| 摘要 |
An expansion dowel has a friction reducing coating on the contacting surfaces formed by an inside surface of an expansion sleeve and an outside surface of the shank contacting the inside surface of the sleeve. The coating effects a smaller friction value between the expansion sleeve and the expansion part than the friction value between the expansion sleeve and the surface of a borehole into which the dowel is inserted. This difference in friction assures an effective re-expansion of the expansion dowel in a fractured or broken tensile zone of a receiving material containing the borehole. In addition to the coating, protrusions arranged in pairs are formed on the outside surface of the expansion sleeve for maintaining contact with the borehole surface, particularly in the broken tensile zone during large displacement of the expansion dowel.
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