JPH0872138A - Bending processing for thermoplastic resin pipe - Google Patents

Abstract

PURPOSE: To subject a thermoplastic resin pipe with good dimensional accuracy to form a bent pipe excellent in quality and small in curvature with high productivity while simplifying equipment and reducing equipment cost. CONSTITUTION: An inner mold 10 composed of a flexible cylindrical body 1 having hermetically sealing plugs 2 provided to both ends thereof is packed with a granular solid 3 and both ends of the inner mold 10 are hemtetically sealed by the hermetically sealing plugs 2 and this inner mold 10 is inserted in a preliminarily heated and softened thermoplastic resin pipe P. This thermoplastic resin pipe P is set to a bending processing outer mold divided up and down while compressed air is supplied into the inner mold 10 from the supply passages 4 provided to the hermetically sealing plugs 2 of the inner mold 10 to bring the inner mold into close contact with the inner wall of the thermoplastic resin pipe P. Thereafter, the outer mold is clamped by a pressure means to perform bending processing in matching relation to the bent shape of the outer mold.

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 thermoplastic resin pipe.

[0002]

2. Description of the Related Art Conventionally, as a method for bending a thermoplastic resin tube to manufacture a bent tube, for example, as described in JP-A-51-73078, baking is performed in a thermoplastic resin tube to be bent. A method is described in which a filler such as sand or a flexible core material is inserted, and a heated and softened thermoplastic resin tube is sandwiched between a bending mold composed of an upper mold and a lower mold to be clamped and bent. .

Further, in addition to the bending method described in Japanese Patent Laid-Open No. 73078/51, in order to deal with the case where the bending curvature is small, both ends of the thermoplastic resin tube to be bent are hermetically sealed. A method of filling and bending with pressurized air has been used.

However, in the above method, since material loss occurs at both ends or the number of processing steps increases and productivity is poor, a rubber cylinder with both ends sealed is inserted into a thermoplastic resin pipe, and the cylinder is filled with air. A method of bending a thermoplastic resin pipe by applying pressure and expansion using hot water or heating oil is used.

[0005]

However, in the method of inserting the rubber cylinder whose both ends are hermetically sealed and pressurizing and expanding the cylinder with air, hot water or heating oil, the air pressure is increased. When processing a curved pipe with a small bending curvature using air, the rubber cylinder is pressed by the force of buckling inside the bend, resulting in deformation of the cylinder due to the compressibility of air. However, there was a problem that the bending process was not performed properly. In addition, the method of pressurizing the cylinder using hot water or heating oil other than air has the reliability of the sealing performance of the cylinder made of rubber, and the equipment cost is high.
There was also the problem of low productivity.

The present invention has been made in view of the above problems, and an object of the present invention is to solve these problems and to perform bending without buckling and with high dimensional accuracy. The present invention provides a method for bending a thermoplastic resin pipe, which is excellent in quality, can bend a bent pipe having a small curvature, has high productivity, and can reduce equipment costs as compared with conventional methods.

[0007]

In the method of bending a thermoplastic resin pipe according to the present invention, a granular solid is formed inside an inner mold made of a flexible tubular body having sealing plugs at both ends. Fill the product and seal both ends with sealing stoppers, insert this inner mold into a thermoplastic resin tube that has been preheated and softened, and set this thermoplastic resin tube in the upper and lower split molds for bending. , Supplying pressure air from a supply passage provided in the inner mold sealing plug to bring the inner mold into close contact with the inner wall of the thermoplastic resin pipe, and thereafter, clamping the outer mold with a pressurizing means, A feature of the present invention is that bending is performed according to the bending shape.

[0008]

In the method for bending a thermoplastic resin pipe according to the present invention, the inside of the flexible tubular body is filled with a granular solid material and both ends are sealed with sealing plugs. Insert the inner mold into the thermoplastic resin pipe that has been heated and softened in advance, supply pressured air into the inner mold to bring it into close contact with the inner wall of the thermoplastic resin pipe, and bend it with the outer mold. Buckling does not occur on the inner side, and there is little uneven thickness on both the outer and inner peripheral sides of the bending, and dimensional accuracy is good and bending can be performed with excellent quality.
In addition, it has become possible to bend curved pipes with a small curvature. Further, the compressed air may have a relatively low pressure, and the inner mold can be repeatedly used, so that the equipment can be simplified and the equipment cost can be reduced, which is suitable for continuous production, and the productivity can be improved.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an example of an inner mold used in the method for bending a thermoplastic resin pipe of the present invention. In FIG. 1, reference numeral 10 denotes an inner mold, and the inner mold 10 includes a flexible tubular body 1 made of synthetic rubber and sealing plugs 2 and 2 provided at both ends of the tubular body 1. Parts are made up. The inside of the tubular body 1 is filled with a granular solid material 3 made of resin pellets or beads having excellent heat resistance, and the sealing plug 2,
It is sealed by 2.

The sealing plugs 2 and 2 are provided with a supply path 4 and a discharge port 4a for pressurized air. The supply path 4 and the discharge port 4a.
The mouthpieces 5 and 5 are provided at the entrance and the exit, respectively. Pipes 7 and 7 to which valves 6 and 6a are connected are connected to the caps 5 and 5, respectively, so that compressed air can be supplied to and discharged from the cylindrical body 1.

As described above, the inner mold 10 filled with the solid material 3 and supplied with the pressurized air is inserted into the thermoplastic resin pipe P which has been preheated and softened, and is bent as described below. It is made into a curved tube through the process.

The method of bending the thermoplastic resin pipe of the present invention will be described below in detail with reference to the sectional views showing an example of the method of bending the thermoplastic resin pipe of the present invention shown in FIGS. . As described above, the inner mold 10 filled with the solid material 3 made of resin pellets and sealed at both ends with the sealing plugs 2 and 2 is a thermoplastic resin pipe P in which the portion to be bent in advance is softened by heating. Insert inside.

Subsequently, the thermoplastic resin pipe P in which the inner mold 10 is inserted is attached to a pressurizing device in advance and is divided into upper and lower parts, and a lower mold 22 of an outer mold 20 including an upper mold 21 and a lower mold 22. Set as shown in FIG. Inside the inner mold 10 set in the lower mold 22, the valve 6 is opened from the pipe 7 connected to the supply path 4, and pressurized air is supplied with the valve 6a closed to expand the inner mold 10. , The inner wall of the thermoplastic resin pipe P is pressed and brought into close contact.

Next, when the hydraulic cylinder 30 provided in the hydraulic device installed above the upper mold 21 of the outer mold 20 and connected to the upper mold 21 is operated to lower the upper mold 21, The thermoplastic resin pipe P is pressed, and the upper mold 21 and the lower mold 2
The upper mold 21, which is bent along the curved shape of 2,
The bending process is completed with the lower die 22 completely closed. Thereafter, the pressurized air in the inner mold 10 inserted into the thermoplastic resin pipe P, which has been bent, is exhausted from the valve 6a on the discharge side.
The container is opened and discharged, cooled by cooling means provided in the outer mold 20, the curved pipe is taken out by opening the mold, and the inner mold 10 is pulled out from the curved pipe.

In the bending process, the pressurization of the inner mold 10 by the pressurized air is auxiliary, and a relatively low pressure is sufficient, so that the pressurizing device can be of a small scale.

Further, there is a gap between the resin pellets, which are the solids 3 filled in the inner mold 10, so that uniform pressure can be applied toward the circumference of the cylindrical body 1. Therefore, since the adhesion between the inner wall of the thermoplastic resin pipe P and the tubular body 1 is good, no sliding phenomenon occurs on both the outer peripheral side and the inner peripheral side of bending, and uneven thickness is small,
Further, since there is sufficient resistance against the force of buckling on the inner peripheral side, buckling does not occur and a curved surface shape with good dimensional accuracy can be secured.

Further, even if the bending curvature is smaller than the conventional one, there is an advantage that the bending process can be performed correspondingly and the product range can be greatly expanded. Further, the inner mold 10 can be continuously used repeatedly, and the bending method of the present invention is suitable for continuous production.

[0018]

According to the method for bending a thermoplastic resin pipe of the present invention, a granular solid material is filled in an inner mold made of a flexible tubular body, and both ends are sealed with sealing plugs. , This inner mold is inserted into a thermoplastic resin tube that has been preheated and softened, and compressed air is supplied into the inner mold to make it adhere to the inner wall of the thermoplastic resin tube.
Buckling does not occur inside the curved pipe, and there is little uneven thickness on both the outer and inner peripheral sides of the bending, and dimensional accuracy is good, and bending with excellent quality can be performed. In addition, it has become possible to bend curved pipes with a small curvature. Further, the pressure air may be relatively low pressure, and the inner mold can be repeatedly used, so that the equipment can be simplified and the equipment cost can be reduced, which is suitable for continuous production, and the productivity can be improved. Therefore, it is suitably used as a method for bending a thermoplastic resin pipe.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an inner mold used in a method for bending a thermoplastic resin pipe of the present invention.

FIG. 2 is a sectional view showing an example of a method for bending a thermoplastic resin pipe of the present invention.

FIG. 3 is a cross-sectional view showing an example of a method for bending a thermoplastic resin pipe of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical body 2 Sealing plug 3 Solid matter 4 Supply path 4a Discharge path 5 Base 6, 6a Valve 7 Piping 10 Inner mold 20 Outer mold 21 Upper mold 22 Lower mold 30 Hydraulic cylinder

Claims (1)

[Claims] 1. An inner mold made of a flexible tubular body having sealing plugs at both ends is filled with a granular solid material and sealed at both ends with sealing plugs. Insert into a heat-softened thermoplastic resin tube, set this thermoplastic resin tube into an outer mold for bending that is divided into upper and lower parts, and supply pressurized air from the supply passage provided in the sealing plug of the inner mold. Then, the inner mold is brought into close contact with the inner wall of the thermoplastic resin tube, and then,
A method for bending a thermoplastic resin pipe, characterized in that the outer die is clamped by a pressurizing means, and bending is performed in accordance with the bending shape of the outer die.