System and method for pre-stretching plastic material

Abstract

A system and method are disclosed for pre-stretching plastic material that is later used in wrapping a plurality of objects. Plastic material is continuously or non-continuously provided to a pre-stretching device including a plurality of rollers. The plastic material is passed around the plurality of rollers within the pre-stretching device and is then fed through an accumulator to a strapping device. The passing of the plastic material around the plurality of rollers causes the plastic material to stretch by a predetermined amount before entering the strapping device.

1 . A method of pre-stretching a plastic material for use in unitizing a plurality of objects, comprising: 
 providing the plastic material to a pre-stretching device including a plurality of rollers;    passing the plastic material around the plurality of rollers within the pre-stretching device; and    feeding the plastic material from the pre-stretching device to a strapping device, wherein the passing of the plastic material around the plurality of rollers cause the plastic material to stretch by a predetermined amount before entering the strapping device.    
   
   
       2 . The method of  claim 1 , wherein the plurality of rollers comprise two groups of rollers.  
   
   
       3 . The method of  claim 2 , wherein each of the two groups of rollers comprise five rollers.  
   
   
       4 . The method of  claim 1 , wherein each of the plurality of rollers include a urethane coating.  
   
   
       5 . The method of  claim 1 , further comprising, before feeding the plastic material to the strapping device, passing the plastic material through an accumulator wheel assembly within an accumulator.  
   
   
       6 . The method of  claim 5 , wherein the accumulator wheel assembly comprises: 
 an accumulator wheel bracket;    a flat accumulator wheel rotatably connected to the accumulator wheel bracket; and    a flanged accumulator wheel rotatably connected to the accumulator wheel bracket and positioned relative to the flat accumulator wheel such that the flanged accumulator wheel and the flat accumulator wheel cooperate to guide the plastic material through the accumulator wheel assembly.    
   
   
       7 . The method of  claim 5 , wherein the position of the accumulator wheel assembly is adjustable relative to the remainder of the accumulator, and wherein the relative position of the accumulator wheel assembly affects the rate at which the plastic material enters the strapping device.  
   
   
       8 . The method of  claim 1 , wherein the plastic material is passed around the plurality of rollers at about four feet per second.  
   
   
       9 . The method of  claim 1 , wherein the plastic material is passed around the plurality of rollers at about five feet per second.  
   
   
       10 . The method of  claim 1 , wherein the plastic material is stretched about five to about ten percent over its original length as it passes through the pre-stretching device.  
   
   
       11 . The method of  claim 1 , wherein the plastic material is stretched about eight percent over its original length as it passes through the pre-stretching device.  
   
   
       12 . The method of  claim 1 , wherein the plastic material is stretched about seven percent over its original length as it passes through the pre-stretching device.  
   
   
       13 . An assembly for pre-stretching a plastic material for use in unitizing a plurality of objects, comprising: 
 a pre-stretching device including: 
 a pre-stretching device entrance region,  
 a pre-stretching device exit region,  
 a plurality of rollers positioned between the pre-stretching device entrance region and the pre-stretching device exit region, and  
 an energy and torque source for driving each of the plurality of rollers at a predetermined rate,  
   wherein the plurality of rollers are positioned to define a pathway for the plastic material through the pre-stretching device, and wherein the plastic material is stretched by a predetermined amount as it passes through the assembly before being fed to a strapping device.    
   
   
       14 . The assembly of  claim 13 , wherein the plurality of rollers comprise two groups of rollers.  
   
   
       15 . The assembly of  claim 14 , wherein each of the two groups of rollers comprise five rollers.  
   
   
       16 . The assembly of  claim 13 , wherein each of the plurality of rollers include a urethane coating.  
   
   
       17 . The assembly of  claim 13 , further comprising an accumulator positioned downstream from the pre-stretching device, wherein the plastic material passes through an accumulator before reaching the strapping device.  
   
   
       18 . The assembly of  claim 17 , wherein the accumulator includes an accumulator wheel assembly comprising: 
 an accumulator wheel bracket;    a flat accumulator wheel rotatably connected to the accumulator wheel bracket; and    a flanged accumulator wheel rotatably connected to the accumulator wheel bracket and positioned relative to the flat accumulator wheel such that the flanged accumulator wheel and the flat accumulator wheel cooperate to guide the plastic material through the accumulator wheel assembly.    
   
   
       19 . The assembly of  claim 18 , wherein the position of the accumulator wheel assembly is adjustable relative to the remainder of the accumulator, and wherein the relative position of the accumulator wheel assembly affects the rate at which the plastic material enters the strapping device.  
   
   
       20 . The assembly of  claim 13 , wherein the assembly is configured to stretch the plastic material between about five and ten percent over its original length as it passes through the assembly.  
   
   
       21 . The assembly of  claim 13 , wherein the assembly is configured to stretch the plastic material about seven percent over its original length as it passes through the assembly.  
   
   
       22 . The assembly of  claim 13 , wherein the assembly is configured to pass the plastic material through the assembly at a rate of about four feet per second.  
   
   
       23 . The assembly of  claim 12 , further comprising a preliminary tower positioned upstream of the pre-stretching device, the preliminary tower guiding the plastic material upstream of the pre-stretching device.  
   
   
       24 . The assembly of  claim 13 , wherein the energy and torque source comprises a bevel gear motor.  
   
   
       25 . The assembly of  claim 13 , wherein the assembly is configured to stretch the plastic material between about eight percent over its original length as it passes through the assembly.