DTH is short for"down-the-hole", its name originated from the fact that the percussion mechanism followed the bit down into the hole. According to the different applications, down-the-hole drilling rigs can be divided into surface and underground. According to the different diameters, down-the-hole drilling rig can be divided into light-duty (80~100mm), medium-sized (130~180mm), and heavy-duty (180~250mm).
The working principle of the down-the-hole drilling rig is: compressed air drives the piston in the impactor, hitting the drill bit for rock drilling. The characteristic of this drilling method is that the drilling speed is balanced and stable, suitable for deep hole drilling, the drilling is not easy to jam under complex geological conditions, the drilling accuracy is high, and the noise is low.
Down-the-hole rock drilling refers to a rock drilling method in which an impact mechanism is submerged into the blasthole. The torque of the slewing mechanism rotates the impactor and the drill bit through the drill rod. The rock ballast is discharged out of the hole by the exhaust gas of the impactor. Since the impactor of the down-the-hole rock drilling advances with the increase of the hole depth, there is no need to extend the drill rod, so the impact energy transmission efficiency will not be reduced due to the depth of the hole.
The biggest difference between down-the-hole hammer and top hammer lies in the position where the impact force acts. As shown in the figure, the down-the-hole type, the impact force directly acts on the tail of the drill bit, which is what we call the drill bit; the top hammer type, generally transmits the hammering force provided by the rock drill to the drill bit at the bottom of the hole to break the rock, and the impact force acts at the top of the drill pipe.