Apparatus and method for injection moulding a thin-walled container having a base wall with a planar interior surface

摘要

Apparatus for moulding a thin-walled article, such as a Petri disk, in which the moulding is effected by injecting from the side of a planar portion of the article. The moulding apparatus has a core piece (10) co- operable with a cavity (12) which together define a space (14) in which the article is to be moulded. At least one of the core (10) or the cavity (12) has a moulding surface (16, 18), corresponding to the planar portion of the finished article, which is non-planar. Preferably, the moulding surface (18) of the cavity (12) has a concave curvature, while the opposing surface (16) of the core (10) inserted therein has a convex curvature. The radius of curvature preferably being larger at the core than at the cavity. The particular configuration allows more material to be supplied to the central area corresponding to the planar portion of the finished article. This material cools more slowly than other portions of the article causing contraction so that the planar portion of the finished article is substantially flat.