Abstract:
A foot-operated propulsion system for small watercraft, such as kayaks. The propulsion system includes a pedal assembly that controls motion of a fluke fin that is submerged beneath the waters surface. The pedal assembly is located in the bow of the watercraft and the paddler works the pedals with his feet. Operating the pedal assembly causes a force to be transmitted to a drive unit located in the stern of the craft, which then controls movement of linkages in the fluke assembly, to force the submerged fluke fin to swing upward and downward, emulating the motion of flukes on a whale, and thereby propelling the watercraft along the surface of the water.

Description:
BACKGROUND INFORMATION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to propulsion systems for small watercraft, more particularly, the invention relates to a foot-operated propulsion system for a kayak. 
         [0003]    2. Discussion of the Prior Art 
         [0004]    Kayaks and other small watercrafts have existed for a long time and are traditionally operated by having a user, i.e., a paddler, use one or more oars or paddles to propel the craft through the water. Kayaking in particular is a popular paddle sport, whereby the paddler operates a relatively long, narrow vessel with a double-sided paddle. The paddler generally sits near the center of the craft such that the paddler&#39;s legs stretch out straight towards the bow, with feet at or near the same level as the paddler&#39;s hips. Traditionally, the paddler uses his/her upper body and arms to manipulate an oar or paddle to propel the watercraft through the water. 
         [0005]    The largest and strongest muscles in a person, however, are typically the leg muscles. It would be advantageous, if the paddler could take advantage of the greater power those muscles can provide. Also, many people have disabilities or handicaps that make it difficult or impossible to operate an oar or paddle. Because of this, it is difficult or impossible for them to participate in activities that include kayaking or canoeing. 
         [0006]    What is needed, therefore, is a propulsion system for small watercraft that is powered by a paddler&#39;s feet. What is further needed is such a system that is easy to use and does not impede beaching, launching, or transporting the watercraft. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    The invention is a foot-operated linear propulsion system for small watercraft that is particularly well suited for use with a kayak. The propulsion system comprises three main assemblies: 1) a pedal assembly; 2) a drive unit; and 3) a fluke assembly that includes a fluke activation mechanism and a fluke fin, often simply referred to as a fluke. The pedal assembly is positioned in the front of the craft, in the bow section, and is easily operated by paddler&#39;s feet. The drive assembly is located in the rear of the craft, i.e., in the stern, and, as the paddler works the pedals, a cable running beneath the paddler transmits a force to the drive unit. The drive unit controls the fluke fin activation mechanism, which causes a submerged fluke fin located outside the craft and extending beyond the stern to move up and down below the surface of the water, thereby propelling the craft along the surface of the water. The movement of the fluke fin mimics that of living water creatures, such as whales and dolphins. A lift mechanism is also provided to selectively raise the fluke assembly before launching, beaching, or transporting the kayak or watercraft. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. The drawings are not drawn to scale. 
           [0009]      FIG. 1  is a side plan view of the system according to the invention. 
           [0010]      FIG. 2A  is a side plan view of the first two embodiments of the pedal assembly. 
           [0011]      FIG. 2B  is a front plan view of a portion of the pedal assembly. 
           [0012]      FIG. 2C  is a top plan view of a portion of the pedal assembly. 
           [0013]      FIG. 2D  is a top plan view of the modified chain link. 
           [0014]      FIG. 2E  is a side plan view of the modified chain link. 
           [0015]      FIG. 2F  is a top plan view of the third embodiment of the pedal assembly. 
           [0016]      FIG. 2G  is side plan view of the third embodiment of the pedal assembly. 
           [0017]      FIG. 3A  is a top plan view of the fluke actuation and output drive assembly. 
           [0018]      FIG. 3B  is a side plan view of the fluke actuation and output drive assembly. 
           [0019]      FIG. 3C  is a partial perspective view of the cable tray. 
           [0020]      FIG. 3D  is a partial perspective view of the stern section of the hull of the kayak, showing the cutout in the hull. 
           [0021]      FIG. 4A  is a cross-section of the drive unit in the cable tray. 
           [0022]      FIG. 4B  is a top plan view of the drive unit. 
           [0023]      FIG. 4C  is a side elevation view of the drive unit. 
           [0024]      FIG. 5A  is a side plan view of the fluke drive. 
           [0025]      FIG. 5B  is a side plan view of the fluke, socket, and fluke plate. 
           [0026]      FIG. 5C  is a top plan view of the elements shown in  FIG. 5B . 
           [0027]      FIG. 5D  is a perspective view of the socket connector. 
           [0028]      FIG. 6A  is a perspective view of a guide rail and carriage assembly for the lift cable. 
           [0029]      FIG. 6B  is cross-sectional view of the drum pulley and the guide rail and carriage assembly for the lift cable. 
           [0030]      FIG. 6C  is a side elevation view of the drum pulley, guide rail, and carriage assembly for the lift cable. 
           [0031]      FIG. 6D  is a side plan view of the lift and stop connections. 
           [0032]      FIG. 6E  is a side elevation view of the lift mechanism in the drive unit. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    The present invention will now be described more fully in detail with reference to the accompanying drawings, in which the preferred embodiments of the invention are shown. This invention should not, however, be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be complete and will fully convey the scope of the invention to those skilled in the art. 
         [0034]      FIG. 1  gives an overview of the major assemblies for a linear propulsion system  100  according to the invention, with intended use with small watercraft. The assemblies comprise a pedal assembly  10 , a drive unit  30 , and a fluke assembly  50  that includes a fluke  70  and a fluke lift mechanism  80 . The pedal assembly  10  is positioned in the bow of the watercraft. The description hereinafter refers to the watercraft in terms of a Kayak K, however, it is understood that the inventive system may be used with other appropriate watercraft. A paddler (not shown) sits in an adjustable seat S that is slidably mounted in the kayak K, such that it is able to slide a distance toward the bow or the stern and, in this manner, able to accommodate the leg length of the particular paddler and thereby allow the paddler to comfortably operate the pedal assembly  10  with his or her feet. Working the pedal assembly  10  causes the drive unit  30  to actuate the fluke assembly  50 , which causes the fluke  70  to move up and down below the surface of the water, thereby propelling the kayak K along the surface of the water. 
         [0035]      FIGS. 2A ,  2 B, and  2 C illustrate the pedal assembly  10 , which is enclosed in a box formed by a cable tray  90  and vertical walls  91  and a top wall  91 A. The cable tray  90  extends along the bottom portion of the kayak K, from beneath the pedal assembly  10  in the bow section of the kayak, back to the stern section beneath the drive unit  30  and is securely and immovably attached to the body of the kayak K. The cable tray  90  serves to guide and protect the cables of the various assemblies and the vertical walls  91  provide the support for the shafts and pulleys of the various assemblies. The walls  91  may extend the entire length of the tray or, as shown in the various figures, may be short walls that extend only partially along the length, so as to accommodate the assemblies, and may also be affixed to the body of the kayak K, as deemed necessary. In these figures, the vertical walls  91  and the top wall  91 A, together with the cable tray  90 , enclose the pulleys and cables, belts, or chains of the pedal unit  10 . The pedal assembly  10  includes a pair of pedal units, each unit including a pedal  12 , a pedal crank arm  14 , and a pedal force transmission means  18 . Each pedal  12  is affixed to its corresponding crank arm  14 , which is coupled to a pedal force transmission means  18  that is mounted on a shaft that also supports the pedal force transmission means  18 . Depending on the particular embodiment of the force transmission means  18 , the crank arm  14  may be connected to a bearing assembly  16 , which is mounted on the same shaft with the pedal force transmission means. Where necessary to illustrate the mechanics of the pedal assembly  10 , the various elements are identified as  12 A and  12 B,  14 A and  14 B,  16 A and  16 B, and  18 A and  18 B, all elements with an “A”, for example, belonging to the units on the left side of the kayak and all with a “B” belonging to the other unit on the right side. 
         [0036]    The kayak K has a centerline CL that extends in the longitudinal direction of the kayak k. Each bearing assembly  16  is positioned at the inner end of a horizontal shaft  15  in the bow of the kayak K, the two horizontal shafts  15  creating an axis that extends transverse to the centerline CL. The crank arm  14  and pedals  12  are mounted on the outside ends of the respective shaft  15 . A drum pulley  26  is mounted on a horizontal shaft  24  that extends transverse to the centerline CL and is positioned behind and parallel to the axis created by the horizontal shafts  15 , the drum pulley  26  being centered about the centerline CL. The force from the pedal  12  may be mechanically transmitted in various ways to the drive unit  30 . 
         [0037]    In a first embodiment, for example, the pedal force transmission means  18  is a chain and sprocket assembly  18 ′ that is used to exert a pull on the drum pulley  26 , so that the pulley oscillates back and forth a distance of approximately plus/minus 45 degrees. In this case, pedal sprockets  18 A and  18 B are mounted on the horizontal shaft  15 , one on each inner end of the respective horizontal shaft  15  and pulley sprockets  23  mounted to the horizontal shaft  24 , one on either side of the drum pulley  26 . A two-chain set  22  is used to convert the action of the two pedals  12  to an oscillating pull on the drum pulley  26 . 
         [0038]    The chain set  22  includes a first chain loop  22 A and a second chain loop  22 B. The first chain loop  22 A runs continuously from the top of the pedal sprocket  18 A around the top of the pulley sprocket  23 A and then from the bottom of the pulley sprocket  23 A to the bottom of the pedal sprocket  18 A. The second chain loop  22 B loops in a crossed manner from the top of the pedal sprocket  18 B to the bottom of the pulley sprocket  23 B and then around the top of the pulley sprocket  23 B to the bottom of pedal sprocket  18 B. 
         [0039]      FIG. 2A  shows that the path of the chain  22 B is crossed, i.e., one section of the chain passes through another section of the same chain. A portion of the pedal sprocket  18 B is cut out to show that the pedal sprocket  18 A is behind the other sprocket.  FIGS. 2D and 2E  illustrate a modified link  25  in the second chain loop  22 B that has a pass-through  25 A that is dimensioned to accommodate the length of travel of the chain  22 B as it oscillates back and forth by the pedal action. Crossing the second chain loop  22 B in this manner allows the chain  22 B to operate in a single vertical plane and serves to reverse the direction of pull on the corresponding pulley sprocket  23 B. So, for example, pushing the right pedal  14 A causes the drum  26  to rotate in the counterclockwise direction and pulls the left pedal  14 B into position for the next push, and pushing the left pedal  14 B causes the drum  26  to rotate in the clockwise direction and pulls the right pedal  14 A into position for the next push. A drive cable  92  is wrapped around the drum pulley  26 , which is dimensioned such that the angle of rotation mentioned above results in a pull length, i.e., stroke, of about six inches on the drive cable  92 . 
         [0040]    A second embodiment of the pedal force transmission means  18  is a belt or cable and pulley system  18 ″. The configuration of this system is similar to that of the sprocket and chain system described above, except that the sprockets are replaced by pulleys and the set of two chains by a set of two belts or cables. 
         [0041]      FIGS. 2F and 2G  illustrate a third embodiment of the pedal force transmission means  18 ′″, which is a system of levers. A ball-end link  19  with a threaded stud  191  at both ends is used to couple a pedal lever  192  from each pedal  12  directly to the drum pulley  26 . The two links  19  are mounted on the respective pedal levers  192  and on opposite sides of the drum pulley  26 . As shown in  FIG. 2G , the links  19  are coupled at different locations on the pedal levers  192  and the pulley  26 , such that a forward push on one pedal  12  forces the pulley  26  to rotate in one direction and a forward push on the other pedal  12  forces rotation in the opposite direction. The ball-end link  19  is a well-known conventional component, such as, for example, a ball joint linkage available from McMaster-Carr. 
         [0042]      FIGS. 3A and 3B  show that the drive unit  30  and a portion of the fluke assembly  50  are assembled in the stern section of the kayak K. To this end, an opening  101  is made in the stern section of the hull of the kayak, the upper end of the opening being above the waterline WL and extending down to the bottom of the hull, and being just wide enough to accommodate linkage for the fluke assembly  50 . The opening is shown in  FIG. 1 , with a dashed or a dotted line across the top and down in front of the drive unit  30  and in  FIG. 3D , which is a perspective view of the stern portion of the bottom hull of the kayak and shows the walls  102  forming a box. The walls  102  of the opening are affixed to the body of the kayak K and form a water-tight barrier between the opening  101  and the inside area of the kayak. Depending on the particular watercraft, the dimensions of the opening may vary. The inventor chose to install this propulsion system  100  in a Twin Heron model of a kayak made by the Old Town Canoe Company, because the shape of its stern is somewhat higher and more rounded than is the case with other types of kayaks. In this particular kayak, the opening  101  is about five inches wide and extends inward approximately 12 inches. 
         [0043]      FIG. 3C  is a perspective partial view of the cable tray  90 , showing a cable guide  97  that serves to maintain the drive cable  92  and the lift cable  83  in proper alignment as they travel from the pedal unit  10  in the bow to the drive unit  30  and to the fluke lift mechanism  80  in the stern of the kayak K.  FIGS. 3A and 3B  illustrate the drive unit  30  and the fluke assembly  50 . A drive cable  92  is wrapped around the drum pulley  26 , passes through an idler pulley  27  and serves to couple the pedal unit  10  to the drive unit  30 , where the drive cable  92  is then routed through a series of drive unit pulleys  32  which are mounted on shafts  99  that extend transverse to the centerline CL between two vertical walls  91  and which serve to align the cable  92 . 
         [0044]      FIGS. 4A-4C  illustrate the drive unit  30  with its corresponding rear drive guide rail  98  and rear carriage assembly  96 . The drive cable  92  is routed through a plurality of drive unit pulleys  32  and then clamped to the rear drive carriage assembly  96  by means of the clamp  93 . The carriage assembly  96  is connected to a drive link  38  by means of a drive link bracket  34 . The drive link  38  extends rearward out through a notch in the stern wall  102  and is coupled to the fluke assembly  50 . The drive cable  92  is pulled back and forth a total travel distance of about six inches by reciprocating action on the pedals  12 , which forces the carriage assembly  96  to travel back and forth along the rear drive guide rail  98 , thereby moving the drive link  38  forward and aft. 
         [0045]      FIGS. 5A ,  5 B, and  5 C illustrate in detail the linkages in the fluke assembly  50  that drive the motion of the fluke  70 . It is generally understood, that a fluke or foil loses its effective lift when the angle of attack exceeds a certain angle and this is taken into consideration in the design of the fluke assembly  50 . In the embodiment shown, the angle of attack is approximately plus/minus 20 degrees on the upstroke and downstroke. The fluke  70  moves vertically a certain distance at a defined and constant angle relative to a horizontal plane and, when reversing direction of travel, the fluke  70  flips, due to the force of the water, changing its angle of attack to the other side of the horizontal plane. In other words, on the upstroke, the force of the water forces the fluke  70  to a downward angle, and on the downstroke, forces the fluke to an upward angle. This motion approximates the natural fluke action of a whale or dolphin, which is known to be a very effective way to propel a mass through water. 
         [0046]    Four-bar linkages are used on the fluke assembly  50  to move the fluke  70  in the desired manner. The fluke assembly  50  extends outward from the stern end of the kayak K and is centered about the centerline CL of the kayak. The support for the fluke assembly  50  is a vertical support bracket  42  that is mounted on the inside of the vertical wall  102  in the opening  101 , shown in  FIG. 3D . A stern bracket  54  is attached to the support bracket  42  through the vertical wall  102 . The stern bracket  54  is a C-channel, the intermediate section of the channel being affixed to the support bracket  42  and the two side sections having bores to support upper horizontal shaft  55 A and lower horizontal shaft  55 B. Horizontal shaft  55 A extends through vertical side walls of the opening  101  into the hull of the kayak. The link  38  is movably coupled to the upper ends of two vertical drive arms  51  at a hinge point  52  and the lower ends of the vertical drive arms and the main elevator arms  58  are coupled to the lower horizontal shaft  55 B. A horizontal drive arm  65  is coupled to a midpoint coupling point  53  on each respective vertical drive arm  51  at one end and to a top pivot point  64 B on a fluke lift plate  62 . The lower end of the main elevator arms  58  are coupled to a horizontal shaft at a lower pivot point  64 A on the fluke lift plate  62 . 
         [0047]    The fluke  70  has a foil-shaped cross-section, as shown in  FIG. 1 . In plan view, the particular shape may vary, although triangular shapes are most similar to the shapes of flukes found on whales and dolphins. The fluke  70  is connected to the fluke assembly linkage  50  so as to be removable for transportation and storage. 
         [0048]      FIGS. 5B and 5C  illustrate the linkages that control the angle of attack of the fluke  70 . Only a partial view of the fluke lift plate  62  is shown here, the portion that has a third coupling point that is coupled via a fluke pivot shaft  72  to the fluke  70  and also to a fluke stop link  77 , which has upper and lower stop edges  73 A and  73 B. A mounting socket  74  with a stop blade  76  connects the fluke  70  with the fluke lift plate  62  and the fluke stop link  77 . The fluke stop link  77  and the blade  76  cooperate to limit the rotation of the fluke  70  to the optimum force transmission arc about the fluke pivot  72 . Thus, when the stop blade  76  contacts the stop edges  73 A and  73 B, the fluke  70  is prevented from swinging further upward or downward. 
         [0049]      FIG. 5D  illustrates details of the mounting socket  74  and the fluke  70 . The leading edge of the fluke  70  has a connector  79  for receiving a mounting socket  74  that is also coupled to the fluke pivot shaft  72 . The mounting socket  74  is aligned with the centerline CL of the kayak, between the trailing ends of the two fluke lift plates  62  and, in addition to the stop blade  76 , also has a socket assembly  75  that is insertable into the connector  79 , which, in the embodiment shown, is a rectangular tubular socket that is dimensioned to receive the socket assembly  75 . The mounting socket  74  aligns with the shape of the foil to provide a smooth transition of fluke to socket, so as to reduce drag on the movement of the fluke and socket through the water. A threaded bore  75 A is shown in the socket assembly  75 . A corresponding bore may be provided in one or both surfaces of the fluke  70 , so that a quick-coupling fastener, for example, may be used to fasten the fluke  70  and mounting socket  74  together, in a manner that allows the fastener to be quickly and easily fastened or released. 
         [0050]      FIGS. 6A-6E  illustrate the lift mechanism  80  that raises the fluke assembly  50  above the bottom level of the kayak, so that the kayak K may be launched, beached, or transported.  FIG. 6E  illustrates a lift cable  83  guided through the drive unit section  30  in a configuration that corresponds closely to how the drive cable  92  is guided through the drive unit, i.e., the cable  83  is guided over a plurality of lift cable pulleys  89  and then held in a cable clamp  93  that is mounted on a rear lift cable carriage assembly  87 B, which in turn is slidably mounted on a rear lift cable guide rail  88 B. The lift mechanism elements are shown in dashed lines, because, when looking at  FIG. 4C , these elements are hidden by the drive unit elements 
         [0051]    A crank  82 , shown in  FIG. 1 , is positioned on the inside end of pedal assembly  10 , outside the box that encloses the drive elements, and is accessible to the paddler. Rotating the crank  82  turns a threaded rod  81  that passes through a threaded bore  85  that is fixedly mounted on the front lift cable carriage assembly  87 A. Turning the rod  81  forces the carriage assembly  87 A to travel along a front lift cable guide rail  88 A, either toward the bow or the stern, depending on the direction of rotation. The lift cable  83  is clamped to the front lift cable carriage assembly  87 A by a cable clamp  93 , so that the travel of the front lift cable carriage assembly  87 A also pulls the lift cable  83  in the corresponding directions. 
         [0052]      FIGS. 4A ,  4 B, and  4 C also illustrate a portion of the lift mechanism  80  in the drive unit section of the cable tray  90 . The lift cable  83  extends along the cable tray  90  and into the drive unit  30  where it is then routed through a series of lift cable pulleys  89 , which are mounted on shafts  99  that extend transverse to the centerline CL between two vertical walls  91 , and which serve to align the lift cable  83 . The lift cable is affixed to a rear lift carriage assembly  87 B by a cable clamp  93 . Referring now to  FIGS. 4B and 6E , a lift post  84  is affixed to and extends outward from the rear lift carriage assembly  87 B through a slot  67  in a vertical wall  91  and is coupled to an extender arm  86  on its outer end. The extender arm  86  is coupled to a lift link  94  which is coupled to the horizontal shaft  55 A inside of the hull. As the lift cable  83  is pulled back or forward the horizontal shaft  55 A rotates. 
         [0053]    Lift arms  95 , shown in  FIG. 6D , are also rigidly mounted to the horizontal shaft  55 A, and are connected to main elevation arms  58  by a lift link  78 C. As the horizontal shaft  55 A rotates, the lift arms  95  pivot up or down, depending on the rotation of the shaft, forcing the lift link  78 C to raise or lower the main elevation arms  58  and the fluke plates  62 , thereby raising or lowering the entire fluke assembly  50  in a vertical plane. 
         [0054]    A link assembly identified in the figures as  78 A and  78 B ensures that the limit in the rotation of the fluke  70  is constant through the full range of fluke plate  62  motion. When the kayak k is first launched, the lift mechanism  80  should be in the highest position thereby keeping the fluke assembly  50  elevated above the bottom on the kayak K. Once in the water, the paddler pushes or paddles to a place in the body of water with sufficient depth to lower and operate the fluke assembly  50 . Once that location has been reached, the paddler turns the crank  82 , thereby lowering the fluke assembly  50  into its operable lower position. As the paddler works the pedals  12 , the force transmitted through the drive unit  30  to the fluke unit  50  causes the fluke  70  to swing alternatingly upward and downward about the fluke pivot  72 , which movement propels the kayak K across the surface of the water. 
         [0055]    The drive mechanisms for the various assemblies have been described as linkages with cables, pulleys, etc. It is understood, that a pedal unit that actuates hydraulic elements may be used to effect the undulating up and down motion of the fluke  70 . 
         [0056]    It is understood that the embodiments described herein are merely illustrative of the present invention. Variations in the construction of the linear propulsion system for small watercraft may be contemplated by one skilled in the art without limiting the intended scope of the invention herein disclosed and as defined by the following claims.