Airtight surface mount fuse with insert cavity

An airtight surface mount fuse with a cavity has a housing, a conductive fuse, a cover and an encapsulant. The housing has an opening and an airtight inner space. The fusible element has a part disposed inside of the airtight inner space and another part exposed from the opening. The cover is configured to fit into the opening. The encapsulant encapsulates the housing, the cover and a segment of the exposing part of the fusible element. The other segment of the fusible element is exposed from the encapsulant. The inner space of the housing is encapsulated by the encapsulant and becomes airtight. The fusible element is disposed inside of the airtight inner space to prevent the hazard occurring from arc spark interacting with flammable gases when a fusible body of the fusible element is fused. It also ensures the fusible body is affected by the external environment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims priority under 35 U.S.C. 119 from Taiwan Patent Application No. 110111991 filed on Mar. 31, 2021, which is hereby specifically incorporated herein by this reference thereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a surface mount fuse, particularly, to a surface mount fuse mounted with a surface mounting technology.

2. Description of the Prior Arts

The conventional fuse includes a fusible element. When an abnormal condition (e.g., overcurrent) occurs to a circuit, having the fuse connected in series for protection, the fusible element is fused due to overheating, so that the protected circuit is opened to achieve the function of protecting the circuit.

Nowadays, the fuses are used in a variety of different circumstances, from factories to outer space. In one circumstance that a conventional fuse is used in a factory environment with flammable gases, the fire hazard may occur since the flammable gases is ignited by a spark causing by an arc when the fusible element is fused. The arc is produced because the electric field intensity at both ends of the break point is extremely strong that makes the air, which should be the insulating medium, easily being broken down. In another circumstance that a conventional fuse is used in a special environment (e.g., outer space), which has no experimental data on how it will affect the fusible element, the conventional fuse could malfunction due to the unknown environmental condition. Therefore, it is necessary to further improve it.

SUMMARY OF THE INVENTION

In view of the shortcomings of the above fuse, the main objective of the present disclosure is to provide an improved airtight surface mount fuse with a cavity, which can be used in different environments.

The main technical features used to achieve the objective of the invention is that the airtight surface mount fuse with a cavity includes:

a housing, comprising an opening and an airtight inner space;

a fusible element, comprising a fusible body, two intermediary portions and two conductive portions, wherein each of the intermediary portions is connected between a corresponding end of the fusible body and the corresponding conductive portion, the fusible body and the two intermediary portions are disposed inside of the inner space of the housing, and each of the conductive portions extends out of the housing from the opening;

a cover, disposed on the opening; and

an encapsulant, encapsulating the housing, the cover and a part of the conductive portions of the fusible element The part of the conductive portion being encapsulated is located at the joint between the housing and the cover.

According to the above explanation, since the airtight surface mount fuse with a cavity includes an encapsulant configured to encapsulate the housing, the cover, and a part of the conductive portion of the fusible element located at the joint between the housing and the cover, the gaps between the housing, the cover and the conductive portion are completely sealed. Thus, the inner space of the housing becomes an airtight inner space. The hazard occurring from arc spark interacting with flammable gases is prevented by disposing the fusible body of the fusible element in the airtight inner space. It also ensures the fusible body is not affected by the external environment since the fusible body is disposed inside of the airtight inner space, so that the airtight surface mount fuse with a cavity can be used in different environments.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring toFIG. 1, a first embodiment of an airtight surface mount fuse1awith a cavity in accordance with the present invention includes a housing10, a fusible element20, a cover30and an encapsulant40.

As shown inFIG. 2, the housing10includes an opening11and an inner space12. In the present embodiment, the housing10is a cuboid and includes a rectangular main wall101and four sidewalls102respectively extending vertically from the four sides of the main wall101. The sidewalls102are connected to each other to form the inner space12and the opening11. The opening11of the housing10is rectangular and includes two opposing first sides111and two opposing second sides112. In an exemplary embodiment as shown inFIG. 1, the height of the two opposing first sides111is higher than the height of the two opposing second sides112. In an exemplary embodiment, the first sides111are the longer sides and the second sides112are the shorter sides. The material of the housing10is a ceramic material, but the present invention is not limited thereto.

As shown inFIG. 2andFIG. 4, the fusible element20is mounted on the opening11of the housing and includes a fusible body21, two intermediary portions22and two conductive portions23. In the present embodiment, each of the intermediary portions22is connected between a corresponding end of the fusible body21and the corresponding conductive portion23in one-piece The fusible body21and the two intermediary portions22are adapted to accommodate into the inner space12of the housing10and curved downward toward the main wall101of the housing10. The two conductive portions23of the fusible element20are disposed, respectively, on the two opposing second sides112of the opening11. In an exemplary embodiment, as shown inFIG. 4, the fusible body21further includes a first segment211and two second segments212respectively facing and extending toward each of the intermediary portions22. The first segment211is linear. The width of the first segment211is less than the width of each of the second segments212. The transverse width of the first segment211is less than the transverse width of each of the second segments212. A gap24is formed in each of the second segments212, so that the distance between both ends of the fusible body21can be lengthen by the gaps24after the fusible body21being fused, and thus reduce the possibility to generate the electric arc. Each of the conductive portions23forms a hole. In an exemplary embodiment, the material of the fusible element20can be metals (e.g., silver, copper, nickel, tin, aluminum, zinc, etc.) or alloys made of the above metals. On the other hand, in another exemplary embodiment of the fusible element20as shown inFIG. 5A, the fusible body21is bent in a non-linear plane path so that the fusible body21extends the total length without increasing the distance between the intermediary portions22to protect circuits with lower rated current (e.g., 10 A to 0.5 A). In addition, the width D1of the fusible body21is greater than the width D2of each intermediary portion22. Further referring toFIG. 5B, before the fusible element20is placed into the inner space12of the housing10as shown inFIG. 2, the fusible body21and the two intermediary portions22of the fusible element20are bent downward and toward the main wall101to form an arc shape, that is, the fusible body21and the two intermediary portions22are bent away from the opening11, and the both sides of the fusible body21are also bent away from the opening11to reduce the width of the fusible body21, so that the fusible element20can be more easily placed into the inner space12of the housing10.

As shown inFIG. 2andFIG. 3, the cover30is adapted to fit into the opening11of the housing to seal the fusible body21of the fusible element20into the inner space12of the housing10. In the present embodiment, the cover30is a cuboid, which means the cover30includes two opposing third sides31and two opposing fourth sides32. The two fourth sides32are disposed on two second sides112of the opening11. Further referring toFIG. 1, the external surface301of the cover30is flush with the two first sides111of the opening11, so that the two conductive portions23of the fusible element20are respectively disposed on the two opposing second sides112of the opening11and exposed out of the opening11. In an exemplary embodiment, the cover30is made of a ceramic material or a plastic material.

As shown inFIG. 1andFIG. 3, the housing10, the cover30, and a part of the conductive portion23located at the joint between the housing10and the cover30are encapsulated by the encapsulant40, so that the gaps between the housing10, the cover30and the conductive portion23can be sealed by the encapsulant40. Therefore, the inner space12of the housing10becomes an airtight inner space12, and the conductive portions23of the fusible element20have a part exposing out of the encapsulant40. Referring toFIG. 1again, the exposing part of the conductive portions23is bent toward to the cover30and attached to a surface401, which corresponds to the surface301of the cover30, of the encapsulant40, so as to form the airtight surface mount fuse1awith a cavity. Each conductive portion23can be easily bent and attached to the encapsulant40due to the hole231formed on each conductive portion23. In an exemplary embodiment, the encapsulant40is formed by embedded insert molding. The encapsulant40can be made of, but not limited to, silicon, epoxy, nylon, or engineering plastics.

In an exemplary embodiment, the exposing part of the conductive portions23of the fusible element20has not yet been bent when the cover is assembled to the fusible element20. The exposing part of the conductive portions23is bent and attached to the surface401of the encapsulant40after the housing10and the cover30are encapsulated by the encapsulant40.

Referring toFIG. 6, illustrating the surface mount fuse1baccording to a second embodiment of the present disclosure, the surface mount fuse1bis similar to the surface mount fuse1ashown inFIG. 1, except that the two opposing first sides111and the two opposing second sides112of the opening11of the housing10are of the same height. The cover30is configured to fit into the opening11, which means the external surface301of the cover30is flush with the two first sides111and the two second sides112of the opening. The two conductive portions23of the fusible element20are respectively toward to the two second sides of the opening11and exposed from the opening11. The housing10, the cover30, and a part of the conductive portion23located at the joint between the housing10and the cover30are further encapsulated by the encapsulant40, and then parts of the two conductive portions23exposing out of the encapsulant40are respectively bent and attached to the encapsulant40encapsulating the corresponding second side112and the external surface of the housing10.

Referring toFIG. 7, illustrating the surface mount fuse1caccording to a third embodiment of the present disclosure. The surface mount fuse1cof the present embodiment is similar to the second embodiment shown inFIG. 6. In the present embodiment, the housing10has two buttonholes113respectively formed on the two opposing second sides112of the opening11. Since the cover30is configured to fit into the opening11, the two opposing fourth sides32of the cover30are respectively corresponding to each buttonhole113formed on the second sides112of the opening11. The cover30has two buttons32horizontally extended from its two opposing fourth sides32and configured to assemble the buttonholes113of the opening11by the interference fit and make the external surface301of the cover30flushing with the two first sides111and the two second sides112of the opening11. In an exemplary embodiment, the cover30is made of a plastic material.

In conclusion, since the inner space of the housing becomes an airtight inner space by encapsulating the housing and the cover with the encapsulant and the fusible body of the fusible element is disposed inside of the airtight inner space, the hazard occurring from arc spark interacting with flammable gases when the fusible body is fused is prevented. It also ensures the fusible body is not affected by the external environment since the fusible body is disposed inside of the airtight inner space, so that the airtight surface mount fuse with a cavity can be used in different environments.