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Патент USA US2407494

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Sept. 10, 1946.
|__ p‘ HART, JR
2,407,493
ELECTRIC APPARATUS
Filéd May 16, 1942v
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Inventor:
Lucas F’. Hart J11,
b‘y ?Hiséttorney.
2,407,493
Patented Sept. 10, 1946
UNETE
STATES PA'E'EQN'E‘
FENCE
2,407,493
ELECTRIC APPARATUS
Lucas P. Hart, J12, Pitts?eld, Mass, assignor to
General. Electric Company, a corporation of
New York
Application May 16, 1942, Serial No. 443,217
1i) Claims. (Cl. 174-17)
1
2
My invention relates to electrical apparatus
having an insulating ?uid and to a synthetic rub“
It is, therefore, another object of my invention
to not only satisfy the above requirement but to
go beyond it and provide a combination in which
the insulating liquid and gasket material coop
her-like material for use in the apparatus and in
contact with the ?uid.
Electrical apparatus, and particularly high ten
sion apparatus, such as transformers are gener
ally ?lled with an insulating ?uid which has a
crate, beyond mere tolerance of each other, so as
to produce a joint that is tighter and otherwise
also more dependable than that which could be
secured by a combination in which the insulating
relatively high insulation strength. However, the
liquid and the gasket material are merely mutu
insulation strength of conventional insulating
?uids, such as insulating liquids, is susceptible of 10 ally neutral.
Further objects and advantages of my inven
deterioration when contaminated by minute
tion will become apparent from the following de
amounts of moisture and other impurities, so
scription referring to the accompanying drawing,
that joints and openings in the apparatus cas~
and the features of novelty which characterize
ing must be maintained relatively tight far be
yond that required for ordinary liquid containers lo my invention will be pointed out with particularity
in the claims annexed to and forming a part of
so as to prevent seepage of the insulating ?uid
this speci?cation.
or entrance of impurities from the atmosphere
In the drawing, Figs. 1 and 2 illustrate curves
into the apparatus casing. Gasket materials of‘
which will be used in the description of my in
various kinds have been used for apparatus where
the susceptibility of contamination of the insulat 20 vention; Fig. 3 is a side elevation, in partial sec
tion, of a relatively high-tension transformer
ing ?uid is relatively unimportant, such as in low
which is provided with an embodiment of my
tension devices, but for electrical apparatus such
invention; Fig. 4 is an enlarged view of a por
as high-tension transformers, common gasket ma
tion of the joint between the cover and the eas
terials have not proven dependable, particularly
ing of the apparatus illustrated in Fig. 3; Figs.
when certain high quality insulating liquids are
5 and 6 illustrate gasket constructions which may
used in the apparatus casing. Thus, in some cases
be employed in the construction illustrated in
it has been the practice to weld the cover to the
Figs. 3 and 4, and Fig. 7 illustrates a joint be
container so as to secure a fluid-tight seal and,
tween a bushing and a cover which may be pro
therefore, prevent the entrance of deleterious im
vided with an embodiment of my invention.
purities into the transformer tank and insulating
By virtue of its resilience, rubber has made an
?uid.
excellent gasket material for many purposes.
It is, therefore, an object of my invention to
Thus, pasteurized, rubber-gasketed, canned or
provide an electrical apparatus having an insu
bottled food products keep unspoiled for years,
lating ?uid with a relatively high insulation
showing that apparently even microscopic con
strength, with an improved arrangement for pro- <
tamination cannot penetrate such a joint. Rub
viding a substantially ?uid-tight seal between a
ber, however, has been found to be unsuccessful
removable portion and the casing of the appa
as a gasket with electric apparatus which contains
ratus.
mineral oil and‘ particularly other insulating
Another object of my invention is to produce
?uids, such as certain halogenated hydrocarbons.
a liquid-insulated high-tension transformer with
Exposed to these hydrocarbons, rubber swells up
a high-quality liquid insulation and a dependably
and disintegrates. It
therefore, been cus
sealed long-life gasketed container superior to
tomary to use cork-composition gaskets for elec
what has been available heretofore and suitable
tric apparatus having an insulating ?uid such as
in many cases as a substitute for a, welded joint.
halogenated hydrocarbons, an example of such a
A further object of my invention is to provide
product being a cyclic chlorinated hydrocarbon
an electrical apparatus with an improved com
including diphenyl, which is described and
bination of an insulating ?uid and a rubber-like
claimed in Patent 1,931,373, issued to Clark, and
material.
assigned to the same assignee as this present in
In providing a gasket between the casing and
cover of an electrical apparatus having an insu 60 vention. Chlorinated hydrocarbons of these
types are strong solvents, and materials used in
lating ?uid therein, an important requirement is
connection with transformers which are resistant
to secure a combination of liquid insulation and
to mineral oils are easily attacked and disinte
gasket material which will be mutually tolerant at
grated by chlorinated hydrocarbons. Some of the
least to the extent of avoiding deleterious effect
on each other.
rubber-like arti?cial compositions which have
2,407,493
3
been developed in recent years and which show
excellent resistance to some hydrocarbons, such
as gasoline, have also been found to swell up
even more than rubber and to deteriorate rapidly
when exposed to various halogenated hydrocar
4
than rubber in chlorinated hydrocarbons, and in
spite of the characteristics described above which
show that this material is unacceptable as a gas
ket material in such chlorinated hydrocarbons as
carbon tetrachloride, I have found that rubber_
bons, such as the group described in the above
like or synthetic elastomer compositions such as
mentioned Clark patent. Thus, in “Product Engi
neering” for March, 1941, at page 152, it is stated
that certain types of synthetic rubber-like ma
terials including copolymerized butadiene and 10
those including butadiene, and particularly those
which include a copolymer of acrylonitrile with
in the range of approximately 25 .to 40%, and
butadiene within the range of approximately 60
to 75% when in contact with hydrocarbons of the
halogenated cyclic or aromatic hydrocarbon type,
such as chlorinated aromatic hydrocarbons in
cluding chlorinated diphenyl, not only swell up
much less than rubber but that the plasticity
thereof is maintained and substantially no
acrylic nitrile or styrene swell up more than rub
ber in the presence of chlorinated hydrocarbons
and organic bases. I have veri?ed this and
found that synthetic rubber-like materials of the
general types described in this publication swell
up to a much higher degree than rubber in such
chlorinated hydrocarbons as benzyl chloride, di
shrinkage, after initial expansion, occurs. Thus,
chloroethylene and chloroform. It was also found
by curve [4, in Fig. 2 I have illustrated such char
that not only did the rubber-like materials show
acteristics of a material having approximately
a much greater swelling than rubber in these 20 40% acrylonitrile and 60% butadiene as the base
chlorinated hydrocarbons but that their tensile
ingredients, the days that the material was im
strength decayed considerably.
mersed in the liquid being plotted as abscissa and
In spite of the general tendency of such syn
the per cent volume increase being plotted as or
thetic rubber-like compositions of swelling con
dinate. Curve l5 indicates the characteristics of
siderably and deteriorating in the presence of
natural rubber, and curve I6 indicates the char
chlorinated hydrocarbons, it is known that nat
acteristics of a rubber-like material having chlor
ural rubber swells considerably more than cer
oprene as the base polymer. Such relative char
tain synthetic rubber-like materials, such as
acteristics were determined with the liquid at a
chlorobutadiene in carbon tetrachloride. Such
temperature of approximately 100° C. It is ap~
characteristics of these rubber-like materials are 30 parent that such a characteristic as curve M for
described in the “India Rubber Journal” for Sep
rubber-like compositions in a chlorinated cyclic
tember 23, 1939, at page 12. It was determined,
hydrocarbon was quite unexpected since the prior
however, that when synthetic rubber-like com
knowledge of the behavior of these materials
positions which contain a copolymer of acrylo
showed them to be unacceptable as a gasket ma
nitrile and butadiene were placed in carbon tetra
terial in chlorinated hydrocarbons.
chloride at elevated temperatures the swelling
Although it appears that a rubber-like com
was not maintained constant but after the mate~
position including butadiene and particularly
rials were in the carbon tetrachloride at around
butadiene copolymerized with acrylonitrile loses
70 degrees C. for a few days they shrank about
its plasticizer in the chlorinated aromatic hydro
40 per cent of the amount they had previously 40 carbons also, such as those including chlorinated
expanded or swelled when they were ?rst placed
diphenyl (as it was observed that the solvent
into the carbon tetrachloride. Such a charac
turned the same brownish color as did the carbon
teristic would, of course, be undesirable if the
tetrachloride), the unexpected property of the
material were being used as a fluid-tight gasket
maintenance of the plasticity of the synthetic
material of the type necessary for high-tension
rubber-like material in the case of the chlori
electrical apparatus referred to above. This
nated aromatic hydrocarbons appears to result
shrinkage after a swelling may be accounted for
from the fact that this particular family of halo
by the plasticizer in the rubber-like composition
genated hydrocarbons has the characteristics of
being dissolved by the chlorinated hydrocarbon.
displacing the dissolved plasticizer and function
This conclusion is verified by the fact that the
durometer hardness during this shrinkage after
the previous swelling increased considerably, thus
indicating that the plasticity of the material de
ing as a plasticizer itself, and thereby substan
creases as it remains in the hot carbon tetra
chloride. Another indication that the plasticizer
is removed is that it was noticed that the carbon
tetrachloride took on a brownish color as the
tially maintaining the plasticity and preventing
shrinkage of the synthetic rubber material after
its initial expansion when placed in the solvent.
Such a synthetic rubber-like material which
has the above desirable characteristics when in
contact with a chlorinated aromatic hydrocarbon
such as of the chlorinated diphenyl type may be
e?iciently employed in an electrical apparatus
rubber-like material began to shrink.
The relative changes in volume for rubber and
which has such a chlorinated hydrocarbon as a
certain types of synthetic rubber-like composi 60 ?uid insulating material. Referring, therefore,
tions in carbon tetrachloride are illustrated in
Fig. 1 in which the number of days that the ma
terial was in the solvent is plotted as abscissa and
the per cent volume increase is plotted as ordi
nate. The curve indicated by the numeral i 0 in~
dicates the characteristic of a synthetic rubber
like composition including approximately 40%
acrylonitrile and 60% butadiene for its base in
gradients. vCurve ll illustrates the increase in '
volume for a synthetic rubber of a composition
including chloroprene, while curve 12 shows the
characteristic of rubber.
However, contrary to this prior knowledge that
synthetic rubber-like materials such as those in
cluding butadiene swell up considerably more
to Fig. 3, I have illustrated a high-tension trans
former which includes a casing 20 having a cover
2|.
On the cover are mounted a high tension
bushing 22 and a low tension bushing 23. In
order to take care of thermal expansion and con
traction a conventional conservator or expansion
chamber 24 is provided, and the casing may be
completely ?lled with any suitable insulating
?uid including a halogenated aromatic hydrocar
bon, such as a mixture of said halogenated hy
drocarbon that also includes halogenated di
phenyl. Within the casing is a magnetic core 25
having a conductor or a relatively high tension
winding 26 which is adapted to be connected to
a stud 21 of the bushing 22.
2,407,493
6
Referring to Fig. 4, the tank and cover are
sealed together so as to provide a relatively ?uid
tight seal through a structure including a shoul
ticizer for said copolymer being dissolvable in
said ?uid at operating temperatures of said ap
paratus, said fluid having the characteristic of
der 28 which may be attached to the outer sur
face of the tank cover around the top. The
replacing the dissolved plasticizer so as to main
tain substantially the plasticity of said gasket
material, whereby a ?uid-tight seal is main
tained between said adjoining portions of said
tank.
shoulder is provided with an outwardly extend
ing ?ange 23 against which the cover 2! is adapt
ed to be tightly secured in any suitable manner
such as by means of bolts 30. The shoulder 29
2. In an electrical apparatus having a tank, a
is .provided with a peripheral recess 3| which is 10 cover for said tank, an insulating ?uid and an
adapted to receive a gasket ‘J2 composed of any
electrical conductor within said tank, said ?uid
suitable material having the improved charac
including a halogenated aromatic hydrocarbon
teristics of having its plasticity maintained with
and being susceptible of contamination with im
purities from the atmosphere, and means in
cluding a gasket between said cover and tank
providing a substantially ?uid-tight seal, said
gasket being formed of a material comprising a
plasticized copolymer of butadiene and acrylo
nitrile, the plasticizer for said copolymer being
dissolvable in said ?uid at operating tempera
tures of said apparatus, said fluid having the
characteristic of replacing the dissolved plasti
cizer so as to maintain substantially the plastic
ity of said .gasket material, whereby a substan
tially fluid-tight seal is maintained between said
a halogenated aromatic hydrocarbon, as de»
scribed above. With the cover bolted tightly in
place against the upper surface of the ?ange 29
the depth of the recess 3| at the joint may have
any suitable size in relation to that of the gasket
32, such as being approximately two-thirds the
height or thickness of the unswollen dimen~
sion of the gasket 32. In this manner the gasket
will be compressed between the adjacent surface
of the cover 2| and the surface de?ning the
recess 3 I.
In Fig. 5 I have illustrated a gasket construc
tion 33 which has a slanted joint 34 in a plane
tank and cover.
parallel to the axis of the ring but not passing
3. A high-tension electrical apparatus com
through the axis. This manner of providing a
seam in the ring makes it easy to manufacture
the ring gasket by slicing a thick sheet material ‘
having its opposite edges beveled on opposite
faces and then having the sheet bent into a tu
bular form. An alternative form of seam is il
lustrated in Fig. 6 in which the plane of the
same will be seen to be slanting with respect to
the axis of the gasket. A slanting seam of either
type results in a tighter seal under the com
prising in combination a container, a cover on
said container, a high-tension electrical conduc
tor and a high-quality liquid insulation within
said container, said insulation including a chlo
rinated aromatic hydrocarbon, a mechanical
joint exposed to said liquid and to an external
medium, gasket means in said joint to maintain
the high quality of said insulation free from
contamination from said external medium, said
gasket means including a copolymer of acrylo
pression due to the bolts 38 and the tendency
nitrile and butadiene, and compression means to
to swell due to any seepage of the enclosed liquid
compress and maintain in compression said gas
into the seam.
40 ket means in said joint, said gasket means and
In Fig. '7 I have illustrated a portion of a bush
compression means providing and maintaining a
ing having a flange 31 which may be attached to
substantially ?uid-tight seal between said con
a cover 38 of any suitable apparatus, such as a
transformer or capacitor in any suitable manner
tainer and cover.
such as through bolts 39. A peripheral recess i’
4B is provided in the upper surface of the cover
21 to accommodate a gasket of the shape shown
in Figs. 5 or 6 and composed of the material as
prising in combination a container, a cover on
described above. By tightening the bolts 39 the
gasket 33 will be compressed to the dimensions
4. A high~tension electrical apparatus com
said container, gasket means between said cover
and said container, said gasket means including
a gasket formed of a composition comprising a
copolymer of acrylonitrile and butadiene, me
chanical means to make fast said cover to said
container and compress said gasket means, said
gasket means and mechanical means providing
of the recess as.
It will be apparent that rubber-like materials,
such as those copolymers including butadiene,
and maintaining a substantially ?uid-tight seal
which have characteristics as described above,
when in contact with halogenated aromatic hy
between said tank and cover, a high-tension
electrical conductor in said container, and an
insulating liquid including a chlorinated aro
drocarbons are suitable not only as a gasket ma
terial but for other uses in an electric apparatus
such as an insulating material when in contact
matic hydrocarbon enveloping said conductor.
with the halogenated aromatic hydrocarbon.
Although I have shown and described particu
prising in combination a container, a cover on
lar embodiments of my invention, I do not de
sire to be limited to the particular embodiments
described, and I intend in the appended claims
to cover all modi?cations which do not depart
from the spirit and scope of my invention.
What I claim as new and desire to secure by
Letters Patent of the United States is:
1. Electrical apparatus comprising in combina
tion a tank having therein an electrical conduc
tor and an insulating ?uid comprising a halo
genated aromatic hydrocarbon, and a gasket ma
terial between adjoining portions of said tank,
said gasket material being exposed to the action
5. A high-tension electrical apparatus com
GO
said container, a high-tension electrical c0nduc—
tor and a high-quality liquid insulation within
said container, said insulation including a chlo
rinated aromatic hydrocarbon, a mechanical
joint exposed to said liquid and to an external
medium, gasket means in said joint to maintain
the high quality of said insulation free from
contamination from said external medium, said
gasket means including a gasket formed of a
composition comprising a copolymer of approxi
mately 25 to 40% acrylonitrile and approximately
75 to 60% butadiene, and compression means to
compress and maintain in compression said gas
of said ?uid and comprising a plasticized co
ket means in said joint, said gasket means and
polymer of butadiene and acrylonitrile, the plas
compression means providing and maintaining
2,407,493
7
8
a substantially ?uid-tight seal between said con~
said container, a high-tension electrical conduc
tor and a high-quality liquid insulation within
said container, said insulation including a chlo
rinated aromatic hydrocarbon, a mechanical joint
tainer and cover.
6. A high-tension electrical apparatus com
prising in combination a container, a cover on
said container, a high-tension electrical con
ductor and a high-quality liquid insulation with
in said container, said insulation including a
chlorinated aromatic hydrocarbon, a mechan
exposed to said liquid insulation and to an ex
ternal medium, gasket means in said joint to
maintain the high quality of said insulation free
from contamination from said external medium,
ical joint exposed to said liquid insulation and
said gasket means including a gasket formed of a
to an external medium, gasket means in said 10 composition comprising a copolymer of acrylo
joint to maintain the high quality of said insu
nitrile and butadiene, and compression means
lation free from contamination from said ex
to compress and ‘maintain in compression said
ternal medium, said gasket means including a
gasket means in said joint to about two-thirds of
gasket formed of a composition comprising a co
its normal unswollen volume, said gasket means
polymer of acrylonitrile and ‘outadiene, and com
and compression means providing and maintain
pression means to compress and maintain in
ing a substantially ?uid-tight seal between said
compression said gasket means in said joint, said
container and cover.
liquid insulation ?lling said container to a level
9. Electrical apparatus comprising in combi
at least as high as the level of said gasket means
nation a tank having therein an electrical con
so that said gasket means will be exposed thereto 20 ductor and an insulating ?uid comprising a
continuously, said gasket means and compression
halogenated aromatic hydrocarbon, and a gasket
means providing and maintaining a substan
between adjoining portions of said tank, said gas
tially ?uid-tight seal between said container and
ket being in contact with said ?uid and com
cover.
'7. A high-tension electrical apparatus com
prising a copolymer of butadiene and acryloni
25 trile, said copolymer having a halogenated aro
prising in combination a container, a cover on
said container, a high-tension electrical con
matic hydrocarbon as a plasticizer for substan
ductor and a high-quality liquid insulation with
in said container, said insulation including a
chlorinated aromatic hydrocarbon, a mechanical
joint exposed to said liquid insulation and to an
external medium, gasket means in said joint to
of said apparatus, and said gasket providing and
maintaining a fluid-tight seal between said ad
joining portions of said tank.
10. Electrical apparatus comprising in combi
maintain the high quality of said insulation free
from contamination from said external medium,
electrical conductor and an insulating ?uid in?
cluding a chlorinated aromatic hydrocarbon
within said container, means including a gasket
between said container and cover, said gasket
being in contact with said ?uid and comprising
a copolymer of butadiene and acrylonitrile, said
said gasket means including a gasket formed of I
tially maintaining its plasticity during operation
nation a container, a cover on said container, an
a composition comprising a copolymer of buta
diene and acrylonitrile, and compression means
to compress and maintain in compression said
gasket means in said joint, said gasket means
copolymer being plasticized with a plasticizer
and compression means providing and maintain 40 dissolvable in said ?uid, said fluid having the
ing a substantially ?uid-tight seal between said
container and cover, and said joint having a
groove in which said gasket is placed so as to
limit the compression of said gasket means to
a predetermined value irrespective of the ten
sion on said means to compress the same.
8. A high~tension electrical apparatus com
prising in combination a container, a cover on
characteristic of displacing the dissolved plasti
cizer and maintaining substantially the plasticity
of said copolymer during operation of said ap
paratus, and the said means which includes said
gasket providing and maintaining a ?uid-tight
seal between said container and cover.
LUCAS P. HART, JR.
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