The present invention relates to air filters, and particularly to disc-type air filters for filtering air with respect to dust or other particles within the air or other gases.
The term “air filters” as used herein is intended to include filters not only for air, but also for other gases.
U.S. Pat. No. 5,797,978, and International Patent Application PCT/ILOO/00351, published Dec. 28, 2000 as International Publication No. WO 00/78428, disclose an air filter comprising a housing having an air inlet, an air outlet, and a stack of filter discs within the housing for removing solid particles from the air passing from the inlet to the outlet. The filter discs in the stack are formed with contacting faces having surface formations defining filtering passageways between adjacent discs for removing solid particles from the air passing through the stack of filter discs. The filter discs in the stack include electrodes spaced from each other axially of the stack and connectable to a voltage source for producing an electrical field attracting solid particles towards the discs to thereby enhance removal of the solid particles from the air passing through the stack of filter discs.
The above-identified US Patent and International Patent Application, the contents of which are hereby incorporated by reference, describe many of the advantages of such an air filter construction.
In the embodiments of air filter constructions described in the above-identified US Patent and International Patent Application, each of the filter discs is of a composite construction, including an electrode layer embedded between two insulating layers. The insulating layers serve as the outer faces of the filter discs and include the surface formations defining the filtering passageways between adjacent discs, while the electrode layers in each filter disc, when connected to a voltage source, produce the electrical field attracting solid particles towards the disc.
The composite disc construction utilized in the filters described in the above-identified US Patent and International Patent Application requires insulating layers on both sides of each disc which definitely increase the thickness of the discs. This limits the number of discs that can be packed in certain dimensions of the filter and accordingly the total filtering passageways that can be provided for the same filter volume. It also limits the amount of dirt particles that can be retained within the filter stack before cleaning or replacing the filter is required. In addition, implementation of the electrode layer in the injection process of the disc has a considerable cost impact which makes the composite disc more expensive to produce and thereby increases the manufacturing cost of such air filters.