RU2393018C1 - Method of material crushing - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to machine building. Proposed method comprises crushing of material by pressure in the gap between rotor and base surface. Radial force is applied to rotor that moves freely radially to make it come in contact with support surface. Material is fed into crusher and rotor runs at angular speed ω, angular frequency Ω of rotor radial vibrations is measured. Contact force and torque are set to keep Ω/ω ratio approximating to r/(R-r) ratio where R and r are, respectively, radii of support surface and rotor at the point of their contact.

EFFECT: increased pressure of rotor on crushed material.

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Description

Technical field

The invention relates to the field of engineering, namely to grinding devices (mills, crushers) with a rotating working element-rotor, and can be used in technological processes of grinding material with high pressure and abrasion.

State of the art

A known method of grinding material by crushing in the gap between a rotating rotor and a supporting surface, which is implemented, for example, in cone crushers described in the book by E.E. Andreev and O. Tikhonov "Crushing, grinding and preparation of raw materials for enrichment", St. Petersburg State Mining Institute, St. Petersburg, 2007, p. 28-48. The material is ground in them in the gap between the conical supporting surface and the conical rotor, which is run on this surface due to the eccentric rotor drive (Fig. 1.3.2) or the unbalance mounted on the rotor (Fig. 1.3.10). The disadvantage of grinding material in cone crushers is that the implementation of high destructive pressure on the material requires a very complex and metal-intensive design (large spherical and cylindrical plain bearings with appropriate lubrication and cooling systems, powerful gearboxes). The consequence of this is the limitation of the speed of rolling the cone, which limits the fineness of the crushed material. There is also a method of grinding, adopted as a prototype, based on the increase in pressure on the material using a rotating rotor with a small mass due to the gyroscopic moment arising from its angular displacement. A description of this method is given in the book of K. Magnus “Gyroscope. Theory and application ", publishing house" Mir ", M., 1977, p.107-108, Fig.3.11. Figure 1 shows a simplified diagram of such a crushing mill with runner rotors in the form of a ball 1 (only one is shown in the figure) and a base (mill bowl) 2. The rotor rolls along the base (due to their contact in the initial period due to gravity ) when transmitting rotation from the drive shaft 3 through the hinge Ш and the rod A. The force of the normal pressure of the rotor due to the gyroscopic moment in the prototype is equal to:

where m is the mass of the rotor 1,

r is the radius of the rotor ball,

ω is the angular velocity of the drive shaft 3.

The disadvantage of this prototype method is a small degree of increase in pressure on the supporting surface (material) with the complexity of the design.

SUMMARY OF THE INVENTION

The objective of the invention is to significantly increase the pressure of the rotor on the crushed material at a high speed of rolling around the rotor. It was solved due to the fact that a rotor with freedom of radial movement is applied with a radial force until it contacts a round supporting surface, then, when the material is fed, the rotor is rotated with an angular frequency ω, the angular frequency Ω of its radial vibrations is measured, and the contact force is set and torque maintain the ratio Ω / ω close to the ratio r / (Rr), where R and r, respectively, are the radii of the supporting surface and the rotor at the point of contact.

List of figures and drawings

The invention is illustrated by drawings.

Figure 1 schematically shows an element of a crushing mill prototype using a gyroscopic effect to increase the pressure of the working body - the rotor.

Figure 2 shows the structural diagram of the grinder, which implements the proposed method.

Figure 3 explains the physical nature of the proposed method.

The proposed method of grinding material by pressure in the gap between the working body - the rotating rotor 1 (figure 2) and the round supporting surface of the housing 2 consists in applying a radial to the rotor having freedom of radial movement (due to the installation of its shaft 3 in a spherical bearing 4) force F from the force sensor 5 (for example, in the form of an electromagnetic device) to contact with the supporting surface of the housing 2. When feeding material into the gap between the rotor and the supporting surface, the rotor is rotated with an angular frequency ω, meas they select the angular frequency Ω of its radial vibrations (the break-in frequency is due to the shaft 3 position sensor combined with the electromagnetic device 5) and the task (regulation) of the force F, which determines the contact force of the rotor with the supporting surface, and the torque applied to the shaft 3 from the engine ( not shown), maintain with an accuracy of 10% the ratio of Ω / ω to the ratio r / (Rr), where R and r, respectively, are the radii of the supporting surface and the rotor at the point of contact.

The proposed method is based on the phenomenon of rolling in the safety bearing of a rotor rotating in a non-contact (for example, electromagnetic) bearing during an emergency failure of this bearing (Yu.N. Zhuravlev. Active magnetic bearings, Polytechnic Publishing House, St. Petersburg, 2003, p. 187). This phenomenon often leads to the destruction of a non-contact bearing, in connection with which various measures are taken to exclude it, for example, the use of simultaneous contact of the rotor with the external and internal supporting surfaces (E. A. Artyukhov et al. Speed limiter for rotor break-in, Gyroscopy and Navigation magazine ”, No. 3 (30), 2000). To prevent break-in in non-contact bearings, they tend to the minimum possible coefficient of friction of interacting surfaces.

According to the proposed method of grinding the material, on the contrary, the run-in is created and maintained using the natural friction force due to the high coefficient of friction of the rotor in the dry grinding material and specially applied external force.

In Fig. 3, a rotor 1 rotating with an angular velocity ω is introduced through the material to be crushed into contact K with the supporting surface of the housing 2 (at initial start-up due to the application of force F). The friction force initially arising at point K tangential to the rotor surface leads to additional rotation (rolling) of the rotor along the supporting surface with an angular velocity Ω relative to the center O with a radius O-O _p equal to (Rr). With an ideal run-in of the rotor (without sliding), the condition that the sum of the linear velocities of the rotation and the run-in of the rotor is equal to zero:

from which it follows that the maximum rolling speed for a given geometry (if we neglect the thickness of the layer of crushed material) is equal to:

In this case, the normal pressure of the rotor 1 with a mass m on the surface of the housing 2 will be:

The actual grinding process occurs with some sliding of the rotor relative to the supporting surface, i.e. with the consumption of energy for grinding, when the real frequency (speed) of the run-in and normal pressure satisfy the conditions:

According to the proposed method, by setting the contact force and torque (which also determines the dispersion of the finished product and the performance of the installation), the following conditions are maintained:

The normal pressure force of the rotor on the material will be:

Moreover, Npean >> F. This means that the magnitude of the force F matters only at the initial stage of the run-in excitation and in case of violation of condition (7).

A comparison of formulas (1) and (7) at the same speeds ω, masses m and radii r of the rotors according to the proposed method and prototype for small values (R-r) gives:

from which it follows that the normal pressure force on the material according to the proposed method is many times higher than the similar pressure in the prototype. For example, with R = 52 mm and r = 50 mm. Nreal / Npr≈60, i.e. the pressure force of the proposed method is tens of times greater than the gyroscopic pressure force on the material in the prototype. Moreover, the implementation of the design of the mill device according to the proposed method is much simpler.

Claims (1)

A method of grinding material by pressure in the gap between a rotating rotor and a circular supporting surface, characterized in that a radial force is applied to the rotor having freedom of radial movement before contact with the supporting surface, when the material is fed, the rotor is rotated with an angular frequency ω, the angular frequency is measured Ω of its radial vibrations, and by setting the contact force and torque, maintain the ratio Ω / ω close to the ratio r / (Rr), where R and r are respectively the radii of the supporting surface and the rotor in the place of their contact KTA.

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