Interlocking mechanism for seat and back of chair

An interlocking mechanism for a seat and a back of a chair comprising:

• a seat body which includes a chassis assembly portion disposed on a front side thereof, a chair-back assembly portion arranged at a rear side thereof, and a spring assembly groove mounted between the chassis assembly portion and the chair-back assembly portion and provided with a rear wall arranged adjacent to the chair-back assembly portion;
• a chair chassis arranged at the chassis assembly portion of the seat body and having at least one first pivot inserted through the chair chassis and the chassis assembly portion of the seat body for pivotal connection with the seat body, a support spring having a rear end connected with a front side of the chair chassis and extending forward from the chair chassis, at least one back spring mounted in the spring assembly groove of the seat body and having a front end connected with a rear side of the chair chassis and a rear end being locked and positioned in a locking portion disposed on the rear wall of the spring assembly groove;
• and
• a pad plate located over the seat body and the chair chassis and including at least one second pivot inserted through the pad plate and the seat body for pivotal connection with the seat body, the pivotal connection between the pad plate and the seat body is located in front of the pivotal connection between the seat body and the chair chassis;
• a front end of the support spring of the chair chassis abuts against a front side of the pad plate.