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Патент USA US2121636

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June '21, 1938.
Filed May 26, 1937
1S7EY6N2/ 1047:‘
2000 2600 2700 2000 2.900 3000 0/00 .2200 3000
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In Ve ht or .
Lewis R. Kol Ier,
by 70
His t’corney.
Patented June 21, 1938
Lewis B. Koller, Schenectady, N. Y., assignor to
General Electric Company, a corporation of
New York
Application May 26, 1937, Serial No. 144,895
2 Claims.
The present invention relates to light-sensitive
devices and more particularly to photo-electric
tubes which respond to ultraviolet light.
(Cl. 250—2'7.5)
envelope and serves to prevent deposition of ac
tive material on the stem. There is an opening
‘Ultraviolet radiation is used for many purposes
l2 in the disk sufficiently large so that the rod 5
can pass through without touching the disk. This
5 such as sterilization, health promoting effects,
prevents short-circuiting of the electrodes by the
etc. In order to obtain the optimum effects from
this type of radiation, it is necessary to measure
and regulate the intensity of the light. For this
purpose, special types of photo-electric tubes
10 have been devised which respond to light of this
However, since the light is limited
to a restricted range in the spectrum, it is di?i
cult to design and. manufacture a tube which will
have its optimum response in that range. It is
15 even more difficult to duplicate tubes of this char
Objects of the present invention are to devise
a photo-electric tube which will respond effi
ciently to ultraviolet radiation or to radiation in
a restricted portion of the ultraviolet region of
the spectrum; to improve the manufacturing
processes of these tubes to the extent that they
can be readily duplicated, even on a quantity pro
duction basis, and to provide a tube in which the
response curve in the ultraviolet region may be
accurately predetermined. In carrying out these
objects, a light-sensitive material of known com
position is obtained by vaporization from a source
of similar composition which can be varied and
30 accurately controlled. The invention will be bet
ter understood when reference is made to the
following speci?cation and the accompanying
drawing in which Fig. 1 is an elevational view of
a photo-electric tube improved in accordance
35 with the present invention; Fig. 2 is a view partly
in section of the tube shown in Fig. 1; and Fig. 3
is a graph showing the response curves of vari
ous types of improved ultraviolet tubes.
In Figs. 1 and 2, numeral l designates a glass
40 envelope containing an anode 2 and a light
sensitive cathode 3. The anode may take the
form of a metal ring supported on the end of
a rigid rod 4 which serves as the leading-in con
ductor. The cathode consists of a composite ma
45 terial which is sensitive to ultraviolet radiation,
and contact is made with the material by means
of a rod 5 which terminates in a platinum ribbon
secured to the glass. The conductors are con
nected to contact pins 6 secured in a base 1.
50 The envelope terminates in a stem 8 in which
the conductors are sealed, the stem carrying an
exhaust tubulation indicated at 9. A mica disk
I0 is secured to the conductor 4 by means of an
angle piece II. This disk is of a size snugly to
55 fit the interior of the small neck portion of the
material which condenses on the disk. Shield l3
prevents active material which passes through
the opening from depositing on the stem 8.
For introducing the light-sensitive material
into the envelope, a capsule I4 is provided. This 10
capsule may be supported from the rod 4. An
alloy having predetermined amounts of cadmium
and magnesium is made and placed in the cap
sule. After the capsule and the anode have been
mounted in position, the envelope is evacuated 15
and the bulb is baked out for an hour at 300
deg. C. At temperatures higher than this, there
is danger of vaporizing the cadmium out of the
alloy in the capsule. After the bake-out, the alloy
is vaporized by heating the capsule by high fre
quency induced currents until the bulb is covered
with an opaque mirror-like deposit. The thick
ness of the deposit is determined by the amount
of alloy contained in the capsule. A window [5
is then formed by torching with a soft bunsen
?ame after which the tube is again baked for
ten minutes at 100 deg. C. to insure uniformity
of the deposit. The envelope may be based in
the usual manner. The bulbous portion of the
envelope except for the window I5 is therefore 30
coated with an alloy of cadmium and magnesium,
which I have found profusely emits photo-elec
trons when exposed to ultraviolet light.
It has also been found that by varying the
cadmium and magnesium, the region within
which the tube has its optimum response in the
ultraviolet region of the spectrum can be varied.
This is clearly shown in Fig. 3. As the cadmium
is decreased and the magnesium increased, the
sensitivity curve moves to the right, indicating 40
an optimum response at a longer wave length.
Thus, increasing the concentration of magnesium
increases the relative response to long-Wave radi
ation, while increasing the concentration of cad
mium increases the relative response to short 45
wave radiation. It may be desirable to cut off
or materially reduce the sensitivity of the tube
at wave lengths less than 2700 Angstroms. In
this case, the envelope may be made of a glass
such as Corex which absorbs light of the unde
sired wave lengths. The curves shown in Fig. 3
were obtained from a tube of this character, and
for that reason the maximum values of the curves
are not true characteristics of the cathode but 55
are determined by the falling transmission of the basis, because the light-sensitive layer is, of a
Hpredetermined character and can be accurately
Corex glass toward the shorter wave lengths.
The process as described, which involves the
use of an alloy or composition within a capsule
for obtaining a light-sensitive layer composed’
of all of the elements of the alloy or composition
is not limited to cadmium or magnesiumrbut may
be employed in connection with'other metals or
materials. vIt is of course highly desirable that
10 the vapor pressure of the materials shall be of
What I claim as new, and desire to 'securer'by ,
Letters Patent of the United States, is:
1. A photo-electric tube comprising an enve
lope containing a light-sensitive cathode and
an anode, said-cathode including cadmium and
2. A photo-electric tube comprising an enve
lope containlng a light-sensitive cathode’ and»
an anode, said cathode consisting of cadmium
posite light-sensitive layer will represent in prop-. and-magnesium, the cadmium‘ ranging from 5%
the samerorder as the temperatures employed in
?ashing the alloy or composition so that the com‘
er proportion'the elements contained within the
. capsule. It is apparent that the improved proc-;
'ess may be employed on ya quantity production
a “in”
Patent No; 2,121,656.
' June 21, 1958.
‘It ishereby certified that error appears in the printed specification
of the above numbered patent requiring correction as follows: Page 2, first
column, line 11, for the word "as" read at; and that the said Letters Pat
ent should be read with this correction therein that‘ the same may conform
to the record of the case in the Patent Office,
Signed and sealed this 9th day of August, A. D. 1958.
Leslie Frazer
Acting Commissioner of Patents.
-7 A
Patent No; 2,121,656.
' June 21, 1958_
‘It ishereby certified that error appears in the printed specification
of the above numbered patent requiring correction as follows: Page > 2, first‘
column, line ll, for the word "as" read at; and that the said Letters Pat
eint should be read with this correction therein that‘ the same may conform
to the record of the case in the Patent Office‘,
Signed and sealed this 9th day of August, A. D. 1958.
Leslie Frazer
Acting Commissioner of‘ Patents.
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