Importance

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Abstract

An anchor comprising a bolt having an upper cylindrical part with an outer thread adjacent its top and a lower conical head, and a sleeve surrounding the bolt, the sleeve comprising an upper cylindrical portion and an annular expander, the expander having multiple slits therein which open to the bottom end and extend axially. The slits form expansion pieces therebetween having curvatures which, before expansion of the pieces, are substantially the same as the curvatures at the corresponding positions of the outer peripheral wall of the conical head, which the pieces contact after expansion. One method of manufacturing the expander comprises the steps of forming a fan-shaped flat material having slits forming pieces between them, shaping the pieces so that their inner peripheral walls form arcs having substantially the same curvatures before expansion as the curvatures at the corresponding positions of the conical head which the pieces contact after expansion, shaping the sheet material into a cylindrical expander, and connecting both ends of the material. Another method of manufacturing the expander comprises the steps of forming a plurality of separate pieces, shaping each of the pieces to have curvatures before expansion substantially the same as the curvatures at the corresponding positions of the adjoining portion of the conical head after expansion of the pieces, and joining the pieces into a cylindrical shape.

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First Claim