Air shoe with roller providing lateral constraint

1. A web-guiding system for guiding a web of media travelling from upstream to downstream along a transport path in an in-track direction, the web of media having a first side and an opposing second side, comprising:

a fixed web-guiding structure having a convex exterior surface, wherein a pattern of air holes are formed through the exterior surface;

an air source for providing an air flow through the air holes; and

a web-guiding roller located in proximity to the web-guiding structure, the web-guiding roller being rotatable around a roller axis;

wherein the web of media travels around the web-guiding roller with the web of media contacting an exterior surface of the web-guiding roller through a wrap angle of less than 5 degrees,

wherein the web of media travels around the fixed web-guiding structure through a wrap angle of more than 10 degrees, the air flow through the air holes lifting the web of media away from the web-guiding structure such that the first side of the web of media is substantially not in contact with the web-guiding structure;

wherein a distance along the transport path between the web-guiding roller and the fixed web-guiding structure is less than 10% of a cross-track width of the fixed web-guiding structure; and

wherein the web-guiding roller has a width in the direction of the roller axis which is less than 20% of a cross-track width of the fixed web-guiding structure.

2. The web-guiding system of claim 1 wherein a distance that the web of media travels along the transport path between the web-guiding roller and the fixed web-guiding structure is less than two diameters of the web-guiding roller.

3. The web-guiding system of claim 1 wherein the web-guiding roller includes one or more grooves formed around the exterior surface of the web-guiding roller.

4. The web-guiding system of claim 3 further including a roller air source for providing an air flow into one or more of the grooves in a direction substantially parallel to the in-track direction of the receiver media and to the grooves, the air flow being directed between the web of media and the exterior surface of the web-guiding roller thereby producing a Bernoulli force to draw the web of media toward the exterior surface of the web-guiding roller thereby increasing a traction between the web of media and the web-guiding roller.

5. The web-guiding system of claim 1 wherein the web-guiding roller and the fixed web-guiding structure are both on the same side of the web of media such that the first side of the web of media contacts the exterior surface of the web-guiding roller.

6. The web-guiding system of claim 1 further including a tensioning mechanism that provides a force on the web-guiding roller to push it toward the web of media.

7. The web-guiding system of claim 1 wherein the web-guiding roller is mounted to the fixed web-guiding structure.

8. The web-guiding system of claim 1 wherein the web-guiding roller is a first web-guiding roller which rotates around a first roller axis, and further including a second web-guiding roller located in proximity to the web-guiding structure, the second web-guiding roller being rotatable around a second roller axis, wherein the web of media travels around the second web-guiding roller with the web of media contacting the second web-guiding roller through a wrap angle of less than 5 degrees.

9. The web-guiding system of claim 8 wherein the first and second web-guiding rollers and the fixed web-guiding structure are all on the same side of the web of media such that the first side of the web of media contacts the exterior surface of the first and second web-guiding rollers.

10. The web-guiding system of claim 8 wherein the first web-guiding roller is located upstream of the fixed web-guiding structure and the second web-guiding roller is located downstream of the fixed web-guiding structure.

11. The web-guiding system of claim 1 further including an air flow control mechanism for controlling which air holes the air flow is provided through in accordance with a width of the web of media.

12. The web-guiding system of claim 11 wherein the air flow control mechanism includes one or more fixed walls internal to the fixed web-guiding structure which define a plurality of air chambers with independently controllable air supplies.

13. The web-guiding system of claim 11 wherein the air flow control mechanism includes one or more moveable walls internal to the fixed web-guiding structure which define an internal air chamber corresponding to the air holes through which the air flow is provided.

14. The web-guiding system of claim 11 wherein the air flow control mechanism includes one or more louvers positioned internal to the fixed web-guiding structure which are repositionable to cover different sets of air holes, thereby blocking air flow through the covered air holes.

15. The web-guiding system of claim 1 wherein the fixed web-guiding structure is a turn-bar which is used to turn over the receiver media.

16. The web-guiding system of claim 15 wherein the turn-bar is oriented at an oblique angle relative to the initial in-track direction of the web of media.

17. The web-guiding system of claim 1 wherein the roller axis of the web-guiding roller is substantially perpendicular to the in-track direction of the receiver media at the location along the transport path where the web of media contacts the web-guiding roller.

18. The web-guiding system of claim 1 further including an air conditioning subsystem to condition the air provided by the air source.

19. The web-guiding system of claim 1 further including a roller control mechanism for adjusting an orientation of the roller axis relative to the in-track direction of the web of media, thereby providing a steering force on the web of media.

20. A web-guiding system for guiding a web of media travelling from upstream to downstream along a transport path in an in-track direction, the web of media having a first side and an opposing second side, comprising:

a fixed web-guiding structure having a convex exterior surface, wherein a pattern of air holes are formed through the exterior surface;

an air source for providing an air flow through the air holes;

a first web-guiding roller located in proximity to the web-guiding structure, the first web-guiding roller being rotatable around a first roller axis, wherein the web of media travels around the first web-guiding roller with the web of media contacting an exterior surface of the web-guiding roller through a wrap angle of less than 5 degrees; and

a second web-guiding roller located in proximity to the web-guiding structure, the second web-guiding roller being rotatable around a second roller axis, wherein the web of media travels around the second web-guiding roller with the web of media contacting the second web guiding roller through a wrap angle of less than 5 degrees;

wherein the web of media travels around the fixed web-guiding structure through a wrap angle of more than 10 degrees, the air flow through the air holes lifting the web of media away from the web-guiding structure such that the first side of the web of media is substantially not in contact with the web-guiding structure;

wherein the first web-guiding roller is located upstream of the fixed web-guiding structure and the second web-guiding roller is located downstream of the fixed web-guiding structure; and

wherein the first and second web-guiding rollers are recessed into the fixed web-guiding structure and are positioned to limit the air flow provided through the air holes from exiting a region between the fixed web-guiding structure and the web-of media in an upstream or downstream direction.

21. The web-guiding system of claim 20 wherein a gap between the fixed web-guiding structure and the first and second web-guiding rollers is less than 0.01 inches around at least 20% of the circumference of the first and second web-guiding rollers.

22. A web-guiding system for guiding a web of media travelling from upstream to downstream along a transport path in an in-track direction, the web of media having a first side and an opposing second side, comprising:

a fixed web-guiding structure having a convex exterior surface, wherein a pattern of air holes are formed through the exterior surface;

an air source for providing an air flow through the air holes; and

a web-guiding roller located in proximity to the web-guiding structure, the web-guiding roller being rotatable around a roller axis;

wherein the web of media travels around the web-guiding roller with the web of media contacting an exterior surface of the web-guiding roller through a wrap angle of less than 5 degrees, and

wherein the web of media travels around the fixed web-guiding structure through a wrap angle of more than 10 degrees, the air flow through the air holes lifting the web of media away from the web-guiding structure such that the first side of the web of media is substantially not in contact with the web-guiding structure; and

wherein a portion of the exterior surface of the web-guiding roller protrudes through an opening in the fixed web-guiding structure.

23. The web-guiding system of claim 22 wherein the opening in the fixed web-guiding structure is centrally-located in a cross-track direction.