Abstract:
A fuse is provided that is suitable for operation in unusual environments and includes an operation indicator that is simple and reliable. A movable arcing tube is released during operation. As the arcing tube moves outside the fuse assembly, a latching spring moves into a receiving groove in the arcing tube to retain the arcing tube in the external operated position.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 60/361,601 filed on Mar. 2, 2002 in the names of G. R. Borchardt et al. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates generally to high voltage fuses and more particularly to a fuse suitable for operation in unusual environments and including an operation indicator.  
           [0004]    2. Description of the Related Art  
           [0005]    Various types of high voltage fuses are known having diverse construction. The fuse shown in U.S. Pat. No. 5,502,427 includes a fuse cartridge coupled to a spring assembly positioned within a fuse tube. The fuse shown in U.S. Pat. No. 4,344,059 includes an arcing rod moving within a conductive fuse tube with the arcing rod being engaged by a catcher when the arcing rod moves during fuse operation so that the arcing rod will not bounce back or reverse direction during and after fuse operation. The catcher includes angled fingers that interact to capture a flange carried by the arcing rod. U.S. Pat. No. 4,058,784 illustrates an indicator-equipped fuse where the indicator that moves outside the casing of the fuse. The fuse in U.S. Pat. No. 4,296,397 is suited for a corrosive atmosphere so as to maintain a non-conductive path after operation.  
           [0006]    While the fusible elements of the prior art may be generally suitable for their intended uses, they do not provide a compact fuse for use in unusual environments and including an operation indicator.  
         SUMMARY OF THE INVENTION  
         [0007]    Accordingly, it is a principal object of the present invention to provide a fuse suitable for operation in unusual environments and including an operation indicator.  
           [0008]    These and other objects of the present invention are efficiently achieved by a fuse that is suitable for operation in unusual environments and includes an operation indicator that is simple and reliable. A movable arcing tube is released during operation. As the arcing tube moves outside the fuse assembly, a latching spring moves into a receiving groove in the arcing tube to retain the arcing tube in the external operated position. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0009]    The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the specification taken in conjunction with the accompanying drawing in which:  
         [0010]    [0010]FIG. 1 is an elevational view, partly in section, of a fuse in accordance with the present invention;  
         [0011]    [0011]FIG. 2 is a sectional view of a fuse link assembly of the fuse of FIG. 1;  
         [0012]    [0012]FIG. 3 is an elevational view of an arcing tube of the fuse link assembly of FIG. 2;  
         [0013]    [0013]FIG. 4 is an elevational view of a lower terminal of the fuse link assembly of FIG. 2;  
         [0014]    [0014]FIG. 5 is an enlarged partial view of the lower terminal of FIG. 4; and  
         [0015]    [0015]FIG. 6 is an elevational view of a latching spring member of the fuse of FIG. 1. 
     
    
     DETAILED DESCRIPTION  
       [0016]    Referring now to FIGS.  1 - 6 , a fuse  10  in accordance with the present invention includes a fuse link assembly  12  (also see FIG. 2) carried within an outer tube  14  and supported with respect to an electrode mounting assembly  16 . The outer tube provides a dielectric and physical barrier to the operating environment external to the fuse link assembly  12 . The electrode mounting assembly  16  provides electrical connection to an arcing tube  18  of the fuse link assembly  12  that is slidably received within the electrode mounting assembly  16 . The electrode mounting assembly  16  also forms an upper terminal for connection to an electrical system. A lower terminal  20  of the fuse link assembly  12  provides electrical connection to protected equipment (not shown) via a contact  23 , similar to that as shown in U.S. Pat. No. 5,502,427. A strain wire  22  provides a mechanical and electrical connection between the arcing tube or upper terminal  18  and the lower terminal  20 , the strain wire  22  also functioning as a fusible element to provide the fusing characteristics of the fuse  10 . The strain wire  22  is retained at a lower end to the lower terminal  20  at  25  and to the arcing tube  18  at an upper end at  27 , e.g. via a swaging operation or the like. The arcing tube  18  is secured with respect to the electrode mounting assembly  16  via an upper housing element  24  and a retaining element  26  that is affixed to the upper end of the arcing tube, e.g. in a specific embodiment, the retaining element  26  is a pop rivet. In a specific embodiment, a sealing compound is applied between the upper housing element  24  and the retaining element  26 . The upper housing element  24  is movable with respect to the electrode mounting assembly  16  and may also be characterized as a portion of the fuse link assembly. A spring  28  is disposed about the arcing tube  18  and within the upper housing element  24 , operating against the electrode mounting assembly  16 . Normally, the spring  28  is in compression. When the current between the electrode mounting assembly  16  and the lower terminal  20  and through the fuse link assembly  12  exceeds a predetermined current, the stain wire  22  becomes disintegral and the spring  28  is released thereby separating the arcing tube  18  and the lower terminal  20  of the fuse link assembly  12  and interrupting the current therethrough.  
         [0017]    In accordance with important aspects of the present invention, the fuse  10  is includes an operation indication facility also characterized as a blown-fuse indicator. Specifically, upon operation of the fuse  10 , the arcing tube  18  moves to the right in FIG. 1 with respect to the electrode mounting assembly  16  and is held in a predetermined operating position. To achieve this end, the arcing tube  18  includes a circumferential recessed portion or groove at  30  and a latching spring  35  (best seen in FIG. 6) that is positioned within a bore  17  of a cylindrical housing portion  19  of the electrode mounting assembly  16 . A retaining washer  34  is also provided along with an elastomeric sealing gasket  32  intermediate the latching spring  35  and the outer end of the bore  17 . Thus, when the arcing tube  18  moves to the right in FIG. 1, the latching spring  32  moves into the groove  30  whereat and whereupon the arcing tube  18  is retained providing a blown fuse indication position. The upper housing element  24  moves with the arcing tube  18  during operation. To this end, a sealing element  36  is provided intermediate the upper housing element  24  and the electrode mounting assembly  16 . During normal conditions, the seal is maintained via the tension in the spring  28 . The outer tube  14  is retained and sealed at the lower end with respect to the lower terminal  20  via the provision of an O-ring sealing element  40  carried within a groove  44  of the lower terminal  20  along with a support washer  42  that is retained by a snap ring  45  carried within a groove  46  of the lower terminal  20  (best seen in FIG. 5.  
         [0018]    While there has been illustrated and described a preferred embodiment of the present invention, it will be apparent that various changes and modifications will occur to those skilled in the art. Accordingly, it is intended in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the present invention.