| 摘要 |
<p>Apparatus and methods for tensioning and steering a moving web (11) in a conveyance machine without contact of the web to the machine by means of a pair of parallel air bars (19, 21) in a single moveable frame (35) which is adapted to pivot controllably about two intersecting orthogonal axes (29, 41) in a plane through the air bars. The tensioning and steering apparatus is preferably isolated in sensing and response from the rest of the conveyance machine by suction feed rollers (15, 17) upstream and downstream from apparatus of the invention. Separate feedback control systems monitor the tension and position of the web and adjust the orientation of the frame about each axis to adjust tension and lateral position of the web independently and continuously. Additional fixed air bars (31, 33) on opposite sides of the web in the web path between the moveable air bars provide high and unvarying web wrap angles on the moveable air bars to increase the tension and steering operating range and sensitivity. An additional moveable air bar (27) is provided downstream of the pair of moveable air bars and is adapted to pivot controllably about another axis (49) orthogonal to the direction of the tensioning and steering axes so that the axial direction (12, 47) of the moving web (11) can be changed. <MATH></p> |
