Apparatus for drying foodstuffs

The invention relates to an improved apparatus (1) for drying food-stuffs, comprising at least a centrifugation basket (5) for drying said product by its rotation, the lateral surface of said basket (5) being holed; a pin (13) rotating coupled with said at least a centrifugation basket (5); and a motor (12), mechanically coupled with said rotation pin (13); said apparatus (1) being characterised in that said motor (12) is a synchronous three-phase electric motor (12) and in that it comprises means (16) for controlling rotation of said motor (12) for adjusting the torque output by said motor (12) with respect to its rotation speed.

PRIORITY INFORMATION

This application claims priority to Italian Patent application No. RM2006A000211 filed on Apr. 12, 2006, which is incorporated by reference in its entirety herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

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.

2. Brief Description of the Art

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 discharge step.

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 opposite ends.

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.

SUMMARY OF THE INVENTION

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 electric motor.

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 motor.

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 from 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.

DETAILED DESCRIPTION OF THE INVENTION

Making reference toFIGS. 1 and 2of the enclosed drawings, it is possible observing apparatus1for drying leaf products according to the invention.

Said apparatus1comprises a drying assembly2, under which a product removal conveyor belt3is provided.

Said drying assembly is mounted on a support structure4. It comprises a rotating centrifugation basket5, mounted on substantially horizontal pins6. Said pins6permit rotation of said centrifugation basket5according to direction A.

Said pins6permits to the centrifugation basket rotation about axis8during the unloading of the dried product by a motor7.

Centrifugation basket5is holed on its surface (holes cannot be seen in the figures).

Discharge outlets9are provided under said centrifugation basket5, connected with discharge cups, for outlet of water extracted from products during centrifugation.

Making now reference toFIG. 3, it can be noted that centrifugation basket5is placed within a hosing housing10, coupled with said pins6, resting on supports11.

Within inner volume of said centrifugation basket5, between the same basket and said housing10, it is provided a synchronous centrifugation electric motor12, for rotating the centrifugation basket according to direction B with respect to its symmetry axis.

Centrifugation basket5is connected with a rotation pin13by the upper part of a rotating joint14. Outer part15of said rotating joint14is fixed on housing10along with motor12. The whole drying assembly2can rotate about said horizontal axis8and about said pins6.

Motor12is provided with an encoder16for controlling the position of the same motor12, a power supply cable17and elements18for water cooling.

During the loading and centrifugation steps, said centrifugation basket5has its opening upward. When the centrifugation step is terminated, centrifugation basket upturns, rotating about axis8by said motor7acting on said pins6, discharging the centrifuged product on the product removal conveyor belt3.

Said centrifuged product is sent to the following workings by said product removal conveyor belt3.

During the centrifugation step of the product contained within the centrifugation basket5, carried out by said motor12, water extracted from the product passes through the holes of the same centrifugation basket5, collects within the housing10and outflows by outlets9and cups9′.

Motor12is 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.

Encoder17, permitting proper operation of said motor12, is an electronic device. It permits detecting speed of rotating members, in this case synchronous three-phase motor12, reading its position.

Said encoder16can be of many kinds. Opto-electronic encoders are widely used, permitting, by excitation of photo-diodes, detecting speed of a rotating member.

Encoder16is connected to a retroaction control circuit (not shown in the figures), connected to supply of said motor12. particularly, once detected speed by said encoder16, control circuit adjust power output to said motor12, thus optimising torque output by the same. Particularly, it is possible obtaining keeping a constant torque of said motor12within 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 pin13of 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 claims.