JP7559648B2 - Manufacturing method of coated pipe - Google Patents

Description

The present invention relates to a method for manufacturing a foam-coated pipe in which a resin pipe is coated with a resin foam (thermal insulation material).

Coated pipes, which are made of a resin pipe covered with a resin foam material, are used as pipes for supplying hot and cold water, especially in cold regions.

The method used to manufacture this coated pipe involves continuously feeding the pipe and foam sheet (sheet-like foam) through a cylindrical former, covering the plastic pipe with the sheet-like foam, bonding both ends of the sheet (the mating ends) by thermal fusion, and continuously taking up the foam-coated pipe with a take-up machine.

In this method, the foam sheet is formed into a cylindrical shape by passing it through a cylindrical former. Therefore, particularly when the foam-coated pipe has a small aperture size or the pipe is covered with a foam sheet that is thick compared to the aperture size, the resistance of the foam sheet when passing through the cylindrical former is large. As a result, the coated foam coming out of the former is stretched by the take-up force of the take-up machine. After passing through the take-up machine, the stretched coated foam shrinks in the longitudinal direction of the resin pipe. The ratio of the shrinkage length of the coated foam to the unit length of the resin pipe is hereinafter referred to as the shrinkage rate of the coated foam.

Methods for suppressing the shrinkage of the covering foam material include shortening the cylindrical former to reduce the resistance to passage, and slowing down the take-up speed. However, shortening the cylindrical former can cause problems such as peeling of the fused joint surface due to insufficient cooling, and slowing down the take-up speed can reduce production efficiency.

To solve these problems, methods have been proposed, such as knurling or threading the inner diameter side of the former to reduce the contact area between the former and the coating material and thus reduce the passage resistance (Utility Model Laid-Open Publication No. 6-55728), arranging multiple guide rollers on the inner diameter side of the former to reduce the passage resistance (JP Patent Publication No. 2003-127220), and arranging a liner or tape between the outer surface of the foam material and the inner diameter side of the former to reduce the passage resistance (JP Patent No. 5271131, JP Patent Publication No. 07-241905).

However, this method requires a complex former structure and a large number of parts, which means it takes time and money to manufacture a former for each aperture size. In addition, it is difficult to perform additional processing to adjust the inner diameter dimensions of the former, which are related to passage resistance, fusion and crimping, and joining.

Japanese Utility Model Application Publication No. 6-55728 JP 2003-127220 A Patent No. 5271131 Japanese Patent Application Publication No. 07-241905

The present invention aims to provide a method for manufacturing a foam-coated pipe that can suppress the shrinkage rate of the foam-coated pipe after removal.

The method for producing a foam-coated pipe of the present invention continuously coats a resin pipe by continuously feeding a resin pipe and a foam sheet to a former, rolling the foam sheet to surround the resin pipe, heating and melting the side ends of the foam sheet in the width direction, and then fusing and joining the side ends together in the former. The method for producing a foam-coated pipe of the present invention is characterized in that it includes a feeder for feeding the resin pipe at a constant speed before passing it through the cylindrical former, a first speed gauge for measuring the feed speed of the resin pipe between the feeder and the cylindrical former, and a second speed gauge for measuring the feed speed of the foam-coated pipe fed from the take-up machine on the outer surface of the coating material, and the difference between the speed of the resin pipe measured by the first speed gauge and the speed of the foam-coated pipe measured by the second speed gauge is set to within 2%.

In one aspect of the present invention, when the feed speed setting value of the resin pipe feeder is Va, the feed speed of the resin pipe measured by the first speed gauge is Vb, the set speed of the take-up machine is Vc, and the feed speed of the foam-coated pipe measured by the second gauge is Vd, the relationship Va = Vb = Vd, Vc > Vd is satisfied.

In one embodiment of the present invention, the line speed (resin pipe feed speed) is 10 m/min or more.

In the method for producing a coated pipe of the present invention, a resin pipe and a foam material sheet are continuously fed to a former, the foam material sheet is rolled to surround the resin pipe, the widthwise side ends of the foam material sheet are heated and melted, and then the side ends are fused together in the former to continuously coat the resin pipe. In this method, the foam material sheet (coated foam material) coated on the outer surface of the resin pipe is fed faster than the resin pipe between the former and the take-off machine, so that the foam material sheet (coated foam material) that was delayed inside the cylindrical former returns to its original position, and the speeds of the resin pipe and the foam material sheet (coated foam material) are roughly equalized at the time of exiting the take-off machine. This suppresses the shrinkage rate of the coated foam material.

4A to 4C are side views showing a method for manufacturing a coated pipe according to an embodiment. 2A, 2B, 2C, and 2D are cross-sectional views taken along lines IIa-IIa, IIb-IIb, IIc-IIc, and IId-IId in FIG. 1, respectively. 1A to 1C are schematic cross-sectional views illustrating a method for producing a coated pipe according to an embodiment.

In one embodiment of the method for producing coated pipes of the present invention, a resin pipe and a foam sheet are each continuously fed into a former, the foam sheet is rolled into a cylindrical shape at the introduction section of the former to surround the resin pipe with the foam sheet, the side ends (jointed end faces) in the width direction of the foam sheet are heated and melted, and then the opposing side ends are fused and joined together in the former to continuously produce coated pipes.

In the present invention, the resin pipe is preferably made of polyolefin and has a diameter of 5 to 50 mm, particularly 10 to 30 mm. The foam sheet is preferably made of polyolefin and has a thickness of 3 to 20 mm, particularly 5 to 10 mm. Examples of polyolefin include cross-linked polyethylene, non-cross-linked polyethylene, and polypropylene.

Next, we will explain the manufacturing method of such a foam-coated pipe with reference to Figures 1 to 3.

The resin pipe 2 manufactured by extrusion molding and the rolls 1 and 3, each wrapped with a band-shaped foaming sheet 4 that has been previously foamed and has a film applied to the outside, are set on the upstream side of the manufacturing process line. The foaming sheet 4, which is continuously drawn out from the roll 3, is aligned with the resin pipe 2, which is continuously drawn out from the roll 1 and fed by the resin pipe feeder 10. Then, at the introduction section of the former 6, the foaming sheet 4 is rolled up to surround the resin pipe 2, as shown in Figure 2(b).

Just before entering the cylindrical former 6, a pair of side ends (mating end faces) of the foaming material sheet 4 are heated and melted by a heater 5, and the foaming material sheet 4 is passed through the inner hole of the cylindrical former 6 so that the ends are butted together, and while squeezing, the mating end faces are pressed together and pressure-bonded. This forms a coated pipe 8 in which the circumference of the resin pipe 2 is coated with the coating foam material made of the foaming material sheet 4, and the coated pipe 8 passes through the cylindrical former 6 and comes out. The coated pipe 8 coming out of the cylindrical former 6 is continuously taken up by the take-up machine 7 and wound up by the winding machine 9 downstream in the manufacturing process.

This coated pipe manufacturing device is equipped with a measuring device 11 for the feed speed of the resin pipe 2, a measuring device 12 for the take-up speed of the coated pipe 8, other measuring devices necessary for quality control, and a control device that controls the feed speed and take-up speed of the feeder 10 and take-up machine 7 (specifically, controls the rotation speed of the drive motor). The take-up speed measuring device 12 measures the speed of the outer surface of the coated foam material of the coated pipe 8.

The resin pipe 2 is fed at a constant speed by the resin pipe feeder 10. As described above, the foam sheet 4 is fed together with the resin pipe 2 and rolled up around the resin pipe 2. Just before entering the cylindrical former 6, both side edges of the foam sheet 4 along the feeding direction are heated and melted by the heater 5. The both side edges are pressed together inside the cylindrical former 6 and pass through the cylindrical former 6.

As mentioned above, inside the cylindrical former 6, the foam material sheet 4 moves in contact with the inner wall of the former 6, so the foam material sheet 4 slows down due to contact resistance with the inner wall of the former 6, and becomes slower than the speed of the plastic pipe 2. As a result, the covering foam material coming out of the former 6 is stretched by the pulling force of the pull-up machine 7. After passing through the pull-up machine 7, the stretched covering foam material shrinks in the longitudinal direction of the plastic pipe 2.

In this embodiment, the take-up speed of the take-up machine 7 is set to be faster than the feed speed of the resin pipe 2, and the surface of the foam material sheet 4 covering the outer surface of the resin pipe 2 is fed faster than the speed of the resin pipe 2 between the former 6 and the take-up machine 7, so that the foam material sheet 4 (covering foam material) that was delayed inside the cylindrical former 6 is brought back (the delay is made up), and the speeds of the resin pipe 2 and the foam material sheet 4 (covering foam material) are roughly matched at the time of leaving the take-up machine 7 (the difference between the two is within 2% of the feed speed of the resin pipe 2), thereby suppressing the shrinkage rate of the covering foam material.

Preferably, when the feed speed setting value of the resin pipe feeder 10 is Va, the feed speed of the resin pipe 2 measured by the speed gauge 11 is Vb, the set speed of the take-up machine 7 is Vc, and the feed speed of the foamed material-coated pipe 8 measured by the gauge 12 is Vd,
Va=Vb=Vd, Vc>Vd
This allows the take-off machine 7 to return only the outer covering foam sheet 4.

The usual method for the take-up machine 7 is to firmly chuck the entire covering foam material to prevent it from shifting, but in this embodiment, the chucking force is loosened appropriately so as not to impede the advancement of the foam material sheet 4.

If the take-up machine 7 is used in a general, normal manner in which the resin pipe 2 and the covering foam material are firmly chucked together to prevent them from slipping, not only the covering foam material but also the resin pipe 2 will be firmly chucked, resulting in the relationship [take-up machine set speed (Vc)] = [resin pipe feed speed (Vb) measured by the speedometer]. Therefore, if the take-up machine 7 is used to return only the covering foam material 4 to its original position by setting the take-up machine set speed (Vc) > the resin pipe feed speed setting (Va), then because Vc = Vb > Va, the resin pipe feed speed (Vb) measured by the speedometer > [resin pipe feed speed setting (Va)] will be satisfied, and this will not hold unless slippage occurs between the resin pipe feeder and the resin pipe. If slippage occurs between the resin pipe feeder and the resin pipe, the length of the resin pipe, which is the standard length of the covering foam material, will fluctuate, and the shrinkage rate of the covering foam material will become unstable.

The present invention exerts a more excellent effect in suppressing shrinkage rate under high-speed conditions with a line speed of 10 m/min or more. This is because the resistance when passing through the cylindrical former 6 increases as the line speed increases.

[Examples 1 and 2, Comparative Examples 1 to 3]
1 to 3, coated pipes were manufactured at various feed rates, and the shrinkage of the coating material in the manufactured foam-coated pipes was measured. The results are shown in Table 1.

In this example and the comparative example, a cross-linked polyethylene resin pipe with a pipe size of 10A (outer diameter 13 mm) and a polyethylene foam sheet with a thickness of 10 mm were used.

Comparative examples 1 and 2 relate to conventional methods for manufacturing foam-coated pipes.

Examples 1 and 2 relate to the method of the present invention, and show cases where the difference between the measured speed of the foam-coated pipe (Vd) and the measured speed of the resin pipe (Vb) is set to 0%.

Comparative Example 3 shows a case where the difference between the measured speed of the resin pipe (Vb) and the measured speed of the foam-coated pipe (Vd) is 6.2%.

As shown in Table 1, the shrinkage rate of the covering foam material is suppressed more in Examples 1 and 2 than in Comparative Example 3.

REFERENCE SIGNS LIST 2 Resin pipe 4 Foaming material sheet 5 Heater 6 Former 7 Coated pipe take-up machine 8 Coated pipe 10 Resin pipe feed machine 11 Resin pipe feed speed measuring device 12 Coated pipe take-up speed measuring device

Claims (3)

The resin pipe and the foaming material sheet are fed into the former in succession.
The foam sheet is rolled to surround the resin pipe;
In the method for producing a foam-coated pipe, the foam sheet is heated and melted at its widthwise side edges, and then the side edges are fused and joined together in the former to continuously cover a resin pipe,
A feeder is provided for feeding the resin pipe at a constant speed before passing it through the cylindrical former, a first speed meter is provided for measuring the feeding speed of the resin pipe between the feeder and the cylindrical former, and a second speed meter is provided for measuring the feeding speed of the foamed material-coated pipe fed from the take-up machine on the outer surface of the coating material,
A method for manufacturing a foam-coated pipe, characterized in that the difference between the speed of the resin pipe measured by the first speed gauge and the speed of the foam-coated pipe measured by the second speed gauge is within 2%. When the feed speed setting value of the feeder is Va, the feed speed of the resin pipe measured by the first speed gauge is Vb, the set speed of the take-off machine is Vc, and the feed speed of the foam-coated pipe measured by the second gauge is Vd,
Va=Vb=Vd, Vc>Vd
2. The method for manufacturing a foam-covered pipe according to claim 1, wherein the above-mentioned condition is satisfied. The method for manufacturing a foam-coated pipe according to claim 1 or 2, characterized in that the line speed is 10 m/min or more.

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