Abstract

A one-piece, malleable iron, expansion shell, and a leaf of such shell, for use in an expansion to be installed in a relatively small (about 1") diameter bore hole with a conventional size (5/8") bolt. The expansion shell, and individual shell leaves have unique features contributing to the effectiveness of the anchor when used either with or without a resin grouting mixture. The slots or spaces between adjacent shell leaves include upper and lower portions, each of constant width, the lower portion being wider than the upper portion, whereby the leaves are narrower in the area where they are bent outwardly from the closed ring at the base than in the area where they are compressionally engaged between the plug and the hole wall. Upper portions of the inner leaf surfaces taper toward the shell axis and the side edges of such surfaces taper toward one another from the upper, free ends of the leaves toward the lower ends. A first group of gripping teeth or serrations on the outer leaf surfaces near the lower ends of the leaves are deeper than a second group outwardly adjacent the plug contact area.