What is the working principle of the screw conveyor?
The working principle of screw Conveying equipments in conveying materials is basically divided into three categories: one is pushing method, the second is centrifugal induction method, and the third is gravity sliding method;
(1) Pushing method. This method generally uses spiral blades to convey materials and is often used for unloading and conveying at the bottom of the silo. The material often fills the spiral, and the granular material is subjected to a large static pressure. The gravity of each particle of material itself is much smaller than other forces (screw thrust, friction, static pressure). The resistance of this spiral is very large, and it has to overcome the friction formed under a large pressure. When working, the material is like a nut, and the spiral acts like a screw. As long as the nut does not rotate (or rotates slowly), the rotation of the screw can move the nut axially. The spiral for unloading at the bottom of the silo often uses a variable pitch spiral, and the pitch at the outlet is larger. How does a screw conveyor work?
(2) Centrifugal induction method. It is used for screw conveyors with steep vertical inclinations or any screw conveyors with high speeds. Its working characteristics are that the material filling volume is between the two. At the high speed of the screw, the loose material is affected by centrifugal force far more than other external forces such as gravity.
(3) Gravity sliding method. The speed of the screw is low, and the material on the screw surface is affected by gravity much more than the centrifugal force. As the screw rotates, the material continues to slide down along the screw surface, thus generating axial displacement. The CX screw conveyor basically belongs to this principle. The filling coefficient value of the screw conveyor based on this principle is generally less than 0.5. Because of overfilling, the material does not slide down along the screw surface, but is stirred by the screw to make the material fall over the screw shaft, and a large axial speed cannot be obtained. Since the material of the slow screw is greatly affected by gravity, it is obvious that it cannot be used for vertical screws or upward conveying with large inclination angles. When using a standard screw, it can not only maintain a faster sliding speed, but also have a certain adaptability to inclined conveying (the inclination angle is generally within 20°).
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