Seat belt retractor with tension relief mechanism

A safety belt retractor comprising:

• a rotatable spool for storing safety belt webbing thereon;
• rewind spring means for exerting a retractive force on said spool to exert tension on said safety belt webbing;
• and
• a tension relief mechanism for selectively reducing the tension exerted on said belt webbing by said rewind spring means, said tension relief mechanism having counterspring means for generating a counteractive force in opposition to said retractive force such that a vehicle occupant may vary the magnitude of said counteractive force between a minimum value and a maximum value, and actuation means operable for establishing a non-actuated mode wherein only said retractive force of said rewind spring means is exerted on said spool, and an actuated mode wherein said counteractive force of said counterspring means is applied to said spool in opposition to said retractive force for reducing the tension on said belt webbing in proportion to the magnitude of said counteractive force, and wherein said actuation means is shifted from said non-actuated mode to said actuated mode in response to the withdrawal of a predetermined length of said safety belt.

A tension relief mechanism for use with a safety belt retractor of the type having a rotatable spool and a rewind spring for exerting a retractive force on the spool for winding the safety belt webbing thereon and tensioning the safety belt webbing, said tension relief mechanism comprising:

• a clutch member capable of rotational movement with respect to the spool;
• a counterspring coupling the spool and said clutch member and exerting a counteractive force on the spool to oppose said retractive force in response to relative rotation between the spool and said clutch member such that a seated occupant may vary the magnitude of said counteractive force between a minimum value for establishing a maximum tension on the belt webbing and a maximum value for establishing a maximum tension on the belt webbing;
• and
• an actuation mechanism having engaging means moveable between a first position for engaging said clutch member to permit relative rotation between the spool and said clutch member and a second position for disengaging said clutch member to permit concurrent rotation of the spool and said clutch member, said actuation mechanism being operable to position said engaging means between said first and second positions in response to withdrawal of a predetermined length of the safety belt webbing.