JPS62189137A - Bend reforming method for plastic pipe - Google Patents

Abstract

PURPOSE:To enable the titled method to reform a bend efficiently without affecting a quality of a pipe, by a method wherein strong bend reformation is performed, to begin with, and the weak bend reformation is performed in order by making use of a caliber roll through a bend reformation machine which is of a three-roll type arranged in a multi-stage state within a specific temperature range. CONSTITUTION:Rolls 61-67 of a bend reformation machine are arranged within a heat insulation tank 5 which is of a hot air circulation type so that their amplitude becomes small in order in a zigzag state in a vertical direction and repeating bending order in a zigzag state in a vertical direction and repeating bending wherein the same is strong at the begining and becomes weak in order is applied to the pipe. The front and rear rolls 61, 67 are of driving rolls for fixation of positions and the intermediate rolls 62-66, which are of idle rolls, provided in a controllable state of a position vertically and bending radii of them can be controlled. A water-cooled cooling tank 8 cooling the reformed pipe is provided with guide rolls 9 at the front and rear of the tank 8. With this construction, the bend of a long-sized thermoplastic pipe 2 wound up into a coiled state can be reformed within a temperature range from the glass transition temperature +20 deg.C up to the fusion point -20 deg.C or the temperature where disassembly is begun.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for straightening the curl of a long thermoplastic plastic/eve wound into a coil.

[Conventional technology]

For example, polyethylene pipes are used for gas piping. And a long one)? Eve is stored and transported in a coiled package for ease of handling, and is used by being stretched straight at piping sites. In this case, if the pipe is simply rewound, there will still be a considerable amount of curling, so it is necessary to correct the curling.

[Problem that the invention seeks to solve]

Conventionally, coiled tubes are wound and unrolled manually, and curls are manually corrected. In this case, it is necessary to bend the pipe back in a direction opposite to the curling direction, and large tensile stress is applied to the outside of the pipe, and large compressive stress is applied to the inside of the pipe, causing flattening, wrinkles, etc. May cause plastic deformation.

This invention does not adversely affect the quality of the pipe.
The purpose of this invention is to provide a method for straightening curves that can efficiently correct curves.

[Means and actions for solving the problem] A long thermoplastic pipe wound into a coil is bent within the range from the glass transition temperature +20°C to the melting point -20°C or the temperature at which decomposition starts. Then, a three-roll type curve straightening machine arranged in multiple stages uses caliber rolls to first perform strong curve straightening, and then sequentially perform weak curve straightening.

This allows for efficient straightening of bends without adversely affecting the pipe.

〔Example〕

An example of an apparatus for carrying out the method of the present invention will be explained with reference to the drawings. In the figure, 1 is a hot air circulation type heating tank for heating the pie f2 wound into a coil.The coil tube 2 is supported by a drum 3, and the pie fP is guided by a guide roll 4 and fed out. ing. Reference numeral 5 denotes a hot air circulation type heat insulating tank, in which a three-roll straightening machine is installed in multiple stages. In this example, the rolls 61 to 67 are arranged in a staggered manner in the vertical direction so that the swing width thereof becomes smaller in sequence, so that repeated bending, which is initially strong and gradually becomes weaker, is applied to the grooves. The front and rear rolls 61 and 67 are drive rolls whose positions are fixed, and the intermediate rolls 62 to 66 are roll rolls whose positions can be adjusted in the vertical direction so that the bending radius can be adjusted. Reference numeral 8 denotes a water-cooled cooling tank for cooling the straightened pipe, and guide rolls 9 are provided at the front and rear. Reference numeral 10 denotes a feeding machine in which driving endless belts are arranged facing each other.

Various tests were conducted using the above device.

Coiled shape due to the material used medium density polyethylene Melting point = 12
0°C, f lath transition point = -120°C, outer diameter =
34.0 revision inner thickness = 3. '7zm 2 length Ib length 10m Coil outer diameter 1.4m Test 1 Roll shape with pipe temperature 20℃ width 300m diameter 150
This was carried out using my cylindrical roll.

The first reverse bending radius is performed in a range twice as large as the coil winding radius, and then the second reverse bending is performed at a radius that is successively larger. As a result of performing the third reverse direction, the curvature after correction was 0.15 to 0.85
m-'9, the target curvature of 0.02 m-' could not be obtained. In addition, if the bending radius is 0.5H, the pipe after straightening will be flattened, and the pipe flatness (minimum pipe diameter/-
J? Iso maximum diameter) was 0.89.

Conclusion: When cylindrical rolls are used, the arm ribs become flattened and are not suitable for practical use.

Exam 2 The experiment was carried out using a single module.

The curvature after straightening is 0.09 to 0.75 m. Furthermore, when the first reverse bending radius is 0.5 H, the pipe after straightening becomes flat, and the degree of flatness is 0.94. became.

5.1v to 12□yeyu, 1. E2. Eve.

It causes flatness and is not practical.

Test 3 F[ni/'P Roll shape at a temperature of 20℃, force! J
Bar diameter I7. O* Direct ff1150m++t(iD
It was carried out using a force IJ bar roll.

The curvature after straightening was 0.018 to 0.084 m, and when the first reverse bending radius was 0.58, the flatness of the pipe after straightening was 0.995, which was a practically perfect circle.

Conclusion: When using a caliber roll, by setting the first reverse bending radius to 0.5R at 20° C., it is possible to straighten the target curvature with a degree of flatness that does not pose a practical problem.

Test 4 Using the caliber roll from Test 3, the pipe temperature was set to 100°C.
It was carried out as follows.

The curvature after straightening was 0.016 to 0.018 m, and the flatness was 0.996 in all cases, meaning it was a practically perfect circle. Conclusion: At 100°C, by using a caliber roll, the first bending In all cases with a radius of 0.5 to 2R, the target curvature can be corrected with a degree of flatness that does not pose a problem in practical use.

Test 5 Material: Polypropylene; Glass transition point: -10°C.

Melting point: 180℃ Pipe outer diameter: 34.0yxm Wall thickness: 3.7cm Length: 10m Coil outer diameter: 1.4m Using the caliber roll from Test 3, set the pipe temperature to 10℃.
The test was carried out under the condition that the first reverse bending radius was 0.5 to 2R.

If the curvature after straightening is 0.019 to 0.090 m-', and the radius of reverse bending is 0.5R, the flatness of the pipe after straightening is 0.995, which is practically a perfect circle. Conclusion: When using a caliber roll, by setting the first reverse bending radius to Q and 5R at 10℃ (glass transition point + 20℃), it is possible to straighten the target curvature with a flatness that does not pose a problem in practical use. It can be carried out.

Test 6 Material Polypropylene; Glass transition point -10℃ melting point 1
80°C Pipe outer diameter: 34.0 Group wall thickness: 3.7 mm Length: 10 m Coil outer diameter: 1.4 m Using the caliber roll from Test 3, the pipe temperature was set to -10°C.
When this test was carried out, cracks etc. occurred in No. 4 Iso under all conditions of the first reverse bending radius of 0.5 to 2R.

Conclusion: If the temperature is at the glass transition point, cracks will occur in the pipe, making it impractical.

Glass transition temperature -120℃, melting point 120℃ as above
In the case of medium-density polyethylene blades, using a caliber roll, the first bending radius is 0.5 R at a temperature of 20°C, and the first bending radius is 0.5 R at a temperature of 100°C.
It was confirmed that the intended bending correction could be performed within the range of R to 2R.

Furthermore, for polypropylene pipes with a glass transition temperature of -10°C and a melting point of 180°C, a caliber roll was used to
The first bending radius is 0 at 'C (glass transition temperature + 20℃)
．． It was confirmed that the desired bending correction could be achieved by setting the radius to 5 R.

〔Effect of the invention〕

The bend straightening method of the present invention is as described above, and the bend can be straightened without adversely affecting the quality of the pipe.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing an example of an apparatus for carrying out the method of the present invention. 61-67...Bending straightening roll.

Claims (1)

[Claims] A long thermoplastic pipe wound into a coil is bent from the glass transition temperature +20°C to the melting point -20°C.
Alternatively, within the temperature range at which decomposition starts, a three-roll straightening machine arranged in multiple stages uses caliber rolls to first perform strong deformation and then sequentially perform weak deformation. A method for straightening bent plastic pipes.