US 3126438 A
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March '24, 1964 H J.,L'0RRIN COAXIAL CABLES WITH SLIT TUBULAR INSULATION Filed Dec. 2. 1960 3 Sheets-Sheet 1' FIG. 7
luvz/vron JEAN LORRlN A TTOR/VE Y March 24, 1964 I J. LORRIN 3,126,438
COAXIAL CABLES WITH SLI'I' TUBULAR INSULATION Filed Dec. 2, 1960 s Sheets-Shet I INVENTOR JEAN LORRIN I BYMW/ Q AT Y J- LORRIN March 24, 1964 COAXIAL CABLES WITH SLIT TUBULAR INSULATION Filed Dec. 2, 1960 5 Sheets-Sheet 3 El v O 4/ I! FIG. 4
JEAN LORRIN A TTORNE Y United States Patent 3,126,438 COAXIAL CABLES WITH SLIT TUBULAR INSULATION Jean Lorrin, Lyons, France, assignor to Compagnie Generate dElectricite, Paris, France, a French corporation Filed Dec. 2, was, Ser. No. 73,458 Claims priority, application France June 8, 1956 9 Claims. (Cl. 174-29) The present application is a continuation-in-part application of my copending application Serial No. 664,591, filed June 10, 1957, now abandoned, the said application Serial No. 664,591 being based on the French application filed in France on June 8, 1956.
High frequency coaxial cables are well-known in which the inner central conductor and the exterior conductor concentric thereto are maintained in relation to each other and at the same time insulated from each other by means of one or more tubular insulating elements pressed he tween the two conductors.
The present invention relates to cables of this type, characterised in this, that the tubular insulating element or elements have at least one slit arranged as a helical spiral; the axis of the helix coincides with the axis of the element, and the latter may comprise several slits arranged along parallel helices.
The cables have an unlimited length and the tubular elements are therefore slitted over their whole length. A tubular element slitted helically can therefore also be defined as a tape wound helically, two consecutive turns among the plurality of turns being in general in contact at certain places. Again, a tubular element having several parallel slits arranged along parallel helices can be defined as several juxtaposed tapes having identical thicknesses and wound along parallel helices. If however a tape is used as starting material which is wound helically it would exert radial resilient forces which would tend to unwind it and would make the manufacture of the cable very difiicult. These resilient forces no longer exist when the starting member is a tubular element and one helical slit or several parallel helical slits are provided therein.
The presence of the slits gives the tubular elements great flexibility in the longitudinal direction, while their mechanical rigidity in the transversal direction remains nearly as great as that of elements without slits.
The tubular insulating elements may be of any crosssection, circular or otherwise. They are preferably made of a material of high resistivity, low dielectric constant and low dielectric losses which becomes rigid when cold, such as polystyrene.
Each of these elements may with advantage be bound by means of one or more thin insulating tapes, preferably wound in the reverse direction to the direction of the helicoidal slit of the element; in this way the transversal slipping of the turns of the element with respect to each other is prevented. It is also possible, instead of winding this binding, to arrange the element axially along a wide, fairly elastic insulating tape of which the edges are then turned back laterally, so as to form a cylinder in which the element is enclosed or wrapped; this prevents excessive stretching of the turns of the element at the time of the various operations before the element is set in position.
The elements constituted in this way are spirally wound around the inner central conductor or arranged in parallel to the conductors; the assembly arranged in this way then can be bound by insulating tapes. For a spiral arrangement, one element is sufficient for securing the spacing between the two conductors if the pitch of the helix is sufficiently small. For an arrangement parallel to the conductors at least three elements are necessary for securing their spacing.
In the attached drawings, by way of example:
FIGS. 1 and 3 are a transverse cross-section and a perspective view, respectively, of a coaxial cable according to the invention with cylindrical tubular elements; FIG. 2 is a transverse cross-section of a coaxial cable according to the invention with hollow insulating elements with substantially triangular cross-section, and FIG. 4 is a partial perspective view of a modified embodiment of a coaxial cable similar to FIGURE 2.
In these figures, 1 is the central conductor of the cable, 2 the slitted insulating elements having helical slits arranged around the latter, 3 the binding arranged around each insulating element and spirally or helically wound in the direction opposite the direction of the helical slits, 4 the binding arranged around the assembly of the elements, and 5 the peripheral conductor of the cable.
The assembly of the insulating elements such as 2 may be applied directly on the central conductor 1, or may rest on a small cord 6, spirally wound around the latter.
Instead of being spirally wound between the two conductors 1 and 5 the elements 2 could also be parallel thereto without anything else being changed in FIG. 3.
The coaxial cable according to FIG. 2 comprises slitted insulated elements 2, with substantially triangular crosssection. In this case, the slit also forms with the axis of the tube an angle of susbtantially constant magnitude. FIGURE 4 is a partial perspective View of a coaxial cable similar to FIGURE 2 in which the slitted insulating elements 2 are also of substantially triangular cross section and are provided each with two parallel helices 7 and 7'. Otherwise, the embodiment of FIGURE 4 is similar to that of FIGURE 2. The insulating elements of each embodiment have extended surfaces facing outwardly toward the outer conductor 5. These surfaces are in supporting relationship with respect to the outer conductor through the bindings 3 and 4 of insulating tape, the support being distributed over an elongated portion of the surface paralleling the axis of the element and in FIGURE 2 this supporting surface has substantial width in the direction circumferentially of the insulating elements as indicated at the curved outer surfaces in the drawing.
1. High frequency coaxial cable comprising an inner central conductor, an outer conductor concentric to said inner conductor and at least three insulating tubular elements formed by tapes, slitted helically, parallel to said two conductors and pressed between them.
2. High frequency coaxial cable according to claim 1, in which each said insulating element is wrapped in a cylinder made of an insulating tape the edges of which have been turned laterally.
3. High frequency coaxial cable according to claim 1, in which each said insulating tubular element is bound by a helically wound tape.
4. High frequency coaxial cable according to claim 1, in which each said insulating tubular element has a substantially triangular cross-section.
5. High frequency coaxial cable according to claim 1, in which an insulating tape is helically wound between each said insulating tubular element and said outer conductor.
6. High frequency coaxial cable comprising an inner central conductor, an outer conductor concentric to said inner conductor and an insulating tubular element slitted along at least two parallel helices, wound helically between said two conductors and pressed between them.
7. High frequency coaxial cable comprising an inner central conductor, an outerv conductor concentric to said inner conductor and at least three insulating tubular elements slitted along at least two parallel helices, parallel to said two conductors and pressed between them.
8. High frequency coaxial cable'cornprising an inner central conductor, an outer conductor concentric to said inner conductor and an insulating tubular element formed by a tape, slitted helically, wound helically between said two conductors and pressed between them, said insulating element being wrapped in a cylinder made of an insulating tape the edges of which have been turned laterally.
9. High frequency coaxial cable comprising an inner central conductor, an outer conductor concentric to said inner conductor and an insulating tubular element formed by a tape, slitted helically, wound helically between said two conductors and pressed between them, said insulating 15 4 tubular element having a substantially triangular cross section.
References Cited in the file of this patent UNITED STATES PATENTS 1,601,817 Forster Oct. 5, 1926 1,904,547 Schumann Apr. 18, 1933 2,038,973 Wentz Apr. 28, 1936 2,116,267 Klirnmer May 3, 1938 10 2,556,244 Weston June 12, 1951 FOREIGN PATENTS 485,946 Great Britain May 27, 1938 7 691,371 Germany May 24, 1940 875,387 France June 22, 1942