Abstract:
A cable stripping tool for the preparation of high voltage cable for termination or splicing by simultaneously removing the semiconducting sheathing from a section of cable and insulation and sheathing from the end section of the cable to expose the conducting core. The tool has a tubular body with a central bore which receives the cable. The body has an adjustable scoring blade disposed in a longitudinal slot which scores the sheathing at a predetermined distance. An insulation cutting blade is radially disposed in the central bore which cuts the sheathing and insulation upon rotation of the body. In one embodiment, a shaft is coupled to the tubular body to provide rotation of the body about the cable by a drill motor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Application Ser. No. 60/123,448 filed on Mar. 9, 1999 which is incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     REFERENCE TO A MICROFICHE APPENDIX 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains generally to the installation of underground cables, and more particularly to an apparatus for stripping the insulation and semiconducting sheathing from an underground cable in preparation for termination or splicing of the cable. 
     2. Description of the Background Art 
     Conductive wires or cables typically have a central conductive core surrounded by one or more layers of insulation and an outer sheath. High voltage electrical cables typically have a semi-conductive outer sheath. Other cables may also have a second conductive layer separated from the conductive core by a layer of insulation. Stripping the end of the cable is necessary to allow an electrical or light energy connection with the cable. 
     Present wire or cable stripping tools known in the art range from simple hand tools to sophisticated motorized machinery. One type of prior art wire stripping tool is a plier like device with notches in the jaws which form a diamond shaped aperture when the jaws are fully closed. The wire to be stripped is placed in one notch and the jaws are closed cutting the insulation and allowing the conductive wire to be withdrawn through the aperture and the insulating sheathing removed thereby. However, the plier type wire strippers known in the art are unsuitable for stripping two levels of insulation or for stripping wires with a comparatively large cross-sectional areas. 
     Another common problem encountered with hand wire stripping tools is that the gripping and stripping of the insulation may cause damage to the conductor. The conductor may be cut completely or nicked thereby reducing the capability of the conductor to conduct current. The notched areas of the conductor may also create hot spots due to concentrations of current as well as weak spots that can result in breakage of the conductor. It has therefore become a practice to leave a small amount of insulation on the cable to be removed by hand so that the conductor is not exposed to or notched by the cutting blade. Care must also be taken when removing the semi-conductive sheathing from a high voltage cable not to cut the insulation layer or to imbed pieces of the sheathing into the insulation layer. 
     Other well known wire strippers have an elongate body with cutting blades which rotate about the exterior of the cable to remove the outer sheath of the cable. Such devices can be rotated by hand or rotated by an electric motor. One deficiency in these types of strippers with a permanently fixed blade is that the stripper cannot accommodate a range of cable insulation diameters. Another deficiency in the prior art hand actuated and motorized stripping devices is that the devices can not be efficiently used in confined spaces. 
     Accordingly, there is a need for a motorized cable stripping device which provides for removal of the sheathing layer of a portion of the cable without cutting the insulation while the end portion of the cable has the sheath and insulation layers removed to expose the conductive core, and which is easy to use and can be used in a confined space. The present invention satisfies those needs, as well as others, and generally overcomes the deficiencies found in the background art. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention generally comprises a cable stripping tool with a cylindrical body having a central bore or hollow throughout its length that can receive the end of the cable to be stripped. The cylindrical body has a longitudinal slot and a laterally disposed discharge port which extends through the walls of body to the central bore. An insulation cutting blade is mounted in the discharge port extending into the central bore and configured so as to remove the sheathing and insulation layers of a cable. The discharge port is preferably positioned near the middle of the length of the device. 
     A scoring blade assembly is disposed above and in the longitudinal slot such that the tip of the scoring blade engages and rides the outer sheath of the cable when it is placed in the central bore. A spring maintains pressure on the scoring blade. An adjustable set screw maintains the depth of the score which does not fully penetrate the sheath. The blade assembly is preferably adjustable and can be positioned at any point along a raceway above the slot. 
     A shaft assembly is mounted opposite the cable receiving end of the elongate body and centered along the central axis of the generally cylindrical body. 
     In use, the cable is inserted into the opening in the open end of the body. A portable drill or other source of rotational power is attached to the shaft. When rotational power is applied to the apparatus, it rotates around the cable, thus stripping the sheath and insulator from a section of the cable with the insulation cutting blade and scoring the semiconducting layer of another section with the scoring blade. The scored sheath is then peeled by hand after scoring to avoid cutting the insulation layer. 
     It is an object of the invention to provide a novel means of preparing insulated cable having at least one insulation layer and a sheath for splicing or termination. 
     Another object of the invention is to provide a cable stripping device that can accommodate insulated cable with a comparatively wide diameter. 
     Yet another object of the invention is to provide a wire stripping device that is efficient, reliable and easy to use. 
     A further object of the invention is to provide a cable stripping device with cutting blades that can be adjusted to cut to a range of depths. 
     Another object of the invention is to provide a cable preparation device that can be readily utilized in confined spaces. 
     Yet another object of the invention is to provide a cable stripping device which is rugged and simple to fabricate. 
     Further objects and advantages of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only: 
     FIG. 1 is an exploded perspective view of a cable stripping and preparation apparatus in accordance with the invention. 
     FIG. 2 is a perspective assembled view of a cable stripping and preparation apparatus shown in FIG.  1 . 
     FIG. 3 is a cross sectional view of the apparatus of FIG. 2 taken along the lines  3 — 3 . 
     FIG. 4 is an exploded perspective view of the adjustable scoring blade assembly used in the apparatus shown in FIG.  1 . 
     FIG. 5 is an assembled perspective view of an alternative embodiment of the adjustable scoring blade assembly shown in FIG. 4 that employs paired anchor members. 
     FIG. 6 is a cross-sectional view of the scoring blade assembly shown in FIG. 5 taken through lines  6 — 6  with the paired anchor members in the unextended position. 
     FIG. 7 is a cross-sectional view showing the anchor members in FIG. 6 in the extended position. 
     FIG. 8 is a cross-sectional view of the scoring blade assembly of FIG. 5 taken through lines  8 — 8  with the scoring blade and blade housing shown in the down position. 
     FIG. 9 is a cross-sectional view showing the scoring blade and blade housing of FIG. 8 in the up or disengaged position. 
     FIG. 10 is a top view of the scoring blade shown in FIG.  4 . 
     FIG. 11 is a side view of the scoring blade shown in FIG. 4 showing the preferred blade angle. 
     FIG. 12 is a perspective view of the scoring blade shown in FIG.  4 . 
     FIG. 13 is a rear view of the scoring blade shown in FIG. 1 showing the preferred angle forming the tip. 
     FIG. 14 is an end view of the insulation cutting blade of the apparatus shown in FIG.  1 . 
     FIG. 15 is a top view of the insulation cutting blade of the apparatus shown in FIG.  1 . 
     FIG. 16 is a rear view of the insulation cutting blade of the apparatus shown in FIG.  1 . 
     FIG. 17 is a rear perspective view of the insulation cutting blade of the apparatus shown in FIG. 1 showing the three cutting edges of the blade. 
     FIG. 18 is an end view of the shaft assembly portion of the of the apparatus shown in FIG.  1 . 
     FIG. 19 is a side view of the shaft assembly portion of the of the apparatus shown in FIG.  1 . 
     FIG. 20 is a cross-sectional view of the shaft assembly shown in FIG. 19 taken along the lines  20 — 20  showing the bearing and bearing cap. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring more specifically to the drawings, for illustrative purposes the present invention is embodied in the apparatus generally shown in FIG.  1  through FIG. 20, where like reference numerals denote like parts. It will be appreciated that the apparatus may vary as to configuration and as to details of the parts without departing from the basic concepts as disclosed herein. 
     As can be seen from the drawings, the invention is a device for preparing the ends of high voltage cable or other insulated wire to be spliced or otherwise terminated. Such high voltage cable typically has a central conductive core surrounded by a rubberized or plastic insulating layer and a semi-conductive outer sheath. The present invention exposes the conducting core at the end of the cable while scoring the outer sheath of a portion of the cable. 
     Referring now to FIG.  1  through FIG. 3, an embodiment of a wire preparation device  10  in accordance with the present invention is generally shown. The device  10  includes an elongate tubular body  12  with a central channel or bore  14  throughout the length of the body. The bore  14  is preferably centered about a central axis with an opening  16  at one end configured to receive a cable to be stripped and prepared by the device. Body  12  has a longitudinal slot  18  which extends through the exterior wall of do the body  12 . Slot  18  is centered within a longitudinal raceway  20  that is also within the wall of body  12 . Device  10  also includes a scoring blade assembly  22  which is configured to slide linearly within raceway  20 , as seen in FIG.  2 . 
     Cylindrical body  12  also has a laterally disposed discharge port  24  which opens from the central bore  14  to the exterior of the device. An insulation removing blade  26  is mounted in the discharge port  24  with a screw  28  and the blade  26  extends into the central bore  14 . As can also be seen FIG.  2  and FIG. 3, the blade  26  is preferably perpendicular to the central axis of the body  12  as well as the longitudinal axis of the cable when it is placed in the central bore  14 . The distance that the blade  26  is set to extend into the central bore  14  is determined by the thickness of the outer sheath and insulating layers of the cable and may be adjusted with mounting screw  28 . Note that screw  28  fits into an elongated slot in blade  26 . Accordingly, the blade  26  can be adjusted to remove the sheath and the insulation layers but not come in contact with the conducting core. The sheath and insulation layers are discharged from the central bore  14  through the discharge port  24  to the exterior of the device. 
     It is also preferred that the junctions  30  between the walls forming the discharge port  24  be curved to facilitate the efficient discharge of the insulation and sheath layers of the cable during use. The curved junctions  30  between walls of port  24  reduce binding of the discharged material during use. 
     In the preferred embodiment, a shaft assembly  32  is mounted to body  12  at the end opposite the cable receiving opening  16  by a pin  34 . The shaft assembly  32  has a cylindrical body section  36  which fits within a socket in body  12 . Shaft assembly  32  has an aperture  38  which is radially disposed through the cylindrical body section  36  to receive pin  34 . Shaft assembly  32  also has shaft  40  which can be placed in the chuck of a hand or motorized rotary drill. At the end of shaft assembly  32  opposite shaft  40  is an end cap  42  that covers a bearing  46 . 
     In FIG. 3, it can be seen that when shaft assembly  32  is positioned in the socket of body  12  and body aperture  44  and shaft assembly aperture  38  are aligned and pin  34  inserted, cap  42  is positioned at the distal end of central bore  14 . It is preferred that cap  42  cover a cap bearing  46  mounted to the shaft body  36  that will allow the cap  42  to rotate freely and independently of the body  36 . 
     It is preferred that the diameter of opening  16  and bore  14  approximate the diameter of the entire cable and after the insulation cutting blade  26  and discharge port  24  reduce down to a diameter which approximates the diameter of the conducting core of the cable. In this configuration, the reduced diameter of bore  14  maintains the proper alignment of the conductor core with respect to cutting blade  26  as the insulation is incrementally removed. 
     It will also be seen from FIG. 3 that it is preferred that insulation cutting blade  26  be positioned ninety degrees relative to the scoring blade assembly  22 . However, other positions are also contemplated by the invention. 
     During use, a cable is placed within bore  14  through opening  16  until it impacts blade  26 . In one embodiment, the blade of the scoring blade assembly  22  can be withdrawn from bore  14  to allow free access of the cable through bore  14  without nicking the exterior semi-conductive sheathing of the cable. 
     Since the base of the adjustable scoring blade assembly  22  fits into a raceway  20  centered over the longitudinal slot  18 , the scoring blade  48  can engage the side of the cable within the bore  14 . The scoring blade assembly  22  can be adjusted to any position along the raceway  20  so that the operator can select the amount of cable sheathing to be scored. Shaft  40  is preferably placed into the chuck of a motorized rotary drill and rotated. It will be appreciated that rotation of shaft  40  will result in the rotation of the entire body  12  around the cable workpiece. Insulation and exterior sheathing are discharged through discharge port  24  when cut by blade  26  and the interior core conductor proceeds into the distal portion of bore  14 . At the same time, the semi-conductive sheathing is scored by scoring blade  48 . When the conductor reaches the end of bore  14  it impacts cap  42 . Cap  42  remains stationary with respect to the cable while the shaft cylindrical body  36  and elongate body  12  rotate around the cable. Consequently, the end of the conductor is not exposed to rotational forces when it comes in contact with cap  42 . This is important if the conductor is composed of twisted multiple strands. Once the conductor reaches the cap  42  the operator ceases rotation of the device and the cable end is removed from the device. 
     Referring now to FIG. 4, an exploded view of the preferred scoring blade assembly  22  is depicted. The scoring blade assembly preferably has a generally inverted “T” shaped base  50  of dimensions that are slightly smaller than the dimensions of raceway  20  so as to freely slide along the length of the raceway without substantial movement of the base to either side of raceway  20 . An anchor member  52  of approximately the same width of base  50  fits into a channel  54  in base  50 . A threaded aperture  56  allows screw  58  to engage the top surface of anchor member  52  and direct member  52  toward the bottom of raceway  20  and, at the same time, force left side rail  60  and right side rail  62  into frictional engagement with the corresponding surfaces of the sidewalls of raceway  20 . Thus, the scoring blade assembly  22  can be positioned at any point along raceway  20  and anchored in position with anchor screw  58 . 
     Referring also to FIG. 5, FIG.  6  and FIG. 7, an alternative embodiment of the anchor member is disclosed. In this embodiment, left  64  and right  66  anchor members are shown in the disengaged and engaged positions, respectively. The anchor screw  58  engages beveled edges  68  and  70  of anchor members  64  and  66 , respectively. As seen in the engaged position of FIG. 7, anchor members  64 , 66  are forced laterally into the sidewalls of raceway  20  by anchor screw  58 . 
     Referring to FIG.  4  and FIG. 5, the scoring blade assembly  22  also includes a blade column  72  which slides in sleeve  74  of base  50 . A pivot arm  76  is preferably coupled to base  50  with pivot pin  78  through pivot pin apertures  80 ,  82  in base  50  and aperture  84  in pivot arm  76 . Springs  86 , 88  are preferably positioned on either side of aperture  84  with the spring elements engaging both the pivot arm  76  and the base  50 . The springs  86 , 88  thereby bias the pivot arm  76  upwardly and the blade column  72  downwardly. 
     Pivot arm  76  is preferably coupled with blade column  72  by a cylindrical pin  90  which can rotate within holes  92  in blade column  72 . In the embodiment shown, pivot arm  76  has a finger  94  which fits into a similarly sized hole  96  in pin  90 . It can be seen that pivotal movement of pivot arm  76  about pivot pin  78  results in the corresponding movement of blade column  72  within sleeve  74 . 
     Blade column  72  preferably has a gently arcuate surface  98  on the bottom section of the column. Column  72  also has a blade chamber  100  which is preferably threaded. Scoring blade  48  and blade spring  102  are placed into chamber  100  and secured into place by blade retaining screw  104 . In order to restrict movement of screw  104  during operation of the device, a screw  106  is secured into threaded aperture  108  and engages or restricts movement of screw  104 . In addition, blade spring  102  is preferably not fully compressed when blade  48  is positioned by screw  104 . 
     FIG. 8 is a cross-sectional view of the scoring blade assembly  22  taken along the line  8 — 8  of FIG.  5 . In FIG. 8, blade assembly  22  is shown in the down or cable engaging position. It will be appreciated that the cutting tip  110  of blade  48  and arcuate surface  98  of blade column  72  are disposed in the central bore  14  through slot  18  when in the down position. It will be apparent to one skilled in the art that the blade column  72  can slide up and down in sleeve  74  when the blade  48  and blade column  72  encounter a cable that is not perfectly circular. Such movement is resisted by springs  86 ,  88 , which also serve to keep the tip  110  of scoring blade  48  fully engaged with the cable when the device is in use. 
     Referring now to FIG. 9, a cross-sectional view of the scoring blade assembly in the up or disengaged position can be seen. The downward movement of pivot arm  76  results in the upward movement of blade column  72  and blade  48  is withdrawn from bore  14  and slot  18 . Removal of the scoring blade from bore  14  is important for the protection of the scoring blade  48  during initial placement of the cable in the device as well as removal of the cable once the insulation stripping and scoring are completed. Removal of the scoring blade  48  from the bore is also important so that tip  110  of blade  48  does not nick the semiconducting sheath of the cable or the conductor during removal. Accordingly, pivot arm  76  is depressed to raise blade column  72  during placement and removal of the cable. 
     Top, side and perspective views of the preferred structure of scoring blade  48  are shown in FIG.  10  through FIG.  13 . As seen in the side view of blade  48  in FIG. 11, the preferred angle is approximately 60° from horizontal. However, a range of blade angles from 30° to 75° has been found to be effective. 
     Referring now to FIG. 13, the angle β of the blade forming tip  110  of blade  48  is preferably approximately 30° from horizontal as shown. However, angles ranging from 15° to 60° have been found to be effective in reducing wandering of the tip  110  of blade  48  during scoring. 
     In addition, blade  48  preferably has a base ridge  112  on the end of the blade opposite the tip  110  which is greater in diameter than the body of the blade to seat spring  102  as well as engage screw  104 . 
     Referring to FIG.  1  and FIG.  14  through FIG. 17, end, rear, top and perspective views of the insulation cutting blade  26  are shown. In the embodiment shown, the cutting depth of cutting blade  26  can be adjusted. Screw  28  can be placed in a slot  114  with a shelf  116  to engage the head of screw  28  and secure blade  26  to discharge port  24  of body  12 . In this configuration, screw  28  can be loosened and the radial position of blade  26  with respect to the center of central bore  14  can be adjusted outwardly to remove less insulation and inwardly to remove more. If blade  26  is cutting into the conducting core of the cable, the blade should be adjusted out and secured by screw  28 . 
     The preferred configuration of insulation cutting blade  26  has three cutting edges: front  118 , top  120  and end  122 . The end cutting edge  122  is generally parallel to the conductor core during cutting. Top cutting edge  120  is generally perpendicular to the conducting core of the wire during cutting. Front cutting edge  118  of blade  26  preferably has a ridge near the converging points of the front, top and side cutting edges as seen in FIG.  17 . 
     Shaft assembly  32  with cylindrical body  36 , shaft  40 , bearing  46  and cap  42  are shown in FIG.  18  through FIG.  20 . As shown in FIG. 1, the shaft assembly  32  is dimensioned to fit in the distal end of elongate body  12 . The assembly  32  is secured by pin  34  so that it is quickly removable for easy cleaning. FIG. 20 is a cross-sectional view of the shaft assembly  32  depicted in FIG. 19 taken along the lines  20 — 20 . Bearings  46  allow the cap to remain motionless with respect to the conducting core of the cable while the body rotates around the cable. 
     Accordingly, it will be seen that this cable stripping and preparation device which can simultaneously score the exterior semi-conductive sheathing for a portion of the cable and remove the sheathing and insulation layers exposing the conductive core of another portion of the cable-prior to splicing or coupling of the cable. 
     Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Thus the scope of this invention should be determined by the appended claims and their legal equivalents. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”