TERMINATION OF CABLE HAVING HELICAL FORMED OUTER CONDUCTOR: METHOD. TOOLS AND CABLE CLAMP THEREFOR

This invention relates to termination of cable and in particular those cables having a helical formed outer conductor.

It is well known in the industry to use electrical cable having a center conductor surrounded by foam insulation that is then overlaid by a conductive sheath having a helical form. The conductive sheath is then covered with a insulative jacket. One particular example of a cable of this type is known as HELIAX of Andrew Corporation, Illinois, U.S.A. In this particular cable the foam is extruded directly onto the center conductor and binds thereto.

In cables of this type, termination and especially field termination presents some problems in that it is difficult to accurately and easily form the necessary configur tion of the cable end in order to attach a connector thereto. At present, field termination is accomplished by way of utility knives, hacksaws etc. One especially difficult area is that with the foam extruded directly onto the center conductor, it is very difficult to remove the foam in a way that assures all of the foam and the residue therefrom is removed from the center conductors such that a reliable electrical connection may be formed therewith. Typically, once the foam is exposed by removing the outer conductor with the helical form, utility knives are used to remove as much of the foam as possible and then emery cloth is used to sand away any remaining foam to produce a clean center conductor. The problem is that it is difficult to tell whether or not the center conductor is fully cleaned and it is a difficult and awkward procedure. in addition, it is desirable to assure that a connector may be reliably attached to the cable. A problem exists in that as the foam insulation is somewhat compressible radial crimping will deform the outer helical

conductor and change the relative radial spacing between the center conductor and the outer conductor. In addition, radial crimping may result in a spreading of the pitch of the helical form on the outer conductor, thereby detrimentally effecting the electrical contribution thereof. What would be desirable is to provide a cable clamp for reliably anchoring a cable having an outer conductor with a helical form thereupon to an electrical connector or other electrical components. Finally, in order to assure proper termination of the cable, it is desirable to provide tooling which will accurately terminate the cable. In cables of this type, it is necessary to form a number of steps such that a length of the center conductor is exposed, followed by a length of the foam insulation and then an exposed length of the formed outer conductor. This involves first facing off the cable to a particular length then forming a radial cut inward to the center conductor and then another cut inward to the foam and a final cut through the jacket to expose the outer conductor. This termination is best seen with reference to Figure 1 as described below.

In order to meet the aforementioned problems, a trimming tool is provided for terminating a cable having a center conductor and a protective jacket thereover, the trim tool comprises a body having a track therein where the cable is to be positioned; a fixing structure on the body to hold the cable in a fixed position relative the body; and a cutter member having a cutter therein where said cutter member is affixed to the body in a manner that enables rotation thereof about an axis defined by the center of the track such that the cutter is advanceable in a scroll-like manner. This structure advantageously provides for reliable cutting of the cable in a manner concentric with the center conductor thereof. In addition, as the cutter location would be known, a positioning tool may be provided that will act as a stop plate so that the various steps necessary for proper termination of a cable may be achieved. These steps may

further be accomplished as the radius of the particular depth of cuts may be calculated based on the characteristic of the cable.

In cases where a cable is used that has a protective jacket or insulative layer formed directly upon the center conductor and this material is bonded thereto, it would be desirable to provide a tool to assure that all of this material is removed so that the center conductor is fully exposed and cleaned in an easy manner. This is accomplished by providing a skiving tool for removing insulative material bonded to a center conductor of a cable, the skiving tool comprising: a base having a seat therein for receiving the center conductor, said seat configured such that the center conductor and the base may move relative to one another in a rotary fashion about the longitudinal axis of the center conductor; a skiving arm carrying a skiving edge thereupon where said skiving arm is pivotally mounted at pivot point to the base with the skiving edge disposed over the seat and aligned generally along the direction corresponding to that of the longitudinal axis of the center conductor when placed in the seat; and a biasing member on the side of the pivot point opposite from the skiving edge that acts to bias the skived edge toward the seat. In order to provide a reliable anchoring system for cables of this type, a cable clamp is provided for a cable having a helical form on an outer conductor of overlaid conductive material that overlies an insulative layer that extends along the length of a center conductor, the cable being terminated with a length of the outer conductor exposed, the cable clamp comprising: a cable nut having a front face and a rear face with a bore extending therebetween, the bore having a helix formed therein for being threadably received upon the helical form of the outer conductor such that a portion extends beyond the front face; a body fittable over the cable and about the cable nut, the body having an internal bore therethrough that includes a shoulder corresponding to the front face

of the nut when the body is placed upon the cable; and where the body and the cable nut are displaceable toward each other such that a portion of the formed outer conductor extending from the cable nut is captivated between the front face and the shoulder.

Finally, a method for terminating a cable having a formed outer conductor encased within an outer jacket and surrounding a generally coaxial center conductor where an insulative layer is disposed therebetween; the method comprising the steps of: sectioning the cable with a cutting tool to provide radial cuts along the length of the cable corresponding to the desired exposure lengths of the cable components, where the cuts are made to the desired radial depths; removing the sections to expose a length of the formed outer conductor, a length of the insulative layer and at least rough removal of the insulative layer about a length of the center conductor; and cleaning the length of the center conductor having the insulative layer partially removed therefrom to fully expose the length of the center conductor for electrical engagement therewith. The tools described above would be usable both with respect to sectioning the cable and cleaning the length of the center conductor.

It is advantageous that the aforegoing tools, method and cable clamp provide for reliable termination of a cable having a helically formed outer conductor. It is an advantage of this invention that the termination may be achieved in the field without the need for complicated tooling in a manner that enables accurate and reliable installation. It is still yet another advantage of this invention that it is easy to use and simple to operate.

The invention will now be described by way of example with reference to the following drawings wherein:

Figure 1 is a side view of a trimmed cable having a helical outer conductor;

Figure 2 is a side view of a trim tool according to the present invention;

Figure 3 is a side sectional view of the trim tool of

Figure 2 ;

Figure 4 is a front view of the trim tool of Figure

2;

Figures 5-19 are detail views of the components used to make-up the trim tool of Figure 2;

Figure 20 is a top view of a setting tool used to properly position the cable so that it will be sectioned to correspond to that Figure 1;

Figure 21 is a side view of a skiving tool according to the present invention;

Figure 22 is a top view of the skiving tool of Figure 21;

Figure 23 is a front end view of the skiving tool of Figure 21; Figure 24 is a partially cut-away side view of a cable clamp according to the present invention for the cable according to Figure 1;

Figures 25-30 are detailed views of the components of the cable clamp of Figure 24; Figure 31 is a side view of the cable of Figure 1 showing the cable clamp of Figure 24 partially assembled with; and

Figure 32 is a side partially cut-away view of the cable clamp affixed to a cable showing an electrical connector attached to the cable clamp.

With reference first to Figure 1, an electrical cable to which the invention is directed, is shown generally at 2. The electrical cable 2 has a front face 4 and a center conductor 6 that is coaxially surrounded by foam insulation 10 extruded upon the center conductor 6 during manufacture. The illustrated center line representing a longitudinal axis of the conductor 6. The foam insulation 10 is overlaid with a conductive continuously formed outer conductor 12 having a helical pitch 14 formed thereupon. The aforegoing structure is then enclosed within a protective outer jacket 18. When properly terminated the cable 2 has a length of center conductor 6 exposed between the front face 4 and a shoulder 8 of the foam insulation

10. The foam insulation 10 is exposed over a length between the shoulder 8 and a face 11 where the helical form of the outer conductor 12 is terminated. The outer conductor 12 extends over a length between the face 11 and a shoulder 16 of the protective jacket 18.

With reference now to Figures 2-4, in order to assure that the cable 2 is terminated in the form described above and shown in Figure 1, a trim tool is shown for performing a sectioning function at each of the shoulders (4,8,11,16) generally at 20. The trim tool 20 includes a body 22 upon which a cutter carrier 24 is rotatably mounted by way of split bearing 26. The cutter carrier 24 can rotate relative to the body 22 in the directions indicated by arrow A (Figure 4) . A cover plate 27 is positioned upon the cutter carrier 24 and a rotatable handle 28 extends therefrom. The rotatable handle 28 may move in the direction of arrow B. The rotatable handle 28 is coupled to a helical gear 30 (Figure 3) such that rotation of the handle 28 induces rotation of the gear 30. A knife carrier 32 has a cutter 34 affixed thereto. The knife carrier 32 is responsive to rotation of the helical gear 30 so that linear movement in the directions of arrow C occurs. The body 22 includes a track 36 wherein the cable 2 is disposed. In order to accommodate different diameter cable, various clamping half-bushings 38a,38b would be selectively insertable into the body 22. In order to clamp the cable 2 in position so that it does not move relative the body 22, at least one fixing screw 40 (Figure 4) is provided that will bias the split-bushings 38a,38b together and engage the cable 2 when inserted therein.

With reference now to Figures 5-7, the body 22 will be described in greater detail. The body 22 is generally block-shaped and includes a forward bearing seat 42 of cylindrical shape that has a lip 44 forward therefrom. The body 22 further includes an interior 46 having a forward guiding region 48 and a rearward fixing section 50 wherein the clamping bushings 38a,38b are received. Notches 52 are included to enable locating of the clamping

bushings 38a,38b and removal thereof.

With respect to Figures 8-10, the clamping bushings 38a,38b are shown. Each bushing portion 38a,38b is symmetrical and could be manufactured as a single component then separated into two by creation of a slit 54. Each of these bushings 38a,38b includes a nose portion 56 receivable in the guiding portion 48 of the body 22 and a clamping portion 58 receivable in the fixing portion 50 of the body. A rear shoulder 60 is configured that will correspond to the notches 52. A center bore 62 is defined by the pair of split-bushings 38a,38b that corresponds to the track 36 such that the cable 2 may be reliably affixed within the trimming tool 20.

With reference now to Figures 11 and 12, the split bearing 26 is provided for affixing the cutter carrier 24 to the body 22. The bearing 26 is made in two parts 26a,26b that are symmetrical about a slice 64, as described above for the clamping bushings 38a, 38b. Each portion 26a,26b includes a counter bore 66 and a bearing bore 68. The counter bore 66 receives the lip 44 and the bearing bore 68 rides upon the bearing seat 42. As these portions 26b,26b are split into two so that the split bearing 26 can be fitted about the bearing seat 42 of the body 22. Mounting holes 70 are disposed upon a front face 72 of each of the portions 26a,26b for affixing the cutter carrier 24 thereto. Once the split bearing 26 is affixed to the cutter carrier 24 by mounting holes 70 in a fixed manner, the split bearing 26 is locked to the body 22 by lip 42. With reference now to Figures 13 and 14, the cutter carrier is shown generally at 24. The cutter carrier 24 is a plate-like member including a main bore 74 that will correspond to the guide portion 48 of the body 22. The cutter carrier 24 includes mounting holes 76 that correspond to the mounting holes 70 such that the cutter carrier 24 may be affixed to the split bearing 26, thereby maintaining the bearing portions 26a,26b about the bearing seat 42 of the body 22. The cutter carrier 24 further

includeε a cutter track 76 in communication with the bore 74 and in further communication with a dog-bone shaped opening 78. The dog-bone shaped opening 78 is in communication with a gear seat 80 having a handle anchoring hole 82 therein. The groove 74 is configured so that the knife carrier 32 is will be slidably disposed therein so that the knife 34 may extend downward into the bore 74 sufficiently to terminate the cable 2 as shown in Figure 1. The dog-bone shaped opening 78 provides clearance for location of the helical gear 30 such that a corresponding helical gear 84 disposed at the end of handle 28 may cooperate therewith in response to rotation of the handle 28.

With reference now to Figures 15-17, the cover plate 27 is provided that is mountable to the cutter carrier 24 in a manner that overlies the cutter track 76, dog-bone shaped opening 74 and the gear seat 80, such that the helical gears 30 and 84, the knife carrier 32 and the cutter 34 are captivated therein. The cover 26 further includes a bore 86 through which the handle 28 extends. With reference now to Figure 18 and Figure 19, the gear train will be described. The handle 28 is shown with helical gear 84 affixed thereto. The helical gear 84 meshes and cooperates with the gear assembly 30. The gear assembly 30 includes a gear member 88 having a bushing 90 therein. The bushing 90 assures that the knife carrier 32 travels in a linear directions corresponding to arrow C (Figure 3) within cutter track 76. The bushing 90 includes a bore 92 wherein the knife carrier 32 would be disposed. With reference once again to Figures 2-4, the device operates by inserting an untrimmed cable into the trim tool 20 and affixing such cable in place by way of the split camping bushings 38a,38b as a result of tightening the fixing screws 40. The cutter 34 may be advanced or retracted by rotating the handle 28 in the direction of arrow B. As is obvious, simple rotation of the handle 28 would not result in the production of a sectioning radial cut around the circumference of the cable. In order to

achieve a sectioning cut around the circumference of the cable to establish the shoulders (4,8,11,16) of Figure 1, it is necessary to further rotate the cutter carrier 24 in the direction of arrow A. However, this would be difficult to accomplish by bringing the cutter 34 to its finished depth then rotating the cutter carrier 24, as the depth of the cut may be sufficient to cause problems. Therefore, it is desirable to combine the rotation of the handle 28 with the rotation of the cutter carrier 24 in order to produce a scroll-like advancement of the cutter 34 across the face. This is accomplished by holding the block 22 stationary and rotating the handle 28 in the direction of arrow A which further induces rotation of the handle 28 in the direction of arrow B. In order to establish all of the faces (4,8,11,16) of the terminated cable 2, a positioning tool is shown generally as a setting plate at 94 in Figure 20. The cable 2 is initially faced off to establish face 4 by setting the cable end against surface 96a when locating surfaces 98a abut a face 100 of the cutter carrier 24 (Figure 2) . The cable is then clamped in place and the handle 28/cutter carrier 24, combination is rotated (through 24 turns for this particular cable) to bring the cutter 34 fully across the face 4 of the cable 2. In order to establish face 8 at the intersection between the center conductor 6 and the foam insulation 10, the setting plate 94 is positioned against the trim tool 20 with locating surfaces 98b corresponding to the face 100 and the cable advanced to contact positioning surface 96b. The handle 28/cutter carrier 24 combination is then rotated through 20 turns such that the cutter 24 is brought down to close contact with the center conductor 6. This procedure is further followed with respect to each of the additional shoulders 11,16 utilizing the corresponding surfaces 96c,98c; 96d,98b. Note; the setting plate 94 could be made cable specific and include markings 99 designating the number of turns for the particular sectioning cut. It may also be desirable to rotate the

cutter carrier independent of the handle at the bottom of the stroke so that a complete revolution at a common radius is established. Once the sectioning cuts for each of the shoulders 4,8,11,16 have been formed, the corresponding sections may be removed to expose the helical form on the outer conductor 12 between faces 11 and 16 and the foam insulation 10 between faces 4 and 11. This exposed section of foam insulation 10 includes a sectioning cut defining shoulder 8 and the material between the face 4 and shoulder 8 may be roughly removed, for example, with a utility knife or other cutting device. Once the foam insulation 10 has been roughly removed between shoulders 4 and 8 from the center conductor 6, any remaining portion of insulation may be removed by emery cloth or through use of a new skiving tool shown generally at 100 in Figures 21-23.

With reference now to Figures 21-23, a skiving tool 100 is shown for removing that portion of the foam insulation 10 that might remain along the length of the center conductor 6 between the front face 4 and the face 8 after rough removal. The skiving tool 100 includes a base 102 having a seat 104 for receiving the center conductor therein. Seat 104 being configured such that the center conductor 6 may lay in the V-shaped groove and enable relative rotation. The base 102 further includes a pivot point 106 that is pivotally coupled to a skiving arm 108. The skiving arm 108 carries a skiving head 110 having a skiving edge 112 that is disposed over the seat 104 in an aligned manner such that the skiving edge 112 would remove the foam insulation 10 as the cable 2 is rotated. A biasing member 114 is provided on the opposite side of the pivot 106 from the skiving edge 112 in order to bias the skiving edge 112 downward toward the seat 104. As a result of rotation of the cable 2 or tool 100, skiving edge 112 removes all of the remaining foam insulation 10 that adhered to the center conductor 6. By properly positioning the skiving edge 112 relative to the center conductor 6 within the seat 104 , it is possible

that the skiving head 112 would further burnish the outer surface of the center conductor 6 assuring a good surface is provided for electrical engagement therewith, especially for soldering. In order to utilize the terminated cable 2 described above, it is necessary that a cable clamp be provided for anchoring the cable 2 to an electrical connector or electrical device. With reference to Figure 24, a particularly advantageous cable clamp is shown generally at 200. The cable clamp 200 includes a cable nut 202 that is fixable upon the helical form of the outer conductor

12, an outer body 204 that overlies the cable nut 202, and an extension 206 extending rearwardly along the cable 2.

With reference now to Figure 25 and Figure 26, the cable nut 202 will be described in greater detail. The cable nut 202 includes a center bore 204 that extends between a front face 205 and a rear face 208. The center bore 204 includes a helical profile 210 having a pitch 212 which could advantageously correspond to the pitch 14 of the helical form of the outer conductor 12. A plurality of flats 214 are formed along an outer surface 216 of the cable nut 202. These flats 214 are for advancing the cable nut 202 along the helical form of the outer conductor 12 by use of such device as a wrench. In addition, the front face 205 includes a plurality of slotted segments 218 that are provided for engagement of the outer conductor 12 as will be described below.

With reference now to Figure 27 and Figure 28, the body 204 will be described in detail. The body 204 includes an internal bore 220 that includes a shoulder 222. Disposed along the interior bore 220 is a threaded portion 224. The interior 220 is sufficiently configured to receive the cable nut 202 therein. The cable nut 202 is received therein with its front face 206 corresponding to the shoulder 222. The interior bore 220 is in communication with a guide bore 226 that extends outward through a interface nose 228 that is configured for attaching the cable clamp 202 to a mating component such

as a connector. The interface nose 228 in this example is a threaded portion to be screwed into the mated component. As can be imagined, other configurations may be used. A plurality of flats 230 are disposed along an outer surface 232 of the body 204. These flats 230 are also for tightening the components of the cable clamp 200 as will be described below.

With respect now to Figures 29 and 30, the extension 206 will be described in greater detail. The extension 206 includes a through bore 234 through which the cable 2 extends. The through bore 232 is configured to receive the portion of the cable 2 therein having the jacket 18 thereover. An irregular section 236 is provided for reliably engaging the jacket. In addition, disposed at a rear end 238 is a tapered flange 240 rearward of a carrying surface 242 which could act to carry a heat shrinkable tube for sealing the cable clamp 200 upon the cable 2 or to carry a strain relief member that may also prevent excessive bending of the cable 2 as it exits the cable clamp 200. The heat shrinkable tubing or strain relief member could be attached in the normal fashion as is known in the art such as through heat and/or cable clamps. In addition, flats 244 are also disposed on the outer surface 246 of the extension 206. These flats 244 are also for tightening the extension 206. A threaded portion 248 is disposed toward a forward end 250. This threaded portion 248 corresponds to the threaded portion 224 along the interior of the body 204.

The cable clamp 200 is attached to the terminated cable 2 by first fitting the extension 206 over a cable 2 terminated according to that shown in Figure 1. If a strain relief or heat shrinkable tube were to be used, this component would have been already inserted over the cable 2. With reference now to Figure 31, the cable nut 202 is then threadably received upon the helical form of the outer conductor 12 such that the rear face 208 abuts the face of the jacket 16. In this position, a portion 252 of the formed outer conductor 12 extends beyond the

front face 205 of the cable nut 202. Furthermore, the center conductor 6 and insulation 10 extend outward therefrom. As can be seen with reference to Figure 32 and Figure 24, the body 204 and the extension 206 are then brought about the cable nut 202 and threadably attached along threaded portions 224,248. As the two components 204,206 are tightened together, the portion 252 of the formed outer conductor 12 that extends beyond the front face 205 of the clamp nut 202 is compressed between the front face 205 and the shoulder 222. The portion 252 is deformed thereagainst and into the slots 218, thereby reliably anchoring the outer conductor 12 in a manner that prevents rotation of the outer conductor 12 relative to the cable clamp assembly 200. In addition, in order to assure that the tightening of the body 204 with the extension 206 does not result in deformation of the cable 2, it may be desirable to have a rear portion 254 (Figure 26) of the cable nut 202 be received within a forward portion 256 of the extension 200, thereby locating the cable nut 202 approximately concentrically relative the extension 206. In addition, it may be desirable that the clamp nut 202 include a rear facing shoulder 258 which would abut the front face 250 of the extension 206 during tightening such that the compressive forces exerted on the clamp nut are not transferred into the cable 2, thereby preventing deformation of the cable 2 or outer conductor 12.

As can be further seen with reference to Figure 32, the cable 2 is then disposed within the cable clamp 200 with the foam insulation 10 extending along the guide bore 226 of the body 204. The center conductor 6 extends outward from the interface nose 228. In order to make use of the cable 2, the cable clamp 200 is then threadably mated with an electrical connector 260. In this example, the electrical connector 260 is disposed at 90° to the cable 2 and cable clamp 200 is a known "N-Type" electrical connector. It is important to note that other components may take the place of the connector 260 shown in Figure

33, as defined by the particular application for which the cable 2 is to be used.

Advantageously then, a method for trimming a cable having a formed outer conductor is provided. In addition, a trim tool 20 and a skiving tool 100 are provided for assuring accurate and simple trimming of the cable 2. Finally, a cable clamp 200 is described for attaching the trimmed cable 2 to a mating component 260 whereby the trimmed cable 2 is reliably anchored in the cable clamp 200. It is an advantage of the aforedescribed that the sequences are easy to carry out even in the field by a cable installer.