Control mechanism for pretensioners in vehicles

A control mechanism for a pretensioner of a safety belt restraining system or for a gas-bag restraining system in a vehicle, comprising a vehicle-sensitive inertia mass movably mounted in a housing and a release number pivotally mounted in said housing and bearing via a roller on a concave cam face of said inertia mass, said housing being hermetically sealed, and said release member being spring biased to hold said roller in said concave cam face and to maintain said inertia mass in a stable position,

• the shape of said concave cam face, the trajectory of said roller upon pivotal movement of said release member and the direction of movement of said inertia mass being selected so that:
• (i) said release member is held n a stable readiness position when deceleration forces do not exceed a predetermined deceleration value at said inertia mass;
• (ii) said roller rolls on the cam face of said inertia mass in a first direction against the action of the spring bias of said release member when deceleration forces exceeding said predetermined deceleration value occur at said inertia mass, and when the deceleration forces decrease said release member returns to its stable readiness position with said roller rolling on said cam face in a second direction opposite said first direction;
• (iii) under the action of deceleration forces at the inertia mass having a magnitude exceeding said predetermined deceleration value and corresponding to a predetermined velocity loss, said roller on said cam face moves past an over-center point to suddenly disengage said release member from said inertia mass;
• and
• (iv) said cam face providing an integrating function wherein deceleration is integrated with respect to time and only deceleration values exceeding said predetermined value are integrated, said release member being disengaged from said inertia mass only when the integral of deceleration equals said predetermined velocity loss.