Golf Club Shaft

The present invention relates to a golf club and to a shaft made of a composite material equipping this club.

A golf club basically comprises a shaft carrying, at its lower end, a head or striking component, and, at its upper end, a handle, commonly termed a "grip."

Conventional golf clubs generally have tapered shafts made of steel, metal alloys, or composite materials. They have a shape whose section changes continuously and whose maximum dimension is measured at the grip, or handle, and whose minimum dimension is measured at the neck, where the club head is attached. This is the most widely used type of shaft.

If one wishes to enhance the mechanical properties of the club, i.e., the elastic line under torsion and/or flection of the shaft, while preserving a club having satisfactory ergonomic qualities in the gripping area of the club, the geometries of conventional shafts offer few opportunities other than the use of fibers having a higher modulus, which is costly, or the incorporation of additional reinforcements of fiber layers which adds undesirable surplus weight.

One of the objects of the invention is to solve this problem, which results basically from the geometry of the shaft and from the design of the various club components.

The club according to the invention has mechanical properties superior to those of conventional clubs, while preserving satisfactory ergonomic properties and lightness.

To this end, the club incorporates a shaft made of a composite material, at the end of which a grip is mounted. This shaft comprises a first, upper tapered portion extending from the upper end and at least partially covered by the grip; a second, lower portion extending to the lower end; and a third, connecting portion. The club is characterized by the fact that the diameter of the section of the lower end of the first of these portion is smaller than the diameter of the section of the upper end of the second, portion.

The invention will be better understood and other advantages and features will better emerge from the embodiments described below and illustrated by the following drawings, in which:

FIG. 1 is a view of a golf club according to prior art;

FIG. 1a is a detail view of the club according to FIG. 1;

FIG. 1b is a view of a shaft of the club shown in FIG. 1;

FIG. 2 is a view of a golf club according to the invention;

FIG. 2a is a view of detail of the grip of the club in FIG. 2;

FIG. 2b is a view of a shaft of the club in FIG. 2;

FIG. 3 is a view of a club according to a second embodiment of the invention;

FIG. 3a is a detail view of the shaft of the club in FIG. 3;

FIG. 4 is a view of another variant of the invention;

FIG. 4a is a view of a shaft of the club in FIG. 4;

FIG. 5 is a view of a club incorporating another variant; and

FIG. 5a is a detail view of the club in FIG. 4.

As illustrated in FIGS. 1 and 1a, the golf club according to prior art is constituted by a shaft 1 whose overall shape is uniformly tapered, i.e., in which the generating line G of the shaft forms, with the longitudinal axis I, I', a positive angle .theta., as shown in FIGS. 1 to 1b. A head 2 is attached to the lower end 10 of this shaft 1, and a grip 3 having a length lg and extending over a portion of the shaft is fitted on its upper end 11. The grip has a tubular wall 30 of variable thickness e, in particular a thickness which increases from the lower end 30a to the upper end 30b of the tubular wall 30. The thickness is an average of approximately 5 to 6 mm at the upper end 30b, and diminishes to reach values of approximately 1.5 to 2 mm at the lower end. This also means that the generating line Gg of the outer surface of the tubular wall 30 is offset from the generating line G by a positive angle .theta.1.

FIGS. 2 and and 2a illustrate a first embodiment of a club according It also incorporates the same assembly of a shaft 1, a head 2, and a grip 3. The shaft 1 is formed from several separate portions, including:

a first, upper tapered portion 12a extending from the upper end 11 and covered at least partially by the grip 3;

a second, lower portion 12b extending to the lower end 10; and

a third, short connecting portion 12c which attaches the first portion 12a to the second portion 12b.

The lower end 120a of the first, upper tapered portion 12a has, at its lower end, a section having diameter d1, which is smaller than the diameter d2 of the section of the upper end 120b of the second, lower portion 12b.

In this first embodiment, the free part 121b of the second, lower portion 12b also advantageously has a tapered shape, and its generating line G2s is at least substantially parallel, to the generating line G1 of the first tapered portion 12a. The lower part 122b of the second portion, which is embedded in the head 2, is preferably a tubular portion having a uniform section.

Furthermore, the length of the first portion 12a is substantially equal to, or slightly less than, the length lg of the grip 3. In addition, the grip 3 has a tubular wall 30 preferably having a fine, uniform thickness 3 of approximately 1 to 2.5 mm, but possibly with a very slight variation of up to about 1 mm to meet molding capabilities, the thickness in that event being greater at the upper end. Moreover, the design could be such that the generating line Gg of the outer surface of the wall 30 merges with the generating line G2 of the free part 121b of the second, lower portion 12b. In this case, the grip 3 is incorporated into the shaft.

FIG. 2b illustrates an example of a club shaft according to the invention. It is made of composite materials, by draping plies of fibers impregnated with duroplastic resin. The second portion 12b has, over at least a substantial length of its free part 121b, a section larger than the section of a conventional shaft, such as that shown in FIG. 1b, and this imparts to the shaft superior mechanical properties.

FIGS. 3 and 3a illustrate a second embodiment of the invention, in which the shaft has a second, lower portion 12b whose geometry differs from that previously described in that it comprises a first, free lower tapered part 123b attached to a second, upper free part 124b, which has a uniform tubular section.

FIGS. 4 and 4a illustrate a third embodiment of the invention, in which the shaft 1 has a second, lower portion 12b comprising a first, free upper part 124b in the shape of an truncated cone inverted in relation to the second, free lower part shaped like a truncated cone 123b, to which it is attached, so that the shaft 1 has a bulge 13 in approximately its median part. The phrase "shaped like an inverted truncated cone" signifies that the generating line G4 of the first, free upper part 124b forms, a negative angle .theta.4 relative to the axis I, I'.

FIGS. 5 and 5a illustrate an improvement made to the embodiment of FIGS. 2 and 2a, consisting of the use of a ring 4 to cover the third, connecting portion 12c. The ring 4 is advantageously of variable thickness e1 and is thicker at its upper end, to protect the fine edge of the grip. This thickness is substantially equal to the thickness e of the grip, protect the grip on the shaft. The ring 4 may, be made of a material having damping properties, e.g., a viscoelastic material, and may have a variable weight according to the type of club, and thus be a factor contributing to the dynamic balancing of the club.

The shafts just described may advantageously be made by a process such as that described in French Patent Applications Nos. 90 15388 and 90 15387.

In the examples described, the generating lines are rectilinear, but they may incorporate a slight curvature, in particular for generating lines G1, G2, G3, and G4.