Abstract:
A fuse system protects an electric fence box from lightning strikes that hit a fence connected to the electric fence box via the fuse system. The fuse system includes at least one fuse connecting an output terminal of the electric fence box to the electric fence and an optional second fuse connecting a ground terminal of the electric fence box to earth ground. Each fuse includes a filament at least 12 inches long inside a non-conductive tube (e.g., Mylar). A first lead connects a first end of the filament to the output terminal of the electric fence box, and a second lead connects a second end of the filament to the electric fence.

Description:
[0001]    A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the reproduction of the patent document or the patent disclosure, as it appears in the U.S. Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
       CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0002]    Not Applicable 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0003]    Not Applicable 
       REFERENCE TO SEQUENCE LISTING OR COMPUTER PROGRAM LISTING APPENDIX 
       [0004]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0005]    The present invention relates generally to electric fence charger (i.e., electric fence box) protection systems. More particularly, this invention pertains to protecting electric fence boxes from lightning. 
         [0006]    Electric fences are used by ranchers and farmers to keep animals in a designated area or out of a designated area. Electric fences include a first length of conductive material (i.e., the fencing) isolated from earth ground by insulators. The fence may also include a second length of conductive material connected to earth ground and spaced apart from the first length of conductive material. The first length of conductive material is connected to a first output of the electric fence box, and the second output of the electric fence box is connected to ground, and optionally to the second length of conductive material. The electric fence box is subject to damage from power line voltage spikes which can cause a surge in input current. Most electric fence boxes include fuses (e.g., round body 125V, 10 A fuses) to prevent over-current conditions from power line surges from damaging the fence box. The power surge burns out the filament in the fuse before the increased voltage and current can damage the electronics in the electric fence box. The largest standard fuses only have about 3 inches between contacts, but even a millimeter of separation between contacts is enough to prevent a 125V source from arcing between the contacts. The electric fence box is also subject to damage from lightning striking the fence. Lightning is a static charge that travels along the length of conductive material to the electric fence box. Lightning develops voltages much higher than 125V and can jump from one electrical contact to another across hundreds of feet. The 0.5″ to 1″ gap between the contacts in most standard fuses, and even the 3″ gap between contacts available in some industrial fuses is not enough to prevent arcing between the contacts. Lightning typically arcs between the contacts in electronic fence box fuses and destroys the fence box when the lightning strikes the electric fence charged by the electric fence box. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    Aspects of the present invention provide a fuse system that protects an electric fence box from lightning strikes that hit a fence connected to the electric fence box. A fuse includes a filament at least 12 inches long inside a non-conductive tube. The fuse connects the electric fence box to the electric fence. 
         [0008]    In one aspect, a fuse system for an electric fence system including an electric fence and an electric fence box includes a first fuse. The first fuse includes a tube, a filament, a first lead, and a second lead. The tube is generally electrically nonconductive. The filament is positioned within the tube. The filament has a first end and a second end opposite the first end. The filament is at least 12 inches long. The first lead is connected to the first end of the filament. The first lead is configured to connect to the electric fence box. The second lead is connected to the second end of the filament. The second lead is configured to connect to the electric fence. 
         [0009]    In another aspect, an electric fence charging system operable to charge electric fence includes an electric fence box and a fuse system. The electric fence box has an output terminal and a ground terminal. The fuse system includes a first fuse. The first fuse includes a tube, a filament, a first lead, and a second lead. The tube is generally electrically nonconductive. The filament is positioned within the tube. The filament has a first end and a second end opposite the first end. The filament is at least 12 inches long. The first lead is connected to the first end of the filament. The first lead is configured to connect to the electric fence box. The second lead is connected to the second end of the filament. The second lead is configured to connect to the electric fence. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0010]      FIG. 1  is a side perspective view of an electric fence and electric fence charging system including a pair of fuses. 
           [0011]      FIG. 2  is an isometric view of a pair of fuses. 
           [0012]      FIG. 3  is a longitudinal cross section of a fuse. 
           [0013]      FIG. 4  is a perspective view of a partially assembled fuse with a filament connected to a first lead. 
           [0014]      FIG. 5  is an isometric perspective view of a partially assembled fuse with a first lead inserted into a first end of a tube. 
           [0015]      FIG. 6  is a side perspective view of a fuse with a sealant sealing a joint between a first lead and a tube of the fuse. 
       
    
    
       [0016]    Reference will now be made in detail to optional embodiments of the invention, examples of which are illustrated in accompanying drawings. Whenever possible, the same reference numbers are used in the drawing and in the description referring to the same or like parts. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention. 
         [0018]    To facilitate the understanding of the embodiments described herein, a number of terms are defined below. The terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as “a,” “an,” and “the” are not intended to refer to only a singular entity, but rather include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as set forth in the claims. 
         [0019]    As described herein, an upright position is considered to be the position of apparatus components while in proper operation or in a natural resting position as described herein. Vertical, horizontal, above, below, side, top, bottom and other orientation terms are described with respect to this upright position during operation unless otherwise specified. The term “when” is used to specify orientation for relative positions of components, not as a temporal limitation of the claims or apparatus described and claimed herein unless otherwise specified. The terms “above”, “below”, “over”, and “under” mean “having an elevation or vertical height greater or lesser than” and are not intended to imply that one object or component is directly over or under another object or component. 
         [0020]    The phrase “in one embodiment,” as used herein does not necessarily refer to the same embodiment, although it may. Conditional language used herein, such as, among others, “can,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment. 
         [0021]    The terms “coupled” and “connected” mean at least either a direct electrical connection between the connected items or an indirect connection through one or more passive or active intermediary devices. 
         [0022]    Referring to  FIGS. 1-6 , an electric fence charging system is operable to charge an electric fence  118 . The electric fence charging system includes an electric fence box  102  and a fuse system. The electric fence box  102  includes a charge terminal  104  and a ground terminal  106 . The ground terminal  106  is operable to connect to earth ground, and the charge terminal  104  is operable to provide a static charge to the electric fence  118 . The fuse system includes a first fuse  108  and optionally, a second fuse  302 . In one embodiment, the first fuse  108  and the second fuse  302  have a similar construction. The electric fence  118  includes a ground line  120 , and optionally, a charge line  124 . The ground line  120  is connected to earth ground via an earth grounding spike  122 . The charge line  124  is connected to the output terminal  104  of the electric fence box  102 . The ground line  120  and the charge line  124  are separated by a first distance  130 . Alternatively, the electric fence  118  may include a charge line  124  without a ground line  120 . In this case, the second fuse  302  is configured to connect the grounding spike  122  to the ground terminal  106  of the electric fence box  102 . In one embodiment, the first fuse  108  is configured to connect between the electric fence  118  and the output terminal  104  of the electric fence box  102 . 
         [0023]    The first fuse  108  includes a tube  110 , a filament  112 , a first lead  114 , and a second lead  116  (see  FIG. 3 ). The tube  110  is generally electrically nonconductive. In one embodiment, the tube  110  is substantially formed from biaxially-oriented polyethylene terephthalate (e.g., Mylar), and the tube  110  is at least partially translucent (e.g., generally transparent). The tube  110  generally extends along a longitudinal axis. The tube  110  has a first end  318  and a second end  320  opposite the first end  318 . In one embodiment, the tube  110  is at least 12 inches long, and in some embodiments the tube  110  is approximately 24 inches long. 
         [0024]    The filament  112  is positioned within the tube  110  the filament  112  has a first end  304  and a second end  306  opposite the first end  304 . The filament  112  is at least 12 inches long. In one embodiment, the filament  112  is approximately 24 inches long. In one embodiment, the filament  112  is bare copper wire with the gauge of approximately 33 American Wire Gauge (AWG) (e.g., a nominal diameter of approximately 0.0071 inches). 
         [0025]    The first lead  114  is connected to the first end  304  of the filament  112 . In one embodiment, the first end  304  of the filament  112  is connected to a wire  316  of the first lead  114  by wrapping the filament  112  around an exposed portion of the wire  316  at the end  322  of the first lead  114  and dipping the exposed end of the wire  316  of the first lead  114  into a solder bath (see  FIG. 4 ). The first lead  114  is configured to connect to the electric fence box  102 . In one embodiment, the first lead  114  is insulated wire, the wire  316  is at least 16 gauge, and the insulation  308  is rated for at least 1000 volts. An end  322  of the first lead  114  is inserted into the tube  110  at the first end  318  of the tube  110  such that the insulation  308  of the first lead  114  extends into the tube  110  (see  FIGS. 3 and 5 ). 
         [0026]    The second lead  116  is connected to the second end  306  of the filament  112 . In one embodiment, the second end  306  of the filament  112  is connected to a wire  314  of the second lead  116  by wrapping the filament  112  around an exposed portion of the wire  314  at the end  324  of the second lead  116  and dipping the exposed end of the wire  314  of the second lead  116  into a solder bath (see  FIG. 4 ). The second lead  116  is configured to connect to the electric fence  118  (e.g., a charge line  124  of the electric fence  118 ). In one embodiment, the second lead  116  is insulated wire, the wire  314  is at least 16 gauge, and the insulation  310  is rated for at least 1000 volts. An end  324  of the second lead  116  is inserted into the tube  110  at the second end  320  of the tube  110  such that insulation  310  of the second lead  116  extends into the tube  110  (see  FIGS. 3 and 5 ). 
         [0027]    As discussed above, the tube  110  extends along a longitudinal axis (see  FIG. 3 ). In one embodiment, a second distance  340  along the longitudinal axis between the end  322  of the wire  316  of the first lead  114  and the end  306  and the end  324  of the wire  314  of the second lead  116  is at least 12 inches. In another embodiment, the second distance is approximately 24 inches. In yet another embodiment, the second distance is selected to be greater than the first distance  130  (i.e., the distance between the charge line  124  and the ground line  120  of the electric fence  118 ). The higher than air resistance of the tube  110  combined with the distance  340  between the ends of the first lead  114  and second lead  116  inside the tube  110  causes the resistance across the fuse  108 ,  302  to be greater than the air resistance between the ground line  120  and the charge line  124  such that lightning arcs between the fence lines and/or through free air instead of through the electric fence box  102 . 
         [0028]    In one embodiment, the first fuse  108  further includes a first sealant  330 , and a second sealant  332 . The first sealant  330  seals water (and generally air) out from a joint between the first lead  114  and the tube  110 . The second sealant  332  seals water (and generally air) out from a joint between the second lead  116  and the tube  110 . In one embodiment, the first sealant  330  and the second sealant  332  are sections of heat shrink tubing placed over the end of the tube  110  and a portion of the corresponding lead and set with a heat gun (see  FIG. 6 ). 
         [0029]    Although described herein in the context of a first fuse  108  connecting between the electric fence  118  and the electric fence box  102  and a second fuse  302  connecting between the electric fence box  102  and the grounding spike  122 , it is contemplated that sufficient protection from lightning strikes for the electric fence box  102  may be achieved by use of either or both fuses at the same time. That is, the first fuse  108  may be used without the second fuse  302 , or the second fuse  302  may be used without the first fuse  108  while still providing sufficient protection for the electric fence box  102 . Further, because the first fuse  108  and the second fuse  302  have a substantially similar construction (e.g., they are generally intended to be identical), it is contemplated within the scope of the claims that the first fuse may be connected between the electric fence  118  and charge terminal  104  of the electric fence box  102  or between the grounding spike  122  and the ground terminal  106  of the electric fence box  102 . Similarly, the second fuse  302  may be connected between the electric fence  118  and charge terminal  104  of the electric fence box  102  or between the grounding spike  122  and the ground terminal  106  of the electric fence box  102 . That is, the first fuse  108  and the second fuse  302  are generally interchangeable. 
         [0030]    This written description uses examples to disclose the invention and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 
         [0031]    It will be understood that the particular embodiments described herein are shown by way of illustration and not as limitations of the invention. The principal features of this invention may be employed in various embodiments without departing from the scope of the invention. Those of ordinary skill in the art will recognize numerous equivalents to the specific procedures described herein. Such equivalents are considered to be within the scope of this invention and are covered by the claims. 
         [0032]    All of the compositions and/or methods disclosed and claimed herein may be made and/or executed without undue experimentation in light of the present disclosure. While the compositions and methods of this invention have been described in terms of the embodiments included herein, it will be apparent to those of ordinary skill in the art that variations may be applied to the compositions and/or methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit, and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope, and concept of the invention as defined by the appended claims. 
         [0033]    Thus, although there have been described particular embodiments of the present invention of a new and useful ELECTRIC FENCE BOX FUSE it is not intended that such references be construed as limitations upon the scope of this invention except as set forth in the following claims.