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BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention is an improved plastic fence. In particular, it is directed to a thin profile prefabricated reinforced plastic fence. 
   2. Description of Related Art 
   Generally, plastic fences are known and described in U.S. Pat. Nos. 4,289,302, 4,796,866, 4,858,891, 5,404,685, and 5,255,899, for example. Moreover, Applicant is the inventor of U.S. Pat. No. 5,613,664, the disclosure of which is fully incorporated herein by reference. 
   Typically, plastic fences are constructed of large fence members and used for corral type applications. Common prior art fences have three or four horizontal and vertical posts and no vertical pickets. When pickets are used, the members are overly large due to the relative lack of strength and sturdiness in plastics as compared to other fencing materials such as metal or wood. Often, plastic fences are too large and heavy to be sold as prefabricated fences. Also, plastic fences frequently need to be filled with a hardening agent such as concrete to strengthen the fence. Thus, a thin profile, lighter, sturdier plastic fence that can be sold prefabricated and does not require a hardening agent is desired. 
   SUMMARY OF THE INVENTION 
   The present invention is a thin profile prefabricated reinforced plastic fence. A preferred embodiment of the fence comprises a top rail having a bottom side with a plurality of picket apertures and a bottom rail having a top side with a plurality of member apertures. The top and bottom rails preferably contain a centering dowel and the bottom rail preferably contains a horizontal strengthening member with a Z-shaped cross-section. The fence has a plurality of pickets placed between the top rail and bottom rail. Each picket sheaths a strengthening member, preferably of metal, that is allowed to slide inside the picket. The top of each picket is inserted into the picket apertures of the top rail and the strengthening member is allowed to slide out and extend from the bottom of the pickets into the member apertures of the bottom rails. The bottom of each picket rests on the top side of the bottom rail and covers the member aperture. The fence ends are adjacent a first post and second post to which the top and bottom rails are attached. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects and features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with its objects and advantages, may best be understood by reference to the following description, taken in connection with the accompanying drawings, wherein like reference numbers represent like structures and wherein: 
       FIG. 1  is a side view of a preferred embodiment of the invention with a top rail; 
       FIG. 2  is a side view of a preferred embodiment of the invention with a picket top configuration; 
       FIG. 3  is a cross-sectional view of a picket and rail embodiment of  FIG. 2 ; 
       FIG. 4  is a cross-sectional view of a picket and rail embodiment of  FIG. 1 ; 
       FIG. 5  is a cross-sectional view of a picket and rail embodiment of the invention with a two rail configuration; 
       FIG. 6  is a cross-sectional view of a post end pair of rails showing a preferred embodiment for connecting a top and bottom rail to a post; 
       FIG. 7  is a plan view of a portion of a top rail showing a preferred embodiment of the picket apertures; 
       FIG. 8  is a plan view of a portion of a bottom rail showing a preferred embodiment of the picket apertures; 
       FIG. 9  is a cross-sectional view of a preferred embodiment of a top rail showing a top rail centering spacer; and 
       FIG. 10  is a cross-sectional view of a preferred embodiment of a bottom rail showing a cross-section of Z-shaped horizontal strengthening member and a bottom rail centering spacer. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventor of carrying out his invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the general principles of the present invention have been defined herein specifically to an improved plastic fence. 
   Referring now to  FIG. 1 , a preferred embodiment of a section of fence  10  constructed according to the present invention is shown. The invention  10  is a section of fence comprising a top rail  20 , a bottom rail  30 , a mid-rail  40 , a plurality of pickets  50 , and a pair of posts  60 . These parts are all preferably thin profile components made from extruded plastic such as polyvinyl chloride (PVC) or polypropylene. 
   The top rail  20  and the mid-rail  40  have a bottom side with a plurality of picket apertures  25 . See  FIG. 7 . The bottom rail  30  and the mid-rail  40  have a top side with a plurality of member apertures  35 . See  FIG. 8 . Each picket aperture  25  in the top rail  20  and each member aperture  35  in the bottom rail  30  corresponds to one of a plurality of pickets  50  between a pair of rails  20 ,  30 . By way of example, four pickets  50  are shown in  FIG. 1 . 
   The mid-rail  40  is an optional bottom side rail used for aesthetic purposes or to add strength to the fence as described below. The mid-rail  40  has apertures on the top and the bottom side. The mid-rail  40  has picket apertures  25  on the top side and has member apertures  35  on the bottom side. 
   A picket strengthening member  55 , as shown in  FIGS. 7 and 8 , passes through the mid-rail  40 . 
   In an alternate form, the fence may not use a top rail  20  as shown in  FIG. 2 . Here the top rail with pickets  52  extending upward from rail  40  becomes pickets  54  extending between rail  40  and bottom rail  30 . 
   Referring to  FIGS. 3 and 5 , an end view of a single picket  50  installed in a two-rail, picket top configuration ( FIG. 3 ) and a two rail configuration ( FIG. 5 ) are shown. Referring to  FIG. 5 , when assembled, the top of the picket  50  is inserted into a picket aperture  25  of the top rail  20  thus locking into place (position) the top end of the picket  50  while the bottom of the picket  50  abuts or rests upon the top side of the bottom rail  30 . The picket  50  sheathes a picket strengthening member  55  shown by hidden lines in  FIG. 5 . The picket strengthening member  55  moves inside the picket  50 . The picket strengthening member  55  is preferably a steel tube or rod. The picket strengthening member  55  can be round or square, or any other convenient shape in cross section. The vertical picket strengthening member  55  traverses the distance between the top and bottom rails  20 ,  30  and drops through the member aperture  35  of the bottom rail  30  to rest upon a horizontal strengthening member  70  located in the bottom rail  30 . Thus, the picket strengthening member  55  provides two functions: 1) strengthen the picket  50 , and 2) lock into place (position) the bottom of the picket  50  on the bottom rail  30  at bottom member aperture  35 . 
   Referring now specifically to  FIG. 4 , an end view of a picket  50  segmented into parts  52  and  54  is shown installed between three rails, a top rail  20 , a bottom rail  30 , and a mid-rail  40 . The concept of the pickets being held in position by picket apertures  25 , member apertures  35  and picket strengthening members  55  extending from the top rail  20 , running through the mid-rail  40  and coming to rest through member aperture  35  in the bottom rail  30  is clearly illustrated. 
   Referring now specifically to  FIG. 3 , an end view of a picket segmented into parts  52  and  54  and installed in a two-rail configuration is shown. Picket  52  sits atop a mid-rail structure  40  and utilizes the picket strengthening member  55 . No top rail is used. A picket strengthening member  55  runs through the top picket segments  52 , through the mid-rail  40 , the bottom picket segments  54 , in the bottom rail  30  through member aperture  35  and rests upon a horizontal strengthening member  70  in the bottom rail  30 . Picket  54  situated between mid-rail  40  and bottom rail  30 , as shown, is installed similar to picket segment  52 . 
   Referring to  FIGS. 3 ,  4 ,  5 , and  6 , an added feature is the location of the bottom horizontal strengthening member  70  located just above the connecting dowel  65 . If pressure is applied to the bottom rail  30 , the stiffening or strengthening member  70  prevents the bottom rail  30  from sagging. The connecting dowel  65  inserted in post  60  through aperture  62  prevents the bottom rail  30  from being displaced (moving out of position). In similar fashion, the top rail  20  and a mid-rail  40  are also secure in position by use of a spacer  80  (see  FIG. 9 ) which holds the connecting dowel  65  and the rail in position. 
   Referring to  FIG. 6 , the centering dowel  65  placed through post apertures  62  in the posts  60  and placed into the horizontal rails  20 ,  30  or  40  through spacers  80  in the top rails and  85  in the bottom rails locks the fence section  10  into place between two posts  60 . Once installed between a pair of posts  60 , the fence is difficult to move out of position. This is true for all terrain conditions, level, slanted or undulating, for example. For terrains that are less than flat, the rails are attached at appropriate bias angles to the post to conform to the sloping ground. 
   The top rail  20 , as shown in  FIGS. 4 and 5 , is preferably hollow and allows the picket  50  to pass through the picket aperture  25  to support the top rail  20  from within. This helps prevent the top rail  20  from sagging along its span between its posts  60 . However, the bottom rail  30  preferably further incorporates a horizontal strengthening member  70  to strengthen the bottom rail  30  and support the picket strengthening members  55  that pass through the member apertures  35  in bottom rail  30 . The horizontal strengthening member  70  preferably has a Z-shaped cross-section as shown in  FIG. 2 . The member  70  is preferably made of metal. 
   The member apertures  35  of the preferred embodiment, as shown in  FIGS. 3 ,  4  and  5 , is smaller than the picket aperture  25  in the top rail  20 . Therefore, the bottom of the picket  50  rests on the top side of bottom rail  30  while the strengthening member  55  passes from the picket  50  through the picket member aperture  35  into the bottom rail  30  and rests on the horizontal strengthening member  70 . Thus, a picket  50  and its strengthening member  55  support and stiffen the top and bottom rails  20 ,  30 . The difference in the apertures  25 ,  35  is best seen in  FIGS. 7 and 8 . 
   Referring to  FIG. 6 , a side cross-sectional view of a top rail  20  and a bottom rail  30  as connected to a post  60  is shown. In particular, a centering dowel  65  is held firmly in place within the top rail  20  by spacer  80 . In similar fashion in a mid-rail  40  is held in place by a similar spacer  80  (now shown). A bottom rail uses a modified spacer  85 . The spacer  80  used for a top rail fills the end of the top rail  20  and mid-rail  40  and thus prevents either the top or mid-tail  20 ,  40  from moving out of place or position. In similar fashion, the bottom rail  30  is held in place or position by a spacer  85 . Both spacers  80 ,  85  provide space for the insertion of a centering dowel  65 . The top rail, mid-rail spacer is best illustrated in  FIG. 9 . The bottom rail spacer is best illustrated in  FIG. 10 . The dowel  65  then passes through the end of the rails  20 ,  30  into a post  60  through a post aperture  62 . The aperture  62  can either terminate in the post  60  or pass through the post  60  so that the dowel  65  can connect to another set of top and bottom rails  20 ,  30  to extend the fence  10 . The dowel  65  is preferably made of metal and can be solid or tubular and can have a variety of cross-sections such as round or square, for example. 
   The posts  60  are preferably hollow and sheath a vertical reinforcement member  67 . The vertical member  67  is preferably metal and can vary in cross-sectional shape and volume. The vertical member  67  can extend past the bottom of the post  60  into the ground  100  ( FIG. 6 ) or into a post foundation or footing to provide additional strength, support, and anchoring for the fence  10 . 
     FIG. 4  shows the use of a mid-rail  40  on the fence  10 . As previously discussed, the pickets  50  traverse between the top and bottom rails  20 ,  30 . However, when a mid-rail  40  is employed, the pickets  50  are segmented into parts,  52  and  54 . The segments  52  and  54  still sheath the picket strengthening member  55 . The top segment  52  is inserted into the picket aperture  25 . However, the bottom of the top segment  52  rests on the top side of the mid-rail  40 . The picket strengthening member  55  passes through the mid-rail  40  through picket aperture  25  and member aperture  35  strengthening the mid-rail  40 . The bottom segment  54  of the picket  50  is inserted into the bottom side of the mid-rail  40  through picket aperture  25 . The bottom of the bottom segment  54  rests on the top side of the bottom rail  30 , while the strengthening member passes into the bottom rail  30  through the member aperture  35 . The ends of the mid-rail  40  can be attached to the posts  60  by centering dowels  65  just as the top rail  20  is attached as disclosed in  FIG. 4 . Thus, the mid-rail  40  is supported by the segmented picket  54  and also provides additional lateral support to the fence  10 . 
   Thus, an improved plastic fence is described above that is relatively sturdy and durable and comprises a simplified construction that permits prefabrication for installation by homeowners. Moreover, no hardening agent such as concrete is required. Furthermore, the use of interlocking members eliminates the need for fasteners such as nails, screws, brackets or rivets to keep the posts of the fence and the fence sections together. In each of the above embodiments, the different positions and structures of the present invention are described separately in each of the embodiments. However, it is the full intention of the inventor of the present invention that the separate aspects of each embodiment described herein may be combined with the other embodiments described herein. Those skilled in the art will appreciate that adaptations and modifications of the just-described preferred embodiment can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.

Summary:
The present invention is a thin profile prefabricated reinforced plastic fence. A preferred embodiment of the fence comprises a top rail having a bottom side with a plurality of picket apertures and a bottom rail having a top side with a plurality of member apertures. The bottom rail preferably contains a horizontal strengthening member and supports the top rail by way of vertical pickets. Each picket sheaths a strengthening member that is slideable inside the picket. The top of each picket is inserted into the picket apertures of the top rail and the strengthening member extends from the bottom of each picket into the member aperture of the bottom rail. The bottom of each picket rests upon the top side of the bottom rail. The fence ends have a first post and second post to which the top and bottom rails are fastened.