DRILLING RIG

摘要

An improved drilling rig having a drillhead assembly positioned onto a mast for vertical movement therewith. The drillhead assembly is hung by cables threaded from a hoist assembly positioned at the top end of the mast. One or more cable return assemblies are positioned at the bottom end of the mast. The cables are counter-wound on the hoist assembly such that the cables roll off of the hoist assembly in the direction towards the drillhead assembly at the same rate the cables are pulled onto the hoist assembly from the direction towards the cable return assemblies. The drillhead assembly has a drive motor assembly rotatably mounted within a frame. A break-out tool assembly is mounted at the lower end of the mast. The break-out tool assembly has means for grasping rotating a length of string so as to separate the lengths of string.