GB2413785A - Fluid power generation/propulsion system incorporating movable vanes - Google Patents

Abstract

Apparatus for oscillating a first vane relative to a fluid stream having a direction of flow, comprising first means (50-56) for oscillating the leading edge of the first vane transverse to the flow direction and second means (51-57) for oscillating the trailing edge of the first vane transverse to the flow direction with a phase lag relative to the first means, whereby the first vane oscillates about an axis substantially at right angles to the flow direction and moves laterally from side to side across the flow direction to imitate a fish tail. The first vane may be oscillated by the current, in which case the apparatus further includes means to harness the movement of the first vane and convert it into useful energy. Alternatively the vane may be oscillated by drive means, such as a pedal mechanism in a vessel, whereby to produce a propulsive effect. A number of different mechanisms are described which include a plurality of vanes operating in antiphase (e.g. in pairs) and with vanes phase lagging others (e.g. in pairs) whereby to create a balanced arrangement. The vanes may be steerable by adjustment of the inclination of the vanes relative to the fluid flow. The phase angle may also be adjustable (58-60).

Description

FLUID POWER GENERATION/PROPULSION SYSTEM

Field of the Invention

The present invention relates to a mechanism for causing an hydrofoil to oscillate in fluid. More particularly, the Invention uses such a mechanism either: (a) to generate power, when the mechanism is caused to oscillate by a fluid flow, or (b) to propel a vessel in fluid (water) when the hydrofoil is oscillated by drive means.

Background to the Invention

Consider first the problems facing mankind in the generation of electricity. Nu merous "alternative" solutions have been proposed over recent years. Wind and fluid power generation appear to be the most promising methods for obtaining "free" electric ity from nature. However, each is beset with its own problems. As far as fluid power generation is concerned, some solutions involve continuous flow of water in one direc tion, for example in hydroelectric power generation. Others attempt to harness the flow of water in rivers and coastal areas where the flow varies in magnitude and direction ac cording to the bees.

Prior attempts at providing efficient, workable systems that do not suffer from in superable maintenance difficulties tend to separate into propeller turbine and cross-flow turbine types. A review of these types and their efficiencies is presented in a paper enti tled Limits of the turbine efficiency for free fluid flow. A.N. Gorban, A.M Gorlov, V.M Sylantiev.

Journal of Energy Resources Technology DECEMBER 2001, Vol. 123 ' 317. Propeller turbines show an efficiency ranging between 16% and 20% whereas cross-flow turbines reach 23-35%. Chief among some of the disadvantages of these designs is that fixed blades cannot be used directly in reversible tidal flows or in shallow waters, whereas Dar reus turbines develop strong pulsations and are mostly not self-starting.

Another inherent problem with propeller turbines is that they do not sweep the full cross-section available to them. This is illustrated in the left hand half of Figure 3. As can clearly be seen, the propellers are inherently capable only of sweeping a cylindrical volume whose crosssectional area is commensurate with their radius. The significance of the right hand half of that figure will become clearer later in this description. Suffice it to say, the right hand half shows a generator employing oscillating vanes using a mechanism in accordance with the present invention. The vanes in this instance are vertical but may - 2 be horizontal. The important feature is that the vanes occupy virtually all of the available cross-section of the water way.

In all of the prior art approaches to power generation by using the energy in wa ter and/or tidal flow there are difficulties in achieving adequate or even design efficiencies and in ensuring that the equipment does not have to be located in positions where main tenance becomes a serious issue. There is therefore a need for an improved design that does not suffer from the above drawbacks and disadvantages.

Turning now to propulsion systems for vessels, propellers have become the norm, largely because of their proven track record. However, they still suffer from disadvan sages such as fouling from underwater debris etc. corrosion and cavitation, to name but three. Of course sail is a "free" alternative but can be unmanageable or unusable, at op posite extremes of the prevailing weather.

Some preliminary attempts have been made to employ hydrofoils as an aid to conventional propulsion (such as in hydrofoil vessels) or as the means of propulsion in its own right. The Voith Schneider propulsion system is the best known of those which uses foils. Its foils go around a circle, a little like a cross flow turbine. This system can create thrust in any direction. It is used mainly for tugs and other boats which need high maneu verability but it is not used for high speeds, or very large scale, because of expense and performance problems. Such hydrofoils or vanes may be driven to cause forward thrust, often sufficient to cause the vessel on which the device is mounted to be propelled for ward. Hitherto, however, such designs have not always been able reliably to produce steerable thrust or reverse thrust and have been somewhat ungainly.

There is therefore a need for an improved vessel propulsion system that does not

suffer from the drawbacks of the prior art.

It is possible that a solution to the problems of existing power generation systems may provide answers to the problems of vessel propulsion. The present invention aims to tackle these problems head on and provide a solution to both In a single invention.

Summary of the Invention

In accordance with the principle aim of overcoming the above problems, the pre sent invention provides, in a first aspect, apparatus for oscillating a first vane relative to a fluid stream having a direction of flow, comprising first means for oscillating the leading - 3 edge of said first vane transverse to said flow direction and second means for oscillating the trailing edge of said first vane transverse to said flow direction with a phase lag relative to said first means, whereby said first vane oscillates about an axis substantially at right angles to said flow direction and moves laterally from side to side across the flow direc tion.

The first vane may be adapted to be oscillated by said current and said apparatus further includes means to harness the movement of said first vane and convert it into use ful energy.

Alternatively, the first vane may be adapted to be oscillated by drive means whereby to produce a propulsive effect.

In a second aspect, the invention comprises power generating apparatus compris ing apparatus as aforesaid supported on a support structure with one or more said vanes adapted to be located in a said fluid flow, whereby said vane or vanes can be oscillated by said fluid flow, and wherein said means to harness movement Is coupled to said vane or vanes to convert said movement into useful energy.

Other preferred features of the apparatus according to the invention are set out In the dependent claims.

It will be appreciated that the conversion of movement into useful energy may in volve the generation of electricity by driving a suitable generator, or the direct use of out put motion, for example in driving a pump for pumping water or some other fluid.

Brief Description of the Drawings

The invention will be described with reference to the following drawings, in which: Figures 1 a-f illustrate a first mechanism for causing a vane to oscillate like a fishtail; Figures 2a-in illustrate a second mechanism; Figure 3 shows the Improvements possible with the present invention; Figure 4 illustrates how lift and drag vary with vane angle; Figures 5a-n Illustrate another mechanism using matched pairs of vanes; Figure 6a-i illustrate another paired mechanism; Figure 7 shows the invention applied to two pairs of vanes; Figure 8 shows the invention applied to four pairs of vanes; Figure 9 shows an adjustable belt drive - 4 Figure 10 shows an alternative adjustable belt drive; Figure 11 shows a device for converting rotary to linear motion; figure 12 shows an application of the Figure 11 device; Figure 13 shows another device for converting rotary to linear motion; Figure 14a-b shows two linear motion devices; Figure 15 shows another application of the Figure 11 device; Figure 16 shows an alternative form of linear motion device; Figure 17 shows a further application of the Figure 11 device; Figures 18,19 and 20 show alternative double acting devices; Figures 21,22 and 23 show alternative rotary drive devices using belts; Figure 24 shows an alternative version of the Figure 23 device; Figure 25 shows a linear motion device; Figures 26,27 and 28 show alternative forms of coupling to a foil; Figures 29 and 30 show different forms of double acting devices; Figures 31 and 32 show two different versions of power generating plant using the principles of the present invention; Figure 33 shows a propulsion mechanism for a pedal boat; Figure 34 shows a variation of the Figure 33 arrangement; Figure 35 shows the disposition of the propulsion device in a pedal boat; Figure 36 shows an adjustable phase device using a chain drive; Figure 37 shows a pedal mechanism; Figure 38 shows an enlarged view of the main bearing axis of the pedal boat; and Figure 39,40 and 41 show alternative versions of drive mechanisms.

Detailed Description of the Illustrated Embodiments Figure 1 a shows a mechanism for causing a vane 1 to be oscillated like a fish tail.

The vane is preferably a hydrofoil section so that when in a fluid flow it can generate "lift" relative to the flow direction. The mechanism consists of a single disc 2 mounted for rota tion about its central axis. A first rod 3 and a second rod 4 are pivotally coupled at one end to the rim of the disc. The other ends of the rods are pivotally coupled to a third rod 5 and a fourth rod 6 respectively. Rod 5 is pivoted at one end to a fixed point of refer ence 7. Likewise, rod 6 is pivoted at one end to a fixed point of reference 8. The oppo - 5 site end of rod 5 is coupled to the rear end of the vane 1 and the opposite end of rod 6 is pivotally coupled to the leading edge of the vane 1.

The coupling at the rear of the vane may take various forms. For the sake of sim plicity at the moment, the coupling is shown as consisting of a sliding coupling in which a pin (not shown) on the rod 5 engages in a longitudinal slot 10 in the vane 1.

When the disc 2 is rotated in the direction of arrow 12, the rods 3, 4 cause the rods 5, 6 to oscillate left and right (in the drawing) when they rotate about their respec tive pivot points 7 and 8. The result of this is that the vane 1 is caused to yaw relative to the current which, in the present example, is taken to be flowing from top to bottom of the page. Not only does the vane oscillate pivot about an axis normal to the plane of the rods, it also translates from side to side.

The sequence of drawings in Figure 1 a through 1 f show how the vane moves. In essence, it mimics the movement of a fish. Consequently, the vane generates thrust in the upward direction in the drawing, i.e. against the current. Enough thrust is generated that the device can be mounted In a vessel and used as its sole source of propulsion.

Figure 2 shows an alternative mechanism. As shown in Figure 2b, the vane 20 is rigidly connected at right angles to a first arm 21 and is pivotally connected at 22 to one end of a second arm 23. The remote end of arm 21 is pivotally connected to rod 24 that extends parallel to arm 23. The rod 24 and arm 23 are connected to each other at the other ends and at an intermediate point by further arms 25 and 26. The arm 23 rotates about the same axis as a wheel 27. The arm 26 is connected for rotation with the wheel 27, which is mounted for rotation about an axis intended to have a fixed location in a ves sel. The parallel arm 23 and rod 24 co-operate with the linking arms 21, 25 and 26 to form a parallelogram.

The wheel 27 has gear teeth around its periphery that engage a rack 28 on a rod 29 which is telescopic so as to enable its length to be adjusted. Once adjusted, the length remains the same until it is re-adjusted. The remote end of the rod 29 is pivotally coupled to the circumference of a first wheel 30. A rod 31 is pivotally connected at its ends to the arm 23 and a point on the circumference of a second wheel 32. The two wheels 30, 32 are interconnected by a belt 36 so that the wheels are constrained to be driven in the same direction. Wheel 30 dictates the angle of the foil and wheel 32 dictates its dis - 6 placement. The radius of wheel 30 can be changed. This alters the range of angles which the foil covers through its cycle. A larger radius will mean a larger range of angles. This will cause a turbine to rotate at a higher frequency and is the equivalent of a lower gear for a propulsion system. A smaller radius means a smaller range of angles, therefore a slower frequency of rotation for a turbine, and a higher "gear" for a propeller. Changing this radius during operation is a means of trimming the turbine to suit the current speed, or the propeller to suit the speed of the boat. It will be noted that the wheels have flanges of different diameter to each other so that the ends of the rods 29 and 31 de- scribe arcs of different radius to each other.

The mechanism operates as follows. When the wheel 30 (say) Is rotated, the rod 29 is reciprocated up and down and, to a lesser extent, oscillates from side to side as shown in the sequence from Figure 2a through Figure 2h. The rack 28 causes the wheel 27 to rotate as the rack reciprocates. Rotation of the wheel 27 opens up the parallelo gram from the position shown in Figure 2a. Rotation of the wheel 30 is transferred to the wheel 32 via the belt 36 so as to cause the rod 31 also to reciprocate, thereby mov ing the arm 23. The combination of these movements causes the vane or hydrofoil 20 to oscillate and traverse like a fish tail as before.

If, say the rotation of wheel 32 causes the hydrofoil 20 to move according to a sine relationship, its velocity follows a cosine relationship. Since the wheel 30 is 90 de grees out of phase with wheel 32, it will create a cycle which is 90 degrees out of phase with the displacement of the foils, that is to say, a cosine relationship. The velocity of the foil and the angle of the foil are therefore dictated by the same function. This synchrony ensures that the angle of the hydrofoil is always appropriate for its movement across the direction of flow.

It will be noticed that from figure 2e onwards that the wheel 32 has not moved whereas the apparent length of the rod 29 has shortened. This is to illustrate the effect of variation of the length of the rod 29. In accordance with the length of the rod 29, the direction of the hydrofoil can be changed, from facing upstream to facing downstream, as shown in Figure 2h. Smaller changes in length can orientate the foils to provide vectored thrust in propulsion systems. Such control can therefore harness energy in water flowing - 7 in two directions and equally can exert propulsive thrust in both forward and reverse di- rections.

In the context of power generation, one distinct advantage of having vanes or hy- drofoils that change orientation relative to the flow can be illustrated by consideration of Figure 4. This shows the lift and drag forces on the blades of a typical rotary turbine.

Flow is shown as pointing downwards in the figure.

The efficiency of the system according to the invention relative to cross flow tur- bines stems not from an ability to line up with the flow, but from the fact that the inven- tion eliminates the non productive component of motion. Any motion of the foils in the direction of the flow cannot produce lift but produces large amounts of drag. Motion across the flow is the only motion that can be productive. The present invention provides essentially a means of isolating the productive component and eliminating the non- productive component.

The arrangement of a "sister" foil a quarter of a cycle out of phase with the first il lustrates this point. A circular motion is essentially the product of two orthogonal sinu- soidal motions, one left and right the other up and down. The foils on the cross flow tur- bine move in both these directions. If the left to right movement is the useful movement, the invention takes the up and down movement and turns it into another left and right movement in the sister foil. It basically dissects a circular motion into two sine waves which are orientated In the ideal direction.

If a foil moving in the way previously described is placed in a current of water, it will create lift in a direction depending on its orientation. At its extremities, it faces di- rectly into the flow and creates no lift. The lift on a single foil is always either rising or fal- ling because of the variation in angle at which it is placed In the flow. In the present inven tion, this can be overcome by arranging for each foil to have a "sister" that follows with a quarter of a cycle delay. In this way, the maximum thrust of one foil is always accompa- nied by the minimum of another, such that the resultant is always substantially constant.

However, another problem caused by the continually changing lateral forces on the foils is instability of the generator within the flow. This can be overcome by the use a "twin" for every foil, which follows exactly the opposite of its twin. The lateral forces cancel one an- other out. The benefits of such system require a minimum of four foils. - 8

In preferred embodiments, the foil mechanism can be such that the levers operat ing the leading and trailing edges of the foils are slightly out of phase so that, in some posi tions, the foils are at right angles to the direction of flow when they pass through the mid dle of their cycle. During normal operation the foils would never be at 90 degrees to the flow. This is an extreme position, in which the system would be placed in order to allow the foils to flip from one orientation to the other. Normally the phase difference would be smaller resulting in a smaller angle to the flow. At this point, if the current changes direction (e.g. because of tides) the foils are urged into the reverse direction and the mechanism can restart with the foils taking advantage of the reversed current and con tinuing to harness power.

Figure 5 shows an embodiment derived from the arrangement of Figure 1 but in which a pair of hydrofoils is moved simultaneously by a single mechanism. In effect, the arrangement of Figure 1 is placed back to back with another such arrangement. The rods 3 and 4 of Figure 1 become rods 54 and 55. Similarly, rods 5 and 6 become rods 50 and 51 are pivoted at fixed reference points 52, 53 respectively, with rod 51 connecting to the tail of each vane through pivoted intermediate rods 51a and 51b. Rods 54, 55 con nect the rods 50, 51 to wheels 56, 57 respectively.

These wheels are arranged to be driven by an arrangement of three intermeshing gear wheels 58, 59 and 60 arranged as in Figure 5. When wheel 55 is rotated, the in termediate gears 58-60 cause wheel 56 to be rotated in the same direction and at the same speed. However, the gears 58-60 are mounted on a frame for movement towards and away from the rods and hydrofoils (i.e. left and right in Figure 5). The control for this movement is represented symbolically by the handle 61. The effect of this is to rotate the wheels 56, 57 slightly relative to one another and thereby to adjust the phase angle be tween the hydrofoils.

Figures 5a-n illustrate the sequence of events when one of the wheels 56, 57 is ro tated. The vanes or hydrofoils can be seen to oscillate and traverse as before but this time in phase opposition to one another. This has the advantage of greater efficiency and balanced operation. The hydrofoils can be completely reversed in direction relative to the direction of flow to harness the power in two-way flows.

Figure 6 shows another mechanism in which a single wheel controls the operation of a pair of opposed hydrofoils. The mechanism is similar to that described in Figure 1, so it will not be described in detail here but basically, the Figure 1 mechanism on one side of the wheel is repeated on the opposite side, the mechanism having an additional set of arms to transfer the drive to the second hydrofoil rather than having a separate set of arms or rods coupled directly to the same one wheel. This mechanism derives benefit from being symmetrical either side of the wheel as far as the operation of the hydrofoils is concerned. The sequence of operation is illustrated in the Figures 6a-f.

The same principles can be applied to drive two pairs of hydrofoils as shown in Figure 7. The mechanism consists essentially of a mechanism according to Figure 6 onto which has been grafted another set of links as illustrated to cause a second pair of op- posed hydrofoils to oscillate with a phase delay relative to the first pair.

Likewise, the same principles can be applied to cause a further set of four hydro- foils as shown schematically in Figure 8 to be driven from a single drive wheel. In this fig ure, the linkages have been removed for clarity only.

As to the details of various possible forms of coupling between sliding and rotating parts of any of the mechanisms described above, brief reference can be had to the follow- ing description of the arrangements illustrated in Figures 9 to 30.

Where a belt, chain or similar coupling is used to transfer rotary motion from one wheel to another, a simple belt entrained around the two wheels will cause equal degrees of rotation in the same direction, provided the wheels are of the same diameter. If one of the bights of belt is shortened compared to the other, e.g. by pressing a roller laterally against it, there will be unequal tensions in the bights and the wheels will be rotated slightly relative to each other so that a phase difference exists between them even after the tensions have equalised. Once moved, the roller, which is located on the side of the belt or chain under tension, is held in place but Is spring-loaded to maintain tension and take up any slack.

A more controllable version of that principle is shown in Figure 9, where a pair of rollers A, B is mounted on a carriage for simultaneous movement transverse to the length of the belt so as to vary the phase difference between the main wheels.

Figure 10 shows a variant of the Figure 9 arrangement. -

Where it is necessary to convert linear motion to rotary motion and viceversa, a simple mechanism such as that shown in Figure 11 may suffice. Here, a pin or the like B rotates as shown by the curved arrow. The pin may be mounted on a wheel, for exam ple. The pin rides in a slot A formed in another component of the mechanism. The result is an oscillatory movement of that component in a lateral direction shown by the straight arrows.

figure 12 shows an application of that principle to a mechanism for causing a pair of rods to oscillate from side to side. The Figure 11 mechanism is coupled to a lateral bar which is pivotally connected to a pair of upright bars pivoted at their lower ends A, only one such end being illustrated for simplicity.

Figure 13 shows an alternative mechanism In which an upright bar is pivoted at its lower end A and a simple connecting rod couples it to a rotary wheel, much like a piston and connecting rod arrangement in an internal combustion engine.

Figure 14a and b illustrate mechanisms in which the Figure 11 principle is applied to a carriage mounted for sliding or rolling movement between rails and the application of a simple wheel and connecting rod arrangement to the carriage.

Figure 15 shows yet another arrangement for applying the Figure 11 principle to a bar E mounted for movement between a set of rollers A-D, whereby the bar E oscillates transversely in the direction of the straight arrow.

The same type of bearing mechanism for the bar E can be used with the simple connecting rod arrangement as shown in Figure 16.

Figure 17 shows the application of the Figure 11 mechanism to an opposed pair of pivoted rods having pivots located at fixed reference points, whereby the free ends of the rods are caused to oscillate from side to side. The lengths of the rods can be varied to cause the amplitudes of the oscillations of the free ends of the rods to vary correspond ingly.

In Figure 18, two L-shaped rods A, B are pivoted at fixed reference points C, D. When their ends E, F are moved in the direction of the vertical arrows, their other ends G. H move laterally as shown by the horizontal arrows. In this way, motion is transferred through 90 degrees. The movement is equal and opposite. - 11

A variation of this construction is shown in Figure 19, where the ends A, B of the L-shaped rods are coupled by link rods to a wheel. In this way, the phase can be varied.

Figure 20 shows a mechanism in which the principle of Figure 12 is applied via bar D to oscillate L-shaped bar A through pivotal connection E. Similarly, the same drive mechanism causes L-shaped bar B to oscillate in antiphase to bar A. Figures 21, 22 show the use of bars A, B provided with sector-shaped members C, D that inter-engage to transfer the oscillatory motion of one bar to the other. The sec- tor surfaces may therefore be toothed, ribbed or otherwise fashioned to enhance driving contact between them.

Figure 22 shows a variant in which two lengths of belt are connected across from one sector to the other to ensure that there Is no slippage and therefore phase variation between the sectors and hence the bars.

Figure 23 is yet another variant in which an intermediate rod A is placed for linear movement between the sectors. However, in this case the belts are connected between the ends of the sectors at B and E and points C and D on the rod A. In this way, rotary motion is transferred between the sectors and therefore their respective rods and simul- taneously, the intermediate rod is caused to move linearly.

A similar result can be achieved by the mechanism in Figure 24, in which a pair of pivotally mounted L-shaped bars B. C are connected by a rolling coupling consisting of rollers and short bars formed at the ends of the upright rod A. When rod A is moved vertically, rotary motion in opposite sense is applied to the L-shaped rods B. C. Figure 25 shows a pair of pulleys A, B around which is passed a belt connected at E and F to a pair of roller carriages C, D rolling between rails. When either of the pulleys rotates, the belt transfers equal and opposite linear motion to the carriages. The car riages may be connected to any of the parts previously described.

figures 26 to 28 illustrate various bearing/coupling mechanisms specifically ap- plied to the trailing and leading ends of the vanes.

In Figure 26, a slider B connected to the tail of the vane runs between rails A, while the leading edge is simply pivoted at C to a drive rod or the like (not shown) of any of the previously described mechanisms. - 12

In Figure 27, the tail end coupling comprises a carriage carrying a pair of rollers that run on the outer edges of a single guide rail.

In Figure 28, the tail is extended or connected to an extension piece A and this ex tension is connected to a carriage similar to that in Figure 27.

Figure 29 shows a mechanism using a system of cranks enabling the vanes or hy drofoils to be oriented at will. This makes it possible for the direction of propulsion to be controlled. There are considerable advantages in this since a vessel equipped with such a mechanism can be literally driven sideways! This makes for exceptional manoeuvrability and enables a vessel at moorings to be literally driven out sideways and into the water way. Thrust direction can then be altered to enable the vessel to travel in any chosen di rection.

In Figure 29, only the elements that control direction are shown for the sake of simplicity. There are two main cranks A, B to which are pivotably mounted four smaller L-shaped cranks. The trailing edges of the vanes or hydrofoils are fixed to the ends of these. Two of these smaller cranks rotate about pivots C and two rotate about pivots D which are used to fix the attach cranks A, B to the vessel. Three rods E connect the ends of the four smaller cranks. If the position of crank F is altered, as indicated by the arrow at its lower extremity, the motion is transmitted via the rods and intermediate smaller cranks to the others (which are coupled to the foils) and they follow suit such that the leading edges of the foils or vanes also follow suit.

Finally, Figure 30 shows a mechanism in which four pulleys are interconnected by three belts, chains etc with no slippage on the pulleys. When the position of pulley B is altered, the pulleys A follow suit and the position of the trailing edges of the vanes is con trolled accordingly.

The Figure 29 arrangement is more preferable for smaller vessels onaccount of the forces generated in the second.

Conclusion and Applications

The present invention therefore provides mechanisms for causing vanes/hydrofoils to oscillate like a fish tail (i.e. lateral oscillation coupled with yaw) thereby to produce propulsive thrust and conversely provides a mechanism that utilises - 13 fluid flow in order to cause vanes/hydrofoils to oscillate in the same manner but to gener- ate power.

Figures 31 and 32 illustrate the application of the power generating mechanisms to a full scale power generating plant located in a waterway. Both figures are stripped of the detail of the mechanisms for simplicity and so as to enable the general layout and in- terrelationship between the parts to be viewed.

Figure 31 shows a system in which the hydrofoils are disposed horizontally. They are mounted on an A-frame anchored to the bed of the waterway. The significance of this construction is that all of the "moving parts", i.e. the mechanism for converting the oscillatory movement of the hydrofoils into linear or rotary movement to harness the en- ergy, are mounted above the water and are therefore easy to inspect and maintain.

There may be as many sets of vanes/hydrofoils as can possibly be mounted on the A- frame but still under water. The system is inherently buoyant and the centre of buoyancy is below waterline and is therefore resistant to rough weather. This structure is therefore eminently suitable for deep water and exposed locations.

Figure 32 shows a system with vertical vanes. It benefits from most of the advan- tages of the previous structure but its layout makes it more suitable for shallow waters such as rivers and sheltered tidal areas. The whole mechanism is intended to be sus- pended from a boom slung between pontoons. The hydrofoils can easily be raised above water for maintenance.

The invention can also be applied to pedal boats. As shown in Figure 33, two pedal mechanisms 330, 331 are interconnected by a chain 332 or other continuous belt with no slippage. This is important to preserve the phase relationship between opposed pairs of foils. However, the actual phase relationship can be altered by a phase adjust ment device as will be explained with reference to Figure 36.

The mechanism is mounted on the boat relative to a cross member 337 spanning across a pair of outboard bodies forming a catamaran-lke structure as shown in Figure 35. The cross-member 337 also carries the main bearings as will be described with refer- ence to Figure 38. A pair of rods 338, 339 is connected to the pedal mechanisms by any of the appropriate couplings already described so that as the pedals are turned, the rods are caused to oscillate from side to side. These rods are also pivotally coupled to main levers 333-336 symmetrically mounted for pivotal movement about the main bearing axis 380 (Fig 38) on the cross member 337. Therefore, as the pedals are turned the main levers 333-336 oscillate about the main axis 380 in a scissor motion.

Consider first the upper or "forward" part of the pedal boat. The ends of the main levers 333, 334 are coupled to the leading edges of the foils so that movement of the levers causes the leading edges of the foils to follow suit. The trailing edges are cou pled by any of the appropriate mechanisms previously described to a series of linkages including crank 341, pivoted to the upper end of member 335, and rods 342, 343 in the manner shown in Figure 33. The lower end of rod 342 is pivotally connected to one arm of a crank 345 rotatable about the main axis 380. The overall result is to cause the for ward pair of foils to perform their "fish tail" movements as previously described. The linkage is symmetrical so, for the sake of clarity, only one side is referenced.

The construction just described for the upper part of Figure 33 is repeated for the lower part, so the lower or "aft" pair of foils is caused to perform their fish tail move meets at the same time but not in phase with the forward pair for reasons already ex plained before.

A lever 340 is pivotally connected to the cross member 337 and is connected via rod 344 to the cranks 345. A similar set of links connects the cranks to a lower trans verse rod 346 terminating in a second lever 347 at the side of the boat. Operation of either of the levers 340, 347 causes the linkages to move so as to adjust the angle at which the foils are oriented relative to the boat. By this technique, it is possible to direct the thrust at varying angles. The boat can therefore be manoeuvred simply and can actu ally be driven sideways and can be rotated through 360 degrees on the spot.

Figure 34 shows the construction of Figure 33, omitting the direction control mechanism for the sake of clarity, and with the leading vanes as they move through a po sition aligned with the direction of flow/motion.

Figure 35 shows the Figure 33 mechanism slung across outboard bodies to create a catamaran-style pedal boat with immense manoeuvrability. The actual mechanism can be covered over with a tarpaulin carrying advertising and/or identification indicia and to protect the mechanism if warranted. 15

Figure 36 shows a suitable means for regulating the phase difference between the pedal mechanisms. In essence it consists of a pair of gears 360 mounted for lateral movement relative to the main axis of the chain 361. This varies the relative lengths of the bights of chain extending between the pedal mechanisms and thereby adjusts the rela- tive phase between them.

Figure 37 is a schematic representation of a conventional bicycle pedal mechanism connected to a right angle gearing for converting the direction of rotation through ninety degrees.

Finally, Figure 38 shows the general construction of main axis 380. The figure in eludes for convenience a plan view of the bearing superimposed over the side elevation.

Further variations The following description relates to an explanation of three different means of controlling the angle of the foil on the end of an oscillating lever, and their relative merits in propulsion systems and energy generators. They are illustrated in Figures 39-41.

All three systems are derivatives of the previously described method where the cycle which controls the angle of the foil is 90 degrees out of phase with the cycle which moves the foils through their oscillation. If the foils describe a motion determined by a sine function, their velocity across the flow is determined by a cosine function. By placing the angle control cycle 90 degrees out of phase with the main drive cycle this ensures that the angle of the foils is also determined by a cosine function.

In the three systems compared, the angle created at the pivot at the main lever is transferred to the foil via a chain, as opposed to the rod, and lever assembly as in the Fig ure 2 arrangement. This is mechanically simpler, and enables the foil to be moved through 360 degrees more easily.

The system shown In Figure 39 is the same in principal to the system described above. The only difference being that the movement in the angle drive cycle is trans ferred to the foil angle control mechanism via a rod and a chain as opposed to simply a rod. Both systems give essentially the same output.

These systems could be regarded as a "Simple cosine system" because the angle of the foil is determined solely by this function. The range of angles covered by the foils, (the "variable pitch" mechanism) can be altered by changing the radius of the angle drive mechanism, or that of the foil angle control mechanism. The foils can be orientated by manipulating the chain In the foil angle mechanism.

Simple tangent system.

As shown in Figure 40, the motion of the angle drive cycle is transferred into an angle in the foil angle control mechanism by coupling it directly to a fixed point on that system.

This system causes the angle of the foil to change rapidly for small changes in the position of the angle drive cycle when the foils are at large angles to the flow.

The range of angles covered by the foils, can be altered by changing the radius of the angle drive, or position of the point on the foil angle mechanism which is coupled to the angle drive.

Complex tangent system.

As shown in Figure 41, one end of the transmission rod is attached to the angle drive cycle. The other is guided by sliding along a fixed track which passes close to the pivot of chain wheel one. Another track is attached radially to the lower chain wheel. The element of the transmission rod which slides in the fixed track also slides in the track at- tached to the lower chain wheel. The angle of the foil changes most rapidly when it is close to facing directly into the flow. The range of angles covered by the foils can be con- trolled in this system either by changing the radius of the angle drive cycle, or by moving the track relative to the centre of chain wheel one.

The shape of the track can be altered to determine exactly what angle the foil pre- sents to the flow at every position in its cycle. This could be of great importance for water turbines where the foil trajectory passes through regions of different flow speed. Each track could be engineered according to the variation in flow speed to ensure that the foil always presents the best possible angle to the flow.

Analysis of the performance of the competing systems.

For a water turbine of this design to work efficiently, the angle of the foils must always have the same sign as the angle of the incident flow, and it must always have a lar- ger magnitude. The graph below shows that only the complex tangent mechanism man ages to meet both these demands. 17

Angle of flow incidence and foil angles in_

_

_

_,, ,, _ _ am --- fir_ _ ' . _,.

O 50,,, . \, fY Angle of flowveloaty \| , . . ., .f Simple tangent mechanism c.' 0.2.a b4 o.s o.e 0,7/ O. off S'mpletangentmechansm -oso ___ \_._ Complextangentmechamsm -loo: ._ L_._ 1 50 9 I -2 00 _ Position In the cycle The graph below shows the difference between the angle of the apparent flow ve- locity and the angle of the foils. The ideal graph for a flapping foils system is shown. The curve for the complex tangent mechanism matches this curve approximately. The others are a long way from coming close.

Angle of flow incidence oat Am. ._. ......

__

0 60.......... . - ... .... __,, . _ _ I,,, ' 0 40 r * i _,.

s^ . en \ 1/ J f Slmecosinemechamsm e O 00, - ' AN / S'mpletangent mechanism \0.1 0.2 o.a;5/ o.e 0.73 em/ 08 Complextangentmechamsm - -O 20. ok. _ - . . .... _ = A. ,,_,- .. Ideal 0:\, C -O 40:< I --. arm_- _ _ C ' V ' ' '; -O 60 -O 60 Angular position - 18 The complex tangent mechanism therefore shows the most promise for applica- tion in generating systems. Furthermore it will be possible to improve on the results pre- sented here by manipulating the shape of the track as described in the explanation of how the system works.

The other mechanisms cannot be discounted however because, they will all work effectively as turbines at low speeds and frequencies, and also as propulsion systems.

When the foils are pushing against the water, rather than vice versa, their angle must have the same sign as the angle of the flow velocity but be smaller in magnitude. The chart below shows how all three systems can achieve this almost equally well.

Angle of flow incidence and foil angles 060.......... _, 0 40 HA. I it -' . ' +_.._-a. ' " ' " ' ' - ' ,,-7' I' ' / 0 20 'I \ \ . // Angleofflowvelocty "it N \ ' // Simple tangent mechanism 0 Do Hi\ , , .. _, . _._, 61 02, '\0.3 04 0.5 0.4 07 / D,$ 09 smpletangentmechansm / Complex tangent mechanism O 20 __ \ / '' -O 40 \= ' -- Position in the cycle The chart below compares the three systems with the ideal angle of flow inci- dence, and once more they are very similar.

Anale of flow incidence 0 60 _, ,, ... ,,, - in. an, ,,, ., I, I. - ,_._, ,' . ',,' ' ,.

0 40.

_, , ,i O 20 _ ____._, ... __ _ ___ _ " i'" t. Slmple cosine mechanism I _ Simple tangent mechanism _ 00 'I 't -7 a- ' "I" I- -'or 0.1 0.2 1 o.$ o.. 06 00 07 | of o.s Complex tangent mechanism e, \ Ideal _ -0 20 I..,, _ _ -O 40._ _.... _.. _.. Am. ct,.

-O 60 - .... .._, _._,._, ,,,,.,_.. _ -o so Angular position The "pulse" system (i.e. the system using vanes or hydrofoils linked to rotating wheels to imitate fish tail movements) therefore seems much less highly strung when it is used as a propulsion system, and it is much less sensitive to the details of its mechanics.

The curve for the complex tangent mechanism in the chart above could again be im- proved by modifying the track. This may be of importance for systems where a small in- crease in efficiency is important. For many other applications however, the attraction of the mechanical simplicity of the other systems will probably outweigh the small decrease in efficiency.

The promise of the 90 degree systems appears to eclipse that of the systems which rely on a small phase difference between two drive cycles which determine the po sition of the front and the rear of the foils. They are mechanically simpler and can be en gineered to give more efficient foil trajectories. -

Claims (36)

1. Apparatus for oscillating a first vane relative to a fluid stream having a di- rechon of flow, comprising first means for oscillating the leading edge of said first vane transverse to said flow direction and second means for oscillating the trailing edge of said first vane transverse to said flow direction with a phase lag relative to said first means, whereby said first vane oscillates about an axis substantially at right angles to said flow di- rection and moves laterally from side to side across the flow direction.

2. Apparatus as claimed in Claim 1, wherein said first vane is adapted to be oscillated by said current and said apparatus further includes means to harness the movement of said first vane and convert it into useful energy.

3. Apparatus as claimed in Claim 1, wherein said first vane is adapted to be oscillated by drive means whereby to produce a propulsive effect.

4. Apparatus as claimed in Claim 3, wherein said drive means comprises a pedal-operated drive source.

5. Apparatus as claimed in any of Claims 1-4, further comprising a second vane adapted to be oscillated with a phase lag relative to said first vane.

6. Apparatus as claimed in Claim 5, further comprising third and fourth vanes adapted to be oscillated with a phase lag relative to said first and second vanes.

7. Apparatus as claimed in any of the preceding claims, wherein said first means comprises a first lever pivoted at one end about a reference axis and coupled at the other end to the leading edge of the first vane, a second lever pivotally coupled at one end to said first lever and at the other end to a first point near the circumference of a first wheel, and said second means comprises a third lever pivoted at one end about a refer ence axis and coupled at the other end to the trailing edge of the first vane, and a fourth lever pivotally coupled at one end to said third lever and at the other end to a second point near the circumference of said wheel.

8. Apparatus as claimed in Claim 7 when dependent from Claim 6, further comprising a respective first and second means as claimed in Claim 7 coupled to operate each of said first, second, third and fourth vanes respectively.

9. Apparatus as claimed in Claim 5, wherein said first vane is coupled at its leading edge to one end of a first lever, the second vane is coupled at its leading edge to - 21 the other end of the first lever, the first lever being mounted at a point intermediate its ends for rotation about a first reference axis; a second lever coupled at one end to the trailing edge of the first vane, a third lever coupled at one end to the trailing edge of said second vane, a fourth lever coupled at its ends to the other ends respectively of the sec ond and third levers, the fourth lever mounted at a point intermediate its ends for rota- tion about a second reference axis, a fifth lever coupled at one end to the first lever, a sixth lever coupled at one end to the fourth lever and the other ends of the fifth and sixth levers respectively coupled to respective points near the circumference of first and second wheels, and means coupling said first and second wheels for simultaneous rotation about respective axes.

10. Apparatus as claimed in Claim 9, wherein said means comprises first, sec- ond and third intermediate wheels disposed in that order between said first and second wheels whereby rotation of one of said first and second wheels is transferred to the other of said first and second wheels.

l 1. Apparatus as claimed in Claim 10, wherein said second intermediate wheel is mounted for movement towards and away from said first and second vanes whereby to adjust the phase angle between said first and second wheels and thereby the phase angle between said first and second vanes.

12. Apparatus as claimed in Claim 1, further comprising a second vane adapted to be oscillated in antiphase relative to said first vane.

13. Apparatus as claimed in Claim 12, wherein said first means comprises a first lever pivoted near one end about a reference axis and coupled at the other end to the leading edge of the first vane, a second lever pivotally coupled at one end to said first lever and at the other end to a first point near the circumference of a drive wheel; said second means comprises a third lever pivoted near one end about a reference axis and coupled at the other end to the trailing edge of the first vane, and a fourth lever pivotally coupled at one end to said third lever and at the other end to a second point near the cir- cumference of said drive wheel, a fifth lever coupled at one end to the said one end of the third lever and at the other end to a point near one end of a sixth lever, said sixth lever pivoted at said one end thereof for rotation about a reference axis, the other end of the sixth lever coupled to the trailing edge of said second vane, a seventh lever pivoted at one - 22 end for rotation about a reference axis and coupled at the other end to the leading edge of said second vane, and an eighth lever coupled to the seventh lever near the said one end thereof and coupled at its opposite end to the said other end of the first lever, whereby the first and second vanes can oscillate in antiphase relative to one another.

14. Apparatus as claimed in Claim 12, further comprising a third vane and a fourth vane, said third and fourth vanes coupled for movement in antiphase relative to one another and with a phase lag relative to the first and second vanes.

15. Apparatus as claimed in Claim 1, comprising four pairs of first and second vanes, the vanes in a first pair moving in antiphase to the corresponding vanes in a second pair, and the vanes in a third pair adapted to oscillate in antiphase to the corresponding vanes in a fourth pair, there being a phase lag between the vanes in the third pair relative to the vanes in the first pair and between the vanes in the second pair relative to the fourth pair.

16. Apparatus as claimed in Claim 1 or 2, wherein said first and second means for oscillating the leading and trailing edges of the vane comprises a first lever rigidly con nected at one end to said vane intermediate its leading and trailing edges and pivotally mounted at said one end to one end of a second lever, the other end of said first lever coupled to one end of a third lever, the other end of which is coupled to one end of a fourth lever, the other end of the fourth lever coupled to the other end of the second lever, the first, second, third and fourth levers thereby forming a parallelogram; a gear wheel pivotally mounted for rotation about an axis on the second lever, a fifth lever mounted at one end for rotation about said axis and at the other end coupled to the third lever, whereby rotation of the wheel adjust the shape of the parallelogram, the gear wheel meshing with a rack on a sixth lever and end of which is coupled to a point near the circumference of a first pulley, a second pulley spaced from the first pulley, a drive belt or chain passing around the first and second pulleys, a seventh lever having one end coupled to a point near the circumference of the second pulley, the other end of the seventh lever coupled to the second lever, the arrangement being such that rotation of either of said pulleys causes the vane to oscillate. - 23

17. Apparatus as claimed in Claim 16, wherein said sixth lever is adjustable in length whereby to adjust the angle of the vane at its rest position halfway between the two extreme angular positions thereof.

18. Apparatus as claimed in Claim 1, further comprising first and second pedal mechanisms for causing first and second bell cranks to rotate about the respective rota- tional axis of the first and second pedal mechanisms, the pedal mechanisms being inter- connected by a chain drive, first and second arms coupled to the respective first and sec- ond bell cranks whereby operation of the pedal mechanisms causes the first and second arms to oscillate about respective reference axes; first, second, third and fourth parallelo gram linkages cross-coupling the vanes so that oscillation of one of said vanes is trans- ferred to the other three of said vanes whereby to cause oscillation of said vanes such that the first and second vanes operate in antiphase relative to one another, the third and fourth vanes operate in antiphase relative to one another, and the first and second vanes operate with a phase relation relative to the third and fourth vanes.

19. Apparatus as claimed in Claim 18, wherein the tension in one length of the chain is adjustable to vary the said phase relation.

20. Apparatus as claimed in Claim 18 or 19, further comprising adjustment means to adjust the angle of inclination of the vanes relative to the flow direction.

21. Apparatus as claimed in Claim l, wherein said first vane is mounted on a first gear wheel for rotation therewith, the first gear wheel mounted for rotation on a first arm pivotable about a reference axis, said first gear coupled by a first chain to a second gear wheel mounted for rotation about said reference axis, a first operating arm rotatable with said second gear wheel and coupled to one end of a first rod whose other end is coupled to a second operating arm mounted for rotation with a third gear wheel having an axis spaced from and parallel to the second gear wheel, the third gear wheel coupled by a second chain to a fourth gear wheel coupled via a third operating arm and a second rod to the first arm, the arrangement being such that rotation of any of said second, third and fourth gear wheels causes said first vane to oscillate.

22. Apparatus as claimed in any of the preceding Claims, wherein the leading edge of a vane is coupled to a lever by means of a pivotal coupling. - 24

23. Apparatus as claimed in any of the preceding claims, wherein the trailing edge of a vane is coupled to a lever by means of a coupling permitting relative rotational and sliding movement.

24. Apparatus as claimed in Claim 23, wherein said coupling is selected from any of the following: a carriage fixed to the trailing edge and provided with rollers rolling on a rod; a carriage pivotally mounted to the lever and provided with rollers rolling on an extension of the trailing edge; a slider fixed to the trailing edge and sliding in a tube or between guide rails; and a slot in the trailing edge co-operating with a pin fixed to the lever.

25. Apparatus as claimed in any of the preceding claims, wherein any of the couplings between moving parts are substantially as described with reference to any of Figures 9-25.

26. A vessel provided with apparatus as claimed in any of the preceding claims.

27. A vessel as claimed in Claim 26, wherein said apparatus is fitted trans versely between a pair of elongate buoyant floats, whereby operation of at least said first vane causes the vessel to propagate.

28. Apparatus as claimed in any of claims 1 or 3-27, substantially as herein de scribed with reference to Figures 1, 2, 5-30 and 35-41 of the accompanying drawings.

29. Power generating apparatus comprising apparatus as claimed in Claim 2 or any of claims 3-6 or 16 when dependent from Claim 2, supported on a support structure with said vane or vanes adapted to be located in a said fluid flow, whereby said vane or vanes can be oscillated by said fluid flow, and wherein said means to harness movement is coupled to said vane or vanes to convert said movement into useful energy.

30. Power generating means as claimed in Claim 29, wherein said structure comprises at least one A-frame having two legs, the lower ends of which are anchored to the bed of the fluid flow, and wherein said vane or vanes is/are supported at an interme diate point along a said leg with the vane or vanes immersed in the fluid flow.

31. Power generating means as claimed in Claim 30, further comprising a plu rarity of sets of apparatus as claimed in Claim 1 supported by the said legs of the said A frame. -

32. Power generating means as claimed in Claim 29, wherein said structure comprises a boom adapted to be set across said fluid flow, and a plurality of apparatus as claimed in Claim 1 supported on said structure with each of said vanes immersed in said fluid flow.

33. Power generating means as claimed in any of claims 29-32, further com prising means to adjust the angle of inclination of said vane or vanes relative to said fluid flow.

34. Power generating means as claimed in Claim 33, wherein said adjustment means comprises means to reverse the direction of said vane or vanes whereby to face upstream or downstream of said fluid flow.

35. Power generating means as claimed in any of claims 29-34, substantially as described herein with reference to Figures 1-32 and 3841 of the accompanying draw ings.

36. Apparatus as claimed in Claim 5 or any of claims 6-35 when dependent on Claim 5, wherein said phase lag is substantially 90 degrees.