JPH01159237A - Manufacture of synthetic resin pipe - Google Patents

Abstract

PURPOSE:To mold a synthetic resin pipe having a uniform thickness and is superior in watertightness by a method wherein two strips of sheet are heated at a specific temperature by interposing a plurality of strips of tapes in between, a tubular body is formed by winding them spirally around an imaginary cylindrical rotating shaft body, fused through press contacting with a press roll and cured through cooling. CONSTITUTION:Two strips of sheet B comprised of low-density polyethylene forming a surface layer and four sheets of strips of tape C comprised of a laminated sheet of high-density and low-density polyethylene sheets, which form an interlayer and having a width of half as wide as that of the strip of sheet B or narrower, are heated at the softening point or higher and the melting point or lower of them by passing them through a hot air heating sphere D. Positions of both side parts of four sheets of strips of tape C each are slid in the crosswise direction and wound spirally round an imaginary cylindrical rotating shaft body A by interposing between the strips of sheet B. At the time of this winding the tape C wound up previously and the tape C wound up afterward form a tubular body (a) so that they juxtapose each other, fused through press contacting with a facing and contacting press roll E and cured through cooling.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing synthetic resin pipes used as water supply and drainage pipes for agricultural and civil engineering, industrial water supply and drainage pipes, etc. A large-diameter synthetic resin pipe with a substantially smooth surface, uniform wall thickness, and excellent watertightness is formed efficiently and continuously near the construction site using sheets and thermoplastic resin strip tape as materials. The present invention relates to a method of manufacturing a synthetic resin pipe that can be used to produce synthetic resin pipes.

[Conventional technology]

Conventionally, the extrusion molding method, in which the pipes are directly formed through an annular slit die of an extruder, has been generally used as a manufacturing method for this type of synthetic resin pipe, but when manufacturing large diameter synthetic resin pipes, the equipment becomes large. Moreover, since a die matching the size of the tube body must be prepared each time, there are drawbacks such as increased manufacturing costs.

Therefore, when manufacturing large-diameter synthetic resin pipes, it is necessary to use a virtual cylindrical rotating shaft as shown in Japanese Patent Publication No. 32-7438, Japanese Patent Publication No. 36-13932, and Japanese Patent Publication No. 36-14139. A method of manufacturing a tube body by spirally winding a band-shaped body and fusing or gluing it together is used.

[Problems to be Solved by the Invention] However, the above manufacturing method uses a single strip when winding the strip in a # spiral shape on the upper surface of the virtual cylindrical rotating shaft, and In order to maintain a specific thickness when a thin-walled belt-like body is used, because the rolled-up belt-like body and the later-wound belt-like body are wound so that they overlap each other at the sides to form a tube. Since the width of the above-mentioned polymerized portion has to be widened, productivity is significantly reduced. On the other hand, when a thick strip is used, it is not only difficult to obtain a uniform wall thickness due to the moldability of the strip. However, there were problems such as a difference in level occurring in the polymerized portion.

The present invention was invented to eliminate the drawbacks of the conventional methods described above.It is an object of the present invention to efficiently produce large-diameter synthetic resin pipes with substantially smooth surfaces, uniform wall thickness, and excellent watertightness. It is an object of the present invention to provide a method for manufacturing a synthetic resin pipe that can be continuously molded.

(Means for Solving the Problems) The present invention was invented in view of the above, and includes two thermoplastic resin strip sheets that are pre-formed to form a surface layer and a sheet that is pre-formed to form an intermediate layer. A plurality of sheets of thermoplastic resin strip tape are heated through a heating region to a temperature above the softening point and below the melting point, and the positions are shifted so that both sides are not located on the same line with each other, so that a strip is formed between the strip sheets. The tape is wound spirally on a virtual cylindrical rotating shaft body with the tape interposed therebetween, and during this winding, at least the band-shaped tape wound earlier and the band-shaped tape wound later are arranged side by side with each other without overlapping. In this manner, the tube is wound to form a tube, and when the tube is still at a temperature above the softening point and below the melting point, the tube is welded under pressure using a pressure roll that is in contact with the virtual cylindrical rotating shaft, and is cooled and hardened. This solved the problem.

Hereinafter, the features of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partially cutaway perspective view illustrating the manufacturing process of the present invention, FIG. 2 is a partially cutaway sectional view of the same, and FIG. Figure 3 is a partially cutaway plan view of the same as above, in which A is a virtual cylindrical rotating shaft body, and B is a thermoplastic resin belt-like sheet forming the surface layer of the tube body a, which has a predetermined thickness and thickness. It is made by collecting a belt-like sheet formed into a long shape with a width into a roll, and C is a plurality of thermoplastic resin belt-like tapes for forming the intermediate layer of the tube body a, The above band-shaped sea 1-B
The sheet B and the tape C are each rolled into a roll in the same manner as above, and these sheet B and tape C are heated to a temperature above the softening point and below the melting point through a heating area using a heat source such as hot air or an infrared lamp. Then, the respective sides are shifted in the lateral direction so that they are not located on the same line with each other, and the virtual cylindrical rotary shaft body A is tilted to the side circumferential surface of one end while interposing the band tape C between the band sheets 8. The tapes are fed simultaneously at an angle and wound into a spiral shape, and during this winding, at least the band-shaped tape C wound earlier and the band-shaped tape C wound later are arranged side by side with each other without overlapping 14. The tube body a is rotated to form a tube body a, and when the tube body a is still at a temperature higher than the softening point and lower than the melting point, it is pressure-welded by a pressure roll E that is in contact with the virtual cylindrical rotating shaft body A to form another body θ. The tubular body a is formed by cooling and hardening while being transferred to the first part side.

The virtual cylindrical rotating shaft A shown here is composed of a plurality of rolls la, lb, . . . it made of round rods,
Each of the rolls la, lb, .
Each of the rolls 1a+lb, . 3 in one direction by a required angle, and by shifting the bearing point of the other end of each roll 1a, lb, . ,lb, ,,li
By twisting and tilting the virtual cylindrical rotating shaft body A around the axis, the belt-shaped sheet B and the belt-shaped tape C are wound into a spiral shape.

A sprocket 4 is provided at the front shaft end of each roll la, lb, . be.

Furthermore, in order to improve the watertightness of the belt-shaped sheet 1-B used in the present invention, when the belt-shaped sheet 1-B is rolled around the virtual cylindrical rotating shaft body A in an end layer, the belt-shaped sheet B that is wound first and the belt-shaped sheet B that is wound later are rolled. It is possible to rotate the pupil as if the rolled belt-shaped sheet B overlaps at the side part, and the level difference at the overlapped part after winding is extremely small (so that it is thinner and wider than the belt-shaped tape C). It is preferable to
In addition, because the band-shaped tape C is relatively thick in the area that is to be punched for molding, the fusion surface is made of thermoplastic resin with a relatively low softening point, such as low-density polyethylene, as shown in Figure 4. It is preferable to use a composite tape layered with .

〔Example〕

Hereinafter, the present invention will be explained in more detail based on the embodiments shown in the drawings. To form a surface layer, two sheets of low-density polyethylene with a thickness of 0.5 mm are formed in advance and rolled up into a roll. A belt-shaped sheet B, a high-density polyethylene sheet with a thickness of 1 mm+ and a width of less than half of the belt-shaped sheet 1-B, which has been preformed and collected into a roll to form an intermediate layer, and a low-density polyethylene sheet. A four-leaf strip tape C made of a laminated sheet is heated to a temperature above the softening point and below the melting point through a heating area using hot air as a heat source, so that both sides of the four-leaf strip tape C are mutually bonded to each other. A virtual cylindrical rotary shaft body A is formed by interposing two parallel strip tapes C, which are shifted in the horizontal direction so as not to be located on the same line, and positioned in two stages, upper and lower, and interposed between the strip sheets 8.
The tubular body a is made by winding it in a spiral manner and winding it so that at least the strip tape C that was wound earlier and the strip tape C that was wound later are arranged side by side with each other without overlapping. When the tube body a is still at a temperature higher than the softening point and lower than the melting point, the tube body a is pressed and fused with a pressure roll E facing the virtual cylindrical rotating shaft body A, and is cooled and hardened to form the shape shown in FIG. A tubular body a having a substantially smooth surface as shown was formed.

〔Effect of the invention〕

As is clear from the above, the present invention provides two thermoplastic resin strip sheets preformed to form a surface layer and a plurality of thermoplastic resin strip tapes preformed to form an intermediate layer in a heated region. The sheets are heated to a temperature above the softening point and below the melting point, and the respective sides are shifted so that they are not located on the same line, and the strip tape is interposed between the strip sheets, and the strips are spirally formed on a virtual cylindrical rotating shaft body. At the same time, during this winding, the tape is wound in such a way that the strip tape wound earlier and the strip tape wound later are arranged side by side with each other without overlapping to form a tube body. The structure is such that when the tube is still at a temperature above the softening point and below the melting point, the tube is welded under pressure using a pressure roll that is in contact with the virtual cylindrical rotating shaft, and is cooled and hardened to form the tube. It has been made possible to continuously mold a tube with a uniform initial wall thickness and a substantially smooth surface, without the step differences that occur due to polymerization, and furthermore, the surface layer and multiple intermediate layers can be subjected to tS at the same time. It has the characteristics that the moldability is significantly improved because of the layered sheet and the tape that is layered is rotated by tS so that the positions are different from each other, and the watertightness is further improved. It is.

[Brief explanation of the drawing]

1 to 3 show embodiments of the present invention; FIG. 1 is a partially cutaway perspective view explaining the manufacturing process of the present invention; FIG. 2 is a partially cutaway sectional view of the same; FIG. 3 is a partially cutaway plan view of the same as above, FIG. 4 is a partially enlarged sectional view showing an example of the thermoplastic resin strip tape used in the present invention, and FIG. It shows a partially enlarged sectional view. A- One imaginary cylindrical rotating shaft body B- One belt-shaped sheet C- One belt-shaped tape D- One heating area E- One Press roll a- One tube body No. 1 (Figure 2 Figure 11 = Depending on the situation)

Claims (4)

[Claims] (1) Two pre-formed thermoplastic resin strip sheets to form the surface layer and a plurality of pre-formed thermoplastic resin strip tapes to form the intermediate layer are passed through a heating region above the softening point and below the melting point. heated to a temperature of , then shifted in the lateral direction so that both sides are not located on the same line with each other, and wound spirally around a virtual cylindrical rotating shaft with a strip tape interposed between the strip sheets. At the same time, during this winding, at least the band-shaped tape wound earlier and the band-shaped tape wound later are wound in such a way that they are arranged side by side with each other without overlapping, forming a tube body, and the tube body is still at its softening point. The method is characterized in that, at a temperature below the melting point, a pressure roll is used to press and fuse the virtual cylindrical rotating shaft body, and the tubular body is cooled and hardened to continuously produce a tubular body with a substantially smooth surface. Method for manufacturing synthetic resin pipes. (2) When winding the belt-like sheet in a spiral shape on the virtual cylindrical rotating shaft, the belt-like sheet is wound so that the first-wound belt-like sheet and the second-wound belt-like sheet overlap at the sides. A method for manufacturing a synthetic resin pipe according to claim 1. (3) The method for manufacturing a synthetic resin pipe according to claim 1, characterized in that the belt-shaped sheet is made thinner and wider than the belt-shaped tape. (4) The method for manufacturing a synthetic resin pipe according to claim 1, characterized in that a composite tape consisting of a laminate of a high-density polyethylene tape and a low-density polyethylene tape is used as the band-shaped tape.