Patent Publication Number: US-2017358908-A1

Title: System and method for electrical infrastructure maintenance

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application Ser. No. 62/349,736 filed Jun. 14, 2016, which is hereby incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a system and method for electrical infrastructure maintenance. 
     BACKGROUND 
     In order to provide electrical service to residential and commercial customers, electrical cables may be routed from an underground service box to a customer meter. The cables may be encased in concrete, fiber, or wood ducts that are connected to steel pipes or conduits. During operation any number of issues may arise, sometimes resulting in the outer, insulating jacket of the electrical cable being damaged. When this happens, a short-circuit may be created, which can cause some or all of the electrical conductors within the cables to be fused to each other, fused to the conduit wall, or both. Removing the damaged cables can be difficult if one or more of them is fused solidly to the wall of the conduit: the bond between the cables and the conduit may be difficult to break, and during the attempt, it is not uncommon for the cables themselves to break. Even where no fusing occurs, cables may break and it may be difficult or impossible to remove them because of the small inner diameter of the pipe. This may lead to only a portion of the cables being removed, with another portion remaining within the conduit. Therefore, a need exists for a system and method for removing cables from an electrical conduit that overcomes some or all of the problems of current systems and methods. 
     SUMMARY 
     At least some embodiments described herein may include a system and method for locating a potential defect within an electrical conduit without trenching the entire length of the pipe. When the defect is a fused cable, the bond may be broken from inside the pipe and the remaining cable removed. At least some embodiments provide a system and method that enters an open end of a buried steel conduit, which is accessed through an excavation pit or interior wall opening. The interior of the conduit is traversed until the fused cable is located from inside the pipe. The fused portion is broken, ground, or otherwise freed-up, and the cable is then gripped and removed from the conduit. In some cases, it may be necessary for the system and method to remove additional obstructions from the conduit, for example, by vacuuming rocks, dirt, and the like so that new cable can be installed. 
     At least some embodiments described herein may include a system for electrical infrastructure maintenance that includes a cutter arrangement configured for insertion into an electrical conduit and operable to cut around at least a portion of an electrical cable disposed within the conduit. The electrical cable may include one or more electrical conductors, such as a single-piece, solid conductor, or a multi-piece, stranded conductor. As used herein, the word “maintenance” can include repair maintenance, preventative maintenance, rehabilitation, the installation of new systems or components, or any combination of these. A gripper arrangement is operable to capture a portion of the electrical cable, and a motor arrangement may be used to rotate and move linearly the cutter arrangement and the gripper arrangement. 
     In at least some embodiments, the cutter arrangement may include a circumferential cutter having a front portion with cutting teeth disposed around a circumference and a rear portion having an aperture disposed therethrough for allowing the electrical cable to pass through. In at least some embodiments, the gripper arrangement may include a plurality of threads disposed on an inside portion thereof such that the threads grip the at least one of the at least one electrical conductor when the gripper arrangement is rotated by the motor arrangement. The system may further include a support structure having the motor arrangement mounted thereon such that the motor arrangement is vertically adjustable on the support structure. Additionally, components of the system—e.g., a cutter, gripper, support structure, etc.—may be used together or separately to perform various tasks. For example, a gripper may be used without a cutter in a configuration if a cutter is not needed to cut the cable from the wall of a conduit but the gripper is needed to grab the cable. 
     At least some embodiments described herein include a system for electrical infrastructure maintenance that includes a tool head including a rotationally-actuated cutter and a gripper, the tool head being operable to cut around at least a portion of an electrical cable disposed within a conduit, and further operable to secure the electrical cable therein. A motor arrangement is operable to rotate the tool head for cutting and securing the electrical cable. 
     At least some embodiments described herein include a method for electrical infrastructure maintenance, including the step of cutting around an outside of an electrical cable adhered to an inside wall of a conduit with a cutter arrangement to detach the electrical cable from the inside wall of the conduit. The method may also include securing an end of the electrical cable with a gripper arrangement after the electrical cable is detached from the inside wall of the conduit, and pulling the electrical cable from the conduit after the end of the electrical cable is secured with the gripper arrangement. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a system for electrical infrastructure maintenance in accordance with an embodiment described herein; 
         FIG. 2  shows a portion of the system shown in  FIG. 1 ; 
         FIG. 3  shows an alternative configuration for the system shown in  FIG. 1 ; 
         FIG. 4  shows a tool head making up a portion of the system shown in  FIG. 1 ; 
         FIG. 5  shows an exploded view of the tool head shown in  FIG. 4 ; 
         FIG. 6  shows an electrical cable captured by a gripper arrangement forming part of the tool head shown in  FIG. 4 ; 
         FIG. 7  shows a tool head arrangement attached to a plurality of extension rods for extending the reach of a system in accordance with embodiments described herein; 
         FIG. 8  shows a universal joint attachable to an extension rod such as illustrated in  FIG. 7 , which provides angular flexibility for a system in accordance with embodiments described herein; and 
         FIG. 9  shows an electrical cable fused to the inside of a conduit. 
     
    
    
     DETAILED DESCRIPTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
       FIG. 1  shows a system  10  for electrical infrastructure maintenance in accordance with at least some embodiments described herein. As a described in more detail below, the system  10  can be used for finding and removing an electrical cable from inside a carrier, such as a conduit. The system  10  includes a support structure  12 , which includes a base  14 , a generally vertical rail system  16 —which includes two stationary rails  18 ,  20  and two movable rails  22 ,  24  respectively disposed adjacent to the stationary rails  18 ,  20 —and two angle braces  26 ,  28 . The base  14  may be manufactured from stainless steel, for example, which, in addition to providing good corrosion resistance, also provides significant weight to stabilize the system  10 . In the embodiment shown in  FIG. 1 , the base  14  is large enough for a system operator to stand on it while work is being performed, which may provide additional stability to the system  10  during operation. 
     The base  14  is shown in  FIG. 1  has adjustable feet  30 ,  32 ,  34 , and although not visible in  FIG. 1 , it is understood that a fourth adjustable foot is attached to the base  14  near the corner closest to the rail  20 . The base  14  also includes a handle  36 , which aids in the portability of the system  10 . The two angle braces  26 ,  28  are attached to the base  14  at brackets  38 ,  40 , respectively. The angle braces  26 ,  28  are telescoping to allow for vertical adjustment between the movable rails  22 ,  24  and the stationary rails  18 ,  20 . The brackets  38 ,  40  allow the angle braces  26 ,  28  to pivot as needed to facilitate the vertical adjustment. The relative position of the movable rails  22 ,  24  relative to the stationary rails  18 ,  20  are set using pins, such as the pin  42  shown engaged with the rail  22  and the rail  18 . It is understood that a similar pin is engaged with the rails  24  and  20 , but which is not visible in  FIG. 1 . Near the bottom of the rails  18 ,  20  are two pins  44 ,  46 , which connect the stationary rails  18 ,  20  to brackets attached to the base  14 : the brackets are inside the rails  44 ,  46  and are therefore not visible in  FIG. 1 . The pins  42 ,  44 ,  46  may be, for example, clevis pens, tab-lock pins, or some other kind of pin or dowel usable to quickly and effectively secure the rails  18 ,  20 ,  22 ,  24 . 
     The angle braces  26 ,  28  are attached to the brackets  38 ,  40  with easily removable pins  48 ,  50 , which may be, for example, hairpin cotters or some other easily insertable and removable pin or clip. A similar mounting configuration is used at the tops of the angle braces  26 ,  28 , although in  FIG. 1 , only the bracket  52  and the removable pin  54  associated with the angle brace  26  are visible. The quick-release mounting features of the angle braces  26 ,  28 , and the handle  36  attached to the base  14 , help to improve portability of the system  10 , which may be moved from location to location as needed to address electrical problems. 
     The system  10  also includes a motor assembly  56 , which is described in more detail in conjunction with  FIG. 2  below. The motor assembly  56  is supported on an angle stand  58 , which is attached to the rails  22 ,  24  via a mounting plate  60 . The motor assembly  56  includes a motor  62  attached to a drill support  64 , which is connected to the angle stand  58 . The motor assembly  56  and the angle stand  58  may be conveniently referred to as a motor arrangement  65 , which operates to rotate and move linearly a tool head  66 . The tool head  66  is connected to the motor  62  through one or more extension rods  68 . This is shown in more detail in  FIG. 2 , where the angle stand  58  is shown detached from the rails  22 ,  24  of the floor mount structure  69 , which is generally made up of the base  14 , the rails  18 ,  20 ,  22 ,  24 , the angle braces  26 ,  28 , and the mounting plate  60 . The motor  62  is operable to rotate the extension rod  68  and the tool head  66  to free a fused electrical cable from inside a conduit and into grab the end of the cable to facilitate removal from the conduit. 
     The angle stand  58  includes a movable section  70  which cooperates with a rack  72  to facilitate linear movement of the motor assembly  56  toward and away from a conduit or other problem site. In the embodiment shown in  FIG. 2 , the movable section  70  may contain one or more pinions—not visible in  FIG. 2 —which mesh with the rack  72 , and which are rotated by rotation of a handle  74 . The handle  74  may be manually rotated by a system operator, who can also adjust an angle brace  76  of the angle stand  58  to adjust the entry angle of the tool head  66  into the problem site. Alternatively, the movable section  70  may be actuated by a motor or other mechanized system. 
     Because the angle stand  58  is removable from the floor mount  69 , additional vertical range can be obtained by mounting the angle stand  58  onto the floor mount  69  with an orientation 180° from that which is illustrated in  FIG. 1 . This configuration is shown in  FIG. 3 , where the tool head  66  is positioned several inches lower than it is in the orientation shown in  FIG. 1 , and yet the position of the rails  22 ,  24  are the same. In at least some embodiments, a configuration utilizing an upward-facing mount, as shown in  FIG. 1 , may allow the tool head  66  to be used at a height of up to nearly 75 inches. With the downward-facing mount, as shown in  FIG. 3 , the tool head  66  may be used at a position as low as 30 inches. Of course, different embodiments may include different lengths of rails, such as the rails  18 ,  20 ,  22 ,  24 , and this will influence the overall vertical range where a tool head, such as the tool head  66 , can be used. 
     As described above, embodiments may provide a system that includes a cutter arrangement, a gripper arrangement, and a motor arrangement, and which can be used to locate and release a fused electrical cable from inside a conduit, and then facilitate removal of the remaining portion of the cable from the conduit. Additional embodiments include cameras and other sensors, which, for example, may include a device for measuring distance, such as a rotary encoder, to determine a distance the tool has traveled into the conduit.  FIG. 4  shows the tool head  66  in greater detail having several of these features described above. The tool head  66  includes a cutter arrangement  77 , which, in the embodiment shown in  FIG. 4 , includes a circumferential cutter  78  having a front portion  80  with cutting teeth  82  disposed around its circumference  84 . The circumferential cutter  78  also includes a rear portion  86  having a hole  88  disposed therethrough, which allows an electrical cable to pass through it and reach a gripper arrangement  90 . 
     The gripper arrangement  90  includes a rotationally-actuated gripper  91  having a plurality of threads  92 , which are illustrated in the left end-view of  FIG. 4 . The gripper arrangement  90  includes an aperture  89  disposed therethrough. As shown in  FIG. 4 , the tool head  66  also includes an extension tube  93 , which is configured to receive an extended length of the electrical cable after it passes through the aperture  89  in the gripper arrangement  90 . An extension tube, such as the extension tube  93 , may be configured in various lengths, and helps to facilitate the cable passing through the gripper into a hollow section of the tool. A driving hub  94  allows the tool head  66  to be rotated by the motor  62 , which may be through one or more extension rods, such as the extension rod  68  shown in  FIG. 1 . In this embodiment, the cutter arrangement  77  and the gripper arrangement  90  are part of the same tool head  66 , but in other embodiments, a cutter arrangement and gripper arrangement may be part of separate tool heads. For example, a gripper arrangement may be hand-held and used by an operator manually—i.e., without a motor. 
       FIG. 5  shows the tool head  66  in an exploded view with the gripper arrangement  90  disassembled so that the internal threads  92  are visible. The gripper arrangement  90  includes a first end  95  and a second end  97 ; in this embodiment, the first end  95  is disposed closer to the cutter arrangement  77  than the second end  97 . As shown in  FIG. 5 , the circumferential cutter  78  has the aperture  88  through a rear portion  86  to allow an electrical cable to pass through it and into the gripper arrangement  90 . As described above, an electrical cable may fuse to the side of a conduit in which it is located, and when this occurs, it may be impossible to remove the cable from the conduit without first breaking the fused cable away from the wall of the conduit. To accomplish this, the tool head  66  is rotated such that the teeth  82  of the circumferential cutter  78  cut through any fused or welded portion of the cable that is bonded to the side of the conduit, thereby freeing the cable for removal. 
     As shown in  FIG. 5 , a longitudinal axis  96  is oriented along a length of the tool head  66 . A line  98  struck perpendicularly to the axis  96  is illustrated to further define the threads  92  of the gripper arrangement  90 . In particular, the threads  92  form an angle θ with the line  98 . In the embodiment shown in  FIG. 5 , the angle θ is approximately 8°; however, in other embodiments the angle formed by the threads in the gripper arrangement may be between 5° and 15°. In other embodiments, the angle of the threads may be steeper or shallower, depending on various considerations, such as manufacturing considerations and the effectiveness of the threads to grab a cable inside a conduit. In this embodiment, the gripper  91  is rotationally actuated; however, in other embodiments, a gripper arrangement may include a gripper that is not rotationally actuated. For example, a gripper may include a series of teeth angled away from an opening; this allows an end of an electrical cable to be inserted linearly into the opening where it engages with the angled teeth. When the gripper is pulled in a direction away from the cable—e.g., toward an open end of a conduit—the teeth engage the cable and pull it out of the conduit. 
       FIG. 6  shows a gripper arrangement  100  formed as two separate pieces  102 ,  104 , similar to the gripper arrangement  90  illustrated and described above. The gripper arrangement  100  includes a plurality of threads  106 , which may be cast into the pieces  102 ,  104 ; alternatively they may be machined into the pieces  102 ,  104 , or they may be cast as a near-net shape and have minimal machining done to them after the casting process. Also shown in  FIG. 6  is a portion of an electrical cable  108 , which has been freed from the inside wall of the conduit—for example, by a cutter arrangement such as illustrated and described above—and which has then been gripped by the threads  106  of the gripper arrangement  100  such that it could be extracted from the conduit. As shown in  FIG. 6 , the internal threads  106  of the gripper arrangement  100  narrow from a first end  109 , where they have a thread diameter (d 1 ), to a second end  111 , where they have a smaller thread diameter (d 2 ). Similar to the gripper arrangement  90  described above in conjunction with  FIG. 5 , the first end  109  of the gripper arrangement  100  will be disposed closer to a cutter arrangement than the second end  111 . 
     Referring back to  FIG. 1 , the process may be accomplished as follows. First, the system  10  would be taken to the site where a problem has been identified. If the conduit can be accessed from inside a building, the system  10  can be at least partially disassembled as described above, taken into the building, and reassembled at the access site. If, however, access to the conduit can only be had at some point underground, an excavation pit can be dug to provide access to the conduit opening. This may still be preferable to digging up the entire conduit and trying to rehabilitate it or replacing it with a new conduit, which requires much more excavation and trenching to accomplish. 
     Once the conduit is accessed, the motor assembly  56  and tool head  66  are moved linearly inside the conduit, for example, by rotating the handle  74 . The motor  62  is then operated to rotate the tool head  66  such that the circumferential cutter  78  cuts through any fused or welded area of the cable and conduit. Then the tool head  66  is further inserted into the conduit by moving the motor assembly  56  and the tool head  66  linearly along the rack  72 —see  FIG. 2 —so that the freed-end of the cable is firmly inserted into the gripper arrangement  90 . Once the cable is twisted firmly within the threads of the gripper arrangement, operation of the motor  62  is ceased, and then the cable is linearly extracted by moving the entire motor assembly  56  and tool head  66  out of the conduit, for example, by rotating the handle  74  in a reverse direction. 
     Although a cutter arrangement and gripper arrangement may be configured to virtually any size effective to perform the tasks described above, in at least some embodiments, the cutter arrangement may be, for example, of a diameter that is just slightly smaller than the inside diameter of the conduit into which it is being inserted. If, for example, the inside diameter of the conduit was approximately 2 inches, the diameter of a corresponding cutter arrangement may be 1.75 inches or even larger to ensure that any fusing or welding of the cable to the inside diameter of the conduit was effectively cut without leaving a significant amount of material along the inside of the conduit. 
     As described above, an electrical cable that has short-circuited inside a conduit may not be easily accessible. In fact, its precise location may not even be known without an inspection prior to the remediation. Therefore, systems and methods in accordance with embodiments described herein may include an inspection camera, which is utilized at an initial stage to locate with some precision the problem site within the conduit. Because it is possible that the welded or fused portion may be at some length within the conduit, and not near the entry point of the conduit, embodiments described herein may include a plurality of extension rods, such as the extension rod  68  illustrated in  FIG. 1 .  FIG. 7  shows a tool head  110  configured similarly to the tool head  66  illustrated and described above. In the embodiment illustrated in  FIG. 7 , the tool head  110  is attached to three extension rods  112 ,  114 ,  116  in series to provide necessary length to reach the fused portion of the electrical cable. Female couplings  113 ,  115 ,  117  are attached to the ends of the rods  112 ,  114 ,  116 , and may be integral with them or attachable through set screws as illustrated in  FIG. 7 . 
     At the end of the last extension rod  116  is a shaft  118  configured for attachment to a motor, such as the motor  62 . The shaft  118  may be hexagonal, square, or any other geometric configuration that provides good mating with a chuck of the motor assembly. The shaft  118  may also have a Morse taper if the motor assembly includes a chuck that is configured with a female Morse taper. As described in detail above, an angle stand, such as the angle stand  58 , may include a mechanism for angular adjustment to allow a tool head, such as the tool head  66 , to enter a conduit at an angle that is not precisely horizontal. To provide further flexibility with regard to angular movement, embodiments described herein also contemplate the use of one or more universal joints, such as the universal joint  120  illustrated in  FIG. 8 . A universal joint, such as the universal joint  120 , may be configured with a rod  122  on one end, and a female coupling  124  on the other end, such that it is attachable at either end or in the middle of a number of extension rods, such as the extension rods  112 ,  114 ,  116  illustrated in  FIG. 7 . 
       FIG. 9  shows a cross section of an electrical conduit  126  that contains an electrical cable  128 . As shown in  FIG. 9 , a first portion  130  of the electrical cable  128  is fused to an inside wall  132  of the conduit  126 . A second portion  134  of the electrical cable  128  is not fused to the conduit  126 , and this may be a result of an attempt to pull an end  136  of the electrical cable  128  out of the conduit  126 . As described above, it is not uncommon for an electrical cable to break in these circumstances. Also shown in  FIG. 9  is a mass  138  of welded metal, which may include material from some or all of the conductors in the electrical cable  128 , and possibly some of the material of the conduit  126 . After the second portion  136  of the cable  128  is removed from the conduit  126 , a method described herein may use a circumferential cutter slightly smaller than an inside diameter of the conduit  126  to cut through the mass  138  to disengage the first portion  130  of the cable  128  from the inside wall  132  of the conduit  126 . The cutter may be deployed into the conduit  126  through an open end  140 , which may be accessed by opening a connection at an electrical meter, or through a small excavation to access a portion of the conduit  126 . Once an end  142  of the cable  128  is detached from the conduit  126 , a gripper arrangement such as described above may be used to secure the end  142  so that it can be removed from the conduit  126 . 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.