diffuser

Abstract

------09 / 04 / 2564------(OCR) This invention relates to a diffuser with a tubular substrate fitted with air inlets and outlets, and a flexible membrane covering the outer surface of the tubular substrate. The flexible membrane has several slits that pass through from its inner to outer surface, and projections extending toward the tubular substrate and outward along its axial direction are arranged on the inner surface of the flexible membrane. ------------ This invention relates to a diffuser with a tubular substrate fitted with an air inlet. And the air passages and a flexible membrane that covers the outer surface of the tubular substrate where the membrane... The elastic membrane has a number of slits that allow passage from the inner surface to the outer surface of the elastic membrane. And the projections that extend towards the tubular substrate and outward in the axial direction of the tubular substrate are positioned at: The inner surface of the elastic membrane.

Description

Air diffuser

[0001] The present invention relates to an air diffuser. This application claims priority based on Japanese Patent Application No. 2018-139431 filed in Japan on July 25, 2018, and the content thereof is incorporated herein by reference.

[0002] As a method for removing organic substances in wastewater, the activated sludge method is widely used. The activated sludge method is a method of decomposing organic substances in the treated water using aerobic microorganisms living in the sludge in the treatment tank. In a wastewater treatment facility using this activated sludge method, in order to enhance the activity of aerobic microorganisms, an air diffuser is installed in the treatment tank, and air sent from a blower (air blower) arranged outside the treatment tank is supplied into the treatment tank using the air diffuser to increase the amount of dissolved oxygen in the treated water.

[0003] As an air diffuser, those using an elastic membrane body provided with a large number of slits are known. The air diffuser using this elastic membrane body has a configuration in which the elastic membrane body is stretched by the pressure of the air sent from the blower to open the slits, and air is discharged as fine bubbles from the opened slits. Air diffusers are classified into tube type, disk type, and panel type according to the shape of the elastic membrane body. The tube type is widely used because it is easy to uniformly stretch the elastic membrane body and is likely to generate fine and uniform bubbles.

[0004] Patent Document 1 discloses an air diffuser (tube type membrane diffuser) having a tube base material and an elastic membrane body (elastic film) covering the outer surface of the tube base material as a tube type air diffuser. In this air diffuser, air is supplied between the tube base material and the elastic membrane body to generate bubbles from the slits of the elastic membrane body. According to this Patent Document 1, by setting the wet aeration resistance and / or the aeration amount of the air diffuser to a predetermined value or less and aerating, it is possible to reduce the diameter of the generated bubbles and narrow the distribution width of the bubbles while suppressing the pressure loss and the burden on the blower during use.

[0005] In the tube-type aeration device using the elastic membrane described above, during aeration operation, the air supplied from the blower applies pressure to the elastic membrane from the inside to the outside of the tube substrate, causing the elastic membrane to stretch outward overall. On the other hand, when aeration operation is stopped, negative pressure generated inside the tube substrate and water pressure from the treated water in the treatment tank are applied to the elastic membrane, pressing the elastic membrane against the tube substrate. Therefore, if aeration operation is performed intermittently and repeatedly, there is a risk that the elastic membrane may tear at the slit portion. Furthermore, when aeration operation is stopped, the application of negative pressure and water pressure to the elastic membrane may cause a part of the slit in the elastic membrane to open, potentially allowing treated water and sludge from the treatment tank to enter the inside of the tube substrate, increasing the pressure loss during aeration operation.

[0006] To solve the problems caused by the application of negative pressure and water pressure to the elastic membrane, various slit shapes have been considered. For example, Patent Document 2 discloses making the slits non-linear in order to prevent the elastic membrane from tearing at the slit portion. Patent Document 2 describes arc-shaped and mountain-shaped (triangular) slits as possible shapes.

[0007] Furthermore, Patent Document 3 discloses that, in order to prevent sludge from entering the tube substrate when aeration is stopped, the cut surface of the slit that penetrates both sides of the elastic membrane is inclined with respect to the radial direction of the elastic membrane.

[0008] Japanese Patent Publication No. 2008-221158, Japanese Patent Publication No. 2000-185245, Japanese Patent Publication No. 2011-125781

[0009] Incidentally, in wastewater treatment facilities, increasing the amount of air supplied from the blower to the aeration device is effective in increasing the amount of dissolved oxygen in the treated water. However, it has been found that when the aeration operation is stopped while the amount of air supplied from the blower is increased, localized wrinkles (bulges) tend to occur in the elastic membrane. This is thought to be because the space between the elastic membrane and the tube substrate widens, making it easier for air to remain partially. In particular, since air tends to move upward, wrinkles tended to occur more easily in the upper part of the elastic membrane.

[0010] When the aeration operation is stopped, wrinkles form in the elastic membrane, and if the aeration operation is performed intermittently, cracks may form in the slit portion of the elastic membrane, starting from the areas prone to wrinkle formation. Therefore, it is important to suppress the formation of wrinkles in the elastic membrane when the aeration operation is stopped. However, it has been difficult to suppress the formation of wrinkles in the elastic membrane when the aeration operation is stopped by modifying the shape of the slits as disclosed in Patent Documents 2 and 3.

[0011] The present invention has been made in consideration of the above circumstances, and its purpose is to provide an aeration device that can suppress the occurrence of wrinkles in the elastic membrane when the aeration operation is stopped, and that can generate bubbles stably over a long period of time, even when the aeration operation is performed intermittently, and that is less likely to cause cracks in the slit portion.

[0012] To solve the above problems, the present invention employs the following means.

[0013] (1) An aeration device according to one aspect of the present invention comprises a tube base material having an air inlet and an air outlet, and an elastic membrane covering the outer surface of the tube base material, wherein the elastic membrane has a plurality of slits communicating from the inner surface to the outer surface, and the inner surface of the elastic membrane is provided with a convex portion that protrudes toward the tube base material and extends in the axial direction of the tube base material.

[0014] According to the above-described aeration device, the rigidity is increased by the thickness of the protrusions provided on the inner surface of the elastic membrane, thereby suppressing the occurrence of twisting of the elastic membrane when the aeration operation is stopped. Furthermore, by arranging the protrusions, the amount of change in shape of the thin parts of the elastic membrane where the protrusions are not provided can be reduced. For this reason, according to the above-described aeration device, the occurrence of wrinkles in the elastic membrane when the aeration operation is stopped can be suppressed.

[0015] (2) In the aeration device described in (1) above, four or more protrusions may be provided. Having four or more protrusions can further suppress the occurrence of wrinkles in the elastic membrane when the aeration operation is stopped.

[0016] (3) In the aeration device described in (1) or (2) above, the protrusion may have a thickness of 1 mm or more and a width of 5 mm or more and a width of 15 mm or less. If the thickness of the protrusion is within the range of 1 mm or more and a width of 3 mm or less, the rigidity of the protrusion can be reliably increased, and when the aeration operation is stopped and negative pressure and water pressure are applied to the elastic membrane, the protrusion will be less likely to deform, and the amount of change in shape of the thin part of the elastic membrane where the protrusion is not provided can be reduced. Furthermore, if the width of the protrusion is 5 mm or more, the rigidity of the protrusion can be more reliably increased, and when the aeration operation is stopped and negative pressure and water pressure are applied to the elastic membrane, the protrusion will be less likely to deform, and the amount of change in shape of the thin part of the elastic membrane where the protrusion is not provided can be reduced. Moreover, if the width of the protrusion is 15 mm or less, an area of ​​the thin part where the protrusion is not provided, i.e., the part that is easily stretched by air pressure, is secured, so that bubbles can be stably generated during aeration operation.

[0017] (4) In the aeration device described in any one of (1) to (3) above, the elastic membrane may be provided with a curved portion that curves toward the opposite side from the tube substrate and extends in the axial direction of the tube substrate. In this case, it is preferable that the radius of curvature of the curved portion is smaller than the radius of the tube substrate. By providing a curved portion in the elastic membrane, a space is formed between the inner surface of the curved portion and the outer surface of the tube substrate. During aeration operation, air flows into this space, reducing wet aeration resistance, improving oxygen transport efficiency, and allowing the entire elastic membrane to be stretched more uniformly, thus enabling stable bubble generation over a long period of time.

[0018] (5) In the aeration device described in (4) above, the curved portion may be provided at a position facing the air outlet provided on the tube base material. By providing the curved portion at a position facing the air outlet, air can flow more easily into the space between the inner surface of the curved portion and the outer surface of the tube base material. This further reduces wet aeration resistance during aeration operation and improves oxygen transfer efficiency.

[0019] (6) In the aeration device described in (5) above, the tube base material may be provided with two air outlets, and the curved portion of the elastic membrane may be positioned opposite each of the two air outlets. By providing the tube base material with two air outlets and the curved portion of the elastic membrane opposite each of the two air outlets, the wet aeration resistance during aeration operation is further reduced and the oxygen transport efficiency is further improved.

[0020] According to the present invention, it is possible to suppress the occurrence of wrinkles in the elastic membrane when the aeration operation is stopped, and even if the aeration operation is performed intermittently, cracks are less likely to occur in the slit portion, making it possible to provide an aeration device that can stably generate bubbles over a long period of time.

[0021] This is a perspective view of an aeration device according to one embodiment of the present invention. This is an exploded perspective view of the aeration device shown in Figure 1. This is a cross-sectional view of the aeration device shown in Figure 1, taken along line III-III. This is a diagram illustrating the elastic membrane of the aeration device shown in Figure 1, where (A) is a cross-sectional view of the elastic membrane and (B) is a longitudinal cross-sectional view of the elastic membrane. This is a diagram illustrating the state of the aeration device shown in Figure 1 when aeration operation is stopped, where (A) is a cross-sectional view of the aeration device and (B) is an enlarged cross-sectional view of the main part of (A). This is a diagram illustrating the state of the aeration device shown in Figure 1 during aeration operation, where (A) is a cross-sectional view of the aeration device and (B) is an enlarged cross-sectional view of the main part of (A).

[0022] Hereinafter, an aeration device according to one embodiment of the present invention will be described with reference to the drawings. The aeration device of this embodiment is used, for example, in a wastewater treatment facility. Specifically, it is installed in a treatment tank for removing organic matter from wastewater by the activated sludge method and is used as an aeration device to supply air sent from a blower located outside the treatment tank into the treatment tank.

[0023] Figure 1 is a perspective view of an aeration device according to one embodiment of the present invention. Figure 2 is an exploded perspective view of the aeration device shown in Figure 1, and Figure 3 is a cross-sectional view of the aeration device shown in Figure 1 taken along line III-III. Figure 4 is a diagram illustrating the elastic membrane of the aeration device shown in Figure 1, where (A) is a cross-sectional view of the elastic membrane (a cross-sectional view obtained by cutting the elastic membrane along line A-A in (B)), and (B) is a longitudinal cross-sectional view of the elastic membrane (a cross-sectional view obtained by cutting the elastic membrane along line B-B in (A)).

[0024] As shown in Figures 1 to 4, the aeration device 10 of this embodiment has a tube base material 20 and an elastic membrane 30 that covers the outer surface of the tube base material 20. The tube base material 20 and the elastic membrane 30 are fixed together by bands 41 and 42. In Figure 3, the arrows indicate the flow of air.

[0025] The tube base material 20 consists of an adapter 21 and a cylindrical body 26. The adapter 21 is a cylindrical body with an air inlet 22 at one end along the central axis and a partition wall 23 at the other end along the central axis. The air inlet 22 is connected to a blower via piping. The adapter 21 has an air outlet 24 on its side. The air outlet 24 blows out the air introduced into the air inlet 22. There are two air outlets 24, positioned opposite each other. These opposite positions are on the side of the adapter 21, facing each other across the central axis of the adapter 21. The adapter 21 also has a cylindrical projection 25 at the other end. The cylindrical projection 25 is attached to the partition wall 23 and has a projection that protrudes outward from the other end. By inserting the cylindrical body 26 into the cylindrical projection 25, the adapter 21 and the cylindrical body 26 are connected to form the tube base material 20.

[0026] There are no particular restrictions on the size of the tube base material 20, but for example, the outer diameter is within the range of 59 mm to 90 mm, and the axial length is within the range of 500 mm to 1000 mm.

[0027] The materials for the adapter 21 and cylindrical body 26 that constitute the tube base material 20 are not particularly limited, but thermoplastic resins such as polyvinyl chloride resin and ABS resin can be used. The adapter 21 and cylindrical body 26 can be manufactured, for example, by injection molding.

[0028] The elastic membrane 30 is tubular in shape and has multiple slits 31 that communicate from the inner surface to the outer surface. The length of the slits 31 is preferably within the range of 1 mm to 2 mm. When the length of the slits is within this range, it becomes easier to generate fine and uniform bubbles.

[0029] The elastic membrane 30 has six protrusions 32 that project toward the tube substrate 20 and extend in the axial direction of the tube substrate 20, and two curved portions 33 that curve toward the opposite side of the tube substrate 20 and extend in the axial direction of the tube substrate 20. The six protrusions 32 and the two curved portions 33 are arranged at equal intervals from each other. Here, extending in the axial direction of the tube substrate 20 means extending in a direction parallel to the axial direction of the tube substrate 20. Projecting toward the tube substrate 20 means that in the cross-sectional view of the elastic membrane 30, the inner surface has a convex shape toward the central axis. Curving toward the opposite side of the tube substrate 20 means that in the cross-sectional view of the elastic membrane 30, the curved portion has a convex shape toward the outer circumference from the central axis.

[0030] The protrusions 32 increase the rigidity of the elastic membrane 30, making it less likely for the elastic membrane 30 to twist when the aeration operation is stopped and negative pressure and water pressure are applied to the elastic membrane 30. Furthermore, when the aeration operation is stopped, the protrusions 32 contact the outer surface of the tube base material 20, suppressing the change in shape of the thinner parts of the elastic membrane 30 where the protrusions 32 are not provided. Each protrusion 32 has a thickness of 1 mm to 3 mm and a width of 5 mm to 15 mm. Here, the thickness of the protrusions 32 is the thickness from the inner wall surface of the elastic membrane 30 (the inner wall surface excluding the protrusions 32 and the curved portion 33) (in other words, it is the total thickness of the protrusions 32 minus the thickness of the elastic membrane 30 (the thickness of the elastic membrane 30 excluding the protrusions 32 and the curved portion 33)). The thickness of the protrusion 32 is more preferably in the range of 1.5 mm to 2.5 mm, and the width is more preferably in the range of 8 mm to 12 mm. If the thickness of the protrusion 32 is less than 1 mm, the function of increasing the rigidity of the elastic membrane 30 may be reduced. On the other hand, if the thickness of the protrusion 32 exceeds 3 mm, the minimum inner diameter of the elastic membrane 30 including the portion on which the protrusion 32 is provided becomes smaller than the outer diameter of the tube base material 20, making it difficult to attach the elastic membrane 30 to the tube base material 20. In addition, even when the aeration device 10 is stopped, the amount of elongation of the elastic membrane 30 may increase, and the slit 31 may remain open. Although not particularly limited, the thickness of the elastic membrane 30 (thickness of the elastic membrane 30 excluding the protrusion 32 and curved portion 33) is preferably in the range of 1.5 mm to 2.5 mm.

[0031] Furthermore, if the width of the protrusion 32 is less than 5 mm, the function of increasing the rigidity of the elastic membrane 30 may be reduced. On the other hand, if the width of the protrusion 32 exceeds 15 mm, the area of ​​the thin part of the elastic membrane 30 where the protrusion 32 is not provided, i.e., the part that is easily stretched by air pressure, becomes relatively smaller, so it may become impossible to stably generate bubbles during aeration operation. Note that the part where the protrusion 32 is provided may or may not have a slit 31.

[0032] The curved portion 33 has a radius of curvature smaller than the radius of the tube base material 20, thereby functioning to form a space 35 between the inner surface of the curved portion 33 and the outer surface of the tube base material 20. Two curved portions 33 are provided, positioned opposite each other on the central axis, and each of the two curved portions 33 is positioned to face an air outlet 24 provided on the tube base material 20. Preferably, the radius of curvature of the curved portion 33 is 19% to 34% of the radius of the tube base material 20.

[0033] A thickened portion 34 is provided on the inner surface of the curved portion 33. The thickened portion 34 prevents the curved portion 33 from being sucked into the air outlet 24 by the negative pressure generated when the aeration operation is stopped. There are no particular restrictions on the thickness of the thickened portion 34, but it is preferably in the range of 3 mm to 5 mm.

[0034] The elastic membrane 30 can be made from rubber materials such as ethylene propylene rubber, silicone rubber, fluororubber, or urethane rubber. The elastic membrane 30 can be manufactured, for example, by compression molding or extrusion molding.

[0035] Next, the operation of the aeration device 10 during aeration operation will be described. Figure 5 is a diagram illustrating the state of the aeration device 10 when aeration operation is stopped, where (A) is a cross-sectional view of the aeration device 10 (a view obtained by cutting the aeration device 10 perpendicular to the axial center line of the tube base material 20), and (B) is an enlarged cross-sectional view of the main part of (A). As shown in Figure 5, in the aeration device 10 when aeration operation is stopped, the protrusion 32 of the elastic membrane 30 is in contact with the outer surface of the tube base material 20. Also, when aeration operation is stopped, the slit 31 of the elastic membrane 30 is closed.

[0036] Figure 6 illustrates the state of the aeration device 10 during aeration operation, where (A) is a cross-sectional view of the aeration device 10 and (B) is an enlarged cross-sectional view of the main part of (A). As shown in Figure 6, during aeration operation, air sent to the air inlet 22 of the aeration device 10 passes through the air outlet 24 and is supplied to the space 35 between the inner surface of the curved portion 33 of the elastic membrane 30 and the outer surface of the tube substrate 20. The air supplied to this space 35 causes the elastic membrane 30 to stretch outward overall. As a result, the convex portion 32 of the elastic membrane 30 separates from the outer surface of the tube substrate 20, forming a space between the convex portion 32 and the outer surface of the tube substrate 20, and the slit 31 opens, from which air is released as fine bubbles.

[0037] As described above, with the aeration device 10 of this embodiment, when the aeration operation is stopped, as shown in Figure 5, the protrusions 32 contact the outer surface of the tube base material 20 without causing twisting in the elastic membrane 30, thereby reducing the amount of change in shape of the thin portion where the protrusions 32 are not provided. For this reason, the aeration device 10 of this embodiment can suppress the occurrence of wrinkles in the elastic membrane 30 when the aeration operation is stopped.

[0038] Furthermore, in the aeration device 10 of this embodiment, since there are six protrusions 32 on the elastic membrane 30, the occurrence of wrinkles in the elastic membrane 30 when the aeration operation is stopped can be further suppressed.

[0039] Furthermore, in the aeration device 10 of this embodiment, the protrusions 32 of the elastic membrane 30 have a thickness of 1 mm to 3 mm and a width of 5 mm to 15 mm. As a result, the rigidity of the protrusions 32 is high, and when the aeration operation is stopped and negative pressure and water pressure are applied to the elastic membrane 30, the protrusions 32 are less likely to deform, and the amount of change in shape of the thin parts where the protrusions 32 are not provided can be reduced. Moreover, since the width of the protrusions 32 is 15 mm or less, a sufficient area of ​​thin parts where the protrusions 32 are not provided, i.e., parts that are easily stretched by air pressure, is secured, so that bubbles can be generated stably during aeration operation.

[0040] Furthermore, in the aeration device 10 of this embodiment, the tube base material 20 is equipped with two air outlets 24, and the curved portions 33 of the elastic membrane 30 are positioned opposite each of the air outlets 24. As a result, during aeration operation, air flows into the space 35 between the inner surface of the curved portion 33 of the elastic membrane 30 and the outer surface of the tube base material 20, thereby reducing wet aeration resistance, improving oxygen transport efficiency, and allowing the entire elastic membrane 30 to be stretched more uniformly.

[0041] Although embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. Embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications are possible without departing from the spirit of the invention. Embodiments also include, for example, those that can be easily conceived by a person skilled in the art, those that are substantially the same, and those that are equivalent.

[0042] For example, in the aeration device 10 of this embodiment, the elastic membrane 30 has six protrusions 32, but it is not limited to this. The number of protrusions 32 may be one, but it is preferable to have four or more. Providing four or more protrusions 32 can further suppress the occurrence of wrinkles when the aeration operation is stopped. On the other hand, if the number of protrusions 32 becomes too large, the area of ​​the thin parts where no protrusions 32 are provided, i.e., the parts that are easily stretched by air pressure, becomes relatively smaller, which may reduce performance. For this reason, it is preferable that the number of protrusions 32 be 10 or less. The area ratio of the parts on the inner surface of the elastic membrane 30 where the protrusions 32 are provided is preferably in the range of 3% to 32%, and more preferably in the range of 13% to 19%.

[0043] Furthermore, although the aeration device 10 of this embodiment has two curved portions 33 in the elastic membrane 30, it is not limited to this. The number of curved portions 33 may be one, but it is preferable to have two or more.

[0044] In addition, in the air diffuser 10 of the present embodiment, although the elastic film body 30 is tubular, it is not limited thereto. For example, the elastic film body 30 may be formed in a sheet shape and wound around the tube base material 20.

[0045] Furthermore, in the air diffuser 10 of the present embodiment, although the convex portion 32 of the elastic film body 30 extends linearly in the axial direction of the tube base material 20, it is not limited thereto as long as it extends in the axial direction of the tube base material 20. For example, the convex portion 32 may be helical or wavy.

[0046] Example 1: As the tube base material, a tube having two air outlets disposed opposite to each other left and right across the central axis in a cross section perpendicular to the central axis was prepared. As the elastic film body, an elastic film body having two convex portions disposed opposite to each other above and below the inner surface in a cross section perpendicular to the central axis across the central axis and two curved portions disposed opposite to each other left and right across the central axis was prepared. Then, the outer surface of the tube base material was covered with the elastic film body so that the curved portion was in a positional relationship opposite to the air outlet, and then the tube base material and the elastic film body were fixed with a band to produce an air diffuser. The tube base material had an outer diameter of 89.0 mm and a length of 500 mm. The elastic film body had an inner diameter of 91.0 mm, a thickness of 2.0 mm, and a length of 500 mm. The convex portion had a width of 10 mm and a thickness of 2.0 mm. The curved portion had a curvature radius of 10 mm (22.5% of the radius of the tube base material) and a thickness of the thick portion of 2.0 mm. In addition, an elastic film body having a plurality of slits with a length of 2 mm communicating from the inner surface to the outer surface was prepared.

[0047] Example 2: An air diffuser was produced in the same manner as in Example 1, except that an elastic film body having a convex portion disposed at the lower part of the inner surface in the cross section, two convex portions disposed at positions where the central angle with respect to the convex portion was 120 degrees, and two curved portions disposed opposite to each other left and right across the central axis was used.

[0048] [Example 3] A diffuser was fabricated in the same manner as in Example 1, except that an elastic film body was used in which four convex portions arranged such that the central angle on the inner surface in the cross section was 90 degrees and two curved portions arranged opposite to each other left and right across the central axis were arranged such that the central angles of the convex portions and the curved portions were 45 degrees.

[0049] [Example 4] A diffuser was fabricated in the same manner as in Example 1, except that an elastic film body was used in which six convex portions and two curved portions were equally spaced from each other in the cross section and the two curved portions were arranged opposite to each other left and right across the central axis.

[0050] [Example 5] A diffuser was fabricated in the same manner as in Example 1, except that a tube base material having two air outlets arranged opposite to each other vertically in the cross section was used and an elastic film body in which six convex portions and two curved portions were equally spaced from each other in the cross section and the two curved portions were arranged opposite to each other vertically across the central axis was used as the elastic film body.

[0051] [Example 6] A diffuser was fabricated in the same manner as in Example 1, except that an elastic film body having the same configuration as in Example 4 except that the width of the convex portion was 5 mm was used as the elastic film body.

[0052] [Example 7] A diffuser was fabricated in the same manner as in Example 1, except that an elastic film body having the same configuration as in Example 4 except that the width of the convex portion was 15 mm was used as the elastic film body.

[0053] [Example 8] A diffuser was fabricated in the same manner as in Example 1, except that an elastic film body having the same configuration as in Example 4 except that the thickness of the convex portion was 3 mm was used as the elastic film body.

[0054] [Comparative Example 1] A diffuser was fabricated in the same manner as in Example 1, except that an elastic film body having no convex portions and curved portions was used. The elastic film body had an inner diameter of 89.6 mm, a thickness of 1.7 mm, and a length of 500 mm.

[0055] [Comparative Example 2] An aeration device was manufactured in the same manner as in Example 1, except that the tube base material had two air outlets arranged opposite each other on the upper and lower sides of the central axis in the cross-section, and the elastic membrane body had no protrusions in the cross-section and two curved portions arranged opposite each other on the upper and lower sides of the central axis.

[0056] [Evaluation] An air transport pipe, which is switchable between a blower and a pressure reducing pump, was attached to the air inlet of the fabricated aeration device, and the device was immersed in a treatment tank filled with water at a depth of 350 mm. Next, an aeration operation was performed in which air sent from the blower was supplied to the air inlet of the aeration device via the air transport pipe at a flow rate of 100 L / min for 30 seconds. During the aeration operation, the air permeability and foaming state were evaluated as described below. After that, the aeration operation was stopped, and the presence or absence of wrinkles in the elastic membrane was evaluated as described below. The evaluation results are shown in Table 1 below.

[0057] (Air permeability) Air permeability was evaluated by wet air permeability resistance during aeration operation. Wet air permeability resistance was determined by measuring the pressure at the inlet of the aeration device at an air supply rate of 200 L / min (converted to 20°C and 1 atm), and subtracting the water pressure value at the depth in which the aeration device was immersed from that value. If the wet air permeability resistance was within the range of 2.8 kPa to 3.8 kPa, it was judged as "A", and if the wet air permeability resistance was outside the above range, it was judged as "C".

[0058] (Foaming State) The foaming state was evaluated by comparing the foaming state at a position 250 mm axially away from the air outlet of the aeration device with the foaming state at a position 500 mm axially away from the air outlet. Based on the comparison of the foaming states, uniform foaming was judged as "A" and non-uniform foaming was judged as "B".

[0059] (Presence or absence of wrinkles) After stopping the aeration operation, the air transport pipe was connected to a vacuum pump and the inside of the tube substrate was reduced to -50 kPa for 30 seconds. During the reduction, the outer surface of the elastic membrane of the aeration device was visually observed. If wrinkles were observed on the surface of the elastic membrane, the location of the wrinkles was confirmed.

[0060] If no wrinkles were observed on the surface of the elastic membrane, the air transport pipe was connected to the blower again, and after performing aeration under the above conditions, the aeration operation was stopped. Then, the air transport pipe was connected to a vacuum pump and the intermittent aeration operation was repeated to reduce the pressure inside the tube substrate under the above conditions.

[0061] As a result, if no wrinkles were observed after repeating the intermittent aeration operation three times, it was judged as "A," and if wrinkles were observed during the first intermittent aeration operation, it was judged as "C."

[0062]

[0063] In the aeration device of Comparative Example 1, which used an elastic membrane without convex or curved portions, the amount of foaming clearly decreased as the distance from the air outlet in the axial direction increased, indicating an uneven foaming state. Furthermore, significant wrinkles appeared on the upper part of the elastic membrane after the aeration operation was stopped. In the aeration device of Comparative Example 2, which used an elastic membrane with only curved portions, the foaming state improved, but wrinkles appeared on both the upper and lower parts of the elastic membrane after the aeration operation was stopped. The reason for the wrinkles on the lower part is thought to be that, after the aeration operation was stopped, the tube substrate and the elastic membrane partially adhered to each other before the air accumulated at the bottom could escape, making it difficult for the air to escape.

[0064] In contrast, in the aeration devices of Examples 3 to 8, which used elastic membranes having convex and curved portions, the foaming state was uniform, and wrinkles were less likely to occur in the elastic membrane after the aeration operation was stopped. In particular, in the aeration devices of Examples 3 to 8, which used elastic membranes with four or more convex portions, no wrinkles occurred in the elastic membrane even after three intermittent operations. In particular, in the aeration device of Example 4, no wrinkles occurred in the elastic membrane even after 10,000 intermittent operations.

[0065] From the results above, it has been confirmed that this embodiment makes it possible to provide an aeration device that suppresses the occurrence of wrinkles in the elastic membrane when the aeration operation is stopped, and that even when the aeration operation is performed intermittently, cracks are less likely to occur in the slit portion, and bubbles can be generated stably over a long period of time.

[0066] 10 Aeration device 20 Tube base material 21 Adapter 22 Air inlet 23 Partition 24 Air outlet 25 Cylindrical projection 26 Cylindrical body 30 Elastic membrane 31 Slit 32 Convex part 33 Curved part 34 Thickened part 35 Space 41, 42 Band

Claims

------09 / 04 / 2564------(OCR) A diffuser consisting of a tubular substrate fitted with air inlets and outlets, and a flexible membrane covering the outer surface of the tubular substrate, where the flexible membrane has several slits allowing passage from the inner to the outer surface of the membrane.Two or more projections extending toward the tubular substrate and outward in the axial direction of the tubular substrate are provided on the inner surface of the flexible membrane diffuser under Reputation 1, where four or more projections are provided; diffusers under Reputation 1 or 2, where each projection has a thickness within the range of at least 1 mm and no more than 3 mm, and a width within the range of at least 5 mm and no more than 15 mm; diffusers under Reputation 1 through 3, where the flexible membrane is provided. It is held in place by a curved section bent on the opposite side from the tubular substrate and extending in the axial direction of the tubular substrate, and the curve has a radius of curvature less than the radius of the tubular diffuser substrate according to claim 4, where the curve is positioned opposite the air paths provided in the tubular diffuser substrate; according to claim 5, where the tubular substrate has two air paths and the curve of the flexible membrane is positioned opposite each of the two air paths.------------1. The diffuser is assembled with:A tubular substrate fitted with air inlets and outlets, and a flexible membrane covering the outer surface of the tubular substrate, which has several slits allowing passage from the inner surface to the outer surface of the flexible membrane.

1. Two or more projections extending toward the tubular substrate and outward in the axial direction of the tubular substrate are arranged on the inner surface of the flexible membrane.

2. A diffuser under claim 1 in which four or more projections are arranged.

3. A diffuser under claim 1 or 2 in which each projection has a thickness within the range of at least 1 mm and no more than 3 mm and a width within the range of at least 1 mm and no more than 15 mm.

4. Any one of the diffusers under claims 1 through 3 in which four or more projections are arranged.

5. A diffuser under claim 4 where the curve is positioned opposite the air outlets provided in the tubular substrate; 6. A diffuser under claim 5 where the tubular substrate has two air outlets and the curve of the flexible membrane is positioned opposite each of the two air outlets;

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