Patent Publication Number: US-11020638-B2

Title: Iron-type golf club head

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority to Japanese patent application No. 2019-086367, filed on Apr. 26, 2019, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to iron-type golf club heads. 
     2. Description of the Related Art 
     When hitting a golf ball with an iron-type golf club head, the flight distance of the golf ball differs depending on whether the golf ball is hit by the sweet area or an area other than the sweet area (off the center) of the face of the iron-type golf club head. This causes the flight distance to be unstable, so that sufficient ball striking performance may not be achieved. Therefore, techniques for improving ball striking performance, such as those described in Japanese Patent No. 2929587, Japanese Laid-open Patent Publication No. 2000-225217, Japanese Patent No. 3006463, Japanese Laid-open Patent Publication No. 2005-137634, and U.S. Pat. No. 8,235,842, have been discussed. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention, an iron-type golf club head includes a body and a face joined to the body. The face includes a front surface including a ball striking surface, and a rear surface facing an interior surface of the body. Multiple independent depressions are formed in the rear surface toward the front surface. Each of the independent depressions is at least partially filled with a non-metallic material. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and not restrictive of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front elevational view of an iron-type golf club head according to an embodiment; 
         FIG. 2  is a rear elevational view of the iron-type golf club head according to the embodiment; 
         FIG. 3  is a sectional view of the iron-type golf club head according to the embodiment; 
         FIG. 4  is a front-side perspective view of a body according to the embodiment; 
         FIG. 5  is a rear-side perspective view of a face according to the embodiment; 
         FIG. 6  is a front elevational view of an iron-type golf club head according to a variation of the embodiment; 
         FIG. 7  is a sectional view of the iron-type golf club head according to the variation; 
         FIG. 8  is a front-side perspective view of a body according to the variation; and 
         FIG. 9  is a rear-side perspective view of a face according to the variation. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT 
     According to an aspect of the invention, an iron-type golf club head that can achieve a stable flight distance is provided. 
     One or more embodiments of the invention are described below with reference to the accompanying drawings. In the following, the same elements or components are referred to using the same reference numeral, and duplicate description thereof may be omitted. 
       FIGS. 1 and 2  are a front elevational view and a rear elevational view, respectively, of an iron-type golf club head  1  (hereinafter, “iron head  1 ”) according to an embodiment.  FIG. 3  is a sectional view of the iron head  1 , illustrating a section taken along a plane indicated by the line III-III of  FIG. 1 , which extends in the face-back direction and passes through the substantial center of a face  20  of the iron head  1 . 
     The front elevational view of  FIG. 1  is a view looking at the iron head  1  on its front surface side, depicting the iron head  1  resting (soled) on a horizontal plane H (corresponding to a ground surface) at a standard lie angle and a standard loft angle. In  FIGS. 1 through 3 , the double-headed arrow d 1  indicates the “toe-heel” (left-right) direction, namely, the direction from the toe side to the heel side or the direction from the heel side to the toe side, of the iron head  1 , the double-headed arrow d 2  indicates the “top-sole” (up-down) direction, namely, the direction from the top side to the sole side or the direction from the sole side to the top side, of the iron head  1 , and the double-headed arrow d 3  indicates the “face-back” (front-rear) direction, namely, the direction from the face side to the back side or the direction from the back side to the face side, of the iron head  1 . 
     The iron head  1  depicted in  FIGS. 1 through 3  is a head for an iron-type golf club, and is a structure including a body  10  and the face  20 . The face  20  is joined to the body  10  by, for example, welding. In each constituent part of the structure, a face-side surface may be referred to as “front surface” and a back-side surface may be referred to as “rear surface.” 
       FIG. 4  is a front-side perspective view of the body  10  according to the embodiment.  FIG. 5  is a rear-side perspective view of the face  20  according to the embodiment. 
     Referring to  FIGS. 4 and 5  as well as  FIGS. 1 through 3 , the body  10  includes a frame  11 , a face placement part  12 , a back  13 , a rear protrusion  14 , and a hosel  15 . 
     The body  10  may be formed using, for example, a metal material such as a titanium alloy, titanium, stainless steel, an aluminum alloy, or carbon steel. The process for manufacturing the body  10  may be, but is not limited to, forging, casting, machining, or any combination thereof. 
     The face  20  includes a face (front) surface  201  and a rear surface  202  that face in opposite directions. The face surface  201  includes a ball striking surface. The face  20  has a predetermined thickness. The face surface  201  defines an exterior surface of the face  20 . The thickness of the face  20  is, for example, 0.5 mm or more and 3 mm or less, and preferably, 1.2 mm or more and 2.1 mm or less. 
     Multiple score lines  21  (grooves formed in the face surface  201  toward the rear surface  202 ) elongated in the toe-heel direction are arranged at predetermined intervals in the top-sole direction in the face surface  201 . 
     The face  20  includes a striking part  205  designed to strike a golf ball and a toe part  206  formed on the toe side of the striking part  205 . The toe part  206  is not designed to strike a golf ball. In the face  20 , the striking part  205  is a region where the score lines  21  are formed in the face surface  201 . The toe part  206  continues (extends) from the striking part  205  on its toe side. 
     The face  20  may be formed using, for example, a metal material such as a titanium alloy, titanium, stainless steel, an aluminum alloy, or carbon steel. The process for manufacturing the face  20  may be, but is not limited to, forging, casting, machining, or any combination thereof. 
     In the body  10 , the face placement part  12  that positions the face  20  is formed inside the frame  11  having a frame shape. The front surface (face-side surface) of the face placement part  12  is at a position set back toward the back  13  from the front surface (face-side surface) of the frame  11 . The front surface of the face placement part  12  contacts the outer edge (peripheral) portion of the rear surface  202  of the face  20 . The amount of setback (the size of depression) of the front surface of the face placement part  12  from the front surface of the frame  11  is approximately equal to the thickness of the face  20 . 
     The back  13  includes a flat part  31  and a protruding part  32 . The flat part  31  is positioned around the center of the back  13  in the toe-heel direction, and has a substantially inversed triangular shape. 
     Two openings  31   x  are provided in the flat part  31  to pierce through the flat part  31 . Each opening  31   x  may be closed with, for example, a non-metallic material  60 . Alternatively, a metal plate such as a nameplate may be so placed on the exterior side of the flat part  31  as to conceal the openings  31   x.    
     The shape of the openings  31   x  is, for example, circular. Three or more openings  31   x  may be provided in the flat part  31 . The technical significance of providing the flat part  31  with the multiple openings  31   x  is described below. 
     The protruding part  32  includes a substantially triangular toe-side protrusion  321  and a substantially triangular heel-side protrusion  322 . The toe-side protrusion  321  is formed on the toe side of the flat part  31  to protrude outward of the iron head  1  relative to the flat part  31 . The heel-side protrusion  322  is formed on the heel side of the flat part  31  to protrude outward of the iron head  1  relative to the flat part  31 . 
     When viewed from the inside of the body  10 , the interior surface of the flat part  31  is depressed to the back side relative to the face placement part  12  and the interior surfaces of the toe-side protrusion  321  and the heel-side protrusion  322  are further depressed to the back side relative to the interior surface of the flat part  31 , within the face placement part  12 . 
     The rear protrusion  14  lies (extends) in the toe-heel direction on the sole side of the back  13  below the center of the iron head  1 , and protrudes rearward of the iron head  1  relative to the back  13 . The rear protrusion  14  forms part of the sole. A surface of the rear protrusion  14  that faces the horizontal plane H when the iron head  1  is soled on the horizontal plane H at a standard lie angle and a standard loft angle forms the sole along with the vicinity of the surface. Here, being below the center of the iron head  1  means being on the sole side of a position whose height is half the maximum height of the face  20 . 
     The interior surface (facing the rear surface  202  of the face  20 ) of the rear protrusion  14  includes a stepped portion. The stepped portion is stepped to form wall faces  141 ,  142 ,  143 ,  144 ,  145  and  146  that are arranged substantially parallel to the rear surface  202  of the face  20 . When viewed in a direction normal to the face surface  201 , the wall faces  141  through  146  are at positions that gradually increase in depth from the rear surface  202  as the positions increase in distance inward from the outer edge of the rear protrusion  14 . Here, being substantially parallel means that the angle formed by two surfaces (planes) is within ±5 degrees (the same applies hereinafter). 
     When viewed in a direction normal to the face surface  201 , the wall face  141  extends in the toe-heel direction at the position closest to the sole in the interior surface of the rear protrusion  14 . The wall face  141  is an elongated portion positioned approximately as deep as the interior surfaces of the toe-side protrusion  321  and the heel-side protrusion  322 . The wall face  141  faces the rear surface  202  of the face  20 . 
     When viewed in a direction normal to the face surface  201 , the wall face  142  is a frame-shaped portion depressed to the back side relative to the wall face  141 . The wall face  142  faces the rear surface  202  of the face  20 . 
     When viewed in a direction normal to the face surface  201 , the wall face  143  is positioned inside the wall face  142 . The wall face  143  is a frame-shaped portion depressed to the back side relative to the wall face  142 . The wall face  143  faces the rear surface  202  of the face  20 . 
     When viewed in a direction normal to the face surface  201 , the wall face  144  is positioned inside the wall face  143 . The wall face  144  includes a frame-shaped portion forming part of the outer edge of the wall face  144  and a flat portion continuing (extending) from the frame-shaped portion and positioned on the heel side in the interior surface of the rear protrusion  14 . The frame-shaped portion and the flat portion of the wall face  144  face the rear surface  202  of the face  20 . 
     When viewed in a direction normal to the face surface  201 , the wall face  145  is positioned inside the wall face  144 . The wall face  145  includes a frame-shaped portion forming part of the outer edge of the wall face  145  and a flat portion continuing (extending) from the frame-shaped portion and positioned around the center of the interior surface of the rear protrusion  14  in the toe-heel direction. The frame-shaped portion and the flat portion of the wall face  145  face the rear surface  202  of the face  20 . 
     When viewed in a direction normal to the face surface  201 , the wall face  146  is positioned inside the wall face  145 . The wall face  146  is a flat portion positioned on the toe side in the interior surface of the rear protrusion  14 . The wall face  146  faces the rear surface  202  of the face  20 . The wall face  146  is the deepest portion (bottommost interior surface) of the rear protrusion  14 . A depth (distance) D from the rear surface  202  of the face  20  to the wall face  146  in a direction perpendicular to the rear surface  202  is, for example, 5 mm or more and 15 mm or less, and preferably, 10 mm or more and 15 mm or less. 
     Referring to  FIG. 5 , the face  20  includes multiple independent depressions  22  formed in the rear surface  202  toward the face surface  201 . Here, being “independent” means, for example, that multiple grooves do not contact or cross each other, namely, that the depressions  22  are out of contact with each other. 
     The depressions  22  may be placed, for example, in a staggered arrangement, but may also be placed in a matrix, at random, or at any positions as required, for example. 
     The shape of the depressions  22  as viewed in a direction normal to the rear surface  202  may be, but is not limited to, for example, a circular shape, and may also be elliptical or polygonal to the extent that the depressions  22  are independent of each other. The depressions  22  may have a more complicated shape such as a star shape. The depressions  22 , however, are preferably circular in terms of the accuracy of formation of the depressions  22 . 
     According to this embodiment, a description is hereinafter given of an example where the shape of the depressions  22  as viewed in a direction normal to the rear surface  202  is circular. The cross-sectional shape of the depressions  22  is, for example, a curved shape deepest at its center. The cross-sectional shape of the depressions  22  may be either spherical or aspherical. 
     The depressions  22  are not placed in a sweet area  20   se  of the face  20 , and are placed in substantially the entirety of the rear surface  202  of the face  20  around the sweet area  20   se . Here, letting the initial velocity of a golf ball (“ball initial velocity”) at which the iron head  1  can gain a maximum flight distance be 100, the sweet area refers to the aggregate area of striking points at which the maximum flight distance can be gained and their surrounding striking points at which a ball initial velocity of 98 or more can be gained. 
     According to the illustration of  FIG. 5 , the face  20  includes an area  20 C 1 , an area  20 C 2 , and  20 C 3  that are successively arranged in order in a direction away from the sweet area  20   se  and are provided with small circular depressions, medium circular depressions, and large depressions, respectively, as the depressions  22 . The medium circular depressions are deeper than the small circular depressions. The large depressions are deeper than the medium circular depressions. The depressions  22  placed in the rear surface  202 , however, are not limited in diameter to these three types. 
     The diameter of the small circular depressions is, for example, 2.00 mm or more and less than 2.75 mm. Where the small circular depressions are deepest, the depth of the small circular depressions is, for example, 0.200 mm or more and less than 0.275 mm. The diameter of the medium circular depressions is, for example, 2.75 mm or more and less than 3.50 mm. Where the medium circular depressions are deepest, the depth of the medium circular depressions is, for example, 0.275 mm or more and less than 0.350 mm. The diameter of the large circular depressions is, for example, 3.50 mm or more and 4.25 mm or less. Where the large circular depressions are deepest, the depth of the large circular depressions is, for example, 0.350 mm or more and 0.425 mm or less. 
     Referring to  FIG. 5 , two lines L 1  and L 2  are drawn parallel to the top-sole direction. The depressions  22  include, for example, a depression  22  whose center is positioned on the line L 1  or L 2 . In the toe-heel direction, respective pitches P 1  of the small circular depressions, the medium circular depressions, and the large circular depressions are, for example, 5.5 mm or more and 8.0 mm or less. In the toe-heel direction, for example, the pitch of the medium circular depressions may be greater than the pitch of the small circular depressions, and the pitch of the larger circular depressions may be greater than the pitch of the medium circular depressions. 
     Referring to  FIG. 5 , two lines L 3  and L 4  are drawn parallel to the toe-heel direction. The depressions  22  include, for example, a depression  22  whose center is positioned on the line L 3  or L 4 . In the top-sole direction, respective pitches P 2  of the small circular depressions, the medium circular depressions, and the large circular depressions are, for example, 5.5 mm or more and 6.0 mm or less. In the top-sole direction, the respective pitches of the small circular depressions, the medium circular depressions, and the large circular depressions may be the same, for example. 
     By thus adjusting the diameter and the pitch of the depressions  22 , it is possible to distribute stress and ensure strength when the face  20  strikes a golf ball. 
     The body  10  and the face  20  are joined by, for example, welding with a space formed between the interior surface of the body  10  and the rear surface  202  of the face  20 . The space is filled with the non-metallic material  60 . 
     More specifically, by joining the face  20  to the face placement part  12  of the body  10 , a space is formed between the respective interior surfaces of the flat part  31 , the protruding part  32 , and the rear protrusion  14  of the body  10  and the rear surface  202  of the face  20 , and the space is filled with the non-metallic material  60 . The non-metallic material  60  is poured into the space from one of the openings  31   x  by, for example, injection, and is cured. The other opening  31   x  serves as an air vent hole. 
     Thus, a space is formed between the interior surface of the body  10  and the rear surface  202  of the face  20 . As a result, it is possible to reduce the loss of flight distance when a golf ball is struck by an area other than the sweet area  20   se . Furthermore, by filling the space with the non-metallic material  60 , the non-metallic material  60  is behind the face  20 . Therefore, impact feel can be improved. 
     Furthermore, as described above, the toe part  206  is formed on the toe side of the striking part  205  in the face  20 , and a space is formed between the interior surface of the body  10  and the rear surface of the striking part  205  and between the interior surface of the body  10  and the rear surface of the toe part  206 . This makes it possible to increase the volume of the space. Therefore, the effects of reduction in the loss of flight distance and improvement in impact feel are further increased. The volume of the space is, for example, 5 cm 3  or more and 22 cm 3  or less, and preferably, 16 cm 3  or more and 20 cm 3  or less. 
     Each of the depressions  22  provided in the rear surface  202  of the face  20  is filled with the non-metallic material  60 . The non-metallic material  60  is in contact with the rear surface  202  of the face  20 , and is continuously formed to fill each depression  22 . Each depression  22 , however, does not have to be completely filled with the non-metallic material  60 , and may be at least partially filled with the non-metallic material  60 . 
     The non-metallic material  60  is preferably elastic. Examples of the non-metallic material  60  include, but are not limited to, resins such as silane resins, thermoplastic polyurethane, and polypropylene and rubbers such as natural rubber, butyl rubber, chlorosulfonated polyethylene rubber, acrylonitrile butadiene rubber, silicone rubber, and styrene rubber. Of these, silane resins, which enjoy a good vibration absorbing characteristic and good adhesion to metal, are preferable in particular. 
     Thus, in the iron head  1 , by forming the depressions  22  in the periphery of the sweet area  20   se  of the face  20 , the face  20  is reduced in thickness locally in the periphery of the sweet area  20   se . Therefore, the coefficient of restitution of the iron head  1  increases in the periphery of the sweet area  20   se . As a result, in the face  20 , an area of high coefficients of restitution extends to the periphery of the sweet area  20   se . Therefore, it is possible to reduce the loss of flight distance of a golf ball when the golf ball is struck by an area other than the sweet area  20   se  (off the center). As a result, it is possible to reduce a difference in the flight distance of a golf ball between when the golf ball is struck by the sweet area  20   se  and when the golf gall is struck by an area other than the sweet area  20   se , so that the flight distance can be stable. 
     Furthermore, the depressions  22  more distant from the sweet area  20   se  are greater in size and depth, so that the face  20  can be further reduced in thickness in an area more distant from the sweet area  20   se . Therefore, it is possible to further reduce the loss of flight distance and to further stabilize flight distance. 
     Furthermore, the individual depressions  22  provided in the rear surface  202  of the face  20  are filled with the non-metallic material  60  to increase the contact area of the rear surface  202  and the non-metallic material  60 . Therefore, the bonding strength of the rear surface  202  of the face  20  and the non-metallic material  60  increases. This makes it possible to prevent the rear surface  202  and the non-metallic material  60  from being detached from or displaced relative to each other by the impact of striking a golf ball. 
     In the case of a hollow structure with a space such as the iron head  1 , the detachment or displacement of the non-metallic material  60  cannot be fixed. Therefore, it is of great significance to increase the bonding strength of the rear surface  202  of the face  20  and the non-metallic material  60  to prevent the rear surface  202  and the non-metallic material  60  from being detached from or displaced relative to each other. 
     Furthermore, an increase in the bonding strength of the rear surface  202  of the face  20  and the non-metallic material  60  increases the vibration damping effect at the time of striking a golf ball, thus making it possible to improve impact feel. 
     Furthermore, the rear protrusion  14  includes the wall faces  141  through  146  that face the rear surface  202  of the face  20 . As a result, when striking a golf ball, a force that the iron head  1  receives in a direction normal to the rear surface  202  of the face  20  reaches the wall faces  141  through  146  through the non-metallic material  60 . Therefore, impact feel can be improved. 
     In particular, the depth D is 5 mm or more and 15 mm or less, and preferably, 10 mm or more and 15 mm or less, at the wall face  146  provided at the deepest portion of the rear protrusion  14 . As a result, it is possible to ensure that the non-metallic material  60  positioned between the rear surface  202  of the face  20  and the wall face  146  has a certain thickness or more. Therefore, it is possible to further increase the impact feel improvement effect and to deepen and lower the center of gravity of the iron head  1 . 
     [Variation] 
     A variation of the embodiment is directed to an iron head having a different face shape. In the description of the variation, a description of the same elements or components as those of the above-described embodiment may be omitted. 
       FIG. 6  is a front elevational view of an iron head  1 A according to the variation.  FIG. 7  is a sectional view of the iron head  1 A, illustrating a section taken along a plane indicated by the line VII-VII of  FIG. 6 , which extends in the face-back direction and passes through the substantial center of a face  20 A of the iron head  1 A. 
     The iron head  1 A depicted in  FIGS. 6 and 7  is a head for an iron-type golf club, and is a structure including a body  10 A and the face  20 A. The face  20 A is joined to the body  10 A by, for example, welding. 
       FIG. 8  is a front-side perspective view of the body  10 A according to the variation.  FIG. 9  is a rear-side perspective view of the face  20 A according to the variation. 
     Referring to  FIGS. 8 and 9  as well as  FIGS. 6 and 7 , the body  10 A includes a frame  11 A, a face placement part  12 A, the back  13 , the rear protrusion  14 , and the hosel  15 . 
     In the body  10 A, the frame  11 A and the face placement part  12 A include a cut  110  on the sole side. That is, while the frame  11  and the face placement part  12  of the body  10  of the iron head  1  have a surrounding frame shape (see, for example,  FIG. 4 ), the frame  11 A and the face placement part  12 A of the body  10 A of the iron head  1 A do not have a surrounding frame shape and are made discontinuous (open) by the cut  110  on the sole side. 
     The face  20 A has a substantially L-shaped sectional shape. Specifically, the face  20 A includes a rearward extension  25  extending rearward (to the back side) from the lower end of the striking part  205  on the sole side. The rearward extension  25  fits into the body  10 A on the sole side to form part of the sole together with part of the rear protrusion  14 . In other respects, the face  20 A is equal to the face  20  (see, for example,  FIG. 5 ). 
     Thus, the face  20 A has a substantially L-shaped sectional shape, so that the coefficient of restitution of the face  20 A can be increased. 
     The face  20 A includes a thin part  27  where the thickness of the face  20 A is reduced. The thin part  27  is elongated in the toe-heel direction near the boundary between the striking part  205  and the rearward extension  25  on the sole side. The thin part  27  is depressed toward the face surface  201  relative to the rear surface of the striking part  205 . The size of depression of the thin part  27  relative to the rear surface of the striking part  205  is, for example, 0.1 mm or more and 1.5 mm or less, and preferably, 0.2 mm or more and 0.6 mm or less. The length of the thin part  27  in the toe-heel direction is, for example, 5 mm or more and 80 mm or less, and preferably, 50 mm or more and 80 mm or less. 
     The rearward extension  25  of the face  20 A is fitted into the cut  110  of the body  10 A. That is, the face  20 A is positioned by the face placement part  12 A on the top side, and the rearward extension  25  is fitted into the cut  110  to connect to the rear protrusion  14  of the body  10 A on the sole side. 
     The wall face  141  of the body  10 A faces and is parallel to the thin part  27 . The space between the thin part  27  and the wall face  141  is filled with the non-metallic material  60 . The thin part  27 , however, does not have to be completely filled with the non-metallic material  60 , and may be at least partially filled with the non-metallic material  60 . 
     Thus, by providing the thin part  27  in a lower portion of the face  20 A, the flexure of the striking part  205  when striking a golf ball can be increased. 
     Furthermore, the thin part  27  of the face  20 A is filled with the non-metallic material  60  to further increase the contact area of the rear surface  202  of the face  20 A and the non-metallic material  60 . Therefore, the bonding strength of the rear surface  202  and the non-metallic material  60  further increases. This makes it possible to further prevent the rear surface  202  and the non-metallic material  60  from being detached from or displaced relative to each other by the impact of striking a golf ball. Furthermore, a further increase in the bonding strength of the rear surface  202  and the non-metallic material  60  further increases the vibration damping effect at the time of striking a golf ball, thus making it possible to further improve impact feel. 
     Furthermore, because the thin part  27  is also positioned below the sweet area  20   se , the coefficient of restitution of the face  20 A can be increased. 
     All examples and conditional language provided herein are intended for pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventors to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority or inferiority of the invention. Although one or more embodiments of the invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.