GB2461819A

GB2461819A - Device for fixing a perforated aeration membrane

Info

Publication number: GB2461819A
Application number: GB0914932A
Authority: GB
Inventors: Udo Meyer
Original assignee: Aquaconsult Anlagenbau GmbH
Current assignee: Aquaconsult Anlagenbau GmbH
Priority date: 2004-05-28
Filing date: 2005-05-04
Publication date: 2010-01-20
Anticipated expiration: 2025-05-04
Also published as: GB0914932D0; GB2461819B

Abstract

The invention relates to apparatus for use when introducing gas bubbles into a liquid. The invention comprises device (1) for fastening a perforated aeration membrane (2) to an aerator base plate (3) as well as to an aerator base plate (3) therefor. The aerator base plate (3) has an undercut groove (4) in at least one rim region thereof, into which a locking body (7) fits clampingly, thereby clamping the membrane (2) in said groove (4), the locking body (7) has a generally circular cross-section, whilst the groove (4) has an at least substantially oval cross-section. The locking body (7) is designed to be generally cylindrical.

Description

A Device for Fastening a Perforated Aeration Membrane The invention relates to a device for fastening a perforated aeration membrane to an aerator base plate that has an undercut groove in at least one rim region into which a locking body clamping the membrane in said groove and having a generally circular cross-section fits clampingly.

The invention also relates to an arrangement for introducing gas bubbles into a liquid, comprising an aerator base plate and a perforated membrane fastened thereto provided above said base plate.

Furthermore, the invention relates to an aerator base plate therefor.

For biologically cleaning waste water, the aerobic process has proved to be successful, in which arrange- ments for introducing gas bubbles into a liquid are po-sitioned on the bottom of a clarification bed. These arrangements comprise a perforated membrane arranged above a plate-shaped base body, wherein the gas, in particular air, to be introduced into the waste water is supplied into the space between the base body and the membrane. From there, the gas can get through the perforations provided in the membrane in the form of bubbles evenly distributed into the waste water in the clarifier.

EP 0 359 698 Bi discloses a plate-shaped gas dis-tributor for aerating water with tine bubbles. Such distributors commonly are also termed "aerators" or "plate aerators", irrespective of whether air or an-other gas is introduced into the liquid. The rims of a rubber-elastical, perforated gas-or air-distributing membrane are clamped in the rim region of a plate-type base body in a gas-tight manner. According to one em-bodiment, the membrane is fixed in a clamping manner in grooves at the narrow sides of the base plate, for which purpose ledges having integrally mounted round beads are used, which retain the membrane rims in the groove. However, this way of fastening the membrane is not satisfactory, since the ledges with the round beads are relatively complex both to produce and to install, maintenance work or an exchange of the membrane being rendered difficult.

From WO 98/21151 Al, moreover, a device is known in which the membrane, by means of integral beads, is mounted in grooves adjacent to the longitudinal rims of the base plate. Here, too, the grooves are circular in cross-section, and the beads of the membrane may have the form of hollow sealing and clamping beads. In this case, it is primarily disadvantageous that the membrane which as such already requires great care in terms of material selection and production with regard to pro- viding the perforations, becomes additionally more com-plicated and expensive in its production, apart from the fact that a secure, tight retention of the membrane on the aerator plate is not ensured.

In other known devices, the membrane is glued to the base plate or connected thereto by vulcanizing.

These options of fastening the membrane have, however, not been successful because maintenance work is ad-versely affected.

It has repeatedly been shown that, also at an in-creased gas pressure, the gas-proof, tight connection between membrane and aerator base plate during opera-tion is critical. In many cases, pressurization of the membrane easily causes an unintentional detachment of the membrane from the base plate. On the other hand, the fastening constructions often are complex and ex-pensive, so that not only production and installation but also maintenance is time-consuming and expensive.

It is now an object of the invention to eliminate these problems and to provide an improved fastening technique, by means of which the membrane shall be eas- ily fastened and shall durably withstand a pressuriza-tion. Moreover, the device shall be easy to handle, and exchanging the membrane for maintenance work shall be easily carried out. Furthermore, the production and in- stallation shall require as little expenditures as pos-sible and involve the lowest costs possible.

With the present device, this object is achieved according to the invention in that the groove has an at least substantially oval cross-section and the locking body is designed to be generally cylindrical, the groove wall and/or the locking body being elastically deformable. The special design of the groove results in an improved combined positive and non-positive locking engagement for the connection of the membrane with the aerator base plate with the aid of the locking body.

When the simple locking body which is inexpensive to produce and which has a cylindrical shape snaps into the elliptical groove, the locking body preferably adapts to the shape of the groove, resulting in a good clamping fit. When pressure is applied to the membrane, tension is exerted on the locking body, with the ten-sile stress being optimally distributed so that the membrane will durably and securely be held in a clamp- ing fit. The aerator base plate with a groove of sub-stantially oval cross-section is, moreover, also simple and inexpensive to produce. Furthermore, it is favor- able that no special measures are required on the mem-brane, whereby also the costs of the membrane can be kept low.

The positive and non-positive engagement connec-tion of the membrane with the aerator base plate can particularly advantageously be achieved if the locking body is formed by a cylindrical tube. The tube may be a rigid tube, in which case the groove walls will be elastically deformable, yet preferably the tube is elastically compressible.

The material for the locking body may be chosen as desired, wherein a synthetic material, e.g. polyethyl-ene, appears to be most suitable, particularly if the locking body is elastically flexible or is elastically deformable.

For easy mounting and dismounting, e.g. for possi-ble maintenance work, it is advantageous if the groove of at least substantially oval cross-section is open towards the upper side of the base plate and extends with its longer cross-sectional axis towards this upper side. In this way, the groove is readily accessible (from the top), and the insertion of the membrane as well as pressing the locking body into the groove can be effected in a simple way.

According to a preferred feature of the invention, it is suitable if the groove externally, on the outer rim of the base plate, is delimited by a web wall which projects upwards when in the operating position. In this respect, it is particularly suitable if the web wall is elastically deflectable. Thereby, the web wall may be used as a hold when detaching the membrane, by elastically deflecting it outwards, whereby the groove opening is widened for taking the locking body out of the groove. In addition, the web wall may also assume the function of a protective side wall.

With regard to a secure clamping, it is preferred that the web wall has an inwardly directed, bead-like thickened portion which defines the undercut portion of the groove on the outer side of the groove. For exam-ple, except for the bead-like thickened portion, the web wall largely has a uniform wall thickness, this be- ing particularly suitable in view of a simpler produc-tion from a synthetic material.

For mounting it is also advantageous if the bottom of the groove of at least substantially oval cross-section, on the outer rim of the base plate is adjoined by a foot web.

Preferably, the foot web and the web wall may merge into each other by forming a uniform, in particu- lar plane, outer surface. This will result in a par-ticularly compact shape of the base plate and, thus, of the aerator, and, moreover, the foot web and the web wall will then together form a carrying and handling portion, wherein by pressing the foot web inwards, a release of the locking body from the base plate can be facilitated.

For storage and transportation purposes it is ad-vantageous if the foot web has a stacking recess on its lower side for engagement with the upper side of the web wall of a corresponding base plate arranged there-below. In this manner, several base plates may simply be stacked one on top of the other.

In some instances it is desirable to provide a fastening in addition to the clamping connection, which will provide the membrane with an intensified retention on the base plate. In this respect, the base plate may have an adhesive face adjacent the groove of the substantially oval cross-section for additionally glu- ing the membrane thereto. The adhesive face is pref era- bly oblique to the upward direction (and inward direc-tion).

Regarding a simple and cost-effective production, the base plate may be formed by an extruded section part as known per se.

To allow a simple gas supply, it is advantageous if the base plate is formed with an, e.g. tubular, gas supply channel with gas passage openings on the upper side thereof. Advantageously, this gas supply channel will be arranged substantially in the area of the mid-dle of the width of the aerator base plate.

For a simple assembly of an aeration arrangement, it is also suitable to provide a fastening plate having an engagement lug to overlap a foot of the foot web.

The engagement lug may also be a hook part obtained by partially cutting out and bending outwards the metal fastening plate.

An object of the invention is also an aerator base plate having a design as previously indicated and de-fined in claims 17 to 27.

The invention will be further explained by way of preferred exemplary embodiments illustrated in the drawings. Therein, Fig. 1 shows a sectional view of an aerator ar- rangement comprising a device according to the inven-tion for fastening a membrane to an aerator base plate; Fig. 2 shows a sectional view of a fastening plate for such a base plate; and Fig. 3 shows a top view onto the fastening plate according to Fig. 2.

In Fig. 1, a device 1 for fastening a perforated aeration membrane 2 to an aerator base plate 3 is sche-matically shown in cross-section. In a manner known per Se, the base plate 3 is formed by a strand section part. By way of precaution it should be mentioned that the term "base plate" 3 here is to be understood as a general and subject-oriented term and, in any event, shall not be limited to (precisely) plane structures.

In the two rim regions at the longitudinal rims of the base plate 3, one undercut groove 4 respectively is formed having a substantially oval cross-section. The groove 4 is open towards the upper side 5 of the base plate 3 and extends vertically with its longer cross-sectional axis 6, i.e. towards the upper side 5. The ratio of the lengths of the longer axis 6 to the shorter transverse axis of the cross-sectional "el- lipse" of the groove 4 may, e.g., be 8:6 or 8:7, pref-erably 8:6.6.

The membrane 2 is tightly clamped in the groove 4 by means of a locking body 7 designed as a generally cylindrical tube (termed tube 7 in short hereinafter).

The tube 7 is made of plastics, e.g., in particular polyethylene, whereby the elasticity during resilient deformation, when it snaps into the groove 4, is read-ily controllable.

In operation, the membrane 2 is slightly lifted off the base plate 3, and this situation is illustrated in Fig. 1. With its rim region, the membrane 2 extends from the inner side of the groove 4 beyond the outer rim of the groove 4, wherein it is shown to lie in con-tact with a web wall 8 that forms a boundary towards the outside. On the inner side of the web wall 8 that faces the membrane 2, an inwardly directed, bead-like thickened portion 10 is formed. It defines substan-tially the undercut portion of the groove 4 on the outer side of the latter. In downward direction, the web all 8 merges into a foot web 9. The web wall 8 and the foot web 9 together form a plane outer surface 11 of the aerator base plate 3.

On the upper side 5 of the aerator base plate 3, the inner side of the undercut groove 4 of substan-tially oval cross-section continues in a adhesive face -10 - 13 adjoining the inner undercut 12. As can be seen from the drawing, the adhesive face 13 extends upwards with an inward inclination, and it may be used for addi-tional gluing of the membrane 2 to the base plate 3.

In the region of the middle of the width of the base plate 3, there is a tubular supply channel 14 hav- ing passage openings 15 on its upper side, which pas-sage openings supply the space 16 between the base plate 3 and the membrane 2 with gas, in particular with air.

In order to equip a clarifier with a thus-designed arrangement for introducing gas bubbles into the waste water contained in the clarifier, several base plates 3 can be arranged in sequence as well as adjacent each other. To fix the aerator base plates 3 in the clari-fier, these base plates 3 can each be arranged on a fastening plate 17 merely indicated at the right-hand side of Fig. 1. In this case, the aerator base plate 3 "stands" with its respective foot web 9 on the fasten-ing plate 17. In the following, an example of such a fastening plate 17 will be explained in more detail by way of Figs. 2 and 3.

The gas supply is obtained through respective con-nections (not shown) to the supply channels 14 of the -11 -base plates 3. In this respect, it may be provided that the supply channels 14 of several adjacent base plates have a common gas connection. For such gas connections, the spaces between the central supply channel 14 and the foot webs 9 located at the rims of the aerator base plate 3 may be utilized, it being possible to lay hoses and the like in these spaces 18 for feeding supply channels 14 of adjacent plate aerators.

The web wall 8 may be designed to be elastically deflectable so as to facilitate removal of the membrane 2 including the tube 7 from the groove 4 in the base plate 3. Such a deflection can also be assisted by pressing the foot web 9 inwards.

The foot web 9 continues in an inwardly directed foot 19. This foot 19 is retained underneath an engage-ment lug 20 of the fastening plate 17, cf. also Figs. 2 and 3. The engagement lug 20 may substantially entirely overlap the foot 19.

On the lower side of the foot web 9 or of the foot 19 a stacking recess 21 is further formed on the outer side thereof. As schematically indicated in the lef t- hand area of Fig. 1, the stacking recess 21 accommo-dates the upper side of a web wall 8 of a corresponding aerator base plate 3 only partially shown in Fig. 1, -12 -arranged below the aerator base plate 3. By providing such stacking recesses 21, the present aerator base plate 3 can be stacked for storing and transporting purposes.

From Figs. 2 and 3, the fastening plate 17 for fixedly retaining the aerator base plate 3 is shown in a sectional view and in top view, respectively. As il-lustrated in Figs. 2 and 3, the fastening plate 17 has two engagement lugs 20 for receiving two feet 19 of an aerator base plate 3 (not shown in Fig. 2), the engage-ment lugs 20 substantially being hook parts projecting from the base plate 17, which hook parts are formed by cutting or punching out and by bending outwards.

Next to the engagement lugs 20, long-hole-type openings 22 are provided in the rim region of the f as-tening plate 17 for fastening the fastening plate 17 to the bottom of the respective clarifier basin. The long- hole openings 22 allow for an adjustment of the fasten-ing plate 17 made of steel sheet or the like on the bottom of the basin.

The base plate 3 consists, e.g., of a strong syn-thetic material, such as, e.g., polyvinyl chloride, polyethylene, polypropylene, polycarbonate, ABS or the like, commonly used for this purpose. The membrane 2 is -13 - formed by a portion of a bendable, elastic sheet mate- rial, e.g. of a polycondensate or a polyaddition prod- uct, such as, in particular, polyurethane, EPDM, sili-cone, Viton, polethylene-trifluoride or polycarbonate, with a plurality of conventional perforations (not il-lustrated).

Instead of being tubular, the locking body 7 may also be designed with a full cross-section and made of an appropriately elastic material, such as polyure-thane.

-14 -

Claims

Claims: 1. A device (1) for fastening a perforated aeration membrane (2) to an aerator base plate (3), with an aerator base plate (3) that has an undercut groove (4) in at least one rim region, and with at least one lock-ing body (7) having a generally circular cross-section, which locking body (7) clampingly fits into said groove (4) thereby tightly clamping the membrane (2), charac- terized in that the groove (4) has an at least substan-tially oval cross-section, the wall of the groove (4) and/or the locking body (7) being elastically deform-able.
2. A device according to claim 1, characterized in that the locking body (7) is formed by a cylindrical tube.
3. A device according to claim 1 or 2, characterized in that the locking body (7) is made of a synthetic ma-terial, e.g. polyethylene.
4. A device according to any one of claims 1 to 3, -15 - characterized in that the groove (4) of at least sub-stantially oval cross-section is open towards the upper side (5) of the base plate (3) and extends with its longer cross-sectional axis (6) towards this upper side (5).
5. A device according to claim 4, characterized in that the groove (4) externally, on the outer rim of the base plate (3), is delimited by a web wall (8) which projects upwards when in the operating position.
6. A device according to claim 5, characterized in that the web wall (8) is elastically deflectable.
7. A device according to claim 5 or 6, characterized in that the web wall (8) has an inwardly directed, bead-like thickened portion (10) which defines the un-dercut portion of the groove (4) on the outer side of the groove.
8. A device according to any one of claims 1 to 7, characterized in that the bottom of the groove (4) of at least substantially oval cross-section is adjoined by a foot web (9) on the outer rim of the base plate -16 -(3).
9. A device according to claim 8 and according to any one of claims 5 to 7, characterized in that the foot web (9) and the web wall (8) merge into each other by forming a uniform, in particular plane, outer surface (11)
10. A device according to claim 8 or 9, characterized in that the foot web (9) has a stacking recess (21) on its lower side for engagement with the upper side of the web wall (8) of a corresponding base plate (3) ar-ranged therebe low.
11. A device according to any one of claims 1 to 10, characterized in that the base plate (3) has an, e.g. oblique, adhesive face (13) adjacent to the groove (4) of the substantially oval cross-section for addition-ally gluing the membrane (2) thereto.
12. A device according to any one of claims 1 to 11, characterized in that the base plate (3) is formed by an extruded section part.-17 -
13. A device according to any one of claims 1 to 12, characterized in that the base plate (3) is formed with an e.g. tubular, gas supply channel (14) with gas pas-sage openings (15) on the upper side thereof.
14. A device according to any one of claims 1 to 13, further comprising a membrane (2) which is tightly clamped to the aerator base plate (3) with the aid of the locking body (7).
15. A device according to any one of claims 8 to 14, characterized in that a fastening plate (17) is pro-vided having an engagement lug (20) for overlapping a foot (19) of the foot web (9)
16. A device according to claim 15, characterized in that the engagement lug (20) is a hook part obtained by partially cutting out and bending outwards the metal fastening plate (17).
17. An aerator base plate (3) having an undercut groove (4) at least in a rim region thereof for fasten-ing a perforated membrane (2), characterized in that the groove (4) has an at least substantially oval -18 -cross-section.
18. A base plate according to claim 17, characterized in that the groove (4) of at least substantially oval cross-section is open towards the upper side of the base plate (3) and, with its longer cross-sectional axis (4) projects towards this upper side (5)
19. A base plate according to claim 18, characterized in that the groove (4) externally, on the outer rim of the base plate (3), is delimited by a web wall (8) which extends upwards when in the operating position.
20. A base plate according to claim 19, characterized in that the web wall (8) is elastically deflectable.
21. A base plate according to claim 19 or 20, charac- terized in that the web wall (8) has an inwardly di-rected, bead-like thickened portion (10) which defines the undercut portion of the groove (4) on the outer side of the groove.
22. A base plate according to any one of claims 17 to 21, characterized in that at the outer rim of the base -19 -plate (3), a foot web (9) is adjoined to the bottom of the groove (4) of at least substantially oval cross-section.
23. A base plate according to claim 22 and according to any one of claims 19 to 21, characterized in that the foot web (9) and the web wall (8) merge into each other by forming a uniform, in particular plane, outer surface (11)
24. A base plate according to claim 22 or 23, charac-terized in that the foot web (9) has a stacking recess (21) on its lower side for engagement with the upper side of the web wall (8) of a corresponding base plate (3) arranged therebelow.
25. A base plate according to any one of claims 17 to 24, characterized in that adjacent to the groove (4) of substantially oval cross-section, the base plate (3) has an, e.g. oblique, adhesive face (13) for addition-ally gluing the membrane (2) thereto.
26. A base plate according to any one of claims 17 to 25, characterized in that the base plate (4) is formed -20 -by an extruded section part.
27. A base plate according to any one of claims 17 to 26, characterized in that the base plate (3) is formed with an, e.g. tubular, gas supply channel (14) with gas passage openings (15) on the upper side thereof.-21 -