FLUORESCENT LAMP WITH PROTECTIVE ASSEMBLY

LAMPE FLUORESCENTE A ENSEMBLE PROTECTEUR

English Abstract

A fluorescent lamp comprises a protective cover
assembly comprising a protective tube preformed of a semi-rigid
non-frangible transparent polymeric material and
received over the glass tube with a clearance between the
outer surface of the glass tube and the inner surface of the
protective tube and extending lengthwise substantially
coextensively with the glass tube and a collar preformed of
a heat-shrinkable polymeric material received in overlapping
relation over a portion of the protective sleeve at each end
thereof and over the flange portion of the adjacent cap, the
collar being heat-shrunk into sealed relation with the
protective tube and the cap flange portion.

French Abstract

Cette invention concerne une lampe fluorescente munie d'un manchon de protection préformé à partir d'un polymère transparent, non cassant et semi-rigide et enfilé sur le tube de verre avec un jeu sensiblement égal sur toute la longueur de la lampe et d'une collerette préformée en polymère thermo-rétrécissable chevauchant une partie du manchon de protection, collerette étant scellé audit manchon et à la jupe de culot à broches de la lampe par rétrécissement thermique.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a fluorescent lamp of the type having an elongated
glass tube and metal caps at each end, the glass tube having
an outer surface and each cap having a peripheral flange
portion, the improvement of a protective cover assembly
comprising a protective tube preformed of a semi-rigid non-frangible
transparent polymeric material that is highly
stabilized against ultra-violet radiation, the protective
tube having an inner surface and being received over the
glass tube with a clearance between the outer surface of the
glass tube and the inner surface of the protective tube and
extending lengthwise substantially coextensively with the
glass tube, a collar preformed of a heat-shrinkable
polymeric material received in overlapping relation over a
portion of the protective tube at each end thereof and over
the flange portion of the adjacent metal cap of the lamp,
the collar being heat-shrunk into sealed relation with the
protective tube and the cap flange portion, a layer of an
adhesive interposed between each collar and the
corresponding end of the protective tube and a layer of an
adhesive interposed between the collar and the corresponding
cap flange portion.

Description

~ ~c~
FLUORESCENT LAMP WITH PROTECTIVE ASSEMBLY
SPECIFICATION
. .
BACKGRoUND OF THE INVENTION
When a fluorescent lamp breaks, fragments of the
glass tube and powders from the phosphor coating inside the
tube are scattered. In many situations in which fluore cent
lighting is used, the food processing industry being a
parti~ularly prevalent example, tha glass fragments and
phosphor powders present an environmental hazard. ~o
prevent glass fragments and powdars from scattering, it is
well-kno~n to pro~ide a protective plastic coating directly
onto the external surface of the glass tube. While such a
coating inhibits sca~tering of materials from a broken lamp,
the pr28ently availabl2 I'sa~ety" type fluorescent lamp~
becom~ di~colored, especially near ~he ends where the light
o~u~ ~rom th~ lamp is highly ultraviol~t, within a few
day~ of bRing placed in service. The discoloration r~nc~
thQ light ou~uL of the lamp and i~ aesth2tically
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displeasing. Also, ~he coating over the glass env~l~ps doas
not always retain the metal cap~ intac~ with th~ ~r~gmen~ed
glass tube, and glass fragmen~s and powder can be rele~sed
if a cap separates.
SUMMARY OF THE INVENTION
An object of the present inven~ion is to provide a
fluorescent lamp having very effective protection against
scattering of glass fragments from the tuhe and powders ~rom
the coatinq in the event that the lamp breaks. A further
object is to provide such protection in a way that does not
reduce the light output during the useful life of the lamp
due to discoloration or clouding of the protective element.
Still another object is to provide a "safety" fluorescent
lamp that i5 easy and inexpensive to produce. The foregoing
and other objects are attained, according to the present
invention, by a protective cover assembly comprising a semi-
ri~id non-frangible pro~ective ~ube prefo~med of a
transparsnt polymeric material and received over the glas~
tube o~ the lamp with a clearance between the out~r surface
of the glass tube and the inner surface of the protective
tube and extending lengthwise substantially coextensively
with the glass tube and a collar preformed o~ a heat-
shrinkable polymeric material received in overlapping
relation over a portion of th~ protective sleeve at each end
thereo~ and over th~ flange portion o~ the adjacent cap, the
collar being heat-shrunk into s~aled relatlon with the
protectlve tube and the cap ~lange portion. In a praferred
o~ltmen~ of th~ invention a layer of an adhesive is
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interpo~ed between each collar and the corresponding end o~
~ the protective tube and the corresponding cap ~lange
portion.
For a ~etter underst~n~ing of the invention
reference may be made to the following description of an
exemplary embodiment, taken in conjunction with the
accompanying drawing.
DESCRIPTION OF THE DRAWI~G
The drawing is a partial side cross-sectional view
of an embodiment of a protective assem~ly as installed on a
conventional fluorescent ~amp.
DESCRIPTION OF THE EM80DIMFNT
Reference numeral 10 designates a conventional,
co~mercially available ~luorescent lamp o~ the type havin~
an elonga~ed glass tube ~2 that necks down slightly at each
and is closed at each end by a cup-like end cap 14 having a
peripheral flange portion 16~ The protsctive asse~bly
consi~t~ of a protective tube 18 preformed from a semi-rigid
non-Prangible transparen~ polymeric materlal and received
over tha glass tube with a clearance l'c" between the outer
sur~ace of the gla~s tube and the inner surface of th~
protec~ivq tube and extending lengthwise substantially
co~xtensively with the glass tu~e and a collar 20 pre~or~ad
from a h~at- hrinkable polymeric material received in
overlappin~ relation over a por~ion o~ th~ protective sleeva
at each end ~hereo~ and over ~he flange portion o~ th~
ad~ac~nt cap. Th~ collar is heat-shru~k into s~aled
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relation with the protective ~ube and th~ cap ~la~ge
portion. A layer 22 of an adhesive is interposed betwe~n
each collar and the corresponding end of the protectiv~ tub~
and the corresponding cap ~lange portion. The adhe~ive
layer i~ not present between the glass tubs of th~ lamp and
the collars.
In a specific example of the invention, as applied
to a 1.50 in. fluorescent tube, the protective tube 18 i a
piece cut to a length such as to extend over the full diam-
eter portion of the lamp tube (bl~t no~ over the necked-down
part~ at either end) from an extrusion of a polycarbonate
res~n that is highly stabilized against ultra-violet radia-
. tion. The tubing is available comm~rcially from Thermo-
plastlc Processors, Incorporated, of Sterling, New Jersey,
1~ -as Product No. 58 W, which is manufactured from a resin is
supplied by Mobay, Incorporated (Resin No. 3207-1112~50).
The protective tube has a wall-thickness o~ 0.015 in., an
inside diameter of 1~ 517 in. and an outside diameter o~
1.547 in. Therefore, on the diameter, the clearance between
the ou~ide o~ ~he glass tube and the insi~e of th~ protec-
tivs tub~ is 0.01? in. The clearance is desirable in that
is provide~ a thermal insulating barrier between to glass
tube and the protective tube that keep~ the protectiv~ tube
~ro~ being highly he~ted. Also, it facilitates a.~se hling
the protective tube onto a finished lamp. The collars 20
are pi~ces cut to a length of 1.5 in. from a tubing product
available commercially fro~ E. H. Canis & Son, Inc., of
MQtuchen, NJ, un~er the trademark "Astramelt." About 1.0
in. o~ the collar overlap~ the protective tub~. Tha
adhe~ i 3M No. 4693 and provides additional mech~cal

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retentlo~ over and above that provided by shrinking the
- collar and also provides a moisture barrier and herme~ic
seal between the lamp and the protective assembly.
If the protected lamp breaks, the protectivs
A~, hly retains the caps and prevents the dispersal of
glass fragments and phosphor powders. The protective
assembly does not appear to reduce the light transmission,
because the protective tube is entirely transparent. The
protective tube of an experimental assembly according to the
above exa~ple has shown no tendency to discolor after a year
in service.
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Representative Drawing