Contact position indicator for an industrial-rated circuit breaker

A circuit breaker contact position indicator assembly includes an indicator lever that interacts with the circuit breaker contact carrier through a indicator lever bell crank and a contact arm bell crank to provide true ON and OFF indication of the circuit breaker contacts.

BACKGROUND OF THE INVENTION 
Air circuit breakers as described within U.S. Pat. No. 3,095,489 entitled 
"Manual Charging Means for Stored Energy Closing Mechanisms of Electric 
Circuit Breakers" and U.S. Pat. No. 3,084,238 entitled "Ratchet Mechanism 
for Charging a Closing Spring in an Electric Circuit Breaker" include 
operating mechanisms that are mainly exposed to the environment. Since the 
air circuit breakers are rated to carry several thousand amperes of 
current continuously, the exposure to convection cooling air assists in 
keeping the operating components within reasonable temperature limits. 
Such air circuit breakers are usually provided with a motor operator such 
as described in U.S. Pat. No. 4,167,988 entitled "Ratcheting Mechanism for 
Circuit Breaker Motor Operator" or a manual handle as described in U.S. 
Pat. No. 3,729,065 entitled "Means for Charging A Stored Energy Circuit 
Breaker Closing Device" for charging the powerful closing springs 
contained within the air circuit breaker operating mechanism. 
When the circuit breaker closing springs are brought to their fully-charged 
conditions, it is important that the springs do not become inadvertently 
discharged while an operator has hold of the charging handle in order to 
avoid damage to the ratchet mechanism and the associated air circuit 
breaker contacts. An early arrangement of a latching means to prevent 
rotation of a closing springs charging handle is found in U.S. Pat. No. 
4,475,021 entitled "Air Circuit Breaker". 
The above-noted U.S. patents include means for opening and closing the 
circuit breaker contacts by direct access to the circuit breaker as well 
as from a remote location. To prevent closing the circuit breaker contacts 
when the associated electric equipment is undergoing replacement or 
repair, interlocks are required. U.S. Pat. No. 5,504,285 entitled "Circuit 
Breaker Indicating Flag Interlock Arrangement Operating Springs" and U.S. 
Pat. No. 5,478,979 entitled "Circuit Breaker Closing and Opening Interlock 
Assembly" provide interlock arrangements acting between the circuit 
breaker ON and OFF buttons to prevent inadvertent turn on of so-called 
"insulated case" circuit breakers wherein the circuit breaker operating 
components are completely contained within a common enclosure. U.S. patent 
application Ser. No. 08/878,594 entitled "Pushbutton Interlock Mechanism 
for an Industrial Rated Circuit Breaker" (filed concurrently herewith) 
describes a recent interlock approach that interacts with the circuit 
breaker indicating assembly to provide the interlock function. 
It is known that circuit breaker contacts can become welded closed upon 
repeated intense overcurrent occurrence, especially when the circuit 
breaker is used within circuits that occasionally carry circuit current in 
excess of the circuit breaker ratings. 
When multipole circuit breakers such as described in the aforementioned 
U.S. Pat. Nos. 3,084,238 and 3,905,489 incur one set of welded contacts 
while the remainder of the contacts within the separate poles remain 
operational, it is essential to provide indication that one of the 
contacts has become welded. 
When higher ampere rated circuit breakers that employ a pair of arcing 
contacts along with a pair of main contacts operate off a common contact 
carrier, the arcing contacts close before the main contacts and open after 
the main contacts to protect the main contacts from arc deterioration. 
However, if either of the pair of arcing and main contacts become welded, 
the contact indicating assembly could indicate that the contacts are in 
the OFF condition since the other pair of the main or arcing contacts has 
separated. 
This problem also arises when the circuit breaker includes three or more 
poles and main as well as arcing contacts are employed within each pole. 
The forces provided by the contact opening springs could overcome the 
holding forces exerted on the contact carrier, that is common to each 
pole, by the welded contacts and motivate the indicating assembly into the 
OFF condition are involved. 
One purpose of the invention, accordingly, is to prevent the contact 
indicating assembly from providing indication of open contacts when at 
least one pair of the circuit breaker contacts are welded in the ON 
condition and the remaining contacts have moved to the OFF condition. 
SUMMARY OF THE INVENTION 
A circuit breaker contact position indicator assembly includes an 
indicating lever that interacts with the circuit breaker contact carrier 
through an indicator lever bell crank and a contact arm bell crank. The 
top lever that interconnects the bell cranks includes a lost motion slot 
that allows both the arcing contacts and the main contacts to become 
separated before moving the indicating lever to the OFF indicating 
position. The top lever also includes a lost motion slot that provides 
accurate positioning of the OFF position indicator.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The air circuit breaker 10 of FIG. 1 is similar to that described within 
the aforementioned U.S. Pat. No. 3,095,489 and includes a metal frame 11 
which supports circuit breaker cover 12, the trip unit programmer 12 A and 
the operating mechanism enclosure 13 having an access cover 13A. The trip 
unit programmer is similar to that described in U.S. Pat. No. 4,672,501 
entitled "Circuit Breaker and Protective Relay Unit". The circuit breaker 
cover further includes a trip or OFF button 19 for releasing the circuit 
breaker operating mechanism contained within the enclosure 13 for 
separating the circuit breaker arcing contacts 49, 50 to their open 
condition and a closing button 20 for moving the contacts to their closed 
position. The condition of the circuit breaker contacts is observed by 
means of the viewing window 21. The circuit breaker contact arms 48 within 
each pole of a three pole circuit arrangement, are interconnected by means 
of the operating mechanism crossbar 46 to insure that all contacts within 
the separate poles both open and close in unison. The ratchet mechanism 22 
allows the operating mechanism closing springs described therein to be 
charged remotely by means of a motor operator. The operating handle 18 
interacts with the ratchet mechanism 22 by means of a pair of plate 
connectors, one of which is indicated at 23A. 
The circuit breaker 10 is depicted in FIGS. 2 and 5 with the circuit 
breaker cover 12 removed from the operating mechanism enclosure 13. The 
circuit breaker cover 12 is positioned with the trip unit access opening 9 
over the trip unit programmer 12A (FIG. 1) and the viewing window 21 over 
the target plate 35 that carries the ON and OFF indicia, 32A, 32B 
respectively. The indicator lever 33 is slidably mounted on a pivot pin 39 
that extends through the support platform 34 attached to the top of the 
operating mechanism enclosure 13. One end of the indicator lever 33 
terminates in a target arm stop slot 37 that is captured about the pivot 
pin 39 and provides a stop when forced against the pivot pin 39 by the 
bias provided by the return spring 37A to accurately position the target 
arm 36, connected to the indicator lever 33 by pivot pin 65 (FIG. 5) and 
pivotally arranged on the pivot pin 39, in the OFF position as shown in 
FIG. 5. Slot 38, formed in the indicator lever 33 can be utilized to 
interact with a variety of circuit breaker accessories. The opposite end 
of the indicator lever 33 is attached to an L-shaped lever 41 which, in 
turn, connects with the indicator lever bell crank 42 by means of the 
common pivot pin 44. The L-shaped lever extends within the operating 
mechanism enclosure 13 by means of the slot 40 and interacts with the 
indicator lever bell crank 42 that forms part of the contact arm connector 
assembly generally depicted at 45. The indicator lever bell crank 42 
connects with the contact arm bell crank 58 by means of the top lever 56 
that is shown connecting with the top of the contact arm bell crank 58 by 
means of the bell crank post 59 that is captured within the lost motion 
slot 62 formed at the end of the top lever 56. A bottom lever 57 connects 
with the bottom of the contact arm bell crank 58 by means of the pin 60 at 
one end and connects with the circuit breaker operating mechanism cross 
bar 46 by means of the opposite end 57A as shown in FIG. 3. 
As shown in FIGS. 3, 4 and 5, the main movable contacts 52 at the end of 
the main contact arm 51 and the arcing movable contacts 49 at the end of 
the arcing contact arm 48, hereinafter "contacts", operate off a common 
pivot 54 and common contact carrier 47 which is attached to the circuit 
breaker operating mechanism crossbar 46. The main fixed contacts 53 and 
the arcing fixed contacts 50, hereinafter also "contacts", are attached to 
the contact support 55. As indicated at 57A, the bottom lever 57 within 
the contact arm connector assembly 45 is attached at one end to the 
crossbar 46. The contact arm bell crank 58 is pivotally attached to the 
operating mechanism enclosure 13 by means of a pivot pin 61. 
FIG. 3 is illustrative of the circuit breaker contact position indicator 
assembly 45 with the circuit breaker contact completely closed, and where 
common contact carrier 47 is oriented in a first position. With the 
circuit breaker contacts completely closed, the bottom lever 57 drives the 
bell crank 58 in a clockwise direction which forces the top lever 56 to 
rotate the indicator lever bell crank 42 also in a clockwise direction. It 
is important to note that the line of action created by the two bell 
cranks and the top lever 56, as shown by the direction of the indicating 
arrows is passing through or very close to the center of the pivot of the 
contact arm bell crank 58 as shown at 61, thereby substantially aligning 
contact arm bell crank pivot 61 with contact arm bell crank post 59 and 
first end of top lever 56 connected to indicator lever bell crank 42. This 
arrangement holds the indicator lever bell crank 42 in a dwell condition 
resulting in only a slight movement of the indicator lever bell crank 
provided that the lines of action are maintained close to the bell crank 
pivot pin 61. 
FIG. 4 is illustrative of the circuit breaker contact position indicator 
assembly 45 after the circuit breaker 10 has been tripped wherein the 
arcing contacts 49, 50 are welded closed, and where common contact carrier 
47 is oriented in a second position. 
When the main movable contacts 52 are open and the arcing contacts 49 are 
closed, as shown in FIG. 4, the line of action is very close to the bell 
crank pivot pin 61. As a result, there is no difference in the position of 
the indicator lever bell crank 42 shown in FIGS. 3 and 4. The controlled 
stability of the indicator bell crank 42 maintains the target plate 35 in 
the CLOSED position over a wide range of contact positions and is an 
important feature of the invention. The rotation of the indicator lever 
bell crank 42 in the clockwise direction by the closing of the circuit 
breaker contacts forces lever 41, which is positioned on a common pivot 
pin 44 with the indicator lever bell crank 42, to rotate clockwise such 
that the indicator lever 33 engages lever 41 through pin 43 and is now 
driven to the position indicated in FIGS. 3 and 4. The target arm 36 
pivotally connects with the end of the indicator lever 33 by means of the 
pivot pin 65 whereby the movement of the indicator lever 33 rotates the 
target arm 36 in a clockwise direction to position the target plate 35 
accordingly under the viewing windows 21 formed on the surface of the 
circuit breaker enclosure 12 such that the ON indicia 32A on the target 
plate 35 is visible under the viewing windows 21. 
FIG. 5 is illustrative of the circuit breaker contact position indicator 
assembly 45 after the circuit breaker 10 has been tripped under normal 
operating conditions, and where common contact carrier 47 is oriented in a 
third position. 
When the circuit breaker is tripped, the arcing and main contact arms 48, 
51 open to the position indicated in FIG. 5. The interaction of the bottom 
lever 57 between the crossbar 46 and the contact arm bell crank 58 rotates 
the contact arm bell crank in the counter-clockwise direction and 
positions the pin 59 away from the end of the slot 62 in the top lever 56. 
The top lever 56 is now free to release the indicator bell crank 42 to 
allow rotation in the counter-clockwise direction under the bias provided 
by the return spring 37A. As described earlier, the return spring 37A can 
now return the slot 37 on lever 33 against the pivot pin 39 thereby 
accurately positioning the OFF indicia 32B into alignment with the viewing 
windows 21 to indicate that the circuit breaker contacts have completely 
separated. It is noted that the position of the pin 59 in the lost motion 
slot 62 provides sufficient lost motion to accommodate manufacturing 
variations so as not to move the off indicia 32B out of alignment with the 
viewing windows 21.