Two piece cradle latch, handle barrier locking insert and cover interlock for circuit breaker

A molded case circuit breaker is provided with a two piece cradle assembly having a cradle portion and a heat-treated portion. The heat-treated portion forms the latch and reset surfaces. The cradle portion is integrally formed from a pair of spaced apart cradle-shaped arms joined together by a connecting portion. The heat treated portion is securely fastened to the connecting portion to form the two piece cradle assembly. A hold down slidably carries a handle barrier with respect to the cover and closes a centrally located aperture in the cover for all handle positions. The handle barrier prevents arc products resulting from a separation of the main contacts from escaping through the centrally located aperture in the cover. Stops are provided in one or both directions to prevent misalignment of the handle barrier with respect to the operating handle. A cover interlock is also provided to prevent the cover from being removed when the circuit breaker is in an "on" position. The cover interlock can either be molded separately or integrallly molded with the handle barrier hold down.

DETAILED DESCRIPTION 
A molded case circuit breaker, generally indicated by the reference numeral 
20, comprises an electrically insulated housing 22 having a molded base 24 
and a molded coextensive cover 26, assembled at a parting line 28. The 
internal cavity of the molded base 24 is formed as a frame 30 for carrying 
the various components of the circuit breaker. As illustrated and 
described herein, a Westinghouse Series C, L-frame molded case circuit 
breaker will be described. However, it should be understood that the 
principles of the present invention are applicable to various types of 
molded case circuit breakers. 
At least one pair of separable main contacts 32 are carried by the frame 
30. More specifically, the pair of main contacts 32 include a rigidly 
mounted main contact 34 and a movably mounted main contact 36. The rigidly 
mounted main contact 34 is mounted to a line side conductor 37 having a 
line side terminal portion 38 at one end. The line side terminal portion 
38 extends outwardly from the housing circuit. The line side conductor 37 
is attached to the frame 30 with a plurality of fasteners 40. 
The movable main contact 36 is carried by a contact arm 42. As will be 
discussed in more detail below, the contact arm 42 is pivotally connected 
to a load conductor assembly 44. The load conductor assembly 44 includes a 
pivot bracket 46, rigidly connected to a load conductor base 48. The load 
conductor base 48 is rigidly mounted to the frame 30 and electrically 
connected to a U-shaped load conductor 50. The U-shaped load conductor 50 
forms a portion of an electronic trip unit 51. One end of the U-shaped 
conductor 560 is secured to the frame 30 and the load conductor base 48. 
The other end of the U-shaped conductor 50 is electrically connected to a 
load side terminal 53 to allow connection to an external electrical 
circuit. 
The electronic trip unit 51 contains one or more internal current sensors 
for detecting current flowing through the main contacts 32. The electronic 
trip unit 51 also includes a latch mechanism 54. The latch mechanism 54 is 
interlocked with an operating mechanism 55 of the circuit breaker 20. Upon 
detection of an overcurrent condition, the electronic trip unit 51 
operates the latch mechanism 54 to unlatch the circuit breaker operating 
mechanism 55 to allow the main contacts 32 to be separated. The electronic 
trip unit 51 also contains a pushbutton (not shown) which allows the 
circuit breaker 20 to be tripped by depressing the button. The electronic 
trip unit 51 does not form a part of the present invention. 
OPERATING MECHANISM 
An operating mechanism 55 is provided for opening and closing the main 
contacts 32. The operating mechanism includes a toggle assembly 56, which 
includes a pair of upper toggle links 58 and a pair of lower toggle links 
60. Each upper toggle link 58 is pivotally connected at one end to a lower 
toggle link 60 about a pivot axis 62. The other end of the lower toggle 
links 60 is pivotally connected about a pivot axis 63 to a U-shaped 
bracket 61, having depending operating arms 64. More specifically, 
apertures 70, provided in the operating arms 64, receive a pin 72 forming 
a pivotal connection between the lower toggle links 60 and the operating 
arms 64 about the pivot axis 63. The U-shaped bracket 61 is rigidly 
connected to a crossbar 65. The operating arms 64 are disposed adjacent 
each side of the contact arms 42 and are pivotally connected to a pair of 
side plates 75, disposed adjacent each side of the center pole, about a 
pivot axis 74. The side plates 75, as will be discussed in detail below, 
are rigidly connected to the molded base 24. Thus, rotation of the 
crossbar 65 about the pivot axis 74 will cause the lower toggle links 60 
to pivot about the pivot axis 63. 
The operating arms 64 are provided with cam surfaces 76. These cam surfaces 
76 allow for the mechanical coupling of the contact arms 42 to the 
operating mechanism 55. More specifically, each of the contact arms 42 are 
provided with a slot 78 for receiving a cam roller pin 80. The cam roller 
pin 80 extends outwardly from the sides of the contact arm 42. Cam rollers 
82 are received on each end of the cam roller pin 80. The cam rollers 82 
cooperate with the cam surfaces 76 to mechanically couple the contact arms 
42 to the operating mechanism 55. In all conditions except a blown open 
condition, the cam rollers 82 are captured in a pocket 83 formed in the 
cam surfaces 76. In a blown open condition, the cam rollers 82 are 
displaced out of the pockets 83 by the magnetic repulsion forces to 
uncouple the operating mechanism 55 from the contact arm assembly 42. This 
allows the contact arms 42 to open independently of the operating 
mechanism 55 as a result of magnetic repulsion forces. Biasing springs 84, 
coupled between the cam roller pin 80 and the pivot axis 74, provide 
contact pressure which must be overcome by the magnetic repulsion forces 
in order to allow the contact arm 42 to be blown open. More specifically, 
in the closed condition, since the cam rollers 82 are not quite seated in 
the pockets 83, but rather, are located slightly adjacent and upward of 
the pocket 83, the contact arm 42 is urged in a counterclockwise direction 
(FIG. 2) by the biasing springs 84, which produces a contact pressure 
between the main contacts 32. 
The upper toggle links 58 are pivotally connected to a cradle assembly 86 
about a pivot axis 88. More specifically, the upper toggle links 58 are 
provided with a U-shaped notch 89 at one end. A pivot pin 90, is supported 
by the cradle assembly 86. The pivot pin 90 is captured by the U-shaped 
notch 89 to define a pivotal connection about the pivot axis 88. The 
cradle assembly 86 is pivotally connected to the side plates 75 about a 
pivot axis 97. 
The cradle assembly 86, which will be discussed in more detail below, is 
provided with a latch surface 92. The latch surface 92 cooperates with the 
latch mechanism 54 on the electronic trip unit 51. More particularly, when 
the latch surface 92 is latched, operating springs 93, connected between 
the pivot axis 62 and operating handle arm 94, bias the operating 
mechanism 55 to cause the upper toggle links 58 and the lower toggle links 
60 to be disposed colinearly with respect to each other when the main 
contacts 32 are closed. In response to an overcurrent condition, the latch 
mechanism 54 on the electronic trip unit 51 releases the latch surface 92 
provided on the cradle assembly 86. The operating springs 93 then cause 
the cradle assembly 86 to rotate in a counterclockwise direction (FIG. 2) 
about the pivot axis 97 which causes the toggle assembly 56 to collapse. 
This causes the operating arms 64 and the attached crossbar 65 to rotate 
in a clockwise direction, thereby rotating the contact arms 42 and 
separating the main contacts 32, if the cam rollers 82 are captured in the 
pockets 83 in the cam surface 76. 
The circuit breaker 20 can also be manually turned off by rotating an 
insulated operating handle 95, mechanically coupled to the handle arm 94, 
in a clockwise direction to the open position. This causes the toggle 
assembly 56 to collapse, which allows the contact arm 42 to rotate 
upwardly under the influence of the operating springs 93. 
The handle arm 94 is formed as a U-shaped member having two depending arms 
98. The free ends 102 of the depending arms 98 are provided with notches 
104 for capturing a pivot pin 106. The pivot pin 106 is carried by 
V-shaped notches 107 provided in the side plates 75. In the closed and 
tripped positions of the circuit breaker 20, the pivot pin 106 is captured 
in a pocket 109 defined by the V-shaped notch 107. In the open position, 
the pivot pin 106 is disposed adjacent the pocket 109. In this condition 
the toggle assembly 56 is collapsed. More specifically, the lower toggle 
links 60 are disposed clockwise relative to their position in a closed or 
an open position. Similarly, the upper toggle links 58 are disposed 
counterclockwise relative to their position in closed or on position. 
Once the latch surface 92 on the cradle assembly 86 has been disengaged 
from the latch mechanism 54 on the electronic trip unit 51, it is 
necessary to reset the operating mechanism 55. This is accomplished by 
rotating the operating handle 95 in a clockwise direction until the latch 
surface 92 on the cradle assembly 86 engages the latch mechanism 54 on the 
electronic trip unit 51. 
A reset pin 108, carried by the operating handle 95, is captured in notches 
110, provided in . the upper portion of the depending arms 98 of the 
U-shaped handle arm 94 when the insulated handle 95 is rotated clockwise. 
The reset pin 108, in turn, engages a reset surface 114 provided on the 
cradle assembly 86. Further rotation of the operating handle 95 causes the 
cradle assembly 86 to rotate clockwise until the latch surface 92 on the 
cradle assembly 86 engages and latches the latch mechanism 54 on the 
electronic trip unit 51. 
SCREW ADJUSTABLE CLINCH JOINT WITH BOSSES 
An important aspect of the invention relates to the pivotally mounted 
contact arm 42 formed as a clinch joint. The clinch joint defines the 
pivotal connection between the contact arm 42 and the load conductor 
assembly 44. The pivotal connection eliminates the need for woven copper 
wire or laminated shunt assemblies used in known circuit breakers. 
A critical aspect of the invention relates to the ability to control the 
contacting surfaces between the contact arm 42 and the pivot bracket 46 in 
order to control the friction and the electrical resistance of these 
surfaces. These two factors need to be controlled because of their effect 
on the performance of the circuit breaker 20. More specifically, the 
electrical resistance has to be controlled to control the current flow 
through the assembly Also, the friction between the contacting surfaces 
has to be controlled since an excessive amount of friction could slow down 
the opening of the main contacts 32. 
The contact arm 42 is a bifurcated assembly formed from two coextensive 
irregular shaped arms 115, joined together at one end 116. The other end 
118 of the arms 115 is bent outwardly forming spaced apart arm portions 
119. The spaced apart arm portions 119 receive the pivot bracket 46. 
Aligned apertures 122 in the arms 115 are aligned with an aperture 124 in 
the pivot bracket 46. A pivot pin 125, received in the apertures 122 and 
124, provides a pivotal connection between the contact arm 42 and the 
pivot bracket 46 about the pivot axis 74. The pivot bracket 46 is 
electrically connected to the load conductor base 48. 
In order to control the contact surfaces between inner surfaces 128 of the 
contact arm 42 and the pivot bracket 46, bosses 130 are provided on the 
pivot bracket 46, concentric with the aperture 124. These bosses 130 are 
provided on each side of the pivot bracket 46 and extend outwardly 
therefrom. The bosses 130 may be coated with silver to provide a 
relatively smooth contacting surface. These bosses 130 provide a 
relatively uniform contact surface between the pivot bracket 46 and the 
inner surfaces 128 of the contact arm 42 in order to allow the friction 
and the electrical resistance of the joint to be controlled. 
Aligned apertures 132, provided in the spaced apart arm portions 119, 
receive a clinch screw 134. Wave washers 136 are disposed about a shank 
portion of the clinch screw 134 at one end. The clinch screw 134 is 
secured at the end opposite a head portion by a nut or other fastener 
causing the wave washers 136 to be captured between the head portion of 
the clinch screw 134 and an outer surface 137 of the contact arm 42. The 
clinch screw 134 and the wave washers 136 allow the friction between the 
inner surfaces 128 of the contact arm 42 and the bosses 130 to be 
controlled. 
Slots 78 are provided in the spaced apart arm portions 119 of the contact 
arm 42 to receive the cam roller pin 80 as discussed above. The biasing 
springs 84, connected between the cam roller pin 80 and the pivot pin 74, 
bias the cam roller pin 80 within the slot 78. 
The above assembly allows the current from the contact arm 42 to be 
transferred from the contact arm 42 to the bosses 130 and into the load 
side conductor base 48 by way of the pivot bracket 46 without the use of 
laminated or woven copper wire shunts. 
TAPERED STATIONARY CONTACT LINE COPPER 
Another important aspect of the invention relates to a line side conductor 
37 which carries the rigidly mounted main contact 34. More specifically, 
the line side conductor 37 is provided as a generally rectangular shaped 
member having a generally U-shaped slot 138 defining two conducting leg 
portions 144 and 146 and a peninsula portion 148 having two oppositely 
disposed edges 149 and 150. The edges 149 and 150 of the peninsula portion 
148 are tapered outwardly toward the base 151 of the peninsula portion 148 
to provide for a larger cross-sectional area of the conductor to provide 
better current density and heat dissipation. The tapered edges 149 and 150 
also allow the cross-sectional area of the peninsula portion 148 to be 
made substantially equivalent to the cross-sectional area of the 
conducting leg portions 144 and 146. 
The U-shaped slot 138 in the line side conductor 37 is for receiving a slot 
motor (not shown) and also to form a portion of the magnetic repulsion 
loop to allow the main contacts 32 to be blown open during relatively high 
level overcurrent conditions. In known devices, the opposing edges of the 
peninsula portion are not tapered. This can result in undesirable 
temperature increase of line side conductor because of the decrease in the 
overall cross-sectional area. This undesirable heat must be dissipated by 
other means, such as by providing a larger size conductor. By utilizing a 
line side conductor configuration as in the present invention, the overall 
cross-sectional area of the conductor is increased which results in better 
current density and heat dissipation without utilizing a relatively larger 
size line side conductor. 
As discussed above, one of the functions of the U-shaped slot 138 is to 
form a magnetic repulsion loop. This is accomplished by causing the 
current in the line conductor 37 to flow in a direction opposite to the 
direction of current flow in the contact arm 42. More specifically, the 
line side conductor 37 contains an electrical terminal portion 38 to allow 
connection between an external electrical circuit and the rigidly mounted 
main contact 34. The current applied to the line side terminal portion 38 
flows in the direction of the arrows shown in FIG. 6. This current is 
divided up between conducting leg portions 144 and 146 as shown in FIG. 6. 
This current in the leg portions 144 and 146 flows together in the 
peninsula portion 148 in a direction opposite that in the conducting leg 
portions 144 and 146. As best shown in FIG. 2, the current which flows 
through the movable main contact 36 in the contact arm 42 is in an 
opposite direction relative to the direction of current flow in the 
peninsula portion 148. Thus, during relatively high level overcurrent 
conditions, the opposing currents develop magnetic repulsion forces which 
cause the main contacts 32 to be blown open by causing the contact arm 42 
to be rotated in a clockwise direction. 
The other function of the U-shaped slot 138 is to receive a slot motor. The 
slot motor assists the contacts 32 blowing open. More particularly, the 
slot motor, consisting either of a series of generally U-shaped steel 
laminations encased in electrical insulation or of a generally U-shaped, 
electrically insulated solid bar, is received in the U-shaped slot 138, 
adjacent the main contacts 32. The slot motor concentrates the magnetic 
field generated upon a relatively high level overcurrent condition to 
increase the magnetic repulsion forces between the peninsula portion 148 
and the contact arm 42. This rapidly accelerates the separation of the 
main contacts 32 which results in a relatively high arc resistance which 
limits the magnitude of the fault current. 
The rigidly mounted main contact 34 is securely fastened to the peninsula 
portion 148. An arc runner 158 is disposed adjacent the main contact 34 to 
allow the arc to travel into arc chutes 160. The arc chutes 160 are used 
to divide a single electrical arc, formed as a result of the separating 
main contacts 32, into a series of electrical arcs thereby increasing the 
total arc voltage which results in a limiting of the magnitude of the 
fault current. 
Another important aspect of the line side conductor 37 relates to the means 
for providing adequate electrical separation between the line side 
conductor 37 and the contact arm 42 when the main contacts 32 are 
separated. More specifically, one side 162 of the line side conductor 37 
is tapered downwardly. This is done to provide more separation between the 
line side conductor 37 and the contact arm 42 when the main contacts 32 
are separated since these two points are at different potentials. 
SIDE PLATE TAPERED TWIST TAB FASTENING DEVICE FOR FASTENING SIDE PLATES TO 
THE BASE 
Another important aspect of the invention relates to the means for 
fastening the side plates 75 to the molded base 24. The side plates 75 are 
used to support a portion of the operating assembly 55 of the circuit 
breaker 20. More specifically, these side plates 75 are disposed adjacent 
the center pole and are used to provide various functions. For example, 
aligned apertures 164 in the side plates 75 define the pivot axis 74 for 
the crossbar 65. Another pair of aligned apertures 166 define the pivot 
axis 97 for the cradle assembly 86. Another set of aligned apertures 168 
receive a stop pin 170 to limit counterclockwise rotation of the cradle 
assembly 86 during tripping of the contacts. A V-shaped notch 107 in the 
side plates 75 captures the pivot pin 106 for the handle arm 94. Lastly, 
an irregular slot 172 allows the crossbar 65 to rotate about the pivot 
axis 74. 
In known circuit breakers, the side plates 75 are connected to the molded 
base 24 by various means, such as tabs extending downwardly from the 
bottom edge with threaded ends, spun over ends or staked ends, received in 
apertures or load bearing plates in the molded base 24. 
In other known circuit breakers, downwardly extending twist tabs are 
provided having straight shank portions and enlarged head portions. These 
twist tabs are received by slots disposed in spin plates carried in the 
underside of the base. The twist tabs are twisted to secure the side 
plates to the base. In this design, it is necessary to control the length 
of the shank portions of the twist tabs relatively closely in order to 
avoid play in the side plates 75 after the twist tabs are twisted, which 
may affect the operation of the operating mechanism. 
The twist tabs 174, provided in accordance with the present invention, 
extend downwardly from the bottom edge of the side plate 75 and are formed 
with shank portions 176, a tapered portion defining a sloped surface 178 
and a head portion 180. The twist tabs 174 are received in slots 182, 
provided in a generally rectangular spin plate 184, carried in a cavity 
185 formed in the underside of the molded base 24. Once the twist tabs 174 
are twisted, the spin plate 184 is captured in the molded base 24. 
The sloped surfaces 178 contact the slots 182 in the spin plates 184. As 
the twist tab 174 is twisted, the shank portion 176 becomes shorter 
thereby drawing a wider portion of the sloped surface 178 into engagement 
with the slot 182 to provide a secure connection between the side plates 
75 and the molded base 24. 
Since the spin plates 184 are stamped, they are configured to be received 
in the cavity 185 in the underside of the molded base 24 such that any 
rough edges on the break side resulting from the stamping process are not 
in engagement with the sloped surfaces 178. More particularly, as a result 
of the stamping process one side of the spin plate 184 is relatively 
smooth while the break side of the spin plate 184 may contain burrs. In 
order to prevent improper orientation of the break side with respect to 
the molded base 24, the spin plate 184 is keyed so that it can only be 
received such that the break side contacts the underside of the molded 
base 24. This is accomplished by providing means for indexing the spin 
plate 184. The indexing means include extending finger portions 186 
disposed generally parallel to each other on diametrically opposite 
corners 188 of the spin plate 184. 
TWO PIECE CRADLE LATCH FOR CIRCUIT BREAKER 
Another important aspect of the present invention relates to the two piece 
cradle assembly 86 comprising a U-shaped cradle portion 190 and an 
L-shaped heat treated portion 192. The heat treated portion 192 includes a 
latch surface 92 and a reset surface 114. Because of the wear on these 
parts, they are generally heat treated. However, due to the complicated 
shape of cradle portion 190 having bends in many different directions, 
heat treating these portions can cause the cradle to become brittle and 
distort. Accordingly, the cradle assembly 86, provided in accordance with 
the present invention, is formed from a two piece assembly wherein only 
the wear surfaces, such as the latch surface 92 and the reset surface 114 
are heat treated. The cradle portion 190 and the heat treated portion 192 
may be fastened together with rivets 194 or other suitable fasteners to 
form the cradle assembly 86. 
The cradle portion 190 is integrally formed from two spaced apart, parallel 
cradle shaped arms 196 joined together at one end by a connecting portion 
198 disposed substantially perpendicular to the cradle-shaped arms 196. A 
first pair of aligned apertures 200 is provided in the cradle shaped arms 
190 which define the pivot axis 90 for the cradle assembly 86 with respect 
to the side plates 75. A second pair of aligned apertures 202, provided in 
the cradle shaped arms 196, define the pivot axis 97 between the upper 
toggle links 58 and the side plates 75. 
The connecting portion 198 joins the cradle shaped arms 196 together. 
Apertures 203 are provided in the connecting portion 198 for receiving the 
rivets 194 to allow the heat treated portion 192 to be fastened thereto. 
The attachment of the heat treated portion 192 to the connecting portion 
198 also serves to reinforce the connecting portion 198. 
The heat treated portion is an integrally formed piece which defines the 
latch surfaces 92 and the reset surface 114. Because the heat treated 
portion is not as complicated as the cradle portion 190 and does not 
contain as many bends in different directions, it is less likely to 
distort as a result of the heat treating. 
Another important aspect of this invention is that the heat treated portion 
192 is formed such that the engaging portions of the latch surface 92 and 
the reset surface 114 are flat, smooth surfaces to distribute the load. 
The use of the flat, smooth surfaces also reduces the friction between the 
components. 
HANDLE BARRIER LOCKING INSERT 
Another important aspect of the invention relates to a handle barrier 
locking insert or hold down device 300 for slidably carrying a handle 
barrier 302 and allowing it to slide with the operating handle 95 to 
prevent any arc products resulting from separation of the main contacts 32 
from escaping through the cover 26. The operating handle 95 extends 
through a centrally located aperture 304 in the cover 26. The aperture 304 
is appropriately sized to allow rotation of the operating handle 95 to 
allow the circuit breaker 20 to be manually operated. With reference to 
FIG. 18, position 306 indicates the "on" position and position 308 
indicates the "off" position. 
The operating handle 95 is formed from an arcuate shaped base portion 310 
and a radially extending handle portion 312. The arcuate shaped base 
portion 310 seats against an arcuate surface 314, formed on the interior 
of the cover 26, adjacent the centrally located aperture 304. The arcuate 
surface 314 conforms to the shape of the arcuate portion 310 of the handle 
95 to allow the handle 95 to be rotated. The width of the centrally 
located aperture 304 is sized relative to the width of the handle portion 
312 of the operating handle 95. Because of space limitations within the 
circuit breaker 20, the arcuate shaped base portion 310 of the operating 
handle 95 is insufficient to close the centrally located aperture 304 in 
the cover 95 to prevent arc products from escaping for all positions of 
the operating handle 95. Thus, a handle barrier 302 is disposed between 
the arcuate shaped portion 310 of the operating handle 95 and the inside 
of the cover 26 and generally aligned with the centrally located aperture 
304. 
The handle barrier 302 consists of a relatively flexible material to allow 
it to conform to the contour of the arcuate shaped base portion 310 of the 
operating handle 95. The handle barrier 302 is formed in a generally 
rectangular shape having a centrally located aperture 318, whose length is 
slightly less than the length of the centrally located aperture 304 in the 
cover 26. The handle barrier 302 is also formed with two pairs of arms or 
tabs 320 and 321, extending outwardly from each corner of the rectangle. 
The arms 321 are relatively larger than the arms 32. These arms 321 are 
captured between the arcuate surface 314, integrally formed on the inside 
of the circuit breaker cover 26, and the handle barrier locking insert 
300. More specifically, sidewalls 324, integrally molded in the circuit 
breaker cover 26, are provided with recesses 326, adjacent the "on" 
position 306. Each sidewall 324 is disposed adjacent the arcuate surface 
314. 
The locking inserts 300 are formed with a contour generally similar to the 
recess 326. Once a locking insert 300 is inserted into the recess 326, a 
groove 329 is defined between each insert 300 and the arcuate surface 314 
forming an arcuate path for the arms 321. The arms 321 are received and 
captured in the grooves 329. The handle barrier locking inserts 300 may be 
secured to the sidewalls 324 by a fastener or adhesive. By capturing the 
the arms 321 in the grooves 329, the handle barrier 302 is captured with 
respect to the circuit breaker cover 26. Thus, when the cover 26 is 
removed, the handle barrier 302 will be slidingly attached thereto. 
A pair of raised ridges 325, formed on the arc shaped base portion 310, 
cooperate with the arms 320 and 321 to move the handle barrier 302 when 
the handle 95 is rotated. More particularly, edge portions 327, are 
disposed generally perpendicular to the arcuate shaped base portion and 
are parallel to the axis of rotation. These edge portions 327 act as 
bearing surfaces during engagement with the arms 320 and 321. Moreover, 
the raised ridges 325 may contain indicia that indicates the status of the 
circuit breaker 20 when viewed through openings 323 in the cover 26. 
In order to prevent overtravel of the handle barrier 302, a portion of the 
recess 326 may be formed to act as a stop surface in the direction toward 
the "on" position 306. The stop surfaces prevent misalignment of the 
handle barrier 302 with respect to the arcuate shaped base portion 310 of 
the handle 95. Since the handle barrier 302 moves with the extending 
handle portion 312 of the handle 95, the stop surface 315 will prevent 
misalignment of the handle barrier 302 due to overtravel of the handle 95 
in the direction toward the "on" position 306, thus closing the centrally 
located aperture 304. 
The recesses 326 may be formed to prevent overtravel in the other 
direction. More specifically, in order to prevent misalignment or 
overtravel when the handle 95 is rotated towards the "off" position 308, 
portions 317 of the recesses 326 are formed to act as stop surfaces. Thus, 
overtravel of the handle barrier 302 is prevented when the handle 95 is 
rotated toward the off position 308. 
COVER INTERLOCK 
Another important aspect of the present invention relates to a cover 
interlock 330 which prevents the circuit breaker cover 26 from being 
removed from the base 24 when the circuit breaker 20 is in the "on" 
position 306. In one embodiment, the cover interlock 330 is formed as a 
generally rectangular block 332, fastened to a ledge 334, integrally 
formed in the sidewalls 324, adjacent the "on" position 306 such that 
longitudinal axis of the blocks 332 are generally parallel to the 
longitudinal axis of the circuit breaker 20. 
The operating handle 95 is coupled to the operating mechanism 55. The cover 
interlock 330 captures a bottom edge 336 of the arcuate shaped base 
portion 310 of the handle in the position 306. However, once the circuit 
breaker is moved away from the "on" position 306, the rectangular block 
332 clears the bottom edge 336 of the arcuate shaped base portion 310 of 
the operating handle 95 to allow the cover 26 to be removed. Since the 
cover interlock 330 is disposed adjacent the locking insert 300 for the 
handle barrier 302, the cover interlock 330 may be either integrally 
molded with the locking insert 300 or may be formed as a separate piece 
and fastened to the ledge 334. 
In an alternative embodiment, the cover interlock is not fastened to the 
sidewall 314, but rather is fastened to an inside surface 341 of the cover 
26. In this embodiment, the cover interlock 340 is formed as a generally 
C-shaped member 342 having an extending lip portion 344 which acts to 
engage the edge 336 of the arcuate shaped base portion 310 when the 
operating handle 95 is in the "on" position 306. In this embodiment, the 
cover interlock 340 may either be attached to the inside surface 341 of 
the cover 26 either by an adhesive or with fasteners (not shown) to the 
surface 341. Moreover, in this embodiment, the cover interlock 340 is 
formed with a slot 348 to provide clearance for the upper contact arm 42. 
Obviously many modifications and variations of the present invention are 
possible in light of the above teachings. Thus, it is to be understood 
that, within the scope of the appended claims, the invention may be 
practiced otherwise than as specifically described hereinabove.