A ribbon supply shaft drive motor ( 8 ) and a ribbon take-up shaft drive motor ( 10 ) are drivingly controlled separately. If the state of a ribbon is not changed after a control cycle is repeated for a set time, the rotational speed of the drive motors ( 8, 10 ) is increased step by step.
1. A printer comprising:
a thermal head which transfers ink applied to an ink ribbon onto a recording medium, thereby printing print data,
a platen which is located opposite the thermal head and conveys the ink ribbon and the recording medium between the platen and the thermal head,
a ribbon supply shaft which supports an ink ribbon supply roll,
a ribbon take-up shaft, which supports an ink ribbon take-up roll, and on which the ink ribbon is wound up after printing,
a stepping motor for a ribbon take-up shaft drive which drives the ribbon take-up shaft,
a tension arm located in a ribbon path between the thermal head and the ribbon take-up shaft in a manner such that the tension arm is urged in a loosening direction of the ribbon, and
a detector for detecting a displacement of the tension arm, in which the stepping motor for the ribbon take-up shaft drive is stopped or driven according to an output of the detector,
wherein if the detector determines that the ink ribbon is loose, the stepping motor for the ribbon take-up shaft drive is initially driven at a
predetermined speed,
if the detector determines that the ink ribbon remains loose after a first predetermined time interval starting from the start of the stepping motor, the stepping motor continues operating at current stepping motor speed,
if the detector determines that the ink ribbon remains loose after a second predetermined time interval starting from the start of the stepping motor, the speed of the stepping motor is increased,
alternatively, if the detector determines that the ink ribbon is in tension, the stepping motor is stopped until the detector next determines that the ink ribbon is loose.
2. The printer according to claim 1 , wherein control for increasing the drive speed of the stepping motor for the ribbon take-up shaft drive is repeated step by step.
3. The printer according to claim 2 , wherein if the output of the detector has not changed even though set step-by-step control for increasing the drive speed of the stepping motor for ribbon take-up shaft drive is repeated predetermined number of times, then a drive of said platen is stopped.
4. A printer comprising
a thermal head which transfers ink applied to an ink ribbon onto a recording medium, thereby printing print data,
a platen which is located opposite the thermal head and conveys the ink ribbon and the recording medium between the platen and the thermal head,
a ribbon supply shaft, which supports an ink ribbon supply roll, and on which the ink ribbon is wound,
a stepping motor for a ribbon supply shaft drive which drives the ribbon supply shaft,
a ribbon take-up shaft, which supports an ink ribbon take-up roll, and on which the ink ribbon is wound up after printing,
a stepping motor for a ribbon take-up shaft drive which drives the ribbon take-up shaft,
tension arms respectively located in a ribbon path between the ribbon supply shaft and the thermal head and in a ribbon path between the thermal head and the ribbon take-up shaft in a manner such that the tension arms are urged in a loosening direction of the ribbon, and
detectors for detecting a displacement of the tension arms, in which the stepping motor for the ribbon supply shaft drive and the stepping motor for the ribbon take-up shaft drive are stopped or driven according to an output of the detectors,
wherein the stepping motor for the ribbon supply shaft drive and the stepping motor for the ribbon take-up shaft drive are driven at
respective predetermined speeds, when the respective stepping motors start, and
during a predetermined time interval starting from the start of the stepping motor for the ribbon supply shaft drive or the start of the stepping motor for the ribbon take-up shaft drive, the detectors corresponding to each stepping motor produce an output, and the outputs of the detectors are monitored to determine whether the output of either detector changes during the predetermined time interval, and
if it is determined that the output of either one of the detectors has not changed during the predetermined time interval, then the stepping motor for the ribbon supply shaft drive and stepping motor for the ribbon take-up shaft drive are driven at speeds obtained by adding their respective predetermined speed to a respective predetermined speed increment, but if it is determined that the output of either one of said detectors has changed then the corresponding motor is stopped.
5. The printer according to claim 4 , wherein control for increasing the drive speed of the stepping motor for the ribbon supply shaft drive and the stepping motor for the ribbon take-up shaft drive is repeated step by step.
6. The printer according to claim 5 , wherein if the output of any one of the detectors has not changed even though set step-by-step control for increasing the drive speed of the stepping motor for ribbon supply shaft drive or the stepping motor for ribbon take-shaft drive is repeated predetermined number of times, then a drive of said platen is stopped.