US20220126178A1 - Golf club shaft - Google Patents

Golf club shaft Download PDF

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Publication number
US20220126178A1
US20220126178A1 US17/491,619 US202117491619A US2022126178A1 US 20220126178 A1 US20220126178 A1 US 20220126178A1 US 202117491619 A US202117491619 A US 202117491619A US 2022126178 A1 US2022126178 A1 US 2022126178A1
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United States
Prior art keywords
flexural rigidity
shaft
point
equal
golf club
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US17/491,619
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English (en)
Inventor
Takashi Nakano
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Sumitomo Rubber Industries Ltd
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Sumitomo Rubber Industries Ltd
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Assigned to SUMITOMO RUBBER INDUSTRIES, LTD. reassignment SUMITOMO RUBBER INDUSTRIES, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: NAKANO, TAKASHI
Publication of US20220126178A1 publication Critical patent/US20220126178A1/en
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    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B53/00—Golf clubs
    • A63B53/10—Non-metallic shafts
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B60/00—Details or accessories of golf clubs, bats, rackets or the like
    • A63B60/0081—Substantially flexible shafts; Hinged shafts
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B2209/00—Characteristics of used materials
    • A63B2209/02—Characteristics of used materials with reinforcing fibres, e.g. carbon, polyamide fibres

Definitions

  • the present disclosure relates to golf club shafts.
  • Physical properties of a golf club shaft such as flexural rigidity and torsional rigidity, can be varied depending on positions of the golf club shaft.
  • the performance of the shaft can be changed by the distribution of physical properties.
  • JP2003-169871A discloses a shaft in which: a position having a minimum flexural rigidity in the shaft is present in a region that extends from 15% to 45% of the shaft full length from the shaft tip end; and a flexural rigidity at a position in a region that extends from the shaft tip end to less than or equal to 10% of the shaft full length is 1.2 to 2.5 times the minimum flexural rigidity.
  • Shafts are required to exhibit excellent performances regarding flight distance, feeling, and directional stability of hit balls, for example.
  • the inventor of the present disclosure has found that a new distribution of flexural rigidity that is different from conventional distributions can improve performance of shafts.
  • One example of the present disclosure is to provide a golf club shaft that is excellent in flight distance performance.
  • a golf club shaft includes a tip end, a butt end, a flexural rigidity E1 at a point located 130 mm apart from the tip end, a flexural rigidity E2 at a point located 230 mm apart from the tip end, a flexural rigidity E3 at a point located 330 mm apart from the tip end, a flexural rigidity E4 at a point located 430 mm apart from the tip end, a flexural rigidity E5 at a point located 530 mm apart from the tip end, a flexural rigidity E6 at a point located 630 mm apart from the tip end, a flexural rigidity E7 at a point located 730 mm apart from the tip end, a flexural rigidity E8 at a point located 830 mm apart from the tip end, a flexural rigidity E9 at a point located 930 mm apart from the tip end, and a flexural rigidity E10 at a point located 1030 mm apart
  • a ratio (E8/E1) is greater than or equal to 2 and less than or equal to 7.
  • the flexural rigidity E1 is less than or equal to 2.5 (kgf ⁇ m 2 ).
  • the flexural rigidity E8 is greater than or equal to 5.0 (kgf ⁇ m 2 ).
  • the golf club shaft satisfies the following relationships R1 and R8:
  • FIG. 1 shows an overall view of a golf club that includes a golf club shaft according to a first embodiment
  • FIG. 2 is a developed view of the golf club shaft in FIG. 1 ;
  • FIG. 3 is a schematic diagram illustrating a method for measuring a flexural rigidity EI
  • FIG. 4 shows a graph on an orthogonal coordinate system having an x-axis that represents a distance (mm) from a tip end and a y-axis that represents a flexural rigidity (kgf ⁇ m 2 );
  • FIG. 5 is a developed view of a golf club shaft according to a second embodiment.
  • the term “layer” and the term “sheet” are used in the present disclosure.
  • the “layer” is a term used for after being wound.
  • the “sheet” is a term used for before being wound.
  • the “layer” is formed by winding the “sheet”. That is, the wound “sheet” forms the “layer”.
  • a layer formed by a sheet s 1 is referred to as a layer s 1 .
  • axial direction means the axial direction of a shaft.
  • circumferential direction means the circumferential direction of a shaft.
  • FIG. 1 shows a golf club 2 in which a golf club shaft 6 according to the present disclosure is attached.
  • the golf club 2 includes a head 4 , the shaft 6 , and a grip 8 .
  • the head 4 is provided at a tip portion of the shaft 6 .
  • the grip 8 is provided at a butt portion of the shaft 6 .
  • the shaft 6 is a shaft for a wood type club.
  • the golf club 2 is a driver (number 1 wood).
  • the shaft 6 is a shaft used for drivers.
  • the head 4 and the grip 8 There is no limitation on the head 4 and the grip 8 .
  • the head 4 include a wood type head, a utility type head, an iron type head, and a putter head.
  • the head 4 is a wood type head.
  • the shaft 6 is formed by a plurality of fiber reinforced resin layers. In the present embodiment, carbon fiber reinforced resin layers are used as the fiber reinforced resin layers.
  • the shaft 6 is in a tubular form. Although not shown in the drawings, the shaft 6 has a hollow structure.
  • the shaft 6 includes a tip end Tp and a butt end Bt. In the golf club 2 , the tip end Tp is located inside the head 4 . In the golf club 2 , the butt end Bt is located inside the grip 8 .
  • a double-pointed arrow Ls in FIG. 1 shows the length of the shaft 6 . This length Ls is measured in the axial direction.
  • the shaft 6 is formed by winding a plurality of prepreg sheets.
  • fibers are oriented substantially in one direction.
  • Such a prepreg in which fibers are oriented substantially in one direction is also referred to as a UD prepreg.
  • the term “UD” stands for unidirectional.
  • the prepreg sheets may be made of a prepreg other than UD prepreg.
  • fibers contained in the prepreg sheets may be woven.
  • the prepreg sheet(s) are also simply referred to as a sheet(s).
  • Each prepreg sheet contains fibers and a resin.
  • the resin is also referred to as a matrix resin.
  • Carbon fibers and glass fibers are exemplified as the fibers.
  • the matrix resin is typically a thermosetting resin.
  • the matrix resin in the prepreg sheet examples include a thermosetting resin and a thermoplastic resin. From the viewpoint of shaft strength, the matrix resin is preferably a thermosetting resin, and more preferably an epoxy resin.
  • the shaft 6 is manufactured by a sheet-winding method.
  • the matrix resin is in a semi-cured state.
  • the prepreg sheets are wound and cured. This “cured” means that the semi-cured matrix resin is cured.
  • the curing process is achieved by heating.
  • the manufacturing processes of the shaft 6 includes a heating process. The heating process cures the matrix resin in the prepreg sheets.
  • FIG. 2 is a developed view of prepreg sheets constituting the shaft 6 .
  • FIG. 2 shows the sheets constituting the shaft 6 .
  • the shaft 6 is constituted by the plurality of sheets.
  • the shaft 6 is constituted by 14 sheets.
  • the shaft 6 includes a first sheet s 1 to a fourteenth sheet s 14 .
  • the developed view shows the sheets constituting the shaft in order from the radial inside of the shaft. The sheets are wound in order from the sheet located on the uppermost side in the developed view.
  • the horizontal direction of the figure coincides with the axial direction of the shaft.
  • the right side of the figure is the tip side of the shaft.
  • the left side of the figure is the butt side of the shaft.
  • FIG. 2 shows not only the winding order of the sheets but also the position of each of the sheets in the axial direction. The same holds true for FIG. 5 described later.
  • an end of the sheet s 1 is located at the tip end Tp.
  • the shaft 6 includes a straight layer, a bias layer, and a hoop layer.
  • An orientation angle of the fibers (hereinafter referred to as fiber orientation angle) is described for each of the sheets in FIG. 2 .
  • a sheet described as “0°” is a straight sheet.
  • the straight sheet forms the straight layer.
  • the straight layer is a layer in which the fiber orientation angle is substantially set to 0° with respect to the axial direction.
  • the fiber orientation may not completely be parallel to the shaft axial direction due to an error in winding, for example.
  • an absolute angle of the fiber orientation angle with respect to the shaft axial direction is less than or equal to 10°.
  • the absolute angle means an absolute value of an angle (fiber orientation angle) formed between the shaft axis line and the orientation of fibers. That is, “the absolute angle is less than or equal to 10°” means that “the fiber orientation angle is ⁇ 10 degrees or greater and +10 degrees or less”.
  • sheets (straight sheets) that form straight layers are the sheet s 1 , the sheet s 8 , the sheet s 9 , the sheet s 11 , the sheet s 12 , the sheet s 13 and the sheet s 14 .
  • the straight layers make a great contribution to flexural rigidity and flexural strength.
  • bias layer is a layer in which the fiber orientation is substantially inclined with respect to the axial direction.
  • the bias layer makes a great contribution to torsional rigidity and torsional strength.
  • bias layers are constituted by a pair of two sheets (herein after referred to as a sheet pair) in which fiber orientation angles of the respective sheets are inclined inversely to each other.
  • the sheet pair includes: a layer having a fiber orientation angle of greater than or equal to ⁇ 60° and less than or equal to ⁇ 30°; and a layer having a fiber orientation angle of greater than or equal to 30° and less than or equal to 60°. That is, the absolute angle in the bias layers is preferably greater than or equal to 30° and less than or equal to 60°.
  • sheets (bias sheets) that form the bias layers are the sheet s 2 , the sheet s 3 , the sheet s 4 , the sheet s 5 , the sheet s 6 , and the sheet s 7 .
  • the sheet s 2 and the sheet s 3 constitute a sheet pair (a first sheet pair).
  • the sheet s 4 and the sheet s 5 constitute a sheet pair (a second sheet pair).
  • the sheet s 6 and the sheet s 7 constitute a sheet pair (a third sheet pair). Each sheet pair is wound in a state where the sheets constituting the sheet pair are stuck together.
  • the shaft 6 includes a plurality of (three) sheet pairs.
  • the fiber orientation angle is described for each sheet.
  • the plus sign (+) and minus sign ( ⁇ ) used with the fiber orientation angle indicate inclined direction of the fibers.
  • a sheet having a plus fiber orientation angle and a sheet having a minus fiber orientation angle are combined in each sheet pair. In each sheet pair, fibers in respective sheets are inclined inversely to each other.
  • the hoop layer is a layer that is disposed so that the fiber orientation substantially coincides with the circumferential direction of the shaft.
  • the absolute angle of the fiber orientation angle is substantially set to 90° with respect to the shaft axial direction.
  • the fiber orientation angle to the shaft axial direction may not be completely set to 90° due to an error in winding, for example.
  • the absolute angle of the fiber orientation angle is usually 80° or greater and 90° or less.
  • the hoop layer makes a great contribution to crushing rigidity and crushing strength of a shaft.
  • the crushing rigidity is a rigidity against crushing deformation.
  • the crushing deformation is caused by a crushing force that is applied to the shaft inward in the radial direction of the shaft. In a typical crushing deformation, the cross section of the shaft is deformed from a circular shape to an elliptical shape.
  • the crushing strength is a strength against the crushing deformation.
  • the crushing strength can relate to the flexural strength.
  • the flexural deformation can involve the crushing deformation. Particularly when a lightweight shaft having a thin wall is used, the flexural deformation is more likely to involve the crushing deformation. Improvement in the crushing strength can contribute to improvement in the flexural strength.
  • a prepreg sheet (hoop sheet) that constitutes the hoop layer is the sheet s 10 .
  • the hoop layer s 10 is sandwiched between the straight layer s 9 and the straight layer s 11 .
  • a united sheet is used for manufacturing the shaft 6 shown in FIG. 2 .
  • the united sheet is formed by sticking a plurality of sheets together.
  • a first united sheet is the combination of the sheet s 2 and the sheet s 3 .
  • a second united sheet is the combination of the sheet s 4 and the sheet s 5 .
  • a third united sheet is the combination of the sheet s 6 and the sheet s 7 .
  • a fourth united sheet is the combination of the sheet s 9 , the sheet s 10 and the sheet s 11 .
  • the sheets and the layers are classified by the fiber orientation angle. Furthermore, in the present disclosure, the sheets and the layers are classified by their length in the axial direction.
  • a layer wholly disposed in the axial direction of the shaft is referred to as a full length layer.
  • a sheet wholly disposed in the axial direction of the shaft is referred to as a full length sheet.
  • the wound full length sheet forms the full length layer.
  • a layer partially disposed in the axial direction of the shaft is referred to as a partial layer.
  • a sheet partially disposed in the axial direction of the shaft is referred to as a partial sheet.
  • the wound partial sheet forms the partial layer.
  • a layer that is the bias layer and the full length layer is referred to as a full length bias layer.
  • a layer that is the straight layer and the full length layer is referred to as a full length straight layer.
  • a layer that is the hoop layer and the full length layer is referred to as a full length hoop layer.
  • the full length bias layers are formed by the sheet s 2 and the sheet s 3 .
  • the full length straight layers are formed by the sheet s 9 , the sheet s 11 , the sheet s 12 , and the sheet s 13 .
  • the shaft 6 includes the plurality of full length straight layers s 9 , s 11 , s 12 and s 13 .
  • the full length hoop layer is formed by the sheet s 10 .
  • the shaft 6 includes the hoop layer s 10 sandwiched between the full length straight layers s 9 and s 11 .
  • a layer that is the bias layer and the partial layer is referred to as a partial bias layer.
  • a layer that is the straight layer and the partial layer is referred to as a partial straight layer.
  • a layer that is the hoop layer and the partial layer is referred to as a partial hoop layer.
  • the partial bias layers are formed by the sheet s 4 , the sheet s 5 , the sheet s 6 and the sheet s 7 .
  • the partial straight layers are formed by the sheet s 1 , the sheet s 8 and the sheet s 14 .
  • a partial hoop layer is not provided.
  • the sheet s 4 and the sheet s 5 are tip partial bias layers p 1 .
  • the tip partial bias layers p 1 are disposed on the tip portion of the shaft 6 .
  • One end of each tip partial bias layer p 1 is located at the tip end Tp.
  • the sheet s 6 and the sheet s 7 are intermediate partial bias layers p 2 .
  • the intermediate partial bias layers p 2 are located apart from the tip end Tp and apart from the butt end Bt.
  • the shaft 6 includes the tip partial bias layers p 1 and the intermediate partial bias layers p 2 .
  • Each tip partial bias layer p 1 does not overlap each intermediate partial bias layer p 2 in the axial direction.
  • the center position of each intermediate partial bias layer p 2 in the axial direction is located on the but end Bt side with respect to the center position of the shaft 6 in the axial direction.
  • the shaft 6 does not include a butt partial bias layer.
  • a region in the axial direction in which each intermediate partial bias layer p 2 is disposed (hereinafter also referred to as the axial directional region of each intermediate partial bias layer p 2 ) includes a point that is located 830 mm apart from the tip end Tp.
  • the axial directional region of each intermediate partial bias layer p 2 includes a point that is located 730 mm apart from the tip end Tp.
  • the prepreg sheets are cut into respective desired shapes in the cutting process. Each of the sheets shown in FIG. 2 is cut out by this process.
  • the cutting may be performed by a cutting machine.
  • the cutting may be manually performed.
  • a cutter knife is used, for example.
  • each united sheet described above is produced by sticking a plurality of sheets together.
  • heating and/or pressing step(s) may be carried out.
  • a mandrel is prepared in the winding process.
  • a typical mandrel is made of a metal.
  • a mold release agent is applied to the mandrel.
  • a resin having tackiness is applied to the mandrel.
  • the resin is also referred to as a tacking resin.
  • the cut sheets are wound around the mandrel.
  • the tacking resin facilitates the application of the end part of a sheet to the mandrel.
  • a wound body is obtained in the winding process.
  • the wound body is obtained by winding the prepreg sheets around the outside of the mandrel.
  • the winding is achieved by rolling the object to be wound on a plane.
  • the winding may be manually performed or may be performed by a machine.
  • the machine is referred to as a rolling machine.
  • a tape is wrapped around the outer peripheral surface of the wound body in the tape wrapping process.
  • the tape is also referred to as a wrapping tape.
  • the wrapping tape is helically wrapped while tension is applied to the tape so that there is no gap between adjacent windings.
  • the tape applies pressure to the wound body. The pressure contributes to the reduction of voids.
  • the wound body after being subjected to the tape wrapping is heated.
  • the heating cures the matrix resin.
  • the matrix resin fluidizes temporarily.
  • the fluidization of the matrix resin can eliminate air between the sheets or in each sheet.
  • the fastening force of the wrapping tape accelerates the discharge of the air.
  • the curing provides a cured laminate.
  • the process of extracting the mandrel and the process of removing the wrapping tape are performed after the curing process.
  • the process of removing the wrapping tape is preferably performed after the process of extracting the mandrel.
  • Both end portions of the cured laminate are cut off in the process.
  • the cutting off flattens the end face of the tip end Tp and the end face of the butt end Bt.
  • the surface of the cured laminate is polished in the process. Spiral unevenness is present on the surface of the cured laminate as the trace of the wrapping tape. The polishing removes the unevenness to smooth the surface of the cured laminate.
  • the cured laminate after the polishing process is subjected to coating.
  • the shaft 6 has a flexural rigidity at each position thereof.
  • the flexural rigidity is also referred to as EI.
  • the value of the flexural rigidity is also referred to as EI.
  • the unit of EI is “kgf ⁇ m 2 ”. EI can be measured at predetermined positions in the axial direction.
  • FIG. 3 shows the method for measuring EI.
  • a universal testing machine “model 2020 (maximum load: 500 kg)” produced by Intesco Co., Ltd. can be used.
  • the shaft 6 is supported from below at a first supporting point T 1 and at a second supporting point T 2 .
  • a load F 1 is applied at a measurement point T 3 from above.
  • the load F 1 is applied vertically downward.
  • the distance between the point T 1 and the point T 2 is 200 mm.
  • the measurement point T 3 is a point that divides the distance between the point T 1 and the point T 2 into two equal parts.
  • the amount of bending (flexure) H when the load F 1 is applied is measured.
  • the load F 1 is applied by an indenter D 1 .
  • the tip end of the indenter D 1 is a cylindrical surface having a radius of curvature of 5 mm.
  • the downwardly moving speed of the indenter D 1 is 5 mm/min.
  • the amount of bending H is a distance in the vatical direction between the position of the point T 3 before the load F 1 is applied and the position of the point T 3 when the indenter D 1 is stopped.
  • EI is calculated by the following formula:
  • F 1 denotes a maximum load (kgf)
  • L is a distance (m) between the support points
  • H is the amount of bending (m).
  • the maximum load F 1 is 20 kgf.
  • the distance L between the support points is 0.2 m.
  • EI at the measurement point 1 is denoted by E1.
  • EI at the measurement point 2 is denoted by E2.
  • EI at the measurement point 3 is denoted by E3.
  • EI at the measurement point 4 is denoted by E4.
  • EI at the measurement point 5 is denoted by E5.
  • EI at the measurement point 6 is denoted by E6.
  • EI at the measurement point 7 is denoted by E7.
  • EI at the measurement point 8 is denoted by E8.
  • EI at the measurement point 9 is denoted by E9.
  • EI at the measurement point 10 is denoted by E10.
  • the unit of E1 to E10 is kgf ⁇ m 2 .
  • the values can be rounded off to the first decimal place.
  • FIG. 4 shows a graph on an orthogonal coordinate system having an x-axis that represents a distance (mm) from the tip end and a y-axis that represents a flexural rigidity (kgf ⁇ m 2 ).
  • FIG. 4 is a graph showing Example 1 explained below. In this graph, the following 10 points having respective coordinates (x, y) are plotted.
  • the point (130, E1) is also referred to as a point E1.
  • the point (230, E2) is also referred to as a point E2.
  • the point (330, E3) is also referred to as a point E3.
  • the point (430, E4) is also referred to as a point E4.
  • the point (530, E5) is also referred to as a point E5.
  • the point (630, E6) is also referred to as a point E6.
  • the point (730, E7) is also referred to as a point E7.
  • the point (830, E8) is also referred to as a point E8.
  • the point (930, E9) is also referred to as a point E9.
  • the point (1030, E10) is also referred to as a point E10.
  • the straight line L 1 can vary from shaft to shaft.
  • the straight line L 1 can be adjusted based on characteristics (e.g., head speed) of a golfer, for example.
  • properties suitable to each shaft can be specified.
  • the gradient “a” of the straight line L 1 can be adjusted by a taper ratio of the shaft, for example.
  • the y-intercept “b” of the straight line L 1 can be adjusted by the overall wall thickness of the shaft (e.g., the thickness of the full length straight layer(s)), for example. When the flexural rigidity on the whole shaft is changed, the value of “b” can be changed.
  • the gradient “a” of the straight line L 1 is preferably great.
  • the gradient “a” is preferably greater than or equal to 0.003, more preferably greater than or equal to 0.004, and still more preferably greater than or equal to 0.005.
  • An excessively great gradient “a” can lead to an excessively small E1 and/or excessively great E8.
  • the gradient “a” is preferably less than or equal to 0.008, more preferably less than or equal to 0.007, and still more preferably less than or equal to 0.006.
  • the y-intercept “b” of the straight line L 1 is less than or equal to 3.0, more preferably less than or equal to 2.0, and still more preferably less than or equal to 1.5.
  • the y-intercept “b” of the straight line L 1 is preferably greater than or equal to ⁇ 1.0, more preferably greater than or equal to 0.0, and still more preferably greater than or equal to 0.5.
  • the point E1 is positioned higher than the straight line L 1 . That is, E1 is greater than (130a+b).
  • the point E3 is positioned lower than the straight line L 1 . That is, E3 is lower than (330a+b).
  • the point E4 is positioned lower than the straight line L 1 . That is, E4 is lower than (430a+b).
  • the point E5 is positioned lower than the straight line L 1 . That is, E5 is lower than (530a+b).
  • the point E7 is positioned higher than the straight line L 1 . That is, E7 is greater than (730a+b).
  • the point E8 is positioned higher than the straight line L 1 . That is, E8 is greater than (830a+b).
  • the point E9 is positioned lower than the straight line L 1 . That is, E9 is lower than (930a+b).
  • the point E10 is positioned lower than the straight line L 1 . That is, E10 is lower than (1030a+b).
  • a portion ranging from the point E3 to the point E5 which constitutes a large part of the intermediate portion of the shaft is positioned lower than the straight line L 1 . Further, a portion ranging from the point E2 to the point E6 (exclusive) is positioned lower than the straight line L 1 .
  • the point E7 is positioned farther from the straight line L 1 as compared to the positional relationship between the point E1 and the straight line L 1 .
  • is greater than
  • the point E7 is positioned farther from the straight line L 1 as compared to the positional relationship between the point E3 and the straight line L 1 .
  • is greater than
  • E7 is positioned farther from the straight line L 1 as compared to the positional relationship between the point E4 and the straight line L 1 .
  • is greater than
  • the point E7 is positioned farther from the straight line L 1 as compared to the positional relationship between the point E5 and the straight line L 1 .
  • is greater than
  • the point E7 is positioned farther from the straight line L 1 as compared to the positional relationship between the point E9 and the straight line L 1 .
  • is greater than
  • the point E10 is positioned farther from the straight line L 1 as compared to the positional relationship between the point E7 and the straight line L 1 .
  • is greater than
  • the point E8 is positioned farther from the straight line L 1 as compared to the positional relationship between the point E1 and the straight line L 1 .
  • is greater than
  • the point E8 is positioned farther from the straight line L 1 as compared to the positional relationship between the point E3 and the straight line L 1 .
  • is greater than
  • E8 is positioned farther from the straight line L 1 as compared to the positional relationship between the point E4 and the straight line L 1 .
  • is greater than
  • the point E8 is positioned farther from the straight line L 1 as compared to the positional relationship between the point E5 and the straight line L 1 .
  • is greater than
  • the point E8 is positioned farther from the straight line L 1 as compared to the positional relationship between the point E9 and the straight line L 1 .
  • is greater than
  • the point E10 is positioned farther from the straight line L 1 as compared to the positional relationship between the point E8 and the straight line L 1 .
  • is greater than
  • a greater ratio (E8/E1) can improve the golfer's feeling and enable the tip portion of the shaft to provide an improved kick to a golf ball (kick means an improved bounce brought by the behavior of the shaft).
  • the improved kick increases flight distance.
  • the ratio (E8/E1) is preferably greater than or equal to 2.0, more preferably greater than or equal to 2.4, and still more preferably greater than or equal to 2.8.
  • An excessively great ratio (E8/E1) leads to a too flexible E1 and/or too rigid E8, which reduces the above-described advantageous effects.
  • the ratio (E8/E1) is preferably less than or equal to 7.0, more preferably less than or equal to 6.0, still more preferably less than or equal to 5.0, and yet still more preferably less than or equal to 4.0.
  • E1 causes difficulty in swinging of the shaft, which also reduces the directional stability of hit balls.
  • a lower E1 allows a golfer to easily feel the bending of the shaft, which improves the feeling of the shaft. Such a lower E1 also accelerates the speed of the tip portion of the shaft, whereby the tip portion can provide an improved kick to a golf ball.
  • E1 is preferably less than or equal to 2.5 (kgf ⁇ m 2 ), more preferably less than or equal to 2.3 (kgf ⁇ m 2 ), and still more preferably less than or equal to 2.1 (kgf ⁇ m 2 ).
  • An excessively small E1 leads to a flexible tip portion of the shaft, which reduces the stability of the shaft at impact and the directional stability of hit balls.
  • E1 is preferably greater than or equal to 1.5 (kgf ⁇ m 2 ), more preferably greater than or equal to 1.7 (kgf ⁇ m 2 ), and still more preferably greater than or equal to 1.9 (kgf ⁇ m 2 ).
  • E8 is preferably greater than or equal to 5.0 (kgf ⁇ m 2 ), more preferably greater than or equal to 5.3 (kgf ⁇ m 2 ), and still more preferably greater than or equal to 5.6 (kgf ⁇ m 2 ).
  • E8 is preferably less than or equal to 6.5 (kgf ⁇ m 2 ), more preferably less than or equal to 6.2 (kgf ⁇ m 2 ), and still more preferably less than or equal to 5.9 (kgf ⁇ m 2 ).
  • E1 is preferably greater than (130a+b), more preferably greater than or equal to (130+b+0.1), and still more preferably greater than or equal to (130a+b+0.2).
  • An excessively great E1 makes the shaft difficult to swing, which reduces the directional stability of hit balls.
  • E1 is less than or equal to (130a+b+0.5)
  • the speed of the tip portion of the shaft is accelerated, whereby the tip portion provides an excellent kick to a golf ball.
  • E1 is preferably less than or equal to (130a+b+0.5), more preferably less than or equal to (130a+b+0.4), and still more preferably less than or equal to (130a+b+0.3).
  • the shaft 6 includes the tip partial bias layers p 1 (see FIG. 2 ).
  • a region in the axial directional in which each tip partial bias layer p 1 is disposed (hereinafter also referred to as the axial directional region of each tip partial bias layer p 1 ) includes the point E1. Since the tip partial bias layers p 1 are included among tip partial layers, E1 is prevented from becoming excessively great.
  • the above relationship R1 can be easily achieved by the tip partial bias layers p 1 .
  • Each tip partial bias layer p 1 contributes to achievement of the relationship R1 regarding the flexural rigidity while increasing the torsional rigidity of the tip portion of the shaft and enhancing the directional stability of hit balls.
  • each tip partial bias layer p 1 in the axial direction is preferably greater than or equal to 130 mm, still more preferably greater than or equal to 140 mm, and yet still more preferably greater than or equal to 150 mm.
  • the length of each tip partial bias layer p 1 in the axial direction is preferably less than or equal to 300 mm, more preferably less than or equal to 260 mm, and still more preferably less than or equal to 220 mm.
  • the shaft 6 satisfies the following relationship R8.
  • the shaft 6 satisfies the following relationship R81.
  • E8 When E8 is excessively small, a proper recovery from bending cannot be obtained, which reduces the head speed.
  • Setting E8 to be greater than (830a+b) increases the stability of the shaft during a swing, which enhances the directional stability of hit balls. Such a greater E8 also provides the golfer with an improved feeling of load applied by the bending of the shaft at immediately before the impact. From these viewpoints, E8 is preferably greater than or equal to (830a+b+0.1), more preferably greater than or equal to (830a+b+0.3), and still more preferably greater than or equal to (830a+b+0.5).
  • An excessively great E8 makes the gripped area of the shaft excessively rigid, which gives a worse feeling to the golfer.
  • E8 is preferably less than or equal to (830a+b+1.0), more preferably less than or equal to (830a+b+0.9), and still more preferably less than or equal to (830a+b+0.8).
  • the straight line L 1 shows the tendency of the overall flexural rigidity distribution of the shaft.
  • properties suitable to each shaft can be specified.
  • the points E3 to E5 are preferably positioned close to the straight line L 1 . Specifically, the points E3 to E5 as explained below are preferable.
  • the point E3 preferably satisfies the following relationship R3, and more preferably satisfies the following relationship R31.
  • the point E4 preferably satisfies the following relationship R4, and more preferably satisfies the following relationship R41.
  • the point E5 preferably satisfies the following relationship R5, and more preferably satisfies the following relationship R51.
  • the flexural rigidity at the point E8 is higher than the straight line L 1 .
  • a portion at and near the point E8 is selectively made rigid relative to the straight line L 1 , which accelerates the speed the tip portion of the shaft to increase the head speed, and enhances the stability of the shaft during a swing, which can provide the golfer with the feeling of the load that is kept until the shaft reaches impact.
  • E9 is positioned inside the grip. For this reason, E9 has a less influence on the stability of swing. However, a lower E9 improves the absorbability of vibration felt by golfer's hands, which can improve the feeling of the shaft. From these viewpoints, E9 is preferably less than or equal to (930a+b ⁇ 0.1), more preferably less than or equal to (930a+b ⁇ 0.2), and still more preferably less than or equal to (930a+b ⁇ 0.3). A sharp decrease from E8 to E9 leads to stress concentration, which can reduce the strength of the shaft. From this viewpoint, E9 is preferably greater than or equal to (930a+b ⁇ 1.0), more preferably greater than or equal to (930a+b ⁇ 0.8), and still more preferably greater than or equal to (930a+b ⁇ 0.6).
  • E10 is positioned inside the grip.
  • E10 has a lesser influence on the stability of swing than E9.
  • a lower E10 improves the absorbability of vibration felt by golfer's hands, which can improve the feeling of the shaft.
  • E10 is preferably less than or equal to (1030a+b ⁇ 0.6), more preferably less than or equal to (1030a+b ⁇ 0.7), and still more preferably less than or equal to (1030a+b ⁇ 0.8).
  • a sharp decrease from E8 to E10 leads to stress concentration, which can reduce the strength of the shaft.
  • E10 is preferably greater than or equal to (1030a+b ⁇ 1.8), more preferably greater than or equal to (1030a+b ⁇ 1.6), and still more preferably greater than or equal to (1030a+b ⁇ 1.4).
  • E10 is preferably lower than E8, and E10 is preferably lower than E9.
  • the shaft 6 includes the sheet s 6 and the sheet s 7 as intermediate partial layers.
  • the intermediate partial layers s 6 and s 7 are located apart from the tip end Tp and apart from the butt end Bt.
  • a region in the axial direction in which the intermediate partial layers s 6 and s 7 are disposed (hereinafter also referred to as the axial directional region of the intermediate partial layers s 6 and s 7 ) includes a point that is located 830 mm apart from the tip end Tp.
  • the axial directional region of the intermediate partial layers s 6 and s 7 includes a point that is located 730 mm apart from the tip end Tp.
  • the number of sheets constituting the intermediate partial layers is two.
  • the number of sheet(s) constituting the intermediate partial layer(s) may be one, or may be three or more, instead of two.
  • the intermediate partial layers s 6 and s 7 partially increase the flexural rigidity of the shaft.
  • the intermediate partial layers s 6 and s 7 contribute to the formation of an upwardly protruded portion (hereinafter also referred to as a “rigidity prominent portion”) relative to the straight line L 1 at and near the point E8 in the graph of FIG. 4 .
  • the intermediate partial layer(s) contributes to increase in [E8 ⁇ (830a+b)].
  • the intermediate partial layers s 6 and s 7 are intermediate partial bias layers p 2 . Since the intermediate partial layers s 6 and s 7 are the intermediate partial bias layers p 2 , the flexural rigidity of the rigidity prominent portion is prevented from becoming excessively great. That is, the intermediate partial bias layers p 2 make [E8 ⁇ (830a+b)] a proper value. In addition, by using the intermediate partial bias layers p 2 , the rigidity of the rigidity prominent portion does not become excessively great even when the length of the intermediate partial layers in the axial directional is made longer to a certain extent. This structure allows the rigidity prominent portion to gradually change its rigidity, which can alleviate stress concentrations at the ends of the rigidity prominent portion.
  • the absolute angle of the fiber orientation angle of the intermediate partial layers (intermediate partial bias layers) is preferably greater than or equal to 20°, more preferably greater than or equal to 30°, and still more preferably greater than or equal to 40°.
  • the absolute angle of the fiber orientation angle of the intermediate partial layers (intermediate partial bias layers) is preferably less than or equal to 70°, more preferably less than or equal to 60°, and still more preferably less than or equal to 50°.
  • a length Lm (see FIG. 2 ) of the intermediate partial layers in the axial direction is preferably greater than or equal to 250 mm, more preferably greater than or equal to 300 mm, and still more preferably greater than or equal to 350 mm.
  • the length Lm is preferably less than or equal to 550 mm, more preferably less than or equal to 500 mm, and still more preferably less than or equal to 450 mm.
  • FIG. 5 is a developed view of prepreg sheets that constitute a shaft according to a second embodiment.
  • the embodiment of FIG. 5 is the same as the embodiment of FIG. 2 , except that intermediate partial layers s 6 and s 7 are intermediate partial straight layers p 3 , not intermediate partial bias layers p 2 .
  • the absolute angle of the fiber orientation angle of the intermediate partial layers is 0°.
  • the absolute angle of the fiber orientation angle of the intermediate partial layers is 45° in the embodiment of FIG. 2 .
  • the intermediate partial layer(s) is/are preferably intermediate partial bias layer(s).
  • FIG. 5 In a table shown below, the embodiment of FIG. 5 is shown as Comparative Examples (Comparative Example 2 and Comparative Example 5). The embodiment of FIG. 5 , however, can also be an Example.
  • the length Ls of the shaft needs to be greater than or equal to 1030 mm.
  • the shaft needs to extends further 100 mm toward the butt end from a point 1030 mm apart from the tip end Tp.
  • the butt end portion of the shaft can be cut off after the measurement of E10.
  • the length Ls of the shaft is preferably greater than or equal to 1030 mm, more preferably greater than or equal to 1080 mm, still more preferably greater than or equal to 1130 mm, and yet still more preferably greater than or equal to 1140 mm.
  • the length Ls of the shaft is preferably less than or equal to 1210 mm, more preferably less than or equal to 1200 mm, and still more preferably less than or equal to 1190 mm.
  • a shaft was produced in accordance with the above explained manufacturing processes of the shaft. Constitution of sheets in the shaft was as shown in FIG. 2 .
  • the length Ls of the shaft was 1143 mm.
  • a driver head and a grip were attached to the produced shaft to obtain a golf club.
  • EI values at the measurement points E1 to E10 were measured for each club.
  • the measured values for each club are shown in Table 1 and Table 2.
  • the flight distance is a distance to where a ball hit by the club finally arrives, and includes a distance by which the ball runs on the ground.
  • the flight distance shown in Table 1 and Table 2 below is an average value of measured values per club.
  • the directional stability of the hit ball was also measured in each of the above performed shots for measuring flight distances.
  • a distance between the final arrival point of each hit ball and a line that passes through the initial position of the ball to be hit and a target position was measured. This distance was regarded as a plus value, irrespective of whether the hit ball flied rightward or leftward relative to the target direction.
  • the average values of the distances of respective clubs were evaluated (classified) on a scale of 1 to 5, where the score 1 is the highest average value and the score 5 is the lowest average value. The higher the score is, the higher the directional stability of hit balls is.
  • the evaluated scores are shown in below Table 1 and Table 2.
  • the head speed was also measured in each of the above performed shots for measuring flight distances.
  • the head speed shown in Table 1 and Table 2 are average values for respective clubs.
  • a golf club shaft including:
  • a ratio (E8/E1) is greater than or equal to 2 and less than or equal to 7,
  • the flexural rigidity E1 is less than or equal to 2.5 (kgf ⁇ m 2 ),
  • the flexural rigidity E8 is greater than or equal to 5.0 (kgf ⁇ m 2 ),
  • the flexural rigidity E9 is less than or equal to (930a+b ⁇ 0.1).
  • the flexural rigidity E10 is less than or equal to (1030a+b ⁇ 0.6).
  • the golf club shaft further satisfies the following relationships R3, R4 and R5:
  • the golf club shaft is formed by a plurality of carbon fiber reinforced resin layers
  • the carbon fiber reinforced resin layers include an intermediate partial bias layer that is disposed apart from the tip end and apart from the butt end, and
  • an axial directional region in which the intermediate partial bias layer is disposed includes a point 830 mm apart from the tip end.

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  • Physical Education & Sports Medicine (AREA)
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US17/491,619 2020-10-22 2021-10-01 Golf club shaft Pending US20220126178A1 (en)

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JP2020177560A JP2022068723A (ja) 2020-10-22 2020-10-22 ゴルフクラブシャフト

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20160354647A1 (en) * 2015-06-05 2016-12-08 Dunlop Sports Co. Ltd. Golf club

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20160354647A1 (en) * 2015-06-05 2016-12-08 Dunlop Sports Co. Ltd. Golf club

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