Liquid purification or separation – With gas-liquid surface contact means
Reexamination Certificate
1999-03-23
2001-08-14
Barry, Chester T. (Department: 1724)
Liquid purification or separation
With gas-liquid surface contact means
C210S615000
Reexamination Certificate
active
06274035
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
Biological filtration is routinely used in applications like sewage and waste water management and in the keeping of tropical and cold water fish by hobbyists, etc. Biological filtration relies on the activity of specific bacteria cultured in the filter to break down toxic waste products into less harmful substances. A good filter material should provide the largest surface area for bacteria to colonize but shall not block the fluid flow. Unfortunately, filters with large surface area (like porous media, foams or sponges) tend to clog up easily, thus reducing the effectiveness of the filter. Moreover, due to the distribution of the size of flow passages, fluid will tend to flow through only a few large passages, thus greatly reduces the effectiveness of the entire filter medium. The filter design discussed in this patent provides uniform size of flow passages thus the fluid flow through the entire filter instead of a few passages, giving the filter a large effective area for the bacteria to colonize. Flow through parallel plates also offers one of the best geometries for low flow resistance in fluid dynamic, thus reducing the chance of clogging. It can be used for both wet/dry and submerged biological filtration systems.
BRIEF SUMMARY OF THE INVENTION
The present parallel sheets filter provides large effective surface area for the colonization of bacteria, but has little or no chance of clogging up.
Some objects and advantages of this invention are to provide compact, efficient filters that can be economically customized and fabricated for use in biological filters for both trickle and submerged filtration systems.
This invention is a sheet filter with precise dimension of the spacers (thick portion) raising above the remaining of the sheet (thin portion). The distance between the spacers defines the width of the flow passage, and the thickness of the spacer defines the depth of the flow passages. It permits controlled variation in the passage size from one end of the filter to the other. It permits controlled variation in the ratio of surface area to total volume of the filter over a substantial range. This combination of desirable properties is unmatched by any prior filter design. Filter of this type may be created quickly and inexpensively by the method described below.
This invention is a practical way to achieve the advantages of flow between parallel plates. Parallel plates with very small clearances between them are ideal form of filter medium because parallel plates theoretically maximize surface area while minimizing losses resulting from fluid friction (i.e., pressure drop).
The filter sheet in this filter is wrapped or stacked upon itself with no folds, dimples or spaces to hold the successive layers apart. The width and depth of the flow passages can be accurately controlled when the sheets are stacked or rolled upon itself. Uniformity of flow passages reduces the tendency of the flow going through a few of the large passages, thus reducing the effective surface area of the filter.
The filter sheets can be sculpted by, machining, chemical etching, or photoetching, or molding out of a single piece of material. It can also be made from thin (thin portion) and thick (thick portion) filaments woven, press-fitted, fused, sintered, or bonded together. The actual manufacture of the filter can consist of nothing more than stacking or rolling the sheet upon a mandrel or upon itself. The stack or roll has great structural integrity and can then be inserted in the cavity of the filter.
By allowing flow passages of varying cross section from one end to the other, this invention permits filters to achieve the optimum combination of the filter surface area and flow resistance at each point along the flow passages, thereby enhancing filter effectiveness.
REFERENCES:
patent: 4184946 (1980-01-01), Kato
patent: 5089137 (1992-02-01), McKown
patent: 5326475 (1994-07-01), Kent
patent: 5348654 (1994-09-01), Fischer
Yuan Chrystal S.
Yuan Jacquelyn K.
Yuan Katherine K.
Yuan Sidney W. K.
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