Expanded Slit Sheet Packaging Material That Interlocks When Layered and Expanded

Abstract

In accordance with a broad embodiment of the invention, a novel paper product is comprised of two or more slit sheet packing material layers, each layer having its own slit pattern design to create interlocking layers of expansion sheet packaging materials. Each layer expands to create a three dimensional open netting of cells of hexagons, and the like, and is designed to have limited nesting with its opposing layer, thereby maximizing the thickness of the combined layers as compared to nested layers. Adjacent layers have differing slit patterns and can be expanded through expander type machinery such that the expansion rates of the differing slit pattern layers can be varied to deliver the same width of exiting expanded material from each layer. Preferably the differing slit pattern produce when expanded, inclined land areas that have the same number of rows per inch, but different angles of inclination of the land areas, such that adjacent layers can interlock, that is, have a restricted amount of nesting.

1 - The method of producing at least a pair of interlocking adjacent layers of a paper packaging product,
 said pair of interlocking adjacent layers being formed of a first sheet of slit paper and a second sheet of slit paper,   said first sheet of slit paper having a first slit pattern and said second sheet of slit paper having said first slit pattern, said slit pattern upon expansion, forming cells that include land regions that are inclined with respect to the plane of the unexpanded sheet,   slitting said first sheet of slit paper and said second sheet of slit paper to produce slits that upon expansion, produce lands regions of said first sheet that have angles of inclination in the range for 50 to 85 degrees,   orienting and expanding said second sheet of slit paper, and causing said land regions to have an inclination angle in the range from 130 to 95° relative to said first sheet of slit paper,   layering said first expanded sheet on said second expanded sheet, and causing said land regions of said first expanded sheet to interlock with said second sheet.   
     
     
         2 - The method of  claim 1 , wherein said slitting of said first sheet and said second sheet forms a substantially straight line cut along one edge of the slit and an angled cut along the other edge of the slit, thus forming a wedge shape that is wider on a first side of the blade entry point that on the other side of the blade entry point. 
     
     
         3 - The method of  claim 1 , wherein said expanding of said first sheet and said second sheet is in the range from about 10 to 20% less than the maximum expansion of each of said first sheet and said second sheet. 
     
     
         4 - The method of  claim 1 , wherein said expanding of said first sheet and said second sheet is in the range from about 100 to 110% of the maximum expansion of each of said first sheet and said second sheet. 
     
     
         5 - The method of  claim 1 , wherein said slitting of said first sheet and said second sheet forms a straight line cut along one edge of the slit and an angled cut along the other edge of the slit. 
     
     
         6 - The method of  claim 1 , wherein said angle of inclination of said first sheet and said angle of inclination of said second sheet are consistent along the length of said first sheet and said second sheet. 
     
     
         7 - The method of  claim 1 , wherein said angle of inclination of said first sheet and said angle of inclination of said second sheet along the length of said first sheet and said second sheet have less than about 20% switch back effect. 
     
     
         8 - The method of  claim 1 , wherein said angle of inclination of said first sheet and said angle of inclination of said second sheet along the length of said first sheet and said second sheet have less than about 10% switch back effect. 
     
     
         9 - The method of  claim 1 , further comprising the step of forming slits in said first and said second sheet of slit paper using a beveled blade having an included angle in the range from 1 to 6 degrees. 
     
     
         10 - The method of  claim 9 , wherein said beveled blade has a first side that forms an angle of about 90 degrees with respect to the plane of the paper being slit. 
     
     
         11 . The method of  claim 1 , wherein upon expansion, said angle of inclination of said first sheet is in the range from 55 to 75 degrees, and said angle of inclination of said second sheet is in the range from 105 to 125 degrees. 
     
     
         12 - The method of  claim 1 , further comprising the steps of;
 winding in a first direction, said first sheet of slit paper into a first roll,   winding in the reverse direction with respect to said first direction, said second sheet of slit paper into a second roll,   feeding said first sheet of slit paper from said roll, clockwise or counterclockwise into a first expander,   simultaneously feeding said second sheet of slit paper from said roll into a second expander, the direction of rotation of said second sheet of slit paper being the same direction that said first sheet of slit is fed into said first expander,   expanding said first sheet of slit paper, said first slit pattern causing said land regions to have an inclination angle in the range for 50 to 85 degrees,   expanding said second sheet of slit paper, said first slit pattern and causing said land regions to have an inclination angle in the range from 130 to 95 degrees,   layering said first expanded sheet on said second expanded sheet, and   causing said land regions of said first expanded sheet to interlock with said second sheet.   
     
     
         13 - The method of  claim 1 , further comprising the step of forming slits in said first and said second sheet of slit paper using a beveled blade against a rotating anvil, said beveled blade having an included angle in the range from 1 to 6 degrees. 
     
     
         14 - The method of  claim 1 , wherein upon expansion, said angle of inclination of said first sheet is in the range from 55 to 70 degrees, and said angle of inclination of said second sheet is in the range from 125 to 110 degrees. 
     
     
         15 - The method of  claim 1 , further comprising forming said first slit pattern and said second slit pattern by slitting with a blade against a rotating anvil, said blade having an angle included angle in the range from 1 to 3 degrees, and wherein said paper is recycled paper, thereby producing an inclination of said first sheet and an angle of inclination of said second sheet that is substantially consistent along the length of said first sheet and said second sheet. 
     
     
         16 - The method of  claim 15 , wherein said anvil is a soft anvil and said blade cuts through said paper and into said anvil. 
     
     
         17 - The method of  claim 1 , wherein one of said first sheet of slit paper and said second sheet of slit paper is Kraft paper, and the other of said first sheet of slit paper and said second sheet of slit paper is soft paper. 
     
     
         18 - An apparatus for producing at least a pair of non-nesting adjacent layers of a paper packaging product, first means for forming in a plurality of rolls of sheet material, slits having a pattern which upon expansion of said roll of sheet material having slits, yields cells having land regions, said land regions having an inclination angle in the range from ab out 50 to 85 degrees,
 said first means including blades having an included angle in the range from about 1 to 6 degrees, and causing a wedge effect at one edge of each of said slits,   second means for drawing clockwise into an expansion region, a first of said plurality of rolls of sheet material having slits,   third means for drawing counterclockwise into an expansion region, a second of said plurality of rolls of sheet material having slits,   fourth means for simultaneously expanding each of a plurality of sheet material having slits, expanding said first of said plurality of rolls of sheet material having slits, and causing said land regions to have an inclination angle in the range for 50 to 85 degrees, and expanding said second of said plurality of rolls of sheet material having slits, and causing said land regions to have an inclination angle in the range from about 130 to 95 degrees,   fifth means for layering said first expanded sheet on said second expanded sheet, and   sixth means for causing said land regions of said first expanded sheet to interlock with said second sheet, said angle of inclination of said first sheet and said angle of inclination of said second sheet being consistent along the length of said first sheet and said second sheet.   
     
     
         19 - A paper packaging product comprising:
 a first sheet of slit paper having a slit pattern that upon expansion, a plurality of slits form a plurality of cells that include land regions that are inclined with respect to the plane of the unexpanded sheet,   said slits having a wedge effect that is sufficient to cause upon expansion, the lands regions of said sheet to have a substantially consistent angle of inclination along the entire length of the expanded sheet and the lands regions, said inclination angle being in the range from 50 to 85 degrees.   
     
     
         20 - The paper packaging product of  claim 19 , further comprising a second sheet of slit paper layered on said first sheet of slit paper, said first sheet and said second sheet being expanded to form a pair of interlocking adjacent expanded sheets of slit packaging material,
 said sheets of slit packaging material having a slit pattern that upon expansion, a plurality of slits that form a plurality of cells having land regions that are inclined with respect to the plane of the unexpanded sheet,   said slits having a wedge effect that is sufficient to cause upon expansion, the land regions of said first sheet to have an inclination angle n the range from about 50 to 85 degrees along the length of the expanded sheet,   the second of said pair of interlocking adjacent expanded sheets having an inclination angle in the range from 130 to 95 degrees,   said first expanded sheet being layered on and interlocking with said second expanded sheet.