One-piece shell chair

A chair adapted to provide postural support to a wide variety of people of different shapes and sizes through a variety of different seated positions, said chair comprising:

• a relatively rigid seat and a backrest joined together to support a user;
• means in said seat and backrest for reacting to the shape and movement of users to maintain appropriate support to the back and seat of users through a variety of different postural positions within the chair;
• flexural support means for supporting said rigid seat in a cantilevered fashion for flexural pivoting of said seat as a unit about a flexural axis passing transversely through a central portion of said seat;
• support means for said chair comprising a tilt mechanism and lever means extending downwardly from said seat to said tilt mechansism adapted to permit resilient rotation of said seat and backrest with respect to said support about a tilt axis beneath the knee and forwardly of the center of gravity of the user such that said seat pivots rearwardly and downwardly upon tilting;
• and
• said tilt mechanism and said flexural axis being so positioned with respect to each other such that any rise in the front portion of the seat due to pivoting of the seat as a unit rearwardly about said flexural axis is negated at least in part by relative downward movement of said front portion of said seat due to rotation of said seat as a unit backwardly about said tilt axis so that upward movement of said seat front portion is minimized during backward tilting of said seat about said tilt axis.