JPH1110716A - Manufacture of synthetic resin tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve cooling efficiency of a molded tubular resin and also improve shape dimension accuracy of a synthetic resin tube to be manufactured. SOLUTION: A molten resin (r) is extruded into a tubular shape out of a resin extrusion section 10. A molding tool 30 of given shape is disposed outside an extruded tubular resin (p), and pressurized gas is introduced inside the tubular resin (p) and atomized cooling liquid is introduced therein, and the tubular resin is pressed on the molding tool by the pressurized gas to mold the tubular resin (p) into the given shape, and the tubular resin (p) is cooled by the atomized cooling liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a synthetic resin tube, and more particularly, to a method for manufacturing a synthetic resin tube used for conveying various gases or liquids or for protecting electric wires.

[0002]

2. Description of the Related Art As a synthetic resin tube, there is a synthetic resin corrugated tube which is used for an electric wire protection tube or the like and has an outer peripheral surface formed in a waveform along an axial direction. Synthetic resin corrugated pipes have features such as flexibility that allows the pipe wall to bend flexibly by making a waveform, and excellent resistance to deformation such that the cross section of the pipe is not easily deformed even when a load is applied. It is widely used for electric wire protection pipes, air supply pipes, etc. for protecting etc.

[0003] As a method for manufacturing a synthetic resin corrugated tube, a method described below is employed. While extruding the molten resin into a tubular shape, pressurized air is fed into the tubular resin in a state where a mold having a desired wavy shape is arranged on 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 wave shape of the molding die. In order to prevent the pressurized air from leaking, a pressurizing plug that blocks the internal space of the tubular resin is disposed downstream of the extruded tubular resin. If the pressurized air is supplied to the upstream side of the pressurization plug, the internal space of the tubular resin can be efficiently pressurized. The molded tubular resin is fed into a cooling water tank or the like and cooled, so that a synthetic resin corrugated tube having a predetermined corrugated shape is obtained.

[0004]

However, in the above-mentioned conventional method of manufacturing a synthetic resin corrugated tube, the tubular resin after passing the mold, that is, the corrugated tube immediately after molding, has not yet been sufficiently cooled. Since it is in a soft state, it may be deformed before it is completely cooled in a cooling water tank or the like. When such deformation occurs, the dimensions and shape of the corrugated tube become inaccurate, and the quality performance of the corrugated tube deteriorates.

In particular, if the moving speed of the tubular resin is increased by increasing the extrusion speed of the tubular resin in order to improve the production efficiency of the corrugated tube, the tubular resin is sufficiently cooled during a short time when it passes through the mold. In addition, the above-mentioned problem becomes serious, and the time required for the corrugated pipe to pass through the cooling water tank is shortened. Therefore, there is a possibility that sufficient cooling is not performed even in the cooling water tank. In order to perform sufficient cooling in the cooling water tank, the cooling water tank may be lengthened to increase the passage time of the corrugated tube,
Then, the size of the apparatus increases and the operating cost increases.

Accordingly, an object of the present invention is to increase the cooling efficiency of a molded tubular resin in the production of a synthetic resin corrugated tube as described above, thereby improving the shape and dimensional accuracy of the produced corrugated tube. .

[0007]

The method for manufacturing a synthetic resin tube according to the present invention includes the following steps. (a) A step of extruding a molten resin into a tube from a resin extrusion section. (b) A mold having a predetermined shape is arranged on the outside of the extruded tubular resin, and a pressurized gas is supplied to the inside of the tubular resin and an atomized cooling liquid is supplied. A step of pressing the resin against a mold to form the tubular resin into a predetermined shape and cooling the tubular resin with atomized cooling liquid.

[0008] Each component will be described. [Synthetic resin tube] The material and dimensions and shapes may be the same as those of a synthetic resin tube such as a normal synthetic resin corrugated tube, and various synthetic resin materials are used in accordance with the application and required performance. Conditions such as the pitch of the waveform are set.

[Resin Extruding Unit] The same structure as that of the resin extruding unit in the extrusion molding apparatus for ordinary synthetic resin is used. The resin extrusion unit includes a hopper to which the synthetic resin material is supplied, a screw feeder with a heater for moving the synthetic resin material while heating and melting, an extrusion port for extruding the molten resin into a tube, and the like. The synthetic resin is extruded by being heated to a molten state capable of being molded by a tubular extrusion and a corrugated mold.

[0010] The tubular resin extruded from the resin extruding section sequentially moves downstream away from the resin extruding section. [Mold] A mold having the same structure as a mold used for manufacturing a synthetic resin pipe such as a normal synthetic resin corrugated pipe is used. The molding die is provided with a mold surface such as a corrugation corresponding to the outer shape of a synthetic resin tube such as a corrugated tube.

In order to properly arrange the mold with respect to the tubular resin that is continuously extruded and moves downstream, a circulation mold is used. The circulation mold has a mold surface block having a mold surface shape corresponding to the outer shape of the corrugated tube. A large number of such mold surface blocks are combined and arranged on the outer periphery of the tubular resin so as to circulate along the moving direction of the tubular resin. Surround the outer circumference of the tubular resin with multiple circulation molds,
A mold corresponding to the entire circumference of the tubular resin is formed.

Each mold surface block of the circulation molding die is arranged on the outer periphery of the tubular resin. The synthetic resin tube can be molded according to the shape of the mold surface block while the mold surface block moves downstream as the tubular resin moves downstream. [Supply of pressurized gas] In order to press and mold the tubular resin against a mold disposed on the outer periphery thereof, air and other various gases are used in a pressurized state. By changing the pressure and supply amount of the pressurized gas, the pressing force of the tubular resin against the mold or the molding conditions can be adjusted. If a low-temperature gas is used as the pressurized gas, cooling of the tubular resin can be promoted.

The pressurized gas contains an atomized cooling liquid. As the cooling liquid, a liquid having a large endothermic property capable of efficiently removing the heat of the tubular resin is preferable. Practically, water at about room temperature is preferable because it is easy to handle. The cooling liquid may be atomized to such an extent that the cooling liquid is transported together with the pressurized gas. If a low-temperature liquid or a liquid cooled in advance is used as the cooling liquid, the cooling effect is enhanced.

For atomization of the cooling liquid, an atomizer for ordinary liquid is used, and a so-called spray device and an ultrasonic atomizer are used. In order to supply the pressurized gas containing the atomized cooling liquid 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, Pressurized gas can be supplied by a pump, a blower or the like installed outside.
The cooling liquid atomizer may be incorporated in the supply path of the pressurized gas, or may be provided with an independent path. In the former case, the supply structure can be simplified, and in the latter case, the supply can be individually controlled.

[Pressurizing Plug] If a pressing plug is disposed downstream of the supply position of the pressurized gas, the pressure of the pressurized gas can be efficiently applied to the tubular resin. The basic structure of the pressure tap is
It may be the same as the pressure stopper in a usual synthetic resin corrugated tube manufacturing apparatus. To install a pressure plug in the inner space of the tubular resin,
The support arm can be extended downstream from the end of the tubular resin, for example, from the end face of the resin extruded portion, to support the pressure plug.

[0016] The pressure tap is disposed downstream of a range in which pressure is applied to the tubular resin by pressurized gas. The pressurized gas is supplied between the pressure tap and the resin extruder. The pressure tap has an outer shape capable of closing the internal space of the tubular resin. However, there is a margin such that the outer diameter of the pressure plug does not contact the inner peripheral surface of the tubular resin. Therefore, the pressure tap does not completely block the movement of the pressurized gas inside the tubular resin. A part of the pressurized gas supplied on the upstream side of the pressurization plug leaks from the gap between the pressurization plug and the tubular resin to the downstream side of the pressurization plug.

[Cooling Apparatus] The tubular resin, that is, the corrugated tube that has come out of the molding die can be further cooled by a cooling apparatus. As the cooling device, a cooling water tank or a blower for cooling air is used.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus for manufacturing a synthetic resin pipe shown in FIG. 1 is for manufacturing a corrugated pipe for an electric wire protection pipe, and includes a resin extruding section 10, a pressurized gas supply section 20, a circulation molding die 30, A pressure plug 40 is provided. [Resin Extruding Section] The resin extruding section 10 includes an extrusion port 12,
The resin r in a molten state is supplied to the extrusion port 12 from an extruder body such as a screw feeder (not shown). The resin r is in a soft, easily flowable and deformable state. The resin r extruded from the extrusion port 12 becomes tubular and sequentially moves downstream from the extrusion port 12 to become a tubular resin p. The tubular resin p is in a soft and easily deformable state.

[Pressurized gas supply unit] Pressurized gas supply unit 20
Has an air supply passage 26 extending from the center of the extrusion port 12 to the tip of the extrusion port 12 through the resin extrusion section 10 from outside the resin extrusion section 10. The air supply passage 26 is connected to a blower device (not shown) and an atomizing water supply device (not shown) outside the resin extruding section 10, and sucks outside air to supply pressurized air to the air supply passage 26. I do. The atomized water supply device atomizes water at normal temperature and sends it into the air, and pressurized air m containing the atomized water is supplied.

At the end of the air supply passage 26, there is provided a cylindrical medium discharge portion 22 having a large number of air supply holes 24 formed on the outer surface.
Pressurized air m containing atomized water discharged from air supply hole 24 is
The inside of the tubular resin p is filled, and the tubular resin p is expanded and deformed toward the outer peripheral side. [Circulation Mold] A circulation mold 30 is disposed above and below a passage of the tubular resin p extruded from the resin extruding section 10. The circulation mold 30 has a plurality of mold surface blocks 32. On the surface of the mold surface block 32, a corrugated mold surface 34 corresponding to the outer shape of the corrugated tube is provided. The mold surface block 32 has a semicircular shape, and has a corrugated mold surface 34 on its inner peripheral surface.
Having. The mold face blocks 32, 32 arranged on the left and right surround the entire outer periphery of the tubular resin p, and the entire periphery 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 pressurized air is pressed against the mold surface 34 to be formed into a waveform along the waveform shape of the mold surface 34. Then, the tubular resin p is cooled by coming into contact with the atomized water existing together with the pressurized air m. Water having a much higher endothermic effect than air cools the tubular resin p efficiently. The tubular resin p is gradually cooled by contact with pressurized air or contact with the mold surface block 32.

It is preferable that the temperature of the tubular resin p is cooled to a temperature at which the tubular resin p does not easily deform at a stage after passing the position of the mold 30. The tubular resin p that has moved downstream after passing the position of the circulation mold 30 is a corrugated tube C having a corrugated outer surface. [Pressure Plug] The pressure plug 40 is arranged inside the tubular resin p on the downstream side of the circulation mold 30. The pressure tap 40 has a disk shape, and its outer diameter is set slightly smaller than the inner diameter of the tubular resin p being formed into a corrugated shape. The pressure tap 40 is
It passes through the center of the tubular resin p and is supported by a support shaft 52 fixed to the end face of the medium discharge unit 22.

The corrugated pipe C that moves downstream after the position of the circulation mold 30 and the pressure plug 40 is cooled to a certain extent by the above-mentioned atomized water. By passing through, it is finally cooled and solidified.

[0024]

According to the method of manufacturing a synthetic resin pipe according to the present invention, the cooling is performed by adding the atomized cooling liquid to the pressurized gas for expanding the tubular resin and pressing it against the mold. The highly effective atomized liquid comes in direct contact with the tubular resin and removes heat, effectively cooling the tubular resin and allowing it to cool to a temperature where it is not easily deformed.

As a result, the corrugated tube after leaving the mold is
It is possible to prevent the problem that the accuracy and quality performance of dimensions and shape are reduced due to deformation due to external force or internal pressure. If the cooling is performed sufficiently at the stage of leaving the mold, the burden of the cooling step in a cooling water tank or the like performed thereafter is reduced, and the cooling device can be simplified. Also, even if the extrusion speed or moving speed of the tubular resin is increased, a sufficient cooling effect can be exhibited,
The production efficiency of the synthetic resin pipe can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an apparatus for manufacturing a synthetic resin corrugated tube according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Resin extrusion part 12 Extrusion port 20 Pressurized gas supply part 24 Air supply hole 30 Circulation mold 32 Mold surface block 40 Pressure tap m Pressurized air containing atomized water r Molten resin p Tubular resin C Corrugated tube

Claims (2)

[Claims] 1. A step of extruding a molten resin into a tube from a resin extruding section, a mold having a predetermined shape is arranged outside the extruded tubular resin, and a pressurized gas is supplied to the inside of the tubular resin. Supplying the atomized cooling liquid, pressing the tubular resin against a mold with a pressurized gas to form the tubular resin into a predetermined shape, and cooling the tubular resin with the atomized cooling liquid. A method for manufacturing a synthetic resin tube. 2. The method according to claim 1, wherein the cooling liquid is water and the pressurized gas is air.