US3373242A - Resilient inner conductor support - Google Patents

Description

March 12, 1968 D. N. SEWELL 3,373,242

RESILIENT INNER CONDUCTOR SUPPORT Filed Feb. 15, 1967 3 Sheets-$heet l March 12, 1968 p.51. SEWELL RESILIENT INNER CONDUCTOR SUPPORT 3 Sheets-Sheet 2 Filed Feb. 15, 1967 March 12, 1968 D. N. SEWELL 3,373,242

RESILIENT INNER CONDUCTOR SUPPORT Filed Feb. 15, 1967 r 3 Sht$-3heet i United States Patent 0 19 Claims. (Cl. 174-41 ABSTRACT 0F THE DISCLOSURE A resilient inner conductor support for use in coupling adjacent, axially-spaced inner conductor sections of a coaxial transmission line to allow, and provide mechanical and electrical compensation for, relative movement between the various portions of the transmission line. Each support includes rigid coupling rings secured to the ends of adjacent inner conductor sections and a relatively rigid beryllium copper connector located therebetween. No portion of the support protrudes beyond the outer circumference of the inner conductor sections. Each connector has a ring-shaped base of smaller diameter than the inner conductor sections and two, axially-spaced, flexible disc portions extending radially outwardly from the base, thereby defining an annular space, channel shaped in cross-section, for receiving a dielectric support that maintains the inner and outer conductors in coaxial relation. A flange at the outer circumference of each disc portion is secured to the adjacent coupling ring. In one disclosed embodiment, the connector is constructed of several circumferentially spaced, arcuate, channel-shaped in cross-section beryllium copper connector portions, each of which has a number of relief slots extending through its base portion and radially outwardly therefrom.

Summary of invention This invention relates to electrical transmission lines and more particularly to coaxial transmission lines that transmit electrical energy at microwave frequencies and to compensation structures for use in such coaxial lines. This application is a continuation-in-part of my copending application, Ser. No. 555,147 filed June 3, 1966.

in high power coaxial transmission lines, such as those employed in high speed search radar systems, internal loadings are imposed on the inner conductor sections. In conventional coaxial line design the anchor connector and the inner conductor is employed to accommodate differential expansion and external forces imposed on the line. The resulting wear or chafimg at the slip connection, however, reduces the contact quality which promotes resistance heating, causing relaxation of the expansion springs, build up of resistive oxides, and allows series arcing to occur which very rapidly destroys the joint and contaminates the adjacent transmission line with the residue. Also, the production of metallic particles may seriously degrade the electrical quality of the transmission lines. Such conductor slipping also generates electrical noise which can significantly impair the quality of electrical signal transmission in the system.

It is an object of this invention to provide a novel and improved coaxial electrical transmission line in which slippage between the inner conductor sections and other components of the line is essentially eliminated.

Another object of the invention is to provide a novel and improved coaxial support structure for a coaxial transmission line that provides compensation for differential movement between the two conductor elements of the line.

Still another object of the invention is to provide a novel and improved insulator spacer support structure that permits differential movement between the inner and outer conductors of the coaxial line without adversely affecting the electrical characteristics of the transmission line.

In accordance with the invention, there is provided a compensation structure for a coaxial transmission line that includes tubular inner and outer conductors. The compensation structure is arranged for connection between adjacent sections of the inner conductor and preferably receives an insulator spacer such as a disc of dielectric material, so that it functions as a support structure to maintain the inner and outer conductors in coaxial relation. The compensation structure comprises two flexible, electrically conductive transition portions of disc configuration that extend radially outwardly to a maximum circumference that equals the outer circumference of the inner conductor and in opposite axial directions from a base portion to the respective sections of the inner conductor. These transition portions permit the inner conduct-or sections to move towards and away from one another without any modification of the electrical conductivity of the inner conductor and thus provide compensation for mechanical stress to which the transmission line is subjected. In a preferred embodiment, the ringshaped compensation structure comprises a plurality of arcuate transition portions of generally channel-shaped cross-section, each of which extends radially outwardly from its base and in opposite axial directions at its outer circumference. The channel base and sides of each transition portion may include a plurality of relief slots to provide for radial movement of the channel base in an elec trical compensation action in addition to axial movement of the structure in response to the differential movement of the inner and outer conductors.

In a particular embodiment a series of sections of inner conductors are assembled with flexible insulator support structures connecting adjacent sections of the series. This assembled length of inner conductor sections is inserted within an outer conductor section that has a length somewhat less than the inner conductor assembly in relaxed condition. An anchor insulator is secured at one end of the outer conductor section and one end of the inner conductor assembly and then the next length of inner conductor is assembled and the anchor insulator joining the two lengths of inner conductor assembly is fixed in place relative to the outer conductor so that the inner conductor is compressed axially loading the resilient support structures in their desired configuration and assuring a positive force condition on the conductor structures throughout its intended range of operation. In this assembly the differential movement compensation structures are preferably distributed along the length of the inner conductor at the several resilient insulator support structures. By appropriate design of the length relationship between the inner and outer conductors, the desired electrical characteristics and compensation for mechanical expansion requirements of the transmission lines are achieved. This structure provides a sturdy support structure that is relatively easy to electrically compensate and which provides a more rigid high power coaxial transmission line which operates at high efiiciency over a large range of internal loadings which might be imposed on the line and without the generation of significant electrical noise due to movements of the several components of the line relative to one another.

Other objects, features and advantages of the invention will be seen as the following description of particular embodiments thereof progresses, in conjunction with the drawings in which:

FIG. 1 is a sectional view of a portion of a coaxial transmission line constructed in accordance with the invention;

PEG. 2 is a sectional view showing details of the insulator spacer support structure employed in the embodiment shown in FIG. 1 in relaxed condition;

FIG. 3 is a view similar to FIG. 2 showing the insulator support structure in compressed condition as occurs during use;

FIG. 4 is a sectional view of a modified form of a transmission line in employing a second form of insulator support structure constructed in accordance with the invention;

FIG. 5 is an exploded view of components of the support structure employed in the line shown in FIG. 4;

FIG. 6 is a sectional view showing details of the support structure construction of the type illustrated in FIGS. 4 and 5;

FIG. 7 is a sectional view of another form of support structure that is slightly different from that structure shown in FIGS. 4 to 6;

FIG. 8 is a sectional view of a transmission line employing a third form of insulator support structure constructed in accordance with the invention;

FIG. 9 is a sectional end view of the structure taken along line 9 9 of FIG. 8;

FIG. 10 is a perspective view of a component of the support structure shown in FIG. 8; and

FIGS. 11 and 12 are diagrammatic plan views of components of the structure shown in FIG. 8.

Description of particular embodiments With reference to FIG. 1 there is shown a coaxial transmission line having an outer conductor 10 made up of sections ltla, 10b, etc. and an inner conductor 12 which is made up of a plurality of sections 12a, 12b, 12c, etc. The sections Illa, 10b of the outer conductor are secured together with conventional flange structures 14 while the sections of the inner conductor 12 are connected together with coupling structures 16, each of which receives and supports a disc insulator 18 which provides support for locating the inner conductor 12 in coaxial relation to the outer conductor to.

The construction of the insulator disc support which connects adjacent sections of the inner conductor together may be better understood with reference to FIGS. 2 and 3. That structure includes a rigid base element 20 in the form of a copper bushing which has a centrally located spacer ridge 22 and a recessed seat surface 24, 26 on either side of ridge 22. Secured to each surface 24, 26 is a beryllium copper flexible disc structure 30, 0.032 inch in thickness that includes a flange portion 32 extending in one direction at its inner periphery and a second flange portion 34 extending in the opposite direction at its outer periphery. The flange portions are formed in a flat disc and then the disc may be subjected to 600 F. for two hours in a heat treating operation. These two flange portions are connected by a generally radially extending transition portion 36. The inner flange portions 32 of each disc are silver soldered to the corresponding surfaces 24 and 26 of the bushing base member 20 so that those flanges are in substantially the same plane as the surface of ridge 22.

The outer flanges 34- are similarly silver soldered to copper ring structures ll? which function as mating connectors for receiving the sections of the inner conductor 12. Each ring 46 is of similar configuration to bushing 20 but of larger diameter and has a surface 42 on which the flange 34 is secured, a surface 44 on which the end of that tubular inner conductor 12 is secured as by brazing or silver soldering, and a spacer ridge 46, the surface of which is flush with the outer surfaces of conductor 12 and flange 34 in assembled condition.

An insulator disc member is is mounted on this support structure, for positioning between the inner and outer conductors after assembly of the compensation structure has been completed.

The assembled length of inner conductor with disc insulators 13 positioned on it has secured to either end anchor insulator structures 59 which cooperate with the flange 14 via disc insulator supports 52 to lock the inner conductor section rigidly relatively to the outer conductor at that point. in the H8. 1 arrangement the disc 52 is rigidly secured at its outer periphery between the elements of flange structure 14 which are secured together by bolts and its inner periphery is clamped by the base as of the anchor support structure. These support structures may be of conventional configuration. The left anchor insulator support structure, it will be noted, projects beyond the end or" the outer conductor in when the inner conductor 12 is in relaxed condition. When the next length of outer conductor is clamped to the flange 1d it forces the disc insulator 52 carried by the anchor structure base 56 to the right compressing each support structure substantially to the position shown in FIG. 3 so that the entire inner conductor structure is placed under a degree of axial compression. The assembly when complete provides a rigid structure suitable for carrying large amounts of power and may be subjected to large mechanical loadings such as are encountered in a high speed search radar system without introduction of electrical degradation, due either to change in the electrical characteristics of the line under the applied loadings, to the production of metallic dust, or noise generated as a result of the movement of one component of the transmission line relative to the other.

A second embodiment of the invention is shown in FIGS. 4 6 in which similar reference numerals are used to denote similar structural elements, with a prime being utilized to denote the modified structure. As will be seen in FIGS. 46 the insulator support structure includes a similar rigid ring 20' that has a central ridge 22' and two support surfaces, 24' and 26. Flexible discs 3% each have an inwardly turned flange 32 at its inner periphery and an outwardly turned flange 34' at its outer periphery which are connected together by the radially extending wall portion 36. The inner flange 32 is received on the support surface 24 in a similar manner to embodiment shown in FIGS. 1-3 while a different type of connector structure 4&3 is employed to couple the support structure to the inner conductor of the transmission line. This connector structure is made in two sections 60, 62 which have mating saw tooth surfaces 64-, 66. Holes 68 are drilled through each section and when the two sections are assembled together as shown in FIG. 4, these holes are aligned so that a suitable fastener such as a bolt 70 (FIG. 7) may be passed through the two sections to secure those sections together. Section 60 includes an annular surface 42' on which outer flange 34' of disc 3% is secured. Section 62 has a similar annular recessed surface 44 which receives the end '72 of the inner conductor 12' in a manner similar to that shown in FIG. 2.

The use of this resilient support structure in an anchor insulator configuration is shown in FIG. 6. In that figure, the inner periphery of an insulator disc 52' is received in supporting relation within the recess formed by the base 22 of the support structure 20 and the flange portions 32' of the flexible disc members 30. One disc is secured to saw tooth connector member 6% that has an axially extending hole through it while the other flexible disc is connected to the anchor insulator structure that includes coupling member 82, spacer ring 84, and a second coupling member 36. Member 82 has an annular recessed surface 88 at its end which receives the flange 34- of a flexible disc so that a smooth continuous surface with the outer diameter of the inner conductor 12' is provided. The spacer ring 8- which has been machined to a length suitable to match the overall length of the outer conductor assembly to the inner conductor assembly, is disposed between the two coupling members 82, 86. An

aligning pin 90 is utilized to define the proper relation between those two coupling members and the structure is assembled together by a bolt 92 which passes through the aperture in coupling section 60 to secure the anchor support structure together.

The flange assembly which receives the anchor insulator 52 at its outer periphery and also secures the adjacent sections of the outer conductor together includes two flange members 100 and 102 which are secured together by a bolt 54' and may include seal member 104 between them to seal the transmission line so that a pressurized gas may be used within the transmission system if desired.

A view of an intermediate support structure of the type employing two saw tooth coupling members for use in the transmission line shown in FIG. 4 is shown in greater detail in FIG. 7.

A third embodiment of the invention is shown in FIGS. 8 through 12 in which similar reference numerals are used to denote similar structural elements, with a double prime being utilized to denote the modified structure. As will be seen in FIGS. 8 and 9, the insulator support structure includes a ring-shaped compensation structure 30" interposed between sections 12g and 121" of an inner conductor approximately 4 inches in diameter. As shown, structure 30 comprises a plurality of circumferentially spaced, beryllium copper arcuate transition portions 31a, 31b, etc., each of which has a substantially channel-shaped cross-section, including a pair of disc portions 36" extending radially outwardly from a base portion 32" having a radius of approximately 2.75 inches, to a maximum radius substantially equal to the outer radius of the inner conductor, and a pair of outer flanges 34" extending axially in opposite directions from the outer periphery of disc portions 36". The thickness of base portion 32", flanges 34" and disc portions 36" is 0.031 inch.

As shown more clearly in FIG. 10, each transition portion 31 includes a plurality of relief slots 33 approximately 0.020 inch wide extending through base portion 32" and radially outwardly through a major portion of the radial width of disc portions 36".

The outer flanges 34" of each transition portion 31 are silver soldered to copper ring structures 40 which function as mating connectors for receiving the sections of the inner connector 12". Each ring 40" has a circumferential, axially-facing groove 41, 0.13 inch deep, in which the flange 34" is secured, a surface 44" on which the end of the adjacent tubular inner connector 12" is secured as by brazing or silver soldering, and a spacer ridge 46.

An insulator disc 18" is mounted on this support structure for positioning between the inner and outer conductors after assembly of the compensation structure has been completed. When several conductor sections are assembled, as in FIG. 1, each support structure is compressed from the position shown in FIG. 12 to substantially the position shown in FIG. 3 so that the entire inner conductor structure is placed under a degree of axial compression. As shown in FIGS. 11 and 12, the differential movement between axially adjacent conductor elements of the inner conductor line which is accommodated by compensation structure 30" results in axial movement of disc portion 36 and radial movement of the free base portion 32". It has been found that the small impedance changes introduced by these coordinated axial and radial movements are to a large measure self-cancelling.

It is frequently desired to locate these resilient loading compensation structures along the inner conductor assembly with non-uniform spacing so that the small impedance changes that may be introduced by the dielectric support elements 18 do not add cumulatively.

While particular embodiments of the invention have been shown and described, various modifications thereof will be apparent to those skilled in the art and therefore 6 it is not intended that the invention be limited to the disclosed embodiments or to details thereof, and departures may be made therefrom within the spirit and scope of the invention as defined in the claims.

What is claimed is:

1. A coaxial transmission line comprising a tubular outer conductor; a tubular inner conductor having a plurality of axially aligned sections; a series of spaced connectors coupling adjacent sections of said inner conductor together,

each said connector providing an electrical connection between said adjacent sections and including a base portion and two flexible, electrically conductive disc portions extending radially outwardly therefrom and providing relatively rigid compensation for differential movement between the inner and outer conductors; and, dielectric spacer members disposed between said inner and outer conductors for maintaining said conductors in coaxial coalition.

2. The transmission line as claimed in claim 1 wherein each said connector is substantially channel-shaped in crosssection and includes a plurality of relief slots extending through said base portion and radially outwardly therefrom through a portion of said disc portions.

3. The transmission line as claimed in claim 2 wherein each said connector includes a plurality of circumferentially-spaced arcuate transition portions, each of said elements having a substantially channel-shaped cross-section.

4. The transmission line as claimed in claim 3 wherein each of said arcuate transition portions includes at least one relief slot extending through the base portion thereof and radially outwardly therefrom through a portion of the radially-extending disc portions of said transition portion.

5. The transmission line as claimed in claim 4 wherein said transition portions are relatively rigid elements of beryllium copper.

6. The transmission line as claimed in claim 1 and further including anchor structures at spaced locations along said transmission line for compressing the inner conductor sections axially relative to the outer conductor so that said radially extending resilient disc portions are maintained under distorting force in normal use of said line.

7. The transmission line as claimed in claim 6 wherein a plurality of said connectors are spaced along said inner conductor at random intervals between said anchor structures.

8. The transmission line as claimed in claim 1 wherein said disc portions are a relatively rigid element of berylliurrr copper.

9. The transmission line as claimed in claim 1 wherein said disc portions form a smooth continuous surface with said inner conductors and no part of said disc portions protrudes beyond the outer circumference of said inner conductor.

10. The transmission line as claimed in claim 9 wherein said dielectric spacer members include a disc insulator support which is positioned between the spaced disc portions of a connector.

11. The transmission line as claimed in claim 10 wherein each said connector further includes a rigid support element of electrically conductive metal and each said .disc portion has a first flange at its inner periphery and a second flange at its outer periphery, said disc portions being positioned on opposite sides of said support element with said first flanges secured in electrically conducting relation to said support element and said second flanges secured in electrically conducting relation to the correspending sections of said inner conductor.

12. A spacer support structure for use in a coaxial transmission line comprising two coupling members of diameters corresponding to the inner conductor of said line and a ring-shaped, electrically conductive connector having a base portion of smaller diameter than said inner conductor and two flexible, electrically conductive disc portions extending radially outwardly therefrom, each disc portion having an outer flange extending in one axial direction, each said flange being secured to the corresponding conductor coupling member, said conductive connector defining an annular space for receiving a radially extending dielectric support member therein for providing support to maintain inner and outer conductors of a transmission line in coaxial relation.

13. The spacer support structure as claimed in claim 12. wherein said base portion comprises an electrically conductive base member and said disc portions each have an inner flange extending in the other direction from the outer flange of said disc portion, said inner flanges being secured in electrically conductive relation to said base member.

14. The spacer support structure as claimed in claim 12 wherein said connector is adapted to form a smooth continuous surface with said inner conductor such that no part of said disc portions protrudes beyond the outer circumference of the inner conductor to which they are to be connected.

15. The spacer support structure as claimed in claim 1.2 wherein said disc portions are relatively rigid elements of beryllium copper.

16. The spacer support structure as claimed in claim 12 wherein said connector is channel-shaped in cross-section and includes a plurality of relief slots extending through said base portion and radially outwardly therefrom through a portion of said disc portions.

17. The spacer support structure as claimed in claim 16 wherein said connector includes a plurality of circumferentially-spaced, arcuate transition portions, each of said transition portions having a substantially channel-shaped cross-section.

18. The spacer support structure as claimed in claim 17 wherein each said transition portion includes at least one relief slot extending through the base portion thereof and radially outwardly therefrom through a major portion of the radially-extending flanges of said transition portion.

1'). The spacer support structure as claimed in claim 18 wherein said transition portions are relatively rigid elements of beryllium copper.

References Cited UNITED STATES PATENTS 3,327,257 6/1967 Weiss 174-28 X 3,331,911 7/1967 Whitehead 174-28 X 2,774,944 12/ 1956 Lintzel 333-96 2,044,580 6/1936 Leach 333-% X 2,589,328 3/1952 Bondon 33396 FOREIGN PATENTS 74,178 5/ 1952 Denmark. 963,860 1/1950 France.

OTHER REFERENCES Cornes, R. W; A Coaxial-Line Support For 0 to 4000 rnc., Proceeding of the Institute of Radio Engineers, vol. 37, No. 1, January 1949.

LARAMIE E. ASKIN, Primary Examiner.

A. T. GRIMLEY, Assistant Examiner.

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