WO2006044316A2 - Improved swim fin with energy storage and release - Google Patents

Improved swim fin with energy storage and release Download PDF

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Publication number
WO2006044316A2
WO2006044316A2 PCT/US2005/036367 US2005036367W WO2006044316A2 WO 2006044316 A2 WO2006044316 A2 WO 2006044316A2 US 2005036367 W US2005036367 W US 2005036367W WO 2006044316 A2 WO2006044316 A2 WO 2006044316A2
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WO
WIPO (PCT)
Prior art keywords
blade
fin
foot pocket
foot
interface section
Prior art date
Application number
PCT/US2005/036367
Other languages
French (fr)
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WO2006044316A3 (en
Inventor
John Melius
Original Assignee
John Melius
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by John Melius filed Critical John Melius
Publication of WO2006044316A2 publication Critical patent/WO2006044316A2/en
Publication of WO2006044316A3 publication Critical patent/WO2006044316A3/en

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Classifications

    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B31/00—Swimming aids
    • A63B31/08—Swim fins, flippers or other swimming aids held by, or attachable to, the hands, arms, feet or legs
    • A63B31/10—Swim fins, flippers or other swimming aids held by, or attachable to, the hands, arms, feet or legs held by, or attachable to, the hands or feet
    • A63B31/11—Swim fins, flippers or other swimming aids held by, or attachable to, the hands, arms, feet or legs held by, or attachable to, the hands or feet attachable only to the feet

Definitions

  • This disclosure relates to a system of swim fins used for diving, swimming underwater or swimming on the surface of the water.
  • This invention relates generally to the field of swimming and diving, and more particularly to a swim fin system with an improved system for storing and then releasing the energy generated by flexing a swim fin blade advantageously attached to a somewhat flexible and elastic interface section contiguous to the foot pocket during swimming.
  • the present invention relates further to a swim fin with an interface section between a foot pocket in which the foot pocket is placed at a more ergonomic angle to the blade and the interface section in which the foot pocket assists the blade and stores energy when bent during a kicking stroke and then releases this energy generated by flexing the blade back into the blade as the blade rebounds back into the blade's original shape and helps to provide an improved angle of attack for the blade and possible tail fin attached to the blade.
  • Swim fins typically comprise a foot pocket and a blade. Since 2002 they may include a secondary "tail fin” as found in United States Patent 6,375,531 , Melius issued 4-2002. When the blade is acting as a "hydrofoil” or “wing”, it is very important that the fin attain a correct angle of attack. This is doubly important with the addition of a second foil, the "tail fin”.
  • the angle of attack (AOA) is the relative angle that exists between the actual alignment of the oncoming flow (i.e., direction of the motion of the swimmer) and the lengthwise alignment of the blade of the fin and the "tail fin” when there is a “tail fin”.
  • a "correct” angle of attack optimizes the conversion of the kicking energy of the swimmer to thrust or propulsion through the water.
  • Excellent water pressure and lift is generated by the foil shapes of both blade and of the "tail fin” when one is used.
  • the flow collides with the fins attacking surface and/or lifting surface at a greater angle. This increases fluid pressure against the blade surface and increases flow rate over thetffihg'sMice.
  • the lift created by the hydrofoil shape of the tail fin adds more power to the conversion of energy for the swimmer into useful movement for the swimmer as is taught in United States Patent 6,375,531.
  • Conventional fins tend to assume different curvatures or angles of attack according to the direction of the movement and the magnitude of the forces applied during use (i.e., the kicking energy or power). Therefore, it is generally known to design a swim fins to provide a particular angle of attack for a particular "kicking strength". For example, such known swim fins are typically designed for either light kicking, medium kicking, or hard kicking. One way to design a fin for one of these particular kicking strengths is by the composition of the material.
  • United States Patent 6,758,708 proposes a solution whereby a biasing system is conFigured to allow the blade to bend within a narrow range of angles of attack under a wide range of loads.
  • This biasing system is composed of one or more biasing members such as a sinusoidal shaped rib or non-linear ribs.
  • the teaching does deal with variations on ribs.
  • ribs have traditionally found broad use in stiffening swim fins to an appropriate degree to facilitate their use by a swimmer.
  • the ribs used in this patent are also located within the left and right edges of the blade that help to create better hydrodynamic flow, but are still non-foil type obstructions which do cause unnecessary drag.
  • ribs can be found in United States Patent 6,290,561.
  • the ribs are extended from about the middle of the sides of the foot pocket well on the outside edge of the blade. This traditional handling of the stiffening agents for the foot pocket and the blade allow little if any flex in the foot pocket-to-blade region and create substantial drag in doing this job. They feel like small anchors when trying to glide in such fins. These ribs begin well within the foot pocket to help strengthen the attachment of the foot pocket to the blade in a sound albeit stiff manner.
  • a swim fin that provides: , a. a desired or optimum angle of attack for a variety or range of kicking strengths or powers. i. It would further be desirable to provide a swim fin apparatus in which the angle of attack is consistently controlled both for the upstroke and for the downstroke so that the ratio of power to the fin area is markedly increased wherein it possible to reduce the overall size of the swim fin without sacrificing total power for various kicking efforts. ii. It would further be advantageous to control the angle of attack both for the blade and for the tail fin when used by structural characteristics of bending in the compliant geometry of the relationships of the foot pocket, interface section, and the blade; whereby the characteristics of materials assisted in this controlled bending. iii. It would further be advantageous to control the angle of attack both for the blade and for the tail fin when used by structural characteristics of bending in the compliant geometry of the relationships of the foot pocket, interface section, and the blade and not merely by the characteristics of materials.
  • a tail fin connected to such a blade or tapered blade to further convert the flow of water over such a foil shape into useful power for the swimmer to focus the flow of water in a vector in the desired direction.
  • a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, and an interface section allowing the blade to bend within a narrow range of angles of attack under a wide range of loads.
  • a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, a tail fin extending from the blade, and an interface section allowing the blade to bend within a narrow range of angles of attack under a wide range of loads. m.
  • a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, and an interface section comprising curved radii allowing the blade to bend within a narrow range of angles of attack under a wide range of loads and allowing the footpocket to flex to store and then release energy from the bending of the blade.
  • a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, a tail fin extending from the blade, and an interface section comprising curved radii allowing the blade to bend within a narrow range of angles of attack under a wide range of loads and allowing the footpocket to flex to store and then release energy from the bending of the blade.
  • a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, and an interface section allowing the blade to bend within a narrow range of angles of attack under a wide range of loads.
  • a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, and an interface section adjoined to a flexible foot pocket and a means for controlling the flexing of the blade.
  • a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, a tail fin extending from the blade, and an interface section adjoined to a flexible foot pocket and a means for controlling the flexing of the blade. r.
  • the present invention relate to method of providing thrust from the kick of a swimmer which is a natural kick involving a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, a tail fin extending from the blade, and an interface section adjoined to a flexible foot pocket that acts as a means of controlling the axis of bending for the blade by providing varying resistance by the flexible interface section and flexible foot pocket.
  • the present invention further relates to various features and combinations of features shown and described in the disclosed embodiments.
  • a swim fin that provides a desired or optimum angle of attack for a variety or range of kicking strengths or powers. It would be better to provide this with fewer parts necessary in manufacture, and fewer parts impairing the flow of water over the fin thus producing better hydrodynamics. It would be better to provide this with an "air foil” shaped blade to increase the "lift” provided by the blade. It would be better to do this with a second lifting foil to provide secondary lift also contributing to the desired goals.
  • a swim fin with such a compliant relationship between the blade, the interface section, and the foot pocket wherein these three work together to control the bending and the angle of attack through their compliant geometry to increase the performance by controlling the angle of attack and converting a higher percentage of the kick energy into thrust.
  • a tapered blade work with the compliant geometry of the interface section and the foot pocket to produce a greater range of usefulness among the different range of kicking styles and powers.
  • a tail fin connected to such a blade or tapered blade to further convert the flow of water over such a foil shape into useful power tor the swimmer focusing the flow of water in a vector in the desired directions.
  • Fig. 1 is a bottom perspective view of a swim fin according to a preferred embodiment with the blade flexed downwards.
  • Fig. 1 introduces parts 8 - 24 [0028] 8 Swim Fin [0029] 10 Axis of Flex for Blade [0030] 12 Tail Fin [0031] 14 Second End [0032] 16 Blade [0033] 17 Bottom of Blade [0034] 18 Interface Section [0035] 19 Bottom of Foot Pocket [0036] 20 Foot Pocket [0037] 21 Bottom of Tail Fin [0038] 22 Heel Strap Boss [0039] 24 First End
  • FIG. 2 is a top perspective view of the swim fin of Fig. 1 with a centerline drawn through it for reference purposes.
  • Fig.2 introduces parts 26 - 52
  • FIG. 3 is a top perspective view of the swim fin of Fig. 1 without a tail fin.
  • Fig. 3 introduces parts 54 - 58 [0058] 54 Swim Fin without Tail Fin [0059] 56 Intersection of Foot Pocket and Blade [0060] 58 Left Side Wall of Foot Pocket Lower Part
  • Fig. 4 is a side perspective view of the swim fin of Fig. 1 with the blade flexed upwards.
  • Fig. 4 introduces 60 - 64 [0062] 60 Right Side Wall [0063] 62 Base Wall of Foot Pocket [0064] 64 Reinforcing Base Wall Rail [0065] 66 Connector Section
  • Fig. 5 is a side view of the swim fin in Fig. 3 with reference dashed lines illustrating the top and bottom planes of the foot and a dashed arrow illustrating the flex directions of the blade.
  • Fig. 5 introduces 68 - 82
  • Fig.6 is a prior art perspective view illustrating where the blade is in line with the bottom of the foot.
  • Fig. 6 i ⁇ troduces 84
  • Fig. 7 is a prior art perspective view illustrating where the blade is in line with the bottom of the foot.
  • FIG. 8 is a prior art perspective view illustrating a swim fin with traditional ribbing securing the foot pocket stiffly to the blade.
  • Figure 8 introduces 86 [0081] 86 Side Ribbing
  • Fig. 9 is prior art perspective view illustrating a swim fin with bias system of ribbing elements.
  • Fig. 9 introduces 88 [0083] 88 Composite Ribbing
  • Fig. 10 is a bottom perspective view of the swim fin of Fig. 1 with an arrow illustrating the energy flow and storage range.
  • Figure 10 introduces 90 - 96 [0085] 90 Solid Arrow showing Storage and Release of Energy [0086] 92 Intersection Edge of Interface Section [0087] 94 Major Influence Edge of Interface Section [0088] 96 Outer Transition Section for Left Side Wall
  • Fig. 11 is a side view of the swim fin of Fig. 3 illustrating a tapered blade and the angle of attachment for the foot pocket.
  • Fig. 12 is a top perspective view of the bottom of a swim fin without an interface section.
  • Fig. 13 is a top perspective view of the bottom of the swim fin of Fig. 12 with a broad interface section. Fig. 13 Introduces [0094] 99 Outer Transition Section for kight Side Wall
  • Fig. 14 is a top perspective view of the bottom of a swim fin of Fig. 12 with a narrower curved interface section.
  • Fig. 15 is a side view of the swim fin of Fig. 3 with a double arrow showing the flow and storage of energy and a crossed arrow.
  • Fig. 15 Introduces 100 - 104
  • Fig. 15 Introduces 100 Crossed Arrow Representing Compression
  • Fig. 16 is a rear perspective view of the swim fin of Fig. 1 with the base wall rails in easy view.
  • Fig. 16 Introduces 106 [00102] 106 Outer Transition Area for Left Side Wall First End
  • Fig. 17 is a rear perspective view of the swim fin of Fig. 1 with the base wall rails altered.
  • Fig. 18 is a perspective view of the bottom of the swim fin of Fig.1 with the addition of an extended connector to the interface section.
  • Fig. 18 Introduces 110 — 114 [00106] 110 Connector Extension [00107] 112 Connector Interface Section [00108] 114 Interface Enlargement
  • Fig. 19 is a graphic representation of four walls connecting at the corners for discussion purposes only. Fig. 19 Introduces 116 - 130
  • Fig. 20 is a graphic representation of four walls connecting at the corners for discussion purposes only.
  • Fig. 20 Introduces 132 - 146 [00119] 132 Lower Left Mixed Corner [00120] 134 Left Wall Mixed [00121] 136 Upper Left Mixed Corner [00122] 138 Top Wall Mixed [00123] 140 Upper Right Mixed Corner [00124] 142 Right Wall Mixed [00125] 144 Lower Right Mixed Corner
  • each apparatus 8 comprises a foot pocket 20, a blade 16, and an interface section 18 conFigured to work together in compliant geometry to accumulate and rebound energy while maintaining the desired angle of attack for a variety or range of kicking strengths or powers.
  • the foot pocket 20, the interface section 18, and the blade 16 are molded of the same elastomer material with good rebound characteristics thus simplifying manufacture while improving performance.
  • the foot pocket 20, interface section 18, and blade 16 could be fused together from different materials to form an integral structure alternatively.
  • FIG. 1 the perspective view of a swim fin apparatus 8 shows it bending downwards around the axis of flex 10, dashed line, for the blade 16.
  • the blade has a tail fin 12 attached to it to enhance performance by using the foil shape of the tail fin to produce lift in the desired direction.
  • the functions of the tail fin are taught in United States Patent 6,375,531, and will not be addressed in detail in this patent.
  • This swim fin has a first end 24 and a second end 14.
  • the foot pocket 20, beginning at the first end, extends out to intersect the blade at the interface section 18 from which the blade extends to the second end.
  • On the side of the foot pocket near the blade is the heel strap boss 22 used for attaching the standard size buckles found in this industry.
  • the bottom of the blade 17, the bottom of the foot pocket 19 and the bottom of the tail fin 21 can also be seen.
  • a dashed line 33 illustrates the centerline of the swim fin of FIG 1 to help demonstrate the generally symmetrical nature of the fin. Asymmetry would not improve performance but may give a swimmer the opportunity to use larger blades without interfering with each other.
  • Such an asymmetrical fin apparatus is not drawn but could easily be conceived by anyone skilled in the art knowing that such an asymmetrical apparatus would have to have a right and left version for the respective right and left feet of the swimmer.
  • Swim fin apparatus is generally produced in a relative symmetry when considered as mirror a mirror image of each half of the apparatus on each side of the centerline 33 as the industry standard. The trailing edge of the tail fin 26 is found at the second end 14 of the same fin apparatus 8.
  • the entire swim fin has a right and left side and is generally symmetrical from right to left.
  • the right side of the tail fin 28, and the left side of the tail fin 30 are shown.
  • the left side of the training edge of the blade 32 and the right side of the trailing edge of the blade 34 are shown.
  • the top of the tail fin 36 is shown extending into the top of the connector section 38 which continues extending into the top of the blade 40 so that the tail fin is attached approximately at the center of the blade via the connector 38.
  • the left side blade overlap of the footpocket extends from the area of the boss 22 into the Left Side of the Blade 52.
  • the top wall of the foot pocket 46 can act as part of the "paddle" of the swim fin apparatus 8 when made flat enough to help push water with the blade 16.
  • the flat top of the footpocket 46 is more flexible than the bottom of the foot pocket 20 as will be explained later.
  • the top wall of the foot pocket 46 extends over to the left side wall of the foot pocket 48 which extends into the left side glade overlap of the foot pocket 50 which connects back into the left side of the blade 52.
  • the rear of the foot pocket 20 When the rear of the foot pocket 20 is closed, it has a "closed footpocket" of a light weight very flexible material.
  • a fin apparatus is not illustrated here but is well known by anyone skilled in the art. What is viewed all of the Fig.'s illustrating fin apparatus is an "open heel” type of swim fin apparatus. The principles taught in this instant invention can be applied equally well to closed heel or open heel swim fin apparatus although the closed heel apparatus is not shown.
  • the intersection of the left side of the foot pocket 52 and the left blade overlap 50 is an important part of the architecture of swim fin apparatus because it helps to create a secure and stable platform for the foot pocket 20 to wield influence over the blade 16 and tail fin 12 (when a tail fin 12 is in the embodiment) causing it to bend on a predetermined axis of flex 10 illustrated in FIG 1.
  • This feature also allows flexibility in the foot pocket in the left side walls 44 and right side walls 48 of the upper sections of the foot pocket and more importantly in the interface section 18.
  • a swim fin apparatus 54 is similar to the swim fin apparatus 8 of Fig.l and is shown without the tail fin 12 of Fig. 1.
  • the intersection of the foot pocket and the blade 56 is also shown.
  • the lower part of the left side wall 58 shows its location below the buckle boss and the left side blade overlap 50 on the left side of the foot pocket.
  • the blade 16 is similar to the blade 16 of Fig.' s 1 and 2 and can be described as a relatively flat foil tapering from the left side blade overlap to the thickest dimension about where the Right Side of Blade 42 is shown and tapering smaller to the second end 14 on both the Left Side Trailing Edge of Blade 32 and the Right Side Trailing Edge of Blade 34.
  • FIG. 4 the swim fin apparatus 8 of Fig. 1 is shown with its blade bending upwards along its axis of flex 10.
  • the right side wall bends 48 around to join the base wall of the foot pocket 58 forming a rectilinear shelled shape better illustrated and described in later views.
  • a small portion of the reinforcing base wall rail 64 can also be seen and is better described later.
  • the purpose of the connector 66 is clearly seen in its ability to affect the separate angle of attack necessary for the tail fin 12 to function at its peak performance through a proper angle of attack. This allows more thrust at lower speeds than can normally be expected from the stiffer blade which can handle much more powerful kicking.
  • the blade 16 By having the axis of flex 10 made of the thicker tapered material of the blade 16, the blade 16 is able to move easily in a small flutter kick because the thinner part of the blade bends easily while still maintaining the correct angle of attack with more forceful kicking because the blade 16 offers more resistance as more of the blade is involved in the stronger kicking motion. This is true for a wide range of materials that can be used to produce the swim fin apparatus 8. This helps to eliminate the need for different fins for different kicking strengths.
  • the Right Side Wall 60 of the foot pocket 20 connect seamlessly into the Bottom Wall of the Foot Pocket 62.
  • the Reinforcing Base Wall Rail 64 helps to stiffen the Bottom Wall of the Foot Pocket 62 offering a better platform for the swimmer's foot (not shown). By controlling the size, number and thickness of the Rail 64 elements, the amount of angle of bend along the axis of bend 10 can be influenced along with the amount of energy stored and returned.
  • the dashed arrow 68 shows the movement of the blade 16 of the swim fin apparatus 54 originally show in Fig. 3.
  • the tapered quality of the blade 16 is a means for controlling the flexing of the blade 16, and the taper enhances the range of motion that can be comfortably and effectively managed by this invention during swimming and diving because it allows a wider range of kicking strengths to be useful and not overpower the fin.
  • the tapered material naturally bends easier under light force and the thicker material maintains its shape while storing energy in the elastomer material such as compressed rubber or polyurethanes or thermal plastics that act like elastomers.
  • FIG. 6 the drawing which is taken from US patent 6,375,531 shows an alternative embodiment of swim fin apparatus 8 with a relatively flat blade 16 having no ribs and a tail fin 12.
  • the Dashed line showing the plane created by top of Foot 73 does not run parallel with the blade 16 because the foot 84 shows the Dashed line showing the plane created by bottom of Foot 71 running parallel to the blade 16. Since the direction of motion of the swimmer is parallel to Dashed line 73, the blade 16 hangs down in the oncoming stream of water and acts like a brake. This causes substantial drag when the swimmer is trying glide through the water because the foot cannot reach back enough to make the blade 16 glide on a path parallel with the direction of motion of the swim. Secondly, the plane of the blade 16 does not run through the ankle of the foot which is the natural point for the ankle to rotate. This makes this swim fin apparatus 54 alternative embodiment less ergonomic.
  • FIG. 7 the drawing was taken from US patent 5,597,336, and the same problems are common to the swim fin apparatus 54 found in Fig 6.
  • the foot pocket must be quite stiff in order to manipulate the blade with any authority again because the foot pocket 20 sits on top of the blade 16 as opposed to the foot pocket 20 intersecting the blade 16 as it does in swim fin apparatus 8 in Fig. 8.
  • the stiffness in the side walls of the foot pocket replace the ribs used by other fins to a large extent, but make the foot pocket substantially uncomfortable because it is not flexible and cannot adapt to a persons foot or boot.
  • the stiffness of the foot pocket also does not allow for a storage or release of energy generated by the bending of the blade 16.
  • Fig. 9 the drawing taken from US patent 6,758,708 show composite ribbing 88 forming a "bias system" in which the ribbing allows more flexing than classical side ribbing does.
  • the amount of flex allows for a greater range of kicking styles to perform well, but this system has elements that are not necessary in this instant invention since the combination of the blade 16, interface section 18 and foot pocket 20 of swim fin apparatus 8 and swim fin apparatus 54 replace the drag causing composite ribbing 88 of the swim fin apparatus drawn in Fig. 9.
  • the instant invention also allows an even greater range of power to be applied more effectively than is possible in the invention of US patent 6,758,708 while also storing and releasing energy with more efficiency and greater effect.
  • the Solid Arrow showing Storage and Release of Energy 90 shows how the energy flows because of the deformation of the blade 16, the interface section 18 and parts of the foot pocket 20 and through the outer transition section of the left side wall 96 of the foot pocket.
  • the walls of the foot pocket 20 and the interface section 18 are built strong enough to be durable, but thin enough to allow them to flex along with the blade 16.
  • the tension in the material used create compression in some parts of the foot pocket 20 and set others in tension all of which helps to store energy in a similar manner to a leaf spring. This energy is released back into the blade 16 as the stress on the blade 16 removed.
  • the compliant geometry of the flexing blade 16, interface section 18 and foot pocket 20 make it possible for energy storage and the correct bending of the blade 16 for the correct angle of attack.
  • the energy is returned to the system as part of the rebound. Since the energy is stored relatively far from the final rebound of the second end of the blade 14 (and or tail fin in some embodiments), the energy is "whipped" forward in the same way that the speed of the end of a wet towel is accelerated pass the speed of sound to create a snapping sound when the wave of energy is caused to cascade to the end of the towel.
  • the original change to the swim fin was in the area defined by the intersection edge of the interface section 92, the major influence edge of the interface section 94, and the Outer Transition Section for Left Side Wall 96 (and the Outer Transition Section for Right Side Wall not shown). These physically define the edges the interface section 18.
  • FIG.l 1 the additional alternative embodiment of swim fin apparatus 54 of Fig. 3 is shown without an interface section 18. It has an intersection edge 92 which creates a stress along the intersection edge 92 because of the forces coming from a moving blade. Either the foot pocket 20 must be very stiff to resist the stresses resulting from the flexing blade 16, or the intersection will become the focus for a destructive concentration of energy which will soon destroy the swim fin apparatus.
  • FIG. 12 the same fin apparatus 54 as in Fig. 11 is shown so that the intersection edge is more clearly seen.
  • This simple intersection of the planes of the foot pocket and the blade are similar to planes that intersect in architecture or engineering in which the loads on them are in conflict at that edge instead of transferring the energy across a radius or curved surface as happens in an arch. This principle is discussed in more detail later.
  • the bottom of the base wall of the foot pocket 98 extends and intersects the blade 16 without a radius created by an interface section 18 as is found in the swim fin apparatus 8 of Fig 1 to help the transition of the forces and the storage and release of energy. The energy then proceeds to stress this intersection edge 92 with unwanted results since this creates a natural tear point for most materials.
  • the interface section is still relatively straight from the right side of the foot pocket to the left side.
  • the outer transitions section for the left wall 96 has been made into a radius between the surfaces (a curved surface branching between the two major planes involved).
  • the major influence edge of the interface section 94 extends substantially back into the base wall of the foot pocket 62 to spread the load of the energy over a larger section of the swim fin. This allows for a thinner wall which can withstand more distortion from the energy resulting from the distortion of the blade during the kicking motion of the swimmer.
  • This allows storage even when the kicking is in the medium to light range, and involves more and more compression in the side walls of the foot pocket 20 when there is heavier kicking action.
  • This allows for a greater range of proper control of the angle of attack for the blade 16 while also storing greater amounts of energy for return in the rebound phase of the kicking stoke.
  • the interface section is curved from left to right sides of the foot pocket to affect the compliant geometry relationships of the blade 16, interface section 18 and the foot pocket 20. This curvature helps to steer the energy into the side walls more quickly where the energy is stored in compression instead of distorting the elastomers. This means that the major influence edge of the interface section 94 will not reach as far towards the first end of the swim fin into the foot pocket base wall.
  • This type of swim fin architecture offers even greater opportunity for a wider range of energy storage and angle of attack control because the elements can be even thinner in their construction since the energy is being placed onto an "arched" or curved form.
  • the flexible nature of the foot pocket 20 and the interface section 18 along with their geometry provide a method for converting the kick of a swimmer in a natural walking type step into propulsion by bending the blade about an axis in a controlled bending of the blade 16 and thus providing the correct angle of attack for the blade (and any tail fin if attached.)
  • the dashed line showing the unchanged base wall 102 illustrates how small the change in the interface section 18 can be to cause substantial change in the durable nature of this region of the swim fin and the energy storage and rebound capacity.
  • the double arrow 104 representing the energy storage and rebound shows the general direction of the storage of energy when the blade is deflected, in a downward motion and the crossed arrow shows the general direction of energy storage when the blade is deflected in the upward direction.
  • the swim fin is seen from the first end of the foot pocket demonstrating the reinforcing base wall rails 64 which add to the overall thickness of the base wall 62 of the foot pocket 20.
  • the curvature of the Outer Transition Area for Left Side Wall First End 106 is less broad as it extends back towards the first end of the swim fin. It has substantially less torque placed on it during operation of the swim fin. This means that 106 can have a changing radius along its length to reflect the forces involved in the use of the swim fin apparatus 8.
  • the reinforcing base wall rails 64 are widened at the interface 108 as they approach the blade 16 to help strengthen the interface section 18 (not shown in Fig. 17) which lies beneath the base wall 62 in this part of the swim fin apparatus 8.
  • This is another compliant geometry architecture for the swim fin to assist in transferring the energy from the kicking stroke into the length of the swim fin's foot pocket. This has the effect of making it a longer and more subtle "spring" for loading in the energy and would be useful for lighter loads of energy in the kicking motion.
  • the base wall rails 64 also allow for easier insertion and removal of the swimmer's boots.
  • the connector extension 110 offers an extension of the connector to help transfer the energy involved in the kicking motion of the swimmer from the tail fin 12 through to this embodiment of the Connector Interface Section 112. This would allow for even more control of the blade in thinner blade 16 embodiments which could be made of thinner and less expensive material than those of the elastomer family, and allow a better transfer of energy to and from the Connector Interface Section 112, Interface Enlargement 114 and foot pocket 20.
  • Fig. 19 and Fig. 20 both illustrate different stable and unstable intersections between surfaces. All of the intersections in Fig. 19 are weaker than any of the intersections illustrated in Fig. 20.
  • the curved intersections are always stronger because they transfer the energy across the surfaces into the adjacent surfaces instead creating conflicting forces at the intersections. Even when the outside of the lower left mixed corner 132 looks like the outside of the lower left corner 120, the curved inside edge creates almost a triangle like stability in that intersection which stabilizes the intersection substantially. Where the left wall 124 intersects the top wall 126, the upper left corner 116 is very weak because it does not overlap the two walls and does not have any means for transferring the forces from one wall to the other wall. The intersection of left wall 124 and the bottom wall 130 is somewhat stronger because the walls do intersect at Lower Left Corner 120. This intersection still creates a hard edge that is a point of weakness.
  • the foot pocket may be partially made of stiff material or the blade made be partially made of stiff material while still allowing for the flexing of the elements for a desired means of controlling the bending of the blade and storing and release of energy.
  • These elements may have markings, grooves or other decorative or performance related changes as to make them more desirable to the buying public or make them easier to manufacture or use. Accordingly, all such modifications are intended to be included within the scope of the present invention as defined in the appended claims.
  • the order of sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments.
  • any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.
  • Other substitutions, modifications, changes and/or omissions may be made in the design, orientation, operating conditions and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the present invention as expressed in the appended claims.

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Abstract

The present invention relates to a swim fin apparatus for use by a swimmer in which a foot pocket is adapted to interface with a tapered blade, with a possible tail fin further enhancing lift, and the incorporation of an interface section between the blade and the flexible foot pocket that is configured to act as a means of control for the blade to bend within a narrow range of correct angles of attack under a wide range of loads while providing storage of the energy generated by a kicking stroke and a return of that energy into the next stroke.

Description

[0001] TITLE OF THE INVENTION: [0002] IMPROVED SWIM FIN WITH ENERGY STORAGE AND RELEASE.
[0003] U.S. Utility Patent Application of
[0004] John Melius
[0005] STATEMENT REGARDING FEDERALLY SPONSORED R&D: Not Applicable. [0006] INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A
COMPACT DISC: Not Applicable.
[0007] RELATED APPLICATIONS: This patent application relies on the filing date of U.S. Provisional Patent Application Ser. No. 60/617,044 filed 10/12/2004 for IMPROVED SWIM FIN WITH ENERGY STORAGE AND RELEASE, which application is incorporated herein by this reference thereto.
[0008] Technical Field
[0009] This disclosure relates to a system of swim fins used for diving, swimming underwater or swimming on the surface of the water.
[0010] Field of Invention
[0011] This invention relates generally to the field of swimming and diving, and more particularly to a swim fin system with an improved system for storing and then releasing the energy generated by flexing a swim fin blade advantageously attached to a somewhat flexible and elastic interface section contiguous to the foot pocket during swimming.
[0012] More particularly, the present invention relates further to a swim fin with an interface section between a foot pocket in which the foot pocket is placed at a more ergonomic angle to the blade and the interface section in which the foot pocket assists the blade and stores energy when bent during a kicking stroke and then releases this energy generated by flexing the blade back into the blade as the blade rebounds back into the blade's original shape and helps to provide an improved angle of attack for the blade and possible tail fin attached to the blade.
[0013] Background of the Invention
[0014] Swim fins typically comprise a foot pocket and a blade. Since 2002 they may include a secondary "tail fin" as found in United States Patent 6,375,531 , Melius issued 4-2002. When the blade is acting as a "hydrofoil" or "wing", it is very important that the fin attain a correct angle of attack. This is doubly important with the addition of a second foil, the "tail fin". The angle of attack (AOA) is the relative angle that exists between the actual alignment of the oncoming flow (i.e., direction of the motion of the swimmer) and the lengthwise alignment of the blade of the fin and the "tail fin" when there is a "tail fin". A "correct" angle of attack optimizes the conversion of the kicking energy of the swimmer to thrust or propulsion through the water. Excellent water pressure and lift is generated by the foil shapes of both blade and of the "tail fin" when one is used. As the angle of attack increases, the flow collides with the fins attacking surface and/or lifting surface at a greater angle. This increases fluid pressure against the blade surface and increases flow rate over thetffihg'sMice. When the correct angle of attack is achieved when using a "tail fin", the lift created by the hydrofoil shape of the tail fin adds more power to the conversion of energy for the swimmer into useful movement for the swimmer as is taught in United States Patent 6,375,531.
[0015] Conventional fins tend to assume different curvatures or angles of attack according to the direction of the movement and the magnitude of the forces applied during use (i.e., the kicking energy or power). Therefore, it is generally known to design a swim fins to provide a particular angle of attack for a particular "kicking strength". For example, such known swim fins are typically designed for either light kicking, medium kicking, or hard kicking. One way to design a fin for one of these particular kicking strengths is by the composition of the material. United States Patent 6,758,708 tells us: "Changing the composition of the material, however, does not efficiently or adequately control the angle of attack, is difficult to match or 'size' to the strength of the swimmer, and requires the swimmer to use the 'prescribed' kicking power for that particular fin. Also, most existing fins can only reach a compromise in that they are either stiff, soft, or somewhere in between. When conventional fins are designed for hard kicking (e.g., made of stiff material), they reach the correct angle of attack when kicked very hard. On a normal, relaxed kick they don't bend far enough and this negatively affects the performance. Fins of this kind will be uncomfortable on the legs, strenuous and with poor performance on a relaxed dive. When conventional fins are designed for light kicking (e.g., made of soft material), they reach the correct angle of attack when kicked very gently. With a strong kick, such as when swimming in a current or needing to get up to speed, the blade is overpowered and there is little or no thrust available. Fins like this might be comfortable on a relaxed dive, but could become unsafe by not being able to provide the thrust to overcome a slight current. When conventional fins are somewhere in between, they can be overpowered when kicked real hard, are still uncomfortable when kicked gently, but cover a wider range of useful kicking power. [0016] When such known fins are used outside their prescribed kicking power, the angle of attach tends to be too low or too high. When the fin blade is at an excessively high or low angles of attack, the flow begins to separate, or detach itself from the low pressure surface of the fin. This tends to cause the fin to be less efficient. Another problem that occurs at higher angles of attack is the formation of vortices along the outer side edges of the fin. This tends to cause drag. Drag becomes greater as the angle of attack is increased. This reduces the ability of the fin to create a significant difference in pressure between its opposing surfaces for a given angle of attack, and therefore decreases the power delivered by the fin." [0017] This tends to cause drag and drag becomes greater as the angle of attack is increased. This reduces the ability of the fin to create a significant difference between its opposing surfaces for a given angle of attack, and therefore decreases the power delivered by the fin. [0018] United States Patent 6,758,708 proposes a solution whereby a biasing system is conFigured to allow the blade to bend within a narrow range of angles of attack under a wide range of loads. This biasing system is composed of one or more biasing members such as a sinusoidal shaped rib or non-linear ribs. The teaching does deal with variations on ribs. Note: ribs have traditionally found broad use in stiffening swim fins to an appropriate degree to facilitate their use by a swimmer. The ribs used in this patent are also located within the left and right edges of the blade that help to create better hydrodynamic flow, but are still non-foil type obstructions which do cause unnecessary drag.
[0019] More typical ribs can be found in United States Patent 6,290,561. In this patent, the ribs are extended from about the middle of the sides of the foot pocket well on the outside edge of the blade. This traditional handling of the stiffening agents for the foot pocket and the blade allow little if any flex in the foot pocket-to-blade region and create substantial drag in doing this job. They feel like small anchors when trying to glide in such fins. These ribs begin well within the foot pocket to help strengthen the attachment of the foot pocket to the blade in a sound albeit stiff manner.
[0020] Other patents such as the earlier mentioned United States Patent 6,375,531 and United States Patent 5,597,336 describe foot pockets which do not have ribs specifically extending into the blades. These patents do not teach a flexible foot pocket, but do have side walls on the foot pockets that are suffϊcietitly stiff as to act like ribs. These foot pockets are rigid because they must be in order to assert sufficient force on the blade in that configuration. As will be explained later in this document, this conFiguration also places the blade in a position that is less ergonomic as well as less conducive to good hydrodynamics while swimming or diving when compared to the instant invention.
[0021] Summary of the Invention
[0022] Accordingly, it would be advantageous to provide a swim fin that provides: , a. a desired or optimum angle of attack for a variety or range of kicking strengths or powers. i. It would further be desirable to provide a swim fin apparatus in which the angle of attack is consistently controlled both for the upstroke and for the downstroke so that the ratio of power to the fin area is markedly increased wherein it possible to reduce the overall size of the swim fin without sacrificing total power for various kicking efforts. ii. It would further be advantageous to control the angle of attack both for the blade and for the tail fin when used by structural characteristics of bending in the compliant geometry of the relationships of the foot pocket, interface section, and the blade; whereby the characteristics of materials assisted in this controlled bending. iii. It would further be advantageous to control the angle of attack both for the blade and for the tail fin when used by structural characteristics of bending in the compliant geometry of the relationships of the foot pocket, interface section, and the blade and not merely by the characteristics of materials.
b. It would be better to provide this with fewer parts necessary in manufacture, and fewer parts impairing the flow of water over the fin thus producing better hydrodynamics. c. It would be better to provide this with an "air foil" shaped blade to increase the useful "lift" provided by the blade. d. It would be better to do this with a second lifting foil to provide secondary lift contributing to the desired goals. e. It would further be desirable to provide a swim fin apparatus in which the angle of attack is accurately controlled both for the upstroke and for the downstroke so that the ratio of power to the fin area is markedly increased which makes it possible to reduce the overall size of the swim fin without sacrificing total power for various kicking efforts. f. This goal would be further enhanced with the use of a blade, interface section and foot pocket that extend the "loaded spring" quality of the blade deformation thus increasing control and the storage of energy in the overall fin. g. It would further be advantageous to control the angle of attack both for the blade and for the tail fin when used by structural characteristics of bending in the compliant geometry of the relationships of the foot pocket, interface section, and the blade and not merely by the characteristics of materials wherein the natural movements and muscles used by the swimmer in "walking" provided the energy for kicking stroke. h. It would be further more desirable to provide a swim fin with such a compliant relationship between the blade, the interface section, and the foot pocket wherein these three work together to control the bending and the angle of attack through their compliant geometry to increase the performance by controlling the angle of attack and converting a higher percentage of the kick energy into thrust. i. It would further be advantageous to provide a tapered blade as part of the compliant geometry extending from the interface section and the foot pocket to produce a greater range of useful resistance across the range of kicking styles and powers ensuring the correct angle of attack for the blade and tail fin if there is one. j. It would further be advantageous to use a tail fin connected to such a blade or tapered blade to further convert the flow of water over such a foil shape into useful power for the swimmer to focus the flow of water in a vector in the desired direction. k. It would be further advantageous for the present invention to relate to a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, and an interface section allowing the blade to bend within a narrow range of angles of attack under a wide range of loads.
1. It would be further advantageous for the present invention to relate to a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, a tail fin extending from the blade, and an interface section allowing the blade to bend within a narrow range of angles of attack under a wide range of loads. m. It would be further advantageous for the present invention to relate to a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, and an interface section comprising curved radii allowing the blade to bend within a narrow range of angles of attack under a wide range of loads and allowing the footpocket to flex to store and then release energy from the bending of the blade. n. It would be further advantageous for the present invention to relate to a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, a tail fin extending from the blade, and an interface section comprising curved radii allowing the blade to bend within a narrow range of angles of attack under a wide range of loads and allowing the footpocket to flex to store and then release energy from the bending of the blade. o. It would be further advantageous for the present invention to relate to a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, and an interface section allowing the blade to bend within a narrow range of angles of attack under a wide range of loads. p. It would be further advantageous for the present invention to relate to a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, and an interface section adjoined to a flexible foot pocket and a means for controlling the flexing of the blade. q. It would be further advantageous for the present invention to relate to a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, a tail fin extending from the blade, and an interface section adjoined to a flexible foot pocket and a means for controlling the flexing of the blade. r. It would be further advantageous for the present invention to relate to method of providing thrust from the kick of a swimmer which is a natural kick involving a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, and an interface section adjoined to a flexible foot pocket that acts as a means of controlling the axis of bending for the blade by providing varying resistance by the flexible interface section and flexible foot pocket. s. It would be further advantageous for the present invention to relate to method of providing thrust from the kick of a swimmer which is a natural kick involving a swim fin apparatus for use by a swimmer with the fin comprising a foot pocket adated to receive a foot of the swimmer, a blade extending from the foot pocket, a tail fin extending from the blade, and an interface section adjoined to a flexible foot pocket that acts as a means of controlling the axis of bending for the blade by providing varying resistance by the flexible interface section and flexible foot pocket. t. And the present invention further relates to various features and combinations of features shown and described in the disclosed embodiments. Other ways in which the objects and features of the disclosed embodiments are accomplished will be described in the following specification or will become apparent to those skilled in the art after they have read this specification. Such othr ways are deemed to fall within the scope of the disclosed embodiments if they fall within the scope of the claims which follow.
[0023] To provide an inexpensive, reliable, and widely adaptable swim fin with improved angle of attack and water flow characteristics, with further reduced drag, further reduced numbers of elements, mainly ribbing of any sort or any extra elements for a biasing system, and possibly enhanced "lift" with a tail fin that avoids the other problems referenced above would represent a significant advance in the art.
[0024] Accordingly, it would be advantageous to provide a swim fin that provides a desired or optimum angle of attack for a variety or range of kicking strengths or powers. It would be better to provide this with fewer parts necessary in manufacture, and fewer parts impairing the flow of water over the fin thus producing better hydrodynamics. It would be better to provide this with an "air foil" shaped blade to increase the "lift" provided by the blade. It would be better to do this with a second lifting foil to provide secondary lift also contributing to the desired goals. It would further be desirable to provide a swim fin in which the angle of attack is accurately controlled both for the upstroke and for the downstroke so that the ratio of power to the fin area is markedly increased (which makes it possible to reduce the overall size of the swim fin without sacrificing total power) for various kicking efforts. This goal would be further enhanced with the use of a blade, interface section and foot pocket that extended the "loaded spring" quality of the blade deformation increasing control and the storage of energy in the overall fin. It would further be advantageous to control the angle of attack both for the blade and for the tail fin when used by structural characteristics of bending in the compliant geometry of the relationships of the foot pocket, interface section, and the blade and not merely by the characteristics of materials. It would be further more desirable to provide a swim fin with such a compliant relationship between the blade, the interface section, and the foot pocket wherein these three work together to control the bending and the angle of attack through their compliant geometry to increase the performance by controlling the angle of attack and converting a higher percentage of the kick energy into thrust. It would further be advantageous to provide a tapered blade work with the compliant geometry of the interface section and the foot pocket to produce a greater range of usefulness among the different range of kicking styles and powers. It would further be advantageous to use a tail fin connected to such a blade or tapered blade to further convert the flow of water over such a foil shape into useful power tor the swimmer focusing the flow of water in a vector in the desired directions.
[0025] To provide an inexpensive, reliable, and widely adaptable swim fin with improved angle of attack and water flow characteristics, with further reduced drag, further reduced numbers of elements (mainly ribbing of any sort) and possibly enhanced "lift" with a tail fin that avoids the other problems referenced above would represent a significant advance in the art.
[0026] Description of the Figures
[0027] Fig. 1 is a bottom perspective view of a swim fin according to a preferred embodiment with the blade flexed downwards. Fig. 1 introduces parts 8 - 24 [0028] 8 Swim Fin [0029] 10 Axis of Flex for Blade [0030] 12 Tail Fin [0031] 14 Second End [0032] 16 Blade [0033] 17 Bottom of Blade [0034] 18 Interface Section [0035] 19 Bottom of Foot Pocket [0036] 20 Foot Pocket [0037] 21 Bottom of Tail Fin [0038] 22 Heel Strap Boss [0039] 24 First End
[0040] Fig. 2 is a top perspective view of the swim fin of Fig. 1 with a centerline drawn through it for reference purposes. [0041] Fig.2 introduces parts 26 - 52
[0042] 26 Tailing Edge
[0043] 28 Right Side of Tail Fin
[0044] 30 Left Side of Tail Fin
[0045] 32 Left Side Trailing Edge of Blade
[0046] 33 Dashed Center Line [0047] 34 Right Side Trailing Edge of Blade
[0048] 36 Top of Tail Fin
[0049] 38 Top of Connector Section
[0050] 40 Top of Blade
[0051] 42 Right Side of Blade
[0052] 44 Right Side of Top Wall of Foot Pocket
[0053] 46 Top Wall of Foot Pocket
[0054] 48 Left Side Wall of Foot Pocket Top Part
[0055] 50 Left Side Blade Overlap of Foot Pocket
[0056] 52 Left Side of Blade
[0057] Fig. 3 is a top perspective view of the swim fin of Fig. 1 without a tail fin. Fig. 3 introduces parts 54 - 58 [0058] 54 Swim Fin without Tail Fin [0059] 56 Intersection of Foot Pocket and Blade [0060] 58 Left Side Wall of Foot Pocket Lower Part
[0061] Fig. 4 is a side perspective view of the swim fin of Fig. 1 with the blade flexed upwards.
Fig. 4 introduces 60 - 64 [0062] 60 Right Side Wall [0063] 62 Base Wall of Foot Pocket [0064] 64 Reinforcing Base Wall Rail [0065] 66 Connector Section
[0066] Fig. 5 is a side view of the swim fin in Fig. 3 with reference dashed lines illustrating the top and bottom planes of the foot and a dashed arrow illustrating the flex directions of the blade. Fig. 5 introduces 68 - 82
[0067] 68 Dashed arrow showing movement of Blade vertically.
[0068] 70 Dashed line showing the plane created by bottom of Boot
[0069] 71 Dashed line showing the plane created by the bottom of the Foot
[0070] 72 Dashed line showing the plane created by top of Boot
[0071] 73 Dashed line showing the plane created by top of Foot
[0072] 74 Buckle Boss attachment part
[0073] 76 Releaseable part of Buckle [0074] 78 Boot tor scuba diving
[0075] 80 Heel Strap
[0076] 82 Dashed line showing center of foot and center of movement
[0077] Fig.6 is a prior art perspective view illustrating where the blade is in line with the bottom of the foot. Fig. 6 iαtroduces 84 [0078] 84 Human Foot without scuba boot
[0079] Fig. 7 is a prior art perspective view illustrating where the blade is in line with the bottom of the foot.
[0080] Fig. 8 is a prior art perspective view illustrating a swim fin with traditional ribbing securing the foot pocket stiffly to the blade. Figure 8 introduces 86 [0081] 86 Side Ribbing
[0082] Fig. 9 is prior art perspective view illustrating a swim fin with bias system of ribbing elements. Fig. 9 introduces 88 [0083] 88 Composite Ribbing
[0084] Fig. 10 is a bottom perspective view of the swim fin of Fig. 1 with an arrow illustrating the energy flow and storage range. Figure 10 introduces 90 - 96 [0085] 90 Solid Arrow showing Storage and Release of Energy [0086] 92 Intersection Edge of Interface Section [0087] 94 Major Influence Edge of Interface Section [0088] 96 Outer Transition Section for Left Side Wall
[0089] Fig. 11 is a side view of the swim fin of Fig. 3 illustrating a tapered blade and the angle of attachment for the foot pocket.
[0090] Fig. 12 is a top perspective view of the bottom of a swim fin without an interface section.
[0091] Fig. 12 Introduces 98
[0092] 98 Bottom of the Base Wall of Foot Pocket
[0093] Fig. 13 is a top perspective view of the bottom of the swim fin of Fig. 12 with a broad interface section. Fig. 13 Introduces [0094] 99 Outer Transition Section for kight Side Wall
[0095] Fig. 14 is a top perspective view of the bottom of a swim fin of Fig. 12 with a narrower curved interface section.
[0096] Fig. 15 is a side view of the swim fin of Fig. 3 with a double arrow showing the flow and storage of energy and a crossed arrow. [0097] Fig. 15 Introduces 100 - 104 [0098] 100 Crossed Arrow Representing Compression [0099] 102 Dashed Line Showing Unchanged Base Wall [00100] 104 Double Arrow Representing Energy Storage and Rebound
[00101] Fig. 16 is a rear perspective view of the swim fin of Fig. 1 with the base wall rails in easy view. Fig. 16 Introduces 106 [00102] 106 Outer Transition Area for Left Side Wall First End
[00103] Fig. 17 is a rear perspective view of the swim fin of Fig. 1 with the base wall rails altered.
Fig. 17 Introduces 108 [00104] 108 Reinforcing Base Wall Rail Widened at Interface
[00105] Fig. 18 is a perspective view of the bottom of the swim fin of Fig.1 with the addition of an extended connector to the interface section. Fig. 18 Introduces 110 — 114 [00106] 110 Connector Extension [00107] 112 Connector Interface Section [00108] 114 Interface Enlargement
[00109] Fig. 19 is a graphic representation of four walls connecting at the corners for discussion purposes only. Fig. 19 Introduces 116 - 130
[00110] 116 Upper Left Corner [00111] 118 Upper Right Corner [00112] 120 Lower Left Corner [00113] 122 Lower Right Corner [00114] 124 Left Wall [00115] 126 Top Wall [00116] 128 Right Wall [00117] 130 Base Wall
[00118] Fig. 20 is a graphic representation of four walls connecting at the corners for discussion purposes only. Fig. 20 Introduces 132 - 146 [00119] 132 Lower Left Mixed Corner [00120] 134 Left Wall Mixed [00121] 136 Upper Left Mixed Corner [00122] 138 Top Wall Mixed [00123] 140 Upper Right Mixed Corner [00124] 142 Right Wall Mixed [00125] 144 Lower Right Mixed Corner
[00126] Detailed Description of Preferred and other Embodiments
[00127] Referring to Fig.l, swim fin apparatus 8 is shown according to a preferred embodiment. Each apparatus 8 comprises a foot pocket 20, a blade 16, and an interface section 18 conFigured to work together in compliant geometry to accumulate and rebound energy while maintaining the desired angle of attack for a variety or range of kicking strengths or powers. [00128] According to a generally preferred embodiment, the foot pocket 20, the interface section 18, and the blade 16 are molded of the same elastomer material with good rebound characteristics thus simplifying manufacture while improving performance. The foot pocket 20, interface section 18, and blade 16 could be fused together from different materials to form an integral structure alternatively.
[00129] In Fig. 1, the perspective view of a swim fin apparatus 8 shows it bending downwards around the axis of flex 10, dashed line, for the blade 16. In this embodiment, the blade has a tail fin 12 attached to it to enhance performance by using the foil shape of the tail fin to produce lift in the desired direction. The functions of the tail fin are taught in United States Patent 6,375,531, and will not be addressed in detail in this patent. This swim fin has a first end 24 and a second end 14. The foot pocket 20, beginning at the first end, extends out to intersect the blade at the interface section 18 from which the blade extends to the second end. On the side of the foot pocket near the blade is the heel strap boss 22 used for attaching the standard size buckles found in this industry. The bottom of the blade 17, the bottom of the foot pocket 19 and the bottom of the tail fin 21 can also be seen.
[0013O]In Fig. 2, a dashed line 33 illustrates the centerline of the swim fin of FIG 1 to help demonstrate the generally symmetrical nature of the fin. Asymmetry would not improve performance but may give a swimmer the opportunity to use larger blades without interfering with each other. Such an asymmetrical fin apparatus is not drawn but could easily be conceived by anyone skilled in the art knowing that such an asymmetrical apparatus would have to have a right and left version for the respective right and left feet of the swimmer. Swim fin apparatus is generally produced in a relative symmetry when considered as mirror a mirror image of each half of the apparatus on each side of the centerline 33 as the industry standard. The trailing edge of the tail fin 26 is found at the second end 14 of the same fin apparatus 8. It is so called in this embodiment because it is the trailing edge of the foil shape of the tail fin 12. The entire swim fin has a right and left side and is generally symmetrical from right to left. The right side of the tail fin 28, and the left side of the tail fin 30 are shown. The left side of the training edge of the blade 32 and the right side of the trailing edge of the blade 34 are shown. The top of the tail fin 36 is shown extending into the top of the connector section 38 which continues extending into the top of the blade 40 so that the tail fin is attached approximately at the center of the blade via the connector 38. The left side blade overlap of the footpocket extends from the area of the boss 22 into the Left Side of the Blade 52. Notice how the blade 16 and the tail fin 12 form a plane which if extended would intersect the boss 22 which is where the ankle of the swimmer is located when the foot of the swimmer is inserted into the foot pocket. The top wall of the foot pocket 46 can act as part of the "paddle" of the swim fin apparatus 8 when made flat enough to help push water with the blade 16. When the foot pocket 20 is flexible, the flat top of the footpocket 46 is more flexible than the bottom of the foot pocket 20 as will be explained later. Starting at the right side of the top wall of the foot pocket 44, the top wall of the foot pocket 46 extends over to the left side wall of the foot pocket 48 which extends into the left side glade overlap of the foot pocket 50 which connects back into the left side of the blade 52.
[00131] When the rear of the foot pocket 20 is closed, it has a "closed footpocket" of a light weight very flexible material. Such a fin apparatus is not illustrated here but is well known by anyone skilled in the art. What is viewed all of the Fig.'s illustrating fin apparatus is an "open heel" type of swim fin apparatus. The principles taught in this instant invention can be applied equally well to closed heel or open heel swim fin apparatus although the closed heel apparatus is not shown.
[00132] In Fig. 2, the intersection of the left side of the foot pocket 52 and the left blade overlap 50 is an important part of the architecture of swim fin apparatus because it helps to create a secure and stable platform for the foot pocket 20 to wield influence over the blade 16 and tail fin 12 (when a tail fin 12 is in the embodiment) causing it to bend on a predetermined axis of flex 10 illustrated in FIG 1. This feature also allows flexibility in the foot pocket in the left side walls 44 and right side walls 48 of the upper sections of the foot pocket and more importantly in the interface section 18. These parts of the swim fin apparatus then do two things very well. They control the amount of bend of the blade 16 along the axis of flex 10, and they allow the interface section 18 and the foot pocket 20 to flex and thus store energy like a leaf spring. When the fin apparatus 8 is released from the pressure exerted on it by kicking the fin apparatus 8 in water, the stored energy in the interface section 18 and the foot pocket 20 are returned to the blade 16 which helps to give the blade extra energy in the next kicking direction.
[00133]In Fig. 3, a swim fin apparatus 54 is similar to the swim fin apparatus 8 of Fig.l and is shown without the tail fin 12 of Fig. 1. The intersection of the foot pocket and the blade 56 is also shown. The lower part of the left side wall 58 shows its location below the buckle boss and the left side blade overlap 50 on the left side of the foot pocket. The blade 16 is similar to the blade 16 of Fig.' s 1 and 2 and can be described as a relatively flat foil tapering from the left side blade overlap to the thickest dimension about where the Right Side of Blade 42 is shown and tapering smaller to the second end 14 on both the Left Side Trailing Edge of Blade 32 and the Right Side Trailing Edge of Blade 34.
[00134]In Fig. 4, the swim fin apparatus 8 of Fig. 1 is shown with its blade bending upwards along its axis of flex 10. The right side wall bends 48 around to join the base wall of the foot pocket 58 forming a rectilinear shelled shape better illustrated and described in later views. A small portion of the reinforcing base wall rail 64 can also be seen and is better described later. The purpose of the connector 66 is clearly seen in its ability to affect the separate angle of attack necessary for the tail fin 12 to function at its peak performance through a proper angle of attack. This allows more thrust at lower speeds than can normally be expected from the stiffer blade which can handle much more powerful kicking. By having the axis of flex 10 made of the thicker tapered material of the blade 16, the blade 16 is able to move easily in a small flutter kick because the thinner part of the blade bends easily while still maintaining the correct angle of attack with more forceful kicking because the blade 16 offers more resistance as more of the blade is involved in the stronger kicking motion. This is true for a wide range of materials that can be used to produce the swim fin apparatus 8. This helps to eliminate the need for different fins for different kicking strengths. The Right Side Wall 60 of the foot pocket 20 connect seamlessly into the Bottom Wall of the Foot Pocket 62. The Reinforcing Base Wall Rail 64 helps to stiffen the Bottom Wall of the Foot Pocket 62 offering a better platform for the swimmer's foot (not shown). By controlling the size, number and thickness of the Rail 64 elements, the amount of angle of bend along the axis of bend 10 can be influenced along with the amount of energy stored and returned.
[00135]In Fig. 5, the dashed arrow 68 shows the movement of the blade 16 of the swim fin apparatus 54 originally show in Fig. 3. In this view, the tapered nature of the blade 16 is easy to see. The tapered quality of the blade 16 is a means for controlling the flexing of the blade 16, and the taper enhances the range of motion that can be comfortably and effectively managed by this invention during swimming and diving because it allows a wider range of kicking strengths to be useful and not overpower the fin. The tapered material naturally bends easier under light force and the thicker material maintains its shape while storing energy in the elastomer material such as compressed rubber or polyurethanes or thermal plastics that act like elastomers. This allows the material to "rebound" back to its original position sometimes with almost all of the energy applied to its deformation thus imparting a snap to the blade in the correct direction for the next kicking stroke. Notice that the centerline 82 of the blade is the centerline of the movement and the centerline for the mass of the foot in this embodiment rotating around the ankle of the boot 78 worn by the swimmer. This is very important since this allows the swimmer to glide in this position with almost no drag at all from the swim fin. This also allows for the foot of the swimmer to rotate naturally as the foot does in walking, running, and climbing making the fin apparatus 54 more ergonomic. This causes the swim fin to be able to be used more efficiently, and the lack of protruding ribs also reduces the drag found in other fins. When the foot in the boot 78 is extended in the plantar flexion position, two dashed lines show the plane created by the Dashed line showing the plane created by bottom of Boot 70 and approximately by the Dashed line showing the plane created by top of Boot 72. The blade 16 is in a better position for gliding when it parallels the Dashed line showing the plane created by top of Boot 72 in the boot because this plane is parallel to the direction of movement of the swimmer and so reduces drag. The part of the buckle that we are calling the buckle boss attachment part 74 and the corresponding releasable part of the buckle 76 are commonly used items throughout the industry and well known to anyone knowledgeable in the art. The heel strap 80 is attached to these buckles to assist in retaining the heel of the foot and the boot in the footpocket.
[00136] In Fig. 6, the drawing which is taken from US patent 6,375,531 shows an alternative embodiment of swim fin apparatus 8 with a relatively flat blade 16 having no ribs and a tail fin 12. The Dashed line showing the plane created by top of Foot 73 does not run parallel with the blade 16 because the foot 84 shows the Dashed line showing the plane created by bottom of Foot 71 running parallel to the blade 16. Since the direction of motion of the swimmer is parallel to Dashed line 73, the blade 16 hangs down in the oncoming stream of water and acts like a brake. This causes substantial drag when the swimmer is trying glide through the water because the foot cannot reach back enough to make the blade 16 glide on a path parallel with the direction of motion of the swim. Secondly, the plane of the blade 16 does not run through the ankle of the foot which is the natural point for the ankle to rotate. This makes this swim fin apparatus 54 alternative embodiment less ergonomic.
[00137] In Fig. 7, the drawing was taken from US patent 5,597,336, and the same problems are common to the swim fin apparatus 54 found in Fig 6. The foot pocket must be quite stiff in order to manipulate the blade with any authority again because the foot pocket 20 sits on top of the blade 16 as opposed to the foot pocket 20 intersecting the blade 16 as it does in swim fin apparatus 8 in Fig. 8. The stiffness in the side walls of the foot pocket replace the ribs used by other fins to a large extent, but make the foot pocket substantially uncomfortable because it is not flexible and cannot adapt to a persons foot or boot. The stiffness of the foot pocket also does not allow for a storage or release of energy generated by the bending of the blade 16. [00138] In Fig. 8, the drawing taken from US patent 6,290,561 shows classic side ribbing 86 that is used to secure a solid connection from the foot pocket to the blade and helps to stiffen the blade. It is easy to see that any surface raised to this height will interfere with the smooth flow of water and thus cause increased drag over any fin without these raised surfaces. This stiff handling of the blade necessitates any bending of the blade 16 to be further in front of the foot than any of the swim fins in Fig.'s 1-7.
[00139] In Fig. 9, the drawing taken from US patent 6,758,708 show composite ribbing 88 forming a "bias system" in which the ribbing allows more flexing than classical side ribbing does. The amount of flex allows for a greater range of kicking styles to perform well, but this system has elements that are not necessary in this instant invention since the combination of the blade 16, interface section 18 and foot pocket 20 of swim fin apparatus 8 and swim fin apparatus 54 replace the drag causing composite ribbing 88 of the swim fin apparatus drawn in Fig. 9. Secondarily, the instant invention also allows an even greater range of power to be applied more effectively than is possible in the invention of US patent 6,758,708 while also storing and releasing energy with more efficiency and greater effect.
[0014O]In Fig. 10, the Solid Arrow showing Storage and Release of Energy 90 shows how the energy flows because of the deformation of the blade 16, the interface section 18 and parts of the foot pocket 20 and through the outer transition section of the left side wall 96 of the foot pocket. The walls of the foot pocket 20 and the interface section 18 are built strong enough to be durable, but thin enough to allow them to flex along with the blade 16. The tension in the material used create compression in some parts of the foot pocket 20 and set others in tension all of which helps to store energy in a similar manner to a leaf spring. This energy is released back into the blade 16 as the stress on the blade 16 removed. The compliant geometry of the flexing blade 16, interface section 18 and foot pocket 20 make it possible for energy storage and the correct bending of the blade 16 for the correct angle of attack. When the distorting energy (the kicking action) is released, the energy is returned to the system as part of the rebound. Since the energy is stored relatively far from the final rebound of the second end of the blade 14 (and or tail fin in some embodiments), the energy is "whipped" forward in the same way that the speed of the end of a wet towel is accelerated pass the speed of sound to create a snapping sound when the wave of energy is caused to cascade to the end of the towel. This has the effect of making the working part of the blade 16 seem longer since the interface section 18 and the foot pocket 20 actively contribute to the blade 16 as if it were a much longer blade 16. The extra blade 16 length effect is in a much smaller package though. This is not just theory. This type of swim fin apparatus 8 has been tested recently an performed extremely well much to the surprise of those testing the apparatus 8 because they expected a performance that was more typical of a smaller sized apparatus. A very small change in the size and shape of prototypes increased the ability of the blade 16 to handle substantially more powerful kicking power while storing this energy for a substantially enhanced rebound snap to the blade. The difference was surprising. The original change to the swim fin was in the area defined by the intersection edge of the interface section 92, the major influence edge of the interface section 94, and the Outer Transition Section for Left Side Wall 96 (and the Outer Transition Section for Right Side Wall not shown). These physically define the edges the interface section 18.
[0014I]In Fig.l 1, the additional alternative embodiment of swim fin apparatus 54 of Fig. 3 is shown without an interface section 18. It has an intersection edge 92 which creates a stress along the intersection edge 92 because of the forces coming from a moving blade. Either the foot pocket 20 must be very stiff to resist the stresses resulting from the flexing blade 16, or the intersection will become the focus for a destructive concentration of energy which will soon destroy the swim fin apparatus.
[00142]In Fig. 12, the same fin apparatus 54 as in Fig. 11 is shown so that the intersection edge is more clearly seen. This simple intersection of the planes of the foot pocket and the blade are similar to planes that intersect in architecture or engineering in which the loads on them are in conflict at that edge instead of transferring the energy across a radius or curved surface as happens in an arch. This principle is discussed in more detail later. [00143]In Fig.12, the bottom of the base wall of the foot pocket 98 extends and intersects the blade 16 without a radius created by an interface section 18 as is found in the swim fin apparatus 8 of Fig 1 to help the transition of the forces and the storage and release of energy. The energy then proceeds to stress this intersection edge 92 with unwanted results since this creates a natural tear point for most materials.
[00144] In Fig. 13, the interface section is still relatively straight from the right side of the foot pocket to the left side. The outer transitions section for the left wall 96 has been made into a radius between the surfaces (a curved surface branching between the two major planes involved). The major influence edge of the interface section 94 extends substantially back into the base wall of the foot pocket 62 to spread the load of the energy over a larger section of the swim fin. This allows for a thinner wall which can withstand more distortion from the energy resulting from the distortion of the blade during the kicking motion of the swimmer. This allows storage even when the kicking is in the medium to light range, and involves more and more compression in the side walls of the foot pocket 20 when there is heavier kicking action. This allows for a greater range of proper control of the angle of attack for the blade 16 while also storing greater amounts of energy for return in the rebound phase of the kicking stoke.
[00145] In Fig. 14, the interface section is curved from left to right sides of the foot pocket to affect the compliant geometry relationships of the blade 16, interface section 18 and the foot pocket 20. This curvature helps to steer the energy into the side walls more quickly where the energy is stored in compression instead of distorting the elastomers. This means that the major influence edge of the interface section 94 will not reach as far towards the first end of the swim fin into the foot pocket base wall. This type of swim fin architecture offers even greater opportunity for a wider range of energy storage and angle of attack control because the elements can be even thinner in their construction since the energy is being placed onto an "arched" or curved form. In the same way than an arch can support surprisingly large amount of feree, this configuration is unusually strong because it places the forces in compression in the materials. Elastomers are stronger, more reliable and last longer in compression mode. This illustration also demonstrates the wide range of possible subtle changes to the interface section and foot pocket 20 and blade 16 that can control the angle of attack and the energy storage of the kicking stroke. [00146] In Fig. 15, the crossed arrow representing compression 100 demonstrates how the upper side wall of the foot pocket 20 also stores energy under compression and releases the same energy back into the kicking stroke. At the same time, the flexible nature of the foot pocket 20 and the interface section 18 along with their geometry provide a method for converting the kick of a swimmer in a natural walking type step into propulsion by bending the blade about an axis in a controlled bending of the blade 16 and thus providing the correct angle of attack for the blade (and any tail fin if attached.) The dashed line showing the unchanged base wall 102 illustrates how small the change in the interface section 18 can be to cause substantial change in the durable nature of this region of the swim fin and the energy storage and rebound capacity. The double arrow 104 representing the energy storage and rebound shows the general direction of the storage of energy when the blade is deflected, in a downward motion and the crossed arrow shows the general direction of energy storage when the blade is deflected in the upward direction. [00147] In Fig. 16, the swim fin is seen from the first end of the foot pocket demonstrating the reinforcing base wall rails 64 which add to the overall thickness of the base wall 62 of the foot pocket 20. The curvature of the Outer Transition Area for Left Side Wall First End 106 is less broad as it extends back towards the first end of the swim fin. It has substantially less torque placed on it during operation of the swim fin. This means that 106 can have a changing radius along its length to reflect the forces involved in the use of the swim fin apparatus 8. [00148] In Fig. 17, the reinforcing base wall rails 64 are widened at the interface 108 as they approach the blade 16 to help strengthen the interface section 18 (not shown in Fig. 17) which lies beneath the base wall 62 in this part of the swim fin apparatus 8. This is another compliant geometry architecture for the swim fin to assist in transferring the energy from the kicking stroke into the length of the swim fin's foot pocket. This has the effect of making it a longer and more subtle "spring" for loading in the energy and would be useful for lighter loads of energy in the kicking motion. The base wall rails 64 also allow for easier insertion and removal of the swimmer's boots.
[00149]In Fig. 18, the connector extension 110 offers an extension of the connector to help transfer the energy involved in the kicking motion of the swimmer from the tail fin 12 through to this embodiment of the Connector Interface Section 112. This would allow for even more control of the blade in thinner blade 16 embodiments which could be made of thinner and less expensive material than those of the elastomer family, and allow a better transfer of energy to and from the Connector Interface Section 112, Interface Enlargement 114 and foot pocket 20. [00150] Fig. 19 and Fig. 20 both illustrate different stable and unstable intersections between surfaces. All of the intersections in Fig. 19 are weaker than any of the intersections illustrated in Fig. 20. The curved intersections are always stronger because they transfer the energy across the surfaces into the adjacent surfaces instead creating conflicting forces at the intersections. Even when the outside of the lower left mixed corner 132 looks like the outside of the lower left corner 120, the curved inside edge creates almost a triangle like stability in that intersection which stabilizes the intersection substantially. Where the left wall 124 intersects the top wall 126, the upper left corner 116 is very weak because it does not overlap the two walls and does not have any means for transferring the forces from one wall to the other wall. The intersection of left wall 124 and the bottom wall 130 is somewhat stronger because the walls do intersect at Lower Left Corner 120. This intersection still creates a hard edge that is a point of weakness. The angled intersection of Upper Right Corner 118 and Lower Right Corner 122 are not any stronger because they cannot help to transfer any stress from the top wall 126 to the Right Wall 128 or on again to the Bottom Wall 130. Because of the radii found in the corners of the Lower Left Mixed Corner 132, the Upper Left Mixed Corner 134, the Upper Right Mixed Corner 140, and the Lower Right Mixed Corner, the corners in Fig. 20 are all stronger. They allow the forces found in the Left Wall Mixed 134, the Top Wall Mixed 138, the Right Wall Mixed 142, and the Bottom Wall Mixed 146 to transfer across the corners. This is one of the reasons that the radii in the swim fin embodiments found in this patent can transfer energy into storage and then release it back into the blade 16 of the swim fin apparatus 8 and 54 respectively.
[0015I]It is also important to note that the construction and arrangement of the elements of the swim fin apparatus with its improvements of angle of attack, and water flow characteristics and energy storage and release as show in the preferred and other exemplary embodiments are illustrative only. Although only a few embodiments of the present invention have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible, (for example variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. For example, the foot pocket may be partially made of stiff material or the blade made be partially made of stiff material while still allowing for the flexing of the elements for a desired means of controlling the bending of the blade and storing and release of energy. These elements may have markings, grooves or other decorative or performance related changes as to make them more desirable to the buying public or make them easier to manufacture or use. Accordingly, all such modifications are intended to be included within the scope of the present invention as defined in the appended claims. The order of sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and/or omissions may be made in the design, orientation, operating conditions and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the present invention as expressed in the appended claims.

Claims

[00152] Claims[00153] What is claimed is:[00154] 1. A swim fin comprising: [00155] a first end, with a foot pocket having i. a base wall, ii. a left side wall, iii. a right side wall, and iv. a top wall wherein the foot pocket is adapted to receive a foot of the swimmer[00156] a second end, opposite the first end, further comprising; a. a blade i. extending from a middle of the foot pocket toward the second end and ii. having tapered surfaces from the direction of the first end towards the second end with the largest thickness of the blade approximately where the blade intersects the foot pocket, and iii. generally having left to right and top to bottom symmetrical airfoil-like surfaces; iv. a blade extends from the generally middle of the foot pocket toward the second end,
1. wherein its top and bottom surfaces taper narrowly from the direction of the first end towards the second end, with the largest thickness of the blade approximately where the blade intersects the foot pocket, and
2. wherein the blade surfaces further comprise left to right and top to bottom symmetrical airfoil-like surfaces; b. an interface section further comprising; i. a transition section
1. wherein the blade intersects the foot pocket to conFigure the interface section for deforming as the blade bends; and
2. wherein a portion of the interface section alternately extends between the right side wall and the left side wall of the foot pocket, and
[00157] whereby the blade bends within a narrow range of angles of attack under a wide range of loads.
[00158] 2. The fin of claim 1 wherein said interface section is conFigured to store and release energy (during use of fin).
[00159] 3. The fin of claim 1 wherein side walls of the interface section are conFigured to store and release energy during the use of fin.
[00160] 4. The fin of claim 1 wherein the foot pocket has at least one reinforcing base wall rail conFigured to assist said interface section to help store and release energy during the use of fin.
PCT/US2005/036367 2004-10-12 2005-10-12 Improved swim fin with energy storage and release WO2006044316A2 (en)

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040127117A1 (en) * 2002-07-19 2004-07-01 Mccarthy Peter T. High deflection hydrofoils and swim fins

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040127117A1 (en) * 2002-07-19 2004-07-01 Mccarthy Peter T. High deflection hydrofoils and swim fins

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