Abstract:
A multiple-material golf club head with an improved scarf joint between the crown and the body is disclosed herein. The golf club preferably is a driver that has a metal body comprising a striking face, a sole, a return portion, a front flange, and a rear flange, and a composite crown having a scarf joint region, a transitional thickness region directly behind the scarf joint region, and a constant thickness region directly behind the transitional thickness region. The thickness distribution along the crown, in combination with the tapered edge of the scarf joint and its intersection with the front flange, greatly reduces the stress placed on critical portions of the club head and improves overall golf club head durability.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Patent Application No. 62/280,077, filed on Jan. 18, 2016, the disclosure of which is incorporated by reference in its entirety herein. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a multiple material golf club head with an improved attachment region between parts of the head. More specifically, the present invention relates to a golf club head with a composite crown having a scarf joint attachment configuration with a face component of the head. 
     Description of the Related Art 
     Golf club manufacturers often combine metallic golf club head bodies with composite crowns to reduce the overall head mass and lower the clubs&#39; center of gravity, thus improving the mass properties of such multiple material heads. The region where the crown is affixed to the body with an adhesive material is typically known as the bond joint. In prior art multiple material golf club heads, manufacturers often employ a lap joint, or “step” structure, examples of which are shown in FIGS. 1 (disclosed in U.S. Pat. No. 6,623,378) and 2 (disclosed in U.S. Pat. No. 6,969,326), at the intersection between the crown and the body. This “step”-type prior art structure, though relatively straightforward to manufacture, is problematic because it creates a high-stress area at the front of the bond joint, which means that a great deal of stress is placed on the adhesive when the golf club head impacts a golf ball. This causes the crown to separate from the body at the bond region, which becomes visible to a golfer after repeated use and often leads to permanent damage to the club. The prior art discloses other types of bond region structures, including a basic scarf joint shown in FIG. 3 (disclosed in U.S. Patent Application Publication Number 2015/0045134), but this structure is not optimized to address the significant stresses placed on the bond region and other parts of the golf club head when the head repeatedly impacts golf balls. 
     Therefore, there is a need for an improved bond region structure that can be manufactured efficiently and that minimizes the significant stresses of impact that cause separation of the crown from the body. 
     BRIEF SUMMARY OF THE INVENTION 
     One aspect of the present invention is a golf club head comprising a body having a flange and a composite crown having a tapered, full or partial scarf joint attachment region. 
     Another aspect of the present invention is a golf club head comprising a hollow body comprising a hosel, a striking face, a face extension, a bond flange extending away from the face extension, a sole, a rear flange extending away from the sole at an angle less than 90°, and an upper opening, and a composite crown, wherein the composite crown is affixed to the body with an adhesive to close the upper opening, wherein the bond flange comprises a front region and a back region, wherein the crown comprises a scarf region with a first average thickness, a transition region with a second average thickness, and a rear region with a first constant thickness, wherein the scarf region comprises a tapered edge, wherein the second average thickness is greater than the first average thickness, and wherein the second average thickness is greater than the first constant thickness. In some embodiments, the front region may not comprise any convex or concave curvature. In others, the bond flange may have a maximum width of no less than 0.100 inch and no more than 0.400 inch, and more preferably a maximum width of approximately 0.300 inch. In some embodiments, the bond flange may have a variable width, while in others the bond flange may have a constant width. 
     In some embodiments, the back region may have a second constant thickness, which may be greater than the first constant thickness. In a further embodiment, the difference in thickness between the second constant thickness and the first constant thickness may be at least 0.010 inch, and more preferably may be approximately 0.015 inch. In some embodiments, the transition region may have a width of at least 0.400 inch, and more preferably at least 0.500 inch. In other embodiments, the first constant thickness may be no less than 0.020 inch and no more than 0.040 inch, more preferably no less than 0.022 inch and no more than 0.035 inch, and even more preferably approximately 0.022 inch. In some embodiments, the crown may be composed of a compression-molded composite material, and in others, the rear flange may comprise a convex curvature. 
     Yet another aspect of the present invention is a driver-type golf club head comprising a hollow metal body comprising a hosel, a striking face, a face extension, a bond flange extending away from the face extension, a sole, a rear flange extending away from an edge of the sole at an angle less than 90°, and an upper opening, and a composite crown, wherein the crown is affixed to the body with an adhesive to close the upper opening, wherein the crown comprises a scarf region with a first average thickness, a transition region with a second average thickness, and a rear region with a first constant thickness, wherein the second average thickness is greater than the first average thickness, wherein the second average thickness is greater than the first constant thickness, wherein the first constant thickness is no less than 0.020 inch and no more than 0.040 inch, wherein the scarf region comprises a tapered edge, wherein the scarf region increases in thickness from the tapered edge to the transition region, wherein the transition region comprises a maximum thickness area proximate the scarf region, and wherein the transition region has a width of at least 0.500 inch. 
     In some embodiments, the crown may be compression molded from SMC material. In others, the bond flange may comprise a region having a second constant thickness, which may be at least 0.015 inch greater than the first constant thickness. In some embodiments, the crown may cover the entirety of the rear flange, and in others, the adhesive may have a thickness of no more than 0.010 inch. 
     Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a prior art golf club head. 
         FIG. 2  is an exploded and partial cross-sectional view of a prior art golf club head. 
         FIG. 3  is a cross-sectional view of a prior art golf club head. 
         FIG. 4  is a top elevational view of a golf club head according to the present invention. 
         FIG. 5  is a top elevational view of the golf club head shown in  FIG. 4  with a forward-most region of the bond flange highlighted. 
         FIG. 6  is a top elevational view of the golf club head shown in  FIG. 4  with the rear edge of the bond flange highlighted. 
         FIG. 7  is a top elevational view of the golf club head shown in  FIG. 4  with the transition surface of the crown highlighted. 
         FIG. 8  is a top elevational view of the golf club head shown in  FIG. 4  with the constant thickness section of the crown highlighted. 
         FIG. 9  is a rear perspective view of the golf club head shown in  FIG. 4  with the intersection area between the crown and the rear edge of the golf club body highlighted. 
         FIG. 10  is a cross-sectional view of the golf club head shown in  FIG. 4  along lines  10 - 10 . 
         FIG. 11  is a cross-sectional view of the golf club head shown in  FIG. 9  along lines  11 - 11 . 
         FIG. 12  is an enlarged view of the circled, cross-sectional area in  FIG. 10 . 
         FIG. 13  is a top perspective view of a traditional golf club head without its crown portion and with stress patterns illustrated across the lap joint surface. 
         FIG. 14  is a top perspective view of the golf club head shown in  FIG. 4  without its crown portion and with stress patterns illustrated across the bond flange surface. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention introduces a solution to the problems set forth above by providing a crown with an improved scarf joint construction and thickness distribution in combination with a golf club head having improved support flanges. 
     A preferred embodiment of the present invention is shown in  FIGS. 4-12 . In this embodiment, the golf club head  10  comprises a body  20  having a striking face  22 , a heel  23 , a sole  24 , a toe  25 , a hosel  26 , a rear side  27 , a face extension  28  extending rearwards away from the striking face  22 , a bond flange  40  extending rearwards away from the face extension  28 , an upper opening, and a rear flange  50  extending away from the rear side  27  of the sole  24  towards the striking face  22  at an angle α that is preferably less than 90°. The golf club head  10  also comprises a crown  30  that is permanently bonded to the body  20  with an adhesive to close the upper opening and preferably is composed of a material such as triax composite, SMC, prepreg plies, or any of the compositions disclosed in U.S. Pat. No. 9,033,822, the disclosure of which is incorporated by reference in its entirety herein. The adhesive  15  should have a thickness of no more than 0.010 inch. 
     The bond flange  40  extends away from the face extension  28 , which preferably has a front-to-back width W 1  of at least 0.200 inch, and more preferably approximately 0.400 inch. The bond flange  40  extends off of the face extension  28  and jogs around the hosel  26  at the heel side  23  to connect with the rear flange  50 , which extends off of the sole  24  and frames at least a portion of the upper opening. The bond flange  40  may have a variable front-to-back width, but preferably has a constant width W 2  that ranges from 0.100 to 0.400 inch, and more preferably is approximately 0.300 inch. It is important that the bond flange  40  have no convex or concave curvature to avoid introducing weak points into the bond between the bond flange  40  and the crown  30  when the golf club head  10  is fully assembled. As shown in  FIGS. 5 and 6 , the bond flange  40  has a front region  42  and a back region  44 . The front region  42  may vary in thickness, but the back region  44  preferably has a constant thickness T 1  to provide consistent support to the crown  30  where it contacts the body  20 . 
     As shown in the Figures, and particularly  FIGS. 10 and 12 , the crown  30  includes a tapered scarf region  32 , which includes a sharp edge  31  where the crown  30  ends, a transition region  34  where the crown thickness increases and then decreases after achieving a maximum thickness at a midpoint  35  of the transition region  34 , and a rear region  36  with a constant thickness. The transition region  34  preferably has a front-to-back width W 3  of at least 0.400 inch, and more preferably at least 0.500, to provide the structural support necessary to distribute stresses evenly without adding too much mass to the crown  30 . The rear region  36  constitutes the remaining area of the crown  30 , and preferably a majority of the area of the crown  30 . The edge  38  of the rear region  36  intersects with the rear flange  50  of the body  20 , which may have a convex curvature to match the curvature of the crown  30 . 
     The scarf region  32  has an average thickness T 2 , defined as the average thickness of points taken along the entire front-to-back width W 2  of the scarf region  32  (which is the same as the front-to-back width of the bond flange  40 , because the scarf region  32  completely covers the bond flange  40 ), the rear region  36  has a constant thickness T 3 , and the transition region  34  has an average thickness T 4  that is greater than both T 2  and T 3 . In the preferred embodiment, the thickness T 3  of the rear region  36  is between 0.020 and 0.040 inch thick, and can be as thin as 0.022 inch if triax material is used to make the crown  30 . If SMC is used to make the crown  30 , then the rear region  36  should be at least 0.035 inch thick. In either case, the thickness T 1  of the back region  44  of the bond flange  40  should be at least 0.015 inch thicker than T 3  to provide adequate support for the crown  30  and to distribute stresses appropriately. 
     The novel intersection of the bond flange  40  with the crown  30  of the present invention dramatically reduces the stress placed on the intersection between the body  20  and the crown  30 . In fact, as shown in  FIGS. 13-14 , when compared with a traditional lap joint, the scarf joint configuration of the present invention reduces average stress on the bond flange  40  by more than 5000 psi. 
     The golf club head  10  of the present invention may be constructed to take various shapes, including traditional, square, rectangular, or triangular. In some embodiments, the golf club head  10  of the present invention may take shapes such as those disclosed in U.S. Pat. Nos. 7,163,468, 7,166,038, 7,169,060, 7,278,927, 7,291,075, 7,306,527, 7,311,613, 7,390,269, 7,407,448, 7,410,428, 7,413,520, 7,413,519, 7,419,440, 7,455,598, 7,476,161, 7,494,424, 7,578,751, 7,588,501, 7,591,737, and 7,749,096, the disclosure of each of which is incorporated by reference in its entirety herein. 
     The golf club head  10  of the present invention may also have variable striking face  22  thickness, such as the thickness patterns disclosed in U.S. Pat. Nos. 5,163,682, 5,318,300, 5,474,296, 5,830,084, 5,971,868, 6,007,432, 6,338,683, 6,354,962, 6,368,234, 6,398,666, 6,413,169, 6,428,426, 6,435,977, 6,623,377, 6,997,821, 7,014,570, 7,101,289, 7,137,907, 7,144,334, 7,258,626, 7,422,528, 7,448,960, 7,713,140, 8,012,041, 8,696,489, and 9,101,809, the disclosure of each of which is incorporated by reference in its entirety herein. 
     The mass of the club head  10  of the present invention ranges from 165 grams to 250 grams, preferably ranges from 175 grams to 230 grams, and most preferably from 190 grams to 205 grams. The crown  30  has a mass preferably ranging from 4 grams to 30 grams, more preferably from 15 grams to 25 grams, and most preferably 20 grams. 
     The golf club head  10  of the present invention preferably has a volume that ranges from 290 cubic centimeters to 600 cubic centimeters, and more preferably ranges from 330 cubic centimeters to 510 cubic centimeters, even more preferably 350 cubic centimeters to 495 cubic centimeters, and most preferably 415 cubic centimeters or 470 cubic centimeters. 
     The center of gravity and the moment of inertia of a golf club head  10  of the present invention are preferably measured using a test frame (X T , Y T , Z T ), and then transformed to a head frame (X H , Y H , Z H ). The center of gravity of a golf club head may be obtained using a center of gravity table having two weight scales thereon, as disclosed in U.S. Pat. No. 6,607,452, entitled High Moment Of Inertia Composite Golf Club, and hereby incorporated by reference in its entirety. 
     The moment of inertia, Izz, about the Z axis for the golf club head  10  of the present invention preferably ranges from 2800 g-cm 2  to 6000 g-cm 2 , preferably from 3000 g-cm 2  to 600 g-cm 2 , and most preferably from 5000 g-cm 2  to 6000 g-cm 2 . The moment of inertia, Iyy, about the Y axis for the golf club head  10  preferably ranges from 1500 g-cm 2  to 5000 g-cm 2 , preferably from 2000 g-cm 2  to 5000 g-cm 2 , and most preferably from 3000 g-cm 2  to 4500 g-cm 2 . The moment of inertia, Ixx, about the X axis for the golf club head  10  preferably ranges from 1500 g-cm 2  to 4000 g-cm 2 , preferably from 2000 g-cm 2  to 3500 g-cm 2 , and most preferably from 2500 g-cm 2  to 3000 g-cm 2 . 
     The golf club heads  10  of the present invention preferably have coefficient of restitutions (“COR”) ranging from 0.81 to 0.875, and more preferably from 0.82 to 0.84. The golf club heads  10  preferably have characteristic times (“CT”) as measured under USGA conditions of 256 microseconds. 
     From the foregoing it is believed that those skilled in the pertinent art will recognize the meritorious advancement of this invention and will readily understand that while the present invention has been described in association with a preferred embodiment thereof, and other embodiments illustrated in the accompanying drawings, numerous changes, modifications and substitutions of equivalents may be made therein without departing from the spirit and scope of this invention which is intended to be unlimited by the foregoing except as may appear in the following appended claims. The section titles included herein also are not intended to be limiting. Therefore, the embodiments of the invention in which an exclusive property or privilege is claimed are defined in the following appended claims.