US Patent 7565717 Hinge assembly

A hinge assembly (100) is provided for joining a flip cover (204) to a main body (202) of a foldable electronic device. A hinge assembly includes a hinge shaft (10), a follower (12), and a cam (20). The follower has an outer peripheral portion. The outer peripheral portion has opposite two ends. The cam has a cam hole (22) closely receiving the follower therein. Then cam has an inner peripheral portion movably contacting the outer peripheral portion. The outer peripheral portion is in the form of a screw formed by a cross-section of the follower rotated from one end to the other. The inner peripheral potion is rifled to receive the follower.