Preloader for use in a webbing retractor

Abstract

A preloader for use in a webbing retractor for retracting an occupant-restraining webbing onto a webbing takeup shaft, and adapted to allow a webbing to be applied to a vehicle occupant with appropriate tightness. An engaging shaft is coaxially coupled with the takeup shaft, and a rotating drum is disposed around the engaging shaft at a fixed distance from the engaging shaft. The rotating drum is held by a plate, and a wire is tightly wound around the outer periphery of the rotating drum. A clamp member is disposed swingably in a direction in which the clamp member engages the webbing and in a direction in which the clamp member moves away therefrom. An urging member is provided for constantly urging the clamp member in a webbing-clamping direction. A trigger member is disposed between the clamp member and the plate, and holds the clamp member in spaced-apart relationship with the webbing. A driving force is imparted to the wire when the vehicle suddenly decelerates, and the wire is tightly wound around the drum, thereby allowing the rotating drum and the engaging shaft to rotate integrally in a webbing-taking-up direction. As the plate rotates with the rotating drum, the state in which the clamp member is held by the trigger member in spaced-apart relationship with the webbing is canceled. Consequently, the webbing is clamped by the clamp member, thereby preventing the tight winding of the webbing and restraining the occupant reliably.