The down the hole drilling rig is an impact rotary drilling rig, and its internal structure is different from that of a general rock drill. Its air distribution and piston reciprocating mechanism are independent, namely the impactor, as shown in Figure 2. Its front end is directly connected to the drill bit, and its rear end is connected to the drill rod. During rock drilling, the impactor penetrates into the hole and, through a valve, the piston (hammer) inside the impactor moves back and forth to strike the tail of the drill, causing the drill bit to impact the rock at the bottom of the hole.