| 摘要 |
PURPOSE:To prevent the deformation or breakage of a ribbon guide by feeding a ribbon at an optimum constant speed, by a method wherein the ribbon is fed by driving a spool by a motor and an outer diameter detection lever is cooperated with the change in a ribbon wind-up diameter to output an electric signal while the number of rotations of the motor is controlled on the basis of said signal. CONSTITUTION:When the movement of a carrier 1 and the printing operation by a printing head 4 are continuously performed, a printing ribbon 12 is wound up by a spool 7 and the outer diameter thereof gradually becomes large. With the increase of the outer diameter, the outer diameter detection lever 13 contacted with the outer periphery of the ribbon 12 under pressure is revolved toward the outside of the spool 7 and the resistance value between one terminal of a resistor 16a and a conductor 16b gradually reduces and, therefore, voltage therebetween also gradually reduces. Hereupon, the input voltage P3 to an amplifier 28 is reduced and output voltage V2 also reduces. Because the output voltage V1 from a flip-flop 27 is held to a constant value, the output voltage V3 from an amplifier 30 is reduced and the rotary speed of a motor 21 is gradually lowered. As a result, the feed speed of the ribbon 12 is kept constant. |
