Shear-pin based inertia igniters with preset no-fire protection for munitions and the like

An inertial igniter for igniting a thermal battery upon a predetermined acceleration, the inertial igniter comprising:

• a base having a first projection;
• a striker mass rotatably connected to the base through a rotatable connection, the base having a second projection, the second projection is aligned with the first projection when the striker mass is rotated towards the base such that the first projection impacts the second projection;
• a member having a first portion, the first portion of the member engaging with a second portion of the striker mass to restrict rotation of the striker mass unless the predetermined acceleration is experienced;
• a movable mass that is movable from a first position where an acceleration is less than the predetermined acceleration and a second position where the acceleration is greater than the predetermined acceleration, the second position permitting the first and second portions to come out of engagement;
• a spring for biasing the movable mass in the first position;
• and
• a shear member for permitting impact of the first and second projections when the predetermined acceleration is experienced and the movable mass moves to the second position.