Among the five commonly used types of crushing machinery, impact crushers and hammer crushers are both machines that crush brittle materials mainly by impact, so they are often called impact crushers. Compared with crushers that are mainly based on extrusion, such as jaw, cone and roller crushers, impact crushers have the following characteristics; A. The broken ratio is big. The crushing ratio of impact crusher can reach more than 50, but it is difficult to exceed 20 for jaw, cone and roller crushers. Therefore, in the occasions that require single-stage crushing, such as limestone crushing in the cement industry, impact crushers are very common. B. The product particles are good. Under the action of impact, the material to be crushed is often broken along its most fragile level. With this selective crushing method, the probability that the particles are in the shape of a cube is higher, so the percentage content of needle-like pieces of the impact crusher product can be lower than 10%, and the percentage content of needle pieces in jaw, cone and roller crushers will be higher than 15%. Therefore, where cubic particles are needed. For example, the non-slip pavement of high-grade highways usually uses impact crushers as final crushing equipment to produce concrete aggregates.

The above characteristics make the impact crusher occupy an important position in many crushing machinery. However, because the impact crusher uses the principle of impact to crush materials, its striking parts, such as hammer heads, plate hammers, and impact plates, wear very quickly during use. This defect will limit the scope of application of impact crushers for a long period of time. It can only be used for the crushing of medium-hard materials. In the early 1950s, with the application of new wear-resistant materials, the German KHD company first introduced the hard rock impact crusher, breaking this limitation. The improved version of this model is still in production.

In the late 1950s, my country had counterattack crushers come out. Before the 1980s, domestic counterattack crushers were limited to handling medium-hard materials such as coal and limestone. It was not until the end of the 1980s that the former Shanghai Construction Machinery Factory introduced the KHD hard rock impact crusher to fill the domestic gap. But it is more than 20 years behind foreign countries. The two impact crushers shown in Figures 1 and 2 are fundamentally different in cavity design, rotor structure, especially the material of the plate hammer and the method of clamping. The domestically-made hard rock impact crusher initially relied on imports for its core components, and the domestically-made plate hammer was listed as a ministerial-level scientific research project during the "Eighth Five-Year Plan" period. After the success of the project, the domestically-made plate hammer not only replaced imports, but also Large quantities are exported to Europe, America, Japan and other countries. The breakthrough of wear-resistant materials has made hard rock impact crushers even more powerful. Just Shanghai Jianshe Road and Bridge Machinery Equipment Co., Ltd. (hereinafter referred to as Jianshe Road and Bridge Company) as an example: in ten years, the sales of hard rock impact crushers have increased by 15 times. Exports increased by 10 times, contributing to my country's capital construction projects. For example, in order to improve the quality of road construction in my country, the Ministry of Communications has proposed a scientific research project for pavement concrete stone crushing stations, which has been included in the national "Eighth Five-Year Plan" project. The trial equipment for this project failed in use at a construction site in the northeast. However, users switch to hard rock impact crushers to produce stone materials, which fully meets the requirements of highway anti-skid pavement concrete. So the reputation of the hard rock impact crusher was greatly improved. The Liaoning Provincial Department of Communications once regarded possession of this equipment as a necessary condition for bidding to undertake highway construction. According to statistics, hard rock impact crushers have been used as pavement stone preparation equipment in the construction of highways in various provinces and cities across the country to crush hard materials such as basalt and andesite with a compressive strength of 300MPa, and reach a gradation below 19.6mm. Stone. The percentage content of needle flakes is less than 10%. At present, more than 400 units are in use in various places, which not only solves a problem in expressway construction, but also blocks imports. As the leading manufacturer of hard rock impact crushers, Shanghai Jianshe Road and Bridge Company has also developed from it. The impact crusher has three series and dozens of specifications. Figure 3 shows the standard type. Figure 4 shows the derivative type III, the allowable feed size is 600mm, which is suitable for the crushing of reinforced concrete. Figure 5 shows the derivative V-shape. After adding the uniform plate, the output particle size distribution can be changed and the proportion of fine materials can be increased.