Fluid reaction surfaces (i.e. – impellers) – Articulated – resiliently mounted or self-shifting impeller... – Including movement limit stop or damping means
Patent
1980-11-25
1983-03-29
Powell, Jr., Everette A.
Fluid reaction surfaces (i.e., impellers)
Articulated, resiliently mounted or self-shifting impeller...
Including movement limit stop or damping means
416 11, 416132B, F03D 704
Patent
active
043781985
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to wind-turbines, and more particularly to wind-turbines having but few blades, mounted on a horizontal shaft. More specifically, the invention relates to means for regulating the position and rotation of the blades of such wind-turbines or windmills.
With respect to the degree of freedom of blade movement relative to the shaft, attachment of the blades to the shaft can be divided into four main groups, these being:
1. Rigid hub with fixed blades, in which the blades are mounted on the turbine shaft so as to be totally immovable relative to a vertical axis. This kind of attachment can only be used with "small" windmills, since it results in the occurrence of very large blade-forces which cannot be controlled.
2. Rigid hub with twistable blades, in which the blades are mounted on the turbine shaft in a manner which renders said blades resistant to torsional forces around said shaft and around an axis at right angles to the blades, but which enables the blades to twist about their own axes. Twisting of a blade about its own axis, sometimes known as feathering, enables the attitude of the blade to change in response to prevailing wind conditions, thereby enabling the blade to be held under a certain amount of control. Feathering can be controlled by the wind forces, a control system, or by a combination of the two.
3. Rocking hub with twistable blades (this method of attachment can only be applied with two-bladed windmills) in which the blades are connected together in a torsion-resistant manner to form a blade-pair which is mounted on the turbine shaft in a manner which renders said blade-pair resistant to torsion forces around the turbine shaft, but capable of rotating about an axis extending at right angles to said shaft and at right angles, or substantially at right angles to the bladepair. The blades are also coupled in a manner such that they can twist about their own axes, either individually or in concert. Rocking about the axis at right angles to, or substantially at right angles to the bladepair is normally a free movement, while feathering is controlled to varying degrees by the co-action of a control system, the wind-forces and rocking.
4. Flapping hub with twistable blades, each of which is attached to the turbine shaft in a manner to render said blade torsion-resistant around said shaft, but rotatable about an axis perpendicular to the turbine shaft and perpendicular or substantially perpendicular to the blade. The blades are either coupled so that they can be twisted together, or are individually twistable about their respective axes. Rotation of the blades about the axis extending at right angles to the turbine shaft--flapping --is generally free, while feathering is controlled to varying degrees through the co-action of a control system, windforces and flapping.
The four main methods of attachment afford in a rising numerical sequence reduction of forces and torque at the blade attachment point and the turbine shaft, since the wind-forces on the blade are balanced by inertia forces to a large extent. Problems of a structural nature increase, however, primarily due to increased requirements of damping and of restricting the limit positions of blade movement.
An object of the invention is to provide a wind-turbine of the aforedescribed kind in which all the advantages of a flapping hub from the power aspect are retained, while all the disadvantages associated with uncontrolled flapping movement are avoided.
Accordingly this invention consists in a wind-turbine or windmill having a substantially horizontal shaft and a flapping hub carrying the turbine blades, characterized in that the flap angle of the turbine blade is adjustable by means of the position of the piston of a double-acting piston-cylinder drive means, and in that the two chambers of the piston-cylinder drive means are connected to one another over a regulatable throttle valve. By means of the invention the flapping movement can be caused to act against a damping force having a varying degree of damping
REFERENCES:
patent: 2484291 (1949-10-01), Hays
patent: 2533785 (1950-12-01), Fumagalli
patent: 3144082 (1964-08-01), Grant et al.
patent: 4073600 (1978-02-01), Doman
patent: 4201514 (1980-05-01), Huetter
Powell Jr. Everette A.
Schaffer Murray
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