U.S. patent number 3,639,678 [Application Number 05/055,902] was granted by the patent office on 1972-02-01 for bushing protective guard.
This patent grant is currently assigned to Central Transformer, Inc.. Invention is credited to Peter W. Muschong.
United States Patent |
3,639,678 |
Muschong |
February 1, 1972 |
BUSHING PROTECTIVE GUARD
Abstract
A protective guard for attachment to a bushing of high-voltage
electrical apparatus, for enclosing and guarding a connector
assembly attached to the bushing. A sleeve of resilient
electrically insulating material surrounds the connector assembly
and has lips which engage the connector assembly and secure the
sleeve thereto. A first knockout provides an aperture toward which
a projecting portion of the connector assembly may extend to act as
a gap electrode and a second knockout provides an aperture for
accommodating a conductor to be laterally connected to the
connector assembly. A cap of electrically insulating material has a
top and a sidewall which fit respectively over and around the
sleeve in engagement therewith. An aperture in the top accommodates
a conductor to be vertically connected to the connector assembly
and at least one aperture in the sidewall of the cap provides
access to one of the knockouts. BACKGROUND OF THE INVENTION This
invention relates to a device for protecting a terminal of
high-voltage electrical apparatus and more particularly to a
protective guard for attachment to a bushing of a transformer or
the like and adapted for enclosing and guarding a connector
assembly attached to the bushing. Protective guards are frequently
desired to protect a connection made at a bushing of high-voltage
electrical apparatus, such as a transformer in a power distribution
system, so as to prevent personnel, birds, or wildlife from coming
into contact with the high voltage connection. In such uses, a need
exists for a protective guard which is both inexpensive and
universal in application. High-voltage connections to power
transformers typically are made by means of a conductor which
approaches the connection at the transformer or other device either
vertically or horizontally. It is also sometimes required that such
high-voltage connections include means for providing a spark gap
electrode adjacent the connection, as for lightning arresting
purposes. It is desirable that a protective guard be capable of use
in each of these various applications. Preferable also, the
protective guard should exhibit electrically nontracking qualities,
i.e., the guard should be of a material which will not develop
paths through which there may be high-voltage leakage or
conduction. Previously proposed protective guards typically have
either not been fully universal in application or have not met all
these requirements, or else have been of relatively complex
construction, e.g., in having tightening hand wheels. Such
complexity has required that the guard be more expensive than is
desired. SUMMARY OF THE INVENTION Among the several objects of the
invention may be noted the provision of a protective guard on
attachment to a bushing of high-voltage electrical apparatus which
accommodates either a horizontally or a vertically approaching
cable connected through a connector assembly attached to the
bushing; the provision of such a guard providing an aperture
therein toward which a projecting portion of a connector assembly
attached to the bushing of high-voltage electrical apparatus may
extend to act as a gap electrode; the provision of such a guard
which is capable of receiving a conductor from two positions
180.degree. apart without changing the mounting of the connector on
the bushing; the provision of such a guard which minimizes the
exposure of electrically live parts; the provision of such a guard
which is of electrically nontracking material; the provision of
such a guard which is extremely simple, inexpensively constructed,
easily installed and long-lasting in use. Other objects and
features will be in part apparent and in part pointed out
hereinafter. Briefly, a protective guard of the present invention
is adapted for attachment to a circular bushing of high-voltage
electrical apparatus and encloses and guards a connector assembly
attached to the bushing, the connector assembly being of the type
including a projecting portion adapted to serve as a gap electrode,
and including means for connecting a conductor. The guard comprises
a generally cylindrical sleeve of electrically insulating and
nontracking elastomeric material. The sleeve includes lip segments
projecting inwardly to resiliently engage the connector assembly
for securing the sleeve thereto. The sleeve has three knockouts
spaced approximately 120.degree. apart around the sleeve. One of
the knockouts provides an aperture aligned with and adjacent the
projecting portion so that the latter may be utilized as a gap
electrode. Each of the additional knockouts provides a respective
aperture for accommodating a conductor to be laterally connected by
the connecting means. A generally cylindrical porcelain cap has a
sidewall fitting around the sleeve in frictional engagement
therewith and has openings registering with each of the knockouts.
A top portion of the cap extending across the upper end of the
sleeve includes an aperture for accommodating a conductor to be
vertically connected by the connecting means.
Inventors: |
Muschong; Peter W. (St. Louis,
MO) |
Assignee: |
Central Transformer, Inc. (Pine
Bluff, AR)
|
Family
ID: |
22000913 |
Appl.
No.: |
05/055,902 |
Filed: |
July 17, 1970 |
Current U.S.
Class: |
174/145; 174/5R;
174/138F; 439/725 |
Current CPC
Class: |
H01B
17/56 (20130101) |
Current International
Class: |
H01B
17/56 (20060101); H01b 017/00 () |
Field of
Search: |
;174/5R,138F,139,145
;339/36,116R,116C,201,202,203,213R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Askin; Laramie E.
Claims
What is claimed is;
1. A protective guard for attachment to a bushing of high-voltage
electrical apparatus and for enclosing and guarding a connector
assembly attached to the bushing, comprising a sleeve of resilient
electrically insulating material adapted to surround the connector
assembly and including means for engaging the connector assembly
and securing the sleeve thereto and having a first knockout to
provide an aperture toward which a projecting portion of the
connector assembly may extend to act as a gap electrode and a
second knockout to provide a further aperture for accommodating a
conductor to be laterally connected to the connector assembly, and
a cap of electrically insulating material having a top and a
sidewall fitting respectively over and around the sleeve in
engagement therewith, the cap having an aperture in said top to
accommodate a conductor to be vertically connected to the connector
assembly and at least one aperture in said sidewall providing
access to one of said knockouts.
2. A protective guard as set forth in claim 1 wherein said engaging
means is constituted by inwardly projecting lip means for
peripherally and resiliently engaging a flange of the connector
assembly.
3. A protective guard as set forth in claim 2 wherein said lip
means comprises a plurality of lip segments.
4. A protective guard as set forth in claim 3 wherein the sleeve
includes at least one recess on the inner surface thereof between a
pair of said lip segments to provide a weep opening.
5. A protective guard as set forth in claim 2 wherein said sleeve
includes means projecting outwardly therefrom for supporting said
cap.
6. A protective guard as set forth in claim 5 wherein said means
projecting outwardly comprises a flange supporting the lower edge
of said cap.
7. A protective guard for attachment to a bushing of high voltage
electrical apparatus and for enclosing and guarding a connector
assembly attached to the bushing, the connector assembly including
a projecting portion and means for connecting a conductor, said
guard comprising a generally cylindrical sleeve of electrically
insulating and nontracking elastomeric material, and having means
projecting inwardly to resiliently engage the connector assembly
for securing the sleeve thereto, the sleeve having three knockouts
spaced approximately 120.degree. apart around the sleeve, a first
one of the knockouts for providing an aperture aligned with and
adjacent said projecting portion whereby said projecting portion
may constitute a gap electrode, the second and third knockouts each
for providing a respective aperture for accommodating a conductor
to be laterally connected by the connecting means, and a generally
cylindrical porcelain cap having a sidewall fitting around the
sleeve in frictional engagement therewith, said sidewall having
opening in registry with each of the knockouts, and a top portion
extending across the upper end of the cap, said top portion having
an aperture for accommodating a conductor to be vertically
connected by the connecting means.
8. A protective guard as set forth in claim 7 in combination with
means for connecting a conductor including a bidirectional clamp
for receiving a conductor approaching the clamp either horizontally
or vertically, said second and third knockouts and the aperture in
said top portion being coplanar and aligned with the clamp.
9. A protective guard as set forth in claim 7 wherein the cap
openings in registry with said second and third knockouts are each
constituted by slots extending upward from the lower edge of the
cap.
10. A protective guard as set forth in claim 7 wherein the sleeve
and the cap each tapers slightly radially outwardly from top to
bottom.
11. A protective guard as set forth in claim 7 wherein the sleeve
is of hydrocarbon rubber.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of an insulating bushing of high-voltage
apparatus including a connector assembly attached to the bushing
and showing in vertical section a protective guard of the invention
enclosing and guarding the connector assembly;
FIG. 2 is a horizontal section of the guard and the connector
assembly taken along line 2--2 of FIG. 1;
FIG. 3 is a plan view of a sleeve of the guard;
FIG. 4 is a vertical section of the sleeve taken along line 4--4 of
FIG. 3;
FIG. 5 is a view of one end of portions of an eyebolt conductor
clamping arrangement of the connector assembly depicted in FIG. 1;
and
FIG. 6 is a fragmental side view of apertures and knockouts of the
sleeve and a cap of the guard, respectively.
Corresponding reference characters indicate corresponding parts
throughout the several views of the drawings.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1, indicated generally at 11 is an insulating
bushing of a power distribution transformer or similar high-voltage
electrical apparatus. A conductor within the bushing 11 is
illustrated at 13 and includes a stud 15 on which is threaded a
connector assembly indicated generally at 17. Assembly 17 is of a
commercially available type having circular flange or disk 19
projecting radially outward from the bottom of assembly 17 and
which includes an annular skirt 20 depending from disk 19 and
fitting around the circular top of bushing 11. Connector 17, which
is of course metallic, is adapted to receive and clamp a conductor
21 (shown in cross section) for electrically connecting the
conductor to the conductor 13 of bushing 11. The connector is of
the so-called bidirectional type permitting connection of a
conductor approaching either horizontally or vertically, as
explained herein.
In accordance with the invention, a protective guard indicated
generally at 23 is fitted over and around connector 17 for
enclosing and guarding the latter to prevent contact therewith by
wildlife (such as birds, squirrels, etc.) or to prevent persons
such as linemen from inadvertently touching the connector. Guard 23
comprises generally a cylindrical sleeve generally indicated 25 of
electrically insulating and nontracking elastomeric material which
resiliently engages the skirt 20 of connector assembly 17. A
porcelain cap, generally 27, also generally cylindrical in shape,
has a sidewall 29 fitting around sleeve 25 in frictional engagement
therewith. A generally flat top 31 of cap 27 fits over the open
ended sleeve 25. Connector 17 includes a body portion 33 against
which the conductor 21 10 clamped by an eyebolt clamp 35. The
latter includes a stem 37 on which is threaded a nut 39, there
being a spring washer 41 positioned between nut 39 and body 33 of
the connector. On the terminal portion of stem 37 of this eyebolt
clamp arrangement is threaded a cap nut or so-called acorn nut 43
including a rounded end portion which extends toward and through
respective apertures 45 and 47 of sleeve 25 and cap 27. Thus this
projecting portion of the connector assembly may serve as a spark
gap electrode. Another electrode 49 (which may be the electrode of
a lightning arrester, for example) is positioned closely adjacent
to but spaced from acorn nut 43 to provide a spark gap between
these electrodes.
Sleeve 25, which is shown more clearly in FIGS. 3 and 4, is
preferably molded of a hydrocarbon-based elastomer such as a
terpolymer of ethylene, propylene and a nonconjugated diene (EPDM)
exhibiting high dielectric strength, high corona resistance, and
high immunity to ozone. Aperture 45, referred to previously, is
provided by punching out a knockout. The sleeve is provided with
three such knockouts which are illustrated in FIG. 3 and designated
generally 51, 53 and 55. These knockouts are spaced at
approximately 120.degree. intervals around the sleeve and are each
defined by a concentric pair of circular score lines or lines of
weakness at each knockout position thereby to provide an aperture
of either a smaller size, such as 1/2 inch in diameter, or a larger
size, such as 3/4 inch. Aperture 45 is indicated as being an
aperture of the larger size. Score lines for knockout 53 are
illustrated in FIGS. 3 and 6 at 57 and 58.
In order to secure sleeve 25 to the periphery of skirt 20, the
sleeve is provided with three inwardly extending lip segments 59,
61 and 63 which are spaced at 120.degree. intervals around the
sleeve and each of which may extend through an arcuate distance of
60.degree.. Each lip extends inwardly a short distance under the
edge of skirt 20 of the connector assembly, as illustrated in FIG.
1. These lips are sloped and have rounded axial edges, as
illustrated in FIG. 4, to facilitate installation and removal of
the sleeve. Weep opening are provided along the interior wall of
sleeve 25 at the intervals between lips 59, 61 and 63 by providing
the interior wall with three recessions 65, 67 and 69 such as by
simply molding sleeve 25 with thinner wall thicknesses at these
locations. The thinner wall thickness of sleeve 25 at these
recessed portions 65, 57 and 69 provides weep spaces between the
interior wall of sleeve 25 and the periphery of skirt 20,
permitting moisture to drain from the guard. At the lower edge of
sleeve 25, there are also provided three outwardly extending
flanges 71, 73 and 75 which are spaced at 120.degree. intervals
around the sleeve and each of which may extend arcuately through an
extent identical with the lip segments 59, 61 and 63.
The wall thickness of sleeve 25 is somewhat less at the top than at
the bottom to provide a slight taper which is apparent in FIG. 1.
This facilitates assembly of the guard.
Cap 27 is provided with three apertures each of which is in
registry with each of the knockouts of sleeve 25. These apertures
are illustrated most clearly in the cross-sectional view of FIG. 2.
Aperture 47 constitutes a first one of these three spaced apertures
and two others are designated at 77 and 79. These three apertures
are spaced at approximately 120.degree. intervals around cap 27.
Unlike aperture 47 which is round, apertures 77 and 79 are
constituted by slots in the cap extending axially from the lower
edge of the cap to the location of the knockout in the sleeve when
the guard is assembled. As FIG. 6 illustrates, the width of these
slotlike apertures 77 and 79 is approximately equal to the diameter
of each of the larger diameter circular score lines providing
knockouts in sleeve 25.
Cap 27 is provided with a further aperture 81 in the top thereof
which is positioned eccentrically with respect to the vertical axis
of the cap so that it is in axial alignment with a conductor
clamped by eyebolt clamp 35 when the guard is assembled, as
depicted in FIG. 1. The diameter of aperture 81 is approximately
equal to that of aperture 47. The sidewall of cap 27 is somewhat
thicker at the top than at the lower edge to provide the interior
of the sidewall with a taper coinciding approximately with the
tapered side of sleeve 25.
As noted previously, connector 17 is of the bidirectional type.
Body 33 thereof is provided with jaws of cruciform shape, as
illustrated in FIG. 5, there being a first pair of jaws 83a, 83b
having a horizontal groove whose axis is perpendicular to the axis
of bushing 11 or that of stud 15, and a second pair of jaws 85a,
85b having a vertical groove whose axis is parallel with the axis
of bushing 11 or stud 15. Eyebolt clamp 35 includes a pair of jaws
87a, 87b which are grooved along an axis aligned with the hole in
the eyebolt clamp, and the latter may be turned so that the jaws
87a, 87b align with either the set of clamp body jaws 83a, 83b, for
clamping a conductor horizontally approaching the clamp, or with
the set of clamp body jaws 85a, 85b, for clamping a conductor
vertically approaching the clamp.
In installing the guard of this invention, sleeve 25 is provided
with apertures of appropriate size at the desired locations by
punching out one or more of knockouts 51, 53 and 55, depending upon
whether a spark gap is to be provided and whether a horizontally
approaching conductor, or conductors, will be connected. Sleeve 25
is pressed onto disk 19 of the connector assembly until lips 59, 61
and 63 are forced past skirt 20 and then resiliently peripherally
engage and extend under the lower edge of the skirt to secure the
sleeve to bushing 11, as shown in FIG. 1. If a conductor is to be
laterally or horizontally connected, the conductor is passed
through the appropriate aperture, such as 77 illustrated in FIG. 2,
and eyebolt clamp 35 is clamped by tightening nut 35 on stud 37 of
eyebolt clamp 35. A sleeve or cover 89 of insulating material on
the conductor may be utilized and may extend through the aperture
into the sleeve, as shown in FIG. 2.
Cap 27 is next placed over sleeve 25 with the slotted apertures of
the cap fitting around any horizontally connected conductors. The
cap is pressed down onto the sleeve until the lower edge of the cap
is resting on flanges 71, 73 and 75 of the sleeve, as shown in FIG.
1. Frictional engagement between the porcelain cap 27 and the
rubber sleeve 25 secures the cap to the sleeve, the relative
dimensions of the cap and sleeve being such as to provide a
relatively tight frictional fit.
Acorn nut 43 is then inserted through the appropriate aperture,
e.g., aperture 47 in FIG. 1, and tightened against nut 39. This use
of an acorn nut is advantageous in accurately fixing the position
of the gap electrode thus provided. Alternatively, the rounded end
of eyebolt stud 37 may itself be satisfactorily used as an
electrode, but the distance of the end of the stud from the
exterior wall of cap 27 may vary somewhat with the size of the
clamped conductor and must be accounted for by adjustment of the
external electrode, e.g., electrode 49 shown in FIG. 1.
As to the assembled guard thus provided, it may be observed that
the apertures provided by sleeve knockouts 53 and 55 (as well as
their associated cap apertures 77 and 79) and aperture 81 in the
cap have centers all coplanar to permit conductors to approach
either horizontally or vertically, or both. As noted hereinbelow,
in-line connections are thus facilitated.
It will be observed that aperture 81 in the top of the cap will
permit rain or other moisture to enter the guard, but this is not
undesirable and in fact is advantageous in keeping the interior of
the guard clean. In any case, moisture will drain through the weep
openings provided by recesses 65, 67 and 69.
A guard of the invention is thus seen to be advantageous in several
respects. Apertures are available in the guard for accommodating
either horizontally or vertically approaching conductors. Also, a
gap electrode is easily provided if desired. Thus the guard is
universal in application as is desirable to permit its use in
different applications. A further advantage is that a conductor may
approach the connector assembly horizontally from opposite
directions, i.e., 180.degree. apart without changing the mounting
of the connector. This is possible since apertures 77 and 79 spaced
120.degree. apart on the guard are aligned with the clamp assembly
of the connector, as shown in FIG. 2. This facilitates in-line
connections of multiple bushings because a single conductor may
enter one of apertures 77 or 79, extend through the eyebolt
opening, and then out through the other aperture, without bending.
The exterior surface of the guard is of porcelain which is
electrically nontracking since it is self-cleaning. Further, the
construction of the guard is exceedingly simple and low in cost,
involving only molding of relatively inexpensive porcelain and
hydrocarbon rubber. These materials have high resistance to adverse
environmental conditions, providing a guard which is long-lasting
in use.
In view of the above, it will be seen that the several objects of
the invention are achieved and other advantageous results
attained.
As various changes could be made in the above constructions without
departing from the scope of the invention, it is intended that all
matter contained in the above description or shown in the
accompanying drawings shall be interpreted as illustrative and not
in a limiting sense.
* * * * *