The invention relates to a screw anchoring device adapted to be inserted in a bored hole and of the type having a tubular anchoring member moulded from plastics material and provided with longitudinally -- for example axially or helically -- extending slits or slots. The anchoring member cooperates with...http://www.google.de/patents/US3942407?utm_source=gb-gplus-sharePatent US3942407 - Expandable screw anchoring devices
