Method for designing golf club face having rear surface constituting contour-line shape

[0001] [Technical field to which the invention belongs] This application is based on a partial continuation application of US Patent Application No. 08 / 735,601 (filed October 23, 1996). The present invention relates to a golf club, and more particularly to a golf club face (ie, a contour-shaped backside) having a contour-shaped surface on the opposite side of the ball striking face. [0002] [Conventional technology] Golf clubs generally consist of shaft, head, and grip parts. The portion of the golf club head having a ball striking face is called a golf club face. "Golf Club Design, Alteration &amp; Repair (4th Ed. 1995)" (R. See Mltby). The golf club face is generally adjacent to or in contact with both the top wall or crown of the club head and the bottom wall or sole of the club head. The "crown" and "sole" are typically used to indicate the top and bottom of a wood-type club head, and the "top wall" and "bottom wall" are similar to wood-type club heads. It is used to indicate the bottom and top of iron types and club heads, and is also used herein as such. [0003] For both wood-type club heads (typically hollow today, but not necessarily hollow, for example, to fill with foam) and cavity back iron club heads, golf club faces are preferred. It has been thinned. Such a golf club face generally defines two sides. :: The ball striking surface (that is, the front surface) and the surface opposite to the ball striking surface (that is, the back side). [0004] When the front of the face of a golf club head hits a golf ball, a large impact force (eg 2000 lbs) is generated. These large impact forces give a load to the club face. In wood-type club head faces and cavity-back iron-type relatively thin faces, these forces create large internal loads, such as large bending stresses. These internal loads will cause destructive material cracks that make the club head unusable. Throughout this specification, this "internal load" refers to the bending moment, shear force, and compressive force experienced by a golf club face as a result of stress (at least, such as the impact of one ball). Is. [0005] Recent calculations and experiments on wood-type club heads and cavity-back iron clubs show that destructive material cracking due to large internal loads often occurs at at least one of the following three face positions: (1) In particular, the ball striking surface (front surface) of the club face at the center of the ball hitting in the area where a large compressive bending stress is generated, which is the area where the score line is located; (2) The back surface (back) of the club face in the area where a large tensile bending stress is generated. Side); and (3) (a) The region of the vertical component with high bending stress, the part where the face and the top wall are located just above the center of the hit ball, and / or (b) the region of the vertical component with high bending stress. The part where the face and the bottom wall, which are located directly below the center of the ball, intersect. The area where the upper face and the top wall of the hitting center intersect (that is, the place where the face and the top wall join) and the area where the lower face and the bottom wall of the hitting center intersect (that is, the place where the face and the bottom wall join) ) Is called the hitting area. The vertical stress distribution through the hitting area on the back side of the face consists of compressive stress (ie, negative) acting in the face / bottom wall crossing region that increases from zero toward the hitting center and is maximal behind the hitting center region. It is known that the tension (positive) is reached, and the compressive (negative) stress decreases toward the face / top wall intersection region through a large compressive stress from zero. The distribution of stress through the ball striking region (ball striking surface) on the front surface of the face is almost the same, but decreases to the opposite factor (ie, a large compressive force at the center of the ball striking force, and to tensile bending stress at the face / top wall intersection region). To increase). [0006] In the design of the golf club head, the golf club face portion must be structurally sufficient to withstand the large repetitive forces that occur in connection with the impact of the ball. Such sufficient strength is achieved by increasing the stiffness of the face portion so that the stress generated by the internal load is below the critical stress level of the material used for the face. Typically, the face portion of the club head uniformly increases the thickness of the face portion and / or adds one or more ribs (ie, separately attached rods or striatum) to the back of the face. Can be stiffened by. [0007] Increasing the face area evenly is sufficient to prevent the internal load from cracking due to impact or fatigue (ie, sufficient to withstand stress such as the impact of a ball) to completely reduce the internal load. Needs to add a large amount of material. However, adding such a large amount of material to the club face generally adversely affects the operability of the club using such a face. The very heavy club face makes the club less manoeuvrable. Moreover, the feel of a club using such a face is adversely affected by the large number of vibrations transmitted through the club. Moreover, if maximum weight is imposed on the club head, the material-added face will not be able to distribute weight to other areas of the desired head (ie, giving the face more weight). Means, for example, reducing the weight along the perimeter of the cavity back iron club head). [0008] Adding ribs to the back of the face to stiffen the face has the advantage that it can be stiffened without adding a large amount of material to the face, but gives the ball striking surface an irregular stiffness distribution. Brings the drawback. Examples of ribs that have been used in conventional golf club head designs include, for example, vertical ribs, horizontal ribs, curved ribs, dendritic ribs, diagonal ribs (ie, V or X shape) circular ribs, or one or one of these. It consists of a combination of types. [0009] These ribs typically increase the strength of the face locally by narrowing it, making it the desired length, or having sufficient depth or thickness, and yet the face. It has geometric features to minimize the increase in weight of the face. Further, typical of such ribs are formed with sharp corners (or curved corners with a small radius of curvature) between the ribs and the back surface of the face to which the ribs are attached. Such corners create stress concentration points, creating the possibility of cracking. In addition, the use of ribs placed perpendicular to the back of the face creates large bending stresses (as described above) over the face / bottom wall intersection area and the face / top wall intersection area, thereby cracking at those points. Produces the result. [0010] An additional problem experienced by using ribs on the back is the manufacturing problem of these faces. Typically, the face is manufactured by casting. It is more difficult to cast a face containing a rib structure that causes non-uniform shrinkage of the material that occurs in the process of cooling the casting. Such non-uniform cooling results in cracks on the surface of the casting that occur along the internal cavities and / or in particular where the ribs are located. These non-uniform coolings also cause face depressions and surface dimples on the ball striking surface opposite the region where the ribs are located. [0011] As described above, the weight distribution of the desired club head can be influenced without impairing the operability, appearance, or feel of the club, and the structural preservation is increased (and less cracking and material damage). A new club face structure is needed.<u style="single">Outline of the invention</u>The present invention comprises a golf club face having a contour-shaped face that solves the above-mentioned problems and a method for designing such a golf club face. The golf club face of the present invention provides structural maintainability for a golf club face of a given size and weight. The contoured golf club faces of the present invention can survive tests in which other club faces experience cracks and / or material damage. The contoured golf club face of the present invention does not adversely affect the operability, appearance, feel, or weight distribution of the golf club, but rather has the size and strength required by a small amount of material. Can be improved by providing. [0012] The contour-shaped golf club face of the present invention has a back surface in which a contour line shape on the opposite side of the ball striking surface is formed. This contour-shaped back surface can be described as a surface whose thickness increases and decreases in steps, and in other embodiments, as a surface whose thickness increases and decreases in the shape of a rounded hill or valley. .. In a preferred embodiment, the contoured back surface is gradually thickened so that the back surface has approximately the same thickness in the area of the face where a similar level of internal load is generated by a constant stress (eg, impact of a ball). Has a face that has been changed to. Furthermore, it is preferred that the region with the highest internal load is the thickest and the region with the lowest internal load is the thinnest (ie, the thickness in the region is approximately experienced or expected in each region. Corresponds to internal load). [0013] Further, preferred embodiments have steps in regions of different thickness and, as described above, stress concentration causing cracks occurs in sharp corners, but the present invention is additional. It is preferred to reduce the internal load by adding the material to the edges of the steps and therefore reduce the possibility of cracking at those edges. In another embodiment, the contoured back surface has contoured surfaces with different thicknesses according to the correlation of internal loads as described above, but with a thickness that gradually increases or decreases between adjacent regions. It has a surface (ie, as opposed to one that clearly increases or decreases in a contour shape). [0014] The particular internal load of the club face that is expected or observed will vary depending on where the stress of the club face (ball impact) acts, and thus the thickness of the stepped portion or the region of the face. You need to be careful. When hitting a ball with a driver-type club, a golf tee is usually used, so the impact of the ball on the club head of that type of club is a classic bell along the central horizontal axis of the hitting surface of the club head. It is expected to follow a curve distribution. Iron-type clubs, on the other hand, are typically used when hitting a ball placed on the ground, so the impact of the ball is more evenly distributed on the club face surface along the lower horizon. In addition, low handicap golfers are expected to consistently obtain ball impact along the same low horizontal axis or near the intersection of that axis with the central vertical axis. [0015] Therefore, a preferred iron-type club head for intermediate to high handicap golfers preferably has a stepped surface that evenly disperses the contour-shaped back surface along a horizontal axis with a low internal load. For example, the contour-shaped back surface preferably has a surface whose thickness varies stepwise so that the club face becomes thinner in the face / top wall crossing region approaching the toe and in the face / top wall crossing region approaching the heel. In this embodiment, the contour shape is roughly defined by a vertically stiffened region and a horizontally stiffened region that gives a deformed "T" to the back of the face (eg, "". The "T" horizontal bar runs along the face near the face / bottom wall intersection area, and the "T" vertical bar runs along the vertical axis of the face). [0016] The region to be laterally stiffened in this embodiment is preferably located approximately along the horizontal axis located along the face near the face / bottom wall intersection region on the back, preferably in gradual reduction. Has a given thickness (ie, thins towards the toe and heel of the club head). The area to be stiffened in the vertical direction is preferably located approximately along the central vertical axis of the back, preferably with a gradual decrease in thickness (ie, thinning towards the face / top wall intersection area). ) Has a predetermined thickness. [0017] The horizontal and vertical stiffened regions preferably define the thickest region at the intersection of the horizontal stiffened region and the horizontal stiffened region (ie, abbreviated, abbreviated. Located at the intersection of the vertical central axis and the face / bottom wall intersection), and approximately at the toe or near toe in the face / top wall area, or in the heel or heel in the face / top wall area. Define the thinnest area near the part. The thickest region is progressively adjacent to the thin region, and the thinnest region is reduced in thickness to a contour shape, thereby giving a contour contour surface. [0018] In another preferred embodiment, the contoured back surface preferably has, at a minimum, a contoured surface whose thickness follows the relationship of internal load described above, and also has a region where the thickness is further increased for aesthetic purposes. .. Further, in another preferred embodiment, the contoured back surface preferably has a surface on which the contoured shape is formed so that the thickness follows the relationship of internal load described above, and the thickness of the region adjacent to one to the other gradually increases. It has an increasing and decreasing surface (eg, a smooth surface such as a hill or valley). [0019] The advantages of the contoured golf club face according to the present invention are that it makes the stress distribution more uniform at a given club face size, makes its stiffness more uniform, and increases structural storage even when the weight is reduced. It is to be. Further, the advantage of the contour-shaped golf club face is that the golf club head having such a face has predetermined acoustic characteristics based on the design of the contour-shaped surface. [0020] Therefore, a primary object of the present invention is to provide a new golf club face with increased strength and shelf life with less weight and material for a given club size, as well as the design of such a golf club face. To provide a method. Another object of the present invention is to provide a golf club face having a contour shape that gives a golf club face whose thickness changes according to an internal load generated by a predicted or measured stress, and to provide such a golf club face. It is to provide a way to design. [0021] [0021] Yet another object of the present invention is to have a thick region in an area where a large internal load is expected, to be thinner in an area where a small internal load is expected, and to gradually progress to a thick region in the thinnest region. It is an object of the present invention to provide a golf club face formed in a contour line shape which is adjacent to each other and gradually becomes thicker toward the thickest region. [0022] Furthermore, it is an object of the present invention to have a thick region in an area where a large internal load is expected and to be thin in an area where a small internal load is expected, and the thinnest region gradually progresses to the thickest region. It is an object of the present invention to provide a golf club face having a contour-shaped shape that is adjacent to each other and is gradually thickened toward the thickest region. [0023] Another object of the present invention is to provide a club face having structural rigidity capable of withstanding deformation due to impact and a method for designing the club face. Yet another object of the present invention is to design a golf club face with a bottom center of gravity that reduces impact stress (stresses such as ball impact) overall and does not cause damage for a long period of time from the start of use. To provide a method. [0024] Other objects of the present invention will be clarified by considering the following description based on the drawings. [0025] BEST MODE FOR CARRYING OUT THE INVENTION As described above, a preferred embodiment of the present invention has a contoured golf club face back surface, the back surface having substantially the same thickness of the face area predicted to receive a substantially similar internal load. The region predicted to receive the highest internal load is the thickest, the region predicted to receive the lowest internal load is the thinnest, and the thickest region is progressively adjacent to the thin region. The surface is formed in a contour shape, and the thickness is changed so that the stress applied to the face formed in the contour shape by the impact of the ball is more evenly distributed as compared with the one not formed in the contour shape. [0026] The golf club head 1 of the preferred embodiment illustrated in FIGS. 1 (A) and 1 (B) has a top wall 4, a bottom wall 6, a toe 8, a heel 10, and a ball striking face 12 (FIG. 1 (A)) and It has a face having a back surface 14 (FIG. 1 (B)) formed in a contour line shape on the opposite side of the ball striking face 12. Although the figures shown here all show cavity back iron type golf club heads, the present invention is equivalent to other types of golf club heads, for example wood type golf club heads. It should be understood as applicable. [0027] As shown in FIGS. 1 (A), 1 (C) and 1 (D), the front hitting surface 12 includes the score line (FIG. 1 (A)), and the back surface 14 is formed in a contour line shape. Preferably, it has a region 2a-2f in which the thickness changes. The back surface 14 can selectively include an area 18 for accommodating an insignia, a logo, and a medal, as shown below and simulated in FIG. 4 (A). [0028] In a preferred embodiment, for example, an exemplary iron-type golf with a simulated ball impact mark 3 expected by intermediate to high handicap golfers (ie, golfers who hit a large number of toes, heels and centers). Shows club face 1 of the club head. FIG. 1 (B) shows the computer-calculated internal load (ie, bending moment, shearing force, compression) experienced by the golf club face 1 when subjected to multiple impacts of the ball in trace 3 of FIG. 1 (A). The distribution of the thickness appearing on the back surface 14 of the golf club face 1 based on the force) is shown. It should be noted that similar calculations can be made using the impact marks of one ball or multiple impact marks at different positions than those shown in them. [0029] Figure 1 (B)-As shown in Figure 1 (E); Region 2f is most likely to receive the maximum internal load due to the impact of the ball in Trace 3 (shown in Figure 1 (A)). Thick, region 2a is the thinnest because the internal load due to the impact of the same ball is expected to be the lowest, regions 2b, 2c, 2d and 2e appear between the regions of two 2a and 2f from the impact of the same ball. internal load gradual since it is expected to increase to, gradually increases the thickness. Therefore, the contour-formed back surface 14 preferably has a club face that is thin in the face / top wall intersection region near the toe and the face / top wall intersection region near the heel, and the thickness of region 2a-2f. Corresponds to the internal load that appears in region 2a-2f due to the impact of multiple balls in trace 3 of FIG. 1 (A). The thickness of region 2a-2f is such that when the club head hits the ball at a position close to or close to the mark 3 used in the initial analysis, the stress is evenly distributed across the face. Brings the result. [0030] In the embodiment of the present invention shown and described here, regions in which an internal load of substantially the same magnitude is expected to appear are grouped together to form each region, but those skilled in the art can use it. It should be noted that more (or less) regions can be defined than those shown using the present invention. The contoured regions 2a-2f are along the approximately vertical rigid regions 20 and horizontal rigid regions 22 shown in FIG. 3, which approximate the shape of an upside down "T". (For example, the horizontal bar of "T" is placed along the face / bottom wall intersection area, and the vertical bar of "T" is placed along the central vertical axis). The horizontal lateral stiffening region 22 is preferably approximately located along the axis along the face / bottom wall intersection region of the back surface 14 and preferably thins towards the toe and heel of the club head 1. It has a predetermined thickness. The vertical stiffening region 20 is located approximately along the central vertical axis of the back surface 14 and has a predetermined thickness such that it becomes thinner toward the face / top wall intersection region near the top wall 4. [0031] The horizontal stiffening region 22 and the vertical stiffening region 20 preferably define the thickest region 2f at the intersection of the horizontal stiffening region 22 and the vertical stiffening region 20 (ie, central vertical). The thinnest areas 2a, 2b, 2c in the face / top wall intersection area near the toe 8 and the face / top wall intersection area near the heel 10 (region approximately located at the intersection of the axis and face / bottom wall intersection). 1 (B), 1 (E)) is defined. [0032] As shown in FIG. 3, the vertical stiffening region 20 is preferably located approximately approximately along the central vertical axis of the back surface 14 and has a predetermined preferred thickness T, as shown in FIG. 1 (D). It has, is gradually increased (ie, thickened) to a predetermined preferred thickness T'and is thickened to another preferred thickness T', and the horizontal stiffening region, as shown in FIG. 22 is preferably located along the back surface 14 in the vicinity of the face / bottom intersection region and is similar to that shown in FIG. 1 (C) at the ends of the horizontal stiffening region 22 (ie, toe and heel regions). ) Is gradually thinned. [0033] As described above, and as shown in FIGS. 1 (B) and 1 (D), the horizontal stiffening region 22 and the vertical stiffening region 20 are the thickest region 2f and the thinnest at their intersection. It defines the thinnest region in regions 2a, 2b, 2c (ie, abbreviated, face / top wall crossing region close to toe 8 and face / top wall crossing region close to heel 10). Similarly, as described above, and as shown in FIGS. 1 (B)-FIG. 1 (E), the thickest region 2f is preferably gradually stepwise into the thinnest regions 2a, 2b and 2c. Gradually adjacent to the thinned thin regions 2e and 2d, which gives a contour-shaped surface. Regions 2a-2f vary in thickness in stages, and as mentioned above, the edges of the steps generally create stress concentrations that can cause cracks, so the present invention describes the steps. At the edge of (ie, the boundary between each region 2a, 2b, 2c, 2e, 2f), incorporate a member thick enough to withstand the expected internal load based on the external force (ie, the impact of the ball). It is preferable to compensate for such cracks by making them able to withstand stress. [0034] The thickness of an exemplary example of region 2a-2f of an example shown in FIGS. 1 (A) and 1 (B) of a club face made of steel is shown. : Region 2a is approximately 0.07 inches, region 2b is approximately 0.08 inches, region 2c is approximately 0.09 inches, region 2e is approximately 0.10 inches, region 2d is approximately 0.12 inches , Region 2f is approximately 0.14 inches. The exemplary width and height of such a golf club face, measured along the central horizontal axis of the club face, is between approximately 3.0 and 4.0 inches, along the central vertical axis of the club face. The measured height is between about 1.5 inches and 2.0 inches. However, in order to give the club face similar structural consistency and maneuverability, the thickness and size of the club face should be the material used (eg, metal, alloy, etc.) and physical properties, of the desired club face. It will be appreciated by those skilled in the art that the values will differ from the exemplary values depending on the particular shape and size. [0035] In another preferred embodiment, FIG. 2 (A) shows an iron club with a simulated impact mark 3 expected by a low handicap golfer (ie, a golfer who is expected to hit most shots in the center). The model of the head shows club face 1. FIG. 2 (B) shows a computer-calculated internal load (ie, bending moment, shear stress, compression) that appears on the golf club face 1 when a large number of ball impact forces in trace 3 (FIG. 2 (A) act). It represents the distribution of the thickness of the back surface 14 of the golf club face 1 based on the force). As mentioned above, similar calculations are possible by using one or more impact marks of balls different from those shown in them. [0036] As shown in Examples and FIGS. 2 (B)-Fig. 2 (E) described above, region 2f of this second embodiment has the maximum internal load due to the impact of multiple balls in trace 3. Areas 2a and 2b are expected to appear, so they are the thickest, and areas 2a and 2b are expected to appear, so they are the thinnest. Areas 2c, 2d, and 2e are gradually increased from between 2a and 2b to 2f, respectively. Since the internal load is expected to increase, the thickness is gradually increasing. [0037] As shown above and in the first embodiment of FIG. 1 (A)-FIG. 1 (E), the contour line shape of this second embodiment (shown in FIGS. 2 (B)-FIG. 2 (E)). The back surface 14 preferably has a plurality of regions 2a-2f of different thickness, the thickness of which is in each region 2a-2f based on the impact mark 3 of the ball (shown in FIG. 2 (A)). It gradually corresponds to the magnitude of the internal stress that is expected to appear. This second embodiment is designed so that the club face is substantially thinner along the central horizontal axis near the toe 8 and near the heel 10. The contour region 2a-2f is located along the vertical stiffening region 20 and the horizontal stiffening region 22 as described above. However, as shown in FIG. 2 (D), the vertical stiffening region 20 of this embodiment has a predetermined thickness in the center, is thickened toward the face / top wall intersection region near the top wall 4, and further. , Thickened towards the face / bottom wall intersection area near the bottom wall 6. As in the previous embodiment, the horizontal stiffening region 22 and the vertical stiffening region 20 of this embodiment are preferably the thickest region 2f (that is, at the intersection of the horizontal stiffening region 22 and the vertical stiffening region 20). The area located at the intersection of the central vertical axis and the face / bottom wall intersection area) is defined. However, in this example, the thinnest regions 2a, 2b, and 2c (see FIG. 2 (B)) are located near the toe 8 and near the heel 10 along the central horizontal axis (see FIG. 2 (B)). Contrary to the one along the face / top wall intersection area of the previous embodiment). [0038] In the second embodiment, substantially, the vertical stiffening region 20 is located substantially along the central vertical axis of the back surface 14 and also has a predetermined thickness T in the center, as shown in FIG. 2 (D). It is made to gradually increase (ie, thicken) to a predetermined preferred thickness T', towards the top wall 4, and to a predetermined preferred thickness T', T'toward the bottom wall 6. The horizontal stiffening region 22 is preferably the same as in the first embodiment (ie, the thickness gradually decreases toward the toe and heel regions). [0039] As described above, and as shown in FIGS. 2 (B)-FIG. 2 (E), the horizontal stiffening region 22 and the vertical stiffening region 20 are preferably the thickest region 2f at their intersection. And define the thinnest areas 2a, 2b and 2c (ie, at or near the toe 8 along the central horizontal axis and at or near the heel 10 along the central horizontal axis). As shown in FIG. 2B, the thickest regions 2e and 2f preferably progressively decrease in thickness towards the thinnest regions 2a, 2b and 2c. They are adjacent to each other, thereby forming a contour shape. [0040] The thickness of the region 2a-2f changes stepwise, and as described above, the stepped edge generally creates a stress concentration that causes cracks. Therefore, in the present invention, it is expected at the step edge. Compensation for such cracks is made by incorporating a material thick enough to withstand internal stresses, thereby at their edges (ie, the boundaries between each region 2a, 2b, 2c, 2d, 2e, 2f). It is desirable that the load be tolerable. [0041] The exemplary specific thickness of the club face embodiment shown in FIGS. 2 (A) and 2 (B) made of steel is preferably shown in FIGS. 1 (A) and 1 (B). It is similar to that of the example shown. As in the previous example above, the thickness of region 2a-2f in this example is compared when the club head 1 impacts the ball at or near the position of trace 3 used in the initial analysis. The result is that the stress is distributed more evenly. [0042] As described above, and as shown in FIGS. 4 (A) -6 (C), other embodiments of the present invention have a thickness corresponding to the internal load described above, and for aesthetic purposes. Includes additional material to increase thickness. As shown in FIGS. 5 (A)-FIG. 6 (C), the back surface 14 of the third embodiment has contour lines formed substantially corresponding to the internal stresses expected to appear in each region 16a-16h. It has other regions 16a-16h with varying thickness. The back surface 14 can selectively include an area 18 for accommodating an insignia, logo or medal, as simulated in FIG. 4 (A). [0043] The contour-shaped back surface 14 of this third embodiment is preferably substantially thinner in the face / top wall intersection region near the toe 8 and in the face / top wall intersection region near the heel 10. It has a plurality of regions 16a-16h that define the change in thickness. Regions 16a-16h, where the contour shapes are formed, are approximately along the vertical stiffening region 20 and the horizontal stiffening region 22, as shown in FIG. A "shaped" shape is given to the back surface 14 (for example, the "T" horizontal bar is located in the face / bottom wall intersection area and the "T" vertical bar is located along the central vertical axis). [0044] The vertical stiffening region 20 is preferably located approximately along the central vertical axis of the back surface 14 and has a predetermined preferred thickness that thins towards the face / top wall intersection region near the top wall 4. .. Therefore, the horizontal stiffening region 22 and the vertical stiffening region 20 are preferably the thickest region 16h at the substantially intersection of the horizontal stiffening region 22 and the vertical stiffening region 20 (FIGS. 4 (A)-FIG. 4 (B)). (See) defined (ie, the area located at the intersection of the vertical central axis and the face / bottom wall intersection area), and the face / top area near toe 8 and the face / top area heel 10 The thinnest regions 16a, 16b and 16c near the area are defined (see Fig. 4 (A) -Fig. 4 (B)). [0045] The thickest region 16h is preferably progressively adjacent to the thinnest regions 16a, 16b and 16c and gradually becoming thinner thin regions 16d, 16e and 16g, thereby giving a contour-shaped surface. As shown in FIG. 3, the vertical stiffening region 20 is preferably located approximately approximately along the central vertical axis of the back surface 14 to a predetermined thickness T'as shown in FIG. 5 (B). It has a predetermined preferred thickness T that gradually increases (thickens). Also, as shown in FIG. 3, the horizontal stiffening region 22 is preferably located approximately approximately along the face / bottom wall crossing region of the back surface 14, and as shown in FIG. 6 (C), the horizontal stiffening region 22. Thickness t towards both ends of region 22₁, T₂Has a predetermined thickness t that diminishes (becomes thinner). [0046] As described above, and as shown in FIGS. 4 (A), 5 (B) and 6 (C), the horizontal stiffening region 22 and the vertical stiffening region 20 preferably intersect with each other. Also, the thickest region 16h, the thinnest region 16a-16b (that is, the portion close to the toe 8 in the face / top region) and 16c (the portion close to the heel 10 in the face / top region) are defined. Also, as described above and as shown in FIGS. 4 (A)-6 (C), the thickest region 16h is preferably gradually thinner in the thinnest regions 16a, 16b and 16c. Gradually adjacent to the thin region 16d-16g, which gives a contour-shaped surface. Regions 16a-16h vary in thickness in stages, and as described above, the stepped edges generally create cracking stress concentrations, which is expected at the stepped edges in the present invention. Compensation for such cracks is made by incorporating a material thick enough to withstand internal stresses, thereby between their edges (ie, each region 16a, 16b, 16c, 16d, 16e, 16f, 16g and 16h. It is desirable that the load at the boundary) be tolerable. [0047] To show the thickness of a exemplary example of region 16a-16h of an example shown in FIGS. 4 (A) and 4 (B) of a club face made of steel; (1) region 16a is about 0.07 inches; ( 2) Areas 16b and 16c are about 0.09 inches; (3) Areas 16d are about 0.11 inches; (4) Areas 16e are about 0.12 inches; (5) Areas 16f and 16g are about 0.13 inches; (6) Areas 16h are about 0.13 inches. It is 0.14 inches. Thus, the examples shown match the minimum thickness of the preferred examples shown in FIGS. 1 (A) and 1 (B), but for aesthetic purposes their thickness. Is increasing. The exemplary width and height of a golf club face is the height measured along the central vertical axis of the club face, with a width measured along the central horizontal axis of the club face between approximately 3.0 and 4.0 inches. The height is between about 1.5 inches and 2.0 inches. However, in order to provide the club face with similar structural storage and maneuverability, the thickness and size of the club face are determined by the materials used (eg, metals, alloys, etc.) and physical properties, of the desired club face. It will be appreciated by those skilled in the art that the values will differ from the exemplary values depending on the particular shape and size. [0048] Illustrated examples of the present invention provide a structurally effective golf club face of a given size, with reduced weight and increased strength. The club face design of the present invention can significantly reduce the face weight compared to similarly strong club faces with uniform thickness (discussed above), thus distributing weight from the face to other areas of the club head. It can be a club with improved operability. [0049] The club face design of the present invention has a more uniform face stiffening region than a club face with ribs incorporated in the back surface of the face as described above. Moreover, the club face design of the present invention is more structurally effective than conventional designs and is therefore usually structural defects and scratches associated with manufacturing such as casting, welding and / or shrinkage. Can be excluded. In addition, the club face design of the present invention increases structural elasticity against the impact of a given ball, which results in (1) hitting center, especially in any region of the scoreline. On the ball striking surface in, (2) on the back surface of the club face at the center of the ball, and (3) at the intersection of the face / top wall and the face / bottom wall directly above or below the center of the ball, respectively, with respect to the applied load. Can be more bearable. [0050] The design of the club face according to the present invention further provides the stiffness of the face more evenly over a large area, so that even when hit off-center, it is as if it were centered (ie, optimal distance and trajectory). You can experience a more uniform stiff face, as you would when hitting in a sweet spot or sweet spot area), and it does not have a structurally decisive adverse effect on the club face. [0051] The contoured face design of the present invention is made by first performing a detailed computerized structural analysis of the proposed head geometry for the impact of a series of simulated different balls, as determined by: Achieved. : (1) For a central hit, the internal load is maximum in the central region and the boundary region between the face / bottom wall and the face / top wall and minimal in the toe and heel region; (2) miss hits (ie) , The internal load is highest at the center of the ball and directly above and below the center of the ball in the face / top wall intersection area and the face / bottom wall intersection area; (3) effective face Stiffness significantly reduces off-center and stiff border edges due to reduced face width (ie, off-center hits result in significant stiffness changes); (4) for almost all hits There are areas where the internal load is low and therefore material (weight) can be removed from such areas without affecting the structural shelf life of the face. The results of these studies are applicable to wood type club heads and cavity back iron type club heads. [0052] Based on these results, and as described above, the club face 1 of the present invention has a face / bottom wall crossing region (eg, FIG. 4 (A)) such that the internal load is safely distributed over the bottom wall region. Designed to be wider at 16h) and have a relatively thick central vertical stiffening region 20 (shown in FIG. 3) below the central region approximately along the central vertical axis of club face 1. To. The thicknesses T and T of the vertical stiffening region (shown in FIG. 5 (B)) were adjusted so that the internal load appearing in that region was lower than the maximum tolerable value of the material. [0053] Also, as mentioned above, this club face has a horizontal stiffening region 22 (shown in FIG. 3) along the horizontal axis near the back face / bottom wall intersection region, and the toe of the club head 1. And reduced thickness t towards the heel area₁, t₂It is designed to have a preferred predetermined thickness t that gradually decreases (ie, becomes thinner) (shown in FIG. 6 (C)). The thickness along these horizontal stiffening regions is adjusted so that the internal load expected to appear in those regions is lower than the maximum that the material can withstand. [0054] Although the embodiments of the present invention have been illustrated and described as described above, various modifications are possible without departing from the scope of the present invention, and those equivalent to all such modifications are covered. Is. For example, in our design, the preferred stiffening region is shown to correspond to the vertical and horizontal axes of the club face. However, the equivalent of such a stiffening region has a different pattern than that corresponding to such an axis (eg, the stiffening region is a pattern off the vertical and horizontal axes, or the stiffening region is It can be based on a pattern that is not approximately orthogonal, or in such a pattern that there are 2 or 3 main stiffening regions). [0055] As a further example, to design a face in which the contour shape is formed based on a given external force, even if it results in a contour shape different from that described here as preferred. There can be an even method of. Such external forces may be, for example, those expected or different from those already known, or those obtained or selected by multiple impacts or one impact of the ball. [Simple explanation of drawings] FIG. 1 (A) predicts the typical face of an iron-type golf club head by intermediate to high-handicap golfers (ie, golfers who are expected to hit the toe, heel, and center). It is a figure which shows with the simulated impact trace. (B) was obtained based on the internal load level experienced by the golf club face when exposed to the impact force of the ball in the traces shown in FIG. 1 (A) calculated by computer, FIG. The preferable thickness distribution that appears in the back cavity of the typical golf club face shown in (A) is shown together with the back part that simulates the undercut part of the cavity. (C) is a cross-sectional view of the golf club face seen along the central horizontal axis indicated by line 1C-1C of FIG. 1 (B). (D) is a cross-sectional view of the golf club face seen along the central vertical axis shown by line 1D-1D in FIG. 1 (B). (E) is a cross-sectional view of the golf club face seen along the high horizontal axis shown by line 1E-1E in FIG. 1 (B). FIG. 2 (A) shows a typical face of an iron-type golf club head with a ball impact mark expected by a low-handicap golfer (that is, a golfer who can be expected to hit most shots in the center). It is a figure which shows. (B) was obtained based on the internal load level experienced by the golf club face when exposed to the impact force of the ball in the traces shown in FIG. 2 (A) calculated by computer, FIG. The preferable thickness distribution that appears in the back cavity of the typical golf club face shown in (A) is shown together with the back part that simulates the undercut part of the cavity. (C) is a cross-sectional view of the golf club face of FIG. 2 (B) as viewed along the central horizontal axis indicated by line 2C-2C of FIG. 2 (B). (D is a cross-sectional view of the golf club face of FIG. 2 (B) as viewed along the central vertical axis shown by line 2D-2D of FIG. 2 (B). (E) is a cross-sectional view of the golf club face of FIG. 2 (B) as viewed along the high horizontal axis indicated by line 2C-2C of FIG. 2 (B). FIG. 3 shows the back surface of an iron-type golf club face of a preferred embodiment of the present invention that schematically outlines the contours of the vertically and horizontally stiffened regions. FIG. 4A is a diagram showing a back surface in which a golf club face according to the present invention is incorporated in a back cavity of an iron type golf club head, together with a back surface portion that simulates an undercut portion of the cavity. .. (B) is a figure which shows the back surface of the golf club face of this invention excluding the golf club head. 5 (A) is a cross-sectional view taken along line 5A-5A of the golf club face of the present invention of FIG. 4 (A). (B) is a cross-sectional view of a stiffened vertical region near the vertical central axis as viewed along line 5A-5A of the golf club face of the present invention in FIG. 4 (A). FIG. 6 (A) is a cross-sectional view of the golf club face of the present invention shown in FIG. 4 (A) as viewed from the high horizontal axis shown in 6A-6A. (B) is a cross-sectional view of the golf club face of the present invention shown in FIG. 4 (A) as viewed from the central horizontal axis shown in 6B-6B. (C) is a cross-sectional view of a stiffened horizontal region as seen from the lower horizontal axis shown in 6C-6C of the golf club face of the present invention of FIG. 4 (A). [Explanation of symbols] 1 club face 3 Ball impact marks 4 Top wall 6 bottom wall 8 toe 10 heels 12 ball striking face 14 back 20 Vertical stiffening area 22 Horizontal stiffening area