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FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to portable devices that may be used, among other things, to elevate a user to assist in the performance of certain tasks, to assist a user in reaching elevated places or items, and to support a user while standing or sitting on the device. More specifically, the present invention relates to a multipurpose step stool that allows the user to variably adjust the height of elevation by rotation and selective orientation of the step stool.  
         BACKGROUND OF THE INVENTION  
         [0002]    Step stools and the like are well known. Indeed, it is common knowledge that a simple step stool can be an indispensable tool in helping an individual to complete daily tasks around the home, in the yard or at work. A step stool may be used to bring the user within reaching distance of an elevated place or object, and may even be used to reduce the user&#39;s exertion in reaching for an object that may not necessarily be out of reach. Depending upon what is desired or required by the user, the height to be obtained by the use of the step stool needs to be variable. Similarly, the step stool itself should allow the user to reach a variety of heights to maximize its usefulness. In the view of these inventors, what is needed is a new and useful step stool that is suitable for use in a wide variety of domestic and industrial applications.  
         SUMMARY OF THE INVENTION  
         [0003]    The present invention provides a new and useful step stool that includes a pair of side support members, each side support member having a plurality of resting surfaces defined within it. In use, each side support member lies in a plane that is generally parallel to the plane that the other side support member lies in. A plurality of combination tread/riser members is provided, each tread/riser member being attachable to and extending generally perpendicularly between the side support members. In this fashion, a first orientation of the step stool provides a first level of elevation, a second orientation of the step stool (having a first rise over run ratio) provides a second, and multiple, level of elevation, and a third orientation of the step stool (having a second rise over run ratio) provides a third, and multiple, level of elevation. Each orientation and each level of elevation is attainable with the use of this single step stool device.  
           [0004]    In the preferred embodiment of the step stool that is constructed in accordance with the present invention, the side support members and the combination tread/riser members are detachable from one another, to facilitate manufacturing, and to allow the step stool to be “knocked-down” flat for shipping and storage. In some versions of this embodiment of the invention, the side support members and the combination tread/riser members include integral interlocking latches and latch openings that are functionally adapted for connecting the tread/riser members to the side support members without using tools. Alternatively, more permanent fastening means may be used such as screws or nuts and bolts. The step stool of the present invention can be produced in many forms, adaptable to a wide range of uses. The step stool may be fabricated from a wide range of metallic and nonmetallic materials, material selection not being a limitation of the present invention. The step stool of the present invention is also adaptable to a wide range of sizes, including tall stools having three or more steps, and smaller, perhaps half scale, stools made specifically for children, size not being a limitation of the present invention either.  
           [0005]    Other aspects and advantages of the new and useful step stool will be apparent to those having skill in the art upon review of the attached drawings and the following detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a top, left and front perspective view of a step stool constructed in accordance with the present invention and showing the step stool as it would be placed on a support surface in a first orientation to provide a first elevation.  
         [0007]    [0007]FIG. 2 is another perspective view of the step stool illustrated in FIG. 1 and showing the step stool as it would be placed on the support surface in a second orientation providing a first tread/riser ratio.  
         [0008]    [0008]FIG. 3 is yet another perspective view of the step stool illustrated in FIG. 1 and showing the step stool as it would be placed on a support surface in a third orientation providing a second tread/riser ration.  
         [0009]    [0009]FIGS. 4A and 4B are schematic diagrams of the generally triangular side support members corresponding respectively to the first and second orientations of the step stool shown in FIGS. 2 and 3, respectively, and illustrating the first and second Rise/Run ratios thereof.  
         [0010]    [0010]FIG. 5 illustrates one of a pair of the generally triangular side support members from an embodiment of the invention in which the combination tread/riser members are detachable from the side members by used of conventional fasteners.  
         [0011]    [0011]FIG. 6 is a perspective view of one of the tread/riser members that is shown molded as one piece. 
     
    
     DETAILED DESCRIPTION  
       [0012]    Referring now to the drawings in detail wherein like numbered elements represent like elements throughout, FIG. 1 shows a preferred embodiment of a step stool, generally identified  10 , constructed in accordance with the present invention. FIGS. 1, 2 and  3  show the step stool  10  as it would rest in a first, second and third orientation on a support surface such as a floor.  
         [0013]    The step stool  10  includes a plurality of tread/riser units, generally identified  50 , fastened between a pair of identically configured side support members  20 . In the preferred embodiment of the device of the present invention, each side support member  20  is constructed in the form of a generally triangular frame having a plurality of integrally formed and intersecting I-beam type members. See FIG. 5. Specifically, each side support member  20  includes a first outer leg member  22 , a second outer leg member  24  and a third outer leg member  26 . The first and second outer leg members  22 ,  24  have the same length and form two sides of an isosceles triangle. The third outer leg member  26  forms the base of the triangle. The acute angle formed by first and second outer leg members  22 ,  24  is about 48° in the preferred embodiment. The acute angles formed by the first and third outer leg members  22 ,  26  and by the second and third outer leg members  24 ,  26  is about 66°. See FIG. 5. It is to be understood, however, that these angles could be varied and are not a limitation of the present invention. It is also to be understood that the outer leg members could be pivotally movable and/or foldable relative to one another as will become apparent later in this detailed description.  
         [0014]    A number of inner support members  32 ,  34 ,  36 ,  38 ,  42 ,  44  are also provided. Each inner support member  32 ,  34 ,  36 ,  38 ,  42 ,  44  is integrally formed as part of the side support member  20  and intersects one of the outer leg members  22 ,  24 ,  26 . See FIG. 5. In the preferred embodiment, each inner support member  32 ,  34 ,  36 ,  38 ,  42 ,  44  is formed in an I-beam cross-section configuration. As shown, the inner support members  32 ,  34 ,  36 ,  38 ,  42 ,  44  each form a part of a generally hexagonal support structure. Also as shown, the inner support members  32 ,  34  are generally collinear. The inner support members  36 ,  42  are generally parallel to one another as are the inner support members  38 ,  44 . The purpose and function of this configuration will become apparent further in this detailed description.  
         [0015]    In the preferred embodiment, a plurality of tread/riser members, generally identified  50 , are provided. See FIG. 6. Each tread/riser member  50  has an upper surface  52 , a pair of side edges  54 ,  55  and a pair of end edges  56 ,  57 . The end edges  56 ,  57  are those portions of the tread/riser members  50  that are engageable with the side support members  20 , and the inner support members  32 ,  34 ,  36 ,  38 ,  42 ,  44  thereof in particular.  
         [0016]    Referring again to FIG. 1, a first pair of generally planar tread/riser members  50   a ,  50   b  are oriented generally parallel to a plane formed by the second outer leg member  24  of each side support member  20 . Referring to FIG. 2, a second pair of tread/riser members  50   c ,  50   d  are oriented generally parallel to a plane formed by the first outer leg member  22 . And referring to FIG. 3, a third pair of tread/riser members  50   e ,  50   f  are shown oriented generally parallel to a plane formed by the third outer leg member  26  of each side support member  20 .  
         [0017]    As shown in FIGS. 2 and 3, the tread/riser members  50   c ,  50   d  and  50   e ,  50   f , respectively, are staggered one from the other. In the embodiment depicted in FIGS. 1 through 4B, the first and third outer leg members  22 ,  26  form an acute angle with each other, and the riser/tread members  50   c ,  50   d , used as treads, are spaced from a point of intersection  27  of projections of the first and third surfaces  22 ,  26 , such that when the step stool  10  is resting in the second orientation, the tread/risers  50   e ,  50   f  form risers for the treads  50   c ,  50   d . This combination forms a first rise over run ratio Rise 1 /Run 1 , which is relatively flat and suitable, for example, in assisting small children to reach important areas such as sinks and toilets.  
         [0018]    When the step stool  10  is positioned in the third orientation, as depicted in FIGS. 3 and 4B, with the third outer leg  26  in contact with a supporting surface, the treads  50   c ,  50   d  form risers to the treads  50   e ,  50   f . This combination forms a second rise over ratio Rise 2 /Run 2  that is steeper than the first rise over run ratio Rise 1 /Run 1 , thereby allowing the user to climb to a height suitable for reaching high spots such as the upper corners of a room or the tops of tall furniture or shelving.  
         [0019]    In the embodiments depicted in FIGS. 1 through 3, the first, second and third outer leg members  22 ,  24 ,  26 , which are also resting surfaces for the stool  10 , extend almost the full length of the sides of the triangular side support members  20  and intersect with one another in rounded corners  28 , rather than being truncated or cut off. Extending the resting surfaces  22 ,  24 ,  26  in this fashion provides increased stability in any of the first, second or third orientations, and also provides a grip rail extending above the treads and platform for the user to grasp while ascending or standing on the treads  50 . This is particularly true where the cross-sectioned construction of each outer leg member  22 ,  24 ,  26  is in the form of an I-beam as previously described.  
         [0020]    As shown in FIG. 4A, the first rise over run ratio Rise 1 /Run 1  is calculated by projecting the first and third resting surfaces  22 ,  26  to a point of intersection  27  beyond the rounded corner  28 , and dividing the difference in vertical distances v1 1 , v1 2  (from the point of intersection  27  of the first and third resting surfaces  22 ,  26  to points of intersection  31 ,  33  of a projection of the working surfaces of the treads  50   c ,  50   d ) by the difference in horizontal distances h1 1 , h1 2  (from the point of intersection  27  of the first and third resting surfaces  22 ,  26  to the points of intersection  31 ,  33  of the projections of the working surfaces of the treads  50   c ,  50   d ).  
         [0021]    The second rise over run ratio Rise 2 /Run 2  is calculated in similar fashion, as shown in FIG. 4B, by utilizing the vertical and horizontal distances v2 1 , v2 2 , h2 1 , h2 2 , from the point of intersection  27  of the projections of the first and second resting surfaces  22 ,  26  to the points of intersection  31 ,  33  of the projections of the treads  50   e ,  50   f.    
         [0022]    In some forms of the step stool  10  of the present invention, it may be advantageous to have some of the component parts, i.e., the treads  50 , or the side support members  20 , integrally joined together in an inseparable unit. In other forms of the step stool  10 , however, it may be advantageous to have some or all of the components of the step stool  10  be detachable from the other components to facilitate manufacturing, shipping, or storage of the step stool  10 . FIGS. 5 and 6 depict an embodiment of the step stool  10  having a pair of identical side support members  20  (only one shown) that are detachable from a series of identical tread units  50  (only one shown) that can be positioned and attached to the side support members  20  as previously described. In this fashion, the first pair of tread/riser members  50   a ,  50   b  are removably attachable to the inner support members  32 ,  34 , respectively, of the side support members  20 . The second pair of tread/riser members  50   c ,  50   d  are similarly removably attachable to the inner support members  44 ,  38 , respectively, of the side support members  20 . And the third pair of tread/riser members  50   e ,  50   f  are removably attachable to the inner support members  36 ,  42 , respectively. It is to be understood that each riser/tread member  50  is attachable to each side support member  20  by use of conventional fastening means. In this fashion, and with this configuration, the second pair of tread/riser members  50   c ,  50   d  serve as the risers for the third pair of tread/riser members  50   e ,  50   f  when those members are used as treads and vice versa.  
         [0023]    The device of the present invention can also be fabricated to be fully collapsible along outer leg member  24 . In this embodiment, each joint  31 ,  33  is actually two joints. For example, tread/riser member  50   e  would have a revolute joint  33  with respect to member  24  whereby member  50   e  is permitted to rotate about that joint  33 . At that same joint  33 , tread/riser member  50   d  is permitted to slide along the outer let member  24  and also is permitted to revolve. In this manner, and as member  50   d  slides downwardly along the outer leg member  24 , member  50   a  is drawn towards the outer leg member  24  until member  50   a  is flush with the outer leg member  24 .  
         [0024]    Similarly, member  50   f  has a revolute joint  31  with respect to the outer leg member  24 . Member  50   c  has a sliding and revolute relationship with member  24 . Thus, as member  50   f  revolves, member  50   c  slides along member  24  until member  50   b  is substantially flush with member  24 .  
         [0025]    Obviously, the step  10  of the present invention stool is required to be a static structure. Therefore, some simple means of transforming the structure from a step stool to a reasonably flat object is also required. In other words, something must allow for transformation of the stepstool  10  from a static structure to a dynamic structure. To that end, member  22  and member  26  may be attached to one another via a quick release joint  27 , of which there are many examples in the art. Member  22  and  24  are also connected via a revolute joint  28 , as are members  26  and  24 . Therefore, as member  26  is rotated upwardly towards member  24 , member  22  is no longer supported outwardly. Therefore, member  22  is permitted to fold toward member  24  causing member  50   e  to rotate downwardly, also allowing member  50   d  to slide downwardly and rotate downwardly. Simultaneously, member  50   f  rotates downwardly and member  50   c  slides and rotates downwardly. At completion, the entire step stool  10  lies flat against member  24 . Now, this description has been given as if the step stool  10  were only two dimensional. The actual step stool  10 , is, of course, three dimensional, but the rotating and sliding parts merely extend along the third axes such that the object can be modeled in two dimensions.  
         [0026]    As an alternative to conventional fastening means, each riser/tread member  50  may be constructed with integral locking tabs (not shown) having latch surfaces which resiliently slide through matching slots (also not shown) in the side support members  20  in such a manner that the treads  50  and side support members  20  can be connected together without the use of tools. In this manner, the step stool  10  can be readily manufactured and shipped in a flat, knocked-down configuration to save on shipping and inventory costs, and the step stool  10  can be readily assembled by the user upon purchase.  
         [0027]    The step stool  10  of the present invention can be fabricated from a wide variety of materials, by a number of methods, and in a number of forms or sizes dependent upon the size of the user, and the nature of the use. In one preferred form of my step stool  10 , the side plates and treads as depicted in FIGS. 1 through 3,  5  and  6  could be cast from aluminum or other metal material. They could also be injection molded from a polypropylene material. When such a material is used, it may be desirable to reinforce the intersection of the first, second and third resting surfaces  22 ,  24 ,  26 , as shown by the partial circular enlargements at reference numeral  28  in FIG. 5. Where such enlargements extend out of the planes defined by the first, second and third resting surfaces  22 ,  24 ,  26 , stability of the step stool  10  on soft surfaces such as carpet or turf may be enhanced by having the enlargements  28  penetrate the supporting surface slightly.  
         [0028]    It is to be understood, therefore, that the scope of the disclosure and appended claims are not limited to the specific embodiments described and depicted herein.

Summary:
A multipurpose step stool includes two substantially parallel, congruent, triangular side support members. The triangular side support members each include first, second, and third resting edges adapted to contact a supporting surface such as a floor. The first treads are oriented parallel to the first resting edges, the second treads are oriented parallel to the second resting edges, and the platform is oriented parallel to the third resting edges. The angle between the first and second resting edges, and the positioning of the first and second treads are selected such that, when the first resting edges are placed on a support surface, a first orientation of the step stool is provided with the first and second treads in combination forming a first rise over run ratio; when the second resting edges are placed on a support surface, a second orientation of the step stool is provided with the second and first treads in combination forming a second rise over run ratio; and when the third resting edges are placed on a support surface, a third orientation of the step stool is provided with the platform elevated above the supporting surface.