Do Golf Clubs Wear Out?

[0026] Two illustrative inserts 112 are shown in FIG. 2A to be inserted into corresponding cavities 115a. Other inserts (not shown) similar to inserts 112 may be inserted into the other cavities 115a, 115b, 115c and 115 in the club head 102. It will be appreciated that inserts and cavities can have different shapes and sizes. The cavities 115b positioned between neighboring grooves can be limited in size by the space between grooves and the need to avoid structurally compromising the efficacy of the grooves.

[0027] The inserts 112 are provided to function as wear indicators to allow an individual such as a golfer to understand the degree of wear that the club has undergone. For example, the insert 112 can indicate that the face has worn sufficiently to affect club performance or that the COR (coefficient of restitution) has declined, that is that the transfer of energy from the club head 102 to a ball has fallen to a level that can effect the carry distance of a golf ball when struck by the club head. The amount of stress and pressure the club head has experienced through repeated impacts in the long run causes deterioration in club head performance. Here, the goal is to inform the golfer of the degree of deterioration though the wear indicator function.

[0028] FIG. 3 provides an illustrative insert 112, which may be divided into two regions 122, 124. The regions 122, 124 each include a variable viscosity material that remains separated from one another in the absence of pressure. However, when the pressure on the regions of the insert 112 exceeds a threshold pressure, the materials in the respective regions 122, 124 mix together. Discussion of such materials and their use is provided in U.S. Pat. No. 7,353,770. The two different regions may have a distinguishable visual appearance from one another such that when the materials mix together, a golfer can visually discern the difference from when the materials in the regions 122, 124 were not mixed. For example, before repeated impacts with a golf ball, the boundary 123 between the regions 122, 124 blends in with the remaining portions of the club head 102 (e.g., the toe portion 109, the heel portion 111, the hosel 104). Over time from repeated impacts to the face 103 of the club head 102 the regions 122, 124 mix or bleed together, and the appearance of the insert 112 gradually changes to contrast (e.g., distinct color difference, variations in color intensity, different shades or patterns, etc.) with the face 103 and/or hosel 104 as a whole. By calibrating the degree of mixture between the two regions 122, 124, the degree of wear the club has undergone may be reflected by the level of contrast between the insert 112 and other portions of the golf club head 102. Those of ordinary skill in the art will appreciate that regions 122 and 124 may be formed of a variety of known materials that have a tendency to mix together to a great degree when under pressure or stress. In one aspect, the regions 122, 124 may be formed of a viscoplastic or non-Newtonian liquid. Viscoplastics behave like solids below a certain stress level such as a yield stress. Above that stress level, the viscoplastics behave like a viscous liquid. The regions 122 and 124 may be formed of another non-Newtonian liquid such as pseudoplastics, which are also referred to as shear thinning liquids, which experience a decreased viscosity upon an increase in shear rate. The insert 112 will in most aspects have a surface coating so that the non-Newtonian liquid is not directly exposed to the environment. The surface coating for an insert 112 on the face 103 is generally durable and able to withstand the repeated impact of the club head face 103 with a golf ball. In one example, the surface coating can be a clear polyurethane coating similar to the material utilized in golf balls. The surface coating may be applied using the methods known by one of ordinary skill in the art such as spray coating, or depositing particles of the coating on the surface and heating the surface so that the particles attach to the surface forming a coating.

[0029] When the golf club head is relatively new, regions 122 and 124 including viscoplastic materials, will generally remain distinct or separate from each other at stresses below the yield stress. As the club head 102, for example the face 103, begins to lose its resiliency or spring like characteristics, the stress on regions 122 and 124 will increase and eventually exceed the yield stress such that the regions 122 and 124 will become viscous and mix together. Since the mixing of the viscous materials causes a visual change to the insert 112, a golfer can visually recognize that the performance
of the club head is deteriorating. For example, the mixing of regions 122 and 124 may cause a progressively darker region to form visually notifying the user that the club head performance has weakened and it is time to obtain a new club. The yield stress may be calibrated to the known rate of wear of a golf club.

[0030] It will be appreciation that regions 122 and 124 may be non-Newtonian viscoplastics or non-Newtonian shear-thinning materials. For example, regions 122 and 124 may be formed of Newtonian materials that have a viscosity such that the degree of mixing of the two regions 122 and 124 may be controlled as a function of pressure as is known in the art. It is also contemplated that the regions 122 and 124 may be formed of a material or materials having a viscosity that decreases as a function of time such that the viscosity of regions 122 and 124 would decrease over time and blending would occur.

[0031] In one aspect, the regions 122 and 124 may be formed of the same material having the same viscosity as a function of pressure on the regions. However, in alternative embodiments, the regions 122 and 124 may be formed of the same material, but may have different viscosities for a given pressure. Moreover, the regions 122 and 124 may be different materials altogether. For example, one of the regions 122, 124 may be a viscoplastic material, while the other is a shear-thinning material. In a further aspect, one of the regions may be formed of a variable viscosity material as described above, while the other material is formed of a solid or a material having a constant viscosity. According to this aspect, the constant viscosity material would have a porosity allowing the variable viscosity material to bleed into the constant porosity material as a function of pressure.

[0032] As discussed, the regions 122 and 124 will have a visually distinct appearance from an unmixed state and a mixed state so that a golfer can visually discern when and how much the regions have blended together. In one example, the region 122 may be clear and the region 124 may include a color dye, such as red dye. Both regions 122 and 124 may be colored with different colored dyes. In these cases, upon a change in viscosity, the two colors can mix together to form a third color as the wear indicator. In another example, both materials may be clear, but one of the regions may have colored particles suspended within the material. Thus, upon wear and the threshold yield stress on the regions 122 and 124 being exceeded, the region including the particles may bleed into the other region so that particles then enter the opposite region.

[0033] An insert in the hosel 104 showing signs of wear will indicate that the hosel is losing some stiffness. Generally speaking, wear exhibited by an insert means that performance of the club head 102 is deteriorating in one or more ways such as through nicks in the face, grooves in the face becoming shallower or losing their shape, and the surface of the face becoming uneven or deviating from the original manufactured structured.

[0034] FIG. 2B shows the golf club head 102 from a rear perspective including cavities 115e, 115f and 115g, which are configured to receive an insert 112. Cavity 115e is provided on the sole portion 105 and configured to receive an insert 112. Cavities 115f are provided on a region of the body 101 on the rear surface (on an opposite side of the body from the face 103) in a region closer to the sole portion 105 than the top surface 117 of the club head 102. Cavities 115g are provided on a region of the body 101 on a rear surface closer to the top surface 117 of the club than the sole portion of the club. One cavity 115a, 115b, 115c, 115d, 115e, 115f or 115g or any combination of cavities may be provided for the club head 102 to allow for a golfer to detect that the golf club is wearing and the degree of wear.

[0035] In still another aspect a substantial portion of the rear surface of the upper member club head 102 may function as the wear indicator. That is, a portion of the rear surface of the body 101 behind the face 103 may be formed as one of the above described materials to provide an indication of the degree of wear a club head has undergone. According to this aspect a translucent coating such as clear polyurethane coating may be provided on the surface such that when the yield stress exceeds the threshold and mixing of materials takes place, a person may be readily able to visually discern the wear state of the club head 102. Alternatively, a clear plastic or clear polymer may function as a window to the wear indicator on the rear surface. In this instance, a color change can be readily seen through the “window”.

[0036] FIG. 4 illustrates a wood-type golf club 120 according to one example of this invention including a club head 121 with cavities 115a, 115b, 115c, 115d and 115h. For ease of reference, some of the same reference numerals have been used for the wood-type golf club 120 as for the iron type golf club 100 and the more detailed descriptions thereof have been omitted. The inserts 112 may be applied to a wood type club head 121 in the same matter as an iron type club head 102 as discussed with respect to FIG. 2A. Though not shown, the cavities 115b in a central portion of the face 103 may be spaced between neighboring grooves 113e and 113f. The grooves may extend through the central region. The cavities 115h are positioned above the grooves and the desired or optimum ball impact zone represented by the substantially circular portion in a center portion of the face 103 between the grooves of the club head 121.

[0037] According to another aspect of an iron-type golf club head, a wear indicator may be provided in a two-part club head as described in commonly assigned, co-pending U.S. patent application Ser. No. 12/564,988 entitled “Golf Club Having Two-Part Head”, which is herein incorporated by reference. FIG. 5A illustrates a front view of a two-part club head 200, which maintains the appearance of a conventional, single piece club head. That is, the face size and profile are similar or substantially similar to a conventional club head. However, the club head 200 is formed of two distinct pieces. The club head 200 shown includes a face 202 having ball striking member 202a which is connected to the hosel region 204, which can be connected to a shaft (not shown). The ball striking member 202a may be connected to the hosel region 204 via known methods of connection, including adhesives, cements, welding, mechanical fasteners, and the like. As another alternative, the ball striking member 202a may be integrally formed with the hosel region 204.

Interesting idea, but I am not sure it is a compelling selling point.