Rotation angle limitation device and portable electronic device having the same

A rotation angle limitation device used by a portable electronic device, with the portable electronic device comprising a top section and a bottom section forming an opening angle;

• wherein the top section rotates respective to the bottom section in a first direction or in a second direction, wherein the second direction is substantially perpendicular to the first direction, with the rotation angle limitation device comprising:
• a base comprising a placed portion and at least one positioning portion;
• a driven element connected to the placed portion and rotatable relative to the base, wherein the driven element has a first position and a second position, and wherein the driven element is secured by the positioning portion when the driven element is in the second position;
• an elastic element disposed between the placed portion and the driven element to provide the driven element with an upward restoration force to move away from the base;
• a first rotation shaft pivotally connected to the placed portion, with the first rotation shaft rotating along the first direction, and wherein the first rotation shaft and the driven element move simultaneously;
• a second rotation shaft pivotally connected to the first rotation shaft, with the second rotation shaft rotating along the second direction;
• and
• at least one cam connected to the second rotation shaft, wherein the at least one cam and the second rotation shaft move simultaneously, wherein each cam comprises a first protruding portion and a concave arc, wherein the first protruding portion is adjacent to the concave arc, wherein when the concave arc substantially comes in contact with the driven element located in the first position, the driven element is separated from the at least one positioning portion and the first rotation shaft rotates along the first direction, wherein when the first protruding portion presses against the driven element, the driven element moves into the second position, the driven element is fixed with the at least one positioning portion and the first rotation shaft cannot rotate along the first direction, wherein the driven element comprises a gear plate;
• wherein the positioning portion is a pillar;
• wherein the gear plate comprises a plurality of gears and a plurality of concave portions arranged in an alternating manner;
• and wherein when the driven element is in the second position, at least a portion of the concave portion of the gear plate is secured with the pillar.