Constant pull safety belt retracting mechanism

摘要

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. The arm is resiliently biased by a spring to maintain the spiral-shaped gear in enmeshment with the pinion during gear rotation.