Patent Publication Number: US-9901792-B2

Title: Golf clubs and golf club heads

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to, and is a continuation-in-part of, co-pending U.S. patent application Ser. No. 13/308,079, filed Nov. 30, 2011. 
    
    
     TECHNICAL FIELD 
     The invention relates generally to ball striking devices, such as golf clubs and golf club heads, utilizing features for transfer of energy and/or momentum. Certain aspects of this invention relate to golf club heads having a rear member configured to transfer energy and/or momentum to the face upon an impact on the face. 
     BACKGROUND 
     Golf clubs and many other ball striking devices can encounter undesirable effects when the ball being struck impacts the ball striking head away from the optimum location, which may be referred to as an “off-center impact.” In a golf club head, this optimum location is, in many cases, aligned laterally and/or vertically with the center of gravity (CG) of the head. Even slightly off-center impacts can sometimes significantly affect the performance of the head, and can result in reduced velocity and/or energy transfer to the ball, inconsistent ball flight direction and/or spin caused by twisting of the head, increased vibration that can produce undesirable sound and/or feel, and other undesirable effects. Technologies that can reduce or eliminate some or all of these undesirable effects could have great usefulness in golf club heads and other ball striking devices. 
     The present devices and methods are provided to address at least some of 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 
     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. 
     Aspects of the disclosure relate to ball striking devices, such as golf clubs, with a head that includes a face member including a face having a striking surface configured for striking a ball and a rear side located behind the face, a rear member connected to the rear side of the face member and having a front surface confronting the rear side of the face member, and a resilient material separating the rear member from the face member, such that the resilient member engages the rear member and the face member and is configured to transfer momentum between the face member and the rear member. The face member has a first projection extending rearwardly from the rear side of the face member proximate a heel side of the head and a second projection extending rearwardly from the rear side of the face member proximate a toe side of the head. The rear member has a first receiver in the front surface on the heel side of the head and a second receiver in the front surface on the toe side of the head, where the first projection is received in the first receiver and the second projection is received in the second receiver. 
     According to one aspect, the resilient material covers the first and second projections and separates the first and second projections from the openings. 
     According to another aspect, the head further includes an engagement member connecting the face member to the rear member, where the engagement member forms a joint between the face member and the rear member. The engagement member may have many different configurations, such as a pin connected to the face member and received in an aperture in the rear member. Additionally, the engagement member may be approximately aligned laterally with a center of gravity of the club head. 
     According to a further aspect, the head may also include a wall extending rearward from the face portion, where the rear member is positioned below the wall, such that the wall covers at least a portion of the rear member, and where the rear member forms at least a portion of a sole of the club head. The wall may cover a front portion of the top surface of the rear member in one configuration. Additionally, the rear member may have perimeter weighting portions located at the heel side and the toe side of the head and a thinned portion between the perimeter weighting portions, and the wall follows contours of the rear member to at least partially cover the perimeter weighting portions and the thinned portion. 
     According to yet another aspect, the rear member has perimeter weighting portions located at the heel side and the toe side of the head and a thinned portion between the perimeter weighting portions, and the first receiver and the second receiver are located in the perimeter weighting portions. 
     According to a still further aspect, the face member has a recess located on a sole of the head, where at least a portion of the rear member is received in the recess, such that the rear member forms at least a portion of the sole. 
     Additional aspects of the disclosure relate to ball striking devices, such as golf clubs, with a head that includes a face member including a face having a striking surface configured for striking a ball and a rear side located behind the face, a rear member connected to the rear side of the face member, and a resilient material separating the rear member from the face member, such that the resilient member engages the rear member and the face member and is configured to transfer momentum between the face member and the rear member. The face member includes a face portion at least partially defining the face and a wall extending rearward from the face portion. The rear member is positioned below the wall, such that the wall covers at least a portion of the rear member, and the rear member forms at least a portion of a sole of the club head. In one configuration, the wall may cover a front portion of the top surface of the rear member. Additionally, in one configuration, the wall and the face portion of the face member may be formed of a single integral piece. 
     According to one aspect, the resilient material is positioned between a front surface of the rear member and a rear surface of the face portion of the face member and between a top surface of the rear member and an underside of the wall. 
     According to another aspect, the face member further includes a first projection extending rearwardly from the rear side of the face member proximate a heel side of the head and a second projection extending rearwardly from the rear side of the face member proximate a toe side of the head. The rear member further includes a first receiver in a front surface of the rear member on a heel side of the head and a second receiver in the front surface on the toe side of the head, and the first projection is received in the first receiver and the second projection is received in the second receiver. The rear member may have perimeter weighting portions located at the heel side and the toe side of the head and a thinned portion between the perimeter weighting portions in one configuration, such that the first receiver and the second receiver are located in the perimeter weighting portions. Additionally, the resilient material may cover the first and second projections and separate the first and second projections from the openings. 
     According to a further aspect, the head also includes an engagement member connecting the face member to the rear member, and the engagement member forms a joint between the face member and the rear member. The engagement member may have many different configurations, such as a pin connected to the face member and received in an aperture in the rear member. Additionally, the engagement member may be approximately aligned laterally with a center of gravity of the club head. 
     According to yet another aspect, the rear member has perimeter weighting portions located at the heel side and the toe side of the head and a thinned portion between the perimeter weighting portions, and the wall follows contours of the rear member to at least partially cover the perimeter weighting portions and the thinned portion. 
     According to a still further aspect, the face member has a recess located on the sole and below the wall, and at least a portion of the rear member is received in the recess. 
     Further aspects of the disclosure relate to ball striking devices, such as golf clubs, with a head that includes a face member including a face having a striking surface configured for striking a ball and a rear side located behind the face, a rear member connected to the rear side of the face member and having a front surface confronting the rear side of the face member, an engagement member connecting the face member to the rear member, and a resilient material separating the rear member from the face member, such that the resilient member engages the rear member and the face member and is configured to transfer momentum between the face member and the rear member. The face member includes a face portion at least partially defining the face and a wall extending rearward from the face portion. The face member further includes a first projection extending rearwardly from the rear side of the face member proximate a heel side of the head and a second projection extending rearwardly from the rear side of the face member proximate a toe side of the head. The rear member is positioned below the wall, such that the wall covers at least a portion of the rear member, and the rear member forms at least a portion of a sole of the club head. Additionally, the rear member has a first receiver in the front surface on a heel side of the head and a second receiver in the front surface on the toe side of the head, and the first projection is received in the first receiver and the second projection is received in the second receiver. The engagement member forms a joint between the face member and the rear member. 
     Other aspects of the disclosure 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/device and configured for gripping by a user. The shaft may be connected to the face member of the head. Aspects of the disclosure relate to a set of golf clubs including at least one golf club as described above. Yet additional aspects of the disclosure relate to a method for manufacturing a ball striking device as described above, including connecting a rear member and/or a resilient material to a face member as described above. 
     Other features and advantages of the invention will be apparent from the following description taken in conjunction with the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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 top rear perspective view of one embodiment of a ball striking device according to aspects of the present invention, in the form of a golf putter; 
         FIG. 2  is a bottom rear perspective view of the ball striking device of  FIG. 1 ; 
         FIG. 3  is a rear view of the ball striking device of  FIG. 1 ; 
         FIG. 4  is a top rear perspective exploded view of the ball striking device of  FIG. 1 ; 
         FIG. 5  is a bottom rear perspective exploded view of the ball striking device of  FIG. 1 ; 
         FIG. 6  is a cross-section view taken along line  6 - 6  of  FIG. 3 ; 
         FIG. 7  is a cross-section view taken along line  7 - 7  of  FIG. 3 ; 
         FIG. 8  is a bottom rear perspective exploded view of another embodiment of a ball striking device according to aspects of the present invention, in the form of a golf putter; 
         FIG. 9  is a cross-section view of another embodiment of a ball striking device according to aspects of the present invention, in the form of a golf putter; 
         FIG. 10  is a top rear perspective view of another embodiment of a ball striking device according to aspects of the present invention, in the form of a golf putter; 
         FIG. 11  is a bottom rear perspective view of the ball striking device of  FIG. 10 ; and 
         FIG. 12  is a bottom rear perspective exploded view of the ball striking device of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     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,” “primary,” “secondary,” 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. 
     The following terms are used in this specification, and unless otherwise noted or clear from the context, these terms have the meanings provided below. 
     “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. 
     “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. 
     The term “shaft” includes the portion of a ball striking device (if any) that the user holds during a swing of a ball striking device. 
     “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, welding, brazing, soldering, or the like. In many bonds made by “integral joining techniques,” separation of the joined pieces cannot be accomplished without structural damage thereto. 
     “Approximately” or “about” means within a range of +/−10% of the nominal value modified by such term. 
     In general, aspects of this invention relate to ball striking devices, such as golf club heads, golf clubs, putter heads, putters, 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 may constitute a substantially flat surface on one face of the ball striking head, although some curvature may be provided (e.g., “bulge” or “roll” characteristics). Some more specific aspects described herein relate to putters and putter heads, although aspects described herein may also be utilized in wood-type golf clubs and golf club heads, including drivers, fairway woods, hybrid-type clubs, as well as iron-type golf clubs, other types of golf clubs or other ball striking devices, if desired. 
     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, fiber-reinforced composites, and wood, and the devices may be formed in one of a variety of configurations, without departing from the scope of the invention. In one 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 materials. It is understood that the head also may contain components made of several different materials. Additionally, the components may be formed by various forming methods. For example, metal components (such as titanium, aluminum, titanium alloys, aluminum alloys, steels (such as stainless steels), and the like) may be formed by forging, molding, casting, stamping, machining, and/or other known techniques. In another example, polymer and/or 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, injection molding, and/or other known techniques. 
     The various figures in this application illustrate examples of ball striking devices and portions thereof 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 to refer to the same or similar parts throughout. 
     At least some examples of ball striking devices according to this invention relate to golf club head structures, including heads for putter-type golf clubs. Such devices may include a one-piece construction or a multiple-piece construction. An example structure of ball striking devices according to this invention will be described in detail below in conjunction with  FIGS. 1-12 , and will be referred to generally using reference numeral “ 100 .” 
       FIGS. 1-7  illustrate an example of a ball striking device  100  in the form of a golf putter, in accordance with at least some examples of this invention. 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. The ball striking head  102  of the ball striking device  100  of  FIGS. 1-7  has a face member  128  that includes a face  112  and a hosel  109  extending therefrom. The face member  128  may include one or more structures connected to and/or located behind the face  112  that may be referred to as part of a “body” of the golf club head  102 . The ball striking head  102  also has a rear member  130  connected to the face member  128 , and a resilient material  140  positioned between the face member  128  and the rear member  130 . The face member  128 , the rear member  130 , and the resilient material  140  may combine to define the golf club head body  107  in some embodiments. The shaft  104  may be connected to the body  107  at the hosel  109 , as shown in  FIG. 1 , and may include a grip (not shown) in some embodiments. 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 Application Publication No. 2009/0062029, filed on Aug. 28, 2007, U.S. Patent Application Publication No. 2013/0184098, filed on Oct. 31, 2012, and U.S. Pat. No. 8,533,060, issued Sep. 10, 2013, all of which are incorporated herein by reference in their entireties and made parts hereof. 
     For reference, the head  102  generally has a golf club head body  107  with a top  116 , a bottom or sole  118 , a heel  120  (also called a heel side or heel edge) proximate the hosel  109 , a toe  122  (also called a toe side or toe edge) distal from the hosel  109 , a front side  124 , and a back or rear side  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  FIGS. 1-7 , the head  102  has a wide, narrow or short face  112 , as the club  100  is designed for use as a putter, intended to hit the ball short distances in a rolling manner. It is understood that the head  102  may be configured as a different type of ball striking device in other embodiments, including other types of putters or similar devices. In other applications, such as for a different type of golf club, the head may be designed to have different dimensions and configurations. If, for example, the head  102  is 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. When configured as a fairway wood head, the club head may have a volume of at least 120-230 cc, and when configured as a hybrid club head, the club head may have a volume of at least 85-140 cc. Other appropriate sizes for other club heads may be readily determined by those skilled in the art. 
     The face  112  is located at the front  124  of the face member  128 , and has a striking surface or ball striking surface  110  located thereon. The ball striking surface  110  is configured to face a ball in use (not shown), and is adapted to strike the ball when the device  100  is set in motion, such as by swinging. As shown, the ball striking surface  110  occupies most of the face  112 . The face  112  may include some curvature in the top to bottom and/or heel to toe directions (e.g., bulge and roll characteristics), and may also include functional face grooves, 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 face member  128  may have multiple ball striking surfaces  110  thereon. In the embodiment shown in  FIGS. 1-7 , the ball striking surface  110  has little to no incline or loft angle, to cause the ball to roll when struck. In other embodiments, the ball striking surface  110  may have an incline or loft angle, to launch the ball on a trajectory, such as for a wood-type or iron-type club head. Additionally, the face  112  may have one or more internal or external inserts in some embodiments. 
     It is understood that the face member  128  and/or the hosel  109  can be formed as a single piece or as separate pieces that are joined together. In the embodiment shown in  FIGS. 1-7 , as well as the embodiments shown in  FIGS. 8-12 , the face member  128 , including the face  112  and potentially the hosel  109 , are formed of a single, integral piece. In other embodiments, the face member  128  may be formed of multiple pieces, such as by using an insert to form all or part of the face  112 , or a separate body member or members connected behind the face  112 . Such multiple pieces may be joined using an integral joining technique, such as welding, cementing, or adhesively joining, or other known techniques, including many mechanical joining techniques, such as releasable mechanical engagement techniques. Further, the hosel  109  may also be formed as a separate piece, which may be joined using these or other techniques, or may be connected to the rear member  130 . In an exemplary embodiment, the face  112  may include a face insert  150  that forms at least a portion of the ball striking surface  110 , including inserts as described in U.S. Patent Application Publication 2010/0234127, which is incorporated by reference herein in its entirety and made part hereof. 
       FIGS. 4-6  illustrate one embodiment of a face insert  150  for the golf club head  102 . In this embodiment, at least a portion of the ball striking surface  110  may be formed separately from the remainder of the face  112  and may include an insert  150  configured to be received in a recess  151  formed in the face  112 . In the embodiment illustrated in  FIGS. 4-6 , the insert  150  includes a plate  152 , into which grooves  153  of various sizes, configurations, shapes, etc. may be machined or otherwise formed. In some examples, the plate  152  may be between 1 mm and 4 mm thick and, in some examples, may be approximately 2 or 3 mm thick. The grooves  153  may, in some arrangements, extend completely through the plate  152  (i.e., forming a through hole in the plate), as shown in  FIGS. 4-6 , or may extend partially through the plate  152 . The plate  152  may be formed of any suitable material, including metals such as aluminum, steel (e.g., stainless steel), titanium, nickel, beryllium, copper, combinations or alloys including these metals; polymers; and the like. The plate  152  may be pressed together (e.g., by “co-molding”) with a moldable, polymer material backing  154 , such as thermoplastic polyurethane or a thermoset material. The polymer material  154  may have a lower hardness than the plate  152  in one embodiment, e.g., as determined by a Shore D hardness test. In another embodiment, the polymer material  154  may have greater hardness. Connecting the polymer material  154  together with the front plate  152  forms the insert  150  having the polymer material  154  filling the grooves  153  formed in the plate  152 , to provide a ball striking surface having two different materials that may have different hardnesses (e.g., metal and polymer) contacting the ball. The surface of the polymer backing material  154  may be pre-formed with projections to fit into the grooves  153 , and/or the polymer material  154  may be forced into the grooves  153  during a pressing and/or molding operation. If necessary or desired, the plate  152  and polymer material  154  may be held together using an adhesive or cement (e.g., double sided tape), mechanical connectors, fusing techniques (e.g., welding, soldering, or brazing), etc. Further, if desired, score lines may be cut into the polymer material  154  and/or the plate  152  after the insert  150  has been manufactured. The insert  150  may be engaged with the recess  151  in the face  112  in any desired manner, such as via any joining techniques described herein, and may be releasably connected in one embodiment. Still further, the resilient material  140  may be any material described in U.S. Patent Application Publication No. 2013/0137533, filed Nov. 30, 2011, which application is incorporated by reference herein in its entirety and made part hereof. 
     The face member  128  in the embodiment of  FIGS. 1-7  has a face portion  160  that defines at least a portion of the face  112  and a rearwardly-extending portion or wall  161  that extends rearwardly from the face portion  160 . The face portion  160  generally defines at least a portion of the striking surface  110 , which may also be partially defined by the face insert  150  in an embodiment as described above. In the embodiment shown in  FIGS. 1-7 , the rear side  127  of the face member  128  has a rear surface  131  opposite the striking surface  110 . The rear surface  131  may be partially or entirely defined on the face portion  160  of the face member  128  in one embodiment, and may be considered to be a rear surface of the face  112  in such a configuration. The face member  128  may also have a recess  155  in the rear side  127  in one embodiment, such as illustrated in  FIGS. 4-7 , which may be located in the sole  118  and below the wall  161 . The wall  161  may define a top surface of the recess  155  in one embodiment, and the rear member  130  may be at least partially received in this recess  155 , as shown in  FIGS. 4-7 , such that the rear member  130  defines at least a portion of the sole  118  of the club head  102  in one embodiment. Additionally, in the embodiment of  FIGS. 1-7 , the wall  161  has approximately the same width (heel-to-toe) as the face portion  160 . As shown in  FIG. 5 , the underside  162  of the wall  161  is contoured similarly to the top surface  138  of the rear member  130 , such that the wall  161  at least partially covers the thinned portion  133  and the perimeter weighting portions  132 , however the underside  162  may have a different structure in another embodiment. For example, the wall  161  may have raised portions  163  proximate the heel  120  and the toe  122  that create enlarged sections  156  of the cavity  155 , as well as a depressed portion  164  proximate the lateral center of the head  102  that creates a narrowed section  157  of the cavity  155 . 
     The face member  128  may further include one or more projections  165  that extend rearwardly from the rear side  127  and engage the rear member  130 . In the embodiment illustrated in  FIGS. 1-7 , the face member  128  has two projections  165  extend rearwardly from the rear surface  131  of the face  112  within the recess  155  and beneath the wall  161 . One of the projections  165  is located proximate the heel  120 , and the other projection  165  is located proximate the toe  122 . In other embodiments. The projections  165  may be located in the enlarged sections  156  of the cavity  155  in one embodiment. The projections  165  are configured to be received in receivers  139  in the rear member  130  in one embodiment, to connect the front member  128  and the rear member  130 , as described in greater detail below. Additionally, the projections  165  are formed as cylindrical posts in the embodiment illustrated in  FIGS. 1-7 , however in other embodiments, the projections  165  may be differently configured. For example, the projections  165  may have a different height or cross-sectional shape, and/or the projections  165  may include locking structures, such as flanges, tabs, recesses, etc., to engage structures on the rear member  130  in complementary manner. In other embodiments, the face member  128  may include a smaller or greater number of projections  165  (including the absence of the projections  165  in one embodiment), and/or the projections  165  may be differently located and oriented. 
     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. The shaft  104  can be formed as a separate piece connected to the head  102 , such as by connecting to the hosel  109 , as described above. In other 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. The shaft  104  may be constructed from one or more of a variety of materials, including metals, ceramics, polymers, composites, or wood. In some exemplary embodiments, the shaft  104 , or at least portions thereof, may be constructed of a metal, such as stainless steel, 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. 
     In general, the head  102  of the ball striking device  100  has a rear member  130  (which may also be referred to as a “weight member”) connected to the face member  128  at the rear side  127  of the face member  128 , and the rear member  130  has a front surface  135  that faces and confronts the rear surface  131  of the face member  128 . In general, the rear member  130  is configured to transfer energy and/or momentum to the face member  128  upon impact of the ball on the striking surface  110 , including an off-center impact. The top surface  138  of the rear member  130  may also confront and/or be at least partially covered by the underside  162  of the wall  161  of the face member  128 , such as in the embodiment of  FIGS. 1-7 . For example, the wall  161  may cover a front portion of the top surface  138  of the rear member  130 , as in the embodiment of  FIGS. 1-7 , or may cover the entire top surface  138  in another embodiment. In one embodiment, the face member  128  and the rear member  130  follow generally the same outer periphery around the heel  120 , sole  118 , and toe  122  of the head  102 , as illustrated in  FIGS. 1-3 , however in other embodiments, the outer peripheries of these members  128 ,  130  may be different. 
     The rear member  130  may have one or more receivers  139  that are configured to receive and/or engage the projections  165  of the face member  128  to assist in retaining the face member  128  and the rear member  130  together. The receivers  139  may be dimensioned in a complementary manner with the projections  165 , and may be equal in number to the projections  165 . In the embodiment of  FIGS. 1-7 , the rear member  130  has two receivers  139  in the front surface  135 , with one receiver  139  proximate the heel edge  136  and one receiver  139  proximate the toe edge  137 . The receivers  139  in this embodiment are also located within the perimeter weighting portions  132 , and are in the form of cylindrical holes that extend rearwardly from the front surface  135 , a portion of the way through the rear member  130 . In other embodiments, the receivers  139  may be different in number, size, shape, orientation, and/or location, and it is understood that different configurations of projections  165  may dictate different configurations of receivers  139 , and vice-versa. As described above, each projection  165  and respective receiver  139  may include complementary retaining structure, such as tabs, slots, ridges, or other interlocking structure, which may have resilient components. It is understood that no receivers  139  may be necessary if the face member  128  includes no projections  165 .  FIG. 8  illustrates an embodiment where the head  102  has no projections  165  or receivers  139 , such that the front surface  135  of the rear member  130  and the rear surface  131  of the face member  128  have flat surfaces confronting each other proximate the heel  120  and the toe  122 , and is otherwise similar or identical to the head  102  of  FIGS. 1-7 . In a further embodiment, the orientations and locations of the projections  165  and the receivers  139  may be transposed, such that one or more of the projections  165  may be located on the rear member  130  and one or more of the receivers  139  may be located on the face member  128 . In still further embodiments, the rear member  130  and the face member  128  may include a different type of complementary interlocking structure. 
     The rear member  130  may be connected to the face member  128  in a number of different configurations that permit energy and/or momentum transfer between the rear member  130  and the face member  128 , several of which are described below and shown in the FIGS. In other embodiments, the rear member  130  may be differently configured, and/or the head  102  may contain multiple rear members  130 . For example, the rear member  130  as shown in  FIGS. 1-7  may be divided into two, three, or more separate rear members  130  in another embodiment, which may be connected to the face member  128  in similar or different configurations. The rear member  130  in all embodiments may affect or influence the center of gravity of the head  102 . Additionally, the rear member  130  (and other weight members described herein) may be made of any of a variety of different materials, which may be selected based on their weight or density. For example, the rear member  130  may be made from a metallic material such as stainless steel and/or tungsten, or may be made from other materials, for example polymers that may be doped with a heavier material (e.g. tungsten). The rear member  130  may also include portions that may be more heavily weighted than others, and may include weighted inserts or other inserts. In one embodiment, the rear member  130  has weights  134  in the perimeter weighting portions  132 , which are illustrated in this embodiment to be removable threaded weights that are received in openings  129  in the sole  118 , as shown in  FIGS. 2 and 4 . The weights  134  may have different weight characteristics in one embodiment, such as different densities and/or geometries, to provide different weighting configurations. Each weight  134  may also be removable and interchangeable with another weight  134  having a different weighting characteristic. For example, the weights  134  can be used to shift the CG of the rear member  130  and/or the entire head  102  toward the heel  120  or the toe  122 , or can be used to increase or decrease the overall weight of the rear member  130  and/or the entire head  102 , among other uses. In one embodiment, the use of the weights  134  to alter the weight of the rear member  130  allows the ratio between the weights of the face member  128  and the rear member  130  to be controlled. Further weighting configurations are recognizable to those skilled in the art. It is understood that the weights  134  may not be present in another embodiment, or the weights  134  may be in a different form in a further embodiment, such as molded weights (e.g., doped polymers). 
     In the embodiment of  FIGS. 1-7 , the rear member  130  is separated from the face member  128  by a resilient member  145  at least partially formed of the resilient material  140 . In this embodiment, the rear member  130  may be considered to be suspended with respect to the face member  128 , at least partially by the resilient material  140  in this configuration. It is understood that an adhesive or other bonding material may be utilized to connect the resilient material  140  to the face member  128  and/or the rear member  130 , and that other connection techniques may be used in other embodiments, such as mechanical fasteners, interlocking designs (e.g. dovetail, tab and slot, etc.) and others. The resilient material  140  may be connected to the face member  128 , the rear member  130 , or both, in various embodiments. The resilient material  140  may be a natural or synthetic rubber material, a polyurethane-based elastomer, or other elastomeric material in one embodiment, but may be a different type of resilient material in another embodiment, including various types of resilient polymers, such as foam materials or other rubber-like materials. Additionally, the resilient material  140  may have at least some degree of resiliency, such that the resilient material  140  exerts a response force when compressed, and can return to its previous state following compression. The resilient material  140  may have a strength or hardness that is lower than, and may be significantly lower than, the strength/hardness of the material of the face member  128  and/or the rear member  130 . In one embodiment, the resilient material  140  may have a hardness of from 30-90 Shore A or approximately 30-90 Shore A. In another embodiment, the resilient material  140  may have a hardness of approximately 50-70 Shore A. The hardness may be determined, for example, by using ASTM D-2240 or another applicable test with a Shore durometer. In an example embodiment, the resilient material  140  may be a polyurethane-based elastomer with a hardness of approximately 65 Shore A. Further, in one embodiment, the resilient material may have compression properties (based on a 0.56 shape factor and determined using ASTM D-575) as follows: 30 psi for 5% deflection, 70 psi for 10% deflection, 110 psi for 15% deflection, 160 psi for 20% deflection, and 220 psi for 25% deflection. 
     The properties of the resilient material, such as hardness and/or resiliency, may be designed for use in a specific configuration. For example, the hardness and/or resiliency of the resilient material  140  may be designed to ensure that an appropriate rebound or reaction force is transferred to the face, which may be influenced by parameters such as material thickness, mass of various components (including the rear member  130  and/or the face member  128 ), intended use of the head  102 , and others. The hardness and resiliency may be achieved through techniques such as material selection and any of a variety of treatments performed on the material that can affect the hardness or resiliency of the resilient material, as discussed elsewhere herein. The hardness and thickness of the resilient material may be tuned to the weight of a particular rear member  130 . For example, heavier weights may require harder resilient material  140 , and lighter weights may require softer resilient material  140 . Using a thinner resilient material  140  may also necessitate the use of a softer material, and a thicker resilient material  140  may be usable with harder materials. In a configuration where the resilient material  140  is a polyurethane-based material having a hardness of approximately 65 Shore A, the resilient material  140  may have a thickness between the rear member  130  and the rear surface  131  of the face member  128  of approximately 5 mm in one embodiment, or approximately 3 mm in another embodiment. 
     In the embodiment shown in  FIGS. 1-7 , the resilient member  145  may be formed as a single, integral piece of the resilient material  140 ; however the resilient member  145  may be formed of separate pieces in various embodiments. The resilient member  145  and/or the resilient material  140  may be formed of multiple components as well, including components having different hardness in different regions, including different hardness distributions. For example, the resilient member  145  and/or the resilient material  140  may be formed of an exterior shell that has a different (higher or lower) hardness than the interior, such as through being made of a different material (e.g. through co-molding) and/or being treated using a technique to achieve a different hardness. Examples of techniques for achieving a shell with a different hardness include plasma or corona treatment, adhesively bonding a film to the exterior, coating the exterior (such as by spraying or dipping). If a cast or other polyurethane-based material is used, the resilient material  140  may have a thermoplastic polyurethane (TPU) film bonded to the exterior, a higher or lower hardness polyurethane coating applied by spraying or dipping, or another polymer coating (e.g. a thermoset polymer), which may be applied, for example, by dipping the resilient material into an appropriate polymer solution with an appropriate solvent. Additionally, the resilient member  145  and/or the resilient material  140  may have different hardness or compressibility in different lateral or vertical portions thereof, which can create different energy and/or momentum transfer effects in different locations. For example, the resilient member  145  and/or the resilient material  140  may have a higher or lower hardness in proximate the heel  120  and/or the toe  122 , which may be achieved by techniques described herein, such as treatments or use of different materials and/or separate pieces. In this configuration, the hardness of the resilient material  140  may be customized for use by a particular golfer or a particular golfer&#39;s hitting pattern. Similarly, an asymmetrical resilient member  145  may also be used to create different energy and/or momentum transfer effects, by providing a larger or smaller amount of material at specific portions of the face member  128 . Such an asymmetrical resilient member  145  may also be used to provide customizability. A variable-hardness or asymmetrical resilient member  145  may also be used in conjunction with an offset connection point, as discussed below, for further customizability. Other embodiments described herein may also employ a resilient material  140  that has a variable hardness or asymmetrical features. A single-component or multi-component resilient member  145  and/or resilient material  140  may be manufactured by co-molding, and may be co-molded in connection with the face member  128  and/or the rear member  130 . 
     As seen in  FIGS. 1-7 , the resilient material  140  is connected between the rear member  130  and the face member  128 . In one embodiment, the rear member  130  has at least one surface that is engaged by the resilient material  140  and at least one other surface that is exposed and not engaged by the resilient material  140 . In the embodiment of  FIGS. 1-7 , the front surface  135  and the top surface  138  of the rear member  130  are engaged by the resilient material  140 , and the underside and rear side of the rear member  130  are exposed and not engaged by the resilient material  140 . As shown in  FIGS. 6-7 , the resilient material  140  is sandwiched between the rear surface  131  on the rear side  127  of the face member  128  and the front surface  135  of the rear member  130  and is also sandwiched between the underside  162  of the wall  161  and the top surface  138  of the rear member  130 . The rear member  130  is spaced from the face member  128 , and the resilient material  140  at least partially fills the spaces  142  between the front surface  135  of the rear member  130  and the rear side  127  of the face member  128  and between the underside  162  of the wall  161  and the top surface  138  of the rear member  130 . Additionally, in the embodiment of  FIGS. 1-7 , the resilient material  140  also covers the projections  165  of the face member  128  and is positioned between the projections  165  and the inner walls of the receivers  139  of the rear member  130 . The resilient material  140  in  FIGS. 1-7  is illustrated as a single-piece resilient member  145  that includes tube members  146  that receive the projections  165  and are received in the receivers  139 . However, in other embodiments, separate tube members  146  may be provided that are formed of a separate piece from the remainder of the resilient member  145 . In the embodiment illustrated in  FIGS. 1-7 , the resilient material  140  is substantially flush with the outer peripheries of the face member  128  and the rear member  130  around the entire periphery of the face member  128 . In other embodiments, the face member  128 , the rear member  130 , and/or the resilient material  140  (or portions of such members) may not be flush or substantially flush around at least a portion of the periphery of the head  102 . The resilient material  140  may be positioned on both opposite lateral sides of the center of gravity (CG) of the face member  128 . In one embodiment, as shown in  FIGS. 6-7 , the resilient material  140  completely or substantially completely fills the spaces  142  between the rear member  130  and the face member  128 . In another embodiment, may have a resilient material  140  that partially fills the spaces  142  between the face member  128  and the rear member  130 , such as the resilient material  140  being positioned between the face member  128  and the rear member  130  at least at the heel  120  and the toe  122 . 
     The rear member  130  may have various different dimensions and structural properties in various embodiments. In the embodiment shown in  FIGS. 1-7 , the rear member  130  has a heel edge  136  and a toe edge  137 , with a lateral width defined between the heel and toe edges  136 ,  137 . The lateral width of the rear member  130  is the same or approximately the same as the lateral width of the face member  128 , measured between the heel  120  and toe  122 . Additionally, the rear member  130  has its mass distributed proportionally more toward the heel and toe edges  136 ,  137 , and has a thickness and a cross-sectional area that are greater at or around the heel and toe edges  136 ,  137  than at the CG of the rear member  130 . In other words, the rear member  130  includes two perimeter weighting portions  132  at the heel and toe edges  136 ,  137  and a recessed portion or thinned portion  133  proximate the center of the rear member  130 . This configuration can achieve greater perimeter weight distribution and increased moment of inertia for the club head  102 . Further, the rear member  130  may be positioned so that the CG of the rear member  130  is substantially aligned with the CG of the face member  128 . In one embodiment, the CGs of the rear member  130  and the face member  128  are laterally aligned, and these respective CGs may additionally or alternately be vertically aligned in another embodiment. In one embodiment, the face member  128  may have alignment indicia (not shown) aligned with the CG of the face member  128  and/or the CG of the rear member  130 , however this indicia may be absent or differently located in other embodiments. 
     The rear member  130  may have varying sizes in different embodiments. For example, in one embodiment, the rear member  130  may make up about 25% or more of the total weight of the head  102 , or about 25-45% of the total weight of the head  102  in another embodiment. In an example embodiment, the total weight of the head  102  may be about 340 g, with the rear member  130  having a weight of about 100 g. 
     In one embodiment, the club head  102  may include an engagement member  180  that rigidly engages both the face member  128  and the rear member  130  to form a point of rigid engagement  181  between the face member  128  and the rear member  130 . The engagement member  180  may be the sole point or area of rigid engagement between the face member  128  and the rear member  130  in one embodiment. For example, in the embodiments of  FIGS. 1-12 , the engagement member  180  forms the sole area of rigid engagement between the face member  128  and the rear member  130 , as the resilient material  140  completely separates the face member  128  from the rear member  130 . In other embodiments, there may be multiple areas of rigid engagement between the face member  128  and the rear member  130 , such as by use of multiple engagement members  180 , or there may be no points of rigid engagement between the face member  128  and the rear member  130 , such as if the club head  102  is not provided with an engagement member. It is understood that “rigid” engagement as defined herein does not necessary imply any fixing or attachment, but instead, means that the surfaces engaging each other are rigid, rather than flexible, and behave rigidly during energy and/or momentum transfer. For example, the engagement member  180  illustrated in  FIGS. 4-6  may rigidly engage the face member  128  and/or the rear member  130  through non-fixed pin/hole engagement. 
     The engagement member  180  may have various structural configurations, locations, and orientations. In various embodiments, the engagement member  180  may be fixed to at least one of the face member  128  and the rear member  130 , and/or the engagement member may rigidly abut at least one of the face member  128  and the rear member  130  (but without being fixedly connected). In the embodiment illustrated in  FIGS. 1-7 , the engagement member  180  is in the form of a pin that extends upwardly through at least a portion of the rear member  130  and at least a portion of the face member  128  to connect the rear member  130  to the face member  128 . The engagement member (pin)  180  in this embodiment extends through an aperture  182  in the rear member  130  and is received within a receiver  184  in the face member  128 . In one embodiment, the engagement member  180  is non-fixedly connected to the face member  128  and/or the rear member  130 , and may be fixedly connected to one of the face member  128  or the rear member  130 , but not both. This configuration permits the engagement member  180  to form a joint  183  between the face member  128  and the rear member  130 , which in turn permits the rear member  130  to transfer energy and/or momentum to the face member  128  through the resilient material  140 , as described below. In the embodiment of  FIGS. 1-7 , the engagement member  180  is fixedly connected to the face member  128  (e.g., via threading connection) and is non-fixedly engaged with the rear member  130 , while rigidly engaging both the face member  128  and the rear member  130 . The engagement member  180  may have an enlarged head that engages the rear member  130  in one embodiment, and the aperture  182  may be countersunk to receive the enlarged head, as shown in  FIG. 6 . The rear member  130  may include a lip  185  that extends forward from the front surface  135  of the rear member  130 , which includes the aperture  182  in one embodiment, as shown in  FIGS. 2 and 4-6 . The face member  128  may include an indent  186  to receive the lip  185 , as also illustrated in  FIGS. 2 and 4-6 . 
     In the embodiment of  FIGS. 1-7 , the resilient material  140  includes a gap  144  allowing the engagement member  180  to extend through the resilient material  140  to engage both the face member  128  and the rear member  130 . The resilient member  140  may further include contours and surfaces to cover and separate the surfaces of the lip  185  and the indent  186 . Additionally, in the embodiment of  FIGS. 1-7 , the engagement member  180  is located approximately at a midpoint between the heel and toe  120 ,  122  and also approximately at a midpoint between the heel and toe edges  136 ,  137  of the rear member  130 . In this location, the engagement member  180  and the joint  183  are also approximately aligned laterally with the CG of the face member  128 , the rear member  130 , and/or the club head  102  as a whole. The engagement member  180  may also be vertically aligned with the CG of one or more of these components, in a further embodiment. In other embodiments, the engagement member  180  may have a different orientation, structure, or location. 
       FIG. 9  illustrates another embodiment of an engagement member  180  that forms a point or area of rigid engagement  181  between the face member  128  and the rear member  130 . In this embodiment, the engagement member  180  is in the form of a sphere (e.g., a ball bearing) that is not fixedly connected to either the rear surface  131  of the face member  128  or the front surface  135  of the rear member  130 . Instead, this engagement member  180  abuts both of these surfaces. The engagement member  180  in this embodiment is located in generally the same lateral position as the engagement member  180  in  FIGS. 1-7 , as described above. Other embodiments of engagement members  180  that may be usable in connection with the head  102  described herein include a projection that is fixed to the rear surface  131  of the face member  128  (i.e., the rear of the face portion  160 ) and abuts the front surface  135  of the rear member  130 , but the engagement member  180  is not fixed or otherwise connected to the rear member  130 . Such a projection may also be transposed, i.e., by being fixed to the front surface  135  of the rear member  130  and abutting the rear surface  131  of the face member. The projection may have various shapes, such as a domed projection, a wedge-shaped projection, a conical or pyramidal projection, etc. Additional configurations of engagement members  180  may be utilized in other embodiments. Further, engagement members  180  according to these additional embodiments may be considered to define a joint  183  between the face member  128  and the rear member  130 , as described above. 
       FIGS. 10-12  illustrate another embodiment of a ball striking device  100  in the form of a golf putter, in accordance with at least some examples of this invention. The ball striking device  100  in  FIGS. 10-12  includes a ball striking head  102  and a shaft  104  connected to the ball striking head  102  and extending therefrom, and includes many components in common with the embodiment described herein with respect to  FIGS. 1-7 . Any such common components in  FIGS. 10-12  are referenced in the drawings using similar reference numbers, and such similar components that have already been described above may not be described again with respect to this embodiment for the sake of brevity. It is understood that the embodiment of  FIGS. 10-12  may include any of the components and/or features described herein with respect to  FIGS. 1-9 , and vice versa. 
     The head  102  in  FIGS. 10-12  has a face member  128  that includes the face  112 , a rear member  130  connected to the face member  128 , and a resilient material  140  positioned between the face member  128  and the rear member  130 , as described above. The face member  128  and the rear member  130  are connected by an engagement member  180 , which forms a joint  183  and a sole point of rigid connection between these two components. In the embodiment illustrated in  FIGS. 10-12 , the engagement member  180  is in the form of a pin that extends upwardly through at least a portion of the rear member  130  and at least a portion of the face member  128  to connect the rear member  130  to the face member  128 , which is configured similarly to the engagement member  180  shown in  FIGS. 1-7  and described elsewhere herein. The rear member  130 , the face member  128 , and the resilient material  140  in this embodiment include additional connecting structure related to the engagement member  180  as also described elsewhere herein, including an aperture  182 , a receiver  184 , a lip  185 , an indent  186 , a gap  144 , etc. Additionally, the engagement member  180  in this embodiment is located in generally the same lateral position (i.e., relative to the heel  120  and toe  122 ) as the engagement member  180  in  FIGS. 1-7 , as described herein. 
     The rear side  127  of the face member  128 , the rear member  130 , and the resilient material  140  in the embodiment of  FIGS. 10-12  have shapes and configurations that are different from the embodiment described above. The face member  128  in this embodiment includes a rearwardly-extending portion or wall  161  that extends rearwardly from the face portion  160 , which is configured differently from the wall  161  of  FIGS. 1-7 . In the embodiment of  FIGS. 10-12 , the rearwardly-extending portion  161  is in the form of two arms  187  extending rearwardly from the face portion  160 , such that the rear member  130  is positioned below the undersides  162  of the arms  187 . The arms  187  are illustrated as having curved top surfaces that are curved downwardly, such that the height of each arm  187  is tapered to decrease from front  124  to rear  126 . Additionally, the arms  187  in this embodiment are completely separate and spaced from each other, and a space  188  is defined between the arms  187 . One or more recesses  155  are defined below the arms  187 , as well as between the arms  187  and on the heel and toe sides of the arms  187  in this embodiment. In another embodiment, a wall or other bridging member may extend rearwardly between the arms  187  and/or outside the arms (i.e., toward the heel  120  and toe  122 ) to further define the recess  155  below the arms  187  and below the wall in another embodiment. Other configurations may be used in other embodiments. The rear surface  131  of the face member  128  below the arms  187  is flat in this embodiment, similar to the embodiment of  FIG. 8 . In another embodiment, the face member  128  and the rear member  130  may include complementary engaging structures such as the projections  165  and recesses  139  illustrated in  FIGS. 1-7 . 
     In the embodiment of  FIGS. 10-12 , the face member  128  has a sole portion  166  that is larger and wider (front to rear) as compared to the face member  128  in  FIGS. 1-7 . The face member  128  and the rear member  130  combine to define the sole  118  of the club head  102  in this embodiment. Additionally, the weights  134  in this embodiment are connected to the face member  128 , rather than the rear member  128 . As illustrated in  FIGS. 11-12 , the weights  134  are removable threaded weights that are received in openings  129  in the sole portion  166  of the face member  128 . Other types and configurations of weights  134  may be alternately used, as described herein. In other embodiments, the weights  134  may be connected to the rear member  130 , or both the face member  128  and the rear member  130  may have weights  134  connected thereto. Further, the face member  128  in this embodiment has the shaft  104  connected directly to the top side of the face member  128 , and has no hosel or similar structure. In another embodiment, the face member  128  may contain a hosel  109  for connection to the shaft  109 , as described herein. The face member  128  in this embodiment has further structures already described herein with respect to the embodiments of  FIGS. 1-9 . For example, the face member  128  has a face insert  150  as described herein. 
     The rear member  130  in the embodiment of  FIGS. 10-12  has a structure that includes a base portion  189  and two legs  190  extending rearwardly from the base portion  189 , with a void  191  defined between the legs  190 . The void  191  in this embodiment is generally V-shaped, with inner edges  192  that angle toward each other (i.e., inwardly) from the rear  126  toward the front  124 , meeting at an interface area  193 . The legs  190  in the embodiment of  FIGS. 10-12  have perimeter weighting portions  132  on the heel side  136  and the toe side  137  that are raised with respect to the other portions of the rear member  130 , such that the perimeter weighting portions  132  extend upward above the undersides  162  of the arms  187 . The other portions of the rear member  130  may be considered to be a recessed portion or thinned portion  133  with respect to the perimeter weighting portions  132  in this embodiment. Additionally, in this embodiment, each of the perimeter weighting portions  132  has a wing  194  extending outwardly on the heel  120  or toe  122  sides, which provides additional perimeter weighting. The combinations of the void  191  and the perimeter weighting portions  132  create increased perimeter weighting of the rear member  130  in this embodiment. The rear member  130  is positioned generally below the arms  187  of the face member  128 , such that the arms  187  cover at least a portion of the rear member  130 . In this configuration, spaces  142  are defined between the front surface  135  of the rear member  130  and the rear side  127  of the face member  128  and between the undersides  162  of the arms  187  and the top surface  138  of the rear member  130 . Spaces  142  are additionally defined between the outer surfaces  195  of the arms  187  and the inner surfaces  196  of the perimeter weighting portions  132  of the rear member  130 . 
     The resilient material  140  in the embodiment of  FIGS. 10-12  is formed as a resilient member  145  that at least partially fills the spaces  142  between the front surface  135  of the rear member  130  and the rear side  127  of the face member  128 , between the undersides  162  of the arms  187  and the top surface  138  of the rear member  130 , and between the outer surfaces  195  of the arms  187  and the inner surfaces  196  of the perimeter weighting portions  132  of the rear member  130 . In this embodiment, the resilient member  140  has a shape that is similar to that of the rear member  130 , having two legs  148  extending rearwardly from a base member  147 , such that the void  191  is also defined between the legs  148  of the resilient material  140 . The resilient material  140  further has fins  149  extending upwardly from the legs  148 , to at least partially fill the spaces  142  between the outer surfaces  195  of the arms  187  and the inner surfaces  196  of the perimeter weighting portions  132 . The top side of the resilient material  140  is exposed in several places in this embodiment, as seen in  FIG. 10 . In another embodiment, as mentioned above, the face member  128  may include one or more walls extending rearwardly and at least partially covering these portions of the resilient material  140 . 
     The rear member  130  in any of the embodiments described herein may be configured such that energy and/or momentum can be transferred between the rear member  130  and the face member  128  during impact, including an off-center impact on the striking surface  110 . The resilient material  140  can serve to transfer energy and/or momentum between the rear member  130  and the face member  128  during impact. Additionally, the rear member  130  may also be configured to resist deflection of the face member  128  upon impact of the ball on the striking surface  110 . The resiliency and compression of the resilient material  140  permits this transfer of energy and/or momentum from the rear member  130  to the face member  128 . As described above, the momentum of the rear member  130  compresses the resilient material  140 , and causes the resilient material  140  to exert a response force on the face member  128  to achieve this transfer of momentum. The resilient material  140  may exert at least a portion of the response force on the face member  128  through expansion after the compression. The rear member  130  may deflect slightly toward the impact point to compress the resilient material  140  in the process of this momentum transfer. The actions achieving the transfer of momentum occur between the beginning and the end of the impact, which in one embodiment of a golf putter may be between 4-5 ms. In the embodiments as shown in  FIGS. 1-12 , the rear member  130  may transfer a greater or smaller amount of energy and/or momentum depending on the location of the impact on the striking surface  110 . For example, upon an off-center impact of the ball centered on the heel side  120 , the face member  128  tends to deflect rearwardly at the heel  120 . As another example, upon an off-center impact of the ball centered on the toe side  122 , the face member  128  tends to deflect rearwardly at the toe  122 . As the face member  128  begins to deflect rearwardly, at least some of the forward momentum of the rear member  130  is transferred to the face member  128  during impact to resist this deflection. During a heel-side impact, at least some of the momentum transferred to the face member  128  may be transferred from the heel edge  136  of the rear member  130  during impact. Likewise, on a toe-side impact, at least some of the momentum transferred to the face member  128  may be transferred from the toe edge  137  of the rear member  130  during impact. Generally, at least some of the momentum is transferred toward the impact point on the face  112 . 
     The resilient material  140  can function to transfer the energy and/or momentum of the rear member  130  to the face member  128  at the heel  120  or toe  122 . In the process of transferring energy and/or momentum during impact, the resilient material  140  may be compressed by the momentum of the rear member  130  and expand to exert a response force on the face member  128 , which resists deflection of the face member  128  as described above. It is understood that the degree of potential moment causing deflection of the face member  128  may increase as the impact location diverges from the center of gravity of the face member  128 . In one embodiment, the energy and/or momentum transfer from the rear member  130  to the face member  128  may also increase as the impact location diverges from the center of gravity of the face member  128 , to provide increased resistance to such deflection of the face member  128 . In other words, the energy and/or momentum transferred from the rear member  130  to the face member  128 , and the force exerted on the face member  128  by the rear member  130 , through the resilient material  140 , may be incremental and directly relative/proportional to the distance the impact is made from the optimal impact point (e.g. the lateral center point of the striking surface  110  and/or the CG of the face member  128 , in exemplary embodiments). Thus, the head  102  will transfer the energy and/or momentum of the rear member  130  incrementally in the direction in which the ball makes contact away from the center of gravity of the head  102 , via the rear member  130  suspended by the resilient material  140 . The transfer of energy and/or momentum between the rear member  130  and the face member  128  can reduce the degree of twisting of the face  112  and keep the face  112  more square upon impacts, including off-center impacts. Additionally, the transfer of energy and/or momentum between the rear member  130  and the face member  128  can minimize energy loss on off-center impacts, resulting in more consistent ball distance on impacts anywhere on the face  112 . The resilient material  140  may have some elasticity or response force that assists in transferring energy and/or momentum between the rear member  130  and the face member  128 . 
     It is understood that any of the embodiments of ball striking devices  100 , heads  102 , face members  128 , rear members  130 , and other components described herein may include any of the features described herein with respect to other embodiments described herein, including structural features, functional features, and/or properties, unless otherwise noted. It is understood that the specific sizes, shapes, orientations, and locations of various components of the ball striking devices  100  and heads  102  described herein are simply examples, and that any of these features or properties may be altered in other embodiments. In particular, any of the connecting members or structures shown and described herein may be used in connection with any embodiment shown herein, to connect the face member  128  and the rear member  130 . 
     Heads  102  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. As another example, a golf club  100  as shown in  FIG. 1  may be manufactured by attaching a rear member  130  to a face member that is provided, such as the face member  128  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 according to one or more embodiments described herein. Such a set may include at least one wood-type club, at least one iron-type club, and/or at least one putter. For example, a set may include one or more wood-type golf clubs and one or more iron-type golf clubs, which may have different loft angles, as well as one or more putters, with each club having a head  102  as described above and shown in  FIGS. 1-12 . The various clubs in the set may have rear members  130  that may be slightly different in shape, size, location, orientation, etc., based on the loft angle of the club. The various clubs may also have an added weight amount or weight distribution (including CG location) that may be different based on characteristics such as the type and loft angle of the club. 
     Different rear members  130  and different locations, orientations, and connections thereof, may produce different energy and/or momentum transfer upon impacts on the striking surface  110 , et seq., including off-center impacts. Additionally, different rear members  130  and different locations, orientations, and connections thereof, may produce different effects depending on the location of the ball impact on the face  112 . Accordingly, one or more clubs can be customized for a particular user by providing a club with a head as described above, with a rear member  130  that is configured in at least one of its shape, size, location, orientation, etc., based on a hitting characteristic of the user, such as a typical hitting pattern or swing speed. Customization may also include adding or adjusting weighting according to the characteristics of the rear member  130  and the hitting characteristic(s) of the user. Still further embodiments and variations are possible, including further techniques for customization. 
     The ball striking devices described herein may be used by a user to strike a ball or other object, such as by swinging or otherwise moving the head  102  to strike the ball on the striking surface  110  of the face  112 . During the striking action, the face  112  impacts the ball, and one or more rear members  130  may transfer energy and/or momentum to the face  112  during the impact, in any manner described above. In one embodiment, the rear member(s)  130  may transfer incrementally greater energy and/or momentum for impacts that are farther from the desired impact point (e.g. the CG). As described below, the devices described herein, when used in this or a comparable method, may assist the user in achieving more consistent accuracy and distance of ball travel, as compared to other ball striking devices. 
     The various embodiments of ball striking heads with rear members described herein can provide energy and/or momentum transfer upon impacts on the striking face, which can assist in keeping the striking face more square with the ball, particularly on off-center impacts, which can in turn provide more accurate ball direction. Additionally, the energy and/or momentum transfer to the face member can reduce or minimize energy loss on off-center impacts, creating more consistent ball speed and distance. The energy and/or momentum transfer may be incremental based on the distance of the impact away from the desired or optimal impact point. Further, the resilient material and/or the spacer(s) may achieve some energy absorption or damping on center impacts (e.g. aligned with the center point and/or the CG of the face). As a result of the reduced energy loss on off-center hits, reduced twisting of the face on off-center hits, and/or reduced energy transfer on center hits that can be achieved by the heads as described above, greater consistency in both lateral dispersion and distance dispersion can be achieved as compared to typical ball striking heads of the same type, with impacts at various locations on the face. The ball striking heads described herein can also provide dissipation of impact energy through the resilient material, which can reduce vibration of the club head and may improve feel for the user. Still further, the use of the rear member on the bottom side of the head can provide an aesthetic option for the resilient material and/or the rear member to not be visible to the user at the address position. Other benefits can be recognized and appreciated by those skilled in the art. 
     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.