Abstract:
A golf club counter-weighting system, viable for both original manufacture and after-marketing, features an expandable weight assembly that is easily installed at a designated location within a golf club shaft and expanded via a user tool so as to become reliably secured in place by frictional pressure against the surrounding shaft. In a primary embodiment, the weight assembly is made to be threadedly engagable by the opposite end of a dual-function user tool enabling the weight assembly, when unexpanded, to be conveniently moved axially for initial installation, relocation and/or removal.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the field of sports equipment, and more particularly to golf club counter-weighting for improving a golfer&#39;s playing and score by more optimally matching the golf club to the dynamic physical characteristics of the individual golfer, by adding a weighting assembly secured at a designated location in a hollow shaft of golf club. 
       BACKGROUND OF THE INVENTION 
       [0002]    There has been an evolution in golf club technology that has led to ultra light-weight thin-wall hollow shafts. These have intensified concern about optimally matching the amount of mass, including its location and distribution in the golf club, to the physical characteristics of the individual golfer, considering swing dynamics. 
         [0003]    Along with attention that has been given to optimizing the mass at the club head end for the lightweight shaft, there has been recognition that better control, distance and accuracy can be obtained by counterbalancing the mass of the club head by the addition of mass at a selected desirable location along the shaft, where a judicial amount of mass can be selected to optimally match the player&#39;s physiological characteristics. 
         [0004]    Typically, a weight element assembly, a.k.a. “counterweight” and “swing-weight” for adding inside the shaft of a previously manufactured golf club, requires special mounting arrangements to provide rugged lateral retention to prevent vibration and metal-to-metal contact, and rugged axial retention to prevent displacement of the added weight element assembly relative to the shaft due to slippage under the rigors and stresses of actual golf play. 
       DISCUSSION OF KNOWN ART 
       [0005]    In the practice of known art, implementations for providing the required axial retention fall into three main categories: 
         [0006]    Category 1: securing the weight assembly to the golf club grip, requiring a custom-designed grip or modification of the cap region of a previously manufactured grip for access to enable insertion, locking in place, adjustment and removal of added weight elements, requiring at least enlargement of any original vent hole; 
         [0007]    Category 2: securing the weight assembly using friction applied against the interior surface of the golf club shaft, either by (a) one or more expansion elements attached to (or constituting) weight elements, typically requiring special tools for installation, location adjustment and removal, (b) specialized resilient sleeves on weight elements, or (c) a specialized resilient lining on the shaft interior surface; however subcategories (b) and (c) present challenging difficulties due to the conflicting requirements of providing both the compressive holding force for reliable frictional axial retention while also enabling convenient axial adjustment and trouble-free removal or readjustment if required, and furthermore accommodating the diameter variations in tapered shafts. 
         [0008]    Category 3: deriving the required axial retention from the top end surface of the golf club shaft, e.g. by an annular flange, configured at the top end of the weight assembly, held under the cap region of an original unmodified grip, thus avoiding grip modification and avoiding dependency on friction-gripping the interior surface of the shaft. The annular flange, dimensioned to fit closely inside the grip, co-operates therewith to also provide radial retention of an upper portion of the weight assembly. 
         [0009]    U.S. Pat. No. 7,481,716 for GOLF GRIP FOR ACCOMODATING SELECTABLE WEIGHT ASSEMBLY by J. Johnson, the present inventor, discloses an example of category 1, implemented with the grip cap modified by a stepped circular opening, in conjunction with category 2(a). 
         [0010]    U.S. Pat. No. 8,177,658 for WEIGHT DEVICE ADJUSTABLY SECURED IN GOLF CLUB SHAFT by J. Johnson, the present inventor, discloses an example of category (1) implemented with the grip cap modified by a (non-stepped) simple circular opening, in conjunction with category 2(a). 
         [0011]    U.S. Pat. No. 8,641,551 for VERSATILE VIBRATION-DAMPED GOLF CLUB SWING WEIGHT and a division thereof, U.S. Pat. No. 9,283,453 issued Mar. 15, 2016 for VERSATILE VIBRATION-DAMPED GOLF CLUB SWING WEIGHT METHOD, by J. Johnson, the present inventor, as an example of category 2(a), discloses and shows in  FIG. 6 , a magnetized tool for removal or upward readjustment. 
         [0012]    U.S. Published Application 2014/0342845 A1 to Dingman (and now Johnson), published Nov. 20, 2014 for GRIP AND INTERNAL WEIGHT SYSTEM FOR SHAFT OF GOLF CLUB, exemplifies category 1, showing in  FIGS. 2-4  and disclosing an insert  34  between the grip  16  and cap  54 , which is coupled by spacer  56  to weight  58 , surrounded by (unexpandable) foam sleeve  60  which resists radial movement but allows axial displacement for installation and removal. Axial securing of weight  58  is derived only from grip  16  via insert  34 , and thus indirectly from the top end of shaft  14 , not from radial expansion against the shaft interior. 
         [0013]    There remains an unfulfilled need for an improved golf club weighting system that (a) provides category 2 secure axial retention of the weight assembly by an expansion element in the shaft, and (b) is readily viable both in original manufacture, after-marketing and user golf play. 
       OBJECTS OF THE INVENTION 
       [0014]    It is a primary object of the present invention to provide an improved expansion/friction type weight assembly implementation that fulfills the above-described unfulfilled need, including structure that engages the weight assembly positively for upward adjustment or removal, and that can be readily and easily incorporated into golf clubs at original manufacture as well as in the aftermarket and user golf play. 
       SUMMARY OF THE INVENTION 
       [0015]    The foregoing object has been met by the disclosed golf club counter-weighting system, viable for original manufacture, after-marketing and user golf play, featuring an expandable weight assembly that is easily installed at a designated location within a golf club shaft and expanded via a user expansion tool so as to become reliably secured in place by frictional pressure against the surrounding shaft. In a primary embodiment, the weight assembly is made to be threadedly engagable by the opposite end of a dual-function user tool that enables the weight assembly, when unexpanded, to be conveniently moved axially for initial installation, relocation and/or removal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The above and further objects, features and advantages of the present invention will be more fully understood from the following description taken with the accompanying drawings in which: 
           [0017]      FIG. 1  is a cross-sectional elevation of an upper portion of a grip and shaft of a golf club equipped with a weight assembly of the present invention. 
           [0018]      FIG. 2  is an enlargement of a portion of  FIG. 1  showing an expansion element frictionally securing the weight assembly to the surrounding shaft portion. 
           [0019]      FIG. 3  is an elevational view of a dual-function tool for (1) securing/releasing the weight assembly of  FIGS. 1 and 2  relative to the shaft and (2) vertical displacement of the weight assembly for installation, relocation and/or removal thereof. 
           [0020]      FIG. 4  depicts the items shown cross-sectioned in  FIG. 1  with the addition of the tool of  FIG. 3  engaging the expansion mechanism, shown expanded, securing the weight assembly to the shaft. 
           [0021]      FIG. 5  shows the items of  FIG. 4  with the tool inverted and threadedly engaging the weight element for insertion, repositioning or removal of the weight assembly. 
           [0022]      FIG. 6  is an enlarged cross-sectional view of an alternative embodiment of the invention wherein the weight assembly includes an attached custom grip cap. 
           [0023]      FIG. 7  is a top view of the grip cap of  FIG. 6 . 
           [0024]      FIG. 8  depicts a single-function tool configured with a hex driver end for deploying/releasing expansion of the weight assembly of  FIG. 6 . 
           [0025]      FIG. 9  depicts the items shown cross-sectioned in  FIG. 6  with the addition of the tool of  FIG. 8  engaging the expansion mechanism, shown expanded, securing the weight assembly at the designated location at the top end region of the shaft. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]      FIG. 1  is a cross-sectional elevation of an upper portion of a golf club having a grip  10  fitted onto a shaft  12  within which a weight assembly  14  of the present invention has been installed and secured at the selected axial location shown. A removable cap  16  in the top of grip  10  is fitted into a central opening in grip  10  sized to allow insertion and installation of weight assembly  14 . Typically cap  16  is configured at top center with a driving recess and traversed there by a small vent passageway as shown. 
         [0027]      FIG. 2  is an enlargement of a portion of  FIG. 1  showing a resilient expansion element  20  expanded and thus frictionally securing the weight assembly  14  to the surrounding portion of shaft  12 . In weight assembly  14 , a metal weight element  18  is coupled onto and drawn against expansion element  20  by a machine screw  22  threadedly engaging an annular pressure plate  24 , in the form of an inverted T-nut, bearing against the bottom side of expansion element  20 . As shown, screw  22  has been tightened to compress the resilient expansion element  20  axially, causing it to expand radially against the interior surface of shaft  12  so as to secure the weight assembly  14  in place at the desired axial working location. 
         [0028]    A foam sleeve  26  surrounding weight element, and typically attached thereto adhesively, is made and dimensioned to hold the weight assembly  14  concentric in shaft  12  at all times, continuously applying a designated relatively low amount of frictional pressure against the surrounding internal surface of shaft  12 . 
         [0029]    Foam sleeve  26  is designed and dimensioned to deliver a particular designated amount of frictional pressure radially onto surrounding shaft  12  such that, with expansion element  20  disengaged from shaft  12 , the friction is (1) sufficiently high enough to hold weight assembly  14  in place in shaft  12  without rotation while screw  22  is being rotated by driver tool end  28 A to deploy/release expansion element  20 , and yet (b) sufficiently low enough to allow convenient axial displacement of weight assembly  14  for relocation or removal by user manipulation of tool  28 , engaged by threaded driver end  28 B as shown in  FIG. 5 . 
         [0030]      FIG. 3  is an elevational view of a dual-function tool  28  configured with (1) a hex driver end  28 A at the lower end as shown, for securing/releasing the weight assembly  14  of  FIGS. 1, 2, 4 and 5  relative to the shaft  12 , and (2) an externally threaded end portion  28 B at the opposite upper end for engaging weight element  18  ( FIG. 2 ) to enable user manipulation of axial displacement of weight assembly  14  for installation, relocation and/or removal thereof, subsequent to releasing expansion element  20  from shaft  12  utilizing hex driver end  28 A as shown in  FIG. 4 . 
         [0031]      FIG. 4  depicts the items cross-sectioned in  FIG. 1  with the addition of the hex tool end  28 A of tool  28  of  FIG. 3  inserted into the bore of weight element  18  and engaging a hex drive recess configured in the head of screw  22 , seated on the lower portion of weight element  18 . The resilient expansion element  20  is shown as having been released from engagement with shaft  12  by the user rotating tool  28  counter-clockwise to reduce the axial compressive pressure in expansion element  20  until its diameter is reduced sufficiently to disengage from shaft  12 , leaving the weight assembly  14  retained in place only by the relatively low radial compressive frictional force from the foam sleeve  26  acting on the surrounding shaft  12 , thus facilitating relocation or removal of the weight assembly  14  by user-manipulation of tool  28 . 
         [0032]      FIG. 5  shows the items of  FIG. 4  with tool  28  having been inverted and its threaded end portion  28 B positively engaging the upper threaded portion of the bore of weight element  18 . Since the expansion element  20  is disengaged from shaft  12 , as described above in connection with  FIG. 4 , vertical displacements of weight assembly  14  for purposes of installation, relocation and removal thereof, are readily accomplished by user-manipulation of tool  28 . 
         [0033]    For installation in original manufacture, aftermarketing and user golf play, weight assembly  14  is initially pre-set to its inherent unexpanded condition by counterclockwise rotation of the tool  28  with its hex driver end  28 A engaging screw  22 . Then tool  28  is inverted and with end  28 B threaded into weight element  18 , the weight assembly  14  is inserted into the shaft  12  to the desired location, unexpanded as shown in  FIG. 5 . Then weight assembly  14  is secured in place by inverting tool  28 , engaging screw  22  with hex end  28 A and rotating tool  28  clockwise to expand the expansion element  20  against shaft  12  until the weight assembly  14  becomes firmly secured in place as shown in  FIG. 2 . Then, with tool  28  removed and cap  16  ( FIG. 1 ) replaced, the weighted golf club is ready for play. 
         [0034]    For removal or relocation of weight assembly  14 , cap  16  (or grip  10 ) is removed, and tool end  28 A is inserted and engaged into screw  22 , as shown in  FIG. 4 , then rotated counterclockwise until expansion element  20  disengages from shaft  12 . Then tool  28  is withdrawn, inverted, inserted and rotated clockwise to thread end  28 B into weight element  18 , whereupon the weight assembly  14  can then be easily and reliably removed or else relocated and secured in place as described above; then as before, with tool  28  removed and cap  16  ( FIG. 1 ) (or grip  10 ) put back in place, the weighted golf club is ready for play. 
         [0035]    Optionally, the low end of screw  22  can be swaged or crimped as shown in  FIG. 6  in order to prevent unintentional unthreading and separation of T-nut pressure plate  24 , thus rendering the weight assembly  14  as an integrated module of which the component parts are not readily separable. 
         [0036]    Optionally, two or more weight assemblies  14  could be installed, as described above, at designated locations in shaft  12 , subject to making tool  28  sufficiently long. 
         [0037]    In the primary embodiment of the invention, cap  16  ( FIG. 1 ) plays no significant role apart from cosmetically filling an access opening in the grip  10  that may be provided as an optional alternative to utilizing a standard grip that would require removal to allow access for installation or removal of a weight assembly. 
         [0038]    The range of available working locations of weight assembly  14 , extending downward from the top end of shaft  12 , is limited by the length of tool  28 , typically made approximately 12 inches long, as considered to be adequate for practically all weighting requirements. 
         [0039]      FIG. 6  is an enlarged cross-sectional view of a secondary embodiment of the invention, wherein a weight assembly  14 , as described above in the primary embodiment, has been modified by addition of an adhesively-attached custom grip cap  16 ′ and omission of foam sleeve  26  ( FIGS. 4 and 5 ) to form a modified weight assembly  14 ′ representing the secondary embodiment distinguished by (a) providing coaxial integrity that holds the weight element  18  centered in shaft  12  and allows elimination of foam sleeve  26  ( FIG. 4 ), (b) being restricted to a single designated working location at the uppermost end region of shaft  12 , and (c) thus eliminating need for tool end driver  28 B and for the internal threading in the upper portion of the bore of weight element  18 . 
         [0040]    Cap  16 ′ is configured with (a) an externally threaded main portion, as shown, for threaded attachment to the grip  10 , (b) a central opening  16 A with hex cross-sectional shape ( FIG. 8 ) serving as a driving recess for cap-rotation driven by a standard hex driver tool, and (c) central opening  16 A traverses cap  16 ′ in hex cross-sectional shape serving to provide ample clearance for insertion of the hex driver end  28 A of tool  28  for engaging screw  22  as shown in  FIGS. 4 and 9 . 
         [0041]      FIG. 7  is a top view of cap  16 ′ of  FIG. 6  showing the hex cross-sectional shape of central opening  16 A described above in connection with  FIG. 6 . 
         [0042]      FIG. 8  depicts a single-function tool  28 ′ configured with a hex driver end  28 A for engaging machine screw  22 , as described in connection with  FIGS. 3 and 9 , to deploy and release expansion of expansion element  20  of weight assembly  14 ′ ( FIG. 6 ). 
         [0043]      FIG. 9  depicts the modified weight assembly  14 ′ of  FIG. 6 , the secondary embodiment, containing the items shown cross-sectioned in  FIG. 6  along with the addition of the single-function (expansion) tool  28 ′ of  FIG. 8  with hex driver end  28 A temporarily remaining engaged with machine screw  22  after having expanded the expansion element  20  as shown, securing the weight assembly  14 ′ at its designated location: the uppermost top end region of the shaft  12 . 
         [0044]    In the secondary embodiment weight assembly  14 ′, the approach of adding cap  16 ′ adhesively attached onto weight element  18 , as shown in  FIGS. 6 and 9 , was a design choice predicated on the special circumstance of anticipation that the primary embodiment weight assembly  14  would be already in production and thus readily available as an adaptable complete assembly or kit of already tooled and existing available component parts, to serve beneficially as the predominant main basis of the second embodiment weight assembly  14 ′, requiring only the addition of custom cap  16 ′, adhesively attached. Sleeve  26 , no longer required, could optionally be omitted or left in place. Another advantage of this approach of attaching cap  16 ′ onto weight element  18  is that these may be made from different optimally-selected materials, e.g. aluminum and brass respectively. 
         [0045]    As an alternative to attaching cap  16 ′ to weight element  18 , these can be combined into a single component designed to serve as an integrated cap/weight element that is fully equivalent functionally, more rugged structurally, and potentially cost effective, considering the elimination of costs and labor associated with sleeve  26 , and eliminating the machining of threading inside the weight element, no longer required due to the designated location of the weight assembly being restricted to the uppermost end region of shaft  12 . 
         [0046]    The invention can be practiced with materials, details, sizes and proportions of the component parts deviating from those indicated in the drawings of the illustrative embodiments shown. Tools and mating drive receptacles shown and described as hex could optionally be implemented in any other equivalent driver configuration. 
         [0047]    This invention may be embodied and practiced in other specific forms without departing from the spirit and essential characteristics thereof. The present embodiments therefore are considered in all respects as illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description. All variations, substitutions, and changes that come within the meaning and range of equivalency of the claims therefore are intended to be embraced therein.