Patent ID: 6966474

Claim:
A web accumulator comprising: first and second sets of rotatably mounted web rollers, each of said web rollers being partially wrapped by a web when looped alternately from a web roller of said first set to a web roller of said second set in consecutive order, said second set of web rollers being mounted for movement relative to said first set of web rollers; a flexible drive element separate from the web for rotating each web roller at approximately the speed of a web portion in contact with it when discharging web from said accumulator and when accumulating web in said accumulator; driving apparatus for driving two of an input web roller, an output web roller and movement of said second set of web rollers relative to said first set of web rollers; and a controller for controlling said driving apparatus to decouple said input web roller and said output web roller, wherein said driving apparatus comprises a first servomotor driving said input web roller and a second servomotor driving said output web roller, wherein said controller comprises a torque feed-forward control system, wherein said torque feed-forward control system provides a proportional, additive, torque command to said second servomotor corresponding to each change in a torque command of said first servomotor, whereby said torque command to said second servomotor will effectively cancel a torque disturbance experienced by said second servomotor through mechanical coupling to said first servomotor.