Expansion dowel assembly

Claim 1

Expansion dowel assembly to be used in a thin-walled structural component, said assembly comprises an axially elongated dowel member having a leading end which is inserted first when said dowel member is placed into a structural component and a trailing end spaced from the leading end in the axial direction thereof, said dowel member being hollow between the leading and trailing ends thereof and comprising a plurality of laterally spaced elongated expansion arms extending as unitary members between the trailing and leading ends and being radially outwardly displaceable and being collapsible in an axial direction, said dowel member comprises a radially outwardly extending flange at the trailing end thereof and a junction member at the leading end thereof interconnecting said arms, means at said junction member for applying a force for radially displacing and axially collapsing said arms, wherein the improvement comprises said expansion arms form an axially extending annular wall with axially extending openings between its arms and the arms are generally flat thin wall members and are in spaced relation to one another from adjacent the trailing end to the junction member, said arms define an axially extending passage for the axial length thereof fully open radially inwardly of said arms, said expansion arms have a buckling location located approximately midway between the leading and trailing ends of said dowel member, said flange is an annular member, an abutment member for providing a positive stop of the axial collapsibility of said arms after a predetermined axial collapse has taken place, said abutment member is located within the passage formed by said arms in said hollow dowel member radially inwardly of and separate from said arms, said abutment member is connected to and extends in the axial direction of said dowel member from said flange toward said junction member for approximately half of the axial direction between said flange and said junction member, said abutment member is a tube-shaped section extending in the axial direction of said dowel member from said flange and having an inside diameter for the axial length thereof, said flange having an inside diameter corresponding approximately to the inside diameter of said abutment member, the opposite end of said abutment member from said flange forms the position stop, said junction member is a thin wall member and includes an annular thin wall section extending transversely of the axial direction of said dowel member with said thin wall section having an opening therethrough in the axial direction of said dowel member with a diameter corresponding approximately to the inside diameter of said abutment member, the surface of said thin wall section facing toward the trailing end of said dowel member contacts the opposite end of said abutment member providing the position stop for the axial collapsibility of said arms.