HIGH STRENGTH COMMUNICATIONS CABLE SEPARATOR

A cable includes a first insulated conductor, a first dielectric tape and a second insulated conductor. The first insulated conductor is twisted with the second insulated conductor with the first dielectric tape residing between the first insulated conductor and the second insulated conductor to form a first twisted pair. The first dielectric tape has at least one strength member embedded therein. A separator may of the cable may also have at least one strength member embedded therein, and serve to separate twisted pairs from each other within the cable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a twisted pair cable for communication of high speed signals, such as a local area network (LAN) cable. More particularly, the present invention relates to a twisted pair cable having a high strength dielectric tape, which may be located between first and second insulated conductors of a twisted pair and/or to a high strength separator, which may separate at least a first twisted pair from at least a second twisted pair.

2. Description of the Related Art

As shown inFIGS. 1 and 2, the Assignee's prior U.S. Pat. No. 6,506,976 shows a LAN cable1having a jacket J surrounding first through fourth twisted pairs A, B, C, D which are spaced from each other by a separator3. Each of the twisted pairs A, B, C, D includes a first insulated conductor5, a dielectric tape7, and a second insulated conductor9, wherein the first insulated conductor5is twisted with the second insulated conductor9with the dielectric tape7residing between the first insulated conductor5and the second insulated conductor9.

As best seen in the close-up cross sectional view of the twisted pair A inFIG. 2, the width of the dielectric tape7, which extends between opposing edges11and13, is set to extend beyond the first and second insulated conductors5and9. By this arrangement, the opposing edges11and13of the dielectric tape7circumscribe an area15, around the twisted pairs A, B, C, D. The area15creates a spacing between the twisted pairs A, B, C, D and the separator3and between the twisted pairs A, B, C, D and the jacket J. This spacing around the twisted pairs A, B, C, D can improve the electrical performance of the cable1, such as by reducing crosstalk.

In typical cables of the background art, the first insulated conductor5would be formed by a first conductor17of about twenty-three gauge size, surrounded by a layer of a first dielectric insulating material19having a radial thickness greater than seven mils, such as about tens mils or about eleven mils for a typical CAT 6 cable. Likewise, the second insulated conductor9would be formed by a second conductor21of about twenty-three gauge size, surrounded by a layer of a second dielectric insulating material23having a same or similar radial thickness.

Related prior art can be found in the following U.S. Pat. Nos. 5,087,110; 6,222,130; 7,999,184; 8,798,419; 9,076,568 and 9,418,775, and the following U.S. Published Applications 2013/0014972; 2013/0161063; 2014/0262427 and 2015/0129277, with all of the above listed U.S. Patents and U.S. Published Applications being herein incorporated by reference.

SUMMARY OF THE INVENTION

Although the cable of the background art performs well, Applicants have appreciated some drawbacks. Applicants have invented a twisted pair cable with new structural features, the object of which is to enhance one or more performance and/or manufacturing characteristics of a LAN cable, such as reducing insertion loss, matching impedance, reducing propagation delay and/or balancing delay skew between twisted pairs, and/or enhancing one or more mechanical characteristics of a LAN cable, such as improving flexibility, reducing weight, reducing cable diameter, reducing smoke emitted in the event of a fire, improving strength attributes of the cable, enabling faster production of the cable, or enabling less costly production of the cable.

The tapes of the present invention have enhanced strength per unit volume and are particularly well suited to enable faster production of the cable, improving the strength of the cable, and allowing for a less bulky tape and smaller cable size.

The invention is for a high-strength twisted pair isolator or separator and/or a bisector tape (depending upon the cable design of interest). The need for increased strength is more precisely described as a need for increased yield strength. There is a demand for increased throughput in production facilities; this translates into increasing manufacturing speeds, which puts increased stress on all components in the twisted-pair communications cable, such as the dielectric tape between insulated conductor and/or the separator between twisted pairs. This invention has several potential embodiments, but in one embodiment a reinforcing material with a greater tensile strength than the base polymer material of the tape or separator is embedded within the base polymer.

The first two embodiments are 1) continuous fiber reinforcement in a flame-retardant polymer, and 2) discontinuous (short) fiber reinforcement in a flame-retardant polymer. The short-fiber reinforcement has advantages, since it could be produced in existing manufacturing equipment. The extrusion process would roughly align the short, discontinuous fibers in the lengthwise orientation, which would help increase the yield strength to the desired levels.

Other embodiments include 3) a paper/hybrid separator tape. This potentially could be made of paper with a fire-retardant coating applied, or a blend of paper and microfibers (PET for example) along with a fire-retardant coating, 4) carbon-fiber reinforced separators, 5) carbon nano-tube reinforced separators, and 6) higher-strength polymers (with higher melt temperatures) used as elements embedded into another polymer to form a reinforced separator or dielectric tape.

Besides the listed materials, any acicular material that could provide improved yield strength in the axial direction to the base polymer material could be substituted. Considerations other than improved tensile yield strength include the enhanced electrical impact of the separator on the cable performance, as well as improved smoke and/or burn results in a simulated fire test.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Like numbers refer to like elements throughout. In the figures, the thickness of certain lines, layers, components, elements or features may be exaggerated for clarity. Broken lines illustrate optional features or operations unless specified otherwise.

FIG. 3is a perspective view of a twisted pair cable31, in accordance with a first embodiment of the present invention.FIG. 4is a cross sectional view of the cable31taken along line IV-IV inFIG. 3. The cable31includes a jacket32formed around and surrounding first, second, third and fourth twisted pairs33,34,35and36, respectively. The jacket32may be formed of polyvinylchloride (PVC), low smoke zero halogen PVC, polyethylene (PE), fluorinated ethylene propylene (FEP), polyvinylidene fluoride (PVDF), ethylene chlorotrifluoroethylene (ECTFE), or other foamed or solid materials common to the cabling art.

A separator37within the jacket32resides between and separates the first and fourth twisted pairs33and36from the second and third twisted pairs34and35. InFIGS. 3 and 4, the separator37is formed by a thin strip of dielectric material, having a thickness of about twenty mils or less, more preferably about eighteen mils or less, or about fifteen mils or less, such as about10mils. However, other sizes and shapes of separators37may be employed in combination with the present invention, such as plus-shaped or star-shaped separators, sometimes referred to as a flute, isolator, or cross-web. The separator37may be formed of any solid or foamed material common to the cabling art, such as a polyolefin or fluoropolymer, like fluorinated ethylene propylene (FEP) or polyvinylchloride (PVC).

In accordance, with a first embodiment of the present invention, the separator37includes embedded strength members50, best seen in the cross section ofFIG. 4. The strength members50may be short segments of acicular material, such as fibers formed of fire retardant material. Suitable materials could include aramid yarns, fiber glass, carbon fibers and carbon nanotubes. The embedded strength members50allow the thickness of the separator37to be reduced while the strength, e.g., the yield strength, of the separator37is maintained or even increased, as compared to a separator formed without strength members50.

As best seen in the cross sectional view ofFIG. 4, the first twisted pair33includes a first insulated conductor38, a first dielectric tape39, and a second insulated conductor40. The first insulated conductor38is twisted with the second insulated conductor40, in a helical fashion, with the first dielectric tape39residing between the first insulated conductor38and the second insulated conductor40.

The second twisted pair34includes a third insulated conductor41, a second dielectric tape42, and a fourth insulated conductor43. The third insulated conductor41is twisted with the fourth insulated conductor43, in a helical fashion, with the second dielectric tape42residing between the third insulated conductor41and the fourth insulated conductor43.

The third twisted pair35includes a fifth insulated conductor44, a third dielectric tape45, and a sixth insulated conductor46. The fifth insulated conductor44is twisted with the sixth insulated conductor46, in a helical fashion, with the third dielectric tape45residing between the fifth insulated conductor44and the sixth insulated conductor46.

The fourth twisted pair36includes a seventh insulated conductor47, a fourth dielectric tape48, and an eighth insulated conductor49. The seventh insulated conductor47is twisted with the eighth insulated conductor49, in a helical fashion, with the fourth dielectric tape48residing between the seventh insulated conductor47and the eighth insulated conductor49.

FIG. 5is a close-up view of the first twisted pair33, which is similarly constructed although not identically constructed (as will be detailed later in the specification) to the second, third and fourth twisted pairs34,35and36. Each of the first through eighth insulated conductors38,40,41,43,44,46,47,49is formed by a conductor K surrounded by a layer of dielectric insulating material R, such as a polymer or foamed polymer, common to the cabling art like fluorinated ethylene propylene (FEP), polyethylene (PE) or polypropylene (PP). Further, the insulating material R may be formed by an enamel coating, or another nonconductive coating from a diverse art like motor armature windings. The conductor K may be solid or stranded, and may be formed of a conductive metal or alloy, such as copper. In one embodiment, the conductor K is a solid, copper wire of about twenty three gauge size.

In one embodiment, the insulating material R may have a radial thickness of about seven mils or less, more preferably about five mils or less. This radial thickness of the insulating layer R is at least 20% less than the standard insulation layer thickness of a conductor in a typical equivalent twisted pair wire, more preferably at least 25% to 30% less. Typically, such a thin insulation layer R would not be possible due to the incorrect impedance obtained when the conductors K of the first and second insulated conductors38and40become so closely spaced during the twisting operation due to the thinner insulating layers R. Typically, such thin insulation layers were not practiced in the background art, because there was no appreciation of a solution to the mechanical and performance problems. By the present invention, the interposed first dielectric tape39eases the mechanical stresses during twisting so that the thinner insulating layer R is undamaged and also spaces the conductors K apart so that a proper impedance may be obtained, e.g., one hundred ohms.

As best seen inFIG. 5, the first dielectric tape39has a first width which extends approximately perpendicular to an extension length of the first dielectric tape39from a first edge51of the first dielectric tape39to an opposing second edge53of the first dielectric tape39. The first width is less than a diameter of the first insulated conductor38plus a diameter of the second insulated conductor40plus a thickness of the first dielectric tape39, wherein the thickness is measured by the spacing created between the first and second insulated conductors38and40. A typical spacing might be between four to twelve mils, such as about eight mils or about ten mils. By this arrangement, the twists of the first twisted pair33occupy a space within the dashed line55, which is circumscribed by the helical twisting of the first and second insulated conductors38and40. In this arrangement, the first through eighth insulated conductors38,40,41,43,44,46,47and49may contact each other if adjacent and also may contact the inner wall of the jacket32.

InFIG. 5, the dielectric tape39is formed as a single unitary structure (e.g., the dielectric tape does not include multiple pieces attached together or layered).FIG. 5Aillustrates that the solid dielectric tape39ofFIG. 5may be replaced with a dielectric tape39A having a hollow core filled with a gas, like air (with a dielectric constant of 1.0) or a foamed insulation material (with a dielectric constant approaching 1.0). By filling the hollow core with a gas or material with a lower dielectric constant than a material used to form said first dielectric tape39or39A, the overall dielectric constant of the first dielectric tape39A may be reduced. The hollow core may extend the entire length of the dielectric tape39A, resulting in a “straw-like” structure. Alternatively, support structures may be formed at intervals along the length of the dielectric tape39A to form closed-cell air pockets, each having a short length, such as ½ inch, one inch, two inches, etc. Alternatively, one or more support structures may be formed within the hollow core, which extend along the length of the dielectric tape39A and connect between the lateral walls of the hollow core to resist crushing of the hollow core during the twisting of the first twisted pair33A. Although the other embodiments of the dielectric tapes of the present invention are illustrated with solid cores, hollow cores, as described in connection withFIG. 5A, may be employed in any or all of the other dielectric tapes. The first twisted pair33A depicted inFIG. 5Amay be substituted into the place of the first twisted pair33depicted inFIG. 4.

The material forming the dielectric tape39/39A is preferably embedded with randomly spaced strength members50, such as the short segments of acicular material used to form the separator37, as detailed above. In the cased of the dielectric tapes39,42,45and48and the separator37, the fibers or materials used to form the acicular material may be randomly oriented within the balls or pellets of polymer loaded into the extruder. As the pellets of are melted within the extruder the acicular materials are randomly directed relative to each other. However, as the melt is extruded through the die opening to form the dielectric tape39,42,45or48or the separator37, the acicular materials will naturally, generally align in the extrusion direction, e.g., along the length of cable.

The general alignment of the acicular materials is best seen inFIGS. 3, 20B, and 23. The general alignment improves the strength of the dielectric tape and the separator in the longitudinal direction, i.e., the direction of the length of the cable. Further, the general alignment of the acicular material in the longitudinal direction improves the flexibility of the cable, e.g., the ability to curve/bend and route the cable during installation.

As best seen inFIG. 3, the first through fourth twisted pairs33,34,35and36may be stranded together in the direction57(see the arrow inFIG. 3) to form a stranded core. In one embodiment, the core strand direction57is opposite to the pair twist directions of the first through fourth twisted pairs33,34,35and36. However, this is not a necessary feature, as the strand direction57may also be the same as the pair twist directions.

In preferred embodiments, the strand length of the core strand is about five inches or less, more preferably about three inches or less. In a more preferred embodiment, the core strand length is purposefully varied, or modulates, from an average strand length along a length of the cable31. Core strand modulation can assist in the reduction of alien crosstalk. For example, the core strand length could modulate between two inches and four inches along the length of the cable31, with an average value of three inches.

The first twist length w (SeeFIG. 3) of the first twisted pair33is preferably set to a short length, such as between approximately 0.22 inches and approximately 0.38 inches. The second twist length x of the second twisted pair34is different from the first twist length w and is between approximately 0.22 inches and approximately 0.38 inches. For example, the first twist length w may be set to approximately 0.26 inches and the second twist length x may be set to approximately 0.33 inches.

In one embodiment, the first twist length w purposefully modulates from a first average value, such as 0.26 inches. For example, the first twist length could purposefully vary between 0.24 and 0.28 inches along the length of the cable. Likewise, the second twist length could purposefully modulate from a second average value, such as 0.33 inches. For example, the second twist length could purposefully vary between 0.31 and 0.35 inches along the length of the cable.

The third twisted pair35would have a third twist length y and the fourth twisted pair36would have a fourth twist length of z. In one embodiment, the third twist length y is different from the first, second and fourth twist lengths w, x and z, while the fourth twist length z is different from the first, second and third twist lengths w, x and y. Of course, the third and fourth twisted pairs35and36could employ a similar twist length modulation, as described in conjunction with the first and second twisted pairs33and34.

FIG. 6is a close-up cross sectional view of a twisted pair60, having a dielectric tape61with an alternative shape, in accordance with a second embodiment of the present invention. The dielectric tape61has a width which extends approximately perpendicular to an extension length of the twisted pair60from a first edge62of the dielectric tape61to an opposing second edge63of the dielectric tape61. The width, in the embodiment ofFIG. 6, is equal to or less than the diameter of the first insulated conductor38. Less material is used to form the dielectric tape61in the embodiment ofFIG. 6. This presents advantages in reducing the amount of consumable material in the case of a fire, and in reducing the amount of smoke emitted from the cable31in the case of a fire. This structure may also reduce the weight and outer diameter of the cable and improve the flexibility of the cable.

As seen inFIG. 6, the dielectric tape61has a cross sectional shape in a direction perpendicular to an extension length of the twisted pair60, which presents a first recessed portion64for seating the first insulated conductor38and a second recessed portion65for seating the second insulated conductor40.

The cross sectional shapes of the dielectric tapes39and61inFIGS. 5 and 6are mirror symmetrical. However, it is not necessary that the shape be mirror symmetrical in order to achieve many of the advantages of the present invention. Further, the first and second recessed portions64and65of the dielectric tape61inFIG. 6are semi-circular in shape. However, it is not necessary that the first and second recessed portions64and65be semi-circular. In fact, the recesses in the dielectric tape39ofFIG. 5for receiving the first and second insulated conductors38and40are not semi-circular in shape. Also, the first and second recessed portions64and65may include serrations to create pockets of air adjacent to the seated portions of the first and second insulated conductors38and40.

FIG. 7is a cross sectional view of a twisted pair cable66employing the first twisted pair60ofFIG. 6. The twisted pair cable66also includes similarly configured second, third and fourth twisted pairs67,68and69. The twists of the first, second, third and fourth twisted pairs60,67,68and69occupy respective spaces within the dashed lines55(SeeFIG. 6). In this arrangement, the first through eighth insulated conductors38,40,41,43,44,46,47and49may contact each other and also may contact the inner wall of the jacket32.

The dielectric tapes61may be formed of a same or similar material in a same or similar manner, as described in connection with the dielectric tapes depicted inFIGS. 3-5A.

FIG. 8is a close-up cross sectional view of a twisted pair70, having a dielectric tape71with an alternative shape, in accordance with a third embodiment of the present invention. The dielectric tape71has a width which extends approximately perpendicular to an extension length of the twisted pair70from a first edge72of the dielectric tape71to an opposing second edge73of the dielectric tape71. The width, in the embodiment ofFIG. 8, is equal to or less than the diameter of the first insulated conductor38.

The embodiment ofFIG. 8illustrates that the dielectric tape71need not have recessed portions64and65(as shown inFIGS. 5 and 6) to seat the insulated conductors38and40. Rather, the dielectric tape71may be formed as a generally flat member. The dielectric tape71will remain between the first and second insulated conductors38and40due to the frictional forces created during the twisting operation, when the twisted pair70is formed.

The dielectric tapes71may be formed of a same or similar material in a same or similar manner, as described in connection with the dielectric tapes depicted inFIGS. 3-5A.

FIG. 8Ais a close-up cross sectional view of a twisted pair70A, having a dielectric tape71A with an alternative shape, in accordance with a fourth embodiment of the present invention. The dielectric tape71A has a width which extends approximately perpendicular to an extension length of the twisted pair70A from a first edge72A of the dielectric tape71A to an opposing second edge73A of the dielectric tape71A. The width, in the embodiment ofFIG. 8A, is equal to or slightly less than (e.g., two to four mils less than) the diameter of the first insulated conductor38plus the diameter of the second insulated conductor40plus a thickness of the dielectric tape71A.

The embodiment ofFIG. 8Aillustrates that the dielectric tape71A may be a generally flat member having a width which is approximately equal the diameter of the first insulated conductor38plus the diameter of the second insulated conductor40plus a thickness of the dielectric tape71A, such as about seventy-two mils plus or minus about three mils.

FIG. 8Bis a cross sectional view of a twisted pair cable76employing the first twisted pair70A ofFIG. 8A, in accordance with a preferred embodiment of the present invention. The twisted pair cable76also includes similarly configured second, third and fourth twisted pairs77,78and79. The twists of the first, second, third and fourth twisted pairs70A,77,78and79occupy respective spaces within the dashed lines55(SeeFIG. 8A). In this arrangement, the first through eighth insulated conductors38,40,41,43,44,46,47and49may contact a plus-shaped separator37A (sometimes referred to as an isolator, a flute or a crossweb) and also may contact inner ends of projections or fins32A on the inner wall of the jacket32.FIG. 8Bshows twelve projections32A, however more or fewer projections may be included, with the goal being to hold the core of twisted pairs70A,77,78and79in the center of the cable76while creating air pockets around the perimeter of the core of twisted pairs.

The dielectric tapes71A and the plus-shaped separator37A may be formed of a same or similar material in a same or similar manner, as described in connection with the dielectric tapes and separator37depicted inFIGS. 3-5A.

FIG. 9is a perspective view of a twisted pair cable81, in accordance with a fifth embodiment of the present invention.FIG. 10is a cross sectional view of the cable81taken along line X-X inFIG. 9. The cable81includes a jacket82formed around and surrounding first, second, third and fourth twisted pairs83,84,85and86, respectively.

The fifth embodiment of the invention, as illustrated inFIGS. 9 and 10, does not include a separator37or37A. However, pair separators (sometimes referred to as tapes, isolators, flutes or crosswebs) may optionally be included, if desired.

As best seen in the cross sectional view ofFIG. 10, the first twisted pair83includes a first insulated conductor88, a first dielectric tape89, and a second insulated conductor90. The first insulated conductor88is twisted with the second insulated conductor90, in a helical fashion, with the first dielectric tape89residing between the first insulated conductor88and the second insulated conductor90.

The second twisted pair84includes a third insulated conductor91, a second dielectric tape92, and a fourth insulated conductor93. The third insulated conductor91is twisted with the fourth insulated conductor93, in a helical fashion, with the second dielectric tape92residing between the third insulated conductor91and the fourth insulated conductor93.

The third twisted pair85includes a fifth insulated conductor94, a third dielectric tape95, and a sixth insulated conductor96. The fifth insulated conductor94is twisted with the sixth insulated conductor96, in a helical fashion, with the third dielectric tape95residing between the fifth insulated conductor94and the sixth insulated conductor96.

The fourth twisted pair86includes a seventh insulated conductor97, a fourth dielectric tape98, and an eighth insulated conductor99. The seventh insulated conductor97is twisted with the eighth insulated conductor99, in a helical fashion, with the fourth dielectric tape98residing between the seventh insulated conductor97and the eighth insulated conductor99.

FIG. 11is a close-up view of the first twisted pair83, which is similarly constructed to the second, third and fourth twisted pairs84,85and86. Like the first embodiment ofFIGS. 3-5, each of the first through eighth insulated conductors88,90,91,93,94,96,97and99is formed by a conductor K surrounded by a layer of dielectric insulating material R. Also, the insulating material R may have a radial thickness of about seven mils or less, more preferably about five mils or less.

Also, the first, second, third and fourth dielectric tapes89,92,95and98may be formed of a same or similar material in a same or similar manner, as described in connection with the dielectric tapes depicted inFIGS. 3-5A.

As best seen inFIG. 11, the first dielectric tape89has a first width which extends approximately perpendicular to an extension length of the first twisted pair83from a first edge101of the first dielectric tape89to a second edge103of the first dielectric tape89. The first width is greater than a diameter of the first insulated conductor88plus a diameter of the second insulated conductor90plus a thickness of the first dielectric tape89, wherein the thickness is measured by the spacing created between the first and second insulated conductors88and90. A typical spacing might be between four to twelve mils, such as about eight mils or about ten mils. By this arrangement, the twists of the first twisted pair83occupy a space within the dashed line105, which is circumscribed by the helical twisting of the first and second edges101and103of the first dielectric tape89. In this arrangement, the first through eighth insulated conductors88,90,91,93,94,96,97and99do not contact each other and also do not contact the inner wall of the jacket82. Rather, a small air pocket107is maintained around the outer perimeter of the dielectric insulating material R. Hence, the first insulated conductor88would be spaced from the inner wall of the jacket82by a first minimum distance, where the first minimum distance could be fixed in the range of one to twenty mils, such as two mils or four mils. Moreover, the first insulated conductor88would be spaced from any other insulated conductor of another twisted pair84,85or86of the cable81by a second minimum distance. The second minimum distance would equal twice the first minimum distance, because the small air pocket107of the first twisted pair83would be added to the small air pocket107of the other twisted pair84,85or86.

As in the first embodiment ofFIGS. 3-5, the first through fourth twisted pairs83,84,85and86may be stranded together in the direction109(see the arrow inFIG. 9) to form a stranded core. In one embodiment, the core strand direction109is opposite to the pair twist directions of the first through fourth twisted pairs83,84,85and86. However, this is not a necessary feature. The core strand length and pair twist lengths w, x, y and z may be tight, as described in conjunction withFIGS. 3-5, and may optionally be modulated.

As best seen in the cross sectional view ofFIG. 11, the first dielectric tape89includes first and second recesses111and113to seat the first and second insulated conductors88and90. The first and second recesses111and113may assist in properly positioning the three parts88,89and90of the first twisted pair83during a manufacturing process, and may also assist in keeping the three parts88,89and90of the first twisted pair83in place during use of the cable81(e.g., pulling of the cable through conduits or ductwork). However, many advantages of the invention may be achieved without the recesses111and113, as will be seen inFIG. 12.

FIG. 12is a close-up cross sectional view of a twisted pair120, having a dielectric tape121with an alternative shape, in accordance with a sixth embodiment of the present invention. The dielectric tape121has a width which extends approximately perpendicular to an extension length of the twisted pair120from a first edge122of the dielectric tape121to a second edge123of the dielectric tape121. Like the embodiment ofFIGS. 9-11, the width of the dielectric tape121is greater than the diameter of the first insulated conductor88plus the diameter of the second insulated conductor90plus a thickness of the first dielectric tape121. The dielectric tape121may be formed as a generally flat member. The dielectric tape121will remain between the first and second insulated conductors88and90due to the frictional forces created during the twisting operation, when the twisted pair120is formed.

The dielectric tape121may be formed of a same or similar material in a same or similar manner, as described in connection with the dielectric tapes depicted inFIGS. 3-5A.

FIG. 13is a close-up cross sectional view of a twisted pair130, having a dielectric tape131with an alternative shape, in accordance with a seventh embodiment of the present invention. The dielectric tape131has a width which extends approximately perpendicular to an extension length of the twisted pair130from a first edge132of the dielectric tape131to a second edge133of the dielectric tape131. The dielectric tape131has a cross sectional shape in a direction perpendicular to an extension length of the twisted pair130, which presents a first recessed portion135for seating the first insulated conductor88and a second recessed portion136for seating the second insulated conductor90.

The first edge132of the first dielectric tape131inFIG. 13will circumscribe an area105around the first twisted pair130, which includes the small air gaps107. However, the width of the first dielectric tape131is only slightly more than one-half the width of the dielectric tape89in the embodiment ofFIGS. 9-11.FIG. 14illustrates a cable140with a jacket141, wherein the first twisted pair130is stranded with three other similarly-configured twisted pairs, namely a second twisted pair142, a third twisted pair143and a fourth twisted pair144.

The dielectric tapes131may be formed of a same or similar material in a same or similar manner, as described in connection with the dielectric tapes depicted inFIGS. 3-5A.

Some of the advantages of the seventh embodiment ofFIGS. 13 and 14over the fifth embodiment ofFIGS. 9-11are that the material cost, and the weight of the cable140can be reduced. Yet, the seventh embodiment ofFIGS. 13 and 14will still create the small air gaps107, primarily due to the tight twist lengths of the first through fourth twisted pairs130,142,143and144.

FIG. 15is a close-up cross sectional view of a twisted pair150, having a dielectric tape151with an alternative shape, in accordance with a eighth embodiment of the present invention. The eighth embodiment is identical to the seventh embodiment ofFIGS. 13 and 14, except that the dielectric tape151does not have recessed seats135and136to seat the first and second insulated conductors88and90. Rather, the dielectric tape151has a substantially rectangular cross sectional shape. The dielectric tape151will remain between the first and second insulated conductors88and90due to the frictional forces created during the twisting operation, when the twisted pair150is formed.

The dielectric tapes151may be formed of a same or similar material in a same or similar manner, as described in connection with the dielectric tapes depicted inFIGS. 3-5A.

FIG. 16is a close-up cross sectional view of a twisted pair160A, having a dielectric tape161A with an alternative shape, in accordance with a ninth embodiment of the present invention. The ninth embodiment includes a first insulated conductor88, a first dielectric tape161A, and a second insulated conductor90. The first insulated conductor88is twisted with the second insulated conductor90with the first dielectric tape161A residing between the first insulated conductor88and the second insulated conductor90to form the twisted pair160A. The dielectric tape161A has a width which extends approximately perpendicular to an extension length of the twisted pair160A from a first edge162of the dielectric tape161A to an opposing second edge163of the dielectric tape161A. The width, in the embodiment ofFIG. 16, is equal to or less than the diameter of the first insulated conductor88.

The embodiment ofFIG. 16is similar in most regards to the embodiment ofFIG. 8, but illustrates that the dielectric tape161A may include a plurality of ridges164A and valleys165A on at least a first side of the first dielectric tape161A facing to the first insulated conductor88. In a preferred embodiment, the first dielectric tape161A includes a plurality of ridges164A and valleys165A on both the first side of the first dielectric tape161A facing to the first insulated conductor88and on a second side of the first dielectric tape161A facing to the second insulated conductor90.

The dielectric tape161A may be formed of a same or similar material in a same or similar manner, as described in connection with the dielectric tapes depicted inFIGS. 3-5A. Alternatively, and as illustrated inFIG. 16A, the dielectric tape161A′ may be formed of a polymer (as listed in conjunction withFIGS. 3-5A) with embedded continuous strands or strengthen members275, which extend from one end of the cable to an opposite end of the cable.FIG. 16Ais a perspective view and two strengthen members275have been illustrated as extending away from the rear end of the dielectric tape161A′, so as to demonstrate the continuous nature of the strengthen members along the entire length of the dielectric tape161A. In practice, the strength members275would be cut flush with the end of the dielectric tape161A.

The insulation layers R of the first and second insulated conductors88and90engage the ridges164A, so that the valleys165A introduces air immediately adjacent to the insulation layers R of the first and second insulated conductors88and90. Air has a dielectric constant of approximately 1.0, and the introduction of air close to the insulation layers R improves the overall dielectric constant of the first dielectric tape161A, e.g., reduces the overall dielectric constant of the first dielectric tape161A.

InFIG. 16, the plurality of ridges164A are shaped in the form of angled peaks, and the plurality of valleys165A are shaped in the form of angled valleys. The actual shapes of the ridges and/or valleys are not critical. Rather, an important aspect is the introduction of air into the first and second surfaces of the first dielectric tape161A, which contact the first and second insulated conductors88and90.

FIG. 17is a close-up cross sectional view of a twisted pair160B, having a dielectric tape161B with an alternative shape, in accordance with a tenth embodiment of the present invention. The tenth embodiment is the same as the ninth embodiment, except that the plurality of ridges164B are shaped in the form of rectangular protrusions, and the plurality of valleys165B are shaped in the form of rectangular recesses.

The dielectric tape161B may be formed of a same or similar material in a same or similar manner, as described in connection with the dielectric tapes depicted inFIGS. 3-5A.

FIG. 18is a close-up cross sectional view of a twisted pair160C, having a dielectric tape161C with an alternative shape, in accordance with an eleventh embodiment of the present invention. The eleventh embodiment is the same as the ninth and tenth embodiments, except that the plurality of ridges164C are shaped in the form of curved protrusions, and the plurality of valleys165C are shaped in the form of curved recesses.

The dielectric tape161C may be formed of a same or similar material in a same or similar manner, as described in connection with the dielectric tapes depicted inFIGS. 3-5A.

FIG. 19is a close-up cross sectional view of a twisted pair160D, having a dielectric tape161D with an alternative configuration, in accordance with a twelfth embodiment of the present invention. The twelfth embodiment is the same as the ninth embodiment, in that the plurality of ridges164D are shaped in the form of angled peaks, and the plurality of valleys165D are shaped in the form of angled valleys. However, in the twelfth embodiment, the first dielectric tape161D is formed of at least two different materials. A first side168of the first dielectric tape161D, facing to the first insulated conductor88, and a second side167of the first dielectric tape161D, facing to the second insulated conductor90, are formed of a first dielectric material. A mid-portion166of the first dielectric tape161D is formed of a second dielectric material. A first dielectric constant of the first material is different from a second dielectric constant of the second material. In a preferred embodiment, the second dielectric constant is lower than the first dielectric constant. The second material improves the overall dielectric constant of the first dielectric tape161D, e.g., reduces the overall dielectric constant of the first dielectric tape161D.

The first dielectric material may be formed of a same or similar material, as described in connection with the dielectric tapes depicted inFIGS. 3-5A. The second dielectric materials may be formed of a material with a lower dielectric constant than the first material, such as a highly foamed polymer.

FIGS. 20 and 20Aare close-up cross sectional views of a twisted pair160E, having a dielectric tape161E with an alternative configuration, in accordance with a thirteenth embodiment of the present invention. The thirteenth embodiment is the same as the twelfth embodiment, in that the plurality of ridges164E are shaped in the form of angled peaks, and the plurality of valleys165E are shaped in the form of angled valleys. However, in the thirteenth embodiment, the construction of the first dielectric tape161E is different. InFIG. 20, the first side168of the first dielectric tape161E, facing to the first insulated conductor88is attached to the second side167of the first dielectric tape161E, facing to the second insulated conductor90along the first edge162and along the second edge164.

Like the embodiment depicted in, and described in relation toFIG. 5A, the first dielectric tape161E has a hollow core which may possess a gas (SeeFIG. 20A), like air166A (with a dielectric constant of about 1.0) or, as depicted inFIG. 20, a foamed insulation material166(with a dielectric constant approaching 1.0, e.g., like 1.3 or 1.2). Again, the material166would have a lower dielectric constant than a material used to form the remaining portions of the first dielectric tape161E. By filling the hollow core with a gas or material with a lower dielectric constant than a material used to form the remaining portions of the first dielectric tape161E, the overall dielectric constant of the first dielectric tape161E may be reduced.

The first dielectric material may be formed of a same or similar material, as described in connection with the dielectric tapes depicted inFIGS. 3-5A. The attachment portions between the first and second sides168and167of the first dielectric tape161E along the first edge162and along the second edge164each include the embedded acicular material, e.g., the high strength fibers. The reinforced strength materials residing entirely around the perimeter of the lower dielectric material will protect the stability of the dielectric tape during high speed production. In other words, the dielectric tape will not tend to tear apart, separate or delaminate at the weaker, lower dielectric layer.

Further, the impact and pressure induced between the dielectric tape and insulation layers R of the first and second insulated conductors88and90by the twisting operation during cable manufacturing will be better tolerated by the high strength material, which is less susceptible to crushing. The lower dielectric material, e.g., the highly foamed material, which can crush more easily, will be protected in the middle of the dielectric tape161E.

The hollow core or the lower dielectric material in the middle may extend the entire length of the dielectric tape161E, resulting in a “straw-like” structure. Alternatively, support structures may be formed at intervals IN1, IN2, IN3, . . . along the length of the dielectric tape161E to form closed-cell air pockets or closed-cell lower dielectric material pockets, each having a short length, such as ½ inch, one inch, two inches, etc., as graphically shown, not to scale, inFIG. 20B. Alternatively, one or more support structures may be formed within the hollow core, which extend along the length of the dielectric tape161E and connect between the first and second sides168and167of the hollow core to resist crushing of the hollow core during the twisting of the twisted pair160E.

In cables of the background art, different twist lengths were applied to each of the four twisted pairs. The different twist lengths had the benefit of reducing crosstalk between adjacent pairs within the cable. However, employing different twist lengths also created drawbacks, such as delay skew (e.g., it takes more time for a signal to travel to the far end of the cable on a relatively tighter twisted pair, as compared to a relatively longer twisted pair in the same cable). Differing twist lengths can also cause relative differences between the twisted pairs in such performance characteristics as attenuation and impedance.

In the background art, the insulation layers R were varied in thickness and/or material composition to compensate for the differences. For example, the insulation layers R of the insulated conductors91and93in the tighter twisted pair84(inFIG. 9) could be formed of a material with a different dielectric constant than the insulation layers R of the insulated conductors94and96in the longer twisted pair85(inFIG. 9). Also, air could be introduced into the insulation layers R to foam the insulation layers R. The foaming could be set at different levels for one or more of the twisted pairs, depending upon their twist length.

Such measures of the background art helped to offset the different performance characteristics induced by the different twist lengths of the twisted pairs. However, there was an added cost in that the insulated conductors used in different twisted pairs of the same cable had to be manufactured differently. This created a need for inventorying different types of insulated conductors and added more complexity in the manufacturing process.

In accordance with one embodiment of the present invention, the insulated conductors38,40,41,43,44,46,47and49of each of the twisted pairs33,34,35and36in the cable31may be made structurally identical (noting that certain non-structural features, like colors, stripe patterns or printed indicia may be employed to merely identify the insulated conductors from each other). In embodiments of the present invention, the dielectric tape structures can be used to mitigate the performance differences, which arise when different twist lengths are employed in the twisted pairs. Moreover, the insulated conductors38,40,41,43,44,46,47and49may be made structurally identical and also be identical in appearance. In embodiments of the present invention, the color of, or indicia on, the first through fourth dielectric tapes39,42,45and48could be used to distinguish between the first through fourth twisted pairs33,34,35and36of the cable31, when the cable31is terminated and a connector is attached thereto.

For example, the dielectric tape of one twisted pair of a given cable may be different in shape, size or material content as compared to the dielectric tape of another twisted pair in the same cable. InFIG. 4, the first dielectric tape39of the first twisted pair33has a first thickness, which sets a spacing distance between the first insulated conductor38and the second insulated conductor40. In the third twisted pair35, the third dielectric tape45has a second thickness, which sets a spacing distance between the fifth insulated conductor44and the sixth insulated conductor46. The second thickness is different from the first thickness, which also means that the shape of the first dielectric tape39is different than the shape of the third dielectric tape45.

In one embodiment, the difference between the second thickness and the first thickness is at least 1 mil. For example, the first dielectric tape39could have a thickness of about 10 mils, whereas the third dielectric tape45could have a thickness of about 8 mils. Such a change in thickness and shape will affect the respective performance characteristics of the first twisted pair33and the third twisted pair35, such as their respective attenuation, impedance, delay skew, etc.

Also inFIG. 4, the first dielectric tape39of the first twisted pair33has a first width, which extends approximately perpendicular to an extension length of said cable31from its first edge51to its second edge53(SeeFIG. 5). In the fourth twisted pair36, the fourth dielectric tape48has a second width, which extends approximately perpendicular to the extension length of said cable31from its corresponding first edge51to its corresponding second edge53.

The second width is different from the first width. For example, the second width may be several mils shorter than the first width, such as about 2 to 12 mils shorter, e.g., about 5 mils shorter. Again, the respective differences in width will serve to create differences in performance characteristics, which can be adjusted and used to offset for the performance differences created by the different twist lengths.

Also inFIG. 4, the first dielectric tape39of the first twisted pair33is formed of a first material having a first dielectric constant. In the second twisted pair34, the second dielectric tape42is formed of a second material having a second dielectric constant. The second dielectric constant is different from the first dielectric constant due to the embedding of a greater number of high strength members, i.e., acicular material (as illustrated by the greater number of end sections of the acicular material visible in the cross section of the second dielectric tape42as compared to the first dielectric tape39). The dielectric constants can also be made different by employing a different base polymer for different tapes and/or due to a different foaming percentage between different tapes using a same base polymer. The dielectric constants can also be made different between dielectric tapes by changing the size or material content of the high strength members in one dielectric tape relative to another dielectric tape. The statement “wherein a number, size or material content of plural first segments of acicular material in a first dielectric tape is different than a number, size or material content of plural second segments of acicular material in a second dielectric tape,” is meant to encompass the situation wherein the numbers are the same, the sizes are the same and only the materials are different. Likewise, the statement would encompass the situation wherein the sizes are the same, but the numbers are different and the materials are different.

For example, the second dielectric constant could differ from the first dielectric constant by about 0.1 to about 0.8, e.g., the first dielectric constant might be 1.2, whereas the second dielectric constant is 1.4, thus illustrating a difference of 0.2 in dielectric constant between the two materials. Again, the respective differences in material will serve to create differences in performance characteristics, which can be adjusted and used to offset for the performance differences created by the different twist lengths. Of course, the differences between the dielectric tapes can also be employed as a supplemental measure in conjunction with differences in insulation layers on the insulated conductors to provide an additional ability to compensate for performance differences between the twisted pairs.

The cables31,66,81and140of the present invention may be manufactured using standard twisting equipment, such as a double twist twinning machine, known in the art of twisted pair cable making. An additional spool would be added to feed the dielectric tape into the twisting machine between the insulated conductors of the twisted pair.

Although, the cables illustrated in the drawing figures have included four twisted pairs, it should be appreciated that the present invention is not limited to cables having only four twisted pairs. Cables having other numbers of twisted pairs, such as one twisted pair, two twisted pairs or even twenty-five twisted pairs, could benefit from the structures disclosed in the present invention. Further, although the drawing figures have illustrated that each of the twisted pairs within the cable have a dielectric tape, it would be possible for less than all of the twisted pairs to have the dielectric tape. For example, the first through third twisted pairs could include a dielectric tape, while the fourth twisted pair could be formed without a dielectric tape. Further, although the drawing figures have illustrated an unshielded cable, it is within the scope of the appended claims that the cable could include a shielding layer and/or a core wrap between the core of twisted pairs and the inner wall of the outermost jacket. Further, although some drawing figures have illustrated a jacket having a smooth inner wall, it is within the scope of the present invention that in all embodiments the inner wall of the jacket could include fins or projections (as illustrated inFIG. 8B) for creating air pockets around the perimeter of the core of twisted pairs. Further, all embodiments of the present invention may include a separator (e.g., tape, isolator, flute, crossweb).

The high strength material, e.g., embedded acicular material, may also be employed for a separator37or37A (e.g., tape, isolator, flute, crossweb) in a cable wherein the twisted pairs are formed without a dielectric tape disposed between the insulated conductors. For example,FIG. 21is a perspective view of a twisted pair cable231.FIG. 22is a cross sectional view of the cable231taken along line XXII-XXII inFIG. 21. The cable231includes a jacket232with six fins293and six recesses295(similar to the twelve fins32A and twelve recesses of the jacket32ofFIG. 8B). The jacket232is formed around and surrounding first, second, third and fourth twisted pairs233,234,235and236, respectively.

A separator37is formed the same as described in relation toFIGS. 3 and 4, i.e., the separator37includes embedded strength members, best seen in the cross section ofFIG. 22. The separator37is formed as a single unitary structure (e.g., the separator37does not include multiple pieces attached together or layered).

As best seen in the cross sectional view ofFIG. 22, the first twisted pair233includes a first insulated conductor238and a second insulated conductor240. The first insulated conductor238is twisted with the second insulated conductor240, in a helical fashion. The second twisted pair234includes a third insulated conductor241and a fourth insulated conductor243. The third insulated conductor241is twisted with the fourth insulated conductor243, in a helical fashion. The third twisted pair235includes a fifth insulated conductor244and a sixth insulated conductor246. The fifth insulated conductor244is twisted with the sixth insulated conductor246, in a helical fashion. The fourth twisted pair236includes a seventh insulated conductor247and an eighth insulated conductor249. The seventh insulated conductor247is twisted with the eighth insulated conductor249, in a helical fashion.

The twist lengths w, x, y and z and core twist57may be set or modulated as described in conjunction withFIGS. 3 and 4.FIGS. 21 and 22also illustrate a shielding layer297. The shielding layer297may be formed of a bi-layered material, such as Mylar and aluminum foil. However, other types of shielding materials may be used. In the depicted embodiment, the shielding layer297is overlapped at area299and may optionally be adhered to itself at area299.

FIG. 23is a perspective view of a twisted pair cable231A.FIG. 24is a cross sectional view of the cable231taken along line XXIV-XXIV inFIG. 23. The cable231A includes a jacket232A with twelve fins293A and twelve recesses295A (the same as the twelve fins32A and twelve recesses of the jacket32ofFIG. 8B). The jacket232A is formed around and surrounding the first, second, third and fourth twisted pairs233,234,235and236. The first, second, third and fourth twisted pairs233,234,235and236may be formed identically to the twisted pairs ofFIGS. 21 and 22.

A separator37A is formed the same as described in relation toFIG. 8B, i.e., the separator37A is a cross web and includes embedded strength members, best seen in the cross section ofFIG. 24.FIGS. 23 and 24also illustrate an alternative shielding layer297A. The shielding layer297A may be formed of a bi-layered material, such as Mylar and aluminum foil. However, other types of shielding materials may be used. In the depicted embodiment, the shielding layer297A is spirally or helically wrapped around the cable core and overlapped at areas299A and may optionally be adhered to itself at areas299A.

FIG. 25is a cross sectional view of a twisted pair cable with a coated paper separator37B. The paper/hybrid separator tape37B is made of a paper layer287with a fire-retardant coating289applied to both sides of the paper layer287. The paper layer287may optionally be formed of a blend of paper and microfibers, PET for example.

The strength data based upon a model of a dielectric tape having a width (from the first edge72A to the second edge73A inFIG. 8A) of about 171 mils and a thickness (from the side in contact with the first insulated conductor38to the side in contact with the second insulated conductor40) of about 10 mils, has been computed. The present production machinery running at top speed for forming a cable with a twisted pair cable employing a dielectric tape71A between the first and second insulated conductor38and40requires a yield strength of about 2000 psi for the dielectric tape71A in order to avoid damage to the dielectric tape71A. A dielectric tape71A without embedded strength members in the dimensions of about 171 mils in width and about 10 mils in thickness has a yield strength of about 1,700 psi. The dielectric tape71A with the embedded strengthen members, in accordance with the present invention, will exceed 2,000 psi in yield strength, so that the manufacturing machinery can produce cables with bisector tapes at full speed. In accordance with preferred embodiments of the present invention, the dielectric tape will exhibit a psi yield strengthen of about 2,300 psi.