Label sheet conveyance device and method of identifying seams between label sheets

A sheet seam determination method of a label conveyance device that conveys a label sheet having a plurality of labels arrayed with a gap therebetween on a sheet, and has a sensor that scans the label sheet and outputs a sensor output value, the sheet seam determination method comprising:

• determining a mode of sensor output values;
• determining a first sheet position in the label sheet conveyance direction where the sensor output value exceeds a first threshold value that is set according to the mode and used for detecting a part of the sheet between labels;
• determining a second sheet position in the label sheet conveyance direction where the sensor output value exceeds a second threshold value that is greater than the first threshold value and is used for detecting a hole in the label sheet;
• determining a third sheet position in the label sheet conveyance direction where the sensor output value becomes less than the second threshold value;
• determining a fourth sheet position in the label sheet conveyance direction that is less than the first threshold value;
• determining the center of a first interval from the first sheet position to the fourth sheet position is the position of a seam in the sheet between labels if the second sheet position and the third sheet position are not identified when the fourth sheet position is identified;
• and
• determining the center of a second interval from the second sheet position to the third sheet position is the position of a seam in the sheet between labels if the second sheet position and the third sheet position are identified when the fourth sheet position is identified.