| 摘要 |
<p>A mining tool for loosening rocks etc. from the roof of a gallery etc., has an arm (13) to which a swinging head (17) is attached by a hinge pin (5). The head has a holder attached to it, into which is locked the tool (25) which is forced into a crevice, and then swung to remove the material from the roof. The holder is attached by a hinge pin (23) so that it can be swung. Between the holder and the head is an actuator piston (27) to cause this swinging movement. Another piston (20) swings the head about its pivot (15) on the arm. Both pistons are controlled by a three way/four way operating valve, and are double acting.</p> |
