DE2162298A1 - Method for eliminating the voids between the outer conductor and the dielectric in coaxial submarine cables - Google Patents

Description

Dip] vPhys. Leo Thul
Patent attorney
7000 Stuttgart - J> 0
Short street 8

CP. G. Smith - 11

INTERNATIONAL STANDARD ELECTRIC CORPORATION, NEW YORK

Method for eliminating the voids between the outer conductor and the dielectric in coaxial submarine cables.

The application relates to the manufacture of coaxial submarine cables. The coaxial submarine cables most commonly used today consist of a steel wire stranded tensile core, a cylindrical inner conductor, which consists of a copper band formed lengthways around the tensile core, a Dielectric extruded over the inner conductor, an outer conductor formed cylindrically around the dielectric from copper or aluminum tape, wherein the longitudinal edges of the tape overlap, and one extruded over the outer conductor Plastic outer sheath.

In the case of coaxial submarine cables, it is necessary that the total air gap between the outer surface of the dielectric and the inner surface of the outer conductor is reduced to a minimum during manufacture. The reason for this is that in the event of any damage to the cable sheath between the outer conductor and the cable sheath, water that has penetrated does not affect the electrical properties of the cable, but the presence of water between the outer conductor and the dielectric has detrimental effects on the cable attenuation the disadvantageous change in attenuation increases with increasing water volume. In the event of cable damage, as a result of which water penetrates between the outer conductor and the dielectric, it is of the utmost importance that the amount of water penetrating is kept as small as possible, which at the same time means that the cavities in the cable must be kept as small as possible depends mainly on the air gap created at the overlap of the outer conductor, on the accuracy with which the outer conductor clings to the dielectric and on the unevenness in the smooth surface of the dielectric. The unevenness in the dielectric surface is due - at least in part - to the machining of the dielectric, which is usually carried out in the manufacture of submarine cables and which leads to helical grooves in the dielectric surface.
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CP. G. Smith - 11

In a known method, to reduce the air gap Filler introduced between the outer conductor and the dielectric, but this has a detrimental effect on the properties of the dielectric may have.

It has also become known that heating of the outer conductor can be used during or after the manufacture of the cable jacket to reduce or eliminate the air gap. At a Such a method, the temperature of the outer jacket during extrusion on the outer conductor is increased so that the heat from the outer conductor to Dielectric is conducted so that this melts on its outer surface and thus in close contact with the inner surface in a platischem state of the outer conductor. This procedure is disproportionate unreliable and has certain disadvantages such as a detrimental effect on the flexibility of the finished cable.

The object of the invention is to provide a new, better method, by which air gaps between the outer conductor and the dielectric are eliminated or at least significantly reduced and the flexibility of the Cable is significantly improved at the same time.

According to the invention this object is achieved in that the outer conductor before or after applying the outer layer with simultaneous application of pressure is inductively heated by means of high frequency.

In this way, the surface of the dielectric is melted and the inner surface of the outer conductor is brought into very close contact with the outer surface of the dielectric, eliminating the gap between them existing air is reduced.

The invention will be further explained with reference to the accompanying Figures 1 to J>.

CF.G. Smith - 11 It show:

Fig. 1 shows the cross section through a coaxial submarine cable before the heating of the Outer conductor,

2 shows the overlap area of the outer conductor in an enlarged illustration of a coaxial submarine cable before the outer conductor is heated,

and

3 shows, in an enlarged representation, the overlap area after heating of the outer conductor.

According to the cross section of the coaxial submarine cable shown in FIG. 1 this from the tensile core 1 stranded from steel wires, the inner conductor 2 - for example a copper tape -, the dielectric 3 - for example Made of polyethylene, the outer conductor 4 and the plastic outer sheath 5 from, for example. High density polyethylene. The outer conductor 4 consists of a cylindrically shaped copper or aluminum tape, which is shaped in such a way around the dielectric 3 that the Overlap the longitudinal edges of the tape at 6. Since the dielectric 3 has an essentially circular cross section, the air gap is created automatically when the outer conductor 4 is formed around the dielectric 3 (see Fig. 2). This air gap, in addition to the air gaps caused by an imprecise adaptation of the outer conductor to the dielectric and through The unevenness of the dielectric caused by machining would be retained in the cable if it were manufactured no action would be taken to remove or substantially eliminate these air gaps.

According to the invention, the entire air gap, including the air gap 7, can be eliminated by inductive heating of the outer conductor using high-frequency current of the broadcast frequency range. To this end the cable, after the outer conductor tape has been formed around the dielectric 3, either before or after the production of the outer sheath an induction coil charged with high-frequency current of a suitable frequency, so that the outer conductor heats up without touching the cable will. As a result, the outer surface of the dielectric 3 melts and the air gap is opened while an external pressure is exerted eliminated on the cable; in the process, the grooves in the dielectric surface are smoothed out and the step at the overlap of the outer conductor is embedded in the dielectric (see. Fig. 3)

209828/0645 * ^{/ #}

CP. G. Smith - 11

By using the inductive high frequency heating, the air gap without eliminating the disadvantages of excessive jacket heating. The temperature of the outer conductor can be adjusted accordingly a control circuit can be controlled, wherein the induction coil can be arranged either in front of or behind the spray head of the jacketing press can.

An important property of coaxial submarine cables is their flexibility, which of the adhesion between the inner surface of the outer conductor and the outer surface of the dielectric or the outer surface of the outer conductor and the Cable sheath depends. By using the inductive high-frequency heating, the outer conductor can reliably with the dielectric and / or be connected to the outer jacket. In addition, a pretreatment of the surfaces, for example an adhesion-improving Means, and by controlling the temperature of the outer conductor with the induction coil's adhesion can be controlled. This controlled adhesion of the various surfaces improves the flexibility of the cable considerably. If necessary, the surfaces can also be finished with a agents preventing liability are dealt with.

Thus, the proposed method provides a possibility that to improve the mechanical and electrical quality of a coaxial submarine cable by that air spaces between the dielectric and outer conductor are removed and the adhesion between the individual surfaces to achieve the desired flexibility is set in a reliable manner.

2 claims
1 sheet with 3 fig.

209828/0645

Claims (2)

CP.G. Smith - 11 years of age 1.J Method for eliminating the cavities between the outer conductor and the dielectric in coaxial submarine cables, which consist of an inner conductor, a dielectric that envelops the inner conductor, an outer conductor consisting of a metal strip that is cylindrically shaped around the dielectric and overlaps at the longitudinal edges, and a plastic outer sheath, thereby characterized in that the outer conductor is heated inductively by means of high frequency before or after the application of the outer jacket with simultaneous application of pressure. 2. The method according to claim 1, characterized in that the adjacent surfaces of the dielectric, the outer conductor and the outer jacket are provided with an adhesion-improving agent and the outer conductor is heated to such a temperature that the pretreated surfaces with simultaneous melting of the dielectric surface enter into a firm bond. 209828 / 064S Blank page