Electricity: electrothermally or thermally actuated switches – Electrothermally actuated switches – Fusible element actuated
Reexamination Certificate
2002-11-21
2003-12-16
Vortman, Anatoly (Department: 2835)
Electricity: electrothermally or thermally actuated switches
Electrothermally actuated switches
Fusible element actuated
C327S280000, C327S273000, C327S234000
Reexamination Certificate
active
06664886
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to fuses for interrupting the flow of current through an electrical circuit upon predetermined overload conditions and, more particularly, to fuses with direct current and alternating current arc interrupting capability.
As is well known, fuses are used in electrical circuits to interrupt the flow of current when there is a short-circuit and/or a full voltage overload current event. Fuses typically include one or more fuse elements electrically connected to two end conductors located at opposing ends of the fuse. In the event of a short circuit and/or a full voltage overload, the temperature of the fuse element increases until a portion of the element melts and breaks. The break in the fuse element typically causes an electric arc to be established.
Sand is typically used to fill the fuse cartridge to surround the fuse elements to assist in quenching an arc. U.S. Pat. No. 4,656,453 describes cartridge fuses that include end plugs that are used for arc quenching. The fuse element passes through the end plugs adjacent to the end conductors. U.S. Pat. No. 5,280,261 describes a current limiting fuse that includes a short circuit strip that has a plurality of 90 degree angle bends along the length of the strip. The multiple bends in the fuse strip cause the strip to contact or come in close proximity of the inside wall of the fuse body. When a short-circuit arc occurs the fuse strip material burns towards the fuse wall creating an interaction with the fuse wall and an increase in pressure, which extinguishes the arc. However, even with the above noted examples of arc quenching, these fuses may not interrupt the circuit satisfactorily.
It would be desirable to provide a fuse that includes arc quenching capabilities during a short-circuit and/or a full voltage overload current interrupt event. It would also be desirable to provide a fuse that reduces arc energy during a short-circuit and/or a full voltage overload current interrupt event.
BRIEF SUMMARY OF THE INVENTION
In an exemplary embodiment of the invention, a fuse includes an arc energy absorbing coating to reduce arc energy during a short-circuit and/or a full voltage overload current interrupt. The fuse includes end conductor elements, and at least one fuse element secured between and making electrical contact with the end conductor elements. An elongate fuse housing, having a passageway extending longitudinally through the housing, extends between the end conductor elements. The fuse element extends through the housing passageway. The fuse includes an arc energy absorbing coating which at least partially coats each end portion of the fuse element.
Prior to assembly of the fuse, an arc energy absorbing coating is applied to the end portions of the fuse element. The fuse element is mechanically and electrically attached to the end conductor elements, typically by soldering, welding or brazing. The end conductor elements are positioned over the ends of the housing and crimped into receiving grooves in the fuse housing. The housing passageway is filled with a filler material, typically prior to positioning the second end conductor element at the end of the housing.
The above described fuse provides arc quenching capabilities during a short-circuit and/or a full voltage overload current interrupt event. The fuse also reduces arc energy during a short-circuit and/or a full voltage overload current interrupt event.
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Armstrong Teasdale LLP
Cooper Technologies Company
Vortman Anatoly
LandOfFree
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