Fluid operated drilling device and a method for drilling a hole using a fluid operated drilling device

A fluid operated drilling device for drilling a hole the drilling device comprising:

• a hammer for creating the hole with a rotating and percussive motion;
• a rotation device for rotating the hammer;
• and
• a drill rod connecting the rotation device to the hammer and transporting operating pressurized drill fluid to the hammer for creating the percussive motion of the hammer, the hammer comprising:
• a tubular main body having a hollow interior;
• a back head, for connecting the hammer to the drill rod, coupled to an upper end of the main body and having a fluid pressure supply passage;
• a cylindrical piston housing connected to the main body inside the main body;
• a reciprocating piston slidably installed in the piston housing, for impacting a drill bit of a bit unit installed at a lower end of the main body, the drill bit being movable for a predetermined length longitudinally relative to the main body, the piston having;
• a first end and a second end, the first end being closer to the drill rod, a lower part and an upper part detachably connected to each other, a hollow portion, a first communication hole connected to the hollow portion and an annular pressurizing portion protruding on an outer circumferential surface;
• of the piston, the hollow portion being open to lead pressurized operating fluid directly to the hollow portion of the piston from the fluid pressure supply passaged;
• a space between the piston and the piston housing divided by the annular pressurizing portion in a radial direction of the piston into a first space portion for elevating the piston and a second space portion for striking the piston, the first space portion and the second space portion being connected to the hollow portion of the piston via the first communication hole;
• a second space in the hollow interior of the main body between the piston and the main body in the racial direction of the piston and between the piston housing and the bit unit in the axial direction of the piston;
• a second hollow portion in the piston for leading discharged fluid through the piston to the drill bit and out of the hammer;
• first communication channels formed in the piston connecting the second space to the second hollow portion for leading discharged fluid from between the piston and the main body back inside the piston to the second hollow portion;
• a valve unit for controlling fluid discharge from the second space portion, the valve unit including a valve exhaust passage for discharging fluid from the second space portion;
• a fluid pressure supply unit for supplying high pressure fluid delivered to the fluid pressure supply passage of the back head to the first space portion and the second space portion;
• and
• an axial exhaust passage formed between the main body and the piston housing for discharging fluid outside the piston housing;
• wherein the fluid discharged from the second space portion is led through the valve exhaust passage and the axial exhaust passage, and the rotation device rotates the bit unit using the drill rod and the main body.