Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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HIGH MANEUVERABILITY STEERING SYSTEM
FOR WORK BOATS AND OTHER WATERCRAFT
RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Patent Application
Serial No.
61/997,404 filed on May 30, 2014.
BACKGROUND
a. Field of the Invention
The present invention relates generally to steering and propulsion systems for
water-
borne vessels, and, more particularly, to a combination Kort nozzle and rudder
steering
system providing a high degree of maneuverability for work boats, seine
skiffs, tugs and
similar watercraft.
b. Related Art
Self-propelled vessels--e.g., ships and boats of various forms--in general
require some
form of steering in order to control the direction of the vessel. Conventional
rudders have
been used since antiquity, and in screw-driven vessels are generally
positioned aft of the
propeller so as to react with the wash as well as with the flow passing over
the hull. Other,
comparatively more recent efforts have focused on shrouds or similar
structures positioned
around the propeller to direct the thrust, leading to steerable (as opposed to
fixed) Kort nozzle
steering systems (sometimes referred to as ducted propellers) that are
frequently installed in
tugs and work boats where maneuverability and the ability to apply a strong
pulling force at
various angles is needed. Other steering systems have been developed as well,
such as
outdrives and outboard motors and jet drives, for example, but for a variety
of reasons these
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are generally less well suited to work boats and other vessels engaged in
heavy towing work,
such as pulling seine nets, for example.
Although rudders and Kort nozzles are therefore the most common form of
steering
for work skiffs, tugs and other craft involved in heavy towing/pushing, each
has significant
limitations, especially in the degree to which it can turn relative to the
propeller and still
remain effective. Beyond certain maximum angles, both rudders and steerable
Kort nozzles
tend to lose their steering effect and can also impede propulsion of the
craft. In the case of
conventional rudders the maximum effective angle relative to the propeller,
sometimes
referred to as the "stall angle,- is generally considered to be about 35 ,
with greater angles
tending to cause turbulence and reduced steering effect. The maximum effective
angle of a
Kort nozzle may be somewhat greater, but is still generally no more than about
35-50 . As a
result, both types are significantly limited in terms of the level of
maneuverability that they
can achieve, and a greater level of maneuverability than that currently
available would be
desirable for many work skiffs, tugs and other vessels.
Accordingly, there exists a need for a steering system for watercraft,
particularly work
craft engaged in heavy towing/pushing, that can achieve a higher degree of
maneuverability
than that provided by conventional rudders and steerable Kort nozzles.
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SUMMARY OF THE INVENTION
The present invention addresses the problems cited above, and provides a
steering
system in which a rudder and steerable Kort nozzle are operated in combination
to provide a
higher degree of maneuverability than is possible with either mechanism
standing alone.
Moreover, the steering is achieved with a high degree of mechanical efficiency
and stability.
The system is particularly suited to use in seine skiffs, work skiffs, tugs,
and similar craft
engaged in heavy towing/pushing activities.
In a broad aspect, the invention provides a steering apparatus comprising (a)
a
steerable Kort nozzle mounted about a propeller that directs wash from the
propeller to
generate a first turning force; (b) a rudder mounted behind the Kort nozzle
that reacts with the
wash of the propeller exiting the Kort nozzle to produce a second steering
force; and (c) a
mechanism that pivots the Kort nozzle and the rudder in the same direction
simultaneously,
with the rudder pivoting at an angular rate greater than the Kort nozzle; (d)
to a predetermined
optimal maximum angle of the Kort nozzle to the wash generated by the
propeller and a
predetermined optimal maximum angle of the rudder to the wash exiting the Kort
nozzle. In a
preferred embodiment, the predetermined optimal maximum angle of the Kort
nozzle to the
propeller may be about 35 and the predetermined optimum effective angle of
the rudder to
the discharge of the Kort nozzle may be about 25 and therefore about 60 to
the propeller.
The mechanism that pivots the Kort nozzle and the rudder may comprise a
linkage that
interconnects the Kort nozzle and the rudder, the linkage having a geometry
selected to pivot
the rudder at a predetermined angular rate greater than the Kort nozzle so
that the rudder and
Kort nozzle arrive simultaneously at their predetermined optimal maximum
angles.
The linkage may comprise a first tiller member mounted to a vertical pivot
shaft of the
Kort nozzle and a second tiller member mounted to a vertical pivot shaft of
the rudder, the
tiller members each having connection portions extending laterally of the
pivot shafts; first
and second linkage rods mounted to the connection portions of the tiller
members on opposite
sides of the pivot posts; forward ends of the linkage rods being mounted to
the connection
portions of the nozzle tiller member at pivot connections spaced relatively
farther from the
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pivot post of the Kort nozzle and rearward ends of the linkage rods being
mounted to the
connection portions of the rudder pivot post at pivot connections spaced
relatively closer to
the rudder pivot post, so that in response to rotation of the Kort nozzle post
by the Kort nozzle
tiller the rudder pivot post is rotated at a greater angular rate by the
rudder tiller.
The Kort nozzle tiller may comprise an extension portion having an end of a
steering
ram mounted thereto, so that the Kort nozzle tiller and the rudder tiller
rotate in a first
direction in response to extension of the steering ram and rotate in an
opposite direction in
response to retraction of the steering ram.
The present invention also provides an apparatus for pivoting a steerable Kort
nozzle
mounted about a propeller that directs wash from the propeller to generate a
first turning force
in conjunction with a rudder mounted behind the Kort nozzle that reacts with
the wash exiting
the Kort nozzle to produce a second turning force, the apparatus comprising a
mechanism that
pivots the Kort nozzle and the rudder in the same direction simultaneously
with the rudder
pivoting at an angular rate greater than the Kort nozzle, to a predetermined
optimal maximum
angle of the Kort nozzle to the wash generated by the propeller and a
predetermined optimal
maximum angle of the rudder to the wash exiting the Kort nozzle. The
predetermined
maximum effective angle of the Kort nozzle to the propeller may be about 35
and the
optimal predetermined optimal maximum effective angle of the rudder to the
wash exiting the
Kort nozzle may be about 25 and therefore about 60 to the propeller. The
mechanism that
pivots the Kort nozzle and the rudder simultaneously may comprise a linkage
that
interconnects the Kort nozzle and the rudder, the linkage having a geometry
selected to pivot
the rudder at a predetermined angular rate greater than the rudder so that the
rudder and Kort
nozzle arrive simultaneously at their predetermined optimal maximum angles.
The present invention also provides a method for steering a watercraft having
a
steerable Kort nozzle mounted about a propeller that directs wash from the
propeller, and a
nozzle mounted behind the Kort nozzle that reacts with the wash exiting the
Kort nozzle to
produce a second steering force, the method comprising the steps of: (a)
pivoting said Kort
nozzle in a first direction at a first rate in response to a helm input; (b)
pivoting the rudder in
said first direction at a second, greater rate in response to the helm input;
(c) to a
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predetermined optimal angle of the Kort nozzle to the wash generated by the
propeller and a
predetermined optimal maximum angle of the rudder to the wash exiting the Kort
nozzle.
The invention also provides a method for pivoting a steerable Kort nozzle
mounted
about a propeller that directs wash from the propeller to generate a first
turning force, in
conjunction with a rudder mounted behind the Kort nozzle that reacts with the
wash exiting
the Kort nozzle to produce a second turning force, the method comprising the
steps of: (a)
pivoting said Kort nozzle in a first direction at a first rate in response to
a helm input; and (b)
pivoting the rudder in said first direction at a second, greater rate in
response to the helm
input; (c) to a predetermined optimal angle of the Kort nozzle to the wash
generated by the
propeller and a predetermined optimal maximum angle of the rudder to the wash
exiting the
Kort nozzle.
These and other features and advantages of the present invention will be more
fully
appreciated from a reading of the following detailed description with
reference to the
accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a combination rudder and Kort nozzle steering
system
in accordance with the present invention, showing the system in relation to
the shaft and
propeller of an example vessel;
FIG. 2 is a series of top schematic and cross-sectional views showing the
relationship
between the linkage components and the Kort nozzle and rudder of FIG. 1 when
in different
turning configurations;
FIG. 3 is a side, cross-sectional view of the steering system of FIG. 1,
showing the
structure of the assembly and the relationship to the propeller and stern of
the vessel in greater
detail;
FIG. 4 is an enlarged side, cross-sectional view of the rudder and nozzle
posts and
associated linkage of the steering system of FIG. 1;
FIG. 5 is a top plan view of the nozzle and rudder tillers of the linkage of
the steering
system of FIG. 1, showing the dimensional and angular relationships thereof in
greater detail;
FIG. 6 is a series of plan views of the hydraulic steering ram and linkage and
tillers of
the steering system of FIG. 1, showing the relationship of the components in
different steering
positions;
FIG. 7 is a schematic view of the linkage and tillers of FIG. 6, illustrating
the manner
in which the elongate steering ram pivots as the linkage and tillers move
between steering
positions;
FIG. 8 is a top schematic view of a steering mechanism of another system in
accordance with another embodiment of the invention, in which simultaneous
rotation of the
Kort nozzle and rudder posts at a predetermined ratio is achieved employing
individual
hydraulically actuated rams mounted to the nozzle and rudder tillers;
FIG. 9 is a top schematic view of a steering mechanism of another system in
accordance with another embodiment of the invention, in which simultaneous
rotation of the
Kort nozzle and rudder posts at a predetermined ratio is achieved employing
individual
hydraulically electrically actuated rams mounted to the nozzle and rudder
tillers;
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FIG. 10 is a top schematic view of a steering mechanism of another system in
accordance with the invention, in which simultaneous rotation of the Kort
nozzle and rudder
posts at a predetermined ratio is achieved by a belt-and-pulley system as
opposed to a linkage
system as shown in FIGS. 1-7;
FIG. 11 is a top schematic view, similar to FIG 8, showing a steering
mechanism of
another system in accordance with the invention, in which rotation of the Kort
nozzle and
rudder posts at a predetermined ratio is achieved by a sprocket-and-chain
mechanism; and
FIG. 12 is a top schematic view of a steering mechanism of another system in
accordance with the invention, in which simultaneous rotation of the Kort
nozzle and rudder
posts at a predetermined ratio is achieved by direct gear mechanism.
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DETAILED DESCRIPTION
FIG. 1 shows a steering system 10 in accordance with a preferred embodiment of
the
present invention. As can be seen, the steering system includes both a
steerable Kort nozzle
12 and a rudder 14, that are pivotable on upper and lower post and bearing
sets 16, 18 and 20,
22. The steerable Kort nozzle forms a shroud about the propeller of the
watercraft--mounted
on the end of drive shaft 24--so as to direct the wash generated by the
propeller, with the
rudder being mounted rearward of the Kort nozzle so as to react the wash
exiting the latter.
A linkage 30 mounted to the two tiller posts 32, 34 interconnects the nozzle
and
rudder. The linkage includes a nozzle tiller 36 having a forward arm that is
mounted to the
end of a laterally-extending steering ram 38, and first and second rearwardly-
angled outer
arms that are connected to corresponding outwardly-projecting arms of a rudder
tiller 40 by
first and second pivotably connected link rods 44.
Extension/retraction of ram 38
consequently acts to pivot the nozzle and rudder simultaneously in one
direction and then the
other, but at different rates and angles to one another as dictated by the
geometry of the
linkage.
As will be described in greater detail below, the geometry of the linkage acts
to pivot
the rudder 14 at a rate and to an angle greater than that of the Kort nozzle.
For example,
when, as is shown in FIG. 2, the helm is centered both the nozzle and rudder
are aligned with
the propeller/shaft and centerline of the craft and therefore there is no
turning effect.
However, when hard over to starboard or port the Kort nozzle is aligned at an
angle of about
35 to the shaft while the rudder is turned about 20 further to a total of
about 60 to the shaft.
In this manner, the nozzle redirects the flow from the propeller by an amount
at or near an
optimal maximum with the propeller, while the rudder is angled at or near an
optimal
maximum relative to the wash leaving the nozzle. A higher degree of
maneuverability is thus
achieved than is possible with either a steerable Kort nozzle or rudder alone.
FIGS. 3-4 show the steering mechanism and its relationship to the hull and
propeller
of the vessel in greater detail. As can be seen in FIG. 3, the steering
assembly 10 is mounted
to the stern section 42 of the craft 34, with the Kort nozzle 12 and rudder 14
being pivotally
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supported on parallel vertical axes 44, 46 by upper bearing assemblies 16, 18
and lower
bearing assemblies 20, 22, the latter being supported in parallel relationship
by a lower spacer
bar 48.
The propeller 50 of the craft is received in the tunnel 52 of the Kort nozzle,
with the
blade tips of the propeller preferably being in a close fitting relationship
with the inner
surface 54 of the nozzle tunnel to achieve a high degree of efficiency. The
intake end 56 of
the nozzle is preferably somewhat flared or bell-shaped a shown. Wash from the
propeller in
turn exits the discharge end 58 of the nozzle and passes over the generally
flat, panel-shaped
body 60 of rudder 14, from the leading edge 62 to the trailing edge 64
thereof. The spacing
between the discharge end 58 of the nozzle and the leading edge 62 of the
rudder is preferably
the minimum necessary to provide clearance between the nozzle and rudder at
the port and
starboard limits, in order to maximize wash that is directed over the rudder
and also to
minimize length of the assembly.
FIG. 4 shows the upper bearing assemblies 16, 18 and associated linkage 30 in
greater
detail. As can be seen therein, the Kort nozzle bearing assembly 16 includes a
tubular port 70
installed through the hull 42 of the craft. The rudder bearing assembly 18
includes a similarly
installed rudder port 72, the rudder port and associated components being
sized somewhat
smaller due to the greater mass of the Kort nozzle relative to the rudder.
UHMW bearings 74,
76 are installed around the nozzle and rudder shafts 80, 82 at the bottoms of
the ports, and are
held against the ends of the ports by washers 84, 86 welded to the shafts. The
main nozzle
and rudder bearings 90, 92 are in turn installed in the upper ends of the
ports 70, 72, and are
held in place by bolts (not shown) passing through radial flanges at the upper
ends of the
ports. UHMW bearings 94, 96 are installed around the shafts above the main
bearings and
below the nozzle and rudder tillers 36, 40, with key stop washers 100, 102
being sandwiched
between the tillers and the UHMW bearings. The tillers are in turn keyed onto
their
respective shafts by cooperating keys and key ways 104, 106.
As can be seen with further reference to FIG. 4 and also FIG. 1, the outwardly-
extending arms of the nozzle and rudder tillers are connected by starboard and
port linkage
rods 110a, 110b that are mounted to the arms by heim joints 112 and retention
collars 114, the
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rods preferably being threaded to permit a degree of adjustment. The linkage
and the bearings
thus cooperate to pivot the Kort nozzle and rudder simultaneously in one
direction and the
other as the hydraulic rod is extended and retracted.
As described above, the turning rates and angles of the nozzle and rudder are
dictated
by the geometry of the linkage. FIG. 5 illustrates the geometry of an example
system in
accordance with a preferred embodiment of the invention, the example
dimensions and angles
being set forth in the following Table A, making reference to the
corresponding letters in the
drawing.
TABLE A
DIMENSION /ANGLE
a 15 inches
7.71 inches
4.987 inches
7.846 inches
1.45 inches
.938 inches
14.742 inches
79.4
79.4
Dimension "g"--the distance between the end points of the lateral arms 116a-b
and
118a-b of the nozzle and rudder tillers 36, 40--is controlled by the length of
the
interconnecting linkage rods 110a-b. It will be understood that the dimensions
and angles
shown in FIG. 5 and listed in Table A are provided by way of illustration
rather than
limitation and may vary depending on the type and size of the installation and
other design
factors.
FIG. 2 illustrates operation of the linkage and the turn angles of the nozzle
and rudder
in greater detail. The upper row of drawings in FIG. 2 illustrates
schematically the
relationship between the nozzle and rudder tillers in turning the assembly
from side-to-side,
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while the lower row shows the relationship and angles of the nozzle and rudder
as controlled
by the linkage.
As can be seen in the upper row in FIG. 2, the linkage connection points on
the nozzle
tiller 36 fall on a circle 120 having a diameter somewhat larger than the
corresponding circle
122 containing the connection points on the rudder tiller 40. Since the
connection points are
joined by the fixed-length rods 110a, 110b (see FIG. 1) of the linkage,
rotation of the nozzle
tiller will cause the rudder tiller to rotate in the same direction but at a
faster rate and to a
greater angle as compared with the nozzle tiller; by way of example, the
diameter of circle
122 in the illustrated embodiment may suitably be about 0.65 that of circle
120. Thus, as the
nozzle tiller is rotated in a counterclockwise direction (as viewed from
above) by the helm
being turned to starboard as indicated by arrow 124, the starboard rod of the
linkage is drawn
forward as indicated by arrow 126 and the port rod 128 is driven aft, causing
the rudder tiller
to also pivot in a counterclockwise direction but at a faster rate; likewise,
in response to the
nozzle tiller being rotated in a clockwise direction by the helm being turned
to port, as
indicated by arrow 130, the port linkage rod is drawn forward as indicated by
arrow 132 and
the starboard rod is driven aft as indicated by arrow 134, causing the rudder
tiller to also
rotate in a clockwise direction but again at a faster rate than that of the
nozzle tiller. The
rudder turns at a rate about two times that of the nozzle; for example, an
overall ratio of about
1.714 between the turning rates of the rudder and Kort nozzle produces the
desired angular
relationship described below.
The lower row in FIG. 2 shows the relationship of the nozzle and rudder with
the
linkage, first centerline and then turned hard to starboard and to port as in
the corresponding
views in the upper row. As can be seen, when the steering is centered the
nozzle and rudder
are both in line with the shaft and propeller, and hence do not exert a
turning action. Then, as
the helm is turned to starboard, the nozzle and rudder pivot to an increasing
angle to the
propeller to generate a steering effect, the rudder pivoting at a faster rate
than the nozzle as
described above. In so doing, the nozzle directs the wash generated by the
propeller to
produce thrust at an angle to the centerline, and the wash exiting the nozzle
reacts with the
rudder to produce additional force at an angle to the centerline, so that the
Kort nozzle and
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rudder in combination produce a greater turning force than would either
working alone.
Furthermore, with the steering hard over as shown the geometry of the linkage
aligns the
nozzle at or near an optimal maximum angle relative to the propeller and also
aligns the
rudder at or near an optimal maximum angle relative to the wash exiting the
nozzle, so that
the nozzle and rudder work in combination to generate turning force. In the
illustrated
embodiment the optimal maximum angle for the Kort nozzle has been found to be
about 35
to the propeller centerline, and with that rudder being about 25 to the
centerline of the nozzle
and therefore a total of about 60 to the propeller, as established by the
geometry of the
linkage as described above. Moreover, the geometry of the linkage results in
the nozzle and
rudder arriving at the optimum effective angles simultaneously. Turning the
steering hard to
port likewise produces angles and generates a steering effect in the opposite
direction, as also
shown in FIG. 2. It will be understood that in some embodiments the Kort
nozzle and rudder
may be pivoted to optimal maximum angles greater (or lesser) than those set
forth above,
however, with the illustrated embodiment the above limits have been found to
provide
maximum maneuverability without excess turbulence and risk of stalling.
A significant advantage of the "two-arm" configuration of the linkage 30, with
connection arms and linkage rods on both sides of the tillers, is that it
provides balanced push-
pull forces on both sides of the tillers, whether turned one way or the other.
The balanced
push-pull forces improve the ability of the steering to overcome resistance
due to forces
acting on the rudder, especially at high steering angles and at high power
levels/high speeds.
The forces result not only from thrust from the nozzle but also from movement
of the craft
through the water; for example, when operating at high power/high speed
astern, the rudder
when hard over may be subjected to loading such that it strongly resists
moving back towards
centerline. In addition, mechanical advantage may be reduced at high steering
angles. The
balanced forces provided by the two-arm linkage of the present invention
allows the rudder to
be returned towards centerline in a reliable and responsive manner even when
subject to
heavy resistance, while maintaining reasonable loads on the linkage and the
ram or other
steering actuator.
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As was described above, rotation of the tillers and therefore the Kort nozzle
and
rudder in the illustrated embodiment is produced by extension and retraction
of hydraulic
steering ram 38. While other forms of steering actuators may be employed, such
as steering
cables, stepper and servo motors with or without linkages, ball screws and
rack-and-pinion
mechanisms, to give just a few examples, hydraulic rams possess advantages
that have made
them a preferred form of a steering actuator for many work skiffs and other
vessels. As a
feature to prevent the steering ram from driving the nozzle and rudder beyond
the maximum
angles described above, and also to prevent the linkage from over-centering,
steering system
includes a stop assembly that arrests rotation of the tiller at the
predetermined angles. As
10 can be seen most clearly in FIG. 6, the stop assembly includes fixed
starboard and port stop
plates 140a, 140, that extend upwardly from a base plate 142 and are supported
by transverse
gusset plate 144. The stop plates 140a-b are positioned and angled to make
contact with the
corresponding outwardly-extending arms of the rudder tiller when the steering
mechanism is
turned hard to starboard and hard to port, as shown in FIG. 6, thereby
arresting the nozzle and
rudder at the designed maximum angles and preventing over-centering of the
linkage by the
ram.
The end of the ram 38 that is mounted to the forward arm 150 of the rudder
tiller
swings through an arch as the ram is extended and retracted, in the circle 120
in the example
shown in FIG. 2. The pivot connection with the arm and a gimbal 146 at the
other end of the
steering ram permit the ram to swing back and forth as this is done.
Therefore, as is shown in
FIG.7, the end of the steering ram pivots on the gimbal as indicated at 152 so
that the long
axis of the ram swings through a range of angles as indicated at 154, while
the pivot
connection at the other end of the ram moves together with the forward arm 150
of the tiller.
FIGS. 8-12 show additional embodiments in which the mechanism that achieves
coordinated, simultaneous rotation of the nozzle and rudder are in forms other
than the
linkage mechanism of the embodiment illustrated in FIGS. 1-7.
FIGS. 8-9 illustrated embodiments in which the mechanism utilizes hydraulic
rams
attached to tillers that are in turn mounted to the rotatable nozzle and
rudder posts 44, 46. In
the system 160 shown in FIG. 8, nozzle and rudder rams 162, 164 are mounted on
opposite
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sides of the centerline, with the ends of the extensible rods thereof being
mounted to tiller
arms 166, 168 mounted on the nozzle and rudder posts 44, 46. Simultaneous
pivoting of the
nozzle and rudder in the same direction (i.e., port or starboard) is thus
achieved by extending
one of the hydraulic cylinders 162-164 and retracting the other at the same
time. Electric
actuators 170, 172 responding to inputs from the helm via wiring 174, 176 or
other
electrical/electronic connection coordinate the extension/retraction of the
rams to achieve and
maintain the desired ratio of turning and relative angles between the two, as
described above,
employing suitable programming or electromechanical controls; for example, the
nozzle can
be pivoting through 35 of rotation on either side of the centerline while the
rudder is pivoted
through 60 of rotation. The actuators may also be operated to pivot the
nozzle and rudder in
an adjusted or different relationship, or independently, if desired. System
180 shown in FIG.
9 similarly employs extensible/retractable hydraulic cylinders 182, 184,
attached to tiller arms
186, 188 mounted to the nozzle and tiller posts 44, 46. In this instance,
hydraulic pressure is
applied to the rams via a hydraulic line 186 connected to a hydraulic actuator
188, with
valving in the actuator, in the supply line or at the rams themselves
proportioning the flow to
achieve the coordinated greater rotation and angles between the nozzle and
rudder. It will be
understood that in some embodiments other forms of controllably
extensible/retractable drive
members may be employed in place of or in conjunction with the hydraulic rams
of the
illustrated embodiments, such as linear motors, rack-and-pinion mechanisms,
ball screws, and
other forms of linear actuators, for example.
FIGS. 10-11 in turn show embodiments in which the mechanism that rotates the
nozzle and rudder utilizes forms of flexible power transmission, rather than
the linkage and
extensible/retractable ram mechanisms described above.
The system 190 illustrated in FIG. 10, for example, utilizes a cable and
pulley
mechanism, with the relative rate of rotation/angular relationship between the
Kort nozzle and
rudder being maintained by the ratio established the relative sizes of pulleys
192, 194
mounted to nozzle and rudder posts 44, 46. Power is applied to the mechanism
from the helm
input, such as by a motor (not shown) or manually operable wheel or tiller,
via a drive sheave
196. The drive sheave is interconnected with a driven sheave 198 on the nozzle
pulley 192 by
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a cable or belt 200, the sheaves 196, 198 having an approximate 1:1 ratio in
the illustrated
embodiment. Driven sheave 198 is keyed onto the nozzle post 44 together with
the pulley
sheave 192, so that rotation by drive sheave 196 results in rotation of both
the nozzle and
pulley sheave 192. A second cable or belt 202 is routed over and interconnects
the nozzle and
rudder pulley sheaves 192, 194, so that rotation of the nozzle pulley results
in rotation of the
rudder pulley, the latter being keyed onto the rudder post 46. A spring
tensioner 204 serves to
maintain the cable or belt in working engagement with the two pulley sheaves.
Therefore,
rotation of the drive sheave 196 in one direction causes the nozzle and rudder
pulley sheaves
to rotate simultaneously in the same direction, but at different rates owing
to the difference in
sizes between the nozzle and rudder pulleys. To achieve the desired relative
rates of rotation
and angular relationship, the nozzle sheave 192 is sized larger in diameter
than the rudder
pulley sheave by a predetermined amount; for example, the nozzle pulley
springs through a
first, smaller angle 01 (e.g., 35 ) side-to-side in response to operation of
the drive pulley 196,
while the rudder pulley sheave rotates through a relatively greater angle 02
(e.g., 60 to the
centerline), achieving the nozzle-rudder relationship described above.
The system 210 shown in FIG. 11 is generally similar to that of FIG. 10,
except for
using a chain-and-sprocket mechanism rather than pulleys and cables/belts.
Analogous to the
arrangement in FIG. 10, drive is inputted to system 210 by a drive sprocket 12
that is
connected to a driven sprocket 214 by a drive chain 216, the driven sprocket
being keyed onto
the nozzle post 44. A larger diameter nozzle sprocket 218 is also keyed onto
the nozzle post,
and is connected to a smaller diameter sprocket 220 on rudder post 46 by a
second drive chain
222, tension being maintained on the chain by a spring tensioner 224. The
relative rates of
rotation and angular relationship between the nozzle and rudder are
established by the ratio
between sizes of the sizes of the sprockets 218, 220, similar to the
corresponding pulley
sheaves of the system in FIG. 10.
FIG. 12, in turn, shows a system 230 employing a straight gear mechanism. A
reversible drive gear 232 is rotated in one direction or the other in response
to a helm input,
and is located intermediate a larger diameter nozzle gear 234 mounted to the
nozzle post 44
and a smaller diameter rudder gear 236 mounted to the rudder post 46. Gears
232, 234, 236
CA 02893382 2015-06-01
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may be of any suitable type, such as spur gears, for example. The reversible
drive gear 232 is
in direct engagement with both the nozzle gear 234 and the rudder gear 236, so
that rotation
of the drive gear in one direction or the other (e.g., clockwise) drives both
gears 234, 236
simultaneously in the opposite direction (e.g., counterclockwise). Similar to
the mechanisms
in FIGS. 10 and 11, the relative diameters of gears 234, 236 establishes the
ratio at which the
nozzle and rudder are pivoted, so as to maintain the desired rate of turning
and angular
relationship.
It is anticipated that other forms of steering mechanisms that serve to rotate
and
establish the angular relationship between the Kort nozzle and rudder in the
desired manner
may occur to those skilled in the relevant art, in addition to those that are
illustrated in
FIGS. 8-12 and FIGS. 1-7.
It will be understood that the scope of the appended claims should not be
limited by
particular embodiments set forth herein, but should be construed in a manner
consistent with
the specification as a whole.
