Composite inertia latch for vehicle seat back

Claim 1

In a motor vehicle seat having a seat part and a back part, a hinge comprising, a lower hinge element fixed to said seat part, an upper hinge element fixed to said back part, first pivot means for pivotally connecting said upper hinge element to said lower hinge element including an engageable stop means, a first element (14) pivotally mounted on said upper hinge element normally engaged with said stop means in a first position capable of preventing forward seat back pivotal movement and including biasing means associated therewith for yieldable disengagement from said stop means through forward pressure on the seat back to permit forward seat back pivotal movement, an inertia element pivotally mounted on second pivot means on said upper hinge element with outer surface means (24) interengaging outer surface means (25) on said first element along respective first ends in said first position (FIG. 1) permitting said yieldable disengagement of said first element in response to said forward pressure on said seat back, said inertia element having a center of gravity offset from said second pivot means defining a blocking means responsive to gravity to pivotally move said inertia element in a first direction away from engagement with said first element during initial forward seat back movement with said vehicle stationary permitting unrestrained additional pivotal movement of said seat back (FIG. 1A), said blocking means also being responsive to inertia to overcome gravity and pivotally move said inertia element in a second opposite direction into blocking engagement with said first element along their outer surfaces at respective second ends (FIG. 1B) upon sudden deceleration of said vehicle wherein further pivotal movement of said seat back is substantially eliminated.