| 摘要 |
In deep bore drilling it is usual to use a fluid operated percussive hammer to provide necessary drive for the boring operation. However a difficulty which is encountered with hammers which are currently in use is that the manufacture of the components for such hammers involves considerable amount of precise machining which not only increases the manufacturing cost of such units but also reduces the service life of the components. Some of the typical hammers in use generally comprise an outer cylindrical casing with a feed tube positioned concentrically within the casing and a piston slidably mounted within the casing and over the feed tube to reciprocate therein and impact on a drill bit mounted in and retained at the bottom of the casing. In order to effect the reciprocating action of the piston fluid passage ways are provided in the feed tube and/or the casing which periodically communicate with ports provided in the piston to periodically admit fluid to the chambers above and below the piston to either lift it away from the drill bit or drive it so as to impact onto the drill bit. |
