Golf club head and method for manufacturing a golf club head

Abstract

To provide a golf club head in which the striking surface is formed with a urethane layer, and in which the durability and adhesion strength of this urethane layer can be enhanced. [Solution] The head 100 is equipped with a face portion 102 that forms a striking surface 102a. The face portion 102 has a face body portion M1 and a urethane layer portion U1 provided on the outside of the face body portion M1. The urethane layer portion U1 has a plurality of scorelines 140 formed on its outer surface and extending from the toe side to the heel side, and a plurality of inner surface protrusions 142 formed on its inner surface and extending from the toe side to the heel side corresponding to each of the scorelines 140. The face body portion M1 has a plurality of body grooves 146 formed on its outer surface and extending from the toe side to the heel side corresponding to each of the inner surface protrusions 142. Each of the inner surface protrusions 142 fits into each of the body grooves 146.

Description

Technical Field

[0001] The present invention relates to a golf club head and a method for manufacturing a golf club head.

Background Art

[0002] Various materials can be used for a golf club head. Composite heads using two or more materials are also known.

[0003] U.S. Patent No. 6,390,932 discloses a golf club head in which a striking face is formed of a dissimilar material (polymer) having predetermined physical properties. The dissimilar material disposed on the striking face can affect the flight characteristics of a struck golf ball.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] From the viewpoint of spin performance and the like, it is preferable that a score line is formed on the striking face. On the other hand, when the striking face is formed of a dissimilar material, the score line can reduce the durability strength of the dissimilar material. Further, when the striking face is formed of a dissimilar material, the adhesion strength of this dissimilar material can become a problem.

[0006] One object of the present invention is to provide a golf club head in which a striking face is formed of a urethane layer and the durability strength and adhesion strength of this urethane layer can be enhanced.

Means for Solving the Problems

[0007] In one embodiment, the present invention is a golf club head having a face portion that forms a striking surface. The face portion has a face body portion and a urethane layer portion made of polyurethane that is provided on the outside of the face body portion. The urethane layer portion has a plurality of scorelines formed on its outer surface and extending from the toe side to the heel side, and a plurality of inner surface protrusions formed on its inner surface and extending from the toe side to the heel side corresponding to each of the scorelines. The face body portion has a plurality of body grooves formed on its outer surface and extending from the toe side to the heel side corresponding to each of the inner surface protrusions. Each of the inner surface protrusions is inserted into each of the body grooves. [Effects of the Invention]

[0008] One aspect of this is that it is possible to provide a golf club head in which the striking surface is formed with a urethane layer, and in which the durability and adhesion strength of this urethane layer can be enhanced. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a plan view of the golf club head of the first embodiment. [Figure 2] Figure 2 is a side view of the golf club head shown in Figure 1, viewed from the toe side. [Figure 3] Figure 3(a) is a front view of the golf club head shown in Figure 1, and Figure 3(b) is a cross-sectional line of the outer surface of the head along line E1 in Figure 3(a). In Figure 3(b), the cross-sectional lines of the scorelines are omitted. [Figure 4] Figure 4 is a front view of the head body of the golf club head shown in Figure 1. [Figure 5] Figure 5 is a cross-sectional view along line AA in Figure 3(a). [Figure 6] Figure 6 is a magnified view of a portion of Figure 5. [Figure 7] Figure 7 is an enlarged view of the area within circle F7 in Figure 6. [Figure 8] Figure 8 is a front view of the golf club head of the second embodiment. [Figure 9] Figure 9 is a front view of the head body of the golf club head in Figure 8. [Figure 10] Figure 10 is a front view of the golf club head of the third embodiment. [Figure 11] Figure 11 is a front view of the head body of the golf club head in Figure 10. [Figure 12] Figure 12 is a front view of the golf club head of the fourth embodiment. [Figure 13] Figure 13 is a front view of the head body of the golf club head in Figure 12. [Figure 14] Figure 14 is a front view of the golf club head of the fifth embodiment. [Figure 15] Figure 15(a) is a front view of the golf club head of the sixth embodiment, and Figure 15(b) is a front view of the head body of this sixth embodiment. [Figure 16] Figures 16(a) and 16(b) are front views of the golf club head of the seventh embodiment. In Figure 16(a), the portion where the marking is provided is shown by hatching. Figure 16(b) is a front view close to the actual appearance of this head, where the portion where the marking is provided is painted black. [Figure 17] Figure 17 is an enlarged cross-sectional view of the face portion 102 of the golf club head of the seventh embodiment. [Figure 18] Figure 18 is a front view of the golf club head of the eighth embodiment. [Figure 19] Figure 19 is a front view of the golf club head of the ninth embodiment. [Figure 20] Figure 20 is a conceptual diagram showing an example of the manufacturing method of the heads of each embodiment. [Figure 21] Figure 21 is a conceptual diagram showing an example of the manufacturing method of the heads of each embodiment. Figure 21 shows a state later in time than Figure 20. [Figure 22] Figure 22 is a conceptual diagram showing an example of the manufacturing method of the heads of each embodiment. Figure 22 shows a state later in time than Figure 21. [Figure 23] FIG. 23 is a conceptual diagram for explaining a reference state.

Embodiments of the Invention

[0010] Hereinafter, the present invention will be described in detail based on preferred embodiments while appropriately referring to the drawings. In each embodiment, the same or common elements are denoted by the same reference numerals, and redundant descriptions are appropriately omitted.

[0011] In the present application, a reference state, a reference vertical plane, a toe - heel direction, a face - back direction, an up - down direction, a face center, a longitudinal section, a cross - section, and a front view are defined.

[0012] A state where the head is placed on the ground plane HP at a specified lie angle is defined as the reference state. As shown in FIG. 23, in this reference state, the shaft axis Z is included in a plane VP perpendicular to the ground plane HP. The shaft axis Z is the center line of the shaft. Usually, the shaft axis Z coincides with the center line of the hosel hole. The plane VP is defined as the reference vertical plane. The specified lie angle is, for example, published in a product catalog.

[0013] A club having an adjustment mechanism capable of adjusting the loft angle, lie angle, and face angle depending on the rotational position of a sleeve provided at the tip of a shaft is known. In this club, the sleeve can be removably fixed to the head by fixing means such as a screw. Therefore, in this club, the shaft can be detached from the head. In this club, the angle of the shaft axis Z can change with respect to the hosel hole. In such a club having an adjustment mechanism, in the above - mentioned reference state, the face angle and loft angle can be neutral, and the lie angle can be at its maximum value. Neutral means the center of the adjustment range.

[0014] In this standard state, the face angle is considered to be 0 degrees. That is, in a plan view from above, the normal to the face center of the striking surface is considered to be perpendicular to the toe-heel direction. The definitions of the face center and the toe-heel direction are described below.

[0015] In this specification, the toe-heel direction is the direction of the intersection line NL between the reference vertical plane VP and the ground plane HP (see Figure 23). The toe side in the toe-heel direction is also simply referred to as the "toe side." The heel side in the toe-heel direction is also simply referred to as the "heel side."

[0016] In this specification, the face-back direction is the direction perpendicular to the toe-heel direction and parallel to the ground plane HP. The face side in the face-back direction is also simply referred to as the "face side." The back side in the face-back direction is also simply referred to as the "back side."

[0017] In this specification, the vertical direction is the direction perpendicular to the toe-heel direction and perpendicular to the face-back direction. In other words, in this specification, the vertical direction is the direction perpendicular to the ground plane HP. The upper side in the vertical direction is also referred to as the "crown side". The lower side in the vertical direction is also referred to as the "sole side".

[0018] In this specification, the face center is determined as follows: First, an arbitrary point Pr is selected near the approximate center of the striking surface in the vertical and toe-heel directions. Next, a plane is determined that passes through point Pr, extends along the normal direction of the striking surface at point Pr, and is parallel to the toe-heel direction. A line is drawn between this plane and the striking surface, and its midpoint Px is determined. Next, a plane is determined that passes through this midpoint Px, extends along the normal direction of the striking surface at point Px, and is parallel to the vertical direction. A line is drawn between this plane and the striking surface, and its midpoint Py is determined. Next, a plane is determined that passes through this midpoint Py, extends along the normal direction of the striking surface at point Py, and is parallel to the toe-heel direction. A line is drawn between this plane and the striking surface, and its midpoint Px is newly determined. Next, a plane is determined that passes through this new midpoint Px, extends along the normal direction of the striking surface at point Px, and is parallel to the vertical direction. A line is drawn between this plane and the striking surface, and its midpoint Py is newly determined. This process is repeated to sequentially determine Px and Py. During this iteration, the new position Py (the last position Py) at which the distance between the new midpoint Py and the immediately preceding midpoint Py first becomes 0.5 mm or less is the face center.

[0019] In this specification, a longitudinal section is a cross-section of the head taken from a plane perpendicular to the toe-heel direction. In this specification, a transverse section is a cross-section taken from a plane perpendicular to the vertical direction. In other words, in this specification, a transverse section is a cross-section of the head taken from a plane parallel to the ground plane (HP).

[0020] In this specification, a front view refers to a perpendicular projection of the club head, obtained by projecting the normal to the face center as the projection direction. Unless otherwise specified, the shape, area, dimensions, etc., of each region of the face are determined from the front view. A drawing in the front view is also referred to simply as a front view in this specification.

[0021] The plan view of the head is a projection image obtained by projecting the head in its standard state onto a plane parallel to the ground plane HP. In this specification, the plan view of the head is also referred to as the plan view.

[0022] Figure 1 is a plan view of the golf club head 100 of the first embodiment, Figure 2 is a side view of the head 100 as seen from the toe side, Figure 3(a) is a front view of the head 100, Figure 3 is a cross-sectional line of the outer surface of the head according to cross-section E1 in Figure 3(a), Figure 4 is a front view of the head body 100a, Figure 5 is a cross-sectional view along line AA in Figure 3(a), Figure 6 is a partial enlargement of Figure 5, and Figure 7 is an enlargement of the area within circle F7 in Figure 6.

[0023] As shown in Figures 1 to 7, the head 100 has a face portion 102, a crown portion 104, a sole portion 106, and a hosel portion 108.

[0024] The head 100 may be wood-type. The head 100 may be hybrid-type. The head 100 may be iron-type. The head 100 may be putter-type. In this embodiment, the head 100 is wood-type. The head 100 is a driver head. As shown in Figure 5, the head 100 has a hollow structure. The head 100 has a hollow section H.

[0025] As shown in Figure 5, the face portion 102 forms a striking surface 102a and a face inner surface 102b. The striking surface 102a contacts the golf ball during impact. The striking surface 102a is the outer surface of the face portion 102. The striking surface 102a is also simply referred to as the face. The face inner surface 102b is the inner surface of the face portion 102. The face inner surface 102b faces the hollow portion H.

[0026] The striking surface 102a is a curved surface. The striking surface 102a is a curved surface that is convex toward the outside of the head 100. As shown in Figure 1, the striking surface 102a has a bulge BG. The bulge BG is a curvature in the toe-heel direction (lateral direction). As shown in Figures 2 and 5, the striking surface 102a has a roll RL. The roll RL is a curvature in the vertical direction (vertical direction).

[0027] The crown portion 104 constitutes the upper surface of the head 100. The crown portion 104 forms the crown outer surface 104a and the crown inner surface 104b. The crown inner surface 104b faces the hollow portion H.

[0028] The sole portion 106 constitutes the lower surface of the head 100. The sole portion 106 forms the outer sole surface 106a and the inner sole surface 106b. The inner sole surface 106b faces the hollow portion H.

[0029] The hosel portion 108 is located on the heel side of the head 100. The hosel portion 108 has a hosel hole 108a. A shaft (not shown) can be inserted into the hosel hole 108a. Alternatively, a sleeve (not shown) attached to the end of the shaft can be inserted into the hosel hole 108a.

[0030] As shown in Figure 3(a), the striking surface 102a has a face center Fc as defined above. The striking surface 102a (and the striking surface area 121 described later) also has a face center region Rc. The face center region Rc is the area within 20 mm of the toe-heel distance from the face center Fc.

[0031] The outer edge of the striking surface 102a can be defined as follows. As shown in Figure 3(a), there are numerous planes E1, E2, E3, etc. that contain the normal to the striking surface 102a at the face center Fc. Figure 3(b) shows the cross-sectional line of the outer surface of the head according to plane E1. In each of these cross-sections along plane E1, etc., a point Q1 is determined where the radius of curvature r of the cross-sectional line of the outer surface of the head first becomes 200 mm when moving from the face center Fc side toward the outside of the striking surface 102a. The set of these points Q1 can be considered the outer edge (outer edge Q1) of the striking surface 102a.

[0032] As shown in Figure 6, the head 100 has a urethane layer U1. The urethane layer U1 is provided on the face portion 102. The head 100 consists of a head body 100a and a urethane layer U1. Figure 4 is a front view of the head body 100a. This head body 100a is the head 100 with the urethane layer U1 removed. The material of the head body 100a is metal. The material of the head body 100a is not limited. The material of the head body 100a may be, for example, carbon fiber reinforced resin. The head body 100a may be composed of multiple materials. The head body 100a may be composed of multiple members.

[0033] As shown in Figure 6, the face portion 102 has a face body portion M1 and a urethane layer portion U1 provided on the outside of the face body portion M1. The urethane layer portion U1 is provided on the outside of the face body portion M1. The face body portion M1 is the part of the face portion 102 that is formed from the head body 100a. The material of the face body portion M1 is metal (titanium alloy). The material of the face body portion M1 is not limited. The material of the face body portion M1 may be, for example, carbon fiber reinforced resin. The face body portion M1 may be composed of multiple materials. The face body portion M1 may be composed of multiple members. The urethane layer portion U1 is made of polyurethane.

[0034] As shown in Figure 7, the face body M1 has an outer surface 120 and an inner surface 122. The face body M1 is part of the head body 100a. The inner surface 122 of the face body M1 faces the hollow portion H. The inner surface 122 of the face body M1 constitutes the face inner surface 102b. The outer surface 120 of the face body M1 is the region of the head body 100a that corresponds to the striking surface 102a. This region is also called the striking surface area 121. The outer surface 120 (striking surface area 121) of the face body M1 extends parallel to the striking surface 102a. The outer surface 120 (striking surface area 121) of the face body M1 has a bulge BG. The outer surface 120 (striking surface area 121) of the face body M1 has a roll RL.

[0035] A urethane layer U1 is provided on the outer surface 120 of the face body M1. The inner surface 124 of the urethane layer U1 is in contact with the outer surface 120 of the face body M1 (however, an adhesive layer 125 is interposed). Other layers may be interposed between the outer surface 120 and the urethane layer U1. Examples of these other layers include the adhesive layer 125 and a primer layer. The outer surface 126 of the urethane layer U1 constitutes the striking surface 102a. The face body M1 supports the urethane layer U1 from the inside of the head 100.

[0036] In this embodiment, the entire outer surface 120 of the face body M1 is covered with a urethane layer U1. In this embodiment, the urethane layer U1 covers the entire outer surface 120 (striking surface area 121) and extends beyond the outer surface 120 (striking surface area 121). The urethane layer U1 may cover only a part of the outer surface 120 of the face body M1. The outer surface 120 of the face body M1 may have a portion covered by the urethane layer U1 and a portion that is not covered by the urethane layer U1 and is exposed to the outside. In the portion exposed to the outside, the face body M1 constitutes the striking surface 102a. In the portion covered by the urethane layer U1, the face body M1 does not constitute the striking surface 102a, and the urethane layer U1 constitutes the striking surface 102a.

[0037] As shown in Figure 4, the head body 100a has a stepped recess 130 for arranging the urethane layer U1. The head 100 is formed when the stepped recess 130 is filled with the urethane layer U1. The stepped recess 130 has a stepped portion 130a along its contour line. The position of the stepped portion 130a coincides with the contour line k1 of the urethane layer U1 (see Figure 3(a)). The height of the stepped portion 130a substantially coincides with the thickness of the urethane layer U1. Therefore, the outer surface of the head 100 is substantially flush with the contour line k1 of the urethane layer U1. There is substantially no step (surface step) formed on the outer surface of the head 100 along the contour line k1 of the urethane layer U1. The height of the surface step at the contour line k1 can be 0.1 mm or less.

[0038] As shown in Figure 3, the urethane layer U1 has scorelines 140 formed on its outer surface 126. That is, the hitting surface 102a has scorelines 140. Multiple scorelines 140 are provided. The scorelines 140 extend from the toe side to the heel side. The multiple scorelines 140 are parallel to each other.

[0039] Scoreline 140 is a groove. In the longitudinal section (Figure 7), the cross-sectional shape of scoreline 140 is U-shaped. The cross-sectional shape of scoreline 140 is composed of a curve that bends so as to be convex toward the face body M1. In addition, the edges Eg on both sides of scoreline 140 are rounded.

[0040] The scoreline 140 has a groove width Wg. The groove width Wg can be measured using the 30-degree measurement method (R&A and USGA test regulations). The scoreline 140 has a groove depth Dg. The groove depth Dg is the depth from the line segment Ls connecting the measurement points in the 30-degree measurement method.

[0041] As shown in Figures 4 and 7, the face body M1 has body grooves 146. The body grooves 146 are provided on the outer surface 120 of the face body M1. Multiple body grooves 146 are provided. Each body groove 146 extends from the toe side to the heel side. Each body groove 146 is provided corresponding to each inner surface projection 142 (described later). The cross-sectional shape of each body groove 146 is U-shaped. The cross-sectional shape of each body groove 146 is arc-shaped. The shape of each body groove 146 is a concave curved surface. The cross-sectional shape of the body groove 146 may be rectangular. In this case, the cross-sectional shape of the body groove 146 may have first and second side surfaces, a bottom surface connecting these side surfaces, and corners defining both sides of the bottom surface.

[0042] As shown in Figure 7, the urethane layer U1 has internal projections 142 formed on its inner surface 124. Multiple internal projections 142 are provided. Each internal projection 142 extends from the toe side to the heel side. Each internal projection 142 is formed at a position corresponding to each scoreline 140. The internal projections 142 and the scorelines 140 are formed simultaneously as the urethane layer U1 curves and extends. Each internal projection 142 extends along each scoreline 140.

[0043] As shown in Figure 7, each of the inner projections 142 is inserted into each of the main body grooves 146. Each of the inner projections 142 is fitted into each of the main body grooves 146. The urethane layer U1 is bent as it is inserted into the main body grooves 146. The urethane layer U1 extends along the inner surface of the main body grooves 146. The inner projections 142 are fitted into the main body grooves 146. The shape of the main body grooves 146 is transferred to form the inner projections 142. Note that although the inner projections 142 are inserted into the main body grooves 146, they do not necessarily have to be fitted into the main body grooves 146.

[0044] In Figure 7, the double arrow t1 indicates the thickness of the urethane layer U1. The thickness t1 of the urethane layer U1 can be measured in a longitudinal section as shown in Figure 7. As shown in Figure 7, an inscribed circle CL1 is defined in the longitudinal section of the urethane layer U1. This inscribed circle CL1 can be determined at any position in the urethane layer U1. The diameter of the inscribed circle CL1 can be taken as the thickness t1 of the urethane layer U1. By defining the inscribed circle CL1, the thickness t1 can be measured at any position, including curved portions of the urethane layer U1. The thickness t1 of the urethane layer U1 is substantially constant. Substantially constant means that the variation range of the thickness t1 of the urethane layer U1 is ±10%, more preferably ±7%, and more preferably ±5%.

[0045] As shown in Figure 4, the main groove section 146 comprises a first groove width section 148 and a second groove width section 150 with a smaller groove width than the first groove width section 148. In Figure 4, the double-headed arrow W1 indicates the groove width of the first groove width section 148. In Figure 4, the double-headed arrow W2 indicates the groove width of the second groove width section 150. The groove width W1 of the first groove width section 148 is greater than the groove width W2 of the second groove width section 150. Although the main groove section 146 is not a groove according to the rules, the 30-degree measurement method (R&A and USGA test regulations) is applied to the measurement of groove widths W1 and W2.

[0046] The second groove width portion 150 is connected to the first groove width portion 148. The second groove width portion 150 is connected to the toe side and / or heel side of the first groove width portion 148. In the embodiment of Figure 4, in all body groove portions 146, the second groove width portion 150 is connected to the toe side and heel side of the first groove width portion 148. The second groove width portion 150 connected to the toe side of the first groove width portion 148 extends from the toe side end of the first groove width portion 148 toward the toe side. The second groove width portion 150 connected to the heel side of the first groove width portion 148 extends from the heel side end of the first groove width portion 148 toward the heel side.

[0047] In the head body 100a (Figure 4), at least one first groove width portion 148 is arranged to traverse the face center region Rc (see Figure 3(a)). In the head body 100a, multiple first groove width portions 148 are arranged to traverse the face center region Rc.

[0048] The second groove width portion 150 may be omitted. The main groove portion 146 may consist only of the first groove width portion 148.

[0049] As can be seen from the comparison between Figure 3(a) and Figure 4, the scoreline 140 is formed in a position corresponding to the first groove width portion 148. The urethane layer U1 fits into the first groove width portion 148. Each of the inner projections 142 is fitted into each of the first groove width portions 148. Each of the inner projections 142, together with the adhesive layer 125, is fitted into each of the first groove width portions 148. The groove width W1 of the first groove width portion 148 allows the urethane layer U1 of thickness t1 to fit into the first groove width portion 148. Preferably, the groove width W1 of the first groove width portion 148 can be greater than twice the thickness t1 of the urethane layer U1.

[0050] The scoreline 140 is not formed in a position corresponding to the second groove width portion 150. The urethane layer U1 does not penetrate the second groove width portion 150. The inner projection 142 is not formed in a position corresponding to the second groove width portion 150. The inner projection 142 is not fitted into the second groove width portion 150. The groove width W2 of the second groove width portion 150 does not allow the urethane layer U1 with thickness t1 to penetrate the second groove width portion 150. The groove width W2 of the second groove width portion 150 may be smaller than the thickness t1 of the urethane layer U1.

[0051] Furthermore, the urethane layer U1 may be inserted into the second groove width portion 150. In this case, the urethane layer U1 does not have to be completely inserted into the second groove width portion 150. That is, the urethane layer U1 does not have to be inserted to the extent that it is aligned with the inner surface of the second groove width portion 150, and a space may exist between the inner surface of the second groove width portion 150 and the urethane layer U1. In other words, the inner surface protrusion formed by being inserted into the second groove width portion 150 does not have to be fitted into the second groove width portion 150. In this case, a scoreline with a groove width Wg smaller than the scoreline 140 formed in correspondence with the first groove width portion 148 may be formed corresponding to the second groove width portion 150.

[0052] As shown in Figure 4, each of the main grooves 146 has a toe end Et and a heel end Eh. In this embodiment, the toe end Et and the heel end Eh are the ends of the second groove width portion 150. The toe end Et is the end of the second groove width portion 150 located on the toe side of the first groove width portion 148. The heel end Eh is the end of the second groove width portion 150 located on the heel side of the first groove width portion 148.

[0053] The ends Et and Eh of the main body groove 146 extend to the outside of the outer edge Q2 of the striking surface area 121. The toe end Et is located outside the outer edge Q2 of the striking surface area 121. The heel end Eh is located outside the outer edge Q2 of the striking surface area 121.

[0054] The main body groove 146 is open toward the heel at the heel end Eh. In other words, the main body groove 146 opens toward the heel at the heel end Eh. As shown in the enlarged view of Figure 4, the main body groove 146 (second groove width portion 150) has a first side surface s1, a second side surface s2, and a bottom surface b1. At the heel end Eh, there is no step between the bottom surface b1 and the adjacent outer surface 120. Since the outer surface 120 of the face main body M1 has a bulge BG, the bottom surface b1 is also a curved surface that follows this bulge BG. The depth of the main body groove 146 (height of the first side surface s1 and the second side surface s2) decreases continuously as it approaches the heel end Eh, and becomes zero at the heel end Eh. The heel end Eh forms a suction opening K1 by opening toward the heel. Similarly, the main body groove 146 is open toward the toe at the toe end Et. The tow end Et opens towards the tow side, forming a suction opening K1. The function of the suction opening K1 will be described later.

[0055] Figure 8 is a front view of the head 200 of the second embodiment, and Figure 9 is a front view of the head body 200a in this head 200. The head 200 is the same as the head 100 except for the shape of the body groove 146 and score lines 140.

[0056] As shown in Figure 9, the head body 200a has one body groove 146 which has a first groove width portion 148 that is interrupted midway and a second groove width portion 150 that connects this interrupted portion. This second groove width portion 150 is also called the intermediate narrow portion 152. Except for the presence of the intermediate narrow portion 152, the head body 200a is the same as the head body 100a of the first embodiment.

[0057] As shown in Figure 8, no scoreline 140 is formed in the portion corresponding to the intermediate narrow portion 152. In the portion corresponding to the intermediate narrow portion 152, a break 141 is formed where the scoreline 140 is interrupted midway. In the head body 200a, the intermediate narrow portion 152 is provided in one location. In the head 200, the break 141 is provided in one location. Except for the presence of the break 141, the head 200 is the same as the head 100 of the first embodiment.

[0058] In the head 200, the break 141 is provided at a position corresponding to the face center Fc. The position corresponding to the face center Fc can be within a circle with a radius of 10 mm centered on the face center Fc. More preferably, the position corresponding to the face center Fc can be within a circle with a radius of 5 mm centered on the face center Fc. The break 141 allows the user to visually confirm the position of the face center Fc.

[0059] Figure 10 is a front view of the head 300 of the third embodiment, and Figure 11 is a front view of the head body 300a in this head 300. The head 300 is the same as the head 100 except for the shape of the body groove 146 and score lines 140.

[0060] As shown in Figure 11, the head body 300a has multiple body grooves 146, each having a first groove width portion 148 that is interrupted midway and a second groove width portion 150 (intermediate narrow portion 152) that connects this interrupted portion. Each of these body grooves 146 has multiple (two) intermediate narrow portions 152. Except for the presence of these intermediate narrow portions 152, the head body 300a is the same as the head body 100a of the first embodiment.

[0061] As shown in Figure 10, no score lines 140 are formed in the portion corresponding to the intermediate narrow portion 152. In the portion corresponding to the intermediate narrow portion 152, a break portion 141 is formed where the score line 140 is interrupted midway. In the head body 300a, multiple intermediate narrow portions 152 are provided. In the head 300, multiple break portions 141 are provided. Except for the presence of the break portions 141, the head 300 is the same as the head 100 of the first embodiment.

[0062] In the head 300, multiple interrupted sections 141 are provided within the range of the face center Ft. The face center Ft can be a circle with a radius of 20 mm centered on the face center Fc. The multiple interrupted sections 141 are arranged along an annular shape surrounding the face center Fc. The interrupted sections 141 allow for visual confirmation of a desirable area for impact.

[0063] Figure 12 is a front view of the head 400 of the fourth embodiment, and Figure 13 is a front view of the head body 400a in this head 400. The head 400 is the same as the head 100 except for the shape of the body groove 146 and score lines 140.

[0064] As shown in Figure 13, the head body 400a has multiple body grooves 146, each having a first groove width portion 148 that is interrupted midway, and a second groove width portion 150 (intermediate narrow portion 152) that connects this interrupted portion. Each of these body grooves 146 has one intermediate narrow portion 152. Except for the presence of these intermediate narrow portions 152, the head body 400a is the same as the head body 100a of the first embodiment.

[0065] As shown in Figure 12, no score lines 140 are formed in the portion corresponding to the intermediate narrow portion 152. In the portion corresponding to the intermediate narrow portion 152, a break portion 141 is formed where the score line 140 is interrupted midway. In the head body 400a, multiple intermediate narrow portions 152 are provided. In the head 400, multiple break portions 141 are provided. Except for the presence of the break portions 141, the head 400 is the same as the head 100 of the first embodiment.

[0066] In head 400, multiple breaks 141 create an area within the face center Ft where scorelines 140 are absent. Due to the presence of multiple breaks 141, this area without scorelines 140 forms a roughly circular area surrounding the face center Fc. The breaks 141 allow for visual confirmation of a desirable area for impact.

[0067] Figure 14 is a front view of the head 500 of the fifth embodiment. The head 500 is the same as the head 100, except for the shape of the body groove 146 and the score lines 140. Although not shown, the body groove of the head body 500a in the head 500 is positioned to correspond to the score lines 140.

[0068] As shown in Figure 14, in the head 500, the scoreline 140 extends to the outside of the striking surface 102a. That is, the scoreline 140 has an inner face portion 140a located on the striking surface 102a, and an outer face portion 140b that extends continuously from this inner face portion 140a and is located on the outside of the striking surface 102a. The urethane layer U1 extends to the outside of the striking surface 102a, and the outer face portion 140b is formed in the urethane layer U1 located on the outside of the striking surface 102a. The inner face portion 140a and the outer face portion 140b are formed by the urethane layer U1 fitting into the main body groove (not shown). In the head body 500a of the head 500, the main body groove (not shown) extends to the outside of the region corresponding to the striking surface 102a (striking surface area 121).

[0069] The head 500 has an extended scoreline 160 that extends from the urethane layer U1 to the outside of the urethane layer U1. In the embodiment shown in Figure 14, the uppermost scoreline 140 is extended to form the extended scoreline 160. A portion of the extended scoreline 160 is the scoreline 140. This scoreline 160 has an external urethane portion 162. The external urethane portion 162 extends continuously from the scoreline 140 and is located outside the urethane layer U1. In this embodiment, the external urethane portion 162 extends continuously from the external face portion 140b. The external urethane portion 162 is provided on the outer surface of the head body 500a. The external urethane portion 162 is a second groove width portion 150 formed in the head body 500a. The external urethane portion 162 is formed when the second groove width portion 150 is exposed without the urethane layer U1 covering it.

[0070] In this embodiment, the urethane outer component 162 is located outside the striking surface 102a. The urethane outer component 162 may also be provided inside the striking surface 102a.

[0071] Figure 15(a) is a front view of the head 600 of the sixth embodiment, and Figure 15(b) is a front view of the head body 600a in the head 600. The head 600 is the same as the head 100 except for the shape of the body groove 146.

[0072] As shown in Figure 15(a), the shape of the scorelines 140 on the head 600 is the same as that of the head 100. Visually, the head 600 is identical to the head 100.

[0073] As shown in Figure 15(b), the head body 600a has a plurality of body grooves 146. Each of the body grooves 146 is located at a position corresponding to each of the scorelines 140. The scorelines 140 are formed when the urethane layer U1 fits into the body grooves 146.

[0074] In the head body 600a, the body groove 146 does not have a second groove width portion 150 as shown in the head body 100a (Figure 4). In the head body 600a, there is only one groove width for the body groove 146. This groove width is the same as the groove width W1 of the first groove width portion 148 in the head body 100a.

[0075] In the head body 600a, each of the body grooves 146 has a suction opening K2. The suction opening K2 is provided at both ends of the body groove 146. The suction opening K2 is provided at the toe end Et of the body groove 146. The suction opening K2 is provided at the heel end Eh of the body groove 146.

[0076] The suction opening K2 of the head body 600a differs from the suction opening K1 of the head body 100a (Figure 4). The suction opening K1 of the head body 100a is formed by the openings at both ends Et and Eh of the body groove 146 extending in the direction of the body groove 146. In contrast, the suction opening K2 of the head body 600a is formed by a through hole h1 that penetrates the face body M1. This through hole h1 extends from the bottom surface b1 of the body groove 146 to the inner surface 122 of the face body M1 (see Figure 5). That is, the through hole h1 extends from the bottom surface b1 of the body groove 146 to the hollow part H of the head 600. The hollow part H is in communication with the hosel hole 108a and can ventilate with the outside of the head 600.

[0077] The position of the suction opening K2 is not limited to both ends Et and Eh of the main body groove 146. The suction opening K2 can be located at any position between the toe end Et and the heel end Eh. For example, the suction opening K2 may be located at a position corresponding to the face center Fc.

[0078] Figures 16(a) and 16(b) are front views of the head 700 of the seventh embodiment. In Figure 16(a), the area with the marking 170 is shown with hatching. In Figure 16(b), the area with the marking 170 is shown with black fill. Figure 16(b) shows an image of the actual appearance of the head 700. Figure 17 is an enlarged cross-sectional view of the face portion 102 of the head 700. Except for the presence of the marking 170, the head 700 is the same as the head 100 of the first embodiment.

[0079] In this embodiment, the urethane layer U1 is transparent. The urethane layer U1 is transparent or semi-transparent.

[0080] As shown in Figure 17, the outer surface 120 of the face body M1 is marked with markings 170. The markings 170 can be formed by, for example, ink, paint, vapor deposition, plating, laser marking, etc. Although the markings 170 are a thin layer, for the sake of clarity in the drawing, the layer of markings 170 is shown with a thick solid line in Figure 17. The markings 170 are formed in the body groove 146. The markings 170 are formed over the entire body groove 146 (first groove width portion 148).

[0081] Because the urethane layer U1 is transparent, the marking 170 is visible from the outside. The marking 170 is located at a position corresponding to the score line 140. The marking 170 is linear. The linear marking 170 is also referred to as the marking line 172. The marking line 172 is located along the score line 140. The marking line 172 has a line width Wm. The line width Wm is measured along the same direction as the groove width Wg of the corresponding score line 140. The line width Wm is greater than the groove width Wg of the score line 140. In this embodiment, the line width Wm of the marking 170 is the same as the groove width W1 of the first groove width portion 148 (see Figure 4). In a front view (Figure 16(b)), the marking line 172 encompasses the score line 140. The marking line 172 (marking 170) is more conspicuous than the score line 140.

[0082] As can be seen from Figure 16(b), the presence of marking line 172 makes score line 140 difficult to see. However, score line 140 is still present, and the performance (spin performance, etc.) due to score line 140 remains unchanged. On the other hand, marking line 172 makes the line corresponding to score line 140 more prominent.

[0083] Figure 18 is a front view of the head 800 of the eighth embodiment. The head 800 consists of a head body 800a and a urethane layer U1. In this head 800 as well, the urethane layer U1 is transparent. Except for the shape of the marking 170, this head 800 is the same as the head 700 of the seventh embodiment.

[0084] At least one marking line 172 has a line break 174. The line break 174 is formed when the marking line 172 is interrupted midway. In this embodiment, multiple (3) marking lines 172 have line breaks 174. The head 800 is provided with multiple (6) line breaks 174. Except for the presence of the line breaks 174, the head 800 is the same as the head 700 of the seventh embodiment.

[0085] In the head 800, multiple line breaks 174 are provided within the range of the face center Ft. The multiple line breaks 174 are arranged along a ring-shaped figure surrounding the face center Fc. The line breaks 174 allow for visual confirmation of areas that are desirable as impact points. By providing the line breaks 174 on the marking lines 172, which are thicker than the scorelines 140, the visual effect of the line breaks 174 is enhanced.

[0086] In addition, in head 800, the main body groove 146 (first groove width portion 148) is located in the area corresponding to the line break 174. Therefore, scorelines 140 are also present in the line break 174.

[0087] Figure 19 is a front view of the head 900 of the ninth embodiment. The head 900 consists of a head body 900a and a urethane layer U1. In this head 900 as well, the urethane layer U1 is transparent. Except for the shape of the marking 170, this head 900 is the same as the head 700 of the seventh embodiment.

[0088] In this embodiment, one marking 170 is provided. The marking 170 constitutes a figure. In this embodiment, this figure is circular. The marking 170 is dotted. Except for the presence of the marking 170, the head 900 is the same as the head 100 of the first embodiment.

[0089] In the head 900, a dot-shaped marking 170 is provided at a position corresponding to the face center Fc. The position corresponding to the face center Fc can be within a circle with a radius of 10 mm centered on the face center Fc. More preferably, the position corresponding to the face center Fc can be within a circle with a radius of 5 mm centered on the face center Fc. This marking 170 allows for visual confirmation of the position of the face center Fc.

[0090] In the manufacturing of the head 100, the head 100 is obtained by fixing the urethane layer U1 to the outer surface of the head body 100a (outer surface 120 of the face body M1, stepped recess 130). Alternatively, the molded urethane layer U1 may be fixed to the head body 100a. Alternatively, as in the manufacturing method described later, the sheet-like urethane layer U1 (urethane sheet U2) may be molded on the head body 100a while being fixed to the head body 100a.

[0091] Figures 20 to 22 are conceptual diagrams showing an example of a manufacturing method for the head 100. Figures 20 and 22 are cross-sectional views along the longitudinal section of the head 100. Figure 21 is a cross-sectional view along the transverse section of the head 100. Figures 20 to 22 show the chronological progression. The manufacturing of the head 100 progresses in the order of Figure 20, Figure 21, and Figure 22. Hatching is omitted in Figures 20 to 22. All of the embodiments described above (heads 100, 200, 300, 400, 500, 600, 700, 800, and 900) can be manufactured by this method. In heads having markings 170 (heads 700, 800, and 900), the markings 170 are applied to the outer surface 120 of the face body M1 in a step prior to this manufacturing method.

[0092] In this manufacturing method, a urethane sheet U2 constituting the urethane layer U1 is prepared (first step). This sheet is made of urethane resin that constitutes the urethane layer U1. The urethane sheet U2 is molded on the outer surface 120 of the face body M1 to become the urethane layer U1. This urethane sheet U2 may also have an adhesive layer 125 (see Figure 7).

[0093] In this manufacturing method, a vacuum bonding device 180 can be used to bond a sheet to a workpiece under vacuum. This vacuum bonding device 180 has a vacuum chamber 182 which can be evacuated, a head holding part 184 provided in the vacuum chamber 182 which can hold a head 100, an opening 186 which connects the vacuum chamber 182 to the outside, and a sheet holding part 188 which can hold the urethane sheet U2 when the urethane sheet U2 is stretched over the opening 186. The head holding part 184 (or the sheet holding part 188) can be driven so that the head 100 moves away from the urethane sheet U2.

[0094] As shown in Figure 20, the head 100 is set in the head holding part 184. Next, the head holding part 184 is driven, and the urethane sheet U2 is placed on the outer surface 120 of the face body part M1. The head 100 is pressed against the urethane sheet U2 (see Figures 21 and 22). At the same time, the vacuum chamber 182 is evacuated. That is, the urethane sheet U2 is pressed against the outer surface 120 of the face body M1, and a vacuum is created between the face body M1 and the urethane sheet U2 (second step). In this second step, the urethane sheet U2 may be heated to a predetermined temperature. The second step may be carried out while heating the urethane sheet U2. The outer surface 120 of the face body M1 has a bulge BG. Therefore, in the second step, the contact area between the urethane sheet U2 and the outer surface 120 of the face body M1 starts from a part of the outer surface 120 of the face body M1, gradually expands in proportion to the amount of pressure the head 100 applies to the urethane sheet U2, and finally reaches the entire portion (step recess 130) where the urethane layer U1 is placed (see Figures 21 and 22). Next, the urethane sheet U2 is cut along the contour line k1 of the urethane layer U1.

[0095] In the second step, the air in the main body groove 146 escapes through the suction opening K1. As described above, the toe end Et and heel end Eh of the main body groove 146 can become the suction opening K1 (see Figure 4). In the second step, as the air in the main body groove 146 is sucked out through the suction opening K1, the urethane sheet U2 is drawn into the main body groove 146, so that a plurality of inner surface protrusions 142 are formed on the inner surface 124 of the urethane layer U1, and a plurality of score lines 140 are formed on the outer surface 126 of the urethane layer U1 corresponding to the inner surface protrusions 142.

[0096] In the second step, the attachment of the urethane sheet U2 may be completed. In this case, an adhesive layer 125 (see Figure 7) may be provided on the urethane sheet U2. Alternatively, after molding the urethane sheet U2 in the second step to obtain a molded body of the urethane layer U1, this molded body of the urethane layer U1 may be removed from the face body M1. For example, this method may be used if the urethane sheet U2 does not have an adhesive layer 125. In this case, an adhesive may be applied to the molded body of the urethane layer U1 or the face body M1, and the molded body of the urethane layer U1 may be attached to the face body M1.

[0097] Each of the embodiments described above may produce the following effects.

[0098] Score lines 140 are provided on the outer surface 126 of the urethane layer U1. Therefore, during impact, the ball's slippage on the outer surface 126 of the urethane layer U1 is suppressed, and the amount of backspin is stabilized.

[0099] In accordance with the score lines 140 on the outer surface 126 of the urethane layer U1, an inner surface projection 142 is formed on the urethane layer U1. Therefore, localized thinning of the urethane layer U1 caused by the presence of the score lines 140 is suppressed. Furthermore, despite the presence of the score lines 140, the thickness t1 of the urethane layer U1 can be kept substantially constant. By suppressing localized thinning of the urethane layer U1, the durability strength of the urethane layer U1 can be improved.

[0100] The inner surface projection 142 of the urethane layer U1 is fitted into the main body groove 146 of the face body M1. This makes it difficult for the urethane layer U1 to shift laterally relative to the face body M1, thereby improving the bonding strength of the urethane layer U1. If the inner surface projection 142 is fitted into the main body groove 146, this bonding strength can be further increased.

[0101] If the urethane layer U1 is transparent, the marking 170 provided on the outer surface 120 of the face body M1 can be seen from outside the urethane layer U1. Therefore, the marking 170 that is visible on the hitting surface 102a can be freely provided without being constrained by the scorelines 140. The specifications of the marking 170 (placement, shape, color, etc.) can be freely set. Since the marking 170 is protected by the urethane layer U1, it will not be erased by wear from impact.

[0102] As shown in Figure 16(b), linear markings 170 (marking lines 172) can be provided at positions corresponding to the scorelines 140 on the urethane layer U1. This configuration improves the visibility of the scorelines 140.

[0103] As shown in the head 700 in Figure 16(b), the line width Wm of the linear marking 170 (marking line 172) can be made larger than the groove width Wg of the score line 140. This configuration further improves the visibility of the score line 140.

[0104] The linear marking 170 can be a solid line or a dashed line. In the head 800 of Figure 18, a portion of the linear marking 170 includes a dashed line portion. The entire linear marking 170 may also be a dashed line.

[0105] The marking 170 may be a dot or a short line. In the head 900 of Figure 19, a dot-shaped marking 170 is provided at a position corresponding to the face center Fc. This configuration improves the visibility of the face center Fc. The dot-shaped marking 170 may be a marking that fits entirely within a circle with a radius of 3 mm. The short line-shaped marking 170 may be a line that fits entirely within a circle with a radius of 3 mm.

[0106] The manufacturing method described above employs vacuum forming, which includes a step (vacuum step) in which a urethane sheet U2 is pressed against the outer surface of the face body M1 while a vacuum is created between the face body M1 and the urethane sheet U2. This vacuum forming improves the adhesion between the face body M1 and the urethane layer U1.

[0107] The face body M1 has multiple body grooves 146 formed on its outer surface 120 and extending from the toe side to the heel side, and suction openings K1 and K2 formed in each of the body grooves 146. In the vacuum step described above, the air in the body grooves 146 is sucked in through the suction openings K1 and K2, while the urethane sheet U2 is drawn into the body grooves 146. As a result, multiple inner protrusions 142 are formed on the inner surface 124 of the urethane layer U1, and multiple scorelines 140 are formed on the outer surface 126 of the urethane layer U1 corresponding to the inner protrusions 142. Because the air in the body grooves 146 is sucked in through the suction openings K1 and K2, the urethane layer U1 (urethane sheet U2) can be made to enter the body grooves 146. In addition, the urethane layer U1 (urethane sheet U2) can be made to adhere tightly to the inner surface of the body grooves 146. As a result, an inner surface projection 142 can be formed on the inner surface 124 of the urethane layer U1, and a score line 140 can be formed on the outer surface 126 of the urethane layer U1.

[0108] The outer surface 120 of the face body M1 has a striking surface area 121 corresponding to the striking surface 102a. At least one end of each of the body grooves 146, either the toe side or the heel side, reaches the outer edge Q2 of the striking surface area 121 or the outside thereof. Since the striking surface area 121 of the face body M1 has a bulge BG, allowing the body groove 146 to reach its outer edge Q2 makes it easier for air to escape from within the body groove 146. By allowing air to escape from within the body groove 146, the inner protrusions 142 can be formed reliably and with high precision. As a result, the adhesion strength of the urethane layer U1 is increased, and the scorelines 140 are formed with high precision.

[0109] The suction opening K1 of the main body groove 146 is formed by opening at least one of the toe end Et or heel end Eh of the main body groove 146. Therefore, the suction opening K1 of the main body groove 146 can be easily formed. In addition, since the outer surface 120 (striking surface area 121) of the face body M1 has a bulge BG, air can easily escape from the ends Et and Eh of the main body groove 146.

[0110] In the head body 100a (Figure 4), head body 200a (Figure 9), head body 300a (Figure 11), and head body 400a (Figure 13), the body groove 146 comprises a first groove width portion 148 and a second groove width portion 150. The second groove width portion 150 is provided connected to both ends of the first groove width portion 148. The groove width W2 of this second groove width portion 150 is smaller than the groove width W1 of the first groove width portion 148. The groove width W2 of the second groove width portion 150 is set so that the urethane layer portion U1 does not penetrate at least completely. Considering that there is a bulge BG on the outer surface 120 of the face body portion M1, in the vacuum step described above, the second groove width portion 150 is less likely to be blocked by the urethane layer portion U1 than the first groove width portion 148. In the vacuum step described above, air in the first groove width portion 148 can easily escape from the second groove width portion 150. That is, the second groove width portion 150 can function as a suction opening. Since the second groove width portion 150 is a groove, it opens in the direction normal to the outer surface 120 of the face body portion M1. This opening allows the second groove width portion 150 to function as a suction opening.

[0111] In head bodies 100a (Figure 4), 200a (Figure 9), 300a (Figure 11), and 400a (Figure 13), the urethane layer U1 does not extend into the second groove width portion 150. Therefore, in these heads, scorelines 140 are not formed at the position corresponding to the second groove width portion 150. In these heads, the groove width W2 of the second groove width portion 150 is smaller than the thickness t1 of the urethane layer U1. By appropriately setting the groove width W2 of the second groove width portion 150, it is possible to prevent the formation of scorelines 140 at the position corresponding to the second groove width portion 150. For this reason, the second groove width portion 150 can be positioned without being constrained by the installation area of ​​the scorelines 140. For example, the second groove width portion 150 can extend to the outer edge Q2 of the outer surface 120 (hitting surface area 121) of the face body portion M1. Furthermore, the second groove width portion 150 can extend to the outside of the outer surface 120 (striking surface area 121) of the face body portion M1. In the embodiment shown in Figure 4, the second groove width portion 150 also extends to the outside of the outer surface 120 (striking surface area 121) of the face body portion M1. The outer surface 120 of the face body portion M1 has a bulge BG. For this reason, in the vacuum step described above, the air in the first groove width portion 148 can easily escape from the second groove width portion 150.

[0112] As shown in head 200 (Figure 8), head 300 (Figure 10), and head 400 (Figure 12), the arrangement of the second groove width portion 150 can form a break 141 in the scoreline 140. This break 141 can serve as an external marker. For example, the break 141 can serve as a marker in the area close to the face center Fc (see Figures 10 and 12). Also, as shown in head body 200a (Figure 9), head body 300a (Figure 11), and head body 400a (Figure 13), the main body groove portion 146 is not interrupted at the break 141 in the scoreline 140. That is, in the portion corresponding to the break 141, the main body groove portion 146 is connected by the intermediate narrow portion 152. Therefore, even when a break 141 is provided, air can be smoothly released from within the first groove width portion 148.

[0113] In head bodies 100a (Figure 4), 200a (Figure 9), 300a (Figure 11), and 400a (Figure 13), at least one first groove width portion 148 traverses the face center region Rc. In head bodies 100a (Figure 4) and 200a (Figure 9), multiple first groove width portions 148 traverse the face center region Rc. This configuration allows for the provision of scorelines 140 that traverse the face center region Rc, which has a high probability of being the point of impact. Furthermore, the groove width Wg of the scorelines 140 can be increased in the face center region Rc, which has a high probability of being the point of impact. As a result, the amount of backspin on the ball can be stabilized.

[0114] In the head bodies 100a (Figure 4), 200a (Figure 9), 300a (Figure 11), and 400a (Figure 13), in the body groove 146 where the first groove width portion 148 crosses the face center region Rc, the second groove width portion 150 is connected to at least one end of the first groove width portion 148. Therefore, scorelines 140 are formed corresponding only to the first groove width portion 148 located in the face center region Rc, making the scorelines 140 more prominent. As a result, alignment at address may be made easier.

[0115] The urethane layer U1 may have different spin performance than the metal hitting surface. The urethane layer U1 may improve the feel of the ball. From the viewpoint of enhancing the effects caused by the urethane layer U1, the thickness t1 of the urethane layer U1 is preferably 0.3 mm or more, more preferably 0.32 mm or more, and even more preferably 0.35 mm or more. If this thickness t1 is excessive, it becomes difficult to form the scorelines 140 accurately. From these viewpoints, the thickness t1 of the urethane layer U1 is preferably 1.0 mm or less, more preferably 0.9 mm or less, more preferably 0.8 mm or less, more preferably 0.7 mm or less, and even more preferably 0.6 mm or less.

[0116] From the viewpoint of spin performance and drainage performance, the groove width Wg of the scoreline 140 is preferably 0.3 mm or more, more preferably 0.32 mm or more, and even more preferably 0.35 mm or more. In order to make the groove width Wg excessively large, it becomes necessary to make the groove width W1 of the main groove portion 146 (first groove width portion 148) excessively large. From this viewpoint, the groove width Wg of the scoreline 140 is preferably 0.9 mm or less, more preferably 0.85 mm or less, and even more preferably 0.8 mm or less.

[0117] From the viewpoint of spin performance and drainage performance, the groove depth Dg of the scoreline 140 is preferably 0.1 mm or more, more preferably 0.12 mm or more, and even more preferably 0.15 mm or more. In the scoreline 140 formed by bending the urethane layer U1, if the groove depth Dg is made too large, the groove width Wg tends to become too large. From this viewpoint, the groove depth Dg of the scoreline 140 is preferably 0.35 mm or less, more preferably 0.32 mm or less, and even more preferably 0.3 mm or less.

[0118] One example of a method for fixing the urethane layer U1 to the face body M1 is to use an adhesive. This adhesive may be provided on the urethane sheet U2 that constitutes the urethane layer U1, as in the above embodiment. Alternatively, this adhesive may be applied to the face body M1. It is also possible to use no adhesive at all. For example, the urethane layer U1 may be fixed to the face body M1 by adhesion alone. By exhausting the space between the urethane layer U1 and the face body M1, the urethane layer U1 and the face body M1 can adhere to each other without the use of an adhesive.

[0119] The adhesive used to fix the urethane layer U1 to the face body M1 is preferably one that provides excellent bonding strength between the two. Examples of such adhesives include "Chemlock 218E," "Chemlock 210," and "Chemlock IMB1040" manufactured by Road Japan Co., Ltd. ("Chemlock" is a registered trademark). Other adhesives include "Metalock C-12" and "Metalock UA" manufactured by Toyo Chemical Research Institute Co., Ltd. ("Metalock" is a registered trademark). Yet another adhesive is a two-component epoxy adhesive. Examples of such two-component epoxy adhesives include "DP420" and "DP460" commercially available from 3M Japan.

[0120] The method for forming the urethane layer U1 is not limited. For example, the urethane layer U1 may be molded separately from the head body and then attached to the head body. For example, the urethane layer U1 may be formed on the face body M1 of the head body 100a by pressing a urethane sheet U2 onto the face body M1 with a mold. In this case, the mold may have protrusions for forming the scorelines 140. However, pressing with a mold tends to stretch and thin the urethane sheet U2 within the body groove 146. From this viewpoint, it is preferable that the urethane layer U1 be manufactured by a manufacturing method that includes a vacuum step, as in the above embodiment.

[0121] From the viewpoint of increasing the adhesion strength of the urethane layer U1, the outer surface 120 of the face body M1 may be roughened. The method of roughening the outer surface 120 of the face body M1 is not limited. The outer surface of the face body may be roughened by molding with a mold or by surface treatment. Examples of surface treatment methods include blasting such as shot blasting and sandblasting, metal etching, CNC machining, laser processing, and combinations thereof. CNC stands for Computerized Numerical Control.

[0122] The urethane layer U1 is formed of polyurethane. Polyurethane is a polymer having urethane bonds. Examples of polyurethane include thermoplastic polyurethane and thermosetting polyurethane. Thermoplastic polyurethane is polyurethane that exhibits plasticity upon heating. Generally, thermoplastic polyurethane refers to polyurethane having a linear structure with a relatively high molecular weight. Thermosetting polyurethane is polyurethane obtained by reacting a low molecular weight urethane prepolymer with a curing agent (chain length extender) to increase its molecular weight when molding the urethane layer. Thermosetting polyurethane is also called two-component curing polyurethane. Thermosetting polyurethane includes polyurethanes with a linear structure and polyurethanes with a three-dimensional crosslinked structure, which can be produced by controlling the number of functional groups in the prepolymer and curing agent (chain length extender) used. Polyurethane may also be a thermoplastic elastomer.

[0123] Thermoplastic polyurethanes are not particularly limited as long as they have multiple polyurethane bonds within their molecules and exhibit thermoplasticity. For example, thermoplastic polyurethanes are products in which urethane bonds are formed within the molecule by reacting polyisocyanate and polyol, and can be obtained by further reacting them with polyamines or the like, if necessary.

[0124] The polyisocyanate component constituting the thermoplastic polyurethane is not particularly limited as long as it has two or more isocyanate groups, for example, aromatic polyisocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 3,3'-vitrylene-4,4'-diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethyl xylylene diisocyanate (TMXDI), and paraphenylenedi diisocyanate (PPDI); and 4,4'-dicyclohexylmethane diisocyanate (H 12This includes one or more alicyclic polyisocyanates or aliphatic polyisocyanates such as MDI, hydrogenated xylylene diisocyanate (H6XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), norbornene diisocyanate (NBDI), etc.

[0125] From the viewpoint of improving scratch resistance, it is preferable to use aromatic polyisocyanates as the polyisocyanate component of polyurethane. By using aromatic polyisocyanates, the mechanical properties of the resulting polyurethane are improved, and a urethane layer with excellent scratch resistance can be obtained. Furthermore, from the viewpoint of improving weather resistance, it is preferable to use non-yellowing polyisocyanates (TMXDI, XDI, HDI, H6XDI, IPDI, H6XDI) as the polyisocyanate component of polyurethane. 12 It is preferable to use MDI, NBDI, etc., and more preferably 4,4'-dicyclohexylmethane diisocyanate (H 12 Use MDI). 4,4'-Dicyclohexylmethane diisocyanate (H 12 MDI has a rigid structure, which improves the mechanical properties of the resulting polyurethane, and yields a polyurethane layer U1 with excellent scratch resistance. From the viewpoint of improving grip, other polyisocyanate components may be selected.

[0126] The polyol component constituting thermoplastic polyurethane is not particularly limited as long as it has multiple hydroxyl groups, and examples include low molecular weight polyols and high molecular weight polyols. Examples of low molecular weight polyols include diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol; and triols such as glycerin, trimethylolpropane, and hexanetriol. Examples of high molecular weight polyols include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), and polyoxytetramethylene glycol (PTMG); condensed polyester polyols such as polyethylene adipate (PEA), polybutylene adipate (PBA), and polyhexamethylene adipate (PHMA); lactone-based polyester polyols such as poly-ε-caprolactone (PCL); polycarbonate polyols such as polyhexamethylene carbonate; and acrylic polyols. A mixture of at least two of the above-mentioned polyols may also be used.

[0127] The average molecular weight of the high molecular weight polyol is not particularly limited, but is preferably 400 or more, and more preferably 1,000 or more. This is because if the average molecular weight of the high molecular weight polyol becomes too low, the resulting polyurethane may become hard and the feel of the ball may decrease. The upper limit of the average molecular weight of the high molecular weight polyol is not particularly limited, but is 10,000 or less, and more preferably 8,000 or less.

[0128] Furthermore, the polyamine constituting the thermoplastic polyurethane is not particularly limited as long as it has at least two amino groups, if necessary. Examples of the polyamine include aliphatic polyamines such as ethylenediamine, propylenediamine, butylenediamine, and hexamethylenediamine, alicyclic polyamines such as isophoronediamine and piperazine, and aromatic polyamines.

[0129] The aromatic polyamine is not particularly limited as long as at least two amino groups are directly or indirectly bonded to the aromatic ring. Here, indirect bonding means that the amino groups are bonded to the aromatic ring, for example, via lower alkylene groups. The aromatic polyamine may be, for example, a monocyclic aromatic polyamine in which two or more amino groups are bonded to one aromatic ring, or a polycyclic aromatic polyamine containing two or more aminophenyl groups in which at least one amino group is bonded to one aromatic ring.

[0130] Examples of monocyclic aromatic polyamines include types in which the amino group is directly bonded to the aromatic ring, such as phenylenediamine, toluenediamine, diethyltoluenediamine, and dimethylthiotoluenediamine; and types in which the amino group is bonded to the aromatic ring via a lower alkylene group, such as xylylenediamine. Furthermore, the polycyclic aromatic polyamine may be a poly(aminobenzene) in which at least two aminophenyl groups are directly bonded, or at least two aminophenyl groups may be bonded via a lower alkylene group or alkylene oxide group. Of these, diaminodiphenylalkanes in which two aminophenyl groups are bonded via a lower alkylene group are preferred, and 4,4'-diaminodiphenylmethane and its derivatives are particularly preferred.

[0131] The configuration of the thermoplastic polyurethane is not particularly limited. Examples of such configurations include: a configuration composed of a polyisocyanate component and a high molecular weight polyol component; a configuration composed of a polyisocyanate component, a high molecular weight polyol component and a low molecular weight polyol component; a configuration composed of a polyisocyanate component, a high molecular weight polyol component and a low molecular weight polyol component and a polyamine component; and a configuration composed of a polyisocyanate component, a high molecular weight polyol component and a polyamine component.

[0132] Examples of the aforementioned thermoplastic polyurethanes include MDI-based polyurethanes in which MDI is used in polyisocyanate, and polyisocyanate with H 12 Examples include hydrogenated MDI-based polyurethanes that utilize MDI.

[0133] Specific examples of the aforementioned thermoplastic polyurethane include, for example, "Elastran XNY90A", "Elastran XNY97A", ​​"Elastran XNY585", "Elastran 1180A10", "Elastran 1185A50", "Elastran 1190A10TR", "Elastran 1195A50STR", and "Elastran 1164D50", which are commercially available from BASF Japan.

[0134] In the present invention, the material of the urethane layer U1 is not particularly limited as long as it contains polyurethane as a base resin component. When the polyurethane is thermoplastic polyurethane, it is desirable that the content of thermoplastic polyurethane in the resin component constituting the material of the urethane layer U1 be 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. It is also a preferred embodiment that the resin component constituting the material of the urethane layer U1 consists substantially of polyurethane only (for example, only thermoplastic polyurethane).

[0135] In addition to the resin components described above, the material of the urethane layer U1 of the present invention may also contain pigment components such as white pigments (e.g., titanium dioxide), blue pigments, and red pigments, specific gravity adjusters such as calcium carbonate and barium sulfate, dispersants, antioxidants, ultraviolet absorbers, light stabilizers, fluorescent materials, or fluorescent whitening agents, to the extent that they do not excessively impair the properties of the urethane layer U1.

[0136] The Shore D hardness of the striking surface 102a is not limited. From the standpoint of feel, this Shore D hardness may be within a predetermined range. The lower limit of the Shore D hardness of the striking surface 102a can be 65 or higher, more preferably 70 or higher, and more preferably 75 or higher. The upper limit of the Shore D hardness of the striking surface 102a can be 99 or lower, more preferably 95 or lower, and more preferably 90 or lower.

[0137] The Shore D hardness of the striking surface 102a is measured in the completed head. The head is stored at 23°C for two weeks, and the hardness of the striking surface of this head is measured using an Asker rubber hardness tester type D. The measurement is performed by pressing the hardness tester against the striking surface of the head. The number of measurements (n) is set to 10, and the average of the 10 data points is taken as the measured value. The measurement is performed in areas without the main body groove 146 or score lines 140.

[0138] Preferred materials for the head body include metal and fiber-reinforced plastic. Examples of metals include titanium alloy, pure titanium, stainless steel, aluminum alloy, maraging steel, and mild steel. An example of fiber-reinforced plastic is carbon fiber reinforced plastic. The head body may have both a metal portion and a fiber-reinforced plastic portion.

[0139] Examples of preferred materials for the face body M1 include metal and fiber-reinforced plastic. Examples of metals include titanium alloy, pure titanium, stainless steel, aluminum alloy, maraging steel, and mild steel. An example of a fiber-reinforced plastic is carbon fiber reinforced plastic. The face body M1 may have a metal portion and a fiber-reinforced plastic portion.

[0140] The following notes are part of the invention included in this invention. [Note 1] A golf club head having a face portion that forms the striking surface, The face portion comprises a face body portion and a urethane layer portion made of polyurethane that is provided on the outside of the face body portion. The urethane layer has a plurality of scorelines formed on its outer surface and extending from the toe side to the heel side, and a plurality of inner projections formed on its inner surface and extending from the toe side to the heel side corresponding to each of the scorelines. The face body portion has a plurality of body grooves formed on its outer surface, which extend from the toe side to the heel side, corresponding to each of the inner protrusions. A golf club head in which each of the aforementioned internal protrusions is fitted into each of the aforementioned grooves on the main body. [Note 2] The golf club head according to Appendix 1, wherein the thickness of the urethane layer is substantially constant. [Note 3] The aforementioned urethane layer is transparent, A golf club head as described in Appendix 1 or 2, wherein at least one of the grooves in the main body is marked. [Note 4] The aforementioned marking is linear, A golf club head as described in Appendix 3, wherein the line width of the marking is greater than the width of the scoreline. [Note 5] A method for manufacturing a golf club head in which a urethane layer is formed on the outside of the face body, and the outer surface of this urethane layer constitutes the striking surface, The first step involves preparing the urethane sheet that constitutes the urethane layer, The method includes a second step in which the urethane sheet is pressed against the outer surface of the face body while a vacuum is created between the face body and the urethane sheet. The face body portion has a plurality of body grooves formed on its outer surface and extending from the toe side to the heel side, and a suction opening formed in each of the body grooves. In the second step, the air in the main body groove is sucked in from the suction opening, and the urethane sheet is drawn into the main body groove, thereby forming a plurality of internal protrusions on the inner surface of the urethane layer, and a plurality of scorelines corresponding to the internal protrusions on the outer surface of the urethane layer, in a method for manufacturing a golf club head. [Note 6] The striking surface has a bulge, The outer surface of the face body portion has a striking surface area corresponding to the striking surface, The manufacturing method according to Appendix 5, wherein in each of the grooves of the main body, at least one end on the toe side and heel side extends to the outer edge of the striking surface area. [Note 7] The manufacturing method according to Appendix 5 or 6, wherein the suction opening of the main body groove is formed by at least one of the toe-side and heel-side ends of the main body groove being open. [Explanation of Symbols]

[0141] 100, 200, 300, 400, 500, 600, 700, 800, 900... Golf club heads 100a, 200a, 300a, 400a, 500a, 600a, 700a, 800a, 900a... Head body 102...Face section 102a... Striking surface 104... Crown section 106...Sole 108...Hosel section 120...Outer surface of the face body 121...Hitting surface area of ​​the head body 122...Inner surface of the face body 124...Inner surface of the urethane layer 126...Outer surface of the urethane layer 130... Step recess 130a... Step section 140...Scoreline 141...Break in the scoreline 142...Inner protrusion 146... Main body groove 148...First groove width portion in the main body groove 150...Second groove width portion in the main body groove 160... Extra innings scoreline 170... Marking 172... Marking line 180... Vacuum bonding device 182...Vacuum chamber 184...Head holding part 186...Opening 188...Seat holding section Fc... Face Center U1... Urethane layer U2... Urethane sheet M1...Face body K1, K2...Suction opening Et... the end of the groove in the main body Eh...heel end of the groove on the main body

Claims

1. A golf club head having a face portion that forms the striking surface, The face portion comprises a face body portion and a urethane layer portion made of polyurethane that is provided on the outside of the face body portion. The urethane layer has a plurality of scorelines formed on its outer surface and extending from the toe side to the heel side, and a plurality of inner projections formed on its inner surface and extending from the toe side to the heel side corresponding to each of the scorelines. The face body portion has a plurality of body grooves formed on its outer surface, which extend from the toe side to the heel side, corresponding to each of the inner protrusions. A golf club head in which each of the aforementioned internal protrusions is fitted into each of the aforementioned grooves on the main body.

2. The golf club head according to claim 1, wherein the thickness of the urethane layer is substantially constant.

3. The aforementioned urethane layer is transparent, The golf club head according to claim 1 or 2, wherein a marking is provided in at least one of the grooves in the main body.

4. The aforementioned marking is linear, The golf club head according to claim 3, wherein the line width of the marking is greater than the width of the scoreline.

5. A method for manufacturing a golf club head in which a urethane layer is formed on the outside of the face body, and the outer surface of this urethane layer constitutes the striking surface, The first step involves preparing the urethane sheet that constitutes the urethane layer, The method includes a second step in which the urethane sheet is pressed against the outer surface of the face body while a vacuum is created between the face body and the urethane sheet. The face body portion has a plurality of body grooves formed on its outer surface and extending from the toe side to the heel side, and a suction opening formed in each of the body grooves. In the second step, the air in the main body groove is sucked in from the suction opening, and the urethane sheet is drawn into the main body groove, thereby forming a plurality of internal protrusions on the inner surface of the urethane layer, and a plurality of scorelines corresponding to the internal protrusions on the outer surface of the urethane layer, in a method for manufacturing a golf club head.

6. The striking surface has a bulge, The outer surface of the face body portion has a striking surface area corresponding to the striking surface, The manufacturing method according to claim 5, wherein in each of the grooves of the main body, at least one end on the toe side and the heel side extends to the outer edge of the striking surface area.

7. The manufacturing method according to claim 6, wherein the suction opening of the main body groove is formed by opening at least one of the toe-side and heel-side ends of the main body groove.

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