Abstract: A web loop control system has first and second roller stations and a web loop disposed therebetween. A dancer arm is biased into engagement with the web loop to maintain tension therein. An optical code disk is secured for rotation with the dancer arm and an optical sensing means cooperates with the code disk to generate dancer arm position information which is relayed to the motor control system to maintain a desired web loop length during both drive and stop modes. The invention as applied to a printer for serialized forms utilizes the dancer arm code disc/optical sensing means combination to insure that a between-forms perforation is present at the fuser roller nip when the system is at rest. The serialized form printing system also provides for controlled acceleration and deceleration between operating speed and a dead stop within 3/8 inch of form length. Acceleration and deceleration are closely controlled to prevent jarring or excessive acceleration of the web loop.

Abstract: A ribbon drive and motor control system in which the instantaneous speed and torque output of a pair of motors are controlled interdependently to bidirectionally transfer ribbon or other web material between a pair of storage reels mechanically coupled to the motors at a uniform ribbon velocity and tension. The motors are electrically excited in series to rotate in the same direction with the back electromotive force of one motor being used to vary the instantaneous excitation voltage applied to the other motor, while drag from said other motor is imparted to the ribbon to control the speed of the first motor. Compensation for variation of the radii of ribbon on the reels during operation is accomplished automatically by variation of motor torque and velocity to minimize variation in ribbon tension and ribbon velocity. A bridge switch actuated by signals initiated by electrical contacts near the ends of the ribbon causes the motors to reverse direction.