Process for pressing materials

A process is disclosed for pressing a material selected from materials of vegetable and animal origin. The process includes the steps of mechanically compressing the material of vegetable or animal origin while simultaneously vibrating the material at an ultrasonic frequency. The ultrasonic frequency going through the material modifies the material's internal state so as to considerably reduce resistance offered by the material to mechanical compression.

DESCRIPTION 
1. Technical Field 
The present invention relates to a process and apparatus for pressing 
materials. 
The invention relates in particular, but without restricting the scope of 
the inventive concept, to the pressing of materials of vegetable or animal 
origin in order to extract the juices and to the pressing of materials 
subject to plastic deformation such as materials extruded to form pellets 
for zootechnical applications. 
2. Background Art 
According to known technology, processes for the extraction of substances 
such as oils or pharmaceutical active ingredients in liquid form or in 
solvent solutions from the solid materials of vegetable origin containing 
them include a mechanical pressing stage effected in mechanical or 
hydraulic presses. 
In some cases, the material to be processed, in addition to being 
mechanically pressed, is also heated by steam and, in other cases still, 
heating may be substituted by, or combined with, the use of solvents. 
Obviously, the characteristic pressure parameters of these processes differ 
from one material to another. However, one disadvantage of all the 
processes known to prior art of the type described above is that they 
require high-intensity compressive forces, applied for considerable 
lengths of time and resulting in high energy consumption. 
Accordingly, the apparatus used to apply the compressive forces with 
sufficiently high intensity must be very large, having structures that are 
complex and expensive to make. 
Moreover, the use of process fluids such as steam and solvents further 
increases the complexity of the apparatus because the latter must be 
equipped with systems to supply the fluids during the process and then to 
remove them when their action has been completed. 
A further disadvantage is that, in some cases, the temperature of the steam 
and/or of the solvents may adversely affect the properties of the material 
being processed. 
SUMMARY OF THE INVENTION 
It is an aim of the present invention to provide a process for pressing 
materials which overcomes the drawbacks mentioned above. Another aim of 
the invention is to provide a process that can be advantageously used for 
materials that are to be subjected to plastic deformation, as in 
extrusion, for example. 
The invention achieves these and other aims by providing a pressing process 
in which the material is subjected to a mechanical pressing stage combined 
with an ultrasonic vibration stage. These two stages are carried out at 
the same time by a sonotrode pressure element that vibrates at an 
ultrasonic frequency. 
The ultrasonic energy which goes through the material during the mechanical 
pressing stage produces the surprising effect of modifying the internal 
state of the material so as to considerably reduce the resistance offered 
by the material to the pressure exerted on it. The mechanical compression 
of the material therefore requires less force. 
Compared to conventional processes, the pressing process achieved by the 
present invention is much more efficient because it requires much less 
power. In fact, all other conditions being equal, the process disclosed by 
the present invention, compared to a pressing process using a conventional 
press, reduces by two orders of magnitude the compressive force required 
and the length of time for which the force must be applied. 
Another advantage of the invention is that it is effective at ambient 
temperature and therefore there is practically no deterioration of the 
material as a result of temperature. 
Since the compressive forces are considerably reduced, the apparatus 
required is much simpler, more economical and longer lasting. 
Moreover, no process fluids are required, with obvious advantages in terms 
of simplicity of construction and operation of the apparatus required to 
implement the process. 
Yet another advantage of the invention is that, if applied to materials 
subject to plastic deformation, it produces the same degree of deformation 
at low temperature that conventional processes, under equal conditions of 
compression, can only achieve at much higher temperatures. 
This, besides being more economical in general, is particularly useful when 
processing temperature-sensitive materials since it totally removes, or at 
least greatly reduces, the importance of heating as a stage in the process 
which is particularly critical and expensive. 
The present invention also provides an apparatus for pressing materials 
which implements the process described above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
With reference to FIG. 1, the numeral (20) indicates an apparatus used for 
pressing materials (21) and basically comprising a sonotrode pressure 
element (1) consisting of a piston connected to ultrasound generator means 
(3) and mounted in such a way that it can slide in a cylindrical metal 
container (2). A force indicated by the arrow (F) in FIGS. 1 and 2 moves 
the sonotrode pressure element (1) alternately between a backward 
position, in which it is at rest, and a forward position, in which it is 
at work on the material (21). 
The container (2) is interconnected with a hopper (4) for feeding the 
material (21) and equipped with a metering valve (5), preferably a gate 
valve, which opens when the sonotrode pressure element (1) is at the rest 
position in order to fill the container (2) by gravity feed or by forced 
feed (for example, using a screw feeder, not illustrated here) and closes 
when the pressure inside the container (2) is high enough to indicate that 
the material (21) being compressed is likely to overflow. 
The container (2) is also equipped with appropriately shaped means (22), 
fitted to the bottom end of a side surface (23) of the container (2), 
designed to tap the juices pressed out of the material (21) and, if 
necessary, also equipped with valves (24) that are synchronized with the 
alternating motion of the sonotrode pressure element (1). 
At the front of the sonotrode pressure element (1), the container (2) 
preferably has a wall (6) that can be opened to enable removal of residue 
material (shown as a broken line and labelled 21c in FIG. 1) at the end of 
the compression process. 
The apparatus (20) can be conveniently used to implement a process for 
pressing a material (21) of vegetable or animal origin in order to squeeze 
the juices it contains out of it. By way of example, without restricting 
the scope of the invention, the apparatus (20) can be used in processes 
for the cold extraction of oils, pharmaceutical active ingredients in 
liquid form and/or in liquid solvent solutions. 
In another embodiment of the apparatus (20), illustrated schematically in 
FIG. 2, the apparatus (20) can be used for pressing materials (21) subject 
to plastic deformation such as those used in conventional extrusion 
processes. In this case, the wall (6) has holes in it to produce rods (26) 
of compressed material and is equipped with means (25) to cut the rods 
(26) into pellets (27). 
When used for this application, the apparatus has several advantages over 
heated screw extruders currently used to extrude thermoplastic materials. 
It is suitable in particular for the production of animal feed, dietary 
supplements and pharmaceuticals in the form of pellets which often contain 
substances which are highly sensitive to temperature. Thanks to the 
process and apparatus disclosed by the present invention, these can be 
manufactured without significant heating and hence without affecting their 
properties. 
Moreover, the apparatus (20) facilitates plastic deformation to such a 
great extent that it can be used to pelletize materials (21) to which 
pelletizing processes according to conventional methods are at present 
difficult, if not impossible, to apply. It is therefore evident that the 
invention as described above fully achieves its aims, and, moreover, is 
simple in construction and, hence, economical. 
The invention described can be subject to modifications and variations 
without thereby departing from the scope of the inventive concept. 
Moreover, all the details of the invention may be substituted by 
technically equivalent elements. 
In practice, modifications and improvements can be made which fall within 
the scope of the claims set out hereunder.