| 摘要 |
<p>ROGERS, BERESKIN /A PARR C A N A D A INVENTION: STACKABLE LID INVENTOR: GEORGE COTRONEO . A molding method and lid construction particularly suited to the molding of stackable lids of very thin construction is described. The method involves injecting a molten thermoplastic material whose cavity defines a lid top having top and bottom spaces, a circular alignment shoulder raised from the top face inset from the periphery of the top, and a circular sidewall extending perpendicularly from the bottom face. The cavity also defines a relatively thin flange that extends radially inwardly from the lid sidewall and has a flat upper surface oriented generally perpendicular to the sidewall to provide a very positive stop (for engagement with the upwardly extending lip circumscribing the opening of a conventional container) despite the very thin construction of the flange. The lid is removed from the mold when partially set, whereafter radial contraction of the lid sidewall dimensions the bottom edge to more closely receive the alignment shoulder of an identical lid. The distribution of material in the sidewall accentuates radial contraction in the vicinity of the bottom edge of the sidewall where it is most required.</p> |
