Patent Publication Number: US-2011067323-A1

Title: Breakaway utility pole with decorative base cover

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to breakaway utility poles, in particular to such poles having a decorative base cover. 
     On occasion, utility poles, such as light poles, disposed along the side of a roadway are impacted by a vehicle. Accordingly, utility poles of the breakaway type have been utilized in order to reduce damage to the vehicle and injury to its passengers. The breakaway feature is provided at a lower portion of the pole such that the pole and/or fasteners joining the pole to a foundation will fracture in response to a predetermined impact force applied to the pole by the vehicle. The predetermined force must be high enough to enable the pole to withstand prescribed wind loads, and yet not so high that excessive damage to the impacting vehicle occurs. 
     In certain instances, it is desired to provide a decorative cover encompassing the lower portion of the pole. In the event of a vehicle impact, the cover would be impacted and fractured before the vehicle strikes the pole. The region of the cover located in the normal impact area is spaced horizontally from the pole by a gap sufficiently large for an appreciable amount of the impact energy to be absorbed by the cover as it fractures, thereby interfering with the breakaway performance of the pole. It would be desirable to prevent the presence of the cover from having an adverse effect on the breakaway performance of the pole. 
     SUMMARY 
     A breakaway pole assembly comprises a pole adapted to be anchored to a foundation by a breakaway device for fracturing upon an impact of predetermined force. A decorative cover extends around that lower section and includes a lower foot and an upper lip. The pole includes an outward bump-out situated within the cover. The bump-out includes an energy transfer portion spaced upwardly from the foot and downwardly from the lip for transferring energy from the cover to the pole. The energy transfer portion has a maximum horizontal spacing from the cover of up to about 6 mm. 
     A breakaway pole installation comprises a vertical pole anchored to a foundation by a breakaway device for fracturing upon an impact of predetermined force. A decorative cover extends around that lower section and includes a lower foot and an upper lip. The pole includes an outward bump-out situated within the cover. The bump-out includes an energy transfer portion spaced upwardly from the foot and downwardly from the lip for transferring energy from the cover to the pole. The energy transfer portion has a maximum horizontal spacing from the cover of up to about 6 mm. 
     A breakaway pole installation comprise a vertical pole having an anchored lower section anchored to a foundation and including a breakaway device for fracturing upon an impact of predetermined force. A decorative cover extends around the lower section and includes a lower foot and an upper lip. The pole includes an outward bump-out situated within the cover, the bump-out including an energy transfer portion spaced below the lip and above the foot for transferring energy from the cover to the pole. The energy transfer portion has a height extending at least 60 mm above and 60 mm below a point disposed about 450 mm above the foundation, and a maximum horizontal spacing from an inner surface of the cover is up to about 6 mm. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  depicts a conventional breakaway pole assembly anchored to a foundation. 
         FIG. 2  depicts the pole assembly of  FIG. 1  having a decorative cover encompassing a lower portion of the pole. 
         FIG. 3  depicts a pole assembly in which the pole has a radial bump-out for transferring energy from the cover to the pole in the event of an impact. 
         FIG. 4  depicts the pole assembly of  FIG. 3  with the cover shown in vertical section. 
         FIG. 5  is a top plan view of  FIG. 3 . 
         FIG. 6  depicts the pole of  FIGS. 3 and 4  anchored by a different form of breakaway device. 
         FIG. 7  depicts yet another form of breakaway device for the pole of  FIGS. 3 and 4 . 
     
    
    
     DETAILED DESCRIPTION 
     A conventional breakaway pole installation depicted in  FIG. 1  includes a pole  10  having a lower or base portion  14  anchored by bolts  15  to a foundation such as a concrete foundation  12  or a granular subgrade  12   a  (shown in  FIG. 7 ). The pole can be formed of any suitable metal such as aluminum or steel, or it could be a fiber reinforced polymer pole. The pole  10  is connected to the base portion  14  by a conventional breakaway device  13  constituted by the manner of welding and socketing the pole to the base portion. The design is such that the breakaway will occur in response to a predetermined impact force F occurring at an assumed point of impact situated above the foundation, e.g., about 450 mm above the foundation. 
     Other forms of breakaway devices could be used. For example,  FIG. 6  depicts a conventional breakaway device in the form of breakaway couplings  40 .  FIG. 7  depicts a conventional breakaway device constituted by a weakened joint  50 . 
       FIG. 2  depicts a conventional decorative cover  16  surrounding the base portion of the pole. The cover comprises two clam-shell shaped half-sections  16   a ,  16   b  which are held together along vertical interfaces  16   c  by frangible couplings (not shown) located respectively at upper and lower ends of the cover. Other cover shapes (not shown) are possible. The cover can be formed of any suitable material, such as aluminum, steel or reinforced polymer for example, and includes a lower foot portion  18  which converges into an upwardly converging a neck portion  20  and finally terminates in a radial upper lip  21  (see also  FIG. 5 ). Other cover shapes are possible in which the neck does not converge upwardly. 
     The breakaway device  13  for the pole of  FIG. 1  would normally be designed to fracture in response to a vehicle impact of no more than a predetermined force F acting on the pole at or near an assumed point of impact. However, with the cover  16  of  FIG. 2  in place, the impact will first occur against a part of the cover which is spaced horizontally from the pole by a gap G sufficiently large for the cover, as it fractures under the impact, to absorb an appreciable amount of the impact energy, possibly adversely affecting the breakaway performance of the breakaway device  13 . 
     To minimize the chances for that adverse affect to occur, there is shown in  FIGS. 3-5  a pole assembly comprised of a pole  30  and a cover  16  encompassing the lower portion of the pole. The cover is the same as that described in connection with  FIG. 2  and whose half-sections  16   a ,  16   b  are secured together by upper and lower frangible connectors  17   a ,  17   b . The pole  30  includes an outward enlargement or bump-out  34  disposed at an elevation so as to be enclosed within the cover. A portion  34   a  of the bump-out located above the foundation  12  and below an upper lip  21  of the cover constitutes an energy transfer structure for maximizing the transfer of energy from the cover to the pole in the event of an impact (i.e., to minimize the absorbing of energy by the cover). The energy transfer portion  34   a  has a horizontal width and height dimensioned for that purpose. The horizontal width is such that the energy transfer portion  34   a  at least substantially contacts the inner surface of the cover, i.e., no portion of the energy transfer portion is spaced from the cover by a distance greater than about 6 mm. The height H of the energy transfer portion  34   a  extends at least 60 mm above and 60 mm below a point P (i.e., an assumed point of impact) located about 450 mm above the foundation  12 . 
     The energy transfer portion  34   a  of the bump-out is thus located and dimensioned to virtually instantly transfer most of the impact energy from the cover to the pole. That is, in the event of a vehicle impact against the cover  16  at a point located within the height H, causing the cover  16  or its frangible connectors  17   a ,  17   b  to break, the fractured cover will instantly contact the energy transfer portion  34   a  of the bump-out and transfer substantially all of the impact energy thereto. That is, the amount of energy absorbed by the cover will be minimal, thereby producing minimal adverse effect on the breakaway performance of the pole&#39;s breakaway device. 
     If the cover is in the form of two clam-shells as shown in  FIG. 2 , wherein the neck of the cover converges upwardly, the shape of the energy transfer portion  34   a  of the bump-out conforms thereto by being upwardly converging, as shown in  FIG. 3 . Other cover shapes (not shown) are possible, and the bump-out can be correspondingly shaped. 
     As explained earlier, the present invention can be used with breakaway devices other than the one depicted in  FIGS. 1-5 . For example,  FIG. 6  depicts the provision of breakaway couplings  40  which space the pole&#39;s base above the foundation.  FIG. 7  depicts a cylindrical device  46  embedded in a granular subgrade type of foundation  12   a  and which is connected to the bottom of the pole by a breakaway device in the form of a weakened joint  50 . 
     Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications and substitutions not specifically described may be made without departing from the spirit and scope of the invention as defined in the appended claims.