VIBRATION CONTROL APPARATUS AND METHOD FOR CALENDER ROLLS AND THELIKE

A vibration control apparatus (20) and method for a calender (18) for controlling vibration between two or more rolls (ex. 22, 24) which controls vibration induced thickness variations in a medium (27) exiting from the nip. The apparatus (20) includes a frame (19), a first and second rolls (22, 24) mounted relative to the frame (19), and a force generator (32), such as an electromechanical active actuator, servo-hydraulic actuator, controllable semi-active damper, Active Vibration Absorber (AVA), or Adaptive Tuned Vibration Absorber (ATVA), provides cancelling forces to control vibration between the first and second roll (22, 24) thereby, controlling such vibration induced thickness variations in the medium (27). Preferably, the apparatus (20) includes at least one sensor (ex. 42, 42', 42", 42'") for providing a signal representative of a vibration condition of at least one of the first or second roll (22, 24), and preferably both, and a digital controller (50) for processing the signal representative of said vibration condition preferably according to a feed-forward-type control and providing a control signal to a force generator (32). Vertical and/or lateral vibration of the rolls (22, 24) may controlled simultaneously. Likewise, fundamental vibrational frequencies and their harmonics may be controlled individually, or in combination.