U.S. patent application number 12/698601 was filed with the patent office on 2011-03-17 for dynamic fin comprising coupled fin sections.
Invention is credited to Klaas Boudewijn VAN GELDER.
Application Number | 20110061579 12/698601 |
Document ID | / |
Family ID | 41076830 |
Filed Date | 2011-03-17 |
United States Patent
Application |
20110061579 |
Kind Code |
A1 |
VAN GELDER; Klaas
Boudewijn |
March 17, 2011 |
DYNAMIC FIN COMPRISING COUPLED FIN SECTIONS
Abstract
A dynamic or aerodynamic fin comprising at least two parallel
arranged fin sections. At least one fin section comprises a
rotational axis for installing the fin section by a rotation shaft.
An end stop is provided for stopping the rotational movement of the
fin section to define an extreme position. In the extreme position
the fin sections provide a substantially cambered shape to the fin.
The dynamic fin is improved in that it comprises a pair of coupling
elements. A first fin section is coupled to a second adjacent fin
section by a pair of a first and second coupling elements. The
first coupling element is complementary to the second coupling
element. The first coupling element is part of, preferably
integral, with the first fin section and the second coupling
element is part of, preferably integral, with the second fin
section.
Inventors: |
VAN GELDER; Klaas Boudewijn;
(Rijswijk, NL) |
Family ID: |
41076830 |
Appl. No.: |
12/698601 |
Filed: |
March 10, 2010 |
Current U.S.
Class: |
114/140 ;
114/151; 416/130; 440/50 |
Current CPC
Class: |
B63B 32/60 20200201;
F04D 29/323 20130101; B63H 25/38 20130101; B64C 9/02 20130101; B64C
5/06 20130101; F01D 5/148 20130101; Y02T 50/673 20130101; B64C 5/10
20130101; Y02E 10/727 20130101; B62D 35/007 20130101; Y02T 10/82
20130101; Y02T 50/60 20130101; B63B 1/28 20130101; F01D 5/147
20130101; B64C 3/48 20130101; B63H 1/26 20130101 |
Class at
Publication: |
114/140 ;
416/130; 114/151; 440/50 |
International
Class: |
F01D 5/12 20060101
F01D005/12; B63B 3/38 20060101 B63B003/38; B63H 25/38 20060101
B63H025/38; B63H 25/46 20060101 B63H025/46; B63H 3/00 20060101
B63H003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 3, 2009 |
NL |
2002486 |
Claims
1. A dynamic fin comprising: at least two parallel arranged fin
sections; an orthogonal coordinate system including a first, a
second, and a third axis defined by the at least two parallel
arranged fin sections; the at least two parallel arranged fin
sections extend in a direction of the first axis wherein at least
one of the fin sections includes a rotational axis for installing
the at least one fin section by a rotational shaft and the
rotational axis extends in a direction of the at least one fin
section and enables a rotational movement of the at least one fin
section; the dynamic fin further comprising at least one end stop
for stopping the rotational movement of the at least one fin
section to define an extreme position, in which extreme position
the at least two parallel arranged fin sections provide a
substantially cantilevered shape to the dynamic fin; and wherein a
first of the at least two fin sections is in rotation, coupled to
an adjacent second of the least two fin sections by a first
coupling element and a complementary second coupling element, and
the first coupling element is part of the first fin section and the
second coupling element is part of the second fin section.
2. The dynamic fin according to claim 1, wherein the first coupling
element is formed by a groove which extends in a longitudinal
direction along an edge of the first fin section.
3. The dynamic fin according to claim 1, wherein the first coupling
element extends over substantially the whole length of the first
fin section.
4. The dynamic fin according to claim 1, wherein the second
coupling element is formed by an outer tongue which is
complementary shaped with respect to the first coupling element and
extends in a longitudinal direction along an edge of the at least
one fin section.
5. The dynamic fin according to claim 1, wherein one or more of the
first and second coupling elements comprise a symmetrical shape in
cross section.
6. The dynamic fin according to claim 1, wherein one or more of the
first and second coupling elements comprise, in the first
direction, a constant shape in a cross section.
7. The dynamic fin according to claim 6, wherein the at least one
fin section comprises a base fin and tip, wherein the constant
shape becomes smaller in a direction away from the base.
8. The dynamic fin according to claim 1, wherein the first coupling
element encloses the second coupling element for mounting the at
least two parallel arranged fin sections by an axially sliding
movement of the at least two parallel arranged fin sections
relative to each other.
9. The dynamic fin according to claim 8, wherein a stopper is
provided for stopping the axially sliding movement.
10. The dynamic fin according to claim 2, wherein the groove of the
first coupling element comprises, in a cross section, an inner
rounded part for receiving the second coupling element, which
second coupling element comprises an outer rounded part in a
transversal cross section.
11. The dynamic fin according to claim 1, wherein the first
coupling element comprises a groove having a receiving opening
which includes an inner protruding portion and wherein the second
coupling element comprises a tongue having an outer protruding
portion for locking the second fin section to the first fin section
in a direction away from the opening of the groove.
12. The dynamic fin according to claim 11, wherein at the least one
end stop is formed by the inner protruding portion.
13. The dynamic fin according to claim 1, wherein the at least two
parallel arranged fin sections are rotatable from one extreme
position to another extreme position under a substantially constant
resistance.
14. A watercraft comprising a dynamic fin according to claim 1.
15. The dynamic fin according to claim 14, wherein the dynamic fin
is configured as a keel or a rudder.
16. The dynamic fin according to claim 14, wherein the dynamic fin
is configured as a tunnel thruster.
17. The dynamic fin according to claim 14, wherein the dynamic fin
is configured as a propulsion element.
18. The dynamic fin according to claim 1, wherein the dynamic fin
is configured as a vane of a turbine.
19. The dynamic fin according to claim 1, wherein the dynamic fin
is configured as a propulsion element in a motor.
20. The dynamic fin according to claim 1, wherein the dynamic fin
is configured as a spoiler.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a dynamic fin which
comprises at least two parallel arranged fin sections. An
orthogonal coordinate system including a first, second and third
axis can be defined, wherein the fin sections extend in a direction
of the first axis. Generally, this first direction is also regarded
as the longitudinal direction. At least one fin section comprises a
rotational axis for installing the fin section by a rotation shaft
in for example a mounting box. The rotational axis extends in the
direction of the fin section and enables a rotational movement of
the fin section. An end stop is provided for stopping the
rotational movement of the fin section to define an extreme
position. In the extreme position the fin sections provide a
substantially cambered shape to the fin. This cambered shape
improves the hydro- or aerodynamic properties of the fin. In the
other extreme position the fin may foam a mirrored cambered shape
in comparison with the cambered shape in the first extreme
position.
[0002] Such a dynamic, in particular dynamic fin is known from the
American patent U.S. Pat. No. 5,181,678. In FIG. 14 of this
American patent, a fin is shown, which is build from multiple rigid
fin sections. The fin sections are joined together by means of
hinges. Two adjacent fin sections are provided with holes which
form a first part of the hinge. The holes of two adjacent fin
sections can be aligned, were after an additional pen can be
mounted to complete the hinge.
[0003] Such a pin-hole hinge construction between adjacent fin
sections brings some problems. A first problem relates to the
manufacturing of the fin sections. To manufacture the fin section,
some extra machining operations like milling and drilling are
necessary to manufacture the holes in the fin sections. Especially,
in an embodiment of the dynamic fin for a surfboard, wherein the
pin-hole hinge has to be very small, it may be a major problem to
manufacture the hinge because of a limited available space for
machining tools to access the fin. Generally, the fin sections are
made from a basic shape which is manufactured by machining of a
prefab plate material, like epoxy plate which may be reinforced by
glass fibres e.g. G10 or moulding of a laminated prepreg material,
like epoxy including glass-fibres or carbon-fibres or injection
moulding of a polymer material.
[0004] Further operations are necessary, to provide the fin with
the pin-hole hinge construction. The construction of the pin-hole
is rather detailed which complicates the manufacturing and the
assembling of the components. Those further operations increase
production efforts and costs.
[0005] Another problem of the known hinge-construction is that it
is susceptible for contamination. An environment with dirt, sand or
salt may cause a failure of the pin-hole hinge construction.
[0006] It is an object of the present invention to overcome at
least partially one or more of the above-mentioned drawbacks and/or
to provide a useable alternative. In particular, the invention aims
to provide a dynamic fin which is more simple to manufacture and/or
to assemble and thus more cost effective and more durable.
[0007] This objective is achieved by a dynamic fin as defined in
claim 1.
[0008] A dynamic fin according to the invention comprises at least
two parallel arranged fin sections. An orthogonal coordinate system
including a first, second and third axis can be defined, wherein
the fin sections extend in a direction of the first axis.
Generally, this first direction is also regarded as the
longitudinal direction, wherein the fin sections extend away from a
base which may define a base plane including the second and third
axis. The base plane may be flat. The third axis is generally
regarded as an outward direction which extends away from the
substantially smooth and flat outer surfaces of the fin. At least
one fin section comprises a rotational axis for installing the fin
section by a rotation shaft to for example a mounting box. The
rotational axis extends in the direction of the fin section and
enables a rotational movement of the fin section. An end stop is
provided for stopping the rotational movement of the fin section to
define an extreme position. In the extreme position the fin
sections provide a substantially cambered shape to the fin. This
cambered shape improves the hydro- or aerodynamic properties of the
fin.
[0009] The dynamic fin according to the invention is improved in
that it comprises a pair of coupling elements. According to the
invention a first fin section is coupled to a second adjacent fin
section by a pair of a first and second coupling element. The first
coupling element is complementary to the second coupling element.
The coupling elements provide a coupling of adjacent fin sections
in a direction of the third axis. The third direction is a
direction outwards the outer surface of fin. Herewith, the second
adjacent fin section will follow a rotational movement of the first
fin section in the third direction around the first axis. The
relative rotational movement of the fin sections makes the fin
dynamic. If the first fin section rotates clockwise, the second
coupled fin section will rotate counter-clockwise.
[0010] The first coupling element is part of, preferably integral,
with the first fin section and the second coupling element is part
of, preferably integral, with the second fin section. Preferably,
the coupling elements are made of the same material as the fin
sections. Herewith, advantageously, the coupling elements may be
integrally manufactured to the fin sections, by for example
moulding or machining. The insight that only a coupling in the
direction of the third axis, which is generally the transversal
direction, between two adjacent fin sections is necessary, instead
of a hinge with a pin and a hole gives the advantage that the
dynamic fin may be manufactured by just a few operations. No
complex shapes, like slotted holes with accurate tolerances need to
be made. No extra components like pins are needed to assemble the
dynamic fin. The complete dynamic fin may be easier to assemble as
a result of the more simple connection between the fin
sections.
[0011] A further advantage is that instead of a permanent hinge
construction, the coupling may be released manually. This may be
advantageous for example for cleaning the fin. It may even be
possible to release the coupling without a hand tool. Especially in
a rough environment with mud, sand and salt this may be
advantageous. The fin according to the invention may be easy
disassembled to clean the fin sections. Cleaning the fin sections
may improve the lifetime of the fin. Preferably, the coupling
elements are rigid which allows well-defined extreme positions and
may reduce a risk of damages.
[0012] In an embodiment of the dynamic fin according to the
invention, the fin sections are rotatable from one extreme position
to another extreme position under a substantially constant
resistance. No springs or elastic materials are provided which
would substantially increase the resistance from a nominal position
to an extreme position. The substantially constant resistance may
increase the effectiveness of the dynamic fin. This substantially
constant resistance allows the fin sections to change quickly from
one camber into another. The fin sections may get already into one
of the extreme positions, while the dynamic forces on the fin are
still relative small. The degree of rotation of the fin sections
may be independent of the amount of the hydro- or aerodynamic force
on the fin. Herewith, the fin provides a substantially increase of
effectiveness, which may be already available at a low speed.
[0013] In a particular embodiment of the dynamic fin according to
the invention, the first coupling element is formed by a groove
which extends in the first direction, which is generally the
longitudinal direction, along an edge of the first fin section.
Preferably, the groove extends over substantially the whole length
over the first fin section. An adjacent fin section having a
complementary coupling element may be coupled to the first fin
section by inserting the second coupling element into the groove.
It may be advantageous when the coupling elements extend over
substantially the whole length of the fin sections, because this
may improve an alignment of the fin sections and may provide a
strong coupling which may withstand a bigger hydro- or aerodynamic
load.
[0014] The groove of the first coupling element defines a receiving
opening into which the complementary coupling element of the second
fin section can be inserted, e.g. by sliding of the fin sections in
the longitudinal direction. Preferably, the second coupling element
may be formed by an outer tongue which is complementary shaped with
respect to the groove of the first coupling element. The tongue may
extend in a longitudinal direction along an edge of the fin
section. The complementary groove and tongue may be positioned onto
a section surface of the adjacent fin sections. The section
surfaces may be brought opposite to each other to assemble the
tongue into the groove, e.g. by sliding the fin sections relative
to each other in the longitudinal direction.
[0015] Preferably, the cross section of one or both coupling
elements is symmetrical to allow a symmetrical rotational movement
of adjacent fin sections from a nominal position. The cross section
may have an axis of symmetry which extends in a direction of the
second axis of the orthogonal coordinate system.
[0016] In a preferred embodiment of the dynamic fin according to
the invention, the first and/or the second coupling element
comprise in the longitudinal direction a constant shape in a cross
section, in particular parallel to a plane in the second and third
direction. This constant shape may be advantageous because it may
provide an opportunity to manufacture the fin section including the
coupling element by machining or moulding. The constant shape
allows a removal of the fin section including the coupling element
out of a mould in just one direction. Advantageously, due to the
constant shape, the mould may remain of a simple design.
[0017] In a further preferred embodiment the constant shape becomes
smaller in dimensions in a direction from a base or foot of the fin
to a tip of the fin section. The smaller dimensions to the tip of
the fin section may provide an improved removal from the mould.
Additionally, a further advantage occurs during use of the dynamic
fin. The decreasing dimensions of the constant shape of the
coupling element provide a unique way to assemble two fin sections.
During assembly of the two fin sections the corresponding coupling
elements may slide along each other in the longitudinal direction
until the coupling elements engage to each other. Herewith, the
dimensions of the shape of the coupling elements in the
longitudinal direction define the positioning of the fin sections.
The simple way of sliding the coupling elements along each other
provides advantageously an easy way to mount or demount the dynamic
fin. This may be useful, for example to clean or otherwise service
or inspect the dynamic fin. Herewith, the fin sections may be
easily manually releasable without any further tools to remove
bolts, pins or the like. The simple and smart releasing of the fin
sections may be robust which may decrease the risks of damaging the
fin during mounting and demounting.
[0018] In a further embodiment of the dynamic fin according to the
invention the groove of the first coupling element comprises in a
cross section, parallel to the plane defined by the second and
third axis, an inner rounded, in particular circular part for
receiving a second coupling element which comprises an outer
rounded, in particular circular part in a transversal cross
section. The circular cross sections define rounded outer surfaces
which may improve the rotational movement of the fin sections with
respect to each other. Advantageously, adjacent fin sections may
better fit to each other to prevent leakages of fluid through the
coupling elements. This may further improve the dynamic properties
of the fin.
[0019] In a further embodiment of the dynamic fin according to the
invention the first coupling element comprises a groove having a
receiving opening which includes an inner protruding portion,
wherein the second coupling element comprises a tongue having an
outer protruding portion. The inner and outer protruding portions
may engage to each other in an assembled dynamic fin, wherein the
engagement of the protruding portions provide a locking of the
second fin section to the first fin section in a direction away
from the opening of the groove, which is in the direction of the
second axis. Preferably, at least one protrusion extends over
substantially the whole length of the coupling element. The locking
further improves a sealing between the adjacent fin sections. A
clearance between the fin sections may be closed automatically at
the high-pressure side ("concave" side) of the fin. Generally, a
high pressure occurs at the concave side of the fin. The improved
sealing may prevent a leakage via the clearance of fluid from the
high pressure side, so called lower camber side, to the low
pressure side, the so called upper camber side (convex or lee side)
of the fin. Herewith, the effectiveness of the fin may be further
increased. The protruding portions may further improve the dynamic
fin to withstand bigger hydro- or aerodynamic forces in a direction
along the fin. Advantageously, the protruding portions may make the
fin stronger.
[0020] In a further embodiment according to the invention the inner
protruding portion may be formed as an end stop. Herewith the end
stop is internal and integral instead of an additional component
like a pin, with the first coupling element, which advantageously
may result in a simpler manufacturing of the fin. The internal
positioned end stop may make the fin less susceptible for damages
or contaminations from outside the fin.
[0021] In an embodiment the dynamic fin according to the invention
comprises a locking element. The locking element may provide for
locking a rotation of the fin sections. Preferably, the locking
element may be used for locking at least one extreme position of
the fin sections. The locking element may be adjustable for
changing an extreme position. In a particular embodiment the
locking element may be applied for locking a nominal or mid
position, wherein the fin is symmetrical over an axis extending in
the second direction.
[0022] Further the invention relates to a watercraft, e.g. sailing
ship or surfboard, provided with a dynamic fin according to the
invention. The fin may be a keel, a rudder or a tunnel thruster.
Generally, the fin according to the invention may be useful for
applications, wherein the fin is susceptible to a interchanging
positive or negative dynamic load. The fin according to the
invention may typically replace conventional symmetrical fins. The
fin according to the invention may provide the same effectiveness
for opposite hydrodynamic loads.
[0023] Other aspects of the present disclosure will become apparent
from the following descriptions when considered in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] A further elucidation of the invention will be given by the
appended drawings which provide a practical embodiment of the
invention, but may not be considered in a limiting sense,
wherein:
[0025] FIG. 1 shows a view in perspective of a dynamic fin
according to the invention;
[0026] FIG. 2 shows a view in more detail of an upper region of the
dynamic fin of FIG. 1;
[0027] FIG. 3 shows a cross-sectional view of a dynamic fin in a
nominal and two extreme positions;
[0028] FIG. 4 shows a simplified cross-sectional view of a dynamic
fin in a nominal and an extreme position; and
[0029] FIG. 5 shows the cross-section of FIG. 3 in more detail,
wherein a pair of coupling elements is shown.
DETAILED DESCRIPTION
[0030] FIG. 1 shows a dynamic fin according to the invention. The
dynamic fin is arranged as a fin which is suitable to serve as a
fin for a surf board. The fin has outer side surfaces, a base and a
tip. The outer side surfaces are substantially smooth. The dynamic
fin comprises two parallelly arranged fin sections. For the
application as a smart fin in a surfboard, the fin sections may be
made from a plastic material including eventually reinforcing
fibres. The fin sections are made sufficient rigid to withstand
dynamic loads. The dynamic fin is formed by a first fin section
which has a rounded front edge which defines a leading edge and
forms a front side of the dynamic fin. The fin has a sharp edge at
a tail which defines a trailing edge. During use a fluid may flow
backwards along the fin from the rounded front side to the tail.
The dynamic fin has a cross-section which is shaped like an airfoil
having a chord which defines an upper chamber and a lower
chamber.
[0031] FIG. 2 shows in a view in more detail an upper region of the
dynamic fin as shown in FIG. 1. The dynamic fin may be considered
as orientated in an orthogonal coordinate system. The coordinate
system comprises a first, second and third axis. The fin sections
extend in a longitudinal direction along the first axis. The
dynamic fin may be installed to a watercraft, in particular a
surfboard, by two rotation shafts 3. The rotation shaft 3 is
connected to the fin section and extends in a direction parallel to
the first axis. The rotation shaft may be heavily loaded and is
therefore made of a strong material, like stainless steel. The
rotation shaft 3 may be glued or clamped to the fin section 1, 2.
The rotation shaft extends away from a mounting surface in a
direction parallel to the first axis. The rotation shaft 3 is
cylindrical at a bottom region. The cylindrical part extends away
from the mounting surface and provides an accurate positioning of
the fin section in a mounting box. As shown in FIG. 1 the rotation
shaft has further a conical part for centring the rotational shaft
in a mounting box, e.g. a Tuttle box. The geometry of the
rotational shaft allows a user to quickly mount or demount the
dynamic fin according to the invention.
[0032] Further, as shown in FIG. 1, the dynamic fin comprises a
pair of coupling elements. The coupling elements comprise a first
coupling element 4 and a second coupling element 5. The first
coupling element 4 is formed as a groove which extends in the
longitudinal direction along an edge of the first fin section. The
second coupling element 5 is complementary shaped to the first
coupling element 4. As shown in FIG. 1, the second coupling element
5 is formed by an outer tongue which is complementary shaped with
respect to the first coupling element and extends in the
longitudinal direction along a straight edge of the fin section.
The coupling elements extend over substantially the whole length of
the edge of the fin section. This may improve the dynamic
properties of the fin, because occurring dynamic loads may be
better distributed over adjacent fin sections.
[0033] The outer tongue has a constant shape which is symmetrical
in cross-section. The constant shape of the coupling elements
becomes smaller in a direction away from the mounting surface.
Herewith, the two fin sections 1, 2 can be mounted to each other by
sliding the two fin sections relative to each other in a direction
parallel to the first axis. The connection of the fin sections is
unambiguous and easy to make by the user. A predefined amount of
play has to remain between the coupling elements to allow a certain
rotational movement of the fin sections relative to each other. The
length dimension of the groove and tongue is designed such that
after assembling of the fin sections, this predefined amount of
play is assured. In a possible embodiment, the groove in the first
fin section may have an end face for stopping the sliding movement
of the second fin section. The tongue 5 extends from the base of
the fin, the mounting surface 6, in a longitudinal direction
towards the tip and ends with a cross cut. After assembly the cross
cut of the tongue 5 may be adjoined positioned to the end face of
the groove 4. Herewith the cross cut of the tongue functions as a
stopper to stop the sliding movement of the fin sections when they
are assembled. In another embodiment, adjacent fin sections may be
axially positioned by an external stopper, wherein the end face of
the groove and the cross cut of the tongue are spaced apart over
e.g. 2 mm. The external stopper, which aligns for instance mounting
surfaces of adjacent fin sections, may simplify the manufacturing
of the fin.
[0034] FIG. 3 shows a cross-sectional top view of the dynamic fin.
The dynamic fin is shown in three different positions. The first
position I shows a nominal position, wherein the fin sections are
aligned to each other. The resulting cross section is symmetrical
in this position. The symmetrical cross section has an axis of
symmetry in a direction of the second axis.
[0035] The back positioned fin section may be rotated around an
axis which is parallel to the first axis of the coordinate system.
The position II is an extreme position of the dynamic fin. The
cross-section has a cambered, substantially air foil shape. In
position II the front positioned fin section is rotated clock wise,
wherein the back positioned fin section is rotated in a counter
clockwise direction. An end stop which is shown in more detail in
FIGS. 4 and 5 is provided to limit the rotational movement of the
fin sections to define the extreme positions II, III. The shown
extreme positions II, III in FIG. 3 are in mirror symmetry.
Herewith, the dynamic fin may obtain similar cambered shapes in its
two extreme positions, which makes the dynamic fin according to the
invention perfectly suitable to serve as a fin for a surfboard or
sail ship. The dynamic fin according to the invention provides the
same advantageous dynamic effects in opposite directions. In other
words, the dynamic fin may generate an improved counter pressure to
the tendency of the surfboard or sail ship to roll in both sailing
directions perpendicular to the wind direction.
[0036] FIGS. 4 and 5 show in more detail a view of the pair of
coupling elements 4, 5. FIGS. 4 and 5 shows the same positions I,
II as shown in FIG. 3. Bold arrows indicate the flow of fluid along
the outer surfaces of the dynamic fin. In position II a pressure
difference will occur between the opposite outer surfaces. This
pressure difference is, as is well known, responsible for the
dynamic properties. It is important to prevent disturbances of the
fluid flow. At the high pressure side of the fin, the outer side
surfaces of the fin sections are smoothly aligned with each other.
This prevents disturbances at the high pressure side of the fin. It
has appeared that a gap at the opposite side of the fin cause
hardly any disturbances to the dynamic properties.
[0037] As shown in FIGS. 4 and 5 in cross section, the second
coupling element 5 has a shape of a fungus. The fungus has a stem
and a head which fits including an amount of play into a smaller
and broader part of the groove 4. As shown in FIG. 4 the rotational
movement of the fin sections is limited by an external end stop 7
and an internal end stop 8. The external end stop 7 is positioned
close to the outer surfaces of the fin sections. The external ends
top 7 limits the rotational movement of the fin sections. The
internal end stop 8 limits also the rotational movement, but
provides further a strong connection between the fin sections in a
direction of the fluid flow. The internal end stop 8 is obtained by
providing an inner protrusion in the groove of the first coupling
element and a corresponding outer protrusion on the tongue of the
second coupling element 5. As a result the groove which has a
receiving opening to receive the tongue 5 of the second coupling
element comprises a smaller portion which locks the tongue 5.
[0038] The fin sections rotate in an extreme position as a result
of a dynamical load. Herewith no active operation by manually
steering or drive means is necessary to get the dynamic fin
according to the invention in one of the extreme positions.
Herewith, the dynamic fin may be classified as a passive fin, which
makes it as in particular suitable to serve as a keel.
[0039] The end stops 7, 8 define contact areas between the fin
sections. These contact areas provide an additional advantage
effect in that they prevent also a leakage of fluid from one side
of the fin to the other side. A leakage of fluid would influence
the pressure difference created by the dynamic effect and is
therefore not desired.
[0040] The smooth transition of the outer surfaces of the fin
sections created by the external stop 7 may prevent swirls in the
passing fluid which further increases the dynamic properties of the
fin.
[0041] The smaller portion in the groove 4 is indicated with letter
"b". The larger portion on the tongue 5 is indicated with letter
"a". The smaller dimension "b" provide a lock to the broadened
portion of the tongue 5 to remove the fin section in a direction
away from the receiving opening.
[0042] FIG. 5 corresponds to FIG. 4 and shows a cross-sectional
view of a dynamic fin in a nominal I and an extreme position II.
The groove 4 and the tongue 5 have rounded parts. The rounded
tongue fits within the rounded groove. The rounded parts gives the
fin sections 1,2 a freedom to rotate relatively to each other to
get a cambered shape. Advantageously, the rounded parts and
eventually other roundings in the contour of the cross section may
make the fin stronger. Unacceptable high local stresses may be
prevented by the smooth contour.
[0043] Besides the shown embodiments, several alternatives are
possible without leaving the scope of protection as defined by the
appendant claims. In a variant the tongue may be formed at a tail
fin section, wherein the groove may be formed at a front fin
section. For example, a further external stop may be created by a
pin which may be adjustable to obtain adjustable extreme positions.
The shown embodiment is designed as a fin for a surf board.
However, the dynamic fin according to the invention is further
applicable as for example a rudder, propeller, a roll stabilisation
fin for ships, a spoiler or other aerodynamic surface.
[0044] Thus, according to the invention a dynamic fin is provided
having improved functionality in that the fin sections are easier
to mount and demount. In addition, the manufacturing of the dynamic
fin is further improved by simplifying the design including the
pair of coupling elements. A preferred embodiment is shown, wherein
it is even possible to manufacture the dynamic fin completely by a
moulding process.
[0045] Although the present disclosure has been described and
illustrated in detail, it is to be clearly understood that this is
done by way of illustration and example only and is not to be taken
by way of limitation. The scope of the present disclosure is to be
limited only by the terms of the appended claims.
[0046] I claim:
* * * * *