Fluted filter medium and process for its manufacture
A fluted filter medium ( 74 ) comprising a corrugated filter sheet, where each flute ( 120 ) has an end closure defined by a regular fold arrangement in the corresponding corrugation. Each regular fold arrangement has at least four folds. A process for manufacturing the fluted filter medium comprising deforming a portion of each corrugation to define at least one foldable tip, and folding the said tip in order to close the corrugation.
1. A fluted filter media construction comprising:
(a) a fluted sheet of filter media comprising a wave pattern of ridges and troughs;
(b) a facing sheet of filter media adhered to the fluted sheet and wherein the fluted sheet and the facing sheet form a plurality of flutes extending there between;
(c) sealant provided between the fluted sheet and the facing sheet;
(d) the plurality of flutes extending between the fluted sheet and the facing sheet comprises a center indented fold pattern that seals the plurality of flutes to the passage of unfiltered air, the center indented fold pattern comprising an indent in each flute, to be closed, at or near an apex of each flute that forms an indented flute portion and a pair of ridges comprising a first ridge and a second ridge, at least one of the first ridge or the second ridge comprising a fold in a direction toward the facing sheet, the center indented fold pattern comprising a flat first layer resulting from the indented flute portion secured to the facing sheet, and a second layer pressed against the flat first layer, the second layer comprising the at least one of the first ridge or the second ridge folded against the flat first layer.
2. A fluted filter media construction according to claim 1 , wherein the plurality of flutes extend from a first face to a second face, and the fold arrangement is provided at one of the first face or the second face.
3. A fluted filter media construction according to claim 2 , wherein the fluted sheet and the facing sheet are coiled into a coiled media structure.
4. A fluted filter media construction according to claim 3 , wherein the coiled media structure comprises the plurality of flutes having a center indenting fold pattern sealing the plurality of flutes to the passage of unfiltered air, and a second plurality of flutes comprising a sealant for sealing the second plurality of flutes to the passage of unfiltered air.
5. A fluted filter media construction according to claim 1 , wherein the fluted sheet of filter media comprises a regular, curved, wave pattern of flutes.
6. A fluted filter media construction according to claim 1 , wherein the flutes have a flute/flat ratio within the range of 1.2-2.0, inclusive.
7. A fluted filter media construction according to claim 1 , wherein:
(a) the fluted sheet and the facing sheet are positioned in a filter to define a set of inlet flutes and a set of outlet flutes extending between an inlet face and an outlet face;
(i) each inlet flute being closed to passage of unfiltered fluid there through, adjacent said outlet face; and
(ii) each outlet flute being closed, to passage of unfiltered fluid therein, adjacent said inlet face.
8. A fluted filter media construction according to claim 7 , wherein:
(b) each inlet flute is closed, by the regular fold arrangement, adjacent the outlet face.
9. A fluted filter media construction according to claim 1 , wherein the indented flute portion comprises an inverted ridge of the flute at its apex.
10. A fluted filter media construction according to claim 1 , wherein the indented flute portion is adhered to the facing sheet by the sealant.