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Патент USA US2300858

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N°V~ 3, 1942-
E. E. ARNOLD ETAL
2,300,858
BUSHING CAP
Filed Jan. 29, 1941
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INVENTORS
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ATTORNEY
NOV- 3, 1942-
_E. E. ARNOLD ETAL
2,300,858
"BUSHING CAP
Filed Jan. 29, 1941
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INVENTORS
Patented Nov. 3_, 1942
2,300,858
vUNITED STATES PATENT OFFICE
2,300,858
BUSHING CAP
Edwin E. Arnold, Pittsburgh, and Harry J. Lingal,
Forest Hills, Pa., assignors to Westinghouse
Electric & Manufacturing Company, East Pitts
burgh, Pa., a corporation of Pennsylvania
Application January 29, 1941, Serial No. 376,424
5 Claims. (01. 174-142)
The present invention relates to high tension
insulating bushings, and it has particular rela
tion to a cap structure for such a bushing. Be
cause of the difference in temperature coeflicients
of expansion of parts of such bushings, it has
?at upper end surface l2, and annular surface
creepage ?anges of a usual type (not shown).
The conductor 4, which may be either solid
or tubular, as illustrated, extends axially through
the casing 2 and may be provided within the eas
ing with a condenser structure (not shown) of
the type well known in condenser bushings. It
will be understood that the position of this con
ducting stud. This problem presents particular
ductor is ?xed with respect to the lower end
di?iculty in the numerous cases where it is re 10 of the casing by means of the mounting ?ange
quired that the cap or terminal member com
or in some other manner well ‘known in the art.
pletely close the end of the bushing without the
Referring particularly to Fig. 1, the terminal
conductor passing therethrough. According to
cap 6 is of a hollow construction and de?nes a
the present invention, a proper uniform electrical
substantially cylindrical interior chamber M ‘at
contact between the conductor and the cap is
its upper end and a somewhat larger chamber
obtained despite any relative movement due to
I6 therebelow. The conductor stud is screw
expansion by means of a spring device biased be
threaded at 18 and a nut 20 disposed thereon,
tween the two members.
while the end of the cap 6 is closed around the
It is accordingly an object of the present in
conductor by means of a plate or flange 22 which
vention to provide a novel and improved cap 20 is secured to the main cap structure by means of
structure for high tension electrical insulating
bolts 24. A collar member 25 having vertical
bushings.
?anges at 28 is disposed around the conductor 4
Another object of the invention is to provide
below the nut 20 and a helical spring designated
a bushing that shall permit relative movement
by 28 is compressed between it and the plate
between the sealed Darts thereof without ad
22 to supply a uniform sealing pressure to the
versely affecting the seal between such parts or
gasket 8. An insulating washer 29 is preferably
the electrical contact between the cap and the
disposed between the spring 26 and the plate
conductor.
22 to prevent electrical contact therebetween.
A further object of the invention is to provide
Another resilient gasket member may be dis
an. insulating bushing cap in which uniform 30 posed between the main cap structure and the
electrical contact is insured between the conduc
plate member 22, as indicated at 30.
tor and the cap by means of a spring device of
To the upper end of the conductor 4 is secured
high conductivity material biased between the
a spring retaining clip 32 while a spring member
two members.
34 is disposed in the upper chamber l4 between
Other objects and advantages of the invention
its surface and the surface of the conductor.
will appear from the following detailed descrip
The spring 34 is preferably of a good electrical
tion taken in accordance with the accompanying
cond-ucting material and its helical turns are in
drawings in which the same reference characters
a conical form. This spring is compressed be
designate corresponding parts throughout. In’ tween the upper retaining clip 32 and a similar
always been a diflicult problem to obtain a proper
seal at the cap and to obtain uniform electrical
contact between the cap structure and the con
the drawings:
Figure 1 is a side view partially in section and
partly in elevation of a terminal cap in accord
ance with the invention secured to an insulating
bushing; and
Figs. 2 and 3 are similar views of modi?cations
of the invention.
The device comprises, in general, an insulating
casing 2, a conductor 4 extending axially there
through and a terminal cap designated by 6 seated
on the end of the bushing with a two piece re
silient gasket structure 8 disposed therebetween.
A screw-threaded terminal I0 is disposed on the
upper end of the cap 6. The dielectric casing
member 2, only the upper end of which is shown,
is preferably constructed of porcelain having a
40 clip 33 located just above the threaded portion
[8 of the conductor 4 so as to be biased against
both the surface of the chamber l4 and that of
the conductor. This spring may be readily
formed by winding the resilient strip material
upon a conical shaped helical mandrel and inner
and outer-edges thereof are preferably machined
to eliminate the corners and provides ?at en
gagement with the surfaces in question. as indi
cated at 3B and 38, respectively. It will be un
50 derstood that while retaining clips 32 and 33
are particularly satisfactory with applicants’
structure, other retaining means may be sub
stituted therefor under some circumstances.
The assembly of the unit is preferably made
by securing the spring 34 in place on the end of
2
2,300,858
the stud before placing the cap 6 thereover while
the remainder of the structure may be assembled
ture expansion characteristics of the stud and
easing.
2. In a bushing for high tension electrical ap
paratus including a tubular casing of insulating
in the art.
The construction of Fig. 2 differs from the U! material and a rigid conducting stud extending
axially through said casing in ?xed relationship
above in that a pair of helical springs of trian
in a manner which will be evident to those skilled
gular cross section are employed to provide con
tact between the cap and stud. The inner of
thereto, a metallic cap engaging an end of said
casing to close it, said cap defining a substan—
these two springs is designated by 110 and is
tially cylindrical chamber about the end of said
wound with its flat edge contacting the stud while 10 stud, and a helical spring comprising substan
tially conically disposed turns of resilient metal
the outer spring 42 is wound with its flat edge
strip arranged around said stud with its opposite
to the outside and engaging the walls of the
chamber Ill. The two springs are compressed by
edges biased against the surface of said stud and
the upper and lower retaining clips 44 and 46,
the surface of said chamber respectively to in
respectively, and are so disposed that each turn
of one of them falls partly within the space be
tween adjacent turns of the other so that a pres
sure is exerted both inwardly against the stud 4
sure uniform electrical contact therebetween de
spite relative movement between the cap and
stud.
3. In a bushing for high tension electrical ap
paratus including a tubular casing of insulating
and outwardly against the cap.
In the modification of Fig. 3, a nut 25’, which 20 material and a conducting stud extending axially
through said casing in fixed relationship there
is used to compress the spring 28 in the same
manner as described with reference to the other
to, a metallic cap engaging an end of said cas
?gures of the drawings is provided with split ?n
ing to close it, said cap de?ning a substantially
cylindrical chamber about the end of said stud,
and a pair of helical springs of substantially tri
angular cross section disposed within said cham
ber about said stud, one of said springs being ar
ranged with one of its sides contacting said stud
and the other being arranged with one of its
sides contacting the surface of said chamber in
staggered relationship to the first said spring
so that the turns of each spring are partially dis
posed within the substantially triangular spaces
between turns of the other.
4. In a bushing for high tension electrical ap~
paratus including a tubular casing of insulat
ing material and a rigid conducting stud extend
gers M3 for engaging the surface of the chamber
l4’. These ?ngers may either be themselves re
silient with an outward bias, or else, they may be
grooved, as indicated at 45, to receive a spring
50. This spring 5!! is of the split ring type which
facilitates assembly of .the device in a manner
which will appear evident from the foregoing de
scription.
With the constructions shown in the present
invention, the spring devices insure a de?nite
and uniform electrical contact between a conduc
tor and the terminal cap despite any relative ax~
ial movement therebetween which may result
from the different coeflicients of expansion of the
casing 2 and the conductor itself. The spring
contact arrangement further cooperates with the
means for clamping the cap in place on the di
electric casing to provide a compact and efficient
arrangement. With the insulating washer 29
disposed between the cap and the main sealing
spring 25 no current can pass through the lat
ter member With the result that no damaging
heating thereof can occur. Even when this
ing axially through said casing in ?xed relation
ship thereto, a metallic terminal cap engaging
an end of said casing to close it and de?ning a
chamber with an even cylindrical surface about
the end of said stud, helical spring means dis
posed around said stud in resilient engagement
with its surface and the surrounding surface of
said chamber, and means projecting from said
stud in engagement with the ends of said spring
washer is not provided the low resistance path
provided by the invention prevents the current
through this spring 25 from reaching a value
means to con?ne it to a predetermined longitu
terpreted in view of the prior art.
paratus including a tubular casing of insulating
dinal portion thereof, whereby said spring means
moves with said stud in sliding electrical contact
50 with said chamber surface in response to rela
high enough to impair its strength,
tive axial movement between said stud and cap
Since various modi?cations of the structure
due to the difference in temperature expansion
shown in the drawings will appear to those
characteristics of the stud and casing.
skilled in the art, it is intended that the inven
5. In a bushing for high tension electrical ap
tion be limited only by the appended claims, in
We claim as our invention:
1. In a bushing for high tension electrical ap
paratus including a tubular casing of insulating
material and a rigid conducting stud extending
material and a conducting stud extending ax
ially through said casing in fixed relationship
thereto, a metallic cap engaging an end of said
casing to close it, said cap de?ning a substantial
axially through said casing in ?xed relationship 60 ly cylindrical chamber about the end of said stud,
thereto, a metallic terminal cap engaging an end
of said casing to close it, said cap de?ning a sub
stantially cylindrical interior chamber about the
end of said stud, and metallic helical spring
means disposed around said stud in resilient en
gagement with its surface and the surrounding
surface of said chamber and in slidable relation
to at least one of said surfaces, whereby said
spring means maintains a slidable resilient elec
trical contact with one of said surfaces in re
sponse to relative axial movement between said
stud and cap due to the difference in tempera
a ?rst helical spring disposed in said chamber
about said stud and having sloping surface por
tions defining an outwardly divergent helical
space between adjacent turns, and a second heli
cal spring disposed in said chamber in engage
ment with the surface thereof and having a cross
section such that a sloping portion thereof ex
tends into said helical space in resilient engage
ment with the turns of said other spring defin
ing it.
EDWIN E. ARNOLD.
HARRY J. LINGAL.
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