From prior art self-flushing particle filters with several sieving elements fitted are known. What characterises these existing particle filters is that they back-flush the filters in the filter body in a continuous flushing process. In other words, the flushing takes place

continuously and as long as the flushing process lasts. Thereby, the flushing out takes place also when the flushing function is moving from one sieving element to another. In this moving phase the back-flushing of the sieving elements themselves is incomplete, or in many cases, completely absent. This leads to the water

consumption for the flushing being unnecessarily high. When the flushing of the existing filters stops, the flushing unit stops in an arbitrary position. This leads to the flushing unit blocking the sieving elements to a greater or smaller extent and reduces the sieving area.

The present invention can be operated by an intelligent control and drive unit which, at any given time, knows and can report which position the flushing unit is in.

SUBSTITUTE SHEET Thereby, it can also be controlled into a desired

position. This can be carried out without sensors or feelers which can be the source of errors over time. The flushing of the filter can thereby take place only when the flushing unit is positioned on one of the concrete filter elements. The flushing water is only then opened and all the flushing water will thereby be utilised for full back-flushing of the filter elements. When the flushing unit is moving to the next filter element, the flushing is shut off. The amount of flushing water will thereby be completely utilised, and will thus be limited to a minimum. The reward for this is a 100% back-flushing, something that leads to a better flushing of the filter and considerably less use of flushing water. Another advantage with this filter is that this intelligent control can drive _. the. flushing unit in a mid-position, after the flushing, and it can stay in this position during normal operation. One will thereby be able to know that all the filter elements are active and the whole of the filter area in the filter will thereby be active and in continuous use.

From prior art, reference is made to US 4,781,825 A, which relates to a filter arrangement comprising a multi-unit of filter units. The arrangement has a top plate that rotates during the washing sequence. The top plate is raised during the filtering.

EP 1254690 A2 relates to a filter assembly with a

possibility of selective flushing by rotation of a bottom plate. During normal filtering the bottom place is lowered so that filtering can continue undisturbed. During the washing phase the plate is raised and is rotated so that each filter element can be flushed separately. WO 00/18488 Al shows an apparatus for continuous

filtering. The apparatus comprises three filter units, where only one filter unit is being used. While one filter is being used another unit is washed. A third unit is set into operation when the other two are being serviced. To vary between the different filter units a rotating valve is used.

US 2,526,372 A refers to a filter assembly. One filter is closed at any time so that it can be opened to be cleaned. A rotating valve is used for the closing.

It is an object of the present invention to provide a solution for selective flushing out of particles in a filter and which thereby reduces the use of flushing water. The invention can, for example, be used for water intake of fresh water and seawater, in well boats or in net cage systems for removal of lice and other impurities in the water. Another application area can be removal of particles in ballast water on board a ship. The invention can, of course, also be used in other contexts.

Understood by the expression particles are all types of particles, including lice and other unwanted elements, which can be collected as the liquids flow through and out of a filter so that the particles remain in the filter.

The above mentioned object is reached with a filter device defined in the independent product claim, in that the filter is placed between a rotary top plate and a rotary bottom plate for the setting up of selective flushing of particles collected in a filter basket and out through an outlet, without the filtering process in other filter baskets being affected, and that the top plate comprises, at least, one valve arranged to close against the filter

SUBSIITilTP-QMPCT baskets that shall not be flushed during the flushing process .

Alternative embodiments of the filter arrangement are given in the dependent product claims.

Said filter baskets can have a circular-cylindrical shape and be placed at the respective openings in the top plate and the bottom plate. Furthermore, the filter housing can comprise an actuator arranged to rotate the top plate and the bottom plate to provide a flushing valve function, whereby one filter basket is arranged to be flushed at a time. The flushing valve of the top plate can be made up of the opening and the associated rotation.

The actuator is preferably arranged to stepwise rotate the top plate and the bottom plate a fixed number of degrees. During normal operation the opening of the top plate can be arranged to lie between two filter baskets.

The valve of the top plate can be in the form of a valve seat that lies against a respective opening in the top plate. The bottom plate can similarly comprise a closing valve arranged to open for filter baskets that shall not be flushed, and to close against the filter basket that shall be flushed, where said actuator controls the closing valve. The closing valve can be shaped as a fixed plate or lid which, during rotation of the bottom plate, is

arranged to close for an opening in the bottom plate.

During normal operation the plate of the closing valve can be arranged to lie between two openings in the bottom plate. The filter housing can comprise a top lid arranged above the filter, where the top lid comprises the outlet.

The actuator can be controlled by the pressure difference in the filter and/or that the actuator is controlled by a timer.

Said objects are also achieved with an embodiment given in the independent method claim for selective flushing of a filter arrangement for removal of particles in a liquid, comprising a filter housing with a main inlet and a main outlet where an internal filter is arranged with several filter baskets for filtering out particles and a liquid is brought to flow through the filter, whereupon particles are collected in the filter, characterised in that a top plate and a bottom plate of the filter are rotated for selective flushing of a filter basket, without the

filtering process in the other filter baskets being affected, and to open a flushing valve in the top plate so that it opens for through-flow of liquid in a filter basket, whereby the particles are flushed out through an outlet.

Alternative embodiments of the method are given in the dependent method claims.

A closing valve in the bottom plate is preferably shut off at the same time as the flushing valve in the top plate is opened.

The rotation of the top plate and the bottom plate can be controlled so that the flushing function moves from one filter basket to another. Furthermore, an actuator can be used for the controlled rotation of the top plate and the

SUBSTITUTE SHEET bottom plate, as the rotation is made stepwise a given number of degrees.

The invention shall now be explained in more detail with the help of the enclosed figures, in which:

Figure 1 shows a filter arrangement according to the invention seen from the front.

Figure 2 shows the filter arrangement according to the invention seen from the side.

Figure 3 shows the filter arrangement according to the invention seen from above.

Figure 4 shows according to the invention a filter with several filter baskets.

Figure 5 shows in more detail a top plate of the filter.

Figure 6 shows in more detail . a bottom plate of the filter.

As the figures 1-2 show the present filter arrangement comprises a filter housing 10 with a lower main inlet 12 for flowing liquid that shall be filtered, and also a central main outlet 14 for filtered liquid. Furthermore, the filter housing 10 comprises a top lid 32 to which an upper outlet 16 for flushing water is arranged. Also fitted onto the top lid 32 is an actuator 18, said

actuator is a control and drive unit for the flushing of the filter, and which at any time monitors and controls the flushing process. This actuator 18 can be connected to a control unit 42 for the opening and closing of the outlet 16.

A filter 20 is arranged inside the filter housing 10 in the -form of several filter baskets 22, as shown in figure 4. The filter baskets 22 can, for that matter, have any shape, but in a preferred embodiment example the filter

UBSTfrOTP §M£iT baskets 22 have a circular-cylindrical form and are mounted between a top plate 24 and a bottom plate 26. The top plate 24 and the bottom plate 26 have respective openings 28, 30 which correspond to top and bottom of each filter basket 22. In the embodiment shown, five filter baskets 22 are located in the filter 20, but fewer or more filters can, of course, be used.

The top plate 24 is placed at an upper part of the filter 20 and furthermore, said top plate is formed as a flushing valve in that the opening 28 of the top plate is rotated to lie above a filter basket that is to be flushed. To shut off the filter baskets 22 that are not to be flushed the top plate can be formed with several valves 34, and as in the embodiment shown is formed as a valve seat 38 in the top plate 24, and which is arranged to close against a respective opening 28 in the top plate 24. During normal operation, i.e. without flushing, all the filter baskets 22 are preferably closed at the top in that the valves 34 are closed. The valves 34 can, for example, be opened during common flushing out from all the filter baskets 22, but as a rule are normally closed.

The bottom plate 26 is placed at a lower part of the filter 20 and is correspondingly formed as a closing valve 36. In the embodiment shown the closing valve 36 is formed as a plate or a lid which, during rotation, is arranged to close for the filter basket 22 which is to be flushed and to let it be open to the filter baskets 22 that are not to be flushed. As figure 6 shows, the plate can close for a selective opening 30.

The lower part of the filter 10, i.e. the bottom plate 26, can be equipped with a downwardly extending conical head 40 to reduce the turbulence in the flowing liquid.

S u IT U ^' s H During normal operation liquid flows into the inlet 12 and further into the bottom of the filter baskets 22, through the filter cloth in the filter baskets, out into the filter housing 10 and further out through the outlet 12 at the side of the filter housing. The top of the filter 20 is then closed. Particles larger than the opening in the filter cloth remain inside the filter baskets 22. To clean a filter basket the flushing valve is opened at the top of the filter with the help of the rotation of the top plate 24. The liquid will now continue straight forward through the filter basket, bringing along the particles that have been filtered out and flushing them out through the flush valve/outlet 16.

In more detail, the closing valve 36, on the underside of the filter basket 22 that is to be flushed, shuts off and liquid will thereby flow in through the other openings in the bottom plate and through the respective filter cloth in the filter baskets, into the filter basket that is to be flushed and out through the opening 28 in the top plate to the filter basket 22 that is open, and further out through the outlet 16. What is unique with the present invention is that one flushes one filter basket 22 at a time without stopping the filtering process in the other filter baskets. The flushing function is controlled by the actuator 18 which in turn can be controlled by time and/or the pressure difference in the filter 10, preferably first by the pressure difference and thereafter, or in combination with, time. The actuator 18 rotates the top plate 24 and the bottom plate 26 in the filter so that the flushing function moves from filter basket to filter basket in turn. In addition, with this solution one achieves a back- flushing of the filter with minimal use of liquid, compared to the traditional back-flushing filters.

During normal operation all filter baskets 22 are open at the bottom and the filter has thus full capacity. This is carried out by the actuator 18 adjusting the opening plate 36 in mid-position between two filter baskets 22 so that liquid can flow to both filter baskets on each side of the plate. The corresponding is valid for the closing of the top plate 24, as the top plate is rotated so that the opening 28 lies between two filter baskets 22. This can be coordinated between the top plate 24 and the bottom plate 26. The flushing/flushing valve is preferably opened first when the actuator/opening in the bottom plate is in position, which gives much lower water consumption during back flushing.

UBSTITUTESHEET