JPS59204525A - Preparation of synthetic resin coated pipe - Google Patents

Abstract

PURPOSE:To contrive the enhancement of productivity, by coating the outer peripheral surfaces of metal pipes with a synthetic resin in such a state that spacers are interposed between adjacent end parts of said metal pipes. CONSTITUTION:Metal pipes 5 each cut into a predetermined dimension are sent in a longitudinally arranged state so as to leave small gaps (l) and spacers 6 are interposed between the metal pipes 5 prior to entering the crosshead die 9 of an extrusion molding machine 8. In this crosshead die 9, the outer peripheries of the metal pipes 5, 5 are coated with a synthetic resin in such a state that the mutually adjacent metal pipes 5, 5 pinch the spacers 6 and, after cooling, the central part of each spacer 6 is cut to obtain a synthetic resin coated pipes. By this method, the synthetic resin coated pipe can be mass-produced by using the metal pipe having an outer diameter of about 10-30mm..

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a synthetic resin-coated pipe using a metal pipe as a core material.

The applicant has developed a new method that reduces manufacturing costs and improves productivity in place of the conventional synthetic resin-coated struts, in which the outer circumferential surface of a metal wire is coated with synthetic resin, and tube end caps for preventing corrosion are attached to both ends with adhesive. In order to provide a synthetic resin-coated support that has good properties (and there is no risk of the tube end cap falling off),
Previously, in Japanese Patent Application No. 57-188791, we disclosed an agricultural and horticultural support that does not require the attachment of tube end caps, and a method for manufacturing the same. The cut metal wires are held in a vertical line with a small gap between them, and are fed one after another to the cross of the extrusion molding machine, so that the distance between the outer circumferential surface of each metal wire and the end surface of each adjacent metal wire The parts were filled with synthetic resin and then each part filled with synthetic resin was cut at the center.

In other words, this method discloses a method for manufacturing synthetic resin-coated pipes used for agricultural and horticultural supports, etc., using wire rods such as iron and aluminum with a diameter smaller than 7 to 8 m. If this is applied to a metal tube with a diameter larger than 7 to 8 fi, a large amount of synthetic resin must be injected and filled between the adjacent ends, and when filling, a large amount of synthetic resin will be inside the metal tube. There was a problem that it could not sufficiently cover both ends of the adjoining ends.

Furthermore, Japanese Patent Application No. 57-188791 discloses that a metal tube cut into a predetermined length in advance is used as a core material, and each of the metal tubes is made of synthetic resin having protrusions at both ends at opposing openings. Insert the stopper and connect the metal pipes in tandem,
The cloth of the extrusion molding machine is fed to the RAD die, and with the plugs still inserted into these metal tubes, synthetic resin is coated from the outer peripheral surface of the metal tubes, and then the center part of the plugs is cut and the same process is carried out. A method of manufacturing synthetic resin struts has been proposed.

However, this proposed method requires a certain degree of precision for the synthetic resin stopper, and for this reason, the stopper with a diameter that corresponds to the metal tube must be prepared in advance in a separate process, which also results in production From a gender perspective, there was room for improvement.

Therefore, this invention was made to solve the problems of the conventional methods, and provides an improved manufacturing method for synthetic resin-coated pipes using metal pipes as the core material, thereby further promoting industrialization. The object of the present invention is to provide a method for manufacturing a synthetic resin-coated pipe that has excellent properties and is inexpensive in -N manufacturing cost.

Hereinafter, the manufacturing method will be explained with reference to FIGS. 1 to 3.

Figure 1 shows the schematic configuration of the continuous manufacturing equipment used in the method of this invention. 1 is a pipe making equipment for forming pipes from flat plates; 2 is a pipe making equipment for removing rust, oil, etc. attached to the outer surface of metal pipes; 3 is an adhesive applicator for applying various adhesives depending on the type of synthetic resin to be coated in the subsequent process, and these are used in a well-known manner to remove metals. The tube is subjected to a so-called pretreatment.

The pretreated long metal tube 5 made of iron, aluminum, or the like is then cut into a predetermined size by a cutter 4, and the end edge 5a of the cut portion is crushed into a leather-like shape. Here, this crushing treatment is performed to prevent both ends of the synthetic resin spacer 6 from entering the inner cavity 5b of the metal tube 5 when the synthetic resin spacer 6 is inserted in the next step. Therefore, if the end edge 5a of the cut portion of the metal tube 5 becomes a leather-like rough surface when cut by the cutter 4, it is not necessary to perform the cutting.

As shown in FIG. 2, the metal tubes 5 cut to a predetermined size are sent to the feed rollers 7 in tandem with a small gap 1 between them before entering the crosshead die 9 of the extrusion molding machine 8. A spacer 6 is inserted between. Here, the spacer 6 is made of a material that is compatible with the synthetic resin that will be coated to form the outer skin layer 7 in the next step, such as soft or semi-hard polyvinyl chloride similar to this synthetic resin, It is formed into an appropriate size from density polyethylene, ABS resin, or other general thermoplastic synthetic resin.

In addition, the small gap formed between the adjacent metal tubes 5.5 is such that both cut portions of the adjacent metal tubes 5.5 are connected to the spacer 6.
The size is set to the extent that it can be held between the two.

As shown in FIG.
0, and the die body 1
By providing the inner die 12 in the inner die 1, a resin passage 13 is formed between the inner periphery of the die body 11 and the outer periphery of the inner die 12, and a resin passage 13 is formed between the inner periphery of the die body 11 and the outer periphery of the inner die 12. The structure is such that the metal tube 5 is introduced from the rear end and is led out from the extrusion port 15 of the die body 11. However, in this crosshead die 9,
By keeping the spacer 6 inserted in the small gap created between the adjacent ends of the metal tubes 5 and supplying them one after another by the feed roller ruff in tandem, each metal tube 5 has its outer periphery A spacer 6 coated with synthetic resin and inserted between the ends of the spacer 6 and between each metal pipe and the spacer 6
The outer peripheral surface of the metal tube 5.5 is also coated with a synthetic resin, and the outer periphery of the adjacent metal tubes 5.5 is coated with a synthetic resin with the spacer 6 sandwiched between them as shown in FIG. is led out from the crosshead die 9 in an integrated state.

In this way, each metal tube 5 becomes an extrusion molded product covered with a synthetic resin jacket 16, and after being cooled through a cooler 17, the center portion of the spacer 6 is cut by a cutter 4, as shown in FIG. This is a synthetic resin-coated pipe.

The synthetic resin coated pipes manufactured by this method are mass-produced using metal pipes with an outer diameter of 1Qm to 30cm, and are used as agricultural and horticultural supports and tent supports.

Used as frame material for other simple furniture.

In addition, although the above-mentioned embodiments used ordinary circular metal tubes as the core material, the present invention is not limited to the use of such metal tubes; A shaped metal tube may also be used.

That is, the metal tube 5 shown in FIG. 5 has pleated lips 51- formed by folding the outer peripheral surface inward along the longitudinal direction during manufacturing of the thin-walled metal tube. When using the metal tube 5 as the core material, it is possible to obtain a synthetic resin-coated pipe that is lightweight and has a structure that is particularly strong against external forces in the bending direction.
Since - prevents the spacer 6 from entering, there is an advantage that the cut edge only needs to be formed into a slight serpentine shape, and productivity is further improved.

Furthermore, in the embodiments described above, the surface of the synthetic resin outer skin layer of the synthetic resin coated pipe is formed into a flat surface, but when the outer skin layer is formed, the protrusions 17 shown in FIG. 6 and the projections 17 shown in FIG. It is also possible to form knot-like flanges 18.-, or to carve vertical grooves around the entire circumference (not shown). Especially protrusion 17...-
The knotted flanges 18, etc. not only improve the appearance of the synthetic resin pipe, but also are effective in preventing tied strings, wires, etc. from slipping out.

Furthermore, as the spacer 6, it is desirable to use a thermoplastic resin, such as a rubber-based resin that has strong impact resistance, blended with polyvinyl chloride resin, and a synthetic resin-coated pipe using such a material may be used, for example. When using the spacer as a support for agriculture and gardening, it has the advantage that it will not break when driven in with a mallet.Also, when cutting the center part of the spacer, as shown in Figure 8, Cutting the spacer portion diagonally has the effect of making it easier to drive and insert into the soil.

As described in detail above, according to the method of the present invention, a spacer is inserted between adjacent ends of a metal tube, and synthetic resin is coated from the outer peripheral surface of the metal tube, thereby eliminating the need for attaching a tube end cap. Synthetic resin-coated pipes can be efficiently produced in large quantities through a continuous process, and thus synthetic resin-coated pipes can be obtained at low manufacturing costs.

In addition, since the spacer is welded and integrated with the synthetic resin it is coated with, there is no need for high-precision molding such as injection molding, and if the spacer is slightly smaller in diameter than the metal tube, the shape may be slightly deformed. It has the advantage of being usable.

Furthermore, in the manufactured synthetic resin coated pipe, the spacer, which is coated with synthetic resin and integrated with the metal pipe, plays the same role as a pipe end cap, so the end is sufficiently protected and there is no risk of rust etc. .

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of a manufacturing apparatus used to carry out the method of the present invention, FIG. 2 is a longitudinal cross-sectional view of a cross-toward radial die, and FIG. 3 is an extrusion molded product (intermediate product) manufactured by the present invention. ), FIG. 4 is a partially cutaway longitudinal sectional view of a synthetic resin-coated pipe manufactured by the present invention, FIG. 5 is a diagram of another embodiment of a metal pipe, FIGS. 7 and 8 are views showing other embodiments of the synthetic resin-coated pipe. (Explanation of symbols) 5 is a metal tube, 5a is a cut edge thereof, and 6 is a synthetic resin spacer. Patent applicant Takiron Co., Ltd. Representative Ryuta Heki 0

Claims (1)

[Claims] 11) A metal tube that has been cut to a predetermined length and whose cut edge has been crushed into a tapered shape is connected to the adjacent metal tube.
゛Synthetic resin spacers are inserted between the ends, and the metal tubes are held in tandem and fed one after another to the crosshead of an extrusion molding machine, and the spacers are sandwiched from the outer peripheral surface of each adjacent metal tube. 1. A method for manufacturing a synthetic resin-coated pipe, which comprises coating the pipe with a synthetic resin in such a state, and then cutting the spacer coated with the synthetic resin from its center.