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Патент USA US2134578

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‘L Get. 25, 1938.
Filed Dec. 14, 1935
2 Sheets-Sheet l
l nventor':
Emil J. Remscheid‘
' b9 2/
is . Attorneg.
Get, 25, 1938,
Filed Dec. 1.4, 1955
2 Sheets-Sheet 2
Emil J. Remscheid,
b 26/y W
L»! .H 6 A
Patented Oct. 25, 1938
Emil J. Remscheid, Scotia, N. Y., assignor to
General Electric Company, a corporation of
New York
Application December 14, 1935, Serial No. 54,522
1 Claim. (Cl. 250—27.5)
My invention relates to insulating and sealing sufficiently to provide a vacuum-tight seal. Pref
means for use in connection with metal recep
erably the coating is of the nature of a porcelain
tacles operating under widely varying tempera
enamel or vitreous enamel baked on the rigid
ture conditions and containing a vapor or gas
5 undera predetermined pressure, such, for ex
ample, as the evacuated metal tanks of mercury
arc recti?ers.
The invention relates particularly to means
for insulating and sealing the cathodes, and in
10 certain cases the anodes, of metal tank mercury
arc rectifiers and the like, and its object'is to
provide means for this purpose which are simple,
of a high degree of reliability in operation, and
of low cost.
metal ring.
In usual mercury arc recti?er apparatus the
anodes are sealed from the evacuated receptacle
by a suitable sleeve insulator molded between an
anode supporting member and a cover member
of the receptacle or an extension thereof. In cer
tain cases, however, particularly in those mer 10
cury arc recti?er devices of the metal tank type
which have only one anode, the anode is prefer
ably directly supported by and electrically con
nected to a metal cover plate or similar member
In the mercury arc recti?er of the iron tank
which is then insulated and sealed from the
type, it is usually desirable to insulate the oath
ode from the metal tank, and for this purpose
the mercury is placed in a metal container be
low the tank and insulated and sealed therefrom.
It has been usual practice heretofore'to pro
vide, for this insulating and sealing of the oath
ode container, a large and heavy porcelain ring
interposed between metal sealing surfaces of the
evacuated tank. It is a feature of the present
invention that prior, not entirely satisfactory ar
rangements for insulating the anode cover plate,
tank and cathode container respectively. - To
25 insure a vacuum-tight seal, hoop-rings of metal,
such as aluminum, deformable under heavy pres
sure, are laid between the upper surface of the
large porcelain ring and the tank surface and
between the lower surface of the ring and the
30 container surface, and pressure is then applied
suiiicient to deform and crush the metal hoop
rings into intimate contact with the porcelain
ring surfaces and the metal sealing surfaces.
Dif?culties have been encountered, however, in
"35 the use of the above-described cathode porcelain
ring, such as breakage of the ring under the ex
tremely severe conditions of heavy pressure and
varying temperature incident to the operation of
high power mercury arc recti?ers. The breakage
40 of the procelain ring necessitates not only a rela
tively costly replacement but also the shutting
down of the recti?er for a protracted period and
the complete degassing of the unit in which the
porcelain ring breakage occurs.
In accordance with the present invention the
above-mentioned and other dif?culties are ob—
viated by the provision, in place of the porcelain
ring, of a rigid metal member or ring arranged
to operate as an insulator‘ by the application to
50 its surface of a coating of insulating material,
this material being of such characteristics, how=
ever, that the coating not only acts e?ectively as
such for example, as mercury seals, are dispensed
with, and the insulating and sealing of the anode
plate is simply and ef?ciently accomplished by
coating the plate with the vitreous material
above described, metal hoop-rings which are in
terposed between the coating and a sealing sur
face of the metal tank being deformed under 25
heavy pressure to form the seal.
My invention will be better understood from
the following description when considered in con
nection with the accompanying drawings and its
scope will be set forth in the appended claim.
Referring to the drawings, Fig. l is an ele
vational view, partially in section, of a mercury
arc recti?er or the like of the metal tank type,
in which a cathode insulating and sealing means
in accordance with my invention has been em
bodied; Fig. 2 is an enlarged sectional view of a
portion of a mercury arc recti?er embodying a
cathode insulator and seal in accordance with
my invention, and Fig. 3 is an elevational view.
partially in section, of a single anode mercury
arc recti?er in which an anode insulating and
sealing means in accordance with my invention
has been embodied.
In Fig. 1 the numeral l0 designates a device
comprising a metal receptacle or tank H con
taining a medium under a predetermined pres“
sure, this device in the present embodiment of
the invention being shown for illustrative pur~
poses as a mercury arc recti?er of the multi—
an insulator but is able to withstand without
anode, evacuated metal tank, mercury pool type
having an opening l2 in the lower portion of
the tank, below which opening is mounted a
metal member [3 constituting a cathode con
cracking, peeling or other damage, the heavy
55 pressure required to deform the metal hoop-rings
tainer. To aid in sealing the opening l2, instead
of the usual porcelain ring I provide a rigid ring
M, which may be in form and size substantially
the same as the porcelain ring, but which is
formed of metal, preferably steel. The ring may
be of substantially square cross section as shown
C71. in Fig. 1, or may be of other suitable section, for
example, the rectangular section shown at IS
in Fig. 2. Hoop rings l6, preferably two, of rela~
tively small cross-section and formed of alumi—
num or other metal deformable under heavy
10 pressure are laid between the ring I4 or l5 and
a metal sealing surface I‘! of the receptacle H,
and a similar pair of hoop rings l8 are laid be
tween the rings 14 or l5 and a metal sealing
surface i9 of the cathode container [3.
To insulate the cathode container I3 from the
receptacle ll the rigid metal rings, M or l5, are
provided with a coating 20 (clearly indicated in
Fig. 2) of insulating material, which in the pres
ent embodiment of the invention is a porcelain
enamel or vitreous enamel preferably having sub
stantially the composition: 8.6% feldspar, 30.4%
borax, 31% silica, 3.7% sodium nitrate, 4% soda
ash, 22.3% calcium carbonate, 1% cobalt oxide,
and 1% nickel oxide. Preferably the ring is given
two coats of the enamel, the first coat being
baked on at a furnace temperature of approxi
mately 830° C. the second coat then being applied,
and baked on at the above temperature. After
the second coat the insulating surface is given a
high potential test, for example, of 3000 volts.
If desirable a third and possibly a fourth coating
of the enamel may be given the ring, all coat
ings being kept relatively light to insure a smooth
When the insulation coated metal rings M or
£5 and the hoop-rings l6 and [8 are in position
in the apparatus 10, the cathode container [3 is
drawn upwardly toward the receptacle I l by suit
able means such as bolts 2 l , causing a heavy pres
iii) sure to be exerted upon the hoop-rings between
the enamel surfaces 20 and the metal sealing
surfaces IT and i 9, thereby deforming and crush
ing the hoop-rings to form a vacuum-tight seal.
The hoop-rings, being of relatively small cross
section, present to the enamel coating a re1a~
tively small area of contact per unit length.
Nevertheless, I have found that the relatively thin
enamel coating withstands, without crushing, the
heavy pressure concentrated along the small area
5; 3 and required to deform and ?atten the hoop
I have found that in operation of the mercury
arc recti?er apparatus illustrated in Figs. 1 and 2,
the insulating and sealing means, comprising the
enamel coated rigid steel rings, 14 or l5, and the
aluminum hoop-rings l6, [8 held under heavy
pressure between the enamel coating 20 and the
metal surfaces 11 and I9, maintains a high vac
uum in the tank H and at the same time with
stands the severe expansion and contraction ef
fects due to the relatively large temperature var
iations incident to the operation of the recti?er.
The cathode insulating and sealing means illus
trated in Fig. 1 therefore retains all the advan
tages of the prior means which included the por
celain ring. Further, however, since the rings M
or I5 are of steel instead of the fragile porcelain,
breakage of the ring, and the attendant above
described expense, is entirely prevented, and the
life of the cathode insulating and sealing portion
of the apparatus is practically unlimited.
In Fig. 3, the numeral 22 indicates a mercury
arc recti?er or like device comprising a metal
receptacle or tank 23 and having only one anode
24, which is supported by the tank cover plate 25.
Preferably the anode is directly connected to the 15
plate 25 as by screwing the anode to a metal
stud 26 which may be welded to the plate. To
insulate from the metal tank 23 the anode 24,
thus electrically connected to cover plate 25, the
plate 25 is provided at least on its under surface
21 with an enamel coating 28 as described in con
nection with Figs. 1 and 2. To seal the anode,
attached to cover plate 25, hoop-rings 29, similar
to hoop-rings l6, l8, are interposed between the
enamel coating 28 and the metal sealing surface
30 of the tank 23, and heavy pressure is applied
to cover plate 25, as by bolts 3|, to deform and
crush the hoop-rings 29 into intimate contact
with the coating 28 and the surface 30.
The operation of the anode insulating and seal 30
ing means illustrated in Fig. 3 will be readily
understood by reference to the description of
operation of the cathode insulating and sealing
means of Figs. 1 and 2.
My invention has been described herein in par C13 Cl
ticular embodiments for purposes of illustration.
It is to be understood, however, that the inven
tion is susceptible of various changes and modi
?cations and that by the appended claim I in
tend to cover any such modi?cations as fall 40
Within the true spirit and scope of my invention.
What I claim as new and desire to secure by
Letters Patent of the United States is:
In an arc discharge apparatus comprising an
evacuated metal receptacle and an electrode,
means to insulate and to seal said electrode from
said receptacle including a metal member, a seal
ing ring of metal deformable only under rela
tively heavy pressure, a thin coating of vitreous
enamel on said metal member including approxi- ,
mately 8.6% feldspar, 30.4% borax, 31% silica,
3.7% sodium nitrate, 4% soda ash, 22.3% calcium
carbonate, 1% cobalt oxide, and 1% nickel oxide,
said sealing ring being interposed between said
coating and a metal sealing surface of said appa
ratus, and means to press said ring between said
coating and said sealing surface to deform sub
stantially said ring, thereby to form a vacuum
tight seal between said metal member and said
sealing surface.
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