BREAKER, SAFETY CIRCUIT AND SECONDARY BATTERY PACK

To provide a breaker capable of ensuring good rigidity and strength of a case, while down-sizing.SOLUTION: A breaker 1 includes a fixed contact 21, a movable piece 4 having an elastic part 43 and a movable contact 41, a thermally-actuated element 5 for shifting the state of the movable piece 4 from a conduction state to a cut-off state by deforming as the temperature changes, a case body 7 for receiving the movable piece 4 and the thermally-actuated element 5, a lid member 8 attached to the case body 7, and a tabular cover piece 9 embedded in the lid member 8. A first fastening face 75 to be fastened to the lid member 8 is formed in the case body 7, and a second fastening face 85 to be fastened to the case body 7 is formed in the lid member 8. A spur 86 projecting toward the first fastening face 75 is formed on the second fastening face 85, and the spur 86 and the cover piece 9 overlap in a plan view from the thickness direction of the cover piece 9.SELECTED DRAWING: Figure 1 【課題】小型化を図りつつ、良好なケースの剛性及び強度が得られるブレーカーを提供する。【解決手段】ブレーカー１は、固定接点２１と、弾性部４３及び可動接点４１を有する可動片４と、温度変化に伴って変形することにより、可動片４の状態を導通状態から遮断状態に移行させる熱応動素子５と、可動片４及び熱応動素子５を収容するケース本体７と、ケース本体７に装着される蓋部材８と、蓋部材８に埋設された板状のカバー片９とを備える。ケース本体７には、蓋部材８に固着される第１固着面７５が形成され、蓋部材８には、ケース本体７に固着される第２固着面８５が形成される。第２固着面８５には、第１固着面７５に向って突出する突出部８６が形成され、突出部８６とカバー片９とは、カバー片９の厚さ方向から視た平面視で重複する。【選択図】図１