A crushing and grading device and method

Abstract

The present invention proposes a crushing and grading device and method, the crushing and grading device comprises a double-roll crusher, a screen inclined downward is arranged below the crushing mechanism of the double-roll crusher, a buffer convex strip is arranged on the screen, the crushing mechanism comprises a fixed roller and a floating roller, the return mechanism comprises an arc-shaped return channel, the arc-shaped return channel is located on the outside of the fixed roller, conveyor chains are arranged at both ends of the arc-shaped return channel, and a scraper plate is arranged between the two conveyor chains; an inclined sliding cleaning roller brush is arranged on the lower side of the screen, a traction rope is connected to the end of the cleaning roller brush, a winding mechanism is arranged at the upper end of the screen, the winding mechanism comprises a connecting frame, a winding gear is rotatably arranged on the connecting frame, a winding wheel is fixed on the winding gear, the traction rope is connected to the winding wheel, and the connecting frame is connected to the telescopic cylinder. The return mechanism and the winding mechanism of the present invention shorten the return path of the coarse material on the screen and also facilitate the cleaning of the screen; the material is fully screened by the buffer convex strip.

Description

Technical Field

[0001] The present invention relates to the technical field of material crushing, and in particular to a crushing and grading device and method. Background Art

[0002] The raw materials of refractory products such as cast bricks and fire bricks need to be crushed and graded first to obtain aggregates of different particle sizes, and then mixed according to the raw material ratio. Existing raw material crushing and grading devices, such as Chinese patent document CN116984065A, disclose a toothed roller crusher with screening and crushing functions, including a crushing box, a crushing roller is arranged in the crushing box, a screen plate is installed under the crushing roller, and a reflux mechanism is arranged on the side wall of the crushing box to return the screened material of the screen plate to the feed hopper. The reflux mechanism is a vertical screw conveyor. This structure is prone to the following problems:

[0003] 1. The screening path of the screen is short, which may cause insufficient screening. The materials with qualified particle size are returned to the crushing mechanism for crushing;

[0004] 2. The screw conveyor is an external structure, which will increase the floor space of the crushing device. Especially for the roller crusher, the fixed roller and the floating roller each correspond to a set of drive mechanisms, and are located on both sides of the roller crusher. Therefore, it is not suitable to use a screw conveyor for returning materials, which will increase the return path length and return cost of the coarse material on the screen;

[0005] 3. The screen is set in the crushing box and is located on the lower side of the crushing roller. If it is blocked and difficult to clean, the equipment needs to be shut down and disassembled. How to clean the screen conveniently and quickly is also a problem that needs to be solved. Summary of the invention

[0006] The present invention proposes a crushing and grading device and method, which, through the cooperation of a material return mechanism and a winding mechanism, not only shortens the return path of coarse materials on the screen, but also facilitates the cleaning of the screen; buffer convex strips are arranged at intervals on the screen to fully screen the material and prevent materials with qualified particle sizes from entering the material return mechanism.

[0007] The technical solution of the present invention is implemented as follows: a crushing and grading device comprises a double-roll crusher, the double-roll crusher comprises a casing, a crushing mechanism is arranged in the casing, a screen inclined downward is arranged below the crushing mechanism, buffer convex strips are arranged at intervals on the screen, the buffer convex strips are perpendicular to the inclined direction of the screen, a return mechanism is arranged outside the crushing mechanism, a feed inlet of the return mechanism is connected to the lower end of the screen, and a discharge port of the return mechanism is located on the upper side of the crushing mechanism;

[0008] The crushing mechanism includes a fixed roller and a floating roller, and the return mechanism includes an arc-shaped return channel. The arc-shaped return channel is located on the outside of the fixed roller. Conveying chains are arranged at both ends of the arc-shaped return channel. The conveying chains are driven circumferentially along the outside of the fixed roller and the floating roller. The return end of the conveying chain and the arc-shaped return channel are coaxially arranged with the rotating shaft of the fixed roller. A scraper plate is arranged between the two conveying chains. The height of the scraper plate is consistent with the radial width of the arc-shaped return channel. The conveying chain drives the scraper plate to move along the screen and the arc-shaped return channel.

[0009] An inclined guide rail is arranged on the lower side of the end of the screen, and the inclined guide rail is parallel to the screen. A sliding cleaning roller brush is arranged between the two inclined guide rails. The end of the cleaning roller brush is rotatably connected to a traction rope. A winding mechanism is arranged in the casing at the upper end of the screen. The winding mechanism includes a connecting frame, and a winding gear is rotatably arranged on the connecting frame. A winding wheel is fixed on the winding gear. The end of the traction rope away from the cleaning roller brush is connected to the winding wheel, the connecting frame is connected to the telescopic cylinder, and the telescopic cylinder is connected to the casing. The winding gear is driven close to and away from the conveying chain through the telescopic cylinder.

[0010] Furthermore, an elastic buffer is arranged at one end of the inclined guide rail close to the winding mechanism, and a steering wheel is arranged on the casing between the inclined guide rail and the winding wheel.

[0011] Furthermore, the arc-shaped return channel includes an inner arc-shaped plate and an outer arc-shaped plate arranged coaxially, a baffle is arranged between the ends of the inner arc-shaped plate and the outer arc-shaped plate, an arc-shaped slide groove is arranged on the baffle, the arc-shaped slide groove is arranged coaxially with the arc-shaped return channel, and the return end of the conveyor chain moves along the arc-shaped slide groove. The movement path of the conveyor chain is limited by the arrangement of the arc-shaped slide groove, thereby ensuring that the return end of the conveyor chain is arranged coaxially with the arc-shaped return channel.

[0012] Furthermore, support gears are provided at both upper and lower ends of the outer side of the fixed roller, and steering gears are provided at both upper and lower ends of the outer side of the floating roller. An arc bracket is provided between the two steering gears, and the arc bracket is located on the outer side of the floating roller. The conveying chain is sleeved on the outer side of the support gear, the steering gear and the arc bracket, and the shaft of a support gear and the rotating shaft of the fixed roller are connected through a transmission gear and a transmission chain. The path of the return end of the conveying chain is adjusted by the cooperation of the steering gear and the arc bracket, and the conveying chain is driven to move by the rotating shaft of the fixed roller, without the need to add an additional driving device.

[0013] Further, a different diameter wheel is fixed to the end of the steering gear, and the different diameter wheel is located at one end of the steering gear away from the scraper plate. During the transmission process of the conveying chain, the different diameter wheel is driven to rotate by the steering gear, thereby vibrating the screen.

[0014] Furthermore, a feed guide plate is arranged at the lower end of the inner arc plate, and a discharge guide plate is arranged at the upper end, and the free ends of the feed guide plate and the discharge guide plate are both facing the fixed roller.

[0015] Furthermore, it also includes a jaw crusher and a multi-layer vibrating screen. The discharge ports of the jaw crusher and the double-roll crusher are connected to the feed port of the multi-layer vibrating screen through a loading elevator. The multi-layer vibrating screen is located above the double-roll crusher. Bins of different particle sizes are arranged on the sides of the double-roll crusher. The discharge port below the screen of the multi-layer vibrating screen is connected to the bin of the corresponding particle size through a chute, and the discharge port above the screen of the multi-layer vibrating screen is connected to the feed port of the double-roll crusher.

[0016] A crushing and grading method, using the crushing and grading device, comprises the following steps:

[0017] (1) The material on the screen enters the roller crusher for secondary crushing. After the secondary crushing, the material is screened by the screen to obtain the fine material under the screen and the coarse material on the screen;

[0018] (2) The conveyor chain drives the scraper plate to move down along the screen, pushing the coarse material remaining on the screen to the arc-shaped return channel. With the transmission of the conveyor chain, the scraper plate drives the coarse material on the screen back along the arc-shaped return channel to the upper side of the fixed roller, and falls between the fixed roller and the floating roller for re-crushing;

[0019] (3) If the screen is clogged and needs to be cleaned, the telescopic cylinder extends and drives the winding gear to approach the conveyor chain through the connecting frame and mesh with the conveyor chain. The conveyor chain drives the winding gear to rotate and reel in the traction rope. The traction rope drives the cleaning roller brush to move up along the inclined guide rail to clean the screen. After cleaning, the telescopic cylinder contracts and drives the winding gear away from the conveyor chain through the connecting frame. The cleaning roller brush moves down along the inclined guide rail under the action of gravity.

[0020] Furthermore, when the conveying chain is driven, the different-diameter wheel is driven to rotate through the direction-adjusting gear, thereby vibrating the screen.

[0021] Furthermore, the method further comprises the following steps: after the raw materials are crushed by a jaw crusher, they are sent to a multi-layer vibrating screen via a feeding elevator;

[0022] After screening by the multi-layer vibrating screen, the oversize material and undersize material are obtained. The undersize material enters the silo of the corresponding particle size through the chute, and the oversize material is subjected to step (1);

[0023] The fine material under the screen in step (1) is sent to the multi-layer vibrating screen via a feeding elevator.

[0024] Beneficial effects of the present invention:

[0025] The present invention, through the cooperation of the material return mechanism and the winding mechanism, is convenient for cleaning the screen on the basis of shortening the return path of the coarse material on the screen, and does not need to stop the machine or disassemble the equipment. The telescopic cylinder is extended to drive the winding gear to approach the conveying chain and mesh with the conveying chain. The conveying chain drives the winding wheel to rotate through the winding gear, and the winding wheel winds up the traction rope, thereby driving the cleaning roller brush to move up along the inclined guide rail to clean the screen. After the cleaning is completed, the telescopic cylinder contracts, driving the winding gear away from the conveying chain, and the winding wheel releases the traction rope, and the cleaning roller brush moves down along the inclined guide rail under the action of gravity. Moreover, through the setting of the elastic buffer, when the cleaning roller brush moves to the upper end of the inclined guide rail, the elastic buffer is compressed, and when the winding gear is away from the conveying chain, the traction force on the cleaning roller brush disappears. At this time, under the gravity of the cleaning roller brush and the thrust of the elastic buffer, the cleaning roller brush moves down, which is more conducive to its reset.

[0026] The present invention shortens the conveying path of the coarse material on the screen by setting the return mechanism, and reduces the workload of the elevator and the multi-layer vibrating screen. In addition, the return mechanism of the present invention is located in the housing of the double-roll crusher, and is set by using the space around the fixed roller and the floating roller, without occupying the external space, so as to facilitate the external layout of the silos with different particle sizes; the movement of the conveying chain is driven by the rotating shaft of the fixed roller, and there is no need to add a driving device; the scraper plate is vertically connected to the conveying chain, and the return end of the conveying chain and the arc-shaped return channel are coaxially arranged, so that when the scraper plate moves in the arc-shaped return channel, it is always in the radial direction of the arc-shaped return channel, so that the scraper plate and the inner wall of the arc-shaped return channel are abutted to avoid leakage.

[0027] The screen of the present invention is provided with buffer ridges at intervals, and the buffer ridges are perpendicular to the inclination direction of the screen. During the vibration screening process, the crushed coarse material can easily pass over the buffer ridges and move down to the lower end of the screen and enter the material return mechanism. The crushed fine material is blocked by the buffer ridges, and the speed at which the fine material moves down along the screen is slowed down, so that the material is fully screened, and it is avoided that the material is not fully screened due to the short screen path, and the material with qualified particle size enters the material return mechanism.

[0028] The discharge ports of the jaw crusher and the roller crusher of the present invention are connected to the feed port of the multi-layer vibrating screen through a loading elevator. The materials crushed by the jaw crusher are first screened and graded by the multi-layer vibrating screen, and the screened materials directly enter the silo of the corresponding particle size through the chute, while the screened materials enter the roller crusher for crushing and screening, so as to avoid over-crushing in the material crushing process and reduce the workload of the roller crusher. Moreover, the multi-layer vibrating screen is located above the roller crusher, and silos of different particle sizes are arranged on the surrounding side of the roller crusher, so as to facilitate the direct transportation of the screened materials through the chute, save costs, and make the entire crushing and screening device centralized, reducing the horizontal occupied space. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a schematic diagram of the structure of the crushing and grading device of the present invention;

[0031] Figure 2 It is a structural schematic diagram of a double-roll crusher;

[0032] Figure 3 It is a schematic diagram of the internal structure of the roll crusher;

[0033] Figure 4 It is a structural schematic diagram of the arc-shaped material return channel;

[0034] Figure 5 It is a structural schematic diagram of the transmission chain;

[0035] Figure 6 for Figure 3 Cross-section of the middle AA;

[0036] Figure 7 It is a structural schematic diagram of a different diameter wheel;

[0037] Figure 8 for Figure 3 A partial enlarged view of B.

[0038] Jaw crusher 1, double roller crusher 2, multi-layer vibrating screen 3, material pit 4, belt conveyor 5, feeding elevator 6, silo 7, chute 8, transmission chain 9, rotating shaft 10, casing 11, screen 12, buffer convex strip 13, fixed roller 14, floating roller 15, conveyor chain 16, supporting gear 17, shaft 18, turning gear 19, inner arc plate 20, outer arc plate 21, baffle 22, arc chute 23, scraper plate 24, feed guide plate 25, discharge guide plate 26, arc bracket 27, different diameter wheel 28, inclined guide rail 29, cleaning roller brush 30, elastic buffer 31, winding mechanism 32, connecting frame 33, winding gear 34, winding wheel 35, turning wheel 36, traction rope 37, telescopic cylinder 38. 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] like Figure 1 As shown, a crushing and grading device includes a jaw crusher 1, a roller crusher 2 and a multi-layer vibrating screen 3. The discharge ports of the jaw crusher 1 and the roller crusher 2 are connected to the feed port of the multi-layer vibrating screen 3 through a feeding elevator 6. Specifically, a material pit 4 is provided at the lower end of the jaw crusher 1, and the feed end of the feeding elevator 6 is placed in the material pit 4. A belt conveyor 5 is provided at the lower end of the roller crusher 2, and the discharge end of the belt conveyor 5 is connected to the material pit 4. The material crushed by the roller crusher 2 is sent to the material pit 4 through the belt conveyor 5. The feeding elevator 6 of the jaw crusher 1 and the roller crusher 2 can also be separately provided, and the jaw crusher 1 and the roller crusher 2 send the crushed material to the multi-layer vibrating screen 3 through their respective corresponding feeding elevators 6.

[0041] The multi-layer vibrating screen 3 is located above the double-roll crusher 2. Bins 7 of different particle sizes are arranged around the double-roll crusher 2. The under-screen discharge port of the multi-layer vibrating screen 3 is connected to the bin 7 of the corresponding particle size through a chute 8, and the screened material is sent to the corresponding bin 7 according to the particle size.

[0042] The screen discharge port of the multi-layer vibrating screen 3 is connected to the feed port of the roller crusher 2, and can be connected through a chute to directly send the screened material to the roller crusher 2 for secondary crushing. If the amount of screened material is large and the processing capacity of the roller crusher 2 is limited, the screen discharge port of the multi-layer vibrating screen 3 can also be connected to the temporary storage bin through the chute 8, and the temporary storage bin and the feed port of the roller crusher 2 are connected through a feed elevator. The screened material is first sent to the temporary storage bin and then sent to the roller crusher 2 via the feed elevator.

[0043] like Figure 2 and 3 As shown, the roller crusher 2 includes a housing 11, a crushing mechanism is arranged in the housing 11, a screen 12 tilted downward is fixed below the crushing mechanism, buffer ribs 13 are arranged on the screen 12 at intervals, and the buffer ribs 13 are perpendicular to the tilt direction of the screen 12. The crushed materials include fine materials with qualified particle sizes and coarse materials that need to be returned. The buffer ribs 13 are arranged to slow down the speed of the fine materials moving down along the screen 12, but do not affect the movement of the coarse materials, so that the materials are fully screened. A return mechanism is arranged on the outside of the crushing mechanism, the feed port of the return mechanism is connected to the lower end of the screen 12, and the discharge port of the return mechanism is located on the upper side of the crushing mechanism.

[0044] Using the crushing and grading device, the crushing and grading method includes the following steps:

[0045] (1) The purchased raw materials are crushed by the jaw crusher 1 and then sent to the multi-layer vibrating screen 3 via the feeding elevator 6;

[0046] (2) After screening by the multi-layer vibrating screen 3, the undersize materials of different layers enter the silo 7 of the corresponding particle size through the chute 8, and the oversize materials enter the roller crusher 2 for secondary crushing;

[0047] (3) After the secondary crushing, the material is screened by the screen 12 to obtain fine material under the screen and coarse material on the screen. The fine material under the screen is sent to the multi-layer vibrating screen 3 through the feeding elevator 6, and step (2) is repeated;

[0048] (4) The coarse material on the screen slides down along the screen 12 to the return mechanism, returns to the feed port of the double-roll crusher 2 through the return mechanism, and is crushed again.

[0049] like Figure 3-5 As shown, the crushing mechanism includes a fixed roller 14 and a floating roller 15, the upper end of the screen 12 is located at the lower side of the floating roller 15, and the lower end of the screen 12 is located at the lower side of the fixed roller 14. The return mechanism includes an arc-shaped return channel, which is located on the outer side of the fixed roller 14 and is coaxially arranged with the rotating shaft of the fixed roller 14. Both ends of the arc-shaped return channel are provided with a conveying chain 16, and the conveying chain 16 is driven along the outer side of the fixed roller 14 and the floating roller 15. Specifically, the outer side of the fixed roller 14 The upper and lower ends of the floating roller 15 are provided with support gears 17, which are fixed on the shaft 18, and the shaft 18 is connected to the housing 11 through bearings. The upper and lower ends of the outer side of the floating roller 15 are provided with adjustment gears 19, which are connected to the housing 11 through bearings. An arc bracket 27 is provided between the two adjustment gears 19, and the arc bracket 27 is fixed on the housing 11. The path of the return end of the conveying chain 16 is adjusted by the cooperation of the adjustment gear 19 and the arc bracket 27. The shaft 18 of the support gear 17 and the rotating shaft 10 of the fixed roller 14 are driven by the transmission gear and the transmission chain 9. The conveying chain 16 is sleeved on the outer side of the support gear 17, the adjustment gear 19 and the arc bracket 27. The rotation of the rotating shaft 10 of the fixed roller 14 drives the support gear 17 to rotate, and the transmission of the conveying chain 16 is driven by the support gear 17.

[0050] like Figure 3 and 6As shown, the arc-shaped return material channel includes an inner arc-shaped plate 20 and an outer arc-shaped plate 21 which are coaxially arranged, and the inner arc-shaped plate 20 and the outer arc-shaped plate 21 are both fixedly connected to the housing 11. A baffle 22 is fixed between the ends of the inner arc-shaped plate 20 and the outer arc-shaped plate 21, and an arc-shaped slide groove 23 is arranged on the baffle 22. The arc-shaped slide groove 23 is coaxially arranged with the arc-shaped return material channel, and the conveying chain 16 moves along the arc-shaped slide groove 23, so that the return material end of the conveying chain 16 and the arc-shaped return material channel are coaxially arranged.

[0051] A scraper plate 24 is connected between the two conveyor chains 16 at intervals. The scraper plate 24 is vertically connected to the conveyor chain 16. The scraper plates 24 are arranged at intervals so as not to affect the feeding of the roller crusher. The height of the scraper plate 24 is consistent with the radial width of the arc-shaped return material channel. At the same time, the return material end of the conveyor chain 16 and the arc-shaped return material channel are arranged coaxially so that when the scraper plate 24 moves in the arc-shaped return material channel, it is always in the radial direction of the arc-shaped return material channel, so that the scraper plate 24 abuts against the inner wall of the arc-shaped return material channel to avoid material leakage and ensure smooth discharge. The conveyor chain 16 drives the scraper plate 24 to move along the screen 12 and the arc-shaped return material channel. Sealing strips are fixed on the four sides of the scraper plate 24 so that its edge abuts against the inner wall of the arc-shaped return material channel to avoid material jamming and affect the movement of the scraper plate 24.

[0052] like Figure 3 As shown, a feed guide plate 25 is fixed to the lower end of the inner arc plate 20, and a discharge guide plate 26 is fixed to the upper end. The free ends of the feed guide plate 25 and the discharge guide plate 26 are both facing the fixed roller 14. The feed guide plate 25 facilitates the coarse material on the screen to enter the arc-shaped return channel, while the discharge guide plate 26 facilitates the coarse material on the screen to enter between the fixed roller 14 and the floating roller 15 for re-crushing.

[0053] The method of returning the coarse material on the screen through the return mechanism is as follows: the conveyor chain 16 drives the scraper plate 24 to move down along the screen 12, and pushes the coarse material on the screen remaining on the screen 12 to the arc-shaped return channel. With the transmission of the conveyor chain 16, the scraper plate 24 drives the coarse material on the screen along the arc-shaped return channel to return to the upper side of the fixed roller 14, and falls between the fixed roller 14 and the floating roller 15 for re-crushing.

[0054] like Figure 3 and 7 As shown, a different diameter wheel 28 is fixed to the end of the steering gear, and the different diameter wheel 28 is located at the end of the steering gear away from the scraper plate 24. When the conveying chain 16 is driven circumferentially, it drives the steering gear 19 to rotate, and the steering gear 19 drives the different diameter wheel 28 to rotate, thereby vibrating the screen 12 to achieve vibration screening of the screen 12.

[0055] like Figure 3 and 8As shown, an inclined guide rail 29 is fixed on the casing 11 at the lower side of the end of the screen 12, and the inclined guide rail 29 is parallel to the screen 12. A sliding cleaning roller brush 30 is arranged between the two inclined guide rails 29, and the end of the cleaning roller brush 30 slides along the inclined guide rail 29. A winding mechanism 32 is arranged in the casing at the upper end of the screen, and an elastic buffer 31 is installed at one end of the inclined guide rail 29 close to the winding mechanism 32. The elastic buffer 31 includes an end plate, and a support spring is connected to the end of the end plate away from the cleaning roller brush 30.

[0056] The winding mechanism 32 includes a connecting frame 33, on which a winding gear 34 is rotatably connected through a bearing, and a coaxial winding wheel 35 is fixed on the winding gear 34, and the winding wheel 35 is located at the end of the winding gear 34 away from the scraper plate 24. A steering wheel 36 is installed on the housing 11 between the inclined guide rail 29 and the winding wheel 35. A traction rope 37 is rotatably connected to the end of the cleaning roller brush 30. The end of the traction rope 37 away from the cleaning roller brush 30 is fixedly connected to the winding wheel 35 through the steering wheel 36. The connecting frame 33 is connected to a telescopic cylinder 38, and the telescopic cylinder 38 is connected to the housing 11. The winding gear 34 is driven to approach and move away from the conveying chain 16 through the telescopic cylinder 38. The telescopic cylinder 38 can be a telescopic cylinder, a hydraulic cylinder or an electric telescopic rod, etc.

[0057] In order to ensure that the cleaning roller brush 30 is smoothly reset and avoid jamming, a reset wheel (not shown in the figure) can also be installed on the casing at the lower end of the screen 12. The reset wheel is connected to the winding rope through a coil spring, and the winding rope is connected to the cleaning roller brush 30.

[0058] If the screen is clogged and needs to be cleaned, the telescopic cylinder 38 extends, and drives the winding gear 34 to approach the conveying chain through the connecting frame 33, and the winding gear 34 meshes with the conveying chain 16, and the conveying chain 16 drives the winding gear 34 to rotate, and the winding gear 34 drives the winding wheel 35 to rotate, and the winding wheel 35 reels the traction rope 37. As the traction rope 37 is reeled, the traction rope 37 drives the cleaning roller brush 30 to move upward along the inclined guide rail 29 to clean the screen, and the elastic buffer 31 is compressed; after cleaning, the telescopic cylinder 38 contracts, and drives the winding gear 34 away from the conveying chain 16 through the connecting frame 33, and the upward traction of the cleaning roller brush 30 disappears. Under the action of gravity and the thrust of the elastic buffer 31, the cleaning roller brush 30 moves down and resets along the inclined guide rail 29.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A crushing and grading device, comprising a double-roll crusher, the double-roll crusher comprising a casing, a crushing mechanism is arranged in the casing, and a screen inclined downward is arranged below the crushing mechanism, characterized in that: The screen is provided with buffer convex strips at intervals, and the buffer convex strips are perpendicular to the inclination direction of the screen. A return mechanism is provided on the outside of the crushing mechanism, and the feed inlet of the return mechanism is connected to the lower end of the screen, and the discharge port of the return mechanism is located on the upper side of the crushing mechanism; The crushing mechanism includes a fixed roller and a floating roller, and the return mechanism includes an arc-shaped return channel. The arc-shaped return channel is located on the outside of the fixed roller. Conveying chains are arranged at both ends of the arc-shaped return channel. The conveying chains are driven circumferentially along the outside of the fixed roller and the floating roller. The return end of the conveying chain and the arc-shaped return channel are coaxially arranged with the rotating shaft of the fixed roller. A scraper plate is arranged between the two conveying chains. The height of the scraper plate is consistent with the radial width of the arc-shaped return channel. The conveying chain drives the scraper plate to move along the screen and the arc-shaped return channel. An inclined guide rail is arranged at the lower side of the end of the screen, and the inclined guide rail is parallel to the screen. A sliding cleaning roller brush is arranged between the two inclined guide rails, and the end of the cleaning roller brush is rotatably connected with a traction rope. A winding mechanism is arranged in a casing at the upper end of the screen, and the winding mechanism includes a connecting frame, and a winding gear is rotatably arranged on the connecting frame, and a winding wheel is fixed on the winding gear. The connecting frame is connected to a telescopic cylinder, and the telescopic cylinder is connected to the casing, and the winding gear is driven to approach and move away from the conveying chain through the telescopic cylinder; An elastic buffer is arranged at one end of the inclined guide rail close to the winding mechanism, and a steering wheel is arranged on the casing between the inclined guide rail and the winding wheel; The arc-shaped return material channel comprises an inner arc-shaped plate and an outer arc-shaped plate which are coaxially arranged, a baffle is arranged between the ends of the inner arc-shaped plate and the outer arc-shaped plate, an arc-shaped slide groove is arranged on the baffle, the arc-shaped slide groove is coaxially arranged with the arc-shaped return material channel, and the return material end of the conveying chain moves along the arc-shaped slide groove; Support gears are arranged at both upper and lower ends of the outer side of the fixed roller, and steering gears are arranged at both upper and lower ends of the outer side of the floating roller. An arc bracket is arranged between the two steering gears, and the arc bracket is located on the outer side of the floating roller. The conveying chain is sleeved on the outer side of the support gear, the steering gear and the arc bracket. The shaft of the support gear and the rotating shaft of the fixed roller are connected through a transmission gear and a transmission chain. A different-diameter wheel is fixed at the end of the steering gear. The different-diameter wheel is located at the end of the steering gear away from the scraper plate. The steering gear drives the different-diameter wheel to rotate, thereby vibrating the screen. A crushing and grading method, using the crushing and grading device, comprises the following steps: (1) The material on the screen enters the roller crusher for secondary crushing. After the secondary crushing, the material is screened by the screen to obtain the fine material under the screen and the coarse material on the screen; (2) The conveyor chain drives the scraper plate to move down along the screen, pushing the coarse material remaining on the screen to the arc-shaped return channel. With the transmission of the conveyor chain, the scraper plate drives the coarse material on the screen back along the arc-shaped return channel to the upper side of the fixed roller, and falls between the fixed roller and the floating roller for re-crushing; (3) If the screen is clogged and needs to be cleaned, the telescopic cylinder extends and drives the winding gear to approach the conveyor chain through the connecting frame and mesh with the conveyor chain. The conveyor chain drives the winding gear and the winding wheel to rotate, and the winding wheel reels the traction rope. The traction rope drives the cleaning roller brush to move up along the inclined guide rail to clean the screen. After cleaning, the telescopic cylinder contracts and drives the winding gear away from the conveyor chain through the connecting frame. Under the action of gravity, the cleaning roller brush moves down along the inclined guide rail to reset.

2. A crushing and grading device according to claim 1, characterized in that: A feed guide plate is arranged at the lower end of the inner arc plate, and a discharge guide plate is arranged at the upper end, and the free ends of the feed guide plate and the discharge guide plate are both facing the fixed roller.

3. A crushing and grading device according to claim 1, characterized in that: It also includes a jaw crusher and a multi-layer vibrating screen. The discharge ports of the jaw crusher and the roller crusher are connected to the feed port of the multi-layer vibrating screen through a loading elevator. The multi-layer vibrating screen is located above the roller crusher. Bins of different particle sizes are arranged on the sides of the roller crusher. The discharge port under the screen of the multi-layer vibrating screen is connected to the bin of the corresponding particle size through a chute, and the discharge port above the screen of the multi-layer vibrating screen is connected to the feed port of the roller crusher.

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