US Patent 8056742 Two-piece child-resistant closure and package

A child-resistant closure includes a plastic inner shell having a base wall with a peripheral skirt, at least one internal thread segment on the peripheral skirt and a plurality of internal lugs on the base wall adjacent to the skirt. A plastic outer shell has a base wall with a peripheral skirt and a plurality of internal L-shaped lugs at a juncture of the base wall and the peripheral skirt. Each of the L-shaped lugs includes a first portion extending radially inwardly along an undersurface of the base wall of the outer shell for engaging the external lugs on the inner shell, and a second portion extending axially along an inner surface of the peripheral skirt of the outer shell for slidably engaging the inner shell and aligning the inner shell within the outer shell. The second portions of the L-shaped lugs preferably have rounded radially inwardly facing surfaces for reduced sliding friction with the skirt of the inner shell.