WO2004014803A1

WO2004014803A1 - Filter cartridge

Info

Publication number: WO2004014803A1
Application number: PCT/EP2003/008641
Authority: WO
Inventors: Mahendrakumar Maganlal Mistry; Nikhileshwar Mukherjee; Dhulipala Ravikumar
Original assignee: Unilever Plc; Unilever Nv; Hindustan Lever Limited
Priority date: 2002-08-07
Filing date: 2003-07-21
Publication date: 2004-02-19
Also published as: AU2003246739A1

Abstract

The invention provides a filter cartridge for the treatment of water which comprises an inlet for the water to be treated, the inlet communicating with a downwardly extending hollow passage (TP) adapted for gravity flow of water there through, the hollow (TP) passage being connected at its lower end to at least one filter media, and an outlet for exiting treated water from the filter media; whereby water flows through the hollow passage (TP) and enters the lowermost end of the filter media (FCC) to travel upwards through the filter media so that entrapped air in the filter media may be released upwards and out of the filter cartridge during the passage of water through the filter media in the upward direction. The flow of water in the upward direction facilitates the release of entrapped air in the system of the invention. This provides for controlled uniform flow of water through the filter cartridge, which generates quality water even after extensive use.

Description

FILTER CARTRIDGE

Field of the Invention

The present invention relates to a filter cartridge for use in gravity-fed water filtration systems.

Background and Prior Art

The use of filter cartridges in water filtration systems including gravity fed filters is well known.

Generally, such filter cartridges are cylindrically shaped and contain water purification resins. US 5273650 discloses a water filter cartridge for use in a water filtration system which comprises a generally cylindrical ceramic pre- filter having a chamber containing a purification resin. An exit cap having a porous disc is attached at a first end of the pre-filter. Water to be filtered passes radially through the pre-filter into the chamber. The water then passes through the purification resin and the porous disc and exits the water filter cartridge through an opening in the exit cap. Although simple to construct, such resin filters are generally unable to filter out the complex varieties of contaminants which are usually found in water, ranging from chemical contaminants, particulate contaminants and even bacteriostatic/pathogenic materials.

US 5,562,824 discloses a gravity percolation water purifier assembly. The assembly includes a cover storage container having a dispensing spigot. A flanged filtration chamber is supported within the cover to receive untreated water. A porous filter cartridge is sealed to an outlet port. The purifier cartridge used in the assembly is threaded to the outlet port and supports multiple treatment chambers containing beds of water treatment media including multivalent iodine, granular activated carbon and a halogen scavenger. In this device, the first of the filter media (a resin chamber) is provided immediately under the filter inlet so that upon entering the filter cartridge during gravity flow downwards the water to be treated first encounters the resin filter media. Thereafter, the water traverses through further filter beds to achieve the desired filtration.

While such multiple filter media based filter cartridges do provide for a wide variety of filter media to be employed to achieve the desired water characteristics, a problem associated with this type of filter cartridge is non-uniform flow and therefore non-uniform filtration through the cartridge.

The present inventors have found that providing a resin bed immediately under the water inlet of the filter cartridge contributes immensely towards the problems of non-uniform flow encountered in the filter cartridges of the type described above. This is because air in the resin bed is forced downwards when contacted with the flowing water to be treated. Not only does the air face resistance against its natural tendency to move up but it is further forced to take a "U" turn before it can move upwards with the water flow.

This therefore is a treacherous path that the air is forced to follow which finally causes air-entrapment or air voids in the filter media. If the volume of the resin in the cartridges is high, the problem gets compounded further, leading to air voids which lead to obstruction of the free flow of the water through the cartridge and also channelling of the water in the cartridge. This results in uneven exposure of the water to be treated to the resin bed and consequential problems with quality and uniformity of water filtration.

Summary of The Invention

The present invention provides a filter cartridge for the treatment of water which comprises an inlet for the water to be treated, the inlet communicating with a downwardly extending hollow passage adapted for gravity flow of water there through, the hollow passage being connected at its lower end to at least one filter media, and an outlet for exiting treated water from the filter media; whereby water flows through the hollow passage and enters the lowermost end of the filter media to travel upwards through the filter media so that entrapped air in the filter media may be released upwards and out of the filter cartridge during the passage of water through the filter media in the upward direction.

The invention solves the problem of entrapped air in the filter media which has been encountered in prior art filter cartridges . The hollow passage in the construction according to the invention provides for a gravity flow of water into the cartridge which avoids any filter media immediately at the entrance of the water into the cartridge . This facilitates effective free downward flow of the water to be filtered in the cartridge without any pressure drop. In the construction according to the invention, the filter media are encountered by the water in the filter cartridge only during the upward flow of the water. In this way, any entrapped air in the filter media is released upwards naturally without facing resistance from any counter-current of water. Instead the flow of water in the upward direction actually facilitates the release of entrapped air in the system of the invention. The construction according to the invention provides for controlled uniform flow of water through the filter cartridge, which generates quality water even after extensive use.

Detailed Description Of The Invention

The filter cartridge according to the invention preferably comprises a plurality of filter media. The selection and disposition of the filter media depends upon the specific end requirements. A variety of filter media can be used including those for filtration of suspended contaminants such as porous fibre, paper, granular activated carbon, cast granular activated carbon and the like. Additionally, the cartridge can involve other filter media for filtration of bacteria and other pathogens, and the various filter media can be maintained in communication by separator filter pads.

A preferred filter cartridge according to the invention comprises an inlet for the water to be treated, the inlet communicating with a substantially vertical tubular hollow passage for gravity flow of water therethrough, the tubular hollow passage being connected at its lower end to a first annular resin chamber which is concentrically disposed with respect to the tubular hollow passage, the first annular resin chamber being connected to a second annular chamber provided over the first annular resin chamber and concentrically disposed with respect to the tubular hollow member, the second annular chamber comprising activated carbon filter media;

whereby water to be treated enters the filter cartridge through the tubular hollow passage, is forced vertically upwards from the lower end of the tubular hollow passage through the first annular resin chamber and thereafter through the second annular activated carbon chamber, and exits from the filter cartridge through a water outlet .

Description Of Preferred Embodiment

The invention will now be further described with reference to the following non-limiting Example, in which:

Figure 1 is a sectional view of an embodiment of a filter cartridge in accordance with the present invention and Figure 2 is a sectional view of a filter cartridge according to the prior art .

Figures 1 and 2 are schematic representations and are not to scale. As illustrated in Figure 1, water to be treated enters the filter cartridge through a hollow central tubular passage (TP) cartridge which is kept free of any filter media. Thereafter it traverses through an "U" path into a first annular concentric chamber (FCC) constituting a resin bed. hereafter after traversing through the resin bed the water is allowed to travel upward into the second annular activated carbon chamber (SCC) , which is again a concentric chamber connected to the annular resin chamber.

By way of this construction, the water in the filter cartridge is allowed to displace any entrapped air in the filter media in the upward direction. This solves the problems of air entrapment and consequential blockage of the flow path of water through the cartridge experienced in the prior art and the accompanying problems of channelling of water and non-uniform.

Figure 2 is a sectional view of a prior art filter which comprises a resin bed (RB) through which the water to be treated is passed in the downward direction. The water then takes a U turn and passes in the upward direction through an annular chamber filled with activated carbon (AC) , before exiting the filter through the exit provided.

Experiments were conducted to determine the flow rate of the filtered water as it passed through the filter cartridges as described in Figures 1 and 2 respectively, under identical conditions of gravity water head. The two filter cartridges were filled with equal volumes of resin. They were also filled with equal volumes of activated carbon. The performance of the filter cartridges was quantified by determining the flow rate for a total of 54 litres.

The data on the performance of the filter cartridge of the invention as described in Figure 1 is compared with the performance of a prior art filter cartridge as described in Figure 2. The results are summarized in Table 1.

Table 1

It is evident from Table 1 that the flow rate achieved with the filter cartridge of the invention described in Figure 1 is much higher and more sustained over a large volume of water flow as compared to the prior art filter cartridge described in Figure 2. The quality of water purified with the Figure 1 filter cartridge was comparable to that with the Figure 2 filter cartridge.

Claims

A filter cartridge for the treatment of water which comprises an inlet for the water to be treated, the inlet communicating with a downwardly extending hollow passage adapted for gravity flow of water there through, the hollow passage being connected at its lower end to at least one filter media, and an outlet for exiting treated water from the filter media;

whereby water flows through the hollow passage and enters the lowermost end of the filter media to travel upwards through the filter media so that entrapped air in the filter media may be released upwards and out of the filter cartridge during the passage of water through the filter media in the upward direction.

2. A filter cartridge according to claim 1 which comprises a plurality of filter media.

3. A filter cartridge for the treatment of water which comprises an inlet for the water to be treated, the inlet communicating with a substantially vertical tubular hollow passage for gravity flow of water therethrough, the tubular hollow passage being connected at its lower end to a first annular resin chamber which is concentrically disposed with respect to the tubular hollow passage, the first annular resin chamber being connected to a second annular chamber provided over the first annular resin chamber and concentrically disposed with respect to the tubular hollow member, the second annular chamber comprising activated carbon filter media; whereby water to be treated enters the filter cartridge through the tubular hollow passage, is forced vertically upwards from the lower end of the tubular hollow passage through the first annular resin chamber and thereafter through the second annular activated carbon chamber, and exits from the filter cartridge through a water outlet.