JPS5857289B2 - Manufacturing method of thermoplastic resin bent pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a bent thermoplastic resin pipe by bending a thermoplastic resin pipe.

Conventionally, when bending a thermoplastic resin pipe by heating, hot sand is filled in the pipe to prevent the bent portion from becoming flat.

However, since the sand is heavy, the bending work is cumbersome, and this problem becomes especially serious as the diameter of the pipe becomes larger.Additionally, sand remains on the inner wall of the pipe, and erosion control adheres to the inner wall of the pipe.

Another method has been proposed in which a bag is inserted into a thermoplastic resin pipe and heated fluid is sealed inside the bag to perform bending, but it is difficult to seal the fluid, and gas is compressed when the fluid is flowing. Because it is easy to do so, it may not be possible to sufficiently prevent flattening.

The purpose of this invention is to solve the above-mentioned drawbacks, and its gist is to manufacture a thermoplastic resin curved pipe by heating and softening the thermoplastic resin pipe and bringing it into contact with a curved surface. A method for manufacturing a bent thermoplastic resin tube, comprising the step of inserting a sphere having an outer diameter approximately equal to the inner diameter of the tube into the thermoplastic resin tube and moving it back and forth within the tube.

The method of this invention will be explained below with reference to an embodiment shown in the drawings.

Reference numeral 1 denotes a thermoplastic resin pipe for bending, such as a hard vinyl chloride pipe, and the pipe 1 is heated and softened to a temperature at which bending can be performed. Insert sphere 2.

Wires 21 and 21 are attached to the left and right sides of the sphere 2, respectively, and the other ends of the wires 21 and 21 are connected to a tensioning device 3.
, 3.

The tube 1 into which the sphere 2 has been inserted is bent along the mold surface 41 by pressing both ends of the tube 1 onto the curved mold 4 with presser plates 5.5.

In this embodiment, both ends of the tube 1 are pressed by the presser plates 5, 5 and bent along the mold surface 41, so in this case it is preferable to heat only the center portion of the tube 1 without heating and softening the ends. ,
Further, it is desirable that the sphere 2 is also inserted in a position at the center of the bent portion of the tube 1.

Thereafter, before the heat-softened portion of the tube 1 has hardened, the tension devices 3°3 are operated alternately to move the sphere 2 back and forth, thereby straightening the bent portion of the tube 1 so that its cross section becomes almost a perfect circle. and cooled by known means such as spraying cooling water.

In addition, it is preferable that the reciprocating movement of the sphere 2 is continued even during the cooling process of the tube 1.

After cooling, the tube 1 is removed from the curved mold 4 and the sphere 2 is pulled out from the tube 1.

In this manner, a curved pipe made of thermoplastic resin is manufactured, and it goes without saying that the curvature of the mold surface 41 of the curved mold 4 is set in accordance with the desired curved pipe.

As described above, the method for manufacturing a curved pipe made of thermoplastic resin according to the present invention does not require filling the entire inside of the pipe with a filler such as sand as in the conventional method, but instead creates a curved mold surface with a single sphere inserted. Since the pipe is bent along the curve, it can be easily bent without requiring a large bending force, and the cross section of the bent part is then corrected to a nearly perfect circle by the movement of the sphere, which simplifies the process of manufacturing the bent pipe. The bent portion can also be made into a booth.

[Brief explanation of the drawing]

1 to 3 are sectional front views showing an embodiment of the method of the present invention in the order of steps, and FIG. 4 is a sectional view taken along the line A--A in FIG. 3. 1... Thermoplastic resin pipe, 2... Sphere,
4... Curved type, 5... Pressing plate.

Claims (1)

[Claims] 1. A method of manufacturing a thermoplastic resin curved pipe by heating and softening a thermoplastic resin pipe and bringing it into contact with a curved surface, in which a sphere having an outer diameter approximately equal to the inner diameter of the pipe is inserted into the thermoplastic resin pipe. 1. A method for manufacturing a bent thermoplastic resin tube, comprising the step of reciprocating the curved tube within the tube.