Ribbon Feed Motor Backcheck Mechanism
Original Publication Date: 1985-Apr-01
Included in the Prior Art Database: 2005-Feb-18
A backcheck mechanism is applied to an output shaft of a ribbon feed motor, which is a four-phase, permanent-magnet stepper motor, to prevent the shaft from turning in the reverse direction when the motor is turned off, which occurs because ribbon lift and index motors are driven from the same drive as the ribbon feed motor and the motors must operate sequentially. The backcheck mechanism eliminates overstrike on the ribbon which has been caused by the ribbon feed motor backing up when it is turned off. A backcheck mechanism includes a backcheck cam 1, which is pivotally mounted on a post 2. A spring 3 urges a cam surface 4 of the cam 1 into engagement with a hub 5, which is fixed to an output shaft 6 of the stepper motor. The cam surface 4 has the center for its radius R1 offset from the pivot of the post 2 by a distance e.