JPS5830132B2 - Method for manufacturing thermoplastic resin pipes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for manufacturing a thermoplastic resin tube that is lightweight, strong, and has excellent flexibility.

Conventionally, thermoplastic resin pipes used for purposes such as cable protection piping generally have a bellows structure in which a uniform wall thickness pipe is axially symmetrical or has a spiral waveform, as shown in FIG.

This structure has the advantage of being strong against lateral pressure without impairing its flexibility, but there is a limit to the ability to achieve both flexibility and crush resistance, and if flexibility is emphasized, the resin pipe may be damaged by unexpected external forces. There was a drawback that it could lead to accidents such as water intrusion into the pipes.

In order to eliminate this drawback of the conventional structure, a thermoplastic resin tube as shown in FIG. 2 has been proposed as a new structure for resin tubes.

This new structure of thermoplastic resin pipe has the following features.

That is, since spiral protrusions are formed on both the outer and inner surfaces, the frictional force is not large when a cable or the like is drawn inward, and even cables with low tensile strength can be drawn in, which is an advantage. It has better flexibility and is easier to handle than the structure shown in FIG.

Furthermore, since the thickness of the protruding portion is thicker than that of the one shown in FIG. 1, it has the advantage that it can be designed to sufficiently withstand pressures such as earth pressure.

The present invention relates to a method for manufacturing a thermoplastic resin pipe having a new structure as shown in FIG. 2, and is based on a novel idea.

FIG. 3 is a schematic diagram for explaining an embodiment of the method for manufacturing a thermoplastic resin pipe of the present invention.

A fixed die 1 and a rotating die 5 arranged concentrically inside the fixed die 1
A thermoplastic resin pipe 3 and a spiral string 6 are simultaneously extruded from each tube and guided to a sizing device.

The sizing device consists of a cylindrical sizing die 4 with exhaust holes 7 on the inner wall and an exhaust device connected to the exhaust holes, and includes a thermoplastic resin pipe and a spiral string led into the sizing die. are welded and integrated by the heat of extrusion, and the outer diameter of the pipe is molded to match the inner diameter of the sizing die.

Thereafter, the resin tube is cooled and solidified in a cooling device to form the structure shown in Figure 4.As shown in Figure 3, the resin tube is By absorbing the water through the gap between the outer surface and the inner wall of the sizing die and draining it through the exhaust pores 7, cooling efficiency is increased and uniform resin pipes can be extruded at high speed.

Furthermore, as shown in FIG. 5, a heating device 14 and a cooling device 15 are provided behind the extrusion device 10, sizing device 11, and cooling device 12, and extrusion, sizing, and cooling are performed, and the product is molded into the structure shown in FIG. By heating the thermoplastic resin pipe again at a temperature higher than the softening temperature of the pipe material to soften it, and then cooling it while applying pressure from the outside, the amount of deformation due to external pressure and shrinkage due to internal stress is reduced to the heat capacity of the thick inner thin wall part of the pipe. By utilizing the fact that there are differences, a structure as shown in FIG. 2 can be obtained.

Further, an embodiment of the manufacturing apparatus of the present invention is shown in FIG.

The details of the extrusion device 10 are as shown in FIG. 3. A rotary die 5 is provided concentrically inside a fixed die 1 and a nipple 2. A thermoplastic resin pipe is passed from the fixed die, and a thermoplastic resin pipe is disposed from the rotating die. The strings are extruded simultaneously in a spiral shape.

A sizing device 11 is provided next to the extrusion device, and a first cooling device 12 is provided after that, but it is also possible to install a hot or cold water tank and maintain a distance from the sizing device. As shown in Fig. 3, water is absorbed from the water tank connected to the sizing device through the gap between the outer surface of the resin pipe and the inner wall of the sizing die, and is drained through the exhaust holes provided in the inner wall of the sizing die. It can also improve cooling efficiency.

After the first cooling device, a feeding device 13, a heating device 14 for reheating, a second cooling device 15, and a winding device 16 are arranged in order. 17, and by using the manufacturing equipment as described above, it is possible to easily manufacture a thermoplastic resin pipe having a spiral protrusion on the inner wall having a structure as shown in FIG.

FIG. 6 shows an embodiment of the pressurizing device 17 provided at the inlet of the second cooling device 150, and shows a circular tubular body 17-1 having a large number of pores 17-2 on the radially inner circumference. By passing pressurized cooling gas through the heated thermoplastic resin pipe through the center of the circular tubular body, the outer diameter of the part of the resin pipe without protrusions was reduced, and the result was as shown in Figure 2. It is possible to obtain a resin pipe with a similar structure.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional thermoplastic resin pipe, FIG. 2 is a cross-sectional view of a thermoplastic resin pipe according to the present invention, FIG. 3 is a schematic diagram of an extrusion device and a sizing device according to the present invention, and FIG. 4 is a cross-sectional view of a conventional thermoplastic resin pipe. 5 is a cross-sectional view of a thermoplastic resin pipe immediately after extrusion sizing, FIG. 5 is a schematic diagram of an apparatus according to the present invention, and FIG. 6 is an embodiment of a pressurizing apparatus according to the present invention. Note that 1 is a fixed die of the extruder, 2 is a rotating die, 4 is a sizing device, 8 is a water tank, and 17 is a pressurizing device.

Claims (1)

[Scope of Claims] 1. A thermoplastic resin pipe having a spiral protrusion on the inner wall is extruded simultaneously from a fixed die and a rotating die concentrically disposed inside the fixed die, and the pipe and the spiral string are extruded simultaneously. In the manufacturing method of melting and integrating the spiral string on the inner wall of the tube and extrusion molding, the pipe portion of the thermoplastic resin pipe that has been extruded and cooled and solidified is heated to a temperature higher than the softening temperature of the material of the pipe portion to soften it. A method for manufacturing a thermoplastic resin pipe, which comprises applying pressure from a fluid such as gas from the outer periphery of a thermoplastic resin pipe having a softened pipe part to reduce the diameter of the pipe part, and cooling and solidifying the pipe part. 2. The thermoplastic resin pipe according to claim 1, characterized in that the diameter of the pipe portion is reduced by blowing pressurized gas onto the outer periphery of the thermoplastic resin pipe having a pipe portion that has been softened by heating. Production method.