Abstract:
A portable golf practice device is disclosed that is easily transported by the golfer and simulates the response of natural turf when impacted by the club head during a golf swing. The device includes a base extension, which can be unfolded and slid under a platform thereon the golfer stands, for maintaining stability during use. The device includes a simulated turf surface fitted in a tray. The tray rests on a roller assembly positioned on a base member having a top surface sloping downward from the aft end to the forward end. When a golf ball placed on the simulated turf surface is struck by a golf club, the tray and the simulated turf surface are driven forward and downward along the slope. Means are provided to return the tray and the simulated turf surface to their original position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not Applicable 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable 
   REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
   Not Applicable 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates in general to a golf practice device, and more particularly to a golf practice device that (1) is practically portable and can easily be transported by the golfer to any indoor/outdoor golf practice facility, and (2) has a surface component that yields or moves when impacted by the head of a golf club to simulate the response of natural turf and facilitate the practice and development of a correct golf swing. 
   2. Prior Art 
   To be skilled at the techniques of golf requires a golfer to practice regularly beyond the time spent on playing the game on golf courses. Many indoor/outdoor golf practice facilities have been created to accommodate golfers&#39; need to practice, and the concept of employing golf practice mats at these facilities is a common and long-established practice. The conventional golf practice mats are available in a variety of materials and have a surface layer simulating natural grass. These mats generally perform adequately for practicing wood shots off a tee, but fall short for practicing iron shots. 
   A correct iron shot requires the golf club head to impact the golf ball on the downswing momentarily before it reaches the lowest point of the swing arc, i.e., the path of the golf club head during a swing. The descending club head will naturally remove a small patch of turf, known as a divot, below and immediately in front of the ball. Conventional golf practice mats are generally of stiff, unyielding construction and do not allow the action of taking a divot. A correct golf swing practiced on such a mat will actually produce the wrong “feel” as the club head, after hitting the ball, is impeded by and bounces off the mat. Further, to lessen the shock to the wrists and elbows and risk of injury, the golfer may alter his swing to “scoop” or sweep the ball off the mat cleanly instead of hitting “down and through” and thus develop an incorrect way of hitting iron shots. Lastly, some golf practice mats have a surface layer consisting of long fibers or inverted brushes to help reduce club head bounce and risk of injury. However, these mats may have too much “give” and more closely simulate fringe grass than fairway turf. 
   Many golf practice devices have been developed over the years in an attempt to simulate the feel of hitting natural turf to the golfer; some are designed to be portable so golfers can carry and use them at golf practice facilities. Examples are shown in the following U.S. patents. 
   U.S. Pat. No. 6,156,396 issued to Florian discloses a device consists of a base pad formed of a resilient elastomeric material and an artificial grass carpet positioned on the base pad. When a golf ball on the carpet surface is struck, the carpet slides a limited distance and is then returned by an elastic biasing mechanism. 
   U.S. Pat. No. 5,888,147 issued to Luedtke discloses a device comprises an anchor piece and a divot piece connected by elastic rubber bands. U.S. Pat. No. 5,692,967 issued to Guyer discloses a device consists of a support frame, a mat and a tray with a set of casters that roll on descending ramps attached to the frame. When a golf ball is hit from the mat, the mat and tray deflect downwardly, the mat slides partially off the tray and the tray rolls down the ramps. The mat and tray return to the original position via a tension spring means. 
   U.S. Pat. No. 4,932,663 issued to Makar discloses a device comprises an artificial turf mat suspended under tension within a rigid frame. The mat is displaced downward upon impact with a golf club. Multiple surface layers can be employed to simulate golf shots from the fairway, rough and sand trap. 
   U.S. Pat. No. 4,875,685 issued to Ballinger, et al. discloses an apparatus that includes a platform for the golfer to stand on, a main frame connected to the platform adjacent thereto, and an inner frame covered with artificial turf surface and mounted within the main frame. The inner frame pivots forward and then downward in a generally arcuate path when the surface is impacted by the golf club head. The platform can be folded to form a carrying case in which the components can be stored. 
   U.S. Pat. No. 4,130,283 issued to Lindquist discloses a device with artificial turf secured to a cushioned support that is movable in the direction of the ball flight and compressible when the surface is struck. The movable and compressible portion returns via a spring means. 
   U.S. Pat. No. 3,712,628 issued to Boss, Jr. discloses a device comprises a rigid housing containing rollers which support an endless belt with simulated grass outer surface. A platform beneath the upper portion of the belt pivots about one end and is held against the inner surface of the belt by an elastic means. 
   While these devices may accomplish their stated objectives, they either (1) are too complex and too expensive to manufacture to be economically viable; or (2) are too heavy or bulky to be practically transportable; or (3) have a height dimension that requires the golfer to stand on an elevated platform; or (4) require a means for the device to be anchored to the ground, which is impractical when the ground is hard surface such as concrete. 
   There exists a need for a golf practice device that is portable so the golfer can easily transport it to a golf practice facility and, when struck by a golf club head during a golf swing, yields or moves in such a manner as to simulate the response of natural turf. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention relates to a golf practice device that is portable, yields or moves when impacted by the head of a golf club, and more accurately simulates what the golfer experiences when hitting a golf ball off natural turf. 
   One aspect of the present invention provides a golf practice device that is relatively compact so it can easily be carried and transported, and does not require any means for it to be anchored or affixed to the ground or other objects. The device includes a base member and a base extension. In use, the device is placed adjacent to a practice platform, which is generally any one of the commercially available golf practice mats used at golf practice facilities. The base extension is unfolded and slid under the practice platform. The combined weight of the practice platform and the golfer on the base extension keeps the device stationary during use. 
   Another aspect of the present invention provides a golf practice device which has a surface component that yields or moves when impacted by the head of a golf club to simulate the response of natural turf. The device includes a base member having a top surface that slopes downward from the aft end to the forward end and a plurality of grooves therein. A roller assembly comprising rods and sleeve bearings is placed on the base member and fits in said network of grooves. The sleeve bearings preferably are made of anti-friction, self-lubricating material and produce minimal friction and noise during operation. A tray rests on top of the roller assembly with a simulated turf layer fitted therein. When a golf ball placed on the simulated turf layer is struck by a golf club, the force imparted to the device sends the tray together with the simulated turf layer sliding forward down a descending slope, thus simulating the feel of hitting natural turf. Means are provided to control the sliding forward and the retraction to their original position of the tray and the simulated turf layer. 
   Yet another aspect of the present invention provides a golf practice device that reduces club head bounce and lessens stress on the golfer&#39;s wrists and elbows, thus reducing negative reinforcement experienced by the golfer and increasing his confidence, which is critical to the development of a correct and reliable golf swing. 
   These and other aspects of the present invention will become apparent after a reading of the following description and accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       FIG. 1  is a perspective view of the preferred embodiment of the portable golf practice device constructed in accordance with the present invention. 
       FIGS. 2   a – 2   d  are a series of perspective views of the portable golf practice device shown in  FIG. 1  showing the base extension through the process of being folded into a transport/storage configuration. 
       FIG. 3  is an exploded perspective view of the portable golf practice device shown in  FIG. 1  illustrating the various layers comprising the device, with the base extension in a storage configuration. 
       FIG. 4  is a perspective view of the portable golf practice device shown in  FIG. 1  disposed adjacent to a platform, drawn in dotted lines, for supporting a golfer. 
       FIG. 5  is an exploded perspective view of the carriage assembly of the portable golf practice device shown in  FIG. 1 . 
       FIG. 6  is a bottom perspective view of the portable golf practice device shown in  FIG. 1 . 
       FIG. 7  is a perspective view of the portable golf practice device shown in  FIG. 1  illustrating the base member and base extension configuration for a left-handed golfer. 
       FIG. 8  is a longitudinal, side elevational view of the portable golf practice device shown in  FIG. 1  with the carriage assembly and simulated turf surface in the at-rest position and the enclosed rail housing omitted for clarity. 
       FIG. 9  is a longitudinal, side elevational view of the portable golf practice device similar to  FIG. 8  with the carriage assembly and simulated turf surface in an extended position and the enclosed rail housing omitted for clarity. 
       FIG. 10  is a perspective view of the portable golf practice device shown in  FIG. 1  with the carriage assembly and simulated turf surface in an extended position. 
   

   It is to be understood that like elements are identified throughout the drawings with like reference numerals. 
   DETAILED DESCRIPTION OF THE INVENTION 
   The portable golf practice device according to the concepts of the present invention and how it functions can best be explained by reference to the attached drawings. As illustrated in  FIGS. 1 and 3 , the preferred embodiment of the portable golf practice device  10  comprises a base member  20 , a base extension  30 , a roller assembly  40 , a carriage assembly  50  and a simulated turf surface  60 . 
   Referring now to  FIGS. 3 and 4 , the base member  20  consists of a bottom panel  21  that is generally rectangular in shape with its longitudinal axis parallel to the path of the head of a golf club during a golf swing, and a pair of parallel enclosed rail housings  22  positioned along the length dimension of the bottom panel  21  on either side to form a U-shaped frame. The top surface of the bottom panel  21  slopes slightly downward from the aft end to the forward end. The cross section, as can be seen in  FIGS. 8 and 9 , is a trapezoid with the vertical sides being the bases. There is a ledge along the length dimension of the bottom panel  21  on the side opposite the base extension  30  for a handle means to be installed such that the device may be lifted easily out of a carrying case or off the ground. The enclosed rail housings  22  have cylindrical cavities for receiving the carriage retraction means  53 , which are part of the carriage assembly  50  that is detailed below with reference to  FIGS. 3 and 5 . The sides of the enclosed rail housings  22  facing the interior of the U-shaped frame have slots  23  to allow the carriage tray  51  to slide forward and retract. The cylindrical cavities and the slots  23  all slope slightly downward from the aft end to the forward end at the same angle as the top surface of the bottom panel  21 . As illustrated in  FIG. 3 , the enclosed rail housings  22  have end caps  24  on the aft end that are fabricated separately. After the carriage assembly  50  has been installed with the carriage retraction means  53  fitted inside the enclosed rail housings  22 , the end caps  24  are then affixed to the ends of the enclosed rail housings  22 , the guide rails  54  and the bottom panel  21  through any conventional means suitable for the material used to fabricate the base member  20  and is generally well known in the art. The base member  20  is supported, as illustrated in  FIG. 6 , by a plurality of support feet  25  fitted in recessed areas in the undersurface of the bottom panel  21  and preferably formed of a resilient material such as rubber. The base member  20  is preferably made of thermoplastics but can be fabricated with generally any structural material such as metals, metal alloys or plastics, and can be either a single-piece construction or assembled from parts. 
   In the top surface of the bottom panel  21  is plurality of transverse grooves  26  which further include a plurality of half-cylinder-shaped recesses  27 . This pattern of indentations is to receive the roller assembly  40  that is detailed below with reference to  FIG. 3 . 
   As illustrated in  FIGS. 1 ,  2 ,  6 ,  7  and  10 , the base extension  30  consists of a foot plate  31  and a plurality of extension plates  32  connected by hinge means  33 . The extension plates  32  have generally the same width dimension but shorter length dimension as the bottom panel  21 , and the foot plate  31  has the same length dimension but shorter width dimension as the extension plates  32 . The hinge means allow the foot plate  31  and extension plates  32  to be folded and stacked one on top of another into a transport/storage configuration, as illustrated in  FIGS. 2   a – 2   d . The underside of the bottom panel  21  has two recessed areas on either side along the length dimension generally of the same dimensions as the foot plate  31 . The foot plate  31  is fitted in one of the recessed areas and secured to the base member  20  by any conventional means that allows disassembly and reassembly by the golfer. As illustrated in  FIG. 6 , screws are used to fasten the base extension  30  to the base member  20 , though any other suitable material and means may be used for this purpose.  FIG. 1  illustrates a base member  20  and base extension  30  configuration suitable for a right-handed golfer; however, the base extension  30  can be disconnected, moved to the opposite side and reconnected for use by a left-handed golfer, as illustrated in  FIG. 7 . 
   The base extension  30  is designed for the purpose of providing stability when the portable golf practice device  10  is in use. As illustrated in  FIG. 4 , the base extension  30  is to be unfolded and slid under a practice platform thereon the golfer stands. The practice platform may be any one of the commercially available golf practice mats used at golf practice facilities, or any suitable piece of material that provides adequate cushion and has a non-skid surface that allows the golfer to maintain his footing through a golf swing. The combined weight of the practice platform and the golfer on the base extension  30  keeps the portable golf practice device  10  stationary during use. Furthermore, the top surface of the extension plates  32  has a plurality of protrusions or studs that create friction between the practice platform and the base extension  30  and further prevent slippage during use. 
   As illustrated in  FIG. 3 , the roller assembly  40  comprises a pair of longitudinal bars  41 , a plurality of transverse rods  42  and a plurality of sleeve bearings  43  fitted over the transverse rods  42 . The number, placement and dimensions of the transverse rods  42  and sleeve bearings  43  correspond to the number, placement and dimensions of the transverse grooves  26  and recesses  27  in the top surface of the bottom panel  21 , respectively. The longitudinal bars  41  are affixed to the base member  20  to hold the roller assembly  40  in place, with the transverse rods  42  and sleeve bearings  43  engaged in the transverse grooves  26  and recesses  27 , respectively.  FIG. 3  illustrates the use of screws as the affixation means; however, other suitable, conventional means may be employed. The sleeve bearings  43  preferably are made of polymers reinforced by fibers and filled with internal anti-friction lubricants so as to minimize friction and noise and reduce wear on the counter surfaces during operation. 
   As illustrated in  FIGS. 3 and 5 , the carriage assembly  50  comprises a generally rectangular carriage tray  51  with sleeves  52  and dual carriage retraction means  53 . Each carriage retraction means  53  further consists of a guide rail  54 , a plurality of forward compression springs  55  and a rearward compression spring  56 , with the compression springs  55 ,  56  generally having the same inner and outer diameters as the sleeves  52 . The sleeves  52  are hollow cylindrical tubes affixed to the sides of the carriage tray  51  positioned toward the aft end and fit over the guide rails  54  sandwiched between the forward and rearward compression springs  55 ,  56 . The top surface of the carriage tray  51  is level and has upstanding edges on all sides. Preferably, the edge on the forward side is lower than the other three. The bottom surface of the carriage tray  51  slopes from the aft end to the forward end at the same angle as the top surface of the bottom panel  21 ; i.e., the two plane surfaces are parallel to each other. The sleeves  52  and the carriage retraction means  53  also slope at the same angle as the bottom surface of the carriage tray  51 . When assembled, the carriage assembly  50  sits on the roller assembly  40  when at rest and slides forward and back over the roller assembly  40  when in motion. The carriage assembly  50  is preferably made of thermoplastics and can be either a one-piece construction or assembled from parts. 
   As illustrated in  FIGS. 1–3 ,  7  and  10 , the simulated turf surface  60 , which may be any one of the commercially available artificial turfs that are made of sturdy plastic and used for golf practice mats, generally fits the dimensions of and is adhesively bonded to the carriage tray  51 . Alternatively, the simulated turf surface  60  may be attached to the carriage tray  51  with hook- and-loop fasteners such as Velcro®. 
   An alternate embodiment of the invention utilizes the same components and means with only several modifications as described below. Typically, plastic-to-plastic moving-part applications create much more friction and wear than plastic-to-metal applications. Roller assembly  40  is employed in the preferred embodiment for the purpose of reducing friction, wear and noise. In the alternate embodiment, the carriage tray  51  and bottom panel  21 , and optionally the sleeves  52  and enclosed rail housings  22 , are fabricated with filled and alloyed plastic composites possessing performance qualities such as: improved abrasion-resistance, lower static and dynamic friction, higher compressive strengths and improved creep resistance. The carriage tray  51  and bottom panel  21  are to be made of dissimilar polymers to ensure low coefficient of friction. The carriage tray  51  thus can sit directly on the bottom panel  21 , eliminating the requirements of the roller assembly  40  and the corresponding transverse grooves  26  and recesses  27  in the bottom panel  21 . 
   In use, the portable golf practice device  10  is disposed adjacent to a practice platform, which is generally any one of the commercially available golf practice mats used at golf practice facilities. The base extension  30  is unfolded and slid under the practice platform. The golfer places a golf ball on the simulated turf surface  60  and takes a swing with a golf club. Referring to  FIGS. 8–10 , when the club head impacts the device, the force imparted to the carriage tray  51  compacts the forward compression springs  55  and moves the carriage tray  51 , together with the simulated turf surface  60 , forward and down the slope, directed by the guide rails  54 , thus simulating the feel to the golfer of striking a golf ball off natural turf and taking a divot. When the resistance from the forward compression springs  55  exceeds the forward force, the carriage tray  51  and the simulated turf surface  60  are then returned to their original position. Rearward compression springs  56  are employed to absorb the retraction force and reduce shock to the aft end of the device. The sliding forward and descending down the slope of the carriage tray  51  and the simulated turf surface  60  also reduces club head bounce and lessens stress on the golfer&#39;s wrists and elbows, allowing the golfer to correctly practice his golf swing and decreasing risk of injury. 
   All of the various layers comprising the portable golf practice device  10  are fabricated to have as low a profile or height as can be practically achieved while meeting all the strength requirements. The optimal height is generally equivalent to the average height of the commercially available golf practice mats used at golf practice facilities so the golfer can practice a standard golf swing with the golf ball being generally at the same level as his feet. If the height of the device deviated materially from that of the commercially available golf practice mats, a custom, complementary practice platform would then be required, thereby resulting in a device merely movable and not realistically portable. 
   Regarding the length and width dimensions of the portable golf practice device  10 , they are to be short enough so the device is realistically portable and long enough to form a hitting area that can easily accommodate missed hits. 
   To conclude, with respect to the above description, it is to be understood that the optimal dimensional specifications for the parts of the invention, including variations in number, size, shape, form, placement, material and the method of fabrication and assembly, are deemed readily apparent to persons skilled in the art upon a reading of the foregoing description, and all equivalent specifications to those illustrated in the drawings and detailed in the description are intended to be encompassed by the present invention. 
   Further, it will be obvious to those skilled in the art that various modifications and revisions can be made to the embodiment shown herein without departing from the spirit and essential characteristics of the invention. It is therefore intended by the appended claims to cover any and all such modifications and revisions within the scope of the present invention.