2. Prior Art Corrugated and paperboard containers are made from pieces that are cut into required shapes from sheet stock, and are assembled to form the walls of a full or partial enclosure. Variations are possible in which several integral parts are formed and then assembled using glue, tape, staples or the like. For example, the container body and lid may be separate parts, or various types of inserts may be used for reinforcement or other purposes such as subdividing the volume of the container into discrete areas. Containers are supplied in a collapsed state because storage or handling of empty containers is wasteful of space. The containers are partly formed, with their parts cut out and certain seams and folds provided. The packer erects the containers prior to loading, finishing any required assembly steps in the process, and finally closes the loaded containers for storage or shipment. For example, a container may be cut out from integral flat stock, folded and scored at the corners of the container (with at least one seam), and supplied with the opposite side and end walls collapsed flat against one another. Top and bottom flaps are likewise integrally attached to the side and end walls at folds or score lines. The packer erects the container from a flat parallelogram into its rectilinear shape, folding the top or bottom flaps inwardly before and after loading, and finally closing the container at seams that are taped, glued or otherwise attached.

It is efficient to provide a form of container in which all the container parts are integral extensions of a single piece of flat material. Separate parts such as discrete lids, partitions and reinforcing inserts involve manual assembly steps. Manual assembly steps are costly and consume worker time. In addition, assembly steps can be physically taxing and may lead to repetitive motion injuries. It is preferable if containers are substantially fully formed when supplied, and require the least possible manual action to deploy, load, close and store or pack the containers for shipment.

Self-erecting paperboard and corrugated containers are known with their respective wall panels and flaps connected in such a way that one or more of the structural parts of the container is pulled into an erected position as the other parts are erected. Commonly owned pending patent application SN 09/129,375, filed August 5, 1998 and entitled Stackable Container, discloses an integral blank container having bellows or gusset corners that couple a bottom panel with side and end wall panels. In this way, an assembler need only pull on one of the panels to pull all of the panels into a rectilinear shape, when the container is erected from a knocked-down-flat configuration.

In another commonly owned pending Patent Application SN 09/253,822, filed February 19,1999, an integral blank container including end walls with spaced inner and outer end wall panels and an upper edge is disclosed. Advantageously, the end wall panels and ledge encompass hollow erectable support columns that are associated with upwardly protruding stacking tabs. The internal hollow columns, which are disposed under the ledge when the container is in an erected state, vertically reinforce the end walls of the container.

U. S. Patent 4,899. 929-Grollman, also discloses self-erecting bottom flaps connected to container side walls by folded-back glued panels arranged to pull the bottom flaps downwardly when the side walls are erected by expanding the container from a flattened parallelogram.

The foregoing commonly owned applications also disclose locking tab structures in which a plural thickness tab protrudes upwardly from the structure of the container end wall to engage an opening in a similar container stacked thereon. One objective of cartons or containers as described is to support the products that have been loaded into the containers, as well as to bear the load of additional containers that may be stacked on a given container. For this purpose, the panels that are folded and glued can include wall panels having multiple thicknesses of glued-together material and/or partition walls that extend between opposite side walls or end walls. These structural reinforcing features add to the vertical stacking strength or load bearing capacity of the container, namely the maximum vertical weight that can be borne without buckling or displacing the container walls. A container should have good vertical stacking strength, but if possible, such stacking strength should be achieved without unnecessarily adding weight to the container. It is also advantageous if stacking strength can be achieved by means of reinforcements that occupy very little of the space that would otherwise be available for carrying product. Thus, considerations of container strength are sometimes at odds with considerations of weight and volume.

Containers are routinely stacked vertically to make efficient use of space, and may be reinforced against vertical crushing by employing multiple thicknesses of material for wall panels or by forming columns, for example as in U. S. Patent 5,330,094-Merz.

Known structures that are reinforced in this manner are constructed using separate inserts or using a container structure that requires various manual operations in order to install or erect the reinforcing structure.

Two or more containers are often stacked in vertical registry to be carried manually, to be stacked in a storage area or for shipping on a pallet or the like, in any number of adjacent columns or in a staggered overlapping arrangement resembling masonry. Stacking maximizes the density of storage, and often enables a group of containers to be handled conveniently as a unit using a fork-lift truck or two wheel hand dolly. Often, it is desirable to provide means for direct access to the interior of the containers, without compromising vertical stacking strength or stability.

Containers in stacks may be subjected to various vertical and lateral forces.

Vertical compression force is applied by the weight of upper containers in a stack and the product they contain. This vertical force is borne by vertically extending structural elements in the underlying cartons. The structural elements that bear vertical forces on a carton or similar container normally occupy only a limited span of lateral width and/or depth. For example, the vertical forces on many cartons are borne exclusively by their vertical side and end walls. If the stacked cartons remain in registry, then the weight of each upper container is coupled, by the side and end walls of the upper container, to corresponding side and end walls of an underlying container. This is because the side and/or end walls of the upper and lower containers are disposed directly over and under one another. However, when the vertical forces on a stack of many cartons are borne exclusively by their vertical side and end walls, it becomes extremely difficult to provide access to the interior of the container, while stacked, for removal of its contents.

The present invention, as in the Sheffer pending applications, provides a site- erected container or carton that is entirely formed from an integral flat blank. The only assembly required is erection from a knocked-down-flat configuration by folding the end walls into position to lock into the bottom panel. In so doing, the end and side walls are simultaneously erected perpendicular to the bottom panel. The container is supplied with substantially all its joints pre-attached and can be produced automatically using a fold- and-glue container production machine, for example as available from Bobst Group, Inc., 146 Harrison Avenue, Roseland, New Jersey 07068 (affiliated with Bobst, SA, Lausanne, CH). At the loading site the user need only fold the various wall panels into place, fill the container and to produce a stackable unit that is readily handled, stacked on a pallet, or otherwise processed for storage or shipment, and which also provides access means for removing a portion of the container's contents when in the stacked configuration.

Summarv of the Invention It is an object of the invention to structure a fold-and-glue knocked-down flat container blank so as to improve the vertical stacking strength of the erected container while also decreasing the reliance on correct registry of the containers by manual action.

It is another object to provide hollow vertical reinforcing columns which columns are erectable from a folded flat configuration during erection of the container and which also provide access means for removing a portion of the container's contents when in a stacked configuration.

It is an object to minimize the manual steps needed to erect the container as described. in particular to cause the end and side walls of the container to erect into a vertical position and the hollow vertical columns to open and deploy, simply by folding the various wall panels inwardly to lock on the bottom of the container.

It is another object of the invention to structure a fold-and-glue knocked-down flat container blank so as to improve the vertical stacking strength of the erected container by providing structural support that does not rely upon the structural rigidity of the sidewalls of the container while also increasing the accessability of the contents of the stacked container.

It is a further object to minimize the manual steps needed to erect the container as described. in particular to cause the end and side walls of the container to erect into a vertical position, simply by folding wall panels inwardly to lock on the bottom of the container while deploying vertical support structures.

These and other objects are accomplished in one embodiment of the invention by a container that is made in a collapsed configuration with bellows fold corners for self- erection, having spaced end walls, spaced side walls, and hollow columns located in the interior corners of the container for vertical reinforcement of the container. Each end wall includes an exterior panel that is joined to the container bottom and an interior panel that extends downwardly to lock, via tabs, into corresponding openings in the bottom. A locking panel is partially precut from the interior panel. A first portion of the locking panel forms a horizontal ledge when the container is erected and a second portion acts to secure the interior and exterior panels and hollow columns in position. The hollow columns extend from the outer peripheral edges of the interior panel, and are formed by partially prescoring, precreasing, and pregluing a panel flap in a predetermined manner.

In this way, each panel flap may be rolled inwardly, back over itself, in accordance with its prescored and precreased portions so as to form a hollow column. In a preferred embodiment, each hollow column is substantially triangularly shaped, and sized so as to fill each corner of the container. Each hollow column includes a double thickness tab protruding from one upper edge to form a registration tab that is used to engage a corresponding opening in the container bottom when two or more containers are stacked together. The container can be made entirely automatically in a knocked-down-flat state by application of glue and folding along prescored and precreased lines, and is erected in a single motion.

Brief Description of the Drawings These and other features and advantages of the present invention will be more fully disclosed in, or rendered obvious by, the following detailed description of the preferred embodiment of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein: Fig. 1 is a perspective view of an erected container according to an embodiment of the invention ; Fig. 2 is a plan view of an integral flat blank prior to being folded, glued, and erected to provide the container shown in Fig. 1; Fig. 3 is a plan view of the integral flat blank of Fig. 2, showing the gluing and folding operations associated with the hollow columns to be formed when erecting the end wall; Fig. 4 is a plan view of the integral flat blank of Fig. 3, showing the gluing and folding operations associated with the bellows corners and front and back walls.

Detailed Description of the Preferred Embodiments FIGURE 1 shows a vertically reinforced stackable and self-erecting container 10 erected and ready for packing, and including corner columns 15 formed according to the invention. Container 10 in the open state defines a rectilinear box including a front wall 22, a back wall 24, and end walls 26, each extending perpendicularly upwardly from a one piece container bottom 28. Walls 22,24,26 are connected to container bottom 28 at right angle fold lines. Bottom 28 comprises a generally rectilinear shape defining a plurality of openings adjacent to its perimeter. A registration slot 29 is positioned in each corner of bottom 28 (Fig. 2). Registration slots 29 are generally semicircularly shaped.

Three equally spaced panel locking slots 27 are formed on each lateral edge of bottom 28 and two equally spaced panel locking slots 27 are formed along each longitudinal edge.

Referring to Fig. 2, front wall 22 and back wall 24 each comprise an outer panel 30 and an inner panel 32 that are separated by a fold line 34. Each outer panel 30 comprises a single thickness of material, and is joined to bottom 28 along a common longitudinally oriented edge defined by a fold line 36. Each inner panel 32 comprises a pair of spaced locking tabs 38 that project outwardly from one longitudinally oriented edge and a pair of spaced elongate slots 40 that are positioned adjacent to the lateral edges of inner panel 32.

Opposing end walls 26 each include an exterior panel 42. a locking panel 43, and an interior panel 44. More particularly, each exterior panel 42 comprises a single thickness of material, and is joined to bottom 28 along a common edge defined by a fold line 46. An exterior panel 42 is attached to each outer panel 30 by a bellows or gusset fold joint 50. Bellows or gusset fold joints 50 are web-like structures extending between outer panel 30 and exterior panel 42, at the corners of container 10, and include a diagonal fold line 52 that divides bellows joint 50 into two substantially triangular portions 53A and 53B (see Fig. 2). Triangular portion 53A includes an upwardly projecting tab 54A, and is joined to exterior panel 42 along a side edge defined by fold line 55. Triangular portion 53A is normally glued to the inner surface of exterior panel 42 (Fig. 4). Triangular portion 53B of bellows joint 50 (across diagonal fold line 52) includes an upwardly projecting tab 54B, and is attached to outer panel 30 along fold line 56, and is not glued. In this way, bellows joint 50 can fold relative to outer wall 30 and/or relative to triangular portion 53A. Tabs 54A, 54B are normally equally sized and shaped, and are arranged so as to conform to the size and shape of the portions of exterior panel 42 and interior panel 44 that are positioned adjacent to them when container 10 is in an erected configuration.

It should be noted that the portions of bellows joints 50 to which glue is applied are shown in the Figs. 3 and 4 by"XXX"patterns. Exposed glue areas are likewise shown in"XXX"patterns. Covered areas containing glue on a rear face of a respective panel are shown in broken line"XXX"patterns.

Bellows joints 50 affix each outer panel 30 to an adjacent exterior panel 42 in the collapsed or KDF state of the blank. In the collapsed state, bellows joints 50 are folded along fold lines 52,55, and 56, and laid flat against the inner surface of exterior panel 42.

For erecting container 10, the panels are raised from parallel to ninety degrees relative to bottom 28. For example, in Fig. 4, exterior panel 42 is rotated toward the right and the end wall is rotated upwardly. Bellows joint 50, via their respective triangular portions 53A, 53B, pull their connected panel and one another up to ninety degrees relative to bottom 28, and in so doing bellows joints 50 are folded on diagonal fold line 52 to rest in a folded condition against exterior panel 42 to which bellows joint triangular portion 53A is glued.

Locking panel 43 projects outwardly from a central portion of exterior panel 42, and defines fold lines 48,49 where it is joined to exterior panel 42. Fold lines 48,49 are disposed in opposing spaced relation to one another so as to define a ledge 50 when locking panel 43 is folded over and engaged with bottom 28 (Fig. 1). Locking panel 43 forms a substantially pentagonally shaped tongue having a tab 52 formed at an edge that is spaced away from fold line 48.

Referring to Figs. 1-4, interior panels 44 are connected to exterior panels 42 by strip portions 57, with the change between panels demarcated by fold line 58. Interior panel 44 includes two spaced parallel slots 59 positioned adjacent to the inner edge of a column-forming flap 60. An opening is formed in interior panel 44 where the pentagonal tongue portion of locking panel 43 has been freed.

Each column-forming flap 60 extends outwardly from each lateral edge of interior panel 44, and comprises four spaced parallel fold lines 62A, 62B, 62C, and 62D, two corresponding registration tabs 64, and a column-lock tab 66. Referring to Fig. 3, column-forming flap 60 is arranged to be folded back upon itself, about fold line 62B, and glued upon itself so that columns 15 and registration tabs 64 comprise a double thickness of material. Once in this arrangement, fold lines 62A and 62C are positioned in overlying parallel relation to one another, fold line 62D is positioned in aligned parallel relation with the free edge of column-forming flap 60, and column-lock tab 66 is caused to project outwardly and away from column-forming flap 60 as a result of bending column-forming flap 60 about fold line 62B.

The panels forming container 10 are cut, folded and attached to one another, and are all integral portions of a single flat blank 70, shown in Figs. 2 and 3. Blank 70 generally comprises a one piece bottom panel 28 from which front wall 22 and back wall 24, and end walls 26 radiate in mutually perpendicular directions along bottom-to-side wall fold lines. Blank 70 is processed, by folding and gluing operations, to provide a knocked-down-flat ("KDF") structure that can be provided to a packer in a compact collapsed arrangement and has tab-and-slot structures that engage one another when the container is erected. Bellows joints 50 cause the front, back and end walls to pull one another into an orientation perpendicular to bottom 28 during erection of container 10.

Preferably, container blank 70 is laid flat, i. e., in the form in which the container is cut as an integral blank from a sheet of flat corrugated board, paperboard or other sheet material. A number of thicknesses can be die cut in a single step. However, blanks 70 preferably are cut out individually so that the blank can be scored or compressed along the lines that are to be folded, at the same time that the perimeter of the blank is cut from the sheet. Along certain lines the blank is folded when it is formed into a collapsed state for shipment, and other lines are folded or partially unfolded when the collapsed blank is erected for packing. Lines representing fold lines are shown in the drawings by broken lines, and can be made by compressing the material along a line, cutting all or part way through the material at spaced intervals, cutting through part of the material thickness, etc.

The combination of an exterior panel 42, locking panel 43, and interior panel 44, for each of the end walls 26 provides vertical strength to the container and resistance to lateral deformation. This is in part because end walls 26 comprise multiple thicknesses of material and in part because the spaced end wall exterior and interior panels 42,44 fit between front wall 22 and back wall 24 and maintain a perpendicular relative orientation between the front and back walls versus the end walls. According to an inventive aspect, container 10 derives additional support, vertical strength, resistance to deformation, and improved stackability as a result of hollow columns 15.

More particularly, with triangular portion 53A of bellow joint 50 glued to the inner surface of exterior panel 42, as disclosed hereinabove, container 10 may be arranged in its KDF state by next folding inner panel 32 of front wall 22 about fold line 34 so that inner panel 32 is positioned in overlying relation to the inner surface of outer panel 30. In this arrangement, locking tabs 38 will be disposed adjacent to panel locking slots 27 in bottom 28. When container 10 is pulled into its fully erect configuration, locking tabs 38 insert into panel locking slots 27 thereby locking inner panel 32 in position against the inner surface of outer panel 30.

Columns 15 are formed and assembled to container 10 at the time that external panel 42, locking panel 43, and interior panel 44 are folded into their final configuration so as to form end walls 26. Referring to Figs. 1 and 3, column-forming flaps 60 are folded along fold lines 62A and 62C so as to yield a substantially triangular hollow column 15. In order to facilitate the disposition of column 15 within the corners of container 10, column-forming flaps 60 are folded away from the inner surface of interior panel 44. Once column-forming flaps 60 have been folded into the substantially triangular hollow column 15, column-lock tab 66 is inserted into slot 59 so that column 15 maintains its shape and position relative to container 10.

Once columns 15 have been formed with column-lock tab 66 positioned in slot 59, interior panel 44 is folded about fold lines 58 inwardly toward bottom 28 of container 10.

As this occurs, locking panel 43 separates from interior panel 44. It will be understood that columns 15 are automatically positioned within the corners of container 10, with registration tabs 64 projecting upwardly, away from container bottom 28 as a result of their location on the lateral edges of interior panel 44. It will also be understood that tabs 54A and 54b of bellows fold joint 50 will be positioned between the portions of exterior panel 42 and interior panel 44 that form strip portions 57. This arrangement provides further structural integrity and rigidity to hollow column 15. Interior panel 44 is rotated until tabs 75, positioned along an outer edge of interior panel 44, are inserted into panel locking slots 27 disposed on the lateral edge of bottom 28. In this position, hollow columns 15 are disposed in coaxial overlying relation with registration slot 29.

To complete the formation of container 10, locking panel 43 is folded along fold lines 48,49 so that tab 52 is positioned adjacent a central panel locking slot 27. Locking panel 43 is then pressed into engagement with the surface of interior panel 44 so that tab 52 is positioned within central panel locking slot 27 (Fig. 1).

Containers 10 may be stacked one upon another by simply positioning registration slots 29 of the upper container in coaxially aligned confronting relation with a corresponding registration tab 64 of each column 15 of the lower container 10. The upper container is then moved towards the lower container until the registration tabs 64 are received by registration slots 29. Columns 15 project outwardly from container 10 and above the fold lines, 34,48 and 49 by about two-to two and a half inches. As a consequence, when container 10 is stacked upon another container 10, there is a gap between the lower surface of bottom 28 of the upper container, and the fold line 34 of each front wall and back wall 22,24 so that the contents of the lower container may be easily accessed.

The invention having been disclosed in connection with the foregoing variations and examples, additional variations will now be apparent to persons skilled in the art.

The invention is not intended to be limited to the variations specifically mentioned, and accordingly reference should be made to the appended claims rather than the foregoing discussion of preferred examples, to assess the scope of the invention in which exclusive rights are claimed.