Pre-tensioner

A pre-tensioner which rotates at take-up shaft of a seat belt retractor in the belt take-up direction to impart pre-tension on a belt in case of emergency, the pre-tensioner comprising:

• a gas generator;
• a plurality of driving members which are accelerated by gas from the gas generator;
• a passage for guiding the driving members;
• a rotational member having a plurality of driving points which are pressed by some of the accelerated driving members to impart rotational torque;
• a mechanism for facilitating the discharge of the driving members left around the driving points of the rotational member after the operation of the pre-tensioner;
• and
• an energy absorbing mechanism which gradually rotates the take-up shaft in the belt withdrawing direction when tension exceeding a predetermined value is exerted on the seat belt, wherein when the energy absorbing mechanism is actuated after the operation of the pre-tensioner, the passage is configured to partially deform or break.

A pre-tensioner which rotates a take-up shaft of a seat belt retractor in the belt take-up direction to impart pre-tension on a belt in case of emergency, the pre-tensioner comprising:

• a gas generator;
• a plurality of driving members which are accelerated by gas from the gas generator;
• a passage for guiding the driving members;
• a rotational member having a plurality of driving points which are pressed by some of the accelerated driving members to impart rotational torque;
• and
• wherein a part of the passage is constructed to be deformed or broken to facilitate the discharge of the driving members out of the passage when the rotational member tends to move in such a direction that the driving points of the rotational member push back the driving members into the passage according to a rotation of the take-up shaft in the belt withdrawing direction.

A pre-tensioner which rotates a take-up shaft of a seat belt retractor in the belt take-up direction to impart pre-tension on a belt in case of emergency, the pre-tensioner comprising:

• a gas generator;
• a plurality of driving members which are accelerated by gas from the gas generator;
• a passage for guiding the driving members;
• a first rotational member having a plurality of driving points which are pressed by some of the driving members to receive a driving force;
• a second rotational member fixed to the take-up shaft;
• and
• a clutch mechanism disposed between the first rotational member and the second rotational member, wherein
• the second rotational member is a pinion having external teeth,
• the first rotational member is a ring gear having internal teeth to be engaged with the external teeth of the pinion and having levers as the driving points on the outer periphery thereof,
• the clutch mechanism engages the internal teeth of the ring gear with the external teeth of the pinion by the accelerated driving members pressing one or more of the levers of the ring gear to move the ring gear, and
• the driving members and the passage are configured to prevent the ring gear from moving in a direction of disengaging the ring gear from the pinion at a power transmitting portion.

A pre-tensioner which rotates a take-up shaft of a seat belt retractor in the belt take-up direction to impart pre-tension on a belt in case of emergency, the pre-tensioner comprising:

• a gas generator;
• a plurality of driving members which are accelerated by gas from the gas generator;
• a passage for guiding the driving members;
• a first rotational member having a plurality of driving points which are pressed by some of the driving members to receive a driving force;
• a second rotational member fixed to the take-up shaft;
• and
• a clutch mechanism disposed between the first rotational member and the second rotational member, wherein
• the second rotational member is a pinion having external teeth,
• the first rotational member is a ring gear having internal teeth to be engaged with the external teeth of the pinion and having as the driving points levers on the outer periphery thereof,
• the clutch mechanism engages the internal teeth of the ring gear with the external teeth of the pinion by the accelerated driving members pressing one or more of the levers of the ring gear to move the ring gear,
• surfaces of the external teeth and the internal teeth, which come in contact with each other when the driving members rotate the ring gear, have pressure angles smaller than 20°.

A pre-tensioner which rotates a take-up shaft of a seat belt retractor in the belt take-up direction to impart pre-tension on a belt in case of emergency, the pre-tensioner comprising:

• a gas generator;
• a plurality of driving members which are accelerated by gas from the gas generator;
• a passage for guiding the driving members;
• and
• a rotational member having a plurality of driving points which are pressed by some of the accelerated driving members to impart rotational torque,
• wherein at least one of the driving members is a ball configured to deform to prevent gas leakage toward the rotational member.

A pre-tensioner which rotates a take-up shaft of a seat belt retractor in the belt take-up direction to impart pre-tension on a belt in case of emergency, the pre-tensioner comprising:

• a gas generator;
• a plurality of driving members which are accelerated by gas from the gas generator;
• a passage for guiding the driving members;
• and
• a rotational member having a plurality of driving points which are pressed by some of the accelerated driving members to impart rotational torque,
• wherein the driving member positioned farthest from the rotational member is a ball configured to deform in response to the gas from the gas generator forcing the driving member into the adjacent driving member.

A pre-tensioner which rotates a take-up shaft of a seat belt retractor in the belt take-up direction to impart pre-tension on a belt in case of emergency, the pre-tensioner comprising:

• a gas generator;
• a plurality of driving members which are accelerated by gas from the gas generator;
• a passage for guiding the driving members;
• and
• a rotational member having a plurality of driving points which are pressed by some of the accelerated driving members to impart rotational torque, wherein
• the driving member nearest the gas generator is a ball configured to contact an inner surface of the passage to prevent gas from the gas generator from leaking by.