Patent ID: 7258719

Claim:
A filter comprising first and second sheets of filter media, said second sheet having a plurality of pleats defined by wall segments extending in zig-zag manner between pleat tips at axially extending bend lines, the pleat tips on one side of said second sheet being in contiguous relation with said first sheet to define axial flow channels, said flow channels having a lateral cross-sectional shape comprising two adjacent included angles comprising a first angle between said first sheet and a first said wall segment of said second sheet, and a second angle between said first sheet and a second said wall segment of said second sheet, each of said first and second angles being greater than 45° and less than 75°, wherein said lateral cross-sectional shape of said flow channels consists of three pleat tips and three included angles, namely said first angle, said second angle, and a third angle between said first and second wall segments, wherein said lateral cross-sectional shape is an isosceles triangle and wherein 45 ⁢ ° < θ < 75 ⁢ ° 0.5 ⁢ ⁢ mm < 2 ⁢ b · sin ⁢ ⁢ 1 2 ⁢ ⁢ θ · cos ⁢ ⁢ 1 2 ⁢ ⁢ θ 1 + sin ⁢ ⁢ 1 2 ⁢ ⁢ θ < 2.9 ⁢ ⁢ mm where θ is said third angle between said first and second wall segments, and b is the length of each of said first and second wall segments.