Co-Injection Moulding

Abstract

The present invention relates to advancements in injection moulding and in particular to a method and apparatus for co-injection moulding articles of complex non symmetrical geometry. The method forms a multilayer injection moulded article comprising an outer skin of a first material and a central core of a second material which is encapsulated by the outer skin. The first and second materials are injected in a single stream into a cavity of an injection mould, with the second material encased within the first material. The flow of the stream is controlled by means of flow paths within the mould cavity such that both the first and second materials are present in at least one first area of the mould cavity and that only the first material is present in at least one second area of the mould cavity. The flow paths include at least one primary flow path in the first mould cavity area which divides into at least two secondary flow paths. The resistance of a first of the secondary flow paths in the at least one first mould cavity area is reduced relative to that of a second of the two secondary flow paths, which is in the at least the second mould cavity area.

1 - 7 . (canceled) 
     
     
         8 . Apparatus for forming a multilayer injection moulded article comprising an outer skin of a first material and a central core of a second material encapsulated by the outer skin, the apparatus comprising:
 an injection mould having a cavity defining the shape of the moulded article;   a device for co-injecting the first and second materials as a single stream into the cavity, with the second material encased by the first material;   the mould cavity comprising a plurality of flow paths to control the flow of the materials such that both the first and second materials are present in at least one first mould cavity area and only the first material is present in at least one second mould cavity area;   the plurality of flow paths including at least one primary flow path in the first mould cavity area, which primary flow path divides into at least two secondary flow paths, of which the first of the secondary flow paths is in the first mould cavity area and has a lower resistance relative to that of the second secondary flow path, which is in the second mould cavity area.   
     
     
         9 . The apparatus as claimed in  claim 8  in which the resistance of the first of the secondary flow paths is reduced relative to that of the second of the secondary flow paths by varying one or more of the following elements of the secondary flow paths relative to each other;
 cross sectional area of the secondary flow paths; 
 length of the secondary flow paths; 
 radii between the primary flow path and the first of the secondary flow paths; and 
 at least one angle between the primary flow path and at least one of the secondary flow paths. 
 
     
     
         10 . The apparatus as claimed in  claim 9  wherein one or more of the secondary flow paths become primary flow paths which divide again to form further secondary flow paths. 
     
     
         11 . The apparatus as claimed in  claim 10  wherein the primary flow path divides into multiple secondary flow paths. 
     
     
         12 . A food or beverage cartridge comprising:
 an outer member comprising an outer skin of a first material and a central core of a second material encapsulated by the first material, the outer member being formed by a plurality of flow paths within a mould cavity such that both the first and second materials are present in at least one first area of the outer member and only the first material is present in at least one second area, the plurality of flow paths including at least one primary flow path in the one first area, the primary flow path dividing into at least two secondary flow paths, wherein the at least two secondary flow paths includes a first secondary flow path in the one first area and a second secondary flow path in the one second area and the resistance of the first secondary flow path is reduced relative to that of the second secondary flow path; and   a sealing member sealed to the outer member at sealing areas.   
     
     
         13 . The food or beverage cartridge as claimed in  claim 12  in which the core material is not present in the sealing areas. 
     
     
         14 . The apparatus as claimed in  claim 8  wherein the primary flow path divides into multiple secondary flow paths. 
     
     
         15 . The apparatus as claimed in  claim 8  wherein one or more of the secondary flow paths become primary flow paths which divide again to form further secondary flow paths.