Expansion dowel

Claim 1

AN EXPANSION DOWEL COMPRISING A HEAD PORTION AND AN INTEGRAL AXIALLY PROJECTING GENERALLY CYLINDRICAL EXPANSIBLE BODY PORTION PROVIDED WITH A PLURALITY OF SLITS EACH SLIT BEING DEFINED BY A PAIR OF PARALLEL WALLS AND EXTENDING FROM THE OUTER END OF THE BODY IN EQUALLY SPACED ANGULAR RELATIONSHIP UP TO THE HEAD PORTION, SAID HEAD PORTION HAVING AN AXIAL BORE ADAPTED TO RECEIVE A FASTENING SCREW, SAID EXPANSIBLE PORTION OF THE BODY HAVING AN AXIAL BORE OF POLYGONAL CROSS-SECTIONAL FORMATION HAVING OPPOSING WALLS WITH ONE WALL BEING SUBSTANTIALLY PARALLEL TO THE OTHER WALL, SAID BORE FORMING AN EXTENSION OF SAID SCREW RECEIVING BORE IN THE HEAD PORTION AND BEING OF SUBSTANTIALLY REDUCED DIMENSIONS IN CROSS SECTION WITH RESPECT TO SAID HEAD PORTION BORE, SAID AXIAL BORE IN THE EXPANSIBLE PORTION COMMUNICATING WITH SAID PLURALITY OF SLITS, SAID SLITS EACH EXTENDING ALONG A HELICAL SURFACE AND HAVING ONE WALL THEREOF FORMING A CONTINUATION OF ONE ADJACENT WALL OF THE BORE OF POLYGONAL CROSS SECTION, SAID SLITS PASSING COMPLETELY FROM SAID BORE OF POLYGONAL CROSS SECTION THROUGH THE BODY AND PASSING THROUGH THE EXTERIOR SURFACE THEREOF, AND EACH SLIT BEING LATERALLY OFFSET FROM THE AXIS OF THE BODY IN A DIRECTION TO LEAD A FASTENING SCREW WHILE ROTATED TO EXPAND THE DOWEL, WHEREBY SCREWING IN OF A FASTENING SCREW UPON CONTACT WITH THE WALLS OF THE AXIAL BORE TENDS TO DEFORM THEM IN A DIRECTION OF CLOSING SAID SLITS.