ELECTRICAL SWITCHING APPARATUS AND
LINKING 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 CHARGING
ASSEMBLY THEREFOR" (Attorney Docket No. 08-EDP-509).
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 linking 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.
Figures 1A-1D show one non-limiting example of a circuit breaker 1
(partially shown) including an operating mechanism 3 (shown in simplified form in
Figure 1A) having a linking assembly 5 that cooperates with a poleshaft 7 to open (e.g.,
separate) and/or close (e.g., electrically connect) the separable contacts 17 (shown in
simplified form in Figure 1 A) of the circuit breaker 1. In the example of Figures 1A-1D,
the linking assembly 5 cooperates with a spring charging assembly 9, although it will be
appreciated that such linking assemblies (e.g., 5) can also be employed in a wide variety
of different electrical switching apparatus (not shown), with or without such a charging
mechanism.
Among other functions, the linking assembly 5 is intended to reduce the
amount of force that is required to be exerted by the accessories (not shown) of the circuit

breaker 1 to effectuate the desired circuit breaker tripping reaction. For example and
without limitation, such an accessory might be employed under certain circumstances to
pivot a D-shaft 19, thereby releasing a hatchet 21 of the linking assembly 5, or to
otherwise actuate (e.g., move) one or more linking elements 21,23,25,27,29 of the linking
assembly 5 and/or a corresponding portion of the circuit breaker operating mechanism 3
(Figure 1A).
As shown in Figure 1C and 1D, in addition to the aforementioned hatchet
21, the example linking assembly 5 includes linking elements 23,25,27,29, resulting in
three stages (e.g., labeled stage 1, stage 2 and stage 3 in Figures 1C and 1D) of force
reduction. While this is sufficient for relatively large accessories capable of exerting
substantial force, it is desirable to provide further force reduction so that existing, readily
available and relatively small accessories can be employed. Providing such a force
reduction is a significant design challenge as it generally requires unacceptable,
unreliable or impossible toggle angles (e.g., angles between linking elements 23,25,27,29
of the linking assembly) in order to provide the desired motion among the hatchet 21,
cradle 25 and linking elements 23,27,29.
There is, therefore, room for improvement in electrical switching
apparatus, such as circuit breakers, and in linking assemblies therefor.
SUMMARY
These needs and others are met by embodiments of the disclosed concept,
which are directed to a linking assembly for the operating mechanism of an electrical
switching apparatus, such as a circuit breaker. Among other benefits, the linking
assembly implements an additional stage of force reduction to reduce forces associated
with electrical fault conditions.
As one aspect of the disclosed concept, a linking assembly is provided for
an electrical switching apparatus. The electrical switching apparatus includes a housing,
separable contacts enclosed by the housing, a D-shaft pivotally coupled to the housing,
and an operating mechanism. The operating mechanism includes a pivotal poleshaft
structured to move the separable contacts between an open position corresponding to the
separable contacts being separated, and a close position corresponding to the separable
contacts being electrically connected. The D-shaft is pivotable between a first position

and a second position. The linking assembly comprises: a hatchet comprising a first
edge, a second edge, and an arcuate portion extending between the first edge and the
second edge, the hatchet being structured to move between a latched position
corresponding to the D-shaft being disposed in the first position and the first edge of the
hatchet engaging the D-shaft, and an unlatched position corresponding to the D-shaft
being disposed in the second position and the hatchet pivoting with respect to the D-shaft
to unlatch the linking assembly; a cradle including a first end, a second end disposed
opposite and distal from the first end, and an intermediate portion disposed between the
first end and the second end; a latch plate structured to be pivotally coupled to the
housing, the latch plate comprising a protrusion structured to cooperate with the hatchet;
a latch link disposed between and pivotally coupled to the cradle and the latch plate; and
a toggle assembly comprising a first linking element and a second linking element, the
first linking element and the second linking element each including a first end and a
second end, the first end of the first linking element being structured to be pivotally
coupled to the poleshaft, the second end of the first linking element being pivotally
coupled to the first end of the second linking element, the second end of the second
linking element being pivotally coupled to the cradle.
The protrusion of the latch plate may be a roller, wherein the roller
extends outwardly from the latch plate. When the hatchet is moved toward the latched
position, the arcuate portion of the hatchet may engage the roller, thereby moving the
latch link with the latch plate. Responsive to the hatchet engaging the roller and moving
the latch link with the latch plate, movement of the hatchet may be transferred into
movement of the cradle. When the hatchet is disposed in the unlatched position and the
hatchet disengages the roller, the latch plate may move with respect to the latch link,
thereby substantially decoupling movement of the hatchet from movement of the cradle.
The electrical switching apparatus may be structured to trip open the
separable contacts in response to a fault condition wherein, responsive to the fault
condition, a tripping force is required to move the linking assembly to trip open the
separable contacts. The hatchet, the cradle, the latch plate, the latch link and the toggle
assembly may cooperate to establish at least four stages of force reduction to reduce the
tripping force. The toggle assembly may further comprise a drive link, and the at least

four stages of force reduction may be a first stage of force reduction, a second stage of
force reduction, a third stage of force reduction and a fourth stage of force reduction. The
first stage of force reduction may be structured to be disposed between the drive link and
the poleshaft. The second stage of feree reduction may be structured to be disposed
between the poleshaft, the first linking element of the toggle assembly, the second linking
element of the toggle assembly and the cradle. The third stage of force reduction may be
disposed between the cradle, the latch link and the latch plate, and the fourth stage of
force reduction may be disposed between the protrusion of the latch plate and the hatchet.
When the hatchet moves from the latched position to the unlatched
position, the hatchet may pivot less than 30 degrees. The hatchet may further comprise a
pivot, wherein the pivot pivotally couples the hatchet to the housing of the electrical
switching apparatus. The arcuate portion of the hatchet may be structured to extend
outwardly from the pivot generally away from the poleshaft. When the hatchet moves
from the latched position to the unlatched position, the hatchet may pivot clockwise about
the pivot.
As another aspect of the disclosed concept, an electrical switching
apparatus comprises: a housing; separable contacts enclosed by the housing; an operating
mechanism including a pivotal poleshaft, the pivotal poleshaft being structured to move
the separable contacts between an open position corresponding to the separable contacts
being separated, and a close position corresponding to the separable contacts being
electrically connected; a D-shaft pivotally coupled to the housing, the D-shaft being
pivotable between a first position and a second position; and a linking assembly
comprising: a hatchet comprising a first edge, a second edge, and an arcuate portion
extending between the first edge and the second edge, the hatchet being movable between
a latched position corresponding to the D-shaft being disposed in the first position and the
first edge of the hatchet engaging the D-shaft, and an unlatched position corresponding to
the D-shaft being disposed in the second position and the hatchet pivoting with respect to
the D-shaft to unlatch the linking assembly, a cradle including a first end, a second end
disposed opposite and distal from the first end, and an intermediate portion disposed
between the first end and the second end, a latch plate pivotally coupled to the housing,
the latch plate comprising a protrusion being cooperable with the hatchet, a latch link

disposed between and pivotally coupled to the cradle and the latch plate, and a toggle
assembly comprising a first linking element and a second linking element, the first
linking element and the second linking element each including a first end and a second
end, the first end of the first linking element being pivotally coupled to the poleshaft, the
second end of the first linking element being pivotally coupled to the first end of the
second linking element, the second end of the second linking element being pivotally
coupled to the cradle.
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 linking assembly for a circuit
breaker, showing the linking assembly position corresponding to the circuit breaker
closing spring being charged and the separable contacts of the circuit breaker being open;
Figure 1B is a side elevation view of the linking assembly of Figure 1A,
modified to show the linking assembly position corresponding to the closing spring being
partially charged;
Figure 1C is a side elevation view of the linking assembly of Figure 1A,
modified to show the linking assembly position corresponding to the closing spring being
discharged and the separable contacts being closed;
Figure 1D is a side elevation view of the linking assembly of Figure 1A,
modified to show the linking assembly position corresponding to the closing spring being
discharged and the separable contacts being open;
Figure 2A is a side elevation view of a linking assembly for a circuit
breaker in accordance with an embodiment of the disclosed concept, showing the linking
assembly position corresponding to the closing spring of the circuit breaker being
charged and the circuit breaker separable contacts being open;
Figure 2B is a side elevation view of the linking assembly of Figure 2A,
modified to show the linking assembly position when the separable contacts are open and
the closing spring is partially charged;

Figure 2C is a side elevation view of the linking assembly of Figure 2A,
modified to show the linking assembly position when the closing spring is discharged and
the separable contacts are closed;
Figure 2D is a side elevation view of the linking assembly of Figure 2A,
modified to show the linking assembly position when the closing spring is discharged and
the separable contacts are open; and
Figure 3 is a side elevation view of a portion of a circuit breaker
employing a linking 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 2 A. 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 - 1D), 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
hereinbelow).
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-1D). 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 feree reduction disposed
between a drive link 348 and the circuit breaker poleshaft 222, a second stage of feree
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 force 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 1 A-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
152 concave portion
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 linking assembly (300) for an electrical switching apparatus (200), said
electrical switching apparatus (200) including a housing (202), separable contacts (204)
enclosed by the housing (202), a D-shaft (208) pivotally coupled to the housing (202),
and an operating mechanism (206), said operating mechanism (206) including a pivotal
poleshaft (222) structured to move said separable contacts (204) between an open
position corresponding to said separable contacts (204) being separated, and a close
position corresponding to said separable contacts (204) being electrically connected, said
D-shaft (208) being pivotable between a first position and a second position, said linking
assembly (300) comprising:
a hatchet (302) comprising a first edge (304), a second edge (306), and an
arcuate portion (308) extending between the first edge (304) and the second edge (306),
said hatchet (302) being structured to move between a latched position corresponding to
said D-shaft (208) being disposed in said first position and the first edge (304) of said
hatchet (302) engaging said D-shaft (208), and an unlatched position corresponding to
said D-shaft (208) being disposed in said second position and said hatchet (302) pivoting
with respect to said D-shaft (208) to unlatch said linking assembly (300);
a cradle (310) including a first end (312), a second end (314) disposed
opposite and distal from the first end (312), and an intermediate portion (316) disposed
between the first end (312) and the second end (314);
a latch plate (318) structured to be pivotally coupled to the housing (202),
said latch plate (318) comprising a protrusion (320) structured to cooperate with said
hatchet (302);
a latch link (322) disposed between and pivotally coupled to said cradle
(310) and said latch plate (318); and
a toggle assembly (324) comprising a first linking element (326) and a
second linking element (328), said first linking element (326) and said second linking
element (328) each including a first end (330,334) and a second end (332,336), the first
end (330) of said first linking element (326) being structured to be pivotally coupled to
said poleshaft (222), the second end (332) of said first linking element (326) being
pivotally coupled to the first end (334) of said second linking element (328), the second

end (336) of said second linking element (328) being pivotally coupled to said cradle
(310).
2. The linking assembly (300) of claim 1 wherein said latch link (322)
comprises a first portion (338) and a second portion (340); wherein the first portion (338)
of said latch link (322) is coupled to the intermediate portion (316) of said cradle (310);
and wherein the second portion (340) of said latch link (322) is pivotally coupled to said
latch plate (318) at or about said protrusion (320).
3. The linking assembly (300) of claim 1 wherein said protrusion (320) of
said latch plate (318) is a roller (320); wherein said roller (320) extends outwardly from
said latch plate (318); wherein, when said hatchet (302) is moved toward said latched
position, said arcuate portion (308) of said hatchet (302) engages said roller (320),
thereby moving said latch link (322) with said latch plate (318); wherein, responsive to
said hatchet (302) engaging said roller (320) and moving said latch link (322) with said
latch plate (318), movement of said hatchet (302) is transferred into movement of said
cradle (310); and wherein, when said hatchet (302) is disposed in said unlatched position
and said hatchet (302) disengages said roller (320), said latch plate (318) moves with
respect to said latch link (322), thereby substantially decoupling movement of said
hatchet (302) from movement of said cradle (310).
4. The linking assembly (300) of claim 3 wherein said latch link (322)
further comprises a first longitudinal axis (342); wherein said latch plate (318) comprises
a second longitudinal axis (344); wherein, when said hatchet (302) is disposed in said
latched position, said first longitudinal axis (342) of said latch link (322) is disposed at an
angle (346) of about 180 degrees with respect to said second longitudinal axis (344) of
said latch plate (318); and wherein, when said hatchet (302) is disposed in said unlatched
position, said first longitudinal axis (342) of said latch link (322) is disposed at an angle
(346) of between about 90 degrees and about 160 degrees with respect to said second
longitudinal axis (344) of said latch plate (318).
5. The linking assembly (300) of claim 1 wherein said electrical switching
apparatus (200) is structured to trip open said separable contacts (204) in response to a
trip condition; wherein, responsive to said trip condition, a tripping force is required to
move said linking assembly (300) to trip open said separable contacts (204); and wherein

said hatchet (302), said cradle (310), said latch plate (318), said latch link (322) and said
toggle assembly (324) cooperate to establish at least four stages of force reduction to
reduce said tripping force.
6. The linking assembly (300) of claim 5 wherein said toggle assembly (324)
further comprises a drive link (348); wherein said at least four stages of force reduction
are a first stage of force reduction, a second stage of force reduction, a third stage of force
reduction and a fourth stage of force reduction; wherein said first stage of force reduction
is structured to be disposed between said drive link (348) and said poleshaft (222);
wherein said second stage of force reduction is structured to be disposed between said
poleshaft (222), said first linking element (326) of said toggle assembly (324), said
second linking element (328) of said toggle assembly (324) and said cradle (310);
wherein said third stage of force reduction is disposed between said cradle (310), said
latch link (322) and said latch plate (318); and wherein said fourth stage of force
reduction is disposed between said protrusion (320) of said latch plate (318) and said
hatchet (302).
7. The linking assembly (300) of claim 1 wherein said first linking element
(326) of said toggle assembly (324) includes a first longitudinal axis (350); wherein said
second linking element (328) of said toggle assembly (324) includes a second
longitudinal axis (352); and wherein, when said hatchet (302) is latched and said
separable contacts (204) are disposed in said open position, said first longitudinal axis
(350) of said first linking element (326) forms an angle (354) of about 90 degrees with
respect to said second longitudinal axis (352) of said second linking element (328).
8. The linking assembly (300) of claim 1 wherein, when said hatchet (302)
moves from said latched position to said unlatched position, said hatchet (302) pivots less
than 30 degrees.
9. The linking assembly (300) of claim 1 wherein said hatchet (302) further
comprises a pivot (356); wherein said pivot (356) pivotally couples said hatchet (302) to
the housing (202) of said electrical switching apparatus (200); and wherein said arcuate
portion (308) of said hatchet (302) is structured to extend outwardly from said pivot (356)
generally away from said poleshaft (222).

10. The linking assembly (300) of claim 1 wherein, when said hatchet (302)
moves from said latched position to said unlatched position, said hatchet (302) pivots
clockwise about said pivot (356).
11. An electrical switching apparatus (200) comprising:
a housing (202);
separable contacts (204) enclosed by the housing (202);
an operating mechanism (206) including a pivotal poleshaft (222), said
pivotal poleshaft (222) being structured to move said separable contacts (204) between an
open position corresponding to said separable contacts (204) being separated, and a close
position corresponding to said separable contacts (204) being electrically connected;
a D-shaft (208) pivotally coupled to the housing (202), said D-shaft (208)
being pivotable between a first position and a second position; and
a linking assembly (300) comprising:
a hatchet (302) comprising a first edge (304), a second edge (306),
and an arcuate portion (308) extending between the first edge (304) and the second edge
(306), said hatchet (302) being movable between a latched position corresponding to said
D-shaft (208) being disposed in said first position and the first edge (304) of said hatchet
(302) engaging said D-shaft (208), and an unlatched position corresponding to said D-
shaft (208) being disposed in said second position and said hatchet (302) pivoting with
respect to said D-shaft (208) to unlatch said linking assembly (300),
a cradle (310) including a first end (312), a second end (314)
disposed opposite and distal from the first end (312), and an intermediate portion (316)
disposed between the first end (312) and the second end (314),
a latch plate (318) pivotally coupled to the housing (202), said
latch plate (318) comprising a protrusion (320) being cooperable with said hatchet (302),
a latch link (322) disposed between and pivotally coupled to said
cradle (310) and said latch plate (318), and
a toggle assembly (324) comprising a first linking element (326)
and a second linking element (328), said first linking element (326) and said second
linking element (328) each including a first end (330,334) and a second end (332,336),
the first end (330) of said first linking element (326) being pivotally coupled to said

poleshaft (222), the second end (332) of said first linking element (326) being pivotally
coupled to the first end (334) of said second linking element (328), the second end (336)
of said second linking element (328) being pivotally coupled to said cradle (310).
12. The electrical switching apparatus (200) of claim 11 wherein said latch
link (322) of said linking assembly (300) comprises a first portion (338) and a second
portion (340); wherein the first portion (338) of said latch link (322) is coupled to the
intermediate portion (316) of said cradle (310); and wherein the second portion (340) of
said latch link (322) is pivotally coupled to said latch plate (318) at or about said
protrusion (320).
13. The electrical switching apparatus (200) of claim 11 wherein said
protrusion (320) of said latch plate (318) of said linking assembly (300) is a roller (320);
wherein said roller (320) extends outwardly from said latch plate (318); wherein, when
said hatchet (302) is moved toward said latched position, said arcuate portion (308) of
said hatchet (302) engages said roller (320), thereby moving said latch link (322) with
said latch plate (318); wherein, responsive to said hatchet (302) engaging said roller (320)
and moving said latch link (322) with said latch plate (318), movement of said hatchet
(302) is transferred into movement of said cradle (310); and wherein, when said hatchet
(302) is disposed in said unlatched position and said hatchet (302) disengages said roller
(320), said latch plate (318) moves with respect to said latch link (322), thereby
substantially decoupling movement of said hatchet (302) from movement of said cradle
(310).
14. The electrical switching apparatus (200) of claim 13 wherein said latch
link (322) further comprises a first longitudinal axis (342); wherein said latch plate (318)
comprises a second longitudinal axis (344); wherein, when said hatchet (302) is disposed
in said latched position, said first longitudinal axis (342) of said latch link (322) is
disposed at an angle (346) of about 180 degrees with respect to said second longitudinal
axis (344) of said latch plate (318); and wherein, when said hatchet (302) is disposed in
said unlatched position, said first longitudinal axis (342) of said latch link (322) is
disposed at an angle (346) of between about 90 degrees and about 160 degrees with
respect to said second longitudinal axis (344) of said latch plate (318).

15. The electrical switching apparatus (200) of claim 11 wherein said
electrical switching apparatus (200) trips open said separable contacts (204) in response
to a fault condition; wherein, responsive to said fault condition, a tripping force is
required to move said linking assembly (300) to trip open said separable contacts (204);
and wherein said hatchet (302), said cradle (310), said latch plate (318), said latch link
(322) and said toggle assembly (324) cooperate to establish at least four stages of force
reduction to reduce said tripping force.
16. The electrical switching apparatus (200) of claim 15 wherein said toggle
assembly (324) further comprises a drive link (348); wherein said at least four stages of
force reduction are a first stage of force reduction, a second stage of force reduction, a
third stage of force reduction and a fourth stage of force reduction; wherein said first
stage of force reduction is disposed between said drive link (348) and said poleshaft
(222); wherein said second stage of force reduction is disposed between said poleshaft
(222), said first linking element (326) of said toggle assembly (324), said second linking
element (328) of said toggle assembly (324) and said cradle (310); wherein said third
stage of force reduction is disposed between said cradle (310), said latch link (322) and
said latch plate (318); and wherein said fourth stage of feree reduction is disposed
between said protrusion (320) of said latch plate (318) and said hatchet (302).
17. The electrical switching apparatus (200) of claim 11 wherein said first
linking element (326) of said toggle assembly (324) of said linking assembly (300)
includes a first longitudinal axis (350); wherein said second linking element (328) of said
toggle assembly (324) includes a second longitudinal axis (352); and wherein, when said
hatchet (302) is latched and said separable contacts (204) are disposed in said open
position, said first longitudinal axis (350) of said first linking element (326) forms an
angle (354) of about 90 degrees with respect to said second longitudinal axis (352) of
said second linking element (328).
18. The electrical switching apparatus (200) of claim 11 wherein, when said
hatchet (302) of said linking assembly (300) moves from said latched position to said
unlatched position, said hatchet (302) pivots less than 30 degrees.
19. The electrical switching apparatus (200) of claim 11 wherein said hatchet
(302) of said linking assembly (300) further comprises a pivot (356); wherein said pivot

(356) pivotally couples said hatchet (302) to the housing (202) of said electrical
switching apparatus (200); and wherein said arcuate portion (308) of said hatchet (302)
extends outwardly from said pivot (356) generally away from said poleshaft (222).
20. The electrical switching apparatus (200) of claim 11 wherein, when said
hatchet (302) of said linking assembly (300) moves from said latched position to said
unlatched position, said hatchet (302) pivots clockwise about said pivot (356).

A linking assembly (300) is provided for an electrical switching apparatus,
such as a circuit breaker (200). The linking assembly (300) includes a hatchet (302)
having first and second edges (304,306) and an arcuate portion (308) extending
therebetween. The hatchet (302) moves between a latched position in which the first
edge engages a D-shaft (208), and an unlatched position in which the hatchet (302) pivots
with respect to the D-shaft (208) to unlatch the linking assembly (300). A cradle (310)
includes first and second opposing ends (312,314) and an intermediate portion (316)
disposed therebetween. A latch plate (318), which is pivotally coupled to the housing
(202), includes a protrusion (320) that cooperates with the hatchet (302). A latch link
(322) is disposed between and is pivotally coupled to the cradle (310) and the latch plate
(318). A toggle assembly (324) includes first and second linking elements (326,328)
coupled between the circuit breaker poleshaft (222) and the cradle (310).