Circuit breaker and arc chute with shield apparatus

An improved circuit breaker and arc chute has a shield apparatus that includes a number of plate-like shield members that have elongated openings formed therein to receive portions of arc plates therethrough. The portions of the arc plates that pass through the shield member are received in receptacles of a support apparatus that supports the arc plates. The arc plates are themselves configured to retain the shield members against the support apparatus to protect the support apparatus from damage in the event of an electrical arc. Advantageously, the retention of the shield members between portions of the arc plates and portions of the support apparatus enables the shield members to be held in place without the use of adhesives or separate fastening systems.

BACKGROUND

1. Technical Field

The disclosed and claimed concept relates generally to circuit interrupters and, more particularly, to a circuit interrupter having an arc chute that includes a shield apparatus.

2. Related Art

Numerous types of circuit interrupters such as circuit breakers are generally known in the relevant art. Such circuit interrupters are intended to interrupt current in a circuit during certain overcurrent and under-voltage conditions and other conditions.

When the separable contacts of a circuit interrupter are opened, an electrical arc often propagates between the separating contacts. Since such arcs are destructive to the circuit interrupter, they preferably are extinguished as quickly as possible. It thus has been known to provide arc chutes and other arc extinguishing and elimination systems in circuit interrupters for the purpose of limiting the damage that is caused by such arcs. While known arc chutes have been generally effective for their intended purposes, they have not been without limitation.

Known arc chutes typically include a plurality of electrically conductive arc plates and an arc horn that are mounted to a support structure. The support structure may be formed of a nonconductive material such as a molded resin. Since molded resins are very susceptible to damage in the presence of an electrical arc, it has been known to provide arc quenching materials in the vicinity of the arc chute that generate gases in the presence of an arc in order to facilitate the extinguishment of the arc. However, such arc quenching materials are relatively costly and have proven difficult to place in the vicinity of the support structure in a cost efficient fashion that still extinguishes an arc and protects the support structure.

SUMMARY

In view of the foregoing, an improved circuit breaker and arc chute has a shield apparatus that includes a number of plate-like shield members that have elongated openings formed therein to receive portions of arc plates therethrough. The portions of the arc plates that pass through the shield member are received in receptacles of a support apparatus that supports the arc plates. The arc plates are themselves configured to retain the shield members against the support apparatus to protect the support apparatus from damage in the event of an electrical arc. Advantageously, the retention of the shield members between portions of the arc plates and portions of the support apparatus enables the shield members to be held in place without the use of adhesives or separate fastening systems.

Accordingly, an aspect of the disclosed and claimed concept is to provide an improved circuit breaker and arc chute having a shield apparatus that generates gases in the presence of an arc to facilitate the extinguishment of the arc.

Another aspect of the disclosed and claimed concept is to provide an improved circuit breaker and arc chute wherein a shield apparatus is configured to protect a support apparatus of the arc chute without the use of adhesives or separate fastening structures to hold the support apparatus in place.

Other aspects of the disclosed and claimed concept are provided by an improved arc extinction apparatus for use in a circuit interrupter, wherein the general nature of the arc extinction apparatus can be generally stated as including a plurality of arc plates, a support apparatus, and at least a first shield member structured to generate gases in the presence of an electrical arc, wherein at least a portion of at least some of the arc plates are engaged with the at least first shield member to retain the at least first shield member between the at least portion of the at least some of the arc plates and at least a portion of the support apparatus.

Still other aspects of the disclosed and claimed concept are provided by an improved circuit interrupter, the general nature of which can be stated as including a line terminal, a load terminal, a set of separable contacts, and an arc extinction apparatus. The arc extinction apparatus can be generally stated as including a plurality of arc plates, a support apparatus, and at least a first shield member structured to generate gases in the presence of an electrical arc, wherein at least a portion of at least some of the arc plates are engaged with the at least first shield member to retain the at least first shield member between the at least portion of the at least some of the arc plates and at least a portion of the support apparatus.

DESCRIPTION

An improved arc chute4in accordance with the disclosed and claimed concept is depicted generally in FIGS.1and3-5, and is depicted schematically inFIG. 2. The arc chute4can be used in a circuit interrupter such as an improved circuit breaker6, which is depicted schematically inFIG. 2. The improved circuit breaker6includes a line terminal8and a load terminal10that are connected by a set of separable contacts12. The circuit breaker6additionally includes the improved arc chute4in the vicinity of the separable contacts12in order to expeditiously extinguish any arc that might be propagated during an arc event that may occur contemporaneous with separation of the set of separable contacts12.

As can be understood fromFIGS. 3 and 4, the arc chute4comprises a plurality of arc plates that are collectively referred to with the numeral14, and further comprises a support apparatus16and an arc horn20. The arc chute4advantageously also comprises a shield apparatus24that is retained between portions of the arc plates14and portions of the support apparatus16in order to retain the shield apparatus24in place without the use of adhesives or separate support structures. The shield apparatus24provides protection to the support apparatus16by generating gases in the event of an arc that help to extinguish the arc and to thereby resist damage to the support apparatus16during an arc event.

The arc plates14include a first arc plate14A that is disposed adjacent the arc horn20, a second arc plate14B that is disposed adjacent the first arc plate14A, a plurality of intermediate arc plates14C, and a last arc plate14D that is disposed at the opposite end of the arc chute4from the first arc plate14A. The arc plates14are formed of an electrically conductive material and, in conjunction with the arc horn20and the shield apparatus24, are configured to break up, disperse, and extinguish an electrical arc during an arc event that may occur contemporaneous with separation of the separable contacts12.

The support apparatus16includes a pair of side supports28and an end support32which, in the exemplary embodiment depicted herein, are formed of a thermosetting resin material. The side supports28each have a plurality of receptacles36formed therein that are structured to receive portions of the arc plates14and the arc horn20. The end support32has a plurality of elongated apertures40formed therein through which gases are vented during an arc event. The support apparatus16further can include a pair of pins44that are received in holes46to hold the support apparatus16together along with the arc plates14, the arc horn20, and the shield apparatus24. When assembled, the pins44are received in the holes46and the ends are deformed in order to cause the pins44to remain fixed within the holes46. When the arc chute4is fully assembled, a pair of lugs48formed on the end support32are received in corresponding sockets52formed in the side supports28.

The shield apparatus24includes a pair of shield members56each have a plurality of parallel elongated openings60formed therein. Each elongated opening60terminates at a termination64that is spaced a predetermined distance from a common edge66of the shield member56. The existence of the elongated openings60in the shield members56thus causes the shield members56to each include a base portion68, an end portion72opposite the base portion68, and a plurality of elongated ribs76extending between the base portion68and the end portion72and along the elongated openings60.

Each arc plate14includes a pair of protrusions80extending in opposite directions therefrom. The arc horn20likewise has a pair of protrusions84protruding therefrom. The protrusions80of the arc plates14each have a notch88formed therein, and the notches88are aligned with one another such that the notches88together form and define a pair of open channels92which each face generally toward the receptacles36of one of the pair side supports28. It can be seen that the protrusions84of the arc horn20do not have a notch formed therein, although a notch potentially could be provided therein in other embodiments (not expressly depicted herein).

As can be best understood fromFIG. 4, the shield members56are received on the arc plates14and are retained between portions of the arc plates14and the side supports28. More particularly, the base portion68is received in the open channel92, and elongated portions of the protrusions80that are disposed adjacent the notches88that are formed in the arc plates14are received in the elongated openings60. It thus can be understood that the elongated ribs76of the shield members52are disposed generally between adjacent pairs of arc plates14and thus protect the side supports28to resist damage thereto during an arc event. The shield members56are advantageously formed of a cellulose-filled melamine (CFM) material or other material which, in the presence of an electrical arc, generates gases that are inert and that cool the arc, thus facilitating the extinguishment of the arc.

As can be best understood fromFIGS. 3-5, the arc plates14A and14D each include a pair of support96A and96D that are engageable with the shield members56and that retain the shield members56in their locations adjacent the side supports28. In this regard it is noted that the arc plate14B likewise includes such a support, but the support is hidden from view in the accompanying drawings. The supports96A and96D each include an engagement surface98A and98D, respectively, that is engageable with a portion of the shield member56at a location adjacent an end of one of the elongated openings60. In this regard, it is understood that the bases of the notches88each serve as a further support96E that each provide a further engagement surface98E (as is shown inFIG. 3) that is likewise engageable with a portion of the shield member56adjacent the terminations64of the elongated openings60. It thus can be understood that the engagement surfaces98A and98D of the arc plates14A and14D (and the engagement surface of the arc plate14B that is hidden from view), as well as the engagement surfaces98E of all of the arc plates14, retain the shield members56between such engagement surfaces98A,98D, and98E of the various arc plates14and the confronting faces of the side supports28. Since the protrusions80of the arc plates14are received in the receptacles36of the side supports28, the shield members56are trapped and are thus retained between portions of the arc plates14and portions of the side supports28without the use of adhesives or separate fastening structures such as screws, clips, and the like. Such a configuration also enables the side supports28to be formed of a relatively inexpensive thermosetting resin material that otherwise might have limited resistance to an arc.

While the engagement surfaces98A,98D, and98E each face generally toward the side supports28and thus provide support to the shield members56in a direction generally directly between the arc plates14and the side supports28, it can be understood fromFIGS. 4 and 5that the protrusions80of the arc plates14provide additional engagement surfaces that retain the shield members56in their protective position. For instance, the portions of the protrusions80that extend through the elongated openings60each further provide additional engagement surfaces98F,98G,98H, and98I. The notches88further provide additional engagement surface98J. All of the engagement surfaces98F,98G,98H,98I, and98J are engageable with the shield members56to provide retention of the shield members56in directions generally parallel with the plane of the shield members56to retain the shield members56in their protective position with respect to the side supports28.

In this regard, it is understood that the engagement surfaces98A,98D,98E,98F,98G,98H,98I, and98J are each engageable with the shield members56to retain the shield members56in their protective position with respect to the side supports28, but this is not to say that all such engagement surfaces98A,98D,98E,98F,98G,98H,98I, and98J are simultaneously engaged with the shield members56. Rather, the shield members56can be configured to permit a slight degree of movement of the shield members56with respect to the side supports28while still retaining the shield members56in a protective position with respect to the side supports28whereby they can generate protective gases during an arc event to resist damage to the side supports28. By permitting a certain amount of movement between the shield members56and the arc plates14, the shield members56can be manufactured to relatively less exacting dimensions, which can reduce costs. Since the shield members56are retained without the use of adhesives or separate attaching structures, further cost savings is achievable, and reliability of the placement and retention of the shield members56is enhanced. Moreover, the cost of assembly of the arc chute4is reduced due to the avoidance of the effort that otherwise would be required to apply such an adhesive or separate attaching structure such as a fastener to the shield member56, the side supports28, or both.