Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-07-31
2002-08-13
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S293000
Reexamination Certificate
active
06432233
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject invention relates to a composite fluid filter cartridge comprising a bundle of hollow microporous fibers housed within an extruded carbon block, wherein the carbon block is fabricated to balance particle retention capacity against absorption capacity to provide a composite filter with desirable pressure drop across the cartridge, improved filter life, and desirable particulate and chemical contamination reduction.
The subject invention also relates to a fluid filtration apparatus, and more particular, to a countertop water filtration unit for domestic use in which such composite fluid filter cartridge may find use.
2. Background of the Related Art
Due to run-off and environmental contamination, drinking water in most areas of the world contains appreciable amounts of dissolved chemicals and suspended particulate material. A number of chemicals and particulates that may be found in drinking water have been associated with possible adverse physiological effects. Other chemicals and particulates in drinking water have been associated with less than desirable taste and sensory perceptions, such as “clouding” of the water or “souring” of the water. Certain chemicals and particulates in a water source may lead to undesirable rings in appliances and commodes using large amounts of water, and may result in unsightly films being placed on items washed in the water. In order to reduce particulate and chemical contamination of drinking water, such water is frequently treated by chemical processes. Of course, such processes themselves may introduce other types of undesirable chemical contaminants into the water. Chemicals are also not infrequently added to water to act as a sanitizing agent, for example, chlorine and bromine. The danger of such chemicals is only now being questioned.
In the estimation of many persons, municipal water treatment plants often fail to adequately deal with these problems. In order to improve water quality, many residences and businesses now employ on-site water filters to improve water streams consumed therein.
Prior Art Fluid Filters
Most systems for improving fluid quality use a series of filters. Filtration is the process of separating particles from a fluid suspension (liquid or gas) by use of a porous medium or by means of a medium possessing chemical properties, such as hydrophobicity, electrostatic charge, etc., which permit such medium to interact and hold the particles which are to be separated from the fluid while permitting the fluid to pass there through. Chemical contaminants are often removed by filters by means of chemical absorption into, or adsorption onto, the surface of the matter comprising the filter medium. Optimally, it is desired that the filter medium retains most of the suspended particles and many of the chemical contaminants, but allows the fluid being filtered to pass through unimpeded. Flow across the filter medium is generally achieved by the application of a driving force, usually in the form of a pressure difference across the filter, which may be generated, for example by external pressure applied upstream, a vacuum applied downstream, gravity, or other force.
Fluid filters are often of such dimensions or fabricated in a construct, so as to form relatively rigid replaceable filter units or “filter cartridges.” Filter cartridges often employ granular activated carbon elements in their construct. Granular activated carbon is useful for removing organic chemicals such as chlorine, hydrogen sulfide, pesticides, herbicides, phenol, chlorophenol and hydrocarbon from water. Other filter elements may be employed in the cartridge construct to help, for example, to remove sediments such as rust and other particles. Silver is sometimes impregnated into one or more filter element to inhibit bacterial growth. Ion exchange resins may also be employed.
While filter cartridges containing granular activated carbon are known to be good at removing contaminants that affect taste, odor of the filtrate, and visible particulate matter, such filter cartridges generally are not fine enough to remove bacteria or viruses. Water may be contaminated with a number of micro-organisms including pathogenic bacteria, amoebae, flagellates, viruses and protozoa. In fact, as some water remains inside carbon granules after filtration, stagnant water in the carbon granules may act as a breeding ground for micro-organisms. Therefore, water discharged after a long period of non-use of a carbon-based filter cartridge may be contaminated with living organisms.
Recognizing that prior art filter cartridges which incorporate only a single filter medium, in particular a carbonaceous medium, suffer from the inability to remove many of the contaminants found in water, there have been developed filter assemblies employing a plurality of filter media, such as disclosed in U.S. Pat. No. 5,188,727. For example, in U.S. Pat. No. 4,828,698 there is disclosed a filter assembly having an outer cylindrically-shaped filter structure with porosity such as to be remove particulate matter, a inner cylindrically-shaped sorbant structure for sorbing chemical contaminants, and an inner-most cylindrically-retained microbiological filter, preferably comprising a microporous membrane for removing microorganisms, surrounding a perforated core housing a central void. By moving water across from the outer structure to the central void, particulates are removed, chemicals are adsorbed or absorbed, and microorganisms are filtered out.
Numerous microporous filter elements are utilized in the art to remove bacteria, viruses and other micro-organisms. Among these elements are hollow fibers having micropores coursing through the fiber walls. As disclosed in U.S. Pat. No. 3,526,001 (the disclosure of which is incorporated by reference herein), hollow selectively permeable fibers for use in filtration have been known for several years. Typical microporous hollow fibers include Celgard™ manufactured by the Questar division of Celanese Corporation. Such hollow fibers offer controlled and relatively uniform porosity as compared to many asymmetric ultrafiltration and microfiltration membranes. Fiber construct is such that there is high membrane surface area-to-volume ratio. The pores in the fibers form tortuous, interconnected channels leading from one surface of the fiber to the other. The pores of these hollow fibers allow the flow of fluid but block passage of many bacteria, colloids and other sub-micron particles. Fibers having pores of 0.05 microns or less are capable of filtering most viruses. In order to assure passage of the fluid through the fiber pores rather than through any end, such fibers are generally potted in an epoxy or other standard potting material at both ends of the fiber in a manner that the openings at both ends remain open.
Microporous hollow fibers have been mounted within filter cartridges in numerous ways including: placing them rectilinearly in the cartridge (e.g., U.S. Pat. Nos. 4,334,993, 5,041,220, 5,554,283), winding them about a cylindrical support (e.g., U.S. Pat. No. 4,045,851), and bundling them in a U-shape (e.g, U.S. Pat. Nos. 5,032,269 and 5,225,079). By judicious selection of hollow tubule lengths, as disclosed, for example, in U.S. Pat. No. 5,032,269 (the disclosure of which is incorporated by reference herein), a U-shaped bundle of microporous hollow fibers aids in maximizing filtration surface area, and thus filtration efficiency, while providing ease of manufacture and placement of the fibers in sealant material.
U.S. Pat. No. 4,636,307 discloses a filter unit housing particulate granulated activated carbon surrounding a bundle of U-shaped porous hollow fibers. Such system is said to aid in both removing chemicals and impurities from the filter water, as well as micro-organisms. While such system improves water filtration, use of mobilizable carbon particles in its construct can be said to suffer from several disadvantages, among these the settling of the particles over time leading to decreased
Bassett Laurence W.
Chen Wei-Chih
Contaxis, III William
Hamlin Thomas J.
Ball Michael W.
Cummings & Lockwood
Cuno Inc.
Piazza Gladys
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