Patent ID: 7436418

Claim:
A thermal printer for printing to a print medium at a controlled print speed comprising: a print head; a paper feed mechanism for conveying the print medium passed the print head at the controlled print speed; a print speed change acquisition unit for establishing the print speed of the paper feed mechanism in a first predetermined time period and for determining the degree of change in the print speed during said first predetermined time period; an evaluation unit for determining if the change in print speed during said first predetermined time period exceeds a predetermined threshold value; and a print speed control unit for controlling the print speed of the paper feed mechanism in response to said evaluation unit based upon speed control factors including at least one or more parameters selected from the group consisting of: the print duty, the temperature of the print head, the printing pattern, the energizing voltage applied to the print head, the print data communication speed and the time required for internal data processing and wherein the print speed control unit limits change in the print speed based on the print speed control factor(s) used for controlling print speed for a second predetermined time period after the evaluation unit determines that the change in print speed exceeds the threshold value.