Gas separation – With nonliquid cleaning means for separating media – Cohesive filter media cleaning
Reexamination Certificate
2000-06-30
2002-04-02
Simmons, David A. (Department: 1724)
Gas separation
With nonliquid cleaning means for separating media
Cohesive filter media cleaning
C055S341100, C055S324000, C055S379000, C095S280000
Reexamination Certificate
active
06364921
ABSTRACT:
FIELD OF THE DISCLOSURE
The present disclosure is related to air filtering systems having housings with non-planar side walls.
BACKGROUND OF THE DISCLOSURE
Many industries often encounter particulate matter suspended in the atmosphere. In some industries, this particulate matter is a valuable product, for example, starch; it would be beneficial if these suspended particulate could be recovered and reintroduced into the process. For other industries, such as metal or wood working, the particulate matter may be simply dust; it is desirable to remove dust particles from the air in order to provide a clear working environment.
Systems for cleaning an air or other gas stream laden with particulate matter include air filter assemblies that have filter elements disposed in a housing. The filter element may be a bag or sock of a suitable fabric or pleated paper. The gas stream, contaminated with particulate, typically is passed through the housing so that the particulate are captured and retained by the filter element. Cleaning is accomplished by periodically pulsing a brief jet of pressurized air into the interior of the filter element to reverse the air flow through the filter element, causing the collected contaminants to be collected . Such air filter assemblies are disclosed in, for example, U.S. Pat. No. 4,218,227 (Frey) and U.S. Pat. No. 4,395,269 (Schuler), which patents are hereby incorporated by reference.
Filter elements are usually used in an air filter assembly to process dust particles from an airstream. In a standard design of air filter assembly, an air filter assembly has a clean air chamber and a dirty air chamber. The two chambers are separated by a sheet metal, commonly referred to as a tube sheet. The tube sheet has a number of openings from which cylindrical filters are aligned. The filters suspend downwardly with or without an angle from the tube sheet openings into the dirty air chamber. Particulate-laden air is introduced into the dirty air chamber, and the particulates collect onto the filter. The filtered air passes through the filters to the interior of the filters, and upwardly out through the openings in the tube sheet into the clean air chamber. From the clean air chamber, the cleaned air is exhausted into the environment, or recirculated for other uses. For example, U.S. Pat. No. 4,424,070 (Robinson), U.S. Pat. No. 4,436,536 (Robinson), U.S. Pat. No. 4,443,237 (Ulvestad), U.S. Pat. No. 4,445,915 (Robinson), U.S. Pat. No. 5,207,812 (Tronto et al.), U.S. Pat. No. 4,954,255 (Muller et al.), U.S. Pat. No. 5,222,488 (Forsgren), and U.S. Pat. No. 5,211,846 (Kott et al.) are prior art examples of prior art cylindrical filter elements of the pleated cartridge type.
It has been found that in many conventional systems, an to attempt to operate these types of dust collectors at an increased airflow results in increased air velocities, which in turn results in a reduction of filter life. An increased airflow, for example, 8315 cubic feet per minute (cfm) or greater, leads to high cabinet air/dust velocity which results in the dust particulate abrading holes in the filter cartridges. The high cabinet air/dust velocity may also inhibit the drop-out of the dust particles into the collection hopper. This results in the filters being plugged and a loss in total dust collection airflow.
SUMMARY OF THE DISCLOSURE
The construction and arrangement of the disclosed air filter assembly helps to overcome the problems of the prior art. In particular, in one embodiment, the structure and arrangement of the assembly of the present disclosure enables the processing of at least 10% more dust laden air, typically at least 20% more dust laden airflow compared to conventional systems. In preferred systems, the assembly of the present disclosure results in a dust laden airflow increase greater than 10%, preferably at least 20%, and most preferably at least 25% without a significant change in the overall size of the filter housing apparatus or the number of filter cartridges required. The present design provides this increase by maintaining the amount of filtration media available for filtering the dirty air rather than increasing the amount of filtration media. Also, the structure and arrangement of the air filter assembly provides more efficient filter retention/sealing, filter housing apparatus manufacturing, and filter handling.
In another embodiment, the structure and arrangement of the assembly of the present disclosure results in an air velocity that is at least 10%, preferably at least 20%, and most preferably at least 25% less than the air velocity of a similar volume of air being filtered by a conventional air filtration assembly.
In particular, the present disclosure is directed to an air filter assembly having distended side wall, in particular, an air filter assembly comprising a housing including an air inlet that provides a dirty air volume to the assembly, an air outlet, and a spacer wall separating the housing into a filtering chamber and a clean air chamber. The housing comprises a plurality of side walls forming the filtering chamber, at least one of the side walls is a non-straight wall, having a first wall portion and a second wall portion. By the term “non-straight”, it is meant that the wall is non-planar; that is, the first and second wall portions are positioned with an angle therebetween. A filter construction is positioned in air flow communication with an air flow aperture in the spacer wall, the filter construction including an extension of filter media defining a filter construction inner clean air chamber. In some embodiments, a third wall portion is included.
In a preferred embodiment, the housing of the air filter assembly has two opposite facing walls, each side wall having a distended portion formed by the first wall portion and the second wall portion.
The filter construction or filter element used in the air filter assembly having the distended side panel of the present disclosure may be any conventional filter construction. A non-cylindrical filter construction, for example, an oval or elliptical filter construction, is one preferred element. In particular, it is preferred that a non-cylindrical filter construction is positioned in the air filter assembly so that a long axis of a cross-sectional area of the filter is parallel to the direction of the incoming dirty air stream.
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Johnson Steven A.
Kosmider Kristofer G.
Raether Thomas D.
Donaldson & Company, Inc.
Pham Minh-Chau T.
Simmons David A.
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