Importance

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Abstract

A web drive cyclically moves a web a fixed distance. First and second spaced draw roll units include separate servo motors. Separate programmed controllers are connected to energize the servo drives with a time motion profile including acceleration and deceleration periods to move the web in a fixed time period. The one programmed controller generates the profile program each cycle during the execution of program to move the web the next cycle. The generated program is down-loaded to the second controller to duplicate energization of the second servo motor. A dancer unit between the drive rolls maintains the tension with a change in web length and includes a movable roll unit. A potentiometer sensor is coupled to the roll unit and establishes an output signal voltage proportional to the direction of the web change and to the length thereof. The second controller includes a drive modifying program connected to the sensor and responsive to the signal voltage to change the second drive profile for the second servo motor for the next succeeding web feed and compensates for the change in web length and move the web in accordance with the modified drive profile. The potentiometer sensor is disabled during a continuous or jog run and serves to hold the web tension.

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First Claim