Comparison of principle, structure and milling performance of pendulum mill and vertical pendulum mill

1 hanging pendulum and vertical pendulum mill working principle
1.1 hanging pendulum mill
A schematic diagram of the main body of the pendulum mill is shown in Figure 1. When the main motor power is decelerated by the gear reducer, the driving central shaft and the plum blossom frame fixed on the central shaft rotate, and the grinding roller assembly hingedly suspended on the plum blossom frame rotates around the central axis, and the grinding roller rotates around the grinding roller shaft, Under the action of centrifugal force, the grinding roller swings outward to compress the grinding ring, so that the material scooped by the blade reaches the pulverizing and grinding action. The pulverized powder is blown by the airflow of the blower to the separator above the main machine for separation. The thicker still falls into the main cavity and re-grinds. The particle size meets the requirements of entering the cyclone collector with the wind flow, and is discharged after being discharged through the powder discharge pipe.

1.2 vertical vertical pendulum mill
The schematic diagram of the vertical pendulum mill is shown in Figure 2. When the main motor power is decelerated by the gear reducer, when the driving central shaft and the plum blossom frame fixed on the central shaft rotate, the grinding roller rotates around the central axis under the action of centrifugal force, and also swings parallel to the longitudinal support shaft, so that the grinding roller is oriented The outer ring is pressed against the outer ring to ensure that the grinding roller and the grinding ring are in maximum surface contact. At the same time, the grinding roller rotates around the grinding roller shaft, so that the material scooped by the blade reaches the pulverizing and grinding action therebetween, and the pulverized powder is blown by the airflow of the air blower to the separator above the main machine for separation, and the coarse particle size still falls into the host. Re-grinding in the chamber, the particle size meets the requirements of the wind flow into the cyclone collector, and after collection, it is discharged through the powder discharge tube.

2 structural analysis
2.1 grinding roller assembly
The pendulum type grinding roller assembly is composed of a grinding roller sleeve, a grinding roller shaft, a grinding roller, a cross roller shaft, and a bearing (Fig. 3), and both ends of the cross arm shaft are horizontally suspended on the plum blossom frame through a rubber sleeve.
The vertical longitudinal pendulum roller assembly (Fig. 4) consists of a grinding roller sleeve, a grinding roller shaft, a longitudinal roller shaft and a bearing. The grinding roller sleeve has a double cylinder structure: the upper and lower bearings are equipped with a grinding roller shaft and a grinding roller through the upper and lower bearings. The left and right cylinders are equipped with longitudinal support shafts through the upper and lower bearings, and the two ends of the longitudinal support shaft are vertically fixed on the upper and lower claws of the plum blossom frame.

2.2 host structure
The structure analysis of the main body of the pendulum mill is shown in Figure 5. Due to the limitation of the structural size of the pendulum mill, the contact between the grinding roller and the grinding ring is not good. It can be seen from the figure that the pore size of the grinding ring is too small, the center of the grinding roller deviates by 5 mm, and the grinding roller and the grinding ring are formed. A negative swing angle of 0.5° reduces the radius of gyration R, thereby reducing the grinding force Fg (due to Fg ∝ R). In addition, the abrasive surface is concentrated in the upper corner, which reduces the abrasive surface of the grinding roller, and thus the irrationality of the structural size is an important reason for the low efficiency of the grinding.

It can be seen from the above analysis that the swing radius of the pendulum mill grinding roller assembly is small, the relative grinding force is small, and the contact area is not constant. When the new grinding roller is loaded into the main machine to start grinding, the unit yield is the lowest. With the wear of the grinding roller, the negative swing angle gradually disappears and the output increases. When the grinding roller continues to wear to a certain extent, a positive swing angle is generated. It is lower because of the above.

The mainframe structure analysis of the vertical pendulum mill is shown in Figure 6. It can be seen from the figure that the grinding roller rotates around the central axis under the action of the centrifugal force Fc, and also swings parallel to the longitudinal axis, so that the grinding roller presses the grinding ring outward in parallel, thereby ensuring the maximum surface of the grinding roller and the grinding ring. Contact, and Fc is all converted to a grinding force Fg. From the above analysis, the grinding force and the grinding area of ​​the vertical pendulum mill are constant compared to the pendulum mill, which determines the output of the vertical pendulum mill compared to the output of the pendulum mill. Be high.
3 parameter analysis
The milling efficiency of the pendulum mill has an important relationship with the grinding force of the grinding roller, increasing the grinding force of the roller to the powder layer, which can improve the milling efficiency. The amount of grinding force depends on the weight of the roller assembly, the position of the center of gravity, the geometry of the mainframe, and the rotational speed. The grinding force of the main machine is driven by the central shaft drive to rotate the grinding roller device through the movable fulcrum to generate centrifugal force, which is transmitted to the grinding roller to act on the abrasive. The abrasive slides between the grinding roller and the grinding ring, and is crushed by the grinding roller. . The calculation formula is:

Fc=Σma (1)
Fg=Fch/H (2)
Fc=Kn2mR (3)

Where: K is a constant coefficient; Fc is the centrifugal force; R is the radius of rotation of the center of gravity of the grinding roller assembly; Fg is the grinding force; h is the length from the suspension point to the center of gravity of the grinding roller assembly; H is the suspension point to the grinding The total length of the center of gravity of the roller; n is the speed of the main engine; m is the mass of the grinding roller assembly.
It can be seen from the formula (3) that when the mass m is constant, the main engine speed is increased and the grinding force is increased. For minerals with higher hardness, the output will be significantly improved; but for materials with low hardness, the increase in yield is not very obvious, because with the increase of the speed, the performance of the blade is poor, affecting the formation of the cushion layer, resulting in empty Grinding, severe vibration and noise, the parts are easily damaged, and the grinding surface is reduced when the vibration is large (the contact between the grinding roller and the grinding ring is point contact or line contact due to vibration). Since h/H<1, Fg<Fc, therefore, the grinding force of the pendulum mill is always smaller than the centrifugal force.
The milling efficiency of the vertical pendulum mill has an important relationship with the grinding force of the grinding roller. Increasing the grinding force of the roller to the powder layer can improve the milling efficiency. The amount of grinding force depends on the weight of the roller assembly, the geometry of the mainframe, and the rotational speed. The grinding roller rotates around the central axis under the action of centrifugal force, and also rotates in parallel around the longitudinal support shaft, so that the grinding roller presses the grinding ring outward in parallel, and the centrifugal force is directly converted into the grinding force, that is, Fc=Fg. In addition, the grinding roller presses the grinding ring in parallel with the longitudinal load shaft to ensure that the grinding roller and the grinding ring are in maximum surface contact. For vertical pendulum mills, the grinding force is equal to the centrifugal force.
4 grinding force comparison
The mass ratio of the pendulum and vertical pendulum grinding rolls produced by Guilin Hengda Mining Machinery Co., Ltd. is 1:1.2 (the ratio of design quality); the center of gravity of the pendulum type grinding roller assembly and the center of gravity of the grinding roller to the suspension point The ratio of the distances is h/H = 0.8 (the ratio calculated from the center of gravity). Driven by the same power motor, Fg, vp / Fg, up=1.2×(10/8)=1.5, therefore, the grinding force of the vertical pendulum mill is 1.5 times larger than that of the pendulum mill. .
From the above analysis and calculation, it can be seen that the vertical pendulum mill has a larger grinding force than the pendulum mill, and the grinding area is constant, so the output is high. From the user's use, the vertical pendulum mill can produce about 30% more than the pendulum mill. However, this structure has the problem of sealing reliability, that is, the vertical longitudinal pendulum mill rotates around the longitudinal axis while the grinding roller rotates around the central axis, but the angle of rotation is in the range of 0 to 10 (swing), swinging The frequency is very high, the reliability of the bearing seal on the longitudinal support shaft in the roller device (or the plum blossom frame assembly) is very difficult, the seal is easy to fail, the bearing is powdered, and the maintenance is frequent, thus restricting the equipment. Promotion.