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  Methods for creating large scale focused blade deflectionsUSPTO Application #: 20080108258Title: Methods for creating large scale focused blade deflections Abstract: Methods are disclosed to design resilient hydrofoils (164) which are capable of having substantially similar large scale blade deflections under significantly varying loads. The methods permit the hydrofoil (164) to experience significantly large-scale deflections to a significantly reduced angle of attack under a relatively light load while avoiding excessive degrees of deflection under increased loading conditions. A predetermined compression range on the lee portion of said hydrofoil (164) permits the hydrofoil (164) to deflect to a predetermined reduced angle of attack with significantly low bending resistance. This predetermined compression range is significantly used up during the deflection to the predetermined angle of attack in an amount effective to create a sufficiently large leeward shift in the neutral bending surface with the load bearing portions of the hydrofoil (164) to permit the hydrofoil (164) to experience a significantly large increase in bending resistance as increased loads deflect the hydrofoil (164) beyond the predetermined reduced angle of attack. The shift in the neutral bending surface causes a significant increase in the elongation range required along an attacking portion of the hydrofoil (164) after the predetermined angle of attack is exceed. Methods are also disclosed for designing the hydrofoil (164) so that it has a natural resonant frequency that is sufficiently close the frequency of the reciprocating strokes used to attain propulsion in an amount sufficient to create harmonic wave addition that creates an amplified oscillation in the free end of the reciprocating hydrofoil (164). Methods are also disclosed for focusing energy storage and blade deflections along focused regions of load bearing members and the hydrofoil (164). Methods are also disclosed for reducing induced drag vortex formation along the lee surface of the hydrofoil (164), reducing drag and increasing the formation of lift forces. (end of abstract) Agent: Peter T. Mccarthy - Oxnard, CA, US Inventor: Peter T. McCarthy USPTO Applicaton #: 20080108258 - Class: 441 64 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20080108258. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001]This application is a continuation of U.S. patent application Ser. No. 11/363,562, filed Feb. 27, 2007 titled METHODS FOR CREATING LARGE SCALE FOCUSED BLADE DEFLECTIONS which is a continuation of U.S. patent application Ser. No. 10/877,969, filed Jun. 25, 2004, titled METHODS FOR CREATING LARGE SCALE FOCUSED BLADE DEFLECTIONS, which is a continuation of U.S. patent application Ser. No. 09/852,155, now U.S. Pat. No. 6,843,693, filed May 9, 2001, titled METHODS FOR CREATING LARGE SCALE FOCUSED BLADE DEFLECTIONS, which claims priority to U.S. Provisional Patent Application No. 60/202,560, filed May 10, 2000, titled METHODS FOR CREATING LARGE SCALE FOCUSED BLADE DEFLECTIONS, and which is a continuation-in-part of U.S. patent application Ser. No. 09/630,374, now U.S. Pat. No. 6,413,133, filed Aug. 1, 2000, titled METHODS FOR CREATING CONSISTENT LARGE SCALE BLADE DEFLECTIONS, which is a continuation of U.S. patent application Ser. No. 09/311,505, now U.S. Pat. No. 6,095,879, filed May 13, 1999, titled METHODS FOR CREATING LARGE SCALE FOCUSED BLADE DEFLECTIONS, which claims priority to U.S. Provisional Patent Application No. 60/085,463, filed May 14, 1998, titled METHODS FOR CREATING LARGE SCALE FOCUSED BLADE DEFLECTIONS. The entirety of each of the above-mentioned prior patent applications and provisional patent applications is hereby incorporated by reference herein and made a part of this specification. BACKGROUND [0002]1. Field of Invention [0003]This invention relates to hydrofoils, specifically to such devices which are used to create directional movement relative to a fluid medium, and this invention also relates to swimming aids, specifically to such devices which attach to the feet of a swimmer and create propulsion from a kicking motion. [0004]2. Description of Prior Art [0005]None of the prior art fins provide methods for maximizing the storage of energy during use or maximizing the release of such stored energy in a manner that produces significant improvements in efficiency, speed, and performance. [0006]No prior fin designs employ adequate or effective methods for reducing the blade's angle of attack around a transverse axis sufficiently enough to reduce drag and create lift in a significantly consistent manner on both relatively light and relatively hard kicking strokes. [0007]Prior art beliefs, convictions, and design principles teach that highly flexible blades are not effective for producing high swimming speeds. Such prior principles teach that high flexibility wastes energy since it permits kicking energy to be wasted in deforming the blade rather than pushing water backward to propel the swimmer forward. A worldwide industry convention among fin designers, manufactures, retailers and end users is that the more flexible the blade, the less able it is to produce power and high speed. The industry also believes that the stiffer the blade, the less energy is wasted deforming on the blade and the more effective the fin is at producing high speeds. The reason the entire industry believes this to be true is that no effective methods have existed for designing blades and load bearing ribs that exhibit large levels of blade deflection around a transverse axis in a manner that is capable of producing ultra-high swimming speeds. Prior fin design principles also teach that the greater the degree of blade deflection around a transverse axis on each opposing kicking stroke, the greater the degree of lost motion that occurs at the inversion point of each stroke where the blade pivots loosely from the high angle of deflection on one stroke, through the blade's neutral position, and finally to the high angle of deflection on the opposite stroke. Prior principles teach that lost motion wastes kicking energy throughout a significantly wide range of each stroke because kicking energy is expended on reversing the angle of the blade rather that pushing water backward. Also, prior principles teach that the greater the degree of flexibility and range of blade deflection, the greater the degree of lost motion and the larger the portion of each kicking stroke that is wasted on deflecting the blade and the smaller the portion of the stroke that is used for creating propulsion. Furthermore, prior principles teach that such highly deflectable blades are vulnerable to over deflection during hard kicks when high swimming speeds are required. Although it is commonly known that highly deflectable blades create lower strain and are easier to use at slow speeds, such highly deflectable blades are considered to be undesirable and unmarketable since prior versions have proven to not work well when high swimming speeds are required. [0008]Because prior fins are made significantly stiff to reduce lost motion between strokes as well as to reduce excessive blade deflection during hard kicks, prior fins place the blade at excessively high angles of attack during use. This prevents water from flowing smoothly around the low-pressure surface or lee surface of the blade and creates high levels of turbulence. This turbulence creates stall conditions that prevent the blade from generating lift and also create high levels of drag. [0009]Since the blade remains at a high angle of attack that places the blade at a significantly horizontal orientation while the direction of kicking occurs in a vertical direction, most of the swimmer's kicking energy is wasted pushing water upward and downward rather that pushing water backward to create forward propulsion. When prior fins are made flexible enough to bend sufficiently around a transverse axis to reach an orientation capable of pushing water in a significantly backward direction, the lack of bending resistance that enables the blade to deflect this amount also prevents the blade from exerting a significant backward force upon the water and therefore propulsion is poor. This lack of bending resistance also subjects the blade to high levels of lost motion and enables the blade to deflect to an excessively low angle of attack during a hard kick that is incapable of producing significant lift. In addition, prior fin design methods that could permit such high deflections to occur do not permit significant energy to be stored in the fin during use and the fin does not snap back with significant energy during use. Again, a major dilemma occurs with prior fin designs: poor performance occurs when the fin is too flexible and when it is too stiff. [0010]One of the major disadvantages that plague prior fin designs is excessive drag. This causes painful muscle fatigue and cramps within the swimmer's feet, ankles, and legs. In the popular sports of snorkeling and SCUBA diving, this problem severely reduces stamina, potential swimming distances, and the ability to swim against strong currents. Leg cramps often occur suddenly and can become so painful that the swimmer is unable to kick, thereby rendering the swimmer immobile in the water. Even when leg cramps are not occurring, the energy used to combat high levels of drag accelerates air consumption and reduces overall dive time for SCUBA divers. In addition, higher levels of exertion have been shown to increase the risk of attaining decompression sickness for SCUBA divers. Excessive drag also increases the difficulty of kicking the swim fins in a fast manner to quickly accelerate away from a dangerous situation. Attempts to do so, place excessive levels of strain upon the ankles and legs, while only a small increase in speed is accomplished. This level of exertion is difficult to maintain for more than a short distance. For these reasons scuba divers use slow and long kicking stokes while using conventional scuba fins. This slow kicking motion combines with low levels of propulsion to create significantly slow forward progress. [0011]Another problem with many prior fin designs is that they exhibit severe performance problems when they are used for swimming across the surface of the water. While kicking the fins at the water's surface, they break through the surface on the up stroke, and then on the down stroke they "catch" or "slap" on the surface as they re-enter the water at a high angle of and downward movement is abruptly stopped. This instantaneous deceleration creates high levels of strain and discomfort for the user's ankles and lower leg muscles. Because downward movement ceases upon impact with the water, this energy is wasted and is not converted into forward propulsion. Over large distances, this problem can create substantial fatigue for snorkeling skin divers, body surfers, and body board surfers who spend most of their tine kicking their fins along the water's surface. It is also a problem for SCUBA divers who swim along the surface to and from a dive site in an attempt to conserve their supply of compressed air. Fatigue and muscle strain to SCUBA divers during surface swims is particularly high because prior SCUBA type fins have significantly long lengthwise dimensions and high angles of attack. This causes increased levels of torque to be applied to the diver's ankles and lower legs as the blade slaps the surface of the water. Because such longer fins create high levels of drag from a decreased aspect ratio, prior SCUBA type fins are significantly slow to re-gaining downward movement after catching on the water's surface. Even below the surface, such prior fins offer poor propulsion and high levels of drag that severely detract from overall diving pleasure. [0012]Prior art fin designs do not employ efficient and methods for enabling the blade to bend around a transverse axis to sufficiently reduced angles of attack that are capable of generating lift while also providing efficient and effective methods for enabling such reduced angles of attack to occur consistently on both light and hard kicking strokes. [0013]Prior art fins often allow the blade to flex or bend around a transverse axis so that the blade's angle of attack is reduced under the exertion of water pressure. Although prior art blades are somewhat flexible, they are usually made relatively stiff so that the blade has sufficient bending resistance to enable the swimmer to push against the water without excessively deflecting the blade. If the blade bends too far, then the kicking energy is wasted on deforming the blade since the force of water applied to the blade is not transferred efficiently back to the swimmers foot to create forward movement. This is a problem if the swimmer requires high speed to escape a dangerous situation, swim against a strong current, or to rescue another swimmer. If the blade bends too far on a hard kick, the swimmer will have difficulty achieving high speeds. For this reason, prior fins are made sufficiently stiff to not bend to an excessively low angle of attack during hard and strong kicking stokes. [0014]Because prior fin blades are made stiff enough so that they do not bend excessively under the force of water created during a hard kick, they are too stiff to bend to a sufficiently reduced angle of attack during a relatively light stroke used for relaxed cruising speeds. If a swim fin blade is made flexible enough to deflect to a sufficiently reduced angle of attack during a light kick, it will over deflect under the significantly higher force of water pressure during a hard kick. Prior fins have been plagued with this dilemma. As a result, prior fins are either too stiff during slower cruise speeds in order to permit effectiveness at higher speeds, or fins they are flexible and easy to use at slow speeds but lack the ability to hold up under the increased stress of high speeds. This is a major problem since the goal of scuba diving is mainly to swim slowly in order to relax, conserve energy, reduce exertion, and conserve air usage. Because of this, prior fins that are stiff enough to not over deflect during high speeds will create muscle strain, high exertion, discomfort, and increased air consumption during the majority of the time spent at slow speeds. [0015]Because prior art fins attempt to use significantly rigid materials within load bearing ribs and blades to prevent over deflection, the natural resonant frequency of these load bearing members is significantly too high to substantially match the kicking frequency of the swimmer. None of the prior art discloses that such a relationship is desirable, that potential benefits are known, or that a method exists for accomplishing this in an efficient manner that significantly improves performance. [0016]Some prior designs attempt to achieve consistent large scale blade deflections by connecting a transversely pivoting blade to a wire frame that extends in front of the foot pocket and using either a yieldable or non-yieldable chord that connects the leading edge of the blade to the foot pocket to limit the blade angle. This approach requires the use of many parts that increase difficulty and cost of manufacturing. The greater the number of moving parts, the greater the chance for breakage and wear. Many of these designs use metal parts that are vulnerable to corrosion and also add undesirable weight. Variations of this approach are seen in U.S. Pat. Nos. 3,665,535 (1972) and 4,934,971 (1988) to Picken, and U.S. Pat. Nos. 4,657,515 (1978), and 4,869,696 (1989) to Ciccotelli. U.S. Pat. No. 4,934,971 (1988) to Picken shows a fin which uses a blade that pivots around a transverse axis in order to achieve a decreased angle of attack on each stroke. Because the distance between the pivoting axis and the trailing edge is significantly large, the trailing edge sweeps up and down over a considerable distance between strokes until it switches over to its new position. During this movement, lost motion occurs since little of the swimmer's kicking motion is permitted to assist with propulsion. The greater the reduction in the angle of attack occurring on each stroke, the greater this problem becomes. If the blade is allowed to pivot to a low enough angle of attack to prevent the blade from stalling, high levels of lost motion render the blade highly inefficient. This design was briefly brought to market and received poor response from the market as well as ScubaLab, an independent dive equipment evaluation organization that conducts evaluations for Rodale's Scuba Diving magazine. Evaluators stated that the fin performed poorly on many kick styles and was difficult to use while swimming on the surface. The divers reported that they had to kick harder with these fins to get moving in comparison to other fin designs. The fins created high levels of leg strain and were disliked by evaluators. A major problem with this design approach is that swimmers disliked the snap or click of the blade reaching its limits at the end of each fin stroke. [0017]This design approach produces poor performance for several reasons. The large range of motion of the blade creates lost motion at the inversion point of each stroke where the fins produces little or no propulsion until it reverses its angle of attack and reaches its limit of pivotal movement. The pivotal hinge approach with abrupt limits in motion creates an unsteady and jerky movement and large gaps in the kick cycle where propulsion is missing. The sudden impact of water pressure created as the blade reaches its limits creates a shock to the user's muscles and joints that increases strain, fatigue, and tendency of cramping. [0018]Because the blade hinges near its leading edge and the restraining chord is connected to this leading edge, the moment arm is very short between the hinging axis and the connecting point of the restraining chord. The force of water exerted on the blade between the hinging axis and the trailing edge of the blade is multiplied many times as it is applied to the restraining chord due to the much shorter leading edge moment arm. A heavy kick can produce extremely high stress on the restraining chord. If the chord is elastic, such a high strain can overextend the chord beyond its yielding point so that the blade's angle of attack increases beyond the desired level. The high level of force created by the short moment arm can suddenly extend a relatively small elastic chord (as shown in many of these design approaches) to its inelastic limit to create an abrupt stop in motion that creates a shock to the user's foot and leg. The chord's vulnerability for over extending is increased because of the relatively small cross-section of the restraining chords used in these examples. Repeated use can cause the chord to stretch out over time so that the blade's range of motion further increases over time to inhibit performance. If a larger size chord is used, the blade will not rotate enough under a light kicking stroke. If the chord is small enough to enable the blade to rotate enough during a light kicking stroke, it will abruptly stop at the outer pivotal limit and transfer a sudden shock to the user's leg during a hard kick. [0019]The large distance the chord must stretch during use in order to restrain the blade further inhibits performance. Because the leading edge rotates up and down relative to the foot pocket during use, the chord must stretch vertically over large distances if the blade is to rotate to significantly reduced angles of attack. Because the chord is short at the neutral position, it must stretch and elongate by several times its original length in order to permit the blade to pivot to significantly reduced angles of attack. For this to occur under the low levels of force created during light kicking strokes, the chord must be extraordinarily elastic and have a very low modulus of elasticity (ratio of stress to strain, or load to deflection). The lower the modulus of elasticity, the weaker the material and therefore the less reliable the holding power of the material. Because stronger materials are less elastic, a stronger material capable of holding well under hard kicks will not permit sufficient deflection under light kicks. No effective methods for solving this issue are disclosed. [0020]Because the chord is significantly short at the neutral position in an effort to reduce the occurrence of slack within the chord, the total volume of the chord's material is relatively small. This causes the high stresses in the chord to be distributed over a very small volume of material. This increases vulnerability to over extension and deformation of the material. The small material volume severely limits energy storage within the material. At the inversion point of the kick cycle, the chord provides poor snap back because its energy storage is significantly low and its moment arm is small. [0021]Another problem is that significant levels of slack exist in the chord as the blade pivots close to the neutral position. As the leading edge pivots back toward the neutral position, the alignment of the restraining chord becomes more horizontal and less vertical. This substantially reduces the chord's ability to apply vertical tension to restrain the blade or control its movement. This reduces the ability for energy stored in the elastic chord to be transferred to the blade for effective propulsion. The chord becomes less able to apply propulsive force as it moves the blade from the pivotal limit back to the neutral position. This is highly undesirable and causes energy to be wasted. The lack of vertical tension near the neutral position also permits the blade to move without restraint or control. This increases the severity of the sudden click created as the tension suddenly abruptly increases at the limit of pivotal range. The lack of tension near the neutral position also prevents energy from being stored in this region and the kinetic energy of the blade is wasted. Because the chord has a significant horizontal inclination throughout the entire range of rotation, a significant portion of the tension within the chord is directed in a horizontal direction that does not assist with the vertical restraint or return movement of the blade. This wastes stored energy and destroys efficiency. [0022]If non-elastic chords are used then there is zero snap back energy at the inversion point of each kick and the blade stops with increased shock at the limits of pivoting. Lost motion is extremely high in this situation and performance is exceptionally poor. Continue reading... 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