Patent ID: 7784832

Claim:
A pretensioner for restraining an occupant with a seat belt by retracting a seat belt buckle, comprising: a wire having one end adapted to be attached to the seat belt buckle, a piston connected to the other end of the wire, a cylinder slidably accommodating the piston therein, a housing having a gas passage therein, and a wire passage formed at one side thereof through which the wire enters the gas passage, said cylinder being attached to and supported by the housing at a side opposite to the wire passage, a seal member disposed around the wire passage at a side of the gas passage for sealing around the wire, a heat resistance agent directly applied to at least a portion of the wire located in the gas passage, and a gas supply unit attached to the housing for supplying gas to the gas passage, wherein a substantially entire one side of the piston directly faces the gas passage and the wire extends to the piston through the gas passage while directly exposing the heat resistance agent to the gas passage so that when the gas supply unit is operated to supply gas to the gas passage, the piston is moved in a direction of retracting the wire while the wire is protected from gas heat by the heat resistance agent, and wherein said housing further includes a seal receiving portion at a side of the gas passage, said seal receiving portion having an inner diameter gradually decreasing in a direction away from the gas passage, and said seal member has a tapered shape gradually decreasing from one side to a side opposite thereto, said seal member with the tapered shape being disposed in the seal receiving portion.