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Патент USA US2135726

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Nov. 8, 1938.
2,135,726
J. H. MITCHELL
GASEOUS ELECTRIC DISCHARGE LAMP
Filed Nov. 8, 1934
12’
mvragm
BY
A
ORNEY
_
Patented Nov. 8, 1938
2,135,726
I
UNITED STATES. PATENT OFFICE
2,135,726
GASEOUS ELECTRIC DISCHARGE LAMP
John 11. Mitchell, Rugby, England, assignor to
General Electric Company, a corporation of
New York
Application November 8, 1934,,Serial No. 752,136
In Great Britain November 8, 1933
(Cl. 176-2)
mium mercury amalgam is formed having the
The present invention relates to gaseous elec
ingredients in the proper proportions for the
tric discharge lamps generally and more particu
larly to such lamps of the type disclosed in the type of lamp desired. This amalgam is formed
1 Claim.
United States Patent Number 1,948,261, granted
5 February 20, 1934, to Victor James Francis and
John Walter Ryde. Such lamps consist of an en
velope containing mercury and activated cath
odes and operate at a mercury vapor pressure
approaching that of the atmosphere. A heat
10 conservator is useful in maintaining the envelope
at an elevated temperature in order to obtain
' this vapor pressure and an evacuated envelope
inclosing the lamp envelope is useful for this
purpose.
into a wire and a portion of wire of the required
weight is cut oil and introduced into the lamp 5
container through the exhaust tube._ The in
troduction in the form of a wire besides being
convenient makes possible the use of a smaller
exhaust tube which simpli?es the sealing oif
operation and improves the lamp as the possibili- 10
ties of cold spots on~which condensation is likely
to occur are removed.
The light given by an electric discharge vapor
Such lamps su?er- from the disadvan- . lamp made according to this invention is a much
1
tage that they are de?cient in red and blue rays
and therefore the light given by them distorts
practically all colours.
The object of this invention is to improve the
color and quality of the light emitted by a
20 gaseous electric discharge lamp using high pres
sure mercury vapour. Another object of the in
vention is to provide a high pressure, unsaturated
vapor lamp which emits light closely approaching
daylight. To these ends the invention consists
nearer approach to daylight than that given by a 15
lamp containing only mercury vapour. The rela
tive intensities of the light in di?erent parts of
the spectrum is readily varied as stated by vary
ing the relative proportions of the mercury and
cadmium. By'inserting the mercury-cadmium 20
mixture as described in measured quantities an
unsaturated vapour pressure for normal opera
tion is readily obtained.
'
In the drawing accompanying and forming‘ part
25 in providing a mixture of vapours in the proper _ of this speci?cation an embodiment of the in- 25
proportions to give the desired result and in a vention is illustrated in a front elevational, partly ‘
method of introducing the vaporizable materials sectional view but as such illustration is primarily
for purposes of disclosure it will be understood
into the lamp.
In carrying this invention into e?ect according of course that numerous changes in the form
30 to one embodiment I provide as a ?lling a mixture and details of the device may be made by those 30
of mercury and cadmium vapour. This mixture' skilled in the art without departure from the
when in the proper proportions greatly improves spirit and scope of the invention.
Referring to the drawing the new and novel
the colour distribution without seriously reducing
the high efficiency of the lamp. I have demon
35 strated that a good, well balanced light is ob
tained by using a vapour pressure of about 62.5%
gaseous electric discharge lamp comprises a glass
container I having approximately spherical ends 35
of mercury and 37.5% cadmium but variations
3 are sealed. A thermionic electrode comprising
a spiral ?lament 4 of tungsten, for example,
wrapped around a rod or bar 5 of electron emit
ting material, such as a mixture of barium and 40
calcium oxides, is attached to each pair of leads
in the colour intensity can be obtained by vary
ing the cadmium content, or by substituting an
r other substance for the cadmium. The exact
quantity of the cadmium introduced depends on
the dimensions of the lamp and on the electrical
supply conditions, such as the voltage, etc., under
which the lamp is operated, but in all cases the
I 1 quantity of the mercury-cadmium mixture intro
duced into the lamp is limited so that the vapour
pressure of the lamp always remains unsaturated
under normal running conditions, that is, at the
operating temperature of the lamp container.
According to one method of introducing the mix
ture of metals into the lamp the cadmium is
formed into a wire from which a suitable length
is cut oil and this with the required weight of
mercury is introduced into the lamp container
v:35 through the exhaust tube. Alternatively a cad- ,
2 into each of which a pair of leading-in wires
3 by spot-welding the ?lament 4 to said leads 3,
for example.
Two turns free of the rod 5 are
used for preventing the conduction of excessive
heat from the electrodes to the seals. The elec- 45
trodes are mounted close to the spherical ends 2
of the container I and are separated not more
than 10 mm. from the wall so that said spherical
ends 2 are heated to approximately the same
temperature than the straight walls of the con
tainer l during the operation of the lamp. Con
densation of metal vapor in said spherical ends 2
is thus avoided. .When desired the container
ends 2 are provided with a coating of material 55
2
8,185,798
which reduces the radiation of heat therefrom,
such as caps oi’ thin metal foil.
-
The container I is mounted in an evacuated
envelope 1 (shown partly in section in the draw
ing) having a stem 8 and a screw base I2 at one
end thereof. Current leads 8 are sealed into said
stem 8 and are connected to the current leads 3
sealed into said container I. 'Said current leads
9 are connected to resilient wire rings II which
10 in turn are connected to the leads 3. Said rings
I3 press against the inner wall of said envelope ‘I
and assist in supporting said container I in said
envelope ‘I.
Said container I has a' starting gas therein,
15 such as argon, at a pressure of a few mm. and
such quantity of mercury and cadmium ‘that
these metals are completely vaporized at a term
perature lower than the operating temperature
of said container I and the vapor pressure in the
20 container I is approximately one atmosphere
when the lamp device is operating on a current
of from 21/2 to 3 amperes. The mercury and
cadmium are introduced into the container I by
the method pointed out heretofore and when the
25 two metals are in the proportions given above the
light emitted by the lamp closely approaches‘
daylight. A wire III is connected to one of the
leads 9 and extends externally along the con
tainer I and is wrapped around the container I
to form a conductive ring II adjacent the elec
trode connected to the other or said leads 9 to
facilitate starting of the device.
While I have shown and described and have‘
pointed out in the annexed claim certain novel
features of the invention, it will be understood
that various omissions, substitutions and changes‘ 10
in the forms and details of the device illustrated
and in its use and operation may be made by
those skilled in the art without departing from
the broad spirit and scope of the invention.
What I claim as new and desire to secure by
Letters Patent of the United States is:
The method of introducing a quantity of amal
gam into a lamp container which consists in
forming said amalgam into a wire of smaller di
ameter than the exhaust tube or said container 20
and passing said wire through said tube into said
container.
JOHN H. m'rcmsLn
25
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