Defect detecting device and bag making apparatus

A defect detecting device for detecting a defect in bag making and for use in a bag making apparatus that intermittently feeds a sheet panel having a web shape in a longitudinal direction of the sheet panel,

• the defect detecting device comprising a detection unit,
• the detection unit comprising:
• a support;
• an arm supported by the support swingably around a swing shaft;
• and
• a sensor for detecting a displacement of the arm relative to the support,
• the arm comprising a first contactor and a second contactor that are spaced at a predetermined angular distance from each other around the swing shaft,
• the defect detecting device further comprising a movement mechanism for moving the detection unit between a first position where the first and second contactors are away from a feed plane for the sheet panel and a second position where the first and second contactors reach the feed plane, the movement mechanism being configured to, during a feed phase of the sheet panel, keep the detection unit located at the first position, and to, during a pause phase of the sheet panel, move the detection unit to the second position and then move the detection unit from the second position,
• the defect detecting device further comprising a determination part configured to determine whether the defect is present at least based on data from the sensor obtained when the detection unit is located at the second position.