Patent Application
20050159239
1. Field of the Invention
The present invention relates to a hollow golf club head, and particularly to a golf club head being of a wood type or similar type thereto.
2. Description of the Related Art
As wood-type golf club heads such as drivers and fairway woods, metallic heads of a hollow shell structure are widely in use. Generally, the hollow wood-type golf club head has a face portion for hitting a ball, a crown portion constituting an upper surface portion of the golf club head, a sole portion constituting a bottom surface portion of the golf club head, a side portion constituting side surface portions on the tow side, the rear side, and the heel side of the golf club head, and a hosel portion. A shaft is inserted into the hosel portion, and is fixed by an adhesive agent or the like. It should be noted that golf clubs called utility clubs are also commercially available on the market in large numbers, and various golf clubs having a head similar to the aforementioned wood-type golf club head (i.e., having the face portion, the sole portion, the side portion, the crown portion, and the hosel portion) are also commercially available on the market.
As metals for forming this hollow golf club head, an aluminum alloy, stainless steel, and a titanium alloy are used. The titanium alloy, in particular, has come to be used widely in recent years.
In JP-A-2002-11122 and JP-A-2002-224249, the hollow golf club head in which the face portion is made of an amorphous alloy such as zirconium group, and the other portions are metallic was described. In these patents, it was described that the face portion made of an amorphous alloy is useful to increase the carry.
Generally, it becomes possible to enlarge the sweet spot by increasing the volume of the hollow golf club head. If the volume is increased, the weight of the golf club head tens to increase correspondingly. Accordingly, to prevent an increase in the weight, it has been conceived to adopt a fiber reinforced plastic whose specific gravity is smaller than those metals.
JP-A-2001-340499 discloses a golf club head in which a face portion and a sole portion are made of a metal, and the other portions including a crown portion and side portions on the tow side and the heel side are formed of a carbon-fiber reinforced thermosetting plastic (CFRP). If the crown portion is made of CFRP, the flexure of the crown portion becomes large during ball hitting, so that it is possible to make the launch angle large, and increase a coefficient of restitution. With this golf club head, however, the seam between a peripheral edge of the face portion, on the one hand, and the crown portion and the side portion formed of CFRP, on the other hand, is in an abutted state. During ball hitting an extremely large stress occurs in this seam between the peripheral edge of the face portion and the crown portion and the side portion. If the golf club head is used repeatedly, this joint portion is likely to peel off.
In the U.S. Pat. No. 6,471,604, a golf club head is described in which the crown front edge portion, the sole front edge portion, and both the side front edge portions are made to be a return portion made of an amorphous alloy, the face plane is a face plate made of an amorphous alloy, a latter half body (aft body) made of resin material is connected to lead to the return portion, and an aluminum plate is disposed on the sole portion.
A first object of the invention is to provide a golf club head that is easily designed in terms of a position of a center of gravity.
The golf club head as disclosed in U.S. Pat. No. 6,471,604 has a small flexure on the sole side when hitting the ball, because the aluminum plate on the sole portion leads directly to the bottom of the return portion. A second object of the invention is to provide a golf club head having a large flexure on the sole side when hitting the ball, and a large restitution coefficient.
To achieve the above objects, according to one aspect of the invention, there is provided a golf club head of a hollow shell structure, including: a first member that includes an amorphous metal material and includes a hosel portion, a face portion and an edge portion continuous with the face portion; a metal plate that is different member from the first member, extends in a direction, which is different from a toe-heel direction of the golf club head, and includes at least a part of sole portion; and a second member formed of a fiber reinforced 20% to 70% of weight of the golf club head.
According to another aspect of the invention, there is provided a golf club head of a hollow shell structure, including: a first member that includes an amorphous metal material and includes a face portion and an edge portion continuous with the face portion; a metal plate that is different member from the first member, extends in a direction, which is different from a toe-heel direction of the golf club head, and includes at least a part of sole portion; and a second member formed of a fiber reinforced plastic, wherein the first member and the metal plate are apart from each other, and the second member joints the first member with the metal plate.
In the golf club head of the invention, the weight of the first member is in a range of 20% to 70% of the weight of the golf club head. Since the second member is made of the fiber reinforced plastic, which has the significantly smaller specific gravity than that of metal, a weight other than the first member can be allocated to the metal plate and a weight member disposed on the metal plate. Thereby, the golf club head can be easily designed to have a center of gravity at lower position or on a rear side, and so on as desired.
In the golf club head of the invention, a portion between the first member made of amorphous metal and the metal plate is flexed when hitting a ball, whereby the coefficient of restitution is great and a carry of the ball is increased.
Preferably, the portion of the second member between the first member and the metal plate recesses from the metal plate and a bottom surface of the first member. By virtue of this arrangement, even if a sole surface of the golf club head strongly strikes the ground, the portion is difficult to become damaged.
Since the second member is fixed on the edge portion in a superposed state, the first member and the second member can be firmly fixed together.
Since a back face of the first member is lined with the fiber reinforced plastic, the first member can be reinforced or made less flexible.
Preferably, widths of a crown portion and a sole portion of the first body are larger on a toe side and a heel side than those of a central portion between these portions. By virtue of this arrangement, the moment of inertia of the golf club hear can be made large.
The invention is suitable for application to a large-size driver head whose weight needs to be suppressed to 180 g -210 g or thereabouts, although its volume is large in a range of 300 cc-500 cc.
Hereafter, a description will be given on an embodiment of the invention with reference to the drawings.
This golf club head 1 is a wood-type golf club head of a hollow shell structure including a face portion 2, a sole portion 3, a side portion 4, a crown portion 5, and a hosel portion 6.
The face portion 2 is a surface for hitting a ball, and is provided with grooves (scoring lines), which are not shown. The sole portion 3 constitutes a bottom portion of the golf club head. The side portion 4 constitutes side surface portions on the toe side, the heel side, and the rear surface side. The crown portion 5 constitutes an upper surface portion of the golf club head. A shaft is inserted into the hosel portion 6, and is secured by means of an adhesive agent.
This golf club head 1 includes a front body 10 formed of an amorphous metal material, a fiber reinforced plastic body (hereinafter referred to as the FRP body) 20, a metallic sole plate 30, and a weight member 40. The weight of this front body 10 is preferably in a range of 20% to 70%, especially 30% to 60% of the total weight of the golf club head.
As shown in
The metal sole portion 13 constitutes a front edge portion of the sole portion 3. The metal side portions 14 and 16 constitute front edge portions of the side portion 4. The metal crown portion 15 constitutes a front edge portion of the crown portion 5. The metal crown portion 15 is continuous with the metal side portion (toe) 14 and the metal side portion (heel) 16. The metal side portion (toe) 14 and the metal side portion (heel) 16 are respectively continuous with the metal sole portion 13. The metal side portions 14 and 16 and the metal sole portion 13 are continuous with the face portion 2.
As for the metal sole portion 13 and the metal crown portion 15, widths in the forward and rearward direction (widths in a direction perpendicular to the face portion 2) are large on the tow side and the heel side, and their widths in the forward and rearward direction in the remaining central portions 13a and 15a are small. As a result, the moment of inertia of the golf club head can be made large. It should be noted that these widths in the forward and rearward direction are made gradually smaller from the toe side and the heel side toward the central portions 13a and 15a.
The length in the toe-heel direction of the center portions 13a and 15a having small widths in the forward and rearward direction is preferably 50%-85% of the maximum width of the front body 10 in the crown portion, and is preferably 55%-80% of the maximum width of the front body 10 in the sole portion.
The width of the central portion 15a of the metal crown portion 15 in the forward and rearward direction is preferably 50%-95%, particularly 55%-70% of the maximum width of the front body 10 in the forward and rearward direction, while the width of the central portion 13a of the metal sole portion 13 in the forward and rearward direction is preferably 50%-95%, particularly 55%-65% of the maximum width of the front body 10 in the forward and rearward direction.
A gap of 4 mm-12 mm, particularly 7 mm-9 mm is formed on an average between a front side 31 of the sole plate 30 and the metal sole portion 13, as clearly shown in
A rear side 34 of the sole plate 30 is located in proximity to a rearmost portion of the golf club head 1, but is located slightly forwardly of the rearmost end of the golf club head 1.
The sole plate 30 is disposed in a whole area in the vicinity of the central portion, in the toe-heel direction, of the metal sole portion 13. As shown in
The length of the front side 31 of the sole plate 30 is preferably 50%-75%, particularly 60%-75% of the length in the toe-heel direction of the central portion 13a of the metal sole portion 13. The length of the rear side 34 is preferably 50%-80%, particularly 55%-75% of the length of that front side 31.
The length of the sole plate 30 in the forward and rearward direction is preferably 65%-90%, particularly 75%-85% of the maximum length of the golf club head 1 in the forward and rearward direction.
This sole plate 30 is formed of a metal material such as stainless steel, aluminum, a copper alloy, a titanium alloy, or the like.
A cylindrical portion 35 protrudes in a rear portion of this sole plate 30 toward the interior of the golf club head 1. The weight member 40 is secured in an inner hole of the cylindrical portion 35 by screwing-in.
The weight member 40 is formed with a flange portion 41 on a lower end thereof. The cylindrical portion 35 is formed with a stepped portion 35a for receiving the flange portion 41 at a lower edge thereof.
The sole plate 30 is slightly depressed around the periphery of the cylindrical portion 35.
The weight member 40 is formed of a metal whose specific gravity is greater than that of the sole plate 30, such as tungsten or a tungsten alloy. The specific gravity of the weight member 40 is preferably 10 or more, particularly in a range of 10 to 13. The central position of the weight member 40 is located on a rear portion side of a center of the golf club head 1 in the forward and rearward direction.
Next, a description will be given on a method for manufacturing the golf club head according to the embodiment of the invention.
To manufacture this golf club head 1, the metallic front body 10, the sole plate 30, and a plurality of prepreg sheets are used. A connecting face between the front body 10 and the FRP body 20 is desirably treated by blasting or spray coating to enhance the connectivity.
The prepreg sheet 51 is directly superposed on the sole plate 30, and has a substantially trapezoidal shape, which is slightly larger than the sole plate 30.
The prepreg sheets 52, 53 and 54 are directly superposed on the prepreg sheet 51 in that order. In order to constitute the lower half of the FRP body 20, each of these prepreg sheets 52 to 54 has such a size that the lower half of the FRP body 20 is developed. A plurality of slits 55 are cut in both sides and rear edges of these prepreg sheets 52 to 54 at predetermined intervals, so that the sides and the rear edges of the prepreg sheets 52 to 54 are easily curved along the inner surface of a molding die.
In the case of the prepreg sheet 52, the carbon fibers are oriented in the toe-heel direction. In the case of the prepreg sheet 53, the carbon fibers are oriented obliquely to the toe-heel direction 60° clockwise. In the case of the prepreg sheet 54, the carbon fibers are oriented obliquely to the toe-heel direction 60° counterclockwise.
The prepreg sheet 60 is used for constituting the upper surface side of the FRP body 20 and is formed with a substantially semicircular notched portion 61, with which the hosel portion 6 engages.
In manufacturing of the golf club head 1, the sole plate 30 is first fitted in the die having a cavity surface conforming to the sole and sides. The prepreg sheets 51 to 54 are superposed in that order. Then, these prepreg sheets 51 to 54 are semihardened on heating for a short time, so as to be formed into the shape of a sole portion 22 of the FRP body 20 and to be integrated with the sole plate 30, as shown in
The prepreg sheet 60 is also fitted in the die having a cavity surface conforming to the crown portion, and is semihardened on heating for a short time, so as to be formed into the shape of a crown portion 21 of the FRP body 20, as shown in
Subsequently, the prepreg sheet 60, the prepreg sheets 51 to 54 with the sole plate and the metallic front body 10 are 1.
At this time, the front edge of the crown portion 21 formed of the prepreg sheet 60 is superposed on the lower surface of the metal crown portion 15 (inner side surface of the head). In addition, the front edge of the sole portion 22 formed of the prepreg sheets 51 to 54 is superposed on the upper surface of the metal sole portion 13 (inner side surface of the head). It should be noted that the front edge of the sole portion 22 projects forwardly of the front side 31 of the sole plate 30, and the rear edge of the sole portion 22 projects rearwardly of the rear side 34 of the sole plate 30, as shown in
Next, the molding die is heated, and gas pressure of air or the like is introduced into the molding die through the cylindrical portion 35. This causes the crown portion 21 and the sole portion 22 formed of the semihardened prepreg sheets to be pressed against the inner surface of the molding die, the prepreg sheets to become fully hardened, the crown portion 21 and the sole portion 22 to be secured to the front body 10, and the crown portion 21 and the sole portion 22 to be joined together.
During this molding, part of the synthetic resin in the prepreg sheets enters the gap between the metal sole portion 13 and the sole plate 30, and the recessed portion in which the FRP body 20 is curved in the arch shape is formed, as shown in
Subsequently, the molded piece is released, the weight member 40 is threadedly secured to the cylindrical portion 35, and finishing such as deburring and coating is performed to form the product golf club head.
With the golf club head thus constructed, since all the portions continuous with the front body 10, including the portion between the front body 10 and the sole plate 30, are formed of FRP, the head can be easily flexed and have high repulsion during ball hitting. At the same time, the center of gravity can be made deep. In particular, in this embodiment, since the crown portion of the FRP body 20 is easily flexed, the launch angle can be made large, and the flight distance can be increased.
Since the FRP body 20 is superposed and fixed on the inner face of the metal sole portion 13, the metal crown portion 15 and the metal side portion 14 of the front body 10, the connection strength between the front body 10 and the FRP body 20 is high. The foremost edge of the FRP body 20 is preferable to contact with the face portion 2.
In this invention, the amorphous metal material is not specifically limited in its composition, as long as it has a supercooling liquid zone, and can form an amorphous phase. Hence, various amorphous metal materials can be employed, but preferably have the composition represented by the general formula of MaXb (a and b are atom %, 65≦a≦100, 0≦b≦35).
Herein, M is al least one selected from the group consisting of Zr, V, Cr, Mn, Fe, Co, Ni, Cu, Ti, Mo, W, Ca, Li, Mg, Si, Al, Pd, and Be, and X is at least one selected from the group consisting of Y, La, Ce, Sm, Md, Hf, Nb, TaAg, Pt, Au, and Pd. Particularly, a Zr-based amorphous alloy (having the greatest atom % of Zr) is desirable. With the Zr-based amorphous alloy, the amorphous structure is relatively easily produced, even if the cooling speed is reduced. The amorphous alloy is not necessarily composed of a single phase of a pure amorphous alloy, but may contain from several vol % to several tens vol % of micro-crystalline or quasi-crystalline phase that can be produced under the manufacturing conditions or heat treatment for an amorphous alloy.
The amorphous alloy is more prone to crack beyond an elastic limit, as the non-crystallinity is higher. Thus, to suppress the flexure at the time of batting the ball, it is preferable to dispose the fiber reinforced plastic layer on the back face of the face portion 2 as well, as shown in
The other constitution of
The non-crystallinity of an amorphous alloy is from 75%-100%, or preferably from 80%-98%, at least on the face portion. If the crystallinity is lower than 75%, there is a fear that the strength of the face portion may be insufficient. If the crystalline phase exists in a part of amorphous metal, the plastic deformation is allowed, whereby the amorphous metal is superior in terms of the workability and strength.
In a golf club having the golf club head of the embodiment that is manufactured by way of trial using a zirconia-based amorphous alloy, a center of a face was batted at a ball speed of 40 m/s, 500 shots, using two piece of golf ball, whereby strength evaluation was conducted.
Thickness of face was 3 mm. Also, workability evaluation for the amorphous metal was conducted based on whether the polishing is easy or not.
As a result, it was found that if the non-crystallinity is 75% or more, especially 80%, strength of the amorphous metal in the head is sufficiently high. Also, it was found that the workability is sufficiently excellent if the non-crystallinity is 60% or more, and remarkably excellent if it is 98% or less.
It is preferred that an amorphous alloy making a face portion in the embodiment has lower Young's modulus than that of a titanium alloy, and has a breakdown characteristic equal to or stronger than that of the titanium alloy.
By making a face portion A with the amorphous alloy having the breakdown characteristic equal to or stronger than that of the titanium alloy, it is possible to configure a thickness of the face portion A in a range of 2.3 mm to 2.9 mm. Moreover, by making the face portion A with the amorphous alloy having Young's modulus in a range of 7000 kgf/mm2 to 9000 kgf/mm2, preferably 7200 kgf/mm2 to 8500 kgf/mm2, the face portion A becomes flexible when hitting a ball, and make an initial velocity of the ball faster even the thickness of the face portion A is equal to that of a face portion B made of titanium alloy.
However, when the thickness of the face portion A is configured to be 2.6 mm and Young's modulus thereof is 5000 kgf/mm2, it is too flexible that the initial velocity of the ball becomes slower than that when hitting the ball with the face portion B made of the titanium alloy.
The breakdown characteristic of the amorphous alloy is preferably equal to or stronger than that of a common titanium alloy (Ti-6Al-4V). If the breakdown characteristic of the amorphous alloy is lower than that of the common titanium alloy, the thickness of the face portion A needs to be thicker so that a flexure of the face portion A can not be fully used when hitting the ball even Young's modulus of the amorphous alloy is set lower than that of the common titanium alloy. Correspondingly, the initial velocity of the ball cannot be faster. Therefore, the equal to or more than 80 kgf/mm2, especially in a range of 100 kgf/mm2 to 160 kgf/mm2.
A thickness of a central portion of the face portion A is configured to be in a range of 2.3 mm to 2.9 mm, a thickness of a peripheral portion of the face portion A connecting to a crown portion and the sole portion is configured to be in a range of 1.3 mm to 1.6 mm so as to be the thinnest portion in the face portion A. By this configuration, strength of a hitting portion becomes stronger and a repulsive force becomes larger. The peripheral portion of the face portion A is preferably in a range of 0.5 mm to 5 mm.
Herein, comparative experiments are conducted with three materials. Material I is employed in the embodiment. Material II and III are comparative examples.
The result of a comparison, a carry of a ball is longest when the ball was hit by a golf club head having a face portion made of Material I. And a carry of the ball is shortest when the ball was hit by a golf club head having a face portion made of Material II.
The foregoing description of preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2003-375836 | Nov 2003 | JP | national |
