The invention relates to a machine for the centrifugal
separation, designed in particular for the oil-producing industry. Nonetheless,
it could also apply to other technical fields.
A machine of the kind forming the subject of the present
invention includes a vertical-axis centrifugal separator and allows separation of
liquids of different densities and features, by means of high peripheral velocity
centrifugation. By providing this machine downstream of a continuous-processing-cycle
plant for the extraction of olive oil at ambient temperature, it permits to separate
oil from "vegetation water" (water contained in the olive) and from any suspended
Presently, the motion to the vertical shaft of a centrifugal
separator is imparted by an electric motor through a gear drive. This kind of transmission
has some drawbacks.
Since in the known centrifugal separator the motion is
transmitted between skew axes, a local, considerable sliding/dragging among the
teeth of the gears occurs, whereby the same are subject to high surface wear. Furthermore,
the contact area between the engaging teeth is extremely limited. This entails a
limit for the load-bearing capacity of a tooth, and consequently, for the transmissible
power. The mechanical efficiency of the transmission is for this reason extremely
low. Besides, the mutual engagement of the teeth gives rise to a high noise, over
80 decibels, thereby forcing the operators to wear individual, hearing protection
Lastly, it should be emphasised that the transmission between
skew axes, besides a (spiral) bevel ring gear and a pinion, also requires the assembling
of a number of mechanical components; thus, the realisation cost of this transmission
is considerably high.
Because of said numerous components, the current transmission
unit also renders its assembling more difficult and increases the time required
for carrying out this job.
The object of the present invention is to eliminate these
In particular, an object of the present invention consists
in the realisation of a both effective and efficient transmission unit arranged
between the electric motor and the vertical shaft of the centrifugal separator.
An additional object of the present invention is the reduction
of the cost of the transmission unit for each centrifugal separator, as compared
with the presently employed transmission unit, by reducing the number of its components,
thereby leading at the same time to less difficult and less time-consuming assembling
A further object of the invention is to design a low-noise
transmission unit which does not require the use of individual (separate) means
for the protection from noise.
Disclosure of the Invention
To achieve the above and further objects, the invention
provides a machine for the centrifugal separation, which is designed in particular
for the oil-producing industry, comprising a vertical-axis centrifugal separator
which is provided with a vertical transmission shaft, the latter receiving the motion
from an output shaft (drive shaft) of an electric motor, wherein the connection
between said vertical transmission shaft and said output or drive shaft is realised
by a transmission unit with a flexible member.
Advantageously, this transmission is a synchronous transmission
unit and the flexible member is a timing belt (positive drive belt) having cogs
which engage with the drive pulley and the driven pulley, and which are provided
with a profile/contour corresponding to that of the belt.
Brief Description of Drawings
The above and further objects and advantages of the invention
will more clearly result from the following detailed description of one of its embodiments
considered in combination with the annexed drawings, wherein:
Description of Preferred Embodiments
FIGURE 1 is a schematic, partially cutaway
front view, of a machine for the centrifugal separation in accordance with the present
FIGURE 2 is a cross-section obtained in
a plane corresponding to line A-A in Figure 1.
The machine for performing centrifugal separation according
to an embodiment of the invention comprises a machine bed 1, a centrifugal separator
with vertical axis (vertical-axis centrifugal separator) generally indicated by
2, and an electric motor 3 which cooperates with the centrifugal separator 2.
As shown in figures 1 and
2 corresponding basically to a front view and a sectional view taken in
a horizontal plane of the machine, the machine bed 1 acts as support of the machine
components. The machine bed 1 is appropriately anchored to the ground at its lower
part, while at its upper part 4 it carries the centrifugal separator 2 and the electric
The centrifugal separator 2 is of the vertical-axis kind;
for instance, the present invention may apply to the model Ramef 2750/G, already
manufactured by the applicant itself, which therefore does not require further explanation.
The centrifugal separator 2 is equipped with a vertical transmission shaft 5 as
shown in the cutaway portion of the front view of Figure
1. It can be seen that the centrifugal separator is fixed to the upper
part 4 of the machine bed in such a manner that the vertical transmission shaft
5 downwardly projects into the machine bed at its lower end.
The electric motor 3 could be an asynchronous three-phase
motor, with a cage-type rotor, two pole pairs, and a rating (power) of 7.5 kW. The
motor flange - not shown in detail - of motor 3 is appropriately fixed to the upper
part 4 of the machine bed 1 with the interposition of a mount plate 6 which is visible
in Figure 2. Plate 6 has an aperture traversed
by the drive shaft (output shaft) 7 of the electric motor 3, the lower end of this
drive shaft projecting downwardly, starting from the upper side 4 of the machine
bed, in a way similar to the vertical transmission shaft 5.
Motor 3 is vertically positioned on one side of the centrifugal
separator 2 so that, according to the present invention, the respective shafts -
i.e. the drive shaft 7 and the vertical transmission shaft 5 - can receive (support)
the mechanical members embodying the motion transmission unit, the latter including
said flexible member and being generally referenced 8 in the figure.
This transmission unit 8 with flexible member comprises
a drive pulley 9, rigidly attached to the lower end of the drive shaft, a driven
pulley 10, rigidly attached to the lower end of the vertical, transmission shaft
5, and a belt 11, connecting the drive pulley 9 and the driven pulley 10 with each
By virtue of this strict design scheme the transmission
unit 8 with flexible member is received inside the machine bed 1 and may be reached
through an aperture, which is normally closed by a removable panel 12, the latter
being provided frontally in the machine bed 1.
The correct strain of the transmission belt is obtained
by directly acting on the plate 6 used to fix the motor, this plate being suitably
shaped for this purpose. Due to functional requirements, linked to the nature of
the separation process carried out by the machine, the transmission 8 with flexible
member is of a synchronous kind. Therefore, the belt has cogs. The cogs (teeth)
of the timing belt 11 (not shown in detail) engage with the drive pulley 9 and the
driven pulley 10, these having a toothed contour corresponding to that of the timing
belt 11. Advantageously, the timing belt 11 has a toothed profile in the form of
a double helix (not shown, since already well-known). This particular profile of
the cogs allows a progressive and continuous engagement of the timing belt 11 with
the drive pulley 9 and the driven pulley 10, thereby insuring, in this way, a considerable
reduction of vibrations and noise. The efficiency of the transmission is particularly
The electric motor 3 is controlled by an inverter that
insures a gradual and progressive delivery of the torque during the most critical
phase, corresponding to the machine starting phase.
The vertical transmission shaft 5, to which the driven
pulley 10 is attached, drives in rotation a drum (not shown) of the centrifugal
separator 2, at a speed of about 6450 rpm, to allow the separation of liquids contained
in the drum, i.e. of oil and water, by virtue of the centrifugal action.
The vertical transmission shaft 5 of the centrifugal separator
2 is supported on its lower side by means of two angular-contact ball bearings,
mounted in an "O" configuration, and which are received within a spherically shaped
support, so that the vertical transmission shaft 5 is free to oscillate. This movement
is in any case limited by springs (not shown) of adequate stiffness, which constitute
an upper elastic support for the vertical transmission shaft 5 of the separator.
The action of the belt 11 on the vertical transmission
shaft 5 causes a tilting moment whose magnitude depends on the transmitted torque.
Surely, the most critical phase is the starting phase, when the machine is started,
during which phase all masses need to be accelerated to their steady-state velocity,
by overcoming the mechanical forces of friction. Defining, by means of the inverter,
a "soft" acceleration ramp for the motor, it is anyway possible to limit/control
the tilting action within acceptable values.
No axial thrust is transmitted to the shaft by the flexible-member
transmission unit 8, due to the double helical profile of the teeth of the timing
The weight of the shaft and of the drum is enough to avoid
a lifting of the shaft during normal machine operation.
The transmission unit 8 with flexible member according
to the present invention does not eliminate the possibility of height-adjusting
the vertical transmission shaft 5 and the drum which is integral with it, which
adjustment is necessary during the assembling of the machine.
The machine for the centrifugal separation according to
the present invention, which is provided with a flexible-member transmission unit,
has several advantages. Some are briefly stated in the following part of the description.
In the machine of the present invention the noise is greatly
reduced, compared with a centrifugal separator of the prior art, due to the specific
double helical profile, or "circular-arc" profile, of the teeth of the timing belt,
which allows a progressive and continuous engagement with the pulleys, thereby reducing
vibrations and consequently the noise of the transmission unit. Moreover, the mesh
is very accurate and no slipping phenomena occur; these phenomena could originate
tooth wear and thus reduce the life of the transmission. Moreover, the uniform transmission
of the loads by the meshing teeth allows to transmit high powers with efficiencies
above 95%. This is a great advantage in terms of energy savings.
Compared with centrifugal separators based on a gear drive,
production costs are reduced by virtue of the lower costs of the employed components
and the shorter time required for mounting the transmission unit to the machine.
Actually, it should be emphasised that assembling and maintenance of the flexible-member
transmission unit are decisively simpler than the same operations performed on a
machine based on the gear drive transmission unit. This simplicity is due to the
fact that both pulleys can be mounted on their respective shafts in a way fully
independent from each other.
When assembling the belt and providing the necessary initial
strain to the belt, the mutual distance between the axes of the transmission is
adjusted by adjusting the mount plate of the electric motor on the machine bed,
as already mentioned above.
To perform maintenance works, all transmission unit components
are easily accessible after the removal of said panel, covering the opening on the
front part of the machine bed.
A further advantage of the present invention is that on
the machine bed there may be provided/fixed several centrifugal separators driven
by a single electric motor by means of flexible-member transmission units analogous
to the one already described.