Note: Descriptions are shown in the official language in which they were submitted.
BOAT PROPELLER
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to boat propellers, and more particularly to a
boat propeller that helps to improve propulsive efficiency.
2. Description of the Related Art
The existing boat propellers structurally have an outer shaft housing, an
inner
shaft housing, and a plurality of blades. The inner shaft housing is received
in the outer
shaft and is connected to the inner peripheral surface of the outer shaft
through a
plurality of rib portions. Each of the blades is integratedly connected to the
outer
peripheral surface of the outer shaft. When the propeller is driven by an
engine to
operate at high speed, the blades push water streams backward and the counter
force
generated thereby can work for propulsion of the boat.
To further enhance propulsion, a known approach is to such design the outer
shaft housing that it has a changing cross-sectional area, which becomes
smaller as the
outer shaft housing extends backward. This helps to accelerate water streams
flowing
therethrough, and to in turn increase the counter force acting on the boat.
However, in
practical use, since the outer shaft housing is tapered in shape and the space
around the
propeller tends to be restricted due to boat design and other factors, the
blades are
consequently limited in terms of dimensional parameter (such as the rake, the
pitch and
more). This hinders the blades from effectively compressing water streams,
leading to
compromised propulsive efficiency.
SUMMARY OF THE INVENTION
The primary objective of the present invention is to provide a boat propeller
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that has improved propulsive efficiency.
To achieve the foregoing objective, the disclosed propeller comprises a gear
box, an impeller, a stream-guiding ring, and a stream-shaping nozzle. The gear
box
includes a casing and a transmission shaft. The transmission shaft is
rotatably installed
in the casing, and the transmission shaft has its front end received in the
casing so that
its rear end juts out the casing. The impeller has an impeller shaft that
includes an outer
shaft housing and a hollow inner shaft housing, both being hollow columnar.
The inner
shaft housing is received in the outer shaft housing and is connected to the
outer shaft
housing through a plurality of rib portions, while being coaxially connected
to the
transmission shaft of the gear box, so that the impeller is driven by the
transmission
shaft of the gear box to rotate. In addition, the impeller further has a
plurality of vanes
that are integratedly formed on the outer peripheral surface of the outer
shaft. The
stream-guiding ring is assembled to the casing of the gear box and houses the
impeller,
so that the impeller rotating draws water streams into the stream-guiding
ring. The
stream-shaping nozzle is connected to the rear end of the stream-guiding ring,
for
shaping the water stream drawn into the stream-guiding ring.
With the foregoing configuration, the disclosed propeller has its water inlet
diameter maximized, thereby improving propulsive efficiency. In addition, with
the
protection provided by the stream-guiding ring, the impeller is unlikely to
harm fishes,
swimmers or divers around the bottom of the boat. This allows a boat having a
shallow
draft safe to be used. Even if the impeller is not fully immersed in water,
propulsion
can still be provided desirably.
Preferably, the stream-shaping nozzle has a ring portion, a hollow axial
portion, and a plurality of stream-shaping portions. The ring portion is
connected to the
rear end of the stream-guiding ring. The hollow axial portion is defined in
the ring
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portion and coaxially connected to the outer shaft housing of the impeller
shaft of the
impeller. The stream-shaping portions are connected between the ring portion
and the
hollow axial portion and arranged equidistantly to circle the hollow axial
portion. The
stream-shaping nozzle uses the stream-shaping portions to shape the water
stream
excited by the impeller into linear ejections, thereby facilitating boat
propulsion.
Preferably, the casing of the gear box has a tapered shaft. The tapered shaft
and the impeller shaft of the impeller do not contact each other. Instead, an
exhaust
channel is left therebetween. Thereby, when the boat moves backward, the
exhaust gas
generated by the engine can escape through the exhaust channel and will not
interfere
with water streams to cause turbulence.
Preferably, the inner shaft housing of the impeller is indirectly connected to
the transmission shaft of the gear box through a bushing. The bushing has a
shock-absorbing layer and a metal layer wrapping the shock-absorbing layer. In
the
event that a foreign object comes to the impeller during operation, the shock-
absorbing
layer serves to absorb impact and prevent the metal layer from burst while
protecting
the transmission shaft from damage.
The detailed structure, features, assembly and/or use of the boat propeller of
the present invention will be explained in detail referred to the following
Detailed
Description. However, one skilled in the art shall understand that the
detailed
description and the specific embodiments in which the invention can be
practiced are
only illustrative and in no way form limitations to the scope of the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a boat propeller of the present invention.
FIG 2 is an exploded view of the boat propeller of the present invention.
FIG 3 is a point view of an impeller in the boat propeller of the present
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invention.
FIG. 4 is a side view of the boat propeller of the present invention.
FIG. 5 is a rear view of the boat propeller of the present invention.
FIG 6 is a partial cross-sectional view of the boat propeller of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
It is to be stated at first that in the disclosure, including the embodiments
to
be described below and the appended claims, all the directional terms are
based on the
orientations of them in the drawings. Besides, in the embodiments to be
described
below and the accompanying drawings, like numerals may refer to identical or
similar
components or structural features.
Referring to FIG 1 and FIG. 2, according to the present invention, a boat
propeller 10 comprises a gear box 20, an impeller 30, a stream-guiding ring
50, and a
stream-shaping nozzle 60.
The gear box 20 is provided with a casing 21. The casing 21 has a tapered
shaft 22, an upper wing 23, a lower wing 24, a connecting portion 25 and an
anti-swirl
baffle 26. The tapered shaft 22 has a changing cross-sectional area that
becomes larger
as it extends backward. The upper wing 23 and the lower wing 24 are
integratedly
connected to top and bottom sides of the tapered shaft 22, respectively. The
connecting
portion 25 is integratedly connected to the top of the upper wing 23 and is
configured
to engage with an engine housing, which is known in the art and not shown
herein. The
anti-swirl baffle 26 integratedly is connected between the upper wing 23 and
the
connecting portion 25. In addition to a gear reduction unit that is known in
the art and
not shown herein, the gear box 20 further has a transmission shaft 27. The
gear
reduction unit is installed in the casing 21, and is configured to connect a
driving shaft
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of an engine, both known in the art and not shown herein. The transmission
shaft 27
has its front end received in the tapered shaft 22 of the casing 21 and
connected to the
gear reduction unit. The transmission shaft 27 has its rear end jutting out
the casing 21
provided with a toothed portion 28. With the foregoing configuration, the
power
generated by the engine is transmitted to the gear reduction unit through the
driving
shaft and then delivered to the transmission shaft 27 after deceleration
caused by the
gear reduction unit, thereby rotating the transmission shaft 27.
The impeller 30 has an impeller shaft 31 and four vanes 38. As shown in FIG.
3, the impeller shaft 31 has a hollow columnar outer shaft housing 32 and a
hollow
columnar inner shaft housing 33. The inner shaft housing 33 is coaxially
received in
the outer shaft housing 32 and is connected to the outer shaft housing 32
through four
rib portions 37. The vanes 38 are integatedly connected to the outer
peripheral surface
of the outer shaft housing 32. Additionally, the outer shaft housing 32 has an
engaging
flange 34 integratedly extending outward from its rear end (as shown in FIG
6), and
the inner shaft housing 33 has a retaining flange 35 and four positioning
recesses 36
formed on the inner peripheral surface in front of the retaining flange 35 (as
shown in
FIG 3 and FIG. 6).
Now referring to FIG 2 and FIG 6, the impeller 30 is indirectly connected
to the transmission shaft 27 of the gear box 20 through a bushing 40. The
bushing 40
has a shock-absorbing layer 41 and a metal layer 43 wrapping the shock-
absorbing
layer 41. The shock-absorbing layer 41 has its outer peripheral surface
provided with a
plurality of positioning ridges 42, and the metal layer 43 has its inner
peripheral
surface formed with a toothed channel 44. When assembled to the transmission
shaft
27, the bushing 40 is inserted into the inner shaft housing 33 so that its
rear end abuts
against the retaining flange 35 of the inner shaft housing 33. The bushing 40
on one
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=
hand uses the four positioning ridges 42 on the shock-absorbing layer 41 to
pair up and
engage with the four positioning recesses 36 of the inner shaft housing 33,
and on the
other hand uses the toothed channel 44 of the metal layer 43 to engage with
the toothed
portion 28 of the transmission shaft 27. Then two gaskets 46 are arranged at
front and
rear ends of the impeller shaft 31 for the transmission shaft 27 to pass. At
last, a nut 47
is assembled to hold all the components together, thereby making the impeller
30 and
the transmission shaft 27 well assembled. As a result, the transmission shaft
27 of the
gear box 20 can transmit power generated by the engine to the impeller 30
through the
bushing 40, thereby driving the impeller 30 to operate. In the event that a
foreign
object comes to the impeller 30 during operation, the shock-absorbing layer 41
serves
to absorb impact and to prevent the metal layer 43 from burst while protecting
the
transmission shaft 27 from damage. Moreover, in the assembly of the impeller
30 and
the transmission shaft 27, there is no direct contact between the impeller
shaft 31 and
the tapered shaft 22 of the casing 21. Instead, an exhaust channel 45 is left
there
between to allow escape of exhaust gas (as shown in FIG 6).
At the top edge of the outer peripheral surface of the stream-guiding ring 50,
two upper supports 51 are symmetrically fixed using fixing members 53 such as
screws. The upper supports 51 jointly hold the anti-swirl baffle 26 in
position and then
the upper supports 51 can be further fixed using fixing members 54 such as
screws. At
.. the bottom edge of the outer peripheral surface of the stream-guiding ring
50, a lower
support 52 is fixed using fixing members 55 such as screws. The lower support
52
holds the lower wing 24 in position and the lower wing 24 can be further fixed
using
fixing members 56 such as screws. After so assembled, the stream-guiding ring
50
houses the entire impeller 30.
As shown in FIG. 2 and FIG 5, the stream-shaping nozzle 60 has a ring
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portion 61, a hollow axial portion 62, and eight stream-shaping portions 63.
The ring
portion 61 is fixed to the rear end of the stream-guiding ring 50 using fixing
members
64 such as screws. The ring portion 61 has a changing cross-sectional area
that
becomes smaller as it extends backward. The hollow axial portion 62 is defined
in the
ring portion 61. The hollow axial portion 62 has its front end provided with
an
engaging socket 65. The engaging socket 65 of the hollow axial portion 62
coaxially
receives the engaging flange 34 of the impeller shaft 31 of the impeller 30
(as shown in
FIG. 6). The stream-shaping portions 63 are integratedly connected between the
ring
portion 61 and the hollow axial portion 62 while being arranged equidistantly
to circle
the hollow axial portion 62. Thereby, water streams drawn into the stream-
guiding ring
50 by the impeller 30 are well shaped into eight linear streams by the eight
stream-shaping portions 63 of the stream-shaping nozzle 60. Then the stream-
shaping
nozzle 60 jets the linear streams backward to provide the boat with
propulsion.
With such a design, the boat propeller 10 of the present invention has the
following advantageous over the prior-art devices:
1) Given that the stream-guiding ring 50 is attached to the casing 21 of the
gear box 20 through the upper and lower supports 51, 52 and that the impeller
shaft 31
of the impeller 30 is not tapered, the diameter of the combined vanes 38 is
enlarged
and so is the water volume to be compressed. As a result, the effective water
inlet
diameter is maximized to provide improved propulsive efficiency.
2) With the protection provided by the stream-guiding ring 50, the impeller
is unlikely to harm fishes, swimmers or divers around to bottom of the boat.
This
allows a boat having a shallow draft safe to be used. Even if the impeller 30
is not fully
immersed in water, propulsion can still be provided desirably. Besides, the
25 stream-guiding ring 50 may be made of aluminum alloy which is of high
strength. In
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this case, the boat propeller 10 is more resident to impact and has a longer
service life.
3) When the boat moves backward, the exhaust gas generated by the engine
can escape through the exhaust channel 45 and will not interfere with water
streams
and cause turbulence.
4) The stream-shaping nozzle 60 uses the eight stream-shaping portions 63 to
shape the water stream excited by the impeller 30 into linear ejections. This
prevents
swirls from formed at the back of the impeller 30 and in turn helps to improve
propulsive efficiency.
5) The transmission shaft 27 of the gear box 20 and the impeller shaft 31 of
the impeller 30 are assembled coaxially, so that the power of the engine can
be
leveraged, while the bushing 40 works as a buffer against external impacting
force.
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