Percussive energy transfer in pneumatic top hammer rock drills

ABSTRACT A mathematical model of pneumatic roll drills is introduced. This model takes into account the local deformation of impact ends of piston and shank adapter. For this model, there is a good agreement between theoretical and experimental results. Two dimensionless parameters related to the mass of piston, the local deformation of impact ends, characteristic impedance of rod, and force-penetration characteristic at bit-rock interface, are introduced. The analysis indicates that the checking of these dimensionless parameters and letting them be in certain ranges are helpful for the design of pneumatic rock drills to achieve high efficiency of energy transfer.