Industrial crushers are used in the recycling and food processing industries. The primary purpose of these machines is to reduce the size of a material to a state where it can be further processed. While the technology found in these devices has changed little over the course of several decades, improvements in metallurgy and engineering have made them more versatile. Modern versions can manipulate a wide variety of materials and can be finely calibrated to output a specific size. This is extremely important in food processing, where granularity is often required.
The earliest industrial crushers were invented in the early 19th Century. They used a reciprocating jaw to exert pressure on material. These machines are still in service in the mining and recycling industry, where they are highly effective at reducing the size of materials of any hardness. During operation, one jaw is fixed while the other, known as a swing jaw, moves back and forth relative to it at high speeds. This is normally achieved using a cam or pitman. Improvements to the design include abrasive-resisting plating and segmented construction. This helps maneuver the machine into tighter spaces during mining operations. While in operation, its size reduction ratio is approximately 3:1.
Rotary crushers are more common. They are typically built with shaft impactors to create considerable force. Ideal for both recycling and food processing, they can be calibrated for a size reduction ratio between 10:1 and 25:1. With these settings, it is possible to achieve uniform granularity. If the intended operation is for foodstuffs, the machine will need to meet USDA and FDA requirements before it can be used. These requirements mostly concern the cleanability of any surfaces that will be contacted. Before processing food, the machine will need to be fitted with stainless steel surfacing and specialty O-rings that are safe for use.
These machines function by generating crushing force with a spinning rotor. Metal hammers are attached to the outside surface of the rotor and strike items as they pass. A material stream is fed the shaft containing the spinning rotor. When the material passes over the rotor, the metal hammers smash into it and propel it against textured surfaces at high speeds. Rotary crushers deliver enough force to greatly reduce the size of the material. However, they are best equipped to handle soft to medium hard items. They can churn through an impressive volume of foodstuffs or recycled items quickly. 3,500 cubic feet of volume can be processed every hour in high-power models.
Crushers can handle a wide variety of items, including sugars, carbonates, crackers, cereals, starches, and salts. They are also used to process frozen foodstuffs such as vegetables, wax, ice, candy, bones, chocolate blocks, pretzels, pastas, spices, food powders, resins, dry wall, chemicals, minerals, clay, glass, shale, and other rocks. Rotary devices come in many sizes, and their power depends on the speed and scare of the spinning rotor. Low-power machines are ideal when uniform granularity is required for softer items, like food powders. For recycled materials, minerals, or frozen items, higher powered devices will be required. Rotary speed varies from 85 rpm to 1,200 rpm. Modern models can be customized with different sets of hammers that enable the machine to work on different materials.
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