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[0001]    The present application is a continuation-in-part of U.S. patent application Ser. No. 10/733,806 filed Dec. 10, 2003. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to golf mats, and more particularly to a golf mat having an artificial turf including a plurality of groups of fibers, each group including both non-linear fibers and substantially straight fibers sewn into a backing through a common opening, and having infill particles adhered to the non-linear fibers and lower portions of the straight fibers. 
       DESCRIPTION OF THE PRIOR ART 
       [0003]    Golf mats for use as a practice playing surface are most effective if they simulate the feel of natural turf. A variety of mat constructions have been designed for this purpose. U.S. Pat. No. 6,156,396 uses a relatively thick base pad of resilient material (foam rubber), and an artificial grass-like carpet that is slidably positioned on the base so as to absorb club force, which is more like a natural turf than a rigidly mounted carpet. 
         [0004]    U.S. Pat. No. 5,830,080 by Reynolds discloses a turf simulating surface including a grass-like carpet layer placed over layers of material, each layer designed to simulate the shock absorbing nature of corresponding layers of soil. 
         [0005]    U.S. Pat. No. 4,497,853 by Tomarin, and U.S. Pat. No. 3,995,079 by Haas, Jr. also include layers of shock absorbing material beneath a grass simulating carpet. They also place granules, such as sand and/or rubber particles, covering/coating a lower portion of the grass-like carpet, giving support for the grass-like fibers and simulating the effect of soil. A disadvantage of the loose infill covering/coating in a golf mat is that it is displaced when impacted by a club head, which can result in undesirable variations in the infill depth, and air-born particles that can be irritating to the golfer. 
       SUMMARY 
       [0006]    It is an advantage of this invention in that it provides a golf playing surface having an improved stability. 
         [0007]    It is a further advantage of this invention in that it provides a golf mat with improved durability. 
         [0008]    It is a still further advantage of this invention in providing a golf mat wherein a club stroke does not bottom out in the mat. 
         [0009]    It is another advantage of this invention in providing a golf mat with improved shock absorption when a club head strikes the mat. 
         [0010]    It is another advantage of this invention in that it provides a golf mat that will hold a golf ball tee without drilling a hole in the mat. 
         [0011]    In one embodiment of this invention, a golf mat includes artificial grass fibers attached to and extending upward from a backing material, which may be one or more layers. The artificial grass fibers include groups of at least two different kinds of fiber sewn through a common path in the backing material. One of the kinds of fibers in each group is shaped so as to appear like a blade of grass. The other kind of fiber in each group is pre-stressed/crimped so that the relaxed shape of the fiber is nonlinear, resembling a curlicued or articulated form having lateral excursions. The lateral excursions cause portions of one such pre-stressed fiber to overlap and interfere with another, forming a mesh. The height of the pre-stressed fibers in their relaxed state in the turf is less than the height of the relatively unstressed artificial grass fiber(s). The crimped fibers form a resilient mat with impact characteristics similar to natural turf. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0012]      FIG. 1A  illustrates a golf mat formed with artificial turf according to the present invention; 
           [0013]      FIG. 1B  is an enlargened view of a portion of  FIG. 1A  configured for illustrating the construction of the mat of  FIG. 1A ; 
           [0014]      FIG. 2  illustrates a golf tee held by the golf mat; 
           [0015]      FIG. 3  illustrates two fibers through one needle, and fiber tension; 
           [0016]      FIG. 4A  shows one type of artificial grass fiber construction; and 
           [0017]      FIG. 4B  shows the fiber of  FIG. 4A  rolled up. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    While the present invention will be described herein with reference to particular embodiments thereof, a latitude of modifications, various changes and substitutions are intended, and it will be appreciated that in some instances some features of the invention will be employed without a corresponding use of other features without departing from the spirit and scope of the invention as described with respect to the preferred embodiments set forth herein. 
         [0019]    A golf mat  10  of the present invention is shown in  FIG. 1A , having artificial turf  11 .  FIG. 1B  is an enlargened view of a section “A” of the mat of  FIG. 1A  for illustrating the construction of the artificial turf  11 , and also showing alternative base layers  13  which can be of any number, thickness and resiliency. The artificial turf  11  includes a backing material  12  with two different kinds of fiber  14  and  16  sewn into it. Groups of fibers, each group including at least one grass-like fiber  14  and one non-linear fiber  16  pass through the same passages  18  through the backing  12 . Fiber  14  is an artificial grass blade that can be constructed in a number of ways to give the turf a grass-like appearance. Fiber  16  is pre-stressed into a non-linear shape. The tops  20  and  22  of the fibers are cut, forming cut ends, and thereby forming a “cut fiber” carpet/artificial turf, resulting in the fiber  14  appearing grass-like. The fibers  14  are relatively un-stressed and have only minor deviations from linearity, similar to a linear/straight grass blade appearance. Fibers  16  are pre-stressed prior to being sewn into the backing  12 , and upon being sewn into the backing  12  and released from the sewing machine, they return to a non-linear shape. The sewing machine applies tension to the fiber  16 , holding it in a linear shape as it is sewn. Once released by the sewing machine, the fibers  16  retract into their pre-stressed non-linear shape, causing them to form a mesh of fibers at a level below that of the straight fibers  14  as shown in  FIG. 1 . In this way, the fiber mesh including a lower portion of the fibers  14  and the fibers  16  resembles grass thatch. The golf mat therefore provides a resistance that is similar to natural grass turf when a golf club head impacts the mat. The club head first impacts the taller, grass-like fiber portions that extend above the height of the non-linear fibers  16 . These portions provide resistance to the club head in a similar manner to natural grass. If the upper portion of grass-like fibers  14  does not stop the club head, the head then impacts the mesh, consisting of lower portions of the fibers  14  and the non-linear fibers  16 , which provides further resistance to the club head, similar to a club head hitting the thatch in natural turf. The non-linear fibers  16  have lateral excursions, for example as indicated by the letters “x” for one fiber  16  in  FIG. 1B .  FIG. 1B  shows 10 groups, such as group  17  of fibers, with each group of fibers sewn through a common path  18  through the backing  12 . The fibers  16  and group spacing “S” are configured so that the lateral excursion of one such fiber  16  of one group overlaps the lateral excursion of a fiber  16  from an adjacent group, and forms a mesh of overlapping fibers  16 . For example, note that the excursion of fiber  16 A of one group overlaps the excursion of fiber  16 B from an adjacent group. The height of the installed non-linear fibers  16  is noted as “H 2 ” which is less than the height H 1  of the grass-like fibers. A preferred height H 1  is ⅞ inch, and a preferred range of H 1  is from ⅞″ to 3″ A preferred height of H 2  is ⅝ inch, and a preferred range of H 1  is from ⅝″ to 2½″ For the golf mat as disclosed, the fibers are preferably sewn with a stitch spacing S in the range of 0.350″ to 0.375″ with a preferred spacing of 0.350″, but other values of S are also included in the present invention. The combination of the grass-like fibers  14  and non-linear fibers  16  provides a shock absorbing and somewhat resilient layer, similar to that experienced on natural turf which generally has a layer of shock absorbent thatch. The tufted carpet/golf mat shown in  FIGS. 1A and 1B  as described includes the fibers  14  and  16  which are yarns/threads of synthetic material such as polypropylene, polyethylene, nylon or other synthetic yarns. The structure of  FIGS. 1A and 1B  is an improvement over the prior art in that it is more durable, is more grass-like in appearance and structure, and provides more cushion. Although two different yarns/fibers are shown sewn through common openings in the backing  12 , the present invention also includes other numbers of yarn/fibers sewn through common openings. The fibers/yarn can have different constructions, denier, twist, and crimp. The golf mat shown is rectangular, but it can be of any shape, including square, octagonal, rectangular, etc. The method of construction of the golf mat  10  differs from the prior art in that it is sewn with multiple yarns through a single needle eye. This will be illustrated more clearly in reference to  FIG. 3 . 
         [0020]    The layer of height H 2  including the crimped/non-linear fibers  16  forms a cushion resembling natural grass thatch, and reduces shock and resists bottoming out of a golf club stroke. This reduced shock and resistance to bottoming out is a significant improvement over artificial turf having only fibers similar to the grass-like fibers  14 . 
         [0021]    Another useful feature/embodiment of the present invention is illustrated in  FIG. 2 , wherein a golf mat  26  constructed as described above, has a lower, more dense portion  27  with fibers including both the straight  14  and crimped  16  fibers, that is sufficiently dense so as to hold a golf tee  28  erect with a golf ball  30  thereon as shown. A preferred height H 1  of the grass-like fibers is approximately ⅞ inch, with a preferred height range of ⅞″ to 3″. A preferred height range of H 2  of the crimped fibers is ⅝ inch, with a preferred range of ⅝″ to 2½″. A preferred weight of the mat, not including alternative layers  13 , is in the range of 60 to 90 ounces per square yard. The structure shown in  FIG. 2  avoids the need for prior art structures such as drilling a hole in the mat for holding a golf tee, or using a vertical rubber tube for simulating a golf tee. 
         [0022]    During the sewing process, fibers  14  and  16  are both threaded together through the same sewing machine needle passages, and therefore pass through the same passages  18  through the backing through which the needle is inserted. Axial/longitudinal tension is provided on the fibers  14  and  16  by the sewing machine, which keeps both fibers  14  and  16  in a controlled/tensioned line, and most importantly, fibers  16  are held in an uncrimped, straight line. Upon being sewn into the backing  12 , the tension on fiber  16  is released and it returns to its pre-stressed/crimped condition, that could be described as curlicued. 
         [0023]    In one embodiment, the fibers  14  are constructed of polyethylene and fibers  16  of nylon. The polyethylene has a slick surface similar to a grass blade, which provides comparable resistance to a golf club head when the turf is in a golf mat. In a further embodiment of the present invention, the turf  11  can be a playing field such as a football field, and the slick surface helps avoid a player from twisting an ankle, which would more easily occur if the turf has a high coefficient of friction. The dimensions of the stitch spacing S and row spacing R, are preferably selected along with the design of the pre-stressed shape of the fiber  16 , so that lateral excursions of a fiber  16  from one passage  18  overlap the excursions of a fiber  16  from an adjacent passage  18 . In this way, in one embodiment an effective mesh of fiber  16  is formed to hold a golf tee. The density of fibers and fiber overlap can also can be configured so as to resemble natural turf. 
         [0024]      FIG. 3  is provided to illustrate the tension applied to the fibers  14  and  16  during the process of sewing. The initial ends  32  of the fibers  14  and  16  are secured during the process. The needle  34  is inserted through the backing  12 , taking both fibers  14  and  16  through a common passage  18 . A hook  36  grabs the loop of fibers and keeps the fibers from retracting back through the passage  18  as the needle  34  is retracted. The sewing machinery then inserts the needle  34  through the backing again at a stitch space “S” ( FIG. 1B ) from the first space  18  and the hook  36  grabs the material again. A cutting tool (not shown) follows along or is integrated with the hook apparatus  36  and cuts the loop ends  38 , at which time the tension on the cut fiber  16  is released and the fiber  16  returns to its curlicued/non-linear state as shown in  FIG. 1B . 
         [0025]    In one embodiment, the fibers  14  are constructed of polyethylene, and extend upward from the backing a distance H 1  of approximately ⅞ inches. The retracted, rest state curlicued fibers  16  extend upward from the backing a distance H 2  of approximately ⅝ inches. Other dimensions are also included in the spirit of the present invention, as will be apparent to those skilled in the art. In general, the height H 2  of the curlicued fiber  16  must be shorter than the height of the relatively straight fiber  14 . 
         [0026]    As described above, the straight fiber  14  may be constructed from polyethylene, which provides a slippery surface similar to grass. Other materials that simulate the grass-like property of low resistance/friction are also included in the spirit of the present invention. The nylon fiber  16  is selected to be resilient. Other materials for fiber  16  are also included in the spirit of the present invention. 
         [0027]    The grass-like fibers  14  can be constructed in a variety of ways that will be apparent to those skilled in the art for use in the turf/mat of the present invention, and the present invention includes the use of these constructions in the turf structure as described in reference to the figures of the present disclosure.  FIG. 4A  illustrates the construction of one type of grass-like structure for use as an artificial grass blade. A length of polyethylene or other material of width “W” is sliced through in places  40  as indicated. The material is then rolled up, or pre-stressed to automatically roll up, as indicated in  FIG. 4B , and when sewn into an artificial turf “backing”, it resembles a blade of grass. 
         [0028]    While the present invention has been described herein with reference to particular embodiments thereof, a latitude of modifications, various changes and substitutions are intended in the foregoing disclosure, and it will be appreciated that in some instances some features of the invention will be employed without a corresponding use of other features without departing from the spirit and scope of the invention as set forth in the appended claims.

Summary:
A golf mat includes artificial grass fibers attached to and extending upward from a backing material, which may be one or more layers. The artificial grass fibers include groups of at least two different kinds of fiber sewn through a common path in the backing material. One of the kinds of fibers in each group is shaped so as to appear like a blade of grass. The other kind of fiber in each group is pre-stressed/crimped so that the relaxed shape of the fiber is nonlinear, resembling a curlicued or articulated form having lateral excursions. The lateral excursions cause portions of one such pre-stressed fiber to overlap and interfere with another, forming a mesh. The height of the pre-stressed fibers in their relaxed state in the turf is less than the height of the relatively unstressed artificial grass fiber(s). The crimped fibers form a resilient mat with impact characteristics similar to natural turf.