Membrane type aeration device

Abstract

To provide a membrane-type aeration device capable of reducing an incidence of defects where adjacent slits communicate through a crack.SOLUTION: A membrane type air diffusion device is formed with a plurality of slits 71, 72 for releasing a gas, a plurality of slit rows 73 in which the plurality of slits are arranged in a row along a first direction A are provided on a membrane, first slits 71 long in the first direction A and second slits 72 long in a second direction 75 inclined with respect to the first direction A are alternately formed in each slit row, the first and second slits of one slit row C1 and the first and second slits of the other slit row C2 adjacent in a third direction B orthogonal to the first direction A are arranged in a staggered manner, and an imaginary straight line 76 passing through a center D1 of the second slits of one slit row C1 adjacent in the third direction B and a center D2 of the second slit of the other C2 slit row closest to the second slit inclines in a direction 77 opposite to the second direction 75.SELECTED DRAWING: Figure 16

Description

[Technical field]

[0001] The present invention relates to a membrane type air diffuser that is installed below the liquid surface and emits air bubbles into the liquid. [Background technology]

[0002] Conventionally, as an example of this type of membrane type air diffuser, there is one that emits a large number of air bubbles 202 into water to be treated 201 in a tank 200, as shown in Fig. 24. This membrane type air diffuser 203 has a membrane 204 formed in a tubular shape, a support tube 205 inserted into the membrane 204, and an air supply unit 206.

[0003] An end of the membrane 204 is fixed watertightly to the support tube 205 with a fastener 207 such as a ring-shaped band. The support tube 205 is connected to an air supply pipe 208. The air supply unit 206 is provided in the center of the support tube 205 in the longitudinal direction A, and has an air passage 209 that communicates from the air supply pipe 208 to between the inner circumference of the membrane 204 and the outer circumference of the support tube 205.

[0004] A plurality of slits 211 for releasing air 210 supplied from an air supply pipe 208 through an air passage 209 of an air supply unit 206 between the inner circumference of the membrane 204 and the outer circumference of the support tube 205 to the outside are formed in the membrane 204. The slits 211 are elongated cuts in the longitudinal direction A of the membrane 204.

[0005] According to this, air 210 is supplied from the air supply pipe 208 through the air flow path 209 of the air supply section 206 to between the inner circumference of the membrane 204 and the outer circumference of the support tube 205, causing the membrane 204 to expand and opening the slits 211, and the air 210 is released from the slits 211 into the water to be treated 201 as air bubbles 202.

[0006] The above-mentioned membrane type aeration device 203 is described in, for example, Patent Document 1 below. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2005-81203 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the conventional type described above, as shown in Figure 25, when the membrane 204 expands during aeration, a tensile force F in the circumferential direction B of the membrane 204 acts on the slit 211, causing the slit 211 to open in the circumferential direction B. This tensile force F can sometimes cause cracks 212 to form at the ends of the slit 211.

[0009] In this case, as shown in Figure 26, a crack 212 occurring at an end of one adjacent slit 211 in the longitudinal direction A may propagate and connect with a crack 212 occurring at an end of the other slit 211, resulting in a problem that the adjacent slits 211 may become connected to each other via the crack 212.

[0010] An object of the present invention is to provide a membrane type air diffuser capable of reducing the incidence of defects in which adjacent slits communicate with each other through cracks. [Means for solving the problem]

[0011] In order to achieve the above object, the first invention is a membrane type air diffuser having an expandable and contractible membrane with a plurality of slits for releasing gas to the outside, A plurality of slit rows are provided in the membrane, each row having a plurality of slits aligned in a first direction; In each slit row, first slits long in a first direction and second slits long in a second direction inclined with respect to the first direction are alternately formed, the first and second slits of one slit row and the first and second slits of the other slit row that are adjacent to each other in a third direction perpendicular to the first direction are alternately arranged in a staggered manner, a virtual straight line passing through a center in the longitudinal direction of a second slit of one of the slit rows adjacent to each other in the third direction and a center in the longitudinal direction of a second slit of the other slit row that is closest to the second slit of the one slit row is inclined in a direction opposite to the second direction, When the membrane expands during aeration, a tensile force in the third direction acts on the first and second slits.

[0012] According to this, when the membrane expands during aeration, a tensile force in the third direction acts on the first and second slits, causing the first and second slits to open, but this tensile force can cause cracks to form at the ends of the first and second slits.

[0013] In this case, because the second slits are inclined with respect to the first slits, the direction in which a crack occurring at the end of the first slit adjacent to each other in the first direction propagates differs from the direction in which a crack occurring at the end of the second slit propagates. This reduces the possibility that a crack occurring at the end of the first slit and a crack occurring at the end of the second slit will connect, thereby reducing the occurrence of defects in which adjacent first and second slits communicate with each other through a crack.

[0014] Furthermore, even if a crack that occurs at an end of a second slit in one slit row that is adjacent to another slit row in the third direction propagates, the virtual straight line is inclined in the opposite direction to the second direction, so that the crack that occurs at the end of the second slit in one slit row and the crack that occurs at the end of the second slit in the other slit row are unlikely to connect, thereby reducing the occurrence of defects in which adjacent second slits are connected via a crack.

[0015] In addition, the second slit is inclined with respect to the first slit, so it is harder to open than the first slit. As a result, when diffusing a small amount of air into the membrane type air diffuser, most of the supplied gas becomes bubbles and is released to the outside through the open first slit, whereas fewer bubbles are released to the outside through the difficult-to-open second slit.

[0016] In addition, when a large volume of air is supplied to the membrane type air diffuser, the second slits open, and as the volume of air supplied increases, the number of open second slits increases, and the supplied gas turns into bubbles and is released to the outside through the open first and second slits.

[0017] As a result, when the amount of air supplied increases or decreases, the number of second slits that open increases or decreases accordingly, so that even if the amount of air supplied increases or decreases, the variation in size of the released bubbles can be reduced, and bubbles of approximately uniform size are released evenly from the entire area where the slits are formed in the membrane.

[0018] In the membrane type air diffuser according to the second invention, the second slits are inclined at an inclination angle of 25° or less with respect to the first slits.

[0019] According to this, the larger the inclination angle of the second slit relative to the first slit, the more difficult it becomes for the second slit to open for the same supply air pressure; however, if the inclination angle is 25° or less, the release of bubbles from the second slit can be adjusted within the normal range of fluctuation of the supply air volume.

[0020] In the membrane type air diffuser of the third invention, the length of the first and second slits is defined as a slit length, the pitch between the first slit and the second slit in the first direction is defined as a slit pitch; If the pitch between adjacent slit rows in the third direction is defined as the row pitch, Slit length < row pitch ≦ slit pitch The relationship is maintained.

[0021] This ensures that adjacent slits are arranged with appropriate spacing throughout the entire slit array, further reducing the incidence of defects such as adjacent first and second slits communicating with each other through cracks.

[0022] In the membrane type air diffuser of the fourth invention, the length of the first and second slits is defined as a slit length, If the distance between the first slit and the second slit in the first direction is defined as the slit distance, Slit length < slit spacing The relationship is maintained.

[0023] This allows adjacent first and second slits in the slit row to be arranged with an appropriate distance between them, further reducing the incidence of defects in which adjacent first and second slits communicate with each other through cracks.

[0024] In the membrane type air diffuser of the fifth invention, the membrane is formed in a tube shape having a hollow insertion portion, A support is inserted into the membrane insertion portion, The membrane is provided with a gas supply, The membrane has a bag-shaped portion formed of two sheet members on the front and back, the gas supply unit has an air passage communicating from the outside to the inside of the bag-shaped portion of the membrane; The first and second slits are formed in a sheet member that constitutes an outer peripheral surface of the bag-shaped portion of the membrane, The first direction is a longitudinal direction of the membrane; The third direction is the circumferential direction of the membrane.

[0025] According to this, when gas is supplied into the bag-shaped portion of the membrane through the ventilation flow path of the gas supply section, the bag-shaped portion expands, and a circumferential tensile force of the membrane acts on the first and second slits, opening the first and second slits, and the gas in the bag-shaped portion is released to the outside through the first and second slits. Effect of the Invention

[0026] As described above, according to the present invention, because the second slits are inclined with respect to the first slits, the direction in which a crack occurring at the end of the first slit adjacent to each other in the first direction propagates differs from the direction in which a crack occurring at the end of the second slit propagates. This reduces the possibility that a crack occurring at the end of the first slit and a crack occurring at the end of the second slit will connect, thereby reducing the occurrence of defects in which adjacent slits communicate with each other through a crack.

[0027] Furthermore, even if a crack that occurs at an end of a second slit in one slit row that is adjacent to another slit row in the third direction propagates, the virtual straight line is inclined in the opposite direction to the second direction, so that the crack that occurs at the end of the second slit in one slit row and the crack that occurs at the end of the second slit in the other slit row are unlikely to connect, thereby reducing the occurrence of defects in which adjacent second slits are connected via a crack. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a perspective view of an air diffusion system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a side view of a membrane type air diffuser provided in the air diffusion equipment according to the first embodiment. [Diagram 3] FIG. 2 is a cross-sectional view of an end portion of the membrane type air diffuser according to the first embodiment. [Figure 4] FIG. 2 is a perspective view of the membrane and the support tube of the membrane type air diffuser of the first embodiment. [Diagram 5] FIG. 2 is a partially cutaway plan view of the membrane of the membrane type air diffuser of the first embodiment. [Figure 6] FIG. 2 is a partially cutaway bottom view of the membrane of the membrane-type air diffuser of the first embodiment. [Figure 7] FIG. 4 is a cross-sectional view of a support tube of the membrane type air diffuser according to the first embodiment. [Figure 8]FIG. 2 is a cross-sectional view of the connecting portion between the membrane type air diffuser and the air supply pipe of the air diffusion equipment according to the first embodiment. [Figure 9] 9 is a view taken along the arrow XX in FIG. 8. [Figure 10] FIG. 2 is a perspective view of a gas supply nozzle of the membrane type air diffuser according to the first embodiment. [Figure 11] 11 is a view taken along the arrow XX in FIG. [Figure 12] 11 is a view taken along the arrow YY in FIG. 10. [Figure 13] FIG. [Figure 14] FIG. 13 is a disassembled view of the adapter, air supply pipe, and gas supply nozzle of the aeration equipment. [Figure 15] FIG. 2 is an enlarged view showing the arrangement pattern of the slits formed in the membrane of the membrane-type air diffuser of the first embodiment, showing the slits in a closed state. [Figure 16] FIG. 16 is a further enlarged view of the slit arrangement pattern shown in FIG. [Figure 17] FIG. 2 is an enlarged view showing the arrangement pattern of the slits formed in the membrane of the membrane-type air diffuser of the first embodiment, showing the slits in an open state. [Figure 18] FIG. 11 is a reference example for the first embodiment of the present invention, and is an enlarged view of an arrangement pattern of staggered slits different from that of the first embodiment, showing a state in which the slits are closed. [Figure 19] FIG. 11 is a reference example for the first embodiment of the present invention, and is an enlarged view of an arrangement pattern of staggered slits different from that of the first embodiment, showing a state in which the slits are open. [Figure 20] FIG. 2 is a diagram showing a procedure of a method for manufacturing the membrane of the membrane type air diffuser in the first embodiment of the present invention. [Figure 21] FIG. 2 is a diagram showing the steps of a method for manufacturing the membrane of the membrane-type air diffuser according to the first embodiment. [Figure 22] FIG. 11 is a perspective view of a membrane type air diffuser according to a second embodiment of the present invention. [Figure 23]FIG. 2 is a partially cutaway view of the membrane-type aeration device as viewed from the longitudinal direction, showing the state during aeration. [Figure 24] FIG. 1 is a diagram of a conventional membrane type air diffuser. [Diagram 25] FIG. 2 is an enlarged view showing the arrangement pattern of slits formed in the membrane of the membrane-type air diffuser of the same embodiment, showing the state where the slits have opened and cracks have occurred. [Figure 26] FIG. 11 is a diagram showing how adjacent slits in the membrane of a membrane-type air diffuser are connected through a crack. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0030] (First embodiment) In the first embodiment, as shown in Fig. 1, reference numeral 1 denotes an aeration system provided in an aerobic tank (not shown) installed in, for example, a sewage treatment plant. The aeration system 1 is immersed below the surface of water to be treated 3 (an example of a liquid) consisting of activated sludge in the tank, and includes a plurality of membrane type aeration devices 10 that emit air bubbles 4 into the water to be treated 3, an air supply pipe 12 that supplies air 11 (an example of a gas for aeration) to each membrane type aeration device 10, an adapter 14 (see Fig. 8) that fixes the membrane type aeration device 10 to the air supply pipe 12, and a blower 15 that supplies air 11 to the air supply pipe 12 from outside the tank.

[0031] As shown in Figures 2 to 6, the membrane type air diffuser 10 has a membrane 17 formed in a tubular (cylindrical) shape with a hollow insertion portion 16 in the center, a support tube 18 (an example of a support) inserted horizontally into the insertion portion 16 of the membrane 17, and a gas supply nozzle 19 (an example of a gas supply portion) provided in the center of the membrane 17 in the longitudinal direction A.

[0032] The membrane 17 has a bag-shaped portion 23 formed into a bag shape by welding two front and back sheet members 21, 22. The front sheet member 21 and the back sheet member 22 are made of a soft elastic synthetic resin, and the front sheet member 21 forms the outer peripheral surface of the bag-shaped portion 23, while the back sheet member 22 forms the inner peripheral surface of the bag-shaped portion 23.

[0033] A circular first opening 24 is formed in the central portion and upper portion of the membrane 17 in the longitudinal direction A. The insertion portion 16 penetrates both ends of the membrane 17, and the insertion portion 16 and the upper portion of the membrane 17 communicate with each other via the first opening 24.

[0034] 8, 9 and 20, circular first through hole 26 and second through hole 27 are formed in the central and lower part of membrane 17 in the longitudinal direction A. Of these, first through hole 26 is formed in sheet member 21 on the front side. Second through hole 27 has a smaller diameter than first through hole 26 and is formed in sheet member 22 on the back side. The center of first through hole 26 and the center of second through hole 27 are coaxial.

[0035] 4 to 6, both sheet members 21, 22 are welded at welded portions 29. These welded portions 29 include end welded portions 29a formed around the entire periphery at both ends of membrane 17, a central welded portion 29b formed around first opening 24, and a longitudinal welded portion 29c formed between end welded portions 29a and central welded portion 29b.

[0036] A large number of first and second slits 71, 72 are formed in the front-side sheet member 21 for releasing to the outside the air 11 supplied from the gas supply nozzle 19 into the bag-shaped portion 23. As shown by the imaginary line in Fig. 6, a non-forming region 31 in which the first and second slits 71, 72 are not formed is provided in the lower part of the front-side sheet member 21, and the first and second slits 71, 72 are formed in the region other than the non-forming region 31 and the welded portion 29.

[0037] 4 and 7, the support tube 18 is a straight circular tube made of resin with both ends open, and a circular second opening 33 is formed in the center and upper part in the longitudinal direction A of the support tube 18. As shown in Figures 8 and 9, when the support tube 18 is inserted into the insertion part 16 of the membrane 17, the position of the first opening 24 of the membrane 17 and the position of the second opening 33 of the support tube 18 coincide with each other.

[0038] 7, a bolt insertion hole 34 is formed in the lower part of the center in the longitudinal direction A of the support tube 18. As shown in Fig. 8 and Fig. 9, the position of the bolt insertion hole 34 of the support tube 18 and the center position of the second through hole 27 of the sheet member 22 on the back side of the membrane 17 coincide with each other.

[0039] 2, 6, 8, 9, 10 to 12, the gas supply nozzle 19 has a circular tubular portion 37, a flange portion 38, and a top plate portion 39. The tubular portion 37 is inserted into the first through-hole 26 (see FIGS. 14 and 20) of the sheet member 21 on the front side of the membrane 17, and protrudes below the membrane 17. A pair of cutout portions 41 and an inlet 42 that opens into the air supply pipe 12 are formed at the lower end of the tubular portion 37.

[0040] The flange 38 is formed at the upper end of the tube portion 37 and projects outward in the radial direction of the tube portion 37, and enters the bag-shaped portion 23 of the membrane 17, as shown in Figures 8 and 9. A plurality of outlet ports 43 that open into the bag-shaped portion 23 are formed on the outer circumferential surface of the flange 38. The entire periphery of the first through-hole 26 (see Figure 14) of the front-side sheet member 21 is welded to the underside of the flange 38, thereby attaching the gas supply nozzle 19 to the membrane 17.

[0041] The top plate portion 39 is formed at the upper end of the cylindrical portion 37, and a bolt insertion hole 45 is formed in the top plate portion 39 so as to pass therethrough in the vertical direction.

[0042] An air flow passage 46 communicating with the inlet 42 and the outlet 43 is formed in the gas supply nozzle 19. As a result, the inside of the air supply pipe 12 and the inside of the bag-shaped portion 23 of the membrane 17 communicate with each other via the air flow passage 46 of the gas supply nozzle 19. In addition, a recess 47 curved in an arc shape along the outer circumferential surface of the support tube 18 is formed on the upper surface of the gas supply nozzle 19.

[0043] As shown in Figures 8 and 9, the membrane type air diffuser 10 is fixed to the air supply pipe 12 via an adapter 14. As shown in Figures 13 and 14, the adapter 14 has a rectangular parallelepiped adapter body 50 sandwiched between the membrane type air diffuser 10 and the air supply pipe 12, and a pair of support parts 55 that support the support pipe 18 of the membrane type air diffuser 10 from below via the membrane 17. The support parts 55 are provided at both ends of the adapter body 50 in the longitudinal direction A of the membrane type air diffuser 10.

[0044] The underside of the adapter body 50 is formed with a recess 52 curved in an arc shape along the outer circumferential surface of the air supply pipe 12, and an O-ring fitting portion 56. The adapter body 50 is also formed with a circular first fitting hole 53 penetrating in the up-down direction. The O-ring fitting portion 56 is formed to surround the periphery of the first fitting hole 53.

[0045] As shown in Fig. 1, the air supply pipe 12 is disposed below the membrane type air diffuser 10 and is perpendicular to the membrane type air diffuser 10 at the center in the longitudinal direction A of the membrane type air diffuser 10. As shown in Fig. 14, a plurality of circular second fitting holes 54 penetrating the air supply pipe 12 from the inside to the outside are formed at the upper end of the air supply pipe 12.

[0046] The position of the first fitting hole 53 of the adapter 14 coincides with the position of the second fitting hole 54 of the air supply pipe 12. As shown in Figures 8, 9 and 14, the cylindrical portion 37 of the gas supply nozzle 19 is fitted from above into the first fitting hole 53 of the adapter 14 and the second fitting hole 54 of the air supply pipe 12, and the lower end portion protrudes into the air supply pipe 12 through the second fitting hole 54.

[0047] In addition, an O-ring 62 (an example of a sealing member) that simultaneously seals between the underside of the adapter 14 and the outer peripheral surface of the air supply pipe 12, and between the inner peripheral surface of the first fitting hole 53 of the adapter 14 and the outer peripheral surface of the cylindrical portion 37 of the gas supply nozzle 19, is fitted into the O-ring fitting portion 56 and held by the adapter 14.

[0048] The air supply pipe 12, the adapter 14, the membrane 17, the support pipe 18 and the gas supply nozzle 19 are connected by a connecting member 51. The connecting member 51 has a T-head bolt 57 and a nut 58.

[0049] The T-head bolt 57 is inserted from below through the second insertion hole 54 of the air supply pipe 12, the bolt insertion hole 45 of the gas supply nozzle 19, the second through hole 27 of the sheet member 22 on the back side of the membrane 17, and the bolt insertion hole 34 of the support pipe 18, and protrudes into the support pipe 18.

[0050] Further, the head 57 a of the T-head bolt 57 is fitted into both notches 41 of the cylindrical portion 37 of the gas supply nozzle 19 from below, and engages with the inner circumferential surface of the upper end portion of the air supply pipe 12 .

[0051] Furthermore, the nut 58 is screwed onto the T-head bolt 57 inside the support tube 18 and engages with the inner peripheral surface of the support tube 18 .

[0052] The entire periphery of the second through hole 27 of the rear sheet member 22 is sandwiched between the outer circumferential surface of the support tube 18 and the top plate portion 39 of the gas supply nozzle 19. A cylindrical gasket 60 made of an elastic material such as rubber is fitted into the bolt insertion hole 34 of the support tube 18. This prevents a portion of the air 11 supplied from the inside of the air supply pipe 12 through the ventilation flow path 46 of the gas supply nozzle 19 into the bag-shaped portion 23 of the membrane 17 from leaking into the support tube 18 from between the bolt insertion hole 34 and the T-head bolt 57.

[0053] The arrangement pattern of the first and second slits 71, 72 formed in the sheet member 21 on the front side of the membrane 17 will be described below.

[0054] As shown in Figures 15 and 16, multiple slit rows 73 are provided in the sheet member 21 on the front side of the membrane 17, in which multiple first and second slits 71, 72 are arranged alternately in a row along the longitudinal direction A (an example of the first direction) of the membrane 17.

[0055] The first and second slits 71, 72 are slits that are closed when air diffusion is not performed and are open when air diffusion is performed.

[0056] The first slits 71 are formed long in the longitudinal direction A of the membrane 17, and the second slits 72 are formed long in a second direction 75 inclined with respect to the longitudinal direction A. The second slits 72 are inclined with respect to the first slits 71 at an inclination angle α of 25° or less.

[0057] Moreover, the first and second slits 71, 72 of the slit row 73 of one side C1 and the first and second slits 71, 72 of the slit row 73 of the other side C2 that are adjacent to each other are alternately arranged in a staggered manner in the circumferential direction B (an example of a third direction perpendicular to the first direction) of the membrane 17. That is, if the pitch between the first slits 71 and the second slits 72 in the longitudinal direction A is taken as the slit pitch P1, the first and second slits 71, 72 of the slit row 73 of the other side C2 are shifted in the longitudinal direction A of the membrane 17 by half the slit pitch P1 (i.e., P1 / 2) with respect to the first and second slits 71, 72 of the slit row 73 of the adjacent one side C1.

[0058] In addition, a virtual straight line 76 passing through the longitudinal center D1 of the second slit 72 of the slit row 73 of one side C1 adjacent to the second slit 72 of the slit row 73 of the other side C2 that is closest to the second slit 72 of the slit row 73 of the first side C1 in the circumferential direction B of the membrane 17 is inclined in the direction 77 opposite to the second direction 75.

[0059] If the length of the first and second slits 71, 72 is the slit length L, and the pitch between adjacent slit rows 73 on one side C1 and slit rows 73 on the other side C2 in the circumferential direction B of the membrane 17 is the row pitch P2, the following magnitude relationship is maintained. Slit length L<row pitch P2≦slit pitch P1 Furthermore, if the distance between the first slit 71 and the second slit 72 in the longitudinal direction A of the membrane 17 is taken as a slit distance E, the following magnitude relationship is maintained.

[0060] Slit length L < slit spacing E During aeration, air 11 is supplied from inside the air supply pipe 12 through the air passage 46 of the gas supply nozzle 19 into the bag-shaped portion 23 of the membrane 17, and when the bag-shaped portion 23 expands, a tensile force F (see Figure 17) in the circumferential direction B of the membrane 17 acts on the first and second slits 71, 72.

[0061] The operation of the above configuration will be described below.

[0062] 1, 8 and 9, by driving the blower 15, the air 11 is supplied from the blower 15 into the air supply pipe 12, and the air 11 in the air supply pipe 12 flows from the inlet 42 of the gas supply nozzle 19 through the air flow passage 46 and into the bag-shaped portion 23 of the membrane 17 through the outlet 43. This causes the bag-shaped portion 23 to expand, and as shown in FIG. 17, a tensile force F in the circumferential direction B of the membrane 17 acts on the first and second slits 71 and 72, opening the first and second slits 71 and 72, and the air 11 in the bag-shaped portion 23 is released to the outside from the first and second slits 71 and 72 of the front sheet member 21, so that a large number of air bubbles 4 are released from the membrane type air diffuser 10 into the water 3 to be treated.

[0063] At this time, the tensile force F may cause cracks 79, 80 to occur at the ends of the first and second slits 71, 72.

[0064] In this case, since the second slits 72 are inclined with respect to the first slits 71, the direction in which a crack 79 occurring at the end of adjacent first slits 71 propagates differs from the direction in which a crack 80 occurring at the end of the second slit 72 propagates. Therefore, the possibility that the crack 79 occurring at the end of the first slit 71 and the crack 80 occurring at the end of the second slit 72 will connect is reduced, and the occurrence rate of defects in which adjacent first and second slits 71, 72 communicate with each other via the cracks 79, 80 can be reduced.

[0065] Furthermore, even if a crack 80 that has occurred at the end of the second slit 72 of the slit row 73 of one side C1 and a crack 80 that has occurred at the end of the second slit 72 of the slit row 73 of the other side C2 that are adjacent to each other in the circumferential direction B of the membrane 17 propagate, since the above-mentioned virtual straight line 76 is inclined in the direction 77 opposite to the second direction 75 (see Figure 16), the crack 80 that has occurred at the end of the second slit 72 of the slit row 73 of the one side C1 and the crack 80 that has occurred at the end of the second slit 72 of the slit row 73 of the other side C2 are unlikely to connect, thereby reducing the occurrence rate of defects in which adjacent second slits 72 are connected via the crack 80.

[0066] In the present invention, as shown in FIG. 16, the first and second slits 71, 72 are arranged in a staggered manner so that the virtual straight line 76 is inclined in the direction 77 opposite to the second direction 75. However, as a reference example, as shown in FIG. 18, if the first and second slits 71, 72 are arranged in a staggered manner so that the virtual straight line 76 passing through the center D1 of the second slit 72 of the slit row 73 of one side C1 and the center D2 of the second slit 72 of the slit row 73 of the other side C2 that is closest to the second slit 72 of the slit row 73 of the one side C1 is inclined in the same direction as the second direction 75 (the inclination angle is slightly different in FIG. 18 but the inclination direction is the same), as shown in FIG. 19, there is an increased possibility that a crack 80 occurring at an end of the second slit 72 of the slit row 73 of one side C1 and a crack 80 occurring at an end of the second slit 72 of the slit row 73 of the other side C2 will connect, and there is a risk of an increase in the occurrence of a defect in which adjacent second slits 72 communicate with each other via the crack 80.

[0067] 17, during the above-described air diffusion, the tensile force F in the circumferential direction B generated in the bag-shaped portion 23 of the expanded membrane 17 becomes a force for opening the first and second slits 71, 72. At this time, the direction in which the first slit 71 opens coincides with the direction of the tensile force F, but since the second slit 72 is inclined at an angle α (see FIG. 16), the direction in which the second slit 72 opens does not coincide with the direction of the tensile force F. That is, the first slit 71 opens with the tensile force F, whereas the second slit 72 opens with a force F' of Fcosα, which is smaller than the tensile force F. For this reason, as the angle α increases, the second slit 72 becomes more difficult to open than the first slit 71.

[0068] As a result, when a small amount of air is supplied from the air supply pipe 12 to the membrane type air diffuser 10, most of the supplied air 11 becomes air bubbles 4 and is released to the outside through the opened first slit 71, whereas the amount of air bubbles 4 released to the outside through the second slit 72 which is less likely to open is small.

[0069] In addition, when a large volume of air is being diffused from the air supply pipe 12 to the membrane type air diffuser 10, the second slits 72 open, and as the volume of air supplied increases, the number of open second slits 72 increases, and the supplied air 11 is released to the outside as air bubbles 4 from the open first and second slits 71, 72.

[0070] As a result, when the amount of air supplied from the air supply pipe 12 to the membrane type air diffuser 10 increases or decreases, the number of second slits 72 that open increases or decreases accordingly. Therefore, even if the amount of air supplied increases or decreases, the variation in size of the released bubbles 4 can be reduced, and bubbles 4 of approximately uniform size are released.

[0071] Furthermore, when the blower 15 is stopped and the air 11 inside the bag-shaped portion 23 of the membrane 17 is released to the outside through the first and second slits 71, 72, the bag-shaped portion 23 shrinks and the tensile force F no longer acts on the first and second slits 71, 72, so that the first and second slits 71, 72 close as shown in Figures 15 and 16.

[0072] A method for manufacturing the membrane 17 of the membrane type air diffuser 10 will be described below.

[0073] First, as shown in FIG. 20 , the tubular portion 37 of the gas supply nozzle 19 is inserted into the first through hole 26 of the front sheet member 21 in which a number of slits 71, 72 are formed, and the gas supply nozzle 19 is attached to the peripheral portion of the first through hole 26.

[0074] 21, an outer periphery 65 (see FIG. 20) of the front sheet member 21 and an outer periphery 66 (see FIG. 20) of the back sheet member 22 are welded to form a rectangular membrane sheet 67 having a bag-shaped portion 23. The dotted portion in FIG. 21 is the welded portion 29 between the front sheet member 21 and the back sheet member 22.

[0075] Thereafter, opposing long sides 68 of the membrane sheet 67 are joined together to form a tube, thereby forming the membrane 17 having a bag-shaped portion 23 inside, an insertion portion 16 in the center, a first opening 24 at the top, and a gas supply nozzle 19 at the bottom, as shown in FIG. 4. (Second embodiment) In the first embodiment described above, as shown in FIG. 4, a membrane type air diffuser 10 having a tubular (cylindrical) membrane 17 is described. However, the membrane type air diffuser is not limited to this form. For example, in the second embodiment described below, as shown in FIGS. 22 and 23, a membrane type air diffuser 102 having a flat membrane 101 may be used.

[0076] The membrane 101 is formed in a rectangular shape and is attached to the upper surface of a rectangular base plate 103 made of plastic, metal, or the like. The periphery of the membrane 101 is fixed to the base plate 103 by fixing parts 104 (e.g., a crimping member, etc.). A ventilation part 105 is formed between the membrane 101 and the base plate 103. In addition, a short cylindrical air supply nozzle 106 is provided at one end of the membrane 101 in the longitudinal direction A. The air supply nozzle 106 communicates with the ventilation part 105 and is connected to an air supply source.

[0077] A large number of first and second slits 71, 72 are formed in the membrane 101 in the same arrangement pattern as in the first embodiment. That is, the membrane 101 is provided with a plurality of slit rows 73, in which a plurality of first and second slits 71, 72 are alternately arranged in a row along the longitudinal direction A (an example of the first direction) of the membrane 101.

[0078] The first slit 71 is formed to be long in the longitudinal direction A of the membrane 101, and the second slit 72 is formed to be long in a second direction 75 inclined with respect to the longitudinal direction A.

[0079] In addition, in the short direction G of the membrane 101 (an example of a third direction perpendicular to the first direction), the first and second slits 71, 72 of the slit row 73 of one side C1 and the first and second slits 71, 72 of the slit row 73 of the other side C2 that are adjacent to each other are arranged alternately in a staggered pattern.

[0080] The operation of the above configuration will now be described.

[0081] During aeration, air 11 is supplied from air supply nozzle 106 to aeration section 105, causing membrane 101 to expand in a mountain shape when viewed from longitudinal direction A, as shown in Fig. 23, and a tensile force F in transverse direction G is generated in membrane 101. This tensile force F acts on first and second slits 71, 72, opening them and discharging air 11 from within aeration section 105 to the outside through first and second slits 71, 72, causing a large number of air bubbles 4 to be discharged from membrane type aeration device 102 into water 3 to be treated.

[0082] At this time, the tensile force F may cause cracks 79, 80 to occur at the ends of the first and second slits 71, 72.

[0083] In this case, since the second slits 72 are inclined with respect to the first slits 71, the direction in which a crack 79 occurring at the end of adjacent first slits 71 propagates differs from the direction in which a crack 80 occurring at the end of the second slit 72 propagates. Therefore, the possibility that the crack 79 occurring at the end of the first slit 71 and the crack 80 occurring at the end of the second slit 72 will connect is reduced, and the occurrence rate of defects in which adjacent slits 71, 72 communicate with each other via the cracks 79, 80 can be reduced.

[0084] Furthermore, even if a crack 80 that has occurred at the end of the second slit 72 of the slit row 73 of one side C1 and a crack 80 that has occurred at the end of the second slit 72 of the slit row 73 of the other side C2, which are adjacent to each other in the short side direction G of the membrane 101, propagate, since the above-mentioned virtual straight line 76 is inclined in the direction 77 opposite to the second direction 75 (see Figure 16), the crack 80 that has occurred at the end of the second slit 72 of the slit row 73 of the one side C1 and the crack 80 that has occurred at the end of the second slit 72 of the slit row 73 of the other side C2 are unlikely to connect, thereby reducing the occurrence rate of defects in which adjacent second slits 72 are connected via the crack 80.

[0085] In the above second embodiment, a type of membrane type air diffuser 102 in which a flat membrane 101 is attached to a base plate 103 is shown, but as shown in the background art, the present invention may be applied to a type of membrane type air diffuser in which a support tube is inserted into a tubular membrane and both ends of the membrane are watertightly fixed to the support tube with fasteners such as bands. [Explanation of symbols]

[0086] 10. Membrane type aeration device 11 Air (gas) 16 Insertion section 17 Membrane 18 Support tube (support body) 19 Gas supply nozzle (gas supply section) 21 Front sheet material 22 Back side sheet material 23 Pouch 46 Ventilation channel 71 First Slit 72 Second Slit 73 Slit Row 75 Second direction 76 Imaginary Line 77 opposite direction 101 Membrane 102 Membrane type aeration device A: longitudinal direction of membrane (first direction) B Circumferential direction of the membrane (third direction) D1, D2: Center of the second slit in the longitudinal direction E Slit Spacing F Tensile force G Short side of membrane (third direction) L slit length P1 Slit pitch P2 row pitch α angle

Claims

1. A membrane type air diffuser having an expandable and contractible membrane with a plurality of slits for releasing gas to the outside, A plurality of slit rows are provided in the membrane, each row having a plurality of slits aligned in a first direction; In each slit row, first slits long in a first direction and second slits long in a second direction inclined with respect to the first direction are alternately formed, the first and second slits of one slit row and the first and second slits of the other slit row that are adjacent to each other in a third direction perpendicular to the first direction are alternately arranged in a staggered manner, a virtual straight line passing through a center in the longitudinal direction of a second slit of one slit row adjacent to the second slit of the one slit row in the third direction and a center in the longitudinal direction of a second slit of the other slit row that is closest to the second slit of the one slit row is inclined in a direction opposite to the second direction, A membrane type air diffuser characterized in that when the membrane expands during air diffusion, a tensile force in a third direction acts on the first and second slits.

2. 2. The membrane type air diffuser according to claim 1, wherein the second slit is inclined at an angle of 25 degrees or less with respect to the first slit.

3. The length of the first and second slits is defined as a slit length, a pitch between the first slit and the second slit in the first direction is defined as a slit pitch; If the pitch between adjacent slit rows in the third direction is defined as the row pitch, Slit length < row pitch ≦ slit pitch 3. The membrane type air diffuser according to claim 1, wherein the following relationship is maintained:

4. The length of the first and second slits is defined as a slit length, If the distance between the first slit and the second slit in the first direction is defined as a slit distance, Slit length < slit spacing 4. The membrane type air diffuser according to claim 1, wherein the following relationship is maintained:

5. The membrane is formed in a tubular shape having a hollow insert, A support is inserted into the membrane insertion portion, The membrane is provided with a gas supply, The membrane has a bag-shaped portion formed in a bag shape by two sheet members on the front and back, the gas supply unit has an air passage communicating from the outside to the inside of the bag-shaped portion of the membrane; The first and second slits are formed in a sheet member that constitutes an outer peripheral surface of the bag-shaped portion of the membrane, The first direction is a longitudinal direction of the membrane; 5. The membrane type air diffuser according to claim 1, wherein the third direction is a circumferential direction of the membrane.

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