Abstract: A crash detector is provided for controlling actuation of an actuator such as a release mechanism for seat belts, an air bag or the like. A main body such as a ball is located in a bore in a housing and retained by a first, relatively weak spring. A firing pin having a portion for actuating the actuator is axially movable in the housing bore. A second spring biases the firing pin towards an inoperative position. The firing pin is moved to an actuating position when the deceleration force acting on the vehicle, and hence the mass body, exceeds a predetermined magnitude.

Abstract: A vehicle deceleration sensing device making it possible to sense whether an occurring collision is powerful or just trivial. The device comprises a first mass body with an actuating member, a second mass body and a blocking member in the form of a cup spring preventing the second mass body from being displaced at an occurring deceleration of the vehicle until the first mass body has been displaced a predetermined distance indicating that the duration and the magnitude of said deceleration are in excess of predetermined values.

Abstract: There is provided an arrangement for tensioning a strap of a vehicle seat safety harness upon or immediately prior to a collision. The arrangement includes strap tensioning means connected to attachment points of the strap adapted to be actuated by a force generating assembly, which assembly is associated with a sensing device responsive to an impact or an imminent impact on the vehicle for initiating the force. Preferably the strap tensioning means comprises two pistons arranged for mutually opposing movement in a common cylinder, each piston being connected via a line to an attachment point whereby actuation of the means effects simultaneous tensioning at the two points.