SU1738383A1 - Method for separation of grain blends - Google Patents

Abstract

Use: sorting and separation of grain materials. SUMMARY OF THE INVENTION: The grain mixture is fed to a vibrating sieve, the resulting grating and sublattice fractions are removed, and the sieve holes are periodically cleaned with brushes from the non-working surface of the sieve. The periodicity of cleaning is set equal to the time of injecting particles of the supergun fraction into the sieve aperture, at which the amount of particles ejected over the non-working sieve surface is equal to the limit value, above which it is no longer possible to push the particles onto the working sieve surface during its cleaning. 4 il.

Description

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The invention relates to the sorting and separation of grain materials and can be used in the grain processing, mining and agricultural industries.

The purpose of the invention is to improve the quality of separation.

During operation of the cleaner, not only particles of the oversize fraction stuck in the holes are pushed onto the working surface of the sieve, but also particles of the undersize fraction that, at the time of the meeting with the brush of the cleaner, do not have time to sink into the hole to a sufficient depth. If, for example, at this point in time, the depth of the particle is smaller than its smallest size, the particle will be pushed out of the hole onto the working surface of the sieve. If the specified depth is close to the maximum particle size, the particle is easy

pass through the hole. Consequently, there is a limiting value of a zapastana h, above which it is no longer possible to push the particles onto the working surface of the sieve during its cleaning. For the fraction of long particles, the depth h and the time t of sinking to this depth are substantially greater than for the fraction of the short (ect.). According to the proposed method for separating grain mixtures, the time for dividing particles of the superlattice (long) fraction to a depth h is determined, and the frequency of purification is set equal to the indicated time. Since the indicated time r / k for short particles of the sublattice fraction is shorter than for long particles, they are freely sieved through the sieve. At the same time, the long particles of the superlattice frac- tion cannot pass into the hole, since they have time to penetrate into the hole on the vein of a 1, larger h, than

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high separation quality is guaranteed.

The purpose of the invention is to improve the quality of separation.

FIG. Figure 1 shows the layout of the closed areas of the sieve when the brush is moving; in fig. 2 is a diagram of a particle getting into the hole when interacting with the working body of the cleaner: in FIG. 3 is a computational scheme for determining the boundary value of the particle ejection over the non-working surface of the sieve; in fig. 4 Principle scheme of a sieve mill of a grain cleaning machine with a device for cleaning sieves.

The implementation of the method involves determining the time g zapajani particles of the long fraction in the sieve holes on the boundary value h. For oval particles, the value of h x, and therefore the time t, can be estimated theoretically. Consider for this purpose a scheme for passing an elongated particle through an opening when it interacts with a purifier (Fig. 2). The particle will pass through the hole if, when meeting with a cleaner, it can freely rotate around the point M of contact with the edge of the hole, without hitting the edges at other points. Otherwise, the particle will jam in the hole, and at some point of its interaction with the cleaner, when a force is formed in the required direction, it will be pushed back to the sieve surface. In the design diagram (Fig. 3), the dimensional characteristics of the particles a, b are given as half-sizes (a b), r. R - profile radii. A, B - length and width respectively. The magnitude of the particle boundary

 (one)

To determine the unknown value x, consider triangle A MS. We relate the sides of this triangle using the Pythagorean theorem,

(d - r) 2 (a - r - x) 2 + (R2 - x2 - R + b) 2 (2) Expression (2) gives a quadratic equation for x, which has two positive roots. And the smaller root is equal to the desired value

where / u (a-r) 2 + (R-bf; v R2 + and - (d-chg

v Rz + / and - (d- hG (4)

The magnitude of the larger profile radius is related to other particle sizes as follows: 55

-Hb +

(6)

(it can be easily obtained, considering similarly the triangle 00 A).

With a known h, the time for the particle to drop by the amount of the boundary departure is determined from the equation of particle motion under the influence of gravity, known from the physics course

  h

where g is the acceleration of free fall.

The value of r can also be determined experimentally.

Let time t for the fraction of long particles be Td. During Td, the brush of the cleaner passes through the sieve section bi V rg, where V is the speed of the brush movement (Fig. 1). In this area, none of the long particles can pass through the hole, because it does not have time to dig into it by an amount greater than h. For short particles, a similar region of D2 is significantly shorter. Therefore, before each brush there is a section of width - 02, where only short particles can be sieved. To eliminate the possibility of screening long particles on the whole sieve, the distance between the brushes should be equal to b ;, or, which is the same, set the frequency of brush action at any sieve point equal to the time rd. Thus, according to the proposed method, the time of sinking into the aperture of particles of the oversize fraction is determined by the value of h and the sieve cleaning frequency is set equal to this time.

The implementation of the method will be shown by the example of cleaning the buckwheat seeds from weeds - wild radish. When approximating the seeds of wild radish with an oval with the dimensions a 4 mm and b 2 mm. g 1.2 mm according to the formula (3) taking into account (4) and (5) get h 7.4 mm. After using the formula (6) it is found 0.038 s. Separation of the mixtures according to the proposed method is possible on any grain cleaning machine with flat screens 1 and their cleaning according to the scheme (fig.Z). In order to provide the same speed V of movement of the brushes 2, they are fixed at an equal distance on the flexible endless belt 3, which is tensioned on the drive 4 and driven 5 drums. The separation is advantageously carried out on a sieve with triangular openings.

The process of separation of the mixture according to the proposed method proceeds as follows.

On the found time, t 0.038 s set the necessary frequency of cleaning. To do this, set the number of revolutions of the leading drum. so that during the time r the brushes move along the sieve surface by the value of b their distances between them, i.e. so that they move with a speed of V b / g. For example, when b 20 cm, the speed of movement of the brushes should be equal to V 5.2 m / s. Grain mixture is fed to the sieve. Buckwheat seeds (undercut fraction) pass freely through the holes, as this requires time, less than 0.038 s. It takes time more than t to pass into the holes of the seeds of wild radish (superstore fraction). Since the frequency of cleaning the holes with brushes does not exceed the value of g, these seeds, when they enter the holes, do not have time to go down there by an amount greater than the limiting value of h and, therefore, are returned by the incoming brushes of the cleaner to the working surface of the sieve. As a result, wild radish is almost completely expelled from the mixture in question.

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FIG.

The proposed method is realized with a layer thickness on the sieve several times larger than the monolayer thickness. Therefore, high separation quality compared with the known method is achieved without loss of productivity.

Claims (1)

Invention Formula The method of separation of grain mixtures, including the supply of the mixture to a vibrating sieve, the output of the resulting grating and undersize fractions and the periodic cleaning of the sieve holes with brushes sides of the non-working surface of the sieve, characterized in that, in order to improve the quality of separation, the time at which the particles of the superlattice fraction sink into the holes is determined the sieve is so large that the amount of their overhang over the non-working surface of the sieve is equal to the limit value, above which it is no longer possible to push the particles onto the working surface of the sieve when it is cleaned, and the cleaning frequency is set equal to the determined time of intake of particles of the above-sieve fraction. / f 1 L / mi / t 2