Molding apparatus

Apparatus for injection molding a hollow plastic tub having an open end, a closed end and an uninterrupted interior side wall surface of circular transverse cross-section, said interior side wall surface diverging toward said closed end whereby the tub has a smaller radius at said open end than at said closed end, said apparatus comprising:

• mold core means for molding an interior surface of said plastic tub, including central core segment means defining a polygonal transverse cross-sectional outer envelope with polygon faces and a plurality of peripheral core segment means surrounding said central core segment means, said outer envelope defined by said polygon faces diverging in a direction toward said closed end of said tub;
• said peripheral core segment means being mutually contiguous and having respective outward faces collectively defining a continuous circular transverse cross-sectional shape with each individual peripheral core segment means defining a continuous, uninterrupted outer surface diverging in a direction toward said closed end for molding said interior surface of said side wall of said plastic tub;
• the divergence of the outer envelope of said central core segment means being greater than the divergence of the uninterrupted outer surface of said peripheral core segment means;
• core collapsing means for causing relative movement between said central core segment means and said peripheral core segment means during a tub extraction phase of operation;
• said means for causing said relative movement including means for imparting at least a component of motion to said peripheral core segment means which is in a radially inward direction relative to said central core segment means and the plastic tub, whereby to reduce the transverse diameter of said mold core means and to provide clearance during said tub extraction phase for said continuous, uninterrupted diverging surfaces of said peripheral core segment means.