Method and device for cleaning paint supply path

Abstract

To reduce cleaning fluid consumption with a simplified structure.SOLUTION: In a first stage of a cleaning process, when a pump 6 is activated, cleaning fluid in a container 34 is sucked by a suction pipe 10, and cleaning is performed using the cleaning fluid. An amount of cleaning fluid flowing into the added container 34 through a small hole 36 is less than an amount suctioned by the pump 6. As cleaning in the first stage progresses, the fluid level of the cleaning fluid in the added container 34 decreases. When the fluid level of the cleaning fluid in the container 34 approaches a suction port 10a of the suction pipe 10, the cleaning process automatically proceeds to a second stage, and air in the added container 34 is sucked together with the cleaning fluid by the pump 6. As a result, the cleaning fluid mixed with bubbles is generated at an upstream end of the suction pipe 10, and a paint supply path 20 is cleaned using the cleaning fluid mixed with bubbles.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a technique for cleaning a paint supply path for supplying paint from a paint source to a painting machine, and more particularly to a method and an apparatus for cleaning a paint supply path.

Background Art

[0002] As a typical example, in a painting process for painting an automobile body, for example, a "cleaning process" is carried out when "changing the color" to paints of different colors. In the cleaning process, the paint supply path is cleaned using a cleaning liquid.

[0003] Patent Document 1 describes in detail a cleaning process for a paint supply path including a painting machine. Patent Document 1 discloses a method for cleaning a paint supply path including a painting machine by supplying a cleaning liquid to the paint supply path under pressure. Summarizing the description of Patent Document 1, conventionally, the paint supply path has been cleaned by supplying a cleaning liquid to the paint supply path under pressure from the beginning to the end of the cleaning process, but there has been a problem that a large amount of cleaning liquid is required. In response to this problem, a method of cleaning the paint supply path using a cleaning liquid mixed with air bubbles in which air is mixed in the cleaning liquid has been adopted.

[0004] As a result of verifying the correlation between the supply of the cleaning liquid and the cleaning effect in the cleaning process, the inventor of Patent Document 1 discovered the fact that the cleaning efficiency rapidly increases with the passage of time at the initial stage of starting to clean with the cleaning liquid, but thereafter, the increase in the cleaning efficiency becomes slow. Based on this fact, Patent Document 1 proposes the following cleaning method and cleaning apparatus.

[0005] Specifically, Patent Document 1 proposes a method of cleaning a paint supply path by alternately switching a cleaning liquid and air to clean the paint supply path. That is, based on a predetermined time chart, first, the cleaning liquid is supplied to the paint supply path under pressure for a predetermined time, then switched from the cleaning liquid to air, and air is supplied to the paint supply path for a predetermined time. Next, it is switched from air to the cleaning liquid, and the cleaning liquid is supplied to the paint supply path for a predetermined time. Further, the cleaning device disclosed in Patent Document 1 has an on-off valve for the cleaning liquid and an on-off valve for air at the upstream end of the paint supply path, and the on-off valves for the cleaning liquid and air are alternately switched between open and closed based on a predetermined time chart. By using this cleaning device, the supply of the cleaning liquid and the supply of air can be sequentially switched to clean the paint supply path.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a method and a device for cleaning a paint supply path that can reduce the amount of cleaning liquid used with a simple configuration.

Means for Solving the Problems

[0008] The cleaning method and cleaning device of the present invention are characterized in that instead of using a cleaning liquid supplied under pressure in the conventional manner to clean the paint supply path, the cleaning liquid is sucked in by itself and the paint supply path is cleaned with the sucked cleaning liquid.

[0009] In order to achieve the above problems, according to the present invention, basically, A method for cleaning a paint supply path for supplying paint from a paint source to a painting machine, The paint supply path has a pump and a suction pipe communicating with the pump. A suction pipe installation step of inserting an upstream end portion of the suction pipe into a cleaning liquid tank that stores a cleaning liquid and is open to the atmosphere; Next, a pump starting step of starting the pump; A bubble-mixed cleaning liquid generation step of sucking air together with the cleaning liquid into the suction pipe through a suction port of the suction pipe by the suction force of the pump, and generating a bubble-mixed cleaning liquid at the upstream end portion of the suction pipe; and There is provided a method for cleaning a paint supply path with the bubble-mixed cleaning liquid.

[0010] The effects and other objects of the present invention will become apparent from the following description of the preferred embodiments of the present invention.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

Examples

[0012] Figure 1 shows an overview of a well-known paint supply system for supplying paint to a painting machine. In the figure, reference numeral 2 indicates the painting machine, and reference numeral 4 indicates the paint tank of the paint source. The paint tank is composed of a tank open to the atmosphere. A pump 6 and a branch valve 8 are interposed between the paint tank 4 and the painting machine 2, and the paint in the paint tank 4 is sucked through a suction pipe 10 by the pump 6. Figure 1 illustrates an example in which a diaphragm pump is employed as the pump 6. The paint discharged from the pump 6 is supplied to the branch valve 8 through a discharge pipe 12, and the paint is supplied from the branch valve 8 to the painting machine 2 and sprayed. On the other hand, the unused paint is returned to the paint tank 4 through a return pipe 14. That is, the branch valve 8 is composed of a three-way valve, and the paint circulates in a state of passing through the three-way valve and being returned to the paint tank 4. The paint supplied from the suction pipe 10 to the three-way valve is supplied to the painting machine 2 by the operation of the three-way valve according to an external signal and is sprayed from the painting machine 2.

[0013] The cleaning method according to the present invention can be suitably applied to the cleaning of a paint supply path 20 composed of a suction pipe 10, a pump 6, a discharge pipe 12, a branch valve 8, and a return pipe 14. Note that the cleaning of the painting machine 2 from the branch valve 8 is performed by another system.

[0014] For reference, a conventional cleaning method of the paint supply path 20 will be described with reference to FIG. 2. In the preparation step before the cleaning step, first, in the suction pipe 10, the upstream end including the suction port 10a is removed from the paint tank 4, and the upstream end of the suction pipe 10 is inserted into a cleaning liquid tank 22. The cleaning liquid tank 22 is composed of a tank open to the atmosphere. Note that the suction port 10a of the suction pipe 10 is composed of a filter attachment 40. The cleaning liquid tank 22 contains a cleaning liquid CL. In the preparation step, second, the downstream end of the return pipe 14 is removed from the paint tank 4 and inserted into a waste liquid tank 24. The waste liquid tank 24 is composed of a tank open to the atmosphere. The preparation step is completed by performing the above first and second operations.

[0015] Once the preparation process is completed, the cleaning of the paint supply path 20 is started by activating the pump 6. The contaminated cleaning liquid generated in the cleaning process is stored in the waste liquid tank 24 through the return pipe 14.

[0016] Examples (Figs. 3 to 7): In the cleaning method of the example, the cleaning device 30 shown in Fig. 3 is used. The cleaning device 30 basically includes a base plate 32 and an additional container 34. The additional container 34 has a form in which one end (the lower end in Fig. 3) of the cylindrical member is closed by the base plate 32. That is, the additional container 34 has a form in which the upper end is open to the atmosphere and the bottom surface is constituted by the base plate 32. Note that in the cleaning liquid tank 22 containing the cleaning liquid CL, the additional container 34 with an open atmosphere is used in a state of standing upright upward from the base plate 32 (Fig. 4).

[0017] Referring to Fig. 4, the cleaning device 30 is a relatively heavy object made of, for example, stainless steel, and the base plate 32 has a size to prevent the cleaning device 30 from tipping over in the cleaning liquid tank 22. In the cleaning liquid tank 22 containing the cleaning liquid CL, the cleaning device 30 has the base plate 32 touching the bottom surface of the cleaning liquid tank 22, and the additional container 34 standing up from the base plate 32 maintains its upright posture.

[0018] When the cleaning device 30 is installed in the cleaning liquid tank 22, the additional container 34 has a length dimension such that its open upper end is located above the liquid level of the cleaning liquid CL in the cleaning liquid tank 22.

[0019] The additional container 34 is provided with a circular small hole 36 at the lower end (Fig. 3). The small hole 36 has a function of allowing the cleaning liquid CL in the cleaning liquid tank 22 to flow into the additional container 34 while restricting the inflow amount. Through the small hole 36, the amount of the cleaning liquid CL flowing into the additional container 34 is less than the suction amount by the pump 6. The additional container 34 may be provided with one small hole 36, but it is preferably provided with a plurality of small holes 36.

[0020] The small hole 36 is an example of a flow rate regulating opening that restricts the amount of cleaning liquid flowing from the cleaning liquid tank 22 into the additional container 34. The shape of the flow rate regulating opening is arbitrary. The flow rate regulating opening may be one or more non-circular holes or one or more slits instead of the one or more circular small holes 36.

[0021] As described above, the flow rate regulating opening, of which the small hole 36 is a typical example, has a function of allowing the cleaning liquid CL in the cleaning liquid tank 22 to flow into the additional container 34 while restricting the inflow amount. Regarding the function of restricting the inflow amount, preferred specific examples will be described below.

[0022] Assuming that the flow rate at which the pump 6 sucks in the cleaning liquid is Qp and the inflow amount of the cleaning liquid flowing into the additional container 34 through the small hole 36 is Qh, Qp > Qh is an absolute condition. The preferred relationship between Qp and Qh is 0.3xQp < Qh < 0.7xQp. By designing the size of the flow rate regulating opening, for example, so that this condition is satisfied, the amount of cleaning liquid used can be reduced by 30% to 70% compared to the conventional cleaning method that uses only the cleaning liquid. More preferably, 0.4xQp < Qh < 0.6xQp. By designing the size etc. of the flow rate regulating opening so that this condition is satisfied, the amount of cleaning liquid used can be halved compared to the conventional cleaning method that uses only the cleaning liquid.

[0023] Referring to FIG. 3, the cleaning device 30 of the embodiment preferably includes a plurality of orifice members 38 having different passage cross-sectional areas. The orifice member 38 has a threaded portion 38a, while the circular small hole 36 is formed by a threaded hole. If necessary, the orifice member 38 having a preferred passage cross-sectional area is detachably screwed into the small hole 36. Thereby, the substantial effective opening area of the small hole 36 can be adjusted by the orifice member 38. By selecting the orifice member 38 having an appropriate passage cross-sectional area, the amount of the cleaning liquid CL flowing into the additional container 34 can be adjusted.

[0024] The orifice member 38 is detachable from the small hole 36 by screw engagement. As a modification, a configuration in which the orifice member 38 is detachably fitted into the small hole 36 may be adopted.

[0025] The inner diameter InD (FIG. 3) of the additional container 34 opened to the atmosphere is preferably set based on the diameter Di of the filter attachment 40 disposed at the upstream end of the suction pipe 10. Specifically, the upstream end portion including the filter attachment 40 is preferably inserted into the additional container 34 from the upper end opening of the additional container 34 and set to the minimum necessary value as much as possible.

[0026] With reference to FIGS. 4 to 6, the operation of the cleaning device 30 of the embodiment will be described. In FIGS. 4 to 6, the illustration of the filter attachment 40 is omitted to avoid complication of the line diagram. The following preparations are made before cleaning the paint supply path 20. Referring to FIG. 4, in the preparation step, the cleaning device 30 is installed in the cleaning liquid tank 22 containing the cleaning liquid CL. Since the upper end of the additional container 34, which is a main component of the cleaning device 30, is open to the atmosphere, when the cleaning device 30 is installed in the cleaning liquid tank 22, immediately, the cleaning liquid CL in the cleaning liquid tank 22 flows into the additional container 34 through the small hole 36, and within a short time, the additional container 34 is filled with the cleaning liquid. Next, the upstream end portion of the suction pipe 10 is removed from the paint tank 4 and inserted into the additional container 34 from the upper end opening of the additional container 34. The suction pipe 10 is positioned such that its suction port 10a is separated from the bottom of the additional container 34 and near the lower end of the container 34. Also, the return pipe 14 is removed from the paint tank 4, and the downstream portion of this return pipe 14 is inserted into the waste liquid tank 24 opened to the atmosphere. By performing the above operations, the preparation for cleaning the paint supply path 20 is completed.

[0027] Once the above preparations are completed, the cleaning process is started by activating the pump 6. The cleaning process is composed of a first stage and a second stage in chronological order. In the first stage, the cleaning liquid in the additional container 34 is sucked by the pump 6 through the suction pipe 10, and the paint supply path 20 is cleaned using the cleaning liquid (Fig. 5). The contaminated cleaning liquid used for cleaning is stored in the waste liquid tank 24 open to the atmosphere. As a result, most of the paint remaining in the paint supply path 20 is removed from the paint supply path 20.

[0028] In the first stage, as the cleaning liquid in the additional container 34 is sucked by the suction pipe 10, the liquid level of the cleaning liquid in the additional container 34 decreases, and at the same time, through the small hole 36, the cleaning liquid CL in the cleaning liquid tank 22 open to the atmosphere flows into the container 34. The relationship between the amount of the cleaning liquid flowing into the container 34 through the small hole 36 and the suction amount of the pump 6 is as described above. That is, the opening area of the small hole 36 is set so that the amount of the cleaning liquid flowing into the additional container 34 through the small hole 36 is less than the suction amount by the pump 6 as described above (Fig. 3). When the small hole 36 is circular, the diameter of the small hole 36 is preferably 1 mm to 5 mm. This 1 mm to 5 mm is merely an example.

[0029] When the cleaning using the cleaning liquid CL performed in the first stage progresses, it automatically shifts to the second stage and is cleaned with the cleaning liquid mixed with air bubbles. That is, when the liquid level of the cleaning liquid in the additional container 34 approaches the suction port 10a of the suction pipe 10, the air above the cleaning liquid in the additional container 34 is sucked by the pump 6 in a state of being mixed into the cleaning liquid (Fig. 6). That is, due to the action of the suction force of the pump 6, air is sucked into the suction pipe 10 together with the cleaning liquid through the suction port 10a of the suction pipe 10. As a result, the upstream end of the suction pipe 10 constitutes a part of the cleaning device 30, and a cleaning liquid mixed with air bubbles is generated at the upstream end of the suction pipe 10. Thereby, in the second stage, the upstream end of the suction pipe 10 exhibits a function of generating a cleaning liquid mixed with air bubbles, and the paint supply path 20 is cleaned with the cleaning liquid mixed with air bubbles.

[0030] As described above, the amount of the cleaning liquid CL flowing into the additional container 34 through the small hole 36 is less than the suction amount of the pump 6. Therefore, in the second stage, when the liquid level of the cleaning liquid in the additional container 34 drops to the vicinity of the suction port 10a of the suction pipe 10, the number of bubbles contained in the cleaning liquid mixed with bubbles increases. However, until the operation of the pump 6 stops, the cleaning of the paint supply path 20 with the cleaning liquid mixed with bubbles continues.

[0031] The base plate 32 and the container 34 included in the above-described cleaning device 30 have a structure in which one additional container 34 is arranged on the base plate 32. As a modification, as shown in FIG. 7, a configuration in which a plurality (for example, four) of additional containers 34 are arranged on one base plate 32 may be provided. In the paint supply system illustrated in FIG. 1, when a gear pump is employed as the pump 6, it is desirable to simultaneously clean the four paint supply paths 20 associated with each of the four painting machines 2. The modification illustrated in FIG. 7 can meet this requirement.

Explanation of Reference Numerals

[0032] 2 Painting machine 4 Paint tanks (paint sources) 6 Pump 8 Branch valve 10 Suction pipe 10a Suction port of the suction pipe 12 Discharge pipe 14 Return pipe 20 Paint supply path 22 Cleaning tank with open atmosphere CL Cleaning liquid contained in the cleaning liquid tank 30 Cleaning device 32 Base plate 34 Additional container open to the atmosphere 36 Small hole (flow rate regulating opening) 38 Orifice member

Claims

1. A method for cleaning a paint supply path for supplying paint from a paint source to a painting machine, comprising: the paint supply path having a pump and a suction pipe communicating with the pump; a suction pipe installation step of inserting an upstream end portion of the suction pipe into a cleaning liquid tank that stores a cleaning liquid and is open to the atmosphere; subsequently, a pump starting step of starting the pump; a bubble-mixed cleaning liquid generation step of sucking air into the suction pipe together with the cleaning liquid through a suction port of the suction pipe by the suction force of the pump to generate a bubble-mixed cleaning liquid at the upstream end portion of the suction pipe; and a method for cleaning a paint supply path, wherein the paint supply path is cleaned with the bubble-mixed cleaning liquid.

2. In the method for cleaning a paint supply path according to Claim 1, further comprising a container installation step of installing an additional container open to the atmosphere in the cleaning liquid tank before the suction pipe installation step, the additional container having a flow rate regulating opening at a lower end portion, the flow rate regulating opening having a function of allowing the cleaning liquid in the cleaning liquid tank to flow into the additional container while restricting the inflow amount thereof; in the suction pipe installation step, the upstream end portion of the suction pipe is inserted into the additional container; a first-stage cleaning is performed in which the pump operates by the pump starting step and sucks up the cleaning liquid in the additional container by the suction force of the pump to clean the paint supply path; and as the first-stage cleaning progresses, the liquid level of the cleaning liquid in the additional container drops, and when the liquid level reaches near the suction port of the suction pipe, it automatically switches to a second-stage cleaning, and the bubble-mixed cleaning liquid generation step is performed. A method for cleaning a paint supply path.

3. In the method for cleaning a paint supply path according to Claim 2, when the flow rate of the cleaning liquid sucked by the pump is Qp and the cleaning liquid flowing into the additional container through the flow rate regulating opening is Qh, the relationship between Qp and Qh is Qp > Qh. A method for cleaning a paint supply path.

4. In the method for cleaning a paint supply path according to Claim 2, when the flow rate of the cleaning liquid sucked by the pump is Qp and the cleaning liquid flowing into the additional container through the flow rate regulating opening is Qh, the relationship between Qp and Qh is 0.3xQp < Qh < 0.7xQp. A method for cleaning a paint supply path.

5. In the method for cleaning a paint supply path according to Claim 2, When the flow rate at which the pump sucks in the cleaning liquid is Qp and the cleaning liquid flowing into the additional container through the flow rate regulating opening is Qh, the relationship between Qp and Qh is 0.4xQp < Qh < 0.6xQp. A method for cleaning a paint supply path.

6. In the method for cleaning a paint supply path according to any one of claims 1 to 5, The method for cleaning a paint supply path, wherein the flow rate regulating opening is constituted by one or a plurality of small holes.

7. In the method for cleaning a paint supply path according to any one of claims 1 to 5, The method for cleaning a paint supply path, wherein the flow rate regulating opening is constituted by one or a plurality of slits.

8. A cleaning device for cleaning a paint supply path having a pump and a suction pipe communicating with the pump and for supplying paint from a paint source to a painting machine. The cleaning device is used in a cleaning liquid tank that stores a cleaning liquid for cleaning the paint supply path and is open to the atmosphere. In a preparation step before the cleaning step of cleaning the paint supply path, the upstream end of the suction pipe is inserted into the cleaning tank. In the cleaning step, the upstream end of the suction pipe has a function of sucking air together with the cleaning liquid into the suction pipe through the suction port of the suction pipe by the suction force of the pump, and generating a cleaning liquid mixed with bubbles at the upstream end of the suction pipe. A cleaning device.

9. In the cleaning device according to claim 8, The cleaning device includes an additional container with a closed lower end and an open upper end to the atmosphere. The additional container has a length that is located above the liquid level of the cleaning liquid in the cleaning liquid tank when the cleaning device is installed in the cleaning liquid tank. The container is provided with one or a plurality of flow rate regulating openings at the lower end. The flow rate regulating opening has a function of allowing the cleaning liquid in the cleaning liquid tank to flow into the additional container while restricting the amount of the cleaning liquid flowing into the additional container. A cleaning device in which, in a preparation step before the cleaning step of cleaning the paint supply path, the upstream end of the suction pipe is inserted into the additional container installed in the cleaning liquid tank.

10. In the cleaning device according to claim 9, The container further includes a base plate that constitutes the bottom surface of the additional container. The base plate has a size that touches the bottom of the cleaning liquid tank and keeps the additional container standing upright when the cleaning device is installed in the cleaning liquid tank. A cleaning device.

11. In the cleaning device according to claim 9 or 10, The cleaning device, wherein the flow rate regulating opening is composed of one or a plurality of small holes.

12. In the cleaning device according to claim 9 or 10, Further comprising a plurality of orifice members having different passage cross-sectional areas, The cleaning device, wherein each orifice member can be detachably fixed to the small hole.

13. In the cleaning device according to claim 9 or 10, The cleaning device, wherein the flow rate regulating opening is composed of one or a plurality of slits.

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