WO2012168896A1

WO2012168896A1 - Percolation filtering system

Info

Publication number: WO2012168896A1
Application number: PCT/IB2012/052880
Authority: WO
Inventors: Maurizio Moretto
Original assignee: Laica S.P.A.
Priority date: 2011-06-07
Filing date: 2012-06-07
Publication date: 2012-12-13
Also published as: CN103619759A; CN103619759B; ITPD20110186A1; KR20140033470A; KR101940291B1

Abstract

A percolating filter device including a housing having an inlet aperture for water to be filtered and an outlet aperture for filtered water, a first filter means in the housing, interposed between the inlet and outlet apertures, a second filter means interposed between the first filter means and the outlet aperture, a chamber defined between the filter means and means for venting the chamber to vent gases collected in the chamber together with the flow of liquid to be filtered through the filter means, characterized in that the first filter means comprise a replaceable filter cartridge, the housing comprises a seat for the cartridge, formed in a divider element which separates a first container for receiving water to be filtered from a second container for receiving filtered water, within the device (1), and wherein the cartridge is housed removably and the chamber is defined between the cartridge and the seat.

Description

PERCOLATION FILTERING SYSTEM DESCRIPTION

The subject of the invention is a percolating filter device of the type including the features mentioned in the preamble to the main claim.

In percolating filter devices, the pressure gradient to which the fluid to be filtered is subjected is quite low since the filtering takes place substantially by gravity. The filter means normally contain layers of activated carbon, ion-exchange resins and similar materials which, owing to their respective surface tensions, may cause air to be trapped in the filter layer. This in turn leads to some disadvantages. A first disadvantage is that, when the filter retains air, the useful cross-section for the through-flow of liquid to be filtered is reduced, slowing down the flow. This leads to a low flow-rate of filtered water and a consequent lengthening of the time required for filtration.

A second disadvantage, which aggravates the first, is due to the fact that those areas of the filter layer which trap air do not take part in the filtering, resulting in non-homogeneous (poor) utilization of the material which forms the filter bed . This leads to premature exhaustion of the filter cartridge and/or to its malfunction towards the end of its useful lifecycle.

Canadian patent CA2350292 addresses these disadvantages by providing, between adjacent layers of filter material, a filter venting chamber through which the air trapped in the filter can be discharged through a vent tube. In many cases these filters may comprise two or more layers of filter material; the last layer may be constituted by hollow fibres which have the known characteristic that they retain germs, bacteria and cysts, reducing the microbial and bacterial load of the filtered water. This layer is generally the most expensive and, fortunately, generally has a relatively long useful life, normally longer than that of the activated carbon or ion-exchange layers. However, when the filter element is formed as a unitary cartridge, it has to be replaced upon the expiry of the component that has the shortest useful life, thus losing a still unexhausted filtering capacity of the other components which have longer useful lives. Moreover, it is not possible to make up the filter layer with the use of standardized filter elements which could also usefully be used in other filter devices.

An alternative solution is described in patent application JP 2000 042536 which describes a filter system in which there are two individually replaceable cartridges. The filter system also comprises a venting duct formed at the point where the filtered liquid comes out of the first cartridge, allowing the air trapped in the second cartridge to be discharged.

However, the pressure exerted by the filtered water coming out of the first cartridge does not permit efficient discharge of the air and consequently does not solve the above-mentioned problems of slowness of the filtering operation and poor homogeneity in the use of the cartridge.

The problem underlying the present invention is that of providing a filter device which is designed structurally and functionally to overcome all of the disadvantages discussed with reference to the prior art mentioned . This problem is solved by the invention by means of a filter device formed in accordance with the appended claims.

The characteristics and the advantages of the invention will become clearer from the detailed description of some embodiments thereof which are described by way of non-limiting example with reference to the appended drawings, in which :

Figure 1 is a schematic section through a first embodiment of a filter device according to the invention;

Figure 2 is a schematic section through a second embodiment of a filter device according to the invention;

Figure 3 is a perspective view of a detail of Figure 2;

Figure 4 is a schematic section through a third embodiment of a filter device according to the invention;

Figure 5 is a schematic section through a fourth embodiment of a filter device according to the invention;

Figure 6 is a plan view showing a detail of Figure 5 from above; and

Figures 7 and 8 are schematic sections through a fifth and a sixth embodiment, respectively, of a filter device according to the invention.

In the drawings, a percolating filter device, generally indicated 1, is of the type in which there is an outer housing 2, for example a jug-shaped housing 2, in which a divider element 4 is suspended by means of a flanged support 3 and separates a first container 5 for receiving water to be filtered from a second container 6 for receiving filtered water.

A flow path for the water to be filtered is defined in the divider element 4 and extends between the first and second containers 5, 6 through first and second filter means 10, 11 which are arranged in sequence and through which the water passes by gravity.

The first filter means 10 comprises a replaceable filter cartridge which, in at least some of the embodiments described below, may be of conventionally known type, for example, of the type known from the description of the Applicant's patent application WO 2009/000374 or WO 2010/116543, the contents of which are incorporated herein by reference. In the specific example of Figure 1, the filter cartridge comprises an upper portion 12 and a lower portion 13 which are joined together in the region of a peripheral rim 14 that projects radially outwards and constitutes a seal by which the filter cartridge 10 is fitted sealingly in a mouth 16 of a seat 17 formed in the base of the divider element 4. Together with the upper portion 12 of the cartridge, which is provided with holes 18, the mouth 16 defines an inlet aperture for the water to be filtered in the flow path. The lower portion 13 contains a filter bed which may be made up, in known manner, of a mixture of materials selected from activated carbons, salts, ion-exchange resins, and the like.

The seat 17 comprises a peripheral shell 19 and a base 20. A chamber 21 is defined between the seat 17 and the casing of the lower portion 13 of the filter cartridge. Venting means, generally indicated 22, are provided for venting the air or gases trapped in the chamber 21 and thus improving the flow of water through the filter bed of the filter cartridge 10. The venting means 22 comprise a vent tube 23 which defines a venting duct and which extends from the base of the lower portion of the filter cartridge 10 in the region of a recess 23a included between two appendages 24 of the cartridge, through a substantial portion of the cartridge and through the filter bed . In the region of the two appendages 24, the cartridge also has holes, not shown in the drawing, which face into the chamber 21 for the outlet of the filtered water from the first filter means. In this embodiment, the vent tube terminates inside the filter cartridge 10 in the vicinity of the upper portion 12. A mesh filter 25 or, preferably, a one-way valve means 26, which is open in the gas venting direction and closed in the opposite direction, is fitted on the end of the vent tube 23. The valve means, which is shown in Figure 3, is formed by a disk valve 26 of the type including a convex diaphragm 27 (with its concavity facing the base of the vent tube), in which one or more slits 28 are cut to form two or more (preferably four) petals 29 which normally bear against one another when the valve is closed but which can open out by resilient deformation, moving apart in the direction of the convexity of the diaphragm, to permit venting of the gases.

Moreover, it is pointed out that, even with a mesh filter, the mesh size will be small enough substantially to limit the flow of liquid coming from the upper reservoir by gravity whilst permitting the discharge of the air which enters the vent tube.

An aperture 30 is formed in the base 20 of the seat 17 for the outlet of the filtered water from the first filter means 10 towards the second filter means 11.

The aperture 30 is provided with an additional filter 31, for example of the screen type, which serves to retain any granules of filter bed which escape from the first filter means into the chamber 21 and the aperture has a collar 32 at the output of the divider element 4. This additional filter 31 may define a non-removable portion of the second filter means.

The second filter means thus comprise a casing 33 which can be coupled with the collar 32 by a quick fitting connection, for example, a screw connection 34 or a bayonet connection, or even simply an interference fit, so as to allow the second filter means 11 to be removed from the divider element 4 individually. The second filter means 11 is preferably but not exclusively constituted by a hollow-fibre filter 35 such as that described in CA2350292 which permits micro-filtering of the water treated, for example, by reverse osmosis.

The life of the second filter means is normally substantially longer than the useful life of the first filter means and, with the structure indicated above, it can be replaced individually.

In a third embodiment of the invention, described with reference to Figure 4, the vent tube 23 extends as far as the vicinity of the upper portion 12 of the filter cartridge where it is inserted in an upper chamber 38 which has an open base (but is otherwise closed), so as to give rise to a siphon effect such that the vented air can be vented into the chamber 38 and can be discharged from the filter cartridge 10 upwards through the open base of the chamber 38, without unfiltered water or filter-bed granules entering the vent tube 23.

In a further variant of the present invention, described with reference to Figure 5, the chamber 21 is vented through a conduit 40 extending between the venting chamber 21 and the upper container 5 for receiving the water to be filtered. The conduit 40 is constituted by a calibrated recess 41 formed in the coupling region between the shells of the cartridge and of its seat in the divider element 4, in the region of the mouth 16, and may be formed purely in the divider element 4, purely in the peripheral rim 14 of the filter cartridge 10, or partially in one of the two components and partially in the other. In the second case, which is shown in Figure 7, the conduit consists of a simple calibrated hole 42 extending through the peripheral rim 14 of the filter cartridge 10. In these last two embodiments described, the conduit may lead to the drainage of a small flow of unfiltered water into the chamber 21, bypassing the first filter means. However, this effect can be eliminated by the formation of a more elaborate passageway 43, shown in Figure 8, which extends beyond the top of the container for receiving water to be filtered, thus venting outside the filter device 1.

The device 1 operates as follows.

The water to be filtered is admitted to the upper container 5 and passes through the filter bed of the first filter means 10 as a result of the hydrostatic head relative to the free surface of the water in the container 5. The pressure produced, however, is slight and, since the flow path comprises several filter layers each of which offers some resistance to the flow of water, air bubbles are created in the filter bed, essentially due to the surface tension of the water-air interface, and are unable to escape through the filter bed and to rise therefrom into the upper container again. If these air bubbles were not vented, the use of the filter bed would be non- homogeneous since the region affected by bubbles would not be able to contribute to the filtration. Moreover, since the useful cross-section for the flow of fluid through the filter bed would be reduced by the presence of regions occupied by air bubbles, the useful flow rate of the filter cartridge would be considerably reduced . With the solution described, however, the air bubbles are conveyed downwards to be collected in the chamber 21 from which they are vented through the vent tube 23 and/or the venting conduits 41, 42, 43. It will be appreciated that a replaceable filter cartridge thus formed is suitable not only for fitting in filter devices with superimposed layers such as those described but also in devices in which the second filter means are of the non-removable type and/or in which the above-mentioned venting problems are present to a lesser extent. It is thus possible to produce standardized cartridges which can be fitted in both filter devices with multiple (or multi-layered) filters, as described above, and in conventional devices in which a single filter means, constituted by a replaceable filter cartridge 10, is provided.

Moreover, the first filter means are suitable for being maintained separately from the second filter means since they are constructed structurally independently of one another and the filter cartridge 10 can thus be replaced more frequently than the hollow fibre filter 11, thus permitting improved utilization of the useful life of the latter. Not least, the above- mentioned advantages are achieved without radical modification of the architecture of conventional filter devices and/or of replaceable filter cartridges, to the benefit of production economy.

Claims

1. A percolating filter device (1) comprising :

- a divider element (4) which separates a first container (5) for receiving water to be filtered from a second container (6), within the device (1), and which is adapted to form a flow path for the water to be filtered between the first and second containers (5, 6);

- a seat (17) formed in the divider element (4), in the flow path, for removably housing first filter means (10), the first filter means (10) comprising a replaceable filter cartridge; and

- an outlet aperture (30), formed in the seat (17), for the water filtered by the first filter means (10);

characterized in that it additionally comprises:

- second filter means (11) placed in the outlet aperture (30);

- a chamber (21) which is formed between an outer casing (13) of the cartridge and the seat (17) when the cartridge is housed in the seat (17), the chamber (21) being located between the filter means (10, 11); and

- venting means (23) for the chamber (21), for venting gases that are collected in the chamber (21) together with the flow of liquid to be filtered through the filter means (10, 11).

2. A filter device (1) according to Claim 1, wherein the second filter means (11) comprises a removable filter (35) which can be engaged with a coupling portion (32) of the outlet aperture (30).

3. A filter device (1) according to Claim 1 or 2, wherein the second filter means (11) comprise a hollow fibre filter (35).

4. A filter device (1) according to any one of Claims 1 to 4, wherein the venting means comprise a vent tube (23) extending at least partially through the cartridge (10).

5. A filter device (1) according to any one of Claims 1 to 4, wherein the venting means comprise a conduit (40) extending through a mouth (16) of the seat (17) and extending between the chamber (21) and the upper container (5) in a coupling area between the shells of the seat (16) and of the cartridge (10).

6. A filter device (1) according to any one of Claims 1 to 4, wherein the cartridge (10) has a rim (14) for coupling with a mouth (16) of the seat (17) and the venting means comprise a conduit (40) extending through the rim (14).

7. A filter device (1) according to Claim 5 or 6, wherein the conduit (40) is made in the form of a calibrated passage (41; 42).

8. A filter device (1) according to any one of Claims 1 to 4, wherein the venting means comprise a conduit (41, 43) extending through a mouth (16) of the seat (17) and extending beyond the top of the container which receives water to be filtered (5).

9. A filter device (1) according to any one of the preceding claims, wherein the second filter means (11) comprise an additional filter (31) of the nonremovable type.

10. A filter device (1) according to Claim 4, wherein a one-way valve means (26), which is open in the direction of gas venting and closed in the opposite direction, is interposed in the tube (23).

11. A filter device (1) according to Claim 10, wherein the valve means comprises a disc valve (26) with a slit diaphragm (27).

12. A filter device (1) according to any one of Claims 2 to 11, wherein the second filter means (35) comprise a quick fitting means of coupling with the outlet aperture (30).

13. A filter device (1) according to Claim 12, wherein the connection portion (32) comprises a threaded collar for quick coupling with the second filter means (35).