US Patent 8176817 Tool coupling structure

A tool coupling structure comprises a first post member including a fitting end disposed on one end thereof and a polygonal cavity mounted on another end thereof; the cavity including a hole formed on an outer wall thereof, and the hole including a biasing element installed therein; a second post member including a coupling end fixed on one end thereof and a polygonal sphere knob formed on another end thereof to be fitted to the cavity of the fist post member, and the sphere knob including an elastic engaging member fixed on a peripheral side thereof in response to the hole of the first post member to be retained in the hole.