Patent Publication Number: US-7717320-B2

Title: Self locking feature for containers

Description:
This application claims the benefit of U.S. Provisional Application No. 60/307,681, filed Jul. 25, 2001, entitled “Poultry Pack”. 

   BACKGROUND OF THE INVENTION  
   1. Field of the Invention 
   This invention relates to packaging. More specifically, the invention relates to a multi-sided container or box made of corrugated paperboard. In particular, the invention relates to a corrugated paperboard tray for containing poultry products, wherein the tray is configured for manual set up and has an improved self locking feature for retaining the walls of the tray in erected position. 
   2. Prior Art 
   Various styles of containers, including paperboard boxes, are known in the prior art for containing a variety of products. Cut poultry pieces, for example, are frequently packed in a paperboard container, and sometimes the poultry pieces are packed with ice. These containers are generally referred to as poultry trays, and are usually made from a unitary blank of corrugated paperboard, which may be treated on one or both sides with wax or other material to impart rigidity and resistance to water degradation. 
   Conventional paperboard containers are configured for either machine set up or manual set up, and generally are either rectangular or octagonal in plan view, with four sides or eight sides, respectively. An example of a prior art eight sided container is disclosed in applicant&#39;s prior U.S. Pat. No. 5,752,648. The embodiment shown in FIGS. 1-3 of that patent is configured for manual set up, and has three overlapping end panels  18 ,  24  and  24 , with notches  30  formed in the top edges of the two end panels  24 , and a roll over flap  34  foldably joined to the top edge of end panel  18  by short narrow webs formed between transverse cuts or relief slits  37  extending in spaced relationship transversely across cut lines  36  and  38 , and interrupting the cut lines. Pairs of short cuts or slits  39  are formed in the webs parallel to the cut lines  36  and  38 , but spaced from one another on opposite sides of the cut lines a distance approximately equal to the combined thicknesses of the three overlapped end panels. The slits  39  promote bending or folding of the webs along fold lines extending through the slits. 
   To erect the container, the two end panels  24  are folded inwardly into overlapping registry with one another, and the end panel  18  is then folded into overlapping relationship with panels  24 . The roll over flap  34  is then folded inwardly and downwardly over the upper edges of the panels  24 , causing the webs to drop into notches  30 , and the upwardly extending portions of panels  24  on opposite sides of the notches to project upwardly through the cuts formed by the cut lines  36  and  38 . The relationship of the relief slits  37  and cut lines  36  and  38  causes a “heel” to be formed on the edge of the roll over flap, and this heel produces an over-center effect when the roll over flap is folded over the panels  24 . The heel engages against the inner surface of the innermost end panel  24  to keep the roll over flap in its folded position, and thereby maintains the container in erected condition. 
   While the arrangement disclosed in U.S. Pat. No. 5,752,648 provides a simple and effective self locking system for holding the container in its erected condition, the thickness of the material of the webs causes them to take a slightly “rounded over” shape as they are pulled down into the notches  30 , and they tend to exert a pull on the roll over flap in a direction to disengage it. Additionally, in order to insure that the webs and related components can be operatively engaged with one another, specific dimensional relationships are maintained between the distance from the bottoms of the notches to the bottom of their associated panels  24 , and the distance which the relief slits  37  extend above the cut lines  36  and  38 , i.e., the length of the relief slits is slightly exaggerated, contributing to a “loose” fit between the components of the self locking arrangement. 
   Accordingly, there is need for a self locking arrangement that provides a tight, secure fit between components, insuring that a container incorporating the arrangement reliably remains in its erected condition. 
   SUMMARY OF THE INVENTION 
   The container of the invention has a self locking arrangement that provides a tight, secure fit between components, insuring that a container incorporating the arrangement reliably remains in its erected condition. The self locking arrangement is similar to that used in U.S. Pat. No. 5,752,648, but is modified to achieve a tighter fit between components of the self locking arrangement and provide a more reliable interlocking of the components. 
   More specifically, the container of the invention has a bottom wall, opposite side walls, and opposite end walls, with means on the end walls that interlock to hold the container in its erected condition. The container is made from a unitary corrugated paperboard blank having a bottom panel that forms the bottom wall, opposite side wall panels foldably joined to opposite sides of the bottom panel and that form the side walls, and end panels extending from opposite ends of the bottom panel and side wall panels, respectively, at least some of the end panels overlapping to form the end walls in accordance with the invention. At least one notch is formed on an upper edge of at least one of the end panels, and a roll over flap is formed on an upper edge of another end panel, in positions to interlock with one another when the end panels are folded into operative relationship with one another to form an erected container. 
   In particular, the self locking structure of the present invention has a plurality of notches formed in the edge of at least one end panel, defining at least one tab projecting upwardly from the edge of the panel, and the roll over flap is foldably joined to its associated end panel by webs formed between a cut line that lies parallel to the fold for the roll over flap, and relief slits that extend transversely across the cut line. The webs are adapted to lie in the notches, with said at least one tab projecting into a slot formed by the cut line when the roll over flap is folded inwardly and downwardly over the end panels. 
   In accordance with the present invention, the webs are at least partially crushed on the side thereof that faces downwardly in the notches so that they lie substantially flat in the notches. In addition, the dimensional relationships of the self locking arrangement are made tighter to effect a tighter fit between components, producing a more reliable interlock. Specifically, the distance from the bottom of the notches to the bottom of their associated panels is made smaller than in a tray having a conventional self locking arrangement, and the length of the relief slits is also made smaller. 
   The invention is a simple, economical and effective way to reliably interlock components of a self locking arrangement in a container constructed for manual set up. It adds no cost to the container. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in greater detail hereinafter with reference to the drawings, wherein like reference characters designate like parts throughout the several views, and wherein: 
       FIG. 1  is a top perspective view of a four sided rectangular container incorporating the self locking means of the present invention. 
       FIG. 2  is a somewhat schematic fragmentary top perspective view showing in single line drawing the self locking means at one end of a container similar to that shown in  FIG. 1 . 
       FIG. 3  is an enlarged fragmentary plan view of one end of a blank used in constructing the container of  FIG. 1 . 
       FIG. 4  is an enlarged plan view of a blank that may be used in constructing a four sided rectangular container of shallow depth. 
       FIG. 5  is a top perspective view of an eight sided octagonal container incorporating the self locking means of the present invention. 
       FIG. 6  is a plan view of a blank for making the eight sided container of  FIG. 5 . 
       FIG. 7  is a greatly enlarged fragmentary plan view of a portion of the blank of  FIG. 6 , showing details of construction. 
       FIG. 8  is a top perspective view of a hexagonal or six sided container incorporating the self locking means of the invention. 
       FIG. 9  is a plan view of a blank for making the six sided container of  FIG. 8 . 
       FIG. 10  is a top perspective view of a seven sided container incorporating the self locking means of the present invention. 
       FIG. 11  is a plan view of a blank used for making the seven sided container of  FIG. 10 . 
       FIG. 12  is a top perspective view of a container of the invention, showing a cover in place on the container. 
       FIG. 13  is a top perspective view of a container incorporating the self locking means of the present invention, and also incorporating a bag cuff grab as described more fully in applicant&#39;s copending application filed on even date herewith, and showing a bag in place and rolled over to form a cuff that is engaged in the notches forming the bag cuff grab. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A rectangular or four sided container incorporating the self locking means of the invention is depicted at  10  in  FIGS. 1-3 . The container  10  comprises a bottom wall  11 , opposite parallel side walls  12  and  13 , and opposite parallel end walls  14  and  15 . Each end wall comprises two end panels  16  and  17  foldably joined to opposite ends of the side walls, and an end panel  18  foldably joined to the end of the bottom wall. 
   A plurality of notches  20  are formed in each end panel  16  and  17  along an outer edge, which becomes the upper edge when the container is set up, forming a pair of upwardly projecting tabs  21  and  22 . 
   A roll over flap  23  is joined to the outer, or upper, edge of end panel  18  by a plurality of webs  24  defined by cuts or relief slits  25  and  26  made transversely across cut line  27 , and interrupting the cut line, which extends completely across the width of panel  18  except at the webs  24 . Short fold promoting slits  28   a  and  28   b  are made parallel to the cut line  27  on opposite sides thereof in locations to define the length of the webs when the roll over flap is folded into its operative, locked position. In other words, the slits  28   a  and  28   b  initiate folding at opposite ends of the web along fold lines extending through the slits. The length of the webs, as defined by the spacing between the slits, and thus between the fold lines extending through them, is substantially the same as the combined thicknesses of the total number of overlapping end panels, minus the thickness of that end panel to which the roll over flap is attached. 
   As indicated by the shading in  FIGS. 3 and 7  (it should be noted that while  FIG. 7  is used to show the details of construction of the self locking arrangement, and reference characters applicable to  FIGS. 1-3  are used,  FIG. 7  actually shows a portion of a blank designed for making the eight sided container of  FIG. 5 ), the web  24  is crushed in the area between the cuts  25 ,  26  and fold promoting slits  28 . The crush is made on the side of the web that faces inwardly of the container when the container is set up. Crushing of the web enables the web to extend more deeply into the notches, and provides a sharper fold along the fold lines promoted by the slits  28   a  and  28   b . It also enables other dimensions of the container to be tightened up, as described more fully below, developing a tighter and more reliable self locking arrangement. 
   To erect the container, the side walls  12  and  13  are folded upwardly, and the end panels  16  and  17  then folded inwardly into overlapping relationship with one another. As seen in the drawings, panel  17  is folded inwardly first, although the sequence of folding the two end panels is not essential. As folded, the notches  20  and tabs  21  and  22  on the two end panels are in registry with one another. The end panel  18  is then folded upwardly over the panels  16  and  17 , and roll over flap  23  is folded inwardly and downwardly over the upper edge of the end panels, causing the webs  24  to drop into the notches and the tabs  21  and  22  to project upwardly through the gap formed by the cut line  27 . Because of the spacing of the cuts  25 ,  26 ,  27  and  28   a  and  28   b , a “heel”  30  is formed on the roll over panel in the areas on opposite sides of the webs, and this heel engages against the inner surface of end panel  17 , holding the roll over flap in its downwardly folded and locked position inside the panel  17 . 
   The dimensional relationships of the self locking structure can best be seen with particular reference to  FIGS. 2 ,  3  and  7 . The spacing “A” between the bottom of the notches  20  and the bottom edge of the associated end panel  16  or  17  is increased slightly over the spacing in the prior self locking arrangement shown in U.S. Pat. No. 5,752,648, and the spacing “B” between the bottom edge of end panel  18  and the closest slit  28   b  is reduced slightly from the spacing in the prior self locking arrangement. The spacing between the slits  28   a  and  28   b , as noted previously, is selected to be substantially the same as the combined width of the total number of overlapping end panels minus the thickness of that end panel to which the roll over flap is attached. It will be noted that the slits  25  and  26  extend slightly beyond slit  28   a  a distance “C”, defining relief slits for the folded roll over flap. Slit  28   a  is spaced from cut line  27  a distance “D” approximately equal to a thickness of one of the end panels, and slit  28   b  is spaced on the opposite side a distance “E” approximately equal to the combined thickness of the total number of overlapping end panels, minus the thickness of one panel. 
   When the roll over flap  23  is folded downwardly alongside panel  17 , the heels  30  extend upwardly and above the fold line that extends through slits  28   b , preventing the flap from disengaging from its locked position. To function properly, the upper edge of the heel, when the roll over flap is in its operative folded position, is spaced below the upper edge of the tabs a distance “F” equal to at least the combined thickness of two panels. 
   A blank for forming a first variation of the invention is indicated generally at  40  in  FIG. 4 . This form of the invention incorporates a self locking arrangement that embodies the same principles and dimensional relationships as that previously described, but differs in that the side walls  41  and  42  and end walls  43  and  44  are not as deep, producing a more shallow container. Additionally, the end panels  45  and  46  do not overlap each other in the erected container. 
     FIGS. 5 ,  6  and  7  illustrate the invention incorporated in an eight sided container  50 . The principles of operation and dimensional relationships of the self locking arrangement are the same as previously described, but the container  50  has mitered corners defined by diagonal corner panels  51 - 54 . In addition, notches  55  and  56  are formed in opposite side edges of end panels  57 , and in the erected container these notches form bag cuff grabs which engage and hold the rolled over upper end of a bag placed in the container to hold the bag in position while product is placed in the bag. Further, only two webs  58  and  59  connect the roll over flap to the end panel, rather than the three webs in the previous embodiment. 
   A six sided container incorporating the self locking arrangement of the invention is shown at  60  in  FIGS. 8 and 9 . This form of the invention also incorporates the same principles of operation and dimensional relationships as that previously described, but has two diagonally opposed mitered corners  61  and  62  and two square corners  63  and  64 . It also has only two webs  65  and  66 . 
   A seven sided container incorporating the self locking arrangement of the invention is indicated generally at  70  in  FIGS. 10 and 11 . This form of the invention also incorporates the same principles of operation and dimensional relationships as that previously described, but has three diagonally opposed mitered corners  71 ,  72  and  73  and one square corner  74 . It also has only two webs  75  and  76 . 
   As shown in  FIG. 12 , a cover is typically placed on the container, and a plastic bag is also sometimes inserted into the container to receive the product (see  FIG. 13 , for example). 
   Although particular embodiments of the invention are illustrated and described in detail herein, it is to be understood that various changes and modifications may be made to the invention without departing from the spirit and intent of the invention as defined by the scope of the appended claims.