Pivotal-axis changing hinge

A pivotal changing hinge for mounting on a cover and a base of a portable device, comprising:

• a pivoting leaf having
• a pivoting end;
• and
• a keyway being formed through one end of the pivoting leaf and being non-circular;
• a stationary leaf having
• an elongated gudgeon being formed through the stationary leaf, corresponding to the keyway of the pivoting leaf, and being elongated and elliptic;
• and
• a parabolic edge being formed near the elongated gudgeon;
• a pintle assembly having a pivotal axis being defined longitudinally through the pintle assembly and extending through and engaging with the keyway of the pivoting leaf and the elongated gudgeon of the stationary leaf;
• a cam having
• a side surface abutting the stationary leaf;
• a center;
• a mounting hole being formed through the center of the cam, being non circular and mounted through by the pintle assembly to allow simultaneous rotation of the pintle assembly and the cam;
• and
• a protrusion protruding from the side surface of the cam and being mounted slidably along the parabolic edge of the stationary leaf;
• thereby when the cover is opened relative to the base, the protrusion of the cam slides along the parabolic edge of the stationary leaf to gradually lift the pintle assembly within the elongated gudgeon upwardly to prevent the cover from hitting the base.