Abstract:
A weight device for golf clubs can be secured at a selected location within the shaft. A cylindrical weight element is typically disposed between two expansion elements, all three elements being traversed by a machine screw that engages a threaded lower end plate. The screw head is made to be engaged and driven by a special elongated tool to put the device in a sliding-friction mode for moving to any desired location within a golf club shaft, where the device can be secured in place by rotating the screw clockwise to expand the expansion elements against the shaft bore in a compression-secured mode. A permanent magnet affixed to the tool enables upward relocation or removal of the weight device.

Description:
PRIORITY 
     Benefit is claimed under 35 U.S.C. 119(e) of pending provisional application 61/009,052 filed Dec. 26, 2007. 
    
    
     This invention is in the field of sports equipment and more particularly relating to the game of golf, providing capability of adding a selectable amount of weight inside the shaft of an existing golf club and affixing the weight at a selectable location anywhere within the length of the shaft. 
     BACKGROUND OF THE INVENTION 
     In ongoing evolution in the game of golf, along with a shift to lighter weight shafts there has been increased interest in custom-matching golf clubs to individual golfers in recognition of the differences that characterize individual golfers such as height, weight, strength, firmness of grip, path and velocity of swing, etc., and the differences in golf clubs such as total length, total weight, weight distribution considering head weight, shaft weight and grip weight, along with other variables such as shaft stiffness and related resonances. The overall result of these variables determines how a particular club “feels” to that particular golfer. 
     For club-matching purposes, the golf industry developed a rating known as “swing-weight”, based on balance measurements made on the club about a fulcrum point usually twelve or fourteen inches from the club cap, characterizing the club on a scale of 77 increments with letters A-G followed by numerals 1-10. Industry standards are D0 or D1 for men and C5 to C7 for women. In another rating system, the MOI (moment of inertia: in physics the product of mass and distance from the axis of rotation) is expressed in terms of total club weight and distance from the center of gravity (balance point) to an arbitrary axis of rotation, usually taken at the club cap end, but suggested by the present inventor as more realistic if taken at an outside point, e.g. twelve inches beyond the cap. 
     Many golfers including pros are not fully satisfied with the existing rating systems and regard them as approximate guidelines at best, so there is an unfulfilled need for after-market accessories that enable even initially “matched” golf clubs to be fine-tuned to more closely match the golfer&#39;s individual physique and needs for improved performance. 
     DISCUSSION OF KNOWN ART 
     U.S. Pat. No. 6,765,156 B2 to Latiri for a GOLF CLUB SWING WEIGHT BALANCE AND SCALE provides detailed description regarding “swing weight” and its measurement. 
     U.S. Pat. No. 5,528,927 to Butler et al for a CENTER OF GRAVITY LOCATOR discloses apparatus and method for measuring “center of gravity” of an object such as a golf club head. 
     U.S. Pat. No. 4,059,270 to Sayers for METHOD FOR CUSTOM FITTING GOLF CLUBS discloses a device utilizing a system of photobeam measurers to detect the speed imparted to a golf ball and the related variables. In describing the method of evaluating and custom-fitting golf clubs to players, this patent sets forth “swing weight” and club length as the two major variable factors relating to optimization of the golf club. 
     As examples of patents that teach adding mass to the club head the Sayer patent cites U.S. Pat. Nos. 1,306,029, 1,538,312, 2,163,091, 2,750,194 and 3,692,306. A more recent example, U.S. Pat. No. 6,514,154 to Finn discloses a GOLF CLUB HAVING ADJUSTABLE WEIGHTS AND READILY REMOVABLE AND REPLACEABLE SHAFT. 
     Approaches to after-market weight-balancing golf clubs have included weights, e.g. in the form of a sleeve or lead tape to be attached on the outside of the shaft. As an environmental hazard, lead tape has become unpopular. Since other external approaches are considered unsightly, alternative internal approaches have included inserting a cork or other weight in the bore of the shaft of the club, pushing it in to an estimated best location where it is retained adhesively or by a tight friction fit such that typically it cannot be removed or even shifted upwardly in the shaft. Known golf club weighting approaches have suffered other drawbacks, for example: 
     (1) unless the weight is made removable, it cannot be replaced to adjust to a lighter value: it can only be increased by adding another weight; 
     (2) readjustment of the weight location, which is often desired, is impossible with adhesive fastening; with frictional fastening, typically the weight can be pushed further downwardly but cannot be shifted upwardly in the shaft; 
     (3) a friction plug of relatively rigid material fails to accommodate the variations in the diameter of the tapered shaft bore, typically decreasing from 0.5 inches at the cap end to about 0.3 inches at the head end, thus the available range of location of any single weight plug is inadequate; and 
     (4) there is a high probability of failure of the weight fastening system, allowing the weight to shift from the desired location under the strong forces applied during the swing stroke and in general handling and transporting of the golf clubs. 
     Numerous patents and approaches such as these have failed to fully satisfy the unfulfilled need for an after-market device for conveniently and reliably “balancing” the club to match the golfer, i.e. adding a judicious amount of weight at a strategic “sweet spot” selected as optimal along the shaft to match the golfer and enhance the level of performance. 
     OBJECTS OF THE INVENTION 
     It is a primary object of the present invention to provide capability of adjusting and setting the balance of any golf club through the addition of a selectable amount of weight inside the shaft in a manner that it can be positioned throughout the length of a tapered shaft bore and secured reliably in place. 
     It is a further object that after being secured in place, the weight can be released, relocated upward or downward and again secured reliably in place. 
     SUMMARY OF THE INVENTION 
     The objects of the invention have been accomplished by a generally cylindrical weight device including at least one expansion element made of sufficiently rubber-like material and dimensioned such that lengthwise compression causes radial expansion to a predetermined diameter range corresponding to at least a major portion of the typical diameter range of golf club shaft bores. 
     The device includes at least one weight element and one expansion element. Typically the device is configured with three cylindrical shaped elements, each with a central passageway, located co-linearly, i.e. a single weight element located between a lower expansion element and an upper expansion element. 
     The lower expansion element is configured at its lower end with a threaded bushing that serves as a compression plate engaged by a captive steel machine screw that traverses the passageways. A washer under the screw head forms a compression plate at the upper end. 
     The device is initially pushed in to place using a special tool with an elongated shaft ending in a hex driver end that engages a hex socket in the head of the machine screw. The tool includes a permanent magnet acting on the screw head so as to retain engagement and to enable the weight device to be pulled upwardly in the golf club shaft. 
     Initially the device is loaded onto the tool with the screw tightened only enough to create light friction in the upper region of the club shaft above the desired location; then it is pushed down to the desired location and then secured in place there by rotating the screw clockwise to tighten it securely then the tool is removed. 
     To relocate the device for “fine tuning” or removal, the tool is reinserted and the screw is rotated counter-clockwise to reduce the holding friction sufficiently to remove the device or shift it up or down as required to a new location where it is again secured as described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational view of a weight device in a primary embodiment of the present invention. 
         FIG. 2  is a cross-section of the weight device of  FIG. 1 , shown installed in a golf club shaft, shown in part. 
         FIG. 3  is an elevational view of a manual driver tool for installing, adjusting and removing the weight device of  FIG. 1 . 
         FIG. 4  is a cross section of the tool of  FIG. 3  inserted through the cap of a grip showing the driver member on the shaft of  FIG. 2  about to engage the weight device of  FIG. 1 , shown in part. 
         FIG. 5  is an elevational view of a secondary embodiment of a weight device of the present invention. 
         FIG. 6  is a cross-section of the weight device of  FIG. 5  installed in golf club shaft, shown in part. 
         FIG. 7  is a three-dimensional view depicting a first alternative non-magnetic tool and bayonet engagement method for weight device relocation/removal. 
         FIG. 8  is a three-dimensional view depicting a second alternative non-magnetic tool and bayonet engagement method for weight device relocation/removal. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is an elevational view of a weight device  10  in a primary embodiment of the present invention. A first expansion element  12  of rubber or other elastic material, a weight element  14  and a second expansion element  16  similar to element  12 , are held together in a collinear elongated cylindrical assembly, as shown, by a machine screw  18  traversing central openings in the three elements and a washer  20  under the head of machine screw  18 . 
       FIG. 2  is a cross-section of the weight device  10  of  FIG. 1 , shown installed in a golf club shaft  22 , shown in part. Screw  18 , engaging a threaded bushing  16 A at the lower end, has been tightened sufficiently to expand the diameter of both expansion elements  12  and  16  so as to bear firmly against the inside surface of shaft  22 , securing weight device  10  in place. The golf club shaft  22  is typically made with a bore that tapers from about 2″ in diameter at the top cap end to about ⅜″ at the lower end. To accommodate this variation, a standard version of weight device  10 , for the major upper portion of the shaft  22 , is made with the weight element  14  and the (unexpanded) expansion elements  12  and  16  typically ⅜″ in diameter, and a scaled-down version for a minor lower portion of the shaft  22 , is made with these elements typically ¼″ in diameter. 
     The weight device  10  is made to have, a designated total weight by the length of the weight element  14  and the density of its material, e.g. brass for high density. It is supported in a firm but resilient manner that prevents any metal-to-metal contact with shaft  22 , as deemed optimal for performance characteristics. At the lower end of screw  18  the threads at the extreme lower end of the threaded portion are crimped so as to keep screw  18  captive and avoid unintended disassembly of weight device  10  during removal or repositioning. In the standard version of weight device  10 , the weight element  14  and the expansion elements  12  and  16  are 3/16″ in diameter. 
       FIG. 3  is an elevational view of a driver tool  24  for installing, adjusting and removing the weight device  10  of  FIGS. 1 and 2 . A metal rod shaft  26 , made approximately the length of a golf club bore, has a blade handle  28  attached at the top end for manual rotation. At the lower end, a hex driver member  30  extends downwardly from a cylindrical permanent magnet  32  attached immediately above. 
       FIG. 4  is a cross-section of shaft  22  equipped with a golf hand grip  34 , and with a weight device  10  ( FIG. 2 ), shown in part, and a tool  24  ( FIG. 3 ) having been inserted through a circular opening  34 A that has been cut in cap portion  34 A of grip  34 . Opening  34 A has a diameter equal or near that of the inside of shaft  22  at its top end. At the bottom end of tool  24 , an Allen hex driver member  30  is in position immediately above the corresponding hex head of machine screw  18  ready for engagement. Magnet  32  is magnetized in a manner to magnetically attract the (steel) head of machine screw  18  when nearby, and to abruptly force closure of the air gap to fully engage the hex driver member  30  in the head of screw  18 . The weight device  10  can then be relocated or withdrawn by first rotating screw  18  counter-clockwise to reduce the axial pressure and partially relax the expansion elements  12  and  16  to release their grip on shaft  22  to an optimally low amount of residual friction to facilitate relocation or withdrawal. For upward relocation or withdrawal, magnet  32  provides the transmission of the necessary amount of tensile pulling force. 
       FIG. 5  is an elevational view of a secondary embodiment of a weight device  10 A of the present invention that has fewer parts and that may serve as an added auxiliary mass that can be located near the primary weight device or elsewhere. A relatively short weight element  14 A is located directly under the head of bolt  18 A, and the single compression element  12  is fitted at the lower end with a threaded “T-nut”  36 , as an alternative to bushing  16 A ( FIG. 2 ). 
       FIG. 6  is a cross-section of the second embodiment weight device of  FIG. 5  installed in golf club shaft  22 , shown in part. T-nut  36 , forming a threaded bottom end plate, is a commercial hardware product that is available with a set of spurs that extend upwardly into the expansion element  12  as indicated, for anti-rotation purposes. Insertion, relocation and removal for this second embodiment weight device are as previously described for the primary embodiment weight device  10 . While the dual expansion element mounting of the primary embodiment is inherently extremely robust with a weight element of practically any desired length, with the secondary embodiment having only the single expansion element, the weight element should be kept relatively short in length and possibly tapered to a smaller diameter at the upper end to prevent possibility of contact with the shaft in the event of off-axis displacement if the expansion element is not adequately secured in place. Possibility of such contact can be avoided by shortening of the weight element  14 A to the extreme of making it simply a metal washer of designated thickness, or a stack of several washers; the expansion element  12  may be lengthened for weight increase. 
       FIG. 7  is a three-dimensional view depicting a first alternative tool  26 A and a corresponding bayonet engagement method for weight device relocation/removal that eliminates the need for a magnet on the tool. In this example, washer  14 B forms a weight element and end plate for expansion member  12 , shown in part. Screw head  18 B is fitted with one of more extending bayonet pins  18 C: in this example a single pin  18 C traversing the head  18 B extends outwardly as two diametrically opposed pins. Tool  26 A may be a hollow tube or may be a solid shaft fitted at the bottom end with a hollow sleeve: near the bottom end tool  26 A is configured with one or more specially shaped T slots  26 B as shown, one for each bayonet pin  18 C on head  18 B. 
       FIG. 8  is a three-dimensional view depicting a second alternative non-magnetic tool utilizing a bayonet engagement method for weight device relocation/removal. In this example the tool  26 C may be a solid rod with the lower end preferably in the bullet shape shown and fitted with a pair of bayonet pins  26 D. A sleeve  18 D fastened to the bolt head of the weight device is configured with a pair of T slots as shown. 
     The configurations of  FIGS. 7 and 8  are essentially inversions of each other, and function in a similar manner. When engaged with pins located at one or other end region of the T slots, the tool can rotate the screw head clockwise or counter-clockwise, and can pull the weight device upwardly for relocation or removal. For release of tool from the screw head, a slight rotation of the tool relocates the bayonet pins centrally in the T slots in line with the slot entrance. In either version, alternatively, a single short pin could be utilized, or a set of two, three or more short pins could be arranged in a polar array and secured in place in drilled holes. Alternatively the slots could be L-shaped, in the manner of well known auto lamp sockets. 
     To provide a range of weight that can be added to a golf club, the weight devices may be made available in selected steps; e.g. three basic weights: 50, 25 and 12.5 grams enable the weight to be set to any desired value from 12½ grams in steps of 12½ grams. The 50 gram weight device can be made in the primary embodiment using a brass weight element ⅜″ by about 4″ long. Weighting can be performed with one, two or more weight devices; they can be located together or located independently anywhere along the shaft. The 12.5 gram weight device, and even a 6¼ gram “fine tuner”, may be made either in the primary embodiment, possibly utilizing a plastic weight element, and/or made in the secondary embodiment. 
     A single weight device may be located anywhere along the shaft length, and with more than one weight device there is full flexibility of locating the devices close together or elsewhere throughout the shaft length. 
     As an alternative to utilizing a magnet for pulling the weight element to move it upwardly, a mechanical system could utilize a bayonet pin/slot type engagement, generally similar to that found on bayonet base electric lamps, particularly automotive lamps. The L shaped slots could be oriented opposite their normal direction, so that the fastening would tend to stay engaged for pulling purposes while urging the tool counter-clockwise. 
     The invention may be embodied and practiced in other specific forms without departing from the spirit and essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention encompassing all variations, substitutions, and changes that come within the meaning and range of equivalency of the claims therefore are intended to be embraced therein.