Abstract:
An interlocking slidable assembly useful for movable extensible platforms, such as a movable or sliding floor or plate extension used with the rear cargo areas of a motor vehicle such as a pickup truck. This assembly includes a first and second plurality of rotatable members spaced apart along parallel axes that slidably interlock with the guide members of the rail or rails. Each of the rotatable members is rotatable about a substantially vertical rotational axis and slidably engages the respective guide member of the rail or rails. One of the guide members or the rotatable members have a recess in the periphery thereof to slidably receive the other of the guide and rotatable members. Because the rotatable members rotate about vertical axes, there is better and more even distribution of weight on the weight-bearing surfaces that makes it easier for slidable movement and decreases the amount of wear. In addition, because the recesses in the rotatable members (or the guide members) are oriented to open horizontally (rather than vertically), dirt and other debris will have less of a tendency to collect in the recesses and thus inhibit slidable movement.

Description:
TECHNICAL FIELD  
         [0001]    The present application relates to an interlocking slidable assembly useful for movable extensible platforms and other movable structural members such as a movable or slidable floor or plate extension for rear cargo areas, such as truck beds and other cargo bed areas, of motor vehicles such as pickup trucks, sport utility vehicles (SUVs), station wagons and vans. The present invention particularly relates to an interlocking slidable assembly having guide members that slidably interlock with rotatable members that rotate about a vertical axis.  
         BACKGROUND OF THE INVENTION  
         [0002]    With the proliferation of compact, mid-size and full-size pickup trucks with short beds, generally ranging from 4 to 6.5 feet in length, there is a limitation on the ability of truck owners to effectively haul longer items typically accommodated by longer beds (e.g., a 4 foot×8 foot sheet of plywood). A similar problem exists with the cargo area of other motor vehicles such as sport utility vehicles (SUVs), station wagons and vans that are also used to haul such items.  
           [0003]    Several approaches have been previously suggested to expand the cargo carrying capacity of pickup truck beds and other motor vehicles used to haul various items. One such approach is to use a tailgate extension device to provide a longer bed floor area. See, for example, U.S. Pat. No. 4,023,850 (Tillery), issued May 17, 1977; U.S. Pat. No. 4,531,773 to (Smith), issued Jul. 30, 1985; and U.S. Pat. No. 5,755,480 (Bryan), issued May 26, 1998. While these prior tailgate extension devices do provide for an expanded cargo floor area, the steps necessary for their assembly and regular use are relatively complex. In addition, when not in use as a bed extension, these prior extension devices serve no other beneficial purpose.  
           [0004]    A variation of the tailgate extension approach is disclosed in U.S. Pat. No. 5,700,047 (Leitner, et al), issued Dec. 23, 1997, involving a U-shaped truck bed extender  11  that can be rotatably mounted to the side walls of the rear portion of a pickup bed and then rotated inside the bed to serve as a storage/retaining compartment for loaded items or outside the bed onto the lowered tailgate to effectively expand the enclosed cargo area. While retention is provided for cargo items that extend onto the lowered tailgate, this truck bed extender does not truly expand or extend the truck bed or cargo area floor.  
           [0005]    Another prior approach to expand the cargo carrying capacity of a pickup truck bed involves slidable assemblies that expand the bed or floor to accommodate larger load items, but can be retracted to a shortened bed length when such capability is not required. See, for example, U.S. Pat. No. 4,950,123 (Brockhaus), issued Apr. 21, 1990; and U.S. Pat. No. 5,816,637 (Adams et al), issued Oct. 6, 1998. While these prior expandable and retractable beds or floors provide for expanded cargo area when needed, their construction and installation is necessarily complex, in that the expansion (and retraction) mechanism is a duplicative element in the manufacture of an entire truck bed.  
           [0006]    Still another approach for slidable assemblies used with work benches, plates, floors, beds, tables and the like that are movable within the pickup bed cargo area involves various types and configurations of rollers for ease of slidable movement. See, for example, U.S. Pat. No. 5,090,335 (Russell), issued Feb. 25, 1992; U.S. Pat. No. 5,513,941 (Kulas et al), issued May 7, 1996; and U.S. Pat. No. 6,059,339 (Madson), issued May 9, 2000. For several of these devices, the rollers can be guided or mounted for movement within or along a track, rail or channel. See U.S. Pat. No. 4,993,088 (Chudik), issued Feb. 19, 1991; U.S. Pat. No. 5,098,146 (Albrecht et al), issued May 24, 1992; U.S. Pat. No. 5,456,511 (Webber), issued Oct. 10, 1995; U.S. Pat. No. 6,065,792 (Sciullo et al.), issued May 23, 2000. The rollers for these prior slidable assemblies cited above are mounted for rotation about the horizontal axis. As a result, the weight distribution is uneven in that the primary weight-bearing surface will be at the bottom of each of the rollers. This can make it more difficult to slidably move the bench, plate, floor, bed or table, especially if the bench, plate, floor, bed or table is relatively heavy. In addition, this uneven weight distribution can greatly increase the amount of wear that occurs on the rollers.  
           [0007]    Some of these slidable assemblies with guided or mounted roller systems use rollers that have grooves or notches for engaging the guiding rail, track or channel. One such system is disclosed in U.S. Pat. No. 5,649,731 (Tognetti), issued Jul. 22, 1997 and involves a workbench that is supported by rollers  58  and  66  having respective grooves  60  and  68  that receive portions of respective rails  46  and  52 . Another such system is disclosed in U.S. Pat. No. 5,938,262 (Mills), issued Aug. 12, 1999 and involves a slidable truck bed extension plate  26  mounted on parallel connecting rails  36  that rotatably mount three pairs of upper and lower rollers  38 ,  40 , each of the rollers having respective wheel well notches  28 ,  32 ; each of the pairs of upper and lower rollers  38 ,  40  are spaced apart to receive a rail  44  supported on truck bed  12  by three spaced rail supports  46 . As with the other prior roller systems for slidable assemblies, the notched or grooved roller systems of the Tognetti and Mills patents are mounted to rotate about a horizontal axis. This means that the primary weight-bearing surface will again be the bottom surface of the rollers with the attendant problems of difficulty in moving the workbench or plate if it is relatively heavy and increased wear on the rollers (especially the lower rollers  38  of the Mills system) because of the uneven distribution of weight. In addition, because the rollers rotate about the horizontal axis, the notches or grooves of the Tognetti and Mills roller systems open vertically and are more likely to pick up, collect and accumulate dirt and other debris. This can increase the degree of friction between the rollers and the respective rails, again making it potentially more difficult to slidably move the workbench or plate.  
           [0008]    Accordingly, it would be desirable to provide a slidable assembly for a movable extensible platform, plate, floor, bed, table or similar movable structural member useable with pickup truck beds and other cargo areas of motor vehicles used to haul various items that: (1) is of relatively simple construction; (2) permits relatively easy movement of the movable structural member, especially between fully extended and fully stored positions; (3) provides for more even weight distribution to permit relatively easy slidable movement between fully extended and stored positions without excessive wear; and (4) is not prone to accumulating dirt and other debris that can inhibit the ability for easily slidable movement.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention relates to an interlocking slidable assembly for movable extensible platforms or other movable structural members used with a base member, such as a movable or sliding floor or plate extension used with the rear cargo areas of a motor vehicle. In one embodiment, this assembly comprises:  
           [0010]    a. a first and second plurality of rotatable members associated with one of the structural member and the base member;  
           [0011]    b. the first plurality of rotatable members being spaced apart along a first longitudinal axis;  
           [0012]    c. the second plurality of rotatable members being spaced apart along a second longitudinal axis spaced laterally from and substantially parallel to the first axis;  
           [0013]    d. each rotatable member of the first and second pluralities being rotatable about a substantially vertical rotational axis;  
           [0014]    e. a guide component associated with the other of the structural member and the base member;  
           [0015]    f. the guide component having a first guide member that slidably engages the first plurality of rotatable members and a second guide member that slidably engages the second plurality of rotatable members so that the guide component slidably interlocks with the first and second plurality of rotatable members;  
           [0016]    g. one of each of the guide members and each of the rotatable members having a recess in the periphery thereof to slidably receive the other of the guide members and the rotatable members.  
           [0017]    In an alternative embodiment of the present invention, this assembly comprises:  
           [0018]    a. a plurality of rotatable members associated with one of the structural member and the base member and spaced apart along a longitudinal axis;  
           [0019]    b. each rotatable member being rotatable about a substantially vertical rotational axis;  
           [0020]    c. a guide component associated with the other of the structural member and having a first guide member and second guide member;  
           [0021]    d. one of each of the guide members and each of the rotatable members having a recess in the periphery thereof to slidably receive the other of the guide members and the rotatable members.  
           [0022]    e. the first and second guide members being oriented on opposite sides of each rotatable member so as that the guide component slidably interlocks with the plurality of rotatable members.  
           [0023]    The above embodiments of the interlocking slidable assembly of the present invention provide a number of advantages over prior slidable assemblies used with movable platforms, floors, plates, beds, tables and similar movable structural members, especially relative to prior slidable assemblies that use rollers that are mounted for rotation about horizontal axes. Because the rotatable members of the present invention rotate about vertical axes, there is a better and more even distribution of weight on the weight-bearing surfaces. This better and more even weight distribution not only makes it easier for slidable movement of the movable structural member, especially from a fully stored to a fully extended position (and vice versa), but can also decrease the amount of wear on the weight bearing surfaces of the rotatable members. In addition, because the recesses in the rotatable members (or the guide members) are oriented to open horizontally (rather than vertically), dirt and other debris will have less of a tendency to collect and accumulate in the recesses and thus inhibit slidable movement.  
           [0024]    Other benefits and advantages of the interlocking slidable assemblies of the present invention include:  
           [0025]    (a) providing a slidable assembly for use with a variety of movable extensible platforms or other movable structural members such as an integrated sliding floor extension for a truck bed and multiple purpose vehicle cargo area to: (1) increase the utility of shorter beds for hauling longer items; and (2) increase the ease of and access to loading and unloading of items stored in the bed or cargo area, rather than leaning into the bed compartment from the side or rear or into the vehicle cargo area to load or retrieve a cargo item.  
           [0026]    (b) providing a slidable assembly that has a relatively simple structure, is relatively easy to operate and is relatively resistant to mechanical malfunction during typical use;  
           [0027]    (c) providing a slidable assembly that can integrate the motor vehicle (e.g., pickup truck or multiple purpose vehicle) cargo area with a sliding floor or extension plate to increase the ease of access to cargo, extend the pickup bed load floor, and provide a multifunctional platform for mounting, attaching or otherwise incorporating cargo dividers/restraining devices, toolboxes, coolers, canoe racks or other such items. This can be achieved whether the cargo area is constructed of metal, composite/plastic or a combination of the two. In particular, the slidable assembly of the present invention is especiallly useful for providing for the bed or cargo area of a motor vehicle (e.g., pickup trucks, vans, SUVs, other passenger vehicles, etc.) a sliding floor or extension to enable the stored or hauled items therein to be easily removed from the rear of the truck or passenger vehicle, as well as to increase the length of the bed/cargo area floor. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    [0028]FIG. 1 is a view from the rear end of the cargo bed of a representative pickup truck (without tailgate) showing an embodiment of the slidable assembly of the present invention used with a sliding floor extension plate.  
         [0029]    [0029]FIG. 2 is an enlarged, sectional view of a portion of the embodiment of the assembly of FIG. 1.  
         [0030]    [0030]FIG. 3 is a top plan view of the truck cargo bed of FIG. 1 with the tailgate down showing the sliding floor extension plate in a fully stored position.  
         [0031]    [0031]FIG. 4 is a top plan view of the truck cargo bed of FIG. 1 showing the sliding floor extension plate in a fully extended position.  
         [0032]    [0032]FIG. 5 is a sectional view taken along line  5 - 5  of FIG. 4.  
         [0033]    [0033]FIG. 6 is a top plan view of an alternative embodiment of the assembly of FIGS. 1 and 2.  
         [0034]    [0034]FIG. 7 is an enlarged sectional view taken along line  7 - 7  of FIG. 6.  
         [0035]    [0035]FIG. 8 is a top plan view of an alternative embodiment of the assembly of FIGS. 1 and 2.  
         [0036]    [0036]FIG. 9 is an enlarged sectional view taken along line  9 - 9  of FIG. 8.  
         [0037]    [0037]FIG. 10 is a side sectional view of a portion of an alternative embodiment of the slidable assembly of the present invention where the rollers are rotatably mounted within the sidewalls of the cargo bed area of the pickup truck.  
         [0038]    [0038]FIG. 11 is a side sectional view of an alternative embodiment of the assembly shown in FIG. 10.  
         [0039]    [0039]FIG. 12 is a side sectional view of a portion of another alternative embodiment of the slidable assembly of the present invention where the rollers are rotatably mounted on the cargo bed floor and the guide members are integral with the sliding plate. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0040]    The present invention can best be understood by reference to the drawings that illustrate various embodiments of the slidable assembly within the scope of the present invention. For illustrative purposes, the embodiments of this interlocking slidable assembly are shown as being used with a movable, extensible platform member in the form of a slidable floor extension plate for a pickup truck bed or similar cargo area such as that of a sport utility vehicle (SUV). However, the slidable assembly of the present invention can be used with a variety of other movable or slidable extensible platforms or other movable support or structural members such as utility trailer floors, loading ramps, all terrain vehicle (ATV) beds, recreational vehicle (RV) storage bins, stereo component racks, marine storage bins and electronic racks, roof carriers, aircraft storage bins, tool box slides, fishing tackle boxes or drawers, food service tray racks, library book shelves, and casket slides, or any other storage bin, rack, box, or shelf that needs slidable access, for a variety of mobile and/or stationary structures, or vehicles.  
         [0041]    Referring initially to FIG. 1, the slidable assembly of the present invention is shown being used with a motor vehicle such as a pickup truck indicated generally as  10  to provide a sliding load floor extension structure indicated generally as  12  for a truck cargo bed area indicated generally as  14 . The slidable assembly of the present invention used in structure  12  is shown in FIG. 1 in the form of a pair laterally spaced apart assemblies or combinations  15  and  16 . Left assembly or combination  15  comprises a guide component in the form of a first or left rail  18  that is slidably received by a first or left set comprising a plurality of rotatable members, one of which is shown in FIG. 1 and indicated generally as  26 . The other right assembly or combination  16  comprises a guide component in the form of a second or right rail  20  that is laterally spaced apart from rail  18  and is slidably received by a second or right set comprising a plurality of rotatable members, one of which is shown in FIG. 1 and indicated generally as  28 . Rails  18  and  20  are shown in FIG. 1 as being associated with the cargo bed floor generally indicated as  22 . Rotatable member  26  and  28  are shown in FIG. 1 as being associated with a movable sliding floor extension plate indicated generally as  23  that has a top surface or load carrying side indicated as  24  and a bottom surface or underside indicated as  25 . Plate  23  can be made of a lightweight molded composite/plastic material, metal plating (encased or not within a shell of composite materials) or other suitable material and is supported by assemblies  15  and  16  for movement between a fully stored position (as shown in FIG. 3), or a fully extended position (as shown in FIG. 4). While FIG. 1 shows a pair of such slidable assemblies or combinations  15  and  16 , it should be understood that assemblies  15  and  16  can also be in the form of one such combination, or can be in the form of a plurality of such combinations where two, three or more of such combinations are used to movably support plate  23 .  
         [0042]    Rails  18  and  20 , as well as rotatable members  26  and  28 , can be made from one or more metal and/or composite/plastic materials and can be formed or associated to be integral with one of the cargo bed floor  22  or the floor extension plate  23 , such as by molding, stamping or other suitable manner of integration, or can be formed separately from such materials, and then mounted, connected, or otherwise attached to the cargo bed floor  22  or floor extension plate  23  mechanically by bolts, screws or other suitable fasteners, adhesively by glue or Velcro, any combination of mechanical or adhesive attachment, or any other suitable manner of attachment. For example, rotatable members  26  and  28  can be mounted on the underside  25  of floor extension plate  23  so that it can be slidably mounted on rails  18  and  20  that are attached to or integral with cargo bed floor  22 . Alternatively, rails  18  and  22  can be integral with or attached to the underside  25  of the floor extension plate  20 , with rotatable members  26  and  28  being rotatably mounted on cargo bed floor  22 . As shown in FIG. 1, assemblies  15  and  16  comprising the rail  18 ,  20  and rotatable member  26 ,  28  combinations are typically identical or similar in construction or configuration, although they need not be so.  
         [0043]    [0043]FIG. 2 of the drawings shows in more detail the construction and configuration of assembly or combination  16  with regard to right rail  20  and one such rotatable member of the right set of rotatable members  28 . (Left rail  18  will be of similar construction and configuration as right rail  20  and the left set of rotatable members  26  will be of similar construction and configuration as rotatable member  28 .) As shown in FIG. 2, rail  20  comprises a lower base segment  32  that is integral with or otherwise attached to cargo bed floor  22  and an upper generally T-shaped guide segment  34 . T-shaped guide segment  34  comprises a lower neck portion  36  connected at one end to base segment  32  and an upper head portion  38  connected to neck portion  36  at the other end thereof. Head portion  36  of guide segment  34  includes an outwardly extending left guide member  40  and an opposite outwardly extending right guide member  42 . As further shown in FIG. 2, rotatable member  28  comprises a cylindrical shaft  46  that is mounted on or otherwise attached to underside  25  of plate  23  and a generally circular or cylindrical wheel or roller  48  that is mounted on shaft  46  for rotation about a substantially vertical axis. Roller  48  has formed in the periphery or circumference thereof a recess in the form of a generally circular notch or groove  50 . The left side of groove  50  (and roller  48 ) is indicated generally as  52 , while the opposite and right side of groove  50  (and roller  48 ) is indicated generally as  54 .  
         [0044]    As shown in FIG. 2, left guide member  40  is configured and sized to slidably fit within groove  50  that opens outwardly on the right side  54  of roller  48 . (For rail  18 , guide member  42  would slidably fit within groove  50  as it opens outwardly on the left side  52  of roller  48 .) So that guide member of  40  (or  42 ) of rail  20  (or  18 ) can easily and slidably move within groove  50  of roller  48 , it is preferred that the surface of guide member  40  (or  42 ) and the surface of groove  50  should comprise materials that provide, in combination, a relatively low coefficient of friction therebetween, and preferably impart additional properties such as relatively high resistance and corrosion resistance. As used herein, the term “a relatively low coefficient of friction” usually refers to a coefficient of friction (both static and dynamic when lubricated) of about 0.1 or less. The surfaces of guide member  40  (or  42 ) and groove  50  can be provided with a combined relatively low coefficient of friction by coating, spraying, dipping adhering, or otherwise applying materials having such a combined relatively low coefficient of friction to such surfaces only, by making guide segment  34  of rail  20  (or  18 ) and roller  48  from such materials, or by simply making rail  20  (or  18 ) and roller  48  entirely from such materials. Suitable combinations of materials that provide a relatively low coefficient of friction therebetween are combinations of a metal such as aluminum, stainless steel, bronze, brass, copper, cadmium, chromium, tungsten carbide, zinc, magnesium, and alloys thereof on one of the surfaces of rail  20  (or  18 ) and roller  48 , with a relatively low coefficient of friction polymer such as ultra high molecular weight polyethylene (e.g., TIVAR brand name ultra high molecular weight polyethylene such as TIVAR 1000 manufactured by Poly Hi Solidur) or polytetrafluoroethylene (e.g., Teflon) on the other surface, combinations of a plastic such as nylon, on one of the surfaces, with a relatively low coefficient of friction polymer on the other surface, or combinations of a relatively low coefficient of friction polymer on both surfaces. Particularly preferred combinations involve using ultra high molecular weight polyethylene for making all or at least the surfaces of rail  20 , and nylon or more preferably aluminum in making roller  48 .  
         [0045]    The operation of the interlocking slidably assembly  12  for supporting plate  23  so that it is movable horizontally from a first position (e.g., fully stored) to a second position (e.g. fully extended) can best be understood by reference to FIGS. 3 and 4. Referring to FIGS. 3 and 4, the cargo area  14  of pickup truck  10  is shown with tailgate  60  in a lowered configuration. FIGS. 3 and 4 also show cargo area  14  of truck  10  as having a left side wall  62 , a right side wall  64  opposite and spaced laterally from side wall  62 , and a forward end or wall  66  spaced laterally from and opposite tailgate  60 . Also shown in FIGS. 3 and 4 are a left wheel well  68  and a right wheel well  70  formed in cargo bed floor  22  which is otherwise typically a substantially planar surface. Plate  23  is shown as having a rectangular configuration and includes a rear or back end  72 , a front or forward end  74  opposite and spaced laterally from end  72 , a left side or edge  76  opposite side wall  62 , a right side or edge  78  spaced laterally from side  76  and opposite side wall  64 . As shown in FIGS. 3 and 4, the width of plate  23  from left side  76  to right side  78  is preferably such that plate  23  can fit between wheel wells  68  and  70 . While plate  23  is shown as having a rectangular configuration, other configurations that fit between wheel wells  68  and  70  are also suitable.  
         [0046]    As particularly shown in FIG. 3, when plate  23  is in a fully stored position, the length of plate  23  from back end  72  to forward end  74  is such that plate  23  fits within the cargo area  14  defined by the forward end of tailgate  60 , side walls  62  and  64  and forward wall  66 . Plate  23  is also preferably provided with a handle  80  at rear end  72  so that plate  23  can be gripped for ease of movement within cargo bed  14 . As also shown in FIGS. 3 and 4, plate  23  can optionally include other components that will allow the truck bed or cargo area to be divided into compartments or to mount, attach or otherwise include containers or other items in the truck bed or cargo area such as a plurality of molded or drilled peg-receiving holes or apertures indicated as  82  for mounting cargo dividers or other restraining devices, specialized containers, toolboxes, and the like.  
         [0047]    As also shown in FIGS. 3 and 4, the first set of rotatable members  26  are spaced apart along a first axis substantially parallel to side  76  of plate  23  to slidably receive elongated rail  18  that is substantially parallel to side wall  62 , while the second set of rotatable members  28  are spaced apart along a second axis spaced laterally from and substantially parallel to the first axis of rotatable members  26  and side  78  of plate  23  to slidably receive elongated rail  20  that is substantially parallel to side wall  64 . While FIGS. 3, 4 and  5  show seven rotatable members for each set  26  and  28 , the particular number of rotatable members can vary depending on the length of plate  23  that is being supported, and like factors, and also need not be the same number for each set, so long as each set  26  and  28  has a plurality of rotatable members, e.g., two, three or more rotatable members.  
         [0048]    The spacing between the sets of rotatable members  26  and  28 , and rails  18  and  20 , is such that assemblies  15  and  16  together provide an interlocking combination or fit (i.e., the guide members  40  or  42  remain within grooves  50  of the rotatable members) yet allow for plate  23  to be easily and slidably moved from one position to another within cargo area  14 . As shown in FIGS. 3 and 4, the sets of rotatable members  26  and  28  are positioned on the inside of rails  18  and  20 . However, if desired, the sets of rotatable members  26  and  28  can be positioned on the outside of rails  18  and  20 , or one set of rotatable members  26  or  28  can be positioned on the outside of one of the rails while the other set of rotatable members  26  or  28  is positioned on the inside of the other rail, so long as assemblies  15  and  16  together provide an interlocking combination that allows for easy and slidable movement of plate  23  from one position to another within cargo area  14 . As shown in FIGS. 4 and 5, when plate  23  is fully extended past lowered tailgate  60 , it can be supported by or rest on supports or pads  86  made from metal and/or composite materials that are fastened or otherwise attached to, or preferably molded/stamped/formed or otherwise made integral with, the inner surface of tailgate  60 .  
         [0049]    An alternative embodiment of the interlocking slidable assembly of the present invention is shown in FIGS. 6 and 7. As shown in FIG. 6 and especially FIG. 7, the guide component can be in the form of a generally L-shaped rail  118  that has a lower base segment  132  attached to or integral with cargo bed floor  22  and an upper generally L-shaped guide segment  134  that includes outwardly extending guide member  142 . As shown in FIG. 7, guide member  142  is again configured to fit and slide within the left side  52  of outwardly opening groove  50  of roller  48 .  
         [0050]    Another alternative embodiment of the interlocking slidable assembly of the present invention is shown in FIGS. 8 and 9. As shown especially in FIG. 8, rotatable members  26  and  28  are positioned on either side of rail  18  or  20 . As also shown in FIG. 8, rotatable members  26  and  28  can also be spaced along their respective longitudinal axes in an offset or staggered configuration, i.e., each rotatable member  26  is not directly opposite a rotatable member  28 . (The rotatable members  26  and  28  shown in the embodiment FIGS. 3 and 4 can also be spaced along the respective longitudinal axes in the same or a similar offset or staggered configuration.) Alternatively, and as shown in FIGS. 3 and 4, each rotatable member  26  can be paired directly opposite a rotatable member  28 . The spacing between rotatable members  26  and  28  is such that guide members  40  and  42  of rails  18  or  20  can fit and slide within the outwardly opening grooves  50  of the respective rollers  48 . Positioning rotatable members  26  and  28  on either side of rail  18  or  20  can provide additional stability for supporting plate  23  (e.g., rotatable members  26  and  28  can be positioned on each side of rails  18  and  20 ) and can also potentially permit the use of a single rail  18  or  20  for supporting plate  23  in an interlocking yet easily slidable configuration. In an alternative embodiment to that shown in FIGS. 8 and 9, the configuration of rotatable members and rails could be reversed, with rails  18  and  20  spaced laterally apart and positioned and oriented on either side a of single set of rotatable members  26  (or  28 ) to provide another suitable slidably interlocking combination.  
         [0051]    Another alternative embodiment of the interlocking slidable assembly of the present invention is shown in FIG. 10 where the rotatable members  26  can be rotatably mounted within recesses  90  in side wall  62  of cargo area  14 , with rotatable members  28  being rotatably mounted similarly within similar recesses in side wall  64 . As shown in FIG. 10, shaft  46  (on which roller  48  rotates) is vertically mounted within recess  90  and is connected at its upper end to upper surface  92  of recess  90  and at its lower end to lower surface  94  of recess  90  so that roller  48  can be rotatably mounted thereon and rotate with recess  90 . As also shown in FIG. 10, sliding extension floor plate  223  has formed integral therewith a guide segment  234 . A guide member in the form of a ridge  240  is formed in and protrudes outwardly from guide segment  234  and is configured to fit and slide within the outwardly opening groove  50  of roller  48 . A similar guide member (not shown) can be provided on the right side of plate  223 . Alternatively, the rotatable members and rails could be reversed, with rails  18  and  20  being mounted on side walls  62  and  64 , respectively, with rotatable members  26  and  28  being mounted on plate  23  proximate the respective sides  76  and  78 .  
         [0052]    An alternative embodiment of the assembly of FIG. 10 is shown in FIG. 11. As shown in FIG. 11, rotatable member  326  comprises a roller  348  that is rotatably mounted on shaft  46 . Roller  348  has an annular ridge  350  formed therein that protrudes outwardly from the periphery of roller  348  proximate the middle thereof on the left side of roller  348  (as indicated by  352 ) and on the right side of roller  348  (as indicated by  354 ). Sliding extension floor plate  323  is shown as being formed integral with a guide segment  334 , with guide segment  334  having a guide member  340  at the peripheral edge thereof. Guide member  340  has an outwardly opening recess or slot  344  formed in the periphery thereof that is configured so that right side  354  of ridge  350  of roller  348  can fit within slot  344 , so that guide member  340  is slidable along ridge  350 . A similar guide member (not shown ) can provided on the right side of plate  323  that can also have a similar slot formed in the periphery thereof that is configured so that the left side  352  of ridge  350  of roller  348  can fit within this slot so that this right guide member is slidable along ridge  350 .  
         [0053]    As shown by the foregoing detailed description, the present invention provides for a slidably interlocking assembly for movable platforms or other movable structural members that can be used with a variety of mobile and stationary structures and in particular with the cargo area of motor vehicles to provide an integrated sliding floor extension that can be pushed forward into a fully stored, non-extended position or pulled rearwardly to a fully extended position past the lowered tailgate of pickup truck or the opening of the cargo area of other motor vehicles such as an SUV to allow for ease of access to load or unload items and/or to accommodate oversized load items. It should also be noted that the specific embodiments of the present invention that are described therein are to be considered illustrative and exemplary of the present invention, are subject to variations in structure, design, application and methodology and are therefore not to be limiting in scope of the present invention. Accordingly, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the present invention as defined in the appended claims.