The present invention relates to a vertical axis turbine for utilizing the energy of flowing fluid, such as, for example, wind.

Prior art vertical axis turbines comprise a generally vertically oriented rotor shaft coupled to a generator. The rotor shaft supports a frame which has a number of doors or vanes hinged to the frame to rotate about axes substantially parallel to the axis of the rotor shaft. The blades resist the flow of a fluid and thus cause the rotation of the rotor shaft which in turn transfers the rotary motion to the generator for conversion into electricity. Common problems associated with such turbines include relatively low efficiency and low stability in strong and/or gusty winds.

The object of the present invention is to provide a more stable and efficient vertical axis turbine.

Accordingly, the present invention provides a turbine for extracting energy from flowing fluid, comprising

a rotor shaft having a rotation axis, the rotor shaft being adapted to be rotatably installed in a substantially vertical orientation;

at least one frame supported by the rotor shaft and projecting radially from the rotor shaft;

at least two doors hingedly supported by the frame, each door having a hinge axis substantially parallel to and radially outwardly spaced from the axis of the rotor shaft; with the hinge axis of a first door being outermost with respect to the axes of the rotor shaft and the second door;

the first door and the second door being rotatable about their hinge axes between open and closed positions in relation to a plane of the frame;

wherein a linkage mechanism connects the first door with the second door so that rotation of the first door in one direction causes the second door to rotate in the opposite direction; and so that when the first door is open, the second door is also open, whereas when the first door is closed, the second door is also closed.

In use of the turbine, the first door rotates about its hinge axis between open and closed positions under the influence of a flowing fluid and centrifugal force. Ideally, the first and the second doors are hinged to the same side of the frame so that they project in the same direction with respect to the frame in the open positions. Preferably, the first door is rotatable about an angle within the straight angle of the plane of the frame at one side of the frame.

Ideally, in the open positions the first and second doors are substantially perpendicular to the plane of the frame, whereas in the closed positions the first and second doors are substantially co-planar and substantially parallel to the plane of the frame. Accordingly, in the closed positions the first and second doors resist the flow causing the rotation of the rotary shaft and in fully open positions no substantial resistance from the flow is encountered so that the frame can travel against the flow. Ideally, in the closed position the first ad the second doors form a continuous door surface for resisting the flow.

In use, the first door closes and opens under the influence of the flow and the centrifugal force, whereas, due to the linkage mechanism, the second door closes and opens against the flow. Thus, when the first door is opening with the flow and under the influence of the centrifugal force, the second door opens against the flow and thus counterbalances the forces acting on the first door thereby resulting in a smoother and stable motion of the first door and avoiding jerks. Preferably, the turbine comprises several frames so that for each frame there is another frame projecting in a substantially opposite direction. In one embodiment the turbine comprises four frames angularly spaced around the rotor shaft axis at regular intervals.

In the arrangement having several frames, the opening of the second door against the flow while the first door of one frame is opening with the flow adds power to the rotation since the second door collects the energy from the flow and provides enough power to the rotor shaft to enable the closure of the second door against the flow on an opposite frame when the first door of that frame is closing under the influence of the flow. Ideally, the width of the second door is smaller than that of the first door and is selected sufficient enable the second door to counterbalance the opening of the first door with the flow on one frame, but not too large so as to prevent the closure of first door on the opposite frame by the flow.

In one embodiment, the linkage mechanism comprises a crank arm rigidly attached to the first door at one end and projecting in a direction substantially perpendicular to the plane of the first door, preferably in the direction opposite the direction of opening of the first door. A connecting rod is hingedly attached by its opposite ends to a free end of the crank arm and to the second door at a location radially spaced from the hinge axis of the second door. Accordingly, the rotation of the first door in one direction causes the rotation of the second door in the opposite direction so that the opening of the first door causes the opening the second door while the closure of the first door causes the closure of the second door.

Ideally, a stop member is provided for preventing the rotation of the first door beyond a predetermined angle in relation to the plane of the frame. Preferably the predetermined angle is a substantially right angle between the first door and the plane of the frame extending between the rotor shaft and the hinge axis of the first door.

The provision of the second door linked to the first door renders the turbine more stable while at the same time providing a greater impact area for resisting the flow thereby resulting in greater efficiency of the turbine compared to known turbines with independent doors.

The turbine of the invention is suitable for use as a wind turbine, but it will be appreciated that the invention is not limited to such use only and it will be apparent to persons skilled in the art that the turbine of the present invention is in fact adaptable for extracting energy from any flowing fluid.

The invention will now be more particularly described with reference to the accompanying drawings, which show by the way of example only, an embodiment of a vertical axis turbine according to the invention. In the drawings: Figure 1 is a plan schematic view of a turbine of the invention; and Figure 2 is a perspective view of one frame of the turbine of Figure 1 with flow resisting doors mounted thereon.

The turbine of the invention is described below used as a wind turbine, but it will be appreciated that the invention is not limited to such use only and it will be apparent to persons skilled in the art that the turbine of the present invention is in fact adaptable for extracting energy from any flowing fluid.

Referring to the drawings, a turbine for extracting energy from flowing fluid in accordance with the invention is indicated generally by reference numeral 1 . The turbine 1 comprises a rotor shaft 6 having a rotation axis 60. In use, the rotor shaft 6 is rotatably installed in a substantially vertical orientation and is connected to a generator or another device as required for converting the rotary motion of the rotor shaft in a required form of energy or motion.

Four frames 3 are supported by the rotor shaft 6 and project radially therefrom. The frames 3 are angularly spaced in plane view around the rotor shaft axis at regular intervals so that for each frame 3 there is another frame 3 projecting in a substantially opposite direction.

Doors 2, 2a are hingedly supported by the frame 3. Each door 2, 2a has a hinge axis 20, 20a, respectively, substantially parallel to and radially outwardly spaced from the axis 60 of the rotor shaft6. The hinge axis 20 of a first door 2 is outermost with respect to the axes 60, 20a of the rotor shaft 6 and the second door 2a, respectively.

The first door 2 and the second door 2a are each rotatable about their respective hinge axes 20, 20a between open and closed positions in relation to a plane 3a of the frame 3.

A linkage mechanism indicated generally by reference numeral 70 connects the first door 2 with the second door 2a so that rotation of the first door 2 in one direction (e.g. clockwise) causes the second door 2a to rotate in the opposite direction (e.g. anticlockwise) and so that when the first door 2 is open, the second door 2a is also open, as on the left frame in Figure 1 and in Figure 2, whereas when the first door 2 is closed, the second door 2a is also closed, as on the right frame in Figure 1 . During operation of the turbine 1 , the first door 2 rotates about its hinge axis 20 between open and closed positions under the influence of wind flow and centrifugal force.

The first and the second doors 2, 2a are hinged to the same side of the frame 3 so that they project in the same direction with respect to the frame 3 in the open positions. The first door 2 rotates about an angle within the straight angle of the plane of the frame at one side of the frame and is restricted from rotation to the other side of the frame 3 by the frame 3 itself. A stop member 1 1 is provided for preventing the rotation of the first door 2 beyond a right angle between the first door 2 and the plane 3a of the frame 3 extending between the rotor shaft 6 and the hinge axis 20 of the first door 2.

In the open positions the first and second doors 2, 2a are substantially perpendicular to the plane 3a of the frame 3, whereas in the closed positions the first and second doors 2, 2a are substantially co-planar and substantially parallel to the plane 3a of the frame 3 and form a continuous door surface for resisting the wind 9. Accordingly, in the closed positions the first and the second doors 2, 2a resist the wind 9 causing the rotation of the rotary shaft 6. In fully open positions, as on the left frame 3 in Figure 1 , no substantial resistance from the wind 9 is encountered so that the frame 3 can travel against the wind 9.

In use of the turbine, the first door 2 closes and opens under the influence of the wind 9 and the centrifugal force, whereas, due to the linkage mechanism 70, the second door 2a closes and opens against the wind 9. Thus, when the first door is opening with the wind and under the influence of the centrifugal force, as on the upper frame 3 of Figure 1 , the second door 2a opens against the wind 9 and thus counterbalances the forces acting on the first door 2 thereby resulting in a smoother and stable motion of the first door 2 and avoiding jerks. The opening of the second door 2a against the wind 9 while the first door 2 of the frame 3 (upper frame 3 in Figure 1 ) is opening with the wind adds power to the rotation since the second door 2a collects the energy from the wind and provides enough power to the rotor shaft 6 to enable the closure as indicated by arrow 90 of the second door 2a against the wind on the opposite frame 3 (lower frame 3 in Figure 1 ) when the first door 2 of that frame 3 is closing as indicated by arrow 91 under the influence of the wind 9. The width of the second door 2a is smaller than that of the first door 2 and is selected sufficient enable the second door 2a to counterbalance the opening of the first door 2 with the wind 9 on one frame 3 (upper frame 3 in Figure 1 ), but not too large so as to prevent the closure of first door 2 on the opposite frame 3 (lower frame 3 in Figure 1 ) by the wind

The linkage mechanism 70 comprises a crank arm 4 rigidly attached to the first door 2 at one end. The crank arm 4 projects substantially perpendicular to the plane of the first door 2 in the direction opposite the direction of opening of the first door 2. A connecting rod 5 is hingedly attached by its opposite ends via hinges 7 to a free end of the crank arm 4 and to the second door 2a at a location radially spaced from the hinge axis 20a of the second door 2. Accordingly, the rotation of the first door 2 in one direction causes the second door 2a to rotate in the opposite direction so that the opening of the first door 2 causes the opening the second door 2a while the closure of the first door 2 causes the closure of the second door 2a.

The present invention is defined in the appended claims, the foregoing description of the preferred embodiments being provided merely for the purpose of illustration of the disclosure. Persons skilled in the art will appreciate that various modifications of the above-described embodiments not explicitly described herein are possible within the scope of the invention as defined in the appended claims.