Note: Descriptions are shown in the official language in which they were submitted.
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MARINE PROPELLER
The present invention relates to a marine propeller used in the propulsion
system of
a ship. More precisely the invention relates to the structure of this kind
propeller and
to a marine propulsion system utilizing this kind of a propeller.
The propulsion systems of ships typically in general level comprise one or
more
engines or motors providing rotational movement and torque, one or more
propeller
shafts for transferring the rotational movement and torque from the one or
more
engines to one or more marine propellers, and marine propellers for
transferring the
rotational movement and torque to thrust for the ship.
The marine propellers used in ships comprise typically a propeller hub to
which the
blades of the propeller are fixed, and via which propeller hub the propeller
is fixed
to the propeller shaft.
The marine propellers can be manufactured as a single piece, i.e. by casting,
wherein the hub and blades of the propeller form a solid propeller. This kind
of pro-
pellers are also called monobloc propellers. Alternatively, the marine
propellers can
be manufactured in pieces, typically the hub and the individual blades as
separate
pieces, wherein the blades are fixed to the hub typically with bolts and studs
to form
an assembled propeller.
Monobloc propellers are generally used, but the larger ship propellers cannot
be
cast in a single casting due to the size of the propeller in relation to the
size of the
available casting equipment, which generally leads to the use of assembled
propel-
ler. Further advantage of the assembled propellers is that individual blades
can be
changed without removing and changing of the whole propeller when the blades
get
damaged, which makes them preferable for example for ice-going vessels. This
makes the repairing process of the propeller easier and can often be carried
out
without drydocking the ship.
The power of engines used in propulsion systems of ships have been
continuously
increasing, which have caused the strength requirements of the marine
propellers
to increase correspondingly. This has caused the weight of marine propellers
to
increase. The increased weight of propellers causes increased structural
demands
and restrictions for the rest of the propulsion system, such as for the
diameter of the
propeller shaft and for the placement of bearings. Further, the increase of
material
used in the manufacturing of the propellers also increases the manufacturing,
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installation, and transportation requirements of the propellers, as well as
increases
the cost of the propellers.
In order to overcome the above problems with the prior art assembled
propellers,
the present invention provides a novel ship propeller, which propeller does
not com-
prise a hub. This allows significant weight savings for the propeller of the
invention
in comparison to the prior art propellers, thus deceasing the related
structural re-
quirements of the propulsion system of the ship and cost of the propeller
itself. Fur-
ther, the propeller of the invention typically comprises less parts than the
prior art
assembled propellers, which makes it easier to manufacture.
The marine propeller of the invention for a propulsion system of a ship
comprises a
plurality of detachable blades, and is configured to be fixed to a propeller
shaft of a
propulsion system of a ship, wherein the detachable blades forming the
propeller
are configured to be fixed to the end surface of the propeller shaft or of a
flange
formed at the end of the propeller shaft.
This allows the hub part of the propeller to be removed from the construction
of the
propeller of the invention, which provides significant weight, and related
cost, sav-
ings.
In the present invention the blades of the propeller are connected to the
propeller
shaft preferably directly, which means that the fixing means, such as bolts
and pref-
.. erably also studs for example, extend to the material of the propeller
shaft.
In the context of the present invention a ship preferably means a marine
vessel of a
suitable size to properly allow the utilization of the advantages obtained
with the
present invention. In practice this means that the ship typically has a length
of 24 m
or more.
The propeller of the invention is preferably a large marine propeller in order
to
properly allow the utilization of the advantages obtained with the present
invention.
In practice this means that the diameter of the propeller is 2 m or more,
preferably
3 m or more. The material of the propeller is preferably metal, such as bronze
or
stainless steel for example, but other metal materials may also be used.
.. In an embodiment of a marine propeller of the invention the propeller
comprises a
cap connected to the detachable blades of the propeller. This cap allows
additional
structural support for the blades and for the whole propeller at the side away
from
the propeller shaft.
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In an embodiment of a marine propeller of the invention number of detachable
blades is three or more. Preferably the number of detachable blades in a
propeller
is four, but the number of detachable blades may also be three, five or six.
In an embodiment of a marine propeller of the invention the detachable blades
are
fixed to the shaft with a fixing system comprising bolts and preferably also
studs.
This allows the separate blades to be replaced and repaired easily when the
need
arises without drydocking the ship and without disassembling the whole
propeller.
The present invention also provides a marine propulsion system for providing
pro-
pulsion for a ship, which propulsion system comprises at least one engine or
motor,
a propeller, and a propeller shaft for conveying the rotational power from the
at least
one engine to the propeller, wherein the propeller is a marine propeller of
the inven-
tion as defined above.
The engine or motor in the propulsion system of the present invention may be
any
suitable device, system and/or arrangement providing rotative motion and
torque for
the propeller via the propeller shaft. Examples of these include combustion
engine,
electrical engine, and turbine.
In addition to the traditional propulsion systems, wherein the propulsion
system is
located inside the hull of a ships, with the exception of the propeller and
part of the
propeller shaft, the propulsion system of the invention may also be
implemented as
a pod-type construction, wherein the propulsion system is located, completely
or
partially, in a separate pod that can be rotated in relation to the hull of
the ship.
In an embodiment of a marine propulsion system of the invention the system may
typically comprises a rope guard.
The present invention also provides a ship that comprises a marine propeller
ac-
cording to the invention and/or a marine propulsion system according to the
inven-
tion. The ship of the invention is preferably an ice class ship, i.e. ship
designed to
travel in at least some thickness of ice, such as an icebreaker, a Polar Class
ship,
or an Arctic Class ship for example, wherein the construction of the propeller
allows
easy repairing of damaged blades. Alternatively, the ship of the invention may
be
an open-water ship wherein the construction of the propeller of the invention
allows
manufacture of very large propellers.
More precisely the features defining a marine propeller in accordance with the
pre-
sent invention are presented in claim 1, the features defining a marine
propulsion
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system in accordance with the present invention are presented in claim 5, and
the
features defining a ship according to the present invention are presented in
claim 7.
Dependent claims present advantageous features and embodiments of the inven-
tion.
Exemplifying embodiments of the invention and their advantages are explained
in
greater detail below in the sense of example and with reference to
accompanying
drawings, where
Figure 1 shows schematically a prior art marine propeller,
Figures 2A and 2B show schematically an embodiment of a marine propeller
of the invention,
Figures 3A-3D show schematically alternative embodiments of the present in-
vention,
Figure 4 shows schematically an embodiment of the present invention as ex-
ploded view, and
Figure 5 shows schematically an embodiment of a ship utilizing the present
invention.
The prior art marine propeller 1 shown in figure 1 as a cross-sectional view
com-
prises a plurality of separate blades 2 comprising a fixing portion 2a via
which fixing
portion the blades are fixed to a propeller hub 3 with bolts. The propeller 1
is fixed
to a propeller shaft 4 in with bolts extending through a flange 5 formed at or
attached
to the end of the propeller shaft and to the hub 3.
In the embodiment of figure 1, the propeller 1 also comprises a propeller cap
6 fixed
at the opposite end of the propeller in relation to the attachment to the
propeller
shaft 4, to cover the hollow portion of the propeller hub 3.
Figures 2A and 2B show an embodiment of the propeller 10 of the invention,
which
comprises a plurality, four in this embodiment as can be seen from figure 2B,
of
separate blades 2 comprising a fixing portion 2a.
In this embodiment the blades 2 forming the propeller 10 are connected
directly to
a flange 5 formed at the end of the propeller shaft 4 via their fixing
portions 2a with
bolts. At the opposite end of the propeller 10 in relation to the flanges of
the propel-
ler shaft 4, to the fixing portions 2a of the blades 2 are fixed a propeller
cap 6. The
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propeller cap 6 in this embodiment provides further structural support for the
blades
2 of the propeller 10.
Figure 2B illustrates the fixing of the fixing portions 2a of the blades 2 to
the flange
5 and/or to the propeller cap 6. In this embodiment four blades 2 are fixed
via their
5 fixing portions 2a to the flange 5 and to the cap 6 with bolts and studs
for forming
the propeller 10.
Figures 3A-3D show alternative embodiments of the propeller 10 of the
invention
attached to the propeller shaft 4 as cross-sectional views.
In the embodiment of figure 3A the blades 2 of the propeller 10 are formed so
that
their fixing portions 2a comprise sections extending radially in relation to
the center
axis of the propeller shaft 4. These sections of the fixing portions 2a of the
blades 2
area for the fixing bolts and holes via which the blades can be attached to
the end
surface of the flange 5 formed at the end of the propeller shaft 4. This
formation of
propeller 10 from the blades 2 in this embodiment also creates a hollow area 8
inside
the propeller, which hollow area is closed with a cap part 6, which also
provides
structural strength for the propeller and its blades.
In the embodiment of figure 3B the blades 2 forming the propeller 10 are fixed
via
first end of their fixing portions 2a on the end surface of the flange 5
formed at the
end of the propeller shaft 4. In the opposite end and at the end surfaces of
the fixing
portions 2a of the blades 2 in relation to the flange 5 is fixed a cap part 6
closing the
hollow area 8 inside the propeller 10. In this embodiment the fixing portions
2a of
the blades 2 extend at an angle in the longitudinal direction of the propeller
shaft 4
so that the diameter formed by the fixing portions 2a is greater at the flange
5 than
at the cap part 6.
The embodiment of figure 30 corresponds substantially to the embodiment of
figure
3B, but in this embodiment the fixing portions 2a of the blades 2 extend at an
angle
in the longitudinal direction of the propeller shaft 4 so that the diameter
formed by
the fixing portions 2a is smaller at the flange 5 than at the cap part 6.
Figure 3D shows an embodiment, there the outer surface of the fixing portions
2a
of the blades 2 forming the propeller 10 are formed curved.
Figure 4, schematically showing an embodiment of the present invention as an
ex-
ploded view, further illustrates the construction of the propeller 10 of the
invention.
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In the embodiment of figure 4 four blades 2 via their fixing portions 2a are
connected
to the end surface of the flange 5 formed at the propeller shaft 4 with bolts
11 and
studs 14. This embodiment also substantially corresponds to the embodiment
shown in figure 2A.
At the opposite end of the fixing portions 2 in relation to the flange 5 is
fixed a cap
part 6 with bolts 12 and studs 13. The cap part 6 gives further support for
the blades
2 of the propeller 10 and also encloses the open space 8 inside the propeller.
Figure 5 shows schematically a ship 20 into which the propeller 10 and
propulsion
system of the present invention can preferably be applied. The ship 20 is in
this
embodiment an icebreaker.
In relation of the propeller 10 of the invention it is to be noted that the
propeller may
be located at the stern of the ship 20, as shown in figure 5, or the propeller
may be
located at the bow of the ship, or in the steering propeller of the ship.
Further, the
propeller 20 of the invention may be an open propeller, as shown in figure 5,
or a
.. ducted propeller.
The specific exemplifying embodiments of the invention shown in the figures
and
discussed above should not be construed as limiting. A person skilled in the
art can
amend and modify the embodiments described in many evident ways within the
scope of the attached claims. Thus, the invention is not limited merely to the
em-
bodiments described.
