HAMMERING SMALL-DIAMETER PROPULSIVE DEVICE CAPABLE OF DEALING WITH GRAVEL

摘要

PROBLEM TO BE SOLVED: To provide a propulsive device which can prevent irrotation of a bit, eliminates draining work in the case of collimation of a target for correcting a direction of the device, and can carry out its boring work easily and in a shorter period of time.;SOLUTION: The propulsive device is constructed by pressing an external pipe and a laid pipe from a shaft into the natural ground, and simultaneously driving and excavating the natural ground by an air hammer device arranged at the tip of the external pipe. According to the propulsive device, a bit main body 3 arranged at the front end of the hammer device 2 is comprised of an annular ring bit 52 engaged with the tip of the external pipe 1 along a central line of the same in a manner being slidable and rotatable over a predetermined width, and a center bit 51 being inserted into the internal periphery of the ring bit 52 to be protruded by a predetermined width by the hammer device 2 while frontward pressing the ring bit 52. Further, an exhaust hole 54 is formed in the center bit 51, which makes its inner diameter smaller from a midpoint thereof and has an opening in a front surface of the center bit. Still further, a guide hole 56 is formed at an intermediate portion of the exhaust hole 54, for returning exhaust air to a groove 55 for removed earth, which is formed in the periphery of the center bit 51.;COPYRIGHT: (C)2001,JPO