Patent ID: 7293615

Claim:
An earth boring apparatus for sinking shafts and removing shaft material from said shaft, said apparatus having; at least two decks, one of said decks being associated with an upper stage portion and the other of said decks being associated with a lower stage portion; extensible drive members acting between said decks for allowing movement of one of the decks relative to the other; releasable anchors associated with respective ones of the decks for engaging walls of the shaft to secure the apparatus in a stationary position; and excavating equipment carried by said lower stage portion, said lower stage portion being adapted to permit deployment of said excavating equipment beyond said lower stage portion and to permit all of said equipment to be completely retracted therethrough such tat the underside of said lower stage portion is devoid of any of said excavating equipment thereby enabling said lower stage portion and said excavating eguipment to be moved away from the bottom of said shaft to permit blasting without moving said upper deck; whereby the releasable anchors of one of the decks engages the wall while the releasable anchors of the other of the decks is released from the wall to allow motion of the other deck along the shaft, under control of said drive members.