Patent ID: 8408647

Claim:
A movable chair backrest comprising: a backrest frame having a front face; an upper board having an upper edge and a bottom edge; a lower board having an upper edge and a bottom edge; a resilient sheet connected to the bottom edge of the upper board and the upper edge of the lower board; wherein the upper edge of the upper board is pivotally attached to the backrest frame about a pivot axis parallel to the upper edge of the upper board; and a bouncing board, connected to the bottom edge of the lower board and connected to the front face of backrest frame at a connection, with the connection spaced from and intermediate the upper and bottom edges of the lower board, with the upper edge of the lower board and the bottom edge of the upper board being parallel to the upper edge of the upper board; wherein the bouncing board pushes the lower board apart from the backrest frame to make a buffering distance between the backrest frame and the backrest, with the bottom edge of the upper board abutable with the front face of the backrest frame intermediate the upper edge of the upper board and the bouncing board.