Abstract:
The invention relates to stripping tools for coaxial cables with a corrugated outer conductor and a hollow inner conductor. The tool comprises three main parts: a jacket cutting part for removing a certain predetermined length of the jacket of the cable, a guide part to be placed around the end of the cable after the jacket has been removed by the jacket cutting part, and a second cutting part to be placed on the guide part during a final preparation of the end of the cable during which the inner conductor, the outer conductor and the dielectric material between inner- and outer conductor are being cut off to appropriate lengths. The guide part is provided with a portion for determining a well-defined longitudinal position of the tool on the cable relative to the pattern of valleys and crests of the corrugation on the outer conductor. Using the tool according to the invention it is thereby possible to: (a) expose a predefined length of outer conductor; (b) cut off the inner conductor and the dielectric material at a predetermined longitudinal position relative to the end of the outer conductor, and (c) ascertain that the outer conductor is cut off substantially at a valley of the corrugation.

Description:
This application claims the benefit of priority under 35 U.S.C. §119(e) for European Patent Application 01109855.5 filed on Apr. 23, 2001, the content of which is relied upon and incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to stripping tools for coaxial cables and more particularly to such tools for coaxial cables with a corrugated outer conductor and a hollow inner conductor. 
     SUMMARY OF THE INVENTION 
     A coaxial cable of the above mentioned kind comprises a hollow inner conductor with a longitudinal axis and coaxially with said inner conductor a tubular layer of insulating material between said inner conductor and an outer conductor which is corrugated in a non-helical manner in order to improve flexibility of the cable, said outer conductor thereby comprising a repeated axial pattern of crests and valleys, and finally provided with an outer insulating jacket. 
     It is an object of the present invention to provide a stripping tool for a coaxial cable with said kind of corrugated outer conductor and a hollow inner conductor, which tool is capable of performing all stripping steps required in order to prepare the cable for insertion into a coaxial connector. 
     More specifically said tool must be capable of providing the correct relative axial locations of the end of the inner conductor, the end of said insulating material provided between the inner and outer conductor, the end of the corrugated outer conductor and the end of the jacket. Furthermore, said correct relative axial locations must be obtained with the tool no matter at what axial location the cable is initially cut off. 
     According to the present invention there is thus provided a stripping tool comprising the following main means: 
     A jacket cutting means for stripping the appropriate axial length of the jacket, thereby exposing the corresponding axial length of said outer conductor. 
     A guide means to be placed coaxially around the coaxial cable after said appropriate axial length of the jacket has been removed as described above, where said guide means during operation of the stripping tool guides a second cutting means and provides a well defined axial abutment surface for this means. The guide means is furthermore provided with position determining means so that it can be located at a well-defined axial position relative to said repeated pattern of crests and valleys thereby positioning said abutment surface at a well-defined axial position relative to said pattern of crests and valleys. 
     A second cutting means for providing the required relative axial positions of the end of the outer conductor, the corresponding end of the insulating material between the inner conductor and the outer conductor and the end of the inner conductor, said second cutting means being guided by said guide means and being provided with cutters, blades or similar means operating while the second means is being displaced axially relative to the cable along said guide means until said abutment between the second cutting means and said guide means is obtained. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in more detail with reference to the accompanying drawings, in which 
     FIG. 1 is an end view of a jacket cutting means according to the invention. 
     FIG. 1 a  is a schematic view of a jacket cutting means according to the invention, 
     FIG. 1 b  is a schematic view of the end of a coaxial cable inserted in the jacket cutting means in an initial position prior to stripping of the jacket; 
     FIG. 1 c  is a schematic view corresponding to FIG. 1 b  with the coaxial cable in the final position with an appropriate length of the outer conductor exposed. 
     FIG. 1 d  is a schematic view of the jacket cutting means according to the preceding Figures provided with a handgrip. 
     FIG. 2 a  is a schematic perspective view of a guide part according to the invention, 
     FIG. 2 b  is a longitudinal sectional view of the guide part shown in FIG. 2 a,    
     FIG. 2 c  is a longitudinal sectional view corresponding to FIG. 2 b  but with a cable prepared with the aid of the jacket cutting means inserted into the operative position in the guide part; 
     FIG. 2 d  is a longitudinal sectional view of an alternative embodiment of the guide part, 
     FIG. 3 a  is a longitudinal partly sectional view of the second cutting means according to the invention, 
     FIG. 3 b  is a schematic view of the second cutting means shown in FIG. 3 a  seen from the direction of the arrow A; and 
     FIG. 4 is a schematic partly sectional view of the finished coaxial cable. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following, a detailed description of a preferred embodiment of the invention is given, but it is understood that other designs of the various details in the stripping tool may be made by a person skilled in the art without departing from the scope of the invention as defined by the following claims. One such alternative embodiment, differing from the first embodiment only with respect to one particular feature is also briefly described. 
     The stripping tool according to the preferred embodiment of the invention consists of three main parts: a jacket cutting means  1  for exposing an appropriate length of the outer conductor of the cable as a necessary preparation for the following steps in the stripping procedure, a guide part  10  to be placed coaxially over the end of the cable prepared by the jacket cutting means  1  in the preceding step and serving as a guide- and abutment means for a second cutting means  18  for providing the correct relative longitudinal extension of exposed outer conductor, inner conductor and insulating material placed between the inner and outer conductors. 
     FIG. 1 a  shows a schematic view of the jacket cutting means  1  of the stripping tool in longitudinal cross section and seen from that end of the jacket cutting means  1  into which the end of a coaxial cable to be prepared for insertion in a connector is to be inserted. The jacket cutting means  1  essentially comprises a tubular body  2 , the inner diameter of which corresponds to the outer diameter of the jacket of the coaxial cable. The tubular body  2  is open at one end  3  where the cable is to be inserted and closed at the other end by a wall  4  substantially perpendicular to the longitudinal axis through the tubular body  2 . A certain length of cable can thus be inserted into the tubular body. At the inner circumferential wall of the tubular body  2  there is provided a cutting means  5  in the form of a knife blade with a cutting edge  6  facing the longitudinal axis. The cutting edge  6  starts at a longitudinal distance  1  from the end wall  4  of the tubular body  2 , this distance  1  corresponding to the longitudinal length of cable jacket to be removed. 
     The operation of the cutting means  1  is depicted in FIGS. 1 b  and  1   c . FIG. 1 b  shows an end of the coaxial cable  7  inserted into the tubular body  2  to an initial position where the end of the cable just touches the end of the cutting edge located the distance  1  from the end wall  4 . After insertion of the cable to this point, the cable is further advanced towards the end wall  4 , the tubular body  2  simultaneously being rotated about its longitudinal axis. The resultant relative movement of the cutting edge  6  and the jacket of the cable results in the jacket being cut off helically over the longitudinal distance l, thereby exposing a corresponding length of the corrugated outer conductor  9 . 
     FIG. 2 a  shows a schematic view of the above mentioned guide part  10  to be placed on that end of the coaxial cable which has been prepared as described above. More specifically the guide part  10  comprises a rotationally symmetrical body composed of two sections: a tubular section  11  made of a resilient material such as hard rubber, to which section is attached a second section  12 ,  13 ,  14  made of a substantially rigid material and longitudinally cut into a number of subsections by a number of slits  15  through the wall of the second section, in this embodiment  4  subsections of equal circumferential dimensions, although other numbers of subsections could of cause also be used. By cutting up the wall of the second section longitudinally in the manner described, it is made possible for this section to undergo radial displacements except al that end of the second section where it is attached to said resilient first section. As shown in FIGS. 2 b  and  2   c , a through bore is provided through the coaxially placed first and second sections, the diameter of this through bore substantially corresponding to the outer diameter of the jacket of the cable. It is thus possible to insert the cable into the guide part  10  from the side of the resilient first section. Furthermore, the second section is at the end hereof facing away from the first section provided with inwardly directed tongues  16 . 
     FIG. 2 c  shows the guide part with a cable prepared by means of the jacket cutting means  1  inserted. Due to the radially resilient construction of the guide part, as provided by the resilient first section and the longitudinal slits  15  in the second section, it is possible to insert the end  8  of the cable to a point beyond said inwardly directed tongues  16 , so that these tongues  16  thereby fit into the corrugation of the outer conductor  9  at those places  17  where the diameter of the outer conductor  9  is smallest, i.e. Into the “valleys” of the corrugation. During operation of the stripping tool the prepared cable is inserted in the guide part  10  so that said tongues  16  fit into that valley of the corrugation which is located closest to the end of the jacket  7  of the cable. In this manner a well-defined longitudinal placement of the guide part  10  on the cable is obtained, which is essential for the further operations of the stripping tool. 
     Referring to FIG. 2 d  there is shown an alternative embodiment of the position determining means, which in the embodiment described above was implemented in the form of the tongues  16  according to FIGS. 2 b  and  2   c . In this alternative embodiment of the position determining means, radially inwardly directed tongues  16 ′ are provided, where the surface of the tongues to be brought into contact with the corrugated outer conductor is provided with a recess to enable it to grip over the top of the crests  33  of the corrugation instead of fitting into the valleys as in the previously described embodiment. Otherwise the construction of the guide part does not differ from the guide part  10  according to the first embodiment. 
     It is understood that the construction of the guide part  10  based on the radially resilient section  11  and the split up second section  12 ,  13 ,  14 ,  16  is chosen in order to provide the end of the guide part  10  which is provided with said tongues  16  with sufficient radial resiliency to make it possible to pass the end of the cable through the through hole in the guide part  10  despite the presence of the radially inwardly directed tongue  16 ,  16 ′ and furthermore to obtain a fixed and reliable positioning of these tongues in the appropriate valley of the corrugation of the outer conductor. The required radial resiliency of the portion of the guide part comprising the tongues  16 ,  16 ′ could, however, also be achieved in other manners without the necessity to split up the second section of the guide part by the longitudinal slits  15 . For this purpose either the end of the guide part  10  comprising the tongues  16 ,  16 ′ could be made of a suitable resilient material with the remaining longitudinal extension of the guide 
     part, including the tubular section  11 , being made of a rigid material, or the whole guide part  10  could be made of a material with sufficient radial resiliency, provided a well-defined abutment surface  13  and a well-defined longitudinal distance s (see FIG. 2 c ) or distance s (see FIG. 2 d ) were still obtained. 
     The outer surface of the second section of the guide part  10  is subdivided into three regions  12 ,  13 ,  14 . In this manner, an abutment surface  13  for the second cutting means  18  mentioned initially is provided, said abutment surface  13  in this manner being located longitudinally at a well defined distance from said tongues  16 , and thereby from the valley  17  in the corrugation of the outer conductor located closest to the end of the jacket (or from a corresponding crest  33  in case of the above second embodiment). 
     The last of the abovementioned three parts of the stripping tool according to the invention, i.e. the second cutting means  18 , is shown schematically in FIGS. 3 a  and  3   b . In FIG. 3 a , a schematic longitudinal partly sectional view of the second cutting means generally indicated by  18  is shown. The second cutting means basically comprises a tubular house  20  to be placed coaxially over the previously described guide part  10 , in such a manner that during operation hereof the circumferential inner surface  21  at one end of the second cutting means  18  fits on the corresponding region  12  of the guide part  10 . Thus, when the guide part  10  is placed on the end of the cable as described in connection with FIGS. 2 a  through  2   d , the second cutting means  18  can during rotation hereof be displaced longitudinally in a well defined manner relative to the end of the cable over a longitudinal distance ultimately determined by the end face  29  during said displacement being brought into contact with the abutment surface  13  on the guide part  10 . In this final position of the second cutting means  18  a well-defined longitudinal relationship between the second cutting means  18  and the various structures of the coaxial cable (i.e. the jacket  7 , the outer conductor  9 , the insulating layer  32  between outer and inner conductor and the hollow inner conductor  31  disposed about hollow interior  30 ) are thus established. 
     As mentioned in the disclosure of the invention the purpose of the stripping tool is to prepare the end of the cable in such a manner that the required longitudinal relationships between said structures of the cable are obtained. This is indicated in FIG.  4 . Specifically the following requirements must be fulfilled: (1) The jacket  7  must be removed over the appropriate length of the outer conductor  9  as indicated by X2 in FIG. 4; (2) The end of the hollow inner conductor  31  and the insulating material  32  must be located at a distance of X1 from the end of the jacket; and (3) in order to achieve a proper fitting of a connector on the cable it is essential that the end of the outer conductor is located substantially at a “valley” of the corrugation, i.e. substantially at a part of the corrugation where this resumes the least diameter, as indicated by B in FIG.  4 . 
     Returning to the detailed description of the second cutting means  18 , said tubular house  20  comprises a first longitudinal section  21  of an inner diameter which fits the outer diameter of the corresponding section  12  on the guide part  10 . In a second longitudinal section of the second cutting means  18  there is provided the cutting means  26  as such, which means  26  comprises guide tracks  24  and  25  and comprises a central longitudinal guide shaft  19  to be inserted into the end of the hollow inner conductor  31 . Coaxially with the guide shaft  19  there is provided a cylindrical cutter means generally indicated by  26  in FIG. 3 a  comprising a first longitudinal portion containing a first cutting edge  22  and having a diameter corresponding to the smallest inner diameter of the outer conductor, so that this portion during operation can operate within the outer conductor without affecting this. When during operation the second cutting means  18  is rotated above its longitudinal axis about drive shaft  27 , and hence relative to the cable, and simultaneously advanced longitudinally relative to the guide part  10 , said cutting edge  22  cuts off the inner conductor  31  and the intermediate insulating material  32  to the appropriate longitudinal distance from the end of the jacket indicated by X1 in FIG.  4 . The cutter means  26  is furthermore provided with a second cutting edge  23  located at one longitudinal end of a larger diameter second portion of the cutter means  26  and at a longitudinal distance d from the first cutting edge  22 . During operation of the second cutting means  18  this second cutting edge  23  cut off the outer conductor  9  to its appropriate longitudinal length relative to the end of the jacket as indicated by X2 in FIG.  4 . Thus the first two of the above-mentioned three requirements are achieved. The last of these requirements, i.e. that the end of the outer conductor be located substantially at a valley of the corrugation, is fulfilled for the following reason: As previously described when the guide part  10  is correctly positioned on the end of the cable as shown in FIG. 2 c , the radial tongues  16  fits into that valley of the corrugation of the outer conductor  9  which is located closest to the end of the jacket. A well-established longitudinal relationship is thereby established between the position of that valley and the abutment surface  13  of the guide part  10 . When hereafter during operation of the second cutting means  18  the end of this means  18  is brought into contact with the abutment surface  13 , the second cutting edge  23  will be located at the appropriate longitudinal position S relative to the abutment surface  13  and hence to said first valley of the corrugation. Provided the longitudinal dimensions of the cutter means  26  are properly chosen, corresponding to the actual longitudinal distance between the valleys of the corrugation, the outer conductor will be cut off substantially at the valley adjacent said first valley, whereby the third requirement mentioned above will be fulfilled. 
     For the sake of clarity the second cutting means  18  according to this embodiment of the invention is shown in FIG. 3 b  seen from the end indicated by A in FIG. 3 a , i.e. from that end into which the cable during operation of the tool is inserted. The relative radial positions of the cutting edges  22  and  23  can be seen from this Figure. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 LIST OF PARTS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 Jacket cutting means 
               
               
                 2 
                 Tubular body of jacket cutting means 
               
               
                 3 
                 Open end of jacket cutting means 
               
               
                 4 
                 End wall of jacket cutting means 
               
               
                 5 
                 Cutting means of jacket cutting means 
               
               
                 6 
                 Cutting edge 
               
               
                 7 
                 Jacket 
               
               
                 8 
                 End of cable 
               
               
                 9 
                 Outer conductor 
               
               
                 10 
                 Guide part 
               
               
                 11 
                 Resilient tubular section 
               
               
                 12 
                 First region 
               
               
                 13 
                 Abutment surface 
               
               
                 14 
                 Second region 
               
               
                 15 
                 Slit 
               
               
                 16 
                 Tongue 
               
               
                 17 
                 Valley of the corrugation 
               
               
                 18 
                 Second cutting means 
               
               
                 19 
                 Guide shaft 
               
               
                 20 
                 Tubular house of second cutting means 
               
               
                 21 
                 First longitudinal section of second cutting means 
               
               
                 22 
                 First cutting edge 
               
               
                 23 
                 Second cutting edge 
               
               
                 24 
                 Guide track 
               
               
                 25 
                 Guide track 
               
               
                 26 
                 Cutter means 
               
               
                 27 
                 Drive shaft 
               
               
                 28 
                 Opening in second cutting means 
               
               
                 29 
                 End face of second cutting means 
               
               
                 30 
                 Hollow interior of inner conductor 
               
               
                 31 
                 Inner conductor 
               
               
                 32 
                 Insulation (dielectric) material between inner- and outer conductor 
               
               
                 33 
                 Crest of corrugation