Patent ID: 6413133
Filing Date: 2002-07-02
Classification: A63B

Abstract:
An improved swim fin, comprising:(a) a foot attachment portion; (b) a blade member secured to said foot attachment portion and forming a substantially forward extension of said foot attachment portion, said blade member having opposing surfaces, outer side edges, a blade root portion adjacent said foot attachment portion and a blade free end portion remote from said blade root portion; (c) at least one substantially flexible elongated load bearing rib member secured to said blade member, said rib member having a rib root portion adjacent said foot attachment portion and a rib free end portion remote from said rib root portion and said foot attachment portion, said rib having a predetermined length between said rib root portion and said rib free end portion, said rib having a longitudinal midpoint, said rib member having a first half portion located between said root portion and said midpoint, said rib having a second half portion located substantially between said midpoint and said rib free end, said rib being made with an extensible load bearing material, said extensible load bearing material being arranged to provide a major portion of the structural support of said blade member relative to said foot attachment portion as relatively light load conditions are exerted on said blade member during an initial light kicking stroke such as used by a swimmer to achieve a relatively slow to moderate swimming speed; (d) said rib having a predetermined degree of flexibility, said predetermined flexibility is arranged to permit a predetermined initial light kick deflection angle of at least 10 degrees under said light load conditions, said rib taking on a corresponding light kick bend around a light kick bending radius; and (e) said rib having a sufficiently tall vertical rib dimension relative to said light kick bending radius to permit a tension surface portion of said extensible load bearing material to experience a predetermined initial light kick elongation of at least 5 percent during said light kick deflection, said rib having a predetermined cross sectional shape along said length of said rib that is arranged to substantially prevent said rib from buckling excessively during said initial light kick deflection, said cross sectional shape of said rib is arranged to permit a significant amount of said light kick bend to occur within said first half portion of said rib, said extensible material is sufficiently extensible to permit said tension surface portion to experience said light kick elongation range during said light kick deflection, said extensible material having sufficient elastic memory to permit the energy stored within said initial light kick elongation range to be released in the form of a substantially strong snapping motion at the end of said stroke.