Anchor bolt assembly

Claim 1

an expansion bolt and anchor assembly suitable for use in supporting the roof of a mine shaft including an expansion shell having a base and a number of expandable fingers axially extending from the top surface of the base, said base being formed of a plurality of arcuate shaped sections that abut each other in assembly along radially extended sidewalls, each base section containing a groove in the outer cylindrical wall thereof opening at the bottom of said base section and having a helically aligned passage inclined at an angle whereby the passage slopes upwardly from the bottom towards the top of the base, each sloping passage decreasing in depth from its entrance region towards its terminal end so that the radial distance at the terminal end is brought to a predetermined dimension, and a cylindrical end cap having an anular inner side wall being arranged to pass over the outer wall of the base in assembly in close sliding relationship therewith, said inner sidewall having inwardly extended elements receivable within said grooves formed in the base so that the top end wall of the cap is drawn into seating contact against the bottom surface of the base as the elements move up the sloping passages to securely support the sections of the base in assembly against axial and radial movement, and the extended elements having a radial length so that said elements move into interferring contact with the bottom wall of the sloping passage at the terminal end thereof.