RU139262U1 - Vibrating Screen - Google Patents

Abstract

1. A vibrating screen containing a box with a vertical axis of symmetry, bounded by sides along the entire perimeter of its bottom, a sifting surface placed on the sides of the box, a supply pipe installed inside the box with a clearance of its lower end relative to the bottom of the box, a casing mounted outside the box intended for collection and continuous unloading of a small product, the drive, characterized in that it contains an additional casing with a pipe for collecting and removing continuously discharged large separation product, mouth the outside of the casing for collecting small product, while the box is rigidly fixed to the casing, which is mounted on soft elastic shock absorbers and is equipped with a vibration drive with two unbalanced vibrators with an adjustable arrangement of their rotation axes and the possibility of fixing the axes in the required position, and the supply pipe is rigidly connected to vibrating box or mounted motionless in space. 2. Vibrating screen according to claim 1, characterized in that it is equipped with an additional screening surface located at the bottom of the box. 3. Vibrating screen according to claim 1, characterized in that the supply pipe has a circular or rectangular cross-section. 4. Vibrating screen according to claim 1, characterized in that the cross-sections of the box can be the same or made in the form of figures having a similarity, whose dimensions are reduced in the direction of the bottom.

Description

The utility model relates to devices for separating bulk materials by size and can be used in the metallurgical, chemical, mining and processing industries, food industry, as well as in agricultural production and in the production of building materials.

Known screens, classifiers and other devices for separating particles of bulk materials by size (hereinafter, in abbreviated form, screens), the screening surfaces of which are in the form of a straight circular cylinder with a vertical axis of symmetry. In addition to gravity, centrifugal forces are used to separate particles in these screens. Two types of such screens are known.

In screens of one type, a cylindrical screen drum rotates around its vertical axis of symmetry (Aut. St. SU 421380, B07B 1/20, publ. 30.03.1974; ed. St. SU 441043, B07B 1/18, publ. 30.08.1974; patent RU 2195371, B04B 03/00, publ. 12/27/2002).

In screens of another type, for example, (Aut. St. SU 242651, B07B 1/20, publ. 04/25/1969; aut. St. SU 1323142, B07B 4/06, publ. 07/15/1987) the vertical screen cylinder is stationary, and a centrifugal effect is created due to the rotation of the device feeding the source material to the inner surface of the sieve drum.

The screens of the two types described above, compared with traditional screens with flat almost horizontally located sieves, have a significantly larger surface area of the sieve per unit area occupied by the screen. However, a significant gain in productivity is not achieved due to the need to feed the starting material onto the sieve with a thin layer. The classification efficiency in these screens is relatively low. This is due to the specifics of unloading a large fraction occurring in the vertical direction under the influence of gravity. Small particles clogging it are also addicted to a large product. The design of these devices also does not solve one of the main problems of operation, screens - the problem of clogging sieve openings.

Known screens with a screening surface in the form of a cone expanding downward, having a vertically located axis of symmetry. The source material is fed to the cone from above along its axis. The movement of the material to the periphery of the screen is either due to the rotation of the conical surface around the vertical axis (patent RU 2184624, B07B 4/06, publ. 10.07.2002; ed. St. SU 1072925, B07B 1/06, publ. 02.15.1984) or due to vibration of the conical surface (Butt A.V., Chumachenko Yu.D. Vibratory separator for hard-to-reach products of the grain processing industry // Storage and processing of grain. - Dnepropetrovsk: LLC IA APK-ZERNO, 2010, No. 11. S. 50-53).

The conical screening surfaces of such screens should be fairly gentle. Therefore, these devices do not give a significant increase in performance compared to the so-called round screens having flat circular screens.

Vibrating screens are also known, in which, unlike those listed above, the screening surface is not a surface of revolution, but consists of two flat screens arranged symmetrically with respect to the vertical plane. These pairs of flat screens are installed either vertically (Aut. St. SU 640766, B07B 1/40, publ. 01/05/1979), or at a slight angle to the aforementioned vertical plane of symmetry (Aut. St. SU 383249. B07B 1/40, publ. 12/22/1967). In these screens, the screening is carried out due to vibration, in which particles of the material alternately undergo collisions with the screening planes. Such designs involve the presence of particles of granular material in the working space in a relatively rarefied, disconnected state. Therefore, the performance of these screens is low, despite the large surface area of the sieves. In addition, the operation of devices in this mode leads to accelerated wear of the sieves and reduces the accuracy of separation.

Closest to the claimed technical solution is a flour sifter (patent RU 2143202, B07B 1/22, publ. 12/27/1967), containing a box with a vertical axis of symmetry, limited to the sides around the entire perimeter of its bottom, a screening surface placed on the sides (side surface) box, the supply pipe installed inside the box with a gap of its lower end relative to the bottom of the box, a casing installed outside the box, designed to collect and continuously unload small product, and the drive.

When the box, which is a cylindrical screen drum, rotates around a vertical axis, the source material is “drawn” from the supply pipe into the working area of the apparatus, distributed over the surface of the sieve and sifted through its cells. A significant disadvantage of the prototype is a semi-continuous mode of operation, in which a small product is unloaded continuously, and unloading large particles is carried out periodically as they accumulate in the working area of the apparatus. To unload a large fraction, it is necessary to stop the apparatus, unscrew the fasteners, remove the supply pipe and carry out a cleaning operation. This reduces the productivity of the device and limits the scope of its application to cases where the proportion of the coarse fraction in the separated material is small, for example, when cleaning the flour from impurities. To solve most other problems associated with the separation of materials by size, this device is not applicable. In addition, the accumulation of a large fraction in the working volume of the apparatus leads to the “blindness” (clogging) of the sieve holes, which reduces the productivity of the apparatus and the separation efficiency.

The tasks to be solved when creating a utility model are a significant increase in the productivity of the screen per unit of area occupied by it, an increase in the separation efficiency due to the low clogging of the screening surface, ensuring the operation of the apparatus in a continuous mode, and expanding its scope.

The tasks are solved as follows.

The vibrating screen incorporates a box with a vertical axis of symmetry, which is limited by the sides around the entire perimeter of the bottom. The screening surface is placed on the sides (side surface) of the box. A feed pipe is installed inside the box through which the material to be shared is fed. There is a gap between the lower end of the pipe and the bottom of the box. Outside the box there is a fixed casing with a pipe for collecting and removing continuously discharged small product. Outside this casing, an additional casing with a nozzle for collecting and removing continuously discharged large product is installed. The box is rigidly mounted on a housing mounted on soft elastic shock absorbers. A vibrating drive is installed on the housing, containing two unbalanced vibrators, each of which is an unbalanced rotor driven into rotation by the engine. It is possible to rotate the axis of the vibrators in space and fix the vibrators in the selected position. The supply pipe has a circular or rectangular cross section. It can be located close to the side of the box or in another place inside the box. In this case, the supply pipe can be rigidly connected with the vibrating box, or it can be installed motionless in space. The shape of the box is such that its transverse (perpendicular to the vertical axis) sections are either the same or represent similar shapes, for example, circles or rectangles, the dimensions of which decrease in the direction of the bottom. Thus, for example, in the case of circular cross sections of the box, it has the shape of a straight circular cylinder or a straight truncated cone, and in the case of rectangular cross sections, it has the shape of a direct prism or a truncated pyramid.

An additional result in increasing productivity is achieved when the screening surface is placed not only on the sides, but also in the bottom of the box.

The device of the vibrating screen and the principle of its operation are illustrated by the drawings, which show: FIG. 1 - diagram of the vibrating screen; figure 2, a - box in the form of a straight circular cylinder, figure 2, b - its axial section, figure 2, c, d (top view) - options for the shape of the cross section of the supply pipe; figure 3, a - box in the form of a direct prism with a rectangular base, figure 3, b - its axial section, figure 3, c-d - options for the shape of the cross section of the supply pipe and its location in the box; figure 4, a - the shape of the box in the form of a straight truncated cone, figure 4, b - its axial section; Fig 5, a, b - the same for the box in the form of a truncated pyramid with a rectangular base.

The vibrating screen (figure 1) includes: a box 1, limited to the sides 2 around the entire perimeter of its bottom 3, and mounted on the housing 4; soft elastic shock absorbers 5, through which the housing 4 is mounted on a fixed base 6; screening surface 7, placed on the sides 2 of the box; a supply pipe 8 mounted inside the box 1 with a gap of the lower end with respect to the bottom 3 of the box 1; a casing 9 with a pipe 10 mounted outside the box 1 and designed to collect and unload a small product; an additional casing 11 with a pipe 12 mounted outside the casing 9 and intended for collecting and unloading a large product; a vibration drive containing two unbalanced vibrators 13 with an adjustable arrangement of the axes of their rotation and the possibility of fixing the vibrators in the desired position.

Vibrating screen works as follows. The source bulk material is fed into the upper part of the supply pipe 8. Under the action of vibration of the housing 4 and the duct 1, created by two unbalanced vibrators 13, which are driven by separate drive electric motors, the material from the lower end of the duct 8 enters the duct and makes an oscillating and circulating movement. Small particles pass through the openings of the screening surface 7 located on the sides 2 (side surface) of the box, enter the casing 9 and are discharged through the nozzle 10. Large particles, due to the effect of vibrational segregation, the presence of circulation flows and the support of the starting material, are concentrated in the upper part of the vibrating box and through the upper edge of the box enter the casing 11 and unloaded through the pipe 12.

The supply of the source material into the vibrating box through the pipe 8 immersed in it is based on the physical effect associated with the unusual behavior of the granular medium in communicating vibrating vessels (On some “anomalous” effects of the behavior of granular medium in communicating vibrating vessels / II Blekhman, L. A. Weissberg, L.I. Blekhman, V. B. Vasilkov, K. S. Yakimova // Ore dressing. 2007. No. 5. P.36-40). It, in particular, consists in the fact that when the vessel is vibrated with a straight tube open at both ends, the loose medium filling the vessel and the tube flows intensively from the lower end of the tube, entering deep into the vessel. The outflow of material occurs when the tube is rigidly connected to a vibrating vessel, and when it is stationary in space. In addition, as shown by experiments, the supply pipe 8 can be located anywhere in the box, including, close to its board (figure 3, d). The pipe 8 may have various sections, however, their circular and rectangular shapes are most appropriate. The shape of the box may also vary. In particular, the box may take the form of a cylinder (FIG. 2), a prism (FIG. 3), a truncated cone (FIG. 4), a truncated pyramid (FIG. 5). This allows you to modify the design of the screen in relation to specific technological conditions and layout restrictions and in accordance with the objectives of the invention provides an extension of the scope of the device.

The amount of material supplied can be controlled by changing vibration parameters, as well as maintaining a certain higher level of material in the nozzle than in the screening box. In conditions of vibrational "liquefaction" this creates an additional pressure similar to hydrostatic.

The process of separation of particles in the proposed device and continuous (in contrast to the prototype) unloading of a large product based on the use of effects of vibrational segregation.

Firstly, the well-known effect of “floating up” of large particles in an oscillating granular medium is used. Secondly, we use the effect of the predominant motion of small particles in a vibrating granular medium in the radial direction, which we discovered in theoretical calculations and experimentally confirmed, from the center to the periphery, i.e. in this case, to the sides of the box. Large particles are located less densely near the sides of the box, with larger gaps than far from the walls. This contributes to the radial "filtering" of small particles through the large ones in the direction of the sides of the box, their unloading through the holes of the screening surface, the formation of new voids and a constant influx of small particles.

The vibrations of the box 1, mounted on the housing 4, are mainly rectilinear harmonic in the vertical direction or screw, the trajectories of which are directed at an angle to the horizontal bottom 3 of the box. Vertical harmonic vibrations of the body and the box are provided by the location and fixation of the axes of the vibrators in a horizontal plane parallel to each other and the antiphase rotation of the unbalances. To create helical vibrations, the vibrators are fixed in a position in which their axes lie on intersecting straight lines. In this case, the material will, in addition to vibrations, circulate not only in the vertical plane, but also in the planes of the cross sections of the box.

Vibrators are driven by separate electric motors. The vibrational exciters, coordinated in frequency and phase, necessary for the excitation of vertical or helical vibrations, are ensured by the self-synchronization phenomenon (Vibrations in engineering: Handbook in 6 volumes, T.4. Vibration processes and machines. - M.: Mechanical Engineering, 1981. P. 472-473; 486-487).

Elastic shock absorbers 5, through which the housing 4 is mounted on a fixed base 6, are soft. This means that the frequency of natural vibrations λ of the body resting on them is at least 3 times less than the operating frequency ω, that is, the ratio ω / λ> 3 is satisfied. The fulfillment of this condition provides reliable vibration isolation of the screen.

The location of the screening surface on the sides of the screen box allows you to significantly increase its area and to obtain high productivity of the apparatus per unit area occupied by it. For example, if the box and, accordingly, the screening surface are in the form of a cylinder with a diameter D and a height H, then the gain in the sieve area equal to the ratio of the side surface area to the base area will be

.

.

At H = 2D, the sieve area increases by 8 times. Similarly, in the case of a box in the form of a direct prism of height H with a square base with side a , the sieve area will increase by 4H / a times. For example, at H = 2 a, the area of the screening surface will increase by 8 times.

The area of the screening surface can be increased if it is placed not only on the sides of the screen box, but also on its bottom, as in traditional screens. This will further improve the performance of the device.

An important advantage of placing the screening surface on the sides of the screen box is also the self-cleaning effect of the sieve. During vertical or helical vibrations of the box, particles stuck in the side openings of the sieve pop out from them due to the action of the moments of gravity of the particles themselves and constant impacts from other particles in the vertical direction from the bottom and top and in the lateral directions. Low clogging of the screening surface provides increased separation efficiency.

To implement the proposed technical solution, a screen box model was made. It was an open steel cylindrical vessel with a diameter of 120 and a height of 140 mm. Holes with a diameter of 8 mm were made in the side walls and bottom of the vessel. In a number of experiments, the holes in the bottom were overlapped by a solid disk fixed to the bottom. The model of the screen box was fixed on the table of the universal vibration stand 157-US. The stand provided the opportunity to vary over a wide range of amplitude, frequency and shape of the oscillations. An artificial mixture consisting of equal mass amounts of small and large particles (peas with a grain size of 5.5–6.5 mm and nuts about 14 mm in size) was used as a shared material. A series of experiments confirmed the basic operability of the apparatus and the possibility of obtaining high technological parameters. (Under optimal conditions, the extraction of fine particles reached 100%). The optimal vibration parameters were comparable to those used on traditional vibrating screens. In particular, the amplitudes of vibration acceleration amounted to (3 ÷ 5) g, where g is the acceleration of gravity. When operating the model with an open sieve in the bottom of the box, productivity increases, but to a lesser extent than with an equivalent increase in the area of the sieve on the side surface of the box.

In parallel with the experiments, mathematical modeling of the separation process was performed using the EDEM software package that implements the discrete element method. The geometric parameters of the model, vibration parameters, and material characteristics were the same as in experimental studies. The calculations are in good agreement with the experimental results. The calculations confirmed the high separation efficiency in the proposed device and showed the possibility of using computer experiments when choosing optimal conditions for the separation of various specific materials.

Thus, the proposed technical solution ensures the operation of the apparatus in a continuous mode and can significantly increase the performance of the screen per unit of space. It also allows you to minimize clogging of the holes of the screening surface, which is the main factor limiting the area of efficient use of screens, and, thereby, increase the separation efficiency. The possibility of varying the shape of the screen box, as well as the location of the supply pipe and the shape of its section in it, allows you to flexibly adapt the design to specific production conditions, which expands the scope of the device. This is also facilitated by the use of a vibratory drive with an adjustable axis arrangement of unbalanced vibrators.

Claims (4)

1. A vibrating screen containing a box with a vertical axis of symmetry, bounded by sides along the entire perimeter of its bottom, a sifting surface placed on the sides of the box, a supply pipe installed inside the box with a clearance of its lower end relative to the bottom of the box, a casing mounted outside the box intended for collection and continuous unloading of a small product, the drive, characterized in that it contains an additional casing with a pipe for collecting and removing continuously discharged large separation product, mouth the outside of the casing for collecting small product, while the box is rigidly fixed to the casing, which is mounted on soft elastic shock absorbers and is equipped with a vibration drive with two unbalanced vibrators with an adjustable arrangement of their rotation axes and the possibility of fixing the axes in the required position, and the supply pipe is rigidly connected to vibrating box or mounted motionless in space. 2. Vibrating screen according to claim 1, characterized in that it is equipped with an additional screening surface located in the bottom of the box. 3. Vibrating screen according to claim 1, characterized in that the supply pipe has a circular or rectangular cross-section. 4. Vibrating screen according to claim 1, characterized in that the cross-sections of the box can be the same or made in the form of figures having a similarity, whose dimensions are reduced in the direction of the bottom.

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