Expansion dowel assembly

Claim 1

Expansion dowel assembly for insertion into a borehole formed in a receiving material, comprising an axially elongated sleeve having a leading end arranged to be inserted first into the borehole and a trailing end, said sleeve having a slit therein extending from the leading end for at least a part of the axial length of the sleeve for affording the radial expandability thereof, an axially extending radially expandable spreading member located in said sleeve adjacent the leading end thereof, said spreading member having a leading end and a trailing end spaced apart in the axial direction thereof, a part of the axially extending inside surface of said sleeve converging inwardly in the direction from the leading end toward the trailing end, an axially elongated bolt having a leading end and a trailing end positioned within said sleeve and being axially displaceable relative to said sleeve between a first position where the dowel assembly is in the pre-expanded position and can be inserted into a borehole and a second position where the leading end of said bolt is displaced in the axial direction into said sleeve toward the leading end thereof into expanding engagement with said spreading member for radially expanding said spreading member and said sleeve, the leading end of said bolt having an axially extending thread-like profile, wherein the improvement comprises that said spreading member has an axially extending passageway therein extending from the trailing end thereof toward the leading end and arranged to be contacted by the leading end of said bolt with the maximum diameter of said passageway being less than the maximum diameter of said bolt adjacent the leading end thereof, abutment means connected to said sleeve for preventing said spreading member from being displaced axially out of the leading end of said sleeve when said bolt is displaced axially from the first position toward the second position into expanding engagement with said spreading member, said thread-like profile being shaped so that said bolt can be driven axially by an impact action thereon from the first position toward the second position through said spreading member and after being driven through and expanding said spreading member can be screwed relative to said spreading member in the direction toward the leading end of said sleeve and toward the trailing end of said sleeve, said sleeve has a flange formed monolithically on the trailing end thereof with said flange arranged to extend radially outwardly beyond the outside surface of said sleeve, displaceable means for retaining said flange radially outwardly beyond the outside surface of said sleeve whereby said flange can be deflected radially inwardly when said means are displaced and do not maintain said flange radially outwardly, and said thread-like configuration on the leading end section of said bolt comprises a saw-tooth like thread.