White rice grading screen

Abstract

This utility model discloses a rice grading sieve, belonging to the field of material screening technology. It includes a primary screening component, a secondary screening component, and a primary chute. The primary screening component includes at least two primary screen plates distributed vertically, with the oversize material from each primary screen plate converging at the same outlet. A primary flow plate is disposed below each primary screen plate, with a front opening and a rear opening at both ends for diverting the undersize material from the primary screen plate. The secondary screening component is located below the primary screening component and includes at least one secondary screen plate. Two primary chute pipes are provided: a first primary chute pipe and a second primary chute pipe. The inlet of the first primary chute pipe is connected to the front opening of the primary flow plate, and the inlet of the second primary chute pipe is connected to the rear opening of the primary flow plate. This application can solve the technical problem of clogging easily occurring in rice grading sieves when increasing output.

Description

Technical Field

[0001] This utility model relates to the field of material screening technology, specifically to a rice grading screen. Background Technology

[0002] A rice grading screen is a sorting device commonly used in rice processing production lines. It is primarily used to effectively grade processed rice according to particle size, such as whole rice, broken rice, and small fragments. This type of equipment typically uses the vibration or rotation of the screen plate to naturally separate particles of different sizes during movement, thus achieving the purpose of grading and screening. It is an important piece of equipment for ensuring the quality and economic benefits of rice products.

[0003] The working principle of a white rice grading sieve: Utilizing the difference in grain shape between broken rice and whole rice, overlapping and rotating on a planar rotating sieve surface, friction propels the rice, creating automatic grading. Broken rice is first graded to the bottom layer, where small particles are sieved through the holes in the sieve plate. Larger particles are sieved at the rear of the sieve layer, while whole particles remain on the sieve plate and are collected in a rice hopper. Existing white rice sieves typically use single-layer sieve plates connected in series; the first layer sieves whole rice, the second layer sieves regular rice, and the third layer sieves large and small broken rice, or multiple layers are used in parallel. Each layer has a flow plate to collect the undersize material, which is then mixed and flows to the front of the next sieve plate for further sieving. To increase output, the sieve plates can be made wider and the number of layers increased.

[0004] However, widening the sieve or increasing the number of layers in parallel operation both lead to problems such as uneven material distribution or clogging. Widening the sieve surface results in uneven material distribution; the wider the sieve, the more difficult it is to separate the material evenly, leading to poorer screening performance. Increasing the number of layers, especially when multiple layers are connected in parallel, results in more undersize material, increasing the likelihood of clogging in the material collection hopper and chute. Furthermore, regardless of whether the chute is located at the front or back end, the undersize material is completely mixed before entering the next connected sieve layer for further screening. Thus, each layer's function is merely to separate the oversize material, while the undersize material is completely mixed before entering the next layer. With this sorting process, the more parallel layers there are, the worse the undersize material's performance becomes, and the higher the likelihood of clogging. Utility Model Content

[0005] This invention provides a rice grading sieve to solve the technical problem of clogging that easily occurs when increasing the output of rice grading sieves.

[0006] According to one aspect of the present invention, a rice grading sieve is provided, comprising a primary screening component, a secondary screening component, and a primary chute; the primary screening component includes at least two primary screen plates distributed vertically, the oversize material of the primary screen plates is collected at the same outlet, and a primary flow plate is respectively provided below each primary screen plate, with a front opening and a rear opening at both ends of the primary flow plate for diverting the undersize material of the primary screen plate; the secondary screening component is located below the primary screening component and includes at least one secondary screen plate; two primary chutes are provided, including a first primary chute and a second primary chute, the inlet of the first primary chute is connected to the front opening of the primary flow plate, the inlet of the second primary chute is connected to the rear opening of the primary flow plate, and the outlets of the first primary chute and the second primary chute are respectively connected to different sides of the secondary screen plate.

[0007] Optionally, a front collecting trough corresponding to the front opening and a rear collecting trough corresponding to the rear opening are provided below the primary flow plate. Both the front collecting trough and the rear collecting trough are provided with guide slopes for guiding the material, and the inlets of the first primary chute and the second primary chute are located at the bottom of the corresponding guide slopes.

[0008] Optionally, the guide slope is set with the middle being higher and the two ends being lower. The first-stage chute is set at both ends of the front collecting trough to divert the flow in the front collecting trough, and the second-stage chute is set at both ends of the rear collecting trough to divert the flow in the rear collecting trough.

[0009] Optionally, it also includes a housing, with the primary screening component and the secondary screening component both located inside the housing. The first and second primary chute pipes are detachably installed on the outer wall of the housing. The bottom end of the guide slope extends to the inner wall of the housing, and the housing is provided with a material passage hole for the material to enter the first or second primary chute pipe from the guide slope.

[0010] Optionally, at least two secondary sieve plates are provided, and a secondary flow plate is provided below each secondary sieve plate. The two ends of the secondary flow plate are respectively provided with a front opening and a rear opening for diverting the material under the secondary sieve plate.

[0011] A tertiary screening component is provided below the secondary screening component, and the tertiary screening component includes at least one tertiary screening plate;

[0012] The box body is equipped with two secondary chute pipes, which include a first secondary chute pipe and a second secondary chute pipe. The inlet of the first secondary chute pipe is connected to the front opening of the secondary flow plate, and the inlet of the second secondary chute pipe is connected to the rear opening of the secondary flow plate. The outlets of the first secondary chute pipe and the second secondary chute pipe are respectively connected to different sides of the tertiary screen plate.

[0013] Optionally, the first-stage chute and the second-stage chute have the same structure, both including a shell with an open structure. The open side of the shell is attached to the outer wall of the box, and together with the outer wall of the box, they form a channel for material to pass through.

[0014] Optionally, a sealing edge is provided around the opening on the housing, and the sealing edge is in close contact with the outer wall of the housing and fixed by bolts.

[0015] Optionally, a material leakage hole is provided at the downstream end of the primary flow plate, the material leakage hole including multiple strip grooves extending along the material movement direction.

[0016] Optionally, two material distribution plates are provided on the side of the primary flow plate away from the material leakage hole, with the downstream ends of the two material distribution plates close to each other to form a flow channel.

[0017] Optionally, there are three material leakage holes on the primary flow plate along the length of the primary flow plate, with the middle material leakage hole corresponding to the guide channel.

[0018] In summary, this application includes at least one of the following beneficial technical effects:

[0019] This invention utilizes a flow plate structure with two openings (front and rear) below each primary sieve plate, along with a first-stage chute and a second-stage chute, to initially separate the undersize material according to particle size. During screening, smaller particles on the primary sieve plate pass through first and fall to the front of the flow plate, while larger particles fall to the rear. Smaller particles are directly introduced into the secondary sieve plate through the front opening and the first chute, while larger particles are introduced through the rear opening and the second chute. The small and large particles are located on different sides of the secondary sieve plate, achieving particle size classification and directional flow during interlayer material transfer. This not only avoids complete mixing of the undersize material but also allows materials of different sizes to enter from different positions in the next screening stage, improving screening efficiency and accuracy. Meanwhile, the dual-channel material conveying method using the first-stage and second-stage material conveying pipes effectively distributes the material transportation load, reduces the risk of localized material accumulation and blockage in parallel screen layers under high load operation, achieves coordinated and unified screening accuracy and operational stability under high production capacity conditions, and solves the technical problems of declining screening efficiency and easy blockage of the material conveying system in traditional white rice screens when pursuing high production.

[0020] In addition to the objectives, features, and advantages described above, this utility model has other objectives, features, and advantages. The present utility model will now be described in further detail with reference to the figures. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an undue limitation of the present invention. In the drawings:

[0022] Figure 1 This is a cross-sectional view of the rice grading sieve structure of this utility model along the transverse direction;

[0023] Figure 2 This is a longitudinal sectional view of the rice grading sieve structure of this utility model;

[0024] Figure 3 This is a schematic diagram of the overall structure of the white rice grading sieve of this utility model;

[0025] Figure 4 This is a schematic diagram of the front-end collection groove structure of this utility model;

[0026] Figure 5 This is a schematic diagram of the rear collection channel structure of this utility model;

[0027] Figure 6 This is a schematic diagram of the structure of the material chute of this utility model;

[0028] Figure 7 This is a schematic diagram of the structure of the primary flow plate of this utility model.

[0029] Legend:

[0030] 1. Primary screening assembly; 11. Primary sieve plate; 12. Primary flow plate; 2. Secondary screening assembly; 21. Secondary sieve plate; 22. Secondary flow plate; 31. First and second stage chute; 32. Second and third stage chute; 33. First and second stage chute; 34. Second and second stage chute; 4. Front end collecting trough; 5. Rear end collecting trough; 6. Housing; 7. Tertiary screening assembly; 71. Tertiary sieve plate; 8. Shell; 9. Sealing edge; 10. Leakage hole; 13. Distribution plate. Detailed Implementation

[0031] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0032] The following is in conjunction with the appendix Figure 1-7 This application will be described in further detail.

[0033] In existing white rice grading screen structures, to improve the processing capacity of the equipment, methods such as widening the screen surface, increasing the number of screen layers, or multi-layer parallel connection are commonly used to expand production capacity. However, these structures have revealed a series of common problems in actual operation: First, widening the screen surface makes the lateral distribution of material on the screen plate uneven, resulting in severe material accumulation in some areas and a decrease in screening efficiency; Second, although the multi-layer parallel structure enables multiple screen surfaces to work simultaneously, the undersize material from each layer is usually mixed in the collection trough and then uniformly transported to the next layer, causing the particle size of the undersize material to be disrupted and the screening path to be disordered. Each screen plate only serves to separate the oversize material, while the undersize material enters the next layer for re-sorting. This repeated process not only seriously reduces the grading accuracy but also easily leads to chute blockage and equipment shutdown under high-production operation; Third, the long undersize material transmission path and high material density increase the burden on the lower screen surfaces, causing a decrease in equipment operating stability and maintenance difficulties.

[0034] To address the aforementioned issues, this invention proposes a compound white rice grading screen based on a front-to-back diversion structure. Each screen layer has a front opening and a rear opening on its flow plate below it. By setting separate front and rear collecting troughs and corresponding chute pipes, preliminary particle size classification and material flow path separation are achieved in the under-screening stage. This effectively avoids the problem of under-screen material mixing and ensures that while each screen layer completes the screening of over-screen material, its under-screen material can also accurately and orderly enter the next screening unit.

[0035] Reference Figure 1 This embodiment discloses a rice grading sieve, including a primary screening component 1, a secondary screening component 2, and a primary chute for cooperation with them. The primary screening component 1 includes at least two primary screen plates 11 arranged vertically for primary screening of rice materials. The primary screen plates 11 have a planar rotary structure, and are driven by a transmission mechanism to achieve horizontal reciprocating motion of the screen surface, allowing materials of different particle sizes to separate naturally during the movement. The material oversize from each primary screen plate 11 is collected through a collection channel and finally converged to a unified outlet area, achieving centralized output of whole rice grains.

[0036] Below each primary sieve plate 11, a primary flow plate 12 is provided to receive and guide the undersize material passing through the sieve holes below the primary sieve plate 11. Each primary flow plate 12 has two symmetrically arranged openings: the one at the front is the front opening, and the one at the rear is the rear opening. These two openings respectively undertake the functions of discharging and guiding undersize materials of different particle sizes, realizing the initial diversion of the undersize material.

[0037] The front opening of the primary flow plate 12 is connected to the secondary screening component 2 below through the first primary chute 31, which is used to guide the undersize material with smaller particle size directly into the rear area of ​​the secondary screening unit for further screening; while the rear opening is connected to the front area of ​​the secondary screening component 2 through the second primary chute 32, which introduces the undersize material with relatively larger particle size into its front section for re-screening.

[0038] The secondary screening component 2 is located below the primary screening component 1 and may include one or more secondary sieve plates 21. Its operation is similar to that of the primary sieve plate 11, also utilizing the horizontal rotary screening principle to further classify the white rice material. Through the orderly guidance of undersize materials of different particle sizes by the primary chute system, the secondary screening component 2 can more effectively undertake the sorting task, improving the overall screening accuracy and equipment operation stability.

[0039] Reference Figure 1 and Figure 2 A front collecting trough 4 is provided below the front opening of the primary flow plate 12 to collect small particles falling from the front screen holes; similarly, a rear collecting trough 5 is provided below the rear opening to collect larger particles under the screen. Both collecting troughs are groove-shaped structures that extend laterally along the flow plate, effectively accommodating underflow material and preventing material accumulation or backflow within the troughs.

[0040] To ensure a smooth transition of material from the collection trough to the chute, both the front collection trough 4 and the rear collection trough 5 are equipped with guide ramps at their bottoms. These ramps slope from high to low, allowing material falling into the collection trough to slide naturally to the discharge port at the bottom of the trough under gravity. This discharge port is directly opposite the inlet of the primary chute, ensuring that material can smoothly enter the corresponding chute channel.

[0041] The inlet of the first-stage chute 31 is located at the bottom of the front guide slope, specifically for receiving small particles of undersize material from the front opening; while the inlet of the second-stage chute 32 is located at the bottom of the rear guide slope, corresponding to guiding larger particles of material. This structure not only physically achieves preliminary particle size differentiation of the undersize material, but also rationally allocates the material flow channels in the spatial path, avoiding mixing, accumulation, or backflow of materials during the falling and conveying process.

[0042] Reference Figure 3 and Figure 4To further optimize the flow path and diversion efficiency of undersize material in the collection tank, the bottoms of the front collection tank 4 and the rear collection tank 5, located below the primary flow plate 12, both adopt a guide slope structure with a higher middle and lower ends. This structural design allows the material falling into the collection tank to automatically slide and converge to both sides of the collection tank under the action of gravity, thereby effectively avoiding material accumulation in the central area of ​​the tank and improving material flowability and discharge efficiency. Specifically, the front guide slope is symmetrically arranged, with its middle height slightly higher than both ends, allowing the material to naturally slide to both ends in the left and right direction after entering the front collection tank 4; the rear guide slope also adopts a similar design, allowing large particles to quickly disperse and be discharged to both sides. This side-guided design not only improves the unloading efficiency but also reduces the risk of blockage caused by material accumulation in the tank.

[0043] Reference Figure 1 and Figure 5 Corresponding to the aforementioned flow guiding structure, two of each of the first-stage chute 31 and the second-stage chute 32 are provided, respectively located at both ends of the front-end collecting trough 4, i.e., one on each side, for simultaneously receiving small particles of material from the front end through two separate flow paths. The second-stage chute 32 is located at both ends of the rear-end collecting trough 5, receiving large particles of material guided by the rear-end flow guide slope. By discharging the two types of materials from two symmetrical discharge channels, not only is the pressure of chute discharge on one side distributed, but also spatial balance and symmetrical structural arrangement of the material flow path are achieved, which is beneficial to the overall force balance and structural stability improvement during equipment operation.

[0044] This bidirectional inclined symmetrical feeding method allows each type of particle size material below the primary screen plate 11 to quickly enter the corresponding chute along its natural flow path after falling, which not only improves logistics efficiency but also enhances the continuity and reliability of sorting.

[0045] To ensure the airtightness, structural stability, and ease of maintenance of the overall equipment, the white rice grading screen in this embodiment is equipped with an integrated housing 6 structure to house and support the primary screening component 1, the secondary screening component 2, and their associated material flow channel structure. In a specific implementation, the housing 6 is constructed entirely of steel or aluminum alloy plates, possessing good strength and corrosion resistance, and capable of withstanding structural loads under continuous vibration and high-frequency screening operations.

[0046] Inside the housing 6, multiple primary sieve plates 11 and secondary sieve plates 21 are fixed sequentially along the height direction, forming a layered screening path. The support structure for each sieve plate is set on the frame structure inside the housing 6 and is fixed by bolts or quick-release clips, facilitating later adjustment or replacement.

[0047] Reference Figure 1In this embodiment, to further improve sorting accuracy and adapt to the classification needs of rice with various particle sizes, a secondary screening component 2 is set below the primary screening component 1 for the white rice grading sieve, and a tertiary screening component 7 can be further extended downwards as needed. This modular multi-stage screening structure makes the screening process progressive, the screening particle size is more refined, and the overall screening effect is improved.

[0048] The secondary screening component 2 includes at least two secondary screen plates 21, arranged horizontally side-by-side within the secondary screening layer area. Similar to the primary screening component 1, each secondary screen plate 21 is also provided with a corresponding secondary flow plate 22 below it for receiving the undersize material. The secondary flow plate 22 has a front opening at the front end and a rear opening at the rear end, corresponding to a front collection trough 4 and a rear collection trough 5, respectively, for preliminary diversion of the undersize material according to position and particle size. Each collection trough has a guide slope at its bottom, also adopting a structure that is higher in the middle and lower at both ends, so that the material can automatically slide into both ends of the collection trough along the direction of gravity after collection. A chute is provided below the slope, which is connected to the first secondary chute 33 and the second secondary chute 34 respectively. In this way, small particles of undersize material from the front opening enter one side of the tertiary screen plate 71 through the first secondary chute 33, while large particles of undersize material enter the other side of the tertiary screen plate 71 through the second secondary chute 34.

[0049] By continuing the structural design of flow plates, openings, collection channels and guide slopes in the secondary screening component 2, not only is the material kept in a hierarchical consistency along the sorting path, but it also provides a foundation for orderly diversion and balanced feeding in the tertiary screening stage. This helps to further improve the sorting efficiency and anti-clogging ability of the tertiary screening component 7, and ensures that the entire equipment system can still operate stably under high-production conditions.

[0050] The tertiary screening component 7 is located below the secondary screening component 2, and its structure is consistent with the first two stages. It includes at least one tertiary sieve plate 71, and multiple tertiary screening zones can be set up or an outlet can be provided for final material classification output according to application needs. Through the linkage configuration of the above-mentioned secondary and tertiary screening structures, materials of different particle size grades can be screened out step by step in the entire sorting process, and the material flow between each stage is diverted and directionally transported according to particle size characteristics, avoiding problems such as mixed screening, missorting, and repeated screening.

[0051] In this embodiment, the first-stage chute 31 and the second-stage chute 32 are detachably installed and fixed to the outer wall of the housing 6. Specifically, the housing 6 has a material passage hole on the outer wall at the position corresponding to the first-stage flow plate 12. The inner edge of the material passage hole is connected to the end of the guide slope, so that the material can directly transition into the inside of the chute after flowing out from the guide slope.

[0052] Reference Figure 6The first-stage chute 31, the second-stage chute 32, the first-secondary chute 33, and the second-secondary chute 34 all adopt an open-shell structure 8, with their open sides fitting against the outer wall of the housing 6 and covering the material passage area. The housing 8 is detachably connected to the outer wall of the housing 6 via bolts or snap-fit ​​structures, ensuring reliable sealing during operation and easy disassembly and assembly during equipment cleaning, maintenance, or replacement. The end structure of the guide slope fits tightly with the material passage holes on the inner wall of the housing 6, forming a smooth material flow transition surface, ensuring that there is no spillage, backflow, or wall accumulation of material during the flow from the first-stage screen plate 11 to the second-stage screen plate 21. This structure also facilitates quick inspection and unblocking of the chute path by cleaning personnel, effectively improving the overall maintainability of the equipment.

[0053] To ensure a good seal during the connection of the chute to the housing 6 and prevent material or dust leakage to the external environment, this embodiment features a surrounding sealing structure around the opening edge of the chute housing 8. This sealing structure is primarily a one-piece molded sealing edge 9, continuously arranged around the opening of the housing 8 to ensure a reliable fit with the outer wall of the housing 6 during installation. The sealing edge 9 can be made of highly elastic materials such as rubber, silicone, or polyurethane, or a combination of a flexible metal bushing and a sealing gasket to accommodate micro-displacements, vibrations, and thermal expansion and contraction during long-term operation. During installation, the housing 8 is bolted to the outer wall of the housing 6 at multiple points along its edge. The sealing edge 9 achieves a static seal under compression, ensuring no dust leakage or material spillage at the junction of the housing 6 and the housing 8.

[0054] Reference Figure 7 To further improve the flow efficiency and screening stability of materials on the flow plate, this embodiment provides several discharge holes 10 for local unloading at the downstream end of the primary flow plate 12. These discharge holes 10 are strip-shaped grooves arranged along the material's running direction, allowing some particles to fall directly through the discharge holes 10 to the corresponding collection path when the material flows through the downstream section of the flow plate, thereby achieving the purpose of load reduction, diversion, and stable material flow. The discharge holes 10 are typically designed as multiple spaced strip-shaped grooves extending along the length direction. The width of each strip-shaped groove is smaller than the sieve hole of the primary sieve plate 11, in order to control the upper limit of the particle size passing through, ensuring that only some broken rice or small broken rice of a specific particle size passes through the holes and falls, while the main material flow continues to move forward along the flow plate. This design not only plays the role of "local pre-discharge + selective particle release", but also alleviates the accumulation of material in the end area, avoiding overload of the rear collection tank 5 or chute blockage caused by short-term concentration of undersize material.

[0055] To further improve the flow path of materials on the primary flow plate 12 and guide some materials to concentrate and transition in a specific direction, this embodiment provides a set of structurally specific distribution plates 13 on the primary flow plate 12. Specifically, two distribution plates 13 are arranged on the primary flow plate 12, near the side away from the discharge hole 10. These two distribution plates 13 are arranged opposite each other, with their upstream ends separated and their downstream ends gradually approaching each other, forming a converging guide channel at the tail of the flow plate. The distribution plates 13 are usually plate-shaped structures, with their bottom edges extending close to the upper surface of the flow plate and their sides slightly higher than the material stack height, used to separate, gather, and guide the surface and middle layers of materials. The arrangement of the two distribution plates 13, which gradually narrows from back to front, causes the material to have a "from dispersed to concentrated" trend during the flow process, effectively guiding some materials located on both sides or in the middle of the flow plate into the set guide channel.

[0056] The flow channel is located between the downstream ends of the two distribution plates 13. Its outlet can be directly opposite the central discharge hole 10 or enter a specific collection structure, thereby achieving precise collection and directional discharge of some materials. In conjunction with the arrangement of the discharge hole 10, the flow channel ensures that materials are discharged along a set path during flow, avoiding problems such as overload of the discharge channel or uneven load at both ends of the screen plate due to disordered distribution. Furthermore, the distribution plate 13 structure also has a certain flow stabilizing effect. When the equipment is under high production load, it can effectively regulate the accumulation trend of materials in the end area of ​​the flow plate, reducing the risk of blockage caused by the surging effect. For materials with poor flowability, high viscosity, or high broken rice content during processing, the distribution channel can also play an auxiliary role in guiding and pressure distribution.

[0057] To achieve precise control over the flow direction and discharge path of the underflow material, this embodiment not only rationally configures the number of discharge holes 10 on the primary flow plate 12, but also achieves structural matching and functional synergy with the guide channel in terms of spatial position. Specifically, the primary flow plate 12 has three discharge holes 10 along its length, respectively arranged in the front, middle, and rear sections. The set of discharge holes 10 located in the middle position is directly opposite the outlet of the guide channel formed by the distribution plate 13, forming a one-to-one correspondence in structure. This arrangement allows some of the material guided by the distribution plate 13 to be discharged directly through the middle discharge holes 10 without accumulation or displacement after entering the guide channel, ensuring a smooth and efficient material flow path from dispersed introduction, concentrated collection to directional unloading. This layout not only improves the accuracy of material distribution at the unloading point, but also further enhances the particle size selectivity and flow control capability during the discharge process by defining the discharge path.

[0058] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A rice grading sieve, characterized in that: It includes a primary screening component (1), a secondary screening component (2), and a primary chute; The primary screening component (1) includes at least two primary screen plates (11) distributed in a vertical direction. Multiple primary screen plates (11) are inclined in the same direction so that the oversize material of multiple primary screen plates (11) is collected at the same outlet. Each primary screen plate (11) is provided with a primary flow plate (12) below it. The two ends of the primary flow plate (12) are respectively provided with a front opening and a rear opening for diverting the undersize material of the primary screen plate (11). The secondary screening component (2) is located below the primary screening component (1) and includes at least one secondary screening plate (21); The primary chute includes a first primary chute (31) and a second primary chute (32). The inlet of the first primary chute (31) is connected to the front opening of the primary flow plate (12), and the inlet of the second primary chute (32) is connected to the rear opening of the primary flow plate (12). The outlets of the first primary chute (31) and the second primary chute (32) are respectively connected to different sides of the secondary screen plate (21).

2. The white rice grading sieve according to claim 1, characterized in that: Below the primary flow plate (12) are a front collecting trough (4) corresponding to the front opening and a rear collecting trough (5) corresponding to the rear opening. Both the front collecting trough (4) and the rear collecting trough (5) are provided with a guide slope for guiding the material, and the inlets of the first primary chute (31) and the second primary chute (32) are located at the bottom of the corresponding guide slope.

3. The white rice grading sieve according to claim 2, characterized in that: The guide slope is set with the middle high and the two ends low. The first stage chute (31) is set at both ends of the front end collection tank (4) to divert the flow of the front end collection tank (4). The second stage chute (32) is set at both ends of the rear end collection tank (5) to divert the flow of the rear end collection tank (5).

4. The white rice grading sieve according to claim 3, characterized in that: The white rice grading screen also includes a box (6), and the primary screening component (1) and the secondary screening component (2) are both located inside the box (6). The first primary chute (31) and the second primary chute (32) are detachably installed on the outer wall of the box (6). The bottom end of the guide slope extends to the inner wall of the box (6), and the box (6) is provided with a material passage hole for the material to enter the first primary chute (31) or the second primary chute (32) from the guide slope.

5. The white rice grading sieve according to claim 4, characterized in that: At least two secondary sieve plates (21) are provided, and a secondary flow plate (22) is provided below each secondary sieve plate (21). The two ends of the secondary flow plate (22) are respectively provided with a front opening and a rear opening for diverting the undersize material of the secondary sieve plate (21); A tertiary screening component (7) is provided below the secondary screening component (2), and the tertiary screening component (7) includes at least one tertiary screening plate (71); The housing (6) is provided with two secondary chute pipes, including a first secondary chute pipe (33) and a second secondary chute pipe (34). The inlet of the first secondary chute pipe (33) is connected to the front opening of the secondary flow plate (22), and the inlet of the second secondary chute pipe (34) is connected to the rear opening of the secondary flow plate (22). The outlets of the first secondary chute pipe (33) and the second secondary chute pipe (34) are respectively connected to different sides of the tertiary screen plate (71).

6. The white rice grading sieve according to claim 4, characterized in that: The first-stage chute (31) and the second-stage chute (32) have the same structure, both including a shell (8) with an open structure. The open side of the shell (8) is attached to the outer wall of the box (6) and together with the outer wall of the box (6), they form a channel for materials to pass through.

7. The white rice grading sieve according to claim 6, characterized in that: A sealing edge (9) is provided around the opening on the shell (8). The sealing edge (9) is in close contact with the outer wall of the box (6) and is fixed by bolts.

8. The white rice grading sieve according to claim 7, characterized in that: The downstream end of the primary flow plate (12) is provided with a material leakage hole (10), which includes multiple strip grooves extending along the material movement direction.

9. The white rice grading sieve according to claim 8, characterized in that: Two material distribution plates (13) are provided on the side of the primary flow plate (12) away from the material leakage hole (10). The downstream ends of the two material distribution plates (13) are close to each other to form a flow channel.

10. The white rice grading sieve according to claim 9, characterized in that: There are three material leakage holes (10) on the primary flow plate (12) along the length of the primary flow plate (12), with the middle material leakage hole (10) corresponding to the flow channel.

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