Title of Invention	A FILTER CARTRIDGE
Abstract	The invention relates to a filter cartridge for filtration of water and more particularly to a cost-effective filter cartridge for gravity filtration of water, so as to render it substantially free of particulate contaminants, which include microorganisms like cysts, while providing for relatively high flow rates. There exists a need to have a cost effective gravity-fed water filter cartridge which provides overall cost effectiveness to the consumer while providing consistently high flow rates and also ensuring the removal of particulate material including micro-organisms and dissolved matter. The filter cartridge is uniquely configured to maximize the filtration efficiency, the throughput of the water to be filtered, the flow rate achieved even from a low gravity head, while minimizing the amount of filter media material being consumed to achieve these ends. According to the invention, there is provided a filter cartridge for filtration of water comprising a carbon block that is seated in a receptacle having an orifice for outlet of water wherein said carbon block is detachably attachable in said receptacle using fastening means and a gasket means such that all inlet water passes through said carbon block before exiting said filter cartridge.

Title of Invention

A FILTER CARTRIDGE

Abstract

The invention relates to a filter cartridge for filtration of water and more particularly to a cost-effective filter cartridge for gravity filtration of water, so as to render it substantially free of particulate contaminants, which include microorganisms like cysts, while providing for relatively high flow rates. There exists a need to have a cost effective gravity-fed water filter cartridge which provides overall cost effectiveness to the consumer while providing consistently high flow rates and also ensuring the removal of particulate material including micro-organisms and dissolved matter. The filter cartridge is uniquely configured to maximize the filtration efficiency, the throughput of the water to be filtered, the flow rate achieved even from a low gravity head, while minimizing the amount of filter media material being consumed to achieve these ends. According to the invention, there is provided a filter cartridge for filtration of water comprising a carbon block that is seated in a receptacle having an orifice for outlet of water wherein said carbon block is detachably attachable in said receptacle using fastening means and a gasket means such that all inlet water passes through said carbon block before exiting said filter cartridge.

Full Text	COMPLETE AFTER PROVISIONAL LEFT 0N 3 O JUN 2006 FORM -2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENT RULES, 2003 COMPLETE SPECIFICATION (See Section 10 and Rule 13) A FILTER CARTRIDGE HINDUSTAN LEVER LIMITED, a company incorporated under the Indian Companies Act, 1913 and having its registered office at Hindustan Lever House, 165/166, Backbay Reclamation, Mumbai -400 020, Maharashtra, India The following specification particularly describes the nature of the invention and the manner in which it is to be performed. FIELD OF INVENTION The present invention relates to a filter cartridge for filtration of water and more particularly to a cost-effective filter cartridge for gravity filtration of water, so as to render it substantially free of particulate contaminants, which include microorganisms like cysts, while providing for relatively high flow rates. BACKGROUND AND PRIOR ART Water typically contains contaminants, which include particulate matter, traces of chemicals and microorganisms. In potable water, it is especially desirable to remove the harmful contaminants from the liquids before consuming it, in order to maintain good health and to prevent water-borne diseases. Several different methods are known for purification of water based on which many devices and apparatus have been designed and are also commercially available. These methods and devices vary, depending on the type of impurities present in water. It is also desirable to remove or kill the harmful microorganisms like protozoan cysts, bacteria and viruses present in potable water. Several methods are employed towards this end. In the absence of a device, water is generally boiled to kill the microorganisms, but this method is cost-intensive and destroys the natural taste of water, making it "flat". Biocides e.g. chlorine and iodine are sometimes added to water kill the microorganisms. These are very effective in killing the microorganisms but additional precautions have to be taken to ensure that the remaining biocide is not consumed by people. Excess chlorine in water provides bad odor and it is also injurious to the human body, whereas intake of excess iodine can be harmful to some individuals. Ultra-violet radiation has also been used in many water-purification devices to kill micro-organisms. But ultraviolet radiation requires continuous availability of electricity, which may not be available at all times, in all places. Particulate matter larger than 3 microns is filtered using cloth filter or depth filters e.g. a bed of activated carbon or clay which has been moulded into a block. 2 Carbon and clay additionally have the advantage of being highly porous materials, which also facilitates the removal of soluble impurities by adsorption e.g. dissolved organic compounds, compounds that make the water have an offensive odour and taste, pesticide and pesticide residues etc. Water available in many remote water-scarce parts of the world is highly contaminated with soil which includes Iron and Aluminium oxides and hydroxides. It is generally known that filter cartridges having carbon blocks get choked frequently when used, especially in gravity water filters and provide very low flow rates of water, after some use, which is undesirable to the consumer. Upon such choking, the consumer often tries to rejuvenate the cartridge by agitating in water or by backflushing. The presently available filter cartridges are difficult to rejuvenate. Thus the consumer is required to replace the filter cartridge with a new filter cartridge which is cost extensive. The present inventors have sought to solve this problem by providing a filter cartridge thereby providing for consistently high flow rates of filtered water, while providing for the ease of cleaning and replacement of the carbon blocks contained therein, at the same time ensuring that the overall cost of the cartridge is minimized. US4753728 (Amway, 1988) describes a double shell filter comprising an inner shell of 80 to 400 U.S. mesh screen carbon particles and an outer shell of bonded 20 to 80 mesh screen carbon particles wherein the inner0 and outer particles are bonded internally to each other and the two shells are bonded together with the help of a specific high molecular polymer binder. The bottom end cap and the top end cap of polypropylene are cast moulded on to the carbon block. This filter is difficult to clean and does not provide for easy removal and replacement of the carbon block from the polymeric end caps. US5328609 (Magnusson, 1994) describes a manifold mounted liquid filtration system including a disposable filter cartridge having first and second radial flow filtration stages containing filtration media of uniform porosity. A first stage includes a pair of annular concentrically mounted, fibrous sediment and cast carbonaceous filter media and the second stage includes an annular cast carbonaceous filter media. While the first stage is used to remove suspended 3 sediments, lead and other heavy metals, the second stage removes suspended bacteria and other organic impurities. The filtration system described in this publication requires the entire filter cartridge to be disposed when completely choked and replaced with a new cartridge which would prove cost-extensive. There thus exists a need to have a cost effective gravity-fed water filter cartridge which provides overall cost effectiveness to the consumer while providing consistently high flow rates and also ensuring the removal of particulate material including micro-organisms and dissolved matter. The present inventors have developed a novel filter cartridge which is uniquely configured to maximize the filtration efficiency, the throughput of the water to be filtered, the flow rate achieved even from a low gravity head, while minimizing the amount of filter media material being consumed to achieve these ends. It is thus the basic object of the present invention to provide for a filter cartridge which ensures desired particulate removal including micro-organisms like cysts while giving the desired high flow rate, consistently over large volumes of inlet water, as compared to the prior art cartridges. Another object of the present invention is directed to a filter cartridge which provides for effective gravity filtration of up to 99.9% removal (three log removal) of even chlorine resistant cysts such as Cryptosporidium parvum and Giardia lamblia which are in the size range of 3 to 6 microns. Yet another object of the present invention is directed to a filter cartridge, which provides high efficiency in terms of the amount of water filtered for a given amount of carbon while ensuring the removal of undesirable impurities in water and while providing high flow rates of water. 4 SUMMARY OF THE INVENTION According to one aspect of the invention there is provided a filter cartridge for filtration of water comprising a carbon block that is seated in a receptacle having an orifice for outlet of water wherein said carbon block is detachably attachable in said receptacle using a fastening means and a gasket means such that all inlet water passes through said carbon block before exiting said filter cartridge. It is particularly preferred that the carbon block is a carbon disc. According to another aspect of the invention there is provided a method of obtaining filtered water at flow rates in the range of 50 to 600 ml/minute comprising the steps of (i) filtering water through a filter cartridge of the invention; and (II) replacing the carbon block in the filter cartridge whenever the flow rate of water is below desired value with a block which provides the desired flow rate. DETAILED DESCRIPTION OF THE INVENTION The first aspect of the invention provides for a filter cartridge for filtration of water comprising a carbon block that is removably fastenable in a receptacle, using a fastening means and a gasket means, suitably positioned to ensure that all inlet water passes through the carbon block before exiting the filter cartridge. The present inventors have determined that when carbon blocks are the filtration media, the progressive reduction in flow rate of the water exiting the filter is principally due to choking of the pores over a relatively short path length from the inlet surface of the carbon block. The present inventors have also determined that sufficiently long path length has to be provided to ensure the necessary reduction in the number of particles or cyst desired to be filtered. Thus the present inventors have selectively chosen the necessary shape configurations of the carbon block necessary to meet these opposing requirements. The carbon block therefore may be short path length blocks which are shaped like a hemisphere, torisphere or trapezoid. A highly preferred carbon block is disc 5 shaped. The disc can have circular, oval, square or polygonal cross-section, preferably a circular cross-section. When a carbon disk is used, it is preferred that the dimensions are such that the ratio of the longest dimension to the thickness is in the range of 2:1 to 20:1, more preferably 3:1 to 15:1. The fastening means preferably is a closure which is snap fit on to the receptacle or a clamp which holds the carbon block on to the receptacle. The gasket means is preferably a gasket, an o-ring or any other means which serves the purpose of a gasket and which provides leak tightness to water when a fastening means is used to fasten two articles together. According to a preferred aspect of the invention, the fastening means is a screw threaded closure which comprises an orifice for inlet of water and is screwable on to the receptacle housing the carbon block. The receptacle is provided with corresponding screw threads for urging the carbon block against the gasket means provided in the base of the receptacle thereby attaching the carbon block in the filter cartridge. The closure may be provided on its bottom surface with downwardly projecting members, which are urged against the top surface of the carbon block, as the closure is screwed on to the receptacle thereby urging the bottom surface of the carbon block against the gasket means placed in the base of the receptacle thereby ensuring the necessary leak tightness. When the carbon block is desired to be detached from the filter cartridge, the closure is unscrewed from the receptacle thereby releasing the carbon block. .One or more orifices are provided on the closure for inlet of water on to the carbon block. It is preferred that the orifice comprises at least 30% of the surface area of the top surface of the closure. The invention is especially suitable and configured to be capable of filtering water which is contaminated with particles including dust and microorgansims e.g. protozoan cyst like Cryptosporidium and Giardia. The invention is capable of providing 99% removal (two log removal) preferably 99.9% removal (three log removal) of cyst. Log removal is defined as the log10 of the number of input particles minus the log 10 of the number of output particles. The carbon blocks are made from activated carbon, more preferably powder activated carbon. 6 It is desirable to include a replaceable sediment filter that externally envelops the carbon block such that water passes through the sediment filter before passing through the carbon block. The sediment filter preferably corresponds to the shape of the carbon block. The sediment filter is generally washable or replaceable and is preferably a woven or non-woven fabric, more preferably a non-woven fabric having micropores. This sediment filter ensures filtration of particles generally above 3 microns. The sediment filter can be washed and rinsed under flowing tap water with mild scrubbing. The receptacle and the fastening means are preferably made of polymeric materials. Preferred polymeric materials include polypropylene, polyethylene, acrylonitrile butadiene styrene, or styrene acrylonitrile. The gasket means is preferably made from natural or synthetic rubber, synthetic elastomers, teflon, nitrile rubber or silicone, The block filters for use in the filter assembly of the invention preferably comprises powder activated carbon (PAC) and a binder material having a Melt Flow Rate (MFR) of less than 5 g/10 minutes, preferably less than 1 g/10 minutes. The melt-flow rate (MFR) is measured using ASTM D 1238 (ISO 1133) test. The test measures the flow of a molten polymer through an extrusion plastometer under specific temperature and load conditions. The extrusion plastometer consists of a vertical cylinder with a small die of 2 mm at the bottom and a removable piston at the top. A charge of material is placed in the cylinder and preheated for several minutes. The piston is placed on top of the molten polymer and its weight forces the polymer through the die and on to a collecting plate. The time interval for the test ranges from 15 seconds to 6 minutes in order to accommodate the different viscosities of plastics. Temperatures used are 2,20, 250 and 300 °C (428, 482 and 572°F). Loads used are 1.2, 5 and 10 kg. The amount of polymer collected after a specific interval is weighed and normalized to the number of grams that would have been extruded in 10 minutes: melt flow rate is expressed in grams per reference time. 7 The binder material is preferably thermoplastic polymers having the low MFR values above described. Suitable examples include ultra high molecular weight polymer preferably polyethylene or polypropylene which have these low MFR values. The molecular weight is preferably in the range of 106 to 109. Binders of this class are commercially available under the trade names HOSTALEN from Tycona GMBH, GUR, Sunfine (from Asahi, Japan), Hizex (from Mitsubishi) and from Brasken Corp (Brazil). Other suitable binders include LDPE sold as Lupolen (from Basel Polyolefins) and LLDPE from Qunos (Australia). The bulk density of the binder material is preferably less than or equal to 0.6 g/cm3, more preferably less than or equal to 0.5 g.cm3, and further more preferably less than or equal to 0.25 g/cm3. The binder material preferably has a particle size distribution substantially the same as that of the PAC but the particles passing 200 mesh is preferably less than 40 wt%, more preferably less than 30 wt%. The carbon block when used preferably comprises powder activated carbon (PAC) having a particle size such that 95 wt % of the particles pass through 50 mesh and not more than 13%, preferably not more than 12%, more preferably not more than 10% pass through 200 mesh. The PAC is preferably selected from bituminous coal, coconut shell, wood, or petroleum tar. The surface area of the PAC is preferably exceeds 500 m2/g, more preferably exceeds 1000 m2/g. Preferably, the PAC has size uniformity co-efficient of less than 2, or more preferably less than 1.5, a carbon tetrachloride number exceeding 50%, more preferably exceeding 60%. The PAC preferably has an Iodine number greater than 800, more preferably greater than 1000. The proportion of the binder material to the PAC particles by weight is chosen such that it is preferably in the range of 1:1 to 1:10, more preferably in the range of 1:2 to 1:6. By way of the above filter cartridge of the invention it is possible to attain average flow rate of water, from a starting height of 200 mm down to 50 mm, under gravity of 600-50 ml/min., preferably 200-50 ml/min., without compromising on the requirements of removal of particulate including microorganisms, and chemical contaminants. A suitable process of preparation of carbon blocks for use in the filter cartridge of the invention has been disclosed in our co-pending application 320/MUM/2004. According to another aspect of the present invention there is provided a method of obtaining filtered water at flow rates in the range of 50 to 600 ml/minute comprising the steps of (i) filtering water through a filter cartridge of the invention; and (ii) replacing the carbon block in the filter cartridge whenever the flow rate of water is below desired value with a block which provides the desired flow rate. The present invention facilitates easy removal of the carbon block from the cartridge to rejuvenate it, after which the carbon block is easily re-attachable in the cartridge. Rejuvenation can be done by agitating the carbon block in water or by back flushing with a jet of cold or hot water. During such a cleaning and replacement process, the carbon block is preferably replaced in the cartridge with the same side-up each time. To facilitate this, the carbon block preferably has indicators thereon to distinguish the top and bottom surfaces. The details of the invention, its objects and advantages are explained hereunder in greater detail in relation to the following non-limiting exemplary embodiments of the invention: 9 BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, Fig. 1 is a schematic of a filter cartridge of the invention with a carbon disc filter assembled. DETAILED DESCRITION OF, THE DRAWINGS Referring to Fig.1, the filter cartridge comprises a carbon block (CB) seated on a gasket (G) provided in the base of a receptacle (R) which has an orifice (OT) for outlet of water. A closure (CL) has an orifice on the top surface (not shown) for inlet of water. The closure has screw threads (ST1) with which it is screwed on to the receptacle provided with corresponding screw threads (ST2). Downwardly projecting members (M) are provided on the closure for urging the carbon block against the gasket as the closure is screwed on to the receptacle. The gasket ensures leak-proof outlet such that all the water fed to the filter cartridge passes though the carbon block before exiting it. When in use, the water enters the closure through the orifice provided thereon and flows through the carbon block enabling filtration and exits the cartridge through the outlet (OT). When a large amount of water has been filtered and the flow rate of water is below desired value, the closure is unscrewed and the carbon block is removed from the cartridge. The carbon block is rejuvenated by cleaning to the desired degree of cleanliness and replaced in the filter cartridge with the same-side-up as in the earlier run. The closure is again screwed on to the receptacle and the cartridge is ready for use again. The filter cartridge provides the high desired flow rates again. This procedure is repeated till the carbon block can no longer be rejuvenated. At this stage the carbon block is replaced with a new one. 10 Examples Example-1: A filter cartridge of the invention (as shown in Fig. 1) with a 35 gram carbon disc (95 mm diameter and 12 mm height) is used to filter water which is contaminated with particulates in a gravity filter with a head of 170 mm of water column. The data on the flow rate of the filtered water obtained is shown in Fig. -2. The filter cartridge removed greater than 99.9% of the cysts present in the inlet water. Comparative Example-2: A filter cartridge as described in prior art made with 127g carbon into 100 mm hemispherical shape with the carbon block glued to a base plate was used to filter water under the same conditions as example-1. The comparative data is shown in Fig-3. This filter also removed greater than 99.9% of the cyst present in the inlet water. The data indicates that by using as less as about 28 weight% of the carbon block as compared to the comparative example-1, the filter cartridge of example-1 could filter about 60% of the water (about 300 litres of water as compared to 500 litres of water using the filter of the comparative example-1). Further, the graphs show that the average flow rate of the water obtained in example-1 was significant higher. Thus the invention provides for a filter cartridge which ensures desired particulate removal while giving the high desired flow rate of water consistently over larger volumes of water while providing a higher efficiency in terms of the amount of water filtered for a given amount of carbon. 11 We claim: 1. A filter cartridge for filtration of water, comprising a carbon block that is seated in a receptacle having an orifice for outlet of water, wherein said carbon block is detachably attachable in said receptacle, using a fastening means and a gasket means, such that all inlet water passes through said carbon block before exiting said filter cartridge. 2. A filter cartridge as claimed in claim 1, wherein said fastening means is a screw threaded closure which comprises an orifice for inlet of water and is screwable on to said receptacle provided with corresponding screw threads for urging said carbon block against said gasket provided in the base of the receptacle. 3. A filter cartridge as claimed in claim 2, wherein the area of the orifice on the closure is greater than 30% of the surface area of the top surface of the closure. 4. A filter cartridge as claimed in any preceding claim, wherein said carbon block is disc shaped. 5. A filter cartridge as claimed in claim 4, wherein said disc has circular cross-section. 6. A filter cartridge as claimed in claim 4 or 5, wherein the ratio of the longest dimension to the thickness of the carbon disc is from 2:1 to 20:1. 7. A filter cartridge as claimed in any preceding claim, wherein a replaceable sediment filter externally envelops said carbon block such that water passes through said replaceable sediment filter before passing through said carbon block. 8. A filter cartridge as claimed in claim 8, wherein said sediment filter is made of non-woven fabric. 12 9. A filter cartridge as claimed in any preceding claim, wherein said receptacle and said fastening means is made of materials selected from polypropylene, polyethylene, acrylonitrile butadiene styrene, or styrene acrylonitrile copolymer. 10. A filter cartridge as claimed in any preceding claim, wherein said gasket means is made from natural or synthetic rubber, synthetic elastomers, teflon, nitrile rubber or silicones. 11. A filter cartridge as claimed in any preceding claim, wherein said carbon block comprises; • powder activated carbon (PAC) having particle size such that 95 wt% of the particles pass through 50 mesh and not more than 13% particles pass through 200 mesh, and • a binder material having Melt Flow Rate (MFR) less than 1 gram/10 minutes. 12. A filter cartridge as claimed in claim 12, wherein said binder material is high molecular weight polyethylene or polypropylene having molecular weight in the range of 106 to 109g/mole. 13. A filter cartridge for filtration of water, substantially as herein described with reference to the accompanying figures and examples. Dated this 30th day of June 2006 Hindustan Lever Limited S. Venkatramani (Senior Patents Manager) 13 Abstract The invention relates to a filter cartridge for filtration of water and more particularly to a cost-effective filter cartridge for gravity filtration of water, so as to render it substantially free of particulate contaminants, which include microorganisms like cysts, while providing for relatively high flow rates. There exists a need to have a cost effective gravity-fed water filter cartridge which provides overall cost effectiveness to the consumer while providing consistently high flow rates and also ensuring the removal of particulate material including micro-organisms and dissolved matter. The filter cartridge is uniquely configured to maximize the filtration efficiency, the throughput of the water to be filtered, the flow rate achieved even from a low gravity head, while minimizing the amount of filter media material being consumed to achieve these ends. According to the invention, there is provided a filter cartridge for filtration of water comprising a carbon block that is seated in a receptacle having an orifice for outlet of water wherein said carbon block is detachably attachable in said receptacle using a fastening means and a gasket means such that all inlet water passes through said carbon block before exiting said filter cartridge. 30 JUN 2006

Full Text

COMPLETE AFTER PROVISIONAL
LEFT 0N 3 O JUN 2006

FORM -2
THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
A FILTER CARTRIDGE
HINDUSTAN LEVER LIMITED, a company incorporated under the Indian Companies Act, 1913 and having its registered office at Hindustan Lever House, 165/166, Backbay Reclamation, Mumbai -400 020, Maharashtra, India
The following specification particularly describes the nature of the invention and
the manner in which it is to be performed.

FIELD OF INVENTION
The present invention relates to a filter cartridge for filtration of water and more particularly to a cost-effective filter cartridge for gravity filtration of water, so as to render it substantially free of particulate contaminants, which include microorganisms like cysts, while providing for relatively high flow rates.
BACKGROUND AND PRIOR ART
Water typically contains contaminants, which include particulate matter, traces of chemicals and microorganisms. In potable water, it is especially desirable to remove the harmful contaminants from the liquids before consuming it, in order to maintain good health and to prevent water-borne diseases.
Several different methods are known for purification of water based on which many devices and apparatus have been designed and are also commercially available. These methods and devices vary, depending on the type of impurities present in water.
It is also desirable to remove or kill the harmful microorganisms like protozoan cysts, bacteria and viruses present in potable water. Several methods are employed towards this end. In the absence of a device, water is generally boiled to kill the microorganisms, but this method is cost-intensive and destroys the natural taste of water, making it "flat". Biocides e.g. chlorine and iodine are sometimes added to water kill the microorganisms. These are very effective in killing the microorganisms but additional precautions have to be taken to ensure that the remaining biocide is not consumed by people. Excess chlorine in water provides bad odor and it is also injurious to the human body, whereas intake of excess iodine can be harmful to some individuals. Ultra-violet radiation has also been used in many water-purification devices to kill micro-organisms. But ultraviolet radiation requires continuous availability of electricity, which may not be available at all times, in all places.
Particulate matter larger than 3 microns is filtered using cloth filter or depth filters e.g. a bed of activated carbon or clay which has been moulded into a block.
2

Carbon and clay additionally have the advantage of being highly porous materials, which also facilitates the removal of soluble impurities by adsorption e.g. dissolved organic compounds, compounds that make the water have an offensive odour and taste, pesticide and pesticide residues etc. Water available in many remote water-scarce parts of the world is highly contaminated with soil which includes Iron and Aluminium oxides and hydroxides. It is generally known that filter cartridges having carbon blocks get choked frequently when used, especially in gravity water filters and provide very low flow rates of water, after some use, which is undesirable to the consumer. Upon such choking, the consumer often tries to rejuvenate the cartridge by agitating in water or by backflushing. The presently available filter cartridges are difficult to rejuvenate. Thus the consumer is required to replace the filter cartridge with a new filter cartridge which is cost extensive. The present inventors have sought to solve this problem by providing a filter cartridge thereby providing for consistently high flow rates of filtered water, while providing for the ease of cleaning and replacement of the carbon blocks contained therein, at the same time ensuring that the overall cost of the cartridge is minimized.
US4753728 (Amway, 1988) describes a double shell filter comprising an inner shell of 80 to 400 U.S. mesh screen carbon particles and an outer shell of bonded 20 to 80 mesh screen carbon particles wherein the inner0 and outer particles are bonded internally to each other and the two shells are bonded together with the help of a specific high molecular polymer binder. The bottom end cap and the top end cap of polypropylene are cast moulded on to the carbon block. This filter is difficult to clean and does not provide for easy removal and replacement of the carbon block from the polymeric end caps.
US5328609 (Magnusson, 1994) describes a manifold mounted liquid filtration system including a disposable filter cartridge having first and second radial flow filtration stages containing filtration media of uniform porosity. A first stage includes a pair of annular concentrically mounted, fibrous sediment and cast carbonaceous filter media and the second stage includes an annular cast carbonaceous filter media. While the first stage is used to remove suspended
3

sediments, lead and other heavy metals, the second stage removes suspended bacteria and other organic impurities. The filtration system described in this publication requires the entire filter cartridge to be disposed when completely choked and replaced with a new cartridge which would prove cost-extensive.
There thus exists a need to have a cost effective gravity-fed water filter cartridge which provides overall cost effectiveness to the consumer while providing consistently high flow rates and also ensuring the removal of particulate material including micro-organisms and dissolved matter.
The present inventors have developed a novel filter cartridge which is uniquely configured to maximize the filtration efficiency, the throughput of the water to be filtered, the flow rate achieved even from a low gravity head, while minimizing the amount of filter media material being consumed to achieve these ends.
It is thus the basic object of the present invention to provide for a filter cartridge which ensures desired particulate removal including micro-organisms like cysts while giving the desired high flow rate, consistently over large volumes of inlet water, as compared to the prior art cartridges.
Another object of the present invention is directed to a filter cartridge which provides for effective gravity filtration of up to 99.9% removal (three log removal) of even chlorine resistant cysts such as Cryptosporidium parvum and Giardia lamblia which are in the size range of 3 to 6 microns.
Yet another object of the present invention is directed to a filter cartridge, which provides high efficiency in terms of the amount of water filtered for a given amount of carbon while ensuring the removal of undesirable impurities in water and while providing high flow rates of water.
4

SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a filter cartridge for filtration of water comprising a carbon block that is seated in a receptacle having an orifice for outlet of water wherein said carbon block is detachably attachable in said receptacle using a fastening means and a gasket means such that all inlet water passes through said carbon block before exiting said filter cartridge.
It is particularly preferred that the carbon block is a carbon disc.
According to another aspect of the invention there is provided a method of
obtaining filtered water at flow rates in the range of 50 to 600 ml/minute
comprising the steps of
(i) filtering water through a filter cartridge of the invention; and
(II) replacing the carbon block in the filter cartridge whenever the flow rate of
water is below desired value with a block which provides the desired flow
rate.
DETAILED DESCRIPTION OF THE INVENTION
The first aspect of the invention provides for a filter cartridge for filtration of water comprising a carbon block that is removably fastenable in a receptacle, using a fastening means and a gasket means, suitably positioned to ensure that all inlet water passes through the carbon block before exiting the filter cartridge.
The present inventors have determined that when carbon blocks are the filtration media, the progressive reduction in flow rate of the water exiting the filter is principally due to choking of the pores over a relatively short path length from the inlet surface of the carbon block. The present inventors have also determined that sufficiently long path length has to be provided to ensure the necessary reduction in the number of particles or cyst desired to be filtered. Thus the present inventors have selectively chosen the necessary shape configurations of the carbon block necessary to meet these opposing requirements. The carbon block therefore may be short path length blocks which are shaped like a hemisphere, torisphere or trapezoid. A highly preferred carbon block is disc
5

shaped. The disc can have circular, oval, square or polygonal cross-section, preferably a circular cross-section. When a carbon disk is used, it is preferred that the dimensions are such that the ratio of the longest dimension to the thickness is in the range of 2:1 to 20:1, more preferably 3:1 to 15:1.
The fastening means preferably is a closure which is snap fit on to the receptacle or a clamp which holds the carbon block on to the receptacle. The gasket means is preferably a gasket, an o-ring or any other means which serves the purpose of a gasket and which provides leak tightness to water when a fastening means is used to fasten two articles together. According to a preferred aspect of the invention, the fastening means is a screw threaded closure which comprises an orifice for inlet of water and is screwable on to the receptacle housing the carbon block. The receptacle is provided with corresponding screw threads for urging the carbon block against the gasket means provided in the base of the receptacle thereby attaching the carbon block in the filter cartridge. The closure may be provided on its bottom surface with downwardly projecting members, which are urged against the top surface of the carbon block, as the closure is screwed on to the receptacle thereby urging the bottom surface of the carbon block against the gasket means placed in the base of the receptacle thereby ensuring the necessary leak tightness. When the carbon block is desired to be detached from the filter cartridge, the closure is unscrewed from the receptacle thereby releasing the carbon block. .One or more orifices are provided on the closure for inlet of water on to the carbon block. It is preferred that the orifice comprises at least 30% of the surface area of the top surface of the closure.
The invention is especially suitable and configured to be capable of filtering water which is contaminated with particles including dust and microorgansims e.g. protozoan cyst like Cryptosporidium and Giardia. The invention is capable of providing 99% removal (two log removal) preferably 99.9% removal (three log removal) of cyst. Log removal is defined as the log10 of the number of input particles minus the log 10 of the number of output particles. The carbon blocks are made from activated carbon, more preferably powder activated carbon.
6

It is desirable to include a replaceable sediment filter that externally envelops the carbon block such that water passes through the sediment filter before passing through the carbon block. The sediment filter preferably corresponds to the shape of the carbon block. The sediment filter is generally washable or replaceable and is preferably a woven or non-woven fabric, more preferably a non-woven fabric having micropores. This sediment filter ensures filtration of particles generally above 3 microns. The sediment filter can be washed and rinsed under flowing tap water with mild scrubbing.
The receptacle and the fastening means are preferably made of polymeric materials. Preferred polymeric materials include polypropylene, polyethylene, acrylonitrile butadiene styrene, or styrene acrylonitrile. The gasket means is preferably made from natural or synthetic rubber, synthetic elastomers, teflon, nitrile rubber or silicone,
The block filters for use in the filter assembly of the invention preferably comprises powder activated carbon (PAC) and a binder material having a Melt Flow Rate (MFR) of less than 5 g/10 minutes, preferably less than 1 g/10 minutes. The melt-flow rate (MFR) is measured using ASTM D 1238 (ISO 1133) test. The test measures the flow of a molten polymer through an extrusion plastometer under specific temperature and load conditions. The extrusion plastometer consists of a vertical cylinder with a small die of 2 mm at the bottom and a removable piston at the top. A charge of material is placed in the cylinder and preheated for several minutes. The piston is placed on top of the molten polymer and its weight forces the polymer through the die and on to a collecting plate. The time interval for the test ranges from 15 seconds to 6 minutes in order to accommodate the different viscosities of plastics. Temperatures used are 2,20, 250 and 300 °C (428, 482 and 572°F). Loads used are 1.2, 5 and 10 kg. The amount of polymer collected after a specific interval is weighed and normalized to the number of grams that would have been extruded in 10 minutes: melt flow rate is expressed in grams per reference time.
7

The binder material is preferably thermoplastic polymers having the low MFR values above described. Suitable examples include ultra high molecular weight polymer preferably polyethylene or polypropylene which have these low MFR values. The molecular weight is preferably in the range of 106 to 109. Binders of this class are commercially available under the trade names HOSTALEN from Tycona GMBH, GUR, Sunfine (from Asahi, Japan), Hizex (from Mitsubishi) and from Brasken Corp (Brazil). Other suitable binders include LDPE sold as Lupolen (from Basel Polyolefins) and LLDPE from Qunos (Australia). The bulk density of the binder material is preferably less than or equal to 0.6 g/cm3, more preferably less than or equal to 0.5 g.cm3, and further more preferably less than or equal to 0.25 g/cm3. The binder material preferably has a particle size distribution substantially the same as that of the PAC but the particles passing 200 mesh is preferably less than 40 wt%, more preferably less than 30 wt%.
The carbon block when used preferably comprises powder activated carbon (PAC) having a particle size such that 95 wt % of the particles pass through 50 mesh and not more than 13%, preferably not more than 12%, more preferably not more than 10% pass through 200 mesh. The PAC is preferably selected from bituminous coal, coconut shell, wood, or petroleum tar. The surface area of the PAC is preferably exceeds 500 m2/g, more preferably exceeds 1000 m2/g.
Preferably, the PAC has size uniformity co-efficient of less than 2, or more preferably less than 1.5, a carbon tetrachloride number exceeding 50%, more preferably exceeding 60%. The PAC preferably has an Iodine number greater than 800, more preferably greater than 1000.
The proportion of the binder material to the PAC particles by weight is chosen such that it is preferably in the range of 1:1 to 1:10, more preferably in the range of 1:2 to 1:6.

By way of the above filter cartridge of the invention it is possible to attain average flow rate of water, from a starting height of 200 mm down to 50 mm, under gravity of 600-50 ml/min., preferably 200-50 ml/min., without compromising on the requirements of removal of particulate including microorganisms, and chemical contaminants.
A suitable process of preparation of carbon blocks for use in the filter cartridge of the invention has been disclosed in our co-pending application 320/MUM/2004.
According to another aspect of the present invention there is provided a method
of obtaining filtered water at flow rates in the range of 50 to 600 ml/minute
comprising the steps of
(i) filtering water through a filter cartridge of the invention; and
(ii) replacing the carbon block in the filter cartridge whenever the flow rate of
water is below desired value with a block which provides the desired flow
rate.
The present invention facilitates easy removal of the carbon block from the cartridge to rejuvenate it, after which the carbon block is easily re-attachable in the cartridge. Rejuvenation can be done by agitating the carbon block in water or by back flushing with a jet of cold or hot water. During such a cleaning and replacement process, the carbon block is preferably replaced in the cartridge with the same side-up each time. To facilitate this, the carbon block preferably has indicators thereon to distinguish the top and bottom surfaces.
The details of the invention, its objects and advantages are explained hereunder in greater detail in relation to the following non-limiting exemplary embodiments of the invention:
9

BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings,
Fig. 1 is a schematic of a filter cartridge of the invention with a carbon disc filter assembled.
DETAILED DESCRITION OF, THE DRAWINGS
Referring to Fig.1, the filter cartridge comprises a carbon block (CB) seated on a gasket (G) provided in the base of a receptacle (R) which has an orifice (OT) for outlet of water. A closure (CL) has an orifice on the top surface (not shown) for inlet of water. The closure has screw threads (ST1) with which it is screwed on to the receptacle provided with corresponding screw threads (ST2). Downwardly projecting members (M) are provided on the closure for urging the carbon block against the gasket as the closure is screwed on to the receptacle. The gasket ensures leak-proof outlet such that all the water fed to the filter cartridge passes though the carbon block before exiting it.
When in use, the water enters the closure through the orifice provided thereon and flows through the carbon block enabling filtration and exits the cartridge through the outlet (OT). When a large amount of water has been filtered and the flow rate of water is below desired value, the closure is unscrewed and the carbon block is removed from the cartridge. The carbon block is rejuvenated by cleaning to the desired degree of cleanliness and replaced in the filter cartridge with the same-side-up as in the earlier run. The closure is again screwed on to the receptacle and the cartridge is ready for use again. The filter cartridge provides the high desired flow rates again. This procedure is repeated till the carbon block can no longer be rejuvenated. At this stage the carbon block is replaced with a new one.
10

Examples Example-1:
A filter cartridge of the invention (as shown in Fig. 1) with a 35 gram carbon disc (95 mm diameter and 12 mm height) is used to filter water which is contaminated with particulates in a gravity filter with a head of 170 mm of water column. The data on the flow rate of the filtered water obtained is shown in Fig. -2. The filter cartridge removed greater than 99.9% of the cysts present in the inlet water.
Comparative Example-2:
A filter cartridge as described in prior art made with 127g carbon into 100 mm hemispherical shape with the carbon block glued to a base plate was used to filter water under the same conditions as example-1. The comparative data is shown in Fig-3. This filter also removed greater than 99.9% of the cyst present in the inlet water.
The data indicates that by using as less as about 28 weight% of the carbon block as compared to the comparative example-1, the filter cartridge of example-1 could filter about 60% of the water (about 300 litres of water as compared to 500 litres of water using the filter of the comparative example-1). Further, the graphs show that the average flow rate of the water obtained in example-1 was significant higher.
Thus the invention provides for a filter cartridge which ensures desired particulate removal while giving the high desired flow rate of water consistently over larger volumes of water while providing a higher efficiency in terms of the amount of water filtered for a given amount of carbon.
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We claim:
1. A filter cartridge for filtration of water, comprising a carbon block that is seated in a receptacle having an orifice for outlet of water, wherein said carbon block is detachably attachable in said receptacle, using a fastening means and a gasket means, such that all inlet water passes through said carbon block before exiting said filter cartridge.
2. A filter cartridge as claimed in claim 1, wherein said fastening means is a screw threaded closure which comprises an orifice for inlet of water and is screwable on to said receptacle provided with corresponding screw threads for urging said carbon block against said gasket provided in the base of the receptacle.
3. A filter cartridge as claimed in claim 2, wherein the area of the orifice on the closure is greater than 30% of the surface area of the top surface of the closure.
4. A filter cartridge as claimed in any preceding claim, wherein said carbon block is disc shaped.
5. A filter cartridge as claimed in claim 4, wherein said disc has circular cross-section.
6. A filter cartridge as claimed in claim 4 or 5, wherein the ratio of the longest dimension to the thickness of the carbon disc is from 2:1 to 20:1.
7. A filter cartridge as claimed in any preceding claim, wherein a replaceable sediment filter externally envelops said carbon block such that water passes through said replaceable sediment filter before passing through said carbon block.
8. A filter cartridge as claimed in claim 8, wherein said sediment filter is made of non-woven fabric.
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9. A filter cartridge as claimed in any preceding claim, wherein said receptacle and said fastening means is made of materials selected from polypropylene, polyethylene, acrylonitrile butadiene styrene, or styrene acrylonitrile copolymer.
10. A filter cartridge as claimed in any preceding claim, wherein said gasket means is made from natural or synthetic rubber, synthetic elastomers, teflon, nitrile rubber or silicones.
11. A filter cartridge as claimed in any preceding claim, wherein said carbon block comprises;

• powder activated carbon (PAC) having particle size such that 95 wt% of the particles pass through 50 mesh and not more than 13% particles pass through 200 mesh, and
• a binder material having Melt Flow Rate (MFR) less than 1 gram/10 minutes.

12. A filter cartridge as claimed in claim 12, wherein said binder material is high molecular weight polyethylene or polypropylene having molecular weight in the range of 106 to 109g/mole.
13. A filter cartridge for filtration of water, substantially as herein described with reference to the accompanying figures and examples.
Dated this 30th day of June 2006 Hindustan Lever Limited

S. Venkatramani
(Senior Patents Manager)

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Abstract
The invention relates to a filter cartridge for filtration of water and more particularly to a cost-effective filter cartridge for gravity filtration of water, so as to render it substantially free of particulate contaminants, which include microorganisms like cysts, while providing for relatively high flow rates.
There exists a need to have a cost effective gravity-fed water filter cartridge which provides overall cost effectiveness to the consumer while providing consistently high flow rates and also ensuring the removal of particulate material including micro-organisms and dissolved matter.
The filter cartridge is uniquely configured to maximize the filtration efficiency, the throughput of the water to be filtered, the flow rate achieved even from a low gravity head, while minimizing the amount of filter media material being consumed to achieve these ends.
According to the invention, there is provided a filter cartridge for filtration of water comprising a carbon block that is seated in a receptacle having an orifice for outlet of water wherein said carbon block is detachably attachable in said receptacle using a fastening means and a gasket means such that all inlet water passes through said carbon block before exiting said filter cartridge.

30 JUN 2006

A FILTER CARTRIDGE

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