Abstract:
A dip-molded grip for a mid-length golf putter is preferably made of plastisol, has a circular cross-section, and a length of about 19 inches. The grip is made by dipping a mold rod into two types of plastisol and baking the plastisol layers. The result is a grip that fits any individual and provides an ideal surface.

Description:
[0001]    This application claims priority from U.S. Provisional Application No. 60/316,146 filed Aug. 30, 2001 for GOLF PUTTER GRIP. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates generally to a golf club grip. In particular, the present invention relates to a one-piece grip for a mid-length putter.  
           [0003]    A popular trend in the golf industry is the mid-length putter. This design is different from conventional putters that typically vary in length from 33 to 35 inches and long putters which vary in length from 46 to 55 or more inches. The key advantage of the mid-length putter is that the player&#39;s mid-section becomes a pivot point for the butt end of the putter grip during the stroke. It increases stability and improves accuracy for most players. Indeed, top PGA pros have experienced an evolution in their putting skill. Vijay Singh, for example, went from a 99 putting rank in 2000 to near the top in 2001. In 1999, Paul Azinger&#39;s putting ranking was 141st and improved to 4th in 2000.  
           [0004]    Every putter model consists of three main components—the putter head, the shaft, and the grip. Ordinarily, the grip is less significant in terms of function, and cosmetics have been the main concern of players and manufacturers alike. Putter grips are basically the same. They measure about one foot in length and have a 0.75 inch diameter.  
           [0005]    The “split” grip concept originated for the long putters, which were introduced more then a decade ago and have seen a resurgence in popularity recently. The split grip allows players to separate their hands to control these extra long designs.  
           [0006]    This leaves the mid-length putter lacking for an ideal grip, and most custom club makers must modify grips intended for the long putter. For example, some shops use just the upper grip of two-piece models.  
           [0007]    A two-piece grip may be appropriate for the long putter, but it has limited application for the mid-length putter. First, there is considerable variation in body size and shape (under 5 feet tall to over 6 feet tall; slim waists and not-so-slim waists) among golfers with each having a different gripping style (placing hands high on the grip or bending over and placing hands low on the grip). A two-piece grip forces players to adapt to the grip rather than giving players the freedom to experiment with what works best for them. Second, grips intended for the long putter are generally too heavy and inappropriate in diameter. To make matters worse, the material is too dense and this hampers putter head “feel,” which is essentially the ability of the player to sense how the putter head is reacting during the stroke. Feel is an important consideration among professional and amateur golfers when considering model choice and purchase.  
           [0008]    Grip weight is critical because of its interrelationship with the shaft and the putter head. If the grip is too heavy, heavier putter heads are necessary for the player to “feel” the stroke and accurately judge feedback when striking the ball. Today&#39;s players are accustomed to a certain look and do not want to adapt to an entirely new one unless it is both pleasing and functional. Furthermore, keeping the putter head size to current compact dimensions improves precision. A few “oversize” putter heads have enjoyed limited success in the marketplace, but the acknowledged common ground is approximately 4-5 inches long and 1-2 inches wide. Forcing players to adapt to a larger putter face is a significant marketing disadvantage. Again, a grip that is too heavy causes the putter head to feel too light.  
           [0009]    Grip density can have a big impact on putter head “feel.” A common material used for conventional putter grips is synthetic rubber, and the common manufacturing process is injection molding. This combination is too dense when used at the length and width required for a mid-length putter.  
           [0010]    Additionally, tactile sense is ignored by manufacturers. It is assumed that either the player does not care or surface material does not matter. This is an unwarranted assumption when it comes to the mid-length putter, because the player must avoid slippage during the putting stroke. Since the main tenant of the body pivot system used with a mid-length putter is an anchored grip against the mid-section, a grip that slips alters the pivot point and this affects accuracy.  
           [0011]    As alluded to above, another key aspect of grip design is the ability to modify weight. It takes at least ten shaft lengths to fit the golfing public to a personal mid-length design, and putter head feel can change drastically with different lengths. For example, assuming putter head weight remains constant, shorter length putters make the head feel lighter while longer lengths make it feel heavier. Once the ideal putter head feel is achieved, reproducing it for all lengths either requires varying putter head weight (an inventory nightmare) or varying grip weight.  
           [0012]    Finally, tooling costs associated with the manufacturing process is expensive for injection molding, the most common method of forming grips. A mold for injection molding can typically cost as much as $30,000.00. In addition, injection molding requires tedious paint-filling to add customized logos.  
         BRIEF SUMMARY OF THE INVENTION  
         [0013]    The present invention is a grip for a golf putter, and a method for making the grip. The grip has a circular cross-section and a length greater than about 11 inches. The method of making the grip is a dip-molded process where a first flexible layer is formed on a mold rod followed by a second flexible layer. The first and second layers coated on the mold rod are baked to cure the layers. The process results in an ideal grip for putters. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1A is a side view of a player using a putter of the present invention.  
         [0015]    [0015]FIG. 1B is a front view of a player&#39;s midsection showing placement of a putter of the present invention.  
         [0016]    [0016]FIG. 2A is a front view of the grip on a putter.  
         [0017]    [0017]FIG. 2B is a cross section of the closed end of the grip on a putter.  
         [0018]    [0018]FIG. 3 is an illustration of preheating a mold rod tool in an oven chamber.  
         [0019]    [0019]FIG. 4 is an illustration of dipping mold rods into plastisol.  
         [0020]    [0020]FIG. 5 is an illustration of mold rods coated with plastisol.  
         [0021]    [0021]FIG. 6 is an illustration of dipping mold rods into foamable plastisol.  
         [0022]    [0022]FIG. 7 is an illustration of mold rods coated with foamable plastisol.  
         [0023]    [0023]FIG. 8 is an illustration of cured grips in an oven chamber.  
         [0024]    [0024]FIG. 9 is an illustration of removing the grips from the mold rods.  
         [0025]    [0025]FIG. 10 is an illustration of inserting a putter shaft into a grip. 
     
    
     DETAILED DESCRIPTION  
       [0026]    [0026]FIG. 1A is a side view of a player using the present invention.  
         [0027]    Putter  10  includes grip  12 , shaft  14 , and head  16 . Shaft  14  of putter  10  is long enough to rest at the mid-section of the player.  
         [0028]    [0028]FIG. 1B is a front view of the player&#39;s midsection while using a putter of the present invention. FIG. 1B shows grip  12  and shaft  14 . Grip  12  is preferably about 19 inches long but can be any length greater than 11 inches when used with a mid-length putter. As shown in FIG. 1A and FIG. 1B, grip  12  is also preferably used on a mid-length putter that rests on the midsection of the player. Most preferably, putter  10  rests at about the naval of the player.  
         [0029]    [0029]FIG. 2A is a front view of the upper end of putter  10 . FIG. 2 shows putter  10  with grip  12  and shaft  14 . Grip  12  further includes closed end  18  and open end  20 .  
         [0030]    [0030]FIG. 2B is a cross sectional view of closed end  18  of grip  12 . FIG. 2B shows shaft  14  and grip  12  with plastisol layer  22  and foamed plastisol layer  24 . Plastisol layer  22  is the first layer covering about a 0.5 inch length of shaft  14 . Plastisol layer  22  is preferably between about 0.03 inch to about 0.06 inch thick and has a durometer hardness of about 70+/−2. The inside diameter is about 0.4 inch, and the outside diameter is between about 0.43 inch to about 0.46 inch. Plastisol layer  22  covers the whole end of shaft  14 . The purpose of the relatively hard plastisol layer is to provide a more durable closed end  18  of grip  12 . With use and abuse shaft  14  might otherwise break through grip  12 .  
         [0031]    Foamed plastisol layer  24  is the second layer preferably covering about 19 inches of shaft  14 . Foamed plastisol layer  24  is preferably has a thickness of about 0.25 inch and a durometer hardness of about 20+/−5. The inside diameter at closed end  18  is between about 0.43 inch to about 0.46 inch, and the outside diameter is about 1.0 inch. The outside diameter may range from about 0.9 to about 1.1 inches for a customized fit for any player. Foamed plastisol  22  also provides an ideal grip surface for a mid-length putter. Grip  12  has a slightly sticky, and yet smooth and tactile surface that avoids slippage during the putting stroke. Additionally, the surface of grip  12  accomodates inexpensive silk-screening for customized logos.  
         [0032]    Plastisol is a suspension resin of finely ground polyvinyl chloride (PVC) particles suspended in a plasticizer. Examples of plasticizers that may be used, but not limited to, include dibutyl maleate, dibutyl phthal ate, dibutyl sebacate, di ethyl phthalate, di-isobutyl phthalate, di-isodecyl phthal ate, id-isononyl phthalate, dimethyl phthalate, dioctyl adipate, dioctyl azelate, dioctyl phthalate, dioctyl sebacate, and trioctyl trimellitate. Heat fuses the PVC particles into a copolymer commonly called “vinyl.” 
         [0033]    Foamed plastisol is plastisol with an added foaming agent or blowing agent. An ideal foaming or blowing agent evaporates quickly at about the same temperature that the PVC particles fuse. The gas formed by evaporation of the blowing agent creates bubbles in the plastisol, which give foamed plastisol its airiness.  
         [0034]    [0034]FIG. 3 illustrates preheating mold rod tool  26 . FIG. 3 shows mold rod tool  26  with mold rods  28  and oven chamber  30 . Mold rod tool  26  is the only major tooling investment required for the process of the present invention. In the first step, mold rod tool  26  is preheated at about 415° F. for about 12 minutes in oven chamber  30 . Each mold rod  28  must be heated such that when it is exposed to the plastisol, the plastisol will begin to polymerize and coat mold rods  28 .  
         [0035]    [0035]FIG. 4 illustrates dipping mold rods  28  into plastisol  34 . FIG. 4 includes mold rod tool  26  with mold rods  28  and vat  32  with plastisol  34 . Mold rods  28  are suspended and lowered into vat  32  containing plastisol  34 , which has a durometer hardness rating of 70+/−2. Mold rods  28  are dipped in about 0.5 inch for a dwell-time of approximately 10 to 15 seconds. The dwell-time is important, because it determines the thickness of the coating on mold rods  28 . If a thicker coating of plastisol is desired, mold rod  18  has a longer dwell-time. If a thinner layer of plastisol is desired, the dwell-time of mold rod  18  is shorter.  
         [0036]    [0036]FIG. 5 illustrates plastisol  34  coated on mold rods  28 . FIG. 5 includes the identical structures to FIG. 4. Mold rods  28  are shown with an approximately 0.5 inch long coating of plastisol  34 . With a dwell-time of about 10 seconds to 15 seconds, plastisol  34  is approximately 0.03 inch to 0.06 inch thick. Since there is no foaming agent nor blowing agent, the thickness of plastisol  34  remains the same even after curing.  
         [0037]    [0037]FIG. 6 illustrates dipping mold rods  28  into foamable plastisol  36 . FIG. 6 includes mold rod tool  26  with mold rods  28  and vat  32  with foamable plastisol  36 . In the next step, mold rods  28 , while being suspended, are lowered into vat  32  containing foamable plastisol  36 , which is a mixture of plastisol having a durometer hardness rating of 20+/−5 and a foaming agent or a blowing agent. Mold rods  28  are dipped into foamable plastisol  36  about 19 inches for a dwell-time of 2.5 minutes. Again, the dwell-time determines the thickness of the coating on mold rod  18 .  
         [0038]    [0038]FIG. 7 shows mold rods  28  coated with foamable plastisol  36 . FIG. 7 includes identical structures to FIG. 6. At this point, the thickness of foamable plastisol  36  is preferably about 0.15 inch. This, however, is the thickness before curing.  
         [0039]    [0039]FIG. 8 illustrates cured grips  12  in oven chamber  30 . FIG. 8 shows mold rod tool  26  with mold rods  28 , foamed plastisol  38 , and oven chamber  30 . Mold rods  28  coated with plastisol  34  and foamable plastisol  36  are cured by baking in oven chamber  30  at about 415° F. for about 9 to 10 minutes. Baking completes polymerization of the plastisol and activates the foaming agent or blowing agent in foamable plastisol  36  to form foamed plastisol  38  shown on mold rods  28 . The thickness of foamed plastisol  38  is approximately 0.25 inch. Foamed plastisol  38  is flexible and slightly elastic. About 1% shrinkage may occur during the curing step. Preferably, grip  12  has a mass between about 145-165 grams.  
         [0040]    [0040]FIG. 9 illustrates removing grip  12  from mold rod  28 . FIG. 9 includes mold rod tool  26  with mold rod  28 , grip  12  with closed end  18  and open end  20 , and air hose  40 . Once removed from oven chamber  30  and cooled, grip  12  is removed from mold rod  28  using air pressure. Air hose  40  blows air into open end  20  of grip  12 , which allows it to slip off of mold rod  28 .  
         [0041]    [0041]FIG. 10 illustrates applying grip  12  over shaft  14  of a putter. FIG. 10 includes grip  12  with closed end  18  and open end  20 , shaft  14 , and air hose  40 . To slip grip  12  over shaft  14 , a small opening is created at closed end  18  of grip  12 , and air hose  40  blows air into grip  12  allowing it to easily slip over shaft  14  of putter  10 . Alternatively, grip  12  can be slipped over shaft  14  without using air pressure.  
         [0042]    The process of the present invention provides an easy way to vary the volumes and diameters of grip  12  by varying the dwell-time in foamable plastisol  36 . Foamed plastisol  38  is lighter and airier so that even large diameter grips do not become too heavy for a mid-length putter. A club builder can easily pair lighter grips to shorter putters and heavier grips to longer putters.  
         [0043]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.