CA1315697C - Vertical axis wind turbine - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A vertical axis wind turbine blade is provided herein. Such blade includes a blade body having a leading edge and trailing edge, the edges being generally parallel to each other. Each blade is substantially-straight and includes opposite, longi-tudinally-extending surfaces exposed to the wind, with each sur-face having a series of troughs formed equispaced and parallel to each other along substantially the entire blade length. Wind striking the blade surfaces, diverges and decelerates as it flows through each trough towards the trailing edge, thereby to effect transferring wind energy to the blades.

Description

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The present invention generally relates to vertical, cross-wind axis wind turbines having plural wind driven blades with variably-adjusted orientation to incident wind.
This application is a division of copending application Serial No. 57~,456 filed July 19, 1988.
Wind axis and cross-wind axis turbines are the predominant wind turbines presently in use and under study. A wind axis turbine includes a number of blades mounted for rotation about a central horizontal column having an axis of rotation that must be closely aligned with the wind to produce power efficiently.
Since wind direction tends to vary over time at most sites, high efficiency can be achieved only if the horizontal axis can be rotated to provide the close alignment. However, structure for rotating the horizontal axis into the wind tends to be expensive, resulting in poor power cost ratios for very high power wind turbines.
Another problem associated with certain known relatively high efficiency cross-wind axis wind turbines is that the blades have complex shapes, thus being expensive to manufacture. Other turbines of this type are inefficient because the blades are not designed so they are always oriented to the wind for optimal wind energy absorption.
~5 Vertical wind driven turbines typically include an assembly of airfoils or blades mounted for wind-driven structure. Ver-tical wind driven turbines respond to wind from any direction ~ ' " ' ' .

~ 3 ~ 7 without shift of the column or base structure thereof. However, to improve blade efficiency, by obtaining a more favourable blade angle of attack to the wind, it is often necessary to rotate each blade about an individual axis thereof as the assembly rotates about the vertical column. Known structures of such vertical wind driven turbines include: the type disclosed in U.S. Patent No. 4,049,362 to Rinee; a ring gear arrangement as disclosed in U.S. Patent No. 3,903,072 to Quinn; or a circular track and bearing arrangement as disclosed in German Patent No. 742,788 to Hartwagner. The blade angle of attack control structures dis-closed in the aforesaid patents also vary the blade in response to changes in wind speed or velocity.
The foregoing blade control arrangements have a number of disadvantages. One disadvantage is that a higher than average on-site wind velocity is often necessary to overcome inertia of the ring gear, gear train or circular track mechanisms to initi-ate turning of the blades. To maintain blade rotation, a certain amount of wind power is necessary to overcome inertia of the ring gear, gear train or circular track mechanisms by initiating turn-ing of the blades. To maintain blade rotation, a certain amount of wind power is necessary to overcome friction generated by these blade control mechanisms. The diverted wind power adverse-ly affects power/cost ratios. Further, since gears employed inthese prior art mechanisms rotate constantly, in wearing contact with each other, and operate under variable wind velocity condi-' ~

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tions, frequent maintenance and/or replacement may be necessary,particularly after periods of excessive wind velocities. To generate sufficient wind power to achieve economical operation, vertical wind turbines generally include large airfoils. Devices to control such large airfoils can be very costly.
In the fields of wind turbines and vertical-axis-types tur-bines in general, the airfoil or blades must perform under con-dition of wind pressure reversal for each revolution of the tur-bine. For each given design shape, the blade must perform well.
However, this is not always the situation. Often a trade-off in performance has been required within the blade design shape in order to give better performance on wind flows on one side than on the other side.
An example of a vertical axis wind turbine with an airfoil design that is far better suited for deriviny energy from one side of an airfoil blade than the other side, is U.S. Patent No.
4,130,380 by Kaiser. In addition, there are designs that use large massive structures in an attempt to improve the channelling and compressing of wind flows; such designs are shown in such patents as U.S. Patent No. ~,490,623 by Goedecke or Canadian Patent No. 1,027,052 by Baumgartner. Yet another type of design used for an improvement of wind flows is one involving the use of an end plate angled on the blade ends. This would give some improvement on one side over the other side thereof, the main function being to keep the air flows from merging on the blade .

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ends. Another design involves means for controlling turbine speed, as provided by U.S. Patent No. 4,255,085 by Evans.
Another design which has been tried involves the use of flexible rubber or plastic blades which bend into a contour shape, to adjust the wind flows to provide circular rotation about the axis, as provided in German Patent No. 282700~4 by Lagarde. This design would, however, have a stability problem, i.e., the blades may get out of synchronous balance with each other and would be subject to fatigue of the blade materials. The use of troughs has been attempted on ship screws and rudders, as indicated by the following patents: U.S. Patent No. 1,465,593 by Barrett et al; and French Patent by Jacquemin 773,033 (which provide a single-sided trough); British Patent No. 838,868, and U.S. Patent No. 2,962,101 (which provide ship screws); U.S. Patent No.
2,899,128 by Vaghi ~which provide an air blower); U.S. Patent No.
2,013,473 by Meyer (which provide a fluid propeller and fan blade); and U.S. Patent No. 1,861,065 by Poot (which provides a propeller screw having serrated blades).
Vertical, wind-driven turbines typically include an assembly of airfoil blades mounted to a wind-driven shaft of a supporting axis-type structure, with a capability to respond to wind flows deriving from any direction without a shifting of the structural ~5 mass. One effect of wind flows on the airfoils causes circula-tory vertical travel about its central path. In addition, a tur-bulent air flow about the airfoil surface is derived from a . ~

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reversing of pressure flows upon the airfoil blades. Another problem of airfoils in general requires the slowing of the air-flows on the wind incident side of the blades, while substan-tially simultaneously requiring an increase in the airflows on the other side of the airfoil. A useful type of airfoil-blade ~ or vertical axis wind turbines that is well suited to the prob-¦ lem of wind pressure reversal, should be an airfoil design that ¦ 10 performs equally well to the high and low pressure changes on the ¦ blades upon exposure of wind thereon. Another desired affect is to cause circulatory travel about a vertical axis to provide an improvement of energy transfer in lower wind velocities onto the blades. Another aim would be to cause the wind flow to slide into the contouring troughs and in so doing to slow-down and modify the wind flows to provide for optimizing the transfer of ¦ wind energies to the turbine blades, thereby to provide a greater output of total energy. A number of wind turbines are presently in use which would need to be improved by the provision of aero-dynamic airfoil blades that are better sulted for the transferr-ing of energy velocities of winds onto the blades for generating sufficient power. This aim is to achieve economical operations, so as to overcome the present cost-to power ratios that adversely affect a useful deveiopment of wind turbines.
It is accordingly an ob~ect of a broad aspect of this inven-tion to provide a vertical axis wind turbine blade for a vertical wind turbine, the blade having a low inertia blade control mech-. ,.~ .. . .. .

~ 3 ~ 7 anism ~or controlling both the speed and orientation of plural vertical blades under variable wind conditions to maximize con-version of wind power to usable power.
An object of another aspect of this invention is to provide a vertical axis wind turbine blade for a wind turbine, the blade having a blade control mechanism that is economical in design and is capable of reliable operation in rugged and hostile environ-ments, as occurs in on-site wind locations.
An object of yet another aspect of this invention is to pro-vide a vertical axis wind turbine blade which has provisions for controlled orientation of blades in the vertical wind turbine to regulake angular velocity of the blades and hence conversion efficiency of the turbine.
By one broad aspect of this invention, a blade is provided for use in a wind driven turbine of the vertical axis type, com-prising: a blade body of elongated rectangular configuration having opposite blade surfaces, a leading edge and a trailing ~0 edge, the edges being generally parallel to each other; each blade being substantially-straight and including opposite, longi-tudinally-extending surfaces exposed to the wind, with each sur-face having a series of troughs formed equispaced and parallel to each other along substantially the entire blade length; whereby wind striking the blade surfaces diverges and decelerates as it flows through each trough towards the trailing edge, there~y to effect transferring wind energy to the blades~

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In one variant of such blade, the troughs intersect a trail-ing edge of the blade and are upwardly tapered across the blade S width in the direction of the leading blade edge, with troughs on opposite blade surfaces being respectively staggered and relative to each other along the blade length, so that each trough defines an airfoil-shaped blade segment in cross-section as in Fig. 12A.
The intersecting troughs troughs formed on each blade sur-face have a ratio of width to depth of approximately 4:1 to 6:1, and are upwardly tapered across the blade width in the direction of the leading blade edger and extend across approximately 80 percent of the blade width in the direction of the leading edge.
One mode for achieving the effects desired for the present invention is provided by a uniquely-shaped blade having a series of contour troughs along its length for channelizing of wind flows therein, to maximize the transferring of energies to the blades. The troughs are respectively staggered in relation to each other along the blade length so that each trough defines an ?Q airfoil-shaped blade segments within a triangulation of inter-secting troughs along the blade length. In such manner, the wind currents striking the blade surface will diverge and decelerate as they flow through each trough towards the trailing edge. This effects a transferring of the wind energies by first slowing air-~5 10ws on the high pressure wind incident side, thereby to channelwithin the troughs to effect a merging of the flows on the oppo-site side of the blade ~the low pressure side of the wind flows) . :

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to cause a dropping of the wind flows. This causes a pressure drop, which speeds up the airflows by the lowering ~f the incur-ring pressures within the trough. The preferred range of the ratio o width (W), to a depth of each trough is approximately 4:1 to ~:1, with 5:1 being best to minimize the total surface area of depths and crests of the troughs and therein also to maintain the optimal design to coact to modify of the wind-air flows on both sides of the blade. This causes a blending and a merging of the wind-air flows, thereby to equalize pressures and velocities, to cause a minimizing of a trailing vortex of the blade wake. There are several designs of the blade to accomplish these effe~ts. In such blade, the highest pressure of the high pressure side of blade (wind incident side) is also the highest pressure of the low pressure side. The other side of the blade having the lowest pressure on the trailing edge provides the lowest pressure on the trailing edge of the wind incident side of the blade. This brings about a merging of airflow within the merging wake of the blade. This is a result of the design of the trough shape using the "laws of Bernoullis flow dynamics" to improve the performance of the blades efficiency and drag coeffi cient.
In the accompanying drawings, Figure 1 is a perspective view of a wind turbine constructed in aecordance with an embodiment of the invention disclosed in the above-identified parent application;

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- 8a -Figures 2 and 3 are schematic sectional views, taken along lines 2-2 and 3-3 of Figure 1 of the blade angle of attack for the blade upper and lower portions;
Figure 4 is a detailed, partial cross-sectional view of an offset control mechanism located in an upper portion of the tur-bine for adjusting the blade attack angles during blade rotation about a central vertical axis of turbine;
Figure S is a sectional view taken along the line 5-5, Fig-ure 4 of a pivotal connection between an offset shaft portion of the control mechanism and the rotating support column to vary the blade attack angles;
Figures 6A and 6B are detailed views illustrating pivotal movement of the control mechanism to adjust the blade attack angle in response to an increase in wind speed;
Figure 7 is a plan view of rack and pinicn connections between each blade and the control mechanism for automatically adjusting the blade attack angles both during rotation about the ~0 support column and in response to changes in wind velocity;

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g Figure 8 is a view similar to Figure 7 of the blade attack angles being adjusted by the control mechanism in r~sponse to an increase in wind velocity;
Figure 9 is a sectional view taken along the line 9-9 of Figure 1 of an interconnection between a wind sensor control means actuated by weights to the blade control mechanism to vary the blade attack angles in response to changes in wind velocity;
Figure 9A-9A is a sectional view taken along the line 9A-9A
of Figure 9, illustrating the cross-sectional air foil shape of each lower spoke;
Figure 10 is a perspective view of a control tube connecting the weights in Figure 9 to the offset control mechanism;
Figures 11 is a top plan view of a preferred form of wind turbine blade constructed according to the invention provided by the present divisional application;
Figure 12 is an end view of the blade shown in Figure 11, illustrating the cross-sectional shape of wind channeling troughs ; formed along the entire blade length;
Figure 12A is a s~ctional view taken along the line 12A-12A
of Figure 11 of the blade profile oriented towards the wind flow-ing through one of the troughs;
Figure 13 is a side plan view of a wind vane accoxding to an aspect of the invention disclosed in the above-identified parent application;
Figure 14 is a top plan view of the wind vane shown in Figure 13; and ~`'' ~ :

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- 9a -Figure 15 is an end plan view of the vane shown in Figures 13 and 14.
Before describing the wind turbine blade of the present divisional application a description of the crosswind axis tur-bine of the above-identified parent application will be given.
Referring to Figure 1, crosswind axis turbine 10 is , ,: , , ~ 3~ ~J~
illustrated as including blade assembly having four, vertically-disposed wind driven air foil blades 12a, 12b, 12c and 12d pivotally connected between upper and lower sets of horizontally extending support spokes 14 and 16, respectively, mounted so the blades can turn independently of each other about vertical axis 19 of each blade. Spoke sets 14, 16 are fixed to upper and lower ends of vertical column 18 rotatably mounted to support base 20 so that assembly 11 turns about column 18 in response to wind incident on the assembly. Output shaft 22 is coaxially mounted in and connected to be rotatably driven by column 18. Shaft 22 projects below column 18, where it is con-nected to a suitable driven mechanism 24 for converting the torque of shaft 22 to usable power. Uniquely designed blades 12a-12d, described infra, are mounted to spoke sets 14, 16 to rotate about two vertical axes, in particular the blades rotate coaxially with column 18 and about the individual longitudinal axes 19 thereof. Blades 12a-12d are constructed so that wind incident thereon is channelled and compressed against each blade for maximum transfer of wind energy to turbine 10. A unique feedback control mechanism 25 responds to wind velocity (i.e. spesd and direction) as detected by a wind vane 26 to differentially adjust the angle of attack of blades 12a-12d to maintain approximate constant rotational speed and output power of shaft 22 over a specified range of- wind speeds i.e., between minimum and maximum speeds. (The blade angle of attack is the angle between the direction of the incident ~ ir ~i ~
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wind on a particular ~la~e and chord 13, Figure 2, of that blade~ The blade chord is a vertically-extending plant intersecting the longitudinal vertically-extending blade axis about which each blade turns and a central apex at the intersection of the blade exterior surfaces).
Before describing the structure in detail, a general overview of the invention is provided by reference to Figures 1-3 and 7 and 8 wherein wind velocity vector W is assumed to be displaced from blade assembly coordinate axis 21' by angle A2. Assembly 11 is rotated in the counter clockwise direction about axis 36 in response to velocity vector W. Vertical axes 19 of the upper portions of blades 12a and 12c are respectively displaced counter clockwise and clockwise about axis 21' by the angle A2 while axes 19 of the upper portions of blades 12b and 12d are respec-tively displaced counter clockwise and clockwise below axis 21' by the angle A2 + 90- Because spoke sets 14 and 16 are rotatable independently about axis 36 and the radial displacement from axis 36 of intersections 1-4 of axes 19 of blades 12a-12d and spoke set 14 is less than that of the intersections 5-8 of axes 19 of blades 12a-12d with spoke set 16, lower intersections 5-8 lag behind intersections 1-4 as assembly 11 rotates about axis 36 so the lower blade portion axes are displaced from axis 21' by angles of A3 and (A3 + 90).
Each of the blades 12a-12d incl~des a longitudinal horizontal axis 13 that intersects axis 19 and edge 73 (Figure 11) at the intersection of opposite faces 70 and `

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70~ of the blades. As assembly 11 is driven by wind vector W about axis 36 each of the blades 12 contlnuously turns about the axis 19 thereof so that the angle of axis 13 of each blade continuously changes relative to wind vector W
5 i.e., the angle of attack of each blade.
The angles of attack for blades 12 are also a function of the magnitude increases. There is a tendency for a greater force to be applied to blades tending to rotate assembly 11 at higher speeds about axis 36. This tendency to overcome to a large degree by changing the angles of attack for blades 12 as they turn about axis 36 so that the surface area of the blades relative to wind vector W
decreases so there is a reduction in the force applied by the wind vector to blade assembly 11, to compensate for the initial tendency of the wind vector to drive assembly 11 at higher speeds.
In the situation illustrated in Figures 2 and 3 it is assumed that velocity vector W has a relatively small magnitude and an angle A2 relative to assembly axis 21' in the plane of poke set 14 so that the vector is directed coincident with the axis 21 from axis 36 to axis 19 of blade 12a, and is directed toward the surface of blade 12a away from axis 36. Under the assumed conditions, the angles of attack of blades 12a, 12b, 12c and 12d, i.e., the angles between axes 13 of blades 12a, 12b, 12c and 12d and vector W in Figure 2, in the plane of spoke set 14 are respectively approximately 45, 20, 27, and 2~ The angles of attack of blades 12a, 12b, 12c and 12d in the ' ' '' ~,' " .

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plane of spo~e set 16 lag slightly behind those in the plane of spoke set 14 by the same approximate 3O angle.
The radial positions of intersections 1-4 relative to axis 36 are substantially the same, inside of the radial positions of intersections 5-~. At these angles, maximum force is imparted by wind vector W to assembly 11 because of the large surface area upwind that blade 12a presents to the vector, as well as the substantial but smaller areas presented by advancing blade 12b and downwind blade 12c.
Axis 13 of retreating blade 12d, however, is almost aligned with vector W, so blade 12d presents a very small area to vector W and does not introduce substantial drag.
Now assume that the magnitude of velocity vector W is substantially larger than previously described and that the angle of the vector is constant. Under these circum-stances, the angles of attack of blades 12a and 12c respectively decrease and increase by relatively significant amounts while the angles of attack of blades 12b and 12d respectively decrease and increase by rela-tively insignificant amounts. The angles of attack ofblades 12a-12d in the planes of spoke sets 14 and 16 change together because axes 19 are mounted at fixed radii in spoke sets 14 and 16. The angles of attack change in the plane of spoke set 14 because wind vane 26 causes sub-~5 stantial radial shift relative to axis 36 of control rods66 connected to pivot controllers 201 and 202 for axes 19 of blades 12a and 12c. Because axes 19 are fixed relative to axis 36, the radial shift of rods 66 drives pivot ., :

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. , . -13~tj$~.t~14 controllers 201 and 202. The radlus of control rods 66 connected to blades 12a and 12c are effectively decreased and increased respectively; to respectively decrQase and increase the angle of attack of blades 12a and 12c. There is only a sight change in the effective radius of control rods 66 respectively connected to pivot controllers 203 and 204 for blades 12b and 12d under the assumed conditions because rods 66 are at right angles to incident wind vector W. Thereby, the angles of attack of blades 12b and 12d do not change substantially. The change in the angle of attack of upwind blade 12a materially reduces the effective area presented by upwind blade 12a to vector W; the change in the angle of attack of downwind blade 12c increases the drag force exerted by blade 12c on assembly llo The changes in the angles of blades 12b and 12d do not normally have a substantial effect on the forces imparted by wind vector W on assembly 11. Thus, the tendency for the increased magnitude of wind vector W to turn assembly 11 at high speeds is compensated by the changes in drag angles of blades 12.
As assembly 11 is turned in response to wind vector W
the angles of attack of blades 12 are constantly changing.
Thus, as assembly 11 turns 90, the angles of attack of blade 12a gradually changes from the position illustrated for it in Figures 2 and 3 to the position illustrated in Figures 2 and 3 for blade 12b. As the direction of wind velocity vector W changes, wind vane 26 controls the angles of blade axes 13 relative to assembly axis 21' so that the ~` '' '' ~ ~ .
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blade angles of attack remain constant relative to the direction of wind vector w for the same angular relation-ship of radius 21 and the wind vector direction. Thus, e.g., for low magnitud~ wind vectors, axis 13 of blade 12a is 45 displaced from radius 21 when radius 21 is aligned with wind vector W~
The mechanism for attaining these results and other improvements is now described in detail.
Support base 20, as best illustrated in Figure 1, includes a pair of tubular support legs 30 each having a semicircular configuration in the vertical plane to elevate blades 12a-12d above the ground or other generally horizontal wind impervious surface to obtain maximum exposure of the blades to the wind, while presenting a narrow, rounded wind profile for improved stability.
Support legs 30 are orthogonally arranged and fixedly mounted on cylindrical support tube 32 (Figure ~), which projects vertically upward from the legs and is coaxially mounted in the lower end of hollow cylindrical column 18.
Column 18 is rotatably supported on tube 32 by thrust bearing 34 and yoke 35. Output shaft 22 extends coaxially in support tube 32 along vertical axis 36 of column 18 and is rotatably supported by axial bearing 38, located in the upper end of the support tube. In response to blades 12 rotating, torque is transmitted from rotating column 18 to output shaft 22 through circular coupling plate 40, horizontally fixed in the column by bolts 42. The upper end of shaft 22 is fixedly connected to plate 40 in central ~ -opening 43 of the plate. As illustrated in Figures 1 and 9, lower spoke set 16 includes four mutually orthogonal, identical hollow spokes 16' extending horizontally and radially from column 18. Each spoke 16' is fixed to the lower end of column 18 by bolts 44.
Each of spokes 16' is shaped in cross section as an airfoil (Figure 9A), preferably along the entire length thereof, to enhance air flow, by pushing air upwardly into the interior of blade assembly 11. The air moved into the interior of assembly 11 helps to create an increase in velocity in the assembly interior to enhance the flow of wind against the blades 12. Spherical bearing 45, mounted in distal end 46 of each spoke 16', receives the lower end of one of each of blades 12 enabling the blades to rotate about longitudinal axis 19 thereof to change the blades angle of attack so that wind force imparted to each blade is maximized.
Upper spoke set 14 also includes four identical hollow spokes 14' extending horizontally radially from column 18 and spaced 90 from each other. Each spoke 14' is fixed to the upper end of column 18 by L-shaped brackets 48. As illustrated in Figures 2 and 3, corresponding pair of spokes 14', 16' are not vertically aligned; instead longi-tudinal axis 21 of each upper spoke is circumferentially advanced with respect to longitudinal axis 21a of each lower spoke so that each blade axis l9.is preferably tilted approximately 3 in the direction of rotation.

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Each of blades 12a-12d is of identical construction and includes a molded structurally strong outer skin layer 50 (Figure 11), defining opposite longitudinally extending surfaces 52a and 52b exposed to the wind. Mass 34 of low density filler, such as expansion foam, is disposed between surfaces 52a, 52b to impart structural rigidity to the blades. Rigidity is also enhanced by shaft 56 extending longitudinally through the blade to define blade axis 19.
Upper and lower ends 56a and 56b of shaft 56 project outwardly through spoiler end panels 58 respectively located at opposite ends of each blade. Lower shaft end 56b is received in spherical bearing 45 (Figure 9) provided in each lower spoke 16' as mentioned above. Upper shaft end 56a extends through axial bearing 60 mounted in the bottom end adjacent the outer end of each spoke 14'.
Pinion 62 fixed to upper shaft end 56a is thereby located in each spoke 14' to mesh with a rack 64 attached to free end 66a of connecting rod 66 that extends longitudinally through spoke 14'. The opposite end 66b of rod 66 is connected to circular connecting plate 68 (Figures 4 and 7) to control adjustment of the angle of attack of each blade as assembly 11 rotates about column 18 as described infra.
Each blade 12a-12b has a teardrop cross section defined by a series of troughs 70 and 70' (Figures 11, 12, and 12A) respectively formed equispaced and parallel to each other between crests 71' along the entire blade length on both surfaces 52a and 52b. Mating troughs 70, 70' on opposite surfaces 52a and 52b are longitudinally aligned ~' .

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with each other to intersect trailing edge 72 as a common longitudinal location and are tapered to have decreasing width and depth as they extend ~rom edge 72 to edge 73 in the direction of 73. The taper extends across approxi-mately 80% of the uniform blade width between edges 72 and 73. The bottom of each trough 70 and 70' are staggered with respect to each other along the blade length so that each trough defines an airfoil shaped blade segment in cross section. In this manner, troughs 70 reduce the speed of wind stri~ing high pressure blade surfaces 52a or 52b, whichever surface is exposed directly to the wind as occurs particularly when the blades are in the upwind position of blade 12a (surface 52a) or downwind position of blade 12c (surface 52c). The wind incident on the surface 52a or 52b diverges across the entire surface and decelerates as it flows smoothly across the concave surface of each trough towards trailing edge 72, to transfer a greater amount of wind energy to the blades. Simultaneously, in the upwind position of blade 12a, crests 71' located on the low pressure side or surface 52b opposite troughs 70 create a high pressure section opposite the high pressure section created by troughs 70 so that the trailing vortex drag of the merging high and low pressure sides is substantially reduced, as also arms on the low pressure surface 52a when the blades are in the downwind position of blade 12c.
When the blades travel into the direct upwind position of blade 12d in Figure 2, trough 70' on high pressure surface 52b primarily coact with troughs 70 on low pressure ` ` , ', ,' ` .'' ' ` , . , ; . :
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surface 52a to reduce vortex drag since the blades in this position are generally aligned with th~ wind. When the blades are in the position of blade 12b in Figure 2, the troughs 70 on high pressure surface 52a narrow in the downwind direction, causing wind to compress and accelerate against the downwind leading edge 73 of the blade to rotate the blade in the direction of rotation.
To minimize the total surface are of troughs 70 and crests 71 (defined by troughs 70') directly channelling wind flow across the width of each blade 12a-12d and thereby minimize skin friction, the preferred range of the ratio of width W to depth D of each trough is approximately 4:1 to 8:1. For optimal results, however, a preferred ratio W:D is 6:1.
As best illustrated in Figure 1 for blades 12a and 12c, blades 12a-12d are mounted on spokes 14' and 16' so the upper portion of each blade is closer to column 18 than the lower portion of the blade wherein blade assembly 11 is similar to a truncated cone having a lower base layer than ; 20 an upper base. Because of this truncated cone arrangement, the pair of downwind blades draws air into the interior of blade assembly 11 through the upper section of the assembly. The air drawn into the upper part of assembly 18 spirals downwardly about column 18 to combine with air flowing upwardly into the assembly through air foil shaped spokes 16'. The upwardly and downwardly directed air currents meet in the interior of assembly 11 where they combine to exit from approximately the lower two thirds of , ..... .. .
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the assembly (i.e., ln the space between spokes 16~ and two thirds of the way up to spokes 14'). The exiting air current flows in the same general direction as the incident wind. With this arrangement, a large volute volume of air is swirled and accelerated in less than the total interior volume ~i.e., the lower two thirds portion) of assembly 11, thereby imparting additional wind energy to blades 12a-12d.
The accelerated, swirling air flow obtained with inclined blades 12a-12d also promotes laminar flow conditions in the interior of assembly 11 without creating a standing wave effect (i.e. wind repeatedly reflecting off the blades in the assembly interior, without escaping from the interior;
the standing wave tends to cause turbulence and impair blade efficiency).
To obtain the accelerated swirling air flow in assembly 11 as described above, the ratio of the diameter of upper spoke set 14 to the diameter of lower spoke set 16 is preferably 2:3 although the ratio can vary from between approximately 1~2 to 4:5; the height of column 18 is preferably equal to the sum of the diameters of upper and lower spoke sets 14, 16 but can be as small as the diameter of the lower spoke set. With the aforesaid preferred ratios, blades 12a-12d are positioned on spokes 14', 16' so axis lg of each blade is inclined from the vertical towards central axis 36 by 6 (inclination angle Al, Figure 9);
while being advanced 3 (blade advance angle A2) in the direction of rotation, as discussed above. However, when the ratio of diameters of the upper and lower spokes 14' ``'`",", ', "

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and 16' as well as the height of column 18, is varied within the above ranges, I have found that the following equations can be used to calculate inclination angles Al and blade advance angle A2, in degrees, to within a 1 accuracy:

Al = 90 - arc tan B T

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where: H = height of column 18 B = diameter of lower spoke set 16 ~ = diameter of upper spoke set 14 Since blade axis 19 is tilted preferably 3 in the direction of blade rotation and preferably 6 towards axis 36 as mentioned above, it can be seen from Figures 2 and 3 that the angle of attack of each blade 12a-12d to the wind increases as the height of each blade increases toward upper spoke set 14 (i.e., B>B' in Figures 2 and 3). This variation in blade attack angle is necessary due to the lower tangential velocity of smaller upper spokes 14' relative to the lower spokes 16' during rotation of assembly 11 about column 18. In this manner, each section along the entire length of blades 12a 12d is respectively maintained at a favorable angle of attack between B and B' to optimize blade efficiency. Furthermore, to produce ~C~C. ~ r, 7 maximum torque with turbine 10, I have found that the following formula can be used to calculate the width (W) of each blade 12a-12d:
W=0.0533~B
Oscillation of each blade 12a-12d about blade axis 19 thereof is controlled by a rack and pinion assembly com-prised of rack 64 pivotally supported in the upper spokes on pillow blocks 65 or slider wheel 65' at outer end 66a of each connecting rod 66; racks 64 respectively mesh ~ith pinions 62 provided at upper end 56a of each blade. As illustrated in Figures 4 and 7, three of connecting rods 66 are pivotally mounted to circular connecting plate 68, located in the upper portion of column 18, by spherical bearings 75 peripherally disposed on the plate 90 from : 15 each other. The inner end of the remaining connecting rod 66', secured to blade 12a, is fixedly attached to the periphery of plate 68 at a location 90 from adjacent bearing 75. Thereby rods 66 are free to pivot about fixed points adjacent the periphery plate 68 while rod 66' always remains fixed in position so the longitudinal axis thereof intersects axis 36.
Spherical bearing 77, mounted in the center of plate 68, receives an upper vertical section 100 of a control shaft 80 that projects through upper end 82 of column 18, covered by a flexible weather seal 84. Wind vane 26, fixed I to the upper end of shaft 80 above upper spoke set 14, ; adjusts the pitch of blades 12a 12d through the assemblies including racks 64 and pinions 62 in re~ponse to changes in :` :
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wind velocity, as described below. Stop 86, fixed to shaft section 100 supports bearing 77 and thereby plate 68 in a horizontal plane immediately below connecting rods 66.
Wind vane 26, as best illustrated in Figures 13-15, is a horizontally-extending structure having a low, relatively thick counterweight profiled forward segment 86 and a thin relatively high rearward segment 90. Segments 88, 90 located on opposite sides of upper section 100 of control shaft 80 (Figure 4), have the same weight for improved stability. Fixed to vertical face 92 of rear segment gO is air scoop 94 having curved wall 95 defining large upwind opening 96 and a smaller downwind opening 97. As wind passes around profiled forward segment 88 and enters upwind opening 96, wall 95 tapered toward~ rear opening 97, causes the passing wind to strike vertical face 92, to turn vane 26 into alignment with the wind and rotate control assembly 80.
Control assembly 80, forming wind speed and direction detector of feedback control mechanism 25, constitutes an important feature of the invention. As illustrated in Figure 4, assembly 80 includes shaft 81 that is located primarily in column 18 and has straight vertically extending upper and intermediate segments loo and 108 connected to each other by inclined segment 104. Upper section 100 extends upwardly through center bearing 77 so it supports vane 26 above blade assembly 11. Rod 81 includes portion 106, projecting downwardly from and inclined relative to segment 108. Shaft portions 100, 104, 106, and 108 are coplanar, with vertical portion 108 radially offset (i.e., non~coaxial) with respect to section 100. Sleeve 110, fixed to offset shaft portion 108, includes an elongated horizontal passage 112 containing horizontal pin 114, having one end attached to an inner surface of sleeve bearing 115. Bearing 115 is coaxial with axis 36 and is rotatably mounted in the upper portion of column 18 by pairs of upper and lower axially spaced bearings 117 located bekween the facing outer walls of bearing sleeve 115 and inner surfaces of column 18.
Vertically extending seats 119 and 122, respectively at the lower ends of inclined shaft portion 106 and sleeve 115 capture opposite ends of compression spring 120, having a horizontal axis to provide a counter force for the tendency of shaft 81 to rock about pin 114 in response to vane 26 tilting as a function of the speed of wind incident on the vane. When the wind calms, spring 120 stabilizes vane 26 in the horizontal plane. The pivot angle of rod 81 rela-tive to pin 114 controls radial displacement on control plate 68 relative to axis 36 of column 18, to control the angular position of ea h blade 12a-12d about the axis thereof at the different angles about axis 36.
To understand the operation assume that each blade 12a-12d is mounted to assume a particular angle of attack relative to the incident wind (see Figure 7) which is aligned with the axis of spoke 16 carrying blade 12a.
Thereby blades 12a and 12c are respectively in upwind and downwind positions, while blades 12b and 12d are in cross .. . ..
-wind positions. Blade 12a i5 rotated by connecting rod 6, rack 64 and pinion 62 connected to it so it has a favorable wind angle of attack, depending upon wind speed, of approximately 45, the approximate angle where maximum wind energy is imparted to rotate the blades. As blade 12a rotates 90 about column axis 36 into the downwind position occupied by blade 12b in Figure 7, the effective wind striking exposed blade surface 52a causes pinion 62 to rotate in meshing engagement with the teeth of rack 64 (pivotally supported within each spoke 14' by a pillow block 65 or grooved control wheel 65') so that blade 12a rotates about axis 19 in a controlled manner to assume a lesser angle of attack of 20 allowing the blade to continue imparting rotative tor~ue to the turbine structure without causing excessive wind resistance. As blade 12a continues travelling downwind into the position occupied by blade 12c in Figure 7, pinion 62 continues to rotate while moving rack 64 so that the blade assumes an angle of attack of 27 allowing wind to smoothly exit from the interior of turbine 10. As blade 12a then rotates in the upwind direction into the position of blade 12d in Figure 7, the angle of attack becomes 2 so that the blade is virtually travelling parallel to the wind to minimize resistance.
Simultaneously, of course, connecting rods 66 which are interconnected through plate 68 move radially to adjust the blade angle positions of the other blades 12b-12c during travel thereof into the aforesaid positions.

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Offset shaft portions 10~, 106 and 108 of control shaft 81, being pivotal in vertical plane 125 about pin 114, advantageously allow radial placement of upper shaft portion 100 and thereby control pla~e 68 so that the effective length of each connecting rod 66 constantly changes during blade rotation about central axis 36 due to the aforesaid movement of racks 64 caused by pinions 62.
By experimentation, it has been found that offset portions 104, 106 and 108 are mounted so as to be offset from the forward or upwind segment 88 of vane 26 in the direction or rotation by an angle e of between 30 and 40, preferably 35. It has been discovered that this mounting relation-ship uniquely operates to create a favorable attack angle of blades 12a-12d for a longer duration during the downwind phase of blade travel, enabling turbine 10 to derive more power from this phase of rotation about axis 36. This arrangement also permits blades 12a-12d to rotate about column 18 at a tangential linear velocity of between 2.3 and 2.6 times greater than wind speed to obtain maximum power output.
Bearings 75, 77 maintain connecting plate 68 in substantially the same horizontal plane as the longitudinal axis of connecting rods 66 continuously change in the aforesaid manner as the blade attack angles change in the aforesaid manner during rotation about axis 36. Further-more, bearings 75, 77 as well as the. aforesaid rack and pinion connections and easy pivoting movement obtained with the offset control shaft 80 within cylindrical bearing 115 27 ~3~
provide low friction, smooth translational movement of conneGting rods 66.
Wind vane 26 uniquely operates as a static wind load control through the aforesaid rack and pinion connections 201-204 and control shaft 80 to provide further blade adjustment in response to changes in wind speed or direction. For example, should wind direction change from W to W' in Figure 8, rotation of vane 26 into realignment with the wind causes corresponding rotation of shaft - lO section 100 and thereby pivotal movement of offset portion 108 so that plate 68 moves radially to reorient the blade angles. Vane 26 rocks backward about pin 114 in response to an increased wind flow entering air scoop 94 (see Figures 6A and 6B), causing plate 68 to translate in the downwind direction by the action of shaft section 100 acting against the plate. Connecting rods 66 between plate 68 and blades 12a-12d are translated causing the effective radii of intersections 1-4 and the attack angles of blades 12a-12d to change, as described supra, so that the blades do not overspeed. Thus constant speed and power output of blades 12a-12d are maintained while excessive stress and possible damage to turbine 10 is avoided.
Should excessive wind conditions develop (e.g., hurricane wind force), racks 64 and pinions 62 respond to control shaft 80 to adjust the blade attack angles to turn blades 12a-12d so axes 13 are aligned with wind velocity vector W to stop turbine 10. The aforesaid arrangement also adjusts the blade angles o~ attack when assembly 11 `''~, , ~ .

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27 a has been braked, to dump high wind loads from blades 12a-12d, thereby avoiding damaye to the blade structures.
A second embodiment of control mechanism 25 for controlling the blade angles of attack in response to changes in wind speed and direction includes a pair of cylindrical weights 120 respectively located inside of two diametrically opposed lower spokes 16'~ As illustrated in Figure 9, each cylindrical weight 120 is slidably mounted between pairs of upper and lower roller bearings 122 and 124, respectively carried in semicylindrical channels 126 of bearing support members 127 and 127a. Roller bearings 122, 124 engage circumferential surfaces of weights 120 to define a horizontal slide path to enable the weights to move radially with respect to column 18 through spokes 16' in response to variations in centrific force caused by changes in wind velocity acting on blades 12a-12d.
Two cables 128, respectively attached to the faces of weights 120 adjacent column 18, pass around pulleys 130, mounted on yoke 35 and extend vertically upward between column 18 and support shaft 32, for attachment to a pair of vertically extending connecting rods 132. Rods 132 are slidably disposed in apertures 134 of coupling plate 40;
upper ends of the rods are connected to horizontal cross plate 136, located above the coupling plate. Connecting rod 137, fixed to the center of plate 136, extends upwardly ; along central axis 36. The upper end of rod 137 passes through opening 138 in plate 139 at tha bottom of hollow, square control tube 140 and is connected to throwout ~ -. .
' 27 b bearing 142, mounted on plate 139. Bearing 142 prevents rotation of control tube 140 with rod 137 and ~eights 120 about the column 36 axis during blade rotation about column 18. Flexible oil tube 141 extends through shaft 22 to supply lubricant from a source (not shown) to bearing 142.
Tube 140 is mounted directly below and coaxially with cylindrical bearing 115 (surrounding offset shaft portion 108) to receive the lower inclined shaft portion 106 between side walls 144. Tube 140 includes side walls 144 one of which has an opening 145 through which the lower end 118 of shaft portion 106 projects. Roller 146, rotatably mounted to upper edge 148 of opening 145, rolls on straight upper inclined surface 150 of shaft portion 106 to vary the position of offset portion 108 in the manner described below. Upper end 153 of L-shaped guide member 152 is fixed to the inner surface of cylinder 115 to extend downwardly to be received between and slide along side walls 144 to maintain square tube 140 in vertical, coaxial alignment with the cylinder. Pin 114 is fixed to the upper portion of guide member 152. Compression spring 121 is horizontally disposed in tube 140 between lower end 118 of inclined portion 106 and seat 122', abutting against the lower edge of the inner surface of the guide member.
With the arrangement of Figure 9, weights 120 slide radially in spokes 16, so the weights move away from column 18 when the wind speed acting on blades 12a-12d increases.
The outward movement of weights 120 draws cables 128 down 27c to exert a downward force on connecting rod 137 through rod 132 and cross plate 136 to pull square tube 140 (which does not rotate with connecting rod 137 by virtue of throwout S bearing 132). As tube 140 moves down, roller 146 exerts a force on inclined .. ~, i ... .

.

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- ~8 -surface 150 so that offset shaft portion 108 pivots on pin 11~ -to increase the attack angles of blades 12a-12d in the manner des-cribed above. Spring 155, connecting plate 136 to coupling plate ~0, is thereby loaded in compression so that weights 120 are retracted by the force of spring 155 when wind speed decreases, allowing square tube 140 and roller 1~6 to move up along surface 150 to restore the blade angles.
Weights 120 in the second embodiment are preferred for use instead of wind vane 26 in large installations. However, weights 120 can be used in combination with vane 26 to vary the blade attack angles in the aforesaid manner. Weights 120, tend to move ~adially back and forth about an equilibrium point within spokes 16' as the weights adjust the blade angles of attack in response to changes in wind speed and direction. After initial adjustment occurs in the aforesaid manner, the weights tend to move radially inward ~if wind speed has increased or wind direction has changed counterclockwise in Figure 2) in response to a lowering of cen-trifugal force acting on the blades ~restored to constant velo-20 city movement~.
While one embodiment of an airfoil blade has been inferen-tially defined hereinabove, it is now desired to provide an explicit description, with reference to Figures 11, 12 and 12A.
A described airfoil blade for use in vertical axis wind tur-bine machines is illustrated in Figure 11. The first surface ofthe blade having section 19 is the pivot-line of support shaft 56a-56b which lS fixed into supporting end plate 58 within : .

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attachment to leading edge 73 through to trailing edge 72. A
cut-away view of the resin and fibre or other molding material of suitable characteristics ~or the outer supporting shell is shown at 50. An optional deposited foam filling material of a rigid low density ~uantity therein is shown at 54. A perspective view of the blade length with the manner of troughs configuration on the blade surface also shows supporting shaft 56. Figure 12, shows the trailing edge of ~he first-part surface with continued reference to troughing sections of a multitude of utilized aero-dynamic sectional assemblies therewith. The air flow parts on leading edge 73, flows over edge 52a, and then into trough 70 to cause a lowering of pressure within the trough to cause a speed-ing up of the flows with contouring on the trailing edge 72. Bycontour means of the trough, a laminar air flow is effected to blend with and then into emerging air flows of the trailing edge of the second part o the blade. The other side of the first part of the ~lade is illustrated in a cut-way view of Figure 12A.
Upon the flow division at 73, the air flows to 52b of the second part and there into the start of the trough 7~ to cause an increase of pressure within the trough 70'. This effects a slowdown of the air flows for a transfer of energy within the air flows to the second part surface of the blade. By the contour of ~5 trough 70' a lamlnar airflow is effected, to blend with the emerging air flows of tralling edge of first part of the airfoil blade.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A blade for use in a wind driven turbine of the vertical axis type, comprising: a blade body of elongated rectangular con-figuration having opposite blade surfaces, a leading edge and a trailing edge, said edges being generally parallel to each other;
each blade being substantially-straight and including opposite, longitudinally-extending surfaces exposed to the wind, with each surface having a series of troughs formed euqispaced and parallel to each other along substantially the entire blade length; where-by wind striking the blade surfaces diverges and decelerates as it flows through each trough towards the trailing edge, thereby to effect transferring wind energy to the blades.

2. A blade as set forth in claim 1, wherein said troughs intersect a trailing edge of the blade and are upwardly tapered across the blade width in the direction of the leading blade edge, with troughs on opposite blade surfaces being respectively staggered and relative to each other along the blade length, so that each trough defines an airfoil-shaped blade segment.

3. A blade as set forth in claim 2, wherein said inter-secting troughs formed on each blade surface have a ratio of width to depth of approximately 4:1 to 6:1, and are upwardly tapered across the blade width in the direction of the leading blade edge, and extending across approximately 80 percent of the blade width in the direction of the leading edge.