Patent ID: 8366151

Claim:
A pretensioner for a seat belt system of an automobile, the pretensioner comprising: a gas generator adapted to release a high-pressure gas when a shock occurs in the automobile; a gas pipe formed to receive therein the gas generator and adapted to guide the gas; a movable member adapted to be moved by a pressure of the gas guided by the gas pipe; and a coupling mechanism connected to the movable member and adapted to be connected to a seat belt of the seat belt system to wind up or pull the seat belt in accordance with the movement of the movable member to increase a restraining force of the seat belt, wherein the gas pipe has a small-diameter section, an intermediate-diameter section and a large-diameter section having a diameter greater than that of the small-diameter section and intermediate-diameter section of the gas pipe, wherein a large shaft portion of the gas generator is fitted into the large-diameter section of the gas pipe, wherein the gas generator and the gas pipe are joined together by a crimping portion which is crimped onto a crimping shoulder formed on the large shaft portion of the gas generator, wherein the large-diameter section of the gas pipe existing around the large shaft portion of the gas generator has a thick-walled region in a vicinity of an end of the gas pipe and a thin-walled region which is thinner than the thick-walled region, and wherein the thick-walled region in the vicinity of the end of the gas pipe includes the crimping portion, and the thick-walled region extends from the crimping portion along the large-diameter section and terminates at an intermediate part of the large-diameter section.