Patent Publication Number: US-6210222-B1

Title: Coaxial cable connector

Description:
FIELD OF THE INVENTION 
     The invention is related to the field of telecommunications and coaxial cable connectors, and more particularly to a one piece F connector which maintains a mechanical and fully shielded electrical connection with a coaxial cable end, while also providing a substantial RF and moisture seal. 
     BACKGROUND OF THE INVENTION 
     Conventional coaxial cables for the cable television industry, such as those shown in FIG. 6, typically include a circular center electrical conductor surrounded by a plastic or foam dielectric insulating layer of substantially constant thickness which forms an annular ring around the center electrical conductor. The outer surface of the dielectric insulating layer is covered by an outer conductor, usually an electrically conductive foil or braid or both of a material such as aluminum, and finally an outer elastomeric jacket surrounds the outer conductor. 
     So-called “F”-type connectors have historically been utilized to terminate the above types of coaxial cables in order to provide a continuous relationship between the center electrical conductor and the conductive foil or braid (or both) in order to effectively transmit a signal without leakage or loss of signal due to the connector and coaxial cable termination devices. F-connectors can include two, three, four, or more pieces, which are assembled together to retain a cable end. A key feature of some, is a hollow post positioned within a metal sleeve, the hollow post including a barrel portion having a raised barb. The barrel portion has a diameter which is slightly larger than the diameter of the inner dielectric insulating layer such that a prepared cable end having an exposed dielectric layer and center conductor can be positioned within the interior of the barrel. The cable is then compressed to complete the connection. 
     Several different methods have been employed historically to terminate the cable and complete the above assembly. Each of these methods have inherent problems. For example, one common termination method is to radially crimp the metal sleeve onto the post and barb using a hex-shaped tool. Using this method, six indents are formed, creating gaps in 60 degree intervals between the connector body and the jacket of the coaxial cable. These gaps potentially allow moisture into the connector and cause potential distortion of the coaxial cable. Moisture produces corrosion, effectively reducing signal strength and increasing resistance between the coaxial cable and the connector. In addition, because the afore mentioned leakage termination paths, RF leakage can also invariably occur between the connector and the coaxial cable&#39;s inner conductive braid shield. 
     Rather than using a radial crimping method for securing the coaxial cable to the connector, other F connector types use varied techniques using axial forces. For example, the EZ-F type connector manufactured by Raychem Corporation includes a compression sleeve, made from plastic or metal, in combination with the post, a retaining nut, and an outer sleeve. The compression sleeve is disposed between the post and the retaining nut and is caused to plastically deform into an open annular space defined in the post by application of an axial or longitudinal tool. 
     In another form of longitudinal crimp cable connector, described in U.S. Pat. No. 5,002,503, a preassembled nut, collar, and post are used in conjunction with an axially movable sleeve which fits within the open end of the collar to create a tight mechanical connection. In all known connectors which utilize longitudinal termination (e.g. use a longitudinal compression tool for termination thereof), the portion of the connector having the rotating nut is held in a stationary position and the portion of the connector body or sleeve accepting the coaxial cable moves axially in a direction toward the rotating nut of the connector. Besides the additional costs associated in the manufacture and assembly of these types of connectors, there are also leakage effects due to loosening of the connector and the cable end given that the forces are applied in the same direction as the assembly of the cable. 
     SUMMARY OF THE INVENTION 
     A primary object of the present invention is to overcome the above noted problems of the prior art. 
     Another primary object of the present invention is to provide a coaxial cable connector which provides a substantial mechanical fit between a coaxial cable and the connector while providing good electrical interconnection between the coaxial cable shielding conductor and the coaxial cable connector with minimal leakage. 
     Yet another primary object of the present invention is to provide an F coaxial cable connector which is adaptable for both environmental as well as non-environmental uses. 
     Therefore and according to a preferred aspect of the invention, there is provided a longitudinally compressed coaxial cable connector used for terminating a drop end of a coaxial cable, said coaxial cable including a center electrical conductor, a dielectric layer surrounding said center electrical conductor, a conductive layer surrounding said dielectric layer, and an outer insulating layer, said connector comprising: 
     an outer tubular sleeve having opposing first and second ends; 
     an inner post press fitted into one of the ends of said outer tubular sleeve, said inner hollow post comprising an annular flange and an extending barrel portion sized for receiving the dielectric layer and center electrical conductor of a prepared cable end inserted into the other end of said outer tubular sleeve, said barrel portion including a raised barb for separating the conductive layer and the outer insulating layer of the inserted cable end; and 
     a rotating nut member attached to said inner post, said rotating nut member having an internal threaded portion for receiving input from a cable termination device, and in which said inner post and said rotating nut are movable within the interior of said outer tubular sleeve toward the cable receiving end of the outer tubular sleeve to crimp the inserted cable end and to complete the termination thereof. 
     According to another preferred aspect of the present invention, there is provided a longitudinally compressed cable connector for terminating a drop end of a coaxial cable, said connector comprising: an outer tubular sleeve having opposing first and second ends; a hollow inner post pressfitted into one of the ends of the outer tubular sleeve, said inner post comprising an annular flange and an extending barrel portion having a diameter sized for receiving a portion of a prepared coaxial cable end inserted into the opposing end of said tubular sleeve, said barrel portion having means for separating portions of said coaxial cable; and a rotating nut fixedly attached to said inner post, said rotating nut having an internal threaded portion for receiving input from a cable termination device wherein said rotating nut and inner post are capable of axial movement in a direction directed toward the cable receiving end of the outer tubular sleeve, said sleeve being stationarily held after insertion of said cable end and in which said outer tubular sleeve includes an opening at the cable receiving end, said opening having a throat for compressing said inserted cable end. 
     According to yet another preferred aspect of the present invention there is provided a method of terminating a coaxial cable using an F connector, said F connector having an inner post fitted within an outer tubular sleeve, said method comprising the steps of: 
     i) preparing one end of a coaxial cable by removing an axial portion of at least one outer layer of said cable; 
     ii) inserting the prepared coaxial cable end into said cable connector wherein insertion causes the axially separated portion to extend through an axial sleeve and separates the outer portion of the remainder of the cable inserted into the connector; 
     iii) driving said cable until the separated ends of said coaxial cable are placed into a circumferential sealing recess; and 
     iv) supporting said sleeve in a stationary position and axially driving the post and rotating nut toward said supported sleeve in order to crimp the cable. 
     According to yet another preferred aspect of the present invention, there is provided an assembly comprising a coaxial cable and a cable connector, said coaxial cable including: 
     a center conductor; 
     an inner insulating layer surrounding said center conductor; 
     at least one outer conductive layer surrounding said inner insulating layer; and 
     an outer insulating jacket surrounding said at least one outer conductive layer, said cable connector comprising: 
     an outer tubular sleeve; 
     an hollow inner post pressfitted said outer tubular sleeve, said hollow inner post having an annular flange and a distal barrel portion extending from said annular flange having a diameter which is smaller than the diameter of the inner conductive layer, said distal barrel portion further having a raised barb on an exterior surface thereof for separating the outer insulating layer and said at least one conductive layer from said inner insulating layer and said center conductor, said inner insulating layer and center conductor extending through said distal barrel portion; and 
     a rotating nut proximally attached to said hollow inner post, in which the rotating nut, hollow inner post, and outer tubular sleeve are preassembled as a one piece connector, and in which said inner post and rotating nut are axially movable toward the distal end of said tubular sleeve in order to crimp an inserted cable end. 
     As opposed to prior art coaxial cable connectors referred to above, the coaxial cable connector according to the present invention operates such that the outer body of the connector where the cable entry port is located remains stationary. The post and the tubular nut are axially driven, using a conventional termination tool, toward the rear of the connector body in which the cable entry port is located. 
     An advantage provided by the present coaxial cable connector is that fewer parts are required in comparison with many known F connectors manufactured for this purpose. Moreover, the connector is provided as a single component to the user in which closure of the connector completes the assembly after a cable end is inserted. No additional external components are required. Therefore, manufacture of the present coaxial cable connector is simpler, less expensive and far less labor intensive. 
     Another advantage is that the coaxial cable connector of the present invention can be used in conditions normally requiring either environmental or non-environmental type connectors, allowing greater versatility and flexibility. 
     Another advantage is that an effective 360 degree seal is produced for the separated as well as the unseparated portions of the coaxial cable which is terminated after a termination tool is used to push the cable/connector assembly together. The seal is effective for both moisture and RF leakage. 
     Yet another advantage of the connector of the present invention is that the termination is performed longitudinally, yet in a direction which is opposite to the direction of cable assembly. The post is internal to the sleeve such that all of the sealing is internal to the connector. According to the invention, the rotating nut and inner post are driven toward the cable receiving end of the sleeve which is held stationary. This form of assembly permits greater assurance that the cable will not be loosened. 
     These and other objects, features, and advantages will herein be described in greater detail in the following Detailed Description which should be read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an F-type coaxial cable connector made in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is an exploded view, taken in section of the coaxial cable connector of FIG. 1; 
     FIG. 3 is a sectional view of the coaxial cable connector of FIGS. 1 and 2, shown in an initial pre-assembled condition; 
     FIG. 4 is the sectional view of FIG. 3, depicting the coaxial cable connector in a partial preassembly condition; 
     FIG. 5 is the sectional view of FIGS. 3 and 4, depicting the coaxial cable connector in a completed preassembly condition; 
     FIG. 6 is a partial sectional view of a coaxial cable as prepared prior to insertion into the coaxial cable connector of the present invention; 
     FIG. 7 is a partial sectional view of the prepared coaxial cable end of FIG. 6 as initially inserted into a preassembled coaxial cable connector made in accordance with a second embodiment of the present invention; 
     FIG. 8 is the partial sectional view of FIG. 7 with the prepared coaxial cable end fully inserted into the cable connector; 
     FIG. 9 is the partial sectional view of FIGS. 7 and 8 showing the completion of the cable/coaxial cable connector assembly process; and 
     FIG. 10 is a partially cutaway perspective view of a completed coaxial cable/cable connector assembly. 
    
    
     DETAILED DESCRIPTION 
     The following description relates to a method for terminating a drop coaxial cable using an F-type cable connector which is made in accordance with certain preferred embodiments of the present invention. Throughout the course of discussion which follows, several terms such as “front”, “back”, “lateral”, “distal” and “proximal” are used to provide a frame of reference with respect to the accompanying drawings. These terms, however, should not be deemed to be limiting of the inventive concepts of the present invention. 
     Referring to the Figs. and more particularly to FIG. 1, there is first shown a coaxial cable connector according to a preferred embodiment of the present invention. The coaxial cable connector  30  includes three (3) major components; namely an outer tubular sleeve  34 , an inner post  38 , and a rotating nut  42 . The connector  30  shown in this view is preassembled; that is, in the condition a user would typically receive the connector from the factory prior to desired cable termination. Both the preassembly of the cable connector and the method of terminating a drop end of a coaxial cable using the connector are herein described below. 
     First, however, and referring to FIG. 2, an exploded view of the coaxial cable connector  30  more clearly illustrates the above noted components. The outer tubular sleeve  34  is a cylindrical member having a pair of open ends  40 ,  46  defining a hollow interior  44 . The distal end  40  of the tubular sleeve  34  includes an inwardly tapering opening  50  which terminates a predetermined axial distance into the sleeve at a narrowed section or throat  48 . The proximal end  46  of the sleeve  34  includes an opening  54  having a diameter which is larger than the distal opening  50 , the hollow interior  44  further having an annular shoulder or ridge  58  disposed a predetermined axial distance from the proximal end  46 . 
     The inner post  38 , like the outer tubular sleeve  34 , is defined by a pair of open ends  39 ,  41 , and a hollow interior  43 . More particularly, the inner post  38  includes an annular flange  60  having a distal barrel portion  64  and a proximal fastening portion  68  extending respectively therefrom. The distal barrel portion  64  includes a raised barb  72  at the distal end  39  which tapers outwardly from the open end to a flattened portion  74 , shown most clearly in FIGS. 3-5. The annular flange  60  includes a distal facing surface  76  having a circumferential recess  78  including an inwardly tapering surface  79  leading to a rectangular shaped slot. The barrel section  64  also includes an outwardly tapered surface  83  extending into the circumferential recess  78 . The proximal fastening portion  68  is defined by an inwardly tapering cylindrical section having an annular tab  82  at the proximal end  41  of the post  38 . 
     The rotating nut  42  includes a distal engagement portion  85  having an opening  84  sized for receiving the proximal fastening section  68  of the post  38 . The nut  42  further includes a female receiving portion  88  for receiving the input end (not shown) of a cable transmission device which is interiorly threaded, the female receiving portion being separated from the receiving opening  84  of the distal engagement portion  85  by an annular recess  90 . According to the preferred embodiment, each of the three major components are made from the same material (e.g. brass), though it will be readily apparent that suitable material variations can be substituted. As shown, each of the three major components are longitudinally aligned along an assembly axis  93 . 
     With the preceding background, the preassembly of the coaxial cable connector  30  will now be described with reference to FIGS. 3-5. Initially, and as shown in FIG. 3, the proximal fastening portion  68  of the inner post  38  is inserted into the receiving opening  84  of the rotating nut  42  until an exposed end  98  of the distal engagement portion  85  engages an edge  96  at the proximal end of the annular flange  60  of the post which prevents further axial movement. 
     According to FIG. 4, an anvil (not shown) or other device is then inserted into the hollow interior  43  of the inner post  38  and more particularly into the proximal fastening portion  68  causing the tapered cylindrical portion thereof to expand and the annular tab  82  at the proximal end  41  of the post  38  to engage the annular recess  90 , the recess being sized to retain the rotating nut  42  into locking engagement. Though the tubular sleeve  34  is shown in FIGS. 3 and 4, this component is not yet necessary for purposes of the described preassembly process. 
     With reference to FIG. 5, the formed post/rotating nut assembly of FIGS. 3 and 4 is then pre-assembled to the outer tubular sleeve  34  with the proximal opening  54  of the outer sleeve being sized to allow a press fit of the annular flange  60  of the inner post  38  within the hollow interior  44  of the sleeve. In this embodiment, the inner post  38  is inserted into the proximal end  46  of the outer sleeve  34  to a predetermined axial distance, creating an annular space  94  about the periphery of the barrel section  64  between the distal facing surface  76  of the annular flange  60  and the throat  48 . In a preferred preassembly, the barrel portion  64  of the inner post  38  is aligned with the distal opening  50  of the tubular sleeve  34  along the axis  93 , FIG. 2, and is located or positioned proximally a short axial distance from the throat  48 . 
     Before discussion of the termination process using a cable connector as described above, reference is now made to FIG. 6 which illustrates a prepared end portion of a coaxial cable  10 . More particularly, the coaxial cable  10  includes a center electrical conductor  14 , such as copper or a copper-clad steel, and a foam dielectric layer  18 , which surrounds the center electrical conductor. A conductive braid  22 , such as aluminum, is disposed about the foam dielectric layer  18 , while an insulating outer elastomeric jacket  26  completes the coaxial cable assembly. Alternately, a conductive foil (not shown) can be included in lieu of or in combination with the conductive braid  22 . Each of the above components and cable manufacture are commonly known and require no further discussion. 
     In preparing the end portion of the coaxial cable  10 , a predetermined axial portion (typically on the order of about 0.25 inches each) of the center electrical conductor  14  and the foam dielectric layer  18  are sequentially exposed from the remaining layers  22 ,  26  of the cable. A portion of conductive braid  22  is wrapped about the outer jacket end. As shown in the FIG. 6, the center electrical conductor  14  extends relative to the end of the dielectric layer  18 , with an axial portion of the dielectric layer extending coextensively from the jacket  26  and the wrapped braid  22 . Each of the preceding preparation steps are commonly known in the field. 
     Referring to FIGS. 7-10, a cable termination end assembly is now described in conjunction with the prepared cable  10  and a coaxial cable connector  10 A manufactured according to a second embodiment of the present invention. In brief, the coaxial cable connector  30 A, like the preceding version, includes an outer tubular sleeve  34 A having an interior  44 A and a narrowed throat  48 A disposed in relation to a distal end  40 A. Within the outer tubular sleeve  34 A is an inner post  38 A defined by an annular flange  60 A with an extending barrel section  64 A and proximal fastening portion  68 A. The proximal fastening portion  68 A is attached though a receiving opening  84 A of a distal engagement portion  85 A of rotating nut  42 A and the resulting rotating nut/inner post subassembly is pressfitted a predetermined axial distance into the hollow interior of the outer tubular sleeve in a manner as described according to the preassembly procedure detailed above. 
     The most noteworthy differences between these embodiments are the exclusion of the tapered cylindrical section and annular tab of the proximal fastening portion  68 A, and an increased axial length of the raised barb  72 A defined on the barrel section  64 A. The termination method herein described, however, is performed in the same manner and according to the same steps using either type connector, as will be readily apparent. For purposes of discussion herein, the above connector further includes a pair of O-rings  104 ,  108  or other sealing members which are disposed between the inner post  38 A and the distal engagement portion of the rotating nut  42 A and within the female receiving portion  88 A, respectively. The O-rings  104 , 108  are each made from an elastomeric material, such as an ethylene propylene, or other resilient material which is resistant to ozone. 
     Referring to FIG. 7, the prepared end portion of the coaxial cable  10  is initially inserted into the tapered distal opening  50 A of the distal end  40 A of the preassembled cable connector  30 A. Upon insertion thereof, the exposed portions  14 ,  18  of the cable  10  easily pass through the tapered distal opening  50 A of the outer tubular sleeve  34 A. The outer portions  22 ,  26  of the cable  10 , however, are compressed due to the constrictive cross section of the narrowed throat  48 A. According to this embodiment, an average compression of about 16-20 percent is achieved. The exposed portions of the center electrical connector  14  and the dielectric layer  18  pass into the aligned hollow opening of the distal barrel portion  60 A with the outer sleeve  26  and the conductive braid  22  being separated from the remainder of the cable  10  by the raised barb  72 A into the annular space  94  defined between the barrel portion  64 A and the interior side of the outer tubular sleeve  34 A. The barb  72 A creates a stretching of the conductive braid and outer jacket. Therefore a slight force is required for insertion of the cable, but in that separation requires a much greater force to withdraw the jacket and braid from the connector. Moreover, the above stretching creates a new larger diameter for the separated jacket and braid so that a mechanical interference or crimp will result when the barb and throat are planarly aligned as described below upon “closing” the connector. 
     The separation of the outer layers  22 ,  26  of the cable  10  and the narrowed throat  48 A further provides a locking force which does not easily permit the separation of the cable from the connector once the cable has been initially inserted as described. 
     Referring to FIG. 8, further axial insertion of the cable  10  causes the wrapped end, including the separated portions of the outerjacket  26  and conductive braid  22 , to engage the circumferential recess  78 A on the distal facing surface  76 A of the annular flange  60 A of the inner post  38 A. The above steps initially position and secure the end portion of the coaxial cable  10  within the connector  30 A and the connector is now ready for termination. 
     Referring to FIGS. 9 and 10, a hand-held or other longitudinal crimping tool (not shown) is then used to engage the rotating nut  42 A and the inner post  38 A, while retaining the outer sleeve  34 A in a stationary position through support herein indicated pictorially by  124 . Longitudinal crimping tools are known in the field and do not form an essential part of the present invention. Therefore, details regarding these tools are not required other than to note that modification of these tools is not required in order to terminate using the above connector  30 A. 
     The inner post/rotating nut assembly is longitudinally driven in an axial direction  120  toward the distal end  40 A of the outer tubular sleeve  34 A, the sleeve as noted above being stationarily held in fixed relation by the tool. The cable end resists loosening when pushed by the inner post in the above direction  120 , due mainly to the attachment of the separated layer ends in the circumferential recess  76 A, the retention of the exposed dielectric layer  18  and center electrical conductor  14  in the hollow interior of the barrel portion  64 A, and the radial compressive force exerted by the throat  48 A. In fact, a portion  126  of the separated layers  22 ,  26  are axially displaced within the annular space  94  defined within the connector due to the compressive force applied by the inner post  38 A against the support  124 . This displacement creates a thicker massing of the outer jacket and braid, which in turn creates coupling for the cable within the connector. 
     The annular shoulder or ridge  58 A along the inner surface of the outer tubular sleeve  34 A provides an axial stop for the post/rotating nut subassembly to prevent further longitudinal movement thereof. In this position, the end of the exposed center electrical connector  14  is axially disposed in the female receiving portion of the rotating nut while the raised barb of the barrel portion  60 A is substantially in the throat  48 A, aiding the seal in the distal end of the connector. In the final crimped position, the cable end is securely maintained within the connector  30 A with greater confidence that the cable  10  has been properly seated with the facing surface of the inner post  38 A assuring a solid electrical connection without the presence of leakage paths. Moreover, O-rings  104  and  108  provide additional seal protection if the connectors are to be used as environmental connectors. 
     
       
         
           
               
             
               
                   
               
               
                 Parts List FIGS. 1-10 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 10 
                 coaxial cable 
               
               
                   
                 11 
                 cable end 
               
               
                   
                 14 
                 center electrical connector 
               
               
                   
                 18 
                 dielectric layer 
               
               
                   
                 22 
                 conductive braid 
               
               
                   
                 26 
                 outer jacket 
               
               
                   
                 30 
                 cable connector 
               
               
                   
                 34 
                 outer tubular sleeve 
               
               
                   
                 38 
                 inner post 
               
               
                   
                 39 
                 distal end - post 
               
               
                   
                 40 
                 distal end - sleeve 
               
               
                   
                 41 
                 proximal end - post 
               
               
                   
                 42 
                 rotating nut 
               
               
                   
                 43 
                 interior 
               
               
                   
                 44 
                 interior 
               
               
                   
                 46 
                 proximal end 
               
               
                   
                 48 
                 throat 
               
               
                   
                 50 
                 tapered opening 
               
               
                   
                 54 
                 proximal opening 
               
               
                   
                 58 
                 annular shoulder or ridge 
               
               
                   
                 60 
                 annular flange 
               
               
                   
                 64 
                 distal barrel portion 
               
               
                   
                 68 
                 nut fastening portion 
               
               
                   
                 72 
                 raised barb 
               
               
                   
                 74 
                 flattened portion 
               
               
                   
                 76 
                 facing surface 
               
               
                   
                 78 
                 circumferential recess 
               
               
                   
                 79 
                 inwardly tapering surface 
               
               
                   
                 82 
                 annular tab 
               
               
                   
                 83 
                 tapered surface 
               
               
                   
                 84 
                 distal opening 
               
               
                   
                 85 
                 distal engagement portion 
               
               
                   
                 88 
                 receiving portion 
               
               
                   
                 90 
                 annular recess 
               
               
                   
                 92 
                 edge 
               
               
                   
                 93 
                 assembly axis 
               
               
                   
                 94 
                 annular space 
               
               
                   
                 104 
                 O-ring 
               
               
                   
                 108 
                 O-ring 
               
               
                   
                 120 
                 axial direction 
               
               
                   
                 124 
                 support 
               
               
                   
                 126 
                 compressed layers 
               
               
                   
                 30A 
                 cable connector 
               
               
                   
                 34A 
                 outer tubular sleeve 
               
               
                   
                 38A 
                 inner post 
               
               
                   
                 39A 
                 distal end - post 
               
               
                   
                 40A 
                 distal end - sleeve 
               
               
                   
                 41A 
                 proximal end - post 
               
               
                   
                 42A 
                 rotating nut 
               
               
                   
                 43A 
                 interior 
               
               
                   
                 44A 
                 interior 
               
               
                   
                 46A 
                 proximal end 
               
               
                   
                 48A 
                 throat 
               
               
                   
                 50A 
                 tapered opening 
               
               
                   
                 54A 
                 proximal opening 
               
               
                   
                 58A 
                 annular shoulder or ridge 
               
               
                   
                 60A 
                 annular flange 
               
               
                   
                 64A 
                 distal barrel portion 
               
               
                   
                 68A 
                 nut fastening portion 
               
               
                   
                 72A 
                 raised barb 
               
               
                   
                 74A 
                 flattened portion 
               
               
                   
                 76A 
                 facing surface 
               
               
                   
                 78A 
                 circumferential recess 
               
               
                   
                 79A 
                 inwardly tapering surface 
               
               
                   
                 83A 
                 tapered surface 
               
               
                   
                 84A 
                 distal opening 
               
               
                   
                 85A 
                 distal engagement portion 
               
               
                   
                   
               
            
           
         
       
     
     Though the preceding has been described based on certain preferred embodiments, it will be readily apparent that certain variations and modifications are possible based on the inventive concepts described herein and according to the following claims.