JP2950352B2 - Powder coating method for pipe inner surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating powder on the inner surface of a pipe, which sprays powder coating on the inner surface of a high-temperature pipe.

[0002]

2. Description of the Related Art In recent years, resin linings such as epoxy resins have been widely used instead of mortar linings as inner linings of water supply pipes and the like. The resin lining usually forms a coating film by applying a liquid paint obtained by mixing a resin, a pigment, an additive, and the like with a solvent or water, and then evaporating and evaporating the solvent to cause a curing reaction of the resin component. However, because of low productivity when applied to the lining of the pipe inner surface,
A powder coating method has been adopted in which a powder coating in which components such as an epoxy resin, a curing agent, a pigment, and an additive are powdered is sprayed on the inner surface of a pipe in a high-temperature state, and the coating film is cured by thermal energy of the pipe. .

As this powder coating method, a pneumatic spraying method using a paint discharging device as shown in FIG. 6 is known. In FIG. 6, reference numeral 51 denotes a lower tank as a paint tank, and reference numeral 52 denotes an upper tank for replenishing the lower tank 51 with paint. In the upper tank 52, upper and lower level detection sensors 53 and 54 composed of electrostatic sensors and the like are provided, which directly detect the level of the powder paint, and when supplying the lower tank 51 with paint, a vibrator 55 is provided. The ball valve 57, the bellows pipe 58, and the pinch valve 59 are supplied while the coating air is supplied to the upper flow tank 56 to flow the coating.
It is made to fall and supply naturally through the.

A lower fluidizing tank 6 is provided below the lower tank 51.
0 and an injection nozzle 61, and the lower tank 5 is supplied with flowing air introduced into the lower flowing tank 60 at the time of discharge.
Increase the air pressure inside 1 and fluidize the paint,
In this state, the paint is introduced into the control pipe by the discharge air flow by ejecting the discharge air from the injection nozzle 61 toward the lower end opening end of the control pipe disposed in the lower tank 51, as shown in FIG. To
The powder discharged from the upper end of the control pipe 62 is received by the collector 63, the powder is discharged from the discharge port 64 provided at the upper end of the lower tank 51, and the powder at the tip of the lance is discharged through the powder hose 65 connected to the discharge port 64. The powder is sprayed from the nozzle 66. 67 is the lower tank 51
It is a vibrator that prevents blocking of powder inside. Reference numeral 68 denotes a pinch valve for dissolving the pressure in the lower tank 51 at the time of refilling the paint, and is connected by a collecting hose 69 to a collecting device for collecting the paint discharged together with the discharged air. Reference numeral 70 denotes a flip-up prevention plate provided at the upper end of the control pipe 62, which prevents paint from flowing into the collector 63 from other than the control pipe 62. 7
Reference numeral 1 denotes a paint amount detection sensor in the lower tank 51, which is configured to supply paint to a position above the lower end of the flip-up prevention plate 70.

[0005] During discharge of the coating material, the lower fluid chamber 60 and the injection nozzle 61, for example, to supply a constant pressure the discharge air of 4 kg / cm ^2, discharge at the time of stop has stopped the supply of the discharge air. Further, as shown in FIG. 7, the discharge amount of the paint is determined by attaching a shade-shaped collector 63 to the tip of a curved tube 72 and rotating the curved tube 72 with a handle 73 to collect the paint.
The amount of powder introduced into the collector 63 is changed by adjusting the relative position between the control pipe 3 and the upper end of the control pipe 62.

[0006]

However, in the above-described paint discharge device, there is a problem that when the discharge is stopped, paint is clogged in the control pipe or the injection nozzle, and it is not possible to stably obtain an appropriate discharge amount. there were.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, the present invention does not cause clogging of the paint in the control pipe or the injection nozzle when the discharge is stopped, and can stably obtain a proper discharge amount of the paint. An object of the present invention is to provide a powder coating method.

[0008]

According to the powder coating method for the inner surface of a pipe according to the present invention, a flowing air is introduced into a lower portion of a paint tank to raise the air pressure in the paint tank and to make the paint fluidized. Injection air is injected from the injection nozzle toward the opening end of the control pipe in the lower part of the paint tank, and the paint introduced into the control pipe by the discharge air flow is discharged from the discharge nozzle connected to this control pipe outside the paint tank. In a powder coating method for a pipe inner surface which is applied by spraying onto a pipe inner surface having a high temperature, a flow air and a discharge air at a lower pressure than at the time of discharge are supplied into the paint tank when the paint is not discharged.

[0009]

According to the present invention, by supplying low-pressure flowing air and discharge air even when the paint is not discharged, the paint does not remain in the control pipe and the injection nozzle when the discharge is not performed, and the clogging of the paint is generated. Can be prevented, and a proper amount of paint can be constantly and stably secured.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In FIG. 1 showing the entire system configuration, reference numeral 1 denotes a pipe to be powder-coated on the inner surface. In the illustrated example, four pipes are coated in parallel, and each pipe is sequentially moved so that each pipe is moved. It is configured to perform four-pass painting every time. Reference numeral 2 denotes a lance inserted into each tube 1, and a discharge nozzle 3 is attached to a tip of the lance. Reference numeral 4 denotes a paint discharge device for feeding powder paint to each of the lances 2, and paint is supplied from a paint supply unit 5 by pneumatic transport means (not shown). Reference numeral 6 denotes a masking hood which is inserted into the receiving portion of the tube 1 to prevent paint from adhering to an unnecessary portion and sucks the scattered paint. The collection hoods are respectively arranged, and these hoods 6, 7, 8 are connected to a collection device 10 via a collection duct 9. Also, the collection hose 14 of the paint discharge device 4
Is also connected to the collection duct 9. The recovery device 10 is configured to separate the paint from the suction air by the cyclone 11, select the paint by the selection device 12, send the paint to the paint discharge device 4, and reuse the paint. The paint dust not separated by the cyclone 11 is collected by the bag filter 13, and is appropriately discarded together with the paint removed by the selective device 12.

In FIG. 2 showing the main body of the powder coating apparatus, a tube 1 is a movable carriage 1 movable in the longitudinal direction of a lance 2.
5 is supported in a horizontal direction on two pairs of rotating rollers 16 and 17 rotatably driven. The lance 2 is arranged so that the height can be adjusted according to the pipe diameter. A collection hood 8 on the insertion side of the pipe 1 is provided at an end of the lance 2 on the movable carriage 15. Reference numeral 18 denotes a pipe end regulating roller that regulates the position of the receiving end of the pipe 1, and is disposed together with the collecting hood 7 on the receiving side on an adjustment carriage 19 whose position can be adjusted according to the length of the pipe. Further, a reciprocating carriage 20 that can reciprocate so as to face the pipe receiving port is provided on the adjusting bogie 19, and a plurality of types of masking hoods 6 corresponding to the pipe diameters are provided.

In FIG. 3 showing the details of the masking hood portion, a plurality (five in the illustrated example) of masking hoods 6 corresponding to the pipe diameters are radially mounted on the revolving body 21, and the revolving body 21 is attached to the collection duct 9. It is rotatably fitted to the suction cylinder 22 connected thereto. The tube 1 is attached to the suction cylinder 22.
The suction port 23 is opened at a position facing the receiving port.
A water cooling jacket 24 is formed on the outer periphery of each masking hood 6 so that the masking hood 6 is heated by radiant heat from inside the tube 1 so that thermosetting paint does not adhere and grow. The outer diameter of the masking hood 6 is
Since the coating film is damaged when it comes into contact with the inner periphery of the receiving port of the pipe 1, a servomotor is provided on the carriage 20 so as to have a slightly smaller diameter and to be located on the same axis. The suction cylinder 2 is moved by the lifting / lowering and turning means (not shown).
The upper and lower positions and the turning angle of the two can be adjusted. The wind speed in the pipe 1 when the masking hood 6 is inserted is set to 4 to 7 m / s from the viewpoint of coating efficiency, smoothness, film quality and the like.

Next, the details of the paint discharging device 4 will be described with reference to FIG. Reference numeral 25 denotes a lower tank serving as a paint tank, and reference numeral 26 denotes an upper tank that supplies paint to the lower tank 25. In the upper tank 26, upper and lower level detection sensors 27, such as electrostatic sensors,
The paint supply unit 5 is provided so as to automatically detect the paint level and automatically supply the paint from the paint supply unit 5 so that the paint level falls within these level ranges. This upper tank 2
When the powder paint is supplied from 6 to the lower tank 25, the blocking of the paint is prevented by the vibrator 29, and the ball valve 31 and the pinch valve 32 are opened in a state where the flowing air is supplied to the upper fluidizing tank 30 to make the fluid flow. Thereby, it supplies by natural fall. Ball valve 31
A straight metal short pipe 3
3 to eliminate clogging due to paint adhesion as in the case of using a bellows tube.

In the lower part of the lower tank 25, a lower fluidizing tank 3 is provided.
4 and an injection nozzle 35 are provided, and are respectively connected to a high-pressure air source 38 via electropneumatic proportional valves 36 and 37 which can arbitrarily set a supply air pressure by an electric signal. Reference numeral 39 denotes a vibrator for preventing the powder from blocking in the lower tank 25. Reference numeral 40 denotes a pinch valve for releasing the pressure in the lower tank 25 when replenishing the paint, and a recovery device 10 for recovering the paint discharged together with the discharged air.
Is connected via a collection hose 14. Reference numeral 41 denotes a paint level detection sensor in the lower tank 25.

In FIG. 5, a perforated plate 42 extending from the wall of the lower tank 25 is provided in a lower flow tank 34 at the lower end of the lower tank 25 so as to supply flowing air to the periphery thereof. Have been. An injection nozzle 35 is disposed upward at the center of the lower fluidized tank 34,
At the center of the lower tank 25, a control pipe 43 whose lower end opening faces above the injection nozzle 35 and whose upper end extends to the upper part of the lower tank is provided. At the center of the upper wall of the lower tank 25, a downward funnel-shaped collector 44 is disposed opposite to the upper end opening of the control pipe 43, and is connected to the lance 2 via a discharge port 45 protruding upward from the lower tank 25. Are in communication. A flip-up prevention plate 46 is attached to the upper end of the control pipe 43 to prevent paint from flowing into the collector 44 from other than the control pipe 43. Note that the paint level detection sensor 41 is arranged so that the paint supply height in the lower tank 25 is lower than the lower end of the flip-up preventing plate 46, whereby the discharge amount at the time of the first paint discharge is extremely large. It is preventing from becoming. A bridge breaker 47 is radially welded to the outer periphery of the lower part of the control pipe 43 to further prevent the inner diameter of the control pipe 43 from being narrowed due to the thermal distortion due to the welding, thereby facilitating clogging of the paint. The inner periphery of the lower end of the control pipe 43 is machined.

In the above configuration, in order to perform powder coating on the inner surface of the tube 1, the inner surface of the tube 1 is subjected to a base treatment such as borrowing, cornering and air blowing, and then the tube 1 is inserted into a heating furnace. I do. Then, the temperature of the tube 1 is set to 230 ° C. ± 10 ° C.
The temperature-adjusted product is carried on the rotating rollers 16 and 17 on the movable carriage 15 and driven to rotate. The paint is discharged from the paint discharging device 4 while moving the movable carriage 15 to the lance 2 side. By spraying paint from the discharge nozzle 3 toward the inner surface of the tube 1, powder coating is performed on the inner surface of the tube 1.

In the paint discharging device 4, when the paint is discharged to the inner surface of the tube 1, the lower fluidizing tank 34 is charged simultaneously with the start of rotation of the tube 1 in order to absorb a time lag until the paint is discharged from the discharge nozzle 3. Flowing air of about 4 kg / cm ² is introduced by the proportional valve 36, thereby increasing the air pressure in the lower tank 25 and fluidizing the paint. In this state, the discharge air is injected from the injection nozzle 35 into the control pipe 43. Discharge. As a result, the paint is sucked into the control pipe 43 by the discharge air, blows up from the upper end thereof toward the collector 44, and is discharged from the discharge pipe 45.
From the discharge nozzle 3 through the lance 2 to the inner surface of the tube 1.

Discharge air adjusted to about 1 to 4 kg / cm ² in accordance with the diameter of the pipe 1 by the electropneumatic proportional valve 37 is supplied to the injection nozzle 35, thereby corresponding to the diameter of the pipe 1. The paint discharge amount can be obtained. Thus, the electropneumatic proportional valve 37
By adjusting the pressure of the discharge air to the injection nozzle 35 to adjust the discharge amount of the paint, the paint discharge amount can be controlled with high accuracy over a wide adjustment range. Powder coating can be performed on the inner surface of the tube having a constant film thickness. For example, in the case of adjusting the discharge amount by manually adjusting the position of the conventional collector shown in FIG. 7, the adjustment can be made only up to about 1800 g / min, but in the present embodiment, the range is from 3000 g / min to 500 g / min. As a result, a stable discharge amount control can be performed automatically and with high accuracy.

When the coating on the pipe 1 is completed, the flowing air is supplied to the electropneumatic proportional valves 36 and 37 at 1 kg / cm ² , and the discharging air is supplied at 0.1 kg / cm ² .
Automatically adjusted to 5 kg / cm ² . As described above, since the pressure of the flowing air and the discharge air is reduced but not completely stopped, the paint does not remain in the control pipe 43 and the paint may be blocked in the control pipe 43. Can be eliminated.

The upper tank 26 and the lower tank 25
The supply of the paint to the tank is performed as follows. That is, the pinch valve 40 opens at the same time as the discharge stop signal, the pressure in the lower tank 25 is released, and the supply tank is ready to receive supply.
In this state, when the paint level detection sensor 41 detects paint shortage, it supplies flowing air to the upper fluidizing tank 30 and the lower fluidizing tank 34, and then opens the lower pinch valve 32 and then opens the ball valve 31, Vibrators 29, 39
Is operated to supply paint. When the replenishment is completed, the vibrators 29 and 39 are stopped, the upper ball valve 31 is closed first, then the pinch valve 32 is closed, and the supply of the flow air to the upper flow tank 30 and the lower flow tank 34 is stopped. . Thus, the ball valve 31
And the pinch valve 32 are not opened and closed at the same time, and the upper ball valve 3 is opened with the lower pinch valve 32 opened.
By opening and closing 1 and operating the vibrators 29 and 39 only during replenishment, defective replenishment due to shelf fishing can be eliminated. Further, the use of the short metal tube 33 at the connection between the two valves 31 and 32 prevents the paint from adhering and growing and causing clogging as in the case of connecting with a bellows tube made of vinyl chloride.

[0021]

As described above, according to the present invention, even when the paint is not discharged, by supplying the low-pressure flowing air and the discharge air, the paint does not remain in the control pipe and the injection nozzle and becomes clogged. Can be prevented, and a proper amount of paint can always be stably secured.

[Brief description of the drawings]

FIG. 1 is a plan view showing the overall system configuration of a pipe inner surface coating apparatus according to an embodiment of the present invention.

FIG. 2 is a front view of a main body of the pipe inner surface coating apparatus of the embodiment.

FIG. 3 is a longitudinal sectional view of a masking hood portion in the same device.

FIG. 4 is a partial cross-sectional front view of a paint discharging device in the device.

FIG. 5 is a partially enlarged sectional view of a main part of a lower tank in the same device.

FIG. 6 is a front view of a conventional paint discharge device.

FIG. 7 is an enlarged sectional view of an upper end portion of a conventional lower tank.

[Explanation of symbols]

 25 Lower tank (paint tank) 34 Lower fluid tank 35 Injection nozzle 36 Electro-pneumatic proportional valve 37 Electro-pneumatic proportional valve 43 Control pipe

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Showa 60-63463 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B05D 1/00-7/26 B05B 7 / twenty four

Claims (1)

(57) [Claims] 1. A method for injecting flowing air into a lower portion of a paint tank to increase an air pressure in the paint tank and fluidize the paint, and then injecting the paint toward an opening end of a control pipe in a lower portion of the paint tank. A powder coating method for the inner surface of a pipe, in which the discharge air is blown out from the nozzle, and the paint introduced into the control pipe by the discharge air flow is sprayed from the discharge nozzle connected to this control pipe to the inner surface of the high-temperature pipe outside the paint tank. A method for coating powder on the inner surface of a pipe, characterized in that a flow air and a discharge air at a lower pressure than during discharge are supplied into the paint tank when the paint is not discharged.