JPH0716927A - Production of synthetic resin coated metal pipe - Google Patents

Abstract

PURPOSE:To continuously, uniformly and efficiently heat a metal pipe over the whole thereof without generating temp. difference in the circumferential direction of the metal pipe by heating the metal pipe while allowing the same to tumble and rotate on a conveyor. CONSTITUTION:Metal pipes 1 each having a synthetic resin tube 2 inserted therein are parallelly arranged on a conveyor 11 to be moved at a constant speed in the direction shown by an arrow (a) crossing the axial direction of the metal pipes at a right angle. The coil 13 having an oval shape of an electromagnetic induction heater 12 is arranged obliquely with respect to the moving direction (a) of the metal pipes 1 so as to surround the metal pipes 1 and the conveyor 11. That is, one loop end 13a of the coil 13 is positioned on the upstream side of the moving direction of the metal pipes 1 and the other loop end 13b thereof is positioned on the downstream side of the moving direction of the metal pipes 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a synthetic resin-coated metal tube in which either or both of the inner surface and the outer surface of the metal tube are coated with a synthetic resin.

[0002]

2. Description of the Related Art Synthetic resin-coated metal pipes are used for the purpose of imparting corrosion resistance, chemical resistance, heat insulation and designability to metal pipes.
The inner surface of the metal tube and / or the outer surface of the tube is coated with a synthetic resin. As a method for producing such a synthetic resin-coated metal tube, for example, there are those disclosed in Japanese Examined Patent Publication No. 60-30547, Japanese Unexamined Patent Publication No. 3-205128, and Japanese Unexamined Patent Publication No. 58-222817.

Although these conventional methods are different in the method of heating a metal tube, in each case, a thermally expandable or heat shrinkable synthetic resin tube coated with an adhesive is used for the inner surface of the tube and / or the tube. The metal tube inserted into the outer surface of the body is moved by a conveyor while being heated, and the synthetic resin tube is thermally expanded or contracted to be brought into close contact with the inner surface of the tube and / or the outer surface of the tube.

The former two adopted a hot air blowing method as a method for heating a metal tube.
As shown in the outline in FIG. 11, the one disclosed in -30547 discloses moving a plurality of metal tubes 1 into which synthetic resin tubes 2 are inserted, respectively, in a direction orthogonal to the tube axis direction, and obliquely with respect to the moving direction. Hot air is blown from the arranged heating furnace 3 to continuously heat the metal tube 1 from one end to the other end. In the figure, 4 is a belt conveyor and 5 is a preheating furnace by blowing hot air. Further, Japanese Patent Laid-Open No. 3-20512
As shown in FIG. 12, according to the publication No. 8 of the publication, a heating furnace 4 by blowing hot air is formed in a V-shape and is continuously heated from the central portion of the metal pipe 1 toward the pipe end.

The latter method, that is, the method disclosed in JP-A-58-222817, employs an electromagnetic induction heating method as a method for heating a metal tube. As shown in FIG. The metal tube 1 is moved in a direction parallel to the direction, and the elliptical electromagnetic induction heating coil 6 arranged so as to surround these metal tubes 1 in a direction orthogonal to the moving direction moves the metal tube 1 from one end to the other end. It is intended to heat continuously toward. In the figure, 7 is an electromagnetic induction heating generator connected to the electromagnetic induction heating coil 6.

[0006]

In the above-mentioned conventional method, since the metal tube does not rotate at all on the conveyor during the movement of the metal tube, in the hot air blowing method, the temperature is high on the upper side of the metal tube exposed to hot air. The lower side tends to be lower. Therefore, the preheating furnace 5 cannot be omitted, and the apparatus becomes complicated. In addition, the temperature control in the heating furnace 3 is extremely difficult because it is easily affected by the ambient temperature of the surrounding air, the charging temperature of the tube body, and the like, and the heating temperature of the metal tube easily changes.
Moreover, the heat loss is large and the thermal efficiency is poor. Furthermore, it takes a long time for the pre-tropical zone and the heating zone to reach the predetermined temperatures, and the metal tube cannot be charged until then, so that the actual working rate is significantly reduced. Also, since it is difficult to heat according to the length of the metal tube, if the tube length is shorter than the projected length of the heating zone in the tube axis direction, the part of the synthetic resin tube protruding from the tube end will be thermally deformed and this will cause It can also cause movement problems in the tube. Therefore, only a tube whose length corresponds to the projected length of the heating zone in the tube axis direction can be manufactured.

Next, in the electromagnetic induction heating method, since the heating is performed by the elliptical electromagnetic induction coil 6, the magnetic flux on the inner circumference of the coil is concentrated on the upper surface and the lower surface closest to the coil for each metal tube. , If the outer diameter of the metal tube exceeds a certain size, the temperature cannot be made uniform by heat transfer, and the heating will be uneven, resulting in a partial thermal deformation of the synthetic resin tube, Can not be completely covered.

The present invention has been made in order to solve the above problems, and can continuously and uniformly and efficiently heat the entire metal tube without requiring a preheating mechanism for the metal tube. It is an object of the present invention to provide a method for producing a synthetic resin-coated metal pipe, which is capable of handling the size and length of the metal pipe, has a high actual operation rate, and can obtain a high-quality product.

[0009]

The present invention employs an electromagnetic induction heating system which can cope with the size and length of a metal tube and which is excellent in temperature controllability, and can be used while moving the metal tube. By rotating or rolling a metal tube on a conveyor, the above problems are solved. That is, the feature of the present invention is that while moving a plurality of metal pipes, each of which has a synthetic resin tube inserted into at least one of the inner surface of the pipe and the outer surface of the pipe, while moving in the direction orthogonal to the pipe axis direction. In the method for producing a synthetic resin-coated metal tube, which comprises heating and causing the synthetic resin tube to thermally expand or contract to closely adhere to the inner surface of the tube and / or the outer surface of the tube, while rotating or rolling the metal tube on a conveyor. Along with moving, the metal pipe is arranged obliquely with respect to the moving direction of the metal pipe, and the metal pipe is directed from one end to the other end by an elliptical electromagnetic induction heating device provided so as to surround the metal pipe and the conveyor. It is intended to heat continuously.

As another aspect of the present invention, the oblong-shaped electromagnetic induction heating device is formed in a V-shape from the pipe central portion on the upstream side to the pipe end portion on the downstream side with respect to the moving direction of the metal pipe. By arranging them, the metal pipe is heated continuously from the central portion toward the pipe end.

[0011]

[Function] Since the metal pipe is rotating or rolling on the conveyor during the movement of the metal pipe, the heating by the electromagnetic induction heating device is uniformly performed in the circumferential direction of the metal pipe, and the temperature difference in the circumferential direction is It hardly happens. Furthermore, since this electromagnetic induction heating device is arranged obliquely with respect to the moving direction of the metal pipe so as to surround the metal pipe, the metal pipe is surrounded by the circumference of the metal pipe in the process of passing through the heating zone. As a result of the heating unit that is uniform in the direction sequentially moving from one pipe end to the other pipe end as the metal pipe moves, uniform heating is continuously performed over the entire metal pipe. Further, by controlling the coil current of the electromagnetic induction heating device, it is possible to easily change the strength of the magnetic field, so that an appropriate heating temperature can be set according to the size of the pipe diameter and the length of the pipe, and The rise time is also fast.

When a V-shaped electromagnetic induction heating device is used, thermal expansion or thermal contraction of the synthetic resin tube progresses simultaneously from the central part of the tube to the end part of the tube. Less likely to occur.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic plan view of an apparatus used in the method of the present invention.
And FIG. 3 is a side view showing an example of a conveyor for moving a metal tube.

In this embodiment, the metal tubes 1 each having the synthetic resin tube 2 inserted into the inner surface of the tube are placed in parallel on the conveyor 11 and moved at a constant speed in the direction of the arrow a orthogonal to the tube axis direction. The coil 13 of the elliptical electromagnetic induction heating device 12 is arranged obliquely with respect to the moving direction a of the metal tube 1, and the coil 13 is formed so as to surround the metal tube 1 and the conveyor 11. . That is, the one loop end 13a of the coil 13 is positioned on the upstream side in the moving direction of the metal tube 1, and the other loop end 13b is positioned diagonally so as to be positioned on the downstream side in the moving direction of the metal tube 1. Therefore, the metal tube 1 is heated when passing through the magnetic field generated by the electromagnetic induction heating coil 13. In the figure, 14 is an electromagnetic induction heating generator connected to the electromagnetic induction heating coil 13.

The conveyor 11 is a skid 1 in the example of FIG.
It is configured by a conveyor 11A with a dog 16 that moves in the vicinity of 5. Since the metal pipes 1 are placed on the skid 15 and are arranged one by one between the adjacent dogs 16, the dogs 16 of the conveyor 11a moving in the a direction are moved.
The metal tube 1 is pushed by and rolls in the b direction indicated by the arrow within the interval between the dogs 16 on both sides. Therefore, the metal tube 1 rolls on the conveyor 11A during its movement.

Further, in the example of FIG. 3, it is constituted by a conveyor 11B with rollers 17 which moves on the skid 15. The metal tube 1 is placed on a pair of rollers 17 attached to the conveyor 11B, and the lower portions of these rollers 17 are in contact with the skids 15, so that when the conveyor 11B moves in the direction a, Due to the frictional force between the roller 15 and the roller 17, each roller 17 rotates in the direction of arrow c, and therefore the metal tube 1 placed on the roller 17 rotates in the direction of arrow d. So in this case,
The metal tube 1 will rotate on the conveyor 11B during the movement.

Since the metal tube 1 is rolling or rotating on the conveyor 11 while the metal tube 1 is moving by the above means, the metal tube 1 is a long elliptical electromagnetic wave arranged obliquely to the moving direction a. When passing through the induction heating coil 13, it is possible to heat uniformly in the circumferential direction, and the heating section that is uniform in the circumferential direction is moved sequentially from one pipe end to the other as the metal pipe 1 moves. To move toward the tube end of the metal tube 1
Can be continuously and uniformly heated from one end to the other end. As a result, the synthetic resin tube 2 inserted into the inner surface of the tubular body successively and thermally expands from one end to the other end, and the synthetic resin tube 2 is brought into close contact with the inner surface of the tubular body by the melted adhesive. Therefore, the synthetic resin tube 2
A portion with insufficient thermal expansion does not occur, and a high-quality synthetic resin-coated metal tube 1A without dents or the like can be obtained. In addition,
In FIG. 1, the metal tube 1 that has passed through the heating zone of the electromagnetic induction heating device 12 is cooled in a cooling zone having a cooling mechanism such as a fan, and is discharged as a synthetic resin-coated metal tube 1A.

FIG. 4 is a schematic manufacturing process diagram in the above embodiment. First, for the metal tube, one metal tube indexing portion 21 is used.
Then, one by one is sequentially placed on the conveyor 11 and loaded into the line. Next, in the synthetic resin tube insertion portion 22, the synthetic resin tube 2 is inserted into the tubular body of each metal tube. The synthetic resin tube 2 is made smaller in diameter than a predetermined outer diameter at the time of its molding so as to have thermal expansion property, and further, an adhesive is applied to the outer peripheral surface thereof, or an adhesive tape is wound around it. In this way, the metal tube 1 into which the synthetic resin tube 2 is inserted moves while rolling or rotating on the conveyor 11 as described above, and then passes through the heating zone 23 of the electromagnetic induction heating device 12. Is continuously and evenly heated, the synthetic resin tube 2 is thermally expanded, and the synthetic resin tube 2 is brought into close contact with the inner surface of the metal tube 1 from one end to the other end. Then, it is cooled in a cooling zone 24 having a cooling mechanism, and a synthetic resin-coated metal tube 1A having an inner surface coated with the synthetic resin tube 2 is manufactured. The synthetic resin-coated metal pipe 1A is then subjected to pipe end treatment and marking in the pipe end treatment / marking band 25, and then bound in a binding band 26.

A steel pipe or a cast iron pipe is used as the metal pipe, and a polyester-based, polyolefin-based, polyvinyl chloride-based, polyacrylic-based, or polyamide-based hard resin pipe is used as the synthetic resin tube.

5 to 7 are sectional views of a synthetic resin-coated metal pipe manufactured by the method of the present invention. Of these, FIG. 5 shows that the synthetic resin tube 2 is attached to the inner surface of the metal tube 1 via an adhesive 28.
FIG. 6 shows a synthetic resin-coated metal pipe 1A when it is coated, and FIG. 6 shows a synthetic resin-coated metal pipe 1B when the outer surface of the tubular body is coated with the synthetic resin tube 2. In the case of FIG. 6, the synthetic resin tube 2 is preliminarily expanded to have a diameter larger than a predetermined outer diameter at the time of molding so as to have heat shrinkability, and an adhesive 28 is applied to the inner peripheral surface thereof. The adhesive 28 may be applied to the outer peripheral surface of the tubular body and dried, or an adhesive tape may be wrapped around it. FIG. 7 shows the inner surface of the metal tube 1 and the outer surface of the metal tube 1 made of synthetic resin tubes 2A, 2
1 shows a synthetic resin-coated metal tube 1C coated with B. Thermal expansion is imparted to the synthetic resin tube 2A on the inner surface side of the tube, and thermal contraction is imparted to the synthetic resin tube 2B on the outer surface side of the tube. The coating of the synthetic resin is usually performed in the order of the inner surface of the tube and then the outer surface of the tube.

Next, FIG. 8 is a schematic plan view showing another embodiment of the present invention. In this embodiment, as shown in the drawing, the electromagnetic induction heating coil 31 is bent and formed in a V-shape, and is V-shaped from the pipe central portion on the upstream side to the pipe end portion on the downstream side with respect to the moving direction a of the metal pipe 1. It differs from the device of FIG. 1 only in that it is arranged in a letter shape. By arranging the electromagnetic induction heating coil 31 in the V-shape in this way, it is possible to continuously heat from the central portion of the pipe to the end portion of the pipe, and heat of the synthetic resin tube 2 inserted into the inner surface of the pipe. Since the expansion proceeds simultaneously from the central part of the pipe to both ends of the pipe, the synthetic resin tube 2 is brought into close contact with the inner surface of the pipe sequentially from the central part of the pipe to both ends of the pipe. Therefore, when the pipe length is long, the risk of poor adhesion is lessened by performing such synthetic resin coating from the central portion of the pipe.

FIG. 9 is a schematic plan view showing still another embodiment of the present invention. In this embodiment, two elliptical electromagnetic induction heating coils 32A and 32B are used and arranged in a V shape. In this case, the metal pipe 1 cannot be loaded into the line from the a direction. Therefore, as shown in the process diagram of FIG. 10, the vertical feed unit 27 laterally feeds the metal pipe 1 in the pipe axis direction to the line. Charge. Since the heating zone 23 can be formed immediately, it is possible to heat the charged metal tube 1 from the central portion of the tube immediately after the charging.

Next, the synthetic resin coated metal pipes (hereinafter referred to as the metal pipe of the present invention) Nos. 1 to 6 produced by the electromagnetic induction heating system shown in FIG. 1 and the conventional hot air blowing system shown in FIG. The results of an examination of synthetic resin-coated metal pipes (hereinafter referred to as comparative metal pipes) Nos. 1 to 5 produced by a method in which the metal pipe is not rotated by the electromagnetic induction heating method will be described.

The manufacturing conditions were as shown in Table 1.

[0025]

[Table 1]

The contents of the investigation are the maximum and minimum temperatures reached in the heating zone (° C.) during manufacturing, product properties, actual working rate (%) when the actual working time per day is 7.95 hours, and actual working efficiency (Ton / Hr) and the survey results are shown in Table 2.

[0027]

[Table 2]

As is apparent from Table 2, the comparative metal tube No. 1 manufactured by the hot air blowing method had good product properties, but both the actual working rate and the actual working efficiency were low. Further, in the comparative metal pipe No. 2 of the same system, the resin coating on the outer surface of the pipe body was softened to cause dents, resulting in poor product properties, making it impossible to manufacture a product. Metal tube N for comparison when the tube length is short
o.3 is impossible to manufacture because the resin tube protruding from the end of the tube cannot be transferred by the conveyor due to thermal deformation and the thermal expansion of the resin tube inserted into the tube is incomplete. there were. Moreover, the electromagnetic induction heating coil is shown in FIG.
With the same arrangement as above, and when heating the metal tube without rotating it, the comparative metal tube No. 4 is good because the temperature difference in the circumferential direction does not appear much if the tube diameter is about 50 A (60.5 mm). Although similar results were obtained, like the comparative metal tube No. 5 under the same conditions, when the tube diameter was 100 A (114.3 mm), the temperature in the circumferential direction became uneven and the tube was inserted into the tube. The thermal expansion of the obtained resin tube was incomplete, and the production was impossible.

On the other hand, the metal tubes Nos. 1 to 6 of the present invention produced by the method of the present invention all have good product properties, and have a high actual operating rate and a high actual operating rate, and have high quality and production efficiency. Both were excellent.

[0030]

As described above, according to the present invention, the electromagnetic induction heating system is adopted, and the metal tube is heated while rolling or rotating on the conveyor while the metal tube is moving. Since there is no temperature difference in the circumferential direction, the entire metal tube can be heated continuously and uniformly and efficiently. As a result, a high-quality synthetic resin-coated metal tube can be obtained, and the working rate is greatly improved. Further, by adopting the electromagnetic induction heating method, the preheating mechanism for the metal tube is not required, and the device is simplified. Furthermore, the rise time at the start of heating is fast and the control of the heating temperature is extremely easy. Furthermore, since the present invention can continuously and uniformly heat regardless of the tube size and the tube length, the application range of the present invention is extremely wide.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing an embodiment of the present invention.

FIG. 2 is a side view showing an example of a conveyor when rolling a metal tube on the conveyor.

FIG. 3 is a side view showing an example of a conveyor when a metal tube is rotated on the conveyor.

FIG. 4 is a schematic process diagram of an example.

FIG. 5 is a sectional view of an inner surface-coated synthetic resin-coated metal tube.

FIG. 6 is a cross-sectional view of a synthetic resin-coated metal tube having an outer surface coating.

FIG. 7 is a cross-sectional view of a synthetic resin-coated metal tube having inner and outer surfaces coated.

FIG. 8 is a schematic plan view showing another embodiment of the present invention.

FIG. 9 is a schematic plan view showing still another embodiment of the present invention.

FIG. 10 is a schematic process diagram in the embodiment of FIG.

FIG. 11 is a schematic plan view showing an example of a conventional hot air blowing method.

FIG. 12 is a schematic plan view showing another example of a conventional hot air blowing method.

FIG. 13 is a schematic sectional view showing an example of a conventional electromagnetic induction heating system.

[Explanation of symbols]

 1 Metal Tube 2, 2A, 2B Synthetic Resin Tube 11 Conveyor 11A Conveyor with Dog 11B Conveyor with Roller 12 Electromagnetic Induction Heating Device 13, 31, 32A, 32B Electromagnetic Induction Heating Coil 15 Skid 28 Adhesive

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location B29L 23:22 (72) Inventor Tetsuo Shinohara 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Inside Steel Pipe Co., Ltd. (72) Inventor, Kazutomo Ezaki 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Steel Pipe Co., Ltd.

Claims (2)

[Claims] 1. A synthetic resin tube in which a synthetic resin tube is inserted into at least one of the inner surface of the tube and the outer surface of the tube is moved in the direction orthogonal to the axial direction of the tube while being heated to move the synthetic resin. In the method for producing a synthetic resin-coated metal tube in which a tube is thermally expanded or thermally contracted to closely adhere to the inner surface of the tube and / or the outer surface of the tube, the metal tube is moved while being rotated or rolled on a conveyor, and the metal is Continuously heating the metal pipe from one end to the other end by an oblong electromagnetic induction heating device that is arranged obliquely with respect to the moving direction of the pipe and is provided so as to surround the metal pipe and the conveyor. A method for producing a synthetic resin-coated metal tube, comprising: 2. A synthetic resin tube having a synthetic resin tube inserted into at least one of the inner surface of the tube and the outer surface of the tube is moved in the direction orthogonal to the axial direction of the tube while being heated to move the synthetic resin. In the method for producing a synthetic resin-coated metal tube in which a tube is thermally expanded or thermally contracted to closely adhere to the inner surface of the tube and / or the outer surface of the tube, the metal tube is moved while being rotated or rolled on a conveyor, and the metal is The metal pipe is continuously arranged from the center to the pipe end by an elliptical electromagnetic induction heating device arranged in a V shape with respect to the moving direction of the pipe and provided so as to surround the metal pipe and the conveyor. A method for producing a synthetic resin-coated metal tube, which comprises heating.