Chair tilt system with leaf spring

A chair comprising:

• a base;
• a seat comprising an upwardly facing seat pan and a forwardly facing seat back;
• a seat support structure mounted to the base beneath the seat, the seat being movable in a rearward tilting direction from a substantially horizontal position through a range of rearwardly tilted positions;
• a leaf spring disposed between the seat support structure and the seat for biasing the seat in a forward tilting direction towards the substantially horizontal position;
• an adjustment mechanism configured to adjust a force curve of the leaf spring, the adjustment mechanism comprising:
• a rear support operatively associated with a rear end portion of the leaf spring and connected to the seat;
• a front support operatively associated with a front end portion of the leaf spring and connected to the seat support structure;
• and
• an intermediate support disposed between the front support and the rear support, the intermediate support operatively associated with an intermediate portion of the leaf spring and configured to support the intermediate portion of the leaf spring thereon, wherein the leaf spring is bowed over the intermediate support concave downwardly between the front and rear end portions thereof to generate a spring reaction force such that an upward force is applied to the rear support by the rear end portion of the leaf spring to bias the seat in the forward tilting direction;
• wherein the front support is mounted to move at least vertically in response to the seat moving in the forward and rearward tilting directions to enable (a) the front end portion of the leaf spring to deflect upwardly for relieving at least a portion of an increase in the spring reaction force induced by downward movement of the rear support as the seat moves in the rearward tilting direction through the range of rearwardly tilted positions, and (b) the front support to deflect the front end portion of the leaf spring downwardly for restoring at least a portion of a decrease in the spring reaction force induced by upward movement of the rear support as the seat moves in the forward tilting direction through the range of rearwardly tilted positions.