Note: Descriptions are shown in the official language in which they were submitted.
CA 02587354 2007-05-04
File number: 11174 - 003
Revision: as filed
Date: 2007-05-04
Title of the Invention
[0001] Power Transmission System for a Wind Turbine
Cross-Reference to Related Applications
[0002] There is no cross-reference to related applications.
Field of the Invention
[0003] The present invention generally relates to electric power generating
systems, and
more particularly, to wind powered generating systems.
Background of the Invention
[0004] The goal of a wind turbine power transmission system is to converts the
kinetic
energy of wind to drive a generator, resulting in the conversion of the wind
force to
electrical energy, or other mechanical devices, directly using the kinetic
energy.
Conventionally, for vertical axis wind turbines, a gear assembly, or a
planetary gear
system, is interposed between a rotor and a generator such that the input
shaft of the gear
assembly is connected to the rotating shaft of the wind turbine rotor, and by
adjusting the
gear ratio of this gear assembly, the rotational speed of the output shaft of
the gear
assembly which is connected to the rotating shaft of the generator is
controlled to be
within a predetermined range of rotational speeds. A main disadvantage of a
gear
assembly is the high maintenance time and cost because of the quantity of
gears needed
to modify the gear ratio, which increases the probability of failure.
Objects of the Invention
[0005] A first object of the present invention is to provide a simpler power
transmission
system for a wind turbine.
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File number: 11174 - 003
Revision: as filed
Date: 2007-05-04
[0006] A further object of the present invention is to provide a power
transmission
system allowing the installation of a plurality of independent power
generation sub-
systems on the same wind turbine rotor.
[0007] Another object of the present invention is to provide a power
transmission system
allowing the installation of more than one independent generator on the same
wind
turbine rotor.
[0008] A still further object of the present invention is to provide a power
transmission
system which can be disconnected from the wind turbine rotor without stopping
the wind
turbine.
[0009] Other and further objects and advantages of the present invention will
be obvious
upon an understanding of the illustrative embodiments about to be described or
will be
indicated in the appended claims, and various advantages not referred to
herein will occur
to one skilled in the art upon employment of the invention in practice.
Summary of the Invention
[0010] The present invention provides a system for transmitting torque from a
wind
turbine rotor having a base to a power generator. The system comprises a
driving surface
attached to said base and a means drivingly connecting the driving surface to
the
generator.
[0011] The present invention is described for a wind turbine rotor having a
plurality of
blades disposed between two circular plates, a top plate and a base plate. The
blades are
preferably located at the circumference of the plates. The torque is
transmitted to the
generator via a drive system that is driven by the wind turbine rotor through
a driving
surface. In the present document, the driving surface refers to the surface on
which a first
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CA 02587354 2007-05-04
File number: 11174 - 003
Revision: as filed
Date: 2007-05-04
gear or a first wheel is in contact with and from which the torque is
transmitted from the
wind turbine rotor to a generator.
[0012] A main advantage of the system described herein is that the
configuration needs
fewer parts compared to conventional power transmission systems that use a
planetary
gear system. Furthermore, a plurality of sub-systems may be connected to the
same wind
turbine rotor. This invention allows each sub-system generator system to be
disengaged
independently. Finally, the fabrication costs are significantly reduced
because the system
is conceived to be tolerant to minor construction faults, misalignments, and
other faults
thus reducing the precision required during the manufacturing process.
[0013] In the present invention, a first friction wheel, a first gear, a first
ribbed wheel or
other similar known means, is in contact with the driving surface and is
driven by the
driving surface. Typically, the first wheel is drivingly connected to the
generator by an
axle but it may be any other known means which is able to transmit a torque.
The driving
surface is located on a surface of the base plate of the wind turbine rotor
(top edge, side
edge or underside) or on a surface of a ridge which is itself attached to the
wind turbine
rotor. The driving surface may be horizontal or vertical.
[0014] In another embodiment, the torque may be transmitted to the generator
through a
second axle. The second axle is driven by a belt (or any other known means to
transmit a
torque) connected to the first axle. The belt may be connected to both axles
or through a
second and a third ribbed wheels (or a friction wheel, a gear or other similar
known
means), attached to the first and second axle, respectively. Obviously, the
belt may
comprise tooth to engage gears or ribbed wheels.
[0015] Means are preferably used to maintain the first wheel, gear or other
similar means
biased against the driving surface. In all cases, a disengaging means is
preferably used to
selectively disengage the driving means.
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File number: 11174 - 003
Revision: as filed
Date: 2007-05-04
[0016] In a first embodiment, the driving surface is the surface under the
base plate,
sometimes referred to as the outside surface. In a second embodiment, an
annular ridge
may be attached under the base plate of the wind turbine and the horizontal or
vertical
(internal or external) surfaces of the annular ridge may be used as the
driving surface. As
stated above, the driving means is preferably biased towards the driving
surface. To
disengage the driving means, the bias is released and the driving means is
displaced so as
to no longer be in contact with the driving surface. It is to be noted that it
is possible to
have electronically disengaging means (electronically deactivate the
generator) instead of
mechanical disengaging means.
[0017] The first friction wheel, the gear or the ribbed wheel (also referred
as the "driving
means") is installed at a radius R from the center of the wind turbine. The
radius R is
chosen in regard of the appropriate ratio R/r for the generator(s) installed
with the wind
turbine. The multiplier ratio of the present invention is R/r, where R is the
radius of the
position of the driving means on the driving surface from the center of the
base plate, and
r is the radius of the driving means.
[0018] Because R is preferably large in relation to r, it would be very costly
to machine a
driving surface having little or neither no deformation nor construction
fault. Such
deformation may cause the driving means to momentarily cease to be in driving
contact
with the driving surface therefore causing an interruption of power.
[0019] Biasing means are used to allow the driving means to follow the
imperfections
and remain in driving contact with the driving surface.
[0020] The contact between the driving means and the driving surface must be
such that
the driving surface will transfer the torque generated by the wind turbine to
the driving
means. High friction surfaces, a gear and a rack or a ribbed wheel and a
ribbed ring are
preferably used.
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CA 02587354 2007-05-04
File number: 11174 - 003
Revision: as filed
Date: 2007-05-04
[0021] The features of the present invention which are believed to be novel
are set forth
with particularity in the appended claims.
Brief Description of the Drawings
[0022] The above and other objects, features and advantages of the invention
will
become more readily apparent from the following description, reference being
made to
the accompanying drawings in which:
[0023] Figures la is a cross-section side view of a first embodiment of the
present
invention.
[0024] Figure lb is a perspective view showing a larger view of a wheel and a
support of
Figure la.
[0025] Figure lc is a perspective view showing another embodiment of a support
for the
wheel.
[0026] Figure 2a is a cross-section side view showing the base of a wind
turbine rotor
with a second embodiment of the present invention.
[0027] Figure 2b is a magnified area of the cross-section view of the Figure
2a.
[0028] Figure 2c an elevation view of the Figure 2b.
[0029] Figure 3a and 3b are a front view and an elevation view of another
embodiment of
the present invention.
[0030] Figure 4 is a schematic view showing a possible configuration for
drivingly
connecting a plurality of sub-system generators on the same wind turbine
rotor.
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File number: 11174 - 003
Revision: as filed
Date: 2007-05-04
[0031] Figure 5 is perspective view showing an embodiment of the power
transmission
system of the present invention as installed on a wind turbine.
[0032] Figure 6 is a side view of an embodiment of the power transmission
system.
[0033] Figures 7a and 7b are a side view and a top perspective view of the
power
transmission system.
Detailed Description of the Preferred Embodiments
[0034] A novel power transmission system for a wind turbine will be described
hereinafter. Although the invention is described in terms of specific
illustrative
embodiment(s), it is to be understood that the embodiment(s) described herein
are by way
of example only and that the scope of the invention is not intended to be
limited thereby.
[0035] A first embodiment is shown in Figures la, lb and lc, in which the
underneath
surface 165 (also referred as the driving surface) of the base plate 160 of a
wind turbine
rotor (not shown) is used to transmit the torque generated by the rotational
movement of
the wind turbine rotor to the generators 115 and 130. As shown in Figure la,
the first
friction wheels 105 and 120 are in driving contact with the driving surface
165 and with
the cylindrical supports 140 and 145. When the base plate 160 rotates under
the action of
the wind, the first friction wheels 105 and 120 rotate and cause axles 110 and
125 to turn
such that torque is transmitted to the generators 115 and 130. It is to be
noted that the
number of generators may vary as is necessary or desired. Figure lb shows a
more
detailed view of the first friction wheel 120 and support 145 assembly of
Figure la. The
support 145 is driven by the first friction wheel 120 and it rotates about a
horizontal axis
of the structure 180. The supports 140 and 145 maintain the vertical position
of the wheel
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CA 02587354 2007-05-04
File number: 11174 - 003
Revision: as filed
Date: 2007-05-04
and thus maintain the contact between the driving surface 165 and the first
friction
wheels 105 and 120. The first friction wheels 105 and 120 are positioned at a
distance R
from the center of the base plate and have a radius r. The multiplier ratio is
thus R/r. It is
possible to install as many generators as needed, the only limitation being
the space
available under the wind turbine rotor, the space needed between each power
generation
system and the torque generated by the wind turbine rotor. It is to be noted
that the
driving surface is not necessarily the underneath surface or the base plate,
it may be an
intermediary surface which rotates with the wind turbine rotor.
[0037] Figure lc shows another embodiment to support the first friction wheel
120. A
first bearing 190 and a second bearing 195 are mounted on the axle 125 and are
all fixed
on the support structure 185. The position of the support structure is
controlled by the
disengaging means 175, which may comprise, for example, a spring, a pneumatic
drive, a
worm drive or any other actuator. Thus the first friction wheel 120 may be
pressed
against the base plate 160 and may be disengaged when the support structure
185 is
pulled down by the disengaging means 175. It is to be noted that even if the
support
structure 185 is shown with two axel supports, it is possible to have only one
or more
than two such supports.
[0038] Figure 2a shows a second embodiment of the present invention comprising
a base
plate 260 of a wind turbine rotor (not shown) and an annular ridge 235 is
fixed under the
base plate 260. A rack or ribbed ring 230 having a radius R is fixed on the
vertical
internal surface, or driving surface, of the annular ridge 235. The first gear
or the first
ribbed wheel 210 having a radius r is shown on the magnified area of Figure 2b
and in
Figure 2c. The first gear 210 is biased with the disengaging means 255 towards
the rack
230 by a spring 250 or other known means to maintain the first gear 210 in
engagement
with the rack 230, as shown in Figure 2c. The bias is applied to the first
gear 210 through
the elongated members 240 and 245 which also retain the biasing wheel 215. As
for the
first embodiment, the ribbed ring 230 preferably has the highest radius R to
increase the
multiplier ratio R/r. Like in the previous embodiment, it is possible to
install as many
generators as needed, the only limitation being the space available under the
wind turbine
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File number: 11174 - 003
Revision: as filed
Date: 2007-05-04
rotor, the space needed between each power generation system and the available
torque.
In both embodiments, even if one has been described with a wheel and the other
with a
gear, the wheel and the gear may be interchanged with proper modifications.
[0039] Figure 3 shows another embodiment of the present invention. There is
the wheel
315 and the gear 310, and between them the space 350 where the annular ridge
and the
rack are normally located. A bias is applied by the disengaging means 355 with
a sliding
part 330 which is comprised in the guiding part 335. The sliding part 330 is
biased
towards the rack by a spring, a pneumatic drive, a worm drive or any other
known means.
The bias maintains the engagement between the rack and the gear or ribbed ring
310. It
also allows the disengagement of the wheel or ribbed ring 310 from the rack
with no need
to stop the wind turbine rotor. To control the motion of the sliding part 330,
a controlled
actuator may be used instead of a spring, such as a pneumatic drive, a worm
drive, or any
other actuator. Thus, when the gear or the ribbed ring 330 is disengaged, the
wheel 315
continues to rotate with the annular portion, but the generator is no longer
connected to
the wind turbine rotor.
[0040] Figure 4 is a schematic view showing the possibility of installing more
than one
generation sub-system. The circle 490 represents the driving surface of a base
plate
similar to the one shown as element 165 in Figure la and each generation sub-
system
410, 412, 414 and 416 comprise a generator (415, 425, 435, 445), a wheel (412,
422, 432,
442) and a shaft (schematically shown in Figure 4 as 417, 427, 437, 447). In
this
embodiment, four generation sub-systems are shown but it is possible to
install more or
less than four generation sub-systems.
[0041] In Figure 5, the power transmission system is shown as installed on a
wind
turbine. The surface 540 is the underside of the base plate of a wind turbine
on which is
attached an annular ridge 510. The annular ridge 510 is schematically
represented by a
planar surface in Figure 5. In reality, the annular ridge would be thicker and
it would
have a ribbed surface to drive the ribbed wheel 520.
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File number: 11174 - 003
Revision: as filed
Date: 2007-05-04
[0042] In the embodiment of the Figure 6, the rotation is transmitted to the
generator (not
shown) with a axle 660. The axle 660 is driven by the third ribbed wheel 650
which is in
turn driven by a belt (not shown). The belt is driven by the second ribbed
wheel 640
which is attached to the same axle than the first ribbed wheel 620 which is
driven by the
driving surface (not shown). The driving surface is to be placed between the
ribbed wheel
620 and the biasing wheel 630.
[0043] In Figures 7a and 7b, it is possible to see in another perspective the
power
transmission system of the Figures 5 and 6. The driving surface (not shown) is
to be
placed between the ribbed wheel 720 and the biasing wheel 730. The generator
770 is
driven by the axle 760.
[0044] While illustrative and presently preferred embodiment(s) of the
invention have
been described in detail hereinabove, it is to be understood that the
inventive concepts
may be otherwise variously embodied and employed and that the appended claims
are
intended to be construed to include such variations except insofar as limited
by the prior
art.
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