PRINTING APPARATUS

PURPOSE:To keep tensile force at the time of taking-up almost constant regardless of the change in a take-up diameter, by setting the speed reducing ratio from the drive source in an ink film take-up apparatus and the transmission torque in a slip mechanism in a predetermined relation. CONSTITUTION:The drive gear 16 meshing with a rack 15 is rotated at an almost constant number of rotations regardless of the variation in printing load by the movement of a carriage 10 and decelerated through gears 17, 18 and a take-up gear 19 to transmit rotatory torque to a take-up reel 20 through a slip mechanism consisting of a reel spring 24, a slip material 25 and a reel table 26. Herein, the transmission torque T of the slip mechanism is calculated according to a formula T=FX(r1+r2) (wherein r2 is the max. radius of an ink ribbon 23, r1 is the min. radius thereof and F is objective tensile force) to set the force of the spring 24 and the area of the slip material. Further, a speed reducing ratio is set so as to become n1=n0Xr2/(r1+r2) on the basis of the take-up number of rotations n1 at the time of the min. radius r1 and take-up number of rotations n0 when no cassette 22 is mounted. By this method, tensile force can be kept almost constant and printing quality can be stabilized.