Connector with positive stop and compressible ring for coaxial cable and associated methods

Description

FIELD OF THE INVENTION

The present invention relates to the field of connectors for cables, and, more particularly, to connectors for coaxial cables and related methods.

BACKGROUND OF THE INVENTION

Coaxial cables are widely used to carry high frequency electrical signals. Coaxial cables enjoy a relatively high bandwidth, low signal losses, are mechanically robust, and are relatively low cost. One particularly advantageous use of a coaxial cable is for connecting electronics at a cellular or wireless base station to an antenna mounted at the top of a nearby antenna tower. For example, the transmitter located in an equipment shelter may be connected to a transmit antenna supported by the antenna tower. Similarly, the receiver is also connected to its associated receiver antenna by a coaxial cable path.

A typical installation includes a relatively large diameter coaxial cable extending between the equipment shelter and the top of the antenna tower to thereby reduce signal losses. Some coaxial cables include a smooth outer conductor while other coaxial cables instead have a corrugated outer conductor. These coaxial cables also have an inner conductor and a dielectric between the outer conductor and the inner conductor. Some inner conductors are hollow, while other inner conductors are formed around an inner conductor dielectric core.

A typical connector for such a coaxial cable includes a connector housing to make an electrical connection to the outer conductor and a center contact to make electrical connection to the inner conductor of the coaxial cable. Such a connector may also include a back nut that is positioned onto the end of the outer conductor and adjacent the outer insulating jacket portion of the coaxial cable.

U.S. Pat. No. 5,795,188 to Harwath, for example, discloses a connector for a coaxial cable having a corrugated outer conductor. The connector includes a connector housing defining a radially outer ramp to contact the inside surface of a flared end portion of an outer conductor of the coaxial cable. A clamping ring is in the corrugation adjacent to the flared end portion of the outer conductor. The clamping ring presses the outer surface of the outer conductor against the radially outer ramp to provide electrical contact therebetween.

U.S. Pat. No. 7,011,546 to Vaccaro discloses a connector for a coaxial cable having a smooth outer conductor. The connector includes a connector housing, a back nut threadingly engaging a rearward end of the connector housing, a ferrule gripping and advancing an end of the coaxial cable into the connector housing as the back nut is tightened, and an insulator member positioned within a medial portion of the connector housing. The insulator member has a bore extending therethrough and includes a forward disk portion, a rearward disk portion, a ring portion connecting the forward and disk portions together, and a tubular outer conductor support portion extending rearwardly from the rearward disk portion for supporting an interior surface of the outer conductor of the coaxial cable.

U.S. Pat. No. 7,077,700 to Henningsen discloses a coaxial cable connector including a removable back nut, an outer body, and a center conductor supported within the outer body by a dielectric. An uncompressible clamp ring is rotatably disposed within the central bore of the back nut. A prepared end of a coaxial cable is inserted through the back nut, and the end portion of the outer conductor of the coaxial cable is flared outwardly. As the back nut is tightened onto the outer body, the flared end of the outer conductor is clamped between mating clamping surfaces formed on the clamp ring and the outer body.

Despite these developments in connector technology, a need remains for connectors that may facilitate easy installation and that may retain a good electrical contact with the coaxial cable under a variety of operating conditions. Further, a need remains for connectors that may be securely attached to a coaxial cable and that are sealed against debris and moisture.

SUMMARY OF THE INVENTION

In view of the foregoing background, it is therefore an object of the present invention to provide an easier to install connector for a coaxial cable that maintains a good electrical contact with the coaxial cable under a variety of operating conditions.

This and other objects, features, and advantages in accordance with the present invention are provided by a connector to be attached to a coaxial cable comprising an inner conductor, an outer conductor, and a dielectric therebetween. The connector may comprise a connector housing and a back nut defining a ramp to receive the outer conductor thereagainst. The connector housing and the back nut may include respective portions defining a positive stop when fully engaged. The positive stop may allow the connector to be attached to the coaxial cable without a torque wrench or other torque limiting tool, as the positive stop indicates to the installer when to stop tightening the back nut and the connector housing together.

An electrically conductive compressible coil spring may compressibly clamp against the outer conductor opposite the ramp. This advantageously provides secure mechanical and electrical connections between the outer conductor and the connector housing. Furthermore, this maintains a sufficient clamping force on the outer conductor opposite the radially outer ramp even if the size and/or shape of the outer conductor changes due to thermal expansion or aluminum creep.

The back nut may comprise a polymer composite back nut.

The connector housing may comprise a rearward portion threadingly received within a forward portion of the back nut. A center contact may be coupled to the inner conductor. At least one insulator member may be in the connector housing for carrying the center contact.

The connector housing may have a spring cavity defined therein and the electrically conductive compressible coil spring may be positioned in the spring cavity. The electrically conductive compressible coil spring may have an axis coaxial with the connector housing.

The connector housing may comprise an enlarged diameter tool engaging portion and the back nut may comprise a forward end. The positive stop may thus be defined by the enlarged diameter tool engaging portion and the forward end.

A forward sealing ring may be carried between opposing portions of the connector housing and the back nut adjacent the positive stop.

The ramp may have a stair-stepped shape. This stair-stepped shape may present an increased friction surface to the outer conductor to help prevent unwanted movement of the outer conductor. This stair-stepped shape may also enhance the electrical contact with the outer conductor. Alternatively, the ramp may be defined by a knurled surface of the back nut.

The at least one insulator member may comprise a first insulator member having a central opening defined therein to carry the center contact. The at least one insulator member may further comprise a second insulator member longitudinally spaced apart from, and positioned forwardly of, the insulator member in the connector housing and also having a central opening defined therein to carry the center contact.

At least one sealing ring may be carried within the back nut. This sealing ring may seal the interior of the connector housing and the back nut from moisture and debris.

The at least one sealing ring may comprise a radially inwardly extending forward end to seal against an exposed portion of the outer conductor of the coaxial cable. Additionally or alternatively, the radially inwardly extending forward end may seal against an exposed portion of the jacket.

The back nut may have a sealing ring cavity therein and the at least one sealing ring may be positioned within the sealing ring cavity so that the coaxial cable compresses the at least one sealing ring when the back nut is attached to the coaxial cable.

The outer conductor of the coaxial cable may comprise a corrugated outer conductor or a smooth outer conductor. Indeed, in some applications, the connector may accommodate both corrugated and smooth outer conductors. This advantageously allows a same connector to be used for multiple cable types.

Another aspect is directed to a method of making connector to be attached to a coaxial cable comprising an inner conductor, an outer conductor, and a dielectric therebetween. The method may comprise forming a connector housing and forming a back nut having a ramp to receive the outer conductor thereagainst, and a forward portion to threadingly receive a rearward portion of the connector housing and to define a positive stop therewith when fully engaged with the connector housing.

The method may also include forming an electrically conductive compressible coil spring to be compressibly clamped against the outer conductor opposite the ramp and forming an insulator member to be positioned in the connector housing for carrying a center contact to be coupled to the inner conductor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a connector installed on the end of a coaxial cable having a smooth outer conductor in accordance with the present invention.

FIG. 2 is a longitudinal cross-sectional view of an alternative embodiment of a connector installed on the end of a coaxial cable having a smooth outer conductor in accordance with the present invention.

FIG. 3 is a perspective cutaway view of the connector of FIG. 2 installed on the end of a coaxial cable having a smooth outer conductor.

FIG. 4 is an exploded longitudinal cross-sectional view of the connector of FIG. 2.

FIG. 5 is a greatly enlarged longitudinal cross sectional view of the spring cavity of the connector of FIG. 2 wherein the electrically conductive compressible coil spring is not shown for clarity.

FIG. 6 is a greatly enlarged longitudinal cross sectional view of the ramp of the connector of FIG. 2 wherein the electrically conductive compressible coil spring is not shown for clarity.

FIG. 7 is a greatly enlarged longitudinal cross sectional view of the ramp of the connector of FIG. 2 wherein the electrically conductive compressible coil spring is shown.

FIG. 8 is a greatly enlarged cross-sectional view of the annular groove and retaining projection of the connector of FIG. 2.

FIG. 9 is a greatly enlarged cross-sectional view of the retaining ring of FIG. 2.

FIG. 10 is perspective view of the retaining ring of the connector shown in FIG. 2.

FIG. 11 is a front elevation view of the electrically conductive compressible coil spring of the connector shown in FIG. 1.

FIG. 12 is an exploded perspective view of the back nut and sealing ring of FIG. 2.

FIG. 13 is a longitudinal cross-sectional view of yet another embodiment of a connector installed on the end of a coaxial cable having a corrugated outer conductor in accordance with the present invention.

FIG. 14 is a longitudinal cross-sectional view of a further embodiment of a connector installed on the end of a coaxial cable having a smooth outer conductor in accordance with the present invention.

FIG. 15 is a perspective cutaway view of the connector of FIG. 14 installed on the end of a coaxial cable having a smooth outer conductor.

FIG. 16 is an exploded longitudinal cross-sectional view of the connector of FIG. 14.

FIG. 17 is a greatly enlarged cross-sectional view of the ramp of the connector of FIG. 14.

FIG. 18 is a greatly enlarged cross-sectional view of an annular groove and retaining projection of an additional embodiment of a connector according to the present invention.

FIG. 19 is a greatly enlarged perspective view of an inner surface and ramp of a back nut of still another embodiment of a connector according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and prime notation and double prime notation are used to indicate similar elements in alternative embodiments.

Referring initially to FIG. 1, a connector 10 attached to a coaxial cable 30 is now described. The coaxial cable 30 comprises an inner conductor 33, an outer conductor 31, and a dielectric 32 therebetween. The inner conductor 33 is a hollow inner conductor with an inner conductor filament 35, and an inner conductor dielectric 34 therebetween. The outer conductor 31 is illustratively a smooth outer conductor with a flared end 27, but could be a corrugated outer conductor in other embodiments. The dielectric 32 may be a foam dielectric or other dielectric as known to those skilled in the art.

The connector 10 includes an internally threaded back nut 13 to receive an externally threaded rearward end of a connector housing 12. A forward o-ring 19 and a rearward sealing ring 22 are illustratively provided to seal respective forward and rearward interfaces adjacent the back nut 13 and reduces or prevents moisture ingress. The sealing ring 22 illustratively has a radially inwardly extending forward end 23 to seal against an exposed portion of the outer conductor 31. This radially inwardly extending forward end 23 also seals against the jacket 34. Of course, the o-ring 19 and the rearward sealing ring 22 may be gaskets, as will be appreciated by one of skill in the art.

The back nut 13 defines a ramp 14 to receive the outer conductor 31 thereagainst. The ramp 14 illustratively has stair-stepped surface, although the skilled artisan will understand that other ramp surfaces may be used. For example, as shown in the embodiment of FIG. 19, the ramp 14″″′ may be defined by a knurled surface of the back nut 13″″′.

The end of the coaxial cable 30 is prepared so that the inner conductor 33 extends longitudinally outwardly beyond the end of the outer conductor 31. In addition, in some embodiments (FIG. 1) portions of the dielectric 32 are removed so that the inner surface of the outer conductor 31 is also exposed. The coaxial cable 30 illustratively includes an outer insulation jacket 34 stripped back a distance so that outer end portions of the outer conductor 31 are exposed. The outer conductor 31 is flared outwardly to define the flared end 27.

A portion of the connector housing 12 and a portion of the back nut 13 include respective portions defining a positive stop 18 when fully engaged. More particularly, the connector housing 12 comprises an enlarged diameter tool engaging portion 17 and the back nut 13 comprises a forward end 16. The positive stop 18 is defined by the enlarged diameter tool engaging portion 17 and the forward end 16 of the back nut 13. The forward o-ring 16 is radially inward of and adjacent to the positive stop 18.

It should of course be understood that other variations of the positive stop 18 are possible. Indeed, the connector housing 12 may have a rear portion to engage with a shoulder of the back nut 13 to define the positive stop 18.

The positive stop 18 helps prevent overtightening of the engagement between the connector housing 12 and the back nut 13 that may generate compression and or shearing forces at potentially damaging levels. The positive stop 18 therefore facilitates easy installation of the connector 10 on the coaxial cable 30 by eliminating the need for a torque wrench or other torque limiting tool.

The connector housing 12 illustratively has a spring cavity 20 to receive an electrically conductive compressible ring 15 (FIG. 11) defined therein. This electrically conductive compressible ring 15 is perhaps best shown in FIG. 6.

The electrically conductive compressible ring 15 compressibly clamps against the outer conductor 31 opposite the ramp 14 as the connector housing 12 and back nut 13 are engaged. The electrically conductive compressible ring 15 illustratively has an axis coaxial with that of the back nut 13.

This clamping helps to provide an electrical connection between the outer conductor 31 and the ramp 14 by providing a constant contact pressure between the outer conductor and the ramp. By maintaining such a secure electrical connection, the intermodulation distortion of signals traveling through the coaxial cable 30 may be reduced.

The electrically conductive compressible coil spring 15 advantageously maintains a sufficient clamping force on the outer conductor 31 even if the outer conductor changes shape or size due to thermal expansion or aluminum creep, for example, whereas an arrangement of two wedging surfaces to clamp the outer conductor might lose clamping force and contact pressure if the outer conductor were to change shape or size. Furthermore, by maintaining a constant clamping force on the outer conductor 31, the electrically conductive compressible coil spring 15 allows the connector 10 to be used with both smooth wall outer conductor coaxial cables 30 corrugated outer conductor coaxial cables. In addition the electrically conductive compressible coil spring 15 allows the connector 10 to be used on a variety of coaxial cables with different thicknesses, and on a variety of coaxial cables with outer conductors having different thicknesses.

Furthermore, the clamping provided by the electrically conductive compressible coil spring 15 reduces radial movement of the connector 10 about the coaxial cable 30. That is, the electrically conductive compressible coil spring 15 acts as an anti-rotational device, such as a lock washer, to clamp the coaxial cable 30 between the connector housing 12 and back nut 13 and bite into the outer conductor 31 to reduce or prevent rotation of the connector 10 about the coaxial cable 30.

A center contact 26 is supported in the connector housing 12 by the insulator member 24a, 24b and is electrically connected to the inner conductor 33. The insulator member 24 is also carries the inner conductor 33 of the cable to reduce or prevent movement to thereby reduce IMD.

The illustrated insulator member 24a, 24b is a two piece unit. Of course, the insulator member 24 may also be a monolithically formed one-piece unit in some applications. Such a monolithic construction would help to reduce the number of connector components and thereby reduce the overall cost of the connector 10.

The back nut 13 includes threads 21 to dig into the jacket 34 to securely attach the back nut to the coaxial cable 30. Of course, those skilled in the art will understand that these threads 21 are optional.

A method aspect is directed to a method of making a connector 10 to be attached to a coaxial cable 30 comprising an inner conductor 33, an outer conductor 31, and a dielectric 32 therebetween. The method comprises forming a connector housing 12 and forming a back nut 13 having a ramp 14 to receive the outer conductor 31 thereagainst and a forward portion to threadingly receives a rearward portion of the connector housing 12 and to define a positive stop 18 therewith when fully engaged with the connector housing.

The method further includes forming an electrically conductive compressible coil spring 15 to be compressibly clamped against the outer conductor 31 opposite the ramp 14, and forming an insulator member 24 to be positioned in the connector housing for carrying a center contact 26 to be coupled to the inner conductor 31.

Those of skill in the art will appreciate that different configurations of the connector housing 12 and back nut 13 may be used. For example, in an embodiment of the connector 10′ now described with reference to FIGS. 2-4, the insulator member 24′ illustratively includes a rearward portion 28′ engaging the dielectric 32′ of the coaxial cable 30′.

Furthermore, a retaining ring 40′ (shown in greater detail in FIG. 10) is carried within the back nut 13′ rearwardly of the sealing ring 22′ (shown in greater detail in FIG. 12). The sealing ring 22′ seals both the jacket 34′ and the outer conductor 31′. The sealing ring 40′ is compressed radially and longitudinally when the back nut is installed on the coaxial cable 30′.

In some applications, the sealing ring 22′ may be molded into the back nut using a two-step molding process. Indeed, the back nut may be formed to have a pattern 55′ to facilitate a better bond between the sealing ring 22′ and the back nut (FIG. 12).

Similarly, in some applications, the back nut 13′ is formed from a polymer composite material and by injection molding. Forming the back nut 13′ from a polymer composite material advantageously reduces the cost of the back nut while reducing the formation of galvanic corrosion between the back nut and the outer conductor 31.′

The retaining ring 40′ comprises a ring base 41′ and a plurality of fingers 42′ extending forwardly therefrom so that the sealing ring 40′ overlaps the plurality of fingers and urges the plurality of fingers radially inwardly onto the coaxial cable 30′ to thereby secure the back nut 13′ onto the coaxial cable 30′. The retaining ring 40′ securely attaches the back nut 13′ on the coaxial cable 30′.

As shown in FIG. 9, each finger has a tooth 50′ to dig into the jacket 34′ to enhance the secure mechanical connection between the back nut 13′ and the coaxial cable 30′. Of course, in some applications, the tooth 50′ may not be present and the fingers 42′ of the back nut may be configured so as to not score or mark the jacket 34′.

The ring base 41′ is a continuous annular base, although of course it need not be continuous in all embodiments. Each of the plurality of fingers 42′ illustratively has a rectangular shape.

The back nut 13′ and the retaining ring 40′ have respective portions defining an interference fit locking arrangement therebetween to limit longitudinal movement of the retaining ring 40′ relative to the back nut 13′. This helps to positively located and retain the retaining ring in the back nut.

This interference fit is best shown with additional reference to FIG. 8. The back nut 13′ has an annular groove 43′ defined on a radially inner surface thereof and the retaining ring 40′ has a retaining projection 44, extending radially outwardly from the ring base 41′ into the annular groove. Alternatively, as shown in FIG. 18, in some applications, the back nut 13″″ may have a retaining projection 44″″ to extend into an annular groove 43″″ of the retaining ring 40″″.

As perhaps best shown in FIG. 5, the spring cavity 20′ includes an enlarged diameter portion 51′ to capture the electrically compressible conductive coil spring 15′ and to prevent longitudinal movement thereof.

Shown in FIGS. 6-7 is the ramp 14′, which illustratively has an outer conductor adhesive removing feature 52′. This outer conductor adhesive removing feature 52′ comprises a series of sharp projections and recesses to help remove any residual adhesive from the outer conductor 31′ as the back nut 13′ is installed on the coaxial cable 30′.

The sealing ring 23′ may comprise an elastomeric material, such as an electrically insulating rubber material. The retaining ring 40′ may comprise an electrically insulating plastic material, but could be other materials as well.

Furthermore, the retaining ring 40′ may be rotated in the annular groove 43′ so that the back nut 13′ is rotatable about the retaining ring when installed on the coaxial cable 30′. Thus, during connector 10 installation, a technician holds the connector housing 12′ stationary and rotates the back nut 13′ onto the connector housing 12′. Rotation of the back nut 13′ onto the connector housing 12′ helps to avoid the creation of metal chips that would be caused by rotation of the center contact 26′ about the inner conductor 33′ during installation. Such loose metal chips may increase intermodulation distortion.

Of course, in some applications, the retaining ring 40′ may be securely fastened into the back nut 13′ so that it may not be rotated in the annular groove 43′. In this case, a technician may hold the back nut 13′ stationary and may instead thread the connector housing 12′ into the back nut. Such a configuration may provide a tighter mechanical connection between the retaining ring 40′ and the back nut. Other elements not specifically mentioned are indicated with prime notation and are similar to the elements described above with reference to FIG. 1. Accordingly, those other elements require no further description herein.

As shown in the embodiment illustrated in FIG. 13, the connector 10″ may be installed on the end of a coaxial cable 30″ having a corrugated outer conductor 31″. Those other elements not specifically mentioned are indicated with double prime notation and are similar to the elements described above with reference to FIG. 2. Accordingly, those other elements require no further description herein.

Those of skill in the art will appreciate that yet more configurations of the connector housing 12 and back nut 13 may be used. For example, in an embodiment of the connector 10″′ illustrated in FIGS. 14-17, the connector housing 12″′ (rather than the back nut 13″′) defines the ramp 14″′. Furthermore, the ramp 14″′ has a wedging portion 59″′ (FIG. 17) to flare the outer conductor 31″′ during attachment of the connector housing 12″′ to the coaxial cable 30″′. In addition, the stair-stepped shape of the ramp 14″′ removes residual adhesive or glue from the inner conductor 31″′ during attachment.

Those other elements not specifically mentioned are indicated with triple prime notation and are similar to the elements described above with reference to FIG. 2. Accordingly, those other elements require no further description herein.

Other details of such connectors 10 for coaxial cables 30 may be found in co-pending applications CONNECTOR WITH POSITIVE STOP FOR COAXIAL CABLE AND ASSOCIATED METHODS, Ser. No. 12/277,103; CONNECTOR INCLUDING COMPRESSIBLE RING FOR COAXIAL CABLE AND ASSOCIATED METHODS, Ser. No. 12/277,125, FLARING COAXIAL CABLE END PREPARATION TOOL AND ASSOCIATED METHODS, Ser. No. 12/277,152, and CONNECTOR WITH RETAINING RING FOR COAXIAL CABLE AND ASSOCIATED METHODS, Ser. No. 12/277,172, the entire disclosures of which are hereby incorporated by reference.

Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.