Abstract:
A ship propulsion system comprising a mechanism to convert mechanical power into a swinging, paddle-like action of a fin-like plate, located at the exterior of a vessel, thereby mimicking the propulsion made by the tail of a fish.

Description:
INTRODUCTION AND BACKGROUND OF THE INVENTION 
       [0001]    Current ship propulsion relies to a great extend on using different forms of rotating propellers in order to convert mechanical power into thrust. 
         [0000]    This method is generally satisfactory. However, there are major drawbacks. First, their mechanical efficiency is generally low and typically does not exceed 70%. That means that typically one-third of the mechanical power input into the propeller shaft is converted into heating the water via a process of turbulence. This can readily be observed in the wake of high speed motor boats. 
         [0002]    Secondly, the propeller speed is limited by a phenomenon called cavitation, where water vapor formed in a vacuum next to the propeller blade collapses further down stream, causing loss of efficiency, noise, and damage to the propeller&#39;s metal. 
         [0000]    Third, propellers are inherently noisy. This effect is especially detrimental to submarines relying on stealth. 
         [0003]    A similar, manual, propulsion system, using a form of a paddle, is exhibited in U.S. Pat. No. 6,709,306 by Brown, William Blake. His device was intended to amplify the thrust of a forearm and the device is not applicable to ship propulsion. 
         [0004]    My invention tries to overcome the above mentioned deficiencies by providing a system that mimics the propulsion method of the tailfins of fish. 
         [0000]    Some of us have observed dolphins racing along or even overtaking ocean liners. They seem to swim almost effortlessly, with no discernable wake left behind. This indicates a very high efficiency in the translation from muscle power to forward thrust.
 
Fishes can regulate the speed of their forward motion by changing the angular excursion of their tails, and by changing the frequency thereof.
 
         [0005]    My invention also takes account of the need to vary the speed of a vessel, by being able to change the angle of excursion of my fishtail substitute. 
         [0000]    Finally, it was observed, that there is a momentary pause in the motion of a fishtail following a power stroke. This allows the displaced water to settle down.
 
How this is accomplished in my invention, and other explanations, are given in the following description of my invention.
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a cross-sectional, central, view of a preferred embodiment of my invention, with the front portion of the depicted vessel removed. 
           [0007]      FIG. 2  is a planar view of the embodiment shown in  FIG. 1  with the second plate removed for clarity. 
           [0008]      FIG. 3  is a schematic view of the linkage arrangement of my invention, depicting the relationship between the rotational input and the angular excursions, shown at its maximum setting. 
           [0009]      FIG. 4  is a schematic view similar as in  FIG. 3 , with the linkage set to produce only one-half of the angular excursions. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    Referring to  FIG. 1 , it shows a vessel  1 , having an open hull  4 , containing therein an engine  2 , having a rotating output shaft  3  solidly connected to an arm  7 , having a slotted opening  13 , and, on one end receiving a pivot pin  8  connecting to a movable beam  9 . Linkage pin  8 , furthermore connects to a adjustable linkage consisting of an outer link  15  and an inner link  14 , the latter being rotably connected to shaft  3 . 
         [0000]    Any rotation of link  14  vis-a-vis shaft  3  causes to pivot pin  8  to slide within slot  13  and thereby alter the radial distance between pin  8  and shaft  3 . This, in turn, causes a change in the excursion of beam  9 . 
         [0011]    Beam  9 , after exciting the hull  4  of the vessel, connects to another arm  10  via a pin  17 . The latter is slidingly arranged in a slotted opening  12  being part of beam  9 . 
         [0000]    Arm  10  in turn is fixedly connected to a shaft  6 , being part of a plate  5 . This plate is supported, together with shaft  6  by a support bracket  18 . The latter being suitably fastened to the hull of the vessel. 
         [0012]    Any outward movement of beam  9  will cause pin  17  to slide a given distance along slot  12  and, thereafter, rotating arm  10  in a clockwise direction. This, in turn, causes arm  5  to swing across an arc, defined by twice the angle α. 
         [0013]    Plate  5  furthermore, has attached to it a second plate  11 , able to swing freely around a shaft  19  over a distance defined by twice the angle β. The amount of rotation in either direction is limited by a pre-defined stop  16 . 
         [0014]    The function of my proposed mechanism will be better understood when viewing  FIGS. 3 and 4 . 
         [0000]      FIG. 3  shows the distance RI (between pivot point  8  and rotating shaft  3 ) at its maximum. Neglecting, for simplicity, the loss of motion by pin  17  in slot  12 , we can see, that when pivot pin is in an outer, horizontal plane (labeled A), beam  9  is fully extended. This causes plate  5  to swing fully in the clockwise direction to point A. Upon rotation of shaft  3  to an upper, vertical direction (B), plate  5  now assumes a neutral, horizontal position B. Upon further rotation to point C, the plate  5  now swings in the opposite direction indicated as C. Continuing the rotation of shaft  3  to point D will reverse the swinging motion of plate  5  towards a neutral, horizontal position again (D); thereafter, the former actions begin anew. 
         [0015]      FIG. 4  depicts a setting of pin at a distance R 2 , being half the distance shown in  FIG. 3 . While actions between rotation of pivot pin  8  and the following excursions of plate  5  between locations A to D are identical, the resultant angular excursions of plate  5  now is only one half the angular distance. This causes a greatly reduced output of mechanical power than the configuration shown in  FIG. 3 , causing the speed of propulsion to decrease, as shall be explained below. 
         [0016]    The Power conversion used to convert mechanical power into a propulsion force can best be understood from the following example; 
         [0000]    Assuming a plate  5 , having an effective area A of 1 square feet and a length L of 1.5 feet, of which ⅔rds being the average effective length. Assuming further, that the velocity of movement of the plate U is 10 feet per second. Note, that the max. plate velocity is obtained when the plate is at the max. angle α corresponding to a position of pivot point of B or D, and while the plate is swinging towards the center position. Since only a portion of the displaced water is pushed backwards, we have to multiply the force by the sinus of the angle α, here assumed to be 40 degrees. The density of water ρ is assumed to be 62 pound per cubic feet. 
         [0017]    From the above, and neglecting efficiencies, we have: 
         [0000]      Horse Power= A× ⅔  L×U×sin α×ρ/ 78.
 
         [0000]    This yields, for the above example, 5.1 Horse Power. 
         [0018]    The reaction force which propulses the ship is given as: 
         [0000]        F =Mass×Velocity 2  
 
         [0000]    Where the mass is: A×⅔L×ρ×sin α/2×32.1=0.62 lbs s 2 /ft,
 
This makes F=0.62×10 2 =62 lbs.
 
         [0019]    It is now recognized, that when the distance R 2  between pivot point  8  and shaft  3  is reduced in half, then the plate velocity at ⅔ L is also only one half. This then makes the horse power requirements only 1.4 HP, or, only 27% of what is needed for the max. R 1  setting. 
         [0020]    This also reduces the mass moved to only 0.16 lbs s 2 /ft. and the resulting force F to 8 lbs. It can be seen, that a reduction of the beam  9  movement by 50% can yield a force reduction down to 13%, or over a ratio of about 8:1. This shows the great effectiveness of using an adjustment of the lever ratio as a means for speed control of a ship. 
         [0021]    The following is a discussion of the purpose of the override provided by slot  12  in beam  9 . Its functions to stop the movement of plate  5  momentarily, once a max excursion of plate  5  is reached in either direction. This will allow time to move arm  7  towards a near vertical position (either up or down), where it can accomplish the highest angular velocity, hence the maximum power input on beam  9  and therefore on plate  5 . Conversely, when arm  7  is in a nearly horizontal position, there will be little movement and velocity of beam  9 . This is when plate  5  in each respective maximum position following a power stroke. 
         [0022]    A power stroke here is defined where arm  7  travels +/−45 degrees from positions B or D. Here beam  9  achieves the highest velocity. 
         [0023]    A second, movable plate is swingingly attached to the end of plate  5 , by means of an axel  19 . The swinging motion of plate  11  is restricted at typically 45 degrees from the longitudinal axis of plate  5 . Any further excursion is limited by stops  16 . The purpose of plate  11  is as follows: During each power stroke of plate  5  (towards the center) there will be resistance by the water. This resistance pressure now forces plate  11  to swing in the opposite direction of plate  5  movement, till the stops  16  limited the tilting, This causes the plate to exert an opposite pressure on the water in contact, thereby helping in the propulsion effort aided by the greater contact angle (angle α plus angle β) than provided by plate  5  alone. The greater angle plus the greater distance between plate  11  and shaft  6  now allow for a greater power conversion than previously discussed. 
         [0024]    While the invention has been discussed in a preferred embodiment, nothing shall preclude additional modifications without departing from the scope of the following claims. For example, instead of providing a slot in beam  9 , such means of override can also be provided in arm  10 . It may also be advisable to make beam  9  adjustable in length, to aid in calibration. Further more, instead of having a rotating linkage arrangement, pivot point  8  may also be distance adjusted by means of a motor driven screw.