JPH0558391B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This patent describes a product made of synthetic resin that is resistant to strong pressure from inside and outside, such as underground drainage pipes, and is watertight and flexible. Pertains to spirally wound pipes.

(Prior art and problems) As a method for manufacturing spirally wound synthetic resin tubes, for example, as disclosed in Japanese Patent Publication No. 60-4772 and Japanese Unexamined Patent Publication No. 60-18333, a core is formed by extruding a molten plastic strip from an extrusion molding machine. A method is known in which a spirally wound tube is formed by supplying gold, wrapping the metal overlappingly so that their ends overlap each other, and joining the pieces, and then sequentially moving the metal in the axial direction of the metal core.

The strip member is shaped to have a continuous bulge in the extrusion direction, and by overlapping each other and adjusting the overlapping condition appropriately, a spirally wound tube in which a spiral hollow reinforcing strip is wound can be formed.

However, with this method, it is impossible to join each other to form a spiral tube unless the band-shaped member with the bulge is rolled up while it is still flexible immediately after extrusion. It is also difficult to maintain the shape of the bulge. In the case of small-diameter pipes, the shape of the bulge is relatively difficult to collapse, but in the case of large-diameter pipes, it is easy to collapse, resulting in a large decrease in pipe strength, and when connecting pipes, the gap between them and the joint becomes large. This may cause water leakage, and if deformation occurs, it will be noticeable and the product value will decrease.

To this end, various methods have been devised, such as inserting or fitting a flexible continuous core material inside the bulge for shape retention, and moving it sequentially in the axial direction to prevent the bulge from forming when it is cooled. Attempts have also been made to slit the bulge in the center to remove the continuous core material and then bond the slit to the outer surface of the bulge by extruding another stream of molten plastic.

However, in this method, various deformations occur in the tube after the bulge is cut and before another stream of molten plastic is extruded onto the outer surface of the bulge and bonded. This is due to the fact that some flexibility remains at that point, the degree of flexibility changes from time to time, and the internal stress caused by the deformation applied to the member when winding the band member in a spiral shape. It is thought that it will happen. The types of deformation shown in FIG. 13 are mixed, and it is impossible to predict what kind of deformation will occur under what conditions, nor can it be made constant. Therefore, even if another flow of molten plastic is extruded and bonded to the outer surface of the bulge, the bonding reliability is low and the strength of the spirally wound tube is reduced.

(Means for Solving the Problems) The inventors of the present invention have conducted various studies to solve these problems and have arrived at the present invention.

That is, the present invention relates to a method of manufacturing a spirally wound plastic tube in which a molten plastic band member is extruded from an extrusion molding machine, and then wrapped and bonded in a softened state, in which the band member is expanded continuously in the extrusion direction. A rib or a thick part that protrudes inward is provided at the tip of the bulging part, and a flexible shape-retaining material is placed inside the bulging part when the band-like member is rolled up. The continuous core material is inserted or inserted, and when it has cooled approximately, the bulge is cut at the center of the rib or thick wall to remove the continuous core material, and then another flow of molten plastic is passed through the bulge. This is a method for manufacturing a spirally wound tube characterized by extrusion coating the outer surface.

An example of a spirally wound tube made by the method of the present invention is shown in Fig. 1 as a side view, a cross section parallel to its axis as shown in Fig. 2, and Fig. 3 as a wall section similar to that in Fig. 2. It is a partially enlarged view. This spirally wound tube has a trapezoidal bulge 3 as shown in cross section in FIG. 4 (when the entire tube is made of homogeneous plastics) and FIG. The spirally wound tube 1 is formed by overlapping and joining the strip member 2 having a flat surface 4 so as to close the opening of the adjacent bulge 3, and a rib 5 is formed inside the center of the bulge 3. It is provided. When making this, bulge part 3
The shape-retaining flexible continuous core material (hereinafter abbreviated as "shape-retaining belt") inserted or fitted inside is removed by tearing the center part of the rib 5 of the bulging part 3, and removing it from the torn part 6.
A cap strip 7 is provided in which a separate stream of molten plastic is extruded and bonded.

The shape of the rib 5 and the cap band 7 can take many shapes as illustrated in FIGS. 5 to 10,
Various other types may be arbitrarily selected.

First, a case where the entire band-shaped member 2 is made of one type of plastic will be explained. Figures 5 to 10
Although the figures are sectional views of the finished products, the shapes of the strip members immediately after extrusion corresponding to those in FIG. 4 in each case are omitted because they can be easily imagined. The rib 5 may have a shape as shown in FIG. 7, which is more appropriately called a thick portion. It is also good to provide a groove 8 in the center to facilitate tearing as shown in FIGS. 3 and 11.

Although it is preferable that the cap band 7 penetrates into the tear portion 6 as much as possible, it is not necessary.
The material of the plastic constituting the cap band 7 may be different from that of the band member 2, and a different material with good adhesive properties may be selected, or the color may be changed. For example, there is a method for manufacturing spirally wound plastic tubes in which molten plastic strips are extruded from an extrusion molding machine, rolled up in a softened state, and bonded together.
-30399, Special Publication Showa 46-12000, Special Publication Showa 46-17919,
Examples include, but are not limited to, Japanese Patent Publication No. 60-4772 and Japanese Patent Publication No. 60-18333. For example, overlapping winding may be performed by moving a core metal or an extrusion molding machine on a rail.

The shape of the rotating support for receiving the band-shaped member extruded from the extrusion molding machine and wrapping it spirally is not a specific condition for carrying out the present invention;
It goes without saying that any type is fine.

An example of an apparatus for carrying out the method of the present invention is shown in FIGS. 11 and 12.

Next, this device will be explained.

FIG. 11 is a schematic top view of the device. The strip member 2 extruded from the main extrusion molding machine 9 is wound over the core bar, but the strip member 2 may be extruded into a flat plate and placed against a molding guide to form the bulge 3. Alternatively, the extrusion die may optionally have a shape as shown in FIG. 4, which corresponds to the cross-sectional shape of the flat strip member 2 having the bulging portion 3. In principle, this device consists of a large number of roll groups 10-1, 10- arranged in a cylindrical shape at positions in contact with the inner surface of the tube to be formed.
2, 10-3, 10-4... are provided, and the rolls are provided approximately within a cylindrical surface and inclined at a constant angle with respect to the axis 11 of the tube to be formed, respectively, and this roll group is connected to the drive device 12. The belt-shaped member 2 extruded by Since it is moved in the axial direction, by adjusting the degree of inclination, the belt-shaped member 2 after one winding can be rolled up with a constant overlap.

A shape-retaining belt 13 inserted or fitted into the bulge 3
is, for example, a rubber V-belt, a spring wire, etc., which is fitted into the bulge 3 of the band 2 at the initial stage of winding the band 2 around the core metal, and is wound together with the bulge. The shape-retaining belt 13 is sealed in the hollow formed by the flat part 4 of the belt-shaped member 2 in front of the rotation, and after remaining sealed for several rotations, the central part of the distal end of the bulge is cut open with the cutter 14, and the shape-retaining belt 13 is removed. taken out. It is preferable that the taken-out shape-retaining belt 13 is wound around the cooling guide roller 15 and sequentially moved to a position where it is first wound around the belt-like member, thereby forming an endless continuous core material. Incidentally, the outer surface of the bulging portion 3, that is, in terms of the product, the peaks formed by the bulging portion 3, ie, 16-1, 16-2, 1 in FIG.
6-3,... valley between 17-1, 17-2, 17
-3, In order to strengthen the connection with the previous band member 2, the pressing belt 18 is wrapped around the tube that is being formed using the same mechanism as the shape-retaining belt 13 and continuously pressed. It's good to do this. A cap band 7 extruded from another extrusion molding machine 19 is extruded and coated on the torn portion 6 from which the shape-retaining belt 13 is taken out. The cap band 7 may be configured to allow the extruded resin flow to flow down onto the tearing portion 6, and the cap band 7 may also be configured to allow the extruded resin flow to flow down onto the tearing portion 6.
1 to make the adhesion strong.

In order to explain the relationship between each of the belts 13, 18 and the strip member 2, FIG. 12 shows a schematic cross-sectional view of the pipe that is being formed, parallel to the plane of the drawing, and which passes through the axis 12 of FIG. 11. At the left end of the figure, the belt 13-1 of the belt-like member 2-1 is fitted into the bulge 3 and wound onto the flat part 4-2 of the belt-like member 2-2 immediately before. Further, a pressure belt 16-1 is wound around a trough formed between the bulging portion 3-1 of the band-like member 2-1 and the bulging portion 3-2 of the band-like member 2-2. After three rotations, the bulging portion 3-4 is cut open with the cutter 14, and then the pressing belt 16-4 is removed, and after two more rotations, the shape-retaining belt 13-7 is removed. After removing the belt, the opening cut with the cutter will close naturally. This closed bulge is covered with a cap band 7 and joined. It is preferable to heat the bulging portion 3 with the heater 20 before covering it with the cap band 7. As a heating method, various local heating methods such as blowing hot air and far-infrared heaters can be used. 1st
For the sake of simplicity, FIG. 1 shows an apparatus for producing a core metal with a constant pipe diameter and helical pitch. In order to make a spirally wound tube with any diameter and spiral pitch, it is necessary to make it possible to adjust the diameter of the cylinder formed by the cylindrical roll group, and to change the pitch of the spirally wound tube, the roll group It is only necessary to make the angle formed with respect to the axis of the spirally wound tube adjustable, and since this can be easily done by those skilled in the art by combining various mechanisms, the explanation will be omitted.

When the entire band member 2 is made of hard plastic as described above, the flexibility of the finished spirally wound tube may be insufficient depending on the purpose of use.
In that case, as shown in FIG. 14, the narrow strip-shaped portion 23 excluding the portions 22, 22' near both edges of the strip-shaped member 2 and the bulging portion 3 may be made of softer plastic than the other portions. The width of the narrow strip-shaped portion 23 satisfies the conditions that it does not overlap the near-edge portion 22 as shown in 1, 2, and 3 in Fig. 14, and that it does not overlap the shoulder portion 24 where the near-edge portion 22 joins when spirally wound. Optional.

When using such a partially soft band-shaped member 2, for example, two extrusion molding machines may be used instead of the main extrusion molding machine 9 shown in FIG. The materials may be fed into two extrusion nozzles, combined within the nozzle, extruded as a band-shaped member 2, and thereafter configured into a spirally wound tube in the same manner.

There is a method using two extrusion molding machines, feeding soft plastics and hard plastics or plastics of different colors from each into one extrusion die and combining them in the die to obtain an integrated extrusion molded product. Since this is a method commonly used in the plastic molding industry, the details will be omitted, but any method may be used.

(Effects of the Invention) The method of the present invention uses a band member with a special cross-sectional shape to cover and reinforce the opening from which the flexible continuous core material for retaining the shape of the bulge is taken out with another flow of plastic. It is possible to significantly improve the bonding strength and eliminate uneven bonding.

In the spirally wound tube manufacturing method of the present invention, the spiral shape of the resulting tube is constant, so the bulge that supports the strength of the tube may be deformed, or the side wall of the bulge may be twisted, resulting in partial strength loss. There is no fluctuation. In addition, the inner surface of the pipe is smooth and when used as a drain pipe, it is less likely that dirt or the like will get caught and obstruct the flow.

Another advantage is that the helical shape of the candy pipe is constant and the joint member of the pipe fits well with each other, with little water leakage.

Furthermore, even when a partially soft band member 2 is used to impart flexibility to the spirally wound tube as shown in Fig. 14, the soft plastic and hard plastic can be joined within the extrusion die, that is, while both are in a molten state. Since the parts to be joined after molding are made of hard plastics, the strength can be maintained as in the case of Figures 5 to 10. For example, if the flat part 4 is made of soft plastics Needless to say, in cases where flexibility is to be imparted as a material, the strength is higher than that when bonded to an adjacent hard plastic.

[Brief explanation of the drawing]

Fig. 1 is a schematic side view of an example of a tube manufactured by the method of the present invention, Fig. 2 is a partial schematic view of a cross section passing through the axis of Fig. 1, and Fig. 3 is a partially enlarged view of the same cross section; FIG. 4 is a schematic cross-sectional view of an example of a strip member, and FIGS.
The figure is a schematic cross-sectional view of a bulging portion of another example of a tube equivalent to FIG. 3 manufactured by the method of the present invention, and FIG. 10 is a schematic cross-sectional view of still another example of a tube manufactured by the method of the present invention. 11 is a schematic top view showing an example of an apparatus for carrying out the method of the present invention, FIG. 12 is a schematic cross-sectional view parallel to the paper plane of the tube being formed in FIG. 11, and FIG.
The figure is a schematic cross-sectional view of a band-like member showing the shape when the bulging portion is cut, and FIG. 14 is a schematic cross-sectional view of a band-like member as another example of a tube manufactured by the method of the present invention. DESCRIPTION OF SYMBOLS 1...Spiral winding tube, 2...Band-shaped member, 3...Bulging part, 4...Plant part, 5...Rib, 6...Tearing part, 7...Cap band, 8...Groove, 9 ...Main extrusion molding, 10-1, 10-2, 10-3, 10-4
... Roll group, 11 ... Axis, 12 ... Drive device,
13... Shape-retaining belt, 14... Cutter, 15...
...Cooling guide roller, 16-1, 16-2, 16
-3, 16-4... Yamabe, 17-1, 17-2,
17-3... Tanibe, 18... Pressure belt, 19...
. . . Extrusion molding machine, 20 . . . Heater, 21 . . . Presser roll, 22, 22' .

Claims (1)

[Scope of Claims] 1. A method for manufacturing a spirally wound plastic tube in which a molten plastic band member is extruded from an extrusion molding machine, rolled up in a softened state, and joined together,
The band-like member has a bulge that continues in the extrusion direction, and a rib or a thick part that protrudes inward is provided at the tip of the bulge, so that when the band-like member is rolled up, the bulge is A flexible continuous core material for shape retention is inserted or inserted inside, and when it has almost cooled, the bulge is cut at the center of the rib or thick part to take out the continuous core material. A method for manufacturing a spirally wound tube, characterized in that a flow of molten plastic is extruded and coated on the outer surface of the bulged portion. 2. The method for manufacturing a spirally wound tube according to claim 1, wherein the narrow band-like part of the band-like member excluding the areas near both edges and the bulging part is made of softer plastic than other parts.