Patent ID: 8398495

Claim:
A coupling device for rotationally coupling a drive shaft of a drive device and a driven shaft of an operation device which are arranged on a rotation axis, the coupling device comprising: a drive portion formed on the drive shaft to face in the circumferential direction and having a drive wall surface extending in the direction of the rotation axis; a driven portion formed on the driven shaft to face the drive wall surface and having a driven wall surface extending in the direction of the rotation axis; a convex curved portion formed on one of the drive wall surface and the driven wall surface and extending along the rotation axis at a position spaced from the rotation axis as viewed in the direction of the rotation axis; and a concave curved portion having a smaller curvature than that of the convex curved portion and formed on the other of the drive wall surface and the driven wall surface to contact the convex curved portion and extending along the rotation axis at a position spaced from the rotation axis as viewed in the direction of the rotation axis.