The drilling assembly consists of drill rods, button bits, and an impactor. Drilling is performed by connecting two drill rods in sequence. The rotation and air-supply mechanism comprises a rotation motor, a rotation reduction gear, and an air-supply swivel unit. The rotation reduction gear is a three-stage, enclosed cylindrical gear unit featuring automatic lubrication via a spiral oil injector. The air-supply swivel unit consists of a connector body, seals, a hollow main shaft, and a drill rod adapter; it is equipped with a pneumatic clamp for connecting and disconnecting drill rods. The lifting and pressure-regulation mechanism utilizes a lifting motor, a reduction gear, and a lifting chain to raise and lower the rotation mechanism and drilling assembly. A pressure-regulation cylinder and a movable pulley block are installed within the closed-loop chain system. During normal operation, the piston rod of the pressure-regulation cylinder pushes the movable pulley block, enabling the drilling assembly to operate under controlled pressure (reducing the load on the bit).
Large-scale open-pit DTH (Down-The-Hole) drilling rigs feature more complex mechanical configurations, primarily comprising: a drill mast, a carriage, a rotation unit, a feed mechanism, a rod-unloading device, a dust-removal system (typically categorized into dry, wet, hybrid, and foam-based methods), a travel mechanism, a chassis, a superstructure rotation mechanism, a mast-swinging mechanism, a compressed-air system, and an impactor.
The working principle of a DTH drill rig is similar to that of a conventional pneumatic percussive-rotary rock drill, except that the impactor operates independently and is submerged at the bottom of the borehole. During operation, the feed mechanism continuously advances the drilling assembly and applies pressure to the hole bottom, while the rotation mechanism continuously rotates the assembly. Simultaneously, the impactor-powered by compressed air-drives a piston to strike the bit repeatedly, fracturing the rock. Rock cuttings generated during fracturing are carried out of the hole through the annular space between the drill rod and the borehole wall by compressed air delivered directly to the hole bottom via the hollow drill rod. In essence, the process combines percussive (intermittent) and rotary (continuous) rock-breaking methods under axial pressure, with the percussive action playing the dominant role.
