Upright human floatation apparatus and propulsion mechanism therefor Number:6,764,363 from the United States Patent and Trademark Office (PTO) owispatent

Title: Upright human floatation apparatus and propulsion mechanism therefor

Abstract: An apparatus for the purpose of floatation and transportation on water comprises a pair of buoyant wing-shaped floats and foot wells in the floats designed to be under the center of buoyancy of each float. The apparatus may further comprise a tether attached to each float at the user's ankle height. Accessories may be attached to one or more floats. The invention further provides a number of propulsion mechanisms, one of which comprises a support structure, a buoyant flap articulated to the support member by an articulation having an axis of rotation that is both within 45 degrees of horizontal and substantially perpendicular to the direction of travel, said flap being movable substantially in rotation about said axis, said rotation being in a semicylindrical space behind said axis, said space being away from said direction of travel. Additional novel features of the apparatus and propulsion mechanism are discussed herein.

Patent Number: 6,764,363 Issued on 07/20/2004 to Rosen

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Inventors:	Rosen; Yoav (Newton, MA)
Assignee:	Wave Walk, Inc. (Newton, MA)
Appl. No.:	10/201,066
Filed:	July 22, 2002

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Current U.S. Class:	441/77
Current International Class:	B63H 16/00 (20060101); B63B 35/83 (20060101); B63B 35/73 (20060101); B63H 16/08 (20060101); B63H 1/32 (20060101); B63H 1/00 (20060101); B63B 35/81 (20060101)
Field of Search:	440/13-21,24,25 441/65,76,77

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References Cited [Referenced By]

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	4698039		October 1987		Watson
	4952184		August 1990		Graziano
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	5192237		March 1993		Pegoraro
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	5421759		June 1995		Morin
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	5593334		January 1997		Thayer
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Foreign Patent Documents

	2249316		Oct., 1972		DE
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	3902367		Aug., 1990		DE
	2212467		Jul., 1989		GB
	8401176		Nov., 1985		NL

Primary Examiner: Morano; S. Joseph
Assistant Examiner: Vasudeva; Ajay
Attorney, Agent or Firm: Landsman; Inna

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Parent Case Text

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CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims the benefit of U.S. Provisional Patent Applications Ser. Nos. 60/307,258; 60/307,259; 60/307,260; 60/307,270; and 60/307,277, all filed Jul. 23, 2001.

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Claims

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What I claim as my invention is:

1. An apparatus to be worn on the feet of a user for the purpose of floatation and transportation on water in a direction of travel, comprising: a first buoyant float and a second buoyant float, each of said first buoyant float and said second buoyant float comprising a center of buoyancy, a bow, and a stern, and further comprising: a sculpted hull, said sculpted hull comprising: a substantially straight and generally flat inward side running from said bow to said stern; a substantially convex outward side having convexity, a top edge and a bottom edge, said substantially convex outward side and said convexity running from said bow to said stern, and said convexity being away from the direction of said substantially straight and generally flat inward side, said substantially convex outward side additionally being farther from said substantially straight and generally flat inward side at said top edge than at said bottom edge; a bottom side in watertight connection with said substantially straight and generally flat inward side and said substantially convex outward side, wherein said substantially straight and generally flat inward side, said substantially convex outward side, and said bottom side form a smooth and continuous exterior surface; and a top surface covering said sculpted hull; a foot well for housing said user's foot and ankle, said foot well disposed through said top surface of said buoyant float and extending toward said bottom side, said foot well further located to position said user's ankle substantially in vertical alignment with the center of buoyancy, and said foot well further comprising a bottom surface that is below said center of buoyancy, wherein said substantially convex outward side and the substantially straight and generally flat inward side act cooperatively to form an aerofoil whereby said sculpted hull experiences a force in the direction generally from said substantially straight and generally flat inward side to said substantially convex outward side when moving in the direction of travel in water; and a support structure attached to one of said first buoyant float or said second buoyant float; and a buoyant flap comprising a leading edge, a trailing edge, a width between said leading edge and trailing edge and an articulation located within the first 25% of said width as measured from said leading edge, said buoyant flap articulated to said support structure at said articulation, said articulation having an axis of rotation that is both within 45 degrees of horizontal and substantially perpendicular to said direction of travel, said buoyant flap being movable substantially in rotation about said axis, said rotation being in a space behind said axis, said space being away from said direction of travel.

2. An apparatus to be worn on the feet of a user for the purpose of floatation and transportation on water in a direction of travel, comprising: a first buoyant float and a second buoyant float, each of said first buoyant float and said second buoyant float comprising a center of buoyancy, a bow, and a stern, and further comprising: a sculpted hull, said sculpted hull comprising: a substantially straight and generally flat inward side running from said bow to said stern; a substantially convex outward side having convexity, a top edge and a bottom edge, said substantially convex outward side and said convexity running from said bow to said stern, and said convexity being away from the direction of said substantially straight and generally flat inward side, said substantially convex outward side additionally being farther from said substantially straight and generally flat inward side at said top edge than at said bottom edge; a bottom side in watertight connection with said substantially straight and generally flat inward side and said substantially convex outward side, wherein said substantially straight and generally flat inward side, said substantially convex outward side, and said bottom side form a smooth and continuous exterior surface; and a top surface covering said sculpted hull; a foot well for housing said user's foot and ankle, said foot well disposed through said top surface of said buoyant float and extending toward said bottom side, said foot well further located to position said user's ankle substantially in vertical alignment with the center of buoyancy, and said foot well further comprising a bottom surface that is below said center of buoyancy, wherein said substantially convex outward side and the substantially straight and generally flat inward side act cooperatively to form an aerofoil whereby said sculpted hull experiences a force in the direction generally from said substantially straight and generally flat inward side to said substantially convex outward side when moving in the direction of travel in water; and a support structure attached to one of said first buoyant float or said second buoyant float; and a flap comprising a leading edge, a trailing edge, a width between said leading edge and trailing edge and an articulation located within the first 25% of said width as measured from said leading edge, said flap articulated to said support structure at said articulation, said articulation having an axis of rotation that is both within 45 degrees of horizontal and substantially perpendicular to said direction, said flap being movable substantially in rotation about said axis, said rotation being in a space behind said axis, said space being away from said direction of travel and generally between a plane parallel to and a plane perpendicular to the direction of travel.

3. An apparatus to be worn on the feet of a user for the purpose of floatation and transportation on water in a direction of travel, comprising: a first buoyant float and a second buoyant float, each of said first buoyant float and said second buoyant float comprising a center of buoyancy, a bow, and a stern, and further comprising: a sculpted hull, said sculpted hull comprising: a substantially straight and generally flat inward side running from said bow to said stern; a substantially convex outward side having convexity, a top edge and a bottom edge, said substantially convex outward side and said convexity running from said bow to said stern, and said convexity being away from the direction of said substantially straight and generally flat inward side, said substantially convex outward side additionally being farther from said substantially straight and generally flat inward side at said top edge than at said bottom edge; a bottom side in watertight connection with said substantially straight and generally flat inward side and said substantially convex outward side, wherein said substantially straight and generally flat inward side, said substantially convex outward side, and said bottom side form a smooth and continuous exterior surface; and a top surface covering said sculpted hull; a foot well for housing said user's foot and ankle, said foot well disposed through said top surface of said buoyant float and extending toward said bottom side, said foot well further located to position said user's ankle substantially in vertical alignment with the center of buoyancy, and said foot well further comprising a bottom surface that is below said center of buoyancy, wherein said substantially convex outward side and the substantially straight and generally flat inward side act cooperatively to form an aerofoil whereby said sculpted hull experiences a force in the direction generally from said substantially straight and generally flat inward side to said substantially convex outward side when moving in the direction of travel in water; and a support structure attached to one of said first buoyant float or said second buoyant float; a flap comprising a leading edge, a trailing edge, a width between said leading edge and trailing edge and an articulation located within the first 25% of said width as measured from said leading edge, said flap articulated to said support structure at said articulation, said articulation having an axis of rotation that is substantially perpendicular to said direction, said flap being movable substantially in rotation about said axis, said rotation being in a space behind said axis, said space being away from said direction of travel; and a torque generating mechanism connected between said flap and said support structure, said mechanism comprising a stressed material exerting torque on said flap, said torque directed so as to rotate said flap toward a position substantially perpendicular to said direction, said torque being exerted on said flap at all rotation positions of said flap.

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Description

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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT NOT APPLICABLE

REFERENCE TO COMPACT DISK APPENDIX

Not applicable

BACKGROUND OF THE INVENTION

The present invention generally relates to the field of aquatic floatation and transportation systems. More particularly, the invention relates to a foot-wearable human floatation apparatus used primarily for water-walking or water-skating, and a propulsion mechanism therefor.

Walking on water, like flying, has been considered an interesting mode of transportation for centuries, if not millennia. Prior attempts at creating a foot-worn floatation/propulsion system have yet to produce a water-walking apparatus that enables a human to take near-normal walking steps with confidence.

The act of walking, on land or on water, can be broken down into a sequence of coordinated basic movement pairs (each pair comprising a left leg movement and a right leg movement). There are four basic movements: Forward, an actual forward movement of the first leg and foot; Backwards, the backwards push against the resistance of the ground during which the second foot does not actually move; Up, the lifting the first leg off the ground or un-weighting of the leg during skating; and Down, applying one's weight on the first leg. The act of walking naturally requires the smooth transition from one action to the next, and from one leg to the next. Any water-walking apparatus should allow for all four movements in the normal sequence and with the natural timing a human has learned when walking on land. A key consideration in walking on any medium is to emulate the assumed "100%" friction typically found when applying the Backwards movement on land. Humans slip and fall when friction is reduced during that portion of the walking cycle. In addition, a water-walking apparatus should allow a user to "step around" a turn as a way to change directions while providing the user a feeling of stability at least somewhat similar to the stability found on solid ground. Thus, a successful water-walking apparatus should limit pitch, roll, and side-to-side motions transmitted from the float to the user without constraining the natural walking up-down, front-back, and yawing motions transmitted from the user to the float.

Skating is different than walking in several ways. Skating is a series of movements optimized for low foot-to-support medium friction situations (ice, roller blades, water), where sliding a foot across the support medium will not completely halt forward progress. Because of the low friction, the Up movement doesn't necessarily imply lifting the foot --a simple easing of the pressure to reduce the (normal force generated) frictional resistance, as in Nordic skiing, is often adequate. Second, skating typically involves a gliding movement; weight is carried on the forward leg while the back leg "pushes off". The person using a skating apparatus lifts the foot that has just finished the Backwards, power movement and lets himself be carried forward by momentum, weight on the forward leg. Depending on the desired speed, the user either continues the one leg glide, brings the rearward foot parallel with the gliding foot and performs a two footed glide, or brings the rearward foot to the forward position in anticipation of the next pushing movement. Note that the skater can alternate the roles of the left and right legs (the normal skating action) or repeatedly use only one leg as the pushing leg (as in powering a scooter).

A typical prior water walking apparatus comprises two elongated floats and some sort of variable resistance propulsion mechanism, typically comprising a multitude of either small rotatable flaps or fixed, rearward facing cups, pouches, or scoops. The typical prior float is generally flat bottomed and straight sided and the typical prior propulsion mechanism does not provide maximum resistance against the water at the point in the walking cycle when it is needed; specifically, the maximum resistance is needed at the beginning of the Backwards (power) movement. Prior propulsion systems either require the user to wait to take each step or allow backwards slippage. For example, U.S. Pat. No. 4,698,039 teaches an apparatus having a pair of symmetric floats, these floats being generally rectangular in cross-section and having a flat bottom over most of their length. Additionally, the '039 patent teaches the use of a series of rotatable flaps with vertical axes spaced along either side of a central keel. The flaps move into their high resistance position only by the rearward slippage at the beginning of each step. Further, each flap is "shadowed" by the flap next in line, greatly reducing their propulsive power. Another attempt to provide a propulsion system with rotatable flaps with vertical axes is described in U.S. Pat. Nos. 4,261,069 and 4,117,562, both by Schaumann. In the '069 patent there are two flaps in series in a tunnel like chamber, completely obviating the functionality of the front flap for pushing backwards against the water. The overall float shape in both these patents is again generally an elongated rectangle. The '069 patent is notable in use of a resilient stop that both prevents the flap from opening beyond the desired point and provides a small push back toward the closed condition. However, the resilient stop only provides an initial push, the energy of which is quickly absorbed by the resistance of the water. Two examples of "horizontal" (viz., having a horizontal axis) flaps or pouches are provided by U.S. Pat. Nos. 5,593,334 and 5,697,822. Again, the linear series of small pouches or flaps are too small to be effective and are self-obviating because of shadowing, and again the float shape is generally conducive to instability.

Some prior devices include a tethering mechanism to keep the floats from separating. Many of these mechanisms are overly constraining--that is, rather than just preventing excessive transverse separation, they instead prevent the user's feet from moving in at least some of the degrees of freedom possible on land. Typically, the tether mechanism, if present, either inhibits a full and natural stride (i.e., the length of a step), introduces friction into what is normally a frictionless forward leg movement, prevents the redirection of a forward stride (yaw) (as is needed for turning), or inhibits the required Up and Down leg movements. For example, the '069 patent includes an intertwined cable tether whose claimed function is explicitly to eliminate virtually all sideways motions, to limit the length of the stride, and to ensure the engagement of a tongue-and-groove mechanism for eliminating up-down motions. Another example of an overly constraining tethering mechanism is shown in U.S. Pat. No. 3,121,892 in which the two floats (actually "skis" in that each float is a thin, flat board similar to conventional water skis) are joined by what amounts to either a single or a double linear bearing that constrains the relative motion between the skis.

It is therefore an object of this invention to provide a water-walking apparatus in which the maximum resistance to the water is achieved at the beginning of, and maintained throughout, the Backward pushing movement. Other objectives can include providing an apparatus in which the user achieves a near land-like stability, which allows the user to transition from deep to shallow water and thence to solid surfaces (land, ice, etc.) while walking, and/or an apparatus with a foot attachment method that allows the user all normal walking motions while providing a quick release for safety. These and other objectives are met through the various embodiments discussed below.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a foot-wearable apparatus for human floatation and transportation on water in a direction of travel. In one embodiment, the apparatus comprises a first buoyant float and a second buoyant float, each of said first buoyant float and said second buoyant float comprising a center of buoyancy, a bow, and a stern. Each float is defined by having a sculpted hull comprising (a) a substantially straight and generally flat inward side running from said bow to said stern, (b) a substantially convex outward side having convexity, a top edge and a bottom edge, said substantially convex outward side and said convexity running from said bow to said stern, and said convexity being away from the direction of said substantially straight inward side, said substantially convex side additionally being farther from said inward side at said top edge than at said bottom edge, and (c) a bottom side in watertight connection with said substantially straight inward side and said substantially convex outward side, said substantially straight side, said substantially convex outward side, and said bottom side forming a smooth and continuous exterior surface. Said hull is covered by a top surface. In addition, said sculpted hull comprises a foot well for housing said user's foot and ankle, said foot well disposed through said top surface of said buoyant float and extending toward said bottom side, said foot well further located to position said user's ankle substantially in vertical alignment with the center of buoyancy, and said foot well further comprising a bottom surface that is below said center of buoyancy. In some embodiments, said apparatus further comprises a tether having a length and connecting said first buoyant float to said second buoyant float. The substantially convex outward side and the substantially straight inward side of the hull act cooperatively to form an aerofoil whereby said sculpted hull experiences an outwardly force in use. In another embodiment, the center of buoyancy of the float is at least as high as the predicted height of said user's ankle in said foot well. In yet another embodiment, the bottom surface of said foot well further extends to the bottom side of the hull. The foot well may also comprise a foot well cover hingedly attached to the top surface of said first or said second buoyant float, said foot well cover being adapted to hold said user's foot in said foot well when said foot well cover is closed. In an even more preferred embodiment, the apparatus comprises a foot interface comprising a first surface connected to said foot well cover, and a second surface adapted to surround the upper surface of said user's foot and the anterior surface of said user's ankle in said foot well. In yet other embodiments, the bottom side further has a generally convex shape having convexity, said convexity being away from the direction of said top surface, said bottom side further comprising a flat platform extending under the bottom surface of said foot well, said platform being generally parallel to the plane of said water.

In another embodiment, the apparatus comprises a track disposed parallel to the water on said substantially straight inward side, and an attachment rider adapted for traversing said track and for accepting said tether, wherein said rider traverses said track when pulled by said tether. In yet another embodiment, the tether restricts movement between said first float and said second float in only one degree of freedom, said degree of freedom being substantially in the direction perpendicular to both the direction of travel and the vertical direction, wherein said restriction is furthermore only a limit on the maximum separation allowed in said direction. Other embodiments for tethering the two floats include a first cable comprising two ends, said two ends attached to said substantially straight inward side of said first buoyant float at two locations at the approximate predicted height of the user's ankle in said foot well, and a second cable intertwined at least once through said first cable, said second cable further comprising two ends attached to said substantially straight inward side of said second float at two locations at the approximate predicted height of the user's ankle in said foot well. In some embodiments, a friction reducing agent is coated on one or more of said cables. Also, the tether may be connected to a buoyant float by an adjustable attachment device, said device connecting said tether to said first float, wherein said adjustable attachment device can be used by a user to adjust the separation between said first float and said second float.

Additionally, other devices can be attached to one or both of said buoyant floats. In one embodiment, an articulation interface is attached to the stern of one float. The articulation interface is adapted for attaching a flap with a forward edge that is perpendicular to said direction of travel. In another embodiment, the buoyant float comprises an outside surface, and one or more accessory attachment interface adaptations for attaching one or more accessories are attached to said outside surface. In one embodiment, the accessory comprises one or more generally pointed protuberances adapted for increasing traction on ice in contact with said protuberances. In yet another embodiment, said accessory comprising a propulsion mechanism retraction interface located at the stern of said first buoyant float and adapted to facilitate the retractable attachment of a propulsion mechanism, which is operational when it is at least partially immersed in the water and not operational when it is substantially retracted from the water, to said float, said retraction interface comprising (a) a pivot bracket attached to said first buoyant float and adapted to pivotally connect to said propulsion mechanism, (b) a fixed anchor point attached to said first buoyant float, and (c) a retention spring adapted for connection between said propulsion mechanism and said fixed anchor point; thus, when a propulsion mechanism is attached to said pivot bracket and said retention spring, said retention spring is stressed, and said stressed retention spring generates a force on said propulsion mechanism directed to keep said propulsion mechanism at least partially immersed in water, wherein said propulsion mechanism can pivot between being at least partially immersed in water and substantially retracted from water in response to torque.

In yet another embodiment, a buoyant float may be comprised of two or more modular members shaped to fit together to form said first buoyant float.

In yet another embodiment, the invention provides a kit for producing a float for floatation and transportation on water, comprising at least two modular members sized to fit together to form a buoyant float having a center of buoyancy, a bow and a stern, said buoyant float further comprising a hull. Each hull comprises (a) a substantially straight and generally flat inward side running from said bow to said stern, (b) a substantially convex outward side having convexity, a top edge, and a bottom edge, said side and said convexity running from said bow to said stern and said convexity being away from the direction of said substantially straight inward side, said substantially convex side further being generally tilted from a top edge to a bottom edge, said top edge being generally farther from said substantially straight inward side than said bottom edge, and (c) a bottom side in watertight connection with said inward side and said outward side, said three sides forming a smooth and continuous exterior surface. Each float further comprises a top surface covering said hull and a foot well for housing said user's foot and ankle, said foot well disposed through said top surface of said float and extending toward said bottom side, said foot well further located to position said user's ankle substantially in vertical alignment with the center of buoyancy, and said foot well further comprising a bottom surface that is below said center of buoyancy of said float. Preferably, at least one of said one modular member comprises an attachment point for a tether at the approximate predicted height of the user's ankle in said foot well.

In other embodiments, the invention provides a propulsion mechanism for propelling a water craft through water in a direction. Such a propulsion mechanism comprises (a) a support structure comprising a support element, said element comprising a first dimension, a second dimension, a third dimension, a first end of said first dimension and a second end of said first dimension, said first end comprising an adaptation for attachment to said water craft, and (b) a buoyant flap comprising a leading edge, a trailing edge, a width between said leading edge and trailing edge and an articulation point located within the first 25% of said width as measured from said leading edge, said buoyant flap articulated to said second end of said support element at said articulation point, said articulation having an axis of rotation that is both within 45 degrees of horizontal and substantially perpendicular to said direction of travel, said buoyant flap being movable substantially in rotation about said axis, said rotation being in a semicylindrical space behind said axis, said space being away from said direction of travel.

In another embodiment, the propulsion mechanism comprises (a) a support structure comprising a support element, said element comprising a first dimension, a second dimension, a third dimension, a first end and a second end, said first end comprising an adaptation for attachment to said water craft; (b) a flap comprising a leading edge, a trailing edge, a width between said leading edge and trailing edge and an articulation point located within the first 25% of said width as measured from said leading edge, said flap articulated to said second end of said support structure at said articulation point, said articulation having an axis of rotation that is both substantially within 45 degrees of horizontal and substantially perpendicular to said direction, said flap being movable substantially in rotation about said axis, said rotation being in a quarter-cylindrical space behind said axis, said space being away from said direction of travel and generally above the horizontal, and (c) a rotation limiting mechanism situated on one of said support structure, said flap or said water craft for preventing the flap from rotating beyond a position substantially parallel to said direction.

In yet another embodiment, the propulsion mechanism comprises (a) a support structure comprising a support element, said element comprising a first dimension, a second dimension, a third dimension, a first end and a second end, said first end comprising an adaptation for attachment to said water craft, (b) a flap comprising a leading edge, a trailing edge, a width between said leading edge and trailing edge and an articulation point located within the first 25% of said width as measured from said leading edge, said flap articulated to said second end of said support structure at said articulation point, said articulation having an axis of rotation that is substantially perpendicular to said direction, said flap being movable substantially in rotation about said axis, said rotation being in a semicylindrical space behind said axis, said space being away from said direction of travel, (c) a rotation limiting mechanism situated on one of said support structure, said flap or said water craft for preventing the flap from rotating beyond a position substantially perpendicular to said direction, and (d) a torque generating mechanism connected between said flap and said support structure, said mechanism comprising a stressed material exerting torque on said flap, said torque directed so as to rotate said flap toward a position substantially perpendicular to said direction, said torque being exerted on said flap at all rotation positions of said flap.

In yet another embodiment, the propulsion mechanism comprises (a) a pivot axis, (b) a pivot support bracket adapted for attachment to said water craft and adapted for supporting said pivot axis, (c) a foot actuated pedal crank comprising a first end connected to said pivot axis, a second end, and a pedal attached to said second end, (d) a support structure comprising a generally elongated bar element, a first end and a second end, said first end attached to said second end of said pedal crank, said attachment forming a predetermined angle between said bar element and said pedal crank, said angle measured in a plane perpendicular to said pivot axis, and (e) a flap comprising a leading edge, a trailing edge, a width between said leading edge and trailing edge and an articulation point located within the first 25% of said width as measured from said leading edge, said flap articulated to said second end of said support structure at said articulation point, said articulation having an axis of rotation that is substantially perpendicular to said direction, said flap being movable substantially in rotation about said axis said rotation being in a semicylindrical space behind said axis, said space being away from said direction of travel. Preferably, said apparatus further comprises a rotation limiting mechanism situated on one of said support structure or said flap for preventing the flap from rotating beyond a position substantially perpendicular to said direction. In another preferred embodiment, said apparatus comprises a torque generating mechanism connected between said flap and said support structure, said mechanism comprising a stressed material exerting torque on said flap, said torque directed so as to rotate said flap toward a position substantially perpendicular to said direction, said torque being exerted on said flap at all rotation positions of said flap. Said flap is preferably buoyant and said axis of rotation is preferably within 45 degrees of horizontal.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The foregoing and other objects, features and advantages of the invention will become apparent from the following description in conjunction with the accompanying drawings, in which reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale; emphasis has instead been placed upon illustrating the principles of the invention. Of the drawings:

FIG. 1 illustrates the invention as it is used for water-walking.

FIG. 2 is a schematic top view of a unitary embodiment of the apparatus showing the tethering assembly.

FIG. 3 is a sectional view of one embodiment of the float, illustrating a typical transverse hull shape.

FIG. 4 is a sectional view of one embodiment of the float illustrating details of one embodiment of the foot attachment mechanism and other float features.

FIG. 5 is a schematic top view of the float illustrating the location of several sectioning planes.

FIGS. 6A through F are several sectional views of the float.

FIG. 7 is a partial sectional view of the float showing one embodiment of a cable clamp.

FIG. 8 illustrates a second embodiment of the tether mechanism.

FIG. 9 is a schematic top view of a modular embodiment of the invention.

FIG. 10 illustrates one embodiment of a propulsion mechanism built according to the invention in its high resistance orientation.

FIG. 11 illustrates the propulsion mechanism of FIG. 10 in its low resistance orientation.

FIG. 12 is a sectional view of a flap from the propulsion mechanism of FIG. 10 taken at the sectioning plane and in the direction indicated by the line 12--12.

FIG. 13 is a partially exploded view of a second preferred embodiment of the propulsion mechanism built according to the invention, as positioned during a gliding or forward step.

FIG. 14 illustrates a cross-section of a flap articulation that includes a torque generation mechanism.

FIG. 15 illustrates the flap articulation of FIG. 14 in the low resistance orientation.

FIG. 16 is a view of an adapter mechanism for attaching one embodiment of the propulsion mechanism to the stern of a float.

FIG. 17 is schematic view of the propulsion mechanism operating as a foot-powered oar during a power stoke.

FIG. 18 is schematic view of the foot-powered oar during a return stoke.

DETAILED DESCRIPTION OF THE INVENTION

Many aquatic activities can be enjoyed by a person in an upright, standing position, for example, fishing, water skiing, surfboarding, and windsurfing. Other upright activities, such as Nordic and alpine skiing, could also be enjoyed on water if proper equipment were available. As shown in FIG. 1, the invention comprises an apparatus 10 that can be embodied for water-walking by an upright human by attaching a propulsion mechanism 200 to each of a pair of floats 100 which have been tethered together by a tethering mechanism (not illustrated). By taking natural walking strides the user can propel himself in the forward direction, indicated by arrow "A". Other embodiments of the invention may be optimized for other aquatic activities. In one aspect the invention is an apparatus resembling pontoon boats, one for each foot, on which a human can stand upright with great stability. Preferably, the apparatus allows each foot and leg to experience all the degrees of freedom normally associated with walking or standing on land while minimizing the unfamiliar foot/leg motions that arise from the fluid nature of water. In one aspect the apparatus comprises two main functional elements; the float, providing stable buoyancy and control, and the foot attachment well, for transmitting foot/leg motions to the float. The presence of the tether is preferable, but not absolutely required, for maintaining two side by side floats in a comfortable relationship. The apparatus also includes accessory attachment interface adaptations to which various accessories and propulsion systems may be affixed. In one embodiment, the primary propulsion force is human power and the primary mode of propulsion is walking and/or skating. In other embodiments, the propulsion mode may include but not be limited to: sailing, wind-surfing, wave-surfing, and river-skiing. Accessory devices such as sails, stabilizers, ice-steppers, etc. are accommodated by the invention. For convenience in the figures, we define a three dimensional coordinate system wherein said forward direction shall be considered the x-direction, the perpendicular to the plane of the water shall be considered the z-direction, and the remaining orthogonal axis shall be considered the y-direction.

Typically, two floats are used in most aquatic activities. In one embodiment, each float comprises a hull, a top surface, and a foot attachment mechanism, and, optionally, may include accessory attachment interface adaptations, fixtures and accommodations for various accessory devices. Preferably, the accessory attachment interface adaptations are located on the outside surface of hull 101. For example, ice walking accessories may be added to the bottom and/or bow of each float. The ice walking accessories typically comprise one or more pointed protuberances or, preferably, aftward facing sawteeth. On solid ice the protuberances supplement the tips of the propulsion mechanism to provide the grip to the ice needed to walk forward. On thin ice the invention breaks through to water and operates normally. In the transition from water to ice, the protuberances at the bow provide extra grip to pull the float up out of the water. In another embodiment, the float comprises an articulation interface located at said stern and adapted for attaching a flap with a forward edge that is perpendicular to said direction of travel.

In other embodiments, the invention provides for one or more articulation interfaces attached at the bottom or one of the side surfaces of the float.

The top view of one of said two floats is shown in FIG. 2. The left float is illustrated in the figure and it will be understood that the right float and left floats are mirror images of each other. As shown in FIG. 2 and in sectional views in FIG. 3 and FIG. 4, float 100 is primarily a generally elongated, buoyant sculpted hull 101 and a flat top surface 104 covering said hull. Hull 101 is formed from a marine material. Examples of such materials include plastic and resin impregnated fiberglass. Other marine materials are well known to those skilled in the art. The float has, preferably, a smoothly varying, continuous surface shell 165 and may be hollow or, preferably, filled with a low-density material 170 such as polyurethane foam.

Typically, each float is sized to support the total weight of the intended user, with an added margin of approximately 5-40%, preferably 5-20%, most preferably 10%. Thus, the volume V of displaced water for each float may be calculated using the density of (fresh) water according the formula:

where U is the mass of the user, m is the mass of the float and D.sub.w is the density of water. While this volume could be distributed in any shape to provide the required buoyancy, the inventor has determined that a float whose length approximates the height, H, of the user and has a width on the order of 20-30 cm, and preferably 25 cm provides a reasonable compromise between stability and maneuverability for many applications. It should be noted, however, that specific applications will require specific hull parameters; a long, thin hull for speed, for example, or a short, deep hull for extra stability when wading for fishing. The volume of said compromise float, which is calculated according to equation (1), is achieved by setting the depth of the float to V/0.25H. For example, a float for a 1.8 meter tall user with a mass of 90 kg might have the general dimensions of 1.8 meters.times.0.25 meters.times.0.28 meters (L.times.W.times.D), where the indicated depth (0.28 meters) is actually greater than required for buoyancy, the extra depth being the height of the float above the waterline. Said extra depth maintains the top surface 104 well clear of the water and helps keep the user dry. Additionally, the extra depth provides reserve buoyancy.

As a matter of definition, the centroid of the displaced water (i.e., the centroid of the hull below the waterline) is the Center of Buoyancy (CoB) and is the point through which the buoyant force appears to operate (in analogy to the center of gravity).

Float and Hull Shape

The inventor has observed that when two parallel floats move through the water, a region of lower pressure is created in the channel formed by the parallel floats, said lower pressure tending to draw the two floats together and cause instability and bumping interference. Therefore, as shown in FIG. 2, hull 101 is generally asymmetric in cross-sections parallel to the plane of the water. This general shape is preferred to typical prior symmetric shapes. The preferred shape is generally an aerofoil, or wing-shaped; a thusly shaped hull 101 counteracts aforesaid low pressure and prevents said instability and bumping.

Addressing the hull shape more specifically, as is well known in the design of other aquatic floatation apparatuses such as kayaks and sailboats, no one preferred hull design exists. Instead, hull design parameters are determined in a give and take trade off to match the expected requirements of different applications and water conditions, various user preferences, various user body mass, muscle power, and morphologies, and so on. With this understanding, the following description of the preferred hull design should be understood as illustrative of the design principles involved rather than definitive hull design, and is not intended to limit the scope of the invention.

Hull 101 has a substantially straight and generally flat inwardly facing side 102 and a substantially convex outwardly facing side 103, where the substantially straight and generally flat side 102 is the side facing the second float 100 on the user's feet used in apparatus 10. Side 102 is substantially straight, running from a bow 140 to a stern 150, while substantially convex side 103 is generally convex, also running from bow 140 to stern 150. Substantially convex outward side 103 has convexity, a top edge, and a bottom edge, said substantially convex outward side and said convexity running from the bow 140 to the stern 150 and said convexity being away from the direction of said substantially straight and generally flat inward side, said substantially convex side additionally being farther from said substantially straight and generally inward side at said top edge than at said bottom edge. As used herein, the term "convexity" refers to the quality of something that is convex, and is not meant to imply an extra limitation or structure other than the convexity already present in the convex side or other convex member. Hull 101 is said to be "generally wing shaped" insofar as the bow-to-stern distance along substantially convex side 103 is longer than the bow-to-stern length of substantially straight and generally flat side 102 and is convex, thereby producing an outward force in the same manner as a wing generates lift. The sides 102, 103 are tapered as they approach both bow 140 and stern 150 to form a smooth and continuous curve without rapidly changing bends that would disrupt hydrodynamic streamlining. Additionally, hull 101 has a bottom side 105 in watertight connection with said substantially straight and generally flat side 102 and said substantially convex side 103, said bottom side 105 being smoothly blended into sides 102 and 103 so as to form a preferred unified sculpted hull.

FIG. 3 shows a sectional view of the float in FIG. 2 taken at the sectioning plane indicated by line 3--3. As illustrated at this section, and at all other transverse sections, the substantially straight and generally flat side 102 is generally vertical while the substantially convex outward side 103 is tapered generally inwardly from top surface 104 toward a keel line 107 at the lowest point on the bottom side 105. As will be described in more detail later, the generally rectangular platform or portion of bottom side 105 that lies directly beneath foot attachment mechanism 400 is substantially flat.

FIG. 4 shows a sectional view of the float in FIG. 2 taken at the sectioning plane indicated by line 4--4. As illustrated at this section, and at generally all other longitudinal sections, bottom side 105 is preferably generally convex. The convexity faces away from the direction of said top surface 104.

In this preferred embodiment, the lowest point along keel line 107 lies directly beneath foot attachment mechanism 400 and, as described above, this generally rectangular portion of bottom side 105 is substantially flat. In a more preferred embodiment, the portion of bottom side 105 that is directly under the foot attachment mechanism 400 is flat while the remainder of the bottom side 105 slants upwards from the flat portion to the bow 140 or stern 150. FIG. 5 and FIGS. 6A-F illustrate the overall changing shape of float 100. FIGS. 6A-E are sectional views of the float in FIG. 5, taken at the indicated sectioning planes, while FIG. 6F is an overlay of all of said sectional views. The rectangular boxes in the figures indicates the position of the foot attachment mechanism and is included in the figures only to provide a frame of reference for the different sectional views.

FIG. 4 also illustrates some of the many optional attachment fixtures that may be included on specific embodiments of float 100. For example, a propulsion mechanism attachment fixture 500 is illustrated at the preferred stern location on float 100, said attachment fixture 500 being adapted to accept available propulsion mechanisms. Similarly, a keel/ballast attachment fixture 510 is shown in its preferred location immediately below foot attachment mechanism 400, said fixture being adapted for adding ballast to lower the system center of gravity or for a stabilizing keel as might be desired for "float surfing" or "river skiing" versions of float 100. Another example of an optional attachment fixture is a mast retention socket 530 into which a mast for float windsurfing or sailing can be placed. A last illustrated example is an ice-gripper attachment fixture 520 near the up-sloping region near the bow of float 100, said ice-gripper being a set of aftwardly facing metal proturbences that provide traction during the ice-to-water transition. Said proturbences would be of particular value on a float that has been adapted for ice rescue missions. It is understood that the various attachment fixtures will be adapted to match the accessory for which they are intended. Preferably, said fixtures will accept accessories without the need for tools and will not interfere with the streamline shape of the hull. For example, a recessed T-groove may be molded into bottom side 105, said T-groove accepting one or more T-shaped projections from a keel or ballast accessory.

In another embodiment, the accessory comprises a propulsion mechanism retraction interface located at stern 150 of float 100 and adapted to facilitate the retractable attachment of a propulsion mechanism to said float that is operational when it is at least partially immersed in the water and not operational when it is substantially retracted from the water. FIG. 16 illustrates this accessory with the propulsion mechanism 200 attached. The retraction interface comprises a pivot bracket 510 attached to float 100 and adapted to pivotally connect to the propulsion mechanism, a fixed anchor point 530 attached to float 100, a retention spring 520 adapted for connection between the propulsion mechanism and the fixed anchor point 530. When the propulsion mechanism is attached to the pivot bracket 510 and the retention spring 520, retention spring 520 is stressed and generates a force on the propulsion mechanism directed to keep the propulsion mechanism at least partially immersed in water. The propulsion mechanism can pivot between being at least partially immersed in water (i.e., an operational position) and substantially retracted from water (i.e., a non-operational position) in response to torque. This accessory is substantially similar to the propulsion mechanism retraction interface described in the context of the propulsion mechanism, below, except that it may be attached without the propulsion mechanism to float 100, and may remain without a propulsion mechanism until a propulsion mechanism is desired.

A modular preferred embodiment of float 100 is illustrated schematically in FIG. 9. In that embodiment, each float comprises three modules, said modules being used to adjust the length of the float to accommodate users of differen