Tripping device reset arrangement

A field-installable circuit breaker trip unit conversion kit in the form of a flux shifter unit that interfaces with the circuit breaker operating mechanism is installable without dismantling the circuit breaker components. The flux shifter unit responds to an electronic trip unit to articulate the circuit breaker operating mechanism and separate the circuit breaker contacts upon occurrence of an overcurrent condition. Expansion springs achieve tolerance take-up for different operating mechanism assemblies to correctly interface with the associated electronic trip unit.

BACKGROUND OF THE INVENTION 
High ampere-rated circuit breakers such as described within U.S. Pat. No. 
3,073,936 entitled "Electric Circuit Interrupter" are currently employed 
within industrial manufacturing facilities to protect the electric 
equipment and buildings from damage due to overcurrent conditions within 
the electrical distribution system. Earlier manufactured circuit breakers 
employed thermal-magnetic trip units to determine overcurrent conditions 
and to articulate the circuit breaker operating mechanism to separate the 
circuit breaker contacts to interrupt the associated electric circuit. 
Later manufactured circuit breakers employed electronic trip units which 
contained so-called "flux shifters" to articulate the operating mechanism 
upon signal from the electronic trip unit. One example of an early 
electronic trip unit is found in U.S. Pat. No. 3,761,778 entitled "Static 
Trip Control Unit for Electric Circuit Breaker". 
Such robust circuit breakers remain in operation to this date without 
needing replacement or repair. However, state of the art digital trip 
units of the type described within U.S. Pat. No. 4,672,501 entitled 
"Circuit Interrupter and Controller Unit", provide more reliable 
protection by better control over the circuit interruption time and 
current parameters. It would be economically advantageous to incorporate 
state of the art digital trip units within existing circuit breakers 
without having to dismantle the circuit breaker operating components in 
the process. 
One purpose of the invention, accordingly, is to provide a conversion unit 
that will incorporate digital trip units within existing circuit breakers 
without having to dismantle the circuit breaker operating components. 
SUMMARY OF THE INVENTION 
In accordance with the invention, an electronic trip unit conversion kit 
includes a flux shifter and reset arrangement to articulate the circuit 
breaker operating mechanism upon the occurrence of an overcurrent 
condition to separate the circuit breaker contacts and to reset the flux 
shifter after the circuit breaker contacts have become separated.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows an industrial-rated circuit breaker 10, such as described in 
aforementioned U.S. Pat. No. 3,073,936, with an operating handle 11 
extending from the top with load straps 12 and line straps 13 arranged at 
opposite ends thereof. The movable contacts 15 at one end of the movable 
contact arm 14 and the fixed contacts 16 on the contact support 17 are 
shown in solid lines in the CLOSED condition and in phantom lines in the 
OPEN condition. As described in the aforementioned U.S. Pat. No. 
3,073,936. the condition of the contacts are controlled by an operating 
mechanism (not shown) that is refrained from articulation by means of a 
trip latch 18. In accordance with the invention, a trip unit conversion 
kit 9 includes a programmer or electronic trip unit 21, such as described 
in aforementioned U.S. Pat. No. 4,672,501, that connects with a trip 
actuator unit 20 by means of a wire conductor 22. Upon receipt of a trip 
signal from the trip unit, the trip actuator releases a trip plunger 19 
which strikes the trip latch 18 allowing the operating mechanism to 
separate the contacts 15, 16 as described in the aforementioned U.S. Pat. 
No. 3,073,936. The connector link 24 is attached to the reset arm 23 to 
return the trip plunger 19 from the actuated position to the to the reset 
position. As will be discussed below, the motion of the movable contact 
arm 14 upon separation of the contacts 15, 16 returns the trip actuator to 
the reset position by connection with the connector link 24 and the reset 
arm 23. 
The trip actuator as shown in FIGS. 2 and 3 is supported between a front 
mounting plate 27 and a rear mounting plate 25. The support bracket 32 
attached to the front plate 27 by means of screws 33 guides the movement 
of the intermediate lever 37 that extends through the slot 36 formed in 
the support bracket. The reset arm 23 is trapped between the rear plate 25 
and the reset plate 29 by means of the pivot pin 28. The bottom of the 
reset arm 23 is connected to the bottom of the reset plate 29 by means of 
the take-up spring 31 which provides automatic tolerance connection with 
the opposite end of the reset arm when the trip actuator is used within 
circuit breakers of different manufacture. The flux shifter unit 26 is 
similar to that described within U.S. Pat. No. 3,693,122 entitled "Flux 
Transfer Device" that releases a flux shifter plunger 39 upon receipt of a 
voltage pulse to counteract the magnetic holding force on the plunger and 
allow the plunger to extend under the urgence of the charged compression 
spring 44. The voltage pulse is supplied to the flux shifter 26 over the 
wire conductor 22 that connects with the trip unit 21 of FIG. 1 by means 
of the plug connector 22A. The trip plunger 19 passes through the U-shaped 
take-up bracket 34 and connects with the top part of the intermediate 
lever 37. The bias spring 35 interfaces between the exterior of the 
bracket 34 and the end cap 41 that holds the spring to the trip plunger 
and connects the end of the plunger to the intermediate lever 37. The bias 
spring 35, along with the adjustment nuts 45, provide tolerance take-up 
facility to the trip plunger to insure good interaction with the trip 
latch 18 of FIG. 1. As best seen in FIG. 3, with the front plate 27 
removed, the bottom of the intermediate lever 37 contacts the end of the 
flux shift plunger 39 as indicated at 37A when the top of the intermediate 
lever abuts the reset pin 40, as indicated at 37B. In the reset position 
of the flux shifter 26, the compression spring 44 is charged and the reset 
plate 29 abuts the stop pin 30 extending from the reset arm 23. The 
arrangement of the stop pin 30 against the reset plate 29 allows the reset 
plate to move in unison with the reset arm when the reset arm is rotated 
in the clockwise direction while allowing the reset arm to move 
independently from the reset plate 29 when the reset arm is rotated in the 
counter-clockwise direction and the reset pin 40 is bottomed against the 
top of the intermediate lever 37 as indicated at 37B. The over-travel of 
the of the reset arm 23 in the counterclockwise direction is controlled by 
the expansion of the take-up spring 31 to allow for differences between 
the various movable contact arms that may be connected with the reset 
lever 23 by means of the connector link 24 shown in FIG. 4. The thru-hole 
23A formed in the opposite end of the reset arm 23 allows the reset arm to 
become attached to the connector link 24 extending from the circuit 
breaker movable contact arm 14 shown earlier in FIG. 1. 
The reset position of the flux shifter 26 is best seen by referring to the 
trip actuator 20 depicted in FIG. 4. The reset arm 23 is attached to the 
end of the connector link 24, and the edge of the reset plate 29 abuts 
against the stop pin 30. The bottom 37A of the intermediate lever 37 abuts 
against the flux shifter plunger 39 with the compression spring 44 fully 
charged and with the top against the extruded bias spring 35. The end of 
the trip plunger 19 is out of contact with the circuit breaker trip latch 
18 and the bias spring 35 on the opposite end of the trip plunger is 
extended. Upon receipt of a trip signal to the flux shifter over conductor 
22, the flux shifter plunger 39, as shown in FIG. 5, extends under the 
urgence of the compression spring 44 against the bottom 37A and drives the 
intermediate lever 37 into counter-clockwise rotation about the pivot 38 
striking the top 37B against the end cap 41 forcing the trip plunger 19 
against the trip latch 18 rotating the trip latch 18 about the latch pivot 
46 to articulate the operating mechanism (not shown) and separate the 
circuit breaker contacts 15, 16 of FIG. 1. In the process of separating 
the contacts, the movable contact arm 14 drives the connector link 24 and 
the attached reset arm 23 to the positions indicated in phantom rotating 
the reset arm 23 counter-clockwise about the pivot pin 28, to extend the 
take-up spring 31 which rotates the reset plate 29 counter-clockwise and 
moves the reset pin 40 on the reset plate into contact with the top 37B of 
the intermediate lever 37 as described earlier. The top end of the 
intermediate lever 37 then rotates clockwise about the pivot 38 and drives 
the bottom end 37A of the intermediate lever 37 against the flux shift 
plunger 39 driving the plunger to its reset position, shown in FIG. 4, to 
charge the compression spring 44. The connection between the reset arm 23 
and the reset plate 29 by means of the take-up spring 31 is an important 
feature of the invention in view of the automatic tolerance adjustment for 
the different movable contact arms, as described earlier.