Universal Coaxial Cable Connector

Abstract

There is disclosed a coaxial cable connector for use with the same nominal size cables of different manufacturers. Although the actual outer diameters of such cables may vary by as much as 10%, the connector includes in the conical bore of a retaining nut a slotted tapered sealing gland whose fingers, when the connector is tightened, are bent inwardly to tightly grip the outer conductor of the cable. The connector also includes a wire mesh ring which, when compressed in the axial direction, expands radially both inwardly and outwardly so as to form a tight mechanical fit and establish good electrical contact and radiation shielding between the outer conductor of the cable and the body of the connector.

Description

This invention relates to coaxial cable connectors, and more particularly to connectors which can be used with cables of nominally the same diameter but which actually have different outer diameters.

The function of a coaxial cable connector is to connect the inner and outer conductors of a coaxial cable to a standard output plug or jack. The standard output plugs and jacks can be of types TNC, N BNC, HN, LC, LT, SMA and UHF, and each can have a male or female configuration. Different connectors are required for different size cables. thus multiplying the total number of possible connectors which may have to be used.

There are many requirements which must be satisfied by a coaxial cable connector. It should be relatively simple to attach the connector to the cable and to make reliable electrical contact with both the inner and outer conductors. The connector, after it is attached, should remain locked in place and no radiation should pass through it except along the inner and outer conductors. Furthermore, the connector should be water-tight so that moisture on the cable outer conductor does not enter into the body of the connector.

One of the major problems with prior art connectors relates to the fact that the actual outer diameters of the same nominal size cables of different manufacturers are not exactly equal. Nominal sizes of coaxial cables are 1/4, 3/8, 1/2, 7/8 and 1-5/8 inches, but the actual outer diameters of cables of the same nominal size may vary by almost 10%. Further variations are encountered when corrugated and non-corrugated cables are compared. (The outer conductors of some cables are corrugated to make them more flexible.) It is exceedingly difficult to provide a single connector of a particular plug or jack type for a particular size cable which can actually be used with the cables of the different manufacturers. For this reason, it is the industry practice to provide separate connectors for the same nominal size cable for use with the cables of different manufacturers. In actual practice, it is not only necessary for a user to stock many more connectors than would be thought necessary, but it is often found that in the field the proper connector for a cable of a particular manufacturer may not be available. In such a case, if a connection is made using a wrong connector it is often unsatisfactory.

It is a general object of our invention to provide a connector which can be used to satisfaction with the cables of different manufacturers which have the same nominal size but whose actual outer diameters may vary.

In accordance with the principles of our invention we provide a slotted plastic sealing gland, of conical shape, which is placed within an internal conical bore of a retaining nut placed around the outer conductor of a coaxial cable. The body of the connector, having a standard plug configuration at its forward end, can be tightened around the retaining nut and includes a central contact for engaging the inner conductor of the cable. Within the body of the connector, and disposed around the outer conductor of the cable, there is a wire mesh ring separated by a washer from the sealing gland. As the body is screwed on the retaining nut, the sealing gland and the wire mesh ring are forced toward each other.

As the connector is thus tightened, the sealing gland is forced into the conical bore of the retaining nut and is thereby tightly clamped around the cable. The slots in the sealing gland allow it to bend inwardly and tightly grip a cable of any outer diameter within the range normally associated with the nominal cable size for which the connector is designed. The axial compression of the wire mesh ring causes its inner diameter to be shortened and its outer diameter to be lenghtened. It is the inner and outer expansion of the ring which insures that good electrical contact is made between the body of the connector and the outer conductor of the cable, and that a tight mechanical fit is maintained between them. The wire mesh ring also provides complete radio frequency interference shielding.

It is a feature of our invention to provide a compressible sealing gland within the retaining nut of a coaxial cable connector for allowing the sealing gland to make tight physical contact with the outer conductor of a cable when it is forced into the retaining nut.

It is another feature of our invention to provide within the body of the connector a wire mesh ring, disposed around the outer conductor of the coaxial cable, which is capable of both inner and outer expansion when it is compressed in the axial direction as the body of the connector is screwed on the retaining nut.

Further objects, features and advantages of our invention will become apparent upon consideration of the following detailed description in conjunction with the drawing, in which:

FIG. 1 is a cross-sectional view of an illustrative embodiment of our invention;

FIG. 2 is a cross-sectional view of another illustrative embodiment of our invention;

FIGS. 3A and 3B are cross-sectional and top views of element 28 of FIG. 1; and

FIG. 4 is a cross-sectional view of element 42 of FIG. 1.

Cable 10 in FIG. 1 includes a conventional outer conductor 12 (of the smooth type, although the connector 20 can be attached to a corrugated cable of the same nominal diameter as well), a central conductor 14 and a layer of dielectric (not shown) which separates the inner and outer conductors. The end of the cable is cut so that the inner conductor extends out past the dielectric and the outer conductor.

The forward end of connector 20 has the standard female-type N configuration. This configuration consists of an inner female contact 42 with fingers 42a which is electrically connected to inner conductor 14 of the cable, and an outer body 22 which is electrically connected through various connector parts to be described below to outer conductor 12 of the cable.

Retaining nut 26 is provided with an outer screw thread 26a, and a conical bore 26b. Inner diameter 26c of the retaining nut surrounds the cable but may not make contact with it. The inner diameter 26c is at least as large as the largest outer diameter of any cable of the nominal size for which the connector 20 is to be used.

Sealing gland 28, shown most clearly in FIGS. 3A and 3B, is preferably made of nylon or Deldrin. The sealing gland is conical in shape so that it mates with the conical bore 26b in the retaining nut. But the sealing gland includes a series of slots 28b around its periphery which define eight fingers 28a which can be bent inwardly. The smaller the outer diameter of a cable, the farther that the sealing gland can be pushed into the bore of the retaining nut. The farther that the sealing gland is pushed into the bore, the greater the inward bend of fingers 28a. The tightening of the connector forces the sealing gland into the conical bore of the retaining nut so that a very tight fit of the retaining nut-sealing gland combination can be had around the cable.

A rubber O-ring 30 is forced into seat 28c of the sealing gland when the connector is tightened. The O-ring deforms to the cross-sectional shape shown in FIG. 1 and provides a water-tight seal so that moisture on the cable, even if it gets under the sealing gland, cannot pass under the O-ring seal to get into the body of the connector.

Brass washer 32 is disposed between sealing gland 28 and wire mesh ring 34. The function of the washer is to separate the wire mesh ring from the retaining nut 26 so that the wire mesh ring rotates as little as possible when body 24 is turned to tighten the connector. This is to prevent tearing of the wire mesh ring.

Wire mesh ring 34 is a solid mesh, preferably made of Monel (stainless steel with an added amount of nickel). The material itself is much like that of the washing pad sold under the mark "Brillo." The function of the wire mesh ring will be described below.

Forward of the wire mesh ring is a metallic bushing 36 having a seat 36a against which the forward end of the cable bears. The seat of the bushing locates the cable along the central axis of the connector so that inner conductor 14 is aligned with the axis of the connector. This facilitates attachment of contact 42 to the inner conductor as will be described below. The bushing also serves another function. Contact 42 includes a plurality of fingers 42b which grip the exterior surface of inner conductor 14. In effect, they increase the diameter of the inner conductor and this necessarily changes the characteristic impedance of the cable which typically may be 50 ohms. The bushing 36 provides an electrical contact between the outer conductor 12 of the cable and the body 24 of the connector. But the bushing, in so doing, provides inductive loading and functions as a "matching ring." The configuration of the bushing, especially its seat 36a, insures that the characteristic impedance of the cable-connector combination remains at 50 ohms despite the fact that the outer diameter of the inner conductor is effectively increased by fingers 42b of contact 42. Bushing 36 fits tightly within body 24 but since it can accommodate even the largest diameter cable within the nominal size range, perfect contact with the cable may not be possible. As will be described below, the necessary reliable contact is made by wire mesh ring 34 when the connector is tightened.

Body section 24 includes inner thread 24a which can be screwed on to thread 26b of the retaining nut 26. It is the turning of body section 24 relative to the retaining nut that tightens the connector. Body section 24 includes a seat 42d against which annular ridge 40a of insulator 40 bears. The insulator fits tightly within body section 24, and serves to separate contact 40 from the exterior conducting portion of the connector.

Contact 42, shown most clearly in FIG. 4, includes inwardly bent tabs 42a which define a female connector and a main shank having a straight knurl 42d for fitting tightly within the insulator 40. The rearward end of the contact includes a plurality of spring fingers 42b which are biased inwardly; when the fingers are forced onto inner conductor 14, they form a reliable electrical connection between the inner conductor and contact 42. The contact includes a seat 42c which bears against annular ridge 40b of the insulator. This is to insure that the contact cannot be pulled forward out of the connector.

The remaining element of the connector is body portion 22 which includes inner thread 22a for engaging outer thread 24a of body portion 24. During manufacture of the connector, a liquid plastic such as that sold under the mark Lock-Tite is placed between the threads. The plastic hardens as it dries to lock the two body portions 22 and 24 to each other, effectively forming a single body which can be screwed onto the retaining nut 26.

During manufacture of the connector, insulator 40 is first forced into body section 24, and contact 42 is then forced into the insulator in a direction from right to left in FIG. 1. Thereafter, body section 22 is attached to body section 24 as described above, and brass bushing 36 is forced into body section 24. All of these elements are permanently secured to each other. In order to ship the connector as a single unit, sealing gland 28, O-ring 30, washer 32, and wire mesh ring 34 can be placed between retaining nut 26 and body section 24, and the body section can then be partially tightened around the retaining nut.

In order to attach the connector to a cable, the body is first screwed off of the retaining nut. The retaining nut is placed on the end of the cable, the sealing gland is then pushed into the conical bore of the nut, and the O-ring is pushed into the seat 28c of the gland. Thereafter, washer 32 is placed over the cable followed by wire mesh ring 34. In the last step, the body, including contact 42, is pushed onto the end of the cable and rotated around the retaining nut. As the connector is tightened, wire mesh ring 34 is forced to the right, pushing washer 32 along with it. The washer bears against the sealing gland and forces it deeper into the conical bore 26b. It is the forcing of the sealing gland into the conical bore that causes the fingers of the sealing gland to be bent inwardly to effect a secure grip with the outer conductor of the cable. At the same time, the axial compression forces applied to the wire mesh ring cause its width to be reduced, its inner diameter to be shortened and its outer diameter to be lengthened. Consequently, the wire mesh ring not only acts as a lock between the outer conductor of the cable and body section 24 by reason of its being in a state of compression, it also makes reliable electrical contact with both the outer conductor of the cable and the body portion. The wire mesh ring also provides the necessary radio frequency interference shielding expected of a connector by reason of the tight fit.

It is important to note that excessive tightening of the connector does not result in the wire mesh ring crushing the cable. In some prior art connectors, excessive tightening of the connector can result in crimping of the outer conductor. But because the wire mesh ring is resilient, if the connector is tightened too much, the wire mesh ring is simply placed under increased compression rather than the inner diameter of the ring shrinking excessively so as to crush the cable.

It is of interest to note that the outer diameter of insulator 40 is smaller toward the forward end of the insulator than it is toward the rearward end. Similar remarks apply to the inner diameter of the insulator. However, the change in the outer diameter is closer to the forward end of the insulator than is the change in inner diameter. Thus, the change in the inner diameter of body part 24 is forward of the change in the outer diameter of contact 42. The slight axial separation between the changes in diameter is due primarily for impedance matching purposes -- to insure that the characteristic impedance of the connector-cable combination is the same as that of the cable alone.

It is the combination of tapered gland 28 and wire mesh ring 34 which allows the same connector to be used with the same nominal size cable of different manufacturers without making any sacrifice in quality. Tight mechanical fits and good electrical contacts are achieved because of the compressibility and slideability of the sealing gland, and the expansibility of the wire mesh ring when under axial compression.

FIG. 2 shows a similar type N connector 60, but having a male plug. To construct such a connector, slightly different forward components must be incorporated in the unit. However, the rear portion of the connector is the same as that of FIG. 1.

Body 22 of the connector of FIG. 1 is replaced by body 62. This element includes a cylindrical section 62b which is required in a male type-N connector. It also includes a circular groove 62a over which snap ring 64 is placed. The snap ring is simply a ring having a radial slot in it. After the snap ring is fitted on the unit, a conventional moisture sealing washer 68 is placed over the cylindrical section 62b, following which coupling nut 66 is forced over the snap ring. While the coupling nut serves a purely mechanical function, it is body portion 62 which is an extension of the cable outer conductor (as is body portion 22 in the connector of FIG. 1). The male connector of FIG. 2 includes a contact 70 whose fingers 70b are comparable to fingers 42b of contact 42, but whose forward end 70a comes to a point rather than being provided with inwardly bent tabs 42a. The only differences between the connectors of FIGS. 1 and 2 are in their forward ends.

From a comparison of FIGS. 1 and 2 it will be apparent that male and female connectors of all types may be constructed simply by providing forward elements of conventional shapes and central contact pins of the required configurations, the rearward end of each pin having spring fingers which may be securely attached to the inner cable conductor without even requiring a solder connection. Although a connector must be stocked for each nominal size cable for each standard type of plug, the same connector can be used in all cases for cables of different manufacturers which are of the same nominal size. This is due to the fact that the tapered gland 28 can be forced into retaining nut 26 so that its fingers 28a are bent inwardly to securely grip a cable whose outer diameter may vary slightly, and wire mesh ring 34, when axially compressed, expands both inwardly and outwardly in the radial direction so as to establish a tight mechanical fit and a good electrical contact between body element 24 and the outer conductor of the cable.

While the invention has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the application of the principles of the invention. Numerous modifications may be made therein and other arrangements may be devised without departing from the spirit and scope of the invention.

Claims

What I claim is:

1. A coaxial cable connector for attachment to any of several coaxial cables of the same nominal size but whose outer diameters are different comprising a retaining nut having a conical bore therein and an inner diameter large enough to permit placement thereof around even the largest diameter cable to which the connector may be attached, a tapered sealing gland disposed in the conical bore of said retaining nut for placement around the outer conductor of a coaxial cable, the inner diameter of said sealing gland being reduceable as the gland is forced rearward into the conical bore of said retaining nut for securely gripping the outer conductor of said coaxial cable, a wire mesh ring disposed forward of said retaining nut and said sealing gland for placement around the outer conductor of said coaxial cable, a contact pin attachable to the inner conductor of said coaxial cable, and a conducting body portion fittable over said wire mesh ring and attachable to said retaining nut, the movement toward each other of said retaining nut and said body portion causing said wire mesh ring to be axially compressed thereby causing it to expand radially both inwardly and outwardly for establishing a mechanical fit and electrical contact between the outer conductor of said coaxial cable and said body portion.

2. A coaxial cable connector in accordance with claim 1 wherein said sealing gland includes a plurality of axial slits therein for defining a plurality of fingers which are caused to bend inwardly as said body portion is attached to said retaining nut and the sealing gland is forced rearwardly into the conical bore of said retaining nut.

3. A coaxial cable connector in accordance with claim 2 wherein said contact pin includes a plurality of spring fingers for tightly gripping an end of said inner conductor which extends forward of the outer conductor of said coaxial cable, and insulator means for centrally locating said contact pin within said body portion but electrically isolating it therefrom.

4. A coaxial cable connector in accordance with claim 3 further including a bushing located within said body portion forward of said wire mesh ring and having a seat therein for aligning the coaxial cable along the central axis of said body portion and for controlling the characteristic impedance of the coaxial cable with the connector attached to it to be equal to the characteristic impedance of the coaxial cable.

5. A coaxial cable connector in accordance with claim 4 wherein the forward end of said sealing gland has a seat therein for surrounding a coaxial cable when said sealing gland is placed therearound, and further including a deformable O-ring for placement around the outer conductor of said coaxial cable within the seat of said sealing gland, and a washer for separating said wire mesh ring from said retaining nut, said sealing gland and said deformable O-ring.

6. A coaxial cable connector in accordance with claim 1 wherein said contact pin includes a plurality of spring fingers for tightly gripping an end of said inner conductor which extends forward of the outer conductor of said coaxial cable, and insulator means for centrally locating said contact pin within said body portion but electrically isolating it therefrom.

7. A coaxial cable connector in accordance with claim 6 further including a bushing located within said body portion forward of said wire mesh ring and having a seat therein for aligning the coaxial cable along the central axis of said body portion and for controlling the characteristic impedance of the coaxial cable with the connector attached to it to be equal to the characteristic impedance of the coaxial cable.

8. A coaxial cable connector in accordance with claim 6 wherein the forward end of said sealing gland has a seat therein for surrounding a coaxial cable when said sealing gland is placed therearound, and further including a deformable O-ring for placement around the outer conductor of said coaxial cable within the seat of said sealing gland, and a washer for separating said wire mesh ring from said retaining nut, said sealing gland and said deformable O-ring.

9. A coaxial cable connector in accordance with claim 1 wherein the forward end of said sealing gland has a seat therein for surrounding a coaxial cable when said sealing gland is placed therearound, and further including a deformable O-ring for placement around the outer conductor of said coaxial cable within the seat of said sealing gland, and a washer for separating said wire mesh ring from said retaining nut, said sealing gland and said deformable O-ring.

10. A coaxial cable connector in accordance with claim 1 further including a bushing located within said body portion forward of said wire mesh ring and having a seat therein for aligning the coaxial cable along the central axis of said body portion and for controlling the characteristic impedance of the coaxial cable with the connector attached to it to be equal to the characteristic impedance of the coaxial cable.

11. A coaxial cable connector comprising a retainer nut for placement around a cable to which the connector is to be attached, a sealing gland disposed in said retaining nut for placement around the outer conductor of a coaxial cable, wire mesh means disposed forward of said retaining nut and said sealing gland for placement around the outer conductor of said coaxial cable, a contact pin attachable to the inner conductor of said coaxial cable, and a conducting body portion fittable over said wire mesh means and tightenable to said retaining nut, the tightening of said body portion to said retaining nut causing said wire mesh means to be axially compressed thereby deforming it to expand radially both inwardly and outwardly for establishing a mechanical fit and electrical contact between the outer conductor of said coaxial cable and said body portion, and causing said sealing gland to securely grip the outer conductor of said coaxial cable.

12. A coaxial cable connector in accordance with claim 11 wherein said sealing gland includes a plurality of axial slits therein for defining a plurality of fingers which are caused to bend inwardly as said body portion is tightened to said retaining nut and the sealing gland is forced rearwardly against said retaining nut.

13. A coaxial cable connector in accordance with claim 12 wherein said contact pin includes a plurality of spring fingers for tightly gripping an end of said inner conductor which extends forwardly of the outer conductor of said coaxial cable, and insulator means for centrally locating said contact pin within said body portion but electrically isolating it therefrom.

14. A coaxial cable connector in accordance with claim 13 further including a bushing located within said body portion forward of said wire mesh means and having a seat therein for aligning the coaxial cable along the central axis of said body portion and for controlling the characteristic impedance of the coaxial cable with the connector attached to it to be equal to the characteristic impedance of the coaxial cable.

15. A coaxial cable connector in accordance with claim 14 wherein the forward end of said sealing gland has a seat therein for surrounding a coaxial cable when said sealing gland is placed therearound, and further including a deformable O-ring for placement around the outer conductor of said coaxial cable within the seat of said sealing gland, and a washer for separating said wire mesh means from said retaining nut, said sealing gland and said deformable O-ring.

16. A coaxial cable connector in accordance with claim 11 wherein said contact pin includes a plurality of spring fingers for tightly gripping an end of said inner conductor which extends forward of the outer conductor of said coaxial cable, and insulator means for centrally locating said contact pin within said body portion but electrically isolating it therefrom.

17. A coaxial cable connector in accordance with claim 16 further including a bushing located within said body portion forward of said wire mesh means and having a seat therein for aligning the coaxial cable along the central axis of said body portion and for controlling the characteristic impedance of the coaxial cable with the connector attached to it to be equal to the characteristic impedance of the coaxial cable.

18. A coaxial cable connector in accordance with claim 16 wherein the forward end of said sealing gland has a seat therein for surrounding a coaxial cable when said sealing gland is placed therearound, and further including a deformable O-ring for placement around the outer conductor of said coaxial cable within the seat of said sealing gland, and a washer for separating said wire mesh means from said retaining nut, said sealing gland and said deformable O-ring.

19. A coaxial cable connector in accordance with claim 11 wherein the forward end of said sealing gland has a seat therein for surrounding a coaxial cable when said sealing gland is placed therearound, and further including a deformable O-ring for placement around the outer conductor of said coaxial cable within the seat of said sealing gland, and a washer for separating said wire mesh means from said retaining nut, said sealing gland and said deformable O-ring.

20. A coaxial cable connector in accordance with claim 11 further including a bushing located within said body portion forward of said wire mesh means and having a seat therein for aligning the coaxial cable along the central axis of said body portion and for controlling the characteristic impedance of the coaxial cable with the connector attached to it to be equal to the characteristic impedance of the coaxial cable.