Patent ID: 8141660

Claim:
The excavating apparatus for underground excavation, comprising: a plurality of bits, the outer diameters of which are smaller than that of an excavating apparatus main body, that advances to and retracts from an excavation side; piston case members, which correspond to the number of the bits and a plurality of which are housed inside the excavating apparatus main body, with built-in pistons that impart strike forces to the bits via the energy of a working fluid; a fluid storage part that stores the working fluid that is fed to each of the piston case members; working fluid distribution paths, a plurality of which are provided corresponding to the number of the piston case members, wherethrough the working fluid fed to each of the piston case members passes; and a rotary body that comprises a plurality of communication holes, which brings the fluid storage part and distribution ports into communication in order to feed the working fluid from the fluid storage part to the distribution ports of the working fluid distribution paths; wherein, the distribution ports are provided in the rotational direction of the rotary body such that the bits are impact driven staggered in time; and the communication holes are provided in the rotational direction with a layout different from that of the distribution ports in order to prevent each of the communication holes from communicating with each of the distribution ports simultaneously and with the same degree of openness wherein, the rotary body comprises working fluid supply holes that, separately from the communication holes, bring the fluid storage part and each of the distribution ports into communication; and the working fluid supply holes are set such that their inner diameters are smaller than those of the communication holes, said working fluid being fed through said supply holes into each of the piston case members in an amount smaller than that which is fed through the distribution ports.