Method and apparatus for injection molding a thin-walled plastic can

Abstract

A mold assembly for producing a container having a closed bottom is disclosed. Inner and outer core members are closely spaced together to provide a cavity for forming a container having a wall thickness on the order of 0.015 inch. The cavity is formed with a plurality of radial flow channels which produce corresponding ribs on the container bottom. The radial channels extend from an axial injection port outwardly to the wall portion of the cavity, where a thickened transition region joins the bottom of the container to the side wall portion thereof. A plurality of vertical flow channels are formed by means of milled flat portions on the surface of the inner core along the length of the side wall. The flow channels cause fluid plastic injected under high pressure to flow radially outwardly, around the bottom corner of the container, and down the vertical flow channels located intermediately of the ends of the ribs. The plastic material flows from the flow channels and then laterally outwardly into the bottom and side walls, thereby permitting a rapid and equallizing distribution of plastic material throughout the cavity. This maintains the inner core member axially located within the outer cavity mold portion of the mold assembly to produce uniform, very thin container walls in a reliable and rapid manner.