Double enveloping worm and gear seat recliner

Abstract

A device for adjusting the relative inclination of two elements, and in particular, the relative inclination of a back member of an automotive seat pivotally connected about a rotational axis to a base member of the seat for movement through a predefined arc is disclosed. The device can include at least an enveloping gear sector for pivotal connection to the base member about an axis generally coaxial with the rotational axis between the back and base members. The gear sector preferably includes plastic concave teeth formed thereon. An enveloping worm is provided for rotatable connection to the base member. The worm preferably is formed of at least one plastic concave worm having at least a single thread. The worm is disposed in double enveloping engagement with the gear sector. A rotatable cam is pivotally connecting the sector gear to the base member. The rotatable cam is pivotal along a predefined arc about an axis of rotation generally coaxial with the rotational axis of the back member. A spring biases the rotatable cam in a rotational direction such that the gear is urged into positive engagement with the worm at any angular position of movement. A drive mechanism is provided for rotating the worm in clockwise and counterclockwise directions. A releasable lock member is also provided for preventing unintentional movement of the worm in either rotational direction.