Quad-Shield Cable

Abstract

A cable includes a conductor, an insulator surrounding the center conductor, and a shield surrounding the insulator, wherein the shield has two foil layers and two braid layers. Each foil layer includes two foil surfaces, each braid layer includes two braid surfaces, and only one of the foil surfaces of the two foil layers confronts only one of the braid surfaces of the two braid layers.

Claims

1. A cable comprising: two foil layers and two braid layers, wherein: each foil layer includes two foil surfaces and each braid layer includes two braid surfaces; and only one of the foil surfaces contacts only one of the braid layers.

2. The cable of claim 1, wherein: the two foil layers are in confrontation with each other; and the two braid layers are in confrontation with each other.

3. The cable of claim 1, wherein the two braid layers surround the two foil layers.

4. The cable of claim 1, wherein: the two foil layers comprise an inner foil layer and an outer foil layer surrounding the inner foil layer; and the two braid layers comprise an inner braid layer surrounding the outer foil layer and an outer braid layer surrounding the inner braid layer.

5. The cable of claim 1, wherein the two foil layers have longitudinal seams which are diametrically offset from each other.

6. The cable of claim 1, further comprising: a conductor; an insulator surrounding the conductor; and a first of the two foil layers surrounding the insulator and a second of the two foil layers surrounding the first of the two foil layers.

7. The cable of claim 6, wherein: a first of the two braid layers surrounds the second of the two foil layers; and a second of the two braid layers surrounds the first of the two braid layers.

8. A cable comprising: a conductor; an insulator surrounding the center conductor; and a shield surrounding the insulator, the shield comprising two foil layers and two braid layers, wherein each foil layer includes two foil surfaces, each braid layer includes two braid surfaces, and only one of the foil surfaces of the two foil layers confronts only one of the braid surfaces of the two braid layers.

9. The cable of claim 8, wherein: the two foil layers are in confrontation with each other; and the two braid layers are in confrontation with each other.

10. The cable of claim 8, wherein the two braid layers surround the two foil layers.

11. The cable of claim 8, wherein: the two foil layers comprise an inner foil layer and an outer foil layer surrounding the inner foil layer; and the two braid layers comprise an inner braid layer and an outer braid layer surrounding the inner braid layer.

12. The cable of claim 8, wherein the two foil layers have longitudinal seams which are circumferentially offset from each other.

13. The cable of claim 12, wherein the longitudinal seams are diametrically offset from each other.

14. A cable comprising: two foil layers and two braid layers; wherein each of the foil layers has an inner foil surface and an opposed outer foil surface; each of the braid layers has an inner braid surface and an opposed outer braid surface; and only a one of the outer foil surfaces of the foil layers is in contact with only a one of the inner braid surfaces of the braid layers.

15. The cable of claim 14, wherein: the two foil layers are in confrontation with each other; and the two braid layers are in confrontation with each other.

16. The cable of claim 14, wherein the two braid layers surround the two foil layers.

17. The cable of claim 14, wherein: the two foil layers comprise an inner foil layer and an outer foil layer surrounding the inner foil layer; and the two braid layers comprise an inner braid layer surrounding the outer foil layer and an outer braid layer surrounding the inner braid layer.

18. The cable of claim 14, wherein the two foil layers have longitudinal seams which are diametrically offset from each other.

19. The cable of claim 14, further comprising: a conductor; an insulator surrounding the conductor; and a first of the two foil layers surrounding the insulator and a second of the two foil layers surrounding the first of the two foil layers.

20. The cable of claim 19, wherein: a first of the two braid layers surrounds the second of the two foil layers; and a second of the two braid layers surrounds the first of the two braid layers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Referring to the drawings:

[0020] FIG. 1 is a side perspective view of a prior art quad-shield coaxial cable;

[0021] FIG. 2 is a side perspective view of an inventive quad-shield cable; and

[0022] FIG. 3 is a schematic illustration of a portion of a process for manufacturing the cable of FIG. 2.

DETAILED DESCRIPTION

[0023] Reference now is made to the drawings, in which the same reference characters are used throughout the different figures to designate the same elements. Briefly, the embodiments presented herein are preferred exemplary embodiments and are not intended to limit the scope, applicability, or configuration of all possible embodiments, but rather to provide an enabling description for all possible embodiments within the scope and spirit of the specification. Description of these preferred embodiments is generally made with the use of verbs such as “is” and “are” rather than “may,” “could,” “includes,” “comprises,” and the like, because the description is made with reference to the drawings presented. One having ordinary skill in the art will understand that changes may be made in the structure, arrangement, number, and function of elements and features without departing from the scope and spirit of the specification. Further, the description may omit certain information which is readily known to one having ordinary skill in the art to prevent crowding the description with detail which is not necessary for enablement. The diction used herein is meant to be readable and informational rather than to delineate and limit the specification; therefore, the scope and spirit of the specification should not be limited by the following description and its language choices.

[0024] FIG. 2 is a side perspective view of an inventive quad-shield cable 20 (hereinafter “QS cable 20” or just “cable 20”). The QS cable 20 includes a center conductor 21 and an insulator 22 encircling and surrounding the center conductor 21. A shield 23 encircles and surrounds the insulator 22. An outer protective jacket 24 encircles and surrounds the shield 23, thereby enclosing or encapsulating the QS cable 20. The cable 20 has a longitudinal axis A extending along the entire length of the cable 20 and about which the cable 20 is rotationally symmetric.

[0025] The center conductor 21 is preferably a single solid wire, constructed from copper-clad steel. In other embodiments, however, the center conductor 21 is multiple wires, such as stranded wire, or may be constructed from other suitably conductive materials, such as copper, aluminum, copper-plated steel, or copper-plated aluminum.

[0026] The insulator 22, a dielectric insulator, is cylindrical and circumferentially encircles and surrounds the center conductor 21. The insulator 22 may have any suitable diameter, generally between about approximately 0.040 inches (approximately 1.016 millimeters) and approximately 0.600 inches (approximately 15.24 millimeters), but not necessarily so limited. The insulator 22 is solid and cylindrical, preferably formed foam polyethylene, polypropylene, or fluorinated ethylene propylene.

[0027] The shield 23 is a conductive portion of the cable 20 surrounding the insulator 22. The shield 23 is a four-layer shield: it has two foil layers and two braid layers. The shield 23 includes an inner or first foil layer 25 and an outer or second foil layer 26 encircling and surrounding the inner foil layer 25, in confrontation and direct contact with the inner foil layer 25.

[0028] The inner foil layer 25 has an inner surface 30 and an outer surface 31. When the inner foil layer 25 is formed, the inner and outer surfaces 30 and 31 are each planar, generally flat and smooth, have no projections or indentations into or out of the plane in which they lie, and are free of discontinuities. When the foil layer 25 is formed into the cylindrical roll shown in FIG. 2, it maintains this freedom from discontinuities. The foil layer 25 is thin, preferably less than approximately 0.005 inches (approximately 0.127 millimeters) in thickness, and the inner and outer surfaces 30 and 31 are parallel to each other locally.

[0029] As can be seen in FIG. 2, the inner foil layer 25 has a longitudinal seam 32 extending parallel to the axis A of the cable 20. In FIG. 2, the seam 32 is on the far side of the cable 20 and is hidden from view; for this reason it is shown in broken line. The seam 32 is formed by two opposed longitudinal edges 33 and 34 of the foil layer 25. In some embodiments, the edges 33 and 34 overlap to form the seam 32. In other embodiments, the edges 33 and 34 meet and abut each other to form the seam 32. In other embodiments, the edges 33 and 34 form an edge-shorting fold: they fold over each other to form the seam 32. In the embodiment shown in FIG. 2, the edges 33 and 34 abut, such that each edge 33 and 34 can be seen in this view. However, their arrangement is not so limited, and description of this arrangement should not be construed to so limit them.

[0030] The outer foil layer 26 is just outside the inner foil layer 25. The outer foil layer 26 has an inner surface 40 and an outer surface 41. When the outer foil layer 26 is formed, the inner and outer surfaces 40 and 41 are each planar, generally flat and smooth, have no projections or indentations into or out of the plane in which they lie, and are free of discontinuities. When the outer foil layer 26 is formed into the cylindrical roll shown in FIG. 2, it maintains this freedom from discontinuities. The foil layer 26 is thin, preferably less than approximately 0.005 inches (approximately 0.127 millimeters) in thickness, and the inner and outer surfaces 30 and 31 are parallel to each other locally.

[0031] As can be seen in FIG. 2, the outer foil layer 26 has a longitudinal seam 42 extending parallel to the axis A of the cable 20. The seam 42 is formed by two opposed longitudinal edges 43 and 44 of the foil layer 26. In some embodiments, the edges 43 and 44 overlap to form the seam 42. In other embodiments, the edges 43 and 44 meet and abut each other to form the seam 42. In other embodiments, the edges 43 and 44 form an edge-shorting fold: they fold over each other to form the seam 42. In the embodiment shown in FIG. 2, the edges 43 and 44 abut, such that each edge 43 and 44 can be seen in this view. However, their arrangement is not so limited, and description of this arrangement should not be construed to so limit them.

[0032] The seams 32 and 42 are diametrically offset and opposed from each other; one seam 32 extends along one side of the cable 20 and the other seam 42 extends along the other, opposite side of the cable 20. The seams 32 and 42 are parallel to each other, each parallel to the longitudinal axis A. This is a preferred, but not requisite, arrangement and orientation of the seams 32 and 42. In other embodiments, the seams 32 and 42 are otherwise circumferentially offset from each other, such that they are not registered on top of each other. In yet other embodiments, the seams 32 and 42 may be registered atop or nearly atop each other. The arrangement and orientation of the seams 32 and 42 with respect to each other is a characteristic of the cable 20 which the manufacturer can control during construction of the QS cable 20 by altering the orientation of the folding tool which applies the inner and outer foil layers 25 and 26 to the insulator 22.

[0033] As shown in FIG. 2, the inner foil layer 25 is applied directly to the insulator 22, in confrontation therewith. The insulator 22 has an outer surface 50, and the inner surface 30 of the inner foil layer 25 directly and continuously contacts this outer surface 50 along the entire length and circumference of the insulator 22. In some embodiments, an adhesive applied between the inner surface 30 of the inner foil layer 25 and the outer surface 50 of the insulator 22 adheres the inner foil layer 25 to the insulator 22. Adhering the inner foil layer 25 to the insulator 22 can assist in making later installation of a connector on the cable 20 easier, because it prevents the foil layers 25 and 26 from lifting up and interrupting or blocking application of the connector onto the cable. In other embodiments, the inner foil layer 25 tightly encircles and conforms to the insulator 22 without adhesive.

[0034] The inner foil layer 25 is disposed between the insulator 22 and the outer foil layer 26. The inner foil layer 25 contacts no part of the cable 20 other than the insulator 22 and the outer foil layer 26.

[0035] The outer foil layer 26 directly overlies the inner foil layer 25. The outer foil layer 26 overlies, encircles, and surrounds the inner foil layer 25 along the entire length and circumference of the inner foil layer 25. The inner surface 40 of the outer foil layer 26 directly and continuously contacts the outer surface 31 of the inner foil layer 25.

[0036] These foil layers 25 and 26 are both formed from large sheets. The material of these sheets is preferably either flexible foil tape or laminate. The sheets are laid out as flat sheets, cut into narrow flat strips, and then rolled or folded into the cylindrical shape they have on the cable 20. When formed to the cylindrical shape of the cable 20, the foil layers 25 and 26 must include seams 32 and 42, and these seams 32 and 42 assume an orientation depending on the method of application of the foil layers 25 and 26 to the insulator 22. As noted above, a preferred manufacturing technique orients the seams 32 and 42 parallel to each other and to the axis A, but circumferentially offset from each other. It has been unexpectedly found that a circumferential offset of the seams 32 and 42, and a diametrically opposite offset especially, assists in the improvement of the shield effectiveness of the cable 20.

[0037] In addition to the foil layers 25 and 25, the shield 23 also includes two braid layers: an inner or first braid layer 55 and an outer or second braid layer 56. The braid layers 55 and 56 confront and directly contact each other. The inner braid layer 55 encircles and surrounds the outer foil layer 26, and the outer braid layer 56 encircles and surrounds the inner braid layer 55. These braid layers 55 and 56 include a conductive RF shield or electromagnetic radiation shield. In embodiments, the braid layers 55 and 56 include a conductive screen, mesh, or braid. In other embodiments, they have a perforated configuration defining a matrix, grid, or array of openings. As shown in FIG. 2, the braid layers 55 and 56 preferably, but not necessarily, are woven as a mesh. The braid layers 55 and 56 each use any suitable weave pattern. The braid layers 55 and 56 are preferably, but not necessarily, constructed from aluminum, copper, or a suitable combination of aluminum and copper.

[0038] The inner braid layer 55 has an inner surface 60 and an outer surface 61. The interwoven nature of the individual elements of the braid layer 55 characterize the inner and outer surfaces 60 and 61.

[0039] Similarly, the outer braid layer 56 has an inner surface 70 and an outer surface 71. The interwoven nature of the individual elements of the braid layer 56 characterize the inner and outer surfaces 70 and 71. Each of the inner and outer braid layers 55 and 56 is rotationally symmetric about the longitudinal axis A.

[0040] As shown in FIG. 2, the inner braid layer 55 is applied directly to the outer foil layer 26, in confrontation therewith. The inner surface 60 of the inner braid layer 55 directly and continuously contacts the outer surface 41 of the outer foil layer 26 along the entire length and circumference of the outer foil layer 26. This is the sole location at which either of the braid layers 55 and 56 contact either of the foil layers 25 and 26.

[0041] The outer braid layer 56 directly overlies the inner braid layer 55. The outer braid layer 56 overlies, encircles, and surrounds the inner braid layer 55 along the entire length and circumference of the inner braid layer 55. The outer braid layer 56 is disposed between the inner braid layer 55 and the jacket 24. The outer braid layer 56 contacts no part of the cable 20 other than the inner braid layer 55 and the jacket 24. The inner surface 70 of the outer braid layer 56 directly and continuously contacts the outer surface 61 of the inner braid layer 55.

[0042] The jacket 24 encircles and surrounds the outer braid layer 56, thereby encapsulating and protecting the cable 10. The jacket 24 is flexible, constructed from a material having flexible and sunlight-resistant characteristics such as polyvinyl chloride (“PVC”), rubber, or the like. The jacket 24 has an insulative characteristic which protects both the performance of the cable 20 and the health and safety of anyone handling the cable 20. The jacket 24 further guards the internal components of the cable 20 from damage from impact or the environment.

[0043] It has been unexpectedly discovered that the QS cable 20 maintains shielding effectiveness despite normal wear and tear. Conventional quad-shield cable is known to suffer rapid shielding effectiveness decay after the typical cyclical flexing stresses of aerial, in-home, or head-end installations. However, the QS cable 20 disclosed herein does not experience such degradation, demonstrating an unexpectedly improved shielding effectiveness over conventional quad-shield cables. The improved shielding effectiveness may be assisted by placing the two foil layers 25 and 26 against each other. The improved shielding effectiveness may also be assisted by placing the two braid layers 65 and 66 against each other. The improved shielding effectiveness may also be assisted by placing the two foil layers 25 and 26 against the insulator 22. The improved shielding effectiveness may also be assisted by encircling the two foil layers 25 and 26 with the two braid layers 65 and 66. The improved shielding effectiveness may also be assisted by encircling the two braid layers 65 and 66 with the jacket 24. The improved shielding effectiveness may also be assisted by placing only one of the two foil layers 25 and 26 against only one of the two braid layers 55 and 56. In the arrangement disclosed herein, only one of the foil layers—the outer foil layer 26—contacts only one of the braid layers—the inner braid layer 55. Moreover, only one of the foil surfaces—the outer surface 41 of the outer foil layer 26—contacts only one of the braid surfaces—the inner surface 60 of the inner braid layer 55.

[0044] FIG. 3 shows a schematic representation of a portion of a process for manufacturing the cable 20. The process moves through two machines from right to left to construct the cable 20, and reference characters are used in this description but not shown in the drawings to indicate correspondence to the cable 20 shown in FIG. 2. A center conductor 21, already encircled by an insulator 22, leaves a plant 80 and enters a first processing machine. A first folding tool 81 applies the inner foil layer 25 to the insulator 22. As shown in FIG. 3, the folding tool 81 has a first, upright orientation. The folding tool 81 places the flat inner foil layer 25 against the insulator 22 and then folds it around the insulator 22. This applies the inner layer 25 with the seam 32 in a first position.

[0045] Next, in a second processing machine, a second folding tool 82 applies the outer foil layer 26. The second folding tool 82 is identical to the first folding tool 81 but has a second orientation which is inverted or rotated one hundred eighty degrees with respect to the first orientation of the first folding tool 81. The second folding 82 places the flat outer foil layer 26 against the inner foil layer 25 on the insulator 22 and then folds it around the inner foil layer 25. This applies the outer layer 26 with the seam 42 in a second position, opposite the seam 32. In other words, when the second folding tool 82 folds the outer foil layer 26 around the inner foil layer 25, the seam 42 of the outer foil layer 26 is diametrically opposed to the seam 32 in the inner foil layer 25.

[0046] The seam 42 is opposed to the 32 because the folding tools 81 and 82 are inverted with respect to each other. However, the first and second folding tools 81 and 82 can be arranged differently, so as to alter the radial orientation of the two foil layers 25 and 26 at any relative angle.

[0047] Once the outer foil layer 26 is applied, the inner and outer braids 55 and 56 are formed over the outer foil layer 26. Two braiding tools 83 and 84 are downstream from the second folding tool 82. The first braiding tool 83 applies the inner braid layer 55 directly over the outer foil layer 26, and the second braiding tool 84 applies the outer braid layer 56 directly over the inner braid layer 55.

[0048] With this construction method, the QS cable 20 has only one surface of a foil layer in contact with a braid layer and no more. The outer surface 41 of the outer foil layer 26 is in contact with the inner surface 60 of the inner braid layer 55. The other surfaces of the foil layers 25 and 26 do not contact the braid layers 55 and 56, and the other surfaces of the braid layers 55 and 56 do not contact the foil layers 25 and 26. As such, abrasive action is minimized, and the QS cable 20 can withstand more flexion than a conventional quad-shield cable without a corresponding degradation of RF shielding performance.

[0049] The QS cable 20 also offers superior connectivity for a male F-type connector. A conventional cable stripping tool is still used to prepare the end of the QS cable 20. The stripping tool has a first blade which cuts through the QS cable 20 as shown in FIG. 2, nearly to the center conductor 21, and a second blade which cuts only through the jacket 24. Forward of the first cut, all the cable layers are removed, thereby exposing the center conductor 21. Forward of the second cut, only a short section of the jacket 24 is removed exposing the shield 23. The QS cable 20 is then further prepared by folding the outer braid 56 back over the jacket 24. Next, the inner braid 55 is folded back over the outer braid 56 and the jacket 24. Alternatively, the inner and outer braids 55 and 56 are folded back together.

[0050] These operations allow the QS cable 20 to be inserted into the F-type connector. Neither the inner foil layer 25 nor the outer foil layer 26 are removed; both are left intact and in place. This allows a technician to prepare the cable 20 much faster than a conventional cable. Moreover, the two foil layers 25 and 26 provide RF shielding performance along their entire lengths, including within the male connector; leaving them intact provides RF shielding entirely to the mating surface of the female F port.

[0051] A preferred embodiment is fully and clearly described above so as to enable one having skill in the art to understand, make, and use the same. Those skilled in the art will recognize that modifications may be made to the description above without departing from the spirit of the specification, and that some embodiments include only those elements and features described, or a subset thereof. To the extent that modifications do not depart from the spirit of the specification, they are intended to be included within the scope thereof.