Patent Publication Number: US-11643241-B2

Title: Process for forming plastic corrugated container and intermediary blank

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 14/580,832 filed Dec. 23, 2014, which claims the benefit of U.S. Provisional Application No. 61/920,570 filed Dec. 24, 2013, the contents of which are incorporated herein by reference. 
    
    
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     N/A 
     TECHNICAL FIELD 
     The present invention generally relates to a reusable plastic corrugated container or more specifically box with smooth outer edges and sealed flap slots, and ultrasonically formed score lines, and to a process for manufacturing reusable plastic corrugated containers and boxes with smooth sealed outer edges and sealed flap slots, and having flap score lines that allow these containers and boxes to be used and reused in conventional paper corrugated packaging automation lines which may include case erectors, case packers, box closure and sealing systems, and palletizers. 
     BACKGROUND OF THE INVENTION 
     Corrugated plastic relates to extruded double-walled plastic-sheets, or liners, produced from polypropylene or polyethylene resin. Corrugated plastic sheets have a generally similar construction to corrugated paperboard. There are two layers of sheets or skins connected by flutes disposed and connected therebetween to form the corrugated sheet. One type of corrugated plastic material is known as “plastic profile board.” As opposed to the flutes being undulating waves, as they are in paperboard corrugation and certain other plastic corrugated materials, the flutes in a plastic profile board are typically more like ribs and the profile is preferably extruded. 
     The plastic corrugated sheets can be transparent to allow light transmission, or they can be custom colored or translucent to signify an owner or manufacturer, or to block the transmission of light. The space between the outer skins act as an insulator. Graphics can also be applied to the outer surfaces and inner surfaces of the outer layers. 
     Chemically, corrugated plastic sheets are inert, with a neutral pH factor. At regular temperatures most oils, solvents and water have no effect, allowing the corriboard to perform under adverse weather conditions or as a product component exposed to harsh chemicals. Standard corrugated plastic sheets can be modified with additives, which are melt-blended into the sheet to meet specific needs of the end-user. Special products that require additives can include: ultra-violet protection, anti-static, flame retardant, custom colors, corrosive inhibitors, static-dissipative, among others. 
     The Wiley Encyclopedia in Packaging Technology (“Boxes, Corrugated” in  The Wiley Encyclopedia of Packaging Technology , eds. Brody A and Marsh K, 2nd ed, John Wiley &amp; Sons, New York) identifies the following standard flute designations used in the United States for paperboard corrugations: 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                   
                   
                 Flute  
                   
                 Flute  
               
               
                 Flute 
                 Flutes per  
                 thickness 
                 Flutes per  
                 thickness 
               
               
                 Designation 
                 linear foot 
                 (in) 
                 linear meter 
                 (mm) 
               
               
                   
               
             
            
               
                 A flute 
                 33 +/− 3  
                  3/16 
                 108 +/− 10 
                 4.8 
               
               
                 B flute 
                 47 +/− 3  
                 ⅛ 
                 154 +/− 10 
                 3.2 
               
               
                 C flute 
                 39 +/− 3  
                  5/32 
                 128 +/− 10 
                 4.0 
               
               
                 E flute 
                 90 +/− 4  
                  1/16 
                 295 +/− 13 
                 1.6 
               
               
                 F flute 
                 128 +/− 4  
                  1/32 
                 420 +/− 13 
                 0.8 
               
               
                   
               
            
           
         
       
     
     Corrugated plastic can be used to form boxes and other similar containers. A variety of equipment has been used to convert paper and plastic corrugated material into boxes. The equipment is selected based on production run size, box size, and box quality in terms of tolerances and aesthetic appearance. This equipment includes flexographic, silk screen and digital printing machines; quick set, rotary, clam shell or flatbed die cut machines; and manual, ultrasonic welding, and automated folding and gluing machines for assembly. 
     Paper corrugated boxes are often used only once and then discarded. After a paper corrugated blank is converted into a box and used, it cannot typically be re-used in automated packaging lines designed to work with new, straight and flat boxes. This is in part because the major and minor flaps of a paper corrugated box will not return to their original vertical alignment after use, and in part because the creases and scores of a paper corrugated box lose integrity with each use. In such instances, the flaps become floppy or limp. Additionally, paper boxes cannot be washed or otherwise cleaned, and therefore cannot be reused in instances where sanitation is important (e.g., food items, etc.) 
     Therefore, the industry has long sought a re-usable container (i.e., one that can be cleaned or sanitized and then re-used), and has attempted to make a re-usable plastic corrugated container. As with paper corrugated containers, it is desirable that plastic corrugated containers are able to be used with conventional paper converting equipment (e.g., equipment that folds a cut/scored blank of material into a box). Previous methods to convert plastic corrugated material into boxes have used conventional paper corrugated converting equipment and process flow. This process flow includes making plastic corrugated material blanks to the appropriate size and then die cutting the blank using quick set, rotary, clam shell or flatbed die cutting machines. The die cut blanks are then assembled by bonding a glue tab and one of the panels to form a box. The blank may also be printed upon. 
     A lingering problem with current attempts to create a re-usable plastic corrugated container is that it must be able to return (after being used in a box form) to a flat state with the flaps aligned or coplanar with the side wall panels of the blank in order to be refolded in the box converting equipment. Industry efforts to this point have failed to provide such a container. In particular, the fold or score lines connecting the upper or lower flaps or panels to the side panels of the box must be able to bend (i.e., during a box forming process), and also have sufficient memory to revert to a straight position (i.e., coplanar or aligned with the box side panel) to again be reformed into a box (after sanitizing) using the converting equipment. However, the score lines cannot be made with too much memory so that after use, they have too much bounce-back or spring-back making them difficult for the converting equipment. 
     In addition, it is desirable to seal the edges to prevent intrusion of water, bacteria, or other debris, bugs or contaminants into the fluted area. This is particularly important for containers used with food and pharmaceutical products. Previous methods for sealing the edges of plastic corrugated material boxes have used either clam shell or flatbed die cutting machines during the converting process. The seal is formed in the die cut process using heat and pressure to pinch and weld together the inner and outer surfaces of the plastic corrugated material along the edge. This forms a sealed, but sharp edge, which is not acceptably ergonomically safe in most applications. Some limited success has been found using these processes for lighter densities of plastic corrugated material. While the process still leaves a sharp edge, the lighter densities make edge sealing acceptable for limited use applications, but not multiple re-use applications. 
     In addition to the above problems, it is also desirable to reduce the number of steps needed to create and process plastic corrugated boxes and to increase the processing speed. Due to environmental concerns, it is anticipated that many companies will insist on or otherwise turn to re-usable containers in the near future. Thus, the demand for such containers will rise and the speed of the plastic container processing will become a more pressing issue. 
     Assignee of the present development, Orbis Corporation has been developing and refining plastic corrugated containers and the processes for forming them. Examples of recent Orbis Corporation developments are described in U.S. patent application Ser. No. 14/265,977, filed Apr. 30, 2014, titled “Plastic Corrugated Container with Sealed Edges”, U.S. patent application Ser. No. 14/265,935, filed Apr. 30, 2014, titled “Plastic Corrugated Container with Manufacturer&#39;s Joint Adding Zero Extra Thickness”, U.S. patent application Ser. No. 13/273,019, filed Oct. 13, 2011, titled “Plastic Corrugated Container with Improved Fold Lines and Method and Apparatus for Making Same,”, U.S. Patent Application No. 61/920,570, filed Dec. 24, 2013, titled “Plastic Corrugated Manufacturing Process”, and U.S. Patent Application 62/062,481, filed Oct. 10, 2014, titled “Plastic Corrugation”, all of which are incorporated herein by reference. 
     Aspects of the present invention are applicable for a variety of container and box types. The most common box style is a regular slotted container (RSC) having four side panels with four top flaps (for forming a top) and four bottom flaps (for forming a bottom). For a rectangular shaped box, the two longer flaps are referred to as the major flaps and the two shorter flaps as the minor flaps. Another common box style is a half slotted container (HSC). The HSC is similar to the RSC except that it only includes the bottom set of flaps and has an open top. In the HSC, the top edge of the blank used to form the box becomes the upper edge of the box side panels. Other types of boxes (e.g., autolock, auto erect or crash lock boxes—ALB) can also be formed using various aspects of the invention as well. 
     The present invention is provided as an improved plastic corrugated container and process for forming the container. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved plastic corrugated box manufacturing process resulting in a plastic corrugated box with safe rounded sealed edges on the edges most frequently contacted by human hands. Sealing is desirable, particularly in certain applications such as transport and storage of food items. Sealing prevents food, insects, water, or other contaminants or debris from entering the interstices of the flutes in the corrugated material, and bacteria or mold from growing therein. 
     The process of the present invention also allows for the creation of a manufacturer&#39;s joint (the connection between one end of a blank with the other end when forming the blank into a box shape) that reduces the amount of bowing in a stack of blanks. Preferably, the manufacturer&#39;s joint adds no additional thickness to each blank. The process also allows for major and minor flap score lines that allow the plastic corrugated material boxes to return to an original straight position for use in conventional automated packaging lines. The process of the present invention also provides a plastic corrugated blank that can be converted into a box using conventional paper corrugated converting equipment. 
     The process confers a number of advantages over the prior art. For example, the resulting edge seals and score lines can be performed in a more controlled and, therefore, consistent process. This results in a more robust plastic corrugated box. Additionally, the plastic corrugated boxes prepared in this manner can be die cut and assembled on conventional paper corrugated converting equipment, including rotary die cutters, and can be processed at higher speeds. Also, the plastic corrugated boxes are able to return to their original shape as the score lines formed by the present invention will have “memory” that return major and minor flaps to straight after each use. 
     In one embodiment, the present invention provides a method for manufacturing a corrugated plastic blank that includes the steps of forming rounded edge seals on the perimeter edges of the blank, pre-sealing portions of the blank to form a plurality of areas in which major and minor flap slots, a glue tab, and a fourth side wall panel edge are desired, scoring the blank to form a plurality of flap hinges, and cutting the blank through the plurality of pre-sealed flap slots, glue tab and fourth side wall panel areas, leaving a sealed edge. The scoring is preferably performed by rotary ultrasonic reshaping of the corrugated structure in the score line. 
     The blank includes fold and/or score lines defining a pair of opposing side wall panels and a pair of opposing end wall panels. The blank also includes bottom and possibly top flaps extending from the pair of opposing side walls, and bottom and possibly top flaps extending from the pair of opposing end walls. The blank further includes rounded seals along the perimeter edges of the blank, and a plurality of flap slots sealed along their edges. 
     In accordance with one embodiment of the invention, a plastic corrugated box which can be reused in box converting machinery is disclosed. The plastic corrugated box comprises at least a first side wall panel having a top portion and a bottom portion and a first bottom flap connected to the bottom portion of the first side wall panel by a first ultrasonically formed score line. It has been found that ultrasonically forming the score line of a plastic corrugated box reshapes the structure of the plastic in that area. The reshaped structure allows for folding the flap about the score line when forming a box, and provides sufficient memory to return the flap to a straight position (i.e., coplanar or aligned with the plane of the side wall panel) after use. This enables the corrugated box to be collapsed and then (along with a stack of other similar boxes) reformed into a box in a box converting apparatus. Such apparatuses require the flaps to be straight and coplanar or aligned with the side wall panels. 
     The first bottom flap can be formed to include a smooth sealed lower edge. For a Half Slotted Container box style, the first side wall panel can be formed to include a smooth sealed upper edge. 
     The plastic corrugated box can further comprise a second side wall panel having a top portion and a bottom portion connected to the first side wall panel by a first fold line, a third side wall panel having a top portion and a bottom portion connected to the second side wall panel by a second fold line and a fourth side wall panel having a top portion and a bottom portion connected to the third side wall panel by a third fold line and to the first side wall panel by a manufacturer&#39;s joint. Similarly, the box can include a second bottom flap connected to the bottom portion of the second side wall panel by a second ultrasonically formed score line, a third bottom flap connected to the bottom portion of the third side wall panel by a third ultrasonically formed score line and a fourth bottom flap connected to the bottom portion of the fourth side wall panel by a fourth ultrasonically formed score line. 
     Again, for the Half Slotted Container style box, all of the bottom flaps can include a smooth sealed lower edge, and all of the side wall panels can include a smooth sealed upper edge. 
     For a Regular Slotted Container box style (and certain other box styles having top flaps), the box can include a first top flap connected to the top portion of the first side wall panel by a fifth ultrasonically formed score line, as well as a second top flap connected to the top portion of the second side wall panel by a sixth ultrasonically formed score line, a third top flap connected to the top portion of the third side wall panel by a seventh ultrasonically formed score line and a fourth top flap connected to the top portion of the fourth side wall panel by an eighth ultrasonically formed score line. Each of the top flaps can include a smooth sealed upper edge. 
     The ultrasonically formed score lines do not have to extend across a full width of the flap and/or corresponding side wall panel. Instead, the ultrasonically formed score line can comprise a plurality of spaced apart ultrasonically formed segments across a width of the flap and/or corresponding side wall panel. 
     In accordance with another aspect of the present invention, a plastic corrugated blank for forming a box is disclosed having a generally rectangular portion of plastic corrugated material. The blank includes a plurality of fold lines forming side edges of a plurality of side wall panels. The plastic corrugated material can have a first plurality of ultrasonically formed score lines where each score line of the first plurality of ultrasonically formed score lines forms an edge between one of the plurality of side wall panels and a bottom flap connected to the one side wall panel. Similarly, the plastic corrugated material can have a second plurality of ultrasonically formed score lines where each score line of the second plurality of ultrasonically formed score lines forms an edge between one of the plurality of side wall panels and a top flap connected to the one side wall panel. The blank can have a smooth sealed top edge and a smooth sealed bottom edge. 
     In accordance with another aspect of the present invention, a process for forming a re-useable plastic corrugated box is provided. The process comprises providing a sheet of plastic corrugated material having a top edge and a bottom edge and ultrasonically forming a first score line in the sheet of plastic corrugated material using an ultrasonic device. 
     The process can further include forming a plurality of fold lines in the sheet of plastic corrugated material where the fold lines define a plurality of side wall panels of the box and the first score line defines a bottom flap for one of the plurality of side wall panels. Additionally, the step of ultrasonically forming a first plurality of score lines in the sheet of plastic material can be performed where each of the first plurality of score lines define a bottom flap for a corresponding side wall panel. 
     The process can further comprise ultrasonically forming a second score line in the sheet of plastic corrugated material where the second score line defines a top flap for the one of the plurality of side wall panels, or ultrasonically forming a second plurality of score lines in the sheet of plastic material where each of the second plurality of score lines define a top flap for a corresponding side wall panel. 
     The process can further include forming a smooth sealed top edge of the sheet and forming a smooth sealed bottom edge of the sheet. The process can also include cutting slots between the bottom flaps and the top flaps, forming a glue tab at a first end of the sheet of corrugated material and, connecting the glue tab to a second opposing end of the sheet of corrugated material. Additionally, the process can include providing automated box converting equipment for opening and folding the sheet of plastic corrugated material. 
     The step of ultrasonically forming the score lines in the sheet of plastic corrugated material can comprise contacting a first surface of the sheet with an anvil of a rotary ultrasonic device. The anvil can be provided with a first projection on a contacting surface of the anvil. Additionally, this step can include contacting a second surface of the sheet opposing the first surface with a horn of the rotary ultrasonic device. The horn is provided to supply the ultrasonic energy. However, either the horn or the anvil can be configured to supply the ultrasonic energy to the sheet. Alternatively, other ultrasonic devices could also be used. 
     The ultrasonically formed score line can be continuous throughout each flap. Alternatively, each ultrasonic score line can be formed by ultrasonically reshaping a plurality of spaced apart linear segments in the sheet. 
     In accordance with yet another embodiment of the invention, a process for forming a plastic corrugated box is provided that comprises providing a generally rectangular sheet of plastic corrugated material having a first outer layer, a second outer layer and a plurality of flutes extending in a first direction between the first and second outer layers. The process further comprises forming a plurality of fold lines on the sheet in the first direction where the fold lines define a plurality of side panels of the box and ultrasonically forming a first plurality of score lines on the sheet in a second direction perpendicular to the first direction where the first plurality of score lines defining a plurality of bottom flaps extending from a bottom portion of the side panels. The process can further include ultrasonically forming a second plurality of score lines on the sheet in the second direction where the second plurality of score lines define a plurality of top flaps extending from a top portion of the side panels. The process further includes cutting a plurality of slots between the bottom flaps and cutting a plurality of slots between the top flaps. The cutting step can be performed in a die cutting machine. 
     Again, the ultrasonic forming of the score line can be performed with a rotary ultrasonic device having a horn and an anvil, or other ultrasonic devices. 
     The process can further include forming a glue tab at a first end of the plastic sheet and connecting the glue tab to a second end of the plastic sheet. The process can use box converting equipment by placing the plastic sheet in a box converting apparatus, opening the box using the apparatus and folding the bottom flaps using the apparatus. 
     One unique aspect of the invention involves pre-sealing portions of the corrugated plastic material in certain areas of the blank prior to performing other operations. As used herein, “pre-sealing” (or “pre-sealed”) refers to crushing and/or welding or ironing the plastic so that it will no longer have memory to later revert to its original shape. This can include sufficiently melting some or all of the material in the area being pre-sealed. In effect, the pre-sealing bonds the two outer skins and intervening flutes of the material together so that the pre-sealed area maintains a permanently flattened state. Pre-sealing allows for forming a manufacturer&#39;s joint that does not (upon formation or later) increase the thickness of the blank. It also enables portions of the blank to be die cut more easily (e.g., for the flap slots) using conventional die cutting apparatuses, and with better results. 
     In accordance with yet another embodiment of the invention, a process for forming a plastic corrugated box having a plurality of side wall panels comprises providing a sheet of plastic corrugated material, forming a plurality of fold lines in the sheet where the fold lines define a plurality of side wall panels, forming a plurality of score lines in the sheet where the score lines define a plurality of flaps extending from the side wall panels, and pre-sealing a plurality of segments on the sheet at positions for forming a plurality of slots between the flaps. This pre-sealing step is performed prior to cutting slots between the flaps. 
     The process can further include pre-sealing at least a first portion of a first end of the sheet and at least a first portion of a second end of the sheet. These pre-sealed end portions can be used for formation of a manufacturer&#39;s joint (the connection of one end of the blank to the other end when forming a box). 
     The process can further include forming a smooth sealed top edge of the sheet and forming a smooth sealed bottom edge of the sheet. The smooth sealed edges can be formed using heated dies. The dies can be curved or arcuate, flat or some other smooth shape. 
     The process further includes cutting slots within the plurality of pre-sealed segments. This can be done by placing the sheet in a die cutting apparatus. The die cutting apparatus can also be used for cutting a second portion of the first end of the sheet to form a centrally located pre-sealing glue tab. 
     The step of pre-sealing a plurality of segments on the sheet at positions for forming a plurality of slots between the flaps can comprise applying heat and pressure to the sheet at the segment positions. Alternatively, this step can comprise ultrasonically welding the sheet at the segment positions. The ultrasonic welding can be performed by a plunge ultrasonic device or by a rotary ultrasonic device. If a rotary ultrasonic device is used the process can include the steps of contacting a rotatable anvil of the rotary ultrasonic device on a first outer surface of the sheet at the segment positions, and contacting a rotatable horn of the rotary ultrasonic device on a second outer surface of the sheet where the horn is aligned or in registration with the anvil. 
     Additionally, the process can include forming air escape holes in the sheet proximate the segment positions. This allows air trapped in the flutes between the outer sheets of the plastic corrugated material to escape during the pre-sealing step. Otherwise, random air holes (caused by trapped air) can form in the blank during this process and squeeze out of molten plastic (during pre-sealing) can extend beyond the blank edge. 
     Another issue that can occur during the pre-sealing process is lumps from excess plastic in the pre-sealed flattened areas. Accordingly, the process can include directing the excess plastic of the sheet formed when pre-sealing the segments into desired locations. One method of directing the excess plastic is providing the anvil (when using a rotary ultrasonic device, or the contacting surface of other types of ultrasonic devices) with a contacting surface having peaks and valleys. The valleys provide a location for the excess plastic to move to during the pre-sealing step. Preferably, the process includes providing an undulating wave pattern of raised ridges on the contacting surface. 
     In accordance with another embodiment of the present invention, a process for forming a plastic corrugated box comprises providing a generally rectangular sheet of plastic corrugated material having a first outer layer, a second outer layer and a plurality of flutes extending in a first direction between the first and second outer layers, forming a plurality of fold lines on the sheet in the first direction where the fold lines define a plurality of side panels of the box and forming a plurality of score lines on the sheet in a second direction perpendicular to the first direction where the plurality of score lines define a plurality of flaps extending from the side panels, and pre-sealing a plurality of segments on the sheet at positions for forming a plurality of slots between the flaps. The step of pre-sealing a plurality of segments on the sheet welds the first outer layer to the second outer layer at the segment positions. 
     Again, the process can include forming air escape holes in the sheet proximate the segment positions, and cutting flap slots in the pre-sealed segments. 
     The step of pre-sealing the plurality of segments comprises contacting the first outer layer of the sheet with an ultrasonic device having a contacting surface with a plurality of ridges. This can be done by rolling a rotatable anvil of the ultrasonic device on the first outer layer where the anvil has an undulating ridge pattern on the contacting surface. 
     In accord with yet another embodiment of the invention, a blank for forming a reusable plastic corrugated box is provided. The blank comprises a sheet of plastic corrugated material having a plurality of fold lines defining a plurality of side wall panels, a first plurality of score lines defining bottom flaps extending from a bottom portion of the side wall panels, and a first plurality of pre-sealed segments at positions for slots between the bottom flaps. 
     The blank can further include a second plurality of score lines. The second plurality of score lines define a plurality of top flaps extending from a top portion of the side wall panels, and a second plurality of pre-sealed segments at positions for slots between the top flaps. 
     The blank can further comprise a pre-sealed portion at a first end of the sheet and a pre-sealed portion at a second end of the sheet. These pre-sealed portions can be used to form a manufacturer&#39;s joint. 
     The blank can be provided with a smooth sealed top edge and a smooth sealed bottom edge. Additionally, the blank can have an air escape hole at each of the first plurality of pre-sealed segments and each of the second plurality of pre-sealed segments. 
     The blank can be further formed to include a cut-out slot in each of the first plurality of pre-sealed segments, as well as each of the second plurality of pre-sealed segments. 
     The first plurality of pre-sealed segments can have a ridge pattern (or other similar pattern) on an upper surface of the sheet. Similarly, each of the second plurality of pre-sealed segments can have a ridge pattern on an upper surface of the sheet, as well as the pre-sealed portion at the first end of the sheet. The pre-sealed portion at the second end of the sheet can have a ridge pattern on a lower surface of the sheet. 
     The pre-sealed portion at the first end of the sheet can be formed into a centrally located glue tab extending outward from the sheet. The glue tab can be connected to the other end of the blank. The corrugated plastic material has a first thickness and the pre-sealed portion at the first end of the sheet and the pre-sealed portion at the second end of the sheet collectively have a thickness less than twice the first thickness. Preferably, the combined thickness is equal to or less than the first thickness. 
     In accordance with another embodiment of the invention, a blank for forming a reusable plastic corrugated box comprises a generally rectangular sheet of plastic corrugated material having a first outer layer, a second outer layer and a plurality of flutes extending in a first direction between the first and second outer layers, a plurality of fold lines in the first direction defining a first side wall panel, a second side wall panel, a third side wall panel and a fourth side wall panel, a first plurality of score lines extending in a second direction perpendicular to the first direction defining a first bottom flap extending from a bottom portion of the first side wall panel, a second bottom flap extending from a bottom portion of the second side wall panel, a third bottom flap extending from a bottom portion of the third side wall panel and a fourth bottom flap extending from a bottom portion of the fourth side wall panel, and a first plurality of pre-sealed segments extending between the first and second bottom flaps, the second and third bottom flaps and the third and fourth bottom flaps. The blank can further comprise a second plurality of score lines extending in the second direction defining a first top flap extending from a top portion of the first side wall panel, a second top flap extending from a top portion of the second side wall panel, a third top flap extending from a top portion of the third side wall panel and a fourth top flap extending from a top portion of the fourth side wall panel, and a second plurality of pre-sealed segments extending between the first and second top flaps, the second and third top flaps and the third and fourth top flaps. 
     Additionally, the blank can have a plurality of air escape holes at each of the first plurality of pre-sealed segments and each of the second plurality of pre-sealed segments. In a later forming step (which may remove the portion of the blank having the air escape holes), the blank can have a cut-out slot in each of the first plurality of pre-sealed segments and in each of the second plurality of pre-sealed segments. 
     Each of the first plurality of pre-sealed segments and each of the second plurality of pre-sealed segments have a ridge pattern on an upper surface of the sheet. After the cut-out slots are formed, a portion of the ridge pattern can remain around each cut-out slot (i.e., the pre-sealed areas are typically wider than the slot cut-out in those areas). 
     Other aspects of the invention are disclosed in the description, claims and figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which: 
         FIG.  1    is a schematic view of the prior art manufacturing process for a plastic corrugated box; 
         FIG.  2    is a perspective view of an extruded plastic corrugated blank for a plastic corrugated box in accordance with the present invention; 
         FIG.  3    is a perspective view of a plastic corrugated blank with its vertical edges sealed in accordance with the present invention; 
         FIG.  4    is a perspective view of plastic corrugated blank sealed across its flutes in accordance with the present invention; 
         FIG.  5    is a perspective view of a plastic corrugated blank with pre-sealed glue tab and fourth panel areas in accordance with the present invention; 
         FIG.  6    is a perspective view of a plastic corrugated blank with pre-sealed major and minor flap areas in accordance with the present invention; 
         FIG.  7    is a perspective view of a plastic corrugated blank with major and minor flap scores in accordance with the present invention; 
         FIG.  8    is a perspective view of a plastic corrugated blank printed with indicia in accordance with the present invention; 
         FIG.  9    is a perspective view of a plastic corrugated blank after the major and minor flap areas and glue tab area and fourth panel area have been die cut; 
         FIG.  10    is an enlarged view of the die cut flap area of  FIG.  9   ; 
         FIG.  11    is a perspective view of a plastic corrugated box constructed in accordance with the present invention; 
         FIG.  12    is a schematic view of an apparatus for sealing the edges of the plastic corrugated blank in accordance with the present invention; 
         FIG.  13    is a perspective view of a manufacturer&#39;s joint of a current blank; 
         FIG.  14    is a perspective view of a manufacturer&#39;s joint in accordance with the present invention; 
         FIG.  15    is a perspective view of an apparatus for sealing the edges of the plastic corrugated blank in accordance with the present invention; 
         FIG.  16    is a perspective view of an apparatus for sealing the edges of the plastic corrugated blank in accordance with the present invention; 
         FIG.  17 A  is a perspective view of a rotary ultrasonic welding apparatus in accordance with the present invention; 
         FIG.  17 B  is a plan view of a rotary ultrasonic welding horn and anvil forming a scoreline in a plastic corrugated blank; 
         FIG.  18    is a perspective view of a rotary ultrasonic anvil in accordance with the present invention; 
         FIG.  19    is a plan view of a rotary ultrasonic anvil and horn in accordance with the present invention; 
         FIG.  20    is side plan view showing a variety of smooth sealed edge configurations; 
         FIG.  21    is a perspective view of a corner of a plastic corrugated container with the edges of the flaps having unsealed open flutes; 
         FIG.  22    is a perspective view of a corner of a plastic corrugated container with the edges of the flaps having a sharp die cut seal; 
         FIG.  23    is a perspective view of a corner of a plastic corrugated container with the edges of the flaps having a smooth seal; 
         FIG.  24    is a front plan view of a rotary ultrasonic device anvil having an undulating, ridged contacting surface for forming a pre-sealed area on a plastic corrugated blank; 
         FIG.  25    is a perspective view of the rotary ultrasonic device anvil of  FIG.  24   ; 
         FIG.  26    is a perspective view (with an enlarged section) of a blank having a plurality of pre-sealed segments formed by the anvil of  FIG.  24   ; 
         FIG.  27    is a perspective view of a blank having a plurality of pre-sealed segments formed by the anvil of  FIG.  24    with a plurality of flap slots cut in the pre-sealed segments. 
         FIG.  28    is a perspective view of sealing dies forming a smooth sealed edge on a corrugated plastic blank; 
         FIG.  29    is front plan view of one of the sealing dies of  FIG.  28   ; 
         FIG.  30    is a perspective view of a blank with a plurality of air escape holes positioned at locations for pre-sealing; 
         FIG.  31    is a perspective view of a blank with a plurality of escape holes and a plurality of pre-sealed segments (with an enlarged portion); 
         FIG.  32    is a perspective view of a stack of corrugated plastic blanks having a manufacturer&#39;s joint that had not been flattened or had reverted back to original thickness on top of a stack of corrugated paper blanks; 
         FIG.  33 A  is side plan view illustrating a pre-sealed glue tab and a pre-sealed edge area of a fourth panel prior to being connected; 
         FIG.  33 B  is side plan view illustrating a pre-sealed glue tab and a pre-sealed edge area of a fourth panel after being connected; 
         FIG.  34    is a perspective view of a stack of corrugated plastic blanks with a manufacturer&#39;s joint that does not add thickness to the blank; 
         FIG.  35    is a perspective view of a plurality of corrugated paper blanks and a plurality of corrugated plastic blanks in a box converting apparatus; 
         FIG.  36    is a perspective view of a corner of a plastic corrugated container with a first sealed portion and a second sealed portion; and, 
         FIG.  37    is a perspective view of a paper corrugated blank with a “window frame” of trim material. 
     
    
    
     DETAILED DESCRIPTION 
     While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated. 
       FIG.  1    illustrates a plurality  10  of progressively formed blanks  12  in a known method of forming plastic corrugated material into boxes using conventional converting equipment. The method includes the steps of obtaining a sized plastic corrugated blank  12 , printing  14  thereon, if necessary, on one or both sides of the plastic corrugated blank  12 , sealing the vertical edges  16  and the horizontal edges  18 , forming scores (sometimes also referred to as scorelines)  20  therein and creating side wall panel fold lines  21  therein, and die cutting slots  26  for the major flaps  22  and minor flaps  24  (which form the top and bottom of the box) and a glue tab  28  at one end of the blank  12 . The steps of sealing the edges  16 ,  18  and forming the scores  20  in the plastic corrugated blank  12  are preferably performed at the same time the blank  12  is die cut. Specifically, the edge seals  16 ,  18  are formed during the die cutting process using heat and pressure to weld together a first outer surface  32  and a second outer surface  34  of the plastic corrugated blank  12 . The scores  20  are also formed by applying heat and pressure during the die cutting. The step of die cutting and forming the scores  20  cuts the plastic corrugated blank  12  into the desired shape, forming the major and minor flaps  22 ,  24 , and the glue tab  28 . 
     The known die cutting involved in this process can include the use of clam shell or flatbed machines. When using a clam shell die cutting machine in current methods, the back of a die board is heated which transfers heat to a heating rule. The heated die board cuts and seals the plastic corrugated material  12  against a steel plate at ambient temperature. When using a flatbed die cutting machine, the known method includes heating a steel cutting surface to transfer heat through the plastic corrugated material as it moves through the die cutting process. A die board at ambient temperature presses and cuts the plastic corrugated material  12  against the heated cutting surface to form a heated edge seal. 
     The step of printing is optional. If printing onto a surface  32 ,  34  of the plastic corrugated blank  12  is desired, it is conventionally performed using flexographic, silk screen, digital or other suitable methods. 
     The method also includes the steps of assembling a manufacturer&#39;s joint (i.e., connecting the glue tab  28  to the other end of the blank  12 ), and converting the glued blanks  12  to make finished boxes. In this instance, the boxes would have four side wall panels. The major and minor flaps would be folded to form a top and bottom to the box. 
     Problems with the known method include variations in quality and robustness of the seal(s) around the edges of the box. In this regard, the heated platen on the die cutter forms a sharp edge on the blank and particularly along the outer edges of the flaps  22 , 24 , resulting in potential lacerations to people involved in the process, and in using the blanks (an enlarged view of the sharp edges  107  after sealing during die cutting is shown in  FIG.  22   ). Moreover, the die cut and scored blanks cannot be re-used currently with conventional converting equipment because (in part) the flaps formed in the known method do not return to a straight orientation generally coplanar with the side wall panels of the box after a first use. The known method also results in relatively slow die cut speeds. Additionally, the known method also produces boxes with a relatively thick manufacturer&#39;s joint. As illustrated in  FIG.  32   , the relatively thick manufacturer&#39;s joint formed in the known method causes a recognizable bowing in the center of a stack  240  of the glued plastic corrugated blanks. 
     The present invention provides a re-useable plastic corrugated box and a process for forming plastic corrugated boxes that can be easily cleaned and reused in conventional converting machinery typically used with paperboard corrugated boxes. The process includes pre-sealing (i.e., pre-crushing and/or welding or ironing of the corrugated plastic to remove memory) certain areas of a blank (i.e., a rectangular sheet of corrugated plastic) to be die cut (such as the flap slot areas and the manufacturer&#39;s joint), ultrasonically forming scorelines, and forming smooth, sealed edges across the flutes of the outer flaps (the smoothed edges can be rounded, flat or other configurations). The pre-sealed, ultrasonically scored and smooth, sealed edged sheet can then be placed in conventional converting systems for forming into boxes, and can be cleaned and reused in the converting systems. The process described herein takes into consideration both the movement or flow of plastic and air during the pre-sealing steps. 
     In accord with an embodiment of the present invention, a plastic corrugated rectangular blank  100  ( FIG.  2   ) is initially formed using current plastic corrugated extrusion methods.  FIG.  2    shows the blank  100  cut to its initial desired size. The size and shape of the blank (and the container or box formed from the blank) will depend on the desired application for which the finished box will be used. Plastic corrugated boxes can be used to store and transport any number of products from food items to automotive parts and can be made in many sizes and shapes. While the present invention is described in terms of a rectangular box having four side panels connected to top and bottom major and minor flaps, containers and boxes of various sizes and shapes (e.g., square, octagonal, etc.), can be made using the techniques and aspects of the invention(s) described herein. 
     When extruded, the blank  100  includes a first outer surface (or skin)  102  and a second outer surface  104 . Between the first and second outer surfaces  102 ,  104  are a plurality of generally parallel flutes  106 . Flutes formed in a profile board style corrugated plastic sheet are created by ribs between the two outer sheets  102 ,  104  (as opposed to undulating waves of material commonly found in paper corrugation and other types of corrugated plastic). As illustrated in  FIG.  2   , the blank  100  includes top and bottom edges  108  and  110  and first and second side edges  112  and  114 . Terms such as “top,” “bottom,” “side” etc., are made with respect to the orientation of the blank, box or other components as shown and positioned in the Figures to facilitate the description thereof. Such terms are not intended to limit the invention in any manner and may change from Figure to Figure. For example, the “top” edge  108  shown in one Figure may end up being the edge of the “bottom” flaps as shown in another Figure. The top and bottom edges  108  and  110  run across the flutes  106  and will form the outer edges of any flaps formed in the blank  112  (or the top edge of the side panels of a half slotted container—HSC). 
     In one embodiment, the blank  100  is sealed along the first and second side edges  112  and  114  in the direction of the flutes  106 , creating a first side edge seal  118  and a second side edge seal  116  (as described below, this can instead be preferably accomplished when pre-sealing an entire strip on either end of the blank  100  to form a manufacturer&#39;s joint and pre-sealing areas for slots between top and bottom flaps).  FIG.  3    shows the second side edge seal  116  in an enlarged portion along the second side edge  114 . It will be understood that the similar first side edge seal  118  will be created at the first side edge  112 . The blank  100  is placed on a conveyor  206  (See  FIGS.  15  and  16   ), where a hot air blower  207  (or multiple blowers) heats the first and second side edges  112  and  114  of the blank  100 . A knife cuts through the flutes  106  on the edge to be sealed. The blank  100  is moved through multiple heated dies  208  to form a smooth edge. The blank  100  is then moved through an identically shaped cooling die  210 . The heating and cooling dies  208  and  210  have generally C-shaped cross-sections  204 . The sealing of both side edges  112 ,  114  can also be performed in a single pass. It is recognized that the die or dies can be progressive, meaning instead of a single die, there are multiple dies having a progressively different shape leading up to a final die with the final desired shape formed therein. 
     The heated dies  208  include a heated sealing and forming die  202  with a generally C-shaped section  204 . The heated sealing and forming die  202  contacts the edges  112  and  114 , and partially melts or reforms the edge to seal it and create a smooth rounded edge surface. 
     The top and bottom edges  108 ,  110  are then sealed as illustrated in  FIG.  28   .  FIG.  28    shows a first sealing die  220  contacting the bottom edge  110  and a second sealing die  222  contacting the top edge  108  as the blank  100  is moved past the dies  220 ,  222 . As shown in  FIG.  29   , the dies  220 ,  222  have an open slot  224  for receiving the edge portion of the blank  100 . A heated element, such as that shown in cross-section in  FIG.  12    contacts the edges of the blank  100  to form a smooth sealed edge as the blank  100  moves past the dies  220 ,  222  (in the direction of the arrow  226 ). The open slot  224  of each die  220 ,  222  can further include a flared portion  228  for receiving the leading portion of the blank  100  as it approaches the dies  220 ,  222 . 
     As evident in  FIG.  28   , prior to entering the dies  220 ,  222 , the edge of the blank  100  has open sides and exposed flutes  106 . After passing through the dies  220 ,  222 , a smooth sealed edge (e.g.,  122 ) is formed and the interior of the blank as well as the flutes are not exposed. 
       FIG.  4    shows the top and bottom edges  108  and  110  sealed using the dies  220 ,  222  creating top and bottom smooth edge seals  120  and  122 , respectively. Top and bottom edge seals  120  and  122  are sealed across the flutes  106 , thereby closing the openings into the flutes which will prevent debris, liquids or other contaminants from becoming trapped in the interior of the sheet between the flutes  106 . Moreover, this smooth sealing provides safe, smooth rounded seals  120  and  122  on the edges of the blank  100  most frequently contacted by human hands, namely the top edge  108  and bottom edges  110 . It will be understood that this sealing process can be performed at any desired point in the process of the present invention. Additionally, the sealed edges can be flat or other shapes so long as they are relatively smooth.  FIG.  20    shows (in cross-section) a rounded smooth sealed edge  120  and a number of possible variations  230 ,  232 ,  234  of smooth sealed edges. 
     As illustrated in  FIG.  5   , after sealing of the top and bottom edges  108 ,  110  (i.e., across the open or exposed flutes  106 ), the blank  100  is pre-sealed proximate the first and second side edges  112  and  114  in the desired area  124  for a glue tab  126  (the glue tab  126  is shown in  FIG.  9   ) and a desired connection area  128  of a fourth side panel  130  (i.e. the glue tab  126  is considered to extend from the first side wall panel  125  of the completed box and is connected to the other end of the box designated as the fourth side wall panel  130 —see e.g.,  FIG.  10   ). As mentioned above, this pre-sealing step can also seal the side edges  112 ,  114  of the blank  100  and thus the separate side edge sealing step discussed above may be eliminated. Moreover, the side edge pre-sealing can be done at the same time as pre-sealing the slot areas  132  (i.e., the areas between the flaps) as shown in  FIG.  6    and discussed below. The pre-sealing can be accomplished using any suitable means, including heat and compression, plunge ultrasonic welding, or rotary ultrasonic welding. 
     In a subsequent step shown in  FIG.  9   , the pre-sealed edge  124  is cut leaving a centrally located glue tab  126 . The glue tab  126  is connected (e.g., glued, although ultrasonic welding or other means may be used) to the pre-sealed area  128  of the fourth side wall panel  130  to create a plastic corrugated box. The glue tab  126  and area of the fourth side wall panel  128  the glue tab  126  is ultimately connected to is referred to as the “manufacturer&#39;s joint.” An object of the invention is to create a manufacturer&#39;s joint that will not cause a stack of unformed boxes to unreasonably bow out in that area. For example,  FIG.  32    which shows a stack  240  of corrugated plastic blanks formed using prior known converting processes on top of a stack  242  of paper blanks. As evident in this Figure, the stack  240  of corrugated plastic blanks has a thicker middle section due to the manufacturer&#39;s joint. Instead, it is desirable to reduce any bowing and have a relatively flat stack  244  of unformed boxes as shown in  FIG.  34   . Accordingly, it is desirable that at least one (and preferably both) of the glue tab  126  and the fourth panel area  128  be flattened during pre-sealing to a thickness less than the blank thickness (i.e., if one or both are pre-sealed to less than the blank thickness, the total thickness in that area will be less than two blank thicknesses). Moreover, it is preferable that the manufacturer&#39;s joint will have no added thickness beyond the thickness of the blank. That is, it is preferred that the glue tab  126  and fourth panel area  128  are pre-sealed so that the combined total thickness of the glue tab  124  and fourth panel area  128  is preferably equal to or less than a single blank thickness as shown in  FIGS.  33 A  and B. 
     As illustrated in  FIG.  14   , a pre-sealed, pre-sealed glue tab  126  is connected to a pre-sealed, pre-sealed area  128  of the fourth side wall panel  130 . This results in a manufacturer&#39;s joint having zero increased thickness  150 . In comparison, a box  154  formed using current methods has an increased thickness  152  (an additional blank thickness) at the manufacturer&#39;s joint as shown in  FIG.  13   . 
     The blank  100  is also pre-sealed in the desired areas to form flattened and sealed segments  132  from which major and minor flap slots  142  of a resulting finished box  136  will be die cut (see  FIGS.  6 - 10   ). The pre-sealing flattens the blank  100  in the desired slot areas, effectively welding the inner and outer surfaces  102 ,  104  and flutes  106  to each other. The pre-sealing can be created by any suitable means, including plunger ultrasonic welding, rotary ultrasonic welding or by using heat and compression rollers, with a preferred method being rotary ultrasonic welding. 
     As shown in  FIG.  7   , score lines  138  are formed in the blank  100 . The score lines  138  will form the major and minor flaps  146 ,  148  of the finished box  136 . The scoring operation can be performed in accord with that disclosed in co-pending U.S. Ser. No. 13/273,019, filed Oct. 13, 2011, now U.S. Pat. No. 8,864,017, the contents of which are incorporated herein by reference. Briefly, the scoring from such application provides an intermittent welded score, leaving some portions of the score lines unwelded (i.e., not welded). Scoring using this method allows the major and minor flaps to be easily closed yet retain enough “memory” or “spring-back” such that after folding the flaps at the score, the flaps will return to its original shape and can be reused (after cleaning) in box converting machinery. It will be understood that the pre-sealing and the scoring can be performed such that the scoring takes place before the pre-sealing. 
     In another embodiment, the score lines  138  are formed using ultrasonic devices, such as with a rotary ultrasonic device, to reshape the corrugated plastic along the score line. The score lines using rotary ultrasonic reshaping can be a continuous line, or can be segmented, with sections of the score line left unchanged. Using rotary ultrasonic reshaping to form the score lines  138  allows easy folding of the major and minor flaps  146 ,  148  while having enough memory to return the flaps to a straight position after use (i.e., having the flaps align with the sides of the box as shown in the stack  244  of  FIG.  34   ). 
     The rotary ultrasonic reshaping step of the present invention includes the plastic corrugated blank  100  being run in an ultrasonic device  300  illustrated in  FIG.  17 A . The ultrasonic device  300  includes an anvil  302  and a horn  304  (see e.g.,  FIGS.  17 - 19   ). The horn  304  imparts ultrasonic energy into the blank  100 , thereby enabling the anvil to form a shaped score into the material. In extreme instances, the device  300  can weld the inner and outer sheets  102  and  104 . Alternatively, the anvil  302  can impart the ultrasonic energy to the blank  100 . Both the horn  304  and the anvil  302  can rotate about an axis. 
     The anvil  302  is shown having a central raised portion or projection  310  along a contacting surface of the anvil. The raised portion  310  is used to form the score lines  138 . In effect, the plastic in the blank  100  reshapes around the projection  310  during the scoring operation to have a generally V-shaped cross-sectional profile as illustrated in  FIG.  17 B . It has been found that an angle  308  on the raised center portion  310  of the anvil  302  in the range of 90° to 120°, with a preferred angle  308  of about 110°, will provide the desired score lines  138  using rotary ultrasonic reshaping. 
     It has also been found that for the step of creating score lines  138  using rotary ultrasonic reshaping, a frequency in the range of 20 kilohertz is preferred. For creating the pre-sealed areas  124 ,  128  or  132  (when using ultrasonic devices) for the glue tab  126 , fourth side wall panel area  128  and the major and minor flap slots  142 , frequencies in the range of 15, 20, or 40 kilohertz are suitable. 
     The blank  100  can be printed upon if desired as shown in  FIGS.  8  and  9   . Printing can be done at any convenient step in the process. Printing can be done with silk screen, flexographic, digital, or any other suitable printing process. Printed indicia  140  on the blank  100  can include product information for products stored in the box, Department of Transportation required information, bar coding, or any other desired indicia. 
     After pre-sealing, the blank  100  can be die cut on any conventional corrugated die cut equipment, including quick set, clam shell, rotary or flatbed die cutting machines. The blank  100  is die cut in the areas having flattened segments  132  that have been pre-sealed where the major and minor flap slots  142  are desired (see  FIGS.  9  and  10   ). The slots  142  are cut in the direction of the flutes  106 . The slots  142  separate the flaps  146 ,  148  from each other. As shown in  FIG.  10   , the die cut slots  142  are narrower than the pre-sealed areas  132 , leaving a sealed edge  144  around each slot  142 . The pre-sealing of the slot areas  132  results in a sealed edge  144  that is more consistent than those formed in die cutting without pre-sealing. The die cut process also forms the glue tab  126 . Alternatively, the major and minor flap slots  142  may also be cut or formed during the crushing and sealing operation described above. The die cut process also forms fold lines  123  separating the middle section of the blank  100  into the four side panels  125 ,  127 ,  129 , and  130 . 
     After being die cut, the blank  100  is folded so that the glue tab  126  is bonded to the edge area  128  of the fourth side wall panel  130 , and the major and minor flaps  146 ,  148  are aligned or coplanar with the respective side wall panels  125 ,  127 ,  129 ,  130 . A stack  244  of such glued blanks  100  is shown in  FIG.  34   . 
     The stack  244  is placed into a box converter to make a completed box. A partially completed box  136  is shown in  FIG.  11   . After opening the box  136  as shown in  FIG.  11   , the flaps are later folded to form a bottom and top of the box (the top flaps are typically folded after loading the box with the product being packaged). As set forth above, the present invention can also be used to form half slotted containers (i.e., open top boxes having only bottom flaps) as well as other types of boxes having different shapes. 
       FIGS.  21 - 23    provide a comparison of the outer edges of prior boxes with the current invention.  FIG.  21    shows a first flap and a second flap of a box with edges that have not been sealed. Instead, the flaps have open edges showing the openings formed between the flutes  106 . Open edges allow debris and liquid to enter the flutes  106  and contaminate the box for further use. Moreover, it would be difficult, if not impossible, to clean such boxes (especially using any automated process).  FIG.  22    shows a first flap and a second flap having edges  107  that were sealed using heat and pressure to weld the edges together. This is typically accomplished during a die cut process. These edges are sharp, requiring those handling the boxes to wear gloves and other protective clothing.  FIG.  23    shows a first flap and a second flap having a smooth rounded seal  120  in accordance with an aspect of the present invention. While the edge  120  of  FIG.  23    is shown as being rounded, it can be flat or another shape (such as those shown in  FIG.  20   ) as long as the box is sealed to a smooth edge at the typical human contact points. Additionally, the slot area between the flaps had been pre-sealed as discussed above, and has a smoother edge than the slot area of the die cut sealed box shown in  FIG.  22   . 
       FIG.  17 B  illustrates forming the scoreline  138  in the blank  100  using the ultrasonic horn  304  and anvil  302 . As shown in cross-section, the projection  310  on the anvil  302  forms a V-shaped section into the bottom of the blank  100 . It has been found that by manipulating certain variables associated with this process (e.g., the gap between the anvil  302  and the horn  304 , the speed of the blank with respect to the anvil  302  and horn  304 , the frequency or energy of the ultrasound, and the profile of the projection) that the resulting scoreline can be as strong or weak as desired for a particular use. For example, to create a scoreline with no or little memory (i.e., to form a limp flap), decrease the gap and speed of the blank and increase the frequency of the ultrasound. In contrast, to form a scoreline having a lot of memory (or spring-back), increase the gap and speed, and decrease the frequency. A multitude of variations in the flap memory or lack thereof are possible by gradually increasing or decreasing some or all of these variables. 
     The present invention is designed to handle various problems that may be encountered during some of the pre-sealing operations that can result in formation of an unacceptable box. For example, excess molten plastic may be formed during a pre-sealing operation. To accommodate this, the present invention provides a mechanism for managing the molten plastic, and directing it where to go. Additionally, the pre-sealing operation can encounter problems due to trapped air (i.e., between the ribs in the flutes) which can form bubbles and blowout holes as the pre-sealed areas are flattened. To fix this problem, air escape holes can be provided in the blank prior to the pre-sealing operation. 
     To direct molten plastic, the present invention contemplates contacting the areas to be pre-sealed with a surface having some shape (e.g., peaks and valleys) that directs the molten plastic to particular areas. For pre-sealing using a rotary ultrasonic device, this can be accomplished by providing a ridged pattern on one or both of a rotary anvil and horn. 
       FIGS.  24  and  25    show a rotary ultrasonic anvil  250  in the form of a roller for use in pre-sealing portions of a corrugated plastic blank  252  (the blank  252  is shown in  FIGS.  26 - 27   ). The anvil  250  includes an outer contacting surface  254  having an undulating, ridged pattern. The anvil  250  is utilized to contact the top or bottom surface of the blank  252  (depending on the area being pre-sealed) during a pre-sealing operation (in contrast, a smooth anvil and horn were utilized for the embodiment of  FIGS.  2 - 10   ). The anvil  250  cooperatively works with a rotary ultrasonic horn (identical or similar to the horn  304  used for forming the scorelines  138 ), which is also in the shape of a roller. The horn typically has a smooth outer surface (although in some embodiments, both the horn and the anvil can include a contacting surface having some structure or pattern). The horn is aligned or registered with the anvil  250  and contacts an opposing side of the blank  254 . Again, while the horn typically provides the ultrasonic energy, either of the horn or anvil  250  can be configured to provide the necessary ultrasonic energy to accomplish the task. As shown, the contacting surface  254  of the anvil  250  has slightly rounded corners  256 . This eliminates a sharp edge that could damage the plastic corrugated material during pre-sealing. 
     The horn and anvil  250  contact the blank  252  on the ends  258 ,  260  of the blank  252  for (later) formation of a glue tab and pre-sealed fourth side panel area, and at the slot locations to form pre-sealed segments  262 . The horn and anvil  252  are each mounted on a caroming mechanism which separates and brings them together at the proper locations on the blank  252  (more than one horn/anvil combination can be used in the forming apparatus). 
     As illustrated in  FIG.  26   , the pre-sealed areas  258  and  262  are shown having an undulating ridged pattern from contacting the anvil  252  (the horn and anvil  250  are reversed for pre-sealing the end  260 —thus the lower surface will have the undulating ridged pattern in that area). The excess molten plastic formed from pre-sealing the corrugated plastic is directed by the pattern  254  on the anvil  250  and forms the ridges of the pattern on the surface of the blank  252 . As shown in  FIG.  27   , a portion of this pattern may remain after cutting the slots  264  and glue tab  266 . 
       FIGS.  30  and  31    illustrate use of an air escape hole during the formation process. A plurality of V-shaped cut outs  268  are made to the smooth sealed edges of the blank  100  at locations that are to be pre-sealed as shown in  FIG.  30   . These cut-outs are also called “bird-bites” because of their V-shape. Making these cut outs  268  in the sealed edge allows air in the pre-sealed areas (e.g.,  132 ) an escape path when the area is being crushed or flattened. Each cut out  268  goes all the way through the flutes that are being crushed. A flattened V-shaped cut  268  remains after the pre-sealing operation as shown in  FIG.  31   . While the cut outs  268  are shown as V-shaped, other shapes (e.g., an arcuate shape) can be used. 
     The cut outs  268  also help provide a place for molten plastic to go (in addition to or possibly in place of the ridged ultrasonic device described above) during the pre-sealing process. Without the cut outs  268 , molten plastic will often squeeze out and migrate past the plane of the smooth edge seal during the crushing process. The cut out  268  is positioned in the area of the pre-seal  132  that is later cut away to form the slot  142 . Accordingly, it does not appear in the completed box. 
     While  FIGS.  30  and  31    show the pre-sealed area  132  having a smooth upper surface, these areas can also be formed using the ridged anvil  250  as discussed above. In this embodiment, the upper surface will have the undulating ridges (or other pattern) shown in  FIG.  24   , along with the V-shaped cut out  268 . 
     In a typical pre-sealing operation, the blank  100  or  252  has a thickness of 0.140 inches. To form the pre-sealed areas the horn and anvil are spaced a distance of 0.013 inches apart. After the pre-sealed areas pass through the horn and anvil, they are flattened to a thickness of 0.052 inches. 
     In accordance with another embodiment, only a minimal amount of sealing is done in the slot area. Because the slot is cut in the direction of the flutes  106 , an existing natural barrier is provided along the sides of the slot. That is, the adjacent flute, or next flute over, provides a wall along the length of the slot that prevents contaminants from collecting or entering the area between the outer sheets of the corrugated plastic material. The only areas that require sealing are the very end of the slot (which will have open flutes) and (possibly) the top of the slot near the smooth sealed edge.  FIG.  36    shows a flap slot that has a small sealed portion  270  at the end of the slot, and small sealed portions  272  on the corner of each flap defining the top of the slot. The bottom and top sealed portions  270 ,  272  can be sealed using heat and pressure or ultrasonic sealing. This approach is possibly lower in capital investment than the other approaches discussed herein. 
       FIG.  35    shows a plurality of plastic corrugated blanks  274  (formed in accordance with the present invention) in a box converting apparatus  276 . The plastic corrugated blanks  274  are intermingled with paper corrugated blanks  278 . 
     Prior to the present invention, when die cutting paper or plastic corrugated boxes, the conventional process used a blank that is slightly larger than the (eventual) die cut box. The die cut process would cut out the entire perimeter of the box (and all cut out portions), leaving a “window frame” of trim material  280  around the perimeter as shown in  FIG.  37   . When die cutting using rotary or flatbed die cut equipment, the window frame  280  is used to pull the blanks through the equipment and is then stripped away. In the present invention, the top and bottom edges of the blank are not cut away and instead are provided a smooth seal. Thus, the present process does not have the wasted “window frame” material. 
     While the term “horn” is typically used to describe the part of the system that emits the ultrasonic energy, it is understood that in any of the embodiments that ultrasonically reshape and/or weld the corrugated plastic material, either the horn or the anvil can emit the ultrasonic energy. 
     While the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention, and the scope of protection is only limited by the scope of the accompanying Claims.