Abstract: A mechanical ignition sensor which can reduce rotational resistance of a trigger lever. An inner periphery of a slit on the side of a spring is formed into an inclined surface which is an abutment surface with an outer peripheral side of the slit opened. An inclined surface of a slide holding portion is formed as a curved surface along a locus of rotation of an abutment leading end portion of the slide holding portion. An angle of inclination .alpha. 1 of an abutment leading end P of an inertial mass body with respect to an axial direction of the mechanical ignition sensor is set small such that only the abutment leading end P abuts against the inclined surface of the slide holding portion. As a result, sliding resistance between the inclined surface of the slit and the inclined surface of the slide holding portion.

Abstract: A mechanical ignition sensor is disclosed having a trigger lever engages an ignition pin and holds the ignition pin at a position separated from a detonating member. When an inertial mass is moved, the trigger lever moves in a direction of separating from the ignition pin so as to allow movement of the ignition pin. A safety device is movable from a position at which the safety device abuts the inertial mass so as to prevent movement of the inertial mass, to a position at which the safety device and the inertial mass are in a state of non-abutment so as to allow movement of the inertial mass. Since movement of the inertial mass is prevented by the safety device, the trigger lever does not move and the mechanical ignition sensor does not operate at the same time that the safety device is released. Thus, the operation of the sensor can be prevented when the safety device is released.