WO2002021556A1

WO2002021556A1 - Circuit interrupter with enhanced operating mechanism securement

Info

Publication number: WO2002021556A1
Application number: PCT/IB2001/001610
Authority: WO
Inventors: Mark O. Zindler; Keith Thomas
Original assignee: Eaton Corporation
Priority date: 2000-09-05
Filing date: 2001-09-03
Publication date: 2002-03-14
Also published as: AU8240101A

Abstract

A circuit interrupter including a housing, separable main contacts disposed in the housing, and an operating mechanism disposed in the housing and interconnected with the contacts. The housing includes a cover positioned on top of a base, with the base including an abutment portion having a bottom surface. The operating mechanism includes a support member situated within the base, the support member including a protrusion situated beneath the abutment portion and positioned to contact the bottom surface for resisting upward movement of the support member.

Description

CIRCUIT INTERRUPTER WITH ENHANCED OPERATING MECHANISM SECUREMENT

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

The present invention relates to circuit interrupters generally and, more specifically, to those kinds of circuit interrupters having a housing with a base and cover, and an operating mechanism positioned within the housing.

DESCRIPTION OF THE PRIOR ART

Molded case circuit breakers and interrupters are well known in the art as exemplified by U.S. Patent No. 4,503,408 issued March 5, 1985, to Mrenna et al., and U.S. Patent 5,910,760 issued June 8, 1999 to Malingowski, et al., each of which is assigned to the assignee of the present application and incorporated herein by reference.

A continuing industry objective with respect to many types of circuit interrupters is to be able to reduce the size and/or footprint of the interrupter housing while at the same time providing the same or improved performance capabilities. A major advantage of creating such a "smaller package" is that it provides increased flexibility in installation. However, a consequence of this objective is that the internal space constraints of such interrupters have become much more limiting, posing certain design obstacles that need to be overcome.

Circuit interrupters typically include a housing having a base and cover.

Within the base is positioned an operating mechanism that is interconnected with the contacts of the circuit interrupter. In the prior art, the operating mechanism sometimes is held in place by an independent securement mechanism such as orbital riveting, twist tabs, or screws. However, such independent securement adds to the cost of assembly, and slows down the assembly process. In addition, such securement mechanisms typically require relatively thick wall or bottom sections in the housing in order to be implemented, housing characteristics which are undesirable in view of the continuing industry objective mentioned above of reducing circuit interrupter size. For those reasons, prior art circuit interrupters have sometimes employed a "floating" operating mechanism that is not secured by an independent securement mechanism. Instead, other structures of the circuit interrupter are usually relied upon to secure the operating mechanism within the base upon completion of the assembly process. For example, the positioning of the cover onto the base can be used for that purpose, with the bottom of the cover designed to contact a top surface of the operating mechanism to hold the mechanism in place. However, a high current interruption event can cause the contact arm to forcibly rise, imparting an upward force on the operating mechanism structure that can cause damage to the bottom of the cover making contact with the operating mechanism. This potential damage to the cover may result in the operating mechanism being insufficiently engaged after such a high current interruption event. This can lead to improper positioning and functioning of the operating mechanism.

It would be advantageous if a circuit breaker existed that provided an efficient, economical, and easy to implement way of holding the operating mechanism in the base, and especially one which would effectively hold the operating mechanism in the base during a high current interruption event.

SUMMARY OF THE INVENTION The present invention provides a circuit interrupter that meets all of the above-identified needs.

In accordance with the present invention, a circuit interrupter is provided which includes a housing, separable main contacts disposed in the housing, and an operating mechanism disposed in the housing and interconnected with the separable main contacts. The housing includes a cover positioned on top of a base, with the base including an abutment portion having a bottom surface. The operating mechanism includes a support member situated within the base, the support member including a protrusion situated beneath the abutment portion and positioned to contact the bottom surface for resisting upward movement of the support member.

This and other objects and advantages of the present invention will become apparent from a reading of the following description of the preferred embodiment taken in connection with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an orthogonal view of a molded case circuit breaker embodying the present invention.

Figure 2 is an exploded view of the base and cover of the circuit interrupter of Figure 1. Figure 3 is side elevational view of an internal portion of the circuit interrupter of Figure 1.

Figure 4 is an orthogonal view of the internal portions of the circuit interrupter of Figure 1 without the base and cover.

Figure 5 is an orthogonal view of an internal portion of the circuit interrupter of Figure 1 including the operating mechanism.

Figure 6 is a side elevational, partially broken away view of the operating mechanism of the circuit interrupter of Figure 1 with the contacts and the handle in the OFF disposition.

Figure 7 is a side elevational, partially broken away view of the operating mechanism with the contacts and the handle in the ON disposition.

Figure 8 is a side elevational, partially broken away view of the operating mechanism with the contacts and the handle in the TRIPPED disposition.

Figure 9 is a side elevational, partially broken away view of the operating mechanism during a resetting operation. Figure 10 is an orthogonal view of the sideplate assembly, cradle, latch, and trip bar assembly of an internal portion of the circuit interrupter of Figure 1. Figure 11 is an exploded view of the internal portion of the circuit interrupter shown in Figure 10.

Figure 12 is an orthogonal view of the base of the circuit interrupter of Figure 1 with a sidewall partially cut away and showing a positioning region. Figure 13 is an orthogonal view similar to Figure 12 with a sideplate inserted into the positioning region.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and Figures 1 and 2 in particular, shown is a molded case circuit breaker 10. The structure and functioning of circuit breaker 10 is substantially similar to that shown and described in U.S. Patent Application Serial No. 09/384,148, filed August 27, 1999, entitled "Circuit Interrupter With Cradle Having An Improved Pivot Pin Connection", the disclosure of which is incorporated herein by reference. Circuit breaker 10 includes a base 12 mechanically interconnected with a cover 14 to form a circuit breaker housing 15 molded of thermoset plastic material in the exemplary embodiment. Holes or openings 16 (Figure 2) are provided in cover 14 for accepting screws or other attaching devices 128 that enter corresponding holes or openings 18 in base 12 for fastening cover 14 to base

12. Holes 20, which feed through cover 14, are provided for internal access to circuit breaker 10. Cover 14 includes a handle opening 22 through which protrudes a handle 24 (Figure 1) that is used in a conventional manner to manually open and close the contacts of circuit breaker 10 and to reset circuit breaker 10 when it is in a tripped state. Handle 24 may also provide an indication of the status of circuit breaker 10 whereby the position of handle 24 corresponds with a legend (not shown) on cover 14 near handle opening 22 which clearly indicates whether circuit breaker 10 is ON (contacts closed), OFF (contacts open), or TRIPPED (contacts open due to, for example, an overcurrent condition). Cover 14 also includes a rectangular opening 23

(Figure 2) through which protrudes a top portion 25A of a button for a push-to- trip actuator. Also shown is a load conductor opening 26 in base 12 that shields and protects a load terminal (not shown). Although circuit breaker 10 is depicted as a single-phase circuit breaker, the present invention is not limited to single-phase operation. Referring now to Figure 3, a longitudinal section of a side elevation, partially broken away and partially in phantom, of circuit breaker 10 is shown having a load terminal 28 and a line terminal 29. There is shown a plasma arc acceleration chamber 30 comprising a slot motor assembly 32 and an arc extinguisher assembly 34. Also shown is a contact assembly 36, an operating mechanism 38, and a trip mechanism 40.

Referring again to Figure 3, and now also to Figure 4 which shows a side elevational view of the internal workings of circuit breaker 10 without base 12 and cover 14, slot motor assembly 32 is shown as including a separate upper slot motor assembly 32A and a separate lower slot motor assembly 32B. Upper slot motor assembly 32A includes an upper slot motor assembly housing 41 within which are stacked side-by-side U-shaped upper slot motor assembly plates 42. Similarly, lower slot motor assembly 32B includes a lower slot motor assembly housing 43 within which are stacked side-by-side lower slot motor assembly plates 44. Plates 42 and 44 are both composed of magnetic material.

Arc extinguisher assembly 34 includes an arc chute 46 within which are positioned spaced-apart generally parallel angularly offset arc chute plates 48 and an upper arc runner 48A. As known to one of ordinary skill in the art, the function of arc extinguisher assembly 34 is to receive and dissipate electrical arcs that are created upon separation of the contacts of the circuit breaker.

Referring now to Figure 5, shown is an orthogonal view of an internal portion of circuit breaker 10. There is shown contact assembly 36 comprising a movable contact arm 50 supporting thereon a movable contact 52, and a stationary contact arm 54 supporting thereon a stationary contact 56.

Stationary contact arm 54 is electrically connected to line terminal 29 and, as discussed below, movable contact arm 50 is electrically connected to load terminal 28. Also shown is a crossbar assembly 60 which traverses the width of circuit breaker 10 and is rotatably disposed on an internal portion of base 12 (not shown). Actuation of operating mechanism 38, in a manner described in detail below, causes crossbar assembly 60 and movable contact arm 50 to rotate into or out of a disposition which places movable contact 52 into or out of a disposition of electrical continuity with fixed contact 56. Crossbar assembly 60 includes a movable contact cam housing 62 in which is disposed a pivot pin 64 upon which movable contact arm 50 is rotatably disposed. Under normal circumstances, movable contact arm 50 rotates in unison with the rotation of housing 62 as housing 62 is rotated clockwise or counterclockwise by action of operating mechanism 38. However, it is to be noted that movable contact arm 50 is free to rotate (within limits) independently of the rotation of crossbar assembly 60. In particular, in certain dynamic, electro-magnetic situations, movable contact arm 50 can rotate upwardly about pivot pin 64 under the influence of high magnetic forces. This is referred to as "blow-open" operation, and is described in greater detail below.

Continuing to refer to Figure 5 and again to Figure 3, operating mechanism 38 is shown. Operating mechanism 38 is structurally and functionally similar to that shown and described in U.S. Patent Application

Serial No. 09/384,148, filed August 27, 1999, entitled "Circuit Interrupter With Cradle Having An Improved Pivot Pin Connection", and U.S. Patent Application Serial No. 09/386,130, filed August 30, 1999, entitled "Circuit Interrupter With Screw Retainment", both disclosures of which are incorporated herein by reference. Operating mechanism 38 comprises a handle arm or handle assembly 70 (connected to handle 24), a configured plate or cradle 72, an upper toggle link 74, an interlinked lower toggle link 76, and an upper toggle link pivot pin 78 which interlinks upper toggle link 74 with cradle 72. Lower toggle link 76 is pivotally interconnected with upper toggle link 74 by way of an intermediate toggle link pivot pin 80, and with crossbar assembly 60 at pivot pin 64. Provided is a cradle pivot pin 82 which is laterally and rotatably disposed between parallel, spaced apart operating mechanism support members or sideplates 84 (formed of metal in the exemplary embodiment). Cradle 72 is free to rotate (within limits) via cradle pivot pin 82. Also provided is a handle assembly roller 86 which is disposed in and supported by handle assembly 70 in such a manner as to make mechanical contact with (roll against) arcuate portions of a back region 87 of cradle 72 during a "resetting" operation of circuit breaker 10 as is described below. A main stop bar 88 is laterally disposed between sideplates 84, and provides a limit to the counter-clockwise movement of cradle 72. Referring now to Figure 6, an elevation of that part of circuit breaker 10 particular associated with operating mechanism 38 is shown for the OFF disposition of circuit breaker 10. Contacts 52 and 56 are shown in the disconnected or open disposition. An intermediate latch 90 is shown in its latched position wherein it abuts hard against a lower portion 92 of a latch cutout region 94 of cradle 72. A pair of side-by-side aligned compression springs (not shown) such as shown in United States Patent No. 4,503,408 is disposed between the top portion of handle assembly 70 and the intermediate toggle link pivot pin 80. The tension in these springs has a tendency to load lower portion 92 of cradle 72 against the intermediate latch 90. In the OPEN disposition shown in Figure 6, latch 90 is prevented from unlatching cradle 72, notwithstanding the spring tension, because the other end thereof is fixed in place by a rotatable trip bar assembly 190 of trip mechanism 40. Trip bar assembly 190 is spring-biased in the counter-clockwise rotational direction against the intermediate latch 90. This is the standard latch arrangement found in all dispositions of circuit breaker 10 except the TRIPPED disposition which is described below.

Referring now to Figure 7, operating mechanism 38 is shown for the ON disposition of circuit breaker 10. In this disposition, contacts 52 and 56 are closed (in contact with each other) whereby electrical current may flow from load terminal 28 to line terminal 29. In order to achieve the ON disposition, handle 24, and thus fixedly attached handle assembly 70, are rotated in a counter-clockwise direction (to the left) thus causing the intermediate toggle link pivot pin 80 to be influenced by the tension springs (not shown) attached thereto and to the top of handle assembly 70. The influence of the tension springs causes upper toggle link 74 and lower toggle link 76 to assume the position shown in Figure 7 which causes the pivotal interconnection with crossbar assembly 60 at pivot point 64 to rotate crossbar assembly 60 in the counter-clockwise direction. This rotation of crossbar assembly 60 causes movable contact arm 50 to rotate in the counterclockwise direction and ultimately force movable contact 52 into a pressurized abutted disposition with stationary contact 56. It is to be noted that cradle 72 remains latched by intermediate latch 90 as influenced by trip mechanism 40.

Referring now to Figure 8, operating mechanism 38 is shown for the TRIPPED disposition of circuit breaker 10. The TRIPPED disposition is related (except when a manual tripping operation is performed) to an automatic opening of circuit breaker 10 caused by the thermally or magnetically induced reaction of trip mechanism 40 to the magnitude of the current flowing between load conductor 28 and line conductor 29. A description of the operation of trip mechanism 40 can be found in U.S. Patent Application Serial No. 09/384,148, filed August 27, 1999, entitled "Circuit Interrupter With Cradle Having An Improved Pivot Pin Connection", the disclosure of which is incorporated herein by reference. For purposes here, circumstances such as a load current with a magnitude exceeding a predetermined threshold will cause trip mechanism 40 to rotate trip bar assembly 190 clockwise (overcoming the spring force biasing assembly 190 in the opposite direction) and away from intermediate latch 90. This unlocking of latch 90 releases cradle 72 (which had been held in place at lower portion 92 of latch cutout region 94) and enables it to be rotated counter-clockwise under the influence of the tension springs (not shown) interacting between the top of handle assembly 70 and the intermediate toggle link pivot pin 80. The resulting collapse of the toggle arrangement causes pivot pin 64 to be rotated clockwise and upwardly to thus cause crossbar assembly 60 to similarly rotate. This rotation of crossbar assembly 60 causes a clockwise motion of movable contact arm 50, resulting in a separation of contacts 52 and 56. The above sequence of events results in handle 24 being placed into an intermediate disposition between its OFF disposition (as shown in Figure 6) and its ON disposition (as shown in Figure

7). Once in this TRIPPED disposition, circuit breaker 10 can not again achieve the ON disposition (contacts 52 and 56 closed) until it is first "reset" via a resetting operation which is described in detail below.

Referring now to Figure 9, operating mechanism 38 is shown during the resetting operation of circuit breaker 10. This occurs while contacts 52 and 56 remain open, and is exemplified by a forceful movement of handle 24 to the right (or in a clockwise direction) after a tripping operation has occurred as described above with respect to Figure 8. As handle 24 is thus moved, handle assembly 70 moves correspondingly, causing handle assembly roller 86 to make contact with back region 87 of cradle 72. This contact forces cradle 72 to rotate clockwise about cradle pivot pin 82 and against the tension of the springs (not shown) that are located between the top of handle assembly 70 and the intermediate toggle link pivot pin 80, until an upper portion 93 of latch cutout region 94 abuts against the upper arm or end of intermediate latch 90. This abutment forces intermediate latch 90 to rotate to the left (or in a counter-clockwise direction) so that the bottom portion thereof rotates to a disposition of interlatching with trip bar assembly 190, in a manner described in more detail below. Then, when the force against handle 24 is released, handle 24 rotates to the left over a small angular increment, causing lower portion 92 of latch cutout region 94 to forcefully abut against intermediate latch 90 which is now abutted at its lower end against trip bar assembly 190. Circuit breaker 10 is then in the OFF disposition shown in Figure 6, and handle 24 may then be moved counter-clockwise (to the left) towards the ON disposition depicted in Figure 7 (without the latching arrangement being disturbed) until contacts 52 and 56 are in a disposition of forceful electrical contact with each other. However, if an overcurrent condition still exists, a tripping operation such as depicted and described above with respect to Figure 8 may again take place causing contacts 52 and 56 to again open.

Referring again to Figures 3, 4, and 5, upper slot motor assembly 32A and lower slot motor assembly 32B are structurally and functionally similar to that described in United States Patent 5,910,760 and plates 42 and 44 thereof form an essentially closed electro-magnetic path in the viscinity of contacts 52 and 56. At the beginning of a contact opening operation, electrical current continues to flow in movable contact arm 50 and through an electrical arc created between contacts 52 and 56. This current induces a magnetic field into the closed magnetic loop provided by upper plates 42 and lower plates 44 of upper slot motor assembly 32A and lower slot motor assembly 32B, respectively. This magnetic field electromagnetically interacts with the current in such a manner as to accelerate the movement of movable contact arm 50 in the opening direction whereby contacts 52 and 56 are more rapidly separated. The higher the magnitude of the electrical current flowing in the arc, the stronger the magnetic interaction and the more quickly contacts 52 and 56 separate. For very high current (an overcurrent condition), the above process provides the blow-open operation described above in which movable contact arm 50 forcefully rotates upwardly about pivot pin 64 and separates contacts 52 and 56, this rotation being independent of crossbar assembly 60. This blow-open operation is shown and described in United States Patent No. 3,815,059 issued June 4, 1974, to Spoelman and incorporated herein by reference, and provides a faster separation of contacts

52 and 56 than can normally occur as the result of a tripping operation generated by trip mechanism 40 as described above in connection with Figure 8.

In connection with the above-described blow-open operation, crossbar assembly 60 and, in particular, cam housing 62 are structurally and functionally similar to that described in United States 5,910,760. In particular, cam housing 62 includes a spring-loaded cam follower (not shown) which, when a blow-open operation has occurred, latches movable contact arm 50 in its blown-open disposition.

Referring now also to Figures 10 and 11 , shown is trip bar assembly

190 in conjunction with a portion of operating mechanism 38 of circuit breaker 10, shown both assembled and disassembled. Trip shaft 192 is shown laterally disposed between parallel sideplates 84 of the sideplate assembly, with its ends positioned within holes or openings 216. This disposition provides a pivot area about which trip bar assembly 190 can rotate. This rotation is influenced by spring 202 (not shown in Figure 10) that rotationally biases assembly 190 in the counter-clockwise direction. Also shown is intermediate latch 90 which, like trip shaft 192, is laterally disposed between sideplates 84. Holes or openings 208 of latch 90 are mated with corresponding circular protrusions or indents 218 in sideplates 84, providing a pivot area for rotation of latch 90. Protrusions or indents 220 in sideplates 84 provide a stop for limiting the rotation of latch 90 in the clockwise direction which occurs during a tripping operation.

As best seen in Figure 10, each of sideplates or support members 84 includes a leg 500 and a leg 502, with a protrusion or foot 503 positioned on the bottom of leg 502 and extending in the direction of contacts 52 and 56 (see Figure 5). In the exemplary embodiment, the top surface of each of sideplates 84 also includes raised or pointed regions 504, for purposes described below.

Referring now to Figure 12, shown is molded base 12 of circuit breaker

10 having sidewalls 510 and 512. In the exemplary embodiment, the internal surface of each of sidewalls 510 and 512 includes a molded, recessed positioning region 514 forming ledges 516A and 516B. The two positioning regions 514 are essentially mirror images of each other. However, for the sake of simplicity, only positioning region 514 of sidewall 512 is shown, with sidewall 510 cut away for clarity of illustration. Each positioning region 514 is shaped to generally correspond to the overall shape of the bottom of a sideplate 84, and includes regions 518 and 520 corresponding to legs 500 and 502, respectively, and an abutment portion or ledge 522. As shown in

Figure 13 (where sidewall 510 is again cut away), sideplates 84 are inserted within positioning regions 514 and vertically supported by ledges 516 in an assembled circuit breaker 10, a single sideplate 84 being shown without the other components of operating mechanism 38 for clarity of illustration. Protrusion or foot 503 of sideplate 84 is positioned beneath abutment portion

522 of positioning region 514. Regions 518 and 520 are sized to be larger than legs 500 and 502, respectively, of sideplate 84 so that sideplate 84 can be easily inserted within or removed from positioning region 514 via movement of sideplate 84 in the direction generally represented by the double-sided arrow labeled "A". However, when a force is applied to sideplate 84 in the direction generally represented by the arrow labeled "B", protrusion or foot 503 of sideplate 84 contacts or abuts against abutment portion 522 of positioning region 514, thereby preventing sideplate 84 from being vertically displaced by the force.

A high current interruption event could cause movable contact arm 50 to forcibly rise (to achieve a contacts OPEN disposition) and impart an upward force on operating mechanism 38. Serving as the support structure or foundation of operating mechanism 38, support members 84 would experience this force, which would be in the direction represented by the arrow labeled "B" in Figure 13. Because, as described above, each sideplate

84 is prevented from being vertically displaced by such a force via the abutment between protrusion or foot 503 of the sideplate 84 and abutment portion 522 of the sidewall of base 12, operating mechanism 38 would effectively be held within base 12 notwithstanding the high current interruption event. While protrusions or feet 503 serve to anchor sideplates 84, and thus operating mechanism 38, within base 12, especially with respect to a force created by a the forcible rising of contact arm 50 due to a high current interruption event, another securement mechanism is employed in the exemplary embodiment in order further secure operating mechanism 38. As mentioned above, the top surface of sideplates 84 include raised or pointed regions 504 (see Figure 10). In addition, as shown in Figures 1 and 2, cover 14 of circuit breaker 10 includes sidewalls that correspond to sidewalls 510 and 512 of base 12. In particular, the bottom surfaces of the sidewalls of cover 14 are designed and configured to generally match up and mate together with the top surfaces of sidewalls 510 and 512 when cover 14 is positioned atop base 12 during the assembly process. In a manner similar to that more fully described and shown in U.S. Patent Application Serial No. 09/386,130, filed August 30, 1999, entitled "Circuit Interrupter With Screw Retainment" (the disclosure of which is incorporated herein by reference), the sidewalls of cover 14 include substantially flat contact surfaces which make contact with the top surfaces of sideplates 84. Raised regions 504 provide sufficient additional height to the top surfaces of sideplates 84 whereby they ensure that the top surfaces will substantially be the first areas within base 12 to be contacted by cover 14 during the assembly process, thus ensuring proper engagement of sideplates 84. This is very beneficial because variability in parts and slight aberrations in the molding process can cause the sidewalls of cover 14 to not mate perfectly with the sidewalls of base 12 and the top surfaces of sideplates 84, potentially causing sideplates 84 to not be sufficiently engaged and held in place (if raised regions 504 did not exist).

When raised regions 504 contact their respective contact surfaces, they accommodate further lowering of cover 14 onto base 12 (as cover 14 is screwed in place) by digging or piercing into the contact surfaces.

The present invention, embodied in the exemplary embodiment by protrusions or feet 503 and abutment portion 522, provides an efficient, economical, and easy to implement way of holding operating mechanism 38 in base 12, and especially one which effectively holds operating mechanism 38 in base 12 during a high current interruption event. By effectively holding operating mechanism 38 in base 12 during a high current interruption event, the present invention also protects those portions of the bottom of cover 14 making contact with operating mechanism 38, thereby enabling cover 14 to continue to securely engage operating mechanism 38 as needed for proper functioning thereof. It should be noted that the exemplary embodiment of the present invention described above is advantageous in that it enables compression molding to be used in order to form positioning region 514 in base 12.

Although the preferred embodiment of the present invention has been described with a certain degree of particularity, various changes to form and detail may be made without departing from the spirit and scope of the invention as hereinafter claimed.

Claims

I CLAIM:

1. A circuit interrupter comprising: a housing including a cover positioned on top of a base, said base including an abutment portion having a bottom surface; separable main contacts within said housing; and an operating mechanism within said housing and interconnected with said separable main contacts, said operating mechanism including a support member situated within said base, said support member including a protrusion situated beneath said abutment portion and positioned to contact said bottom surface for resisting upward movement of said support member.

2. The circuit interrupter as defined in claim 1 wherein said base includes a sidewall in which said abutment portion is formed.

3. The circuit interrupter as defined in claim 2 wherein said sidewall includes a positioning region formed therein having a ledge, and wherein said support member is positioned within said positioning region and vertically supported by said ledge.

4. The circuit interrupter as defined in claim 1 wherein said support member is formed of metal, and said base is formed of thermoset plastic.

5. The circuit interrupter as defined in claim 1 wherein said support member includes a leg from which said protrusion extends.

6. The circuit interrupter as defined in claim 1 wherein said support member includes a front portion closest to said separable main contacts, and wherein upward rotational movement of said front portion is resisted by contact between said protrusion and said abutment portion.

7. The circuit interrupter as defined in claim 6 wherein said protrusion extends from said front portion in a direction towards said separable main contacts.

8. The circuit interrupter as defined in claim 6 wherein said base includes a positioning region formed therein in which said support member is positioned, and wherein said support member includes a back portion farthest from said separable main contacts, and wherein said abutment portion, said positioning region, and said support member are sized and shaped such that, when said cover is not positioned on top of said base, said support member may be removed from said base by upward rotational movement of said back portion.

9. The circuit interrupter as defined in claim 1 wherein said support member includes a top surface, and wherein said cover includes a bottom surface that engages said top surface of said support member for further resisting upward movement of said support member.

10. The circuit interrupter as defined in claim 1 wherein said base further includes a second abutment portion having a second bottom surface, and said operating mechanism further includes a second support member situated within said base, and wherein said second support member includes a second protrusion situated beneath said second abutment portion and positioned to contact said second bottom surface for resisting upward movement of said second support member.

11. A circuit interrupter comprising: a housing including a cover positioned on top of a base, said base including an abutment portion having a bottom surface; separable main contacts within said housing, one of said separable main contacts being a movable contact attached to a movable contact arm which moves in a first rotational direction when achieving a contacts open disposition and a second rotational direction when achieving a contacts closed disposition; and an operating mechanism within said housing and interconnected with said separable main contacts, said operating mechanism including a support member situated within said base, said support member including a protrusion situated beneath said abutment portion and positioned to contact said bottom surface for resisting upward movement of said support member attributable to a force imparted by said movable contact arm moving in said first rotational direction.

12. The circuit interrupter as defined in claim 11 wherein said support member includes a front portion in close proximity to said movable contact arm and from which said protrusion extends.

13. The circuit interrupter as defined in claim 12 wherein said front portion includes a leg from which said protrusion extends.

14. The circuit interrupter as defined in claim 12 wherein said protrusion extends from said front portion in a direction towards said separable main contacts.

15. The circuit interrupter as defined in claim 11 wherein said base includes a sidewall in which said abutment portion is formed.

16. The circuit interrupter as defined in claim 15 wherein said sidewall includes a positioning region formed therein having a ledge, and wherein said support member is positioned within said positioning region and vertically supported by said ledge.

17. The circuit interrupter as defined in claim 11 wherein said support member is formed of metal, and said base is formed of thermoset plastic.

18. The circuit interrupter as defined in claim 11 wherein said support member includes a top surface, and wherein said cover includes a bottom surface that engages said top surface of said support member for resisting upward movement of said support member.

19. The circuit interrupter as defined in claim 11 wherein said base further includes a second abutment portion having a second bottom surface, and said operating mechanism further includes a second support member situated within said base, and wherein said second support member includes a second protrusion situated beneath said second abutment portion and positioned to contact said second bottom surface for resisting upward movement of said second support member attributable to a force imparted by said movable contact arm moving in said first rotational direction.

20. The circuit interrupter as defined in claim 11 wherein said base includes a positioning region formed therein in which said support member is positioned, and wherein said support member includes a back portion farthest from said separable main contacts, and wherein said abutment portion, said positioning region, and said support member are sized and shaped such that, when said cover is not positioned on top of said base, said support member may be removed from said base by upward rotational movement of said back portion.