Electrical switching apparatus and movable contact arm assembly therefor

A movable contact arm assembly is provided for an electrical switching apparatus, such as a circuit breaker. The movable contact arm assembly includes a first member, and a second member attached to the first member. The first member is made from a first material, such as steel, and the second member is made from a second different material, such as copper. The first and second members each include first and second ends. The first end of the first member cooperates with the operating mechanism of the circuit breaker. The first end of the second member is attached to the second end of the first member. A movable contact is disposed on the second end of the second member.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to commonly assigned, copending U.S. patent application Ser. No. 13/692,296, filed Dec. 5, 2012, entitled “ELECTRICAL SWITCHING APPARATUS AND CONDUCTOR ASSEMBLY THEREFOR”.

BACKGROUND

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 movable contact arm assemblies for electrical switching apparatus.

2. 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. The electrical contact assemblies include stationary electrical contacts and corresponding movable electrical contacts that are typically mounted on movable (e.g., pivotable) arms. The stationary and movable contacts are in physical and electrical contact with one another when it is desired that the circuit breaker provide electrical current therethrough to a load. When it is desired to interrupt the power circuit, the movable contact arm is pivoted, thereby moving the movable contact away from the stationary contact creating a space therebetween.

The movable contact arms of some circuit breakers are unitary members made from one single piece of material and including a first end, which cooperates with the circuit breaker operating mechanism (e.g., without limitation, operating handle), and a second end where the movable contact is disposed. Typically, the movable contact arms and movable contacts are made from copper. Thus, as the cost of copper increases, the cost of the movable contact arm assembly correspondingly increases.

There is, therefore, room for improvement in electrical switching apparatus, such as circuit breakers, and in movable contact arm assemblies therefor.

SUMMARY

These needs and others are met by embodiments of the disclosed concept, which are directed to a movable contact arm assembly, which among other benefits, employs a plurality of members made from different materials to reduce the amount of copper required.

As one aspect of the disclosed concept, a movable contact arm assembly is provided for an electrical switching apparatus. The electrical switching apparatus includes a housing, separable contacts enclosed by the housing, and an operating mechanism for opening and closing the separable contacts. The movable contact arm assembly comprises: a first member; and a second member attached to the first member. The first member is made from a first material and the second member is made from a second different material.

The first member and the second member may combine to form a bimetallic movable contact arm. The first material of the first member may be steel, and the second material of the second member may be copper.

The first member and the second member may each include a first end and a second end. The first end of the first member may be structured to cooperate with the operating mechanism, the first end of the second member may be attached to the second end of the first member, and a movable contact may be structured to be disposed on the second end of the second member. The second end of the first member may have a first shape, the first end of the second member may have a second shape, and the first shape of the first member may compliment the second shape of the second member. The second end of the first member may comprise a recess, and the first end of the second member may comprise a protrusion, wherein the protrusion is disposed within the recess.

An electrical switching apparatus comprising at least one of the aforementioned movable contact assemblies, is also disclosed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As employed herein, the term “fastener” refers to any suitable connecting or tightening mechanism expressly including, but not limited to rivets, screws, bolts and the combinations of bolts and nuts (e.g., without limitation, lock nuts) and bolts, washers and nuts.

As employed herein, the statement that two or more parts are “attached” shall mean that the parts are directly joined together, without any intermediate parts.

FIG. 1shows a movable contact assembly100for an electrical switching apparatus, such as for example and without limitation, a circuit breaker2, in accordance with one non-limiting embodiment of the disclosed concept. The circuit breaker2includes a housing4, separable contacts6,8enclosed by housing4, and an operating mechanism, such as for example and without limitation an operating handle10, for opening and closing the separable contacts6,8.

InFIG. 1, the separable contacts6,8include a stationary contact6and a movable contact8(partially shown in hidden line drawing inFIG. 1), and are shown in electrical contact with one another, corresponding to the circuit breaker2being disposed in the ON position.

FIG. 2shows the operating handle10, separable contacts6,8, and other circuit breaker components in their respective positions corresponding to the circuit breaker2being disposed in the OFF position, such that the movable contact8(shown in hidden line drawing inFIG. 2) is separated, and electrically disconnected, from the stationary contact6, as shown.FIG. 3shows the circuit breaker2and corresponding components (e.g., without limitation, separable contacts6,8; operating mechanism10; movable contact arm assembly100) in their respective positions corresponding to the circuit breaker2being disposed in the TRIPPED position.

It will be appreciated that while the example non-limiting embodiment shown and described herein includes a single movable contact arm assembly100and a single pair of separable contacts6,8, any known or suitable alternative number and/or configuration of movable contact arms (e.g.,100) and corresponding sets of separable contacts (e.g.,6,8) could be employed, without departing from the scope of the disclosed concept.

Continuing to refer toFIGS. 1-3, and also toFIGS. 4A and 4B, the example movable contact arm assembly100includes a first member102and a separate second member104, which is attached to the first member102, as will be described in greater detail hereinbelow. Specifically, the first member102is made from a first material and the second member104is made from a second, different material.

In one non-limiting embodiment, in accordance with the disclosed concept, the first member102and the second member104combined to form a bimetallic movable contact arm100. The term “bimetallic” as used herein refers to an assembly of a plurality (e.g., at least two) of metal parts attached or otherwise suitably joined together (see, for example and without limitation, bimetallic movable contact arm100, best shown inFIG. 4B). For example and without limitation, preferably the first material of the first member102is steel, and the second material of the second member104is copper. In this manner, the amount of copper required for the movable contact arm assembly100is reduced. In other words, in accordance with the disclosed concept, rather than a single unitary piece of copper being used for the entire movable contact arm, in accordance with conventional designs, a substantial reduction in the amount of copper used is achieved by replacing copper with steel or another suitable material in the non-conducting portion of the movable contact arm assembly100.

As shown inFIGS. 1-3, the aforementioned movable contact8(shown in hidden line drawing inFIGS. 2 and 3) is disposed on the second member104. Specifically, the first and second members102,104each include first ends106,110and second ends108,112, respectively. The first end106of first member102cooperates with the operating mechanism10(e.g., without limitation, opening handle). The first end110of the second member104is attached to the second end108of the first member102. The movable contact8is disposed on the second end112of the second member104, as shown. It will be appreciated, however, that the movable contact8could alternatively comprise an integral portion or segment of the second member104. In other words, it is not a requirement of the disclosed concept for the separable contact8to be a separate part that is attached to the second member104. It is anticipated that it could alternatively comprise an integral portion or segment of the second member104.

Referring again toFIGS. 4A and 4B, the second end108of the first member102has a first shape, and the first end110of the second member104has a second shape. The first shape of the first member110compliments the second shape of the second member104, as shown. Specifically, as used herein, the term “compliments” refers to two opposing shapes, surfaces or configurations of two separate parts that are structured to be attached together such that the opposing surfaces abut and correspond to one another so as to provide a precise interface between the two parts. This relationship will be appreciated, for example and without limitation, with reference to the non-limiting embodiment shown and described with respect toFIGS. 4A and 4B. In the example shown and described, the second end108of the first member102includes a recess114, and the first end110of the second member104includes a protrusion116. As shown inFIG. 4Bthe protrusion116is disposed within the recess114to complete the movable contact arm assembly100.

More specifically, the second end108of the example first member102preferably includes first and second opposing legs118,120, wherein the recess114is formed between such legs118,120, as best shown inFIG. 4A. Accordingly, the protrusion116is disposed within the recess114between the first and second legs118,120to complete the assembly100, as shown inFIG. 4B. Preferably, the first and second legs118,120, which are made, for example and without limitation from steel, are compressed inwardly against the protrusion116, which is made, for example and without limitation from copper, in order to further secure the copper second member104to the steel first member102.

Referring again toFIGS. 1-3, the example circuit breaker2further includes a bimetal structure12and a flexible shunt14. The flexible shunt14preferably extends between and electrically connects the second member104of the movable contact arm assembly100to the bimetal structure12, as shown. It will, however, be appreciated that any known or suitable alternative type and/or configuration of electrical connection (not shown) could be employed, without departing from the scope of the disclosed concept.

In addition to the aforementioned movable contact arm assembly100, the example circuit breaker2includes a conductor assembly200(FIGS. 1-3,5A,5B and5C), which also functions to advantageously further reduce the amount of copper required to be used in the circuit breaker2.

As best shown inFIGS. 5A-5C, the disclosed conductor assembly200includes a first conductor member202, a second conductor member204, and a plurality of fasteners206,208for mechanically fastening and electrically connecting the first conductor member202to the second conductor204. The first conductor member202is made from a first material, such as for example and without limitation, copper, and the second conductor member204is made from a second, different material, such as for example and without limitation, aluminum. Accordingly, the first and second conductor members202,204combine to form a bimetallic conductor assembly200, which substantially reduces the amount of copper required.

As shown inFIGS. 1-3, the first conductor member202is structured to extend from the exterior22of the circuit breaker housing4into the interior20. The fasteners, which in the example shown and described herein are rivets206, fasten (e.g., rivet) the second conductor member204to the first conductor member202within the interior20of the housing4. More specifically, the first conductor member202includes a terminal portion210, which is accessible from the exterior22of the circuit breaker housing4, and a mounting portion212. The example mounting portion212is an upturned flange (best shown inFIGS. 5A and 5C), wherein the second conductor member204includes opposing first and second ends214,216, and a first pair206of the aforementioned rivets206,208fastens the first end214of the second conductor member204to the upturned flange212of the first conductor member202, within the interior20of the circuit breaker housing4, as shown. In the example shown and described herein, the second conductor member204further includes first and second opposing sides222,224, wherein the second side224of the first end214of the second conductor member204is riveted to the upturned flange212using the first pair of rivets206, as best shown inFIGS. 5A-5C. It will, however, be appreciated that any known or suitable alternative number, type and/or configuration of fastener could be employed, without departing from the scope of the disclosed concept.

Referring toFIGS. 5A-5C, the second conductor member204preferably further includes a bend218disposed between the first and second ends214,216. Accordingly, as shown inFIG. 5B, the second end216of the second member204is disposed at an angle220with respect to the first end214of the second conductor member204. As shown inFIGS. 1-3, this configuration of the second end216being disposed at an angle220(FIG. 5B) with respect to the first end214, functions to position the second end216of the second conductor member204of the conductor assembly200in the desired orientation with respect to other internal electrically conductive components, such as for example and without limitation, the bimetallic structure12.

In the example ofFIGS. 1-3, the second end216of the second conductor member204is electrically connected to the bimetal structure12by a flexible shunt16, as shown. The example second conductor member204includes a second pair of rivets208disposed at or about the second end216of the second conductor member204. In one non-limiting embodiment, the flexible shunt16is mechanically fastened and electrically connected to the second end216of the second conductor member204by a corresponding one of the rivets208. It will, however, be appreciated that any known or suitable alternative configuration and/or mechanism for electrically connecting the conductor assembly200to other circuit breaker components (e.g., without limitation, bimetal structure12) could be employed, without departing from the scope of the disclosed concept.

It will further be appreciated that the aforementioned conductor assembly200could be employed independently within any known or suitable electrical switching apparatus (e.g., without limitation, circuit breaker2ofFIGS. 1-3) with, or without, the aforementioned movable contact arm assembly100(FIGS. 1-4C).

Accordingly, the disclosed concept provides a number of assemblies (e.g., without limitation, movable contact arm assembly100; conductor assembly200) that utilize a unique bimetal structure that, among other benefits, serves to reduce the amount of copper required to be used within the circuit breaker2(FIGS. 1-3).