Patent Publication Number: US-7588460-B2

Title: Coaxial cable connector with gripping ferrule

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/923,817, filed on Apr. 17, 2007, which is incorporated by reference herein in its entirety for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to connectors for terminating coaxial cable. More particularly, the present invention relates to a coaxial cable connector having structural features to enhance gripping of a coaxial cable and to provide sealing of the interior of the connector from the environment, while minimizing the steps required to prepare the end of a coaxial cable. 
     It has long been known to use connectors to terminate coaxial cable so as to connect a cable to various electronic devices such as televisions, radios and the like. Prior art coaxial connectors generally include a connector body having an annular collar for accommodating a coaxial cable, an annular nut rotatably coupled to the collar for providing mechanical attachment of the connector to an external device and an annular post interposed between the collar and the nut. A resilient sealing O-ring may also be positioned between the collar and the nut at the rotatable juncture thereof to provide a water resistant seal thereat. The collar includes a cable receiving end for insertably receiving an inserted coaxial cable and, at the opposite end of the connector body, the nut includes an internally threaded end extent permitting screw threaded attachment of the body to an external device. 
     This type of coaxial connector further typically includes a locking sleeve to secure the cable within the body of the coaxial connector. The locking sleeve, which is typically formed of a resilient plastic, is securable to the connector body to secure the coaxial connector thereto. In this regard, the connector body typically includes some form of structure to cooperatively engage the locking sleeve. Such structure may include one or more recesses or detents formed on an inner annular surface of the connector body, which engages cooperating structure formed on an outer surface of the sleeve. A coaxial cable connector of this type is shown and described in commonly owned U.S. Pat. No. 6,530,807. 
     Conventional coaxial cables typically include a center conductor surrounded by an insulator. A conductive foil is disposed over the insulator and a braided conductive shield surrounds the foil covered insulator. An outer insulative jacket surrounds the shield. In order to prepare the coaxial cable for termination, the outer jacket is stripped back exposing an extent of the braided conductive shield which is folded back over the jacket. A portion of the insulator covered by the conductive foil extends outwardly from the jacket and an extent of the center conductor extends outwardly from within the insulator. Upon assembly to a coaxial cable, the annular post is inserted between the foil covered insulator and the conductive shield of the cable. 
     Needless to say, the process of preparing an end of a coaxial cable for installation into a connector requires a modicum of skill and is somewhat time consuming. A further problem with current coaxial connectors is that in order to properly attach the connector to the coaxial shielded cable, a good deal of manual force must be applied to push the coaxial shielded cable over the barbs of the post. During conventional installation, the cable can buckle when the post with the barb is pushed between the foil and the braid and create an unsatisfactory electrical and mechanical connection. Thus, a mistake made in the preparation process may result in a faulty connector installation. 
     Another problem with current coaxial connectors is that they are often difficult to use with smaller diameter coaxial cables. In particular, current coaxial connectors often do not adequately grip smaller diameter coaxial shielded cables. Moreover, sealing the interior of the connector from outside elements also becomes more challenging with smaller diameter cables. 
     It is, therefore, desirable to provide a coaxial connector which minimizes the steps required to prepare an end of a coaxial cable. It would be further desirable to provide a coaxial cable connector that eliminates the need to use excessive force to push the post into the coaxial shielded cable and prevents buckling of the coaxial shielded cable. It would be still further desirable to provide a coaxial cable connector with structural features to enhance gripping and sealing, particularly with smaller diameter cables. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a coaxial cable connector for terminating a coaxial cable. 
     It is a further object of the present invention to provide a coaxial cable connector which reduces the steps required to prepare an end of a coaxial cable. 
     It is still a further object of the present invention to provide a coaxial cable connector having structure to enhance gripping and sealing of a coaxial cable, especially a small diameter coaxial cable. 
     In the efficient attainment of these and other objects, the present invention provides a coaxial cable connector. The connector of the present invention generally includes a connector body having a rearward cable receiving end, a locking sleeve movably coupled within the rearward cable receiving end of the connector body for locking the cable in the connector and a gripping ferrule disposed between the connector body and the locking sleeve. The gripping ferrule includes axially opposite gripping ends which move in a radially inward direction upon compression between the locking sleeve and the connector body to grip the outer surface of the cable. 
     In a preferred embodiment, the gripping ferrule preferably includes at least one flexible finger disposed at each opposite end of the ferrule, which deflects radially inward upon insertion of the locking sleeve into the connector body to grip a cable inserted into the connector and to prevent rearward removal of the cable from the connector body. The flexible fingers of the gripping ferrule preferably include a tapered forward end defining a sharp edge to enhance gripping of the cable. The connector body preferably includes an internal ramp portion for deflecting a forward flexible finger of the gripping ferrule radially inward and the locking sleeve preferably includes an internal ramp portion for deflecting a rearward flexible finger of the gripping ferrule radially inward upon insertion of the locking sleeve into the connector body. The gripping ferrule further preferably includes an internally threaded or corrugated inner surface adapted to threadably or otherwise engage an outer surface of a coaxial cable. 
     The connector further preferably includes an annular post disposed within the connector body and a nut rotatably coupled to the post. The annular post has a rearward cable insertion end disposed within the connector body, which preferably defines a sharp edge adapted to penetrate an end of the cable as the gripping ferrule is threaded on the outer surface of the cable. 
     The present invention further involves a method for terminating a coaxial cable in a connector. The method according to the present invention generally includes the steps of inserting an end of a cable into an axially movable locking sleeve disposed within a rearward cable receiving end of a connector body which has a gripping ferrule supported therein and moving the locking sleeve forward to compress opposite ends of the gripping ferrule around the cable at two locations. As a result of the present invention, the time required to prepare the end of a coaxial cable prior to installation on the connector is drastically reduced. 
     A preferred form of the coaxial connector, as well as other embodiments, objects, features and advantages of this invention, will be apparent from the following detailed description of illustrative embodiments thereof, which is to be read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a coaxial cable being inserted into the coaxial cable connector of the present invention. 
         FIG. 2  is a cross-sectional view of the cable and connector shown in  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the cable inserted into the connector of the present invention with the locking sleeve in an open position. 
         FIG. 4  is a cross-sectional view of the cable inserted into the connector of the present invention with the locking sleeve in a closed position. 
         FIG. 5  is a cross-sectional view of the connector of the present invention with the cable not shown for clarity. 
         FIG. 6  is another cross-sectional view of the cable inserted into the connector of the present invention with the locking sleeve in a closed position. 
         FIG. 7  is a perspective view of the preferred embodiment of the gripping ferrule of the present invention in isolation. 
         FIG. 8  is a perspective view of the gripping ferrule shown in  FIG. 7  with the fingers shown deflected radially inward. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, the coaxial cable connector  10  of the present invention generally includes a connector body  12 , a locking sleeve  14  and a gripping ferrule  16 . As will be discussed in further detail below, the connector of the present invention further preferably includes an annular post  18  and a rotatable nut  20 . It is however conceivable that the connector body  12  and the post  18  can be integrated into one component and/or another fastening device other than the rotatable nut  20  can be utilized. 
     The connector body  12 , also called a collar, is an elongate generally cylindrical member, which is preferably made from plastic to minimize cost. Alternatively, the body  12  may be made from metal or the like. The body  12  has a forward end  22  coupled to the post  18  and the nut  20  and an opposite cable receiving end  24  for insertably receiving the locking sleeve  14 , as well as a prepared end of a coaxial cable  100  in the forward direction as shown by arrow A. Also disposed within the cable receiving end  24  of the connector body  12  is the gripping ferrule  16 . The cable receiving end  24  of the connector body  12  defines an inner sleeve engagement surface  26  for coupling with the locking sleeve  14  and an inner ferrule engagement surface  28  disposed forward of the sleeve engagement surface  26  for frictionally engaging the gripping ferrule  16 , as will be described in further detail below. 
     The locking sleeve  14  is a generally tubular member having a rearward cable receiving end  30  and an opposite forward connector insertion end  32 , which is movably coupled to the inner surface  26  of the connector body  12 . As will be described in further detail hereinbelow, the forward outer cylindrical surface of the sleeve  14  includes a plurality of ridges or projections  34 , which cooperate with a plurality of recesses or grooves  36  formed in the inner sleeve engagement surface  26  of the connector body to allow for the movable connection of the sleeve  14  to the connector body  12  such that the sleeve is axially moveable along arrow A of  FIGS. 2-6 , toward the forward end  22  of the connector body from a first position, as shown in  FIGS. 1-3  and  5 , which loosely retains the cable  100  within the connector  10 , to a more forward second position, as shown in  FIGS. 4 and 6 , which secures the cable within the connector. 
     Specifically, formed on the outer cylindrical surface of the sleeve  14 , between the rearward cable receiving end  30  and the forward insertion end  32  is at least one radially outwardly extending ridge or projection  34 , which rests in a correspondingly sized groove  36  formed in the sleeve engagement surface  26  of the connector body  12 . Preferably, there are two ridges  34  to provide locking of the sleeve  14  in both its first and second positions. Each ridge  34  is further preferably defined by a rearwardly facing perpendicular wall  38  and a forwardly facing chamfered wall  40 . This structure facilitates forward insertion of the sleeve  14  into the body  12  in the direction of arrow A and resists rearward removal of the sleeve from the groove  36  of the body. 
     Moreover, the ridges or projections  34  of the present invention may take other forms. For example, while each ridge  34  is shown in the drawings to be continuous about the circumference of the locking sleeve  14 , it is conceivable to provide gaps or spaces in one or more ridges to increase the ridge&#39;s flexibility. Also, the ridges  34  can be provided on the inner sleeve engagement surface  26  of the connector body, while the grooves are formed on the outer cylindrical surface of the sleeve  14 . 
     The locking sleeve  14  further preferably includes a flanged head portion  42  disposed at the rearward cable receiving end  30  thereof. The head portion  42  has an outer diameter larger than the inner diameter of the body  12  and includes a forward facing perpendicular wall  44 , which serves as an abutment surface against which the rearward end of the body  12  stops to prevent further insertion of the sleeve  14  into the body  12 . 
     Referring additionally to  FIGS. 7 and 8 , the gripping ferrule  16  is a generally tubular member having a rearward cable gripping end  46  and an opposite forward cable gripping end  48 . The gripping ferrule  16  is preferably made from a strong, durable plastic material to reduce costs, but may also be formed of a resilient metal. The tubular gripping ferrule  16  is preferably provided with a threaded inner surface  49  adapted to threadably engage the cable  100 . The internal thread of the surface  49  has a diameter slightly smaller than the outside diameter of the cable for which the connector  10  is adapted to secure. Alternatively, the inner surface of the ferrule  16  can be corrugated or provided with other ridges or protrusions to enhance gripping of the cable  100 . The gripping ferrule  16  further includes an outer surface  50 , which frictionally engages the inner ferrule engagement surface  28  of the connector body  12  to retain the ferrule within the rearward end  24  of the connector body  12 . 
     The locking sleeve  14  has a first inner diameter  52  at its forward end  32  that is sized to receive the rearward cable gripping end  46  of the gripping ferrule  16 . Disposed rearward of the first inner diameter  52  is a smaller second inner diameter  54 , which is sized to receive the outer diameter of the cable  100 . Thus, as assembled, the forward connector insertion end  32  of the locking sleeve  14  is sandwiched between the outer surface  50  of the rearward cable gripping end  46  of the gripping ferrule  16  and the inner sleeve engagement surface  26  of the rearward cable receiving end  24  of the connector body  12 . As a result, the locking sleeve  14  is axially movable between the gripping ferrule  14  and the connector body  12 . 
     The locking sleeve  14  further includes an internal ramp portion  56  formed on its inner surface, which slopes radially outward in the forward direction. The internal ramp portion  56  defines a transition region on the inner surface of the locking sleeve  14  between the first diameter  52  and the smaller second diameter  54 . The internal ramp portion  56  terminates at the smaller second diameter  54  at a forward facing wall  57 . As will be discussed further below, the internal ramp portion  56  of the locking sleeve  14  serves to radially compress the rearward cable gripping end  46  of the gripping ferrule  16  upon forward insertion of the locking sleeve into the rearward end of the connector body  12 . During this forward insertion, the wall  57  of the locking sleeve  14  retains the gripping ferrule  16  within the connector body  12 . 
     Similarly, the inner ferrule engagement surface  28  of the connector body  12  is formed with an internal ramp portion  58 , which slopes radially inward in the forward direction. The internal ramp portion  58  of the connector body  12  serves to radially compress the forward cable gripping end  48  of the gripping ferrule  16  upon forward insertion of the locking sleeve  14  into the rearward end  24  of the connector body  12 . 
     Specifically, the gripping ferrule  16  is designed to expand radially inward at its opposite rearward and forward cable gripping ends  46  and  48 , when compressed by the locking sleeve  14  in the axial direction along arrow A. This radially inward expansion of the rearward and forward cable gripping ends  46  and  48  will cause the gripping ferrule  16  to engage the outer surface of the cable  100  at two axially spaced locations to further secure the cable to the connector. Secondly, the ferrule  16  provides a redundant sealing point to prevent the ingress of water or other contaminants into the connector assembly  10 . 
     To enhance such radially inward expansion, the forward and rearward cable gripping ends  46  and  48  of the gripping ferrule  16  are preferably formed with a plurality of circumferentially arranged flexible fingers  60  extending in opposite longitudinal directions. The fingers  60  may be formed simply by providing longitudinal slots or recesses  62  at the forward and rearward ends  46  and  48  of the ferrule  16 . Moreover, a lateral groove  64  can also be provided between the fingers  60  and the body of the ferrule to increase the flexibility of the fingers. The lateral grooves  64  also preferably define forward and rearward facing banking surfaces, which abut against the internal ramp structure  56  and  58  respectively formed on the inner surface of the locking sleeve  14  and the connector body  12  to prevent further compression of the ferrule within the rearward end  24  of the connector body. 
     In this embodiment, the internal ramp structure  56  and  58  respectively formed on the inner surface of the locking sleeve  14  and the connector body  12  forces the forward and rearward flexible fingers  60  of the gripping ferrule  16  to deflect radially inward during insertion of the locking sleeve  14  into the body  12 . These inwardly directed fingers  60  engage the cable  100  at two axially spaced locations to enhance the gripping of the cable within the connector  10 . In this regard, each of the fingers  60  may further include a tapered end so as to form a relatively sharp edge  66 . The sharp edge  66  tends to bite into the cable to provide even greater gripping force and prevent the cable from being pulled out of the connector  10 . 
     As mentioned above, the connector  10  of the present invention further preferably includes an annular post  18  coupled to the forward end  22  of the connector body  12 . The annular post  18  includes a flanged base portion  68  at its forward end for securing the post in the connector body  12 . The flanged base portion  68  can include one or more radially outwardly extending protrusions  70 , which are received in correspondingly sized recess or grooves  71  formed in the inner surface of the connector body  12  to “snap-fit” lock the post  18  in the connector body. 
     The annular post  18  further includes an annular tubular extension  72  extending rearwardly within the body  12  and terminating adjacent the forward end  48  of the gripping ferrule  16 . The rearward end  73  of the tubular extension  72  can include a radially outwardly extending ramped flange portion or “barb” (not shown) to enhance compression of the outer jacket of the coaxial cable  100  against the forward end  48  of the gripping ferrule  16  to secure the cable within the connector. In any event, the rearward end  73  of the tubular extension  72  preferably terminates in a sharp edge, which facilitates separation of the metallic foil from the metallic shield of the cable during installation, as will be discussed in further detail below. The tubular extension  72  of the post  18 , the gripping ferrule  16  and the body  12  define an annular chamber  74  for accommodating the jacket and shield of the inserted coaxial cable  100 . 
     The present invention is particularly suited for coaxial connectors having an integral terminal pin, although use in other types of connectors is fully contemplated. In integral pin-type connectors, the post  16  further includes an internal pin  76  centrally disposed therein and having a central bore  77  formed in a rearward distal end thereof for receiving the central conductor  102  of a cable  100 . In this embodiment, the post  16  further includes one or more annular insulators  78  to support the pin  76  in an axially central orientation within the post. 
     As mentioned above, the present invention may also be incorporated in a coaxial cable connector which does not utilize an integral pin. The coaxial cable connector in this embodiment would be identical to the connector shown in the drawings with the exception that the integral pin  76  and the annular insulators  78  would be removed from the post  18 . Use would also be the same except for a slight variation in the preparation of the coaxial cable  100 . In particular, a longer extent of the center conductor  102  would need to be provided in order for the cable  100  to be installed in a connector not having an integral pin. 
     The connector  10  of the present invention further preferably includes a nut  20  rotatably coupled to the forward end  22  of the connector body  12 . The nut  20  may be in any form, such as a hex nut, knurled nut, wing nut, or any other known attaching means, and is rotatably coupled to the connector body  12  for providing mechanical attachment of the connector  10  to an external device. A resilient sealing O-ring  80  is preferably positioned in the nut  20  to provide a water resistant seal thereat. 
     The connector  10  of the present invention is constructed so as to be supplied in the assembled condition shown in the drawings, wherein the locking sleeve  14  and the gripping ferrule  16  are pre-installed inside the rearward cable receiving end  24  of the connector body  12 . In such assembled condition, and as will be described in further detail hereinbelow, a coaxial cable  100  may be inserted through the rearward cable gripping end  46  of the gripping ferrule  116  to engage the post  18  of the connector  10 . However, it is conceivable that the locking sleeve  14  and the gripping ferrule  16  can be first slipped over the end of a cable  100  and then be inserted into the rearward end  24  of the connector body  12  together with the cable. 
     Having described the components of the connector  10  in detail, the use of the connector in terminating a coaxial cable  100  may now be described. Coaxial cable  100  includes an inner conductor  102  formed of copper or similar conductive material. Extending around the inner conductor  102  is an insulator  104  formed of a dielectric material, such as a suitably insulative plastic. A metallic foil  106  is disposed over the insulator  104  and a metallic shield  108  is positioned in surrounding relationship around the foil covered insulator. Covering the metallic shield  108  is an outer insulative jacket  110 . 
     The present invention reduces the steps required to prepare the end of the cable. Specifically, instead of having to strip back the jacket  110  to expose an extent of shield  108  and then folding the shield back over the jacket, the present invention merely requires the jacket  110  of the cable  100  to be cleanly cut leaving a portion of the foil covered insulator  104  exposed and then cutting the insulator  104  so that a length of the center conductor  102  extends outwardly therefrom (“¼ to ¼ prep”). The end of the cable  100  is then inserted into the connector body  12  so that the cable jacket  110  makes contact with the cable engagement surface  49  of the gripping ferrule  16 . With a threaded cable engagement surface  49 , the cable  100  and the connector body  12  can then be oppositely rotated or twisted with respect to each other so that the threads of the cable engagement surface  49  bite into the outer jacket  110  of the cable. 
     The gripping ferrule  16  and/or the inner ferrule engagement surface  28  of the connector body  12  can be provided with structure to prevent rotation of the ferrule with respect to the connector body during such threading motion. For example, the outer surface  50  of the gripping ferrule  16  can be formed with one or more longitudinal grooves  51 , which engage one or more tabs  53  provided on the inner ferrule engagement surface  28  of the connector body  12  to prevent rotation of the ferrule with respect to the connector body. 
     As the connector body  12  is threaded onto the cable  100 , the cable is brought further forward into the connector body whereby the sharp edge  73  of the post  18  is driven between the metallic foil  106  and the metallic shield  108  of the cable. Also during this threading motion, the center conductor  102  of the cable is received within the central bore  77  of the integral pin  76 . As may be appreciated, the threading motion between the connector body  12  and the cable  100  provides a mechanical advantage in driving the end of the cable into engagement with the post  18 . Moreover, the short tubular extension  72  of the post  18  and its position at the end of the ¼ to ¼ prep, before the jacket, decreases the insertion force for the cable. As a result, the force required for installing the cable  100  into the connector  10 , along with the associated possibility of buckling the coaxial cable, is greatly reduced as compared with conventional coaxial cable connectors. 
     Once the cable  100  is fully inserted in the connector body  12 , the locking sleeve  14  is moved axially forward in the direction of arrow A from the first position shown in  FIGS. 1-3  and  5  to the second position shown in  FIGS. 4 and 6 . This may be accomplished with a suitable compression tool. As the sleeve  14  is moved axially forward, it provides compressive force on the gripping ferrule  16 , which in turn causes the opposite rearward and forward ends  46  and  48  of the ferrule to expand radially inward. The rearward cable gripping end  46  of the ferrule  16  expands inward to grip the outer surface of the cable jacket  110 , while the forward cable gripping end  48  of the ferrule expands inward to compress the foil covered insulator  104  against the outer surface of the tubular extension  72  of the post  18 . 
     As described above, such radially inward expansion is facilitated by the internal ramped structure  56  and  58  provided in the locking sleeve  14  and the connector body  12 . In the preferred embodiment, the internal ramp  56  of the locking sleeve  14  works against a plurality of flexible fingers  60  formed at the rearward end  46  of the gripping ferrule  16 , while the internal ramp  58  of the connector body  12  works against a plurality of flexible fingers  60  provided at the forward end  48  of the gripping ferrule, wherein the fingers  60  at each end deflect inwardly to exert a radial compressive force on the cable  100  at two axially spaced locations. 
     Thus, as a result of the present invention, the cable  100  is prevented from being easily pulled out of the connector  10  by two separate and spaced points of pressure. The present invention further allows for faster and easier preparation of the cable, regardless of cable diameter, percentage of braid and jacket material type (e.g., PE, PVC, Plenum). 
     Although the illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention. 
     Various changes to the foregoing described and shown structures will now be evident to those skilled in the art. Accordingly, the particularly disclosed scope of the invention is set forth in the following claims.