EP4688202A1

EP4688202A1 - Filtering unit, filtering apparatus comprising the filtering unit and use of the filtering apparatus

Info

Publication number: EP4688202A1
Application number: EP24728084.5A
Authority: EP
Inventors: Zoltán PALIK
Original assignee: Individual
Current assignee: Individual
Priority date: 2023-03-30
Filing date: 2024-03-27
Publication date: 2026-02-11
Also published as: WO2024201089A1; HUP2300108A1

Abstract

Filtering unit (10) with filter trays (11) arranged in parallel planes and with a plurality of settling depressions (12) on each filter tray (11), characterised by that the filtering unit (10) contains at least three filter trays (11), where the filter trays (11 ) are located relative to each other in such a way that the settling depressions (12) of the filter trays (11) located directly below each other are offset by at least 50% of the diameter of the settling depression (12) in the plane of the filter trays (11).

Description

Filtering unit , filtering apparatus comprising the filtering unit and use of the filtering apparatus

The field of the invention

The present invention relates to a filtering unit comprising filter trays for filtering water, a filtering apparatus comprising the filtering unit , and the use of the filtering apparatus .

The state of the art

The cleanliness of the water supply to garden pools , ponds and streams must be guaranteed by various filtering apparatus . In the same way, in the case of industrial processes , in the production of various materials , the water demand of the process requires water of suf ficient purity .

It is possible to pre-clean the water and liquid feed with di f ferent filters . A drum filter is a cylindrical drum that rotates in a circle , on the mantle of which the filtering material is located . The filtration process is carried out by passing the liquid to be cleaned through the material under the centri fugal force of the rotation of the drum, the filtering particles are caught on this material and thus surface filtration is achieved . This process wastes energy, requires a lot of water in dense cycles to clean the filter surface , it is noisy, cannot be pressuri zed, and cannot filter out very small , floating, sludge-like impurities and is expensive to manufacture .

In the case of the sponge filter, the liquid to be cleaned flows through the sponge , which captures the impurities . Its biggest disadvantage is that it is very cumbersome and almost impossible to clean . I f it is saturated, water cannot flow through it , so the flow of water stops . Its ef ficiency decreases drastically as it approaches saturation, and it is also unable to filter out very small impurities .

In the case of the vortex filter, the water to be cleaned is let into a large tank in such a way that the water continuously circulates in the tank, and then, using the rotation of the water, the structure collects the impurities in the center of the tank, some of which can be removed afterwards . This solution takes up too much space, and the water has to stay in the tank for a long time to settle the impurities . And there is no ef fective solution for draining the impurities .

Another solution is the use of a filter tray, which is shown, for example , in the utility model CN214071004 U . Here , the filter tray is equipped with holes , through which part of the particles fall to the bottom of the apparatus during the process . This filter tray is suitable for separating small particles from larger particles , but it is not suitable for completely cleaning the liquid .

Utility model CN214071004 U shows a rainwater filtering apparatus using several filter trays and a sponge . By placing the sponge between the perforated filter trays , the apparatus becomes suitable for filtering rainwater . But it is only suitable for cleaning the liquid flowing from the top down, and cleaning the sponge is cumbersome .

As a result of the above , there is currently no apparatus available that can be used to filter water and liquids simply and with the apparatus being easy to clean . Brief description of the invention

The aim of the present invention is to provide an easy-to- clean, simple-to-use filtering apparatus for water .

The present invention is based on the recognition that the filter trays with settling depressions placed one above the other and of fset from each other according to the pattern of the settling depressions can easily remove impurities from the water during the flow of the water to be puri fied . This is achieved by the parts of the settling depressions extending towards the lower filter tray breaking the path of the water flow and directing it towards the settling depressions of the lower tray, i f the settling depressions are not located one below the other . At the same time , the space above the settling depressions widens , so the flow slows down, making the settling of particles in the settling depressions more ef ficient . Furthermore , by changing the position of the filter trays and the flow direction, the apparatus can be easily cleaned .

According to the above , the present invention relates to a filtering unit which has filter trays arranged in parallel planes with a plurality of settling depressions on each filter tray, and which is characterised by the fact that the filtering unit contains at least three filter trays , where the filter trays are located relative to each other in such a way that the direct the settling depressions of the filter trays located below each other are shi fted in the plane of the filter trays by at least 50% of the diameter of the settling depression . A preferred embodiment of the filtering unit according to the invention is characterised by the fact that the filter trays are of fset by at least 100% of the diameter of the settling depressions .

Another preferred embodiment of the filtering unit according to the invention is characterised by the fact that the arrangement of the settling depressions on each filter tray is the same as the other filter trays located at a distance of two from the filter tray .

Another preferred embodiment of the filtering unit according to the invention is characterised by the settling depressions being closed settling depressions .

Another preferred embodiment of the filtering unit according to the invention is characterised by the fact that the settling depressions are open settling depressions and the filter trays have gaps .

Another preferred embodiment of the filtering unit according to the invention is characterised by the fact that the settling depressions have ribs .

Another preferred embodiment of the filtering unit according to the invention is characterised by the fact that the material of the filter trays is plastic or sheet metal .

The present invention also relates to a filtering apparatus that has a filtering unit equipped with at least one inlet and at least one outlet for maintaining a water flow and which is characterised by that the filtering unit is designed as described above . A preferred embodiment of the filtering apparatus according to the invention is characterised by the fact that it has a sealing .

Another preferred embodiment of the filtering apparatus according to the invention is characterised by the fact that it has at least one sensor .

A preferred embodiment of the filtering apparatus according to the invention is characterised by the fact that it has a service window .

The present invention also relates to the use of the filtering apparatus in the case of flowing water containing impurities with a particle si ze of five millimeters or less at a speed of 10 cm/ s or less .

In the figures

Figure 1 shows a perspective front view of the filtering unit formed by a plurality of filter trays with closed settling depressions according to the invention;

Figure 2 shows the detail of the filtering unit according to the invention marked with C in Figure 1 with the closed settling depressions , in a perspective front view;

Figure 3 shows the filtering unit according to the invention, where each filter tray has open settling depressions , in a perspective front view;

Figure 4 shows a detail of the filtering unit according to the invention with open settling depressions , in a perspective front view; Figure 5 shows a cross-sectional representation of the filtering apparatus according to the invention in a side view;

Figure 6 shows a cross-sectional representation of the filtering apparatus according to the invention during the first cleaning step, in side view;

Figure 7 shows a cross-sectional representation of the filtering apparatus according to the invention during the second cleaning step, in side view;

Figure 8 shows a cross-sectional representation of the filtering apparatus according to the invention during the third cleaning step, in a side view;

Figure 9 shows a cross-sectional representation of the filtering apparatus according to the invention in a top view with the bearings forming the axis of rotation;

Figure 10 shows an enlarged detail of Figure 9 with a bearing .

Detailed description of the invention

The essence of the filtering apparatus according to the invention is that the filtering unit inside it contains several filter trays with settling depressions placed one above the other, where the filter trays are arranged in such a way that the settling depressions located on each filter tray are of fset from the filter trays adj acent to the filter tray .

In the context of the present invention, a filter tray is a tray that is provided with settling depressions . These settling depressions are used to settle the impurities to be filtered . In the context of the present invention, a filtering unit is understood to mean several filter trays placed on top of each other in such a way that there is suf ficient space between them for the flow of water .

In the context of the present invention, an impurity is defined as shaped bodies in the water to be puri fied, which can be physically separated from the water . Within the scope of this description, unless speci fically mentioned otherwise , the term impurity does not mean chemical and biological impurities .

The filtering unit 10 shown in Figure 1 consists of several filter trays 11 , which are provided with closed settling depressions 12a . Figure 2 shows the area marked C in Figure 1 enlarged . Thus , it can be seen that the closed settling depressions 12a of the adj acent filter trays 11 are of fset from each other and not exactly below each other . Between the adj acent filter trays 11 there is preferably a space equal to the height of the closed settling depression 12a as a spacer . Of course , we do not rule out the possibility that the space between the individual adj acent filter trays 11 is greater than the height of the closed settling depression 12a ( e . g . by using spacers between the individual filter trays 11 ) , but this may reduce the ef ficiency of settling . During the flow of the water to be cleaned in this space , the impurities in the water are deposited in the closed settling depressions 12a .

The arrangement of the filter trays 11 and the closed settling depressions 12a placed on them have two roles in the ef ficiency of the settling : the flow cross-section above the closed settling depressions 12a increases , so the water flow rate slows down . Furthermore , the closed settling depressions 12a break the direction of the flow, which also increases the ef ficiency of settling of impurities from the water . Thus , the closed settling depressions 12a of an upper filter tray 11 break the flow of water, slowing it down and diverting the water towards the closed settling depressions 12a of the lower filter tray 11 , because the closed settling depressions 12a are not located below each other . The ef ficiency of changing the flow direction can be advantageously further increased i f the outer surface of the closed settling depressions 12a is provided with ribs (not shown) . These ribs represent an additional surface on which the flow is broken and the flowing water is forced to change its direction . The closed settling depressions 12a are no longer able to perform their task when they become saturated with impurities , so the water then continues without filtration . In such a case , the filtering unit 10 needs to be cleaned ( see below for details ) .

The displacement of the closed settling depressions 12a of the filter trays 11 is necessary at least to the extent of 50% of the diameter of the closed settling depressions 12a . By this we mean that the closed settling depressions 12a placed on the filter trays 11 below each other are shi fted from each other by hal f the width of the diameter determined by the upper part of the closed settling depression 12a formed on the surface of the filter tray 11 . I f the design of the upper part of the closed settling depressions 12a is not approximately circular, then diameter is the largest distance between the two sides of the closed settling depressions 12a in the hori zontal plane perpendicular to the direction determined by the flowing water . Therefore , the width of the closed settling depressions 12a perpendicular to the A-B direction shown in Figure 5 determines the amount of displacement . The upper part of the closed settling depression 12a besides being round, can be , for example , ellipse , octagon, hexagon and similar shapes . Figures 3 and 4 show the filter trays 11 of the filtering unit 10 according to the invention with open settling depressions 12b . Adj acent filter trays 11 are of fset from each other in the case of open settling depressions 12b, similarly to filter trays 11 with closed settling depressions 12a, where the upper part of the open settling depressions 12b has a similar shape to the closed settling depressions 12a . The di f ference between the two embodiments is that in the case of open settling depressions 12b, the filter trays 11 are preferably also provided with holes 13 .

The role of the holes 13 is to allow the lower, funnel-like tapered part of the open settling depressions 12b to be suf ficiently long and to reach the upper part of the open settling depression 12b located with the two filter trays 11 below it through these holes 13 ( see Figure 4 ) . Thus , in the open settling depressions 12b, the sedimented impurities do not accumulate , but flow down into the next open settling depression 12b and so on . Since the lower, funnel-like tapered part of the open settling depressions 12b is thinner than the upper, wide part of the open settling depression 12b, it does not prevent the settling of impurities from the water flowing between the filter trays 11 into the given open settling depression 12b . It is important that the part of the open settling depressions 12b extending through the hole 13 is signi ficantly smaller than the middle and upper part of the open settling depressions 12b up to the hole 13 due to the funnel-like tapering, so it does not break the flow direction . That is , the middle part of the open settling depressions 12b starting from the filter tray 11 and extending to the hole 13 is wide enough to break the direction of the flow and thus to slow down the flow so that the middle part of the open settling depressions 12b diverts the water towards the opening in the upper part of the lower open settling depressions 12b and improve settling ef ficiency . On the other hand, the lower part of the open settling depressions 12b is thin enough so as not to signi ficantly divert the flowing water from the upper part of the opening of the open settling depression 12b, which is advantageously located below it .

The impurities enter the part below the filter trays 11 through the open settling depressions 12b and thus the open settling depressions 12b do not become saturated . The advantage of the arrangement is that there is no need for a cleaning step, at least the removal of impurities collected under the filter trays 11 can be carried out even with continuous operation . Furthermore , the open settling depressions 12b can also be provided with ribs that increase the ef ficiency of changing the flow direction . The distance between the filter trays 11 is adj usted with a spacer, which without the presence of the holes 13 is greater than the height of the open settling depressions 12b, so that the settling impurities can be emptied from the open settling depressions 12b onto the filter tray 11 below . After that , these impurities can enter the open settling depressions 12b of the filter tray 11 below . Of course , even with this solution, we do not rule out the possibility that a thicker part of the funnel-like tapering of the open settling depressions 12b sits on top of the hole 13 , so that the open settling depression 12b itsel f functions as a spacer in the design .

I f the filter trays 11 do not have holes 13 , the impurities from the open settling depressions 12b are emptied onto the filter tray 11 below them, from where the flowing water carries them into the open settling depression 12b on the given filter tray 11 . However, the thus increased amount of impurities may clog the open settling depressions 12b . Figure 5 shows the filtering apparatus 100 , which includes the filtering unit 10 with filter trays 11 and settling depressions 12 , an inlet 21 , an outlet 22 , preferably a sensor (not shown) , a tap 23 and a sealing 24 . The filtering unit 10 is positioned in the filtering apparatus 100 in such a way that there is suf ficient space for water and/or impurities in all directions . We introduce the water to be cleaned at inlet

21 . Depending on the design, even several inlets 21 can be imagined on a filtering apparatus 100 . After the introduction, the water to be cleaned passes over the filtering unit 10 , then flows down the side of the filtering unit 10 marked with "A" into the filtering unit 10 and flows back over the filter trays 11 with settling depressions 12 . The puri fied water exits the filtering unit 10 on the side marked "B" and flows upwards , and finally the puri fied water leaves at the outlet

22 . The two sealings 24 ensure that the introduced and then discharged water cannot flow in other directions .

The role of the optional sensors is to determine whether a cleaning step needs to be performed on the filtering apparatus 100 . This sensor can be a simple time-measuring device that signals after a certain period of time has elapsed, but it can also be a more sophisticated sensor that detects impurities in the water, which signals when the level of impurities in the puri fied water is too high . It is also possible to imagine an automated filtering apparatus 100 where an automatic cleaning step is started without any other intervention when the sensor signals .

Through the tap 23 , the impurities that protrude to the bottom of the filtering apparatus 100 can be drained, i f during the filtration process the impurities do not settle only in the settling depressions 12 of the filter trays 11 , for example because the settling depressions 12 are full , or because the water to be cleaned contains signi ficantly more impurities than expected .

The role of the sealings 24 is to block the path of water in unwanted directions . The sealing 24 is preferably a flexible metal plate , which is attached to the wall of the filtering apparatus 100 and which, in case of contact with a given edge of the filtering unit 10 , is pressed against it and holds the filtering unit 10 in place , as shown in Figure 5 . Since the sealing 24 is fixed along the length of the filtering apparatus 100 to the wall of the filtering apparatus 100 and is also in continuous contact with the edge of the filtering unit 10 , the sealing 24 blocks the path of the flowing water here , so it can only proceed by entering the filtering unit 10 on the side marked "A" . The sealing 24 on the diagonally opposite side of the filtering unit 10 works in a similar way . The sealing 24 also allows the filtering unit 10 to be moved during the cleaning process , maintenance or installation .

In addition, the two side walls (not shown) of the filtering unit 10 are preferably provided with insulation 15 ( shown in Figure 10 ) , which prevents the flow of water in unwanted directions , but unlike the rigid metal covering, does not prevent the rotation of the filtering unit 10 in the filtering apparatus 100 . That is , the insulation 15 covers two additional sides perpendicular to the plane of the filter trays 11 , outside the sides marked "A" and "B" ( i . e . the sides according to the plane of the figure according to Figure 5 ) , thus preventing water from flowing in a direction that is not the same as the flow direction . Thus , the water flows from the side marked "A" to the side marked "B" , because the other two side walls of the filtering unit 10 are sealed by the insulation 15 . The material of the filter trays 11 is preferably a plastic or metal plate , on which the settling depressions 12 are formed . The closed settling depressions 12a are preferably in the shape of a truncated cone or a truncated pyramid . The open settling depressions 12b are also shaped like a truncated cone or a truncated pyramid, with the di f ference that they are open at the bottom, possibly pushed with a cylindrical section with a diameter corresponding to their lower opening .

The shape of the filtering apparatus 100 is determined by the filtering unit 10 and the inlets 21 and outlets 22 in addition to the water flow . It is important that there be suf ficient space between the walls of the filtering unit 10 and the filtering apparatus 100 for the flow of water, the si zing belonging to the obligatory knowledge of a professional taking into consideration the pump that pumps the water, or in the absence of a pump, the speed of the water flowing in another way into the filtering apparatus 100 . Furthermore , on the back side of the filtering apparatus 100 ( on the right side according to Figure 5 ) , preferably, instead of sharp corners , cut surfaces are formed to help the water flow .

Practically, the filtering apparatus 100 is provided with service windows 25 from the front . The role of the service window 25 is that the filtering unit 10 can be inserted through it , depending on the si ze of the service window 25 either per filter trays 11 or all together in the filtering apparatus 100 . In addition, various repair works and replacement of elements are also possible through the service window 25 . Of course , we do not rule out the possibility that the service window 25 is located on another side of the filtering apparatus 100 . During the operation of the filtering apparatus 100, water flows into the filtering apparatus 100 through the inlet 21. When the water reaches the rear part of the filtering apparatus 100, it travels to the space closed by the sealing 24 and passes through the filtering unit 10 from the rear part ("A") to the front (ie. in the direction of the side marked with "B") . During the passage through the filtering unit 10, the impurities in the water settle out in the settling depressions 12. The purified water leaves the filtering apparatus 100 at the outlet 22.

The particle size of the impurities that can be removed with the apparatus according to the present invention can range from a few microns to 5 mm. The water flow rate is a maximum of 10 cm/s, preferably 5 cm/ s .

When the settling depressions 12 are saturated and are unable to absorb more impurities, the efficiency of the filtration deteriorates significantly and essentially ceases. In such a case, the filtering unit 10 has to be cleaned according to the signal of the sensor, or the degree of contamination of the water flowing through the outlet 22, or by detecting the problem through the service window 25.

Cleaning consists of four steps, which are shown in Figures 5 - 8. Figure 5 shows the basic state or operating state, which shows how the filtering unit 10 is located in the filtering apparatus 100 during the filtering of the water to be purified, and this is the state in which the need to clean the filtering apparatus 100 can be sensed. In the first step, the filtering unit 10 is rotated so that it stands as shown in Figure 6, i.e., looking at Figure 6, we turn it a quarter of a turn clockwise, so that the back side "A" of the filtering unit 10 faces the bottom of the filtering apparatus 100. Because of the sealing 24 and the insulation 15 covering the sides , the water introduced at the inlet 21 ( this can be clean water or even the water itsel f to be cleaned) flows from side B to side A of the filtering unit 10 . This step is important because impurities that does not exceed the particle si ze but extends in the longitudinal direction, such as hair, plastic fiber, various fibers , can stick to and wind up on the individual filter trays 11 and settling depressions 12 . These fibrous impurities and some of the impurities settled in the settling depressions 12 are washed into the bottom of the filtering apparatus 100 with this step, from where the flowing water removes them from the filtering apparatus 100 through the outlet 22 . During puri fication, the water flow rate reaches , preferably exceeds , 10 cm/ s , so it can remove stuck impurities from the settling depressions 12 with greater force , and the impurities that have already been picked up by the water is less likely to settle again .

Figure 7 shows the state obtained after the second step . In the second step, the filtering unit 10 is turned clockwise by a quarter turn as shown in the figure so that the "B" side faces the back of the filtering apparatus 100 . In this way, residual impurities are also removed from the 12 settling depressions with the help of gravity and flowing water .

Figure 8 shows the state obtained after the third step . During the third step, the filtering unit 10 is turned clockwise again by a quarter of a turn according to the figure , thereby washing of f any impurities that may have stuck to the filter trays 11 . Thus , after the third step, side "A" faces the upper part of the filtering apparatus 100 . The basic state shown in Figure 5 is reached with another rotation, so the cleaned filtering unit 10 is ready for operation .

During each of the four cleaning steps , the cleaning water (which can therefore also be the water to be cleaned) is continuously flowed through the inlet 21 , so that the filtering unit 10 can be thoroughly washed from all directions . The filtering unit 10 can be rotated around an axis during the washing steps . Figure 9 shows a possible design for rotating the filtering unit 10 in a cross-sectional view from above , and Figure 10 shows a detail of Figure 9 . In the figures , the bearing 14 , attached to a frame 10a, enables the rotation of the filtering unit 10 . The rotation axis is , for example , a plastic sliding bearing attached to two sides of the filtering unit 10 , which fits into the hole formed on the filtering apparatus 100 . The sealing is ensured by a flexible rubber "0" ring . Preferably, a rotating arm or gear can be connected to the bearing 14 to facilitate or automate the rotation . The figures also show the insulation 15 located between the frame 10a and the wall of the filtering apparatus 100 .

Another cleaning method can also be used to clean the filtering unit 10 , during which the filtering unit 10 is removed and turned on its side and washed manually using a water source .

In the case of the open settling depressions 12b, cleaning can be omitted i f long fibrous materials do not enter the filtering unit 10 , because they can clog the narrow opening of the open settling depressions 12b . More precisely, the cleaning step consists of removing the impurities deposited on the bottom of the filtering apparatus 100 through the tap 23 shown in Figure 5 , i f the filtering apparatus 100 has such a tap 23 . I f the filtering apparatus 100 does not have such taps 23 , it has to be stopped and the bottom to be cleaned . Furthermore , we do not exclude the above-described four-step cleaning procedure in the case of the use of the filtering unit 10 containing the open settling depressions 12b .

Of course , we do not exclude the use of other liquids of liquid nature instead of water during the invention .

Examples

Example 1 : filtering unit 10 with closed settling depressions 12a

The filtering unit 10 according to Figure 1 , which consists of ten filtering trays 11 , which are provided with closed settling depressions 12a . As shown in Figure 2 , the filter trays 11 are hori zontally of fset from each other by a distance equal to a closed settling depression 12a . Vertically, the distance between the individual filter trays 11 is one and a hal f times the height of the closed settling depressions 12a, which is provided by the spacers between the individual filter trays 11 . The material of the filter trays 11 is sheet metal .

Example 2 : filtering unit 10 with closed settling depressions 12a

The filtering unit 10 according to example 1 with the modi fication that it is provided with eighteen filter trays 11 , which are located vertically at a distance corresponding to the closed settling depressions 12a . Since the closed settling depressions 12a themselves lie on the surface of the filter trays 11 below them, there is no need to use separate spacers . Furthermore , the material of the filter trays 11 is plastic .

Example 3 : filtering unit 10 with open settling depressions 12b

A filtering unit 10 according to Figures 3 and 4 , which consists of three pieces of filter trays 11 , which are provided with open settling depressions 12b and holes 13 . As shown in Figure 4 , the filter trays 11 are of fset in the hori zontal plane by a distance of one open settling depression 12b, so that the lower, thin cylindrical part of the open settling depressions 12b passes through the holes 13 of the intermediate filter tray 11 . Vertically, the distance between the individual filter trays 11 is equal to hal f the height of the cone-shaped part of the open settling depressions 12b . Therefore , the bottom of the open settling depressions 12b is above the opening of the open settling depression 12b of the second filter tray 11 below them . The material of the filter trays 11 is plastic .

Example 4 : filtering unit 10 with open settling depressions 12b

The filtering unit 10 according to Example 3 with the modi fication that it is equipped with twenty- four filter trays 11 , which are vertically spaced at a distance greater than the height of the open depressions 12b . Furthermore , the material of the filter trays 11 is sheet metal .

Example 5 : The filtering apparatus 100 equipped with filtering units 10 according to Example 1 The filtering apparatus 100 equipped with filtering units 10 according to example 1 , which also has two inlets 21 and two outlets 22 .

Example 6 : The filtering apparatus 100 according to Example 5

The filtering apparatus 100 according to Example 5 , which further has a sealing 24 and a sensor . The sensor is the turbidity meter built into the outlet 22 .

Example 7 : The filtering apparatus 100 according to Example 5

The filtering apparatus 100 according to Example 5 , which further has a sealing 24 and a service window 25 .

Example 8 : The filtering apparatus 100 comprising filtering units 10 according to Example 4

The filtering apparatus 100 equipped with filtering units 10 according to Example 4 , which also has four inlets 21 and four outlets 22 , taps 23 and sealings 24 .

The advantage of the present invention is that it can be produced easily and filters the water to be puri fied with high ef ficiency . An additional advantage of the present invention is that it is quiet during use and can be used during cleaning and also under pressure. The filtering apparatus (100) according to the present invention can be used, for example, to clean garden ponds, outdoor swimming pools, streams, and wells.

Claims

1. Filtering unit (10) with filter trays (11) arranged in parallel planes and with a plurality of settling depressions (12) on each filter tray (11) , characterised by that the filtering unit (10) contains at least three filter trays (11) , where the filter trays (11 ) are located relative to each other in such a way that the settling depressions (12) of the filter trays (11) located directly below each other are offset by at least 50% of the diameter of the settling depression (12) in the plane of the filter trays (11) .

2. The filtering unit (10) according to claim 1, characterised by that the filter trays (11) are offset by at least 100% of the diameter of the settling depressions (12) .

3. The filtering unit (10) according to claim 1 or 2, characterised by that the arrangement of the settling depressions (12) on each filter tray (11) is the same as that of the additional filter trays (11) at a distance of two trays from the filter tray (11) .

4. The filtering unit (10) according to any one of the preceding claims, characterised by that the settling depressions (12) are closed settling depressions (12a) .

5. The filtering unit (10) according to any one of claims 1- 3, characterised by that the settling depressions (12) are open settling depressions (12b) and the filter trays (11) have holes (13) .

6. The filtering unit (10) according to any one of the preceding claims, characterised by that the settling depressions (12) have ribs.

7. The filtering unit (10) according to any one of the preceding claims, characterised by that the material of the filter trays (11) is plastic or sheet metal.

8. Filtering apparatus (100) equipped with a filtering unit (10) , at least one inlet (21) and at least one outlet (22) for maintaining a water flow, characterised by that it has a filtering unit (10) according to any one of claims 1-7.

9. The filtering apparatus (100) according to claim 8, characterised by that it has a sealing (24) .

10. The filtering apparatus (100) according to any one of claims 8-9, characterised by that it has at least one sensor .

11. The filtering apparatus (100) according to any one of claims 8-10, characterised by that it has a service window (25) .

12. The use of the filtering apparatus (100) according to claims 8 - 11 in the case of water containing impurities with a particle size of five millimetres or less flowing at a speed of 10 cm/ s or less into the filter apparatus.