JP-7854599-B2 - Drip prevention mechanism for two-fluid spray system

JP7854599B2JP 7854599 B2JP7854599 B2JP 7854599B2JP-7854599-B2

Inventors

後藤孝夫
木村達夫
小川修

Assignees

パナソニックＩＰマネジメント株式会社

Dates

Publication Date: 20260507
Application Date: 20230907

Claims (6)

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 side, and the pressure on the secondary side, which is the second water supply pipe side, 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.
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.
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.
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.
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.
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.

Description

This invention relates to a drip prevention mechanism for a two-fluid atomizing device that sprays gas and liquid in a mist-like manner. Traditionally, factories have used two-fluid mist nozzles to spray extremely fine mist particles with a Sauter mean diameter of approximately 10 μm, thereby humidifying the environment. This reduces the generation of static electricity, preventing a decline in manufacturing quality or an increase in product defect rates due to foreign matter adhesion or equipment malfunction. For example, in the component mounting process, it can prevent static-related problems such as electrostatic discharge damage to components or mounting defects on circuit boards. Furthermore, it can improve the comfort of the workspace or reduce the air conditioning load due to the cooling effect of evaporative cooling. Thus, mist spraying using two-fluid mist nozzles does not require large boilers, and localized humidification can be performed while keeping running costs low, making its introduction welcome from the perspective of CO2 reduction. As shown in Figure 5A, such a two-fluid mist nozzle spraying system has a water supply source 102 to which a main water pipe 104 is connected via an on/off water control valve 103. Mist nozzles 101 are connected to the downstream ends of multiple water branch pipes 106, whose upstream ends are connected to the main water pipe 104. Similarly, an air supply source 112 is connected to an air supply source 114 via an on/off air control valve 113. Mist nozzles 101 are connected to the downstream ends of multiple air branch pipes 116, whose upstream ends are connected to the main air pipe 114. The mist spraying is controlled by opening and closing the control valves 103 and 113 from a control panel based on humidity detected by a humidity sensor. In such a spraying device, when mist spraying is stopped for some reason, liquid drips from the tip of the mist nozzle 101. To prevent this, a method has been proposed that uses an extrusion system, providing 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. This bypass path 122 uses air to push out and blow away the water in the water branch pipe 106, thereby preventing dripping from the nozzle 101 (Patent Document 1). However, in large factories, for example, draining all the water from a 50-meter-long water branch pipe 106 results in a long time required to stop spraying. Furthermore, refilling the water branch pipe 106 with water before spraying can begin also increases the time required to start spraying. To solve this problem, a residual pressure release method is known, as shown in Figure 5B. This method involves opening the drain valve 130 connected to the main water pipe 104 when spraying stops, reducing the water pressure in the main water pipe 104 to release residual pressure, and then reducing the water pressure in the branch water pipe 106. This maintains the water pressure upstream of the mist nozzle 101 at a level lower than atmospheric pressure, preventing water from flowing into the nozzle 101 and thus preventing dripping. The check valve 125 in the branch water pipe 106 also functions to prevent backflow of air from the nozzle 101 and maintain negative pressure. Patent application No. 2022-556972 Schematic diagram showing the configuration of a two-fluid spray device according to one embodiment of the present invention.Perspective view showing the nozzle area of a two-fluid spray system, including the drip prevention mechanism.Diagram illustrating a configuration in which a third check valve without cracking pressure is installed in a branch pipe for water.Graph showing the relationship between water pressure and time in the configuration of Figure 3A.Diagram illustrating a configuration that includes a bypass pipe to spray water from the nozzle when spraying stops.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.In this embodiment, the diagram illustrates the conditions under which liquid dripping from each nozzle is less likely to occur, even though water remains in the main water piping (some piping is omitted).Diagram illustrating the spray standby operation of the two-fluid spray device according to this embodiment.Diagram illustrating the spray operation of the two-fluid spray device according to this embodiment.Diagram illustrating the operation of draining water from each nozzle of the two-fluid spray device according to this embodiment.Diagram illustrating the humidity of the installation space of the two-fluid spray device according to this embodiment and the open/closed state of each valve.Diagram illustrating a conventional configuration that prevents liquid dripping using an extrusion method.Diagram illustrating the conventiona