Golf Club Head to Shaft Connection

This invention relates generally to golf clubs, and more particularly to connection of a golf club head to a shaft to achieve certain advantages.

Many efforts have been made to reallocate metallic weight from the hosel area of a golf club to the head itself, in order to achieve higher energy availability for transfer when the club is swung. Such greater energy or momentum is then transferred to the golf ball when struck. This requires, for example, reduction of metal at the hosel area of the club.

Such efforts have included configurations wherein a shaft is passed through the head of a persimmon wood. Typical of such configurations were: Wilson's staff model "Dynopower Fluid Feel" wood, produced around 1957; Wilson's "Helen Hicks" wood, produced in the 1920's; and certain MacGregor woods produced in the late 1930's. See also U.S. patent application Ser. No. 204,704 entitled "Iron Golf Club Heads", assigned to Callaway Golf Company, disclosing a hosel characterized by reduced mass or weight.

No way was known, to our knowledge, to connect a shaft to a golf club iron head, where the shaft passed to the bottom of the head and was reduced in diameter at or near the sole of the head so as not to interfere with an edge or edges of the sole; also, no way was known to connect such a shaft to a specially non-constant tapered bore in an iron hosel to provide a tight interference fit along the shaft and bore, upon axial assembly, enabling very good tactile "feedback" sensing, to the player, of head to ball impact.

It is a major object of the invention to provide an improved connection between a golf club head and shaft which meets the above needs, the head typically being an iron, such term also referring to a wedge, chipper, putter, wood, or other type. Basically, the invention includes or comprises:

a) a socket defining an inner wall that variably tapers toward the bottom of the head,

b) the shaft lower end recessed so as to be collapsible when forced downwardly against the socket inner wall,

c) the shaft wall thickness and the socket taper so related as to assure good connection of the shaft to the socket as the shaft is forced into the socket.

As will be seen, the socket may have intersection with the bottom of the head, the section lower ends closing toward one another at or near that intersection, whereby a limit or resistance to collapse of the cantilever sections is produced along with formation of a frictionally jammed together connection, the latter also enhanced by adhesive bonding. In this regard, the sections lower ends typically may have lateral interengagement proximate the intersection. The lower end of the shaft alternatively may not intersect the bottom of the head.

Another object is the provision of spacial relationship of the hosel/face leading edge junction, characterized by desired continuity while allowing for socket-sole intersection, achieved without interruption of such leading edge continuity.

A further object is the provision of a graphite shaft tapered end connection to a head hosel, as will be seen.

These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which:

FIG. 1 is an elevation showing a golf club incorporating the invention;

FIG. 2 is a perspective view of the front and bottom of the FIG. 1 head;

FIG. 3 is a perspective view of a mid-upper section of the hosel;

FIG. 4 is a rear end perspective view of the section of the FIGS. 1-3 head and hosel;

FIG. 5 is a top plan view taken at the upper end of the hosel;

FIG. 6 is a perspective view of the shaft lower end before its reception into the hosel and tapered socket;

FIG. 6a is like FIG. 6 but shows shaft cantilever portions closed together at their lower ends;

FIG. 7 is a vertical section taken through the tapered socket in the lower end of the hosel;

FIG. 8 is a fragmentary perspective view of a tapered graphite shaft;

FIG. 9 is an endwise cross section taken through the FIG. 8 shaft; and

FIG. 10 is a view showing the FIG. 8 shaft assembled into a club head.

In the drawings, a golf club 10, such as an iron, has a head 11 and a ferrule 12. Also shown is a hosel 13, typically formed or cast as part of the head, the latter consisting of metal or other material. A socket 14 is associated with the head and has an inner wall, the lower extent of which tapers in an endwise downward direction, generally toward the bottom 15 of the head at the heel. In this regard, the socket preferably has intersection at 16 with the head bottom 15, proximate heel 11b, that intersection typically being oval shaped due to angularity of bottom 15 relative to the socket axis.

FIGS. 5 and 7 show that the socket taper commences at a zone indicated by line or plane 18 below a lengthwise straight, circular cross section bore 19 in the hosel and that extends from the upper end 21 of the hosel to horizontal plane 18. Bore 19 may be conical. The taper angle of the socket interior wall 22 preferably varies as for example appears in FIGS. 5 and 7, though such variable taper may approach zero, defining a cone. Thus, the forward (leading) side 22a of wall 22 has relatively greater taper angularity .alpha., relative to vertical, and the rearward (trailing) side 22b of the wall 22 has relatively lesser angularity .beta. (typically zero) relative to vertical, providing differential tapers, as shown. The taper angles of wall sides 22c and 22d lie between .alpha. and .beta.. Thus, the tapered bore 80 is eccentric relative to the cylindrical outer surface 13a of the upper hosel, above plane 18, and relative to the hosel bore 13b above that plane. Further, the socket bore cross sections are circular or near circular, as at planes 18a and 18b parallel to 18, which are normal to hosel axis 91. In this regard, the forward stroking direction is that indicated by arrow 25 in FIGS. 4, 5 and 7, i.e., the direction toward which the head front face 11a faces (the ball striking direction). Angle .beta. may be reduced to zero, as for a cylindrical shaft, or may be equal to a standard taper (0.00375 inches per inch of length on one side). Angle .alpha. is between about 1 to about 8 degrees.

Further in this regard, the wall thickness of the hosel above plane 18 may also vary, as indicated, and may be circular, conical, or elliptical, for example. Thus, the thickness t.sub.1 at the forward side of the hosel may be about the same as or greater than the thickness t.sub.2 at the rearward side of the hosel. This relationship may be produced by forming bore 19 eccentrically relative to the cylindrical outer surface of the hosel, or it may be non-cylindrical or ellipsoidal. The main axis of the bore/shaft and the main axis of the outer configuration of the hosel proper may be approximately aligned or slightly skewed. These relationships contribute to a spacial relationship of the hosel to the head face leading edge juncture 50 and 51 allowing reallocation of weight to the head itself (i.e., between the toe, top, and sole area) for greater or more focussed momentum during club swinging.

Yet another feature of the invention is the provision of a shaft lower end portion forcibly received into the socket, that shaft lower end portion having recess means whereby the lower end portion is collapsed at least in part into the recess means in response to its forcible reception into the socket. To this end, the lower end portion 30 of shaft 31 may advantageously have circularly spaced, cantilevered sections 32 which extend endwise, and have lower free ends or terminals 33, as seen in FIG. 6. Endwise extending slots 34 are formed between the metallic sections or tongues 32 to allow closure together of the sections (see FIG. 6a) when the sections are frictionally jammed downwardly into the tapered socket. Three to eight slots are workable. Note in FIG. 6a that the edges 32a of successive tongues may interengage at their lowermost locations 32a'. See also FIGS. 1 and 2. Such edge interengagement or near interengagement occurs at or near the intersection locus 16; and a plug 36 of material may be filled into the central opening 37 formed by the closing sections. In such instances, the shaft may not physically intersect the head sole itself, although the theoretical intersection still exists. A suitable plastic or powdered metal plug may be used. Also, the lower end portion 30 of the shaft may be bonded to the hosel and socket inner walls, as by a suitable bonding agent, epoxy being one example. Thus a positively jammed together and bonded connection is provided. The shaft typically consists of steel.

If the lowermost ends of the cantilever sections project below the intersection 16 upon assembly, they may be trimmed off, as by grinding.

Accordingly, a very strong, sturdy connection of the shaft to the head is provided, facilitating maximum reallocation or location of weight to or at the head itself, with maximum feel, as well as maintaining continuity of the hosel leading edge 48, and face leading edge 49, with no intersection of exit hole 16 interfering at juncture 50, 51, should such intersection at 16 exist.

The head typically comprises a metal (steel) casting, with:

a) the head being a cast metal head having a socket with an inner wall tapering in an endwise direction generally toward the bottom of the head,

b) the shaft having a lower end portion forcibly received into the socket, the lower end portion deformed by and against the tapering inner wall, which defines casting irregularities acting to further deform the shaft lower end portion.

Likewise, the method of forming shaft to head connection includes:

a) casting the head to have a bore tapering downwardly with variable taper,

b) forcing the shaft lower end portion downwardly, into the variably tapered bore to effect partial collapse of the shaft lower end portion against the tapered bore.

Also, the head is typically cast to form surface irregularities at the bore, and against which the shaft lower end portion becomes deformed, as well as locked against twist relative to the bore.

In FIGS. 8 and 9, a graphite shaft 60 is tubular and defines a cylindrical bore 61 having an axis 62. The shaft has a lower portion 60a below a plane 63 normal to axis 62, that lower portion 60a tapering toward the lowermost end 60b of the shaft. The shaft wall thickness is greater at one side of the bore (see wall section 64) than at the opposite side of the bore (see wall thickness 65 below level of plane 63). As shown in FIG. 9, the wall section 65 has an outer surface 65a that tapers, toward end 60b, whereas wall section 64 has outer surface 64a that is parallel to axis 62. The degree of taper of the shaft surfaces between 65a and 64a decreases from 65a to 64a, about the axis 62.

FIG. 10 shows the graphite shaft assembled into the hosel socket 66 in iron club head 67. The hosel socket has an upper bore 68, which is cylindrical, to receive cylindrical shaft extent 69 above plane 63. The socket also has a lower bore 70, which is tapered to match the taper of the shaft lower portion 60a. Thus, the hosel socket lower portion also defines an axis, corresponding to axis 62, and has an inner wall 70a tapering relative to that axis in an endwise direction to receive and seat the shaft tapered surface 65a. Socket opposite wall 73 receives sideward jamming engagement with the shaft wall surface 64a, as a result of jamming of shaft surface 65a against hosel tapered wall 70a. Adhesive, such as epoxy, may be used to bond the shaft and hosel walls together. The shaft tapered wall 65 faces forwardly, i.e., in the same direction as the head ball-striking face 82, i.e., in the direction of head swing.

Upon assembly, the protruding lowermost end 60b of the graphite shaft is typically ground off to produce the shaft flush end 60f in FIG. 11; and filler 80 may be introduced into the shaft bore lower end to close and seal the bore, and produce a smooth surfaced, lower surface of the head. The head itself may consist of metal, such as steel.