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Oct. 22, 1946.
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2,409,715
ELECTRIYC ARC DEVICE
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Filed Jan. 27, 1942
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ATTORNEY
Patented @ct. 22, 1946
2,409,715
UNITED STATES PATENT OFFICE
2,409,715
ELECTRIC ARC DEVICE
Charles M. Slack, Glen Ridge, and Edward G. F.
Arnott, Upper Montclair, N. J., assignors to
Westinghouse Electric Corporation, East Pitts
burgh, Pa., a corporation of Pennsylvania
Application January 27, 1942, Serial No. 428,352
11 Claims. (Cl. 250—27.5)
1
2
This invention relates to electric are devices
and particularly to such devices having a liquid
cathode which operates with a stationary starter
or make-alive device, and constitutes a pulser
as well as a means for rectifying, controlling or
converting high voltage, and is directed to im
provements which have been introduced for the
purpose of overcoming difficulties encountered in
electric vapor-arc devices of the prior art.‘
The invention contemplates use of a vapor
izable reconstructing liquid cathode, constituting
and often designated a pool cathode. Inasmuch
as the pool is more often a liquid than a solid, and
ciently great to bring the electron up to the ion
izing speed before impact, ionization will take
place, the collision in this case resulting in more
electrons and positive ions being given off from
the gas molecule, the positive ions passing to the
cathode and releasing further electrons, this
process being cumulative and sustaining gaseous
conduction. The electrical conduction through
the gas increases with its pressure and the mean
10 free path of an electron becomes progressively
shorter with increases in pressure.
In view of the above dissertation, it will now
be recognized that an object of the present in
vention is to provide a pool type of electric arc
as mercury is commonly employed for the pur~
pose, the pool will be hereinafter designated as 15 device which will withstand high voltages effec
mercury, but it is to be understood that such
tively and without loss of control.
designation is merely a matter of convenience
A further object of the invention is to provide
and not to be construed as limiting, as the pool
a pool type of electric arc device which will not
may be of known substitutes of which various
only withstand high voltages effectively without
amalgams, as well as lead, cadmium, caesium, tin, 20 loss of controhbut which also will pass high
etc., are examples.
Analogous devices of the prior art have shown
ability to pass relatively high current at low
currents.
A still further object of the invention is to pro
vide 3, p001 type of electric arc device which will
. voltage, but to employ high potential with either
withstand high voltage, will pass high current,
high or low current, particularly at high fre 25 and yet which will have a rapid recovery time
quency, has heretofore eluded adequate solution.
, sufficient to enable the 'device to be used with
The invention herein set forth is directed to meet
higher frequencies than can be utilized in present
the present-day need of a pulser which will
effectively, and with long life, function with high
voltage, say 50,000 volts more or less.
day analogous devices.
Another object is to provide a device with
30 cathode-anode spacing relatively short and ar
‘
Operation of devices of the general character
ranged to eliminate long paths of electron travel.
Yet another object of the invention is to main
tain low vapor pressure during operation.
Still another object is to ignite the device by
cathode spot is formed, if the voltage between 35 low energies as compared with energies required
cathode and anode is sufficient, the main dis
by present-day standard form of ignitors.
charge will start. However, because of the ioniza
Additional objects include reduction of dis
tion present in the device, the possibility of loss
tortion of the electric ?eld by the ignitor; to
of control is considerably increased and has
maintain uniform electric ?eld between anode
proved to be a serious handicap in prior art de 40 and cathode; to coat all parts with glass which
vices. Study of the involved situation makes it
are subject to high gradients; to secure simplicity
clear that tendency towards loss of control in
of construction and operation; to prevent ac
under consideration depends upon use of a make
alive electrode, commonly referred to as a starter
or ignitor, to form a cathode spot. When the
part depends directly on the gas or vapor.v den
cumulation of ‘ mercury on undesirable portions
sity in the device; that lack of control increases
of the envelope; and to obtain other advantages
as the vapor density increases; that these factors 45 and results as will appear to those skilled in the
of gas and vapor density affect the mean free
art as the description progresses, both by direct
path of electron travel; and that loss of control
statement thereof and by implication from the
is more prevalent as the mean free path of elec
trons is shortened.
.
context.
‘
Referring to the accompanying drawing in
The mean free path of an electron in a gas, as 50 which like numerals of reference indicate simi
herein meant, is the average distance which an
lar parts throughout the several views;
electron travels under the in?uence of an electric
Figurel is an elevation of an electric are de
?eld impressed on the gas between impacts with
vice constructed in accordance with the present
gas molecules (or atoms) ._ If ‘the potential dif
invention;
.
V
ference through which the electron passes is suf? 55
Figure 2 is a central vertical-section‘thereof
2,409,715
3
with the scale of drawing enlarged over Fig. 1;
and
Figure 3 is a cross-sectional view on line III—
III of Fig. 2.
In the speci?c emboliment of the invention
illustrated in said drawing the reference numeral
l0 designates a metallic cathode cup next the
bottom of the device and numeral 1 i designates a
similar anode cup next the top of the device, the
hollows of the cups being directed toward each
other. The said cups are preferably composed of
a nickel-cobalt-iron alloy sold under the trade
name “Kovar.”
The rims of the cups are sealed
into the opposite ends of a cylindrical glass or
other suitable insulative body portion 12 inter
vening between the said cups and forming there
with a sealed and evacuated chamber [3.
By
preference, said body portion I2 comprises boro~
silicate glass for obtaining a permanent joint
In fact, we prefer to position and arrange said
cap so sputtered mercury passing beneath the
rim of the cap will strike the exposed part of the
cathode cup well below the lower edge of the
glass. In other words, an imaginary line from
the meniscus next the starter which extends out
wardly so as to be tangent at the under edge of
the rim of the cap and projected therebeyond,
will terminate at the envelope wall on the cathode
cup portion thereof below the glass part. Con
sidering such imaginary line the hypotenuse of
a right triangle of Which the other less are the
line of mercury surface and the height of inter
section with the side wall above the mercury,
calculation of proper spacing of the cap from
the mercury is obtained by solving a simple ratio,
the radius of the cap being known. The said
cap is preferably substantially semi-spherical
and as small as practical for accomplishing its
with the said cups which will not readily crack 20 purpose, reducing to a minimum any distortion
of the electric ?eld between the pool and the
or leak in use.
anode. According to the present showing, pro
The middle portions of-both cups are spun
or otherwise fabricated to form outwardly pro
jection of the cap above the pool is not sub
stantially greater than projection of the cathode
jecting hollow necks l4, l5, of which the neck I5
in the anode or upper cup constitutes an evacuat
cup thereabove.
ing opening which is ?nally sealed by a bead I6
likewise preferably of borosilicate glass.
It is desirable to keep the cathode pool as near
room temperature as practical, and in any event
at or below the temperature of the glass portion
!2 of the envelope which in turn should be at or
Cathode cup [0 has a starter electrode I'I
projecting upwardly and axially through said
neck l4.
As here shown, the said neck is cen
trally disposed with respect to the cup, thereby
'
30 below the temperature of the anode. Exemplary
of means for the purpose ?ns 23 are shown
locating the axis of the starter electrode coin
cident with the axis of the chamber and thus
equidistant in all radial drections with respect
to the side wall of the cup. The cathode cup is
partially ?lled with the mercury or other pool ma
radiating from and attached to the exterior of
the cathode cup. Other cooling or radiator
terial is, preferably leaving approximately half
the depth of the side wall of the cup exposed
one milliampere at one to two thousand volts
rod. This cap is downwardly facing, and by pref;
erance is dome-shaped and hollow, for providing
vTf desired, the thickness of the dielectric coating
means may be employed, however.
The tube constituting the present invention
may be ignited by very low energies, less than
being suf?cient. This is in contrast to many
above the mercury surface level.
amperes required with the standard form of
Electrode I‘! may conveniently comprise a wire 40 ignitor. There is no actual flow of current but
a static ?eld is formed between the dielectric
or rod of suitable metal such as tungsten or other
covered rod and the mercury pool which causes a
conductive or partially conductive material, said
tiny cathode spot to form on the mercury ad
wire being sealed by a glass or other bead l9 to
jacent to the ignitor which is su?icient to allow
neck M of the cathode cup. The structure con
templates glass-coating all of that portion of
the arc to form passing large currents with low
tube drop.
the wire or rod I‘! below the mercury level, an
upward extension 20 of glass in continuation of
It has been found that the introduction of the
the glass of bead l9 being shown for the purpose.
ignitor through the pool does not increase ap
An insulative cap or shield ‘2|, preferably of
preciably the energy requirements for igniting yet
glass, is carried at the upper end of the wire or
greatly increases the voltage standing ability.
an area for receiving mercury which sputters
from the cathode spot and to return that sput
tered mercury by gravity to the pool. By virtue
of the dome-shape of cap, the same presents an
outward and downwardly directed rim and said
rim is' brought into close proximity to the mer
below the mercury may be increased, thus lower
ing the electrical capacity as well as decreasing
the energy of ?ring and at the same time de
creasing the likelihood of failure due to electrical
puncture. The thickness of the dielectric at
the point of emergence from the mercury plays
the predominant roll in determining the voltage
cury surface level, but leaves a gap 22 between
requirements for initiating the arc.
60
the rim and the surface of the mercury.
Emphasis is given to the fact that present-day
Spacing and positioning of the rim of the cap
pool devices of analogous type to the present
invention, while capable of passing large currents,
with respect to the surface level of the mercury
as well as spacing with respect to the meniscus
of the mercury next the electrode, and with
respect to the exposed wall of the cathode cup are
important for several reasons of which one is
suffer partial or complete loss of control when
attempt is made to operate them at high voltages.
avoiding loss of control in operation, and another
is obtaining sharp and accurately timed valve
action. The cathode spot forms generally at
life and even at relatively high frequencies as
The device as constructed in accordance with the
foregoing description will, however, withstand
high voltage and operate successfully with a long
compared with other present-day pool devices.
or near the meniscus, and mercury sputtered 70 For instance, tests have demonstrated adequacy
thereby travels in nearly straight lines except as
of the present invention to function in the range
gravity may be effective to de?ect it downward.
of 1000 cycles and 100 amp. peak with applied
Accordingly, the cap is arranged to intercept any
potentials of 60,000 volts, to 2,000 cycles, 40 amp.
mercury sputtered in directions above the junc
peak and 30,000 volts. Structural features lend
ture of the glass body portion and cathode cup. 75 ing themselves to this accomplishment include the
2,409,715
6
r 5
limited projection of the ignitor with presence of
having opposed upper and lower metallic cups
the edges whereof are directed toward each other
and non-interferring character of the shield or
cap, reducing distortion of the electric ?eld be
and having an intervening insulative portion
tween pool cathode and anode; the described
sealed to and separating said edges and cups, a
spacing of cap edge from the mercury surface, to 25 cathode pool partially ?lling the lower one of said
obtain sharply synchronized valve action; the
cups‘, an ignitor electrode projecting upwardly
short distance between pool cathode and anode,
‘through said pool and above the same a distance
eliminating long paths over which an are back
less than projection of the said lower cup above
or glow discharge might form; prevention of un
the pool, and a shield around said electrode open
due rise in temperature of the pool cathode, 10 toward and in spaced proximity to and above the
maintaining low vapor density and limitation on
pool a distance materially less than spacing of the
mean free path of electrons; avoidance of mer~
lower edge of said insulative portion of the enve
cury deposit on the glass body of the envelope,
lope from the pool.
7
preventing formation of adverse conditions or
5. An electric arc device comprising an envelope
discharge thereby; protection of metal parts, such 15 having opposed upper and lower metallic cups the
as the starter electrode and the edges of the metal
edges whereof are directed toward each other and
cups by glass to avoid their being subjected to
having an intervening insulative portion sealed
high gradients and consequent break-down or
to and separating said edges and cups, a cathode
possible incipient discharges originating at either
pool partially ?lling the lower one of said cups, an
the anode or cathode end of the device; avoidance
ignitor electrode projecting upwardly through said
of sharp corners which might produce points of
pool and above the same, and a hollow shield
possible incipient discharge; and other features of
around said ignitor electrode opposed to and hav
construction and operation.
ing its lower edge in spaced proximity to a
Since the various details of construction and
portion of the pool thereby forming a continuous
steps involved in the method, as well as the pre
gap around the ignitor electrode between the
cise relation and functioning of parts are subject
shield and cathode pool, the space between the
to variation and change without departing from
pool and anode being entirely unobstructed at
the inventive concept or scope of the invention,
the sides of and above said shield, and said
it is intended that all matter contained in the
shield intervening in all straight-line directions
speci?cation or illustrated in the drawing, shall be 30 between said electrode and the said insulative
interpreted as exemplary and not in a limiting
portion of the envelope.
sense. It is also to be understood that the follow
6. An electric arc device comprising an enve
ing claims are intended to cover all of the generic
lope having an anode and a pool cathode spaced
and speci?c features of the invention herein
from the anode, said envelope having an in
shown and described and all statements of the b: ;, sulating cylinder as part thereof in the area oppo
scope of the invention herein set forth as a matter
site the space between the anode and cathode,
of language which might be said to fall there
an ignitor electrode protruding through said pool,
between.
and shield means intervening in all straight-line
We claim:
directions between said ignitor electrode and said
,1. An electric arc device comprising an envelope 40 insulating cylinderenabling said device to With
having an anode and cathode, said cathode pro
stand high Voltage effectivelyand without loss of
viding a pool, an ignitor electrode protruding
control.
through the pool, and a shield around said elec
'7. An electric arc device comprising an envelope
trode, said shield having a lower edge parallel
having an anode and a pool cathode opposed to
to the pool surface in spaced proximity to an 45 each other, an ignitor electrode protruding
underlying portion of said pool surface thereby
through said pool, and shield means supported by
forming a gap the length whereof parallels the
and overlying said electrode and having a free
pool surface and the width whereof is normal to
edge spaced radially therefrom and spaced from
the pool surface said lower edge of said shield
the pool cathode providing a continuous peri
constituting a limitation to exposure of the elec 50 pheral gap between said edge and cathode open
trode thereunder.
to the electrode enabling said device to withstand
2. An electric arc device comprising an envelope
high voltage effectively and without loss of con
having an anode and cathode at opposite end
trol.
portions thereof, said cathode providing a pool,
8. An electric arc device comprising an envelope
an ignitor electrode protruding through the pool, 55 having an anode and a pool cathode opposed to
and a downwardly directed hollow shield around
each other, an ignitor electrode protruding
said electrode, said shield having a lower edge
through said pool, insulation on said electrode
above and in spaced proximity to a portion of the
extending upwardly thereon above the pool sur
pool surface with the spacing from said surface
face with part of the electrode exposed thereabove,
providing a continuous, even and open gap at 60 and shield means supported by and overlying said
the entire lower edge of the shield, the entire lower
electrode and horizontally opposed to all exposed
edge of the shield constituting a peripheral limita—
area of said electrode enabling said device to with
tion to exposure of the electrode thereunder.
stand high voltage effectively without loss of con
3. An electric arc device comprising an envelope
trol and to pass high currents.
having an anode at one end portion thereof and 65 9. An electric arc device comprising an envelope
having a metallic cup at the opposite end thereof
having an anode and a pool cathode opposed to
and said envelope providing an insulative por
each other, an ignitor electrode protruding
tion between said cup and said anode, a cathode
through said pool, insulation on said electrode
pool partially ?lling said cup, an ignitor electrode
extending upwardly thereon above the pool sur
projecting into said cup from beneath said pool, 70 face with part of the electrode exposed there
a dielectric interposed ‘between said electrode and
beyond, and shield means supported by and over
the material forming said pool, and a shield sup
lying said electrode and having a free edge spaced
ported in its entirety by said ignitor electrode and
radially therefrom and spaced from the pool
situated in its entirety above said cathode pool.
cathode closer thereto than the spacing of the
4. An electric arc device comprising an envelope 75 exposed part of electrode from the pool cathode
I
2,409,715
7
8
whereby all straight-line directions radiating from
edge of the sides of said cathode cup for prevent
the exposed part of the electrode and passing un
der said free edge are prevented from sloping
the electrode going above the said sides of the
upwardly outwardly thereby enabling said device
to withstand high voltage effectively without loss
of control and pass high currents and promoting
rapid recovery time enabling the device to be
used with frequencies of 60 cycles and over.
ing sputtering of the pool material from adjacent
cathode cup.
11. An electric arc device comprising an enve
lope having an anode at one end thereof and a
metallic cathode cup at the opposite end thereof
below the anode, a pool cathode in said cup ex
tending partially of the height of the sides of
10. An electric arc device comprising an enve
lope having an anode at one end thereof and a 10 said cup, an ignitor protruding through said pool,
and a cup-like downwardly open shield entirely
metallic cathode cup at the opposite end thereof
above the pool cathode, said shield intercepting
below the anode, a pool cathode in said cup ex
all straight line directions of sputtering between
tending partially of the height of the sides of said
the point of protrusion of the ignitor through the
cup, an ignitor centrally disposed with respect to
the pool surface, and a cup-like downwardly open 15 pool and all points above the upper edge portion
of said cathode cup.
shield entirely above the pool cathode, said shield
CHARLES M. SLACK.
having a rim interposed in the straight line path
EDWARD G. F. ARNOTT.
from the center of said pool surface to the upper
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