Patent Publication Number: US-2009235531-A1

Title: Tube cutter to prevent damage to internal electrical or optical cables

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to apparatus for cutting the outer tube of steel conduit cables, and, more particularly, for cutting the outer tube of such conduit cables that contain electrical or optical cables. 
     2. Description of the Prior Art 
     The installation of electrical steel conduit cables on-site requires that the outer tube be cut to the required length for termination and pressure sealing. Such a tube has a relatively thin wall and cutting the tube requires a great deal of skill not to damage the electrical insulation inside the tubing. While a triangular file is often used for such cutting, the site conditions can prevent the technician gaining access to both view and perform the required 360° cut with a suitable filing action. If two cables exist in a side by side relationship, this task is doubly more difficult. 
     Conventional tube cutters require a lot of space and the cutting device often uses a hardened steel blade which rotates around the tube, cutting into the material by cold working and deformation of the tube wall material. This type of cutter causes a flow of material into the inside bore and can damage the cable insulation as a result of this “necking” and the sharp edge that then results when the cable is broken. 
     A tool would therefore be advantageous that performs a cutting action that notches the tubing without deformation to the tube bore and that it is able to be operated between at least two exiting cables in close proximity to one another. It would also be advantageous if the tool could produce a chamfer at the same time to allow seals to be fitted over the tubing without damaging the seals when fitted. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, tube cutter apparatus is provided comprising a body which is generally cylindrical in shape and which has a bore through the body. The tube cutter apparatus further comprises a device to prevent lateral movement of the tube to be cut during a cutting operation, and a revolving unit containing a tool for cutting the tube. 
     In one embodiment, tube apparatus according to the present invention includes a bearing tube which defines a portion of the bore and through which the tube that is to be cut is inserted. A coupling radially surrounds a portion of the bearing tube and is in contact with the bearing tube. The coupling comprises at least one device to secure the tube to be cut in place when the tube is inserted in the bore and thereby prevent lateral movement of the tube during the cutting operation. 
     In one embodiment, the revolving unit of tube cutter apparatus in accordance with the present invention comprises a retaining flange proximate the coupling wherein the retaining flange also engages a portion of the load bearing tube. In this embodiment, the revolving unit also includes a rotary tool holder which is proximate the retaining flange and which is also in contact with a portion of the bearing tube, and the rotary tool holder includes a cutting tool for cutting the tube. The revolving unit of this embodiment additionally comprises an end flange proximate the rotary tool holder, and the end flange the retaining flange and the rotary tool holder are coupled together so that they may revolve as a unit. 
     Tube cutter apparatus in accordance with the present invention further comprises apparatus for setting the depth of cut of the cutting tool and for setting the point at which the cutting operation stops. In one embodiment, this apparatus includes a grub screw to set the depth of cut of the cutting tool and a second grub screw to set the stop point for the cutting tool. 
     A tube cutter according to the present invention produces a chamfered cut on the tube. This chambered end facilitates the attachment of seals to the end of the tube that has been cut. 
     In one embodiment, the securing device in the coupling comprises at least one socket cap screw. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a perspective drawing of one embodiment of a tube cutter in accordance with the present invention. 
         FIG. 2  is an exploded diagram of the component parts of the tube cutter illustrated in  FIG. 1 . 
         FIG. 3  is a top view of a tube which has been cut using the tube cutter apparatus of  FIGS. 1 and 2 . 
     
    
    
     DESCRIPTION OF THE SPECIFIC EMBODIMENTS 
     It will be appreciated that the present invention may take many forms and embodiments. In the following description, some embodiments of the invention are described and numerous details are set forth to provide an understanding of the present invention. Those skilled in the art will appreciate, however, that the present invention may be practiced without those details and that numerous variations and modifications from the described embodiments may be possible. The following description is thus intended to illustrate and not to limit the present invention. 
     Referring first to  FIG. 1 , tube cutter apparatus  10  in accordance with the present invention comprises a body which is generally cylindrical in shape and which has a bore through the body through which the tube  30  to be cut is inserted. 
     Referring to  FIGS. 1 and 2 , tube cutter apparatus  10  comprises a bearing tube  13  which defines a portion of the bore of the tube cutter apparatus  10 , and the bearing tube  13  is located at one end of the tube cutter apparatus  10 . A coupling  11  surrounds a portion of the bearing tube  13  and is in contact with a portion of the bearing tube  13 . Coupling  11  comprises at least one device to secure the tube  30  to be cut in place so that no lateral movement of the tube  30  occurs during the cutting operation. In the embodiment illustrated in  FIGS. 1 and 2 , coupling  11  comprises two shaft half couplings  11   a  and  11   b , which, when tightened, will prevent lateral movement of the tube during the cutting operation. 
     Still referring to  FIGS. 1 and 2 , tube cutter apparatus  10  further comprises a revolving unit which includes a retaining flange  12  which is proximate to the coupling  11  and which is also in contact with a portion of the bearing tube  13 . The revolving unit further comprises a rotary tool holder  14  which is proximate the retaining flange  12  and which is also in contact with a portion of the bearing tube  13 . The rotary tool holder  14  includes a cutting tool  16  which is securely coupled to radius arm  15  with screw  20 . The radius arm, once assembled with cutting tool  16 , may advantageously be installed in rotary tool holder  14  by using dowel  17 . Cutting tool  16  may, for example, be fabricated from high speed steel (HSS). 
     The revolving unit of tube cutter apparatus  10  in accordance with the present invention further includes an end flange  18  which is proximate to the rotary tool holder  14 . The combination of end flange  18 , rotary tool holder  14  and retaining flange  12  may be coupled together by using screws  19 , and screws  24  may be utilized to further couple retaining flange  12  and rotary tool unit  14  together. 
     The revolving unit of tube cutter apparatus  10  further comprises devices for setting the depth of cut of the cutting tool and for setting the point at which the cutting tool will stop cutting the tube. In the embodiment illustrated in  FIGS. 1 and 2 , these devices comprise grub screws  21  and  22 . Grub screw  21  is in threaded engagement with the body of rotary tool holder  14 , and one end of grub screw  21  impinges on radius arm  15  so as to set the depth of the cut by cutting tool  16 . The combination of spring  23 , grub screw  22  and lock nut  25  function to set the point at which the cutting operation will stop. 
     By utilizing tube cutter apparatus  10  in accordance with the present invention, the cutting of two tubes which are in proximity to one another is facilitated. In addition, the cutting tool  16  produces a chamfered cut  30   a  on tube  30  as illustrated in  FIG. 3 . The chamfered cuts provide good surface finishes for fitting seals at the end of the tube  30 . 
     While the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.