Drip prevention mechanism for two-fluid spray system

Abstract

To provide a liquid sagging prevention mechanism of a two-fluid spray device which prevents liquid sagging in residual water, shortens a time to stop of spray, reduces the influence of a height of installation of a first non-return valve or the influence of an external environment such as air biting, and enhances robust property.SOLUTION: A bypass pipe 22 is provided which connects a first air supply pipe 14 and a secondary side of a first non-return valve 5 of a second water supply pipe 6 through a second non-return valve 21, supplies air to the second water supply pipe from the first air supply pipe only when a primary side pressure of the second non-return valve is higher than a secondary side pressure thereof, and discharges water in the second water supply pipe and a two-fluid nozzle 1. The first non-return valve has a predetermined cracking pressure larger than a difference between a residual pressure on the primary side of the first non-return valve 5 and an atmospheric pressure. When water supply is stopped, a pressure difference between the primary side of the first non-return valve and the secondary side thereof is less than the cracking pressure, water does not flow and spray is stopped, the pressure on the primary side of the second non-return valve becomes higher than the pressure on the secondary side thereof, and water in the second water supply pipe and the nozzle is discharged by air supply.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a liquid dripping prevention mechanism for a two-fluid spraying device that sprays gas and liquid in the form of mist.

Background Art

[0002] Conventionally, in a factory, fine particles with a Sauter mean diameter of about 10 μm are sprayed as ultrafine mist from a two-fluid mist nozzle of gas and liquid for humidification. This makes it difficult to generate static electricity and prevents deterioration of manufacturing quality such as foreign matter adhesion or malfunction of equipment, or an increase in product defect rate. For example, in the component mounting process, it is possible to prevent problems caused by static electricity such as electrostatic breakdown of components or poor mounting of the substrate, and it is also possible to improve the comfort of the working space or reduce the cooling and air conditioning load due to the cooling effect of the heat of vaporization. Thus, mist spraying by a two-fluid mist nozzle does not require a large boiler or the like, can locally humidify while reducing running costs, and its introduction is welcomed from the perspective of CO2 reduction.

[0003] As shown in FIG. 5A, such a spraying device using a two-fluid mist nozzle has a main water pipe 104 connected to a water supply source 102 via an on-off control valve 103 for water, and a mist nozzle 101 is connected to the downstream end of a plurality of branched water pipes 106 whose upstream ends are connected to the main water pipe 104. Also, a main air pipe 114 is connected to an air supply source 112 via an on-off control valve 113 for air, and a mist nozzle 101 is connected to the downstream end of a plurality of branched air pipes 116 whose upstream ends are connected to the main air pipe 114. The control panel controls the opening and closing of each control valve 103, 113 based on the humidity detected by the humidity sensor to control the mist spraying.

[0004] In such a spraying device, when the mist spraying stops due to some factor, liquid dripping occurs from the tip of the mist nozzle 101.

[0005] To prevent this, a method has been proposed that uses an extrusion system, which includes a bypass path 122 that can supply air from the main air pipe 114 to the water branch pipe 106 via an on / off valve 121. By using the bypass path 122 to push out and blow away the water in the water branch pipe 106 with air, the system aims to prevent dripping from the nozzle 101 (Patent Document 1).

[0006] However, in large factories, for example, all the water in a 50m-long water branch pipe 106 must be drained, which increases the time required to stop spraying. Furthermore, when spraying starts, water must be refilled into the water branch pipe 106 before spraying can begin, which also increases the time required to start spraying.

[0007] To solve this problem, a residual pressure release method is known, as shown in Figure 5B, in which, when spraying stops, a drain valve 130 connected to the main water pipe 104 is opened to reduce the water pressure in the main water pipe 104 and release the residual pressure, and the water pressure in the branch water pipe 106 is also reduced, keeping the water pressure upstream of the mist nozzle 101 lower than atmospheric pressure, thereby preventing water from flowing into the nozzle 101 and preventing dripping. The check valve 125 of the branch water pipe 106 has the function of preventing backflow of air from the nozzle 101 and maintaining negative pressure. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent application No. 2022-556972 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, such devices are susceptible to the influence of the liquid piping path, as well as the influence of the air layer within the liquid piping path, and also suffer from issues such as dripping (water dripping from the nozzle tip). In other words, unless the water pressure upstream of the nozzle is controlled to be below atmospheric pressure, taking into account the effects of the head difference due to the vertical length of the liquid piping, the influence of the air layer within the liquid piping path (i.e., air entrapment), or both of these effects, dripping will occur.

[0010] Therefore, the object of the present invention is to solve the above problems and provide a drip prevention mechanism for a two-fluid spray device that is less affected by the liquid piping path, less affected by the air layer within the liquid piping path, prevents dripping, in other words, prevents dripping due to residual water, shortens the time until spraying stops, reduces the influence of the height at which the first check valve is installed or the influence of external environmental factors such as air entrapment, and increases robustness. [Means for solving the problem]

[0011] To achieve the aforementioned objective, the present invention is configured as follows.

[0012] According to one aspect of the present invention, a gas and a liquid are supplied to at least one two-fluid nozzle that sprays the gas and the liquid, A water supply source that supplies water as the liquid is connected via a first on-off valve to a first water supply pipe that supplies the water, A second water supply pipe connects the first water supply pipe and the liquid-side inlet of the two-fluid nozzle via a first check valve, and supplies water from the first water supply pipe to the liquid-side inlet of the two-fluid nozzle. A first air supply pipe is connected via a second on-off valve to an air supply source that supplies air as a gas at a pressure lower than the water supply pressure, and supplies the air. A two-fluid spray device comprising a first air supply pipe and a second air supply pipe that connects the first air supply pipe to the gas-side inlet of the two-fluid nozzle and supplies the air from the first air supply pipe to the gas-side inlet of the two-fluid nozzle, The first air supply pipe and the secondary side of the first check valve of the second water supply pipe are connected via a second check valve, and air is supplied from the first air supply pipe to the second water supply pipe only when the pressure in the first air supply pipe on the primary side of the second check valve is higher than the pressure in the second water supply pipe on the secondary side of the second check valve, and a bypass pipe is provided to discharge water from the second water supply pipe and the two-fluid nozzle, The first check valve has a predetermined cracking pressure greater than the pressure difference between the residual pressure on the primary side of the first check valve and atmospheric pressure. When the difference between the pressure on the primary side of the first check valve, which is the first water supply pipe, and the pressure on the secondary side, which is the second water supply pipe, exceeds the cracking pressure of the first check valve, water flows from the first water supply pipe to the second water supply pipe via the first check valve through the first water supply pipe, the second water supply pipe, and the nozzle, and the spraying is performed. When the first shut-off valve is closed to stop the supply of water from the water source to the first water supply pipe, the difference between the pressure on the primary side of the first check valve (the first water supply pipe side) and the pressure on the secondary side (the second water supply pipe side) becomes less than the cracking pressure of the first check valve, and the water does not flow from the first water supply pipe to the second water supply pipe via the first check valve through the first water supply pipe, the second water supply pipe and the nozzle, thus stopping the spray. Furthermore, as the water supply is stopped, the pressure on the primary side of the second check valve in the bypass pipe becomes higher than the pressure on the secondary side, and air is supplied from the first air supply pipe to the second water supply pipe, causing the water in the second water supply pipe and the nozzle to be discharged. This invention provides a drip prevention mechanism for a two-fluid spray device. [Effects of the Invention]

[0013] According to the above-described aspect of the present invention, air is supplied from the first air supply pipe to the second water supply pipe only when the pressure in the first air supply pipe on the primary side of the second check valve is higher than the pressure in the second water supply pipe on the secondary side of the second check valve, and a bypass pipe is provided through which water in the second water supply pipe and the two-fluid nozzle is discharged, and the first check valve is configured to have a predetermined cracking pressure greater than the pressure difference between the residual pressure on the primary side of the first check valve and atmospheric pressure. Therefore, when the first on-off valve is closed and the water supply is stopped, the pressure difference between the primary and secondary sides of the first check valve becomes less than the cracking pressure, and the water does not flow through the first water supply pipe, the second water supply pipe and the nozzle via the first check valve, thus stopping the spray. Furthermore, as the water supply is stopped, the pressure on the primary side of the second check valve in the bypass pipe becomes higher than the pressure on the secondary side, and air is supplied from the first air supply pipe to the second water supply pipe, causing the water in the second water supply pipe and the nozzle to be discharged. As a result, there is no dripping due to residual water, the time until spraying stops is shortened, the influence of the height at which the first check valve is installed or the influence of external environmental factors such as air entrapment is reduced, and robustness is increased. [Brief explanation of the drawing]

[0014] [Figure 1] Schematic diagram showing the configuration of a two-fluid spray device according to one embodiment of the present invention. [Figure 2] Perspective view showing the nozzle area of ​​a two-fluid spray system, including the drip prevention mechanism. [Figure 3A] Diagram illustrating a configuration in which a third check valve without cracking pressure is installed in a branch pipe for water. [Figure 3B] Graph showing the relationship between water pressure and time in the configuration of Figure 3A. [Figure 3C] Diagram illustrating a configuration that includes a bypass pipe to spray water from the nozzle when spraying stops. [Figure 3D] This graph shows the relationship between water pressure and time in a configuration of the two-fluid spray device of this embodiment, in which a first check valve having a predetermined cracking pressure is installed in the branch pipe of the water. [Figure 3E]Explanation diagram of conditions for more reliably preventing liquid dripping from each nozzle, even though water remains in the main water pipe, in this embodiment (some pipes are omitted) [Figure 4A] Explanation diagram of the spray standby operation of the two-fluid spray device according to this embodiment [Figure 4B] Explanation diagram of the spray operation of the two-fluid spray device according to this embodiment [Figure 4C] Explanation diagram of the operation of draining water in each nozzle of the two-fluid spray device according to this embodiment [Figure 4D] Explanation diagram of the humidity in the installation space of the two-fluid spray device according to this embodiment and the opening and closing states of each valve [Figure 5A] Explanation diagram of a conventional configuration for preventing liquid dripping by an extrusion method [Figure 5B] Explanation diagram of a conventional configuration for preventing liquid dripping by a residual pressure release method

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments according to the present invention will be described in detail based on the drawings.

[0016] FIG. 1 is a schematic diagram showing the configuration of a two-fluid spray device according to this embodiment, and FIG. 2 is an example of an integrated four-direction nozzle body in which air flows in from above and branches in four directions and water flows in from below and branches in four directions, and is a perspective view showing the vicinity of the nozzle including the liquid dripping prevention mechanism of the two-fluid spray device.

[0017] The two-fluid spray device according to this embodiment includes at least one two-fluid nozzle 1, a main water pipe 4 as an example of a first water supply pipe, a branched water pipe 6 as an example of a second water supply pipe, a main air pipe 14 as an example of a first air supply pipe, and a branched air pipe 16 as an example of a second air supply pipe.

[0018] The two-fluid nozzle 1 is arranged to be suspended from a fixture 41 attached to, for example, the main water pipe 4 and the main air pipe 14 of the factory, and at least one, for example, more than one, specifically four in Figure 1, are provided, to which a gas, such as air, and a liquid, such as water, are supplied respectively, and the air and water are sprayed in a mist. As an example, the four nozzles 1 are arranged in a cross shape along the horizontal direction, with the spray openings of the nozzles 1 facing in four directions, and the height of each spray opening is approximately the same.

[0019] The main water pipe 4 is arranged, for example, to extend laterally along the ceiling of the factory and is connected to a water supply source 2 that supplies water as a liquid via a first on-off valve 3 to supply water. By opening and closing the first on-off valve 3, the supply of water from the water supply source 2 to the main water pipe 4 is controlled and stopped. The first on-off valve 3 is configured as a water solenoid valve unit 3A having a water solenoid valve as an example.

[0020] The water branch pipe 6 is, for example, a branch pipe that extends downward from the main water pipe 4, which is arranged along the ceiling of the factory, and is mostly arranged vertically. It connects the main water pipe 4 and the liquid side inlet of the two-fluid nozzle 1 via a first check valve 5, supplying water from the main water pipe 4 to the liquid side inlet of the two-fluid nozzle 1. The water branch pipe 6 includes, for example, a common water branch pipe 6a whose upstream end is connected to the main water pipe 4 and which has a first check valve 5 located in the middle, and individual water branch pipes 6b whose upstream ends are connected to the downstream end of the common water branch pipe 6a and whose downstream ends are connected to the liquid side inlet of each two-fluid nozzle 1.

[0021] The main air piping 14 is arranged, for example, to extend laterally along the ceiling of the factory and is connected via a second on-off valve 13 to an air supply source 12 that supplies air as a gas at a pressure lower than the water supply pressure. By opening and closing the second on-off valve 13, the supply of air from the air supply source 12 to the main air piping 14 is controlled and stopped. The second on-off valve 13 is configured as an air solenoid valve unit 13A having an air solenoid valve as an example.

[0022] The air branch pipe 16 branches off from the main air pipe 14, which is, for example, located along the ceiling of the factory, and is mostly arranged vertically so as to extend downwards. It connects the main air pipe 14 to the gas-side inlet of the two-fluid nozzle 1, supplying air from the main air pipe 14 to the gas-side inlet of the two-fluid nozzle 1.

[0023] The drain valve 30 is installed in the middle of the drain pipe 31, which is branched from the main water pipe 4 downstream of the first shut-off valve 3. When the first shut-off valve 3 is opened, the drain valve 30 is closed, and when the first shut-off valve 3 is closed, it is opened to drain the water in the main water pipe 4 and reduce the residual pressure. However, when the first shut-off valve 3 is closed, the drain valve 30 is temporarily opened to drain the water. If the drain valve 30 remains open, eventually all the water in the main water pipe 4 will be drained. The drainage here is to reduce the water pressure in the main water pipe 4, not to drain all the water from the main water pipe 4. On the contrary, if all the water in the main water pipe 4 is drained, it will be necessary to fill the main water pipe 4 with water the next time it is started, which will take time and waste water. When the first shut-off valve 3 is used as an opening valve, it is configured to open in only one direction.

[0024] The drain pan 32 consists of a round tray suspended from a fixing device 41 attached to the main water pipe 4 and the main air pipe 14, and positioned below the four nozzles 1. In the event that liquid drips from the spray nozzles 1, the drain pan 32 catches it, preventing the installation space from getting wet.

[0025] Furthermore, the two-fluid spray device is equipped with a bypass pipe 22 as a drip prevention mechanism, and the first check valve 5 has a predetermined cracking pressure greater than the pressure difference between the residual pressure on the primary side of the first check valve 5 and atmospheric pressure.

[0026] First, the bypass piping 22 connects the main air piping 14 and the downstream side, or secondary side, of the first check valve 5 of the water branch piping 6 via the second check valve 21. This second check valve 21 ensures that air is supplied from the main air piping 14 to the water branch piping 6 only when the pressure on the primary side of the second check valve 21, i.e., the pressure inside the main air piping 14, is higher than the pressure on the secondary side of the second check valve 21, i.e., the pressure on the secondary side of the first check valve 5 of the water branch piping 6. As a result, water inside the water branch piping 6 and the nozzle 1 is discharged from the spray port of the nozzle 1. The second check valve 21 also ensures that when the pressure inside the main air piping 14 is less than or equal to the pressure downstream of the first check valve 5 of the water branch piping 6, neither air nor water flows through the bypass piping 22.

[0027] Furthermore, a predetermined cracking pressure is set for the first check valve 5, which is greater than the pressure difference between the residual pressure on the primary side of the first check valve 5 and atmospheric pressure.

[0028] Here, we will explain in detail the arrangement of the bypass piping 22 and the drip prevention mechanism, which involves setting a predetermined cracking pressure in the first check valve 5.

[0029] Regarding preventing dripping, we have considered the following:

[0030] First, let's consider a configuration in which a third check valve 105 without cracking pressure is installed in the water branch pipe 106, as shown in Figure 3A.

[0031] In this configuration, closing the first on-off valve 103 and opening the drain valve 130 to drain the main water pipe 104 and release the residual pressure in the main water pipe 104 stops the water supply to the nozzle 101. However, if the water pressure remaining on the primary side of the third check valve 105 is greater than atmospheric pressure, the water will flow towards the nozzle due to that pressure, resulting in dripping (see Figure 3B). Therefore, it is necessary to drain the water until the residual pressure on the primary side of the third check valve 105 falls below atmospheric pressure, which takes time to stop the spray. Furthermore, even if the water on the primary side of the third check valve 105 does not flow, if the gas supply pressure is removed, there is a problem that a small amount of water remaining in the nozzle 101 will flow out of the nozzle 101, causing a fine spray.

[0032] Therefore, in order to prevent fine spraying from the nozzle 101, a configuration is considered in which a bypass pipe 122 is provided to spray water from inside the nozzle 101 when spraying stops, as shown in Figure 3C.

[0033] Even with this configuration, it takes time to drain the water until the residual pressure on the primary side of the third check valve 105 falls below atmospheric pressure, resulting in high running costs. Furthermore, there are issues such as low robustness due to the height at which the third check valve 105 is installed or air entrapment.

[0034] To solve these problems, as shown in Figures 1 and 3D, the two-fluid spray device of this embodiment is configured such that a first check valve 5 having a predetermined cracking pressure (greater than 0 kPa, for example 50 kPa) greater than the pressure difference between the residual pressure on the primary side of the first check valve 5 and atmospheric pressure is installed in the water branch pipe 6. With this configuration, when the difference between the residual pressure on the primary side of the first check valve 5 and atmospheric pressure falls below 50 kPa, the water supply to the nozzle 1 is stopped and no dripping occurs. Therefore, there is no need to wait until the residual pressure on the primary side of the first check valve 5 falls below atmospheric pressure, and the time until spraying stops is shortened. In addition, the influence of the height at which the first check valve 5 is installed vertically below the main water pipe 4, or the influence of external environmental factors such as air entrapment, is reduced, and robustness is improved. In other words, if the cracking pressure is set to a pressure lower than the difference between the residual pressure on the primary side of the first check valve 5 and atmospheric pressure, cracking will occur and liquid leakage will occur. However, if the cracking pressure is set to a pressure higher than the difference between the residual pressure on the primary side of the first check valve 5 and atmospheric pressure, cracking will not occur, that is, water will not flow to the nozzle side through the first check valve 5, and liquid leakage can be prevented. Therefore, the cracking pressure should be set to be at least greater than the difference between the residual pressure on the primary side of the first check valve 5 and atmospheric pressure.

[0035] Furthermore, the vertical arrangement relationship between the water solenoid valve of the first on-off valve 3 and the first check valve 5 will be explained. In other words, the conditions under which dripping is more reliably prevented from each nozzle 1, even though water remains in the main water pipe 4, will be explained based on Figure 3E.

[0036] A water solenoid valve unit 3A, which has a water solenoid valve as the first on-off valve 3, contains a pressure sensor (not shown) that detects the water pressure in the main water pipe 4 downstream of the first on-off valve 3.

[0037] By opening the drain valve 30, which is installed in the middle of the drain pipe 31 that branches off from the main water pipe 4 downstream of the first shut-off valve 3, the water in the main water pipe 4 can be drained to atmospheric pressure through the drain pipe 31. The drain valve 30 is closed by control of a control unit 50 such as a control panel when the pressure sensor detects a predetermined value or when a predetermined time has elapsed after the drain valve has been opened.

[0038] For example, suppose the drain valve 30 is set to close when the pressure sensor's detected value P1 reaches 150 kPa. In this case, when the water head H1 from the main water pipe 4 in the ceiling to the water solenoid valve unit 3A is 2 m, or 2 × 9.8 = 19.6 kPa, the pressure in the main water pipe 4, i.e., the ceiling pipe pressure P2, will be P2 = P1 - H1 = 150 - 19.6 = 130.4 kPa. Therefore, when the detected value P1 is 20 kPa, the drain valve 30 is closed and the flow is blocked, and according to Bernoulli's theorem, the pressure in the main water pipe 4 in the ceiling will remain constant at 130.4 kPa.

[0039] In this case, assuming that the first check valve 5 is located 1 m below the main water pipe 4, when the water head H2 from the main water pipe 4 to the first check valve 5 is 1 m = 9.8 kPa, the primary side pressure P3 of the first check valve 5 is P3 = P2 + H2 = 130.4 + 9.8 = 140.2 kPa. Air is supplied to the secondary side of the first check valve 5 via the bypass pipe 22 and the air branch pipe 16, and pneumatic pressure is acting on it. However, when the air supply is eventually stopped and the pressure returns to atmospheric pressure, (P3 - atmospheric pressure) < cracking pressure 50 kPa, and the difference (P3 - atmospheric pressure ≈ 38.9 kPa) cannot exceed the cracking pressure of 50 kPa. Therefore, the water remaining in the main water pipe 4 on the ceiling does not flow from the primary side to the secondary side of the first check valve 5, and despite water remaining in the main water pipe 4, no liquid drips from each nozzle 1. Note that when using gauge pressure, atmospheric pressure becomes the zero reference point, and the values ​​are relative to it. However, for the sake of easier understanding, the pressures explained here are absolute values.

[0040] In this case, when draining, if you wait until the pressure sensor's detected value P1 reaches atmospheric pressure, a negative pressure will be created without setting a cracking pressure, and the water will not flow. However, this will significantly increase the time required for draining.

[0041] Therefore, by setting a cracking pressure for the first check valve 5 and using the time elapsed until the detected value P1 of the pressure sensor reaches 150 kPa, the spray stop operation time is shortened. In conclusion, from the above considerations, the cracking pressure of the first check valve 5 should be set to a pressure greater than the difference between the sum of the pressure P2 of the main water pipe 4 and the water head H2 from the main water pipe 4 to the first check valve 5 and atmospheric pressure.

[0042] With this configuration, since water remains in the pipes 4 and 6 between the first on-off valve 3 and the first check valve 5, it is possible to achieve the effect of faster startup when resuming spraying.

[0043] In the two-fluid spray device according to this embodiment, the second check valve 21 of the bypass piping 22 can be positioned, for example, near the secondary side of the first check valve 5. With this configuration, the distance from the secondary side of the first check valve 5 to the secondary side of the second check valve 21 via the bypass piping 22 can be shortened, thereby reducing the amount of residual water that accumulates in this path after spraying stops. This improves robustness against dripping.

[0044] Furthermore, it is preferable that the secondary side of the second check valve 21 is positioned below the spray opening of the nozzle 1 and connected by a U-shaped pipe or the like. This configuration allows the bypass pipe 22 to be shortened, thereby reducing the amount of water remaining inside the pipe 22. Also, when the secondary side of the second check valve 21 is positioned below the spray opening of the nozzle 1 rather than above it, water is less likely to flow through the pipe, making it more effective in preventing dripping.

[0045] Furthermore, when multiple nozzles 1 are arranged, for example, the first check valve 5 and the second check valve 21 can be placed on the primary side of two adjacent nozzles 1. This configuration allows for space saving and eliminates any influence on mist spraying, as the sprayed mist will not wet the first check valve 5 and the second check valve 21.

[0046] Furthermore, the first check valve 5, which has cracking pressure, can be used as a substitute for a relief valve. With this configuration, the relief valve has less variation in flow rate components, ensuring a stable flow rate.

[0047] Next, the operation of the two-fluid spray device according to this embodiment will be described, including the spray standby operation, the spray operation, and the operation of draining water from each nozzle 1.

[0048] <Spray standby operation> As shown in Figures 4A and 4D, both the first on-off valve 3 for water and the second on-off valve 13 for air are closed. Therefore, the water supply pressure and air supply pressure to each pipe 4, 6, 14, 16 and each nozzle 1 are zero, and neither water nor air is supplied to each nozzle 1. As a result, spraying is stopped and the system is in standby mode.

[0049] <Spraying operation> As shown in Figures 4B and 4D, both the first on-off valve 3 and the second on-off valve 13 are opened to achieve a predetermined humidity level through spraying. For example, a water supply pressure (i.e., water pressure) of 0.449 MPa (absolute pressure) (= gauge pressure 0.348 MPa + atmospheric pressure 0.101 MPa) and an air supply pressure (i.e., air pressure) of 0.353 MPa (absolute pressure) (= gauge pressure 0.252 MPa + atmospheric pressure 0.101 MPa) are supplied to the respective pipes 4, 6, 14, and 16 and each nozzle 1. Specifically, air at an air pressure of 0.353 MPa is supplied from the air supply source 12 to each nozzle 1 via the main air pipe 14 and the branch air pipe 16. Water at a water pressure of 0.449 MPa is supplied from the water supply source 2 to each nozzle 1 via the main water pipe 4 and the branch water pipe 6. At each nozzle 1, air and water are supplied to perform mist spraying.

[0050] Here, at point C at the upstream end of the bypass pipe 22, an air pressure of 0.353 MPa in the main air pipe 14 acts, and at point D at the downstream end, a water pressure of 0.449 MPa in the main water pipe 4 acts. Since the pressure at point C, about 0.353 MPa of air pressure < the pressure at point D, about 0.449 MPa of water pressure, water does not flow from point D to point C due to the second check valve 21.

[0051] When air or water is flowing through the pipe, there is a pressure loss, so the pressure drops. However, if it is assumed that the main pipes for air and water use pipes with a sufficiently large diameter, the influence of the pressure loss becomes small. Therefore, it can be considered that the pressure at any point in the pipe is approximately the supply pressure. However, since the branch pipes for air and water that branch from the main pipe and branch to the nozzles have a smaller diameter than the main pipe, some pressure loss occurs. Strictly speaking, the pressures before and after the second check valve 21 do not exactly match the values of each supply pressure, but they are close to those values. So, it can be said that they are pushing against each other with pressures of about each supply pressure. Also, on the water side, it is necessary to consider the water heads H1 and H2. As this difference, several tens of kPa is taken into account on the primary side of the first check valve 5. Including this, it is recognized as being about the supply pressure.

[0052] On the other hand, before water flows through the main water pipe 4 etc., air flows to point B on the secondary side of the first check valve 5 faster than water through the bypass pipe 22. Therefore, an air pressure acts on point B. Thus, while point B has a pressure of about 0.353 MPa of air pressure, when water flows through the main water pipe 4, point A on the primary side of the first check valve 5 has a pressure of about 0.449 MPa of the water pressure in the main water pipe 4. Therefore, since the pressure difference between point A and point B exceeds the cracking pressure of 50 KPa, water flows from point A to point B through the first check valve 5, and water is supplied to each nozzle 1 through the water branch pipe 6.

[0053] <Operation to drain water in each nozzle 1> As shown in Figures 4C and 4D, when the spraying stops after the humidity reaches a predetermined level, the first shut-off valve 3 for water is closed to stop the water flow (at this time, for example, P1 will not become atmospheric pressure because there is residual pressure in the main water pipe 4). Therefore, the drain valve 30 of the drain pipe 31, which is branched and connected from the main water pipe 4 downstream of the first shut-off valve 3, is opened to drain the water in the main water pipe 4 and reduce the residual pressure, thereby lowering the water pressure and maintaining negative pressure. When the water supply is stopped, only air is supplied to the main air pipe 14 and continues to be supplied to each nozzle 1 via the air branch pipe 16. At this time, the air supplied to the main air pipe 14 flows through the bypass pipe 22 to the water branch pipe 6 and each nozzle 1, blowing out the water in the bypass pipe 22, the water branch pipe 6, and each nozzle 1.

[0054] Specifically, at point C of the bypass pipe 22, the air pressure of the main air pipe 14, approximately 0.353 MPa, acts, eliminating the water pressure acting at point D, resulting in atmospheric pressure. As a result, the air pressure at point C (approximately 0.353 MPa) is greater than the atmospheric pressure at point D, allowing air to flow from point C to point D via the second check valve 21. This blows out and discharges all the water from the bypass pipe 22 through the water branch pipe 6 to nozzle 1, as well as the water in pipes 22, 6, and nozzle 1. The air supply is stopped after all the water in each nozzle 1 has been blown out. "All the water has been blown out" means, for example, 10 seconds, although this may vary depending on the length of the pipes, as defined by time control.

[0055] On the other hand, at point B, a pressure of approximately 0.353 MPa acts until the air supply is stopped, and at point A, the residual pressure is less than the sum of atmospheric pressure and cracking pressure due to the water supply being stopped. Therefore, the pressure difference between the two points does not exceed the cracking pressure of 50 kPa at the first check valve 5. As a result, even if water remains in the main water pipe 4, that water will not flow from point A to point B. The cracking pressure is designed to be the primary side pressure P3 of the first check valve 5 (residual pressure when water is stopped) - atmospheric pressure < cracking pressure, so the primary side pressure P3 of the first check valve 5 will be discharged until it becomes atmospheric pressure + cracking pressure.

[0056] <Spray standby operation> As shown in Figures 4A and 4D, after blowing out all the water in each nozzle 1 and then stopping the air supply, both the first water valve 3 and the second air valve 13 are closed. As a result, the water supply pressure and air supply pressure to each pipe 4, 6, 14, 16 and each nozzle 1 are zero, and neither water nor air is supplied to each nozzle 1.

[0057] If the height from the maximum height of the main water pipe 4 to point A is, for example, a maximum of 2m (approximately 20kPa), and the height from the main water pipe 4 to the water solenoid valve unit 3A is a maximum of 3m (approximately 30kPa), the cracking pressure of the first check valve 5 will not exceed 50kPa, and therefore water will not flow from the main water pipe 4 due to the water head.

[0058] When spraying is stopped (in spray standby mode), the primary side of the first check valve 5 in the water path is full of water and is being pushed by the water head. The secondary side of the first check valve 5 can be considered to be at atmospheric pressure even if there is residual water.

[0059] On the other hand, during spraying, air flows from the bypass path 22 to the secondary side of the first check valve 5. The air pressure decreases slightly due to pressure loss relative to the air supply pressure, but this is negligible, and the air pressure on the secondary side of the first check valve 5 can be considered equivalent to the "air supply pressure." Meanwhile, on the primary side of the first check valve 5, cracking pressure is at play, and initially, there is residual pressure before water can pass through, with a vertical water head acting as part of that residual pressure. When water supply begins, the water pressure increases, resulting in a situation where the water supply pressure plus the water head pressure is applied. The first check valve 5 finally opens when the pressure on the primary side of the first check valve 5 (= water supply pressure + water head pressure) > air supply pressure (- air pressure loss (negligible and negligible)) + cracking pressure. When water flows out, the pressure loss within the water piping must also be considered. Therefore, the water pressure on the primary side of the first check valve 5 is, at this time, the water supply pressure + hydrostatic pressure - pressure loss. In addition, pressure loss also occurs in the first check valve itself when water passes through it. The water supply pressure is defined as the pressure (P1) supplied from the solenoid valve unit 3A, which has the first on-off valve 3 for water, to the main water piping 4.

[0060] According to the above embodiment, air is supplied from the main air pipe 14 to the water branch pipe 6 only when the pressure in the main air pipe 14 on the primary side of the second check valve 21 is higher than the pressure in the water branch pipe 6 on the secondary side of the second check valve 21, and a bypass pipe 22 is provided to discharge water from the water branch pipe 6 and the nozzle 1. The first check valve 5 is configured to have a predetermined cracking pressure greater than the pressure difference between the residual water pressure on the primary side of the first check valve 5 and atmospheric pressure. Therefore, when the first shut-off valve 3 is closed and the water supply is stopped, the pressure difference between the primary and secondary sides of the first check valve 5 becomes less than the cracking pressure, and water does not flow through the main water pipe 4, the branch water pipe 6, and the nozzle 1 via the first check valve 5, stopping the spray. Furthermore, as the water supply is stopped, the pressure on the primary side of the second check valve 21 in the bypass pipe 22 becomes higher than the pressure on the secondary side, and air is supplied from the main air pipe 14 to the branch water pipe 6, causing the water in the branch water pipe 6 and the nozzle 1 to be discharged. As a result, no dripping occurs due to residual water, the time until spraying stops is shortened, the influence of the height at which the first check valve 5 is installed or external environmental factors such as air entrapment is reduced, and robustness is increased.

[0061] Furthermore, by appropriately combining any embodiment or modification from the various embodiments or modifications described above, the effects of each can be achieved. In addition, it is possible to combine embodiments with each other, or embodiments with each other, or embodiments with each other, as well as to combine features from different embodiments or embodiments. (Note) Based on the above description of embodiments, the following technologies are disclosed.

[0062] (Technology 1) A gas and a liquid are supplied, and at least one two-fluid nozzle sprays the gas and the liquid, A water supply source that supplies water as the liquid is connected via a first on-off valve to a first water supply pipe that supplies the water, A second water supply pipe connects the first water supply pipe and the liquid-side inlet of the two-fluid nozzle via a first check valve, and supplies water from the first water supply pipe to the liquid-side inlet of the two-fluid nozzle. A first air supply pipe is connected via a second on-off valve to an air supply source that supplies air as a gas at a pressure lower than the water supply pressure, and supplies the air. A two-fluid spray device comprising a first air supply pipe and a second air supply pipe that connects the first air supply pipe to the gas-side inlet of the two-fluid nozzle and supplies the air from the first air supply pipe to the gas-side inlet of the two-fluid nozzle, The first air supply pipe and the secondary side of the first check valve of the second water supply pipe are connected via a second check valve, and air is supplied from the first air supply pipe to the second water supply pipe only when the pressure in the first air supply pipe on the primary side of the second check valve is higher than the pressure in the second water supply pipe on the secondary side of the second check valve, and a bypass pipe is provided to discharge water from the second water supply pipe and the two-fluid nozzle, The first check valve has a predetermined cracking pressure greater than the pressure difference between the residual water pressure on the primary side of the first check valve and atmospheric pressure. When the difference between the pressure on the primary side of the first check valve, which is the first water supply pipe, and the pressure on the secondary side, which is the second water supply pipe, exceeds the cracking pressure of the first check valve, water flows from the first water supply pipe to the second water supply pipe via the first check valve through the first water supply pipe, the second water supply pipe, and the nozzle, and the spraying is performed. When the first shut-off valve is closed to stop the supply of water from the water source to the first water supply pipe, the difference between the pressure on the primary side of the first check valve (the first water supply pipe side) and the pressure on the secondary side (the second water supply pipe side) becomes less than the cracking pressure of the first check valve, and the water does not flow from the first water supply pipe to the second water supply pipe via the first check valve through the first water supply pipe, the second water supply pipe and the nozzle, thus stopping the spray. Furthermore, as the water supply is stopped, the pressure on the primary side of the second check valve in the bypass pipe becomes higher than the pressure on the secondary side, and air is supplied from the first air supply pipe to the second water supply pipe, causing the water in the second water supply pipe and the nozzle to be discharged. A drip prevention mechanism for a two-fluid spray system.

[0063] With this configuration, when the first on-off valve is closed and the water supply is stopped, the pressure difference between the primary and secondary sides of the first check valve becomes less than the cracking pressure, and the water does not flow through the first water supply pipe, the second water supply pipe and the nozzle via the first check valve, thus stopping the spray. Furthermore, as the water supply is stopped, the pressure on the primary side of the second check valve in the bypass pipe becomes higher than the pressure on the secondary side, and air is supplied from the first air supply pipe to the second water supply pipe, causing the water in the second water supply pipe and the nozzle to be discharged. As a result, no dripping occurs due to residual water, the time until spraying stops is shortened, the influence of the height at which the first check valve is installed or the influence of external environmental factors such as air entrapment is reduced, and robustness is increased.

[0064] (Technical 2) The first water supply pipe extends laterally along the ceiling side of the space in which the nozzle is installed, The second water supply pipe extends along the vertical direction of the installation space of the nozzle, and the first check valve is located in the second water supply pipe. The cracking pressure of the first check valve is set to a pressure greater than the difference between the sum of the pressure in the first water supply pipe and the water head from the first water supply pipe to the first check valve and atmospheric pressure (i.e., P3 - atmospheric pressure). A drip prevention mechanism for the two-fluid spray device described in Technical 1.

[0065] With this configuration, when the air supply is eventually stopped after the water supply is stopped and atmospheric pressure is restored, (P3 - atmospheric pressure) < cracking pressure, and the difference (P3 - atmospheric pressure) cannot exceed the cracking pressure. For example, water remaining in the first water supply pipe on the ceiling side does not flow from the primary side to the secondary side of the first check valve, and even though water remains in the first water supply pipe, there is no dripping from each nozzle. In addition, since water remains in the piping between the first on / off valve and the first check valve, it is possible to achieve the effect of faster startup when spraying is restarted.

[0066] (Technical 3) The second check valve of the bypass piping is located near the secondary side of the first check valve. A drip prevention mechanism for a two-fluid spray apparatus as described in Technology 1 or 2.

[0067] This configuration allows for a shorter distance from the secondary side of the first check valve to the secondary side of the second check valve via the bypass piping, thereby reducing the amount of residual water that accumulates in this path after spraying stops. This improves robustness against dripping.

[0068] (Technical 4) The secondary side of the second check valve is positioned below the spray opening of the nozzle. A drip prevention mechanism for a two-fluid spray device described in any one of the technologies 1 to 3.

[0069] This configuration allows for shorter bypass piping, reducing the amount of water remaining inside the pipes. Furthermore, when the secondary side of the second check valve is positioned below the nozzle's spray opening rather than above it, water flows less easily through the pipes, making it more effective at preventing dripping.

[0070] (Technical 5) Multiple nozzles are arranged, and the first check valve and the second check valve are arranged on the primary side of the nozzles. A drip prevention mechanism for a two-fluid spray apparatus as described in any one of the technologies 1 to 4.

[0071] This configuration allows for space saving and eliminates any interference with mist spraying, as the first and second check valves are not wetted by the sprayed mist.

[0072] (Technical 6) The first on-off valve is a water solenoid valve, When the cracking pressure of the first check valve is set to a pressure greater than the difference between the sum of the pressure in the first water supply pipe and the water head from the first water supply pipe to the first check valve and atmospheric pressure, the pressure in the first water supply pipe is the value obtained by subtracting the water head of the water solenoid valve from the pressure acting on the water solenoid valve. A drip prevention mechanism for the two-fluid spray device described in Technical 2.

[0073] This configuration allows us to achieve the effects of Technology 2. [Industrial applicability]

[0074] The drip prevention mechanism for a two-fluid spray device according to the above-described aspect of the present invention prevents dripping due to residual water, shortens the time until spraying stops, reduces the influence of the height at which the first check valve is installed or the influence of external environmental factors such as air entrapment, and increases robustness. It is useful, for example, for humidifying a factory by spraying a two-fluid mist of air and water from a mist nozzle. [Explanation of Symbols]

[0075] 1. Two-fluid nozzle 2 Water source 3. First shut-off valve 3A Water Solenoid Valve Unit 4. Main water pipe 5. First check valve 6. Water branch piping 6a Common branch piping for water 6b Individual branch piping for water 12. Air supply source 13. Second shut-off valve 13A Air Solenoid Valve Unit 14 Main air piping 16. Air branch piping 21. Second check valve 22 Bypass piping 30 Drain valve 31 Drainage piping 32 Drain pan 41 Fixtures 50 Control Unit 101 Nozzles 102 Water source 103 Water control valve 104 Main water piping 105 Third check valve 106 Water branch piping 112 Air supply source 113 Air control valve 114 Main air piping 116 Air branch piping 121 Shut-off valve 122 Bypass piping 125 Check valve 130 Drain valve H1 Head from main water pipe 4 in the ceiling to water solenoid valve unit 3A H2 Water head from main water pipe 4 to first check valve 5 P1 Pressure sensor detection value P2 Water main pipe 4 pressure P3 Primary side pressure of the first check valve 5

Claims

1. A gas and a liquid are supplied, and at least one two-fluid nozzle sprays the gas and the liquid, A first water supply pipe is connected to a water supply source that supplies water as the liquid, via a first on-off valve, and supplies the water. A second water supply pipe connects the first water supply pipe and the liquid-side inlet of the two-fluid nozzle via a first check valve, and supplies water from the first water supply pipe to the liquid-side inlet of the two-fluid nozzle. A first air supply pipe is connected via a second on-off valve to an air supply source that supplies air as a gas at a pressure lower than the water supply pressure, and supplies the air. A two-fluid spray device comprising a first air supply pipe and a second air supply pipe that connects the first air supply pipe to the gas-side inlet of the two-fluid nozzle and supplies the air from the first air supply pipe to the gas-side inlet of the two-fluid nozzle, The first air supply pipe and the secondary side of the first check valve of the second water supply pipe are connected via a second check valve, and air is supplied from the first air supply pipe to the second water supply pipe only when the pressure in the first air supply pipe on the primary side of the second check valve is higher than the pressure in the second water supply pipe on the secondary side of the second check valve, and a bypass pipe is provided to discharge water from the second water supply pipe and the two-fluid nozzle, The first check valve has a predetermined cracking pressure greater than the pressure difference between the residual water pressure on the primary side of the first check valve and atmospheric pressure. When the difference between the pressure on the primary side of the first check valve, which is the first water supply pipe, and the pressure on the secondary side, which is the second water supply pipe, exceeds the cracking pressure of the first check valve, water flows from the first water supply pipe to the second water supply pipe via the first check valve through the first water supply pipe, the second water supply pipe, and the nozzle, and the spraying is performed. When the first shut-off valve is closed to stop the supply of water from the water source to the first water supply pipe, the difference between the pressure on the primary side of the first check valve (the first water supply pipe side) and the pressure on the secondary side (the second water supply pipe side) becomes less than the cracking pressure of the first check valve. As a result, water does not flow from the first water supply pipe to the second water supply pipe via the first check valve through the first water supply pipe, the second water supply pipe and the nozzle, and the spraying stops. Furthermore, as the water supply stops, the pressure on the primary side of the second check valve in the bypass pipe becomes higher than the pressure on the secondary side, and air is supplied from the first air supply pipe to the second water supply pipe, causing the water in the second water supply pipe and the nozzle to be discharged. A drip prevention mechanism for a two-fluid spray system.

2. The first water supply pipe extends laterally along the ceiling side of the space where the nozzle is installed. The second water supply pipe extends along the vertical direction of the installation space of the nozzle, and the first check valve is located in the second water supply pipe. The cracking pressure of the first check valve is set to a pressure greater than the difference between the sum of the pressure in the first water supply pipe and the water head from the first water supply pipe to the first check valve, and atmospheric pressure. A drip prevention mechanism for a two-fluid spray apparatus according to claim 1.

3. The second check valve of the bypass piping is located near the secondary side of the first check valve. A drip prevention mechanism for a two-fluid spray apparatus according to claim 1 or 2.

4. The secondary side of the second check valve is positioned below the spray opening of the nozzle. A drip prevention mechanism for a two-fluid spray apparatus according to claim 1 or 2.

5. Multiple nozzles are arranged, and the first check valve and the second check valve are arranged on the primary side of the nozzles. A drip prevention mechanism for a two-fluid spray apparatus according to claim 1 or 2.

6. The first on-off valve is a water solenoid valve, When the cracking pressure of the first check valve is set to a pressure greater than the difference between the sum of the pressure in the first water supply pipe and the water head from the first water supply pipe to the first check valve and atmospheric pressure, the pressure in the first water supply pipe is the value obtained by subtracting the water head of the water solenoid valve from the pressure acting on the water solenoid valve. A drip prevention mechanism for a two-fluid spray apparatus according to claim 2.

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