Windmill having blades which alter their pitch angles automatica

Details Windmill having blades which alter their pitch angles automatica Windmill having blades which alter their pitch angles automatica

1992-08-10

1993-07-13

Look, Edward K.

Fluid reaction surfaces (i.e., impellers)

Articulated, resiliently mounted or self-shifting impeller...

Sectional, staged or nonrigid working member

416132B, 416135, 416237, 416240, F03D 106, F03D 704

Patent

active

052268055

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention relates to windmills.
With the depletion of the world's mineral resources alternative sources of energy have become more popular and one of these is wind power. It has been proposed to erect large windmills having wind drive blades connected with generators for producing electricity. However, the large variations in wind speed have necessitated the incorporation of pitch variation for the blades so that a generally constant blade rotation is approximated.
GB-A-2,169,663, in the name of the present applicant, discloses a construction for a windmill blade wherein the blade is connected to a hub by means of an intermediate portion, the intermediate portion being connected to the hub and to the blade by first and second parallel hinges and being itself hinged along a third axis extending diagonally between the parallel hinges. The hub, blade and intermediate portion are moulded integrally from plastics material, the hinges comprising resilient creases in the plastic. In a rest condition, the creases orient the blade at an angle to its plane of rotation and rotation of the blade creates a centrifugal force on the blade which tends to flatten out the hinge creases, thereby reducing the pitch angle of the blade in response to changes in its speed of rotation caused by variations in wind speed.
The blade of GB-A-2,169,663 thus reacts automatically to changes in wind speed by reducing its pitch angle as the wind speed increases and increasing its pitch angle as the wind speed drops. However, it is not responsive to variations in the torsional loading on the shaft which it is driving, i.e. at any given wind speed the pitch angle will not change in response to changes in torque at the shaft.


SUMMARY OF THE INVENTION

It is an object of the present invention to provide a windmill having blades which alter their pitch angles automatically in response to changes in both wind speed and load.
According to the present invention there is provided a windmill including a plurality of windmill blades extending outwardly from and spaced equi-angularly about a central axis of rotation and each having a leading edge and a trailing edge, the blades being connected together at a central hub portion and adapted to rotate about said central axis in a plane of rotation normal to said central axis, each of said blades having an inner section hingeably attached to said hub portion along a first hinge axis and an outer section hingeably connected to said inner portion along a second hinge axis, said second hinge axis extending from a point on the trailing edge of the blade adjacent to the first hinge axis to a point on the leading edge of the blade remote from the first hinge axis, the inner section being resiliently biased towards a rest position wherein it lies in a plane at an angle to the plane of rotation and wherein the outer section is disposed at a pitch angle relative to the plane of rotation, such that force applied to the blade against the bias force tends to reduce the angle between the plane of the inner section and the plane of rotation and the pitch angle of the outer section.
Preferably, said hub portion is attached to a rotatable shaft extending rearwardly from the hub along the axis of rotation, and said inner section of each blade is angled outwardly and rearwardly from the hub when in its rest position.
Preferably also, said inner section of each blade is biased towards its rest position by at least one resilient bias element connected between the hub portion and the inner section.
Preferably also, said hub portion includes an anchoring member spaced from the first hinge axes along the axis of rotation, said at least one resilient bias member of each blade having a first end connected to the anchoring member and a second end connected to the inner section of the blade.
Preferably also, said second end of said at least one resilient member of each blade is attached to a plate member secured to an inner surface of the inner section facing the axis of rotation.
Suitably, said

REFERENCES:
patent: 1043830 (1912-11-01), Heath
patent: 2050142 (1936-08-01), White
patent: 4191506 (1980-03-01), Packham
patent: 4310284 (1982-01-01), Randolph
patent: 4909703 (1990-03-01), Jacobs

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