BACKGROUND OF THE INVENTION THIS invention relates to a turbine. More specifically, the invention relates to a variable geometry vertical axis turbine.

Variable geometry vertical wind axis turbines are known in the art. One such turbine is disclosed in European patent document EP0095600 by Erich Herter, et al. The Herter patent discloses a turbine having vanes on the opposing ends of a rotor supported on a shaft, wherein each vane is arranged so as to travel through a space not swept by the other vane. This turbine has a number of disadvantages, one of which being the incapability of properly balancing the turbine to prevent vibration. To prevent vibration, rotating machinery such as turbines must be balanced. Vibration caused by unbalanced rotating machinery may result damage or ultimately failure in bearings, support structures and even on the structure of the rotating machinery itself.

Typically, there are three levels or forms of balance, namely:

• static (one plane) balance;

• dynamic (two plane) balance; and

• balance of other specific forces, such as aerodynamic balance in the case of wind turbines. It is known in the art that passive and active balancing may be used to achieve static and dynamic balance of rotating machinery. Passive balancing typically includes the identification of resultant forces and resultant moments, which are then countered by the addition of counterweights positioned at specific radii and angles. Active balancing typically includes a form of sensing pending or actual imbalance and the generation of some corresponding intervention to correct the imbalance.

Passive balancing works relatively well for rotating machinery with only static and dynamic imbalance. However, vertical axis wind turbines (for example) are also affected by aerodynamic imbalance as the aerodynamic forces imposed on the turbine vary throughout the azimuth. Active balancing might attempt to correct the effect of aerodynamic imbalance, but the further complication of axial blade disposal, encountered in high productivity configurations, might make balance virtually impossible to attain.

Another known variable geometry turbine is disclosed in United States patent document US4421458 by Peter Musgrove, et al. The Musgrove patent discloses a vertical axis wind powered turbine having rotor blades carried on a rotor arm, in which the blades can be reefed to reduce torque on the turbine. The blades of the Musgrove turbine have two portions pivotable with respect to one another by the reefing means so as to move from a position parallel to the rotation axis to a position at which they form an angle about a plane perpendicular to the rotation axis. As with the Herter turbine, the Musgrove turbine has a number of disadvantages, the complexity of the blades being just one.

It is an object of the current invention to address the disadvantages of the prior art. SUMMARY OF THE INVENTION

According to the invention there is provided a turbine including: a shaft; a plurality of aerofoil blades; and a plurality of connecting arms, the connecting arms being pivotally connected at a first end to the shaft and at a second end to at least one of the aerofoil blades, the aerofoil blades being: movable between a retracted position, wherein the aerofoil blades lie against or in close proximity to the shaft, and an extended position, wherein the aerofoil blades are spaced away from the shaft; and configured into corresponding aerofoil blade pairs, wherein each of the aerofoil blades making up a corresponding aerofoil blade pair maintain a common radial location with respect to the shaft and maintain a location, with respect to one another, being on opposite sides of and equidistant from a plane being perpendicular to a longitudinal axis of the shaft and located between first and second ends thereof; such that the aerofoil blades are symmetrical about the perpendicular plane, whether in the retracted position, the extended position or any other position therebetween, thereby placing the shaft of the turbine in balance.

Typically, the aerofoils are configured to retain a substantially parallel orientation with respect to the shaft whether in the retracted position, the extended position or any other position therebetween.

Generally, the turbine is a vertical-axis turbine and the shaft is supported in a substantially vertical orientation. Preferably, the aerofoil blades on each of the respective sides of the perpendicular plane are equally spaced circumferentially about the shaft. More preferably, three aerofoil blades are located on each of the respective sides of the perpendicular plane and circumferentially spaced apart from one another by 120 degrees.

The points at which each of the connecting arms are pivotally connected to the shaft may be axially spaced along the shaft. Alternatively, the points at which each of the connecting arms are pivotally connected to the shaft are axially common or proximate to one another.

Generally, the aerofoil blades, moving between the retracted and extended positions, are movable radially away from the shaft and either axially towards or away from the perpendicular plane. Typically, the connecting arms are substantially parallel with the shaft with the aerofoils blades in the retracted position and substantially perpendicular with the shaft with the aerofoils blades in the extended position.

The shaft may be rotatably supported at or near one end, at both ends or at a location where the perpendicular plane intersects the longitudinal axis of the shaft.

Furthermore, the aerofoil blades on the same side of the perpendicular plane may be flexible and integral with one another to form a continuous aerofoil blade. In this embodiment, the aerofoil blades are preferably a plurality of individual aerofoil blades jointly following a common path. Alternatively, the continuous aerofoil blade or common path followed by the individual aerofoil blades is helical or spiral in shape.

The pivotal movement of each of the connecting arms relative to the shaft and the respective aerofoil blade to which it is connected may be limited to movement in a single common plane. Preferably, the single common plane is co-planar with the shaft.

The connecting arms may be aerofoils, contributing to the power generating capacity of the turbine. Alternatively, the connecting arms have an aerodynamically efficient profile to minimize drag. Preferably, the aerofoil blades and/or the connecting arms of corresponding aerofoil blade pairs are linked such that their movement is mirrored about the perpendicular plane. Furthermore, the aerofoil blades and/or the connecting arms of the aerofoil blades on the same side of the perpendicular plane are linked such that their movement is synchronous. More preferably, the aerofoil blades and/or the connecting arms are linked mechanically, pneumatically, hydraulically or electrically.

In one preferred embodiment, the movement of the aerofoil blades between the retracted and extended positions is as a result of wind energy acting thereon, wherein the turbine comprises self-starting capability in low energy and low speed winds with the aerofoil blades in the retracted position, and further wherein the aerofoil blades, under centrifugal force, are moveable into the extended position as the energy and speed of the wind increases.

The turbine may include means for controlling the movement of the aerofoil blades, the control means being actuated by sensors measuring wind speed, wind direction, turbine rotational speed and/or any other parameter.

According to a second aspect of the invention, there is provided a turbine including: a shaft; a plurality of aerofoil blades; and a plurality of connecting arms, the connecting arms being pivotally connected at a first end to the shaft and at a second end to at least one of the aerofoil blades, the aerofoil blades being: movable between a retracted position, wherein the aerofoil blades lie against or in close proximity to the shaft, and an extended position, wherein the aerofoil blades are spaced away from the shaft; and configured on the shaft so as to sweep a common area about the shaft and to retain a substantially parallel orientation with respect thereto whether in the retracted position, the extended position or any other position therebetween.

Typically, the aerofoils are configured to retain a substantially parallel orientation with respect to the shaft whether in the retracted position, the extended position or any other position therebetween. Furthermore, the turbine is preferably a vertical-axis turbine and the shaft is supported in a substantially vertical orientation.

The aerofoil blades may be are equally spaced circumferentially about the shaft. Generally, three aerofoil blades are circumferentially spaced apart from one another about the shaft by 120 degrees.

In one embodiment, the points at which each of the connecting arms are pivotally connected to the shaft may be axially common or proximate to one another. Furthermore, the aerofoil blades, moving between the retracted and extended positions, are movable radially away from the shaft and either axially towards or away from a common end of the shaft.

Generally, the connecting arms are substantially parallel with the shaft with the aerofoils blades in the retracted position and substantially perpendicular with the shaft with the aerofoils blades in the extended position.

The shaft may be rotatably supported at or near one end, at both ends or at a location between the two ends.

Typically, the pivotal movement of each of the connecting arms relative to the shaft and the respective aerofoil blade to which it is connected is limited to movement in a single common plane. Preferably, the single common plane is co-planar with the shaft. The connecting arms may be aerofoils, contributing to the power generating capacity of the turbine. Alternatively, the connecting arms have an aerodynamically efficient profile to minimize drag. The aerofoil blades and/or the connecting arms may be linked such that their movement is synchronous. In a preferred embodiment, the aerofoil blades and/or the connecting arms are linked mechanically, pneumatically, hydraulically or electrically. In one preferred embodiment, the movement of the aerofoil blades between the retracted and extended positions is as a result of wind energy acting thereon, wherein the turbine comprises self-starting capability in low energy and low speed winds with the aerofoil blades in the retracted position, and further wherein the aerofoil blades, under centrifugal force, are moveable into the extended position as the energy and speed of the wind increases.

The turbine may include means for controlling the movement of the aerofoil blades, the control means being actuated by sensors measuring wind speed, wind direction, turbine rotational speed and/or any other parameter.

The aerofoil blades may have a variable pitch. Preferably, the turbine is coupled to a machine to convert the energy captured by the turbine into another form of energy. More preferably, the machine is a generator for generating electrical power.

It will be appreciated that reference to "substantially" in this specification, in the context "substantially vertical orientation", "substantially parallel orientation", "substantially parallel" or "substantially perpendicular", will be understood to include exact vertical orientation, parallel or perpendicular relationship, as well as any small deviation therefrom, where a small deviation is within 20 degrees to either side of the exact orientation or relationship. Preferably, the small deviation is within 10 degrees to either side of the exact orientation or relationship. Most preferably, the small deviation^ is within 5 degrees to either side of the exact orientation or relationship.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a side view of a first embodiment of a turbine in accordance with the present invention;

Figure 2 is a side view of a second embodiment of the turbine;

Figure 3 is a side view of a third embodiment of the turbine; and

Figure 4 is a perspective view of a fourth embodiment of the turbine.

DETAILED DESCRIPTION OF THE DRAWINGS

A turbine according to a preferred embodiment of the invention is designated generally with reference numeral 10 in figure 1. The turbine 10 includes a shaft 12 and a plurality of aerofoil blades 14 connected to the shaft by connecting arms 6 .

Although the turbine may take many different configurations, it will be appreciated that for the purposes of describing the invention, a vertical-axis wind turbine, and particularly of a Darrieus-type of turbine, will be made reference to.

The vertical shaft 12 of the turbine 10 is supportable in many different ways. Although not shown, one way is by supporting the shaft 12 at or near a first bottom end 12A in a cantilever support formation. Another way is by supporting the shaft 12 at or near the first bottom end 12A and a second upper end 12B, the second upper end 12B being supported by a housing located over the shaft by a number of guide wires secured between the housing and the ground (not shown).

Yet another way of supporting the shaft 12 is by supporting it at some other point (not shown) between the first bottom end 12A and the second upper end 12B thereof. It will be appreciated that although the shaft 12 is supportable in many different ways, it is preferable that it be supported on bearings, more preferably a combination including thrust bearings.

The connecting arms 16 are pivotally connected to the shaft 12 at a first end and pivotally connected to one of the aerofoil blades 14 at an opposite second end. In use, the aerofoil blades are movable between a retracted position and an extended position.

In the retracted position, the aerofoil blades 14 lie against or in close proximity to the shaft 12, with the connecting arms 16 being substantially parallel with the shaft 12. In the extended position, the aerofoil blades are spaced away from the shaft 12 with the connecting arms 16 being substantially perpendicular with the shaft 12.

The aerofoil blades 14 are configured on the shaft 12 so as to sweep a common area about the shaft 12, and to retain a substantially parallel orientation with respect thereto whether in the retracted position, the extended position or any other position therebetween.

Although the turbine 10 may comprise any number of aerofoil blades 14, it preferably comprises three aerofoil blades circumferentially spaced apart from one another by 120 degrees. More preferably, the connecting arms 16 are pivotally connected to the shaft 12 at an axially common location 18, or at least proximate to one another.

The aerofoil blades 14 and/or the connecting arms 16 are linked such that their movement is synchronous. The aerofoil blades 14 and/or the connecting arms 16 are linked mechanically, pneumatically, hydraulically or electrically. It will be appreciated that the aerofoil blades 1 are movable between the retracted and extended positions by the energy of wind acting there upon or by some actuating means. With reference now to figure 2, and for the purposes of increased efficiency and balancing the turbine 110 more effectively, the turbine 110 may include more than one aerofoil blade set 111A, 111B. The aerofoil blade sets 111A, 111 B are configured into corresponding aerofoil blade pairs 114Α ^,2,3 ,114Β ¹ · ^2,3 wherein each of the aerofoil blades making up a corresponding aerofoil blade pair (for example aerofoil blade pair 114A ¹ and 114B ¹ ), maintain a common radial location with respect to the shaft 112. Furthermore, the corresponding aerofoil blade pair 114A ¹ , 114B ¹ maintain a location, with respect to one another, being on opposite sides of and equidistant from a plane 115, being perpendicular to a longitudinal axis of the shaft 112 and located between first and second ends 112A.112B thereof. In this manner, the turbine 110 is balanced as a result of the corresponding aerofoil blades pairs 114A ^,2,3 ,114B ¹ ' ² ' ³ being symmetrical about the perpendicular plane 115, whether in the retracted position, the extended position or any other position therebetween.

The turbine 110 illustrated in figure 2 comprises aerofoil blades 114A,114B, pivotally connected by the connecting arms 116 at pivot locations 118, which in use move radially outwardly from the shaft 112 and axially toward the perpendicular plane 115 as they move between the retracted and extended positions.

With reference now to figure 3, and using like reference numerals to designate like components of the turbine 210, the aerofoil blades 214A.214B can be made to move in use radially outwardly from the shaft 212 and axially away from the perpendicular plane 215 as they move between the retracted and extended positions by re-locating the pivoting connecting location 218 of the connecting arms 216 to the shaft 212.

Although the turbine 110,210 illustrated in figure 2 and figure 3 show three aerofoil blades per blade set, it will be appreciated that any number of aerofoil blades may be used in each blade set, so long as the number of aerofoil blades in each of the blade set is equal.

The aerofoil blades 114A,114B; 214A.214B of the turbine 110,210 within a corresponding blade pair and/or a corresponding blade set are linkable mechanically, pneumatically, hydraulically or electrically such that their movement is mirrored about the perpendicular plane 215.

Figure 4, shows yet another embodiment of the turbine 310, with like reference numerals again designate like components. In this embodiment, the points 318 at which the connecting arms 316 pivotally connect to the shaft, 312 are neither at a common axial location on the shaft 312 nor in close proximity, but rather axially spaced away from one another along the length of the shaft 312.

With respect to all of the embodiment of the turbine 10,1 0,210,310 illustrated in the figures, it will be appreciated that the pivotal movement of each of the connecting arms relative to the shaft and the respective aerofoil blade to which it is connected is limited to movement in a single common plane. It will be appreciated further that the single common plane is co-planar with the shaft. It will be appreciated further that the connecting arms may be designed to have an aerodynamically efficient profile to minimize drag during operation. Alternatively, the connecting arms may be designed to contribute to the power generating capacity of the turbine. To increase the power generating capacity of the turbine further, the aerofoil blades may have a variable pitch.

To generate electricity, the turbines in use are coupled to generators for converting the wind power into electrical power.

It will be appreciated that turbine offers a variable solidity turbine, capable of operating at higher coefficients of performance over a wider range of wind speeds. The variable geometry of the vertical axis wind turbine enable self starting more easily than conventional vertical axis wind turbines, and furthermore, offers the capability of reducing solidity for the purposes of running at high speeds for power generation. Where wind speeds become too high, the solidity of the turbine may be increased to counter the wind speeds. It is envisaged that the solidity of the turbine is controllable by sensors, controllers and actuators together with onboard intelligence.

Although the invention has been described above with reference to preferred embodiments, it will be appreciated that many modifications or variations of the invention are possible without departing from the spirit or scope of the invention.