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Patented Oct. 15, '_1946
2,409,360
UNITED STATES PATENT OFFICE
2,409,360
SEAL STRUCTURE FOR ELECTRIC LAMPS
.
AND SIMILAR DEVICES
Eric Kettlewell, Kingsbury, London, England, as
signor to General Electric Company, a corpora
tion of New York
Application March 30, 1944, Serial No. 528,660
In Great Britain April 3, 1942
7 Claims.
1
This invention relates to devices of the type
comprising an envelope of quartz or similar re
fractory material and an electrode therein (with
currentylead connections to the exterior), which
electrode would become overheated in ordinary
operation if provision were not ‘made for cooling
it. This is especially the case with high pres
sure metal vapor discharge devices, such as mer
cury vapor lamps having an energy consumption
of some 5 to 10 kW. or upward. 'In a high pres
sure discharge device operated on D. C., the elec
trode which thus tends to overheat is usually the
anode. It is an aim of this invention to provide
for bringing cooling ?uid into eiiective cooling
(Cl. 176—126)
2
aperture in a relatively thick quartz plate or
disc 4 (whereof the tube 2 is thus in effect a
portion) which closes the inner end of a quartz
tube 5 that forms part of the discharge enve
lope wall. Thus the outward extending tube 2
affords a reverse internal pocket within a larger
main reentrant external pocket formed by the
inward extending tube‘5. As illustrative dimen
sions, the electrode rod I may be 8 mm. in di
10 ameter, the wall of the tube 2 may be 1% mm.
thick, the plate 4 may be 4 mm. thick, and the
tube 5 may be some 20 mm. in internal diameter,
with a wall about 4 mm. thick. Thin molybdenum
strips 6 lie between the outer surface of the tube
relation or thermal contact with an electrode that 15 5 and the surrounding quartz tube or sleeve struc
needs cooling.
.To provide conveniently for cooling the elec
trode by a stream or ?ow of cooling ?uid (usually
water or air), the electrode is attached to the
inside 'of the envelope wall, and a cooling con
duit is attached to the outside of the envelope
wall so that the fluid therein covers an external
wall area which in turn substantially covers 0r
ture l, which is ultimately heated and softened
and so collapsed on the strips 6, 6 and the tube
5, and interfused with and sealed to the latter.
For the sake of clearness as regards fabrication
of the device, the drawing shows the bulb neck
‘i and the tube 5 as separate parts, before being
fused and sealed together, with slight clearance
between them and between each of them and the
corresponds with the internal attachment or con
tact of the electrode as aforesaid. In the form
of embodiment of the invention here illustrated
and described, part of the electrode lies in a thin
shown in section is consistent with their lying
walled vitreous refractory tube that forms part
even the single lines representing them would
two strips 6, 6. That these strips 6, ?-arevnot
behind the plane of section represented in the
drawing, as Well as'with their being so thin that
of the envelope wall and projects into one end ‘7 exaggerate their thickness. At each end, each
of a surrounding larger external tube or conduit, . strip '6 is joined in the usual manner to stouter
through whose other end a stream of coolant can
leads 8, 9. The leads 8 extend to the exterior
be introduced and withdrawn. Instead of pass
of the device; the leads 9 are connected to the
ing through the envelope wall right where the
electrode is attached thereto, current leads to
electrode l at points inside the envelope.
An
annular seal ID of quartz around the quartz sleeve
‘lv forms the junction of the parts shown with the
the electrode are shown as strip seal leads lying
between the exterior of said larger tube (or of
a yet larger tube surrounding it) and a surround
rest of the envelope, not shown except fragmen
ing vitreous structure internally sealed to the
the envelope or bulb.
tarily.
The sleeve 1 forms as it were a neck for
last-mentioned tube, and forming a portion of
, If this were all, and a coolant were introduced
the envelope wall or associated therewith, the 40 into the tube 5, the coolant might cool the upper
seal being conveniently .formed by heating, sof
part II of the tube-Which lies inside the enve
tening, and collapsing the structure in question
upon the tube directly within it, and interfusing
it therewith.
'
'
Other features and advantages of the inven
tion will become apparent from the description
lope: and forms a portion of its wall-suiiiciently to
form‘ an undesirable cold» spot, where mercury
would condense so that the desired pressure could
not be maintained in the envelope. According
ly, the (relatively thin) intermediate tube or con
of a species or form of embodiment.
duit wall I2 is introduced between the tubes 5
The single ?gure of the drawing shows an axial
and
2 and is spaced at an interval from each,
section through a portion of a discharge device ’
envelope structure and associated parts which 50 with its inner end attached or sealed to the plate
4. For the above-indicated dimensions of the
embody and exemplify the invention.
tubes 2 and 5, the tube l2‘ may be of about 12
The discharge electrode in question is here
mm. diameter. The coolant circulates within
shown as a tungsten rod I ?tting as closely as
this tube l2 around the tube 2 and comes in
possible into a quartz tube 2 that is closed at its
outer end 3 and has its other end sealed into an 55 contact with the latter and cools it, but it is sep
arated from the part II of the outside envelope
2,409,360
3
or pocket wall by the insulating space [3, so that
it is out of contact with this wall and so does
not produce a materially or excessively cooled
wall area around the electrode l. Good thermal
contact between the rod l and the tube 2 is never
theless assured by the mercury that will condense
in any interstices between them.
The tube or wall [2 may be dispensed with by
making the plate 4 sufficiently thick to hinder
heat transference through it and attaching the
annular envelope seal to the sleeve 1 substan
tially at the plane or level of the plate 4, as shown
in dotted lines at [0’, in other ‘words, virtually
attaching the seal It!’ to the rim of the plate.
With this arrangement, the part II of the tube
5 lies outside the envelope and forms no portion
of its wall, so that it does not matter for it to be
cold.
In general, and as a practical matter, refrac
tory envelope material similar to quartz is any
highly silicious vitreous material which has a
coefficient of expansion of not more substan
tially than 1.5><10—6 per degree centigrade, as
compared with a corresponding coe?icient of ex
pansion of 0.55><10—6 per degree centigrade for
fused quartz o1‘ quartz glass itself.
What I claim as new and desire to secure by
Letters Patent of the United States is:
1. The combination with a vitreous refractory
envelope wall having an outward projecting vitre
ous portion affording an internal pocket, and a
discharge electrode ?tted into said pocket, of an
external ?uid conduit wall attached to said en
velope wall around its said outward projecting
portion, and means for circulating cooling ?uid .'
in the conduit in contact with said outward pro
jecting wall portion to the inside of which said
electrode is attached, thus cooling said electrode.
2'. The combination with a vitreous refrac
tory envelope wall having an outward projecting
relatively thin portion affording an internal
pocket, with a relatively thick zone around said
outward projecting portion, of a discharge elec
trode fitted into said vpocket, an external fluid
conduit wall attached to the thickened envelope
4
ing a main pocket, and with a discharge electrode
attached to the inner side of the bottom pocket
wall, or a ?uid conduit Wall attached to the outer
side of the bottom pocket wall, within the pocket
and around an external area of said bottom wall
covering the internal attachment of said electrode
thereto, and means for circulating cooling fluid
in said conduit in contact with said area, but out
of contact with the main pocket wall around the
said conduit wall, thus cooling said electrode
without producing a materially cooled envelope
wall area around the electrode.
5. The combination with a vitreous refractory
envelope wall having a reentrant portion afford
ing a main pocket, with a relatively thin portion
of the main pocket wall projecting outward into
said main pocket and thus affording a reverse
pocket, and with the main pocket wall around
said reverse pocket relatively thick, of a dis
charge electrode ?tted into said reverse pocket,
a ?uid conduit wall attached to the outer side
of the thickened bottom main pocket wall at
an interval around said reverse pocket, and means
for circulating cooling fluid in said conduit around
and in external contact with said reverse pocket,
but out of contact with the main pocket wall
around the said conduit wall, thus cooling said
electrode without producing a materially cooled
envelope wall area around the electrode.
6. The combination with a vitreous refractory
envelope wall and a vitreous refractory tube
sealed therethrough having an inner end wall
with a portion projecting reversely outward into
the tube and thus affording an internal pocket
in said end wall, of a discharge electrode fitted
into said pocket, current lead means extending
inward in the thickness of the tubular wall to
said electrode, and means for circulating cooling
?uid around and in external contact with said
outward projecting wall portion inside ‘said other
tube, thus cooling said electrode.
7. The combination with a vitreous refractory
main envelope wall having an opening and a.
sleeve portion around said opening, and a vitreous
' refractory tube extending through said sleeve
portion inward beyond said main wall and having
an inner end wall with a portion projecting re
projecting wall portion, and means for circulat
versely outward into the tube and thus affording
ing cooling ?uid in the conduit in contact with
an internal pocket in said end wall, of a discharge
said outward projecting wall portion, thus cool
, electrode fitted into said pocket, current lead
ing said electrode without producing an excessive
means extending inward between said sleeve and
ly cool envelope wall area around the electrode.
tube to said electrode, said sleeve and tube hav
3. The combination with a vitreous refractory
ing their inner and outer surfaces sealed together
envelope wall having a reentrant portion afford
with said current lead means embedded in the
ing a main pocket, with a relatively thin portion
another tube Within the tube aforesaid
of the main pocket wall projecting ‘outward into
around ‘the said pocket having its inner end sealed
said main pocket and thus affording a reverse
to the aforesaid inner end wall of the ?rst-men
pocket, of a discharge electrode attached to the
tioned tube, and means for circulating cooling
inside of said reverse pocket, and means for cir
fluid around and in external contact with said
culating cooling fluid in said main pocket in ex
ternal contact with said reverse pocket, thus 60 outward projecting ‘wall portion inside said other
tube, thus cooling said electrode.
cooling said electrode.
4. The combination with a vitreous refractory
envelope Wall having a reentrant portion afford
ERIC KE’I'I’LEWELL.
wall zone at an interval around said outward
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