Drilling device for drilling a core in deep drill holes

摘要

In a core drilling apparatus wherein a core bit is driven by a hydraulically actuated Moineau type motor, control valve means are provided whereby drilling fluid can be directed through the core sleeve to remove debris from its interior, and, subsequently diverted outside of the core sleeve when drilling begins. Alternative constructions are shown whereby the flushing of the core sleeve can be accomplished with the motor drive in an inactive mode or in an operating mode.