| 摘要 |
<p>The present invention relates to apparatus for performing operations on a web of material (4) including a frame (1), an operating mechanism (2, 3) mounted on the frame for performing operations on the web of material, and a web feeding mechanism (6, 7, 23, 24) for feeding the web past the operating mechanism so that operations can be performed on the web by the operating mechanism. The web feeding mechanism comprises forward feed apparatus (6, 7) for feeding the web in a forward direction past the operating mechanism and mounted on the frame downstream of the operating mechanism relative to the direction of forward feed of the web, and web tensioning apparatus. The web tensioning apparatus includes at least one pair of pressure wheels (23, 24) rotatably mounted on the frame upstream of the operating mechanism relative to the direction of forward feed of the web, so that the pressure wheels abut against opposite surfaces of a web being fed by the forward feed apparatus, whereby movement of said web causes rotation of the pressure wheels, and means (33) for restricting the rotation of at least one of the pressure wheels. The pressure wheels exert a retarding force on a web being fed between the pressure wheels and thereby tension the web as it passes the operating mechanism.
<??>In accordance with the invention each of the pressure wheels (23, 24) is flexible in the axial direction so as to permit lateral movement, in the axial direction relative to the pressure wheels, of a web being fed between the pressure wheels, whereby alignment relative to the operating mechanism (2, 3) of a web (4) being fed by the forward feed apparatus (6,7) is controlled wholly by the forward feed apparatus. </p> |
