JPH04160709A - Water-proof type cable against water travelling inside of metal sheath with corrugation - Google Patents

Abstract

PURPOSE:To improve the block efficiency for preventing water-travelling by eccentrically providing a push type cushion layer previously on a cable core, and making this cushion layer bite a recessed part of a metal sheath with corrugation. CONSTITUTION:The periphery of a central cable conductor 1 is covered with an internal semi-conductive layer 2, an insulating member 3 and an external semi-conductive layer 4 in order. A cushion layer 5 to be provided thereon is extruded eccentrically for covering so that the upper part thereof is thick and the lower part is thin. In this case, the water absorbing and swelling polymer is applied to the whole of the cushion layer 5 or the periphery thereof. Water-proof property against the water travelling inside of the metal sheath with corrugation can be improved by forming eccentrically the cushion layer 5 without change of outer diameter and cross section of the cushion layer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cable having a corrugated metal sheath.

[Prior Art] In a conventional power cable having a spirally corrugated metal sheath, an internal semiconducting layer 2. An insulator 3 and an external semiconducting layer 4 are formed, a cushion layer 5 with water absorption and swelling properties is applied thereon, and a string-like body 6 with or without water absorption and swelling properties is further applied thereon. Although not shown, a corrugated metal sheath is applied to this outer periphery. At this time, as shown in the side sectional view of FIG.
By reducing the volume of the void 8 formed by the peak 7'', this spiral void 8 is partially blocked to prevent water running.

[Problems to be Solved by the Invention] In this way, in order to increase the blocking effect for waterproofing water running inside the corrugated metal sheath, it is necessary to thicken the cushion layer 5 and reduce the troughs of the corrugated metal sheath 7. However, increasing the depth of the grooves 7' of the corrugated metal sheath 7 uniformly over the entire circumference of the cushion layer 5 increases the material cost accordingly. At the same time, it is necessary to increase the processing pressure of the corrugating machine during the corrugating process, and it is also necessary to increase the capacity of the corrugating machine, which cannot be easily realized.

In addition, the difference in the inner diameter of the metal sheath 7 before corrugation and the outer diameter of the cushion layer 5, that is, the gap, is the size of the extruder when applying an extrusion type sheath such as an aluminum sheath as the corrugated metal sheath 7. Since the thickness cannot be made smaller than a certain value, there is a limit to how thick the cushion layer 5 can be made as described above.

This invention has been made in view of the above points, and provides a novel water-running rib-type corrugated metal sheathed cable that can eliminate the drawbacks of the prior art described above and improve the blocking effect of preventing water running. The purpose is to provide

[Means for Solving the Problems] The present invention is characterized in that an extruded cushion layer is applied eccentrically on the cable core in advance, and the cushion layer is applied so as to bite into the valleys of the corrugated metal sheath. This is a waterproof cable that runs inside a corrugated metal sheath.

The present invention also provides a water-tight cable running inside a corrugated metal sheath, characterized in that the entire cushion layer or its outer periphery contains a water-absorbing and swelling polymer.

Furthermore, the present invention is a waterproof cable running in a corrugated metal sheath, characterized in that a semiconductive tape containing a water-absorbing and swelling polymer is applied to the outer periphery of the extruded cushion layer.

[Function 1] By applying the cushion layer eccentrically, the running water resistance inside the corrugated metal sheath can be improved without changing the outer diameter and cross-sectional area of the cushion layer, and of course without changing the finished outer diameter of the cable. can be improved.

[Example] Hereinafter, the present invention will be described in detail based on the drawings. 1st
The figure is a cross-sectional view showing the configuration of a water running type cable in a corrugated metal sheath. That is, the inner semiconducting layer 2. An insulator 3 and an outer semiconducting layer 4 are sequentially coated. The cushion layer 5 provided thereon is extruded and coated on the external semiconductive layer 4 in an eccentric manner so that the upper part is thicker and the lower part is thinner. In this case, the cushion layer 5
A water-absorbing and swelling polymer is applied to the entire body or its outer periphery, but this may be in the form of a tape or in the form of an extrusion, as shown in Figure 3. It is sufficient that the structure is such that it swells when water enters the void 8 formed inside the peak 7'' of the corrugated metal sheath 7 provided thereon. The trough 7 of the corrugated metal sheath 7 reaches the position indicated by the dotted line in the figure.
It is formed by pressing it with a corrugating machine so as to bite into it.

As a result, the penetration depth H of the troughs 7' of the corrugated metal sheath 7 into the cushion layer 5 becomes larger than in the case of the prior art shown in FIG. 2, the volume of the void 8 becomes smaller, and the cable The blocking effect when flooded is improved, and the water running and waterproofing properties are improved. In this example, the string-like body 6 provided on the cushion layer 5 may be provided as necessary.

[Effects of the Invention] As explained above, the corrugated metal sheathed water-tight cable of the present invention can be manufactured without requiring new equipment because the cushion layer is simply applied eccentrically. Furthermore, since the volume of the void portion is reduced, the performance of preventing water running is improved. Furthermore, since the outer diameter of the cushion layer can be made the same as in the case of the prior art, no special material cost is required and the cost does not increase.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of a water-running waterproof cable in a corrugated metal sheath according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing the structure of a conventional water-running prevention cable. FIG. 3 is a longitudinal sectional view showing the structure of the sheath portion for explaining the state in which the corrugated metal sheath is bitten into the cushion layer. l...Conductor 2...Inner semiconducting layer 3.
...Insulator 4...Outer semiconducting layer 5...Cushion layer 6...String body 7...Corrugated metal sheath 8...Gap patent applicant Hitachi Cable, Ltd.

Claims (3)

[Claims] (1) Inside the corrugated metal sheath, characterized in that an extruded cushion layer is applied eccentrically on the cable core in advance, and the cushion layer is applied so as to bite into the troughs of the corrugated metal sheath. Water running waterproof cable. (2) The water-tight cable running in a corrugated metal sheath according to claim (1), characterized in that the entire cushion layer or its outer periphery contains a water-absorbing and swelling polymer. (3) The water-tight cable in a corrugated metal sheath according to claim (1), wherein a semiconductive tape containing a water-absorbing and swelling polymer is applied to the outer periphery of the extruded cushion layer.