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Патент USA US2128070

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Aug. 23, 1938.
2,128,070
w. E. BAHLS
'ELECTRIC DISCHARGE DEVICE
Filed Jan. 10, 19:56‘
5.9
WITNESSES:
INVENTOR
MZZBI'EBd/Z 25.
BY
\7.‘
I
ATTORN
2,128,070.
Patented ‘Aug. 23,
1 UNITED STATES mes-r OFFICE
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2,128.0"
nwcrnrcnrscnsaoa navron
'Walter E. mm, Wilkinaburg. Pa” alaignor to
Westinghouse Electric a Manufacturing Com
pany, East "Pittsburgh, Pa” a corporation of
Pennsylvania
Application January 10, 1938, Serial No. 58,533
(Cl. 250-275)
Fig. 6 is a circuit diagram‘ illustrating one use
This invention relates to space discharge de
3 vClaims.
vices and is particularly adapted to those devices
which have a hot cathode and gas or mercury
vapor or‘ a combination of ‘the two for their
I a cathode 3.
‘working atmosphere.
It is an object of this invention to produce a‘
10
II
25
30
35
40
The cathode is provided with a
heating circuit including leads I and 6 which
device of the class described which may be used
for a recti?er having a high current-carrying ca?
extend through the press 2 to the ends of the
following description and the accompanying
cathode is also within the envelope.
cathode proper 3. The cathode proper consists
pacity and being capable of withstanding a heavy of a corrugated ribbon wound into helical form
and secured to the two leads 5 and 6. From one
difference of potential between the anodes with
of the leads depends a support ‘I holding a sup
out back?re occurring.
ply 8 of a getter-metal'which acts as a clean-up
‘It is a further object of this invention to pro
device when freeing the tube from gas prior to
vide a device of the class described with an elec
filling it with the desired atmosphere.
trostatic shield which assists in preventing back
The tube has two anodes l0 and H supported 15
?re and‘ also may act as a grid to control the
from the press by leads l2 and [3. »Where the
starting of the current.
It is a further object 01 the invention to pro- ' lead I2 emerges from the press, it is surrounded
vide a circuit such that the single grid controlling by an insulator M which may be the same glass
the device having a‘ cathode and a plurality of as the press or may be other ceramic material.
anodes may have impressed upon it a controlling Similarly, the lead I3 is surrounded with insu 20
lator IS. The insulators i4 and I5 surround the
potential.
'
leads substantially up to the terminal blocks II
It is a further object of this invention to pro
vide a circuit of the sort described in which the and II which constitute the anodes‘ proper.
A hollow cylinder l8 surrounds the anode HI
part of the cycle during which any one anode
carries current may be a predetermined fraction and a cylinder l9 surrounds the anode II‘. The 25
cylinders may be made of sheet metal and pro-.
of a cycle.
1
vided with ?anges 2| and 22 by which the two
It is a further object of this invention to ‘pro
halves of the cylinders are joined together. A
vide a shield which shall act as a barrier sepa
similar ?ange 23 constitutes the middle portion
rating the anodes.
'
of the shield and the junction of the two cylin 30
It is a further object of this invention to so
The shield as a whole namely l8, l9, 2|, 22
locate the openings in said barrier that they ders.
and
23
is designated 24 and it may be supported
shall, in effect, provide substantially distinct from the
press by a standard 25. It is electrically
paths between the cathode and the several an
although it may have been made of
odes, and any particular path shall be free and _ continuous
several portions united together. As shown in 35
unobstructed between the cathode and its anode.
It is a further object of the invention to so the illustration, the ?anges 2|, 22 and 23 are
spot welded together but any other desirable way
select the atmosphere in the tube, gas, mercury of uniting them into an electrically continuous
vapor, or mixture of gas and vapor, that the arc whole may be employed. It is unnecessary to re
drop and the starting potential shall have the 'de
sort to connections outside the tube to make the 40
sired values.
whole shield electrically continuous but all parts
Other objects of the invention and details of of the shield are connected within the envelope
the proposed structure will be apparent from the and if desired the connection of the shield to the
drawing, in which
45
of the device.
In Fig. l, the device is provided with an en
velope I having a press 2 upon which is mounted
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The inside of the envelope is equipped as
Figure 1 is a central vertical sectional view of shown at 26 with a conductive coating prefer
one form of my device.
a
ably formed by covering the inside or the en
Fig. 2 is a similar view, the plane of the sec
velope with a graphite solution. A conductor 28,
tion being at right angles to that of Fig. 1.
preferably of very ?ne ?exible wire, extends up
Fig. 3 is a similar section of another form of _ward from one terminal of the cathode 3 into
my device.
’
.
Fig. 4 is a sectional, view taken on the line
IV—IV of Fig. 3..
Fig. 5 is a sectional view taken on the line V-V
01' Fig. 4, and
contact with the coating 26. The whole of the
inside of the envelope is not coated, but only‘ the
portion adjacent one end of the space discharge
paths. In the form shown in Figs. 1 and 2 the
coating extends slightly below the upper end of 55
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8,198,070
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the shield 34.‘ In thefform shown in?!‘ 3'the . cated in Fig. 6 ‘by ‘the lead‘, II. For supplying
coating extends slightly belowthe anodes.
‘ ‘power to the anodes a transformerv "is shown
The thin and flexible wire 23 is
at one " in Fig. 6. A small secondary of the same trans
end of the cathode, and the cathode, anodes and , former or of another, .not'shown, is indicated at
5 shield are mounted in the press before-the press ' I53, as supplying the leads I and I and the oath
is united with the rest of theenvelope. Whenv
the tube is completed by putting the press into
Each anode is connected to the respective end
its place within the rest of .the envelope, the of the secondary of transformer 53. 4 The center
‘wire 23 comes into contact with the coating 2'; of said secondary is connected to the center of
10 No special care need he exercised in determining the secondary 53 and thus to the cathode. The
the length of the wire 23, as it is made long connection includes the load which is represent 10
enough to surely contact the envelope and can ed by the resistor 54 although it ,need not be
bend to accommodate itself to the space in which merely‘ resistive.
'
it is finally located.
r
_
The primary 5! of a transformer I‘ is illus
15 It will be'seen upon inspection of the shield trated as connected in parallel with the primary
‘
shown inv Fig. 1 that there is a direct line from of transformer 52. The transformer 3! includes 15
the anode ‘l0 to the left hand part of the cath-, ‘a primary 55, a coil 51 and a secondary coil II.
ode 3 uninterrupted by the shield and similarly The coil 51 is connected to the'same terminals
.a. direct line from anode II to the right-hand as the coil 55, an adjustable resistor 53 being in
part of the cathode 3 is not crossed by the shield. cluded in ‘one connection. The electromotdive
By a direct line I do not necessarily mean a forces induced in the secondary 53 are dependent
straight line, but one over which ions can travel both as regards phase and intensity on the ad
. without change of direction abrupt enough to Justment of the resistor 53. The coil 53 delivers
materially increase the ‘likelihood of the ions go
current to a full wave rectifier 83, preferably of
25' ing somewhere else instead of to the cathode, the copper oxide, type, whereby current flows
In Fig. 3_ the anodes ill and H are at the up
through one-half of the coil 33 and one-half of
per ends of standards continuous with the leads the full-wave rectifier during one-half cycle, and
I! and I3. The cathode is heated through leads through the other half of the coil and the other
,I and 0 which extend to. its twoends, as shown half of the rectifier during the next half cycle.
ode.
most clearly in Fig.‘ 5. A trough-shaped portion
'
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.
The transformer is so designed that the current
delivered by the secondary 53 has a sudden rise
to a maximum each half-cycle with small current
30 of the shield surrounds the cathode except at
the top thereof and is equipped with insulators
3| and 32 through which the leads 5 and 6 ex
tend. The trough "is open at the top and the
35 opening is divided by a shield 33 which extends
between the anodes it‘ and it into the space sur
during the other portion of the half cycle._ Al
though the drawing indicates one way of design
ing such a transformer, other ways may be used‘.
rounded by the coating 26.
7
The shield 33 is supported bytwo portions 35
and 36 which extend downwardly along the end
walls of the trough. The central portion of the
shield 33 extends into the interior of the trough,
abutting the inner face of the end portions as
‘shown at 3'8 and 38. The lower edge 38 of the
The return connection from the recti?er to
the middle of the coil 58 is through a resistor 30.
A connection between the end of the resistor 80
nearest the recti?er and the shield 50 is made by
means of a resistor 6|. A battery 82 is connected
between the end of the resistor 60 nearest the
transformer 55 and the middle of the second
ary 53.
shield is as near to the cathode 3 as it can con
veniently be located without danger of contact
therewith. The trough 30 is supported by a pair
of standards 4! and 42 which are joined together
' and supported from the press as clearly shown
'
When the tube is completed and evacuated it
is filled with neon or other desired gas to the
pressure decided upon. A small amount of mer
cury is also’ introduced if desired. With low pres
sure gas only the voltage drop along the arcs
in Fig. 3 at W. A weld or other securing means , formed between cathode and the several anodes
illustrated at 48 unites each standard to the is greater than if mercury also is present. With
trough.
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It will be noted that the shield of Fig. 3 af-‘
i'ords a direct line from the left hand partvof
cathode 3 through the left hand half of the top
of the trough to anode i0 and a direct line from
the right hand part of the cathode through the
5
right hand half of said top to anode Ii.
.
In Fig. 6 the cathode leads 5 and 6 and the
anodes I0 and II are identi?ed by the same
60 numbers. The shield designated 50 in Fig. 6
may have either the form'shown in Fig. 1 or that
shown in Fig. 3, or any other desired form. The
standards supporting the shield are illustrated
_ in Figs. 1 and 3 as if they terminated in the
65
press.
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The coating 26 in Fig. 3 is connected by a fine
flexible wire 23 to the shield. The coating is
thus kept at the same potential as the shield.
JI‘his is different from the arrangement of Fig. 1
0* in which when the shield connections are inside
of the envelope the coating is connected to the
other end of the cathode from the shield. If it
is desired to control the potential of the shield
by connections outside of the envelope, the stand
“ ard must extend through the envelope as indi
-mercury present the current characteristics of
the tube vary with temperature.
The djvice illustrated in Fig. 1 can operate
with th
shield disconnected from all external
connections or with "the shield connected to a
system such as is shown in Fig. 6.‘ If desired,
connection between the shield and a pointy of '
predetermined potential, such as one end of the
cathode, may be made within the tube. The
standard 25 does not then extend outside of- the
press. When this connection is used, the ?exible
connector 28 is connected to the opposite end of
the cathode 3 so that the shield is -at the poten
tial of one end of the cathode 3 and the interior
coating is at the potential of the opposite end.
When the tube is thus connected, during the
half cycle when the anode I 0 is positive, elec
trons ?ow from the cathode 3 to the anode II.
In the are thus established, there is a drop in
potential close to the cathode v3 the gradient of 70
which is much greater than the gradient through
out the rest of the arc.
In this space where the
gradient is large, the electrons from the cathode
travel at a speed sumcient to produce more ioni
zation than elsewhere in the gas with which the 75
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_ > tube is filled.
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9,128,070‘
hand, the shield can act as a grid, preventingthe
are from starting to the positive anode until a
certain critical potential has been passed. The
nearer the edge of the opening 'in the shield to
region, ‘surrounding the cath
' ode .and- usually not very thick ~‘ is called the
cathode space-charge sheath.
The sheath in which the electrons produce
most ionization in. the gas has a well-marked
the cathode, the greater is this grid effect. It is,
becomes greater this region becomes more nar
distance of ten times the thickness of the space
therefore, undesirable to have the shield much
boundary. 'Its thickness varies with the pressure ‘closer
to the cathode than the above-speci?ed
and the current density. As the current density
- row.
charge sheath.
Within this region the ions which are
attraction from the cathode. Most of these ions
fall into the cathode but not with su?lcient ve
cur for even at high potential a discharge will.
not form between the anodes. Around the nega
tive anode the shield and coating present a region
where the field is insufiicient compared to the field 15
locity to damage it because ‘the distance they fall
Electrons which escape from the space
charge
sheath
move to the anode Hi. There will
15
not be much acceleration of these electrons be—
'
is small.
of the cathode to move ions to the negative anode
tween the boundary of the space-charge sheath
and the anode because the potential gradient here
in sufilcient number to form an arc. ' The nega
is small. It is small because the space charge
to be overcome is small, being largely neutralized
by the ions present. The ions here are acted
being established.
tive anode is thus protected from anarc thereto
sheath. " That is the ions in the long part of’
the arc diffuse more than those in the narrow
space-charge sheath. The ions within the sheath
do not diifuse much because of the stronger elec
trostatic forces there. The diffusion of ions tends
to produce ionization throughout the tube but
negative anode. Although the negative potential
anode ll, very few ions will enter.
Ions between the mouth of cylinder l9 and the
cathode are attracted by the cathode 3, which
has a negative potential. The anode II has a
much stronger negative potential but it is sur;
rounded by the cylinder I! which is at the po
tential of one end of the cathode. The space
between the cathode 3 and the adjacent mouth‘ of
charge sheath, outside of which ions~may diffuse,
but ,within which little diffusion occurs. Ions
may proceed by diffusion to fill the space on one
side of the partition 33 within the trough and 40
form an arc stream between the trough and the
positive anode, but few ions will be present in the
tube on the side of the partition 33 toward the
the cylinder I 9 is near the coating 26 which
differs from the potential of the shield‘ I9 by
s
negative anode.
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When it is desired that the shield shallact as
a grid in either form of the device, it may be
connected to an external source of potential, as
indicated in Fig. 6. At the beginning of any par
The attraction of the negative anode ll upon
the ion between the cathode 3 and the opening
at the upper end of the cylinder l9 is'largely
neutralized by the shield 24 and the coating 26.
ticular cycle, current will ?ow through the resis
tor- Bll and through one-half, of the rectifier 63.
This current is toward the left in Fig. '6. The
right hand end. of the resistor 60 is therefore more
positive than the lower end of the battery 82 and
They therefore move toward the cathode 3.
It is different with‘ the ions between the oath
ode 3 and the mouth of the cylinder It. The
anode Ill therein is strongly positive at the time
and an arc is maintained between it and the
cathode 3, the ions in said are moving toward
the cathode and the electrons therein. moving to
ward the anode in the usual way. Therefore, al
though the ions in the long part of the arc stream
can diffuse and do diffuse, very few of them enter
‘ the region enclosed by the cylinder around the
anode ll. When thereversal of the potential
being rectified occurs, and‘the anode H becomes
positive, while the anode III becomes negative,
the arc stream will form between’the cathode 3
andv the anode l I and the cylinder l8 of the shield
will prevent the ions from proceeding to the
(now negative) anode l0.
cathode.‘ If preferred the. potential of the shield
may be controlled by connections extending out-‘
side the envelope as illustrated in Fig. 6, or by
other external connections if desired. This bar
rier prevents ions from being attracted by the
of the negative anode is strong compared to the
negative potential of the cathode, the ions do not
proceed to the negative anode because of this
electrostatic action of the shield. Around the
cathode .is formed the above-described space
into the cylinder I3 surrounding the negative.
>
I
lar considerations apply. The anodes are not
surrounded by the shield in this form, but a bar
rier is presented by the shield 33 which, together
with the trough 30, affords an electrostatic shield
at a potential corresponding to one end of the
that within the space-charge sheath. The er
‘ratio motion of the ions, similar to ‘that of gas
molecules, therefore, produces a more readily
recognized effect here than in the space-charge
only a small amount.
,
In the modi?cation shown in Figs. 3 to 5, simi
upon by a-potential gradient “small compared to
‘
In order that this action may take place de
p'endably,-although the di?erence in potential be
' tween the anodes be high, it is necessary that the
edges of the cylinders l8 and I 9 be fairly. close
to the cathode 3. In general it may be said that
the distance from the cathode to the nearest edge
of the opening in the shield ought not to be
more‘ than ten times the thicknessof the above
75 described space-charge sheath. 0n the other
70
‘
The device can be used effectively with high
anode potentials because back-?re does not oc
10 formed by the ionization are subjected to strong
the drop over the resistor must be subtracted
from the potential provided by the battery to ob
tain the potential of shield 50. When the result
ant potential of the shield is no longer sufficiently
negative to prevent the formation of an arc, the
arc starts. By proper adjustment of the resistor
59, and, if necessary, adjustment of the ratio be
tween the potential of the battery 62 and the re
sistance of the resistor 60, this critical potential
of the shield may be reached at any desired period
in the half cycle. All of these adjustments except
that of the resistor 59 are preferably permanent
and made when the apparatus is ?rst designed or
manufactured. The anode, which is at this time
active, can be made, therefore, to carry current
during only a fraction of that half cycle, and thus
the average current carried-by that anode can be 10
regulated.
During the next half cycle, the current ?ows
through the other half of the recti?er 63, but is
in'the same direction through the resistor ill, and,
the shield therefore, arrives at, the critical poten- 75
1
4
3,128,070
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tial at the same fraction of the next hall’ cycle. ‘cooled. The ?lament consists of seven turns- 01-‘ .
The other anode will thus carry an adjusted por; corrugated ribbon, .075 inch wide, and .007 inch . I
tion of current in the same way.
_ thick. It is 5% inches long before being corru
Another way of regulating the starting voltage ' gated and 4% inches long after corrugating. It
is by proper choice of~>the atmosphere filling the ' is wound into a coil of seven turns, 11; of an inch
tube.
II the atmosphere be wholly a gas, such as
between ends, % inch being allowed at each end
neon, the starting potential is smaller, but the
for mounting.v The shield 24 has a cylinder .531
voltage drop across the arc is higher than it the
inch internal diameter. The two external ?anges
tube be filled with mercury vapor.
By proper
10 combination of the two, any desired relation be
are a’, of an inch wide.
The ?at part of the cen
tween the starting voltage and the arc drop can
tral ?ange is 5'0! an inch wide, and the central 10
part has .062 inch internal diameter where it fits
be obtained.
the standard 2!.
' '
If the tube has some liquid mercury in it when
cold, the heat generated within the tube when
15 energized will vaporize the mercury increasing the
mercury vapor in the tube. The mercury vapor
will cause a diminution in the arc drop and thus,
at constant output, a diminution in the heat pro
duced. The tube will soon arrive at a steady
state in which the temperature is constant and
thus the pressure in the tube is also constant.
Thus the voltage drop and the starting potential
will each be fixed.
In order to disclose this invention more com
pletely, I am stating here the dimensional details
concerning one type of this tube which is in
extensive commercial use. I do not wish to be
understood as saying that this is the only type
which has achieved commercial success, nor do
I intend the speci?cation and claims to be lim
ited by the dimensional description here given.
This tube is used as a full-wave recti?er.
The
cathode is oxide coated and directly heated. The
heating current is 6.4 amperes and is supplied
with 2.5 volts. It requires 30 seconds to reach its
>
It will be apparent to those skilled in the. art
that many modi?cations besides those here ex
pressly described, can be produced. I, therefore,
do not desire that the invention be limited to 1a
what is here explicitly described. No limitation
not required by the prior art or expressed by the
claims is intended.
I claim as my invention:
20
1. A space discharge device including an en
velope, a cathode and a plurality of anodes, an
electrostatic shield electrically continuous within
the envelope separating said anodes and forming
a chamber about each anode with an opening for
each anode which leaves the direct line from such
anode to the cathode unimpeded, said shield ex
tending across all direct paths between any two
anodes.
,
2. A space discharge device including an en 30
velope, a cathode and a plurality of anodes, a
plurality of metal cylinders, open ends on said
cylinders, said anodes being respectively posi
tioned within said cylinders, said cylinders con
stituting electrostatic shields electrically continu
working temperature when starting cold. The" ous within the envelope and crossing all direct 35
alternating voltage between the anodes may be paths between any two anodes while said open
as high as 440 volts, and the average anode cur
ends leave unimpeded the direct line from each
rent output may be as high as 1 ampere. When anode to said cathode.
an anode reaches a potential of 30 volts positive
3. A space discharge device comprising a cath
with respect to the cathode, it will always have ode comprising a solid conducting body, a pair
started to carry current and the arc drop for the
conductive period will average about 131/2 volts.
The tube is 6% inches long from the top of the
part of the envelope, which is coated interiorly at
26 to the bottom of the connecting pins upon the
socket, which is not shown in the drawing. It is
2%; inches in diameter. It is ?lled with argon to
a pressure of 0.6 millimeter of mercury and is air
of anodes, and a pair of interconnected metallic
cylinders within which said anodes are respec
tively positioned to form a single electrically con
tinuous electrostatic shield having a portion in
terposed between said anodes, said shield having
two openings through which the direct lines from
each anode to the cathode pass.
WALTER E. BAHLS.
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