Stacker crane

A stacker crane for travelling along a rail, comprising:

• a lower travelling vehicle main body;
• a first mast and a second mast extending in a vertical direction, the first mast and the second mast being provided in the lower travelling vehicle main body such that the first mast and the second mast are spaced away from each other in a travelling direction;
• a first travelling wheel and a second travelling wheel configured to roll on a top surface of the rail, the first travelling wheel and the second travelling wheel being provided in the travelling vehicle main body such that the first travelling wheel and the second travelling wheel are spaced away from each other in the travelling direction;
• a first drive wheel unit and a second drive wheel unit provided in the lower travelling vehicle main body such that the first drive wheel unit and the second drive wheel unit are spaced away from each other in the travelling direction;
• and
• first connecting plates and second connecting plates each including a lower portion that is wider than an upper portion of the respective connecting plate;
• wherein
• the first connecting plates are located on both sides of the first mast, extend outward of the first mast in the travelling direction, and support the first travelling wheel;
• the second connecting plates are located on both sides of the second mast, extend outward of the second mast in the travelling direction, and support the second travelling wheel;
• the first drive wheel unit includes:
• a first driving wheel configured to contact a first side surface of the rail;
• and
• a second driving wheel attached to the lower travelling vehicle main body such that the second driving wheel is pivotable and the second driving wheel is urged toward the first driving wheel to contact a second side surface of the rail;
• and
• the second drive wheel unit includes:
• a third driving wheel configured to contact the first side surface of the rail;
• and
• a fourth driving wheel attached to the lower travelling vehicle main body such that the fourth driving wheel is pivotable and the fourth driving wheel is urged toward the third driving wheel to contact the second side surface of the rail.