JPH0131942B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for applying a powder coating to the inner surface of a tube, more specifically a method for applying a powder coating such as epoxy, epoxy polyester, or polyethylene resin to the inner surface of a heated tube by fusing it. This is related to the device.

Conventionally, the following methods are known as methods for forming a resin coating on the inner surface of a tube.

(1) A method in which powder paint is filled into a heated pipe and fused to the inner surface, and then the excess powder paint is removed.

(2) A method in which powder paint is blown together with air into a heated pipe to fuse it to the inner surface.

(3) A method in which the powder paint is passed through a heated tube over a powder tank in which the powder paint is suspended, and the powder paint is sucked together with air into the tube and fused to the inner surface.

(4) A method in which an electrode with a DC voltage applied to the powder paint outlet is inserted into a heated pipe, and the powder paint is blown in with air, and the powder paint is applied to the inner surface of the pipe by the attraction of static electricity.

However, in method (1), the powder coating is filled into the tube, and in methods (2) to (4), the powder coating is blown or sucked into the tube, so in both cases, it is difficult to form a film. This method requires a larger amount of powder than it contributes to, necessitating the installation of a large-scale collection and reuse system, and has the disadvantage that the recovered powder coating not only deteriorates in quality but also changes its powder size distribution. In addition, in methods (2) to (4), since they are mixed with air and supplied into the pipe, the air acts as a cooling agent and not only makes the temperature of the pipe uneven, but also causes uneven temperature on the surface to be painted. Since the floating speed of the powder changes, the disadvantage is that the powder does not adhere uniformly over the entire inner surface of the tube.

This invention eliminates the drawbacks of the conventional method as described above, eliminates the need to supply excess powder paint that does not contribute to film formation, eliminates the need to install a collection and reuse system, and does not depend on air flow. It is an object of the present invention to provide a method for applying a powder coating material and an apparatus therefor, which can form a coating film having a uniform thickness by supplying the powder coating material to the powder coating material.

That is, in the method of this invention, a heating tube is placed horizontally, and a cylindrical rotating dispersion device whose tip is closed and a plurality of discharge ports are formed on the peripheral wall is inserted into the heating tube and rotated. Powder paint is supplied to the rotating dispersion tool while moving the tool and the heating tube relatively in the axial direction of the tube, and the powder paint is discharged from the discharge port by centrifugal force, melting onto the inner surface of the heating tube. It is characterized by being worn.

The first apparatus of the present invention for carrying out the above method includes a tank in which a powder coating material is stored, a base end connected to this tank, and a cylindrical rotary dispersion device rotatably disposed at a distal end. a horizontally oriented transport pipe, a transport member disposed within the transport pipe to send the powder coating material from the tank to the rotary dispersion tool, a drive member for rotating the rotary disperser, and a heating tube placed horizontally. and a traveling carriage arranged to approach or move away from the rotary dispersing device, the rotary dispersing device having a closed end and a plurality of discharge ports on a peripheral wall. It is characterized by being formed.

The second feature of the device of the present invention is a tank in which the powder paint is stored, a horizontal transport pipe whose base end is connected to the tank, and an opening at the distal end of the transport pipe disposed within the transport pipe to transport the powder paint. a support pipe that accommodates and supports the transport pipe in the axial direction; an air supply pipe that supplies air into the support pipe; The air motor has a rotatably housed turbine, and a cylindrical rotation dispersion device is attached to the end of the turbine that protrudes outside the support tube, and the heating tube is placed horizontally. a traveling cart disposed close to or away from the rotary dispersing device, the distal end opening of the transport pipe opens into the rotary dispersing device, and the distal end of the rotary dispersing device is closed. It is characterized by having a large number of discharge ports formed in the peripheral wall.

Embodiments will be described below with reference to embodiments shown in the drawings.

As shown in FIGS. 1 to 6, a plurality of turning rollers 2 are arranged at front and rear positions on a traveling truck 1, and these turning rollers 2 are rotated by a drive motor 3, and a plurality of turning rollers 2 are arranged on the traveling truck 1 at front and rear positions. A tube 4 arranged laterally is adapted to rotate. 5 is a hydraulic cylinder for raising and lowering the pipe 4 via a support rod 6, 7 is a powder collector, and 8 is an exhaust duct.

A stirring screw 11 that is connected to a variable speed motor 10 and rotates is disposed at the inner bottom of the tank 9 that accommodates the powder coating material. One end of a powder transport pipe 12 opens in the tank 9, and the transport pipe 12 is disposed within a support pipe 13 whose base end is fixed to a pedestal 9' and supported by a number of retaining rings 14. A spring conveyor 15 is accommodated within the transport pipe 12, and like the stirring screw 11, this spring conveyor 15 is connected to a variable speed motor 10 for rotation.

An air motor 16 is attached to the other end of the support tube 13. The air motor 16 includes a housing 19 having a head cap 17 and an end cap 18 at the front and rear ends, respectively.
A turbine 20 is housed in the head cap 9 with its front end protruding from the head cap 17.
is rotatably supported by the housing 19 via a bearing 21. Both ends of the support tube 3 are closed ends 22, 22', and an intake hole 2 is formed in alignment with the closed end on the distal end side and the end cap 18.
3, the inside of the support tube 13 and the inside of the housing 19 communicate with each other. The housing 19 is provided with an exhaust hole 24 , and the exhaust hole 24 is connected to an exhaust pipe 25 provided on the outer periphery of the support tube 13 . Support tube 13
Inside, there is an air supply pipe 2 provided with a regulator 27.
6 opens through the proximal closed end 22', and the air supplied into the support tube 13 through the air supply tube 26 is fed into the support tube 13 through the passage hole 28 provided in the retaining ring 14. The air enters the housing 19 through the intake hole 23 and is discharged from the exhaust pipe 25 through the exhaust hole 24, thereby causing the turbine 20 to rotate.

A rotary distributor 29 is attached to the projecting end 34 of the turbine 20 from the headcap 17. The rotary dispersion device 29 is formed by fixing a plurality of rectangular plates between the front and rear end plates 30 and 31 so as to have an overall cylindrical shape and a screen-like shape, and the rear end plate 31
A protruding end 34 of the turbine 20 from the head cap 17 is fitted into a hole 33 provided in the head cap 17 and fixed therein. The gap between the rectangular plates 32 serves as a discharge port for powder coating material.

The transport pipe 12 disposed within the support pipe 13 passes through the closed end of the support pipe 13, is loosely fitted into the center hole 35 of the turbine 20, and has an end opening into the rotary dispersion device 29. .

Next, a powder coating operation using the above-mentioned apparatus will be explained.

While supplying the powder paint to the tank 9, air is sent into the support pipe 13 from the supply pipe 26 to rotate the turbine 20 of the air motor 16, thereby rotating the rotating dispersion tool 29 at a rotation speed of 800 to 10,000 R.PM. . Thereafter, the screw 11 is rotated by a variable speed motor whose rotational speed is set in advance to stir the powder paint, and at the same time, the spring conveyor 15 is rotated, thereby transferring the powder paint in the tank 9 to the transport pipe 1. It is fed into the rotary dispersion tool 29 through the. A centrifugal force acts on the powder coating material within the rotary dispersing device 29, whereby the powder coating material is discharged from the gap between the rectangular plates 32 and spread.

On the other hand, a preheated tube 4 to be coated is placed on a turning roller 2 of a traveling truck 1, and the tube 4 is rotated by a drive motor 3. In this state, trolley 1
is caused to travel toward the rotary dispersing tool 29, and at the same time as the powder coating material is diffused from the rotary dispersing tool 29, the rotary dispersing tool 29 is inserted into the tube 4. As a result, the diffused powder paint is thermally fused and applied to the inner surface of the tube 4, and is applied to the entire inner surface of the tube 4 as the truck 1 travels.

In the above-mentioned application operation, the powder coating material is not supplied into the tube 4 by filling or by an air stream, as is conventional, but by a rotating dispersing device 29.
Since the centrifugal force generated by the rotation of This eliminates the need to set up a large-scale collection and reuse system.

By making the rotary dispersing device 29 cylindrical and in the shape of a griddle and rotating it at high speed, it is possible to disperse the dispersion onto the inner surface of the tube 4 in a wide pattern. By adjusting the circumferential speed of , the number of times of recoating can be changed. The relational expression is: C=PG/L where C: moving speed of the tube G: circumferential speed of the tube L: circumferential length of the tube P: pattern (powder dispersion) For example, the moving speed of the tube Assuming that C is constant, the larger the pattern P is, the greater the number of times of overcoating (L/G).

In addition, the transport pipe 12 is placed inside the support pipe 13, that is, both pipes constitute a double pipe, and the inside of the support pipe 13 is used as a flow path for the air that rotates the turbine 20, so that this air can be used during painting. The temperature of the powder paint in the transport pipe 12 located in the heated pipe 4 can be prevented from rising, and the powder paint will not exhibit melting or softening phenomena. If this air is cooled, the effect can be further increased.

Normally, coating is done while the trolley 1 is moving back and forth.
In the case of a thin film finish, it may be applied only on one side.

To give an example, 150mm preheated to 220-240℃
When painting a φ pipe back and forth, the diameter is 80 mm, and the length is
Using a rotating dispersion tool with a discharge gap of 120 mm and a discharge gap of 3 mm,
Traveling trolley speed 2.5m/mm Pipe rotation speed 160R.PM Rotating dispersion tool rotation speed 7000R.PM Powder paint discharge amount
At 600g/mm, a coating film with a thickness of 500μ could be obtained. Although the tube does not necessarily need to be rotated, a coating film with a uniform thickness can be formed by applying the powder coating while rotating the tube.

The rotary dispersing tool 29 shown in FIGS. 5 and 6 has a cylindrical shape. In the case of this rotary dispersing tool 29, if the inner diameter of the pipe 4 to be coated is large, the distance from the inner surface of the pipe is large, and the coating area is also large. Since it is large, a large amount of powder coating material can be supplied, and the powder coating material can be discharged over the entire length direction of the rotary dispersion tool 29, so that a large pattern can be obtained. However, if the inner diameter of the pipe to be painted is small, the distance between the inner surface of the pipe and the inner surface of the pipe will be small, contrary to the above.
In addition, since the coating area is small, the amount of powder paint supplied is small and the powder paint is discharged only from near the entrance of the rotary dispersion tool 29, making it impossible to form a large pattern.

A rotary dispersion device 36 shown as another embodiment in FIG.
This is used for painting tubes with a particularly small inner diameter, and is formed into a truncated conical tube that slopes to widen toward the tip. That is, the diameter of the end plate 31 at the rear end is made smaller than that of the end plate 30 at the front end, and two intermediate rings 37, 37 are arranged between both end plates 30, 31, and the distance between the end plates 30, 31 is 3.
It is divided into three zones A, B, and C. And A, B,
The gaps between the rectangular plates 32 in the C zone are coarse, medium, and fine, respectively. According to such a rotary dispersing tool 36, even if the powder paint supplied inside is small, it is widely and uniformly dispersed throughout, and is evenly discharged over the entire length direction of the rotary dispersing tool 36.
The pattern becomes larger and a uniform coating can be formed.
As a result of the experiment, it was found that the angle of inclination α is preferably in the range of 5 to 15 degrees.

As shown in FIG. 8, the outer periphery of the rotary dispersion tool 29 (or 36) may be formed of a circular rod 38 instead of the rectangular plate 32. In this case, the circular rods 38 are not limited to being arranged in a single layer as shown in Fig. 8a, but also as shown in Fig. 8b.
You can also place it twice like this.

FIG. 9 shows another embodiment of the air pipe 26, in which the air pipe 26 is branched into first and second air pipes 26a and 26b. The first and second air supply pipes 26a and 26b extend inside the support pipe 13 by passing through the closed end 22' on the proximal side of the support pipe 13, and the first air supply pipe 26a is connected to the intake port 22'.
3, and the turbine 20 is rotated by air supplied through this pipe 26a. The second air supply pipe 26b opens at the closed end on the distal end side of the support pipe 13, and the air supplied through this pipe 26b is discharged to the outside through a through hole 39 provided at the closed end 22'. This prevents the powder paint inside from rising in temperature.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made to the present invention.

This invention is as described above, and a cylindrical rotary dispersing device is inserted into the heating tube and rotated, and the powder paint supplied to the rotary dispersing device is discharged by centrifugal force and fused to the inner surface of the tube. , there is no need to supply powder coating other than those that contribute to film formation, therefore there is no need to install a collection and reuse system, and the supply of powder coating to the inner surface of the tube does not depend on air flow. The tube is no longer cooled by air, and a coating film with a similar thickness can be formed.

By housing and supporting the powder paint transport pipe in the support pipe and supplying air through the air supply pipe into the support pipe, the powder paint in the transport pipe located in the heating pipe is removed from the support pipe during painting. Air prevents temperature rise and prevents the powder coating from melting and softening.

[Brief explanation of drawings]

1 is a schematic front view showing the entire apparatus of the present invention, FIG. 2 is a cross-sectional view taken along the line in FIG. 1, and FIG. 3 is a sectional view taken along the line in FIG. 1. 4 is a vertical sectional view showing an enlarged main part, FIG. 5 is a front view showing an example of a rotary dispersion tool, and FIG. 6 is a cross section taken along the line - in FIG. 5. 7 is a front view showing another example of the rotary dispersing device, and FIG. 8 is a sectional view showing another example of the rotary dispersing device.
FIG. 9 is a drawing similar to FIG. 4 showing another example of the air pipe. 1... Traveling truck, 4... Heating tube, 9... Tank, 12... Transport pipe, 13... Support pipe, 15...
Spring conveyor (transportation member), 16... Air motor, 20... Turbine, 29, 36... Rotating dispersion device.

Claims (1)

[Scope of Claims] 1. A heating tube is placed horizontally, and a cylindrical rotary dispersion device with a closed tip and a plurality of discharge ports formed on the peripheral wall is inserted into the heating tube and rotated,
Powder paint is supplied to the rotary disperser while relatively moving the rotary disperser and the heating tube in the axial direction of the tube, and the powder paint is discharged from the discharge port by centrifugal force, and the powder paint is discharged from the discharge port by centrifugal force. A method for applying powder coating to the inner surface of a tube, which is characterized by fusion to the inner surface. 2. A tank in which the powder coating is stored, a horizontal transport pipe whose base end is connected to this tank and a cylindrical rotary dispersion device is rotatably disposed at the tip, and a powder coating disposed within the transport pipe. a transport member for transporting body paint from the tank into the rotary dispersing device; a driving member for rotating the rotary dispersing device; and a heating tube configured to be placed horizontally and close to the rotary dispersing device. A powder coating application device comprising: a rotating dispersion tool, and a traveling cart arranged so as to be spaced apart from each other; the rotary dispersion tool has a closed end and a plurality of discharge ports formed in a peripheral wall. . 3. A tank in which powder paint is stored, a horizontal transport pipe whose base end is connected to this tank, and a transport member disposed within this transport pipe to send the powder paint toward the distal opening of the transport pipe. , a support pipe that accommodates and supports the transport pipe along the axial direction; an air supply pipe that supplies air into the support pipe; and a turbine that is rotatably housed outside the transport pipe within the support pipe. The air motor has a cylindrical rotary dispersion device attached to the end protruding outside the support tube of the turbine, and the heating tube is placed sideways and is close to the rotary dispersion device. , or a traveling carriage arranged to be spaced apart, the distal end opening of the transport pipe opens into the rotary dispersing device, the distal end of the rotary dispersing device is closed, and a plurality of discharge ports are provided in the peripheral wall. A powder coating application device characterized in that: