Abstract:
A golf club having variable face to body transition is disclosed herein. More specifically, the present invention relates to a golf club head having an indented transition region that helps facilitate the transition of thickness variation from the striking face to a rear aft body. The indented transition region may be located on the crown, the skirt, or the sole, and achieves improved performance by achieving an increased thickness reduction slope.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/025,535, filed on Sep. 12, 2013, now U.S. Pat. No. 9,144,721 issued on Sep. 29, 2015, the disclosure of which is incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a golf club head with a variable thickness face to body transition. More specifically, the present invention relates to a golf club head having a plurality of indentations around the aft portion of the clubhead that transitions from the striking face towards the body portion creating improved performance. 
     BACKGROUND OF THE INVENTION 
     In order to improve the performance of a golf club, golf club designers are often faced with the dilemma of trying to maximize the discretionary weight of a golf club, allowing that discretionary weight to be shifted and placed at more strategic locations within the golf club head. 
     In order to fully understand the challenges behind the very basic design guideline above, it is worth first investigating the meaning and importance of the concept of “discretionary weight”. Once the concept of discretionary weight has been explained, the discussion can then move towards how and where to strategically place the discretionary weight within a golf club head to improve the performance of a golf club. 
     Discretionary weight, as it is commonly known in the golf industry, refers to any additional weight that is not used up in the creation and formation of the basic elements of the golf club such as the face, the crown, the sole, the skirt, the hosel, and or any accompanying components. Because there are several components in a golf club, and each of those specific components has a minimum amount of weight required, there is a “theoretical minimum amount of weight” needed for the formation of a golf club. However, with the advances in material sciences and construction methodology, this “theoretical minimum amount of weight” can often be a floating number that decreases over time, resulting in an increase in the amount of discretionary weight that can be achieved in a golf club head. 
     Discretionary weight to a golf club designer is important because it allows the center of gravity of the golf club to be changed to achieve center of gravity goals to meet different design objectives. Because the laws of physics govern the impact between a golf club and a golf ball, the resultant trajectory of a golf ball is heavily influenced by the center of gravity of a golf club. Having a low and deep center of gravity will generally promote a golf club with high launching and low spinning golf ball, while having a high and forward center of gravity will promote a low launching and high spinning golf ball. Ultimately, determining the exact location of the center of gravity may be just as much of an art form as it is precise science, but having the maximum amount of discretionary weight allows the golf club designer the flexibility to achieve the maximum amount of center of gravity movements. 
     Hence, based on the above, it can be seen that one of the main concerns of a golf club designer is to maximize the amount of discretionary weight of a golf club by eliminating weight from locations of the golf club head that are now unnecessary due to certain material, design, or process improvements. By being conscious of the location where weight can be saved increases the discretionary weight, which can ultimately lead to improved golf club performance. U.S. Pat. No. 5,997,415 to Wood illustrates the concept of discretionary weight in a golf club head and one of the earlier attempts of increasing discretionary weight by using rings and frames. 
     U.S. Pat. No. 5,318,300 to Schmidt shows another one of the earlier attempts to manipulate the thickness of the striking face of a golf club head to improve performance. Although the intent of the Schmidt patent was to improve the ballspeed across the striking face, the thinning of specific portions of the striking face also saves weight and can help increase the discretionary weight. 
     U.S. Pat. No. 7,144,331 to Poynor shows another attempt to increase the discretionary weight of a golf club by having a wrap around face insert welded to the front face, resulting in an unsupported face area. This concept removes unnecessary material from certain portions of the golf club head to increase the discretionary weight within the golf club head. 
     Up till recently, most of the manipulation of wall thickness of a golf club head has always been focused on the thickest portion of the golf club head, the striking face. However, this portion of the club head, despite having the highest thickness, can only be thinned so much due to the fact that it must withstand the stresses of an impact with a golf ball. Hence, in order to find more discretionary weight, other portions of the golf club head must also be considered. 
     U.S. Pat. No. 7,789,773 to Rae et al. attempts to increase discretionary weight by adjusting the crown portion of a golf club head. U.S. Pat. No. 7,789,773 to Rae et al. attempts to do this by altering the geometry of the crown with recesses towards the ground plane to include a plurality of drop angles and recovery angles to create a crown portion that deviates from the conventional shape and geometry. This attempt, although could potentially be helpful in generating more discretionary weight, distorts the aesthetic appeal of a golf club head. Moreover, when the crown of a golf club head is manipulated, it often results in a destruction of the sound quality of golf club, further decreasing its desirability. 
     Hence, it can be seen that there exists a need for ways to further explore and increase the discretionary weight of a golf club head without disfiguring the aesthetic appeal of the golf club head itself. More specifically, there is a need in the field for ways to increase discretionary weight by focusing on the transition portion between the striking face and the aft portion of the golf club that leads to an increase in performance by normalizing the stresses at the crown portion of the golf club head and preserves the aesthetic appeal and audio feedback of a golf club head. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect of the present invention is a golf club head comprising a striking face portion located at a frontal portion of said golf club head, a body portion connected to an aft portion of the striking face portion, wherein the body portion further comprises of a crown portion connected to an upper portion aft of the striking face portion, a sole portion connected to a bottom aft of the striking face, and a skirt portion circumferentially connecting the crown portion to the bottom portion. Moreover, at least one of the crown portion, the sole portion, and the skirt portion comprises of an indented transition region, wherein the indented transition region has an Indented Transition Region Thickness Reduction Slope of greater than about 0.06, the Indented Transition Region Thickness Reduction Slope is defined as a change in thickness of the indented transition region divided by a length of the indented transition region. 
     In another aspect of the present invention is a golf club head comprising a striking face portion located at a frontal portion of said golf club head, a body portion connected to an aft portion of the striking face portion, wherein the body portion further comprises of a crown portion connected to an upper portion aft of the striking face portion, a sole portion connected to a bottom aft of the striking face, and a skirt portion circumferentially connecting the crown portion to the bottom portion. The crown portion further comprises of a central transition region and a plurality of two or more indented transition regions, wherein the plurality of two or more indented transition regions are located away from the central transition region in a heel and toe direction. 
     In a further aspect of the present invention is a golf club head comprising a striking face portion located at a frontal portion of said golf club head, a body portion connected to an aft portion of the striking face portion, wherein the body portion further comprises of a crown portion connected to an upper portion aft of the striking face portion, a sole portion connected to a bottom aft of the striking face, and a skirt portion circumferentially connecting the crown portion to the bottom portion. Moreover, at least one of the crown portion, the sole portion, and a skirt portion comprises of an indented transition region, wherein the indented transition region is placed internally within a cavity of the golf club head. 
     These and other features, aspects and advantages of the present invention will become better understood with references to the following drawings, description and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features and advantages of the invention will be apparent from the following description of the invention as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form a part of the specification, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. 
         FIG. 1  of the accompanying drawings show a perspective view of a golf club head in accordance with an exemplary embodiment of the present invention; 
         FIG. 2  of the accompanying drawings show a top view of a golf club head in accordance with an exemplary embodiment of the present invention illustrating cross-sectional lines A-A′ and B-B′; 
         FIG. 3  of the accompanying drawings show a cross-sectional view of a golf club head in accordance with an exemplary embodiment of the present invention along cross-sectional line A-A′ as shown in  FIG. 2 ; 
         FIG. 4  of the accompanying drawings show an enlarged cross-sectional view of circular region x shown in  FIG. 3 ; 
         FIG. 5  of the accompanying drawings show a cross-sectional view of a golf club head in accordance with an exemplary embodiment of the present invention taken along cross-sectional line B-B′ as shown in  FIG. 2 ; 
         FIG. 6  of the accompanying drawings show an enlarged cross-sectional view of circular region y shown in  FIG. 5 ; 
         FIG. 7  of the accompanying drawings show a perspective view of a golf club head in accordance with an alternative embodiment of the present invention; 
         FIG. 8  of the accompanying drawings shows show a cross-sectional view of a golf club head in accordance with an alternative embodiment of the present invention along cross-sectional line B-B′ as shown in  FIG. 2 ; 
         FIG. 9  of the accompanying drawings show an enlarged cross-sectional view of circular region z shown in  FIG. 8 ; 
         FIG. 10  of the accompanying drawings show a perspective view of a golf club head in accordance with a further alternative embodiment of the present invention; 
         FIG. 11  of the accompanying drawings show a toe side view of the golf club in accordance with a further alternative embodiment of the present invention illustrating cross-sectional line C-C′; 
         FIG. 12  of the accompanying drawings show a cross-sectional view of the golf club head shown in  FIG. 11  taken along cross-sectional line C-C′; and 
         FIG. 13  of the accompanying drawings show an enlarged cross-sectional view of circular region w shown in  FIG. 12 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
     Various inventive features are described below that can each be used independently of one another or in combination with other features. However, any single inventive feature may not address any or all of the problems discussed above or may only address one of the problems discussed above. Further, one or more of the problems discussed above may not be fully addressed by any of the features described below. 
       FIG. 1  of the accompanying drawings shows a perspective view of a golf club head  100  in accordance with an exemplary embodiment of the present invention having a striking face portion  102  and a body portion attached to the rear aft portion of the golf club head  100 . The body portion of the golf club head may generally have a crown portion  104  connecting to an upper portion aft of the striking face portion  102 , a sole portion  106  connecting to a bottom portion aft of the striking face portion  102 , and a skirt portion  108  circumferentially connecting the crown portion  104  with the sole portion  106 . In addition, the crown portion  104  of the current embodiment may contain a central transition region  110  and a plurality of two or more indented transition regions  112  to adjust the thickness of the crown portion  102 . The plurality of indented transition regions  112  may look like scallops, troughs, concavities, or contain any other indented geometry all without departing from the scope and content of the present invention. In this exemplary embodiment, the plurality of two or more indented transition regions  112  are placed near the frontal portion of the crown  104  near the striking face portion  102  away from central transition region  110  in a heel toe direction. However, in other alternative embodiment, the indented transition regions  112  may be placed at alternate portions of the golf club head  100  without departing from the scope and content of the present invention. 
     Although the plurality of two or more indented transition regions  112  may look purely like cosmetic features on the crown  104 , they actually server several very important functions in improving the performance of a golf club head  100 . First and foremost, the plurality of two or more indented transition regions  112 , being strategically placed at the location shown, may serve to reduce weight at portions of the crown  104  that experience less stress; thus increasing the discretionary weight of a golf club head  100 . The second benefit, being closely related to the first, is the benefit of helping redistribute the high stress levels on the forward portion of the crown  104  away from the part of the crown  104  that experiences the highest stress during impact with a golf ball. The current golf club  100  achieves this by thinning out the heel and toe portion of the crown  104  near the frontal transition with the striking face  102  to help relieve the high stress area that normally occurs at the central transition region  110 . Finally, the plurality of two or more indented regions  112  shown in the current  FIG. 1  could also be strategically placed to improve the acoustic sound of the golf club head  100  as it impacts a golf ball. 
       FIG. 2  of the accompanying drawings shows a top view of a golf club head  200  allowing cross-sectional lines A-A′ and B-B′ to be shown. Cross-sectional line A-A′ bisects the golf club head in a forward and aft direction, passing through the center of the striking face portion  202 . This cross-sectional will allow geometry of the central transition region  210  to be shown more clearly in  FIG. 3 . In addition to the above,  FIG. 2  also allows the cross-sectional line B-B′ to be identified, wherein the cross-sectional view of the golf club head along this line will yield more detail regarding the shape and geometry of the plurality of one or more indented regions  212  in  FIG. 5 . 
     In addition to providing the information needed for the cross-sectional view of the golf club head  200 ,  FIG. 2  also provides several dimensions that can help describe and distinguish between the central transition region  210  and the plurality of two or more indented regions  212 . More specifically,  FIG. 2  shows a crown frontal transition line  220  that indicates the beginning portion of the crown  204 , a indented region transition line  222  indicating the end of the transition from the face to the crown at the indented region  212 , and a central region transition line  224  indicating the end of the transition from the face to the crown at the central region  210 ; with distance d 1  signifying the distance between the crown frontal transition line  220  and the central region transition line  222  and distance d 2  signifying the distance between the crown frontal transition line  220  and the indentation region transition line  224 . In order to more clearly show the definition and relationship between all the distances,  FIGS. 3 through 5  showing the cross-sectional view of the cross-sectional lines A-A′ and B-B′ are provided. 
       FIG. 3  of the accompanying drawings shows a cross-sectional view of a golf club head  300  taken along cross-sectional line A-A′ as shown in  FIG. 2 , illustrating the geometry of the central transition region  310 . Based on the cross-sectional view of the golf club head  300 , it can be seen that the central transition region  310  changes from a first thickness t 1  near the crown frontal transition line  320  to a second thickness t 2  near the central region transition line  324  with the central transition region  310  having a length of d 1 . In order to further examine the transition of the crown portion from a first thickness to a second thickness,  FIG. 4  is provided with an enlarged view of circular region x. 
       FIG. 4  of the accompanying drawings shows an enlarged view of the circular region x as shown in  FIG. 3 , showing the crown transition between the striking face portion  302  towards the crown  304 . This enlarged view of the circular region x shows a crown frontal transition line  420  and a central region transition line  424  separated by a distance d 1 . The crown frontal transition line  420 , as shown in the current exemplary embodiment, may generally signify the beginning of the central transition region  410  from the thickened portioned of the crown towards a thinned portion of the crown. This crown frontal transition line  420 , as defined in the current invention, is defined as the line that begins at the terminal portion of the internal radius of curvature of the golf club head  400  as it transitions from the striking face portion  402  to the crown. The thickness t 1  at the crown frontal transition line  420  may generally be thicker than the rear portion of the crown because it needs to facilitate the transition of thicknesses from the thickest portion of the golf club head  400  to the thinner portion of the crown at the lower stress bearing portion of the crown. 
     The central region transition line  424 , as shown in the current exemplary embodiment, may generally signify the ending of the central transition region  410 . This central region transition line  424 , as defined in the current invention, is the location of the crown where the thickness decreases to a point equal to or less than 0.50 mm. 
     Thickness t 1  in the current exemplary embodiment may generally be greater than 1.00 mm. Because the rear portions of the crown may not be subjected to as much stress as the frontal portions, the thickness t 2  of the crown after the central region transition line  424  may generally be equal to or less than 0.50 mm. Finally, distance d 1 , illustrating the length or distance it takes to transition from thickness t 1  to thickness t 2  at the central transition region, may generally be greater than about 10.00 mm, more preferably greater than about 10.50 mm, and most preferably greater than about 11.00 mm. Alternatively speaking, distance d 1  refers to the portion of the crown of the golf club head  400 , measured in a front to back direction, where the thickness of the crown is equal to or greater than 0.50 mm. In another word, distance d 1  refers to the portion of the crown of the golf club head  400 , measured from a front to back direction, wherein the thickness of the crown goes from a thickness that is greater than 1.00 mm to a thickness of equal to or less than 0.50 mm. 
     Based on the thickness of t 1  and t 2  above, combined with the length d 1  it takes to transition from thickness t 1  to thickness t 2 , the central transition region thickness reduction slope can be determined. The central transition region thickness reduction slope may generally refer to the rate of change of the thickness of the crown at the central transition region  410 , which may generally be less than about 0.06, more preferably less than about 0.055, and most preferably less than about 0.05. The central transition region thickness reduction slope may be calculated based on Equation (1) below: 
     
       
         
           
             
               
                 
                   
                     Central 
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                     Transition 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Region 
                     ⁢ 
                     
                         
                     
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                     Thickness 
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                     ⁢ 
                     Reduction 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Slope 
                   
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                       1 
                     
                   
                 
               
               
                 
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       FIG. 5  of the accompanying drawings shows a cross-sectional view of a golf club head  500  taken across cross-sectional line B-B′, as shown in  FIG. 2 , illustrating the geometry of the indented transition region  512 . Similar to above, it can be seen that the indented transition region  512  transitions from a first thickness t 1  near the crown frontal transition line  520  to a second thickness t 2  near the central region transition line  324  wherein the indented transition region has a length of d 1 . Similar to the above description, the first thickness t 1  may generally be greater than 1.00 mm, while the second thickness t 2  may generally be equal to or less than 0.50 mm. 
       FIG. 6  of the accompanying drawing shows an enlarged view of the circular region y, as shown in  FIG. 5 , to show the crown transition between the striking face portion  502  towards the crown  504 . In this enlarged view, it can be seen clearly that the thickness reduction slope at the indented transition region  612  is very different from the thickness reduction slope at the central transition region  410 . Here, the thickness of t 1  and t 2  are the same, but the distance d 2  is significantly smaller than d 1 , resulting in a higher thickness reduction slope. More specifically, distance d 2  may generally be less than about 7.0 mm, more preferably less than about 6.5 mm, and most preferably less than about 6.0 mm. Given the thickness of t 1  and t 2 , combined with the length or distances of d 2 , the Indented Region Thickness Reduction Slope may be calculated to be greater than about 0.06, more preferably greater than about 0.07, and most preferably greater than about 0.08. The indented transition region thickness reduction slope may be calculated based on Equation (2) below: 
                     Indented   ⁢           ⁢   Transition   ⁢           ⁢   Region   ⁢           ⁢   Thickness   ⁢           ⁢   Reduction   ⁢           ⁢   Slope     =         t   ⁢           ⁢   1     -     t   ⁢           ⁢   2         d   ⁢           ⁢   2               Eq   .           ⁢     (   2   )                 
It should be noted that the indented transition region  612  need not have a consistent thickness reduction slope throughout the entire indented transition region  612  to meet the requirements above. In fact, the golf club head  600  shown in  FIG. 6  clearly shows this by illustrating a crown transition portion that does not have a consistent thickness reduction slope. The thickness reduction slope described above is only concerned with the distance d 2  it takes for the crown portion to transition from any thickness greater than 1.00 mm to a point that has a crown thickness of equal to or less than 0.50 mm.
 
       FIG. 7  of the accompanying drawing shows a perspective view of a golf club head  700  having a plurality of two or more crown indented transition regions  712  in accordance with an alternative embodiment of the present invention. Here, the hidden lines in the crown indented transition regions  712  indicate that the change in thickness is occurring internally, hidden from view from the outside of the club head  700 . In order to illustrate the shape and geometry of the internal crown indented transition regions  712 , the cross-sectional view of the golf club head  700  is shown in  FIG. 8 , taken along cross-sectional line B-B′ as previously shown in  FIG. 2 . 
       FIG. 8  of the accompanying drawings shows a perspective view of a golf club head  800  in accordance with an alternative embodiment of the present invention taken across cross-sectional line B-B′ as previously shown in  FIG. 2 , illustrating the shape and geometry of one of the plurality of one or more crown indented transition region  812 . In this embodiment the indented transition region  812  may have the thickness reduction transition occurring internally within the cavity of the golf club head  800 , making the changes in the thickness invisible externally. Here, the thickness t 1  of the crown indented transition region  812  at the crown frontal transition line  820 , similar to previous discussions, may generally be greater than 1.00 mm; while the thickness t 2  of the rear of the crown indented transition region  812  at the indented region transition line  822  may be equal to or less than 0.5 mm. In order to provide a closer view of this crown indented transition region  812 , a close up of circular region z is provided in  FIG. 9 . 
       FIG. 9  of the accompanying drawings provides an enlarged cross-sectional view of circular region z as shown in  FIG. 8 , to illustrate the shape and geometry of the crown indented region  912  between the striking face portion  902  and the crown  904 . Here, in  FIG. 9 , the enlarged view of the internal crown indented transition region  912 , shows how the thickness of the crown indented transition region  912  changes from a thickness t 1  of greater than 1.00 mm to a point where the thickness t 2  is equal to or less than 0.50 mm within an internal cavity of the golf club head  900 . As previously mentioned, this change of the thickness can be invisible from an external portion of the golf club head  900 . Despite the change in the polarity of the indentation placement, the Indented Region Thickness Reduction Slope, in the current internal embodiment, may generally be the same as if the indentations are external to achieve the same type of weight savings at non-stress bearing portions of the crown. The Indented Region Thickness Reduction Slope in this embodiment may also be greater than about 0.06, more preferably greater than about 0.07, and most preferably greater than about 0.08. 
       FIG. 10  of the accompanying drawings shows a perspective view of a golf club head  1000  in accordance with a further alternative embodiment of the present invention. More specifically, the golf club head  1000  shown in  FIG. 10  may incorporate one or more indented transition region  1012  that may extend into the skirt portion  1008  of the golf club head  1000  in addition to the indented transition regions  1012  that already exist on the crown portion  1004 . The reason that the indented transition region  1012  can also be added to the toe portion of the skirt portion  1008  is because that portion of the golf club head  1000 , similar to the heel and toe portions of the crown  1004 , may not be subjected to as much stress during contact with a golf ball; allowing excess material to be removed. 
       FIG. 11  of the accompanying drawings shows a toe side perspective view of a golf club head  1100  in accordance with this alternative embodiment of the present invention. It can be seen from this figure that cross-sectional line C-C′ is created to illustrate the internal shape and geometry of the indented transition region  1112  on the toe portion of the skirt in  FIG. 12 . 
       FIG. 12  of the accompanying drawings shows a cross-sectional view of a golf club head  1200  in accordance with this alternative embodiment of the present invention. In this figure, circular region w is identified, allowing a close up of the indented transition region  1212  to be shown in  FIG. 13 . Similar to the indented transition region  1112  on the crown portion  1104  (shown in  FIG. 11 ), the indented transition region  1312  on the toe skirt portion may also have an Indented Region Thickness Reduction Slope of greater than about 0.06, more preferably greater than about 0.07, and most preferably greater than about 0.08. 
     It should be noted here that the toe skirt indented transition region  1312  may exist independently or in conjunction with other indented transition region  1112  in the crown portions (shown in  FIG. 11 ), the heel portion, the sole portion, or even the hosel portion of the golf club head  1100  (shown in  FIG. 11 ) all without departing from the scope and content of the present invention. Alternatively speaking, it can be said that at least a portion of the transition region between the striking face portion to the body portion contains an indented transition region  1312  with an Indented Region Thickness Reduction Slope of greater than about 0.06, more preferably greater than about 0.07, and most preferably greater than about 0.08. 
     Other than in the operating example, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages such as those for amounts of materials, moment of inertias, center of gravity locations, loft, draft angles, various performance ratios, and others in the aforementioned portions of the specification may be read as if prefaced by the word “about” even though the term “about” may not expressly appear in the value, amount, or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the aforementioned specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. 
     Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values inclusive of the recited values may be used. 
     It should be understood, of course, that the foregoing relates to exemplary embodiments of the present invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.