US Patent 9451829 Foldable chair frame

A foldable chair frame includes two spaced leg units, two spaced backrest units, a connecting unit, and a linkage unit. Each of the leg units includes a front leg and a rear leg. The connecting unit is pivotally connected between the leg units. The linkage unit includes at least one link module pivotally connected between the backrest units. The link module includes two links each having a first pivot portion pivotally connected with one of the backrest units and a second pivot portion located opposite to the first pivot portion. Thus, the foldable chair frame is folded in its longitudinal direction and is also folded in its transverse direction to reduce its whole volume to the minimum.