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BACKGROUND OF THE INVENTION 
     The present invention relates to a beam configuration for use in a frame of a screened enclosure, such as a patio or pool screen enclosure. 
       FIG. 1  is a perspective view of a basic screened enclosure  11  attached to another structure such as a house  12 . 
     Most pool screen and screened enclosure applications use individual metal beams that must be assembled together. Each beam is comprised of half sections that are fitted to one another and then screwed or riveted. 
       FIG. 2  is a side cross-sectional view of two beam half sections  14 , 16  of a first prior art beam assembly. A common problem with the illustrated structure is keeping and supporting the beam half sections in the configuration shown in  FIG. 2 . For example, if beam half section  14  is positioned on top of beam half section  16 , the legs or flanges  18 , 20  of upper beam half section  14  can fall in the direction of arrow A ( FIG. 3 ) and no longer be adjacent the legs or flanges  22 , 24  of half beam section  16 , as shown in  FIG. 3 . 
     A second example prior art beam assembly is illustrated in  FIG. 4  and disclosed, for example, in U.S. Pat. No. 6,385,941, the disclosure of which is incorporated herein by this reference. The assembly illustrated in  FIG. 4  addresses the slippage problems note above with reference to  FIGS. 2 and 3 . In the  FIG. 4  structure, flange  36  of beam half section  28  abuts and is seated against angled lip  40  of beam half section  26  while flange  30  of beam half section  26  abuts and is seated against angled lip  38  of beam half section  28 . On the other hand, flange  34  of beam half section  28  abuts to an exterior facing rib  42  of flange  30  of half beam section  26  and flange  32  of half beam section  26  abuts to exterior facing rib  44  of flange  36  of beam half section  28 . 
     While the abutment end seating of flanges  30  and  36  respectively against inwardly angled lips  38 , 40 , respectively, addresses the slippage in direction A mentioned with reference to  FIG. 3 , that is not to say that further improvement of the beam structure cannot be realized. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The existing self mating beams used in the patio/pool enclosure industry tend to have a failure mode, in bending and axial loading, of buckling of the flanges of the beam half sections. 
     The invention provides for extra restraints to the flanges thus increasing the allowable loads before flange buckling will occur. Accordingly, the invention provides for an improved structural beam that provides increased strength of the beam. 
     Thus, the invention may be embodied in a beam assembly for defining a portion of a frame of a screened enclosure, comprising a first longitudinal half beam section having a first upper flange, a first lower flange, and first main portion connecting the first upper flange to the first lower flange; a first interior lip connected to an inside portion of the first upper flange, and forming a first interior receptacle with the first upper flange; a first exterior lip connected to an outside portion of the first lower flange, and forming a first exterior receptacle with the first lower flange; a second longitudinal half beam section having a second upper flange, a second lower flange, and second main portion connecting the second upper flange to the second lower flange; a second exterior lip connected to an exterior portion of the second upper flange, and forming a second exterior receptacle with the second upper flange; a second interior lip connected to an interior portion of the second lower flange, and forming a second interior receptacle with the second lower flange; wherein a free end edge of the first upper flange of the first longitudinal half beam is received in and restrained by the second exterior receptacle of the second longitudinal half beam while a free end edge of the first lower flange of the first longitudinal half beam is inserted into the second interior receptacle of the second longitudinal half beam, and wherein a free end edge of the second upper flange of the second longitudinal half beam is received in and restrained by the first interior receptacle of the first longitudinal half beam section while a free end edge of the second lower flange of the second longitudinal half beam section is inserted into the first exterior receptacle of the first longitudinal half beam section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a basic screened structure; 
         FIG. 2  is a side-cross sectional view of two half beam sections of a first example prior art; 
         FIG. 3  is a side-cross sectional view showing a slide problem of the beam half sections of  FIG. 2 ; 
         FIG. 4  is a side cross-sectional view of a second example prior art beam section; 
         FIG. 5  is a side cross-sectional view of a first example beam assembly embodying the invention; 
         FIG. 6  is a side cross-sectional view of a second example beam assembly embodying the invention; 
         FIG. 7  is a side cross-sectional view of a third example beam assembly embodying the invention; 
         FIG. 8  is an enlarged view of a first corner detail of  FIG. 7 ; and 
         FIG. 9  is an enlarged view of a second corner detail of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the illustrated embodiments, each half beam section identically corresponds in shape and configuration to the beam half section with which it is engaged, overlapped, and locked. For ease of description, however, the respective beam half sections are assigned respective independent reference numerals as are the legs or flanges thereof. 
     In example embodiments of the invention, an extra restraint is provided in the form of a lip for receiving and engaging the free end of the exteriorly disposed flange of each of beam half section so that both the inner flange and outer flange of each beam half section abuts and is seated by a respective lip. 
     A first example embodiment of a beam assembly for a screened patio or pool enclosure is illustrated in  FIG. 5 . More specifically, in this embodiment the beam assembly includes two beam half sections  46 , 48 . On the exterior of beam half sections  46 , 48  are grooves  50 , 52 , 54 , 56  for receiving spline that is used with screening of enclosures, which is not a part of the subject invention and is therefore not illustrated. 
     Beam half section  46  has flanges  58 ,  60 , generally parallel to one another. Two U-shaped receptacles  66 , 68  face one another with prongs  70 , 72  having triangular shapes and located in the inside corners of the beam half section  46  adjacent the flanges  58 , 60 . A nesting receptacle  74  and inner lip  76  are formed adjacent the inner corner where flange  58  meets the main section of beam half section  46 . Likewise, beam half section  48  has flanges  78 , 80  generally parallel to one another. A nesting receptacle  86  and lip  88  is formed adjacent the inner corner of where flange  80  meets the main section of beam half  48 . 
     In accordance with an example embodiment of the invention to fully rigidify the lapped and locked flanges of the beam half sections, a second nesting receptacle and lip is formed for engaging and holding the free end of the respectively outer flange of the beam half sections. Thus, as illustrated in  FIG. 5 , a nesting receptacle  90  and lip  92  are defined to receive and hold the free end edge of flange  58  and a nesting receptacle  94  and lip  96  are defined for engaging the free edge of flange  80 . Thus, the free end edges of each of the flanges of the respective beam half sections are received in a respective nesting receptacle and locked therein by the respective lip. 
     In the illustrated example embodiment, flange  58  is stepped at  59  to define an abutment for lip  92 . Likewise, flange  80  is stepped as at  81  to define an abutment step for engaging lip  96 . The respective inner flanges of the beam half sections  46  and  48  are also stepped. More specifically, flange  78  is stepped at  79  and flange  60  is stepped at  61 . It will be noted that the steps of the respective inner flanges  78  and  60  are remote from lips  76  and  88  respectively to effectively lock the stepped tip of the respective outer flanges  58  and  80  in a respective receptacle  91  and  95  defined by and between steps  79  and  61  and the nesting receptacles  90 , 94  and lips  92 , 96 . 
     An installer of beam  10  can take beam half  46  and position flange  58  over flange  78  of beam half  48  while simultaneously positioning flange  60  adjacent to flange  80 . By overlying the beam half sections  46 , 48 , the end of flange  78  abuts against nesting lip/receptacle  74 , 76  while flange  60  abuts against nesting lip/receptacle  86 , 88 . Further, the end of flange  58  abuts against lip/nesting receptacle  90 , 92  while flange  80  abuts against nesting lip/receptacle  94 , 96 , and allows the installer to easily position the beam half sections together. 
     As mentioned above, U-shaped receptacles  66 , 68  are formed between two inwardly facing prongs  70 , 72  and the respective wall  46  of the beam for receiving one end of a connection plate (not illustrated). The aforementioned connecting plates slid into U-shaped receptacles  66 , 68  allow beam  10  to be connected to an axially adjacent beam. Additionally, although not illustrated, respectively adjacent flanges  58 , 78 , 60 , 80  of beam half sections  46 , 48  may be secured together by screwing fastener screws therethrough. 
     A second example embodiment of a beam assembly for a screened patio or pool enclosure is illustrated in  FIG. 6 . More specifically, in this embodiment the beam assembly includes two beam half sections  146 , 148 . On the exterior of beam half sections  146 , 148  are grooves  150 , 152 , 154 , 156  for receiving spline that is used with screening of enclosures, which is not a part of the subject invention and is therefore not illustrated. 
     Beam half section  146  has flanges  158 , 160 , generally parallel to one another with grooved surface  162  on the interior surface of flange  158  and a grooved surface  164  on the exterior of flange  160 . Two U-shaped receptacles  166 , 168  face one another with prongs  170 , 172  having triangular shapes and located in the inside corners of the beam half section  146  adjacent the flanges  158 , 160 . A nesting receptacle  174  and inwardly angled lip  176  is formed adjacent the inner corner where flange  158  meets the main section of beam half section  146 . Likewise, beam half section  148  has flanges  178 , 180  generally parallel to one another with groove surface  182  on the interior surface of flange  180  and groove surface  184  on the outer surface of flange  178 . A nesting receptacle  186  and inwardly angled lip  188  are formed adjacent the inner corner of where flange  180  meets the main section of beam half  148 . 
     As noted above, in accordance with example embodiments of the invention, to fully rigidify the lapped and locked flanges of the beam half sections, a second nesting receptacle and lip is formed for engaging and holding the free end of the respectively outer flange of the beam half sections. Thus, as illustrated in  FIG. 6 , a nesting receptacle  190  and lip  192  are defined to receive and hold the free end edge of flange  158  and a nesting receptacle  194  and lip  196  are defined for engaging the free edge of flange  180 . As illustrated, the inner surface of, e.g., lip  192  is tapered so that the entry end of receptacle  190  is enlarged. Thus, the free end edges of each of the flanges of the respective beam half sections are received in a respective nesting receptacle and locked therein by the respective lip. 
     In the illustrated example embodiment, flange  158  has a rib  159  to define an abutment surface for the lip  192 . Likewise, flange  180  has a rib  181  to define an abutment step for engaging lip  196 . As illustrated in  FIG. 6 , each rib  159 ,  181  projects outwardly from the respective flange so as to have first and second lateral sides, one of which defines the stepped surface that engages the respective exterior lip  192 ,  196 , and an outer surface substantially coplanar with an outer surface of the respective exterior lip. As also understood from  FIG. 6 , each rib  159 ,  181  has a width between the first and second lateral sides thereof that is substantially less than the corresponding dimension of the respective flange. 
     An installer of beam  110  can take beam half  146  and position flange  158  over flange  178  of beam half  148  while simultaneously positioning flange  160  adjacent to flange  180 . By overlying the beam half sections  146 , 148 , the end of flange  178  abuts against nesting receptacle/lip  174 , 176  while flange  160  abuts against nesting receptacle/lip  186 , 188 . Further, the end of flange  158  abuts against nesting receptacle/lip  190 , 192  while flange  180  abuts against nesting receptacle/lip  194 , 196 , and allows the installer to easily position the beam half sections together. 
     As mentioned above, U-shaped receptacles  166 , 168  are formed between two inwardly facing prongs  170 , 172  and the respective wall  146  of the beam for receiving one end of a connection plate (not illustrated). The aforementioned connecting plates slid into U-shaped receptacles  166 , 168  allow beam  110  to be connected to an axially adjacent beam. Additionally, although not illustrated, respectively adjacent flanges  158 , 178 , 160 , 180  of beam half sections  146 , 148  may be secured together by screwing fastener screws therethrough. 
     A third example embodiment of a beam assembly for a screened patio or pool enclosure is illustrated in  FIG. 7 . More specifically, in this embodiment the beam assembly includes two beam half sections  246 , 248 . On the exterior of beam half sections  246 , 248  are grooves  250 , 252 , 254 , 256  for receiving spline that is used with screening of enclosures, which is not a part of the subject invention and is therefore not illustrated. 
     Beam half section  246  has flanges  258 ,  260 , generally parallel to one another with grooved surface  262  on the interior surface of flange  258  and a grooved surface  264  on the exterior of flange  260 . Two U-shaped receptacles  266 , 268  face one another with prongs  270 , 272  having triangular shapes and located in the inside corners of the beam half section  246  adjacent the flanges  258 , 260 . A nesting receptacle  274  and inwardly angled lip  276  is formed adjacent the inner corner where flange  258  meets the main section of beam half section  246 . Likewise, beam half section  248  has flanges  278 , 280  generally parallel to one another with grooved surface  282  on the interior surface of flange  280  and grooved surface  284  on the outer surface of flange  278 . A nesting receptacle  286  and inwardly angled lip  288  are formed adjacent the inner corner of where flange  280  meets the main section of beam half  248 . 
     As noted above, in accordance with example embodiments of the invention to fully rigidify the lapped and locked flanges of the beam half sections, a second nesting receptacle and lip is formed for engaging and holding the free end of the respectively outer flange of the beam half sections. Thus, as illustrated in  FIG. 7 , a nesting receptacle  290  and lip  292  are defined to receive and hold the free end edge of flange  258  and a nesting receptacle  294  and lip  296  are defined for engaging the free edge of flange  280 . As illustrated, the inner surface of, e.g., lip  292  is tapered so that the entry end of the receptacle  290  is enlarged. Likewise, an inner surface of lip  296  is tapered so that the entry end of receptacle  294  is enlarged. Thus, the free end edges of each of the flanges of the respective beam half sections are received in a respective nesting receptacle and locked therein by the respective lip. 
     An installer of beam  210  can take beam half  246  and position flange  258  over flange  278  of beam half  248  while simultaneously positioning flange  260  adjacent to flange  280 . By overlying the beam half sections  246 , 248 , the end of flange  278  abuts against nesting lip/receptacle  274 , 276  while flange  260  abuts against nesting lip/receptacle  286 , 288 . Further, the end of flange  258  abuts against nesting lip/receptacle  290 , 292  while flange  280  abuts against nesting lip/receptacle  294 , 296 , and allows the installer to easily position the beam half sections together. 
     As mentioned above, U-shaped receptacles  266 , 268  are formed between two inwardly facing prongs  270 , 272  and the respective wall  246  of the beam for receiving one end of a connection plate (not illustrated). The aforementioned connecting plates slid into U-shaped receptacles  266 , 268  allow beam  210  to be connected to an axially adjacent beam. Additionally, although not illustrated, respectively adjacent flanges  258 , 278 , 260 , 280  of beam half sections  246 , 248  may be secured together by screwing fastener screws therethrough. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Summary:
Two U-shaped beam half sections are attached together by having nesting ledges/receptacles on the flanges of the half sections. While the flanges of each beam half overlap against each other, the nesting ledges/receptacles hold the beam half flanges to fixed locations. Fasteners such as screws can be driven through the sides of the beam half flanges to fixedly lock the beam half sections to one another.