Non-symmetric multiple layer injection molded products and methods

Abstract

A mold for molding an injection molded article comprises a mold cavity with a non-symmetrical portion. At least one flow leader in the non-symmetrical portion of the cavity produces a symmetrical flow boundary in a multilayer flow downstream of the non-symmetrical portion of the mold cavity. The at least one flow leader may be a variable thickness flow leader or may alternatively be a plurality of flow leaders having a flow path length that differs from the flow path length of an adjacent flow leader by no more than about 15%. The multilayer flow comprising an inner layer, an outer layer, and an interior layer. Co-injection molding apparatus and methods that may use the foregoing mold are disclosed. Similarly, co-injection molded articles and containers that may result from the foregoing mold, apparatus, and methods are disclosed.

1 . A mold for molding an injection molded article, the mold comprising:
 a mold cavity comprising a plurality of flow leaders in a non-symmetrical portion of the mold cavity that produce a symmetrical flow boundary in a multilayer flow downstream of the non-symmetrical portion, wherein
 the multilayer flow comprises an inner layer, an outer layer, and an interior layer, 
 the inner layer and the outer layer are of a first molding material and the interior layer is of a second molding material, and 
 each flow leader of the plurality of flow leaders in the non-symmetrical portion is adjacent to at least another flow leader of the plurality of flow leaders; and 
   at least one injection gate configured for injection of the first and second molding materials into the plurality of flow leaders.   
     
     
         2 . The mold of  claim 1 ,
 wherein the non-symmetrical portion of the mold cavity is nonsymmetric with respect to the at least one injection gate.   
     
     
         3 . The mold of  claim 1 , wherein the at least one injection gate is located adjacent to the non-symmetrical portion of the mold cavity. 
     
     
         4 . The mold of  claim 1 , wherein the at least one injection gate is remote from the non-symmetrical portion of the mold cavity. 
     
     
         5 . The mold of  claim 1 , wherein each of the plurality of flow leaders has a respective flow path length that differs from a flow path length of any adjacent flow leader by no greater than about 15%. 
     
     
         6 . The mold of  claim 5 , wherein the respective flow path length of each of the plurality of flow leaders differs from the flow path length of any adjacent flow leader by no greater than about 10%. 
     
     
         7 . The mold of  claim 6 , wherein the respective flow path length of each of the plurality of flow leaders differs from the flow path length of any adjacent flow leader by no greater than about 5%. 
     
     
         8 . The mold of  claim 1 , wherein the plurality of flow leaders are configured to produce a flow boundary downstream of which a velocity of a combined flow front of the inner and outer layers of the first molding material, injected through the at least one injection gate into the plurality of flow leaders, is effectively perpendicular to a periphery of the mold cavity so that a velocity vector of the combined flow front has no significant tangential component. 
     
     
         9 .- 10 . (canceled) 
     
     
         11 . The mold of  claim 1 , wherein the plurality of flow leaders are configured so that a velocity of a leading edge of the interior layer exiting distal ends of the plurality of flow leaders is substantially equal to the product of a velocity of a combined flow front of the inner and outer layers of the first molding material multiplied by the quotient of a flow distance from the leading edge of the interior layer to a periphery of the mold cavity divided by a flow distance from the combined flow front to the periphery of the mold cavity. 
     
     
         12 . The mold of  claim 1 , wherein the plurality of flow leaders are configured so that a velocity of a leading edge of the interior layer exiting distal ends of the plurality of flow leaders is greater than the product of a velocity of a combined flow front of the inner and outer layers of the first molding material multiplied by the quotient of a flow distance from the leading edge of the interior layer to a periphery of the mold cavity divided by a flow distance from the combined flow front to the periphery of the mold cavity. 
     
     
         13 .- 39 . (canceled) 
     
     
         40 . A method of molding a multiple layer article, comprising:
 (a) injecting at least one first flowable material into a mold cavity configured to form a molded article comprising the at least one first flowable material, the mold cavity comprising a nonsymmetrical portion relative to an injection location of the at least one first flowable material;   (b) co-injecting at least one second flowable material into the mold cavity and interior to the at least one first flowable material; and   (c) modifying the flow of the at least one first flowable material and the at least one second flowable material with a plurality of flow leaders in the nonsymmetrical portion of the mold cavity to produce a symmetrical flow boundary downstream of the nonsymmetrical portion and to cause the at least one second flowable material to flow throughout substantially the entire mold cavity, wherein each flow leader of the plurality of flow leaders in the nonsymmetrical portion is adjacent to at least another flow leader of the plurality of flow leaders.   
     
     
         41 . (canceled) 
     
     
         42 . The method of  claim 40 , wherein the at least one first flowable material and the at least one second material comprise different materials. 
     
     
         43 . The method of  claim 40 , wherein the at least one second flowable material is relatively more gas impermeable than the at least one first flowable material 
     
     
         44 .- 46 . (canceled) 
     
     
         47 . The method of  claim 40 , wherein each of the plurality of flow leaders has a respective flow path length that differs from a flow path length of any adjacent flow leader by no greater than about 15%. 
     
     
         48 . The method of  claim 40 , wherein each of the plurality of flow leaders has a respective flow path length that differs from a flow path length of any adjacent flow leader by no greater than about 10%. 
     
     
         49 . The method of  claim 40 , wherein each of the plurality of flow leaders each having has a respective flow path length that differs from a flow path length of any adjacent flow leader by no greater than about 5%. 
     
     
         50 . The method of  claim 40  wherein the at least one flow leader is configured to produce a flow boundary downstream of which the velocity of the combined flow of molding material, injected through the at least one injection gate into the at least one flow leader, is effectively perpendicular to the periphery of the mold cavity so that the velocity vector of the combined flow has no significant tangential component. 
     
     
         51 .- 52 . (canceled) 
     
     
         53 . The method of  claim 40 , wherein the plurality of flow leaders are configured so that a velocity of a leading edge of an interior layer of the second flowable material exiting distal ends of the plurality of flow leaders is substantially equal to the product of a velocity of a combined flow front of inner and outer layers of the first flowable material multiplied by the quotient of a flow distance from the leading edge of the interior layer to a periphery of the mold cavity divided by a flow distance from the combined flow front to the periphery of the mold cavity. 
     
     
         54 . The method of  claim 40 , wherein the plurality of flow leaders are configured so that a velocity of a leading edge of an interior layer of the second flowable material exiting distal ends of the plurality of flow leaders is greater than the product of a velocity of a combined flow front of inner and outer layers of the first flowable material multiplied by the quotient of a flow distance from the leading edge of the interior layer to a periphery of the mold cavity divided by a flow distance from the combined flow front to the periphery of the mold cavity. 
     
     
         55 . The method of  claim 40  further comprising:
 delaying the start of the step of co-injecting the at least one second flowable material into the mold cavity until after the start of the step of injecting the at least one first flowable material by a period of time calculated to cause the at least one second flowable material to flow throughout substantially the entire mold cavity. 
 
     
     
         56 .- 121 . (canceled)