Liquid purification or separation – Diverse distinct separators – Including a filter
Reexamination Certificate
2000-11-21
2003-03-04
Savage, Matthew O. (Department: 1723)
Liquid purification or separation
Diverse distinct separators
Including a filter
C210S317000, C210S323200, C210S346000, C210S486000, C210S487000, C210S489000, C210S492000, C210S493200
Reexamination Certificate
active
06527954
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a filter element to be installed into a housing in order to constitute a filter assembly, which is composed of a non-woven fabric, porous membrane or the like for separation of solids from a mixture fluid that is a gas or a liquid, passageway material extending along the non-woven fabric, and a sleeve joining them together for installation into the housing.
2. Discussion on Related Prior Art
Various filtration technologies for separation of solids from a mixture fluid utilizing “non-woven fabric, porous membrane or the like (hereinafter referred to as porous thin film)” have been in wide use for filtering operation in the field of foods, pharmaceuticals, semiconductors or the like and a further development has been sought for. Namely, various functions of the porous thin film have been developed, and at the same time filter cartridges (although “filter cartridge” is defined as “the filter elements of pleat state, cylinder state, etc.” in JIS K 3832, hereinafter “filter cartridge” is renamed “filter element” including “filter elements of bag state in the present invention”, wherein JIS means Japanese Industrial Standard) and filter assemblies (hereinafter “filter assembly” is defined as “filter elements assembled in a housing or holder”, as shown in JIS K 3832) have been also developed.
It is, however, well-known that passages in porous thin film become gradually blocked or clogged during filtration, accordingly a filtration rate decreases in separation of solids from a mixture fluid, and at last it is necessary in a filtration process to exchange the clogged filter assembly for another filter assembly which is arranged in parallel with the clogged filter assembly in order to continuously operate the filtration process. Then, it is laborious for an operator to exchange filter assemblies and replace with a new filter assembly or a new filter element whenever a filtration rate decreases. Besides, there even occur occasionally process shutdowns when he fails to exchange the filter assemblies or replace them with the filter assembly or the filter element.
Nevertheless, there has not always been spent a great deal of effort to improve a filter element made of a porous thin film and a filter assembly constituted of the filter element and “a housing” (hereinafter referred to as “a vessel containing an element”, as shown in JIS K 3802), since there was developed “a folded tubular membrane filter element” having a central opening as a passageway for a filtrate, for example, as disclosed in Japanese Patent Application Publication Nos. 62-59962/1987 (corresponding to U.S. Pat. Nos. 4,588;464 and 4,663,041) and 5-41284/1993. Merely, there were other patent applications disclosing “a filter element having a filtering medium in the form of a spiral wound bag where screen mesh spacers are arranged along the inside and outside surface of the bag”, which can increase a filtration area per unit volume of housing because of no necessity of a central opening, as shown in Japanese Patent Application Laid-Open Specification No. 2-2838/1990 (hereinafter the filter element is referred to as “a spirally wound bag filter element”), and another filter element to be named hereinafter “a bundled porous hollow fiber membranes filter element” in which porous hollow fiber membranes are bundled and joined with “two tube sheets” (although “tube sheet” is defined as “a portion for fixing the end of an opening of a hollow fiber membrane or a tubular membrane” in JIS K 3802, hereinafter it is redefined as including a portion for fixing an end of openings of baggy filtering mediums and a portion for fixing an end of an opening of a filtering medium in the form of a “pleats-folded” bag as explained in the present invention later) in Japanese Patent Application Publications Nos. 6-61431/1994, 7-34850/1995 (corresponding to U.S. Pat. Nos. 4,980,060 and 5,066,039, respectively).
However, there are also a lot of defects in the spiral wound bag filter element. Namely, a filtration surface at the inside of a filtering medium of the element is apt to be wrinkled due to winding a bag, made in advance as a radius of the element is small, so that it fails to function effectively during filtration, in addition the other filtration surface at the outside of the filtering medium is apt to be.broken because of tension caused by winding the bag. From the aspect of bonding technology, it is almost impossible to form into the spirally wound bag without wrinkle and tension by bonding after winding spirally in advance two porous thin films with screen mesh spacers. Besides it is also difficult to increase the number of spirals, maintaining certainly each interval between adjacent spirals, and it is inevitably hard to expect a large flow rate of “a mixture of fluid and solid (hereinafter referred to as a supply fluid)” because there is only allowed a flow from the surface of a disc-shaped bottom of the spirally wound bag filter element, except the other flow from its.peripheral surface, which cannot almost penetrate into its central portion.
On the other hand, there are also difficulties in the bundled porous hollow fiber membranes filter element, for example, it is almost impossible to expect a large flow rate in each of porous hollow fiber membranes, because it is difficult to maintain a form of each of the hollow fiber membranes, even if it can have a big inner diameter with its wall thickness thin and because it is also substantially impossible to insert support material into each of the porous hollow fiber membranes for reinforcement.
SUMMARY OF THE INVENTION
It is a main object to enlarge a filtration area per unit volume of filtration space in a housing or unit volume of filter element, in order to get a feed period of a supply fluid as long as possible, so that ample time is allowed for exchange of filter assemblies or the filter element in the assembly due to decrease of frequency of exchange and replacement.
It is another object to provide a novel manufacturing process for the filter element having a large filtration area per unit volume of filtration space.
According to the present invention, a filter element to be installed into a housing in order to constitute a filter assembly for separation of solids from a supply fluid containing solids comprises constructing a series of parallel layered elements obtained by dividing a filtration space in the housing in parallel with its lengthwise direction, from baggy filtering mediums made of a porous thin film, whose opening portions are joined fluid-tightly with a sleeve to be installed into a housing and which have interior layered passageways, and from exterior layered passageways between every two of the baggy filtering mediums adjacent to each other, one after the other so as to rebuild almost the whole of the optional filtration space, and equipped with passageway materials in at least either of both kinds of layered passageway.
At the same time, the present invention also attained another development derived from the above-mentioned filter elements for separation of solids from a supply mixture fluid. Namely, instead of a series of baggy filtering mediums made of a porous thin film having an equal depth and equipped with passageway materials, inside and outside, a few or preferably only one rectangular baggy filtering medium (therefore, which is longer in width) with the depth equipped with the passageway materials inside and outside, was “folded repeatedly back and forth upon itself in parallel with a lengthwise direction of the filter element, giving each width and thickness nearly equal to respective width and thickness of each of the series of layered elements, so as to form into a similar shape to the filtration space in the housing (hereinafter, referred also to as “pleats-folded”, in order to describe in short)” and joined fluid-tightly at a pleated opening portion (or pleated opening portions in case of a few rectangular baggy filtering mediums) with a sleeve to be installed into t
Savage Matthew O.
Wood Phillips Katz Clark & Mortimer
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