FLAPPING MANUAL PROPULSION SYSTEM FOR PERSONAL WATERCRAFT

Abstract

A watercraft propulsion system includes a shaft slidably disposed through an opening formed in a hull, a pull-up cable coupled to the shaft at a predetermined location of the shaft for pulling the shaft upward, a pull-down cable coupled to the shaft at the predetermined location of the shaft for pulling the shaft downward, a fluke disposed beneath a bottom of the watercraft, the fluke having a front portion and a horizontal plate behind the front portion, the front portion being solely and removably attached to a lower end of the shaft, wherein when the shaft is pulled downward by the pull-down cable, the horizontal plate tilts upward, and when the shaft is pulled upward by the pull-up cable, the horizontal plate tilts downward.

Description

BACKGROUND

The present disclosure relates generally to propulsion systems for personal watercrafts, and, more particularly, to a flapping manual propulsion system for personal watercrafts.

Personal watercrafts, such as canoes, kayaks and standup paddle boards, are traditionally propelled using one or more paddles manipulated by the hands and arms of a user. One disadvantage of using paddles for propulsion is that the paddles provide propulsion only part of the time. After one stroke, the user recovers the paddle above the water. Further, the user's arms are generally weaker than legs, and therefore the user's power is not fully utilized. Furthermore, the user may need to use hands to steer the watercraft or operate a fishing apparatus while the watercraft still needs to be propelled. These make the hand-powered personal watercrafts less desirable.

In an alternative approach, U.S. Pat. No. 6,022,249 to Ketterman discloses an oscillating fin propulsion that is driven by feet and legs. However, Ketterman's fins extend vertically into the water thus prone to be damaged in shallow water. Further, Ketterman's oscillating fin propulsion system employs a complex thus less efficient mechanism to convert foot pumping motion to fin oscillating.

As such, what is desired is an efficient foot-powered propulsion system for a personal watercraft.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1A and 1B are side views of a personal watercraft with an exemplary flapping propulsion system according to embodiments of the present disclosure.

FIG. 2 is a side view of the personal watercraft shown in FIGS. 1A and 1B with another exemplary flapping propulsion system according to embodiments of the present disclosure.

FIG. 3 is a perspective view of a flapping propulsion system with a rotatable fluke according to embodiments of the present disclosure.

FIG. 4 is a perspective view of a structure for engaging the fluke to the shaft according to embodiments of the present disclosure.

FIG. 5 is a side cross-sectional view of a frame that supports the pulley wheels and the shaft according to embodiments of the present disclosure.

FIG. 6 is a rear cross-sectional view of the frame that supports the pulley wheels and the shaft shown in FIG. 5 according to embodiments of the present disclosure.

The drawings accompanying and forming part of this specification are included to depict certain aspects of the disclosure. A clearer conception of the disclosure, and of the components and operation of systems provided with the disclosure, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings, wherein like reference numbers (if they occur in more than one view) designate the same elements. The disclosure may be better understood by reference to one or more of these drawings in combination with the description presented herein.

DESCRIPTION

The present disclosure relates to a flapping manual propulsion system for a personal watercraft. A preferred embodiment of the present disclosure will be described hereinafter with reference to the attached drawings.

FIGS. 1A and 1B are side views of a personal watercraft with an exemplary flapping propulsion system according to embodiments of the present disclosure. Referring to FIG. 1A, the flapping propulsion system includes a fluke 110 pivotally attached to a lower end of a shaft 120 by a pin 123. The shaft 120 vertically passes through a hole 105 formed in the hull of a personal watercraft 102 to situate the fluke 110 below the hull of the personal watercraft 110. An upper end of the shaft 120 with an attachment fixture 127 is attached to a pull-up cable 160R and a pull-down cable 160L. The pull-up cable 160R wraps around a pull-up pulley wheel 142 to be attached to a right crank 180L. The pull-down cable 160L wraps around a pull-down pulley wheel 146 to be attached to a left crank 180L. In an embodiment, the pull-up pulley wheel 142 is vertically aligned with the pull-down pulley wheel 146, so that the shaft 120 is pulled directly or vertically up and down.

As shown in FIG. 1A, when a user pushes a right foot pedal 187R, which is pivotally attached to the right crank 180R, forward, the pull-up cable 160R will pull the shaft 120 upward. The upward movement of the shaft 120 in turn pulls, through the pull-down cable 160L, the left crank 180L backward.

Conversely, as shown in FIG. 1B, when the user pushes a left foot pedal 187L, which is pivotally attached to the left crank 180L, forward, the pull-down cable 160L will pull the shaft 120 downward. The downward movement of the shaft 120 in turn pulls, through the pull-up cable 160R, the right crank 180R backward.

As shown in FIG. 1A, when the shaft 120 slides upward, a rear end of the fluke 110 tilts downward at the pressure of a water. In an embodiment, a vertical through hole 113 formed in the front end of the fluke 110 that accommodates the shaft 120 has an hourglass shaped interior wall, i.e., a top and bottom of the vertical through hole 113 is wider than a middle section of the vertical through hole 113. The pin 123 is positioned in the middle section of the vertical through hole 113. As shown in FIG. 1A, the middle section of the vertical through hole 113 snuggly accommodates the lower end of the shaft 120, but the top and bottom of the vertical through hole 113 has rooms for the shaft 120 to wiggle. The amount of the wiggle room determines a degree of tilting by the flake 110. As the vertical through hole 113 has a fixed interior shape, the tilt angles, both downward (shown in FIG. 1A) and upward (shown in FIG. 1B) are fixed as well by design. In embodiments, the tilt angle, of either downward or upward, is less than 45 degree in reference to a water surface (not shown) which is substantially parallel to the hull of the watercraft 102. Preferably, the tilt angle is between 15 degree and 30 degree.

As shown in FIG. 1A, when the shaft 120 moves further upward, the fluke 110 will remain tilted downward while also moving upward. Such tilted upward movement by the fluke 110 provides a forward thrust to propel the watercraft 102.

As shown in FIG. 1B, when the shaft 120 moves downward, the rear end of the fluke 110 tilts upward at the pressure of the water. As the shaft 120 moves further downward, the fluke 110 will remain tilted while also moving downward. Such tilted downward movement by the fluke 110 also provides a forward thrust to propel the watercraft 102.

As shown in both FIGS. 1A and 1B, the right crank 180R and the left crank 180L are pivotally attached, through a pin 173, to a base 170 mounted on the watercraft 102, so that right foot pedal 187R and the left foot pedal 187L can swivel back and forth pedaled by the user.

FIG. 2 is a side view of the personal watercraft shown in FIGS. 1A and 1B with another exemplary flapping propulsion system according to embodiments of the present disclosure. The exemplary flapping propulsion system shown in FIG. 2 employs an additional upper pulley wheel 246 mounted at approximately the same height as the pull-up pulley wheel 142 to change the direction of the pull-down cable 260L, so that beginning portions of the pull-down cable 260L and the pull-up cable 260R have similar movements. The beginning portion of the pull-down cable 260L refers to a portion of the cable suspended between the left crank 180L and the upper pulley wheel 246. The beginning portion of the pull-up cable 260R refers to a portion of the cable suspended between the right crank 180R and the pull-up pulley wheel 142. For the symmetrical movements, the pull-down cable 260L and the pull-up cable 260R are attached to the left crank 180L and the right crank 180R, respectively, at approximately the same height. In addition, the pull-up pulley wheel 142 and the upper pulley wheel 246 are mounted close to each other when viewed from a direction perpendicular to a side of the watercraft 102. The closeness is limited by a factor that a middle portion of the pull-down cable 260L may interfere with the attachment fixture 127 of the shaft 120 when the pull-up pulley wheel 142 and upper pulley wheel 246 are too close. The middle portion refers to a portion of the pull-down cable 260L suspended between the upper pulley wheel 246 and the pull-down pulley wheel 146.

In an embodiment, as the upper pulley wheel 246 is closer to the front of the watercraft 102 than the pull-up pulley wheel 142, the upper pulley wheel 246 is mounted at a slightly different height than that of the pull-up pulley wheel 142. In a case, the beginning portion of the pull-up cable 260R and the beginning portion of the pull-down cable 260L incline upward, the upper pulley wheel 246 is mounted slightly lower than the pull-up pulley wheel 142 by an amount determined by the inclining angle and a distance between the upper pulley wheel 246 and the pull-up pulley wheel 142. In another case, the beginning portion of the pull-up cable 260R and the beginning portion of the pull-down cable 260L incline downward, the upper pulley wheel 246 is mounted slightly higher than the pull-up pulley wheel 142 by an amount also determined by the inclining angle and a distance between the upper pulley wheel 246 and the pull-up pulley wheel 142. Specifically, the height difference is a calculated by a distance between axes of the upper pulley wheel 246 and the pull-up pulley wheel 142 times a tangent of the inclining angle.

Referring again to FIG. 2, an alternative fluke 210 has a concave space 212 in a front portion of the fluke 210 to tightly accommodate the lower end of the shaft 120. The fluke 210 is secured to the lower end of the shaft 120 by the pin 123. In an embodiment, the front portion of the fluke 210 is made of a flexible material such as polyvinyl chloride (PVC) or polypropylene with a thinner section 215 next to a rear portion of the fluke 210, so that the fluke 210 can bend to a certain degree when the fluke 210 is driven up and down by the shaft 120. Such bent fluke 210 can provide a propulsive thrust to the watercraft 102 when the shaft 120 moves up and down. A degree of the bending is determined by material properties and dimensions (width and thickness) of the front portion, particularly the thinner section 215 of the fluke 210. In embodiments, the rear portion of the fluke 210 is made of a rigid material such as polycarbonate or acrylic. The front portion and the rear portion of the fluke 210 are molded together through, for instance, a tongue and groove structure.

FIG. 3 is a perspective view of a flapping propulsion system with a rotatable fluke 110 according to embodiments of the present disclosure. As shown in FIG. 3, the pull-up cable 160R is not directly attached to the shaft 120 and instead to a right protruding member 305R of a ring 302. The pull-down cable 160L is also not directly attached to the shaft 120 and instead to a left protruding member 305L of the ring 302. The ring 302 surrounds the shaft 120 and allows the shaft 120 to rotate horizontally relative to the ring 302. The shaft 120 has an upper protruding member 312 right above the ring 302 and a lower protruding member 316 right below the ring 302, so that the ring 302 is vertically fixed to a predetermined location of the shaft 120 between the upper protruding member 312 and the lower protruding member 316.

As shown in FIG. 3, when the pull-up cable 160R pulls up the ring 302, the ring 302 will lift the shaft 120 by the same distance the ring 302 travels. Similarly, when the pull-down cable 160L pulls down the ring 302, the ring 302 will pull down the shaft 120 by the same distance the ring 302 travels.

As shown in FIG. 3, an upper end of the shaft 120 has a handle 320 to facilitate a user to rotate the shaft 120 relative to the ring 302. When the ring 302 is limited to its ability to swivel horizontally, rotating the shaft 120 will rotate the fluke 110 horizontally, so that the watercraft can be propelled in different directions. In an embodiment, the handle 320 has an arrow to indicate an orientation of the fluke 110, so that the user knows the orientation of the fluke 110 albeit the fluke 110 is beneath the watercraft 102.

FIG. 4 is a perspective view of a structure for engaging the fluke 210 to the shaft 120 according to embodiments of the present disclosure. A front portion of the fluke 210 has a vertical column 410 with a concave space 212 to tightly accommodate the lower end of the shaft 120. The shaft 120 and the column 410 are secured together by an exemplary pin 421 inserted a hole in the column 410 and a hole in the shaft 120.

As shown in FIG. 4, the column 410 has a protruding upper vertical plate 413 above a body of the fluke 210 and a protruding lower vertical plate 416 below the body of the fluke 210. The term, “body of the fluke”, as used herein refers to a part of the fluke 210 that is behind the column 410 which is at the front portion of the fluke 210. In embodiments, the body of the fluke 210 is a horizontal, paddle-shaped plate shaped like and having a cross-sectional profile of a whale's tail fluke.

In an embodiment, a front portion 432 of the body of the fluke 210 is made of a flexible material while a rear portion 434 of the body of the fluke 210 is made of a rigid material so that the body of the fluke 210 can tilt to a predetermined angle when the shaft 210 moves up and down. As shown in FIG. 4, the upper vertical plate 413 serves to limit the upward tilting of the body of the fluke 210; and the lower vertical plate 416 serves to limit the downward tilting of the body of the fluke 210. At the same time, both the upper vertical plate 413 and the lower vertical plate 416 can serve as a rudder for the watercraft.

FIG. 5 is a side cross-sectional view of a frame 510 that supports the pulley wheels 142, 146 and 246 and the shaft 120 according to embodiments of the present disclosure. The frame 510 is exemplarily mounted to the watercraft 102, so that the pulley wheels 142, 146, and 246 that are mounted to the frame are stationary. The frame 510 has a front opening 246 for the pull-up cable 260R and pull-down cable 260L to pass through. The frame 510 also has an upper opening 517 and lower opening 515 that is vertically aligned with the upper opening 517. The upper opening 517 and the lower opening 515 are for the shaft 120 to pass through and keep the shaft 120 upright while sliding up and down.

As shown in FIG. 5, there is a hole in the shaft 120 to accommodate a removable pin 520. When the pin 520 is inserted in the hole, the frame 510 prevents the pin 520 along with the shaft 120 from descending. In embodiments, the hole in the shaft 120 is located in a spot that keeps the fluke 110 in a raised position close to the bottom of the watercraft, so that the watercraft will not be stuck in a shallow water.

FIG. 6 is a rear cross-sectional view of the frame 510 that supports the pulley wheels 142, 146 and 246 and the shaft 120 shown in FIG. 5 according to embodiments of the present disclosure. The ring 302 encircles the shaft 120 and is vertically secured at a predetermined location of the shaft 120 by the upper protruding member 312 and lower protruding member 316. The ring 302 also has a left protruding member 305L for attaching the pull-down cable 260L thereto and a right protruding member 305R for attaching the pull-up cable 260R thereto. In an embodiment, the left protruding member 305L and the right protruding member 305R are at opposite sides of the ring 302.

As shown in FIG. 6, an end of the left protruding member 305L is inserted in a left vertical slot 610L, and an end of the right protruding member 305R is inserted in a right vertical slot 610R. The left vertical slot 610L and the right vertical slot 610R limit the left protruding member 305L and the right protruding member 305R, respectively, to only vertical movements, so that the ring 302 can only move up and down without swivel movement. Therefore, when the shaft 120 rotates, the ring 302 does not follow the rotation and remains engaged with the pull-down cable 260L and pull-up cable 260R in the same angle, respectively.

As shown in FIG. 6, the pull-down pulley wheel 146 together with the upper pulley wheel 246 and the pull-up pulley wheel 142 are grooved to accommodate the corresponding pull-down cables 260L and pull-up cables 260R, respectively. The pull-down pulley wheel 146 is mounted close to a floor of the frame 510, so that the pull-down cable 260L cannot escape, sideways, from the groove of the pull-down pulley wheel 146. Similarly, both the upper pulley wheel 246 and the pull-up pulley wheel 142 are mounted close to a ceiling of the frame 510, so that the pull-down cable 260L cannot escape, sideways, from the groove of the upper pulley wheel 246; and the pull-up cable 260R cannot escape, sideways, from the groove of the pull-up pulley wheel 142.

Although the disclosure is illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the disclosure and within the scope and range of equivalents of the claims. Accordingly, it is appropriate that the appended claims be construed broadly and, in a manner, consistent with the scope of the disclosure, as set forth in the following claims.

Claims

1. A propulsion system for a watercraft, the system comprising:

a shaft slidably disposed through an opening formed in a hull of the watercraft;

a pull-up cable coupled to the shaft at a predetermined location of the shaft for pulling the shaft upward;

a pull-down cable coupled to the shaft at the predetermined location on the shaft for pulling the shaft downward;

a fluke disposed beneath a bottom of the watercraft, the fluke having a front portion and a horizontal plate behind the front portion, the front portion being solely and removably attached to a lower end of the shaft,

wherein when the shaft is pulled downward by the pull-down cable, the horizontal plate tilts upward with a rear end of the horizontal plate higher than a front end of the horizontal plate; and when the shaft is pulled upward by the pull-up cable, the horizontal plate tilts downward with the rear end of the horizontal plate lower than the front end of the horizontal plate.

2. The system of claim 1, wherein the shaft is rotatable in the opening for changing an orientation of the fluke.

3. The system of claim 2, further comprising:

a handle attached to the shaft for facilitating the rotation of the shaft; and

an indication on the handle aligned with the orientation of the fluke.

4. The system of claim 1, wherein the pull-up cable wraps around a pull-up pulley wheel disposed at an upper position; and the pull-down cable wraps around a pull-down pulley wheel disposed at a lower position below the upper position.

5. The system of claim 4, wherein the pull-up cable is attached to a first crank after wrapping around the pull-up pulley wheel, wherein the first crank pivots around an axis mounted to the hull of the watercraft; and the pull-down cable is attached to a second crank after wrapping around the pull-down pulley wheel, wherein the second crank also pivots around the axis.

6. The system of claim 5, wherein the pull-down cable further wraps round an upper pulley wheel disposed at a same height as the pull-up pulley wheel before being attached to the second crank.

7. The system of claim 6, wherein a first distance from the axis to an attaching point of the pull-up cable on the first crank is same as a second distance from the axis to an attaching point of the pull-down cable on the second crank.

8. The system of claim 7, further comprising a frame attached to the hull of the watercraft for mounting the pull-up pulley wheel, the pull-down pulley wheel and the upper pulley wheel.

9. The system of claim 8, further comprising a first pin removably inserted in a hole formed in the shaft, wherein when the first pin is inserted in the hole in the shaft, a portion of the first pin protruding from the shaft engages the frame for preventing the shaft from descending.

10. The system of claim 8, further comprising a ring encircling the shaft at the predetermined location on the shaft, wherein the pull-up cable is attached to a first protruding member of the ring, and the pull-down cable is attached to a second protruding member of the ring.

11. The system of claim 10, wherein the first and second protruding member being at opposite sides of a circumference of the ring.

12. The system of claim 10, wherein a first end of the first protruding member is confined in a first vertical slot formed in the frame and a second end of the second protruding member is confined in a second vertical slot formed in the frame.

13. The system of claim 10, wherein an inner diameter of the ring is larger than an outer diameter of the shaft at the predetermined location of the shaft to allow the shaft to rotate within the ring.

14. The system of claim 10, wherein the shaft has a third protruding member above the ring and a fourth protruding member below the ring, wherein both the third and fourth protruding members extend beyond an inner circumference of the ring to prevent vertical relative displacement between the shaft and the ring.

15. The system of claim 1, wherein the front portion of the fluke has a vertical through hole for accommodating the lower end of the shaft and a horizontal hole for accommodating a second pin protruding from the shaft, wherein the front portion is pivotable around the second pin by a predetermined degree.

16. The system of claim 15, wherein an inner surface of the vertical through hole is hourglass shaped with a middle section snuggly accommodating the shaft and a wider top and bottom opening, wherein a diameter of the top opening and a diameter of the bottom opening determine the predetermined degree.

17. The system of claim 16, wherein the front portion of the fluke is rigidly connected to the horizontal plate of the fluke.

18. The system of claim 1, wherein the front portion of the fluke has a concave space for tightly accommodating the lower end of the shaft, wherein the front portion of the fluke is secured to the lower end of the shaft by a third pin protruding from the shaft and inserted in a hole of the front portion of the fluke.

19. The system of claim 18, wherein the front portion of the fluke is connected to the horizontal plate of the fluke by a flexible material for allowing the upward and downward tilting.

20. The system of claim 19, wherein the front portion of the fluke has a fifth protruding member above the horizontal plate and a sixth protruding member below the horizontal plate for limiting a degree of the upward tilting and a degree of the downward tilting, respectively.