Apparatus and method for non-contact active tensioning and steering of moving webs

Apparatus for conveying a web, comprising:

• a) a machine frame;
• b) a source of web material having first and second sides, said web material passing along said machine frame;
• c) a first air bar having a first substantially cylindrical surface and a first axis, and being pivotably disposed on said machine frame, said first web side being wrapped at least partially along said first cylindrical surface through a first wrap angle;
• d) a second air bar having a second substantially cylindrical surface and a second axis, said second air bar being spaced apart from said first air bar and said second axis being parallel to said first axis, and being pivotably disposed on said machine frame, said second web side being wrapped at least partially along said second cylindrical surface through a second wrap angle;
• e) means for pivoting said first and second air bars in fixed relative relationship about a third axis parallel to and between said first and second axes, to tension said web through said apparatus;
• and
• f) means for drawing said web through said apparatus.

Apparatus for conveying a web, comprising:

• a) a machine frame;
• b) a source of web material having first and second sides, said web material passing along said machine frame;
• c) a first air bar having a first substantially cylindrical surface and a first axis, said first web side being wrapped at least partially along said first air bar surface through a first wrap angle;
• d) a second air bar having a second substantially cylindrical surface and a second axis, said second web side being wrapped at least partially along said second air bar surface through a second wrap angle;
• e) a supporting frame disposed on said machine frame for supporting said first and second air bars in fixed relationship with said first and second axes spaced apart and substantially parallel;
• f) means for controllably pivoting said supporting frame about a third axis substantially parallel to and between said first and second axes to tension said web through said apparatus;
• g) means for controllably pivoting said supporting frame about a fourth axis orthogonal to said third axis and intersecting said third axis between said first and second axes, to steer said web;
• h) first and second fixed air bars having substantially cylindrical surfaces in the web path between said first and second pivotable air bars and being fixedly mounted on said machine frame on opposite sides respectively of the plane through said first and second axes, said second web side being wrapped at least partially along said first fixed air bar cylindrical surface and said first web side being wrapped at least partially along said second fixed air bar cylindrical surface, to provide values of each of said first and second wrap angles between 30 and 210 degrees;
• and
• i) means for drawing said web through said apparatus.

In an apparatus for conveying web having first and second sides, a method for steering and tensioning said web comprising the steps of:

• a) partially wrapping said web along the first and second surfaces, respectively, of first and second spaced apart air bars having first and second axes, respectively, said first side of said web facing said first surface and said second side of said web facing said second surface, said air bars being fixed in relation to one another with said first and second axes being parallel, said pair of air bars being adapted to be controllably rotated about a third axis substantially parallel to and between said first and second axes and simultaneously about a fourth axis orthogonal to said third axis and substantially parallel to or within a plane through said first and second axes;
• b) driving said web through said apparatus;
• c) controllably rotating said pair of air bars about said fourth axis to steer said driven web to a new lateral position;
• and
• d) controllably rotating said pair of air bars about said third axis to change the web path length to maintain tension in the web.

Apparatus for tensioning and steering a moving web having first and second sides without contact between the web and the apparatus, comprising:

• a) a first pivotable air bar having a first substantially cylindrical surface and a first axis, said first web side being wrapped at least partially along said first cylindrical surface through a first wrap angle;
• b) a second pivotable air bar spaced apart from said first air bar, having a second substantially cylindrical surface and a second axis parallel with said first axis, said web having a path between said first and second air bars causing said second web side to be wrapped at least partially along said second cylindrical surface through a second wrap angle;
• and
• c) means for simultaneously and controllably pivoting said first and second air bars together about a third axis parallel to and between said first and second axes to tension said web and about a fourth axis orthogonal to said third axis to steer said web.