US Patent 8056186 Automatically opening hinge assembly for portable electronic devices

A hinge assembly (100) includes a cam (13), a follower (14), a first spring (12), a control member (18) and a second spring (16). The cam has a cam surface. The follower has a latching cam surface engaging with the cam surface. The first spring provides an elastic force causing the cam surface of the cam and the latching cam surface of the follower to resist each other. The control member slidably resists the follower. The second spring provides an elastic force to return the control member. The control member is movable to push the follower to rotate to realize the cam surface of the cam to rotate relative to the latching cam surface of the follower.