JP5986754B2 - Pipe inner surface coating apparatus and pipe inner surface coating method - Google Patents

Description

  The present invention relates to a pipe inner surface coating apparatus and a pipe inner surface coating method, and more particularly to a coating apparatus and method for beautifully finishing the inner surface of a pipe with a powder resin paint.

Conventionally, cast iron pipes are widely used for water pipes and the like, and the inner and outer surfaces are coated for corrosion prevention.
As a method for coating the inner surface of a cast iron pipe, so-called powder coating, in which a resin layer is formed by spraying a thermosetting epoxy resin powder coating on the inner surface of a preheated pipe, is widely used.

  For example, as shown in FIG. 5, this powder coating is performed by inserting a coating lance 102 having a nozzle 103 at one end into a preheated tube 4 ′ rotating around an axis and moving it in the tube axis direction A. The powder coating 104 is sprayed from the nozzle outlet 105 toward the inner surface of the tube 4 '. The other end of the coating lance 102 is fixed to a lance axial movement means (not shown), and the lance has a cantilever support structure.

In this coating method, the powder coating is sprayed spirally on the inner surface of the tube without gaps by the rotation of the tube and the axial movement of the coating lance, and a resin layer is formed on the entire inner surface of the tube.
For this reason, if the amount and scattering state of the powder coating material discharged from the nozzle are not stable, the powder coating material may not be uniformly distributed on the inner surface of the tube, and a spiral pattern or the like may occur in the finish.

  As a countermeasure, a powder coating device that provides a smooth and beautiful coating finish by attaching a cylindrical nozzle with slit holes and a guide plate to the tip of the lance and spraying the powder coating uniformly on the inner surface of the pipe is disclosed. Has been. (For example, see Patent Document 1)

JP-A-11-319679

However, when the structure of the nozzle at the tip of the coating lance becomes complicated, the nozzle becomes larger and the lance bends due to weight increase. When powder coating is applied to a thin pipe (small diameter pipe), the inserted nozzle or lance May contact or interfere with the inner surface of the tube.
Such contact and interference not only cause damage to the pipes and lances, but also may cause paint failure and poor coating.

  An object of the present invention is to provide a pipe inner surface coating apparatus and method capable of preventing damage to a pipe and a lance even in the inner surface powder coating of a small-diameter pipe and, moreover, finishing the coating beautifully.

In order to solve the above problems, a pipe inner surface coating apparatus of the present invention inserts a paint pipe into a pipe and sprays a powder paint flowing through the paint pipe onto the inner face of the pipe to perform powder coating. In pipe inner surface coating equipment,
Open the tip of the paint pipe that extends in a straight line in the horizontal direction on a plane perpendicular to the axis of the paint pipe, and attach a disc-shaped reflector so that one side of the paint pipe faces the opening. The powder coating is applied to the reflector and sprayed over the entire circumference of the opening from the gap between the reflector and the opening, and the discharged powder coating is scattered in a form spreading in the radial direction of the coating pipe. While forming an exit, it was set as the structure which attached to the paint piping the lens-shaped support roller which supports a paint piping from the bottom.

As a result, since the powder coating is not sprayed in a spiral shape, it is difficult to form a spiral pattern in the finished coating, and the coating on the inner surface of the tube is finished beautifully with a uniform film thickness.
In addition, since the paint pipe is supported from below by a ball-shaped support roller, the paint pipe does not directly contact the inner surface of the pipe.

Next, the pipe inner surface coating method of the present invention is a pipe inner surface coating method in which powder coating is performed on the pipe inner surface using the pipe inner surface coating apparatus.
After the paint piping is inserted deep inside the pipe, the powder coating on the inner surface of the pipe is finished only by painting the return path in which the powder paint is ejected from the paint discharge port while moving the paint pipe in the direction of extracting from the pipe.
Thereby, since the support roller of the target lens shape does not come into contact with the coating surface before curing (uncured) immediately after application, a beautiful coating finish can be obtained without damaging the coating surface.

  The pipe inner surface coating apparatus and the pipe inner surface coating method of the present invention can prevent damage to the pipe and the coating lance even in the case of inner surface powder coating of a small-diameter pipe, and can also finish the coating beautifully.

1 is an overall side view of a pipe inner surface coating apparatus in an embodiment of the present invention. It is an expanded sectional view of the paint piping tip part of a pipe inner surface painting device same as the above. It is an enlarged side view of the principal part of a pipe inner surface coating apparatus. BRIEF DESCRIPTION OF THE DRAWINGS In the explanatory drawing of the coating method in embodiment of this invention, (a) is before a coating start, (b) represents the state in process of coating. It is explanatory drawing of the conventional pipe inner surface coating state.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4.
FIG. 1 is an overall side view of a pipe inner surface coating apparatus according to an embodiment of the present invention.

The pipe inner surface coating apparatus 1 is mainly composed of a paint discharging apparatus 2 and a transport carriage 3.
The paint discharge device 2 includes a paint pipe 21 extending linearly in the horizontal direction (lateral), a paint supply machine 24 that connects one end of the paint pipe 21 and cantileverly supports the paint pipe 21 and sends powder paint to the paint pipe. A hopper 23 that is attached to the upper part and feeds powder coating material into the coating material supply machine 24 from above, and an elevator 22 that supports the coating material supply machine 24 from below so as to be movable up and down.

  The transport carriage 3 rotates wheels 31 for traveling along the axial direction of the paint pipe 21 and a rotating roller 31 that rotates the cast iron pipe 4 placed around the pipe axis and the pipe axis along the axial direction of the paint pipe. I have.

  The paint pipe 21 includes a supply pipe 27 extending straight from the paint supply machine 24, a paint discharge port 25 formed at the tip thereof, and two support rollers 26, 26 attached to the lower side of the outer surface of the supply pipe 27. ing.

FIG. 2 is an enlarged cross-sectional view of the vicinity of the tip of the paint pipe 21.
One end of the socket 28 is inserted and fixed to the outside of the distal end portion of the supply pipe 27. The other end of the socket 28 is opened, and its end surface is orthogonal to the axial direction of the supply pipe.
A core rod 291 is attached inside the socket 28.
The core rod 291 extends coaxially with the supply pipe and the socket from the tip of the supply pipe 27 to the tip of the opening of the socket 28.

  The reflection plate 29 is a disk-shaped baffle plate having an outer diameter larger than that of the socket 28, and has a shaft hole in the center, and a core rod 291 is fitted coaxially into the shaft hole. Further, one surface of the reflecting plate is an inclined (tapered) conical surface, and the reflecting plate has a shape of a top that rotates around the core rod.

The reflector is supported by a core rod 291 and fixed so that its conical surface faces the socket 28. The fixing position is a position where a predetermined gap is formed over the entire circumference of the opening between the inner peripheral edge (opening 281) at the tip of the socket 28 and the conical surface.
This gap becomes the paint discharge port 25, and the scattering position (discharge pattern) and the discharge amount of the discharged paint can be adjusted by changing the fixing position of the reflection plate 29 to increase or decrease the gap.

The flow of the powder paint when the paint is ejected passes through the supply pipe 27, passes between the fixed beams 292, enters the socket 28, and travels toward the tip opening 281. Up to this point, the flow is along the axial direction of the paint pipe.
Near the tip (opening portion 281) of the socket, the flow is regulated by the reflecting plate 29 and spreads in the radial direction of the socket (paint pipe) over the entire circumference of the opening at the socket tip. That is, the flow in the axial direction of the paint pipe 21 is changed to a flow spreading in the radial direction by the reflecting plate 29.

FIG. 3 is an enlarged side view of a main part during painting.
Ball-shaped support rollers 26 and 26 are attached to the outer surface of the supply pipe 27. This support roller is a roller in which a perfect sphere 261 is rotatably held in an arbitrary direction, and is commonly called a ball caster.

  3, the support roller is radially attached to the supply pipe so that the tip of the sphere is farthest from the axis of the supply pipe 27, and the tip of the sphere is inside the cast iron pipe 4. In contact with the surface.

Further, the two support rollers 26 and 26 are attached to the lower side of the outer surface of the supply pipe 27 while being slightly shifted in the circumferential direction. From the position directly below the supply pipe 27, they are attached in the opposite direction by the same angle while being shifted in the circumferential direction of the supply pipe.
Further, the supply pipe 27 is also attached with a slight shift in the pipe axis direction.

Next, a coating method using the pipe inner surface coating apparatus 1 will be described.
FIG. 4 is an explanatory diagram of a coating method in the embodiment of the present invention.
First, the preheated cast iron pipe 4 is placed on the transport carriage 3, and the rotary roller 31 is rotated to rotate the pipe around the axis. As it is, while the paint pipe 21 is inserted into the cast iron pipe 4, the transport carriage is run toward the paint discharge device 2 (direction of arrow B: forward path).
The transport carriage 3 is moved to a position where the sprayed powder paint reaches the far end of the painting required portion on the inner surface of the pipe so that no unpainted portion is left. (See Fig. 4 (a))

After the paint pipe 21 is inserted deep into the cast iron pipe 4, the powder paint starts to be ejected from the tip of the paint pipe 21 (paint discharge port 25).
Simultaneously with the start of the spraying of the powder coating material, the transport carriage 3 is moved (retracted) at a constant speed in the direction opposite to the previous direction, that is, the direction in which the paint pipe 21 is extracted from the cast iron pipe 4 (direction of arrow C: return path) ). (See Fig. 4 (b))
The support cylinder 5 (see FIG. 1) is operated immediately before the support rollers 26 and 26 are protruded from the end of the cast iron pipe 4 due to the retreat of the transport carriage, and the paint pipe 21 cannot be supported from below. Supports the front side of the paint piping from below instead of the support roller.
When the coating of the powder coating is completed over the entire length of the tube, the spraying of the powder coating is stopped. When the coating film thickness can be sufficiently ensured by this one-time return coating, the transport carriage 3 moves back to a predetermined position as it is.

If the coating film thickness cannot be sufficiently secured by only one return path coating, the paint pipe 21 is casted into the cast iron pipe again after the coating is completed until the paint applied to the inner surface of the pipe is cured. Insert into the back and start spraying the powder paint, and move the carriage back at a constant speed to paint the second return pass.
The same painting operation is repeated until the coating film thickness can be secured.

As described above, the pipe inner surface coating method according to the present embodiment is applied when the carriage is moved backward (that is, when the paint pipe is moved in the direction in which the paint pipe is extracted from the pipe) without reciprocating the transport carriage during the spraying of the powder paint. It is a return paint that only finishes.
Therefore, the support rollers 26 and 26 are in contact with only the unpainted portion on the inner surface of the pipe or the painted portion after the paint is cured, and do not contact the uncured portion immediately after the coating (the range indicated by the symbol D in FIG. 4). .

  Moreover, since the support rollers 26 and 26 are formed of spherical rollers that can freely rotate in any direction, the rotational speed of the cast iron pipe and the moving speed of the transport carriage can be arbitrarily set.

Using the tube inner surface coating apparatus and the tube inner surface coating method in this embodiment, inner surface powder coating of a small-diameter tube was performed.
As a pipe to be coated, a ductile cast iron pipe (straight pipe) having a nominal diameter of 50 mm and a length of 4 m was used.
The inner surface of the tube to be coated is polished to a smooth finish, placed in a heating furnace, preheated to 200 ° C or higher, placed on a transport carriage and rotated at a constant speed, and the paint has an outer diameter of about 30 mm. The pipe was inserted to the back of the pipe.
The powder paint sprayed on the pipe inner surface is an epoxy powder resin paint, and the traveling speed and the number of reciprocations of the transport carriage are set so that the thickness of the paint film (resin layer) on the pipe inner face is 300 microns or more only by the return coating. The discharge amount of the powder paint was adjusted.
The inner surface of the tube finished painting under the above conditions was smooth and beautifully finished without spiral patterns, spots or scratches.

  In this embodiment, the cast iron pipe placed on the transport carriage moves along the axial direction of the paint pipe. However, the cast iron pipe does not move in the axial direction, and the paint pipe moves in the axial direction. Can also be adopted.

1 Pipe inner surface coating equipment
2 Paint Discharge Device 21 Paint Pipe 22 Elevator 23 Hopper 24 Paint Supply Machine 25 Paint Discharge Port 26 Support Roller 27 Supply Pipe 28 Socket 281 Opening 29 Reflector 291 Core Rod 292 Fixed Beam 3 Carriage 31 Rotating Roller 4 Cast Iron Pipe (Pipe)
5 Support cylinder

Claims (2)

In the pipe inner surface coating apparatus that inserts the paint pipe into the pipe, sprays the powder paint flowing in the paint pipe onto the inner surface of the rotating pipe, and performs powder coating,
Open the tip of the paint pipe that extends in a straight line in the horizontal direction on a plane perpendicular to the axis of the paint pipe, and attach a disc-shaped reflector so that one side of the paint pipe faces the opening. The powder coating is applied to the reflector and sprayed over the entire circumference of the opening from the gap between the reflector and the opening, and the discharged powder coating is scattered in a form spreading in the radial direction of the coating pipe. Two ball-shaped support rollers that form the outlet and support the paint pipe from below are attached to the paint pipe. The paint pipe is supported only from below in the pipe , and the two support rollers are connected to the circumference of the paint pipe. inner surface coating device according to claim isosamples also shifted in the axial direction of the tube with shifted in a direction attached under side of the outer surface of the paint pipe. In the pipe inner surface coating method of performing powder coating on the pipe inner surface using the pipe inner surface coating apparatus according to claim 1,
After the paint pipe is inserted into the inside of the pipe, the powder coating on the inner surface of the pipe is finished only by the return path spraying out the powder paint from the paint discharge port while moving the paint pipe in the direction to extract from the pipe. Pipe inner surface painting method.