JPS6029625B2 - Manufacturing method of thermoplastic resin branch pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is capable of greatly improving the strength of branch pipe welds of branch pipes such as T-shaped pipes (referred to as cheese pipes) and cross pipes (referred to as cross pipes). The present invention relates to a method for manufacturing a thermoplastic resin branch pipe having a diameter of the same size.

Conventionally, branch pipes such as thermoplastic resin pipes, cross pipes, etc.
An extrusion mold is inserted into the main pipe where the part to be branched is heated, and that part is extruded outward to provide a branching protrusion, and the branching protrusion and the branch pipe are manufactured by butt melting. Another method is to heat one end of the tube, expand it with a press-expanding mold, and weld it to the protrusion of the main tube.

However, such conventional manufacturing methods have the following drawbacks.

That is, in many cases, the diameter and wall thickness of thermoplastic resin pipes are standardized, and the larger the diameter, the larger the wall thickness. Therefore, especially when a small-diameter branch pipe is branched from a large-diameter main pipe, there is a large difference between the wall thickness of the protruding part of the main pipe and the wall thickness of the branch pipe, which creates a step in the welded part and causes stress to concentrate. Become the weak part. Further, if the end of the branch pipe is enlarged and welded, there is a problem that cracks are likely to occur in the welded part due to distortion in the remaining part of the enlarged part. The present inventors solved the above-mentioned conventional problems and provided a method for manufacturing a thermoplastic resin branch pipe that has particularly excellent strength at the welded part between the branch pipe and the main pipe even when using standard pipes for the secondary pipe. As a result of intensive study, the present invention has been arrived at.The gist of the invention is to connect one end of a thermoplastic resin pipe of a standard size with a diameter larger than the flea of a branch pipe of a desired standard size to a desired standard size. The branch pipe is made by drawing to the diameter of the branch pipe of the desired standard size, and separately, the part of the thermoplastic resin pipe for the main pipe with a standard size that is larger than the diameter of the branch pipe of the desired standard size is heated and that part is drawn outward. A thermoplastic resin branch whose branch pipe has a diameter of a desired standard size, characterized in that the branch pipe is extruded to provide a branching protrusion, and the larger diameter end of the branch pipe is butt welded to the protrusion. It depends on the manufacturing method of the pipe.

Hereinafter, the manufacturing method of the present invention will be explained in detail with reference to the accompanying drawings.

FIG. 1 is a schematic cross-sectional view of an example of a thermoplastic resin branch pipe drawn to the diameter of a branch pipe of a desired standard size used in the present invention;
Fig. 2 is a schematic cross-sectional view of an example of a method for providing a protrusion in a main pipe of standard size, and Fig. 3 is a schematic plan view showing an aspect of a thermoplastic resin main pipe and a branch pipe before welding in an example of the manufacturing method of the present invention. , FIG. 4 is a schematic cross-sectional view of a cheese tube obtained by welding the tube shown in FIG. 3 and a third tube connected thereto. In the figure, 1 is the drawing part of the branch pipe, 2 is the joining part of the branch pipe, 3 is the main pipe, 4 is the branching protrusion, 5 is the butt weld line, 6 is the extrusion mold, and 7 is the third pipe. be. In an example of the manufacturing method of the present invention, first, as shown in FIG. One end of the resin pipe is drawn to form a drawn part 1 having a branch pipe diameter of a desired standard size, and the other end, which is not drawn, and has a larger diameter, is made a joint part 2 of the branch pipe. The drawing process can be easily produced by forcing a heated tube into a hollow cylindrical drawing die having a tapered inner surface. At this point, the outer diameter or inner diameter of the drawn portion is adjusted to a desired size by the connection shape of the third pipe (for example, 7 in FIG. 4) connected to the branch pipe.
For example, in the case of hard vinyl chloride VP pipe specified in JISK 6741, the degree of constriction is nominally 100 ribs (outside diameter 114
If the pipe is made of willow (with a wall thickness of 7 ribs), it can be squeezed up to an outer diameter of about 9 squares, and if the pipe is nominally 200 willow (with an outer diameter of 216 sides and a wall thickness of 1 rib), it can be squeezed to an outer diameter of about 160 ribs. can. Separately, a branching protrusion 4 is provided on the main pipe 3. That is, as shown in FIG. 2, the portion 31 of the main pipe 3 to be branched is heated and softened, and the extrusion mold 6 inserted into the main pipe 3 causes the portion to protrude outward.
The extrusion die 6 has a cylindrical ridge 61 provided through an arcuate shoulder 62, and the ridge 61 pushes out the portion to be branched outward as shown by the dotted line in FIG. Then, by cutting and smoothing the tip of the extruded portion, the branching protrusion 4 is formed. The diameter of this protruding portion 4 is determined by the diameter of the joint portion 2 of the branch pipe.
Match the diameter of Next, as shown in FIG. 3, the joint portion 2 of the branch pipe in FIG. 1 obtained above is placed opposite to this protrusion, and both are butt welded to form the desired branch pipe in FIG. 4. The cheese tube shown is manufactured. Then, the third pipe 7 is connected to the drawn portion 1 of the branch pipe by an appropriate method. Similarly, a cross pipe or the like having a branch pipe having a diameter of a desired standard size can be manufactured. The manufacturing method of the present invention is as described in detail above, and according to this method, the strength of the welded portion of a branch pipe of a desired standard size of a branch pipe such as cheese or cloth can be improved.

In other words, the diameter and wall thickness of the joint part of the branch pipe of the desired standard size are larger than in the conventional method, and the main pipe side of the standard size has a larger diameter and wall thickness than the branch pipe of the desired standard size. Since the wall thickness of the protruding part is reduced, the wall thickness of the protruding part after thinning and the wall thickness of the joining part of the branch pipe of the desired standard size can be made closer than ever before, or even equal in some cases, In addition, the butt weld line is longer than in the conventional method, and the cross-sectional area of the welded portion is increased, resulting in improved folding strength and water pressure resistance. Furthermore, the method of the present invention has the following advantages over the conventional improved method of welding an enlarged end of a branch pipe of a desired standard size.

That is, when welding an enlarged branch pipe, cracks are likely to occur in the welded part, but in the present invention, a portion drawn to the diameter of the branch pipe of the desired standard size (hereinafter referred to as a drawn product) is used as the branch pipe. Since welding is performed using the original outer diameter end of the pipe without drawing, butt welding can be performed without cracking. In addition, in enlarged products, the joint portion of the branch pipes becomes thinner due to the enlarging process, resulting in a decrease in strength, but in drawn products, there is no risk of this happening.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of an example of a thermoplastic resin branch pipe drawn to the diameter of a desired standard size branch pipe, Fig. 2 is a cross-sectional schematic view of an example of a method for providing a protrusion in a main pipe of standard size, and Fig. 3
The figure is a schematic plan view showing an aspect of the thermoplastic resin main pipe and branch pipes before welding in an example of the manufacturing method of the present invention, and FIG.
It is a sectional view of a cheese tube obtained by melting the one shown in the figure and a third tube connected to the cheese tube. 1... Drawing part of the branch pipe, 2... Joining part of the branch pipe, 3... Main pipe, 4... Protruding part for branching, 5... ...Hat welding line, 6...Extrusion mold. Ono Zuriki 2, O 3, and so on

Claims (1)

[Claims] 1 One end of a thermoplastic resin pipe with a standard size larger than the diameter of a branch pipe with a desired standard size is drawn to the diameter of a branch pipe with a desired standard size, and a separate pipe with a desired standard size is drawn. The diameter of the branch pipe: The part of the thermoplastic resin pipe for the main pipe of the standard size with the larger diameter is heated and the part is pushed outward to provide a protrusion for branching, and this protrusion has a diameter of the branch pipe. A method for manufacturing a thermoplastic resin branch pipe in which the branch pipe has a diameter of a desired standard size, characterized in that the larger end is butt welded.