Category:Books by Ian TalbotIn many printing applications, including dye diffusion thermal transfer printing and lithography, a continuous web of paper or other print-receiving material is drawn from a supply roll or rolls past one or more printheads. In an ink-jet printing system, the printheads are usually mounted to a movable carriage that traverses the web along a bi-directional path defining the print zone. As the web is moved beneath the printheads, a predetermined amount of ink is applied to the web. In a printing process that includes multiple passes of the web past the printhead, ink is applied in each pass until the desired image is printed onto the web. During each pass, the web and printheads are advanced a desired distance and the image on the web is incrementally formed.
In one known configuration of a printing apparatus, the supply roll or rolls of paper or other print-receiving material are held on a supply spool. As the web is unwound from the supply spool, it is drawn over a roller located between the supply spool and the supply roll. The drive roller is known in the art as a take-up spool and is used to take-up the web as it is unwound from the supply spool. The take-up roller maintains tension on the web so that it does not slacken during the printing process. The web is drawn past the printing heads and then over a guide roller to prevent the web from wandering off-center. The guide roller also forms a desired starting position for the web as it is unwound from the supply roll.
FIG. 1 shows a conventional printing apparatus 100 that includes a take-up roller 102 for take-up purposes. The take-up roller 102 is disposed between a supply roll 106 and a supply spool 108. An intermediate roll 110 is disposed between the supply spool 108 and a take-up spool 102. The intermediate roll 110 takes up the slack in the web as it is unwound from the supply spool 108, while providing tension to the web so that the web is pulled tight between the supply spool 108 and the take-up spool 102. The take-up roll 102 maintains tension on the web by drawing the web onto the take-up spool 102. The take-up roll 102 has an adjustable speed so that the rate at which the web is pulled onto the take-up spool 102 is controlled in accordance 0b46394aab