EP0655751A2 - Ein Koaxialkabel und Kern und Verfahren zu seiner Herstellung - Google Patents

Ein Koaxialkabel und Kern und Verfahren zu seiner Herstellung Download PDF

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Publication number
EP0655751A2
EP0655751A2 EP94308821A EP94308821A EP0655751A2 EP 0655751 A2 EP0655751 A2 EP 0655751A2 EP 94308821 A EP94308821 A EP 94308821A EP 94308821 A EP94308821 A EP 94308821A EP 0655751 A2 EP0655751 A2 EP 0655751A2
Authority
EP
European Patent Office
Prior art keywords
dielectric layer
cable core
coaxial cable
electrostatic capacity
core
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP94308821A
Other languages
English (en)
French (fr)
Other versions
EP0655751A3 (de
Inventor
Monbara Takeo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Junkosha Co Ltd
Original Assignee
Junkosha Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Junkosha Co Ltd filed Critical Junkosha Co Ltd
Publication of EP0655751A2 publication Critical patent/EP0655751A2/de
Publication of EP0655751A3 publication Critical patent/EP0655751A3/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H01B13/06—Insulating conductors or cables
    • H01B13/14—Insulating conductors or cables by extrusion
    • H01B13/146—Controlling the extrusion apparatus dependent on the capacitance or the thickness of the insulating material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B11/00—Communication cables or conductors
    • H01B11/18—Coaxial cables; Analogous cables having more than one inner conductor within a common outer conductor
    • H01B11/1834—Construction of the insulation between the conductors

Definitions

  • the present invention concerns a cable core with electrical characteristics being uniform in the lengthwise direction.
  • the present invention also concerns a coaxial cable in which said core is used and a method for manufacturing the same.
  • ePTFE expanded polytetrafluoroethylene material
  • One common construction method with this type of coaxial cable employs a strip of ePTFE tape wrapped around the outside of an internal conductor in a spiral to form a dielectric layer.
  • An external conductor layer, consisting of a braided conductor or similar structure, is then positioned around the outside of the dielectric layer, and the outside of this external conductor layer is then covered with an insulator as needed.
  • the dielectric layer of such a coaxial cable has excellent dielectric characteristics in that its dielectric constant is low and its dielectric loss tangent is also small, so these cables are often used for high-speed digital signal transmission in a variety of applications, such as in computers. From the standpoints of higher signal transmission speed, noise elimination, etc., there is a need for further enhancement of various electrical characteristics of such coaxial cables, e.g., their electrostatic capacity, characteristic impedance, and propagation delay time, etc.
  • the strip of ePTFE tape that serves as the dielectric layer in such a coaxial cable tends to be very susceptible to plastic deformation by external forces. For instance, it can be flattened out by tension while it is being wound in a spiral around the outside of the internal conductor, which leads to local changes in the dielectric constant.
  • Other areas of concern include the tape overlap width varying during spiral winding, or the tape being flattened out during the positioning of the external conductor layer of the coaxial cable.
  • coaxial cables have been developed in which a second dielectric layer composed of a thermoplastic resin in the form of a relatively thin tape (hereinafter sometimes referred to as a "skin layer") is wound so as to cover the outside of the above-mentioned dielectric layer.
  • a skin layer composed of a thermoplastic resin in the form of a relatively thin tape
  • the present invention was conceived in light of these problems encountered with prior art, and its objective is to offer a coaxial cable core with which at least one property from among electrical characteristics of the coaxial cable, such as its electrostatic capacity, characteristic impedance, and propagation delay time, can be made uniform in the lengthwise direction of the coaxial cable, and also to offer a coaxial cable in which said core is used and a method for manufacturing the same.
  • the present invention is an improved core for use in a coaxial or differential cable that provides the desired level of electrical performance while being readily processed with minimal concern to damage to the dielectric layer during manufacture.
  • the cable core of the present invention is equipped with a conductor, a first dielectric layer that covers this conductor, and a second dielectric layer that covers the outside of this first dielectric layer.
  • the thickness of the second dielectric layer is adjusted in the lengthwise direction so that at least one property from among electrostatic capacity, characteristic impedance, and propagation delay time is controlled (e.g., made uniform) in the lengthwise direction of the cable.
  • the method for manufacturing a cable core of the present invention comprises: (i) an extrusion step in which a cable core is molded by extruding a second dielectric layer composed of a thermoplastic resin such that it covers the outside of a first dielectric layer that covers a conductor; (ii) a step in which the electrostatic capacity per unit of length and the outside diameter of the above-mentioned cable core are each measured; (iii) a computation step in which any difference in electrostatic capacity per unit of length or the outside diameter of the cable is determined; and (iv) a control step in which the amount in and/or pressure at which the above-mentioned thermoplastic resin is extruded in the above-mentioned extrusion step is controlled based on the output signal from the computation step. In this manner, the thickness of the above-mentioned second dielectric layer is thereby regulated.
  • Controlling the thickness of the second dielectric layer in the cable core of the present invention allows a composite dielectric constant of the above-mentioned first and second dielectric layers and the outside diameter of the cable core to be fine tuned. This permits exact selection and control of at least one of the above-mentioned electrical characteristics required of the cable to be kept within the required range over the entire length of the cable.
  • the above-mentioned second dielectric layer also provides the same effect as a conventional skin layer.
  • the outside diameter of this cable core and the electrostatic capacity per unit of length of this coaxial cable core are each automatically measured on the extrusion step manufacturing line after the extrusion step in which the second dielectric layer is formed. These measurement results are processed through a computation step and a control step and reach a system of feedback to the extrusion step, which permits the thickness of the second dielectric layer to be controlled.
  • the thickness of the second dielectric layer is modified by adjusting the amount or pressure, or both, of the thermoplastic resin that is extruded in the extrusion step. Example of how this may be accomplished include maintaining line speed and adjusting molten plastic flow, or maintaining plastic flow constant and adjusting line speed.
  • the outside diameter and the composite dielectric constant of the first and second dielectric layers of the cable core can be fine tuned, and one or more of the various electrical characteristics, such as electrostatic capacity, characteristic impedance, and propagation delay time, required of a cable in which this cable core is used can be kept within the desirable and required range thereof.
  • Figure 1 is a cross-section view illustrating a practical example of a cable core pertaining to the present invention.
  • Figure 2 is a cross-section view illustrating a practical example of the coaxial cable pertaining to the present invention, in which the cable core shown in Figure 1 is used.
  • Figure 3 is a plan view illustrating a practical example of the cable core manufacturing method pertaining to the present invention, which is used to manufacture the coaxial cable core shown in Figure 1.
  • the cable core of the present invention a coaxial cable in which said core is used, and the manufacturing method thereof will now be described by giving specific examples, but, naturally, the present invention is not limited to or by these practical examples, and variations are possible within the technological essence of the present invention.
  • Figure 1 is a cross-section illustrating an embodiment of a cable core of the present invention.
  • the cable core 9 is the product of forming a first dielectric layer by wrapping a strip of ePTFE tape in a spiral around the outside of a conductor 1 (having an outside diameter d) until an outside diameter D' is reached, and then covering the outside of this first dielectric layer with a second dielectric layer composed of a thermoplastic resin so that the outside diameter of the cable core 9 will be D.
  • Thickness t of the second dielectric layer is regulated such that at least one of the various electrical characteristics required in the lengthwise direction of this coaxial cable, such as electrostatic capacity, characteristic impedance, and/or propagation delay time, can be kept within the required range thereof by the method described below.
  • the material of the second dielectric layer can be an extrusion-moldable fluororesin, such as a tetrafluoroethylene - perfluoroalkyl vinyl ether copolymer (PFA), a tetrafluoroethylene - hexafluoropropylene copolymer (FEP), or another such thermoplastic fluororesin, or polyethylene, polyester, polyolefin, or another thermoplastic resin.
  • PFA tetrafluoroethylene - perfluoroalkyl vinyl ether copolymer
  • FEP tetrafluoroethylene - hexafluoropropylene copolymer
  • thermoplastic fluororesin or polyethylene, polyester, polyolefin, or another thermoplastic resin.
  • FIG 2 is a cross-section of a practical example of a coaxial cable in which the cable core 9 shown in Figure 1 is used. Those constituent components that are the same as in Figure 1 are indicated by the same labels, and redundant descriptions will be omitted.
  • the coaxial cable 10 is the product of further enveloping the outside of the cable core 9 with an external conductor layer 11, and then covering these components with an insulation covering 12.
  • the electrostatic capacity C, the characteristic impedance Zo, the propagation delay time Tr, and other such electrical characteristics are dependent on the outside diameter D of the core, the outer diameter d of the conductor, and the composite dielectric constant e of the first dielectric layer 2 and the second dielectric layer 3 of the coaxial cable core 9.
  • the composite dielectric constant e can be computed if the electrostatic capacity C and the outside diameter D are given, and since the characteristic impedance Zo is proportional to ⁇ 1n ⁇ D ⁇ d) ⁇ ⁇ e ⁇ and the propagation delay time Tr is proportional to ⁇ e, these characteristics can also be computed.
  • the diameter of the core may be measured through use of a continuous outer diameter measuring apparatus employing a laser beam, such as one available from Anritsu Electric Co., Ltd., in Japan. Capacitance may be measured by using a continuous static capacity meter, such as Type 40E0128 manufactured by Brunorichter in Germany.
  • Figure 3 is a plan view illustrating one practical example of the manufacturing method used to manufacture the coaxial cable core shown in Figure 1.
  • the constituent components that are the same as in Figure 1 are indicated by the same labels, and redundant descriptions will be omitted.
  • This is preferably performed by inputting the output signals S5 into a computer 7, while the electrostatic capacity from the outer periphery of the conductor 1 to the outer periphery of the dielectric layer 3 per unit of length (including the measured outside diameter portion) is measured by an electrostatic capacity measurement apparatus 6, and these measurement results (i.e., the output signals S6) are input to the computer 7.
  • the computer 7 will compute this difference, and the resulting output signal S7 is input to the control apparatus 8 from the computer 7.
  • a control output signal S8 is output to the extrusion apparatus 4 from the control apparatus 8, and the thickness t of the dielectric layer 3 may be adjusted by control of the resin pressure, resin quantity, etc., in the extrusion apparatus 4.
  • the resin pressure and resin quantity can be left constant and the line speed or draw rate can be raised or lowered to alter thickness.
  • the end result is a uniformity in the lengthwise direction of the coaxial cable in terms of the electrostatic capacity C, the characteristic impedance Zo, the propagation delay time Tr, and/or various other electrical characteristics. It should be evident that the same apparatus may likewise be used to provide controlled changes in any of these or other electrical properties at desired locations along the length of a given cable.
  • the diameter D will be greater by the control of the extrusion volume. If the value of impedance which is really measured is larger than the value of impedance which is predetermined, during operation, the diameter D will be smaller by the control of the extrusion volume. If the value of signal propagation delay time which is really measured is larger than the value of signal propagation delay time which is predetermined, during operation, the diameter D will be greater by the control the extrusion volume.
  • an evaluation as to whether the variety of electrical characteristics required of a coaxial cable are within their desired ranges can be accomplished at a stage prior to the step in which the external conductor layer 11 is positioned, i.e., during the manufacture of the core 9. This can eliminate the unnecessary work after the manufacture of the core 9 that would occur in the event that the electrical characteristics of the coaxial cable were outside their predetermined specific ranges when the electrical characteristics of the coaxial cable were examined after the external conductor layer, etc., had been positioned, as with a conventional manufacturing method.
  • the present invention offers a cable core with the desired uniformity of one or more of the various required electrical characteristics, such as electrostatic capacity, characteristic impedance, and propagation delay time, in the lengthwise direction, and offers a coaxial cable or differential cable in which said core is used. Also, with the manufacturing method of the present invention, adjusting the thickness of the second dielectric layer based on the results of measuring the electrostatic capacity per unit of length and the outside diameter of the cable core provides a benefit unique to the present invention in that it is possible to manufacture a coaxial cable core that has the desired uniformity of one or more of a variety of electrical characteristics, such as electrostatic capacity, characteristic impedance, propagation delay time, in the lengthwise direction, as well as a coaxial cable in which said core is used.
  • the core of the present invention is for use in coaxial cables, it should be appreciated that the core may also be useful in other electrical applications, such as in differential signal transmission cable (e.g., twin ax or quad ax cables) and the like.
  • differential signal transmission cable e.g., twin ax or quad ax cables

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)
EP94308821A 1993-11-29 1994-11-29 Ein Koaxialkabel und Kern und Verfahren zu seiner Herstellung. Withdrawn EP0655751A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP326313/93 1993-11-29
JP5326313A JPH07153330A (ja) 1993-11-29 1993-11-29 同軸ケーブル用コア、これを用いた同軸ケーブル、およびその製造方法

Publications (2)

Publication Number Publication Date
EP0655751A2 true EP0655751A2 (de) 1995-05-31
EP0655751A3 EP0655751A3 (de) 1996-08-28

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP94308821A Withdrawn EP0655751A3 (de) 1993-11-29 1994-11-29 Ein Koaxialkabel und Kern und Verfahren zu seiner Herstellung.

Country Status (2)

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EP (1) EP0655751A3 (de)
JP (1) JPH07153330A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19918539A1 (de) * 1999-04-23 2000-10-26 Eilentropp Kg Koaxiales Hochfrequenzkabel
WO2008057514A3 (en) * 2006-11-06 2008-07-03 Du Pont Periodic variation of velocity of propagation to reduce additive distortion along cable length
WO2018044782A1 (en) * 2016-08-31 2018-03-08 Commscope Technologies Llc Systems and methods for tamper proof cables

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5603970B2 (ja) * 2008-03-25 2014-10-08 宇部エクシモ株式会社 同軸ケーブル用中空コア体の製造装置
JP2011198487A (ja) * 2010-03-17 2011-10-06 Junkosha Co Ltd 同軸ケーブル

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH462910A (de) * 1967-02-13 1968-09-30 Gen Cable Corp Verfahren und Vorrichtung zum Aufbringen von Kunststoffschichten auf einen elektrischen Leiter
US4174236A (en) * 1977-08-31 1979-11-13 Western Electric Company, Inc. Methods of and apparatus for controlling capacitance unbalance-to-ground in cables
DE3515574A1 (de) * 1984-05-03 1985-11-07 Osakeyhtiö Nokia AB, Helsinki Koaxialkabel und verfahren zur herstellung einer den innenleiter dieses kabels umgebenen isolierung
US5210377A (en) * 1992-01-29 1993-05-11 W. L. Gore & Associates, Inc. Coaxial electric signal cable having a composite porous insulation

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19918539A1 (de) * 1999-04-23 2000-10-26 Eilentropp Kg Koaxiales Hochfrequenzkabel
WO2008057514A3 (en) * 2006-11-06 2008-07-03 Du Pont Periodic variation of velocity of propagation to reduce additive distortion along cable length
WO2018044782A1 (en) * 2016-08-31 2018-03-08 Commscope Technologies Llc Systems and methods for tamper proof cables
US10811169B2 (en) 2016-08-31 2020-10-20 Commscope Technologies Llc Systems and methods for tamper proof cables

Also Published As

Publication number Publication date
EP0655751A3 (de) 1996-08-28
JPH07153330A (ja) 1995-06-16

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