Abstract:
An end connector is disclosed for cables, particularly coaxial cables of the type employed in the cable television industry. The crimping sleeve of the connector has external ribs and internal serrations designed to accommodate a wide range of cable sizes in a manner which insures a reliable electrical connection, a secure mechanical coupling, and a weather tight seal.

Description:
This is a divisional application of application Ser. No. 364,303, filed June 12, 1989 U.S. Pat. No. 4,990,106 issued Feb. 5, 1991. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to end connectors used to connect cables to equipment ports, terminals or the like. The invention is particularly useful in, although not limited to, end connectors for coaxial cables in the cable television industry. 
     2. Description of the Prior Art 
     The conventional coaxial cable usually consists of a centrally located inner electrical conductor surrounded by and spaced inwardly from an outer electrical conductor. A dielectric insulator is interposed between the inner and outer conductors, with the outer conductor being surrounded by a protective dielectric jacket. The outer conductor can comprise a sheath of fine braided metallic strands, a metallic foil, or multiple layer combinations of either or both. 
     The conventional end connector is generally tubular in configuration, with a front end carrying an appropriate fastener designed to mate with equipment ports or terminals, and with a rear end having inner and outer radially spaced open ended concentric sleeves. The inner sleeve is designed to be inserted into a cable end in electrical contact with the outer conductor and electrically isolated from the inner conductor by means of the dielectric insulator. The outer sleeve is then crimped to securely couple the connector to the cable end and to achieve an electrical ground connection and weather seal. 
     In the past, in order to achieve a secure coupling of the connector to the cable end as well as a weather tight seal therebetween, it has been considered essential to carefully size the outer connector sleeve to the particular cable size. In a system employing a wide range of cable sizes, this can present serious inventory control problems. More importantly, however, the mistaken use of an improperly sized connector can produce a faulty connection, either because the outer sleeve is too small, causing the cable end to be damaged during crimping, or because the outer sleeve is too large, resulting in inadequate coupling and/or sealing. In all of these cases, the resulting faulty connection is likely to be the source of costly and disruptive maintenance problems. 
     Prior attempts at connector standardization have been largely ineffectual, with the result that the above-described problems have continued to plague the industry. 
     The principal objective of the present invention is the provision of an improved end connector designed to accommodate a wide range of cable sizes in a manner which insures a reliable electrical connection, a secure mechanical coupling, and a weather tight seal. 
     SUMMARY OF THE INVENTION 
     An end connector in accordance with the present invention has an internal tubular post with front and rear ends, the rear end being defined by an open ended cylindrical first sleeve. A fastener on the front end of the post provides a means of attaching the connector to an equipment port or the like. A tubular body is supported on the front end of the post at a location adjacent to the fastener. The tubular body has a rearwardly extending cylindrical open ended second sleeve surrounding the first sleeve and defining an annular chamber therebetween. The second sleeve has a grooved interior surface defining a plurality of circular serrations and a grooved exterior surface defining a plurality of axially spaced circular ribs. 
     The first sleeve is adapted for insertion into an end of the cable in electrical contact with the outer conductor and electrically isolated from the inner conductor by the dielectric insulator. The protective dielectric cable jacket and an externally folded portion of the outer conductor are received in the annular chamber defined by the first and second connector sleeves. The ribs on the outer surface of the second sleeve are deformable into a hexagonal configuration, with an accompanying inward radial deformation of the circular serrations on the inner surface of the second sleeve towards the first sleeve and into an indented mechanical engagement with the cable jacket and/or the externally folded portion of the outer conductor. 
     Preferably, the grooved interior surface of the second sleeve tapers outwardly to a maximum internal diameter at its open rear end. Advantageously, the diameters of the ribs on the external surface of the second sleeve are non-uniform, with the largest diameter ribs being located at the rear of the second sleeve. 
     In order to achieve optimum inward radial deformation of the circular serrations on the inner surface of the second sleeve, the circular ribs on its external surface are preferably provided with diameters which are greater than f/0.866 where &#34;f&#34; is the distance between any two opposed flats of the hexagonal configuration imparted to the ribs during crimping. 
     Preferably, the exterior surface of the first sleeve is also grooved to provide a series of circular serrations which are surrounded by at least some of the circular serrations on the interior surface of the second sleeve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view showing a typical equipment port, an end connector in accordance with the present invention, and an end of a typical coaxial cable which has been prepared for insertion into the end connector; 
     FIG. 2 is a sectional view on an enlarged scale taken along line 2--2 of FIG. 1; 
     FIG. 3 is a sectional view taken along line 3--3 of FIG. 2; 
     FIG. 4 is an enlarged sectional view showing a portion of the outer second connector sleeve prior to its being crimped onto the end of the coaxial cable; 
     FIG. 5 is a diagrammatic illustration showing the relationship between the original diameter of the external circular ribs on the second connector sleeve and their ultimate crimped hexagonal configuration; 
     FIG. 6 is a side elevational view with portions broken away showing the end connector after it has been inserted onto the end of the cable and crimped in place; 
     FIG. 7 is a partial sectional view on an enlarged scale taken along lines 7--7 of FIG. 6; 
     FIG. 8 is a view similar to FIG. 4 showing the internal circular serrations on the second sleeve after they have been crimped into an indented relationship with the end of the cable; and 
     FIG. 9 is an illustration cf a crimping tool used to crimp the end connector of the present invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     With reference initially to FIGS. 1-3, an end connector in accordance with the present invention is shown at 10 between a typical externally threaded equipment port 12 and an end of a conventional coaxial cable 14 which has been prepared to receive the end connector. 
     In the example herein selected for illustrative purposes, the cable 14 includes an electrical inner conductor 16 surrounded by and spaced inwardly from an electrical outer conductor comprising a layer of metallic foil 18 directly underlying a layer of braided metallic mesh 20. The inner and outer conductors are electrically isolated one from the other by a dielectric insulator 22 interposed therebetween. A dielectric protective covering or jacket 24 surrounds the outer conductor. 
     The end of the cable is prepared for coupling with the end connector by first removing a length 1 1  of the jacket 24 to thereby expose an end segment 20a of the braided metallic mesh. The exposed end segment of mesh is then folded back over the jacket as illustrated in the drawings, thus exposing an end segment 18a of the metallic foil. Thereafter, a shorter length 1 2  of the exposed metallic foil segment 18a and the underlying dielectric insulator 22 are removed to thereby expose an end segment 16a of the inner conductor. 
     The end connector 10 of the present invention comprises an inner tubular post 26 having a first flange 28 at a front end thereof and a cylindrical first sleeve 30 at a rear end thereof. The first sleeve is externally grooved to define a series of circular first serrations indicated typically at 32. 
     A fastener 34 is rotatably received on the front end of the post 26. The fastener is internally threaded as at 36, and is provided with a second flange 38 arranged to coact in mechanical interengagement with the first flange 28 on the post 26. 
     A tubular body 40 is supported on the front end of the post 26 at a location adjacent to the first flange 28. An O-ring seal 42 is interposed between the tubular body 40 and the fastener 34, and a cylindrical second sleeve 44 extends rearwardly from the tubular body 40. The second sleeve 44 surrounds and is spaced radially from the first sleeve 30 of the post 28 to thereby define an annular chamber 46 therebetween. The second sleeve 44 has an open rear end leading to the annular chamber 46. 
     Referring additionally to FIG. 4, it will be seen that the interior surface of the second sleeve 44 is provided with a series of grooves 48 spaced one from the other by truncated conical intermediate surfaces 50. The intermediate surfaces 50 lie on a common conical reference plane P 1  tapering outwardly towards the rear end of the second sleeve. 
     The grooves 48 are each defined by leading and trailing conical surfaces 52,54 extending radially outwardly from their respective adjacent intermediate surfaces 50 to converge at the groove bottoms 56. Circular serrations 58 are defined at the junctures of the trailing surfaces 54 and their adjacent intermediate surfaces 50. Thus, the second sleeve 44 has an interior surface tapering outwardly to a maximum internal diameter &#34;ID&#34; at its open rear end (see FIG. 2), with grooves 48 defining a plurality of axially spaced serrations 58. 
     The exterior surface of the second sleeve 44 is grooved as at 60 to define a plurality of axially spaced ribs 62a-62e. The innermost rib 62a has an outer diameter OD 1 , the next rib 62b has a larger outer diameter OD 2 , and the last three outermost ribs 62c, 62d and 62e located at the rear end of the second sleeve have a still larger diameter OD 3 . 
     The application of the end connector 10 to the prepared end of the cable 14 will now be described with additional reference to FIGS. 5-9. The prepared end of the cable is axially inserted into the open rear end of the connector, bringing the front end of the exposed segment 18a of the foil flush with the front end of the post 26, and allowing the exposed segment 16a of the inner conductor to protrude slightly beyond the threaded front end of the fastener 34. This axial insertion is accompanied by an insertion of the first sleeve 30 between the foil 18 and the braided metallic mesh 20. The outer dielectric jacket 24 and the folded over segment 20a of the mesh are received between first and second sleeves 30, 44 in the annular chamber 46 defined therebetween. 
     A standard tool of the type illustrated at 64 in FIG. 9 is then employed to crimp the second sleeve 44. The tool has cooperating pivotal jaws 66,68 which are appropriately notched to define a hexagonal opening 70 when in the closed position. 
     During the crimping operation, the jaws 66,68 impart a hexagonal configuration to the ribs 62a-62e, as partially illustrated in FIG. 7. 
     With reference to FIG. 5, those skilled in the art will appreciate that the development of a hexagonal cross sectional configuration from a round is governed by the formula ##EQU1## where: F =distance across opposed flats of the hexagonal configuration 
     D =diameter of round. 
     The typical conventional crimping tool 64 has an &#34;f&#34; dimension of 0.0360&#34; and in accordance with the foregoing formula, is used to crimp rounds having a diameter D of 0.4157&#34;. 
     The present invention departs from conventional practice by providing the circular ribs 62a-62e with external diameters OD 1 , OD 2  and OD 3  which are larger than f/0.866. During the crimping operation, as illustrated in FIG. 8, the ribs 62a-62e are compressed radially inwardly. Most of the rib material flows into and fills the hexagonal configuration defined by the notched jaws 66,68 of the crimping tool. Thus, the diameters OD 1 , OD 2  and OD 3  are reduced to the flat sided dimension &#34;f&#34;. The excess rib material flows radially inwardly, causing the serrations 58 to twist inwardly as indicated by the arrows 72 and to bite into the cable jacket 24 and the folded over braided mesh segment 20a. 
     As a result of this crimping operation, and as can best be seen in FIGS. 6 and 7, the cable jacket 24 and folded over braided mesh segment 20a are gripped between the serrations 58 on the second sleeve 44 and the serrations 32 on the first sleeve 30, thus establishing a positive and reliable interlock. The jacket material flows into and fills the inner and outer confronting grooves of the sleeves 30, 44, completely filling the annular chamber 46 and thus creating a weather tight seal. 
     In light of the foregoing, it will now be appreciated by those skilled in the art that the end connector of the present invention embodies a number of advantageous features. For example, the outwardly tapering inner surface of the second sleeve 44 to a maximum internal diameter at the open rear end enables the end connector to accommodate a range of cable sizes. The configuration of the second serrations 58 and their relationship to the purposely oversized external circular ribs 62a-62e results in a unique crimping action, with the serrations 58 twisting inwardly to bite into the cable jacket and externally folded braided mesh segment 28. The serrations 58 coact with the serrations 32 on the first sleeve 30 to securely grip the cable therebetween without squashing or otherwise damaging the cable. The dielectric insulator 22 and the metallic foil 18 remain round, even after crimping, which is of importance in maintaining proper impedance for the normal cable. The material of the cable jacket flows into and effectively fills the grooved confronting surfaces of the first and second sleeves 30,44 to provide an effective weather tight seal.