REVERSE CIRCULATION DRILLING APPARATUS HAVING A CASING

摘要

The present invention relates to a reverse circulation drilling bit apparatus having a casing preventing excavated soil from blocking a discharge channel during excavation of soft ground by mounting a casing outside an introduction pipe. The reverse circulation drilling bit apparatus comprises the introduction pipe, a cylinder, a piston hammer, a drill bit, a discharge pipe, and the casing. Compressed air is introduced to the introduction pipe. The cylinder is connected to the introduction pipe. The piston hammer is stored inside the cylinder and ascended or descended by introduction or discharge of the compressed air. The drill bit is disposed in a lower portion of the piston hammer and strikes bedrock by a descending motion of the piston. The discharge pipe is stored inside the piston hammer and the drill bit and discharges the excavated soil crushed by the striking of the drill bit to the outside. The casing is formed to cover the introduction pipe.