JPH07108198A - Coating device - Google Patents

Abstract

PURPOSE:To effectively prevent the generation of coating defects, such as film thickness fluctuations, by maintaining the discharge rate of an extruding thinner by a gear pump as constant as possible at the time of a color change. CONSTITUTION:This coating device is constituted to wash a coating gun 2 and coating material supply routes 3, 20, 11 to this coating gun 2 while extruding the coating materials before the color change remaining in the coating gun 2 and the coating material supply routes to the coating gun 2 by the thinner and executing the coating at the end period of the stage by the remaining coating materials. The gear pump 20 for supply is installed between the coating gun 2 and a color change valve unit 3, A regulator 16 for regulating the thinner pressure is installed between this color change valve unit and a thinner supply source 5. The coating device has a pressure sensor 18 for detecting the outlet side pressure of the gear pump 20 and a controller 19 for controlling the regulator 16 so as to equalize the outlet side pressure and the inlet side pressure of the gear pump 20 in accordance with the detection signal from the pressure sensor 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus, and more particularly to a so-called extrusion thinner for coating at the end of a process with a residual paint of a previous color at the time of color change and cleaning a coating gun and a coating supply path to the coating gun. The present invention relates to a coating device adapted to be used in a method.

[0002]

2. Description of the Related Art Conventionally, as a coating apparatus, at the time of color change, a paint gun and a paint before color change remaining in a paint supply path to the paint gun (previous color residual paint) are extruded with a paint solvent such as thinner. Thus, a so-called extrusion thinner system in which the coating gun and the coating supply path to the coating gun are cleaned while the final coating of the remaining coating is performed is well known. By adopting such an extrusion thinner method, it is possible to reduce the cost and the color change time by suppressing wasteful paint consumption at the time of color change.

By the way, a pump device is usually provided in the paint supply path to the coating gun in order to keep the supply amount of the paint constant, and this pump device is controlled to the number of revolutions by controlling the number of revolutions. A so-called gear pump, which can obtain a corresponding discharge amount, is generally widely used. Further, on the upstream side of the gear pump, a regulator for adjusting the pressure on the pump inlet side by appropriately lowering the original pressure from the supply source is generally provided between the gear pump and the coating supply source. For example, Japanese Utility Model Application Laid-Open No. 3-123557 discloses that a gear pump and a regulator are respectively provided between a color change valve unit as a color change valve device and a paint supply source for supplying paint of each color. .

As is well known, the gear pump is constructed by incorporating a rotary gear in the casing of the pump. However, variations in size, shape, etc., during processing of each component are absorbed to make the rotary gear smooth. A small gap is provided between the rotating gears and between the rotating gears and the inner wall of the casing so as to ensure the rotating operation. For this reason, when the pump is operating, a certain amount of leakage usually occurs internally through this gap, and in order to obtain the required discharge amount, this internal leak (leakage) amount must be taken into consideration before the difference between the pump inlet and outlet. It is necessary to determine pump operating conditions such as pressure and rotation speed.

[0005]

By the way, in the coating apparatus adopting the above-mentioned extrusion thinner method, at the time of color change,
It is conceivable to configure the system so that the thinner is supplied to the downstream side by using a gear pump for supplying paint, but in this case, there is a considerable difference in viscosity between the paint and the thinner, so the gear pump The internal leak amount may fluctuate significantly, which may interfere with the extrusion of the residual paint by the thinner. That is, since the viscosity of thinner is much lower than that of ordinary paint, as shown in FIG. 3, for example, the suction side (inlet side) and the discharge side (outlet side) of the gear pump are shown.
If the pressure difference ΔP is the same as
When the fluid is thinner (see the broken line in FIG. 3), the internal leak amount ΔL of the gear pump is larger than in the case of normal paint (see the solid line in FIG. 3), and the required pump discharge amount is reduced. It cannot be secured.

Therefore, the coating gun and the coating material remaining in the coating material supply path to the coating gun cannot be sufficiently extruded, and problems such as insufficient coating film thickness tend to occur. In this case, it is possible to reset the operating conditions of the gear pump according to the viscosity of the thinner, but even in this case, since the internal leak amount is originally large, the pump discharge amount fluctuates greatly and the thinner supply amount is sufficiently controlled. Since it is difficult to do so, there are problems that the coating film thickness becomes non-uniform and various coating defects easily occur.

The present invention has been made in order to solve the above problems, and when the color is changed, the discharge amount of the extrusion thinner by the gear pump is kept as constant as possible to effectively prevent the occurrence of coating defects such as film thickness variation. An object of the present invention is to provide a coating device that can be used.

[0008]

Therefore, the present invention provides
A color change valve device connected to a paint solvent supply source is arranged between the coating gun and a paint supply source capable of supplying paints of a plurality of types of colors, and at the time of color change, the color change valve device is connected to the color change valve device. By interrupting the supply of the paint and supplying the paint solvent, the paint before color change remaining in the paint gun and the paint supply path to the paint gun is extruded by the paint solvent to end the process by the remaining paint. In a coating apparatus for cleaning the coating gun and a coating supply path to the coating gun while performing coating, while a gear pump for supply is provided between the coating gun and the color change valve device, A pressure adjusting means for adjusting the pressure of the paint solvent is arranged between the color change valve device and the paint solvent supply source, and a pressure detecting means for detecting the outlet side pressure of the gear pump, and a pressure detecting means from the pressure detecting means. Based on detection signal In which the outlet pressure and the inlet-side pressure of the serial gear pump and control means for controlling said pressure adjusting means to be equal.

[0009]

According to the present invention, the pressure can be adjusted so that the pressure on the outlet side and the pressure on the inlet side of the gear pump become equal to each other. Therefore, at the time of color change, a thinner is supplied to the coating gun and the coating supply path to the gun. In this case, internal leakage of the gear pump can be eliminated. As a result, the amount of thinner supplied by the gear pump can be kept constant, and the amount of residual paint extruded to the coating gun side can be kept constant. As a result, when changing colors, in the final process of painting with the previous color paint,
It is possible to effectively prevent the occurrence of coating defects such as insufficient coating film thickness, unevenness, and color unevenness. In this case, by providing a gear pump for supply between the coating gun and the color change valve device, this gear pump can be shared for both the steps of painting and cleaning, and the number of gear pumps installed It is possible to reduce the number and simplify the coating device.

[0010]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram schematically showing the overall configuration of the coating apparatus according to this embodiment. As shown in this figure, in the coating apparatus 1, a predetermined color paint is selected for the coating gun 2 on the upstream side of the coating gun 2 which sprays the coating onto an object to be coated (not shown). A color change valve unit 3 is provided as a color change valve device for supplying electricity. The color change valve unit 3 includes a plurality of paint valves 7, and each paint valve 7 is connected to a paint supply source 4 that stores a paint of a predetermined color. A pressure adjusting valve (regulator) 15 for adjusting the supply pressure of the paint is provided in the middle of a paint supply pipe 12 connecting the paint supply source 4 and the paint valve 7 corresponding thereto.

Although FIG. 1 shows that the pressure regulating valve 15 and the paint supply source 4 are connected only to the paint valve 7 and the paint supply pipe 12 at the left end, the other paint valves 7 ,. Although not shown in the figure, the pressure regulating valve 15 and the paint supply source 4 are also shown in the same manner as the leftmost one.
Are connected. Paints of different colors are stored in the respective paint supply sources 4, and a predetermined paint valve 7 is provided.
Open and close the other paint valves 7, ..., 7
The paint of a predetermined color can be selectively introduced into the color change valve unit 3 and the paint can be supplied to the painting gun 2.

The coating apparatus 1 uses a coating solvent (thinner in this embodiment) for the paint before the color change (previous color residual paint) remaining in the paint gun 2 and the paint supply path to the paint gun 2 at the time of color change. Is a so-called extrusion thinner system, in which the coating gun 2 and the coating supply path to the coating gun 2 are cleaned while the final stage of coating is performed with the residual coating. Color change valve unit 3
An upstream end of the air valve 9 is provided with an air valve 9 for guiding compressed air from an air pressure source (not shown) into the color change valve unit 3 and a thinner valve 8 connected to the thinner supply source 5. ing.

The thinner valve 8 is opened at the time of color change, after the paint valve 7 of the previous color is closed, that is, in a state where all the paint valves 7 are closed. The thinner from the thinner supply source 5 is introduced to the valve unit 3, and this thinner allows the unpainted paint remaining in the paint gun 2 and the paint supply path to the paint gun 2 to be pushed out to the paint gun 2 side. ing. In addition, a regulator 16 as a pressure adjusting means for adjusting the supply pressure of the thinner is provided in the middle of a thinner supply pipe 13 connecting the thinner valve 8 and the thinner supply source 5.

In the present embodiment, a so-called gear pump 20 is provided in the middle of the supply pipe 11 from the color change valve unit 3 to the coating gun 2 in order to keep the amount of coating material supplied constant. This gear pump 20 is well known in the art, and for example, as shown in FIG. 2, a pair of rotary gears 22 and 23 is incorporated in a casing 21, and the rotary gears 22 and 23 are connected to a motor 17 (see FIG. 1), the fluid is discharged in the direction indicated by the alternate long and short dash line curve in FIG.
By controlling the number of revolutions of 2,23, it is possible to obtain the ejection amount according to the number of revolutions.

In the gear pump 20, as is well known, it is possible to secure the smooth rotational movement of the rotary gears 22 and 23 by absorbing the variations in the size and shape of the components 21, 22 and 23 during processing. So that this rotary gear 22,23
A small gap is provided between the rotating gears 22 and 23 and the inner wall of the casing 21. For this reason,
When the pump is operating, a certain amount of leakage usually occurs internally through this gap, and in order to obtain the required discharge amount, this internal leak (leakage) amount must be taken into consideration before the differential pressure or rotation between the pump inlet and outlet. The pump operating conditions such as the number are set.

In this embodiment, the gear pump 2 is used when changing colors.
When the extrusion thinner is supplied in place of the paint, the gear pump 20 causes the viscosity difference between the paint and the thinner.
In order to prevent the internal leak of thinner from increasing and the discharge amount of thinner to fluctuate and the extrusion effect to become insufficient, the inlet side pressure of the gear pump 20 and the inlet side pressure should be equalized. The side pressure can be adjusted. That is, the gear pump 2 of the supply pipe 11
A pressure sensor 18 for detecting the pressure (static pressure) at the outlet side of 0 is attached, and the detection signal of the pressure sensor 18 is input to the controller 19 of the coating apparatus 1. ing.

The controller 19 is mainly composed of a microcomputer, for example, and outputs a control signal to the motor 17 and the regulator 16. still,
Although not specifically shown, the controller 19
Control signals to the trigger valve (not shown) of the coating gun 2, the valves 7, ..., 7, 8, 9 of the color change valve unit 3 and the pressure adjusting valves 15 ,. It can be output. Then, at the time of color change, when supplying the extrusion thinner, the inlet side pressure of the gear pump 20 is made equal to the outlet side pressure detected by the pressure sensor 18 based on the detection signal from the pressure sensor 18. A control signal for controlling the opening of the regulator 16 is output.

As described above, according to the present embodiment, the thinner pressure can be adjusted so that the outlet side pressure and the inlet side pressure of the gear pump 20 become equal to each other. When the thinner is supplied to the paint supply paths 3, 20, 11 to the coating gun 2, the internal leak of the gear pump 20 can be eliminated. As a result,
Keep the amount of thinner supplied by the gear pump 20 constant,
It is possible to secure a constant extrusion rate of the residual paint to the coating gun 2 side. As a result, it is possible to effectively prevent the occurrence of coating defects such as insufficient coating film thickness, non-uniformity, or uneven color in the final step of coating with the previous color paint during color change. Further, in this case, by providing the supply gear pump 20 between the coating gun 2 and the color change valve unit 3, the gear pump 20 can be shared in both the steps of coating and cleaning. The number of gear pumps installed can be reduced to simplify the coating apparatus 1.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a coating apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory sectional view of a gear pump incorporated in the coating apparatus.

FIG. 3 is a graph showing changes in the internal leak amount with respect to the pressure difference between the inlet side and the outlet side of the gear pump.

[Explanation of symbols]

 1 ... Painting device 2 ... Painting gun 3 ... Color change valve unit 4 ... Painting supply source 5 ... Thinner supply source 11 ... Supply pipe 13 ... Thinner supply pipe 16 ... Regulator 18 ... Pressure sensor 19 ... Controller 20 ... Gear pump

Claims (1)

[Claims] 1. A color change valve device connected to a paint solvent supply source is arranged between a coating gun and a paint supply source capable of supplying paints of a plurality of types of colors. By shutting off the supply of paint to the valve device and supplying the paint solvent, the paint before color change remaining in the paint gun and the paint supply route to the paint gun is pushed out by the paint solvent and remains there. A coating device for cleaning the coating gun and the coating supply path to the coating gun while performing the final stage of coating with a paint, wherein a gear pump for supplying between the coating gun and the color change valve device. While providing a pressure adjusting means for adjusting the pressure of the paint solvent between the color change valve device and the paint solvent supply source, pressure detecting means for detecting the outlet side pressure of the gear pump, Detection from pressure detection means Coating apparatus being characterized in that a control means for controlling the pressure regulating means such that the outlet pressure and the inlet pressure of the gear pump equal on the basis of the issue.