| 摘要 |
A drilling head includes a tubular body having removable means for sealing the body to a kelly or other drive tube, a drive bushing releasably mounted in the sealing means to turn the sealing means with the drive tube, the sealing means including a seal tube having a rotating seal means for sealing with the body and a non-rotating seal means for sealing with the drive tube, both seal means being releasably held to the seal tube by common retainer means, such sealing means being rotatably mounted on the body on removable outboard mono-stratum double acting anti-friction thrust bearing means at the top of the body, the outer bearing race being held between annular flanges, one flange being integral with the body and the other releasably connected to the body, and the inner bearing race being held between annular plates releasably connected to the seal tube, the body having a side outlet and flange connection for the drilling fluid return line substantially flush with the body.
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