JP3375118B2 - Method and apparatus for manufacturing synthetic resin pipe - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a synthetic resin pipe, and more specifically, a method for producing a synthetic resin pipe used for carrying various gases or liquids, electric wire protection pipes, etc. Regarding the device.

[0002]

2. Description of the Related Art As an electric wire protection tube, there is a synthetic resin corrugated tube whose outer peripheral surface is corrugated along the axial direction. Synthetic resin corrugated pipe has features such as flexibility that allows the pipe wall to bend flexibly and that the cross section of the pipe does not easily deform even when a load is applied. It is widely used for electric wire protection pipes, air pipes, etc. that protects etc.

As a method of manufacturing a synthetic resin corrugated pipe, the following method is adopted. While extruding the molten resin into a tubular shape, pressurized air is fed into the tubular resin in a state where a molding die having a desired wave shape is arranged around the outer periphery of the extruded tubular resin. The tubular resin expanded and deformed to the outer peripheral side by the pressurized air is molded according to the corrugated shape of the molding die. A pressure plug that blocks the internal space of the tubular resin is arranged downstream of the extruded tubular resin so that pressurized air does not leak. By supplying pressurized air to the upstream side of the pressurizing plug, the internal space of the tubular resin can be efficiently pressurized. The tubular resin after molding is immediately cooled to obtain a synthetic resin corrugated pipe having a predetermined corrugated shape.

[0004]

However, in the above-mentioned conventional method for manufacturing a synthetic resin corrugated pipe, the corrugated pipe is excessively expanded and deformed by the pressurized air leaked from the pressurizing plug to the downstream side, and the corrugated shape is increased. There was a problem that became unstable.
The cause is considered as follows.

The tubular resin extruded gradually moves to the downstream side, whereas the pressure plug is fixed at a predetermined position in the downstream side of the molding die. In order to prevent the soft tubular resin from being caught in the pressure plug and deforming or passing smoothly, it is necessary to set the outer diameter of the pressure plug slightly smaller than the inner diameter of the tubular resin. is there. Therefore, a gap is created between the pressure plug and the tubular resin, and pressurized air leaks from this gap.

In the corrugated tubular resin, a portion having a small inner diameter and a portion having a large inner diameter are alternately present. With a pressurizing plug whose outer diameter is set to correspond to the smallest inner diameter portion of such a corrugated tubular resin, when the location where the inner diameter of the tubular resin is large moves to the position of the pressurizing plug, the pressurizing plug A gap is created between the inner diameter of the tubular resin and the inner diameter of the tubular resin, and the leakage of the pressurized air increases.

If the pressure of the pressurized air acts from the inside of the tubular resin at the stage downstream of the pressurizing plug without restriction by the molding die and until the cooling and solidification of the tubular resin is completed, The resin easily expands and deforms, and the shape molded by the molding die collapses or cannot be accurately maintained. In recent years, in order to improve the productivity of corrugated pipe manufacturing, the extrusion rate of tubular resin has been increased. Then,
Since the extruded tubular resin is likely to move to the downstream side of the molding die without being sufficiently cooled, the above-mentioned expansion and deformation of the tubular resin due to the pressurized air becomes remarkable.

[0008] Therefore, an object of the present invention is to prevent the dimensional accuracy of the corrugated pipe from being lowered due to leakage of pressurized air from the pressurizing plug.

[0009]

A method for manufacturing a synthetic resin corrugated pipe of the present invention includes the following steps. (a) A step of extruding a molten resin into a tubular shape from a resin extruding section. (b) A molding die of a predetermined shape is placed outside the extruded tubular resin, and a pressure plug that blocks the internal space of the tubular resin is placed inside the tubular resin. A step of supplying a pressurizing medium between the resin extruding part and the resin extruding part on the upstream side, and pressing the tubular resin against the molding die by the pressurizing medium to form the tubular resin into a corrugated shape.

(C) A step of guiding the pressurized medium leaking from the upstream side to the downstream side of the pressure plug to the resin extruding part side from the downstream side of the pressure plug and discharging it to the outside of the tubular resin. Each component will be described. [Synthetic resin pipe] The material and dimensions may be similar to those of ordinary synthetic resin corrugated pipes, and various synthetic resin materials are used according to the application and required performance. Conditions such as waveform pitch and height are set.

[Resin Extruding Section] The same structure as that of the resin extruding section in an extrusion molding apparatus for ordinary synthetic resin is used. The resin extruding section is provided with a hopper to which a synthetic resin material is supplied, a screw feeder with a heater for moving the synthetic resin material while heating and melting it, an extrusion port for extruding the molten resin into a tubular shape, and the like. The synthetic resin is heated and extruded in a molten state to the extent that it can be extruded in a tubular shape and can be formed by a corrugated forming die.

The tubular resin extruded from the resin extruding section sequentially moves to the downstream side away from the resin extruding section. [Molding Mold] A mold having a structure similar to that of a molding die used for manufacturing a conventional synthetic resin corrugated pipe is used. The molding die is provided with a mold surface having a predetermined shape such as a corrugated shape corresponding to the outer shape of a tube such as a corrugated tube.

A circulation mold is used to properly position the mold with respect to the tubular resin continuously extruded and moving to the downstream side. The circulation molding die includes a mold surface block having a shape of a mold surface corresponding to the outer shape of the corrugated pipe. A large number of such mold surface blocks are combined and arranged on the outer periphery of the tubular resin so as to circulate and move along the moving direction of the tubular resin. Enclose the outer circumference of the tubular resin with multiple circulation molds,
A molding die corresponding to the entire circumference of the tubular resin is constructed.

Each mold surface block of the circulation molding die is arranged on the outer periphery of the tubular resin. The tubular resin can be molded according to the shape of the mold surface block while the mold surface block also moves downstream as the tubular resin moves to the downstream side. [Supply of Pressurizing Medium] If the tubular resin can be molded by being pressed against the outer peripheral molding die arranged on the outer periphery thereof, air or other various gases are used in a pressurized state. By changing the pressure or supply amount of the pressurizing medium, the pressing force of the tubular resin to the molding die or the molding conditions can be adjusted.

To supply the pressurized medium to the inside of the tubular resin, a pipe or the like is inserted and arranged inside the tubular resin from the end of the tubular resin, that is, the resin extruding portion side which is the upstream side, and a pump installed outside. The pressurized medium can be supplied with a blower or the like. [Pressurizing Plug] The basic structure of the pressing plug may be the same as that of the pressing plug in a general synthetic resin corrugated pipe manufacturing apparatus. In order to install the pressure plug in the internal space of the tubular resin, the pressure arm can be supported by extending the support arm downstream from the end of the tubular resin, for example, the end face of the resin extruded portion.

The pressure plug is arranged on the downstream side of the range in which the pressure is applied to the tubular resin by the pressure medium. The pressurizing medium is supplied between the pressurizing plug and the resin extruding section. The pressure plug has an outer shape capable of closing the inner space of the tubular resin. However, it is necessary to have a margin such that the outer diameter of the pressure plug does not contact the inner peripheral surface of the tubular resin. Therefore, the pressurizing plug cannot completely block the movement of the pressurizing medium inside the tubular resin. A part of the pressurizing medium supplied on the upstream side of the pressurizing plug leaks to the downstream side of the pressurizing plug through a gap between the pressurizing plug and the tubular resin.

[Discharge of Pressurized Medium] In order to discharge the pressurized medium that has leaked to the downstream side of the pressure plug, an inlet for the pressurized medium is arranged on the downstream side of the pressure plug, and this inlet is used. It is possible to arrange a discharge passage communicating with the outside of the tubular resin on the resin extruding portion side. If a discharge pipe arranged along the axial direction inside the tubular resin is used as the discharge passage, it does not interfere with the supply of the pressurized medium or the molding of the tubular resin. An intake port may be formed through the tip of the discharge pipe. If the pressure plug is supported in the middle of the discharge pipe, the discharge pipe can have both functions of supporting the pressure plug and discharging the pressurized medium. The discharge pipe can be supported by a structural member or the like of the resin extruding portion.

The end of the discharge pipe may only be open to the atmosphere outside the tubular resin. In this case, the pressure medium is naturally discharged due to the pressure difference between the pressure of the pressure medium on the downstream side of the pressure plug and the atmosphere. If the discharge pipe is connected to an exhaust device such as an exhaust blower or an exhaust pump arranged outside the resin extruding section, the pressurized medium can be promptly and forcibly discharged.

By discharging the pressurized medium to the outside of the tubular resin, it is possible to prevent the pressurized medium from expanding and deforming the tubular resin inside the tubular resin on the downstream side of the pressure plug. Therefore, in both of the natural discharge and the forced discharge, the pressurizing medium may be discharged so that the internal pressure on the downstream side of the pressurizing plug is maintained to the extent that expansion deformation of the tubular resin does not occur. .

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A synthetic resin pipe manufacturing apparatus shown in FIGS. 1 and 2 is for manufacturing a corrugated pipe for a wire protection pipe, and includes a resin extruding section 10, a pressurizing medium supplying section 20, and a circulation molding die. It is provided with 30, a pressure plug 40, and an exhaust unit 50. [Resin Extruding Section] The resin extruding section 10 is provided with an annular die section 12, and the molten resin r is supplied to the die section 12 from an extruding apparatus main body such as a screw feeder (not shown). The resin r is soft and in a state in which it is easy to flow and deform. The resin r extruded from the mouthpiece portion 12 becomes a tubular shape, moves away from the mouthpiece portion 12 and moves toward the downstream side, and becomes a tubular resin p. The tubular resin p is soft and easily deformed.

[Pressure Medium Supply Unit] Pressurization medium supply unit 20
Has an air supply path 26 that penetrates through the resin extruding portion 10 from the outside of the resin extruding portion 10 and extends from the center of the die portion 12 to the tip of the die portion 12. The air supply passage 26 is connected to a blower device (not shown) outside the resin extruding portion 10 and supplies pressurized air to the air supply passage 26. At the tip of the air supply passage 26,
It has a cylindrical medium discharge part 22 having a large number of air supply holes 24 on the outer surface. The pressurized air discharged from the air supply hole 24 is filled inside the tubular resin p and expands and deforms the tubular resin p toward the outer peripheral side.

[Circulation Mold] The circulation mold 30 is provided above and below the passage of the tubular resin p extruded from the resin extruding section 10.
Are arranged. The circulation molding die 30 is composed of a large number of mold surface blocks 32, and the surface of the mold surface block 32 is provided with a corrugated mold surface 34 corresponding to the outer surface shape of the corrugated pipe.

The mold surface block 32 has a semi-circular shape, and has a corrugated mold surface 34 on its inner peripheral surface. The mold surface blocks 32, 32 arranged on the left and right surround the entire outer periphery of the tubular resin p,
The entire circumference of the tubular resin p is formed into a waveform. That is, the tubular resin p expanded and deformed to the outer peripheral side by the supply of the pressurizing medium is pressed against the mold surface 34 to be formed into a corrugated shape along the corrugated shape of the mold surface 34.

[Pressure Plug] The pressure plug 40 is arranged inside the tubular resin p on the downstream side of the circulation molding die 30. Pressure plug 40
Has a disk shape, and its outer diameter is set to be slightly smaller than the inner diameter of the tubular resin p which is being formed into a corrugated shape. The pressure plug 40 is supported by an exhaust pipe 52 passing through the center of the tubular resin p.

[Exhaust Portion] The exhaust pipe 52 constitutes a part of the exhaust portion 50. The exhaust pipe 52 extends to the downstream side of the pressure plug 40 and the circulation molding die 30. An intake port 54 penetrates the downstream end of the exhaust pipe 52. Exhaust pipe 52
Extends to the upstream side, passes through the center of the medium discharge part 22, passes through the inside of the air supply path 26, passes through the outer wall of the resin extruding part 10, and extends outside. Exhaust pipe 5 outside the resin extrusion unit 10
2 is connected to an exhaust blower (not shown).

Air leaking to the downstream side of the pressure plug 40 inside the tubular resin p enters the exhaust pipe 52 from the tip of the intake port 54, moves through the exhaust pipe 52 to the upstream side, and is discharged to the outside. .
As a result, on the downstream side of the pressurizing plug 40, a large pressure difference does not occur between the outer space and the inner space of the tubular resin p, and it is possible to prevent the tubular resin p, that is, the corrugated pipe C before cooling and hardening from expanding and deforming. .

The corrugated pipe C moving past the positions of the circulation molding die 30 and the pressure plug 40 is cooled and solidified by blowing cold air or passing through a cooling water tank. The wave-corrugated tube C that has been cooled and solidified is collected and collected. Corrugated tube C
May be collected by winding it as a continuous body,
It is also possible to collect it while cutting it to a certain size.

[0028]

According to the method and apparatus for producing a synthetic resin pipe of the present invention, the pressurized medium leaking to the downstream side of the pressure plug is guided to the resin extruding portion side and discharged to the outside of the tubular resin. As a result, expansion and deformation of the tubular resin after molding can be prevented. The outer shape of the tubular resin remains exactly as it was molded by the molding die, and a synthetic resin tube with high dimensional accuracy can be obtained.

Since the pressurized medium leaking to the downstream side of the pressure plug can be immediately discharged on the spot, the extrusion speed of the tubular resin can be increased to improve the productivity, or the tubular resin on the downstream side of the pressure plug can be increased. Even when the temperature remains high, the pressure on the downstream side of the pressure plug can be appropriately maintained, and the expansion and deformation of the tubular resin due to the pressure medium can be reliably prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a synthetic resin corrugated pipe manufacturing apparatus that represents an embodiment of the present invention.

[Explanation of symbols]

10 Resin extrusion section 12 Ring base 20 Pressurizing medium supply unit 24 air vents 30 Circulation mold 32 type block 40 pressure plug 50 exhaust 52 Exhaust pipe 54 intake r Molten resin p tubular resin C corrugated tube

Continuation of the front page (56) Reference JP-A-5-16142 (JP, A) JP-B 46-9674 (JP, B1) JP-B 47-34824 (JP, B1) JP-B 51-43497 (JP , B2) JP-B-57-10819 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 47/88-49/80 B29D 23/18

Claims (5)

(57) [Claims] 1. A step of extruding a molten resin into a tubular shape from a resin extruding portion, a molding die having a predetermined shape is arranged outside the extruded tubular resin, and an inner space of the tubular resin is blocked inside the tubular resin. A pressurizing plug is arranged, a pressurizing medium is supplied between the pressurizing plug and the resin extruding portion on the upstream side of the pressurizing plug, and the tubular resin is pressed against the molding die by the pressurizing medium so that the tubular resin is predetermined. A step of molding into a shape, and a step of discharging the pressurized medium leaking from the upstream side to the downstream side of the pressure plug to the outside of the tubular resin by guiding it from the downstream side of the pressure plug to the resin extrusion part side. A method for producing a synthetic resin pipe containing. 2. The method for producing a synthetic resin pipe according to claim 1, wherein the step of discharging the pressurized medium is performed by natural discharge. 3. The method for manufacturing a synthetic resin pipe according to claim 1, wherein the step of discharging the pressurized medium is performed by forced discharge. 4. A resin extruding portion for extruding a molten resin into a tubular shape, a circulation molding die disposed outside the extruded tubular resin and having a die surface of a predetermined shape that circulates and moves downstream together with the tubular resin, A pressurizing plug that is arranged inside the tubular resin and that blocks the internal space of the tubular resin, and a pressurizing medium between the pressurizing plug and the resin extruding portion on the upstream side of the pressurizing plug inside the tubular resin. A pressurizing medium supplying means for supplying and a pressurizing medium intake port on the downstream side of the pressurizing plug, and a discharging means for guiding the pressurizing medium to the resin extruding part side and discharging it to the outside of the tubular resin. An apparatus for manufacturing a synthetic resin pipe, comprising: 5. The discharge means is disposed inside the tubular resin along the axial direction, has the inlet on the tip side, and supports the pressurizing plug midway in the axial direction. The synthetic resin pipe manufacturing apparatus according to claim 4, further comprising an exhaust pipe that is supported on the extruding portion side.