U.S. patent application number 09/682027 was filed with the patent office on 2001-10-25 for draw out unit.
Invention is credited to Bernier, Richard E., Bynum, Edward B. JR., Piper, Charles, Soares, Gilbert, Struble, John J. JR., Yee, Edgar.
Application Number | 20010034149 09/682027 |
Document ID | / |
Family ID | 23737790 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010034149 |
Kind Code |
A1 |
Bernier, Richard E. ; et
al. |
October 25, 2001 |
Draw out unit
Abstract
A draw out unit mounts switching devices within a switchgear
unit and electrically connects the switching devices to electrical
bus bars. A cutout portion in draw out unit receives an insulative
housing for a lug adapter assembly. Lug adapter assembly includes a
plurality of clip assemblies positioned within receptacles formed
on insulative housing. Each clip assembly slidably accepts one bus
bar, thereby providing an electrical connection to bus bars. Lug
adapter assembly also includes lugs, which are electrically
connected to clip assemblies via a conductive bar. Lugs accept
wires, which extend from lugs in switching device. Lugs are
arranged to minimize bending of wires.
Inventors: |
Bernier, Richard E.;
(Mebane, NC) ; Piper, Charles; (Burlington,
NC) ; Soares, Gilbert; (Mebane, NC) ; Yee,
Edgar; (Chapel Hill, NC) ; Struble, John J. JR.;
(Mebane, NC) ; Bynum, Edward B. JR.; (Chapel Hill,
NC) |
Correspondence
Address: |
CANTOR COLBURN, LLP
55 GRIFFIN ROAD SOUTH
BLOOMFIELD
CT
06002
|
Family ID: |
23737790 |
Appl. No.: |
09/682027 |
Filed: |
July 11, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09682027 |
Jul 11, 2001 |
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09437765 |
Nov 9, 1999 |
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6280216 |
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Current U.S.
Class: |
439/251 |
Current CPC
Class: |
H02B 11/12 20130101;
H02B 1/21 20130101 |
Class at
Publication: |
439/251 |
International
Class: |
H01R 013/64 |
Claims
1. A draw out unit arranged for mounting a switching device within
a switchgear unit and electrically connecting the switching device
to an electrical bus bar, the draw out unit comprising: a frame
arranged for supporting the switching device within the switchgear
unit; an insulative housing secured to said frame; a clip assembly
arranged within said insulative housing, said clip assembly for
slidably receiving an edge of the bus bar; a conducting plate
electrically connected to said clip; and a conductive lug
electrically connected to said conducting plate, said lug being
formed from a block of electrically conductive material, said
conductive lug including a first side having a first hole disposed
therein for accepting a first electrical wire, said first
electrical wire extending from an associated lug on the switching
device, said first hole having an axis aligned with the associated
lug, and a second side having a second hole disposed therein for
accepting a first set screw, said first set screw for securing said
first wire within said first hole.
2. The draw out unit of claim 1 wherein said first side of said
conductive lug includes: a third hole disposed therein for
accepting a second electrical wire, and said second side of said
conductive lug includes a fourth hole for accepting a second set
screw, said second set screw for securing said second wire within
said third hole.
3. The draw out unit of claim 1 wherein said conductive lug further
includes: a third side, said third side having a shoulder formed
thereon for contacting an edge of said conducting plate and
aligning said conductive lug with said conducting plate.
4. The draw out unit of claim 1, wherein said clip assembly
includes: a first clip arranged for slidably receiving said edge of
the bus bar; said first clip including a first contact arm arranged
for contacting a first side of the bus bar, and a second contact
arm arranged for contacting a second side of the bus bar opposite
said first side, said first and second contact arms extending a
first distance from said edge; and a second clip arranged for
slidably receiving said edge of the bus bar, said second clip
including a third contact arm arranged for contacting said first
side of the bus bar, and a fourth contact arm arranged for
contacting said second side of the bus bar opposite said first
side, said third and fourth contact arms extending a second
distance from said edge, said second distance being less than said
first distance.
5. The draw out unit of claim 4, wherein said first and third
contact arms are formed from a first piece of electrically
conductive material, and said second and fourth contact arms are
formed from a second piece of electrically conductive material.
6. The draw out unit of claim 5, wherein said clip assembly further
includes: a first common root portion formed from said first piece
of electrically conductive material, said first and third contact
arms extending from said first common root portion; a first base
portion formed from said first piece of electrically conductive
material, said first base portion extending from said common root
portion and contacting said conducting plate; a second common root
portion formed from said second piece of electrically conductive
material, said second and fourth contact arms extending from said
second common root portion; and a second base portion formed from
said second piece of electrically conductive material, said second
base portion extending from said common root portion and contacting
said conducting plate, said first root portion being attached to
said second root portion.
7. The draw out unit of claim 5, further including: a common root
portion formed from said first piece of electrically conductive
material, said first and second contact arms extending from said
common root portion, and wherein said first and second contact arms
each have a first width where said first and second contact arms
join said root portion, and said first and second contact arms each
have a second width at a free end of said first and second contact
arms, said first width being greater than said second width.
8. A draw out unit arranged for mounting a switching device within
a switchgear unit and electrically connecting the switching device
to an electrical bus bar, the draw out unit comprising: a
conductive lug including a first side having a first hole disposed
therein for accepting a first electrical wire, said first
electrical wire extending from an associated lug on the switching
device, said first hole having an axis aligned with the associated
lug, and a second side having a second hole disposed therein for
accepting a first set screw, said first set screw for securing said
first wire within said first hole, the axis of the first hole being
perpendicular to an axis of the second hole.
9. The draw out unit of claim 8 wherein said first side of said
conductive lug further comprises a third hole disposed therein for
accepting a second electrical wire, and said second side of said
conductive lug further comprises a fourth hole for accepting a
second set screw, said second set screw for securing said second
wire within said third hole.
10. The draw out unit of claim 9 further comprising a conducting
plate, wherein said conductive lug further comprises a third side,
said third side having a shoulder formed thereon for contacting an
edge of said conducting plate and aligning said conductive lug with
said conducting plate.
11. The draw out unit of claim 10 wherein the conductive lug
further comprises a tab having a fifth hole, the fifth hole for
receiving a retaining bolt securing the conducting plate to the
conductive lug.
12. The draw out unit of claim 9 wherein the second hole and the
fourth hole are threaded.
13. The draw out unit of claim 9 wherein the second side of the
conductive lug is sloped and wherein the second hole and the fourth
hole are offset from each other.
14. The draw out unit of claim 9 wherein the longitudinal axis of
the second hole and a longitudinal axis of the fourth hole are
parallel, and wherein the longitudinal axis of the first hole and a
longitudinal axis of the third hole are parallel.
15. The draw out unit of claim 8 further comprising a switching
device, the switching device having a switching device lug as the
associated lug.
16. The draw out unit of claim 15 wherein the switching device is a
circuit breaker.
17. An electrical distribution system comprising a switchgear, the
switchgear comprising a plurality of draw out units and a bus bar,
each draw out unit comprising: a switching device having a
switching device lug; a frame arranged for supporting the switching
device within the switchgear; an insulative housing secured to the
frame; a clip assembly arranged within the insulative housing, the
clip assembly for slidably receiving an edge of the bus bar; a
conducting plate electrically connected to the clip; a conductive
lug electrically connected to the conducting plate; and, a first
electrical wire connecting the switching device lug to the
conductive lug.
18. The electrical distribution system of claim 17 wherein the
frame of each draw out unit includes a bottom side, the clip
assembly extending from the bottom side, and further wherein the
first electrical wire is securable within the conductive lug
through a top side of the frame.
19. The electrical distribution system of claim 17 wherein the
insulative housing of each draw out unit comprises a plurality of
receptacles for receiving a plurality of clip assemblies.
20. The electrical distribution system of claim 17 wherein the
insulative housing of each draw out unit includes a pair of spaced
apart walls for receiving the conducting plate.
21. A draw out unit arranged for mounting a switching device within
a switchgear unit and electrically connecting each phase of the
switching device to a separate electrical bus bar, the draw out
unit comprising: a frame arranged for supporting the switching
device within the switchgear unit; a plurality of clip assemblies,
each clip assembly for slidably receiving an edge of a bus bar;
and, an insulative housing secured to the frame, the housing having
a plurality of receptacles, each receptacle receiving a clip
assembly.
22. The draw out unit of claim 21 wherein the insulative housing
includes a plurality of dowels for placing within holes of the
frame.
23. The draw out unit of claim 21 wherein the insulative housing
includes a pair of mounting guides.
24. The draw out unit of claim 23 wherein each mounting guide
includes a slot for slidably accepting a portion of the frame.
25. The draw out unit of claim 21 further comprising a conducting
plate in electrical contact with the clip assemblies, the
insulative housing comprising an opening for receiving the
conducting plate.
26. The draw out unit of claim 21 wherein each receptacle is formed
by an upper wall, a lower wall, and a pair of side walls.
27. The draw out unit of claim 26 wherein each upper and lower wall
includes a V-shaped cutout.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. Patent Application
No. 09/437,765 entitled "LUG ADAPTER ASSEMBLY HAVING REDUCED FORCE
CLIPS", filed on Nov. 9, 1999, currently pending, which is herein
incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] This invention relates generally to electrical distribution
equipment, and more specifically to a draw out unit with a lug
adapter assembly having current carrying clips (stabs) for
attaching cable conductors to electric busway systems.
[0003] The use of switchgears in electrical distribution systems is
well known. The switchgear houses a plurality of draw out units,
with each draw out unit housing one or more switching devices, such
as motor controllers and circuit breakers, which are releasably
interconnected to one or more busbars. Periodically, the draw out
units are removed from the switchgear to allow for maintenance of
the equipment. The switching devices within the draw out units make
electrical contact with the busbars through a plurality of clip
connectors which extend from the draw out unit. Each clip connector
is electrically connected to an electrical conductor for connection
to the switching devices of the switchgear.
[0004] Clip connectors of the prior art are generally mounted
within an insulative housing that is affixed to a frame of the draw
out unit. Each clip connector is typically constructed of an
electrically conductive material formed into a "U" shape. The two
free ends of the "U"-shaped clip form contact arms, which extend
within the clip housing and are aligned for electrical connection
with a specific busbar. As the draw out unit is inserted into the
switchgear, the busbar slides between the two contact arms, and the
contact arms frictionally engage the busbar. Typically, only one
clip connector attaches to each bus bar.
[0005] The design of the contact clip requires each contact arm to
have a surface area in contact with the bus bar to reduce
resistance to current flow and thereby prevent inefficient thermal
losses. In the U-shaped contact clips found in the prior art, a
contact surface is formed along the entire width of each of the two
contact arms. Ideally, these contact surfaces remain parallel to
the bus bar when the bus bar is engaged between the two contact
arms, thus allowing the full width of the contact arm to be in
contact with the bus bar. However, inaccuracies during
manufacturing and mishandling during installation can cause
deformities the contact arms and their contact surfaces. Such
deformities allow only a small portion of the contact arm to
actually contact the bus bar, resulting in an increase in
resistance to current flow.
[0006] The design of the contact clip also requires that the
contact arms exert a minimum compressive force (force per unit of
area in contact with the bus bar) onto the busbar. This force is
required to overcome the electromagnetic force generated by current
flow in the contact arms, which tends to part the arms from the bus
bar. Problematically, the required minimum compressive force is
proportional to the amount of force required to insert the contact
clips onto the busbar. In other words, clips having a high
compressive force are difficult to slide onto the busbar. As a
result, it is necessary to use a racking mechanism in order to
develop sufficient insertion force to install the draw out unit
into the switchgear. The need for a racking mechanism increases the
equipment cost for switchgear installation and maintenance. In
addition, the need for a racking mechanism necessitates that
clearance space be provided for the racking mechanism within the
switchgear. The additional clearance space increases the size and
cost of the switchgear itself.
SUMMARY OF INVENTION
[0007] The above-identified drawbacks of the prior art are overcome
or alleviated by a draw out unit arranged for mounting a switching
device within a switchgear unit and electrically connecting the
switching device to an electrical bus bar.
[0008] In an exemplary embodiment, the draw out unit of this
invention comprises a frame arranged for supporting the switching
device within the switchgear unit, an insulative housing secured to
the frame, a clip assembly arranged within the insulative housing,
the clip assembly for slidably receiving an edge of the bus bar, a
conducting plate electrically connected to the clip, and a
conductive lug electrically connected to the conducting plate, the
lug being formed from a block of electrically conductive material,
the conductive lug including a first side having a first hole
disposed therein for accepting a first electrical wire, the first
electrical wire extending from an associated lug on the switching
device, the first hole having an axis aligned with the associated
lug, and a second side having a second hole disposed therein for
accepting a first set screw, the first set screw for securing the
first wire within the first hole.
BRIEF DESCRIPTION OF DRAWINGS
[0009] Referring now to the drawings wherein like elements are
numbered alike in the several Figures:
[0010] FIG. 1 is a partially exploded perspective view of a draw
out unit with a lug adapter assembly of the present invention;
[0011] FIG. 2 is a perspective view of a housing for the lug
adapter assembly of Figure
[0012] FIG. 3 is a perspective view of a clip assembly for the lug
adapter assembly of FIG. 1;
[0013] FIG. 4 is a perspective view of a lug for the lug adapter
assembly of FIG. 1;
[0014] FIG. 5 is a side elevational partial cutaway view of an
assembled lug adapter assembly within the draw out unit of FIG.
1;
[0015] FIG. 6 is a perspective view of one side of an alternate
embodiment of the clip assembly; and
[0016] FIG. 7 is a perspective view of the alternate embodiment of
the clip assembly.
DETAILED DESCRIPTION
[0017] FIG. 1 is partially exploded view of a draw out unit 10 for
mounting switching devices 12,14 within a switchgear unit (not
shown) and electrically connecting the switching devices 12,14 to
electrical bus bars 16. Switching devices 12,14 include, for
example, a circuit breaker 12 and a starter unit 14. Draw out unit
10 includes a frame 18 having a bottom 20, two ends 22, 24, and
side supports 26. Switching devices 12,14 are mounted to a support
plate 28, which, in turn, is mounted to bottom 20. A cutout portion
30 on bottom 20 and side 22 receives an insulative housing 32 for a
lug adapter assembly 34. Lug adapter assembly 34 includes a
plurality of clip assemblies 36 positioned within receptacles 38
formed on insulative housing 32. Housing 32 is arranged within the
draw out unit 10 so that clip assemblies 36 are aligned with
vertical bus bars 16. Each clip assembly 36 slidably accepts one
bus bar 16, thereby providing an electrical connection to bus bars
16. Lug adapter assembly 34 also includes lugs 40, which are
electrically connected to clip assemblies 36 via a conductive bar
42. Lugs 46 extend upward within frame 18 when insulative housing
32 is installed in frame 18. Lugs 40 accept wires 44, which extend
from lugs 46 in switching device 12. Clip assemblies 36, conductive
bars 42, and lugs 40 are constructed from electrically conductive
materials such as copper or aluminum to provide a current path from
the bus bars 16 to wires 44 and, in turn, to the associated
switching device 12.
[0018] As best shown in FIG. 2, insulative housing 32 includes the
plurality of receptacles 38, which extend substantially
perpendicular from a top portion of a wall 50. In the embodiment
shown, three receptacles 38 are used. However, it will be
understood by one skilled in the art that housing 32 could include
any number of receptacles 38, depending on the number of phases in
the associated electrical distribution circuit. Wall 50 of housing
32 includes a substantially rectangular opening 52 at each
receptacle 38. Each receptacle 38 is formed by an upper wall 54, a
lower wall 56, and a pair of side walls 58, which frame rectangular
openings 52. Each upper and lower wall 54, 56 includes a V-shaped
cutout 60 therein. The cutout 60 extends from an edge 62 of walls
54,56 distal to wall 50, to an arcuate apex 64 located between wall
50 and front edge 62. Arcuate apex 64 is generally aligned with the
clip assemblies 36 (see FIG. 3), allowing bus bars 16 to be
received by clip assemblies 36.
[0019] A cover 66 extends from a side of wall 50 opposite
receptacles 38. Cover 66 includes sides 68, which are attached to
opposing side edges of wall 50 and extend perpendicular to wall 50.
Cover 66 also includes a wall 70, which extends from side wall 68
to side wall 68. Wall 70 of cover 66 is substantially parallel to
wall 50, forming a space between the two walls 50,70 for accepting
conductive bar 42 (FIG. 1).
[0020] A pair of walls 72 extends from the wall 50 and between the
receptacles 38 in the same plane as the upper wall 54 of the
receptacles 38. Walls 72 are generally rectangular, and protrude no
further than the arcuate apex 64. Walls 72 act as stiffening
members to provide rigidity to housing 32.
[0021] The lower portion of wall 50 forms a detente surface 74,
which contacts frame 18 of the draw out unit 10 (FIG. 1) when
housing 32 is installed in the draw out unit 10. Located below the
rectangular openings 52, three dowels 76 extend from the detente
surface 74 in a direction opposite receptacles 38. When housing 32
is installed in the draw out unit 10, dowels 76 extend within holes
in the frame 18 of the draw out unit 10 to secure housing 32 to the
draw out unit 10. Extending outwardly from the sides of wall 50 and
side walls 68 are a pair of mounting guides 78. Slots 80 within
mounting guides 78 extend substantially parallel to wall 50 for
slidably accepting a portion of the draw out unit frame 18, further
securing housing 32 to the draw out unit 10.
[0022] Referring to FIG. 3, clip assembly 36 is shown attached to
conductive bar 42. Clip assembly 36 includes a rectangular base 100
electrically connected to conductive bar 42, a root portion 102
extending perpendicularly from the base portion 100, and upper and
lower clips 104,106 extending from the root portion 102. The clip
assembly 36 is mounted on the conductive bar 42 above a hole 108
passing through the conductive bar 42.
[0023] Conductive bar 42 is substantially rectangular in shape,
having a length "l" greater than that of rectangular opening 52 of
the housing 32 (FIG. 2) and a width "w" substantially equal to the
width of the rectangular opening 52 (FIG. 2). The conductive bar 42
includes hole 108 disposed in a lower portion of conductive bar 42
for receiving a threaded bolt 110. Hole 108 is substantially square
in shape for receiving a square portion on bolt 110 and thereby
preventing bolt 110 from spinning within hole 108.
[0024] Rectangular base 100 is affixed to a rear surface 112 of an
upper portion of the conductive bar 42. Rectangular base 100 has a
width substantially equal to the width "w" of conductive bar 42 and
a length substantially equal to half the length "l" of conductive
bar 42.
[0025] The lower clip 106 is disposed below and extends further
forward than the upper clip 104. Each clip 104,106 extends from
root portion 102. The root portion 102 includes a horizontally
disposed, narrow slot 114 that extends partially into the root
portion 102 between the clips 104,106. Each clip 104,106 is
constructed from two symmetric contact arms 116, 118. Each contact
arm 116, 118 depends angularly away from the other to define a
first portion 120 of each contact arm 16, 118. From the first
portion 120 of contact arms 116, 118, each member depends angularly
inward therefrom to define a second portion 122. Furthermore, the
second portion 122 of lower clip 118 is longer than second portion
122 of upper clip 104, thereby resulting in the further extension
of the lower clip 118. Each contact arm 116,118 is turned-out,
defining an oblique angle therebetween for guiding clips 104,106
onto the bus bars 16. A gap 124 is included between contact arms
116,118 at each second portion 122. The width "W" of gap 124 is
smaller than the thickness "T" of the edge of vertical bus bar 16
to be inserted within each clip 104,106 allowing clips 104,106 to
frictionally engage bus bar 16 between contact arms 116,118.
[0026] Referring to FIGS. 2 and 3, base 100, root portion 102, and
clips 104,106 of each clip assembly 36 are formed from two pieces
of electrically conductive material, which are secured together at
the root portion 102 by welding or by a mechanical fastener as is
well known in the art. When the clip assembly 36 is mounted within
the housing 32, the root portion 102 passes through the rectangular
opening 52, and the clips 104,106 are vertically aligned and extend
horizontally from the root portion 102 within the receptacle
38.
[0027] Referring to FIG. 4, an exemplary embodiment of the lug 40
of the present invention is shown. The lug 40 comprises a flat
bottom surface 150 from which a rear surface 152 and an opposing
front surface 154 perpendicularly depend. Front surface 154 is
substantially rectangular. Rear surface 152 is planar and has a
horizontal step (shoulder) 156 defining its end. The step 156 has a
depth substantially equal to the thickness of the conductive bar
42. An inclined surface 158 depends in a rearward direction from
the front surface 154. A horizontally disposed surface 160 extends
rearward from the inclined surface 158. A rectangular tab 162
extends upwardly between the horizontally disposed surface 160 and
the horizontal step 156.
[0028] A first threaded hole 164 is positioned horizontally passing
into the front surface 154 and further extending into a first
through hole 166. The first through hole 166 extends from the
bottom surface 150 partially through the lug 40 and is disposed
approximate the front surface 154. The axes of the first threaded
hole 164 and the first through hole 166 form a substantially
perpendicular intersection. A set screw 165 is installed in first
threaded hole 164 for securing an electrical wire in first through
hole 166.
[0029] A second through hole 168 extends from the bottom surface
150 and extends partially through the lug 40. The axis of the
second through hole 168 is disposed parallel to the first through
hole 166 and further aligned with a plane defined by the axes of
the first through hole 166 and the threaded hole 164. A second
threaded hole 170 is disposed above and parallel to the first
threaded hole 164 having its axis on the plane formed by the axes
of the holes 164,166 and 168. The second threaded hole 170 extends
through the second through hole 150. A set screw 171 is installed
in second threaded hole 170 for securing an electrical wire in
second through hole 168.
[0030] Inclined surface 158 includes a cutout 172 extending
vertically into the inclined surface 158. The cutout 172 passes
partially into the inclined surface 158 wherein the cutout 172
intersects the second threaded hole 170. The tab 162 includes a
hole 174 for receiving the retaining bolt 110 (FIG. 3).
[0031] As best shown in FIG. 5, the lug 40 is bolted to the
conductive bar 42. Ends of cable 44 are inserted into hole 168 and
retained therein by set screw 171. Another cable (not shown) may be
secured in hole 166 in a similar manner. Lug 40 is retained at wall
50 by mounting the lug 40 on the threaded bolt 110 and retaining
the lug 40 with the nut 111 thereon. Mounting the lug 40 on the
conductive bar 42 of the lug assembly 34 provides a current path
from the bus bars 16 to the cable 44. Step 156 on lug 40 abuts an
end of conductive bar 42 for aligning lug 40 with conductive bar
42.
[0032] The conductive bar 42 is positioned flush with wall 50 and
clips 104,106 extend perpendicular to wall 50 and within receptacle
38. Each clip 104,106 is centered within the receptacle 38, thereby
being aligned with a vertical bus bar 16. Top cover 66 of
insulative housing 32 resists forces developed by insertion and
removal of the clips 104,106 onto the bus bar 16.
[0033] Within each lug 40, the hole 168 for accepting wire 44 has
an axis that extends in a direction towards its corresponding
switching device lug 46. This arrangement allows wire 44 to extend
in a substantially linear fashion between lug 40 and lug 46, with
no severe bending of wire 44. Because, there is no need to
accommodate the bending radius of wire 44, the distance between
switching device 12 and lug 40 can be made smaller than if bending
of wire 44 was required. Decreased distance between switching
device 12 and lugs 40 allows frame 18 to have smaller dimensions,
thus making a more efficient use of space within the draw out unit
10 and rendering the draw out unit 10 more manageable.
[0034] Referring to FIGS. 2, 3, and 5, upon insertion of the draw
out unit 10 into the switchgear (not shown), bus bars 16 enter into
the V-shaped cutout 60 in housing 32 and into the gap 124 formed
between contact arms 116,118 of lower clip 106. The bus bar 16
expands contact arms 116, 118 of the lower clip 106 before
commencing entry and expansion of the contact arms 116,118 of the
upper clip 104. The insertion will continue until the detent
surface 74 contacts a stop bar (not shown) of the switchgear--i.e.
when insertion is complete and the bus bar 16 is fully inserted
within the clip assembly 36. Staggering the clips 104,106 reduces
the insertion force needed to expand the contact arms 116,118 by
reducing the size and engagement area of each contact arm 116,118.
Indeed, an insertion force of about 40 percent of the insertion
force of a typical clip assembly is required because the clips are
staggered. In addition, the use of more than one clip within each
clip assembly helps to insure that each clip assembly will have
more than one contact point on the bus bar.
[0035] Referring now to FIGS. 6 and 7, another embodiment of clip
assembly 36 having four clips 243 is illustrated. FIG. 6 shows a
first side 200 of clip assembly 36 having four contact arms. The
side shown can be combined with a symmetrical second side 200 to
produce the clip assembly 36 (see FIG. 7). Side 200 has an
approximately rectangular root portion 202. The rectangular root
portion 202 defines a circular aperture 204, which is preferably
disposed in the center of the rectangular root portion 202. A base
portion 206 depends perpendicularly from a first long edge 207 of
the rectangular root portion 202. The base portion 206 is
preferably the same thickness and length as the rectangular root
portion 202. The base portion 206 defines two circular apertures
208, 210, which are preferably disposed approximately centrally
within the top half 212 and the bottom half 214 of the base portion
206. The rectangular root portion 202 has a notch 216 disposed on a
first short edge 218 of the rectangular root portion 202. A
rectangular tab 220 depends perpendicularly forward along a second
short edge 222 of the rectangular root portion 202. The tab 220
extends far enough from the rectangular root portion 202 to enable
bending of the tab 220 over the second side 200 of the clip
assembly 36 (see FIG. 7). The notch 216 is wide enough and deep
enough to accept the width and the thickness of the tab 220 on the
second side 200 of clip assembly 36.
[0036] A second long edge 224 of the rectangular root portion 202
has an upper protrusion 226 and a lower protrusion 228, with a
recessed portion 230 disposed therebetween. Four contact arms 232
depend from the second long edge 224 of the rectangular root
portion 202. Each contact arm 232 comprises a first portion 234
disposed against the second long edge 224 and depending angularly
backwards from a plane formed by the root portion. From the first
portion 234, each contact arm 232 depends angularly forward
therefrom to define a second portion 236, which terminates with a
turned-out portion 238 that angles backward. Turned-out portions
238 define oblique angles that guide the clip assembly 250 onto the
bus bar 16. Each contact arm 232 is trapezoidal in shape, with the
width "x" of the first portion 234 along the second long edge 224
being greater than the width "y" of the free end at the turned-out
portion 238. If a width "x" at the ends of the contact arms 232
were the same or less than the width "y", then the contact arms 232
would be more likely to bend at and with respect to the root
portion 202 than if the width "x" is greater than the width "y".
Thus, the trapezoidal-shape of the contact arms 232 prevent
rotation of the contact arms 232 with respect to the root portion
202.
[0037] The contact arms 232 depend from the second long edge 224:
one contact arm 232 from the upper protrusion 226, one contact arm
232 from the lower protrusion 228, and two contact arms 232 from
the recessed portion 230. The contact arms define three narrow
slots 240, which extend from the turned-out portions 238 to radii
formed on second long edge 224. The radius r2 formed between the
middle two contact arms 232 is greater than the radii r1 formed
between contact arms 232 and upper and lower protrusions 226, 228.
The different radii allow the material stress all contact arms 232
to be approximately equal when bus bar 16 is slidably engaged by
the clip assembly 36. That is, as shown in FIGS. 6-7, the clip
assembly 36 includes four clips, each clip including a pair of
contact arms arranged for contacting opposite sides of the bus bar
16. The clip assembly 36 may further comprise two sections of
electrically conductive material as shown in FIG. 7. Thus, a first
clip which includes first and second contact arms would comprise a
first contact arm on one piece of electrically conductive material
and a second contact arm on the other piece of electrically
conductive material. A second clip would include third and fourth
contact arms which would comprise a third contact arm on one piece
of electrically conductive material and a fourth contact arm on the
other piece of electrically conductive material. A third clip would
include fifth and sixth contact arms which would comprise a fifth
contact arm on one piece of electrically conductive material and a
sixth contact arm on the other piece of electrically conductive
material. A fourth clip would include seventh and eighth contact
arms which would comprise a seventh contact arm on one piece of
electrically conductive material and an eighth contact arm on the
other piece of electrically conductive material. Thus, one piece of
electrically conductive material, such as shown in FIG. 6, would
include the first, third, fifth, and seventh contact arms and the
other piece of electrically conductive material would include the
second, fourth, sixth, and eighth contact arms. The radii r1 may
thus be seen between the first and third contact arms and the fifth
and seventh contact arms and the radius r2 is shown between the
third and fifth contact arms. In other words, the design of radii
r1 and r2 is such that the material stress in similar portions of
each contact arm 232 will be approximately equal. It will be
appreciated that the attachment of two of the contact arms 232 to
the recessed portion 230, and two of the contact arms to the upper
and lower protrusions 226, 228 causes the contact arms 232 attached
to the upper and lower protrusions 226, 228 to extend outward from
the rectangular root portion 202 further than the contact arms 232
that are attached to the recessed portion 230.
[0038] Turning now to FIG. 7, assembly of the clip assembly 36 is
done by first fitting together the two sides 200 in such a way so
that the rectangular root portions 202 are placed proximate each
other, with the circular apertures 204 aligned, and with base
portions 206 lying in the same plane and extending in opposite
directions. The tang 220 of each side 200 is disposed against the
first short edge 218 and within the notch 216 of the other side
200, and the long edges 207, 224 of each side 200 are disposed
adjacent to the same long edges 207, 224 of the other side 200.
[0039] It will be appreciated that this fitting together of two
sides 200 will align opposing contact arms 232 in symmetrical pairs
that define four individual clips 243, which in turn define four
gaps 244. Additionally, the individual rectangular root portions
202 of the two sides 200 will together form a single clip assembly
root 203. As in the previous embodiment, the gap 244 will be
narrower than the width of the bus bar 16.
[0040] The individual clips 243 that depend from either of the
protrusions 226, 228 will extend from the clip assembly root 203 a
greater distance than the clips 243 that depend from the recessed
portion.
[0041] To facilitate the proper and secure joining of the two sides
200, a rivet or similar fastening device (not shown) may be
inserted through the circular apertures 204 disposed in the
rectangular root portions 202. The use of a fastener will
facilitate the proper alignment of the two sides 200, and will
supplement the effectiveness of the rectangular tangs 220. To
complete the assembly, tang 220 on one side 200 is bent over the
rectangular root portion 202 of the other side 200 so that a
portion of the tang 220 is disposed in a parallel plane to, and in
intimate contact with, the rectangular root portion 202 of the
other side 200. The same process is then performed on the other
tang 220.
[0042] The clip assembly 250 of this embodiment can be attached to
a conductive bar 42 (see FIGS. 1,3, and 5) by four bolts and four
nuts or other connecting devices (not shown) that pass through the
circular apertures 208, 210 in the base portion 206 of each side
200 of the clip assembly 36. The conductive bar 42 in this
embodiment has holes (not shown) that align with the circular
apertures 208, 210 in the clip assembly 36. The clip assembly 36
can also be fastened to the conductive bar 42 by spot welding, or
any other means well known in the art, as in the first embodiment.
The clip assembly 36 of this embodiment can be used in the lug
adapter assembly 34 described above, and in any manner consistent
therewith.
[0043] Upon installation of this embodiment of the present
invention on a bus bar 16, the two protruding clips 3 will engage
the bus bar 22 before the two recessed clips 243. As in the first
embodiment, the force required to properly mount the clip
assemblies 36 on the bus bar 16 is thereby significantly
reduced.
[0044] The invention provides the advantage of requiring less force
for insertion of the clips onto the bus bars, thus allowing a
switching device to be inserted by hand while dispensing with the
need for complex racking mechanisms. The invention further requires
less space for housing the switching device because there is no
racking mechanism. Furthermore, the lug of the present device
provides for attachment of electric cable to the switching device
without the need for large bend radii, allowing the size of the
draw out unit to be reduced.
[0045] While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
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