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Publication numberUS2510358 A
Publication typeGrant
Publication dateJun 6, 1950
Filing dateMar 20, 1946
Priority dateMar 20, 1946
Publication numberUS 2510358 A, US 2510358A, US-A-2510358, US2510358 A, US2510358A
InventorsWolf Lester J
Original AssigneeRca Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Art of making concentric transmission lines
US 2510358 A
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Description  (OCR text may contain errors)

June 6, 1950 WOLF 2,510,358

ART OF MAKING CONCENTRIC TRANSMISSION LINES Filed March 20, 1946' IN! IN TOR.

465561 J 1461/ BY @QM irrakwsy Patented June 1950 ART OF KING GONGENTBIC TRANS- MISSION LINES Lester J. Well, Audubon,

Corporation oi America, ware N.J., assignmaeorporaflon to Radio of Dela- Application March 20, 1946, Serial No. 655,697 4 China. (Cl. 174-28) making electrical transmission lines, particularly concentric transmission lines, and has special reference to the provision of improvements in so called button type insulators for maintaining the separate conductors of such a line in spaced relation.

The prior art shows both elastic and non-elastic button' type insulators for supporting an inner conductor in coaxial relation with respect to an outer conductor. Elastic buttons, constituted of paragutta or other rubber-like materials, possess the advantage of being tight-fitting (in that they are self-biased into engagement with the outer conductor) but are seldom used because such materials exhibit a higher power factor and a higher dielectric constant than is desirable where currents of radio frequencies are involved. On the other hand, spacers constituted of many of the common plastic or ceramic materials possess the requisite insulating properties but, because of their non-elastic nature, are not tight-iitting. This latter disadvantage is especial- 1y objectionable when the line is called upon to handle currents of substantial voltage since, in this case, even a relatively minute air-space around the periphery of the button (1. e. between the button and the inner surface of the outer conductor) augments the possibility of corona discharge.

Accordingly, the principal object of my present invention is to obviate the foregoing and other less apparent objections to present day transmission lines.

A related object of my invention is to provide a coaxial cable which shall exhibit an extremely low attenuation factor for currents of radio frequency, and one wherein the possibility of corona discharge is minimized.

Another and specific object of my invention is to provide an improved button-type insulating spacer for the inner conductor of a coaxial cable, and one which is capable of being maintained in intimate, non-yielding contact with the inner surface of the outer conductor.

Still another object of my present invention is to provide a simple yet reliable method of manufacturing a concentric transmission line and one which in its practice ensures the correct permanet and rigid alignment of the inner conductor with respect to the outer conductor.

Stated generally, my invention is predicated upon an appreciation of the fact, and its application to the art of making electrical transmission lines, that certain non-elastic yet distortable 2 synthetic plastic materials, when distorted, exhibit a "plastic memory," i. e. the ability, especially when heated, to return to the shape and dimensions which they possessed when cast, or prior to being distorted. Among the materials possessing this property, as well as the insulating properties required for the purposes of this invention, are (1) polyethylene, (2) polytetrafluorethylene, (3) cross-linked polystyrene, (4) cross-linked polymethyl methacrylate resin (5) polyamide resins and (6) solid silicones.

In carrying my invention into effect I either cast, or cut from a sheet of such material, a desired number of buttons each of a diameter slightly larger than the inner diameter oi the outer conductor of the transmission line and string said buttons in spaced relation on the wire or tube which is to comprise the inner conductor of the line. Prior to the "stringing operation I distort the said buttons to permit the assembly to be entered into the bore of the outer conductor and, finally, I heat the spacers, either by conduction or with an electric field, to cause them to assume substantially the original shape and dimensions dictated by their plastic memory.

Other details of construction together with additional objects and advantages will be apparent and my invention itself will be best understood by reference to the following specification and to the accompanying drawing, wherein:

Fig. l is a view in perspective of a button-type spacer which is constituted, in accordance with my invention, of a distortable insulating material, having a plastic memory;

Fig. 2 is a similar view of the button of Fig. 1, when distorted;

Fig. 3 is a broken-away view of a concentric line showing the manner in which the inner condoctor and its distorted spacers are assembled within the outer conductor;

Fig. 4 is a sectional view of a button distorted in an alternative form and Fig. 5 is a broken-away view of the transmission line of Fig. 3 after the button-like spacers oi. Figs. 2 and 3 have been caused to assume the original shape and dimensions dictated by their plastic memory.

In the drawing wherein I have used like reference characters to designate the same or corresponding parts in all figures I designates the inner conductor, and 2 the outer conductor of a concentric transmission line or cable. The dimensions of the cable which are pertinent to my invention are the inner diameter D of the outer conductor and the outer diameter d of the inner conductor. In the completed cable shown in Fig. the inner conductor i is supported within the outer conductor 2 by insulating button-like spacers 3 which are formed in accordance with my invention of a material (e. g. polyethylene) having a plastic memory.

As shown in Fig. 1 the button 3 in its original form, has parallel major faces a and b and has an outer diameter D slightly larger than the inner diameter D of the outer conductor 3, and an inner diameter d slightly less than the outer diameter d of the inner conductor i. As previously indicated this button 3 may conveniently be cut or punched from a thin sheet of material, though it may be formed by casting in a mould. Subsequently, preferably prior to their assembly upon the inner conductor, the buttons 3 are placed in a coining die or pressure mold (not shown) and forced to change their shape, for example in one of the patterns shown in Figs. 2, and 3, or 4. In Figs. 2 and 3 the button has been shaped by the die in the form of a convex cone and, in the embodiment of Fig. 4 comprises a hollow right circular cone wherein the thickness of its walls is greater adjacent the apex of the cone than it is at the base or lower perimeter. I prefer the latter form for high voltage work since the thickness of the material is greatest adjacent to the inner conductor where the lines of force of the field are the more concentrated. Irrespective of the exact shape for the button the coining die should operate to compress the blanks in such a way that the outer diameter is made slightly less than the inner diameter D of the outer conductor and the inner diameter of central aperture is made slightly larger than the outer diameter d of the inner conductor i which it is designed to accommodate.

When the insulating blanks of Fig. 1 have been distorted into one of the forms shown in Figs. 2 or- 4 they are assembled or strung in spaced relation on the inner conductor 51 which is then placed, with the spacers properly positioned, within the outer conductor 2. As shown in Fig. 3, at this time the insulators 3 are loose in the outer conductor and on the inner conductor. Thereafter the insulating buttons or, alternatively, the entire assembly is heated to a temperature (say 300 C. or higher) sufficient to activate the plastic memory of the insulating material so that the buttons are urged to change their shape in accordance with their past history. In the instant case the buttons tend to go back to the shape shown in Fig. 2. As a result the buttons are urged into intimate contact with both the inner and outer conductors l and 2, though because of their original oversizeddimensions they will not quite achieve their original shape.

It will now be apparent that my invention atfords a simple yet reliable method of manufacturing a concentric transmission line having an extremely lowattenuation factor for currents of radio frequencies and one wherein the possibility of corona is minimized.

I claim:

1. A spacer for supporting an inner conductor within an outer conductor, said spacer comprising a button having a curved face of a diameter less than the inner diameter of said outer conductor and formed by distorting a blank of a relatively larger diameter constituted of a distorteble insulating material of the type having a plastic memory.

2. The invention as set forth in claim 1 and wherein said button comprises a cone having a concave face.

ing said spacers to permit said assembly to be' entered into said outer conductor, and then heating said spacers to cause them to assume the original shape and dimensions dictated by their plastic memory.

LESTER J. WOLF.

REFERENCES omen The following references are of record in the file of this patent:

UNI'Im STATES PATENTS

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2636923 *Dec 30, 1948Apr 28, 1953Standard Telephones Cables LtdLow capacitance cable and method of making the same
US2736175 *Jun 12, 1953Feb 28, 1956 Electrically operated absorption
US2774812 *Apr 27, 1953Dec 18, 1956Clark Richard UHermetically sealed electric terminal
US2847670 *Nov 12, 1953Aug 12, 1958British Telecomm Res LtdImpedance matching
US3270577 *Dec 7, 1964Sep 6, 1966Consolidation Coal CoIdler rollers and method of making the same
US3299492 *Aug 14, 1963Jan 24, 1967Simmonds Precision ProductsElectroformed inner tube for tank unit
US3345450 *Jul 26, 1965Oct 3, 1967Westinghouse Electric CorpElectric power transmission system
US3943470 *Sep 20, 1974Mar 9, 1976Sealectro CorporationRight angle connector
US4507631 *Dec 22, 1982Mar 26, 1985Thomson-CsfDevice comprising a cavity and a linear resonator fixed within said cavity, and a method of assembly of said device
US4772112 *Jun 19, 1986Sep 20, 1988Cvi/Beta Ventures, Inc.Eyeglass frame including shape-memory elements
US4895438 *Jun 1, 1988Jan 23, 1990Cvi/Beta Ventures, Inc.Eyeglass frame including shape-memory elements
US4896955 *Dec 5, 1988Jan 30, 1990Cvi/Beta Ventures, Inc.Eyeglass frame including shape-memory elements
US4954095 *Mar 1, 1989Sep 4, 1990Cogan Kenneth LCable employing tubular conductors
US5870064 *Oct 1, 1997Feb 9, 1999Tx Rx Systems Inc.Signal transmission antenna mast
US5880402 *Jul 22, 1996Mar 9, 1999Nugent; Steven FloydHigh fidelity audio interconnect cable
US6653555Nov 6, 2001Nov 25, 2003Steven Floyd NugentBare-wire interconnect
US6974912 *Mar 5, 2004Dec 13, 2005Selby Peter EInsulator and connect cable and method of making same
US7777130Jun 18, 2007Aug 17, 2010Vivant Medical, Inc.Microwave cable cooling
US7849928Jun 13, 2008Dec 14, 2010Baker Hughes IncorporatedSystem and method for supporting power cable in downhole tubing
US8093500Jun 14, 2010Jan 10, 2012Vivant Medical, Inc.Microwave cable cooling
US8519268Feb 12, 2009Aug 27, 2013Rohde & Schwarz Gmbh & Co. KgCoaxial line with supporting rings
US20110253409 *Jun 29, 2011Oct 20, 2011John Mezzalingua Associates, Inc.Coaxial cable connector insulator and method of use thereof
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WO2013160493A1 *Apr 25, 2012Oct 31, 2013TORIBIO CANTERO, Josť AntonioElectric cable for transmitting analog and/or digital signals
Classifications
U.S. Classification156/47, 333/244, 174/167, 174/110.0SR, 439/578, 285/124.3, 174/28, 29/600, 174/138.00R, 285/423, 29/601, 174/111
International ClassificationH01B11/18
Cooperative ClassificationH01B11/186
European ClassificationH01B11/18D8B