GB2472981A

GB2472981A - Pair of fins for swimming

Info

Publication number: GB2472981A
Application number: GB0914722A
Authority: GB
Inventors: Ian Thwaites
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-08-24
Filing date: 2009-08-24
Publication date: 2011-03-02
Also published as: GB0914722D0

Abstract

A pair of fins comprises a left fin (12, figure 1) and a right fin 14. Each fin includes foot pocket 16 and a blade 18. The foot pocket 16 has a sole portion (20, Figure 3) with a first central axis 34 substantially in a first plane, and the blade 18 has a second central axis 36 substantially in a second plane, the first axis 34 being angularly offset from the second axis 36 in the plane of the first plane (angle α in figure 4), and the second plane being disposed at an angle of between 20° and 45° relative to the first plane (angle β in figure 4). The offset may be between 20° and 45°. The fins may be manufactured as an integral moulding from an elastomeric material.

Description

Title: Pair of Fins for Swimming The present invention relates to a pair of fins for swimming and particularly but not exclusively to a pair of fins for use as a swimming training aid in flutter and dolphin kicking, during swimming and kicking training.

Background to the Invention

tt is understood, for example from US 4.948,385 (HULL) to provide a pair of fins, otherwise known as flippers, for a swimmer to maintain a race speed in training, with a lower associated physical exertion than that involved in attaining and maintaining race speed without the aid of fins. In order to become a successful competition swimmer, it is important to train at race speed or at a speed above the swimmer's natural maximum pace in order to condition the body in co-ordination of movement and breathing. The demands of co-ordination, physical fitness, speed of movement and strength are much greater when swimming unassisted at a race speed.

Generally, short fins are preferred in training, because a swimmer can achieve a natural foot rhythm, for example, a 6-beat kick within the natural stroke. Longer fins offer too much resistance for the swimmer to maintain a rapid kick and consequently affect the timing of the entire stroke.

Swimming at a race speed requires a good kicking technique. In flutter and dolphin kicking, the movement of the foot towards the anterior (front) side of the body is the most effective part of the kick. During this part of the kick, pressure of water during the whipping action of a kick acts against the kicking foot bringing the foot into its most extended position, which in turns allows the foot to push water backwards at a more effective angle. Pushing water at this angle creates a vortex of rotating water, which maximises forward propulsion of the swimmer.

It is also understood that "toeing in" improves the effectiveness of kicking by presenting the dorsal surfaces of the feet at an optimal angle for deflecting water backwards. In dolphin kicking, this also presents the largest and flattest portions of the dorsal surface of the feet in combination, creating a larger surface for deflecting water backwards. Toeing in is achieved by extension (pointing of) the toes, adduction (turning the toes inward) and supination (rolling the feet outwards). This requires great ankle flexibility, because the ankle and foot rotate in a medial and oblique plane, as well as in the vertical plane. World-class swimmers also include medial femoral rotation (rotation of the thigh to move the kneecaps inwards). This medial femoral rotation has two benefits. Firstly it allows the swimmer to use the shins for propulsion (as well as the feet). Secondly, it allows the dorsal surface of the foot to angle back as far as possible against the water, allowing a swimmer using dolphin kick to create one combined large, flat surface from the two feet rather than two flat surfaces disposed at an angle to each other.

At the start of a kick, the feet are positioned furthest towards the posterior (rear) side of the body. The knees and hips are also partly flexed. The drive involves hip flexion followed by knee extension, pushing the dorsal surface of the foot against the water and consequently creating maximal ankle extension. Also, at the start of the kick, a world class swimmer prepares the most efficient kicking position by bringing the ankles far enough apart to allow adduction and supination to an extent that the big toes are almost touching.

Generally, a pair of fins includes two identical fins with foot pockets which are symmetrical, enabling each fin to be worn on either foot. As explained previously, these fins are necessarily short to facilitate, for example, a six beat kick, but they do not allow toeing in, because the fins collide or overlap, thus preventing a swimmer adopting the optimum kicking position. US 4,9234 19 (MCARTHY) addresses this problem to some extent by providing an offset foot pocket, which allows adduction of the foot during a kick. However, when the swimmer toes in fully by extension, adduction and supination during the flutter kick, the result is that the blade portion of each fin is at an angle to the direction of the kick and to the dorsal surface of the foot, causing the fin to shear through the water. This decreases efficiency, creates added turbulence, reduces forward propulsion and increases swimmer exertion. n the dolphin kick, the combined surface of the fins presented to the water is a substantially V-shaped surface, with the same result. The physical embodiment of the MCARTHY design in use today is more often used as a breaststroke fin, because it is most effective in the supination-pronation plane.

Statement of Invention

According to the present invention there is provided a pair of fins for swimming, each fin comprising a foot pocket and a blade, the foot pocket having a sole portion with a first central axis substantially in a first plane, the blade having a second central axis substantially in a second plane, the first axis being angularly offset from the second axis in the plane of the first plane, and the second plane being disposed at an angle of between 20° and 45° relative to the first plane.

The invention is advantageous because the combination of the angular offset and downward tipping of the blade relative to the foot pocket enable a swimmer to swim with the fins in training to improve performance when kicking with a dolphin or flutter kick. Furthermore, the fins allow and encourage the swimmer to use the most efficient kicking technique. This is because when dolphin kicking, the dorsal surfaces of the blades present a substantially singular planar surface to the water, when toeing in fully as described above, which increases propulsion in the water and enables a race speed to be relatively easily obtained.

When performing a flutter kick with good technique, the surfaces of the blades present substantially planar surfaces to the water. Due to the shape of the fins, the surface of the fins is not rotated relative to the motion of the kick, but is substantially perpendicular thereto, thus presenting the maximum surface area to the water and reducing shear.

The second plane may be disposed at an angle of between 20° and 45° relative to the first plane, and preferably the second plane is disposed at an angle of approximately 40° relative to the first plane.

The foot pockets of the respective fins may not be symmetrical, but may be handed with one designed for the left foot and one designed for the right foot.

Each foot pocket may be adapted to substantially enclose a swimmer's foot, the foot pocket including an upper adjoining the sole portion and lying partially beneath the blade.

The upper may include a proximal portion, a lateral portion, a medial portion, a dorsal portion and a foot aperture disposed between the portions, the dorsal portion sloping downwardly from the medial side adjacent the foot aperture towards the lateral side at the distal end of the foot pocket, in use, the dorsal portion substantially following the downward contour of the dorsal portion of a swimmer's foot.

The foot pocket and blade may be integrally formed from an elastomeric material.

The second axis is angularly offset relative to the first axis in a lateral direction. In other words, when left and right handed fins are worn by a swimmer, the blades are angled outwardly to left and right of the sagittal plane of the swimmer's body.

The second axis may be angularly offset relative to the first axis by an angle of between 20° and 45°, and preferably the second axis is angularly offset relative to the first axis by an angle of around 30°.

Reinforcing ribs may extend along opposed side edges of each blade, which channel water, provide strength to the blade and reduce flexion when the fins are in use.

A reinforcing element may be provided on the dorsal surface of each blade between the side edges and extends from the distal end of the blade part way along the dorsal surface. The reinforcing element also acts to reduce flexion, but does not tend to separate the water flowing over the blade in the manner of a rib, which would reduce propulsion and impair performance.

The distal end of each fin may be shaped with a concave contour between each of the opposed side edges and the reinforcing element.

The foot pocket may be provided in a plurality of sizes for different sized feet.

Description of the Drawings

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a schematic perspective view of a pair of fins; Figure 2 shows a schematic side view of the right fin of Figure 1; Figure 3 shows a schematic perspective view of a foot pocket of the left fin of Figure 1; and Figure 4 shows a three-dimensional set of axes and the relative angular positions of the central axis of the sole portion of the foot pocket relative to the blade's central axis.

Description of Preferred Embodiments

Referring firstly to Figure 1, a pair of fins for swimming is indicated generally at 10.

The fins are designed specifically for enhanced performance when flutter and dolphin kicking. The fins 10 are not symmetrical, there being a left fin 12 for the left foot of a swimmer and a right fin 14 for the right foot of a swimmer. Each fin is integrally moulded from a suitable elastomeric material and includes a foot pocket 16 and a blade 18.

Referring also to Figure 3, a left foot pocket of the invention is shown. The foot pocket includes a sole portion 20, a proximal portion 22, a medial portion 24, a lateral portion 26, a dorsal portion 28, a distal portion 30 and a foot aperture 32 disposed between the portions. The dorsal portion 28 is designed to substantially follow the downward contour of the dorsal portion of a swimmers foot, and slopes downwardly from the medial side adjacent the foot aperture 32 towards the lateral side at the distal end of the foot pocket 16. The contour of the dorsal portion is indicated by the contour lines 33. The dorsal portion 28 lies partially under the medial end of the blade 18 and is integrally formed therewith. A central longitudinal axis of the sole portion of the foot pocket 16 is indicated in broken line at 34.

The blade 18 does not lie in alignment with the central axis 34 of the sole portion 20 of the foot pocket 16, but rather is offset towards the lateral side of the foot pocket 16.

This can be seen in Figure 1, but also in Figure 2, which shows the right-footed fin 14.

A central axis lying on the surface of the blade 18 is indicated in broken line at 36.

Opposed reinforcing ribs 38, 40 are provided along the outer longitudinal medial and lateral edges of the blades 18 and an optional central reinforcing element 42, shown in Figure 1, is provided on the face of the blades. The reinforcing element 42 extends from the distal end of each blade 18 approximately a quarter of the way along the blade. The reinforcing element 42 has a low profile and is curved to ensure that it does not separate a flow of water moving over the dorsal face of the blade.

The relative positions of the blade 18 relative to the foot pocket 16 can he seen most clearly in Figure 4, which shows three perpendicular axes, X,Y,Z. The central longitudinal axis 34 of the sole portion 20 of the foot pocket 16 lies on the X-axis.

The central axis of the blade 36 cuts the X-Y plane and is angled upwardly to meet the Z-axis. The lateral offset of the blade, when viewed along the Z-axis (ie from above the fins 12, 14) is indicated at a and is between 20° and 45° and is preferably around 30°. The slope of the dorsal surface of the blade 18 relative to the sole portion 20 of the foot pocket 16 is indicated at 3 and is between 20° and 45°, may be between 30° and 45°, and is preferably around 40°. The angles of offset of 30° and slope of 40° are intended to deliver optimum performance for a swimmer using the flutter and dolphin kicks, when fully toeing in.

The fins 10 are highly advantageous in use, because a swimmer can fully toe-in and generate optimum propulsion when flutter or dolphin kicking, to attain and maintain a race speed. The fins 10 enhance training in co-ordination, physical fitness, speed of movement, flexibility and strength, and are particularly effective in training a swimmer to toe-in. When used correctly, the medial reinforcing ribs 38 should lie side by side in a dolphin kick and the blade surfaces should form a single substantially co-planar surface. In flutter kicking the medial reinforcing ribs 38 should pass close to one-another, and should create a substantially co-planar surface at the crossing point. A swimmer can feel when the toe-in position is correct and a trainer can see the position of the fins 10 and can advise correction as required.

Claims

CLAIMS1. A pair of fins for swimming, each fin comprising a foot pocket and a blade, the foot pocket having a sole portion with a first central axis substantially in a first plane, the blade having a second central axis substantially in a second plane, the first axis being angularly offset from the second axis in the plane of the first plane, and the second plane being disposed at an angle of between 200 and 45° relative to the first plane.
2. A pair of fins as claimed in claim 1, in which the second plane is disposed at an angle of between 30° and 450 relative to the first plane.
3. A pair of fins as claimed in claim 1 or claim 2, in which the second plane is disposed at an angle of approximately 40° relative to the first plane.
4. A pair of fins as claimed in any preceding claim, in which the foot pockets of the respective fins are not symmetrical, but are handed.
5. A pair of fins as claimed in any preceding claim, in which each foot pocket is adapted to substantially enclose a swimmer's foot, the foot pocket including an upper adjoining the sole portion and lying partially beneath the blade.
6. A pair of fins as claimed in claim 5, in which the upper includes a proximal portion, a lateral portion, a medial portion, a dorsal portion and a foot aperture disposed between the portions, the dorsal portion sloping downwardly from the medial side adjacent the foot aperture towards the lateral side at the distal end of the foot pocket, in use, the dorsal portion substantially following the downward contour of the dorsal portion of a swimmers foot.
7. A pair of fins as claimed in any preceding claim, in which the foot pocket and blade are integrally formed from an elastomeric material.
8. A pair of fins as claimed in any preceding claim, in which the second axis is angularly offset relative to the first axis in a lateral direction.
9. A pair of fins as claimed in any preceding claim, in which the second axis is angularly offset relative to the first axis by an angle of between 200 and 45°.
10. A pair of fins as claimed in claim 9, in which the second axis is angularly offset relative to the first axis by an angle of around 30°.
11. A pair of fins as claimed in any preceding claim, in which reinforcing ribs extend along opposed side edges of each blade.
12. A pair of fins as claimed in claim 11, in which a reinforcing element is provided on a dorsal surface of each blade between the side edges and extends from the distal end of the blade part way along the dorsal surface.
13. A pair of fins as claimed in claim 9, in which the distal end of each fin is shaped with a concave contour between each of the opposed side edges and the reinforcing element.
14. A pair of fins as claimed in any preceding claim, in which the foot pocket is provided in a plurality of sizes for different sized feet.
15. An apparatus substantially as described herein with reference to and as illustrated in Figures 1 -4 of the accompanying diagrams.