Importance

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Abstract

A continuous web of sheet material is fed through the lip of a first pair of driven pull rolls around a series of idler rollers and through the nip of a second pair of driven pull rolls. The pairs of pull rolls are selectively rotated to exert a desired tension on the web in a tension zone formed between the pairs of rolls. One pair of pull rolls operates as feed rolls to advance a preselected length of the web to a rotating cutter mechanism so that envelope blanks of a selected length are cut from the web for each revolution of the cutter mechanism. The feed rolls are operated by a servo-controlled motor responsive to an operator initiated signal to adjust the feed length without interrupting the feed of the web to the cutter mechanism. The second pair of pull rolls operates as tension rolls and is servo-motor controlled to maintain a preselected tension on the web fed to the cutter mechanism. The web in the tension zone is rotatably supported by idler rolls having load cells for generating a signal to a controller proportional to the tension applied to the web. Operator input through a keypad to the controller actuates the tension rolls at a gear ratio for generating a desired tension in the web. A deviation in the applied tension from the commanded tension actuates the servo-motor for the tension rolls to adjust the rotation thereof to restore the desired tension in the web.

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First Claim