| 摘要 |
<p>A method of making a protective unit comprising the steps of:
forming a mold including a split outer mold section defining a cavity having an end wall, an annular flange surrounding an opening spaced from the end wall and angled side walls extending between the end wall and the flange wall and having symmetry about an axis centered on the end wall and opening and diameters that vary along said axis, a radially collapsible core having a core end wall, a core flange wall and core side walls extending between said core end walls and core flange wall, said core walls being somewhat smaller radially than the corresponding walls of the outer mold section so that when the core is positioned coaxially in the cavity in its uncollapsed state, the corresponding walls of the core and outer mold section are substantially parallel and defme a continuous gap between them;
filling said gap with molten thermoplastic material;
allowing the thermoplastic material to harden;
collapsing the core so that the maximum diameter of the core side walls is appreciably smaller than that of the opening and sliding the core axially from the outer mold section through said opening, and
splitting the outer mold section and removing the set thermoplastic material therefrom to reveal said impact-energy management structure as a thin-wall enclosure having an end wall, a flange and side walls extending between the enclosure and wall and flange.</p> |
