Roll crusher working principle & structure

1. Overview

Roll crusher is an old crushing machine. The main advantages of the roll crusher are: simple structure, compact and light body, low price, reliable work, easy to adjust, less over-crushing phenomenon, can crush sticky wet materials. Because of the above advantages of the roll crusher, there are still some industrial sectors using it, and there are new improvements and developments.

The disadvantages of roll crusher are: low production capacity, requirement for feeding the material evenly and continuously to the full length of the roll, otherwise the roll wears unevenly, and the size of the product is not uniform, which may need frequent repair. For smooth roll crusher, the size of the fed material is much smaller than the diameter of the rolls, so it cannot crush large pieces of material, and it is not suitable for crushing hard materials, either. It is usually for medium and fine crushing of medium-hard or soft materials. Although the toothed roll crusher can clamp into larger materials, it is limited to medium crushing, and the compressive strength of the material cannot exceed 60.8MPa, otherwise the tooth prongs will break easily.

According to the number of rolls, roll crushers can be divided into four types: single-roll, double-roll, three-roll and four-roll; according to the shape of the roll surface, they can be divided into three types: smooth, grooved and toothed roll crushers. The specification of the roll crusher is expressed by the diameter of the roll ø x the length of the roll L.

2.The working principle and structure of roll crusher

A. Double Roll Crusher

Double roll crusher is a commonly used roll crusher, whose structure is detailed in Figure 1. Its crushing mechanism is a pair of cylindrical rolls mounted horizontally parallel to each other on the frame. The material is added to the feed box 16 and falls on top of the rotating rolls. The material is pulled between the rolls under the action of friction on the surface of the rolls and crushed by the extrusion of the rolls. The crushed material is pushed out by the rotating rolls and discharged downward. Therefore, the crusher is continuous operation, and there is a forced discharge, crushing sticky wet material is not blocked.

The roll is mounted on a welded frame 3 and consists of a roll core 4 mounted on a shaft 11 and a roll sleeve 7 set on the roll core, both of which are tightened by a tapered ring 6 and tensioned with bolts 5 to keep the roll sleeve tightly set on the roll core. When the working surface of the roller sleeve is worn, it can be removed and replaced. The shaft of the front roller is installed in the roller bearing, bearing seat 18 is fixed on the frame, and the bearing 19 of the rear roller is installed in the guide rail of the frame, which can be moved back and forth on the guide rail, and the bearing of the rear roller is pressed on the top seat 12 with strong spring 14, and when the hard things fall in between the rotating rollers, the spring is compressed, and the rear roller moves back a certain distance to let the hard things fall down, and then returns to the original position under the action of spring tension. The pressure of the spring can be adjusted by the bolt 15, and there are replaceable steel shims 13 between the bearing 19 and the top seat 12, and the distance between the two rollers can be adjusted by replacing the shims of different thickness.

Figure 1 double roll crusher structure

The front roller is driven by motor through reduction gear 9 and 10 drive shaft 8 and pulley 20, while the rear roller is rotated in opposite directions by a pair of gears 17 mounted on the roller shaft by the front roller with action. In order to make the rear roller backward when the two gears can still engage, the gears use non-standard long teeth. The working surface of the roller can be chosen as smooth (such as rear roller 2), grooved (such as front roller 1) or toothed according to the requirements of application.

Smooth rollers mainly crush materials by extrusion, it is suitable for crushing medium-hard or hard materials. In order to strengthen the crushing of materials, the speed of the two rollers can be inconsistent. At this time the rollers also applies the grinding and stripping effect to the materials, it is suitable for clay and brittle material fine crushing, product size is small and uniform.

Slotted roller with grooves, when crushing materials, in addition to the extrusion effect, also apply shear effect, so it is suitable for the crushing of brittle or sticky wet materials with little strength, the product size is uniform, slotted roller can also help the ripping of the material block, when the need to obtain a larger crushing ratio is appropriate to use slotted roller.

The toothed roller is shown in Figure 2. The roller is made of a piece of steel plate 1 with teeth 5, and the steel plate is mounted on the shaft 2 with key 3, and the bolt 4 connects each piece of steel plate in series and tightens it into a whole. Tooth surface roller crushing materials, in addition to pressure, but also the splitting effect, so it is suitable for crushing soft and low hardness brittle materials with flaky shape, such as coal, dry clay, shale, etc., the size of the crushed product is more uniform, tooth surface and groove surface roller are not suitable for crushing hard materials.

Figure 2 Toothed roll structure

B. Single roll crusher

The structure of the single roll crusher is shown in Figure 3. The crushing mechanism consists of a rotating roll 1 and a jaw plate 4. The jaws are mounted on a bolt with a tooth bushing 2 on the core of the roll, with the tip of the tooth sticking forward like a hawk’s beak, which can be removed and replaced when the bushing wears out. The roller shaft is supported on bearings mounted on both sides of the frame wall, and only the roller rotates during operation. If there is a hard material falling in, the force generated will cause the spring to compress and the jaws will leave the roller and increase the discharge opening, so that the hard material can be discharged to avoid damage to the machine. The roller shaft is equipped with a flywheel to balance the kinetic energy of the crusher.

Figure 3 single roll crusher structure

Single roll crusher is actually a combination of some structures of jaw crusher and roll crusher, thus it has the characteristics of both crushers, and this machine type is also called jaw roll crusher. The single roll crusher has a large feed opening and in addition the roll surface is equipped with different crushing teeth. When large pieces of material are fed, the higher teeth clamp the large pieces of material and crush them by splitting and impacting methods, then they fall to the bottom and are further crushed to the required size by the smaller teeth. In a crusher, there are pre-crushing area and secondary crushing area, so it can be used for coarse crushing materials, and the crushing ratio is relatively large, up to 15. When crushing, the material block is plucked by the tooth prongs on the roller and discharged out of the machine, so it is forced discharge, and the crushing of sticky and wet materials does not cause blockage.

Single roll crusher is suitable for crushing medium hard or soft materials, such as limestone, hard clay and coal blocks. When the material is relatively sticky and wet (such as limestone with soil, etc.), its crushing effect is better than using both jaw crusher and cone crusher, especially for crushing flaky clay materials, compared with jaw or cone crusher, it is superior in performance and body compactness. The specifications of single roll crushers are expressed in terms of roll diameter and length.

C.Three-roll and four-roll crushers

In order to improve the crushing ratio of crushers, reduce the floor space, reduce the number of material transfers and simplify the operation, three-roll and four-roll crushers are produced. The three roll crusher is essentially a single roll crusher and a double roll crusher overlapped together, and similarly the four roll crusher is made by overlapping two double roll crushers. The four roll crusher is suitable for crushing coke, limestone, marl, chalk, slag and other materials.

Figure 4 shows the structure of the four-roll crusher, which consists of two double-roll crushers with the same specifications overlapping each other. The material is fed into the machine through feed opening 1, crushed by rolls 7 and discharged to the bottom. The bearing of one roll is fixed and the bearing of the other roll is pressed towards the shims by spring 6, which is the crusher’s safety device.

The electric motor 10 drives the rollers through the reducer 9 and coupling 8, where one motor drives the upper right roller and the other motor drives the lower left roller, while the other end of each roller spindle is equipped with a pulley. The pulley of the upper right roller drives the pulley of the lower right roller to make the lower right roller rotate; the pulley of the lower left roller, drives the pulley of the upper left roller to make the upper left roller rotate. As the direction of the movable bearing movement is perpendicular to the direction of the belt drive, the tension of the drive belt does not change much when the movable bearing moves. After the material is crushed by the upper and lower rollers, it is discharged out of the machine from below.
Figure 4 four roll crusher structure
The machine itself is equipped with two sets of cutting devices for turning roll skins 5. When the smooth roll surface are worn or grooved or pitted, the rolls can be repaired directly by using the cutting devices without disassembling the rolls, and the cutting devices are mounted on the walking tool holder and then the chain is hooked to the sprocket 12. This repair method can reduce the stopping time, improve the operation rate of the equipment, ensure the roller surface is smooth and the crushing product particle size is uniform.