JPH0442648B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to a spacer that is used as an element of an optical fiber cable and protects and supports a plurality of optical fibers.

《Prior art and its drawbacks》 When optical fibers are made into cables for use as communication lines, spacers are used in which various spiral grooves are formed with thermoplastic resin around the outer periphery of the tensile strength wires, and the optical fibers are inserted into these grooves. is accommodated and carried.
This type of spacer includes one in which a spiral groove is simply formed in one step with thermoplastic resin around the outer periphery of a tensile strength wire such as a steel wire or twisted steel wire, and one in which a spiral groove is simply formed in one step around the outer periphery of the tensile strength wire to improve the shape accuracy of the spacer. It has been proposed to provide a primary coating with a thermoplastic resin and then form a spiral groove on the outer periphery.

On the other hand, in the case of an optical fiber cable in which an optical fiber is housed in a groove of a spacer and its outer periphery is sheathed, it is necessary to connect the cables together when the cables are branched during installation. At this time, the tensile strength wires of both cables must be connected to each other due to strength issues. For connection, it is necessary to peel off and remove the thermoplastic resin forming the spacer at the end of the cable to expose the tensile strength wire. Conventionally, peeling of thermoplastic resins did not require special tools, so the tensile strength wires were exposed by cutting with a cutter knife, etc. However, this type of spacer is generally designed with special considerations in mind during peeling work. It took a lot of time because there wasn't one.

In particular, when the outer diameter of the spacer is large, the peeling time becomes longer and the spiral groove on the outer periphery also becomes an obstacle to the peeling operation, so there has been a demand for the development of a spacer that can be easily peeled off.

The present invention has been made based on the above-mentioned requirements, and its purpose is to achieve high dimensional accuracy such as groove width and groove depth, and to facilitate peeling and removal of the spiral coating layer during connection work of optical fiber cables. Another object of the present invention is to provide a spacer for supporting an optical fiber having a novel configuration.

<<Structure of the Invention>> In order to achieve the above object, the present invention includes a primary coating layer formed in an annular shape by a thermoplastic resin on the outer periphery of a tensile strength wire, and a longitudinal direction formed by a thermoplastic resin on the outer periphery of the primary coating layer. A spacer for supporting an optical fiber comprising a secondary coating layer having a plurality of spiral grooves extending in the spacer, the primary coating layer and the secondary coating layer adjusting the surface temperature of the primary coating layer. and extrusion forming the secondary coating layer around the outer periphery of the primary coating layer at a temperature that does not reach the point where the surface of the primary coating layer substantially melts. It is characterized in that the secondary coating layer is releasably bonded to the primary coating layer afterwards.

To explain in more detail, the tensile strength wire used in the present invention is a metal wire such as a single steel wire or a twisted steel wire with a thickness depending on the required tensile properties, or a hardened reinforcing fiber. A primary coating layer is applied to the outer periphery of this tensile strength wire using a thermoplastic resin that can be extruded, and then, if necessary, the outer periphery of this primary coating layer is By shaping, the outer diameter is made uniform.

Next, when inserting the wire coated with this primary coating layer into a die for secondary coating, the surface temperature of the primary coating layer is adjusted so that the primary coating layer and the secondary coating layer can be roughly peeled off afterwards. do.

In the present invention, adjusting the surface temperature of the primary coating layer means adjusting the temperature immediately before entering the secondary coating die.
The temperature is such that the surface of the primary coating layer does not substantially melt at the time of contact with the secondary coating resin. This surface temperature depends on the outer diameter of the primary coating layer, the structure and insertion speed of the secondary coating die to be inserted, but is preferably 60° C. or less, taking into consideration the preheating effect of the die.

Note that the thickness of the base of the secondary coating layer formed on the outer periphery of the primary coating layer, that is, between the spiral groove root diameter and the outer diameter of the primary coating layer, is approximately 0.2 to 1 mm in the shape of the spacer.
Desirable from the standpoint of accuracy and subsequent removability.

In addition, the thermoplastic resin that can be used in the present invention basically does not matter as long as it can be melt-extruded, but from the viewpoint of physical properties as a cable element and economical aspects, high-density polyethylene ( Polyethylene-based resins such as HDPE (hereinafter abbreviated as HDPE) and its various modified resins are recommended.Also, the combination of resins used for the primary coating layer and secondary coating layer is such that both layers can be peeled off after the fact, but spacers are recommended. It is desirable to use resins that are compatible with each other because it is necessary to adhere to a degree that satisfies the physical properties of the materials.

<<Embodiments>> Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

1 to 3 show an embodiment of an optical fiber supporting spacer according to the present invention.

First, a method for manufacturing an optical fiber supporting spacer according to the present invention will be explained.

As the tensile strength wire A, a galvanized steel stranded wire made by twisting seven 1.4φ steel wires is used, and this is connected to the rotating drum 1.
It is inserted into the die 5 of the forming extruder 4 of the primary coating device B, and a ring-shaped
It was coated with HDPE (M=0.1) so that the outer diameter was 10.5 mm. Next, this is cooled and solidified in a cooling tank 6, and then the outer diameter is made uniform by a shaping device 7 equipped with a nozzle with an inner diameter of 10 mm, and after being wound up by a take-up machine 9, it is preheated as shown in FIG. The mixture was introduced into the apparatus 10, heated so that the surface temperature of the primary coating layer B immediately before entering the die 12 for forming the secondary coating layer C was 50° C., and then supplied to the extruder 11.

In the extruder 11, while rotating the die 12,
HDPE (M = 0.1) is supplied, and as shown in Figure 3, it has 12 continuous grooves, the outer diameter is 16.7 mm, and the root diameter is 16.7 mm.
A secondary coating layer C of 11.9 mm and a helical pitch of 700 mm was applied.

In this case, the temperature of die 12 was set at 210°C.

The product to which the secondary coating layer C was applied in the extruder 11 was introduced into the cooling tank 13 and cooled, and then wound up in the take-up machine 15.

The spacer manufactured in this way has a cross-sectional shape as shown in FIG.
No dimensional change was observed between the two layers even in alternating tests at 80°C.

On the other hand, the peelability between the primary coating layer B and the secondary coating layer C was measured as follows.

First, prepare a sample with a length of 100 mm as a measurement sample, put a pair of scored lines around the entire circumference at 20 mm intervals in the center, and then add scored lines along the longitudinal direction between the scored lines. After that, the secondary coating layer C was peeled off from the marked line portion for half a circumference.

Then, as shown in FIG. 4, the end of the secondary coating layer C is peeled off after being set in a measuring jig 30 having a pair of supporting pieces having circular holes facing each other at a predetermined interval. was gripped with a gripper 32 and pulled up at a pulling speed of 5 mm/min in an ambient temperature of 23° C., and the peeling force was measured.

As a result, the sample of this example has a peel strength of 6 kg/cm, and if the secondary coating layer C is partially peeled off as described above, then it can be pulled by pinching it with tools such as pliers. Almost all of it can be peeled off relatively easily.

<Comparative example> In contrast to the above example, the procedure was basically the same except that the primary coating layer B was passed through the preheating tank 10, the surface temperature of the primary coating layer B was set at 80° C., and the surface temperature was set at 80° C., and the material was inserted into the die 12 for forming the secondary coating layer C. A spacer was manufactured under the same conditions as in the example. In the sample according to this comparative example, the primary coating layer B and the secondary coating layer C were strongly adhered to each other and it was extremely difficult to separate them.

<<Operations and Effects of the Invention>> As explained in detail above, in the spacer for supporting an optical fiber according to the present invention, the primary coating layer and the secondary coating layer constituting the spacer portion are completely fused and bonded to each other. Since the surface temperature of the primary coating layer during secondary coating is adjusted to prevent excessive adhesion, both layers can be easily peeled off afterwards. Therefore, after creating an optical fiber cable by storing optical fibers in the grooves of the secondary coating layer, when connecting these cables, the secondary coating layer at the end of the cable can be easily peeled off and the remaining This makes it easier to remove the primary coating layer, and it also becomes possible to use a jig such as a stripper to remove this annular coating portion.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are schematic diagrams showing an example of the process of manufacturing the optical fiber supporting spacer of the present invention,
FIG. 3 is a schematic diagram schematically showing a cross-sectional state of an example of the spacer of the present invention, and FIG. 4 is an explanatory diagram of a state in which peeling force is measured. 2... Tensile wire, 5... Dice, 6... Cooling tank, 7... Shaping device, 10... Preheating device, 1
2...Die, A...Tensile strength wire, B...Primary coating layer, C...Secondary coating layer.

Claims (1)

[Scope of Claims] 1. A primary coating layer formed in an annular shape from a thermoplastic resin on the outer periphery of the tensile strength wire, and a 2. A substrate for supporting an optical fiber comprising a secondary coating layer, wherein the primary coating layer and the secondary coating layer are arranged so that the surface temperature of the primary coating layer is adjusted so that the surface of the primary coating layer is substantially The secondary coating layer is later releasably bonded to the primary coating layer by extrusion forming the secondary coating layer around the outer periphery at a temperature that does not reach the point of melting the secondary coating layer. A spacer for supporting optical fibers. 2. The spacer for supporting an optical fiber according to claim 1, wherein the thickness of the base of the secondary coating layer is 0.2 to 1 mm.