Modular trip bar assembly for multipole circuit breaker

A modular plastic trip bar assembly joins separate single pole molded case circuit breakers into a single multipole circuit breaker. The addition of the trip cam to the trip bar assembly allows four and five pole combinations to operate in unison.

BACKGROUND OF THE INVENTION 
The introduction of American-made molded case residential circuit breakers 
into the European community requires the fabrication of four and five pole 
circuit breakers not commonly used within the United States. 
Early attempts to join individual single pole circuit breakers by means of 
a common trip bar are described within U.S. Pat. No. 3,288,965 entitled 
"Multiple Circuit Breaker Assembly with Common Tripping" which limited the 
number of individual circuit breakers to a single pair to insure tripping 
in unison when one of the circuit breakers experienced an overload. 
U.S. Pat. 4,066,989 entitled "Trip Unit Tie Bar Having Integral Flexibly 
Connected Links" and U.S. Pat. No. 4,179,675 entitled "Trip Bar Means 
Subassembly" describe flexible tie bars for multi-pole circuit breakers 
wherein the individual poles are designed to interrupt independently from 
each other. 
In accordance with the requirement that all poles interrupt in unison upon 
occurrence of an overcurrent in any of the individual poles to prevent 
so-called "single phasing", an arrangement is required that is capable of 
converting four or five individual single pole circuit breakers into a 
unitary four or five pole circuit breaker with all poles interrupting in 
unison. 
One purpose of the invention is to provide a modular trip bar that is 
operative with four and five individual circuit breakers and which causes 
the individual circuit breakers to trip in unison with minimum added cost. 
SUMMARY OF THE INVENTION 
A modular trip bar arrangement incorporates the individual trip cams 
integral with the trip bar to insure motivation of the trip assemblies in 
every pole of a multi-pole composite circuit breaker. The trip bar 
arrangement extends within each of the individual single pole circuit 
breakers within the composite circuit breaker to allow the individual cams 
to interact directly with the individual trip assemblies.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A standard single pole molded case circuit breaker produced in an automated 
assembly process is depicted at 10 in FIG. 1. The circuit breaker operates 
in the manner described in aforementioned U.S. Pat. No. 3,288,965 and 
consists of a molded plastic case 11 to which external electric connection 
is made by means of the load terminal 12 at one end and the line terminal 
13 at the opposite end thereof. The contacts 14,15 become separated to 
interrupt circuit current in response to the operation of the 
thermal-magnetic trip unit 16 whereby the end of the cradle 17 releases 
from the latch 18 and drives the top part of the cradle against the trip 
cam 20 that carries the trip bar 21, shown in section. The trip cam is 
pivotally supported on a hub (not shown) that is integrally-formed on the 
interior surface of the case 11 by means of the pivot pin 22. 
Rather than manufacture increasingly larger multi-pole circuit breakers, it 
is economically advantageous to join individual single pole circuit 
breakers together to form a multi-pole composite circuit breaker 30, as 
shown in FIGS. 2 and 4, and employ a common trip mechanism in the form of 
the modular trip bar 24 to insure that the individual circuit breakers 
trip in unison. The single pole circuit breakers 10A-10D are aligned such 
that the apertures 23 are on-center to receive the modular trip bar 24 and 
the through-holes 28 are aligned to receive the attachment rivets 27. The 
trip cam 20, of FIG. 1, is omitted from the individual circuit breakers 
and the modular trip bar 24 is shaped to include integrally-formed trip 
cams 26A-26D on the plastic carry rod 25. Also integrally-formed with the 
trip cams is a central phase barrier unit 31 that insures that any gaseous 
byproducts generated during circuit interruption in the individual circuit 
breakers 10A,10B are not transmitted to the individual circuit breakers 
10C, 10D and visa versa. The rear wails 11A, 11D of the two outermost 
circuit breakers 10A, 10D are left intact so that the corresponding hubs 
29A,29D receive and support the ends of the carry rod 25. To facilitate 
rotational response of the rod, lubricating grease can also be applied to 
the ends. 
With the composite multi-pole circuit breaker 30 assembled, as now depicted 
in FIG. 3, the modular trip bar 24 extends across the individual circuit 
breakers 10A-10D such that the integral trip cams 26A-26D exactly align 
with the corresponding cradles 17A-17D whereby the displacement of any of 
the individual cradles into contact with the corresponding trip cam is 
sufficient to rotate the remaining cams within the remaining individual 
circuit breakers into the corresponding latches 18 (FIG. 1) causing the 
remaining cradles to release and separate each of the associated contacts 
to open all the circuits connected with the composite multi-pole circuit 
breaker 30. 
A reliable and inexpensive modular tie bar for combining a plurality of 
individual single pole circuit breakers into a composite multi-pole 
circuit breaker has herein been disclosed. The composite multi-pole 
circuit breaker finds application in the European industrial community.