Abstract: A seat structure comprises a base configured to be a chair base assembly; a seat support located above the base, wherein a front part of the seat support has rotary connection with the front part of the base through a transition link; a chair back assembly having rotary connection with a rear part of the base through a pivot; a lever driving member linked between the chair back assembly and the seat support, and having rotary connection with a rear part of the seat support, wherein the lever driving member and the seat support are approximately on the same surface. When the chair back assembly rotates rearward around the pivot from the initial position, the rear part of the seat support is raised diagonally to the rear through the lever driving member, meanwhile the transition link and the front part of the seat support are pulled up.

Abstract: A gravity self-adapted chassis of chair has the first plug pin, second plug pin, third plug pin, forth plug pin, tilting plate, first connecting rod, and the second connecting rod of the chassis form into a four-point connecting rod mechanism so as to form the conduction of the force, the backrest is fixedly connected with the tilting plate to offer the driving force of the four-point connecting rod mechanism, the gravity applied onto the seat by the users forms into the reset force applied onto the four-point connecting rod mechanism through the third plug pin hinged with the bracket, and the driving force and the reset force of the four-point connecting rod mechanism form into the confrontation relationship.

Abstract: A seat structure comprises a base configured to be a chair base assembly; a seat support located above the base, wherein a front part of the seat support has rotary connection with the front part of the base through a transition link; a chair back assembly having rotary connection with a rear part of the base through a pivot; a lever driving member linked between the chair back assembly and the seat support, and having rotary connection with a rear part of the seat support, wherein the lever driving member and the seat support are approximately on the same surface. When the chair back assembly rotates rearward around the pivot from the initial position, the rear part of the seat support is raised diagonally to the rear through the lever driving member, meanwhile the transition link and the front part of the seat support are pulled up.

Abstract: A gravity self-adapted chassis of chair has the first plug pin, second plug pin, third plug pin, forth plug pin, tilting plate, first connecting rod, and the second connecting rod of the chassis form into a four-point connecting rod mechanism so as to form the conduction of the force, the backrest is fixedly connected with the tilting plate to offer the driving force of the four-point connecting rod mechanism, the gravity applied onto the seat by the users forms into the reset force applied onto the four-point connecting rod mechanism through the third plug pin hinged with the bracket, and the driving force and the reset force of the four-point connecting rod mechanism form into the confrontation relationship.