High maneuverability steering system for work boats and other watercraft

Abstract

A combined Kort nozzle and rudder steering system for vessels requiring a high degree of maneuverability. A Kort nozzle is mounted around the propeller to direct the wash to generate a first turning source, and a rudder is mounted behind the Kort nozzle to react with the wash exiting the nozzle to produce a second turning force. The nozzle and rudder are pivoted in the same directions simultaneously, but with the rudder being pivoted at a faster rate than the nozzle. The nozzle is pivoted to an optimal maximum angle relative to the wash generated by the propeller and the rudder is pivoted to an optimal maximum angle to the wash exiting the nozzle.

Description

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Ser. 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 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.

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 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 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.

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;

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.

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 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 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
b 7.71 inches
c 4.987 inches
d 7.846 inches
e 1.45 inches
f .938 inches
g 14.742 inches
h 79.4°
i 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, 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 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.

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 10 includes a stop assembly that arrests rotation of the tiller at the predetermined angles. As 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 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 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 θ₁ (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 θ₂ (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 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.

Claims

1. A steering apparatus for a water-borne vessel, said steering apparatus comprising:

a steerable Kort nozzle mounted above a propeller that directs wash from the propeller to generate a first turning force;

a propeller mounted behind said Kort nozzle that reacts with said wash of said propeller exiting said Kort nozzle to produce a second steering force; and

a mechanism that pivots said Kort nozzle and said rudder in the same direction simultaneously, with said rudder pivoting at an angle greater than said Kort nozzle;

to a predetermined optimal maximum angle of said Kort nozzle to said wash generated by said propeller and a predetermined optimal maximum angle of said rudder to said wash exiting said Kort nozzle.

2. The steering apparatus of claim 1, wherein said predetermined optimal maximum angle of said Kort nozzle to said propeller is about 35°, and said predetermined optimal effective angle of said rudder to said discharge of said Kort nozzle is about 25° and therefore about 60° to said propeller.

3. The steering apparatus of claim 2, wherein said mechanism that pivots said Kort nozzle and said rudder comprises:

a linkage that interconnects said Kort nozzle and said rudder, said linkage having a geometry selected to pivot said rudder at a predetermined angular rate greater than said Kort nozzle so that said rudder and said Kort nozzle arrive substantially simultaneously at said predetermined optimal maximum angles.

4. The steering apparatus of claim 3, wherein said linkage that interconnects said Kort nozzle and said rudder comprises:

a first tiller member mounted to a vertical pivot shaft of said Kort nozzle;

a second tiller member mounted to a vertical pivot shaft of said rudder;

said first and second tiller member each having connection portions extending laterally of said pivot shafts;

first and second linkage rods mounted to said connection portions of said tiller members on opposite sides of said pivot posts;

forward ends of said linkage rods being mounted to said connection portions of said nozzle tiller member at pivot connections spaced relatively farther from said pivot post of said Kort nozzle, and rearward ends of said linkage rods being mounted to said connection portions of said rudder pivot post at pivot connections spaced relatively closer to said rudder pivot post;

so that in response to rotation of said Kort nozzle post by said Kort nozzle tiller said rudder pivot post is rotated at a greater angular rate by said rudder tiller.

5. The steering apparatus of claim 4, wherein said Kort nozzle tiller comprises:

an extension portion having an end of a steering ram mounted thereto, so that said Kort nozzle tiller and said rudder tiller rotate in a first direction in response to extension of said steering ram, and rotate in an opposite direction in response to retraction of said steering ram.

6. The steering apparatus of claim 2, wherein said mechanism that pivots said Kort nozzle and said rudder comprises:

a flexible power transmission interconnecting said Kort nozzle and said rudder, said flexible power transmission having a ratio selected to pivot said rudder at a predetermined angular rate greater than said Kort nozzle so that said rudder and said Kort nozzle arrive substantially simultaneously at said predetermined optimal maximum angles.

7. The steering apparatus of claim 6, wherein said flexible power transmission that interconnects said Kort nozzle and said rudder comprises:

a pulley and cable mechanism.

8. The steering apparatus of claim 6, wherein said flexible power transmission that interconnects said Kort nozzle and said rudder comprises:

a sprocket and chain mechanism.

9. The steering apparatus of claim 2, wherein said mechanism that pivots said Kort nozzle and said rudder comprises:

a gear train interconnecting said Kort nozzle and said rudder, said gear train having a ratio selected to pivot said rudder at a predetermined angular rate greater than said Kort nozzle so that said rudder and said Kort nozzle arrive substantially simultaneously at said predetermined optimal maximum angles.

10. A steering 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 said Kort nozzle that reacts with said wash exiting said Kort nozzle to produce a second turning force, said apparatus comprising:

a mechanism that pivots said Kort nozzle and said rudder in a same direction simultaneously and with said rudder pivoting at an angular rate greater than said Kort nozzle;

a predetermined optimal maximum angle of said Kort nozzle to said wash generated by said propeller and a predetermined optimal maximum angle of said rudder to said wash exiting said Kort nozzle.

11. The steering apparatus of claim 10, wherein said predetermined optimal maximum angle of said Kort nozzle to said wash generated by said propeller is about 35°, and said predetermined optimal maximum effective angle of said rudder to said wash exiting said Kort nozzle may be about 25° and therefore about 60° to said propeller.

12. The steering apparatus of claim 10, wherein said mechanism that pivots said Kort nozzle and said rudder simultaneously may comprise a linkage that interconnects said Kort nozzle and said rudder, said linkage having a geometry selected to pivot said rudder at a predetermined angular rate greater than said rudder so that said rudder and said Kort nozzle arrive simultaneously at said predetermined optimal maximal angles.

13. A method for steering a water borne vessel having a steerable Kort nozzle mounted about a propeller that directs wash from said propeller with said wash exiting said Kort nozzle to produce a second turning force, said method comprising the steps of:

pivoting said Kort nozzle in a first direction at said first rate in response to a helm input;

pivoting said rudder in said first direction at a second, greater rate in response to said helm input;

to a predetermined optimal angle of said Kort nozzle to said wash generated by the propeller and a predetermined optimal maximum angle of said rudder to said wash exiting said Kort nozzle.

14. A method for pivoting a steerable Kort nozzle mounted about propeller that directs wash from the propeller to generate a first turning force in conjunction with a rudder mounted behind said Kort nozzle that reacts with said wash exiting said Kort nozzle to produce a second turning force, said method comprising the steps of:

pivoting said Kort nozzle in a first direction at a first rate in response to a helm input; and

pivoting said rudder in said first direction at a second, greater rate in response to said helm input;

to a predetermined optimal angle of said Kort nozzle to said wash generated by the propeller and a predetermined optimal maximum angle of said rudder to the wash exiting said Kort nozzle.