[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 61/418,240, filed November 30, 2010, and U.S. Provisional Application No. 61/541,767, filed September 30, 2011, both of which prior applications are incorporated herein in their entireties and made part hereof. TECHNICAL FIELD

[0002] The invention relates generally to ball striking devices, such as golf clubs and heads. Certain aspects of this invention relate to golf clubs and golf club heads having a face that has an impact response that is distributed between the face and the body of the head. BACKGROUND

[0003] Golf is enjoyed by a wide variety of players– players of different genders, and players of dramatically different ages and skill levels. Golf is somewhat unique in the sporting world in that such diverse collections of players can play together in golf outings or events, even in direct competition with one another (e.g., using handicapped scoring, different tee boxes, etc.), and still enjoy the golf outing or competition. These factors, together with increased golf programming on television (e.g., golf tournaments, golf news, golf history, and/or other golf programming) and the rise of well known golf superstars, at least in part, have increased golf's popularity in recent years, both in the United States and across the world. [0004] Golfers at all skill levels seek to improve their performance, lower their golf scores, and reach that next performance "level." Manufacturers of all types of golf equipment have responded to these demands, and recent years have seen dramatic changes and improvements in golf equipment. For example, a wide range of different golf ball models now are available, with some balls designed to fly farther and straighter, provide higher or flatter trajectory, provide more spin, control, and feel (particularly around the greens), etc. [0005] Being the sole instrument that sets a golf ball in motion during play, the golf club also has been the subject of much technological research and advancement in recent years. For example, the market has seen improvements in golf club heads, shafts, and grips in recent years. Additionally, other technological advancements have been made in an effort to better match the various elements of the golf club and characteristics of a golf ball to a particular user's swing features or characteristics (e.g., club fitting technology, ball launch angle measurement technology, etc.). [0006] Despite the various technological improvements, golf remains a difficult game to play at a high level. For a golf ball to reliably fly straight and in the desired direction, a golf club must meet the golf ball square (or substantially square) to the desired target path. Moreover, the golf club must meet the golf ball at or close to a desired location on the club head face (i.e., on or near a "desired" or "optimal" ball contact location) to reliably fly straight, in the desired direction, and for a desired distance. Off-center hits may tend to "twist" the club face when it contacts the ball, thereby sending the ball in the wrong direction, imparting undesired hook or slice spin, and/or robbing the shot of distance. Club face/ball contact that deviates from squared contact and/or is located away from the club's desired ball contact location, even by a relatively minor amount, also can launch the golf ball in the wrong direction, often with undesired hook or slice spin, and/or can rob the shot of distance. The distance and direction of ball flight can also be significantly affected by the spin imparted to the ball by the impact with the club head.

Various golf club heads have been designed to improve a golfer’s accuracy by assisting the golfer in squaring the club head face at impact with a golf ball. [0007] The flexing behavior of the ball striking face and/or other portions of the head during impact can influence the energy and velocity transferred to the ball, the direction of ball flight after impact, and the spin imparted to the ball, among other factors. The flexing or deformation behavior of the ball itself during impact can also influence some or all of these factors. The energy or velocity transferred to the ball by a golf club also may be related, at least in part, to the flexibility of the club face at the point of contact, and can be expressed using a measurement called“coefficient of restitution” (or“COR”). The maximum COR for golf club heads is currently limited by the USGA at 0.83. Generally, a club head will have an area of highest response relative to other areas of the face, such as having the highest COR, which imparts the greatest energy and velocity to the ball, and this area is typically positioned at the center of the face. In one example, the area of highest response may have a COR that is equal to the prevailing limit (e.g., currently 0.83) set by the United States Golf Association (USGA), which may change over time. However, because golf clubs are typically designed to contact the ball at or around the center of the face, off-center hits may result in less energy being transferred to the ball, decreasing the distance of the shot. In existing club head designs, the face is somewhat flexible and typically acts in a trampoline-like manner during impact with the ball, deforming inward upon impact and transferring energy to the ball as the face returns to its original shape. In this configuration, the face typically has the area of highest response (as described above) at or near the center of the face, which produces the greatest energy transfer and highest COR of the face. Typically, the“trampoline” action is maximized at the area of highest response, or in other words, the amplitude of the face deformation is typically highest there. Accordingly, club head features that can increase the energy transferred to a ball during impact, without exceeding applicable COR limit, can be advantageous. [0008] The present device and method are provided to address the problems discussed above and other problems, and to provide advantages and aspects not provided by prior ball striking devices of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the

accompanying drawings. BRIEF SUMMARY

[0009] The following presents a general summary of aspects of the invention in order to provide a basic understanding of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a general form as a prelude to the more detailed description provided below. [0010] Aspects of the invention relate to ball striking devices, such as golf clubs, with a head that includes a face having a ball striking surface configured for striking a ball and a body connected to the face and extending rearwardly from the face. The body has an impact- influencing structure positioned adjacent at least one peripheral edge of the face, wherein at least a portion of a force generated by impact with a ball is absorbed by the impact-influencing structure, and at least a portion of a response force generated by the head upon impact with the ball is generated by the impact-influencing structure. The face has a stiffness proximate a geometric center of the face that is from about 4,600-5,600 lb-in ² , which may be determined using the equation S = E × I, as described below. [0011] According to one aspect, the impact-influencing structure includes at least one elongated, recessed channel extending around a periphery of the body adjacent the at least one peripheral edge of the face. The channel may be located on an outer surface of the body, or the channel may be located on an interior surface of the body. [0012] According to another aspect, the impact-influencing structure may include a region of the body formed of a flexible material having a modulus that is lower than a material of the face. [0013] According to a further aspect, the face has a stiffening structure increasing the stiffness of the face. [0014] According to yet another aspect, the face includes a face plate forming the ball striking surface and a porous stiffening structure connected to an inner side of the face plate. The porous stiffening structure may include a plurality of interior walls forming a honeycomb structure having hexagonal chambers. The face may further include a rear plate, such that the porous stiffening structure is sandwiched between the face plate and the rear plate. [0015] According to a still further aspect, a majority of the force generated by impact with the ball is absorbed by the impact-influencing structure, and a majority of the response force generated by the head upon impact with the ball is generated by the impact-influencing structure. [0016] Additional aspects of the invention relate to a ball striking device that includes a face having a ball striking surface and being defined by a plurality of face edges and a body connected to the face and extending rearward from the face edges to define an enclosed volume, where the body has a heel side, a toe side, a crown, and a sole. A channel is defined by first and second boundary edges extending continuously around an entire circumference of the body and generally equidistant from the face edges. The channel is recessed from outer surfaces of the body between the first and second annular boundary edges, and the channel includes a crown channel portion extending at least partially across the crown, a sole channel portion extending at least partially across the sole, and additional channel portions extending around the heel and the toe sides to interconnect the crown channel portion and the sole channel portion to form the channel in a continuous shape. The channel is spaced rearwardly from the face edges by a spacing portion, and the channel is configured such that at least some energy from an impact on the ball striking surface is transferred through the spacing portion and absorbed by the channel, causing the channel to deform and to exert a response force on the face. [0017] According to one aspect, the channel is configured such that a majority of the energy of the impact is absorbed by the channel, and a majority of a face response of the face during the impact is derived directly from the response force exerted by the channel on the face. [0018] According to another aspect, the face has a stiffness proximate a geometric center of the face that is from about 4,600-5,600 lb-in ² . [0019] According to a further aspect, the face also includes a face plate having the ball striking surface thereon and a cellular stiffening structure engaged with an inner surface of the face plate. [0020] Further aspects of the invention relate to a ball striking device including a face having a ball striking surface and being defined by a plurality of face edges, and a body connected to the face and extending rearward from the face edges to define an enclosed volume, where the body has a heel side, a toe side, a crown, and a sole. A first channel is defined on the body by first and second boundary edges extending between a first end proximate the heel side and a second end proximate the toe side, such that the first channel extends at least partially across the crown of the body. A second channel is also defined on the body by third and fourth boundary edges extending between a third end proximate the heel side and a fourth end proximate the toe side, such that the second channel extends at least partially across the sole of the body. The first and second channels are each recessed inwardly from outer surfaces of the body between the respective boundary edges. The first end of the first channel is spaced from the third end of the second channel, and the second end of the first channel is spaced from the fourth end of the second channel, such that the first channel and the second channel are completely separate. The first and second channels are spaced rearwardly from the face edges by spacing portions, and the first and second channels are configured such that at least some energy from an impact on the ball striking surface is transferred through the spacing portion and absorbed by at least one of the first and second channels, causing the at least one of the first and second channels to deform and to exert a response force on the face. [0021] According to one aspect, at least a portion of the body including the first and second channels has a stiffness that is lower than a stiffness of the face. [0022] According to another aspect, the first end and the second end are both located on one side of an outermost periphery of the head, and the third end and the fourth end are both located on an opposite side of the outermost periphery. [0023] According to a further aspect, a portion of the body, including at least the first and second channels, is formed of a flexible material having a modulus that is lower than a material of a second portion of the body. The second portion of the body may include the spacing portions in this configuration. [0024] According to yet another aspect, the face has a stiffening structure increasing the stiffness of the face. [0025] According to a still further aspect, the face includes a face plate forming the ball striking surface and a porous stiffening structure connected to an inner side of the face plate. The porous stiffening structure may include a plurality of interior walls forming a honeycomb structure having hexagonal chambers. Additionally, the face may also include a rear plate in this configuration, where the porous stiffening structure is sandwiched between the face plate and the rear plate. [0026] According to an additional aspect, a majority of the force generated by impact with the ball is absorbed by the impact-influencing structure, and a majority of the response force generated by the head upon impact with the ball is generated by the impact-influencing structure. [0027] According to another aspect, the first channel is recessed deeper proximate a center of the first channel than at the first and second ends and a depth of the first channel tapers deeper from the first and second ends to the center. The second channel is also recessed deeper proximate a center of the second channel than at the third and fourth ends and a depth of the second channel tapers deeper from the third and fourth ends to the center. [0028] According to yet another aspect, the face is formed as part of a face member and the head further includes a body member connected to the face member and forming at least a portion of the body. The face member may be a plate member in one configuration, and may include the face and a wall extending rearwardly from the face in another configuration, such that the wall combines with the body member to define the body. In this configuration, the first channel and the second channel may be located entirely within the wall. [0029] Still further aspects of the invention relate to a ball striking device that includes a face having a ball striking surface and being defined by a plurality of face edges, and a body connected to the face and extending rearward from the face edges to define an enclosed volume, where the body has a heel side, a toe side, a crown, and a sole. A band of flexible material extends around at least a portion of a circumference of the body and is generally equidistant from the face edges. The flexible material has a stiffness that is lower than a stiffness of the face and a modulus that is lower than a modulus of another portion of the body. The band is configured such that at least some energy from an impact on the ball striking surface is transferred through the spacing portion and absorbed by the band, causing the band to deform and to exert a response force on the face. [0030] According to one aspect, the band may be spaced rearwardly from the face edges by spacing portions. [0031] According to another aspect, the head may include a first channel defined on the body by first and second boundary edges extending between a first end proximate the heel side and a second end proximate the toe side. The first channel is recessed inwardly from outer surfaces of the body between the first and second edges, and the first channel is spaced rearwardly from the face edges by a spacing portion. The first channel may be positioned within the band, such that the flexible material forms the first channel. In this configuration, the channel may be a 360° channel, such that the first and second boundary edges may extend continuously around an entire circumference of the body and are generally equidistant from the face edges, and the first channel includes a crown channel portion extending at least partially across the crown, a sole channel portion extending at least partially across the sole, and additional channel portions extending around the heel and the toe to interconnect the crown channel portion and the sole channel portion to form the first channel in a continuous circumferential shape. Alternately, the first channel may extend at least partially across the crown of the body, and the head may also include a second channel defined on the body by third and fourth boundary edges extending between a third end proximate the heel side and a fourth end proximate the toe side, such that the second channel extends at least partially across the sole of the body. The second channel is recessed inwardly from the outer surfaces of the body between the third and fourth edges. The second channel may also be positioned within the band, such that the flexible material forms the second channel, and the second channel may be spaced rearwardly from the face edges by an additional spacing portion. The first end of the first channel is spaced from the third end of the second channel, and the second end of the first channel is spaced from the fourth end of the second channel, such that the first channel and the second channel are completely separate. [0032] According to a further aspect, the face includes a face plate forming the ball striking surface and a porous stiffening structure connected to an inner side of the face plate. [0033] According to yet another aspect, the face is formed as part of a face member and the head further includes a body member forming a portion of the body, such that the band connects the face member to the body member. The band may be joined to at least one of the face member and the body member by a lap joint. [0034] Other aspects of the invention relate to a golf club or other ball striking device including a head or other ball striking device as described above and a shaft connected to the head and configured for gripping by a user. Aspects of the invention relate to a set of golf clubs including at least one golf club as described above. Yet additional aspects of the invention relate to a method for manufacturing a ball striking device as described above, including forming a ball striking device as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] To allow for a more full understanding of the present invention, it will now be described by way of example, with reference to the accompanying drawings in which: FIG.1 is a front view of an illustrative embodiment of a wood-type ball striking device according to aspects of the present invention; FIG.2 is a perspective view of a head of the ball striking device of FIG. 1;

FIG.3 is a bottom view of the head of FIG. 2;

FIG.4 is a top view of the head of FIG. 2;

FIG. 4A is a side view of the head of FIG. 2;

FIG. 4B is a top view of an alternative embodiment of the head of FIG. 4;

FIG.5 is a cross-sectional view of the head of FIG. 2, taken along lines 5-5 of FIG. 2;

FIG. 5A is a cross-sectional view of an alternative embodiment of the head of FIG. 5;

FIG.6 is a cross-sectional view of the head as shown in FIG. 5, illustrated during impact with a ball;

FIG.7 is a cross-sectional view of another illustrative embodiment of a wood- type ball striking device according to aspects of the present invention;

FIG.8 is a cross-sectional view of the head as shown in FIG. 7, illustrated during impact with a ball;

FIG.9 is a cross-sectional view of another illustrative embodiment of a wood- type ball striking device according to aspects of the present invention;

FIG. 9A is a cross-sectional view of an alternative embodiment of the head of FIG. 9;

FIG. 9B is a cross-sectional view of another alternative embodiment of the head of FIG. 9;

FIG. 10 is a cross-sectional view of the head as shown in FIG. 9, illustrated during impact with a ball;

FIG. 11 is a cross-sectional view of an example of an existing wood-type ball striking device, illustrated during impact with a ball;

FIG. 12 is a bottom view of another illustrative embodiment of a wood-type ball striking device according to aspects of the present invention;

FIG. 13 is a cross-sectional view of another illustrative embodiment of a wood- type ball striking device according to aspects of the present invention;

FIG. 14 is a cross-sectional view of another illustrative embodiment of a wood- type ball striking device according to aspects of the present invention; FIG. 15 is a cross-sectional view of another illustrative embodiment of a wood- type ball striking device according to aspects of the present invention;

FIG. 16 is a cross-sectional view of another illustrative embodiment of a wood- type ball striking device according to aspects of the present invention;

FIG. 17 is a cross-sectional view of another illustrative embodiment of a wood- type ball striking device according to aspects of the present invention;

FIG. 18 is rear view of a face member of another illustrative embodiment of a wood-type ball striking device according to aspects of the present invention, illustrated with portions of the head removed to show detail on the rear of the face;

FIG. 19 is a cross-sectional view of another illustrative embodiment of a wood- type ball striking device according to aspects of the present invention;

FIG. 20 is a magnified view of a portion of a face of the head of FIG. 19;

FIG. 21 is a cross-sectional view of a portion of the face of the head of FIG. 19, viewed along lines 21-21 of FIG. 20;

FIG. 22 is a cross-sectional view of another illustrative embodiment of a wood- type ball striking device according to aspects of the present invention; and

FIG. 23 is a cross-sectional view of another illustrative embodiment of a wood- type ball striking device according to aspects of the present invention.

[0036] It is understood that the relative sizes of the components in these Figures and the degrees of deformation of the components shown in FIGS. 5-11 may be exaggerated in order to show relevant detail. DETAILED DESCRIPTION

[0037] In the following description of various example structures according to the invention, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration various example devices, systems, and environments in which aspects of the invention may be practiced. It is to be understood that other specific arrangements of parts, example devices, systems, and environments may be utilized and structural and functional modifications may be made without departing from the scope of the present invention. Also, while the terms "top," "bottom," "front," "back," "side," "rear," and the like may be used in this specification to describe various example features and elements of the invention, these terms are used herein as a matter of convenience, e.g., based on the example orientations shown in the figures or the orientation during typical use. Additionally, the term "plurality,” as used herein, indicates any number greater than one, either disjunctively or conjunctively, as necessary, up to an infinite number. Nothing in this specification should be construed as requiring a specific three dimensional orientation of structures in order to fall within the scope of this invention. Also, the reader is advised that the attached drawings are not necessarily drawn to scale. [0038] The following terms are used in this specification, and unless otherwise noted or clear from the context, these terms have the meanings provided below. [0039] "Ball striking device" means any device constructed and designed to strike a ball or other similar objects (such as a hockey puck). In addition to generically encompassing "ball striking heads," which are described in more detail below, examples of "ball striking devices" include, but are not limited to: golf clubs, putters, croquet mallets, polo mallets, baseball or softball bats, cricket bats, tennis rackets, badminton rackets, field hockey sticks, ice hockey sticks, and the like. [0040] "Ball striking head" means the portion of a "ball striking device" that includes and is located immediately adjacent (optionally surrounding) the portion of the ball striking device designed to contact the ball (or other object) in use. In some examples, such as many golf clubs and putters, the ball striking head may be a separate and independent entity from any shaft or handle member, and it may be attached to the shaft or handle in some manner. [0041] The terms "shaft" and "handle" are used synonymously and interchangeably in this specification, and they include the portion of a ball striking device (if any) that the user holds during a swing of a ball striking device. [0042] "Integral joining technique" means a technique for joining two pieces so that the two pieces effectively become a single, integral piece, including, but not limited to, irreversible joining techniques, such as adhesively joining, cementing, and welding (including brazing, soldering, or the like), where separation of the joined pieces cannot be accomplished without structural damage thereto. [0043] “Approximately” or“about” means within a range of +/- 10% of the nominal value modified by such term. [0044] In general, aspects of this invention relate to ball striking devices, such as golf club heads, golf clubs, and the like. Such ball striking devices, according to at least some examples of the invention, may include a ball striking head and a ball striking surface. In the case of a golf club, the ball striking surface is a substantially flat surface on one face of the ball striking head. It is understood that some golf clubs or other ball striking devices may have more than one ball striking surface. Some more specific aspects of this invention relate to wood-type golf clubs and golf club heads. Alternately, some aspects of this invention may be practiced with iron-type golf clubs and golf club heads, hybrid clubs, chippers, putters, etc. [0045] According to various aspects of this invention, the ball striking device may be formed of one or more of a variety of materials, such as metals (including metal alloys), ceramics, polymers, composites (including fiber-reinforced composites), and wood, and may be formed in one of a variety of configurations, without departing from the scope of the invention. In one illustrative embodiment, some or all components of the head, including the face and at least a portion of the body of the head, are made of metal. It is understood that the head may contain components made of several different materials, including carbon-fiber and other composites. Additionally, the components may be formed by various forming methods. For example, metal components (such as titanium, aluminum, titanium alloys, aluminum alloys, steels (including stainless steels), and the like) may be formed by forging, molding, casting, stamping, machining, and/or other known techniques. In another example, composite components, such as carbon fiber-polymer composites, can be manufactured by a variety of composite processing techniques, such as prepreg processing, powder-based techniques, mold infiltration, and/or other known techniques. [0046] The various figures in this application illustrate examples of ball striking devices according to this invention. When the same reference number appears in more than one drawing, that reference number is used consistently in this specification and the drawings refer to the same or similar parts throughout. [0047] At least some examples of ball striking devices according to the invention relate to golf club head structures, including heads for wood-type golf clubs, such as drivers, fairway woods, etc. Other examples of ball striking devices according to the invention may relate to iron-type golf clubs, such as long iron clubs (e.g., driving irons, zero irons through five irons), short iron clubs (e.g., six irons through pitching wedges, as well as sand wedges, lob wedges, gap wedges, and/or other wedges), as well as hybrid clubs, putters, chippers, and other types of clubs. Such devices may include a one-piece construction or a multiple-piece construction. Example structures of ball striking devices according to this invention will be described in detail below in conjunction with FIG. 1, which illustrates an example of a ball striking device 100 in the form of a golf driver, in accordance with at least some examples of this invention. [0048] FIGS. 1-6 illustrate a ball striking device 100 in the form of a golf driver, in accordance with at least some examples of the invention, and FIGS. 7-21 illustrate various additional embodiments of a golf driver in accordance with aspects of the invention. As shown in FIG. 1, the ball striking device 100 includes a ball striking head 102 and a shaft 104 connected to the ball striking head 102 and extending therefrom. As shown in FIG. 2, the ball striking head 102 of the ball striking device 100 of FIG. 1 has a face 112 connected to a body 108, with a hosel 109 extending therefrom. For reference, the head 102 generally has a top 116, a bottom or sole 118, a heel 120 proximate the hosel 109, a toe 122 distal from the hosel 109, a front 124, and a back or rear 126. The shape and design of the head 102 may be partially dictated by the intended use of the device 100. In the club 100 shown in FIG. 1, the head 102 has a relatively large volume, as the club 100 is designed for use as a driver, intended to hit the ball 106 (shown in FIGS. 5 and 6) accurately over long distances. In other applications, such as for a different type of golf club, the head may be designed to have different dimensions and configurations. When configured as a driver, the club head may have a volume of at least 400 cc, and in some structures, at least 450 cc, or even at least 460 cc. If instead configured as a fairway wood, the head may have a volume of 120 cc to 230 cc, and if configured as a hybrid club, the head may have a volume of 85 cc to 140 cc. Other appropriate sizes for other club heads may be readily determined by those skilled in the art. [0049] In the embodiment illustrated in FIGS. 1-6, the head 102 has a hollow structure defining an inner cavity 107 (e.g., defined by the face 112 and the body 108). Thus, the head 102 has a plurality of inner surfaces defined therein. In one embodiment, the hollow inner cavity 107 may be filled with air. However, in other embodiments, the head 102 could be filled with another material, such as foam. In still further embodiments, the solid materials of the head may occupy a greater proportion of the volume, and the head may have a smaller cavity or no inner cavity at all. It is understood that the inner cavityl07 may not be completely enclosed in some embodiments. In the embodiment illustrated in FIGS. 1-4, the body 108 of the head 102 has a rounded rear profile. In other embodiments, the body 108 of the head 102 can have another shape or profile, including a squared or rectangular rear profile as shown in FIG. 12, or any of a variety of other shapes. It is understood that such shapes may be configured to distribute weight away from the face 112 and/or the geometric/volumetric center of the head 102, in order to create a lower center of gravity and/or a higher moment of inertia. The body 108 may be connected to the hosel 109 for connection to a shaft 104, as described below. [0050] The face 112 is located at the front 124 of the head 102, and has a ball striking surface 110 located thereon and an inner surface 111 (FIGS. 5-6) opposite the ball striking surface 110. The ball striking surface 110 is typically an outer surface of the face 112 configured to face a ball 106 in use, and is adapted to strike the ball 106 when the device 100 is set in motion, such as by swinging. The face 112 is defined by peripheral edges, including a top edge 113, a bottom edge 115, a heel edge 117, and a toe edge 119. Additionally, in this embodiment, the face 112 has a plurality of face grooves 121 on the ball striking surface 110, which do not extend across the center of the face 112. In another embodiment, such as a fairway wood head or a hybrid wood-type head, the face 112 may have grooves 121 that extend across at least a portion of the center of the face 112. [0051] As shown, the ball striking surface 110 is relatively flat, occupying most of the face 112. For reference purposes, the portion of the face 112 nearest the top face edge 113 and the heel 120 of the head 102 is referred to as the“high-heel area” the portion of the face 112 nearest the top face edge 113 and toe 122 of the head 102 is referred to as the“high-toe area”; the portion of the face 112 nearest the bottom face edge 115 and heel 120 of the head 102 is referred to as the“low-heel area”; and the portion of the face 112 nearest the bottom face edge 115 and toe 122 of the head 102 is referred to as the“low-toe area”. Conceptually, these areas may be recognized and referred to as quadrants of substantially equal size (and/or quadrants extending from a geometric center of the face 112), though not necessarily with symmetrical dimensions. The face 112 may include some curvature in the top to bottom and/or heel to toe directions (e.g., bulge and roll characteristics), as is known and is conventional in the art. In other embodiments, the surface 110 may occupy a different proportion of the face 112, or the body 108 may have multiple ball striking surfaces 110 thereon. In the illustrative embodiment shown in FIG. 1, the ball striking surface 110 is inclined slightly (i.e., at a loft angle), to give the ball 106 slight lift and spin when struck. In other illustrative embodiments, the ball striking surface 110 may have a different incline or loft angle, to affect the trajectory of the ball 106. Additionally, the face 112 may have a variable thickness and/or may have one or more internal or external inserts in some embodiments. [0052] It is understood that the face 112, the body 108, and/or the hosel 109 can be formed as a single piece or as separate pieces that are joined together. For example, in one embodiment, face 112 may be wholly or partially formed by a face member with the body 108 being partially or wholly formed by a body member including one or more separate pieces connected to the face member, for example, as in the embodiment shown in FIGS. 19-20. These pieces may be connected by an integral joining technique, such as welding, cementing, or adhesively joining. Other known techniques for joining these parts can be used as well, including many mechanical joining techniques, including fasteners and other releasable mechanical engagement techniques. If desired, the hosel 109 may be integrally formed as part of the body member or the face member. Further, a gasket (not shown) may be included between the face member and the body member in some embodiments. FIG. 5A illustrates one embodiment of the head 102 of FIGS. 1-5, where the head 102 includes a face member 128 connected to a body member 129 using lap joint connections 160. It is understood that other techniques may be used to secure the lap joints 160, such as welding, brazing, bonding, press-fitting, etc. If the face member 128 is welded to the body member 129, a butt joint may be used instead of a lap joint in one embodiment. As seen in FIG. 5A, the lap joints 160 are located rearwardly of the channels 130, so as to not affect the stiffness of the channels 130 and to not result in the channels 130 being spaced too far rearwardly from the face 112. However, in another embodiment, lap joints 160, butt joints, or other joint connections may be formed forwardly of the channels 130, such as in the portions of the body 108 spacing the channels 130 from the face 112. Additionally, it may be advantageous to weld in a location where the heat affected zone (HAZ) of the weld does not penetrate the channel 130 and/or affect the flexibility of the channel 130. In one embodiment, the weld is no closer than about 4mm from the channel 130. The face member 128 shown in FIG. 5A is in the form of a cup-face structure, however other configurations of face members 128 may be used. [0053] The ball striking device 100 may include a shaft 104 connected to or otherwise engaged with the ball striking head 102, as shown in FIG. 1. The shaft 104 is adapted to be gripped by a user to swing the ball striking device 100 to strike the ball 106. The shaft 104 can be formed as a separate piece connected to the head 102, such as by connecting to the hosel 109, as shown in FIG. 1. Any desired hosel and/or head/shaft interconnection structure may be used without departing from this invention, including conventional hosel or other head/shaft interconnection structures as are known and used in the art, or an adjustable, releasable, and/or interchangeable hosel or other head/shaft interconnection structure such as those shown and described in U.S. Patent 6,890,269 dated May 10, 2005, in the name of Bruce D. Burrows, U.S. Published Patent Application No. 2009/0011848, filed on July 6, 2007, in the name of John Thomas Stites, et al., U.S. Published Patent Application No. 2009/0011849, filed on July 6, 2007, in the name of John Thomas Stites, et al., U.S. Published Patent Application No.

2009/0011850, filed on July 6, 2007, in the name of John Thomas Stites, et al., and U.S.

Published Patent Application No. 2009/0062029, filed on August 28, 2007, in the name of John Thomas Stites, et al., all of which are incorporated herein by reference in their entireties. In other illustrative embodiments, at least a portion of the shaft 104 may be an integral piece with the head 102, and/or the head 102 may not contain a hosel 109 or may contain an internal hosel structure. Still further embodiments are contemplated without departing from the scope of the invention. [0054] The shaft 104 may be constructed from one or more of a variety of materials, including metals, ceramics, polymers, composites, or wood. In some illustrative embodiments, the shaft 104, or at least portions thereof, may be constructed of a metal, such as stainless steel or titanium, or a composite, such as a carbon/graphite fiber-polymer composite. However, it is contemplated that the shaft 104 may be constructed of different materials without departing from the scope of the invention, including conventional materials that are known and used in the art. A grip element 105 may be positioned on the shaft 104 to provide a golfer with a slip resistant surface with which to grasp golf club shaft 104, as shown in FIG. 1. The grip element 105 may be attached to the shaft 104 in any desired manner, including in conventional manners known and used in the art (e.g., via adhesives or cements, threads or other mechanical connectors, swedging/swaging, etc.). [0055] In general, the head 102 has a face 112 with increased stiffness relative to existing faces and a body 108 that has impact-influencing structural features that can affect the physics of the impact of the ball 106 with the face 112, such as the COR measured according to USGA testing procedures. The impact influencing features may take the form of one or more flexible portions that extends around at least a portion of the periphery of the body 108, adjacent to the peripheral edges 113, 115, 117, 119 of the face 112. The flexible portion(s) may be formed in many ways, including by channels or other structural features and/or by the use of flexible materials. In one embodiment, a majority of the force generated by impact with a ball 106 is absorbed by the impact-influencing features, and a majority of a response force generated by the head 102 upon impact with the ball 106 is generated by the impact-influencing structure. In existing golf club heads, the face 112 absorbs a significant majority of the impact force and generates a significant majority of the response force. [0056] In the embodiment shown in FIGS. 1-6, the head 102 has a channel or channels 130 extending around the body 108 adjacent and generally parallel to the peripheral edges 113, 115, 117, 119 of the face 112. The channels 130 illustrated in FIGS. 2-6 allow at least a portion of the body 108 to flex, produce a reactive force, and/or change the behavior or motion of the face 112, during impact of a ball on the face 112. In this embodiment, the channels 130 permit

compression and flexing of the body 108 during an impact on the face 112, and also produce a reactive force that can be transferred to the ball 106, as well as changing the motion and behavior of the face 112 during impact. As shown in FIGS. 3-4A, in this embodiment, the body 108 has two elongated channels 130, one extending across the top 116 of the head 102 from an end 133 at the heel 120 to an end 133 at the toe 122, and the other extending across the bottom 118 of the head 102 from an end 133 at the heel 120 to an end 133 at the toe 122. As seen in FIGS. 3-4A, these channels 130 are spaced rearwardly approximately the same distance from the face 112, and are generally in alignment and symmetrically positioned on the head 102. In another embodiment, the head 102 may have a single channel 130 extending around all or part of the periphery of the head 102. For example, in one embodiment, the ends of the channels shown in FIGS. 3-4A may be joined to form a single channel 130. In another embodiment, as shown in FIG. 4B, the top and/or bottom channels 130 may not extend to the outermost periphery (i.e. the periphery defining the largest outer dimension) of the head 102 and may converge to a point short of the outer periphery. In this embodiment, the channel 130 has distal ends 133 that stop short of the outer periphery and are spaced toward the center of the head 102 from the outer periphery, with surfaces of the body 108 extending between the ends 133 of the channel 130 and the outer periphery. In other words, the ends 133 of the channel are both on the same (top) side of the outermost periphery of the head 102, and are both on the same (top) side of a plane defined by the outermost periphery. The head 102 may contain a single channel 130 on the crown 116, a single channel on the sole 118, or channels 130 on both the crown 116 and the sole 118 in various configurations. It is understood that if the head 102 contains a channel 130 on the sole 118, this channel 130 may be similarly configured such that the ends 133 do not extend to the outer periphery of the head 102, and the ends 133 are both on the same (bottom) side of the outermost periphery. [0057] The channels 130 illustrated in FIGS. 2-6 are recessed inwardly with respect to surfaces of the head 102 that are in contact with the boundary 131 defining the channel 130, as shown in FIGS. 4A-6. The channels 130 in this embodiment have a trough-like shape, with sloping sides 132 that are smoothly curved, as seen in FIGS. 5-6. Additionally, the channels 130 have a tapering width in this embodiment, such that the channels 130 are narrower (measured between the boundaries 131 transverse to the direction of elongation of the channel 130) at the ends 133 than at the center. The channels 130 further have a tapering depth in this embodiment, such that the channels 130 are shallower (measured by the degree of recess of the channel 130) at the ends 133 than at the center. The geometry of each channel 130 can affect the flexibility of the channel 130 and the corresponding response transferred through the face 112 to the ball 106. Accordingly, in one embodiment, different heads 102 can be produced having faces 112 with different responses, by using channels 130 with different geometries. [0058] In other embodiments, the head may contain one or more channels 130 that are different in number, size, shape, depth, location, etc. For example, the channel(s) 430 of the head 402 in FIG. 12, have a more constant width than the channels 130 of FIGS. 2-6. As another example, the channel(s) 130 may have a sharper and/or more polygonal cross-sectional shape and/or a different depth in some embodiments. As a further example, the channel(s) 130 may be located only on the top 116, the bottom 118, the heel 120, and/or the toe 122 of the head 102. As yet another example, the wall thickness of the body 108 may be increased or decreased at the channels 130, as compared to the thickness at other locations of the body 108, to control the flexibility of the channels 130. As a still further example, the channels 130 may be located on an inner surface of the body 108, such as in the head 202 shown in FIGS. 7-8. Still other configurations may be used and may be recognizable to those skilled in the art in light of the present specification. [0059] As mentioned above, the face 112 has increased stiffness relative to existing faces for golf club heads. The increased stiffness of the face 112 can be achieved through various different means and structures, including through the use of high-strength and high-modulus materials and/or through the use of stiffening structures in the face 112. As used herein, stiffness is calculated using the equation: S = E × I where“S” refers to stiffness,“E” refers to Young’s modulus of the material, and“I” refers to the cross-sectional moment of inertia of the face 112. Accordingly, stiffness depends not only on the modulus (flexibility) of the material, but also on the thickness and shape of the face 112. In one example, the face 112 can be made from a material having higher modulus and/or may also be made thicker than a normal face 112. In one embodiment, the face 112 may have a stiffness that is about 10 times greater than the stiffness of a typical titanium driver face (e.g. with a height of about 2.3 inches (57-58mm) and a thickness of about 3mm, and a modulus of 105 GPa), such as about 4,600-5,600 lb-in ² , or about 5,100 lb-in ² (about 13.3-16.2 N-m ² , or about 14.7 N-m ² ) in one example. These stiffness figures are measured at the geometric center and/or the hot zone of the face, which may be the cross-section plane of the face with the greatest height. Additionally, these stiffness figures are measured on the vertical axis, i.e. for bending across the thickness of the face 112 based on a force applied to the striking surface 110. Examples of materials having high modulus that may be used in the face include a variety of high-strength steel and titanium alloys, composites (including titanium-based composites and carbon fiber and other fiber- reinforced composites, and various other composites containing metals, polymers, ceramics, etc.), beryllium and beryllium alloys, molybdenum and molybdenum alloys, tungsten and tungsten alloys, other metallic materials (including alloys), high-strength polymers, ceramics, and other suitable materials. In one embodiment, the face 112 may utilize a material that has a modulus of at least 280 GPa. In another example, the face 112 may have stiffening structure that increases the stiffness of the face 112, such as through adding increased modulus and/or increasing the cross-sectional moment of inertia (I) of the face 112. Some examples of such stiffening means and structures are shown in FIGS. 13-21 and described below, including inserts and reinforcing structures. As a further example, any of the stiffening structures disclosed in U.S. Published Patent Application No. 2010/0130303, filed on November 21, 2008, in the name of John T. Stites et al., or variations thereof, may be utilized to give increased stiffness to the face or localized areas thereof, which application is incorporated by reference herein and made part hereof. It is understood that a face 112 may include any combination of these stiffening techniques in some embodiments. [0060] The face 112, or at least a portion of the face 112 including the CG and/or the geometric center of the face 112, may have a stiffness that is greater than the stiffness of at least a portion of the body 108. In one embodiment, a majority of the face 112 including the geometric center of the face 112 may include such increased stiffness. For example, in one embodiment, the face 112 may have a stiffness that is greater than the stiffness of any portion of the body 108. In another embodiment, the face 112 may have a stiffness that is at least greater than the stiffness of the channel(s) 130. The channel 130 may also have a lower stiffness than at least some other portions of the body 108, which may be accomplished through the use of structure and/or materials (e.g. as in FIGS. 9-10). Other embodiments described herein may utilize faces and body features having similar stiffness or relative stiffness, including other embodiments of channels 230, et seq. [0061] FIGS. 5-6 illustrate an impact of a ball 106 on the face 112 of the head 102 as shown in FIGS. 2-6. As shown in FIG. 6, when the ball 106 impacts the ball striking surface 110, the stiffened face 112 has very little to no deformation, and the force of the impact is transferred to the channels 130 on the top 116 and bottom 118 of the head 102. The channels 130 deform due to the impact force, as shown in FIG. 6, and return to their original configurations, as shown in FIG. 5, producing a response force that is transferred through the face 112 to the ball 106, propelling the ball 106 forward. In contrast, FIG. 11 illustrates an existing driver head 10, having a face 12 and a body 14 connected to the face 12, during an impact with the ball 106. As illustrated in FIG. 11, most or all of the deformation of the head 10 on impact occurs in the face 12, and the face 12 creates most or all of the response force on the ball 106, in contrast to the head 102 described above. The configuration shown in FIGS. 1-6 can achieve increased energy and velocity transfer to the ball 106 and increased response (COR) for impacts that are away from the center or traditional“sweet spot” of the face 112, such as high or low impacts or heel or toe impacts. The face 112 does not depend solely on localized“trampoline” effect for response force, and the response-producing channels 130 extend toward the heel 120 and toe 122, and overlap the heel and toe edges 117, 119 of the face 112. Additionally, in some embodiments, the flexing of the channels 130 can create a more gradual impact with the ball 106 as compared to the traditional head 10 (FIG. 16), which results in a smaller degree of deformation of the ball 106 as compared to the traditional head 10. This smaller degree of deformation can result in greater impact efficiency and greater energy and velocity transfer to the ball 106 during impact. The more gradual impact created by the flexing can also create a longer impact time, which can result in greater energy and velocity transfer to the ball 106 during impact. [0062] FIGS. 7-10 and 12 illustrate additional embodiments that include different impact- influencing features on the body. FIGS. 7-8 illustrate another embodiment of a head 202 having impact-influencing features on the body 208. Many features of this embodiment are similar or comparable to features of the head 102 described above and shown in FIGS. 1-6, and such features are referred to using similar reference numerals under the“2xx” series of reference numerals, rather than“1xx” as used in the embodiment of FIGS. 1-6. Accordingly, certain features of the head 202 that were already described above with respect to the head 102 of FIGS. 1-6 may be described in lesser detail, or may not be described at all. The head 202 of FIGS. 7-8 has one or more channels 230 on the inner surfaces of the body 208, which act as impact- influencing features, similarly to the channels 130 described above. In this embodiment, the head 202 has a single channel 230 that extends around the entire inner periphery of the body 208 and is spaced rearwardly from the face 212. However, in other embodiments, the head 202 may have multiple channels 230, such as channels 230 that are arranged similarly to the channels 130 of FIGS. 2-6. The head 202 of FIGS. 7-8 may utilize a stiffened face 212, as described herein. FIG. 8 illustrates an impact of a ball 106 on the face 212 of the head 202. When the ball 106 impacts the ball striking surface 210, the stiffened face 212 has very little to no deformation, and the force of the impact is transferred to the channels 230 on the top 216 and bottom 218 of the head 202. The channels 230 deform due to the impact force, as shown in FIG. 8, and return to their original configurations, as shown in FIG. 7, producing a response force that is transferred through the face 212 to the ball 106, propelling the ball 106 forward. The head 202 of FIGS. 7-8 can produce similar results and advantages as the head 102 of FIGS.2-6 described above. [0063] FIGS. 9-10 illustrate another embodiment of a head 302 having impact-influencing features on the body 308. Many features of this embodiment are similar or comparable to features of the head 102 described above and shown in FIGS. 1-6, and such features are referred to using similar reference numerals under the“3xx” series of reference numerals, rather than “1xx” as used in the embodiment of FIGS. 1-6. Accordingly, certain features of the head 302 that were already described above with respect to the head 102 of FIGS. 1-6 may be described in lesser detail, or may not be described at all. The head 302 of FIGS. 9-10 has one or more areas or regions of flexible material 330, having higher flexibility relative to the material of the face 312 and/or the material of the adjacent areas of the body 308, which acts as an impact- influencing feature, similarly to the channels 130 described above. In this embodiment, the head 302 has a contiguous band of flexible material 330 that extends around the entire periphery of the body 308, across the top 316, bottom 318, heel, and toe of the head 302. The band of flexible material 330 is located immediately adjacent the peripheral edges 313, 315 of the face 312. The head 302 of FIGS. 9-10 may utilize a stiffened face 312, as described herein. The flexible material 330 may be connected to the face 312 and/or the body 308 by a variety of different techniques, including welding, brazing, bonding with an adhesive or other bonding material, fasteners and interlocking pieces, and/or a variety of joints and other mechanical connections, including lap joints, dovetail joints, press-fit arrangements, etc. [0064] The flexible material 330 may be a different material than the face 312 and/or the body 308, or may be the same or a similar material that has characteristics increasing its flexibility. For example, the flexible material 330 may include materials such as a super elasto- plastic titanium alloys (“gum metal”), vitreous alloys, metallic glasses or other amorphous metallic materials, composite materials (carbon fiber and others), or other relatively flexible metals or metal alloys. In this embodiment, the flexible material 330 is more flexible than the material of the stiffened face 312, and is also more flexible than the material of the body 308, and extends approximately 1” behind the face 312. In other embodiments, the head 302 may have multiple, disconnected regions of the flexible material 330, and may have the flexible material 330 spaced rearwardly from the peripheral edges 313, 315 of the face 312, rather than immediately adjacent. In yet another embodiment, the entire body 308 may be made of the flexible material, such as the entire body 308 being made of a carbon fiber composite or other composite material. It is understood that the flexible material 330 may have a stiffness and/or a modulus that is lower than the stiffness and/or modulus of the face, and may also be lower than the stiffness and/or modulus of another portion of the body 308. For example, the flexible material 330 may have a modulus that is lower than the modulus of the material at least in the portions of the body 308 spacing the flexible material 330 from the face 312. [0065] FIG. 9A illustrates one embodiment of a head 302A configured similarly to the head 302 of FIGS. 9-10, where the flexible material 330 is connected to a face member 328 and a body member 329 using lap joint connections 360. It is understood that other techniques may be used to secure the lap joints 360, such as welding, brazing, bonding, press-fitting, etc. FIG. 9B illustrates another embodiment of a head 302B configured similarly to the head 302 of FIGS. 9- 10, where the head 302B contains channels 130 as shown in FIG. 5 and described above with respect to the head 102 of FIGS. 1-5. In this embodiment, the channels 130 are formed of the flexible material 330, which can increase the flexibility and/or responsiveness of the channels 130. The flexible material 330 may be connected to the head 302B using any technique described herein. [0066] FIG. 10 illustrates an impact of a ball 106 on the face 312 of the head 302. When the ball 106 impacts the ball striking surface 310, the stiffened face 312 has very little to no deformation, and the force of the impact is transferred to the flexible material 330 around the face 312. The flexible material 330 deforms due to the impact force, as shown in FIG. 10, and returns to its original configuration, as shown in FIG. 9, producing a response force that is transferred through the face 312 to the ball 106, propelling the ball 106 forward. The head 302 of FIGS. 9-10 can produce similar results and advantages as the head 102 of FIGS. 2-6 described above. [0067] FIG. 12 illustrates another embodiment of a head 402 having impact-influencing features on the body 408. Many features of this embodiment are similar or comparable to features of the head 102 described above and shown in FIGS. 1-6, and such features are referred to using similar reference numerals under the“4xx” series of reference numerals, rather than “1xx” as used in the embodiment of FIGS. 1-6. Accordingly, certain features of the head 402 that were already described above with respect to the head 102 of FIGS. 1-6 may be described in lesser detail, or may not be described at all. The head 402 of FIG. 12 has a stiffened face 412 with a channel 430 extending around the entire periphery of the body 408, generally parallel to the peripheral edges 415 of the face 412 and spaced rearwardly from the face 412. The channel 430 has a trough-like cross-sectional shape, similar to the channel 130 described above. In this embodiment, the channel 430 has a width that is not tapered, and is fairly constant around the length of the channel 430, unlike the channel 130 described above. The channel 430 functions in a similar manner to the channel 130 shown in FIG. 6 on impact with a ball 106, and the head 402 of FIG. 12 can produce similar results and advantages as the head 102 of FIGS. 2-6 described above. Additionally, the head 402 of FIG. 12 has a squared rear peripheral shape and profile, in contrast to the rounded rear profile of the head 102 of FIGS. 1-6. Other features of the head 402 are similar to the head 102 of FIGS. 1-6. [0068] FIGS. 13-21 illustrate different embodiments having stiffening structures for creating a stiffened face 112 or portion of the face 112. The embodiments of FIGS. 13-21 are illustrated as having a typical wood-type body, such as the body 14 shown in FIG. 11. However, it is understood that any of the embodiments of faces 512, 612, 712, 812 shown in FIGS. 13-21 and described below can be utilized in connection with bodies 108, 208, 308, 408 according to any of the embodiments described above, including any of the heads 102, 202, 302, 402 having impact- influencing features described above and shown in FIGS. 1-12. In further embodiments, other types of stiffening structures can be used, in addition or in place of the stiffening structures described herein, including stiffening structures as described in U.S. Published Patent

Application No. 2010/0130303, referenced above. [0069] FIG. 13 illustrates an embodiment of a head 502 having a stiffened face 512. Many features of this embodiment are similar or comparable to features of the head 102 described above and shown in FIGS. 1-6, and such features are referred to using similar reference numerals under the“5xx” series of reference numerals, rather than“1xx” as used in the embodiment of FIGS. 1-6. Accordingly, certain features of the head 502 that were already described above with respect to the head 102 of FIGS. 1-6 may be described in lesser detail, or may not be described at all. The face 512 of this embodiment includes stiffening structure in the form of a thickened portion 540 located around the area of highest response at the approximate center of the face 512. This thickened portion 540 increases the cross-sectional moment of inertia (I) of the face 512, and thus, can increase the stiffness (S) of the face 512. The thickened portion 540 may have a circular or slightly elliptical shape to correspond to the area at the center of the face 512 where impacts most frequently occur, although in other embodiments, the thickened portion 540 may have a different size, shape, and/or relative thickness. For example, the face 512 may have an area of variable thickness, which may be formed, for example, by a plurality of ridges, peaks, etc. on the inner surface 511 of the face 512. The body 508 of the head 502 of FIG. 13 may include impact-influencing features as described above. [0070] FIGS. 14-17 illustrate embodiments of heads 602 having faces 612 that are stiffened through the use of face inserts 640A-D as stiffening structures. Many features of this

embodiment are similar or comparable to features of the head 102 described above and shown in FIGS. 1-6, and such features are referred to using similar reference numerals under the“6xx” series of reference numerals, rather than“1xx” as used in the embodiment of FIGS. 1-6.

Accordingly, certain features of the head 602 that were already described above with respect to the head 102 of FIGS. 1-6 may be described in lesser detail, or may not be described at all. The inserts 640A-D shown in FIGS. 14-17 are generally made of a material that has a higher modulus and/or hardness than the other portions of the face 612, increasing the stiffness of the face 612. For example, the inserts 640A-D can be made of any of the high-strength and/or high modulus materials described above, or another such material. Additionally, the inserts 640A-D illustrated in FIGS. 14-17 are all positioned at and around the center of the face 612, to provide added stiffness in the areas where the ball 106 contacts the face 612 most frequently. Further, the inserts 640A-D can increase stiffness both through the modulus of the material and by increasing the cross-sectional moment of inertia (I) of the face 612. The inserts 640A-D may be connected to the face 612 using many different joining techniques or combinations of such techniques, including welding or other integral joining techniques, adhesive substances, mechanical connectors, etc. [0071] The face 612 illustrated in FIG. 14 has a stiffening insert 640A positioned behind the face 612 and connected to the inner surface 611 of the face 612, to provide increased stiffness to the face 612. The face 612 illustrated in FIG. 15 has a stiffening insert 640B positioned in an opening 642 in the face 612 and extending completely through the face 612, from the inner surface 611 to the ball striking surface 610 of the face 612, to provide increased stiffness to the face 612. The face 612 illustrated in FIG. 16 has a stiffening insert 640C positioned within a recess 644 in the ball striking surface 610 of the face 612, to provide increased stiffness to the face 612. The face 612 illustrated in FIG. 17 has a stiffening insert 640D positioned within a recess 644 in the inner surface 611 of the face 612, behind the ball striking surface 610, to provide increased stiffness to the face 612. The body 608 of each of the heads 602 of FIGS. 14- 17 may include impact-influencing features as described above, as well as other features described herein. In other embodiments, the head 602 may contain a different insert 640A-D, which may be differently shaped, sized, and/or configured. For example, the inserts 640A-D may take up a larger or smaller portion of the face 612, and may cover all or nearly all of the outer and/or inner surfaces 610, 611 of the face 612. In one example, the insert 640A in FIG. 14 can be an additional layer that is coated or otherwise adhered to the inner surface 611 of the face 612. Other examples and embodiments can be used as well. [0072] FIG. 18 illustrates an embodiment of a head 702 having a stiffened face 712. Many features of this embodiment are similar or comparable to features of the head 102 described above and shown in FIGS. 1-6, and such features are referred to using similar reference numerals under the“7xx” series of reference numerals, rather than“1xx” as used in the embodiment of FIGS. 1-6. Accordingly, certain features of the head 702 that were already described above with respect to the head 102 of FIGS. 1-6 may be described in lesser detail, or may not be described at all. The face 712 of this embodiment includes a stiffening structure on the inner surface 711 of the face 712. The stiffening structure in this embodiment is formed by a plurality of ribs 744 arranged in a crossing pattern on the inner surface 711 of the face 712. The ribs 744 in this embodiment extend inwardly from the inner surface 711 of the face 712, defining gaps 746 between the ribs 744. These ribs 744 provide strength and support to the face 712, and also increase the cross-sectional moment of inertia (I) in this embodiment, and accordingly, can increase the stiffness of the face 712. In other embodiments, the face 712 may have ribs 744 having a different size, shape, orientation, and/or configuration. It is understood that FIG. 18 depicts only the face 712 of the head 702, and does not depict any body or body member extending rearwardly from the face 712, although the face 712 may be used in connection with any of the heads 104, et seq., described above, including by connecting the face 712 to a body member 108, 208, 308, 408 as described above, having impact-influencing features. [0073] FIGS. 19-21 illustrate an embodiment of a head 802 having a stiffened face 812. Many features of this embodiment are similar or comparable to features of the head 102 described above and shown in FIGS. 1-6, and such features are referred to using similar reference numerals under the“8xx” series of reference numerals, rather than“1xx” as used in the embodiment of FIGS. 1-6. Accordingly, certain features of the head 802 that were already described above with respect to the head 102 of FIGS. 1-6 may be described in lesser detail, or may not be described at all. The face 812 of this embodiment includes a stiffening structure within the face 812. As shown in FIG. 20, the face 812 includes a thin, stiff face plate 850 and rear plate 852, with a porous stiffening structure 854 sandwiched between the face plate 850 and the rear plate 852. In this embodiment, the stiffening structure 854 is formed in a honeycomb pattern, including a plurality of internal walls 856 defining hexagonal-shaped chambers 858 in a honeycomb-like configuration. The stiffening structure 854 may be formed of the same material as the face plate 850 or a different material, and is connected to an inner surface 811 of the face plate 850. In one embodiment, the face plate 850 and the rear plate 852 are made from titanium, and the stiffening structure 854 is formed of a titanium composite material, such as a

titanium/Nomex composite or a composite formed of titanium and another fiber material. Use of titanium in the stiffening structure can enhance weldability. In another embodiment, the stiffening structure 854 may be formed of titanium or titanium alloy or other metallic material, and may be connected to a metallic face plate 850 or rear plate 852 by welding, brazing, or other technique. In a further embodiment, the stiffening structure 854, the face plate 850, and/or the rear plate 852 may be formed of a polymer material or a polymer-fiber composite material. In embodiments where the stiffening structure 854 is made from a polymer material or polymer- fiber composite and the face plate 850 and/or the rear plate 854 is made from a metallic material, the stiffening structure 854 may be connected to the metallic components via adhesive or another bonding material. Further, in such embodiments, the face 812 may be connected to the body 808 using adhesive or another bonding material rather than welding, to ensure that welding temperatures do not affect the integrity of the polymer or the bonding material. As described elsewhere herein, the face 812 having the polymeric stiffening structure 854 (or other polymeric component) may be in various forms, including a plate or a cup face structure. In other embodiments, the face 812 may not include a rear plate 852. [0074] The stiffening honeycomb structure 854 in this embodiment can increase stiffness of the face 812 through increasing the cross-sectional moment of inertia (I) of the face 812, with the internal walls 856 of the structure 854 acting as braces for the face 812. The honeycomb structure 854 in this embodiment can also have a high modulus, such as at least 280 GPa, in one example. In other embodiments, the face plate 850, the rear plate 852, and/or the stiffening structure 854 are made from different materials. The face plate 850, the rear plate 852, and the stiffening structure 854 may have varying thicknesses in different embodiments. For example, in one embodiment, the face 812 has a total thickness of 0.25 in., with the face plate 850 having a thickness of up to about 1/32 in. (or about 0.03 in.). In another embodiment, the face 812 may have a total thickness of up to about 0.25 in. Additionally, in one embodiment, the thicknesses of the internal walls 856 of the stiffening structure 854 are about 0.002 - 0.006 in. The rear plate 852, if present, may have a thickness comparable to that of the face plate 850 in each of these embodiments. As a further example, the chambers 858 may each have a width of from about 0.008 in. to 0.25 in. in one embodiment, or may have different widths in other embodiments. For example, in one embodiment, the chambers 858 may each have a width of 0.108 in., with a the internal walls 856 thickness of 0.004 in. In other embodiments, the structures may have different sizes and/or configurations. For example, in some embodiments, a different type of porous stiffening structure 854 may be used, such as having a different, non-honeycomb configuration. As another example, in some embodiments, the rear plate 852 may not be included, and the face 812 may contain only the face plate 850 and the stiffening structure 854. [0075] The face 812 in FIGS. 19-21 is welded or otherwise integrally joined to a body member 828 to form the head 802, as shown in FIG. 19. In one embodiment, the face plate 850, the rear plate 852, and/or the honeycomb structure 854 may have varying thicknesses, which can influence the response of the face 812, and can also improve weldability. As shown in FIG. 19, the face 812 is joined to the body member 828 by welding at the ends of the face plate 812.

However, in another embodiment, the face 812 may be welded only at the side (e.g., welding to the rear plate 852 only), rather than at the ends, and the body member 828 may contain additional supporting structure for the face 812. In a further embodiment, the face 812 may be formed as a cup-face structure adapted for connection to a body member 828 to form the head 802, as described above. In yet another embodiment, the face 812 may be joined to the body member 828 in another manner, such as by using fasteners or another mechanical joining technique, or by using adhesives. [0076] A face 812 of this type illustrated in FIGS. 19-21 may have superior stiffness as compared to existing faces, but may have much less mass due to the porous structure, which permits weight savings in the face 812 to be added to a different part of the head 802 as desired. For example, a head 802 using the face 812 of FIGS. 19-21 may have a face 812 that has a thickness of 5-7mm and a mass of 25g in one embodiment, and 35g in another embodiment. When impacted by the ball, all 25g of the face will be involved in the impact, since the impact does not involve localized deformation or response on the face 812. In another embodiment, the face 812 may have a mass that is up to about 35g, such as a face 812 with a mass of 20-35g. In a further embodiment, the face 812 may have a mass that is between 25-30g. In the embodiments described above, the remainder of the head 802 may have a weight of between 185-210g, with the weight of the remainder of the head 802 in one embodiment being 200g. This weight includes the hosel 809 and any adjustability structures associated with the hosel 809. The total weight of the portions of the head 802 behind the channel(s) 830 may be approximately 135- 160g, with approximately 27% of the weight of the head 802 being located from the channel(s) 830 forward and approximately 73% of the weight being located behind the channel(s) 830. In contrast, a typical face may have a thickness of about 3mm and may have a mass of 45-50g. When impacted by a ball 106, the mass of the face material that is involved in the impact (i.e. deforms and/or is located around the impact area) is around 5g. Accordingly, the face 812 is lighter than existing faces, which permits the additional (e.g. 25g) mass to be positioned on the body 808 while retaining the same total weight. Strategic positioning of this additional weight can be used to control the position of the center of gravity and/or the MOI of the head 802. The mass of the face 812 can be further lowered by using lighter materials. Likewise, the other embodiments of faces 112, et seq., described herein can have reduced mass through the use of lighter materials and/or porous or other lightweight structures. [0077] In the embodiment illustrated in FIGS. 19-21, the head 802 has the face 812 connected to a body 808 similar to the body 108 described above and shown in FIGS. 2-6. The body 808 has one or more channels 830 extending around the body 808 generally parallel to the face 812 and spaced rearwardly from the face 812, as described above. The channel(s) 830 function in a similar manner to the channels 130 shown in FIG. 6 on impact with a ball 106, and the head 802 of FIGS. 19-21 can produce similar results and advantages as the head 102 of FIGS. 2-6 described above. In other embodiments, other features of heads 102, et seq., described herein may be incorporated into the head 802 of FIGS. 19-21, including any of the impact- influencing features described above and shown in FIGS. 7-10 and 12. Likewise, the features of the head 802 of FIGS. 19-21, including the stiffened face structure, can be incorporated into the other embodiments of heads 102, et seq., described herein. [0078] FIGS. 22-23 illustrate embodiments of a head 902 having a stiffened face 912. Many features of this embodiment are similar or comparable to features of the head 102 described above and shown in FIGS. 1-6, and such features are referred to using similar reference numerals under the“9xx” series of reference numerals, rather than“1xx” as used in the embodiment of FIGS. 1-6. Accordingly, certain features of the head 902 that were already described above with respect to the head 102 of FIGS. 1-6 may be described in lesser detail, or may not be described at all. The face 912 of this embodiment includes a stiffening structure within the face 912 that is similar to the structure of the face 812 of FIGS. 19-21. In the head 902 of FIG. 22, the face 912 is connected as part of a face member 928 that includes the face plate 950, the stiffening structure 954, and walls 925 connected to the face 912 and extending rearward from the face 912. The walls 925 are joined to a body member 929 to form the head 902, such that the body member 929 and at least a portion of the walls 925 define the body 908. In this embodiment, the channel(s) 930 are formed in the walls 925 of the face member 928. However, in another embodiment, the channel(s) 930 may be formed in the body member 929, such as if the juncture between the face member 928 and the body member 929 is located in the portions of the body 908 spacing the channel(s) from the face 912. FIG. 22 illustrates the face 912, including the stiffening structure 954 and the face plate 950 as being a separate piece connected to the walls 925, such as by welding. The walls 925 may define a recess or cavity on the front and/or rear side to receive the face 912 in this configuration. However, in another embodiment, part or all of the face 912 may be integrally connected or formed with the walls 925. For example, in FIG. 23, the face plate 950 is integrally formed with the walls 925, and the stiffening structure 954 is connected to the back of the face plate 950. In further embodiments, the face 912 may be connected in a different manner. Additionally, the face member 928 may also include a rear plate (not shown) as described above. Other configurations are possible. [0079] Several different embodiments have been described above, including the various embodiments of golf clubs 100 and heads 102, 202, 302, 402, 502, 602, 702, 802 (referred to herein as 102, et seq.) and portions thereof described herein. It is understood that any of the features of these various embodiments may be combined and/or interchanged. For example, as described above, various different combinations of club heads 102, et seq., with differently configured faces 112, et seq., may be used, including the configurations described herein, variations or combinations of such configurations, or other configurations. In one particular example, any of the club heads 102, et seq., described herein may include face stiffening features and/or impact-influencing body features as described above. In further embodiments, at least some of the features described herein can be used in connection with other configurations of iron-type clubs, wood-type clubs, other golf clubs, or other types of ball-striking devices. [0080] Heads 102, et seq., incorporating the features disclosed herein may be used as a ball striking device or a part thereof. For example, a golf club 100 as shown in FIG. 1 may be manufactured by attaching a shaft or handle 104 to a head that is provided, such as the head 102 as described above.“Providing” the head, as used herein, refers broadly to making an article available or accessible for future actions to be performed on the article, and does not connote that the party providing the article has manufactured, produced, or supplied the article or that the party providing the article has ownership or control of the article. In other embodiments, different types of ball striking devices can be manufactured according to the principles described herein. In one embodiment, a set of golf clubs can be manufactured, where at least one of the clubs has a head 102, et seq., according to features and embodiments described herein. [0081] The ball striking devices and heads therefor as described herein provide many benefits and advantages over existing products. For example, as described above, the impact between the ball and the face can provide a high degree of response (COR), energy transfer, and ball velocity for impacts occurring away from the center of the face, such as high, low, heel, and toe impacts, as compared to existing club heads, because the face does not depend on localized “trampoline” effect for response force. Further, certain embodiments described herein can result in mass savings in the face, which allows for additional mass that can be strategically placed on the body to affect the center of gravity, weight distribution, and/or MOI of the club head. Still other benefits and advantages are readily recognizable to those skilled in the art. [0082] While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and methods. Thus, the spirit and scope of the invention should be construed broadly as set forth in the appended claims.