JPS59173166A - Powder coating method on pipe joint - Google Patents

Abstract

PURPOSE:To coat simultaneously powder on the inside and outside surface of a pipe joint with a simple stage by masking the un-coating part then coating the powder on the pipe joint while supplying air in the masked part. CONSTITUTION:Masking jigs 22, 23 are first mounted on the un-coating part of a toric material 1 to be coated. Air regulated to a suitable flow rate is fed from an air feed surce to the air feed type masking jigs 22, 23 through a feed hose 21, then the air is supplied through fine holes 25 and discharging ports 26 to the gaps between the screw part of the elbow 1 and the jigs 22, 23 so that a suitable rate of air is blown to the inside and outside surfaces of the elbow 1. Powder is then sprayed from an electrostatic spray gun 17. The powder is thus surely and simultaneously coated on the inside and outside surface except the masked part.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for coating the inner and outer surfaces of pipe joints and the like with resin powder.

In recent years, pipe joints whose inner and outer surfaces are coated with resin for purposes such as anticorrosion and aesthetics have been widely used for water supply and other piping applications.

Methods for coating pipe joints of this type include the fluidized dipping method, the static coating method, and the powder introduction method (suction or pressure feeding), and these methods are used alone or in combination. In any of these methods, it is difficult due to coating technology to treat the inner and outer surfaces of the pipe joint at the same time, so they are generally treated separately.

However, separate processing requires many steps such as attaching and detaching the coated material (pipe fitting), masking, and baking of the resin, making the work complicated and requiring many man-hours, resulting in low productivity and high manufacturing costs. It is disadvantageous.

Therefore, we have developed a coating method that solves the above technical problems and achieves simplified processes, labor savings, dramatically improved productivity, and reduced manufacturing costs compared to conventional methods.

That is, it is a system that simultaneously coats the inner and outer surfaces of a pipe joint. An example of this will be explained with reference to FIG.

Attach a pre-heated pipe joint elbow (hereinafter referred to as elbow) 1 to the lower masking jig 2, and insert the horizontal masking jig 5 into the threaded part of the sliding device 4 and shell box 1 (Fig. 1 shows the horizontal masking jig). (This shows the state with tool 3 inserted)
. Although the names of the lower masking jig 2 and the horizontal masking jig 5 have been changed for convenience depending on the insertion position of the threaded portion of the elbow 1, they are structurally the same.

When the suction source 5 is activated in this state, the lower masking jig 2, the elbow 1, the horizontal masking jig 3, the upper introduction pipe 7, the hose 8, and the powder recovery device 9 are removed from the opening of the lower introduction pipe 6. An air flow is created which passes through the suction source 5.

Next, the elevating and lowering introduction pipe 10 is raised by operating the elevating device 11 and connected to the lower introduction pipe 6. Since the elevating and lowering introduction pipe sink 10 is installed in the powder fluidized bed 13 in the fluidized tank 12, the mixture of powder and air is instantly sucked and rises, and after passing through the elbow 1, it is removed by the body recovery device. Only the powder is collected at 9°. Since the elbow 1 is preheated, when the powder passes through the elbow 1, it melts on the inner surface of the elbow 1, forming an inner surface coating film 14. Note that the powder in the fluidization tank 12 is made to flow in advance by introducing air through the air inlet 15 and the perforated plate 16.

Simultaneously with the above operation (after completion of masking), υ powder is sprayed onto the elbow 1 using electrostatic spray guns 17a and 17b. The powder is sent by air from the control unit 18, and while a high voltage is applied, it approaches the periphery of the elbow 1 in a cloud-like state with the conveying air, and is uniformly adhered and melted by static electricity to the outer surface. A coating film 19 is formed.

However, even with this method, there are still problems. This will be explained with reference to FIG.

FIG. 2 is a sectional view showing a part of the elbow 1 and the masking jig 2.6 during the simultaneous processing in the above description. In this state, the inner surface is under suction by the suction source 5, that is, under negative pressure, while the outer surface is under a slight positive pressure, that is, the powder is transported by pressurized air. Therefore, outside air and powder enter the small gap between the masking jig 2.5 and the threaded portion of the elbow 1 and pass through to the inner surface. At this time, since the elbow 1 has been heated in advance, powder for the outer surface is welded to the threaded portion (as shown by a welded portion 20), resulting in a defective thread.

In order to solve the above-mentioned problem, the present invention improves the masking jig and the like and realizes simultaneous processing.

The details will be explained below with reference to FIGS. This is what is shown. During simultaneous processing, when air adjusted to an appropriate air volume flows from an air supply source (not shown) through the υ supply hose 21 to the air supply type masking jig 22.23, this air flows to the air supply type masking jig 22.23. The air is supplied through the air inlet 24 of 23, through the small hole 25 of the air supply type masking jig 22.23, and from the discharge port 26 to the gap between the threaded part of the elbow 1 and the air supply type masking jig 22.25, and 1 An appropriate amount of air is blown out on the inner and outer surfaces. In other words, the gap between the threaded portion of the elbow 1 and the air supply type masking jig 22.2S is brought into an appropriate positive pressure state to prevent powder from entering from the outside surface. Note that the amount of air blown out from the discharge port 26 varies depending on the size and type of the pipe joint, but can be sufficiently adjusted by adjusting the inner diameter and number of the supply hose 21, the pores 25, and the discharge ports 26. Further, as shown in FIG. 4, it is preferable that the discharge ports 26 are provided at several locations on the circumference. Furthermore, if the position of the discharge port 26 is within the range a shown in FIG. 5, a sufficient effect of discharging air can be obtained.

Next, Table 1 shows examples of the present invention.

As can be seen from the examples shown in Table 1, the present invention reduces defects caused by threaded parts without compromising quality, and reduces the time required for coating from 4 to 10 hours to 1 hour. Since it can be shortened to a certain degree, it contributes to labor saving and productivity improvement, and has an extremely economical effect.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a part of an example of a powder coating method for a pipe joint, Fig. 2 is an enlarged sectional view of the main part, and Fig. 3 is an enlarged sectional view of the main part showing an example of the present invention. FIG. 4 is a perspective view showing an example of an air supply type masking jig used in the present invention, and FIG. 5 is an enlarged sectional view of the main part. 1: elbow, 5: suction source, 6: lower introduction pipe, 7: upper introduction pipe, 12: fluidized tank, 13: powder fluidized bed, 17a,
17b: Electrostatic spray gun, 22.23; Air supply type masking jig agent Patent attorney Takashi Honma Procedural amendment (self-restraint April 27, 1980 Commissioner of the Patent Office Kazuinu Wakasugi 1, indication of the matter) 1981 Patent Application No. 45327 2, Name of the invention: Powder coating method for pipe joints 3, Relationship with the case of the person making the amendment Patent Applicant: Address: 2-1-2 Marunouchi, Chiyoguchi 1-ku, Tokyo No. Name (Name) (5
08) Hitachi Metals Co., Ltd. Representative 〆n■ Norio No 4, Agent Contents of amendment in [Detailed description of the invention] column 1, the name of the invention on page 1 of the specification is corrected as follows. °. "Powder coating method" 2゜The claims on the same page of the same book are amended as follows. Characterized by coating method. ” 3. Change “is” in the second line of page 5 of the same book to [and,
The gist is that a masking jig is attached to the non-coated part of the annular material to be coated, and the material to be coated is coated with powder while supplying gas to the part where the non-coated part and the masking jig are attached. This is a unique powder coating method. ” is corrected. That's all (yl

Claims (1)

[Claims] A masking jig is inserted into the threaded part of the material to be coated (pipe fitting), and while supplying gas to the insertion part between the threaded part and the masking jig, resin powder is applied to the inner surface of the masking jig and the inner surface of the material to be coated. 1. A method for powder coating a pipe joint, comprising: passing resin powder through a body, and spraying resin powder onto the outer surface of the material to be coated.