LAMPE A DECHARGE SOUS GAZ BASSE PRESSION

LOW PRESSURE DISCHARGE LAMP

Abrégé anglais

ABSTRACT OF THE DISCLOSURE
The low pressure discharge lamp has at least one glass
tube containing therein mercury and a rare gas and provided with
a fluorescent layer on its inner wall and electrodes set up in a
single base place in an air tight manner. Each end of the glass
tube is bonded with an adhesive to the base plate such that each
of the electrodes is received in an open end thereby to form a
sealed space by the glass tube and the base plate. Two glass
tubes are connected in series via through holes in the base
plate. With the structure, damage to the glass tube in the
sealing process is prevented and the structure of the lamp is
made compact while manufacture of the lamp is simplified.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A low pressure discharge lamp comprising a ceramic
base plate, at least one pair of electrodes passing air-tightly
through and extending from said base plate, and at least one
bent glass tube which is coated on its inner wall with a
fluorescent layer; contains mercury and a rare gas and has its
both open ends in juxtaposition, each of open ends of said glass
tube being air-tightly bonded to said base plate while receiving
therein one of said electrodes, two glass tubes being connected
in series via through holes in said base plate.
2. The low pressure discharge lamp according to claim
1, wherein said through holes in said base plate have their
openings at the same side of the extension of said electrodes.
3. The low pressure discharge lamp according to claim
1 or 2, wherein said base plate is made of ceramics.

Description

so
The present invention relates to a low pressure disk
charge lamp such as a fluorescent lamp. More particularly, it
else to a low pressure discharge tamp having a curved glass
tube making its structure compact.
The present invention will be illustrated by reference
to -the accompanying drawings, in which:-
inure 1 is a front view partly cross sectioned show-
in the construction of the conventional U-shaped fluorescent
lamp;
Figure 2 is a perspective view showing a fluorescent
lamp formed by further bending the conventional U-shaped glass
tube;
Figure 3 is a perspective view of a fluorescent lamp
according to an embodiment of the present invention;
Figure 4 is an exploded view of Figure 3; and
figure 5 is a perspective view of another embodiment
of the fluorescent lamp according to the present invention.
Generally, a fluorescent tamp is so constructed that
electrodes are disposed at both ends of a linear glass tube and
luminescence is caused by an exciting gas contained in -the glass
tube due to the electric discharge between the electrodes. The
lumillescence efficiency increases as the distance between the
electrodes, namely, the length of electric discharge path is
increased. Accordingly, if luminescence efficiency is con-
ridered to be important, the use of a longer glass tube is
advantageous. However, discharge tamps are used as slight
sources in a variety of positions and it may be desirable for
users to have one having a compact structure which is con-
lenient -to handle. Various proposals have thus been made for a
discharge lamp with a curved glass tube so that luminescence
efficiency is maintained at a high level to some extent while
the size of the lamp is reduced by making its structure compact.

Figure 1 shows a U-shaped fluorescent lamp as a typic
eel example of the discharge lamp of this -type in which at both
ends of a U-shaped glass tube 1 on the inner wall of which a
fluorescent layer I is former, glass stems 3 each holding an
electrode 2 are provided in an air tight manner.
The fluorescent lamp having the construction described
above is utilized in the field requiring a compact light source
since such lamp imparts substantially the same luminescence
characteristic as an ordinary fluorescent lamp using a linear
glass tube although the length of -the lamp is one half.
However, the discharge lamp having the construction
above-mentioned has the disadvantage that it is more comply-
acted to manufacture it in comparison with the conventional
discharge lamp using a linear glass tube. Particularly, it is
difficult to attach a glass stem to the end portion of the glass
tube 1 to seal it. Namely, a general method of seal-bonding a
glass stem 3 to the end of the glass tube 1 is that the glass
stem 3 is brought to contact with the end of the glass tube
which is previously bent into a U-shape; heat is applied to the
periphery of the contacting par-t by a gas burner (no-t shown) to
soften glass thereby causing melt bonding of the glass -tube and
the glass stem.
In the discharge lamp having the shape shown in Figure
1, however, since both parts to be sealed are disposed keynote-
guzzle to each other, it is difficult to apply heat from the
burner to those parts thereby possibly causing defects such as
cracking during sealing operations. Further, the conventional
discharge lamp is no-t always of sufficiently compact structure
because the linear glass -tube is bent only once.
Figure 2 shows a fluorescent lamp of compact strut
lure disclosed in Japanese Unexamined Publication 83147/1980 in
which the fluorescent lamp has a base plate 23 to one surface of
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which is integrally attached a lamp base 9 and the other surface
of wtlich is firmly secured to a glass tube 1 as a luminescence
tube. 'Lowe glass tube 1 is in a general saddle shape and is
formed by bending a linear glass -tube at its intermediate port
lion into a U-shape and further bending the U-shaped glass tube
by 180 in the direction perpendicular to the axis of -the
bending. The discharge lamp also provided, similarly to the
conventional lamp, with glass stems 3 attached to both ends of
the glass tube 1 and electrodes 2 held by the glass sterns 3.
in the discharge lamp having a doubly curved glass
tube as above mentioned bending operations of the glass tube
are more complicated because a shaped glass tube is further
bent into double U-shapes. Furthermore, in the second bending
operations, two portlorls in the glass tube are simultaneously
bent- and accordingly, if there is a large curvature, defects may
result in the glass tube. Therefore, there has been restriction
ion compact structure of dischclrge lamps.
The proselyte inverlti.orl eliminates -the disadvantages of
the corlventional discharcJe lalnp and provides a low pressure
discharge lamp for preventing brealcing of the glass tube in the
sealing process and making its manufacture easy, which comprises
a base plate, electrodes attached to the base plate in an air
tight manner and at least one glass tube both of whose open ends
are adhesively bonded air-tightly -to the base plate both open
ends receiving -therein the electrodes, to form a sealed space
between the glass tube and -the base plate. Two glass tubes are
connected in series via through holes in the base plate.
The present invention also provides a low pressure
discharge lamp comprising a base plate provided with electron
dyes and through holes and at least one glass tube, each open end
of which is adhesively bonded -to the base plate such -that each
of the electrodes is contained in an open end, certain open ends
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of the glass tube being connected to each other via the through
holes of the base plate, whereby at least a second bending
operation to form a U-shape of the glass tube is eliminated
-thereby simplifying the manufacturing steps and providing a come
pact construction of the lamp.
An embodiment of the present invention will be desk
cried with reference to Figures 3 and 4.
In Figures 3 and 4, there is shown a circular ceramic
base plate which is divided in-to two parts along a radial direct
shunner i.e. a bottom part 12 and a cover part 13 covering the entirety of one surface of -the bottom part 12. An elliptical
through hole 15 is formed in the half area of the bottom part 12
and two circular through holes, 14,14 are formed in the cover
pat 13. The through holes 14,14 are above the elliptical hole
15 at the time of bonding the bottom part 12 and the cover part
13 with an adhesive such that a communication hole 8 having the
through holes 14,14 as open ends is formed. Two electrodes 2
extending from a semi-circular area of the cover par-t 13
opposite an area where two -through holes 14,14 are formed and
lead wires 16 to support the electrodes 2 pass out through the
bottom part 12.
Two glass tubes 1 each bent in-to a U-shape and having
open ends are attached to the base plate 23 so that respective
one ends of the glass -tubes are air-tightly bonded with the
adhesive 4 to the cover part 13 containing therein the elect
trove 2 and the other ends are air-tightly bonded with the
adhesive 4 to the cover part 13 around the periphery of the
respective through holes 14 whereby these other ens commune-
gate through the communication hole 8. A fluorescent layer 11
is coated on the inner wall of the glass tubes 1 which contain
-therein specified amount of mercury and a rare gas such as argon
gas. A base metal 9 is bonded to the base plate 23 with its
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side surface bonded with an adhesive (not shown). Terminals 10
of a conductive material are attached to the bottom surface ox
the base metal 9 to be electrically connected with the lead
wires 16 supporting the electrodes 2.
In the fluorescent lamp having the construction above-
mentioned, when a voltage is applied across the electrodes 2
through the terminals 10, there takes place an electric disk
charge -through an electric path formed by: one of the electrodes
2 - zone of the glass tubes lo communication hole 8
the other of the glass tubes 1 - the other of the electrodes
2.
In this way, it is easy to make a fluorescent lamp of
the embodiment shown in Figures 3 and 4 since only one bending
operation to the glass tube 1 is required to form a U-shape.
Furthermore, with the single bending structure, it is possible
to give a large curvature to a portion to be bent so that both
leg portions of the glass tube 1 are in a close juxtaposition.
also, even in use of two glass -tubes, this relationship is
applicable. Accordingly, all the legs of the glass -tubes 1 can
be gathered closely to the central axis of the base plate 23
whereby a further compact structure of the lamp is obtainable.
In the embodiment shown in Figures 3 and 4, -the base
plate 23 is divided in its radial direction into two parts.
The present invention is not limited to this embodiment and it
is possible that only upper portion of the base plate is divided
at a position related at least to -the communication hole 15 or
without dividing the base plate 23, a communication hole 8 is
formed to provide openings at the side surface of -the base plate
23 as shown in Figure 5. In this case, if the electrodes 2 are
provided at positions corresponding to each of the openings, a
low pressure discharge lap making its manufacture easy and ox a
fresh design can be obtained.
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Further, when soda glass or lead glass is used for the
glass tube 1, ceramics its suitable to the base plate 23. It is,
however, possible to use the same glass material as -the glass
tube 1.
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