Circuit breaker with bumper

An improved circuit breaker includes a case, a movable arm, and a bumper retained within a receptacle formed on the case. The bumper is retained in the receptacle by a number of spaced ribs that engage certain portions of the bumper yet permit deformations of other portions of the bumper into an expansion region. By employing a bumper made of a material having a low coefficient of restitution, deformation of the bumper tends to dissipate the energy of a removable arm impacting the bumper. The bumper can be installed, removed, and replaced substantially without requiring the use of an adhesive. The movable arm engages the bumper on a corner of the bumper to provide the bumper with an effectively progressive spring rate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to circuit breakers and, more particularly, to a circuit breaker having a bumper.

2. Description of the Related Art

Circuit breakers are generally well known and are used in numerous applications. Circuit breakers can be used to interrupt a circuit under certain predetermined circumstances, and can be used for other purposes.

A typical circuit breaker might include a set of separable contacts that can be separated in certain predetermined circumstances to open a circuit. The separable contacts might include one or more movable contacts that are disposed on a movable arm which, when moved, can separate the movable contacts from one or more stationary contacts to interrupt the circuit. The movable arm may, for example, be a movable arm that is movable by an operating mechanism. While circuit breakers have been generally effective for their intended purposes, such circuit breakers have not, however, been without limitation.

Circuit breakers are oftentimes required to interrupt a circuit very rapidly. The operating mechanism may need to pivot the movable arm at a high speed in order to interrupt the circuit. In addition to including an operating mechanism, some circuit breakers may be configured to further include a “blow open” feature. Such a “blow open” feature may be provided, for instance, by arranging the conductors within the circuit breaker in such a fashion that the electrical fields around the conductors magnetically propel the movable arm to rapidly pivot in certain overcurrent conditions.

A movable arm that is moving at a high velocity must ultimately be stopped and the kinetic energy thereof dissipated in some fashion. Some circuit breakers include hard stops against which the movable arms impact, although such hard stops have drawbacks that should be apparent. While certain cushioning systems can be employed to decelerate a movable arm, many cushioning systems have only a limited ability to dissipate the energy of the movable arm, which can undesirably result in a rebounding of the movable arm and potential consequent reclosing of the circuit.

The mounting and retention of such cushioning systems within circuit breakers has also had limitations. While some cushioning systems have been adhered within circuit breakers, the adhesives employed have been known to become unreliable over time. Moreover, the use of such adhesives tends to introduce various uncertainties into the operation of the breaker based upon, for example, the quantity of adhesive employed, the techniques used in applying and curing the adhesive, and the like. Additionally, an adhered cushioning system can be difficult to replace. It thus would be desirable to provide an improved circuit breaker having an improved cushioning system.

SUMMARY OF THE INVENTION

An improved circuit breaker includes a case, a movable arm, and a bumper retained within a receptacle formed on the case. The bumper is retained in the receptacle by a number of spaced ribs that engage certain portions of the bumper yet permit deformations of other portions of the bumper into an expansion region. By employing a bumper made of a material having a low coefficient of restitution, deformation of the bumper tends to dissipate the energy of a movable arm impacting the bumper. The bumper can be installed, removed, and replaced substantially without requiring the use of an adhesive. The movable arm engages the bumper on a corner of the bumper to provide the bumper with an effectively progressive spring rate.

Accordingly, an aspect of the invention is to provide an improved circuit breaker having a bumper that decelerates a movable arm of the circuit breaker.

Another aspect of the invention is to provide an improved circuit breaker having a bumper mounted within a receptacle on the case of the circuit breaker.

Another aspect of the invention is to provide an improved circuit breaker having a bumper that is removably retained on a case of the circuit breaker.

Another aspect of the invention is to provide an improved circuit breaker having a bumper disposed on a case of the circuit breaker, with the bumper being retained on the case substantially without requiring the use of adhesive materials to adhere the bumper to the case.

Another aspect of the invention is to provide an improved circuit breaker having a bumper disposed on a case of the circuit breaker, with the bumper being structured to decelerate a movable arm of the circuit breaker.

Another aspect of the invention is to provide an improved circuit breaker having a bumper mounted on a case of the circuit breaker, with the bumper being structured to dissipate the kinetic energy of a movable arm contacting the bumper.

Accordingly, an aspect of the invention is to provide an improved circuit breaker, the general nature of which can be stated as including a case, a plurality of retention members disposed on the case, a resilient bumper engaged by at least a pair of retention members of the plurality of retention members to retain the bumper on the case, and a movable arm disposed on the case. The movable arm is structured to impact the bumper in at least a first predetermined situation to dissipate kinetic energy of the movable arm.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An improved circuit breaker2in accordance with the invention is indicated schematically inFIG. 1. The circuit breaker2can be generally stated as including a case4, a line conductor6, a load conductor8, and a set of contacts10that are separable to interrupt a circuit. The load conductor8includes a movable member in the form of a movable arm12that is pivotable with respect to the line conductor6in a direction indicated generally by the arrow14inFIG. 1in certain predetermined circumstances. The movable arm12can be considered to be a component of a contact carrier assembly23that is shown in part inFIG. 2and that can, for example, be operated by an operating mechanism22in a well known fashion to separate the set of contacts10. The circuit breaker2additionally and advantageously includes a bumper16that is engageable by the movable arm12, as will be set forth in greater detail below.

The set of contacts10includes a stationary contact18that is disposed on the line conductor6and a movable contact20that is disposed on the movable arm12of the load conductor8. A circuit that includes the circuit breaker2generally is interrupted when the stationary contact18and the movable contact20are separated from one another.

The operating mechanism22is cooperable with the contact carrier assembly which pivots the movable arm12in response to signals from a trip unit24of the exemplary circuit breaker2. It is understood that the operating mechanism22and the trip unit24can be of numerous configurations and that their depiction inFIG. 1is representative.

The exemplary line conductor6of the exemplary circuit breaker2additionally includes a reverse loop26that is configured such that magnetic forces between the reverse loop26and movable arm12can cause the movable arm12to pivot in the direction indicated by the arrow14in certain predetermined overcurrent situations to separate the set of contacts10. The reverse loop26thus provides to the circuit breaker2an exemplary “blow open” feature, although it is noted that the circuit breaker2can be configured to not include the “blow open” feature without departing from the concept of the invention.

A portion of the circuit breaker2is shown in a cut away fashion inFIG. 2. As can be seen inFIG. 2, the bumper16is disposed in a receptacle28which, in the depicted exemplary embodiment, is formed in the case4. It is understood that in other embodiments (not shown) a receptacle can be provided in other fashions without departing from the concept of the invention. As will be described in greater detail below, the exemplary bumper16is removably retained in the receptacle28.

As can be further seen fromFIG. 2, the bumper16can be said to include a retained portion30and a protruding portion32, with the retained portion30being disposed substantially within the receptacle28, and with the protruding portion32generally protruding outwardly from the receptacle28. The exemplary bumper16is formed of a resilient material which can, for example, be a fluoroelastomer such as may be sold under the name VITON by DuPont Dow, although other materials can be appropriately employed without departing from the concept of the invention. As employed herein, the expression “resilient” and variations thereof shall refer broadly to a material property which enables an item to have a tendency to return to substantially its original shape after being strained in a predetermined environment. The material of the bumper16may be chosen, for example, based upon one or more of the following considerations or other considerations: a temperature range that is suited to use within the circuit breaker2, flame resistant properties that are suited to the environment within the circuit breaker2, toughness in an arc chamber environment, an ability to dissipate energy by having a low coefficient of restitution, and the like. In the exemplary embodiment presented herein, the bumper16is configured to include a corner34that is engageable by the movable arm12during a rotation of the movable arm12to effectively provide the bumper16with a progressive spring rate.

As can be understood fromFIG. 3, the exemplary bumper16is configured as a two-part member, that is, the bumper16includes a first cushion36and a second cushion38that are disposed adjacent one another with a space40therebetween. In the exemplary embodiment depicted herein, the movable arm12is configured to be engageable with both the first cushion36and the second cushion38when the movable arm12is pivoted in the direction indicated by the arrow14. The first and second cushions36and38advantageously are deformable by the movable arm12in a fashion that decelerates the movable arm12and that dissipates at least a portion of the rotational energy of the movable arm12in a fashion that limits rebound of the movable arm12away from the bumper16. In other embodiments (not shown) the bumper16can include only of a single piece of material or can include more than two pieces of material without departing from the concept of the invention.

As can be understood fromFIGS. 3 and 4, the case4is formed to include a first wall42, a second wall44, a third wall46, a fourth wall48, a fifth wall50, a sixth wall52, a seventh wall54, and an eighth wall56that generally define the receptacle28and are thus disposed adjacent the receptacle28. As can be understood fromFIGS. 2–4, the case4additionally includes a relief62formed therein that is in communication with the receptacle28. A ledge64is disposed between receptacle28and relief62and is, in the depicted exemplary embodiment, of a generally planar configuration.

The case4additionally includes a plurality of elongated first protrusions58that are formed on the first and fifth walls42and50, and further includes a pair of elongated second protrusions60formed on the first and fifth walls42and50. The first and second protrusions58and60are elongated in a direction extending generally into an interior of the receptacle28from a location at an exterior thereof and are generally in the form of ribs. The first protrusions58are arranged on the first and fifth walls42and50in opposing pairs and each protrude away from the first wall42or the fifth wall50in a direction toward the receptacle28. The second protrusions60similarly are arranged on the first and fifth walls42and50in an opposed pair and each protrude away from the first wall42or the fifth wall50in a direction toward the receptacle28. Each first protrusion58includes a generally planar frontal surface68that is engageable with the bumper16. Each second protrusion60includes a pair of lateral surfaces70that are each engageable with the bumper16. The first protrusions58, the second protrusions60, and the second, fourth, sixth, and eighth walls44,48,52, and56can all be considered to be retention members which resist movement of a portion of the bumper16that is contacted by the respective retention member but permit deformation of regions of the bumper16adjacent the regions contacted by the respective retention members. The bumper16can also be said to be slidable engaged by the first protrusions58, the second protrusions60, and the second, fourth, sixth, and eighth walls44,48,52, and56. The ledge64can also be said to be such a retention member, but the bumper16is not slidably engaged by the ledge64. Rather, the ledge64serves as a substantially rigid stop against which the bumper16is engageable to resist sliding movement of the bumper16in a direction into the receptacle28toward the relief62.

As can be understood fromFIG. 3, the first and second cushions36and38are retained in the receptacle28by engagement with the first protrusions58, the second protrusions60, the second wall44, the fourth wall48, the sixth wall52, and the eighth wall56. The exemplary first and second cushions36and38are each of a rectangular parallelepiped configuration. More particularly, and by way of example, the first cushion36has an exterior surface72that includes a first surface74, a second surface76, and a third surface78, as well as other surfaces. The first surface74and the second surface76meet one another at a first intersection80. The second surface76and the third surface78meet one another at a second intersection82. The exemplary first and second intersections80and82are in the form of corners.

The second surface76is engageable with the frontal surfaces68of a pair of the first protrusions58disposed on the fifth wall50. The first intersection80is engageable with the sixth wall52, and the second intersection82is engageable with one of the lateral surfaces70of the second protrusion60disposed on the fifth wall50.

It can be seen that the portions of the first cushion36that are contacted by the first protrusions58at the second surface76are resisted from being deformed in a first direction indicated by the arrow90. However, regions of the first cushion36adjacent those regions contacted by the aforementioned first protrusions58are permitted to be deformable in the first direction90.

In this regard, it can also be seen that the receptacle28is configured to provide an expansion region84that is disposed adjacent the bumper16. The expansion region84includes, for example, the space between the second surface76and the fifth wall50, as is indicated generally by the numeral86. Other similar regions can be seen at other locations between the bumper16and the first and fifth walls42and50. Similarly, another expansion region is depicted as including the space between the first surface72and the region bounded by the sixth, seventh, and eight walls52,54, and56, as is indicated generally by the numeral88. The expansion region84can also be said to include the space40between the first and second cushions36and38, and further can be said to include the relief62.

In a situation where the movable arm12impacts the bumper16in the manner depicted generally inFIG. 2, portions of the bumper16that are not contacted by a retention member can be deformed, for example, in the first direction90generally into the portion of the expansion region86, in a second direction92into the portion of the expansion region88, in a third direction94into the space40between the first and second cushions36and38, and in a fourth direction96(FIG. 4) into the relief62. Other such deformations into the aforementioned expansion region84will be apparent. Deformation of a portion of the bumper16into the relief62likely would result from the bumper16engaging the ledge64, with deformation of portions of the bumper16not engaged with the ledge64being deformable into the relief62.

The low coefficient of restitution of the exemplary bumper16allows the bumper16to dissipate the kinetic energy of the movable arm12through deformation of the bumper16. As such, while movable arm12may approach the bumper16with a high level of rotational kinetic energy, the rotational kinetic energy is in large part transferred to the bumper16where, upon deformation of portions of the bumper16into the expansion region84, the energy is dissipated. As such, rebound of the movable arm12from the bumper16is largely avoided, which thereby resists, for example, reinitiation of current flow between the stationary and movable contacts18and20.

The engagement of the first intersection80with the sixth wall52, and the engagement of the second intersection82with the lateral surface70of one of the second protrusions60, for example, causes the expansion region84to be large and to therefore permit significant deformations of the bumper16into the expansion region84, which dissipates energy, while still securely retaining the bumper16within the receptacle28. In this regard, the first and second cushions36and38typically will be installed in the receptacle28with at least a nominal interference fit between at least some of the retention members.

With regard to engagement, for example, of the first intersection80with the sixth wall52, it can be seen that the sixth wall52is oriented oblique to both the first surface74and second surface76. As employed herein, the expression “oblique” and variations thereof shall refer broadly to a relationship that is neither parallel nor perpendicular. The same type of oblique arrangement exists between the second intersection82and the lateral surfaces70of the respective second protrusion60. Other similar oblique arrangements can be seen inFIG. 3. Such oblique arrangements allow the expansion region84to be relatively large, thereby facilitating deformation and dissipation of energy, and further provide to the bumper16a progressive spring rate with regard to deformations in the direction of, for example, the sixth wall52, the aforementioned lateral surface70, and the like.

The bumper16, i.e., the first and second cushions36and38, can be readily installed in the receptacle28with the nominal interference fit, and the nominal interference fit retains the first and second cushions36and38in the receptacle28. Such nominal interference fit advantageously retains the first and second cushions36and38in the receptacle28without requiring the use of an adhesive to adhere the first and second cushions36and38to the case4.

The first and second cushions36and38can be readily removed and replaced, if needed, which is a distinct advantage over systems wherein energy absorbing and/or dissipating members are adhered to surfaces within circuit breakers. Each time the movable arm12engages the bumper16, the bumper16is re-seated within the receptacle28and against the ledge64. Such engagement can, for example, occur when the movable arm12is pivoted in response to, for example, a tripping event or switching the circuit breaker2to an OFF position. Depending upon the configuration of the circuit breaker2, a resetting operation of the operating mechanism22might cause the movable arm12to engage the bumper16and to provide a re-seating function.

The bumper16disposed in the receptacle28thus, when engaged by the movable arm12, dissipates the energy of the movable arm12in a desirable fashion while re-seating the bumper16in the receptacle28. The configuration of the retention members that are engaged with the bumper16facilitates retention of certain portions of bumper16while permitting deformation of other, adjacent portions of the bumper16, with such deformation dissipating the energy of the movable arm12. The bumper16can be retained in the receptacle28without requiring the use of an adhesive in contact with the bumper16, and the bumper16can be readily removed and replaced if desired.