US Patent 9016437 Personal stair lift

A personal stair lift to transport an individual up and down a stairway on a chair assembly supported on a rail mounted rack comprising a carriage assembly configured to support a lift mechanism including a drive member coupled to a reversible drive motor to rotate the drive member wherein the carriage assembly includes at least one pair of upper rollers and at least one pair of lower rollers movably mounted on a stationary rail disposed on each side of the carriage assembly and a rack mounted to one of the stationary rails disposed to engage the drive member to selectively move the chair assembly and person up or down the stairway when the reversible motor rotates the drive member.