Patent Publication Number: US-2005139279-A1

Title: Multi-compartment aerial duct

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application is a continuation of U.S. patent application Ser. No. 10/401,222 filed Mar. 27, 2003, which claimed the benefit of U.S. Provisional Patent Application Ser. No. 60/368,317 filed Mar. 29, 2002. 
    
    
     TECHNICAL FIELD  
      This invention relates to a duct which is adapted to be carried overhead by utility poles or the like and which can itself carry multiple communication cables or the like in separate compartments.  
     BACKGROUND ART  
      Conduits or ducts which are designed to carry communication and other cables or the like are typically either buried in a network formed in the ground or carried overhead by utility poles. The aerial system is far less expensive to install and maintain, and thus, where utility poles are available, it is the preferred system.  
      Known aerial ducts merely consist of a tube, usually formed of some high tensile strength plastic material, such as high density polyethylene, which can be attached to the utility poles and which provides a single compartment within the tube for the passage of a communication cable or the like. Such tubes are normally provided at the work site on reels. However, because of their density and weight, it is only feasible to provide a limited length of the tubing on a reel. Moreover, because of its weight, the tube is expensive to ship and install. In particular, the high coefficient of friction between the cable and the tube precludes the installation of the cable by means of long pulls. Rather, only shorter lengths of cable can be pulled through the tube at one time.  
      Most significantly, the prior art aerial ducts are only designed to hold one cable. Thus, if after a cable is pulled through the system and is in use, if more communication capacity is needed, an additional cable cannot readily be pulled through the same tube. While such is possible, all of the problems discussed above are compounded in that it is very difficult and time consuming to attempt to pull a second cable into a tube that already has one cable randomly positioned therein. Thus, rather than merely adding a cable to an existing installed aerial system, the prior art generally dictates that a second system be installed when increased capacity is desired.  
     DISCLOSURE OF THE INVENTION  
      It is thus an object of the present invention to provide a duct which can readily be carried by utility poles or the like and which is formed with one or more pockets of a pliant or flexible material.  
      It is another object of the present invention to provide a duct, as above, which can carry more cables, and yet not consume any more space than the prior art ducts.  
      It is a further object of the present invention to provide a duct, as above, which is of a material which is resistant to the weather and the environment.  
      It is an additional object of the present invention to provide a duct, as above, which is lightweight and easy to install.  
      It is yet another object of the present invention to provide a duct, as above, which is of a material having a low coefficient of friction so that longer portions of cables may be pulled therethrough.  
      It is a still further object of the present invention to provide a duct, as above, which is configured so that large volumes thereof may be placed on, and shipped on, a reel.  
      These and other objects of the present invention, as well as the advantages thereof over existing prior art forms, which will become apparent from the description to follow, are accomplished by the improvements hereinafter described and claimed.  
      In general, a duct made in accordance with one aspect of the present invention includes a plurality of longitudinally extending layers of a pliant material. At least one longitudinally extending pocket is formed between at least one set of adjacent layers. A loop is formed adjacent to the pockets and carries a strength member.  
      In accordance with another aspect of the duct of the present invention, the layers of material each have a first lateral edge spaced from a second lateral edge. The layers are attached to each other near their first lateral edges, and one of the layers has a portion which passes over the second lateral edges of the other layers. At least some of the layers are attached to each other near their second lateral edges and are attached to the one layer to not only form pockets between adjacent layers, but also to form a loop adjacent to the pockets.  
      In accordance with another embodiment of the present invention, a duct includes a plurality of enclosed loops positioned adjacent to each other and forming pockets. An additional loop is formed in one of the loops and a strength member is received in the additional loop.  
      According to another embodiment of the invention, a duct includes a plurality of longitudinally extending layers of material having different lateral widths. At least one longitudinally extending pocket is formed between adjacent layers. A loop is formed adjacent to each pocket and a strength member is received in the loop.  
      An aerial system adapted to carry cables between poles includes a duct having a plurality of pockets formed between layers of fabric. The duct includes a loop having a strength member therein. A clamp is adapted to be carried by a pole and engages the strength member so that the duct may be carried by the pole.  
      A preferred exemplary aerial duct incorporating the concepts of the present invention is shown by way of example in the accompanying drawings without attempting to show all the various forms and modifications in which the invention might be embodied, the invention being measured by the appended claims and not by the details of the specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an exploded perspective view of a duct made in accordance with the concepts of the present invention.  
       FIG. 2  is a fragmented side elevational view of the duct of the present invention assembled.  
       FIG. 3  is an enlarged sectional view taken substantially along line  3 - 3  of  FIG. 2 .  
       FIG. 4  is an enlarged view similar to  FIG. 3  but showing one cable in the duct.  
       FIG. 5  is a schematic, perspective view showing the duct being carried by utility poles.  
       FIG. 6  is a fragmented, somewhat schematic, perspective view showing the manner in which the duct is carried by a utility pole.  
       FIG. 7  is a somewhat schematic view, like the sectional view of  FIG. 3 , of an alternative embodiment of a duct of the present invention before the layers of material are attached.  
       FIG. 8  is a somewhat schematic view, like  FIG. 7 , but showing a slightly different version of the duct of  FIG. 7 .  
       FIG. 9  is a view like  FIG. 8  but showing the layers of material attached.  
       FIG. 10  is a somewhat schematic view, like the sectional view of  FIG. 3 , of yet another alternative embodiment of a duct of the present invention before the layers of material are fully attached. 
    
    
     PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION  
      A duct which is especially suited for aerial applications is indicated generally by the numeral  10 . Duct  10  includes a plurality of thin, pliant layers of material, three layers  11 ,  12 , and  13  being shown by way of example. Layers  11 ,  12  and  13  extend in a longitudinal direction potentially for several thousand feet, and such a length of duct  10  may be stored on a reel for ease of shipment and installation. Layer  11  includes spaced lateral edges  14 ,  15 , layer  12  includes spaced lateral edges  16 ,  17 , and layer  13  includes spaced lateral edges  18 ,  19 .  
      Layers  11 ,  12  and  13  may be attached near their lateral edges  14 ,  16  and  18 , respectively, as by stitching  20  or the like. While stitching is the preferred manner to attach layers  11 ,  12  and  13 , it should be evident, dependent on the precise material selected for layers  11 ,  12  and  13 , that other forms of attachment such as heat fusing, ultrasonic welding, or the like could be employed.  
      As shown, it is preferable that the spacing between the lateral edges  16  and  17  of layer  12  and the lateral edges  18  and  19  of layer  13  be generally equal. That is, layers  12  and  13  are generally of the same width. A loop, generally indicated by the numeral  21 , is formed adjacent to lateral edges  17  and  19  of layers  12  and  13 , respectively. While loop  21  could be formed in several manners, as best shown in  FIG. 1 , it is most conveniently formed from layer  11  by extending layer  11  over the lateral edges  17  and  19 . As such, layer  11  is initially formed wider than layers  12  and  13 . That is, its lateral edges  14  and  15  are spaced a greater distance than the lateral edges of layers  12  and  13 . As shown, layer  11  is approximately twice as wide as layers  12  and  13 , and, as such, its edge  15  extends to a point generally adjacent to lateral edges  14 ,  16  and  18 . However, as will be more fully hereinafter discussed, layer  11  could have its edge  15  terminate generally adjacent to lateral edges  17  and  19  of layers  12  and  13 , respectively.  
      Loop  21  can be conveniently formed at the same time that the lateral end of duct  10  opposite edges  14 ,  16  and  18  is closed, by stitching  22  or its equivalent as previously described. Thus, stitching  22  extends through layer  12  near lateral edge  17 , layer  13  near lateral edge  19 , and extends through layer  11  at two locations, one location being a distance from lateral edge  14  generally equivalent to the width of layers  12  and  13 , and the other location being a distance from lateral edge  15  generally equivalent to the width of layers  12  and  13 . In this configuration, as shown in  FIG. 1 , stitching  20 , previously described, will also extend through layer  11  twice, once near lateral edge  14  and the other time through layer  11  near lateral edge  15 . However, as discussed above, if edge  15  of layer  11  were to be positioned generally adjacent to lateral edges  17  and  19 , only stitching  22  would pass through layer  11  twice.  
      As a result of stitching  20  and  22 , in addition to the formation of loop  21 , pockets or compartments  23 ,  24  and  25  are also formed in duct  10  between adjacent sets of layers. Pocket  23  is thus formed between one portion of layer  11  and layer  12 , pocket  24  is formed between layer  12  and layer  13 , and pocket  25  is formed between layer  13  and the other portion of layer  11 . Although a duct  10  with three pockets is thus being shown, it is to be understood in accordance with the present invention that as many pockets as desired may be formed in a duct  10 . Thus, for example, if one were to provide and attach an additional layer of fabric, an additional pocket would be formed. Conversely, if, for example, lateral edge  15  of layer  11  were to terminate near stitching  22 , which was previously suggested as a possibility, then only two pockets would be formed—unless additional intermediate layers would be added.  
      Duct  10  also includes a longitudinally extending stiffening and strength member  26  positioned in loop  21 . Strength member  26  may be made of any suitable metallic or equivalent material, for example, in the form of a metal stranded cable, so as to provide duct  10  with a sufficient amount of stiffness or strength to enable it to be attached to an aerial system as will hereinafter be described.  
      Each pocket of duct  10  may also be provided with a conventional longitudinally extending pull tape  27 . As is well known in the cable installation art, a cable, such as cable  28  shown in  FIG. 4 , may be installed in duct  10  by attaching it to a pull tape  27  at one longitudinal end of duct  10 . Then, by pulling tape  27  at the other longitudinal end of duct  10 , cable  28  is threaded through a pocket of duct  10 . Ropes may be utilized instead of tapers  27 , if desired.  
      So as to readily be able to receive a cable  28  therethrough, the pliant layers  11 ,  12  and  13  of duct  10  may be made of any suitable lightweight natural or synthetic fabric having a low coefficient of friction, high abrasion resistance and high tear resistance. The fabric should also not be water absorbent. The fabric disclosed in U.S. Pat. No. 6,304,698, which is incorporated herein by reference for whatever details may be necessary to understand this invention, if treated for protection from the weather and other environmental occurrences, such as ultraviolet light, would be one suitable fabric for duct  10 .  
      As is schematically shown in  FIG. 5 , duct  10  is particularly suited for being carried by a system of utility poles  30 . Thus, duct  10  is preferably connected to each pole  30  and spans the space therebetween. The manner in which duct  10  may be connected to each pole  30  is shown in  FIG. 6 . There it can be seen that a clamp, generally indicated by the numeral  31 , has opposed jaws  32  which can receive and otherwise engage the strength member  26  which is positioned in loop  21 . Bolts  33  are tightened so that jaws  32  securely engage member  26 , and thus, duct  10 . An extension bracket, generally indicated by the numeral  34 , includes a base  35  which can be attached to a pole  30  as by fasteners  36  and an arm  37  extending outwardly from base  35 . Arm  37  can be attached to clamp  31  by a fastener  38  so that duct  10  is supported from poles  30  at the desired clearance distance.  
      As previously described, when initially installed, duct  10  will usually have a pull tape  27  positioned in each pocket  23 ,  24  and  25 . As shown in  FIG. 3 , such results in a duct having a very narrow end profile. That is, its total thickness is only the thickness of layers  11 ,  12  and  13  and that of tapes  27 . In fact,  FIG. 3  is an exaggerated depiction of the total thickness of duct  10  which, in reality, would only be no more than about 0.125 inch thick. As such, it presents very little top surface areas for the accumulation of ice, snow, dust and the like. Even when a cable  28  is installed in one of the pockets  23 ,  24 , or  25 , as shown in  FIG. 4 , the thickness of a portion of duct  10  would rarely exceed an inch, and thus, surface accumulations of snow and the like is again avoided.  
      An alternative embodiment of the duct of the present invention is schematically shown in  FIG. 7  and indicated generally by the numeral  40 . Duct  40  is shown as including three enclosed loops  41 ,  42  and  43  of a pliant material of the same type of material as duct  10 . Loop  41  thus includes a set of adjacent layers  44  and  45 , loop  42  includes a set of adjacent layers  46  and  47 , and loop  43  includes a set of adjacent layers  48  and  49 . A pocket or compartment  50  is thus formed in loop  41  between layers  44  and  45 , a pocket or compartment  51  is formed in loop  42  between layers  46  and  47 , and a pocket or compartment  52  is formed in loop  43  between layers  48  and  49 . Each pocket may be provided with a pull tape  53  which, like tape  27  of the embodiment of  FIGS. 1-6 , may be used to pull a cable into a pocket of duct  40 .  
      As shown in  FIG. 7 , loops  41 ,  42  and  43  are of the same length, but when they are connected, as by stitching  54  or an equivalent attachment, the ends of loop  42  are not aligned with the ends of loops  41  and  43 . As such, when stitching  54  is applied, a second pocket or loop  55  is formed within loop  42 . Pocket  55  is shown as carrying a strength member  56 , which like strength member  26 , enables duct  40  to be attached to an aerial system such as shown in  FIG. 6 .  
       FIG. 8  shows the duct  40  with one modification. That is, as shown, loops  41 ,  42  and  43  are not of equal length. Rather, loop  42  is longer than loops  41  and  43 . As such, pockets  50 ,  51  and  52  are generally of the same size while pocket  55  is still formed to carry strength member  56 .  FIG. 9  shows duct  40  of  FIG. 8  after the stitching  54  has been applied to attach layers  44 - 49 .  
      Another embodiment of the duct of the present invention is schematically shown in  FIG. 10  and indicated generally by the numeral  60 . Duct  60  is made up of a plurality of layers of a pliant material, preferably the same material described with respect to the other embodiments. Thus, duct  60  includes layers  61 ,  62 ,  63  and  64  which are preferably of differing lateral widths so that when they are connected near their lateral edges, as by stitching  65  or an equivalent attachment, the layers will buckle to form compartments or pockets  66 ,  67  and  68  between adjacent sets of layers. As in the other embodiments, pockets  66 ,  67  and  68  may be provided with a pull tape  69  to be utilized to install a cable in each pocket when desired.  
      The longest layer, layer  64 , may be provided with a cuff  70  that is received around one lateral edge of layers  61 ,  62  and  63  prior to applying stitching  65 . Thus, stitching  65  will extend through layer  64  twice at the area of cuff  70 . A loop  71  is formed at the other lateral edge of layer  64  prior to applying stitching  65 , and thus, stitching  65  will extend through layer  64  twice at the area of loop  71 . Loop  71  forms a pocket  72  to receive a strength member  73  which enables duct  60  to be attached to an aerial system such as shown in  FIG. 6 .  
      It should also be appreciated that duct  60  could be formed of one continuous piece of material with the stitching  65  forming the pockets between the layers of that continuous piece of material.  
      In view of the foregoing, it should be evident that a duct constructed in accordance with any of the embodiments described herein is very useful for aerial applications, accomplishes the objects of the present invention, and otherwise substantially improves the art.