23 April, 2011
Working Principle of Linear Vibrators
Linear vibratory feeders are used for feeding of components to various Machines. The actuation / Vibrations take place by electromagnets. The Linear vibratory feeder is a device that converts Electro-magnetically produced vibrations into mechanical vibrations. These mechanical vibrations are utilised for movement of the workpiece along the track or tray.
Magnetic coil, which is fixed to the counter mass is energised with supply of electric current, producing a force, which in turn attracts and releases the magnet armature. As the magnet is rigidly fixed to the top spring holder, the vibrations are transferred to the spiral-conveying track of the bowl. Depending on the angle of gradient of the leaf springs and lead angle of the helix of conveying track, the workpieces move with every vibration above the track in small jumps.
During one period of 50 cycle AC mains the magnet attains its maximum attraction twice since the magnetic force is not dependent on the direction of current flow. Thus the magnet produces a vibrating frequency of 100 cycles, which is necessary for smooth & reliable movement of small & light weight workpieces. Some vibratory Feeder manufacturers use 50 Cycles / HALF WAVE Bowl Feeders too.
Thus a linear vibratory feeder consists of a tray or track mounted on a base by inclined leaf springs or packs of springs. The springs constrain the track / tray so that, as it travels vertically. As the components move up the track. One to two electromagnets, mounted on the lower counter weight / heavy base, generates the force to drive the track / tray feeder. The counter weight rests on rubber feet, which serve to isolate the vibration of the vibratory feeder.
The components are conveyed in the track / tray by one of two modes: sliding or hopping. In the sliding mode, motion is produced from friction between the part and the track / tray. As the track / tray rises and turns, the friction between the track and the part pushes the part forward with the track. When the track descends and turns backward, the force of friction is smaller and the part slides forward relative to the track / tray. In the hopping mode, the part moves forward with the track / tray as it rises and turns, but it experiences freefall when the track / tray’s downward acceleration exceeds the acceleration of gravity. During free-fall, forward motion is created as the track / tray moves backward relative to the part.