, the description should be considered as
illustrative of the invention only and not as limiting its
scope as defined in accordance with the accompanying
claims.

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