MXPA99009523A - Filter cartridge for gravity-fed water treatment devices - Google Patents

Abstract

A filter cartridge (20) for a gravity-fed water treatment device having a porous particulate filter (24) disposed therein. The porous particulate filter (24) has an open upper end, a closed lower end, and sidewalls therebetween. Water is treated as it flows through the sidewalls of the filter. The cartridge also contains granular media (26) disposed within the porous particulate filter.

Description

FILTER CARTRIDGE FOR GRAVITY-BASED WATER TREATMENT DEVICES Field of the Invention This invention relates to filter cartridges for use in water treatment systems fed by gravity. In particular, this invention relates to a filter cartridge having a novel filter medium.

Background of the Invention Domestic water treatment devices are known in the art. Among these devices are integrated systems that process water in batches. The examples of the batch devices are pitchers / jugs and large tanks where the treated water is poured, for example, from a tap. These integrated systems usually have upper and lower chambers separated by a filter cartridge. They rely on gravity to force the water from the upper chamber, through the cartridge, and into the lower chamber, thereby producing treated water. The presence of unwanted and potentially harmful contaminants in water, especially in drinking water, is of concern to many people. This concern creates a desire for water treatment devices in the home and elsewhere. Many devices and methods of water treatment have been developed to remove or neutralize chemical and particulate contaminants. Some of these devices and methods incorporate chemically active materials to treat water. For example, activated carbon is able to remove the bad taste and odor of water, as well as chlorine and other reactive chemicals. Ion exchange resins are useful for removing metal ions and other ions from water. However, no single material or chemical product has been found to remove all contaminants. In addition to chemical and particulate contaminants, water often contains biological contaminants. These contaminants often can not be removed entirely by activated carbon, ion exchange resins, or other chemically active water purifiers. Biological contaminants may be susceptible to harsher chemical treatment, but these chemicals are usually themselves contaminants, or they can not be easily incorporated into gravity-fed treatment devices, especially those used in the home. In addition to being resistant to removal by conventional chemical elements, many of these biological contaminants, such as protozoan cysts such as cryptosporidium, are only about the size of a few microns.

Due to its small size and lack of relative availability of chemical removal methods suitable for these biological contaminants, it has been very difficult to develop a gravity-fed water treatment device that can remove protozoan cysts and still retain a speed of satisfactory flow. The present devices that filter cysts from water require pressurization, either from the tap or by manual pumping, to achieve a satisfactory flow rate. However, these devices are relatively complex and expensive, and in the case of manual pressurization systems, harder to operate. Accordingly, there is a need for a gravity-fed water treatment device that is capable of removing biological contaminants, including cysts such as cryptosporidium, while providing an acceptable flow velocity.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a filter cartridge for a water treatment fed by gravity. In one aspect of the invention, the filter cartridge includes a porous particulate filter having an open upper end, a closed lower end, and side walls between the two ends. The porous particulate filter is sealed to a portion of the filter cartridge by a connecting member. The water is treated as the water flows to the open top end and through the side walls of the porous particulate filter. The air inside the filter, which moves through the incoming water, flows out of the open upper end of the filter. In another aspect of the invention, the filter cartridge includes a porous particulate filter with side walls and an inlet. The granular medium is contained within the side walls of the filter. Water is treated as it flows through the filter inlet, through the granular medium, and radially outward through the side walls of the filter. In a further aspect of the invention, the filter cartridge includes a porous particulate filter that includes glass fibers and a hydrophilic binder. The porous particulate filter is sealed to a portion of the filter cartridge by a connecting member. The water treated by the filter cartridge has more than 99.95 percent of cysts particles removed from 3 to 5 micras. These and other advantages and features of novelty characterizing the invention are pointed out with particularity in the claims appended hereto. However, for a better understanding of the invention and its advantages, reference should be made to the drawings, which form an additional part hereof, and to the accompanying descriptive matter, wherein a preferred embodiment of the invention is illustrated and described. invention.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the present invention will be described with reference to the accompanying drawings, in which the like reference numerals identify the corresponding parts: Figure 1 is a perspective view separated into parts of a modality of a filter cartridge according to the present invention. Figure 2 is a partial cross-sectional view of the filter cartridge shown in Figure 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The filter cartridge 20 described herein can be used in a variety of gravity-fed water treatment devices. Referring to Figures 1 and 2, this preferred embodiment of the filter cartridge 20 contains a porous particulate filter 24 with a granular medium 26 disposed within the particulate filter 24. The filter cartridge 20 also has a cover 22 surrounding the filter cartridge 20. porous particulate filter 24 to provide mechanical support for the particulate filter. The cover 22 has a collar 36 which seals the porous particulate filter 24 to the cartridge 20, such that the water flowing through the cartridge must pass through the porous particulate filter 24, and is thus treated. The porous particulate filter 24 mechanically filters particles and biological contaminants, such as protozoan cysts, out of the water. To effectively filter biological contaminants, the porous particulate filter 24 must have pores smaller than the size of the contaminants to be filtered. Biological cysts, such as cryptosporidium, are only a few microns in size. An effective cryptosporidium filter should have pores less than about 5 microns, and preferably less than about 2 microns in diameter. Accordingly, the porous particulate filter 24 is preferably microporous, which means that the particulate filter has pores that are about 1 to 3 microns or smaller in size. Preferably, the porous particulate filter 24 removes more than 99.95 percent of the cyst particles from 3 to 4 micras of the water treated with the filter cartridge. The level of cyst filtration determined using the NSF 53 protocols, sections 6.5 and 6.12, incorporated herein by reference. The porous particulate filter 24 is preferably formed in a configuration having sidewalls 25 and an open top end. The side walls 25 of the porous particulate filter 24 are substantially cylindrical. However, other forms of the side walls are also included within the scope of the invention. Moreover, the side walls 25 of the particulate filter 24. Moreover, the side walls 25 of the particulate filter 24 may be flat or pleated, as shown in Figure 1. The pleated side walls provide a larger surface area of the filter than the flat side walls, for an otherwise identical filter configuration. However, the folds should not be closely spaced, or the flow velocity through the folds will decrease. The upper end of the particulate filter 24 is at least partially open, so that water can flow into the particulate filter 24, and the air inside the particulate filter 24 can escape as it is displaced by the water. 'The lower end of the porous particulate filter may be closed (not shown) or open (see Figures 1 and 2). If the lower end is open, then the porous particulate filter 24 must be attached to an object, such as a lower cover 29 of the cover 22, which will prevent the flow of water out from the open lower end of the particulate filter 24. Porous particulate filter 24 can be formed from a wide variety of materials. Preferably, the side walls 25 of the porous particulate filter 24 are made of a microporous hydrophilic filter medium. Optionally, if the lower end of the porous particulate filter 24 is closed, then the bottom can also be made of the microporous hydrophilic filter medium. An example of a suitable microporous hydrophilic filter medium is a block of carbon that has been made hollow to create side walls and an open top end. The preferred microporous hydrophilic filter medium for the construction of the porous particulate filter 24 is a fibrous sheet filter medium. The fibers of this sheet filter medium may be natural, such as fiber made of cellulose or cellulose derivatives, or synthetic, such as fibers made from polymers or glass. Preferably, the fibers are synthetic fibers, and more preferably, the fibers are glass microfibers. Frequently natural fibers, such as cellulose fibers, are thicker than synthetic fibers, resulting in fewer pores and a correspondingly slower flow velocity. The flow velocity of the water through a given porous particulate filter is of critical importance in determining the acceptability of the porous particulate filter 24 for a gravity-fed water treatment device. The flow rate is usually determined by the size of the pores, the pressure applied to the water to push it through the pores, and the composition of the filter. In gravity-fed devices, such as cans or household water storage containers, the pressure exerted on the water to push it through the filter cartridge 20 is only due to a force of gravity on the water itself. For gravity-fed water treatment devices for the home, such as cylinders, the pressure exerted on the water is usually less than about 0.5 pounds / square inch (about 3,400 Pa). Consequently, the flow velocity induced by gravity through a typical microporous particle filter is very slow, and is not practical for a gravity-fed water treatment device. To overcome this limitation, the preferred porous particle filters 24 of the invention contain hydrophilic material. Hydrophilic materials, as defined for the purposes of the present invention, are those materials which, when dried, are rapidly moistened (ie, they absorb water droplets rapidly). The hydrophilicity of these materials is due to a force of attraction between the hydrophilic material and water, which is greater than the surface tension of water at the water / filter interface (ie, the attractive force between individual water molecules). in the interface). The hydrophilicity of the porous particulate filter 24 may be a result of the hydrophilic nature of the fibers or other porous particulate filter material. Alternatively, the hydrophilicity of the filter may be due to an additive to the filter material. This additive may be able to create a hydrophilic particulate filter, even when the filter contains non-hydrophilic or hydrophobic fibers. A hydrophilic additive to the filter can also be used for other functions inside the filter material. An example of this additive is a hydrophilic binder that is added to the medium, not only to impart hydrophilicity to the binder, but also to bond the microfibers of the medium together to form a sheet. The hydrophilic sheet filter medium having these properties is available from Alhstrom, Mt. Holly Springs, PA (Grade 2194-235). The suitable hydrophilic binder for use in the glass microfiber bond is available from Goodrich (Part No. 26450). The sheet filter medium was obtained from the above-mentioned source. The sheet filter medium had an average pore size of approximately 1.2 millimeters, and a thickness of approximately 0.024 inches (approximately 0.061 centimeters). The porous particulate filter was approximately 3 inches (approximately 7.5 centimeters) in height, and had an outer diameter of 1.75 inches (approximately .4.4 centimeters). The porous particulate filter was pleated to give 40 uniformly spaced folds around the filter, with a fold depth of approximately 0.25 inches (approximately 0.64 cm), giving the filter an internal diameter of 1.25 inches (approximately 3.2 centimeters). To protect the porous particulate filter 24 from damage, a cover 22 may be provided around the filter 24. The cover 22 has three connectable parts, an upper cover 28, a lower cover 29, and a body 30, as shown in FIGS. Figures 1 and 2. This configuration allows the particle filter 24 to be easily placed in the filter cartridge 20. Other cover configurations can be used, and are included within the scope of the invention. The cover 22 also has one or more inlet openings 32, and one or more outlet openings 34, through which water enters and exits the filter cartridge 20, respectively. The inlet openings 32 are placed in an upper portion of the cover 22, either in the upper cover 28 (see Figures 1 and 2), or in an upper portion of the body 30 (not shown). The outlet openings 34 are normally located in the lower cover 29, but could also be on the side of the body 30. The inlet openings 32 and the outlet openings 34 are placed inside the cover 22, such that the water which flows inwardly from the inlet openings 32 passes through the granular medium 26 and the porous particulate filter 24, before exiting through the outlet openings 34. The porous particulate filter 24 is adhesively connected to the lower cover 29 for providing a seal in order to prevent water from flowing around the bottom of the filter 24. The bottom cover 29 also contains one or more columns with flanges 31 which, when sliding the bottom cover 29 into the body 30, will contact with a lip of an indentation 35 in the inner portion of the body 30, to firmly hold the lid 29 in place. There are spaces between the flanged columns 31 of the cover 29, to allow water to flow out of the filter cartridge 20, through the outlet openings 34 in the lower cover 29. The cover 22 also has a collar 36 which it acts as a connecting member, which provides a seal between the porous particulate filter 24 and the filter cartridge 20, such that the water therein. flow through the inlet openings 32 must pass through the porous particulate filter 24 before exiting through the outlet openings 34. The collar 36 has an annular cup formed by a cylinder 37 and a base 39. The filter of porous particles 24 adhesively bonds inside the annular cup formed by the cylinder 37 and the base 39, to provide a waterproof connection to the collar 36. Other methods for sealing the porous particulate filter 24 to the cartridge 20 are also included. within the scope of the invention. The cover 22 _ is usually constructed of a plastic or polymeric material. The cover 22 is preferably made of a molded plastic. The flow rate of the water through the porous particulate filter 24 is often decreased by the presence of air adjacent the porous particulate filter 24. The air trapped near the particulate filter 24 forms an interface with the water in the particulate filter. 24. There will be a surface tension associated with this interface. Unless there is enough pressure to break this surface tension, water will not flow. Accordingly, it is desirable that there be a path for the escape of air as it is displaced by the water flowing into the filter cartridge 20. An advantage of the filter configuration illustrated in FIGS. 1 and 2 is that the air inside the shape configured by the porous particulate filter 24, may flow out of the open upper end of the porous particulate filter 24, and exit the filter cartridge 20 through the inlet openings 32. When provided the cover 22 around the porous particulate filter 24, air can also be trapped in the gap 38 between the cover 22 and the particulate filter 24. The presence of trapped air can reduce the flow velocity through the filter 24, as the water level rises within the hollow 38. The air outlet openings 40 are provided in the cover 22, such that air can escape from the hollow 38, especially when the outlet openings 34 are below the water level of the water treatment device. Air outlet openings 40 are often provided near the upper end of the recess 38 that is proximate the sealed connection between the cover 22 and the porous particulate filter 24. This configuration will allow most or all of the air to escape from the air. cartridge, since the air will naturally rise to the highest possible level, due to the floating of the air in the water. In addition to providing an exhaust path for the air, the air outlet openings 38 can also function as water outlet openings. The granular medium 26 is normally disposed inside the cover 22 to provide additional water purification. As shown in Figure 2, the granular medium 26 is preferably disposed inside the porous particulate filter 24. This configuration is convenient, because the particulate filter 24 will prevent the granular medium 26 from leaving the filter cartridge 20. In addition, the granular medium may be disposed within a separate granular media containment region 41 of the cover 22 (see Figure 2). The granular medium 26 comprises chemicals or materials that are suitable for the treatment of water. The granular medium 26 typically includes chemicals or other materials that are capable of removing, reducing, or deactivating one or more of the following elements: bad odor, bad taste, organic contaminants, chemical contaminants, and metal ions or other unwanted ions, such as chlorine. Suitable granular medium 26 includes carbon, zeolites, an ion exchange resin, or a combination thereof. A preferred form of carbon for use as a granular medium is granular activated carbon. A preferred granular medium for use in the filter cartridges of the invention is a mixture of a weak acid cation exchange resin and granular activated carbon. In one embodiment of the invention, at least a portion of the granular medium 26 is hydrophilic. The hydrophilic granular medium includes granular activated carbon. A hydrophilic granular medium disposed within the porous particulate filter 24 can facilitate the flow of water through the porous particulate filter 24. The hydrophilic granular medium in contact with the porous particulate filter 24 can provide a less resistive flow path for the filter. water towards and through the side walls (preferably hydrophilic) of the porous particulate filter 24. It should be understood that the present invention is not limited to the preferred embodiment described above, which is illustrative only. Changes can be made in the detail, especially in the matters of form, size, configuration of parts, or component materials within the principles of the invention, to the full extent indicated by the broad general meanings of the terms in which they are used. they express the appended claims.

Claims (31)

1. A filter cartridge for a gravity-fed water treatment device, which comprises: a hydrophilic porous particulate filter having an open top end, a closed bottom end, and at least a side wall therebetween; and a connecting member that seals the hydrophilic porous particulate filter to a portion of the filter cartridge proximate the upper end of the filter; wherein the filter cartridge is configured and arranged to allow water to flow by the force of gravity into the open upper end, and through the side walls of the porous particulate filter, as the air moves outward of the open top end.

2. The filter cartridge of claim 1, wherein the side wall of the hydrophilic porous particulate filter is substantially cylindrical.

3. The filter cartridge of claim 1, wherein the porous hydrophilic particulate filter is microporous.

The filter cartridge of claim 1, wherein the hydrophilic porous particulate filter comprises a sheet filter means.

5. The filter cartridge of claim 1, wherein the porous hydrophilic particulate filter is pleated.

6. The filter cartridge of claim 1, wherein the porous hydrophilic particulate filter comprises glass microfibers and a hydrophilic binder.

The filter cartridge of claim 1, wherein the filter cartridge further comprises a cover having an inlet and an outlet, the cover being arranged around the porous hydrophilic particulate filter, wherein the water is treated as it flows from the inlet of the cover, to the open upper end of the porous hydrophilic particulate filter, through the side wall of the filter, and outwards through the outlet of the cover.

The filter cartridge of claim 7, wherein the cover further comprises one or more air outlet openings, such that, when water enters the cartridge through the inlet of the cover, air is also displaced. outward from the air outlet openings in the cover.

9. A filter for a gravity-fed water treatment device, comprising: a porous particulate filter having an inlet and at least one side wall defining an internal volume; and a granular medium disposed through an entire portion of the internal volume, which extends between opposite sides of the porous particulate filter; the porous particulate filter and the granular medium being constructed and arranged in such a way that the water flows by the force of gravity towards the inlet, through the granular medium, and radially outwardly through the side wall of the porous particulate filter. as it is.

The filter of claim 9, wherein the porous particulate filter comprises a sheet filter means.

The filter of claim 9, wherein the side wall of the porous particulate filter is substantially cylindrical.

12. The filter of claim 9, wherein the porous particulate filter is pleated.

The filter of claim 9, wherein the porous particulate filter comprises hydrophilic material.

The filter of claim 9, wherein the porous particulate filter comprises glass microfibers.

15. The filter of claim 14, wherein the porous particulate filter further comprises a hydrophilic binder to hold the glass microfibers together.

16. The filter of claim 9, wherein the porous particulate filter is capable of removing protozoan cysts.

17. The filter of claim 9, wherein the porous particulate filter is microporous.

18. The filter of claim 9, wherein the granular medium is carbon, an ion exchange resin, or a combination thereof.

19. The filter of claim 18, wherein the carbon in the granular medium comprises granular activated carbon.

The filter of claim 9, wherein the granular medium is hydrophilic.

21. A filter cartridge for a gravity-fed water treatment device, comprising: a porous hydrophilic particulate filter having glass fibers and a hydrophilic binder to bind the fibers together, the filter being capable of removing more 99.95 percent of cyst particles 3 to 4 microns of water; and a connecting member that seals the porous particulate filter to a portion of the filter cartridge.

22. The filter cartridge of claim 21, wherein the glass fibers comprise glass microfibers.

23. The filter cartridge of claim 21, wherein the porous particulate filter has at least one side wall.

24. The filter cartridge of claim 21, wherein the porous particulate filter is substantially cylindrical.

25. The filter cartridge of claim 21, wherein the porous particulate filter comprises a sheet filter means.

26. The filter cartridge of claim 21, wherein the porous particulate filter is pleated.

27. A filter cartridge for a gravity-fed water treatment device, which comprises: a self-supported porous hydrophilic particulate filter along the length of the filter, and having at least one side wall through the filter. which water can flow by the force of gravity, thus treating the water; a member sealingly connects the filter to a portion of the filter cartridge, thereby separating the untreated water from the treated water.

28. The filter cartridge of claim 27, wherein the filter is tube-shaped.

29. The filter cartridge of claim 27, wherein said member sealingly connects the filter proximal to an upper end of the filter.

30. The filter cartridge of claim 27, wherein said member sealingly connects the filter proximal to a lower end of the filter.

31. The filter cartridge of claim 27, wherein said member comprises an adhesive material.