The present invention relates to an improved apparatus
for drying foodstuffs.
More specifically, the invention relates to an apparatus
of the above kind, particularly studied and realised for removing humidity from
leaf products, permitting optimised power consumption for every situation.
As it is well known, many apparatuses or machines exist
for drying leaf products, such as vegetables or fruit, or for removing water from
the same. Particularly, different kind of said apparatuses or machines exist exploiting
centrifugal force for removing said residual humidity.
Above mentioned machines are usually comprised of a rotating
basket, with vertical or horizontal axis, containing the product to be dried. Said
basket is driven by an electric, hydraulic or pneumatic motor. Drying cycle is a
batch cycle, providing a basket loading step, a centrifugation step and a product
Rotation speed and working time can be usually adjusted.
Some of these machines are loaded and unloaded on the same side and thus mechanisms
for upturning the same are provided. Other machines are loaded and unloaded from
Known machines providing electric motors usually use asynchronous
three-phase motors. Said motors overheat at low speed due to their design criteria,
i.e. during the loading and unloading steps, and, moreover, they have a peak of
power absorption at the start, thus when beginning the centrifugation, with a very
low torque generated.
In view of the above, known electric centrifugal apparatuses
must provide oversized motors, with cooling device for operation at low speed. This
increases their dimensions, thus making the same not convenient.
Furthermore, asynchronous three-phase motors must provided
transmission pulleys for reduction of number of revolution, as well as electronic
speed regulators (inverter), the adjustment range of which is in any case very limited
(ratio between about 1 and about 3).
As far as centrifugal machines or apparatuses driven by
hydraulic motors, it is known that they can have an even torque with low regime,
but that they are huge, being activated by suitable stations. Therefore, they are
more complex to be realised and assembled but, particularly, in case of oil leakages,
they can contaminate the product.
In view of the above it is object of the present invention
that of providing an apparatus for removing surface humidity of different products
by centrifugal force, having high capacity, reduced dimensions and driven by an
Another object of the invention is that of providing an
apparatus outputting a uniform torque with low regime.
It is therefore specific object of the present invention
an improved apparatus for drying foodstuffs, comprising at least a centrifugation
basket for drying said product by its rotation, the lateral surface of which is
holed; a pin rotating coupled with said at least a centrifugation basket; and a
motor, mechanically coupled with said rotation pin; said apparatus being characterised
in that said motor is a asynchronous three-phase electric motor and in that it comprises
means for controlling rotation of said motor for adjusting the torque output by
said motor with respect to its rotation speed.
Always according to the invention, said control means can
comprise an encoder for detection of the rotation speed or of the position of said
Still according to the invention, said control means can
comprise a feedback control device connected with said encoder for adjusting supply
and/or power output to said motor on the basis of the value of the motor speed detected
by said encoder.
Preferably, according to the invention, said apparatus
can comprise a support housing, within which said at least a centrifugation basket
is placed, rotating coupled with the same housing, said housing collecting liquid
due to drying said product exiting through the holes on the lateral surface of said
rotating centrifugation basket, said housing and said centrifugation basket realising
a centrifugation assembly; at least an axis fixed to said housing; motion means
mechanically coupled with said at least an axis, said motion means permitting rotation
of said centrifugation basket with respect to its axis, in order to bring the same
in the loading and unloading positions.
Furthermore, according to the invention, said motor can
be placed between said housing and said centrifugation basket by a joint, said joint
being fixed to said housing and rotating coupled with said rotation pin.
Always according to the invention, said motion means can
comprise a motor, preferably an electric motor.
Preferably, according to the invention, said at least one
axis can be a substantially horizontal axis.
Still according to the invention, said housing can comprise
at least a discharge for outflow of said liquid arriving fro the product drying.
Preferably, according to the invention, said improved apparatus
can comprise means for discharging the dried product, such as a conveyor belt.
Still according to the invention, said improved apparatus
can comprise a structure for supporting said centrifugation assembly.
The present invention will be now described, for illustrative
but not limitative purposes, according to its preferred embodiments, with particular
reference to the figures of the enclosed drawings, wherein:
- figure 1 shows a lateral view of drying apparatus for foodstuffs, particularly
leaf products according to the present invention;
- figure 2 shows a section front view of apparatus according to figure 1; and
- figure 3 shows a lateral section view of the drying group of apparatus according
to figure 1.
Making reference to figures 1 and 2 of the enclosed drawings,
it is possible observing apparatus 1 for drying leaf products according to the invention.
Said apparatus 1 comprises a drying assembly 2, under which
a product removal conveyor belt 3 is provided.
Said drying assembly is mounted on a support structure
4. It comprises a rotating centrifugation basket 5, mounted on substantially horizontal
pins 6. Said pins 6 permit rotation of said centrifugation basket 5 according to
Said pins 6 permits to the centrifugation basket rotation
about axis 8 during the unloading of the dried product by a motor 7.
Centrifugation basket 5 is holed on its surface (holes
cannot be seen in the figures).
Discharge outlets 9 are provided under said centrifugation
basket 5, connected with discharge cups, for outlet of water extracted from products
Making now reference to figure 3, it can be noted that
centrifugation basket 5 is placed within a hosing housing 10, coupled with said
pins 6, resting on supports 11.
Within inner volume of said centrifugation basket 5, between
the same basket and said housing 10, it is provided a synchronous centrifugation
electric motor 12, for rotating the centrifugation basket 5 according to direction
B with respect to its symmetry axis.
Centrifugation basket 5 is connected with a rotation pin
13 by the upper part of a rotating joint 14. Outer part 15 of said rotating joint
14 is fixed on housing 10 along with motor 12. The whole drying assembly 2 can rotate
about said horizontal axis 8 and about said pins 6.
Motor 12 is provided with an encoder 16 for controlling
the position of the same motor 12, a power supply cable 17 and elements 18 for water
During the loading and centrifugation steps, said centrifugation
basket 5 has its opening upward. When the centrifugation step is terminated, centrifugation
basket upturns, rotating about axis 8 by said motor 7 acting on said pins 6, discharging
the centrifuged product on the product removal conveyor belt 3.
Said centrifuged product is sent to the following workings
by said product removal conveyor belt 3.
During the centrifugation step of the product contained
within the centrifugation basket 5, carried out by said motor 12, water extracted
from the product passes through the holes of the same centrifugation basket 5, collects
within the housing 10 and outflows by outlets 9 and cups 9'.
Motor 12 is of the asynchronous three-phase type. It usually
is used for high precision tools and in all those cases requiring a high torque
at low regime along with a high precision of movements.
Encoder 17, permitting proper operation of said motor 12,
is an electronic device. It permits detecting speed of rotating members, in this
case synchronous three-phase motor 12, reading its position.
Said encoder 16 can be of many kinds. Opto-electronic encoders
are widely used, permitting, by excitation of photo-diodes, detecting speed of a
Encoder 16 is connected to a retroaction control circuit
(not shown in the figures), connected to supply of said motor 12. particularly,
once detected speed by said encoder 16, control circuit adjust power output to said
motor 12, thus optimising torque output by the same. Particularly, it is possible
obtaining keeping a constant torque of said motor 12 within a wide speed range (in
the described embodiment between about 0 and 1000 rpm).
This kind of motors has a further positive feature. In
the water cooled type, it has reduced dimensions, so as to be directly placed on
the rotating pin 13 of the centrifugation basket.
These positive features, combined with a good design, permit
realising a device with high capacity, high precision, reliability and reduced dimensions.
On the basis of the above specification, it can be noted
that basic feature of the present invention is that of using a synchronous three-phase
motor in a drying apparatus, employing a retroaction control device, permitting
maintaining a constant torque in a very wide speed range.
An advantage of the present invention is due to the reduced
dimensions of the apparatus.
The present invention has been described for illustrative
but not limitative purposes, according to its preferred embodiments, but it is to
be understood that modifications and/or changes can be introduced by those skilled
in the art without departing from the relevant scope as defined in the enclosed