Abstract:
A steering assist system for a marine vessel includes a steering vane that extends into the water in the vicinity of a steering device for the vessel and that is pivotable about an at least generally vertical axis by an electromechanical drive unit. The drive unit is energized by an actuator assembly in response to the imposition of external forces on the steering system. The actuator assembly includes an actuator that is movable in response to the imposition of external forces in the steering system and a switch that is selectively engageable by the actuator arm to energize the drive unit to drive the steering vane to pivot. The actuator assembly may additionally comprise a biasing assembly that resists movement of the actuator to create a force threshold that must be overcome to engage the switch. The biasing assembly may take the form of one or more springs, preferably having a settable preset.

Description:
CROSS REFERENCE TO A RELATED APPLICATION 
       [0001]    The present application claims the benefit of U.S. Ser. No. 61/256,041, filed Oct. 29, 2010, the disclosure of which is incorporated herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to marine steering systems and, more particularly, relates to a method and apparatus for controlling operation of a steering vane or tab that counteracts externally imposed steering torques imposed on the outboard engine or other steering device of a vessel. 
         [0004]    2. Discussion of the Related Art 
         [0005]    Marine steering systems sometimes employ a moveable steering vane or tab that moves so as to counteract external forces imposed on the steering device of the vessel, reducing or negating the need for the operator to impose steering forces to counteract these forces. These devices most typically are used in conjunction with outboard engines, in which case the engine itself is the steering device and is steered by pivoting about a vertical axis. In this case, the steering vane typically is disposed within the slip stream of the propeller of the outboard engine to channel the water in the strip stream in a manner that opposes external forces imposed on the engine during operation. Publications describing these systems often refer to the actuated vane or tab as a trim tab. However, such a reference is not technically accurate when referring to tabs that pivot about a vertical axis because trim tabs most typically pivot about a horizontal axis to adjust the fore-to-aft orientation or “trim” of a boat. Accordingly, this document utilizes the term “steering vane” or “steering tab” to refer to a structure that pivots about an at least generally vertical axis or otherwise moves at least generally from side to side to counteract externally forces imposed externally on a rudder, outboard engine, or other steered device during operation. 
         [0006]    Most steering vanes employed to date are operated mechanically and passively, such as by using the combination of a push pull cable and a passive hydraulic cylinder. One such vane is disclosed in U.S. Pat. No. 4,482,331, the subject matter of which is hereby incorporated by reference. Another example is disclosed in U.S. Pat. No. 4,349,341 (the &#39;341 patent) to Morgan et al., the subject matter of which is also incorporated by reference. The &#39;341 patent discloses the use of a control lever pivotally mounted to the steering control element of the boat. Movement of the lever in one direction or the other by the steering control element generates tensile forces in an appropriate control cable to pivot a steering vane. 
         [0007]    One shortfall of the system disclosed in the &#39;341 patent is the inclusion of a lost motion linkage between the steering arm and the control rod of the steering mechanism of a boat. The necessity of a lost motion linkage creates a lag in steering response, which can affect the handling of a boat. Another disadvantage of this type of system is that the lost motion linkage potentially allows the propulsion unit to be steered by external forces such as waves or current, which will cause course deviations. Passive systems also necessarily have limited effectiveness at counteracting forces imposed on the steering device. 
         [0008]    Computer based actuator systems have been developed to in an attempt to address at least some the disadvantages of passive mechanical based systems. For instance, U.S. Pat. No. 4,787,867 (the &#39;867 patent) to Takeuchi et al., discloses a steering vane or tab that is supported on the propulsion unit of a marine engine and that can be pivoted in a direction opposite to the operator&#39;s steering direction so as to create a hydrodynamic force to assist in the steering of a vessel immediately upon the detection of a given steering import force. The steering vane position, however, is determined by a computer system using a selected one of plurality of pre-mapped positions. Such a system is at the mercy of the accuracy of the pre-mapped positions and on the operator&#39;s ability to select the appropriate map. Furthermore, a computerized system of this type must be customized to particular boat characteristics such as engine and propeller characteristics, trim settings, and overall boat designs. Such a system therefore is relatively expensive and difficult to implement. It also cannot be used, without modification, on a variety of different vessels or retrofitted onto an existing vessel. 
         [0009]    It thus would be desirable, in a marine steering system, to automatically actuate a powered steering vane to actively reduce or counteract the external forces imposed on the steering system of a boat or other marine vessel during operation. 
         [0010]    It would also be desirable to provide a marine steering system which lacks a substantial lost motion connection in the actuating system for the steering vane or tab thereof and which, therefore, does not induce a lag to an operator-initiated steering command response. 
         [0011]    It is yet further desirable to provide a steering vane actuator assembly that is versatile so as to be capable of being attached to or retrofitted on a variety of boats without reconfiguration. 
       SUMMARY OF THE INVENTION 
       [0012]    In accordance with a first aspect of the invention, a steering system for a marine vessel includes a steering vane that extends into the water in the vicinity of a steering device for the vessel. The steering vane preferably is pivotable about an at least generally vertical axis and is driven by an electromechancial drive unit. An electromechanical drive unit is energized by an actuator assembly in response to the imposition of external forces on the steering system. The actuator assembly includes an actuator that is movable in response to the imposition of external forces in the steering system and a switch that is selectively engageable by the actuator to energize the drive unit to drive the steering vane to pivot or otherwise move. 
         [0013]    The actuator assembly preferably comprises a biasing assembly that resists movement of the actuator to create a force threshold that must be overcome to engage the switch. The biasing assembly may take the form of one or more springs, preferably having a settable preset. 
         [0014]    The steering vane and its actuator assembly may be used with, along other things, either mechanically or hydraulically steered vessels. If used with a mechanically steered vessel, the actuator assembly preferably is actuated mechanically and may be employed within or at an end of a steering linkage connecting a push-pull cable or the like to a steering arm. For instance, the actuator could be a pivoting arm driven by the steering system. 
         [0015]    If used with a hydraulically steered vessel, the actuator assembly preferably is actuated hydraulically and is fluidically coupled to a steering cylinder for the vessel. For instance, the actuator could be a lever arm responsive to movement of a hydraulically driven piston. 
         [0016]    The invention additional relates to a method of automatically actuating an electromechanically driven steering vane of a marine vessel to counteract external forces imposed on the vessel&#39;s steering system during operation. 
         [0017]    These and other features and advantages of the invention will become apparent to those skilled in the art from the following detailed description and the accompanying drawings. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Preferred exemplary embodiments of the invention are illustrated in the accompanying drawings in which like reference numerals represent like parts throughout, and in which: 
           [0019]      FIG. 1  is a schematic perspective view of a boat the steering system of which incorporates an electromechanically driven steering vane constructed and actuated in accordance with a preferred embodiment of the present invention; 
           [0020]      FIG. 2  is a top plan view of the steering vane and related components of the boat; 
           [0021]      FIG. 3  is a side elevation view thereof; 
           [0022]      FIG. 4  is a top plan view of an actuator assembly for the steering vane of  FIGS. 1-3 ; 
           [0023]      FIG. 5  is a side sectional elevation view of the actuator assembly of  FIG. 4 , taken generally along the lines  5 - 5  in  FIG. 4 ; 
           [0024]      FIG. 6  is an end sectional elevation view of the actuator assembly of  FIG. 4 , taken generally along the lines  6 - 6  in  FIG. 4 ; 
           [0025]      FIG. 7  is a top plan view of a portion of a marine steering assist system constructed in accordance with a second embodiment of the invention; 
           [0026]      FIG. 8  is a top plan view of an actuator assembly for a steering vane of the steering system of  FIG. 7 ; 
           [0027]      FIG. 9  is a sectional elevation view of the actuator assembly of  FIG. 8 , taken generally along the lines  9 - 9  in  FIG. 8 ; 
           [0028]      FIG. 10  is an end elevation view of the actuator assembly of  FIGS. 8 and 9 ; 
           [0029]      FIG. 11  is a sectional elevation view of the actuator assembly of  FIGS. 8-10 , taken generally along the lines  11 - 11  in  FIG. 10 ; 
           [0030]      FIG. 12  is a top plan view of a portion of a marine steering system constructed in accordance with a third embodiment of the invention; and 
           [0031]      FIG. 13  is a sectional view view of an actuator assembly for a steering vane of the steering system and related components of  FIG. 12 , taken generally along lines  13 - 13  in  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]    Electromechanically actuated steering vanes constructed in accordance with the present invention may be used on a variety of marine vessels powered by a variety of propulsion systems and steered by a variety of steering devices. For instance, they are usable with boats and other vessels having either an inboard engine or an outboard engine. They could also be used with vessels whose rudder or other steering device is either integrated with the engine, as is typically the cause with an outboard engine, or is separate from the engine. Hence, while embodiments of the invention will now be described primarily in conjunction with relatively small boasts powered and steered by outboard engines having integrated rudders, the invention is in no way limited to those embodiments. 
         [0033]    Referring to  FIG. 1 , a boat  20  incorporating an electromechanically actuated steering vane constructed in accordance with a first preferred embodiment of the present invention is illustrated at least someone schematically. The boat  20  of  FIG. 1  includes a hull  22  having a bow  24 , a stern  26 , and a transom  28  formed on the stern  26  of the hull  22 . The boat  20  also includes a helm assembly  30  and an outboard engine  32  mounted on the transom  28 . The engine  32  is pivotable about a generally vertical axis  34  under the application of steering forces transmitted from the helm assembly  30  via a steering arm  36 . The helm assembly  30  includes a steering wheel  40  and a flexible push-pull cable  42  that responds to steering wheel rotation. The push-pull cable  42  extends to the stern  26  of the boat  20  and is operatively connected to the steering arm  36  by a linkage assembly  44 . Referring to  FIGS. 2 and 3 , the linkage assembly  44  includes a first link  46  that may be formed from an end of the cable  42  and a second link  48  that is operatively connected to the first link  46  at one end thereof and to the steering arm  36  (via an adapter plate  80  of an actuator assembly  70 ) at the other end thereof. The steering arm  36  is able to respond to the linear movement of the push-pull cable  42  to pivot the engine  32  about the axis  34  in the commanded direction to steer the boat  20 . 
         [0034]    Referring particularly to  FIGS. 2 and 3 , a steering vane or tab  60  is mounted on the rear of the engine  32  and extends downwardly into the slipstream created by the engine&#39;s propeller  50 . The steering vane  60  is connected to an electromechanical drive unit  62  by a shaft  64  so as to be pivotal about an at least generally vertical axis. The drive unit  62  may be any electrically powered motor or other electromechanical drive capable of driving the steering vane  60  to pivot about shaft  64 . It preferably contains a permanent magnet DC motor. The drive unit  62  is electrically connected to an actuator assembly  70  by a wire or cable  66 . The actuator assembly  70  is, in turn, connected to a cable  72  leading to a main fuse box  74  of the boat  20  ( FIG. 1 ). The actuator assembly  70  is responsive to the application of external forces to engine  32  to activate the drive unit  62  to drive the steering vane  60  to pivot about its vertical axis to counteract the external forces. 
         [0035]    Referring now to  FIGS. 4-6 , the actuator assembly  70  includes an adapter plate  80 , an actuator arm  82 , and a switch assembly  84 . The actuator arm  82  is connected to the steering linkage assembly  44  and is mounted for limited movement with respect to the adapter plate  80 . The switch assembly  84  is responsive to that limited actuator arm movement to actuate the drive unit  62 . 
         [0036]    The adapter plate  80  comprises rigid L-shaped plate that is bolted or otherwise attached to the steering arm  36  at its rear end and that has a slot  86  formed in its front end. The actuator arm  82  is centered in the slot  86  in the adapter plate  80  with a gap “G” formed on either side of the actuator arm  82 . The width of each gap G represents the maximum distance the actuator arm  82  can move relative to the adapter plate  80 . An actuator pin  88  extends vertically upwardly from a front end of the actuator arm  82 . The second end of second link  48  of the steering linkage  44  is pivotally connected to the actuator arm  82  near the rear end thereof via a bolt and bushing assembly  89 . The link  48  is stationary in a no-steer situation. 
         [0037]    Still referring to  FIGS. 4-6 , the switch assembly  84  is maintained in a switch housing  90  that is mounted on the front end of the adapter plate  80  by bolts  92 . The switch housing  90  also is pivotally attached to the actuator arm  82  by a bolt and bushing assembly  94  extending through the actuator arm  82  between the bolt and bushing assembly  89  and the actuator pin  88 . 
         [0038]    As can be seen in  FIG. 5 , the switch housing  90  houses two switches  100   a  and  100   b  located on opposite sides of the actuator pin  88 . These switches  100   a  and  100   b  have plungers that are in contact with the actuator pin  88 . Depression of one of the plungers will activate the corresponding switch  100   a  or  100   b  to activate the drive unit  62  to pivot the steering vane  60  in one direction or the other. 
         [0039]    The switch housing  90  also contains a biasing assembly that resists pivoting movement of the actuator arm  82  relative to the adapter plate  80 , hence setting a resistance or force threshold that must be overcome to activate the drive unit  62 . The threshold preferably is between 5 and 10 lbs. In this embodiment, the biasing assembly takes the form of a spring assembly  110  mounted in a cross bore  112  in the switch housing  90  as best seen in  FIG. 5 . Spring assembly  110  includes two springs  114   a  and  114   b,  two inboard spring guides  116   a,  and  116   b,  and two outboard spring retainers  118   a  and  118   b.  Each spring  114   a  or  114   b  abuts against an associated side of the actuator pin  88  via the associated spring guide  116   a  or  116   b.  The positions of the outboard spring retainers  118   a  and  118   b  within the bore  112  are adjustable using set screws  120   a  and  120   b  ( FIG. 4 ), hence permitting the pretention on the springs  114   a  and  114   b  to be adjusted to adjust the reaction force threshold that must be applied on the actuator assembly  70  by the engine  32  to activate the drive unit  62 . 
         [0040]    The switches  100   a  and  100   b  in this system preferably are wired in a way that, when they are not activated, the two wires leading from the switches are shorted together. This shorting generates an electromagnetic pulse in the motor of the drive unit  62  that acts as a brake to stop the motor immediately upon switch deactivation. This feature stops the steering vane  60  from continued movement after the drive unit  62  has been deenergized. 
         [0041]    In use, the steering link  48  is stationary in a no-steer situation. If a reaction force, applied to the adapter plate  80  by the engine  32  and the steering arm  36 , is of sufficient magnitude to overcome the spring pressure of one the springs  114   a  and  114   b,  the actuator arm  82  will pivot relative to the adapter plate  80  and the switch housing  90  through a stroke determined by the width of the associated gap “G”. This pivoting will cause the actuator pin  88  to activate one of the switches  100   a  or  100   b.  The switch  100   a  or  100   b  will energize the motor in the drive unit  62 , which will rotate the steering vane  60  in a direction to counter the force applied to the adapter plate  80  by the engine  32 . When the force applied to the adapter plate  80  becomes less than the spring-applied force, the actuator arm  82  will move back to its centered neutral position under the spring force. The switch  100   a  or  100   b  will be deactivated, and the motor in the control until  62  will stop the movement of the steering vane  60 . At this time, the outboard engine  32  can be steered without further movement of the steering vane  60  if the external operating parameters remain beneath the threshold determined by the spring  114   a  or  114   b.  If the external operating parameters change and the load imposed on the adapter plate  80  becomes high enough to overcome the spring force keeping the actuator arm  82  centered within the slot  86 , the position of the steering vane  60  will again be adjusted to compensate for the change in the external operating parameters. 
         [0042]    Referring now to  FIGS. 7-11 , a second embodiment of the invention is illustrated that differs from the first embodiment primarily in that the actuator assembly  170  is mounted within the steering linkage  148  rather than between the steering linkage and the engine steering arm  36 . The engine  32 , helm  30 , etc. are thus identical to the first embodiment. The actuator assembly  170  of this embodiment includes a stationary bracket  180  and a movable actuator arm  182 . Stationary bracket  180  is attached to the steering cable or link  146  by a bolt  184 . The actuator moveable arm  182  is free to pivot about bolt  184 . A link  148  is pivotally attached to the actuator arm  182  at one end thereof and to the steering arm of the engine at the other end thereof. 
         [0043]    The actuator arm  182  is held in a center position with respect to the bracket  180  by a spring assembly which, like the spring assembly of the first embodiment, sets an initial or threshold force that the engine will have to apply to the actuator arm  182  before the steering vane  60  will be moved. As best seen in  FIG. 11 , the spring assembly includes a single spring  214  housed in a bore  216 . One end of spring  214  holds a spring guide  218  against one end of the bore  216 . A sleeve  220  is held in place on the other end of the bore  216  by a set screw  222  that sets the position of the sleeve  220  to determine the preset of the biasing force imposed by the spring  214 . The other end of the spring  214  forces a spring guide  224  against the end of the sleeve  220 . 
         [0044]    When the actuator arm  182  is moved in one direction or the other by forces imposed thereon by the engine  32 , the associated spring guide  218  or  224  will compress the spring  214  to generate a force tending to move the actuator arm  182  back to its center position. 
         [0045]    Centering screws  230  and  232  also are housed in the bracket  180 . The screws  230  and  232  center the actuator arm  182  within the bracket  180  and create an equal gap “G” between each side of the actuator arm  182  and the bracket  180 . This gap defines the maximum movement that arm  182  can move with respect to the bracket  180 . Centering screws  230  and  232  are adjustable to come into contact with the spring guides  218  and  224 . 
         [0046]    Referring especially to  FIGS. 8 and 9 , a pair of actuator pins  240  and  242  is mounted on the bracket  180 , and a switch  244  is mounted on the actuator arm  182  between the pins  240  and  242 . Movement of the actuator arm  182  in one direction or another will cause one of two plungers  246  and  248  on the switch  244  to engage an associated actuator pin  240  or  242  to activate the switch  244  and energize the drive unit  62  to drive the steering vane to move in one direction or the other. 
         [0047]    The operation of the system is as follows. Under a no-steer condition, the steering cable  146  is stationary. When the engine  32  produces a force in one direction or the other, the cable  146  and link  148  will move actuator arm  182  in that direction. Movement of the actuator arm  182  causes one of the actuator pins  240  or  242  to be contacted with the plunger  244  or  248  of the switch  244 , activating the switch  244  and actuating the drive unit  62  to pivot the steering vane  60  ( FIGS. 1 and 2 ) a direction to counteract the force produced by the engine  32 . 
         [0048]    Turning now to  FIGS. 12 and 13 , another embodiment of the invention is illustrated that is applicable to a hydraulically steered system. The engine  32 , vane  60 , and drive unit  62  of this embodiment are identical to those of the first two embodiments. In this embodiment, the engine  32  is pivoted by a piston  300  that is movable axially within a cylinder  302  in either direction. Pressurized fluid flows to and from chambers  304  and  306  on opposed sides of the piston  300  via hydraulic lines  308  and  310  attached to the helm assembly (not shown). A link  312  is attached to opposed axial ends of the piston  300 , extends through opposed ends of the cylinder  302 , and is attached to the engine steering assembly  370 . 
         [0049]    Still referring to  FIG. 13 , the actuator assembly includes a self contained unit  370  coupled to the steering cylinder  302  by hydraulic lines  372  and  374  teed to the lines  308  and  310 , respectively. The unit  370  includes a housing  380  having a bore  382  formed therein that is sealed at its opposed ends by end caps  384 ,  386 . A piston  380  is disposed in the bore  382  between first and second chambers  371  and  373 , each of which opens into an associated one of the lines  372 ,  374 . A rod  390  extends through the piston  388  and the end caps  384  and  386 , where it engages opposed lever arms  392  and  394  disposed adjacent opposite sides of housing  380 . Each lever arm  392 ,  394  rotates about an associated pin  396 ,  398  located behind piston  390 . The lever arms  392  and  394  are biased into a neutral position by a spring  400  mounted in a bore  402  formed into the housing  380  behind the pivot pins  396 ,  398 . Each end of the spring  400  rests against a spring guide  404 ,  406 . Each spring guide  404 ,  406  rests against an adjustment screw  408 ,  410  threaded through the associated lever arm  392 ,  394 . The pretension of the spring  400 , and hence the force required to actuate the steering vane  60 , can be adjusted by rotating one or both of the threaded adjustment screws  408  and  410 . Switches  412  and  414  are mounted on the housing  380  behind the adjustment screws  408  and  410 . Each switch contains a plunger  416 ,  418  that is engaged upon pivoting movement of the associated lever arm  392 ,  394  to activate the associated switch and energize the drive unit  62  to pivot the steering vane  60  in the appropriate direction. 
         [0050]    In operation, engine movement in response to external forces generates a force that is transmitted to the steering cylinder  302  by way of steering arm  36 . That force causes the piston  300  to move in one direction or the other relative to the cylinder  302 , causing hydraulic fluid to flow out of one of the chambers  304  or  306  and into the other  306  or  304 . This fluid flow will create a pressure differential between the chambers  371  and  373  on the opposed sides of the actuator assembly piston  388 , forcing the rod  390  towards one of the lever arms  392  or  394 . When the pivoting forces imposed on the relevant lever arm  392  or  394  by this pressure differential are high enough to overcome the biasing force of the spring  400 , the piston  388  and the rod  390  will move in one direction or the other, causing the associated lever arm  392  or  394  to depress the associated switch plunger  416  or  418 . This plunger depression will activate the associated switch  412  or  414 , energizing the drive unit  62  to move the steering vane  60  to counter the force created by engine  32 . 
         [0051]    Many changes and modifications could be made to the invention without departing from the spirit thereof. For instance, the system need not be used with a traditional tiller-based steering system. For instance, the system of  FIGS. 12 and 13  can be used with a tiller-based steering system having a hydraulic lock as disclosed and claimed in U.S. Pat. No. 7,325,507, the subject matter of which is hereby incorporated by reference. When the system is used with the hydraulic lock, a second set of switches is needed. These switches are activated by movement of the tiller handle, and they override switches  412  and  414  of the actuator assembly  370 .