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How Pneumatic Rock Drill Work?
Oct 03, 2018

Structure and working principle of pneumatic rock drill

 

Structure and working principle of pneumatic rock drill


Air-Leg Rock Drill-Whole Set--.jpg


The pneumatic rock drill mainly consists of an impact gas distribution mechanism, a (slewing) rotating mechanism, a powder discharging mechanism, a lubricating mechanism and an operating mechanism. The main difference between them is the impact gas distribution mechanism and the rotating mechanism.


1. Working principle of impact gas distribution mechanism


(1) Piston stroke


The piston stroke is the impact stroke, which refers to the whole process of the piston moving forward from the rear end of the cylinder to the striking tail, as shown in Fig. 1.



Structure-1.jpg

Figure 1 Impact stroke gas path


1-manipulator valve air hole; 2-handle body air chamber; 3- ratchet hole; 4-valve cabinet hole; 5-annular air chamber; 6-gas valve right end valve sleeve hole; 7- gas valve left end air chamber; A-piston right end face; B-piston left end face


At the beginning of the impact stroke, the piston is at the left end and the valve is at the extreme left position. The compressed air from the venting of the valve passes through the handle chamber, the ratchet hole, the valve cabinet hole, the annular chamber and the valve sleeve hole at the right end of the valve to enter the left chamber of the cylinder, and pushes the piston forward to form an impact stroke. At this time, the right chamber of the piston is open to the atmosphere through the exhaust port. When the right end of the piston passes over the exhaust port, the gas in the front chamber of the cylinder is compressed by the piston to form an air cushion, and the instantaneous air pressure is increased, and the compressed gas in the front cavity is returned to the left end air chamber of the gas distribution valve through the return passage. When the piston continues to advance, the air pressure gradually increases, forcing the valve to have a front (right) shifting tendency. When the left end of the piston passes over the exhaust port, the air pressure in the left chamber of the cylinder is exhausted from the exhaust port, and the air pressure in the left chamber is sudden. Lower, then the pressure of the left end of the gas distribution valve pushes the valve forward. At this time, the valve and the valve sleeve are closed, and the gas path of the left cavity of the cylinder is cut off, and the piston impacts the drill rod instantaneously, and the stroke ends, and the return stroke starts.


(2) Piston return


The piston returns to the stroke, as shown in Figure 2.


Structure-2.jpg

Figure 2 return stroke gas path


1-spiral rod; 2-valve 3-valve; 4-valve; 5-cylinder; 6-piston; 7-guide sleeve; 8-ratchet; 11-operated valve;


At the beginning of the return stroke, the piston is at the right end and the valve is at the extreme right position. At this time, the pressure from the air vent of the control valve passes through the shank air chamber, the ratchet hole, the valve cabinet hole, the gap between the valve cabinet and the valve, the left end air chamber of the air distribution valve, and the return hole into the right chamber of the cylinder, and the piston left The cavity is open to the atmosphere through the exhaust port, so the piston begins to move to the left. When the left end of the piston passes over the exhaust port, the gas in the left chamber of the cylinder is compressed by the piston to form an air cushion, and the air pressure is increased, forcing the valve to have a rear (left) shifting tendency when the right end of the piston passes over the exhaust port. That is, the air pressure in the right chamber of the cylinder block suddenly drops, so that the pressure of the air chamber in the left chamber of the cylinder pushes the valve back, the valve and the valve cabinet are closed, and the return stroke ends. The compressed air enters the left chamber of the cylinder again and begins the next working cycle.


2. Working principle of rotating brazing mechanism


The turning mechanism of the GD28 rock drill is shown in Figure 3.



Structure-3.jpg

Figure 3 The drilling mechanism of the rock drill


1- ratchet; 2-thorn; melon; 4-piston; 5-rotating sleeve;


6-shank sleeve; 7-braker; ┄→ stroke direction of each part;


─→The direction of movement of each part during the return journey


The spiral rod is inserted into the spiral mother in the large end of the piston, and the head is provided with four spines. These spines are against the internal teeth of the ratchet under the action of the tower spring. The ratchet is fixed between the cylinder and the shank by the positioning pin and cannot be rotated. The left end of the rotating sleeve has a spline hole, which cooperates with the spline on the piston, and the right end is fixed with a solder tail sleeve. There is a hexagonal hole in the stalk sleeve, and a hexagonal shank is inserted therein. The entire rotating mechanism is inserted through the cylinder and the head. Since the ratchet mechanism has the unidirectional intermittent rotation characteristic, when the piston strokes, the spiral rod is rotated by a certain angle in the direction indicated by the dashed arrow in FIG. 3 by the action of the spiral female on the large head of the piston. In this case, the spiny is in the cog position, which compresses the spring and rotates with the auger. When the piston returns, the spine is in the reverse tooth position, and under the action of the tower spring, it resists the spiral internal teeth and prevents the spiral rod from rotating. At this time, due to the action of the spiral mother, the piston is forced to rotate along the spiral groove on the spiral rod in the direction indicated by the solid line in FIG. 3 during the return stroke, thereby driving the rotating sleeve and the solder tail sleeve to rotate the drill by an angle. In this way, the hammer rotates once for each impact of the piston. The angle of each rotation of the drill is related to the lead of the spiral bar and the stroke of the piston.


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