US2116267A - Conductor with air space insulation - Google Patents

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May 3, 1938. KUMMER 2,116,267

CONDUCTOR WITH AIR SPACE INSULATION Filed Nov. 15, 1935 Patented May 3, 1938 UNiTED STATES PATENT OFFICE many, assignor to Felten & werk Actien-Gesellschaft,

Germany Guilleaume Carls- Colome-Mulheim,

Application November 15, 1935, Serial No. 50,034 In Germany November 15, 1934 Claims. (01. 173-265) For the transmission oi high frequencies use is made of coaxial conductors which, for the purpose of obtaining as small a capacity as possible between the conductors, are provided with an air space insulation.

The capacity is reduced in proportion with the amount of insulating material employed and in proportion with the. dielectric constant of 'the insulating material. Naturally, the economy in insulating material must not be carried so far that the mechanical strength is thereby affected. In order to avoid large losses the angle of loss of the insulating material must be small.

The object of the invention is to construct such a cable in such a manner that whilst the capacity is as small as possible the required mechanical strength is ensured to a high degree.

According to the invention, the conductors are separated from one another by a holder consisting of a helix or helices which is or are self-sustaining, being made of an insulating material capable oi retaining the helical shape, the said helix or helices being "hollow and open. The latter expression is tobe understood as defining a helix the 2 interior or which is not filled by another material and the turns of which do not touch each other .but leave an air gap between them.

The said hollow and open helices may be either 1 parallel to the axis of the conductor or in their turn surround the inner conductor in helical lines. In this way the advantage is attained that a very small amount of insulating material is employed to secure a large air-space insulation, whilst at the same time great mechanical 35 strength is attained. Moreover, a cable constructed in this manner isvery flexible and the helices are stressed only with respect to torsion.

A iurther advantage of the construction acw cording to the present invention consists in the easy manner of manufacture of such cables. The individual elements of the cable may be simply bundled together and surrounded by the outer cover it their axes are to run parallel or they may 5 be stranded together in a known manner and then be surrounded by the outer cover.

Polystyrol has been found a suitable insulating material since it has a small dielectric constant, a small angle of loss, great mechanical strength,

. 3 more particularly with respect to torsion, and can easily be shaped.

In order that the distance between two successive turns of the helix shall remain the same at all points during the manufacture of the cable, as may be made of a helix which contains an insertion consisting .of a thin thread capable of resisting tensional stress. This insertion has the further advantage that in the case of breakage the helix does not. unwinditself but=remains in its predetermined position on the conductor.

'If it is desired further to ensure that the helix will not be displaced on the conductor, after the helix has been provided thereon itmay be secured by means of a thread provided thereon and laid in an opposite'direction. This thread also assists in holding the helix onthe conductor.

Various forms of carrying the invention into efiect are illustrated, by way of example, in the accompanying drawing.

Figure 1 illustrates in elevation and Figure 1a in cross-section a cable with a concentric arrangement of the conductors and-having a number or helices parallel to the axis.

Figure 2 illustrates in cross-section a cable with a plurality of conductors anda plurality oi helices Figure 3 illustrates a cable with concentric arrangement of conductors and a distance holder in the form of a helix which is helically arranged.

Figure 4 illustrates a helically arranged helix having inserted therein a threadcanable of resisting tensional stresses.

Figure 5 illustrates an arrangement in which the hellxis secured on the conductor by means of a thread capable of resisting tensional stresses.

Referring to Figures 1 and la, l is the inner conductor, 3 the outer conductor and 2 are helical threads of insulating material provided between the said two conductors, helices run parallel to the axis of the conductor.

. Figure 2 shows in cross-section an arrangement having a number of coaxial conductors. The

middle conducting layers 5 and 6 are separated The axes of the.

from the inner conducting layer 4 and the outer conducting layer '1, as well as from one another by hollow and open helices of insulating material 8.

In theconstruction illustrated in Figure 3 the hollow and open helix I0 is in its turn so arranged as to-run helically around a conductor 9,

being surrounded by the coaxial conductor i I.

Figure 4 illustrates a conductor in which the helix acting as a distance member is providedwith a thread capable of resisting tensional stresses. i2 is the storage reel of the helix it which is provided with the said tension resisting thread it, the conductor [5 being wound with the said helix from the storage reel l2.

Figure 5 illustrates a cable in which the conductor' I. is surrounded by an insulating hollow and open helix I! provided with a tension resisting thread It, which is held on the conductor by means of a thread I9. A winding 20, which may consist offlexible bands of polystyrol, is provided thereon. The outer conductor 2|, consisting of an individual number of copper bands, may be further provided with a protecting covering against induction 22, consisting of magnetizable 7 material.

Thematerial of the threads I! and I9 'must be such as to be capable of resisting tensional stresses; preferably, use is made for this purpose of insulated material having fa small dielectric loss, such as for instance polysty 01. The threads used should be as thin as possible in order to reduce the proportion of the air in the conductor insulation as much as possible,

What I claim is:-

1. In air space insulated high frequency conductors comprising an inner conductor and an 7 outer surrounding conductor, a distance holder between the said two conductors consisting of a self-sustaining hollow and open helix of an insulating material capable of retaining the helical shape the said two conductors lying outside the said helix.

2. In air space insulated high frequency conductors comprising an inner conductor and an outer surrounding conductor, a distance holder between the said two conductors consisting of a self-sustaining hollow and open helix of an insu-.

lating material capable of retaining the helical shape, which self-sustaining helix is in its turn helically arranged between the said "two conductors.'

3. In air space insulated high frequency con-' ductors comprising an inner conductor and an outer surrounding conductor, a distance holder between the said two conductors consisting of a self-sustaining hollow and open helix of an insulating material capable of retaining the helical shape the said two conductors lying outside the said helix and a thin thread capable of resisting tensional stresses lying in the said self-sustaining helix for the purpose of taking up the tension togetherwith the self-sustaining helix.

4. In air space insulated high frequency conductors comprising an inner conductor and an outer surrounding conductor, a distance holder between the said two conductors consisting of a self-sustaining hollow and open helix of an insulating material capableof retaining the helical shape the said two conductors lying outside the said helix and a thread laid on the inner conductor in opposite direction to the said helix for holding the latter in position on the inner conductor.

5. In air space insulated high frequency conductors comprising an inner conductor and an outer surrounding conductor, a distance holder between the said two conductors consisting of a self-sustaining hollow and open helix of polystyrol which is capable of retaining the helical shape the said two conductors lying outside the said helix.

FRANZ KLIMMER.

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