Method and apparatus for forming extruded striped plastic products with variations in width of the stripes along the length of the products and for blow molding articles formed from such extruded parts

Abstract

A multicolored drinking cup is formed by blow molding a multicolored parison. The parison is formed by feeding the outputs of a plurality of controllable rate extruders into an extruding head and varying the flow rates of the extruders in a controlled manner under computer control to produce a parison in which the colors vary in width along the height. The parison is then blow molded to form the container.

1 . A method of extruding plastic parts having multicolored stripes extending along the extrusion axis, the stripes being of varying width along the length of the part, comprising: 
 providing a plurality of controllable rate extruders each feeding plastic of a different color,    controlling the feed rates of each extruder by signals generated by a computer, the signals varying during the extrusion time in a complementary manner; and    connecting the outputs of each extruder to adjacent flow passages of an extruding head.    
   
   
       2 . The method of  claim 1  wherein the plastic parts constitute tubes useful as parisons in a subsequent blow molding operation.  
   
   
       3 . The method of  claim 2  wherein the extruding head has a plurality of flow passages arrayed at equal intervals about its perimeter and each flow passage is connected to one of the extruders and the adjacent two flow passages are connected to another of the extruders.  
   
   
       4 . The method of  claim 1  wherein the computer is equipped with a unique program for each extruded part to be generated.  
   
   
       5 . The method of  claim 1 , further including computer controlled accumulators connected to augment the outputs of the extruders.  
   
   
       6 . Apparatus for extruding plastic parts having multicolored stripes extending along the extrusion axis, the stripes being of varying width along the length of the parts, comprising: 
 a plurality of controllable rate extruders each feeding plastic of a different color;    a computer connected to the extruders so as to simultaneously control their flow rates;    a control program for the computer operative to cause to the computer to generate control signals for each extruder in a complementary time varying manner; and    an extrusion head having a plurality of flow passages with adjacent flow passages connected to receive the outputs of differing extruders.    
   
   
       7 . The apparatus of  claim 6  wherein the plastic parts constitute tubes and the extruding head contains a plurality of flow passages arranged at equal intervals about its perimeter with each flow passage being connected to one of the extruders, and adjacent flow passages being connected to different extruders.  
   
   
       8 . A method of extruding plastic parts having multicolored stripes extending along the extrusion axis, the stripes being of varying width along the length of each part, comprising: 
 providing a plurality of controllable rate extruders each feeding plastic of a different color;    controlling the feed rates of each extruder in a time varying manner during the extrusion of a part; and    connecting the outputs of each extruder to adjacent flow passages of an extruding head, with each flow passage receiving the plastic output of one extruder and adjacent flow passages receiving outputs of a different extruder.    
   
   
       9 . A method of forming blow molded plastic parts having multicolored stripes extending from one end of the part to the opposite end, the stripes being of varying width along the length of the part, comprising: 
 providing a plurality of controllable rate extruders each feeding plastic of a different color;    controlling the feed rates of each extruder to vary the feed rates during the formation of a part in a complementary manner;    connecting the outputs of each extruder to flow passages of an extruding head with each passage being connected to the output of one extruder, and the adjacent passages being connected to outputs of different extruders;    extruding a tubular parison having multicolored stripes of varying width extending along the extrusion axis; and    blow molding the parison into a part having the shape of a surface of revolution with the diameter of the part varying along the height of the part.    
   
   
       10 . The method of  claim 9  wherein the part comprises a container having one closed end and one open end.  
   
   
       11 . The method of forming a blow molded plastic container in the form of a surface of revolution having a varying diameter along a height extending between an open top and a closed bottom and having colored stripes of varying widths extending along its height, comprising: 
 extruding a tubular parison employing a plurality of controllable rate extruders feeding different plastics having their outputs connected to flow passages in an extruding head having the flow passages arranged at equal distances in a circle, with each flow passage being connected to one extruder and adjacent flow passages being connected to other extruders; and    blow molding the parison to form said container.    
   
   
       12 . The method of  claim 11  in which the plastics differ in color.  
   
   
       13 . The method of  claim 11  in which the plastics differ in density.  
   
   
       14 . Apparatus for forming a drinking cup in the form of a surface of revolution having a flat bottom at one end and an open top surrounded by a lip at the other end, with the container varying in diameter along its height and being formed of multiple colored plastics, comprising: 
 a plurality of controllable rate extruders each feeding a different form of plastic;    a signal generator for the extruders adapted to control their extrusion rates;    an extrusion head having a plurality of extrusion passages arranged in a circle with each passage being connected to the output of one of the extruders, the head being adapted to extrude a tubular parison of varying color; and    blow molding apparatus being adapted to receive the parison and to blow mold said drinking cup.    
   
   
       15 . The apparatus of  claim 14  further comprising accumulators connected to modify the outputs of the extruders.  
   
   
       16 . The apparatus of  claim 13  in which the accumulators are of the cylinder and piston type and are computer controlled.  
   
   
       17 . The apparatus of  claim 14  in which the plastics are of different colors.  
   
   
       18 . The apparatus of  claim 14  in which the plastics are of different densities.