Steering system for watercraft

A steering system is provided for watercraft having a hull and first and second thrust producing devices capable of providing forward or reverse thrust relative to the hull, wherein the first and second thrust producing devices provide thrust along first and second thrust axes, respectively, comprising a first rudder assembly positioned forward of the first thrust producing device, wherein the first rudder assembly is pivotally connected beneath the hull; a second rudder assembly positioned forward of the second thrust producing device, wherein the second rudder assembly is pivotally connected beneath the hull; first actuation device operatively connected to the first rudder assembly for actuating a change in the rotational position of the first rudder assembly; second actuation device operatively connected to the second rudder assembly for actuating a change in the rotational position of the second rudder assembly; and a control device operatively connected to the first and second actuation devices for controlling the rotational position of the first and second rudder assemblies independent of one another, the control device further including a selector for selectively defining the operation of the first rudder assembly or the second rudder assembly in one or more predetermined configurations.

BACKGROUND OF THE INVENTION
 I. Field of the Invention
 The present invention relates generally to steering systems for watercraft,
 and more particularly to the definition and control of predetermined
 rudder configurations used in maneuvering watercraft.
 II. Description of Prior Art
 Flanking rudders, as the term is used herein, are rudders which are located
 forward of the main thrust producing device(s), typically propellers or
 "screws," for a particular watercraft. Whether the watercraft includes a
 single screw or several, it would be common to employ a flanking rudder
 directly in front of each of the screws. The basic concept of flanking
 rudders has been understood at least as early as the 1800's when such
 rudders were used in connection with paddle wheeled steamboats. At the
 present time, flanking rudders are commonly installed on towboats that
 push barges on the inland river systems of North and South America. The
 primary function of flanking rudders is to provide the watercraft with a
 means of steering as the watercraft travels in reverse. For example, as
 the screws or other thrust-producing device directs reverse thrust toward
 the front of the watercraft, the flanking rudders are employed in tandem
 to steer the watercraft in the desired direction. This is particularly
 useful in the case of utility boats, such as tug boats, which routinely
 change from forward and reverse thrust in assisting larger ships, such as
 oil tankers and cargo ships, into a docking position in a river; with
 towboats that push barges on inland rivers and coastal waters; and,
 seagoing vessels.
 Although the presence of flanking rudders operating in tandem mode is a
 significant enhancement to the maneuverability of any of these types of
 vessels, there are situations where greater control over the operation of
 the flanking rudders would be highly desirable. For example, in many
 instances, tug boats must attach to one side of a ship having a deeper
 draft than the tug boat. When reverse thrust is applied over conventional
 flanking rudders to pull the larger ship, the thrust is necessarily
 directed against the hull of the larger ship. The undesirable effect is
 for the stem of the tug boat to be urged away from the ship, thus losing
 some control over the larger ship. While lines can be used to tie the tug
 boat to the larger ship, this is an imperfect solution. Ideally, the
 flanking rudders would be subject to independent control to allow the
 innermost flanking rudder to remain parallel to the keel of the ship,
 while the outermost flanking rudder is used to direct thrust in the
 desired direction. Also, once independent control of the flanking rudders
 is implemented, it would be quite useful to operate the flanking rudders
 in a converging or diverging mode, such that the flanking rudders can be
 placed in a flared position for braking when the vessel is moving forward
 or moving astern, and for redirection of thrust. Consequently, the present
 invention is provided as a solution to the foregoing problems by
 illustrating a novel flanking rudder steering system capable of being
 controlled in a variety of predefined operational modes by one or more
 controlling devices.
 SUMMARY OF THE INVENTION
 It is therefore an object of this invention to provide a steering system
 for watercraft which employs flanking rudders for use in connection with
 reverse thrust.
 It is also an object of this invention to provide a steering system for
 watercraft which allows independent control of the flanking rudders.
 It is a further object of this invention to provide a steering system for
 watercraft which permits the selection of one or more predetermined rudder
 control configurations useful to operators in the maneuverability of the
 watercraft.
 Yet another object of this invention is to provide a steering system for
 watercraft which employs flanking rudders and an accompanying control
 system which be retrofitted to existing watercraft.
 These and other objects and advantages of the present invention will no
 doubt become apparent to those skilled in the art after having read the
 following description of the preferred embodiment which are contained in
 and illustrated by the various drawing figures.
 Therefore, in a preferred embodiment, a flanking rudder system is provided
 for watercraft having a hull and first and second thrust producing devices
 capable of providing forward or reverse thrust relative to said hull,
 wherein said first and second thrust producing devices provide thrust
 along first and second thrust axes, respectively, comprising a first
 rudder assembly positioned forward of said first thrust producing device,
 wherein said first rudder assembly is pivotally connected beneath said
 hull; a second rudder assembly positioned forward of said second thrust
 producing device, wherein said second rudder assembly is pivotally
 connected beneath said hull; first actuation means operatively connected
 to said first rudder assembly for actuating a change in the rotational
 position of said first rudder assembly; second actuation means operatively
 connected to said second rudder assembly for actuating a change in the
 rotational position of said second rudder assembly; and control means
 operatively connected to said first and second actuation means for
 controlling the rotational position of said first and second rudder
 assemblies independent of one another, said control means further
 including selection means for selectively defining the operation of said
 first rudder assembly or said second rudder assembly in one or more
 predetermined configurations. While it is generally contemplated that the
 first and second thrust producing devices are propellers, it is also
 possible that the thrust may be produced by other means.
 In one embodiment, said first rudder assembly and said second rudder
 assembly each include a single rudder. However, in an alternate
 embodiment, said first rudder assembly and said second rudder assembly
 each include a pair of rudders connected to said first actuation means and
 said second actuation means, respectively, so as to enable said pair of
 rudders to remain parallel at all rotational positions. Although not
 specifically required, said first actuation means and said second
 actuation means each comprise an electro-hydraulic mechanical linkage
 assembly.
 The control means comprises at least one control lever operatively
 connected to said first actuation means and said second actuation means,
 respectively, to control the rotational position of either said first
 rudder assembly or said second rudder assembly. Furthermore, the selection
 means comprises a console adjacent to said control means, wherein said
 console includes an electrical switching device having a plurality of
 selectable settings corresponding to said predetermined configurations.
 One of said predetermined configurations defines said first rudder assembly
 and said second rudder assembly to operate in tandem, such that operation
 of said control means causes said first and second rudder assemblies to
 remain parallel to one another. Another of said predetermined
 configurations defines said first rudder assembly to remain fixed in a
 rotational position parallel to said first thrust axis of said first
 thrust producing device, and wherein the rotational position of said
 second rudder assembly is controlled by said control means. Another of
 said predetermined configurations defines said second rudder assembly to
 remain fixed in a rotational position parallel to said second thrust axis
 of said second thrust producing device, and wherein the rotational
 position of said first rudder assembly is controlled by said control
 means. Yet another of said predetermined configurations defines said first
 rudder assembly and said second rudder assembly to operate opposed to one
 another, wherein the rotational position of said first rudder assembly and
 said second rudder assembly are controlled by said control means.
 Also, in a preferred embodiment, a method is provided for steering a
 watercraft having a hull and first and second thrust producing devices
 capable of providing forward or reverse thrust relative to said hull,
 wherein said first and second thrust producing devices provide thrust
 along first and second thrust axes, comprising: (a) providing said
 watercraft with a first rudder assembly positioned forward of said first
 thrust producing device, a second rudder assembly positioned forward of
 said second thrust producing device, first actuation means operatively
 connected to said first rudder assembly for actuating a change in the
 rotational position of said first rudder assembly, second actuation means
 operatively connected to said second rudder assembly for actuating a
 change in the rotational position of said second rudder assembly, and
 control means operatively connected to said first and second actuation
 means for controlling the rotational position of said first and second
 rudder assemblies independent of one another, said control means further
 including selection means for selectively defining the operation of said
 first rudder assembly or said second rudder assembly in one or more
 predetermined configurations; (b) selecting one of said predetermined
 configurations from said selection means; and (c) operating said first and
 second thrust producing devices to direct reverse thrust against said
 first and second rudder assemblies in said predetermined configuration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Turning now to FIG. 1A, a top schematic view is shown of the stem 1 of a
 twin-screw watercraft depicting, in a preferred embodiment, the relative
 positions of the screws 2,3, the main steering rudders 4,5, and the
 flanking rudder assemblies 6,7 as the watercraft travels forward under
 forward thrust. For the purposes herein, the screws 2,3 are only one
 specific example of a "thrust producing device" for causing water to be
 forcefully moved against the vertical surfaces of a rudder, irrespective
 of whether such rudders are used for main steering or as flanking rudders.
 Persons of ordinary skill in this field will appreciate that some other
 types of devices capable of producing a thrust may be equally applicable
 to the present invention. The screws 2,3 shown in FIG. 1A are depicted as
 pointing toward the bow of the watercraft, meaning that the watercraft is
 traveling forward as the thrust is directed aft past the main steering
 rudders 4,5. Each screw 2,3 includes a thrust axis 8,9 which represents
 the axis through which the force of the water is directed relative to the
 hull. It should also be noted that the principles illustrated herein are
 applicable for single-screw vessels, twin-screw vessels, and triple-screw
 vessels, including vessels having any number of thrust producing devices
 that employ rudders for steering the watercraft.
 With respect to a single-screw application, such a watercraft is shown
 traveling in a forward direction in FIG. 1B and including a single thrust
 producing device, or screw 10, positioned centrally along the vessel's
 longitudinal axis 11, a main steering rudder 12, and a pair of flanking
 rudders 13,14. A further explanation of the present invention with respect
 to both single-screw and twin-screw arrangements will now be given. Unless
 otherwise indicated, operation of the flanking rudders 13,14 in a
 single-screw application are identical to operation of the first and
 second flanking rudder assemblies 6,7 of the twin-screw application.
 In the twin-screw version of the invention depicted in FIG. 1A, each
 flanking rudder assembly 6,7 is positioned forward of their respective
 screws 2,3, wherein each flanking rudder assembly 6,7 is comprised of a
 pair of rudders 16,17 and 18,19, respectively. Rudders 16,17 of the first
 flanking rudder assembly 6 are pivotally connected beneath the hull of the
 vessel via shafts 20,21. Similarly, rudders 18,19 of the second flanking
 rudder assembly 7 are pivotally connected beneath the hull of the vessel
 via shafts 22,23. Rudders 16,17 of first flanking rudder assembly 6
 operate in tandem, meaning that any rotation of rudder 16 is matched by
 rudder 17. Similarly, rudders 18,19 of second flanking rudder assembly 7
 operate in tandem, meaning that any rotation of rudder 18 is matched by
 rudder 19. Most importantly, first flanking rudder assembly 6 and second
 flanking rudder assembly 7 are capable of being controlled independently
 of one another. In other words, in the present invention herein described,
 the rotational position of first flanking rudder assembly 6 may be changed
 by the operator of the vessel without regard to the rotational position of
 second flanking rudder assembly 7, and vice versa. The flexibility of this
 type of operation will become clearer in the ensuing explanation of the
 various predetermined settings for the flanking rudder control means 34.
 The rotational position of first and second flanking rudder assemblies 6,7
 is accomplished by first actuation means 24 operatively connected to the
 first flanking rudder assembly 6 and by second actuation means 25
 operatively connected to the second flanking rudder assembly 7. Although a
 wide variety of electrical and mechanical systems may be employed to
 effect such motion, it is preferred that both first and second actuation
 means 24,25 be comprised of a conventional electrical-over-hydraulic
 actuator. One example of such an actuator is schematically depicted in
 FIG. 1E, wherein each set of flanking rudder assemblies 6,7 includes a
 pair of control members 27,28 which are in turn rotatably connected to one
 another by a connecting rod 26 or "jockey bar." The connecting rod 26 is
 rigidly attached to the ram 29 of a hydraulic cylinder 30, while the
 hydraulic cylinder 30 is free to pivot about the surface to which it is
 attached. Suitable hydraulic hoses 31,32 connect the hydraulic cylinder 30
 to an electrically operated hydraulic pump and reservoir 33, as is common
 understood. The hydraulic pump 33 is operated using by electricity
 provided by a local power supply (not shown) located on the vessel.
 Importantly, the operation of the hydraulic pump 33 is controlled by the
 settings of the control means 34 located in the pilot house 60. The
 control means 34 is operatively connected to the first and second
 actuation means 24,25 for controlling the rotational position of the first
 and second rudder assemblies 6,7 independent of one another. In the
 specific embodiment depicted in FIG. 1E, the control means 34 includes a
 suitable electronic package 35 containing logic information regarding the
 various settings to be used by the operator. The electronic package 35 is
 operatively connected to the hydraulic pump 33 of the vessel such that any
 control commands resulting from manipulation of the control means 34 are
 passed through the electronic package 35 and translated into the
 appropriate mechanical output, e.g. changing the rotational position of
 the rudder assemblies 6,7.
 A more detailed and specific embodiment of the control means 34 is depicted
 in FIG. 5. While such control means 34 may comprise a wide variety of
 forms, one example would comprise a base 38 having a control lever 36, an
 angle indicator gauge 37, and a panel of four buttons 41-44. Control lever
 36 operates similarly to the control levers found on many vessels that
 might be retrofitted with the present invention. Simply, a vertical
 position of control lever 36 corresponds to a straight position of the
 flanking rudders assemblies 6,7, meaning that no steerage is being
 applied. As control lever 36 is moved in either direction, the rudder(s)
 being controlled will move to an angular orientation indicated by the
 angle indicator gauge 37. Buttons 41-44 are preferably of the type wherein
 depression of one button deactivates the remaining buttons such that only
 one of the buttons 41-44 can be activated at any given time. The purpose
 of each button 41-44 is to define a predetermined operational mode or
 configuration for the first and second rudder assemblies 6,7. Depending
 upon the particular operational mode selected, the effect of moving the
 control lever 36 will change in accordance with the following modes
 described below.
 Although one example of the assignment of modes to the buttons 41-44 will
 be illustrated, any of the modes described herein may be assigned to any
 one of the buttons 41-44. Button 41 sets the flanking rudder control means
 34 to tandem mode, represented best by FIGS. 2A and 2B with respect to a
 twin-screw vessel. In tandem mode, the rotational position of first and
 second rudder assemblies 6,7 are caused to be the same through their
 entire range of motion, which is the traditional manner in which flanking
 rudders have been operated. In other words, when button 41 is depressed,
 movement of control lever 36 causes identical movement of both first and
 second rudder assemblies 6,7. Button 42 sets the flanking rudder
 assemblies 6,7 to starboard mode, shown in FIG. 3A, which allows control
 lever 36 to control only the starboard rudder assembly 6, while the port
 rudder assembly 7 is automatically maintained in a forward or "zero
 azimuth" position parallel to the keel of the vessel. Similarly, button 43
 sets the flanking rudder assemblies 6,7 to port mode, shown in FIG. 3B,
 which allows control lever 36 to control only the port rudder assembly 7,
 while the starboard rudder assembly 6 is automatically maintained in a
 forward or "zero azimuth" position. Finally, button 44 automatically sets
 the flanking rudder assemblies 6,7 to a flared mode, shown in FIG. 4,
 wherein the rotational position of rudder assemblies 6,7 are caused to
 operate opposed to one another through their entire range of motion. In
 this manner, control lever 36 is used to control the included angle A
 between rudder assemblies 6,7.
 It should be understood and appreciated that the foregoing modes are
 equally applicable to triple-screw vessels. For example, in a triple-screw
 vessel, each of the screws 54-56 includes a flanking rudder assembly
 51-53, such as that shown in FIG. 1C. In tandem mode, all three of the
 flanking rudder assemblies 51-53 are operated parallel to one another. In
 port or starboard mode, only the outermost flanking rudder assembly 51 or
 53, as applicable, is independently controlled by the operator using
 control lever 36, while the central flanking rudder assembly 52 and the
 opposite flanking rudder assembly are held automatically in a forward or
 zero azimuth position. In flared mode, the outermost flanking rudder
 assemblies 51, 53 are operated in opposite rotational modes, while the
 central flanking rudder assembly 52 is held automatically in a forward
 position.
 Likewise, the foregoing modes are applicable to twin-screw vessels having a
 single flanking rudder 71,72 positioned forward of each screw 2,3, as
 illustrated in FIG. 1D. Because of the presence of the shaft for each
 screw 2,3, each flanking rudder 71,72 is typically offset toward the
 outside of the thrust axis 74,75. However, the method of control for these
 flanking rudders 71,72 is otherwise identical to the method described with
 respect to the flanking rudders of FIG. 1A.
 The aforementioned modes of operation, in addition to the traditional
 tandem mode, are particularly advantageous to the operator of a ship
 assist tug boat for the following reasons. A ship that is operated in
 close proximity to another ship having a draft which is deeper than the
 object vessel, such a ship assist tug boat, will experience difficulty in
 laying along side of the deeper draft ship. In this situation, the port
 and starboard modes previously described will alleviate problems
 associated with staying close to the ship being moved. When the invention
 is set to operate in starboard mode or port mode, represented by buttons
 42 and 43, the flanking rudder located proximal to the deeper-draft ship
 will remain parallel to that ship's keel, while the distal flanking rudder
 will be independently controlled by the control lever 36. These modes of
 operation are also desirable when the vessel is operated near a wharf,
 river locks, or the shoreline for at least two reasons. First,
 maneuverability of the watercraft is enhanced by increased control over
 the flanking rudders. Second, through the use of a predetermined rudder
 configuration, the operator may direct thrust in such a manner so as to
 reduce routing damage. In the flare position, represented by button 44,
 the rearward convergence of the flanking rudders 6,7 separates and directs
 the thrust toward port and starboard and away from the vessel's keel. This
 action provides substantially greater braking control than that provided
 by reverse thrusting past traditional flanking rudders. By directing
 thrust away from the keel, the cavitation that normally takes place when
 reverse thrust is directed under the vessel is reduced. Thus, the screws
 are permitted to continue to operate at maximum thrust through the
 non-cavitated denser medium.
 Although the present invention has been described in terms of specific
 embodiments, it is anticipated that alterations and modifications thereof
 will no doubt become apparent to those skilled in the art. For example,
 the aforementioned concepts may also be applied to the control of steering
 systems positioned aft of the thrust producing devices. It is therefore
 intended that the following claims be interpreted as covering all such
 alterations and modifications as fall within the true spirit and scope of
 the invention.