Abstract:
The present invention provides a bulk bin having a greater column strength by being resistant to wall bulging. The bulk bin is formed mainly of multiple wall corrugated board with the corrugations in a first wall oriented vertically and the corrugations in a second wall oriented horizontally. The orthogonal orientation of the corrugations results in a greater wall stiffness and less wall bulging, maintaining the wall in linear vertical orientation and retaining maximum column strength.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of corrugated shipping containers, and more particularly to large shipping containers made of multiple wall corrugated board. 
     BACKGROUND OF THE INVENTION 
     Corrugated shipping containers are used to package, store and ship a myriad of products, e.g. from potato chips on the low density end to ball bearings on the high density end of the range. Filled corrugated shipping containers are stacked for storage or transport to as high a height as practical to make optimum use of truck and warehouse space. Typically, lower density materials are packed in large containers made of light wall corrugated board and, conversely, higher density materials are packed in small containers made of stronger wall corrugated board. The ultimate limitation of corrugated wall strength is how many additional filled cartons can be stacked on top of a bottom carton before the bottom carton collapses. 
     Corrugated shipping containers are made of corrugated board. Corrugated board is produced by feeding three sheets of paper into a machine in parallel layers, with the middle layer fed at a greater speed than the two outer layers. The middle layer is alternately bent upward and downward to become a sinusoidal wave, or rippled form, also known as flutes. The upper and lower layers are kept flat and adhered to the peaks of the middle layer. For greater load bearing strength, double wall corrugated boards are used to make containers. A double wall corrugated board has three flat sheets interspersed with two rippled sheets, creating a heavy and strong composite. The rippled sheets may be equal in peak height or different. 
     Most corrugated containers are three dimensional square or rectangular boxes. Conventional container construction, as well as limitation of corrugated board manufacturing equipment, dictate that the corrugations in the traditional finished box are oriented vertically. Also, vertical corrugations serve as substantially rigid columns, increasing the weight bearing capacity of the board. In the plastics industry, large cartons variously known as bulk bins or gaylords are used for shipping and storing granulated plastic resin. The plastic resin granules are later melted and formed by molding or extruding into plastic products. These bulk bins are generally made of double wall corrugated board and may be loaded with up to 1800 pounds of resin pellets. In contrast to smaller corrugated containers where the box top is closed by folding four integral flaps, bulk bins are usually closed by a separate tray-like lid that is placed on the filled container bottom. Because the resin granules are small and smooth, a volume of granules tends to act as a quasi-liquid, i.e. the weight forces lower portions of the pellet mass to expand laterally against the bulk bin wall, causing the bulk bin to bulge outward. When bulging occurs, the columnar weight bearing strength of the wall is diminished, increasing the bulging further. 
     In order to reduce the tendency of the walls to bulge, many bulk bins have been made in an octagonal cross sectional shape, as viewed from above, to reduce the lateral wall length and increase the effective stiffness of the wall. While this octagonal shape reduces the bulging and makes the shipping containers more reliable, the octagonal shape detracts from the weight of plastic pellets that a bulk bin can carry and increases the ultimate storage space required for each ton of pellets. 
     SUMMARY OF THE INVENTION 
     The bulk bin shipping containers described below are formed from multiple wall corrugated board having the corrugated flutes in a first wall thereof oriented vertically and the corrugated flutes in a second wall thereof oriented horizontally. By laminating two or more walls of corrugated board with their flutes orthogonal to each other, the resultant multiple wall board achieves greater stiffness and resistance to bulging under load. Reducing the degree of bulging of the walls of bulk bins maintains the column strength and minimizes carton failures. The second wall is laminated to the first wall only in the area intended to become vertical wall portions of the bulk bin being formed, with the bottom closure flaps remaining at a single wall thickness. For reasons described below, a butt joint is required in the wall having horizontally oriented flutes, the butt joint preferably being located away from a score line of the bulk bin. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is best understood in conjunction with the accompanying drawing figures in which like elements are identified by similar reference numerals and wherein: 
         FIG. 1  is a front perspective view of a bulk bin shipping container of the invention formed in a square configuration. 
         FIG. 2  is a sheet in flat layout as cut and scored in preparation for forming the square bulk bin of  FIG. 1 . 
         FIG. 3  is a front perspective view of a bulk bin shipping container of the invention formed in a modified octagon configuration. 
         FIG. 4  is a sheet in flat layout as cut and scored in preparation for forming the modified octagon bulk bin of  FIG. 3 . 
         FIG. 5  is an enlarged view of the corrugated board within circle  5  of  FIG. 3 . 
         FIG. 6  is a schematic top plan view of a multiple wall corrugated board of the invention in which the width of the board is enlarged for clarity. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , a substantially square bulk bin shipping container  10  is illustrated in front perspective view according to the present invention. Bulk bin  10  is situated on a pallet  12 . The common industry practice of supporting a single bulk bin  10  on a pallet  12  provides support for the large weight, e.g. of plastic resin pellets, to be transported and stored within bulk bin  10 . Bulk bin  10  is formed of a front panel  20 , a right side panel  22 , a rear panel  24  and a left side panel  26 , with an overlap panel  30  extending from left side panel  26  to be affixed in contact with front panel  20 . Overlap panel  30  is affixed to front panel  20  by adhesive, staples or other means. A series of bottom flaps (not shown) are folded beneath bulk bin  10  to reside upon pallet  12 . As shown, bulk bin  10  substantially overlies the entire top surface of pallet  12 . Pallet  12  and bulk bin  10  are typically formed to have each side having a length S on the order of approximately 36 to 50 inches. 
     Referring now to  FIG. 2 , a cut and scored sheet for the formation of the bulk bin of  FIG. 1  is shown in flat layout form. The flat sheet shows overlap panel  30 , left side panel  26 , rear panel  24 , right side panel  22  and front panel  20 . Each of panels  30 ,  26 ,  24 ,  22  and  20  are separated by score lines, shown in dashed lines. A front flap  20   a  resides below front panel  20 . A right side flap  22   a  resides below right side panel  22 . A rear flap  24   a  resides below rear panel  24 . A left side flap  26   a  resides below left side panel  26 . Flaps  20   a ,  22   a ,  24   a  and  26   a  are separated from panels  20 ,  22 ,  24  and  26  by a score line shown as a dashed line. It is noted that there is no flap below overlap panel  30 . 
     Referring further to  FIG. 2 , with the length S (see  FIG. 1 ) of a side of bulk bin  10  on the order of 36 to 50 inches, the length L of the flat layout illustrated in  FIG. 2 , including overlap panel  30 , is generally on the order of 152 to 208 inches. A butt joint  36 , shown as a dotted line, is positioned between two panel sheets that are laminated to the back side of visible panels  30 ,  26 ,  24 ,  22  and  20 . Butt joint  36  is positioned offset from the score line between panels  22  and  24  to retain optimum wall strength. The two laminated sheets connected by butt joint  36  do not extend to the area identified as flaps  26   a ,  24   a ,  22   a  and  20   a  since the flaps are intended to be supported on a pallet. 
     Referring now to  FIG. 3 , a bulk bin  40  in the form of a modified octagon is illustrated in front perspective view as a second embodiment. The modified octagon configuration of bulk bin  40 , i.e. where the sides are unequal in length, provides alternating relatively long panels interspersed with relatively short panels in order to optimize the volume of material contained while reducing the tendency for panel bulging. Bulk bin  40  is positioned on a pallet  42 . Bulk bin  40  is made up of a left side panel  50 , a left corner panel  52 , a front panel  54 , a front corner panel  56 , a right side panel  58 , a right corner panel  60 , a rear panel  62 , a rear corner panel  64  and an overlap panel  66 . Overlap panel  66  is affixed to left side panel  50  by adhesive, staples or other means. 
     Referring now to  FIG. 4 , a cut and scored sheet for the formation of the bulk bin  40  of  FIG. 3  is shown in flat layout form. The flat sheet shows overlap panel  66 , rear corner panel  64 , rear panel  62 , right corner panel  60 , right side panel  58 , front corner panel  56 , front panel  54 , left corner panel  52  and left side panel  50 . Each of panels  66 ,  64 ,  62 ,  60 ,  58 ,  56 ,  54 ,  52  and  50  are separated by score lines, shown in dashed lines. A series of flaps  64   a ,  62   a ,  60   a ,  58   a ,  56   a ,  54   a ,  52   a  and  50   a  reside respectively below each of the noted panels. The flaps are separated from the panels by a score line shown as a dashed line. It is noted that there is no flap below overlap panel  66 . 
     Referring further to  FIG. 4 , a butt joint  68  exists between a pair of sheets that are laminated to the back surface of the panels  50 - 64 . Butt joint  68  is positioned offset from the score line between panels  56  and  54  to retain optimum strength. The two laminated sheets connected by butt joint  68  do not extend to the area identified as flaps  64   a ,  62   a ,  60   a ,  58   a ,  56   a ,  54   a ,  52   a  and  50   a.    
     The essence of the present invention is depicted in the enlarged perspective view of  FIG. 5  and in the edge plan view of  FIG. 6 , respectively. In previously known multiple wall corrugated board containers, all flutes are vertically oriented to provide a rigid column and support the weight of full upper bulk bins. As discussed above, the quasi-liquid nature of a quantity of plastic resin pellets creates a substantial lateral force against the walls of a bulk bin, causing a tendency for wall bulging. When one or more additional bulk bins full of plastic pellets are placed on top of a first bulk bin, the weight of the upper bulk bins causes a greater lateral force in the lower bulk bins, resulting in more bulging. The end effect when the walls of the lower bulk bins bulge, the column strength diminishes and one or more walls of the lower bulk bins will ultimately collapse. 
     Continuing with  FIGS. 5 and 6 , the present invention provides a multiple wall corrugated board construction in which the corrugations in one board are oriented vertically and the corrugations in the other board are oriented horizontally. By creating a board with one set of corrugation flutes vertical and the other set of corrugation flutes horizontal, the board becomes significantly more resistant to flexure and bulging, thus ultimately retaining more column strength. 
     Referring further to  FIGS. 5 and 6 , a first board A is formed with corrugations oriented vertically and a second board B is formed with corrugations oriented horizontally. For added strength, board A and board B are each formed as a double wall board, having two layers of corrugations glued between three flat paper sheets. As illustrated, the two corrugated layers in the example shown are of different thickness. Boards A and B are laminated together to form a double wall board. It is understood that the principles of the invention are similarly applicable to boards having three walls. Board A has a front sheet  72 , a first corrugation  74 , a middle sheet  76 , a second corrugation  78  and a back sheet  80 . As illustrated, the first corrugations  74  and the second corrugations  78  are oriented vertically. Board B has a front sheet  82 , a first corrugation  84 , a middle sheet  86 , a second corrugation  88  and a back sheet  90 . As illustrated, the first corrugations  84  and the second corrugations  88  are oriented horizontally. 
     As discussed above, manufacturing of corrugated sheet involves feeding three or five sheets of paper into a laminating machine with the intermediate second and fourth paper sheets being fed at a higher linear rate of speed and formed into a sinusoidal wave, also known as flutes. The flutes are glued to the adjacent flat paper sheets to achieve relative rigidity of the composite board. 
     Referring further to  FIG. 6 , a plan view is shown of the edge of board  40 , with the corrugations in board A visible in end view as a series of flutes, and the corrugations in board B being laterally oriented and seen in side view. Therefore, the dimensions of multiple wall board  40  permit the corrugations in board A to be formed in continuous web to be as long as required. However, the corrugations in board B, being transverse to the direction of the corrugations in board A are limited by the width of the corrugating machine that is available. The largest width of a known corrugating machine enables production of corrugated board of 125 inches width. As noted above, a bulk bin may be formed of a corrugated board that may be as much as 208 inches long. Therefore, to laminate board B across the width of board A, two portions of board B, designated as portion C and portion D are required. According to the preferred embodiments of the invention, portions C and D are depicted as being different in width. A main emphasis is that butt joint  68  between portion C and portion D does not coincide with any of the scores (see  FIG. 4 ) for folding bulk bin  40 . Portion C and portion D are glued to board A to complete the laminated construction with a first set of flutes  74 ,  78  oriented vertically and a second set of flutes  84 ,  88  oriented horizontally. For a bulk bin intended to handle a greater weight of liquid or quasi-liquid material, or to have more fully loaded bulk bins stacked on top of the lowest bulk bin, a triple wall laminated board may be produced. Such a triple wall laminate would preferably have a second board A laminated to the opposite surface of board B, creating a vertical-horizontal-vertical flute composite construction. 
     Referring further to  FIG. 6 , it is noted that first corrugations  74  are formed relatively narrow and second corrugations  78  are formed relatively wide, according to conventional multiple wall board construction methods. However, it is within the spirit and scope of the present invention to form corrugations  74  and  78  substantially equal in width. 
     Pursuant to standard industry practice, a lid (not shown) is provided for bulk bin  10  (see  FIG. 1 ) and for bulk bin  40  (see  FIG. 3 ). The lid is generally planar with a peripheral lip extending downward around the edge of the respective bulk bin  10 ,  40 . 
     While the description above discloses preferred embodiments of the present invention, it is contemplated that numerous variations and modifications of the invention are possible and are considered to be within the scope of the claims that follow.