JPH06304503A - Color changing device for paint and color changing method - Google Patents

Abstract

(57) [Summary] [Purpose] Prevents the occurrence of coating defects due to the mixing of push-back air into the paint. [Composition] A positive / negative reversible positive displacement pump 11 is arranged between a manifold 5 connected to a plurality of color change valves 4 and a gun side manifold 19, and the gun side manifold 19 has an air for pushing back paint. A paint color changing device provided with a supply source 22. A method of changing the color of the paint that pushes the paint in the paint hose 12 back to the positive displacement pump 11 from the gun side manifold 19 at a pressure lower than the paint circulation pressure. Positive displacement pump 1
No. 1 cannot boost the pressure of gas. Therefore, when backflowing the paint, only the paint is pushed back, the air is not returned,
Air mixing is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paint color changing device for changing a paint color from one paint color to another paint color and selectively changing the paint color when a plurality of paint colors are selectively applied by one painter. Regarding the method.

[0002]

2. Description of the Related Art When a plurality of paint colors are applied by one paint machine, a paint having an arbitrary paint color is selected by a color changing device. Generally, a method is used in which a color changing valve connected to each paint supply pipe is arranged in one manifold, and this manifold and a coating gun are connected by a hose. If a paint color in the hose is pushed out with compressed air or thinner and discharged to the outside of the system in order to change it to another color after a certain paint color is selected, the discharged paint becomes useless. However, there is also an environmental problem of discharging the organic solvent in the paint. To select this, JP-A-4-2604
Japanese Patent Laid-Open No. 63 proposes a color changing device of a painting machine in which high pressure air is sent from the hose downstream side of the paint in the hose downstream of the color changing valve and pushed back to the paint tank through the color changing valve. In this device, a flow rate sensor is provided near the color changing valve, and when the flow rate sensor detects that the paint in the hose has been exhausted, the supply of push-back air is stopped.

[0003]

However, in the color change method of the type in which the paint is pushed back to the paint tank side by using high pressure air at the time of color change, as much paint as possible in the hose is transferred to the paint tank. Since the flow sensor is placed near the color change valve to return it, even if the supply of the push-back air is stopped when the flow sensor detects that the paint in the hose is exhausted, the flow rate sensor exceeds the color change valve and reaches the upstream side. There is a problem that air is mixed into the side and the mixed air causes a crater-like defect on the work coated surface during the next coating.

An object of the present invention is to provide a paint color changing device and a color changing device which can automatically stop mixing of high-pressure air into the paint in the paint tank when pushing the paint back to the paint tank side when changing the paint color. To provide a method.

[0005]

A paint color changing apparatus and a paint color changing method of the present invention for achieving the above-mentioned object respectively include the following apparatuses and methods. (1) A manifold connected to a paint tank for each paint color through a color change valve provided for each paint color, and a paint passage provided between the manifold and the paint gun, to the paint gun for paint. Positive displacement pump for controlling the feed rate of
In the paint color changing device, the positive displacement pump is reversible, and a part of the paint path between the positive displacement pump and the coating gun is upstream from the color changing valve. A paint color changing device in which a supply device for air for pushing back paint adjusted to a pressure lower than the paint pressure on the side is connected via a valve. (2) Stop the positive displacement pump provided in the paint passage between the manifold and the paint gun, which is connected to the paint tank for each paint color via the color change valve provided for each paint color, until then. Coating of the coating color is completed, the positive displacement pump is reversed, and the paint on the downstream side of the positive displacement pump is fed back to the upstream side of the positive displacement pump, and at the same time between the positive displacement pump and the coating gun. From the paint path portion of the color change valve is sent compressed air for paint push back adjusted to a pressure lower than the paint pressure on the upstream side to push back the paint on the downstream side of the positive displacement pump to the upstream side of the positive displacement pump, Then, a cleaning agent is made to flow from the manifold side to the downstream side to wash the paint path on the downstream side from the manifold, and after washing, a color change valve for another coating color is opened, and the pump for the volume is rotated in the normal direction. Repaint the paint color How to open and change the color of paint.

[0006]

In the above apparatus and method of the present invention, when the positive displacement pump is reversed and the pushing back air is supplied, the positive displacement pump sucks the paint in the hose downstream thereof and returns it to the upstream side. The push-back air pushes the paint in the hose downstream of the positive displacement pump back to the position of the positive displacement pump. When the entire amount of the paint on the downstream side of the positive displacement pump is sent back to the upstream side of the positive displacement pump, the reverse displacement positive displacement pump automatically stops pushing back the paint because there is no paint to be sucked. In this case, the positive displacement pump can send viscous paint to the upstream side, but the air cannot flow because it leaks through the gap between the gear and the casing, and the push-back air cannot be sent to the upstream side of the positive displacement pump. Will not be sent back to.
Since the pressure of the pushback air is set to be lower than the paint pressure on the upstream side of the color change valve, the paint between the color change valve and the positive displacement pump is no longer pushed back to the paint tank side by the pushback air. There is no such thing. Therefore, the push-back air will not enter the paint tank upstream of the positive displacement pump, and will not cause craters in the next coating. It should be noted that the amount of paint in the hose downstream of the positive displacement pump is large, and by pushing it back, the amount of paint discarded is greatly reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a paint tank 1, a paint pump 2, a circulation pipe 3, and a color change valve 4 are provided for each coating color, and each circulation pipe 3 is connected via a color change valve 4 to a single unit. It is connected to one manifold 5. The structure of the color change valve 4 is as shown in FIG. 2, and the needle 4a is pneumatically turned on and off to open and close the port 4b to the manifold 5.
The paint pump 2 is constantly driven, and when the color change valve 4 is closed, the paint sent by the paint pump 2 is returned to the paint tank 1 via the return portion 3a of the circulation pipe 3, but the color change valve When 4 is open, the paint from paint pump 2 is sent to manifold 5.

A cleaning thinner supply device 6 is connected to the manifold 5 through a valve 7, and when the valve 7 is opened, the cleaning thinner from the cleaning thinner supply device 6 is sent to the manifold 5. Further, a cleaning air supply source 8 is connected to the manifold 5 via a valve 9,
When the valve 9 is opened, high-pressure air from the cleaning air supply source 8 is sent to the manifold 5. Further, a positive displacement pump 11 for quantitatively supplying the paint to the coating gun 10 is connected to the manifold 5, and the coating gun 10 is connected to the positive displacement pump 11 via a hose 12. Normal,
The distance between the coating gun 10 and the positive displacement pump 11 is much longer than the distance between the positive displacement pump 11 and the manifold 5 and the length of the manifold 5 itself. The positive displacement pump 11 and its drive device are reversibly rotatable.

The positive displacement pump 11 is, for example, a gear pump. The positive displacement pump 11 may be a vane pump or a rotary pump. The positive displacement pump 11 is rotationally driven by a servo motor 13. The servomotor 13 is composed of a reversible rotation motor, and its speed is also variable. When the servo motor 13 is normally rotated and the positive displacement pump 11 is normally rotated, the paint is sent from the manifold 5 to the coating gun 10 side, and when the servo motor 13 is reversely rotated and the positive displacement pump 11 is reversely rotated, the paint is From the paint gun 10 side to the manifold 5
Sent back to the side. A bypass supply 14 is provided for the positive displacement pump 11, and the bypass valve 1 is provided in the bypass passage 14.
5 is provided to open and close the bypass path 14. The bypass passage 14 is provided for flowing a large amount of thinner to the hose 12 during cleaning.

A trigger valve 16 is provided immediately upstream of the coating gun 10, and the paint is sprayed from the coating gun 10 when the pull valve of the trigger valve is pulled. A gun cleaning agent supplying device 17 for supplying a cleaning agent (for example, thinner) for cleaning the coating gun 10 is connected between the trigger valve 16 and the coating gun 10 via a valve 18. When the valve 18 is opened, the cleaning agent is discharged through the coating gun 10 to clean the coating gun 10. A gun-side manifold 19 is provided between the hose 12 and the trigger valve 16. The gun side manifold 19 has four ports 19a, 19b, 19c, 19 as shown in FIG.
consisting of a single manifold with d, first port 19
The a is connected to the hose 12, and the second port 19b is connected to the trigger valve 16. The third port 19c of the gun-side manifold 19 is connected via a dump valve 21 to a recovery thinner receiver 20 for recovering the thinner from the hose interior cleaning thinner supply device 6 when it is discarded.
When recovering the thinner, the dump valve 21 is opened.

Fourth port 19 on the gun side manifold 19
A push-back air supply device 22 that supplies high-pressure air that returns the paint in the hose 12 in cooperation with the positive displacement pump 11 to the upstream side of the positive displacement pump 11 is connected to the d via a valve 23. There is. The pressure of the high-pressure air supplied from the push-back air supply device 22 is set to be smaller than the paint pressure in the circulation pipe 3 on the upstream side of the color change valve 4. Accordingly, when the positive displacement pump 11 is reversed, the positive displacement pump 11 cannot send air after the entire amount of the paint in the hose 12 has been sent back to the upstream side of the positive displacement pump 11. The pressure in the circulation pipe 3 (the discharge pressure of the paint pump 2) is applied to the paint upstream of the die pump 11 from one side, and at the same time the push-back air pressure is applied from the other side, but the push-back air pressure is circulated. Since the pressure is lower than the pressure in the working pipe 3, the paint cannot be pushed back any further. Here, the reason why the positive displacement pump 11 can send the paint but cannot send the air is that the paint has a large viscosity, so that the gap between the gear 11a and the casing 11b (necessary for the rotation of the gear 11a is necessary). This is because the paint does not leak through the gap), but in the case of air, the air freely leaks through the gap between the gear 11a and the casing 11b and the pressure cannot be increased.

Next, the color changing method of the paint of the present invention which is carried out by using the above apparatus will be explained.

FIG. 5 shows the operation performed in each step and the operating state of each device at that time when the coating color of the first color is switched to the coating color of the second color.

First, during the coating of the first color in the step 1, the coating material selected by the first color changing valve 4 is sent by the positive displacement positive displacement pump 11, the hose 12 and the trigger valve 1.
It is supplied to the coating gun 10 through the nozzle 6. At this time, the valves 23, 9, 7, 18, 21 are turned off and closed.

Next, in step 2, the positive displacement pump 11 is stopped, the trigger valve 16 is also closed, and the coating of the first color is completed. At this time, the paint pump 2 of the first color remains driven, and the paint is circulated to the paint tank 1 through the return pipe 3a.

Next, in step 3, the paint of the first color is returned to the paint tank 1 side to collect the paint. For that purpose, the positive displacement pump 11 is reversed and the valve 23 is turned on to open, and high pressure air pressure from the push-back air supply device 22 is applied to the paint in the hose 12 from the downstream side to the upstream side. As a result, a large amount of paint in the hose 12 having a long distance is sucked by the positive displacement pump 11, and the circulation pipe 3
The pressure is higher than the internal pressure and returns, but the hose 12
When the paint in the interior is collected and the hose 12 becomes air only, the function of the positive displacement pump 11 to increase the pressure of the paint is lost, and the high pressure air is supplied from the positive displacement pump 11 to the manifold 5
Since it is not sent to the side, the back feeding of the paint is stopped.
In this case, if only the positive displacement pump 11 sucks and the paint for pushing back is not pushed to the upstream side, the hose 1
In some cases, the entire amount of paint in 2 may not be sent back to the upstream side of the positive displacement pump 11. Further, even if the pushing-back air is supplied, the positive displacement pump 11 that is rotating in the reverse direction cannot pressurize the air and send it to the upstream side, so that the air automatically stops at the position of the positive displacement pump 11. Therefore, air will not be mixed into the paint on the upstream side of the color changing valve 4 to cause a crater-like defect on the surface to be coated in the next coating of the first coating color. In step 3, valves 9, 7, 1
8, 16, and 21 are turned off and closed.

Next, in step 4, a small amount of the first amount of residual first paint remaining in the short paint path from the manifold 5 to the positive displacement pump 11.
The paint of this color is washed with a cleaning agent such as thinner in order to avoid mixing with the second color. The thinner of the cleaning agent and a small amount of the paint are collected in the collected thinner receiver 20.
In order to perform this cleaning, it is necessary to flow thinner than the displacement of the positive displacement pump 11, so the bypass valve 15 is opened and the valve 7 is turned on to open the thinner from the cleaning thinner device 6 to the manifold. Send to 5, positive displacement pump 11
Rotate forward. Further, the valve 21 is turned on to open and flow the thinner to be recovered to the recovery thinner receiver 20. In step 4, both the color change valve 4 for the first color and the color change valve for the second color are turned off and closed, and the valves 23, 9,
18 and 16 are also turned off and closed.

Next, in step 5, thinner, which is a cleaning agent, is purged with air. Therefore, the air valve 9 is opened to allow the air from the cleaning supply source 8 to flow into the manifold 5, and the valve 21 is opened to discharge the purge air to the collecting thinner receiver 20 side. In step 5, both the first color change valve 4 and the second color change valve 4 are closed, and the valves 23, 7, 1
8 and 16 are also turned off and closed.

Next, in step 6, the first color paint remaining on the tip of the coating gun 10 is washed. For this purpose, the valve 18 is turned on and opened, and the thinner from the gun cleaning thinner supply device 17 is discharged through the coating gun 10. In step 6, the color change valve 4, valves 23, 9, 7, 1
6, 21 are turned off and are closed.

Since the cleaning of the paint of the first color and the air purge of the cleaning agent have been completed by the above steps, the application of the paint of the second color is started in step 7. Therefore, the color change valve 4 of the first color remains closed, the color change valve 4 of the second color is turned on and opened, the positive displacement pump 11 is normally rotated, and the trigger valve 16 is turned on. Open and paint. Process 7
Valve 23, 9, 7, 18, 21 is OFF
And is closed. After that, the above is repeated.

In the above-mentioned method of the present invention, the push-back air does not go upstream from the position of the positive displacement pump 11 and is not mixed with the paint in the paint tank 1. Therefore, even if the first paint is applied again, crater-like defects on the coated surface due to the mixed air do not occur.

[0022]

According to the first aspect of the present invention, the air having a higher air pressure than the paint circulation pressure is simply sent from the coating gun side,
When the paint is returned to the paint tank, air mixes into the pipe, and it becomes fine bubbles that remain in the paint, causing craters and
Although defects such as pinholes occur, the present invention can prevent the inclusion of bubbles. In addition, when the color is changed, the paint in the hose is pushed back to the upstream of the positive displacement pump by air pressure, and the pressure is reversed by the positive displacement pump and collected in the paint tank. Was reduced from 250 cc / cycle to 10 cc / cycle. Also in the invention described in claim 2, the same effect as described above can be obtained.

[Brief description of drawings]

FIG. 1 is a system diagram of a paint color changing device according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of the vicinity of a color change valve and a manifold of the coating colors of FIG.

FIG. 3 is an enlarged sectional view of a positive displacement pump of the apparatus shown in FIG.

4 is an enlarged cross-sectional view of a gun side manifold of the apparatus of FIG.

FIG. 5 is a process chart of a paint color changing method according to an embodiment of the present invention.

[Explanation of symbols]

 1 Paint Tank 2 Paint Pump 3 Circulation Piping 4 Color Change Valve 5 Manifold 6 Cleaning Thinner Device 8 Cleaning Air Supply Source 10 Painting Gun 11 Positive Displacement Pump 12 Hose 13 Servo Motor 14 Bypass Passage 15 Bypass Valve 16 Trigger Valve 17 Gun Cleaning thinner supply device 19 Gun side manifold 20 Collected thinner receiver 22 Paint supply air supply device 23 Valve

Claims (2)

[Claims] 1. A manifold connected to a paint tank for each paint color through a color change valve provided for each paint color, and the paint applied to a paint path between the manifold and the paint gun. A paint color changing device, comprising: a positive displacement pump, which controls a feed speed to a gun, wherein the positive displacement pump is reversible, and the positive displacement pump and the positive displacement pump are included in the paint passage. In the portion between the coating gun and a paint gun, a paint push back air supply device adjusted to a pressure lower than the paint pressure on the upstream side of the color change valve is connected through the valve, and the paint color is characterized. Replacement device. 2. A positive displacement pump provided in a paint passage between a manifold and a paint gun, which is connected to a paint tank for each paint color via a color change valve provided for each paint color, is stopped. Finish the coating of the coating color until then, while reversely rotating the positive displacement pump to feed back the downstream paint from the positive displacement pump to the upstream side of the positive displacement pump,
Paint on the downstream side of the positive displacement pump by sending compressed air for pushing back the paint adjusted to a pressure lower than the paint pressure on the upstream side of the color change valve from the paint passage portion between the positive displacement pump and the coating gun. Is pushed back to the upstream side of the positive displacement pump, then a cleaning agent is flowed from the manifold side to the downstream side to wash the paint path from the manifold to the downstream side, and after the washing, a color change valve of another paint color is opened, and the volume is changed. A method for changing the color of a paint, characterized in that the mold pump is rotated in the normal direction to restart the painting of the other paint color.