Constant edge angle dimple design for ball

Abstract: A golf ball (10) having three or more sets of dimples (11, 12, 13) on its surface (14) with all dimples within a set having substantially the same diameter and each set diameter differing substantially from each other set diameter and in which each set has substantially the same dimple edge angle (e,e′e″) as each other set.

Description: Background of The Invention In the past, golf ball dimple designs typically included 250 to 500 dimples, all having the same specific diameter, depth, and shape, usually chosen to maximise the aerodynamic effectiveness of the dimples. Today, it is not uncommon to find several different sizes of dimples on a single ball, such as described in GB Patent Application 2203954, wherein dimples of two or three differing diameters are distributed over the ball's surface. In these designs, the different- sized dimples are typically configured to all have the same depth, or the same enclosed volume, or the same depth/diameter ratio (see US Patent No. 5,033,750), or with no particular relationship at all. None of these schemes maximises the aerodynamic effectiveness of each dimple size. US-A-4,979,747 describes a golf ball having dimples of frusto-conical form, the cone angles of the dimples being substantially equal to give an edge angle of from 11 to 14 degrees, and their aspect ratios set within a defined range but arranged so that dimples of smaller diameter have greater depth. Summary of The Invention According to a first aspect of the present invention, a golf ball has an outer surface periphery with a plurality of sets of spherical or saucer-shaped dimples positioned therein wherein each dimple set has dimples of a selected diameter which diameter differs from each other set and where each and every dimple set has an edge or edges which diverge from the spherical outer surface of the ball at substantially the same angle, measured between tangents to the surfaces of the dimple and the ball respectively. According to a second aspect of the invention, a golf ball has three or more sets of spherical or saucer-shaped dimples on its surface with all dimples within a set having substantially the same diameter and each set diameter differing substantially from each other set diameter, and characterised in that the edge angles of the dimples in each set are all within two degrees of each other and all such edge angles are in the range of 14 to 26 degrees, measured between tangents to the spherical ball surface and tangents to the dimple surface. It is a feature that a ball has dimples over 50 percent and preferably about 70 to about 80 percent of the outer surface of the ball. Brief Description of The Drawings Fig. 1 is a prescriptive view of an unfinished ball with dimples of varying diameter; Fig. 2 is a sectional view taken along line 2-2 of Fig. 1 through the centre of two adjacent dimples; and Fig. 3 is a partial sectional view of a dimple of a finished ball. Description Of The Preferred Embodiment In Figures 1 and 2, ball 10 has a plurality of dimples 11, 12, 13, etc. with dimples 11 and 12 shown in section in Fig. 2. Dimple 11 is a spherical concave dimple with spherical wall 11w. Wall 11w is a segment of a sphere with center C and radius DR. The edge angle e of dimple 11 is measured at point P where wall 11w diverges from ball periphery surface 14. A line tangent to ball periphery surface 14 at P determines tangent T 1 . T 2 is a tangent to dimple wall 11w at point P. Dimple edge angle e is the angle between tangents T 1 and T 2 . Also shown is non-dimple area or land L. Adjacent dimple 11 is a saucer shaped dimple 12 which includes dimple wall arcuate areas 12a and 12c and dimple bottom area 12b. The edge angle of this non-spherical dimple 12, which has a larger diameter than dimple 11, is angle e′, the angle between tangents T 1 ′ and T 2 ′. Tangent T 1 ′ is a line tangent to ball periphery surface 14 at point P′, where dimple wall area 12a diverges from surface 14. Tangent T 2 ′ is a line tangent to dimple wall area 12a at point P′. Edge angle e is substantially equal to edge angle e′. Preferably edge angles e and e′ are between 14 to 22 degrees for optimum aerodynamic ball performance with balls having 70-80 percent dimple coverage. Where dimple coverage is about 50 percent or more; a dimple edge angle of 14-26 degrees is preferred. While the edge angles of dimples may vary a small amount where all dimple angles fall within a range of about 2 degrees the dimple angles are considered to be substantially the same. Turning to Fig. 3, ball 10 is shown as a finished ball including layers of paint and clear coat which creates a varied curvature at the demarcation between ball periphery surface 14 and dimple wall 11w. This curvature makes the location of the dimple edge indistinct. In this case, the edge angle e″ is defined to be the angle between tangents T 1 ″ and T 2 ″. T 2 ″ is the tangent to the dimple wall 11w at the inflection point I. T 1 ″ is is the tangent to the ball periphery surface 14 at point X which is the intersection of T 2 ″ and periphery 14. Dimple edge angles, diameters, depths, and other dimensions are normally measured on an unfinished molded ball or the master pattern used to create the ball mold, which usually are substantially the same. The unfinished ball is then coated with thin layers of paint and/or clearcoat, which coats vary in thickness and tend to be slightly thinner at the dimple edges. Thus, the edge angles and other dimple dimensions on a finished ball may vary somewhat from the unfinished ball or the master pattern. The edge angles of the present invention are determined using unfinished ball or master pattern dimensions.

Claims: A golf ball (10) having an outer surface periphery (14) with a plurality of sets of spherical (11) or saucer-shaped (12) dimples positioned therein wherein each dimple set has dimples (11, 12) of a selected diameter which diameter differs from each other set and where each and every dimple set has an edge or edges which diverge from the spherical outer surface (14) of the ball (10) at substantially the same angle (e, e', e''), measured between tangents (T 2 , T 2 ', T 2 ''; T 1 , T 1 ', T 1 '') to the surfaces of the dimple (11w, 12c) and the ball (14) respectively. A golf ball (10) having three or more sets of spherical (11) or saucer-shaped (12) dimples on its surface with all dimples within a set having substantially the same diameter and each set diameter differing substantially from each other set diameter, and characterised in that the edge angles (e, e', e'') of the dimples in each set are all within two degrees of each other and all such edge angles (e, e', e'') are in the range of 14 to 26 degrees, measured between tangents (T 1 , T 1 ', T 1 '') to the spherical ball surface (14) and tangents (T 2 , T 2 ', T 2 '') to the dimple surface (11w, 12a). A golf ball of Claim 1 or Claim 2, in which the edge angles (e, e', e'') of the dimples are all in the range of 14 to 22 degrees.

Inventors: AOYAMA STEVEN, AOYAMA, STEVEN
Applicants: ACUSHNET CO, ACUSHNET COMPANY
Application year: 1992
Main classification: A63B37
IPC codes: A63B37