US 1998826 A
Description (OCR text may contain errors)
April 23, 1935.
J.'F. WENTZ ELECTRICAL CONDUCTING SYSTEM Filed March 16, 1955' 7 FIG.
INVENTOR J. F WENTZ B) i V g ATTORNEY Patented Apr. 23,- 1935 s I I UNITEDYSTATES PATENT OFFICE ELECTRICAL CONDUCTING SYSTEM Jesse F. Wentz, New York, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application March 16, 1933, Serial No. 661,025
8 Claims. (01. 173-265) This invention relates to electrical conducting contact with either of the conductors, which systems and more particularly to 'the mechanical makes for low leakage losses. structure of systems in which the conductors are Another feature is that the contact between in coaxial relation. r the insulating member and the conductor is not An object of the invention is to improve the continuous, which not only tends to reduce the 5 mechanical and electrical properties of a coaxial leakance, but also reduces the amount of solid conductor system. insulating material traversed by the highly con- A more particular object'of the invention is to centrated electric field immediately around the increase the ruggedness and flexibility of' the central conductor.
10 insulating structure separating the members-of Other objects and features of the invention may 10 a coaxial conductor system, and to reduce the appear from a consideration of the specific illusenergy loss attributable to said structure. trative embodiment which is shown in the acv For electrical signaling systems operating at companying drawing and which is now to be defrequencies extending into the radio frequency scribed.
range atransmission system comprising a central Fi 1 WS 008x131 conductor assemblage, l5 conductor and atubular return conductor coaxial and Fig. 2 s w schematically Separator in therewith is especially. well adapted. One of accordance with the invention. the chief advantages of the structure is that the The coaxial pair illustrated in Fig. 1 comprises dielectric between the conductors is not subject a central conductor I and a tubular return conto varying atmospheric conditions but can be ductor 2, the latter being preferably made up of 20 maintained in a uniformly dry condition. The a number of profi d Strips 5 held in Place y it ideal dielectric from an electrical standpoint me lli indin 4,111 accordance w pp wouldbe purely gaseous or vacuum. There would invention as described in his application for then be no solid material traversed by the elec- Letters Patent bearing Serial No. 630,552, filed tromagnetic fields associated with the signaling August 26, 1932. Connected to the terminals of 25 currents, and the signal attenuation due to eddy the pa is represented Signaling apparatus currents would accordingly be low. So also there which may be, for example, the terminal circuits would be no loss caused by signaling currents of a high frequency carrier communication syspassing by conduction through the dielectric tem, a suitable form of which is shown in Espenfrom one conductor to the other. The capacischied et al. Patent 1,835,031, December 8, 1931. 30
tance, a third factor affecting signal attenuation, The separator 3, shown in greater detail in should likewise-b e as low as possible and for this Fig. 2, comprises a strip of tough, resilient inreason the efi'ective dielectric constant of the isulating material which has been twisted on its medium separating the conductors should be as own longitudinal axis and then wound in a relanearly unity as possible. tively long spiral about the central conductor I. 35
The mechanical requirements of the system, The dielectric constant of the material should however, demand that a sufilcient amount of solid be as low as possibleof the Various materials material be used to maintain the inner conductor now available, 6811111058 acetate has been found in a central position within the outer conductor. to have the best combination of electrical End Since the conducting pair is subject to bending mechanical charactefistics for the present u 40 during manufacture and installation a certain P other mateflflls may be used, bvluslyv degree 1 resiliency and ruggedness in the where factors other than optimum mechanical rating member is necessary and electrical performance are controlling.
In accordance with the present invention, there The proportions of the various members of the is provided an insulating or separating member axial conductor system harem described my for coaxial conductors which meets with eminent be g is i gag on the success the electrical and mechanical requirement absolu e name rs W W an e mechanical and electrical requirements to bemet. In a just described In brief the typical embodiment therewere used a central an elongated insulating member greater. in width conductor of two millimeters, diameter and return 50 than in thickness, a fiat strip, for example, twisted cdndilctor of seven millimeters. internal diameter, on'its own longitudinal axis and wound spirall The insulating strip was twisted with a pitch of about the central conductor. ten millimeters and wound about the central con- A feature of the foregoing construction is that ductor in a helix having a pitch of twenty millionly the edge of the insulating member comes in meters and a sense opposite to that of the twist of the strip. In this particular case the thickness of the strip was 0.3 millimeter. The thickness should generally be not less than one-tenth the width of the strip or suilicient rigidity may not be obtained. As a general rule, the pitch of twist should be roughly five times the diameter of the central conductor and the pitch of the helix approximately twice as great as that. v
The effective dielectric constant obtained with the specific embodiment of the invention herein described was 1.08, which compares very favorably with that obtainable with other types of separators of equal mechanical strength heretofore known. The leakance loss is practically negligible.
This application is in part a continuation of applicants copending application for patent, supra. Another specific embodiment of the present invention is disclosed and claimed in a copending application for patent bearing Serial No. 1,149, filed by this applicant on January 10, 1935.
- What is claimed is:
l. A radio frequency transmission system comprising a pair of coaxial conductors connected one as the return for the other, the outer of said conductors comprising a hollow, self-supporting tube, and means maintaining the inner of said conductors in position comprising an elongated insulating member of non-circular crosssection twisted on its longitudinal axis. and spiralled about said inner conductor so that it supports said inner conductor only at recurrent points where the longer axis of said cross-section lies in a radial position between said conductors, the remainder of the space between said conductors being substantially gaseous.
2. A system for the transmission of intelligence comprising a pair of coaxial conductors connected one as the return for the other and means for maintaining said conductors in coaxial relation comprising an integral insulating structure twisted on itself and spiralled about the inner of said conductors, saidinsulating structure being non-circular in cross-section and arranged to support said inner conductor only at points where a longer axis of said cross-section liesin a radial position between said conductors.
3. A system for the transmission of intelligence comprising a pair of coaxial conductors connected one as the return for the other and means for maintaining said conductors in coaxial relation comprising an elongated integral insulating structure having a greater cross-sectional dimension in one direction than in another separating said conductors, the greater cross-sectional dimension of said structure occupying only at discrete points along said conductors a radial position between said conductors, the remainder of the space between said conductors being substantially gaseous.
4. A system for the transmission of intelligence comprising a pair of coaxial conductors connected one as the return for the other and means for maintaining the relative positions of said conductors comprising a flat strip of flexible insulating material spiralled about the inner of said conductors, said strip presenting successively its opposite edges to each of said conductors.
5. A system for the transmission of intelligence comprising a pair of coaxial conductors connected one as the return for the other and means for maintaining said conductors in coaxial relation comprising a iiat strip of flexible insulating material twisted on its longitudinal axis and spiralled about the inner of said conductors so that the longer cross-sectional axis of said strip lies substantially radially between said conductors at spaced intervals along said pair.
6. A system for the transmission of intelligence comprising a pair of coaxial conductors connected one as the return for the other and means for maintaining said conductors in coaxial relation comprising a flat strip of flexible insulating material twisted on itself and spiralled about the inner conductor, said spiral being in an opposite sense to and having a pitch approximately twice that of the twist of said strip. i
7. A system for the transmission of intelligence at frequencies of hundreds of kilocycles per second comprising a pair of coaxial conductors and means to separate the two conductors electrically and maintain them in coaxial relation comprising a thin strip of cellulose acetate twisted on itself and spiralled in an opposite sense about the inner of said conductors with a lay roughly twice the pitch of said twist, said separating means being so proportioned that the dielectric between said conductors is chiefly gaseous.
8. A system for the transmission of intelligence at frequencies of hundreds of kilocycles per second comprising a pair of coaxial conductors and means to separate the two conductors electrically and maintain them in coaxial relation comprising a thin strip oi. resilient insulating material twisted about its longitudinal axis with a pitch approximately iive times the diameter of the inner of said conductors, said twisted strip being woimd spirally around said inner conductor in a helical sense opposite to that of the twist of the strip and with a lay approximately twice the pitch of said twist, said separating means being so proportioned that the dielectric between said conductors is largely gaseous.
JESSE F. WENI'Z.