Abstract:
A coaxial connector ( 10 ) for a coaxial cable ( 100 ) having a corrugated outer conductor ( 108 ), including one which is helically corrugated. An adapter ( 40 ) of the connector can include a crimpable sleeve ( 44 ) within which is a bushing ( 70 ) initially having an axial slot ( 72 ) of selected dimension. The inner surface ( 74 ) of the bushing is fluted defining ridges and grooves (for cable of annular corrugation), or a continuous helical ridge ( 76 ) and associated groove ( 78 ) defining a thread of corresponding pitch, and general inner diameter permitting cable insertion. Upon full threading of the cable end into adapter ( 40 ), crimp sleeve ( 44 ) is crimped thus closing axial slot ( 72 ) and stopping the crimp process to achieve a minimum desired inner diameter. The adapter may be a discrete subassembly and securable to a forward connector portion in modular fashion by complementary threaded flanges ( 32,46 ). A connector ( 500 ) can also include one or more radial holes ( 514 ) extending to the cable-receiving region permitting solder ( 522 ) or conductive epoxy to be deposited following cable insertion, for mechanically and electrically connecting the rearward connector portion to the cable outer conductor ( 510 ) other than by crimping.

Description:
RELATED APPLICATION INFORMATION 
     This is a Continuation-in-Part application of Ser. No. 08/062,100 filed May 14, 1993, now abandoned. 
    
    
     FIELD OF INVENTION 
     The present invention is related to electrical connectors and more particularly to connectors for coaxial cable having a corrugated outer conductor. 
     BACKGROUND OF THE INVENTION 
     Generally coaxial cable includes an inner conductor surrounded by a layer of dielectric material and precisely centered within an outer conductor, and having an outer jacket of dielectric material. In certain coaxial cable, the outer conductor defines a ground return path necessary for microwave signal transmission, and is termed semirigid coaxial cable. In certain semirigid coaxial cable, the outer conductor is strengthened by corrugation, and in certain such cable the corrugation is helical, as is described in proposed draft Military Specification MIL-C-28830/AA. U.S. Pat. No. 5,154,636 discloses a connector for such cable includes a forward connector assembly with an inner contact disposed within a dielectric insert in an outer conductive housing, with the outer housing including a rearwardly extending threaded flange in which a flaring ring is disposed. A rear connector portion is assembled separately to the cable end, and comprises a clamping member having a threaded inner surface to match the helical corrugations of the outer cable conductor. The flaring ring has an inner diameter at least as small as the inside diameter of the helically corrugated outer cable conductor, and includes a bevelled end which engages the inner surface of the open end of the outer cable conductor to flare the engaged portion outwardly against a complementarily bevelled surface along the forward end of the clamping member, as the forward connector assembly is threaded onto the end of the clamping member. U.S. Pat. No. 5,137,470 discloses a similar connector. 
     Other connectors for coaxial cable with helically corrugated outer conductor are disclosed in U.S. Pat. Nos. 3,199,061; 4,047,291; 4,995,832 and 4,824,400. Additional connectors for coaxial cable having an annularly corrugated outer conductor are disclosed in U.S. Pat. Nos. 4,046,451 and 4,800,351. 
     It is desired to provide a coaxial connector for coaxial cable having a corrugated outer conductor which is easily assembled thereto and mechanically secured thereto. 
     It is further desired to provide such a connector which is easily assembled to the cable without deforming the outer conductor of the cable and which assures an electrical connection of the inner surface of the outer conductor with the outer conductive housing of the connector. 
     SUMMARY OF THE INVENTION 
     The present invention includes a connector having a forward or mating portion of standard or conventional configuration, and a rearward portion adapted to receive a prepared cable end thereinto. The rearward portion includes a bushing entrapped within a sleeve of the outer conductive housing of the connector and cooperatively receives the corrugated cable outer conductor thereinto for being either crimped thereagainst or soldered thereto to establish an assured ground connection therewith as well as a mechanical connection thereto. The bushing is initially C-shaped in cross-section which is manufactured to be disposed in the sleeve of selected inner diameter so that the axial slot is partially open to initially define a gap of selected spacing, with the bushing fabricated such that the general inner diameter after assembly within the sleeve is related closely to the general outer diameter of the cable outer conductor. 
     The interior surface is profiled into alternating ridges and grooves to match the corrugations of the outer conductor of the coaxial cable, and initially permits the cable end to easily be inserted thereinto until the inner conductor is matingly received into a socket contact section of the forward connector portion and the end of the cable&#39;s outer conductor abuts an annular interior flange of the sleeve. In a first embodiment, the sleeve is then crimped with crimp tooling against the bushing, urging the bushing against the corrugated cable outer conductor at least substantially closing the axial slot and compressing the ridges of both the cable conductor and the bushing into the opposing grooves of the other in an interference fit. The gap of the axial slot is precisely dimensioned to permit sufficient reduction in bushing inner diameter so that the general inner diameter of the bushing complements the outer diameter of the cable outer conductor to define a compression fit with controlled slight deformation of the outer conductor, with either the crimp tooling or ultimately the closing of the axial slot acting to control crimping to avoid deformation of the cable outer conductor into the underlying insulation. In another embodiment, the sleeve and bushing include one or more aligned apertures radially thereinto through which solder or conductive epoxy may be deposited to flow between the bushing inner surface and the cable outer conductor outer surface and harden or cure. 
     In a particular embodiment of the present invention for use with cable having a helically corrugated outer conductor, the interior surface of the bushing is threaded to have a pitch equivalent to the pitch of the helically corrugated outer conductor, and has a general inner diameter permitting the cable end to be threaded into the bushing without undue effort. The cable end is threaded into the bushing held within the sleeve until the inner conductor is matingly received into a socket contact section of the forward connector portion and the forward edge of the outer conductor abuts a rearwardly facing surface of an annular interior flange of the sleeve. This embodiment is useful with either the crimping or soldering approaches. 
     Where the connector is to be crimped onto the cable, the bushing&#39;s interior surface is profiled to define a helical ridge or thread and associated helical groove, with the profile precisely dimensioned to assure that upon crimping the surfaces defining the groove of the bushing abut and are compressed into the opposing surfaces of the ridge of the cable outer conductor, but the surfaces defining the ridge of the bushing does not engage the surfaces defining the groove of the cable outer conductor. Such arrangement assures that the bottom of the groove of the cable outer conductor is not engaged and deformed radially inwardly and into the insulative foam, while controllably deforming the ridge of the cable outer conductor to a limited extent to clinch the crest of the ridge which does not deform into the insulative foam and does not affect impedance of the cable. The leading edge of the outer conductor, which is initially urged tightly against the annular flange of the sleeve containing the bushing when threaded into the adapter, is pressed even more tightly thereagainst further enhancing the electrical connection of the inner surface of the outer conductor at a plurality of points about the circumference between the inner surface of the cable outer conductor and the connector outer conductive housing. 
     In one particularly useful form of the present invention, the forward connector portion is a subassembly including the inner contact within a dielectric housing, and the rear face of the portion includes a threaded annular flange. The rearward connector portion includes a forwardly extending annular flange complementarily threaded to be threaded onto the annular flange of the forward connector portion. Thus the rearward subassembly can be dimensioned to the specific size of the cable, while the forward subassembly can be one selected from several varieties thereof having standardized threaded flanges, in modular fashion. The modular arrangement permits utilization of the same rearward subassembly with a right angle forward connector configuration, for example, or one having a socket style or a pin style forward inner contact section as desired, or one having a circuit board mountable forward contact section. 
     It is an objective of the present invention to provide a coaxial connector suitable for use with semirigid coaxial cable of the type having corrugated outer conductor. 
     It is also an objective to provide such a connector for use with cable having a helically corrugated outer conductor. 
     It is additionally an objective to provide a coaxial connector crimpable to a corrugated cable outer conductor with only slight deformation of the cable outer conductor radially inwardly toward the inner conductor and yet establishing an assured mechanical and electrical connection. 
     It is also an objective to provide a coaxial connector which is solderable to a corrugated cable outer conductor to establish an assured mechanical and electrical connection. 
     It is a further objective to provide a cable-engaging connector portion which can be utilized in modular fashion with one of a variety of forward connector portions. 
     Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of the coaxial cable connector of the present invention, with the bushing and adapter exploded from the forward connector assembly; 
     FIG. 2 is a longitudinal section view of the bushing and adapter of the connector of FIG. 1, with a prepared cable end to be inserted thereinto; 
     FIGS. 3 and 4 are longitudinal section views of the connector of FIG. 1 threaded onto the coaxial cable and then crimped onto the helically corrugated outer conductor, and with the adapter threadedly coupled to a flange of the forward connector assembly; 
     FIGS. 5 and 6 are enlarged partial longitudinal section views of the cable end and the bushing, with FIG. 5 being diagrammatical showing the relationship of the bushing profile and the cable outer conductor profile, and FIG. 6 illustrating the crimped condition; 
     FIG. 7 is similar to FIG. 4 with an embodiment of connector for use with a larger diameter coaxial cable; 
     FIG. 8 is a longitudinal section view of another embodiment of connector applied to a coaxial cable, with the inner contact having a socket contact section and being matable to the connector of FIG. 4; 
     FIG. 9 is a view similar to FIG. 4 of another connector embodiment, with the forward connector assembly being a right angle connector; and 
     FIGS. 10 and 11 are isometric and sectional views of yet another connector embodiment for being joined to a coaxial cable by solder or conductive epoxy. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The coaxial connector of the present invention includes a forward connector portion and a rearward connector portion, with the rearward connector portion having a body section  42  and including a bushing  70  which will be disposed within a crimp sleeve portion  44  extending rearwardly from body portion  42 . Preferably the rearward connector portion is a discrete adapter assembly  40 , as shown in FIGS. 1 and 2, which is securable to a forward connector assembly  10  which enables modularity as will be described. Forward connector assembly  10  includes an outer conductive housing  12  and an inner conductor or contact  14  held coaxially therewithin by a dielectric insert  16  as shown in FIG.  3 . Mating interface  18  of the connector is seen in FIG. 1 to include a pin contact section  20  coaxially surrounded by an outer contact section  22  defined by four cantilever spring arms  24 . A coupling nut  26  is rotatably affixed to the outer conductive housing  12  and facilitates assured mating of the connector with a mating or complementary connector (see FIG.  8 ). 
     Extending rearwardly from an assembly face  28  of forward connector assembly  10  is a socket contact section  30  of inner contact  14  matable with the inner conductor of the cable. Outer conductive housing  12  includes an externally threaded flange  32  extending axially rearwardly from assembly face  28 , cooperable with internally threaded flange  46  extending forwardly from body section  42  of adapter  40 , enabling assured mechanical and grounding coupling of adapter  40  with forward connector assembly  10 . Bushing  70  is shown to be a member C-shaped in cross-section initially having a defined axial slot  72  therealong with a gap of selected dimension. Bushing  70  has an internal surface  74  which is profiled to define parallel adjacent grooves  76  between ridges  78  of selected spacing at a slight angle from being orthogonal to the axial direction to define an approximate helical thread, and which when bushing  70  is compressed to at least substantially close gap  72 , define a substantially continuous helical thread. 
     Referring to FIG. 2, cable  100  is shown to have an inner conductor  102  having an exposed section  104  extending from cable  100  preferably shaped to define a pin contact section matable with a socket contact. Inner conductor  102  is disposed within a dielectric sleeve  106  (in phantom), which maintains it coaxially within outer conductor  108  contained within an outer jacket  110 . Outer conductor  108  comprises a corrugated shape having alternating ridges  112  and grooves  114  which as shown is a helical corrugation in which actually one continuous ridge is wound along the length thereof such as at a groove-to-groove spacing of about 0.105 inches, with the dimension between the crest of the rounded ridge and the groove bottom may be about 0.032 inches. The outer conductor extends to a leading edge  116  which is preferably orthogonal to the inner conductor. In such cable electrical current is carried adjacent inner By surface  118  of outer conductor  108  which may have a thickness of about 0.008 inches. Spaces  120  defined along inner surface  118  inwardly of ridges  112  is air-filled surrounding insulative layer  106  which may be low loss foam polyethylene. 
     Adapter  40  is assembled by placing bushing  70  into large rearward cavity  48  until leading edge  80  abuts rearwardly facing surface  50  defined by annular interior flange  52 . A rear edge portion of sleeve  44  is then inturned to form an inturned flange  54  along rear edge  82  of bushing  70 , as seen in FIG. 3, which presses against rear bushing edge  82  and tightly secures bushing  70  between annular flange  52  and inturned sleeve portion  54 . When adapter  40  is threaded onto forward connector assembly  10 , socket contact section  30  is disposed within forward cavity  56  of body section  42 . The entire connector assembly is ready to receive a prepared cable end thereinto for termination; alternatively, the adapter  40  may be applied to the cable end prior to securing adapter  40  to forward connector assembly  10 . 
     The prepared cable end is threaded into the cable receiving rearward end  58  of adapter  40  until leading edge  116  of outer conductor  108  abuts against annular interior flange  52  and inner conductor pin section  104  becomes matingly engaged with socket contact section  32 . Sleeve  44  is then crimped with crimping tool (not shown) in a manner similar to crimping procedures followed with other electrical connectors, which thus deforms sleeve  44  radially inwardly so that inner surface  60  of large cavity  48  is pressed against the outer surface of bushing  70  and compresses bushing  70  to a smaller diameter by closing gap  72  (FIG.  1 ). Crimp tooling includes dies which are closed to a fixed crimp diameter as is conventional with crimp tooling in general, to control the amount of crimp of the present invention to minimize deformation of the cable outer conductor; as an ultimate control on crimping, the gap along the axial slot of the bushing will stop the crimping procedure when facing edges  84  defining gap  72  abut stopping further deformation of sleeve  44 . 
     As a result, as seen in FIG. 4, inner surface  74  of bushing  70  is moved snugly against the outer surface of outer conductor  108  as ridges  78  move into grooves  114  and ridges  112  of outer conductor  108  are pressed into grooves  76  of bushing  70 , without deforming the outer conductor radially inwardly but with compression clinching of ridges  112  therearound. The outer conductor will thereafter maintain a spring bias radially outwardly against the bushing&#39;s inner surface  74 , providing a substantial frictional engagement between cable outer conductor  108  and bushing inner surface  74  preventing inadvertent unthreading of the cable end from the connector due to handling or to vibration during in-service use. Further, it is believed that the corners of edges  84  of gap  72  along inner surface  74  would tend to dig into cable outer conductor  108  to assist in preventing inadvertent unthreading. Cable  100  is thus firmly secured to adapter  40  and an assured electrical connection is established between inner conductor  102  and contact member  14  and between outer conductor  108  and annular flange  52  of adapter  40  and to outer conductive housing  12  of connector assembly  10 . 
     The profile of the bushing inner surface  74  and the cable outer conductor is illustrated in FIGS. 5 and 6. Preferably the crests of ridges  76  of the bushing have a lower “height” than the depth of the bottoms of corresponding grooves  114  of cable outer conductor  108 , so that upon engagement of the groove bottoms  78  of the bushing with crests of ridges  112  of the cable outer conductor, the bushing crests  76  are spaced from the groove bottoms  114  of the cable outer conductor. The width of the axial slot  72  is selected so that in the crimped state the general inner diameter (along the crests) of the bushing is greater than the diameter of the cable outer conductor along the groove bottoms along the outwardly facing surface, thus acting to ultimately prevent overcrimping and radially inward deformation into the insulative layer  106 . 
     Abutment of bushing and outer conductor preferably only occurs within the regions identified as ER or “engagement regions”, and no engagement occurs in the regions identified as NR or “nonengagement regions”. The precise dimensions of tile bushing profile are selected to accommodate variations within manufacturing tolerance of the cable so that assured engagement occurs when the cable is at its smallest concerning outer diameter of the outer conductor and radius of the groove bottom  114 , which are dimensions controlled by cable standards. The resultant radius R 1  of the ridge  112  of the outer conductor is at its largest within specification limits, and the radius R 2  of the bushing groove  78  must be selected to assure abutment and clinching along as much of the axial length of regions ER as possible. Clinching in these regions will incrementally deform the ridges of the cable outer conductor into air-filled spaces  120  but will not affect the controlled inner diameter of the cable outer conductor nor deform the insulative layer  106 . Also such clinching along leading edge  116  of cable outer conductor  108  will urge the leading edge incrementally forwardly more tightly against annular flange  52  further enhancing compression of the inwardly facing surface  118  of the outer conductor thereagainst for much of the circumference of the leading edge. Such clinching or plastic deformation of annealed brass with essentially no spring properties deformed to press against the outer conductor, against the cable outer conductor with distinctly elastic deformation and therefore stored spring okra energy upon the adapter being crimped thereonto, produces a cold weld therebetween. 
     An example of adapter assembly  40  can include a member comprising body section  42 , sleeve portion  44  and flange  46  is machined of half hard brass such as Alloy No. C36000 with the sleeve portion annealed to enhance the property of malleability achieving suitability for crimping, and then silver plated. Bushing  70  is formed and then machined of half hard brass, for example Alloy No. C36000, which is annealed, and then gold plated with the outer surface knurled. Both ends  80 , 82  are preferably chamfered along the outer and inner edges to facilitate insertion of either end into sleeve  44  and to facilitate receipt into either end of the leading edge  116  of cable outer conductor  108 . To facilitate appropriate crimping, the outer surface of sleeve portion  44  includes a visible indicia axially therealong at the location overlying the axial slot of the bushing therewithin, to orient the adapter within the tool for the slot and indicia to be centered along the bottom of an arcuate crimping surface of one of the opposed crimping dies. 
     Standards for a 50 ohm cable of copper outer conductor, foam polyethylene insulative layer and copper-clad steel wire inner conductor, are a nominal outer diameter at the groove bottom of 0.186 inches and permissible tolerance variation of ±0.005 inches, and at the ridge top of 0.250 inches +0.005 inches; groove-to-groove spacing L of 0.105 inches and permissible tolerance variation of ±0.010 inches; and groove radius of 0.020 inches and permissible tolerance variation of ±0.005 inches; and outer conductor thickness of 0.008 inches ±0.0006 inches; and inner conductor diameter of 0.075 inches ±0.001 inches. A bushing  70  therefor can be machined to define a helical thread therethrough having a ridge crest radius of 0.032 inches, groove radius R 2  of 0.038 inches and depth of 0.023 inches, and an inner diameter before crimping of 0.224 inches; and then machined to have a slot width of about 0.100 inches, permitting an inner diameter after crimping of no less than about 0.191 inches with the slot closing at the outer bushing diameter. The resulting minimum inner bushing diameter thus is no less than the maximum permissible cable outer conductor diameter of 0.186+0.005 inches, or 0.191 inches. 
     A second embodiment of coaxial connector is illustrated in FIG. 7 wherein connector assembly  200  has a forward connector assembly  202 , adapter assembly  204  adapted for a cable  206 . Cable  206  is shown to have a larger diameter relative to the mating face of the connector than cable  100  of FIGS. 1 to  4 . Outer conductor  208  is larger in diameter, and bushing  210  and sleeve  212  of adapter  204  are correspondingly larger in diameter. Inner conductor  214  is larger in diameter, and socket contact section  216  is correspondingly larger. Internally threaded forward flange  218  of adapter assembly  204  is larger in diameter, as is externally threaded flange  220  of forward connector assembly  202 . This embodiment maintains the same dimensions of mating interface  222  as mating interface  18  of the embodiment of FIGS. 1 to  4 . 
     FIG. 8 illustrates an embodiment of coaxial connector  300  adapted for a cable  302  having the same dimensions as cable  100  of FIGS. 1 to  4 , but wherein inner contact  304  within forward connector assembly  306  has a socket contact section  308  at the mating interface  310 . The embodiment of connector  300  also includes a threaded surface  312  defined along the outer surface of the outer conductive housing  314 . Connector  300  is thus adapted to be complementary to and matable with the coaxial connector  10 . Adapter assembly  316  secured to forward connector assembly  306 , however, is identical to adapter assembly  40  of FIGS. 1 to  4 . 
     A right angle connector  400  is illustrated in FIG. 9, again using an adapter  402  identical to adapter assembly  40  of FIGS. 1 to  4 , for use with a cable  404  having the same dimension as cable  100  thereof. Forward connector assembly  406  includes a right angle outer conductive housing  408  includes a tubular section  410  to which adapter assembly  402  is securable. The inner conductor is shown to comprise a first inner contact member  412  extending from the mating interface  414  around the right angle bend, to a second inner contact member  416  affixed to an inner end thereof, which concludes in the socket contact section  418  matable with the pin section of the cable inner conductor  420 . A dielectric insert  422  is fabricated to contain the right angle inner contact assembly in appropriate centered position within the right angle outer conductive housing. 
     FIGS. 10 and 11 illustrate another embodiment of the coaxial connector of the present invention. Connector assembly  500  includes an outer shell  502  having a rearward sleeve  504  within which is disposed a bushing  506  having a helically threaded groove  508  complementary with the helically corrugated outer conductor  510  of coaxial cable  512 . Solder-receiving holes  514  are seen through the rearward sleeve  504  and are aligned with solder-receiving holes  516  through bushing  506  to intersect a respective ridge  518  and thus conclude at a complementary groove  520  of the cable outer conductor  510 . Solder  522  can be flowed through holes  514 ,  516  and reflowed around the cable outer conductor  510  following groove  520  and solidifying therein to define a solder joint joining bushing  506  and cable outer conductor  510 . Solder  522  may be of the type reflowable at low temperature such as 93° C., such as Ostalloy No. 200 sold by Arconium Specialty Alloys, Providence, R.I., having 44% indium, 42% tin and 14% cadmium. Alternatively conductive epoxy may be used in lieu of solder, such as EPO-TEK H20E silver epoxy sold by Epoxy Technology, Inc., Billerica, Mass. dispensable by syringes and which is said to cure at 80° C. for 90 minutes. 
     The present invention can comprise an adapter section of a unitary outer conductive housing of a coaxial connector, and including a sleeve section within which a bushing is disposed and crimpable to a prepared coaxial cable end. The embodiments of FIGS. 8 and 9 are illustrative of the benefits of the modular nature of the adapter assembly of the present invention, when it is embodied in the form of a discrete adapter assembly rather than an integral part of an outer conductive housing of the connector. 
     Other variations and modifications can occur to the artisan and are within the spirit of the invention and the scope of the claims.