Breaker and safety circuit equipped with the same

A breaker comprising:

• a fixed contact,
• a movable piece comprising an elastic portion formed in the form of a plate and being elastically deformable, and a movable contact formed in one end portion of the elastic portion in a long direction of the movable piece, the movable piece for pressing the movable contact against the fixed contact so as to contact therewith,
• a thermally-actuated element deforming with a change in the temperature so as to shift the movable piece from a conduction state in which the movable contact contacts with the fixed contact to a turn-off state in which the movable contact is separated from the fixed contact, and
• a case accommodating the fixed piece, the movable piece, the thermally-actuated element,
• wherein
• the case has a side wall extending in the long direction of the movable piece, and
• the side wall is provided, around the thermally-actuated element, with a convex portion protruding in a short direction orthogonal to the long direction toward the outside of the case,
• wherein
• the case has a top wall which intersects with the side wall,
• a cover piece is formed in the form of a plate and embedded in the top wall,
• the cover piece is provided partially in the long direction with a wide portion wider in the short direction than other portions on both sides of the wide portion in the long direction, and
• a dimension in the long direction, of the wide portion of the cover piece is larger than a dimension in the long direction, of the convex portion of the side wall.