Filter and forming system

1. Forming apparatus for forming a filter, said 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 and defining axial flow channels, said flow channels having a lateral cross-sectional shape comprising two adjacent included angles each greater than 45° and less than 75°, said forming apparatus comprising first and second star gears each having a plurality of teeth interdigitated with a plurality of roots therebetween, said gears rotating in intermeshed relation with the tooth of one gear in the root of the other gear, said gears passing said second sheet therebetween, said gears gathering and folding said second sheet along crease lines at said pleat tips, said crease lines providing said axially extending bend lines, wherein each said tooth has an outer end and a pair of convexly bowed sides extending from said outer end generally radially inwardly to respective roots spaced on opposite sides of the tooth.

2. Forming apparatus for forming a filter, said 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 and defining axial flow channels, said flow channels having a lateral cross-sectional shape comprising two adjacent included angles each greater than 45° and less than 75°, said forming apparatus comprising first and second star gears each having a plurality of teeth interdigitated with a plurality of roots therebetween, said gears rotating in intermeshed relation with the tooth of one gear in the root of the other gear, said gears passing said second sheet therebetween, said gears gathering and folding said second sheet along crease lines at said pleat tips, said crease lines providing said axially extending bend lines, and comprising a pair of parallel guide bars spaced on opposite sides of the intermeshing of said gears, said bars extending parallel to the direction of travel of said second sheet through said gears, said bars being spaced from each other by a gap less than 10 mm along a direction perpendicular to said travel direction and perpendicular to the gear rotation axis, said bars receiving said pleats and engaging said pleat tips.

3. The forming apparatus according to claim 2 wherein said second sheet is fed forwardly through said gears from an inlet region to an outlet region, said guide bars have upstream ends at said gears, and downstream ends at said outlet region and spaced from said gears.

4. The forming apparatus according to claim 3 wherein said gears rotate about respective rotation axes, and said upstream ends of said guide bars are upstream of said rotation axes.

5. A method of configuring and shaping a filter, said filter comprising first and second sheets of filter material, 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 and defining axial flow channels, said flow channels having a lateral cross-sectional shape comprising two adjacent included angles each greater than 45° and less than 75°, said method comprising feeding said second sheet through first and second star gears each having a plurality of teeth interdigitated with a plurality of roots therebetween, rotating said gears in intermeshed relation with the tooth of one gear in the root of the other gear, gathering and folding said second sheet through said gears along crease lines at said pleat tips, said crease lines providing said axially extending bend lines, and comprising feeding said second sheet through said gears to a pair of guide bars, spacing said guide bars on opposite sides of the intermeshing of said gears.

6. The method according to claim 5 comprising extending said guide bars parallel to the direction of travel of said second sheet through said gears, spacing said guide bars from each other by a gap less than 10 mm along a direction perpendicular to said travel direction and perpendicular to the gear rotation axis, and receiving said pleats and engaging said pleat tips with said guide bars.

7. The method according to claim 6 comprising feeding said second sheet forwardly through said gears from an inlet region to an outlet region, providing said guide bars with upstream ends at said gears, and downstream ends at said outlet region and spaced from said gears.