Note: Descriptions are shown in the official language in which they were submitted.
Summaries of the Inven-tion
According to one aspec-t of the invention, energy
conversion apparatus operable by a flow of fluid comprises
endless travelling belt means and a plurali-ty of inter-spaced
hydrodynamic foil members mounted on the endless belt means
whereby lift forces are generated by passage of fluid over the
foil members and are made to drive the endless belt means.
The apparatus may include means controllably varying the
angle of incidence of the foil members between a low value
obtaining at a low fluid flow velocity and higher values
obtaining at higher fluid velocities.
The apparatus may include start-up means to provide an
initial movement to the foil members and, hence, of the endless
travelling belt means, at low angles of incidence of the foil
members i.e. at low fluid velocities. The start-up means may
comprise a wind driven rotor coupled to the endless travelling
belt means.
According to the invention also energy conversion means
comprises:
a rigid frame structure;
first and second endless travelling belt circulating parts
supported for rotation about a first axis defined in the said
frame structure'
third and fourth endless travelling belt circulating parts
supported for rotation about a second axis defined in the said
frame structure;
a first endless travelling belt engaging the said first
and third said circulating parts;
a second endless travelling belt engaging the said second
3 and fourth said circulating parts;
a multiplicity of arm members distributed at intervals
along the said endless belts, being each pivotally connected to
the said belts at spaced apart positions along the arm members;
a multiplicity of hydrodynamic surfaces respectively
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supported by the said arm members;
spring means linking -the said endless belts; and
a load in -the form of a rotary member adapted to be driven
by rota-tion of the said fourth wheel;
-the arrangement being such that lift forces acting on the
said hydrodynamic surfaces, as a result of passaage of fluid
over the said surfaces, causes the said arm members to pivot
against the action of the said spring means, under the load of
the said rotary member, about their connections with the said
belts, thereby to cause the hydrodynamic surfaces to adopt an
angle of incidence determined by -the veloci-ty of the fluid over
the said surfaces and the lift velocity of -the hydrodynamic
surfaces.
The said spring means may link two belt circulating parts
sharing the same axis. The said axis may be shared by the
first and second said belt circulating parts.
The apparatus may comprise mean~ operable in response -to
variation in fluid flow direction to orientate the hydrodynamic
surfaces so as to maximise the lift forces developed thereon.
This aspect of the inven-tion may be used to generate
electricity, to pump water, or to propel a ship by coupling the
endless belt means to a water-screw propeller.
According to another aspect of the invention, energy
conversion apparatus operable on fluid comprises endless belt
means, a plurality of inter-spaced foil members mounted on the
endless belt means such that, when the endless belt means are
driven, lift forces are generated by movement of the foil
members through the fluid.
Means are preferably provided whereby the pitch of the
foil members may be varied.
This alternative aspect of the invention may be used to
propel a ship by disposing the foil members in water.
As used herein, the term "endless belt means" includes,
ropes, cables, chains and like endless driven or drive means.
The invention also comprises any novel subject matter or
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combination including novel subject matter herein disclosed.
Brief Description of the Drawings
Embodiments of the invention will now be described by way
of example only with reference to the accompanying drawings,
wherein:
Figure 1 is a side view, in section, of energy conversion
apparatus,
Figures 2 and 3 are side and front views of the apparatus,
Figure 4 is a front view of a modified form of apparatus,
Figure 5 is a section, taken on the lines D - D of Figure
4,
Figures 6 and 7 illustrate the principle of operation of
the arrangement,
Figures 8 and 9 illustrate how pitch of a foil member is
varied,
Figures 10 and 11 illustrate details of the endless cable
means,
Figures 12 to 16 illustrate details of the yoke wheels and
pitch control mechanism used by the apparatus, and
Figures 17 to 20 collectively illustrate an alternative
: construction of the endless belt and associated circulating
parts.
Detailed Descriptions of the Preferred Embodlments
:
: With reference to Figures 1 to 3, energy conversion
apparatus 20 operable by a flow of fluid (wind) comprises a
rigid frame structure S, endless travelling belt means 21
suppor-ted by the frame structure S, and a plurality of inter-
spaced aerodynamic surfaces of foil members 22 mounted on the
endless belt means 21 so that lift forces are generated by
passage of wind over -the foil members 22 and are made to drive
the endless belt means 21. The foil members 22 are, in lateral
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cross-section, high speed aerofoils. The bights of the endless
belt means 21, which is disposed substantially vertically,
extend around belt circulating parts, being upper and lower
parts of yoke wheels 23, 24. The frame S of the apparatus 20
incorporates a pillar 25 by which the apparatus is supported
above the ground.
The endless belt means 21 comprises two endless cables 27,
2~ arranged for movement in respective parallel planes, the
cables extending round the upper and lower yoke wheels 23, 24
respectively mounted for rotation on horizontal shafts 29, 30.
The shaft 30 is connected to an electric generator 31 by way of
a belt (32) and pulley (33) system, as well as a magnetic
clutch 34. Tension springs are provided, (see Figures 8 and
13), which~ acting through the endless belt means 21, serve to
keep the foil members 22 thereof in a start-up condition, until
the twin opposing forces of lift and reaction, (i.e. the load
developed by the generator 31), cause the springs to stretch to
the limits imposed by mechanical restraints of the linkage.
This is the maximum lift and maximum speed mode of the
apparatus 20.
Thereafter when lift or reaction are absent the springs
will return the foil members 22 to their original, i.e. start-
up positions.
Rotation of shaft 30 results in the production of useful
electric power from generator 31.
A start-up propeller 35 is provided.
Figures 6 and 7 illustrate the principle of lift-force
generation by a foil member 22. In Figure 6, a cantilevered
arm 53 is disposed so that the leading edge of the foil member
3 22 it supports faces into the wind. The wind direction is
indicated by arrow 45. The lift force acting on -the foil
member 22 is indicated by the arrow 47.
A component of the lift force 47 will act along the cable
2~3, and, as the belt means 21 begins to move along i-ts path,
the apparent wind direction changes and increases in velocity.
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.
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In response to these changes, the foil member 22 has to tilt
toward the new apparent wind direction (45a - see Figure 7),
and to the desired angle of incidence to it. Lift increases in
proportion to the square of the velocity and continues to cause
the cables 27, 28 to travel faster, reaching an optimum power
condition when the lif-t force approaches an angle of
approximately 82 to the cable, as shown in Figure 7. Beyond
this point the now very large lift force would begin to lose
effectiveness as its direction approaches one which is normal
to its most desired direction, having zero effect at 85 or 86
and rapidly increasing negative influence from thereon. In
comparison, the conventional windmill blade sees a changing
speed along its length which reaches the maximum efficiency
element but goes right on past it to the zero effect point
mentioned above. The foil members 22 however, can be at or
near this maximum efficiency setting over their en-tire lengths,
giving an advantage over the windmill blade on an area-to-area
basis of up to 6:1, in the case of a high speed aerofoil.
R.A.F. No. 15 is an example of such an aerofoil.
The apparatus 20 includes an upright, elongate rigid
structure 50 (Figure 2) which also serves as a directional
stabilizer structure. The structure 50 is in the form of a
sheet metal, aerodynamic mast which is acted on by the wind so
as to rotate the structure 50 and foil members 22 so that the
foil members face into the wind as the wind direction changes.
As is seen in Figure 8, each foil member 22 is pivotally
connected to cable 27 at one end of a cantilever arm 53 by
pivot structure 54, and is pivotally connected intermediate the
ends of arm 53 to cable 28 by pivot structure 55. The arm 53
is connected to the foil member 22 generally mid-way along the
foil member and mid-way across the foil member. Movement of
cable 27 relative to cable 28 will move the arm 53 so that the
foil member 22 can move from a start, low-lift, position shown
in chain-dotted lines, to a full-lift position shown in
continuous lines. The tension springs described above bias the
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foil members to their start-up positions until lift forces
generated by the wind flowiny overcomes the spring force and
can move the arm 53 until it meets a stop. All the arms 53 are
moved together when cable 27 moves relative to cable 28.
Figures 10 and 11 illustrate another form of pivot
structure 54 or 55. Stainless steel or "KEVLAR" (Registered
Trade Mark) cable 27 has ends received on slotted eyelets 60
-through which extend lugs 61 formed on connecting spaced plates
62 (stainless steel or titanium) which clamp between them a
trunnion 63. The trunnion 63, in respect of the forward cable
28, is part of the arm 53, and, in respect of the aft cable 27,
provides a pivot for the end of the arm 53. Snap rings (or
"CIRCLIPS") 64 secure the end of arm 53 and both trunnions 63.
Rotation of the arm 53 in a trunnion 63 takes place whenever
either of the couplings 54 or 55 precedes the other, either on
to, or off of, the associated yoke wheel.
With cables 27, 28 in sections connected by the couplings
54, 55 assembly and replacement of parts is relatively easy and
the size of the unit can be changed by adding or removing
sections. Spacing of the foil members 22 is fixed.
Because the foil members 22 are spaced forward of the
cables on arms 53, drag and turbulence in the region of the
foil members is reduced.
The bias springs return the foil members 22 to their
start-up or datum positions when the wind speed is too low to
generate useful power.
The pitch of the foil members 22 is variahle for two
reasons:-
1. Windmill/wind belt blades/foils are designed to
operate at a cer-tain speed relationship to the wind speed.
When that relationship is in the order of 9 to 1, the blade
tip/foil chord (pitch) angle is close to being at right angles
to the wind (85).
After stopping due to lost wind, such an arrangement will
not start up again for a light wind because the foil members
, .. . .
~25a~
will not develop enough lif-t whilst almost flat on to the wind.
The foil members must be partially feathered to start up or
power must be applied through the generator 31 to get it
moving.
2. Excessive winds will destroy the machine, so a means
must be employed to limit the speed at which it may run. One
way to accomplish this is to reduce the pitch angle so that the
foil members now run a-t a lower speed relationship to the wind.
In the case of the present invention, the pitch angle of a foil
member can be reduced to zero, causing it to stop completely,
if desired.
Three methods can, for example, provide the desired
control. Feathering for start-up is achieved by resisting the
lift leverage forces of a cantilever 53 with a spring. When
there is little or no lift, the spring will return the foil
member to a "start-up" position. When the wind picks up and
lift forces cause the endless belt means 21 to start moving,
increasing speed and lift will continue to stretch the springs
until the foil members 22 reach their maximum setting, when
stop means arrest movement.
The pitch change system will maintain the foil members 22
at that setting, where they will run at a substantially
constant ratio to the wind speed up to a certain maximum speed,
as determined by the forces to be dealt with. At that point, a
governor will commence to reduce the differential between the
yoke wheel pairs 23, 24, thereby reducing the foil chord angle
; and the relative speed ratio to the wind.
Lift-generating attitudes are assumed during both forward
and reverse runs of the endless belt means 21.
The yoke wheels 23, 24 are designed so as to accommodate
relative vertical movement between the endless cables 27, 28.
With reference first to Figure 12, a wheel 24 is of spoked
form, each of the spokes 70 thereof carries a pair of spaced-
apart studs 71, 72 to which the ends of tension springs 73
(Figure 13) are anchored. Ea_h stud 71 is dtspose3 on the far
.
side of the wheel 24, whereas each stud 72 is disposed on the
near side thereof.
Referring now to Figure 13, each pair of yoke wheels 24
(and similarly wheels 23) are coupled by the tension springs 73
which are disposed between the wheels. The springs 73 bias the
wheels to positions whereby their spokes 70 are non-aligned as
shown in phantom, i.e~ zero pi-tch position of the foil members
22.
The front or drive wheel 24 is fixed to the shaft 30 and
therefore will resis-t rotation through the magnetic particle
clutch 34 and genera-tor 31. This resistance enables foils 22
to enact a leverage through cantilevers 53 as shown in Figure
8, and in accordance with the force of lift being applied, will
stretch the springs 73, permitting the drive (front) wheel to
move ahead of the rear wheel, thereby changing the foil pitch.
Figures 14, 15 and 16 illustrate how (Figures 14, 15) the
wheels of a yoke wheel pair 24 (or 23) can move relative to
each other both axially and angularly on their common support
shaft 30 and how (Figure 16) original settings of the wheels
can be made.
With reference first to Figures 14 and 15, this apparatus
acts to reverse the previously described pitch change when the
wind speed exceeds a certain predetermined speed. Weigh-ts 81
are attached to force transposer wheels 82 which are mounted to
the front yoke wheel 24. 'G' forces on the weights 81 tend to
rotate the force transposer wheels which, through links 83, in
turn tend to rotate the sleeve 84 and the clamp ring 85 clamped
to it in an adjustable manner through ring adjuster 86.
Referring now to Figure 16, rollers 87 on the clamp ring
85 push against pins 88 extending from the rear yoke wheel 24,
which is free to rotate and slide on the shaft 30 as the pitch
of the foils 22 is reduced as wind speed increases fur-ther.
Referring to Figure 15, a spring ring 89 serves to retain
the inner link pins 9O whilst set into a groove in sleeve 84.
~ second groove set back from the first, allows pins to be
extracted to link 83 release position but retains the pins in
place.
As shown in Figures 1 to 3, a maintenance/safety platform
120 is secured below the upper end of the pillar 25. The
platform 120 can be folded (as in Figures 2 and 3).
On start-up of the apparatus 1, the propeller 35 is turned
by the wind. A centrifugal clutch 36 (Figure 1) is used to
couple the propeller 35 with endless belt means 21 as soon as
propeller speed allows. The clutch 36 can then be
disconnected.
As the endless belt means 21 moves the foil members 22
take up "full-pitch" positions, against their tension spring
loads. Angular movement between the wheels of wheel pairs 23,
24 then takes place, which movement is accommodated as
explained above.
Figures 4 and 5 illustrate a modifica-tion provided with
wind force booster means 100, comprising a funnel-like
structure, (when viewed in plan), which causes the wind to
increase speed over the foil members 22.
Referring, next, to Figures 17 to 20, in an alternative
construction of the energy conversion apparatus, an endless
travelling belt comprises a strong plastic belt 101 of e.g.
KEVLAR (Registered Trade Mark). The belt 101 has a
multiplicity of thrust receiving portions 103 distributed at
intervals therealong. Each thrust receiving portion 103
comprises two closely spaced transverse rib portions, 107a,
; 107b, respectively, integral with the main body 105 of the belt
101 .
The belt 101 may support fixed pitch aerodynamic foils as
109, or it may support variable pitch foils as 111.
Fixed pitch foils, as 109, are bonded to side surfaces, as
113, of the belt 101 at right angles to the plane of the belt.
Variable pitch foils, as 111, are angularly displaceable about
resiliently flexible couplings constituting hinges the axes of
which are defined in the belt 101 at right angles to the plane
of the belt.
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In the arrangement of E'igures 17 to 20 variable pitch
foils 111 each carry a control vane 115 operable to vary the
incidence of the associated foil 111, in dependence upon wind
velocity. In Figures 17 and 18 the foil llla is shown in the
start-up position, and the foil lllb at maximum speed pi-tch.
Figures 19 and 20 contain a representation of the belt the
circulating parts employed in connection with the belt of
Figures 17 and 18. Here the circulating parts each comprise a
spider shaped wheel 117. There is a hub portion 119 from which
radiate the several legs 121 of the wheel. Each leg 121 has
first and second portions 123a, 123b, secured to the hub
portion 119 and each having a ~adial component of direction;
and a longitudinally extending portion 125, integral with the
outer extremities of the radial portions 123a, 123b, of a
length equal substantially to the length of the thrust
receiving portions 103 of the belt 101. The chordal distance
between the portions 125 is equal to the spacings between the
thrust receiving portions 103 of the belt 101.
In operation, the spider wheels 117 are driven by
progressive engagement of the portions 125 between the
transverse rib portions 107a, 107b.
The foils, as 109, may be curved in cross-section and may
have weakened portions 127 permitting the foils to snap fold in
damaging winds.
Some of the advantages of the present invention, compared
with the conventional windmill, are as follows:-
(a) An electrical generator can be disposed at the bottom
of the apparatus instead of having to be at the top, reducing
structural loading and simplifying maintenance.
3 (b) Area for area, a foil member 22 is several times as
efficient as a wlndmill blade.
(c) Being able to reduce the total foil surface to about
one sixth of that required for a conventional windmill blade
sweeping an equivalent area, reduces the total foil member
volume and mass to about a fourteenth. This mass is
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furthermore broken down into a greater number of foil
components so that -the sor-t of dynamic loading associa-ted with
a conventional windmill simply will not apply. Additional mass
reduction will result from being able to fabricate the much
lower stressed foil members with their non-catastrophic failure
character, out of the lighter materials.
(d) Foil member pitch control allows the invention to
operate in much higher wind speeds than can a conventional
windmill.
(e) Because of the much simpler aspect of straight rather
than circular deflectors, the invention is particularly suited
to wind enhancement techniques. By channelling the adjacent
wind outward behind the foil members, (using structure lO0), a
low-pressure area is created in the centre which speeds up the
air~low over the foil members. In its most efficient
arrangement, the means lO0 could be expected to increase power
in the same ratio that intersected area is increased.
Thus an increase in power can be obtained without
additional dynamic components. Also, because all wind speeds
are increased, the minimum effective wind speed instead of
being about seven m.p.h., might now be lowered to perhaps 5
m.p.h. enhanced to 7 m.p.h.
(f) Deploying the invention in a "wind farm" situation
would make better utilisation of the available acreage because
its vertical disposition would allow it to intersect a greater
cross-section of the wind, given the same spacing and the same
width of sweep as blade diameter for the conventional windmill.
The actual extent of the improvement would be determined by the
maximum height to width ratio to which the invention can be
economically built.
(g) The invention is expected to be more responsive to
wind direction changes without inducing high stresses due to
blade precession.
(h) The apparatus l could throw (i.e. lose) a foil member
22 wi-th no more effect than reduced power.
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(i) Pitch control is automatic partly through the spring
versus lift force arrangement.
(j) Expansion of an apparatus 1 is possible up to some
maximum height as determined by future tests.
(k) Start-up is automatic partly through the multi-
bladed, coarse pitch, start up rotor.
(1) The maintenance/safety platform 120 toge-ther with the
lighter nature of components in general will ease construction
and maintenance.
The invention is not confined to the conversion of wind
energy, or indeed air as a driving fluid. In a modified form,
it may be driven for example, by river water flow or by tidal
streams.
It may also be "reversed" by driving the endless belt
means whereby the apparatus may be used for propulsion.
Basically the belt loop requires a minimum of two
circulating points one of which is a drive. The drive unit can
be on or near the ground and the passive unit supported above
it from the side of a building for instance. The units can be
made to swivel, or not, depending on the local wind direction
constancy. But either way the basic simplicity and convenience
of such units would make them cheaper than a conventional
windmill to the extent they would be worth placing in less than
optimum settings. Buildings, bridges, water towers, radio
masts, lamp standards, power pylons, cooling towers and other
tall structures can be utilized.
Because the windbelt is so passive it would be much more
acceptable for use on the windy tops and corners of city
buildings for not only have vibrations been minimized but
3o personal danger from a separated windbelt foil is miniscule to
that from a separated windmill blade. New highrise buildings
can be designed to incorporate large areas of windbelts, giving
them a distinct economic advantage as well as an architectural
enhancement.
; 35 One obvious market for the windbelt is wind farms. This
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is because the ver-tical form of windbelts enables them to
intersect more vertical area from the available land acreage
-~han do conventional windmills, thereby increasing power per
acre. Here the conventional windmill -tower would most likely
be replaced with a more cost effective means of deployment such
~s a trestle in which a n~ber of windbelts are strung side by
side beneath a continuous beam. The windbelts can also be
tilted to be normal to the local wind which on a mountain is
rarely horizontal.
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