Gravel crushing and screening system and method

Abstract

The invention discloses a gravel crushing and screening system and method. The gravel crushing and screening system comprises a multi-stage crushing and screening system for performing graded crushing and screening on materials according to particle size grades of the materials; comprising crushing and screening systems from the first stage to the Nth stage, and materials are conveyed between every two adjacent crushing and screening systems through a conveying belt; each stage of crushing and screening system comprises a crushing unit and a screening unit, and the screening unit comprises a detachable screen; materials are crushed by the crushing unit and then enter the lower screening unit, and the materials are screened by the screen. The crushing units of the first k stages of crushing and screening systems comprise detachable cross-shaped crushing cutters, and materials are crushed by the rotary cross-shaped crushing cutters; the crushing units of the (k + 1) th stage to the Nth stage of crushing and screening systems comprise multi-tooth-roller crushers, and k + 1 < = N; the multi-tooth-roller crusher comprises a plurality of detachable parallel tooth rollers with adjustable tooth roller spacing; the distance between the rotating outer circle outlines of every two adjacent tooth rollers is smaller than or equal to the screening particle size value of the crushing and screening system of the stage. The system is simple in structure, reasonable in design and easy and convenient to install and arrange.

Description

Technical Field

[0001] The present invention relates to the technical field of sand and gravel system crushing and screening, and in particular to a sand and gravel crushing and screening system and method. Background Art

[0002] At present, in the production of modern industry, a conveyor belt often overlaps with two or more conveyor belts in the sand and gravel system to realize dynamic control of the production process. Due to the uncertainty of sand and gravel system production, it is usually necessary to adjust its production process or material flow direction. When frequent operations are required, the operation process is more complicated; and after the sand and gravel aggregates are crushed, there are usually a large number of other blocky or spherical stones inside the particles. Sometimes manual or machine screening is required again, and the integration of crushing and screening cannot be achieved. The steps are slightly cumbersome. If the machine is stopped for operation, it will often affect production efficiency. If the machine is not stopped for operation, it will often increase safety risks and operational difficulties. Therefore, there is a lack of a sand and gravel system crushing and screening device with a simple structure and reasonable design, which is easy to operate and can effectively complete crushing and screening.

[0003] Based on this, the technical problem to be solved by the patent of the present invention is to provide a sand and gravel system crushing and screening device and its use method in response to the deficiencies in the above-mentioned prior art. The device has a simple structure, reasonable design and low cost, is easy to operate, and is convenient for frequent operation. It can effectively complete crushing and screening, has high safety without affecting production efficiency, and is highly practical. Summary of the invention

[0004] The present invention provides a sand and gravel crushing and screening system and method to solve the technical problems existing in the known technology.

[0005] The technical solution adopted by the present invention to solve the technical problems existing in the known technology is:

[0006] A sand and gravel crushing and screening system comprises a multi-stage crushing and screening system arranged in sequence according to the material flow direction; the multi-stage crushing and screening system performs graded crushing and screening of materials according to the material particle size level, and comprises the 1st to Nth stage crushing and screening systems, and materials are transmitted between two adjacent stages of the crushing and screening systems through a conveyor belt; each stage of the crushing and screening system comprises a crushing unit and a screening unit located below the crushing unit, and the screening unit comprises a detachable screen; after the materials are crushed by the crushing unit, they enter the screening unit below, and the screen screens the materials; the crushing units of the 1st to kth stage crushing and screening systems comprise a detachable cross crushing knife, and the materials are crushed by the rotating cross crushing knife; the crushing units of the k+1th to Nth stage crushing and screening systems comprise a multi-tooth roller crusher, k+1≤N; the multi-tooth roller crusher comprises a plurality of detachable parallel tooth rollers with adjustable tooth roller spacing; the distance between the rotating outer circle contours of two adjacent tooth rollers is ≤ the screening particle size value of the crushing and screening system at this stage.

[0007] Furthermore, in the 1st to kth stage crushing and screening systems, part or all of the crushing units include a box body and a plurality of cross crushing knives arranged in the box body; the plurality of cross crushing knives are distributed in a plum blossom shape when projected on a horizontal plane; the distance between the rotating outer circular contours of the cross crushing knives and between the rotating outer circular contours of the cross crushing knives close to the side walls of the box body and the side walls of the box body is ≤ the screening particle size value of the crushing and screening system of this stage; a plurality of detachable and adjustable parallel mounting plates are provided at the bottom of the box body, and the gaps between the mounting plates are greater than the screening particle size value of the crushing and screening system of this stage; a number of cross crushing knives are arranged on each mounting plate; the cross crushing knives are rotatably connected to the mounting plates through bearings; and the material is crushed by the rotating cross crushing knives and falls into the screening unit below through the gaps between the mounting plates.

[0008] Furthermore, the crushing unit includes a driving device for driving the cross crushing knife to rotate, and the driving device includes: a motor, a driving gear fixedly connected to the output shaft of the motor, a driven gear fixedly connected to the handle of the cross crushing knife, and a toothed belt or a sprocket; the toothed belt or the sprocket is respectively meshed with the driving gear and the driven gear, and the motor rotates to drive the driving gear, and then drives the driven gear through the toothed belt or the sprocket, and the driven gear drives the cross crushing knife to rotate.

[0009] Furthermore, the nth-stage crushing and screening system and the n+1th-stage crushing and screening system are arranged up and down, 1≤n≤N-1; one of them is located above the other; and the conveying direction of the conveyor belt that transports materials between the two is horizontal or inclined to the horizontal direction.

[0010] Furthermore, the nth level crushing and screening system or the n+1th level crushing and screening system is in the same horizontal plane as the n+2th level crushing and screening system; 1≤n≤N-2, and the transmission direction of the conveyor belt for transmitting materials between two adjacent levels of crushing and screening systems is inclined to the horizontal direction.

[0011] Furthermore, the conveyor belt is supported by a plurality of sets of parallel roller brackets, and each set of roller brackets includes a left roller, a middle roller and a left roller that enclose a trapezoidal opening.

[0012] Furthermore, the screening unit is provided with a downwardly inclined material guide port; materials with a particle size larger than the screening particle size of the crushing and screening system at this level are guided out from the material guide port and are recycled and sent to the conveyor belt.

[0013] Furthermore, each stage of the crushing and screening system includes a fixed bracket; the crushing unit and the screening unit are installed on the fixed bracket; the screening unit includes a screen and a push-pull device that reciprocates back and forth; side panels are provided on the left and right sides of the screen, and the left and right side panels of the screen are hinged to the fixed bracket through multiple parallel connecting rods, and the push-pull device is fixedly connected to the screen to drive the screen to reciprocate back and forth; the push-pull device includes an electric cylinder, an air cylinder or a hydraulic cylinder with a telescopic rod, and the telescopic end of the telescopic rod is fixedly connected to the screen.

[0014] Furthermore, each level of the crushing and screening system includes a fixed bracket; the crushing unit and the screening unit are installed on the fixed bracket; the screening unit includes a screen and a push-pull device that reciprocates back and forth; side panels are provided on the left and right sides of the screen, slide rails are provided on the outer sides of the side panels, and slideways that slide with the slide rails are provided on the fixed bracket; the push-pull device is fixedly connected to the screen to drive the screen to reciprocate back and forth; the push-pull device includes an electric cylinder, an air cylinder or a hydraulic cylinder with a telescopic rod, and the telescopic end of the telescopic rod is fixedly connected to the screen.

[0015] The present invention also provides a sand and stone crushing and screening method, which is provided with a multi-stage crushing and screening system arranged in sequence according to the material flow direction; the multi-stage crushing and screening system performs graded crushing and screening on the material according to the material particle size level, the multi-stage crushing and screening system is provided with a first to an Nth stage crushing and screening system, and the material is transmitted between two adjacent stages of the crushing and screening systems by a conveyor belt; each stage of the crushing and screening system is provided with a crushing unit and a screening unit located below the crushing unit, and the screening unit is provided with a detachable screen; after the material is crushed by the crushing unit, it enters the screening unit below, and the screen screens The material is screened; the crushing units of the 1st to kth stage crushing and screening systems are provided with detachable cross crushing knives, and the materials are crushed by the rotating cross crushing knives; the crushing units of the k+1th to Nth stage crushing and screening systems include multi-tooth roller crushers, k+1≤N; the multi-tooth roller crusher includes a plurality of detachable parallel tooth rollers with adjustable tooth roller spacing; the distance between the rotating outer circle contours of two adjacent tooth rollers is ≤ the screening particle size value of the crushing and screening system at this stage; according to the material crushing process requirements, the cross crushing knives, tooth rollers and screens that meet the process requirements are replaced, and the tooth roller spacing is adjusted.

[0016] The advantages and positive effects of the present invention are:

[0017] The sand and gravel crushing and screening system of the present invention has a simple structure, reasonable design, easy installation and layout, low investment cost, good use effect, and is easy to promote and use.

[0018] The multi-stage crushing and screening system crushes and screens the materials according to the material particle size. The first few stages of crushing use cross crushing knives to crush the materials, and the latter stages use double-toothed roller crushers for extrusion and crushing. The screening particle size of the screening unit gradually becomes smaller. The cross crushing knives, toothed rollers and screens can be disassembled and replaced according to the material crushing process requirements. The cross crushing knives, toothed rollers and screens that meet the process requirements can also be adjusted to adjust the toothed roller spacing.

[0019] In summary, the present invention has a simple structure, is easy to operate, can effectively change the flow direction of materials on the conveyor belt, has a low investment cost, has a good use effect, and is easy to promote and use. It has high safety and does not affect production efficiency, and is highly practical. The present invention is suitable for crushing and screening a variety of materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of a sand and gravel crushing and screening system of the present invention.

[0021] Figure 2 It is a schematic diagram of the structure of a crushing unit of the present invention.

[0022] Figure 3 It is a schematic diagram of the structure of a screening unit of the present invention.

[0023] In the figure: 1. feeding device; 2. box body; 3. cross crushing knife; 4. slideway; 5. push-pull rod; 6. screen; 7. conveyor belt; 8. gear roller; 9. gear roller driven gear; 10. gear roller driving motor; 11. gear roller driving gear; 12. mounting plate; 13. bolts for fixing the mounting plate; 14. material guide port; 15. slideway connecting plate; 16. side plate of the screen; 17. slide rail. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0025] In the description of the present invention, the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention rather than requiring the present invention to be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention. The terms "connected" and "connection" used in the present invention should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection; it can be a direct connection or an indirect connection through an intermediate component; it can also be an electrical connection or signal transmission; for those of ordinary skill in the art, the specific meanings of the above terms can be understood according to the specific circumstances.

[0026] See also Figures 1 to 3A sand and stone crushing and screening system comprises a multi-stage crushing and screening system arranged in sequence according to the material flow direction; the multi-stage crushing and screening system performs graded crushing and screening of materials according to the material particle size level, and comprises the 1st to Nth stage crushing and screening systems, and the materials are transmitted between two adjacent stages of the crushing and screening systems by a conveyor belt 7; each stage of the crushing and screening system comprises a crushing unit and a screening unit located below the crushing unit, and the screening unit comprises a detachable screen 6; the materials enter the screening unit below after being crushed by the crushing unit, and the screen 6 screens the materials; the crushing units of the 1st to kth stage crushing and screening systems comprise a detachable cross crushing knife 3, and the materials are crushed by the rotating cross crushing knife 3; the crushing units of the k+1th to Nth stage crushing and screening systems comprise a multi-tooth roller 8 crusher, k+1≤N; the multi-tooth roller 8 crusher comprises a plurality of detachable parallel tooth rollers 8 with adjustable tooth roller 8 spacing; the distance between the rotating outer circle contours of two adjacent tooth rollers 8 is ≤ the screening particle size value of the crushing and screening system at this stage.

[0027] Preferably, in the 1st to kth stage crushing and screening systems, part or all of the crushing units may include a box body 2 and a plurality of cross crushing knives 3 arranged in the box body 2; the plurality of cross crushing knives 3 are distributed in a plum blossom shape when projected on a horizontal plane; the distance between the rotating outer circular contours of the cross crushing knives 3 and the rotating outer circular contours of the cross crushing knives 3 close to the side wall of the box body 2 and the side wall of the box body 2 is ≤ the screening particle size value of the crushing and screening system of this stage; the bottom of the box body 2 may be provided with a plurality of detachable and adjustable parallel mounting plates 12, and the gaps between the mounting plates 12 are greater than the screening particle size value of the crushing and screening system of this stage; a plurality of cross crushing knives 3 are arranged on each mounting plate 12; the cross crushing knives 3 are rotatably connected to the mounting plate 12 through bearings; and the material is crushed by the rotating cross crushing knives 3 and falls into the screening unit below through the gaps between the mounting plates 12.

[0028] Preferably, the crushing unit includes a driving device for driving the cross crushing knife 3 to rotate, and the driving device may include: a motor, a driving gear fixedly connected to the output shaft of the motor, a driven gear fixedly connected to the handle of the cross crushing knife 3, and a toothed belt or a sprocket; the toothed belt or the sprocket is respectively meshed with the driving gear and the driven gear, the motor rotates to drive the driving gear, and then drives the driven gear through the toothed belt or the sprocket, and the driven gear drives the cross crushing knife 3 to rotate.

[0029] Preferably, the nth stage crushing and screening system and the n+1th stage crushing and screening system can be arranged up and down, 1≤n≤N-1; one of them is located above the other; the conveying direction of the conveyor belt 7 for transmitting materials between the two can be horizontal or inclined to the horizontal direction.

[0030] Preferably, the nth level crushing and screening system or the n+1th level crushing and screening system can be on the same horizontal plane as the n+2th level crushing and screening system; 1≤n≤N-2, and the transmission direction of the conveyor belt 7 for transmitting materials between two adjacent levels of crushing and screening systems can be inclined to the horizontal direction.

[0031] Preferably, the conveyor belt 7 may be supported by a plurality of sets of parallel roller supports, and each set of roller supports may include a left roller, a middle roller and a left roller that enclose a trapezoidal opening.

[0032] Preferably, the screening unit may be provided with a downwardly inclined material guide port 14 ; materials with a particle size larger than the screening particle size of the crushing and screening system at this stage are guided out from the material guide port 14 and recycled to the feeding device 1 .

[0033] Preferably, each stage of the crushing and screening system includes a fixed bracket; the crushing unit and the screening unit are installed on the fixed bracket; the screening unit includes a screen 6 and a push-pull device that reciprocates back and forth; side panels are provided on the left and right sides of the screen 6, and the left and right side panels of the screen 6 are hinged to the fixed bracket through multiple parallel connecting rods, and the push-pull device is fixedly connected to the screen 6 to drive the screen 6 to reciprocate back and forth; the push-pull device includes an electric cylinder, an air cylinder or a hydraulic cylinder with a telescopic rod, and the telescopic end of the telescopic rod is fixedly connected to the screen 6.

[0034] Preferably, each stage of the crushing and screening system includes a fixed bracket; the crushing unit and the screening unit are installed on the fixed bracket; the screening unit includes a screen 6 and a push-pull device that reciprocates back and forth; side panels are provided on the left and right sides of the screen 6, and slide rails 17 are provided on the outer sides of the side panels, and a slideway 4 that slides with the slide rails 17 is provided on the fixed bracket; the push-pull device is fixedly connected to the screen 6 to drive the screen 6 to reciprocate back and forth; the push-pull device includes an electric cylinder, an air cylinder or a hydraulic cylinder with a telescopic rod, and the telescopic end of the telescopic rod is fixedly connected to the screen 6.

[0035] The present invention also provides a sand and stone crushing and screening method, which is provided with a multi-stage crushing and screening system arranged in sequence according to the material flow direction; the multi-stage crushing and screening system is used to grade and crush and screen the material according to the material particle size level, the multi-stage crushing and screening system is provided with a first to an Nth stage crushing and screening system, and the material is transmitted between two adjacent stages of the crushing and screening systems through a conveyor belt 7; each stage of the crushing and screening system is provided with a crushing unit and a screening unit located below the crushing unit, and the screening unit is provided with a detachable screen 6; after the material is crushed by the crushing unit, it enters the screening unit below, and the screen 6 is used to screen the material Screening; The crushing units of the 1st to kth stage crushing and screening systems are provided with detachable cross crushing knives 3, and the materials are crushed by the rotating cross crushing knives 3; The crushing units of the k+1th to Nth stage crushing and screening systems include multi-tooth roller 8 crushers, k+1≤N; the multi-tooth roller 8 crushers include a plurality of detachable parallel tooth rollers 8 with adjustable tooth roller 8 spacing; The distance between the rotating outer circular contours of two adjacent tooth rollers 8 is ≤ the screening particle size value of the crushing and screening system at this stage; According to the material crushing process requirements, replace with the cross crushing knives 3, tooth rollers 8 and screens 6 that meet the process requirements, and adjust the tooth roller 8 spacing.

[0036] The structure and working principle of the present invention are further described below with reference to a preferred embodiment of the present invention:

[0037] A sand and gravel crushing and screening system comprises a multi-stage crushing and screening system arranged in sequence according to the material flow direction; the multi-stage crushing and screening system performs graded crushing and screening of materials according to the material particle size level, and comprises the first to third stage crushing and screening systems, and materials are transmitted between two adjacent stage crushing and screening systems through a conveyor belt 7; each stage crushing and screening system comprises a crushing unit and a screening unit located below the crushing unit, and the screening unit comprises a detachable screen 6; after being crushed by the crushing unit, the material enters the screening unit below, and the screen 6 screens the material; the crushing unit of the first to second stage crushing and screening systems comprises a detachable cross crushing knife 3, and the material is crushed by the rotating cross crushing knife 3; the crushing unit of the third stage crushing and screening system comprises a multi-tooth roller 8 crusher; the multi-tooth roller 8 crusher comprises three detachable parallel tooth rollers 8 with adjustable tooth roller 8 spacing; the distance between the rotating outer circle contours of two adjacent tooth rollers 8 is ≤ the screening particle size value of the crushing and screening system at this stage.

[0038] Each of the three gear rollers 8 is connected to a gear roller driven gear 9; the output shaft of the gear roller driving motor 10 is fixedly connected to the gear roller driving gear 11, and the gear roller driving gear 11 and the three gear roller driven gears 9 are meshed in sequence. When the gear roller driving motor 10 rotates, the gear roller driving gear 11 rotates with it, driving the three gear roller driven gears 9 to rotate synchronously. The rotation direction of the middle gear roller driven gear 9 among the three parallel gear rollers 8 is the same as that of the gear roller driving gear 11, and the rotation direction of the other two gear roller driven gears 9 is opposite to that of the gear roller driving gear 11. The material is squeezed and ground.

[0039] In the first to second stage crushing and screening systems, all crushing units include a box body 2 and a plurality of cross crushing knives 3 arranged in the box body 2; the plurality of cross crushing knives 3 are distributed in a plum blossom shape when projected on a horizontal plane; the distance between the rotating outer contours of the cross crushing knives 3 and the rotating outer contours of the cross crushing knives 3 close to the side wall of the box body 2 and the side wall of the box body 2 is ≤ the screening particle size value of the crushing and screening system at this stage; the bottom of the box body 2 is provided with 6 detachable and adjustable parallel mounting plates 12, and the mounting plates 12 are fixed to the box body 2 by bolts 13 for fixing the mounting plates. The gap between the mounting plates 12 is greater than the screening particle size value of the crushing and screening system at this stage; 4-5 cross crushing knives 3 are arranged on each mounting plate 12; the cross crushing knives 3 are rotatably connected to the mounting plate 12 through bearings; the material is crushed by the rotating cross crushing knives 3 and falls into the screening unit below through the gap between the mounting plates 12.

[0040] The cross crushing blade 3 may be provided with a split blade handle; the blade handle may be a standard part with the same outer dimensions, and may be plug-in-installed with the blade heads of the cross crushing blades 3 of different dimensions.

[0041] Each level of crushing and screening system includes a fixed bracket; the crushing unit and the screening unit are installed on the fixed bracket; the screening unit includes a screen 6 and a push-pull device that reciprocates back and forth; side panels are provided on the left and right sides of the screen 6, and a slide rail 17 is provided on the outer side of the side panel, and the slide rail 17 is fixedly connected to the screen 6; a slideway 4 that slides with the slide rail 17 is provided on the fixed bracket; the push-pull device is fixedly connected to the screen 6 to drive the screen 6 to reciprocate back and forth; the push-pull device includes a push-pull rod 5 and an electric cylinder, a cylinder or a hydraulic cylinder with a telescopic rod, and the telescopic end of the telescopic rod is fixedly connected to the push-pull rod 5. The push-pull rod 5 is fixedly connected to the slide rail 17. The slideway 4 is fixedly connected to the fixed bracket through the slideway connecting plate 15.

[0042] The above-mentioned push-pull device, feeding device 1, crushing unit, screening unit, box body 2, cross crushing knife 3, split handle, slide 4, push-pull rod 5, screen 6, conveyor belt 7, gear roller 8, gear roller driven gear 9, gear roller drive motor 10, gear roller active gear 11, mounting plate 12, bolts 13 for fixing the mounting plate, material guide port 14, slide connecting plate 15, side plate 16 of the screen, slide rail 17, electric cylinder, air cylinder, hydraulic cylinder, telescopic rod, bearing, connecting rod, etc. can all adopt components and devices in the existing technology, or adopt components and devices in the existing technology and adopt conventional technical means to construct.

[0043] The embodiments described above are only used to illustrate the technical ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. The patent scope of the present invention cannot be limited only by this embodiment, that is, any equivalent changes or modifications made to the spirit disclosed by the present invention still fall within the patent scope of the present invention.

Claims

1. A sand and gravel crushing and screening system, characterized in that: It includes a multi-stage crushing and screening system arranged in sequence according to the material flow direction; the multi-stage crushing and screening system crushes and screens the material according to the material particle size level, which includes the 1st to Nth stage crushing and screening systems, and the materials are transmitted between the two adjacent stages of the crushing and screening systems through a conveyor belt; each stage of the crushing and screening system includes a crushing unit and a screening unit located below the crushing unit, and the screening unit includes a detachable screen; the material enters the screening unit below after being crushed by the crushing unit, and the screen screens the material; the crushing units of the 1st to kth stage crushing and screening systems include a detachable cross crushing knife, and the material is crushed by the rotating cross crushing knife; the crushing units of the k+1th to Nth stage crushing and screening systems include a multi-tooth roller crusher, k+1≤N; the multi-tooth roller crusher includes a plurality of detachable parallel tooth rollers with adjustable tooth roller spacing; the distance between the rotating outer circle contours of two adjacent tooth rollers is ≤ the screening particle size value of the crushing and screening system at this stage.

2. The sand and gravel crushing and screening system according to claim 1, characterized in that: In the 1st to kth stage crushing and screening systems, part or all of the crushing units include a box body and a plurality of cross crushing knives arranged in the box body; the plurality of cross crushing knives are distributed in a plum blossom shape when projected on a horizontal plane; the distance between the rotating outer circle contours of the cross crushing knives and between the rotating outer circle contours of the cross crushing knives close to the side wall of the box body and the side wall of the box body is ≤ the screening particle size value of the crushing and screening system of this stage; a plurality of detachable and adjustable parallel mounting plates are provided at the bottom of the box body, and the gap between the mounting plates is greater than the screening particle size value of the crushing and screening system of this stage; a number of cross crushing knives are arranged on each mounting plate; the cross crushing knives are rotatably connected to the mounting plates through bearings; after the materials are crushed by the rotating cross crushing knives, they fall into the screening unit below through the gap between the mounting plates.

3. The sand and gravel crushing and screening system according to claim 1, characterized in that: The crushing unit includes a driving device for driving the cross crushing knife to rotate, and the driving device includes: a motor, a driving gear fixedly connected to the output shaft of the motor, a driven gear fixedly connected to the handle of the cross crushing knife, and a toothed belt or a sprocket; the toothed belt or the sprocket is respectively meshed with the driving gear and the driven gear, and the motor rotates to drive the driving gear, and then drives the driven gear through the toothed belt or the sprocket, and the driven gear drives the cross crushing knife to rotate.

4. The sand and gravel crushing and screening system according to claim 1, characterized in that: The nth-stage crushing and screening system and the n+1th-stage crushing and screening system are arranged up and down, 1≤n≤N-1; one of them is located above the other; and the conveying direction of the conveyor belt for transmitting materials between the two is horizontal or inclined to the horizontal direction.

5. The sand and gravel crushing and screening system according to claim 1, characterized in that: The nth-stage crushing and screening system or the n+1th-stage crushing and screening system is on the same horizontal plane as the n+2th-stage crushing and screening system; 1≤n≤N-2, and the transmission direction of the conveyor belt for transmitting materials between two adjacent crushing and screening systems is inclined to the horizontal direction.

6. The sand and gravel crushing and screening system according to claim 1, characterized in that: The conveyor belt is supported by a plurality of sets of parallel roller brackets, and each set of roller brackets includes a left roller, a middle roller and a left roller which enclose a trapezoidal opening.

7. The sand and gravel crushing and screening system according to claim 1, characterized in that: The screening unit is provided with a downward inclined material guide port; materials with a particle size larger than the screening particle size of the crushing and screening system at this level are discharged from the material guide port and recycled to the conveyor belt.

8. The sand and gravel crushing and screening system according to claim 1, characterized in that: Each level of the crushing and screening system includes a fixed bracket; the crushing unit and the screening unit are installed on the fixed bracket; the screening unit includes a screen and a push-pull device that reciprocates back and forth; side panels are provided on the left and right sides of the screen, and the left and right side panels of the screen are hinged to the fixed bracket through multiple parallel connecting rods, and the push-pull device is fixedly connected to the screen to drive the screen to reciprocate back and forth; the push-pull device includes an electric cylinder, an air cylinder or a hydraulic cylinder with a telescopic rod, and the telescopic end of the telescopic rod is fixedly connected to the screen.

9. The sand and gravel crushing and screening system according to claim 1, characterized in that: Each level of the crushing and screening system includes a fixed bracket; the crushing unit and the screening unit are installed on the fixed bracket; the screening unit includes a screen and a push-pull device that reciprocates back and forth; side panels are provided on the left and right sides of the screen, slide rails are provided on the outer sides of the side panels, and slideways that slide with the slide rails are provided on the fixed bracket; the push-pull device is fixedly connected to the screen to drive the screen to reciprocate back and forth; the push-pull device includes an electric cylinder, an air cylinder or a hydraulic cylinder with a telescopic rod, and the telescopic end of the telescopic rod is fixedly connected to the screen.

10. A sand and stone crushing and screening method, characterized in that: The method arranges a multi-stage crushing and screening system in sequence according to the material flow direction; the multi-stage crushing and screening system crushes and screens the material according to the material particle size level, the multi-stage crushing and screening system is provided with the first to Nth stage crushing and screening systems, and the material is transmitted between two adjacent stages of the crushing and screening systems through a conveyor belt; each stage of the crushing and screening system is provided with a crushing unit and a screening unit located below the crushing unit, and the screening unit is provided with a detachable screen; after the material is crushed by the crushing unit, it enters the screening unit below, and the screen screens the material; the first stage The crushing units of the k-th crushing and screening systems are provided with detachable cross crushing knives, and the materials are crushed by the rotating cross crushing knives; the crushing units of the k+1 to N-th crushing and screening systems include multi-tooth roller crushers, k+1≤N; the multi-tooth roller crushers include a plurality of detachable parallel tooth rollers with adjustable tooth roller spacing; the distance between the rotating outer circle contours of two adjacent tooth rollers is ≤ the screening particle size value of the crushing and screening system at this level; according to the material crushing process requirements, the cross crushing knives, tooth rollers and screens that meet the process requirements are replaced, and the tooth roller spacing is adjusted.

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