KR102606404B1 - Iron golf club - Google Patents

Abstract

[Project] Provision of an iron golf club that has a high head-shaft compatibility and good ball capture.
[Solution] The iron golf club 2 has a head 4, a shaft 6, and a grip 8. The head center of gravity distance, which is the distance between the center of gravity (Gh) of the head 4 and the axis (Z) of the shaft 6, is set to Db (mm), and the shaft torque of the shaft 6 is set to Ts (°). . At this time, Db is 37 mm or more. Also, Ts is less than 4.0°. Additionally, Db/Ts is 9.7 or higher. This iron golf club (2) has good grip and excellent distance performance.

Description

Iron Golf Club{IRON GOLF CLUB}

The present invention relates to iron golf clubs.

Iron golf clubs differ from wood golf clubs in many respects. Iron shafts are used for irons. Japanese Patent No. 5439259 discloses a shaft set used in an iron set. In this shaft set, the bending rigidity of the shaft is changed for each turn.

Japanese Patent No. 5439259

As a result of the present inventor's intensive study, new knowledge was obtained regarding the compatibility of the iron head and shaft.

The purpose of the present invention is to provide an iron golf club that has high head-shaft compatibility and good ball capture.

In one aspect, this iron golf club has a head, shaft, and grip. The head center of gravity distance, which is the distance between the center of gravity of the head and the axis of the shaft, is Db (mm). The shaft torque of the shaft is Ts (°). Db may be 37 mm or more. Ts may be less than 4.0°. Db/Ts may be 9.7 or higher.

The distance from the center of gravity of the shaft to the tip end of the shaft is Lg, and the length of the shaft is Ls. In another aspect, Lg/Ls may be 0.50 or more.

The club weight is in Wc (grams) and the club length is in Lc (meters). In another aspect, Wc × Lc may be 360 (g·m) or less.

In another aspect, the shaft may be formed of a plurality of fiber reinforced layers. The shaft may have a tip bias layer and a butt bias layer.

An iron golf club with excellent shaft and head compatibility and good ball capture can be obtained.

1 shows a golf club according to one embodiment.
Figure 2 is a front view of the head.
Figure 3 is an exploded view showing an example of a stacked configuration of a shaft.
Fig. 4 is a schematic diagram showing a method for measuring shaft torque.

Hereinafter, preferred embodiments are described in detail, with appropriate reference to the drawings.

1 shows a golf club 2 according to one embodiment. Club (2) is an iron golf club. The loft angle of an iron golf club is usually 15 degrees or more and 70 degrees or less. In addition, in this application, the loft angle means the real loft angle. The real loft angle is the loft angle with respect to the shaft axis.

The golf club 2 has a head 4, a shaft 6, and a grip 8. A head 4 is mounted on the distal end of the shaft 6. Head 4 is an iron-type golf club head. A grip (8) is mounted on the rear end of the shaft (6).

The shaft 6 has a tip end (Tp), a butt end (Bt), a shaft length (Ls), and a shaft center of gravity (Gs). The shaft center of gravity (Gs) is the center of gravity of the shaft (6) alone. In Fig. 1, indicated by the positive arrow Lg is the distance from the tip end Tp to the shaft center of gravity Gs. The shaft length (Ls) and distance (Lg) are measured along the axis (Z) of the shaft (6).

The shaft length (Ls) of the iron shaft is usually 860 mm or more and 991 mm or less.

Fig. 2 is a view of the head 4 viewed from the front of the striking surface. The head 4 has a sole 10, a striking surface 12, and a hosel 14. The hosel 14 has a hosel hole 16. A score line (gv) is formed on the hitting surface 12. Except for the score line (gv), the hitting surface 12 is flat.

The head 4 has a center of gravity Gh. The head center of gravity Gh is the center of gravity of the head 4 alone. The striking surface 12 has a sweet spot (SS). The sweet spot (SS) is the intersection point of the striking surface 12 with a straight line that passes through the head center of gravity Gh and is perpendicular to the striking surface 12. In Figure 2, the sweet spot (SS) and the head center of gravity (Gh) overlap.

Herein, the head center of gravity distance is defined. The head center of gravity distance is the distance between the shaft axis (Z) and the head center of gravity (Gh) in front view. Front vision means a projection projected onto a plane parallel to the face plane. This projection surface is placed in front of the face surface. The direction of this projection is perpendicular to the face plane. Figure 2 is a front view of the head 4. This head center of gravity distance (Db) is shown in FIG. 2. Additionally, the shaft axis Z coincides with the center line of the hosel hole 16.

Herein, shaft torque is defined. Shaft torque is an index indicating the torsional rigidity of the shaft 6. Herein, shaft torque is denoted by Ts. The method of measuring shaft torque is described later.

The shaft 6 is a so-called carbon shaft. Preferably, the shaft 6 is formed by curing a prepreg sheet. In this prepreg sheet, the fibers are substantially oriented in one direction. A prepreg in which the fibers are substantially oriented in one direction in this way is also called a UD prepreg. “UD” is an abbreviation for unidirection. Prepregs other than UD prepreg may be used. For example, the fibers contained in the prepreg sheet may be woven.

The prepreg sheet contains fibers and resin. This resin is also called matrix resin. Typically, this fiber is carbon fiber. Typically, this matrix resin is a thermosetting resin.

The shaft 6 is manufactured by the so-called sheet winding manufacturing method. In the prepreg, the matrix resin is in a semi-cured state. The shaft 6 is formed by winding and curing a prepreg sheet.

As the matrix resin of the prepreg sheet, in addition to epoxy resin, thermosetting resin or thermoplastic resin other than epoxy resin can also be used. From the viewpoint of shaft strength, the matrix resin is preferably an epoxy resin.

Hereinafter, details of the configuration of the shaft 6 are explained.

Figure 3 is an example of an exploded view (laminated configuration diagram) of the prepreg sheet constituting the shaft 6.

The shaft 6 is comprised of a plurality of sheets. The shaft 6 is comprised of 12 sheets from the first sheet s1 to the twelfth sheet s12. This development diagram shows the sheets constituting the shaft in order from the radial inner side of the shaft. These sheets are wound in order, starting from the sheet located on the upper side in the developed view. In this developed view, the left and right directions of the drawing coincide with the axial direction of the shaft. In this developed view, the right side of the drawing is the tip end (Tp) side of the shaft. In this developed view, the left side of the drawing is the butt end (Bt) side of the shaft.

This development diagram shows not only the winding order of each sheet, but also the arrangement of each sheet in the shaft axis direction. For example, in FIG. 3, the end of the ninth sheet s9 is located at the tip end Tp. For example, in FIG. 3, the end of the fifth sheet s5 is located at the butt end Bt.

In this application, the phrases “layer” and “sheet” are used. “Layer” is a title after being wound. In contrast, “seat” is a title used before being wound. A “layer” is formed by winding a “sheet.” In other words, the wound “sheet” forms a “layer.” Additionally, in this application, the same symbols are used for layers and sheets. For example, the layer formed by the sheet s1 is the layer s1.

The shaft 6 has a straight layer, a bias layer, and a hoop layer. In the development diagram of the present application, the orientation angle (θf) of the fiber is written on each sheet. This orientation angle (θf) is an angle with respect to the shaft axis direction.

The shaft 6 has six layers of bias layers. These bias layers constitute a set of three bias layers. That is, the embodiment in FIG. 3 has a first bias layer set (b1), a second bias layer set (b2), and a third bias layer set (b3).

The first bias layer set (b1) is composed of a bias layer (s1) and a bias layer (s2). Between the bias layer (s1) and the bias layer (s2), the fibers are inclined in opposite directions to each other. The second bias layer set (b2) is composed of a bias layer (s3) and a bias layer (s4). Between the bias layer (s3) and the bias layer (s4), the fibers are inclined in opposite directions to each other. The third bias layer set (b3) is composed of a bias layer (s10) and a bias layer (s11). Between the bias layer (s10) and the bias layer (s11), the fibers are inclined in opposite directions to each other.

The sheet described as “0°” constitutes the straight layer. The sheets that make up the straight layer are also called straight sheets.

The straight layer is a layer in which the angle (θf) is substantially 0°. Due to errors during winding, etc., the angle θf is usually not completely 0°.

Typically, in a straight layer, the absolute angle (θa) is 10° or less. The absolute angle (θa) is the absolute value of the orientation angle (θf). For example, the absolute angle θa is 10° or less, meaning that the angle θf is between -10° and +10°.

In the embodiment of Fig. 3, the straight sheets are sheet s5, sheet s6, sheet s8, sheet s9, and sheet s12.

The bias layer has a high correlation with the torsional rigidity and torsional strength of the shaft. Preferably, the bias sheet includes two sheets where the orientation of the fibers is inclined in opposite directions to each other. From the viewpoint of torsional rigidity, the absolute angle (θa) of the bias layer is preferably 15° or more, more preferably 25° or more, and even more preferably 40° or more. From the viewpoint of torsional rigidity and bending rigidity, the absolute angle (θa) of the bias layer is preferably 60° or less, and more preferably 50° or less.

As described above, in Fig. 3, the angle θf is described for each sheet. The fiber inclination angles of the bias sheet (s1) and bias sheet (s2) constituting the first bias layer set (b1) are opposite to each other. Plus (+) and minus (-) in the angle (θf) indicate that the fibers of the bias sheet are inclined in opposite directions to each other. The same applies to the second bias layer set (b2) and the third bias layer set (b3).

As indicated by the two slanted lines in FIG. 3, the tilt direction of the fibers of the sheet s2 is equal to the tilt direction of the fibers of the sheet s1. However, the sheet s2 is turned over and attached to the sheet s1. As a result, the angle θf of the sheet s1 and the angle θf of the sheet s2 become opposite to each other.

The shaft 6 has a hoop layer. In the shaft 6, the hoop layer is layer s7. In the shaft 6, the sheet constituting the hoop layer is the seventh sheet s7. The sheet constituting the hoop layer is also called a hoop sheet. The hoop layer is preferably a carbon fiber reinforced layer.

Preferably, the absolute angle θa in the hoop layer is substantially 90° with respect to the shaft axis. However, due to errors during winding, etc., the orientation of the fibers may not be completely 90° with respect to the shaft axis direction. Typically, in the hoop layer, the angle θf is between -90° and -80° or below, or between 80° and 90°. In other words, usually in the hoop layer, the absolute angle (θa) is 80° or more and 90° or less.

The number of plies (number of turns) of one sheet is not limited. For example, when the number of plies of a sheet is 1, the sheet is wound one turn in the circumferential direction. For example, when the number of plies of a sheet is 2, the sheet is wound for 2 turns in the circumferential direction. For example, when the number of plies of a sheet is 1.5, the sheet is wound 1.5 times in the circumferential direction. When the number of plies of the sheet is 1.5, the sheet forms one layer at the circumferential position of 0 to 180° and two layers at the circumferential position of 180° to 360°.

Although not shown, the prepreg sheet before use is sandwiched between cover sheets. Typically, this cover sheet is a release paper and a resin film. The prepreg sheet before use is sandwiched between release paper and a resin film. A release paper is pasted on one side of the prepreg sheet, and a resin film is pasted on the other side of the prepreg sheet. Hereinafter, the surface to which the release paper is affixed is also referred to as the “release paper side surface”, and the surface to which the resin film is affixed is also referred to as the “film side surface.”

The developed view of the present application is a drawing in which the surface on the film side is the front side. That is, in FIG. 3, the front side of the drawing is the film side surface, and the back side of the drawing is the release paper side surface.

To wind a prepreg sheet, first, the resin film is peeled off. When the resin film is peeled off, the surface on the film side is exposed. This exposed surface has tackiness (adhesiveness). This tackiness results from the matrix resin. That is, because this matrix resin is in a semi-cured state, adhesiveness is developed. The edge portion of the surface on the exposed film side is also called the winding start edge portion. Next, the winding start edge portion is attached to the winding object. Due to the adhesiveness of the matrix resin, the attachment of the winding start edge portion can be performed smoothly. The winding object is a winding product formed by a mandrel or another prepreg sheet wound around a mandrel. Next, the release paper is peeled off. Next, the winding object is rotated, and the prepreg sheet is wound around the winding object. In this way, after the resin film is peeled off and the winding start edge portion is attached to the winding object, the release paper is peeled off. By this procedure, wrinkles and winding defects in the sheet are suppressed. This is because the sheet to which the release paper is attached does not wrinkle easily because it is supported by the release paper. Release paper has high bending rigidity compared to a resin film.

In the embodiment of Fig. 3, some of the sheets become composite sheets. The bias sheet is wound in the state of a composite sheet. A composite sheet is formed by joining two or more sheets together. The first bias layer set (b1) is a composite sheet in which the sheet (s1) and the sheet (s2) are combined. The second bias layer set (b2) is a composite sheet in which the sheets s3 and s4 are combined. The third bias layer set (b3) is a composite sheet in which the sheet (s10) and the sheet (s11) are combined.

As described above, depending on the orientation angle of the fibers, sheets and layers are classified. Additionally, depending on the axial length, sheets and layers are classified.

In this application, a layer disposed approximately throughout the axial direction is referred to as a full-length layer. In this application, a sheet disposed approximately throughout the axial direction is referred to as a full-length sheet. The wound full-length sheet forms a full-length layer.

The area from a point 20 mm away from the tip end Tp in the axial direction to the tip end Tp is the first area. Additionally, the area from a point 100 mm away from the butt end Bt in the axial direction to the butt end Bt is the second area. The influence of the first region and the second region on the performance of the shaft is limited. From this point of view, the full-length sheet does not need to be present in the first area and the second area. Preferably, the full length sheet extends from the tip end (Tp) to the butt end (Bt). In other words, the full-length sheet is preferably disposed throughout the shaft axis direction.

In this application, a layer partially disposed in the shaft axis direction is referred to as a partial layer. In this application, a sheet partially disposed in the shaft axis direction is referred to as a partial sheet. The wound partial sheets form a partial layer. The axial length of the partial sheet is shorter than the axial length of the full-length sheet. Preferably, the axial length of the partial sheet is less than half the total length of the shaft.

In this application, the full-length layer, which is a straight layer, is referred to as a full-length straight layer. In the embodiment of Figure 3, the full-length straight layers are layer (s6) and layer (s8). The full-length straight sheets are sheet s6 and sheet s8. The full-length straight layer is preferably a carbon fiber reinforced layer.

In this application, the full-length layer, which is a bias layer, is referred to as a full-length bias layer. In the embodiment of Figure 3, the full-length bias layers are layer (s1) and layer (s2). The full-length bias layer is preferably a carbon fiber reinforced layer.

In this application, the full-length layer, which is a hoop layer, is referred to as a full-length hoop layer. In the embodiment of Figure 3, the full length hoop layer is layer s7.

In this application, a partial layer that is a straight layer is referred to as a partial straight layer. In the embodiment of Figure 3, the partially straight layers are layer s5, layer s9, and layer s12.

In this application, the partial layer that is the bias layer is referred to as the partial bias layer. In the embodiment of Figure 3, the partial bias layers are layer s3, layer s4, layer s10, and layer s11.

In this application, the term butt sublayer is used. As this butt partial layer, a butt partial straight layer can be mentioned. In the embodiment of Figure 3, the butt portion straight layer is layer s5.

Another butt partial layer may be a butt partial bias layer. In the embodiment of Figure 3, the butt portion bias layers are layer s3 and layer s4. As described above, these layers (s3) and (s4) constitute the second bias layer set (b2). The butt portion bias layer is preferably a carbon fiber reinforced layer.

The axial distance between the butt partial layer (butt partial sheet) and the butt end (Bt) is preferably 100 mm or less, more preferably 50 mm or less, and more preferably 0 mm. In this embodiment, this distance is 0 mm for all butt sublayers.

In this application, the term tip partial layer is used. Examples of this tip partial layer include a tip partial straight layer and a tip partial bias layer. In the embodiment of Figure 3, the tip portion straight layers are layer s9 and layer s12. The tip portion bias layers are layer (s10) and layer (s11). As described above, these layers (s10) and (s11) constitute the third bias layer set (b3). The tip portion bias layer is preferably a carbon fiber reinforced layer.

The axial distance between the tip partial layer (tip partial sheet) and the tip edge (Tp) is preferably 40 mm or less, more preferably 30 mm or less, more preferably 20 mm or less, and more preferably 0 mm. In this embodiment, for all tip sublayers, this distance is 0 mm.

[2. [Outline of the shaft manufacturing process]

The outline of the shaft manufacturing process is as follows.

(1) Foundation process

In the cutting process, the prepreg sheet is cut into the desired shape. Through this process, each sheet shown in FIG. 3 is cut out.

Cutting may be done using a cutting machine. Cutting may be done manually. For manual work, for example, a cutter knife is used.

(2) Bonding process

In the bonding process, the above-described composite sheet is produced.

In the bonding process, heating or pressing may be used. More preferably, heating and pressing are used together. In the winding process described later, during the winding operation of the composite sheet, misalignment between sheets may occur. This deviation reduces winding precision. Heating and pressing improve the adhesion between sheets. Heating and pressing suppress misalignment between sheets during the winding process.

(3) Winding process

In the winding process, a mandrel is prepared. A typical mandrel is made of metal. A release agent is applied to this mandrel. Additionally, an adhesive resin is applied to this mandrel. This resin is also called tacking resin. On this mandrel, the cut sheet is wound. This tacking resin makes it easy to attach the sheet edge to the mandrel.

The sheets are wound in the order described in the development diagram. The sheet on the upper side in the developed view is wound first. The sheets involved in the above bonding are wound in the state of joined sheets.

Through this winding process, a wound body is obtained. This wound body is made up of a prepreg sheet wound around the outside of a mandrel. Winding is achieved, for example, by rolling the object to be wound on a flat surface. This winding may be done manually or by a machine. This machine is called a rolling machine.

(4) Tape wrapping process

In the tape wrapping process, a tape is wound around the outer peripheral surface of the winding body. This tape is also called a wrapping tape. This tape is wound while tension is applied. Pressure is applied to the wound body by this tape. This pressure reduces voids.

(5) Curing process

In the curing process, the wound body after tape wrapping is heated. By this heating, the matrix resin hardens. During this curing process, the matrix resin is temporarily fluidized. By fluidizing this matrix resin, air between sheets or within the sheets can be discharged. The discharge of this air is promoted by the pressure (fastening force) of the wrapping tape. Through this curing, a cured laminate is obtained.

(6) Mandrel drawing process and wrapping tape removal process

After the curing process, the mandrel drawing process and the wrapping tape removal process are performed. From the viewpoint of improving the efficiency of the wrapping tape removal process, it is preferable that the wrapping tape removal process is performed after the mandrel drawing process.

(7) Both ends cut process

In this process, both ends of the cured laminate are cut. By this cut, the cross section of the tip end Tp and the cross section of the butt end Bt become flat.

In addition, in order to facilitate understanding, in the developed drawing of this application, the sheet size after cutting both ends is shown. In reality, cuts at both ends are considered in the dimensions at the time of cutting. That is, in reality, the dimensions of the portion where both ends are cut are added and cutting is performed.

(8) Polishing process

In this process, the surface of the cured laminate is polished. Spiral irregularities exist on the surface of the cured laminate. These irregularities are traces of the wrapping tape. By polishing, these irregularities disappear and the surface becomes smooth. Preferably, in the polishing process, overall polishing and tip portion polishing are performed.

(9) Painting process

The cured laminate after the polishing process is painted.

Through the above-described processes, the shaft 6 is obtained.

[3. [Relationship between head center of gravity distance (Db) and shaft torque (Ts)]

In the head 4, the head center of gravity distance Db is 37 mm or more. As the head center of gravity distance (Db) increases, the moment of inertia of the head around the shaft axis (Z) increases, and the directional stability of the batted ball increases. Additionally, it becomes easier for the hitting point and sweet spot (SS) to coincide, and the rebound performance can be improved.

On the other hand, it was found that as the head center of gravity distance (Db) becomes longer, ball capture becomes worse.

Ball capture is a concept related to the direction of the face at impact. “Good ball capture” means that the face does not open at impact and the ball can be caught properly. “Poor ball catching” means that the face is open at impact and the ball cannot be caught. Capturing the ball is also simply referred to as catching.

It was found that by reducing the shaft torque (Ts), the capture becomes good even if the head center of gravity distance (Db) is large. By satisfying the following, a golf club with excellent grip can be obtained while enjoying the advantage of a long head center of gravity distance (Db).

(a) The head center of gravity distance (Db) is 37 mm or more.

(b) Shaft torque (Ts) is less than 4.0°

(c) Db/Ts is 9.7 or more.

From the viewpoint of the directional stability and rebound performance of the batted ball, the head center of gravity distance (Db) is preferably 37 mm or more, more preferably 38 mm or more, and even more preferably 39 mm or more. Considering the limitations in design freedom, the head center of gravity distance (Db) is preferably 45 mm or less, more preferably 43 mm or less, and still more preferably 41 mm or less.

From the viewpoint of capture, the shaft torque Ts is preferably less than 4.0°, more preferably 3.9° or less, and even more preferably 3.8° or less. From the viewpoint of shaft strength, the shaft torque (Ts) is preferably 2.0° or more, more preferably 2.2° or more, and even more preferably 2.4° or more.

From the viewpoint of ensuring good capture while ensuring the directional stability of the batted ball, Db/Ts is preferably 9.7 or more, more preferably 9.8 or more, more preferably 9.9 or more, more preferably 10.0 or more, and 10.1 or more. It is more preferable, 10.2 or more is more preferable, 10.3 or more is more preferable, 10.4 or more is more preferable, and 10.5 or more is more preferable. Considering the limit of design freedom, Db/Ts is preferably 15.0 or less, more preferably 14.8 or less, and even more preferably 14.5 or less.

[4. Lg/Ls]

As described above, Lg is the distance from the shaft center of gravity (Gs) to the tip end (Tp), and Ls is the shaft length. It was found that by increasing Lg/Ls, capture became better. Lg/Ls is preferably as follows.

(d) Lg/Ls is 0.50 or more.

As Lg/Ls increases, the shaft center of gravity (Gs) approaches the grip (8). In this case, the head 4 can be made heavier while maintaining the normal swing weight. For this reason, it becomes easier for the head to move in the downswing, making it easier for the face to return. This results in better capture. Additionally, since the head 4 can be made heavier, the rebound performance is improved.

From the viewpoint of capture and repelling performance, Lg/Ls is preferably 0.50 or more, more preferably 0.51 or more, and even more preferably 0.52 or more. Considering the limit of design freedom, Lg/Ls is preferably 0.60 or less, more preferably 0.59 or less, and even more preferably 0.58 or less.

From the viewpoint of ease of swing, the swing weight (14 inch system) is preferably D5 or lower, more preferably D3 or lower, and even more preferably D1 or lower. The larger the head weight, the better the rebound performance. From this viewpoint, the swing weight is preferably C7 or higher, more preferably C8 or higher, and even more preferably C9 or higher.

[5. Relationship between club weight (Wc) and club length (Lc)]

A golf club that is lightweight relative to the club length (Lc) ensures ease of swing, increases head speed, and increases distance. It is desirable that the club weight (Wc) (grams) and the club length (Lc) (meters) satisfy the following relationship.

(e) Wc × Lc ≤ 360 (g·m)

In a golf club where Wc × Lc is 360 (g·m) or less, the swing speed increases. Because of this, the time required for the downswing is shortened and it is easy to hit the face without returning completely. In other words, while head speed increases, capture tends to worsen. By setting Db/Ts to 9.7 or more, capture becomes good even if Wc × Lc is 360 (g·m) or less.

From the viewpoint described above, Wc x Lc is preferably 360 (g·m) or less, more preferably 350 (g·m) or less, and even more preferably 345 (g·m) or less. Considering the limit of design freedom, Wc

From the viewpoint of suppressing Wc × Lc, the weight of the shaft is more preferably 54 g or less, more preferably 52 g or less, more preferably 50 g or less, and more preferably less than 50 g. From the viewpoint of shaft design freedom, the shaft weight is preferably 40 g or more, more preferably 42 g or more, and more preferably 44 g or more.

[6. Shaft lamination composition and club performance]

The stacked structure of the shaft described above contributes to improving the performance of the golf club.

[6-1. [Tip part bias layer and butt part bias layer]

By distributing the bias layer on the tip portion and the butt portion, the weight of the entire bias layer can be suppressed while the shaft torque can be effectively reduced. As a result, a shaft that is lightweight, easy to swing, and has good grip is obtained.

From the viewpoint of reducing shaft torque, it is desirable to arrange the bias layer at the tip portion. Regarding capture, in addition to the proximity of the head, the torsional rigidity of the part close to the grip (golfer's hands) is likely to have an effect. By distributing the bias layer to the tip portion and the butt portion, good capture can be achieved while suppressing the weight of the bias layer (bias dispersion effect).

Additionally, in this embodiment, the weight of the butt portion bias layer is greater than the weight of the tip portion bias layer. For this reason, Lg/Ls can be increased while enjoying the above bias dispersion effect.

[6-2. Butt part straight layer fiber]

The layer (s5) described above is a butt portion straight layer. The butt portion straight layer is not necessary. When forming a butt partial straight layer, examples of fibers of the butt partial straight layer include carbon fiber and glass fiber. In this embodiment, the butt portion straight layer is a glass fiber reinforced layer. The specific gravity of glass fiber is greater than that of carbon fiber. From the viewpoint of increasing Lg/Ls, it is preferable that the butt portion straight layer is a glass fiber reinforced layer.

[6-3. [Tip part straight layer fiber]

The layer (s9) described above is a tip portion straight layer. This layer (s9) is a tip portion straight layer, not the outermost layer. This tip portion straightening layer s9 is a glass fiber reinforced layer. This glass fiber reinforced layer increases the shock absorption energy of the tip portion.

[6-4. Glass fiber reinforced layer at the tip and butt area]

By arranging a glass fiber reinforcement layer with a large specific gravity in the tip portion and the butt portion, the moment of inertia of the shaft around the shaft center of gravity (Gs) increases. Accordingly, the behavior of the shaft during swing can be stabilized. Additionally, the weight of the butt portion glass fiber reinforced layer s5 is greater than the weight of the tip portion glass fiber reinforced layer s9. This contributes to increasing Lg/Ls.

[6-5. Tip partial layer and butt partial layer]

In the embodiment of Figure 3, butt portion bias layers (s3, s4), butt portion straight layers (s5), tip portion bias layers (s10, s11), and tip portion straight layers (s9, s12) are formed. As the weight distribution to both ends of the shaft increases, the moment of inertia of the shaft around the shaft center of gravity (Gs) increases. For this reason, the behavior of the shaft during swing can be stabilized. As a result, deviation in the direction of the hit ball can be suppressed.

[7. measurement method]

The measurement method is as follows.

[7-1. Shaft torque (Ts)]

Figure 4 shows a method for measuring shaft torque. A portion from a point 40 mm from the tip end Tp to the tip end Tp is fixed with the jig M1. This fixation is achieved by an air chuck, the air pressure of which is 2.0 kgf/cm2. The jig M2 is fixed to a portion 50 mm wide from a position 750 mm away from the jig M1. This fixation is achieved by an air chuck, the air pressure of which is 1.5 kgf/cm2. The jig M2 was rotated while the jig M1 was fixed, and a torque of 13.9 kg·cm was applied to the shaft 6. The twist angle caused by this torque is the shaft torque (°).

[7-2. Club Length (Lc)]

Place the sole of the club on the ground plane according to the club's lie angle. Among the points on the intersection of the sole side outer surface of the head and a plane perpendicular to the ground plane and including the shaft axis Z, the point at which the distance from the ground plane is 0.625 inches is taken as the reference point (k). The axial distance between this reference point (k) and the butt side edge of the grip is the club length (Lc).

[7-3. Swing weight (14 inch balance)]

The swing weight is measured using the brand name “BANCER-14” manufactured by DAININ. This swing weight has a 14 inch balance.

Swing weight is expressed by a symbol that is a combination of one letter and number. The alphabet is one of A to F. The number is an integer from 0 to 9. Additionally, decimal places in these numbers are rounded off. For this swing weight, the fulcrum is 14 inches from the grip end. Swing weight is determined based on the axial distance (in inches) from this fulcrum to the club's center of gravity multiplied by the club weight (in ounces). This number is classified into 6 levels from A to F. Additionally, for each of A to F, subdivision is made by numbers from 0 to 9. The farther from A to F, the larger the swing weight is, and the larger the number, the larger the swing weight.

[8. Examples of available prepregs]

Examples of prepregs that can be used in the shaft of the present disclosure are shown in Tables 1 and 2 below. By selection from these many materials, the specifications of the shaft can be adjusted.

Example

Hereinafter, the effects of the present disclosure will become clear through examples, but the present disclosure should not be construed as limited based on the description of these examples.

[Example 1]

A shaft for a 6-iron was manufactured through the process described above. The laminated structure was as shown in FIG. 3. The butt portion straight layer (s5) and the tip portion straight layer (s9) were made of glass fiber reinforced layers, and the other layers were made of carbon fiber reinforced layers. The golf club of Example 1 was obtained by attaching a grip and a 6-iron head to this shaft. The specifications and evaluation results of Example 1 are shown in Table 3 below.

[Examples 2 to 7 and Comparative Examples 1 to 2]

Golf clubs of Examples 2 to 7 and Comparative Examples 1 to 2 were obtained in the same manner as in Example 1 except for the specifications shown in the table below. Their specifications and evaluation results are shown in Tables 3 and 4 below.

Additionally, in all examples and comparative examples, the swing weight (14 inch system) was set to D0. The head weight, etc. was adjusted so that the swing weight was D0. In Examples 1 to 4, since Lg/Ls was changing, the head weight was adjusted and the swing weight was set to D0. In Examples 5 and 6, the shaft weight, grip weight, and head weight were adjusted, and the swing weight was set to D0.

In Comparative Example 2, the butt portion bias layers (s3, s4) and tip portion bias layers (s10, s11) were not used. Instead of not using these layers (s3, s4, s10, and s11), the weight of the full-length bias layer (s1, s2) was increased, and the weight of the bias layer was the same as in Example 1. Therefore, in Comparative Example 2, the weight distribution to the tip portion and butt portion of the shaft is less than that of the other Examples and Comparative Examples.

The evaluation method is as follows.

[Misalignment of batted ball direction]

Ten right-handed testers conducted a live hitting test. The distance (yards) of deviation from the target direction was measured. This distance becomes positive when it deviates to the right, and becomes negative when it deviates to the left. The farther to the right, the worse the capture. Ten testers hit five balls with each club. The average value of 50 data is shown in the “Displacement of batted ball direction” column.

[Misalignment Width]

In the above actual hit data, among the five pieces of data for each tester, the absolute value of the deviation of the batted ball to the rightmost and the absolute value of the deviation of the batted ball to the leftmost were summed. The average value of this total is shown in the “misalignment width” column. The larger the deviation width, the greater the deviation in the direction of the hit.

[Flying distance]

In the above actual hitting test, the flying distance was also measured. The distance to the final destination was measured. The average value of 50 data is shown in the “Flying Distance” column.

As shown in Table 3 and Table 4, the Examples were evaluated higher than the Comparative Examples. From this evaluation result, the superiority of the present disclosure is clear.

This disclosure may be applied to iron golf clubs.

2: Iron Golf Club
4: head
6: shaft
8: grip
Gs: Shaft center of gravity
Gh: Head center of gravity
Z: shaft axis
s1 to s12: prepreg sheet (layer)

Claims (4)

Equipped with a head, shaft and grip,
The head center of gravity distance, which is the distance between the center of gravity of the head and the axis of the shaft, is Db (mm),
When the shaft torque of the shaft becomes Ts (°),
Db is 37 mm or more,
Ts is less than 4.0°,
Db/Ts is 9.7 or higher,
The length of the shaft is 860 mm or more and 991 mm or less,
When the distance from the center of gravity of the shaft to the tip end of the shaft is Lg and the length of the shaft is Ls,
An iron golf club with Lg/Ls of 0.50 or more. According to claim 1,
The shaft is formed by a plurality of fiber reinforced layers,
An iron golf club, wherein the shaft has a tip bias layer and a butt bias layer. The method of claim 1 or 2,
When the club weight is in Wc (grams) and the club length is in Lc (meters),
An iron golf club where Wc × Lc is 360 (g·m) or less. delete