Abstract:
An improved fuse including a fuse body, a fusible element, end terminations and insulated plugs used to seal a cavity formed within the fuse body to extinguish electrical arcs when an overcurrent condition occurs.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    Embodiments of the invention relate to the field of circuit protection devices. More particularly, the present invention relates to a fuse having insulated plugs used to seal a cavity formed within a fuse body to extinguish electrical arcs when an overcurrent condition occurs. 
         [0003]    2. Discussion of Related Art 
         [0004]    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. When an occurrence of a specified fault condition occurs, the fusible element melts or otherwise opens to interrupt the circuit path and isolate the protected electrical components or circuit from potential damage. 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 element. Thus, by varying the size and type of fusible element, different operating times may be achieved. 
         [0005]    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 become smaller and smaller to accommodate electrical circuits, there is a need to reduce manufacturing costs of these fuses. This may include reducing the number of components and/or less expensive components as well as reducing the number and/or complexity of associated manufacturing steps. 
         [0006]    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. 
       SUMMARY OF THE INVENTION 
       [0007]    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. 
         [0008]    Various embodiments are generally directed to a fuse having a fuse body formed of an electrically insulating material. The fuse body defines a cavity which extends from a first end of the fuse body to a second end of the fuse body. A fusible element is disposed within the cavity and extends from a first end face of the first end of the fuse body to a second end face of the second end of the fuse body. Insulated plugs are disposed within the cavity at the first and second ends wherein the plugs form a seal closing the internal cavity. First and second end terminations cover respective first and second end faces of the fuse body. The first end termination is in electrical contact with the fusible element at the first end face and the second end termination is in electrical contact with the fusible element at the second end face. Other embodiments are described and claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1A  illustrates a perspective exploded view of an exemplary fuse. 
           [0010]      FIG. 1B  illustrates a side cross sectional view of assembled fuse. 
           [0011]      FIG. 2A  is a perspective exploded view of an exemplary fuse. 
           [0012]      FIG. 2B  illustrates a side cross sectional view of assembled fuse. 
           [0013]      FIG. 3  illustrates a logic flow in connection with the fuse shown in  FIGS. 1A ,  1 B. 
           [0014]      FIG. 4  illustrates a logic flow in connection with the fuse shown in  FIGS. 2A ,  2 B. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0015]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention, however, 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 this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements throughout. 
         [0016]      FIG. 1A  is a perspective exploded view of an exemplary fuse  10  in accordance with the present disclosure. The fuse  10  includes a fuse body  20  which defines a cavity  25  extending from a first end face  26 -A to a second end face  26 -B. The shape of the fuse body  20  can be, for example, rectangular, cylindrical, etc., with various cross-sectional configurations. The fuse body  20  may be formed from an electrically insulating material such as, for example, glass, ceramic, plastic, etc. The fuse  10  includes a fusible element  30  disposed within the cavity  25  which extends from the first end face  26 -A of the fuse body  20  to the second end face  26 -B. In particular, the fusible element  30  has a first end  30 -A which is bent or otherwise contiguous with respective end face  26 -A of fuse body  20  and a second end  30 -B which is also bent or otherwise contiguous with respective end face  26 -B of fuse body  20 . Fusible element  30  may be disposed within cavity  25  of fuse body  20  in a diagonal configuration from the end face  26 -A to end face  26 -B. Fusible element  30  is configured to melt or otherwise cause an open circuit under certain overcurrent conditions. The fusible element  30  may be a wire, metal link, spiral wound wire, a film, an electrically conductive core deposited on a substrate or any other suitable configuration to provide a circuit interrupt. 
         [0017]    Fuse  10  also includes insulated plugs  40 -A and  40 -B which are disposed within cavity  25  at respective ends of the fuse body  20 . Insulated plugs may be an adhesive material disposed in cavity  25  to close openings thereto at respective ends of the fuse body  20 . In particular, insulated plugs  40 -A,  40 B may be a ceramic adhesive dispensed in cavity  25  after fusible element  30  is positioned within fuse body  20 . In addition, insulated plugs  40 -A,  40 -B may be positioned to allow the respective ends  30 -A and  30 -B of fusible element  30  to be disposed between the plugs and an inside surface of cavity  25  of fuse body  20  to allow ends  30 -A and  30 -B to extend to surface  26 -A and  26 -B respectively. In particular, portion  31 -A of fusible element  30  proximate first end  30 -A is positioned between insulated plug  40 -A and a surface of cavity  25  of fuse body  20  to allow end  30 -A of the fusible element to extend out from cavity  25  and be disposed on surface  26 -A of fuse body  20 . Similarly, portion  31 -B of fusible element  30  proximate second end  30 -B is positioned between insulated plug  40 -B and a surface of cavity  25  of fuse body  20  to allow end  30 -B of the fusible element to extend out from cavity  25  and be disposed on surface  26 -B of fuse body  20 . 
         [0018]    Fuse  10  includes first  50 -A and second  50 -B end terminations disposed on the first  26 -A and second  26 -B end faces, respectively, of fuse body  20  which also covers insulated plugs  40 -A,  40 -B. In particular, the first end termination  50 -A is in electrical contact with at least end  30 -A of fusible element  30  at end face  26 -A and the second end termination  50 -B is in electrical contact with at least end  30 -B of fusible element  30  at end face  26 -B. In this manner, a current path is defined between the end terminations  50 -A,  50 -B and fusible element  30 . First and second end terminations  50 -A,  50 -B may be a silver paste applied to the ends of the fuse body  20 . Each of the end terminations  50 -A and  50 -B connect the fuse  10  in an electrical circuit. The end terminations  50 -A and  50 -B may also be plated with nickel (Ni) and/or tin (Sn) to accommodate soldering of the fuse  10  to a circuit board or other electrical circuit connection. 
         [0019]      FIG. 1B  illustrates a side cross sectional view of assembled fuse  10 . As can be seen, fusible element  30  is oriented diagonally within cavity  25  of fuse body  20  with end  30 -A disposed on end face  26 -A, and end  30 -B disposed on end face  26 -B. Insulated plug  40 -A is disposed within cavity  25  with portion  31 -A of the fusible element  30  being disposed between plug  40 -A and a surface of cavity  25  of fuse body  25 . Similarly, insulated plug  40 -B is disposed within cavity  25  with portion  31 -B of the fusible element  30  being disposed between plug  40 -B and a surface of cavity  25  of fuse body  25 . When an overcurrent condition occurs, the fusible element  30  melts which interrupts the circuit to which it is connected. When the fusible element melts, an electric arc may form between the un-melted portions of the fusible element  30  remaining within cavity  25  forming an arc channel. The arc channel continues or grows until the voltage in the circuit is lower than that required to maintain the arc and it is subsequently extinguished. The insulated plugs  40 -A,  40 -B serve to reduce this arc channel within cavity  25  by decreasing the length “d” of cavity  25  defined between insulated plugs  40 -A and  40 -B as well as providing an insulated seal at respective ends of the fuse body  20  thereby ceasing the fault current quickly. In addition, the insulated plugs  40 -A,  40 -B may be made from a ceramic adhesive which do not have gas evolving properties. Therefore, when an overcurrent condition occurs and an arc is generated, the insulated plugs  40 -A,  40 -B do not emit gas into cavity  25  which would otherwise feed the arc. 
         [0020]    End termination  50 -A is disposed over end face  26 -A of fuse body  20 , end  30 -A of fusible element  30  and insulated plug  40 -A. End termination  50 -B is disposed over end face  26 -B of fuse body  20 , end  30 -B of fusible element  30  and insulated plug  40 -B. As mentioned above, end terminations  50 -A,  50 -B may be made from a silver paste applied to respective ends of the fuse body  20 . The insulated plugs  40 -A,  40 -B provide a surface for the end terminations  50 -A,  50 -B, respectively, to be deposited on. Otherwise, multiple applications of a layered paste such as, for example, silver would have to be deposited and each layer subsequently dried before another deposition of paste is applied in order to close or seal the ends of cavity  25  before end terminations  50 -A,  50 -B are disposed over respective end faces  26 -A,  26 -B. Thus, the use of insulated plugs reduces manufacturing time and associated costs by avoiding multiple deposition of layers to seal cavity  25  and providing a surface for end terminations  50 -A and  50 -B. 
         [0021]      FIG. 2A  illustrates an exploded perspective view of an alternative exemplary embodiment of fuse  100 . The fuse  100  includes a fuse body  120  which defines a cavity  125  extending from a first end face  126 -A to a second end face  126 -B. As mentioned above, fuse body  120  may be formed from an electrically insulating material such as, for example, glass, ceramic, plastic, etc. A fusible element  130  is disposed within cavity  125  which extends from the first end face  126 -A of the fuse body  120  to the second end face  126 -B. The fusible element  130  has a first end  130 -A which is bent or otherwise contiguous with respective end face  126 -A of fuse body  120  and a second end  130 -B which is also bent or otherwise contiguous with respective end face  126 -B of fuse body  120 . The ends  130 -A,  130 -B of fusible element  130  is shown as being spaced away from respective end faces  126 -A,  126 -B, however, this is shown for explanatory purposes. Ends  130 -A,  130 -B of fusible element  130  are disposed on respective end faces  126 -A,  126 -B of fuse body  120 . As noted above, fusible element  130  is configured to melt or otherwise cause an open circuit under certain overcurrent conditions depending on the fuse rating. 
         [0022]    A metalized coating  160 -A is disposed on the end face  126 -A of fuse body  120  and is in electrical contact with end  130 -A of fusible element  130 . Similarly, metalized coating  160 -B is disposed on the end face  126 -B of fuse body  120  and is in electrical contact with end  130 -B of fusible element  130 . The metalized coatings are not deposited on the surface of the cavity  125  of fuse body  120 . The metalized coatings  160 -A,  160 -B also assists in forming an electrical contact between ends  130 -A,  130 -B of fusible element  130  and respective end terminations  150 -A,  150 -B as described below. Insulated plugs  140 -A and  140 -B are disposed within cavity  125  at respective ends of the fuse body  120 . As mentioned above, insulated plugs  140 -A,  140 B may be a ceramic adhesive dispensed in cavity  125  after fusible element  130  is positioned within fuse body  120  with ends  130 -A and  130 -B disposed on respective end faces  126 -A,  126 -B. Metalized coatings  160 -A,  160 -B are applied to end faces  126 -A,  126 -B, respectively. Insulated plugs  140 -A,  140 -B are positioned to allow the respective ends  130 -A and  130 -B of fusible element  130  to be disposed between the plugs and an inside surface of cavity  125  of fuse body  120  to allow ends  130 -A and  130 -B to extend to surface  126 -A and  126 -B respectively. 
         [0023]    Fuse  100  includes first  150 -A and second  150 -B end terminations disposed on the first  126 -A and second  126 -B end faces of fuse body  120  which also covers respective insulated plugs  140 -A,  140 -B. In particular, the first end termination  150 -A is in electrical contact with end  130 -A of fusible element  130  and metalized coating  160 -A at end face  126 -A of fuse body  120 . Second end termination  150 -B is in electrical contact with end  130 -B of fusible element  130  and metalized coating  160 -B at end face  126 -B of fuse body  120 . In this manner, a current path is defined between the end terminations  150 -A,  150 -B and fusible element  130  via metalized coatings  160 -A,  160 -B. Each of the end terminations  150 -A and  150 -B connect the fuse  100  in an electrical circuit. 
         [0024]      FIG. 2B  illustrates a side cross sectional view of assembled fuse  100  wherein fusible element  130  is oriented diagonally within cavity  125  of fuse body  120  with end  130 -A disposed on end face  126 -A, and end  130 -B disposed on end face  126 -B. Metalized coating  160 -A is disposed on end face  126 -A and forms an electrical connection between end  130 -A of fusible element  130  and end termination  150 -A. Similarly, metalized coating  160 -B is disposed on end face  126 -B and forms an electrical connection between end  130 -B of fusible element  130  and end termination  150 -B. Insulated plug  140 -A is disposed within cavity  125  which seals cavity  125  from end termination  150 -A and insulated plug  140 -B is disposed within cavity  125  which seals cavity  125  from end termination  150 -B. When an overcurrent condition occurs, the fusible element  130  melts which interrupts the circuit to which it is connected. When the fusible element melts, an electric arc may form between the un-melted portions of the fusible element  130  remaining within cavity  125 . The insulated plugs  140 -A,  140 -B serve to reduce this arc within cavity  125  by decreasing the length of cavity  125  as well as providing an insulated seal at respective ends of the fuse body  120  thereby ceasing the fault current quickly. In addition, the insulated plugs  140 -A,  140 -B may be made from a ceramic adhesive which does not have gas evolving properties. Therefore, when an overcurrent condition occurs and an arc is generated, the insulated plugs  140 -A,  140 -B do not emit gas into cavity  125  which would otherwise feed the arc. 
         [0025]    Included herein are flow chart(s) representative of exemplary methodologies for performing novel aspects of the present disclosure. While, for purposes of simplicity of explanation, the one or more methodologies shown herein, for example, in the form of a flow chart or logic flow, are shown and described as a series of acts, it is to be understood and appreciated that the methodologies are not limited by the order of acts, as some acts may, in accordance therewith, occur in a different order and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology could alternatively be represented as a series of interrelated states or events. Moreover, not all acts illustrated in a methodology may be required for a novel implementation. 
         [0026]      FIG. 3  illustrates one embodiment of a logic flow  300  in connection with the fuse  10  shown in  FIGS. 1A ,  1 B. A fusible element is threaded through the fuse body at step  310 . For example, fusible element  30  is threaded through fuse body  20  where ends  30 -A and  30 -B are disposed on end faces  26 -A and  26 -B. A ceramic adhesive is deposited within cavity  25  of fuse body  20  at step  320 . The ceramic adhesive adheres to the interior surface of cavity  25  and serves to close or seal cavity  25 . The adhesive is dried at, for example, 150° C. for a predetermined time period at step  330 . End terminations  50 -A,  50 -B in the form of a silver termination paste are applied to each end of fuse body  20  at step  340 . The end terminations  50 -A,  50 -B are dried at 150° C. and sintered at 500° C. at step  350 . The end terminations  50 -A,  50 -B may be plated with Nickel (Ni) and/or Tin (Sn) at step  360  to accommodate solderability of fuse  10  to one or more electrical connections. 
         [0027]      FIG. 4  illustrates one embodiment of a logic flow  400  in connection with fuse  100  shown in  FIGS. 2A ,  2 B. A fusible element is threaded through the fuse body at step  410 . For example, fusible element  130  is threaded through fuse body  120  where ends  130 -A and  130 -B of fusible element  130  are disposed on end faces  126 -A and  126 -B. A metalized layer is deposited on end faces  126 -A,  126 -B of fuse body  120  at step  420 . A ceramic adhesive is deposited within cavity  125  of fuse body  120  at step  430 . The ceramic adhesive adheres to the interior surface of cavity  125  and serves to close or seal cavity  125 . The adhesive is dried at, for example, 150° C. for a predetermined time period at step  440 . End terminations  150 -A,  150 -B in the form of a silver termination paste are applied to each end of fuse body  120  at step  450 . 
         [0028]    While the present invention has been disclosed with reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the sphere and scope of the present invention, as defined in the appended claim(s). Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.