| 摘要 |
PROBLEM TO BE SOLVED: To solve such problems that the inner peripheral part of a cut off packing is pulled by a rod when the rod goes up and down at the time of upward drilling by directing the drilling rod upwards or compressed drilling, the inner peripheral part of the cut off packing is caught by the rod and the inner peripheral part is deformed in the vertical direction, the press fitting force gets loose and air leaks. SOLUTION: Recessed grooves are formed along the peripheral direction at the inner and outer peripheral faces of the cut off packing. By actuating the pressure of a pressurized fluid on the recessed grooves of the packing outer periphery, the cut off capacity of the drilling hole rod is strengthened. COPYRIGHT: (C)2006,JPO&NCIPI
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