Article elevating device

An article elevating device comprising:

• a holder configured to hold an article;
• an elevating device configured to raise and lower the holder;
• and
• a controller configured to control the elevating device,
• wherein the elevating device comprises:
• a drum;
• a belt that is wound around the drum in such a manner as to be capable of unwinding from the drum and wound around the drum;
• a drive motor configured to drive the drum to rotate;
• and
• a transmission mechanism configured to transmit driving force from the drive motor to the drum,
• wherein the elevating device lowers the holder by unwinding the belt from the drum and raises the holder by winding the belt around the drum, while the holder is suspended with the belt, and
• wherein, while the controller performs an elevation operation that is at least either an operation of lowering the holder or an operation of raising the holder, the controller (i) calculates a unit elevation amount, which is an amount by which the holder is raised or lowered per unit rotation amount of the drive motor in an elevation operation range that is a range of heights of the holder in the elevation operation, in accordance with a change in a diameter of an outer circumferential surface of the belt wound around the drum due to winding of the belt and unwinding of the belt, and (ii) determines a rotation amount of the drive motor for the elevation operation based on the unit elevation amount,
• wherein the holder is initially arranged at a reference height and lowered toward a target height which is lower than the reference height before the elevation operation is performed to (i) calculate the unit elevation amount, (ii) determine the rotation amount for the elevation operation, and raise or lower the holder to the target height.