US 3531576 A
Description (OCR text may contain errors)
Se t; 29; 1970 H. HILDEBRAND v 3,531,576
COAXIAL HIGH FREQUENCY CABLE Filed May 24, 1968 FIG.1 F|G.2
INVENTOR. He'lmu'r Hildebrand BY 6 a. m"
ATTORNEY United States Patent Office K Int. Cl. H01b 11/18 US. Cl. 174-28 1 Claim ABSTRACT OF THE DISCLOSURE A coaxial high frequency cable having dielectric spacers between the inner and outer conductors thereof, which are in separated relation to each other and are of a construction which minimizes losses.
BACKGROUND OF THE INVENTION In coaxial high frequency cables it is known that the losses therein are made up of losses due to high-frequency resistance of the conductors; and losses due to leakage from the dielectric means which spaces the outer conductor from the inner conductor. Such leakage losses have a substantial effect on the total losses, and their magnitude depends on the type of dielectric material used, the geometrical structure of the spacer and the volume of the spacer as compared to the total volume of the space between the conductors.
Thus, for low loss power transmission through a coaxial cable, it is necessary that a solid dielectric be used which has a small dielectric loss angle, a small dielectric constant and a volume which is minimal as compared to the total volume of the space between the conductors.
In particular, to meet the last mentioned requirement, it has been proposed to use dielectric discs suitably mounted on the inner conductor at determined axial spacings; the discs being formed of a minimum amount of material, and with openings in the discs to further reduce the quantity of material used.
Also, dielectric spacers have been provided in the form of three upstanding columnar support members extending radially from a ring shaped member at 120 intervals; the ring shaped member being adapted to be snapped about the inner conductor. Further, in another form of known dielectric spacer construction, the individual columnar members are afiixed in upstanding relation to a continuous strip at a determined spacing from each other, the strip then being wound helically about the inner conductor. In this case, the columnar members include a T shaped outer end portion for hearing against the inner surface of the outer conductor, the outer end portion extending substantially axially of the cable, thus being particularly effective in supporting outer conductors of the corrugated type.
However, with all of the known dielectric spacer constructions, it has been found that leakage losses are still relatively large. Also, such spacers are of a complicated construction, expensive to manufacture, and finally, in the case of corrugated inner and/or outer conductors, either can not be used, or if used, must have an increased volume of material in order to provide the necessary support stability.
Accordingly, an object of this invention is to provide improved dielectric spacer means for coaxial cables comprising individual spacer members arranged in spaced relation to each other and being individually mounted on the inner conductor so as to greatly minimize leakage losses.
3,531,576 Patented Sept. 29, 1970 Another object of this invention is to provide dielectric spacer members of the character described, which provide high mechanical load capacity.
Still another object of this invention is to provide dielectric spacer members of the character described which provide materially reduced amounts of solid dielectric in zones immediately adjacent the inner conductor where the highest field strength is found in the dielectric portions at the inner conductor.
Yet another object of this invention is to provide improved dielectric spacer members of the character described, which materially reduce the amount of solid dielectric required, thus reducing manufacturing costs, while retaining good load capacity and providing a substantial reduction in leakage losses.
Other objects in part will be obvious and in part hereinafter described.
BRIEF DESCRIPTION OF THE DRAWING In the drawing, FIG. 1 is a transverse elevational view showing a dielectric spacer construction embodying the invention;
FIG. 2 is a side elevational view thereof;
FIG. 3 is a view similar to that of FIG. 1, showing the spacer construction applied to a corrugated inner conductor; and
FIG. 4 is a side elevational view thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS. 1 and 2, 10 designates a dielectric spacer construction embodying the invention. The same comprises individual spacer members generally indicated at 11 which are fixed in upstanding relation to the usual inner conductor 12. v
The spacer members 11 are formed of molded synthetic resin of suitable dielectric value and include a tapered pin portion 13 extending downwardly from a footing portion 14 which is adapted to seat on the outer surface of inner conductor 12. The inner conductor 12 is prepunched with spaced openings for receiving the pin portions 13. The openings are arranged to locate members 11 in spaced relation to each other, and preferably in a spiral line about conductor 12.
The taper of the pin portions 13 and the metal portions pressed out in the formation of the openings in inner conductor 12, serve to insure a tight connection between members 11 and inner conductor 12; the pressed out metal portions forming barbs or tangs for engaging the pin portions 13.
Alternatively, the pin portions 13 may be of metal, particularly when the inner conductor 12 is quite thin. In such case, the metal pin portions 13 may be pressed directly into the wall of inner conductor 12, at the selected locations.
The spacer members 11 include reinforcing rib portions 15 and an elongated support surface 16 at the outer ends thereof. Preferably, the members 11 are so mounted on inner conductor 12 so as to have the elongated support surfaces 16 thereof extending axially of the conductor 12 to thereby provide support for the usual outer conductor, not shown, found in coaxial cables.
In FIGS. 3 and 4 is shown another embodiment of the invention, wherein the inner conductor 12 is corrugated, the corrugations being shown at 17. In this case, members 11 have their footing portions 14 formed with ribs 18 to be received in corrugations 17.
It will be apparent, that with the individual dielectric spacer members 11, the amount of dielectric material adjacent the inner conductor 12, is materially reduced, thereby reducing leakage losses. Yet, such members 11 provide good mechanical load capacity for supporting the outer conductor, not shown.
It is understood that members 11 may be secured to inner conductor 12 by other means, as by adhesive, or the like.
As various changes might be made in the herein disclosed embodiments without departing from the spirit of the invention, it is understood that all matter herein shown or described shall be deemed illustrative and not by way of limitation, except as set forth in the appended claim.
1. A coaxial high frequency cable having inner and outer conductors, dielectric spacer means extending between said conductors, said spacer means comprising a plurality of separate, longitudinally spaced spacer members, each spacer member comprising an intermediate portion of limited, minimal cross section, a footing portion integral with the inner end of said intermediate portion and seated on a limited outer surface portion of said inner conductor, and pin means integral with and projecting from said footing portion, the wall of said inner conductor being formed with successive openings in axially and circumferentially displaced relation to each other for tightly receiving and engaging pin means of the respective spacer members, wherein said inner conductor is corrugated and the footing portion of said spacer members includes a rib portion receivable in said corrugations.
References Cited UNITED STATES PATENTS 2,428,051 9/ 1947 Touraton 174-28 FOREIGN PATENTS 482,912 4/ 193 8 Great Britain.
- LEWIS H. MYERS, Primary Examiner A. T. GRIMLEY, Assistant Examiner US. Cl. X.R. 174--99, 102