Electromagnetic vibration feeder

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An electromagnetic vibration feeder is a relatively new type of quantitative feeding equipment. It can transport both loose materials and lumpy or powdered materials with a size of 500 mm or less; therefore, it is widely used in the industrial sector. It has many advantages that other feeders cannot match. It has no moving parts relative to each other, resulting in almost no mechanical friction; there are no lubrication points. It features good sealing properties, low power consumption, and can operate in wet and hot environments. It is easy to manufacture, simple to install, convenient to operate and maintain, and requires low maintenance costs. In particular, it facilitates automatic control, enabling the automation of the production process. 　　Structure and working principle of electromagnetic vibration feeders: An electromagnetic vibration feeder is a device that combines mechanical and electrical components. Similar to motors, they are both types of energy converters that convert electrical energy into mechanical energy; the difference is that motors produce rotational motion, while electromagnetic vibrators generate high-frequency vibrations. 　　The electromagnetic vibration feeder consists of four parts: a tank, a vibrator, a shock absorber, and an electrical controller. 　　An electromagnetic vibrating feeder is an elastic system with two-degree-of-freedom directed forced vibration. Composed of the tank body, connecting forks, armature, and 10%–20% by mass of the material inside the tank body, resulting in a mass of m1 ； The vibrator housing, core, coil, etc. constitute a mass m2. The two masses, m1 and m2, are connected by a bundle of plate springs, forming an elastic system for dual-mass oscillation. Based on the resonance principle, the natural vibration frequency w0 of the feeder is tuned to be close to the frequency W of the electromagnetic excitation force, so that the ratio Z = W/W0 ranges from 0.185 to 0.19. Therefore, the machine operates near resonance, which results in low power consumption. 　　The electromagnetic coil of the electromagnetic vibrator is powered by a single-phase AC supply through a rectifier. When the circuit is connected to the power supply, the supply voltage, after being rectified, generates a half-wave voltage across the electromagnetic coil during the positive half-cycle; as a result, current flows through the coil. This creates a pulsed electromagnetic force that attracts the armature to the core, causing the slot assembly to move backward. At this point, the leaf spring deforms and stores a certain amount of potential energy ； During the negative half-cycle, the rectifier does not conduct, so no current flows through the coil; the electromagnetic force acting on the coil disappears. Thanks to the potential energy stored in the leaf springs, the armature and core move in opposite directions, causing the slot body to move forward. This movement occurs in a back-and-forth oscillation at a frequency of 50 Hz, or 3000 times per minute, thereby pushing the material forward along the feed slot. 　　Calculation of the main parameters of electromagnetic vibration feeders (1) Amplitude a: The feeding capacity of the feeder is proportional to the amplitude. Therefore, increasing the amplitude can improve the feeding capacity, but this increases the likelihood of damage to the material particles; thus, the amplitude is generally kept between 015 and 115 mm. 　　(2) The vibration angle β; the optimal vibration angle β corresponds to the mechanical index K. The selected range for the vibration angle is generally 20° to 45°. Currently, a power frequency of 20° (3) is most commonly used. When the vibration angle remains constant, the feeding capacity depends on the product of frequency and amplitude; therefore, if one of these values decreases, the other must increase. The vibration frequency of the electromagnetic vibrating feeder is 3600 times per minute (when the power supply frequency is 60 Hz) and 3000 times per minute (when the power supply frequency is 50 Hz). (4) Installation angle: The electromagnetic vibration feeder can be installed horizontally (referring to the trough body) or at an inclined angle. For materials with good fluidity, it can be tilted downward by 12° to facilitate transportation. The feeding capacity is proportional to the inclination angle (see Figure 6225). The inclination angle ranges from –12° to +12°; for every 1-degree change, the feeding capacity changes by 3%. However, an excessive inclination angle increases the wear of the groove body. 　　Installation, adjustment, and commissioning of electromagnetic vibration feeders (1) Installation: The electromagnetic vibration feeder does not need to be disassembled before installation; it can be installed directly according to the installation drawings. 　　Before installation, it is necessary to check the tightness of all parts of the vibrator. The connection pins between the tank body and the connecting fork, as well as the tightening pins for the leaf springs, must be retightened before installation. The tightness of the tensioning pin of the leaf spring directly affects the tuning value of the feeder. The air gap between the core and the armature should be checked and adjusted to 118–211 mm; the surfaces of the core and the armature must remain parallel and clean. Then, the adjustment bolts and fixing bolts of the core frame should be tightened one by one. The hoist rod of the feeder is made of steel wire rope, and the frame that supports the hoist rod must have sufficient stiffness; if the frame exhibits significant vibration, it will affect the proper operation of the feeder. The suspension rods along the length direction of the feeder should be vertical, while those in the width direction may each tilt outward by 10°. Excessive silo pressure (the pressure of the material inside the silo) is not allowed on the surface of the feeder trough; otherwise, it will affect the amplitude and thereby reduce the material handling capacity. The feed and discharge chutes that are connected to the feeder tank must not come into contact with the feeder, in order to avoid affecting the feeder’s vibration and generating noise. The material must be vibrated during installation. After the feeder is installed and positioned, it is necessary to check whether the direction of the trough is horizontal; otherwise, the material will shift to one side during transportation. The feeder must be provided with grounding protection. After the feeder is installed, the service screws on the upper and lower surfaces of the vibrator housing should be loosened (they are used to adjust and fix the position of the coupling fork during maintenance); otherwise, it will affect the vibration of the feeder. 　　(2) Adjustment and trial operation: After the electromagnetic vibration feeder is installed, it must first be adjusted with no load. After the feeder has been adjusted, it should operate continuously for more than 8 hours under rated voltage, current, and amplitude conditions. During this process, the values of amplitude and current should remain constant, aside from naturally fluctuating with the grid voltage. During debugging, it is necessary to ensure that the air gap between the armature and the core is between 118 and 211 mm. Attention should also be paid to the tightness of the plate spring tensioning screws as well as the screws used to fix the core and the armature. Once debugging is complete, it can operate normally. 　　Key points for the use and maintenance of electromagnetic vibration feeders: When using and maintaining electromagnetic vibration feeders, the following points should be noted: (1) Before starting the electromagnetic vibration feeder, adjust the potentiometer to its minimum position. After connecting the power supply, turn the knob of the potentiometer to gradually increase the amplitude to the rated value of 1175–115 mm; at this point, the current also reaches the rated value. This device allows for direct starting and stopping under load at the rated voltage. 　　(2) The adjustment of the feeder’s production capacity can generally be achieved through the following methods: 1) Adjusting the inclination angle of the feeder’s trough to increase or decrease the production volume, although the maximum inclination angle should not exceed –20°. 　　 2) Adjust the size of the discharge gate in the storage hopper to increase or decrease the thickness of the material layer in the tank. 　　 3) The production capacity of the feeder varies depending on its amplitude, and the amplitude can be adjusted by controlling the current level. 　　(3) During the operation of the feeder, pay constant attention to changes in current; if significant variations are detected, an inspection must be carried out.