Abstract: A filter element and a method for manufacturing the filter element is disclosed wherein filter paper is folded in a zigzag manner to form a filter material, and a circumferential portion of the filter material is fastened by an adhesive so as to fasten the zigzag filter material and to divide the filter material into a dust side and a clean side. Thus, the structure of the filter element is simplified and a filter performance is enhanced.

Abstract: An air filter element incudes a plurality of filter paper units each composed of a sheet of filter paper corrugated into a number of folds extending from one side to the other of the sheet, the filter paper units being arranged such that ridges of the folds extend on or parallel to radial lines extending radially outwardly from a center of the air cleaner element, and at least one connector interconnecting side edges of the filter paper units. With the air cleaner element incorporated in an air cleaner, air drawn into the air cleaner from an air inlet flows into a space above the air cleaner element, and then flows through the air cleaner element at a uniform speed over the entire area of the air cleaner element. Therefore, the air can uniformly be filtered, and the resistance to the air flow of the air cleaner element is reduced. The area of the air cleaner element which is open to the air flow is several times greater than the cross-sectional area of the air inlet.

Abstract: A filter medium comprises nonwoven fabric of a lower fiber density and filter paper of a higher fiber density, the nonwoven fabric and the filter paper being superposed in a laminated structure. The nonwoven fabric and the filter paper are disposed upstream and downstream, respectively, in a direction in which a fluid to be filtered flows. Since the nonwoven fabric of a lower density is disposed upstream and the filter paper of a higher density is disposed downstream, relatively large particles are trapped by the upstream nonwoven fabric to promote the formation of a dust cake layer on the surface of the filter paper. Such surface trapping may prevent the particles from being embedded within the filter medium, thus preventing the filter medium from being clogged therein.

Abstract: A filter medium for filtration of a fluid to flow therethrough from an upstream side to a downstream side thereof, said filter medium comprising a substrate having a density gradient wherein the density is high on the upstream side and low on the downstream side of the substrate.