Flutter suppression air foils

A non-contact apparatus for reducing flutter of a web in an open draw caused, in part, by cross-machine-direction and machine-direction components of flowing air, whereby said flutter includes an amplitude and frequency, said apparatus comprising:

• a pair of air foils disposed proximate to a pair of opposing planar surfaces of said web, each of said air foils having first and second integral convex surfaces facing said web and disposed in contact with said flowing air;
• said first convex surfaces forming a first venturi structure having a first wide gap portion and a first narrow gap portion, said wide gap portion disposed for receiving said cross-machine direction component of said flowing air and said first narrow gap portion disposed proximate to an edge of said web;
• said second integral convex surfaces forming a second venturi structure having a second wide gap portion and a second narrow gap portion, said second wide gap portion disposed for receiving the machine-direction component of said flowing air.

A non-contact method for reducing at least an amplitude of flutter of a moving web caused, in part, by flowing air over the surface of said web in an open draw, said method comprising:

• disposing a pair of air foils proximate to a pair of opposing planar surfaces of said web, each of said air foils having at least a first convex surface facing said web and disposed in contact with said flowing air;
• producing a venturi effect with said air foils, said venturi effect causing a reduction of said flutter amplitude in said open draw.

A non-contact apparatus for reducing web flutter caused, in part, by air flowing along the surface of a web in an open draw, wherein said web has a moisture content whereby said flutter includes an amplitude and frequency, said apparatus comprising:

• a pair of air foils disposed proximate to a pair of opposing planar surfaces of said web, each of said air foils having at least a first convex surface facing said web and disposed in contact with said flowing air for producing a venturi effect for reducing at least said flutter amplitude in said open draw;
• at least one of said air foils comprising reduction means for reducing said moisture content of said web.

A non-contact apparatus for reducing flutter caused, in part, by air flowing along the surface of a web in an open draw, whereby said flutter includes an amplitude and frequency, said apparatus comprising:

• a pair of air foils disposed proximate to a pair of opposing planar surfaces of said web, each of said air foils having at least a first convex surface facing said web and disposed in contact with said flowing air for producing a venturi effect for reducing at least said flutter amplitude in said open draw.