Safety belt pretensioner and force limiter
AssigneeVolvo Car Corporation
InventorClas Jernström
Life of this patent
Estimating the term…
Abstract
A belt pretensioner and force limiter in a vehicle having a piston-cylinder device with a cylinder chamber containing an explosive charge in which the piston has a piston rod that protrudes from the cylinder and is joined to a cable. The cable, via a drum and a planetary gear set, drives a reel mechanism for the belt in a winding-up direction when the explosive charge is detonated. The planetary gear set is engaged so that the gear ratio is about 1:1 between the drum and the reel mechanism when the drum rotates in the winding-up direction. The planetary gear set is engaged in the opposite direction so that the return movement of the piston a certain distance in the cylinder corresponds to a several times longer feed-out of the web from the reel mechanism.
Claims8
A device for pretensioning and force-limiting a safety belt web joined to a reel mechanism in a vehicle, the device comprising:
- a cylinder,
- a piston displaceable in the cylinder and having a piston rod, the piston rod joined to one side of the piston and extending through an opening in a first end wall of the cylinder,
- a motion-transmitting element acting between the piston rod and the reel mechanism, said element achieving rotation of the reel mechanism in a winding-up direction of the belt web upon displacement of the piston in one direction,
- a pyrotechnic charge causing, when detonated, a pressure increase in a cylinder chamber between the piston and a second end wall of the cylinder whereby the piston is displaced in said one direction,
- wherein the motion-transmitting element is joined to a ring gear of a planetary gear set so that displacement of the piston in the cylinder results in rotation of the ring gear,
- wherein the planetary gear set is so disposed and coupled to the reel mechanism that the gear ratio between the ring gear and the reel mechanism is about 1:1 upon rotation of the ring gear in the winding-up direction of the web,
- wherein the planetary gear set is so structured that the gear ratio between the ring gear and the reel mechanism is higher when rotating in an opposite direction, whereby a return movement of the piston over a certain distance in the cylinder corresponds to a several times longer feed-out of the web from the reel mechanism.
Dependencies are inferred from the claim text.