Seating structures with flexible backs

A seating device comprisingly:

• a seat back body which has sufficient stiffness to support the back of a user but is rearwardly flexible to conform to movements of the user's back;
• said body having a lower mounting portion extending upwardly at the center of the user's back, and having two upper portions both carried movably by said lower mounting portion and extending upwardly and laterally outwardly therefrom in opposite directions respectively to support the back of a user at opposite sides of the spine;
• said two upper portions of said body having a combined overall width substantially greater than the maximum width of said lower mounting portion between two opposite side edges thereof;
• said body containing an upwardly opening slit which extends downwardly into the body from an upper end thereof, at a laterally central location and between said two upper portions of the body, and which terminates downwardly at a lower end of the slit above said lower mounting portion of the body;
• said body having two flexible connector portions joining said two upper portions of the body respectively with said lower mounting portion thereof and extending between said lower end of said slit and the upper extremities of said opposite side edges of said lower mounting portion;
• said device being constructed at the location of said slit to avoid support of a user's back along the spine, from the upper end of said slit downwardly to approximately said lower end of the slit, and to thereby allow the spine to project rearwardly farther than do laterally adjacent portions of the user's back which are supported by said two upper portions of said body.