THERMAL-MAGNETIC TRIPPING MECHANISM

Magnetothermal release mechanism for a circuit-breaker electrical cutoff apparatus, comprising a magnetic circuit with a mobile vane (2) that is pivotable relative to a fixed cylinder head (1) forming the rest of the magnetic circuit, said cylinder head (1) having a U-shaped cross-section and surrounding a thermal bimetal switch (3) that is electrically connected to a terminal (4) of the apparatus, a return means (9) retaining the vane (2) in an open position relative to the cylinder head (1) in the absence of a short-circuit current. The terminal (4) and the cylinder head (1) are attached to each other and to an intermediate piece (6) having pivotable bearings (7, 7) for the vane (2), the assembly forming a subassembly in a single piece.