Iron club head for golf

A fiber reinforcement, which can be of solid or hollow construction, and a synthetic resin back up are disposed in a recess provided on the side of the club head remote from the shooting surface. A mass can be adjustably imbedded in the synthetic resin backup so as to increase the inertial moment of the club head. A rise member extending upwardly from the sole face of the club head can also be provided so that the center of gravity can be more easily adjusted. The fiber reinforcement is relatively thin for shorter shafted golf clubs having high degrees of loft, and increases progressively to a greater thickness for longer shafted golf clubs having relatively small degrees of loft. A back plate made of a woven cloth can be provided adjacent the fiber reinforcement to aid in reinforcing the shooting surface and to withstand the tension acting across the rear of the club head upon impact. The synthetic backup can be transparent or semi-transparent to expose the esthetics of the woven cloth. Bonding tape can be provided between the fiber reinforcement and the main body and between the fiber reinforcement and the back plate to facilitate the manufacture of the club head and to minimize the shock and vibration effect caused by striking a ball.

BACKGROUND OF THE INVENTION 
The present invention relates to an improved iron club head for golf, and 
more particularly relates to an improvement in construction of an iron 
club head for golf which is provided with a fiber reinforcement attached 
in a rear recess of the shooting face. 
Two types of iron club heads for golf are presently used in practice. In 
the case of a sole-piece type, the head is wholly made of metal such as 
stainless steel, cast iron or brass. In the case of a composite type, a 
head made of metal is combined with a fiber reinforcement in particular 
made of carbon fiber reinforced plastic. 
An iron club head of the second type is proposed in Japanese Patent 
Application Sho. 60-214297. In the case of this earlier proposal, a recess 
is formed on the rear side of the shooting face of a club head, a fiber 
reinforcement is attached in the recess and a ring is force inserted into 
the recess to fix the fiber reinforcement in the recess. 
With this conventional construction, however, the process of setting the 
ring takes time and trouble, thereby seriously lowering the productivity. 
In addition, use of the ring tends to make adjustment in center of gravity 
very difficult. As a consequence, increase in inertia moment of the iron 
club head cannot be achieved easily. In addition, since a flat fiber 
reinforcement is used, distribution of weight is made quite uniform in the 
peripheral area around the center of the shooting face, i.e. the sweet 
spot, of the iron club head. Such uniform weight distribution leads to 
insufficient weight in the peripheral area and, as a consequence, increase 
in inertia moment of the iron club head cannot be achieved well. 
SUMMARY OF THE INVENTION 
The basic objects of the present invention are to raise the productivity, 
provide reinforcement for the striking surface of the club head, damping 
means for minimizing shock and vibrations, means for increasing the 
inertial moment of an iron club head for golf and adjusting the center of 
gravity of a club head. 
In accordance with the first basic aspect of the present invention, a fiber 
reinforcement is attached to a recess formed on the rear side of the 
shooting face of an iron club head and a synthetic resin backup is filled 
in the recess covering the fiber reinforcement. 
In accordance with the second basic aspect of the present invention, a 
fiber reinforcement is attached to a recess formed on the rear side of the 
shooting face of an iron club head and the thickness of the fiber 
reinforcement is larger in the peripheral region than in the central 
region. 
In accordance with another aspect of the present invention, a fiber 
reinforcement member and a back insert of chip-like carbon or aramide 
fibers are united with the main body of the golf club head by a 
transparent resin.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIGS. 1 and 2, a head main body 1 is made of, for example, stainless 
steel, cast iron or brass and has a substantially triangular transverse 
cross sectional profile so that its shooting face 2 has a prescribed loft 
angle. More specifically, when seen in the shooting direction, as in FIG. 
2, the sole face 3 is thicker than the blade side 1a. On the rear side of 
the shooting face 2, a recess 4 is formed which has a bottom 4a 
substantially parallel to the shooting face 2. A fiber reinforcement 5 is 
placed in the recess 4 in close contact with the bottom 4a of the recess 
4. The fiber reinforcement 5 is made of highly elastic material such as 
carbon fiber reinforced plastic (CFRP). Thus, the section of the head main 
body 1 supporting the shooting face 2 has a double composite construction. 
Further, a synthetic resin backup 6 is also placed in the recess 4 
covering the fiber reinforcement 5 in order to lock the latter against 
accidental fall. In production, crude synthetic resin is filled in the 
recess 4 after setting of the fiber reinforcement 5, which resin is 
subjected to proper hardening. 
The thickness of the section of the head main body 1 providing the shooting 
face 2 should preferably be in a range from 0.5 to 3.0 mm. and the 
thickness of the fiber reinforcement 5 should preferably be in a range 
from 1.0 to 5.0 mm. Thus, the weight of the head main body 1 is reduced by 
addition of the fiber reinforcement 5 which has a lower volumetric mass 
than the metals of which the main body 1 is practically comprised. 
In the case of the embodiment shown in FIG. 3, a mass 7 is embedded in the 
synthetic resin backup 6. The weight of the mass 7 substantially 
corresponds to the weight of the head main body 1 reduced by the use of 
the fiber reinforcement 5. By properly adjusting the position of the mass 
7, the inertial moment of the iron club head can be increased. 
In production of the fiber reinforcement 5, several sheets of reinforcing 
fibers are combined in layers and the layered combination is impregnated 
with solution of non-hardened synthetic resin such as unsaturated 
polyester resin for hardening. Alternatively, several thin, hardened FRP 
sheets are bonded together in layers. 
The fiber reinforcement is given in the form of two-dimensional or 
three-dimensional woven or knitted cloth. A cloth, a combination of a 
cloth with rovings, a mat or a mat combined with another cloth or cloth 
may be used. The fiber reinforcement may preferably contain, in addition 
to carbon fibers as the major component, aromatic polyamide fibers, glass 
fibers, boron fibers, silicon carbide fibers and/or alumina fibers. 
In the case of the embodiment shown in FIG. 4, the fiber reinforcement 5 
has a cavitatious or hollow construction similar in cross-section to the 
transverse cross-sectional profile of the head main body 1 so that no 
significant depression should appear on the rear face of the head main 
body 1 for aesthetic effect. 
In the case of the embodiment shown in FIG. 5, an upwardly extending rise 8 
is formed near the sole face 3 partly covering the synthetic resin backup 
6 for better adjustment of the center of gravity. The rise 8 is of a 
predetermined site, i.e., length, width and/or weight, to accomplish the 
desired adjustment on the desired club head (for longer shafted/smaller 
lofted clubs or for shorter shafted/larger lofted clubs). 
An iron club head in accordance with the second basic aspect of the present 
invention is shown in FIG. 6. Like the one shown in FIG. 2, the head main 
body has a rear recess 4 which receives a fiber reinforcement 5. One or 
more undercuts 9 are formed continuously or locally on the periphery of 
the bottom 4a of the recess 4 in engagement with the periphery 5a of the 
fiber reinforcement 5 in order to lock the latter against accidental 
separation. The fiber reinforcement 5 has a flat inner face 51 and a 
concave outer face 52. By properly adjusting the degree of concavity of 
the outer face 52, the peripheral section of the fiber reinforcement 5 is 
thicker than the central section and the distribution of weight in the 
peripheral section of the iron club head can be easily and freely adjusted 
in order to increase the inertial moment of the iron club head. 
One example of the process for producing such an iron club head is shown in 
FIGS. 7 to 9. First, a head main body 1 is fixed on a table (not shown) 
with its shooting face 2 on the underside as shown in FIG. 7. Next, a 
crude fiber reinforcement 11 is deposited on the bottom 4a of the recess 4 
and urged to fill the overhang or overhangs 9 as shown in FIG. 8. A 
presser 12 having a convex head 12a is applied to the exposed face of the 
crude fiber reinforcement 11 as shown in FIG. 9 to form the concave outer 
surface 52 shown in FIG. 6. 
An iron club head in accordance with another aspect of the present 
invention is shown in FIG. 10. This embodiment is similar to the 
embodiment shown in FIG. 5 in that it also includes an upwardly extending 
rise 8 in the configuration of the main body 1. In this embodiment, a back 
insert 20 and a back plate 21 facilitate the reinforcement of the shooting 
face 2. The thickness of the back insert 20 can be varied in accordance 
with the type of club. That is, the back insert 20 is thinner or more 
narrow for shorter shafted irons having relatively large lofts, and 
becomes progressively thicker for longer shafted irons having relatively 
small lofts. Since the relatively small loft on the longer shafted irons 
causes the application of a larger shock on the striking surface when a 
golf ball is struck therewith, the back insert 20 is required to have a 
larger thickness to reinforce the striking surface 2 against such a large 
shock. 
The back insert 20 is made from several layers of chip-like carbon or 
aramide fibers of about 1 inch in length and several layers of chip-like 
boron fibers. These layers are bonded together to form the back insert 20. 
A back insert bonding tape 22 is utilized to maintain the position of the 
back insert 20 prior to uniting the back insert 20 with the back plate 21 
by means of a synthetic resin backup 6. Similarly, a double-bonding tape 
23 is used to maintain the position of the back plate 21 with respect to 
the back insert 20 prior to the introduction and setting of the epoxy 
resin 6. Both the back insert bonding tape 22 and the double-bonding tape 
23 have adhesive on both sides such that there is no space between the 
back insert 20 and the main body 1 or between the back plate 21 and the 
back insert 20 for the resin to flow. The back plate 21 is made of a cloth 
woven from carbon fibers or aramide fibers. This is advantageous as the 
epoxy resin backup 6 is transparent or semi-transparent such that the back 
plate 21 and its texture is exposed on the rear side of the club head. 
Thus, the texture of the woven cloth of the back plate 21 provides 
aesthetic design and pleasing visual appearance of the club head when 
viewed from the rear. 
The back plate 21, being made of a woven cloth, also facilitates the 
endurance of the club head as the club head undergoes a bending moment 
when striking a golf ball. To explain, when a club head strikes a ball, 
the maximum compression force acts on the striking surface 2 whereas the 
maximum extension force acts of the rear surface of the club head. That 
is, extension occurs across the rear of the club head and compression 
occurs across the striking surface 2 of the club head, while a neutral 
axis, somewhere between the striking surface 2 and the rear of the club 
head, undergoes substantially no change insofar as compression or 
extension is concerned. Thus, the greater the distance between the back 
plate 21 and the neutral axis, the larger the tension acting across the 
rear of the club head. A woven cloth is capable of withstanding such a 
large tension especially when the longitudinal fibers in the woven cloth 
coincides with the direction of the maximum extension force acting across 
the rear surface of the club head. 
Another aspect of the present invention which is enhanced by the embodiment 
shown in FIG. 10 is that of a damping mechanism. In this embodiment, not 
only does the epoxy resin backup 6, which can be quite elastic in nature, 
absorb a considerable degree of the shock and vibration caused by striking 
a ball, but the arrangement between the back insert 20 and the back plate 
21 also facilitates the damping of such shock and vibration gradients. 
This stems from the use of the back insert bonding tape 22 and the double 
bonding tape 23. Upon striking a ball, a considerable degree of the shock 
and vibration is absorbed by the resin 6 because of the specific 
properties thereof. However, some shock and vibration gradients may 
remain. This portion of the shock and vibration caused by striking a ball 
causes small mutual displacement between the main body at the striking 
surface 2, the back insert 20 and the back plate 21. This necessarily 
leads to friction between these elements and the bonding tapes 22 and 23. 
More specifically, friction will occur between the back insert bonding 
tape and the bottom of the recess, between the back insert bonding tape 22 
and the back insert 20, between the double bonding tape 23 and the back 
insert 20, and between the double bonding tape 23 and the back plate 21. 
This friction has the advantageous effect of damping a portion of the 
shock and vibration imparted to a players hand when striking a ball. 
I should also be noted that the resiliency of the epoxy resin 6 ensures 
that no cracks are developed at the interfaces between the main body at 
the striking surface, the back insert 20, the back plate 21, the back 
insert bonding tape 22 and the double bonding tape 23. 
Thus, while the foregoing description and figures illustrate some preferred 
embodiments of the improved iron club head in accordance with the present 
invention, it should be appreciated that certain modifications, including 
the interchangeability of the various features from the various 
embodiments, could be made and are encouraged to be made in the materials 
and techniques of the disclosed embodiment without departing from the 
spirit and scope of the present invention which is intended to be captured 
by the claims set forth immediately below.