Raw material screening device for plastic instrument shell production

Abstract

The invention relates to the technical field of plastic instrument shell production, in particular to a raw material screening device for plastic instrument shell production. Comprising a rack which is provided with a feeding part and a discharging part; the multiple screening shells are connected to the rack in a sliding mode, and every two adjacent screening shells are fixedly connected; the number of the top screening plates is the same as that of the screening shells, and the top screening plates are fixedly connected to the upper portions of the adjacent screening shells correspondingly; and the number of the middle screening plates is the same as that of the screening shells, the middle screening plates are fixedly connected to the middles of the adjacent screening shells correspondingly, the discharging part is fixedly connected with the adjacent screening shells, and besides the screening shell close to the discharging part, at least one screening shell is provided with symmetrically-distributed material guiding cavities. The material guiding cavity is additionally arranged, materials falling from the top screening plate are guided to the side close to the discharging part, the materials are separated from materials on the middle screening plate, and then the filtering effect on the materials falling from the top screening plate is improved.

Description

Technical Field

[0001] The invention relates to the technical field of plastic device casing production, and in particular to a raw material screening device for producing plastic device casings. Background Art

[0002] Plastic equipment casings are usually produced by injection molding machines, and the raw materials for injection molding are usually PE plastic particles. When the particle size of the plastic particles used by the injection molding machine is not uniform, the melting speed and temperature rise speed of plastic particles of different sizes are inconsistent, resulting in different temperatures of plastic particles at different positions in the injection molding machine, resulting in different viscosities of the plastic melt at different positions. When the viscosity of the plastic melt extruded by the injection molding machine is different, the density of different positions of the produced plastic equipment casing is not equal, affecting the quality of the final product. Therefore, before pouring the plastic particles into the injection molding machine, a vibrating screen is needed to screen the material.

[0003] The principle of vibrating screen screening is as follows: the material is passed horizontally through filters of different precisions, with a minimum of two layers of filters, and then plastic particles with larger, smaller and qualified particle sizes are screened to different positions, and different types of plastic particles are discharged outwardly, and the material discharged from between the two layers of filters is the required qualified material, because during the screening process, some materials are difficult to contact the lower filter when rolling. For example: when the upper material moves to near the discharge port, it passes through the upper filter and falls between the two filters. This part of the material will directly fall on the upper side of the material on the lower filter, and move to the discharge port with the material on the lower filter, making it difficult for this part of the material to pass through the lower filter. Some of the too small materials will be discharged together with the qualified materials, resulting in reduced filtration accuracy, which in turn affects the production quality of the injection molding machine. Summary of the invention

[0004] In order to overcome the disadvantage that some materials accumulate on the upper side of qualified materials after being filtered by the upper filter and are discharged without being filtered by the lower filter, the present invention provides a raw material screening device for producing plastic device casings.

[0005] The technical solution is: a raw material screening device for the production of plastic device casings, comprising: The frame is provided with a material discharging part and a material discharging part; There are a plurality of screening shells, all of which are slidably connected to the frame, and two adjacent screening shells are fixedly connected; Top screening plates, the number of which is the same as the number of screening shells, are respectively fixed to the upper parts of adjacent screening shells; The number of the middle screening plates is the same as that of the screening shells, and they are respectively fixed to the middle parts of the adjacent screening shells. The material discharge part is fixed to the adjacent screening shells. Except for the screening shell near the material discharge part, at least one of the screening shells is provided with a symmetrically distributed material guide cavity. The middle screening plate near the material guide cavity is fixed with a symmetrically distributed first material baffle plate and a symmetrically distributed second material baffle plate. The material guide cavity is used to guide the material screened by the adjacent top screening plate to the side of the adjacent middle screening plate near the material discharge part. The auxiliary screening mechanisms, the number of which is the same as the number of the screening shells, are respectively arranged on adjacent screening shells to assist in moving materials on various parts of the adjacent screening shells.

[0006] Furthermore, the lower portion of the material guiding cavity is gradually inclined downward from the material discharging portion toward the material discharging portion, and the lower portion of the material guiding cavity is inclined from the middle portion of the adjacent middle screen plate toward the outer side of the adjacent middle screen plate.

[0007] Furthermore, the distance between the symmetrically distributed first material baffle plates is greater than two-thirds of the width of the adjacent middle screening plates.

[0008] Furthermore, the auxiliary screening mechanism includes: A plurality of sliding frames are slidably connected to adjacent screening shells, and the sliding frames are fixed with a top push plate and a middle push plate, the top push plate and the adjacent top screening plate are mutually fitted, and the middle push plate and the adjacent middle screening plate are mutually fitted; There are a plurality of third material baffle plates, each of which is fixed to the adjacent middle push plates, and the third material baffle plates are in contact with the adjacent first material baffle plates; There are a plurality of fixing columns which are respectively fixed to the lower sides of the adjacent screening shells. The fixing columns penetrate the adjacent sliding frames, and an elastic member is installed between the two.

[0009] Furthermore, the minimum thickness of the top screen plate is equal to the minimum thickness of the middle screen plate, and the maximum sliding distance of the sliding frame relative to the screen shell is less than twice the minimum thickness of the top screen plate.

[0010] Furthermore, the third material baffle plates on the same middle push plate are commonly fixed with a material dividing column, the material dividing column is located on the upper side of the adjacent middle push plate, and a protrusion is provided at the lower part of the material dividing column.

[0011] Furthermore, the top push plate and the middle push plate are both provided with symmetrically distributed inclined surfaces for pushing the materials on their upper sides to different directions.

[0012] Furthermore, the top screening plate is provided with a plurality of first protrusions, and the middle screening plate is provided with a plurality of second protrusions, the number of the first protrusions and the number of the second protrusions are equal to the number of the sliding frames, the first protrusions are located on the side adjacent to the top push plate close to the discharge portion, and the second protrusions are located on the side adjacent to the middle push plate close to the discharge portion.

[0013] Furthermore, the material blocking plates, the number of which is equal to the number of the second protrusions, are respectively fixed to the adjacent screening shells, the number of the material blocking plates is equal to the number of the sliding frames, the material blocking plates are located on the upper side of the adjacent second protrusions, and the material blocking plates are provided with a plurality of spaced-apart protrusions.

[0014] Furthermore, it also includes: Fixed platforms, the number of which is equal to the number of the screening shells, and the fixed platforms are fixedly connected to the frame; The number of the fixed plates is equal to that of the sliding frames, and they are respectively fixed to the adjacent fixed platforms. The fixed plates correspond to the sliding frames one by one. The fixed plates are fixed with magnetic parts, and the magnetic parts are magnetically matched with the adjacent sliding frames.

[0015] Compared with the prior art, the present invention has the following advantages: the present invention guides the material falling from the top screen plate to the side close to the discharge part by adding a material guide cavity, and separates this part of the material from the material on the middle screen plate, thereby improving the filtering effect of the material falling from the top screen plate.

[0016] The present invention bounces the materials upward by the top push plate and the middle push plate on the sliding frame, so that these parts of the materials are scattered and mixed with each other in the air, and the stratification of the materials is changed, so that the materials in various places have the opportunity to contact with the top screening plate and the middle screening plate, thereby improving the filtering effect of the top screening plate and the middle screening plate on the materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention; Figure 2 A cross-sectional view of a frame and a screening shell of the present invention; Figure 3 It is a three-dimensional structural schematic diagram of the screening shell, the sliding frame and the fixed platform of the present invention; Figure 4 A cross-sectional view of the screening shell, the top screening plate and the sliding frame of the present invention; Figure 5 An exploded view of the top screening plate, the first raised portion and the top push plate of the present invention; Figure 6 It is a schematic diagram of the three-dimensional structure of the second material baffle plate, the middle push plate and the third material baffle plate of the present invention; Figure 7 It is a schematic diagram of the three-dimensional structure of the middle screening plate, the third material baffle plate and the material blocking plate of the present invention; Figure 8 It is a schematic diagram of the three-dimensional structure of the material blocking plate of the present invention; Fig. 9 It is a schematic diagram of the three-dimensional structure of the screening shell, the sliding frame and the fixed column of the present invention; Fig.10 It is a schematic diagram of the three-dimensional structure of the fixing platform, the fixing plate and the magnetic member of the present invention.

[0018] In the figure: 1. frame, 101. discharge part, 102. discharging part, 2. screening shell, 201. material guide cavity, 3. top screening plate, 301. first protrusion, 4. middle screening plate, 401. first baffle plate, 402. second baffle plate, 403. second protrusion, 5. sliding frame, 501. top push plate, 502. middle push plate, 503. third baffle plate, 504. material dividing column, 505. material blocking plate, 6. fixed column, 7. fixed table, 8. fixed plate, 9. magnetic part. DETAILED DESCRIPTION

[0019] Although the present invention can be described with respect to specific applications or industries, those skilled in the art will recognize the broader applicability of the present invention. Those of ordinary skill in the art will recognize that any numerical designations such as: first or second are only exemplary and are not intended to limit the scope of the present invention in any way.

[0020] A raw material screening device for producing plastic device casings, such as Figure 1-Figure 6 As shown, it includes: a frame 1, which is provided with a discharge part 101 and a discharge part 102; a plurality of screening shells 2, which are all slidably connected to the frame 1, and two adjacent screening shells 2 are fixedly connected; top screening plates 3, the number of which is the same as the number of screening shells 2, are respectively fixedly connected to the upper parts of adjacent screening shells 2; middle screening plates 4, the number of which is the same as the number of screening shells 2, are respectively fixedly connected to the middle parts of adjacent screening shells 2, and the discharge part 102 is fixedly connected to the adjacent screening shells 2. Except for the screening shells 2 close to the discharge part 101, at least A screening shell 2 is provided with a symmetrically distributed material guide cavity 201, and a symmetrically distributed first material baffle plate 401 and a symmetrically distributed second material baffle plate 402 are fixedly connected to the middle screening plate 4 near the material guide cavity 201. The material guide cavity 201 is used to guide the material screened by the adjacent top screening plate 3 to the side of the adjacent middle screening plate 4 near the discharge part 101; the auxiliary screening mechanisms, the number of which is the same as the number of the screening shells 2, are respectively arranged on adjacent screening shells 2, and are used to assist the movement of materials in various parts of the adjacent screening shells 2.

[0021] Further, such as Figure 5 and Figure 6As shown, the lower portion of the material guiding cavity 201 gradually tilts downward from the material discharging portion 102 toward the material discharging portion 101 , and the lower portion of the material guiding cavity 201 tilts from the middle of the adjacent middle screening plate 4 toward the outer side of the adjacent middle screening plate 4 .

[0022] Further, such as Figure 6 As shown, the distance between the symmetrically distributed first material blocking plates 401 is greater than two-thirds of the width of the adjacent middle screening plates 4 .

[0023] The above scheme aims to solve the problem that some materials that pass through the upper filter screen later are difficult to be filtered through the lower filter screen after being accumulated on the upper side of qualified materials after falling. The discharge part 101 and the bottom of all screening shells 2 are equipped with vibration motors, and the vibration motors are electrically connected to the external control terminal. The discharge part 102 is provided with a plurality of outlets, and the number of outlets is equal to the total number of the top screening plate 3 and the middle screening plate 4 on a screening shell 2 plus one. The top screening plate 3 is used to screen out oversized materials, and the middle screening plate 4 is used to screen out oversized materials. The staff can increase the number of middle screening plates 4 on each screening shell 2 according to specific needs, and then perform multi-stage screening on the materials to obtain materials of different particle sizes. In this scheme, only one layer of middle screening plate 4 is provided on each screening shell 2; a plurality of material guide cavities 201 can be provided on a screening shell 2 to disperse the materials screened out on the top screening plate 3 to different positions on the rear side of the adjacent middle screening plate 4. In this scheme, a screening shell 2 is only provided with two left-right symmetrical material guide cavities 201, which are used to disperse the materials screened on the top screening plate 3 to the left and right sides of the rear of the adjacent middle screening plate 4. In this scheme, considering that the amount of materials on the rearmost screening shell 2 is the largest, the material guide cavity 201 is not provided on the rearmost screening shell 2 to avoid affecting the smoothness of the materials falling from the rearmost top screening plate 3 to the adjacent middle screening plate 4; the material guide cavity 201 is tilted to the left or right side of the rear of the adjacent middle screening plate 4, so that the materials screened by the top screening plate 3 automatically slide to the rear of the adjacent middle screening plate 4 under the action of the vibration motor; by making the minimum height in the material guide cavity 201 greater than twice the aperture of the adjacent top screening plate 3, the probability of material blockage in the material guide cavity 201 is reduced; the distance between the symmetrically distributed first material baffle plates 401 is greater than two-thirds of the width of the adjacent middle screening plate 4, so as to promote the smooth movement of the materials on the middle screening plate 4 to the discharge part 102.

[0024] The working process of this scheme is as follows: when the staff needs to screen the raw materials, first start all the vibration motors through the control terminal. After the vibration motor is started, it drives all the screening shells 2, the discharge part 101 and the discharging part 102 to vibrate together. The staff then pours the materials into the discharge part 101 continuously. The materials enter the screening shell 2 at the rear side from the discharge part 101, and then gradually move from the rear screening shell 2 to the front screening shell 2. After passing through all the screening shells 2, the materials enter the discharging part 102 and are discharged outward from different outlets.

[0025] When the material is in the screening shell 2 at the rear end, the material passing through the top screening plate 3 falls directly onto the lower middle screening plate 4, and gradually moves forward driven by the screening shell 2, while the material that is too small on the middle screening plate 4 passes through the middle screening plate 4 during the movement and falls into the bottom of the screening shell 2, and this part of the material also moves forward under the action of the vibration motor, and when the material on the middle screening plate 4 contacts the second baffle plate 402 during the movement, the material is gradually guided to the middle of the front middle screening plate 4 (between the symmetrical first baffle plates 401), and then the material continues to move forward under the vibration of the front middle screening plate 4.

[0026] When the material is in the screening shell 2 not at the rear end, the material first falls into the adjacent material guide cavity 201 when passing through the top screening plate 3. At this time, the vibration motor drives the material in the material guide cavity 201 to move to the left and right sides of the rear of the adjacent middle screening plate 4 (the material falling into the left material guide cavity 201 moves to the left side of the rear of the middle screening plate 4, and the material falling into the right material guide cavity 201 moves to the right side of the rear of the middle screening plate 4). When the material falls from the material guide cavity 201 to the rear of the adjacent middle screening plate 4, this part of the material falls into the back side of the symmetrically distributed first material baffle plates 401 on the adjacent middle screening plate 4, so that this part of the material is separated from the material between the symmetrically distributed first material baffle plates 401, avoiding contact between this part of the material and the material on the middle screening plate 4, thereby reducing the probability of too small materials accumulating on the upper side of the materials on the middle screening plate 4 and failing to pass through the middle screening plate 4 and fall downward.

[0027] After all materials are discharged from the discharging portion 102, the staff turns off all vibration motors through the control terminal.

[0028] Further, such as Figure 4-Figure 7 and Fig.10As shown, the auxiliary screening mechanism includes: a sliding frame 5, which has several pieces and is slidably connected to the adjacent screening shells 2. The sliding frame 5 is fixed with a top push plate 501 and a middle push plate 502. The top push plate 501 fits with the adjacent top screening plate 3, and the middle push plate 502 fits with the adjacent middle screening plate 4; a third baffle plate 503, which has several pieces and is respectively fixed to the adjacent middle push plates 502, and the third baffle plate 503 fits with the adjacent first baffle plate 401; a fixed column 6, which has several pieces and is respectively fixed to the lower side of the adjacent screening shells 2. The fixed column 6 penetrates the adjacent sliding frame 5, and an elastic member is installed between the two.

[0029] Further, such as Fig.10 As shown, the minimum thickness of the top screen plate 3 is equal to the minimum thickness of the middle screen plate 4 , and the maximum sliding distance of the sliding frame 5 relative to the screen shell 2 is less than twice the minimum thickness of the top screen plate 3 .

[0030] In the above scheme, two sliding frames 5 are arranged on each screening shell 2, and the two sliding frames 5 are both located on the side of the adjacent screening shell 2 close to the discharge part 101, so as to promote the mixing of the materials just entering the screening shell 2; the elastic member between the fixed column 6 and the sliding frame 5 is a spring, which is used to drive the sliding frame 5 to vibrate up and down with the adjacent screening shell 2. At this time, the sliding frame 5 slides up and down relative to the screening shell 2 during the vibration process, so that the top push plate 501 and the middle push plate 502 on the sliding frame 5 slide relative to the top screening plate 3 and the middle screening plate 4 respectively. The materials passing through the top push plate 501 and the middle push plate 502 are thrown upward relative to the top screening plate 3 and the middle screening plate 4, so as to promote the materials on the top screening plate 3 to exchange positions with each other, and the materials on the middle screening plate 4 to exchange positions with each other, thereby reducing the probability that the too small materials cannot pass through the middle screening plate 4 because they are accumulated on the upper side of the qualified materials; by limiting the maximum sliding distance of the sliding frame 5, it is ensured that the top push plate 501 and the middle push plate 502 always maintain contact with the adjacent top screening plate 3 and the middle screening plate 4 respectively during the movement relative to the screening shell 2.

[0031] Further, such as Figure 6 and Figure 7 As shown, the third material blocking plate 503 on the same middle push plate 502 is fixedly connected with a material dividing column 504 . The material dividing column 504 is located on the upper side of the adjacent middle push plate 502 , and a protrusion is provided at the lower part of the material dividing column 504 .

[0032] Further, such as Figure 4-Figure 7 As shown, the top push plate 501 and the middle push plate 502 are both provided with symmetrically distributed inclined surfaces for pushing the materials on their upper sides to different directions.

[0033] Further, such as Figure 4-Figure 7As shown, the top screening plate 3 is provided with a plurality of first protrusions 301, and the middle screening plate 4 is provided with a plurality of second protrusions 403. The number of the first protrusions 301 and the number of the second protrusions 403 are equal to the number of the sliding frames 5. The first protrusions 301 are located on a side of the adjacent top push plate 501 close to the discharge portion 102, and the second protrusions 403 are located on a side of the adjacent middle push plate 502 close to the discharge portion 102.

[0034] Further, such as Figure 7 and Figure 8 As shown, it also includes: material blocking plates 505, the number of which is equal to the number of second protrusions 403, which are respectively fixed to adjacent screening shells 2, the number of material blocking plates 505 is equal to the number of sliding frames 5, the material blocking plates 505 are located on the upper side of the adjacent second protrusions 403, and the material blocking plates 505 are provided with a plurality of spaced apart protrusions.

[0035] In the above scheme, the number of the material distribution columns 504 can be changed according to needs, and the lower side of the material distribution column 504 can be provided with a semicircular protrusion or other irregularly shaped protrusions. In the present scheme, the material distribution column 504 is set to be a triangular prism, and one of the edges is located directly below the material distribution column 504, which is used to guide the material thrown upward by the middle push plate 502 to the front and rear sides, thereby promoting the mixing effect of the material after being thrown up. By setting symmetrical inclined surfaces on the top push plate 501 and the middle push plate 502, after the material is thrown up by the top push plate 501 and the middle push plate 502, the material is subjected to different forces at the front and rear, thereby causing the material at different positions to be moved to different directions. The material is thrown up to promote the mixing of materials in the air; the material blocking plate 505 is used to prevent the thrown material from moving significantly toward the discharge part 102, thereby preventing the material from being thrown forward quickly and affecting the screening process of the material by the middle screening plate 4. At the same time, by setting the first protrusion 301 and the second protrusion 403, the material on the front side of the first protrusion 301 and the front side of the second protrusion 403 can be quickly moved forward, thereby reducing the probability of the thrown material falling on other materials, so as to increase the possibility of the thrown material passing through the top screening plate 3 or the middle screening plate 4 after falling, thereby improving the screening efficiency of the top screening plate 3 and the middle screening plate 4.

[0036] Further, such as Figure 3 , Fig. 9 and Fig.10 As shown, it also includes: fixed platforms 7, the number of which is equal to the number of screening shells 2, and the fixed platforms 7 are fixedly connected to the frame 1; fixed plates 8, the number of which is equal to the number of sliding frames 5, are respectively fixedly connected to adjacent fixed platforms 7, the fixed plates 8 correspond to the sliding frames 5 one by one, and the fixed plates 8 are fixed with magnetic parts 9, which are magnetically matched with the adjacent sliding frames 5.

[0037] In the above scheme, the magnetic member 9 can be a normal magnetic magnet or an electromagnet. The magnetic member 9 can be located at the lower side of the sliding frame 5 or at the front and rear sides of the sliding frame 5. It is only necessary to ensure that when the screening shell 2 drives the sliding frame 5 to move up and down, the sliding frame 5 can always be subjected to the magnetic force of the adjacent magnetic member 9. When the sliding frame 5 moves downward with the screening shell 2 under the action of the adjacent elastic member, the sliding frame 5 is affected by the magnetic force of the magnetic member 9 and is subjected to a downward force. When the screening shell 2 moves upward under the action of the vibration motor, the sliding frame 5 remains stationary under the action of the magnetic member 9, and the elastic member on the sliding frame 5 accumulates force. When the elastic member accumulates force to the limit state, the screening shell 2 directly drives the sliding frame 5 to move upward until the sliding frame 5 moves upward to the magnetic force range out of the magnetic member 9. At this time, the sliding frame 5 quickly moves upward and resets under the elastic force of the adjacent elastic member, thereby increasing the force of the top push plate 501 and the middle push plate 502 on the sliding frame 5 to bounce off the materials thereon, thereby promoting rapid mixing of the materials.

[0038] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A raw material screening device for the production of plastic equipment casings, characterized in that: Included are: The frame (1) is provided with a material discharge portion (101) and a material discharge portion (102); There are a plurality of screening shells (2), all of which are slidably connected to the frame (1), and two adjacent screening shells (2) are fixedly connected; Top screening plates (3), the number of which is the same as the number of screening shells (2), and are respectively fixed to the upper parts of adjacent screening shells (2); The number of middle screening plates (4) is the same as the number of screening shells (2), and they are respectively fixed to the middle parts of the adjacent screening shells (2); the discharge portion (102) is fixed to the adjacent screening shells (2); except for the screening shell (2) close to the discharge portion (101), at least one of the screening shells (2) is provided with a symmetrically distributed material guide cavity (201); the middle screening plate (4) close to the material guide cavity (201) is fixed with a symmetrically distributed first material baffle plate (401) and a symmetrically distributed second material baffle plate (402); the material guide cavity (201) is used to guide the material screened by the adjacent top screening plate (3) to a side of the adjacent middle screening plate (4) close to the discharge portion (101); The auxiliary screening mechanisms, the number of which is the same as the number of the screening shells (2), are respectively arranged on adjacent screening shells (2) and are used to assist in the movement of materials in various parts of the adjacent screening shells (2).

2. A raw material screening device for producing plastic device casings according to claim 1, characterized in that: The lower part of the material guiding cavity (201) gradually tilts downward from the material discharging portion (102) toward the material discharging portion (101), and the lower part of the material guiding cavity (201) tilts from the middle of the adjacent middle screening plate (4) toward the outer side of the adjacent middle screening plate (4).

3. A raw material screening device for producing plastic device casings according to claim 2, characterized in that: The distance between the symmetrically distributed first material blocking plates (401) is greater than two thirds of the width of the adjacent middle screening plates (4).

4. A raw material screening device for producing plastic device casings according to claim 3, characterized in that: The auxiliary screening mechanism comprises: A plurality of sliding frames (5) are slidably connected to adjacent screening shells (2); the sliding frames (5) are fixedly connected with a top push plate (501) and a middle push plate (502); the top push plate (501) and the adjacent top screening plate (3) are in contact with each other, and the middle push plate (502) and the adjacent middle screening plate (4) are in contact with each other; A plurality of third material blocking plates (503) are respectively fixed to the adjacent middle push plates (502), and the third material blocking plates (503) are in contact with the adjacent first material blocking plates (401); There are a plurality of fixed columns (6) which are respectively fixed to the lower sides of the adjacent screening shells (2); the fixed columns (6) penetrate the adjacent sliding frames (5), and an elastic member is installed between the two.

5. A raw material screening device for producing plastic device casings according to claim 4, characterized in that: The minimum thickness of the top screen plate (3) is equal to the minimum thickness of the middle screen plate (4), and the maximum sliding distance of the sliding frame (5) relative to the screen shell (2) is less than twice the minimum thickness of the top screen plate (3).

6. A raw material screening device for producing plastic device casings according to claim 4, characterized in that: The third material baffle plate (503) on the same middle push plate (502) is fixedly connected with a material distribution column (504), the material distribution column (504) is located on the upper side of the adjacent middle push plate (502), and a protrusion is provided at the lower part of the material distribution column (504).

7. A raw material screening device for producing plastic device casings according to claim 6, characterized in that: The top push plate (501) and the middle push plate (502) are both provided with symmetrically distributed inclined surfaces, which are used to push the materials on their upper sides to different directions.

8. A raw material screening device for producing plastic device casings according to claim 7, characterized in that: The top screening plate (3) is provided with a plurality of first protrusions (301), and the middle screening plate (4) is provided with a plurality of second protrusions (403), the number of the first protrusions (301) and the number of the second protrusions (403) are both equal to the number of the sliding frames (5), the first protrusions (301) are located on a side adjacent to the top push plate (501) close to the discharge portion (102), and the second protrusions (403) are located on a side adjacent to the middle push plate (502) close to the discharge portion (102).

9. A raw material screening device for producing plastic device casings according to claim 8, characterized in that: Also included are: The material blocking plates (505) are equal in number to the second protrusions (403) and are respectively fixed to the adjacent screening shells (2). The material blocking plates (505) are equal in number to the sliding frames (5). The material blocking plates (505) are located on the upper side of the adjacent second protrusions (403). The material blocking plates (505) are provided with a plurality of convex columns distributed at intervals.

10. A raw material screening device for producing plastic device casings according to claim 9, characterized in that: Also included are: Fixed platforms (7), the number of which is equal to the number of the screening shells (2), and the fixed platforms (7) are fixedly connected to the frame (1); The number of the fixed plates (8) is equal to the number of the sliding frames (5), and they are respectively fixed to the adjacent fixed platforms (7). The fixed plates (8) correspond to the sliding frames (5) one by one. The fixed plates (8) are fixed with magnetic parts (9), and the magnetic parts (9) are magnetically matched with the adjacent sliding frames (5).

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