Combination seat belt retractor mechanism

Abstract

A combination seat belt retractor particularly useful for motor vehicles is described. The seat belt retractor according to this invention converts between an emergency locking retractor which locks only when the vehicle is subjected to a deceleration level above a predetermined level to an automatic locking mode wherein the seat belt webbing cannot be withdrawn from the retractor. The convertible feature is particularly advantageous since an emergency locking retractor does not provide the desired firm positioning of child restraint systems. The emergency locking retractor, however, has advantages in terms of occupant comfort and convenience since they permit free movement of the occupants within the vehicle. In accordance with this invention, the retractor is converted to the automatic locking mode by first fully withdrawing the seat belt webbing therefrom. Such action causes a switching lever to force a leaf spring in a position against the retractor locking bar. When, however, a predetermined amount of seat belt webbing is returned upon the retractor spool, the leaf spring returns to its normal position, thereby restoring emergency locking operation to the retractor.

What is claimed is: .[.1. A seat belt retractor which may be operated either as, an emergency locking retractor which prevents seat belt webbing from being withdrawn when the retractor is subjected to deceleration above a predetermined level, or as an automatic locking retractor which acts to retract said webbing but does not permit substantial withdrawal of said webbing comprising; 
     
        .Iadd.11.  In a motor vehicle seat belt retractor which may be operated either as an emergency locking retractor which prevents seat belt webbing from being withdrawn when the retractor is subjected to deceleration above a predetermined level, or as an automatic locking retractor which acts to retract said webbing but does not permit substantial withdrawal of said webbing, including a retractor frame, a spool rotatable within said frame and having a spindle upon which said webbing is wrapped and a pair of toothed sprockets on opposite ends thereof, a locking bar engageable with said toothed sprockets for restricting withdrawal of said webbing from said spool, and an inertia sensitive actuator acting upon said locking bar to cause engagement of said locking bar with said toothed sprockets when a deceleration of said vehicle above said predetermined level is sensed, the improvement comprising: a leaf spring positioned between said toothed sprockets and having two ends and a center portion between said ends, each of said ends being mounted to said retractor frame at attachment points fixed with respect to said retractor frame and separated by a distance less than the free length of said spring, said spring being movable between a first state wherein said spring center portion is deflected away from said spool and disengaged from said locking bar wherein said locking bar is permitted to operate solely in response to said internal sensitive actuator whereby said retractor operates as an emergency locking retractor, and a second state wherein the center portion of said spring is deflected toward said spool and acts by direct contact with said locking bar biasing said locking bar into engagement with said toothed sprockets causing said locking bar to engage with said toothed sprockets to engage the teeth of said sprockets to restrict withdrawal of said webbing while allowing said locking bar to ride over said teeth upon retraction of said webbing whereby said retractor operates as an automatic locking retractor; and   a web sensing lever pivotably mounted to said retractor frame and defining first and second arms on either side of said pivot axis, said lever being pivotable between a first position and a second position, in said second position said first arm engaging said spring center portion and forcing said spring into said second state, said second arm positioned to engage said webbing when substantially all of said webbing has been withdrawn from said spool causing said lever to move to said second position through contact with said webbing, and when said lever is in said second position and said webbing is being retracted onto said spool, said spring is oriented such that when the diameter of the total wraps of webbing on said spool reaches a predetermined diameter, said wraps directly contact said spring center portion forcing said spring to switch from said second state   
     
     
        to said first state. .Iaddend. .Iadd.12.  The seat belt retractor of claim 11 wherein said leaf spring ends are tapered and each of said ends engage notches formed by said retractor frame at said mounting points. .Iaddend. .Iadd.13. The seat belt retractor of claim 12 wherein one of said notches is formed by a cross member component of said retractor frame. .Iaddend. 
     
     
        .Iadd.14.  The seat belt retractor of claim 11 wherein said leaf spring further forms an offset adjacent one of said ends. .Iaddend. .Iadd.15. The seat belt retractor of claim 11 wherein said pivot axis for said web sensing lever is parallel to the axis of rotation of said spool. .Iaddend. .Iadd.16. The seat belt retractor of claim 11 wherein said spring is unstable at intermediate positions between said first and second states and is stable at either of said first and second states. .Iaddend. .Iadd.17. The seat belt retractor of claim 16 wherein said spring assumes an arcuate configuration in both of said first and second states such that said center section of said leaf spring is disposed on one side of a straight line between said spring ends in said first state and on an opposite side of said line in said second state and said spring center portion intersecting said line when said spring is in an intermediate state between said first and second states. .Iaddend. .Iadd.18. The seat belt retractor of claim 11 wherein when said spring is in said second state acting upon said locking bar, retraction of said webbing onto said spool causes said locking bar to ratchet along said toothed sprockets against the biasing force exerted by said leaf spring. .Iaddend.