Self-locking folding bracket and folding chair

A self-locking folding bracket, comprising two symmetrical foldable side supporting structures and a linkage assembly connected between the two side supporting structures;

• wherein the linkage assembly comprises two groups of side rods, two groups of cross rods and two groups of connecting rods, and the two groups of cross rods are disposed in an X-shaped crossed manner to form a first hinged point;
• one end of the cross rod is hinged with a lower end of the side supporting structure to form a second hinged point, and an other end of the cross rod is hinged with the side rod through the connecting rod;
• the side rod is hinged with an upper end of the side supporting structure, a lower end of the side rod is hinged with the cross rod, the side rod and the cross rod form a third hinged point, and the third hinged point is located between the first hinged point and the second hinged point;
• when two hinged points of the connecting rod are on an extension line of the cross rod to realize collineation, the cross rod and the connecting rod have an extreme position in a rotation process, the linkage assembly is in a working state when the cross rod passes down the extreme position and the cross rod is abutted to the side rod, and the linkage assembly is in a folding state when the cross rod moves upward past the extreme position and away from the side rod;
• and when the linkage assembly is in the working state, the linkage assembly is unfolded and maintains a distance between the two side supporting structures, and when the linkage assembly is in the folding state, the linkage assembly causes the two side supporting structures to be close to each other.