Liquid level detection device and wet paint booth

Abstract

To accurately detect the liquid level in a liquid tank provided in a space where the air pressure is adjusted. [Solution] The present invention provides a liquid level detection device 30 for detecting the liquid level of a liquid tank 24 provided in a space 23 with adjusted air pressure, and comprises a liquid level control tank 31 connected to the liquid tank 24, a pressure equalization section 32 that equalizes the air pressure within the liquid level control tank 31 with the air pressure in the space 23, and a detection section 33 that detects the liquid level in the liquid level control tank 31.

Description

[Technical Field]

[0001] The present invention relates to a liquid level detection device and a wet paint booth equipped with the liquid level detection device. [Background technology]

[0002] A known wet paint booth includes a paint chamber where workpieces are placed and painted, a cleaning chamber equipped with a swirl plate, a liquid tank installed below the paint chamber and the cleaning chamber, and a partition above the liquid tank that separates the paint chamber from the cleaning chamber. In this wet paint booth, negative pressure is generated in the cleaning chamber, and air containing paint mist is drawn into the cleaning chamber through the gap between the partition and the liquid surface in the liquid tank, generating a water film and fog droplets that capture the paint mist in the air.

[0003] In such wet painting booths, the amount of treatment liquid decreases as operation continues, but in order to maintain paint mist collection performance, it is necessary to maintain the distance between the liquid level of the treatment liquid stored in the liquid tank and the partition within a specified range.

[0004] Patent Document 1 listed below proposes a technology for detecting the liquid level of the processing liquid in a liquid tank by providing a level gauge tank that is connected to the liquid tank independently from the liquid tank, detecting the liquid level in the liquid tank based on the liquid level in the level gauge tank, and controlling the liquid level of the processing liquid in the liquid tank based on the detection result. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-225361 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in order to ensure stable and continuous operation of the wet coating booth, it is necessary to detect the liquid level of the processing liquid with high accuracy.

[0007] SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a liquid level detection device capable of detecting the liquid level of a treatment liquid with high accuracy, and a wet coating booth equipped with the liquid level detection device. [Means for solving the problem]

[0008] While the inventors were diligently researching technologies for maintaining the liquid level in a wet paint booth, they discovered that detecting the liquid level in the liquid tank below the cleaning chamber is important for maintaining paint mist collection performance.

[0009] In other words, when negative pressure is generated in the cleaning chamber, a pressure difference occurs between the coating chamber and the cleaning chamber, and the liquid level in the liquid tank is higher below the cleaning chamber than below the coating chamber. If the amount of liquid in the liquid tank changes in this state, the liquid level difference between the coating chamber and the cleaning chamber also changes, but the liquid level in the cleaning chamber changes more significantly than the liquid level in the coating chamber.

[0010] Therefore, if the liquid level in the liquid tank is controlled based on the liquid level in the coating chamber, the treatment liquid may not be supplied properly to the liquid tank even though the liquid volume has decreased and the liquid level in the cleaning chamber has dropped, or the treatment liquid may be supplied excessively to the liquid tank even though the liquid level in the cleaning chamber has risen due to the supply of treatment liquid to the liquid tank.

[0011] In other words, the inventor discovered that in order to detect the liquid level that reflects the amount of liquid in the liquid tank when negative pressure is generated in the cleaning chamber, it is necessary to detect the liquid level in the cleaning chamber, which is affected by the negative pressure, and this led to the completion of the present invention.

[0012] The present invention includes the embodiments shown below.

[0013] [1] A liquid level detection device that detects the liquid level of a liquid tank located in a space with adjusted air pressure, comprising: a liquid level control tank that communicates with the liquid tank; a pressure equalization unit that equalizes the air pressure in the liquid level control tank with the air pressure in the space; and a detection unit that detects the liquid level in the liquid level control tank.

[0014] [2] A liquid level detection device according to [1] above, comprising a liquid storage tank connected to the liquid tank via a connecting pipe, and the liquid level control tank being connected to the connecting pipe and communicating with the liquid tank.

[0015] [3] The liquid level detection device according to [1] or [2] above, wherein the pressure equalizing unit includes a vent pipe connecting the space and the liquid level control tank.

[0016] [4] A wet coating booth comprising: a coating chamber in which workpieces are placed; a cleaning chamber in which negative pressure is generated to discharge purified air; a liquid tank located at the bottom of the coating chamber and the cleaning chamber; a partition section that separates the coating chamber from the cleaning chamber and forms an air inlet section between the coating chamber and the cleaning chamber and the liquid surface of the liquid tank; a spiral plate located below the partition section and within the cleaning chamber; a liquid level control tank connected to the liquid tank; a pressure equalizing section that equalizes the air pressure in the liquid level control tank with the air pressure in the cleaning chamber; and a detection section that detects the liquid level in the liquid level control tank.

[0017] [5] A wet coating booth as described in [4] above, comprising a liquid storage tank connected to the liquid tank via a connecting pipe, and the liquid level control tank being connected to the connecting pipe and communicating with the liquid tank.

[0018] [6] The wet paint booth according to [4] or [5] above, wherein the pressure equalizing section is provided with a ventilation pipe connecting the cleaning chamber and the liquid level control tank. [Effects of the Invention]

[0019] According to the present invention, the liquid level of the processing liquid that accurately reflects the liquid volume in the liquid tank can be detected with high precision. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic cross-sectional view of a wet paint booth according to an embodiment of the present invention; [Figure 2] Block diagram showing the control configuration of the wet paint booth in Figure 1 DETAILED DESCRIPTION OF THE INVENTION

[0021] A wet paint booth 10 according to one embodiment of the present invention will be described with reference to the drawings.

[0022] (1) Overview of Wet Paint Booth 10 As shown in Figure 1, the wet paint booth 10 includes a paint chamber 11 in which the workpiece (object to be painted) W is placed, an exhaust device 20 that exhausts air from the paint chamber 11, a liquid level detection device 30 that detects the liquid level of the treated water in a liquid tank 24 provided in the exhaust device 20, and a control device 50 for the wet paint booth 10.

[0023] In the wet painting booth 10, for example, a worker holds a painting device in a painting room 11 to paint a workpiece W, and the paint mist generated during this process is captured by an exhaust device 20 and exhausted outside the painting room 11.

[0024] In this embodiment, the wet paint booth 10 will be described as a natural air intake type booth that does not have an air intake device to pressurize air into the paint chamber 11. However, the wet paint booth 10 may also be a push-pull type booth in which air is pressurized from an air intake device to the paint chamber 11 and the air in the paint chamber 11 is sucked into an exhaust device 20 and exhausted.

[0025] (2) Exhaust system 20 Next, a specific configuration of the exhaust device 20 will be described.

[0026] The exhaust device 20 comprises an exhaust fan motor 22 that drives the exhaust fan 21, a cleaning chamber 23 which is a space whose interior is adjusted to a negative pressure by the exhaust fan 21, and a liquid tank 24 provided below the coating chamber 11 and the cleaning chamber 23, and captures paint mist and dust with treatment liquid (water, paint treatment agent, etc.) stored in the liquid tank 24.

[0027] The cleaning chamber 23 is provided with a partition 25 facing the coating chamber 11. The partition 25 separates the coating chamber 11 from the cleaning chamber 23 above the liquid tank 24. A sawtooth-shaped sawtooth portion 25a is provided on the lower side of the partition 25, and a gap 26 is formed between the sawtooth portion 25a and the liquid surface of the treatment liquid stored in the liquid tank 24. The gap 26 between the sawtooth portion 25a and the liquid surface of the treatment liquid functions as an air inlet 26 that draws air from the coating chamber 11 into the cleaning chamber 23. A swirl plate 27 and multiple eliminators 28 are provided inside the cleaning chamber 23. The swirl plate 27 is provided at the bottom of the partition 25, and a portion of it extends toward the coating chamber 11 below the liquid surface of the treatment liquid.

[0028] The exhaust fan 21 and the exhaust fan motor 22 are provided at the top of the cleaning chamber 23. The exhaust fan 21 generates negative pressure in the cleaning chamber 23 by being driven to rotate by the exhaust fan motor 22, and the air in the cleaning chamber 23 is sucked upward and discharged to the outside through the exhaust duct 29.

[0029] When the exhaust fan 21 rotates and the exhaust device 20 operates, an ascending air current is generated in the cleaning chamber 23, and air from the coating chamber 11 flows into the cleaning chamber 23 through the air inlet 26 located between the saw blade portion 25a and the liquid surface of the liquid tank 24. At this time, paint mist and dust contained in the air are captured by the treatment liquid near the saw blade portion 25a. The treatment liquid that has captured the paint mist and dust is drawn into the cleaning chamber 23 via the vortex plate 27 following the ascending air current in the cleaning chamber 23. The treatment liquid drawn into the cleaning chamber 23 is broken into droplets as it passes through the vortex plate 27, rises while hitting multiple eliminators 28, and is drained before being discharged to the outside through the exhaust duct 29 by the exhaust fan 21.

[0030] (3) Liquid level detection device 30 Next, we will explain the liquid level detection device 30. The liquid level detection device 30 includes a liquid level control tank 31, a pressure equalizing unit 32, a detection unit 33, and a liquid storage tank 34, and detects the liquid level in the liquid tank 24 below the cleaning chamber 23, the interior of which is in a negative pressure state due to the operation of the exhaust device 20.

[0031] Specifically, the liquid level control tank 31 is connected to the liquid tank 24 via a connecting pipe 35, allowing the processing liquid to move between the liquid level control tank 31 and the liquid tank 24. In other words, the liquid level control tank 31 communicates with the liquid tank 24 via the connecting pipe 35, and contains the processing liquid up to a level corresponding to the liquid level of the liquid tank 24. The liquid level control tank 31 is preferably an airtight container.

[0032] The pressure equalizing unit 32 equalizes the air pressure inside the liquid level control tank 31 with the air pressure inside the cleaning chamber 23. In this embodiment, the pressure equalizing unit 32 is made up of a vent pipe that connects the inside of the cleaning chamber 23 with the liquid level control tank 31, and equalizes the pressure between the cleaning chamber 23 and the liquid level control tank 31.

[0033] Because the pressure equalizing unit 32 equalizes the pressure inside the liquid-level control tank 31 with the atmospheric pressure inside the cleaning chamber 23, when the exhaust device 20 operates and the pressure inside the cleaning chamber 23 becomes negative, the pressure inside the liquid-level control tank 31 also becomes negative. As a result, the liquid level of the processing liquid in the liquid-level control tank 31 rises compared to when the pressure inside the liquid-level control tank 31 is at atmospheric pressure, and becomes approximately equal to the liquid level in the liquid tank 24 below the cleaning chamber 23. In other words, the liquid level in the liquid tank 24 located below the cleaning chamber 23 when the exhaust device 20 is operating can be simulated inside the liquid-level control tank 31.

[0034] The detection unit 33 is a level gauge that detects the level of the treatment liquid in the liquid level control tank 31. Various types of level gauges can be used for the detection unit 33, but a non-contact level gauge such as a laser type or ultrasonic type is preferable. When the detection unit 33 detects the level of the treatment liquid in the liquid level control tank 31, it transmits the detection result to the control device 50.

[0035] The liquid storage tank 34 is a container that stores the processing liquid supplied from a supply device 36 via a supply pipe 37. The liquid storage tank 34 is connected to the liquid tank 24 by a connecting pipe 35, allowing the processing liquid to move between the liquid storage tank 34 and the liquid tank 24. In this embodiment, a liquid level control tank 31 is connected to the middle of the connecting pipe 35 that connects the liquid storage tank 34 and the liquid tank 24. When the amount of processing liquid in the liquid tank 24 decreases and the liquid level in the liquid tank 24 below the cleaning chamber 23 drops, the processing liquid is supplied to the liquid storage tank 34 from the supply device 36.

[0036] (4) Control device 50 As shown in FIG. 2, the control device 50 is configured by, for example, a computer, and is connected to the exhaust fan motor 22, the detection unit 33, the supply device 36, and a control panel 38 for operating the control device 50.

[0037] When the control device 50 receives an instruction to start the wet paint booth 10 from the control panel 38, it starts the exhaust fan motor 22 to rotate the exhaust fan 21 at a predetermined rotation speed to operate the wet paint booth 10. This generates negative pressure in the cleaning chamber 23, causing air from the painting chamber 11 to flow into the cleaning chamber 23 through the air inlet 26, and paint mist and dust are removed inside the cleaning chamber 23 before being exhausted to the outside.

[0038] Furthermore, when the liquid level in the liquid level control tank 31, input from the detection unit 33 of the liquid level detection device 30, falls below a predetermined level while the wet coating booth 10 is in operation, the control device 50 causes the supply device 36 to supply a predetermined amount of treatment liquid to the liquid storage tank 34. Immediately after the treatment liquid is supplied to the liquid storage tank 34, the liquid level in the liquid storage tank 34 rises, but thereafter the treatment liquid in the liquid storage tank 34 flows into the liquid level control tank 31 and the liquid tank 24 via the connecting pipe 35, and the liquid levels in the liquid storage tank 34, the liquid level control tank 31, and the liquid tank 24 are equalized. As a result, the treatment liquid in the liquid storage tank 34 is supplied to the liquid tank 24, and the liquid level in the liquid tank 24 below the cleaning chamber 23 rises and is adjusted to an appropriate level.

[0039] (5) Effects In this embodiment, the pressure equalizing unit 32 equalizes the pressure inside the liquid level control tank 31 with the atmospheric pressure inside the cleaning chamber 23, thereby making it possible to simulate the liquid level of the liquid tank 24 located below the cleaning chamber 23 when the exhaust device 20 is in operation, inside the liquid level control tank 31. Therefore, by detecting the liquid level in the liquid level control tank 31 with the detection unit 33, it is possible to detect the liquid level of the liquid tank 24 located below the cleaning chamber 23 when the exhaust device 20 is in operation, and the liquid level in the liquid tank 24 can be maintained at an appropriate level even when the wet paint booth 10 is in operation.

[0040] In this embodiment, the pressure equalizing section 32 consists of an air vent pipe connecting the inside of the cleaning chamber 23 and the liquid level control tank 31, so that the air pressure inside the liquid level control tank 31 can be made equal to the air pressure inside the cleaning chamber 23 with a simple configuration without requiring a power source or control signal.

[0041] In this embodiment, the liquid level control tank 31 is connected to the connecting pipe 35 connecting the liquid storage tank 34 and the liquid tank 24. When the amount of treatment liquid in the liquid tank 24 decreases due to operation of the wet coating booth 10 or when treatment liquid is supplied to the liquid storage tank 34 from the supply device 36, the treatment liquid flows through the connecting pipe 35 from the liquid storage tank 34 to the liquid tank 24. However, the treatment liquid in the liquid tank 24 containing the captured paint mist and dust is unlikely to flow from the liquid tank 24 to the liquid level control tank 31. This allows the treatment liquid in the liquid level control tank 31 to be maintained at a high level, preventing erroneous detection by the detection unit 33. Furthermore, because the treatment liquid in the liquid level control tank 31 is highly clean, various types of level gauges can be used as the detection unit 33.

[0042] (6) Example of change Next, modified examples will be described. Various modifications can be made to the above embodiment without departing from the spirit of the invention. Several modified examples will be described below, and any one of the modified examples described below may be applied to the above embodiment, or any two or more of the modified examples described below may be applied in combination. Furthermore, in addition to the modified examples below, various omissions, substitutions, and modifications can be made without departing from the spirit of the invention.

[0043] (6-1) Change example 1 In the above embodiment, the liquid level detection device 30 was described as being applied to a wet painting booth 10, but the liquid level detection device 30 can be applied to various devices to detect the liquid level in a liquid tank located in a space with adjusted air pressure.

[0044] (6-2) Change example 2 In the above embodiment, the pressure equalizing unit 32 is constituted by a vent pipe connecting the interior of the cleaning chamber 23 and the liquid-level control tank 31, but the pressure equalizing unit 32 is not limited to this. For example, the pressure equalizing unit may be constituted by an air pressure detection unit that detects the air pressure inside the cleaning chamber 23, an air pressure adjustment unit that can supply and exhaust air inside the liquid-level control tank 31, and a control device that controls these, and the air pressure inside the liquid-level control tank 31 may be made equal to the air pressure inside the cleaning chamber 23 by the control device controlling the air pressure adjustment unit based on the detection value of the air pressure detection unit.

[0045] (6-3) Change example 3 In the above-described embodiment, the liquid level control tank 31 is connected midway through the connecting pipe 35 connecting the liquid storage tank 34 and the liquid tank 24, and part of the connecting pipe connecting the liquid storage tank 34 and the liquid tank 24 is made common to the connecting pipe connecting the liquid level control tank 31 and the liquid tank 24, or the connecting pipe connecting the liquid storage tank 34 and the liquid tank 24 and the connecting pipe connecting the liquid level control tank 31 and the liquid tank 24 may be provided separately. [Explanation of symbols]

[0046] 10...wet paint booth, 11...painting room, 20...exhaust device, 21...exhaust fan, 22...exhaust fan motor, 23...cleaning room, 24...liquid tank, 25...partition section, 25a...saw blade section, 26...air introduction section, 27...volute plate, 28...eliminator, 29...exhaust duct, 30...liquid level detection section, 31...liquid level control tank, 32...pressure equalization section, 33...detection section, 34...liquid storage tank, 35...connecting pipe, 36...supply device, 37...supply pipe, 50...control device

Claims

1. A liquid level detection device for detecting the liquid level of a liquid tank provided in a space where the air pressure is adjusted, a liquid level control tank communicating with the liquid tank; a pressure equalizing unit that equalizes the air pressure in the liquid level control tank with the air pressure in the space; a detection unit for detecting the liquid level in the liquid level control tank; a liquid storage tank connected to the liquid tank via a connecting pipe; Equipped with The liquid level detection device has the liquid level control tank connected to the connecting pipe and communicating with the liquid tank.

2. The liquid level detection device according to claim 1 , wherein the pressure equalizing section includes a vent pipe connecting the space and the liquid level control tank.

3. a paint room in which the workpiece is placed; a cleaning chamber that generates negative pressure and discharges purified air; a liquid tank disposed below the coating chamber and the cleaning chamber; a partition section that separates the coating chamber from the cleaning chamber and forms an air inlet section between the partition section and the liquid surface of the liquid tank; a swirl plate provided below the partition and within the cleaning chamber; a liquid level control tank communicating with the liquid tank; a pressure equalizing unit that equalizes the air pressure in the liquid level control tank with the air pressure in the cleaning chamber; a detection unit for detecting the liquid level in the liquid level control tank; a liquid storage tank connected to the liquid tank via a connecting pipe; Equipped with The liquid level control tank is connected to the connecting pipe and communicates with the liquid tank.

4. A wet paint booth as described in Claim 3, wherein the equalizing section is provided with a ventilation pipe connecting the cleaning chamber and the liquid level control tank.

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