The systems that use the vibration technique can be divided into the following categories:
• freely oscillating systems, which will be described in this guide
• oscillating systems bound to resonance, which require specific in-depth research. Please contact the Technical Sales Service
of Italvibras if these systems are required.
The free oscillation system includes two different methods:
• rotational: the vibrating force is directed in all directions through 360° in a rotational way, either clockwise or anticlockwise.
• unidirectional: the vibrating force is directed in one single direction in fade-free sinoidal reciprocating mode.
The “rotational” method is obtained by using a single electric vibrator.
The “unidirectional” method is obtained by using two electric vibrators with the same electro-mechanical characteristics,
each turning in the opposite direction to the other.
The following examples illustrate a few typical uses:
The choice of the vibration method and vibration frequency able to achieve the utmost efficiency for each type of process,
depends on the specific weight and granulometry (or piece size) of the material used in the process itself (consult the Table on
Regardless of the selected vibration method, the electric vibrators can be mounted on the machine, elastically insulated with
its axis in a horizontal or vertical position or, if necessary, in an intermediate position between the two directrices.
The angle of incidence “i” (measured in degrees) of the line of force in relation to the horizontal plane should be taken into due
consideration when electric vibrators are applied with the “unidirectional” method.
Important: the line of force for any angle of incidence must pass through center of gravity “G” of the elastically insulated machine
(see figure below).
Determination of the angle of incidence of the line of force depends on the type of process and must be within the indicated
Use the Table on page (92) to select the vibration method and the required number of vibrations per minute depending on
the process and the granulometry of the material.
Now move to the diagram (amongst those on pages 93 – 102) corresponding to the obtained number of vibrations per minute.
Choose the corresponding curve on the diagram, for a previously calculated angle of incidence «i» of the line of force (consult
the descriptions on page 89).
Using that diagram and that curve: eccentricity value «e» or peak-to-peak amplitude «App», measured in mm and required to
obtain the previously mentioned theoretic product advancement speed value «VTEO» or «VTEOc» can be identified for a required
theoretic product advancement speed «VTEO» (m/h or cm/s) or «VTEOc» (m/h or cm/s) for tilted machines.
«VTEO» is determined by the flow of material, taking a reduction coefficient into account (see conveyor channel example below).
Given eccentricity value «e», it is possible to determine the value of the total static moment «Mt» (Kg.mm) of the electric
vibrator or vibrators. This value is calculated by means of the following formula:
Mt = e x Pv
where: Pv = Pc + Po
Pv = total weight of the vibrating complex (Kg);
Pc = weight of the elastically isolated appliance (Kg);
Po = weight of the installed electric vibrator (or vibrators) (Kg); hypothetic weight to be subsequently compared to that of the
Important: calculated moment Mt is the total moment of the electric vibrators. For example, if the vibrating machine has two
electric vibrators, the calculated moment must be divided by two to obtain the static moment of each vibrator.
Once the static moment of the vibrator has been calculated, consult the catalogue to determine the type of electric vibrator
Having chosen the type of electric vibrator, centrifugal force value «Fc» (in Kg) of the vibrator itself can now be found in the
Use formula a = Fc/Pv (measured n times g)
to establish acceleration value «a» along the line of force. This value must be within the range indicated in the Table (on
page 92) for the required type of process.
Attention: if the chosen vibration method is “unidirectional”, value «Fc» to use in the above mentioned formula will
obviously be twice the value indicated in the catalogue as two electric vibrators are installed.
If free oscillation systems are used, it is advisable to fit anti-vibration mounts (such as helical steel springs, rubber supports or
pneumatic actuators) to allow the vibrating machine to freely move in all directions.
Do not use connecting rods, leaf springs or flat springs, etc., for free oscillation systems.
The non-vibrating element must be of adequate capacity, able to bear a weight equal to total weight «Pt» (i.e. the sum of the
weights of the elastically insulated machine, or the electric vibrator or vibrators «Pv» and the material bearing on the machine
itself «Ps») multiplied by the factor of safety, the value of which is between 2 and 2.5. Capacity «Q» of the elastic element
will therefore be:
Now determine the camber «f.»of the elastic system by means of diagram A, depending on the vibration frequency (rpm of
the electric vibrator) and considering a resonance ratio «r.» (between the vibration frequency of the vibrating complex and
the frequency of the elastic system itself) between 3 and 5.
The elastic constant of the anti-vibrating mount thus equals:
The capacity «Qkg» and the elastic constant «Kkg-mm» are the two entities required to choose the anti-vibration mounts on
It is absolutely essential to distribute the load of the vibrating complex evenly over the elastic system.
Diagram B gives the percentage of elastic insulation (I%) between the vibrating structure and bearing structure, depending
on ratio «r».
The anti-vibration mounts must be positioned so that the flexure is the same on all the elements, in order to balance the
Important: the bearing structure to which the anti-vibration mounts of the vibrating complex are fastened must be rigidly
anchored to the ground or to some other type of bearing structure and always without any further anti-vibration elements.