Abstract:
An arrangement for providing the low-speed steering control of a boat having at least two outboard thruster motors ( 2, 3 ) which are interconnected preferably by means of a tie-rod ( 6 ), wherein the tie-rod ( 6 ) comprises at least one tie-rod part ( 4, 5 ) which can be independently driven forward and backward directions to preferably independently turn the thruster motors ( 2, 3 ) vertically

Description:
FIELD OF INVENTION 
       [0001]    This invention relates to a tie-rod arrangement providing for steering control of boats with two outboard motors, and more specifically relates to a tie rod arrangement connected between the motors for superior steering control while an outboard motorboat is docked at low speeds. 
       BACKGROUND OF INVENTION 
       [0002]    It is sometimes necessary to make motorboats approach to mooring platforms from their larboard or starboard sides and this operation may turn into nightmare for boat users. As a matter of fact, it may not be always possible to find a large space to approach the boat to a desired place at the dock or marina. Therefore, docking the boat to an empty parking area makes countless and repeated steering attempts necessary for the user of boat. 
         [0003]    Many solutions have been proposed for controlling the low-speed steering of motorboats, such as docking to an immobilized platform. U.S. Pat. No. 5,016,553, for instance, discloses a device that having a main propeller controlled by means of a joystick-like arm and a stern side thruster, and that provides for low-speed steering control. Additionally, the IPS® system of Volvo, the ZEUS® system (ZF®), and the Axius® system of Mercury do perform this function in a very-expensive manner by means of stern drives and under-hull propeller mechanisms, along with electronic controllers and circuits issuing separate directional commands to each drive unit. 
         [0004]    WO 2000/13967 discloses a boat comprising a water jet drive and a front thruster. There, the movement of the water jet nozzle and front thruster is controlled by means of a joystick so that the steering of boat is controlled at lower speeds. 
         [0005]    JP 10 181692 discloses an assembly by which a stern propeller and bow thruster are controlled for controlling the movement of a marine vessel. 
         [0006]    The proposals given above are for use with boats with inboard motors (not towards boats with full outboard motors), and they are complicated and expensive as they require additional motors and thrusters, as well as a system providing the drive control thereof for ensuring low-speed steering control. 
       DESCRIPTION OF INVENTION 
       [0007]    One object of the present invention is to provide a low-speed steering control of boats with two outboard motors by means of an arrangement which is efficient with respect to functionality and cost. 
         [0008]    In order to achieve this object, this invention relates to an arrangement for providing the low-speed steering control of a boat with two outboard thruster motors which are preferably interconnected by means of a tie-rod. The tie-road comprises at least one tie-rod part which is independently driven forward and backward directions to independently turn the thruster motors around vertical axis. The tie-rod part or parts of the invention is/are driven preferably by means of a hydraulic cylinder-piston or electrical piston mechanism. 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0009]    The present invention is to be evaluated together with annexed figures briefly described hereunder to make clear the subject embodiment and the advantages thereof. 
           [0010]      FIG. 1  is a rear perspective view of a motorboat with two thruster motors. 
           [0011]      FIG. 2  is a top perspective view of a motorboat with two thruster motors. 
           [0012]      FIG. 3  is a rear perspective view, while the front parts of thruster motors are positioned close to each other. 
           [0013]      FIG. 4  is a below view of the positioning given in  FIG. 3 . 
           [0014]      FIG. 5  is an above view of the positioning given in  FIG. 3 . 
           [0015]      FIG. 6  is a rear perspective view, while the front parts of thruster motors are positioned far from each other. 
           [0016]      FIG. 7  is a below view of the positioning given in  FIG. 6 . 
           [0017]      FIG. 8  is an above view of the positioning given in  FIG. 6 . 
           [0018]      FIG. 9  shows the tie-rods while they are in the open position. 
           [0019]      FIG. 10  shows the tie-rods while they are neither in the open, nor in the closed position. 
           [0020]      FIG. 11  shows the tie-rods while they are in the closed position. 
       
    
    
     REFERENCE NUMBERS OF PARTS IN FIGURES 
       [0000]    
       
           1  Hull 
           2  Thruster motor 
           3  Thruster motor 
           4  Tie-rod part 
           5  Tie-rod part 
           6  Tie-rod 
           7  Propeller 
         F 2x  Horizontal force component of the thruster motor 
         F 2y  Vertical force component of the thruster motor 
         F 3x  Horizontal force component of the thruster motor 
         F 3y  Vertical force component of the thruster motor 
       
     
       DETAILED DESCRIPTION OF INVENTION 
       [0032]    As seen in  FIG. 1 , the stern of the hull ( 1 ) according to the present invention is provided with two thruster motors ( 2 ,  3 ), which are positioned side by side and comprise propellers ( 7 ) connected to each other preferably by means of a tie-rod ( 6 ) having two parts ( 4 ,  5 ). During a normal cruise, one of the thruster motors ( 2 ,  3 ) supported so as to turn around the vertical axis with the rudder being steered is turned around this vertical axis, such that the other thruster motor is synchronously turned around the vertical axis at the same direction by means of the tie-rod ( 6 ). Thus the steering of a boat is controlled at higher speeds. In other words, the parts ( 4 ,  5 ) of the tie-rod are displaced to a certain extent at both sides with respect to the center of the tie-rod ( 6 ), as illustrated in  FIG. 4 , and held at that position. It is appreciated here that the number of thruster motors may be three or more. 
         [0033]    The steering control of thruster motors ( 2 ,  3 ) particularly at lower speeds, such as during docking, is achieved by turning these motors around vertical axes with respect to water, preferably independently, or optionally, in an interconnected manner. According to the preferred embodiment of the invention, the parts ( 4 ,  5 ) of the tie-rod are independently driven at forward and backward directions for this purpose so that the thruster motors ( 2 ,  3 ) are turned vertically. The drive of the tie-rod parts ( 4 ,  5 ) may either be provided by means of a telescopic hydraulic mechanism, such as a piston-cylinder couple, or a mechanical or an electrical or a magnetic-based mechanism. Alternatively, a single tie-rod part may also be made to turn two thruster motors. 
         [0034]    By means of a proper arrangement of a preferred embodiment according to the present invention, as illustrated in  FIG. 5 , the thruster motors ( 2 ,  3 ) are turned vertically to dock a boat from the left, for instance. In this example, the parts ( 4 ,  5 ) of the tie-rod are brought close to each other so that the propellers of the thruster motors ( 2 ,  3 ) are brought far from each other, and one of the motors ( 2 ) is rotated in the forward direction so that the boat is moved forward, while the other motor ( 3 ) is rotated to provide rearward movement. As illustrated in  FIG. 2 , while the opposite vertical force components (F 2y , F 3y ) of thruster motors ( 2 ,  3 ) eliminate each other, the resultant force of the components at the same direction (F 2x , F 3x ) moves the boat to the left. The leftward steering of the boat may alternatively be provided by means of bringing the parts ( 4 ,  5 ) of the tie-rod away from each other, so that the propellers of the thruster motors ( 2 ,  3 ) are brought close to each other. This positioning of thruster motors is given in  FIGS. 6 to 8 . In this example, the thruster motor ( 2 ) is rotated to move the boat backwards, while the other motor ( 3 ) is rotated to move same forward. 
         [0035]    When the motor is to be steered rightward, this is achieved by means of bringing the parts ( 4 ,  5 ) of the tie-rod close-far to-from each other and changing the rotational direction of thruster motors ( 2 ,  3 ), in a manner similar to that described above. Since the parts ( 4 ,  5 ) of the tie-rod can independently be driven at desired amounts, the steering of the boat to the sides can also be achieved by following any desired docking path.