Abstract:
A water propulsion assembly operatively connected to a watercraft moving on or through a body of water, may produce a propulsive force by sweeping fins in an oscillating motion in a generally transverse direction relative to a longitudinal axis of the watercraft. The fins may be rotatable about a first axis coplanar to the center longitudinal axis of the watercraft. Drive members rotatable about a second axis that is canted relative to the first axis may be operatively connected to the fins. The oscillatory motion of the fins may be controlled by torque applied at the canted second axis by reciprocating the drive members in a plane generally parallel to the center longitudinal axis of the watercraft. The oscillating fins may provide a propulsive force during both oscillating directions of the fins as they sweep back and forth.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application Ser. No. 62/123,446, filed Nov. 17, 2014, U.S. Provisional Application Ser. No. 62/123,805, filed Nov. 29, 2014, U.S. Provisional Application Ser. No. 62/125,283, filed Jan. 16, 2015, U.S. Provisional Application Ser. No. 62/125,874, filed Feb. 2, 2015, U.S. Provisional Application Ser. No. 62/177,008, filed Mar. 3, 2015, U.S. Provisional Application Ser. No. 62/177,786, filed Mar. 23, 2015, and U.S. Provisional Application Ser. No. 62/178,201, filed Apr. 2, 2015, which applications are incorporated herein in their entireties by reference. 
    
    
     BACKGROUND 
     The present invention relates to a water propulsion system, and more generally, to a thrust generating oscillating fin propulsion assembly adapted for underwater propulsion. 
     Pedal operated propulsion apparatus, such as a foot operated paddle boat described in U.S. Pat. No. 3,095,850, are known in the art. Other pedal operated means linking rotatable pedals to a propeller have been proposed. Some have looked to the swimming motion of sea creatures to design mechanically powered propulsion systems. Generally speaking, the swimming behavior of sea creatures may be classified into two distinct modes of motion: middle fin motion or median and paired fin (MPF) mode and tail fin or body and-caudal fin (BCF) mode, based upon the body structures involved in thrust production. Within each of these classifications, there are numerous swimming modes along a spectrum of behaviors from purely undulatory to entirely oscillatory modes. In undulatory swimming modes thrust is produced by wave-like movements of the propulsive structure (usually a fin or the whole body). Oscillatory modes, on the other hand, are characterized by thrust production from a swiveling of the propulsive structure at the attachment point without any wave-like motion. A penguin or a turtle, for example, may be considered to have movements generally consistent with an oscillatory mode of propulsion. 
     In 1997, Massachusetts Institute of Technology (MIT) researchers reported that a propulsion system that utilized two oscillating blades of MPF mode produced thrust by sweeping back and forth in opposite directions had achieved efficiencies of 87%, compared to 70% efficiencies for conventional watercraft. A 12-foot scale model of the MIT Proteus “penguin boat” was capable of moving as fast as conventional propeller driven watercraft. Another MIT propulsion system referred to as a “Robotuna,” utilized a tail in BCF mode propulsion patterned after a blue fin tuna, achieved efficiencies of 85%. Based upon limited studies, higher efficiencies of 87% (and by some reports 90-95% efficiency) may be possible with oscillatory MPF mode propulsion that may enable relatively long distances of human powered propulsion being achieved both on and under the water surface. 
     U.S. Pat. No. 6,022,249 describes a kayak having a propulsion system that extends below the water line. The propulsion system includes a pair of flappers in series, each adapted to oscillate through an arcuate path in a generally transverse direction with respect to the central longitudinal dimension of the kayak. 
     SUMMARY 
     In an oscillating fin propulsion assembly operatively connected to a watercraft moving on or through a body of water, a propulsive force may be produced by a pair of fins adapted to sweep back and forth in a generally transverse direction relative to the longitudinal axis of the watercraft. The fins may be rotatable about a first axis coplanar to the center longitudinal axis of the watercraft. Drive members rotatable about a second axis that is canted relative to the first axis may be operatively connected to the fins. The oscillatory motion of the fins may be controlled by torque applied at the canted second axis by reciprocating the drive members. The oscillating fins may provide a propulsive force to propel the watercraft longitudinally forward during both oscillating directions of the fins as they sweep back and forth. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features, advantages and objects of the present invention are attained can be understood in detail, a more particular description of the invention briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. 
       It is noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is a partially broken away perspective view of an oscillating fin propulsion assembly mounted to a rear region of a floatation device. 
         FIG. 2  is a perspective view of a canted journal block of the oscillating fin propulsion assembly shown in  FIG. 1 . 
         FIGS. 3A-3G  are perspective views illustrating multiple positions of the fins upon actuation of the drive handles of the oscillating fin propulsion assembly shown in  FIG. 1 . 
         FIG. 4  is a perspective view of a user operating the oscillating fin propulsion assembly shown in  FIG. 1 . 
         FIGS. 5A-5C  are partially broken away perspective views of a second embodiment of an oscillating fin propulsion assembly mounted to a rear region of a floatation device. 
         FIG. 6  is a perspective view of a user operating the oscillating fin propulsion assembly shown in  FIGS. 5A-5G . 
     
    
    
     DETAILED DESCRIPTION 
     Referring first to  FIG. 1 , a water floatation device, such as a swim board, a paddle board, a surfboard and the like is illustrated outfitted with an oscillating fin propulsion system generally identified by the reference numeral  100 . The propulsion assembly  100  may include transversely spaced apart left and right longitudinal shafts  102  and  104  rigidly secured to a rear region of a water floatation device  106 . Alternatively, the shafts  102 ,  104  may be fixed at central or forward regions of the floatation device  106 . The shafts  102 ,  104  may include laterally extending members (not shown in the drawings) in order to distribute forces acting on the shafts  102 ,  104  more broadly within the core of the floatation device  106 . When utilizing wood or other solid board material for fabrication of the floatation device  106 , holes may be bored into the floatation device  106  and the shafts  102 ,  104  glued in place. In yet another fabrication example, the floatation device  106  may be blow molded having a foam interior. Support for the shafts  102 ,  104  may be at an edge region of the blow molded shell. 
     Left and right canted journal blocks  110  and  112  may be rotatably secured to respective shafts  102 ,  104 . The canted journal blocks HO,  112  may include an axial borehole  114 , better shown in  FIG. 2 , for receiving a respective shaft  102 ,  104  therethrough. The canted journal blocks  110 ,  112  may include first axes A 1  and B 1 , respectively, coincident with the center longitudinal axis of the boreholes  114 . The axes A 1  and B 1  may extend parallel to the longitudinal center axis of the floatation device  106 . 
     Referring still to  FIGS. 1 and 2 , each canted journal block  110 ,  112  may include a pair of spaced apart upstanding tabs  116 . The tabs  116  may include through holes  118  that are axially aligned with one another. Lower distal ends of elongated drive handles  120  may be rotatably secured between the tabs  116  of each canted journal block  110 ,  112  by a shaft  122 . The lower distal end of the drive handles  120  may comprise a hollow tube fixed to or integrally formed with the drive handles  120  extending transversely to the longitudinal axis of the drive handles  120 . 
     The left and right canted journal block  110 ,  112 , may further include second axes A 2  and B 2  defining the longitudinal axes passing through the center of axially aligned through holes  118  of the tabs  116 . The second axes A 2 , B 2  may be displaced and canted relative to the first axes A 1 , B 1  of the canted journal block  110 ,  112 . The first axes A 1 , B 1  and the second axes A 2 , B 2  of the left and right canted journal blocks  110 ,  112  may be angularly displaced from one another by an a canted angle of about ten (10°) to about eighty (80°) degrees. Preferably, the canted angle may be about forty-five (45°) degrees. The canted angle may be directed from the front to the rear in an inwardly direction, or alternatively, the canted angle may be directed from the front to the rear in an outwardly direction. 
     In the drawings, the illustrated canted angle is forty-five (45°) degrees. Adjusting the canted angle to more or less than forty-five (45°) degrees will result in an increase or decrease of lateral forces encountered at the drive handles  120  during propulsion and maneuvering of the floatation device  106 . Optimum canted angles may be determined for specific applications. For example, but not by way of limitation, at canted angles greater than forty-five (45°) degrees, the displacement or movement of the drive handles  120  may be generally greater compared to the displacement or movement of the fins  140 . Conversely, canted angles less than forty-five (45°) degrees may result in rapid and greater displacement or movement of the fins  140  compared to relatively less displacement or movement of the drive handles  120 . A canted angle of less than forty-five (45°) degrees may require a user to apply greater force to move the drive handles  120  during propulsion of the floatation device  106 . 
     Referring again to  FIG. 1 , a fin  140  may be connected to each of the canted journal blocks  110 ,  112 . The fins  140  may include a generally rigid spine  142  and a generally flexible region  144 . The fins  140  may comprise a substantially flat body that is thicker along their leading edge defined by the spine  142 . The thickness of the fins  140  may gradually decrease from the spine  142  to a trailing edge  146 . The stiffness or rigidity of the fins  140  is generally greater at the spine  142  and decreases toward the trailing edge  146 . Combinations of different materials in the manufacture of the fins  140  or other manufacturing means may alter the stiffness characteristics of the fins  140 . 
     Continuing now, the left and right drive handles  120  may be rotatably secured to the left and right canted journal blocks  110 ,  112 . A foot strap  124  may connect the left and right drive handles  120 . A portion  130  of the foot strap  124  may be fabricated of rigid material having opposite ends operatively connected to ball joints  126  and  128 , respectively, for maintaining a constant distance between the ball joints  126 ,  128 . 
     Referring now to  FIGS. 3A-3F , multiple positions of the fins  140  are illustrated upon movement by a user of the foot strap  124  to different positions and configurations. Movement of the foot strap  124  and consequently the drive handles  120 , along a plane that is laterally centered with respect to the transverse center of the floatation device  106  and where the motion of the ball joints  126 ,  128  occurs in equal left and right arc paths P 1  (illustrated in  FIG. 4 ), results in the forward motion of the floatation device  106 . Deviation of the arc paths P 1  of the ball joints  126 ,  128  may result in thrust forces including both propulsion and maneuvering components. Thrust as well as maneuverability is possible depending upon the deviated arc paths (illustrated in  FIGS. 1  as P 2  and P 3 ) of the ball joints  126 ,  128 , respectively. For example, but not by way of limitation, if a user reciprocates the drive handles  120  generally to the left, the floatation device  106  will yaw or turn right. In addition to yaw control, a user may change the direction that the floatation device  106  is pointing as well as rotate the floatation device  106  about a vertical axis. Roll control is also possible in the situation when a user may want to cause rotation about the center longitudinal axis of the floatation device  106  causing the left or right side of the floatation device  106  to rise out of the water. The efficiency of generating significant lateral thrust with the fins  140  combined with the efficiency of generating thrust in a forward direction, results in a fast and highly maneuverable floatation device  106 . 
     It should be noted that the canted axis blocks  130 ,  132  may be molded identically (as illustrated throughout the drawings) where oscillation of the fins  150  ranges between ten and two o&#39;clock positions when viewing a diver moving horizontally facing downwardly. However, for example, but not by way of limitation, where oscillation of the fins  150  may range between one and five o&#39;clock positions, distinct and separately molded left and right canted axis blocks  130 ,  132  may be required, where the canted axes A 2  and B 2  of the canted axis blocks  130 ,  132  are identically oriented for the left and right sides of the propulsion apparatus, however, the bosses  154  may have a left side orientation and a right side orientation relative to the axes A 1  and B 1 , respectively. 
     Referring now to  FIGS. 5A-5C  and  FIG. 6 , a second embodiment of an oscillating fin propulsion system is generally identified by the reference numeral  200 . As indicated by the use of common reference numerals, the propulsion system  200  is similar to the propulsion assembly  100  described hereinabove with the exception that drive handles  120  include individual foot straps  224  fixedly secured to the upper distal ends of the drive handles  120 . Providing independent control of the fins  140  may increase the complexity for the user in maneuvering the floatation device  106  but provides greater variations in the movements of the drive handles  120  and the fins  140 . In may be noted that individual control of the drive handles  120  may require a user to manipulate the drive handles  120  laterally while propelling the floatation device  106  is a forward direction, thereby requiring greater user coordination and involve use of additional muscle groups. 
     In  FIGS. 5A-5C , perspective views are shown illustrating multiple positions of the fins  140  relative to the position of the drive handles  120  actuated by a user. In  FIG. 6 , a user lying on his back on a floatation device  106  is illustrated alternately and independently pushing and pulling the drive handles  120  to oscillate the fins  140  providing propulsion to move the floatation device  106  is a desired direction. 
     As described above with reference to the propulsion system  100 , the canted journal blocks  110 ,  112  include two axes that are canted relative to each other. During normal operations of the oscillating fin propulsion systems described herein, axial and lateral forces acting on the canted journal blocks  110 ,  112  may be encountered that may require axial and radial load bushings, for example but not by way of limitation, flanged sleeve and/or conically shaped bearing bushings. UHMW, ceramic, graphite, or other non-metallic materials may be utilized in load bushing concentric with shafts  102 ,  104  providing interface surfaces between the shafts  102 ,  104  and the drive handles  120 . Alternatively, metal such as phosphor bronze or stainless  440 C may be utilized in such load bearings. 
     While several embodiments of oscillating fin propulsion apparatus have been shown and described herein, other and further embodiments of oscillating fin propulsion apparatus may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims which follow.