Abstract:
A line guard is configured so as to have a very large air gap with a small overall physical size of the device. Opposed interleaved sets of plural insulating leaves are formed along a discontinuity extending along the length of the line guard so as to greatly extend the length of the air gap. This air gap structure allows the overall size of the line guard to be small thus providing advantages of reduced weight, ease of handling, and ease of storage. A two piece coupler apparatus is provided for joining adjacent line guards in a way that is both flexible and provides sufficient dielectric to operate at high voltages in a small package.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 60/740 343, filed Nov. 29, 2005, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to devices that protect workers from contact with electrically energized conductors. More specifically, the present invention relates to an insulating cover that encloses an energized conductor to provide protection from contact with the conductor, thus protecting linemen or other workmen from accidental contact with energized electrical conductors. 
       BACKGROUND OF THE INVENTION 
       [0003]    Protective covers for power lines, commonly referred to as “line guards” have been used by linemen working in the vicinity of energized electrical conductors to cover the nearby conductors and associated hardware, such as insulators on which the conductors are mounted, to prevent workers or equipment from accidentally coming into contact with energized conductors. Such contact would clearly be hazardous causing shock and possibly death. These protective covers are typically formed of a dielectric material such as rubber, fiberglass, or plastic. The protective covers are generally used by being placed over the conductors and possibly associated insulators while the workmen are in the vicinity of the conductor. 
         [0004]    Some protective covers have been embodied as elongated tubes with spiral passage ways extending from the exterior of the tube to a central space within the tube sized to fit the conductor. For additional details of such protective covers, reference can be made to U.S. Pat. No. 4,628,145, U.S. Pat. No. 3,835,238, U.S. Pat. No. 2,770,667 and U.S. Pat. No. 2,871,282. 
         [0005]    Other protective covers have been embodied in the form of elongate structures that fold around an electrical conductor and snap together to enclose the conductor. For additionally details of such protective covers, reference can be made to U.S. Pat. No. 6,239,357 and U.S. Pat. No. 6,020,560. 
         [0006]    A problem with the protective covers that are available for use on high voltage conductors is that they are bulky or heavy. The protective covers made of rubber are quite heavy because of their large size that is dictated by the need for a large air gap. The protective covers made from other materials may not be as heavy as rubber ones, but they also rely upon a large air gap for insulation, and the large air gap makes the protective covers large and bulky. In either case, the protective covers are awkward to work with and place over or remove from the electrical conductors. Additionally, the bulky protective covers pose a storage challenge since they take up so much space when not in use. 
         [0007]    Thus, what is needed is a way to isolate energized conductors at high voltages (e.g., 25 kV) without need for a protective cover that is bulky or heavy. 
       SUMMARY OF THE INVENTION 
       [0008]    One aspect of the present invention is the use of plural interleaving dielectric leaves that provide a large air gap in a small overall package. 
         [0009]    Another aspect of the present invention is that it provides isolation from an energized conductor at high voltage without the protective tube being made of heavy rubber. 
         [0010]    Yet another aspect of the present invention is that it provides isolation from an energized conductor at high voltages without a protective tube needing to be bulky. 
         [0011]    By making the protective tube out of a lightweight plastic (for example, polyethylene) and using interleaving dielectric leaves to provide a large air gap, a number of advantages accrue. A protective cover embodied according to the present invention has a relatively small size, has low weight, and is easy to store since it is not bulky and takes up less space. 
         [0012]    A coupler is used to join together more than one such protective cover in series. The coupler is of a two piece construction with a first inner insulation barrier that has interleaving dielectric leaves like those of the protective cover. A second outer insulating barrier surrounds the first insulating barrier. The inner insulating barrier has a thinned portion providing a hinge for opening flexibility. The second outer insulating barrier covers the hinged portion of the inner barrier and provides a spring bias to help keep the dielectric leaves of the first barrier joined together in an interleaved relationship. 
         [0013]    Additional features and advantages of the present invention will become evident upon review of the following detailed description in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  illustrates a perspective view of the combination of an electric wire protective tube and a coupler apparatus according to embodiments of the present invention. 
           [0015]      FIG. 2  illustrates a cross sectional view of an electric wire protective tube according to embodiments of the present invention. 
           [0016]      FIG. 3  illustrates an end on elevational view of an electric wire protective tube according to embodiments of the present invention. 
           [0017]      FIG. 4  illustrates a detailed perspective view of one end of an electric wire protective tube according to embodiments of the present invention. 
           [0018]      FIG. 5  illustrates a bottom plan detail view of one end of an electric wire protective tube according to embodiments of the present invention. 
           [0019]      FIG. 6  illustrates an end on elevational view of a coupler apparatus according to embodiments of the present invention. 
           [0020]      FIG. 7  illustrates a side elevational view of a coupler apparatus according to an embodiment of the present invention. 
           [0021]      FIG. 8  illustrates a perspective view of a coupler apparatus according to an embodiment of the present invention. 
           [0022]      FIG. 9  illustrates a bottom plan detail view of one end of coupler apparatus according to embodiments of the present invention. 
           [0023]      FIG. 10  illustrates a cross sectional view of a coupler apparatus according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    When it is desired to isolate an energized conductor from possible contact with a worker, the conductor is wrapped within an insulating material. When the conductor is energized at great voltages, the thickness of the insulating material, or the air gap provided by the design of the material, must be of a commensurate large size. Although it is not a challenge to find a material that will insulate an energized conductor at 25 kV, it remains a challenge to provide an air gap of sufficient size. The air gap is useful in order to allow for the cover to be installed over and removed from the electric conductor without removing the electric conductor from its circuit. 
         [0025]    Rather than making the gap larger by making the part larger, as is done in conventional devices, the present invention makes the length of the air gap long by the use of overlapping dielectric leaves, so that the overall size of the protective tube (or “line shield”) could be maintained relatively small. This provides advantages in weight and required storage space. 
         [0026]    A coupler apparatus is useful to join together line guards in series with one another while maintaining their protective properties at the joint. According to the present invention, a two piece coupler configuration has been discovered that allows for sufficient flexibility for the coupler to be easily applied, while at that same time providing sufficient dielectric so as to provide shielding at high voltages, for example, at 25 kV. 
         [0027]    Referring to  FIG. 1 , a line guard  10  according to the present invention is shown in perspective in combination with a coupler  20  also according to the present invention. The line guard  10  and the coupler  20  are separable from one another, but are shown in a joined state. 
         [0028]    Referring to  FIG. 2 , a cross sectional view of a line guard according to the present invention is illustrated. An insulating tube  102  forms the main body of the line guard. A discontinuity  104  is formed along the entire length of the insulating tube  102 . The discontinuity  104  is formed in the insulating tube  102  for the purpose of permitting the insulating tube  102  to be placed over a conductive wire (not shown). 
         [0029]    A pair of mutually confronting insulating legs  106 ,  110  project radially outwardly from the insulating tube  102 . Plural planar leaves  108  extend from one insulating leg  106  toward the other insulating leg  110 . Plural planar leaves  112  extend from that insulating leg  110  to the opposed insulating leg  106 . These opposed sets of insulating leaves  108 ,  112  are arranged so as to interleave with one another, thereby providing an elongated air gap extending from the discontinuity  104  through the interstitial spaces between the leaves  108 ,  112  to the exterior of the line guard. The elongation of the air gap increases the withstand voltage of the line guard and creeping distance along the insulating leaves  108 ,  112  is increased. This reduces the risk of creeping discharge while maintaining a small overall device size. 
         [0030]    The insulating leaves  108 ,  112  protrude a relatively larger amount toward the outside and a relatively smaller amount toward the inside. This arrangement strikes a balance of provide for a long creeping distance while also making it easier to place the line guard over the electric wire. Although the invention may be alternatively embodied so as to have all the leaves  108 ,  112  protrude the same amount so as to provide for an even greater creeping distance, such a configuration has been found to be more difficult to place onto an electric wire. 
         [0031]    Adjacent each of the insulating legs  106 ,  110  is a respective insulating wall  114 ,  116 . The insulating walls  114 ,  116  extend from the outside of the insulating tube  102  so as to cover the joint where the insulating legs  106 ,  110  extend radially outward from the insulating tube  102 , and terminate so as to be touching the insulating legs  106 ,  110 . The insulating walls  114 ,  116  provide enhanced insulating strength due to the combination of an added thickness of insulating material and due to the cavity of air formed between the insulating walls  114 ,  116 , the insulating tube  102 , and the insulating legs  106 ,  110 . 
         [0032]    Referring to  FIG. 3 , an end on elevational view of a line guard  10  according to the present invention is illustrated. The discontinuity  104  is shown as extending all the way to the end of the line guard  10 . The insulating legs  106 ,  110  and the insulating walls  114 ,  116  are shown where they end at the end of the insulating tube  102  (refer to  FIG. 2 ). The insulating walls  114 ,  116  contact the sides of the insulating legs  106 ,  110  and the spaces therebetween are exposed to view from this end on view. A flange  118  is disposed at the end of the line guard  10  and is adapted to fit into a coupler according to the present invention to connect with the coupler and indirectly with an adjacent line guard. Likewise, a flange  120  (refer to  FIG. 4 ) is disposed at the opposite end of the line guard  10 , adapted to the same purpose. 
         [0033]    Referring to  FIG. 4 , a detail perspective view of an end of a line guard according to the present invention is illustrated. The insulating tube  102  can be seen as extending toward the end and terminating with a flange  120 . The flange  120  is provided for interconnection with a coupler according to the present invention. An outer edge  122  of the flange  120  is beveled to enhance ease of insertion of the line guard into a coupler. The discontinuity  104  is shown as extending all the way to the end of the line guard. The insulating legs  106 ,  110  and the insulating walls  114 ,  116  are shown as extending outwardly from the exterior of the insulating tube  102  and extending along the insulating tube  102  all the way to its end. The insulating leaves  108 ,  112  are shown as extending toward the respective opposed insulating legs  106 ,  110  so as to interleave with one another. 
         [0034]    An optional feature of the line guard is to form the insulating tube  102  in two layers having preferably contrasting colors. The boundary of these two layers is indicated in  FIG. 4  by the phantom line on the end face of the line guard. The material of the layers is the same (e.g., polyethylene) so as to provide consistent insulating properties, but the different colored layers act as a wear indicator. If either layer is worn away to the extent that the contrasting color of the other layer shows through, this acts as a visual indication that enough wear has occurred sufficient to compromise the protective properties of the line guard. The user would then know to take the line guard out of service due to the excessive wear bringing about a potentially unsafe condition. 
         [0035]    Referring to  FIG. 5 , a bottom plan detail view is illustrated of one end of a line guard according to embodiments of the present invention. The end of insulating tube  102  ending at flange  120  is shown. According to the illustrated embodiment, the leaves  108 ,  112  are shaped at the ends so as to form a “V” profile gap  124  as viewed from the bottom of the line guard. The leaves  108 ,  112  have a like gap (not shown) formed at the other end of the line guard. These V profile gaps at the extreme ends of the insulating leaves  108 ,  112  facilitate the line guard being placed over an electrical conductor by reducing the amount of effort necessary to initiate insertion of the electrical conductor into the line guard. 
         [0036]    Referring to  FIG. 6 , an end on elevation view of a coupler apparatus according to the present invention is illustrated. The coupler  20  has an inner insulating cover base  210  surrounded by an insulating outer cover  230 . The cover base  210  has a gap  212  at its apex which enhances the flexibility of the coupler in opening up to engage with the juxtaposed ends of adjacent line guards. Additionally, the cover base  210  has a flared flange  214  that also aids in engaging the coupler  20  with the end of a line guard. This flared profile at the end of the coupler  20  facilitates the coupler  20  being placed over an end of a line guard by reducing the amount of effort necessary to initiate insertion of the line guard into the coupler  20 . 
         [0037]    The cover base  210  has a pair of insulating closing bodies  216 ,  218  that extend outwardly from the cover base  210  and converge toward one another in an opposed manner. Plural insulating leaves  220  extend from one closing body  216  toward the opposed closing body  218 . Likewise, plural insulating leaves  222  extend from that closing body  218  toward the other closing body  216 . The plural leaves  220 ,  222  are arranged so as to interleave with one another and thus, provide a long air gap from the interior of the coupler through the interstitial spaces between the leaves  220 ,  222  to the outside of the coupler  20 . As with the insulating leaves  108 ,  112  of the line guard  10 , the insulating leaves  220 ,  222  of the coupler  20  increase the withstand voltage and the creeping distance via the elongated air gap. Optionally, the insulating leaves  108 ,  112 ,  202 ,  222  of the line guard  10  and the coupler  20  can be formed having a tapered shape to make it easy for the respective leaves to be fit together. 
         [0038]    The outer cover  230  provides additional insulation over the hinge structure (not shown) of the cover base  210  and provides a spring bias that pushes the closing bodies  216 ,  218  toward one another. 
         [0039]    Referring to  FIG. 7 , a side elevational view of the coupler apparatus according to the present invention is illustrated. The outer cover  230  is shown with the cover base  210  extending from its bottom side. The flared flange  214  of the cover base is shown on the left. On the right the phantom lines indicate where a line guard would extend from the coupler when connected thereto. 
         [0040]    Referring to  FIG. 8 , a perspective view of a coupler apparatus  20  according to the present invention is illustrated. The cover base  210  is shown with the pair of extending members  216 ,  218  extending downward and in an opposed manner to one another, with their opposed insulating leaves  220 ,  222  interleaving with one another. The flared flange  214  is shown with a hinge gap  212  provided for flexibility to enable engagement with a line guard. The outer cover  230  is shown extending around the top of the cover base  210 . 
         [0041]    When a line guard is inserted into the coupler  20 , the line guard and coupler are removably secured to one another by engagement of a flange  118 ,  120  (refer to  FIGS. 3 ,  4 ) on the end of the line guard with a recess  226  inside the coupler  20 . The end face of the line guard abuts a stop wall  228  that prevents insertion of the line guard past the point where the flange aligns with the recess. Another recess (not shown) is disposed on the other side of the stop wall  228  to removably secure a second line guard inserted into the coupler  20  from its other end in a like fashion. 
         [0042]    Raised beads  211  are provided on the interior surface of the cover base  210 . These raised beads  211  are shaped to provide contact with the exterior surface of an inserted line guard while reducing the contacting area between the flange  118  of the line guard and the coupler  211  to make it easier to insert the flange into the coupler. 
         [0043]    If it is desired to secure a line guard to a coupler in a more permanent fashion, the coupler and the line guard can be welded together where a protruding part of the coupler contacts the line guard. For example, sonic welding is a suitable way to permanently secure the coupler over an end of a line guard. 
         [0044]      FIG. 9  illustrates a bottom plan detail view of one end of coupler apparatus according to embodiments of the present invention. The end of the coupler having the flared flange  214  extending out of the outer cover  230  is shown. According to the illustrated embodiment, the leaves  220 ,  222  are shaped at the ends so as to form a “V” profile gap  225  as viewed from the bottom of the coupler. The leaves  220 ,  222  have a like gap (not shown) formed at the other end of the coupler. These V profile gaps at the opposite ends of the insulating leaves  220 ,  222  facilitate the coupler being placed over an electrical conductor by reducing the amount of effort necessary to initiate insertion of the electrical conductor into the coupler. 
         [0045]    Referring to  FIG. 10 , a cross sectional view of a coupler apparatus  20  according to the present invention is illustrated. The cover base  210  is shown with opposed ridges  220 ,  222  and a hinge  224  at its apex. Additionally a recessed portion  226  is shown for engagement with a flange, for example either of the flanges  118  (refer to  FIG. 3 ),  120  (refer to  FIG. 4 ) disposed at opposing ends of the line guard. The outer cover  230  is shown with a blister portion  232  to extend up and over the hinge structure  224  of the cover base  210 . The blister portion  232  provides additional insulation over the hinge structure  224 . The withstand voltage performance of the device is increased by providing a space between the cover base  210  and the outer cover  230 . 
         [0046]    The coupler apparatus  20  has a two piece configuration in order to make the creeping distance longer and to make shaping easier. Formation of the hinge  224  structure is easier if the cover base  210  is shaped so as to be open in a natural state. Placing the outer cover  230  over the cover base  210  accomplishes two things: it increases the withstand voltage about the hinge  224  and it provides opposed forces to close the cover base  210 . 
         [0047]    The outer cover  230  has circumferential ends  231  that elastically nip tapered faces of the cover base  210 . This leaves the outer cover  230  attached to the cover base  210  by contact of the ends  231  each contacting a step portion of the base  210 . This configuration of the outer cover  230  with respect to the cover base  210  provides for formation of the space therebetween discussed above and it is not necessary to otherwise fasten the outer cover  230  to the cover base  210  because once assembled to one another as an integrated coupler apparatus it becomes difficult to detach the outer cover  230  from the cover base  210 . Alternatively, the outer cover  230  is ultrasonically welded to the cover base  210  to affix them permanently to one another. 
         [0048]    Although polyethylene has been described as an example of a suitable material from which to form devices according to the present invention, any material having similar dielectric and plastic properties would be suitable for practicing the invention. 
         [0049]    Although the present invention has been described above in terms of exemplary embodiments, it will be understood by those of ordinary skill in the art that various modifications and improvements may be made with respect to the described embodiments without departing from the spirit and scope of the present invention.