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BACKGROUND OF THE INVENTION 
     1. Field of the Present Disclosure 
     This disclosure relates generally to attic flooring structures and more particularly to a portable flooring for supporting individuals and storage materials on attic beams and joists. 
     2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
     Wright, US 2007/0062147 discloses a portable folding floor unit with two or more sections, each of the sections being essentially identical rectangular planar sections. The sections are connected to one another along their lengths with the use of hinges, providing a flooring unit that can fold up in an accordion style for easy transportation and use. An alternate embodiment of the portable folding floor unit has two rectangular planar end sections with protruding hinge pieces along one length. A series of middle sections are provided with protruding hinge pieces along opposing lengths such that the two end sections and middle sections can be interlocked. A series of rods can be placed through the interlocking hinge pieces to produce the portable folding floor unit with an accordion style folding. 
     Landey, US 2006/0075711 discloses an Attic Floor Joist Grid System for Weight Bearing Storage called an Attic Grid System. This system features low profile, flat, open and high strength grid panels that are supported by a joist system. The panels install directly onto the ceiling joists in an attic or storage area for residential and commercial applications. The panels are nominal widths that extend essentially to the center points of supporting joists. The system provides a simple and strong support surface which only requires simple, easy to use tools for installation. The panels are easily trimmed to size for non-standard operations and for encircling mechanical and electrical objects. The system is “see-through” and permits full air movement. Hence it does not contribute to moisture entrapment, mold and mildew. The materials are fire resistant and do not collapse or emit toxic fumes in the presence of a flame. 
     Sullivan, U.S. Pat. No. 7,389,614 discloses herein a rack apparatus and storage panel assembly for implementing across two or more beams. The storage panel assembly is most typically implemented in attic storage space lacking a flooring surface on which to place and store items. The storage panel assembly comprises at least one rack apparatus, two or more railings to be positioned onto a series of rack apparatus and a panel configured to rest on two parallel railings. The assembly provides a continuous platform by sitting between the truss creating a planer surface between the top of the panel and the top of the truss. The method of assembly allows positioning of the rack apparatuses between the truss connections and allows the railings and panel to slide under any transverse obstructions bearing on top of truss. 
     Fischer, US D539933 discloses the ornamental design for an attic flooring extrusion. 
     Ellingson, U.S. Pat. No. 7,108,902 discloses a commercial floor mat with a plurality of aluminum rails arranged in closely spaced side-by-side relationship and connected together by hinged connectors beneath the rails. Each rail has a pair of downwardly facing grooves on its underside extending along respective edges of the rail. Each connector has a flexible central web and a pair of spaced upstanding tabs disposed in the downwardly facing grooves of adjacent rails. The tabs have flexible barb-shaped ribs extending along their opposed faces to anchor the tabs in the grooves with a friction fit. The flexible central webs of the connectors facilitate hinged movement of connected rails to permit the mat to be rolled onto itself into a compact configuration. 
     Eadie, U.S. Pat. No. 6,968,652 discloses a flooring device for positioning on joists so as to allow for easy maneuvering on floor joists in an attic. The flooring device includes a plurality of substantially rigid panels arranged adjacent to each other in a series. The invention also includes a connecting mechanism located at a juncture between each of the panels in the series for connecting each panel to an adjacent panel. The connecting mechanism permits adjacent panels of the series to pivot about a pivot axis with respect to each other, with the pivot axis of the mechanism at one juncture of the series being positioned adjacent to the top sides of the panel adjacent to the juncture and the pivot axis of the mechanism at an adjacent juncture being positioned adjacent to the bottom side of the panels adjacent to the juncture such that the series of panels are foldable in accordion fashion between collapsed and extended conditions. 
     Fetzer, U.S. Pat. No. 5,239,790 discloses a preassembled attic shelf unit, which includes a pair of shelf support members connected to each other with wooden connectors, so that outward facing surfaces of the support units are engageable with portions of adjacent roof trusses located on fixed centers. Each shelf support member may be rectangular wooden stock material formed with an elongate rectangular groove in an inward facing surface thereof so that the opposing grooves respectively receive longitudinal edges of the shelf in sliding supporting engagement. Nails may be utilized to fasten the shelf supporting members directly to the portions of the trusses such as web member portions interconnecting top and bottom chord members of the trusses together. 
     Max, U.S. Pat. No. 5,033,241 discloses a portable, foldable dance floor having a top surface of parquet panelling mounted on a flat plywood base, and composed of identical half-sections which open horizontally on a flat surface and close vertically parallel to each other. 
     Shreiner, U.S. Pat. No. 4,877,672 discloses a floor mat which is composed of a multiplicity of rigid elongated rails arranged parallel to each other, each rail having a body portion adapted to receive a tread member and a coupling portion by which it is joined to an adjacent rail. The body and coupling portions are found by extrusion of a rigid high-impact strength thermoplastic polymeric material and are joined by a living hinge of a highly flexible thermoplastic elastomer formed by coextrusion with the body and coupling portions. Each rail includes at least two ribs along its underside laterally spaced apart from each other and adapted to support the rail on a surface, each rib being formed by coextrusion with the body and coupling portions and the living hinge of a soft, compressible thermoplastic polymeric material and serving as a cushion and an anti-slip element of the mat. 
     Balzer et al., U.S. Pat. No. 4,654,245 discloses a roll up floor mat with rails or sections hingedly interconnected by alternating, flexible strips, which, in turn serve to cushion the mat by use of laterally extending flaps interposed between the floor or other supporting surface and the rail sections, the flaps being integral with the hinge assemblies between the sections. 
     Balzer, U.S. Pat. No. 4,568,587 discloses a floor mat which includes a plurality of rigid, elongated rails each having a side edge positioned in substantially parallel, spaced relationship to a respective side edge of an adjacent rail. A passageway opens inwardly from each rail side edge and includes an outer portion adjacent to the side edge and an inner portion. The passageway inner portions have greater cross-sectional dimensions than the passageway outer portions. Each pair of adjacent rails is interconnected by an elongated, flexible hinge member which is comprised of a pair of opposite, spaced flanges extending longitudinally with respect to the hinge member. The flanges are interconnected by a web having a cross-sectional thickness less than a cross-sectional thickness of each of the flanges. The hinge member flanges are each slidably received in a respective passageway inner portion. The hinge member is adapted to maintain the rails in a substantially parallel, predetermined spacing and to bend transversely with respect to the rails thereby allowing transverse angular displacement of the rails relative to each other. 
     The related art described above discloses solutions to the need for attic surfaces for storage and other needs. Wright and Eadie each teaches a plurality of boards that are abutted and joined along their long edges by hinges so that they may be folded accordion style when not in use and can be laid flat when installed on attic joists. Balzer, Balzer et al, Shreiner and Ellington each teaches a roll out mat that may be used for attic flooring. These structures are complex and of questionable practicality due their expense in production and assembly. The prior art fails to disclose an inexpensive and self stabilized relatively simple structure useful as a roll-out attic flooring that requires no installation hardware. The present disclosure teaches such an apparatus and its use and therefore distinguishes over the prior art providing heretofore unknown advantages as described in the following summary. 
     BRIEF SUMMARY OF THE INVENTION 
     This disclosure teaches certain benefits in construction and use which give rise to the objectives described below. 
     An interlocking portable rollout attic flooring having a plurality of planks laid side-by-side in a mutual abutting relationship of side edges of the planks, thereby defining a common, continuous, longitudinally extensive, top and bottom surfaces, the common bottom surface having longitudinally directed notches oriented orthogonal to the side edges. The longitudinally directed notches engaged with spaced apart beams for support and stability of the flooring. The side edges of the planks configured in a mutually overlapping relationship wherein each plank supports a portion of weight applied to each adjacent plank. Preferably, two longitudinally directed and spaced apart flexible straps fixed to the top surface of the flooring to secure the planks in the abutting relationship while allowing the planks, alternatively, to be rolled into a cylindrical bundle configuration for easily carrying the flooring. A shoulder strap may be attached to one of the planks. 
     A primary objective inherent in the above described apparatus and method of use is to provide advantages not taught by the prior art. 
     Another objective is to provide an assembly of planks providing a utility surface capable of being walked on or supporting the weight of stored items. 
     Another objective is to provide such an assembly that is easily installed on attic beams without tools for fasteners. 
     Another objective is to provide such an assembly that is able to nest with the attic beams or joists so as to prevent lateral movement of the assembly after installation. 
     Another objective is to provide such an assembly that is capable of being rolled into a compact form secured by a circumferential strap and carried using an integral shoulder strap. 
     Another objective is to provide such an assembly wherein adjacent planks have overlapping edges so that weight is distributed from each plank to an adjacent neighbor plank. 
     Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the presently described apparatus and method of its use. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       Illustrated in the accompanying drawing(s) is at least one of the best mode embodiments of the present invention In such drawing(s): 
         FIG. 1  is a perspective view of one embodiment of the presently described apparatus wherein planks are spaced apart and each of the planks is notched at both ends for securement on beams while preventing lateral movement of the planks; 
         FIGS. 2  is an elevational end view of the embodiment of  FIG. 1 , further showing the engagement of the planks with the beams; 
         FIG. 3  is a further elevational end view of a second embodiment of the present invention wherein the planks are notched for spanning and overlapping adjacent beams; 
         FIG. 4  is a still further elevational end view of a third embodiment of the present invention the planks are notched for spanning multiple beams; 
         FIG. 5  is a plan view of a fourth embodiment of the present invention wherein two plank assemblies are positioned side-by-side with their mutually adjacent ends resting on a common beam and wherein the adjacent ends of the planks are in alternating interleaved positions; 
         FIG. 6  is a side elevational view of a fifth embodiment wherein side edges of the planks are mutually nested and overlapped; 
         FIG. 7  is a top plan view of the arrangement of  FIG. 6  showing a shoulder strap and a circumferential strap attached to the planks; 
         FIG. 8  is an elevational view of the embodiment of  FIG. 6  wherein the planks are vertically oriented, rolled up, and secured by the circumferential strap; and 
         FIG. 9  is a perspective view of one of the planks of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The above described drawing figures illustrate the described apparatus and its method of use in at least one of its preferred, best mode embodiment, which is further defined in detail in the following description. Those having ordinary skill in the art may be able to make alterations and modifications to what is described herein without departing from its spirit and scope. Therefore, it should be understood that what is illustrated is set forth only for the purposes of example and should not be taken as a limitation on the scope of the present apparatus and its method of use. 
     In a preferred embodiment of the present invention, as shown in  FIGS. 3 ,  6 ,  7 ,  8  and  9 , an interlocking portable rollout attic flooring with overlapping planks  10  is defined as an assembly. The planks  10  are preferably made of wood or plastic and may be mill cut or extruded to a final configuration. The planks  10  may be made of other structural materials as well. The planks  10  are preferably arranged in a side-to-side edge abutting series as shown in  FIGS. 6 and 7  and are laid out, when deployed, in a longitudinal arrangement. The planks may also be non-abutting as shown in  FIGS. 1 and 5 . As shown in  FIG. 9 , each plank  10  has a top surface  11  and a bottom surface  12 , opposing side edges  13 , and side edge notches  13 N which extend along and are integral with side edges  13 . The planks  10  each also have at least one pair of longitudinally oriented and spaced apart bottom surface notches  12 N. Notches  12 N may be L-shaped, as shown in  FIGS. 1 and 2 , or U-shaped as shown in  FIGS. 3 ,  4  and  9 . Notches  13 N are L-shaped as shown in  FIGS. 6 and 9 . 
     From  FIGS. 6 and 9  we see that the top surface  11  is contiguous with one notch  13 N along one side edge  13 , while the bottom surface  12  is contiguous with a second notch  13 N along the opposing side edge  13 . In this manner, when the edges  13  of adjacent planks  10  are mutually engaged, each plank  10  shares loads with one adjacent plank  10  other than a plank  10  that is positioned at the end of the series of planks  10 . In this embodiment, straps  20  are engaged with planks  10  to assure that planks  10  are mutually engaged. 
     As shown in  FIG. 7 , two longitudinally oriented straps  20  of a non-elastic, flexible material such as nylon strapping are engaged with all of the planks  10  on their top surfaces  11 . Preferably, the two straps  20  are joined in a loop  25  at one end of the assembly. Straps  20  may be engaged with planks  10  in many ways such as by nail or brad fasteners  30  shown in  FIG. 6 . As shown in  FIG. 7  a further strap  50  may be engaged with one of the planks  10  and the further circumferential strap  50  is long enough to extend around the planks  10  when they are rolled-up into a coiled shape or bundle as shown in  FIG. 8 . The ends of circumferential strap  50 , when drawn around the coiled planks  10 , are mutually fastened using hook and loop fastener material, snaps  52 A and  52 B, or by other common fastening means. When coiled and fastened, as shown in  FIG. 8 , the assembly is easily carried by its shoulder strap; loop  25 . 
     In an alternate embodiment shown in  FIG. 1 , the present invention includes a pair of spaced apart, horizontally oriented, beams  40  such as ceiling joists which extend longitudinally and are fixed in place relative to a building structure (not shown). Such beams  40  are typically made of wood or metal and are arranged in mutually parallel positions and spaced apart according to building codes, as for instance on  16 ″ centers. Each of the beams  40  has an upwardly facing, top beam surface  42 . 
     The plurality of spaced apart, mutually parallel planks  10 , are laid across and rested on the beams  40 . Depending on the weight that planks  10  must support, they may vary in thickness, rigidity, specific gravity and strength. Planks  10  are considered to be structural members capable of supporting an individual standing or walking on them, or supporting storage materials, such as boxes of heavy items such as books, dishes, etc. 
     In  FIG. 1 , strips  20  are shown as preferably mounted on the top surface  11  of planks  10 , but they may be mounted just as easily on the bottom surface  12  or even on the ends of planks  10 . Also, strips  20  are shown as relatively narrow bands, however, they may be broader and may even be as long as the planks  10 , depending on the utility service. Therefore, in this disclosure, although we discuss two strips  20 , it should be understood that the strips  20  may be of any size, number, attachment means, and may be attached to the planks  10  in any way known to those of skill in the art, as long as the planks are held by the strips  20  in their desired locations and sequence.  FIG. 1  shows one embodiment of the present invention whereby strips  20  are secured to planks  10  by nails, brads, screws or other common hardware. 
     A key and important feature of the present invention is that at least one of the planks  10 , and preferably all of them, has a surface conformation that thwarts or prevents disengagement of the planks  10  from the beams  40  by lateral motion of the planks  10 . This is a critical feature since when walking atop the planks  10 , or when sliding boxes or other storage materials around on the top surfaces  11  of the planks  10 , lateral forces may be applied to the planks  10  and this may cause them to move laterally and thereby lose contact with one or both beams  40 . Should this happen, whatever is supported by the planks  10  may fall between beams  40  and possibly damage a ceiling structure. Attachment of the planks  10  to the ceiling joists  40  with screws and nails one may prevent lateral motion, but such fastening requires considerable work in fixing the planks  10  to the joists or beams  40  and more work when removing them. With the present invention, as will be shown, installation and removal of the planks  10  is as simple as mere roll-out to install and rollup to remove. No installation tools or hardware is required. However, it may be desirable to tack the first and the last plank in place for improved permanency. 
     As shown in  FIG. 2 , notches  12 N may be placed at the very ends of planks  10 . Alternately, as shown in  FIGS. 3 and 4 , notches  12 N may be placed at locations other then at the ends of the planks  10  including medially. From this it is clear that notches  12 N may be U-shaped, or L-shaped. 
     As shown in  FIG. 4 , planks  10  may be used to span three or more of the beams  40 . However, wider assemblies may be too heavy and unwieldy to manipulate during installation and removal, and cumbersome also for storing when not in use or when transporting. A better solution may be to place two or more of a narrower assembly in a side by side relationship, such as shown in  FIGS. 2 and 5 , in order to cover a larger surface area within an attic. In  FIG. 2  we see that the top beam surface  42  is common to two side-by-side plank assemblies, and surface  42  has a width sufficient for simultaneously resting the ends of two collinearly aligned said planks  10 . In  FIG. 5 , when the common beam  40  is not wide enough, or when greater overlap of the ends of planks  10  is desired, the solution lies in providing a spacing between planks  10  that is equal to, or greater, then the width of each of the planks  10 . 
     The enablements described in detail above are considered novel over the prior art of record and are considered critical to the operation of at least one aspect of the apparatus and its method of use and to the achievement of the above described objectives. The words used in this specification to describe the instant embodiments are to be understood not only in the sense of their commonly defined meanings, but to include by special definition in this specification: structure, material or acts beyond the scope of the commonly defined meanings. Thus if an element can be understood in the context of this specification as including more than one meaning, then its use must be understood as being generic to all possible meanings supported by the specification and by the word or words describing the element. 
     The definitions of the words or drawing elements described herein are meant to include not only the combination of elements which are literally set forth, but all equivalent structure, material or acts for performing substantially the same function in substantially the same way to obtain substantially the same result. In this sense it is therefore contemplated that an equivalent substitution of two or more elements may be made for any one of the elements described and its various embodiments or that a single element may be substituted for two or more elements in a claim. 
     Changes from the claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalents within the scope intended and its various embodiments. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements. This disclosure is thus meant to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, what can be obviously substituted, and also what incorporates the essential ideas. 
     The scope of this description is to be interpreted only in conjunction with the appended claims and it is made clear, here, that each named inventor believes that the claimed subject matter is what is intended to be patented.

Summary:
An interlocking portable rollout attic flooring having a plurality of planks laid in a mutual abutting relationship of side edges of the planks, to define a common longitudinally extensive top and bottom surfaces, the common bottom surface having longitudinally directed notches oriented orthogonal to the side edges. The longitudinally directed notches engaged with spaced apart beams for support and stability of the flooring. The side edges of the planks configured in a mutually overlapping relationship wherein each plank supports a portion of weight applied to each adjacent plank. At least one longitudinally directed flexible strap fixed to the top surface of the flooring to secure the planks in the abutting relationship while allowing the planks to be rolled into a cylindrical configuration.