Patent ID: 8608819

Claim:
An air filter device for filtration of gaseous fluids in internal combustion engines, comprising: a spirally wound filter element ( 1 ) including: a spirally rolled filter sheet ( 7 ) having first and second oppositely positioned axial end faces and provided with parallel extending flow channels ( 2 a , 2 b ) for the fluid extending between said end faces, said spirally rolled filter sheet having radially inwardly positioned windings and radially outwardly positioned windings; wherein said radially outwardly positioned windings have a different axial length than said radially inwardly positioned windings; wherein said flow channels of said filter element vary in length with said differing axial lengths of said radially outwardly positioned and said radially inwardly positioned windings; wherein neighboring flow channels of said parallel flow channels are alternatingly open or closed off at oppositely positioned axial end faces of said filter element; wherein said parallel flow channels in said rolled state end at different axial positions at one of said axial end faces of said filter element; wherein said filter element at said second end face is provided with a geometry deviating from that of said first end face; wherein all of said parallel extending flow channels at the second oppositely positioned end face of the filter element end are positioned in a common end face plane at identical axial positions; wherein said end face with said parallel extending flow channels ending at identical axial positions forms an inflow side and said oppositely positioned end face forms an outflow side ( 4 ) of said filter element; wherein said filter sheet ( 7 ) in the not-yet rolled spread-out state forms a generally trapezoidal shape with oppositely positioned parallel terminal edges ( 8 , 9 ) having different lengths; wherein said terminal edges ( 8 , 9 ) represent the start of rolling or the end of rolling of said filter element; wherein said second lateral edge ( 11 ) between the terminal edges ( 8 , 9 ) is curved.