Patent Abstract:
A connector is provided for interconnecting a coaxial cable to an electrical device. The connector has an internal body and an external body which are assembled together, and which can be activated to clamp upon and seal to an inserted coaxial cable without disassembling the external body from the internal body. The external body includes a deformable inner collar that permits the connector to be attached and sealed to cables of varying thickness as are found on common single foil and braid cable, Tri Shield cable and Quad Shield cable.

Full Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to a connector for coaxial cable, such as the type used for cable TV transmission.  
         BACKGROUND OF THE INVENTION  
         [0002]    Coaxial cable connectors that require crimping are associated with certain disadvantages. Crimping tools tend to wear out with repeated use, and crimping does not provide a satisfactory seal. A number of crimpless connectors have been developed which attempt to overcome these problems.  
           [0003]    One type of crimpless connector receives a compression sleeve, which is first broken away from a plastic ring mounted on the connector, and then slid over the cable and finally inserted into the annular cavity between the inner wall of the connector and the jacket of the cable. A tool is used to push the compression sleeve fully into the connector with a snap engagement.  
           [0004]    A problem with this connector is that it can be awkward to break the compression sleeve away from the connector and then thread it onto the cable, particularly when used in field installations where there may be adverse weather conditions. The compression sleeve can as well be inadvertently threaded onto the cable backwards, and it can also be dropped and lost.  
           [0005]    An alternative crimpless connector has more recently been provided, which permits the cable to be secured to it by means of an integral grip bushing that surrounds an internal mandril defining an annular gap that may receive the jacket and braiding of an inserted cable. The bushing can thereafter be moved so as to squeeze and hold the braiding and jacket of the cable, forming a seal therewith. While this grip bushing cable connector has many advantages, it does not lend itself to use with coaxial cables of different thicknesses.  
           [0006]    Within the cable television industry, RG6 and RG59 cable are the most prevalent standard. Common RG6 and RG59 cable has a central conductor, a dielectric insulator with a single aluminum foil cover, one layer of braided shield surrounding the foil covered dielectric insulator, and a plastic insulating jacket covering the braided shield.  
           [0007]    In addition to common RG6 and RG59 cable, so called “Tri Shield” and “Quad Shield” versions are also increasingly widely used. Tri Shield cable has a second layer of foil which covers the braided shield. Quad Shield cable has both a second layer of foil and a second layer of braided shield over the second layer of foil.  
           [0008]    As a result of the additional shielding layers, Tri Shield and Quad Shield RG6 and RG59 cables have overall thicknesses or diameters greater than that of common RG6 and RG59 cable. The standard diameter of common RG6 cable, for example, is 0.272 inches. For Tri Shield RG6 cable the standard diameter is 0.278 inches. For Quad Shield RG6 cable the standard diameter is 0.293 inches.  
           [0009]    Due to the close tolerances required for the known grip bushing connectors, a single connector cannot properly accommodate and attach to all three thicknesses of cable. At least two different sizes of connector are required: one for common cable and Tri Shield cable, and a second one for Quad Shield cable.  
           [0010]    This situation is inconvenient for installation technicians, and represents an undesirable cost to cable television companies and suppliers. Not only do two separate inventories of connectors have to be maintained, the two different sizes of connectors can be easily mixed up, leading to installation difficulties.  
         BRIEF SUMMARY OF THE INVENTION  
         [0011]    The purpose of the present invention is to obviate or mitigate the disadvantages of known connectors for coaxial cable.  
           [0012]    In accordance with the invention, a connector is provided for use with coaxial cables of the type having a central conductor, a dielectric insulator with at least one foil cover encasing the central conductor, and either one or more layers of braided shield around the dielectric insulator beneath an outer jacket.  
           [0013]    The connector comprises an internal body, threaded nut means for interconnecting the connector to a mating connector or port, and an external body that includes a deformable inner collar, assembled together so as to resist subsequent disassembly. The connector is adapted to receive and to tightly hold and seal to cables of different thicknesses, such as common RG6 cable, Tri Shield RG6, and also Quad Shield RG6 cable.  
           [0014]    The internal body is preferably in the form of a mandril that has a bore of a diameter to receive the dielectric insulator of the coaxial cable. The mandril has a sleeve with an end adapted to engage the cable beneath the jacket and the braided shield, whether the braided shield is in one layer, as in common RG6 cable and Tri Shield RG6 cable, or more layers, as in Quad Shield RG6 cable.  
           [0015]    The threaded nut means is rotatably engaged to the mandril at the end which is remote from the sleeve end that is adapted to engage the cable.  
           [0016]    The internal body also includes a cylindrical wall concentric to the sleeve of the mandril, defining an annular channel between them which is dimensioned to receive the jacket and the braided shield of an inserted cable, with a gap between the jacket and the wall. The size of the gap depends on the thickness of the cable, that is, the number of layers of braided shield.  
           [0017]    The external body is preferably in the form of a gripping bushing that is mounted to the connector surrounding a portion of the mandril and concentric to it. At its free end it has a mouth of a diameter to receive the cable. The deformable inner collar of the external body is preferably positioned proximal to the mouth of the bushing.  
           [0018]    The bushing is moveable from a first position in which the collar is remote from the annular gap, to a second position in which the collar is partially within the annular gap.  
           [0019]    The connector can be attached to a cable by inserting the cable into the mouth of the bushing while it is in its first position, pushing the dielectric insulator of the cable into the bore of the mandril with the sleeve end thereof engaging beneath the braided shield and the jacket of the cable, and subsequently moving the bushing to its second position, thereby wedging the inner collar into the annular gap, where it becomes deformed to fill the annular gap and squeezes the braided shield and jacket of the cable, holding it tightly and sealing the connector to it.  
           [0020]    Preferably, the connector includes an O ring retained in a groove on the mandril sealing it to the threaded nut means.  
           [0021]    A single size of connector of the present invention can be used with common RG6 and Tri Shield RG6 cable, and also with Quad Shield RG6 cable. The invention thus eliminates the need to have two sizes of grip bushing connectors for these different sizes of cables. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    In order that the invention may be more clearly understood, reference will be made to the accompanying drawings which illustrate a preferred embodiment of the coaxial cable connector of the present invention, and in which:  
         [0023]    [0023]FIG. 1 is a cross-sectional side view of a cable connector of the present invention;  
         [0024]    [0024]FIG. 2 is a cross-sectional side view of the same connector as shown in FIG. 1, with a coaxial cable having been inserted therein;  
         [0025]    [0025]FIG. 3 is a cross-sectional side view of the same connector as in FIG. 2, with the coaxial cable having been inserted further therein; and  
         [0026]    [0026]FIG. 4 is a cross-sectional side view of the same connector as in FIG. 3, with the outer bushing of the connector having been moved from its original position, in which the connector can receive the coaxial cable, to its final position, in which the connector tightly holds the inserted coaxial cable and forms a seal therewith. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]    In the drawings, the coaxial cable connector is denoted generally by reference number  10 . The cable is denoted by reference number  40  and is of a standard configuration comprising a central conductor  41 , a dielectric insulator  42  with a foil cover  43 , a braided shield  44  and a plastic jacket  45 .  
         [0028]    The connector  10  comprises a mandril  11 , a nut member  12 , an O-ring  13 , a retainer  14  and a bushing  15  having an internal collar  35 . The O-ring  13  is made of a compressible, elastomeric material, such as rubber or plastic. The mandril  11 , nut member  12 , retainer  14 , and bushing  15  are all made of a rigid material, preferably metallic, such as brass. The collar  35  of the bushing  15  is made of a deformable material such as Delrin®, an acetal resin available from E.I. Dupont de Nemours and Company.  
         [0029]    The mandril  11  is generally cylindrical having an enlarged base with a sleeve  17  extending therefrom. A flange  16  projects outwardly from the end of the enlarged base of the mandril  11 . The sleeve  17  has a tapered end  18  with a barb  19 . A bore  20  extends through the mandril  11  having a diameter to receive the dielectric  42  and its foil cover  43  and the conductor  41 .  
         [0030]    The nut member  12  is mounted rotatably to the mandril  11 . The nut member  12  has an inwardly projecting flange  23  that engages the flange  16  of the mandril  11  to permit free rotation between the nut member  12  and the mandril. The nut member  12  is provided with internal threads  25  and hexagonal flats  24 .  
         [0031]    The enlarged base  21  of the mandril  11  has an annular groove  28  in which sits the O-ring  13 . The O-ring  13  is of a size and dimension to seat in the annular groove  28 , and to contact sealingly with the flange  23  of the nut member  12 .  
         [0032]    The retainer  14  is generally cylindrical and is fixedly mounted to the mandril  11 . The retainer  14  has a base  26  with a wall  27  extending therefrom. The base  26  has an internal diameter that allows it to be mounted to the enlarged base  21  of the mandril  11  and held securely by frictional engagement. The sleeve  17  of the mandril  11  and the wall  27  of the retainer  14  define an annular cavity  32  with a tapered entry  33 .  
         [0033]    The bushing  15  is also cylindrical and has a mouth  31  at one end dimensioned to receive the coaxial cable  40 . The other end of the bushing  15  is adapted to be mounted to the retainer  14  with a close fitting slidable engagement.  
         [0034]    The wall  27  of the retainer  14  has a stepped external surface such that a step  29  provides a positive stop for the bushing  15  to seat against when the bushing  15  has been activated to slide into its clamping position, as shown in FIG. 4.  
         [0035]    The bushing  15  has an internal collar  35  made of a deformable plastic material, such as Delrin®. The collar  35  is generally cylindrical and is retained within the bushing proximal the mouth  31 . The outward facing rim  39  of the collar  35  is generally flat and seats at the mouth end of the bushing  15 . The inward facing rim  38  of the collar  35  has a tapered edge  36 . The collar  35  also has an external annular groove  37 .  
         [0036]    The connector  10  is assembled by first mounting the O-ring  13  to the mandril  11 , then mounting the nut member  12 , and subsequently mounting the retainer  14 , which prevents the O-ring  13  and the nut member  12  from subsequent removal from the mandril  11 . The collar  35  is inserted into the bushing  15 . Finally, the bushing  15  is mounted to the retainer  14  as shown in FIG. 1.  
         [0037]    In mounting the connector  10  to the coaxial cable  40 , the cable is first prepared by exposing a length of the central conductor  41 , and also stripping a further length of the dielectric  42  and foil-cover  43 . The braided shield  44  is cut slightly longer than the jacket  45  and is folded back over the edge thereof, as shown in FIG. 2.  
         [0038]    Attachment of the connector  10  to the cable is shown in FIGS. 2-4. The prepared cable  40  is first inserted into the connector  10  such that the conductor  41 , the dielectric  42  and the foil  43  are received within the bore  20  of the mandril  11 . The tapered end  18  of the mandril slides beneath the braided shield  44  and the jacket  45  of the cable  40 . The barb  19  on the sleeve  17  of the mandril  11  resists subsequent removal of the cable  40  from the mandril  11 .  
         [0039]    The trimmed end of the jacket  45  of the cable  40  and the folded back portion of the braided shield  44  are accommodated within the annular cavity  32 , entering at the tapered entry  33 .  
         [0040]    When the cable  40  has been fully inserted into the connector  10  such that the conductor  41  extends into the nut member  12 , the connector is placed in a levered squeezing tool (not shown) by means of which the bushing  15  can be forced to slide over the retainer  14 .  
         [0041]    As the bushing is moved the tapered edge  36  of the inner collar is inserted in the entry  33  of the annular cavity  32 , between the end  18  of the sleeve  17  of the mandril  11  and the end of the wall  27  of the retainer  14 . The inward facing rim  38  of the inner collar  35  is deformed to fill the gap  34  between the jacket  45  of the cable  40  and the retainer wall  27 , such that the cable  40  is clamped tightly and sealed by the connector  10  when the bushing  15  is squeezed fully onto the retainer  14 . The collar  35  deforms so as completely to fill the gap  34  between the cable  40  and the retainer wall  27  whether the cable has either one or two layers of braided shield  44  beneath the outer jacket  45 . The annular groove  37  of the collar  35  provides a region of weakness to promote the desired deformation of the collar  35  when the bushing  15  is compressed within the retainer  14 .  
         [0042]    It will of course be appreciated that many variations are possible within the broad scope of the invention. For example, the retainer and mandril could be an integral body. The configuration of the connector and its component parts could also be modified. Means other than the threaded nut member could be substituted for engagement of the connector to an electronic device. The O-ring could be replaced with a different type of sealing means between the mandril and the nut member, and the placement of such O-ring or other sealing means could as well be altered. Moreover, the connector can be dimensioned for use with RG59 or other cables as well as RG6 cable.

Technology Classification (CPC): 7