JPS62269774A - Method for coating tube - Google Patents

Abstract

PURPOSE:To easily and uniformly coat the whole surface of a tube having a fin with a narrow pitch by providing plural nozzles in the circumferential direction of the periphery of the tube, and atomizing and spraying paint from the nozzles. CONSTITUTION:Plural paint nozzles 5a and 5b are provided in the circumferential direction around the tube 1 at regular intervals in the coating of the spirally finned tube for heat exchange. Paint is atomized from the paint nozzles 5a and 5b, and sprayed on the tube 1. As a result, a coated film having uniform thickness is formed over the whole surface of the tube 1 and the spiral fin 2, even when the interval between the spiral fins is narrow. The entry of the tube 1 is detected by a photoelectric cell 4. Since the injection of the paint from the nozzle 5 and the stopping of the injection are controlled at the position of the transferred tube 1, only the desired range can be painted.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a tube coating method suitable for coating a tube with spiral fins for heat exchange.

(Prior art and its problems) Conventionally, in order to paint a tube with spiral fins, as shown in FIG. Painting was carried out by letting the paint drip down by gravity from nozzles 03 that were surrounded by a predetermined interval (referred to as a flow coater method).

In this flow coater method, when the distance between the spiral fins 01 is narrow, for example, about 2.5 fi, the paint 04 does not reach the base of the spiral fins 01, resulting in an uncoated area 05, as shown in FIG. There was a problem.

The only way to deal with this is the so-called dipping method, in which the tube with spiral fins is immersed in paint stored in a paint tank, but with this dipping method, paint also adheres to the weld groove at the end of the tube. Therefore, the end of the tube must be masked in advance using a cap or tape, and this masking must be removed after painting, which not only requires time and effort, but also makes automation difficult. was there.

(Means for Solving the Problems) The present invention was invented in order to solve the above problems, and its gist is that the tubes are arranged around the tube at predetermined intervals along the circumferential direction. The method of painting a tube is characterized in that the paint is atomized and sprayed onto the tube from a plurality of disposed nozzles.

(Function) Since the present invention has the above configuration, the paint mist ejected from the plurality of nozzles reaches the base of the tube and the fins installed on the outer periphery of the tube and spreads evenly over the outer surface of the tube. adhere to.

(Example) An example of the present invention will be specifically described with reference to FIGS. 1 and 2.

In FIG. 1, l is a tube having a total length l, and a spiral fin 2 is installed in the middle of the tube.

The tube 1 is placed horizontally on a plurality of rollers 3, and some of the drive rollers 3a are placed horizontally on a plurality of rollers 3.
is conveyed along the axial direction toward the right in the figure. Photoelectric switch 4 along the transport path of tube 1, distance behind it! , the upper paint nozzle 5a
But there is a distance l behind it! A lower paint nozzle 5b is disposed across from the lower paint nozzle 5b, and an air nozzle 6 is disposed in this order behind the lower paint nozzle 5b.

As shown in FIG. 2, a plurality of paint nozzles 5a and 5b are arranged around the tube 1 at predetermined intervals along the circumferential direction. These plurality of paint nozzles 5a.

Piston valves 8a and 8b are interposed in each paint supply pipe 7a and 7b communicating with the paint supply pipe 5b, and these piston valves 8
a.

Solenoid valves 10a and 10b are interposed in air pipes 9a and 9b that supply air for driving the solenoid valves 8b.

Reference numeral 11 denotes a control device incorporating a pulse oscillation device, etc., which receives a signal from the photoelectric switch 4 and opens and closes the solenoid valves 10a and 10b based on the output thereof.

This control device 10 has the entire length of the tube l! , unpainted lengths a and b are input in advance. 12 is an air pipe that supplies air to the air nozzle 6.

Thus, the tube 1 is conveyed at a constant speed, and when the tip reaches the photoelectric switch 4, the photoelectric switch 4 detects this and sends a signal to the control device 11. Then, the pulse oscillator of the control I device 10 starts counting, and when a certain count is reached, that is, when the tube l is on the predetermined path j
il(It, +b) and when the front end of the coating range C reaches the position of the upper nozzle 5a, the control device 11 outputs an output to the solenoid valve 10a to open it. Then, driving air is supplied to the piston valve 8a to open it, and the paint flows through the paint supply pipe 7a to the upper nozzle 5a.
from where it is atomized and sprayed into the tube 1 in a fan-shaped pattern. When the count of the pulse oscillator reaches another set value, i.e. when the tube l reaches the distance #fi+
When the front end of the coating range C reaches the position of the lower nozzle 5b after being conveyed by +1t +b, the control device 11 outputs an output to the solenoid valve 10b to open it, and the driving air opens the piston valve 8b, causing the paint to flow. The lower nozzle 5
Atomize from b and spray into tube 1. Tube l is distance 1. When the tube l has been conveyed by +b+c, a signal from the control device 11 stops the ejection of paint from the upper nozzle 5a, and when the tube l has been conveyed by a distance jilL +i +b, +c, a signal from the control device 11 stops the ejection of paint from the upper nozzle 5a. Spraying of paint from nozzle 5b is stopped. When the tube 1 is further conveyed and passes through the air nozzle 6, the air blown out from the nozzle 6 blows away the paint excessively attached to the tube 1, thereby preventing the paint from dripping.

Thus, a plurality of nozzles 5a are arranged around the tube 1 at predetermined intervals along the circumferential direction.

Since the paint is atomized from 5b and sprayed into tube l,
Even if the spacing between the spiral fins 2 is narrow, the paint reaches the base of the spiral fins 2 and forms a coating film with a uniform thickness over the entire outer surface of the tube 1 and the spiral fins 2 installed therein. I can do it. Then, the photoelectric switch 4 detects the entrance of the tube 1, and the transport position of the tube 1 is determined based on the signal from now on. is sensed by counting the pulses emitted from the pulse oscillator of the control device 11, and when the tube 1 is conveyed a predetermined distance, the control device 1
By controlling the spraying and stopping of the paint from the paint nozzles 5a and 5b using signals from the paint nozzles 1, it is possible to paint only the required range C without painting the predetermined ranges a and b at the end of the tube l. Therefore, unlike the conventional method, masking and removal of the end portion of the tube are not necessary, so that the tube can be coated automatically.

Although we have described an example in which the present invention is applied to the painting of tubes with spiral fins, it can of course be applied to the painting of tubes with disk-shaped fins and spine fins, as well as paired tubes and round bars. It is also possible to apply it to

(Effects of the Invention) In the present invention, since paint is atomized and sprayed onto the tube from a plurality of nozzles disposed around the tube at predetermined intervals along the circumferential direction, the tube has narrow pinch fins. However, the entire surface can be easily and uniformly coated.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, FIG. 1 is a system diagram of the entire coating apparatus, and FIG. 2 is a layout diagram showing the positional relationship between tubes and nozzles. Figures 3 and 4 show a conventional flow coater complete painting method, Figure 3 is a layout diagram showing the positional relationship between the tube and nozzle, and Figure 4 is a partial cross section showing the state of paint adhesion to the tube. It is a diagram. Tube-4, nozzle-5m, 5b, photoelectric switch-4, piston valve-8a, 8b, paint supply pipe-7a.

Claims (1)

[Claims] A method for painting a tube, comprising atomizing paint and spraying the paint onto the tube from a plurality of nozzles disposed around the tube at predetermined intervals along the circumferential direction.