Abstract:
Golf shots lose both distance and directional accuracy when the ball is struck at a clubface location not aligned with (i.e. directly in front of) the clubhead center of gravity (a “mishit”). High moment of inertia clubhead designs (i.e., extreme toe heel weighting) only partially reduce mishit distance loss and are limited by practical clubhead size and weight. The subject invention reduces, or totally eliminates mishit distance loss regardless of clubhead moment of inertia via designs which absorb more ball impact energy for on-center hits versus mishits thus equalizing distance. The invention allows for the use of integral or attached metal or plastic faceplates without impeding the function of such variable energy absorbing mishit corrective devices, thereby greatly improving clubhead durability, feel, and practicality, especially for irons and putters.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to all golf clubheads, but more particularly irons and putters, where consistent distance and direction are more desirable than the maximum distance usually sought with low lofted woods and metalwoods. The present invention relates specifically to improved clubhead and clubhead insert designs, which substantially reduce or totally eliminate mishit distance loss. 
     Golf shots lose both distance and directional accuracy when a golf ball is struck at a clubface location not aligned with (i.e. directly in front of) the clubhead center of gravity. Misdirection is primarily caused by the angular rotation of the clubhead upon impact with a ball not aligned with the “clubhead center of gravity” (which includes the effect of clubshaft weight). Mishit distance loss is caused by both the misdirection [one minus the cosign of angular difference between initial line and post impact deflected line] and clubhead energy lost to clubhead rotation rather than transferred to the ball at impact. 
     These effects have long been postulated and intuitively observed by skilled golfers and club designers. Only in the past decade, however, have these effects been quantitively and empirically measured using ball striking robots featured in club and ball test reports in popular golf literature. Irons and woods (including metalwoods) have been tested with the famous “Iron Byron” and similar robots. Putter tests using Dave Pelz&#39;s “Perfy™” were periodically published in  Golf Magazine  (i.e. July 1994 pg. 64-65; March 1995). 
     Pelz putter test percent distance losses for ⅜″ and ¾″ mishits are summarized below: 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Odyssey 
                 Zebra 
                 Titlest 
                 Wilson 8802 
               
               
                   
                 Rossie II 
                 (mallet) 
                 Bullseye 
                 Blade 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 ±⅜″ 
                  5.56% 
                  6.85% 
                  9.07% 
                 10.56% 
               
               
                 ±¾″ 
                 18.33% 
                 18.89% 
                 31.48% 
                 32.41% 
               
               
                   
               
             
          
         
       
     
     The above published Pelz data indicates that putterheads with the highest moment of inertia around the center of gravity tended to have the lowest percent distance loss. Doubling the mishit distance (i.e. from ⅜ in. to ¾ in.) tripled the distance loss. 
     In the art, Beaumont (U.S. Pat. No. 5,529,543) and Rohrer (U.S. Pat. No. 5,766,093), the disclosures of which are both incorporated herein by reference, both claim clubhead insert devices reducing mishit distance loss via variable energy absorption (more at center than periphery). Beaumont claims improved irons using a single energy absorbing “component” or “plug” of variable thickness (thickest at club center). In some claims, the single energy absorbing plug is behind a rigidly attached thin plate of stiff or hard, but flexible, material. 
     Softer elastomeric striking faces are less desirable than harder polymer or metal faces for both putters and irons for durability, feel, and acoustic reasons. Beaumont anticipates some of the above limitations in his claims 9-19 by rigidly affixing “by epoxy or the like” to the rigid clubhead body, a “thin plate . . . which is stiff, or hard, but deformable upon impact . . . ” over the energy absorbing void or elastomer. 
     Rohrer uses a plurality of energy absorbing elastomer “elements”, plugs, or components with or without faceplates with the deadest elements at the center of the clubhead and elements of more lively material more remote to reduce or eliminate mishit distance loss on putters. 
     Others have used either a single uniform thickness insert on putters to influence total distance (increase or decrease) and for feel (vibration feedback), but not to reduce mishit distance loss. Still, others have used multiple hardness materials to influence mishit ball direction or feel, but not to reduce mishit distance loss. 
     SUMMARY OF THE INVENTION 
     The subject invention provides alternative means to correct for mishit distance loss in putters and irons using more durable, compact, and practical variable energy absorbing designs than the prior art. The undesirable “trampoline or spring face” and “incompressibility” effects of the prior art are overcome. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     It is important to recognize that an elastomer&#39;s (or any other solid material) hardness (as typically characterized as Durometer or Elastic Modulus) is totally distinct from, and unrelated to, its energy absorbing properties (typically characterized as Bayshore Rebound % or Coefficient of Restitution). Some hard elastomers (like a squash ball) can be very dead while much softer elastomers (like multi-colored urethane “superbounce” toy balls) can be extremely lively. 
     Putter tests conducted by Rohrer using an impact robot (“Stainless Steve” who produces repeatable identical velocity strokes) on the constructions taught and claimed in Beaumont Claims 9-19, show that when thin metal or rigid plastic flexible faceplates or coverplates are rigidly attached to part or all of a clubhead periphery, most or all of the effect of any underlying variable energy absorbing mishit distance correcting mechanisms are lost for the following reasons: 
     1. To be durable and practical, Beaumont&#39;s thin cover plates must be metallic or have comparable stiffness and durability properties. When a metal cover plate is “rigidly attached” or affixed around all or part of its periphery to a rigid clubhead body (defined herein as, that when there is little or no relative movement between the coverplate and clubhead body at the attachment points), then the coverplate produces a “trampoline or spring face effect” which may actually absorb less energy than a solid clubhead with on-center hits (Reference 11-98 , Golf Smith Magazine , pgs. I-1, I-2, I-7 &amp; I-8). If an energy absorbing (low rebound rate or viscoelastic) elastomer is placed behind a “stiff hard” rigidly affixed flexible faceplate of practical thickness, the impact with a golf ball will not produce sufficient faceplate and underlying elastomer deflection to absorb the clubhead kinetic energy required to correct for a typical mishit. For purposes herein, a flexible faceplate is defined as a cover layer of a material of equal or greater hardness than a golf ball or ball cover and of sufficient durability for practical multiple ball strikes which cover layer would deflect, but not permanently yield or deform, upon typical impact velocity of play if said cover layer were not partially or fully attached or constrained around its periphery. 
     2. An energy absorbing, low rebound rate, viscoelastic elastomer constrained in a cavity behind any thin and stiff, or hard faceplate, can only absorb energy if it is sufficiently deformed. Elastomers behave like incompressible fluids. Even if the rigidly affixed faceplate overcame the trampoline effect limitations described above, the elastomer&#39;s fluid-like incompressibility would require that the faceplate deflect outward at locations remote from the ball impact point to provide sufficient viscoelastic deformation for adequate energy absorption. We shall hereinafter refer to this as the elastomer “incompressibility effect.” To illustrate the above effects, clubheads according to FIGS. 1 through 4 were constructed and tested using an impact robot, “Stainless Steve”, which reproduces identical clubhead velocity throughout the tests. FIG. 1 (A &amp; B view) was a solid aluminum putterhead. FIGS. 2 (A &amp; B view) and  4  used a ⅜ in. deep high energy absorption (&lt;10% Bayshore Rebound) elastomer of approximately 70 Durometer A hardness embedded (cast) into an aluminum clubhead cavity. In FIG. 4, a thin, hard (stainless steel) coverplate in intimate contact with (bonded to) the elastomer was rigidly attached (epoxied) to the clubhead body (a softer acetel plastic coverplate was similarly attached and tested). In FIG. 3, the same two coverplates (0.060 in. acetel and 0.060 stainless steel) were again epoxied to the clubhead with the viscoelastic inserts removed. 
     The FIG. 2 insert showed a 30% distance loss (versus the FIG. 1 solid aluminum clubhead) when struck before the clubhead center of gravity and 50% loss with ±¾ in. mishits (laterally). FIG. 3 showed no distance loss versus FIG. 1 with either the stainless steel or acetel cover plates illustrating the “trampoline effect” discussed above. FIG. 4 showed no distance loss with the stainless cover plate (due to both the trampoline and incompressibility effects previously discussed). With the acetel cover plate, FIG. 4 distance loss was reduced to about half the FIG. 1 values. Thus, even with a relatively elastic acetel faceplate, not durable enough for practical iron play, and a very deep (0.375 in.) insert of extremely dead material (&lt;10% Bayshore Rebound) we could only get about half of the center of clubface energy absorption required for full mishit distance correction. 
     It is highly desirable in clubhead design to make mishit distance correctly energy absorbing inserts for both irons and putters as thin or compact, and therefore efficient, as possible thus, allowing them to be incorporated into existing popular clubhead designs without making such clubheads appear fat or bulky. The subject invention allows greater clubface deflection and thus, greater elastomer deformation and energy absorption thus, allowing energy absorbing inserts to be more efficient and compact. 
    
    
     Advantages of the subject invention will be understood and appreciated by reference to the following drawings and descriptions, which are not to scale for irons or putters and exaggerate some features for clarity. 
     FIGS. 1-4 were previously discussed and illustrate practical and performance deficiencies in the prior art. FIG. 5 illustrates how a protective faceplate or coverplate ( 1 ) can be flexibly attached (defined herein as, allowing relative movement upon ball impact between the faceplate periphery and the adjacent rigid clubhead body) over an energy absorbing elastomer insert ( 3 ) embedded into a rigid clubhead body ( 2 ) to avoid or diminish any “trampoline or incompressibility effects.” The protective faceplate ( 1 ) can be as hard and durable as necessary. Nylon, acetel, or other plastic faceplates are durable enough for putters. Metal, reinforced composites, or metal faced reinforced composites, are suitable for irons or woods. The faceplate ( 1 ) is not rigidly attached to the rigid clubhead body ( 2 ), but is in intimate contact (bonded) with the viscoelastic insert ( 3 ). The flexible attachment is accomplished by allowing a sufficient thickness of elastomeric material behind all portions of the faceplate such that the faceplate periphery can move relative to the rigid clubhead body upon ball impact and faceplate deflection. Rigid clubhead bodies, for purposes herein, are defined as putter or iron clubhead sections (excluding integral or attached striking faceplates or inserts) of metal or polymer, cast, molded, or machined, which exhibit little or no deflection or deformation upon ball impact. FIG. 6 shows a minor alternative to FIG. 5 where the periphery of the faceplate ( 4 ) is in contact with the clubhead ( 2 ), but not adhered to it by either the viscoelastic ( 3 ) or any other more rigid means again leaving the periphery unconstrained to move upon faceplate impact and deflection. 
     In FIG. 7, the faceplate ( 1 ) is connected to the clubhead ( 2 ) by one or more viscoelastic elements ( 3 ) with an opening ( 5 ) or void (not shown) behind the center of the clubhead (“intended strikepoint”). In this arrangement, upon ball impact and faceplate deflection, one or more viscoelastic elements absorb energy primarily via shear deformation (and to a lesser degree by compressive deformation). The faceplate deflects rearward while moving laterally at its periphery upon impact with the ball. 
     In FIG. 8, the protective faceplate ( 1 ) is connected to the rigid clubhead ( 2 ) by one or more viscoelastic elements ( 3 ) so arranged that the elements absorb energy via both shear and tension as the faceplate deflects rearward upon impact while moving laterally at its periphery. 
     FIG. 9 (A &amp; B view) partially overcomes the trampoline and incompressibility effects previously described by milling or casting multiple slots ( 6 ) into a faceplate, which is rigidly attached to the clubhead ( 2 ) or an integral part thereof. The slots may coincide with the horizontal “grooves” common to most irons. The horizontal slots ( 6 ) free trampoline type periphery constraints in the vertical direction and create multiple lateral face bars ( 7 ) such that only a portion of the face bars, normally contact the ball upon impact, thereby increasing faceplate deflection and energy absorption by the viscoelastic insert(s) ( 3 ) behind said bars ( 7 ). 
     FIG. 10 (A &amp; B view), like FIG. 9, employs lateral slots ( 6 ) through the faceplate ( 1 ) and one or more lateral face bars ( 7 ) rigidly attached to the clubhead ( 2 ) or integral to the rigid clubhead body material. The flexibility of the face bars is further enhanced by at least one vertical slot ( 8 ) through the face bars ( 7 ). 
     FIG. 11 is a frontal view of multiple faceplate striking elements ( 9 ) to enhance faceplate flexibility in intimate contact with, and substantially covering, one or more energy absorbing elastomer elements. Such faceplate striking elements may be rigid or flexible, metal or plastic and hexagonal (shown), square, rectangular, or any other shape. 
     FIG. 12 addresses the fluidic incompressibility problems of energy absorbing elastomer inserts, especially those constrained in a clubhead cavity ( 3 ) and covered with a hard protective faceplate ( 1 ). The single or multiple elastomer elements are segmented with multiple vertical and/or horizontal slots ( 10 ), or numerous small boreholes, or a waffle pattern creating multiple voids such that compression of the insert upon ball impact produces localized lateral deformation of the elastomer into the slots, holes, or other multiple voids ( 10 ). 
     FIG. 13 (A &amp; B view) also addresses the fluidic incompressibility constraints on energy absorbing elastomer deformation and energy absorption efficiency previously discussed. Rather than fully surrounding the elastomer insert by the rigid clubhead body, the top and/or bottom of the insert cavity remains open or not in intimate contact with the elastomer via a void thus, allowing the elastomer upon impact with a golf ball to deform upward and/or downward thus, increasing elastomer deformation and energy absorption. 
     In FIG. 14, the cavity ( 13 ) in intimate contact with the less energy absorbing elastomer(s) ( 11 ), and the more energy absorbing elastomer ( 3 ), is shaped to allow more angular deflection at points progressively remote from the intended strikepoint thus, at least partially correcting misdirection caused by mishits. The center more energy absorbing element ( 3 ) is thickest behind the strikepoint for maximum energy absorption at the center and progressively less at points more remote for mishit distance correction. 
     FIG. 15 utilizes fluidic (gas or liquid) throttling (multiple shock absorbers) for energy absorption. A flexible faceplate ( 1 ) is either flexibly attached to a rigid clubhead via one or more elastomeric elements ( 14 ) or alternatively rigidly attached to the clubhead. Multiple small pistons ( 15 ) are attached to either the faceplate ( 1 ), as shown, or the clubhead body, or molded integral with it. The piston nearest the clubcenter strikepoint ( 16 ), has means for absorbing more energy via either a longer piston stroke, a larger piston diameter, and/or a larger throttling orifice ( 17 ). If a fluid is used rather than air, the throttling orifices ( 17 ) upon ball impact would exhaust into a fluid reservoir (not shown). 
    
    
     The above invention is useful in putters where ball impact velocity is generally insufficient to allow enough rigidly attached faceplate deflection and energy absorbing elastomer element deformation to get substantial or full mishit distance correction. The invention is also useful in irons where the faceplate must be hard and durable enough for useful playing life while the absorbing element(s) must be thin enough for popular iron designs. 
     Various embodiments of the present invention have been described above and illustrated in the figures. The figures are not necessarily to scale and in many cases, enlarge the features being described. All features of the invention can be incorporated into putters, iron and wood clubheads, which can retain current traditional external shape and appearance. Described or claimed features of the invention can be used in combination with other features or claims. While most of the distance and directional corrective features are described and claimed for lateral (horizontal) mishits, the same features and claims can also correct vertical mishits, although vertical mishits produce substantially less distance loss and misdirection than lateral mishits of equal distance from the clubface strikepoint. 
     The present invention is not limited to the embodiments shown, as many variations will be evident to one skilled in the art, which variations are intended to be encompassed in the present invention as set forth in the following claims.