US3657000A

US3657000A - Method for painting inner surface of pipe

Info

Publication number: US3657000A
Application number: US835705A
Authority: US
Inventors: Kimiaki Kasano; Ichiro Kaya
Original assignee: Kansai Paint Co Ltd
Current assignee: Kansai Paint Co Ltd
Priority date: 1968-07-02
Filing date: 1969-06-23
Publication date: 1972-04-18
Anticipated expiration: 1989-04-18
Also published as: US3705569A

Abstract

A method and apparatus for interior painting of pipe, particularly of small diameter, is characterized by filling of a pipe with both ends open with paint, hanging the pipe vertical and passing a ball of a diameter smaller than the inside diameter of the pipe from the upper end of the pipe to fall down by its gravity through the pipe and strip off excessive paint so as to form a film of uniform thickness of paint of the inner surface of the pipe.

Description

States Patent asano et a1.

[15] 3,657,000 51 Apr. 18,197

METHOD FOR PAINTING INNER SURFACE OF PIPE Inventors: Kimiaki Kasano, Amagasaki-shi, l-lyogoken; Ichiro Kaya, Sakai-shi, Osaka-fu,

both of Japan Assignee: Kansai Paint Company Limited, Hyogoken, Japan Filed: June 23, 1969 Appl. No.: 835,705

Foreign Application Priority Data July 2, 1968 Japan ..43/46399 U.S. Cl. ..117/97, 117/132 B, 117/132 BE, 117/132 C, 117/161 KP, 117/161ZB, 118/105, 118/408, 118/DIG. 10

Int. Cl. ..B44d l/09, 844d 1/02 Field of Search ..117/95, 97, 64, 161 KP, 1612B; 118/408, 105, DIG. 10; 166/163 [5 6] References Cited UNITED STATES PATENTS 2,100,587 11/1937 Chalker ..118/105 2,318,060 5/1943 Cortese ..1 17/97 X Primary Examiner-Alfred L. Leavitt Assistant Examiner-Edward Whitby At!0rneyLars0n, Taylor, and Hinds [5 7] ABSTRACT A method and apparatus for interior painting of pipe, particularly of small diameter, is characterized by filling of a pipe with both ends open with paint, hanging the pipe vertical and passing a ball of a diameter smaller than the inside diameter of the pipe from the upper end of the pipe to fall down by its gravity through the pipe and strip off excessive paint so as to form a film of uniform thickness of paint of the inner surface of the pipe.

3 Claims, 4 Drawing Figures METHOD FOR PAINTING INNER SURFACE OF PIPE This inventionrelates to a method for painting the inner surface of a pipe and is aimed at providing pipe particularly of small diameter with inner surface evenly painted.

In the conventional methods uniform coating of the inner surface of a pipe extremely large inside diameter could be performed by means of spraying, but with long pipe of smaller inside diameter, such as less than 53 mm inside diameter, uniform coat of the inner surface could not be obtained. And, for example, when a pipe of smaller diameter is first filled with paint, and then the pipe is hung vertical to let paint in excess flow down, there inevitably results difference in the thickness of coat between at lower and upper ends, failing to provide uniform thickness of the coat, and is accompaniedby sagging and furthermore it takes longer time in coating work. No such sprayer is known in the art, being capable of painting the inner surface of a pipe of less than 53 mm inside diameter. Also high viscosity paint can not be used in spray painting for this purpose.

The object of the invention is to provide a method for forming uniform coat of paint by a simple operation by using a relatively high viscosity paint in painting the inner surface of a pipe, particularly of small diameter. According to the invention, in forming a film of uniform thickness on the inner surface of a pipe with open ends, the pipe is first filled with paint, and then hung vertical, and preferably, after the paint has partly flowed down, then a ball having diameter slightly smaller than the inside diameter of the tubular body is inserted through the upper end of the pipe to fall down through the hollow, whereby uniform film is formed on the inner surface of the pipe. Thus, according to the invention uniform film of paint as desired is formed, by first filling the hollow portion of a pipe with both ends open with paint, hanging the pipe substantially vertical, preferably, after letting the paint within fall down to some extent, and then passing aball of a diameter allowing a clearance necessary for producing required thickness of film, from upper end of the pipe to fall down by its gravity, so as to strip off excessive paint.

The invention will be hereinafter explained according to the attached, drawings, in which.

FIG. 1 is a side elevation with a partial longitudinal section of a preferred embodiment of the invention.

FIG. 2 is enlarged longitudinal section of part of FIG. 1.

FIG. 3 is a sectional view along AA line of FIG. 2. and

FIG. 4 is an enlarged sectional view along B-B line of FIG. 1.

In FIG. I, pipe 1 is suspended from tact-conveyor 3 by hanger 2, said tact conveyor moving intermittently at regular intervals in the direction of arrow head. When pipe I hung on tact conveyor 3 reaches paint inlet 5 by movement of tact conveyor 3, tact conveyor stops, paint inlet 5 moves upward actuated by arm operator 6 held by stay 21, to fit the lower opening of pipe 1. Then coating composition in tank 8 is'pumped into pipe 1 by pump 7 through hose l9 and hollow arm 4. When pipe 1 is filled to the upper extremity, paint inlet 5 and hollow arm 4 are lowered by arm operator 6, and tact conveyor again moves in the direction of arrow head.

On the other hand, the ball is supplied to pipe 1 in the following manner during operation. Number of balls are kept in box 20 provided on the upper part of tact conveyor 3, and when pipe filled with paint at the upper end or its vicinity as above reaches below ball outlet 23 of box 20, shutter 22 at the outlet 23 of box 20 opens and a ball is lowered to the upper opening of pipe 1 below the outlet 23. When shutter 22 is opened shutter 25 provided in ball feed pipe 24in a distance from shutter 22 of slightly larger than the diameter of ball 13 is shut to let only one ball drop from ball exit 23. When ball 13 has dropped shutter 22 is shut whereby another ball is delivered into pipe 24. All the above supply of paint into pipe and the supply of ball 13 are carried out automatically by means of a regulator.

The above operation takes place in a given length of time, and conveyor 3 is driven again by means of time switch. The supply of the balls may also be done manually. Ball 13 in pipe 1 falls by gravity within the pipe while conveyor 3 is moving, forcing down paint 16 to produce required thickness of film l8. Hanger 2 provided on conveyor 3 is equipped with at least a pair of catches 27 having teeth 26 at the end, facing diagonally and movable up and down, and between these opposing catches 27 pipe 1 is inserted and by slightly lowering pipe 1 teeth 26 of catches 27 engage with outside surface of pipe I to be suspended. Balls falling through pipe 1 are collected in ball receptacle l5, and are washed for reuse in a separate tank with an organic solvent which dissolves the paint. Excessive paint 16 which is stripped off from pipe 1 is delivered to paint tank 8 for recirculation. Pipes 1 on which film of paint is formed further move successively and are baked as required by baking oven 17 to obtain final products. In this way of painting, the coated film is sufficiently thin according to the viscosity of paint used after the ball is passed through and no sagging is liable to occur. The manner of the ball passing through pipe 1 is shown in FIG. 2 and 3. in-enlarged drawings. In FIG. 2 and 3, the paint filling the pipe 1 is stripped off by ball 13 to result in desired thickness of coat. In the invention, the method of filling pipe 1 with paint is not limited to filling from the lower end, and it can be done, for example, by plugging the bottom end of pipe 1 and charging it from upper end and removing the plug for further operation.

When the ball is inserted from the upper end of pipe 1 it is inevitable that the ball is somewhat shaken in the direction of the diameter of the ball for a length of about 10-20 mm from the upper end, but after that the ball will fall straight through the center of pipe 1. Accordingly, either by cutting off such length of 10-20 mm from the end or by temporarily joining a sperate pipe of same inside diameter to the upper end of pipe 1 for coating and removing it after coating, uniform thickness of the coat can be obtained throughout.

The prefered embodiment of the present invention is advantageous in that after filling pipe 1 with paint, the paint is allowed to partly fall down (see drawings) to let the ball fall through-the center of pipe rapidly, whereby the thickness of film within is unified. I

The paints to be used in the invention may vary, but generally tar-epoxy resin-based paints of viscosity of about 60-130 KU (Krebs Unit), polyvinyl chloride sol-based paints of about -110 KU, epoxy resin-based paints of about 60-130 KU and polyurethane resin-based paints of about 60-90 KU, etc. are used. These paints are selected by considering the inside diameter of pipe to be painted, thickness of film to be formed, specific gravity of balls used, etc. As the balls to be used are desirable those of a material having specific gravity of about l.0-8.0. Steel balls (specific gravity of about 7.8), Porcelain balls (generally specific gravity of about 3.5), plastics balls (generally specific gravity of about 1.0-2.0), stainless steel balls (generally specific gravity of about 7.8), glass balls (generally specific gravity about of 2.2-6.3), etc. can be effectively used. The diameter of these balls is selected in consideration of inside diameter of pipe and clearance from said inside diameter of pipe, necessary to produce film of paint to the desired thickness. The clearance generally is about 1.3-2 times the desired thickness of film depending on the concentration of paint, for example, the clearance of about -220 g is desirable to obtain a film 1 10 ,u. thick. The specific gravity of the balls can be selected freely according to the viscosity of paint and the diameter of pipe. The method of the invention can be most advantageously applied to the painting of steel pipe of 12.7 mm 52.9 mm inside diameter. The pipe, ball and paint in various combinations according to the method of the invention are exemplified in Table 1 below.

A SGP (12.7) Steel 70-80 60-80 A SGP l6.l) Steel 7.0-8.0 60-110 A SGP (2 l .6) Steel 70-80 60-110 A SGP (27.6) Steel 7.0-8.0 60-130 32A SOP (35.7) Steel 7.0-8.0 60-130 40A SGP (41.6) Steel 70-80 90-130 Porcelain 3.0-4.0 60-90 50A SGP (52.9) Porcelain 3.0-4.0 90-130 Plastics l.0-2.0 60-90 In the method of the invention it is also possible to introduce relatively pressurized air into pipe after inserting the ball from the upper opening of pipe to facilitate the fall of the ball through pipe.

The method of the invention can be said to have an extremely high industrial value in that the interior surface of a pipe of smaller diameter is painted to uniform and desired thickness by a simple operation.

Concrete explanation of the method of the invention is done by Examples to follow.

EXAMPLE 1 By the equipment as shown in FIG. 1 interior coating was carried out under the following conditions:

between pipes Speed oftact conveyor Stop 35 sec. and advance 5 sec.

Drying conditions No sagging was observed in the film immediately after coating and after minutes, and uniform film of 210:15 u was obtained. The upper end of the pipe was cut off by 10 mm.

EXAMPLE 2 By the equipment of FIG. 1 was conducted interior painting under the following conditions.

TABLE 3 inside l2.7 mm 52.9 mm diameter (10A SGP) (50A SGP) Pipe Length 5.5 m 5.5 m Material Steel Steel Diameter 12.2 mm 52.0 mm Ball Weight 7.4 g 260 3 Material Steel Porcelain Viscosity 60 KU 1 l0 KU Paint Type Epoxy-resin Tar-epoxy based enamel resin-based enamel Clearance 0.25 mnt 0.45 mm Falling ve- 43-50 sec/ l5-l8 sec/ Operlocity of ball 5.5 m 5.5 m ation con- Distance be- 50 mm 50 mm ditions tween pipes Speed of tact Stop 60 sec Stop 20 sec conveyor Advance 5 sec Advance 5 sec Drying conditions CXIS min. 20 C:5 24 hr.

By coating under the above conditions A and B, the thickness of obtained film was i 10120 n for A and 300135 a for B, and the thicknesses were substantially uniform throughout, exhibiting no notable differences between upper and lower parts, and even after 30 minutes vertical suspension of the pipes no sagging was observed.

What we claim are:

1. A method for painting the interior of a pipe comprising filling a pipe having both ends open with paint while said pipe is hanging vertically and permitting a ball of a diameter slightly smaller than the inside diameter of the pipe from the upper end of the pipe to fall down through the hollow portion of the pipe under gravitational forces only so as to form a film of uniform thickness of paint on the inner surface of the pipe.

2. A method according to claim 1 wherein said pipe comprises ferrous metal.

3. A method according to claim 2 wherein said pipe comprises steel pipe having an inside diameter of 12.7 to 52.9 mm.

Claims

2. A method according to claim 1 wherein said pipe comprises ferrous metal.
3. A method according to claim 2 wherein said pipe comprises steel pipe having an inside diameter of 12.7 to 52.9 mm.