Abstract:
A support assembly for supporting a high voltage electrical conductor suspended from a lattice-type tower during maintenance and repair includes a pair of elongate support arms, each of the support arms having an aperture extending therethrough intermediate its ends, the aperture opening in a direction transverse to the length of the support arms, and an elongate conductor support bar slidably received in the apertures of the support arms and extending between the support arms to define with the support arms a generally H-shaped support assembly, the support arms being slidable on the support bar for adjusting the distance between the arms and being movable on the support bar between a first position wherein the arms are parallel to each other and a second position wherein the arms are arranged at an angle to each other.

Description:
FIELD OF THE INVENTION 
   The present invention relates to support assemblies for high voltage electrical conductors and, more particularly, to a support assembly for supporting an electrical conductor during insulator replacement on lattice-type towers. 
   BACKGROUND OF THE INVENTION 
   High voltage power transmission lines carrying voltages in the hundreds of kilowatt range have been constructed to extend from spaced towers or poles in terrain which is often practically inaccessible to land vehicles. In recent years, a number of methods and devices have been developed to facilitate the repair and maintenance of high voltage power transmission lines which are accessed by helicopter. 
   Lattice-type towers are employed for supporting multiple high voltage electrical conductors. The conductors are typically supported under the arms or bridges of such towers using a pair of suspension insulators per conductor. Periodically, it is necessary to replace the insulators because they are visibly damaged or as part of a general maintenance plan. Typically, insulators are attached via pins to the towers and via pins to a yoke plate which supports the conductor. These pins must be manually removed by linemen placed on the tower via helicopter in order to replace the insulators. Damaged or worn insulators are removed from the tower via helicopter and replacement insulators are delivered to the tower via helicopter. It will be appreciated that high voltage electrical conductors are extremely heavy and their great weight hanging from the end of an insulator makes it impossible to unpin and remove the insulator without first creating slack in the insulator. To accomplish this the conductor must be supported in some fashion during insulator removal and replacement. In the past, lineman have improvised temporary rigging to support the conductors. For example, multiple chain hoists have been used which are supported via multiple nylon slings at multiple spaced locations along tower girders. Such improvisation requires large amounts of equipment, is time consuming and fails to adequately distribute the weight of a supported conductor over a large area of the tower structure. 
   Accordingly, there exists a need for a device which may be safely emplaced on a tower via helicopter, which is light enough to be handled by a lineman on a tower, which is strong enough to support a heavy electrical conductor, which will be stable on a structure such as a lattice-type tower and which will distribute the weight of a supported conductor over the tower structure. 
   SUMMARY OF THE INVENTION 
   It is, therefore, a primary object of the present invention to provide a novel and improved conductor support assembly which can be safely handled and used on a lattice-type tower by lineman emplaced on the tower by a helicopter. 
   It is also an object of the present invention to provide a novel and improved conductor support assembly which is sufficiently lightweight that it can be hand positioned by a lineman on a lattice-type tower yet sufficiently strong to support a heavy high voltage conductor. 
   It is another object of the present invention to provide a novel and improved conductor support assembly which includes means for stabilizing the assembly when emplaced on a lattice-type tower. 
   It is yet another object of the present invention to provide a novel and improved conductor support assembly which is capable of distributing the weight of the conductor over as much of the tower as possible. 
   It is still another object of the present invention to provide a novel and improved conductor support assembly which can be easily reconfigured on the tower to accommodate both parallel and non-parallel girder configurations, and which can be supported upon and will distribute the weight of the conductor to both girder configurations. 
   The foregoing and other objects are achieved in accordance with the present invention by providing a conductor support assembly for supporting a high voltage electrical conductor suspended from a lattice-type tower during maintenance and repair comprising: 
   a pair of elongate support arms, each of said support arms having an aperture extending therethrough intermediate its ends, said aperture opening in a direction transverse to the length of said support arms; and
         an elongate conductor support bar slidably received in the apertures of said support arms and extending between said support arms to define with said support arms a generally H-shaped support assembly, said support arms being slidable on said support bar for adjusting the distance between said arms and being movable on said support bar between a first position wherein said arms are parallel to each other and a second position wherein said arms are arranged at an angle to each other. In one embodiment, as seen in planes passing through the apertures and longitudinally along each support arm, the support bar is generally rectangular in cross section and the apertures are generally rectangular in cross section.       

   In another aspect of the invention, there is provided a conductor support assembly wherein the cross-sectional length of the rectangular apertures in the longitudinal direction is sufficient in relation to the cross-sectional length of the support bar in the longitudinal direction to permit said support arms to be movable between said first and second positions. Desirably, the cross-sectional length of the rectangular apertures is 50% to 150% longer than the cross-sectional length of the support bar, preferably 100% longer. 
   In still another aspect of the invention, there is provided a conductor support assembly for use on a lattice-type tower comprising a plurality of interconnected girders, the support assembly being supported on the tower with each of the support arms positioned on a girder, the elongate support arms having a width at least as wide as the width of the girder on which it is positioned, whereby the weight of a support conductor is distributed over the tower structure. In a preferred embodiment, the support assembly further includes girder engaging tabs attachable to and adjustably positionable at spaced locations along the support arms for engaging the girders on which the support arms are positioned for preventing the support assembly from sliding on said girders. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front elevational view of a typical lattice-type tower for supporting high voltage power transmission lines. 
       FIG. 2  is a top sectional view of the lattice-type tower taken along line  2 - 2  in  FIG. 1 . 
       FIG. 3  is a top plan view of the conductor support assembly of the present invention. 
       FIG. 4  is a front elevational view of the conductor support assembly of  FIG. 3 . 
       FIG. 5  is a perspective view of the conductor support assembly of  FIG. 3 . 
       FIG. 6  is a schematic top view of the lattice-type tower showing the conductor support assembly of the present invention emplaced on the parallel girders of the central bridge and on the inclined girders of one of the arms of the lattice-type tower of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1 and 2  there is shown a conventional steel lattice H-structure tower  40  for supporting multiple (frequently three) high voltage conductors  16 . The lattice tower  40  comprises two legs  42  extending to the ground which support a central bridge  44  having left and right side extending tower arms  46 . In addition, a pair of goat heads  48  extend upwardly and outwardly at an acute angle from the bridge  44  for supporting shield wires  50  via shield wire hardware  52 . The lattice structure is typically constructed of angle stock. Central bridge structure  44  comprises an elongate rectangular box formed of angled stock girders, which gives the bridge a width as well as a depth. Left and right side extending tower arms  46  also comprise elongate boxes formed of angled stock girders except, as can be seen in  FIGS. 1 and 2  respectively, the girders forming the tower arms  46  incline toward each other in both the vertical and horizontal planes. Conductors  16  are supported under each tower arm  46  and under central bridge  44  by a pair of suspension insulators  18  per conductor, with each pair of insulators  18  being spaced apart along the tower arms  46  and central bridge  44  to define a triangle formed by the two insulators  18  and the tower arms  46  or the central bridge  44 , from which the insulators  18  depend. Typically, one end of each insulator  18  is connected via pins (not shown) to the tower arms  46  or central bridge  44  and the other end of each insulator  18  is connected via pins (not shown) to a yoke plate  49 , which also supports conductor  16 . 
   Referring to  FIGS. 3-6 , conductor support assembly  10  is designed to be safely emplaced on a lattice-type tower via helicopter, light enough to be handled by a lineman on a tower, strong enough to support a heavy electrical conductor, stable on a structure such as a lattice-type tower and capable of distributing the weight of a supported conductor over the tower structure. 
   The conductor support assembly  10  includes a pair of generally parallel elongate support arms  12 , each of which has an elongate base member  14  extending in the longitudinal direction, a pair of generally right triangular web rib sections  16  supported on the base member  14  and extending in opposite directions along the base member  14  from a centrally disposed rectangular frame member  19 . Rectangular frame member  19  has top, bottom and opposing side walls, designated  20 ,  22 ,  24  and  26  respectively, defining an elongate rectangular aperture  28 . In one form of the invention, the base member  14 , triangular web sections  16  and rectangular frame member  18  are welded to each other to form unitary support arms  12  which are generally triangular in side view (see  FIG. 4 ) with the apex of the triangle approximately at the midpoint of the support arms  12 . An elongate tubular support bar  30  extends between the generally parallel arms  12  and is slidable within apertures  28 . Support bar  30  is generally rectangular, preferably square, in cross-section and has a cross-sectional length L extending in the longitudinal direction defined by base members  14  and a cross-sectional height H, which is perpendicular to its length L. As can be seen most clearly in  FIG. 3 , support bar  30  defines with support arms  12  a generally H-shaped support assembly  10 . Bolt-receiving apertures  32  are desirably formed in opposing walls adjacent the ends  34 ,  36  of support bar  30 , preferably in top wall  30   a  and bottom wall  30   b , for receiving headed stop bolts (not shown), which prevent the ends of support bar  30  from sliding out of apertures  28  after they have been inserted therein. Desirably, each of support arms  12  includes multiple girder engaging tabs  38  which are attachable to and adjustably positionable at spaced locations along base member  14  for engaging the girders underlying the base member  14  to prevent conductor support assembly  10  from sliding along the girders. Inasmuch as support girders vary in thickness and spacing, in order for the conductor support assembly  10  to be useful on most any lattice-type tower, the tabs  38  must be attachable to base member  14  in a variety of ways, e.g., via clamps, bolts, etc., and at multiple locations along the base member  14 . In one preferred embodiment, tabs  38  are positioned along the underside of a support girder and bolted to base member  14  using bolt holes (not shown) which may be formed in the tabs  38  and the base member  14 . 
   In use, the conductor support assembly  10  is positioned on the central bridge or arm girders, as shown in  FIG. 6 , at a location above the conductor  16  to be supported. In order to facilitate the stable positioning of the conductor support assembly  10  on the girders, the support arms  12  are each slidable on support bar  30  and, in this manner, the distance between them can be adjusted to allow each arm  12  to sit upon the girders of the central bridge  44  or tower arms  46 . Desirably the width of each of the base members  14  is at least as wide as the width of the girder on which it sits in order to spread the weight of the supported conductor  16  over as much of the tower structure as possible. Although the top girders of the central bridge  44  are generally parallel, it can be seen from  FIG. 2  that the top girders of the tower arms  46  taper toward each other in the direction away from the central bridge  44 . To accommodate this taper and to be certain that the support arms  12  sit fully upon the girders of the tower arms, apertures  28  in support arms  12  are desirably rectangular in shape with the long sides  20 ,  22  of the rectangle extending along the longitudinal extent of base members  14  and having a greater length than the cross-sectional length L of support bar  30 . Aperture  28  is slightly oversized along the short sides  24 ,  26  of the rectangle relative to the cross-sectional height dimension H of the support bar  30 . This allows the support arms  12  to be easily slidable along support bar  30  and to be angled toward each other sufficiently to match the taper of the tower arms  46 . Desirably, the length of rectangular apertures  28  is sufficient to allow the support arms  12  to be angled to match the taper of the tower arms  46  while still performing their guiding and sliding function relative to support bar  30 . To accomplish this the long sides  20 ,  22  of rectangular apertures  28  are desirably 50% to 150% longer than the corresponding cross-sectional length dimension L of the support bar  30 , preferably about 100% longer. To assure easy sliding of the support bar  30  within rectangular apertures  28 , the short sides  24 ,  26  or height of rectangular apertures  28  (i.e., in a direction perpendicular to base member  14 ) are desirably 10% to 20% longer than the corresponding cross-sectional height dimension H of support bar  30 , preferably about 10% to 15% longer. 
   After the conductor support assembly  10  has been positioned on the central bridge or tower arm girders, as shown in  FIG. 6 , at a location above the conductor  16  to be supported, assembly  10  can be used in various ways to support the conductor  16 . In one preferred usage of the assembly  10 , a nylon sling is hung over support bar  30  and the free ends of the sling are attached to a bracket to which a chain hoist is also attached. The free end of the chain hoist desirably attaches to the yoke plate  48  where the conductor  16  and insulators  18  come together. The chain hoist may then be operated, e.g., via a manually operated ratchet hoist, to lift the conductor  16  toward the support bar  30 , thus creating slack in insulators  18  and allowing them to be unpinned. After an insulator  18  is unpinned it is carried away via a helicopter and a replacement insulator  18  is delivered to the work site for pinning to the yoke plate  49  and the central bridge  44  or tower arms  46 . In an alternate usage of the assembly  10 , a second nylon sling can be positioned under the conductor  16  and its free ends attached to a second bracket to which the free end of the chain hoist is also attached. 
   For purposes of illustration only, a useful conductor support assembly includes a base plate  14  of each support arm  12  having a length of about 48″ and a width of about 3″, the triangular web has a thickness of about ½″ and the aperture  28  is a rectangle measuring about 5″ in length and 2¾″ in height. Support bar  30  is usefully 2½″ square tubing formed of high strength steel and is about 5′ long. Girder engaging tabs  38  are each about 3″ long, ½″ high and ½″ wide. 
   While the present invention has been described in terms of specific embodiments thereof, it will be understood that no limitations are intended to the details of construction or design other than as defined in the appended claims.