Technical Field
[0001] 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.
Background Art
[0002] 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 solid residues.
[0003] 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.
[0004] 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 devices.
[0005] 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.
[0006] 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.
[0007] The object of the present invention is to eliminate these disadvantages.
[0008] 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.
[0009] 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 operations.
[0010] 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
[0011] 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.
[0012] 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
[0013] 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:
FIGURE 1 is a schematic, partially cutaway front view, of a machine for the centrifugal
separation in accordance with the present invention, and
FIGURE 2 is a cross-section obtained in a plane corresponding to line A-A in Figure
1.
Description of Preferred Embodiments
[0014] 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.
[0015] 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 motor 3.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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 other.
[0020] 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.
[0021] 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 high.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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 belt 11.
[0027] The weight of the shaft and of the drum is enough to avoid a lifting of the shaft
during normal machine operation.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
1. A machine for the centrifugal separation, designed in particular for the oil-producing
industry, comprising a vertical-axis centrifugal separator (2) which is provided with
a vertical transmission shaft (5), the latter receiving the motion from an output
shaft (7) of an electric motor (3), characterised in that the connection between said vertical transmission shaft (5) and said output or drive
shaft (7) is formed by a transmission unit (8) with a flexible member.
2. A machine according to claim 1, characterised in that said transmission unit (8) with flexible member includes a drive pulley (9) rigidly
attached to the output shaft (7), a driven pulley (10) rigidly attached to the vertical
transmission shaft (5), and a belt (11) connecting the drive pulley (9) and the driven
pulley (10) to each other.
3. A machine according to claim 2, characterised in that said transmission unit (8) is a synchronous transmission unit and the belt (11) is
a timing belt, having teeth meshing with the drive pulley (9) and the driven pulley
(10) which are provided with a profile or contour corresponding to that of the belt
(11).
4. A machine according to claim 3, characterised in that said timing belt has teeth with a double helical profile.
5. A machine according to claim 1, characterised by the presence of a machine bed (1), supporting several centrifugal separators (2)
which are connected to a single electric motor (3).
6. A machine according to claim 5, characterised in that said machine bed (1) houses the transmission unit (8) with the flexible member.