JPS5848232B2 - Method for coating the inner surface of metal tubes with resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for coating the inner surface of a preheated metal tube, particularly a deformed metal tube such as an S-shaped tube or an O-shaped tube, with a resin.

Traditional methods for forming a resin coating layer on the inner surface of a metal tube include spraying powdered resin with an electrostatic gun or passing the powdered resin along with an airflow through a preheated metal tube to adhere the resin to the inner surface of the tube. However, with the former method, it is difficult to insert the gun into the metal tube when the inner diameter is small, and the gun requires repeated reciprocating movements, so it is difficult to insert the gun into the tube. The work requires a lot of time and effort, and it is impossible to coat the inner surface of irregularly shaped pipes such as semicircularly bent pipes and S-shaped pipes.

On the other hand, the latter method has good workability, but in the case of irregularly shaped pipes, the flow of powdered resin flowing through the pipe is biased outward at the bent part of the pipe due to centrifugal force, and a large amount of powdered resin is deposited in that part. Not only does the layer thickness become extremely uneven due to welding, but there are also disadvantages in that there are portions on the inside where the resin coating layer is not formed.

The present invention eliminates these drawbacks and makes it possible to continuously and smoothly coat the inner surface of metal pipes with resin, by sequentially providing an upper connector communicating with a powder resin flow tank, a butterfly valve, and a bypass valve. In addition, the upper and lower open ends of the preheated metal tube are connected between the lower end and the lower connector, which is in communication with the resin suction and recovery device, and the bypass valve of the lower connector is communicated with the outside air, and the resin suction and recovery device is connected. With the butterfly valve in constant operation, the powder resin in the powder resin flow tank is allowed to flow into and fill the metal tube by closing the butterfly valve, and after a predetermined period of time, the butterfly valve is opened and the powder resin is poured from the lower end opening of the metal tube. The present invention provides a method for coating the inner surface of a metal tube with resin, which is characterized by suctioning and recovering the metal tube.

An embodiment of the present invention will be explained with reference to the drawings. Fig. 1 shows an apparatus for carrying out the method of the present invention, in which 1 is a powder resin fluidized tank, and a perforated plate 2 is disposed in the lower part of the inside of the tank.
The inside of the upper part is divided into a powder resin chamber 1a, and the inside of the lower part is divided into an air supply chamber 1b.

Reference numeral 3 denotes a guide cylinder which is fixed to the perforated plate 2 and the center of the bottom plate of the tank 1, with its upper end opening communicating with the powder resin chamber 1a and its lower end protruding downward from the bottom plate of the tank 1.
An upper connector 5 is connected to the projecting end via a conduit 4 that is vertically expandable and retractable.

6 is a fluid pressure cylinder attached to the center of the ceiling frame of tank 1;
A valve body 6a is fixed to the lower end of the piston rond, and the upper end opening of the guide cylinder 3 is opened and closed by the valve body 6a.

Reference numeral 7 denotes a compressed air supply pipe connected to and communicating with one side of the air supply chamber 1b of the tank 1.

A lower connector 8 is disposed opposite to the upper connector 5 at an appropriate distance below the connector 5. A butterfly valve 9 is integrally connected to the lower end of the lower connector 8, and a bypass valve is attached to the butterfly valve 9. 10 is connected, and this discharge pipe 11 is connected and communicated with a suction and recovery device 12.

Now, with the open end of the guide tube 3 closed by the valve body 6a by the cylinder 6, the powder resin a is accommodated in the chamber 1a of the powder resin fluidization tank 1, and then a modified shape such as a preheated S-shaped pipe is placed. The tube b is oriented vertically and its upper and lower open ends are connected to an upper connector 5 and a lower connector, respectively.

Next, when air is forced into the chamber 1b through the air supply pipe 7, air is ejected from the perforated plate 2 into the powder resin chamber 1a, and the chamber 1
Powder resin a in a is brought into a fluid state.

In this state, when the guide tube 3 is opened by operating the cylinder 6 and moving the valve body 6a upward, the powder resin a in a fluid state flows from the guide tube 3 to the conduit 4 and the upper connector 5.
It flows into the irregularly shaped tube b through the tube.

At this time, the powder resin a is uniformly and sufficiently applied to the irregularly shaped tube b in a short time.
In order to fill the inside, it is sufficient to apply shock or vibration to the irregularly shaped tube b, and by doing so, the appearance of the resin layer welded to the inner surface of the tube can be improved and a coating layer with a uniform thickness can be obtained. It's a monkey.

Furthermore, while the powder resin a is being filled, the butterfly valve 9 is closed, but the suction and recovery device 12 is always operated with the bypass valve 10 open.

In this way, after filling the inside of the irregularly shaped tube b with the powdered resin a, this state is maintained for a certain period of time to heat-fuse the powdered resin to the inner surface of the preheated irregularly shaped tube b to a desired layer thickness at the preheating temperature, Thereafter, the bypass valve 10 is closed, and the butterfly valve 9 connected to the lower connector 8 is opened, and the powdered resin inside the tube that has not adhered to the inner surface of the tube is removed by suction by a suction machine.

In this way, the deformed tube b whose inner surface has been coated with a resin coating layer of a predetermined thickness is removed from the upper and lower connectors 5 and 8, and the inner surface of the next tube is coated with resin.

In this case, if the suction and recovery device is stopped, it will take a long time from startup to reach the specified vacuum pressure compared to the time required for the resin to adhere to the inner surface of the tube.
Since the recovery device is always in operation, the resin coating on the inner surface of the metal tube can be carried out smoothly one after another.In addition, even though the suction and recovery device is in continuous operation, there is no bypass when filling the metal tube with resin. Since the valve 10 is opened, there is no risk of mechanical stress, and by interlocking the bypass valve 10 and the butterfly valve, the resin coating process can be performed efficiently.

Next, specific examples of the present invention will be shown.

Example 1. J preheated to 150℃ to the upper and lower connectors of the device
IS G5527 (Spheroidal graphite cast iron deformed pipe for water supply) 1
Connect an Otsu-shaped tube with a diameter of 0.00 mm and flow the epoxy resin powder paint into the tube from the resin fluidization tank (filling time 0.2 seconds).
The powder coating was deposited on the inner surface of the tube for a welding time of 5 seconds.

Next, the lower end of the tube was opened, and the powder paint that did not adhere to the inner surface of the tube was suctioned and removed for 0.5 seconds.

The measurement results of the layer thickness of the inner resin-coated tube thus obtained are shown in the following table.

In the table, A, B, C, D, and E indicate the lengthwise measurement parts of the tube (Fig. 2), and x, y, z1, and z indicate the upper circumference, lower circumference, and both sides of each part. As is clear from this table showing the inner surfaces of the circumferential portions, the inner surface of the Otsu-shaped tube is coated with a resin coating having a sufficient and substantially uniform thickness over the entire surface.

Example 2. Object to be painted JIS B230, 4-1
80° elbow, 3 inch diameter Powder paint Polyethylene resin powder paint tube heat temperature 240℃ Powder paint filling time 0.2 seconds Powder paint welding time 12 seconds Powder paint suction removal time 0.8 seconds or more Under the following conditions, the inner surface of the 1800 elbow was coated with resin using the above apparatus.

The results of measuring the resin coating and coating layer thickness of the obtained pipes are shown in the table below.

In the table, A, B, C, D, and E indicate the measurement parts in the length direction of the tube (shown in Figure 3), and X, Y, Z1, and Z2 indicate the upper local part, lower peripheral part, and both sides of each part. As is clear from the table showing each inner surface of the circumference, the inner surface of the 1800 elbow is coated with a resin coating layer of sufficient and substantially uniform thickness over its entire length.

In addition to the above-described embodiments, in order to coat the inner surface of a T-shaped tube with resin as shown in FIG. Connect the lower connector 8 to the lower end opening, and then connect the upper connector 5,
5' may be connected and communicated with the powder resin fluidization tank 1 in the same manner as in the previous embodiment.

As described above, the present invention provides a preheated metal connector between the upper connector that communicates with a powder resin fluidized tank and the lower connector that is sequentially provided with a butterfly valve and a bypass valve, and whose lower end is connected to and communicates with a resin suction and recovery device. The upper and lower open ends of the pipes are connected, the bypass valve of the lower connector is communicated with the outside air, and the butterfly valve is closed while the resin suction and recovery device is constantly operating, and the powder resin in the powder resin fluidization tank is transferred to the metal. The inner surface of a metal tube is characterized by the following features: after a predetermined period of time has elapsed, a valve attached to the lower connector is opened to suck and collect the powdered resin filled in the metal tube using a suction device communicated with the lower connector. Since this method is related to the resin coating method, the inner surface can be coated with resin one after another by simply installing the preheated metal tube vertically between the upper and lower connectors without inverting or rotating it, which improves work efficiency. Since the metal tube is once filled with powder resin from the powder resin fluidization tank above, the powder resin is reliably kept in close contact with the inner circumferential surface of the metal tube, making it suitable for not only straight tubes but also S-shaped tubes. It is possible to form a coating layer with a substantially uniform thickness over the entire surface of irregularly shaped pipes such as pipes and O-shaped pipes, without leaving any unformed parts of the resin coating layer in the lengthwise or circumferential direction. It is.

Furthermore, according to the method of the present invention, since the resin suction and recovery device is activated in advance, the butterfly valve is operated while maintaining an appropriate suction force and after the resin welding time in seconds to the inner peripheral surface of the pipe has elapsed. Just by opening the pipe, the remaining resin inside the pipe can be quickly sucked and collected in succession with the welding process. The inner surface of the pipe can be efficiently coated with resin one after another, and since the bypass valve is opened to suck outside air when filling the pipe with resin, there is no mechanical stress on the suction and collection equipment. This enables stable operation without causing any problems.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention. Fig. 1 is a simplified front view of a part of the device in cross section, Fig. 2 is a front view of an otsu-shaped tube whose inner surface is coated with resin, and Fig. 3 is a front view of an Otsu-shaped tube whose inner surface is coated with resin. FIG. 4 is a front view of the 180° elbow and is an explanatory view of the case where the inner surface of the T-tube is coated with resin. 1...Powder resin fluidized tank, 2...Porous plate, 4...Conduit, 5...Upper connector, 8...Lower connector , 10... Bypass valve, 12... Suction and recovery device, a...
... Powder resin, b... Deformed tube.

Claims (1)

[Claims] 1. Connect the upper and lower open ends of a preheated metal tube between the upper connector that communicates with the powder resin fluidization tank, and the lower connector that is connected to and communicates with the resin suction and recovery device, with the butterfly valve and bypass valve installed in sequence, and the lower end connected to the resin suction and recovery device. The bypass valve of the lower connector is connected to the outside air, and the butterfly valve is closed while the resin suction and recovery device is constantly operating, and the powdered resin in the powdered resin fluidization tank is flowed into the metal pipe and filled. and after a predetermined period of time has elapsed, a butterfly valve is opened to suck and collect the powdered resin filled in the metal tube using a resin suction and recovery device.