JPH07222953A - Coating of ceramic pipe - Google Patents

Abstract

PURPOSE:To reduce the loss of a coating material and coating irregularity and to achieve labor conservation by automation in spray coating work applying the coating material prepared by mixing a ceramic fine powder and a thermosetting adhesive to a ceramic pipe. CONSTITUTION:Both end parts of ceramic pipes 12, ... are placed on two belts 13 moving in parallel to rotate the ceramic pipes at a predetermined position. A coating material prepared by mixing a ceramic fine powder and a thermosetting adhesive is ejected and applied to the ceramic pipes 12, ... along the longitudinal direction thereof by high pressure air with blowoff pressure of 1-7kg/cm<2> by using a spray gun 4 reciprocally moving along the longitudinal direction of the ceramic pipes 12, ... at equal speed so as to be held to predetermined height and spraying the coating material so that the shape of the spray range thereof becomes oval and the spray range in the short diameter direction thereof is equal to or less than the outer diameter of the ceramic pipes 12, ....

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 a ceramic pipe for a heater by spraying a paint containing a mixture of fine ceramic powder and a thermosetting adhesive on the surface of the heater ceramic pipe.

[0002]

2. Description of the Related Art Generally, since a ceramic pipe containing silicon carbide as a main component has good heat generation efficiency, it is used as a heater by attaching electrodes to both ends thereof. If this ceramic pipe is used as a heater as it is manufactured, the surface will be oxidized at high temperature and its life will be short, so in order to prolong the life, it is necessary to use a thermosetting adhesive with a ceramic powder that is less susceptible to oxidation than silicon carbide. The paint mixed with the agent is applied to the ceramic pipe. As for the coating method, both ends of the ceramic pipe are placed on two conveyor belts that are fed in parallel, and while the ceramic pipe is being rotated, a wicking type that contains a paint in which ceramic fine powder and a thermosetting adhesive are mixed A hand-held spray gun with a container was used by a worker to see the painted surface and move while painting.

Usually, when coating a metal tubular body,
A method is adopted in which a shaft is inserted into both ends of the tubular body, and by rotating the shaft, a coating is performed with a spray gun that automatically moves while rotating the tubular body. Since it cannot be applied to a ceramic pipe having low strength, the above-mentioned industrial method has been adopted.

[0004]

However, in the method in which an operator paints with a hand-held spray gun, since the shape of the spray range of the hand-held spray gun is a circle whose diameter exceeds the outer diameter of the ceramic pipe, the ceramic pipe is painted. In this case, there is a portion where the paint is not applied to the ceramic pipe, and more than half of the sprayed paint is wasted. Especially, when the paint is expensive, this waste causes high cost and is a problem. ing.

Further, since the coating is performed while the ceramic pipe is being rotated, it is necessary to accurately judge the coating state during the rotation. For this purpose, skill is required, and when a beginner works, the coating is performed. Inconsistency often occurs, and it has been a problem that the number of workers is limited. Further, since the hand-held spray gun is used, the worker is required to work hard during the work, and labor saving cannot be achieved.

According to the present invention, it is possible to reduce coating loss, reduce coating unevenness, and save labor by automation in the work of spray-coating a coating mixture of ceramic fine powder and a thermosetting adhesive on a ceramic pipe. It is intended to provide a painting method.

[0007]

The method for coating a ceramic pipe according to the present invention achieves the above-mentioned object. The ceramic pipe is placed on two belts for transferring both ends of the ceramic pipe in parallel, and the ceramic pipe is placed at a predetermined position. It is rotated and reciprocates at a constant speed along the longitudinal direction of the ceramic pipe at a constant speed, and the shape of the spray range is elliptical, and the spray range in the minor axis direction is less than the outer diameter of the ceramic pipe. Spray paint with a mixture of fine ceramic powder and thermosetting adhesive along the longitudinal direction of the ceramic pipe and blow out pressure 1 to 7 kg / cm ²
The high pressure air is used for spray coating.

As the ceramic fine powder used in the present invention, a ceramic powder having excellent oxidation resistance such as glass powder is desirable, and its particle size is preferably 5 to 50 μm, and most preferably 10 to 20 μm. As a result, uniform coating can be performed without creating a gap, and uniform heat generation without temperature unevenness can be obtained. As the thermosetting adhesive used in the present invention, various thermosetting adhesives having excellent heat resistance can be used, but the cellulose thermosetting adhesive is most suitable in terms of heat resistance, compatibility, etc. .

The spray gun used in the present invention is preferably a gas-liquid external mixing type spray gun having a paint injection hole in the center and high-pressure air injection holes on both sides thereof. The high-pressure air injection hole is such that the injection direction is inclined in the central direction by about 25 to 75 °, whereby the shape of the spray range can be changed into various elliptical shapes having different major and minor axes. In addition to the air injection holes described above, air injection holes for promoting the injection of the paint may be provided near the paint injection hole. Various methods are adopted as a method for supplying the paint to the spray gun, but a high-pressure air is supplied to the paint storage tank and pressure-fed by pressurizing the high-pressure air, and the pressure of the high-pressure air is adjusted. It is desirable that the amount of paint and the blowing pressure can be adjusted by changing the amount.

The pressure of the high-pressure air injected from the high-pressure air injection hole must be 1 to 7 kg / cm ^2, and the pressure is 1 to 3 kg / cm ^2.
Kg / cm ² is preferred. If the pressure of the high-pressure air is less than 1 kg / cm ² , the valve of the central paint injection hole may not open, resulting in significant unevenness. When the pressure of the high-pressure air exceeds 7 kg / cm ² , the pressure of the high-pressure air is too strong, so that the shape of the spraying range is hard to be collected and a paint loss occurs, which is not preferable. Further, it is necessary to make the shape of the spraying range of the spray elliptical and suppress the spraying range in the minor axis direction to be equal to or less than the outer diameter of the ceramic pipe. This makes it possible to maintain high coating efficiency and reduce coating loss.

When a ceramic pipe is coated while rotating, in order to obtain a uniform coating surface, it is generally important to select the peripheral speed of rotation of the ceramic pipe, the amount of spray coating and the moving speed of the nozzle. The peripheral speed is high, the amount of sprayed paint is small, and the nozzle moving speed is low, it is easy to obtain a uniform coated surface. The nozzle moving speed is preferably 3 to 30 m / mm, and particularly preferably 5 to 25 m / mm. Among the above three types of speed, the rotating peripheral speed of the ceramic pipe is always adjusted by properly adjusting the spray paint amount and the nozzle moving speed regardless of the diameter and type of the ceramic pipe to be painted. It is possible to have a constant speed. When determining the peripheral speed of rotation of this ceramic pipe, consider the viscosity of the paint, the diameter of the ceramic pipe, etc. and determine an appropriate peripheral speed so that the paint does not scatter due to the action of centrifugal force due to the peripheral speed of the pipe. This is very important. Nozzle moving speed is 3 ~ 8m / mm, spraying paint amount is 0.
1-3 g / mm is desirable.

It is desirable that the amount of sprayed paint and the moving speed of the spray nozzle can be adjusted steplessly. It is also desirable to be able to apply multiple layers. The reason for this is that if the peripheral speed of the pipe is set to a constant speed, there is a closer relationship between the spray paint amount and the nozzle movement speed, which are other factors, and there is a restriction on the adjustment, so measures must be taken. This is because that. As a countermeasure for this, a method of repeatedly coating the entire coating outer diameter is often used. The degree of overcoating is 2
~ 5 times is desirable. The best condition for the coated surface is the limit adhesion condition where the paint will flow out if it adheres further. In the case of one-time application, the ceramic pipe is painted while sucking the paint to some extent,
Since the painted surface is not stable and it is difficult to determine when it has reached its limit, it is easy to obtain a beautiful painted surface by dividing it into several small portions and painting each surface while stabilizing it. Easy to get caught. To determine if the ceramic pipe was painted uniformly, after painting, put it in a heat curing oven to fix the paint and let it harden, but after that process, it will be in a state that can be easily identified and uneven. In some cases, it is treated as a defective product.

[0013]

According to the present invention, since the coating is performed while rotating both ends of the ceramic pipe at predetermined positions on the two belts that are fed in parallel, the ceramic pipe can be coated without damage. Using a spray in which the shape of the spray range is elliptical and the spray range is equal to or less than the outer diameter of the ceramic pipe, paint with a mixture of ceramic fine powder and a thermosetting adhesive is turned into high-pressure air with a blowing pressure of 1 to 7 kg / cm ^2. Since the coating is performed while maintaining a predetermined height along the longitudinal direction of the ceramic pipe, it is possible to reduce the loss of the coating while keeping the coating efficiency high, and to eliminate the coating unevenness and to make the product uniform.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 Using the apparatus shown in FIGS. 1 and 2, the diameter is 30 mmφ and the length is
Painting was performed on the 2500 mm ceramic pipe 12. In the above apparatus, both ends of the ceramic pipe 12 to be coated are placed on the conveyor belts 13 and 13 ', and the placed ceramic pipe 12 has a fixed base 5 and a movable base 6 at both ends thereof. The position is defined by ceramic pipe positioning stoppers 11 and 11 'which are provided upright, and the conveyor belts 13 and 13' are rotated to rotate at the same position. The movable table 6
Is movable according to the length of the ceramic pipe 12 by operating the movable base moving drive unit 9. Ceramic pipe 1 mounted on conveyor belts 13 and 13 '
A gas-liquid external mixing type spray nozzle 4 is provided above the unit 2, and is reciprocated at a constant speed along the longitudinal direction of the ceramic pipe 12 by operating the spray nozzle moving drive unit 8. It is designed to move. The spray nozzle 4 is supplied with the paint stored in the paint tank 1 and the high-pressure air supplied through the high-pressure air supply pipe 3. The supply of paint and high pressure air is controlled by the coiling tube 1 so that the spray nozzle 4 can move.
Supplied via 0. In addition, reference numerals 2 and 2 ′ are pressure reducing valves, and 7 is a tray for the paint.

22 m / min of conveyor belts 13 and 13 '
Move at the speed of, and the ceramic pipe 12, ...
Both ends were placed and rotated at a constant peripheral speed of 22 m / min. Depressurize paint stored in paint tank 1 (ceramic fine powder consisting mainly of glass fine powder with an average particle size of 10 μm, cellulosic thermosetting adhesive, viscosity 1000 CP at room temperature) to the paint supply hole of spray nozzle 4. 0.4 g / mm was supplied by the valve 2 at a pressure of 1 kg / cm ² , and the high pressure air supplied to the spray nozzle 4 was supplied by the pressure reducing valve 2 ′ at a pressure of 2 kg / cm ² . The shape of the spray range of the spray nozzle 4 is elliptical,
The minor axis direction was made to be almost the same as the outer diameter of the ceramic pipe. The feed speed of the spray nozzle 4 is 3m / min
The number of reciprocations is 3, and the thickness of the coating film is 300 μm.
When fine ceramic powder was applied to the entire surface of the ceramic pipe 12, excluding both ends, a good coated surface could be obtained. Since both ends of the obtained ceramic pipes 12, ... Are used as support portions of the heater, they are used for the heater in this state.

The paint was supplied at a pressure of Example 2 paint supply holes to 2Kg / cm ² of the spray nozzle 4, except that the pressure of the high pressure air supplied to the spray nozzle 4 and 4 Kg / cm ² is as in Example 1 Similarly, when a ceramic pipe having a diameter of 30 mmφ and a length of 2500 mm was coated, a good coated surface could be obtained with two reciprocations.

Comparative Example 1 A coating was carried out under the same conditions as in Example 1 except that the high pressure air supplied to the spray nozzle 4 and the pressure supplied to the paint supply hole were set to 0.5 kg / cm ^2. Even if the number of reciprocations was increased, a uniform coated surface could not be obtained because the amount of paint sprayed was extremely uneven.

Comparative Example 2 The paint supply pressure supplied to the spray nozzle was 7.5 kg / cm.
² and set the high pressure air pressure to the spray nozzle to 8Kg
When coating was carried out in the same manner as in Example 1 except that / cm ² was applied, the shapes in the spray range were not organized and scattered materials were generated in the periphery.

[0020]

As is apparent from the above description, according to the present invention, it is possible to paint a ceramic pipe without damaging it, to prevent uneven coating, to make the product uniform, and to improve the coating efficiency. It has become possible to reduce paint loss while maintaining. In addition, multiple ceramic pipes can be placed on the conveyor belt at the same time, and spray nozzles can be installed in advance according to the number of ceramic pipes, so that multiple pipes can be automatically coated at the same time. The efficiency could be improved significantly.

[Brief description of drawings]

FIG. 1 is a schematic front view of a ceramic pipe coating apparatus used in the present invention.

FIG. 2 is an enlarged side view of a main part of the ceramic pipe coating apparatus of FIG.

[Explanation of symbols]

 1 paint tank 2, 2'pressure reducing valve 3 high pressure air supply pipe 4 gas-liquid external mixing type spray nozzle 5 fixed base 6 movable base 7 saucer 8 spray nozzle moving drive unit 9 movable base moving drive unit 10 coiling tube 11 ceramic pipe Positioning stopper 12 Ceramic pipe 13 Conveyor belt

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C04B 41/81 Z

Claims (1)

[Claims] 1. Both ends of a ceramic pipe are placed on two belts that are fed in parallel, rotated at a predetermined position, and reciprocally moved at a constant speed while maintaining a predetermined height along the longitudinal direction of the ceramic pipe. And the shape of the spray range is elliptical, and the spray range of the minor axis direction is equal to or less than the outer diameter of the ceramic pipe, and the ceramic fine powder and the thermosetting adhesive are mixed along the longitudinal direction of the ceramic pipe. A method for coating a ceramic pipe, characterized in that the coating material is spray-applied with high-pressure air having a blowout pressure of 1 to 7 kg / cm ² .