DESCRIPTION

The present invention relates to a self-cleaning filter for liquids. Such a filter is particularly usable whenever it is necessary to remove solid particulates and/or insoluble liquid from a liquid to be filtered, usually water. Such a system is usually used in purification plants, treatment plants, or for the filtration of water for industrial, civil, naval or other use.

Self-cleaning filters are known in the state of the art. Such filters comprise an inlet opening, a delivery opening, a tubular element for filtering the liquid flowing from the inlet opening to the delivery opening, and a plurality of shoes arranged inside the tubular element, in particular in proximity to the internal surface. Such shoes, rotating with respect to a central axis, are capable of sweeping substantially the entire internal surface of the tubular element. The shoes are each provided with a respective suction opening, capable of withdrawing dirt from the internal surface of the tubular element.

In US 2014/021125 Al, the suction shoes are T-shaped and have a longitudinally extending suction slot. Such suction shoes were unsatisfactory in terms of flow/suction flow distribution along the suction slot. In fact, it is maximum in the central part at the discharge opening of the shoe and minimum in the end parts.

A further filter is shown in EP 3424578 Al, in the name of the same Applicant. Such a filter is similar to the previous ones, but comprises brushes fixed to the suction shoes. The combined action of the brushes and suction allows to significantly improve the efficiency of the self-cleaning system with respect to the previous filters.

The filter described in EP 3044165 Al is further known. In this filter, the suction openings of the shoes are selectively activatable. In particular, in a first step of the cleaning cycle the shoes act without suction, but only through the mechanical action of the brushes. This mode removes coarser dirt, which is then made to outflow through a first discharge line, connected in fluid communication with the internal surface of the tubular element.

In a second mode, the suction openings of the shoes are activated, so as to collect the finer dirt particles. Such dirt particles are then expelled through a second discharge line, placed in fluid communication with the suction openings.

SUMMARY OF THE INVENTION

All the known self-cleaning filters, except for the filter of EP ‘578, require a prefilter connected upstream of the self-cleaning filter itself. Such a prefilter has the function of removing the larger particles of contaminant dirt which would otherwise quickly saturate the self-cleaning filter. Such prefilters comprise a grille which intercepts the liquid flow upstream of the self-cleaning filter.

Unfortunately, in addition to making the system more complex, the prefilters must be subject to a maintenance cycle distinct from that of the self-cleaning filter. In the state of the art, the prefilters are periodically extracted and cleaned by the operator by hand. To carry out this operation it is necessary to block the system, losing the main advantage of the self-cleaning of the filter.

The filter of EP ‘578 manages to overcome the disadvantage of the prefilter by carrying out a two-stage cleaning process, which is capable of removing both the largest and the smallest dirt particles from the inside of the filter. It should be noted, however, that this advantageous solution is achieved by significantly increasing the complexity of the filter, since it requires the presence of two separate discharge lines, one for coarse dirt and the other for finer dirt.

In this context, the technical task underlying the present invention is to propose a self-cleaning filter which overcomes the drawbacks of the prior art mentioned above. In particular, an object of the present invention is to provide a self-cleaning filter which does not require a prefilter and, at the same time, which simplifies the hydraulic connections to the system and the control of the cleaning process.

The technical task mentioned and the objects stated are substantially achieved by a self-cleaning filter, comprising the technical features set out in one or more of the appended claims.

In particular, a self-cleaning filter according to the present invention comprises the technical features of claim 1.

Such a device solves the technical problem, as it can operate in two distinct steps. In the first step, the rubbing carried out by the contact cleaning means, i.e., by the brushes, allows the larger dirt particles to be detached from the filter by mechanical action. By opening the bypass valve, the suction acts mainly through the latter and not through the suction apertures of the cleaning elements, allowing the coarsest dirt to be removed and made to outflow to the discharge line directly through the bypass valve.

Subsequently the bypass valve is closed. Thereby, a greater suction is generated at the suction apertures of the shoes, and the smaller dirt particles can also be removed, which can be made to outflow from the same discharge opening.

This filter operating mode no longer requires the prefilter as in the state of the art, since the larger particles settle directly inside the self-cleaning filter and can be disposed of during a normal cleaning cycle. In addition, the cleaning cycle of the self-cleaning filter according to the present invention allows both coarse and fine dirt to flow through a single discharge line, thereby simplifying both the structure of the filter and the control of the cleaning process. In fact, to switch from one mode to another it is necessary to act exclusively on the bypass valve, while the suction is kept active throughout the cycle. LIST OF FIGURES

Further features and advantages of the present invention will become more apparent from the description of an exemplary, but not exclusive, and therefore non-limiting preferred embodiment of a self-cleaning filter, as illustrated in the appended figures, in which:

Figure 1 shows a sectional front view of the self-cleaning filter in accordance with the present invention;

Figure 2 shows a perspective view of the self-cleaning filter of Figure 1 ;

Figure 3 shows an enlarged perspective and partially sectional view of a detail of the self-cleaning filter of Figures 1 and 2;

Figure 4 shows a perspective view of a detail of the filter of Figure 1; and Figure 5 shows an exploded perspective view of the detail of Figure 3.

DETAILED DESCRIPTION

With reference to the accompanying figures, the number 1 indicates a self-cleaning filter in accordance with an embodiment of the present invention.

The filter 1 comprises a casing 21. This casing 21 encloses a volume adapted to contain both the fluid to be filtered and the filtered fluid. In particular, the casing 21 has a first 21a and a second end 21b arranged along a longitudinal development direction “A”. Depending on the applications, the longitudinal development direction “A” can be oriented horizontally, vertically or in any other intermediate direction.

More in detail, the casing 21 has an inlet opening 2 through which the fluid to be filtered is introduced. The casing 21 also has a delivery opening 3 from which the filtered fluid flows. The casing 21 is further provided with a discharge opening 24, distinct from the delivery opening 3, the function of which will be illustrated in a subsequent part of the present description.

A tubular filtering element 10 is inserted in the casing 21. Such a tubular element 10 is configured to be passed through by a fluid to be filtered. The tubular element 10 extends in particular along the aforementioned longitudinal development axis “A”. Preferably, the tubular element 10 is arranged between the ends 21a, 21b of the casing 21 and, even more preferably, has a cylindrical shape. In accordance with a preferred embodiment, the tubular element 10 consists of a filtering mesh.

In detail, the tubular element 10 defines an internal zone 22 within the casing 21. Such an internal zone 22 is adapted to be placed in communication with a source of fluid to be filtered, in particular through the inlet opening 2. An internal surface 10a faces the internal zone 22, and is adapted to receive and retain the suspended contaminant in the fluid to be filtered. An external surface 10b is opposite the internal surface 10a.

The tubular element 10 further defines an external zone 23 within the casing 21. Such an external zone 23 is in particular comprised between the external surface 10b of the tubular element 10 and the casing 21. The external zone 23 receives the filtered fluid from the tubular element 10 and allows it to flow through the delivery opening 3.

To remove the contaminant which deposits on the tubular element 10, the self cleaning filter 1 comprises one or more cleaning elements 4 placed within the internal zone 23. The cleaning elements 4 are spaced from each other along the longitudinal development direction “A”. Multiple elements can be placed in the same position on the longitudinal axis “A”. In this case, these cleaning elements 4 are arranged angularly equally spaced from each other around the longitudinal development axis “A”. Preferably, the cleaning elements 4 arranged adjacent along the longitudinal development direction “A” are angularly spaced by 120°.

The cleaning elements 4 are in particular configured to rotate around the longitudinal development direction “A”. In detail, the filter 1 comprises a hollow shaft 8 arranged centrally and oriented along the longitudinal development direction “A”. The cleaning element 4 are connected to the shaft 8 which, by rotating, rotates them with respect to the tubular element 10.

With reference to the illustrated embodiment, each cleaning element 4 has an advancement direction “B” In other words, as a result of the rotation around the longitudinal development direction “A” of the tubular element 10, each cleaning element travels along the internal surface 10a advancing along an advancement direction “B”, as shown for example in figure 4.

More in detail, each cleaning element 4 comprises a suction aperture 5. In use, the suction aperture 5 faces the internal surface 10a of the tubular element 10, in particular placed near the internal surface 10a, in particular in contact therewith. Such a first suction aperture 5 has the function of sucking the filtered impurities from the internal surface 10a of the tubular element 10.

In further detail, the suction aperture 5 comprises a slot 15, preferably of constant width, which extends along the longitudinal development direction “A” for more than 90% of the length of the cleaning element 4.

According to an embodiment, the cleaning elements 4 are spaced along the longitudinal development direction “A” so that, following the rotation thereof around the longitudinal development direction “A” of the tubular element 10, the surfaces swept by the suction apertures 5 of two adjacent cleaning elements 4 overlap with a ratio of overlapping area to total area of the suction aperture 5 in a range between 5% and 35%.

Each cleaning element 4 comprises in particular a pair of rods 6 and a shoe 7. Each rod 6 is oriented radially with respect to the tubular element 10. In particular, each rod 6 has a first end 6a and a second end 6b. The first end 6a is connected to the shaft 8 mentioned above.

The shoe 7 is connected to the second ends 6b of the rods 6, and is in particular arranged transversely with respect thereto. Said shoe 6 is arranged in a zone near the internal surface 10a of the tubular element 10, in particular substantially in contact therewith.

As shown for example in figure 4, each cleaning element 4 is provided with quick connection means 19 active between the rod 6 and the shoe 7. Such quick connection means 19 have the function of connecting/disconnecting the rod 6 from the shoe 7. Advantageously, the quick connection means 19 ensure a stable fixing of the shoe 7 on the rod 6, useful in particular when the cleaning element 4 is extracted from the tubular element 10 to perform maintenance operations.

It should be noted that the shoe 7 extends substantially parallel to the longitudinal development direction “A”. The first suction aperture 5, described above, is obtained on the shoe 7.

Each cleaning element 4 can advantageously comprise at least one elastic element 37, in particular an elastic bellows, connected to the shoe 7 and configured to push it against the internal surface 10a. Advantageously, the shoe 7 can be made of plastic material.

It should be noted that, according to the invention, each cleaning element 4 comprises contact cleaning means 9, arranged in particular on the shoe 7. Such contact cleaning means 9 are configured to rub on the internal surface 10a of the tubular element 10, so as to remove dirt. In particular, the contact cleaning means 9 are positioned in front of the first suction aperture 5 along the advancement direction “B”

In greater detail, the contact cleaning means 9 comprise a plurality of brushes 11. Each brush 11 is fixed to a respective cleaning element 4, and is configured to slide in contact with the internal surface 10a of the tubular element 10 along the aforementioned advancement direction “B” Advantageously, the brush 11 allows a greater amount of dirt to be removed by mechanic al action.

More in detail, each cleaning element 4 has a seat 12, in particular obtained on the shoe 7. The aforementioned brush 11 is arranged inside the seat 12. In further detail, each brush 11 is insertable/removable in/from the seat 12, so as to be connected/disconnected to the respective cleaning element 4. More in detail, a pair of plugs (not illustrated) fixes the brush 11 inside the seat 12. Such plugs are in themselves a fixing mechanism known to those skilled in the art, and will therefore not be described further.

Advantageously, the removability of the brushes 11 allows to replace them when they are worn and/or to select a particular type of brush 11 more suitable for the particular type of tubular element 10 mounted in the filter 1.

The self-cleaning filter 1 further comprises a suction conduit 16 arranged within the tubular element 10, in particular within the shaft 8, and configured to rotate with respect to the tubular element 10.

Preferably, the suction conduit 16 is arranged coaxially with respect to the tubular element 10.

In accordance with an embodiment, in order to allow the rotation of the cleaning elements 4 with respect to the tubular element 10, the cleaning elements 4 are fixed in rotation to the suction conduit 16 and project radially from the suction conduit 16.

In particular, the suction conduit 16 has a plurality of connection openings 17. Each connection opening 17 is connected to a respective cleaning element 4 through a respective connection conduit 18. It should be noted that the connection conduit is defined within at least one of the two rods 6 forming the cleaning element 4, preferably within both rods 6.

It should now be noted that the above-mentioned discharge opening 24 is arranged to expel the dirt removed from the internal surface 10a. In particular, the discharge opening 24 is placed in fluid communication with the internal zone 22 and, in particular, with the suction apertures 5 of the cleaning elements 4. The filter 1 further comprises a discharge valve 25 placed at the discharge opening 24.

More in detail, the discharge opening 24 is formed at the first end 21a of the casing 21. In particular, a chamber 27 is arranged coaxially to the tubular element 10, and is placed at the first end 21a. The discharge opening 24 is formed at such a chamber 27. The aforementioned shaft 8 coaxially passes through the chamber 27.

In accordance with the present invention, the filter 1 is provided with at least one bypass valve 30. Such a bypass valve 30 is placed in parallel with respect to the suction apertures 5 of the cleaning elements 4. In use, the bypass valve 30 can be opened, so as to put the internal zone 22 directly in fluid communication with the discharge opening 24. In particular, the bypass valve 30 is placed between the internal zone 22 and the chamber 27. In the embodiment shown in figure 1, the filter 1 comprises a single bypass valve 30. In alternative embodiments, not shown, there can be any number of bypass valves 30.

In more detail, as shown for example in figure 3, the bypass valve 30 comprises a bypass opening 31, which is placed between the chamber 27 and the internal zone 22. In particular, the filter 1 comprises a separation wall 34 arranged between the chamber 27 and the internal zone 22. The bypass opening 31 is then formed on the wall 34.

A stem 32 is associated with the bypass opening 31, and is movable with respect thereto to open and/or close it. In particular, in the described embodiment the stem is oriented substantially parallel to the longitudinal development direction “A”.

The bypass valve 30 further comprises actuating means 33 for the stem 32, so as to be able to move it with respect to the bypass opening 30. Such actuating means 33 comprise a cylinder 35 and a piston 36, inserted in the cylinder 35 and slidable therein. The piston 36 is connected to the stem 32, in particular to the opposite end of the bypass opening 31. In the preferred embodiment, the cylinder 35 and the piston 36 are of a pneumatic type. In alternative embodiments, the piston 35 and the cylinder 36 can be of another type, for example of the hydraulic type. More generally, the actuating means 33 can be of any type, as long as they are suitable for the purpose. For example, the actuating means 33 can comprise an electric linear actuator.

The object of the present invention is also a self-cleaning process of the filter 1 described above. In particular, in a first step a rough cleaning is carried out by rotating the cleaning elements 4 to sweep the internal surface 10a of the tubular element 10. At the same time, fluid is sucked from the discharge opening 24, and the bypass valve 30 is opened. Thereby the contaminant, mainly the larger particles, is removed from the brushes 11 and flows predominantly from the bypass opening 31 directly to the discharge opening 24.

Subsequently the bypass valve 30 is closed. The cleaning elements 4 are kept in rotation, but now the dirt is sucked through the suction apertures 5 of the shoes 7. Thereby, even small dirt particles can be removed by suction. They are also discharged through the aforementioned discharge opening 24.

It should be noted that, during the self-cleaning process, the cleaning elements 4 move exclusively along a circumferential direction of the internal surface 10a of the tubular element 10. In other words, the shoes 7 do not move along a direction parallel to the longitudinal development direction “A” of the filter 1.