JPH01277809A - Production of spacer for optical communication cable - Google Patents

Abstract

PURPOSE:To obtain a spacer section having good accuracy by extruding a resin which is passed through a throttling part provided in an annular shape in a resin passage from a mouthpiece in which plural projections rotate on the inside circumference, thereby forming a spacer provided with plural lines of core housing grooves. CONSTITUTION:An annular dike part 31 is provided to the intermediate part of a mandrel 30 in a resin passage 41 to form the throttling part 40. The resin past the throttling part 40 is extruded from the mouthpiece 12 which has the plural projects on the inside circumference and rotates to coat the resin on tension members 2 and to simultaneously provide plural lines of the optical core housing grooves 22 on the resin surface. The resin which flows in the form of layer is, therefore, throttled by the dike part 31 of the mandrel 30, by which the pressure is increased and the resin pressure of the annular body in a head is uniformized. The resin is thus coated uniformly on the tension members 2. The spacer section having high accuracy is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the manufacture of optical communication cables, and particularly to a method of manufacturing a spacer having an optical core storage groove on its outer periphery for storing an optical fiber core.

[Prior Art] Generally, the structures of optical communication cables include a spacer type, a twisted type, a unit type, and the like. Among these, the spacer-type optical fiber cable has a structure in which the fiber core (optical core) is housed in a groove provided on the outer periphery of the spacer and protected from external forces, and is suitable for optical fiber cables with 12 fibers or less.

Usually, in this spacer-type optical fiber cable, in order for the optical fiber to withstand the tension during cable installation, a tensile strength member (tension member 2) such as a steel wire is attached to the spacer 21 as shown in FIG. In addition, the optical core storage groove 22 on the outer periphery of the spacer is formed in a spiral shape to twist the optical fibers in the cable so that excessive tension is not applied to the optical fibers when the cable is bent. Make it.

An outline of a conventional spacer manufacturing method will be explained using FIG. 4.

First, the tension member 2 is sent out from the delivery drum 1. In the extrusion 113, resin such as polyethylene (PE) or polyvinyl chloride (PVC) is pushed out to the crosshead 4, and the rotary drive device 6 passes the sprocket 5 to the base holder. 11 and the base 12 are rotated. Resin is extruded through the interior of the base 12 which is rotated zero, and the tension member 2 is coated with the resin, forming a spacer 21 (FIG. 3). At this time, the spacer 21 is provided with a plurality of protrusions 12a on the inner periphery of the tip of the base 12 in the circumferential direction.
An optical core storage groove 22 as shown in FIG. 3 is formed in a spiral shape on the outer peripheral surface of the optical core. The extruded spacer 21 is cooled and solidified in a cooling water tank 7, taken up by a take-up machine 8, and wound up on a take-up drum 9.

Extrusion in the extrusion head section is performed as follows.

In FIG. 1, first, the extrusion screw 10 of the extruder 3
The resin is extruded and flows to the crosshead 4, and the resin flow path 1
4, crosses to form an annular body, and reaches the cap 12. The tension member 2, which is being pulled to the left in FIG. 1 by the pulling machine 8, enters the mandrel holder 13, passes through the mandrel 20 at its tip, passes through the mouthpiece 12, and exits the extrusion head. This tension member 2, base 1
The distal end of No. 2 is coated with resin. In this case, the rotary cap holder 11 rotatably supported on the flange 17 by a bearing 19 is connected to the motor of the rotation drive device 6 via the sprocket 5, and by rotating the motor, the rotary cap holder 11 and the cap are rotated. 12 rotate together.

Therefore, the spacer 21 extruded from the base 12 is extruded in the form of a tension member-containing spacer having a helical optical core storage groove 22.

Note that 15 and 16 are fixing bolts for the mandrel holder 13 and flange 17, and 18 is a rotating gasket.

[Problem to be solved by the invention] However, the resin extruded by the extrusion screw 10 is
The resin flows across the resin passage 14 and forms a laminar flow, but flows straight through the resin passage 14 over the cap holder 11 and the cap 12. As a result, the pressure inside the head, the so-called annular body resin pressure, is no longer uniform, causing the optical core storage groove to collapse and the spacer cross-sectional shape to collapse.
That is, irregularities in dimensions such as wall thickness, protrusion width, protrusion height, etc., uneven thickness, etc. occur.

Furthermore, since the cross section of the spacer may be eccentric, the extrusion speed, that is, the take-up speed must be slowed down, resulting in a problem of poor productivity.

The present invention was made in view of the above-mentioned problems, and it is possible to uniformize the laminar flow of the annular body resin pressure and obtain a spacer cross section with good accuracy without groove collapse, irregularities in shape and dimensions, eccentricity, etc. The object of the present invention is to provide a method for manufacturing a spacer for an optical communication cable.

[Means for Solving the Problems] The method for manufacturing a spacer for an optical communication cable of the present invention includes providing a ring-shaped dam in the middle part of a mandrel in a resin passage to form a constricted part between the inner wall of the resin passage and the inner wall of the resin passage. Then, by extruding the resin that has passed through the constriction part through a rotating base that has a plurality of protrusions on the inner periphery, the tension member is coated with the resin, and at the same time, a plurality of optical core storage grooves are formed on the resin surface. This method involves extruding the spacer, cooling it, and then taking it off.

[Operation] The resin that has flowed laminarly through the resin passage in the form of an annular body is transferred to the outside in the radial direction by the dam of the mandrel, is squeezed by passing through the constriction part, and the pressure increases, causing the head to The resin pressure in the inner annular body becomes uniform. The annular resin whose pressure has become uniform reaches the die and is extruded. Therefore, the resin flows effortlessly and smoothly in the direction of rotation of the base and is evenly coated on the tension member, so that the extruded spacer has
When looking at the cross section of the spacer, groove collapse or irregularities in shape and dimensions.

Eccentricity etc. will not occur.

[Example] - Hereinafter, the present invention will be described with reference to illustrated embodiments.

The extrusion method and procedure are almost the same as the conventional method, and the difference is that a mandrel 30 shown in FIG. 2 is used in place of the conventional mandrel 20 shown in FIG.

In FIG. 2, this mandrel 30 has a dam part (dam part) 31 that bulges out in a ring shape in the radial direction from its center, and the radius is the diameter of the resin passage 14 of the mouthpiece 11 or the mouthpiece 12. It is made slightly smaller than the inner wall diameter, and a narrow passage through which the resin passes, that is, a constricted part 40 is formed between the dam part 31 and the resin passage inner wall. The cross-sectional shape of the dam part 31 of the mandrel 30 is formed as a mandrel expansion part 32,33 that gradually becomes thicker from the middle toward the base, and in particular, the mandrel expansion part 32 on the upstream side in the extrusion direction is The slope is the downstream mandrel extension 3.
It is formed with a gentler slope than No. 3. In the extrusion head, a layer transfer section 41 is formed on the front wall side to uniformly transfer the resin flowing laminarly in the resin passage 14 to the circumferential outer wall in an annular shape, and a constriction section is formed on the front wall side. This is to form a pressure release part 42 on the rear wall side to release the pressure of the resin squeezed by the pressure release part 40. In the case of this embodiment, the diameter of the mandrel 30 is different on both sides of the dam part 31, and the diameter on the upstream side in the extrusion direction is larger than the diameter on the downstream side, but it is not always necessary to make it elongated. There isn't.

Since the mandrel 30 is configured as described above, first, when the resin extruded by the extrusion screw 10 passes through the resin passage 14 and flows laminarly into an annular body, the resin is formed in the mandrel expansion part 32. The resin is guided by the layer transfer section 41 in the resin passage 14 and transferred to the radially outer circumferential inner wall. Then, it passes through the constriction section 40 near the inner wall of the rotating cap holder 11 or the cap 12. That is, the layer-transferred resin is
The pressure is increased through a narrow passageway of zero, and becomes uniform in the circumferential direction, that is, in the annular shape. Thereafter, the annular body resin whose pressure has become uniform flows into the pressure release part 42, reaches the mouthpiece body, and is extruded.

In this way, by providing the dam 40 to make the resin pressure of the annular body uniform in the circumferential direction, the resin flows effortlessly and smoothly in the rotational direction of the base 12, and the tension member 2 is coated uniformly. Therefore, as shown in FIG. 3, the extruded spacer 21 has groove collapse and
Disturbances in shape and dimensions, eccentricity, etc. are eliminated, and a spacer cross section with extremely high precision can be obtained.

[Effects of the Invention] Since the present invention is configured as described above, it has the following effects.

(1) An extremely good spacer cross section with no groove collapse in the longitudinal direction of the spacer and no eccentricity etc. can be obtained;
The performance of optical communication cables will also be further improved.

(2) Since there is no groove collapse in the spacer cross section, the take-up speed can be increased several times compared to the conventional method, and productivity can be greatly improved.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the head assembly that pushes out the spacer;
The figure is a sectional view of a mandrel with a dam part and a resin passage used in the present invention, FIG. 3 is a sectional view of an extruded spacer, and FIG. 4 is a block diagram showing a conventional spacer production line apparatus. In the figure, 1 is the delivery drum, 2 is the tension member, and 3
is an extruder, 4 is a crosshead, 5 is a sprocket, 6 is a rotary drive device, 7 is a cooling water tank, 8 is a take-up machine, 9 is a winding drum, 10 is an extrusion screw, IJ is a mouth holder, 1
2 is a cap, 13 is a mandrel holder, 14 is a resin passage, 1
9 is a bearing, 20 is a mandrel, 21 is a spacer, 22 is an optical core storage groove, 30 is a mandrel, 31 is a dam, 32゜33
Reference numeral 40 indicates a mandrel expansion portion, 40 a constriction portion, 41 a layer transition portion, and 42 a pressure relief portion.

Claims (1)

[Claims] 1. A ring-shaped dam is provided in the middle of the mandrel in the resin passage to form a constricted part between it and the inner wall of the resin passage, and the resin passed through the constricted part has a plurality of protrusions on the inner periphery. An optical communication cable characterized in that a tension member is coated with a resin by extrusion from a rotating base, and at the same time a plurality of optical core storage grooves are formed on the resin surface, a spacer is extruded, the spacer is cooled, and the cable is removed. Spacer manufacturing method.