PURPOSE: To apply rotation and impact reaction force at a right angle to a bit so as to prevent its damage by forming a tilt surface in an end part of both blocks of a device, which receives impact force of a hammer and turning force of a hammer cylinder, and vertically implanting the bit.
CONSTITUTION: A pair of blocks 10a, 10b of almost semicircular bottom surface are constituted of planes 12a, 12b in point end surfaces of these blocks, surfaces 13a, 13b tilted in an axial directional base end side of a device 2, 14a, 14b and tilt surfaces 16a, 16b in end parts of end surfaces 15a, 15b of blocks 5a, 5b. Next, a plurality of bits 4... are vertically implanted respectively in these surfaces. When the device 2 is rotated, the tilt surfaces 16a, 16b are protruded from the peripheral surface of the device 2 by turning the blocks 10a, 10b. Further the blocks 10a, 10b receive turning force of the device 2 to excavate the ground by stopping turning of the blocks 10a, 10b with the straight end surfaces 15a, 15b in contact with each other.
SATO SHIGERU
TSUJIMOTO KATSUAKI
