JPH054071A - Coating material coating method on internal thread of tube joint - Google Patents

Abstract

PURPOSE:To offer a coating material coating method which is able to apply a coating film having no air bubble and uniform in thickness on an internal thread of a tube joint in a short time. CONSTITUTION:The plate coating head 1 having the same incline as the internal thread of the tube joint in outer diameter and provided with the nozzle hole 6 on the outer surface is inserted in rotating state from the end of the tube joint with a certain space between the internal thread 2 of the tube joint and the outer surface 3 of the coating head 1 and after that a certain amount of the coating material is discharged from the nozzle 6 of the rotating coating head 1 and after kept to rotate for a certain time, the coating head 1 is pulled out from the tube joint in rotating state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method for obtaining a uniform coating film on the inner surface of a female thread of a pipe joint.

[0002]

2. Description of the Related Art As a conventional method for applying paint to a female thread of a pipe joint, there is a method of performing the following steps. 1. 1. Place the end face of the pipe joint to be applied on the upper surface of the tank device containing the paint, 2. While applying a load to the upper surface of the pipe joint so as to prevent paint from leaking from the end face of the pipe joint to the outside of the tank device, 3. Apply pressure to the tank device to raise the paint liquid level in the tank to fill the entire female thread from the end face of the pipe joint to the inner part of the female thread with paint. 4. Maintaining the filled state for a certain period of time to float air bubbles adhering to the female screw, 5. Lower the level of the paint in the tank to discharge the paint downwards from the pipe joint. After that, hold it for a while until the excess paint adhering to the female screw falls, and 7. Remove the pipe fitting from the tank device. The coating material coating method performed in the above order is generally performed.

[0003]

In the prior art, when applying paint, it takes time to allow the paint to flow into and out of the female thread of the pipe joint, and to remove air bubbles and run out of sag. A lot of time was required for the coating process such as time. That is, in order to shorten the process time, for example, when the paint inflow time is shortened, air is entrapped on the surface of the internal thread and many bubbles adhere to the surface of the internal thread after application. If the time for sagging is shortened, the thickness of the coating film will not be uniform. Further, since the inflow and outflow are repeated each time it is applied, there is a lot of contact with the air, and the organic solvent contained in the paint scatters or evaporates in the air and the concentration of the paint gradually changes. There is a problem that is not uniform.

[0004]

DISCLOSURE OF THE INVENTION The gist of the present invention is that a pipe-shaped coating head having an outer diameter having the same gradient as a female thread of a pipe joint and having a nozzle hole on the outer diameter surface is rotated. After inserting the head from the end surface of the pipe joint while keeping a constant distance between the female thread of the joint and the outer diameter surface of the coating head, a certain amount of paint is discharged from the nozzle hole of the rotating coating head. Then, the coating head is retained for a certain period of time, and then the coating head is pulled out from the pipe joint while the coating head is rotated.

[0005]

Since the present invention has the above-described structure, the coating head maintains a constant interval, and a fixed amount of the coating material is discharged from the nozzle provided on the outer surface of the head while rotating. For this reason, the discharged paint is sprayed and quickly applied to the entire female screw, and air bubbles do not remain on the surface of the female screw. Moreover, since the discharge amount of the paint is determined according to the pipe joint, it is not applied to unnecessary parts other than the female thread. Furthermore, since the paint comes into contact with air only at the nozzle of the application head, there is almost no scattering or evaporation of the solvent in the paint, and a new paint is ejected each time it is applied, so the paint concentration is stable and the film thickness is uniform. Is obtained.

[0006]

EXAMPLES Examples of the present invention will be described below. Figure 1
FIG. 3 is a cross-sectional view showing a state in which a conical coating head 1 is inserted into a female screw 2 at the end of a pipe joint. The head 1 is provided with a plurality of nozzle holes 6 opened from the axial center toward the outer diameter surface, and a certain amount of paint is discharged from the nozzle holes 6 while the head 1 is rotating. FIG. 2 shows another embodiment of the coating head in which the side surface is cut out to form a conical plate shape, and a part of the remaining arcuate side surface is cut out at an angle with respect to the center line on the inclined surface 7 in the axial direction of the head. FIG. 4 is a cross-sectional view showing a state in which parallel elongated slits 8 are provided, and further one or a plurality of nozzles 6 are provided in the slits as an application head inflow pipe 11, which is inserted into the end face of the pipe joint.

When the coating head 1 or 11 is inserted into the pipe joint too deeply into the female screw 2, the gap 4 between the female screw 2 and the outer diameter surface of the head 1 or 11 disappears. The position of the joint and the coating head is properly maintained. Coating head 11
Then, the paint discharged from the nozzle hole 6 is applied to the internal thread while being filled in the vertical groove 8, but at this time, it is pushed out into the space 10 formed between the side surface 9 of the head 11 and the internal thread 2. Since the air escapes quickly, air bubbles do not occur on the screw surface because it is applied.

Next, an example of coating conditions will be shown below. Pipe fitting Female thread diameter 1 inch Gap between outer diameter of coating head and inner diameter of female thread 4 0.5 Rotation speed of coating head 100 RPM Paint discharge amount from nozzle hole of head 1 g Paint discharging time from nozzle hole of head 0. 8 seconds Application head holding time after paint discharge 4 seconds Under the above conditions, after inserting the head from the end face of the pipe joint with a constant space between the female thread of the pipe joint and the outer diameter surface of the application head, A fixed amount (1 g) of coating material was discharged from the nozzle hole of the rotating coating head, and then the rotating coating head was held for a certain period of time (4 seconds). Then, the coating head was rotated and then from the pipe joint. As a result of pulling out and applying on the surface of the female screw, a uniform coating film was obtained from the circumferential direction and the inner diameter of the female screw to the root diameter. No bubbles were observed in the coating film on the female screw surface.

[0008]

According to the coating method of the present invention, the coating can be performed in an extremely short time as compared with the conventional method and without bubbles adhering to the surface of the female screw. Further, since the paint does not evaporate or scatter, the concentration of the paint is stable and a coating film having a uniform thickness can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part in an axial direction showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view in the axial direction of an example using another coating head of the present invention.

[Explanation of symbols]

 1 coating head 2 female thread for pipe joint 3 outer diameter surface of coating head 4 gap 5 stopper 6 nozzle hole 7 slope 8 vertical groove 9 head side surface 10 space 11 coating head

Claims (1)

Claim: What is claimed is: 1. A female thread for a pipe joint, wherein a plate-shaped coating head having an outer diameter having the same gradient as that of the female thread for the pipe joint and having a nozzle hole on the outer diameter surface is rotated. After inserting the coating head from the end surface of the pipe joint with a constant distance between the coating head and the outer diameter surface of the coating head, a fixed amount of the coating material is discharged from the nozzle hole of the rotating coating head, and thereafter. A method for applying paint to a female thread of a pipe joint, characterized in that the rotation of the coating head is maintained for a certain period of time, and then the coating head is pulled out from the pipe joint while rotating.