| 摘要 |
PROBLEM TO BE SOLVED: To provide a pretensioner to prevent gas pressure applied on a piston to remove looseness of a seat belt at the time of emergency from interfering motion of an energy absorption mechanism. SOLUTION: It is constituted to provide gas vent holes 46, 47 passing through along the moving direction of a piston 40 on a base end part of the piston 40 and devised free to hold gas pressure until a pretensioner works while the gas pressure does not fall in a short period of time by viscous resistance of passing gas and to fall inside pressure of gas remaining in the inside of a cylinder 24 down to a required sufficient value until an energy absorption mechanism works. |
