Development History Of Vibrating Feeders

Vibrating feeders originated in the mid-20th century. At that time, American scientists designed and manufactured a K-type mechanical reciprocating feeder (as shown in Figure 1). It works by connecting rod and eccentric shaft transmission. Due to the novel design of this mechanical feeder, it attracted widespread attention as soon as it was introduced. In addition, it can liberate workers from heavy work and greatly improve productivity. Therefore, it has been widely used in mine production, especially in underground coal mines. The K-type mechanical feeder is mainly composed of a support, vibrating body, outlet pipe, gate and idler roller. When working, the motor is started first. The motor drives the vibrating body to make linear reciprocating motion on the idler roller through the coupling, belt and other means, so as to evenly unload the coal onto other equipment. The disadvantages of this feeder are that it has a simple structure, high energy consumption, high operating cost, and heavy equipment. Under the conditions at that time, it was inconvenient to transport. Moreover, the processing capacity is small and it cannot feed evenly. Its advantages include durability, low maintenance costs, low chassis height required for installation, and low requirements on the physical properties of materials such as composition, particle size, and moisture content. However, with the rapid development of science and technology, the level of intelligence in mining machinery has greatly improved, and this type of mechanical feeder can no longer meet the needs of later industrial production.

In this context, the electromagnetic vibrating feeder emerged and has developed rapidly. The electromagnetic vibrating feeder is a dual-mass resonance type quantitative feeding device, which can adapt to the requirements of continuous production and is therefore widely used in mining, metallurgy, and coal industries.

The working principle of an electromagnetic vibrating feeder: The current in the vibrator's electromagnetic coil is rectified by a single-phase half-wave rectifier. When the coil is switched on, current flows during the positive half-cycle, generating a pulsed electromagnetic force that attracts the armature and the iron core. At this time, the trough moves backward, and the main spring of the vibrator deforms, storing potential energy. During the negative half-cycle, no current flows through the coil, the electromagnetic force disappears, and the main spring releases energy, causing the armature and iron core to move forward away from the trough in the opposite direction. Thus, the electromagnetic vibrating feeder reciprocates at a frequency of 3000 times per minute using AC power. Because the horizontal plane of the trough makes an angle with the direction of the excitation force, the material in the trough moves continuously forward along a parabolic trajectory. The magnitude of the excitation force is controlled by adjusting the rectified voltage, thereby controlling the feed rate of the electromagnetic vibrating feeder. The electromagnetic vibrating feeder uses a thyristor rectifier for power supply. The output voltage is directly related to the conduction angle of the thyristor; therefore, the output voltage is generally controlled by adjusting the conduction angle during operation. Meanwhile, depending on the different usage environments, different signals can be selected to control the conduction angle of the thyristor, so as to achieve the purpose of automatic quantitative feeding of the feeder.