JPH035229B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a method of applying an ultraviolet curable coating liquid to the outer circumferential surface of a pipe. Examples of pipes to which the present invention is applied include metal pipes such as steel pipes and galvanized pipes, and plastic pipes. The present inventors have completed an invention that can efficiently and uniformly coat the outer circumferential surface of a pipe with an ultraviolet curing paint having a viscosity higher than the viscosity range applied to normal spraying methods, and have filed a patent application for this invention in Japanese Patent Application No. 131336/1983. It's inside. The contents of this pending invention are as follows. 1 While conveying the tube in its length direction, an ultraviolet curing paint liquid is supplied to the outer peripheral surface of the tube, the supplied paint liquid is then squeezed and applied to the outer peripheral surface of the tube, and then ultraviolet rays are irradiated to cure the applied paint liquid. A method of painting the outer peripheral surface of a pipe, which is characterized by curing. 2. Means for conveying the tube in its length direction, means for supplying an ultraviolet curable coating liquid to the outer circumferential surface of the tube, and means for applying the supplied coating liquid to the outer circumferential surface of the tube, which are arranged sequentially along the direction of conveyance of the tube. What is claimed is: 1. A coating device for the outer circumferential surface of a tube, comprising a squeezing means and an ultraviolet irradiation means for curing a coating liquid, and characterized in that at least the squeezing means and the ultraviolet ray irradiation means are provided between adjacent tube conveying means. In this pending invention, the means for supplying the ultraviolet curing paint liquid to the outer circumferential surface of the pipe being conveyed in the length direction has a structure that allows the paint liquid to be discharged from the discharge port toward the pipe under gravity or under pressure. However, in order to avoid leaving unpainted surfaces during the subsequent scrubbing process for pipes that are transported at high speeds such as 60 to 90 m/min, it is necessary to apply the paint liquid evenly to the outer surface of the pipe. It is desirable to be able to supply it. For this purpose, a head having one or more discharge slits whose opening degree can be varied and adjusted, or a head having one or more discharge holes having a diameter of, for example, 0.3 to 2 mm, or a combination thereof, is preferably provided on the outer circumferential surface of the tube. It is advantageous to arrange an appropriate number of them. Alternatively, a ring-shaped head may be used that surrounds the outer circumferential surface of the tube and has a plurality of small holes for discharging the paint liquid onto the outer circumferential surface of the tube. Of course, if it is difficult to uniformly supply the coating liquid to the outer circumferential surface of the tube with one head, the number of heads may be increased, or the various heads described above may be used in combination. By supplying the paint liquid to the outer peripheral surface of the tube in a curtain-like or shower-like manner using such a supply means,
Compared to supplying paint liquid by atomization using the normal spray method, this method has the advantage of preventing contamination of the working environment due to paint liquid scattering, and also allowing the use of paint liquid with a viscosity in areas that are difficult to coat using the spray method. . When the paint liquid is supplied to the outer circumferential surface of the pipe being transported by the supply means, a part of the paint liquid may enter the pipe depending on the supply method. The paint that has entered the pipe is useless and uneconomical for the purpose of painting the outer circumferential surface of the pipe, and it is difficult to cure when the outer circumferential surface of the pipe is irradiated with ultraviolet rays and remains sticky forever. There is a risk that it may flow out of the pipe during handling, staining the painted outer surface and contaminating the working environment. To prevent this, the openings at both ends of the tube may be closed in advance with means (eg, caps) that are easily removed later. Further, in terms of the device, the paint liquid may be supplied to the front end of the tube from the rear thereof or to the rear end of the tube from the front of one or more heads. For example, when using one head or a set of heads, when a tube passes in front of the head, a sensor captures this and transmits the signal to the supply means, which directs the paint liquid toward the tip of the tube. At the same time as the paint starts to be supplied, the head is swung in a direction opposite to the direction in which the tube is conveyed, and then the paint up to the rear end of the tube is removed before the rear end of the tube passes in front of the head. The supply may be stopped after the supply is completed. The tube into which the paint liquid has been supplied to the outer circumferential surface by the above-mentioned supply means is then passed through a squeezing means to uniformly apply the paint over the entire outer circumferential surface. This straining means is divided into two types: (1) one that uses an inelastic body with an opening that is similar in shape to and larger than the cross-sectional shape of the pipe, and (2) one that uses an inelastic body that has a similar shape to or similar to the cross-sectional shape of the pipe. They are broadly divided into those that use an elastic body with smaller openings. The former (1) is a type similar to a metal die, and the thickness of its opening and the gap between the opening and the outer peripheral surface of the tube are factors in adjusting the film thickness. The latter (2) is of the rubber plate or rubber ring type having such an opening. In order to reinforce this elastic body and improve the accuracy of film thickness uniformity, an inelastic reinforcing body ( For example, it is preferable that a metal plate) is also concentrically protected. The material of the elastic body is appropriately selected depending on its durability against the paint liquid used and its abrasion resistance. According to the latter (2) straining method, the material of the elastic body, the thickness of the opening, the dimensional ratio between the opening and the outer shape of the tube, etc. become factors for adjusting the film thickness.
Therefore, based on this viewpoint, the size of the opening is
It may be selected as appropriate within the scope of the above regulations. In addition, as in the case of the former (1), it goes without saying that the viscosity of the coating liquid used, the tube conveyance speed, etc. are also factors in adjusting the film thickness. The above-mentioned straining means can be arranged individually, in plurality, or in combination to adjust the film thickness. In this manner, a coating film having the desired thickness can be obtained by the ironing means. In addition, the relevant training methods (i.e., the former (1) and the latter
(2)) is preferably configured to be movable in a direction parallel to and perpendicular to the tube conveyance direction. According to this, it is possible to avoid uneven coating of paint caused by vibrations during pipe transport and bending of the pipe itself, and it is possible to more accurately maintain uniformity in film thickness over the entire outer circumferential surface of the pipe. can. The paint uniformly applied to the outer peripheral surface of the tube by the above-mentioned rubbing means is then irradiated with ultraviolet rays to be cured. As the ultraviolet irradiation source, a known high-pressure mercury lamp, metal halide lamp, or the like may be used. In the pending invention, it is advantageous to configure the means so that the outer circumferential surface of the tube is uniformly irradiated with the ultraviolet ray irradiation source in the circumferential direction. In the pending invention, at least the above-mentioned squeezing means and ultraviolet irradiation means are arranged between adjacent tube conveying means. This can prevent the uncured coating film from coming into contact with the pipe conveying means and being damaged. Note that if it is difficult to cure the coating film on the entire outer peripheral surface of the tube sufficiently with the ultraviolet irradiation means provided between the tube conveying means, first remove the tube conveying means as disclosed in Japanese Patent Publication No. 55-8229. The coating film in the area that comes into contact with the means is irradiated with ultraviolet rays in a focused manner to fully cure it, and then another ultraviolet irradiation means is attached after the tube has passed through the conveying means, thereby coating the entire outer peripheral surface of the tube. The film may be sufficiently cured. Next, the pending invention will be specifically explained with reference to FIGS. 1 to 3. 1 and 1' are roll means for conveying the tube 2 in its length direction. The direction of conveyance of the tube 2 can be oriented horizontally or obliquely, but the horizontal direction is advantageous for the device as shown. 3 is a means for supplying an ultraviolet curing paint liquid to the outer peripheral surface of the pipe 2 being conveyed by means 1 and 1', and the paint liquid is discharged from the heads 4 and 4' toward the pipe 2, and excess paint is removed. The paint is collected through the lower pan 5 into the paint tank 6 and sent to the paint tank 6 via the filter 7, pump 8 and line 9 for use. Reference numeral 10 denotes a means for squeezing and uniformly applying the paint supplied to the tube 2 by the means 3, the details of which are shown in FIGS. 2 and 3. The plate 12 is reinforced by concentrically fixed metal plates 13 with openings on both sides thereof, and the ironing plate formed in this way is inserted and supported in the casing 14, and the casing 14 is provided with a buffer body against the frame 15. 16 (for example, a spring) so as to be freely movable up, down, left, right, front and back. Reference numeral 17 denotes a stopper for preventing the above-mentioned ironing plate from moving more than necessary in the same direction along the conveying direction (arrow) of the tube 2. Reference numeral 18 denotes ultraviolet irradiation means for curing the paint uniformly applied to the outer peripheral surface of the tube 2 by the ironing means 10, and a plurality of irradiation sources 19 are arranged evenly in the circumferential direction of the tube 2. There is. In the illustrated example, a squeezing means 10 and an ultraviolet irradiation means 18 are provided between the tube conveying means 1 and 1'.
At the same time, a paint liquid supply means 3 is also arranged. Using the illustrated apparatus constructed as described above, a steel pipe having a length of 5.5 m and a diameter of 50.8 mm was coated with an ultraviolet curable coating liquid containing polyester acrylate as the main component under the conditions shown in Table 1. The thickness of the resulting coating film was measured using an electromagnetic film thickness meter. The second result is
Shown in the table. The measurement points for the film thickness are approximately 500 mm (a) and 2750 mm from the tip of the steel pipe along the conveyance direction (arrow) as shown in Figure 4.
(b), about 5000 mm (c), and in the circumferential direction of the steel pipe, it is on the quarter line (B to D) from the upper end A, as shown in FIG.

【table】

【table】

[Table] When a rubber elastic plate 12 having an opening 11 smaller in size than the cross-sectional outline of the tube 2 is used as the squeezing means 10 in the prior invention, the outer periphery of the tube to which the coating is first applied If the surplus paint liquid on the surface adheres to the opening peripheral edge of the elastic plate 12, the adhered paint liquid will adhere to the front end surface of the elastic plate 12 when the tube for next application comes into contact with the elastic plate 12. In this way, if a particularly large amount of excess paint liquid adheres to the front end face of each subsequent pipe, it will not only deteriorate the appearance of the painted pipe, but also cause the paint to be removed if it is temporarily rust-proofed. It becomes difficult to remove the film from that part when the film is applied, and the weldability of the pipe is deteriorated when welding the pipe connection. The present invention solves the problems of the prior invention that occur in the coating operation using such a specific elastic plate 12, and the gist thereof is the above-mentioned method for coating the outer peripheral surface of a pipe according to the prior invention. In particular, when applying a paint liquid to the outer circumferential surface of a pipe using an elastic body having an opening similar in shape to the cross-sectional shape of the pipe and smaller in size,
The method is characterized in that after the tube passes through the elastic body, the adhering paint liquid is removed from the tube. Removal of the adhering paint liquid from the elastic body, especially from the opening periphery that comes into contact with the front end surface of the tube, may be carried out using any suitable means, but at a tube feeding speed of 60 to 90 m/s.
When high-speed operation is employed, it is effective to blow out the paint liquid by blowing compressed air into the area concerned. The compressed air injection timing is from after a certain tube passes through the elastic body until the next tube comes to the elastic body. The compressed air may be ejected obliquely toward the periphery of the opening by arranging one or more nozzles on the paint liquid adhering side of the elastic body at a position that does not interfere with the conveyance of the tube. It is advantageous for the nozzles to be arranged in a plurality of rings around the tube conveyance path.
Furthermore, compressed air may also be applied from the opposite side of the elastic body to the side on which the paint liquid is applied. In the latter case, it is more effective to apply compressed air alternately from both sides to remove the adhered paint liquid. As an example of a specific configuration for removing such paint liquid adhering to an elastic body, in the above-mentioned illustrated apparatus,
Between the paint liquid supply means 3 and the squeezing means 10, 12 nozzles ("1/8 KSH0400" manufactured by Kyoritsu Gokin Seisakusho, orifice diameter 2.0 mm) are placed at a distance of 100 mm from the elastic body 12, with the conveyor pipe axis as the center. They were arranged at equal intervals on a circumference with a radius of 150 mm, the nozzle angle was adjusted so that the center of the ejected air was evenly located at the position where the tube 2 contacted the elastic body 12, and a compressed air pressure of 4 kg/cm ² was adopted. After the pipe 2 passes through the squeezing means 10, air is injected for 3 seconds, and then the next pipe 2 passes the squeezing means 10.
Here is an example of how to reach . By adopting such an improved method, adhesion of paint liquid to the front end surface of the tube can be eliminated. Of course, uniform coating on the outer peripheral surface of the tube is not hindered in any way.

[Brief explanation of the drawing]

Fig. 1 is a simplified side view showing the whole of an example of the device of the prior invention, Fig. 2 is a front view of the laddering means, Fig. 3 is a partially sectional plan view thereof, and Figs. 4 and 5 are of the painted pipe. 1 is an explanatory diagram showing a film thickness measurement site,
1' is a pipe conveying means, 2 is a pipe, 3 is a paint liquid supply means,
4, 4' are its heads, 10 laddering means, 12
Reference numeral 13 indicates an elastic body having a predetermined opening 11, 13 a reinforcing member thereof, and 18 an ultraviolet irradiation means.

Claims (1)

[Scope of Claims] 1. While conveying the tube in its length direction, an ultraviolet curable coating liquid is supplied to the outer peripheral surface of the tube, and then the supplied coating liquid is passed through an opening having a shape similar to the cross-sectional outline of the tube and smaller in size. In a method for painting the outer circumferential surface of a pipe, the coating liquid is applied to the outer circumferential surface of the pipe by squeezing it with an elastic body having a A method characterized by removing. 2. The method of item 1 above, in which the adhering paint liquid is removed by applying compressed air to the elastic body.