US 3275737 A
Description (OCR text may contain errors)
Sept. 27, 1966 J. M. CALLER COAXIAL CABLE TERMINATING MEANS Filed April l5, 1964 Y n I /4 585 5J 2/ 20A) L42 /3 F/g' 2 JNVENTOR.
James M. Cal/er ,MQMW
A/forney United States Patent O 3,275,737 COAXIAL CABLE TERMINATING MEANS James M.r Caller, Albuquerque, N.r` Mex., assignor, by
mesne assignments, to the UnitedStates of America as representedby the United States Atomic Energy Conrmission Filed Apr. 15, 1964, Ser. No. 360,153
3 Claims.. '(Cl.' 1744-89) The present invention relates generally to electrical connectors for shielded cablesand more particularly to connector structure f or terminating a coaxial cable and for retaining and sealing the cable in the connector.
Ain object of the present. inventi-on is to provide new andv improvedielect-rical connectors wherein coaxial-ly dis'- posed conductors are coupled thereto 'by newv and irnproved conductor `termination systems.
Another'object of the invention is to provide improved cablel retention means yfor firmly securing coaxial cables to electrical connectors while simultaneously providing complete environmental protection.`
A further object of the invention is to, facilitate the miniaturization of electrical connectors by providing coaxial cable terminating and cable yfastening structure unique for its simplicity and ease -ofassemblv A further object of 'the invention is to provide a new and improved coaxial cable connector -wherein a metal shield braid forming the outer conductor of a coaxial cable is clamped to connector structure in a firm and low resistance connection.
A still further object of the invention is to |provide connectors of various configurations including elbow and T- shaped connectors with injection molded insulators of single piece construction. i
Other and further objects of the invention will be obvious upon an understanding yof the illustrative embodiment about to be described "or will'be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.
A preferred embodiment/of the invention has been chosen for purposes' of illustration and description. The preferred embodiment illustrated is not intended to be exhaustive nor to limit the invention to the precise form disclosed. It is chosen and described in order to best explain the principles of the invention and their application inv practical use tothereby enable others skilled in the art to best utilize the invention in various embodiments and modifications as are Ibest adapted to the particular use contemplated.
In the accompanying drawing:
FIG. 1 is a sectional view of a preferred form of the present invention; and
FIG. 2 is a sectional and partly cut away view of a portion of the connector illustrated in FIG. l.
While the preferred form of the present invention relates to electrical connectors particularly suitable for coaxial conductors or cables wherein `a single inner conductor is encircled by a braided outer conductor, other types of cables, such as, for example, a multiple conductor cable 'with a braided encircling grounding shield (not shown) may lbe used with connectors constructed in accordance with the teachings of the present invention. Therefore, the terms electrical conductor and coaxial cable used herein Imay be construed as being inclusive of grounding rshields and cable arrangements wherein a single conductor encircles a plurality of conductors respectively.
Referring again to FIG. y1 there is shown an assembled electrical connector comprising a plug portion electrically coupled to a T-shaped receptacle portion 11,
details of which will be set forth below. The plugportion 10 maybe coupled to the: receptacle llrby a threaded sleeve '113k rotatablyfsecured tothe plug 10 'by a snap ring or the like 14` and mating with a threaded surface on-the crossarm of the receptacle portion 11; but, if desired, other types of coupling arrangements may be used, such as, for example, a? bayonet-type coupling. f
The plug portion, as shown in'` FIGS.'1 and 2, may be used with a coaxial cable 15 which may comprise a single center or inner conductor 16 -separated from a braided outer conductor 17` bya tubular insulator or dielectric member 18'andwith the conductors and insulator enclosed in a jacket or covering 19 of a suitable rubber or plastic material. The plug portion'imay comprise a tubular or cylindrical metal Vhousing o r kshell 20"y with a threaded outer surface 21` at one end'thereof andan annular groove 22 at the other end 'thereof for reception of a deformable annular .sealing member 24 of elastomeric material to provide -a seal between the plug and receptacle when they are drawn together as shown in FIG; l. The axial length of the' inner :surface or periphery of the shell 20v may contain sections having different diameters, the largest of which may lie beneath the threaded end or surface 2,1
such as to define an annular shoulder 25 with the'face thereof disposed in the direction of the shell having the threaded o-uter surface 'at a location between the ends of thesheuzo.y H f To prepare `the coaxial cable 15 for reception -in the shell` of the plug portion 10 the 'center conductor 16 may be provided with a contacting element suchy as a pin 28l in anyw suitable manner such as soldering or crimping `and, the outer "conducto'r 17A and the jacket 19 terminated at locationsjin retard of or spaced axially rearwardly from the leading end of the dielectric member The center conductor \1=6, pin 28, and insulator -1'8A may, in turn, be disposedin a tubular insulating member or bushing 29 of any suitable material that may contain therein a suitable projection 30 for engaging the leading endof the cable dielectric 18 so as toproperly position the pin 218. This bushing 29 may be' provided with sections -of different outer, diameters as indicated at 32 and 33 that are separated from each other-by an annular projection or shoulder 34. The annular shoulder 34 and -a length of the bushing 4section 33 provide supporting structure =for a retaining member 36 which is constructed to `receive and retain the braid shield or outer conductor 17.
As best shown in FIG. 2, the retaining member 36 may be of a generally cylindrical configuration and comprise an annular main body portion 37 'encircling the bushing section 33 and abutting against the shoulder 34 with an axially extending annular base portion 39Fdisposed about the 'bushing section 33 and terminating at a location axially spaced from the eind the'reofj The lbase portion 39 may be provided with a tapering cross section longitudinally of the cable 15`and convergingn from the main body portion 37 toward the distal end of th'e base portion for providing 'a ramp-like structure to facilitate the reception lofan end section of the outer conductor .17 in the retaining member 36 as will be described in detail below.
The main body portion 37 of the retaining memberv 36 may be provided with a plurality of axially extending and circumferentially oriented tines' or segments 40 laterally outwardly spaced from the base portion 39 to form an annularslot 42 therebetween for rreception of the conductor 17. While these segments 40 areshown extending along the base portion 39 in a converging disposition lgenerally parallel to the tapered surface on the base portion, they are preferably initially oriented in a plane generally parallel with the axis of thec'onnectorto facilitate the placement of the conductor'l'l in the slot 42. Also, while any number'ofsegments40 may beused, the structure rtaining member.
shown may be provided with four segments 40 circumferentially spaced apart from each other to provide a soldering space therebetween.
In attaching the cable 15 to the plug portion 10 the cable may be prepared as above described such that the dielectric member 18 and conductor 16 are passed through the retaining member and positioned in the bushing 29. The bushing section 33, which may be relatively thin with respect to the bushing section 32 and provided with a tapered distal end, may be passed between the dielectric member 18 and the conductor 17, stretching or expanding the braid forming the outer conductor v17 such that the latter is passed tonto the cuter surface of the tapered base portion 39 and into the annular slot 42 of the retaining member, thereby encircling a section of the bushing section 33 and substantially the full length of the tapered surface on the base portion 39.
With the braid of conductor 17 in the slot 42, the tines or segments 40 may be crimped Ior otherwise moved against the conductor braid to clamp the latter in the re- Solder or the like, such as indicated at 44 in FIG. 2, may be placed in the grooves between adjacent tines or segments to assure the connection of the conductor 17 to the retaining member and to establish a low resistance electrical coupling therebetween. This electrical coupling may be enhanced yby the forcing of the conductor 17 up the wedge-shaped or tapered base portion 39 such that the braid of the conductor 17, which tends to resist stretching or expanding, bears tightly against the louter surface of the tapered base portion 39.
In lorder to orient Ithe cable 15 and the attached retaining member 36 in the connector shell 20, the main body portion 37 of the retaining member may be provided with an annular upper or outer portion 45 axially extending in a direction opposite to the base portion 39 and having dimensions such that it encompasses the outermost surface of the projection 34 and abuts against the shell shoulder 25 when the retaining member is pla-ced in the shell 20. The annular outer portion 45 may have an axial length greater than the axial length of the projection 34 such that it extends lover a portion of the bushing section 32. Inasmuch as the retaining member 36 provides an electrical continuation for the conductor 17, it may be desir-able to electrically couple the retaining member to the leading end of the connector receptacle 11 by suitable current conveying means to be supplemented by the electrical coupling provided thnough the shell 20 and the sleeve 13. Satisfactory results have been attained by utilizing a yieldable member 48 which may be in the form `of a heli-cally wound spring or the likedisptosed about the bushing section 32 with one end abutting against lthe projection 34 and the other end extending to a location adjacent the leading end tof the bushing 29. The yieldable cable 15 as described above may be maintained in the connector shell 20 by environmental protection and cable retention means generally indicated at 51. The cable protecting andretaining means may comprise a cylindrical or tubular deformable gasket 52 of elastomeric material such as silicone rubber or the like having a ldurometer hardness of about 50. The gasket 52 may be disposed between a pair of ferrules 54 and 55 having outer diameters slightly less than the inner diameter of the shell 20 beneath the threaded surface 21 and radially inwardly extending lianges or lips -56 and 57 respectively, abutting opposite end surfaces of the gasket 52. The lip 56 on the ferrule 54 is preferably disposedintermedate the ends thereof so as to enable one end of the ferrule to abut against the upper body portion 45 of the retaining member 36 while the lip 57 on the ferrule 55 is preferably at one end thereof to provide a surface against which a detachable end cap 58 may bear to squeeze or deform the gasket 52 to provide the environmental seal while simultaneously forcing the ferrule 54 against the retaining member 36 to securely position the latter in the shell. Ihe end cap 58 may be provided with a threaded inner surface mateable with the threaded surface 21 on the shell 20 and a slotted end for facilitating the use of a suitable cap turning tool (not shown).
The gasket 52 preferably extends along a considerable length of the cable jacket 19 including part of the jacket overlying the tapered base portion 39 to enable the attainment of a positive seal against the jacket surface without overly deforming the jacket or outer conductor in a relatively small area which may lessen the desirability and reliability of the seal. For example, a plug portion 10 with an axial length of about 1.15 inches may contain a gasket of about 0.25 of an inch in length. The present seal is particularly advantageous in providing positive seals with cable jackets fwhich may have irregularities in the surface thereof and urging a section of the conductor 17 against the tapered base portion 39 to enhance the coupling of the conductor to the retaining member 36. The length of the gasket affords another unique feature in that the ends of the ferrules encircling the gasket are spaced apart from each other a suicient distance as to enable a portion or segment of the gasket to be squeezed therebetween `and bear against the inner surface of the shell` 20. Thus, with only a relatively small portion of the gasket 52 bearing against the shell as compared to the large area engaging the cable jacket, the gasket 52 may be tightly held against-.the shell while attaining a relatively light yet suflicient sealing pressure against the cable jacket. The ferrules may be adhesively bonded to the gasket to unitize the seal structure for facilitating assembly of the connector.
In FIG. 2 the bushing 29 is shown axially extending beyond the distal end of the base portion 39 of the retaining member 36 to provide further electrical isolation between the braided conductor 17 and the inner conductor 16 to facilitate the use of high voltages in the plug by increasing the effective length of the voltage creepage path between the inner and outer conductors. The use of the bushing extension as shown in FIGS. 1 and 2 is desirable for high voltage applications, but if the connector is to be used with only low voltages, the bushing section 33 is not necessary and the ramp of a retaining member having an inner'diameter slightly larger than the outer diameter of the insulator 18 may be placed directly over the dielectric member 18. For example, a plug portion of a coaxial cable connector such as illustrated in FIGS. 1 and 2 may have a 7 kilovolt (kv.) rating and be tested at 14 kv. with the center conductor 16 being spaced or electrically isolated about 0.64 of an inch from the braid 17 as provided by the bushing extension; but if the distance between the inner and outer conductors is decreased by about 0.14 of an inch such as by removing a portion `of the bushing extension or section 33, the connector rating drops to 5 kv. tested at l0 kv. If the entire bushing extension or section 33 is removed, as above described, the connector rating drops to about 2.5 kv.
Referring now more particularly to FIG. l, the T- shaped receptacle portion 11 may comprise a pair of tubular housing or shell portions 60 and 61 joined to each other at 62 by any suitable fastening means such las brazing or the like. A pair of center or inner conductors 64 and 65 are disposedin the shell portions 60 and 61 respectively, at right angles to each other such that the conductor 64 extends to contacting elements such as contact pin receiving sockets 67 adjacent opposite ends of the receptacle crossarm while the conductor 65 is aflixed to the conductor 64 and provides an electrical path from the sockets 67 to the terminal 68. The shell portions 60 and 61 and the inner conductors 64 and 65 may be electrically isolated from each other by an insulator 69 of single piece construction which may be injection molded into the shell portions by using any suitable injection molding procedure. The homogeneous insulator 69 formed in this manner facilitates substantial miniaturization of electrical connectors and overcomes several objectionable problems which previously hampered the introduction of a high-voltage series of miniature connectors. For example, a T-shaped coaxial cable connector receptacle having a crossarm length of about one inch and 4a shank length of about one inch Iwith an insulator diameter of about 0.15 of an inch may withstand testing requirements at 10,000 volts D.C. and be rated for operation on electrical potentials up to 5000 volts D.C. (peak). This high voltage rating for such a 'miniaturized T-shaped receptacle is attributable to maintenance of solid or unbroken insulation throughout the interior of the shell particularly around the bends or turns, as provided by the homogeneous single piece insulator. Thus, injection molding enables connector portions to be formed with bends or turns such as in T and L-shaped receptacles and plugs without suffering the high-voltage standoff limitation normally present in such connector configurations particularly when assembling them with mitered joints at the corners as previously required with machined insulators.
While any suitable molding material may be used to form the insulator 69, satisfactory results have been achieved with polychlorotriuoroethylene, such as Kel-F 81 obtainable from Minnesota Mining and Manufacturing Company of St. Paul, Minnesota.
As various changes may be made in the form, construction and arrangement of the parts herein without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in a limiting sense.
1. In an electrical connector, a coaxial cable having an inner conductor, an outer conductor encircling the inner conductor and spaced therefrom by dielectric means, a retaining and connecting member for said outer conductor including a pair of circumferentially disposed and radially spaced apart inner and outer skirt portions connected by an end wall portion with said portions together forming a slot, an end section of said outer conductor seated in said slot between the skirt portions, the outer skirt portion being lnwardly deflected and clamping said end section of the outer conductor between said skirt portions, deformable sealing means in -close proximity to an outer periphery of said inner skirt portion, a tubular insulator Circumierentially disposed between said outer conductor and said dielectric means a-t a location radially inwardly of said inner skirt portion and said end section of the outer conductor, yand housing means enclosing said retaining member and said sealing means and constricting the latter to iirm engagement with said outer conductor.
2. The electrical connector claimed in claim 1 wherein said sealing means secures and seals the inner and outer conductors in said housing means and comprises a generally tubular member circumferentially disposed about said outer conductor, a displacea'ble member secured to said housing and movable with respect thereto for constricting and deforming the tubular member, and a pair of ferrules disposed adjacent opposite ends of the tubular member with each ferrule having a portion thereof overlying a section of said tubular member and with said ferrule portions being axially spaced from each other to facilitate the reception of a deformed segment of the tubular member therebetween, one of said ferrules engages an outer portion of said retaining member and the other of said ferrules contacts said displaceable member.
3. The electrical connector claimed in claim 1 wherein said tubular member provides a seal along a greater axial length of the outer conductor than of the housing, and wherein a portion of said outer conductor is disposed between said tubular member and said inner skirt portion of the retaining member.
References Cited by the Examiner UNITED STATES PATENTS 2,422,982 6/ 1947 Quackenbush 174-2 X 2,854,487 7/1956 Carr e-t al 174-71 FOREIGN PATENTS 460,156 1/1937 Great Britain.
851,712 10/1939 France.
LEWIS H. MYERS, Primary Examiner. DARRELL L. CLAY, Examiner.