Abstract:
A stackable box formed from a one-piece blank cut of corrugated paperboard material has integrated right-angle stacking tabs protruding upwardly from each top corner of the box which matingly interlock with openings on each bottom corner of a second similarly constructed box so as to prevent sideways slipping of the boxes when stacked. The box folds and assembles without the need for fasteners, glue or other parts. The sides are assembled to have four-wall thickness and the ends are assembled to have two-wall thickness for improved strength.

Description:
FIELD OF THE INVENTION 
   The present invention relates to stackable boxes preferably made of corrugated cardboard. More particularly, the present invention relates to a box formed from a single sheet of material, preferably die cut corrugated cardboard, that can be manually folded to form a stackable box for holding various articles. A feature of the box is that when stacked the interlocking mechanism reduces the possibility of sideways movement. 
   BACKGROUND OF THE INVENTION 
   Stackable corrugated boxes for stable transport of articles, such as food products, are known in the art and are being used with increasing frequency because of the low cost, convenient flat storage ability until needed, sufficient strength and durability, and low weight. It would be desirable to have a stackable box formed of a single die cut material that would interlock with another similar box to permit vertical stacking of a number of boxes while maintaining sufficient sidewall strength and ease of use. It would further be desirable for such a box to have corner tabs that are sufficiently strong that when stacked can substantially reduce or prevent sideways slippage, yet durable for repeated use without appreciably deforming for a reasonable length of time. 
   SUMMARY OF THE INVENTION 
   Generally described, the present invention provides in one exemplary embodiment a stackable box formed of preferably a single sheet of preferably die cut material, such as corrugated paperboard that has been selectively cut, scored or had fold lines made thereon. The box has a raised stacking tab extending upward from each upper corner of the assembled box which mate with openings in each lower corner of the box. The tabs are created as part of the box when the sheet is folded. Two boxes or more boxes can be stacked and the interlocking or mating of the stacking tabs and openings reduce sideways slippage during shipping. 
   The sheet comprises the following general sections: a bottom panel having preferably a plurality of slots formed adjacent opposing side edges, a left side panel comprising an inner panel and an outer panel, the outer panel having at least one tab that can be inserted in the slots in the bottom panel and a right side panel similar in construction to the left side panel. The inner panels are foldably connected to the bottom panel. A first end having an opening therein for a handle comprises an inner panel having left and right foldable flaps, and, foldably connected to the inner panel is an outer panel also having left and right foldable flaps. The inner panel is foldably connected to the bottom panel. The second end is constructed in manner similar to the first end. The sheet is formed with spaces adjacent the corners of the bottom panel, the inner first and second side panels, and inner first and second end panels such that when folded the spaces create an opening sized to receive the tabs formed by the particular construction of the first and second inner and outer panels. 
   To assemble the box the first end outer panel is folded to meet the first end inner panel. The first end flaps are folded inward to be perpendicular to the panels associated therewith. The second end panels and flaps are similarly folded. The first and second end folded subassemblies are then folded inward at the inner panel-bottom panel fold, respectively. The outer panels of the sides are folded over the respective end panel flaps and the outer panel tabs are inserted in the bottom panel slots to maintain the outer side panels in the assembled position. When assembled the stacking tabs and openings are thus formed. 
   The box side panels may comprise four thicknesses of material (two panels and two end flaps) and thus have substantial vertical and horizontal strength. The end panels comprise two thicknesses of material and also possess substantial strength for containing and shipping items, such as sweet potatoes or other articles. One box may be stacked on another box by registering the tabs and openings appropriately. The stacked boxes are resistant to sideways slippage with respect to one another. 
   Other features and advantages of the present invention will become apparent upon reading the following detailed description of embodiments of the invention, when taken in conjunction with the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is illustrated in the drawings in which like reference characters designate the same or similar parts throughout the figures of which: 
       FIG. 1  is a top plan view of one exemplary embodiment of the present invention. 
       FIG. 2  is a perspective view of the embodiment of  FIG. 1  shown from above the horizontal. 
       FIG. 3  is a perspective view of the embodiment of  FIG. 1  shown from below the horizontal. 
     FIG.  4 . is a perspective view of two boxes of the embodiment of  FIG. 1  shown in position for stacking. 
       FIG. 5  is a perspective view of two boxes of the embodiment of  FIG. 1  shown stacked. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows one exemplary embodiment of the present invention in which a preferably one-sheet blank  10  of material from which a box  12  of the present invention is formed. The material can be made of any suitable material known to those skilled in the art or developed hereafter, such as, but not limited to, paperboard, paper, cardboard, plastic corrugated material, plastic, wood, ceramic, composite, mixtures thereof and the like. The material can be plain, coated or otherwise treated. The material is preferably corrugated paperboard. The material may be single wall, double wall or multiple wall construction. The panels forming the box, as described below, may be solid or have holes therein for reducing weight, providing ventilation and/or for other purposes. 
   In the Figures described below, dotted lines indicate score lines, double dotted lines indicate double parallel score lines, dashed lines indicate cuts between panels, and, solid lines indicate cuts between panels, or edges or areas where a cut is made. In alternative embodiments of nonfoldable materials, such as wood, the fold lines can represent the abutment lines (i.e., representing the space between adjacent panels) between two panels of wood and having hinges attached to the panels to facilitate folding. The terms score, cut, cut out, and fold are intended to have their ordinary meaning as is known to those skilled in the art. 
   The blank  10  has a bottom panel  16 , side A first panel  18 , side A second panel  20 , side B first panel  22  and side B second panel  24 . The blank  10  also has an end C first panel  30 , end C second panel  32 , end D first panel  34  and end D second panel  36 . 
   The bottom panel  16  preferably has a plurality of cut outs  38 ,  40 ,  42 , and  44 . The corners  44 ,  46 ,  48  and  50  of the bottom panel  16  are part of a cut out area, preferably somewhat rounded, that, when the panels are folded as described below, form an aperture that can receive a tab, as described below. 
   The bottom panel  16  is attached to the panels as follows: to the side A first panel  18  by a fold line  52 ; to the side B first panel  22  by a fold line  54 , to the end C first panel  30  by a fold line  56 ; and to the end D first panel  34  by a fold line  58 . 
   The side A first panel  18  has cut out notches  60  and  62  and edges  64  and  66 . It is to be understood that the term notch is meant to include a space, either angled, rounded, curved, or the like having a regular or irregular geometry. The panel  18  is connected to the side A second panel  20  by at least one and preferably a pair of parallel score lines  68 . The panel  20  has a pair of inner cut outs  70  and  72  and a pair of outer cut outs  74  and  76 . Along an outer edge  78  the panel  20  has at least one and, as shown, preferably a pair of tabs  80  and  82  capable of being inserted into the slots  38  and  40 , respectively. 
   The side B panel construction is substantially similar to that of side A. 
   End C first panel  30  is connected to the bottom panel  16  by a fold line  56  and has notches  100  and  102 . A top edge  104  is slightly recessed, creating notched or rounded edges  106  and  108 . The panel  30  preferably also has a handle opening  110  created by flap  112  that is cut out all the way around except for a foldable side  114 . The panel  30  has a first flap  116  and a second flap  118 . Each flap  116 ,  118  is foldably joined to the panel  30  along fold lines  120  and  122 , respectively. Flap  116  has an inner notch  124  and a corner  126 . Similarly, flap  118  has an inner notch  128  and a corner  130 . The flaps  116  and  118  are preferably cut so that the top and bottom edges  117 ,  119 , respectively, of each, are angled slightly. 
   The end C second panel  32  is constructed generally in a similar manner as the panel C, with certain differences. The panel  32  has a cut out  132  forming a handle area. The outside edge  134  has notches  136  and  138 . The panel  32  has flaps  140  and  142 , connected by score lines  144  and  146  to the panel  32 . The flap  140  has a corner  148  and a notch  150 . The flap  142  has a corner  152  and a notch  154 . The panel  32  has an edge  156  and notched or rounded edges  158  and  160 . The panel  32  is connected by fold lines  162  and  164 . There are also cut out areas  166  and  168 . 
   The end D construction is substantially similar to that of end C. 
   The box  12  is assembled by folding the panels is described in an exemplary, but non-limiting manner, as follows. It is to be understood by those skilled in the art that the sequence and/order of panel folding may be modified as desired. The cut outs are removed. The end C second panel  32  is folded over top of end C first panel  30  so that the two panels are generally parallel. The end D second panel  36  is similarly folded on top of end D first panel  34 . The end C flaps  116 ,  140  are folded so as to be substantially perpendicular to the panels  30 ,  32  and the corresponding end D flaps on the same side of the side panel A are folded to be perpendicular to the panels  34 ,  36 . The side A second panel  20  is folded over the flaps  116 ,  140  so that the tabs  80 ,  82 , are inserted into the slots  38 ,  40 , respectively. In a similar manner, the side B second panel  24  is folded over the flaps  118 ,  142  and the corresponding flaps end D flaps on the same side of the side panel B so that the tabs are inserted into the slots  42 ,  44 . The box  12  is now formed. The handle flaps  112  are folded inward toward the center of the box so as to form the handles of the box  12 . 
   As shown in  FIGS. 2-3 , the box  12  has stacking two-wall right-angle tab assemblies  150 ,  152 ,  154  and  156  protruding upwardly from one box  12 , which fit within the openings  158 ,  160 ,  162 , and  164  of a second box  12  so as to interlock and permit stacking with minimal sideways movement, as shown in FIG.  5 . The resulting box  12  has two-wall end panel construction ( 30 ,  32  and  36 ,  36 , respectively) and four wall side panel ( 18 ,  20  plus  116 ,  140 , and  22 ,  24  plus  118 ,  142 , respectively). 
   An advantage of the present invention is that the notch and opening construction is formed of a single die cut blank of material without the need for separate tab construction material or assembly steps. The tabs and openings permit the person stacking the boxes to quickly and with accurate registration stack a number of boxes. The multiple side and end wall construction creates substantial strength and permits a number of boxes loaded with heavy items, such as sweet potatoes, to be stacked. The tabs permit stacking while reducing or eliminating sideways movement during shipping, e.g., by truck or train. The box of the present invention can be stored unassembled in flat sheets and a large quantity can be stored in relatively little space until needed. Additionally, the box of the present can be formed without the need for glue or other adhesives or fastening means. The box of the present invention can be designed for single or repeated use. If desired, the areas forming the stacking tabs can be reinforced, such as by forming metal or other durable rigid caps on the tab areas either as part of the manufactured blank, or slid over the tabs when assembled. 
   Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. It should further be noted that any patents, applications and publications referred to herein are incorporated by reference in their entirety.