Drive systems for vibratory equipment vary substantially in terms of size, design and operation. The different methods all provide their own pros and cons. This article will try and outline some of the drive systems that Vibroflow is familiar with.
The two methods of exciting a vibratory unit is either through an electromagnetic or electromechanical motor. Vibroflow only provides equipment with electromechanical motors and this article will focus on drive systems based on these motors.
The two main categories of drives that use electromechanical motors are as follow:
- Direct Drive
- Sub Resonant Tuned
This is the most common and simplest type of vibratory equipment. The idea is two vibratory motors mounted at the desired drive angle through the center of gravity will provide a linear vibratory motion. This can also be achieved through an independent out of balance excitor and electrical motor connected via belt.
The advantages of this drive system are it's simplicity. The only mechanical parts are the motors which are easy to replace.
When a direct drive unit is overloaded, it will just bog down and material will stop flowing. This is considered a safety benefit for some but a detriment to production for others.
This drive system is not very energy efficient and due to it's nature it requires strong supporting frames if it is going to be elevated.
Material control is also limited on equipment with this drive system as the only way to adjust the strokes is through the out of balance weights on the motors or excitors. This requires the units to be stopped and manually adjusted.
See below for cases that have direct drive systems:
Sub Resonant Tuned
Sub resonant equipment (commonly identified as twin mass) uses a machines natural frequency to reduce energy requirements during operation.
The drive and spring system are tuned to work together so that the vibratory motor operates a just below (hence the word 'sub') the spring systems resonance.
The benefits of this system are not just in energy efficiency; the stroke can be electronically controlled by changing the electrical input frequency via VSD.
Equipment that is of a twin mass design is also dynamically balanced which reduces the support requirement compared to direct drive equipment.
When overloaded, the spring system and motor come closer to resonance and therefore increase stroke. As with direct drive, this is either a maintenance issue as the unit may overstroke or a blessing to production as it maintains the required capacities.
Sub resonant equipment is also more complicated that direct drive as it not only has drive motors but also includes a counter mass, drive springs and stabiliser springs.
See below for cases that have sub resonant systems: