Seat belt security release mechanism

In a security release mechanism for connection between a safety seat belt and an anchoring means to produce automatic opening of the belt after a given time following an impact, comprising a belt attachment member, a first piece having a slot for receiving said member, means for locking said member in said slot, and means including a spring submitted to the belt tension transmitted by said attachment member for controlling delayed disengagement of said locking means to release said member after said tension has exceeded a given value, the improvement wherein said locking means comprises two balls disposed in housings in said first piece adjacent part of said slot which receives said member, said member having an opening which faces said housings when said member is located in said slot, at least one of said balls being movable away from the other into its housing, and at least one retractable abutment normally holding said movable ball against the other ball in said opening of said member to lock said member in said slot, said delayed-disengagement control means comprising means for retracting said abutment to allow said movable ball to move away from the other to free said belt attachment member.