U.S. patent number 3,697,932 [Application Number 05/128,729] was granted by the patent office on 1972-10-10 for electrical connector.
This patent grant is currently assigned to Westinghouse Electric Corporation. Invention is credited to James R. Farley, August I. Keto.
United States Patent |
3,697,932 |
Keto , et al. |
October 10, 1972 |
ELECTRICAL CONNECTOR
Abstract
An electrical connector for connecting a plurality of electrical
load circuits to an electrical distribution loop via a removable
element, such as a current limiting fuse. The connector includes a
housing formed of an insulating resin system, including a chamber
in which the removable element is disposed. First and second spaced
contacts are carried by the housing which cooperate with first and
second spaced electrodes carried by the removable element, to
interconnect the first and second spaced contacts via the removable
element. The housing defines first and second integral, tubular
outward projections in which contacts are disposed which are
connected to the first contact, and a plurality of additional
integral, tubular outward projections in which contacts are
disposed which are connected to the second contact. The first and
second tubular projections are adapted to removably receive and
electrically interconnect first and second electrical cables,
respectively, in the electrical distribution loop, and the
plurality of additional tubular projections are adapted to
removably receive electrical cables connected to load circuits. Arc
extinguishing members are carried by the housing and by the
removable member, to make the assembly and disassembly of the
connector load-make and load-break at the contact connected to the
electrical distribution loop.
Inventors: |
Keto; August I. (Sharon,
PA), Farley; James R. (Pittsburgh, PA) |
Assignee: |
Westinghouse Electric
Corporation (Pittsburgh, PA)
|
Family
ID: |
22436687 |
Appl.
No.: |
05/128,729 |
Filed: |
March 29, 1971 |
Current U.S.
Class: |
439/183;
174/72R |
Current CPC
Class: |
H02G
15/12 (20130101); H01R 31/02 (20130101) |
Current International
Class: |
H01R
31/00 (20060101); H01R 31/02 (20060101); H02G
15/10 (20060101); H02G 15/12 (20060101); H01r
013/68 () |
Field of
Search: |
;339/147,111,213,242,94
;174/71C,72,73 ;337/187,201,188,189,202 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Moore; Richard E.
Claims
We claim as our invention:
1. An electrical connector for interconnecting an electrical
distribution loop with a plurality of electrical circuits via a
removable connecting element, comprising:
an insulating housing formed of a resin system, including a
substantially cylindrical main body portion which defines a chamber
having open and closed ends, first and second substantially tubular
portions which extend outwardly from the main body portion near the
closed end of the chamber, and a plurality of additional
substantially tubular portions axially spaced from the first and
second tubular portions, which also extend outwardly from the main
body portion, said first and second and said plurality of
additional substantially tubular portions each defining a recess
having an open and a closed end,
first contact means carried by said insulating housing, including
first, second and third interconnected contact members, said first
contact member extending coaxially into said chamber through its
closed end, and said second and third contact members extending
coaxially into the recesses of said first and second substantially
tubular portions, respectively, through their closed ends,
second contact means carried by said insulating housing, axially
spaced from said first contact means, said second contact means
including a tubular contact member disposed coaxially with the
chamber of the insulating housing, having an inner surface which is
accessible from within the chamber, and a plurality of contact
members fixed to said tubular contact member which extend into the
recesses of said plurality of additional substantially tubular
portions, respectively, through the closed ends of the
recesses,
means removably disposed in the chamber of said insulating housing
having first and second spaced contact assemblies, and means
electrically interconnecting said first and second spaced contact
assemblies, said first and second contact assemblies engaging the
first contact member of said first contact means, and the inside
surface of the tubular contact member of said second contact means,
respectively,
a first resilient, electrically conductive tubular member having
first and second ends, disposed in each of said first and second
and additional plurality of substantially tubular portions of said
insulating housing, with the first end of the first resilient
electrically conductive tubular member starting at the closed end
of its associated recess, and surrounding the contact member which
extends into the recess,
whereby the first and second substantially tubular portions of said
housing are adapted to receive plug-in connectors connected to the
electrical distribution loop, and the additional plurality of
substantially tubular portions of said housing are adapted to
receive plug-in connectors connected to the electrical circuits to
be connected to the electrical distribution loop via said means
removably disposed in the chamber of said insulating housing.
2. The electrical connector of claim 1 including an electrically
conductive coating disposed on the outer surface of the insulating
housing.
3. The electrical connector of claim 1 wherein the outer surfaces
of each of the first resilient electrically conductive tubular
members are bonded to the insulating housing.
4. The electrical connector of claim 1 including a second tubular
resilient member having first and second ends disposed in each of
the recesses defined by the first and second and additional
substantially tubular portions of the insulating housing, with its
first end overlapping the second end of the first resilient member
to provide a seal, and its second end starting adjacent to the open
end of the recess.
5. The electrical connector of claim 4 wherein the second tubular
resilient member includes an electrically conductive portion
starting at its second end and an insulating portion starting at
its first end, with the electrically conductive insulating portions
joining intermediate the first and second ends.
6. The electrical connector of claim 5 including an electrically
conductive coating disposed on the outside surface of the
insulating housing, with the electrically conductive portion of
each of the second tubular resilient members contacting said
electrically conductive coating.
7. The electrical connector of claim 1 wherein the means removably
disposed in the chamber of the insulating housing includes a
current limiting fuse.
8. The electrical connector of claim 1 wherein the plurality of
contact members fixed to the tubular contact of the second contact
means include at least one elongated metallic member having first
and second ends, with an intermediate portion of the elongated
metallic member being fixed to the outer surface of the tubular
contact, and with the first and second ends of the elongated
metallic member extending into different recesses.
9. The electrical connector of claim 8 including a second elongated
metallic member having first and second ends, with an intermediate
portion of the second metallic member being fixed to the outer
surface of the tubular contact, and with its first and second ends
extending into different recesses.
10. The electrical connector of claim 1 wherein the means removably
disposed in the chamber of the insulating housing seals the open
end of the chamber.
11. The electrical connector of claim 1 including a cylindrical
metallic housing having first and second open ends, with the second
open end adjustably disposed about the insulating housing, and
including cover means for closing the first open end of the
cylindrical metallic housing.
12. The electrical connector of claim 11 including an intermediate
housing of insulating material disposed within the cylindrical
metallic housing, which encloses and seals the open end of the
insulating housing.
13. The electrical connector of claim 1 including first and second
arc extinguishing members carried by the insulating housing and
means removably disposed in the chamber of the insulating housing,
respectively, which are disposed to confine and extinguish an arc
formed between the first contact member of the first contact means
and the first contact assembly of the means removably disposed in
the chamber of the insulating housing.
14. The electrical connector of claim 1 including an auxiliary
removable element having a single contact adapted to engage the
tubular contact member of the second contact means, and including
an electrically conductive shaft member connected to said single
contact, with said electrically conductive shaft member being
accessible external to the electrical connector, enabling it to be
visibly connected to ground.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to electrical connectors, and more
specifically to load-make, load-break connectors for connecting a
plurality of electrical circuits to an electrical distribution
loop.
2. Description of the Prior Art
The primary and secondary distribution systems of electrical
utilities have been primarily of the overhead type, with the most
common circuit arrangement being the radial system. Underground
distribution of electrical power has been increasing in recent
years due to the increasing number of new subdivisions resorting to
underground distribution of electrical power for esthetic reasons.
Underground residential distribution systems are inherently more
costly than distribution systems of the overhead type, and their
cost is further increased because they utilize the more reliable
loop system. The cost of the loop system is further increased,
compared with the overhead system, when a small distribution
transformer is specified for each residence, or for two adjacent
residences. In this instance, the underground shielded cable, which
is buried near the curb line, loops into each of the distribution
transformers, crossing a front yard twice for each transformer, as
each transformer is located adjacent to the residence, or
residences, it serves. This arrangement requires two high voltage
splices and two stress cones at each transformer, two high voltage
bushings on each transformer, and two runs of high voltage shielded
cable between the street and location of the transformer adjacent
the residence, or residences.
The cost of the underground distribution system could be
substantially reduced by using a loop-radial circuit arrangement,
wherein the primary circuit loops through a subdivision of houses
along the curb line, with laterals or radials being tapped off the
loop for each transformer. Thus, only one run of high voltage
shielded cable is required between the loop system and the
distribution transformer, and distribution transformers with a
single high voltage bushing may be utilized. The success of this
arrangement, however, depends upon providing a low cost connector
for tapping the radial feeders into the loop cables, quickly and
efficiently, while making a reliable, moisture-proof, low stress
connection.
Underground residential distribution systems which utilize a
distribution transformer disposed immediately adjacent to the
residence, or residences, it serves, also present the problem of
protecting the loop system against faults in the connected high
voltage cable and transformers. For example, the loop system should
be protected from faults in the connected high voltage cable due to
dig-ins which may occur in the front yard of a residential user.
Thus, in addition to providing a low cost connector for tapping a
radial feeder into a shielded cable which is part of a loop
distribution feed system, it would also be desirable to provide
some means for protecting the loop system from faults in the high
voltage radial feeder cable and distribution transformers.
Co-pending application Ser. No. 798,294, filed Feb. 11, 1969, now
U.S. pat. No. 3,602,872 issued Aug. 31, 1971, which is assigned to
the same assignee as the present application, discloses a connector
suitable for such applications. It would be desirable, however, to
make the insertion and removal of the load circuits to the radial
loop load-make and load-break, respectively, and to also provide a
new and improved housing and cable connection arrangement for the
electrical connector which facilitates the manufacture and assembly
thereof, without sacrificing reliability and other essential
features of such a connector.
SUMMARY OF THE INVENTION
Briefly, the present invention is a new and improved electrical
connector for connecting a plurality of electrical load circuits to
an electrical distribution loop via a removable element, such as a
current limiting fuse. The connector includes an insulating housing
formed of a resin system which not only defines a chamber for
receiving the removable element, but also forms integral tubular
projections which form plug-in receptacles for receiving suitably
prepared ends of the high voltage cable in the loop distribution
system, and similarly prepared ends of the high voltage cable in
the plurality of load circuits connected to the loop system via the
removable element.
First and second spaced contact means are partially embedded in the
insulating housing, with portions thereof accessible within the
chamber for receiving the removable portion and engaging its
contacts. Portions of each of the first and second spaced contact
means are also accessible at the inner ends of different tubular
projections, providing contact members for making electrical
contact with the high voltage cables, when the high voltage cables
are plugged into the tubular projections.
A resilient, electrically conductive tubular member or boot is
disposed in each of the integral tubular projections of the
housing, with the outer surface of each boot being bonded to the
inside wall of its associated tubular member, and with the contact
member of the tubular projection being disposed within the opening
of the electrically conductive boot.
The high voltage cable of the electrical distribution loop may thus
be cut at any point at which it is desired to connect load circuits
thereto, with the resulting two ends of the cable being suitably
prepared and plugged into predetermined tubular projections on the
insulating housing, which reestablishes the continuity of the
electrical distribution loop through the first contact means. The
high voltage cable of the laterals or load circuits to be connected
to the electrical distribution loop are also suitably prepared and
plugged into tubular projections in which contact members
associated with the second contact means are disposed. Assembly of
the removable member in the chamber of housing bridges the first
and second contact means, connecting the electrical distribution
loop to the load circuits via the removable element. The removable
element has first and second contacts or electrodes which engage
the first and second contact means of the housing, respectively,
with cooperative arc extinguishing members being provided for the
removable element and for the housing, which members make the
assembly and disassembly of the removable element load-make and
load-break, respectively.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be better understood, and further advantages and
uses thereof more readily apparent, when considered in view of the
following detailed description of exemplary embodiments, taken with
the accompanying drawings, in which:
FIG. 1 is a schematic diagram of an electrical distribution loop
which may advantageously utilize electrical connectors constructed
according to the teachings of the invention;
FIG. 2 is an elevational view, partially in section, of an
electrical connector constructed according to the teachings of the
invention;
FIG. 2A is a perspective view of the insulating housing portion of
the electrical connector shown in FIG. 2;
FIG. 3 is a sectional view of the connector shown in FIG. 2, taken
along the lines III--III;
FIG. 4 is a sectional view of the connector shown in FIG. 2, taken
along the lines IV--IV;
FIG. 5 is a fragmentary elevational view of the connector shown in
FIG. 2, taken in the direction of arrows V--V;
FIG. 6 is a sectional view of a composite resilient member which
surrounds each high voltage cable when the cable is assembled with
the connector shown in FIG. 2;
FIG. 7 is an elevational view, partially in section, of the
removable element of the connector shown in FIG. 2;
FIG. 7A is a fragmentary view of the removable element shown in
FIG. 7, except modified to include fuse elements of smaller
ratings;
FIG. 8 is a elevational view, partially in section, of another
removable element which may be used with the connector shown in
FIG. 2, when it is desired to use the connector as a sectionalizing
switch; and
FIG. 9 is an elevational view, partially in section, of still
another removable element which may be used with the connector
shown in FIG. 2, when it is desired to ground the load circuit
during maintenance thereof.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, and FIG. 1 in particular, there is
shown a schematic diagram of a three-phase electrical distribution
system, represented generally by conductor 10, and a single-phase
electrical distribution loop 12 connected to the three-phase system
10 via switches 14 and 16. The single-phase distribution loop,
which may be underground, and at a distribution voltage level of
the 15 KV class, or any other distribution voltage level, includes
a sectionalizing switch 18, which is connected to the loop 12 at
about its midpoint, and a plurality of electrical connector
switches 20, 22, 24 and 26. Each of the electrical connector
switches connect a plurality of electrical load circuits to the
electrical distribution loop 12 via a connecting element, such as a
current limiting fuse, with each load circuit including a
distribution loop 12 via a connecting element, such as a current
limiting fuse, with each load circuit including a distribution
transformer which serves one or more residences. For example,
connector switch 22 includes a fused removable element 28, and four
load circuits 30, 32, 34 and 36. Each of the load circuits are
connected to a distribution transformer, such as distribution
transformer 38, which is shown connected to load circuit 36, with
the transformer 38 being connected to one or more residences, such
as residence 40. The electrical connector switches 20, 22, 24 and
26, as well as the sectionalizer switch 18, may all be constructed
according to the teachings of the invention, and they are
illustrated as having plug-in type connections, as taught by the
invention. For example, electrical connector 22 is illustrated as
having first and second plug-in connectors 42 and 44, to which the
high voltage cable of the electrical distribution loop 12 is
connected, and plug-in connectors 46, 48, 50 and 52, to which the
high voltage cables of the load circuits 30, 32, 34 and 36 are
respectively connected.
FIG. 2 is an elevational view, partially in section, of an
electrical connector 60 constructed according to the teachings of
the invention. Connector 60, which may be used for the electrical
connectors shown in FIG. 1, underground, above grade, vault
mounted, or in any other suitable arrangement, includes a fixed
receptacle 62 and a removable connecting element 64. The fixed
receptacle 62, which is shown in perspective in FIG. 2A, includes a
housing 66 formed of a cast insulating resin system, such as the
filled epoxy resin system disclosed in U.S. Pat. No. 3,547,871,
which is assigned to the same assignee as the present application.
However, any other suitable insulating resin system may be used
which is weather resistant, and which possesses the requisite
electrical and mechanical strengths. The fillers for the resin
system should be selected to closely match the coefficient of
thermal expansion of the resulting resin system with that of
metallic inserts embedded therein, such as copper or aluminum
contacts, which embedments will be hereinafter described. Finely
divided quartz flour, lithium aluminum silicate, beryllium aluminum
silicate, and alumina trihydrate are examples of suitable fillers,
with the latter being used in combination with other fillers when
arc and track resistance is required.
The insulating housing 66 includes a generally cylindrical main
body portion 68 having first and second ends 69 and 71,
respectively, with the main body portion 68 defining an elongated
chamber 70 having first and second ends 72 and 74 which are open
and closed, respectively. The insulating housing 66 also includes
first and second substantially tubular portions 76 and 78, which
are integrally formed with the main body portion 68, with the
tubular portions 76 and 78 extending perpendicularly outward in
opposite directions from the main body portion 68, near the closed
or blind second end 74 of the chamber 70. Tubular portions 76 and
78 are also shown in FIG. 4, which is a cross-sectional view of
insulating housing 66 taken along the line IV--IV.
A plurality of additional substantially tubular portions 82, 84, 86
and 88 are also integrally formed with the main body portion 68,
with the tubular portions 82 and 84 extending perpendicularly
outward from one side of the main body portion 68, in spaced,
parallel relation with one another, and with tubular portions 86
and 88 extending perpendicularly outward from the other side of the
main body portion 68, in spaced parallel relation with one another,
with the centerlines of the tubular projections 82 and 86 being in
alignment, and with the centerlines of the tubular projections 84
and 88 being in alignment. Tubular portions 82, 84, 86 and 88 are
also shown in FIG. 3, which is a cross-sectional view of the
insulating housing 66 taken along the line III--III.
Each of the outwardly extending tubular portions 76, 78, 82, 84, 86
and 88 define an opening or recess having an inner closed end and
an outer open end, such as the recess 90 in tubular portion 86,
which has a closed inner end 92 and an open outer end 94.
First and second spaced contact means 96 and 98, respectively, are
carried by the insulating housing 66, with portions thereof
embedded in the cast resin system of the main body portion.
The first contact means 96 includes a substantially U-shaped
conductor 100, which is formed of copper, aluminum or other good
electrical conductor, with the U-shaped conductor 100 having first
and second spaced parallel leg portions 102 and 104, respectively,
which are interconnected by bight 106. First, second and third
contact members 108, 110 and 112, respectively, are all connected
to the U-shaped conductor 100. The first contact member 108 may be
threadably secured to the bight 106 by a pin 114 which extends
perpendicularly through an opening in the bight 106, with the
contact member 108 extending outwardly from the bight 106 in
parallel relation with, and between the spaced leg portions 102 and
104 of the first contact means 96. The second and third contact
members 110 and 112, which are elongated pin-like members, are
fixed to legs 102 and 104, respectively, of the U-shaped conductor
100, extending perpendicularly outward from the outermost sides of
the legs 102 and 104, near their extreme ends. The longitudinal
centerlines of the contact members 110 and 112 are substantially
coaxial.
The U-shaped conductor 100 of the first contact means 96 is
completely embedded in the cast solid resin system of the main body
portion 68 of the housing 66, such that pin 114 has one end
embedded in the cast resin system, and a threaded end which extends
coaxially into chamber 70 through the closed end 74 of the chamber,
enabling the first contact member 108 to be removably fastened to
pin 114 by inserting the first contact member 108 into the chamber
70 and threadably engaging it with the pin 114, using a suitably
designed tool.
The second and third contact members 110 and 112 may be partially
embedded in the cast resin system, adjacent their ends which are
connected to the first and second legs 102 and 104, respectively,
of the U-shaped conductor 100, with the extreme outer ends of the
contact members 110 and 112 extending coaxially into the recesses
defined by the integral tubular extensions 78 and 76, respectively,
through the blind or closed ends of the recesses.
First and second resilient, electrically conductive tubular members
or boots 116 and 118 are disposed to surround the portions of the
second and third contact members 110 and 112, respectively, which
extend into the recesses defined by the tubular extensions 78 and
76. The resilient boots 116 and 118 may, for example, be formed of
an electrically conductive rubber. Each of the resilient boots have
first and second ends, such as first and second ends 120 and 122,
respectively, on boot 118, with a small opening being provided
through the first end of the boot for snugly receiving the
associated contact member which extends into the recess of the
tubular projection, and a larger opening at its second end. The
inside surface of each of the electrically conductive boots has a
circumferential groove disposed adjacent to but uniformly spaced
from the second end of the boot by a predetermined dimension, such
as the circumferential groove 124 in boot 118.
The outer surfaces of the electrically conductive boots 116 and 118
are bonded to the resin system of the main body portion 68 of
housing 66, with it being convenient to dispose the boots over
their associated contact members, and cast the boots in this
position when the main body portion 68 is cast. In other words, the
first contact means 96, with the electrically conductive boots 116
and 118 in position about conductive members 110 and 112, may be
placed as an assembly within the mold prior to introducing the
resin system therein. Wire brushing the external surfaces of the
boots 116 and 118 will promote excellent adhesion between the cast
resin system and the outer surfaces of the boots, insuring that
there will be no air trapped in the interface between the boots and
resin system which may ionize during the usage of the electrical
connector 60. The electrically conductive boots 116 and 118 will be
at substantially the same electrical potential as the first contact
means 96, when the first contact means 96 is energized, reducing
the potential gradient between the contact members and the inner
surfaces of their respective boots, to substantially zero. This
arrangement increases the effective radii of the contact members
110 and 112 to that of the outer surfaces of their associated
boots. The potential gradient at the outer surface of each of the
boots is thus substantially less than that which would occur at the
surface of the conductive members 110 and 112 in the absence of a
boot. Then, the fact that there is no air at the interface of the
boot and cast resin insulating system, further reduces the chance
of corona formation, as the cast resin system has a higher
electrical breakdown strength than air.
The first contact means 96 is completed by an insulating sleeve or
tube 119 formed of a suitable arc extinguishing material.
Insulating sleeve member 119 is constructed to surround contact
member 108, and it includes an opening which is coaxially aligned
with the opening in contact member 108, through which the contact
of the removable member 64 proceeds just prior to its engaging
contact member 108. Insulating sleeve 119 cooperates with an
insulating probe or rod formed of arc extinguishing material which
is carried by the removable portion 64, as will be hereinafter
explained, to provide the desired load-break capability for the
electrical connector 60, with the term "load-break capability" also
including load-make and fault close-in capabilities.
The second contact means 98 includes a metallic, tubular,
cylindrical contact member 126, which is formed of aluminum or
copper, and which has an opening 128. First and second elongated,
rod-like, electrically conductive contact members 130 and 132,
which are also formed of aluminum or copper, are fixed in spaced
parallel relation with one another to opposite points on the curved
outer surface of the tubular contact member 126, perpendicular to
the axis of opening 128.
The second contact means 98 is partially embedded in the cast resin
system of the main body portion 68 of housing 66. The second
contact means 98 is axially spaced, along chamber 70, from the
first contact means 96, with the opening 128 in its tubular contact
member 126 being coaxial with the longitudinal axis of chamber 70.
The inner surface 133 of the tubular contact member 126 is
accessible from within chamber 70. The chamber 70 may have a
substantially uniform diameter from its closed end 74 to the
uppermost end of the tubular contact member 126, which diameter is
substantially the same as the inside diameter of the tubular
contact member 126, and then chamber 70 may taper slightly outward,
such as indicated at 134, with the taper terminating at a slightly
larger inside diameter, which may be uniformly maintained from the
end of the taper 134 to the open end 72 of the chamber 70.
Each of the electrically conductive contact members 130 and 132
have first and second ends, with each of their ends functioning as
an electrical contact. The first and second electrically conductive
contact members 130 and 132 are oriented, when the main body
portion 68 of housing 66 is cast, such that their outwardly
extending ends extend coaxially into the recesses defined by the
tubular extensions, through the inner or closed ends of the
recesses. For example, the first and second ends of the first
contact member 130 extend into the recesses defined by tubular
extensions 82 and 86, respectively, and the first and second ends
of the second contact member 132 extend into the recesses defined
by the tubular extension 84 and 88, respectively.
Electrically conductive rubber boots 136, 138, 140 and 142 are
disposed within the recesses defined by tubular extensions 82, 84,
88 and 86, respectively, about the ends of the contact members 130
and 132 which extend into the recesses, with the electrically
conductive boots being constructed and placed relative to their
associated contacts and tubular extensions of main body portion 68,
as hereinbefore described relative to the electrically conductive
boots 116 and 118.
A metallic hasp 150, having a slot-like opening 152 therein, is
pivotally mounted to the first end 69 of the insulating housing 66,
such as by embedding a tapped metallic insert 154 into the first
end of the insulating housing, to which the hasp 150 may be
threadably secured by a suitable fastener. A hinge 156 enables the
hasp 150 to pivot and secure the removable element 64 in assembled
relation with the insulating housing 66, as will be hereinafter
described.
The insulating housing 66 is threaded on its external surface, as
illustrated at 144, starting near its first end 69, which threads
cooperate with a tubular metallic extension or housing 146, to make
the electrical connector 60 accessible from above the grade or
ground level 148, as will be hereinafter explained.
The insulating housing 66 has an electrically conductive coating
158 disposed uniformly over its external surface, as indicated
within circle 160, which circle indicates a magnified view of the
outer surface of housing 66. The electrically conductive coating
158 may be an electrically conductive paint, such as an aluminum
paint, which is brushed, sprayed, or otherwise uniformly applied to
the outer surface of housing 66.
Housing 66 is completed by fastening a metallic angle 162 to its
external surface, in contact with the electrically conductive
coating 158, such as by inserting bolts 164 and 166 through
openings disposed in one side of the metallic angle 162, which
bolts threadably engage tapped metallic inserts embedded in the
cast resin of which the housing 66 is formed. FIG. 5 is a
fragmentary elevational view of housing 66, taken in the direction
of arrows V--V, which illustrates the location of the metallic
angle 162, and the metallic angle 162 is also shown in FIGS. 2A and
4. A plurality of openings 168 are disposed through the remaining
side of the metallic angle 162 for receiving fasteners which
connect a ground rod and the wire strapping of shielded cables to
the metallic angle 162.
The shielded cables of the electrical distribution loop and of the
various load circuits may be quickly prepared in the field for
plug-in connection with the contacts disposed in the insulating
housing 66. As illustrated in FIGS. 2, 3 and 4, shielded cables 170
and 172 are from the electrical distribution loop, and their ends
are plugged into the recesses defined by the tubular extensions 78
and 76, respectively, to reestablish the electrical continuity of
the electrical distribution loop, and to energize the contact
element 108. Shielded cables 176, 178 and 180 cooperate with
tubular extensions 82, 84 and 88, respectively, to energize their
respective load circuits via the removable connecting element 64. A
similar shielded cable (not shown) would be plugged into the recess
defined by tubular extension 86.
Cable 180 is shown plugged into the tubular extension 88 in FIG. 3,
and unplugged in FIG. 2, in order to better illustrate its
construction, and since each cable is prepared in a similar manner,
only the preparation and construction of the end of cable 180 will
be described in detail.
The first step in preparing the end of cable 180 is to remove the
cable insulation and shield from the end of the cable, exposing a
predetermined length of the stranded or solid conductor 182 of the
cable, and a female or socket terminal 184 is then crimped onto the
bared conductor 182, such that the socket terminal 184 is butted up
against the cable insulation at 186. Socket terminal 184 has an
opening 186 at its other end which cooperates with the male contact
member disposed in the recess of the tubular extension 88,
expanding slightly when it is coupled with the male contact member
to provide and maintain good electrical contact between the
engaging contacts. The semiconductive cable shield 188 is then cut
back to 190, exposing the cable insulation 192 for a predetermined
longitudinal dimension.
Next, a specially prepared composite resilient sleeve 194 is
provided, which is shown in an enlarged cross-sectional view in
FIG. 6. Sleeve 194 is slipped over the end of the cable 180 prior
to insertion of the cable 180 into the tubular extension of the
housing 66. Resilient sleeve 194 has first and second ends 195 and
197, respectively, and it includes first and second axially
connected portions 196 and 198, respectively, bonded together at
200, with the first portion 196 being formed of an electrically
conductive rubber and the second portion 198 being formed of an
insulating rubber. The second portion 198 has an inside diameter
202 sized to snugly receive the outside diameter of the portion of
cable 180 which has only the semiconductive shield 188 removed,
i.e. the portion with insulation 192 exposed, and this diameter
continues into the second portion 196 of the composite sleeve for a
predetermined dimension, and then the diameter increases at 206 to
a larger diameter 208 sized to snugly receive the portion of cable
180 which has its semiconductive layer intact, i.e. portion 188. A
circumferential ridge 210 encircles the outside diameter of portion
198, adjacent to end 197, which cooperates with a circumferential
groove 212 disposed in resilient boot 140, as will be hereinafter
explained. The outside diameter of the composite sleeve 194 is
slightly tapered, decreasing in diameter from end 195 to end 197,
which cooperates with a complementary taper on the inside diameter
of the tubular extension 88, to provide a moisture-proof seal. A
flange 214 may be provided on the composite sleeve, near end 195,
if desired, which will butt up against the outwardly extending end
of the tubular projection 88, but the flange is not essential.
Prior to telescoping the composite sleeve 194 over the end of cable
180, the inside diameter of the composite sleeve 194 and portion
192 of electrical cable 180 should be coated with a silicon grease
to facilitate their assembly, and also to force air out of the
assembly. Once the composite sleeve 194 is in the proper position
on cable 180, the semiconductive shield layer 188 contacts the
electrically conductive portion 196 of the composite sleeve 194.
The cable 180 is now ready to be plugged into the recess defined by
the tubular extension 88. The inside diameter of the tubular
extension should be coated with silicon grease, as well as the
outside diameter of insulating portion 198 of the composite sleeve
194, to facilitate their assembly and to force air out of the
resulting assembly. The cable 180 is inserted into the tubular
extension until the circumferential ridge 210 on the end of the
composite sleeve 194 snaps into the cooperative groove 212 on the
inside diameter of the electrically conductive boot 140. The
conductive portion 196 of the composite sleeve 194 electrically
connects the semiconductive shield layer 188 on the cable 180 to
the electrically conductive coating 158 on the housing 66. The wire
strapping on cable 180, indicated at 216, is twisted together and
connected to the metallic angle 162, with suitable fastening means,
such as a nut and bolt assembly. In like manner, the remaining ends
of the cables will be prepared and plugged into their associated
recesses, and their wire strappings are also twisted and connected
to the metallic angle 162.
The removable element 64, shown in FIG. 2, is shown in an enlarged
elevational view in FIG. 7. The removable element 64 includes a
fuse 220, which is a fuse of the non-vented current limiting type.
Fuses of the current limiting type are disclosed in U.S. Pat. Nos.
2,496,704, 2,502,992 and 3,134,874, for example, all of which are
assigned to the same assignee as the present application. Current
limiting fuse 220 includes an insulating fuse tube 222, which is
formed of a suitable material such as glass melamine, first and
second ferrules or electrodes 224 and 226, respectively, which may
be pressed over and secured to the fuse tube 222 by a suitable
adhesive, or otherwise suitably fixed to opposite ends of the fuse
tube. A fusible element (not shown) is disposed through the opening
in the fuse tube 222, and connected between the first and second
electrodes 224 and 226. The fusible element is usually formed of a
flat ribbon of silver with a plurality of spaced notches which
extend inwardly from the sides thereof, periodically reducing the
width of the strip and providing a series of arcs during the
operation thereof, with the sum of the plurality of arc voltages
providing the current limiting effect required. Arc extinction
without requiring venting of the fuse is obtained by filling the
fuse tube 222 with a pulverulent or granular arc quenching
material, such as silica sand.
The first and second electrodes 224 and 226 have means connected
thereto, such as axially extending threaded stud members 228 and
230, respectively, for connecting electrical contact members
thereto. The current limiting fuse 220 provides protection for the
loop distribution system against faults in cables, transformers and
loads connected to the load side of the electrical connector 60,
with the current limiting fuse terminating an overload or short
circuit current at the designed let-through current. The current
limiting fuse 220 also protects operating personnel, as the current
limiting fuse may be safely connected into the circuit even when
the circuit has a low impedance fault. The current limiting fuse
will open a faulted circuit without exploding or otherwise
initiating hazardous operating conditions.
The first electrode 224 of the fuse 220 includes a contact member
232 in the form of a garter spring, which is formed of
beryllium-copper, or other suitable material, with the garter
spring 232 being held in position adjacent to electrode 224 of the
fuse 20 by a retaining member 234. The retaining member 234 is an
electrically conductive member which is shaped similar to an
inverted hat, having a generally cylindrical portion with a closed
end, except for a small centrally located opening therein, and an
open end, which is terminated by an outwardly extending flange 236.
The opening in the closed end of the retaining member 234 accepts
the stud member 228 on the electrode 224, with the flange portion
236 holding the garter spring against the electrode 224. This
construction is suitable when the rating of the current limiting
fuse is such that the diameter of the ferrule 224 is sufficient to
support the garter spring 232. Smaller ratings of the current
limiting fuse for a specified voltage would maintain the same
longitudinal dimension, but the outside diameters of the fuse tube
and ferrules would be reduced. When the diameter of the ferrule 224
is not sufficient to support the garter spring 232, an additional
support plate may be disposed over the stud member 228, with the
additional support plate having the required diameter to provide
support for the garter spring 232. This embodiment of the invention
is illustrated in FIG. 7A, which is a fragmentary view of the
removable element 64 shown in FIG. 7, except with a smaller
diameter fuse electrode, given the reference numeral 224', and
including a support plate 238 which is used to provide the required
support for the garter spring 232.
Referring again to FIG. 7, retaining member 234 is held in position
by a ball joint or universal assembly 240, which has first and
second portions 242 and 244. The first portion 244 includes a
threaded stud member 246 and a socket, and the second portion 244
includes a ball disposed in the socket of the first portion, and a
tapped opening 248. The stud 228 connected to the electrode 224
cooperates with the tapped opening 248 to secure the ball joint
assembly 240 to the fuse 220, and also to secure the retaining
member 234 securely against the electrode 224.
The stud member 246 on portion 242 is then threadably engaged with
a tapped opening in one end of an insulating operating shaft member
250, which shaft may be formed of a suitable resin, such as an
epoxy resin system, or a glass filled methylmethacrylate.
Insulating shaft member 250 may taper outwardly near its other end,
as indicated at 252, to guide the shaft 250 as the removable
element 64 is rammed into the housing 66 with a hot stick. The ball
joint 240 facilitates the insertion of the fuse 220 and its
operating shaft 250 into the chamber 70 of the insulating housing
66, preventing a bending moment from being applied to the fuse as
the connector 66 is threaded into the first end of chamber 70.
Since connector 60 will usually be mounted below the grade level
148, or in a vault which may become flooded, it is essential that
the opening to chamber 70 be sealed by the removable element 64,
when the removable element 64 is assembled with the housing 66.
Thus, the removable element 64 must include means for sealing the
opening 72 to the chamber 70 adjacent the first end 69 of the
housing 66. The sealing means may be in the form of a stopper or
seal 254, which is formed of a resilient material, such as rubber,
with the stopper or seal 254 being expandable, if desired, such as
by turning a metallic eye bolt 256, or by pivoting a cam operating
mechanism which expands the seal. The eye bolt 256 may be disposed
through an opening in the stopper 254, and threadably engage a
tapped opening in the insulating operating shaft 250, enabling the
removable element 64 to be handled by a hot stick inserted through
the opening in the eye bolt 256.
The electrode 226 of fuse 220 includes a second contact member of
fuse 220, which is a cylindrical, elongated terminal or contact
258. Contact 258, which has an outside diameter sized to cooperate
with the inside diameter of the contact member 108 fixed to the
housing 66, is threadably secured to the stud member 230 depending
from the ferrule or electrode 226 of the fuse 220.
A probe type insulating member 260 is carried by contact 258 at its
outward end, with the outside diameter of insulating member 260
being the same as the outside diameter of contact 258. The
insulating member 260 functions as a snuffer rod, cooperating with
the insulating sleeve 119 carried by the housing 66 to squeeze an
arc formed between the contact rod 258 and the female contact 108,
between the probe or snuffer rod 260 and the sleeve 119, and
extinguish the arc by liberating arc-extinguishing gases.
The insulating probe 260 and sleeve 119 are both formed of
arc-extinguishing materials. There are many different insulating
materials which possess arc-extinguishing characteristics, as
opposed to arc tracking characteristics, with the arc-extinguishing
materials producing gases when being subjected to the heat of an
arc, which gases expand to blast, cool and deionize the arc.
Further, the by-products of a good arc-extinguishing material will
not track or create a path for electrical current to flow. For
example, the arc-extinguishing members may be formed of a high
molecular weight polyoxylmethylene, as disclosed in U.S. Pat. No.
3,059,081, which is assigned to the same assignee as the present
application; or, preferably, the arc-extinguishing members may be
formed of a material which includes glass fiber dispersed in a
methylmethacrylate polymer, which construction is disclosed in
co-pending application Ser. No. 1,827, filed Jan. 9, 1970, which
application is assigned to the same assignee as the present
application. Arc-extinguishing members formed of glass filled
methylmethacrylate interrupt and extinguish an arc without
excessive gas formation, and without providing excessive amounts of
conductive particles, such as free carbon, which makes its use in
closed type electrical connectors particularly attractive.
The longitudinal dimension of the inner surface 133 of the tubular
contact member 126 is selected such that the contact 232 of the
removable portion or element 64 makes contact with the tubular
contact member 126 prior to the engagement of the lower contacts
258 and 108, and conversely such that upon removal of the removable
element 64, contacts 258 and 108 will disengage prior to contact
232 leaving the inner surface 133 of the tubular contact member
126. This arrangement insures that the load-make and load-break
functions occur at the lower contact assembly, where the
arc-extinguishing members are disposed to extinguish the arc.
In the installation and operation of the electrical connector 60,
connector 60 is disposed in the trench in which the cable of the
high voltage distribution loop is to be buried, in the embodiment
of the invention where the connector is used with underground
residential distribution systems. The cable of the high voltage
distribution loop is cut and the ends prepared, as hereinbefore
described. The prepared ends of the cable are then plugged into the
recesses defined by the tubular extensions 76 and 78. To insure
that the cables will not be pulled out when earth is placed about
the electrical connector 60, a length of heat shrinkable tubing may
be placed about each of the cables before they are plugged into the
tubular extension, with the heat shrinkable tubing then being
directed to cover the joint formed between the cable and tubular
extension. Heating the heat shrinkable tubing will shrink it
tightly about the joint, preventing the cable from being
accidentally pulled out of contact or engagement with the housing
66. FIGS. 2 and 4 indicate a length of heat shrinkable tubing 262
in place about the joint between the cable 172 and tubular
extension 76.
The cables for the various load circuits may be similarly prepared
and plugged into the tubular extensions 82, 84, 96 and 88, and they
may also be secured in assembled relation with the housing 66 by
using heat shrinkable tubing. If less than four cables are required
for the load circuits, the unused recesses should be plugged with
moisture-proof plugs.
The metallic housing 146, which is preferably formed of a
non-corrosive material, such as cast iron, is then threadably
engaged with the threads 144 on the outer surface of housing 66,
and turned to advance it onto the housing until the top of the
housing 146 is at the desired elevation relative to the grade level
148. A metallic grounding strap 264 is connected to the metallic
housing 146 and also to the metallic angle 162, as illustrated in
FIG. 5. The grounding strap 264 may be advantageously connected to
housing 146 by providing a tapped opening in the housing for
receiving a bolt 266 which may be tightened to securely fasten the
grounding strap 264 to the housing 146. The other end of the strap
264 may be independently grounded, if desired.
The fused removable member 64 may then be inserted into chamber 70,
to connect the plurality of load circuits to the source of
electrical potential via the current limiting fuse 220. The hasp
150 may then be pivoted to direct the eye bolt 256 through the slot
152 in the hasp, and a lock 268 may be looped through the opening
in the eye bolt 256 and locked to prevent unauthorized removal of
the element 64. An additional inner seal may be provided about the
upper end of housing 66, which will prevent water from accumulating
and freezing about the hasp 150 and eye bolt 256. The inner seal
may be in the form of a tubular insulating housing 270, formed of a
material such as hard rubber, which has an inside diameter sized to
snugly fit over the first end of the housing 66. A gasket member
272 may be disposed between the outside diameter of the housing 66
and the inside diameter of the tubular inner housing 270. An
insulating cap member 274 is then disposed to seal the upper open
end of the inner housing 270.
A cover 276 is then disposed to seal the opening to the metallic
outer housing 146, with a gasket member 278 being disposed between
the cover 276 and the housing 146 to provide a hermetic seal. Cover
276 may be of the type which has a plurality of outwardly extending
tangs which cooperate with flanges disposed on the housing, to
force the cover against the gasket 278 when the cover 276 is
rotated to mesh the outwardly extending tangs with the cooperative
flanges on the metallic housing. The earth removed from the trench
may then be disposed about the electrical connector 60.
The electrical connector 60 may be used as a sectionalizing switch,
such as for switch 18 shown in FIG. 1, by replacing the current
limiting fuse 220 with a solid metallic bar 280, as shown in FIG.
8. The resulting removable portion is given the reference numeral
64', and like elements in FIGS. 7 and 8 are indicated with like
reference numerals. A retainer plate 238, such as shown in FIG. 7A,
may be used to hold the garter spring 234, and a similar plate 238'
may be disposed adjacent contact 258, as a guide in directing
contact 258 into proper engagement with the contact member 108. In
this instance, one of the cables of the electrical distribution
loop would be plugged into one of the bottom tubular extensions,
and one would be plugged into one of the top tubular extensions,
with the remaining tubular extensions being sealed with
moisture-proof plugs.
When it is necessary for maintenance personnel to work on the load
circuits, the load circuits may be grounded by using a removable
grounding element 290, which is shown in FIG. 9. Grounding element
290 includes a garter spring 232 and inverted cap type retaining
member 234, as hereinbefore described relative to FIG. 7, but
instead of using an insulating rod 250 for an operating shaft, a
metallic rod member 292 is connected to contact 232 and to the eye
bolt 256. Eye bolt 256 may be grounded, as indicated, and an
insulating rod 298 may be secured to contact 232 with a threaded
pin 296, which pin is also threadably engaged with the metallic rod
292. A retainer cap 294 may be used to help support the garter
spring 232. Thus, when it is desired to take the load circuits out
of service for maintenance reasons, the removable element 250 shown
in FIG. 7 may be removed, and the removable element 290 shown in
FIG. 9 inserted in order to positively insure that the circuits
being maintained are grounded.
While the lower cooperative contact members of the removable
element 64 and housing 66 are illustrated with the female contact
fixed to the housing 66 and the male contact fixed to the removable
element 64, it is to be understood that this structure may be
modified such that the male contact is fixed to the housing 66, and
the female contact is carried by the removable connecting element
64. In this instance, the arc extinguishing members would also
exchange positions, with the insulating tubular sleeve member being
carried by the removable element 64, and the snuffer rod being
mounted on the upwardly extending end of the male element, fixed to
the insulating housing 66.
In summary, there has been disclosed a new and improved electrical
connector for interconnecting an electrical distribution loop with
a plurality of electrical circuits via a removable connecting
element, such as a current limiting fuse. The new and improved
electrical connector utilizes all plug-in connectors, connecting
both the source of electrical potential and the load circuits to
the connector with plug-in connections, without incurring a cost
penalty that ordinarily would accompany the use of the plug-in
concept. This advantageous result is obtained by a new and improved
insulating housing for the electrical connector, in which the
plug-in receptacles are integrally formed with the main body
portion of the housing, and also due to new and improved first and
second spaced contact structures which are carried by and embedded
in the housing, which contact structures may be manufactured for a
relatively low cost, but which provide extremely effective and
reliable electrical joints when coupled with the contacts of the
removable element. The first contact structure includes a U-shaped
metallic member with three contact members attached and extending
outwardly therefrom, and the second contact structure is a metallic
tube with two metallic rods or pins attached thereto, with these
contact structures providing the male contacts of fixed plug-in
receptacles, and a contact which cooperates with the lower contact
carried by the removable element 64.
Further, the new and improved electrical connector has load-break
capability, making it unnecessary to utilize auxiliary switches,
which would otherwise be required prior to closing and opening the
electrical connector. Also, a current limiting fuse is provided
which protects the electrical distribution loop against short
circuits in the cables, transformers and connected loads, which are
connected to the electrical connector.
The disclosed electrical connector may also be used as a
sectionalizing switch; and, by using an auxiliary removable
element, the load circuit may be quickly and easily grounded when
maintenance personnel desire to take the load circuits out of
service for maintenance purposes.
* * * * *