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You are an expert at summarizing long articles. Proceed to summarize the following text: 
TECHNICAL FIELD 
     The present invention relates to a window screen. More particularly, the invention relates to a window screen having strong components that may be used as an impact protective system, particularly for window protection from impacts due to debris from wind storms, hurricanes, tornados and the like, as well as vandalism. 
     BACKGROUND OF THE INVENTION 
     Windows are typically provided in structures such as residential homes, schools, office buildings and other buildings designed primarily for human occupation. Oftentimes it is desirable to allow for the windows to be opened so that outside air may enter the building. Screens are typically provided on such window openings so that air may pass through the window opening, but undesirable objects such as insects are kept outside of the building. Most prior art screens are made of aluminum mesh and do not have adequate strength to protect against window breakage. Also, whether the window can open or not, prior art screens are known that can protect window glass from damage, if strong enough. 
     In areas that are subject to high winds, such as areas that may experience hurricanes or tornados, it is desirable to provide a screen that will protect window glass from flying debris. Additionally, buildings that are prone to be vandalized, such as schools and low income housing, use screens to protect against glass breakage. One prior art screen that provides protection against glass breakage comprises stainless steel mesh within an aluminum frame. 
     However, in the prior art, the mesh and the glass are proximate one another. As a result, deflections of the mesh from impacts to the mesh by objects could result in glass breakage. 
     SUMMARY OF THE INVENTION 
     The invention of the application is a high strength window screen frame adapted to fit within a window opening in an exterior wall of a building in front of a window pane. The window screen frame includes an extruded metal frame that defines an opening for receiving mesh. A fascia portion of the extruded metal frame is provided on the frame proximate the opening. A standoff leg portion of the extruded metal frame extends rearward from the fascia portion. The standoff leg portion is longer than the fascia portion to provide sufficient separation between the window pane and the mesh to prevent deflections in the mesh from making contact with the window pane. Heavy duty mesh screen is preferably used with the high strength window screen frame of the invention. The window screen frame is screwed by fasteners to an exterior wall surrounding a window opening of a structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a window screen frame of the invention. 
     FIG. 2 is a front view of the window screen frame of FIG.  1 . 
     FIG. 3 is a back view of a screen frame of FIG.  1 . 
     FIG. 4 is perspective cross sectional view of the window screen frame of the invention taken along line  4 — 4  of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a high strength window screen frame  10  includes an extruded metal frame  12 . Preferably, the extruded metal frame is a hollow extruded aluminum frame. Variations may exist in the cross-sectional configuration, depending upon building materials and the type of window used in conjunction with the high strength window frame  10 . High strength window frame  10  is made up of window frame units  11  (FIGS.  1 - 3 ) mounted together to make up a single screen for a window. Window frame units  11  have a front  14 , a back  16 , and four frame members  17  that define an opening  18 . Extruded metal frame  12  is designed to be used in conjunction with a window opening in a wall  13  of a structure. 
     Frame  12  is L-shaped, having a fascia portion  20  (FIGS. 1,  2 , and  4 )of frame  12  that is provided on a forward end of extruded metal frame units  11  nearest openings  18 . Screen plate portion  20  has a front face  24 FIGS. 1,  2 , and  4 ), a rear face  26  (FIG.  3 )and an inside surface  28 . A standoff leg portion  30  (FIG. 4) of frame  12  extends rearwardly from fascia portion  20 . Standoff leg portion  30  is provided with longitudinal teeth or serrations  31 . Standoff leg portion  30  extends rearward from rear face  26  approximately 1.4 times the dimension of front face  24  from outer edge  35   b  of frame  12  to inside surface  28  in the preferred embodiment. Preferably, front face  24  is approximately 1.4 inches from outer edge  35   b  to inside surface  28  of frame  12 , inside surface  28  is approximately 0.5 inches from front face  24  to rear face  26 , and standoff leg portion  30  extends approximately 2.5 inches rearward from front face  24  to a rear face at groove  40 . The relatively longer length of the standoff leg portion  30  results in an extended standoff of mesh  32  relative to glass pane  34  (FIG.  4 ). The standoff is between approximately 2 to 5 inches in the preferred embodiment, which protects glass pane  34  from damage that might occur from any deflection of mesh  32  that might be caused by an impact of an object with the mesh. It should be noted that the dimensions recited herein are provided for the purpose of example only. Other suitable dimensions may be used within the scope of the invention. 
     Within a single window, depending on the length, there may be several frame units  11 . The upper edge  35   a  (FIGS. 1,  2 , and  4 ) of the lowest frame unit  11  abuts the lower edge  35   b  (FIGS. 1,  2  and  4 ) of the next upward frame unit  11 . The drawings show three frame units  11 . A cap  36  (FIGS. 3 and 4) is provided to fit over ends of standoff leg portion  30  to secure multiple window frame units  11  together. Cap  36  is a metal channel member with two side walls  37   a ,  37   b  and a base  38  (FIGS. 3,  4 ). A serrated portion  39  (FIG. 4) is on an inside surface  38  of each sidewall  37   a ,  37   b  for engaging longitudinal serrations  39  on standoff leg portion  30 . Standoff leg portions  30  are preferably provided with channels or grooves  40  that mate with a tongue  40   a  on cap  36 . Additionally, end bracket supports  41  (FIG. 3) may be provided at ends of window frame units  11  that are not adjacent to other window frame units  11 . End bracket supports  41  provide additional strength to window frame units  11 . 
     Referring now to FIG. 4, a metal screen plate stiffener  52  is removably affixed to rear face  26  of fascia portion  20  with a plurality of self-tapping sheet metal screws  54 . Screen plate stiffener  52  is a channel strip, having a pair of outer rims  56  and a base  57  that define a longitudinal channel  58 . An inner slot  60  is formed on an inner surface of outer rims  56 . A slidable plastic cover  62  is received within interior slots  60  on the screen plate stiffener  52 . Screen plate stiffener  52  is secured to the rear face  26  for securing a heavy duty mesh screen  32 . Screws  64  (FIGS. 1-3) extend through front face  24  and the standoff portions  30  of frame  12  around the perimeter of frame  12 . Screws  64  engage structure within an opening in an exterior wall to secure frame  12  within the opening. 
     In use, the window screen frame  10  of the invention is positioned within an opening in wall  13 . Screws  64  (FIGS. 1,  2  and  3 ) secure extruded metal frame  12  to wall  13 . Screws  64  extend through frame  10  to secure window frame  12  within wall  13 . Window pane  34  is recessed from mesh screen  32  a considerable distance. The extended standoff leg portion  30  provides a standoff distance from mesh  32  to glass pane  34  that provides additional protection to glass pane  34 . Additionally, multiple window frame units  11  result in fascia portions  20  that extend horizontally across the face of the window frame  10 . The fascia portions  20  are integral parts of the individual window frame units  11 . The use of individual window frame units  11  provide strength to the window frame  10  and provide additional support to the mesh  32 . Standoff leg portion  30  of adjacent window frame units  11 , which contact one another, are secured together with cap  36 . 
     The invention has numerous advantages. The window frame of the invention has features to protect window glass and to provide extra strength to the window frame. The high strength construction of the frame, when used in conjunction with heavy steel mesh screen, provides an impact protective system that protects window glass from flying debris. The extended standoff leg portion of the window frame provides an extended standoff of the window pane from the mesh screen. Additionally, the multiple window frame units are combinable to form a strong window frame having connected adjoining cross-members. The window frame of the invention provides strength and protection to windows and is an attractive alternative to other devices, such as burglar bars or boarding up windows. An additional advantage is that the high strength window screen frame of the invention may be easily installed on existing structures. 
     While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.

Summary:
A high strength window screen frame that includes an extruded metal frame that fits within a window opening in a building. The frame is made up of a plurality of window frame units, each defining an opening and covered with mesh. A standoff leg portion of the window frame units provides a standoff separation of the mesh from a glass pane so that when objects strike the mesh and deflect the mesh, the glass pane is not impacted.