ELECTRICAL SWITCHING APPARATUS AND
CHARGING ASSEMBLY THEREFOR
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to commonly assigned, concurrently filed:
United States Patent Application Serial No. , filed
, 2009, entitled "ELECTRICAL SWITCHING APPARATUS AND LINKING
ASSEMBLY THEREFOR" (Attorney Docket No. 08-EDP-515).
BACKGROUND
Field
The disclosed concept relates generally to electrical switching apparatus
and, more particularly, to electrical switching apparatus, such as circuit breakers. The
disclosed concept also relates to charging assemblies for electrical switching apparatus.
Background Information
Electrical switching apparatus, such as circuit breakers, provide protection
for electrical systems from electrical fault conditions such as, for example, current
overloads, short circuits, abnormal voltage and other fault conditions. Typically, circuit
breakers include an operating mechanism which opens electrical contact assemblies to
interrupt the flow of current through the conductors of an electrical system in response to
such fault conditions as detected, for example, by a trip unit.
Some low and medium voltage circuit breakers, for example, further
employ a spring-operated stored energy assembly. Specifically, the operating mechanism
of such circuit breakers typically includes an opening assembly having at least one
spring, which facilitates the opening (e.g., separation) of the electrical contact assemblies,
a closing assembly including a number of springs that close the electrical contact
assemblies, and a charging mechanism for charging the spring(s). The contact assemblies
are closed by releasing the stored energy of the closing assembly spring(s). The spring(s)
is/are charged by a charging assembly which is operated manually, using a manual
charging mechanism such as, for example, a charging handle, and/or automatically using
a motor-driven charging mechanism or other suitable electromechanical charging
mechanism.

Figures 1A-1D show one non-limiting example of a circuit breaker 1
(partially shown) having a spring charging assembly 9 for charging a number of closing
springs 11 (one is shown in the side elevation view of Figures 1A-1D). The spring
charging assembly 9 includes a charging cam 13 and a compression arm 15, which
cooperates with the charging cam 13 to compress and thereby charge the closing spring
11 (see Figure 1A). The compression arm 15 pivots (e.g., counterclockwise from the
perspective of Figures 1A-1D) in response to the contact force applied to it by the closing
spring 11. Thus, by virtue of the design (e.g., without limitation, shape) of the
compression arm 15 and/or the charging cam 13, the closing spring 11 has the effect of
producing a relatively significant amount of torque on the compression arm 15.
Consequently, interaction of the compression arm 15 with relatively small changes in the
curvature of the charging cam 13 undesirably results in relatively large changes in torque.
As such, very close control must be kept of the precise shape of the charging cam 13 to
control movement of the spring charging assembly 9 and ultimately, the latch load (e.g.,
the force applied by the closing spring 11 to the linking assembly 5 of the spring charging
assembly 9).
Among other disadvantages, the requirement for such close control of the
charge cam geometry increases the cost to manufacture the spring charging assembly 9
and, in particular the charging cam 13 therefor, and decreases the robustness of the
overall design because certain components (e.g., without limitation, charging cam 13;
compression arm 15) are exposed to considerable force during operation, which
undesirably increases wear and tear.
There is, therefore, room for improvement in electrical switching
apparatus, such as circuit breakers, and in charging assemblies therefor.
SUMMARY
These needs and others are met by embodiments of the disclosed concept,
which are directed to a charging assembly for an electrical switching apparatus, such as a
circuit breaker. Among other benefits, the charging assembly includes a charging cam
and compression arm which are structured to reduce undesirable torque on the assembly,
thereby improving the robustness of the design.

As one aspect of the disclosed concept, a charging assembly is provided
for an electrical switching apparatus. The electrical switching apparatus includes a
housing, separable contacts enclosed by the housing, and an operating mechanism
structured to move the separable contacts between an open position corresponding to the
separable contacts being separated and a closed position corresponding to the separable
contacts being electrically connected. The operating mechanism includes a linking
assembly and a closing assembly. The closing assembly includes a biasing element and
an impact member coupled to the biasing element. The biasing element is movable
between a charged position and a discharged position. When the biasing element moves
from the charged position to the discharged position, the impact member engages and
moves the linking assembly thereby moving the separable contacts to the closed position.
The charging assembly comprises: a compression arm including a pivot structured to
pivotally couple the compression arm to the housing of the electrical switching apparatus,
a first leg, and a second leg, each of the first leg and the second leg comprising a first end
and a second end disposed opposite and distal from the first end, the first end of the first
leg being disposed at or about the pivot, the second end of the first leg extending
outwardly from the pivot in a first direction, the first end of the second leg being disposed
at or about the pivot, the second end of the second leg extending outwardly from the
pivot in a second direction; an engagement portion disposed at or about the second end of
the first leg; a shaped contact surface disposed at or about the second end of the second
leg, the shaped contact surface comprising a first edge and second edge disposed at an
angle with respect to the first edge; and a charging cam structured to be pivotally coupled
to the housing of the electrical switching apparatus, the charging cam including an outer
cam surface structured to cooperate with the engagement portion of the first leg of the
compression arm. When the charging cam pivots, the outer cam surface engages the
engagement portion of the first leg, thereby pivoting the compression arm about the
pivot. Responsive to the compression arm pivoting about the pivot, the first edge of the
shaped contact surface of the second leg is structured to engage and move the impact
member of the closing assembly, thereby moving the biasing element from the
discharged position toward the charged position. When the biasing element is disposed

in the charged position, the second edge of the shaped contact surface of the second leg is
structured to engage the impact member.
The first leg may further comprise a first longitudinal axis extending from
the pivot of the compression arm through the second end of the first leg in the first
direction, and the second leg may further comprise a second longitudinal axis extending
from the pivot of the compression arm through the second end of the second leg in the
second direction. The first longitudinal axis may be disposed at an angle with respect to
the second longitudinal axis of between about 80 degrees and about 110 degrees. The
second leg of the compression arm may be disposed generally perpendicularly with
respect to the first leg of the compression arm in order that the compression arm has a
generally L-shape.
The outer cam surface of the charging cam may comprises a variable
radius, wherein the variable radius comprises a point of minimum radius and a point of
maximum radius. The variable radius may increase gradually from the point of minimum
radius to the point of maximum radius. When the biasing element is disposed in the
charged position, the point of maximum radius of the charging cam may be structured to
be cooperable with the engagement portion of the first leg and, when the biasing element
of the closing assembly is disposed in the discharged position, the point of minimum
radius of the charging cam may be structured to cooperate with the engagement portion
of the first leg of the compression arm. The outer cam surface of the charging cam may
further comprise a transition point, and the variable radius may further comprise a first
downslope and a second downslope, wherein the first downslope is disposed between the
point of maximum radius and the transition point, and wherein the second downslope is
disposed between the transition point and the point of minimum radius. The second
downslope may be greater than the first downslope.
As another aspect of the disclosed concept, an electrical switching
apparatus comprises: a housing; separable contacts enclosed by the housing; an operating
mechanism structured to move the separable contacts between an open position
corresponding to the separable contacts being separated and a closed position
corresponding to the separable contacts being electrically connected; a linking assembly;
a closing assembly including a biasing element and an impact member coupled to the

biasing element, the biasing element being movable between a charged position and a
discharged position, when the biasing element moves from the charged position to the
discharged position, the impact member engages and moves the linking assembly thereby
moving the separable contacts to the closed position; and a charging assembly
comprising: a compression arm including a pivot pivotally coupling the compression arm
to the housing, a first leg, and a second leg, each of the first leg and the second leg
comprising a first end and a second end disposed opposite and distal from the first end,
the first end of the first leg being disposed at or about the pivot, the second end of the
first leg extending outwardly from the pivot in a first direction, the first end of the second
leg being disposed at or about the pivot, the second end of the second leg extending
outwardly from the pivot in a second direction, an engagement portion disposed at or
about the second end of the first leg, a shaped contact surface disposed at or about the
second end of the second leg, the shaped contact surface comprising a first edge and
second edge disposed at an angle with respect to the first edge, and a charging cam
pivotally coupled to the housing of the electrical switching apparatus, the charging cam
including an outer cam surface cooperating with the engagement portion of the first leg of
the compression arm. When the charging cam pivots, the outer cam surface engages the
engagement portion of the first leg, thereby pivoting the compression arm about the
pivot. Responsive to the compression arm pivoting about the pivot, the first edge of the
shaped contact surface of the second leg engages and moves the impact member of the
closing assembly, thereby moving the biasing element from the discharged position
toward the charged position. When the biasing element is disposed in the charged
position, the second edge of the shaped contact surface of the second leg engages the
impact member.
BRIEF DESCRIPTION OF THE DRAWINGS
A full understanding of the disclosed concept can be gained from the
following description of the preferred embodiments when read in conjunction with the
accompanying drawings in which:
Figure 1A is a side elevation view of a spring charging assembly for a
circuit breaker, showing the spring charging assembly in the charged and open position;

Figure 1B is a side elevation view of the spring charging assembly of
Figure 1 A, modified to show the spring charging assembly in the open and partially
charged position;
Figure 1C is a side elevation view of the spring charging assembly of
Figure 1 A, modified to show the spring charging assembly in the discharged and closed
position;
Figure 1D is a side elevation view of the spring charging assembly of
Figure 1 A, modified to show the spring charging assembly in the discharged and open
position;
Figure 2A is a side elevation view of a charging assembly in accordance
with an embodiment of the disclosed concept, showing the charging assembly in the
charged and open position;
Figure 2B is a side elevation view of the charging assembly of Figure 2A,
modified to show the charging assembly in the open and partially charged position;
Figure 2C is a side elevation view of the charging assembly of Figure 2 A,
modified to show the charging assembly in the discharged and closed position;
Figure 2D is a side elevation view of the charging assembly of Figure 2A,
modified to show the charging assembly in the discharged and open position; and
Figure 3 is a side elevation view of a portion of a circuit breaker
employing a charging assembly in accordance with an embodiment of the disclosed
concept.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Directional phrases used herein, such as, for example, left, right,
clockwise, counterclockwise and derivatives thereof, relate to the orientation of the
elements shown in the drawings and are not limiting upon the claims unless expressly
recited therein.
As employed herein, the term "biasing element" refers to refers to any
known or suitable stored energy mechanism such as, for example and without limitation,
springs and cylinders (e.g., without limitation, hydraulic cylinders; pneumatic cylinders).
As employed herein, the term "downslope" refers to the decreasing radius
of the outer cam surface of the disclosed charging cam upon movement from one

predetermined location on the outer cam surface (e.g., without limitation, the point of
maximum radius) to another predetermined location on the outer cam surface (e.g.,
without limitation, the transition point).
As employed herein, the statement that two or more parts are "coupled"
together shall mean that the parts are joined together either directly or joined through one
or more intermediate parts.
As employed herein, the term "number" shall mean one or an integer
greater than one (i.e., a plurality).
Figures 2A-3 show a charging assembly 100 for an electrical switching
apparatus such as, for example, a circuit breaker 200 (partially shown in simplified form
in phantom line drawing in Figure 3). As shown in simplified form in Figure 3, the
circuit breaker 200 includes a housing 202 (partially shown in phantom line drawing),
separable contacts 204 (shown in simplified form) enclosed by the housing 202, and an
operating mechanism 206 (shown in simplified form). The operating mechanism 206 is
structured to move the separable contacts 204 between an open position, corresponding to
the separable contacts 204 being separated, and a closed position, corresponding to the
separable contacts 204 being electrically connected. The operating mechanism 206
includes a linking assembly 300 and the closing assembly 210. The closing assembly
210 includes a biasing element such as, for example and without limitation, the spring
212, which is shown and described herein. However, it will be appreciated that any
known or suitable alternative number, type and/or configuration of biasing element(s)
could be employed, without departing from the scope of the disclosed concept.
An impact member 214 is coupled to the spring 212, as shown, and is
movable, along with the spring 212, between a charged position in which the spring 212
is compressed, as shown in Figure 2A, and a discharged position in which the spring 212
is extended, as shown in Figures 2C and 2D. When the spring 212 moves from the
charged position of Figure 2A to the discharged position, the impact member 214
engages and moves the linking assembly 300 (described in greater detail hereinbelow), as
shown in Figure 2C, thereby moving the separable contacts 204 (Figure 3) to the
aforementioned closed position.

The example charging assembly 100 includes a compression arm 102
pivotally coupled to the housing 202 of the circuit breaker 200 by a pivot 104. More
specifically, the compression arm 102 and, in particular, the pivot 104 thereof, is
preferably pivotally coupled to a sideplate 220, which is, in turn, coupled to a portion of
the circuit breaker housing, as shown in simplified form in Figure 3. It will, therefore, be
appreciated that the circuit breaker may include more than one sideplate (only one
sideplate 220 is shown), and that the closing assembly 210 is substantially disposed on a
corresponding one of the sideplates 220, as shown.
The compression arm 102 includes a first leg 106 having opposing first
and second ends 110,112 and a second leg 108 having opposing first and second legs
114,116. More specifically, the first end 110 of the first leg 106 is disposed at or about
the pivot 104 of the compression arm 102, and the second end 112 of the first leg 106
extends outwardly from the pivot 104 in a first direction. Similarly, the first end 114 and
the second leg 108 is disposed at or about the pivot 104 of the compression arm 102, and
the second end 116 extends outwardly from the pivot 104 in a second direction, which is
different from the first direction of first leg 106, as shown. In the example shown and
described herein, the first leg includes a first longitudinal axis 132 extending from the
pivot 104 of the compression arm 102 through the second end 112 of the first leg 106 in
the first direction, and the second leg 108 includes a second longitudinal axis 134
extending from the pivot 104 through the second end 116 of the second leg 108 in the
second direction, as shown in Figure 2A. Preferably, the first longitudinal axis 132 of the
first leg 106 is disposed at an angle 136 with respect to the second longitudinal axis 134
of the second leg 108 of between about 80 degrees and about 110 degrees. More
preferably, the second leg 108 of the compression arm 102 is disposed generally
perpendicularly with respect to the first leg 106, in order that the compression arm 102
has a generally L-shape, as shown. Accordingly, it will be appreciated that the legs
106,108 of the example compression arm 102 are substantially straight as they extend
outwardly from the pivot 104 of the compression arm 102, unlike known compression
arms (see, for example, compression arm 7 of Figures 1A - ID), which are not
substantially straight but rather include a number of relatively substantial curves or bends
(see, for example, the bend of the first leg of compression arm 7 in Figures 1A-1D).

The charging assembly 100 further includes an engagement portion 118
disposed at or about the second end 112 of the first leg 106, and a shaped contact surface
120, which is disposed at or about the second end 114 of the second leg 108. The
example shaped contact surface 120 includes a first edge 122 and a second edge 124
disposed in an angle 126 (see Figure 2B) with respect to the first edge 122. Preferably
the angle 126 (Figure 2B) between the first and second edges 122,124 is less than 90
degrees. The shaped contact surface 120 of the second leg 108 of the example
compression arm 102 further includes a convex portion 150 disposed between the first
and second edges 122,124 of the shaped contact surface 120, thereby providing a
relatively smooth transition between the edges 122,124. The convex portion 150
cooperates with a circular protrusion 216 of the closing assembly impact member 214,
which also has a convex exterior 218. Specifically, as the spring 212 of the circuit
breaker closing assembly 210 is moved from the discharged position (Figures 2C and 2D)
to the charged position of Figure 2A (see also the partially charged position of Figure
2B), the convex portion 150 of the compression arm shaped contact surface 120 engages
the convex exterior 218 of the impact member circular protrusion 216 (e.g., without
limitation, pivot pin) to move it and compress (e.g., charge) the spring 212. In other
words, the two edges 122,124 of the second leg 108 result in vastly different moment
arms (about the pivot 104) for the force of the charging spring(s) 210. See, for example
and without limitation, moment arms 160 and 170 of Figures 2A and 2B, respectively.
The moment arm 170 (Figure 2B) from the first edge 122 produces much more torque
about the pivot 104 and thus higher forces between the first leg 106 and the charging cam
128, than the moment arm 160 (Figure 2A) second edge 124. Accordingly, the amount of
resulting torque that causes the compression arm 102 to rotate becomes much less when
the circuit breaker 200 is fully charged (Figure 2A). As a result of less force being
produced, the shape of the charging cam 128 advantageously has less absolute influence
on cam shaft torque. The additional benefits of this reduced sensitivity of shape are
further described herein. For example and without limitation, force on the cam shaft is
reduced which also results in reduced load for the linking assembly 300 (described
here in be low).

The charging assembly 100 further includes a charging cam 128.
Preferably the charging cam 128 is pivotally coupled to the sideplate 220 of the circuit
breaker housing 202, proximate to the compression arm 102, as shown. The charging
cam 128 includes an outer cam surface 130, which cooperates with the engagement
portion 118 of the first leg 106 of the compression arm 102 to facilitate operation of the
charging assembly 100, as will now be described in greater detail. Specifically, when the
charging cam 128 pivots (e.g., counterclockwise in the direction of the arrows shown in
Figures 2A and 2B), the outer cam surface 130 engages the engagement portion 118 of
the first leg 106 of the compression arm 102, thereby pivoting (e.g., clockwise from the
perspective of Figures 2A-3) the compression arm 102 about the pivot 104. Responsive
to the compression arm 102 pivoting about such pivot 104, the first edge 122 of the
shaped contact surface 120 of the second leg 108 engages and moves the impact member
214 of the circuit breaker closing assembly 210, as shown in Figure 2B. This, in turn,
moves the spring 212 of the closing assembly 210 from the discharged position of
Figures 2C and 2D toward the charged position of Figure 2A. When the spring 212 is
disposed in the charged position, the second edge 124 of the contact surface 120 of the
second leg 108 of the compression arm 102, engages the impact member 214, as shown
in Figure 2A.
Accordingly, it will be appreciated that the unique configuration of the
shaped contact surface 120 of the compression arm 102, in combination with the
improved charging cam 128 (described in greater detail hereinbelow) of the disclosed
charging assembly 100, overcomes the disadvantages associated with known charging
assemblies (see, for example, charging assembly 1 of Figures 1A-1D) by reducing the
amount of torque on the compression arm 102. Consequently, wear and tear on the
compression arm 102 and charging cam 128 is reduced and the robustness of the charging
assembly design is improved. Additionally, the necessity to very closely control the
charging cam geometry in an attempt to minimize such excessive torque, is
advantageously minimized. As such, the manufacturing cost associated with the charging
assembly 100 is reduced.
As best shown in Figure 2A, the second leg 108 of the example
compression arm 102 further includes a concave portion 152. Specifically, the concave

portion 152 is disposed on the first edge 122 of the shaped contact surface 120 of the
second leg 108, as shown. Accordingly, when the charging cam 128 pivots to initially
move the compression arm 102 into engagement with the impact member 214 of the
circuit breaker charging assembly 210, the concave portion 152 of the compression arm
102 cooperates with (e.g., engages) the convex exterior 218 of the circular protrusion 216
(e.g., without limitation, pivot pin) of the closing assembly impact member 214, as shown
in Figure 2D.
Referring again to the charging cam 128 of the charging assembly 100, it
will be appreciated that the outer cam surface 130 of the charging cam 128 has a variable
radius 138. Specifically, the variable radius 138 includes a point of minimum radius 140
and a point of maximum radius 142, wherein the variable radius 138 increases gradually
from the point of minimum radius 140 to the point of maximum radius 142.
Accordingly, in operation, when the spring 212 of the circuit breaker closing assembly
210 is disposed in the charged position, the point of maximum radius 142 of the charging
cam 128 cooperates with (e.g., engages) engagement portion 118 of the first leg 106 of
the compression arm 102, as shown in Figure 2A. Then, when the spring 212 of the
closing assembly 210 is disposed in the discharged position, the point of minimum radius
140 on the outer cam surface 130 of the charging cam 128 cooperates with (e.g., engages)
the engagement portion 118 of the first leg 106 of the compression arm 102, as shown in
Figure 2C.
The outer cam surface 130 of the charging cam 128 further includes a
transition point 144, such that the variable radius 138 has a first downslope 146 disposed
between the point of maximum radius 142 and the transition point 144, and a second
downslope 148 disposed between the transition point 144 and the point of minimum
radius 140. Preferably, the second downslope 148 is greater than the first downslope
146, as shown. In other words, the radius of the outer cam surface 130 decreases more
gradually in the area of the first downslope 146, from the point of maximum radius 146
to the transition point 144, whereas the radius of the outer cam surface 130 transitions
(e.g., decreases) more rapidly on the opposite side of the transition point 144, in the area
of the second downslope 148. Consequently, the operation of the charging assembly 100
and, in particular, the cooperation of the charging cam 128 with the engagement portion

118 of the compression arm 102 is advantageously improved, for example, by controlling
the amount of torque between the components 102,128 via the controlled interaction of
the cam outer surface 130 with the engagement portion 118 of the compression arm 102
as the spring 212 of the circuit breaker closing assembly 210 is charged.
The aforementioned linking assembly 300 will now be described in greater
detail with continued reference to Figures 2A-3. It will be appreciated that, while the
linking assembly 300 is shown and described herein in conjunction with the
aforementioned charging assembly 100, that the disclosed linking assembly 300 could
also be employed independently, for example and without limitation, in any known or
suitable alternative electrical switching apparatus (not shown) that does not require such
an assembly.
The example linking assembly 300 includes a hatchet 302 having first and
second edges 304,306 and an arcuate portion 308 extending therebetween. The hatchet
302 is movable between a latched position, shown in Figures 2A (shown in solid line
drawing), 2C and 3, and an unlatched position, partially shown in phantom line drawing
in Figure 2A (also shown in Figures 2B and 2D). More specifically, the hatchet 302
cooperates with a D-shaft 208 that preferably extends outwardly from the aforementioned
circuit breaker sideplate 220, and is movable (e.g., pivotable) between a first position and
a second position. When the hatchet 302 is disposed in the latched position, the D-shaft
208 is disposed in the first position such that the first edge 304 of the hatchet 302 engages
the D-shaft 208, thereby maintaining the hatchet 302 in the position shown in Figures 2A
(shown in solid line drawing), 2C and 3. When the D-shaft 208 pivots to the second
position, for example in response to a fault condition, the D-shaft 208 pivots out of
engagement with the first edge 304 of the hatchet 302 such that the hatchet 302 pivots
with respect to the D-shaft 208 to unlatch the linking assembly 300, as shown in Figures
2B and 2D.
The linking assembly 300 further includes a cradle 310 having first and
second opposing ends 312,314 (both shown in Figures 2A and 2B) and an intermediate
portion 316 (Figures 2A and 2B) disposed therebetween. A latch plate 318 is pivotally
coupled to the circuit breaker housing 202 and includes a protrusion, which in the
example shown and described herein is a roller 320. The roller 320 cooperates with the

hatchet 302, as will be described in greater detail hereinbelow. A latch link 322 is
disposed between and is pivotally coupled to the cradle 310 and the latch plate 318, as
shown. A toggle assembly 324 includes first and second linking elements 326,328. The
first and second ends 330,332 of the first linking element 326 are respectively pivotally
coupled to the circuit breaker poleshaft 222 and the first end 334 of the second linking
element 328, and the second end 336 of the second linking element 328 is pivotally
coupled to the cradle 310, as shown in Figures 2A, 2B and 3.
Among other benefits, the latch plate 318 and latch link 322 of the
disclosed linking assembly 300 provide an additional stage of force reduction that
reduces the force(s) associated with tripping the circuit breaker 200 (Figure 3) open in
response to fault conditions. These components (e.g., without limitation, 318,322) also
effectively decouple the hatchet 302 and cradle 310 under certain circumstances
(described hereinbelow), thereby accommodating a more acceptable movement and
configuration among the components (e.g., without limitation, angles between and
movement of first and second linking elements 326,328 of toggle assembly 324; degrees
of swing or movement of hatchet 302) of the linking assembly 300, as compared with
known linking assemblies (see, for example, linking assembly 5 of Figures 1A-1D).
This, in turn, enables relatively small, or conventional accessories (not shown) to be
employed with the circuit breaker 200 (Figure 3), because the associated tripping forces
are advantageously reduced by the linking assembly 300. It also enables the overall size
of the circuit breaker 200 (Figure 3) to be reduced.
As shown, for example, in Figures 2A and 2B, the example latch link 322
includes a first portion 338 coupled to the intermediate portion 316 of the cradle 310, and
a second portion 340 pivotally coupled to the latch plate 318 at or about the roller 320
thereof. The roller 320 extends outwardly from the latch plate 318 such that, when the
hatchet 302 is moved toward the latched position of Figures 2A, 2C and 3, the arcuate
portion 308 of the hatchet 302 engages the roller 320, thereby moving the latch link 322
with the latch plate 318. In other words, under such circumstances, the latch plate 318
and latch link 322 move collectively together, but not independently with respect to one
another. Consequently, responsive to the hatchet 302 and, in particular, the arcuate
portion 308 thereof, engaging the roller 320 and moving the latch link 322 with the latch

plate 318, movement of the hatchet 302 is transferred substantially directly into
movement of the cradle 310. On other hand, when the hatchet 302 is disposed in the
unlatched position of Figures 2B and 2D, the hatchet 302 disengages the roller 320 such
that the latch plate 318 moves with respect to the latch link 322, thereby substantially
decoupling movement of the hatchet 302 from movement of the cradle 310. This is a
unique design, which is entirely different from known single latch element designs (see,
for example, single latch element 23 between hatchet 21 and cradle 25 of linking
assembly 5 of Figures 1 A-ID). Specifically, this decoupling functionality enables
sufficient movement of the linking assembly 300 to establish the necessary tripping
forces while occupying relatively little space within the circuit breaker housing 202
(partially shown in phantom line drawing in Figure 3).
Continuing to refer to Figures 2A and 2B, it will be appreciated that the
latch link 322 includes a first longitudinal axis 342, and the latch plate 318 includes a
second longitudinal axis 344. When the hatchet 302 is disposed in the latched position
(Figure 2A), the first longitudinal axis 342 of the latch link 322 is disposed at an angle
346 of about 180 degrees with respect to the second longitudinal axis 344 of the latch
plate 318, as shown in Figure 2A. When the hatchet 302 is disposed in the unlatched
position (Figure 2B), the first longitudinal axis 342 of the latch link 322 is disposed at an
angle 346 of between about 90 degrees and about 160 degrees with respect to the second
longitudinal axis 344 of the latch plate 318.
Accordingly, it will be appreciated that the hatchet 302, cradle 310, latch
plate 318, latch link 322, and toggle assembly 324 of the disclosed linking assembly 300
preferably cooperate to establish at least four stages of force reduction to reduce the
aforementioned tripping force which is necessary to trip open the separable contacts 204
(shown in simplified form in Figure 3), for example, in response to a fault condition.
Specifically, as shown in Figures 2C and 2D, the non-limiting example linking assembly
300 shown and described herein includes a first stage of force reduction disposed
between a drive link 348 and the circuit breaker poleshaft 222, a second stage offeree
reduction disposed between the poleshaft 222, the first linking element 326 of the toggle
assembly 324, the second linking element 328 of the toggle assembly 324, and the cradle
310, a third stage of feree reduction disposed between the cradle 310, the latch link 322,

and the latch plate 318, and a fourth stage of feree reduction disposed between the
protrusion (e.g., roller 320) of the latch plate 318 and the hatchet 302. The relative
positions of the stages (e.g., stages 1-4) when the linking assembly 300 is disposed in the
latched and unlatched positions are labeled and shown in Figures 2C and 2D,
respectively.
Referring again to Figure 2A, it will be appreciated that the first linking
element 326 of the toggle assembly 324 includes a first longitudinal axis 350, and the
second linking element 328 of the toggle assembly 324 includes a second longitudinal
axis 352. When the hatchet 302 is latched and the separable contacts 204 (Figure 3) are
disposed in the open position corresponding to Figure 2A, the first longitudinal axis 350
of the first linking element 326 forms an angle 354 of about 90 degrees with respect to
the second longitudinal axis 352 of the second linking element 328. Additionally, as
previously discussed, the hatchet 302 of the disclosed linking assembly 300
advantageously moves (e.g., pivots) a relatively small distance compared to the hatchets
(see, for example, hatchet 21 of Figures 1A-1D) of known linking assembly designs (see,
for example, linking assembly 5 of Figures 1A-1D). For example, comparing the
position of the hatchet 302 shown in solid line drawing in Figure 2A, corresponding to
the latched position, and the position of the hatchet 302 partially shown in phantom line
drawing, corresponding to the unlatched position, the hatchet 302 pivots a distance 362,
which is preferably less than about 30 degrees. Accordingly, the disclosed hatchet 302
moves (e.g., pivots) substantially less than known hatchets, such as, for example, the
hatchet 21 of Figures 1A-1D, which pivots in excess of 40 degrees when it moves from
the latched position of Figures 1A and 1C to the fully unlatched position of Figure 1D.
This reduced hatchet movement allows for a relatively compact linking assembly design
which, in turn, enables the overall size of the circuit breaker 200 (Figure 3) to be
advantageously reduced.
The hatchet 302 of the disclosed linking assembly 300 is further
distinguishable from prior art designs in that the arcuate portion 308 of the hatchet 302
extends outwardly from the pivot 356 that pivotally couples the hatchet 302 to the
housing 202, in a direction that is generally away from the circuit breaker poleshaft 222.
In other words, the hatchet 302 extends upwardly (from the perspective of Figures 2A-3),

which is generally opposite of the configuration of known hatchets (see, for example,
hatchet 21 of Figures 1A-1D, which extends generally downwardly). Additionally, when
the hatchet 302 moves from the latched position of Figures 2A, 2C and 3, to the
unlatched position of Figures 2B and 2D, it pivots clockwise about the pivot 356 in the
direction of arrow 360 of Figure 2A. This is also opposite the direction (e.g.,
counterclockwise from the perspective of Figures 1A-1D) that the hatchet 21 of Figures
1A-1D pivots when it moves from the latched position (Figures 1A and 1C) to the
unlatched position (Figures 1B and 1D).
Accordingly, the disclosed linking assembly 300 provides for a relatively
compact design that minimizes the relative movement f the components (e.g., hatchet
302; cradle 310; latch plate 318; latch link 322; toggle assembly 324) thereof. This
advantageously enables the overall size of the circuit breaker (Figure 3) to be reduced.
Additionally, the linking assembly 300 decouples the hatchet 302 from the cradle 310,
when desired, and provides an additional stage of feree reduction (e.g., fourth stage of
force reduction, shown in Figures 2C and 2D) to advantageously reduce the tripping force
experienced by the circuit breaker 200 (Figure 3).
While specific embodiments of the disclosed concept have been described
in detail, it will be appreciated by those skilled in the art that various modifications and
alternatives to those details could be developed in light of the overall teachings of the
disclosure. Accordingly, the particular arrangements disclosed are meant to be
illustrative only and not limiting as to the scope of the disclosed concept which is to be
given the full breadth of the claims appended and any and all equivalents thereof.

REFERENCE CHARACTER LIST
1 circuit breaker
3 operating mechanism
5 linking assembly
7 poleshaft
9 spring charging assembly
11 closing spring
13 charging cam
15 compression arm
100 charging assembly
102 compression arm
104 pivot
106 first leg
108 second leg
110 first end of first leg
112 first end of second leg
114 second end of first leg
116 second end of second leg
118 engagement portion
120 shaped contact surface
122 first edge
124 second edge
126 angle
128 charging cam
130 outer cam surface
132 first longitudinal axis
134 second longitudinal axis
136 angle between axes
138 variable radius
140 point of minimum radius
142 point of maximum radius
144 transition point
146 first downslope
148 second downslope
150 convex portion
160 moment arm
152 concave portion
170 moment arm
200 electrical switching apparatus
202 housing
204 separable contacts
206 operating mechanism
208 D-shaft
210 closing assembly

212 biasing element
214 impact member
216 circular protrusion
218 convex exterior
220 sideplate
222 poleshaft
300 linking assembly
302 hatchet
304 first edge of hatchet
306 second edge of hatchet
308 arcuate portion of hatchet
310 cradle
312 first end of cradle
314 second end of cradle
316 intermediate portion of cradle
318 latch plate
320 protrusion
322 latch link
324 toggle assembly
326 first linking element
328 second linking element
330 first end of first linking element
332 second end of first linking element
334 first end of second linking element
336 second end of second linking element
338 first portion of latch link
340 second portion of latch link
342 first longitudinal axis of latch link
344 second longitudinal axis of latch plate
346 angle
348 drive link
350 first longitudinal axis of first linking element
352 second longitudinal axis of second linking element
354 angle
356 pivot
360 arrow
362 angle

WE CLAIM
1. A charging assembly (100) for an electrical switching apparatus (200),
said electrical switching apparatus (200) including a housing (202), separable contacts
(204) enclosed by the housing (202), and an operating mechanism (206) structured to
move said separable contacts (204) between an open position corresponding to said
separable contacts (204) being separated and a closed position corresponding to said
separable contacts (204) being electrically connected, said operating mechanism (206)
including a linking assembly (300) and a closing assembly (210), said closing assembly
(210) including a biasing element (212) and an impact member (214) coupled to said
biasing element (212), said biasing element (212) being movable between a charged
position and a discharged position, when said biasing element (212) moves from said
charged position to said discharged position, said impact member (214) engages and
moves said linking assembly (300) thereby moving said separable contacts (204) to said
closed position, said charging assembly (100) comprising:
a compression arm (102) including a pivot (104) structured to pivotally
couple said compression arm (102) to the housing (202) of said electrical switching
apparatus (200), a first leg (106), and a second leg (108), each of said first leg (106) and
said second leg (108) comprising a first end (110,114) and a second end (112,116)
disposed opposite and distal from the first end (110,114), the first end (110) of said first
leg (106) being disposed at or about said pivot (104), the second end (112) of said first
leg (106) extending outwardly from said pivot (104) in a first direction, the first end (114)
of said second leg (108) being disposed at or about said pivot (104), the second end (116)
of said second leg (108) extending outwardly from said pivot (104) in a second direction;
an engagement portion (118) disposed at or about the second end (112) of
said first leg (106);
a shaped contact surface (120) disposed at or about the second end (114)
of said second leg (108), said shaped contact surface (120) comprising a first edge (122)
and second edge (124) disposed at an angle (126) with respect to the first edge (122); and
a charging cam (128) structured to be pivotally coupled to the housing
(202) of said electrical switching apparatus (200), said charging cam (128) including an

outer cam surface (130) structured to cooperate with said engagement portion (118) of
said first leg (106) of said compression arm (102),
wherein, when said charging cam (128) pivots, the outer cam surface
(130) engages said engagement portion (118) of said first leg (106), thereby pivoting said
compression arm (102) about said pivot (104),
wherein, responsive to said compression arm (102) pivoting about said
pivot (104), the first edge (122) of said shaped contact surface (120) of said second leg
(108) is structured to engage and move said impact member (214) of said closing
assembly (210), thereby moving said biasing element (212) from said discharged position
toward said charged position, and
wherein, when said biasing element (212) is disposed in said charged
position, the second edge (124) of said shaped contact surface (120) of said second leg
(108) is structured to engage said impact member (214).
2. The charging assembly (100) of claim 1 wherein said first leg (106)
further comprises a first longitudinal axis (132) extending from said pivot (104) of said
compression arm (102) through the second end (114) of said first leg (106) in said first
direction; wherein said second leg (108) further comprises a second longitudinal axis
(134) extending from said pivot (104) of said compression arm (102) through the second
end (116) of said second leg (108) in said second direction; wherein said first longitudinal
axis (132) is disposed at an angle (136) with respect to said second longitudinal axis
(134); and wherein said angle (136) is between about 80 degrees and about 110 degrees.
3. The charging assembly (100) of claim 2 wherein said second leg (108) of
said compression arm (102) is disposed generally perpendicularly with respect to said
first leg (106) of said compression arm (102) in order that said compression arm (102)
has a generally L-shape.
4. The charging assembly (100) of claim 1 wherein the outer cam surface
(130) of said charging cam (128) comprises a variable radius (138); wherein said variable
radius (138) comprises a point of minimum radius (140) and a point of maximum radius
(142); wherein said variable radius (138) increases gradually from the point of minimum
radius (140) to the point of maximum radius (142); wherein, when said biasing element
(212) is disposed in said charged position, the point of maximum radius (142) of said

charging cam (128) is structured to be cooperable with said engagement portion (118) of
said first leg (106); and wherein, when said biasing element (212) of said closing
assembly (210) is disposed in said discharged position, the point of minimum radius
(140) of said charging cam (128) is structured to cooperate with said engagement portion
(118) of said first leg (106) of said compression arm (102).
5. The charging assembly (100) of claim 4 wherein the outer cam surface
(130) of said charging cam (128) further comprises a transition point (144); wherein the
variable radius (138) further comprises a first downslope (146) and a second downslope
(148); wherein the first downslope (146) is disposed between the point of maximum
radius (142) and the transition point (144); and wherein the second downslope (148) is
disposed between the transition point (144) and the point of minimum radius (140).
6. The charging assembly (100) of claim 5 wherein the second downslope
(148) is greater than the first downslope (146).
7. The charging assembly (100) of claim 1 wherein said shaped contact
surface (120) of said second leg (108) of said compression arm (102) further comprises a
convex portion (150) disposed between the first edge (122) of said shaped contact surface
(120) and the second edge (122) of said shaped contact surface (120); and wherein said
angle (126) between the first edge (122) and the second edge (124) is less than 90
degrees.
8. The charging assembly (100) of claim 7 wherein said impact member
(214) of said closing assembly (210) includes circular protrusion (216) having a convex
exterior (218); and wherein, when said biasing element (212) is moved from said
discharged position to said charged position, said convex portion (150) of said shaped
contact surface (120) is structured to cooperate with the convex exterior (218) of said
circular protrusion (216).
9. The charging assembly (100) of claim 8 wherein said second leg (108) of
said compression arm (102) further comprises a concave portion (152); wherein said
concave portion (152) is disposed on the first edge (122) of said shaped contact surface
(120) of said second leg (108); and wherein, when said charging cam (128) pivots to
initially move said compression arm (102) into engagement with said impact member
(214) of said closing assembly (210), said concave portion (152) of said compression arm

(102) is structured to cooperate with the convex exterior (218) of said circular protrusion
(216) of said impact member (214).
10. An electrical switching apparatus (200) comprising:
a housing (202);
separable contacts (204) enclosed by the housing (202);
an operating mechanism (206) structured to move said separable contacts
(204) between an open position corresponding to said separable contacts (204) being
separated and a closed position corresponding to said separable contacts (204) being
electrically connected;
a linking assembly (300);
a closing assembly (210) including a biasing element (212) and an impact
member (214) coupled to said biasing element (212), said biasing element (212) being
movable between a charged position and a discharged position, when said biasing
element (212) moves from said charged position to said discharged position, said impact
member (214) engages and moves said linking assembly (300) thereby moving said
separable contacts (204) to said closed position; and
a charging assembly (100) comprising:
a compression arm (102) including a pivot (104) pivotally coupling
said compression arm (102) to the housing (202), a first leg (106), and a second leg (108),
each of said first leg (106) and said second leg (108) comprising a first end (110,114) and
a second end (112,116) disposed opposite and distal from the first end (110,114), the first
end (110) of said first leg (106) being disposed at or about said pivot (104), the second
end (112) of said first leg (106) extending outwardly from said pivot (104) in a first
direction, the first end (114) of said second leg (108) being disposed at or about said
pivot (104), the second end (116) of said second leg (108) extending outwardly from said
pivot (104) in a second direction,
an engagement portion (118) disposed at or about the second end
(112) of said first leg (106),
a shaped contact surface (120) disposed at or about the second end
(114) of said second leg (108), said shaped contact surface (120) comprising a first edge

(122) and second edge (124) disposed at an angle (126) with respect to the first edge
(122), and
a charging cam (128) pivotally coupled to the housing (202) of
said electrical switching apparatus (200), said charging cam (128) including an outer cam
surface (130) cooperating with said engagement portion (118) of said first leg (106) of
said compression arm (102),
wherein, when said charging cam (128) pivots, the outer cam
surface (130) engages said engagement portion (118) of said first leg (106), thereby
pivoting said compression arm (102) about said pivot (104),
wherein, responsive to said compression arm (102) pivoting about
said pivot (104), the first edge (122) of said shaped contact surface (120) of said second
leg (108) engages and moves said impact member (214) of said closing assembly (210),
thereby moving said biasing element (212) from said discharged position toward said
charged position, and
wherein, when said biasing element (212) is disposed in said
charged position, the second edge (124) of said shaped contact surface (120) of said
second leg (108) engages said impact member (214).
11. The electrical switching apparatus (200) of claim 10 wherein said first leg
(106) of said compression arm (102) of said charging assembly (100) further comprises a
first longitudinal axis (132) extending from said pivot (104) of said compression arm
(102) through the second end (114) of said first leg (106) in said first direction; wherein
said second leg (108) further comprises a second longitudinal axis (134) extending from
said pivot (104) of said compression arm (102) through the second end (116) of said
second leg (108) in said second direction; wherein said first longitudinal axis (132) is
disposed at an angle (136) with respect to said second longitudinal axis (134); and
wherein said angle (136) is between about 80 degrees and about 110 degrees.
12. The electrical switching apparatus (200) of claim 11 wherein said second
leg (108) of said compression arm (102) is disposed generally perpendicularly with
respect to said first leg (106) of said compression arm (102) in order that said
compression arm (102) has a generally L-shape.

13. The electrical switching apparatus (200) of claim 10 wherein the outer
cam surface (130) of said charging cam (128) of said charging assembly (100) comprises
a variable radius (138); wherein said variable radius (138) comprises a point of minimum
radius (140) and a point of maximum radius (142); wherein said variable radius (138)
increases gradually from the point of minimum radius (140) to the point of maximum
radius (142); wherein, when said biasing element (212) is disposed in said charged
position, the point of maximum radius (142) of said charging cam (128) cooperates with
said engagement portion (118) of said first leg (106); and wherein, when said biasing
element (128) of said closing assembly (210) is disposed in said discharged position, the
point of minimum radius (140) of said charging cam (128) cooperates with said
engagement portion (118) of said first leg (106) of said compression arm (102).
14. The electrical switching apparatus (200) of claim 13 wherein the outer
cam surface (130) of said charging cam (128) further comprises a transition point (144);
wherein the variable radius (138) further comprises a first downslope (146) and a second
downslope (148); wherein the first downslope (146) is disposed between the point of
maximum radius (142) and the transition point (144); and wherein the second downslope
(148) is disposed between the transition point (144) and the point of minimum radius
(140).
15. The electrical switching apparatus (200) of claim 14 wherein the second
downslope (148) is greater than the first downslope (146).
16. The electrical switching apparatus (200) of claim 10 wherein said shaped
contact surface (120) of said second leg (108) of said compression arm (102) of said
charging assembly (100) further comprises a convex portion (150) disposed between the
first edge (122) of said shaped contact surface (120) and the second edge (122) of said
shaped contact surface (120); and wherein said angle (126) between the first edge (122)
and the second edge (124) is less than 90 degrees.
17. The electrical switching apparatus (200) of claim 16 wherein said impact
member (214) of said closing assembly (210) includes circular protrusion (216) having a
convex exterior (218); and wherein, when said biasing element (212) is moved from said
discharged position to said charged position, said convex portion (150) of said shaped

contact surface (120) cooperates with the convex exterior (218) of said circular protrusion
(216).
18. The electrical switching apparatus (200) of claim 17 wherein said second
leg (108) of said compression arm (102) of said charging assembly (100) further
comprises a concave portion (152); wherein said concave portion (152) is disposed on the
first edge (122) of said shaped contact surface (120) of said second leg (108); and
wherein, when said charging cam (128) pivots to initially move said compression arm
(102) into engagement with said impact member (214) of said closing assembly (210),
said concave portion (152) of said compression arm (102) cooperates with the convex
exterior (218) of said circular protrusion (216) of said impact member (214).
19. The electrical switching apparatus (200) of claim 10 wherein said biasing
element (212) of said closing assembly (210) is at least one spring (212); wherein, when
said at least one spring (212) is disposed in said charged position, said at least one spring
(212) is compressed; wherein, when said at least one spring (212) is disposed in said
discharged position, said at least one spring (212) is extended; and wherein said at least
one spring (212) biases said impact member (214) of said closing assembly (210) toward
engagement with said linking assembly (300).
20. The electrical switching apparatus (200) of claim 10 wherein said
electrical switching apparatus is a circuit breaker (200); wherein the housing (202) of said
circuit breaker (200) includes a number of sideplates (220); wherein said closing
assembly (210) is substantially disposed on a corresponding one of said sideplates (220);
and wherein said charging cam (128) of said charging assembly (100) and said pivot
(104) of said compression arm (102) of said charging assembly (100) are pivotally
coupled to said corresponding one of said sideplates (220).

A charging assembly (100) is provided for an electrical switching
apparatus, such as a circuit breaker (200). The charging assembly (100) includes a
compression arm (102) and a charging cam (128). The compression arm (102) includes a
pivot (104) and first and second legs (106,108) extending outwardly from the pivot (104),
preferably in a generally L-shape. An engagement portion (118) disposed at or about a
second end (114) of the first leg (106) cooperates with an outer cam surface (130) of the
charging cam (128). A shaped contact surface (120) disposed at or about a second end
(116) of the second leg (108) includes a first edge (122) for engaging and moving an
impact member (214) of the circuit breaker closing assembly (210) to charge a biasing
element (212) of the closing assembly (210), and a second edge (124). The second edge
(124) is disposed at an angle (126) with respect to the first edge (122), and is structured to
engage the impact member (214) when the biasing element (212) is disposed in the
charged position.