Two material three/five layer preform

Abstract

A plastic preform from which a plastic container is blow molded. The preform replaces a three layer preform by providing a preform which is of a five layer construction in the base forming portion thereof and wherein a secondary material which forms the core layer of the three layer preform construction is divided into an inner intermediate layer and an outer intermediate layer by a third injection of material. The third injected material is preferably the same material as the primary material which is first injected. This results in the reduction of the cost of the preform and also provides remaining in the injection nozzle a quantity of the last injected material which is the same as the first injected material for the following preform in the same preform injection mold cavity.

We claim: 
     
       1. An injection molded plastic preform for blow molding to form a container, said preform being in part formed in three layers and in part five layers, said preform comprising a neck finish portion, a shoulder forming portion, a body forming portion, and a base forming portion, at least said body forming portion and said base forming portion having inner and outer layers formed of a primary material and separated by a layer of a secondary material; said preform being improved in that in said base forming portion a central part of said secondary material is replaced by a core layer of material other than and less costly than said secondary material, thus producing said five layer part, said preform at least in said body forming portion being formed of only three layers with said secondary material forming a relatively thick core layer. 
     
     
       2. A preform according to claim 1 wherein said preform in said base forming portion being of a five layer construction with said secondary material separated into relatively thin inner and outer intermediate layers. 
     
     
       3. A preform according to claim 2 wherein said material other than said secondary material is the same as said primary material whereby said preform is of a two material construction. 
     
     
       4. A preform according to claim 2 wherein said material other than said secondary material is the same as said primary material whereby said preform is of a two material construction and the material last injected into a preform injection mold cavity is the same as the material first injected into a preform injection mold cavity. 
     
     
       5. A preform according to claim 1 wherein said material other than said secondary material is the same as said primary material whereby said preform is of a two material construction. 
     
     
       6. A preform according to claim 1 wherein said material other than said secondary material is the same as said primary material whereby said preform is of a two material construction and the material last injected into a preform injection mold cavity is the same as the material first injected into a preform injection mold cavity. 
     
     
       7. A preform according to claim 1 wherein said primary material and said secondary materials are of preselected metered quantities and said material other than said second material is of a quantity to complete filling of a preform injection mold cavity. 
     
     
       8. A preform according to claim 1 wherein said secondary material extends as a core through said shoulder forming portion into said neck finish portion. 
     
     
       9. A preform according to claim 1 wherein said base forming portion includes a part forming an extension of said body forming portion and of an increased wall thickness as compared to an adjacent part of said body forming portion. 
     
     
       10. A plastic container formed by blow molding a preform according to claim 1. .Iadd.11. An injection molded plastic preform for blow molding to form a container, said preform being in part formed in three layers and in part five layers, said preform comprising a neck finish portion, a shoulder forming portion, a body forming portion, and a base forming portion, at least said body forming portion and said base forming portion having inner and outer layers formed of a primary material and separated by a layer of secondary material; said preform being improved in that in said base forming portion a central part of said secondary material is replaced by a core layer of material other than said secondary material, thus producing said five layer part, said preform at least in said body forming portion being formed of only three layers with said secondary material forming a relatively thick core layer. .Iaddend. .Iadd.12. A preform according to claim 11 wherein said preform in said base forming portion being of a five layer construction with said secondary material separated into relatively thin inner and outer intermediate layers. .Iaddend. .Iadd.13. A preform according to claim 12 wherein said material other than said secondary material is the same as said primary material whereby said preform is of a two material construction. .Iaddend. .Iadd.14. A preform according to claim 12 wherein said material other than said secondary material is the same as said primary material whereby said preform is of a two material construction and the material last injected into a preform injection mold cavity is the same as the material first injected into a preform injection mold cavity. .Iaddend. .Iadd.15. A preform according to claim 11 wherein said material other than said secondary material is the same as said primary material whereby said preform is of a two material construction. .Iaddend. .Iadd.16. A preform according to claim 11 wherein said material other than said secondary material is the same as said primary material whereby said preform is of a two material construction and the material last injected into a preform injection mold cavity is the same as the material first injected into a preform injection mold cavity. .Iaddend. .Iadd.17. A preform according to claim 11 wherein said primary material and said secondary materials are of preselected metered quantities and said material other than said second material is of a quantity to complete filling of a preform injection mold cavity. .Iaddend. .Iadd.18. A preform according to claim 1 wherein said secondary material extends as a core through said shoulder forming portion into said neck finish portion. .Iaddend. .Iadd.19. A preform according to claim 11 wherein said base forming portion includes a part forming an extension of said body forming portion and of an increased wall thickness as compared to an adjacent part of said body forming thickness. .Iaddend. .Iadd.20. A plastic container formed by blow molding a preform according to claim 11. .Iaddend.