Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a propeller device for
a vessel, which propeller device comprises two propellers
arr~mged to rotate on a common rotating shaft in opposite
directions, the driving power being brought to the essentially
hor:Lzontal shafts of the propellers by a vertical shaft and an
ang:Le gear.
Propeller devices equipped with propellers rotating in
opposite directions are known in the Prior Art. When two
propellers are installed to the same propeller device axially one
after the other to rotate in opposite directions, the ma;ority of
the energy bound to the whirls of the tra~ling flow of the front
propeller can be made use of in the rear propeller with suitable
design of the rear propeller. Then the load on both propellers
will diminish and the cavitation conditions improve, and the
efficiency of the propeller device will increase. As the
efficiency will be improved, it is possible to use smaller-
diameter propellers with the consequence that a vessel equipped
with this klnd of propeller devlce will also be able to operate
in shallow waters. These propeller devices cr~ate high thrusts
compared with conventional propeller devices with small propeller
diameters, on the other hand, due to the high efficiency of the
propeller device, high thrusts are attained with lower engine
powers than in conventional systems. This will reduce the total
costs of the system. Propeller devices with opposite-rotating
2s propellers have earlier been described for instance in US Patents
2 691 356, 2 987 031, 3 094 967 and in the DE Patent Publication
870 655 and in the DE Publication Print 1 145 048.
This kind of propeller device equipped with propellers
rotating in opposite directions can be considered exceptionally
feasible when both propellers of the propeller device are
arranged to the same side of the angle gear of the propeller
device, i.e. when both propellers either pull or push. Then the
angle gear of the propeller device will not cre-
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ate flows interfering the operation of the rear propeller;inst:ead, energy bound in the swirls of the trailing flow of the
front propeller can be better made use of in the rear propeller.
This arrangement has before been described for instance
S in the SE Patent 433 599.
On the other hand, also such an arrangement has been
used in the Prior Art in which there is, for changing the flow
conditions of the propeller, an annular propeller nozzle around
the propeller. A propeller nozzle is usually used to improve the
thrust of the propeller particularly in slow speeds, in which the
propeller nozzle is used to accelerate the propeller flow in
order to provide improved thrust. This kind of arrangement is
generally used for instance in tugs. As a propeller nozzle
improves the thurst, one may, in association with a propeller
device, use a smaller-diameter propeller as compared with the
situation that a propeller without a propeller nozzle would be
! used. This kind of propeller device equipped with a propeller
nozzle ls formerly described for lnstance in the FI Applicatlon
830 373. A common benefit of the propeller devices described
above is that they are simple to make turning so that they can be
used for steering the boat.
The present invention provides a new type of propeller
device, with which all benefits of the propeller devices known in
the Prior Art are attained, but whose efficiency and thrust are
essentially better than those of the Prior Art propeller devices.
According to the inventlon the propeller device is equipped with
at least one annular propeller nozzle in such a way that at least
one of the propellers of the propeller device is arranged to
rotate within said propeller nozzle. Among the benefits of the
invention when compared with solutions of the Prior Art is that a
propeller device in accordance with the invention provides a very
high thrust with an essentially smaller propeller diameter than
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what is required in known propeller devices for the same thrust.
In other words, the efficiency of a propeller device in accord-
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1 ance with the invention is essentially better than the efficiency of the
known systems. Another essential benefit is that a propeller device in
accordance with the invention can easily be made turning, 80 that the
propeller tevice can be used for steering the vèssel.
The invention will now be described in detail with reference to the
figures of the accompanying drawing, which schematically illustrate
various embodiments of a propeller device in accordance with the inven-
tion.
Figures lA to lC illustrate various embodiments of a propeller device in
accordance with the invention, in which propeller devices both propel-
lers are of the pushing type.
Pigures 2A to 2D illustrate various embodiments of a propeller device in
accortance with the invention, in which which propeller devices one pro-
peller is of the pushing type, and the other one is of the pulling type.
First we refer to figures lA to lC, in which a propeller device in ac-
2~
cortance with the invention is general}y indicatet with ref. number 10.
Power is brought to the propeller device in a conventional way with a
vertical shaft 12, from which it is transferret by an angle gear 11 to
the shafts of the propellers 13 ant 14. In figures lA to lC both propel-
lers 13 and 14 of the propeller device 10 are of the pushing type. ~he
propellers~l3 and 14 are arranged to rotate in opposite rotating direc-
tions, for instance as is describet in the SE patent 433 599. The pro-
peller shafts are therefore installed coaxially one within the other in
such a way the shaft of the first propeller 13 or the front propeller is
tubular, ant it is arranget on the shaft of the secont propeller 14 or
the rear propeller with bearings 80 as to rotate arount it. As stated
above, the shafts of the propellers 13 and 14 are rotatet by means of an
angle gear 11 in opposite rotating directions.
The size of the propellers 13 and 14 used in the propeller devices i8
chosen in the known fashion 80 that the diameter of the first propeller
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1 13 or the front propeller is larger than the diameter of the second pro-
peller 14, whereat the point whirls of the front propeller blates do not
cause cavitation in the second propeller 14 or the rear propeller. As
~nown, it i8 also feasible to use a larger number of blades in the se-
cond propeller 14 or the rear propeller than in the first propeller 13
or the front propeller. The blade number of the ~econd propeller 14
should favourably be selected one higher than the blade number of the
first propeller 13, which is very important in order to avoid harmonic
vibrations between the blades of propellers 13 and 14. These dimension-
lQ ing principles are generally valid for all embodiments of a propeller
device in accordance with the invention.
Figure lA illustrates the first embodiment of a propeller device in ac-
cordance with the invention. As shown in figure lA, the propeller device
~-~ 10 is equipped with propellers 13 and 14 arranged to rotate in oppositetirections. The propeller 10 is also equipped with a propeller nozzle
15A, which is in the a~ial direction long enough to cover both propel-
lers 13 and 14 of the propeller device 10. In other words, the a~ial
length of the propeller nozzle 15A is such that both propellers 13 and
2~ 14 are axially located in the area between the leading edge 16A and the
trailing edge 17A of the propeller nozzle. The elements with which the
- propeller zzle 15A is supported to the propeller device lO itself are
not shown in the figure; the supporting elements may be arran8ed in any
suitable way.
Figure lB illustrates another embodiment of a propeller device 10 in
accordance with the invention. In this embodiment the first propeller 13
or the front propeller i8 arranged within the propeller nozzle 15B, ant
the second propeller 14 or the rear propeller is arrsnged as an open
propeller. This arrangement may be considiret the most feasible from the
point of view of the invention. This is because at the front propeller
water flows slower than at the rear propeller, whereat the additional
thrust provided by the nozzle is also greater. The location of the first
propeller 13 within the propeller nozzle 15B, i.e. a~ially between the
leadigg edge 16B and the trailing edge 17B of the propeller nozzle, is
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favourably 80 selected ehat the first propeller 13 is located beeween
the center of the axial length of the propeller nozzle 15B and its
trailing edge 17B. By positioning the first propeller 13 within the pro-
peller nozzle 15B in this way, the additional thrust provided by the
propeller nozzle lSB to the first propeller 13 is at its maximum.
Figure lC illustraees another alternative embodiment of a propeller de-
vice 10 in accordance with the invention. In this embodiment the first
propeller 13 or the front propeller is arranged as an open propeller and
1Q the second propeller 14 or the rear propeller is arranged within ~hepropeller nozzle 15C. At low speeds, an arrangement shown in figure lC
is not as favourable as the embotiment shown in figure lB, but the 801-
ution shown in figure lC is feasible at higher speeds. In the embodiment
t5 shown in figure lC, the second propeller 14 is installed within the pro-
peller nozzle 15C, i.e. axially in the area between the leading edge 16C
ant the trailing etge 17C of the propeller nozzle in such a way that
sait propeller 14 is favourably located in the area between the axial
center ant the trailing edge 15C of the propeller nozzle 15C. As figure
2~ lA, neither figures lB or lC show the elemer.ts with which the propeller
nozzle 15A is supported to the propeller device 10; the supporting el-
ements may be arranget in any suitable way.
Figures 2A and 2B show different embodiments of a propeller device 20 in
accordance with the invention. In these the first one 23 of the propel-
ler3 of the propeller tevice has been arranget to push and and the se-
cond one 24 of the prop211ers of the propeller device has been arranged
to pull. The power is brought to the propeller device 20 with the verti-
cal shaft 22, and the power is further transmitted by angle gear 21 to
~0 the propeller shafts 23 and 24.
Figure 2A shows an alternative embodiment of a propeller device 20 in
accordance with the invention. As in the embotiment of Fig. 2A, the
first propeller 23 of the propeller device, the pulling front propeller,
- 35 is arranged to be an open propeller and the second propeller 23, the
pushing rear propeller is arranget within the propeller nozzle 25A. The
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second propeller 24 is a~cially arranged between the leading edge 26A ant
the trailing edge 27A in such a way that it i9 favourably located in the
range between the center of the axial length of the propeller nozzle 25A
and the trailing edge 27A. With this arrangement all the advantages
described above with reference to figures lA to lC are attained.
The embodiment illustrated in Fig. 2B otherwi~e corresponds to the em-
bodiment illustrated in Fig. 2A, but in Fig. 2B also the first propeller
23, the pulling front propeller, is arranged within the propeller nozzle
1~ 25B. Therefore, according to this embodiment, two propeller nozzles 25A
and 25B are uset in the propeller device 20. The first propeller 23 is
also suitably arranged within the propeller nozzle 25B in such a way
that, in the axial direction, it i~ located between the leading edge 26B
and the trailing edge 27B of the propeller nozzle 25B, in the area be-
~5 tween the center of the axial length of the nozzle and the trailing edge
27B.
A propeller tevice illustrated in ~ig. 2C differs from those illustrated
in figures 2A and 2B 80 that in this embodiment the first propeller 23,
2~
the pulling front propeller, is arranget within the propeller nozzle
25C, whereas the other propeller 24, the pushing rear propeller, is
arranged as an open propeller. In this embodiment the first propeller 23
is arranged within the propeller nozzle 23 in the same way a~ in-the
previous embodiment, i.e. in such a way that in the a~ial direction the
first propeller 23 is locatet between the leading edge 26C ant the
- trailing edge 27C of the propeller nozzle 25C, in the area between the
center of the a~cial length of the nozzle 25C and the trailing edge 27C.
Figure 2D shows such an embodiment of the invention in which both the
first propeller 23 and the second propeller 24 are arranged within the
common propeller nozzle 25D. This embotiment is not as favourable a~ the
previous ones, as, due to the design of the propeller device 20, the
propeller nozzle 25D must inevitably be extremely long. The location of
the propellers 23 and 24 within the propeller nozzle 25D is also noc the
best possible, as in this embodiment the fir~t propeller 23 will be
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located near the leading edge 26D of other propeller nozzle 25D
whereas the second propeller 24 will be located near the trailing
edge 27D of the propeller nozzle.
A design in accordance with the invention may also be
s applied otherways than what is illustrated in the figures of the
drawing. One possibility is to arrange both propellers of the
propeller device to pull. A twin-propeller propeller-nozzle
combination may also be applied to conventional power
transmission arrangements, in other words when power is brought
to the propellers with a "long" propeller shaft. In these cases
the power transmission can be arranged for instance so that the
power brought to the propellers is divided in the power drive
line as near the propellers as possible, with for instance a
planetary gear and by using coaxial propeller shafts. This kind
of drive line arrangement is yet complex and inconvenient to
arrange; therefore using a twin-propeller propeller-nozzle
combination is considerably more feasible, and it is easier to
arrange in association with propeller devices 10 and 20
illustrated in figures, and particularly in the embodiments Gf
Fig. lA to lC, because in these arrangements very short propeller
shafts can be used. The propeller devices can also be arranged
to turn around the vertical shaft 12, 22 in such a way they can
be used for steering the vessel.
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