Patent Publication Number: US-9427631-B1

Title: Golf club head with molded cavity structure

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority from U.S. Provisional Patent Application No. 62/167,701, filed May 28, 2015, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to a golf club head with a molded cavity structure. 
     BACKGROUND 
     A golf club may generally include a club head disposed on the end of an elongate shaft. During play, the club head may be swung into contact with a stationary ball located on the ground in an effort to project the ball in an intended direction and with a desired vertical trajectory. 
     Many design parameters must be considered when forming a golf club head. For example, the design must provide enough structural resilience to withstand repeated impact forces between the club and the ball, as well as between the club and the ground. The club head must conform to size requirements set by different rule setting associations, and the face of the club must not have a coefficient of restitution above a predefined maximum (measured according to applicable standards). Assuming that certain predefined design constraints are satisfied, a club head design for a particular loft can be quantified by the magnitude and location of the center of gravity, as well as the head&#39;s moment of inertia about the center of gravity and/or the shaft. 
     The club&#39;s moment of inertia relates to the club&#39;s resistance to rotation (particularly during an off-center hit), and is often perceived as the club&#39;s measure of “forgiveness.” In typical club designs, high moments of inertia are desired to reduce the club&#39;s tendency to push or fade a ball. Achieving a high moment of inertia generally involves moving mass as close to the perimeter of the club as possible (to maximize the moment of inertia about the center of gravity), and as close to the toe as possible (to maximize the moment of inertia about the shaft). In iron-type golf club heads, this desire for increased moments of inertia have given rise to designs such as the cavity-back club head and the hollow club head. 
     While the moment of inertia affects the forgiveness of a club head, the location of the center of gravity behind the club face (and above the sole) generally affects the trajectory of a shot for a given face loft angle. A center of gravity that is positioned as far rearward (away from the face) and as low (close to the sole) as possible typically results in a ball flight that has a higher trajectory than a club head with a center of gravity placed more forward and/or higher. 
     While a high moment of inertia is obtained by increasing the perimeter weighting of the club head or by moving mass toward the toe, an increase in the total mass/swing weight of the club head (i.e., the magnitude of the center of gravity) has a strong, negative effect on club head speed and hitting distance. Said another way, to maximize club head speed (and hitting distance), a lower total mass is desired; however a lower total mass generally reduces the club head&#39;s moment of inertia (and forgiveness). 
     In the tension between swing speed (mass) and forgiveness (moment of inertia), it may be desirable to place varying amounts of mass in specific locations throughout the club head to tailor a club&#39;s performance to a particular golfer or ability level. In this manner, the total club head mass may generally be categorized into two categories: structural mass and discretionary mass. 
     Structural mass generally refers to the mass of the materials that are required to provide the club head with the structural resilience needed to withstand repeated impacts. Structural mass is highly design-dependent, and provides a designer with a relatively low amount of control over specific mass distribution. On the other hand, discretionary mass is any additional mass that may be added to the club head design for the sole purpose of customizing the performance and/or forgiveness of the club. In an ideal club design, the amount of structural mass would be minimized (without sacrificing resiliency) to provide a designer with a greater ability to customize club performance, while maintaining a traditional or desired swing weight. 
     SUMMARY 
     A golf club head includes a crown and a sole, and further includes a forward section that includes a strike face and a body section that is coupled with the forward section. The body section has an upper portion that defines a portion of the crown and a lower portion that that defines a portion of the sole. The upper portion is formed from a molded polymeric material and includes an internal wall extending into contact with the lower portion. The lower portion defines an opening extending through the sole, and the internal wall and the crown at least partially define a cavity that is in communication with the opening. 
     In one configuration, the internal wall is one or more internal walls, the opening is one or more openings, and the cavity is one or more cavities. The number of cavities is greater than or equal to the number of openings, and each of the one or more cavities is in communication with a respective one of the one or more openings. 
     The above features and advantages and other features and advantages of the present technology are readily apparent from the following detailed description when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic top perspective view of a golf club head. 
         FIG. 2  is a schematic bottom perspective view of a golf club head. 
         FIG. 3  is a schematic perspective view of an upper portion of the body section of a golf club head. 
         FIG. 4  is a schematic top perspective view of a golf club head, with an upper portion of the body section removed. 
         FIG. 5  is a schematic cross-sectional view of the golf club head of  FIG. 1 , taken along line  5 - 5 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, wherein like reference numerals are used to identify like or identical components in the various views,  FIG. 1  schematically illustrates a wood-type golf club head  10  that includes a forward section  12  and a body section  14 . The club head  10  may be mounted on the end of an elongate shaft  16 , which may be gripped and swung by a user to impart a generally arcuate motion to the club head  10 . 
     When the club head  10  is held in a neutral hitting position (i.e., where the shaft  16  is maintained entirely in a vertical plane and at a prescribed lie angle relative to a horizontal ground plane) the club head  10  may generally include a crown  18  and a sole  20 , where the sole  20  is disposed between the ground plane and the crown  18 . For the purpose of this description, the crown  18  may meet the sole  20  where the outer surface of the club head  10  has a vertical tangent (i.e., relative to the horizontal ground plane). The club head  10  may further include a hosel  22  that generally extends from the crown  18  and is configured to receive a shaft adapter or otherwise couple the club head  10  with the elongate shaft  16 . 
     The forward section  12  of the club head  10  includes a strike face  26  that is intended to impact a golf ball during a normal swing, a frame  28  that surrounds the strike face  26 , and may further include the hosel  22 . Because an impact with a ball can generate considerably large stresses near the point of impact and the hosel  22 , the forward section  12  may be formed from one or more metallic materials that are suitable to withstand any expected impact loading. Examples of suitable materials may include, but are not limited to, various alloys of stainless steel or titanium. 
     The strike face  26  generally forms the leading surface of the club head  10  and has a slight convex/arcuate curvature that extends out from the club head  10 . In one embodiment, the curvature (i.e., bulge and/or roll) of the strike face  26  has a radius of from about 7 inches to about 20 inches. Additionally, as is commonly understood, the strike face  26  may be disposed at an angle to a vertical plane when the club is held in a neutral hitting position. This angle may be generally referred to as the loft angle or slope of the club. Wood-type club heads (including hybrid woods), such as illustrated in  FIG. 1 , may most commonly have a loft angle of from about 8.5 degrees to about 24 degrees, though other loft angles are possible and have been commercially sold. 
     In one configuration, the frame  28  may include a swept-back sidewall portion  30  that extends away from the strike face  26 . The sidewall portion  30  may form a portion of both the sole  18  and the crown  20 , and may further include one or more surface profile features, such as an indented compression channel  32 . The frame  28  may be rigidly attached to the strike face  26  either through integral manufacturing techniques, or through separate processes such as welding, brazing, or adhering. 
     The body section  14  may be coupled with the forward section  12 , and may include an upper portion  40  that defines a portion of the crown  18  (as shown in  FIG. 1 ) and a lower portion  42  that defines a portion of the sole  20  (as shown in  FIG. 2 ). The body section  14  and forward section  12  may cooperate to generally define an internal volume, which, as will be discussed below, can be segregated into discrete sections or cavities. 
     To reduce the structural weight of the club head  10  while increasing the design flexibility, the upper portion  40  of the body section  14  may be formed from a molded polymeric material and adhered, or otherwise affixed to both the lower portion  42  and the forward section  12 . Techniques and joint designs for adhering the upper portion  40  of the body section  14  to the lower portion  42  and/or forward section  12  are described in U.S. patent application Ser. No. 14/724,328, filed May 28, 2015 and entitled “GOLF CLUB HEAD WITH MOLDED POLYMERIC BODY” which is incorporated by reference in its entirety. 
     In one configuration, to achieve the desired level of design flexibility, the polymeric material may be molded into shape using a molding technique, such as, injection molding, compression molding, blow molding, thermoforming or the like. To provide the maximum design flexibility, the preferred molding technique is injection molding. 
     While weight savings and design flexibility are important, the polymeric material must still be strong enough to withstand the stress that is experienced when the club head  10  impacts a ball. This may be accomplished through a combination of structural and material design choices. With regard to material selection, it is preferable to use a moldable polymeric material that has a tensile strength of greater than about 200 MPa (according to ASTM D638), or more preferably greater than about 250 MPa. Additionally, for ease of molding, if the polymeric material is filled, then the material should desirably have a resin content of greater than about 40%, or even greater than about 55% by weight. 
     In one embodiment, the upper portion  40  of the body section  14  may be formed from a polymeric material that may be a filled thermoplastic. The filled thermoplastic may include, for example, a resin and a plurality of discontinuous fibers (i.e., “chopped fibers”). The discontinuous/chopped fibers may include, for example, chopped carbon fibers or chopped glass fibers and are embedded within the resin prior to molding the body section  14 . In one configuration, the polymeric material may be a “long fiber thermoplastic” where the discontinuous fibers are embedded in a thermoplastic resin and each have a designed fiber length of from about 5 mm to about 15 mm. In another configuration, the polymeric material may be a “short fiber thermoplastic” where the discontinuous fibers are similarly embedded in a thermoplastic resin, though may each have a designed length of from about 0.01 mm to about 3 mm. Additionally, in some configurations, discontinuous chopped fibers may be characterized by an aspect ratio (e.g., length/diameter of the fiber) of greater than about 10, or more preferably greater than about 50, and less than about 1500. In one configuration, the filled polymeric material may generally have a fiber length of from about 0.01 mm to about 12 mm and a resin content of from about 40% to about 90% by weight, or more preferably from about 55% to about 70% by weight. 
     One suitable material may include a thermoplastic polyamide (e.g., PA6 or PA66) filled with chopped carbon fiber (i.e., a carbon-filled polyamide). Other resins may include certain polyimides, polyamide-imides, polyetheretherketones (PEEK), polycarbonates, engineering polyurethanes, and/or other similar materials. 
     While it is preferable for the upper portion  40  to be formed from the polymeric material, the lower portion  42  may be formed from either the polymeric material (i.e., in a similar manner as the upper portion  40 ), or may be alternatively formed from a metallic material. For example, in one configuration, the lower portion  42  may be formed from the same or similar metallic material as the frame  28 , and may either be welded to the frame  28  or integrally formed with the frame  28 . 
     A lower portion  42  that is formed from a polymeric material may provide advantages such as structural weight reduction and increased design flexibility. While these are beneficial qualities, a metal lower portion may also present certain advantages. For example, a metallic lower portion may provide increased durability to the sole  20 , which routinely impacts the ground. Also, a metallic lower portion may provide increased sole weighting that may move the center of gravity lower (particularly when paired with a polymeric upper portion). A lower club head center of gravity tends to produce a ball impact with more spin and a higher launch angle, which are seen as desirable qualities to certain golfers and/or in connection with clubs having certain loft angles. 
     Referring to  FIG. 2 , in one configuration, the polymeric upper portion  40  and the lower portion  42  may combine to form unique club head geometries that may not be feasible with an all-metal design under current consumer-driven weight constraints. More specifically, the present polymer-body construction may provide for a wood-style club head that includes one internal cavity structures  44  (“cavities  44 ”) that are open/exposed through the sole  20 . As the cavity structures  44  become more complex or numerous, it becomes less likely that a comparable design formed from metal would satisfy desired head-weight constraints. 
     The cavity structure of the present design is made possible, in part, by the design of the upper portion  40  of the body structure  14 . More specifically, as best shown in  FIG. 3 , the upper portion  40  includes one or more internal walls  46  that extend from an underside  47  of the crown  18 . The one or more internal walls  46  cooperate with the crown  18  to at least partially define one or more cavities  44 . When assembled, the walls  46  extend toward the lower portion  42  of the body structure  14 , and at least a subset may contact, and be secured to the lower portion  42 . 
     The lower portion  42 , as shown in  FIG. 4 , may define one or more openings  48  that extend through the sole  20 . As illustrated in both  FIG. 2  and  FIG. 5 , each of the one or more cavities  44  may be in communication with a respective one of the one or more openings  48 . In this manner, each cavity  44  may be an “open cavity” that is accessible from outside the club head  10  (i.e., contrasted with a “closed cavity” that is entirely sealed/isolated from the external environment). 
     If multiple openings  48  are provided, then it is important that an internal wall  46  contact the lower portion  42  between the respective openings. This is needed to ensure that the club head  10  conforms to applicable regulations and each cavity  44  is only in communication with one of the openings  48 . 
     In one configuration, one or more of the internal walls  46  may be secured to the lower portion  42  and may be operative to stiffen the club head  10 . More specifically, a secured internal wall  46  may serve as a strut or flange that reinforces the crown  18  and/or sole  20  and increases one or more modal frequencies of the structure. This stiffening may be useful in the sole  20 , particularly in the vicinity of openings  48  (i.e., where the opening  48  compromises the structural integrity of the shell) and/or between adjacent openings  48 . Likewise, any internal wall (though particularly walls that are secured to the lower portion  42 ) may stiffen/reinforce the polymeric crown  18  that would otherwise require additional thickness to match the strength of a comparable metal crown  18 . 
     One manner of securing the polymeric, internal wall  46  to the lower portion  42  is schematically shown in  FIGS. 3-4 . More specifically, this design includes a tongue-in-groove style joint that enables the internal wall  46  to be adhered to the lower portion  42  via a flange  50  that extends up from the sole  20 . Such a joint-design maximizes bonding area while minimizing required joint-weight and providing a smooth/continuous finish to the inside of the cavity  44 . 
     As shown in  FIGS. 3-4 , the lower portion  42  includes a flange  50  that extends from the frame sole  20  and is configured to be inserted into a mating receiving portion  52  of the internal wall  46 . More specifically, in one configuration, the receiving portion  52  may define a channel that is configured to receive the flange  50 . When assembled, the flange  50  extends within the channel such that the receiving portion  52  extends to opposing sides of the flange  50 . Once in position, the flange  50  may be secured in place using, for example, a suitable adhesive or other fastening means. Suitable adhesives may include, for example, two-part acrylic epoxies or high viscosity cyanoacrylate adhesives. This design may emphasize sheer bond strength (which is generally superior to peel strength for certain adhesive-polymer bonds) by physically permitting removal of the flange  50  only along a direction that is substantially parallel to the majority of the bond area (i.e., where the bond area is within 45 degrees of parallel to the direction of removal). 
     In one configuration, the one or more internal walls  46  that separate adjacent openings  48  may generally be referred to as primary internal walls  54 . As noted above, each primary internal wall  54  must contact the lower portion  42  and is preferably secured to the lower portion  42  to provide a structural reinforcement. In addition to any primary internal walls  54 , there may also be one or more secondary internal walls  56 . As shown in  FIG. 5 , a secondary internal wall  56  may subdivide a larger cavity into two smaller cavities that share a common opening  48 . These secondary internal walls  56  need not contact the lower portion  42  and may be provided primarily for aesthetic purposes. 
     Finally, the upper portion  40  may include a forward wall  58  that separates the one or more cavities  44  from the forward section  12  of the club head  10 . More specifically, the forward wall  58  may at least partially define a closed cavity  60  between the forward wall  58  and the forward section  12  and/or strike face  26 . In one configuration, the forward wall  58  may contact and/or be affixed to the lower portion  42  and/or sole  20 . Affixing the forward wall  58  to the lower portion  42  and/or sole  20  may be advantageous by preventing liquids from entering, and potentially becoming trapped within the closed cavity  60 . 
     According to this illustrative embodiment, in one configuration, the upper portion  40  of the body section  14  may include one or more internal walls  46  that may include, for example, one or more primary walls  54 , one or more secondary internal walls  56 , and/or a forward wall  58 . The lower portion  42  of the body section  14  may define one or more openings  48  extending through the sole  20 ; and the crown  20  and the one or more internal walls  46  may at least partially define one or more cavities  44 , with each cavity  44  being in communication with a respective one of the one or more openings  48 . In one configuration, the number of cavities  44  is greater than or equal to the number of openings  48 , such as by utilizing one or more secondary internal walls  56 . Likewise, the number of cavities  44  may include two or more cavities  44 , and the number of cavities  44  may be greater than the number of openings  48 . 
     In another configuration, the upper portion  40  may include a plurality of internal walls  46 , where the plurality of internal walls  46  and the crown  18  at least partially define three or more cavities  44 , and each of the three or more cavities  44  is in communication with a respective one of the plurality of openings. Further, the number of cavities  44  is greater than or equal to the number of openings, such as by utilizing one or more secondary internal walls  56 . Additionally, in a further variation of this configuration, there may be at least two more of the cavities  44  than the openings  48 , such as shown in  FIG. 5 . At least one of the plurality of internal walls  46  may further be a primary internal wall  54  that is adhered to the lower portion  42 . 
     “A,” “an,” “the,” “at least one,” and “one or more” are used interchangeably to indicate that at least one of the item is present; a plurality of such items may be present unless the context clearly indicates otherwise. All numerical values of parameters (e.g., of quantities or conditions) in this specification, including the appended claims, are to be understood as being modified in all instances by the term “about” whether or not “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows some slight imprecision (with some approach to exactness in the value; about or reasonably close to the value; nearly). If the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. In addition, disclosure of ranges includes disclosure of all values and further divided ranges within the entire range. Each value within a range and the endpoints of a range are hereby all disclosed as separate embodiment. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated items, but do not preclude the presence of other items. As used in this specification, the term “or” includes any and all combinations of one or more of the listed items. When the terms first, second, third, etc. are used to differentiate various items from each other, these designations are merely for convenience and do not limit the items.