Abstract: A safety belt retracting mechanism having constant pull includes a rotatable spool for storing the belt inside a housing. A conventional, positive coefficient of force spring inside the housing applies a retracting force to the spool and belt as the belt is pulled by the occupant. The spring is coupled between the housing and spool through a variable gear ratio gear train having a negative coefficient of force transfer characteristic. The negative transfer characteristic of the gear train compensates for the positive characteristic of the spring to provide constant pull to the belt between fully retracted and fully protracted belt positions. Three embodiments of the invention are disclosed. In one embodiment, the changing gear ratio is produced by a pair of oppositely oriented cone gears connected respectively to the spring and to a spindle supporting the belt spool.

Abstract: A safety belt retracting mechanism having constant pull includes a spindle supporting a rotatable spool for storing the belt within a housing. A conventional, positive coefficient of force spring inside the housing applies a retracting force to the spool and belt as the belt is pulled by the occupant. The spring is coupled between the housing and spool to a gear train having a negative coefficient of force transfer characteristic. The negative transfer characteristic of the gear train is caused by a changing gear ratio which compensates for the positive force characteristic of the spring to provide constant pull to the belt. The changing gear ratio is produced by a spiral-shaped gear coupled to a constant radius pinion formed on one end of the spindle. The spiral-shaped gear is formed on the hub of a containment member enclosing the spring. The containment member is mounted to the housing on a pivot arm.