Golf Practice Mat
A golf practice mat comprising a backing defining an upper surface and a lower surface, a first plurality of elongated polyethylene fibers stitched onto the backing so as to project upwardly from the upper surface thereof, a second plurality of durable nylon fibers stitched onto the backing adjacent to and curled about the first plurality of fibers, the first and second pluralities of fibers being adhesively bonded to the backing and a shock absorbing pad bonded to the lower surface of the backing.
The present invention relates to an improved golf practice mat for instructional and practice purposes. It is usable indoors and outdoors and simulates the look and feel of natural grass. The use of artificial mats in lieu of natural grass as a practice surface before hitting golf balls is well known and wide spread due to the maintenance and area requirements for using natural grass as a practice surface. A properly stuck iron shot contacts the ball before the hitting surface, driving the ball and club downwardly and through the grass, leaving a divot in the grass. The repetitive striking of balls as occurs during practice is obviously quite damaging to the natural hitting surface. Accordingly, the ball striking area must be constantly moved to fresh grass while the previously used area is regenerated. The resulting maintenance and area requirements can be alleviated by the use of an artificial hitting surface.
A variety of artificial golf practice surfaces, also known as golf mats, have here to fore been developed as a substitute for natural grass. The surfaces attempt to simulate the look and feel of a natural grass surface. The results of such efforts, however, have not proved overly successful and golfers universally prefer natural grass for practice over artificial surfaces. A typical golf mat is comprised of synthetic turf attached to a shock absorbing pad.
Mechanical devices have also been employed which allow the hitting section of the mat to move upon impact. None of such devices, however, have proved successful in simulating the resistance in give of hitting down and through natural grass. These mechanical devises also have limited utility due to premature wear of their relatively small hitting surface which must take the impact of each hit. In addition, most golfers prefer the convenience of being able to hit different shots from various areas of the practice mat rather than having to carefully place the ball in the exact spot before each shot.
More typical golf mats, however, either comprise synthetic turf attached to a shock absorbing pad or synthetic brush like bristles attached to a base without the inclusion of a shock absorbing pad. Both types of mat typically employ a nylon which is a highly durable material but also high in friction. Brush style mats utilizing nylon bristles exhibit an even higher coefficient of friction than the synthetic turf mats and, without a shock absorbing pad, present a very hard surface resulting in an overall very poor feel for the golfer. Synthetic turf mats comprised of a nylon fiber such as ASTRO TURF (a federally registered trademark of Textile Management associates, Inc.) also exhibit high frictional drag at impact, again resulting in a poor feel for the golfer. Synthetic turf base mats comprised of polypropylene fibers are also known. While polypropylene fiber turf is less durable than nylon and has a lower coefficient of friction than a nylon turf, it still exhibits sufficient drag at impact so as not to replicate the feel of natural grass. Synthetic turf comprised of polyethylene fiber has also been developed but has not proved satisfactory in golf practice mats due to its poor durability producing an unacceptably short product life.
It would be highly desirable to produce a golf mat formed of synthetic material or materials which retains the durability of the practice mats heretofore available but which more accurately replicate the feel of natural grass when striking a golf ball resting on the practice surface. The golf mat of the present invention obtains that result.
SUMMARY OF THE INVENTIONThe golf mat of the present invention comprises a synthetic turf formed of a first plurality of elongated durable fibers having a low coefficient of friction, a second plurality of thinner, curled and twisted highly durable supporting fibers and a backing for securing the fibers to a shock absorbing resilient pad. The elongated fibers are preferably formed of a durable polyethylene copolymer that provides the actual hitting surface for the mat and provides that surface with a low coefficient of friction resulting in an exceptional feel and simulating the look and feel of natural grass. The curled supporting fibers are preferably formed of a durable nylon fiber that provides a resiliency to the mat for an extended wear life. The fibers are secured to durable synthetic backing, preferably by means of a tufting process and the backing, with the attached fibers thereto, is bonded to the pad. The shock absorbing resilient pad is preferably formed of a chemically cross-linked polyethylene foam that provides a highly durable shock absorber for the mat capable of retaining its configuration and shock absorption properties after repeated usage thus, contributing to both the durability and feel of the golf mat over the life of the mat. The resulting turf and pad combination reduces the bouncing effect found in conventional golf mats, allowing the club to move down and through the ball after impact simulating the feel of striking a golf ball on natural grass.
Referring now in detail to the drawings, the artificial practice surface or golf practice mat 10 of the present invention, also referred to as a golf mat, can be formed in any desired area size depending on its application and comprises a first plurality of elongated fibers 12, a second plurality of supporting fibers 14, a turf backing 16 and pad 18. The backing 16 with the fibers 12 and 14 that are stitched thereto, as will be described, are collectively referred to as the turf. The first plurality of fibers must be very durable, particularly when subjected to a load in a transverse direction, and exhibit a low coefficient friction to provide the surface with the proper feel. Polyethylene fibers marketed by Ten Cate Thiolon under the designation Thiolon XP have proved to provide such characteristics. Such fibers are extruded and formed as fibrillated band fibers and have a fineness of about 8500-11,500 denier with about 10,000 denier being most preferable.
While most polyethylene fibers have a low coefficient of friction, they lack sufficient durability for use in a golf mat. When a synthetic fiber is subjected to a load in a transverse direction of the type generated by a golf club striking a ball, the fiber must have a tensile strength at break of greater than 1 megapascal (MPa) or >145 psi/in2 and an elongation of >50%. The Thiolon fibers 12 that are preferably employed in the present invention have a measured coefficient of friction of 0.174, yet have a tensile strength at break of about 2.8 MPa and an elongation of 100% in contrast to a standard polyester fiber which may have a slightly lower coefficient of friction but a tensile strength at break of 0.3 MPa and 2% elongation when tested in the transverse direction. The coefficient of friction of the elongated, fibrillated fibers 12 was determined by using the following test parameters and procedure:
Using the above methodology, the coefficient of friction was measured for both the elongated polyethylene fibers 12 and the supporting fibers 14 (which, as will be discussed, are formed from eight strands of nylon 66 fibers). Additionally, the coefficient of friction was determined for a conventional polyethylene fiber from Bonar Plastics, Inc. (Bonar Yarns No. 29/42). The results of this testing are illustrated in
The Thiolon XP fibers 12 that provide both the desired mechanical strength and low coefficient of friction are comprised of two synthetic compounds wherein the first compound comprises a polymer and the second compound comprises a plastomer. The first compound is polyethylene and both (linear) low-density polyethylene or high density polyethylene can be utilized. The plastomer comprising the second compound is a copolymer of ethene, with one or more alpha.-olefins having 3-10 carbon atoms, in particular propene, isobutene, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene as the comonomer. Alternatively, the plastomer could comprise a copolymer of ethene, with 1-octene as the comonomer. The proportion of comonomer ranges between about 0 and 50 wt. %. More preferably, the proportion of comonomer ranges between about 5 and 35 wt. %. The proportion of the plastomer in the fiber is about 30-80 wt. %. More preferably, the proportion of the plastomer in the fiber is about 35-50 wt. %. The density of the plastomer generally ranges between about 860 and 970 k/m3. It is to be understood, however, that other fibers exhibiting such a low coefficient of friction and also having the above-described desired durability characteristics could be utilized in forming the elongated fibers 12.
The supporting fibers 14 are very durable and are curled and twisted about the elongated fibers 12 as illustrated in
In one embodiment of the present invention, the backing 16 of golf mat 10 that carries the fibers 12 and 14 is formed of two layers 16A and 16B (see
To prevent the backing from warping while retaining its flexibility, it is important that the backing does not become rigid during the stitching of the fibers thereon. Accordingly, on open weave is employed to relieve the tension in the pile. However, in a conventional turf forming process, after the fibers are stitched onto the backing, the backing and attached fibers are inverted such that the adhesive that locks the fibers to the backing is applied from above to the backside of the backing and the pad, if any, is placed thereover. With an open weave material, the adhesive will seep downwardly therethrough and onto the exposed fibers extending from the backing. Accordingly, a second or upper backing layer 16B is used above and adjacent the primary lower backing 16A which is formed of a more dense material to prevent the seepage of the adhesive through the backing and onto the fibers. The second backing layer 16B is bonded to the primary layer 16A by the adhesive seeping through the more porous primary backing layer 16A onto the second layer 16B.
In the above-described first embodiment of backing 16, the primary backing 16A is formed of a material that provides a dimensionally stable foundation for superior tuftability and pattern definition. It also combines strength with moisture and mildew resistance along with easy handling and long term durability, while offering highly versatile characteristics throughout the manufacturing and installation process. A woven polypropylene material marketed by Propex Fabrics in Dalton, Ga. under the registered trademark POLYBAC® has proved to provide these desired characteristics. This material is of an open weave configuration and has a pick count of 13 (number of weaves per inch). A pick count of about 11-22 would be acceptable to provide the desired flexibility.
In addition to being made of a denser material so as to prevent adhesive from seeking therethrough, the second or upper backing layer 16B should also provide mechanical stability for the fibers 12 and 14, be tear resistant, dyeable, weldable, non-fraying and easy to laminate. A thermally bonded spunlaid non-woven material marketed by Colback Fabrics in the Netherlands under the name COLBOND UTM 100 has proved to provide these desired characteristics for the second backing layer 16B. This material is a thermally bonded spunlaid non-woven material made from a bicomponent filament having a polyester core and a polyamide (nylon 6) skin. The material has a density of about 100 g/m2 and prevents the adhesive from seeping therethrough. The resultant laminated backing 16 that carries fibers 12 and 14 gives the golf mat 10 superior turf bond and dimensional stability (resistance to stretching and/or shrinkage).
The elongated fibers 12 that exhibit both durability and a low coefficient of friction and the durable supporting fibers 14 are concurrently secured to backing 16 by a process known as tufting in which the synthetic fibers are inserted into the backing material. The same process is used in the manufacture of carpet. In the tufting process of the present invention, the two separate fibers 12 and 14 are fed through each tufting needle which requires large tufting needles and very sharp cutting blades to handle concurrently both fibers 12 and 14. Two manufacturers who have the capability of making the dual fiber turf of the present invention are Turfstore located in Calhoun, Ga. and Grass Tex, Inc. located in Dalton, Ga. In addition to the materials employed in the manufacture of the turf portion of the golf mat 10, the stitch rate, gauge rate and pile height are significant factors in the construction of the mat that affect the product density and product performance.
Tufting involves high-speed machines with numerous “stitching” (tufting) needles lying side by side across the width of the turf. A typical tufting machine is a large sewing machine with 369 to 480 needles across a 15 foot width. The separation between these needles is the gauge rate. Synthetic turf typically has a ⅜-inch or ½-inch gauge. To provide the golf mat of the present invention with increased density a gauge rate of ⅜-inch is preferably employed. Grass Tex, Inc. has equipment capable of tufting the dual fiber configuration of the present invention on a ⅜-inch gauge. The number of tufts along the length of turf is known as the stitch rate. A stitch rate is measured in stitches per three inches along the length of the turf. In mat 10, a stitch rate of 22 stitches per three inches was employed. The pile height, which is the third component of turf density, is measured from the upper surface of the backing 16 to the top of the elongated fibers 12 and 14 which are preferably cut to the same height. The curling of the supporting fibers 14 results from the fibers being subjected to elevated temperatures during the curing of the adhesive and gives those fibers the appearance of being shorter in the final product. The pile height, i.e., the height of the turf, is preferably about ¾ of an inch to provide the golf mat 10 with its desired appearance and feel.
While the above-identified parameters have been utilized in the successful manufacture of golf mat 10, variations in these parameters could be employed. The density of the turf provides a measure of durability; the higher the density the more durable the turf. The density is the weight of the pile yarn (fibers) in a unit volume of carpet. U.S. government FHA density (D), expressed in ounces per cubic yard, is given by the formula: D=(W×36)/T in which D is the density; W is the “face weight” or the combined weight of the fibers in ounces per yard; and T is the pile height or thickness in inches. Thus, in the aforesaid example of the present invention in which the gauge=½ inch, pile height=¾ inch, stitch rate=22 and face weight=56 oz., the density is 2484 ounces per cubic yard. Thus, the density, and hence the durability, of the golf mat 10 can be enhanced by increasing the stitch rate and/or the face weight of the fibers. Utilizing a gauge of ⅜ in. would provide a density up to 3300 ounces per cubic yard. However, if the turf is made overly dense, the club face would bounce off the golf mat 10 and not pass down and through the turf as intended. It is believed that a density range for the turf of about 1600 to 3300 oz./cu. yd. is preferred.
The adhesive that is used in forming golf mat 10 should exhibit good tensile strength, be flexible, durable, water resistant and adhere to high surface energy materials such as those likely to be employed in backing 16. Polyurethane adhesives are preferably employed in formation of the golf mat 10, more particularly, a single component heat cured polyurethane adhesive comprised of polyols and isocyanates which polymerize when heated to form a urethane linkage based polymer that exhibits all of the above-described physical characteristics.
To form the golf mat 10 using a conventional turf forming process, the two backing layers disposed in an adjacent disposition are fed into a tufting machine that stitches the fibers 12 and 14 onto the adjacent backing layers 16A and 16B to form the turf which can then be formed into a roll 50 for storage and handling. The uncoated roll of turf 50 is then directed to a coating station 52 (see
The shock absorbing pad 18 preferably employed in the present invention is comprised of chemically cross-linked foam and provides the golf mat with improved performance over conventional padding material. The foam has a thickness of about 0.7 inches and can be obtained from Armacell LLC in South Holland, Ill. under the designation OLETEX CAJN 400. The material is a closed cell polyethylene foam and is lighter in weight for the same compressive strength than the PVC/nitrile foam commonly used for golf mats and, more importantly, has less of a tendency to remain compressed than the foams heretofore commonly used in golf mat applications. Tests have shown that such foam after 50% compression for 24 hours still recovers about 80-84% of its original thickness. Such foam incorporated into the golf mat 10 of the present invention has been shown to retain its shock absorbing and resilient properties after over 150,000 simulated impacts or compression cycles, thus providing improved shock absorption and better feel over the life of the golf mat 10.
In a second and preferred embodiment of the present invention, the backing 16 is of a single layer construction and formed of a durable and mildew resistant and relatively open material to relieve tension in the pile such that when the fibers 12 and 14 are stitched thereon, it will allow the turf to lay flat without curling. In the preferred construction of this second embodiment of the invention, the backing 16 is formed of the same POLYBAC open-weave polypropylene textile material used in the lower layer 16A of the prior embodiment. To avoid seepage of the adhesive through the backing during fabrication, the backing 16 with the fibers 12 and 14 stitched thereon by tufting machine is adhesively bonded to the shock absorbing pad 18 by a process in which the adhesive is applied directly to the upper surface of 18′ of the foam pad 18.
An example of such a process is schematically illustrated in
In the two embodiments of the golf mat of the present invention, the various desired physical characteristics of the two fibers 12 and 14, backing 16, shock absorbing pad 18 and adhesive 20 are identified and examples of particular products having those characteristics are set forth. It is to be understood that these examples are illustrative of materials that have been successfully employed in the manufacture of the present invention. Other materials exhibiting comparable characteristics could be employed in carrying out the present invention without departing from the spirit and scope thereof. In addition, changes and/or modifications to the methods of manufacturing the present invention could also be made without departing from the spirit and scope of the present invention. For example, the two fibers 12 and 14 comprising the turf could be tufted in separate needles. The gauge of the turf might be made as tight as 0.25 inches and every other needle could be offset in a zigzag pattern. Insofar as these and other changes and/or modifications are within the purview of the appended claims, they are to be considered as part of the present invention.
Claims
1. A golf practice mat comprising a backing defining an upper surface and a lower surface, a first plurality of elongated polyethylene fibers stitched onto said backing so as to project upwardly from said upper surface thereof, a second plurality of durable nylon fibers stitched onto said backing adjacent to and curled about said first plurality of fibers, said first and second pluralities of fibers being adhesively bonded to said backing and a shock absorbing pad bonded to said lower surface of said backing.
2. The golf practice mat of claim 1 wherein said polyethylene fibers have a coefficient of friction within the range of 0.125-0.200 and a tensile strength having a break point in excess of 1.5 megapascals.
3. The golf practice mat of claim 1 wherein said first and second plurality of fibers define a turf having a density within the range of 1600-3300 ounces per cubic yard.
4. The golf practice mat of claim 2 wherein said nylon fibers have a fineness within the range of 3570-4830 denier.
5. The golf practice mat of claim 2 wherein said polyethylene fibers have a fineness within the range of 8500-11,500 denier.
6. The golf practice mat of claim 5 wherein said nylon fibers have a fineness within the range of 3570-4830 denier.
7. The golf practice mat of claim 2 wherein said backing is comprised of an open weave material having a pick count within the range of 11-22.
8. The golf practice mat of claim 2 wherein said first and second plurality of fibers define a turf having a density within the range of 1600-3300 ounces per cubic yard.
9. The golf practice mat of claim 2 wherein said first and second plurality of fibers comprise a turf, said turf having a gauge within the range of about 0.375-0.500 in. and wherein said first plurality of fibers define a pile height of about 0.750 in.
10. The golf practice mat of claim 2 wherein said first and second pluralities of fibers are adhesively bonded to said backing by a single component heat cured urethane adhesive comprised of polyols and isocyanates.
11. The golf practice mat of claim 4 wherein said first and second plurality of fibers define a turf having a density within the range of 1600-3300 ounces per cubic yard.
12. The golf practice mat of claim 4 wherein said backing is comprised of an open weave material having a pick count within the range of 11-22.
13. The golf practice mat of claim 1 wherein said backing is comprised of an upper backing layer and a lower backing layer, said lower backing layer being adhesively bonded to said upper layer and formed of an open weave woven material and wherein said upper layer is comprised of a non-woven material having a density greater than the density of said lower backing layer.
14. The golf practice mat of claim 2 wherein said backing is comprised of an upper backing layer and a lower backing layer, said lower backing layer being adhesively bonded to said upper layer and formed of an open weave woven material and wherein said upper layer is comprised of a non-woven material having a density greater than the density of said lower backing layer.
15. The golf practice mat of claim 13 wherein said open weave material comprises polypropylene and said non-woven material comprises a thermally-bonded spun laid non-woven material.
16. The golf practice mat of claim 2 wherein said pad is comprised of chemically cross-linked closed cell polypropylene foam.
17. A golf practice mat comprising a backing defining an upper surface and a lower surface, a first plurality of elongated fibers stitched onto said backing so as to project upwardly from said upper surface thereof, a second plurality of fibers stitched onto said backing adjacent to and curled about said first plurality of fibers, said first and second plurality of fibers being adhesively bonded to said backing and a shock absorbing pad bonded to said lower surface of said backing and wherein said first plurality of fibers define a coefficient of friction within the range of 0.125-0.200 and a tensile strength having a breaking point in excess of 1.5 megapascals and wherein said second plurality of fibers are comprised of a nylon material having a fineness within the range of 3570-4830 denier.
18. The golf practice mat of claim 17 wherein said pad is comprised of chemically cross-linked closed cell polypropylene foam.
19. The golf practice mat of claim 17 wherein said backing is comprised of an open weave material having a pick count within the range of 11-22 stitches per 3 inches.
20. The golf practice mat of claim 17 wherein said first and second plurality of fibers define a turf having a density within the range of 1600-3300 ounces per cubic yard.
21. The golf practice mat of claim 15 wherein said first plurality of elongated fibers are comprised of polyethylene and said backing is comprised of an open weave material having a pick count within the range of 11-22 stitches per 3 inches.
22. The golf practice mat of claim 17 wherein said first and second plurality of fibers comprise a turf, said turf having a gauge within the range of about 0.375-0.500 in. and wherein said first plurality of fibers define a pile height of about 0.750 in.
23. The golf practice mat of claim 20 wherein said backing is comprised of an open weave material having a pick count within the range of 11-22.
24. The golf practice mat of claim 20 wherein said first and second plurality of fibers comprise a turf, said turf having a gauge within the range of about 0.375-0.500 in. and wherein said first plurality of fibers define a pile height of about 0.750 in.
25. The golf practice mat of claim 20 wherein said backing is comprised of an open weave material is comprised of polypropylene.
26. The golf practice mat of claim 23 wherein said first plurality of elongated fibers are comprised of polyethylene.
27. The golf practice mat of claim 26 wherein said backing is comprised of an open weave material is comprised of polypropylene.
28. The golf practice mat of claim 19 wherein said pad is comprised of chemically cross-linked closed cell polyethylene foam.
29. The golf practice mat of claim 20 wherein said pad is comprised of chemically cross-linked closed cell polyethylene foam.
30. The golf practice mat of claim 22 wherein said pad is comprised of chemically cross-linked closed cell polyethylene foam.
Type: Application
Filed: Oct 24, 2006
Publication Date: Apr 24, 2008
Inventors: Edison R. Lara (Palos Verdes Estates, CA), Charles H. Jackson (Los Angeles, CA), Donald Williams (Tarzana, CA), James Howard Robbins (Hudson, OH)
Application Number: 11/552,476
International Classification: A63B 69/36 (20060101);