| 摘要 |
<p>Hall 2 R O C K D R I L L I N G A P P A R A T U S Rock drilling apparatus wherein a motor and chuck assembly is mounted for slidable movement on a mast and elevated and lowered by a pair of endless chains, the endless chains passing through openings in stabilizer units slidably mounted on the mast for vertical movement and which rotatably and slidably brace the drill stem. The chains carry detents which are arranged so that when the endless chains are operated to elevate the motor and chuck, the stabilizers are also elevated in spaced relationship so as to stabilize the drill stem.</p> |
