Fuse with arc-quenching silicone composition

Abstract

To quickly extinguish an arc generated when a soluble element is separated by overcurrent.SOLUTION: A fuse 10 includes: a tubular electric insulating fuse body 12; a first end cap 18 and a second end cap 20 that are arranged on both ends of the fuse body 12 and have conductivity; a fusible element 24 that extends through the fuse body 12 and connects the first end cap 18 to the second end cap 20, in which the fusible element 24 has a central part 25 adapted so as to be melted in an overcurrent state in the fuse and separated; and a first arc barrier 30a and a second arc barrier 30b arranged on both sides of the central part 25 on the fusible element 24, in which the first arc barrier 30a and the second arc barrier 30b are formed from a silicone composition containing an arc extinguishing filler 32 suspended in a silicone resin.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] [background] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 092,075, filed October 15, 2020, which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates generally to the field of circuit protection devices. More particularly, the present disclosure relates to fuses having arc barriers formed from arc-quenching silicone compositions. [Background technology]

[0003] Fuses are commonly used as circuit protection devices and are typically installed between a source of electrical power and a component in an electrical circuit to be protected. A typical fuse includes a fusible element disposed within a hollow, electrically insulating fuse body. When a fault condition, such as an overcurrent condition, occurs, the fusible element melts or otherwise separates, interrupting the flow of electrical current through the fuse.

[0004] When a fuse's fusible elements separate as a result of an overcurrent condition, it is sometimes possible for an electrical arc to propagate between the separated portions of the fusible element (e.g., through residual vapor particles between the separated portions of the fusible element). If not extinguished, the electrical arc may allow a large subsequent current to flow from the source of electrical power to a protected component in the circuit, resulting in damage to the protected component despite the fusible elements being physically open. Furthermore, the heat generated by the electrical arc can burn and / or rupture the fuse body of the fuse, potentially causing damage to surrounding components. Therefore, it is desirable to extinguish the electrical arc as quickly as possible to prevent or mitigate much of the resulting damage to connected surrounding components.

[0005] With respect to these and other considerations, the present improvements may be useful. Summary of the Invention

[0006] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter.

[0007] A fuse according to a non-limiting embodiment of the present disclosure may include an electrically insulative tubular fuse body; electrically conductive first and second end caps disposed on opposite ends of the fuse body; a fusible element extending through the fuse body and connecting the first end cap to the second end cap, the fusible element having a central portion adapted to melt and separate under an overcurrent condition within the fuse; and first and second arc barriers disposed on either side of the central portion on the fusible element, the first and second arc barriers being formed from a silicone composition including an arc-quenching filler suspended in a silicone resin.

[0008] A method of making and dispensing an arc-quenching silicone composition according to the present disclosure may include adding an arc-quenching filler to a silicone resin in a liquid state, mixing the arc-quenching filler and the silicone resin to form a homogeneous composition, dispensing the composition onto a fusible element of a fuse, and curing the composition. [Brief explanation of the drawings]

[0009] [Figure 1A] 1 is a cross-sectional side view of a fuse according to an exemplary embodiment of the present disclosure under normal operating conditions;

[0010] [Figure 1B] 1B is a cross-sectional side view of the fuse of FIG. 1A during an overcurrent condition.

[0011] [Figure 2] FIG. 1 is a flow diagram illustrating an exemplary method for mixing and dispensing an arc-quenching silicone composition according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012]

[0023] Exemplary embodiments of fuses having arc barriers formed from arc-quenching silicone compositions according to the present disclosure will now be described more fully with reference to the accompanying drawings. However, fuses may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will convey certain exemplary aspects of fuses to those skilled in the art.

[0013] Referring to FIG. 1A , a cross-sectional side view is shown illustrating a fuse (hereinafter “fuse 10”) having an arc barrier formed from an arc-quenching silicone composition according to an exemplary embodiment of the present disclosure. In various embodiments, fuse 10 may be a cartridge fuse having a tubular fuse body 12. The present disclosure is not limited in this respect. In various alternative embodiments, fuse 10 may be a surface-mount fuse or other type of fuse having a fusible element extending through a generally hollow fuse body. Fuse body 12 may be formed from an electrically insulating and preferably heat-resistant material. Examples of such materials include, but are not limited to, ceramic and glass.

[0014] A pair of conductive end caps 18, 20 may be disposed on opposite ends of the fuse body 12 and may be adapted to facilitate electrical connection of the fuse 10 in a circuit. A fusible element 24 may extend through the hollow interior of the fuse body 12 and may be connected to the end caps 18, 20 in electrical communication therewith, such as by solder. The end caps 18, 20 may be formed from a conductive material, including but not limited to, copper or one of its alloys, and may be plated with nickel or other conductive, corrosion-resistant coatings. The fusible element 24 may be formed from a conductive material, including but not limited to, tin or copper, and may be configured to melt and separate upon the occurrence of a predetermined fault condition, such as an overcurrent condition in which an amount of current exceeding a predetermined maximum value flows through the fusible element 24. This maximum value is typically referred to as the “rating” of the fuse 10.

[0015] The fusible element 24 may be any type of fusible element suitable for the desired application, including, but not limited to, wire, corrugated strip, wire wound around an insulating core, etc. The central portion 25 of the fusible element 24 may be thinner, narrower, perforated, or otherwise weakened relative to other portions of the fusible element 24 to ensure that the fusible element 24 separates at the central portion 25. In various embodiments, a quantity of dissimilar metal 26 (hereinafter, “metal spot 26”), sometimes referred to as a “Metcalf spot,” may be applied to the central portion 25 of the fusible element 24. The metal spot 26 may be formed from one or more of nickel, indium, silver, tin, or other metals having a lower melting temperature than the base metal (e.g., copper) from which the fusible element 24 is formed. Thus, the metal spot 26 may melt and diffuse into the base metal of the fusible element 24 more readily than the base metal of the fusible element 24 during an overcurrent condition. The base metal of fusible element 24 and the dissimilar metals of metal spot 26 are selected so that diffusion of one into the other results in an intermetallic phase that has a lower melting temperature and higher resistivity than that of the base metal alone, causing center portion 25 of fusible element 24 to melt more easily than other portions of fusible element 24. In various embodiments of fuse 10, metal spot 26 may be omitted entirely.

[0016] The fuse 10 may further include arc barriers 30a, 30b disposed on the fusible element 24 along the length of the fusible element 24 on either side of the central portion 25. Each of the arc barriers 30a, 30b may radially surround the fusible element 24 and extend from the fusible element 24 to or near the inner surface of the fuse body 12. The arc barriers 30a, 30b may be formed from a silicone composition formed from an arc-quenching filler 32 suspended in a silicone resin 34. In various embodiments, the arc-quenching filler 32 may be a melamine powder. The present disclosure is not limited in this respect. In various alternative embodiments, the arc-quenching filler 32 may include one or more of guanidine, guanine, hydantoin, allantoin, urea, melamine formaldehyde, melamine cyanurate polymer, boric acid, and derivatives or mixtures thereof, or other fillers that exhibit similar endothermic, arc-quenching properties upon combustion, as described below. The arc-quenching filler 32 may be dispersed substantially uniformly throughout the silicone resin 34 and may comprise approximately 5-70% by weight of the silicone composition.

[0017] When an overcurrent condition occurs in the fuse 10, the central portion 25 of the fusible element 24 may melt and separate, allowing an electric arc 36 to propagate across the gap left between the separated ends of the fusible element 24, as shown in FIG. 1B. The heat from the electric arc may burn and decompose the silicone of the arc barriers 30a, 30b, which may contain the electric arc 36 and the heat generated thereby. As the silicone decomposes, the arc-quenching filler 32 within the arc barriers 30a, 30b may become exposed or be burned by the heat from the electric arc 36. As the arc-quenching filler 32 burns and decomposes, it undergoes an endothermic chemical reaction that absorbs heat, thereby rapidly cooling the electric arc 36. Furthermore, depending on the particular arc-quenching filler 32 (e.g., melamine) incorporated into the arc barriers 30a, 30b, certain by-products of the endothermic chemical reaction may be non-conductive gases (e.g., ammonia), which may interfere with the ability of the electric arc 36 to sustain itself. Furthermore, another by-product of the endothermic chemical reaction may produce water, which may further cool the electric arc 36. Thus, when an electrical overcurrent condition occurs in the fuse 10, the arc-quenching filler 32 may absorb heat, release gases adverse to maintaining the electric arc, and produce water that may further cool the electric arc, all of which may contribute to rapid arc quenching, thereby protecting components connected to and / or located near the fuse 10 from damage that may otherwise result if the electric arc 36 were allowed to persist.

[0018] Referring to Figure 2, a flow diagram illustrating an exemplary method for mixing and dispensing the silicone composition of the present disclosure is shown. The method will now be described in conjunction with the diagram of fuse 10 shown in Figures 1A and 1B.

[0019] In block 100 of the exemplary method, an arc-quenching filler (e.g., melamine powder) may be added to the silicone resin in a liquid state. In various embodiments, the arc-quenching filler may comprise 5 to 70 weight percent of the total mass of the silicone composition. The present disclosure is not limited in this respect. When melamine powder is used as the arc-quenching filler, the size of the powder particles may be within a range of 5 μm to 100 μm in length or diameter. The present disclosure is not limited in this respect.

[0020] At block 110 of the exemplary method, the silicone and the arc-quenching filler may be mixed together to form a homogeneous or nearly homogeneous silicone composition. At block 120 of the method, the silicone composition may be dispensed onto the fusible element. For example, with reference to FIG. 1A , the silicone composition may be dispensed onto the fusible element 24 along the length of the fusible element 24 on either side of the center portion 25.

[0021] In block 130 of the exemplary method, the dispensed silicone composition may be cured or otherwise hardened to form the arc barriers 30 a, 30 b. In various examples, the silicone composition may be heat cured, moisture cured, UV cured, etc. The disclosure is not limited in this respect.

[0022] As used herein, elements or steps described in the singular and preceded by the word "a" or "an" should be understood as not excluding a plurality of elements or steps, unless such exclusion is expressly stated. Furthermore, references to "one embodiment" of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0023] While the present disclosure refers to particular embodiments, numerous improvements, modifications, and variations to the described embodiments are possible without departing from the spirit and scope of the present disclosure, as defined by the appended claims. Accordingly, it is intended that the present disclosure not be limited to the described embodiments, but rather have the full scope defined by the language of the following claims and their equivalents.

Claims

1. A fuse, an electrically insulating tubular fuse body; conductive first and second end caps disposed on opposite ends of the fuse body; a fusible element extending through the fuse body and connecting the first end cap to the second end cap, the fusible element having a central portion adapted to melt and separate under an overcurrent condition within the fuse; a first arc barrier and a second arc barrier disposed on the fusible element on either side of the central portion, the first arc barrier and the second arc barrier being formed from a silicone composition including an arc-quenching filler suspended in a silicone resin; Equipped with the first arc barrier and the second arc barrier extend radially from the fusible element to an inner surface of the fuse body; Fuse.

2. The arc-quenching filler is one or more of melamine, guanidine, guanine, hydantoin, allantoin, urea, melamine formaldehyde, melamine cyanurate polymer, boric acid, and derivatives thereof.

10. The fuse of claim 1.

3. The arc-quenching filler is melamine powder, and the particle size of the melamine powder is in the range of 5 μm to 100 μm in length or diameter.

3. The fuse of claim 2.

4. The arc-quenching filler accounts for 5 to 70% by weight of the total mass of the silicone composition.

4. The fuse of claim 1.

5. The central portion of the fusible element is thinner, narrower, perforated, or otherwise weakened relative to other portions of the fusible element such that the fusible element separates at the central portion.

5. The fuse of claim 1.

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