A deceleration sensor, comprising a pair of U-shaped pendulums pivotally suspended from upper parts of a casing at their upper ends by way of pivot shafts extending in parallel with each other, one of the pendulums being received by the other in such a manner that they are permitted to pivot around their respective pivot shafts without interfering with each other, a pair of biasing springs for opposing movement of the pendulums against their inertia forces, a firing pin slidably received in the guide bore, a drive spring urging the firing pin toward a fuse which is intended to be activated by the deceleration sensor, a swing arm which is pivotally attached to the sensor casing at its one end and engaged by one of the pendulums at its other end; and a trigger arm which is pivotally attached to a middle part of the swing arm so as to be able to swing in a same plane as the swing arm, and is engaged by the other of the pendulumns at its one end and engages the firing pin against the spring force of the drive spring at its other end. Thus, the firing pin can be activated when at least one of the pendulums is activated by its inertia so as to disengage the swing arm or the trigger arm therefrom, and a high reliability can be achieved with a simple and compact structure.

Claims data not available