RU164464U1 - Vibrating Screen - Google Patents

Abstract

1. A vibrating screen containing a frame mounted on elastic supports, on which a supporting box with a bottom and sides is fixed, and a vibrodrive kinematically connected with it, and also containing inclined side screening surfaces approaching in the direction of the bottom, characterized in that the bottom also represents a screening surface and forms with an inclined side screening surface a sieve having the shape of a tray open from the discharge end, while determining the size of the openings of the side screening screen there are fewer surfaces than the determining size of the openings of the bottom of the sieve. 2. Vibrating screen according to claim 1, characterized in that the internal angle of inclination of the planes of the screening surfaces to the plane of the bottom is 110-135 °. 3. Vibrating screen according to claim 1 or 2, characterized in that the determining sizes of the said holes are in the ratio: P / P = 0.7-0.9, where P is the determining size of the holes of the side screening surfaces, P is the size of the holes of the bottom of the sieve .

Description

The invention relates to devices for separating bulk materials by size and can be used in the mining, metallurgical, construction industries, etc.

In vibrating screens, the separation of raw materials by a given size occurs under the influence of vibrations due to the passage of small pieces through a flat horizontal or inclined screen (with discharge into the so-called under-sieve product), and by unloading pieces larger than the size of the holes in the screen, top (oversize product).

In the context of this application, the term "determining the size of the holes" (characteristic size) means: for round holes - its diameter, for square holes - the side of the square, for rectangular - the short side of the rectangle, for regular polygons - the diameter of the inscribed circle, etc. Due to the inappropriateness of using holes with narrow slots for the purposes of this utility model, such holes of a screening surface (sieve) are not considered.

To date, the possibilities of increasing the productivity of vibrating screens by increasing the geometric dimensions of their boxes are practically exhausted, which is due to the limit of their mechanical reliability. Also, the possibilities of increasing the performance of the screens by increasing the frequency of their vibrations have been exhausted. Therefore, around the world, the predominant vibration frequency of the screen box is an oscillation frequency of about 16 Hz, created by vibration exciters equipped with electric drives with a rotor speed of 950-1000 rpm.

Designs of a vibrating screen consisting of a box (supporting structure) based on elastic elements, vibration exciters and a working screening surface are known and widely used. A sieve installed horizontally or at an angle to the horizontal, and made in the form of a plate with a hole size selected for classification, is used as a working surface [Reference “Vibrations in Engineering”, ed. E.E. Lavendela. - M.: Mechanical Engineering, 1981, v. 4, p. 349-352]. Bulk material, moving along the sieve under the action of vibration to the discharge end, is sifted - particles with a particle size less than the determining size of the holes pass through a sieve. One of the representatives of the “classical” type of screens is the GIL 051 Inertial Screen [for information, see the Internet http://vibromotors.ru/files/docs/manuals/astek/11_grohot_inercionnyy_gi1052.pdf]

The relatively low efficiency of separation by size on screens with flat sieves is especially often observed at high specific loads of raw materials entering the sieve, and especially when screening a relatively light material, for example coal. In these cases, screening is forced to take place in a thick layer of material to be separated, and it is obvious that the fine fraction of material to be passed into the lower (sublattice) product must first pass through a layer of larger particles, i.e., pass the stage of vertical vibrational segregation. This naturally reduces the speed and efficiency of the separation of the material on the screen.

Known roar for sifting granular materials, for example, gravel [USSR patent No. 383249, publ. 05/23/1973]. The screen consists of a support frame on which a housing is mounted on elastic elements with screening surfaces mounted at an acute angle to the vertical plane, forming a symmetrical vertically oriented channel, the upper loading window of which is larger than the lower unloading window. The screen is equipped with a vibration exciter installed in such a way that the direction of the disturbing force is perpendicular to the direction of movement of the material. During the operation of the screen, the screened material in free fall passes the screening channel, while small particles are thrown to the inclined screening surfaces under the influence of an exciting force. Coarse material, passing through the discharge opening, falls on the central conveyor located below it, and small particles pass through the inclined screening surfaces and fall on the conveyors running on both sides of the central one. The main disadvantage of this design is the lack of efficiency, due to the fact that not all small particles located in the axial zone of the channel manage to reach the side screening walls, and they fall together with the large particles on the axial conveyor.

An improved design of the screen with inclined screening surfaces is the Vibrating screen described in the patent of the Russian Federation for utility model No. 139262, publ. 04/10/2014. The vibrating screen described in the patent with a vertical axis of symmetry includes: a box, limited to the sides along the entire perimeter of its bottom, and mounted on the body; shock absorbers for installation on the base, a sieving surface placed on the sides of the box; a supply pipe installed inside the box with a gap of the lower end relative to the bottom of the box. Outside the box there is a casing covering it intended for collecting and unloading a small product through an appropriate pipe. An additional casing with a pipe is installed outside the casing and is designed to collect and unload a large product. The screen has a vibratory drive. The vibration screen described in patent No. 139262, namely the example shown in FIG. 5 of the patent, with inclined walls of the screening surfaces converging to the bottom, is selected as a prototype as the closest to the achieved result and as having side inclined screening surfaces. However, the roar described in the prototype is effective only when classifying relatively thin material (less than 1 mm), and is not effective enough for a larger one.

Thus, there is a technical contradiction: reliable and relatively simple vibrating screens with a flat sieve, due to the specifics of the design, are not able to sift the materials poured in a thick layer, and therefore have a relatively low productivity per unit occupied area. On the other hand, vibrating screens with a vertical axis of symmetry are devoid of this drawback, but they have a significantly more complex structure. At the same time, both of them do not have a sufficiently high screening efficiency ε (ε is the weight ratio of the amount of material passing through the holes in the sieve to the amount of material of this size contained in the source material [Encyclopedia of Mechanical Engineering XXL. Machines for the production of non-metallic building materials p. 372. Internet resource http://mash-xxl.info/page/045017191250245058220141228137203150065203237083/])

The utility model is based on the task of expanding the arsenal of tools and creating a new and relatively simple construction of a vibrating screen with increased screening productivity per unit screen area. Achievable technical result - increased screening efficiency.

The problem is solved in that the vibration screen comprises a frame mounted on elastic supports with a supporting box having a bottom and sides. A vibration drive is kinematically connected to the box. The screen also has an inclined side screening surface, approaching each other in the direction of the bottom. It differs from the prototype in that the bottom also represents a screening surface and forms a sieve having inclined lateral screening surfaces with a tray shape open from the discharge end. Moreover, the determining size of the holes of the side screening surfaces is less than the determining size of the holes of the bottom of the sieve.

In a preferred embodiment, the internal angle α of the planes of the screening surfaces to the plane of the bottom is 110-135 degrees.

Also preferred is the observance of the ratio:

P _side / P _day = 0.7-0.9,

Where:

P _side - determining the size of the holes of the side screening surfaces,

R _days - determining the size of the holes of the bottom of the sieve

In order to better demonstrate the distinctive features of the utility model, as examples, not having any restrictive character, the preferred embodiment is described below with respect to the vibrating screen, schematically represented in the Figure.

The vibrating screen incorporates a carrier box 1, with a bottom 2, which at the same time is a screening surface, sides 3 and an end wall 4. The box 1 is mounted on a carrier frame 5, which is mounted on elastic supports 6 and kinematically connected to the vibrodrive 7. Inside the box 1, inclined lateral screening surfaces 8 are fastened together in the direction of the bottom 2. Thus, the bottom 2, or rather its central part adjacent to the inclined side screening surfaces 8, and the inclined surfaces 8 themselves a sieve having the shape of a tray open on the discharge end side and expanding to the top is called. The sides 3 of the box and the side screening surface 8 may be in contact on the upper edge. The determining sizes of the openings of the side screening surfaces and the bottom, their ratio, are given below. Under the carrier box, a collecting box for the under-mesh product (not shown in the Figure) can be installed.

During the operation of the vibrating screen, the bulk material to be screened is fed into the loading part of the screen (from the side of the blind end) through a loading funnel or through a metering feeder (not shown in the Figure). Depending on the properties of the material (coarseness of fractions, humidity, bulk density, etc.), the layer thickness can reach 0.3 side height 3 boxes. Under the action of the vibration created by the vibrodrive 7, a small class of material passes through the openings of the bottom 2 of the sieve and the holes of the side screening surfaces 8 and is unloaded into a collecting box for the under-sieve product, and a large fraction of bulk material passes through the sieve and is unloaded through its open end.

Below are examples of implementation and tables confirming the achievement of the stated result and the significance of the signs. The tests were subjected to a vibrating screen with orbital vibrations of the box with a frequency of 16 Hz, the supporting box (and, accordingly, the sieve) was located at an angle of 14 degrees to the horizon plane with a slope towards the discharge side. The area of the mirror box in the horizontal projection (projection on a horizontal plane) is 0.5 m ² . The tests were carried out on vibrating screens, both using screens of the design described above - in the form of a tray with inclined side screening surfaces and with holes in the bottom, and identical screens with a flat screen (holes only in the bottom) were tested for comparison, and screens were tested on prototype. In the tables below, experiments with screens with flat screens and experiments with screens of the prototype are marked with the corresponding entries. In this case, experiments were carried out with screening surfaces with both square holes and round ones. In the following table. 1, tab. Figure 2 shows examples using screening surfaces with square holes with a square side (defining size) of 1.6 mm in the bottom, and the size of the holes on the side screening surfaces changed. Using sieves with round holes, similar results were obtained.

A sample of crushed apatite ore with a particle size of less than 5 mm and with a natural moisture content of 4% with a constant output feed rate in the range of 1.00-1.50 t / (m ² / h), which was provided by the use of an adjustable vibrating feeder, was fed to the screen. The layer thickness was 0.2-0.3 the height of the side of the screen. The indicated screening capacity for the initial power supply was calculated on the area of the box mirror 0.5 m ² . Screening efficiency in the class of 1.6 mm was calculated by the conventional method [see Vaysberg L.A., Kartavy A.N., Korovnikov A.N. Screening surfaces of screens. - St. Petersburg, ed. VSEGEI, 2005, p. 22-24].

The influence of the ratio of the determining size of the holes P _side / P _bottom on the screening efficiency is illustrated by the examples given in Table. 1. The data are given for the implementation in which the side screening surfaces are located at an internal angle α = 120 degrees to the plane of the sieve bottom.

As can be seen from Table. 1 the highest screening efficiency in the size class of 1.6 mm is achieved in the range of 0.7 <P _side / P _day <0.9 and reaches, for example, with a feed capacity of 1.0 t / (m ² / hour), values higher 90% At high capacities, this indicator slightly decreases, but in all the examples cited it is 8-10% higher than that of the prototype and approximately the same as that of screens with a flat sieve.

In the table below. 2 shows the influence of the angle of inclination α of the side surfaces of the sieve on the screening efficiency with orbital vibrations of the screen. The experimental conditions are as described above. The results corresponding to the implementation with the determining size of the holes of the side screening surfaces of 1.2 mm or 0.75 units, from the determining size of the holes of the bottom of the sieve, are presented. The power productivity calculated on the area of the box mirror 0.5 m ² was 1.25 and 1.50 t / (m ² / hour). The internal angle of inclination α of the side screening surfaces to the plane of the bottom was varied in the range from 105 to 145 degrees.

As can be seen from Table. 2, the highest screening efficiency (85-91%) is achieved when the internal angle α of the inclination of the planes of the screening surfaces to the plane of the bottom is 110-135 degrees.

A semi-industrial self-synchronizing screen with rectilinear vibrations of the box with a frequency of 16 Hz was also tested, in which the box is located at an angle of 2 degrees to the horizon plane with a bias towards the discharge side. A sample of crushed coal with a particle size of less than 20 mm and with a moisture content of 3% was fed to the screen. The area of the mirror box in horizontal projection is 0.5 m ² .

The tests were carried out using both the sieves of the construction described above - in the form of a tray with inclined side screening surfaces and with holes in the bottom, and for comparison, using flat sieves (holes only in the bottom). Screening surfaces with round holes were used. The diameter of the holes in the bottom (determining the size of the holes) was 5.0 mm, the diameter of the holes of the side screening surfaces was 4 mm or 0.80 units. from the size of the bottom holes. The internal angle of inclination α of the inclined side screening surfaces to the plane of the bottom was changed in the range from 105 to 145 degrees. The power productivity calculated on the area of the box mirror 0.5 m ² was 2.0 and 3.0 t / (m ² / hour). The screening efficiency according to the size class of 5 mm was calculated by the generally accepted method for the output of the specified class into the under-sieve product compared to its content in the initial feed, the values are given in Table. 3.

As can be seen from the data given in Table. 3, the angle of inclination of the side screening surfaces has an effect on screening efficiency, and the results show that this figure is significantly higher than that of the prototype. The best results were obtained with implementations with an inclination angle in the range: 110 <α <135 degrees.

Thanks to this design, the proposed vibrating screen allows high-efficiency classification of raw materials in a thick layer of material and, thus, to increase the specific (per unit area) screen productivity. The technical effect of the proposed solution is based on the physical phenomenon of decreasing sliding friction and internal friction in a mixture of grains of bulk materials with a decrease in the content of grains (fractions) of small size in a polydisperse mixture. Due to this phenomenon, when removing part of the fine fractions through the side inclined surfaces of the sieve into the sieve product during vibratory screening, a whole increase in screening productivity and efficiency is achieved. In addition, the presence of inclined lateral screening surfaces causes a decrease in the thickness of the bulk layer at the peripheral zones of the screening tray tapering to the bottom. That is, the thickness of the bulk layer at the edges of the sieve (over inclined screening surfaces) decreases with distance from the longitudinal plane of symmetry, which also helps to increase the efficiency of screening.

Claims (3)

1. A vibrating screen containing a frame mounted on elastic supports, on which a supporting box with a bottom and sides is fixed, and a vibrodrive kinematically connected with it, and also containing inclined side screening surfaces approaching in the direction of the bottom, characterized in that the bottom also represents a screening surface and forms with an inclined side screening surface a sieve having the shape of a tray open from the discharge end, while determining the size of the openings of the side screening screen there are fewer surfaces than the determining size of the openings of the bottom of the sieve. 2. Vibrating screen according to claim 1, characterized in that the internal angle of inclination of the planes of the screening surfaces to the plane of the bottom is 110-135 °. 3. Vibrating screen according to claim 1 or 2, characterized in that the determining sizes of said holes are in the ratio: P _side / P _day = 0.7-0.9, where P _side - determining the size of the holes of the side screening surfaces, P _days - determining the size of the openings of the bottom sieve.

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