Box-opening device

A box-opening device configured to unfold a folded cardboard box sheet in which a first side surface and a second side surface overlap with a third side surface and a fourth side surface and form a square-tube-shaped cardboard box in which the first side surface, the second side surface, the third side surface, and the fourth side surface are arranged in this order, the box-opening device comprising:

• a first grasping part that grasps the first side surface;
• a first arm that has a second grasping part that grasps the fourth side surface and changes a posture while the second grasping part grasps the fourth side surface;
• a control part that controls a movement of the first arm so that an initial action, in which a gap is formed between the first and second side surfaces and the third and fourth side surfaces of the folded cardboard box sheet overlapping each other, and a main action, which is performed after the initial action and in which the cardboard box sheet is formed into a square tube shape, are executed as an action of unfolding the cardboard box sheet;
• the first arm configured to move at or slower than a predetermined speed in the initial action, and the first arm configured to move faster than the predetermined speed in the main action;
• and
• the control part controlling configured to control the movement of the first arm based on an angle formed by the first side surface and the fourth side surface, such that the initial action comes to an end when the angle reaches a target angle, the target angle being determined according to a length of a side of the cardboard box sheet.