An automatic sand and gravel screening machine for municipal highway construction

Abstract

The present invention discloses an automatic screening machine for sand and gravel used in municipal highway construction, which belongs to the technical field of municipal highway construction. The present invention comprises a vertically placed cylinder, the lower end of which is provided with a discharge port, and the upper end of which is fixedly provided with a hopper; it also comprises: an auger, which is fixedly connected to the output end of the motor, the outer side of the upper end shaft of the auger is keyed to a sliding sleeve, and the outer side of the sliding sleeve is evenly fixedly connected to a fixed column, and the lower end of the fixed column is fixedly connected to a grinding piece; a dispersion seat, which is arranged above the grinding piece, and the grinding piece and the dispersion seat are connected by a connecting assembly; a guide assembly, which is arranged between the cylinder and the dispersion seat; and a screening assembly, which is arranged on the inner side of the lower part of the cylinder. The automatic screening machine for sand and gravel used in municipal highway construction can automatically clear the screen, and can automatically convey and grind large-grained sand and gravel, and can use the grinding heat to achieve drying and spreading of sand and gravel, thereby improving screening efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of municipal highway construction, in particular to an automatic sand and gravel screening machine for municipal highway construction. Background Art

[0002] During the construction of municipal roads, a large amount of sand and gravel raw materials are needed. In order to ensure the construction quality of the road, the sand and gravel raw materials need to be screened to remove large-sized sand and gravel. Therefore, an automatic sand and gravel screening machine is needed.

[0003] The prior art (application number: 202410326040.9, Chinese patent with application date of 2024-03-21) discloses a road construction gravel screening device, comprising a hollow supporting metal plate, a plurality of anti-slip elastic plates are arranged at both ends of the lower surface of the hollow supporting metal plate, an adjustable screening mechanism for screening gravel is arranged above the hollow supporting metal plate, a storage driving mechanism for position adjustment of the adjustable screening mechanism is arranged on the upper surface of the hollow supporting metal plate, the adjustable screening mechanism comprises a movable metal box, and a detachable metal mesh screen is arranged inside the movable metal box; the sand and gravel are screened quickly and fully by moving the screening structure in multiple positions, and the retained stones are automatically and quickly discharged by changing the posture of the screening device, so that the user does not need to frequently manually maintain the screening structure, the processing efficiency of the screening device is significantly improved, and the use of the screening device is more convenient;

[0004] Although the sand and gravel screening machine in the prior art can screen the sand and gravel by moving in multiple positions, it is unable to grind and recycle the screened large-particle sand and gravel, resulting in low utilization rate of raw materials and certain usage defects. Summary of the invention

[0005] The purpose of the present invention is to provide an automatic sand and gravel screening machine for municipal highway construction, so as to solve the problem raised by the above background technology that the automatic sand and gravel screening machines on the market are unable to grind and recycle the screened large-particle sand and gravel, resulting in low utilization rate of raw materials.

[0006] To achieve the above object, the present invention provides the following technical solution: an automatic sand and gravel screening machine for municipal highway construction, comprising a vertically placed cylinder, a discharge port is provided at the lower end of the cylinder, a hopper is fixedly installed at the upper end of the cylinder, a fixing frame is fixedly installed on the hopper, and a motor is fixedly installed at the center position of the fixing frame;

[0007] It also includes: an auger, fixedly connected to the output end of the motor, the outer side of the upper end shaft of the auger is keyed to a sliding sleeve, and the outer side of the sliding sleeve is evenly fixedly connected to a fixing column, and the lower end of the fixing column is fixedly connected to a grinding piece, and the upper part of the sliding sleeve is fixedly connected to a connecting seat; a fixing cylinder, fixedly installed on the lower surface of the fixing frame;

[0008] The dispersion seat is arranged above the grinding piece, the grinding piece and the dispersion seat are connected by a connecting component, and the bottom of the dispersion seat is fixedly connected with a conveying cylinder by a connecting piece; the guide component is arranged between the cylinder body and the dispersion seat; the screening component is arranged on the lower inner side of the cylinder body to realize sand and gravel screening.

[0009] Preferably, the hopper and the dispersion seat are coaxially arranged, and the lower opening of the hopper and the top of the dispersion seat are arranged correspondingly up and down, and the dispersion seat is arranged in a conical structure, and the outer side wall of the dispersion seat is evenly provided with guide plates with an arc structure.

[0010] By adopting the above technical solution, when the sand and gravel in the hopper falls onto the surface of the dispersion seat, the guide plate can divert and guide the sand and gravel, thereby extending the residence time of the sand and gravel on the surface of the dispersion seat, and at the same time making the subsequent falling of the material more uniform.

[0011] Preferably, during the rotation of the auger, the grinding part is driven to rotate synchronously through the sliding sleeve and the fixed column, and a reciprocating thread is provided on the outer wall of the lower end of the fixed cylinder, and a connecting seat is fixedly connected to the upper end of the sliding sleeve, and the connecting seat and the reciprocating thread are threadedly connected.

[0012] By adopting the above technical solution, the rotation of the auger can drive the sleeve to rotate synchronously, so that the sleeve drives the connecting seat to rotate outside the fixed cylinder, and then the connecting seat is connected to the reciprocating thread thread, which can drive the connecting seat to drive the grinding part to be raised and lowered through the sleeve.

[0013] Preferably, the connecting assembly includes a connecting ring fixedly mounted on the lower surface of the dispersion seat, and a sliding groove is opened on the inner side of the connecting ring, and the top of the fixed column is set as a spherical structure, and the spherical structure on the top of the fixed column and the sliding groove on the connecting ring are slidably connected, and the grinding part drives the dispersion seat to be synchronously lifted and lowered through the fixed column and the connecting ring, the outer side of the dispersion seat is evenly fixedly mounted with a fixing part, and the inner wall of the cylinder is evenly fixedly mounted with a guide seat, and the fixing part and the guide seat constitute a sliding structure.

[0014] By adopting the above technical solution, when the grinding piece rotates and rises and falls, the dispersion seat can be driven to perform synchronous lifting and lowering adjustment, so that the dispersion seat promotes the transportation and dispersion of sand and gravel on its surface through vibration.

[0015] Preferably, the dispersion seat drives the conveying cylinder through a connecting piece to perform synchronous lifting and lowering adjustment, the screening assembly includes a screen for screening sand and gravel, and the conveying cylinder is in contact with the upper surface of the center position of the screen during the downward movement, and the lower end of the auger is in contact with the center position of the screen.

[0016] By adopting the above technical solution, the large-particle sand and gravel screened out at the center of the screen can be covered during the downward movement of the conveying cylinder, so that the conveying cylinder covers the lower end of the auger, and the auger can intermittently transport the screened large-particle sand and gravel.

[0017] Preferably, the conveying cylinder passes through the center of the grinding piece, and the upper end of the conveying cylinder is flush with the upper end of the grinding piece, and the distance between the grinding piece and the dispersion seat gradually decreases from the center to the edge. At the same time, the grinding piece and the dispersion seat grind large particles of sand and gravel during rotation.

[0018] By adopting the above technical solution, the grinding piece and the dispersion seat can grind the large-particle sand and gravel screened out, thereby improving the screening utilization rate of the sand and gravel. At the same time, the grinding piece and the dispersion seat can be synchronously shaken during the grinding process, further promoting the grinding effect.

[0019] Preferably, the dispersion seat and the guide plate are both made of heat-conducting materials, and the dispersion seat and the guide plate heat the sand and gravel on the dispersion seat through the heat generated by grinding.

[0020] By adopting the above technical solution, the heat generated by the grinding element and the dispersion seat during the grinding process can heat the sand and gravel transported on the dispersion seat, thereby reducing the probability of the sand and gravel getting damp and agglomerating, and avoiding affecting the subsequent screening operation.

[0021] Preferably, the dispersion seat and the screen are coaxially arranged, the outer diameter of the lower end of the dispersion seat is smaller than the outer diameter of the upper end of the screen, and the screen is arranged in a funnel shape.

[0022] By adopting the above technical solution, the screen can receive the sand and gravel falling from the dispersion seat, thereby realizing automatic screening.

[0023] Preferably, the screening assembly also includes a fixed seat fixedly mounted on the lower inner wall of the cylinder, and a telescopic rod is evenly penetrated through the fixed seat for telescopic connection, and a spring is connected between the lower end of the telescopic rod and the fixed seat, while the upper end of the telescopic rod is fixedly connected to the lower surface of the screen, and the screen is pushed downward during the downward movement of the conveying cylinder.

[0024] By adopting the above technical solution, the screen can be pushed to vibrate elastically during the downward movement of the conveying cylinder, thereby clearing the blockage of the screen, and at the same time facilitating the collection and transportation and grinding of large-particle sand and gravel after screening.

[0025] Compared with the prior art, the invention has the following beneficial effects: the automatic sand and gravel screening machine for municipal highway construction can automatically clear the screen, automatically transport and grind large-grain sand and gravel, and utilize the grinding heat to dry and spread the sand and gravel, thereby improving the screening efficiency. The specific contents are as follows;

[0026] 1. A sliding sleeve, a connecting seat and a conveying cylinder are provided. As the auger rotates, it will drive the sliding sleeve and the grinding piece to rotate synchronously, so that the connecting seat and the fixed cylinder are threadedly connected, and then the grinding piece, the dispersion seat and the conveying cylinder are driven to be raised and lowered synchronously, so that the lower end of the conveying cylinder is intermittently attached to the middle of the screen, thereby intermittently conveying the large-particle sand and gravel screened on the screen;

[0027] Furthermore, as the grinding element rotates, it can cooperate with the lower surface of the dispersion seat to automatically grind the large-grained sand and gravel delivered to the surface of the grinding element, thereby improving the utilization rate of the sand and gravel;

[0028] 2. A dispersion seat is provided. The dispersion seat can be adjusted along with the lifting of the grinding piece to disperse the sand and gravel falling on it. At the same time, the heat generated during the grinding process can further heat and dry the sand and gravel on the dispersion seat, thereby further promoting the dispersion of the sand and gravel and preventing the sand and gravel from being wet and sticky and affecting the subsequent screening operation;

[0029] 3. A conveying cylinder and a screen are provided. As the conveying cylinder is raised and lowered back and forth, the conveying cylinder can fit and push the screen downward during the downward movement, so that the screen vibrates elastically under the action of the spring force, thereby realizing automatic clearing of the screen and the gathering of large-grained sand and gravel, which is convenient for subsequent conveying and grinding. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the main structure of the present invention;

[0031] Figure 2 It is a schematic diagram of the cross-sectional structure of the cylinder of the present invention;

[0032] Figure 3 It is a schematic diagram of the main cross-sectional structure of the present invention;

[0033] Figure 4 This is a schematic diagram of the installation structure of the dispersion seat of the present invention;

[0034] Figure 5 This is a schematic diagram of the cross-sectional structure of the dispersion seat of the present invention;

[0035] Figure 6 This is a schematic diagram of the installation structure of the sliding sleeve and the connecting seat of the present invention;

[0036] Figure 7 This is a schematic diagram of the screen installation structure of the present invention;

[0037] Figure 8 For the present invention Figure 5 Enlarged structural diagram at A in the middle.

[0038] In the figure: 1. cylinder; 2. hopper; 3. fixed frame; 4. motor; 5. auger; 6. sliding sleeve; 7. fixed column; 8. grinding part; 9. connecting seat; 10. fixed cylinder; 11. reciprocating thread; 12. connecting ring; 13. dispersion seat; 14. guide plate; 15. fixing part; 16. guide seat; 17. conveying cylinder; 18. connecting part; 19. fixed seat; 20. telescopic rod; 21. spring; 22. screen. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Example 1: Please refer to Figure 1-Figure 5 and Figure 7-Figure 8 As shown, the existing automatic sand and gravel screening machine is inconvenient to disperse the sand and gravel during use, and it is inconvenient to automatically clear the filter screen, thereby reducing the screening efficiency. In order to solve this technical problem, this embodiment discloses the following technical content;

[0041] An automatic sand and gravel screening machine for municipal highway construction comprises a vertically placed cylinder 1, a discharge port is provided at the lower end of the cylinder 1, a hopper 2 is fixedly installed at the upper end of the cylinder 1, a fixing frame 3 is fixedly installed on the hopper 2, and a motor 4 is fixedly installed at the center position of the fixing frame 3;

[0042] It also includes: an auger 5, which is fixedly connected to the output end of the motor 4, and the outer side of the upper end shaft of the auger 5 is keyed to a sleeve 6, and the outer side of the sleeve 6 is evenly fixedly connected to a fixing column 7, and the lower end of the fixing column 7 is fixedly connected to a grinding piece 8, and at the same time, a connecting seat 9 is fixedly connected to the top of the sleeve 6; a fixed cylinder 10, fixedly installed on the lower surface of the fixed frame 3; a dispersion seat 13, which is arranged above the grinding piece 8, and the grinding piece 8 and the dispersion seat 13 are connected by a connecting assembly, and the bottom of the dispersion seat 13 is fixedly connected to a conveying cylinder 17 by a connecting piece 18; a guide assembly, which is arranged between the cylinder body 1 and the dispersion seat 13; a screening assembly, which is arranged on the inner side of the lower part of the cylinder body 1, and is used to realize sand and gravel screening.

[0043] The hopper 2 and the dispersion seat 13 are coaxially arranged, and the lower opening of the hopper 2 and the top of the dispersion seat 13 are arranged correspondingly up and down, and the dispersion seat 13 is arranged in a conical structure, and the outer side wall of the dispersion seat 13 is evenly provided with guide plates 14 with an arc structure.

[0044] During the rotation of the auger 5, the grinding member 8 is driven to rotate synchronously through the sliding sleeve 6 and the fixed column 7, and a reciprocating thread 11 is provided on the outer wall of the lower end of the fixed cylinder 10, and a connecting seat 9 is fixedly connected to the upper end of the sliding sleeve 6, and the connecting seat 9 and the reciprocating thread 11 are threadedly connected.

[0045] The connecting assembly includes a connecting ring 12 fixedly mounted on the lower surface of the dispersion seat 13, and a sliding groove is opened on the inner side of the connecting ring 12, and the top of the fixed column 7 is a spherical structure. At the same time, the spherical structure on the top of the fixed column 7 and the sliding groove on the connecting ring 12 are slidably connected, and the grinding part 8 drives the dispersion seat 13 to be synchronously lifted and lowered through the fixed column 7 and the connecting ring 12. The outer side of the dispersion seat 13 is evenly fixedly mounted with a fixing part 15, and the inner wall of the cylinder 1 is evenly fixedly mounted with a guide seat 16, and the fixing part 15 and the guide seat 16 constitute a sliding structure.

[0046] The dispersion seat 13 drives the conveying cylinder 17 to be synchronously lifted and lowered through the connecting piece 18. The screening assembly includes a screen 22 for screening sand and gravel, and the conveying cylinder 17 is fitted to the upper surface of the center position of the screen 22 during the downward movement, and the lower end of the auger 5 is fitted to the center position of the screen 22. The dispersion seat 13 and the guide plate 14 are both made of heat-conducting materials, and the dispersion seat 13 and the guide plate 14 heat the sand and gravel on the dispersion seat 13 through the heat generated by grinding. The dispersion seat 13 and the screen 22 are coaxially arranged, and the outer diameter of the lower end of the dispersion seat 13 is smaller than the outer diameter of the upper end of the screen 22, and the screen 22 is arranged in a funnel shape.

[0047] The screening assembly also includes a fixed seat 19 fixedly mounted on the lower inner wall of the cylinder 1, and a telescopic rod 20 is evenly penetrated and telescopically connected on the fixed seat 19, and a spring 21 is connected between the lower end of the telescopic rod 20 and the fixed seat 19, and the upper end of the telescopic rod 20 is fixedly connected to the lower surface of the screen 22, and the screen 22 is pushed downward when the conveying cylinder 17 moves downward.

[0048] By adopting the above technical solution, sand and gravel are poured into the hopper 2, so that the sand and gravel fall to the upper surface of the dispersion seat 13 through the opening at the lower end of the hopper 2, and then the motor 4 is started, so that the motor 4 drives the auger 5 to rotate. At this time, the auger 5 will drive the connecting seat 9 to rotate synchronously through the sliding sleeve 6, so that the reciprocating thread 11 provided on the outer side of the connecting seat 9 and the fixed cylinder 10 is connected, and then the sliding sleeve 6 is driven to drive the grinding piece 8 to perform synchronous reciprocating lifting and lowering adjustment through the fixed column 7. At this time, the ball at the upper end of the fixed column 7 slides along the groove of the connecting ring 12, and at the same time, the fixed column 7 drives the dispersion seat 13 to reciprocate and lift through the ball at the upper end and the connecting ring 12. At the same time, the fixed column 7 drives the dispersion seat 13 to reciprocate and lift through the ball at the upper end and the connecting ring 12. The fixed piece 15 will be lifted and slid along the guide seat 16 to realize the guide limit. As the dispersion seat 13 shakes, it can shake and disperse the sand and gravel above, so that the sand and gravel can fall evenly onto the screen 22. As the dispersion seat 13 is lifted and lowered, it can drive the conveying cylinder 17 to be lifted and lowered synchronously through the connecting piece 18, so that the conveying cylinder 17 can contact and push the screen 22 to move downward during the downward movement. At this time, the telescopic rod 20 on the screen 22 will be telescopically adjusted with the fixed seat 19 and stretch the spring 21, so that the screen 22 can be elastically shaken under the drive of the conveying cylinder 17, thereby improving the screening effect of the screen 22 and avoiding blockage of the screen 22.

[0049] Embodiment 2: The technical content disclosed in this embodiment is a further improvement on the above embodiment 1. The existing automatic screening machine for sand and gravel is inconvenient to circulate and grind the screened large-size sand and gravel. In order to further solve this technical problem, this embodiment discloses the following technical content, such as Figure 4-Figure 6 and Figure 8 As shown;

[0050] The dispersion seat 13 drives the conveying cylinder 17 to be synchronously raised and lowered through the connecting piece 18. The screening assembly includes a screen 22 for screening sand and gravel, and the conveying cylinder 17 is attached to the upper surface of the center position of the screen 22 during the downward movement, and the lower end of the auger 5 is attached to the center position of the screen 22.

[0051] The conveying cylinder 17 passes through the center of the grinding piece 8, and the upper end of the conveying cylinder 17 is flush with the upper end of the grinding piece 8, and the distance between the grinding piece 8 and the dispersion seat 13 gradually decreases from the center to the edge. At the same time, the grinding piece 8 and the dispersion seat 13 grind the large particles of sand and gravel during rotation. The dispersion seat 13 and the guide plate 14 are both made of heat-conducting materials, and the dispersion seat 13 and the guide plate 14 heat the sand and gravel on the dispersion seat 13 through the heat generated by grinding.

[0052] By adopting the above technical solution, as the conveying cylinder 17 moves downward, the conveying cylinder 17 will fit the center position of the screen 22, so that the conveying cylinder 17 can cover the lower end of the auger 5 and the large-particle sand and gravel screened out. At this time, the auger 5 can cooperate with the conveying cylinder 17 to intermittently lift and convey the large-particle sand and gravel screened out. When the large-particle sand and gravel move to the upper end of the conveying cylinder 17, they will fall to the upper surface of the grinding member 8. As the grinding member 8 rotates, the grinding member 8 can cooperate with the dispersion seat 13 to grind and refine the circulated large-particle sand and gravel, and the heat generated during the grinding process can be conducted through the dispersion seat 13 and the guide plate 14, thereby realizing the heating and drying of the sand and gravel on the dispersion seat 13, thereby further improving the dispersion effect of the sand and gravel, and facilitating subsequent screening.

[0053] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0054] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An automatic sand and gravel screening machine for municipal highway construction, comprising a vertically placed cylinder (1), a discharge port being provided at the lower end of the cylinder (1), a hopper (2) being fixedly mounted at the upper end of the cylinder (1), a fixed frame (3) being fixedly mounted on the hopper (2), and a motor (4) being fixedly mounted at the center of the fixed frame (3); It is characterized in that Also includes: An auger (5) is fixedly connected to the output end of the motor (4); the outer side of the upper shaft of the auger (5) is keyed to a sliding sleeve (6); the outer side of the sliding sleeve (6) is evenly fixedly connected to a fixing column (7); the lower end of the fixing column (7) is fixedly connected to a grinding piece (8); and the upper part of the sliding sleeve (6) is fixedly connected to a connecting seat (9); during the rotation of the auger (5), the grinding piece (8) is driven to rotate synchronously through the sliding sleeve (6) and the fixing column (7); a reciprocating thread (11) is provided on the outer wall of the lower end of the fixing cylinder (10); and the upper end of the sliding sleeve (6) is fixedly connected to the connecting seat (9); and the connecting seat (9) and the reciprocating thread (11) are threadedly connected; A fixed cylinder (10) fixedly mounted on the lower surface of the fixed frame (3); A dispersion seat (13) is arranged above the grinding member (8), the grinding member (8) and the dispersion seat (13) are connected via a connection assembly, and a conveying cylinder (17) is fixedly connected to the bottom of the dispersion seat (13) via a connection member (18), the connection assembly comprises a connection ring (12) fixedly mounted on the lower surface of the dispersion seat (13), a slide groove is provided on the inner side of the connection ring (12), and the top of the fixed column (7) is a spherical structure, and the spherical structure on the top of the fixed column (7) and the slide groove on the connection ring (12) are slidably connected, and the grinding member (8) drives the dispersion seat (13) to be synchronously raised and lowered through the fixed column (7) and the connection ring (12), the outer side of the dispersion seat (13) is evenly fixedly mounted with a fixing member (15), and the inner wall of the cylinder (1) is evenly fixedly mounted with a guide seat (16), and the fixing member (15) and the guide seat (16) constitute a sliding structure; A guide assembly, arranged between the cylinder (1) and the dispersion seat (13); A screening assembly is arranged on the inner side of the lower part of the cylinder (1) and is used to screen sand and gravel. The dispersion seat (13) drives the conveying cylinder (17) to be synchronously raised and lowered through a connecting piece (18). The screening assembly includes a screen (22) for screening sand and gravel. The conveying cylinder (17) is attached to the upper surface of the center position of the screen (22) during the downward movement, and the lower end of the auger (5) is attached to the center position of the screen (22).

2. The automatic sand and gravel screening machine for municipal highway construction according to claim 1 is characterized by: The hopper (2) and the dispersion seat (13) are coaxially arranged, and the lower opening of the hopper (2) and the top of the dispersion seat (13) are arranged in correspondence with each other, and the dispersion seat (13) is arranged in a conical structure, and the outer side wall of the dispersion seat (13) is evenly provided with guide plates (14) with an arc structure.

3. The automatic sand and gravel screening machine for municipal highway construction according to claim 1 is characterized by: The conveying cylinder (17) passes through the center of the grinding piece (8), and the upper end of the conveying cylinder (17) is flush with the upper end of the grinding piece (8), and the distance between the grinding piece (8) and the dispersion seat (13) gradually decreases from the center to the edge. At the same time, the grinding piece (8) and the dispersion seat (13) grind large particles of sand and gravel during rotation.

4. The automatic sand and gravel screening machine for municipal highway construction according to claim 3 is characterized by: The dispersion seat (13) and the guide plate (14) are both made of heat-conducting materials, and the dispersion seat (13) and the guide plate (14) heat the sand and gravel on the dispersion seat (13) through the heat generated by grinding.

5. The automatic sand and gravel screening machine for municipal highway construction according to claim 1 is characterized by: The dispersion seat (13) and the screen (22) are coaxially arranged, the outer diameter of the lower end of the dispersion seat (13) is smaller than the outer diameter of the upper end of the screen (22), and the screen (22) is arranged in a funnel shape.

6. The automatic sand and gravel screening machine for municipal highway construction according to claim 1 is characterized by: The screening assembly further comprises a fixing seat (19) fixedly mounted on the lower inner wall of the cylinder (1), and a telescopic rod (20) is evenly penetrated through the fixing seat (19) and is telescopically connected, and a spring (21) is connected between the lower end of the telescopic rod (20) and the fixing seat (19), and the upper end of the telescopic rod (20) is fixedly connected to the lower surface of the screen (22), and the screen (22) is pushed downward when the conveying cylinder (17) moves downward.

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