JPH02247910A - Formation of groove on plastic coating or on plastic pipe - Google Patents

Abstract

PURPOSE:To accurately position a housed object by forming grooves being accurate and according to a prototype on a longthy cable or on a plastic pipe having a plastic coating, while burying therein objects to be housed such as a communication wire, a detection wire and optical fibers. CONSTITUTION:A power cable formed of a central conductor 6 coated with an insulator 5 and a metal sheath 4, around the outer periphery thereof, is coated with polyvinylchloride 7 and grooves 7a is provided on this periphery in the following method. That is, polyethylene 8, which can not thermally be fused with vinyl, is concurrently pushed out with the coated vinyl 7 on the formation parts of the grooves 7a for being cooled and to be once taken-up on a drum, and simultaneously with stripping string-shaped polyethylene 8 on the parts of the grooves 7a, this is used as a guide wire in order to house the objects, for instance, an optical fiber unit or the like in the generated grooves 7a. In this way, the grooves 7a generated by stripping of polyethylene are made to a prescribed size so that formation is made accurately and efficiently. Further, as compared with the method using a flexible metal stripe, manufacture gets along with few processes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] This invention relates to improvements in various cables or pipes having plastic sheathing and methods for forming grooves on the outside of plastic pipes and the like.

[Prior Art] For example, when storing communication lines, detection lines, etc. in the outer sheath of a power cable, as shown in the cross-sectional view of FIG.
Insulator 5. A metal sheath 4 and a plastic sheath 3 formed with a groove 3a along the length of the cable on its outer periphery.
The communication line 2 is housed in the groove 3a, and the outer periphery is covered with an external protective coating 1. recently,
With the rapid development of optical fibers, there are many cases where it is required to provide cables containing optical fibers.

[Problem to be solved by the invention] As described above, when storing communication lines, detection lines, etc., it is necessary to form grooves along the cables in the plastic coating, but conventionally, grooved dies are used to extrude the cables. Although grooves were formed in the plastic coating using this method, (1) After the plastic coating was extruded and before it was cooled, it hit a roll, etc., and the shape of the grooves was different from the original shape.

■After the plastic coating is extruded, the shape of the grooves will differ from the original due to shrinkage of the plastic during cooling.

■When storing communication lines, detection lines, or optical fibers in plastic-covered grooves, it is difficult to guide and store them accurately to their positions.

There were drawbacks such as.

In addition, as a method to improve the above-mentioned drawbacks of the prior art, a plastic coating is formed in the first step, and then lead or a flexible metal is wound in an oven spiral on top of this coating layer in the second step. Turning 1 Next, as a third step, a material similar to the above-mentioned coating layer material or a material that can be heat-sealed is extruded to a thickness that is almost the same as the circumscribed circle of this metal strip layer, and then as a fourth step, the above-mentioned metal strip is peeled off. Although it has been proposed (see Japanese Patent Publication No. 39943), this method has the following drawbacks and is not necessarily suitable for industrialization.

■When forming using a conventional grooved die, it can be manufactured in -steps, but this method requires 4 steps,
It is extremely uneconomical.

■Moreover, it requires expensive metal strips such as lead, which further impairs economic efficiency.

(2) Since the groove is formed by winding a metal strip, only a spiral groove can be formed.In other words, when a metal strip is used, there is a problem that it will fall if arranged in a straight line. In this way, it is unsuitable or almost impossible to form linear grooves parallel to the coating layer.

The present invention has been made in view of these points, and an object of the present invention is to provide a more accurate and superior method for forming grooves.

[Means and effects for solving the problem] This invention has the following features:
The groove part is coated with a plastic that is difficult to heat-seal to each other, or is different from the pipe body, and is formed by extruding it simultaneously with the pipe body. After cooling, the plastic in the groove part is peeled off to form the original shape. It forms precise grooves. A common head or the like can be used to extrude the desired plastic at the same time as covering the groove portion or integrally with the pipe body.

[Example] Hereinafter, the present invention will be described in detail based on the drawings. 1st
The figure is a cross-sectional view showing the structure of an example of an electric cable in which grooves are formed by simultaneously extruding polyvinyl chloride (hereinafter referred to as PvC) coating on the electric cable and polyethylene on the outside. That is, an insulator 5. is placed around the outer periphery of the central conductor 6. In order to provide a full 7a around the outer periphery of the PvC sheath 7 in the power cable covered with the metal sheath 4, a groove 7 is formed along with the PvC of the sheath 4.
The portion 8 of a is formed by coextruding PvC and polyethylene that is not heat-sealed using a common head. The cable formed by extrusion is cooled and then wound onto a drum.

Then, in the next step, the string-like polyethylene 8
At the same time, it is peeled off and wound up, and at the same time, it is used as a guide wire, and an optical fiber unit, for example, is housed in this pad 7a.

This peeling operation can be performed in the same process as extrusion, but it can also be performed in a separate process.

Also, communication lines and detection lines are finally stored in the groove.

In the process of storing optical fibers and the like, the plastic is peeled off at the same time, and the plastic to be peeled off can be used as a guide wire to guide the objects to be stored into the groove, making it even more efficient.

As described above, in the present invention, the PVC coating and the polyethylene in the groove portion are integrally coated and formed by coextrusion.

The grooves formed by peeling off the polyethylene are of predetermined dimensions and can be formed accurately and efficiently. Furthermore, compared to a method using a flexible metal strip, the manufacturing steps can be significantly reduced, and economical efficiency can also be significantly improved.

The shape and number of these grooves may be circular, semicircular, U-shaped, etc., as long as they can be formed on the outer periphery of the coating or pipe body.
■Character shape, square shape, etc.←m Any type of groove, linear or spiral with respect to the shaft.

Any form such as SZ shape is possible. After the object is placed in the groove, an outer covering can be applied for protection purposes.

The jacket can also be integrated with the grooved plastic jacket by using a heat-sealable material.

Furthermore, the fiber unit can be reliably and efficiently housed in the formed groove using the peeled polyethylene as a guide wire. As a result of checking the various characteristic values including the mechanical properties of the optical composite capeple thus completed, all were found to be satisfactory.

In the above example, a groove is formed in the PVC sheath of the power cable, but this may also be a plastic tube.Also, the combination of plastics used for the sheath and groove may be PvC and polyethylene. Although the case where they are not thermally fused to each other has been described, the grooves are not limited to this, and if there is a risk of thermal fusion, it is also possible to form grooves using a mold release agent.

Then, in order to improve the removability of the plastic in the groove and strengthen its strength as a guide wire when storing objects, the plastic extruded into the groove is mixed with a fibrous substance. It is also possible to take other measures.

[Effects of the Invention] As explained above, according to the present invention, it is possible to accurately form grooves in the original shape in the plastic coating of a long cable, a plastic pipe, etc., efficiently and at low cost. Further, objects to be stored such as communication lines, detection lines, optical fibers, etc. can be reliably and efficiently stored in the groove. Recently, there has been a demand for improved reliability in various cables, vibrators, etc., and the need for failure detection systems, monitoring systems, etc. is rapidly increasing.For these purposes, communication lines, The number of cases in which detection lines, optical fibers, etc. are combined is rapidly increasing, and the present invention enables a much more economical and highly reliable solution.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a state in which grooves are formed on the outer periphery of the PvC coating of a power cable as an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the configuration of the communication line composite type cable. 3.7...Plastic coating 3a, 7a...Groove 4...Metal sheath 5...Insulator 6...Conductor 8...Polyethylene

Claims (4)

[Claims] (1) In a method of forming one or more grooves on the outer periphery of a plastic coating or a plastic pipe such as a cable or pipe, the plastic coating or a plastic pipe is formed by extrusion, and the groove part is filled with the above plastic coating or A plastic coating or a plastic pipe characterized in that the plastic used to form the plastic pipe and a different type of plastic are formed by co-extrusion, and after cooling is completed, the different type of plastic in the groove portion is peeled off. How to form grooves. (2) A claim characterized in that the plastic material of the groove portion is made of a material that is difficult to thermally fuse with the plastic coating or the plastic of the plastic pipe, or is formed using a mold release agent. 1. The method of forming grooves in a plastic coating or a plastic pipe according to 1. (3) The method for forming grooves on a plastic coating or plastic pipe according to claim 1, characterized in that fibers or the like are mixed with the plastic in the groove portion to facilitate peeling. (4) Forming a groove in a plastic coating or plastic pipe according to claim 1, characterized in that when the plastic in the groove portion is peeled off, the plastic is used as a guide wire for storing an object to be stored in the groove. Method.