Abstract: A design of crown of drill bit for percussive rock drilling with big “V” shape front flushing grooves, small central “dead” area will reduce the repeatedly crushing of broken rock cuttings. It will not only improve the rate of penetration, but also decrease the hole deviation, as well as the erosion to the outer surface of drive sub and case tube of DTH hammer.

Abstract: Floating pistons are implemented in hydraulic rock drilling hammer, or hydraulic hammer breaker, or fluid DTH hammer. The chambers confined by the impact piston and the body case are connected via ports and the floating pistons. The pistons balance the pressure difference when pressure pulsation happens in the chambers during the reciprocating movement of impact piston. It dampens the pulsation, prevents cavitations and assists the forwarding and returning movement of impact piston. The device will also be potential to increase the efficiency and impact power of hammers.