Games using tangible projectile – Golf – Club or club support
Reexamination Certificate
1997-01-22
2001-02-13
Chapman, Jeanette (Department: 3711)
Games using tangible projectile
Golf
Club or club support
C473S314000, C473S349000
Reexamination Certificate
active
06186905
ABSTRACT:
BACKGROUND OF THE INVENTION
The field of the present invention is golf club heads and, more particularly, inertially tailored golf club heads and methods of designing the same.
In recent years, substantial attention has been directed to the development of two types of golf club heads, cavity backed heads for iron or wedge type golf clubs (shown in FIGS.
1
(
a
)-
1
(
c
)), and oversized heads for metal wood type golf clubs (shown in FIGS.
2
(
a
)-
2
(
c
)). When these golf club heads are designed utilizing conventional design methodologies, substantial efforts have been undertaken to locate the center of gravity (CG) of the golf club head in a predetermined or preferred position relative to the face.
Prior to this time, however, conventional design methodologies have failed to take into consideration the complete inertia tensor or moments and products of inertia of a golf club head. As a result, golf club heads developed in accordance with conventional design criteria and/or conventional design methodologies often do not perform optimally and display large coupled dynamic responses as they travel through a typical swing motion.
Accordingly, it is believed that those skilled in the art would find a method of designing golf club heads that addresses and takes into consideration the entire inertia tensor of a golf club head to enhance the performance of the golf club head to be quite useful. It is also believed that those skilled in the art would find inertially tailored golf club heads developed in accordance with such methods to be quite useful.
SUMMARY OF THE INVENTION
In one innovative aspect, the present invention is directed toward a method of designing a golf club head that takes into consideration the entire inertia tensor of the golf club head, thus allowing coupled dynamic responses during a swing motion to be minimized.
In one preferred form, the inertia tensor of a golf club head is defined using the magnitude and direction of the principal moments of inertia (i.e., the magnitude and direction of the maximum moment of inertia, the minimum moment of inertia, and an intermediate moment of inertia) of the golf club head. Thus, in accordance with the present invention, a preferred location of a center of gravity (CG) of a golf club head may be selected, magnitudes and directions of the principal moments of inertia of the golf club head may be selected, and mass may be distributed within the golf club head such that the center of gravity of the golf club head is located at the selected location, and such that the principal moments of inertia of the golf club head have the selected magnitudes and directions.
Those skilled in the field of dynamics will appreciate that the axes of the principal moments of inertia define a unique coordinate frame, wherein the inertia properties of the golf club head are completely uncoupled (i.e., wherein all products of inertia are 0), and wherein the moment of inertia about a first principal axis corresponds to the absolute maximum body inertia, the moment of inertia about a second principal axis corresponds to the absolute minimum body inertia, and the moment of inertia about a third axis is an intermediate value. Thus, by defining the magnitudes and directions of the principal moments of inertia of a golf club head, one inherently defines a complete inertia tensor of the golf club head. It further follows that a golf club head designed in the manner described above will exhibit those dynamic properties that are defined by the complete inertia tensor of the club head.
In another innovative aspect, the present invention is directed toward methods of improving golf club head performance by tailoring the mass distribution of a golf club head in a fashion that will minimize coupled dynamic club head motion as the golf club head progresses, for example, through the motion of a swing. To achieve this objective, it is presently preferred to have the axes of the principal moments of inertia of a golf club head point in directions that closely align with the directions of the primary forces that act upon the golf club head during a typical swing. These forces include the force that is exerted upon the golf club head as a ball impacts the face of the club head, and the aerodynamic drag, inertia and centrifugal forces that are exerted upon the golf club head as the club head travels through a typical swing. It will be understood that the inertia force is a swing-produced dynamic force that is tangent to the swing path of the center of gravity of a golf club head. Thus, in a golf club head designed in accordance with a preferred form of the present invention, one of the principal axes of inertia may point in a ball impact direction or in the direction of the inertia force at the moment of ball impact (i.e., may be located in a horizontal plane and be perpendicular to a line defined by the intersection of a plane of the face and the horizontal plane), and another principal axis of inertia may be perpendicular to the first and point in the direction of the centrifugal force that is produced during the swing motion. As the direction of the centrifugal force that results during the swing motion will vary depending upon shaft flex and dynamic toe-down effects, it is presently preferred that the principal axis of inertia associated with that force be oriented in a direction ranging from vertical to a direction coincident with the lie angle of the golf club head. The final principal axis of inertia is preferably perpendicular to the other two principal axes of inertia and generally may be oriented within the plane of the face of the golf club head and in a near horizontal direction.
In still another innovative aspect, the present invention is directed toward a method of directly controlling the dynamic behavior of a golf club head by adjusting the magnitudes and directions of the principal moments of inertia of the golf club head. For example, the effective sweet spot region of a golf club head may be increased by increasing the moment of inertia about a principal axis that passes through the center of gravity of the golf club head and is oriented, for example, in a vertical direction; the resistance to changes in the dynamic loft of the golf club head upon ball impact may be increased by increasing the moment of inertia about a principal axis oriented, for example, along a line defined by an intersection of a horizontal plane and a face plane of the golf club head; and an overall club toe-down effect may be altered by changing the moment of inertia about a principal axis oriented, for example, in a horizontal plane and pointing in a direction of ball impact. Finally, decreasing the inertia about the hosel (or shaft) axis of a golf club head will decrease the required player-supplied wrist torque needed to bring the club face to square at the moment of ball impact.
In still another innovative aspect, the present invention is directed toward improved golf club heads that are designed in accordance with the above-described methods. For example, in one preferred embodiment, a golf club head for an iron golf club may have a principal axis of inertia that is oriented such that an inertia loft angle (&thgr;
inertia
) of the golf club head is less than the geometric loft angle (&thgr;
GL
) of the golf club head. Indeed, in the preferred embodiment shown in FIG.
5
(
a
), one of the principal axes of inertia (PA
1
) of the golf club head is oriented in the vertical direction, thus reducing the inertia loft angle (&thgr;
inertia
) of the golf club head to 0.° In other preferred embodiments, a golf club head may have at least one principal axis of inertia that is aligned with a direction of a force that acts upon the golf club head when the golf club head impacts a golf ball. The golf club head may also have a principal axis of inertia that is aligned with a direction of a centrifugal force that acts upon the golf club head as the golf club head travels through a swing motion.
In still further embodiments, a golf club head in accordance with the present invention may
Blau Stephen L.
Callaway Golf Company
Catania Michael A.
Chapman Jeanette
Lyon & Lyon
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