CN219483439U - Grain size screening machine for corn grits - Google Patents

Abstract

The utility model relates to the technical field of corn grain size screening, in particular to a corn grits grain size screening machine, which uniformly spreads piled corn grains through a magnetic attraction device, adsorbs metals in the corn grains and reduces metal mixing during discharging; dust in the corn kernels is blown up through the sand screening device, fine particles are screened out, and the practicability of the equipment is improved; dust floating in the box body is collected through the dust falling device, so that impurities in corn kernels and dust in the box body are reduced, and the environmental protection of the equipment is improved; the corn grains are rapidly screened according to the size through the grain size screening device, so that the production efficiency of the equipment is improved; comprises a machine body and a screening device, wherein the screening device is arranged on the machine body; the device also comprises a box body, a magnetic attraction device, a sand and stone screening device, a dust fall device and a particle size screening device.

Description

Grain size screening machine for corn grits

Technical Field

The utility model relates to the technical field of corn particle size screening, in particular to a corn particle size screening machine.

Background

The utility model discloses a corn grain size screening device, which is characterized in that corn grains of good grain crops need to be separated according to the size before corn sowing, so that corn grains of the same batch are uniform in size, sowing is not missed, and corn grains with similar sizes are high and uniform after seedling emergence, so that precision sowing is convenient, the corn grains need to be screened through mechanical equipment, and the corn grain size screening device disclosed in the patent of the utility model with the publication number of CN201220530037.1 in the prior art comprises a machine body and a screening device, can be used for screening the corn grains according to the grain size rapidly, and has good screening effect; however, the above-mentioned devices have the following problems in practical use: in the first screening process, equipment vibration drives corn kernels to vibrate to generate a large amount of smoke dust, so that the health of operators is endangered; second, in the course of a large number of sieves, the screening board does not set up edge protection, and the kernel of corn can drop to the equipment periphery and cause extravagant increase operating personnel's intensity of labour.

Disclosure of Invention

In order to solve the technical problems, the utility model provides a magnetic device for uniformly spreading piled corn grains, adsorbing metals in the piled corn grains and reducing metal mixing during discharging; dust in the corn kernels is blown up through the sand screening device, fine particles are screened out, and the practicability of the equipment is improved; dust floating in the box body is collected through the dust falling device, so that impurities in corn kernels and dust in the box body are reduced, and the environmental protection of the equipment is improved; the corn grains are rapidly screened according to the size through the grain size screening device, and the production efficiency of the equipment is improved.

The utility model relates to a corn grits grain size screening machine, which comprises a machine body and a screening device, wherein the screening device is arranged on the machine body; the device comprises a box body, a magnetic attraction device, a sand screening device, a dust fall device and a particle size screening device, wherein the magnetic attraction device is arranged on the box body and is used for leveling feeding and screening out metals in the feeding; the sand and stone screening device is arranged on the box body, blows dust in the raw materials and screens out fine impurities; the dust falling device is arranged on the box body and collects dust floating in the box body; the grain size screening device is arranged on the box body, screens the corn grains according to the size and sends out the corn grains out of the equipment; uniformly spreading the piled corn grains through a magnetic attraction device, adsorbing metal in the piled corn grains, and reducing metal mixing during discharging; dust in the corn kernels is blown up through the sand screening device, fine particles are screened out, and the practicability of the equipment is improved; dust floating in the box body is collected through the dust falling device, so that impurities in corn kernels and dust in the box body are reduced, and the environmental protection of the equipment is improved; the corn kernels are rapidly screened according to the size through the particle size screening device, so that the production efficiency of the equipment is improved.

Preferably, the box body comprises a screening box, supporting legs, a vibration motor and a feeding table, wherein a plurality of groups of supporting legs are connected with the lower end face of the screening box, the vibration motor is arranged in the middle of the lower end face of the screening box, the front end of the screening box is provided with a feeding hole, the feeding table is arranged on the feeding hole, and the rear part of the screening box is inclined downwards; the corn kernels are placed on the feeding table, the vibrating motor is started, and the vibrating motor drives the bottom of the screening box to vibrate, so that the corn kernels slide into the rear part of the screening box.

Preferably, the magnetic attraction device comprises a first gear motor, a leveling shaft and magnets, wherein the first gear motor is arranged at the front part of the left end face of the screening box, the leveling shaft is arranged at the front part in the screening box, the left end face of the leveling shaft penetrates through the left end face of the screening box to be connected with the output end of the first gear motor, and a plurality of groups of magnets are arranged on the leveling shaft; the first gear motor is started, the first gear motor transmits power to the leveling shaft to drive the leveling shaft to rotate, the rotating leveling shaft drives the magnet to level the piled corn kernels, metal scraps therein are adsorbed, metal mixed in the corn kernels is reduced, and the practicability of the equipment is improved.

Preferably, the sand screening device comprises a sand box, a box door, a plurality of groups of sand screening holes, a reinforcing plate, an air cylinder, a mounting plate, a limiting rod, a thimble and a sand screening baffle block, wherein the sand screening baffle block is mounted at the middle part of the inner bottom of the screening box, a plurality of groups of sand screening holes are formed in the front side of the sand screening baffle block, the front end of a vibrating motor is provided with the sand box, the reinforcing plate is mounted at the front end and the rear end of the sand box, the box door is mounted at the lower end of the sand box, the middle part in the sand box is provided with a supporting plate, the fixed end of the air cylinder is connected with the upper end surface of the supporting plate, the mounting plate is connected with the mounting plate, the plurality of groups of limiting rods are mounted at the upper end surface of the mounting plate, the limiting rods can be connected onto the lower end surface of the screening box through the sand screening holes, and the lower part of the limiting rods penetrate through the lower part of the mounting plate to limit the mounting plate; the sand screening stop block is used for blocking corn kernels to enable the corn kernels to be piled on the upper side of the sand screening hole, fine particles in the corn kernels are piled on the bottom of the sand screening hole through vibration of the vibration motor to fall into a sand box, when the sand screening hole is blocked by the corn kernels, the cylinder is opened, the cylinder stretches to enable the thimble to penetrate through the sand screening hole to dredge the sand screening hole, and the sand box is reinforced through the reinforcing plate, so that stability and practicability of equipment are improved.

Preferably, the dust settling device comprises a first fan, a dust collecting box, a filter screen, a second fan, an air pipe and a dust collecting head, wherein the first fan is arranged on the front end face of the reinforcing plate, the output end of the first fan penetrates through the reinforcing plate and sand Dan Xiang to be communicated with the inside of the sand and stone box, the dust collecting box is arranged on the upper end face of the screening box, the rear part of the upper end face of the screening box is connected with the air pipe, the dust collecting head is connected on the lower end face of the air pipe, the upper end face of the air pipe penetrates through the upper end face of the screening box to extend to the inner front part of the dust collecting box, the filter screen is arranged in the inner middle of the dust collecting box, and the second fan is arranged on the rear end face of the supporting leg; the first fan is started, the first fan conveys air to the inside of the sand box, dust in corn kernels is blown up through the sand screening holes, then the second fan is started to pump out the air in the dust box, the dust in the screening box is input into the dust box through the air pipe by the dust collecting head, and then the dust is filtered through the filter screen, so that the dust in the screening box is reduced, and the environmental protection performance of equipment is improved.

Preferably, the particle size screening device comprises a plurality of groups of screening baffles, a plurality of groups of small particle size screening holes, a plurality of groups of large particle size screening holes, a discharging box, a discharging hopper, a plurality of groups of rollers, a conveyor belt, a second gear motor and a discharging pipe, wherein the rear part of the bottom end in the screening box is provided with a plurality of groups of small particle size screening holes and a plurality of groups of large particle size screening holes, the small particle size screening holes are positioned at the front sides of the large particle size screening holes, a plurality of groups of screening baffles are arranged between the two groups of small particle size screening holes and between the two groups of large particle size screening holes, the rear part of the lower end surface of the screening box is provided with the discharging box, the inside of the discharging box is divided into a front part and a rear part through the baffles, the front part of the discharging box and the lower end surfaces of a plurality of groups of small-particle-size screening holes, the rear part of the discharging box is provided with a plurality of groups of large-particle-size screening holes, the front end surface and the rear end surface of the inside of the discharging box are respectively provided with a discharging funnel, a second gear motor is arranged on the rear end surface of the discharging box, the output end of the second gear motor penetrates through two groups of rollers respectively positioned at the front part and the rear part of the inside of the discharging box to extend to the front end surface of the discharging box, a plurality of groups of rollers are arranged inside the discharging box, two groups of conveyor belts are respectively sleeved on the plurality of groups of rollers at the front part and the rear part of the inside of the discharging box, and a discharging pipe is arranged behind the large-particle-size screening holes; the corn kernels are piled on the small-grain-size screening holes and the large-grain-size screening holes through the screening baffle, the corn kernels fall into the discharging box according to the size through equipment vibration, the discharging hopper of the discharging box is concentrated onto the conveying belt, the second gear motor is started, the second gear motor drives the rollers to rotate through power transmission, the conveying belt rotates to output the corn kernels which are separated according to the grain sizes, and large sundries which cannot be screened out from the corn kernels are discharged out of the equipment through the discharging pipe, so that the working efficiency of the equipment and the practicability of the equipment are improved.

Compared with the prior art, the utility model has the beneficial effects that: uniformly spreading the piled corn grains through a magnetic attraction device, adsorbing metal in the piled corn grains, and reducing metal mixing during discharging; dust in the corn kernels is blown up through the sand screening device, fine particles are screened out, and the practicability of the equipment is improved; dust floating in the box body is collected through the dust falling device, so that impurities in corn kernels and dust in the box body are reduced, and the environmental protection of the equipment is improved; the corn kernels are rapidly screened according to the size through the particle size screening device, so that the production efficiency of the equipment is improved.

Drawings

FIG. 1 is a schematic view of a first cross-sectional structure of the present utility model;

FIG. 2 is a schematic diagram of a sand screening device of the present utility model;

FIG. 3 is a schematic view of the axial structure of the present utility model;

FIG. 4 is a schematic view of the magnetic attraction device of the present utility model;

FIG. 5 is a schematic view of a second cross-sectional structure of the present utility model;

the reference numerals in the drawings: 1. a screening box; 2. a support leg; 3. a vibration motor; 4. a feed table; 5. a first gear motor; 6. leveling the shaft; 7. a magnet; 8. a sand box; 9. a door; 10. screening sand holes; 11. a support plate; 12. a reinforcing plate; 13. a cylinder; 14. a mounting plate; 15. a limit rod; 16. a thimble; 17. a screen Sha Dangkuai; 18. a first fan; 19. a dust box; 20. a filter screen; 21. a second fan; 22. an air duct; 23. a dust collection head; 24. screening baffle plates; 25. small particle size screening holes; 26. large particle size screening holes; 27. a discharging box; 28. a discharge hopper; 29. a roller; 30. a conveyor belt; 31. a second gear motor; 32. a drainage tube.

Detailed Description

In order that the utility model may be readily understood, a more complete description of the utility model will be rendered by reference to the appended drawings. This utility model may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

As shown in fig. 1, 2, 3, 4 and 5, the magnetic attraction device, the sand screening device, the dust settling device and the particle size screening device are all arranged on the box body;

firstly, corn is placed on a feeding table 4, then a vibration motor 3 is started, the bottom of a screening box 1 is driven to vibrate through the vibration motor 3 to enable the corn to slide towards the rear part of the screening box 1, then a first gear motor 5 is started, the first gear motor 5 transmits power to a leveling shaft 6 to drive the leveling shaft 6 to rotate, the rotating leveling shaft 6 drives a magnet 7 to level piled corn grains and absorb metal scraps therein, the corn grains are piled in the front part of a sand screening baffle 17, fine grains fall into a sand box 8 through equipment vibration, then a cylinder 13 is started, a thimble 16 is controlled to pass through the sand screening hole 10 to dredge the sand screening hole 10 through repeated extension of the cylinder 13, then a first fan 18 is started, the first fan 18 conveys air into the sand box 8 and blows out the sand through the sand screening hole 10, blowing dust in corn kernels, starting a second fan 21 to pump out air in a dust box 19, inputting the dust in a screening box 1 into the dust box 19 through an air pipe 22 by a dust collecting head 23, filtering the dust through a filter screen 20, sliding the corn kernels to the upper ends of a small-particle-size screening hole 25 and a large-particle-size screening hole 26, enabling the corn kernels to fall into a discharging box 27 according to the size through equipment vibration, intensively falling onto a conveyor belt 30 through a discharging hopper 28 of the discharging box 27, starting a second speed reducing motor 31, transmitting power to a roller 29 by the second speed reducing motor 31 to drive the roller 29 to rotate, so that the conveyor belt 30 rotates to output the corn kernels separated according to the particle size, and discharging larger sundries which cannot be screened out of the corn kernels through a discharging pipe 32;

the box body comprises a screening box 1, supporting legs 2, a vibration motor 3 and a feeding table 4, wherein a plurality of groups of supporting legs 2 are connected with the lower end face of the screening box 1, the vibration motor 3 is installed in the middle of the lower end face of the screening box 1, the front end of the screening box 1 is provided with a feeding hole, the feeding table 4 is installed on the feeding hole, and the rear part of the screening box 1 is inclined downwards;

the magnetic attraction device comprises a first gear motor 5, a leveling shaft 6 and magnets 7, wherein the first gear motor 5 is arranged at the front part of the left end surface of the screening box 1, the leveling shaft 6 is arranged at the front part in the screening box 1, the left end surface of the leveling shaft 6 penetrates through the left end surface of the screening box 1 to be connected with the output end of the first gear motor 5, and a plurality of groups of magnets 7 are arranged on the leveling shaft 6;

the sand screening device comprises a sand box 8, a box door 9, a plurality of groups of sand screening holes 10, reinforcing plates 12, air cylinders 13, mounting plates 14, limiting rods 15, ejector pins 16 and sand screening baffle blocks 17, wherein the sand screening baffle blocks 17 are mounted at the middle part of the inner bottom end of the screening box 1, the plurality of groups of sand screening holes 10 are formed in the front side of the sand screening baffle blocks 17, the sand screening holes 10 are positioned at the front end of a vibrating motor 3, the sand box 8 is mounted at the lower side of the sand screening holes 10, the reinforcing plates 12 are mounted at the front end and the rear end of the sand box 8, the box door 9 is mounted at the lower end of the sand box 8, a supporting plate 11 is arranged at the middle part in the sand box 8, the fixed ends of the air cylinders 13 are connected with the upper end faces of the supporting plates 11, the mounting plates 14 are connected to the moving ends of the air cylinders 13, the upper end faces of the mounting plates 14 are provided with a plurality of groups of limiting rods 15, the limiting rods 15 can be connected to the lower end faces of the screening box 1 through the sand screening holes 10, the lower parts of the limiting rods 15 penetrate through the lower parts of the mounting plates 14 to limit the mounting plates 14;

the dust settling device comprises a first fan 18, a dust box 19, a filter screen 20, a second fan 21, an air pipe 22 and a dust collecting head 23, wherein the first fan 18 is arranged on the front end face of a reinforcing plate 12, the output end of the first fan 18 passes through the reinforcing plate 12 and a sand box 8 to be communicated with the inside of the sand box 8, the dust box 19 is arranged on the upper end face of a screening box 1, the rear part of the upper end face of the screening box 1 is connected with the air pipe 22, the dust collecting head 23 is connected on the lower end face of the air pipe 22, the upper end face of the air pipe 22 passes through the upper end face of the screening box 1 to extend to the inner front part of the dust box 19, the filter screen 20 is arranged in the middle of the dust box 19, and the second fan 21 is arranged on the rear end face of a supporting leg 2;

the particle size screening device comprises a plurality of groups of screening baffle plates 24, a plurality of groups of small particle size screening holes 25, a plurality of groups of large particle size screening holes 26, a discharging box 27, a discharging hopper 28, a plurality of groups of rollers 29, a conveying belt 30, a second reducing motor 31 and a discharging pipe 32, wherein the rear part of the bottom end in the screening box 1 is provided with a plurality of groups of small particle size screening holes 25 and a plurality of groups of large particle size screening holes 26, the small particle size screening holes 25 are positioned at the front side of the large particle size screening holes 26, a plurality of groups of screening baffle plates 24 are arranged between two groups of small particle size screening holes 25 and between two groups of large particle size screening holes 26, the rear part of the lower end surface of the screening box 1 is provided with a discharging box 27, the inside of the discharging box 27 is divided into a front part and a rear part through baffle plates, the front part of the discharging box 27 and the lower end surfaces of a plurality of groups of small-particle-size screening holes 25, the rear part of the discharging box 27 is provided with a plurality of groups of large-particle-size screening holes 26, the front end surface and the rear end surface of the inside of the discharging box 27 are respectively provided with a discharging funnel 28, a second gear motor 31 is arranged on the rear end surface of the discharging box 27, the output end of the second gear motor 31 extends to the front end surface of the discharging box 27 through two groups of rollers 29 respectively positioned at the front part and the rear part of the inside of the discharging box 27, a plurality of groups of rollers 29 are arranged inside the discharging box 27, two groups of conveying belts 30 are respectively sleeved on the plurality of groups of rollers 29 at the front part and the rear part of the inside of the discharging box 27, and a discharging pipe 32 is arranged behind the large-particle-size screening holes 26;

uniformly spreading the piled corn grains through a magnetic attraction device, adsorbing metal in the piled corn grains, and reducing metal mixing during discharging; dust in the corn kernels is blown up through the sand screening device, fine particles are screened out, and the practicability of the equipment is improved; dust floating in the box body is collected through the dust falling device, so that impurities in corn kernels and dust in the box body are reduced, and the environmental protection of the equipment is improved; the corn kernels are rapidly screened according to the size through the particle size screening device, so that the production efficiency of the equipment is improved.

As shown in figures 1 to 5, in the corn grain size screening machine, when the corn grain size screening machine works, corn is firstly placed on a feeding table 4, then a vibration motor 3 is started, the vibration motor 3 vibrates to drive the bottom of a screening box 1 to vibrate so that the corn slides towards the rear part of the screening box 1, then a first gear motor 5 is started, the first gear motor 5 transmits power to a leveling shaft 6 to drive the leveling shaft 6 to rotate, the rotating leveling shaft 6 drives a magnet 7 to level stacked corn grains and adsorb metal scraps therein, the corn grains are stacked at the front part of a screening sand baffle 17, fine grains fall into a sand box 8 through equipment vibration, then a cylinder 13 is started, a thimble 16 is controlled to pass through a sand screening hole 10 to dredge the sand box 10, then a first fan 18 is started, the first fan 18 conveys air to the inside of the screening box 8, dust in the corn grains is blown up through the sand box 10, then a second fan 21 is started to pump air in a dust box 19, the dust in the screening box 1 is pumped out through the dust box 22, the dust in the dust box 23 is conveyed to the dust box 19 through the dust box 22, metal scraps in the dust box are adsorbed, the dust grains are then deposited on the dust box 19, the dust box is discharged through a large-separating box 25, the dust box is discharged through a small hole 30, and the dust grain size is discharged through a large-size reducing motor 30, and the dust box is discharged through a small-size-reducing motor 30, and the dust particle size-reducing device is discharged through a large-size-reducing filter screen 29, and the dust-size-reducing device is discharged through a large-size-free roller hole 30, and the dust-reducing device is discharged through a small-gap hole 30, and the dust-is discharged through a small-gap pipe, and the dust-gap filter, and the dust-is discharged through a dust-gap, according to a dust pipe.

The installation mode, the connection mode or the setting mode of the corn grits grain size screening machine are common mechanical modes, and the corn grits grain size screening machine can be implemented as long as the beneficial effects can be achieved; the first fan 18, the second fan 21, the discharging hopper 28, the second gear motor 31 and the cylinder 13 of the corn grits grain size screening machine are purchased in the market, and the corn grits grain size screening machine can be installed and operated by a person skilled in the art according to the attached use instruction without creative labor of the person skilled in the art.

All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this utility model belongs. The terminology used herein in the description of the utility model is for the purpose of describing particular embodiments only and is not intended to be limiting of the utility model. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

The foregoing is merely a preferred embodiment of the present utility model, and it should be noted that it will be apparent to those skilled in the art that modifications and variations can be made without departing from the technical principles of the present utility model, and these modifications and variations should also be regarded as the scope of the utility model.

Claims (6)

1. A sieving machine for grain size of corn grits comprises a machine body and a sieving device, wherein the sieving device is arranged on the machine body; the device is characterized by further comprising a box body, a magnetic attraction device, a sand screening device, a dust fall device and a particle size screening device, wherein the magnetic attraction device is arranged on the box body and is used for leveling feeding and screening out metals in the feeding; the sand and stone screening device is arranged on the box body, blows dust in the raw materials and screens out fine impurities; the dust falling device is arranged on the box body and collects dust floating in the box body; the grain size screening device is arranged on the box body, and screens the corn grains according to the size and sends out the corn grains out of the equipment.

2. The corn grits grain size screening machine according to claim 1, wherein the box body comprises a screening box (1), supporting legs (2), a vibrating motor (3) and a feeding table (4), wherein the supporting legs (2) are connected with the lower end face of the screening box (1), the vibrating motor (3) is installed in the middle of the lower end face of the screening box (1), the front end of the screening box (1) is provided with a feeding port, the feeding table (4) is installed on the feeding port, and the rear part of the screening box (1) is inclined downwards.

3. The corn grits grain size screening machine according to claim 2, wherein the magnetic attraction device comprises a first gear motor (5), a leveling shaft (6) and magnets (7), the first gear motor (5) is arranged at the front part of the left end face of the screening box (1), the leveling shaft (6) is arranged at the front part in the screening box (1), the left end face of the leveling shaft (6) penetrates through the left end face of the screening box (1) to be connected with the output end of the first gear motor (5), and a plurality of groups of magnets (7) are arranged on the leveling shaft (6).

4. The corn grits grain size screening machine according to claim 2, wherein the grits screening device comprises a grits box (8), a box door (9), a plurality of groups of sand screening holes (10), a reinforcing plate (12), a cylinder (13), a mounting plate (14), a limit rod (15), a thimble (16) and a sand screening baffle (17), wherein the middle part of the inner bottom of the screening box (1) is provided with the sand screening baffle (17), the front side of the screen Sha Dangkuai (17) is provided with the plurality of groups of sand screening holes (10), the sand screening holes (10) are positioned at the front end of the vibrating motor (3), the lower side of the sand screening holes (10) is provided with the grits box (8), the front end and the rear end of the grits box (8) are provided with reinforcing plates (12), the lower end of the grits box (8) is provided with the box door (9), the middle part of the grits box (8) is provided with a support plate (11), the fixed end of the cylinder (13) is connected with the upper end surface of the support plate (11), the moving end of the cylinder (13) is provided with the mounting plate (14), the upper end surface of the mounting plate (14) is provided with the limit rod (15), the upper end of the mounting plate (14) can be connected with the sand screening holes (15) through the sand screening holes (15) at the upper end of the limit rod (15) through the sand screening holes (10) and the upper end of the sand screening holes (10) at the two groups of the sand screening holes (1), the lower part of the limiting rod (15) penetrates through the lower part of the mounting plate (14) to limit the mounting plate (14).

5. The corn grits grain size screening machine according to claim 2, characterized in that the dust settling device comprises a first fan (18), a dust accumulation box (19), a filter screen (20), a second fan (21), an air pipe (22) and a dust collecting head (23), wherein the first fan (18) is installed on the front end face of the reinforcing plate (12), the output end of the first fan (18) penetrates through the reinforcing plate (12) and the sand stone box (8) to be communicated with the inside of the sand stone box (8), the dust accumulation box (19) is installed on the upper end face of the screening box (1), the rear part of the upper end face of the screening box (1) is connected with an air pipe (22), the dust collecting head (23) is connected on the lower end face of the air pipe (22), the upper end face of the air pipe (22) penetrates through the upper end face of the screening box (1) to extend to the inner front part of the dust accumulation box (19), the filter screen (20) is installed in the middle of the inner part of the dust accumulation box (19), and the second fan (21) is installed on the rear end face of the supporting leg (2).

6. The grain size screening machine according to claim 2, wherein the grain size screening device comprises a plurality of groups of screening baffles (24), a plurality of groups of small grain size screening holes (25), a plurality of groups of large grain size screening holes (26), a discharge box (27), a discharge hopper (28), a plurality of groups of rollers (29), a conveyor belt (30), a second speed reduction motor (31) and a discharging pipe (32), wherein the plurality of groups of small grain size screening holes (25) and the plurality of groups of large grain size screening holes (26) are formed at the rear end of the inner bottom end of the screening box (1), the small grain size screening holes (25) are positioned at the front side of the large grain size screening holes (26), a plurality of groups of screening baffles (24) are arranged between the two groups of small grain size screening holes (25) and between the two groups of large grain size screening holes (26), the discharge box (27) is arranged at the rear end of the lower end surface of the screening box (1), the inside of the discharge box (27) is divided into a front part and a rear part by the baffles, the front part of the discharge box (27) and the lower end surface of the plurality of groups of small grain size screening holes (25) are arranged at the rear end of the lower end of the discharge hopper (27) respectively, the output end of the second gear motor (31) penetrates through two groups of rollers (29) which are respectively positioned at the front part and the rear part in the discharging box (27) and extend to the front end face of the discharging box (27), the plurality of groups of rollers (29) are arranged in the discharging box (27), the two groups of conveyor belts (30) are respectively sleeved on the plurality of groups of rollers (29) at the front part and the rear part in the discharging box (27), and a discharging pipe (32) is arranged behind the large-particle-size screening hole (26).