Pleated filter element with tapering bend lines

A filter element having an upstream inlet and a downstream outlet and pleated along a plurality of bend lines, said bend lines extending axially along an axial direction and comprising a first set of bend lines extending from said upstream inlet axially towards said downstream outlet, and a second set of bend lines extending from said downstream outlet axially towards said upstream inlet, said filter element having a plurality of wall segments extending in serpentine manner between said bend lines, said wall segments extending axially and defining axial channels therebetween, said channels having a height along a transverse direction, said transverse direction being perpendicular to said axial direction, said channels having a lateral width along a lateral direction, said lateral direction being perpendicular to said axial direction and perpendicular to said transverse direction, at least some of said bend lines tapering in said transverse direction as they extend axially in said axial direction, said wall segments comprising a first set of wall segments alternately sealed to each other at said upstream inlet to define a first set of tetrahedron channels having open upstream ends, and a second set of tetrahedron channels interdigitated with said first set of tetrahedron channels and having closed upstream ends, said wall segments comprising a second set of wall segments alternately sealed to each other at said downstream outlet to define a third set of tetrahedron channels having closed downstream ends, and a fourth set of tetrahedron channels interdigitated with said third set of tetrahedron channels and having open downstream ends, said first set of bend lines comprising a first subset of bend lines defining said first set of tetrahedron channels, and a second subset of bend lines defining said second set of tetrahedron channels, said second subset of bend lines tapering in said transverse direction as they extend from said upstream inlet axially towards said downstream outlet, said second set of bend lines comprising a third subset of bend lines defining said third set of tetrahedron channels, and a fourth subset of bend lines defining said fourth set of tetrahedron channels, said fourth subset of bend lines tapering in said transverse direction as they extend from said downstream outlet axially towards said upstream inlet, wherein said wall segments extending in said serpentine manner define a laterally extending serpentine span comprising a first said wall segment laterally adjacent a second said wall segment and joined thereto by a first said bend line and continuing in said serpentine manner along said serpentine span to a third said wall segment laterally adjacent said second wall segment and joined thereto by a second said bend line, and so on along said serpentine span, wherein said serpentine span extends along said lateral direction, such that the taper of said bend lines tapering in said transverse direction is perpendicular to said serpentine span along said lateral direction.