Controlled pressure release for seatbelt pretensioning devices

Abstract

The seatbelt pretensioner, which is designed for reducing slack in seatbelt webbing upon deployment in response to a triggering event, comprises an igniter that generates gas in response to the triggering event, an elongate body defining a chamber for receiving and the confining gas generated by the igniter, a piston movable within the elongate body by the gas generated, a slack-reducing assembly that responds to movement of the piston and is connected to at least a portion of seatbelt webbing, movement of the piston causes the slack-reducing assembly to move the seat belt webbing reducing slack in the seatbelt webbing; and a controlled pressure release that enables gas to escape from the elongate body after deployment, relieving gas pressure within the pretensioner. The controlled pressure release may comprise one or more of various pressure relieving features such as a porous intermediate disposed between the vent hole and the gas within the elongate body, a piston having a porous portion and/or a safety valve, and one or more plugs that seal vent holes in the elongate body that become unsealed by loosening the pretensioning assembly.