Arch reinforced golf club head

A golf club head made of metal has a hollow construction with a pair of arcuate reinforcing ribs extending in horizontal and vertical planes with the arcuate ribs terminating at the striking plate of the golf club where a base structure of reinforcing ribs interconnect the ends of the arcuate ribs. The rib structure is molded integrally with the walls of the hollow club head and function to desirably reinforce the club head to prevent collapse or other distortion while providing a relatively large sweet spot and preventing undesired torque on the club head when a golf ball is hit at an off center location on the striking plate.

CROSS-REFERENCE TO RELATED APPLICATIONS 
This application is related to provisional application Ser. No. 60/035,669, 
filed Jan. 22, 1997, for Parabolic Arch Reinforced Golf Club Head and 
priority to that application is hereby claimed. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to metal wood golf club heads and more 
particularly, to means for reinforcing such golf club heads. 
2. Description of Relevant Art 
The term "woods" in relation to golf clubs embraces a family of rather 
long, and shallow lofted clubs that were previously almost exclusively 
made of persimmon or laminated maple wood. The family includes drivers and 
fairway woods with fairway woods having a greater loft than drivers and 
having shafts that are somewhat shorter. Wood clubs made of persimmon and 
laminated maple have lost popularity to metal woods that are typically 
hollow in construction and might be made of various metals such as 
stainless steel, aluminum or titanium. Stainless steel clubs are typically 
made of either stainless 304 or stainless 17-4 with the densities of these 
stainless steel heads being approximately 8.02 g/cm.sup.3 and 7.75 
g/cm.sup.3 respectively. Aluminum metal as used in golf club heads 
conventionally has a density of 2.72 g/cm.sup.3 while titanium as used in 
golf club heads usually has a density of 4.50 g/cm.sup.3. 
As will be appreciated, if metal wood golf clubs were made of solid metal, 
they would be far too heavy and as a result, virtually all metal woods are 
primarily hollow. 
The problems associated with hollow heads are numerous as are the attempts 
to overcome these problems. Some of the more common problems experienced 
with hollow metal woods are that the face of the club collapses upon 
repetitive impact with golf balls or the hollow shell behind the face 
crumples or fractures. One solution to the collapsing striking face has 
been to include reinforcement behind the face, but all too often this has 
led to an uneven dispersion of energy through the club head. More 
recently, several developments have occurred which have provided more 
satisfactory remedies to the above problems. 
Particularly, new metal alloys have come into vogue, particularly 
duraluminum and a titanium alloy including aluminum and vanadium (commonly 
called Ti-6-4). While none of these alloys eliminate the distortion of the 
club head, they have assisted in resisting the overall compression of the 
heads during impact with the golf ball and minimize the possibility of 
crumpling and fracture of the hollow metal heads. 
Another simultaneous evolution in the design of golf club heads is an 
enlargement in the head in the belief that the broader the head, 
particularly in hollow clubs which are of necessity perimeter weighted, 
the straighter the golf ball flight will be when the ball impacts the 
striking face at an off center location. Volumes of 250 cm.sup.3 and more 
are now common in hollow golf club heads. As will be appreciated even with 
low density metal alloys, wall thicknesses must be thinned and design 
considerations therefore continue to be of concern to keep the weight of 
the club within reasonable ranges. 
Furthermore, longer clubs, having up to fifty inch shafts, are also 
reaching the market. To keep moments of inertia of such a driver to a 
tolerable level due to increased club head speeds, the heads must weigh as 
little as approximately 180 grams. Further, such a head must be large in 
volume to counter the vision problems of perspective a player will have as 
he addresses the ball some three to seven inches further away than has 
been conventional with normal length shafts. 
It can be seen that the recent trends in golf club design continue to press 
in the direction of attenuated wall thicknesses to solve the aforenoted 
problems and the issues that are raised with longer shafts and bigger golf 
club heads. 
Thus, it is an objective of this invention to decrease the tendency of the 
golf club head to be deformed when impacting golf balls. It is a further 
objective to reduce the wall thickness of the several sections comprising 
the head such that a finite amount of mass can be liberated and 
judiciously moved to other locations. 
SUMMARY OF THE INVENTION 
The golf club head of the present invention is integrally molded with 
parabolic reinforcement in the form of an arcuate ribbed primary 
superstructure and a base superstructure that uniquely uses the interior 
wall portion of the head to balance and minimize weight and to provide 
superior reinforcement. The reinforcement is not a separate structure but 
instead is integrally molded into the walls of the head. The reinforcement 
creates unique superstructures wherein each superstructure or reinforcing 
rib protrudes from the interior surface of the club head walls and into 
the predominantly hollow club head interior. The cross-section of the 
reinforcing ribs is preferably semi-circular. 
The primary superstructure includes a first arcuate rib integrally molded 
perpendicular to horizontal when the club is resting normally on the 
ground, and forms a substantially parabolic arch. Hence, the first arcuate 
rib runs along the interior of the top wall of the club head to the 
relatively narrow rear of the club and returns along the sole plate. 
A second arcuate rib also forms part of the primary superstructure and is 
integrally molded parallel to horizontal and is, therefore, at right 
angles to the first arcuate rib. The second arcuate rib runs along the 
side wall of the club head, which includes a toe portion, a rear portion, 
and a heel portion, so that the two arcuate ribs cross at the rear of the 
club head. 
The base superstructure protrudes from the interior surface of the striking 
plate or face of the golf club head and is comprised of a vertical rib, a 
horizontal rib, and additional supplementary ribs which interconnect the 
ends of the aforenoted first and second arcuate superstructures. The base 
superstructure predominantly prevents distortion of the club head by 
interconnecting the ends of the arcuate ribbed superstructures. The 
vertical rib of the base superstructure protrudes from the interior 
surface of the striking plate and runs from the top wall to the sole 
plate. The vertical rib passes substantially through the center of the 
striking face and interconnects the ends of the first arcuate ribbed 
superstructure. The horizontal rib of the base superstructure protrudes 
from the interior surface of the striking face and runs horizontally 
across the striking plate so as to interconnect the ends of the second 
arcuate ribbed superstructure. 
As mentioned, supplementary ribs connect the ends of the first arcuate 
ribbed superstructure to the ends of the second arcuate ribbed 
superstructure so that four contiguous triangles are defined by the base 
superstructure. 
The arcuate primary superstructure ribs and the base superstructure ribs 
cooperate in resisting compression and distortion of the body of the club 
head, irrespective of whether or not the player impacts the golf ball on 
the center of the club face or has a mis-hit at an off center location. 
Other features and advantages of the present invention will become apparent 
from the following detailed description in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The golf club head 10 of the present invention can be seen in FIGS. 1 
through 8 to comprise a hollow body 12 having a neck 14 near the heel of 
the body to which a golf shaft (not shown) can be conventionally 
connected. The golf club head can be made of any one of the known metals 
from which golf club heads are made, such as stainless steel, aluminum 
alloys or Ti-6-4. The golf club head is typically investment cast in 
accordance with the well known "lost wax process". 
If the head 10 is made from stainless steel 304, the preferred metal 
density is 7.02 g/cm.sup.3, while if the club head is made of stainless 
steel 17-4, the preferred density is 7.75 g/cm.sup.3. If an aluminum alloy 
is used, the preferred density is 2.72 g/cm.sup.3, while use of Ti-6-4 
would have a preferred density of 4.50 g/cm.sup.3. 
The hollow body 12 of the club head 10 as best seen in FIGS. 1 and 2 
includes an upper body portion 16 comprised of a relatively flat striking 
face or plate 18, an arched top wall 20, and a curved side wall 22. The 
curved side wall has a toe portion 24, a rear portion 26, and a heel 
portion 28. The side wall extends from the toe edge 39 of the striking 
plate 18 to the heel edge 32 of the striking plate while following the 
perimeter of the top wall 20. This entire upper body portion is preferably 
integrally molded. The neck 14 may be molded or welded into the top wall 
adjacent to the location at which the side wall intersects the heel edge 
of the striking plate with the neck consisting of a generally hollow 
cylindrical extension sized to slidably receive the tip of a golf club 
shaft. 
The golf club head further includes a sole plate 34 which is a relatively 
flat plate positioned in spaced confronting relationship with the top wall 
and extending rearwardly from the lower edge 36 of the striking plate 18 
to the rear portion 26 of the side wall. The sole plate is preferably 
formed separately from the upper body portion 16 of the club head and is 
later welded to the upper body portion along its leading edge 38 to the 
lower edge of the striking plate and along its remaining peripheral edges 
40 to the lower edge of the side wall 22. 
While the relative thicknesses of the walls of the club head can vary 
depending upon the metal used, in the preferred embodiment of a club head 
made of Titanium 6-4 designed for use on a fifty inch golf club shaft and 
having a total volume of 290 to 300 cc, the top and side walls would 
preferably have a thickness of approximately 1.0 mm, the sole plate 1.1 mm 
and the striking plate 2.85 cm and the weight would be 178 grams. 
Each of the top wall, side wall, striking plate, and sole plate as best 
seen in FIGS. 3 through 8 has integrally formed therewith a rib or ribs 
which in combination cooperate to define primary and base ribbed 
superstructures to reinforce the club head thereby preventing collapse or 
distortion of the club head upon impact with a golf ball and in desirably 
dispersing the impact forces throughout the club head. For purposes of 
disclosure, the ribbing is illustrated removed from the club head in FIG. 
3, but it is understood that the primary superstructure and base structure 
do not comprise distinct and separate components from the afore-described 
upper body and sole plate, but rather are integral with associated 
portions of the club head body and sole plate and are only shown removed 
for purposes of description. 
The primary superstructure 42, as best seen in FIGS. 3 through 6, consists 
of two arcuate ribs which are somewhat parabolic in configuration with a 
first arcuate rib 44 extending in a substantially vertical plane and the 
second arcuate rib 46 extending in a substantially horizontal plane. The 
first arcuate rib extends from a centered location adjacent the front edge 
of the top wall 20 along the top wall toward the rear of the golf club 
where it crosses the rear portion 26 of the side wall 22 and is 
subsequently continuous along a centered path across the sole plate 34 to 
a centered location of the leading edge of the sole plate. The second 
arcuate rib 46 extends along the side wall 22 from a location at the toe 
edge 39 of the striking plate to a location at the heel edge 32 of the 
striking plate. As will be appreciated, the first and second arcuate ribs 
intersect perpendicularly to each other at the rear portion 26 of the side 
wall. It will be appreciated that with the exception of the portion of the 
first arcuate rib 44 that extends across the sole plate 34, the arcuate 
ribs are continuous since they are molded into the walls of the integral 
upper body portion 16 of the club head. When the sole plate is welded to 
the upper body portion of the club head, the portion of the arcuate rib 44 
extending across the sole plate is aligned with, and is effectively 
continuous with, the remaining portion of the first arcuate rib. 
The base superstructure 50, as best seen in FIGS. 3, 4 and 7, is formed on 
the internal face of the striking plate 18 and includes a straight 
vertical rib 52, a straight horizontal rib 54, and four supplementary 
straight ribs 56 interconnecting the ends of the vertical and horizontal 
ribs 52 and 54 respectively. The upper and lower ends of the vertical rib 
52 are integral and continuous with the ends 58 of the first arcuate rib 
44, while the ends of the horizontal rib 54 are integral and continuous 
with the ends 60 of the second arcuate rib 46 with the vertical and 
horizontal ribs intersecting at approximately the center of the striking 
plate. The supplementary ribs 56 in the base structure connect each end of 
the first arcuate rib 44 to the ends of the second arcuate rib 46. Each 
rib in the base superstructure is straight and therefore the ribs define 
in combination four contiguous right triangles. The triangles defined by 
the base superstructure prevent distortion of the ribs in the base 
superstructure and the striking plate during impact with a golf ball and 
the base superstructure in whole provides support for the first and second 
arcuate ribs of the primary superstructure. 
As will be appreciated, the arcuate configuration of the first and second 
arcuate ribs 44 and 46 respectively employ the physical principals of the 
arc in resisting club head compression or deformation. In the case where 
the club head strikes a golf ball at the center of the striking plate 18, 
the two arcuate ribs act jointly to resist distortion and deformation. In 
the event of a mis-hit at an off center location on the striking plate, 
the combination of the four triangles in the base superstructure 50 dampen 
the force by virtue of the enlarged sweet spot or reinforced area that 
they form. The forces generated by an off center hit are thus transmitted 
to the nearest of the first or second arcuate ribs and thereafter 
transmitted toward the rear of the club head where the load can be shared 
between the arcuate ribs. 
The primary superstructure 42 and the base superstructure 50 of the present 
invention resist distortion of the club head, maximizing the efficiency or 
the transfer of energy from the club head to the ball while minimizing 
problems related to off center hits on the striking plate. The design 
further permits judicious thinning of the walls defined by the hollow club 
head such that the center of gravity of the head is repositioned toward 
the rear, providing a higher launch angle of the ball, without increasing 
the loft of the striking plate, the loft can be lessened which as an 
alternative, allows a more efficient transfer of energy from the club head 
to the ball, it being fundamental knowledge that the more vertical the 
striking plate, the more efficient the transfer of energy to the golf 
ball. 
While the ribs in both the primary and base superstructure could be formed 
of different cross-sectional configurations, it is preferable that they 
have a semi-circular cross section as shown in FIG. 7. An alternative 
might be a triangular cross section as shown in FIG. 10 but the triangular 
configuration is not as advantageous for reasons to be discussed 
hereafter. It is further desirable that the ribs have a depth D that is no 
greater than the width W as this provides the desired reinforcement and 
structural rigidity to the club head without adding unnecessary weight 
which would otherwise require further thinning of the wall thicknesses of 
the club head. While the preferred cross section is semi-circular, the 
ribs could be quadrilateral in cross section but, again, the depth would 
preferably be no greater than the width of the ribs so as to give the 
desired rigidity to the club head without adding unnecessary weight. 
It will be appreciated from the above that a golf club head 10 has been 
described which allows the head to be made of desired metals while 
permitting the golf club incorporating the head to have an overall weight 
and swing weight in a desirable range. The size of the reinforcing ribs 
can be varied depending upon the desired weight and size of the club head 
but preferably the ribs have a depth that is no greater than the width, 
with the width, for example, being approximately 4.4 mm. In a 
semi-circular configuration as shown in FIG. 9 the depth would therefore 
be approximately 2.2 mm while in the configuration shown in FIG. 10 the 
depth would be approximately 4.4 mm. Increasing the cross-sectional size 
of the ribs improves the resistance to club head deformation and improves 
the transfer of energy from the club head to the ball but adds weight to 
the club head. 
As mentioned previously, the desired cross-sectional configuration for the 
rib is semi-circular inasmuch as the stiffness provided by the rib, which 
might be referred to as the section modulus, is greater per unit size than 
in other geometric configurations. By way of example, the section modulus 
for a semicircular rib is r.sup.3 /24.times.C where r is the radius of the 
semi-circle and C is a constant. It will, therefore, be appreciated that 
very small changes in the radius have a dramatic effect on the stiffness 
of the rib and, thus, the reinforcement of the club head without adding 
significant weight. The section of modulus for a triangle varies by the 
square of the height of the triangle given a constant base and, therefore, 
while the triangular configuration does provide desired stiffening, it is 
not as efficient a system for stiffening as is the semi-circle. 
It has been found in a golf club head made in accordance with the desired 
parameters identified above for a titanium 6-4 metal, that if the club 
head is not reinforced, there will be approximately 50% failures of the 
club head when normally impacted with a golf ball. If the golf club head 
is reinforced with ribs in accordance with the present invention that are 
of semi-circular cross section having a 2.2 mm radius, the number of golf 
club failures drops to nearly zero while only adding 3 grams of weight to 
the normally 178 gram club head. Accordingly, due to the reinforcement 
design of the present invention, a golf club head, can be made to 
dependably resist, without failure to the golf club head, the normal 
impact of golf balls with minimal addition of weight. As mentioned, when 
the ribs are semi-circular in cross-section, the efficiency in obtaining 
the desired strength while keeping the weight at a minimum is optimized. 
Use of the arcuate and somewhat parabolic rib superstructures in 
combination with the base superstructure also enlarges the sweet spot 
while preventing torque in the club head and at the same time desirably 
prohibits collapse or other distortion of the club head. As also 
mentioned, the design of the club head allows the center of gravity to be 
positioned toward the rear of the club head so as to provide higher launch 
angles of the golf ball without increasing the loft of the striking plate. 
Although the present invention has been described with a certain degree of 
particularity, it is understood that the present disclosure has been made 
by way of example, and changes in detail or structure may be made without 
departing from the spirit of the invention as defined in the appended 
claims.