| 摘要 |
An apparatus is described for forceably pulling a well casing down into a drilled hole from the casing bottom end during a percussion drilling procedure, through use of the percussion drill tool. An anvil is fixed to the casing and projects inwardly to coact with the hammer surface on a precussion bit. The bit includes an interlock feature that allows selective disengagement with the anvil and allows the bit to be lowered past the anvil for drilling purposes. The anvil is situated above the drive shoe along a lower casing section. The lower casing section acts as a material accumulator, cooperating with the drilling bit and anvil shoulder to seal drilled areas and facilitate removal of drilled material from the drilled hole.
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