Patent Description:
Fuses are used as circuit protection devices and form an electrical connection with a component in a circuit to be protected. One type of fuse includes a fusible element disposed within a hollow fuse body. Upon the occurrence of a specified fault condition, such as an overcurrent condition, the fusible element melts or otherwise opens to interrupt the circuit path and isolate the protected electrical components or circuit from potential damage. Such fuses may be characterized by the amount of time required to respond to an overcurrent condition. In particular, fuses that comprise different fusible elements respond with different operating times since different fusible elements can accommodate varying amounts of current through the fusible element. Thus, by varying the size and type of fusible element, different operating times may be achieved.

The publication <CIT> describes a fuse comprising a body including a center portion and two end portions surrounded by endcaps and a fusible element comprising a central wire extending diagonally between first and second coils. Further similar fuse arrangements are disclosed in the publications <CIT>, <CIT>, <CIT> and <CIT>.

When an overcurrent condition occurs, an arc may be formed between the melted portions of the fusible element. If not extinguished, this arc may further damage the circuit to be protected by allowing unwanted current to flow to circuit components. Thus, it is desirable to manufacture fuses which extinguish this arc as quickly as possible. In addition, as fuses decrease in size to accommodate ever smaller electrical circuits, there is a need to reduce manufacturing costs of these fuses. This may include reducing the number of components and/or using less expensive components, as well as reducing the number and/or complexity of associated manufacturing steps.

Consequently, there is a need to reduce the number of components and/or manufacturing steps to produce a fuse with improved arc extinguishing characteristics. It is with respect to these and other considerations that the present improvements have been needed.

In accordance with the invention, a fuse as set forth in claim <NUM> is provided.

Further embodimentsw are inter alia disclosed in the dependent claim.

The use of the word "embodiment" below in this description merely implies the illustration of examples or exemplary embodiments, if not otherwise defined by the appended claims. The scope of the invention is thus defined by the appended claims.

The accompanying drawings illustrate exemplary approaches of the disclosed embodiments so far devised for the practical application of the principles thereof, and in which:.

The drawings are merely representations, not intended to portray specific parameters of the disclosure. The drawings are intended to depict typical embodiments of the disclosure, and therefore should not be considered as limiting in scope. In the drawings, like numbering represents like elements.

Furthermore, certain elements in some of the figures may be omitted, or illustrated not-to-scale, for illustrative clarity. Furthermore, for clarity, some reference numbers may be omitted in certain drawings.

Embodiments in accordance with the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings. The devices/systems/fuses may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the system and method to those skilled in the art.

As will be discussed in greater detail herein, the disclosure provides protection devices, such as fuses, having a fusible element including coiled ends and a central wire extending diagonally between the coiled ends. The fusible element may be used for high breaking capacity fuse applications, and bears at least the following features and technical advantages. First, the coiled fusible element free ends promote robust element-termination bonding/connection beneficial for thermal cycling reliability. For example, in one embodiment, the coiled free ends provide good solder coverage for Nano fuses. In another embodiment, the coiled free ends provide a good mechanical bond with mechanical structures, such as tubes, of the endcaps in the case of a solderless design.

Second, the coiled fusible element effectively lengthens the wire element, which results in higher I2t values applicable to high surge applications. The higher the I2t value, the higher the surge or in-rush current and more loading cycles the fuse could withstand before opening, which is typical in LED lighting, AC/DC power adaptor and Telecom equipment system. Third, the coil loops, when supplied with an electric current, create a magnetic field which helps confine arc plasma, enhancing the breaking capacity of the fuse.

Fourth, an interior area of the coil loops provides an area to hold an arc quenching material, such as silicone, for additional arc quenching capability. The diameter of the coil loops, which is dependent on the body/enclosure area, also help aids in the alignment of the fusible element.

Fifth, providing a straight diagonal central wire of the fusible element ensures the weak spot to be at the center of the fusible element, giving faster and safer clearing time. Additionally, the diagonal orientation eliminates or minimizes issues of the central wire touching the body, which is a common root cause of standard Nano OL failure.

<FIG> illustrates a perspective view of a protection device, such as a fuse <NUM>, in accordance with a non-limiting embodiment of the present disclosure. As shown, the fuse <NUM> may include a body <NUM>. The body <NUM> may be ceramic, plastic, or other suitable electrically non-conducting material. In exemplary embodiments, the body <NUM> is hollow. A first endcap <NUM> may be coupled to, or fit over, a first end <NUM> of the body <NUM>, and a second endcap <NUM> may be coupled to, or fit over, a second end <NUM> of the body <NUM>.

The fuse <NUM> further includes a fusible element <NUM>, such as wire. The fusible element <NUM> may be disposed within the body <NUM>. As shown, the fusible element <NUM> includes a first coil <NUM> coupled to the first endcap <NUM> and a second coil <NUM> coupled to the second endcap <NUM>. Extending diagonally between the first and second coils <NUM>, <NUM> is a central wire <NUM>. In some embodiments, the central wire <NUM> may be substantially straight.

In some embodiments, solder <NUM> may be disposed within each of the first and second endcaps <NUM> and <NUM>. More specifically, the solder <NUM> may be disposed between the first end <NUM> of the body <NUM> and the first endcap <NUM>, and between the second end <NUM> of the body <NUM> and the second endcap <NUM>. As shown, the solder <NUM> may be electrically and mechanically connected to the first coil <NUM> and the second coil <NUM>.

In some embodiments, the body <NUM> includes a central portion <NUM> extending between the first and second ends <NUM>, <NUM>. The central portion <NUM> has an outer cross-sectional profile of a first size. In some embodiments, the first and second ends <NUM>, <NUM> of the body <NUM> have an outer cross-sectional profile of a second size, where the second size is less than the first size. However, the first size and the second size may be the same in other embodiments.

The fusible element <NUM> extends through a cavity that is defined between an outer periphery of the first end <NUM> and an inside surface of the first endcap <NUM>. The fusible element <NUM> extends along a substantially diagonal path through a center of the cavity and terminates at the second end <NUM>, which is at least partially covered by the second endcap <NUM>. The cavity enables the solder <NUM> to completely surround at least a portion of the fusible element <NUM> disposed therein. In exemplary embodiments, the fusible element <NUM> does not come into direct contact with the interior surfaces of the body <NUM> defining the cavity.

<FIG> illustrates a perspective view of a protection device, such as a fuse <NUM>, in accordance with a non-limiting embodiment of the present disclosure. The fuse <NUM> may share many of the same features to the fuse <NUM> described above. As such, some aspects of the fuse <NUM> may not be described in detail for the sake brevity. As shown, the fuse <NUM> may include a body <NUM>. The body <NUM> may be ceramic, plastic, or other suitable electrically non-conducting material. In exemplary embodiments, the body <NUM> is hollow. A first endcap <NUM> may be coupled to, or fit over, a first end <NUM> of the body <NUM>, and a second endcap <NUM> may be coupled to, or fit over, a second end <NUM> of the body <NUM>.

In this non-limiting embodiment, the fuse <NUM> may be solderless. Instead, the first coil <NUM> is coupled to, or wound about, a first tube <NUM> of the first endcap <NUM>. The second coil <NUM> is coupled to a second tube <NUM> of the second endcap <NUM>. The first tube <NUM> and the second tube <NUM> may be an type of post or support extending from respective endcaps <NUM>, <NUM> towards the body <NUM>. In one embodiment, the first and second tubes <NUM>, <NUM> may each be metallic a tubes.

The fusible element <NUM> extends through a cavity that is defined between an outer periphery of the first end <NUM> and an inside surface of the first endcap <NUM>. The fusible element <NUM> extends along a substantially diagonal path through a center of the cavity and terminates at the second end <NUM>, which is at least partially covered by the second endcap <NUM>. In exemplary embodiments, the fusible element <NUM> does not come into direct contact with the interior surfaces of the body <NUM> defining the cavity.

Turning now to <FIG>, a fusible element <NUM> according to embodiments of the present disclosure will be described in greater detail. The fusible element <NUM> may be the same or similar to the fusible element <NUM> and fusible element <NUM> described above. As shown, the fusible element <NUM> may include a first coil <NUM> opposite a second coil <NUM>. A central wire <NUM> extends diagonally between the first and second coils <NUM>, <NUM>. As shown, each of the first and second coils <NUM>, <NUM> may include a plurality of loops winding generally about a central axis, A-A. Each of the first and second coils <NUM>, <NUM> may have any number of loops depending on the application. In exemplary embodiments, the central wire <NUM> is non-parallel with the central axis A-A.

During use, the first and second coils <NUM>, <NUM> may create a bottle configuration of magnetic lines <NUM>, which can confine an arc <NUM> around an approximate midpoint of the central wire <NUM>. With the arc <NUM> confined at the center between the first and second coils <NUM>, <NUM>, damage to the first coil <NUM>, the second coil <NUM>, the body and the endcaps (not shown) is mitigated. In this non-limiting embodiment, the first and second coils <NUM>, <NUM> are wound in a same direction (e.g., clockwise).

As shown in <FIG>, the first and second coils <NUM>, <NUM> of the fusible element may be wound in opposite directions. In this embodiment, the magnetic field lines <NUM> create magnetic repulsion between the first and second coils <NUM>, <NUM>. The repulsion aids with separation of the fusible element <NUM> following a break. In some embodiments, the fusible element <NUM> may include an arc quencher material <NUM> (e.g., silicone) within and/or around the first and second coils <NUM> and <NUM>, as shown in <FIG>.

<FIG> illustrates a cross-sectional view of the inventive fuse <NUM>. The body <NUM> includes a central portion <NUM> disposed between a first end <NUM> and a second end <NUM>. As shown, the central portion <NUM> may have an outer square cross-sectional profile. However, embodiment of the present disclosure are not limited to any particular shape or cross-sectional profile. For example, in some embodiments, the body <NUM> may have a generally circular profile in cross-section, e.g., as viewed from the first end <NUM> and the second end <NUM>. The central portion <NUM> includes a central cavity <NUM> extending between the first end <NUM> and the second end <NUM>, and a plurality of exterior surfaces defining the outer cross-sectional profile of a first size. In a non-limiting embodiment, the body <NUM> includes four (<NUM>) generally flat exterior surfaces. The body <NUM> may be ceramic, plastic, or other suitable electrically non-conducting material. A first endcap <NUM> may fit over the first end <NUM> of the body <NUM>, and a second <NUM><NUM> may fit over the second end <NUM> of the body <NUM>.

As shown, solder <NUM> is disposed within the central cavity <NUM> and along a first end surface <NUM> of the first end <NUM> of the body <NUM>. The first coil <NUM> has a free end (not shown), which is surrounded by the solder <NUM> proximate the first end <NUM> of the body <NUM>. Similarly, the solder <NUM> extends along a second end surface <NUM> of the second end <NUM> of the body <NUM>. The second coil <NUM> has a free end, which is surrounded by the solder <NUM> proximate the second end <NUM> of the body <NUM>. In some embodiments, an arc quenching material (e.g., silicone) may be disposed within the central cavity <NUM>.

As further shown, the central wire <NUM> of the fusible element <NUM> is disposed within the central cavity <NUM> of the body <NUM>. The central wire <NUM> is a diagonal wire extending between the first and second coils <NUM>, <NUM>. More specifically, the central wire <NUM> includes a first end <NUM> integrally coupled with a first end <NUM> of the first coil <NUM>. A second end <NUM> of the central wire <NUM> is integrally coupled with a second end <NUM> of the second coil <NUM>. The first and second coils <NUM>, <NUM> are positioned within the first endcap <NUM> and the second endcap <NUM>, respectively. The first coil <NUM> also extends within the central cavity <NUM> proximate the first end <NUM> of the body <NUM>, and the second coil <NUM> extends within the central cavity <NUM> proximate the second end <NUM> of the body <NUM>. As described above, depending on the winding direction of the first and second coils <NUM>, <NUM>, when the loops of the first and second coils <NUM>, <NUM> are supplied an electric current, a magnetic field is created, which helps confine arc plasma, enhancing the breaking capacity of the fuse <NUM>. Although not shown, the loop area of the first and/or second coils could also hold a silicone material for additional arc quenching capability. It will be appreciated that a number coils, thickness of material, and diameter of the loops, among other parameters, may vary, and may be dependent in part on the geometries of the body <NUM> and the central cavity <NUM>, as well as the rating of the fuse <NUM>.

Although not shown, in some embodiments, the free end of the first and/or second coils <NUM>, <NUM> may extend along respective first and second end surfaces <NUM>, <NUM>. In yet other embodiments, the fusible element <NUM> may also extend along the partially along the one or more of the plurality of exterior surfaces of the body <NUM>.

In sum, provided herein is a fusible element having coils disposed at opposite ends of a diagonal wire. The first and second coils may be wound in a same direction, thus creating a magnetic bottle configuration (also called magnetic mirror), which can advantageously confine an arc at the center of the diagonal wire. With the arc confined at the center, damage of the fuse terminals/caps and body will be mitigated. Alternatively, the first and second coils may be wound in opposite directions. As a result, the first and second coils will advantageously repel one another once a strong magnetic field is created, e.g., in the event of an overcurrent condition.

The foregoing discussion has been presented for purposes of illustration and description and is not intended to limit the disclosure to the form or forms disclosed herein. For example, various features of the disclosure may be grouped together in one or more aspects, embodiments, or configurations for the purpose of streamlining the disclosure. However, it should be understood that various features of the certain aspects, embodiments, or configurations of the disclosure may be combined in alternate aspects, embodiments, or configurations.

Accordingly, the terms "including," "comprising," or "having" and variations thereof are open-ended expressions and can be used interchangeably herein.

The phrases "at least one", "one or more", and "and/or", as used herein, are open-ended expressions that are both conjunctive and disjunctive in operation.

All directional references (e.g., proximal, distal, upper, lower, upward, downward, left, right, lateral, longitudinal, front, back, top, bottom, above, below, vertical, horizontal, radial, axial, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of this disclosure. Connection references (e.g., attached, coupled, connected, and joined) are to be construed broadly and may include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other.

Furthermore, identification references (e.g., primary, secondary, first, second, third, fourth, etc.) are not intended to connote importance or priority but are used to distinguish one feature from another. The drawings are for purposes of illustration only and the dimensions, positions, order and relative sizes reflected in the drawings attached hereto may vary.

Furthermore, the terms "substantial" or "substantially," as well as the terms "approximate" or "approximately," can be used interchangeably in some embodiments, and can be described using any relative measures acceptable by one of ordinary skill in the art. For example, these terms can serve as a comparison to a reference parameter, to indicate a deviation capable of providing the intended function. Although non-limiting, the deviation from the reference parameter can be, for example, in an amount of less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, less than <NUM>%, and so on.

Claim 1:
A fuse (<NUM>) comprising:
a body (<NUM>) including a center portion extending between a first end (<NUM>) and a second end (<NUM>);
a first endcap (<NUM>) surrounding the first end (<NUM>) and a second endcap (<NUM>) surrounding the second end (<NUM>); and
a fusible element (<NUM>) disposed within a central cavity of the body (<NUM>), the fusible element (<NUM>) comprising:
a first coil (<NUM>) disposed within the first endcap (<NUM>) and a second coil (<NUM>) disposed within the second endcap (<NUM>); and
a central wire (<NUM>) extending diagonally between the first and second coils (<NUM>,<NUM>);
wherein the first coil (<NUM>) has a free end that is connected to a first end surface within the first end (<NUM>) of the body (<NUM>) with solder (<NUM>), and wherein the second coil (<NUM>) has a free end that is connected to a second end surface within the second end (<NUM>) of the body (<NUM>) with solder (<NUM>).