Note: Descriptions are shown in the official language in which they were submitted.
CA 02752903 2013-12-20
CAM CLAMP FOR ELECTRICAL CONNECTOR
BACKGROUND OF THE INVENTION
100011 The present invention relates to electrical cable connectors, such as
connectors for
joining two or more electrical cables, loadbreak connectors, and deadbreak
connectors. More
particularly, aspects described herein relate to an electrical cable connector
that allows for
rapid connection and disconnection of the connector.
SUMMARY OF THE INVENTION
[0002] In accordance with one aspect of the present invention, there is
provided a connector
comprising an electrical connector yoke tap having a first spade portion
having a bore
therethrough, a power cable having a second spade portion having an opening
therethrough
configured to align with the bore in the first spade portion, and a cam clamp
for securing the
first spade portion to the second spade portion, wherein the cam clamp
comprises a pin having
a head and a shaft, wherein the shaft extends through the bore in the first
spade portion of the
tap and the opening in the second spade portion of the power cable, a
compression element
positioned between the bore and the head of the pin, and a cam member
rotatably mounted to
an end of the shaft opposing the head and configured to move between a first
position and a
second position, wherein the cam clamp is configured to secure the second
spade portion to
the first spade portion when the cam member is rotated from the first position
to the second
position, wherein the cam member includes a length and a width, wherein the
length of the
cam member projects away from the second spade portion when the cam member is
in the
first position, and wherein the width of the cam member projects away from the
second spade
portion when the cam member is in the first position, and wherein the length
of the cam
member is sufficient to prevent installation of a receptacle cover over the
first spade portion
and the second spade portion when the cam member is in the first position.
[0002.1] In accordance with another aspect of the present invention, there is
provided an
electrical connector assembly for connecting a first spade portion of an
electrical connector
yoke tap to a second spade portion coupled to a power cable, comprising a cam
clamp pin
having a head and a shaft, the shaft comprising a transverse bore therethrough
at an end
opposite to the head, a compression element for positioning on the pin
proximate the head,
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and a cam member configured to rotatably mount to the transverse bore and
configured to
move between a first position and a second position, wherein the cam clamp pin
is inserted
through a bore in the first spade portion so that the compression element
engages the head,
wherein the second spade portion is positioned between the first spade portion
and the cam
member, and wherein movement of cam member between the first position and the
second
position causes the compression element to exert a compressive force between
the cam
member, the second spade portion and the first spade portion, wherein a length
of the cam
member is sufficient to prevent installation of a cover over the first spade
portion and the
second spade portion when the cam member is in the first position.
[0002.2] In accordance with a further aspect of the present invention, there
is provided a
method for connecting a first spade portion of an electrical connector yoke
tap to a second
spade portion coupled to a power cable, comprising positioning a compression
element on a
cam clamp pin having a shaft and a head, inserting the shaft of the cam clamp
pin in a bore in
the first spade portion, wherein the bore in the first spade portion comprises
an enlarged upper
portion for receiving the head of the cam clamp pin, such that the head of the
cam clamp pin
does not project above the an upper surface of the first spade portion when
the shaft of the
cam clamp pin is fully inserted through the bore in the first spade portion,
rotatably coupling a
cam member to an end of the shaft opposite to the head, receiving the second
spade portion in
a gap between the cam member and the first spade portion, and rotating the cam
member
between a first position and a second position to secure the second spade
portion to the first
spade portion, wherein the length of the cam member is sufficient to prevent
installation of a
receptacle cover over the first spade portion and the second spade portion
when the cam
member is in the first position, installing a receptacle cover when the cam
member is rotated
into the second position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] Figure 1 is a schematic cross-sectional diagram illustrating a power
cable yoke
assembly consistent with implementations described herein;
[0004] Figure 2A is an exploded, schematic, partial cross-sectional diagram
illustrating a
portion of the power cable yoke assembly and one of the cam clamps of Fig. 1;
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[0005] Figure 2B is an exploded, schematic, partial cross-sectional diagram
illustrating the
portion of the power cable yoke assembly and cam clamp taken along the line A-
A in Fig. 2A;
[0006] Figure 3 is a schematic, partial cross-sectional diagram of the portion
of the power
cable yoke assembly and cam clamp of Figs. 2A and 2B in an assembled state;
[0007] Figure 4A is a schematic, plan view diagram of a power cable spade
assembly
consistent with implementations described herein;
[0008] Figures 4B and 4C illustrate connection of the power cable spade
assembly of Fig.
4A to the power cable yoke assembly and cam clamp of Fig. 3;
[0009] Figure 5 is a schematic, partial cross-sectional diagram of the
connected power cable
spade assembly of Fig. 4C illustrating an uninstalled receptacle; and
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[00101 Figures 6A and 6B are schematic, partial cross-sectional diagrams
illustrating
clamping of the cam clamp of Figs. 3-5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] The following detailed description refers to the accompanying drawings.
The same
reference numbers in different drawings may identify the same or similar
elements.
[0012] Fig. 1 is a schematic cross-sectional diagram illustrating an exemplary
power cable
splicing assembly 100 consistent with implementations described herein. As
shown in Fig. 1,
power cable splicing connector 100 may include a three-way (e.g., a "Y") yoke
102 for
enabling connection of power cables 104-1, 104-2, and 104-3 (collectively
"power cables
104," and individually "power cable 104-x"). For example, power cable 104-1
may be a
supply cable and cables 104-2 and 104-3 may be load cables. Although described
for used
with yoke 102, other types of power cable connectors may be configured in
accordance with
implementations described herein, such as four-way yoke connectors, two-way
connectors,
etc.
[0013] In one implementation, yoke 102 of power cable splicing connector 100
may
include a central conductor 106 (also referred to as bus bar 106) and number
of taps 108-1 to
108-3 (collectively "taps 108," and individually "tap 108-x"). Central
conductor 106 may be
formed of a suitably conductive material, such as copper, aluminum, or other
conductive
alloy. Further, as shown in Fig. 1, central conductor 106 may include bus
extensions 110-1
to 110-3 (collectively "bus extensions 110," and individually "bus extension
110-x") that
project from respective taps 108-x in yoke 102. As described in additional
detail below,
central conductor 106 may connect each of power cables 104-x to each other
power cable
104-x, such that power applied to one cable is transferred to each other
cable.
[0014] Bus extensions 110 may be configured to receive connector portions of
power
cables 104 in the manner consistent with embodiments described herein. For
example, each
bus extension 110-x may include a spade portion 112 (also referred to as yoke
spade portion
112) having a bore 114 (shown in Fig. 2) therethrough. Each power cable 104
may be
prepared by connecting the power cable 104 to a crimp connector 116. Crimp
connector 116
may include a substantially cylindrical assembly configured to receive a cable
conductor 118
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of power cable 104-x therein. During preparing of power cable 104-x, a portion
of crimp
connector 116 may be physically deformed (e.g., crimped) to fasten crimp
connector 116 to
cable conductor 118.
[0015] Crimp connector 116 may include a forward spade portion 120 (shown in
Figs. 4A-
4C) (also referred to as crimp connector spade portion 120) configured to be
securely
fastened to a spade portion 112 of bus extension 110-x of central conductor
106. For
example, forward spade portions 120 of each crimp connector 116 may include an
opening
therein (described below) configured to align with bore 114 in yoke spade
portion 112.
Consistent with implementations described herein, a cam clamp 122 may be used
to secure
crimp connector spade portion 120 to yoke spade portion 112 of bus extension
110. The
structure and function of cam clamp 122 is described in additional detail
below with respect
to Figs. 2A-6B. In the embodiment of Fig. 1, power cable splicing connector
100 may
include three cam clamps 122.
[0016] As shown in Fig. 1, each of the prepared power cables 104 may further
include an
adapter 124 disposed rearwardly relative to crimp connector 116. Adapter 124
may be
affixed to power cable 104-x and may provide a frictional engagement with a
rearward
portion of respective cable receptacles 126. In one implementation, adapter
124 may be
formed of an insulative material, such as rubber, a thermoplastic, or epoxy.
[0017] As shown in Fig. 1, each tap108-x includes a cable receptacle interface
that
includes a substantially cylindrical flange or cuff portion configured to
frictionally engage a
cable receptacle 126-x (individually, cable receptacle 126-x, or collectively,
cable receptacles
126). For example, an inside diameter of a forward end of cable receptacle 126-
x may be
sized to frictionally engage the cuff portion of tap 108-x. Each cable
receptacle 126 be
substantially cylindrical and may be configured to surround and protect an
interface between
power cables 104 and bus extensions 110.
[0018] Yoke 102 may include a semi-conductive outer shield 128 formed from,
for
example, a peroxide-cured synthetic rubber, commonly referred to as EPDM
(ethylene-
propylene-dienemonomer). Within shield 128, yoke 102 may include an insulative
inner
housing 130, typically molded from an insulative rubber or epoxy material.
Central
conductor 106 may be enclosed within insulative inner housing 130.
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[0019] Regarding cable receptacles 126, each cable receptacle 126-x may
include an
EPDM outer shield 132 and an insulative inner housing 133, typically molded
from an
insulative rubber or epoxy material. Cable receptacle 126-x further includes a
conductive or
semi-conductive insert 134 having a bore therethrough. Upon assembly, cable
receptacle 126
surrounds the interface between power cable 104-x and bus extension 110-x. In
one
implementation, forward ends of insert 134 and outer shield 132 may be
configured to
frictionally engage a portion of yoke inner housing 130 at each tap 108 upon
assembly of
splicing connector 100, thereby ensuring the electrical integrity of splicing
connector 100.
[0020] In one exemplary implementation, power cable splicing connector 100 may
include
a voltage detection test point assembly 136 for sensing a voltage in splicing
connector 100.
Voltage detection test point assembly 136 may be configured to allow an
external voltage
detection device, to detect and/or measure a voltage associated with splicing
connector 100.
[0021] For example, as illustrated in Fig. 1, voltage detection test point
assembly 136 may
include a test point terminal 138 embedded in a portion of yoke inner housing
130 and
extending through an opening within yoke outer shield 128. In one exemplary
embodiment,
test point terminal 138 may be formed of a conductive metal or other
conductive material. In
this manner, test point terminal 138 may be capacitively coupled to the
electrical conductor
elements (e.g., central conductor 106) within splicing connector 100.
[0022] Consistent with implementations described herein, a test point cap 140
may
sealingly engage portion test point terminal 138 and outer shield 128. In one
implementation, test point cap 140 may be formed of a semi-conductive
material, such as
EPDM compounded with conductive additives. When test point terminal 138 is not
being
accessed, test point cap 140 may be mounted on test point assembly 136.
Because test point
cap 140 is formed of a conductive or semi-conductive material, test point cap
140 may
ground the test point when in position. Test point cap 140 may include an
aperture 142 for
facilitating removal of test point cap 140, e.g., using a hooked lineman's
tool.
[0023] Figure 2A is an exploded, schematic, partial cross-sectional diagram
illustrating a
portion of yoke 102 including a portion of center conductor 106, and spade
portion 112 of
bus extension 110, and one of the cam clamps 122 of Fig. 1. Figure 2B is an
exploded,
schematic, partial cross-sectional diagram illustrating the portion of yoke
102 and cam clamp
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122 taken along the line A-A in Fig. 2A. Fig. 3 is a schematic, partial cross-
sectional
diagram showing assembly and installation of cam clamp 122 in yoke 102.
[0024] As shown, in Figs. 2A and 2B, cam clamp 122 may include a cam clamp pin
200,
compression element 205, gap spring 210, washer 215, cam member 220, pivot pin
225, and
retaining member(s) 230. Cam clamp pin 200 may be substantially bolt-like and
may include
a head portion 235, and a shaft portion 240. During assembly of cam clamp 122,
cam clamp
pin 200 is received in bore 114 in spade portion 112, such that shaft portion
240 projects
through bore 114. Shaft portion 240 may include a transverse bore 245
therethrough for
receiving a pivot pin 225, as described in detail below. In some
implementations, bore 114
may include an enlarged upper opening for receiving a head portion 235 in a
recessed
manner (relative to an outside surface of spade portion 112).
[0025] Compression element 205 may include an element or combination or
elements
configured to provide resilient compression between head portion 235 of cam
clamp pin 200
and spade portion 112 of bus extension 110. That is, compression element 205
may exert a
biasing force between cam clamp pin 200 and spade portion 112. As described
below, when
cam member 220 is placed into its clamping position, compression elements 205
may cause a
predetermined amount of force to be applied against spade portion 112 of bus
extension 110
and forward spade portion 120 of crimp connector 116, thereby securing power
cable 104 to
yoke 102. Although secure, the resilient nature of compression element 205 may
allow some
movement of forward spade portion 120 relative to yoke spade portion 112 when
cam
member 220 is placed into its clamping position. This relative movement
capability prevents
or substantially reduces a likelihood that spade portion 120 or yoke spade
portion 112 will
break upon movement of yoke 102 or power cable 104.
[0026] In one implementation, compression element 205 includes a number of
resilient
washers or wave springs, each having a bore therethrough for shaft portion 240
of cam clamp
pin 200. For example, as shown in Figs 2A-3, compression element 205 includes
three
concave (e.g., Belleville) washers. Each washer 205 may be positioned relative
to the other
washers 205, such that compression of the washer exerts a known amount of
resilient force.
Furthermore, in one embodiment, washers 205 may be sized to fit within the
upper opening
of bore 114. Washers 205 may be formed of any suitable material, such as
spring steel,
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stainless steel, etc. In other implementations, compression element 205 may
include a spacer
formed of a resilient material, such as a rubber or polymer.
[0027] Gap spring 210 may include a resilient member configured to maintain
washer 215
and cam member 220 in a spaced relationship relative to spade portion 112 of
bus extension
110 prior to connection of crimp connector spade portion 120. For example, as
shown in Fig.
4B, gap spring 210 may be configured to maintain washer 215 a distance D3 from
a lower
portion of spade portion 112, where D3 is at least slightly larger than D4,
the thickness of
crimp connector spade portion 120. By maintaining distance D3, gap spring 210
prevents
cam clamp 122 from unnecessary movement within bore 114 that would make
connecting
crimp connector spade portion 120 to cam clamp 122 difficult. In exemplary
embodiments,
gap spring 210 may include a helical spring formed of a resilient material,
such as spring
steel, stainless steel, plastic, rubber, etc.
[0028] Washer 215 may include a flat washer or similar element for providing a
substantially flat biasing surface between gap spring 210 and spade portion
112. In addition,
as described below, washer 215 may provide substantially flat biasing surface
between gap
spring 210 and cam member 220. In some implementations, washer 215 may include
a plate,
spacer, or other non-circular element. In addition, in some embodiments,
washer 215 may
include a resilient or compressive element, such as a wave washer or spring,
for providing
increased compressive force upon engagement of cam member 220. Washer 215 may
be
formed of a semi-rigid or rigid material, such as hardened steel, spring
steel, stainless steel,
plastic, etc,
[0029] Cam member 220 may include a pin receiving portion 250 and a tool
engagement
portion 255. As shown in Fig. 5, a total length Ll of cam member 220 may be
configured to
prevent installation of receptacle 126 over cam clamp 122 prior to compression
of cam
member 220 (e.g., via rotation of cam member 220 relative to cam clamp pin
200). In one
implementation, Li is ranges from approximately 1 inch to approximately 1.375
inches.
Furthermore, a width W1 of cam member 220 may be less than length Li, and may
range
from approximately 0.5 inches approximately 0.75 inches.
[0030] More specifically, as shown in Fig. 5, receptacle 126 may include an
inside radius
R1 that defines a distance from a central axis of receptacle 126 to an inside
surface of
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insulative inner housing 133. Consistent with embodiments described herein,
length Li of
cam member 220 may be sufficient to cause at least a portion of cam member 220
to project
from a central axis of receptacle 126 a distance greater than R1, when cam
member 220 is in
an uncompressed position. In this manner, any attempt to install receptacle
126 on power
cable 104 and yoke 102 prior to compression of cam member 220 will cause
forward end 500
of receptacle 126 to abut cam member 220, thereby preventing installation of
receptacle 126.
[0031] Upon compression of cam member 220 (in the manner described below), cam
member 220 is rotated such the projection of cam member 220 from the central
axis of
receptacle 126 is reduced (e.g., by Li-WI). This reduced projection enables
receptacle 126
to be installed on yoke 102.
[0032] Returning to Figs. 2A and 2B, pin receiving portion 250 may include a
recess or
slot 260 formed in cam member 220 and sized to receive an end of cam clamp pin
200
therein. Pin receiving portion 250 may include a transverse bore 265
therethrough
configured to align with bore 245 in pin shaft portion 240 following insertion
of pin 200 into
pin receiving portion 250. During assembly, cam clamp pin 200 may be placed
through
compression elements 205, bore 114 in yoke spade portion 112, gap spring 210,
washer 215,
and received into pin receiving portion 250 of cam member 220.
[0033] Bore 265 in cam member 220 may be spaced a predetermined distance from
the
edges of cam member 220. For ease of understanding, a first edge of cam member
220 may
be referred to as uncompressed edge 251 and a second edge of cam member 220
may be
referred to as compressed edge 252. The distance from the outside diameter of
bore 265 to
uncompressed edge 251 is shown as D1 and the distance from the outside
diameter of bore
265 to compressed edge 252 is shown as D2. The relative difference between
distance D1
and distance D2 establishes the clamp displacement of cam clamp 122 as
described below.
An optimal ratio between D1 and D2 is based on an amount of compression
applied by
compression element 205. A corner of cam member 220 between uncompressed edge
251
and compressed edge 252 may be rounded to increase the ease in transitioning
cam member
220 between uncompressed edge 251 and compressed edge 252.
[0034] Pivot pin 225 may be sized to fit through bore 265 in cam member 220
and bore
245 in cam clamp pin 200. Pivot pin 225 may be secured within bores 265/245 by
one or
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more retaining members 230. In some implementations, retaining members 230 may
include
snap rings or similar elements to retain pivot pin 225 within bores 265/245.
In other
implementations, retaining members 230 may include threaded nuts, end caps, or
rivets.
[0035] Installation of pivot pin 225 in bores 265/245 rotatably secures pin
200 to cam
member 220. As shown, slot 260 in pin receiving portion 250 of cam member 220
may
enable rotational movement of cam member 220 relative to washer 215.
[0036] Tool engagement portion 255 of cam member 220 may include a cavity 270
for
receiving a tool therein. In one implementation, cavity 270 may be
substantially cylindrical
and may be sized to receive a tool, such as a screwdriver. Cavity 270 may be
angled with
respect to a longitudinal axis of cam member 220 to provide a maximum range of
motion
during engagement of cam member 220 in the manner described below.
[0037] In an initial uncompressed state, uncompressed edge 251 may be provided
adjacent
washer 215. In this state, crimp connector spade portion 120 may be received
on cam clamp
pin 200. Rotation of cam member 220 about pivot pin 225 (e.g., via rotation of
a tool receive
in cavity 270) places compressed edge 252 adjacent to washer 215 and increases
the effective
width of cam member 220 (by the difference between D2 and D1). This causes
compression
element 205 to apply compressive forces to crimp connector spade portion 120,
thereby
securing crimp connector spade portion 120 to yoke spade portion 112.
[0038] Fig. 4A is a top view of an exemplary crimp connector 116 and crimp
connector
spade portion 120. As shown crimp connector spade portion 120 may include an
opening
400 therein for enabling crimp connector spade portion 120 to be installed
around gap spring
210 and cam clamp pin 200 following initial assembly of cam clamp 122 to yoke
spade
portion 112. In one implementation, a width of opening 400 may be
substantially equal to an
outside diameter of gap spring 210.
[0039] Figs. 4B and 4C illustrated connection of the crimp connector 116 to
cam clamp
122 installed on yoke spade portion 112. As shown, opening 400 in crimp
connector spade
portion 120 may be aligned with gap spring 210 and pin 200 of the installed
cam clamp 122.
Gap spring 210 may maintain washer 215 a distance D3 from an opposing surface
of yoke
spade portion 112. As described above, the width D4 of crimp connector spade
portion 120
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is slightly less than D3 thereby allowing opening 400 of crimp connector spade
portion 120
to receive gap spring 210 and pin 200, as shown in Fig. 4C.
[0040] Figures 6A and 6B are schematic, partial cross-sectional diagrams
illustrating
clamping of the cam clamp 122. As shown in Fig. 6A, when in an initial
uncompressed or
"open" state, uncompressed edge 251 may be provided adjacent washer 215. A
suitable tool
600, such as a screwdriver or the like, may be inserted into cavity 270 to
affect rotation of
cam member 220 about pivot pin 225. Rotation of tool 600 (as shown by the
arrow in Fig.
6A) may cause cam member 220 to rotate about pivot pin 225, thereby placing
compressed
edge 252 of cam member 220 adjacent to washer 215 (e.g., into a compressed or
"closed"
state). This in turn causes pin 200 to be further drawn into slot 260 in cam
member 220,
thereby causing compression element 205 to compress and impart compressive
forces
between washer 215 and the opposing surface of yoke spade portion 112,
effectively securing
crimp connector spade portion 120 to yoke spade portion 112 in a resilient
manner.
[0041] Following "closing" of cam member 220, tool 600 may be removed. Cable
receptacle 126 may be moved into overlying position over cam clamp 122, as
shown in Fig.
1.
[0042] The above-described cam type clamp assembly provides an effective and
repeatable means for securing power cable spade assemblies together. More
specifically, a
cam clamp assembly may be provided that includes a cam clamp pin, one or more
compression elements, and a cam member rotatable secured to an end of the cam
clamp pin
after the cam clamp pin is installed in one of the spade assemblies. Once the
other spade
assembly is installed onto the cam clamp pin, the cam member is moved from an
open
position to a closed position, thus compressing the compression element and
securing the two
spade assemblies together. In addition, consistent with aspects described
herein, the above
described cam clamp assembly prevents unsecured and unsafe assembly by
disabling
installation or connection of power cable receptacles unless the cam clamps
are in their
closed positions. In addition, the above described cam clamp electrical
connector may be
installed to a desired compression without requiring the use of a torque
wrench of other
complex/expensive tools.
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[0043] The foregoing description of exemplary implementations provides
illustration and
description, but is not intended to be exhaustive or to limit the embodiments
described herein
to the precise form disclosed. Modifications and variations are possible in
light of the above
teachings or may be acquired from practice of the embodiments. For example,
implementations described herein may also be used in conjunction with other
devices, such
as high voltage switchgear equipment, including 15 kV, 25 kV, or 35 kV
equipment.
[0044] For example, various features have been mainly described above with
respect to
electrical connectors, and splicing or yoke-type connectors in particular. In
other
implementations, other medium/high voltage power components may be configured
to
include the connection mechanism configurations described above.
[0045] Although the invention has been described in detail above, it is
expressly
understood that it will be apparent to persons skilled in the relevant art
that the invention may
be modified without departing from the spirit of the invention. Various
changes of form,
design, or arrangement may be made to the invention without departing from the
spirit and
scope of the invention. Therefore, the above-mentioned description is to be
considered
exemplary, rather than limiting, and the true scope of the invention is that
defined in the
following claims.
[0046] No element, act, or instruction used in the description of the present
application
should be construed as critical or essential to the invention unless
explicitly described as
such. Also, as used herein, the article "a" is intended to include one or more
items. Further,
the phrase "based on" is intended to mean "based, at least in part, on" unless
explicitly stated
otherwise.
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