A sieve for separating tobacco stems

Abstract

The present invention discloses a sieve for separating tobacco stems, comprising: a sieve plate, on which a plurality of groups of screening holes are formed, the centers of each group of the plurality of groups of screening holes are distributed on a sine curve, the tangents at the peaks and valleys of the sine curve are parallel to the length direction of the sieve plate, and any two adjacent groups of the plurality of groups of screening holes are arranged at a preset distance interval in the width direction of the sieve plate; a plurality of guide strips, which are respectively fixedly connected to the sieve plate, the plurality of guide strips are bent in a sine curve in their length direction, the sine curves of the plurality of guide strips are equal in wavelength to the sine curves of the plurality of groups of screening holes, one of the guide strips is arranged between any two adjacent groups of the plurality of groups of screening holes, and the widths of the plurality of guide strips gradually decrease from the bottom to the top.

Description

Technical Field

[0001] The present invention relates to the technical field of tobacco stem material sieves, and specifically, to a sieve for separating tobacco stems. Background Art

[0002] In the tobacco industry, separating and classifying tobacco stems, cut tobacco shreds, etc. according to specified sizes requires both high efficiency and high accuracy, which is very difficult. The difficulties lie in the measurement theory and separation technology. Since tobacco stem materials are moving and flipping in the vibrating sieve of the vibrating trough on the production line, and there is a large flow of tobacco stem materials on the production line, it is very difficult to accurately measure their sizes and complete the separation; especially small-sized tobacco stems are easily broken during the production of cut tobacco on the stem line, making it very difficult to separate a large number of stem chips mixed in the cut tobacco. Therefore, the separation of tobacco stems is extremely important. Summary of the Invention

[0003] To solve at least one of the above problems, the present invention provides a sieve for separating tobacco stems, including: a sieve plate, on which a plurality of groups of screening holes are provided, the centers of each group of the plurality of groups of screening holes are distributed on a sine curve, the tangents at the wave crests and wave troughs of the sine curve are parallel to the length direction of the sieve plate, and any two adjacent groups of the plurality of groups of screening holes are arranged at a preset distance interval in the width direction of the sieve plate; a plurality of guide strips, which are respectively fixedly connected to the sieve plate, the plurality of guide strips are bent in a sine curve in their length direction, the sine curves of the plurality of guide strips are equal in wavelength to the sine curves of the plurality of groups of screening holes, one of the plurality of guide strips is arranged between any two adjacent groups of the plurality of groups of screening holes, and the widths of the plurality of guide strips gradually decrease from bottom to top.

[0004] Preferably, the amplitudes of the sine curves of the plurality of guide strips are equal to the amplitudes of the sine curves of the plurality of groups of screening holes.

[0005] Preferably, the section perpendicular to the tangent vector of the guide strip includes a bottom edge and a top edge, the bottom edge is a straight line, the length of the bottom edge is less than the preset distance between two groups of the screening holes on both sides of any of the guide strips, the top edge is a curve corresponding to half the wavelength of the sine curve, and the midpoint of the bottom edge corresponds to the wave crest of the top edge.

[0006] Preferably, the sieve plate includes a plurality of unit plates, each unit plate includes a group of screening holes, and the plurality of unit plates are fixedly connected in sequence.

[0007] Preferably, fixing holes are symmetrically provided on both sides of each of the plurality of unit plates, and the corresponding fixing holes between adjacent unit plates are fixedly connected by cylindrical pins.

[0008] Preferably, a screening cavity is formed on the unit board. The screening hole is the inlet of the screening cavity, and the outlet of the screening cavity is formed below the screening hole. The screening plate is provided with a discharge chute at the outlet of the screening cavity. The width of the discharge chute is greater than the width of the outlet of the screening cavity. The discharge chute communicates with the side wall of the unit board corresponding to the screening hole adjacent thereto, and the discharge chute communicates with the lower surface of the unit board.

[0009] Preferably, the screening cavity adopts a first screening curved surface. The first screening curved surface is a rotating curved surface formed by rotating a first generatrix along a first trajectory. The rotation axis is a perpendicular line passing through the center of the screening hole. The first generatrix includes a first arc segment and a second arc segment. The radius of the first arc segment is equal to the diameter of the screening hole. The center of the first arc segment is on the circumference of the screening hole. The starting point of the first arc segment is a point on the screening hole. The end point of the first arc segment is directly below the center of the screening hole. The radius of the second arc segment is equal to the diameter of the screening hole. The connection line between the center of the second arc segment and the center of the first arc segment passes through the center of the screening hole. The starting point of the second arc segment coincides with the end point of the first arc segment. The end point of the second arc segment is between the starting point of the second arc segment and the center of the first arc segment. The first trajectory is an arc segment on the screening hole. The connection line between the starting point and the end point of the first trajectory passes through the center of the screening hole.

[0010] Preferably, the screening cavity adopts a second screening curved surface. The second screening curved surface is a rotating curved surface formed by rotating a second generatrix along a second trajectory. The rotation axis is a perpendicular line passing through the center of the screening hole. The second generatrix is an arc of a vertical plane passing through the center of the screening hole. The radius of the second generatrix is equal to the radius of the screening hole. The center of the second generatrix coincides with the center of the screening hole. The starting point of the second generatrix is on the circumference of the screening hole. The central angle of the second generatrix is a preset angle. The connection line between the starting point and the end point of the second trajectory passes through the center of the screening hole.

[0011] Preferably, positioning holes are formed at the bottom of the flow guiding strip. Limiting holes matched with the positioning holes are formed on the unit board. The positioning holes are threaded holes. The positioning holes and the limiting holes are connected with screws in a matching manner.

[0012] Preferably, the positioning holes are formed at the positions corresponding to the peaks and valleys of the sine curve of the flow guiding strip.

[0013] The screen for separating tobacco stems in the embodiments of the present invention has the following beneficial effects: improving the performance of the vibrating screen, extending the screening path of the material, balancing the moving speed of the material, the sine curve guiding strips for the tobacco stem material providing an alternating normal force, and the alternating tangential direction on the curve making it easier for the screening holes to capture the tobacco stem material to improve the screening efficiency; the improvement of the screening accuracy of the tobacco stems can increase the utilization rate of the tobacco stems and reduce the production cost; through the fixed-length wire making of the reconstituted tobacco shreds and the fixed-length screening of the cut tobacco, the screening accuracy of the fixed-length cut tobacco is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] To better understand the above and other objects, features, advantages and functions of the present invention, reference may be made to the embodiments shown in the drawings. The same reference numerals in the drawings refer to the same components. Those skilled in the art should understand that the drawings are intended to schematically illustrate the preferred embodiments of the present invention and have no limiting effect on the scope of the present invention, and the components in the drawings are not drawn to scale.

[0015] Figure 1 It is a schematic structural diagram of the screen for separating tobacco stems in the embodiments of the present invention;

[0016] Figure 2 It is a schematic structural diagram of the screen plate and the guiding strip of the screen for separating tobacco stems in the embodiments of the present invention;

[0017] Figure 3 It is a schematic structural diagram of the unit plate of the screen for separating tobacco stems in the embodiments of the present invention;

[0018] Figure 4 It is a schematic connection structure diagram of multiple unit plates of the screen for separating tobacco stems in the embodiments of the present invention;

[0019] Figure 5 It is a schematic structural diagram of the guiding strip of the screen for separating tobacco stems in the embodiments of the present invention;

[0020] Figure 6 It is a schematic cross-sectional structure diagram of the guiding strip of the screen for separating tobacco stems in the embodiments of the present invention;

[0021] Figure 7 It is a schematic partial structure diagram of the unit plate of the screen for separating tobacco stems in the embodiments of the present invention;

[0022] Figure 8 It is a schematic cross-sectional structure diagram of the first screening curved surface of the screening cavity of the screen for separating tobacco stems in the embodiments of the present invention;

[0023] Figure 9 It is a schematic cross-sectional structure diagram of the second screening curved surface of the screening cavity of the screen for separating tobacco stems in the embodiments of the present invention;

[0024] Figure 10Another schematic cross-sectional view of the second screening surface of the screening chamber of the screen for separating tobacco stems according to an embodiment of the present invention;

[0025] Figure 11 Another schematic cross-sectional view of the second screening surface of the screening chamber of the screen for separating tobacco stems according to an embodiment of the present invention;

[0026] Figure 12 Schematic analysis diagram of the circle and function curve of the screening holes of the present invention in the coordinate system.

[0027] Reference numerals:

[0028] 1. Unit plate; 2. Screen plate; 3. Cylindrical pin; 4. Fixing hole; 5. Screw; 6. Limiting hole; 7. Positioning hole; 8. Flow guiding strip; 9. Screening hole; 10. Screening chamber; 11. Discharge chute; 12. Guard plate. Detailed implementation manners

[0029] The following describes exemplary embodiments of the present disclosure with reference to the accompanying drawings. Various details of the embodiments of the present disclosure are included to assist understanding, and they should be considered merely exemplary. Therefore, those of ordinary skill in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present disclosure. Similarly, for clarity and conciseness, descriptions of well-known functions and structures are omitted below.

[0030] As used herein, the term "including" and its variants mean open inclusion, that is, "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "at least partially based on". The terms "an exemplary embodiment" and "an embodiment" mean "at least one exemplary embodiment". The term "another embodiment" means "at least one additional embodiment". The terms "first", "second", etc. may refer to different or the same objects. There may also be other explicit and implicit definitions below.

[0031] To at least partially solve one or more of the above problems and other potential problems, an embodiment of the present disclosure provides a sieve for tobacco stem separation, including: a sieve plate 2, on which a plurality of groups of screening holes 9 are formed, the centers of each group of screening holes 9 among the plurality of groups of screening holes 9 are distributed on a sine curve, the tangents at the peaks and valleys of the sine curve are parallel to the length direction of the sieve plate 2, and any two adjacent groups of screening holes 9 among the plurality of groups of screening holes 9 are arranged at a preset distance interval in the width direction of the sieve plate 2; a plurality of diversion bars 8, the plurality of diversion bars 8 are respectively fixedly connected to the sieve plate 2, the plurality of diversion bars 8 are bent in a sine curve in their length direction, the sine curve of the plurality of diversion bars 8 has the same wavelength as the sine curve of the plurality of groups of screening holes 9, one diversion bar 8 is arranged between any two adjacent groups of screening holes 9 among the plurality of groups of screening holes 9, and the widths of the plurality of diversion bars 8 gradually decrease from the bottom to the top.

[0032] Specifically, as Figures 1-4 shown, the upper surface of the sieve plate 2 is a plane, the plurality of groups of screening holes 9 are distributed on the screening plate according to a sine function curve, and the centers of the screening holes 9 are on this sine function curve. Taking the length direction of the sieve plate 2 as the x-axis and the width direction of the sieve plate 2 as the y-axis, the distribution of a group of screening holes 9 on the sieve plate 2 conforms to the following equation:

[0033] y = asin(ωx).

[0034] Design the screening holes 9 on the sine curve S1, the amplitude a and the angular frequency ω can be optimized; the wavelength λ = 2π / ω, on the sine curve corresponding to the wavelength λ, k holes are processed by the average interpolation method, k takes 5, 9, 17,..., then the change amount Δt of the x coordinate value of each hole on the x coordinate axis is equal, and a total of M holes are processed, then:

[0035]

[0036] Then for the screening holes 9 processed on the sieve plate 2 according to the sine curve change rule, in the x coordinate axis direction position serial number M, the center coordinate positions are as follows:

[0037]

[0038] Among them, M takes a positive integer, M = 1 means punching 1 hole at the coordinate of x = 0, and the number of punched holes on this curve is M.

[0039] Furthermore, by translating the curve in the coordinate system, N such function curves and the center coordinates of the screening holes 9 are obtained. Similarly, N groups of screening holes 9 can be designed. Using the S1 function curve y = asin(ωx), it is translated only in the positive y-axis direction by a value of b, where b is the preset distance between the centers of adjacent groups of screening holes 9. The preset distance between adjacent groups of screening holes 9 is defined as the preset distance (b - 2r) between the boundaries of adjacent groups of screening holes 9, and r is the radius of the screening hole 9. Then the S2 function curve after one translation:

[0040] y = b + asin(ωx),

[0041] The S3 function curve obtained after two translations:

[0042] y = 2b + asin(ωx),

[0043] The S4 function curve obtained after three translations:

[0044] y = 3b + asin(ωx),

[0045] The S N+1 function curve obtained after translating N times:

[0046] y = (N - 1)b + asin(ωx).

[0047] Furthermore, the initial phases of the sine function curves corresponding to the multiple flow guiding strips 8 are equal to the initial phases of the sine function curves corresponding to each group of screening holes 9, and the wavelengths are equal. Then the sine function curve M1 corresponding to the bottom center line of the flow guiding strip 8 in the coordinate system of the sieve plate 2:

[0048] y = m + csin(ωx),

[0049] where the curve M1 is the central curve of the screening hole curve S1 and the screening hole curve S2. Let m = b / 2, and the curve equation of M1 is:

[0050] y = b / 2 + csin(ωx),

[0051] The bottom width of the flow guiding strip 8 is preset as t. Using the M1 function curve, it is translated up and down by t / 2 values only on the y-axis. The curve corresponding to the first side of the bottom surface of the flow guiding strip 8 is:

[0052] y = (b - t) / 2 + csin(ωx),

[0053] The curve corresponding to the second side of the bottom surface of the flow guiding strip 8 is:

[0054] y = (b + t) / 2 + csin(ωx).

[0055] Those skilled in the art can understand that the initial phase of the sine function corresponding to multiple groups of screening holes 9 can be set according to preset requirements. For example, if the initial phase is π / 2, then for the S1 function curve y = asin(ωx + π / 2), the initial phase of each group of screening holes 9 in the corresponding multiple groups of screening holes 9 is π / 2, and the initial phase of the corresponding sine function of each guide bar 8 is π / 2.

[0056] When the initial phase of the multiple groups of screening holes 9 and the initial phase of the guide bars 8 are π / 2, the screening hole curve S1 is expressed as:

[0057] y = acos(ωx),

[0058] For the amplitude a and angular frequency ω of the screening hole curve S1, preferably, ω is taken as 1, λ = 2π, k holes are processed on the sieve plate 2 by the average interpolation method, k is taken as 5, the diameter of the screening hole 9 is L, and the coordinates of the centers of the screening holes 9 on the screening hole curve S1 are:

[0059]

[0060]

[0061] Among them, reference can be made to Figure 12 , M is a positive integer, M = 1 means punching 1 hole at the coordinates of x = 0 and y = a, and the total number of punched holes on the screening hole curve S1 is M. The circular equations of each screening hole 9 within the first wavelength of the screening hole curve S1 are as follows. The equation of the screening hole d1 in the coordinate system of the sieve plate 2:

[0062]

[0063] The equation of the screening hole d2 in the coordinate system of the sieve plate 2:

[0064]

[0065] The equation of the screening hole d3 in the coordinate system of the sieve plate 2:

[0066]

[0067] The equation of the screening hole d4 in the coordinate system of the sieve plate 2:

[0068]

[0069] The equation of the screening hole d5 in the coordinate system of the sieve plate 2:

[0070]

[0071] Further, the amplitude a and angular frequency ω of the screening hole curve S2 are preferably selected. When ω is 1, λ = 2π, and k is 5, the center coordinates of the screening holes 9 on the screening hole curve S2 are as follows:

[0072]

[0073]

[0074] Among them, M is a positive integer. When M = 1, one hole is drilled at the coordinates of x = 0 and y = a + b. The total number of holes drilled on the screening hole curve S2 is M. Thus, the circular equation of the screening holes 9 within the first wavelength of the screening hole curve S2 is as follows. The equation of the screening hole d1-1 in the coordinate system of the sieve plate 2:

[0075]

[0076] The equation of the screening hole d2-1 in the coordinate system of the sieve plate 2:

[0077]

[0078] The equation of the screening hole d3-1 in the coordinate system of the sieve plate 2:

[0079]

[0080] The equation of the screening hole d4-1 in the coordinate system of the sieve plate 2:

[0081]

[0082] The equation of the screening hole d5-1 in the coordinate system of the sieve plate 2:

[0083]

[0084] According to the equations of the screening holes 9 in the coordinate system of the sieve plate 2, it can be seen that the boundaries of the screening holes 9 on the screening hole curve S1 and the screening hole curve S2 neither intersect nor are tangent to each other.

[0085] In some embodiments, the amplitude of the sine curve of the plurality of guide bars 8 is equal to the amplitude of the sine curve of the plurality of groups of screening holes 9.

[0086] Specifically, as Figure 5 shown, the amplitude c of the sine curve of the guide bar 8 is equal to the amplitude a of the sine curve of the plurality of groups of screening holes 9. In other embodiments, the amplitude c of the guide bar 8 is less than or equal to the amplitude a of the plurality of groups of screening holes 9 to avoid interference between the boundary of the guide bar 8 and the screening holes 9 on both sides thereof.

[0087] In some embodiments, the cross-section of the diversion bar 8 perpendicular to its tangent vector includes a bottom edge and a top edge. The bottom edge is a straight line, and the length of the bottom edge is less than the preset distance between two groups of screening holes 9 on both sides of any diversion bar 8. The top edge is a curve corresponding to half the wavelength of a sine curve, and the midpoint of the bottom edge corresponds to the peak of the top edge.

[0088] Specifically, as Figures 5-6 shown, the width direction of the diversion bar 8 is parallel to the width direction of the sieve plate 2. Then the bottom edge of the diversion bar 8 is parallel to the y-axis of the coordinate system of the sieve plate 2, and taking the vector perpendicular to the surface of the sieve plate 2 as the z-axis, the height direction of the diversion bar 8 is parallel to the z-axis. Then the cross-section of the diversion bar 8 is parallel to the yoz plane of the coordinate system of the sieve plate 2. The bottom surface of the diversion bar 8 is a planar structure parallel to the upper surface of the sieve plate 2. Then the bottom edge of the cross-section is a straight line, and the length of the bottom edge of the diversion bar 8 is equal to the width of the diversion bar 8. The width of the diversion bar 8 is less than the preset distance (b - 2r) between two adjacent groups of screening holes 9, where r is the radius of the screening hole 9. The top edge of the cross-section of the diversion bar 8 is a curve, and the curve corresponds to half the wavelength of a sine function. The sine function curve equation corresponding to the top edge is: z = a1sin(ω1y).

[0089] The peak of the top edge is the midpoint of the curve corresponding to the half-wavelength sine function, that is, the top edge is symmetric about the line connecting the midpoint of the top edge and the midpoint of the bottom edge. In some embodiments, a1 > 1, ω1 > 1; for example, a1 = 1.5, ω1 = π, λ1 = 2π / ω1 = 2.

[0090] In other embodiments, the top edge of the cross-section of the diversion bar 8 is less than half a wavelength. As Figure 6 shown, improper selection of the t value will cause the diversion bar 8 to periodically interfere with the screening holes 9. The following takes the first side of the diversion bar 8 and the screening hole 9d4 as an example to determine. The first side M of the diversion bar 8 1-1 Function curve equation:

[0091] y = (b - t) / 2 + acos(ωx),

[0092] Equation of the screening hole 9d2:

[0093]

[0094] By solving the condition for the unique solution of the above two equations, the maximum value of t can be determined.

[0095] Or, in another embodiment, the top edge of the cross-section of the diversion bar 8 is less than half a wavelength, and the midpoint of the bottom edge corresponds to the peak of the top edge. The maximum value of t is determined using the normal equation. Specifically, the first side M of the diversion bar 8 1-1 The first derivative of the function curve is:

[0096]

[0097] It is exactly the equation of the slope k of the tangent line P passing through the point on the curve: Then the slope of the normal line N passing through this point is:

[0098]

[0099] And the normal line N passes through the center of the screening hole 9d2. The normal line equation N can be obtained by the point - slope form; since the intersection point of the normal line equation N and the screening hole 9d2 conforms to the first side M of the flow - guiding strip 8 1-1 For the function curve equation, the maximum value of t can be determined.

[0100] Or, in other embodiments, the top edge of the cross - section of the flow - guiding strip 8 is less than half a wavelength, and the mid - point of the bottom edge corresponds to the wave crest of the top edge. Although an improper selection of the t value will interfere with the screening hole 9, it is relatively easy to handle in CAD / CAM through mechanical design. The flow - guiding plate is designed with the curve M1 function;

[0101] y = m + a cos(ωx),

[0102] The waveform corresponding to the top edge of its cross - section adopts the sine function:

[0103] z = a1 sin(ω1y),

[0104] Take its λ1 / 2 waveform design, a1>1, ω1>1. If a1 = 1.5, ω1 = π, λ1 = 2π / ω1 = 2, then the curve function corresponding to the top edge of such a cross - section is:

[0105] y = 1.5 sin(πx),

[0106] Then the mid - line M1 of the flow - guiding strip 8 passes through the mid - point M1 between the t1 point and the t2 point, and it is also the mid - point of the half - wavelength λ1 / 2, M 1-1 The function curve passes through the t1 point, M 1-2 The function curve passes through the t2 point. The flow - guiding strip 8 designed with such a sine curve is assembled into the sieve plate 2. The values of t1 and t2 that do not interfere with the screening hole 9 are checked in CAD / CAM, and the optimal t value is the distance between the t1 point and the t2 point. For example, as Figure 6 shown, preferably t = 0.9. The X - coordinate of t1 in the figure is 0.05, the X - coordinate of t2 is 0.95, and λ1 / 2 = 1.

[0107] In some embodiments, the sieve plate 2 includes a plurality of unit plates 1, and each unit plate 1 includes a group of screening holes 9, and the plurality of unit plates 1 are fixedly connected in sequence.

[0108] Specifically, as Figure 3 and Figure 4As shown, multiple unit plates 1 of the sieve plate 2 are fixedly connected in sequence. The width of each unit plate 1 is greater than twice the sum of the amplitude of the sine function corresponding to the screening holes 9 and the radius of the screening holes 9, so that a group of screening holes 9 are distributed on the same unit plate 1. Then, the preset distance between two adjacent groups of screening holes 9 is greater than twice the amplitude of the sine function of the screening holes 9.

[0109] In some embodiments, fixing holes are symmetrically formed on both sides of each unit plate 1 among the multiple unit plates 1, and the corresponding fixing holes between adjacent unit plates 1 are fixedly connected by cylindrical pins 3.

[0110] Specifically, as Figure 4 and Figure 7 shown, multiple fixing holes are formed on each unit plate 1 among the multiple unit plates 1, and the multiple fixing holes are symmetrically distributed on both sides of the unit plate 1, that is, the coordinates of a group of fixing holes symmetrically arranged on both sides of the same unit plate 1 on the x-axis of the coordinate system of the sieve plate 2 are the same. When the multiple unit plates 1 are connected in sequence, the coordinates of the corresponding fixing holes for connecting the same cylindrical pin 3 between adjacent unit plates 1 on the x-axis of the coordinate system of the sieve plate 2 are the same.

[0111] In other embodiments, multiple fixing holes are arranged on one side of the unit plate 1, and multiple cylindrical pins 3 are fixedly arranged on the other side of the unit plate 1, and the multiple fixing holes and the multiple fixing pins correspond one by one. When the multiple unit plates 1 are fixedly connected, the fixing holes on one side of the unit plate 1 are connected to the cylindrical pins 3 of the adjacent unit plate 1 on the adjacent side, and the cylindrical pins 3 on the other side of the unit plate 1 are connected to the fixing holes of the adjacent unit plate 1 on the adjacent side.

[0112] In some embodiments, a screening cavity 10 is formed on the unit plate 1, the screening holes 9 are the inlets of the screening cavity 10, the outlet of the screening cavity 10 is formed below the screening holes 9, a discharge chute 11 is formed at the outlet of the screening cavity 10 of the sieve plate 2, the width of the discharge chute 11 is greater than the width of the outlet of the screening cavity 10, the discharge chute 11 communicates with the side wall of the unit plate 1 close to the corresponding screening holes 9, and the discharge chute 11 communicates with the lower surface of the unit plate 1.

[0113] Specifically, as Figure 7As shown, the screening chamber 10 is a chamber composed of a rotating surface opened below the screening holes 9. The top opening of the screening chamber 10 is the inlet, and the inlet of the screening chamber 10 coincides with the screening holes 9. The outer edge of the side wall of the screening chamber 10 below the screening holes 9 encloses the outlet of the screening chamber 10. The discharge chute 11 is opened below the screening holes 9, and the discharge chute 11 communicates with the outlet of the screening chamber 10. The width of the discharge chute 11 is defined as the length of the projection of the discharge chute 11 in the length direction of the unit plate 1. The width of the outlet of the screening chamber is defined as the maximum value in the length direction parallel to the unit plate 1 of the distance between the boundary of the projection of the screening chamber 10 on the upper surface of the sieve plate 2 and the screening holes 9. Each screening hole 9 corresponds to a discharge chute 11. The discharge chute 11 communicates with the side wall of the unit plate 1 on the side close to the center of the corresponding screening hole 9. When the center of the screening hole 9 corresponding to the discharge chute 11 is located on the center line of the unit plate 1, the discharge chutes 11 corresponding to the multiple screening holes 9 located on the center line communicate with the two side walls of the unit plate 1 at intervals.

[0114] In another embodiment, the sieve plate 2 adopts a flat plate structure with a certain thickness, and the screening holes 9 are cylindrical through holes opened on the sieve plate 2, and the screening holes 9 communicate with the upper and lower surfaces of the sieve plate 2.

[0115] In some embodiments, the screening chamber 10 adopts a first screening surface, and the first screening surface is a rotating surface formed by rotating a first generatrix along a first trajectory. The rotation axis is a perpendicular line passing through the center of the screening hole 10. The first generatrix includes a first arc segment and a second arc segment. The radius of the first arc segment is equal to the diameter of the screening hole 9. The center of the first arc segment is on the circumference of the screening hole 9. The starting point of the first arc segment is a point on the screening hole 9, and the end point of the first arc segment is directly below the center of the screening hole 9. The radius of the second arc segment is equal to the diameter of the screening hole 9. The connection line between the center of the second arc segment and the center of the first arc segment passes through the center of the screening hole 9. The starting point of the second arc segment coincides with the end point of the first arc segment. The end point of the second arc segment is between the starting point of the second arc segment and the center of the first arc segment. The first trajectory is an arc on the screening hole 9, and the connection line between the starting point and the end point of the first trajectory passes through the center of the screening hole 9.

[0116] Specifically, as Figure 8As shown in the figure, it represents a cross-section passing through the center of the screening hole 9. The perpendicular line of the screening hole passes through the center of the screening hole and is perpendicular to the plane where the screening hole is located. The line segment CD represents the diameter passing through the center O of the screening hole 9, which is the diameter L of the screening hole 9. CC1 represents the first arc segment (as the generatrix) with the center at D and the radius L, and C1D1 represents the second arc segment with the center at C and the radius L. The first locus is a semi-circle passing through the screening hole 9, and the corresponding central angle is 180 degrees. Then the first screening surface is a rotational surface formed by rotating the generatrix composed of the first arc segment CC1 and the second arc segment C1D1 by 180 degrees around OC1. The distance from any point on the CC1 arc to point D, and the distance from any point on C1D1 to point C are both L. Define the "rise" of the X1 screening hole 9, that is, the horizontal projection distance between the end point (point D1) of the second arc segment of the screening surface in the vertical cross-section passing through the center of the screening hole 9 and the screening hole 9 (point D).

[0117] When X1≥L / 2, the central angle β1 of the first arc segment CC1:

[0118]

[0119] When X1 = L / 2, point D1 coincides with point C, and the central angle β1 of the first arc segment CC1 is 60°. It can also be proved geometrically that points C, C1, and D can form an equilateral triangle with side length L, which is called the a1 type of rotational surface. When X1 > L / 2, it is called the a2 type of rotational surface. For example, when β1 = 45°, When β1 = 30°,

[0120] When X1≤L / 2, the central angle β2 of the second arc segment C1D1:

[0121]

[0122] Obviously, when X1 = L / 2, β2 = 0. When The central angle β2 of the second arc segment C1D1 = 30°; because the value of X1 is related to the material outlet efficiency and separation accuracy, preferably β2 < 30°.

[0123] Therefore, the optimal value range of X1: Preferably X1 = L / 2, When X1 = L / 2, it is called the a1 type of rotational surface; when X1 < L / 2, it is called the a2 type of rotational surface; when X1 > L / 2, it is called the a3 type of rotational surface.

[0124] In some embodiments, the screening cavity 10 adopts a second screening surface, which is a rotating surface formed by rotating a second generatrix along a second trajectory. The rotation axis is a vertical line passing through the center of the screening hole 10. The second generatrix is an arc of a vertical plane passing through the center of the screening hole 9. The radius of the second generatrix is equal to the radius of the screening hole 9. The center of the second generatrix coincides with the center of the screening hole 9. The starting point of the second generatrix is on the circumference of the screening hole 9. The central angle of the second generatrix is a preset angle. The connection line between the starting point and the ending point of the second trajectory passes through the center of the screening hole 9.

[0125] Specifically, as Figures 9-10 shown, the line segment CD represents the diameter passing through the center O of the screening hole 9, and the diameter of the screening hole 9 is L; the arc CD1 of the second generatrix represents an arc with O as the center and a radius of L / 2, which is an arc on the spherical surface obtained by taking the vertical line passing through the center of the screening hole as the rotation axis. It can be proved geometrically that points C, D1, and D can form an isosceles right triangle with the waist being . Define X2 as the horizontal distance between the ending point of the first generatrix and point D on the screening hole 9. At this time, X2 = L / 2, and the central angle β3 of the first generatrix CD1 is 90°.

[0126] When L / 2 ≤ X2 < L, the central angle β3 of the arc CD1:

[0127]

[0128] Then, when, the central angle β3 of the arc CD1 is 30°; when, the central angle β3 of the arc CD1 is 45°; when X2 = 1.5L, the central angle β3 of the arc CD1 is 60°. The central angle β3 of the arc CD1 in the cross-section takes values from 30° to 90°.

[0129] At this time, the optimal value range of X2: Preferably that is, it is most suitable to take β3 = 45°; its theoretical control length value is designed as L according to the process requirements. For the case where the flow rate of tobacco stems is small, the consistency of the directional flow direction is high, the flow velocity of tobacco stems is fast, and the accuracy requirement of the separation process is not high. Since there are few control length arc surfaces, the separation efficiency is high.

[0130] If further high-precision fine screening of tobacco stems is required, an additional designed arc segment D1D2 is added. As Figure 11 shown, its central angle β4 is 30°. After rotating in space, it is defined as a "spherical crown" in geometry. When 0 < X2 < L / 2, the central angle β4 of the arc D1D2:

[0131] β4 = sin -1 (1 - 2X2 / L),

[0132] When β4=30°, X2=L / 4; when β4=45°, At this time, the optimal value range of X2 is: When X2=L / 4 and X2=L / 2, it is called b1 type rotation surface; X2<L / 2时,称为b2类旋转曲面;X2> When L / 2, it is called a b3 type rotation surface.

[0133] The efficiency and accuracy of tobacco stem separation and classification, and both cannot be achieved at the same time, depend on the value of X1 or X2. The X1 or X2 value that meets the requirements should be selected based on the physical and chemical characteristics, flow rate and physical properties of the specific tobacco stem material.

[0134] Since the width Y of the discharge chute 11 includes and exceeds the values of X1 and X2, i.e., Y ≥ X1 or Y ≥ X2, the size of Y affects the jamming, efficiency, or scientificity of tobacco stem discharge. Therefore, the width Y can be designed so as not to interfere with the fixing holes and the adjacent screening chamber 10. Of course, a larger length Y of the discharge chute will result in smoother discharge.

[0135] like Figure 7 , dimension Z1 is the depth of the processed discharge trough 11, the thickness of the unit plate 1 is Z, Z-Z1≤2mm, the size of Z-Z1 theoretically affects the dimensional accuracy of tobacco stem separation, although its influence is very small, it can be eliminated through mechanical design and manufacturing; Z-Z1 is preferentially based on the material of the unit plate 1, such as using stainless steel, Z-Z1 can be 1mm, or 0.5mm, such as aluminum alloy, Z-Z1 can be 1mm.

[0136] In some embodiments, a positioning hole 7 is provided at the bottom of the guide bar 8 , and a limiting hole 6 is provided on the unit plate 1 to match the positioning hole 7 . The positioning hole 7 is a threaded hole, and the positioning hole 7 and the limiting hole 6 are connected with screws 5 .

[0137] Specifically, if Figure 5 As shown, the positioning hole 7 is a threaded hole opened at the bottom of the guide bar 8, and the limiting hole 6 is a through hole connecting the upper and lower surfaces of the sieve plate 2, so that the screw 5 passes through the limiting hole 6 from the lower surface of the unit plate 1 and is screwed into the positioning hole 7 to fix the connection between the guide bar 8 and the sieve plate 2.

[0138] In some embodiments, the positioning holes 7 are provided at positions corresponding to the crests and troughs of the sine curve of the guide bar 8 .

[0139] Specifically, if Figure 7 As shown, the positioning holes 7 are opened at the peaks and troughs, and the sieve plate 2 is provided with limiting holes 6 corresponding to their positions. The discharge trough 11 corresponding to the screening holes 9 on the sieve plate 2 and the limiting holes 6 are respectively located on both sides of the screening holes 9 to avoid interference. In other embodiments, the positioning holes 7 can also be opened at any preset position to avoid interference between the limiting holes 6, the fixing holes and the discharge trough 11.

[0140] In some embodiments, such as Figure 1 shown, it further includes a guard plate 12, and the guard plate 12 includes two side plates and an end plate. The two side plates are respectively arranged on both sides of the sieve plate 2, the end plate is arranged at one end of the sieve plate 2, and both ends of the end plate are fixedly connected to the adjacent side plates respectively.

[0141] The various embodiments of the present disclosure have been described above. The above description is exemplary and not exhaustive, and is also not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to technologies in the market, or to enable other ordinary skilled persons in the art to understand the present disclosure.

Claims

1. A sieve for separating tobacco stems, characterized in that, Including: A sieve plate, on which a plurality of groups of screening holes are formed. The centers of each group of screening holes among the plurality of groups of screening holes are distributed on a sine curve. The tangents at the peaks and troughs of the sine curve are parallel to the length direction of the sieve plate. Any two adjacent groups of screening holes among the plurality of groups of screening holes are arranged at a preset distance interval in the width direction of the sieve plate; A plurality of guide strips, which are respectively fixedly connected to the sieve plate. The plurality of guide strips are bent in a sine curve in their length direction. The sine curves of the plurality of guide strips have the same wavelength as the sine curves of the plurality of groups of screening holes. One of the guide strips is arranged between any two adjacent groups of screening holes among the plurality of groups of screening holes. The widths of the plurality of guide strips gradually decrease from the bottom to the top; The amplitudes of the sine curves of the plurality of guide strips are equal to the amplitudes of the sine curves of the plurality of groups of screening holes; The section perpendicular to the tangent vector of the guide strip includes a bottom edge and a top edge. The bottom edge is a straight line, and the length of the bottom edge is less than the preset distance between two groups of screening holes on both sides of any of the guide strips. The top edge is a curve corresponding to half the wavelength of the sine curve. The midpoint of the bottom edge corresponds to the peak of the top edge; The sieve plate includes a plurality of unit plates. Each unit plate includes a group of screening holes, and the plurality of unit plates are fixedly connected in sequence; Fixing holes are symmetrically formed on both sides of each of the plurality of unit plates. The corresponding fixing holes between adjacent unit plates are fixedly connected by a cylindrical pin; Positioning holes are formed at the bottom of the guide strip, and limiting holes are formed on the unit plate and are matched with the positioning holes. The positioning holes are threaded holes, and the positioning holes and the limiting holes are connected by screws; 2. The screen according to claim 1, wherein, A screening cavity is formed on the unit plate. The screening hole is the inlet of the screening cavity. The outlet of the screening cavity is formed below the screening hole. The sieve plate is provided with a discharge groove at the outlet of the screening cavity. The width of the discharge groove is greater than the width of the outlet of the screening cavity. The discharge groove communicates with the side wall of the unit plate close to the corresponding screening hole, and the discharge groove communicates with the lower surface of the unit plate; 3. The screen according to claim 2, characterized in that, The screening cavity adopts a first screening curved surface. The first screening curved surface is a rotating curved surface formed by a first generatrix rotating along a first track. The rotation axis is a perpendicular line passing through the center of the screening hole. The first generatrix includes a first arc segment and a second arc segment. The radius of the first arc segment is equal to the diameter of the screening hole. The center of the first arc segment is on the circumference of the screening hole. The starting point of the first arc segment is a point on the screening hole. The end point of the first arc segment is directly below the center of the screening hole. The radius of the second arc segment is equal to the diameter of the screening hole. The connection line between the center of the second arc segment and the center of the first arc segment passes through the center of the screening hole. The starting point of the second arc segment coincides with the end point of the first arc segment. The end point of the second arc segment is between the starting point of the second arc segment and the center of the first arc segment. The first track is an arc segment on the screening hole. The connection line between the starting point and the end point of the first track passes through the center of the screening hole.

4. The screen according to claim 2, wherein The screening cavity adopts a second screening surface, which is a rotating surface formed by rotating a second generatrix along a second trajectory. The rotation axis is a vertical line passing through the center of the screening hole. The second generatrix is an arc of a vertical plane passing through the center of the screening hole. The radius of the second generatrix is equal to the radius of the screening hole. The center of the second generatrix coincides with the center of the screening hole. The starting point of the second generatrix is on the circumference of the screening hole. The central angle of the second generatrix is a preset angle. The connection line between the starting point and the ending point of the second trajectory passes through the center of the screening hole.

5. The screen according to claim 1, characterized in that, The positioning holes are opened at positions corresponding to the peaks and valleys of the sine curve of the flow guiding strip.

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