Abstract:
A mounting bracket for mounting a high voltage surge arrester to a power distribution system including a main body with a first end securable to the high voltage surge arrester and an opposite second end securable to a power distribution system bracket and a plurality of laterally extending weathersheds located between the first and second ends, the second end including a fastening hole that receives a fastener for attaching the second end to the power distribution system bracket, and the main body being formed of polymer plastic blend.

Description:
RELATED APPLICATIONS  
       [0001]    The application is a divisional of U.S. patent application Ser. No. 09/984,175 to John A. Krause et al. entitled Unitary Arrester Housing And Support Bracket, filed on Oct. 29, 2001, the subject matter is hereby incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention generally relates to a support bracket for a surge arrester formed of a material sufficiently rigid to support the arrester on a pole bracket and flexible enough to avoid damage to the arrester.  
         BACKGROUND OF THE INVENTION  
         [0003]    A surge arrester is a protective device for power distribution systems. In particular, a surge arrester directs any over current in the system to ground. Conventional surge arresters include a current path to ground through resistance or varistor elements that dissipate the surge in current without damage to the utility line equipment.  
           [0004]    During a catastrophic failure, the arrester can no longer perform its function and must be removed from the system. To accomplish removal of the arrester, disconnectors are provided within the arrester, such as an explosive charge, to permanently separate the ground line from the arrester. A weakened or thinner section of the arrester directs the explosion at the physical connection of the arrester and the ground line.  
           [0005]    Conventional arresters are mounted to a utility pole of the power distribution system by a standard NEMA bracket recommended by the National Electrical Manufactures Association attached to the utility pole. In particular, conventional arresters include separate rigid support brackets coupled to the arresters that mate with the NEMA bracket of the utility pole. The support brackets are generally formed separately and are made of a different material, such as polyester, than the housing of the arrester, thereby increasing costs and assembly time. Also, the support brackets of conventional arresters are easily damaged in both shipment and handling by utility lineman.  
           [0006]    Examples of conventional arresters include U.S. Pat. No. 5,406,033 to Pazdirek; U.S. Pat. No. 5,434,550 to Putt; U.S. Pat. No. 4,609,902 to Lenk; and U.S. Pat. No. 4,972,291 to Cunningham.  
         SUMMARY OF THE INVENTION  
         [0007]    Accordingly, an object of the present invention is to provide an arrester than includes a unitary housing and support bracket.  
           [0008]    Another object of the present invention is to provide an arrester that is easily assembled.  
           [0009]    Yet another object of the present invention is to provide an arrester having a housing and support bracket formed of a material sufficiently rigid to support the arrester on a pole bracket and flexible enough to prevent damage to the arrester during shipping and handling of the arrester.  
           [0010]    The foregoing objects are basically attained by an arrester comprising a dielectric housing that includes a body portion that has a substantially cylindrical wall with opposing first and second ends that form inner cavity therebetween. A support mounting bracket portion is formed as a unitary, one-piece extension of the body portion and extends laterally from the second end. The housing has sufficient rigidity to maintain the bracket portion in a position substantially perpendicular to the body portion. At least one varistor element is received in the inner cavity of the housing.  
           [0011]    The foregoing objects are also attained by a method of making an arrester that has a dielectric housing that receives a plurality of varistor elements. The method comprises the steps of placing the plurality of varistor elements between first and second electrically conductive end terminals to form a block assembly, and molding the housing of the arrester around the block assembly so that the block assembly is received in a body portion of the housing and a support mounting bracket portion is formed as a unitary one-piece extension of the body portion.  
           [0012]    The foregoing objects are also attained by a mounting bracket for mounting a high voltage surge arrester to a power distribution system including a main body with a first end securable to the high voltage surge arrester and an opposite second end securable to a power distribution system bracket and a plurality of laterally extending weathersheds located between the first and second ends, the second end including a fastening hole that receives a fastener for attaching the second end to the power distribution system bracket, and the main body being formed of polymer plastic blend.  
           [0013]    By fashioning the arrester in the above manner, the arrester can be manufactured faster and with less cost, and damage to the arrester due to shipping an handling is largely reduced.  
           [0014]    Other objects, advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with annexed drawings, discloses the preferred embodiments of the present invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    Referring to the drawings which form a part of this disclosure:  
         [0016]    [0016]FIG. 1 is a side elevational view of an arrester in accordance with a first embodiment of the present invention, showing the arrester mounted to a utility pole bracket;  
         [0017]    [0017]FIG. 2 is a side elevational view in section of the arrester illustrated in FIG. 1;  
         [0018]    [0018]FIG. 3 is a top plan view of the arrester illustrated in FIG. 1, with a first conductive terminal connected to the arrester removed; and  
         [0019]    [0019]FIG. 4 is a side elevational view in cross section of an arrester in accordance with a second embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    Referring to FIGS.  1 - 3 , an arrester  10  in accordance with an embodiment of the present invention generally includes a housing  12  that receives a varistor block assembly  14 . Arrester  10  is mountable to a utility pole of a power distribution system by a standard NEMA bracket  16 , and provides protection for the system against over current, as is well known in the art. Block assembly  14  is electrically connectable to the power distribution system via first and second conductive terminals  18  and  20 .  
         [0021]    Housing  12  of arrester  10  includes a body portion  22  and a support mounting bracket portion  24  that extends from body portion  22 , as seen in FIG. 1. Body portion  22  and bracket portion  24  form a one-piece unitary housing or member. A one-piece unitary member is defined as a single piece without a discernible dividing line, and does not include any portion that is separately formed and then attached to the member. Body portion  22  receives block assembly  14  and bracket portion  24  supports arrester  10  with respect to pole bracket  16 .  
         [0022]    One-piece unitary housing  12  is made of a dielectric plastic polymer blend capable of sustaining a mechanical load. Some examples of a plastic polymer blend include polypropylene, polyethylene, acrylate polymers, vinyl acetate, epoxy, and rubber plastic bends. The plastic polymer blend of housing  12  is described in detail in commonly assigned U.S. Pat. No. 6,031,186 to Sakich et al., the subject matter of which is hereby incorporated by reference, including details of the examplary plastic polymer composites. Housing  12  has sufficient rigidity to maintain bracket portion  24  in a substantially perpendicular position with respect to body portion  22  so that arrester  10  is substantially upright when mounted to pole bracket  16  via support bracket portion  24 , as seen in FIG. 1. Housing  12  also has some flexibility that allows bracket portion  24  to slightly move or bend with respect to body portion  22 . This flexibility assists in preventing damage to arrester  10  during shipping and handling, particularly damage to bracket portion  24 .  
         [0023]    As seen in FIG. 2, body portion  22  of housing  12  generally includes a cylindrical wall  26  with opposing first and second ends  28  and  30  forming an inner cavity  32  therebetween for receiving block assembly  14  and defines a central longitudinal axis  34 . First end  28  is near first conductive terminal  18  and is open to provide access to inner cavity  32 . Second end  30  is unitary with bracket portion  24  and near second conductive terminal  20 . A cavity  36  for receiving an explosive charge  38  is located in second end  30  between inner cavity  32  and second conductive terminal  20 . Explosive charge  38  isolates arrester  10  during a catastrophic failure, as is well known in the art. A plurality of weather sheds  40  extend from an outer surface  42  of cylindrical wall  26 , as is well known in the art. Although weather sheds  40  are preferably used, they are not required. Additionally, a weakened or thinner section  41  of arrester housing  12  is located at second end  30  near explosive charge  38  to provide a directed pressure relief during a failure, as is well known in the art.  
         [0024]    Bracket portion  24  extends laterally from second end  30  of body portion  22  and defines a longitudinal axis  44 , as seen in FIG. 2. Longitudinal axis  44  is substantially perpendicular to longitudinal axis  34  of body portion  22 . Bracket portion  24  includes a generally cylindrical main section  46  extending from body portion  22  and a generally flat section  48  at a distal end  50  of bracket portion  24 . Although main section  46  is preferably cylindrical, main section  46  can be any structural shape, such as square, T-shaped, or U-shaped. The size and thickness of section  48  is determined by the strength required to support arrester  10  on pole bracket  16 . Weather sheds  52  are preferably employed which extend from tubular section  46 , but are not required.  
         [0025]    Flat section  48  includes a securing surface  54  that engages pole bracket  16 . Specifically, securing surface  54  includes a fastening hole  56  disposed within flat section  48  that receives a fastener  58 , as seen in FIGS. 1 and 2. Fastener  58 , such as a screw, extends through a hole (not shown) of pole bracket  16  and through fastening hole  56  of flat section  48  with a nut  60  therebetween, thereby releasably mounting arrester  10  via bracket portion  24  to pole bracket  16 . Although bracket portion  24  is preferably coupled with pole by a fastener and fastening hole arrangement, any known attachment can be used to secure bracket portion  24  of arrester  10  to bracket  16 .  
         [0026]    The varistor block assembly  14  received in arrester housing  12 , generally includes conventional varistor elements or MOV blocks  62  stacked and compressed between first and second conductive end terminals  64  and  66 , as best seen in FIG. 2. Varistor elements  62  are electrically connected to first and second conductive terminals  18  and  20 , respectively, via first and second end terminals  64  and  66 , respectively, as is well known in the art. End terminals  64  and  66  can alternatively be plastic with a direct electrical connection being between conductive terminals  18  and  20 , respectively, and block assembly  14 . This would require a hole (not shown) in each end terminal  64  and  66  to allow terminals  18  and  20 , respectively, to extend therethrough and contact block assembly  14 . Although two varistor elements are shown, more or less varistor elements can be employed.  
         [0027]    Varistor elements  62  are compressed together by rigid members or rods  68 , as best seen in FIG. 2. Compression of varistor elements  62  ensures a good electrical connection between first and second conductive terminals  18  and  20  through block assembly  14 . Rods  68  extend between first and second end terminals  64  and  66 , as seen in FIG. 2, and are received in slots  70  of each end terminal, as seen in FIG. 3. Rods  68  are fixed to end terminals  64  and  68  by any known attachment such as wire ties or crimping. Rods  68  are preferably fiberglass rods but can be any rigid member. Although four rods  68  are shown in FIG. 3, any number of rods can be used, such as less than or greater than four. Conventional Belleville springs (not shown) can also be located between varistor elements  62  and each end terminal  64  and  66 , respectively, to provide additional compression on varistor elements  62 .  
         [0028]    Assembly  
         [0029]    Arrester  10  can be assembled by two different methods. The first method initially requires assembly of block assembly  14  by stacking varistor elements  62  between first and second end terminals  64  and  66 , as is well known in the art. To complete the assembly of block assembly  14 , rods  68  are placed between end terminals  64  and  66  and beside the stacked varistor elements  62  so that the ends of rods  68  extend through slots  70  of each end terminal  64  and  66 . Compression force is then applied to end terminals  64  and  66  and varistor elements  62  through rods  68 . Once compression is complete, the ends of rods  68  can be cut off to be generally flush with each end terminal  64  and  66 , respectively.  
         [0030]    Once block assembly  14  has been assembled, it is placed in a mold for arrester housing  12 . Explosive charge  38  is also placed in the mold. Housing  12  can then be molded around block assembly  14  so that cylindrical wall  26  of body portion  22  surrounds block assembly  14  and first end terminal  64  of block assembly  14  closes off the open or first end  28  of body portion  22 , as seen in FIG. 2. Also, second end  30  surrounds explosive charge  38 . First conductive terminal  18  is connected to first end terminal  64  of block assembly  14  and second conductive terminal  20  extends into housing second end  30  and connects to second end terminal  66  with explosive charge  38  located therebetween.  
         [0031]    The second method of assembling arrester  10  initially requires molding arrester housing  12 . This is accomplished by placing a core mandrel (not shown) having the approximate size of block assembly  14  within the mold for housing  12 . End terminal  66  and rods  68  of block assembly  14  are also placed in the mold with the core mandrel. Housing  12  can then be molded around the core mandrel, end terminal  66  and rods  68  extending through slots  70  of terminal  66  with cylindrical wall  26  of body portion  22  surrounding the core mandrel end terminal  66  and rods  68 . Once housing  12  is molded, the core mandrel is removed, thereby exposing inner cavity  32  of body portion  22 .  
         [0032]    Varistor elements  62  of block assembly  14  are then placed into inner cavity  32  through open end  28  of body portion  22  by first placing explosive charge  38  within cavity  32 , and stacking varistor elements  62  on top of charge  38  and second end terminal  66 . First end terminal  64  is placed on top of the stacked varistor elements  62  so that the ends of rods  68  extend through slots  70  of first end terminal  54 . A compressive force is then applied to first end terminal  64 , varistor elements  62 , and second end terminal  66 , through rods  68 . The ends of rods  68  can then be cut off to be generally flush with first end terminal  64 . First and second conductive terminals  18  and  20  can then be connected to block assembly  14  in the same manner as described above with respect to the first method of assembly.  
         [0033]    Mounting arrester  10  to a utility pole requires coupling bracket portion  24  of arrester housing  12  with pole bracket  16  by inserting fastener  58  through a fastening hole of pole bracket  16  and through fastening hole  56  of bracket portion  24 , and employing nut  60  for tightening fastener  58 , thereby releasably mounting arrester  10  to the utility pole.  
         [0034]    Embodiment of FIG. 4  
         [0035]    Arrester  110  in accordance with a second embodiment of the present invention is the same as arrester  10 , except for the addition of a rigid member  180  in the bracket portion  124  of arrester  110 .  
         [0036]    Like arrester  10 , arrester  110  includes a housing  112  that has a body portion  122  and a support mounting bracket portion  124  that extends from body portion  122 . Body portion  122  and bracket portion  124  form a one-piece unitary housing in the same manner as described above with respect to housing  12  of arrester  10 . Body portion  122  receives block assembly  114  and bracket portion  124  supports arrester  110  with respect to pole bracket  16  (not shown in FIG. 4).  
         [0037]    Body portion  122  of housing  112  generally includes a cylindrical wall  126  with opposing first and second ends  128  and  130  forming an inner cavity  132  therebetween for receiving block assembly  114  and defines a central longitudinal axis  134 . First end  128  is near first conductive terminal  118  and is open to provide access to inner cavity  132 . Second end  130  is unitary with bracket portion  124  and near second conductive terminal  120 . A cavity  136  for receiving an explosive charge  138  is located in second end  130  between inner cavity  132  and second conductive terminal  120 . A plurality of weather sheds  140  extend from an outer surface  142  of cylindrical wall  126 , as is well known in the art. Although weather sheds  140  are preferably used, they are not necessary.  
         [0038]    Bracket portion  124  extends laterally from second end  130  of body portion  122  and defines a longitudinal axis  144 . Longitudinal axis  144  is substantially perpendicular to longitudinal axis  134  of body portion  122 . Like bracket portion  24  of arrester  10 , bracket portion  124  includes a generally cylindrical main section  146  extending from body portion  122  and a generally flat section  148  at a distal end  150  of bracket portion  124 . Although main section  146  is preferably cylindrical, main section  146  can be any structural shape, such as square, T-shape, or U-shaped. The size and thickness of section  148  is determined by the strength required to support arrester  110  on pole bracket  16 . Weather sheds  152  can be employed which extend from tubular section  46 , but are not required. Flat section  148  includes a securing surface  154  that engages pole bracket  16 . Specifically, securing surface  154  includes a fastening hole  156  disposed within flat section  148  that receives a fastener.  
         [0039]    Rigid member  180  is located within bracket portion  124  to provide rigidity thereto. Rigid member  180  is preferably a thermo set plastic rod but can be any rigid material, such as fiberglass. Member  180  extends along substantially the entire length of bracket portion  124  between block assembly  114  and the distal end  150  of bracket portion  124  and defines a central longitudinal axis  182  that is co-axial with longitudinal axis  144  of bracket portion  124 . A fastening hole  184  is located in the end  186  of rigid member  180  and aligns with fastening hole  156  of bracket portion  124  so that the fastener can extend through both bracket portion  124  and rigid member  180 . Arrester  110  can then be mounted to pole bracket  16  in the same manner as described above with respect to arrester  10 .  
         [0040]    Varistor block assembly  114  is the same as block assembly  14  and therefore will not be described. Additionally, arrester  110  is assembled in the same manner as described above for arrester  10  except rigid member  180  is placed in the housing mold prior to molding housing  112  so that bracket portion  124  surrounds rigid member  180 .  
         [0041]    While particular embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.