Abstract: A fluid operated rock drill hammer includes an annular hammer body with the upper end of the hammer body adapted to be connected to a drill string and with a drill chuck mounted at the lower end of the hammer body. A drill bit extends through the drill chuck into the body. A piston is slidably mounted in the hammer body to move between the drill bit and the upper end of the hammer body for striking the portion of the drill bit that extends through the drill chuck. The force for moving the piston is provided by a fluid that is circulated through the drill string into the hammer body. A restricted exhaust port is provided for preventing back hammering of the piston by maintaining a high fluid pressure in the space between the piston and the upper end of the hammer body when the bit is off bottom.

Abstract: A fluid operated rock drill hammer includes an annular hammer body with the upper end of the hammer body adapted to be connected to a drill string and with a drill chuck mounted at the lower end of the hammer body. A drill bit extends through the drill chuck into the body. A piston is slidably mounted in the hammer body to move axially between the drill bit and the upper end of the hammer body for striking the portion of the drill bit that extends through the drill chuck. The force for moving the piston is provided by a circulating fluid that is transmitted through the drill string into the hammer body. All of the fluid is transmitted between the hammer body and the piston at a single fixed axial position along the length of the hammer body.