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Патент USA US2122932

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July 5, 1938-
Filed March 23, 1934
2 Sheets~Sheet 1
July 5, 1938-
I Filed March 23, 1934
2 Sheets-Sheet 2
‘Patented July 5, 1938
Ora S. Du?’endack and Ralph A. Wolfe, 'Ann
Arbor, Mich.
Application March 23, 1934, Serial No. 716,972
10 Claims.
This is a continuation in part of our prior ap
plication Serial Numbe r 668,753, ‘?led May 1,
This invention has to do with a gaseous dis
charge tube distinguished from prior tubes in.
that when relatively low voltages are ‘applied to
it, it will permit passage of very large currents
‘without undue disintegration of- the electrodes.
Thus when subjected to voltages as low as 100
10 to 200 volts peak currents of the order of 100 to
125 amperes may ?nd their way through the tube.
Our tube is capable of operating in this manner
‘ at very short intervals and enduring such opera
tion for a long period of time.
Another characteristic of our improved tube is
that the breakdown voltage is critical. Thus un
til the required voltage is reached, the tube acts
as an excellent insulator, but when that voltage
is attained, the tube becomes almost instantly an
excellent conductor. This is of advantage espe
cially in engine ignition circuits where the amount
of energy available to produce the spark is lim
ited and needs to be conserved.
The rapid breakdown of the tube sets up in
the tube circuit a high frequency wave. The high
frequency of the discharge is of especial use in
ignition systems in that it practically removes the
possibility of failure of plugs to spark because of
leakage paths such as result from carbon and
other deposits on the insulator.
Another feature of our preferred form of tube
is that with certain designs and types of elec
trodes it is sensitive to the action of light, espe
cially after it has been in use a sufficient time so
that metal volatilized by the arc has formed a
coating on the interior of the tube.
Our improved tube in its preferred form is
(Cl. 250-275)
erably not greater than on the order of 1.75 mm.
From another point of view an essential re
quirement other than low work function is that
the gas pressure and distance between the elec
trodes shall be such that the latter is ‘at least
greater than the mean free path of the electrons.
In the use, of the tube as a photoelectric tube,
the design requirements are necessarily different.
Fundamentally the only essentials seem to be
that the low work function electrodes immersed 10
in the inert gas be impressed with a voltage slight
ly less than the breakdown voltage of the tube
and that there be provided within the tube, either
on the electrodes themselves, or on the wall of the
container or in the form of a third member, a sur
face which gives oif photoelectrons when exposed
to light. These photoelectrons then ionize the
gas and so reduce the voltage across the gap that
an are forms.
This mode of operation is distin~
guished from that commonly employed in photo
electric tubes in that the electrons from the pho
toelectrically active surface do not serve as the
chief conductor for the arc current but function
primarily to “trigger off" the are between elec
trodes which are of substantial size and of good
Another important difference is
that in the conventional photoelectric tube the
photoelectrons serve as the principal carriers of
current while in our tube their principal function
is to ionize the gap to permit passage of current
in the manner customary in are or glow discharge.
In the drawings we have illustrated in Figure 1
one form of tube.
, :
Figure 2 is a top plan view and Figure 3 is a
bottom plan view of one of the electrodes of
Figure 1.
Figures 4, 5, 6, and 7 are views showing modi?ed
characterized by electrodes of durable material
of low work function in an atmosphere consisting forms of electrodes.
Figure 8 is a perspective view of the electrodes
~10 of an inert gas or mixtures of inert gases, with
shown in Figure 7.
or without the addition of mercury vapor to re
Figure 9 is a section through another design of
duce the break-down voltage.
The tube has been especially developed for use.
with the impulse ignition circuits described and the electrodes of Figure 9.
Figures 11 and 12 show other forms of elec
in claimed in the prior application of Ora S. Duffen
dack, Donald W. Randolph and Ralph A. Wolfe, trodes.
Figure 13 shows our improved photoelectric
Serial No. 668,754, ?led May 1, 1933, and in the tube.
application of Donald W. Randolph and Hector
Rabezzana, Serial No. 727,888, ?led May 28, 1934,
and for such use we have found it essential that
the work function of the electrodes shall be less
than on the order of 2.4 electron volts, that the
gas pressure shall not be less than on the order
of 2.4 cm., and that the distance between elec
trodes shall be not less than .20 mm., and pref
Inasmuch as this tube was developed primarily
for use in the impulse ignition circuits previously
referred to we shall ?rst refer brie?y to the re
quirements for successful operation of a'tube in
such circuits and shall then describe the con
struction of the tube which satis?es them. In
such circuits a magneto, or battery and interrupt
er, or the like are connected to the terminals of a 55
2 .
. condenser to intermittently‘ charge it. The tube
and the primary of a step-up transformer, ar
‘ ranged in series, are connected across the termi
of the electrodesof Figures 1 to 3,-and'in addi- :
tion the advantage that the discharge is shielded
- from the action of light. Such shielding is of
nals of the. condenser. The secondary 'of the
transformer is connected through a conventional
distributor to the usual spark plugs. When the
value in case ‘the electrodes contain or give off
materials which become active when exposed to
light and affect the starting voltage of the tube
charge on the condenser has attained the neces
as hereinafter described.
In Figures 9 and 10 there is illustrated a modi
sary potential at discharge takes place betweenv
the tube electrodes producing a spark at the plug ?cation of the electrodes of Figures 7 and 8 in
10 to which the distributor directs current. It is that one end of the cylindrical electrode is
required of the tube that it shall not break down closed.
Figure 11 shows electrodes having hollowed
until the voltage applied to the condenser reaches
a su?iciently high value so that the energy stored portions facing each other. The advantage of
in it is ample to provide a spark at the plug this is that the electrodes may be set with the
edges so close together that the discharge will
15 capable of igniting the mixture. At the same time
not strike to the edges but plays on the inner
the break down voltage of the tube must be suffi
ciently low to ‘permit the use of magnetos or other hollowed portions and thus the disintegration
charging devices of simple, inexpensive construc- , ' of the edges is prevented.
tion. Satisfactory tubes have carried peak cur
rents as high as 125 amperes when subjected to
around 115 volts.
We have illustrated one of the tubes in Fig
ures 1 to 3.
The tube consists of an envelope,
preferably of glass, within which are sealed two
electrodes, slightly spaced apart. The envelope
contains an inert gas "or mixture of gases, with
or without addition of a metallic vapor such as
mercury as described later on.
In Figure 4 we have shown one of the ?rst
forms of electrodes we have used.
The surfaces
of the electrodes are closest to each other along
the axis and then separate. as the edge of the
electrodes is approached.‘ This design has the
advantage that the discharge will be con?ned
35 to the region adjacent to the axis instead of
playing upon the electrode edges and at times
jumping to the backs of the electrodes. However it has the disadvantage that the life of
the tube is likely to be reduced because the dis
charge plays upon but a small part of the velec
trode surface and may soon destroy it, thereby
increasing the distance between electrodes so
that the tube may fail to operate.
We have also used electrodes having the shape
45 shown in Figure 5. Here the ?attened central
portions afford a considerable area for the play
After some experience with all of these elec
trode shapes we have standardized on electrodes 20
in the form of simple disks such as are shown
in Figure 12 with faces approximately 18 mm.
in diameter and 2 mm. thick. With this shape
there is a' tendency for the discharge to strike
to the edges of the disks and to shift about in 25
position. Such shapes, of course, have the ad
vantageof simplicity of manufacture.
For cold operation the cathode at least must
be made either wholly or partly of materials of
low work function. The electrodesmust like 30
wise be durable and capable of resisting the ef
fects of the are over .long periods of time.
In general, we have found it to be essential
for the successful operation of the tube in the
ignition‘ circuit that the cathode have a work
function not greater than 2.4 electron volts.
This work function corresponds approximately _
to that‘ of a nickel-barium alloy of approximately
17% barium content. The elements strontium,
barium,‘ rubidium, caesium, potassium, sodium
and lithium have work functions within this
limit. . Magnesium ‘is on the border line, having
hardly low enough work function for continu
ous successful operation.
While use of pure metals of sufficiently low
workfunction is indicated, in practice it has
been found that they are too unstable to with
of the discharge.
We have also successfully employed electrodes stand the action of the arc. It has consequently
of the typeshown in Figure 6 but here again
50 the life of the tube maybe reduced owing to
the fact that the discharge is con?ned to a rela
tively small portion of the surfaces of the elec
been necessary to use stable alloys or other com
pounds containing comparatively high. propor
tions of the low work function material. We
have had the best results with alloys of nickel,
copper and barium; nickel, copper, chromium
In Figures 1 to 3 we have shown a design ' and barium; aluminum and barium; copper and
barium. The ?rst two give similar character
exposure of the tube to light is not ob
jectionable. This design is much the same as istics to the tubes and are in most respects
that shown in Figure 5 except that a hole I! is equivalent. Aluminum-barium alloys used were
drilled in the center of each electrode. The hole somewhat porous and full of gas, the release of
reduces the initial starting voltage, operating which caused somewhat erratic operation of the
tube. The specimens of copper-barium alloy (Si)
upon what is known as the hollow cathode prin
ciple. This action is due in part to the greater tested contained less barium than is necessary
curvature at the edges of the hole. The effect, for‘ satisfactory operation over a long period of
however, does not persist on account of the
We have found it very desirable that the elec
transfer of electrode material from the cathode
to the anode. ‘Another characteristic of this ‘trodes be made of uniform material. In gen
design is the hollowing out of the back of the ' eral, it is our conclusion that the sounder, the
electrodes at l5. This is done to‘ reduce the mass more homogeneous and the cleaner the alloys,
of the electrodes so that less treatment will be the more satisfactory was the operation of elec
. trodes-made from them.‘
required to outgas them.
We have had most success with alloys contain
In Figures '7 and 8 we have shown another de
sign in which one electrode is in the form of ing nickel and barium. We have made a num
a solid cylinder and the other is in the form of ber of tests to determine the percentage of barium
a longer hollow cylinder surrounding the ?rst. that is necessary in the electrodes of the neon
This has all the advantages of large discharge tubes. Neon ?lled tubes have been operated suc
75 surface, and rounded edges just as in the case cessfully for as long as 200 hours-at 6,000 sparks
‘seems to us to be the lower‘ limit of barium con—
tent for successful commercial operation. Tubes
‘?tted with alloys containing 6%- barium have
been} operated for more than 900 hours and it
‘per minute when ?tted with‘ electrodes contain
.ing as low as 0.7% barium, and this. amount
seem that this ‘amount of bariunnisaxade
, We have successfully employed in our tubes
disappear more rapidly, shortening the life of
The. inert gases suitable for use in the tube
are helium, neon, argon, krypton and xenon.
Ourexperience indicates the possibility of their
vapors'such as mercury, caesium, potassium and
electrodes made of alloys of nickel, copper and‘
Tubes have been made to operate satisfactorily
barium and of nickel,.copper, barium and chro
when ?lled with neon, helium, argon or krypton.
mium described and claimed in the copending _ Owing principally to its availability and low cost
application of D. W. Randolph, _S.
740,537, most of our work has been done with neon gas
‘ filed August 18, 1934.
Of all of the compositions so far tested, the
following has given the best results:
Nickel _______________ __» _____ __'_,_ _____ __ 58%»,
Copper _____ _‘_ ________________________ __ 35
Barium _________________________ __‘ ____ __
Chromium ____________________________ __
either alone or as the principal gaseous constit
Marked improvement in the operating char
acteristics of the neon tubes has resulted from
the addition of traces of argon, krypton, or mer
cury vapor. ‘ These added materials have lower
ionizing potentials than neon, and hence in 210
creased ionization results. As a consequence the
‘The electrodes must be thoroughly outgassed
starting voltage of the tube is reduced. The ad
in order that the gas in the tube may remain
25 pure and the current and voltage characteris
dition of 0.01 per cent to 1 per cent of argon or
. tics of the tube remain constant. This outgas
use either alone, or in mixtures of'varied propor
lions, with or without the addition of metallic
'mercury vapor, for instance, will, reduce the
starting voltage of a neon tube‘from about 150
volts to about‘ 100 volts. Such a reduction of
starting voltage is of extreme importance in the
sing may be accomplished in various ways. One
method consists in operating thetube at a low
gas pressure and a relatively high voltage, of the use of these tubes in the ignition circuit previous
30 order of 2,000 to 10,000 volts alternating cur
rent or‘ direct current. A current of 200 milli
In addition, the introduction of argon, krypton, 30
amperes at 2,000 volts will quickly heat the elec
or mercury vapor'into the neon, results in the pro
trodes to incandescence. The same thing can ’ duction of ‘sparks of greater energy.
be accomplished by a less current at higher volt
Mercury has the added bene?cial effect of act
age or by a larger current and lower voltage. ing as a “getter”, particularly for hydrogen. The
Thus itwas found possible to outgas the barium
action on hydrogen is important because this gas 35
nickel alloy electrodes by operating the tube on a is less easily removed from the rare gases than are
220 volt circuit. Either alternating current or other contaminations. It has been observed fur
direct current may be employed for this pur
ther ‘that there is no tendency for the electrodes
pose, but alternating current is preferred as to bridge over and short circuit when the mixed
then both electrodes have the same "treatment,
gases‘are used, particularly when mercury is pres
We have had especially good results by operat-,
ing the tube ?lled'with a charge of ‘neon gas in av
220 volt, 60 cycle alternating current circuit un
til the ‘electrodes are brightly incandescent. . The
' gas used is later pumped‘ out. While this process
. is somewhat wasteful of gas and the electrodes
! are‘somewhat dulled by the treatment, the re
sults have been very satisfactory.
Another ‘method consists in heating the elec
trodes with high frequency induced currents in
a high'vacuum.
Pumping of the tube is con
tinued during the degassing proce‘ss. The elec
trodes retain bright surfaces throughout, the
There is some evaporation of the
The mercury-neon mixture has the disadvan
tage that the concentration of mercury vapor is
not constant but varies with the temperature of
the tube. Thus in very cold-weather the amount
of mercury vapor is reduced at the start and its
effect on the discharge is likewise reduced. Tubes
?lled with a mixture of neon and argon do not
have this defect as argon does not condense at
the lowest temperature that would prevail in
winter. Therefore,‘ neon-argon mixtures are to
be preferred over neon-mercury mixtures.
combination of ‘neon, argon, and mercury has
been found to be most satisfactory as the argon
metal and a thin film of metal accumulates on . reducing the starting voltage of the cold tube suf
the‘surface of the tube but this does not impair
its operation. We believe this method is prefer
able for electrodes of nickel-barium alloy con
?ciently and ‘the bene?cial e?ects of the mercury
are active shortly after the tube has been put
into operation. A mixture containing argon at
taining 4% or more of barium.
.01 mm. pressure and the mercury vapor that is _
As a modi?cation of the last mentioned method .‘ ' represented by the saturated vaporat the tem
y it may be desirable to give the electrodes prelim
, inary treatment in a separate vacuum chamber
before mounting them in the tubes. If a thOI“.
ough outgassing is accomplished in an auxiliary
chamber, it is not necessary to heatthe electrodes ‘
to ‘the point where they begin to evaporate rap
idly after they are mounted in the tube. By this
method the‘ deposition of metal and metallic ox
ides on the walls of the tube is minimized.
To permit passage of current of su?icientlyi
high peak value it is essential that'the tube be‘
?lled with gas, preferably inert gas, although this
is not essential. The advantage’ of using inert‘
‘ gases'is that they do not readily “clean up” or
otherwise disappear from the tube. Other gases
perature of the tube has been found to be very 60
satisfactory and tubes so ?lled‘ have practically‘,
‘no varition in starting voltage with the tempera;
ture. The neon pressure should be about 65 cm.
of mercury.
We have also introduced into the tube inert gas
or mixtures of inert gases together with caesium
vapor, potassium vapor or lithium vapors and
have obtained substantially the same effects as
in the casev of- mercury. , These vapors not only
reduce the starting voltage of the tube and in
crease the energy of the spark, but also act as
getters and alloy with the electrodes to keep the
work-rfunction down. In general some or all of
theseeffects may be expectedto be attained by
any of themetals that will persist in the vapor
state atthe operating temperature of the tube
and possess a lower ionizing potential than the
gases employed.
In filling the tubes with gas we have found it
highly desirable‘ to take especial precautions to
remove impurities from the gases introduced. In
because any accumulation of metal on one of the ~
electrodes, due to sputtering or some other proc
ess, may cause a bridging of the gap and the
short-circuiting' of the tube. Gap distances on
the order of 1.75 mm. appear to be the maximum
desirable in practice. Best results have been ob
tained with nickel-barium electrodes of from 4%
to 6% barium content, gas pressures of 60 to '15
cm. of mercury, together with gap distances of
order to removethe contaminations, a charcoal
trap was interposed between the neon supply and
from .5 mm. to 1.75 mm.
10 the tube to be ?lled. Cocoanut charcoal, cooled
We have discussed the principal factors that de
to the temperature of liquid air, removes prac
tically all the common gases by absorbing them, termine the performance of this tube, 1. e.; work
function of the electrodes, gas pressure, distance
whereas not a great quantity of neon is ab
sorbed. 'In addition, various “getters” such as between electrodes and the character of gas, with
15 magnesium, barium, and lithium, and various or without metallic vapor, employed in the tube. 15
combinations of these, were flashed in the tube We have speci?ed that for satisfactory operation
being ?lled or in the connecting lines to the in the ignition system herein disclosed the oath
gas supply or both. By these methods, much ode, at least, should have a work function not
purer gases were introduced into the discharge more than 2.4 electron volts; that the gas pres
sure should be not less than 2.4 cm. of mercury; 20
'20 tubes, and, as a result, the starting voltage of that
‘the distance between electrodes should be
the tube was lowered and remained much more
nearly constant. The “getter” ?ashed in the not less than .020 cm., and, with existing elec
tube itself had no effect on the operation of the trode materials, not greater than approximately,
tube and took upany contaminating gas that .175 cm. We have also grouped pressure and dis- .
25 might be released from the electrodes or tube _ tance together under the criterion that the gas .
walls during the operation of the tube. It seems
necessary to ?ash a “getter” in each tube not con
taining mercury in order to insure that it will
have a constant starting voltage and this practice
30 has been adopted as standard.
We have varied the gas pressure over a range
pressure times gap distance shall be such that
the latter is greater than the mean free path of
the electrons. These relations between all of these
variables may also be indicated by the following
(Gas densityXgap distance)
from .5 cm. of mercury to above atmospheric
pressure, 1. e. '76 cm. At the lower pressures
there is a tendency for the discharge to take the
35 form of a glow and to limit the current to too
shall not be less than K, where K‘ is a constant
dependent upon the kind of gas or gas and vapor
I small a value. For this form of discharge, elec
trodes of larger effective area than have been
used are demanded, and the performance will be
equation the limits of the quantities in the case
Work function
employed and the units used in measuring den
sity, distance and work function. Inserting in the
subject to the disadvantages previously pointed
40 out. The higher the gas pressure, the greater is
the peak current of the discharge and hence, the
larger the E. M. F. developed in the secondary of
the transformer of the ignition system. A high
of neon we have
initial pressure is desirable on account of the
45 gradual clean up of the gas. The higher the
shall not be less than K or .000000237 shall not be
less than K. In other words, .000000237 is the
initial pressure the longer, in general, will be the
life of the tube, but there is the accompanying
disadvantage that the gap break-down voltage
increases with increase in pressure.
27%X.000902 (gr. per cm.3))<.02 (cm.))
2.4 (electron-volts)
value of K for neon if density is measured in
grams per cubic centimeter, distance in centime
ters and work function in electron volts.
Our research indicates that any tube conform
We have found the lower practical limit of . ing to these requirements will give satisfactory
gas pressure to be on the order of 2.4 cm. of mer
cury. The preferred pressure is near atmos
pheric between 70 and 75 cm. Trouble is experi
enced in sealing the tubes if an attempt is made
55 to use pressures above atmospheric.
A number of tests were made to determine the
optimum distance between the electrodes. This
distance depends on the pressure of the gas and
the starting voltage desired. At low values of
60 this product, however, the law is not valid and
the starting voltage again rises with decreasing
values of the product. Thus at the lower gas
pressures it is possible to have the electrodes so
operation in the ignition circuits of the character
previously referred to.
The'interrelation of factors indicated in the
formula is, of course, involved in any specific
design of tube and may be made clearer by the
following discussion. It will be apparent that the
lower the ‘work function of the electrode, the
higher may the gas pressure be raised and still
maintain satisfactory operation characteristics.
In generaL'the peak voltage increases with an 60
increase in gas pressure and when the pressure
becomes too great the .peak voltage may become
higher than the voltage that can be developed
close together that the starting voltage is above‘
across the condenser. . But ‘the peak voltage also
65 the minimum. Over ‘a considerable range of
values of this product, near the value for mini
depends upon the work function and hence a
lower work function material will permit increas
ing the gas pressure. The lower the work func
tion the greater can be the separation of the
mum’ starting voltage, the starting voltage
changes-very slowly with changes in the value
of this product. It is‘in this range that it is de
sirable to have the tube operate.
In general the product of gas pressure and
distance between the electrodes should be greater
thanthe mean free path of the electrons. From
‘ the standpoint of practical manufacture and op
75 eration gaps of less than .20 mm. are undesirable
electrodes for the same reason.
For high speed operation, a low work function 70
cathode is essential. At high speedshthe con
denser cannot be charged to as high voltage as
at lower speeds. Hence, the starting voltage of
the tube must not be higher than the voltage
that can be attained at’ the highest operating
speed, and yet the peak current passed by the
tube must be sufficient to develop an E. M. F. in
the secondary of the transformer high enough
to cause a spark at the gap. In order to attain
the required current, the gas pressure must be
adequateand so a low work function material
for the cathode is demanded.
Our tube is capable of operation within a wide
range of temperatures.
We have successfully
operated a tube chilled to the temperature of
liquid air, i. e. -196° C. We have also employed
heated cathodes. In the application of heat
there is no limit to the temperatures which may
be employed other than such as are imposed by
disintegration of the electrodes or of the mate
rials of which the tube walls are made.
If it is convenient to heat the electrodes, in
spite of the cost, inconvenience, and complica
tion, then a greater choice of electrode materials
is afforded for the application of heat increases
, the emission of electrons. We have successfully
employed in gas ?lled tubes such as herein
The tube is so designed that the voltage ap
plied to it is slightly below that necessary to
break down the gap in the tube. When light
strikes the coating 40 the photoelectrons given
off by the action of light ionize the gas in the 5
gap causing it to break down under the action 01'
the applied voltage.
It will be understood that our photoelectric
tube may also be employed to close any circuits
desired, for example, lighting circuits, and if de
sired no provision need be made for subsequent
opening of the circuit other than the usual hand
operated switches. In general, the tube will be
of use in any of the relations in which photoelec
tric tubes with their usual relay circuits are now
employed. For example the motor illustrated in
Figure 13 may be employed to open a door and the
circuit breaker or breakers could be operated
by the door operating mechanism so that when
the movement was completed the circuit would
be broken and reset for the next cycle of opera
tions which, by the employment of suitable re
disclosed, electrodes made of a base material, versing motor and reversing switches, might, if
such as nickel, coated with compounds of elec desired,
accomplish subsequent closing of the
tron emitting materials as in vacuum tube manu
iacture, such as the oxides or carbonates of the
alkaline earth metals, especially barium and
strontium. Such electrodes are preferably acti—
vated in known manner to increase their emis
sivity as by heating in vacuum for a certain
period of time. Where heating is permissible, a
number of elements, such as pure tungsten, will
‘ give satisfactory
emission, as will also alloys such
as described herein with too little material of
low work function for cold operation. Heating
of the cathode may be accomplished by radiation
from an adjacent ?lament supplied with current
from'a battery or other source. Gas ?lled tubes
such as herein disclosed provided with heated
40 cathodes made of a wide range of materials will
give satisfactory results, but the necessity of at
least preliminary heating makes them less desir
able for many uses. Heating of the cathode per
mits some reduction of the minimum gas pres
sure but ‘if too low pressure is used, for example
on the order of a fraction of a millimeter of
mercury, the secondary voltage at the spark
is reduced and becomes too low to produce con
stant sparking of the plugs.
We have also discovered that certain of our
tubes possess marked photo-electric properties.
The tubes possessing these properties are made
with the nickel barium alloys, and the best of
them have coatings of metal or metal oxides or
55 both on- the walls of the envelope. The most
light sensitive of the tubes are those having
electrodes containing nickel, copper and barium,
and the coatings on the envelopes are believed
to consist of, copper oxide,‘ nickel oxide, and bari
60 um, nickel and copper metal volatilized by the
discharge. Of these materials barium and cop
per oxide are known to possess marked photo
electric properties and it is believed they account
for the performance. We have also noted this
action in tubes containing chromium in addition
to the materials just mentioned and‘ in such
case it is likely that the coating contains a pro
portion of chromium metal.
In Figure 13 there is illustrated one form of
such tube. It is of the construction previously
described consisting of spaced electrodes 36 in an
atmosphere of inert gas. 40 indicates a light
sensitive coating onthe interior walls of the en
The electrodes may be supplied with
power from any suitable source.
It will be understood that when our tube is
used as a photoelectric tube to control the flow
of a considerable current through the action of
light, it is necessary to apply to the electrodes
a voltage almost but not quite equal to the break 30
down voltage of the gap. The photoelectrons
given ‘oif by the action of light on the photo
sensitive surfaces break down the gap by ioniza
tion by impact, so that the phenomenon may
properly be described as trigger action.
It is quite clear that the photo-sensitive sur
face need not be on the walls of the tube but
may be on one or both of the electrodes or may
be in theform of a third member. It is clear, too,
that the light sensitive member need not be made 40
of material volatilized from the electrodes but
may be formed separately of any suitable light
sensitive materials and mounted in the tube. Or
if desired it may be formed as a ?lm on the walls
of the envelope by volatilizing metals therein by
the same methods now in use in introducing get
ters inside the tube. It will be apparent that
should the tube be used to carry a steady current
there is no way in which the flow when once
initiated may be interrupted by light action. It
will of course be necessary to provide for open
ing of contacts in the circuit by the device, for
example, a servo-motor, that may be actuated
by the flow of current through the tube.
It will be apparent that our improved tube is
capable of many uses. It, in effect, constitutes
an electric valve which breaks down on the ap
plication of relatively low voltages and permits
passage of currents of high peak value and is
further characterized by long life and constant
performance characteristics. It is to be expected
that many uses other than those herein men
tioned will develop in the future. As a possible
example, the tube may‘ ?nd use as a lightning
arrester or protector for transmission lines.
It has been previously pointed out that if the
tube is photoelectrically active and voltage is
applied to it that is slightly below the breakdown
voltage of the gap, a beam of light may be used
to ionize the gap and cause the tube to discharge.
Obviously under the same conditions, the gap
may be broken down by a momentary application
of higher voltage instead of by the use of light.
If the circuit containing the tube is supplied
with alternating current, the discharge in the
8, 122,938
phere consisting predominantly of neon with
tube, once initiated, will be either continuous or
discontinuous depending on the frequency. If
the frequency is su?lciently high so that there is?
not suilicient time between alternations to permit
the gap to de-ionize, the discharge will be con-'
small proportions of another inert gas and a
metallic vapor, said last-named gas and vapor
being of lower ionizing potential than neon, the
pressure of said atmosphere being not‘ less than
tinuous in the sense that any flow of alternating -
current is continuous. If the frequency is so low
that there is su?icient time for de-ionization be
tween alternations there will be but one discharge
vless than 3%, said tube containing an atmosphere
of inert gas at a pressure not less than 2.4 cm.,
the distance between electrodes being not less
with direct current there will be but one surge
of current followedby continuous discharge. ‘In
such case, of course, but one impulse will be re
ceived in the coupled circuit.
Obviously the ?ow of energy released in either a
main circuit or coupled circuit as a result of dis
We claim:
than on the order of .2 mm.
7. An arc discharge tube comprising a plurality
of spaced, durable electrodes, one of which con
sists of a homogeneous alloy containing nickel,
copper and barium, the barium content being at
least on the order of 31%, said tube containing an
atmosphere of neon together with small propor 20
charge through the tube maybe used in any way
in which electrical energy is used, as to produce,
heat, light, radiation or mechanical movement.
6. An arc discharge tube comprising a plurality
of spaced, durable electrodes one of which con
sists oi.’v a homogeneous alloy containing nickel,
copper and barium, the barium content being not .
through the tube. Where the circuit is supplied
on the order of 2.4 cm.
tions of argon and mercury at a pressure not less
than 2.4 cm., the distance between electrodes be
ing not less than on the order of .2,mm., and not
greater than on the order of 1.75 mm.
8. An arc discharge tube comprising a plurality 25;
of spaced, durable electrodes one of which con
tains from 4 to 6% barium, said tube containing
an atmosphere consisting predominantly of neon
with small proportions of argon and mercury, the
pressure of said atmosphere being on the order of
1. An arc ‘discharge tube comprising a plurality
of spaced, durable, electrodes, one of said elec
trodes comprising material of low work function,
said tube containing a gaseous atmosphere inert
25 to the electrode material and the tube wall, the
product of gas ‘pressure times gap distance divided
by work function being not less than .000000237
times a constant characteristic of the inert gas
2. A gaseous dischargev tube containing neon
and a pair of electrodes, one of which is composed i from 60 to 75 centimeters of mercury, said elec
of an alloy of nickel, copper, barium and trodes being separated from each other by not
less than approximately .5 millimeter and not
3. An arc discharge tube comprising a plurality more than approximately 1.75 millimeters.
. 9. An arc discharge tube comprising a plurality
35 of spaced, durable electrodes one of which con
‘spaced, durable electrodes, twb of which com
sists of a homogeneous alloy containing at least
.7% barium, said tube containing an atmosphere
consisting predominantly of neon with small pro
portions of argon and mercury, the pressure of
40 said atmosphere being not less than 2.4 cm., the
distancebetween electrodes being greater than
on the order of .2 mm, but not greater than on
the order of 1.75 mm.
prise material of low work function and having
opposed active surfaces of substantial area, said
tube, containing a gaseous atmosphere inert to
the electrode material and the tube wall, the 40
product of gas pressure times gap distance divided
by work function being not less than .000000237
times a constant characteristic of the inert gas
4. An arc discharge tube comprising a plurality employed.
10. An arc discharge tube comprising a pair of
'45 of spaced, durableelectrodes one of which con ' spaced, durable electrodes each consisting of a
sists of a homogeneous alloy containing from .7%
homogeneous alloy containing from .7 %, to 6%
to 6% barium, said tube containing an atmos
phere consisting predominantly of neon with barium and having opposed active surfaces of
small proportions of another material. of lower substantial area, said tube containing an atmos
potential at a pressure not less than on phere consisting predominantly of neon with
small proportions of another material of lower
the order of 2.4 cm., said electrodes being sepa
potential at a pressure not less than on
_ rated from each other by not less than approxi
the order of 2.4 cm., said electrodes being sepa
mately .2 mm.
5. An arc discharge tube comprising a plurality rated from each other by not less than approxi
spaced, durable electrodes one of which con-v mately .2 mm.
sists of a homogeneous alloy containing from .'I-%
to 6% barium, said tube containing an atmos
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