Rotating shaft and industrial robot employing same

A retractable rotating shaft that is connected to a first counterpart member and a second counterpart member and transfers torque between the first and second counterpart members, the rotating shaft comprising:

• a first shaft member that includes a rail member having a rectangular shape in a cross section and extending in a shaft direction of the rotating shaft, and a first connecting portion which is disposed at an end of the rail member and can be connected to the first counterpart member;
• and
• a second shaft member that includes:
• a slider having a U-shape to hold the rail member and movably installed to the rail member;
• a holder which holds the slider;
• a tubular unit which extends in the shaft direction and has a first end and a second end, and of which the first end is secured to the holder so that the rail member is inserted inside the tubular unit as the slider moves toward the first connecting portion;
• and a second connecting portion which is disposed at the second end of the tubular unit and can be connected to the second counterpart member, wherein
• the slider includes:
• a slider main unit to which the holder is fixedly attached;
• and a plurality of rolling elements which is held by the slider main unit, and rolls between the slider main unit and the rail member as the slider moves,
• the holder includes:
• a main unit portion having a U-shape in a cross section to hold the slider;
• and a tubular unit securing portion extending from an end of the main unit portion to receive the rail member inside, the tubular unit securing portion being engaged in the tubular unit to connect the tubular unit to the slider via the holder, and
• plurality of rolling elements includes:
• a plurality of first rolling elements which rolls along a first rolling path formed in a location between the slider main unit and the rail member, and when torque to relatively rotate the first shaft member with respect to the second shaft member in a first direction is inputted to the first shaft member or the second shaft member, transfers running torque between the slider and the rail member;
• and a plurality of second rolling elements which rolls along a second rolling path formed in a location that is between the slider main unit and the rail member and is different from the location of the first rolling path, and when torque to relatively rotate the first shaft member with respect to the second shaft member in a second direction, which is opposite of the first direction, is inputted to the first shaft member or the second shaft member, transfers running torque between the slider and the rail member.