Patent CA-2479517-A1 (CA)
Title: Libra tower for wind turbine
Inventor: MATHIEU ALFRED L
IPC: F03D13/20
Filed: 2004-09-15
Abstract: The purpose of the invention is to create a tower termed the Libra Tower that has a primary function of being sufficiently high for modern wind turbine generators, is of relatively simple construction, is non-rigid in structure, and has the wind turbine on top of the vertical tower operating in a horizontal and rotatable position.   The secondary function of they Libra Tower is to have the ability of limited rotation and thus easily lowering the tower with the turbine to ground level, more or less, for critical repairs, without the use of an industrial crane. Thus the "down time" which can be a crucial economic factor as well as the untimely inconvenience for its customers is reduced. In the event that a storm is being forecasted, the Libra Tower can be lowered to the ground level, similar to a ship lowering its sails, and avoid significant damage. Once the storm has passed, the tower can be quickly raised and power restored.  This feature would be especially appreciated after a natural disaster like a hurricane or an earthquake when normal electrical grids are inoperative. Thus the Libra Tower can be installed not only in inland areas where the wind is economically viable for turbines but in remote areas where inclement weather and high winds are the noun.   The Libra Tower is geometrically designed by combining a primary base form of a 60 degree hexagon, superimposed with a 6 sided 60 degree pyramid tapering to the apex, the Libra Scales, and 2 old fashioned wagon wheels with a hand brake.   The dimensions of the structure axe mathematically proportionate; each side of the hexagon is 10 meters more or less, and the base of each corner of the pyramid is fixed at each vertex of the hexagon, and each corner of the pyramid, acting as braces, is at a 60 degree angle. Thus the skeletal lattice structure of each corner to the apex is then 20 meters more or less. This proportion permits a tower to be emplaced in the centrality of the pyramid at a height of 35 meters, more or less. The basic building component of the tower is a rectangular pre-fabricated lattice structure, the width and depth are varied according to the tensile strength that is needed, each is 10 meters in length, each with the capability of interlocking with an add-on lattice. This basic building component is ideal for mass production.   In order to emplace the tower centrally in the center, the basic pyramid structure is halved, each half resulting in a 3 sided pyramid and between each half is a vertical and horizontal passage-way throughout of 2 meters, more or less, permitting the tower to be installed vertically and also allow for its limited rotation, the whole complemented by its necessary support structure.     The altitude of each half pyramid structure, the distance from the apex to the base, is 17.3 meters, more or less, and this altitude represents one half, more or less, of the total height of the tower to be 35 meters, more or less. Two face to face vertical support structures in the passageway center support the tower, which is fixed at the center by a sufficiently large, permanent horizontal fulcrum axle, that is on a reinforced plate, below each apex of the pyramidal braces. This axle holds the Libra Tower in place centrally and it also cohesively bridges the two halves. A second removable horizontal axle, of similar diameter is installed at the base above the ground level, and fixes the tower in a vertical mode when operating, and when removed, the tower is free to rotate to an obtuse angle of 150 degrees more or less to a servicing mode. There the turbine can be sheltered during cold and snowy weather conditions and servicing can proceed.   Each axle is secured according to earthquake standards so as to absorb the vibrations from the propeller rotors and even minor earthquakes. A buttress at the base keeps the base of the tower from over passing the center when it is being raised vertically. The top of the tower can be customized to fit whatever design the turbine base has in order to fit congruently.   The Libra Scale feature of the Libra Tower is the ballast inserted at the base that is equal in weight, more or less, to the weight of the turbine. The turbine may weigh 750 kilograms, for example and to achieve balance when in rotation, the ballast must be introduced in the base structure that is equal to the weight of the turbine, more or less.     The ballast at its base contributes greatly to the stability of the tower.   The tower structure is reinforced to support the extra weight of the turbine and the ballast, especially when in a horizontal position. This is attained by two "bridge" trusses, one on the upper side and one on the lower side of the tower. The two trusses are supported by a perpendicular diametric arm from the fulcrum axle, and complemented with the lattice framework radiating to both ends that strengthen and stabilize the tower.   The third feature of the Libra Tower is a simulated wagon wheel on each side of the tower on the fulcrum axle, acting as a brake and support. The rim of the wheels are the brake drums and each wheel has 2 brake pads adjacent to the rims that are secured on the stationary rectangular structures supporting the tower. The brakes on the wheels have cables directly connected to the hand brake at ground level and can be activated by an operator so that the turbine is lowered very slowly or brought to a complete stop. This an essential safety component.   Winch cables attached to the front bumper of an utility vehicle are used to raise or lower the tower. The cables are attached to secure appendages on the top and at the base of the tower.