GB2215621A

GB2215621A - Golf ball with improved dimple configuration

Info

Publication number: GB2215621A
Application number: GB8900889A
Authority: GB
Inventors: Michael Shaw
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1988-02-11
Filing date: 1989-01-16
Publication date: 1989-09-27
Also published as: FR2627093A1; GB8803107D0; AU2870889A; GB8900889D0; ZA89470B; JPH01268580A

Abstract

A golf ball is provided with dimples (10) in which each dimple consists of a first cavity (11) and a second cavity (13), the cavities being immediately adjacent each other on a great circle of the ball. The dimple arrangement minimises aerodynamic drag (air-resistance) when the ball is in play. A second embodiment shows a circular cavity (22) surrounded by an annular cavity (21). <IMAGE>

Description

GOLF BALL WITH IMPROVED DIMPLE CONFIGURATION This invention relates to a golf ball with an improved dimple configuration and in particular to a golf ball having a dimple configuration which contributes to the reduction of aerodynamic drag when the ball is in flight.

Figures 1 to 3 of the accompanying drawings illustrate the background to the present invention.

Aerodynamic drag (air-resistance) takes place in a direction opposite to the direction of flight.

The drag force experienced by the ball is influenced by the flow of air close to the ball surface (the boundary layer) (Figures 1 and 1A). High drag results if the boundary layer flow is laminar at the point where the boundary layer separates from the ball surface (the separation point).

To minimise drag it is necessary to ensure that flow in the boundary layer is turbulent at the separation point (Figure 2) and that the final separation point itself is as far as possible towards the rear of the ball (relative to the direction of flight). It has also been found that the thickness of the boundary layer is important, in that an increase in the thickness of the boundary layer results in an increase in aerodynamic drag.

The present invention aims to provide a golf ball in which the surface pattern minimises boundary layer thickness and also generates separation and subsequent re-attachment of the boundary layer to the ball surface (Figure 3).

It is well established that such separation can be made to occur at a discontinuity in the outer surface of the ball, for example, at the edge of a dimple or similar cavity.

Accordingly, the present invention provides a golf ball having a plurality of dimples in its spherical outer surface, in which each dimple comprises a first cavity and a second cavity, said first and second cavities being immediately adjacent each other on a great circle of the ball.

Although it is not intended that the present invention be construed according to any particular theory, it is believed that the edge of the first cavity triggers separation of the boundary layer and that the air flow over the second cavity causes reattachment of the boundary layer.

In a first preferred embodiment of the present invention, the first and second dimple cavities are of substantially the same dimensions and configuration.

Alternatively, the first dimple cavity may be of small dimensions and configuration relative to the second cavity.

In a second preferred embodiment of the present invention, the first dimple cavity may comprise an annulus, concentric with the second cavity, whereby the dimple has, overall, an identical configuration irrespective of the direction of motion of the ball.

Preferably, the dimples may be distributed over the spherical outer surface of the ball in a uniform regular pattern.

The invention will be illustrated, merely by way of example, with reference to Figures 4 to 7 of the accompanying drawings.

In the drawings: Figure 4 is a plan view of a dimple according to a first preferred embodiment of the present invention; Figure 5 is a section on line V-V of Figure 4; Figure 6 is a plan view of a dimple according to a second preferred embodiment of the present invention; Figure 7 is a section on line VII-VII of Figure 6.

Figures 4 and 5 show a dimple 10 having an outer diameter in the range 2 mm to 5 mm and a depth in the range 0.1 mm to 0.3 mm. The dimple 10 comprises two adjacent cavities 11 and 13, separated by divider 12. Divider 12 has a height in the range 0.05 mm to 0.3 mm.

Figures 6 and 7 show a dimple 10 comprising an annular first cavity 21 concentric with a generally circular second cavity 22. The width of annular cavity 21 may be in the range 0.1 mm to 2 mm and its depth may be in the range 0.05 mm to 0.15 mm. Circular cavity 22 may have a depth in the range 0.05 mm to 0.3 mm and a diameter in the range 2 mm to 5 mm.

The radial distance between cavities 21 and 22 may be up to 1 mm.

Claims

CLAIMS:

1. A golf ball having a plurality of dimples in its spherical outer surface, in which each dimple comprises a first cavity and a second cavity, said first and second cavities being immediately adjacent each other on a great circle of the ball.

2. A golf ball according to Claim 1, in which the first and second cavities are of substantially the same dimensions and configuration.

3. A golf ball according to Claim 1, in which the first cavity is of small dimensions and configuration relative to the second cavity.

4. A golf ball according to Claim 1, 2 or 3, in which the first cavity comprises an annulus concentric with the second cavity.

5. A golf ball according to any one of Claims 1 to 4, in which the dimples are distributed over the spherical outer surface of the ball in a uniform regular pattern.

6. A golf ball, substantially as hereinbefore described, with reference to and as illustrated in Figures 4 and 5 of the accompanying drawings.

7. A golf ball, substantially as hereinbefore described, with reference to and as illustrated in Figures 6 and 7 of the accompanying drawings.