GB1438621A - Tensioning device - Google Patents

Abstract

1438621 Tightening seat belts SOC NATIONALE DES POUDRES ET EXPLOSIFS 18 Dec 1974 [20 Dec 1973] 54642/74 Heading A3V [Also in Division F2] A seat belt is tightened by a piston moved within a cylinder by release of high pressure gas triggered by an impact detector. At a predetermined pressure a frangible link holding an auxiliary piston fractures and activates a jamming mechanism preventing further advance of the piston. Forward movement of the wearer is damped as gas is compressed by return of the piston. The belt is attached to a rod 2 fixed to piston 6 movable within a cylinder 7. The cylinder is held in casing 30 by a frangible ring 9. Ignitable pyrotechnic charges 27 are. housed in a damping chamber 11, which communicates via ports 13 with expansion chamber 12. A residual damping chamber 19 communicating via small ports 31 is provided in the casing; alternatively a venting valve is provided. An auxiliary piston is housed in piston 6, and is in communication with the expansion chamber via passageways 20. In the embodiment shown the auxiliary piston 17 carries a disc 33 which retains balls 34. It is held by a frangible ring 16. In a modification (Figure 5, not shown) the auxiliary piston (39) is annular. In the embodiment of Figure 6 (not shown) has a central weakened link (41) and a conical head (42) contacting radial rods (43). The rods act against a ring retaining the balls. When the charges are ignited, piston 6 is driven to the right, tightening the belt when the force of the wearer thrown against the belt resists piston advance, the gas pressure rises until the retaining ring or link of the auxiliary piston fractures. Further movement of the piston in that direction is prevented by the jamming action of the balls. Continued forward movement of the wearer against the belt withdraws the piston to its initial position. Fracture of ring 9 releases the cylinder 7 so that damping is continued as gas is compressed in chamber 23.