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BACKGROUND OF THE INVENTION 
     This invention relates to stair assemblies, and more particularly to modular stair assemblies with different modules or components that can be connected together to suit a wide variety of different applications. 
     Prefabricated stair assemblies are often designed for a single application or particular use. For example, it is common to prefabricate stair assemblies for new homes, trailer homes, and so on. These stair assemblies are typically constructed of cement, and are therefore relatively heavy in weight, difficult to transport, position, and secure in place. The removal of such stair assemblies is labor-intensive and often requires special equipment. For temporary structures or structures at temporary locations, such as platforms for presentations or speeches, trailer homes, and so on, the ability to install and/or remove the stair assembly for various applications in a quick and efficient manner is desirous. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention, a modular stair assembly comprises a stair module having a pair of spaced stair support frames with each stair support frame including an elongate base member, a rear upright support member connected to a rear end of the base member, a stringer extending diagonally from a forward end of the base member to an upper end of the rear support member, and a plurality of L-shaped risers connected to the stringer. Each riser has a vertical riser portion that extends upwardly from the stringer and a horizontal riser portion that extends rearwardly from the vertical riser portion toward the stringer. The vertical and horizontal riser portions are rigidly fixed together. A plurality of steps extend between the stair support frames and are supported by the horizontal riser portions. 
     In accordance with a further aspect of the invention, at least one of a transportation module, deck module, handrail module, extension deck module, and extension handrail module can be provided with the stair module so that the modular stair assembly is readily adaptable to a wide variety of different applications. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
     FIG. 1 is an isometric view of a modular stair assembly according to a first embodiment of the present invention; 
     FIG. 2 is an isometric view of the modular stair assembly with an attached transportation module in accordance with the invention; 
     FIG. 3 is an isometric view of the modular stair assembly with an attached handrail module in accordance with the invention; 
     FIG. 4 is an isometric view of the modular stair assembly with an attached deck module in accordance with the invention; 
     FIG. 5 is an isometric view of the modular stair assembly with attached deck and handrail modules in accordance with the invention; 
     FIG. 6 is an isometric exploded view of the modular stair assembly of FIG. 5 as viewed from the left side thereof, 
     FIG. 7 is an isometric view of the deck module; 
     FIG. 8 is a side elevational view of a pair of modular stair assemblies in back-to-back relationship; 
     FIG. 9 is an isometric view of a modular stair assembly with an attached extension deck module and extension handrail module in accordance with a further embodiment of the invention; 
     FIG. 10 is an isometric view of a modular stair assembly with an extension deck module and a pair of extension handrail modules in accordance with an even further embodiment of the invention; 
     FIG. 11 is an isometric view of the extension deck module as shown in the FIG. 10 embodiment; 
     FIG. 12 is a left side isometric view of a stair step in accordance with the invention that can form part of the modular stair assemblies of the previous embodiments; 
     FIG. 13 is a side elevational view of the stair step; and 
     FIG. 14 is a bottom plan view of the stair step. 
    
    
     The invention will now be described in greater detail with reference to the drawings, wherein like parts throughout the drawing figures are represented by like numerals. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and to FIG. 1 in particular, a modular stair assembly  5  in accordance with the present invention is illustrated. The modular stair assembly includes a stair module  10  with a pair of spaced stair support frames  12  and  14 , a plurality of steps  16  extending between the support frames, and a cross member or brace  18  extending diagonally between the support frames  12  and  14  for added structural support. 
     With additional reference to FIG. 6, each of the stair support frames  12  and  14  is generally triangular in shape and includes an elongate base member  20  that contacts a horizontal support surface, such as a floor, platform, ground, and so on, a rear upright support member  22  connected to a rear end of the base member  20 , and a stringer  24  extending diagonally from a forward end of the base member  20  to an upper end of the rear support member  22 . Preferably, the base member  20 , the rear upright support member  22  and the stringer  24  are L-shaped in cross section and formed of a metal material, such powder-coated steel or anodized aluminum to inhibit rust and/or discoloration. It will be understood that the structural members can be constructed with other materials and/or finishes. A plurality of L-shaped risers  26  are connected to the stringer  24  for supporting the steps  16 . Each riser  26  is preferably constructed of a single piece of material and includes a vertical riser portion  28  and a horizontal riser portion  30  that is rigidly connected to the vertical riser portion. With the exception of the forward-most riser  26 , the ends  32  and  34  of the risers  26  are securely connected to the stringer, preferably through welding, although fasteners, brackets, or other securing means can be used. As shown, the forward-most riser  26  has one end  32  that is also connected to the stringer  24  and another end  34  that is connected to the forward end of the base member  20  at a more forward position than the stringer  24 . Each of the horizontal riser portions  30  includes a pair of spaced apertures  36  through which threaded bolts or studs  38  are received for securing the steps  16  to the risers  26 . 
     The steps  16  are preferably trapezoidal in shape with an upper surface  40  that is wider than a lower surface  42 . Each step  16  is preferably constructed of a slip-resistant cement material with the studs  38  embedded therein and extending downwardly from the lower surface  42 . It will be understood that the steps  16  can be constructed of other materials and shapes. 
     With the above-described arrangement, the stair module  10  is relatively light weight, rigid, and easily transported and erected when the individual components are shipped separately and bolted or otherwise connected together at the installation site. When the stair module  10  is used for temporary structures or displays, the bolted configuration allows for relatively quick and easy disassembly. 
     With reference now to FIG. 2, a transportation module  48  in the form of wheels or casters  50  can be connected to the base members  20  of the support frames  12  and  14  to facilitate movement and positioning of the modular stair assembly  5 . This configuration is especially advantageous when the modular stair assembly  5  is installed at temporary locations or must be moved for accessing or preventing access to different parts of a structure. The wheels  50  can be of the locking and/or swiveling type. The wheels  50  may additionally or alternatively be of the retracting type so that the frame can be solidly supported on a surface when positioned at a desired location. 
     With reference now to FIGS. 3 and 6, the modular stair assembly  5  can include a handrail module  60 . As shown, the handrail module  60  has a front upright post  62 , a rear upright post  64 , a lower support bar  66  that extends between the front and rear posts, an upper rail  68  that connects to and extends beyond the front and rear posts, and spindles  70  that extend between the lower support bar  66  and the upper rail  68 . The components of the handrail module  60  are preferably constructed of a durable material, such as steel or aluminum, and can be separately formed and rigidly connected together through welding, fasteners, or other attachment means. Alternatively, the handrail module  60  may be formed as a unitary structure of plastic or other material. The front upright post  62  is preferably connected to a front mounting tab  72  that is rigidly connected to and extends upwardly from the base member  20  of each support frame  12 ,  14 . The rear upright post  64  is preferably connected to the rear upright support member  22  of one of the support frames  12 ,  14 . The rear upright support members  22  and the front mounting tabs  72  preferably have mounting holes  74  that are in alignment with holes  76  (FIG. 6) on the front and rear posts  62  and  64 , respectively, for receiving a bolt or other fastener to thereby secure the handrail module  60  to one or both of the support frames  12 ,  14 . 
     With reference now to FIGS. 4,  6  and  7 , the modular stair assembly  5  can include a deck module  80 . As shown, the deck module  80  has a pair of spaced deck frames  82  and  84  and a plurality of platform portions  86  extending between the deck frames. Although not shown, a cross member can extend diagonally between the deck frames  82  and  84  for added structural support. 
     Each of the deck frames  82  and  84  is of generally C-shaped configuration and includes a lower support member  88 , a rear upright support member  90  connected to a rear end of the lower support member  88 , and an upper support member  92  connected to an upper end of the upright support member  90 . Preferably, the lower, upper and rear upright support members are L-shaped in cross section and formed of a metal material, such powder-coated steel or anodized aluminum to inhibit rust and/or discoloration. A lower connection tab  94  is secured to a forward end of each of the lower support members  88  and extends generally upwardly therefrom. An upper connection tab  96  is secured to a forward end of each of the upper support members  92  and extends generally forwardly therefrom. A hole  98  is preferably formed in each of the connection tabs  94 ,  96  and corresponding holes  100  (FIG. 6) are preferably formed in the rear upright support members  22  through which threaded bolts or other fasteners are received for securing the deck module  80  to the stair module  10 . It will be understood that the deck module can be connected to the stair module through other fastening means, such as clamping, welding, adhesive bonding, and so on. 
     Each of the upper support members  92  preferably includes pairs of spaced apertures  102  through which threaded bolts or studs (not shown) are received for securing the platform portions  86  to the upper support members  92 . It will be understood that more or less pairs of spaced apertures  102  can be used depending on the length of the deck module  80  and thus the total number of platform portions  86 . As with the rear upright support members  22  of the stair support frames  12  and  14 , the rear upright support members  90  of the deck frames  82  and  84  have mounting holes  105  that are in alignment with holes  76  (FIG. 6) on the rear posts  64  of the handrail module  60  for receiving a bolt or other fastener to thereby secure the handrail module  60  to one or both of the stair support frames  12 ,  14  and the deck frames  82 ,  84 . It will be understood that the structural members can be constructed with other materials and/or finishes. It will be further understood that the deck frames are not limited to the C-shaped configuration. 
     The platform portions  86  are preferably similar in construction to the steps  16  and are preferably trapezoidal in shape with an upper surface  104  that is wider than a lower surface  106 . Each platform portion  86  is preferably constructed of a slip-resistant cement material with studs (not shown) embedded therein and extending downwardly from the lower surface  106 . It will be understood that the platform portions  86  can be constructed of other materials and shapes. 
     Although only three steps  16  and two platform portions  86  are shown for the stair and deck modules, respectively, it will be understood that more or less steps and/or platform portions can be used, it being understood that the structural members would be lengthened and/or shortened to accommodate the different numbers of steps and/or platform portions, as shown for example in FIG.  9 . 
     The modular stair assembly  5  can include one or more of the modules as previously described. As shown in FIG. 1, the modular stair assembly includes the stair module  10 . In FIG. 2, a transportation module  48  is added. In FIG. 3, the modular stair assembly  5  includes a combination of the stair module  10  and the handrail module  60 . In FIG. 4, the modular stair assembly includes a combination of the stair module  10  and the deck module  80 . In FIGS. 5 and 6, the modular stair assembly includes a combination of the stair module  10 , the handrail module  60 , and the deck module  80 . Other combinations of the different modules can be used depending on the particular requirements at the installation site. 
     With reference now to FIG. 8, a modular stair assembly  110  in accordance with a further embodiment of the invention includes two modular stair assemblies  5  in back-to-back relation to form a raised platform  112  that can be accessed from either stair module  10 . As in the previous embodiment, each of the stair assemblies  5  may be arranged with a single stair module  10  or different combinations of modules to produce the desired effect. 
     Referring now to FIGS. 9 and 11, a modular stair assembly  120  in accordance with a further embodiment of the invention includes a stair module  122 , a deck module  124  connected to a rear end of the stair module, a handrail module  126  connected to a forward end of the stair module  122  and a rearward end of the deck module  124 , an extension deck module  128  connected to a rear end of the deck module  124 , and an extension handrail module  130  connected to a side of the extension deck module  128 . The stair module  122 , deck module  124  and handrail module  126  are similar in construction to the stair module  10 , deck module  80  and handrail module  60 , respectively, with the exception that some of the structural components are lengthened to accommodate an increased height of the stair module  122  and the increased number of steps  16 . The size of the structural components may also be increased to accommodate more weight. 
     The extension deck module  128  has a pair of spaced extension deck frames  132  and  134 , cross members  136 ,  138  and  140  extending diagonally between the extension deck frames  132  and  134 , and a plurality of platform portions  86  extending between the extension deck frames. 
     Each of the extension deck frames  132  and  134  is preferably generally square or rectangular in shape and includes a lower support member  142 , an upper support member  144 , a front upright support member  146  and a rear upright support member  148  extending between forward and rearward portions, respectively, of the lower support member  142  and the upper support member  144 . Preferably, the lower, upper, front and rear support members are L-shaped in cross section and formed of a metal material, such powder-coated steel or anodized aluminum. It will be understood that the support members can be constructed of other cross sectional shapes and/or materials. 
     As shown, the cross member  136  extends diagonally from a lower portion of the front upright support member  146  of the extension deck frame  132  to an upper portion of the front upright support member  146  of the extension deck frame  134 . Likewise, the cross members  138  and  140  extend diagonally from a lower portion of one of the rear upright support members  148  to an upper portion of the other rear upright support member  148 . Although three cross members are shown, it will be understood that more or less cross members can be provided. 
     As with the deck module  80 , each of the upper support members  144  of the extension deck module  128  preferably includes pairs of spaced apertures (not shown) through which threaded bolts or studs (not shown) are received for securing the platform portions  86  to the upper support members  144 . It will be understood that more or less pairs of spaced apertures can be used depending on the length of the extension deck module  128  and thus the total number of platform portions  86 . 
     The extension deck module  128  is preferably connected to the rear of the deck module  124  through fasteners, such as threaded bolts and nuts, but may alternatively be connected through clamping, welding, adhesive bonding, or other fastening means. 
     As shown in FIG. 9, the extension handrail module  130  has a front upright post  150 , a rear upright post  154 , a lower support bar  156  that extends between the front and rear posts, an upper rail  158  that extends between the front and rear posts, and spindles  160  that extend between the lower support bar  156  and the upper rail  158 . The components of the extension handrail module  130  are preferably constructed of a durable material, such as steel or aluminum, and can be separately formed and rigidly connected together through welding, fasteners, or other attachment means. Alternatively, the extension handrail module  130  may be formed as a unitary structure of plastic or other material. The front upright post  150  is preferably connected to the front upright support member  146  of one or both support frames  132 ,  134  (FIG. 11) Likewise, the rear upright post  154  is preferably connected to the rear upright support member  148  of one or both support frames  132 ,  134  through fasteners, such as threaded bolts and nuts, but may alternatively be connected together through clamping, welding, adhesive bonding, or other fastening means. The use of two or more extension handrail modules with the extension deck module  128  is contemplated. 
     With the above-described embodiment, one or more stair modules  122 , deck modules  124 , handrail modules  126 , extension deck modules  128 , and/or extension handrail modules  130  can be connected together in different combinations and orientations to accommodate a wide variety of circumstances and applications. As in the FIG. 8 embodiment, two modular stair assemblies  120  can be positioned in back-to-back relation to form an extended raised platform that can be accessed from both stair modules  122 . 
     With reference now to FIG. 10, a modular stair assembly  160  in accordance with a further embodiment of the invention is illustrated. The modular stair assembly  160  is similar in construction to the modular stair assembly  120  previously described, with the exception that the extended deck module  128  is connected to a side of the deck module  124  and a second extension handrail module  162  is connected to a forward portion of the extended deck module  128 . The handrail module  126  is also repositioned on an opposite side of the stair module  122  and the deck module  124 . 
     With the above-described embodiments, it can be readily seen that the modular stair assembly can be configured in a wide variety of different ways to accommodate a wide variety of different applications. 
     Turning now to FIGS. 12-14, a step  170  in accordance with a further embodiment of the invention is illustrated. The step  170  can be used with any of the stair modules of the previously described embodiments and includes a tread portion  172  and an overhang portion  174  that extends generally downwardly from the tread portion  172 . Openings  176  are formed in a lower surface  178  of the tread portion  172 . The openings  176  are adapted to receive threaded studs or bolts (not shown) for connecting the steps  170  with the risers  26  as previously described. Alternatively, studs, bolts, clamps, or other fastening means can be integrally molded with the steps  1700  for connection with the risers  26 . The step  170  is preferably constructed of a slip-resistant cement material, although other materials may be used. 
     It will be understood that terms of orientation and/or position as may be used herein such as vertical, horizontal, front, rear, upper, lower, and so on, as well as their respective derivatives and equivalent terms refer to relative, rather than absolute, orientations and/or positions. Moreover, it will be understood that the term “preferably” as used herein refers to an exemplary arrangement of the invention, and therefore is not intended to portray the invention in any limiting sense. 
     It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It will be understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Summary:
A modular stair assembly includes a stair module and at least one of a transportation module, deck module, handrail module, extension deck module, and extension handrail module that can be interconnected in various configurations to suite a wide variety of different applications.