Patent ID: 6877776

Claim:
A pretensioner device comprising: a connecting member, one end portion of the connecting member being operatively connected to a webbing for restraining a vehicle occupant; a piston connected to another end portion of the connecting member; a cylinder formed in a tubular shape corresponding to the piston and accommodating the piston such that the piston is movable toward one side in an axial direction; a gas chamber which communicates with another side of the cylinder, and through which an intermediate portion of the connecting member is inserted; an entrance portion provided at a side of the gas chamber opposite to a side at which the cylinder is provided, an intermediate portion of the connecting member being slidably inserted through the entrance portion; a gas discharging portion including a bleeder opening freely connecting a region ahead of and behind the piston, said bleeder opening being sufficiently small in cross section so as not to interfere with the moving of the piston from the gas pressure during a normal operation of the pretensioner device; a gas generating device provided so as to be able to supply gas to the gas chamber, and generating gas by being ignited, and, in a predetermined case, the pretensioner device igniting the gas generating device, and due to pressure of gas supplied into the cylinder from the gas chamber, the pretensioner device moving the piston toward the one side of the cylinder and tensing the webbing in a direction of restraining a vehicle occupant, wherein a protecting member, at least a portion of which is formed from a thermally conductive material, is disposed within the gas chamber.