Patent ID: 7645087

Claim:
An expander nut, comprising: a cylindrical base nut centrally having a threaded hole; a first wedge half having a first tapered surface; a second wedge half having a second tapered surface, wherein the second tapered surface interlocks with the first tapered surface and when the first wedge half and the second wedge half are combined, the two wedge halves jointly forms a close circular ring, the first wedge half being connected to the base nut, and the two wedge halves being allowed to move relatively against the two tapered surfaces; a top cap having centrally a through hole and having a preload portion at a bottom thereof for contacting a top of the second wedge half; a bolt passing through the through hole of the top cap and getting engaged with the threaded hole of the base nut; an annular accommodating groove formed at a periphery of the base nut for receiving a flange extending inward from a bottom of the second wedge half, the base nut having an anti-rotation device for preventing the first wedge half from sliding along the accommodating groove, the anti-rotation device being a grub screw extended radially in the base nut and engaging one end of the flange; and a plurality of protruding castellations spaced at a predetermined distance from one another and formed at the top of the second wedge for being received by through slots in the top cap, tops of the protruding castellations being preload surfaces for contacting the preload portion of the top cap.