Rotary disc filter and module for constructing same

(54) (56) (57)

AGENT

NAME

CALLED PUBLICATIONS: - - SUMMARY

A disk filter device (1) comprises a rotatable drum (2) around its central longitudinal axis. The disk filter device (1) is intended to receive a liquid which is to be filtered. The device (1) comprises at least one disc-shaped filter member (3) which extends outwardly in the transverse direction of the drum (2) and has a filter body (11) and at least one filter portion (4) supported thereon. A first fluid passage extends from the drum (2) through the filter member (3) and out through the filter portion (4). The filter portion (4) is formed by filter segments (13) removably anchored on the filter body (11). At least one second fluid channel extends between adjacent filter segments (13) to provide fluid communication between the filter segments (13). Also described is a module (12) for building a filter body (11) for a disk filter (1). The module (12) comprises two inner body portions (17) and two outer body portions (16) for at least partial enclosure of two adjacent filter segments (13) and an intermediate body portion (15) intended to be arranged between the two adjacent filter segments (13).

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The numbers in parentheses indicate the INID code.

526 692

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SUMMARY

A disk filter device (1) comprises a rotatable drum (2) around its central longitudinal axis. The disk filter device (1) is intended to receive a liquid to be filtered. The device (1) comprises at least one disc-shaped filter means (3) which extends outwardly in the transverse direction of the drum (2) and has a filter body (11) and at least one filter portion (4) supported thereon.

A first fluid passage extends from the drum (2) through the filter member (3) and out through the filter portion (4). The filter portion (4) is formed by filter segments (13) removably anchored on the filter body (11). At least one second fluid channel extends between adjacent filters 15 segments (13) to provide fluid communication between the filter segments (13). Also described is a module (12) for building a filter body (11) for a disk filter (1). The module (12) comprises two inner body portions (17) and two outer body portions (16) for at least partial enclosure of two adjacent filter segments (13) and an intermediate body portion (15) intended to be arranged between the two adjacent filter segments (13).

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Field of the Invention

The present invention relates to a disk filter device comprising a drum having a central longitudinal axis rotatably disposed about it and intended to receive a liquid to be filtered, and at least one disc-shaped filter member extending outwardly of the drum into the drum. transverse direction and having a filter body and at least one filter portion supported thereon, wherein a first fluid passage extends from the drum through the filter means and out through the filter portion and wherein the filter portion is formed by filter segments which are releasably anchored to the filter body. The invention also relates to a module for building a filter body for a disk filter.

Technical background

Disc filter devices are known, for example, by SE-C-224 131. In this device, water is fed through one end of a central rotatable drum and through openings in the perimeter of the drum radially outward to disc shaped filter chambers. Each of the filter chambers is delimited by an annular filter member having reciprocally separated filter portions supported by an annular filter body disposed therebetween. The filter means are mounted parallel to each other along the longitudinal axis of the drum. As water flows out through the filter portions, particles are retained in the filter chambers. When cleaning the filter portions, the drum is rotated and water is spilled onto the filter portions from outside the upper region of the filter device, whereby particles and water flow into the upper region of the drum and are collected in a groove extending through the drum. The filter portions comprise annular filter cloth portions on the sides of the filter bodies.

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SE-B-465 857 (WO 91/12067) discloses a disc filter assembly of similar type, wherein the disc-shaped filter members comprise a plurality of separate disc-shaped filter sections, which together form annular filter members. Because the annular filter members are divided into a plurality of separate units, the filter cloth is also divided into smaller pieces, so that in the case of a local damage to the cloth you only need to replace the cloth on one of the filter sections instead of on a whole annular disc.

In the two disk filter devices described above, the filter cloth can be attached in one of several different ways. In a conventional solution, the filter cloth is glued directly to the filter body on the sides facing away from each other.

This is especially common when the fabric consists of some textile or plastic material. The cloth can also consist of metal. In this case, it is often welded to the filter body, whereby reinforcing ribs are welded on the outside of the filter cloth wherever possible for better anchoring of the filter cloth. In yet another way of attaching the cloth to the body, the cloth is shaped like a bag, which is threaded around a filter body and shrunk onto it.

Disc filter designs of this kind are fraught with several problems. The filter cloth has a limited service life under normal use and must be replaced at regular intervals. Furthermore, the filter cloth is sensitive and can easily be damaged so that an early replacement of the filter cloth is required. If the fabric is damaged, an entire filter cloth section must be replaced.

Disc filter devices with detachably anchored filter segments have therefore been developed. Such a disk filter device is described in WO 99/30797. Here is described a disk filter device having a filter portion consisting of several filter segments. The filter segments are releasably anchored to a filter frame and include a frame and a filter cloth tensioned by the frame. The frame and filter frame are made of metal. With removably anchored disc filter segments, it is easier to replace parts of the filter. This disk filter works satisfactorily, though

526 692 it is desirable to further improve it by, for example, making manufacturing less costly. It would also be desirable to make these disk filter devices lighter and less bulky when sized for large flows. Furthermore, it would be desirable for the filter discs to carry with them a smaller amount of water in their rotary motion than hitherto. Less water would then accompany the disc filter device drain to drain away filtered particles, which could thus increase the capacity of the disc filter device.

Summary of the Invention

It is an object of the present invention to provide a disk filter device which, in comparison with known disk filter devices, is more compact and thus has a higher filtration capacity on the retained applied surface area.

Another object of the invention is to provide a disk filter device which is lighter than known disk filter devices.

A further object is to provide a disk filter device which can be manufactured at a lower cost compared to the prior art.

A particular object of the present invention is to provide a module which enables the construction of a filter body for a more compact disk filter device.

Yet another object is to provide a module which allows a cheaper structure of a filter body for a disk filter device.

A further object is to provide a module for the construction of a lighter disk filter device.

These objects are achieved according to the invention by giving the disk filter device of the kind initially mentioned, the characteristics which appear from the following claims 1. Preferred embodiments are shown in the subclaims 2-8. The objects are also achieved by means of a module according to claim 9, wherein preferred embodiments are defined in the dependent claims 10-15.

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The inventive disk filter device has at least one second fluid channel extending between adjacent filter segments to provide fluid communication between the filter segments. In this way, fluid can move between the filter segments and is therefore not drawn into the rotary motion. This increases the capacity of the disk filter device.

In one embodiment of the invention, the other fluid channels comprise voids in the filter body. Liquid communication between the filter segments can thus be very easily achieved.

The filter body between the filter segments preferably comprises a truss structure, the cavities of which form the other liquid channels. In this way, fluid communication can be easily achieved, while the body with good material economy can be made sufficiently strong.

According to a preferred embodiment of the invention, the filter body is made up of modules. A rational structure can thus be ensured.

Two modules preferably form a filter body around a filter segment and the two modules are then interconnected with each other at a distance from the surrounding filter segments. Joints can thus be avoided between the filter segments, which makes a dense construction easier to achieve.

The filter segments may be anchored to the filter body by means of grooves extending in the filter body in the plane of the filter segments. The filter segments can thus be securely anchored in the filter body at the same time as it is easy to insert and remove the filter segments. Furthermore, some self-sealing effect can be achieved.

According to one embodiment of the invention, the filter body forms at least a portion of a casing surface of the drum. Thus, the drum can be manufactured with a reduced material consumption.

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The filter body is preferably made of plastic and can thus be manufactured at a relatively low cost. Furthermore, the filter body becomes corrosion resistant.

The inventive module for constructing a filter body comprises two inner body portions and two outer body portions for at least partial enclosure of two adjacent filter segments and an intermediate body portion intended to be arranged between the two adjacent filter segments. With such modules, a filter frame can be effectively constructed.

The intermediate body comprises at least one fluid channel for providing fluid communication between adjacent elements. As a result, fluid can move between the filter segments and is therefore not pulled when the filter body rotates during the operation of the disk filter. The capacity of the disc filter can thus be increased.

The intermediate body portion advantageously comprises a truss structure, the cavities of which constitute fluid channels for providing fluid communication between adjacent filter segments. The truss construction provides good strength with minimized material consumption and in addition provides simple channels for the fluid passage between the filter segments.

One end of the outer body portions and the inner body portions preferably has means for interconnecting two modules. The modules can thus easily be connected to a filter body.

The inner body parts are advantageously arranged to form portions of a casing surface of the drum, which allows the drum to be built up with little material consumption.

The outer body portions and the inner body portions are preferably arranged symmetrically on the intermediate body portions. Only one type of module is thus needed for the construction of the filter body.

The inventive module may comprise grooves for anchoring filter segments, which grooves extend in the plane of the filter segments. This makes it possible to safely

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526 692 anchor the filter segments in a way that makes the segments easy to attach and remove.

According to a preferred embodiment, the inventive module is made of plastic. It can thus be manufactured relatively cheaply and allows for a lightweight filter body.

Brief description of the drawings

The invention will be described in more detail below with reference to the accompanying schematic drawings which, by way of example, illustrate presently preferred embodiments of the invention.

Fig. 1 is a perspective view schematically showing the principle of a prior art disk filter.

Fig. 2 is an end view of a disk filter device according to the invention with some hidden parts shown in broken lines.

Fig. 3 is a side view of the disk filter device of Fig. 2 with some hidden parts shown in broken lines.

Fig. 4 is a perspective view of an inventive module for building a filter body.

Fig. 5 is a perspective view of a sealing means for anchoring filter segments in the disk filter device according to the invention.

Fig. 6 is a plan view of a filter segment.

Detailed description of a preferred embodiment

The principal function of a disk filter according to the invention is in large part the same as for known disk filters of the kind shown in Fig. 1. The function of the inventive disk filter will therefore be explained with reference to Fig. 1. The disc filter 1 has a slowly rotating drum 2 which carries a number of disc shaped filter elements 3, the normal direction of which is parallel and concentric to the longitudinal axis or rotation axis C of the drum 2 and which on its lateral surfaces, which are axially directed and have radial extension, carry filter cloth 4. The liquid A to be filtered is passed through an inlet 5 to the interior of the drum 2,

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From the interior of the drum 2, the filtration liquid A is further passed through openings in the casing surface 6 of the drum 2 to the interior of the disc-shaped filter elements 3. From there, the filtration liquid A is finally discharged in a filtering direction through the filter cloth 4. Any particles in the filtration liquid A become stuck on the inside of the filter cloth 4. . The disc filter 1 is provided for cleaning the filter cloth 4 with flush nozzles 7 mounted on a plurality of flushing pipes 8 which project between the disc shaped filter elements. These flushing pipes 8 are intended to direct flushing liquid to the flushing nozzles 7 and are coupled to an elongated liquid-conducting pipe 9 running parallel to the center axis of the drum C. The flush nozzles flush the filter cloth axially from the outside in the opposite direction to the filtering direction, and the flushed particles are collected in a drain channel 10 located inside the drum 2 in the upper portion thereof.

As can be seen in Fig. 2, according to a preferred embodiment of the invention, the filter elements 3 have a filter body 11 which extends radially outwards in the transverse direction of the drum 2, made up of a plurality of modules 12. The filter body 11 forms compartments in which filter segments 13 are placed. The filter segments 13, as shown in Fig. 6, consist of a frame 14 which tension the filter cloth 4.

The modules 12 have, as shown in Fig. 4, an intermediate body portion 15 from which at one end two outer body portions 16 extend outwards. From the other end of the intermediate body portion 15, two inner body portions 17 extend outward. The intermediate body portion 15 consists of a truss structure 18 with cavities 19. In the inner body portions 17 are openings 20 for passage of the liquid to be filtered from the interior of the drum 2. At its ends, the inner and outer body portions 17, 16 have holes 21 for inserting screws for interconnecting two modules 12. On either side of the intermediate body portion 15 are two grooves 22 which extend parallel to the intermediate body portion 15 in the plane of the filter body 11. In each of the inner bump portions 17 there are

526 692 two parallel grooves 23 which are parallel to the inner body portion 17 and extend in the plane of the filter body 11.

Fig. 6 shows a closure means in the form of a lid 24 for anchoring the filter segments 13 in the filter body 11.

In the construction of the disk filter device 1, seven modules 12 are attached to each other by screws in the holes 21, so that the modules form a semicircle. Two such semicircles are then mounted on the drum 2 and bolted together to form a filter body 11. By joining the modules 12 substantially in the middle of the filter segments 13, the density is improved compared to the joining between two filter segments 13.

In each of the compartments that the filter body 11 forms between two adjacent modules 12, a filter segment 13 is pushed into the grooves 22 and 23 on either side of the modules 12. The cover 24 is threaded outside the outer body portions 16 of two adjacent modules 12 and the two parallel filter segments 13 which these modules 12 enclose together. The cover 24 is screwed into the outer body portions 16 of the modules 12. However, a plurality of disc-shaped filter elements 3 are mounted on the drum 2 to provide the disc filter device 1. In the illustrated embodiment, ten filter elements 3 have been mounted on the drum 2. However, as many as twenty-two filter elements can be arranged on a drum 2 with a larger disc filter 1. capacity.

In the operation of disc filter 1, liquid A, preferably contaminated water, is supplied to be filtered through the inlet 5 at one end of the drum 2 and is passed along a first fluid channel extending from the interior of the drum 2 through the openings 20 in the inner body portions 17 of the modules 12 and through the filter elements 3. filter cloth 4. The drum 2 rotates slowly and the filter segments 13 located in the lower part of its circulation are flowed through the liquid A. Pollution then gets stuck on the inside of the filter cloth 4. When the filter segments 13 are in the upper part of their

526 692 orbits are cleaned with the aid of the flushing equipment 7, 8, 9 described above. The flushed contaminants are removed by means of the drain channel 10.

The cavity frame 19 in the truss structure 18 of the intermediate portions 15 forms a second fluid channel along which the liquid A can move between the filter segments 13. Unlike in the known disc filters, the liquid A will therefore not be brought into the rotating movement of the filter elements 3. The amount of liquid that accompanies the contaminants out of the drainage channel 10 is thereby reduced. The rotational speed of the drum 2 can thus be increased, which causes the capacity of the disk filter 1 to be increased. The disc filter 1 can therefore be made more compact than known disc filters. The load on the drum's suspension and drive is also reduced.

The disc filter 1 can be built up in the factory and delivered completely, but the module structure also makes it possible to deliver modules 12 for the construction of the disc filter 1 at the place where it is to be used. The module structure also makes it easy to expand an existing disk filter 1 to increase capacity. Modules 12, filter segments 13 and lids 24 to one or more new filter elements 3 can then be delivered and built into the existing disc filter 1.

The modules 12 are manufactured in the described example by injection molding of ABS plastic. Other plastic materials can also be used and the appropriate manufacturing method is then chosen with respect to the type of plastic. Plastic has the advantage of being a relatively inexpensive and easily processed material and is also corrosion resistant. Other materials may also be selected, but it should be noted that it is appropriate to use a material which, relative to its strength, has a relatively low weight, so as to minimize the weight of the finished disk filter device.

The frame 14 of the filter segments 13 is advantageously formed of prestressed fiberglass, which makes the frame 14 strong, light and corrosion resistant. The frame 14 may alternatively be made of metal, preferably stainless steel. For

526 692 sealing the filter segment 13 against the filter body 4, the frame 14 is surrounded by a rubber strip, for example EPDM rubber. To facilitate insertion and removal of the filter segments 13 in the grooves 22, the rubber mold on its outside is flocculated, which reduces the friction against the filter body 11. The seal is also promoted to a certain extent by the fact that the filter segments 13 as the liquid A passes out through the filter cloth 4 of the liquid pressure, so that that the frame 14 is pressed against the outer boundary walls of the grooves 22, 23.

The filter cloth 4 which is tensioned by the frame 14 is in the illustrated embodiment a microfilter cloth with filter openings in the range 10-100 µm. The filter cloth 4 is selected based on the filtration ability desired.

The disc filter device according to the invention can conveniently be cleaned by means of a cleaning device of the kind described in SE-C-515 001 (WO 00/37159).

It will be appreciated that a variety of modifications to the embodiments of the invention described herein are possible within the scope of the invention as defined in the appended claims.

In the example shown, the modules 12 are mounted on a drum 2 in whose casing surface 6 there are openings for the passage of the liquid from the interior of the drum 2 into the filter segments 11. The light modules 12 allow you to choose only one skeleton for one drum and instead allowing the inner bump portions 17 to form the drum's outer surface of the skeleton.

Instead of forming the intermediate body portions 15 with a truss construction 18, the intermediate body portions can be given a smooth life in which holes are drilled to provide the fluid communication between the filter segments.

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