US Patent 7475947 Extendable cutter drum for a boring machine

A mining machine that includes a rotor assembly disposed on a mobile frame. A cutter drum assembly includes an intermediate drum section and a pair of end drum sections. The end drum sections are drivingly connected by the intermediate drum section. The end drum sections include an axially fixed drum portion and a drum extension that is axially movable on the drive shaft to extend the length of the cutter drum assembly. A hydraulic piston and cylinder arrangement is disposed in shafts supporting the end drum sections, and extends and retracts the drum extension with respect to the fixed drum portion. A torque transfer arrangement is disposed between the fixed and extension drum portions for mutual rotation.