Abstract:
The boat control system is a propulsion system for controlling the direction of passage of a vessel underway at low speeds. Six thruster nozzles are installed around the hull so that, used individually or in combination, the boat can be maneuvered forward, backward, laterally or turned on its axis. Each impeller is driven by a water-cooled reversible DC electric motor, which allows the thruster apparatus to operate for long periods. In some embodiments, the motors are installed concentrically within their respective thruster ducts, with water flow through the ducts cooling the motors during operation. The system is controlled by a joystick located at the operator&#39;s station of the boat.

Description:
REFERENCE TO RELATED PATENT APPLICATION  
       [0001]     This application is a continuation in part of U.S. patent application Ser. No. 11/135,410, filed on May 24, 2005. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention disclosed herein relates to a propulsion system for controlling the direction of passage of a vessel underway at relatively low speeds without utilizing the power of the vessel&#39;s main engine(s). The invention particularly relates to a boat control system that includes at least one thruster installed in the bow or stern of a vessel, especially a power or a sail pleasure boat, that can selectively propel the craft forward, backward or laterally. The system&#39;s design allows the thruster apparatus to operate for long periods without overheating.  
         [0004]     2. Description of the Related Art  
         [0005]     The use of thrusters as a means of enhancing the turning capability of a boat or ship is well known in the marine arts. When maneuvering to enter or exit a dock or marina, boats of moderate or larger size and ships of any length are in tight quarters and are at the mercy of the prevailing current, wind direction, and the tendency for a single engine prop to turn the boat&#39;s stern. A miscalculation in where the boat&#39;s engine, just turning above stalling RPM, and the boat&#39;s corresponding momentum will take the craft can result in an ever so seemingly light contact with a bulkhead or another boat in its slip. Yet, that light contact damage may cost thousands of dollars to remedy. But the experienced boater knows the risk can be remedied by installing one or more bow thrusters. They can turn the bow quicker in short distances than a rudder and engine combination. That gives the captain more control.  
         [0006]     One or more thrusters can also be installed in the stern of the boat, preferably connected to the transom. These provide a capability to turn the stern laterally and, in concert with the bow thruster(s), rotate the boat on its axis. Stern thrusters are also of great assistance to single engine boats when they are backing into a slip. Depending on which way the engine shaft rotates, the boat&#39;s prop in reverse gear turns the stern of the boat to port or starboard, but with stern thrusters installed and operating to port or starboard, this tendency can be balanced to allow the boat to back straight into the slip.  
         [0007]     Another advantage of bow and stern thrusters is their capability to move the boat forward or backward at extremely slow speed when operated in tandem. When entering a crowded fairway of a marina, the flow of the thrusters can be directed to the stern of the boat and thereby provide a small forward motion to the vessel with an instant capability to turn the vessel, if necessary. A longitudinally oriented stern thruster is also of value to the sport fisherman for moving the boat slowly over the water while trolling.  
         [0008]     One problem that compromises the scope of use of bow or stern thrusters in the current art is the use of air-cooled electric motors to power the thrusters. Air-cooled electric motors tend to heat up with prolonged use and must be shut down before they are damaged. Therefore, they cannot be used continuously during a cruise, so some of their advantages are not always available to the captain. Nor can they be used for trolling in open waters.  
         [0009]     U.S. Pat. No. 3,675,611, issued to Glass, describes a boat having a plurality of water jet nozzles at the bow and stern to assist in steering the boat. The water jet nozzles also provide auxiliary drive to propel the boat. As described, the water jets of the Glass &#39;611 patent are restricted to maneuvering in and about the marina and are not capable of extended, continuous operation.  
         [0010]     U.S. Pat. No. 3,911,851, issued to Canazzi, describes bow thrusters and stern thrusters for maneuvering a boat in confined places. The four thrusters receive their stream of water from a single point source, which distributes the water to the thrusters from four circumferentially spaced outlet ports at 90° intervals. Precise lateral movement of the boat under this feed configuration is questionable, as is the net forward thrust provided to the boat when all four thrusters are in play.  
         [0011]     Japanese Patent No. 10-086,895, published on Apr. 7, 1998, describes (according to the drawings and English abstract) a maneuvering thruster for a ship, the device having a single water inlet below the waterline and opposed outlets above the waterline. A single motor and pump are provided, with a selector valve determining the direction of outflow.  
         [0012]     Japanese Patent No. 2002-087,389, published on Mar. 27, 2002, describes (according to the drawings and English abstract) a maneuvering thruster having both inlet and outlet ports oriented in the same direction for each unit. Flow may be reversed through the duct, but it appears that the similar orientation of the inlet and outlet ports for each unit would reduce the efficiency of the device. The motor is located outside the duct.  
         [0013]     None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus, a boat control system solving the aforementioned problems is desired.  
       SUMMARY OF THE INVENTION  
       [0014]     The boat control system for independently steering or propelling a boat at low speed includes six thruster ports and nozzles, or three pressure and three suction thruster nozzles, connected to water pumps containing two reversible impellers. The pumps are driven or operated by water-cooled DC reversible electric motors connected to the boat&#39;s battery bank or to the main engine electric system. Four of the thrusters are installed through the hull of the boat and one thruster is installed amidships in the stern, preferably through the transom. All of the thrusters are installed just below the static water line or displacement line on the hull or transom and obliquely eject pressurized water outwardly into the seawater.  
         [0015]     The ejection of the pressurized water into the seawater by the thrusters produces an opposite reaction force that effects a turning moment on the hull of the boat, which, when the thrusters are operated selectively, turns or propels the craft to port or starboard, moves the boat laterally along the hull line to starboard or port, or propels the craft forward at low speed. The boat control system is capable of operating with any combination of thrusters in play, from one to five. Accordingly, there is a large selection of low speed turning and propulsion options available to the captain of the vessel simply from the choice of thrusters to operate. The craft can be propelled forward at low speed or rotated in place on its axis or propelled laterally as in an approach to a crowded gas dock. Some of these maneuvers are well beyond the scope of the boat&#39;s main engine(s) to accomplish, particularly at very low speeds.  
         [0016]     Thruster systems have heretofore typically not been placed in operation in open waters, for their usefulness in open waters requires long periods of operation compared to their operation in congested marinas and back waters. Such thruster systems are often operated by air-cooled DC electric motors installed in the hull in relatively hot locations on the boat. Accordingly, protracted continuous operation of these thruster system motors in open water overheats the motors and causes severe damage. However, it has been discovered that this drawback of previous thruster systems can be overcome by operating the thruster system with reversible direct current water-cooled electric motors.  
         [0017]     The advantages of operating the thruster system with water-cooled motors are significant. As a result, the boat control system of the present invention can be used to propel the boat for long periods at low speeds previously unattainable with the high horsepower main engine(s). Consequently, when trolling for fish, a separate, outboard trolling motor is no longer necessary. The boat control system thrusters can maintain low trolling speeds for long periods, so the need for a trolling motor is overcome.  
         [0018]     The long operating hours attainable by the boat control system of the present invention provides another important advantage to the boat owner, viz., fuel efficiency. Very often, a relaxing day of boating consists mainly of very slow cruising around an attractive river or bay with family and friends. The main boat engine(s) can propel the boat slowly enough at very low revolutions per minute, but at the cost of very low fuel efficiency coupled with exhaust smoke and noise. The boat control system of the present invention overcomes that disadvantage when tied into the rechargeable battery bank of the boat. The desirable slow gentle speed can be achieved with only two or more thrusters on and the main engine(s) off. No fuel is consumed, and exhaust fumes and combustion noises are eliminated.  
         [0019]     Three reversible water-cooled electric motors may be used in the boat control system of the present invention: one in the bow and two in the stern of the boat. These motors are each connected by a drive shaft to a pump containing two impellers of opposite rotation and water inlet and outlet apertures or holes or openings. The outlet aperture of the pump is connected preferably by hoses to the starboard and port bow thruster nozzles at the thruster apertures in the hull just below the port and starboard high water line. The water inlet aperture of the pump is connected, preferably by hose, either to an outlet water aperture on the water-cooled reversible motor heat exchanger casing, or to a first water intake aperture through the hull below the starboard or port water line.  
         [0020]     The water-cooled reversible electric motor is contained in a metal heat exchanger casing. An aperture on the heat exchange casing is connected to the water intake through hull apertures. The water passes through the motor casing and exits the heat exchanger through another aperture, which is connected by hose or conduit to the water intake opening on the pump housing.  
         [0021]     Other embodiments of the present boat control system place the thruster motors generally or substantially concentrically within the thruster duct, thereby obviating the need for an external drive shaft between the motor and the impeller shaft and its corresponding requirement for a dynamic seal. Moreover, ambient water flowing through the thruster duct during operation provides cooling for the motor within the duct without need for additional coolant lines and the like. Greater motor output, which results in greater heat output, also results in greater water flow through the duct to provide the cooling necessary.  
         [0022]     While the foregoing explanation of the thruster and motor installation is directed to the bow thruster, the two stern installations of pumps and water-cooled electric motors are similar to the bow thruster installation. One stern installation provides an operational thruster to the stern port side and to the stern starboard side just below the high water line. The inlet water for the pump can be acquired from the motor heat exchanger casing or, optionally, can be taken directly from a stern hull aperture placed in the hull below the stern or forward propulsion thruster water line.  
         [0023]     The second stern installation includes a thruster directing a stream of pressurized water into the sea directly aft of the transom for forward propulsion. The exact placement of the stern forward propulsion thruster nozzle shall be determined by one skilled in the art at the site, as the stern design of both power and sailboats vary significantly from manufacturer to manufacturer. However, the thruster nozzle shall be obliquely directed downward into the water from a placement several inches below the stern water line.  
         [0024]     Each of the three reversible, water-cooled DC electrical motors for the bow, stern and transom thruster installations is fully wired and connected to a battery bank and a thruster control joystick at the captain&#39;s wheel station. The instrumentation at the control joystick is known to those skilled in the art and allows the captain to select, start up and shut down any combination of thrusters for maneuvering the boat. Each independent pump is equipped with two impellers. Through the reversibility of the motor, the captain can select either the starboard or port side impeller to become engaged to discharge seawater through the selected thruster nozzle to turn the bow. In a similar manner, the stern thruster installation can be energized to operate either the port or starboard impeller to turn the boat&#39;s stern. If the captain prefers, both bow and stern thruster installation can be made operational simultaneously.  
         [0025]     These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIG. 1  is a diagrammatic top view of the thruster installation in a boat control system according to the present invention.  
         [0027]      FIG. 2  is a diagrammatic rear view of a bow thruster in a boat control system according to the present invention as viewed from the transom.  
         [0028]      FIG. 3  is a diagrammatic side view of the bow thruster installation in a boat control system according to the present invention, illustrating the cooling water installation for the electric motor and impeller.  
         [0029]      FIG. 4  is a diagrammatic top view of the integrated motor and thrusters installation in a boat control system according to the present invention.  
         [0030]      FIG. 5  is a partially broken away detailed perspective view of an exemplary alternate embodiment of a boat control system according to the present invention, showing a single impeller lateral thruster with the motor being installed concentrically within the duct.  
         [0031]      FIG. 6  is a detailed side elevation view in section of another exemplary alternate embodiment of a boat control system according to the present invention having dual impeller lateral thruster with the motor installed concentrically within the duct.  
         [0032]      FIG. 7  is an environmental side elevation view of an exemplary boat having the present boat control system installed therein, showing the positions of the thruster nozzles below and above the waterline when the boat is respectively in static and dynamic (planing) displacement modes.  
         [0033]      FIG. 8  is a block diagram showing the operation of the joystick controller of a boat control system according to the present invention. 
     
    
       [0034]     Similar reference characters denote corresponding features consistently throughout the attached drawings.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0035]     Referring to  FIG. 1 , a diagrammatic top view is presented showing the general shape of a boat  10 . The bow thruster impeller pump  20  and reversible electric motor  12  are installed in the hull centered between the hull sides. The bow thruster nozzles  14  and  16  are connected to the pump  20  by flexible piping  18 . The stern side lateral thrusters  22  and  24  and reversible electric motor and impeller pump  26  are installed in the hull close to the centerline of the hull. The forward and reverse unit, comprising the reversible electric motor and water impeller pump  28 , is installed in the center line of the hull next to the transom  30 , with one thruster nozzle installed on the stern and connected to the pump  28 . The forward thruster nozzle is pointed obliquely down and to the rear into the seawater.  
         [0036]     The system illustrated in  FIG. 1  offers 360° thrust angles, including true straight lateral movement. The thruster units are controlled by one 3-axis joystick.  
         [0037]     Referring to  FIG. 2 , a diagrammatic view is presented of the bow lateral thruster as seen from the transom  30 . The keel  11  of the boat is shown, together with the pump impellers  13 , right angle drive  15 , and bearings  17 . The water-cooled reversible electric motor  19  is encased in a water-cooling jacket  21  having water circulating lines  23  and  25 .  
         [0038]     Referring to  FIG. 3 , a diagrammatic side view is presented of the bow lateral thruster. The view shows the electric motor  40  connected to impeller  42  via a right angle drive  44 . Cooling water supply and return lines  46  and  48  are connected to the electric motor heat exchanger casement  50 .  
         [0039]     Referring to  FIG. 4 , a diagrammatic top view of the pump and electric motor is shown. The water-cooled, reversible DC electric motor  27  is shown, together with motor cooling water enclosure  29  and a motor cooling water supply line. The motor shaft is connected to the pump drive by drive coupler  33 . The pump impellers  35  and  37  are encased in an aluminum tube  39 . The body of the pump includes a right angle gear drive  41 . A seawater feed circulation line (not shown) is included from an available raw seawater inlet source or provided through a conduit from another aperture in the hull below the boat&#39;s sea water line.  
         [0040]      FIGS. 5 through 8  of the drawings illustrate additional embodiments and features of a boat control system according to the present invention wherein the thruster motors are installed generally concentrically within the thruster ducts, rather than being disposed externally to the ducts and driving the impeller shaft by means of a geared jackshaft. The embodiments of  FIGS. 5 through 8  immerse the motor case within the ambient water flow through the duct, thus cooling the motor without need for external cooling lines and related apparatus. Moreover, the impeller drive shaft is integral with the motor shaft, obviating any need for gearing and additional bearings, other than the conventional bearings within the motor case.  
         [0041]      FIG. 5  provides a partially broken away perspective view of a concentric motor thruster  110  for a boat control system, the thruster  110  having a thruster impeller drive motor  112  generally disposed concentrically within the thruster duct  114 . A clamp  116  may be installed about the motor  112 , with the clamp  116  having laterally opposed wings or extensions  118 , which are captured between the corresponding opposed edge flanges  120  of the duct  14 . Optionally, other means of securing the motor  112  within the duct  114  may be provided, e.g., radially disposed struts or arms, etc.  
         [0042]     The duct  114  includes opposite first and second open ends, respectively  122  and  124 , with open ports  126  and  128  extending respectively therefrom. The ports  126  and  128  may include flanges or lips  130  extending therefrom, to facilitate attachment and sealing of the assembly through a boat hull. The thruster  110  of  FIG. 5  is configured for mounting through the forward portion of a boat hull H (shown in broken lines in  FIG. 5 ), with it being understood that substantially the same configuration is used for the longitudinal and lateral stern thrusters, with only minor changes to the two outlet ports being required.  
         [0043]     The impeller drive motor  112  is a sealed unit to preclude the entry of water therein. The seals are conventional, comprising a dynamic seal at the drive shaft end and a static seal at the point where the electrical power cable  132  enters the motor. (The assembly also includes a static seal  134  at the point of passage of the cable  132  through the side of the duct  114 .) As the thruster duct  114  is installed below the static waterline of the boat (as shown in  FIG. 7  and discussed further below), the motor  112  is immersed in water at all times. The water flowing through the duct  114  cools the motor  112  during its operation, with greater power output resulting in greater heat output, but with the resulting greater flow of water through the duct providing more cooling for the motor  112 .  
         [0044]     The motor  112  includes a first end  136  and opposite second end  138 . The first end  136  includes a drive shaft  140  extending directly therefrom, i.e., without intervening gearing or other mechanisms. The drive shaft  140  has an impeller  142  attached directly thereto, with directional rotation of the impeller  142  (and thus the direction of water flow through the duct  114 ) being controlled by the direction of rotation of the motor drive shaft  140  in accordance with the control system discussed further below. The opposite second end  138  of the motor  112  provides for the connection of the electrical power cable  132  thereto.  
         [0045]      FIG. 6  provides a side elevation view of an alternative embodiment of a boat control system having a duct assembly  210  in which the motor  212  drives two opposed impellers. The duct  214  is generally the same as the duct  114  of  FIG. 5 , having opposed first and second ends  222  and  224  with first and second outlet ports  226  and  228  extending therefrom. The motor  212  is secured concentrically within the duct  214 , e.g., in the manner described above for the thruster  110  of  FIG. 5 .  
         [0046]     The motor  212  has a first end  236  and opposite second end  238 , with each end having a drive shaft end extending concentrically therefrom in substantially the same manner as the drive shaft  140  of the motor  112  of  FIG. 5 . Each end of the single continuous drive shaft includes an impeller, respectively  242  and  244 , installed directly thereto. The electrical cable  232  connects to some point between the two ends  236 ,  238  of the motor  212 , thus allowing the single drive shaft to extend from both ends of the motor. The two impellers  242 ,  244  both rotate in the same direction relative to one another according to drive shaft rotation, depending upon the direction of rotation demanded of the device in accordance with the control input as described further below.  
         [0047]      FIG. 7  is a right side elevation view of an exemplary boat B to which the boat control system may be installed. The boat B is shown in its stationary or slow speed displacement in solid lines, whereby the hull H is supported by static displacement. However, the boat B is a relatively high performance craft, capable of planing at cruise speeds. When the boat B is planing, it is supported by dynamic displacement due to its speed over the surface of the water. Accordingly, the boat B rides somewhat higher in the water, as shown by the boat B position shown in broken lines in  FIG. 7 .  
         [0048]     The boat B of  FIG. 7  preferably includes a system of three thrusters installed thereon or therein, comprising a laterally disposed bow thruster assembly, a laterally disposed stern thruster assembly, and a longitudinally disposed stern thruster assembly, with the two stern thruster assemblies extending from the transom T of the boat. The various thruster assemblies may comprise either the single impeller embodiment  110  of  FIG. 5 , or the dual impeller embodiment  210  of  FIG. 6 , as desired. In the case of the bow thruster assembly, only the right side outlet port is shown, as the remainder of the assembly is installed within the bow or forward portion of the hull H of the boat B.  
         [0049]     The various thrusters are specifically positioned on or in the hull relative to the static and dynamic displacement waterline of the boat B. As the boat B rides lower in the water in its static displacement mode when at rest or at relatively slow speeds, the various thrusters and their ports, e.g., bow thruster port  128   a,  laterally disposed stern thruster assembly  110   a,  and longitudinally disposed stern thruster assembly  210   a,  are positioned below the waterline W, where they are free to draw in and expel water when actuated. However, when the boat B is on plane or in dynamic displacement mode, as shown in broken lines in  FIG. 7 , the hull H is riding somewhat higher in the water. This positions the various thrusters above the waterline, as indicated by the position  128   b  of the bow thruster port and the positions  110   b  and  210   b  of the respective lateral and longitudinal stern thrusters. (The longitudinal thruster  210   b  is shielded by the wake of the transom T when the boat B is at planing speed.)  
         [0050]     Thus, all of the various outlets, openings, or ports of the various thrusters are positioned clear of the waterline W when the boat B is planing, thereby avoiding the hydrodynamic drag, which would otherwise be produced by the ports passing through the water at speed. This configuration also avoids the possibility of any of the thrusters or their ports fouling upon some object (e.g., fishing line, floating net, etc.) in the water when the boat B is at speed.  
         [0051]      FIG. 8  is a schematic top plan view of a joystick controller for operating the thrusters of a boat control system according to the present invention. The joystick  150  moves in three degrees of freedom, i.e., laterally left and right as indicated by the respective left and right positions  150   a  and  150   b  in broken lines; longitudinally fore and aft, as indicated by the respective fore and aft positions  150   c  and  150   d  in broken lines; and rotationally about its elongate axis, as indicated by the rotational arrow R. The stick  150  is electrically connected to the various thrusters of the boat control system, and controls the thrusters in accordance with joystick movement using conventional electronic control systems.  
         [0052]     If the operator of the boat wishes to drive the boat forward at a slow speed, the joystick  150  is moved forwardly to, or toward, the position  150   c  shown in broken lines in  FIG. 8 . This engages the drive for the longitudinally disposed rear thruster, with other thrusters remaining inoperative in this maneuver. The joystick  150  system preferably includes proportional control, e.g., using subminiature potentiometers or the like, to control motor speed, and therefore thrust, in proportion to the amount of movement of the joystick. This is preferably the case with each axis of movement and corresponding thruster(s) control using the joystick. If the operator wishes to move the boat slowly rearwardly, the stick  150  is shifted toward the rear, as indicated by the stick position  150   d.  This reverses the rotation of the motor and impeller(s) of the fore and aft thrusters, causing the thrust to be directed forwardly and the resulting reaction to drive the boat rearwardly.  
         [0053]     The boat is turned by a corresponding rotation of the joystick  150 , as indicated by the rotational arrow R, which results in the actuation of two of the thrusters. When turning, the bow thruster is actuated in one direction, while the lateral stern thruster is actuated in the opposite direction. This causes the boat to pivot generally about its center, thereby performing a tight maneuver. Lateral movement of the stick to the positions  150   a  or  150   b  also simultaneously actuates the bow and lateral stern thrusters. However, in this scenario both thrusters are driven in the same direction, thereby moving the boat laterally without changing its heading. Various combinations may be achieved in accordance with the position of the joystick  150 , e.g., positioning the stick forward and to the right while rotating the stick clockwise will result in the bow thruster developing more thrust to the right than the lateral stern thruster, thereby driving the boat to the right, but causing the bow of the boat to rotate to the right as well. The forward displacement of the stick will actuate the longitudinal stern thruster as well, driving the boat slowly forward as well.  
         [0054]     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.