| 摘要 |
PURPOSE: Closing unit structure of a top sub is provided to prevent attachment of foreign materials and to remove the foreign materials moving upward while the foreign materials are held in a closing unit. CONSTITUTION: Closing unit structure of a top sub composing a hammer bit for excavating comprises a screw unit connected to a rod on an upper outer circumference; a pneumatic pressure inlet hole(1a) letting on pneumatic pressure generated in an engine motor in the center; a top sub forming a closing unit(A) opening by a check valve(4) on lower end of the pneumatic pressure inlet hole; a first and second isolating protrusions(1b,1d) mounted on the closing unit; and a collecting groove formed between the first isolating groove and the second isolating groove. Thereby, the closing unit is isolated by the check valve to improve tightness. If foreign materials are attached on a surface, the foreign materials are discharged outside by rounding a surface of the first and second isolating protrusions.
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