JP2684482B2 - Plastic tube fusion method - Google Patents

Abstract

PURPOSE:To provide a method for fusion-bonding a pair of thermoplastic tubes efficiently in a short time without projecting molten bead inside an internal surface of the fusion-bonded part. CONSTITUTION:A heating body 5 is provided with an adapting cavity 6 and an adapting cavity 7, into which a core 4 is fitted, on both faces coaxially. A press body 3, which is made of split pieaces having a diameter nearly equal to the internal diameter of the adapting cavity 6, is fitted into an end part 1a of a plastic tube 1, with the projecting part 3a leaving outside. The plastic tube 1 comes in contact with the heating body 5, with the projecting part 3a fitted into the adapting cavity 6, and also a plastic tube 2 comes in contact with the heating body 5, with the plastic tube 2 fitted on the projecting part 4a of the core 4 of the adapting cavity 7. Then, end faces 1b and 2b of both plastic tubes 1 and 2 are fused by heating them. After that, both plastic tubes 1 and 2 are separated from the heating body 5, and immediately, both end faces 1b and 2b are jointed by butting them with each other, with the press body 3 held. After cooling, the press body 3 is drawn out from the integrated plastic jointed tube by splitting the press body 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fusing plastic pipes suitably used in the semiconductor industry, food industry, pharmaceutical industry, biotech industry, chemical industry and the like. The present invention relates to a butt fusion method for a plastic pipe, in which the molten bead does not project on the inner surface of the fusion-bonded portion and the inner surface is finished smooth.

[0002]

2. Description of the Related Art Conventionally, it has been difficult to join a plastic pipe made of polyethylene, polybutene, polytetrafluoroethylene (hereinafter, PTFE), polyvinylidene fluoride (hereinafter, PVDF), etc. with an adhesive. Is being done.

Recently, attention has been paid to a method in which a molten bead does not protrude from the inner surface of a welded portion of a plastic tube from the purpose of use, and various methods have been proposed. The main method among them is disclosed in JP-A-1-110127. In the method disclosed in this publication, the inner surface of the fusion-bonded portion of the plastic pipe is smooth, but the fusion-bonding takes time and there is a problem in work efficiency.

The present inventors have diligently studied to solve this problem, invented a fusing method capable of fusing in a short time and preventing the molten bead from protruding on the inner surface of the fusing part. Applied for a patent. (Japanese Patent Application No. 3-112739)

[0005]

In the method of fusing a plastic pipe according to the above application, the fusing work is completed in a short time,
Further, the inner surface of the fusion-bonded portion of the plastic tube had no protrusion of the molten bead and a smooth surface was obtained.

However, in this method, there is a risk that when the two plastic pipes are fusion-bonded to each other, the abutting surface of the pressing body fitted to the both plastic pipes becomes flush with the fusion-bonding faces of both pipe ends. As a result, it was found that the molten bead slightly protruded on the inner surface of the fusion-bonded portion and a smooth inner surface could not be obtained.

The present invention has been made in view of the problems of the invention of the prior application as described above, and an object thereof is to perform fusion in a short time, and there is a risk that the molten bead protrudes on the inner surface of the fused portion. It is an object of the present invention to provide a further improved method for fusing a plastic pipe.

[0008]

The structure of the present invention will be described with reference to FIGS. 1 to 6 corresponding to the embodiment. Fusion-bonding plastic pipes 1 and 2 provided on both sides with the same axis. 6, which has an inner diameter approximately equal to the inner diameter of
7 is provided, and one of the receiving ports 7 is fitted with a heating body 5 to which a core 4 having a diameter substantially equal to its inner diameter and having an axial length larger than its depth is fitted. The projecting portion 3 has a pressing member 3 that is movable in the same axial line as the receiving ports 6 and 7 and has an end 1a having a diameter substantially equal to the inner diameter of the receiving port 6. 3a is left fitted with the plastic pipe 1 fitted in the receiving portion 6 with the projecting portion 3a, and the other plastic tube 2 is fitted into the projecting portion 4a of the core 4 of the receiving opening 7. By bringing them into contact with each other in a fitted state, both plastic pipes 1,
The two pipe end faces 1b, 2b are heated and melted, then the plastic pipes 1, 2 are separated from the heating body 5, and immediately the both pipe end faces 1b, 2b are butted, and the integrated plastic pipe 10 after fusion bonding is completed. The pressing body 3 is taken out from the inside.

The other inventions are as described in claims 2 to 4 of the claims.

The plastic pipe used in the present invention is an olefin resin such as polyethylene, polypropylene or polybutene, a fluororesin such as PTFE or PVDF,
It is made of a material such as PEEK resin that cannot be strongly joined by adhesion, and its shape is not limited to a straight pipe, and includes end pipes such as curved pipes, joint pipes and valves. .

Further, the material of the core fitted in the receiving port of the heating body and the material of the pressing body fitted in the end of the plastic tube is not limited to metal, and may be plastic having heat resistance. Further, the shape is preferably cylindrical or cylindrical, and further,
For the pressing body composed of the divided pieces, the work efficiency is improved by dividing the pressing body into two or three pieces in order to facilitate the taking out from the pipe after the fusion bonding is completed.

[0012]

Since the present invention has the above-mentioned structure, the pipe end faces 1b and 2b of the plastic pipes 1 and 2 are sufficiently melted over the entire circumference, and the pipe end faces 1b and 2 are also melted.
When b is abutted and fused, the pressing body 3 is disposed so as to cross the fusion portion, so that sufficient fusion strength can be obtained, and the fusion bead generated during fusion may protrude to the inner surface of the pipe. To be prevented.

If the pressing body 3 is composed of three divided pieces 3b, 3c and 3d, and a strip-shaped body 9 for taking out is attached to each or one of them (see FIG. 3), It is possible to easily pull out the pressing body 3 from the inside of the pipe after completion of the bonding and joining.

[0014]

Embodiments of the present invention will be described below with reference to the drawings, but it goes without saying that the present invention is not limited to the embodiments shown below.

FIG. 1 is a vertical cross-sectional view of a main part showing a state before the end faces of a pair of plastic pipes are heated and melted by a heating body.

In the figure, reference numerals 1 and 2 denote PVDF plastic pipes (hereinafter referred to as PVDF) fixed (not shown) to a device capable of advancing and retreating with the axes of the both being the same.
Tube). Reference numeral 3 denotes a PTFE columnar pressing body fitted to the end portion 1a of the PVDF tube 1. The pressing body 3 is fitted with the protruding portion 3a of 5 to 10 mm left, and the protruding portion 3a is a portion fitted into the receiving opening 6 of the heating body 5 described later and is substantially equal to the inner diameter of the receiving opening 6. Dimension set to diameter. When the PVDF pipes 1 and 2 are fusion-bonded, the pressing body 3 accurately provides the parallelism between the PVDF pipes 1 and 2, and the fusion-bonding portions are arranged to cross each other. Is prevented from protruding to the inner surface of the pipe (see FIG. 6).

As shown in FIGS. 3 and 4, the pressing body 3 is composed of three divided pieces 3b, 3c and 3d.
The structure of the pressing body 3 is not limited to this. To facilitate removal from the fusion spliced tube, it is convenient to provide each axial contact surface of the three-piece segment with a taper.
Further, the length of the pressing body 3 in the axial direction is not particularly limited, but in consideration of work efficiency, it is better to set it to a relatively short size.

Reference numeral 9 is a cord-like body attached to the pressing body 3 and made of hemp, cotton, synthetic resin, wire or the like. PVD
After the fusion-bonding of the F-tubes 1 and 2 is completed, each divided piece can be easily taken out by pulling the string-like body 9 when taking out the pressing body 3 from the inside of the joining pipe 10. It suffices if the string-like body 9 is attached to at least one division piece, but it is better to attach it to each division piece in consideration of work efficiency. Further, when each divided piece of the pressing body 3 is taken out at once, in order to allow each divided piece to come out with a time difference, at least the length of the divided piece is different in the length of the string. This will make it easier to take out each divided piece.

7 to 9 are vertical sectional views showing another embodiment of the pressing body. In the figure, 12 is a truncated cone-shaped central core around which a segmented piece 13a, 13b, 13c is combined to form a cylindrical pressing body 13. The central core 12 and the divided pieces 13a, 13
Concave cutouts 14 and 15 are provided in the peripheral portion where b and 13c contact.
Are provided so as to face each other, and the central core 12 and the three divided pieces are connected by a string-like body 16 fixedly enclosed in the notches 14 and 15. The length of the string-shaped body 16 is not particularly limited, but as shown in FIG.
It is necessary to make the length such that a space 17 is formed at least between the cord 2 and the pressing body 13 when the cord 2 is pulled out by the string-shaped body 18.

Needless to say, if the end corners of the pressing body 3 and the core 4 described above are cut out and a small taper surface is provided, the fitting operation proceeds smoothly.

Reference numeral 5 is a pipe end surface 1 of the PVDF pipes 1 and 2.
It is a heating body that heats and melts by contacting with b and 2b. A heater 8 is built in the center of the heating body 5, and receptacles 6 and 7 formed of circular concave grooves are provided on both sides of the heater 8 with the same axis. The inner diameter of the receiving ports 6 and 7 is PVD
The dimensions are set to be substantially equal to the inner diameters of the F pipes 1 and 2 (that is, substantially equal to the diameter of the pressing body 3), and the end peripheral surfaces 6a and 7a of the receiving ports 6 and 7 and the PVDF pipe are heated and melted. The tube end faces 1b and 2b are provided so as to be in contact with each other.

Although the receiving ports 6 and 7 are provided integrally with the heating body 5 in this embodiment, both receiving ports may be separately manufactured so that they can be easily attached to the heating body 5. Absent.

A cylindrical core 4 made of PTFE is fitted in the receiving port 7. The core 4 has a diameter substantially the same as the inner diameter of the receiving port 7 like the pressing body 3, and has a length in the axial direction larger than its depth.
When the tube end surface 2b of the tube end surface 2 is heated and melted, the protrusion 4a thereof is fitted to the inner surface of the end 2a of the PVDF tube 2. The length of the protruding portion 4a of the core 4 is not limited, but may be 5 to 10 like the protruding portion 3a of the pressing body 3.
It is preferable to set the thickness to about mm from the viewpoint of fusion work. It should be noted that if a projection or the like that can be grasped by tools or the like is provided on the side surface of the projecting portion 4a of the core 4 in order to facilitate the removal from the receiving port 7, the work becomes easier.

An experimental example of the fusion bonding method based on the above description will be shown below. First, the circularly movable sockets 6 and 7 having an inner diameter of 50 mm and a depth of 20 mm, which are fixed so as to be movable in the circumferential direction, are provided with the same axis line, and the heating body 5 heated to 290 ° C. is placed at the center. PVDF pipes 1 and 2 having a diameter of 50 mm and a wall thickness of 3 mm, which are fixed to a device capable of advancing and retreating in the same manner as the axes of the receiving ports 6 and 7, are arranged on both sides of the heating body 5.

Next, a PTFE pressing body 3 consisting of three divided pieces each having a length of 25 mm and a diameter of about 50 mm is attached to the protruding portion 3 of 5 mm.
It is fitted into the PVDF pipe 1 leaving a, while the length is 25 m.
The core 4 having a diameter of 50 mm and a diameter of about 50 mm was fitted into the receiving port 7 while leaving the protruding portion 4a of 5 mm. After moving the PVDF pipes 1 and 2 closer to the heating body 5 from both sides, the projection 3a of the pressing body 3 is fitted into the receiving port 6 and the projection 4a of the core 4 is fitted into the PVDF pipe 2, and then the PVDF pipe 2 is fitted. The pipe end faces 1b and 2b of the pipes 1 and 2 were brought into contact with the end peripheral faces 6a and 7a of both receptacles substantially at the same time (see FIG. 2).

The tube end surface 1 is maintained for 60 seconds while maintaining the contact state.
After sufficiently heating and melting b and 2b, both the PVDF pipe 1 and the PVDF pipe 2 with the pressing body 3 fitted therein were separated from the heating body 5 (the same state as in FIG. 1). Next, the heating body 5 is moved in the circumferential direction of the PVDF pipe to move it away from the PVDF pipes 1 and 2, and the PVDF pipes 1 and 2 are immediately moved in the axial direction to approach the protrusion 3 a of the pressing body 3 to the PVDF pipe 2. Was fitted to the tube end portion 2a, and both tube end surfaces 1b and 2b were butted. At this time, the pressing body 3 was in a state in which the fused portions were crossed as shown in FIG.

The method of abutting the PVDF pipes 1 and 2 may be, for example, a method in which the PVDF pipe 1 is fixed and the PVDF pipe 2 is moved, and is not particularly limited. 30
After allowing to cool for about 60 seconds while maintaining the fusion-bonded state, the integrated joining pipe 10 is removed from the fixing device, the nylon string 9 attached to the divided pieces of the pressing body 3 is pulled, and the divided pieces are respectively separated. The joint pipe 10 was taken out.

The fusion-bonded portion of the PVDF-bonded pipe 10 obtained as described above is uniformly fused over the entire circumference, and
No molten bead was projected on the inner surface of the fusion-bonded portion, and the surface was smooth. Therefore, both the pressure resistance and the tensile strength of the obtained PVDF joined pipe 10 were completely satisfactory in use.

[0029]

As described above, according to the method for fusing a plastic pipe of the present invention, the following effects can be obtained. 1. The fused portion of the plastic pipe can be fused uniformly over the entire circumference, and since the molten bead does not project on the inner surface of the fused portion, a smooth inner surface can be obtained. Therefore,
The flow of the fluid in the pipe becomes smooth, and problems such as generation of bacteria such as bacteria, accumulation of pollutants, and deterioration of purity of pure water do not occur. 2. Since the fusion work can be completed in a short time, the work efficiency is improved as compared with the conventional general method. 3. It is possible to obtain a fusion tube suitable for ultrapure water piping lines in the semiconductor industry and piping lines in other industries.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view of a main part showing a state before an end surface of a plastic tube is brought into contact with a heating body.

FIG. 2 is a vertical cross-sectional view of a main part showing a state where the end surface of the plastic tube is simultaneously heated and melted by a heating body.

FIG. 3 is a perspective view showing a state in which a pressing body is fitted in a plastic pipe.

FIG. 4 is a perspective view of a pressing body formed by combining divided pieces.

FIG. 5 is a side view of the heating element.

FIG. 6 is a vertical cross-sectional view of a main part showing the positions of a plastic pipe and a pressing body after completion of fusion bonding.

FIG. 7 is a vertical cross-sectional view showing another aspect of the pressing body.

8 is a left side view of the pressing body shown in FIG.

9 is a vertical cross-sectional view showing a state in which a central core of the pressing body shown in FIG. 7 is pulled out.

[Explanation of symbols]

 1, 2 ... Plastic tube 1a, 2a ... End of plastic tube 1b, 2b ... End of plastic tube 3 ... Pressing body 3a ... Projection part 3b, 3c, 3d ... -Split piece 4 ... Core 4a ... Projection part 5 ... Heating body 6,7 ... Receptacle 6a, 7a ... Receptacle end peripheral surface 8 ... Heater 9 ... String Shaped body 10 ... Joined pipe 11 ... Molten bead 12 ... Central core 13 ... Pressing body 13a, 13b, 13c ... Three divided pieces 14, 15 ... Notch 16 ... String Strip 17 ... Void 18 ... String

Claims (4)

(57) [Claims] 1. Receptacles 6 and 7 having the same inner diameters as the inner diameters of the plastic pipes 1 and 2 to be fused, which are provided with the same axis on both sides thereof, and one of the receptacles is provided. A core 7 having a diameter substantially equal to the inner diameter of the core 7 and having a length in the axial direction larger than the depth thereof is fitted to a heating body 5 having the same axis as the receiving ports 6 and 7. A plastic pipe in which a pressing body 3 made of a divided piece having a diameter substantially equal to the inner diameter of the receiving port 6 is fitted to the end portion 1a of the plastic tube 1 so that the end portion 1a can be moved forward and backward. 1 with the projecting portion 3a fitted into the receiving port 6, and the other plastic pipe 2 with the core 4 of the receiving port 7.
Of the plastic pipes 1 and 2 are heated and melted by being brought into contact with each other while being fitted to the protruding portion 4a of the plastic pipes 1 and 2 and then the plastic pipes 1 and 2 are separated from the heating body 5 and immediately A method for fusing a plastic pipe, characterized in that the end faces 1b, 2b are butted and the pressing body 3 is taken out from the inside of the integrated plastic pipe 10 after completion of fusion bonding. 2. The method of fusing a plastic pipe according to claim 1, wherein the pressing body 3 and the core 4 have a cylindrical shape or a cylindrical shape. 3. The method for fusing a plastic pipe according to claim 1, wherein the pressing body 3 is formed of three divided pieces. 4. The pressing body 3 is a cylindrical body composed of a combination of a central core 12 having a truncated cone shape and at least three divided pieces 13a, 13b and 13c arranged around the central core 12, and 2. The plastic according to claim 1, wherein the central core 12 and the divided piece are connected at a contact surface portion thereof by a string-like body 16 having a length such that at least a space 17 is formed between the central core 12 and the divided piece when the central core 12 is pulled out. Tube fusion method.