| 摘要 |
1323966 Percussive drills BAKER OIL TOOLS Inc 4 Oct 1971 [23 Dec 1970 5 May 1971] 46022/71 Heading B4C [Also in Division E1] In a down-the-hole percussive drill comprising a casing 10 having a cylinder of diameter T and a cylinder of greater diameter S, and a hammer piston 28 engaging the walls of the cylinders, driving fluid is directed into the cylinder of diameter T above the smaller diameter piston portion 45 and into the cylinder of diameter S above the larger diameter piston portion 33 to drive the hammer piston to impact against an anvil 18 carrying, or associated with a bit C. With parts of the drill positioned as shown driving-air passes through the drill string B, past a non-return valve 200 which prevents water entering the drill, and through annulus 20, ports 23 and duct 50 to raise the hammer piston for a return stroke. As a shoulder 58 on the hammer piston passes ports 23 driving-air enters an annulus 44 about the piston to force the hammer piston downwardly for an impact stroke. As a shoulder 57 on the hammer piston moves into the region of an exhaust groove 31 driving-air is exhausted from the drill through ducts 47, 49 to scavenge drillings from the hole. The anvil and bit are retained in the casing by a two part nut 16 having internal projections meshing with external grooves on the anvil which permit rotation of the bit by the drill string. |
