JPH06285980A - Manufacture of lined metal pipe - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a metal pipe lined with a synthetic resin pipe which is glued firmly to be hardly stripped off. CONSTITUTION:The middle part of a metal pipe 1 carried into a preheating furnace 5 is preheated with a far-infrared heater 5a. In the next step, the outside of the metal pipe 1 carried into a furnace 6 is heated with far-infrared heaters 6a-6d at high temperatures from its middle part to the both ends so that a synthetic resin pipe 2 inserted into the metal pipe 1 is expanded from its middle part to both ends to be bonded with the metal pipe 1. After the metal pipe 1 is extracted from the furnace 6, pressurized fluid is introduced into the synthetic resin pipe 2 so that its outside is pressed on the inside of the metal pipe 1. In this way, both pipes are glued together firmly without bubbles between them, producing a metal pipe lined with a synthetic resin pipe which is hardly stripped off.

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 an inner surface lining metal pipe in which the inner peripheral surface of a metal pipe such as a steel pipe or a cast iron pipe is covered with a synthetic resin pipe.

[0002]

2. Description of the Related Art Conventionally, when coating the inner peripheral surface of a metal pipe such as a steel pipe or a cast iron pipe with a synthetic resin pipe, the thermally expansive synthetic resin pipe is inserted into the metal pipe and placed on a conveyor. The outer peripheral surface of the metal pipe carried into the heating furnace while being conveyed is heated with hot air from one end to the other end, or from the center to both ends, and the synthetic resin pipe inserted into the metal pipe is connected to the one end. To the other end, or from the center to both ends, the inner peripheral surface of the metal pipe was covered.

[0003]

However, in the case of this conventional method, heating unevenness occurs when the metal tube is heated in the heating furnace, and the metal tube cannot be heated to a predetermined temperature gradient in the longitudinal direction. There was an occasion. That is, when the metal pipes placed in parallel on the conveyor are sequentially loaded into the heating furnace, the flow of hot air is disturbed by the outside air flowing in from the inlet of the heating furnace, and the temperature distribution in the heating furnace becomes uneven. Therefore, the metal tube could not be heated to a predetermined temperature gradient. For this reason,
Uneven expansion due to uneven expansion of the synthetic resin pipe inserted in the metal pipe, uneven melting of the adhesive, etc., and air bubbles between the inner peripheral surface of the metal pipe and the outer peripheral surface of the synthetic resin pipe may cause poor adhesion. Occasionally, the synthetic resin pipe may peel off from the inner peripheral surface of the metal pipe.

Further, in this conventional manufacturing method, since a heating device for generating hot air, a blower, a duct, etc. are required, the equipment is inevitably large in scale, and there is a problem that the temperature control of the hot air blower is very troublesome. It was

The present invention has solved the above problems and is capable of heating a metal pipe to a predetermined temperature gradient in the longitudinal direction with simple equipment, and a synthetic resin pipe on the inner peripheral surface of the metal pipe. The present invention provides a method for manufacturing an inner surface lining metal tube, which is strongly adhesively bonded and does not peel off.

[0006]

According to the present invention, first, a thermally expandable synthetic resin pipe having an outer diameter slightly smaller than the inner diameter of the metal pipe and slightly longer than the metal pipe is prepared. A hot melt adhesive is evenly applied to the outer peripheral surface of the tube. Next, the synthetic resin pipe is inserted into the metal pipe so that each end of the pipe is projected from the end of the metal pipe, and a pipe end holder is attached to each end of the metal pipe. Therefore, the central portion of the metal tube is preheated by the far infrared heater in the preheating furnace while the metal tube is placed on the conveyor and conveyed. Next, the metal tube carried into the heating furnace is heated to a high temperature from the center to both ends by a far infrared heater, and the synthetic resin tube inserted in the metal tube is successively heated from the center to both ends. It is intimately contacted with the inner peripheral surface of the metal tube while expanding in the direction. Finally,
After carrying out the metal pipe from the heating furnace and connecting the conduit to the pipe end holder attached to the end of the metal pipe, a pressurized fluid is pressed into the synthetic resin pipe through the conduit to It is characterized in that the outer peripheral surface is cooled while being pressed against the inner peripheral surface of the metal tube.

[0007]

With the above construction, the central portion of the metal tube carried into the preheating furnace is preheated to a predetermined temperature by the far infrared heater, and then the metallic tube carried into the heating furnace is subjected to the far infrared heater at both ends from the central portion. Since the metal pipe is heated to a high temperature, the synthetic resin pipe inserted into the metal pipe gradually expands in the radial direction from the central portion toward both end portions and comes into close contact with the inner peripheral surface of the metal pipe. Therefore, when a pressurized fluid is pressed into the synthetic resin pipe, the outer peripheral surface of the synthetic resin pipe is pressed against the inner peripheral surface of the metal pipe to be adhesively bonded.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic plan view of an apparatus used in the present invention, and FIG.
1 is a schematic front view of the apparatus shown in FIG. 1, FIG. 3 is an array diagram of far-infrared heaters arranged in a preheating furnace and a heating furnace, and FIG. 4 is a cross-sectional view of essential parts in a state in which a pressurized fluid is pressed into a synthetic resin pipe. And
In the figure, 1 is a metal tube, and 2 is a heat-expandable synthetic resin tube.

In the present invention, a metal pipe 1 such as a steel pipe or a cast iron pipe can be used. At this time, when the metal pipe 1 whose outer peripheral surface is rust-proof coated with an organic paint is used, when the outer peripheral surface of the metal pipe 1 is heated by a far infrared heater during the preheating and heating steps described later, the organic paint is used. Since infrared rays are efficiently absorbed by the above, there is an advantage that the metal tube 1 can be quickly heated.

On the other hand, the heat-expandable synthetic resin tube 2 has an outer diameter slightly smaller than the inner diameter of the metal tube 1, and the metal tube 1
Use a slightly longer tube. The thermally expandable synthetic resin tube 2 is obtained, for example, by extruding a polyvinyl chloride resin, a crosslinked polyethylene resin or the like into a tubular shape and then reducing the diameter.

In the present invention, first, the inner peripheral surface of the metal tube 1 is subjected to surface treatment such as sand blasting or shot blasting, or
Alternatively, the metal pipe 1 is immersed in a cleaning tank to pickle the inner peripheral surface of the pipe. Further, the hot melt adhesive is evenly and uniformly applied to the outer peripheral surface of the heat-expandable synthetic resin tube 2 and dried. Therefore, the synthetic resin pipe 2 is inserted into the metal pipe 1, the pipe end holders 3 are attached to the respective ends of the metal pipe 1, and the end portions of the synthetic resin pipe 2 are fixed by the pipe end holders 3. To do.

The pipe end holder 3 is provided with a receiving port 32 at one end of the main body 31 and a female screw 33 at the other end, and the end of the metal pipe 1 is inserted into the receiving port 32. And then secure with bolts 34. Further, the tip of the bolt 35 screwed into the main body 31 is brought into contact with the outer surface of the end of the synthetic resin pipe 2 to fix the pipe end. By doing so, it is possible to prevent the synthetic resin tube 2 from contracting in the axial direction of the tube and the tube end portion thereof moving backward from the end surface of the metal tube 1 during the preheating and heating steps described later. .

Next, the metal tube 1 in which the synthetic resin tube 2 is inserted
While being placed and conveyed on the conveyor 4, the far infrared heaters of the preheating furnace 5 and the heating furnace 6 heat the outer peripheral surface of the metal tube 1.
At this time, the metal tube 1 may be conveyed by the conveyor 4 while rotating around the tube axis. Far infrared heater 5 of preheating furnace 5
a is provided on the upper surface side of the conveyer 4, and far infrared heaters 6a to 6d of the heating furnace 6 are arranged on both upper and lower sides of the conveyer 4 so as to face each other, and these far infrared heaters 5a and 6a to
6d is arranged as shown in FIG.

The arrow B in FIG. 3 indicates the moving direction of the conveyor 4, and the metal tube 1 carried into the preheating furnace 5 is preheated to a predetermined temperature by the far infrared heater 5a at the central portion in the longitudinal direction, The far-infrared heaters 6a to 6d of the heating furnace 6 heat to a predetermined temperature gradient. The far-infrared heaters 6a to 6d are divided into groups, and the outputs of the heaters 6a to 6d are set so that 6d ≦ 6c <6b ≦ 6a. The far-infrared heater 5a of the preheating furnace 5 is set to have an output substantially equal to that of the far-infrared heater 6d of the heating furnace 6.

Therefore, the metal tube 1 is moved from the preheating furnace 5 to the heating furnace 6.
When the metal pipe 1 is carried in, the central portion of the metal tube 1 is first heated to a high temperature, and the metal tube 1 is moved to the both end portions from the central portion as the conveyor 4 moves. Then, the synthetic resin pipe 2 inserted into the metal pipe 1 expands in the radial direction from the central portion toward both end portions, and between the inner peripheral surface of the metal pipe 1 and the outer peripheral surface of the synthetic resin pipe 2. The intervening air is smoothly discharged from the center toward both ends. Further, the heating melts the hot-melt adhesive applied to the outer peripheral surface of the synthetic resin tube 2, and the inner peripheral surface of the metal tube 1 and the outer peripheral surface of the synthetic resin tube 2 are tightly bonded and joined.

During this heating, the synthetic resin pipe 2 expands in the radial direction and a stress is generated so as to contract in the axial direction of the pipe. Since it is fixed by, the pipe end portion does not recede deeper than the end face of the metal pipe 1.

After the metal tube 1 is carried out from the heating furnace 6, the conduit 7 is connected to the tube end holder 3 attached to the end of the metal tube 1. That is, as shown in FIG. 4, the joint portion 71 of the conduit 7 is screwed into the female screw 33 of the pipe end holder 3 and the pressurized fluid is press-fitted into the synthetic resin pipe 2 to fix the outer peripheral surface of the synthetic resin pipe 2. Cooling is performed while maintaining the state of being pressure-bonded to the inner peripheral surface of the metal tube 1. Finally, the pipe end holder 3 is removed from the end of the metal pipe 1, and the surplus end of the synthetic resin pipe 2 protruding from the end of the metal pipe 1 is cut off, so that the inner peripheral surface of the metal pipe 1 is synthesized. An inner lining metal pipe in which the resin pipe 2 is firmly adhesively bonded is obtained.

In the above embodiment, first, the central portion of the metal tube is preheated to a predetermined temperature by the far infrared heater, and then the metallic tube is heated to a high temperature from the central portion to both ends by the far infrared heater. However, the present invention is not limited to this configuration. For example, a uniform preheating furnace may be installed in front of the preheating furnace, and the uniform preheating furnace may first heat the metal tube to a uniform temperature of 50 to 60 ° C. over the entire longitudinal direction. In this way, if the metal tube is first heated to a uniform temperature, then when the metal tube is loaded into the preheating furnace and the heating furnace in sequence and heated, the metal tube is more likely to move from the center to both ends. It has the advantage that it can be heated to a precise temperature gradient.

[0019]

As described in detail above, according to the present invention, the central portion of the metal tube is preheated to a predetermined temperature by the far infrared heater in the preheating furnace.
Next, the far-infrared heater heats the metal tube brought into the heating furnace to a high temperature from the central part to both ends, so there is not much influence of outside air flowing into the heating furnace unlike heating by conventional hot air. The metal tube can be heated to a predetermined temperature gradient along the longitudinal direction.

As a result, the synthetic resin pipe inserted into the metal pipe expands in the radial direction from the central portion toward both ends and is brought into close contact with the inner peripheral surface of the metal pipe. No air bubbles are present between the outer peripheral surface of the synthetic resin pipe and the outer peripheral surface of the synthetic resin pipe. In addition, after the synthetic resin pipe is adhered to the inner peripheral surface of the metal pipe,
Further, since a pressurized fluid is press-fitted into the synthetic resin pipe to bring the outer peripheral surface of the synthetic resin pipe into pressure contact with the inner peripheral surface of the metal pipe, the metal pipe and the synthetic resin pipe are firmly adhered to each other and are not separated from each other. An inner lined metal tube is obtained.

[Brief description of drawings]

FIG. 1 is a schematic plan view of an apparatus used in the present invention.

FIG. 2 is a schematic front view of the device shown in FIG.

FIG. 3 is an array diagram of far-infrared heaters arranged in a preheating furnace and a heating furnace.

FIG. 4 is a cross-sectional view of essential parts in a state where a pressurized fluid is introduced into the synthetic resin pipe.

[Explanation of symbols]

 1 Metal Pipe 2 Thermally Expandable Synthetic Resin Pipe 3 Pipe End Holder 4 Conveyor 5 Preheating Furnace 6 Heating Furnace

Claims (1)

[Claims] 1. An inner surface lining metal, characterized in that, when the inner peripheral surface of the metal tube (1) is covered with the thermally expansive synthetic resin tube (2), it comprises the following forming steps a) to d). Pipe manufacturing method. a) A thermally expandable synthetic resin pipe (2) having an outer diameter slightly smaller than the inner diameter of the metal pipe (1) and slightly longer than the metal pipe (1) is prepared, and the synthetic resin pipe (2) is prepared. Hot melt adhesive is uniformly applied to the outer peripheral surface of b), and b) the synthetic resin pipe (2) is then inserted into the metal pipe (1) so that each end portion is the end of the metal pipe (1). The pipe end holder (3) is attached to each end of the metal pipe (1) while protruding from the section, and c) the metal pipe (1) is placed on a conveyor (4) and conveyed. In the preheating furnace (5), the central part of the metal tube (1) is preheated by the far infrared heater (5a), and then the metal tube (1) carried into the heating furnace (6) is heated by the far infrared heaters (6a to 6d).
At a high temperature from the central part toward both ends, the synthetic resin pipe (2) inserted into the metal pipe (1) is expanded in the radial direction from the central part toward both ends, and The metal pipe (1) is brought out from the heating furnace (6) and brought into close contact with the inner peripheral surface of the pipe (1), and a pipe end holder (3) attached to the end of the metal pipe (1). )
After connecting the conduit (7) to the pipe, a pressurized fluid is press-fitted into the synthetic resin pipe (2) from the conduit (7) to make the outer peripheral surface of the synthetic resin pipe (2) the inner periphery of the metal pipe (1). Cooling while crimping to the surface,