Gripping mechanism and gripping tool

A gripping mechanism comprising:

• two gripping pieces that are pivoted relative to each other about a pivot axis;
• a base that supports at least one of the two gripping pieces at a distal-end portion in a pivotable manner;
• a pulling pulley that is supported so as to be rotatable about a rotation axis that is parallel to the pivot axis;
• and
• a wire that is wound around the pulling pulley, in which one end of the wire is secured to one of the two gripping pieces or the base, and that causes, with a pulling force applied to an other end of the wire, tensile forces that move the rotation axis in one direction to act on both sides of the pulling pulley, between which the rotation axis is interposed,
• wherein the pulling pulley is disposed so that a resultant force of the tensile forces of the wire acting on the rotation axis becomes greater than the pulling force and generates a moment that causes the two gripping pieces to be pivoted in a direction that causes the two gripping pieces to be closed relative to each other,
• the base is provided with a first elongated hole that extends from a distal end toward a proximal end of the base,
• at least one of the two gripping pieces is provided with a second elongated hole that extends, along a plane that is orthogonal to the pivot axis, in a direction that is inclined in one direction with respect to a longitudinal axis of the first elongated hole, and
• the rotation axis is provided so as to be movable in a direction along longitudinal axial directions of the first elongated hole and the second elongated hole;
• wherein, in the state in which the two gripping pieces are closed, the following conditional expression is satisfied:
• cos α/sin θ>1,
• where
• θ is an angle formed between the longitudinal axis of the first elongated hole and a longitudinal axis of the second elongated hole, and
• α is an angle formed between a line segment that connects the rotation axis and the pivot axis and the longitudinal direction of the second elongated hole.