BACKGROUND OF THE INVENTION
[0001] The present invention relates to an azimuth thruster for use in ships, the azimuth
thruster being mounted to ships together with a screw for improving maneuverability.
[0002] Heretofore, the thruster for ships is mounted to the bow or stern other than the
screw. Most conventional thrusters are a type of the tunnel type oneway thruster directed
to the port and starboard. As the 360 degree rotatable thruster, there have been developed
the Z-peller propeller and the like thrusters. However, since these thrusters have
a structure such that the propeller thereof projects downwards from the bottom of
the ship, they are disadvantageous in that their use is largely restricted in depth
of water in shallow sea, particularly near quay and hence are not widely used.
[0003] To avoid this disadvantage there is proposed a cone- jet thruster in Japanese Patent
Publication No. 58-35919, published on August 5, 1983, (corresponding to West German
Patent Application No. P 2757454.5), in which a frustoconical casing, which is provided
with a through water passage having a water inlet and outlet opening at the bottom
thereof and directed obliquely downward, is rotatably received in a recess formed
in the bottom of a ship, the casing having a propeller pump mounted within the water
passage. However, this thruster is complicated in structure.
SUMMARY OF THE INVENTION
[0004] Accordingly, it is an object of the present invention to provide a 360 degree rotatable
azimuth thruster which is less complicated in structure and is operable at a relatively
small depth of water, particularly near quay.
[0005] With these and other objects in view the present invention provides an azimuth thruster
for a ship, including: an outboard housing mounted within a substantially conical
recess to turn about a vertically axis, the conical recess formed in the bottom of
a hull of the ship to converge upwards; a turning unit, mounted to the hull, for turning
the outboard housing about the vertical axis; a propeller shaft rotatably supported
by the outboard housing to cross the vertical axis of the outboard housing with an
acute angle; a propeller mounted on the lower end of the propeller shaft to be located
outside the outboard housing and within the conical recess and to provide a thrust
upwards in the direction of the propeller shaft; and a propulsion unit for rotating
the propeller shaft.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006]
FIG. 1 is a partial vertical section taken along the longitudinal direction of a ship,
illustrating an azimuth thruster constructed according to the present invention;
FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1;
FIG. 3 is an enlarged plan view of the turning unit in FIG. 1; and
FIG. 4 is an enlarged vertical section of the azimuth thruster in FIG. 1.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0007] Referring to FIGS. 1 and 2, reference numeral 10 designates a hull of a ship, in
the bottom 12 of which is formed a conical, more exactly, frustoconical recess 14
which converge upwards. As clearly shown in FIG. 4, a cylindrical casing 16 vertically
passes through a frame 18, which defines the top of the frustoconical recess 14, and
is supported in a conventional watertight manner by the frame 18 to be rotatable about
its axis. 78 and 82 indicate bearing members and sealing member respectively. The
cylindrical casing 16 has at its top a worm gear 20 integrally and concentrically
formed with it, the worm gear 20 engaging a worm 22 which forms part of an outboard
housing turning unit 23 mounted on the frame 18 within a thruster room 25. The cylindrical
casing 16 is rotated by a hydraulic oil motor 60 (FIG. 3) through the worm 22 and
the worm gear 20. At the bottom end 24 of the cylindrical casing 16 there is provided
an outboard housing 26 which has a hollow tubular portion 28 and a propeller shaft
supporting portion 30 integrally formed with the tubular portion 28 and having a teardrop
or streamline shape. The tubular portion 28 of the outboard housing 26 is concentrically
and watertightly bolted to the lower end 24 of the cylindrical casing 16 as shown
in FIG. 4. A vertical shaft 32 coaxially extends through and rotatably supported by
the cylindrical casing 16 and the tubular portion 28 of the outboard housing 26 through
bearing members 76 and 76, the vertical shaft 32 having an upper beveled gear 34 mounted
at its upper end and a lower beveled gear 36 at its lower end. A propeller shaft 38
is rotatably supported by the propeller shaft supporting portion 30 of the outboard
housing 26 through bearing members 74 and 74 to cross the axis of the vertical shaft
32 at an angle α. The lower end 40 of the propeller shaft 38 projects form the propeller
shaft supporting portion 30 and has a propeller 42 mounted on it to provide a thrust
upwards and in the direction of the axis of the propeller shaft 38. 80 designates
a sealing member. The upper beveled gear 34 of the vertical shaft 32 engages a drive
beveled gear 42 mounted on an output shaft 44 of a propulsion unit 46 and the lower
beveled gear 36 engages a driven beveled gear 48 mounted on an upper end portion 50
of the propeller shaft 38. With such a construction, the driving force of the propulsion
unit 46 is transmitted to the propeller shaft 38 through the output shaft 44, drive
beveled gear 42, upper beveled gear 34, vertical shaft 32, lower beveled gear 36 and
driven beveled gear 48, thereby rotating the propeller 42. Further, actuation of the
turning unit 23 rotates the cylindrical casing 16 and the outboard casing 26 to thereby
turn the propeller 42 about the axis of the vertical shaft 32.
[0008] In this embodiment, the inclined angle a defined between the axis of the vertical
shaft 32 and the propeller shaft 38 is set to 65° and the inclined angle formed between
the wall of the recess 14 of the hull base line or the horizontal line H.B.L. is set
to 25
0. The angle a is generally in the range from 45° to 75° and the angle 8 is generally
in the range from 15
0 to 45
0. The shape of the recess 14 need not be exactly frustoconical, and may be substantially
conical.
[0009] The propulsion unit 46 includes a main engine 52, which is connected to the output
shaft 44 through a clutch 54 which incorporates an oil hydraulic pump (not specifically
shown) into it. The output shaft 44 is provided with an air brake 56 for preventing
the rotation of the propeller 42 when the clutch 54 is disengaged. The turning unit
23 includes the oil hydraulic pump which is incorporated within the clutch 54, an
oil hydraulic motor 60 (FIG. 3) actuated by the hydraulic pump, a cooler 62 for cooling
the operating oil, a filter 64 for filtering the operating oil and an oil pump 66
for lubricating rotating portions of the unit. The rotation of the oil hydraulic motor
60 is transmitted through the worm 22, the worm gear 20, and the cylindrical casing
16 to the outboard housing 26. The rotation angle of the outboard housing 26 is detected
by a turning angle detector 68. The outboard housing 26 is provided at its tubular
portion 28 and propeller shaft supporting portion 30 with several fairing or straightening
plates 70. 72 designates a fixing plate integrally formed with each straightening
plate 70 for attaching it to the outboard housing 26 and has a streamline shape. FIG.
1 illustrates a state in which the propeller 42 is directed toward the stern (to the
left). When the propulsion unit 46 is actuated in this state, the propeller 42 is,
as previously described, rotated to thereby produce a thrust at the same angle as
the inclined angle a, that is, a thrust directed upwards and parallel to the axis
of the propeller shaft 38. Thus, the ship is propelled to the right in FIG. 1. During
this operation, water flows in the form of an arc along the wall of the recess 14
from the right to the left in FIG. 1. Since the outboard housing 26 is provided with
the straightening plates 70, water flows to the propeller 42 smoothly or less turbulently.
Thus, the efficiency of the propeller 42 is increased and the generation of cavitation
is reduced. Further, the oscillation of the bottom 12 of the ship due to turbulent
flow is reduced.
[0010] In order to change the direction of thrust of the propeller 42, the turning unit
23 is actuated to thereby turn the propeller 42 toward a desired direction together
with the outboard housing 26. FIG. 2 shows the outboard housing 26 turned 90° from
the position in FIG. 1. The outboard housing 26 may be rotated 360° or more and equal
thrust is obtained at any turned position of the outboard housing 26.
[0011] The number and dimensions of the straightening plates 70 depend on dimensions of
the propeller 42 but the straightening plates 70 are not necessarily provided.
[0012] The propulsion unit and the turning unit are not restricted to those shown in the
drawings. For example, the driven beveled gear 48 may be mounted on the propeller
shaft 38 as indicted by the phantom line in FIG. 4, in which case the lower beveled
gear 36 is modified to engage the driven beveled gear indicated by the phantom line.
Various combinations of toothed wheels other than toothed wheels shown in the drawings
or other transmission means may be adopted.
[0013] While the invention has been disclosed in specific detail for purposes of clarity
and complete disclosure, the appended claims are intended to include within their
meaning all modifications and changes that come within the true scope of the invention.
1. An azimuth thruster for a ship, comprising:
an outboard housing mounted within a substantially conical recess to turn about a
vertically axis, the conical recess formed in the bottom of a hull of the ship to
converge upwards;
turning means, mounted to the hull, for turning the outboard housing about the vertical
axis;
a propeller shaft rotatably supported on the outboard housing to cross the vertical
axis of the outboard housing with an acute angle;
a propeller mounted on a lower end of the propeller shaft to be located outside the
outboard housing and within the conical recess and to provide a thrust upwards in
the direction of the propeller shaft; and
propulsion means for rotating the propeller shaft.
2. An azimuth thruster as recited in Claim 1, wherein the outboard housing comprises
a tubular portion vertically supported on the conically recessed bottom of the hull
to be rotatable about its axis and a streamlined, propeller shaft supporting portion
integrally formed with the tubular portion.
3, An azimuth thruster as recited in Claim 2, wherein the acute angle is within a
range of about 45 to about 75°; and wherein an angle formed between the wall of the
conical recess and a horizontal line is within a range of about 15 to about 45°.
4. An azimuth thruster as recited in Claim 3, wherein the outboard housing comprises
a plurality of straightening plates mounted thereon so that water flow is supplied
to the propeller less turbulently.
5, An azimuth thruster as recited in Claim 4, wherein: the turning means comprises
a cylindrical casing vertically and watertightly passing through and rotatably supported
on an apex portion of the wall of the conical recess, the cylindrical casing having
a lower end concentrically watertightly bolted to the upper end of the tubular portion
of the outboard housing; a worm gear coaxially and integrally formed with the upper
end of the cylindrical casing; and a worm engaging with the worm gear.
6. An azimuth thruster as recited in Claim 5, wherein the propulsion means comprises
a vertical shaft concentrically passing through and rotatably supported on the cylindrical
casing and the tubular portion of the outboard housing, the vertical shaft connected
at an upper end portion thereof to a prime mover; a first beveled gear mounted on
the lower end of vertical shaft; and a second beveled gear mounted on the propeller
shaft to engage the first beveled gear for transmitting the rotational force to the
propeller shaft.