High performance data cable

The present invention is for a high performance data cable which has an interior support or star separator. The star separator or interior support extends along the longitudinal length of the data cable. The star separator or interior support has a central region. A plurality of prongs or splines extend outward from the central region along the length of the central region. Each prong or spline is adjacent with at least two other prongs or splines. The prongs or splines may be helixed or S-Z shaped as they extend along the length of the star separator or interior support. Each pair of adjacent prongs or splines defines grooves which extend along the longitudinal length of the interior support. At least two of the grooves have disposed therein an insulated conductor. The star separator in particular improves control of near end cross-talk and allows for the achievement of positive ACR ratios when twisted pair conductors are disposed in the grooves. The interior support can have a first material and a different second material. The different second material forms an outer surface of the interior support.

FIELD OF INVENTION
 This invention relates to a high performance data cable utilizing twisted
 pairs. The data cable has an interior support or star separator around
 which the twisted pairs are disposed.
 BACKGROUND OF THE INVENTION
 Many data communication systems utilize high performance data cables having
 at least four twisted pairs. Typically, two of the twisted pairs transmit
 data and two of the pairs receive data. A twisted pair is a pair of
 conductors twisted about each other. A transmitting twisted pair and a
 receiving twisted pair often form a subgroup in a cable having four
 twisted pairs.
 A high performance data cable utilizing twisted pair technology must meet
 exacting specifications with regard to data speed and electrical
 characteristics. The electrical characteristics include such things as
 controlled impedance, controlled near-end cross-talk (NEXT), controlled
 ACR (attenuation minus cross-talk) and controlled shield transfer
 impedance.
 One way twisted pair data cables have tried to meet the electrical
 characteristics, such as controlled NEXT, is by utilizing individually
 shielded twisted pairs (ISTP). These shields insulate each pair from NEXT.
 Data cables have also used very complex lay techniques to cancel E and B
 fields to control NEXT. Finally, previous data cables have tried to meet
 ACR requirements by utilizing very low dielectric constant insulations.
 The use of the above techniques to control electrical characteristics has
 problems.
 Individual shielding is costly and complex to process. Individual shielding
 is highly susceptible to geometric instability during processing and use.
 In addition, the ground plane of individual shields, 360.degree. in
 ISTP's, lessens electrical stability.
 Lay techniques are also complex, costly and susceptible to instability
 during processing and use.
 Another problem with many data cables is their susceptibility to
 deformation during manufacture and use. Deformation of the cable's
 geometry, such as the shield, lessens electrical stability. Applicant's
 unique and novel high performance data cable meets the exacting
 specifications required of a high performance data cable while addressing
 the above problems.
 This novel cable has an interior support with grooves. Each groove
 accommodates at least one signal transmission conductor. The signal
 transmission conductor can be a twisted pair conductor or a single
 conductor. The interior support provides needed structural stability
 during manufacture and use. The grooves also improve NEXT control by
 allowing for the easy spacing of the twisted pairs. The easy spacing
 lessens the need for complex and hard to control lay procedures and
 individual shielding.
 The interior support allows for the use of a single overall foil shield
 having a much smaller ground plane than individual shields. The smaller
 ground plane improves electrical stability. For instance, the overall
 shield improves shield transfer impedance. The overall shield is also
 lighter, cheaper and easier to terminate than ISTP designs.
 The interior support can have a first material and a different second
 material. The different second material forms the outer surface of the
 interior support and thus forms the surface defining the grooves. The
 second material is generally a foil shield and helps to control
 electricals between signal transmission conductors disposed in the
 grooves. The second material, foil shield, is used in addition to the
 previously mentioned overall shield.
 This novel cable produces many other significant advantageous results such
 as:
 improved impedance determination because of the ability to precisely place
 twisted pairs;
 the ability to meet a positive ACR value from twisted pair to twisted pair
 with a cable that is no larger than an ISTP cable; and
 an interior support which allows for a variety of twisted pair dimensions.
 Previous cables have used supports designed for coaxial cables. The
 supports in these cables are designed to place the center conductor
 coaxially within the outer conductor. The supports of the coaxial designs
 are not directed towards accommodating signal transmission conductors. The
 slots in the coaxial support remain free of any conductor. The slots in
 the coaxial support are merely a side effect of the design's direction to
 center a conductor within an outer conductor with a minimal material cross
 section to reduce costs. In fact, one would really not even consider these
 coaxial cable supports in concurrence with twisted pair technology.
 Some cables have used supports in connection with twisted pairs. These
 cables, however, suggest using a standard "X" or "+" shaped support,
 hereinafter both referred to as the "X" support. The standard "X" support
 is completely different than this support. Protrusions extend from the
 standard "X" support. These protrusions have substantially parallel sides.
 The prongs or splines in this invention provide a superior crush resistance
 to the protrusions of the standard "X" support. The superior crush
 resistance better preserves the geometry of the pairs relative to each
 other and of the pairs relative to the other parts of the cables such as
 the shield. In addition, the prongs or splines in this invention
 preferably have a pointed or slightly rounded apex top which easily
 accommodates an overall shield.
 SUMMARY OF THE INVENTION
 In one embodiment, we provide a data cable which has a one piece plastic
 interior support. The interior support extends along the longitudinal
 length of the data cable. The interior support has a central region which
 extends along the longitudinal length of the interior support. The
 interior support has a plurality of prongs. Each prong is integral with
 the central region. The prongs extend along the longitudinal length of the
 central region and extend outward from the central region. The prongs are
 arranged so that each prong of said plurality is adjacent with at least
 two other prongs.
 Each pair of adjacent prongs define a groove extending along the
 longitudinal length of the interior support. The prongs have a first and
 second lateral side. A portion of the first lateral side and a portion of
 the second lateral side of at least one prong converge towards each other.
 The cable further has a plurality of insulated conductors disposed in at
 least two of the grooves.
 A cable covering surrounds the interior support. The cable covering is
 exterior to the conductors.
 Applicants' inventive cable can be alternatively described as set forth
 below. The cable has an interior support extending along the longitudinal
 length of the data cable. The interior support has a central region
 extending along the longitudinal length of the interior support. The
 interior support has a plurality of prongs. Each prong is integral with
 the central region. The prongs extend along the longitudinal length of the
 central region and extend outward from the central region. The prongs are
 arranged so that each prong is adjacent with at least two other prongs.
 Each prong has a base. Each base is integral with the central region. At
 least one of said prongs has a base which has a horizontal width greater
 than the horizontal width of a portion of said prong above said base. Each
 pair of the adjacent prongs defines a groove extending along the
 longitudinal length of the interior support.
 A plurality of conductors is disposed in at least two of said grooves.
 A cable covering surrounds the interior support. The cable covering is
 exterior to the conductors.
 The invention can further be alternatively described by the following
 description. An interior support for use in a high-performance data cable.
 The data cable has a diameter of from about 0.300" to about 0.400". The
 data cable has a plurality of insulated conductor pairs.
 The interior support in said high-performance data cable has a cylindrical
 longitudinally extending central portion. A plurality of splines radially
 extend from the central portion. The splines also extend along the length
 of the central portion. The splines have a triangular cross-section with
 the base of the triangle forming part of the central portion, each
 triangular spline has the same radius. Adjacent splines are separated from
 each other to provide a cable chamber for at least one pair of conductors.
 The splines extend longitudinally in a helical, S, or Z-shaped manner.
 An alternative embodiment of applicant's cable can include an interior
 support having a first material and a different second material. The
 different second material forms an outer surface of the interior support.
 The second material conforms to the shape of the first material. The
 second material can be referred to as a conforming shield because it is a
 foil shield which conforms to the shape defined by the outer surface of
 the first material.
 Accordingly, the present invention desires to provide a data cable that
 meets the exacting specifications of high performance data cables, has a
 superior resistance to deformation during manufacturing and use, allows
 for control of near-end cross talk, controls electrical instability due to
 shielding, and can be a 300 MHz cable with a positive ACR ratio.
 It is still another desire of the invention to provide a cable that does
 not require individual shielding, and that allows for the precise spacing
 of conductors such as twisted pairs with relative ease.
 It is still a further desire of the invention to provide a data cable that
 has an interior support that accommodates a variety of AWG's and
 impedances, improves crush resistance, controls NEXT, controls electrical
 instability due to shielding, increases breaking strength, and allows the
 conductors such as twisted pairs to be spaced in a manner to achieve
 positive ACR ratios.
 Other desires, results, and novel features of the present invention will
 become more apparent from the following drawing and detailed description
 and the accompanying claims.

DETAILED DESCRIPTION
 The following description will further help to explain the inventive
 features of this cable.
 FIG. 1 is a vertical cross-section of one embodiment of this novel cable.
 The shown embodiment has an interior support or star separator (10). The
 interior support or star separator runs along the longitudinal length of
 the cable as can be seen in FIG. 2. The interior support or star
 separator, hereinafter, in the detailed description, both referred to as
 the "star separator", has a central region (12) extending along the
 longitudinal length of the star separator. The star separator has four
 prongs or splines. Each prong or spline (14), hereinafter in the detailed
 description both referred to as splines, extends outward from the central
 region and extends along the longitudinal length of the central region.
 The splines are integral with the central region. Each spline has a base
 portion (15). Each base portion is integral with the central region. Each
 spline has a base portion which has a horizontal width greater than the
 horizontal width of a portion of said spline above said base.
 Each spline also has a first lateral side (16) and a second lateral side
 (17). The first and second lateral sides of each spline extend outward
 from the central region and converge towards each other to form a top
 portion (18). Each spline has a triangular cross section with preferably
 an isosceles triangle cross section. Each spline is adjacent with at least
 two other splines. For instance, spline (14) is adjacent to both adjacent
 spline (20) and adjacent spline (21).
 The first lateral side of each spline is adjacent with a first or a second
 lateral side of another adjacent spline. The second lateral side of each
 spline is adjacent to the first or second side of still another adjacent
 spline.
 Each pair of adjacent splines defines a groove (22). The angle (24) of each
 groove is greater than 90.degree.. The adjacent sides are angled towards
 each other so that they join to form a crevice (26). The groove extends
 along the longitudinal length of the star separator. The splines are
 arranged around the central region so that a substantial congruency exists
 along a straight line (27) drawn through the center of the horizontal
 cross section of the star separator. Further, the splines are spaced so
 that each pair of adjacent splines has a distance (28), measured from the
 center of the top of one spline to the center of the top of an adjacent
 spline (top to top distance) as shown in FIG. 3. The top to top distance
 (28) being substantially the same for each pair of adjacent splines.
 In addition, the shown embodiment has a preferred "tip to crevice" ratio of
 between about 2.1 and 2.7. Referring to FIG. 3. The "tip distance" (30) is
 the distance between two top portions opposite each other. The "crevice
 distance" (32) is the distance between two crevices opposite each other.
 The ratio is measured by dividing the "tip" distance by the "crevice"
 distance.
 The specific "tip distance", "crevice distance" and "top to top" distances
 can be varied to fit the requirements of the user such as various AWG's
 and impedances. The specific material for the star separator also depends
 on the needs of the user such as crush resistance, breaking strengths, the
 need to use gel fillings, the need for safety, and the need for flame and
 smoke resistance. One may select a suitable copolymer. The star separator
 is solid beneath its surface.
 A strength member may be added to the cable. The strength member (33) in
 the shown embodiment is located in the central region of the star
 separator. The strength member runs the longitudinal length of the star
 separator. The strength member is a solid polyethylene or other suitable
 plastic, textile (nylon, aramid, etc.), fiberglass (FGE rod), or metallic
 material.
 Conductors, such as the shown insulated twisted pairs, (34) are disposed in
 each groove. The pairs run the longitudinal length of the star separator.
 The twisted pairs are insulated with a suitable copolymer. The conductors
 are those normally used for data transmission. The twisted pairs may be
 Belden's DATATWIST 350 twisted pairs. Although the embodiment utilizes
 twisted pairs, one could utilize various types of insulated conductors
 with the star separator.
 The star separator may be cabled with a helixed or S-Z configuration. In a
 helical shape, the splines extend helically along the length of the star
 separator as shown in FIG. 2. The helically twisted splines in turn define
 helically twisted conductor receiving grooves which accommodate the
 twisted pairs.
 The cable (37) as shown in FIG. 2 is a high performance shielded 300 Mhz
 data cable. The cable has an outer jacket (36), e.g., polyvinyl chloride.
 Over the star separator is a polymer binder sheet (38). The binder is
 wrapped around the star separator to enclose the twisted pairs. The binder
 has an adhesive on the outer surface to hold a laterally wrapped shield
 (40). The shield (40) is a tape with a foil or metal surface facing
 towards the interior of the jacket. The shield in the shown embodiment is
 of foil and has an overbelt (shield is forced into round smooth shape)
 (41) which may be utilized for extremely well controlled electricals. A
 metal drain wire (42) is spirally wrapped around the shield. The drain
 spiral runs the length of the cable. The drain functions as a ground.
 My use of the term "cable covering" refers to a means to insulate and
 protect my cable. The cable covering being exterior to said star member
 and insulated conductors disposed in said grooves. The outer jacket,
 shield, drain spiral and binder described in the shown embodiment provide
 an example of an acceptable cable covering. The cable covering, however,
 may simply include an outer jacket.
 The cable may also include a gel filler to fill the void space (46) between
 the interior support, twisted pairs and a part of the cable covering.
 An alternative embodiment of the cable utilizes an interior support having
 a first inner material (50) and a different second outer material (51)
 (see FIG. 5). The second material is a conforming shield which conforms to
 the shape defined by the outer surface of the first material (50). The
 conforming shield is a foil shield. The foil shield should have enough
 thickness to shield the conductors from each other. The shield should also
 have sufficient thickness to avoid rupture during conventional manufacture
 of the cable or during normal use of the cable. The thickness of the
 conforming shield utilized was about 3 mm. The thickness could go down to
 even 0.3 mm. Further, although the disclosed embodiment utilizes a foil
 shield as the conforming shield, the conforming shield could alternatively
 be a conductive coating applied to the outer surface of the first material
 (50).
 To conform the foil shield (51) to the shape defined by the first
 material's (50) outer surface, the foil shield (51) and an already-shaped
 first material (50) are placed in a forming die. The forming die then
 conforms the shield to the shape defined by the first material's outer
 surface.
 The conforming shield can be bonded to the first material. An acceptable
 method utilizes heat pressure bonding. One heat pressure bonding technique
 requires utilizing a foil shield with an adhesive vinyl back. The foil
 shield, after being conformed to the shape defined by the first material's
 outer surface, is exposed to heat and pressure. The exposure binds the
 conforming shield (51) to the outer surface of the first material (50).
 A cable having an interior support as shown in FIG. 5 is the same as the
 embodiment disclosed in FIG. 1 except the alternative embodiment in FIG. 5
 includes the second material, the conforming shield (51), between the
 conductors and the first material (50).
 The splines of applicants' novel cable allow for precise support and
 placement of the twisted pairs. The star separator will accommodate
 twisted pairs of varying AWG's and impedance. The unique triangular shape
 of the splines provides a geometry which does not easily crush.
 The crush resistance of applicants' star separator helps preserve the
 spacing of the twisted pairs, and control twisted pair geometry relative
 to other cable components. Further, adding a helical or S-Z twist improves
 flexibility while preserving geometry.
 The use of an overall shield around the star separator allows a minimum
 ground plane surface over the twisted pairs, about 45.degree. of covering.
 The improved ground plane provided by applicant' shield, allows applicant'
 cable to meet a very low transfer impedance specification. The overall
 shield may have a more focused design for ingress and egress of cable
 emissions and not have to focus on NEXT duties.
 The strength member located in the central region of the star separator
 allows for the placement of stress loads away from the pairs.
 It will, of course, be appreciated that the embodiment which has just been
 described has been given by way of illustration, and the invention is not
 limited to the precise embodiments described herein; various changes and
 modifications may be effected by one skilled in the art without departing
 from the scope or spirit of the invention as defined in the appended
 claims.