Patent ID: 7140677

Claim:
A ball chair comprising: a seat having a top face, a bottom face, a front edge, a rear edge, two side edges, a passage defined in the top surface of the seat, at least three legs formed in the bottom surface of the seat and each leg having a free end, and a supporting base formed on the rear edge of seat having a top surface, a recess defined in the top surface and having an attached bottom defined in the recess, a backrest assembly mounted on the supporting base on the seat and having a backrest having a bracket mounted on the supporting base of the seat having two side walls, a bottom, a rear, two supporting tabs formed on the bottom of the bracket at the rear and abutting against the supporting base, and a holder mounted on the bottom of the bracket beside the supporting tabs and abutting with the attached bottom of the recess defined in the supporting base, and a fixed arm mounted on the bracket, and a ball cushion mounted inside the passage in the seat.