Patent Publication Number: US-2010126124-A1

Title: Bag filter assembly

Description:
FIELD OF THE INVENTION 
     This invention relates to bag filters. More particularly, the present invention relates to a bag filter assembly that is injection molded as a single part from a plastic material. 
     BACKGROUND OF THE INVENTION 
     Bag filters are an established product in the treatment of fresh supply and recirculated air in buildings. Inflated by a steady airflow, bag filters offer a large media area for better dust holding and lower pressure drop. Bag filters are effectively used in applications where in-line space is not an issue and high dust holding over extended periods is required. 
     Bag filters consist of a series of individual synthetic media pockets supported by a rigid metal header frame supplied in certain depths. Bag filters are also available with plastic header frames, which are lighter in weight making them easier to transport, non-corrosive in a moist environment and generally easier to install. 
     The background art includes many different types of filter apparatus and bag filters for air filtration. For example, U.S. Patent Pub. No. 2004/0163370, filed in the name of Haufe et al., discloses a filter grid array having an air filter media removably mounted in a rigid frame. The filter media includes closed end pockets opposing the frontal opening and the frontal opening having an outer edge defining a circumference conforming to the circumference of the central opening of the rigid frame. The rigid frame includes a retaining ring, which secures the filter media to the frame, and a rod member for mounting the filter bag to the frame. The filter bag comprises a layer of non-woven synthetic fibers, however, other suitable filter media material may be employed. 
     U.S. Pat. No. 6,755,879, issued to Watvedt, describes a filter device wherein the filter element adsorbs or traps particles of liquid from the gas flow due to gravity wherein the particles are collected in a bottom portion. The filter device is a bag filter and formed of a synthetic material or a non-woven material having a coating of a water-repellent material on the surface of the fabric. Watvedt is primarily concerned with providing means necessary to collect liquid particles within the bottom or lower portion of the bag filter. 
     U.S. Pat. No. 5,215,609, issued to Sanders, relates to a pocket type unit filter with a frame inserted into the pocket produced with select pocket seams thereof being ultrasonically welded during a continuous automated manufacturing process. Sanders also describes amorphous network of polyester fibers and ultrasonic welding method for forming and manufacturing bag filters. 
     There are many problems associated with prior bag filters. For example, since they are assembled from at least 15 to 20 parts, more parts mean lesser integrity and greater assembly time and piece part price, and more chance for mistakes in the manufacturing process. Significant labor savings and increased integrity can be realized by eliminating costs associated with machining, cutting, screwing and clean-up operations following the machining and cutting steps. 
     What is needed is a bag filter assembly that consolidates the number of parts from al least 15 to 20 parts to 1 part and that eliminates costs associated with the machining and cutting of the bag filter assembly. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a bag filter assembly. In one embodiment, the bag filter assembly includes a filter header; filter media; and a plurality of cover strips and one or more living hinges, coupled to the header, for holding pockets of the media. The header, the cover strips and the living hinges are injection molded as a single part from a plastic material. In another embodiment, the cover strips and the living hinges form one or more pocket rings, coupled to the header, for keeping the media open. An adhesive is applied to the header. 
     The media comprises one of the following: fiberglass and synthetic media. In one embodiment, the media is a polypropylene lofted microfiber. The plurality of cover strips comprises between about 6 and about 10 cover strips. 
     The filter assembly may be formed using any injection molding technique, equipment and/or machine known in the art. 
     In another embodiment, a method of fabricating a bag filter assembly is disclosed. The method comprises providing a filter header and fixing a plurality of cover strips and one or more living hinges to the header; wherein the fixing comprises injection molding the header, the cover strips and the living hinges as a single piece of molded plastic. The method also comprises coupling filter media to the single piece. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a plan view of a bag filter assembly, in accordance with one embodiment of the present invention. 
         FIG. 2  shows a partial perspective view of bag filter assembly, in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  describes a bag filter assembly  100  for air filtration that is injection molded as a single one-piece unit from a plastic material, in accordance with one embodiment of the present invention. The filter assembly  100  includes a header (or header frame)  105 , a plurality of cover strips  110  and living hinges  140 . The cover strips  110  hold pockets of filter media (not shown) with the living hinges  140  and eliminate any dust bypass between pockets of the media. In one embodiment, the cover strips comprise between 6 and 10 cover strips. The bag filter assembly  100  may be formed using any injection molding technique, equipment and/or machine known in the art. 
     An adhesive is applied to the periphery of the header  105  and, optionally, along the opening of each of the pockets of the media. This ensures that the pockets will not blow out or pull away from the header  105 . In one embodiment, the cover strips  110  and the living hinges  140  forms a retainer ring  120 , which holds and keeps the media open. The living hinges  140  snap the media to the cover strips. The header  105  or holding frame may be of any suitable type, e.g. for front, rear or side withdrawal mounting. 
     Any media, including any number or combination of materials, can be inserted or used in the filter assembly  100 . For example, materials of dimensionally planned, spun or chopped glass fibers or synthetic, or natural fiber materials can be employed. In one embodiment, a fibrous material of a pre-selected mixture by weight and number of glass and synthetic fiber material can be employed. In some embodiments, ultra-fine fiberglass or synthetic media pockets are attached to the header  105 . In other embodiments, dual denier polyester in 1 or 2 ply can be used. In another embodiment, the media is polypropylene lofted microfiber. The material may be treated, e.g. with an antimicrobial agent to resist microbial mould growth and build up of moulds or mildews. 
     The header  105 , cover strips  110  and living hinges  140  are made of a plastic material and, in one embodiment, are made of the same material and are integrally formed in one piece by plastic injection molding. The plastic or thermoplastic material used for manufacturing the assembly  100  is at least one of the following: polystyrene, acrylonitrile butadiene styrene, polyamide, polypropylene, polyethylene, and polyvinyl chloride or PVC. Plastics reinforced with short fibers can also be injection molded. 
     The bag filter assembly  100  of the present invention allows inexpensive production of large quantities, while consolidating the number of parts from about 15 to 20 parts to 1 part. This decreases the piece part price while also decreases the labor costs involved. 
       FIG. 2  describes a bag filter assembly  200  that is injection molded as a single one-piece unit from a plastic material, in accordance with one embodiment of the present invention. The filter assembly  200  includes a header  205 , a plurality of cover strips  210  and living hinges  250 . The header  205 , the cover strips  210  and the living hinges  250  are made of a plastic material and are made of a plastic injection-molded part. The living hinges  250  snap the filter media (not shown) to the cover strips  210 . In one embodiment, the header  205 , the cover strips  210  and the living hinges  250  are made of the same plastic material. In another embodiment, the cover strips  210  and the living hinges  250  forms a retainer ring  220 . 
     In another embodiment, the present invention includes a method of fabricating a bag filter assembly. The method includes providing a filter header; fixing a plurality of covers strips and one or more living hinges to the header; wherein the fixing comprises injection molding the header; the cover strips and the living hinges as a single piece of molded plastic; and coupling filter media to the single piece. 
     The bag filter assembly of the present invention consolidates the number of parts from at least 15 to 20 parts to 1 part and eliminates costs associated with the machining and cutting of the bag filter assembly. Fewer parts mean greater integrity and lower assembly time and piece part price, and less chance for mistakes in the manufacturing process. Significant labor savings and increased integrity are realized by eliminating costs associated with machining, cutting, screwing and clean-up operations following the machining and cutting steps. 
     The present invention has been described in terms of specific embodiments incorporating details to facilitate the understanding of principles of construction and operation of the invention. Such reference herein to specific embodiments and details thereof is not intended to limit the scope of the claims appended hereto. It will be apparent to those skilled in the art that modification may be made in the embodiments chosen for illustration without departing from the spirit and scope of the invention