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Патент USA US2403745

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July 9, 1946.
2,403,745
R, L. NORTON
APPARATUS AND METHOD FOR MAKING lwusns '
Filed Dec. 21, 1945
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INVENTOR
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ATTORNEY _
2,403,745
Patented July 9, 1946
UNITED STAT'ESPATENT OFFICE]
2,403,745
AND METHOD FOR MAKING ,
APPARATUS
TUBES
-
Robert Leigh Norton, Burlingame, Calif., assignor
to Eitel-McCullough, Inc., San Bruno, Calif., a
corporation of California
Application December 21, 1943, Serial No. 515,189
9 Claims. (01. sis-a6)
-
My invention relates to vacuum tubes, and
more particularly to improvements in apparatus
and methods for treating such tubes during
manufacture‘ thereof.
-
It is desirable, at various stages during the
making of a vacuum tube, to heat an internal
part, such as a plate electrode, either for driving
out occluded gas or for some other treating pur
pose. For example, it is necessary to heat in
ternal tube parts during the exhaust process to
outgas the metal; otherwise the gas would be re
leased during subsequent operation, causing the
tube to go soft.
Thoroughly outgassing the plate '
electrode is particularly important because this
is a relatively massive part.
.
A method commonly used for heating an elec
_ trode during exhaust is known as f‘internal bom
'
2
my method. Tube 2 to be
exhausted is connected by tubulation 3 to a suit
able vacuum pump- 4. The latter preferably in
cludes an oil diffusion pump capable of producing .
a high degree of vacuum in the envelope of the
‘ system embodying
tube.
For purposes of simplicity I have shown a
single tube, it being understood that a group of
tubes may be pumped simultaneously by my'
method.
'
_
While the tube is being evacuated, cathode 6
is heated by suitable means to provide a source
of electrons. ' Thus the ?lamentary cathode illus
trated is connected to secondary 1 of a trans
former 3. Primary 9 of this transformer is con
nected through a voltage regulator H to a suit
able- source of A.‘ C. power supplied at terminals
l2.. Regulator ll permits adjusting the ?lament '
bardmentff involving bombarding the electrode
with electrons from the cathode. This system
voltage to obtain thesdesired emission from the
cathode.
.the internal bombardment method, however is
the occluded gas.- Gas liberated _from the plate
In the practice of the invention an electrode,
has numerous advantages over heating tube 20 such as plate l3, to beoutgassed is bombarded
parts by high frequency. induction. A problem in
with electrons to heat the same for driving out
that electron collision‘with gas atoms or mole-,
is withdrawn from the tube .by pump 4 which
cules in the tube is likely to cause excessive ioni
operates continuously during the process. vAs
25
zation. This is bad for several reasons. One is
hereinbefore pointed out,r.the principal problem
that positive ion bombardment of the cathode is
encountered in this system of electrode heating
destructive.
is that electron collision with gas atoms and mole
cules causes excessive ionization. This subjects
'
It is among the objects of my invention to over
come the above diiiiculties by providing a method 30 the cathode to harmful positive ion bombard
of electronically bombarding an electrode to heat
ment. Furthermore, ionized. gas is materially
the same without causing harmful ionization in
harder to remove from the tube than unionized
the tube.
. I
gas, making-it more difficult if not impossible to
The invention possesses other objects and fea
achieve a high degree of vacuum.
‘
tures of advantage, some, of which, with the fore
In order to overcome this problem I bombard
going, willvbe set forth in the following descrip
tion of my invention, It is to be understood that
I do not limit myself to this disclosure of species
of my invention as I may adopt variant embodi
ments thereof within the scope of the claims.
Referring to the drawing:
'
'
Figure 1 is a diagrammatic view showing a sys
tem for carrying out my method in conjunction
with exhausting a tube; and
I
_
_
Figure 2 is a similar view showing a modi?ed
pumping system.
-
v
In terms ofbroad inclusion, my invention in
volves periodically bombarding an electrode with
electrons, and limiting each period of bombard
ment to a time intervalso small that the ioniza
tion of gas in the tube is insui?cient to cause de
structive bombardment of. the cathode.
When
used in a pumping system the tube is continu
35 the plate periodically, and limit each period of
bombardment to a time interval so small that the
ionization of gas-in the tube is insumcient to
cause destructive bombardment of the cathode.
40 While. little is known of the exact time required
for a gas to ionize, dependent as it is upon so
many variables such as the nature, of the gas,
number, of, collisions between electrons and gas
atoms orImolecules, etc.; nevertheless a measur
45 ableiperiod is required.
For practical purposes
this period may be de?ned as less- than‘about 25
microseconds. I have used pumping Systems in
which electron bombardment of an electrode was
limited to periods as short as 1/2 to 6 micro
seconds with good results.
7
I
.
In Figure 1 the periodic bombardment is accom
plished by intermittently applying, short pulses
of positive potential to plate l3 of the tube, the
pulse lengths being of the order mentionedabova
Figure 1 shows a plate pulsed type of pumping 55 For this purpose a suitable pulser I4 is provided
_ ously evacuated during such bombardment.
In greater detail, and referring to the drawing,
2,403,745
3
with its positive output terminal connected to
4
bombarding the electrode with electrons to heat
plate l3 by conductor l5 and its negative ter
minal connected to the cathode circuit by con
ductor l6. In this set up grid I1 is not specially
heated and is therefore merely tied to the cathode
the same for driving out occluded gas, limiting
each period of bombardment to a time interval so
small that the ionization of gas in the tube is in
by conductor [8.
the cathode, and evacuating the tube during said
‘The voltage applied to the plate and the repe
tition rate of the pulses may be varied within wide
su?icient to cause destructive bombardment of
bombardment.
4. The method of making a vacuum tube hav
ing a cathode and another electrode, which com
limits, as long as su?icient power is applied to
heat the plate to the desired temperature for 10 prises heating the cathode to provide a source of
driving out the occluded gas. I have used poten
electrons, intermittently applying a positive po
tials up to 30,000 volts and repetition rates from
tential to said other electrode to intermittently
500 to 4,000 cycles per second with satisfactory
bombard it with said electrons to heat the elec
results, it being understood that still higher volt
trode for driving out occluded gas, limiting each
ages and other repetition rates may be employed. 15 period of bombardment to a time interval so
It is also understood that other electrodes in a
small that the ionization of gas in the tube is in
tube may be heated in a similar manner by
su?icient to cause destructive bombardment of
applying pulses of positive potential thereto, and,
the cathode, and evacuating the tube during said
if desired, two electrodes may be heated simul
bombardment.
taneously by alternate application of pulses to 20
5. The method of making a vacuum tube
them. In any case the advantages of my inven
having a cathode and grid and another electrode,
tion are obtained if the pulse length is so short
which comprises heating the cathode to provide
that the ionization of gas in the tube is insu?i
a source of electrons, applying ‘a positive poten
cient to cause destructive bombardment of the
tial to said other electrode, applying su?icient
cathode.
[6 CH negative potential to the grid to cut oil’ the elec
Figure 2 shows a modi?ed pumping system in
tron stream from the cathode to said other elec
which bombardment of the plate is controlled by
trode, intermittently making the grid positive
the grid. For this system a D. C. power supply
with respect to the cathode to intermittenly bom
19 capable of delivering up to say 30,000 volts is
bard the other electrode With said electrons to
provided with its positive terminal connected to 30 heat it for driving out occluded gas, limiting each
plate [3 by a conductor 20 and its negative term
period of bombardment to a time interval so
inal connected to the cathode circuit by con
small that the ionization of gas in the tube is
ductor 2|, a suitable condenser 22 being con
insu?'icient to cause destructive bombardment of
nected’ externally between the plate and cathode.
the cathode, and evacuating the tube during said
bombardment.
In this case periodic bombardment of the plate
is controlled by biasing the grid to cutoii (viz.,
applying su?icient negative potential to the grid ‘
6. The method of making a Vacuum tube hav
ing a cathode and another electrode, which com
prises heating the cathode to provide a source of
to normally cut off the electron stream from the
cathode to the plate) and intermittently apply
electrons, intermittently applying a positive po
ing pulses of positive potential to grid I1. The 40 tential to the other electrode to periodically at
positive terminal of a pulser 23 is connected to
tract electrons from the icathodeklimiting each
the grid by conductor 24 and the negative term
period of said applied potential to a time interval
inal is connected to the cathode circuit by con
less than about 25 microseconds, said interval
ductor 26. Pulser 23 is designed to deliver a
being so small that the ionization of gas in the
suitable potential, say up to 5,000 volts, the length
tube is insufficient to cause destructive bombard
of pulse being less than about 25 microseconds
ment of the cathode, and simultaneously evacu
as hereinbefore discussed. Bias voltage is sup
ating the tube.
plied by suitable means, as by a battery 21 inter
'7. In apparatus for making a vacuum tube
posed in lead 24 with its negative terminal con
having a cathode and another electrode, the com
nected to the grid. Su?‘icient battery voltage is 60 bination with means for heating the cathode to
used to normally bias the grid to cut off the
provide a source of electrons, of a pulser for in
electron stream from the cathode to the plate.
termittently applying a positive potential to said
As a result, no electrons bombard the plate ex
other electrode to effect intermittent ‘electron
cept during the periods when positive pulses are
bombardment thereof, and thereby to heat the
applied to the grid.
I claim:
1. The method of making a vacuum tube hav
ing an electrode, which comprises intermittently
bombarding the electrode with electrons emitted
G1 at
electrode for driving out occluded gas, said pulser
limiting each period of bombardment to a time
interval so small that the ionization of gas in the
tube is insu?icient to cause destructive bombard
ment of the cathode, and means for evacuating
by a continuously heated cathode to heat the (EU the tube during said bombardment.
electrode. and limiting each period of bombard
8. Apparatus for making a vacuum tube having
ment to a time interval so small that the ioniza
a cathode, a grid, and another electrode, the
tion of gas in the tube is insu?icient to cause de
combination with means for heating the cathode
structive bombardment of the cathode.
to provide a source of electrons, of means for
2. The method of making a vacuum tube havapplying a positive potential to said other elec
ing an electrode, which comprises intermittently
bombarding the electrode with electrons emitted
by a continuously heated cathode to heat the
electrode. and limiting each period of bombard
ment to a time interval less than about 25 micro
seconds. said interval being so small that the
ionization of gas in the tube is insu?icient to
cause destructive bombardment of the cathode.
3. The method of making a vacuum tube having
an electrode, which comprises intermittently
trode, means for applying su?icient negative po
tential to the grid to cut off the electron stream
from the cathode to said other electrode, a pul
ser for intermittently making the grid positive
with respect to the cathode to effect intermittent
electron bombardment of the other electrode to
heat the latter for driving out occluded gas. said
pulser limiting each period of bombardment to
a time interval so small that the ionization of gas
the tube is insu?icient to cause destructive
2,403,745} a
heat the bombarded electrode for driving out 00
bombardment v‘of the cathode, and means for
cluded gas, said pulser limiting each period of
,
5
evacuating the tube during said bombardment.
9. In apparatus for making a vacuum tube
having a cathode and other electrodes, the com-,
bination with means‘for heating the cathode to
provide a source ofrelectrons, of a pulser for in
termittently applying a positive potential to an
I
electrode to effect intermittent electron bombard- “ r
ment of one-0f said electrodes, and thereby to
6
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l
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7
' ‘bombardment to a time interval so‘ small that
n the ionization of gas in the tube is insu?icient
to cause destructive bombardment of the cathode,
_ ' and means for evacuating the tube during said 7
‘
bombardment.
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ROBERT’ LEIGH NORTON.
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