EP0116760A1 - Solderless connectors for semi-rigid coaxial cable - Google Patents

Abstract

A solderless connector for semi-rigid coaxial cable (3) having an elongate annular outer conductor (4), a center conductor (5) coaxial with said outer conductor and a dielectric material (6) spacing the inner and outer conductors apart, the connector comprising a housing (1) having an annular portion defining a bore (2) adapted to encompass said outer conductor and a bushing (13) defining a bore to engage the exterior of the annular portion to circumferentia- ly compress said annular portion upon telescoping movement of said bushing over said annular portion, said housing bore having, integral therewith, means (16) adapted to engage said outer conductor upon said circumferential compression to provide a mechanical and electrical interface between said housing and said outer conductor.

Description

• The present invention relates to solderless connectors suitable for use with semi-rigid coaxial cable.
• Semi-rigid coaxial cable, which is used, particularly, where a high degree of RF shielding is required, comprises a solid tubular outer conductor, usually of copper, centrally disposed within which is an inner conductor spaced from the outer conductor by a dielectric material.
• Direct solder attachment of connectors to semi-rigid cable has, until now, been the only reliable arrangement where a connector is required to function reliably in extreme environmental conditions which may include high vibration levels and high continuous/oscillating mechanical and thermal stress.
• Such direct solder attachment of the connector body to the copper sheath of a semi-rigid coaxial cable has always been a production problem because of the experience and skills that have to be developed to maintain an efficient operation. A narrow time/temperature range is needed to promote solder flow while minimizing undesirable heating effects on the confined cable dielectric. In addition, precision equipment is necessary for repeatable connector positioning. In spite of these difficulties, mechanical cable/connector junctions have not gained wide acceptance. Bulk, cost, lack of permanency, and to some extent, poor performance have been against mechanical connectors. Special cable preparation has led to only limited acceptance of a connector design utilizing a crimp to preknurled cable arrangement. Nevertheless, a mechanical concept, with designed-in control of the assembly is desirable for consistent performance and for improved productivity.
• Although solderless connectors are well-known and have been widely used in many applications for flexible and semi-rigid cable assemblies, there useful application has been limited to situations in which vibration and stress are not problems.
• A basic requirement in providing a solderless connector for use in such extreme environment conditions is that of providing mechanical and electrical interconnection of high integrity between the outer conductor and the connector itself. A recent attempt at providing such a connector is embodied in AMP Incorporated's SMA coaxial connector which is described and illustrated on Pages 261 and 262 of AMP Inc.'s catalog entitled "AMP Guide to RF Connectors," Catalog 80-570 published 7/82.
• The AMP connector for semi-rigid coaxial cables utilizes a ferrule or gripper ring which interconnects the main housing of the connector with the outer conductor of the semi-rigid cable. The gripper ring in this design includes a plurality of teeth extending from the annular end of the ring axially of the connector and arranged to be deformed or bent radially inwardly to engage the outward conductor of the cable upon the application of a force to telescope the ferrule and housing together. By this telescoping action the teeth are bent inwardly to engage the outer conductor while the main housing achieves an interference fit with the ferrule thereby to retain the connector on the cable. In this design the mechanical and electrical integrity of the mounting of the connector on the cable involves, firstly, the integrity of the connection between the ferrule and the outer conductor of the cable and, secondly, the interference fit between the ferrule and the housing. Failure of either of these will destroy the integrity of the mounting of the connector on the cable. In particular, it has been found that the interference fit between the ferrule and the housing is subject to failure upon the application of a longitudinally acting force on the connector relative to the cable which is of a magnitude insufficient to damage the cable or the connection of the ferrule with that cable.
• It is an object of the present invention to provide an improved solderless connector for semi-rigid coaxial cable which provides high mechanical and electrical integrity under extreme environmental conditions in a design which is simple and economical to install (and repair or replace) using simple tools and which is more economical to produce and compact in form.
• According to the present invention there is provided a solderless connector for semi-rigid coaxial cable comprising a connector housing including a portion defining a cable encompassing opening having cable engaging means formed integrally therewith and means to circumferentially compress said portion about a said cable, when in said opening, to bring said engaging means into engagement with said cable and to maintain that engagement.
• The invention will now be described, by way of example, with reference to the accompanying drawings in which:
• Figure 1 is a sectional elevation of a solderless connector in the form of a straight cable plug ready for installation on the prepared end of a semi-rigid coaxial cable, only the portion of the cable on one side of the center line of the connector being shown;
• Figure 2 is an enlarged fragmentary view of the connector illustrated in Figure 1 showing in greater detail the arrangements for mounting the connector and the cable when in position preparatory to such mounting;
• Figure 3 is a fragmentary view similar to that of Figure 2 with the connector mounted on the cable;
• Figure 4 is a sectional elevation of a solderless straight cable jack utilizing the mounting arrangements of the connector illustrated in Figures 1, 2 and 3; and
• Figure 5 is a solderless straight cable plug utilizing the mounting arrangement of the connector illustrated in Figures 1, 2 and 3.
• With reference first to Figure 1, an annularmonolithic housing 1 defines acylindrical bore 2 of a diameter to accommodate in close spaced relationship the outside surface of a semi-rigidcoaxial cable 3. This cable comprises an annular elongate copper outer conductor 4 concentrically within which extends acopper center conductor 5 with adielectric material 6 disposed therebetween. Acoupling nut 7 is mounted on the housing for rotation relative thereto aboutcentral axis 8. The coupling nut has an inwardly extendingannular flange 9 arranged to cooperate with an outwardly extendingannular flange 10 on the exterior of thehousing 1 to permit the mechanical and electrical interconnection of the connector cable assembly with, for example, a corresponding cable jack such as that illustrated in Figure 4, upon the engagement of the female thread 11 of thenut 7 with the corresponding male thread 12 (see Figure 4) of that jack.
• Abushing 13 is pre-loaded onto therear end 14 of thehousing 1 prior to the assembly of the connector onto thecable 3. The preloading of thebushing 13 serves to provide for ease of handling and holds thenut 7 captive.
• With reference now to both Figures 1 and 2, thehousing 1 has acylindrical counterbore 15 concentric with theaxis 8 at itsrear end 14 with a plurality ofelongate teeth 16 projecting inwardly from the cylindrical surface of the counterbore toward theaxis 8. The tips of these teeth define an imaginary cylindrical surface of the same diameter, prior to the mounting of the connector of acable 3, as and coaxial with thebore 2.
• Four equally spaced apart rows of teeth are provided. These rows each comprise four teeth, equally spaced apart round the circumference of thecounterbore 15, lying in a plane normal to theaxis 8. The teeth are of generally symmetrical triangular cross-section and have a length, around said circumference, approximately equal to the space, around said circumference, between adjacent teeth.
• While the exemplary form of connector has been described with a specific arrangement of teeth, it will be appreciated that other arrangements and shapes of teeth, for example, different numbers of rows, different arrangements of teeth from row to row, elongate teeth some of which extend parallel to theaxis 8, teeth forming individual closed circles (with or without holes, extending radially through saidrear end 14 therein), teeth of asymmetric cross-section to asymmetrically resist longitudinal and/or torsional forces applied to the connector relative to the cable or of conical or frusto-conical form may be utilized without departing on the concept of the present invention.
• The mounting of the connector onto thecable 3 is achieved by sliding the connector onto the cable into the position shown in Figure I with thebore 2 and the tips of theteeth 16 in close proximity to the outer surface of the outer conductor 4. Thehousing 1 and bushing 13 are then telescoped together by the application of a telescoping force longitudinally of theaxis 8 as may be applied by a hand operated tool adapted for this purpose. This telescoping action compresses therear end 14 of the housing circumferentially, and thereby moves theteeth 16 radially inwardly, by virtue of the interaction ofcylindrical bore 17 of bushing 13 with the cylindricalouter surface 18 of therear end 14 of thehousing 1, thebore 17 being of a smaller diameter than thesurface 18. The radial thickness and outer diameter of therear end 14 is chosen relative to the material and dimensions of thebushing 13 to provide a desired movement ofteeth 16 radially inwardly towardaxis 8. Interacting frusto-conical surfaces 19 on thebushing 13 and therear end 14 disposed at appropriate angle toaxis 8 to facilitate initial telescoping action to bring thebore 17 into initial contact with thesurface 18. The telescoping action is continued until thehousing 1 and bushing 13 occupy the position illustrated in Figure 3 with thebushing 13 abutting the outwardly extendingannular flange 10 of the housing.
• The radially inward deformation of the rear end causes the surface ofcounterbore 15 to engage and theteeth 16 to engage and deform the surface of the conductor 4 to provide a positive mechanical and electrical interface therewith. The circumferential extension of the teeth provides substantial annular communication between the housing and the outer conductor thereby to strongly resist the longitudinal movement of the housing on the cable upon the application of axial forces on the connector relative to the cable. The circumferentially extending gaps between the teeth serve to resist torsional forces attempting to twist the connector aroundaxis 8 about the cable.
• With the connector of the present invention, the integrity of the mechanical and electrical interconnection between the outer conductor of the cable and the connector depends upon only a single interface, namely the interface between theteeth 16 andrear end 14 with the outer conductor and the cable. The superiority of such an arrangement over the prior art connector described above with its reliance upon two serially disposed interfaces for mechanical and electrical mounting integrity, with the resulting double chance of failure will be readily apparent to one skilled in the art.
• With reference now to Figure 4, there is illustrated astraight cable jack 21 having mounting arrangements similar to those described with reference to Figures 1, 2 and 3, for the mounting of the jack onto a semi-rigid coaxial cable. In this arrangement thehousing 22 has arear end 14 similar to that illustrated in Figures 1, 2 and 3 on which is preloaded abushing 13. Inaddition housing 22 supports opposed electricallyinterconnected contacts 23 by means of a dielectric 24, one adjacent therear end 14 for engagement with the center conductor of a cable upon which thejack 21 is mounted. Theforward end 25 has amale thread 25 to facilitate connection with a plug such as described with reference to Figures 1, 2 and 3, by means of engagement of thecoupling nut 7 with theforward end 25; the center conductor of the cable upon which that plug is mounted engaging the otherfemale contact 23 which is located adjacent theforward end 25.
• The annular face terminating theforward end 25 is adapted when the jack is connected to a plug as shown in Figures 1, 2 and 3, to sealingly engage an annular gasket 27 captively mounted in an annular groove formed in an exterior surface ofhousing 1 adjacent the outwardly extendingflange 10, within thecoupling nut 7.
• Figure 5 illustrates a cable plug having mounting arrangements similar to those described with reference to Figures 1, 2 and 3 with the housing of this plug supporting electrically interconnected female and male contacts by means of a dielectric, the female contact being adapted to communicate with the center conductor of a cable on which the cable plug is mounted and with the male contact projecting into the interior of a coupling nut for engagement with a cable jack such as illustrated in Figure 4.
• While the present invention has not been described with reference to the use of any particular materials, suitable materials will be apparent to a man skilled in the art, including constructing the electrically conductive components from any suitable material including stainless steel and that these components may be be gold plated.

Claims (16)

1. A solderless connector for semi-rigid coaxial cable having an elongate annular outer conductor, a center conductor coaxial with said outer conductor and a dielectric material spacing the inner and outer conductors apart, the connector characterized by a housing (1) having an annular portion defining a bore (2) adapted to encompass said outer conductor and a bushing (13) defining a bore to engage the exterior of the annular portion to circumferentially compress said annular portion upon telescoping movement of said bushing over said annular portion, said housing bore having, integral therewith, means (16) adapted to engage said outer conductor upon said circumferential compression to provide a direct mechanical and electrical interface between said housing and said outer conductor.

2. A connector according to claim 1 characterized in that said housing is a monolithic structure.

3. A connector according to claim 2 characterized in that said housing bore is cylindrical and said means comprise a plurality of radially inwardly extending teeth.

4. A connector according to claim 3 characterized by one or more of the following: (a) said teeth are elongate teeth extending and spaced apart round the circumference on the cylindrical surface of said housing bore; or (b) said teeth are elongate and aligned to form a row of teeth, extending from the cylindrical surface, disposed circumferentially about said housing bore.

5. A connector according to claim 4 subparagraph (b) characterized by a plurality of said rows of teeth spaced apart longitudinally of the axis of the housing bore.

6. A connector according to claim 3 characterized in that the circumferential extension of each tooth is approximately equal to the circumferential spacing between adjacent teeth.

7. A connector according to claim 1 characterized by one or more of the following: (a) said bushing is adapted for pre-loading engagement with said annular portion; (b) said means are spaced apart teeth projecting radially inwardly from said annular portion; (c) in the form of a cable plug further characterized by a coupling nut captively mounted on said housing for rotation relative thereto; (d) in the form of a cable jack characterized in that said housing defines a forward end carrying a male thread and supports opposed electrically interconnected female contacts within the housing, by means of a dielectric material, to provide electrical interconnection between a cable to which a cable is mounted and a cooperating cable plug; or (e) said housing defines an abuttment to positively limit telescoping motion of the bushing over said annular portion.

8. A connector according to claim 7 subparagraph (a) characterized in that the bushing bore is smaller in diameter than the outer diameter of said annular portion to an extent whereby upon telescoping movement of said bushing over said annular portion a desired circumferential compression of said annular portion occurs to produce desired radial inward deformation of said annular portion to cause said engaging means to engage and press into said outer conductor to a desired extent only.

9. A connector according to claim 8 characterized in that said bushing and said annular portion are provided with cooperating frusto-conical surfaces angled to facilitate initiation of telescoping movement of the bushing over said annular portion upon the application of longitudinally acting forces to produce said telescoping movement.

10. A connector according to claim 7 subparagraph (b) characterized in that said spaced apart teeth are of symmetrical triangular cross section.

11. A connector according to claim 7 subparagraph (b) characterized in that said teeth are of asymmetric cross section oriented to asymmetrically resist longitundinal forces applied to said connector relative to a cable to which the connector is attached.

12. A connector according to claim 7 subparagraph (e) characterized in that said connector is a cable plug further comprising a coupling nut disposed for rotation about said housing and held captive between said abuttment on said housing and a further abuttment surface on said bushing.

13. A solderless connector for semi-rigid coaxial cable characterized by a connector housing including a portion defining a cable encompassing opening having cable engaging means formed integrally therewith and means to circumferentially compress said portion about a said cable, when in said opening, to bring said engaging means into engagement with said cable and to maintain that engagement.

14. A solderless connector according to claim 13 characterized in that said engagement means are a plurality of teeth and said compression means is a bushing adapted to telescope over said housing in an interference fit with said portion to achieve and maintain said compression.

15. A solderless connector according to claim 14 characterized in that said housing, including said portion and engaging means, is monolithic.

16. A solderless connector according to claim 15 characterized in that said teeth are disposed in a plurality of parallel spaced apart circumferentially extending rows, said teeth of each row being spaced apart about and elongate in said circumferential extension.

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