US3778535A - Coaxial connector - Google Patents

Abstract

A coaxial cable connector featuring inner and outer ferrules between which the outer conductor of a semi-rigid cable is squeezed. The assembly of the connector onto the cable is accomplished with ordinary standard hand wrenches operating on an outer coupling containing the outer ferrule nut threadedly engaging a connector body containing the inner ferrule. The structure of the connector preserves the critical diameters of the coaxial cable thereby reducing or eliminating reflective loss of radio frequency energy.

Description

United States Patent [191 Forney, J r.

[ 1 Dec. 11, 1973 COAXIAL CONNECTOR [75] Inventor: Edgar Wilmot Forney, Jr.,

Harrisburg, Pa. [73] Assignee: AMP Incorporated, Harrisburg, Pa.

[22] Filed: May 12, 1972 [21] Appl. No.: 252,791

[521 U.S. C1. 174/88 C, 174/89, 339/89 C, 339/177 R [51] lnt. Cl ..1l02g 15/08 [58] Field 01 Search 174/88 C, 75 C, 89;

339/177 R, 177 E, 89 C [56] References Cited I UNITED STATES PATENTS 2,296,766 9/1942 Bruno 339/177 R 2,328,469 9/1943 Laffly 174/89 3,551,882 12/1970 OKeefe 174/75 C 3,184,706 5/1965 Atkins 174/89 X 3,469,014 9/1969 Papadopulos 174/89 X 2,995,388 9/1961 Morello, Jr. et al. 174/88 C X 3,245,027 4/1966 Ziegler, Jr 174/88 C X 3,701,086 10/1972 Somerset R 3,492,604 1/1970 Fan X 3,498,647 3/1970 Schroder 339/177 R X Primary ExaminerBernard A. Gilheany Assistant ExaminerA. T. Grimley Att0rneyWilliam J. Keating et al.

[57] ABSTRACT 8 Claims, 6Drawing Figures SHEET 10? 2 PATENTEU DEC 1] 1975 PAIENIEDUEC n ma 3778535 sum 2 OF 2 COAXIAL CONNECTOR BACKGROUND OF THE INVENTION Semi-rigid coaxial cables have been developed for handling radio and ultrahigh frequency energy. Such cables typically have a center copper conductorand aluminum outer shield with air alarge part of the dielectric medium thereinbetween. These. conductors or cables are light weight and are'especially suitable for use in cable television systems. However, considerable difficulty has been experienced in developing a suitable connector for terminating the coaxial cable. ,Moreparticularly, difficulty is experiencedin securing the connector shell to the cable shield with sufficient strength so that the two will not separate underphysicalloads or fail under thermal cycling which are normal in actual field operations.

In general, workers in the field have developed several approaches in terminating coaxial cable. One approach has been to provide-a clamp or collet having interior teeth which are driven into the .outer conductor so as to provide the mechanical gripping action.

The approach noted above and other similar approaches well known to those skilled in theart possess some drawbacks. The first is that-the outer cable conductor is unsupported by the relatively weak cable dielectric at the clamping point so thatit-begins to collapse under load, i.e.,. itreduces radiallyso-that the electrical and mechanical connectionto theconnector body deteriorates.

In order to counter the collapse of'the outer conductor under clamping pressure a practicewas developed to insert a sleeve orferrule within and next to the outer cable conductor toprovide support. Thishelpedthe collapsing problem considerably but introduced another problem; the characteristic impedance of a coaxial cable is a function of the inner dimensions; thus, by inserting the ferrule into the cable,,the impedance at this point is changed and there is a reflective loss -in the frequency energybeing transmitted.

Accordingly, the present invention provides a device for terminating or connecting semi-rigid coaxial cable of the type having a center conductor surrounded by a dielectric medium and an outer conductor having a given inner diameter held to agiven close tolerance for efficient signal transfer, which comprises a threaded insert assembly which includes a coupling nut having external threads on one end and two longitudinal concentric bores therein, one of the bores being larger than the second, a outer ferrule having a sleeve portion and radially extending rim portion, the sleeve portion .adapted to slide into the coupling nut, and a retaining ring having teeth on the inner edges, the ring adapted to fit onto the cable, and.an adapter assembly which includes a connector body having .intemal threads adapted to receive the external threads on the coupling nut, .and also having three, longitudinal, concentric bores of differingdiameters, and'a inner ferrule having a beveled end, the ferruleadapted to'be vhoused in one of the bores in the connector body and further adapted to be inserted into aendof the cablewhen the coupling nut and connector body are threadedly joined.

BRIEF DESCRIPTION OFTHE DRAWINGS FIG. 1 illustrates a-CATV directional tap to .which semi-rigid coaxial cable is connected utilizing the present invention;

FIG. 1A shows details of the coaxial cable of FIG. 1;

FIG.2 is a perspective, exploded and partially sectioned view of one half of the connector construction in accordance with the present invention;

FIG. 3 is a perspective exploded and partially sectioned view of another half of the connector constructed in accordance with the present invention; and

FIGS. 4 and 5 illustrate the assembly of the connector shown in FIGS. 2 and 3 to a coaxial cable.

DESCRIPTION OF THE PREFERRED EMBODIMENT A CATV directional tap, designated at 10 in FIG. 1, .is used, either on over-head lines or underground, to provide television signals, entering therein from distributioncoaxial cable 12 attached thereto via coaxial vconnector14, to the homes located along the TV cable.Tap 10 is a conventional directional coupler and splitter such as manufactured by Jerrold Electronics, Inc. In the modelshown in FIG. 1,tap 10 contains a circuitry -(not,shown).which sends the TV signals into .four different homes via house tapslS (of which only two are seen).

Cable 12 is one type of semi-rigid coaxial cable whose structure can be seen in FIG. 1A. The cable includes anouter conductor 16 and a center conductor .18. The dielectric material separating the two conductors is airv filled chamber, designated at 20, thereinbe- .tween.Disks 22 of dielectric material such as polyethylene arepositioned at spaced intervals along the inside ofcable 12, to support and centralize center conductor As is well known, one of the critical dimensions in coaxial cable such ascable 12 is the diameter of the inner surface of outer conductor16 shown as D in FIG. 1A.

It is very important to avoid or at least minimize any change in this dimension. Where a change results in a mismatch of cable impedance and from that a reflective loss of radio frequency (R.F.) energy.

In accordance with the inventive concept a termination ofcoaxial cable 12 shown in FIG. 1A is provided throughcoaxial connector 14 which eliminates damaging deformation tocable 12 and which provides a means for attachingcable 12 to tap 10 without the use of special tools.Coaxial connector 14 is shown in detail in FIGS. 2 and 3 to which reference is now made.

FIG. 2 shows threadedinsert assembly 24 ofcoaxial connector 14. The assembly includes a housing orcoupling nut 26,outer ferrule 28 andcable retaining ring 30. FIG. 2 also showsguage 32 which is provided to insure proper installation ofconnector 14 ontocable 12 aswill-be described in detail below.

Coupling nut 26 containsexternal threads 34 onend 35, and ahexagonal surface 36 onend 37. Internally,coupling nut 26 defines two concentric bores of differing diameters. The smallest diameter bore 38, beginning attend 37, meets thelargest diameter bore 40 which begins atend 35. The diameter ofsmallest bore 38 is slightly greater than the outer diameter ofouter ferrule 28.

Outer ferrule 28 consists of asleeve 44 and arim 46.

.Sleeve.44 is thin walled and is slightly longer thancoupling nut 26. Rim 46extends outwardly for a distance slightly less than the root diameter of external threads '34 oncoupling nut 26. Internally,outer ferrule 28 defines .a bore .48, andwithin rim 46 a internal, annular recess having .astep 51. The diameter ofbore 48 is slightly greater than the outer diameter ofcoaxial cable 12 and the diameter ofrecess 50 withinstep 51 is sized to receive thereincable retaining ring 30.

Cable retaining ring 30 is characterized by having serrations orspring fingers 52 on itsinner edge 54. The inner diameter ofring 30 with theinner spring fingers 52 in a nondeformed position is slightly less than the outer diameter ofcoaxial cable 12. The outer diameter ofring 30 is slightly smaller than the diameter ofgroove 50 located inouter ferrule 28.

Guage 32 is a thin-walled plastic or heavy paper collar whose inner diameter is only large enough to allow the collar to he slipped overthreads 34 oncoupling nut 26.

FIG. 3 shows feed-through adapter assembly 58 ofcoaxial connector 14. The assembly includes aninner ferrule 60 andconnector body 62.

Inner ferrule 60 is a thin-walled cylinder whose forward or leading end '64 (toward the left of the drawing) is beveled inwardly. The outer diameter ofinnerferrule 60 other thanbeveled end 64 is slightly greater than inner diameter D ofcoaxial cable 12.

. Connector body62 containsexternal threads 66 on one end which are sized to be received by internal threads (not shown) intap 10. Further,connector body 62 has ahexagonal surface 68 to facilitate assembly via a standard wrench. Arecess 70, located betweenthreads 66 andsurface 68, is provided to receive O-ring 72. Internally,connector body 62 defines three concentric bores of differing diameters. The largest diameter bore is 74 and it contains internal threads 76 which mate withexternal threads 34 oncoupling nut 26. Arecess 78, located immediately adjacent to threads 76, receives O-ring 80. The next larger diameter bore is 82 and where it meets bore 74 ashoulder 84 is formed. The corner betweenbore 82 andshoulder 84 has been beveled as shown at 86. The diameter ofbore 82 is large enough to accommodateinner ferrule 60 therein. The smallest diameter bore is 88 and whereit meets bore 82,shoulder 90 is formed.Shoulder 90 is of the same thickness asinner ferrule 60 and the diameter ofbore 88 equals the inner diameter ofinner ferrule 60.

ASSEMBLY OF THE PREFERRED EMBODIMENT FIGS. 4 and 5 illustrate the assembly ofcoaxial connector 14 ontocoaxial cable 12.

Prior to assembly on cable,outer ferrule 28 is inserted intocoupling nut 26 to whererim 46 abuts againstend 35 of the coupling nut. The portion ofsleeve 44 which extends beyondend 37 ofcoupling nut 26 is flared outwardly as shown ,in FIG. 4 so that the outer ferrule cannot move longitudinally but can move rotationally.Cable retaining washer 30 is inserted intorecess 50 inrim 46, coining overstep 51 to lock the ring in place.Guage 32 is slid over threads34 oncoupling nut 26.

Connector body 62, withinner ferrule 60 staked into an interference fit inbore 82, is threaded ontocoupling nut 26 as far asguage 32 permits.

Coaxial cable 12 is then inserted into the partial assembly described above until touching contact is made withinner ferrule 60. At that point the cable cannot be slid further in without considerable force thus alerting the assembler that the cable has been pushed throughcable retaining washer 30 the optimum distance. As the cable is pushed in, the inwardly extendingspring fingers 52 tightly graspwasher 30 around the cable thereby looking it in threadedinsert assembly 24.

Connector body 62 is now backed offcoupling nut 26. Feed through adapter assembly'58 may now be attached to a cable televisiondirectional tap 10 viaexternal threads 66 and internal threads (not shown) on the tap as seen in FIG. 1 on the right side oftap 10. O-ring 72 seals the attachment in a manner well known in the art.

With reference to FIG. 5, final assembly ofcoaxial connector 14 takes place when threadedinsert assembly 24, withcoaxial cable 12 attached thereto via the manner disclosed above and withguage 32 removed, is threadedly attached to feed throughadapter assembly 58. Ascoupling nut 26, which can rotate freely aboutouter ferrule 28 andcable 12 attached thereto, is threaded intoconnector body 62,inner ferrule 60 enters insideouter conductor 16 and begins to spread it radially outwardly,beveled end 64 aiding in a manner well known in the art. As the inner ferrule is advanced farther into the cable, the outer conductor is squeezed againstrim 46 where it becomes thinned; i.e., the outer conductor is longitudinally extruded in either direction away from the rim. In addition, both a portion ofsleeve 44 andouter conductor 16 is expanded radially outwardly intobore 40 incoupling nut 26 with the net result that the inner diameter of the outer conductor is maintained throughcoaxial connector 14 andcoaxial cable 12 is securely attached thereto without sever deformation as would occur in a clamp or crimp type connection.

Ascoupling nut 26 bottoms out clampingrim 46 toconnector body 62, O-ring seals the connector against entry of water along the threads as seen in FIG. 5. A metal-to-metal seal in the expanded area ofsleeve 44 andouter conductor 16 prevents water entry along the outer cable conductor.

A novel feature of the present invention is that assembly ofconnector 14 is accomplished entirely with only standard wrenches; no special tools such as hand crimping devices are needed.

As is now apparent, the assembly is quick, sure and uncomplicated so that only simple installation instructions are required.

Another novel feature of the present invention is that the coaxial connector disclosed herein maintains the characteristic impedance of the coaxial cable to which it is attached.

Though the invention has been described with respect to a specific preferred embodiment thereof, many variations and modifications thereof will immediately become apparent to those skilled in the art. It is therefor the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.

What is claimed is:

l. A connector for terminating a semi-rigid coaxial cable of the type having a center conductor surrounded by a dielectric medium and an outer conductor having a given inner diameter, which comprises:

a. a insert assembly comprising 1. a coupling nut having external threads on one end and a longitudinal bore therethrough,

' 2. an outer ferrule adapted to receive said cable, said ferrule having a sleeve and on one end of said sleeve a radially extending rim, said rim having a inwardly facing recess, said sleeve adapted to be positioned in said bore in said coupling nut, 3. A connector for terminating a semi-rigid coaxial 3. a retaining ring having teeth on the inner edge, cable for the propogation of high frequency signals,

said ring positioned in said recess in Said rim and said coaxial cable having a metallic tubular outer conadapted to fit onto said cable whereby said teeth d t hi h omprises;

p Said Cable; and 5 a. an outer ferrule adapted to receive an end of said an adapter assembly comprising coaxial cable inserted therein;

an inner ferrule adapted to be inserted into Said b. an inner ferrule adapted to be driven into an end cable i inner ferrule hailing an inner diameter of said coaxial cable whereby said outer conductor substannany equal to the diameter of Said is pressed radially against said outer ferrule; and

outer conductor; 1

2. a connector body having a passageway therethrough with a portion therein adapted to receive said inner ferrule and internal threads at one end adapted to threadedly receive said insert assembly whereby as said coupling nut threadedly engages said connector body, said inner ferrule is driven into said cable positioned within said outer ferrule thereby expanding said outer conductor against said outer ferrule.

2. A connector to connect an end of a semi-rigid cable to a cable television directional tap or the like, said connector comprising:

a. an inner ferrule having a beveled end, said ferrule c. housing means to contain said outer and inner ferrules.

4. The connector of claim 3 wherein the inner diameter of said inner ferrule substantially equals the inner diameter of said metallic tubular outer conductor.

5. The connector of claim 3 wherein said outer ferrule has a deformable inelastic sleeve portion whereby as said inner ferrule presses said outer conductor outwardly and radially, said outer conductor and said sleeve portion surrounding said conductor are deformed outwardly and radially.

6. The outer ferrule of claim 5 wherein a rim is posi tioned at one end of said sleeve portion and as said adapted to be inserted into the end of Said cable, inner ferrule presses said outer conductor thereagainst, b. a first housing adapted to hold said inner ferrule, Sald outer conductor exirlldes f lY- c. an outer ferrule adapted to receive said cable in- T fonnector of F 3 whereln 531d means to d therethrough, contain said outer and inner ferrules includes: (1. a ring having serrations on its inner edge and a couplmg nut adapted to Comm" 531d Outer adapted to slide over the end of said cable protrud- Yule thefeln; and i th h id outer f l id serrations b. a connector body adapted to contain said inner adapted to engage said cable, ferrule and further adapted to receive said coupling e. a second housing adapted to receive said outer ferrule and ring and further adapted to mate with said 8. The coupling nut of claim 7 wherein said outer ferfirst housing whereby said inner ferrule is driven rule is rotatably mounted therein. into said end of said cable.

Claims (11)

1. A connector for terminating a semi-rigid coaxial cable of the type having a center conductor surrounded by a dielectric medium and an outer conductor having a given inner diameter, which comprises: a. a insert assembly comprising 1. a coupling nut having external threads on one end and a longitudinal bore therethrough, 2. an outer ferrule adapted to receive said cable, said ferrule having a sleeve and on one end of said sleeve a radially extending rim, said rim having a inwardly facing recess, said sleeve adapted to be positioned in said bore in said coupling nut, 3. a retaining ring having teeth on the inner edge, said ring positioned in said recess in said rim and adapted to fit onto said cable whereby said teeth grip said cable; and b. an adapter assembly comprising 1. an inner ferrule adapted to be inserted into said cable, said inner ferrule having an inner diameter substantially equal to the inner diameter of said outer conductor; 2. a connector body having a passageway therethrough with a portion therein adapted to receive said inner ferrule and internal threads at one end adapted to threadedly receive said insert assembly whereby as said coupling nut threadedly engages said connector body, said inner ferrule is driven into said cable positioned within said outer ferrule thereby expanding said outer conductor against said outer ferrule.

2. an outer ferrule adapted to receive said cable, said ferrule having a sleeve and on one end of said sleeve a radially extending rim, said rim having a inwardly facing recess, said sleeve adapted to be positioned in said bore in said coupling nut,

2. A connector to connect an end of a semi-rigid cable to a cable television directional tap or the like, said connector comprising: a. an inner ferrule having a beveled end, said ferrule adapted to be inserted into the end of said cable, b. a first housing adapted to hold said inner ferrule, c. an outer ferrule adapted to receive said cable inserted therethrough, d. a ring having serrations on its inner edge and adapted to slide over the end Of said cable protruding through said outer ferrule, said serrations adapted to engage said cable, e. a second housing adapted to receive said outer ferrule and ring and further adapted to mate with said first housing whereby said inner ferrule is driven into said end of said cable.

2. a connector body having a passageway therethrough with a portion therein adapted to receive said inner ferrule and internal threads at one end adapted to threadedly receive said insert assembly whereby as said coupling nut threadedly engages said connector body, said inner ferrule is driven into said cable positioned within said outer ferrule thereby expanding said outer conductor against said outer ferrule.

3. a retaining ring having teeth on the inner edge, said ring positioned in said recess in said rim and adapted to fit onto said cable whereby said teeth grip said cable; and b. an adapter assembly comprising

3. A connector for terminating a semi-rigid coaxial cable for the propogation of high frequency signals, said coaxial cable having a metallic tubular outer conductor, which comprises: a. an outer ferrule adapted to receive an end of said coaxial cable inserted therein; b. an inner ferrule adapted to be driven into an end of said coaxial cable whereby said outer conductor is pressed radially against said outer ferrule; and c. housing means to contain said outer and inner ferrules.

4. The connector of claim 3 wherein the inner diameter of said inner ferrule substantially equals the inner diameter of said metallic tubular outer conductor.

5. The connector of claim 3 wherein said outer ferrule has a deformable inelastic sleeve portion whereby as said inner ferrule presses said outer conductor outwardly and radially, said outer conductor and said sleeve portion surrounding said conductor are deformed outwardly and radially.

6. The outer ferrule of claim 5 wherein a rim is positioned at one end of said sleeve portion and as said inner ferrule presses said outer conductor thereagainst, said outer conductor extrudes longitudinally.

7. The connector of claim 3 wherein said means to contain said outer and inner ferrules includes: a. a coupling nut adapted to contain said outer ferrule therein; and b. a connector body adapted to contain said inner ferrule and further adapted to receive said coupling nut.

8. The coupling nut of claim 7 wherein said outer ferrule is rotatably mounted therein.

Images