Patent ID: 7258527

Claim:
A vertical axis wind engine comprising: a vertical axis mounted on a base; a transmission provided in a lower portion of the vertical axis for rotational movement output from the vertical axis; at least one arm, each arm having an end rotatably coupled to the vertical axis wherein at least one pair of upper and lower arms are adapted to define an airfoil receiving space therein; at least one airfoil, each airfoil including two pivot pins provided at a top and a bottom thereof respectively, the pivot pins being located distal to the vertical axis, and each airfoil being adapted to be pivotably mounted within the respective airfoil receiving space by pivoting about the pivot pins; at least one elastic stop member provided on each arm proximate to the airfoil and spaced from the pivot pin, each stop member being adapted to limit a pivot angle of the respective airfoil; wherein each stop member is adapted to lift the pivot limitation of each respective airfoil for allowing the airfoil to pivot when the airfoil experiences a pushing force of the wind that is larger than a maximum resistance force thereof; wherein each of some airfoils are adapted to exhibit a narrow contour for offering the least resistance to wind disposed at the leeward side of the respective airfoils; wherein each of some airfoils are adapted to exhibit a wide contour for offering the most resistance to wind by pivoting the respective stop members to their limits when the respective airfoils are disposed at their leeward side; and two opposite pivotal pawl elements at each pair of the arms, each pawl element being located near a free end of respective arms distal to the vertical axis; wherein each pawl element is adapted to pivot toward a predetermined direction only in response to force exerted thereon and is adapted to return to its original position after the force is removed, such that the pawl elements are adapted to stop and prevent the airfoils from pivoting counterclockwise to their windward sides from their leeward sides and enable the airfoils to have a wide contour; and wherein each airfoil is adapted to pivot clockwise to contact and pass the pawl elements after the pivot limitations imposed on the airfoils by the respective stop members have been lifted by a strong wind so as to enable each airfoil to have a normal wide contour.