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Патент USA US3073993

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Jan- 15, 1963
Filed July 21, 1959
—_—_—____________ ___
35' 7E 27 Tar-5
Patented Jan. 15, 1953
molded and fused in the ceramic insulator 18 so that the
Rolia B. Custer, Rte. 4, Box 429, San Joaquin, Calif, and
Clarence Field, 1335 17th Ave., Santa Cruz County,
inner cylindrical Wall 180 of the insulator ring forms the
upper side wall of the cathode pool container.
The metal dome 12 has an upper central opening ‘Silt,
and the annular portion of the dome around the open‘
ing is fused in a second ceramic insulator 52 which may
be made of aluminum oxide powder or the like. A tung
sten rod 54 is fused in the insulator 52 and extends down
Filed July 21, 1959, Ser. No. 828,514
4 Claims. (Cl. 313--165)
This invention relates to mercury pool discharge de
wardly through the insulator into the tube. Connected
vices and more particularly to an improved tube for such 10 to the lower end of the rod 54 is an igniter or control
electrode 56 which projects down into the mercury of
the cathode pool so that an electric current may be passed
An object of the present invention is to provide a dou
through the mercury to cause a spark which will initiate
ble mercury pool type tube wherein the mercury vapor or
the start of conduction or discharge of current from the
plasma must travel only a very short distance with the
result that the tube has a low plasma arc drop voltage and 15 cathode pool to the anode pool. For certain installa
tions, a keep-alive anode 58 may be fused in the ceramic
low power loss in the tube in relation to its electrical
insulator 52. The inside surface of the metal dome 12 is
lined with a coating 60 of an insulating, ceramic-enamel,
Another object is to provide an improved, liquid cooled
high temperature type material which is fused on the in
mercury pool type anode electrode that is free from
ner surface of the dome in a high temperature furnace.
damage from heat, electrical overloads, arc-backs, mer
The coating 66 prevents the metal of the dome from be
cury vapor ion bombardment and gas release and by the
coming an active part of the anode electrode and decom- limitations of radiation cooling such as is the case with
posing due to ion bombardment.
tubes using internal carbon anodes.
A further object is to provide an improved liquid
From the foregoing description, it will be noted that
cooled mercury pool type cathode electrode.
‘ 25 the envelope of the tube is formed by the closed dome 12,
the annular base plate 14, the cylinder 16, the insulating
Another object is to provide an effective automatic
ring 18, and the container 22.
It will be noted also that the cathode pool C is directly
and coaxially under the opening in the center of the
Another object of the present invention is to provide
a tube design which facilitates the design and construc 30 anode pool A. This orientation of the electrodes permits
the current conducting plasma discharge to flow upward
tion of a ceramic insulator having metal-ceramic seals
from the surface of the cathode pool to all parts of
that are vacuum-tight, mechanically strong and easily
the surface of the anode pool. The distance of travel
for the plasma is very short and, as a result, the tube
A further object is to provide a tube which is con
has a very low arc drop power loss. The anode pool A
structed of high temperature melting point metal and
is made much larger than the cathode pool because there
ceramic materials, and which can be heat treated and de
mercury level control for a double mercury pool type
gassed in order to obtain very high vacuum.
Another object is to provide a tube design wherein
is more heat developed at the anode than at the cathode.
A copper cooling jacket 79, which is brazed to the
lower surface of the base plate 14, is provided with pas
sages 72 through which water, oil, or a refrigerant may
be circulated to maintain the temperature of the mercury
in the anode pool within a proper operating range. This
A further object is to provide a tube design which sim
copper jacket is also used to provide terminals for con
pli?es the construction and attachment of liquid cooling
nection of conventional current carrying conductors.
Another object is to provide an improved cooling 45 Similarly, a second copper cooling jacket 75, which is
brazed to the external side of the base plate 22a of con
jacket which can also be used for high capacity current
tainer 22, is provided with passages 76 for a liquid cool
terminals and for tube mounting means.
ant. It is to be particularly noted that the circular area
Other and further objects and advantages of the pres
of contact between‘ the plate 22a and the jacket 75 is
ent invention will be apparent from the following de
scription taken in connection with the accompanying 50 large compared to the area of the upper surface of the
cathode pool. With this arrangement, particularly eifec~
drawing which illustrates, more or less diagrammatically,
tive cooling of the cathode pool is obtained. The jacket
a vertical central section through the tube of the present
75' also functions as the cathode current terminal and as
all the component parts can be made in molds or dies or
can be machined to close dimensions for production line
In the tube of the present invention an anode mercury
a means for bolting the tube to a buss bar for mounting
pool A is disposed in spaced relation above a cathode 55 purposes.
The external surface of the dome 12 is cooled by
mercury pool C. The anode pool A is contained in an
means of air forced thereover, or by means of a cooling
annular retainer which is formed by a lower generally
jacket (not shown) similar to cooling jackets 70 and 75.
cylindrical wall 12a of a generally hemi-spherical metal
Means is provided for maintaining the surface of the
dome 12, an annular base plate 14 which is welded at 15
to the end wall 12a, a cylinder 15 which is welded to and 60 anode pool at a desired level. During operation, mer
cury is condensed on the cooled, generally spherical
projects downwardly from the inner circular edge of an
shaped inner surface of the dome 12 and, as drops are
nular plate 14, an annular horizontal surface lea of a
formed, they drop back into the anode pool. This auto
ring-shaped ceramic insulator 18, and an upwardly pro
matic level control device comprises a small diameter
jecting wall 18b of the insulator ring. The annular plate
metal tube 80 which is fused in and projects through the
14 and the cylinder 16 may be made of stainless steel or
upstanding annular wall 18b of insulator 18 at a point
Kovar, while the insulator ring 18 may be made of very
somewhat Ibelow the desired surface level of the anode
high purity aluminum oxide powder or a material hav
pool. The tube 80 is bent upward at a right angle, and
ing similar insulating properties.
its upper over?ow lip or edge is at an elevation equal to
The cathode mercin'y pool is retained in a metal con
tainer 22. which has a circular base plate 22a of stainless 70 the desired level of the surface of the mercury in the
anode pool. When the surface of the mercury in the
steel or Kovar to the periphery of which is welded a
anode pool rises above the desired level, the excess mer
cylinder 22%) of similar material. The cylinder 22b is
pool type cathode with an area of 8 square inches.
Since both electrodes are forced liquid cooled, a continu
ous current rating of several thousand amperes is permit
ted. This is an improvement over present commercial
tubes using a radiation cooled carbon anode by a factor
of about 50, on the basis of cubic inch of tube size per
The exposed part of the overflow tube is shielded from
watt of power controlled.
While we have described a particular embodiment of
the plasma rising from the cathode pool by means of a
generally semi-cylindrical cover 82 which is closed at its
the invention, it will be apparent to those skilled in the
upper end and has a lower open end projecting down in 10 art that many changes and modi?cations may be made
to the cathode pool. The longitudinal edges of this ce<
without departing from our invention in its broader as
ramic cover 82 are disposed in close sealing engagement
pects, and we aim, therefore, to cover in the appended
claims all such changes and modi?cations as fall within
with the inner wall of the insulator ring18 and therefore
the plasma cannot use the over?ow tube as a short cut to
the true spirit and scope of our invention.
cury will pass over the upper edge of the over?ow tube
and a drop at a time will fall down into the cathode‘ pool.
With this arrangement the exact desired level is auto
matically maintained without the danger of a short cir
cuit, such as would occur if mercury were allowed to
?ow to the cathode pool in a solid stream.
the anode.
If for any reason excess mercury enters the
‘cathode pool, it may be removed by turning the tube up~
side-down for a moment and then returning it to upright
The mercury will automatically level off at
What we claim as new and desire to protect by Letters
Patent is:
. In a mercury pool recti?er tube, an envelope com
that vacuum tight seals be formed between the insulator
prising a dome shaped member closed at its upper end
and open at its lower end, an annular anode pool con
tainer having a ?rst wall connected to the lower end of
said dome shaped member and a second wall projecting
both upwardly and downwardly from said ?rst wall, a
ring and the adjacent parts of the envelope. In accord
cup shaped cathode pool container disposed below said
each pool.
As mentioned above, the insulator ring 18 forms part
of the envelope of the tube. Accordingly, it is necessary
annular container and having an upstanding side wall,
ance with the present invention, the insulator is molded
and an annular insulator in vacuum tight engagement
of aluminum oxide powder or like material with the two
with the downwardly projecting wall of said anode con
cylindrical members 16 and 22b embedded therein, un~
tainer and the upstanding side wall of said cup shaped
der very high pressure in a steel mold. After the mold
ing operation, the composite member is sintered in a
2. In a mercury pool discharge tube, a ?rst container
high temperature furnace until it becomes a solid fused
body which is resistant to heat and mechanical stress and 30 adapted to retain a mercury anode pool, an over?ow pipe
associated with said ?rst container and having an over—
strain. The cylinders 16 and 22b form, e?icient vacuum
tight seals with the ceramic and, for this reason, the cyl
?ow lip determining the height of the mercury in the
anode pool, a second container adapted to hold a mer
inders are electroplated with silver or copper and have
cury cathode pool disposed directly below said over?ow
holes cut in them in the area embedded in the insulator
to enable the ceramic material to form a better bond at 35 lip to receive mercury over?owing from said anode pool,
the interface, and also to make possible a stronger grip
and means de?ning an insulated conduit enclosing said
of the ceramic material on the metal. The metal is thin,
the gage being such that the slight difference in the co
efficients of expansion of the two materials cannot cause
overflow pipe and providing a passage for said over?ow
ing mercury that is shielded from the path of movement
cracking or other damage. Further, the insulator ring is
made very thick and is therefore much stronger than the
of plasma leaving the cathode pool.
3. In a mercury pool discharge device, a closed hol
metal cylinders.
low body, a pair of spaced pools of mercury disposed
within said body and providing an anode pool spaced
All materials used in the construction of the tube can
withstand high temperature and will not contaminate
permitting vaporized mercury from said cathode pool to
mercury under any condition. This enables the tube to
be degassed and evacuated in a high temperature bake
above a cathode pool with a passageway therebetween
move toward said anode pool, an over?ow conduit com
municating with said anode pool and projecting into said
out oven with the result that an excellent vacuum is
vapor passageway, and means disposed in said passage
more readily obtained, after which mercury may be dis
tilled into the tube and the evacuating tubulation 99,
which is fused into and through the top ceramic insu- '
later 52, is sealed 0E.
way and enclosing said overflow conduit to isolate the
interior of said conduit from vapor ?owing through said
passageway and to provide flow communication between
said over?ow conduit and said cathode pool.
4. In a mercury pool recti?er tube, a cathode electrode
comprising an insulator having a central opening and an
annular lower wall, a metal cup shaped member disposed
below said insulator and having a base larger in cross
In operation, the only exposed electrode material is
mercury, which cannot be damaged by bombardment of
mercury vapor ions, arc~backs, or heat. The aluminum
oxide coating and insulator are also inert to the effects
of heat and mercury arc bombardment, and so is tungsten.
Therefore, the current conducting capacity is limited only
sectional area than the area of said central opening and
having an upstanding wall embedded in said insulator at
a point spaced radially outwardly from said central open
by the mercury vapor pressure, which if too high can
ing, and a pool of mercury disposed in said cup shaped
prevent the operation of the tube, but cannot damage it
and, since the vapor pressure is kept under control by 60 member and extending under said annular lower wall
and upwardly into the central opening of said insulator.
the e?icient cooling system, the current capacity is di
rectly related to the rate of ?ow of the liquid coolant
References Cited in the ?le of this patent
through the jackets that are mounted under the pools and
to the cooling of the upper dome. In the present tube
the cooling is very eifective because almost the complete (i5
Szilard ______________ __ June 4, 1929
outer area of the tube is cooled and, accordingly, heat
is removed just as fast as it is developed.
The tube design of the present invention makes possi
ble the control of extremely large currents by a tube
having quite small physical dimensions. For example, 70
in a tube 12 inches in diameter and 9 inches high,_there
will be an anode electrode in the form of a mercury
pool with an area of 100 square inches and a mercury
Nagoaka et al _________ __ Dec. 17, 1929
Swann ______________ __ Dec. 1, 1931
Gaudenzi ____________ __ July 5,
Dawley ______________ __ Dec. 24,
Warmoltz ____________ __ July 25,
Hernqvist ____________ __ Dec. 29,
Riebs ________________ __ Dec. 6,
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