FILTER FOR FLUIDS, PARTICULARLY FOR IRRIGATION WATER OR FOR HOUSEHOLD WATER IN GENERAL

Technical Field

The present invention relates to a filter for fluids, particularly for irrigation water or household water in general.

Background Art

As is known, in agricultural microirrigation systems the filtration of so-called open-air water is commonly performed by using grit filters, in which the filtering mass is provided by a layer formed by a plurality of granular bodies made of quartz or other stone-like material.

A first type of grit filter is known which is. constituted by an outer cylindrical enclosure, which is arranged so that its axis is vertical and is provided, in its upper part, with an intake port for introducing a stream of water to be filtered and is provided internally with a filtering layer made of grit, which is generally arranged above a transverse partition provided with openings for the passage of the filtered water, which in turn are connected to a discharge manifold arranged in the lower part of the enclosure.

With this type of filter, in order to remove the impurities retained in the grit layer and thus regenerate the filter, it is necessary to perform the so- called backwashing of the filter, i.e., reverse the direction of flow of the water inside the enclosure, introducing water into the enclosure through the discharge manifold and then making it exit through a suitable discharge port provided in the upper part of said enclosure.

The drawback of this type of grit filter arises indeed from the fact that in order to perform backwashing it is necessary to interrupt normal filtration operations, with the obviously related inconvenience.

In order to try to solve this problem, double-chamber filters have been proposed which are constituted generally by an outer cylindrical body which has a horizontal axis and is divided internally by a transverse partition into two filtration chambers, each of which accommodates a grit filtering layer

and is connected to an intake manifold through respective intake ports which open in the upper part of the side wall of the outer cylindrical body. A discharge manifold duct is further accommodated inside the outer cylindrical body and crosses longitudinally the lower region of the filtration chambers in order to collect the filtered water through passage openings formed along its axial extension.

Although it is valid conceptually, since it allows to filter the water by means of one of the two chambers even during the backwashing of the other, avoiding the interruption of the delivery of filtered water, this solution, however, does not allow to utilize the filtering layer in an optimum manner.

Due to the position in which the discharge manifold duct is arranged with respect to the filtering layer, the water, in its path inside each chamber, in fact is not distributed uniformly in all the regions of the filtering layer but on the contrary tends to flow through small preferential passage channels, with consequent deterioration of the filtration results.

Disclosure of the Invention

The aim of the present invention is to obviate the drawbacks cited above by providing a filter for fluids, particularly for irrigation water, which in addition to offering high effectiveness in filtration allows to perform backwashing of the filtering layer without necessarily having to interrupt filtration operations.

Within this aim, an object of the invention is to provide a filter which is particularly simple from a structural standpoint and has very small dimensions.

Another object of the invention is to provide a filter which allows to use lower-power pumps than those used in the background art to perform filtration and backwashing.

Still another object of the invention is to provide a filter which can be obtained easily starting from commonly commercially available elements

and materials and is further competitive from a merely economical standpoint.

This aim and these and other objects, which will become better apparent hereinafter, are achieved by a filter for fluids, particularly for irrigation water or household water in general, characterized in that it comprises at least one filtration assembly which has an outer cylindrical enclosure, which is arranged so that its own axis is substantially vertical and forms internally at least two filtration regions, which are mutually separated hermetically and are each provided with a respective intake port for the inflow of the fluid to be filtered and a respective discharge port for the outflow of the filtered fluid, each of said at least two filtration regions accommodating at least one filtering element, which is interposed between the corresponding intake port and the corresponding discharge port.

Brief Description of the Drawings Further characteristics and advantages of the invention will become better apparent from the detailed description of a filter according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a schematic longitudinal sectional view of the invention; Figure 2 is a schematic longitudinal sectional view of another possible embodiment of the invention;

Figure 3 is a partially sectional elevation view, taken along the broken line III-III of Figure 4, of a constructive variation of the filter according to the invention; Figure 4 is a top plan view of the variation of Figure 3, with parts shown partially in phantom lines in order to highlight its interior;

Figure 5 is a schematic longitudinal sectional view of another constructive variation of the invention;

Figure 6 is a top plan view of the filter according to the invention, with the upper part omitted in order to show the interior in a possible

embodiment;

Figure 7 is a top plan view of the filter according to the invention, in which the upper part has been removed in order to show another possible embodiment of the interior; Figure 8 is a schematic partially sectional side elevation view of another constructive variation of the invention;

Figure 9 is a sectional view, taken along the line IX-IX of Figure 8;

Figure 10 is a top plan view of the interior of the variation of Figure 9 according to a different embodiment. Ways of carrying out the Invention

With reference to the figures, the filter for fluids, particularly for irrigation water according to the invention, generally designated by the reference numeral 1, is constituted by at least one filtration assembly 2, which has an outer cylindrical enclosure 3 which is arranged so that its axis is substantially vertical.

More preferably, there are at least two filtration assemblies 2, which are mutually superimposed, as shown schematically in the example of Figure 2 and conveniently can be connected to an intake manifold 4, which is arranged advantageously above the stack formed by the filtration assemblies 2, and to a discharge manifold 5, which is arranged preferably below the filtration assemblies 2.

Conveniently, the several filtration assemblies 2 are mutually superimposed, arranging their respective cylindrical enclosures 3 coaxially to each other so as to limit lateral space occupation. The mutual assembly of the several filtration assemblies 2 can be provided for example by interposing gaskets, so as to allow their optional disassembly, or, more preferably, the cylindrical enclosures 3 of each filtration assembly 2 are mutually interconnected so as to form a single body. According to the invention, each filtration assembly 2 defines

internally at least two filtration regions 6a and 6b, which are hermetically separated one another.

In the upper part of each of the filtration regions 6a, 6b there opens at least one respective intake port, which allows the inflow of the fluid to be filtered and is conveniently provided by diffusers 7 arranged at the end of a corresponding inflow duct 8, which can be connected to the intake manifold

4 and optionally lies so as to cross in an axial direction the overlying filtration assemblies 2.

Conveniently, at least the filtration assembly 2 arranged at the upper end of the stack can be closed in an upward region by a plate 3a, which acts as a supporting element for the inflow ducts 8 and is connected advantageously to the cylindrical enclosure 3 by means of a flanged peripheral connection 3b. Preferably, at the upper end of the stack there is also a cambered upper closure lid 3c, which also can be connected to the body of the stack by means of flanged connection elements or the like, in order to allow easy inspection of the interior of the upper filtration assembly

2.

At the lower part of each filtration region 6a, 6b there are also one or more discharge ports for the filtered fluid, constituted advantageously by a plurality of stub pipes 9, which are connected to the discharge manifold 5 and open onto a flat bottom 10, which delimits in a downward region the filtration regions 6a, 6b.

As pointed out in the example shown in Figure 1 , it is also possible to provide, for each filtration region 6a, 6b, a respective discharge manifold 5, from which a corresponding outflow duct 5a for conveying outwardly the filtered fluid can extend.

Preferably, the filtration regions 6a, 6b are located substantially side by side. Merely by way of example, the filtration regions 6a, 6b can be mutually separated by at least one side wall 11 , which is substantially circular and advantageously can be arranged concentrically or eccentrically

with respect to the axis of the cylindrical enclosure 3.

Conveniently, at the axial ends of each filtration assembly 2, at the side wall 1 1 , there are fork-shaped gaskets 1 1a which straddle the edges of the wall 1 1, so as to achieve hermetic separation among the filtration regions 6a, 6b of the several superimposed filtration assemblies 2.

According to a constructive variation shown in Figure 6, the filtration regions, designated in particular by the reference numerals 6a, 6b and 6c, can be delimited by partitions 30 which lie radially with respect to the axis of the cylindrical enclosure 3. In another possible embodiment, shown in Figure 7, the internal space of the cylindrical enclosure 3 can be divided by providing at least two filtration regions, designated by the reference numerals 6a and 6b in the example, which are delimited by respective side walls 11 and are arranged side by side on diametrically opposite sides with respect to the axis of the cylindrical enclosure 3, and other filtration regions, which are designated by the reference numerals 6c and 6d again in the example of Figure 7 and are delimited by the cylindrical enclosure 3 and by the side walls 1 1.

Conveniently, in the several filtration regions there are one or more filtering elements 12, which can be of different types according to requirements and are interposed between said intake and discharge ports of the filtration regions 6a, 6b so that they can be crossed by the fluid to be filtered.

Preferably, the filtering elements 12 are provided by a granular filtering mass constituted for example by sand, grit, pieces of quartz and the like, whose particle size can vary according to the filtration requirements.

Advantageously, the filtering elements 12 are accommodated in the filtering regions 6a, 6b detachably so as to be able to vary their type depending on the type of filtration to be performed.

It should be noted that for each filtration region 6a, 6b there is conveniently a respective discharge duct 13, which is designed to allow the

outflow of the fluid used to perform the backwashing of the filtration regions 6a, 6b. Optionally, the different discharge ducts 13 lead into a tank 14 for collecting the fluid which contains the dirt removed by backwashing, as shown in Figure 2. Advantageously, the discharge duct 13 of each filtration region 6a, 6b can open directly into the corresponding filtration region 6a, 6b, as shown in Figure 1, or can extend from a three-way control valve 15 arranged on the inflow duct 8 of the corresponding filtration region 6a, 6b, as shown in the example of Figure 2. Preferably, at least one of the filtration assemblies 2 has its filtration regions 6a, 6b connected, by means of the corresponding stub pipes 9, to a common or corresponding intermediate manifold 16, which is provided for example by an interspace which is formed below the flat bottom 10 and acts as a region for collecting the filtrate that originates from the filtration regions 6a, 6b before it is conveyed toward the discharge manifold 5 by means of a connecting duct 17 which preferably crosses axially the underlying filtration assemblies.

More preferably, each filtration assembly 2, except optionally for the one located at 'the lower longitudinal end of the stack formed by said filtration assemblies 2, is provided with a respective intermediate manifold 16, which conveniently can be connected to the corresponding connecting duct 17 by interposing a control valve 18 which can be accessed from the outside of the filtration assemblies 2.

Advantageously, at least one throttling valve 19 is interposed along the intake manifold 4 and allows to interrupt the inflow of the fluid to be filtered in at least one of the filtration assemblies 2.

As shown in particular in the example of Figure 2, the intake manifold 4 can then be connected, by means of a flow control valve 20, to a dispensing line 21, which originates from an external circuit which constitutes for example an irrigation system or a domestic water system and

optionally can be connected, by means of a branching duct 22 controlled by a connecting valve 23, to the discharge manifold 5 so as to allow to bypass the several filtration assemblies 2.

Again with reference to the example shown in Figure 2, each filtration assembly 2 can be connectable advantageously to a supply line 24 for a washing liquid, such as for example clean water or an appropriate chemical substance, which allows to provide specific cleaning of the filtering elements 12. In particular, said supply line 24 can be connected to inflow means 25, which are capable of dispensing in the filtration regions 6a, 6b the washing liquid with a flow in countercurrent with respect to the direction of flow of the fluid during filtration.

For the sake of completeness, it should further be added that on the side wall of the cylindrical enclosure 3 of each filtration assembly 2 there are inspection openings 26, which allow access to the filtration regions 6a, 6b for maintenance of the corresponding filtration elements 12.

In the practical operation of the embodiments of the invention shown in particular in Figures 1, 2 and 3, by opening the throttling valve 19 and the several three-way control valves 15, the fluid to be treated is introduced, by means of the inflow ducts 8, in the several filtration assemblies 2, so that by flowing out of the diffusers 7 it can enter the corresponding filtration regions 6a, 6b, consequently crossing the corresponding filtering elements 12, until it arrives at the stub pipes 9, through which it flows out of the filtration regions 6a, 6b and collects in the intermediate manifold 16 (if provided) to be then conveyed toward the discharge manifold 5 by the corresponding connecting duct 17.

With the structure described above, in order to clean the filtering elements 12 provided in one of the filtration assemblies 2 it is possible to reverse the flow inside one of its filtration regions, so as to provide backwashing, and still maintain the direction of flow that allows filtration in the other filtration region.

Substantially, in order to perform this operation, one proceeds by closing the inflow duct 8 which is connected to the filtration region to be subjected to backwashing, which can be for example the one designated by the reference numeral 6a, and by opening the corresponding discharge duct 13 by acting on the corresponding three-way control valve 15. In this manner, the fluid that arrives from the intake manifold 4 is introduced exclusively in the other filtration region 6b of the filtration assembly and, once it has exited into the intermediate manifold 16, is partly conveyed toward the discharge manifold 5 and partly toward the stub pipes 9 of the filtration region which is subjected to backwashing.

Of course, if one wishes for example to perform backwashing of the filtration region designated by the reference numeral 6b, one proceeds in a manner similar to what has been described above for the filtration region 6a.

According to another embodiment of the invention, shown in Figure 5, each of the several filtration regions 6a, 6b of the filtration assemblies 2 can also be connected, by means of its discharge port, preferably formed, as in the preceding examples, by stub pipes 9, to the intake port of a corresponding filtration region which is formed inside the filtration assembly that lies directly below the corresponding filtration assembly 2. With this arrangement, in practice corresponding filtration regions of the several filtration assemblies 2 are not mutually arranged in parallel, as in the examples shown in Figures 2 and 3, but, according to an electrical comparison, in a series arrangement, since, with reference to Figure 5, the fluid to be filtered, which arrives from the intake manifold 4, enters, through . the diffusers 7, the several filtration regions 6a, 6b of the upper filtration assembly to arrive, after crossing the corresponding filtering elements 12, at the corresponding stub pipes 9, where it exits from the filtration regions 6a, 6b of the upper filtration assembly to pass to the corresponding filtration regions 6a, 6b of the lower filtration assembly, which are crossed by the fluid until the filtrate reaches the discharge manifold 5.

It should be noted that in order to perform backwashing with this embodiment it is sufficient to close the inflow duct 8 that corresponds to the filtration regions connected in series that one wishes to clean (for example, the ones designated by the reference numeral 6a) and to open the corresponding discharge duct 13, by means of the corresponding three-way control valve 15, so as to draw fluid from the discharge manifold 5 and make the drawn fluid pass through the filtration regions to be cleaned in the opposite direction with respect to the passage direction that allows filtration.

It is obvious that the remaining filtration regions connected in series to each other in the several filtration assemblies 2 (i.e., the ones designated by the reference numeral 6b in the example of Figure 5) can continue to be crossed by the fluid to be filtered along the passage direction which goes from the intake manifold 4 to the discharge manifold 5, so as to allow to avoid interrupting filtration. As shown again in Figure 5, for the outward discharge of the backwashing fluid it is optionally possible also to provide auxiliary discharge outlets 27 which can be controlled conveniently by means of appropriately provided closure valves 27a and open into the upper part of the several filtration regions 6a, 6b of the filtration assembly or assemblies 2 arranged below the assembly that lies closest to the intake manifold 4, so as to facilitate the evacuation therefrom of the dirt retained by the corresponding filtering elements 12.

It should also be noted that with this solution it is advantageously possible to accommodate in the filtration regions arranged in series to each other filtering elements 12 which are adapted to provide different degrees of filtration along the path of the fluid and in particular a higher filtration toward the filtrate discharge region with respect to the intake region of the fluid to be filtered.

For this purpose, it is possible for example to introduce in the individual filtration regions 6a, 6b of each filtration assembly 2 filtering

elements 12 which are constituted by granular filtering masses which have a larger particle size than the filtering masses provided in the subsequent filtration regions in the direction of flow of the fluid to be filtered.

Thus, for example, with reference to the example of Figure 5, the particle size provided for the filtering masses in the filtration regions 6a, 6b of the upper filtration assembly is larger than the particle size of the filtering masses accommodated in the various filtration regions 6a, 6b formed by the lower filtration assembly.

Another possible variation of the invention is shown in Figure 8. In this embodiment, as in the ones described above, there is at least one filtration assembly 2 formed by an outer cylindrical enclosure 3 which has a substantially vertical axis, which forms a plurality of filtration regions designated by the reference numerals 6a, 6b and 6c, which are mutually hermetically separated, within the cylindrical enclosure 3, preferably by means of circular side walls 1 1, which are arranged eccentrically with respect to the axis of the outer cylindrical enclosure 3, as shown in Figure 9 or, as an alternative, arranged concentrically with respect to the axis of the outer cylindrical enclosure 3, as shown schematically in Figure 10.

According ^" to the embodiment of Figure 8, at least one of the filtration regions 6a, 6b, 6c can be connected, by means of the corresponding discharge port, to the intake port of at least one of the other filtration regions which are provided within said outer cylindrical enclosure 3 and therefore belong to the same filtration assembly 2.

More preferably, as shown in Figure 8, the filtration regions 6a, 6b, 6c are arranged in series to each other along the path of the fluid to be filtered within the filtration assembly 2.

In particular, the first filtration region in the series arrangement along the direction of the flow of the fluid from the intake manifold 4 to the discharge manifold 5, i.e., the one designated by the reference numeral 6a in the example of Figure 8, is connected in input to the intake manifold 4 by

means of an inflow valve 28, while the last filtration region in the series arrangement, which in Figure 8 is the one designated by the reference numeral 6c, is connected in output to the discharge manifold 5 with the interposition of a filtrate discharge valve 29. It should be noted that conveniently the intake manifold 4 can be connected to the discharge manifold 5 by means of a bypass valve 31 and that preferably the discharge manifold 5 can be connected to a supply line of the system, designated by the reference numeral 100, for example by means of a dispensing valve 101. As in the preceding examples, in the embodiment of Figure 8 also the intake ports of the filtration regions 6a, 6b, 6c can be provided advantageously by diffusers 7 which are connected to respective inflow ducts 8 and the discharge ports of the filtration regions 6a, 6b, 6c can be formed by a plurality of stub pipes 9 formed in a flat bottom 10 which closes in a downward region the filtration regions 6a, 6b, 6c.

Conveniently, for each filtration region 6a, 6b, 6c there is a collection chamber 32 for the filtered fluid, which is connected to the discharge port of the corresponding filtration region.

Advantageously, a respective connecting duct 33 protrudes from each collection chamber 32, crosses axially the corresponding filtration region and is connected to the inflow duct 8 of the next filtration region, in the series arrangement, by way of the interposition of a connecting valve 34.

It can be seen that the eccentric arrangement of the side walls 1 1 with respect to the axis of the outer cylindrical enclosure 3 shown in the example of Figure 9 allows to have available more space for the passage of the connecting ducts 33 in the respective filtration regions 6a, 6b, 6c with respect to the embodiment of Figure 10, in which the side walls 1 1 are arranged concentrically with respect to the axis of the outer cylindrical enclosure 3. Moreover, it should be noted that the connecting duct 33 of the last

filtration region 6c, in the series arrangement, can be connected to the discharge manifold 5 by means of the discharge valve 29.

Conveniently, respective ducts 35 for dispensing the backwashing fluid further lead into the various collection chambers 32 and are connected, by means of respective dispensing valves 36, to a branching line 37 which extends from the discharge manifold 5 and preferably has a first connecting valve 37a and a second connecting valve 37b which are interposed respectively upstream and downstream of the dispensing valves 36 along the direction of flow of the fluid that arrives from the discharge manifold 5, said valves allowing to control the flow-rate conveyed into the branching line 37 from and toward the dispensing ducts 35.

In the embodiment of Figure 8 also, in order to allow the discharge of the fluid used for backwashing, each filtration region 6a, 6b, 6c is provided with a respective discharge valve 13, which is conveniently connected to the corresponding inflow duct 8, which, by means of its diffuser 7, allows to convey the fluid used for backwashing of the corresponding filtration region toward the outside and more preferably toward a discharge line 38, which is advantageously common to all the filtration regions 6a, 6b, 6c.

With the 'series arrangement of the several filtration regions 6a, 6b, 6c, as in the example of Figure 8, it is possible to introduce in the filtration regions 6a, 6b, 6c filtering elements 12 which can be of different kinds depending on the type of filtration to be performed.

Thus, for example, if the filter according to the invention is applied to perform traditional domestic water treatment, it is possible to introduce a resin for removing iron from the water in the first filtration region 6a along the direction of flow of the water to be filtered within the filtration assembly 2, a resin for softening the water in the next filtration region 6b, and activated carbon, in order to remove bad odors and taste from the water, in the last filtration region 6c. Conveniently, the inflow duct 8 of the first filtration region 6a, in the

series arrangement, can be connected by way of ejection means 39 constituted for example by a Venturi device or by an electronically- controlled dispensing device of a known type, to a tank 40 which contains a substance for regenerating and cleaning the filtering elements 12, such as for example a brine, if the filter is used for domestic water treatment.

Advantageously, control of the several valves and of the ejection means 39 can be entrusted to a single automatic control device, such as for example a PLC, which is capable of driving the opening or closure of the several valves and optionally the activation of the ejection means 39 in order to perform the ordinary filtration operations or the operations for cleaning the filtering elements 12.

Conveniently, in order to allow more practical execution of maintenance interventions and make the structure more compact, the inflow valve 28, the discharge valve 29, the discharge valves 13, the connecting valves 34, the connecting valves 37a, 37b, the dispensing valves 36 and the dispensing ducts 35 can be grouped together, preferably at the upper part of the filtration assembly 2, so as to have all the main valves of the filter close to each other in a single region of the structure of said filter.

As can be understood easily, with the embodiment of Figure 8 it is possible to combine in a single body all the types of filtration required for water treatment, with the advantage of having smaller overall dimensions for the system, since individual different filters for each type of filtration are no longer required and there is further a greater possibility, with respect to the background art, to adapt the filter to the different filtration requirements of different fields of application, since the filtering characteristics of the filter can be modified simply by varying the filtration elements 12 inserted in the several filtration regions 6a, 6b, 6c.

As regards operation, with the arrangement shown in Figure 8, by opening the inflow valve 28 and closing the dispensing valves 36 the fluid to be filtered, which arrives from the intake manifold 4, can cross the

filtering element of the first filtration region 6a, according to the series arrangement, and by entering the corresponding connecting duct 33 can pass to the next filtration region 6b, in the series arrangement, from which it can exit by passing through the corresponding filtration element and the corresponding connecting duct, reaching the last filtration region 6c, from the collection chamber of which the filtered fluid can finally be conveyed through the discharge valve 29 into the discharge manifold 5.

With the embodiment of Figure 8, in order to perform backwashing of the several filtration regions 6a, 6b, 6c it is possible to close the connecting valves 34, the inflow valve 28 and the discharge valve 29 and open the discharge valves 13, the first connecting valve 37a, the dispensing valves 36 and the bypass valve 31, so that the fluid that arrives from the branching line 37 can be conveyed into the dispensing ducts 35 in order to be introduced, through the stub pipes 9, into the corresponding filtration regions and then pass through the corresponding filtering elements 12 in the opposite direction with respect to the normal filtration flow, until it reaches the diffusers 7, through which the fluid used for backwashing exits from the filtration regions so that it can be conveyed, by means of the discharge valves 13, into the discharge line 38. As an alternative, backwashing of the filtration regions 6b and 6c can be also performed while keeping active the filtration performed by the filtration region 6a. To achieve this, one proceeds by closing the first connecting valve 37a, the connecting valves 34 and the discharge valve 29 and by opening the dispensing valves 36, the discharge valves 13 of the filtration regions 6b and 6c, and the second connecting valve 37b, so that the fluid to be filtered can, by means of the inflow valve 28, enter the first filtration region 6a and pass through its filtering element, until the filtered fluid reaches the corresponding collection chamber, from which it exits, by means of the corresponding dispensing duct, in order to reach the branching line 37, from which it is conveyed partly toward the dispensing ducts 35 of

the other filtration regions 6b and 6c, which are then subjected to backwashing and partly toward the outside, by means of the second connecting valve 37b. It should be noted that differently from what has been described above, the second connecting valve 37b can also be kept closed and the first connecting valve 37a can be left open, thus allowing part of the filtered fluid that exits from the first filtration region 6a, in the series arrangement, to be conveyed, by means of the branching line 37, toward the supply line of the system 100, while its remaining part is used for backwashing of the filtration regions 6b and 6c. It is also possible to perform backwashing only of the last filtration region 6c, in the series arrangement, without interrupting filtration in the other filtration regions 6a and 6b, which precede it in the series arrangement, along the direction of flow of the fluid to be filtered. By closing the first connecting valve 37a, the connecting valve 34 which is interposed between the filtration region 6b and the filtration region 6c and the discharge valve 29 and by opening the dispensing valves 36 (optionally except for the one related to the first filtration region 6a, in the series arrangement), the discharge valve 13 of the last filtration region 6c and the second connecting valve 37b, the fluid to be filtered can enter, by means of the inflow valve 28, the first filtration region 6a and then cross the filtering element 12 of the first filtration region 6a and, after passing through the connecting duct 33 of the first filtration region 6a, also the filtering element 12 of the next filtration region 6b, until the fluid thus filtered reaches the collection chamber 32 of the filtration region 6b to be conveyed, by means of the corresponding dispensing duct 35, partly toward the last filtration region 6c, through the corresponding dispensing valve 36, thus allowing its backwashing, and partly toward the outside, through the second connecting valve 37b. It should be added that it is also possible to keep the first connecting valve 37a open together with or instead of the second valve 37b, so as to be able to convey part of the filtered fluid toward the supply line of

the system 100, by means of the branching line 37, while another part of the filtrate is used for the backwashing of the last filtration region 6c.

Moreover, if there are connection means (not shown) which are adapted to connect, by means of the interposition of appropriately provided control valves (also not shown), the intake port of the filtration region 6b, which follows the first filtration region 6a in the series arrangement, and optionally also the intake port of the last filtration region 6c, in the series arrangement, to the intake manifold 4, it is possible to perform backwashing of the first filtration region 6a, in the series arrangement, without requiring interruption of filtration in the other filtration regions 6b, 6c.

By closing the inflow valve 28 and opening the control valves of said connecting means, the discharge valve 13 of the first filtration region 6a and each of the dispensing valves 36, intake of the fluid to be filtered, which arrives from the intake manifold 4, into the filtration regions 6b, 6c which follow the first one in the series arrangement, is allowed, with the result that the filtrate in output therefrom can be used partly to perform backwashing of the first filtration region 6a, conveying it by means of the corresponding dispensing ducts 35, in a manner which is fully similar to what has been described above; and can be sent partly to the system, for example by means of the first connecting valve 37a.

It should also be noted that backwashing of the various filtration regions 6a, 6b, 6c should conveniently be followed by a step for re- compaction or resettling of the granular filtration masses, which, in the case of the example of Figure 8, can be performed advantageously by means of the second connecting valve 37b.

In detail, after performing for example backwashing of the first filtration region 6a in order to achieve the packing of its filtration mass, it is possible to close its discharge valve 13 and its connecting valve 34, which connects it to the next filtration region 6b, in the series arrangement, and to open its dispensing valve 36, the inflow valve 28 and the second connecting

valve 37b, so as to introduce fluid, which arrives from the intake manifold 4, in the first filtration region 6a by means of its diffuser 7 and then make it flow outwardly through its dispensing valve 36 and through the second connecting valve 37b, thus reversing the direction of flow of the fluid within the first filtration region 6a with respect to the direction of flow during backwashing, and consequently achieving automatic resettling of the granular material that constitutes the filtration mass.

In practice it has been found that the filter according to the invention fully achieves the intended aim, since it allows to clean the filtering elements without requiring complete interruption of filtration.

Another advantage of the invention is that it allows, by means of the internal division into a plurality of filtration regions of the filtration assemblies, an improved efficiency of the backwashing operation, since said operation can be performed with reduced flow-rates with respect to the background art.

Another important aspect of the invention further consists in that the stacked arrangement of the several filtration assemblies and the presence inside them of a plurality of filtration regions allow to obtain large filtering surfaces while keeping the space occupation of the filter extremely low. It should also be added that the filter according to the invention can be used effectively to filter water used in a domestic environment or in irrigation systems for agriculture or also for the filtration of liquids that derive from industrial processes in general.

All the characteristics of the invention indicated above as advantageous, convenient or the like may also be omitted or be replaced with equivalents.

The individual characteristics described with reference to general teachings or particular embodiments may all be present in other embodiments or may replace characteristics in such embodiments. The invention thus conceived is susceptible of numerous

modifications and variations, all of which are within the scope of the appended claims.

In practice, the materials used, so long as they are compatible with the specific use, as well as the shapes and dimensions, may be any according to requirements.

All the details may further be replaced with other technically equivalent elements.

The disclosures in Italian Patent Application No. VR2006A000007 from which this application claims priority are incorporated herein by reference.