FILTERING DEVICE

Abstract: A filtering device for the filtration of a fluid, consists of a container (1) having a fluid inlet (11) and a fluid outlet (13) and accommodating therebetween a particulate filtering material (2). A first fluid-permeable unit (16) is loosely disposed between the inlet (11) and the filtering material (2), and a second fluid-permeable unit (17; 17') is fixedly disposed, in the direction of flow, between the filtering material (2) and the outlet (13). The fluid permeability of the first unit (16) is lower than that of the second unit (17), such that said units together ensure that the filtering material (2) in the container (1) is closely packed together when the fluid flows through.

Description: FILTERING DEVICE The present invention relates to a filtering device for the filtration of a fluid, such as drinking-water. A filtering device of this type often constitutes a replaceable inset in an outer container forming part of a filtering unit for the filtration of drinking-water. The inset consists of a container having a fluid inlet and a fluid outlet and accommodating, between said inlet and said outlet, a particulate filtering material, such as activated carbon. During handling of the container which, initially, is completely filled with a particulate filter¬ ing material, such as activated carbon, the filtering ma¬ terial subsides so that its volume is reduced. Then, the filtering material no longer completely fills the con¬ tainer, and consequently the particles merely whirl about in the container when water is flowing through. Since a considerable amount of the water passes between the par¬ ticles and not through them, the filtration of the water is impaired. German Offenlegungsschrift 1,436,244 presents a solu¬ tion to this problem in providing a filtering device in which a first fluid-permeable unit substantially covering the throughflow area of the container is loosely disposed between the fluid inlet and the filtering material, and a second fluid-permeable unit substantially covering the throughflow area of the container is fixedly disposed, in the direction of flow, between the filtering material and the fluid outlet. The first unit is pressed against the filtering material by means of a spring, such that the filtering material is kept closely packed together. The object of the present invention is to solve the same problem, i.e. to provide a filtering device in which the filtering material is maintained in place closely packed together, independently of the degree of filling- up, but this device has been simplified so that the spring can be dispensed with. According to the invention, this object is achieved., by a filtering device of the type described above, charac¬ terised in that the fluid permeability of the first unit is lower than that of the second unit, such that said units together ensure that the filtering material in the container is closely packed together when the fluid flows ' through. In a preferred embodiment, the first unit consists of a first fluid-permeable disc, and the second unit is made up of a second fluid-permeable disc. Preferably, the two discs are made of the same material, the first disc being thicker than the second disc. In another preferred embodiment, the first unit con¬ sists of a first fluid-permeable disc and a piston unit in the form of a cylindrical bowl, the bottom of which is applied against the first disc and has throughgoing fluid ducts, and the second unit is made up of a second fluid- permeable disc. Suitably, the two discs are made of a porous, fluid- permeable polyethylene material. The invention will be described in more detail below, reference being had to the accompanying drawing. Fig. 1 shows a first embodiment of the invention, which is used in a filtering unit for the filtration of drinking-water. Fig. 2 shows a second embodiment of the invention, which is used in a similar filtering unit. Each of the filtering devices shown in Figs. 1 and 2, comprises a cylindrical container 1 accommodating a parti- culate filtering material 2, such as activated carbon. Figs. 1 and 2 show a filtering device used in a filtering unit for the filtration of drinking-water, said unit com¬ prising a cylindrical outer container 3 in which the cy¬ lindrical container 1 is positioned. In the lower region of its shell, the outer container 3 has an inlet 4 for connection to a drinking-water conduit (not shown), and an outlet 5 is formed in the centre of the bottom of the outer container 3. The outer container 3 is closed by means of a lid 6 screwed thereon and an intermediary seal ing ring 7. An annular sealing flange 8 is formed in one piece with the bottom of the outer container 3 and locate at a distance from the inner wall of the outer container. The outside diameter of the sealing flange 8 increases downwardly, which gives the flange a wedge-shaped cross- section. The inner container 1 accommodating the filtering material 2 is closed by means of a snap-on lid 9, the upper side of which has, along its circumference, uniform ly distributed pins 10 of which only two are shown in the drawing and against which the lid 6 of the outer containe 3 is pressed. The lid 9 has a large number of through holes 11 uniformly distributed over its entire surface. A large number of through holes 13 are disposed in the bot¬ tom 12 of the inner container 1 and are uniformly distri¬ buted over the entire surface of said bottom. An annular sealing flange 14 is formed in one piece with the under- side of the inner container 1 and extends along the cir¬ cumference of the inner container. Suitably, the inner container 1, as well as its flange 14 and lid 9, is made of plastic material. When the inner container 1 which, as will appear fro the drawing, is readily exchangeable, has been positioned in the outer container 3, the lid 6 of the latter is screwed on, and the inner container is pressed down hard in consequence of the engagement between the pins 10 and the underside of the lid 6. The relationship between the diameters of the two sealing flanges 8 and 14 is such that, when the inner container 1 is pressed down, the in¬ side of the sealing flange 14 will be applied against the outside of the sealing flange 8 and be pressed slightly outwards as a consequence of the wedge-shaped cross-sec- tion of the sealing flange 8. Thus, a highly reliable sea is established by the two sealing flanges 8 and 14. The outside diameter of the inner container 1 is slightly smaller than the inside diameter of the outer - container 3, for which reason there is a circumferential gap 15 between the outside of the inner container 1 and the inside of the outer container 3. This gap 15 commu¬ nicates with the inlet 4 of the outer container 3. Water from the drinking-water conduit is introduced into the outer container 3 via the inlet 4. The water is distributed round the inner container 1 and flows upwards in the circumferential gap 15. At the upper end of the gap 15, the water is uniformly distributed over the entire surface of the lid 9, such that the filtering material is used efficiently over the entire throughflow area of the inner container 1. The filtered water is discharged via the outlet 5. The filtering unit described thus far is already known. The filtering device used therein, i.e. the inner container 1, has, in a preferred first embodiment (Fig. 1) of the invention, an upper disc 16 positioned on the fil- tering material 2, and a lower disc 17 positioned on the bottom 12 of the inner container 1. The diameters of the two discs 16 and 17 correspond to the inside diameters of the inner container 1 in the respective positions. The discs 16 and 17 are made of the same water-permeable ma- terial, such as a porous plastic material made of HD poly¬ ethylene in a sintering process. The upper disc 16 is thicker than the lower disc 17, and its permeability is lower. When water is introduced into the inner container 1 via the holes 11 in the lid 9, the upper disc 16 loosely disposed in the inner container 1 is pressed against the filtering material 2 which is thus closely packed to¬ gether. The degree of packing can be adjusted by varying the thickness of the two discs 16 and 17. Since the upper disc 16 is constantly pressed against the filtering mate- rial 2 when the filtering device is used, the particles of the filtering material cannot whirl about in the inner container 1 when the water passes therethrough. Thus, a proper filtering of the water is obtained, since the wat mainly passes through the particles and not between them. The second preferred embodiment according to the in vention, shown in Fig. 2, differs from the embodiment de scribed above in that a piston unit 18 is positioned on the upper disc 16'. The piston unit 18 consists of a cy¬ lindrical bowl whose outside diameter corresponds to the inside diameter of the inner container 1 and whose botto is applied against the upper disc 16'. Like this disc, t piston unit 18 is loosely disposed in the inner containe 1. A large number of through holes 19 are disposed in th bottom of the bowl 18 and are uniformly distributed over its entire surface. In the embodiment shown in Fig. 2, much thinner, and therefore less expensive discs 16' and 17' can be used than in the embodiment shown in Fig. 1. The two discs 16' and 17' in the embodiment in Fig. 2, as well as the discs 16 and 17 in the embodiment in Fig. 1, are made of the same material, e.g. the above-mentioned polyethylene material. The discs 16' and 17' have the sam thickness and therefore essentially the same water perme¬ ability. The unit consisting of the bowl 18 and the upper disc 16' has, however, a lower water permeability than th lower disc 17', and its water permeability, and conse¬ quently the degree of packing of the filtering material 2 is suitably adjusted by means of the area of the holes in the bottom of the bowl 18. The embodiment in Fig. 2 func¬ tions in the same manner as the embodiment in Fig. 1.

Claims: CLAIMS 1. A filtering device for the filtration of a fluid, such as drinking-water, said device comprising a container (1) having a fluid inlet (11) and a fluid outlet (13) and accommodating, between said inlet and said outlet, a par¬ ticulate filtering material (2), such as activated carbon, a first fluid-permeable unit (16; 16', 18) substantially covering the throughflow area of the container (1) and be¬ ing loosely disposed between the fluid inlet (11) and the filtering material (2), and a second fluid-permeable unit (17; 17') substantially covering the throughflow area of the container (1) and being fixedly disposed, in the di- rection of flow, between the filtering material (2) and the fluid outlet (13), c h a r a c t e r i s e d in that the fluid permeability of the first unit (16; 16', 18) is lower than that of the second unit (17; 17'), such that said units together ensure that the filtering material (2) in the container (1) is closely packed together when the fluid flows through. 2. A filtering device as claimed in claim 1, c h a ¬ r a c t e r i s e d in that the first unit consists of a first fluid-permeable disc (16), and that the second unit is made up of a second fluid-permeable disc (17). 3. A filtering device as claimed in claim 2, c h a ¬ r a c t e r i s e d in that the two discs (16, 17) are made of the same material, the first disc (16) being thicker than the second disc (17). 4. A filtering device as claimed in claim 1, c h a ¬ r a c t e r i s e d in that the first unit consists of a first fluid-permeable disc (16' ) and a piston unit (18) in the form of a cylindrical bowl, the bottom of which is applied against the first disc (16') and has throughgoing fluid ducts (19), and that the second unit is made up of a second fluid-permeable disc (17'). 5. A filtering device as claimed in any one of claim 2-4, c h a r a c t e r i s e d in that the two discs (16, 17; 16*, 17') are made of a porous, fluid-permeable polyethylene material.

Inventors: GUSTAFSSON BROR, GUSTAFSSON, BROR
Applicants: VAESTBO PLAST AB, AKTIEBOLAGET VAESTBO PLAST
Application year: 1989
Main classification: B01D24
IPC codes: B01D24