JPH05200855A - Processing method for bending of plastic pipe - Google Patents

Abstract

PURPOSE:To safely subject a plastic pipe to bending, easy in processing and by the use of a simple mechanism, so as not to deform the end part of the plastic pipe in the diameter direction thereof. CONSTITUTION:After a core material having an almost circular cross section formed by laminating a plurality of thin plates 11 is inserted in a plastic pipe 2, a plate shaped heater 3 formed by coating electric heating wires arranged in a planar state with a heat-resistant resin or rubber type insulating material is brought into contact with the local part to be subjected to bending processing of the plastic pipe 2 to heat and soften the local part and, subsequently, the plastic pipe 2 is subjected to bending molding and cooled before the core material 1 is pulled out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for bending a plastic pipe, and is useful for manufacturing a plastic bend pipe used in a bent portion of a pipe.

[0002]

2. Description of the Related Art When a gas pipe, a water pipe or a sewer pipe is formed by using a plastic pipe, a plastic bend pipe is used for a bent portion.

When manufacturing this plastic bend pipe, a plastic pipe of a predetermined length is heated and softened and then bent and formed. Conventionally, as a method of heating the plastic pipe, a method of placing it in an oven for a predetermined time or at a high temperature is used. A method of immersing in an oil tank for a predetermined time and a method of filling a heating compressed fluid in the pipe are performed.

[0004]

However, in such a conventional method of bending a plastic pipe,
Even if any of the above heating methods is used, since the heating and softening is performed over the entire plastic pipe, both ends of the plastic pipe processed as the insertion port or the receiving port have strains which are included in the plastic pipe during bending after heating and softening. It was often deformed in the radial direction by the opening of

Further, in the method of heating the plastic pipe by filling it with the heated compressed fluid, it is necessary to close both ends of the plastic pipe, so that it is necessary to devise a method for ensuring the airtightness and to ensure safety. Since effort is required, the work or mechanism becomes complicated.

In view of the above problems, the present invention allows bending of a plastic pipe so that the end portion of the plastic pipe is not deformed in the radial direction, and the bending of the plastic pipe is simple in work and mechanism and high in safety. The purpose is to provide a processing method.

[0007]

In order to achieve the above object, a method of bending a plastic pipe of the present invention is such that a heat-resistant resin or heat-resistant rubber insulating material is coated on and under a heating wire laid in a plane. The plate heater thus formed is brought into surface contact with a local portion of the plastic tube to be bent, and the plastic tube is bent after the local portion is heated and softened.

[0008]

In the method of bending a plastic pipe of the present invention,
Since only the local part of the plastic tube to be bent can be softened by heating and bent, the end of the plastic tube is not deformed in the radial direction during the bending. Further, when heating the plastic tube, it is only necessary to make surface contact by wrapping a plate heater or the like, and no complicated work or mechanism is required.

[0009]

Embodiments of the present invention will be described below in detail with reference to FIGS. 1 and 2 are cross-sectional views showing a heating step in the method for bending a plastic tube of this embodiment, FIG. 3 is a plan view showing a plate heater used in this heating step, and FIG. 4 is a plastic tube of this embodiment. FIG. 6 is a cross-sectional view showing a bending step in the bending method of FIG.

In order to bend the plastic pipe 2 (polyethylene pipe) by the method of this embodiment, first, a plurality of thin plates 11 are formed.
A core material 1 having a circular cross section in which (ultra high molecular weight polyethylene plate) is laminated is inserted into a plastic tube 2. Here,
When the plastic tube 2 is not a circular tube but a deformed tube such as an oval tube or an elliptic tube, a core material having a cross-sectional shape of the plastic tube is used. Also, the core material 1
Is longer than the plastic tube 2, and is made to project from both ends of the plastic tube 2 when inserted into the plastic tube 2.

Next, the plate-shaped heater 3 is locally bent (excluding both ends) where the plastic tube 2 is to be bent.
Wrap around the outer surface of the to make surface contact. The plate heater 3
As shown in (a) and (b) of FIG. 3, the heat-resistant resin-based or heat-resistant rubber-based insulating material 32 (for example, elastic silicone resin) is formed on the upper and lower sides of the heating wire 31 laid in a plane. The heating wire 31 is wired so as to have a substantially uniform density over the entire surface. 3A and 3B show two types of heating wires 31 having different wiring states. However, if the heating wires 31 are wired at a substantially uniform density, plate heaters other than those shown in the drawing are shown. 3 may be used. The plate-shaped heater 3 is wound around the outer surface of the plastic tube 2 by a steel tension coil spring 4 and held by a fixing member 5. In addition,
Instead of the tension coil spring 4, a band or the like may be used.

When the plastic tube 2 is locally softened by heating, the plate heater 3 is promptly removed from the outer surface of the plastic tube 2, and the thin plates 11 of the core material 1 are formed by using the molds 6 and 7.
The plastic tube 2 is bent and molded while sliding between each other. In bending, the plastic pipe 2 is installed in one mold 6 and then the plastic pipe 2 is pushed and bent by the other mold 7. By sliding between the thin plates 11 of the core material 1, the bending reaction force generated in the core material 1 is relaxed,
Pressurization of the molds 6 and 7 can be easily performed. Also,
When the thin plates 11 of the core material 1 slide against each other, the cross-sectional shape of the core material 1 can be maintained in a circular shape.
The cross-sectional shape of can also hold the original circular shape.

When the plastic tube 2 has cooled,
The core material 1 is pulled out from the plastic tube 2. Since the bending reaction force generated in the core material 1 by sliding between the thin plates 11 of the core material 1 during bending of the plastic pipe 2 is alleviated, the core material 1 can be easily pulled out. When the plastic pipe 2 is locally softened by heating, if the end of the plastic pipe may be heated by heat conduction, a water cooling jacket (not shown) is provided on the outer peripheral surface of the end. Good.

The bending of the plastic pipe 2 is completed by these operations. If the pipe is large in diameter and thick in plastic, and it takes time to heat only from the outer surface, if the plate-shaped heater of the present invention is wound on the inner surface of the pipe to make surface contact, a short time is required. It is possible to heat and soften the local part of the tube.

That is, in the method of bending the plastic pipe 2 of this embodiment, only the local portion of the plastic pipe 2 to be bent can be softened by heating and bent, and therefore the plastic pipe 2 can be bent at the time of bending. The ends do not deform in the radial direction. Therefore, the work is easy to perform when the end portion of the plastic tube 2 is subjected to the bending process and the mouth end process or the receiving process. Further, since the core material 1 in which a plurality of thin plates 11 are laminated is also used, it is possible to prevent flattening of a portion other than both ends of the plastic tube 2 during bending.

Further, when heating the plastic pipe 2, it is only necessary to wind the plate heater 3 into surface contact with the plastic pipe 2, and the plastic pipe is heated by filling the heating compressed fluid with the plastic pipe. Since it is not necessary to close both ends of 2, the work or mechanism is simple and the safety is high.

Further, since the heating wire 31 of the plate-shaped heater 3 is wired at a substantially uniform density, the plastic resin tube 2 is heated uniformly. Therefore, in the lengthwise direction of the plastic pipe 2, the compression force and the stretching force act evenly during bending and the variation in wall thickness does not occur.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific structure is not limited to this embodiment, and there are design changes and the like within the scope not departing from the gist of the present invention. Also included in the present invention. For example, if the plate heater has a function of adjusting the heating temperature, the plastic pipe is not limited to a general-purpose resin pipe such as a polyvinyl chloride pipe, a polyethylene pipe, a polypropylene pipe, and an ABS resin pipe. Bending can be performed even in the case of the engineering resin pipe of.

Further, in the present embodiment, the core material is formed by laminating a plurality of thin plates, but needless to say, it may be filled with conventionally used sand or the like.

[0020]

As described above, in the method of bending a plastic pipe of the present invention, since only the local portion of the plastic pipe to be bent is softened by heating and bent, the plastic pipe is bent at the time of bending. There is no radial deformation of the tube end. Therefore, it is possible to obtain an effect that the work can be easily performed when the end portion of the plastic pipe is subjected to the bending process or the mouth end process.

When heating the plastic pipe,
Since it is only necessary to wind the plate heater into surface contact with it, it is possible to obtain an effect that work or mechanism is simple and safety is high.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a heating step in a method for bending a plastic pipe according to this embodiment.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a plan view showing a plate-shaped heater used in the heating step, in which (a) and (b) have different heating wire wiring states.

FIG. 4 is a cross-sectional view showing a bending forming step in the method for bending a plastic pipe according to the present embodiment.

[Explanation of symbols]

 1 core material 2 plastic tube 3 plate heater 31 heating wire 32 insulating material

Claims (1)

[Claims] 1. A plate heater, which is formed by coating a heat-resistant wire or a heat-resistant rubber-based insulating material above and below a heating wire laid in a plane, is brought into surface contact with a local portion of a plastic tube to be bent, A method for bending a plastic pipe, which comprises bending and shaping the plastic pipe after locally heating and softening it.