| 摘要 |
1. Down-the-hole pneumatic drilling hammer, which comprises a tubular body (1) supplied with compressed air and carrying a drilling bit (3) and in which a ramming piston (21) is made to perform a reciprocating movement inside an internal sleeve (7) forming a casing by means of a mechanism for distributing compressed air alternately above and below the ramming piston in such a way that it cyclically strikes the bit and rises again, characterised in that the hammer has two separate sources (16, 18) of compressed air, a high-pressure one and a low-pressure one respectively, the distribution mechanism ensuring alternately the supply of high-pressure air to the upper chamber (51) above the piston (21) so as to project the latter towards the bit, while the lower chamber (50) allows the air to escape, and the supply of low-pressure air to the lower chamber (50) so as to cause the piston (21) to rise again, while the upper chamber (51) allows the air to escape. |
