the axis of the assembly until the setback locking balls 43 are no longer constrained to engage the striker mass 39 to the cylindrical part 38 of the housing 31 if the acceleration event is not sufficient to provide this motion i e the acceleration time profile is less than the predetermined threshold the setback collar will return to its start position under the force of the setback spring the schematic of the inertial igniter 30 with the setback collar 46 moved down certain distance as a result of an acceleration event which is not sufficient to unlock the striker mass 39 from the cylindrical part 38 of the housing 31 is shown in fig5 assuming that the acceleration time profile was at or above the specified u201c all fire u201d profile the setback collar 46 will have translated down full stroke allowing the striker mass 39 to accelerate down towards the percussion cap primer 37 in such a situation since the locking balls 43 are no longer constrained by the shoulder 42 of the setback collar 46 the downward force that the striker mass 39 has been exerting on the locking balls 43 will force the locking balls 43 to move in the radial direction toward the housing wall 32 once the locking balls 43 are tangent to the outermost surface of the striker mass 39 the downward motion of the striker mass 39 is impeded only by the elastic force of the striker spring 41 which is easily overcome by the impulse provided to the striker mass 39 as a result the striker mass.