| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a rotary driving type drilling apparatus which can quickly switch the reciprocative motion of a piston hammer arranged on a rear side of a cylinder, by employing a simple structure, and can ease an impact force accompanying the switching of the reciprocative motion, to thereby protect the apparatus from being damaged. <P>SOLUTION: According to the rotary driving type drilling apparatus which is composed such that a driving force is applied to a drill bit 4 by a down-the-hole hammer, the cylinder 2 has a cushion camber 30 formed on a rear end thereof, which is sealed when an external peripheral portion of the piston hammer 1 makes sliding contact with the same, and a diameter-expanded portion 29 formed in front of the cushion camber, which defines a communication gap in cooperation with the external peripheral portion of the piston hammer 1. Thus when the piston hammer 1 recedes, pressurized air is delivered via the communication gap formed between the diameter-expanded portion 29 and the external peripheral portion of the piston hammer 1, to the rear of the piston hammer 1, and further while the pressurized air is confined in the cushion chamber 30 to increase the pressure in the cushion chamber 30, the reciprocative motion of the piston hammer 1 is switched. <P>COPYRIGHT: (C)2007,JPO&INPIT |
