Crushing is an important link in the rapidly developing industrial mineral processing field, and crusher is a kind of equipment widely used in mining machinery. It occupies a very important position in various metal, nonmetal, chemical, building materials, electric power and other industrial sectors. From the economic point of view, in the concentrator, the production cost of grinding operation accounts for more than 40% of the total cost of mineral processing, and the equipment investment accounts for about 60% of the total investment. From the point of view of energy and environmental protection, the crushing operation consumes a lot of energy, and the working environment is seriously polluted due to the sound, vibration, friction and dust generated during the crushing of materials. Therefore, people in the industry at home and abroad have been studying how to realize energy-saving and efficient crushing technology, from theoretical research to new product development (including the transformation of old equipment) to changing production technology, in order to achieve less investment, low energy consumption, less pollution, high efficiency, small over-crushing, uniform product granularity and meet the technological requirements of new equipment and new technology systems. Coal mine is the most widely used industry of crusher. Raw coal crushing in open-pit coal mines and raw material pretreatment in coal preparation plants are inseparable from crushing equipment. Because coal is a brittle medium-hard rock, the crushing technology has developed for a long time. The crushing equipment used includes jaw crusher, rotary crusher, hammer crusher and ring hammer crusher, impact crusher, selective crusher, toothed roller crusher and so on. In recent 10 years, the crushing technology has made great progress. With the deepening of people's understanding of the crushing process, new crushing methods and crushing equipment are constantly emerging. Countries are constantly adopting new technologies, new processes and new materials in their respective crusher industries, and the reliability of products has been continuously improved, and effective progress has been made in terms of product wear resistance, reducing excessive crushing amount and strictly controlling the particle size of broken products. Especially the toothed roller crusher for coal, with its advantages of simple manufacture, convenient maintenance, low energy consumption, low cost, large crushing capacity and durability, has become a leader in product structure, technical performance and industrial application.

1. 1990 front tooth roll crusher

Before the 1990s, the technology of tooth roller crusher had some shortcomings, such as unable to strictly control the particle size of broken products, large crushing amount of broken products, large impact load on the machine body, easy damage to broken teeth, large overall noise and large maintenance. For example, in order to prevent the broken teeth from being damaged by hard materials such as miscellaneous wood, iron, gangue and rocks, tension springs are installed at the lower end of the crushing plate of the single-tooth roller crusher, and compression springs are installed at both ends of the crushing roller of the double-tooth roller crusher. In order to increase the stress on the crushing plate or toothed roller when large pieces of materials or hard materials fall into the crushing cavity and cannot be broken, the compression springs increase the discharge gap of the crushing cavity to discharge hard objects. Then, the movable crushing plate or toothed roller returns to its initial position by the restoring force of the spring. Therefore, the particle size of crushed products cannot be strictly controlled.

1987 the former Yanzhou coal mine design institute designed the then advanced 4pgc-380/350x1000 toothed roller crusher on the basis of digesting and absorbing the Arak 36DAM crusher produced by REXNORD Company of the United States. A prominent technical feature of this crusher is the adoption of "nitro" control system. The system can independently adjust the distance between the upper toothed rollers to control the feeding granularity of the lower section. The distance between the lower toothed rollers can also be adjusted independently to control the product granularity, so that the crushing program can be adjusted flexibly according to the requirements of the crushing process. At the same time, the crusher integrates a device for adjusting the distance between toothed rollers and a safety device, and adopts a hydraulic-pneumatic system: the piston rod of the oil cylinder is connected with the movable toothed roller, a certain amount of hydraulic oil is pumped into the oil cylinder cavity with the piston rod, and a certain pressure of gas is pumped into the oil cylinder cavity without the piston rod to form an air column spring. In this way, the position of the piston can be changed according to the amount of oil pumped in, so as to determine the distance between the toothed rollers and achieve the purpose of controlling the product particle size. When hard or unbreakable objects enter the crusher, due to the increase of crushing force, the movable toothed roller compresses the air column to make the hard objects pass through, and then the movable toothed roller can be reset. There is also the problem of strictly controlling product granularity.

Second, the tooth roll crusher 1990

After entering the 1990s, with the strengthening of China's reform and opening up, great changes have taken place in the coal sales market. People put forward higher requirements for coal preparation technology and equipment. These include reducing the content of fine particles, the uniformity of product particle size, reducing the over-limit particle size and improving the processing capacity, which promotes the development and progress of crusher technology.

First of all, Tangshan Branch of the General Research Institute of Coal Science developed a 2PL series of powerful crushers. The technical progress of the crusher is mainly to cancel the yield spring safety device of the original double-roll crusher, fix the double-roll crushing roller, and adopt new technology and new materials to prevent the crushing teeth from being damaged by hard objects, so as to strictly control the oversized particles in the crushed products.

1994 development of TFP500 series classification crusher by Pingxiang Coal Preparation Design Institute. This series of crushers are driven by a single motor and protected by hydraulic coupler overload. Its transmission system is that the motor drives the hydraulic coupler, drives a pair of bevel gears to change the rotation direction, and drives the active crushing roller to rotate, and the active crushing roller drives the passive roller to rotate through a group of spur gears at the other end. The crushing teeth are arranged in a spiral shape, and the small particles in the feed are easily discharged through the gap between the crushing rollers, while the large pieces are crushed by the shearing and stretching forces of the teeth, which improves the uncontrolled material crushing in the traditional crusher.

In the mid-1990s, 2PGL series double-toothed roller crusher was developed and produced. This series crusher is directly driven by double motors, double hydraulic couplers and double gear boxes. A crushing roller is moved by manual hydraulic system, and the spacing between toothed rollers is adjusted, so as to control the discharging granularity. The machine has overload protection of hydraulic coupler and electric control overload protection, which can effectively prevent broken teeth from being damaged by hard objects. The whole machine has compact structure, low body height and small impact load.

In the same period, Tangshan Branch of Coal Research Institute has successively developed 2PLF series classification crusher, 2FJP600 series strong classification crusher, 4 PG series strong crusher and DP series single tooth roller crusher. 2PLF series classification crusher adopts V-belt and big pulley in transmission form, which has simple transmission structure and low failure rate. Because the big pulley has energy storage function, the required motor power is less than that of direct drive. Double-tooth roller crusher adopts reverse rotation mode, crushing teeth adopt bullet type, and cemented carbide surfacing welding has high strength, high crushing efficiency and easy repair after wear. The twin rollers of 2FJP600 series high-strength grading crusher rotate to the two side walls respectively, the crushing plates on the tooth rollers are assembled, and the hard alloy is surfacing on the casting matrix with good toughness, which not only has high strength, but also can crush hard objects, and the broken teeth are "bent without folding". When the hard object is stuck or bent, the broken tooth can be directly repaired without replacing the broken plate on site. Comb plates are installed on the two side walls respectively, which have two functions: (1) The crushing process is completely shear and tensile crushing, and it is not easy to produce over-broken objects; (2) it plays the role of grid screen. Large pieces of materials that need to be crushed can be screened out through the materials that need to be crushed, and the particle size of the crushed products can be strictly controlled, thus controlling the three-dimensional size of the crushed materials. The rotation of the two toothed rollers in the direction of their respective side walls can also ensure that the materials that have reached the required particle size will not be broken again. Directly discharged from the discharge port between the toothed rollers and the discharge port between the toothed rollers and the comb plate, reducing energy consumption and excessive crushing caused by extrusion crushing. The two crushing rollers have two sets of independent driving devices, so that the two crushing rollers can work independently. In actual crushing, the working system can be changed according to the amount of feed, that is, when the feed is small, a single machine is started, and when the feed is long, two machines are started, so that users can save more energy. Each crusher can be equipped with type A, B and C teeth, and each tooth corresponds to a product granularity. Users don't need to change the crusher, but can adjust the product granularity by changing the tooth type, so as to realize multi-purpose of one machine and reduce the repeated investment of users. In addition, because this series of crushers are powerful crushers, it is not necessary to manually pick the gangue with a belt during the process layout, and the raw coal is directly fed into the crushers without pre-screening, which simplifies the coal preparation process, reduces the height of the workshop and reduces the construction investment and production cost of the coal preparation plant. 4PGG series four-tooth roll crusher and DP series single-tooth roll crusher are derived from 2FJP series. Except that the machine body of 4PGG series crusher adopts building block structure, the upper and lower machine bodies can be assembled and separated, and can be installed according to the actual production site to improve the crushing ratio, other structures and crushing principles are basically the same as those of 2FJP series.