JP3474598B2 - Tube extrusion mold - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tube extrusion mold used for obtaining a tube-shaped molded product by molding a glass or plastic material by an extrusion molding method.

[0002]

2. Description of the Related Art For example, glass or plastic material is used as a covering member for protecting an optical fiber.
Generally, in the process of manufacturing an optical fiber, the coating member is formed by coating a glass or plastic tube serving as a coating member on the outside of the preform that will become the optical fiber main body at the preform stage. Such a tube is manufactured by a vertical or horizontal extrusion molding method. One of the biggest factors that influence the quality of tubes produced by this extrusion method
One of them is an extrusion mold used in this production (hereinafter referred to as a tube extrusion mold). If this tube extrusion mold is not appropriate, a tube having a predetermined size cannot be obtained. In particular, since a tube used as a covering member for an optical fiber has a severe allowable dimensional accuracy, it is necessary to use a tube extrusion mold capable of molding a tube having high dimensional accuracy. In this case, in the horizontal extrusion method, the roundness of the tube is poor because the tube immediately after extrusion and the liner are in constant contact with each other. Therefore, when high dimensional accuracy of a tube used as a covering member of an optical fiber is required, the vertical tube extrusion molding method is usually used.

FIG. 7 is a sectional view of a conventional vertical tube extrusion mold, FIG. 8 is a plan view of a conventional vertical tube extrusion mold, and FIG. 9 is a conventional vertical tube extrusion mold. It is sectional drawing of a tube extrusion molding apparatus.

As shown in FIGS. 7 and 8, this conventional tube extrusion mold has a nozzle die portion 100.
And a mandrel portion 200 supported in the nozzle portion 101 which is a through hole formed in the nozzle die portion 100. In the nozzle portion 101 of the nozzle die portion 100, a support area 101a having a step portion for supporting the mandrel portion is provided in this order from the top, and the support area 10a.
A deformation area 101b having a diameter gradually decreasing from 1a, a molding area 101c which is a minimum diameter portion following the deformation area 101b and serves to regulate the outer shape of the tube, a relief area 101d and a liner portion 101e which follow the molding area. Has been formed.

Further, the mandrel portion 200 is provided with a cored bar portion 202 which functions to regulate the inner shape of the tube at the center of three support arms 201 formed in a substantially Y shape. is there. The mandrel portion 200 has a supporting arm 20.
1 is supported by the nozzle portion 101a, the core metal portion 2
02 is the central portion of the nozzle portion 101, that is, the molding area 10
It is located at the center of 1c.

Here, in this conventional tube extrusion molding die, the length of the molding region 101c in the extrusion direction is substantially zero, and the tip of the cored bar 202 is the molding region 1.
It is in the same plane as the plane containing 01c.

As shown in FIG. 9, this conventional tube extrusion mold has a die holder 300 at the bottom thereof.
Further, a container 500 for accommodating the forming raw material 400 is attached to the upper part thereof. These are housed in the housing 700 and can be heated by the heater 800. Further, a plunger 600 is slidably fitted in the container 500, and the molding raw material 4 in the container 500 is fitted by the plunger 600.
00 is molded into a tube shape through a nozzle die portion 100 and a mandrel portion 200, and is extruded into a liner 900 connected to the lower portion of the nozzle die portion 100.

[0008]

By the way, in the vertical extrusion molding method as in the above-mentioned conventional example, the extruded tube is elongated in the longitudinal direction by its own weight in the process of cooling to room temperature. The higher the molding temperature, the greater the amount of extension. Therefore, in order to obtain a tube with high dimensional accuracy, a lower temperature range (for example, in the case of lead glass,
Molding at a temperature of 108 to 109 poise) is desired.

However, it has been found that the following problems occur when this conventional tube extrusion mold is used for low temperature high viscosity extrusion molding.

During tube extrusion molding, molding raw material 400
Is to be temporarily branched by the supporting arm 201 of the mandrel unit 200, and the divided raw materials are merged again in the nozzle unit 101 and fused while passing through the deformation region 101b and the molding region 101c. However, in the above-mentioned conventional tube extrusion molding die, since the length (ΔL) of the molding region 101c in the extrusion direction is substantially zero,
In the deformation area 101b and the molding area 101c, the glass as the forming raw material is extruded before the glass is sufficiently fused and a trace of fusion is left on the surface, or the stress is released to return to the original diameter. (temporal deformation), further, particularly inner shape because of such greatly influenced by the change in the size of such a profile, a problem that dimensional accuracy is reduced is generated in the outer shape within the form both of the shaped tube.

Further, in the above-mentioned conventional tube extrusion molding die, since the supporting arm 201 for fixing the core metal 202 of the mandrel portion 200 to the central portion of the nozzle portion 101 of the nozzle die portion 100 is Y-shaped, When the flow path of the forming raw material passing through the support arm 201 is divided into three directions, and the flow in one direction becomes faster or slower, the formed tube is bent, and similarly, there is a problem that the dimensional accuracy is lowered.

From the above, the conventional tube extrusion mold cannot obtain the required dimensional accuracy of the tube.

The present invention has been made under the above-mentioned background, and its purpose is to provide a roundness of a molded tube,
It is an object of the present invention to provide a tube extrusion mold that can achieve higher dimensional accuracy such as straightness and cylindricity.

[0014]

In order to solve the above-mentioned problems, a tube extrusion mold according to the present invention is (Construction 1): A tube extrusion molding for extruding a molding raw material and passing it through to obtain a tubular molded body. Type,
A nozzle die part having a nozzle part for passing the forming raw material and a forming region formed in the nozzle part for controlling the outer shape of the tube, and an inner shape of the tube arranged in the center part of the nozzle part. In a tube extrusion mold having a mandrel part having a plurality of supporting arms for supporting the cored bar part and the cored bar part in the center part of the nozzle part, molding in the nozzle die part The length of the zone in the extrusion direction is a finite length, and the tip end portion of the mandrel portion in the extrusion direction of the cored bar is projected toward the extrusion direction side from the surface surrounded by the molding zone. As a mode of this constitution 1, (constitution 2) A tube extrusion molding die for obtaining a tubular molded body by extruding and passing a molding raw material, A nozzle die portion having a nozzle portion for passing the forming raw material and a forming region formed in the nozzle portion and having a function of regulating the outer shape of the tube;
A mandrel portion provided in the central portion of the nozzle portion and having a function of regulating the inner shape of the tube; and a mandrel portion having a plurality of support arms for supporting the metallic core portion in the central portion of the nozzle portion. In the tube extrusion mold having the configuration, the support arm is formed in a cross shape, and (Configuration 3) In the tube extrusion mold of Configuration 1 or 2, the length in the extrusion direction of the molding region is ΔL,
ΔL / r when the nozzle radius in the molding area is r
Is 0.035 to 0.85, and the protrusion amount of the tip end of the cored bar portion in the extrusion direction to protrude in the extrusion direction side from the surface surrounded by the molding zone is 0.2 to 2.0 m.
The configuration is characterized in that it is m.

[0015]

According to the above configuration 1, the length of the nozzle in the extruding direction of the molding region (molding region length) is set to a length exceeding 0 (finite length), so that the deformation region of the molding die and the molding region. In order to give sufficient time for the forming raw material to be fused, no trace of fusion is left on the surface of the molded tube. Also, the molding area is 0
In the conventional case described above, the molding tube that has passed this molding region is deformed over time by trying to return to the size of the diameter before molding by releasing the stress, but in the configuration of the present invention, the molding region is Since it has a finite length, this change over time is always made to be a substantially constant amount, and the precision of the shape of the molded tube, especially the outer shape, can be improved.

Further, by projecting the tip end of the cored bar from the surface surrounded by the molding zone, the inner diameter is given after the outer diameter of the tube is determined after passing through the molding zone. As a result, the roundness and cylindricity of the molded tube are particularly well maintained, and for example, a tube having high accuracy required as a tube used as a covering member in a preform for an optical fiber can be obtained. You can

Further, according to the configuration 2, the supporting arm for fixing the core metal of the mandrel portion to the central portion of the nozzle die portion has a cross shape, so that a plane perpendicular to the direction of the flow of the forming raw material is considered. Then, the supporting arm is symmetrical with respect to the X axis and the Y axis. From this fact, the flow path of the forming raw material when passing through the support arm of the mandrel part is divided into four directions of left-right vertical symmetry, so that even if the flow in one direction is fast or slow, The faster or slower flow in the opposite direction prevents the bending of the counter-shaped molded tube. Further, even if the flows in the symmetrical directions are not completely equal, there is less bending as compared with the conventional Y-shaped one.
Therefore, the dimensional accuracy such as straightness and cylindricity of the molded tube can be improved.

Further, by increasing the number of supporting arms by one, the total strength can be increased, and the width or cross-sectional area of the supporting arms can be made smaller, which is advantageous for glass fusion or uniform glass flow. Becomes In the present invention, the supporting arm is formed in a cross shape, but if it is increased more than this, there is a problem that the flow resistance becomes too large, or that the molded body that has passed through the supporting arm of the mandrel becomes difficult to fuse. Occurs.

According to the structure 3, when the length of the molding area in the extrusion direction is ΔL and the nozzle radius of the molding area is r, ΔL / r is 0.035 to 0.85, and The roundness of the tube to be molded by setting the projection amount of 0.2 to 2.0 mm that causes the tip end of the cored bar portion in the extrusion direction to protrude from the surface surrounded by the molding region to the extrusion direction side, Dimensional accuracy such as straightness and cylindricity can be improved.

When ΔL / r is less than 0.035,
The dimensional accuracy of the tube is poor because it is pushed out before the dimensional accuracy becomes stable. Δ / r is 0.85
Above, the molding resistance increases and the radial expansion of the extruded product increases.

Further, the protrusion amount of the tip of the core metal is 0.2 to
The preferred amount is 2.0 mm, but 0.2 m
If it is less than m, the variation of the outer diameter of the tube affects the inner diameter. On the other hand, when the thickness exceeds 2.0 mm, not only the protruding effect cannot be improved, but also the friction between the tube and the nozzle die increases, and the pressure required for molding increases. Therefore, in any case, high dimensional accuracy cannot be obtained.

[0022]

EXAMPLE 1 FIG. 1 is a sectional view of a tube extrusion mold according to Example 1 of the present invention, and FIG. 2 is a plan view of the tube extrusion mold according to Example 1 of the present invention. Example 1 will be described below with reference to these drawings.

As shown in FIGS. 1 and 2, the tube extrusion molding die of this embodiment includes a nozzle die portion 1 and
It is composed of a mandrel portion 2 supported in a nozzle portion 11 which is a through hole formed in the nozzle die portion 1.

The nozzle die portion 1 is formed by forming stainless steel into a substantially cylindrical shape, and forming a nozzle portion 11 which is a through hole along the cylindrical axis. The nozzle portion 11 has, in order from the top, a support area 11a having a step portion for supporting the mandrel portion, a deformation area 11b having a diameter gradually decreasing from the support area 11a, and a minimum diameter following the deformation area 11b. A molding region 11c that functions as a part to control the outer shape of the molded tube, a relief region 11d following the molding region 11c, and a liner portion 11e are formed. A step portion 1a for fitting a container (not shown) is formed on the outer peripheral portion of the nozzle die portion 1.

The support zone 11a, the upper is maximized through, after following the lower predetermined thickness in this way, becomes a stepped portion, the diameter size at this stage difference portion is inclined from a predetermined amount smaller more Following the gradually decreasing deformation area 11b. Here, the pushing direction (axial direction) of the inclined surface of the deformation area 11b
The angle α formed with respect to is the push-out angle. The length L of the deformation area 11b in the extrusion direction is the deformation area length.

The molding region 11c is the smallest diameter portion following the deformation region 11b and serves to regulate the outer shape of the molded tube. In this embodiment, the length of the molding region 11c in the extrusion direction, that is, the nozzle molding region length is set to a finite length ΔL. Further, assuming that the diameter of the forming region 11c is the nozzle radius r, the ratios L / r and ΔL / r of the nozzle radius r to the deformation region length L and the forming region length ΔL are set to be in predetermined ranges. In this example, L = 8 mm, Δ
L = 0.5 mm, r = 5.8 mm, L / r = 1.38,
ΔL / r = 0.086.

The relief area 11d is an area in which the outer peripheral portion of the molded tube molded by the molding area 11c is prevented from contacting, and conventionally, the relief area is formed so as to be perpendicular to the extrusion direction. However, in this embodiment, the inclined surface forms an escape angle β with respect to the pushing direction. This clearance angle β is also set within a predetermined range. In this example, β = 31.6 °.

Further, the liner portion 11e is a region for taking out the molded tube, and is a liner not shown (see FIG. 7).
This is the part where the tip of is attached.

Further, the mandrel portion 2 is provided with a cored bar portion 22 which functions to regulate the inner shape of the molded tube at the center of three support arms 21 formed in a substantially Y shape. Is. The mandrel portion 2 has its supporting arm 21 placed and supported on the nozzle portion 11a so that the cored bar portion 22 is located at the central portion of the nozzle portion 11, that is, at the center of the molding region 11c. . Here, conventionally, the tip of the cored bar 22 is made to be in the same plane as the surface including the molding area 11c. However, in this embodiment, the tip end of the cored bar 22 is formed from a surface surrounded by the molding area 11c. A predetermined distance is projected in the extrusion direction. This protrusion amount δL is also set within a predetermined range. In this example, δL = 1 mm. The outer diameter of the tip of the cored bar 22 was 2.8 mm.

Further, the three support arms 21 are formed so that their longitudinal directions form 120 ° with each other, and the length thereof is l (el), and as shown in FIG. When the width included in the plane perpendicular to is b and the height in the extrusion direction is h, the ratio of b: h: l needs to be set within a predetermined range. In this example, b = 4
mm, h = 5 mm, l = 14 mm, b: h: l = 0.
It was set to 8: 1: 2.8.

When the area whose diameter is the upper outer diameter of the nozzle die portion 1 is A ₀ and the area whose diameter is the opening diameter of the molding region 11c is A ₁ , A ₀ / A ₁ represents the extrusion ratio. However, this extrusion ratio also needs to be within a predetermined range. In this example, A ₀ / A ₁ = 9.1.

Embodiment 2 FIG. 4 is a sectional view of a tube extrusion mold according to Embodiment 2 of the present invention, FIG. 5 is a plan view of the tube extrusion mold according to Embodiment 1 of the present invention, and FIG. 6 is a support arm. FIG. Example 1 will be described below with reference to these drawings. Since this embodiment has the same structure as that of the above-described first embodiment except that the mandrel portion has a cross shape, the same reference numerals are given to common portions and the description thereof will be omitted. The mandrel portion peculiar to this embodiment will be described below.

In the mandrel portion 220 of this embodiment, four supporting arms 221 are formed in a cross shape so that their longitudinal directions are 90 ° with each other. Now each support arm 2
If the length of 21 is l (ell), and the width included in the plane perpendicular to the extrusion direction is b and the height in the extrusion direction is h as shown in FIG. 6, b: h :
It is necessary to set the ratio of l within a predetermined range. In this example, b = 3 mm, h = 5 mm, l = 14 mm, b:
It was set to h: l = 0.6: 1: 2.8. The other structure is the same as that of the first embodiment.

According to the embodiments of the actions and effects described above in Example, molding region 11c of the nozzle portion 11
By setting the molding region length ΔL of the above to a length (finite length) exceeding 0, the molding raw material shunted by the support arm is sufficiently fused while passing through the deformation regions 11b and 11c. No trace of fusion remains on the surface of the molded tube. Further, in the conventional case in which the molding area is set to 0, the molding tube that has passed this molding area is deformed with time by trying to return to the size of the diameter before molding by releasing the stress. Since the length is finite, the change with time is always made to be a substantially constant amount, and the precision of the shape of the molded tube, particularly the outer shape, can be improved.

Furthermore, by projecting the tips of the cored bars 22, 222 from the surface surrounded by the molding region 11c, the inner diameter is given after the outer diameter of the tube is determined after passing through the molding region 11c. As a result, the roundness and cylindricity of the molded tube are particularly well maintained, and for example, a tube having high accuracy required as a tube used as a covering member in a preform for an optical fiber can be obtained. You can

In addition to this, according to the second embodiment,
Since the supporting arm for fixing the core metal 222 of the mandrel portion 220 to the central portion of the nozzle die portion 1 has a cross shape, when the surface perpendicular to the direction of the flow of the forming raw material is considered, the supporting arm has the X-axis. , And is symmetrical about the Y axis. From this, the flow path of the forming raw material when passing through the support arm 222 is divided into four directions of left-right and up-down symmetry, and even if the flow in the one direction is fast or slow, it becomes symmetrical. The flow in the direction of
Prevents bending of the molded tube. Further, even if the flows in the symmetrical directions are not completely equal, there is less bending as compared with the conventional Y-shaped one. Therefore, the accuracy of shape of the molded tube such as straightness and cylindricity can be improved.

Further, by increasing the number of supporting arms by one, the total strength can be increased and the width or cross-sectional area of the supporting arms can be made smaller, which is advantageous for glass fusion or uniform glass flow. Becomes

Next, a glass tube was formed by using the forming die of each of the above-described examples and a case of forming by the conventional forming die shown in FIGS. 7 to 9 was obtained. FIG. 10 shows the result of comparison of dimensional accuracy of molded products. The molding device used is the device shown in FIG. 9, and the molding raw material to be filled in the container 500 is FDS9.
n Lead glass (conventional example, Example 1, Example 2-1) and F
Colored glass (Example 2-2, Example 2-3) in which 1% CuO was contained in DS9n lead glass was 35 mmφ × 30.
What was cut out into mm was used. Also, the container 500
Inside, the molding raw material is heated to 535 ° C. and held for about 40 minutes.
Extrusion was carried out by applying a pressure of 0 Kg / cm ² .
The dimensions of the molding die of each example are as described above, but the dimensions of the molding die of the conventional example are as follows.

Dimensions of support arm 201; b = 4 mm, h = 5
mm, l = 14 mm, b: h: l = 0.8: 1: 2.8 Extrusion ratio; A ₀ / A ₁ = 8.5 Extrusion angle; α = 38.7 ° Deformation zone length (L) / nozzle Radius (r); L = 5 mm, r =
6 mm, L / r = 0.83 Clearance angle; β = 90 ° Further, in FIG. 10, the circularity is the value of the difference between the radius of the circle circumscribing the closed curve to be measured and the radius of the inscribed circle. is there. The cylindricity is the value of the difference between the radius of the cylindrical surface circumscribing the measurement target cylindrical surface and the radius of the inscribed cylindrical surface.

As is apparent from FIG. 10, the dimensional accuracy of the tube molded by each of the above-described molds of the examples is remarkably improved as compared with the tube molded by the conventional example.

In the molding die of the present invention, it has been confirmed that a certain effect can be obtained by setting the dimensions of the respective parts within the following ranges in addition to the above-mentioned examples.

The extrusion ratio A ₀ / A ₁ may be 8.5 or more. Is less than 8.5, not completely fused even after the molded body diverted in the mold has been merged.

The extrusion angle α may be in the range of 21.8 to 31.6. When the extrusion ratio A ₀ / A ₁ and the length L of the deformation zone 2 are constant, when α is 21.8 ° or less, the molding resistance increases, which is disadvantageous to the flow of the molded body and cannot be extruded. There is also. Further, when it exceeds 31.6 °,
The mandrel cannot be fixed properly.

L / r may be 1.13 to 1.74. If L / r is less than 1.13, the object to be molded is extruded before it is sufficiently fused in the deformation region 2, and if it exceeds 1.74, pressure transmission becomes poor and the necessary extrusion pressure becomes large. In the case of high-viscosity molding, extrusion may not be possible.

The escape angle β of the nozzle may be 30 to 60 °. If β is less than 30 °, the extruded product may come into contact with the inner peripheral surface of the mold under the nozzle outlet.
Further, if it exceeds 60 °, the strength of the nozzle outlet decreases,
When extruding at high pressure, the dimensional accuracy of the tube decreases due to the deformation of the nozzle.

A ratio b / of the width b and the height h of the longitudinal section of the support arm
h may be 0.5 to 0.7. When b / h is less than 0.5, the supporting arm is deformed, the position of the tip of the core metal is changed, and the inner diameter of the tube is changed. On the other hand, when it exceeds 0.7, the flow path of the molded body of the support arm portion becomes narrow, which is disadvantageous in the flow and fusion of the molded body, and may not be extruded.

It should be noted that the angular portion existing in the flow path through which the forming raw material passes, for example, the corner portion 2 of the support arms 21 and 221.
By rounding 1a and 221a (see FIGS. 3 and 6),
As a result, the flow resistance of the forming raw material can be reduced, and smooth extrusion can be performed.

[0048]

As described above in detail, according to the tube molding die of the present invention, the length of the molding region in the nozzle die portion in the extrusion direction is a finite length, and the core metal portion of the mandrel portion is The tip end portion in the extrusion direction is projected toward the extrusion direction side from the surface surrounded by the molding region,
Alternatively, by forming the supporting arm of the mandrel portion in a cross shape, it is possible to obtain a tube in which the dimensional accuracy of the outer diameter and the inner diameter is improved overall.

[Brief description of drawings]

FIG. 1 is a sectional view of a tube extrusion mold according to Example 1 of the present invention.

FIG. 2 is a plan view of the tube extrusion mold according to the first embodiment of the present invention.

FIG. 3 is a sectional view of a support arm.

FIG. 4 is a sectional view of a tube extrusion mold according to Example 2 of the present invention.

FIG. 5 is a plan view of a tube extrusion mold according to Example 2 of the present invention.

FIG. 6 is a sectional view of a support arm.

FIG. 7 is a sectional view of a conventional tube extrusion mold.

FIG. 8 is a plan view of a conventional tube extrusion mold.

FIG. 9 is a sectional view of a conventional tube extrusion molding apparatus.

FIG. 10 is a diagram showing a comparison of dimensional accuracy of tubes molded using the tube extrusion molds of the example and the conventional example.

[Explanation of symbols]

1 ... Nozzle die part, 2, 220 ... Mandrel part, 2
1, 221 ... Support arm, 11 ... Nozzle portion, 11c ... Molding area, 22, 222 ... Core metal portion.

Continuation of front page (56) Reference JP-A-63-71330 (JP, A) JP-A-55-77533 (JP, A) JP-A-55-97931 (JP, A) JP-A-60-193628 (JP , A) JP 2-59317 (JP, A) JP 4-316824 (JP, A) JP 62-218122 (JP, A) JP 1-131030 (JP, A) JP 4-209726 (JP, A) Actual Kaihei 5-7434 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 47/00-47/96 C03B 17/00-17 / 06

Claims (3)

(57) [Claims] To 1. A tube extrusion mold to obtain a tubular molded body by passing the forming material extruded
In the above , it is assumed that a nozzle part for passing the forming raw material, a forming region formed in the nozzle part for controlling the outer shape of the tube, and formed continuously in this forming region.
A relief area having an inner diameter larger than the inner diameter of the molding area
And the extrusion direction of the molding raw material continuously in this escape area
A nozzle die portion having a liner portion formed by extending to a core portion, a cored bar portion disposed in the central portion of the nozzle portion and configured to control the inner shape of the tube, and the cored bar portion. of a tube extrusion die having a mandrel section having a plurality of support arms for supporting the heart, the finite length Satoshi extrusion direction length of the forming zone in the nozzle die part, and the Rutotomoni protrudes the tip toward the extrusion direction of the core portion in the extrusion direction from the surface to be surrounded by the molding zone in the mandrel portion, before
The inner peripheral surface of the relief area in the nozzle die is
Make a sloped surface that forms an escape angle β with respect to the extrusion direction of the raw material.
A tube extrusion mold characterized in that 2. The supporting arm of the mandrel portion is formed in a cross shape.
The tube extrusion mold according to claim 1, wherein the tube extrusion mold is formed. 3. The tube extrusion mold according to claim 1, wherein ΔL / r is 0, where ΔL is the length of the molding region in the extrusion direction and r is the nozzle radius of the molding region. .035
To 0.85, and the amount of protrusion that causes the tip of the cored bar in the extrusion direction to protrude in the extrusion direction from the surface surrounded by the molding zone is 0.2 to 2.0 mm. A tube extrusion mold.