DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Referring to FIG. 1, an embodiment of a golf putter 10 in accordance with the present invention is shown. The putter 10 includes a shaft 12 having a top end 14 and a bottom end 16. Shaft 12 can be constructed of any of the industry standard shaft materials, for example, stainless steel, graphite or other composite materials. Shaft 12 includes a hand grip 18 located at top end 14. Operably attached to bottom end 16 of shaft 12 is a putter head 20.

[0037] As depicted in FIGS. 2, 3 and 4, head 20 includes a front side or face 22, a rear surface or heel 24, a forward surface or toe 26, a rear side 28, a bottom surface 30 and a top surface 32. Located on face 22 is a proportional EVR insert 34. Bottom surface 30 has a slightly arcuate shape from face 22 to rear side 28 for the purpose of avoiding accidental grounding of head 20 during a swing as well as to reduce dragging of head 20 on the ground surface. Top surface 32 includes an alignment groove 36 in perpendicular alignment with the plain of face 22. In the present invention, alignment groove 36 has a width 38 greater than is typical in current putter designs. Alignment groove 36 is further accentuated through the application of a highly visible coating 40. Coating 40, most typically paint, is chosen to distinguish from the color of head 20. Typical colors for coating 40 can include white, yellow and orange though other colors having similar distinguishing characteristics can be used as well. The body of head 20 can be constructed of any of the common materials currently used in golf putters such as aluminum, bronze, nickel, steel, titanium and other suitable materials.

[0038] Referring to FIG. 5, an EVR insert 34 comprises a multi-layer configuration including an outer striking surface 42 and at least one proportional damping layer 44. Striking surface 42 can comprise a variety of materials such as stainless steel, bronze, nickel, titanium or suitable polymers. In one embodiment, an Ultra High Molecular Weight (UHMW) polymer, for example UHMW polyethylene with a molecular weight of between 3 million and 6 million can be used. In a preferred embodiment, striking surface 42 is selected to meet a minimum hardness requirement of 90 durometer or greater on the Shore A scale as dictated by rules of the United States Golf Association. Proportional damping layer 44 typically comprises a damping material and has no hardness requirement. Examples of suitable damping materials include polymers and polymeric foams. In an embodiment, a proportional damping layer 44 can comprise a vinyl or urethane foam such as those manufactured by Aero Specialty Composites of Indianapolis, Ind. or Rogers Corp. of Woodstock, Conn. Proportional damping layer 44 can also comprise a plurality of layers, each layer imparting its own damping characteristic. In one embodiment, striking surface 42 and proportional damping layer 44 have material properties that allow for quick and permanent bonding, for example through the use of thermal processes, adhesive processes, molding processes or other suitable bonding processes.

[0039] Generally, face 22 includes a recess 46 in which EVR insert 34 is inserted and attached. Attachment of EVR insert 34 within recess 46 can be permanent through adhesive, thermal or pressing means or EVR insert 34 can be removable attachable through the use of screws or other suitable fasteners. In the case of EVR insert 34 being removably attached with in the recess 46, a user can alter the proportional damping properties of putter 10 by swapping a first EVR insert with a second EVR insert having an alternative damping proportion.

[0040] In use, a golfer grips putter 10 using the handgrip 18. The golfer aligns himself, the putter 10 and the ball relative to the target, most commonly a golf hole. Using alignment groove 36, the golfer positions the face 22 in a perpendicular arrangement to the desired line for the putt. The golfer then swings the putter 10 with a generally parallel swing such that EVR insert 34, and more specifically the striking surface 42, contacts the ball and propels it toward the hole. While the use of putter 10 is simple to describe, putting a golf ball consistently and accurately is one of the most difficult skills to acquire when learning the sport of golf. Consistency is difficult as many variables such as putt length, body mechanics, green contours, weather conditions and course conditions make each putt different.

[0041] Through the use of a multi-layer design including proportional damping layer 44, EVR insert 34 has a proportional damping characteristic that is proportional to the impact energy supplied by putter 10. Statistically, the use of EVR insert 34 including the proportional damping characteristic reduces overall distance variability of putts around a target as compared to typical solid metal putters or putters having hard polymer inserts that lack proportional damping qualities.

[0042] An EVR insert 34 can be constructed to exhibit optimum proportional damping qualities at a desired range of putt distances, for example 10-20 feet. Similarly, a maximum EVR effect for EVR insert 34 can be constructed specifically for short putts, mid-range putts and longer putts. Even when putt distances are outside the design range of EVR insert 34, a damping effect will occur that reduces the effects of common swing mistakes such as those typically encountered with very short putts.

[0043] In actual use, an EVR insert 34 can be constructed using a specifically selected proportional damping layer 44 to impart an overall damping proportion of 0.30 or other desired damping proportions. In other words, the impact energy imparted to the golf ball through the EVR insert 34 is reduced by 30% over the desired range of putt distances. A golfer with a 30% EVR putter will have to hit the ball 30% harder to hit the ball comparatively the same distance than when using a putter without any proportional damping qualities. Golfers readily adjust their swings to compensate for a required increase in impact energy as they routinely make similar adjustments to putter weight, green speeds, wet greens and other environmental variables that are experienced between golf courses.

[0044] Referring now to FIGS. 7 and 8, an alternative embodiment of a golf putter 200 including EVR properties is depicted. Similarly to putter 10, golf putter 200 includes a shaft 202 having a top end 204 and a bottom end 206. Shaft 202 includes a handgrip 208 located at top end 204. Operably connected to shaft 202 at bottom end 206 is a configurable EVR head 210.

[0045] As illustrated in FIGS. 7, 8, 9, 10 and 11, configurable EVR head 210 comprises a head body 212 and an EVR insert assembly 214. Head body 212 is generally defined by a top surface 216, a bottom surface 218, a front surface or toe 220, a rear surface 222, a front side 224 and a rear side 226. As shown in FIGS. 10 and 11, a head cavity 228 extends between front side 224 and rear side 226. Head cavity 228 is defined by a top cavity surface 230, a bottom cavity surface 232 and a pair of side cavity surfaces 234a, 234b, a front opening 236 and a rear opening 238. Front opening 236 is undersized as compared to rear opening 238 such that a front cavity surface 240 surrounds the perimeter of front opening 236. Front cavity surface 240 includes a pair of head bores 242a, 242b extending into head body 212 such that the head bores 242a, 242b do not extend to the front side 224. Head bores 242a, 242b can include an internal thread or other suitable attachment means.

[0046] As illustrated in FIGS. 12 and 13, EVR insert assembly 214 comprises a striking layer 244, a proportional damping layer 246 and a backplate 248. Striking layer 244 has a striking surface 250 projecting from a flange surface 252. Striking surface 250 is sized and shaped to fit snugly within front opening 236. Proportional damping layer 246 is constructed to have a perimeter equivalent to flanged surface 252. Backplate 248 has a plate surface 254 and a pair of projecting arms 256a, 256b. Projecting arms 256a, 256b include arm flanges 257a, 257b and insert bores 258a, 258b. Projecting arms 256a, 256b and plate surface 254 are dimensioned to snugly accommodate the striking layer 244 and the flange surface 252 of striking layer 244. Projecting arms 256a, 256b are dimensioned such that the distance between insert bores 258a, 258b corresponds to the distance between head bores 242a, 242b.

[0047] To assemble EVR head 210, EVR insert assembly 214 is positioned such that striking surface 250 fits within front opening 236 as shown in FIG. 14. When properly positioned, striking surface 250 and head body 212 form the substantially smooth and uninterrupted front side 224. When striking surface 250 is positioned within the front opening 236, flange surface 252 and arm flanges 257a, 257b are in contact with front cavity surface 240 such that head bore 242a is aligned with insert bore 258a and head bore 242b is aligned with insert bore 258b. Finally, a pair of fasteners 260a, 260b, such as a pair of screws, is directed into the insert bores 258a, 258b and subsequently into head bores 242a, 242b to operably couple the EVR insert assembly 214 and the head body 212.

[0048] Due to the ability to attach and remove the EVR insert assembly 214 from the head body 212, it is possible for a golfer to specifically configure the golf putter 200 to have a desired EVR profile, for example High Gain EVR, Low EVR profile or High EVR profile. A golfer can replace a first EVR insert assembly with a second EVR assembly wherein the second EVR insert assembly has a selected proportional damping layer 246 different from that of the first EVR insert assembly. In another alternative embodiment, a golfer could replace EVR insert assembly 214 with EVR insert assembly 262 illustrated in FIG. 15 such that the proportional damping layer 246 is replaced with a first damping layer 264 and a second damping layer 266. In another alternative embodiment, the EVR properties of the EVR insert assembly 214 can be specifically tailored by removing mass from the plate surface 254 as shown in FIGS. 16, 17 and 18. As shown, a plurality of perforations 268, such as channels or spheres, can be fabricated as part of plate surface 254.

[0049] In order to illustrate the effect of proportional impact damping on putt length variability, an experiment is conducted in which a golfer hits 10 twelve-foot putts with a standard hard (either metallic or polymer) striking surface. The golfer fails to make any of the putts but instead, the putts are distributed around the hole, half being long and half being short. With respect to the distribution, the average length is twelve feet, the range is 8 feet and the standard deviation is 2.74 feet as shown in Column A of Table 1 below.

[0050] When the same 10 golf balls are putted with a proportional damping putter having a damping proportion of 0.30, the corresponding putt lengths and variability are as indicated in Column B of Table 1. Note that the measures of putt average, putt range and putt deviation are 30% less than the values displayed in Column A.

[0051] The average length of Column B putts is only 8.4 feet, which is 3.6 feet short of the required 12 foot required putt length. However, this is not the expected result of using a proportional damping putter. Instead, golfers quickly adapt and learn to hit an EVR putter harder, just as golfers quickly learn to swing harder on slower greens as opposed to fast greens, to swing harder on wet greens as opposed to dry greens, and to swing harder with a light putter as opposed to a heavy putter.

[0052] Column C shows the results wherein a golfer using a proportional damping putter hits the 10 twelve-foot putts 30% harder, on average, than with the standard metal or polymeric faced putter. The average 30% increase in swing force required to distribute the 30% damped putts around the 12 foot target results in an average of 3.6 feet being added to putt lengths shown in Column B to produced the distribution of putts in Column C. Note that the variability measures of the Column C putts are 30% less than the original putts in Column A. Thus, hitting putts harder as required by an EVR putter, does not reduce the accuracy gained with using the EVR putter. 1

[0053] Quantitatively, putting accuracy with an EVR putter improves by ρ, on average, over putting accuracy with a comparable non-EVR putter where accuracy is measured by standard deviation, where S_c=1−ρ (S_A).

[0054] S_C: Standard deviation of putts with a proportional damping putter

[0055] S_A: Standard deviation of putts with a comparably non-EVR putter

[0056] ρ: The damping proportion.

[0057] A second experiment was conducted as described above with putters having different damping constructions to illustrate that using different damping materials results in EVR putters with differing EVR profiles. FIG. 6 presents EVR measurements for the three EVR insert configurations used in the experiment.

[0058] The experiment was conducted using a putting machine programmed with seven putting force levels. Each of four putters hit eight matching golf balls at each force level. The putters were identical in construction with respect to putter length, head weight and striking surface. The putting machine hit the golf balls on a moderately fast putting green with a green speed stimpmeter reading of 11.3 feet. The only variable between each of the four putters was the insert construction as described below:

[0059] Putter 1: A putter similar to putter 10 including an insert consisting of a UHMW polyethylene striking surface meeting the USGA hardness standard.

[0060] Putter 2: A putter similar to putter 10 including an insert with the same striking surface used in Putter 1 backed with a 0.03 inch thick layer of urethane foam (Part Number 4701-50-30031-04, produced by Rogers Corp. of Woodstock, Conn.).

[0061] Putter 3: A putter similar to putter 200 including an insert with the same striking surface used in Putters 1 and 2 backed with a 0.03 inch thick layer of less dense urethane foam (Part Number 4701-30-25031-04, produced by Rogers Corp. of Woodstock, Conn.), and with the insert backplate cut-out in the fashion depicted in FIG. 16.

[0062] Putter 4: A putter similar to putter 10 including an insert with the same striking surface used in Putter 1, 2 and 3 backed by a 0.03 inch thick layer of soft urethane foam (Part Number 4701-30-25031-04, produced by Rogers Corp. of Woodstock, Conn.).

[0063] The EVR profiles displayed in FIG. 6 indicate the EVR obtained at the impact force levels required to propel a golf ball the distances indicated on the abscissa. EVR data points for the EVR putters were determined at a given impact force level by comparing the error variance (standard deviation) for a given EVR putter with the error variance (standard deviation) for the standard putter and plotting the percentage difference (error variance reduction) at that level. Best fit trend lines were drawn through the data points for each putter/insert configuration and are shown in FIG. 6 for each configuration.

[0064] The EVR of each of the EVR inserts was determined at a given impact force level by comparing the average ball distance travel produced by the damping inserts as compared to the average ball distance travel produced by the standard non-EVR insert at that same force level. The procedure was repeated at each of the seven force levels, producing the EVR profiles for each of the four putter as shown in FIG. 6. A best-fit trend line was drawn through the data points for each insert configuration. These trend lines are also shown in FIG. 6.

[0065] The EVR profile for Putter 2 presents a generally linear decreasing EVR, from 9% at 4.5 feet to 3.5% at 18.4 feet.

[0066] The EVR profile for Putter 3 shows a steep rate of EVR decrease from 18% at 4.5 feet to 9% at 12 feet and then a shallower linear decrease to 4.5% for putts at 18.4 feet.

[0067] The EVR profile of Putter 4 shows a rate of EVR decrease accelerating from 16% at 4.5 feet to 7% for putts at 18 feet.

[0068] The results shown in FIG. 6 demonstrate the feasibility of designing putters with differing EVR profiles. The EVR profiles for Putters 2, 3 and 4 in FIG. 6 show the greatest accuracy gain for short and medium length putts. These particular EVR profiles would be most helpful to golfers who have trouble with short distance putts. More specifically, Putter 3 would be the most helpful for golfers who jerk or yip their stroke on short putts.

[0069] In addition to the EVR profiles demonstrated with Putters 2, 3 and 4 of FIG. 6, putter inserts that that produce level or increasing EVR with increasing putt lengths can be created by layering materials with different damping characteristics.

[0070] The present invention has been described above with reference to a preferred embodiment. However, those skilled in the art will recognize that changes and modifications may be made to the preferred embodiments without departing from the spirit and scope of the present invention.