Seat pivoting mechanism and chair height locking system

A chair comprising a chair bottom, a chair back, a chair base, a pivoting mechanism that supports the chair bottom and the chair back to pivot in relation to the chair base, a height adjustment mechanism for selectively permitting an adjustment of a height of the chair bottom and the chair back in relation to the chair base, and a height locking mechanism with a first, restraining condition wherein actuation of the height adjustment mechanism is prevented and a second, non-restraining condition wherein actuation of the height adjustment mechanism is permitted;

• wherein the pivoting mechanism comprises a mechanism body with at least a first support structure pivotally engaged with the mechanism body to pivot about a pivot axis;
• at least a first pivoting resistance mechanism for providing resistance to a pivoting of the first support structure relative to the mechanism body
• wherein the height adjustment mechanism comprises an extendable and retractable cylinder with an actuating tip and a pivotable lever with a first end comprising a handle, a second end comprising a tip, and a pivot axis between the first and second ends, wherein the lever has a zone of operation wherein, over one portion of the zone of operation, the tip of the lever is disengaged from the actuating tip of the cylinder and wherein, over a second portion of the zone of operation, the tip of the lever actuates the actuating tip of the cylinder to permit adjustment of the height of the chair bottom and the chair back in relation to the chair base;
• wherein the height locking mechanism, when in the first, restraining condition, limits the zone of operation of the lever to prevent the lever from pivoting into actuating engagement with the actuating tip of the cylinder and wherein the height locking mechanism, when in the second, non-restraining condition, permits the lever to pivot to actuate the actuating tip of the cylinder;
• and
• wherein the height locking mechanism comprises a height locking member that can be selectively extended to the first, restraining condition where the height locking member presses against the lever spaced from the tip and the pivot axis of the lever and thereby to limit the zone of operation of the lever to prevent the lever from actuating the actuating tip of the cylinder and wherein the height locking member can be selectively retracted to a second, non-restraining condition to free the lever to pivot into actuating contact with the actuating tip of the cylinder.