JPS5830133B2 - Method for manufacturing thermoplastic resin pipes - Google Patents

Description

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

Conventionally, thermoplastic resin conduits used for applications such as cable protection piping have generally had a bellows structure with an axially symmetrical or spiral waveform on a uniform-walled tube, as shown in Figure 1. .

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.

In other words, the tube shown in Fig. 2 has spiral or ring-shaped valleys on the inner and outer surfaces of the tube, so it does not significantly impair its flexibility, and it also has smooth spiral or ring-shaped protrusions on the inner surface of the tube. Because of this, the friction when the cable is pulled into the pipe is smaller than that of a smooth pipe without protrusions, and since the protrusions are thick inside and outside, it has the advantage of having a large crushing resistance against tonosho etc. In addition, since there are not many thin parts, the pipe itself has the advantage of being less elongated under tension during installation, compared to a bellows pipe with a uniform thickness as shown in FIG.

The present invention relates to a method and apparatus for manufacturing thermoplastic resin pipes having this new structure, 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 2 arranged concentrically inside the fixed die 1
A thermoplastic resin pipe 3 and a spiral string 4 are simultaneously extruded from each tube and introduced into a sizing device (.

The sizing device consists of a cylindrical sizing die 5 having an exhaust hole 6 on its inner wall and a spiral protrusion 5-1 on its inner surface, and an exhaust device connected to the exhaust hole. The guided thermoplastic resin pipe and the spiral string are welded together by the heat of extrusion, and the outer diameter of the pipe is formed to match the inner diameter of the sizing die.

Thereafter, the resin tube is cooled and solidified in a cooling device, and as shown in FIG. By absorbing the water through the gap between the surface and the inner wall of the sizing die and draining it through the exhaust pores 6, cooling efficiency is increased and the rotation of the sizing die becomes smooth, enabling high-speed extrusion molding of uniform resin pipes. becomes.

The rotary die and the sizing die are rotated in the same direction and at the same speed, and the string extruded from the rotary die is inserted into the flat part of the sizing die (the middle part between the protruding parts).
It is necessary to maintain the mutual positional relationship between the rotary gouer and the sizing die so that they are welded and integrated with the pipe.

Furthermore, in the manufacturing method according to the present invention, the molten resin is directly molded and spirally corrugated. Thermoplastic resin tubes with an extremely uniform structure can be extruded without being affected by speed fluctuations.

[Brief explanation of drawings]

Figure 1 shows thermoplastic resin pipes commonly used in the past.
The figure shows a newly proposed thermoplastic resin pipe, and FIG. 3 shows an extrusion molding diagram according to the present invention. Note that 1 is a fixed die, 2 is a rotating guide, 3 is a thermoplastic resin pipe, 4 is a spiral string, 5 is a sizing die, and 5-
1 is a protrusion, 6 is an exhaust hole, 7 is a water tank, and 8 is water.

Claims (1)

[Claims] 1 A pipe and a spiral string made of thermoplastic resin are simultaneously extruded from a fixed die and a rotating die arranged concentrically inside the fixed die, and guided to a sizing device, and the spiral string is integrally welded to the inner wall of the pipe. In this method, the inner wall of the sizing die has a spiral protrusion, and the string extruded from the rotary die is attached to the flat surface of the sizing die. The sizing die is arranged so as to maintain a mutual positional relationship between the rotary die and the sizing die so as to be welded and integrated with the pipe at the section, and the sizing die is rotated in synchronization with the rotary die in the same direction and at the same speed. . A method for manufacturing a thermoplastic resin tube, comprising forming spiral irregularities on the outer surface of a portion of the tube made of the thermoplastic resin that has no inner wall protrusions.