Littelfuse, Inc.

Joseph W Kowalik

Heraclio R Gomez

G Todd Dietsch

David J Krueger

Robert G Swensen

Cesar T Herbias

A device for providing a visual indication of the status of a fuse, i.e., whether or not the fuse has blown. The device includes a substrate onto which the elements of the visual indication device are printed. A pair of conductive terminals is screen printed upon that substrate, preferably spaced apart from each other along that substrate. Between the terminals, at least two spaced apart resistance elements are positioned upon the substrate. These two resistance elements are in series with each other, and they are also in series with the pair of conductive terminals. The first of these at least two resistance elements is comprised of a combination of a substance which melts at an elevated temperature, and also of carbon. The second of these at least two resistance elements is comprised solely of carbon.

Flexible blown fuse indicator

The invention is a component for an electrical or electronic fuse. In one preferred embodiment of the invention, the component comprises a body of resilient, compressible material having a front face and a rear face. A fusible element is disposed within the body of resilient material, and the fusible element extends through a passageway within the body. At least one of the faces includes a flange section extending outwardly from that one face.

Compressible body for fuse

A blown fuse indicator, having an insulating element, a current-carrying element overlaying the insulating element, and a substantially transparent window. A chemical composition coats at least a portion of the insulating element. The improvement comprises a meltable link in generally parallel proximity to the insulating element. The meltable link, which can be made of solder, melts to open an indicating circuit of the blown fuse indicator upon predetermined thermal overload conditions.

Blown fuse indicator for electrical fuse

Fuses and a subassembly component for fuses. The fuse includes an insulating housing, a short circuit fusible element, and an arc barrier-forming body. The arc barrier-forming body is fitted around, and intimately surrounds a portion of the short-circuit fusible element. The arc barrier-forming body is formed from a silicone rubber sealant which is free flowing at room temperature but upon exposure to air increases in viscosity until it essentially becomes a solid. The arc barrier-forming body provides protection against 'burn-back' within the fuse.

Form fitting arc barrier for fuse links

A time delay fuse and various subassembly components for that time delay fuse. The fuse includes a housing made of an insulating material. The housing encloses a short-circuit fusible element, preferably a copper or copper alloy strip having a plurality of slots. The housing also encloses one or more rigid meltable fusible elements, preferably a plurality of solder bars. A body of resilient, compressible insulating material has at least one passageway through which each of the time delay fusible elements extends. When the rigid meltable fusible elements melt, the circuit through the fuse opens. In addition, the passageway which surrounded the rigid meltable fusible elements collapses upon its melting. This provides protection against 'arc-back.'

Time delay fuse

A time delay fuse comprises an initially open end insulating housing having conductive terminals at the opposite ends thereof, a current-heatable strip connected to one of said terminals, a thermal mass in heat communication with the current-heatable strip and a coil spring and current shunt strip electrically coupled between the current-heatable strip and the other terminal to complete a circuit between the terminals. A heat meltable solder connection is located between said thermal mass and the coil spring and current shunt strip, the spring and current shunt strip being spring urged away from the thermal mass so that upon the melting of the heat meltable solder connection the coil spring and current shunt strip will be pulled away from the thermal mass to break the physical and electrical connection of the coil spring and current shunt strip with the current-heatable strip. The current-heatable strip, thermal mass, coil spring and current shunt strip form a sub-assembly insertable as an untensed unit into an initially open end of the fuse housing before the associated terminal is applied thereto. The coil spring and current shunt strip are suspended from the initially open end of the housing and the rest of the sub-assembly is pushed axially inward thereof to stretch the coil spring. The housing is then deformed permanently inward to engage a portion of the sub-assembly to hold the coil spring in its stretched condition.

A slow-blow electrical fuse structure features one or more conducting fuse links for high-current blow-out protection and located in individual chambers filled with arc-quenching filler and in thermal contact with a spring-loaded piston-and-guide structure soldered into an extended position and similarly soldered to one of the fuse links by an extension leading through a chamber-separating insulating partition washer. At overload the heat from the fuse links melts the aforementioned soldered junctions, causing the spring to collapse the piston over the guide, simultaneously withdrawing it from the chamber, thereby breaking the circuit. A similar chamber-defining washer is captively affixed to the opposite end of the piston-and-guide assembly affixed to the optional second fuse link, both partition-forming washers being rotatingly captively secured to the ends of the piston-and-guide assembly by specially configured apertures therein. A modified version of these support washers allows the use of multiple fuse assemblies.

Growing community of inventors

Skokie, IL, United States of America

Joseph W Kowalik