Patent ID: 11944873
Assignee: NATURE'S WING FIN DESIGN, LLC
Field: Furniture, games (Other fields)
Classification: CPC A | IPC A

Claim 14:
15. A method for providing a swim fin, said method comprising:
(a) providing a foot attachment member and a blade member in front of said foot attachment member, said blade member having a longitudinal alignment relative to said foot attachment member, said blade member having opposing surfaces, blade member outer side edges and a blade member transverse dimension between said blade member outer side edges, two sideways spaced apart elongated rib members that are connected to said blade member adjacent to said blade member outer side edges, said elongated rib members each having a rib upper edge portion and a rib lower edge portion with a vertical rib dimension between said rib upper edge portion and said rib lower edge portion and a rib vertical midpoint that is midway between said rib upper edge portion and said rib lower edge portion, a rib member midpoint transverse plane of reference that extends in a transverse direction between said rib vertical midpoints of said two sideways spaced apart elongated rib members, a root portion adjacent to said foot attachment member and a free end portion spaced from said root portion and said foot attachment member, a blade member length between said root portion and said free end portion, a longitudinal midpoint between said root portion and said free end portion, a three quarter position between said root portion and said midpoint, a one quarter position between said longitudinal midpoint and said free end portion, a first half portion between said root portion and said longitudinal midpoint, a second half portion between said longitudinal midpoint and said free end portion, a three quarter portion between said three quarter position and said free end portion, and a one quarter portion that is between said one quarter position and said free end portion, said blade member having a blade member longitudinal center axis midway between said outer side edges;
(b) providing said blade member with a flexible membrane region made with a significantly flexible thermoplastic material;
(c) providing said flexible membrane region with at least one expandable folded membrane member having at least one vertically oriented fold formed around a substantially lengthwise axis and having a predetermined amount of looseness when said swim fin is in said motionless state of rest, said vertically oriented fold having a vertically oriented fold transverse cross sectional shape that has two transversely spaced apart substantially vertical wall portions and a fold apex region of said vertically oriented fold where said two transversely spaced apart substantially vertical wall portions converge, said expandable folded membrane having two membrane outer side edge portions and a membrane outer side edge transverse plane of reference extending between said membrane outer side edge portions, said vertically oriented fold transverse cross sectional shape having a resting state fold transverse dimension between said membrane outer side edge portions adjacent said two transversely spaced apart substantially vertical wall portions when said swim fin is in said motionless state of rest;
(d) providing a biasing force that is arranged to cause said vertically oriented fold transverse cross sectional shape to have a fold vertical dimension between the concave surface of said fold apex region that is at least 125% of said fold transverse dimension along at least 25% of the length of said blade member when said swim fin is at said motionless state of rest; and
(e) arranging said at least one vertically oriented fold to experience expansion from a substantially folded condition existing when said swim fin is in said motionless state of rest to a significantly expanded condition under said exertion of water pressure created during at least one phase of said reciprocating kicking stroke cycle while using said cruising speed kicking stroke force.