Abstract:
A connector is provided for interconnecting a coaxial cable to an electrical device. The connector has an internal body with a rotatable nut and an external body with a rotatable nut 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 is axially moveable and when activated to clamp upon the inserted coaxial cable, also engages the sealing ring positioned around the internal body to form a seal with the rotatable nut.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to a connector for coaxial cable, such as the type used for cable TV transmission. 
     BACKGROUND OF THE INVENTION 
     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. 
     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. 
     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. 
     An alternative crimpless connector has more recently been provided, which permits the cable to be secured to it simply by pushing the cable into the connector and subsequently pulling it back. The body of this “push-pull” connector has a bushing mounted within it near the cable receiving end having a diameter to closely receive the cable. The body of the connector also has within it an annular mandril having a bore to receive the stripped core of the cable, and having a sleeve adapted to engage the cable beneath the jacket by pushing the cable and the mandril together. This stretches the jacket of the cable to a diameter greater than the internal diameter of the bushing. 
     The mandril is moveable from a position in which the sleeve is surrounded by the bushing in which the sleeve may be engaged to the cable, to a position in which the sleeve is at least partially within the bushing in which the jacket is frictionally engaged by the bushing by pulling the cable away from the connector after it has been pushed onto the mandril sleeve. 
     While the push-pull cable connector has many advantages, it does not lend itself to all applications. In some publicly accessible installations, for example, it is the usual practice to cover the threaded posts to which the cables are connected by a security ring, making the threaded portion of an installed cable connector inaccessible to finger manipulation or common wrenches or pliers. Unauthorized removal of the cable is thereby discouraged as a special tool is needed to fit within the security ring. 
     Due to the close tolerances of the standard security ring, the dimensional limitations of the push-pull connector present a significant obstacle. The internal bushing and mandril of the push-pull connector require a larger body diameter than can be accommodated in the standard sized security ring. While a larger security ring could be substituted, doing so would present additional costs. 
     It has also been found that the push-pull connector can be awkward to use with coaxial cable having multiple layers of braided shielding. Because of the limited travel of the mandril and bushing, the inserted cable must be trimmed to expose only a short distance of braided shielding. Folding back one layer of braided shielding presents little difficulty. However, manipulating multiple layers of braided shielding that are as short as required can be awkward. While a push-pull connector could be made with a longer travel for the mandril and bushing, thus allowing a longer trimmed section for the cable, this would require a longer overall connector length which would increase material costs. 
     BRIEF SUMMARY OF THE INVENTION 
     The purpose of the present invention is to obviate or mitigate the disadvantages of known connectors for coaxial cable. 
     In accordance with the invention, a connector is provided for use with a coaxial cable of the type having a central conductor, a dielectric insulator with a foil cover encasing the central conductor, at least one braided shield surrounding the foil covered dielectric insulator, and a plastic jacket covering the braided shield. 
     The connector comprises an internal body, means for interconnecting the connector to an electrical device, and an external body, assembled together so as to resist subsequent disassembly. The connector is adapted to receive a coaxial cable and to tightly hold the cable and form a seal with it by moving the external body relative to the internal body without disassembling the external body from the internal body. 
     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 braided shield and jacket. 
     The interconnecting means comprises threaded nut means which is rotatably mounted to the internal body at the end thereof remote from the sleeve end adapted to engage the cable. 
     The external body is preferably in the form of a gripping bushing that is mounted to the connector partially surrounding the mandril and concentric to it. At its free end it has a bore of a diameter to receive the jacket of the cable. The bushing is moveable from a first position in which the bore of the bushing and the sleeve of the mandril define an annular gap to receive the braided shield and the jacket of the cable, to a second position in which the annular gap between the bushing and the sleeve of the mandril is reduced, thereby squeezing the braided shield and the jacket of the cable. 
     Preferably the nut means is rotatably mounted to the mandril and retained thereto by a flange on the mandril. More preferably, the sleeve of the mandril is tapered and barbed. 
     Advantageously the gripping bushing is assembled with the mandril by close frictional contact and is moveable slidingly from its first position to its second position by means of a squeezing tool. 
     The connector also includes an O-ring retained upon the internal body close to the nut means, and the external body slides over the O-ring when it is moved into its second position. 
     It has been found that the connector of the present invention provides an effective solution to the problems presented by known prior art coaxial cables, as described above. 
     The connector of the present invention is preassembled. No separate pieces are involved that must be threaded onto the cable, and which can be misoriented or lost. The dimensional tolerances of the connector of the present invention, moreover, enable it to be used with the standard sized security ring. In addition, the connector of the present invention easily accepts coaxial cable having multiple layers of braided shielding with longer trimmed sections that facilitate folding of the braided shielding back over the cable jacket. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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: 
     FIG. 1 is an exploded perspective view of a cable connector of the present invention, shown with a coaxial cable; 
     FIG. 2 is a cross-sectional side view of the connector of FIG. 1; 
     FIG. 3 is a cross-sectional side view of the same connector as shown in FIG. 2, with a coaxial cable having been inserted therein; 
     FIG. 4 is a cross-sectional side view of the same connector as in FIG. 3, with the coaxial cable having been inserted further therein; and 
     FIG. 5 is a cross-sectional side view of the same connector as in FIG. 4, 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 
     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 . 
     The connector  10  comprises a mandril  11 , a nut member  12 , an O-ring  13 , a retainer  14  and a bushing  15 . The O-ring  13  is made of a compressible, elastomeric material, such as rubber or plastic, and the mandril  11 , nut member  12 , retainer  14 , and bushing  15  are all made of a rigid material, preferably metallic, such as brass. 
     The mandril  11  is generally cylindrical having an enlarged base w 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 receiving the dielectric  42  and its foil cover  43  and the conductor  41 . 
     The nut member  12  is mounted rotatably to the mandril  11 . The nut member  12  has a collar  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 . 
     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 of the mandril  11  and held securely by frictional engagement. A square shoulder  22  on the enlarged base of the mandril  11  provides a seat for the base  26  of the retainer  14 . 
     The collar  23  of the nut member  12  and the enlarged base of the mandril  11  and the base  26  of the retainer  14  together define 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 extend slightly beyond the retainer  14 . 
     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 but slidable engagement. 
     The bushing  15  has a stepped internal surface. A first step  29  reduces the internal diameter of the bushing from a dimension corresponding to the outside diameter of the retainer  14  to a dimension corresponding to the inside diameter of the wall  27  of the retainer  14 . The first step  29  of the bushing  15  seats against the end of the wall  27  of the retainer  14  when the bushing  15  has been activated to slide into its clamping position, as shown in FIG. 5. A second step  30  on the internal surface of the bushing  15  defines the depth of the mouth  31 . 
     The connector  10  is assembled by first mounting the nut member  12  to the mandril  11 , then mounting the O-ring  13 , and subsequently mounting the retainer  14 , which prevents the O-ring  13  and the nut member  12  from subsequent removal from the mandril  11 . Finally, the bushing  15  is mounted to the retainer  14  as shown best in FIG.  2 . 
     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 its 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.  1 . 
     As shown in FIGS. 3 and 4, the cable  40  is 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 . 
     The trimmed end of the jacket  45  of the cable  40  and the folded back portion of the braided shield  44  encounter a flared shoulder  21  on the sleeve  17  of the mandril  11 . A cavity  33  between the internal surfaces of the bushing  15  and retainer  14  and the external surface of the sleeve  17  accommodates the jacket  45  and the folded back portion of the braided shield  44  of the cable  40 . 
     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  and the O-ring  13 . 
     As the bushing is moved, the gap  32  between the bushing  15  and the tapered end  18  of the mandril  11  is reduced, as shown in FIG.  5 . The second step  30  of the bushing  15  impinges upon the cable  40 , squeezing the braided shield  44  and jacket  45  between the mouth  31  of the bushing  15  and the tapered end  18  of the mandril  11  such that when the bushing  15  is collapsed fully onto the retainer  14 , with the first step  29  seated upon the end of the wall  27 , the cable  40  is clamped tightly by the connector  10  with a moisture seal formed between the jacket  45  of the cable and the mouth  31  of the bushing  15 . 
     In addition, the end of the bushing  15  that is mounted to the retainer  14  contacts and compresses the O-ring  13  within the annular groove  28  to provide a more secure seal between the nut member  12  and the mandril  11 . 
     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 bring or other sealing means could as well be altered.