RU180678U1 - Two-mass resonant vibrating screen - Google Patents

Abstract

The device relates to vibration technology and can be used in all industries for separation processes into fractions of lumpy and bulk materials, the solid phase of pulps and suspensions into products of various sizes, as well as their transportation using sieving surfaces. The main field of application for vibrating screens is the mining and processing industry. The task is to create a new energy-saving vibrating screen using combination parametric resonance, which allows to expand the functional and operational capabilities. The technical result is to achieve high stability of resonant vibrations in the system, which can significantly increase the efficiency and speed of screening at low energy costs. Two-mass vibrational resonance This roar is characterized in that the means for exciting and maintaining stable working resonant vibrations is a pair of self-synchronizing parametric vibration exciters installed on one of the working bodies of the vibrating screen, due to the use of buffer elements mounted on both working bodies, the system implements a stable vibration-shock mode of vibration, which allows significantly increase the peak acceleration on the screening surface of the working body installed on the working bodies b Fernie elements are designed as rigid stops onto which the elastic covering.

Description

The device relates to vibration technology and can be used in all industries for separation processes into fractions of lumpy and bulk materials, the solid phase of pulps and suspensions into products of various sizes, as well as their transportation using sieving surfaces. The main field of application for vibrating screens is the mining and processing industry.

Most modern designs of vibrating screens operate in a resonant mode of vibration, and the vibrations are excited by an unbalanced vibrator. A large reactive power circulating in the oscillatory system of such machines is necessary to overcome inertial forces, which reduces their energy efficiency. Increasing productivity and reducing energy costs of a vibrating screen is possible due to the phenomenon of resonance. In the resonant mode of operation of the vibrating machine, the elastic and inertial forces are mutually balanced, while the energy of the vibration exciter is spent only on overcoming dissipative forces, and the working body makes a movement close to its own. The main difficulty in the practical use of resonant vibration machines is their high sensitivity to changes in the technological load and parameters of the oscillatory system.

As a prototype, a two-mass model of a vibrating screen with a resonant tuning is adopted, containing two working bodies connected with each other and with the foundation by elastic systems. Two inertial (unbalanced) vibrators with directed driving force are fixed on the box of the lower working body. [Weisberg L.A. Design and calculation of vibrating screens. .M .: Nedra, 1986, p. 18, tab. one.].

The prototype has the following disadvantages:

• In the two-mass model with the resonant tuning, only one mode of vibration is used to ensure the technological process, and two masses are used only to increase the area of screening surfaces.

• Constant clogging of the cells of the screening surface, which leads to a decrease in screening efficiency. To clean screening surfaces, the process must be stopped.

• Out-of-resonance mode of operation implies the use of engines whose power is 4-5 times higher than the power required to operate in the out-of-resonance zone in order to slip through the region of intense resonant oscillations.

• Low peak accelerations on the screening surface of the working body, which affects the productivity and quality of screening.

• Irrational use of low-frequency modes, since for this it is necessary to significantly increase the mass of unbalances to obtain the necessary driving force. This leads to an increase in the load on the bearings of the exciter, which significantly reduces their service life.

• When setting the vibration exciter in a resonance way, the energy generated by the rotation of the unbalance is spent not only on overcoming the friction forces, but also the inertia forces of the masses included in the oscillatory system.

These shortcomings can be eliminated by the proposed solution. The task of creating a new energy-saving vibration screen using Raman parametric resonance, which allows to expand the functional and operational capabilities.

The technical result is the achievement of increasing the stability of resonant vibrations in the system, which can significantly increase the efficiency and speed of screening, at low energy costs.

The technical result is achieved by the fact that in a two-mass vibrational resonant screen, the means for exciting and maintaining stable working resonant vibrations is a pair of self-synchronizing parametric vibration exciters mounted on one of the working bodies of the vibrating screen, buffer elements are installed on both working bodies and are made in the form of rigid stops, on which an elastic coating is applied.

The two-mass model of the vibrating screen shown in FIG. 1, consists of two working bodies (boxes) of mass m ₁ , m ₂ (upper 1 and lower 2, respectively), held by the main 3, rigidity with ₁ , and auxiliary 4, rigidity with ₂ , elastic bonds. Auxiliary elastic ties made in the form of springs are mounted on a fixed base 5, which is rigidly attached to the foundation 6. Moreover, the stiffness of the main springs is much higher than the stiffness of the auxiliary springs, which allows the necessary vibration isolation of the base. Two vibrators 7 are mounted on the working body 1 so that the driving force passes through the center of mass of the working body. As a vibrator, a parametric resonant vibration exciter is used [Antipov V.I. Vibration exciter: Patent No. 2072661 of the Russian Federation MKI V06V 1/16 // Bull. No. 3, 1997]. Also, buffer elements 8 are installed on both working bodies of the screen. Previously, buffer elements were used as limiters of the oscillation amplitude or to create a piecewise linear characteristic of elastic force. In the proposed screening model, they are used to implement a vibration-shock mode of operation, the implementation of which will significantly increase peak accelerations on the grids, which in turn will solve the problem of clogging the screen grids and increase the screening speed. As buffer elements, stops with an elastic coating are used. Due to the high stability of the resonant mode of oscillation, buffer hits against each other do not lead to a loss of oscillation stability.

 In the general case, the working bodies 1 and 2 of the vibrating screen perform spatial oscillations, however, in the resonant (working) mode it can be considered as a system that performs unidirectional vibrations. The necessary form of the trajectory of the working body is provided by the unidirectional rigidity of the main elastic system and due to the synchronous operation of two vibration exciters. The coordinated work of two vibration exciters on the working body 1 is achieved thanks to the generalized principle of self-synchronization, which is based on the principles of self-synchronization such as unbalanced rotors and Huygens synchronization.

, где $${\lambda }_1,{\lambda }_2$$

– парциальные собственные частоты маятников ИЭ и рабочего органа соответственно. При этом $${\lambda }_1=\nu \omega$$

, где ν определяется только свойствами и габаритами самого диска ИЭ, т.е. изменение зоны резонанса и частоты колебаний рабочего органа возможно за счёт изменения свойств и габаритов диска ИЭ. Vibrating screen works as follows. During the uniform rotation of the rotors of inertial elements (IE) with frequencies close to the resonant frequencies in the opposite direction, the oscillations of the working body 1 are excited, which in turn begins to swing the working body 2. When the rotors rotate on an oscillating working body according to the principle of self-synchronization, the rotation frequencies are aligned “Invisible unbalances” arising from the rolling of rolling elements along racetracks. The IE rotor with a developed moment of inertia plays the role of a flywheel and a kinetic energy accumulator. When the machine enters the resonance region, oscillations in the system begin to be excited at frequencies λ ₁ and λ ₂ associated with the frequency of parametric excitation (rotor speed) ω by the relation $$\omega ={\lambda }_{\mathrm{one}}+{\mathrm{<figure-callout\; id="2"\; label="\lambda "\; filenames="00000005.png"\; state="\{\{state\}\}">\lambda </figure-callout>}}_2$$

where $${\lambda }_{\mathrm{one}},{\lambda }_2$$

- partial eigenfrequencies of the IE pendulums and the working body, respectively. Wherein $${\lambda }_{\mathrm{one}}=\nu \omega$$

, where ν is determined only by the properties and dimensions of the IE disk itself, i.e. changing the resonance zone and the oscillation frequency of the working body is possible due to changes in the properties and dimensions of the IE disk.

The operating mode of a two-mass vibrating screen includes two areas with different forms of vibrations. The first mode of vibration, in which both working bodies oscillate in the same phase, is applicable when screening materials at low frequencies and with good throughput of the screening surface. The second form of oscillation, in which the working bodies move in antiphase, is applicable for screening sticky and difficult to sift materials, leading to constant clogging of the cells of the sifting surface. To start the mode according to the first form of oscillations, it is necessary to enter the machine into the first resonance region. To start the mode in the second mode of vibration, it is necessary to increase the frequency of rotation of the motors in order to exit the operating mode with the first waveform and enter the second resonance zone. Thanks to the buffer elements mounted on the boxes in the second resonance zone, the machine implements vibration shock mode. During the maximum approximation of the working bodies, a collision of buffers occurs, which leads to a sharp increase in peak acceleration on the surfaces of the working bodies. High peak accelerations can significantly improve the process of passage of the material through the screening surface and solve the problem with clogging of cells. To stop the screening process, it is enough to remove the machine from the resonance region, which will significantly reduce the time to stop the technological operation. When using classic unbalanced vibrators, vibrations in the system will be present until the rotation of the vibrator motor is completely stopped.

The proposed two-mass resonant vibrating screen has important advantages that give the machine new qualities.

1. High stability of resonant oscillations of the working body of large amplitude at low frequencies.

2. The implementation of vibro-shock mode of operation significantly increases peak accelerations on the screening surface of the working body, which allows to solve the problem of clogging of cells and, as a result, to improve the quality and speed of screening.

3. The ability to work two working bodies both in one phase and in antiphase without additional settings, only by changing the working area. Antiphase vibrations allow you to implement vibration-shock mode, without stopping the process.

4. A wide resonance zone allows you to change the frequency and amplitude of the oscillations in significantly greater limits than the unbalanced resonant screen. This allows you to control the process only by changing the generation frequency.

5. The resonant screen is characterized by low power consumption and high efficiency of the machine compared to resonant vibrating screens using unbalanced vibration exciters.

The analysis shows that the proposed solution meets the criteria of “novelty” and “industrial applicability”.

Claims (1)

Two-mass vibrational resonant screen, characterized in that the means for exciting and maintaining stable working resonant vibrations is a pair of self-synchronizing parametric vibration exciters installed on one of the working bodies of the vibrating screen, buffer elements mounted on both working bodies and made in the form of rigid stops on which elastic coating applied.

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