JPS61142612A - Melt resin extrusion for resin covered wire - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a resin-wave Vri electric wire that coats a core wire inserted into a crosshead with molten resin extruded from an extruder main body into a crosshead. The present invention relates to a molten resin extrusion method, and particularly to an improvement in a resin extrusion method suitable for forming a thin insulating layer on a core wire in the manufacturing process of insulated wires for communication cables.

(Prior art) Communication cables are generally formed by twisting together a large number of thin insulated wires, but the insulated wires for communication cables are A core wire made of a copper conductor whose surface is coated with a thin resin insulation layer is used.

This insulating layer is extremely thin, with a diameter of 0°4sm.
The thickness is the thinnest when a core wire of 1 is used.Incidentally, when the non-foamed solid layer of polyethylene resin is used as the insulating layer, the thickness of the insulating layer is 130 μm, and it is even thicker when the insulating layer is used as the insulating layer of the foam opening. , weighing only 90 tons.

When insulated wires are twisted together to form a communication cable, a thin insulating layer is required to maintain electrical properties such as maintaining uniform capacitance between a plurality of insulated wires. For this reason, it is required that the insulating layer be coated with as uniform a thickness as possible over the entire circumference of the core wire, and that there be no so-called uneven thickness.

When manufacturing actual insulated wires, when the maximum thickness of the insulating layer is a and the minimum thickness is b, the value of the ratio a/b is 1
．． It is required that the number be 10 or less. Therefore, when the above-mentioned core wire having a diameter of 0.4 mm is made of a polyethylene solid insulating layer with a minimum thickness of 125 μm, the requirement is to suppress the value of the deviation a-b to 12.5 μm or less. Similarly, if the minimum thickness of the foam insulation layer is 85 μm,
The required condition is to suppress the value of the deviation a-b to 8.5 μm or less.

Furthermore, such insulated east wires are generally manufactured by extruding molten resin around a core wire that advances within the crosshead, but the advancing speed of this core wire is extremely high, several thousand TrL/min. It is difficult to satisfy the above requirements. Moreover, these requirements tend to become stricter year by year.

FIG. 4 is a longitudinal sectional view of a crosshead that has been most commonly used in the manufacturing process of insulated east wires. In FIG. 4, the molten resin extruded from the extruder main body (not shown) flows into the inlet hole 12 formed at the inlet of the crosshead main body 10, and is extruded toward the outer peripheral surface of the nipple body 14. The molten resin travels along the traveling direction of the core line A shown by the arrow R while spreading so as to wrap around the nipple body 14,
Finally, the flow wraps around the entire outer circumferential surface of the nipple body 14 to become an annular flow, and is then extruded around the core 1i1A through the tapered passage 18 formed between the tip of the nipple body 14 and the die 16, and is melted. The outer peripheral surface of the core wire A is coated with resin to produce an insulated wire. Furthermore, dice 16
is held by a pair of die holders 20a and 20b, and its position relative to the nipple body 14 is adjusted by bolts 22a and 22b, and the position of the nipple body 14 in the direction of arrow R is adjusted by a threaded rod 24a and 124b.

When the crosshead shown in FIG. 4 is used for manufacturing insulated cables, the following problems occur. In other words, the flow path length of each part of the molten resin from when it flows into the inflow hole 12 of the crosshead until it becomes an annular flow is, for example, the flow of the molten resin that goes straight in the upper part of the figure and the flow that goes around the lower part of the figure. As is clear from comparing the flows of the molten resin as they advance, the annular flow cannot be uniform over the entire circumference because they are different.

Therefore, in order to manufacture an insulated wire that satisfies the above-mentioned requirements using such a loss head, it is necessary to delicately adjust the bolt 22a to the threaded rod 24b, and the adjustment requires extremely skill. At the same time, a large amount of molten resin and core wire had to be wasted during the adjustment work.

In consideration of the above circumstances, a method for manufacturing insulated cables called the so-called shunting method has been developed in recent years.

This splitting method means that the flow of molten resin extruded from the extruder main body into the crosshead is once divided into multiple flows of equal volume that are symmetrically located around the core line A that advances inside the crosshead. In this manufacturing method, the divided flows are then recombined to form an annular flow, which is then extruded and coated around the core wire A.

A representative example of such prior art (Japanese Patent Publication No. 54-10984) will be explained with reference to FIGS. 5 and 6.

Fig. 5 is a longitudinal cross-sectional view of the crosshead, and Fig. 6 is a cross-sectional view of the crosshead.
FIG. 3 is a perspective view showing a molten resin distribution passage portion taken out from the figure. In FIG. 6, parts given the same reference numerals as those in FIG. 5 indicate the same or equivalent parts.

First, the molten resin extruded into the crosshead from the screw 30 of the extruder main body (not shown) flows through the inlet hole 34 formed at the inlet of the crosshead main body 32 through the inlet hole 34 formed on the outer periphery of the first sleeve 36. It flows into the first lateral groove 38, is bent toward the advancing direction of the core line A shown by the arrow R, and further flows into the semi-annular groove 40, where it is divided into divided flows flowing in two directions in the circumferential direction. Each split stream passes through a semi-annular groove 40 into a first
At positions spaced apart from the lateral grooves 38 by 90 degrees in the circumferential direction, they flow into second lateral grooves 42, respectively. The molten resin flows through the second lateral groove 42 in the direction of the reverse arrow R, travels a predetermined distance, and flows into the communication hole 44 at the end of the second lateral groove 42 . In the communication hole 44, the flow direction of the molten resin changes toward the center of the core line Δ.

Next, each divided flow flows into four third lateral grooves 48 formed in the tapered outer peripheral surface of the second sleeve 50 through a passage 46, and is divided into four divided flows of equal volume. Each divided flow advances along the arrow R direction at 90° intervals in the circumferential direction with the core line A as the center, gently inclining towards the center of the core line A, and forms a fan-like shape at the terminal end of the third lateral groove 48. Afterwards, the four divided streams flow into the first taper passage 52, where the four divided streams merge to form an annular flow. The first tapered passage 52 is formed between a tapered inner peripheral surface 54 of the first sleeve 36 and a tapered outer peripheral surface 56 of the second sleeve 50.

This annular flow flows into the second tapered passage 64 formed between the tapered inner circumferential surface 60 of the die 58 and the tapered outer circumferential surface of the nipple body 62, and after being reduced in diameter while progressing in the direction of arrow R, the core wire The core wire A is extruded onto the outer circumferential surface of the core wire A, the core wire A is further reduced in diameter by the covering portion 66 of the die 58, and the core wire A is then discharged together with the core wire A from the crosshead.

In the figure, 68 indicates the first sleeve 36 and the second sleeve 750.
and a nut for fixing the nipple body 62 to the crosshead body 32.

When the loss head is used to manufacture insulated wires as described above, the molten resin extruded from the screw 30 is transferred to four The molten resin layer extruded to the outer peripheral surface of the core wire A has an uneven thickness over the entire circumference because the flow is divided into equal amounts of divided flows flowing through the three lateral grooves 48 and then merged in the first tapered passage 52 to form an annular flow. This makes it possible to form a coating layer with a more uniform thickness than in the case not shown in FIG.

Also, as in the case of Fig. 4, the bolt 22a to the threaded rod 24b
This eliminates the need for adjustment work, so it is so-called atonal.

It also has the advantage of being a heart crosshead.

However, such prior art has the following problem when attempting to satisfy the above-mentioned requirements for PA thickness of the coating layer, which are becoming stricter year by year. In other words, four third horizontal grooves 4
If the cross-sectional area of the third lateral groove 48 is set equal, each divided flow flowing through the third lateral groove 48 should be divided into equal amounts of divided flow. 3 horizontal groove 48
Subtle changes occur in the flow of molten resin due to dimensional accuracy, variation in finish, etc., and there is a limit to making each divided flow a uniform and equal flow. Therefore, in order to satisfy the above-mentioned strict requirements, the dimensional accuracy and finish of each passage through which molten resin flows must be extremely precisely aligned when manufacturing the crosshead, which requires a great deal of effort. There is a problem in that it requires cost.

In order to solve the above-mentioned problems, the inventors of the present invention repeatedly conducted various experiments, and found that if a constriction section was provided in the middle of the flow of molten resin and flow path resistance was applied to the flow of molten resin, the constriction section On the downstream side, the flow of molten resin becomes uniform, and
We found that the original annotation also remains constant.

Based on the above characteristics, the inventors of the present invention have devised the present invention with the aim of improving the so-called split flow resin extrusion method.

(Objective of the Invention) The present invention is capable of forming a coating layer with a uniform thickness over the entire circumference of a core wire by utilizing the above-described characteristics regarding the flow of molten resin, and moreover, it is possible to manufacture a crosshead at low cost. The purpose of the present invention is to provide a method for extruding molten resin for resin-coated electric wires.

(Structure of the Invention) The present invention allows the flow of molten resin extruded from the extruder main body into the crosshead to be applied to a plurality of positions having a symmetrical ffi relationship with respect to a core wire for a resin-coated electric wire inserted into the crosshead. The divided flows are then merged around the core wire to form an annular flow, and this annular flow is passed through a constriction part of a predetermined distance while remaining annular, and then extruded around the core wire to form a resin. This is a method for extruding a resin-coated electric wire using a molten resin.

(Example) FIG. 1 is a longitudinal cross-sectional view of a crosshead used for manufacturing insulated wires for communication cables when the molten resin extrusion method according to the present invention is applied to the manufacture of insulated wires for communication cables. Second
The figure is a cross-sectional view taken along the line nn in FIG. 1, and FIG. 3 is a perspective view showing the passage portion of the molten resin shown in FIG. 1. In FIG. 3, parts given the same reference numerals as those in FIG. 1 indicate the same or equivalent parts.

In FIG. 1, 100 is a crosshead main body, which is fixed to the extruder main body (not shown) located above in the figure. The crosshead body 100 has a tapered hole 102.
An inflow hole 106 consisting of a cylindrical hole 104 and a cylindrical hole 104 are formed, through which a molten resin such as polyethylene extruded from the extruder main body flows downward. A through hole 108 is formed in the center of the crosshead body 100, and the center line direction of the through hole 108 is orthogonal to the center line direction of the inlet hole 106, and the center line direction of the through hole 108 is perpendicular to the center line direction of the inlet hole 106, and the center line direction of the through hole 108 is perpendicular to the center line direction of the inlet hole 106. It matches the direction of travel.

The lower end of the cylindrical hole 104 is open on the inner surface of the through hole 108, and a substantially cylindrical first sleeve 110 is fitted therein. The first sleeve 110 consists of a flange 112 provided at the left end in the figure, a large diameter section 114 at the center, and a small diameter section 116 at the right end. The large diameter portion 114 is tightly fitted into the through hole 108 and fixed to the crosshead body 100 with a nut 120 screwed into a threaded portion 118 formed at the right end of the large diameter portion 114.

The inner surface of the first sleeve 110 has a threaded portion 126, a stepped portion 128, a fitting portion 130, a tapered surface 132, a stepped portion 134, and a die fitting portion 136 that are continuous from the left end to the right end. A flange 140 of a second sleeve 138 is engaged with the stepped portion 128 , and a flange 140 of the second sleeve 138 is engaged with the fitting portion 130 .
The large diameter portion 142 of the die 144 is tightly fitted into the stepped portion 134, the left end surface of the die 144 having the tapered hole 143 is engaged with the step portion 134, and the outer peripheral surface of the die 144 is tightly fitted into the die fitting portion 136. They are mated.

Furthermore, a third sleeve 148 is fitted into the through hole 146 of the second sleeve 138 . The flange 150 of the third sleeve 148 is engaged with the end surface of the flange 140, and
The large diameter portion 152 of the sleeve 148 is tightly fitted into the through hole 146, and the j-pa portion 156 of the third sleeve 148 protrudes from the through hole 146 and is continuous with the tapered portion 158 of the second sleeve 138. A through hole 160 through which the core wire A is inserted is formed in the center of the third sleeve 148.

The seventh flange 150 of the third sleeve 148 is pressed by a nut 162 that is screwed into the threaded portion 126, and the second sleeve 138 and the third sleeve 148 are fixed to the first sleeve 110.

An annular groove 164 is formed continuously to the left of the large diameter portion 142 of the second sleeve 138, and the annular groove 164 and the fitting portion 1
An annular passage 165 is formed between 30. Annular groove 1
A tapered surface 166 and a cylindrical surface 168 are continuously formed on the left side of the sleeve 64, and the cylindrical surface 168 has a cylindrical shape between the fitting portion 130 of the first sleeve 110 as shown in FIG. 1a. A second constriction portion 169 is provided with a predetermined minute gap therebetween. The second aperture portion 169 is, for example, 10j+1II.
The cross-sectional area of the resin passage is set to be narrowed down to, for example, about 40 to 50 g over a length L2 of about I.

The tapered portion 158 is continuous with the tapered portion 156, and the tapered portion 1
56 and the tapered portion 158 are positioned concentrically with a predetermined gap in the tapered surface 132 and the tapered hole 143 that are continuous across the first sleeve 110 and the die 144, and form a tapered passage 159.

Note that the die 144 is fixed to the first sleeve 110 with a cap 172 that is screwed into a threaded portion 170 formed at the right end of the first sleeve 110.

With the first sleeve 110 fixed in this manner, a semi-annular groove 122 having a substantially U-shaped cross section is formed on the outer peripheral surface of the large diameter portion 114 at a position facing the cylindrical hole 104 . The semi-annular groove 122 is connected to the first sleeve 110 as shown in FIG.
The flow of molten resin flowing down the inflow hole 106 is divided into two directions, and these two divided flows are arranged at symmetrical positions around the core line A, that is, in the circumferential direction.
It is formed to guide to positions spaced apart by 0 degrees.

As shown in FIG. 3, both ends of the semi-annular groove 122 have communication holes 1
It is connected to 24. The communication hole 124 is perpendicular to the direction of movement of the core mA, and extends toward the center of the core A in the first sleeve 1.
10 is perforated.

Therefore, the inflow hole 10 is arranged in a positional relationship such that the distribution center line of the molten resin passing through the inflow hole 106 of the crosshead main body 100 and the molten resin distribution center line of the semi-annular groove 122 are orthogonal to each other.
6 and a communication hole 124 are arranged.

Each of the communication holes 124 is continuous with two fan-shaped passages 174, and the fan-shaped passages 174 are formed so as to expand into a fan shape as they advance in the direction of arrow R. As shown in FIG. 3a, there is a first hole near the connection part with the communication hole 124 in the fan-shaped passage 174.
A constricted portion 177 is formed. Specifically, the cross-sectional area of the inlet of the fan-shaped passage 174 (C-C cross-section in the figure) is determined by, for example, 40
It is set to be as small as ~50.

As shown in FIG. 3, the fan-shaped passage 174 extends in the direction of arrow R while converging at a gentle inclination angle toward the core line A, and the terminal end of the fan-shaped passage 174 is connected to the annular passage 165, the second constricted part 169, and the tapered part. The passages 159 are successively connected to each other.

Tapered passageway 159 is continuous with sheath 141 (FIG. 1) of die 144.

Next, the operation, ie, the method of extruding the molten resin, will be explained. As shown in FIG. 3, the molten resin flowing down the cylindrical hole 104 of the inflow hole 106 flows into the semi-annular groove 12 of the first sleeve 110'.
2 and is divided into two divided streams. Semi-annular groove 12
The molten resin flowing into the communication hole 124 from both ends of the core wire A flows toward the center of the core wire A, and flows into the fan-shaped passage 174.

The molten resin flows through the fan-shaped passage 174 and passes through the first constriction section 1.
It is narrowed down at 77.

At this time, the flow of the molten resin is hindered by the increase in flow path resistance due to the first constriction part 177, and the pressure increases on the upstream side of the first constriction part 177, and this pressure increase causes the first constriction part 17
The flow of the molten resin on the downstream side of the first throttle part 177 is rectified, and the flow rate of the molten resin flowing through the fan-shaped passage 174 on the downstream side of the first throttle part 177 is made uniform.

The molten resin flows from the end of the fan-shaped passage 174 to the annular passage 165.
When flowing into the fan-shaped passage 174, the two divided flows that have passed through the fan-shaped passage 174 merge into the annular flow, and are then throttled by the second constriction section 169.

At this time, the flow of the molten resin is impeded by the increase in flow resistance due to the second constricted portion 169 which is continuous over the entire cylindrical circumference, and the pressure in the annular passage 165 rises. The flow of molten resin is rectified over the entire circumference, and the flow of the molten resin in the tapered passage 159 is
The flow rate of molten resin flowing through is made uniform.

The flow of molten B & resin after passing through the second constriction part 169 flows into the covering part 141 of the large diameter part 114 through the tapered passage 159, and in the covering part 141, a uniform predetermined thickness is formed on the outer peripheral surface of the core wire A. covered with.

(Effects of the Invention) As explained above, the method for extruding molten resin for resin-coated electric wires according to the present invention allows the flow of molten resin extruded from the extruder main body into the crosshead to be applied to the resin-coated electric wires inserted into the crosshead. The divided flows are once divided into a plurality of flows having a symmetrical positional relationship around the core line of After passing through the core wire, the core wire is extruded and coated with resin, so the following effects can be achieved.

That is, the molten resin that has merged into a single annular flow in the annular passage 165 is squeezed as it passes through the second constriction section 169 and flows into the second flow.
The flow is obstructed by the increase in flow path resistance due to the constriction part 169, and the pressure in the annular passage 165 increases, and the flow of molten resin in the tapered passage 159 is rectified over the entire circumference due to this pressure pressure, so that the coating part The molten resin can be flowed into the core wire 141 in a rectified state over the entire circumference of the core wire A. In addition to this rectifying effect, the flow rate of the molten resin is adjusted by the second constriction portion 169, so that the flow a of the molten resin in the tapered passage 159 can be made uniform.

Therefore, the flow of molten resin flowing from the annular passage 165 into the tapered passage 159 is uniform and equal over the entire circumference, making the thickness of the resin layer coated by the covering portion 141 uniform over the entire circumference of the core MA. be able to.

Therefore, compared to the prior art shown in FIGS. 5 and 6, the entire thickness of the coating layer coated on the outer peripheral surface of the core wire A can be achieved without forming the molten resin passage with high precision. It can be formed with a uniform thickness over the circumference, and the cost required for manufacturing the crosshead can be significantly reduced.

(Another embodiment) (1) The present invention is not limited to the case where both the first aperture part 177 and the second I' two parts 169 are provided as in the embodiment,
If at least the second constriction section 169 is provided, the first constriction section 177 is not necessarily necessary, and the first constriction section 177
This applies even if the system is not equipped.

(2) The shape of the passage of the molten resin until it joins the annular flow in the annular passage 165 is not limited to the embodiment shown in FIG. 3; for example, the direction and shape of the communication hole 124 may be modified as appropriate. Generally speaking, the key point is that the flow of molten resin extruded from an extruder passes through several passages and becomes multiple split streams, and each split stream merges while maintaining a symmetrical positional relationship around core line A. Good to have. In addition, the fan-shaped passage 174 has two
It is not limited to a tree, but may be a plurality of trees such as four trees.

(3) The present invention is not limited to manufacturing insulated N wires for communication cables as in the embodiments, but can also form a thick coating layer, and the core wire A is a solid copper shelf. However, the wire is not limited to the above, and may be a thin electric wire coated with a resin layer, or may be a pipe-shaped wire.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a crosshead used in carrying out the present invention, FIG. 1a is an enlarged longitudinal sectional view showing the second constriction part, and FIG. 3 is a perspective view showing the passage portion of the molten resin in FIG. 1, FIG. 3a is a sectional view taken along line a-a in FIG. 3 without showing the first constriction part, and FIG. FIG. 5 is a longitudinal sectional view showing another conventional example, and FIG. 6 is a perspective view showing the molten resin passage portion of FIG. 4. 100...
・Crosshead body, 106...Inflow hole, 110...
- First sleeve, 122... semi-annular groove, 124...
Communication hole, 138... second sleeve, 144... die, 148... third sleeve, 164... annular groove,
164... Annular groove, 168... Cylindrical surface, 169...
・Second throttle part, 174... Fan-shaped passage, 177... First throttle part, A... Core wire patent applicant Dainichi Nippon Electric Cable Co., Ltd. Figure 3 Figure 2

Claims (1)

[Claims] The flow of molten resin extruded from the extruder main body into the crosshead is once divided into a plurality of flows having a symmetrical positional relationship around the core wire for the resin-coated electric wire inserted into the crosshead, and then A resin-coated electric wire characterized in that split flows are merged around a core wire to form an annular flow, and this annular flow is passed through a constriction part of a predetermined distance while remaining annular, and then extruded around the core wire to be coated with resin. molten resin extrusion method.