Positive Drive Swim Fin

Europaisches Patentamt 0 337 221 J) European Patent Office 0 Publication number: A1 Office europeen des brevets

© Priority: 12.04.88 US 180544 © Applicant: Mc Carthy, Kevin I. 6841 Via Verano © Date of publication of application: Carlsbad California 92008(US) 18.10.89 Bulletin 89/42 © Inventor: Mc Carthy, Kevin I. © Designated Contracting States: 6841 Via Verano DE FR GB IT Carlsbad California 92008(US)

® Representative: Hoeger, Stellrecht & Partner Uhlandstrasse 14 c D-7000 Stuttgart 1(DE)

© The specification herein shows a swimmer's fin (10) having a foot pocket (30) and a blade portion wherein the blade portion is offset from the foot pocket (30) to compensate for the natural supination during a flutter kick, stroke or beat, regardless of whether or not it is a backstroke, kick, or a crawl stroke kick. The fin can be molded in a symmetrical manner so that it can be interchanged between the feet and provided with an offset ankle strap (14) in order to create a more comfortable relationship during the swimming movement. The fin also (10) in- cludes an improved blade end having inner and outer curves wherein the outer curve from the body is of a larger radius than the inner curve. The offset of the foot pocket from the blade can be such wherein the axis of the blade and the axis of the foot ^pocket intersect within the foot pocket area (12) to provide for improved performance.

Xerox Copy Centre I =P 0 337 221 A1

3OSITIVE DRIVE SWIM FIN

=IELD OF THE INVENTION rotation and medial femoral (upper leg) rotation. Of substantial concern is the ankle and foot undergo motion in a horizontal and oblique plane as well as This invention relates to swimming with a swim in the vertical plane. This horizontal movement is fin which can be used by scuba divers as well as s limited to inward or medial rotation and commonly those free divers and other people who use swim referred to as pigeon-toeing, toeing-in or turning-in. fins. More particularly, it relies upon the overall The anatomical term is supination, which is defined aspects of providing a proper orientation to the as inversion and adduction of the ankle and tarsel drive portion of a swim fin due to the natural . joints of the foot. supination that takes place by the foot during the io Supination or toeing-in results from the ana- flutter kick of an individual. tomical structure of the ankle and foot. Also, the water pressure against the foot's surface, the relax- ation of appropriate muscles and the conscious BACKGROUND OF THE INVENTION awareness of the optimal foot position contributes 75 to supination. Swimmers possessing a naturally propelling flutter kick display varying degrees of This invention is a new aquatic body propulsion supination both in the up-stroke and the down- device or swim fin for attachment to the human stroke. foot. It is designed for swimmers and swim fin During the down-stroke the foot supinates natu- users involved in various surface and underwater 20 rally in order to contact more water with the top of swimming sports. Such sports include recreational the foot. This in turn pushes the water backwards swimming, competitive swimming, surfing, body- at a more effective angle, as the foot can be surfing, kick-boarding, body-boarding, knee-boar- extended further in this position. In many cases ding, free-diving, snorkeling, skin-diving, scuba-div- hyperextension of the lower foot is achieved ing and the like. 25 through supination, thereby adding more pushing This new fin is economically designed to take power in the downward stroke. advantage of the natural movements of the torso, When the anatomical centeriine of the foot has legs and feet commonly found in the flutter kick. angled inwardly during supination, the alignment of This enables improved hydrodynamic, propulsion the toes changes in reference to the direction of and efficiency. To effectively illustrate the advan- 30 travel of the swimmer. This toe line which can be * tages of this new swim fin, the critical yet often 65 offset from the anatomical line of the foot, can overlooked aspects of the flutter kick will be de- increase to an approximate 90° angle, perpendicu- scribed. lar to the direction of travel. The flutter kick is fundamentally an alternating During the upstroke the foot rotates laterally oscillation involving the legs and feet with a defini- 35 but stops short of anatomical alignment, thus re- tive up-stroke and down-stroke. The primary pur- taining a degree of supination. Importantly, it pose of each sequential "whip-like" stroke is to should be noted that the angle of supination in both effectively and efficiently push against the water. the upward and downward strokes relates directly This in turn causes a reactive forward propulsion of to the speed and force of the flutter kick. Test the body through the water. 40 results show that the more vigorous the kick the Many experts recognize the flutter kick as a greater the degree of natural supination. crucial counteraction to stabilize the upper torso This toe-in or supinated position is observed in during the crawl stroke. This kick may involve a the flutter kick of both the crawl stroke (when the sequence of flexion, extension and rotation of var- swimmer is ventral side down) and the back stroke ious joints from the lumbar vertebrae of the lower 45 (when the swimmer is ventral side up). The foot back to the flanges of the toes. The specific posi- moves into supination only during the leg stroke tion of the lower foot for accelerating into the that moves the foot towards the ventral side of the whipping sequence determines the effectiveness swimmer. The foot moves away from supination and quantity of force generated. The foot position and back towards anatomical alignment during the desired is one which provides the widest and flat- so leg stroke that moves the foot toward the dorsal or test surface possible for pushing potential. back side of the swimmer. Therefore, since the The primary movements involved in the flutter terms upstroke and downstroke can become con- kick are anatomical flexion and extension of the fusing when speaking of the crawl and back hips, knees and ankles. However, many swimmers strokes, we will now use the terms ventral and display styles that incorporate body rotation, hip dorsal when examining the flutter kick motion.

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Once again defined as inversion and adduction together during the kicking action. )f the lower foot, supination, as applied to a swim- The patent to Decorlieu, namely, U.S. Patent ner's foot motion, is somewhat different than foot 2,588,363, shows somewhat of an offset. However, supination in a standing or weight bearing position, it is not tantamount to this invention, nor is it in the n the flutter kick, a strong emphasis is placed on 5 configuration as to the symmetry of the swim fin nversion of the foot and less emphasis on adduc- herein for wearing on both feet. ion. However, since similar foot muscles control The patent to W. H. Smith, U.S. Design Patent joth positions, a significant degree of adduction is 132,377 shows somewhat of an offset with a fin. jsually present. This can be undesirable because it However, this fin and shoe combination cannot be angles or pitches the foot into a position less than (0 used effectively for swimming. optimal for propulsion. U.S. Patent D 124,013 to Churchill shows a Swimmers with substantial adduction in their particularly interesting prior art fin. In a top view the supinated foot position, will inwardly rotate the fem- Churchill fin is symmetrical whereas its foot pocket 3r or thigh to an appropriate degree that tilts the has no offset with reference to the rails. It should :oot back into a position for optimal push against is be kept in mind that the basic design of the Chur- tie water. chill fin is such that hydrodynamic flow favors the Now therefore, there are three significant foot direction parallel to the anatomical center line of xcurrences which compose a Kenetically Im- the foot. Droved Kicking position in the ventral kick. They Virtually all swim fins today largely exhibit a are: (1) foot supination; (2) an adjusting and propor- 20 standard symmetry as viewed from the top. That is, tionate degree of inward femoral rotation; and (3) the medial and lateral sides of the fin follow a foot extension. In the dorsal kick therefore the foot similar diverging line in relation to the foot pocket and leg return back to anatomical alignment. area as shown in the prior art. The aforementioned anatomical movements in- One can only assume that the foot pocket to volved in the flutter kick are in general observed 25 blade parallelism stems from a traditional philos- and practiced by proficient and competitive partici- ophy that either the foot seldom wavers from an pants in the field of swimming and finswimming anatomical line during the flutter kick, or that pre- disciplines, disciplines. vention or discouragement of this action will have This complete motion of the ventral and dorsal no ill consequence on power, hydrodynamics or kick can be termed the Kinetically Improved Kick- 30 comfort. Supination allows for increased extension, ing Cycle or the KIK Cycle. A specific definition of aligning of the foot with the leg in a vertical plane, the KIK Cycle is as follows: The complete flutter therefore maximizing hydrodynamics and power. kick cycle of a leg, including the ventral and dorsal The typical swim fin user when implementing exist- kicks, whereby the foot undergoes changes in posi- ing or available products must either conform to tion which optimize its alignment for push against 35 the hydrodynamic line of the fin and sacrifice the water. supination, or overcome the hydrodynamic line of The KIK Cycle will vary among swimmers de- the fin to achieve supination. pending upon foot and ankle flexability, swimming in the first case, the swim fin user must sacri- style and experience. This invention specifically fice maximum extension and hyperextension of the addresses supination and the KIK cycle by adapt- 40 foot. This decreases his angle for an efficient push ing to and allowing for these natural movements, against the water. In the second case, the swim fin while increasing performance and comfort. user overcomes the natural hydrodynamic line of the' fin to increase extension and push efficiency, but loses the hydrodynamics of the fin and in THE PRIOR ART 45 actuality drags the fin through the water sideways. A determining factor as to movement in most cases is the overall length and size of the fin. If the There have been many fins of the prior art that fin is relatively small and short the swim fin user have been designed but never directed to the has better movement. The swimmer will accept invention herein. In particular, the fin of D.L. Jayet, so decreased hydrodynamics in the horizontal plane shown in U.S. Patent 2,865,033, shows a fin having for increased hydrodynamics in the vertical plane. a spread-out orientation but not necessarily offset This causes the swimmer to gain a better angle for in the manner provided herein. The fin therein does pushing, by way of increased foot extension. not account for supination. Furthermore, the offset If the fin is long and cumbersome, it is usually of the midline is simply shifted. In addition, al- 55 more efficient to kick with no supination. The me- though the fins can be symmetrical, it is such dial drag is a greater force than a relaxed and wherein they would have a difficult time working, natural supination tendency. In such cases the foot inasmuch as the tips very well might be knocked cannot extend as far in true anatomical extension.

3 5 EP 0 337 221 A1 vlany swim fin manufacturers, particularly diving fin edge of the blade will exhibit two rounded edges of manufacturers, have attempted to compensate for unequal radial sweep which fair into the side rails :his by turning the blade of the fin downwardly or of the blade, the lateral or outward side radius •otating the foot pocket upwardly to help align at being the larger, and the medial or inward side east the fin blade if not the foot pocket with the 5 radius being the smaller. This radial relationship eg. This adaptation still discourages supination and can vary in ratio from 1 .5 to 1 up to 6 to 1 . eaves the anatomically extended foot in a position With regard to the offset foot pocket, and its Df poor hydrodynamic ability. axial relationship to the axis of the fin blade, this The basic problems of encouraging the foot to invention reveals the importance of an axial inter- sxtend without supination while using swim fins are ro section substantially located within the foot pocket three fold. Firstly, the foot will not extend to its full area. This position balances the blade with the foot potential (hyperextension) without a significant de- to prevent stress and twisting of the ankle and gree of supination. Despite attempts to vertically lower foot. adjust the fin blade the foot and foot pocket still increase drag by not fully aligning with the leg. f5 Secondly, it is uncomfortable for the foot to sus- SUMMARY OF THE INVENTION pend a large swim blade directly off the end of the foot. This more often than not results in fatigue and cramping of the muscles in the mid-foot or arch In summation, this invention comprises a sym- area. Thirdly, because of isolated pressure and 20 metrical swim fin which can be used on either foot rubbing on the tops of the second and third toes and has an offset foot pocket in order to provide during the downward stroke, chafing and blistering optimization of the supination of the foot during occur. swimming movements. This invention solves the problems of the prior The swim fin has a blade portion that extends art by the fin blade having a medial-lateral sym- 25 from a foot pocket. The foot pocket is offset as to metry in its top view which runs parallel to the base the relative midline direction of the swim fin blade. reference line or direction of travel. In this respect, The axis of the swim fin blade intersects the axis of the outermost position of the fin is typical in gen- the foot pocket within the foot pocket area. eral design. However, the innermost portion of the In particular, the swim fin blade extends from blade is more asymmetrical because of its adapta- 30 the foot pocket at an angle away from the normal tion to the offset rotated foot pocket. This foot direction of the foot pocket. The blade can termi- pocket can be offset from a range varying from nate in a relatively squared or angularly normal end 15* to 35* in reference to the base line for proper portion or terminate in an asymmetrically rounded accommodation of the natural and varying degrees end, whereby the radial relationship of these round- of supination of the foot. 35 ed edges can vary from a ratio of 1.5 to 1 up to 6 The fundamental concept hereof provides for to 1. an angular offset of the foot pocket in relationship The foot pocket is provided with an ankle strap to the reference line or drive line of the fin to molded therewith. The ankle strap is offset from the compensate for the average supinated position. general line of the foot pocket area in a manner to This average supinated position is approximately 40 provide a comfortable movement of the foot within 25* from the reference or base line or direction in the foot pocket during the supination driving effect which the fin is to be driven to provide the power. of the blade. The fin can effectively function substantially within The entire foot fin can be molded from the ranges of 15* to 35* from the offset as far as elastomeric or plastic material in a number of dif- the offset pocket is concerned, as will be seen in 45 ferent types of molding processes to provide for a the following specification. completed swim fin that has a foot pocket, foot The foot pockets of the prior art were all sym- strap, and support rails along the edges thereof. metrically rounded at the toe end or squared off. The support rails help to provide resiliency to the The foot pocket of this invention is angled from the entire fin as well as enhancing the overall flow of big toe area to the smaller toes to provide for so water from the foot fin as it is being moved through increased comfort. Unlike the prior art, this foot the water. pocket also exhibits a cavity area that tapers or The foot pocket of this invention narrows or narrows from the inward side of the pocket toward tapers outwardly so as to conform to the thinning of the outward or lateral side of the pocket. the foot in this same lateral direction. Due to the To improve performance, the blade edge of 55 angle of the end of the foot pocket following the this invention can be asymmetrically curved in a contour of the toes, the fin has substantially im- similar direction and pattern to the asymmetrically proved comfort, fit and functional features. Accord- angled foot pocket end. Therefore, the outermost ingly, forces applied to the foot by the said fin

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blade are absorbed by the more lateral side of the Figure 16 shows a pair of fins of this inven- side foot due to allowed supination, thereby substan- . tion showing the symmetry thereof on either tially distributing pressure over all five toes evenly, whereby the left and right fins are interchangeable and substantially dismissing stress to the instep with each other, and showing the fin on one side area. s that can be worn on the right foot and the fin on the other side that can be worn on the left foot. Figure 17 shows a fin similar to Figure 1 but 3RIEF DESCRIPTION OF THE DRAWINGS turned 180 degrees and incorporates an elongated blade beyond that of the fin shown in Figure 1 . 10 Figure 18 shows a fin similar to Figure 17 The invention will be more clearly understood with an asymmetrically rounded blade end dotted by reference to the description below taken in thereover. conjunction with the accompanying drawings Figure 19 is a sectional view of the foot fin in wherein: the direction of lines 19-19 of Figure 18 showing Figure 1 is a plan view looking downwardly 75 the narrowing of the foot pocket toward the outer on the foot fin when it is to be used with the left side of the foot. foot. Figure 20 shows a plan view of this invention Figure 2 is a sectional view of the foot fin with a modified asymmetrical blade end with the generally in the direction of lines 2-2 of Figure 1. blade having a relatively long dimension. Figure 3 is a sectional view through the outer 20 Figure 21 shows a plan view of this invention portion of the fin showing the enlarged rail portion with a relatively average blade length as shown in thereof in the direction of lines 3-3 of Figure 1 . Figure 16 but including the modified blade end Figure 4 is a side elevation view of the fin portion. with a foot therein. Figure 22 shows a plan view of a shortened Figure 5 shows a user with the foot fin in 25 and modified blade end of this invention. operation emphasizing the direction of propulsion Figure 23 shows a swimmer's left leg looking provided by the fin and the general direction of downwardly with the use of this invention in a drive. supinated manner, in the ventral kick position. Figure 6 shows a swimmer's foot looking Figure 24 shows a swimmer's left leg looking downwardly at the foot when it is being moved in a 30 downwardly while using this invention in an ana- » supinated manner during a natural swimming tomically aligned position during the dorsal kick. movement. Figure 25 shows a right foot fin of this inven- Figure 7 shows a fin of this invention being tion in a top and bottom plan view, the top view driven through the water when the foot is in the being on the left and the bottom view being on the supinated position generally shown in Figure 6. 35 right, and wherein the invention as shown herein is Figure 8 shows a prior art foot fin that is not interchangeable between the feet inasmuch as shown in the offset position due to the supination of there is a separate left and right fin. the foot during the kicking movement as is seen in Figure 26 shows a sectional view in the Figure 6. direction of lines 26-26 of Figure 25,indicating a Figure 9 shows a substantially elongated foot 40 narrowing or tapering of the foot cavity with a fin of the prior art without supination of the foot. radiused top portion and a relatively fiat bottom Figure 10 shows a foot fin of the prior art portion. when the foot is in the supinated position. Figure 1 1 shows a swimmer naturally kicking in the side view showing supination of the foot in 45 the same manner as is seen in Figure 6. DESCRIPTION OF THE PREFERRED EMBODI- Figure 12 shows a side view of this invention MENTS and generally corresponds to the showing as seen in Figure 7. Figure 13 shows a side view of the enlarged 50 Looking particularly at Figure 1 , it can be seen fin shown in Figure 9. that a foot fin 10 of this invention is shown having a Figure 14 is a mid line sectional view as bulbous and symmetrical top and bottom foot shown in the direction of lines 15-15 of Figure 4. pocket area 12. An ankle strap 14 is shown with a Figure 15 shows the view of the fin as seen space 16 therein for receipt of the ankle of the in Figure 14 as to the sectional view therein with a 55 user. A blade portion 18 is shown with a rail on foot in place detailing the offset supination of the either side. In particular, rails 20 and 22 are shown. foot. Rail 20 extends backwardly toward the foot pocket area 12, while rail 22 extends almost to the point of

5 3 =P 0 337 221 A1 10 tie ankle opening 16. as a whole, the foot fin can be seen as being A pair of oppositely opposed drainage ports 24 completely symmetrical on each side and extend- are provided on either side of the fin. ing toward the end in a rather squared off or The fin is symmetrical on either side. This can angularly normal configuration as to the axis of the be seen in Figures 14 and 17 wherein the same fin 5 fin. is turned over so that it can be used on the left and The details of the fin shown in Figures 1 and right foot respectively. The showing of Figure 17 14 are exemplified also by the opposite view or has been turned in such a manner such that the fin 180° rotated view in Figure 17. The blade 18 is is rotated 180° around its axis to show the op- shown with the foot pocket area 12, opening 24 or posite side of the showing of Figure 1. Thus, the io port as well as the ankle strap 14. Additionally, the symmetry of the fin on either side is symmetrical rail 20 is shown in its rotated position as well as the and provides for usage on either foot. This allows rail 22. the stocking of identical fins for both the left and In order to more fully exemplify the character- the right foot. istics of the foot fin of this invention, a center line Looking more particularly at Figure 2, it can be 75 of the main blade or propulsion area of the foot fin seen wherein the cross sectional view exemplifies is shown as line 52. Line 50 is in parallel relation- the characteristics of the interior of the foot pocket ship to line 52 which also extends in a direction area 12. This showing in the direction of lines 2-2 parallel to the axis of the blade or fin in general. indicates a foot pocket 30 having a relatively nar- The axial lines 50 and 52 are in alignment with row end 32. This allows a stretching of the narrow 20 an axial line of the fin and extend in a manner so end 32 of the V-shaped configuration of the foot that they can be defined as being generally an- pocket to receive the toes of the user in a com- gularly normal to the end of the blade 18. In fortable manner so that they do not chafe and particular, the end of the blade 18, namely end 54 move backwardly and forwardly. shown being in a substantially perpendicular or The ankle strap 14 is shown in its sectioned 25 squared off relationship in its angular normality to configuration necked down at the end thereof. In lines 50 and 52. The foot pocket is shown having a particular, the ankle strap of this invention is line 56 which is the general axial orientation of the necked down from approximately 1-5/8 inches to foot. pocket. It is this axial orientation of the foot 3/4 of an inch in thickness. However, these mea- pocket as defined by line 56 which can be seen in surements can vary. Although the foregoing dimen- 30 its offset relationship to the axial lines 50 and 52 of sions-can vary, it exemplifies the fact that the ankle the swim fin. strap 1 4 does neck down to the narrower portion at The offset relationship of the foot pocket area the end of the strap, detailed as strap portion 14a. 12 from the direction or axis of the entire fin is The blade portion 18 can be seen with the rail exemplified by lines 52 and 54, wherein the foot * 20. The rail 20 has been faired upwardly over the 35 pocket is offset by 25 . Thus, line 56 which is the foot pocket so as to allow for movement of water general axis of the foot pocket 12 is offset by 25° over the foot pocket. In particular, the rail 20 is from the axis of the fin. This offset has been found faired in the area 21 to accommodate a smoothly to be of favorable orientation but is not absolute. It " appearing foot fin rail portion 20 fairing into the foot has been found that the fin can be effective when pocket area 12. The rail 20 extends downwardly 40 the offset ranges from 12° to 40°. This of course and upwardly on either side so that the symmetry is dependent upon the user and the characteristics thereof as seen on the bottom side underlying the of the user's supination. In effect, if the user blade 18 is exemplified as a continuous rail portion supinates more or less the offset would be atten- symmetrical on either side of the blade 18. dantly more or less to accommodate for the The rail portion 22 continues backwardly to- 45 supination of a user's foot. However, from a prac- ward the foot pocket area and the ankle strap as tical point of view, unless the fin is to be custom can be exemplified in Figure 3. This shows the designed as to each user's degree of supination, blade 18 in its molded configuration fairing sym- the fin should have approximately a 25° offset to metrically into the rail portion 22 on the other side accommodate the average supination. of the foot. 50 In order to provide for a comfortable foot pock- As can be seen from the showing of Figure 14, et area of foot pocket 12, the axis of the ankle the fin is symmetrical on each side, or what would opening 16 and of course the defining characteris- be the top and bottom, so that it can be used on tics of the strap 14 therearound is shown with a the left and right foot interchangeably. In particular, midline axial orientation line 60. This midline axial the foot pockets 12 shown from trie left and right 55 orientation line 60 is offset from the axial lines of fin that are to be used on the left and right foot the foot fin by 12°. In effect, line 60 which is the respectively are symmetrical. Furthermore, the midline of the ankle opening, is offset 12° from the blade portion is symmetrical on each side. Taken axial orientation of the fin, namely, that axial ori-

6 1 EP 0 337 221 A1 12 sntation which can be defined by lines 50 and 52. If the fin of this invention is not used, a numoer Here again, it has been found that the axially of circumstances happen within the usage of the jriented and offset ankle strap defining the pocket prior art fins. 1 6 can be offset to a greater or lesser degree, To exemplify this, Figure 8 shows a prior art fin rhus, it can be offset instead of the 12° by a 5 which is offset in the same direction as the foot at ange of 5* to 20°. The foregoing offset accom- its angle of supination. In this particular case, the nodates for the supination of the foot and the drive axial line of the prior art fin shown in Figure 8 Df the fin when it is in use so that the foot is which can be seen as axial line 94 is in the same comfortably held within the space 16 as secured direction as the foot shown in Figure 6. Thus, a 3y the ankle strap 1 4. '0 loss of power is encountered due to the fact that In order to exemplify the action of a user's foot, vectorial forces are not in the same direction as the -igure 16 shows the fin orientation shown in Figure direction of the movement of the user or swimmer. 1 5 with a user's foot 70 offset to a degree of Figure 9 shows an extremely elongated fin supination with the user's leg 72. This toeing in or wherein an axial line 96 is shown. This extremely supination of the user's foot 70 is exemplified in is elongated fin is such that it does not allow for tie other showings of the various movements of supination, inhibits full extension and therefore tie swimmer as seen in Figures 5, 6, 7, 8, 10, 11 causes the foot to drag in a downward manner. and 12. This creates an inefficient stroke and a degree of The axial line 52 is the same general direction fatigue upon the part of the user. as the forward movement of the body and of io Looking at Figure 10, a prior art fin can be :ourse axial direction of the leg. The attendant shown wherein the blade has been angled. Here power stroke when kicking can be seen in its offset again, there is not a degree of sufficient output of relationship of the foot 70 or toed-in relationship the power stroke of the fin to allow for proper and is accommodated so that the same axially forward movement. The fin has an advantage by direct drive in the direction of line 52 is provided. It 25 virtue of having a larger amount of material on one is this axially directed drive which allows for im- side than the other. Nevertheless, this larger proved performance so that a greater degree of amount of material is not sufficient to provide any power can be applied to- the foot fin although the degree of advantage to a user due to the fact that foot is in a position of supination. the main thrust of the fin is in an angular offset Looking more particularly at Figure 5, a like 30 manner to the desired direction of travel. showing of the orientation of the fins as to that Figure 13 exemplifies a side elevation view of shown in Figure 1 6 with the inventor's fin hereof is the showing of Figure 9, while Figure 12 shows the exemplified. Figure 5 shows the fin 10 moving side elevation of the view of the fin of this invention upwardly in the direction of line 76 as to specific operating in the manner shown in Figures 5 and 7. fin 78. The fin is moving downwardly in the direc- 35 Notice the increased extension of the supinated tion of line 80 with respect to specific fin 82. Both foot in Figure 12 as compared to Figure 13. This is specific fins 78 and 82 are fins 10 which are seen by angular reference lines respectively num- symmetrical and worn on the left and right foot bered 83 and 85. respectively. Thus, fin 82 is on the user's right foot As can be seen from the foregoing showings, and fin 78 is on the user's left foot and comprise 40 the drive forces in the direction of the axial lines 50 the same symmetrical fin 10 in its 180° rotated and 52 are generally maintained even though the position. foot 70 as shown in Figure 15 actually supinates. From the showing of Figure 5 it can be seen This thereby enhances the overall blade exposure wherein the lines 76 and 80 are directed in the to the direction of movement. Furthermore, with the same axial direction as the user's leg in that show- 45 squared-off blade 54 which is angularly normal to ing. These lines 76 and 80 are generally the lines the axial direction of lines 50 and 52 the blade which are aligned with the axial lines 50 and 52 of optimizes its overall drive as exemplified by the Figure 15 and power the swimmer in the direction drive showings of Figures 5, 7 and 12. With this in in which the fin can be optimally used rather than mind, it can be seen that the blade, although the in the direction of supination. so end 54 can be offset, is enhanced by having gen- Looking more particularly at Figure 6, it can be erally a squared-off end. The blade can be convex- seen wherein the foot is in the position of supina- edly or interiorly curved as in prior art blades so tion. This supination of the foot would normally not that it is not substantially squared across the end provide as much power with the prior art fin inas- 54. However, substantial deviations from the direc- much as it does not come into as great a degree of 55 tion of lines 50 and 52 as to the normality of the contact vectorially with the water. The side view of end of blade 18 or the perpendicularity thereof, the foot in its supinated position can be seen in reduce the overall effectiveness of the lower drive, blade 18 is Figure 1 1 . inasmuch as less surface of the ex-

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Dosed to the driving function. The overall blade line 31 to the top of the foot pocket 12 when nay be extended in length for added thrust poten- measured equally from either end of line 31. This tial and stiil remain true to the characteistics herein ratio conforms to the average foot contour. To the described. This is shown in Figure 17 where the extent of any significant narrowing, ratios from 1.5 Dlade 18 has been extended by length L. 5 to 1 up to 4 to 1 are effective to provide an The end of the foot pocket as seen in Figure 1 appropriate foot pocket contour. is shown by outline 32a. This outline follows from This same tapered feature is viewed in an the big toe area at 33a to the little toe area at 35a. asymmetrical manner in Figure 26. Here, area 124 Accordingly, the end of the foot pocket 12 follows is considerably larger than area 125. The asym- the contour of the ends of the toes. This is pro- w metrical aspects overly the flattened surface area vided regardless of whether the symmetrical foot 126 at the bottom of the foot pocket to accom- pocket is on the left or right foot. Thus, forces modate the contour of the foot. applied to the foot by the said fin blade are ab- An asymmetrically rounded blade end de- sorbed by the more lateral side of the foot due to scribed in and dotted in Figure 18 is effective in allowed supination, thereby substantially distribut- 75 encouraging the natural KIK Cycle in several dif- ing pressure over all five toes evenly, and substan- ferent blade lengths as seen in Figures 20, 21 and tially diminishing stress to the instep area. 22. As the blade length changes, the position be- The blade end 54 can be modified to improve tween curved edges 102 and 104 and the cor- hydrodynamic flow and increase the moveability of responding rails 20 and 22 is altered. Figure 20 the foot throughout the KIK Cycle by a particular 20 shows an adaptive curve 101 between rail portion radial ratio at the end of the blade. As shown in 22 and curve 102. An adaptive curve 103 joins Figure 18, the blade end 54 can be modified to curve 102 with curve 104. An adaptive curve 105 exhibit as asymmetrically rounded end, with two joins curve 104 with rail 20. The length of these unequal radial sweeps, 102 and 104. The radial adaptive curves can be substantially altered by distance 112, from axis 116 to circumference line 25 changing the blade length, as noticed in Figures 102, is significantly greater than the distance 114, 20, 21 and 22. from axis 118 to circumference 104. The difference Notice in Figures 20 through 22, the axis of the between the greater distance 112 and the lesser fin blade intersects the axis of the foot pocket distance 114, causes a difference between the within the foot pocket area. Contrary to the prior art length of curve 102 and 104. The ratio is about 3.4 30 which shows an insignificant offset with an axial to 1 as to the larger radius compared to the smaller intersection substantially outside or beyond the foot radius, respectively 112 and 114. This ratio can be area, this invention is intended to balance the blade as high as 6 to 1 with respect to the ratio between with the drive force of the foot in a manner which radius 112 and 114. The significance of this ratio is promotes superior comfort, power and aligned le- exemplified in Figures 23 and 24 where the left leg 35 verage. of a fin swimmer is shown in the two opposing Blade length, in relation to this invention has a positions of the KIK cycle. direct effect on the performance features of the fin In Figure 23 a ventral kick is shown as blade with regard to the KIK Cycle. As the blade is edge 104 serves to stabilize the fin movement into lengthened, the degree of offset is reduced, due to supination and reduce surface drag on the inward 40 its inhibiting affect on the foot's ability to supinate. side of the blade. In Figure 24, a dorsal kick is Also, because of the adpative design of the blade shown as blade edge 102 serves to lead the blade to the foot pocket, the axial intersection point 55 laterally as the foot returns to an anatomically will rise significantly up the axial line of the foot aligned position. A longer radial sweep 102 is pocket 56, as shown in Figure 20. As the blade is needed on this lateral side to enhance the 45 shortened, the degree of offset can increase up to hydrodynamics of the blade, which has much more the functional average offset of the uninhibited KIK exposure to water resistance in this outward posi- Cycle. tion. Also, since the origin of rail 22 is located Keeping in mind the significant and workable ° higher on foot pocket 12, radial curve 102 meets range of offset, that being 12° to 40 , the axial rail 22 at a higher point on the blade without 50 intersection 55 will be higher on the foot pocket disrupting the dynamic functions of said rail. axis 56 with an offset of 12° and lower on the foot , ° The foot pocket 12 although angularly asym- pocket axis 56 with an offset of 40 . The exact metrical in the view of Figure 18, is quite symmetri- location of the axial intersection 55 at any given cal in a sectional view as seen in Figure 19. The offset within the foot pocket, will depend on the foot pocket cavity 30 narrows in a lateral manner to 55 overall contour of the fin as a whole. the outward portion 32. The distance 34 from cen- The symmetrical nature of this invention, as ter line 31 to the top of the foot pocket 12, is three shown in Figure 16, has manufacturing, distribution, times greater than the distance 36 from the center retail and consumer advantages. However, the ba-

8 5 :P 0 337 221 A1 sic principles of this design can be incorporated 4. The swim fin as claimed in oiaim i wnerein: nto a nonsymmetrical fin, whereby a separate left said swim fin is symmetrical on the top and bottom md right fin are provided and cannot be interchan- thereof so as to allow the swim fin to be interchanged. Figure 25 exemplifies this by showing several ged between the left and right foot. isymmetical properties. In this showing, the foot 5 ' 5. A swim fin formed with a foot pocket and a Docket 121 is raised above the blade substantially blade comprising: o hold the foot in a manner as sectionally shown in an ankle strap for securing said swim fin to a user's -igure 26. ankle having an axis which is offset from the axis of The outline 129 of the foot pocket, as shown in said foot pocket within the range of 5° to 20° . =igure 25, is seen only on the top side of the fin, to 6. The swim fin as claimed in Claim 5 wherein: ivhereas the underside would remain relatively flat said swim fin is symmetrical as to form on either as viewed by fin side 122. side thereof so as to allow the swim fin to be The underside foot opening 128 recesses be- interchanged between the left and the right foot. yond the top side opening, and a vent port 123 can 7. A swim fin adapted for interchangeable utili- De present on one side only. Rail portion 127 can rs zation between the left and the right foot compris- :air higher on this modification, and be raised sub- ing: stantially into the foot pocket as shown in Figure a foot pocket section formed from an elastomeric 26. material and having an ankle strap connected The ankle strap 14 can be formed as an adjust- thereto that is formed in a manner so that the top able strap with or without a buckle or bale and 20 and bottom thereof are interchangeable respectiv- adjustable for length in any suitable manner. Also, ley between the left and right foot and wherein the the blade can be seated or formed for flow through top and bottom is substantially symmetrical to ef- the vent as in prior fins referred to as a Rocket or fectuate the interchange between the left and right Jet Fin as patented by Beauchat. foot; As can be seen from the foregoing, this inven- 35 a blade extending from said foot pocket formed as tion is a substantial step over the prior art in an elongated blade therefrom which is substantially reorienting the foot pocket and blade portions of a symmetrical on the top and bottom thereof so that swim fin as well as the strap portion to- provide when said respective foot pocket and said blade optimum driving by one's legs in a symmetrical fin are turned in either direction on the major surfaces that can be interchanged between the left and right 30 thereof, the fin can be used respectively on the left foot. As a consequence, it should be read broadly or the right foot; and wherein, the when the follow- a foot pocket is angularly offset from the axis of in light of prior art considering * ° ing claims. said blade portion within the range of 1 2 to 40 . 8. The fin as claimed in Claim 7 further com- 35 prising: Claims rails on the edge regions of said fin which are substantially symmetrical on either side of said foot 1 . A swim fin formed with a foot^pocket and a blade and which extend from said pocket blade wherein the improvement comprises: toward the end of said blade in a diminishing an offset within the range of 12° to 40° of said 40 manner. foot pocket angularly from the axis of said blade in 9. The fin as claimed in Claim 7 further com- a direction to cause the offset to compensate for prising: the supination of the foot during a swimmer's flutter at least one port within said foot pocket. kick and place the axis of the blade in the general 10. The fin as claimed in Claim 7 further com- direction of a swimmer's leg during a flutter kick 45 prising: motion. an ankle strap connected to said foot pocket which ° 2. The swim fin as claimed in claim 1 further is offset as to its axis within the range of 5 to 20 comprising: from the axis of said foot pocket. rail portions of a greater cross sectional thickness 1 1 . A swim fin wherein the improvement corn- at the edge regions of said blade for providing so prises: resiliency and strength to said blade. a fin formed with a foot pocket which receives a 3. The swim fin as claimed in 1 further com- foot therein; and, prising: a blade extending from said foot pocket that is at an ankle strap for securing said swim fin to a user's an offset angle of 12° to 40° in the direction to ankle having an axis which is offset from the axis of 55 compensate for a swimmer's supinated movement said foot pocket within the range of 5° to 20° . so that the supinated angular position of the swim-

9 17 EP 0 337 221 A1 18 mer's foot when toed in allows for the blade portion 22. A swim fin formed with a foot pocket and a to be directed in its axial direction in substantially blade wherein the improvement comprises: the same direction as a user's leg and body. an offset of said foot pocket angularly from the axis 12. The swim fin as claimed in Claim 11 of said blade in a direction to cause the offset to wherein: 5 compensate for the supination of the foot during a said fin has a symmetrical foot pocket on its top swimmer's flutter kick and place the axis of the and bottom so that it can be interchanged with the blade in the general direction of a swimmer's leg left or right foot. during a flutter kick motion wherein the intersection 13. The swim fin as claimed in Claim 11 further of the axis of the foot pocket and the axis of the comprising: 70 blade is within the foot pocket. rail portions extending from said foot pocket in the 23. The swim fin as claimed in Claim 22 direction of the end of said blade to reinforce and wherein: provide resiliency to said fin. the offset is within the range of 12° to 40° . 14. The swim fin as claimed in Claim 11 further 24. The swim fin as claimed in Claim 22 comprising: 75 wherein: an ankle strap connected to said foot pocket which said swim fin is symmetrical on the top and bottom is angularly offset form the axis of said foot pocket thereof so as to allow the fin to be interchanged * ° within the range of 5 to 20 . between the left and right foot. 15. The swim fin as claimed in Claim 11 25. The swim fin as claimed in Claim 22 further wherein: 20 comprising: said blade portion end is substantially at a right a curved end of said blade wherein the curve on angle to the axis of said blade portion. the inside of the user's foot has a radius smaller 16. The swim fin as claimed in Claim 11 than the curve on the outside of the user's foot wherein: wherein this ratio of the inside curve to the ratio of said blade portion end is assymetrically curved so 25 the curve on the outside is within the range of 1 to that one side has a greater radius than the other 1 .5 to 1 to 6. side. 26. A swim fin formed with a foot pocket and a 17. The swim fin as claimed in Claim 16 blade wherein the improvement comprises: wherein: a blade having curved ends on the inside and said blade portion end radii are in a ratio range of 30 outside portions with a respective radius of the 1.5 to 1, to 6 to 1. inside portion within the range of a ratio to the 1 8. A swim fin formed with a foot pocket and a outside portion of 1 .0 to 1 .5 to 1 .0 to 6. blade wherein the improvement comprises': 27. The swim fin as claimed in Claim 26 further a foot pocket having a tapered portion extending comprising: from the inner portion of a user's foot to the outer 35 an offset of said foot pocket angularly from the axis portion in order to accomodate for the size of the of said blade in a direction to cause the offset to foot narrowing from the inside to the outside. compensate for the supination of a foot during a 19. The swim fin as claimed in Claim 18 further swimmer's flutter kick to place the axis of the blade comprising: in the general direction of a swimmer's leg during a an offset of said foot pocket angularly from the axis 40 flutter kick motion. of said blade in a direction to cause the offset to 28. The swim fin as claimed in Claim 25 further compensate for the supination of the foot during a comprising: swimmer's flutter kick to place the axis of the blade an ankle strap for securing said swim fin to a user's in a general direction of a swimmer's leg during a ankle having an axis which is offset from the axis of flutter kick motion, wherein the offset is within the 45 said foot pocket within the range of 5° to 20° . * * range of 1 2 to 40 . 29. The swim fin as claimed in Claim 26 further 20. The swim fin as claimed in Claim 18 further comprising: comprising: said swim fin being formed symmetrically on the an ankle strap for securing said swim fin to a user's top and bottom thereof so as to allow the swim fin ankle having an axis which is offset from the axis of 50 to be interchanged between the left and the right ° ' said foot pocket within the range of 5 to 20 . foot. 21. The swim fin as claimed in claim 18 wherein: said swim fin is symmetrical on the top and bottom thereof so as to allow the swim fin to be interchan- 55 ged between the left and the right foot.

10 EP 0 337 221 A1

17.03.89. 18:41 EP 0 337 221 A1

17.03.89. 18:41 EP 0 337 221 A1 33. B9. 13:42 EP 0 337 221 A1

17.03.89. 18:43 EP 0 337 221 A1 European Patent Application numoer EUROPEAN SEARCH REPORT Dffice

EP 89105765.5 DOCUMENTS CONSIDERED TO BE RELEVANT Citation of document with indication, where appropriate, Relevant CLASSIFICATION Ur IHfc Category of relevant passages to claim APPLICATION (Int. CI* ) DE - B - 1 075 997 I, 2,3, A 63 B 31/11 (LANGHANS) 5,10, * Fig . 1,2,4; page 1 , column II, 13, 3, lines 1-4 * 19,22, 27

CH - A - 351 204 I, 2,5, (ALPHA) 7,10, * Fig. 1,2, belonging text * II, 22, 27

GB - A - 613 609 1,5,7, (CORLIEU) 10,11, * Totality * 22,27

US - A - 2 423 571 1,5,7, (WILEN) 10,11, * Fig. 9,12; claims 1,10,16 * 22,27

P,A US - A - 2 588 363 1,5,7, (CORLIEU) 10, 11, TECHNICAL FIELDS * Fig. ; claim 1 * 22,27 SEARCHED |lnt. Cl.-i

P,A DP - Al - 259 353 1,5,7, A 63 B 31/00 ( BRAUNKOHLENKOMB INAT ) 10, 11, * Fig. 1; abstract *. 22, 27

P,A US - A - 2 865 033 4,6,7, (JAYET) 12,21, * Fig. 1,2; claims * 24,29

FR - A - 1 351 417 16,25, (LLOPIS) 26 * Fig. 1, belonging text *

The cresent search report has been drawn up for all claims Place of search Oate of completion of me search Examiner VIENNA 14-07-1989 SCHONWALDER

CATEGORY OF CITED DOCUMENTS T : theory or principle underlying the invention E : earlier patent document, but published on. or X : particularly relevant if taken alone after the filing date a Y : particularly relevant if combined with another D : document cited in the application document of the same category L : document cited for other reasons E A : technological background O : non-written disclosure & : member of the same patent family, corresponding P : intermediate document document