JPH0295115A - Pipe cable and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce the shrinkage amount of a PE tube to be used in real circumstances for a long period of time and to obtain high reliability by the application to a pneumatically feeding and mounting optical cable by determining the molding time remaining distortion of the tube to be used to a specific value or less. CONSTITUTION:In a pipe cable in which several pipes 2 each made of a PE tube to be used for a pneumatically feeding optical cable laying system are associated and a sheath 1 is provided thereon, the molding time remaining distortion of the tube 2 to be used is set to 1% or less. Thus, when the long term use is considered in normal temperature circumstances, i.e., in a temperature range of -40 to 80 deg.C, the shrinkage amount of the tube is small. Accordingly, the retraction of the tube 2 in the vicinity of the end of the cable is reduced. Therefore, an increase in the slack generated in the tube 2 of the contained optical fiber unit, i.e., a large increase in the excessive length is suppressed, and the optical fiber having high reliability after laying is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is used for a pneumatic optical fiber cable installation system in which an optical fiber unit in which a single-core or multi-core optical fiber is coated with a coating layer is laid by pneumatic feeding. The present invention relates to a pipe cable in which a plurality of pipes made of polyethylene tubes are assembled and covered with a jacket, and a method for manufacturing the same.

[Conventional technology]

As a method of laying an optical fiber cable, an optical fiber unit formed by applying a coating layer such as a foam coating layer to a single-core or multi-core optical fiber is connected to a single or multiple polyethylene tube (hereinafter referred to as PE tube). There is a method in which a pressurized gas such as air is fed and housed in a so-called pipe cable consisting of a tube (for example, JP-A-59-104607@). This pressurized gas pumping method is used to install optical fiber cables, and during installation, no external force such as tension is applied to the optical fibers, so there is no damage to the optical fibers. This makes it possible to install optical fibers along complicated routes, as well as to replace optical fibers after installation and to install additional optical fibers, which is effective in facilitating maintenance and reducing installation costs.

FIGS. 2a and 2b illustrate the cross-sectional structure of a conventional pipe cable of this type. Figure 2a shows an example in which two PE tubes 4 are assembled and a LAV sheath (laminated aluminum PVC sheath) 3 is applied to the outer periphery to form a 2-tube pipe cable.
This is an example in which a 7-tube pipe cable is assembled by applying an AP sheath (laminated aluminum polyethylene sheath) 1 to its outer periphery.

[Problem to be solved by the invention]

In the conventional pipe cable structure as illustrated in FIGS. 2a and 2b, under long-term usage environment, due to the relaxation behavior of residual strain during extrusion molding of the PE tube, for example, the third
As schematically shown in the figure, due to the contraction of the PE tube 4 at the end of the pipe cable, the PE tube 4 is retracted by a retraction amount l from the end of the LAP sheath 1, for example.
The so-called pull-in phenomenon occurs, and the end treatment of pipe cables,
There is a problem in that there is concern that an increase in the extra length of the housed optical fiber unit will affect the transmission characteristics.

The present invention solves the conventional problems, improves the stability of the terminal processing part, and reduces the influence on the housed optical unit for long-term use in actual environments. The purpose of this invention is to provide a highly reliable pipe cable for use in a system and a method for manufacturing the same.

[Means to solve the problem]

In order to achieve the above-mentioned object, the pipe cable of the present invention is used in a pneumatic optical fiber cable installation system that installs an optical fiber unit in which a single-core or multi-core optical fiber is coated with a coating layer by pneumatic feeding. A pipe cable in which a plurality of pipes made of PE tubes are assembled and coated, characterized in that the P'E tubes forming the pipes have a residual strain of 1% or less during molding. It is said that

Further, the method for manufacturing a pipe cable of the present invention involves forming a PE tube by extrusion molding, heat-treating the PE tube formed by extrusion molding to reduce the residual strain to 1% or less, and reducing the residual strain during the molding. This method is characterized by a step of applying a LAP sheath to the outer periphery of a plurality of PE tubes.

Note that the step of heat-treating the PE tube formed by extrusion molding to reduce the residual strain to 1% or less is a means of suppressing residual strain during molding. It is effective to freeze the material as much as possible and then heat it to release residual strain.

[For production]

Since the pipe cable according to the present invention has a residual strain of 1% or less during molding of the PE tube used, it is suitable for long-term use under normal temperature environments, that is, in the temperature range of -40°C to 80°C. In this case, since the amount of contraction of the PE tube is small, the pulling phenomenon of the PE tube near the end of the pipe cable explained in the schematic diagram of Fig. 3 is reduced, and therefore the inside of the PE tube of the stored optical fiber unit is reduced. This suppresses the drastic increase in slack that occurs in the cable, that is, the increase in excess length, resulting in an optical cable that is highly reliable in practice after installation. Examples will be described below based on the drawings.

〔Example〕

FIG. 1 is a cross-sectional structural diagram of an example of a pipe cable of the present invention. This is a pipe cable constructed by assembling seven cross-linked PE tubes 2 whose residual strain during molding is reduced or suppressed to 1% or less, and a LAP sheath 1 is applied to the outer periphery of the tubes.

PE tube material has a density of 0.92 (g/cc)
A material based on low density polyethylene with an MI (melt index) of 0.25 (8710 minutes) and containing a small amount of additives was used.

By extrusion molding the PE tube material of the above material, the inner diameter is 6.
mmφ, extrusion linear speed 10 to tube with outer diameter 8mmφ
It was extruded at m/min. A PE tube manufactured by this extrusion molding is referred to as Comparative Example 1.

The PE tube of Comparative Example 1 was heat-treated by passing it through hot water at a temperature of 80° C. for a sufficient time to maintain its cross-sectional shape. The PE tube subjected to this heat treatment is referred to as Comparative Example 2.

Furthermore, the PE tube of Comparative Example 1 was
After crosslinking by irradiation equivalent to 8 Mrad, heat treatment was performed by passing through hot water at a temperature of 8C1c.

This PE tube is Example 1 according to the present invention.

Similarly, the PE tube of Comparative Example 1 was crosslinked by irradiating it with an electron beam irradiator equivalent to 36 Mrad, and then passed through hot water at a temperature of 80°C to perform heat treatment.

This PE tube is Example 2 according to the present invention.

Seven P and E tubes of each of Comparative Example 1.2 and Examples 1 and 2 were assembled, and ordinary black polyethylene for sheathing was coated around the outer periphery of each of the assembled tubes A and β.
A so-called LAP sheath with a sheath thickness of 2 mm was obtained by applying 1200 μm glue and AP tape. Furthermore, this comparative example 1
In four types of pipe cables using the PE tubes of , 2 and Example 1゜2, the LAP sheath and each P
The so-called core pulling force between the PE pipe cores made of E-tubes was approximately 10 kg for a tensile length of 50 cm.

The above-mentioned prototypes, four types of manufactured pipe cables, and PE tubes were evaluated on the items shown in Table 1, and the heat shrinkage rate of each PE tube and the retraction rate corresponding to β shown in Figure 3 of the pipe cables were evaluated. Assessed quantity.

From the evaluation results in Table 1, it is clear that heat treatment of the PE tube of Comparative Example 2 alone can greatly reduce the heat shrinkage rate at a temperature of 100°C.
As with the E-tube, by applying heat treatment after crosslinking treatment, residual strain during molding can be achieved at a level of 1% or less. Moreover, by increasing the degree of crosslinking, that is, by increasing the gel fraction, it was possible to further reduce the heat shrinkage rate. Furthermore, the amount of retraction of the PE tube at the end of the pipe cable made using these PE tubes has a strong correlation with the heat shrinkage rate of the PE tube used, and the heat shrinkage rate of the PE tube was suppressed to 1% or less. P.E.
The length of the pipe cable using a tube is 50mm.
It is possible to obtain a pipe cable that is stable for long-term use and has high reliability.

It was confirmed that when cross-linked P and E tubes were used, thermal deformation due to lateral pressure of the cable at high temperatures was smaller than when uncross-linked PE tubes were used.

In addition to the low-density polyethylene mentioned in the examples, the PE tube used in the present invention includes medium-density, high-density, and linear low-density polyethylene, and any material can be used as a pipe cable. In this case, the configuration according to the present invention can be applied.

Further, in the embodiments, the pipe cable of the present invention has a structure that does not include a tensile strength member in the vicinity of the PE tube aggregate core, for example, inside or outside the PE tube aggregate core, but the present invention is limited to the above embodiments. It is clear that the present invention can also be applied to a method of manufacturing a pipe cable having a structure in which a tensile strength member is arranged in the vicinity of a PE tube assembly core.

Table 1: The amount of PE tube retraction at both ends of the sample pipe cable (maximum and minimum amount of retraction of the 7 PE tubes collected) after 100 heat cycles of ℃ to +80℃/8 hours) Measure the average value of the amount of retraction of the five PE tubes (excluded) and display it as the amount of retraction per one end.

*1: Immersed in xylene at a temperature of 120°C for 16 hours,
Residue rate (%) after filtration and vacuum drying at 100°C for 2 hours.
display.

*2: PE tube 30cm (marked line 20'cm)
is heated on a talc bed at a temperature of 100℃, and the shrinkage rate (%) after sufficient time (96 hours) to reach the saturation value
Measure.

*3: Bundle the pipe cable with a diameter of 1.2 mφ,
As explained above, the pipe cable according to the present invention has a sample length of 20 m.
Since the residual strain of the PE tube used during molding is 1% or less, the amount of shrinkage of the PE tube can be reduced for long-term use under actual conditions in the temperature range of -40°C to 80°C. This reduces the pull-in phenomenon of the PE tube at the terminal end, and improves the stability of the pipe cable terminal processing section, which reduces the impact on the stored optical fiber unit, that is, the deterioration of transmission characteristics due to increased excess length. It is effective to reduce the noise level and ensure high reliability by applying the present invention to pneumatically installed optical fiber cables.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural diagram of a pipe cable embodiment of the present invention.
Figures 2a and 2b are cross-sectional structural diagrams of conventional pipe cable examples,
FIG. 3 is a schematic diagram of the phenomenon of the PE tube being drawn in at the end of the pipe cable. Patent Applicant Sumitomo Electric Industries Co., Ltd. Agent Patent Attorney Tama Mushi Kugobe@plane structure of the pipe cable embodiment of the present invention Figure 1 Cross-sectional structure diagram of a conventional pipe cable example Genealogy Phenomenon of the PE tube at the end of the pipe group schematic diagram of

Claims (3)

[Claims] (1) A plurality of pipes made of polyethylene tubes used in a pneumatic fiber optic cable installation system in which an optical fiber unit with a coating layer applied to a single or multi-core optical fiber is installed using pneumatic feeding, and A pipe cable characterized in that the polyethylene tube forming the pipe has a residual strain of 1% or less during molding. (2) A plurality of pipes made of polyethylene tubes used in a pneumatic fiber optic cable installation system in which an optical fiber unit with a coating layer applied to a single or multi-core optical fiber is installed using pneumatic feeding, and In the method for manufacturing a pipe cable, a polyethylene tube is formed by extrusion molding, the polyethylene tube formed by extrusion molding is heat-treated to have a residual strain of 1% or less, and the polyethylene tube has the residual strain at the time of molding. A method for manufacturing a pipe cable, comprising the step of applying a LAP sheath to the outer periphery of a plurality of pipe cables. (3) The step of subjecting the polyethylene tube formed by extrusion molding to heat treatment to reduce the residual strain to 1% or less is characterized in that the heat treatment is performed after irradiation and crosslinking with an electron beam irradiation machine. method of manufacturing pipe cables.