Background Art In many fields of technology there is the need to sort and separate products which are initially mixed together.

The methods currently used to perform sorting use the different characteristics of the mixed products, i. e., their size characteristics, as occurs for example in separation performed by screening; their different behavior in an electromagnetic field, as occurs for example in separation by electromagnets to separate ferromagnetic products from other products; their different water- solubility, in order to separate water-soluble products from insoluble products; etcetera.

It is also known to separate products as a function of their different aerodynamic characteristics. This is known as pneumatic separation, in which the separation element is a carrier fluid which strikes the products to be separated.

The separation methods currently in use, however, are not capable of ensuring effective separation for particular types of product, such as for example to separate the various elements that compose products such as forage for

animal feeding.

These products are generally constituted by a combination of stalks and leaves; the stalks, after harvesting or after drying in specifically provided units, have mutually different sizes and a degree of humidity which differs from stalk to stalk and cannot be easily separated from each other with fully satisfactory results as regards both precision in separation and as regards productivity in relation to the costs involved.

Disclosure of the Invention The aim of the present invention is to solve the above problem by providing a method and an apparatus for separating, by using a stream of a carrier fluid, products having different ratios of mass to surface of impact with the carrier fluid, achieving high precision in separation and economically convenient productivity.

Within the scope of this aim, an object of the invention is to provide a method and an apparatus which are particularly adapted to separate the various elements that compose forage for animal feeding, particularly forage such as Medicago sativa or the like.

Another object of the invention is to provide a method and an apparatus which can be manufactured using commonly commercially available elements.

This aim, these objects and others which will become apparent hereinafter are achieved by a method for separating, by using a stream of a carrier fluid, products having a different ratio of mass to surface of impact with the carrier fluid, characterized in that it comprises the steps of: introducing the products to be separated into a

tunnel which runs substantially horizontally and has a product inlet located in an upper region of the tunnel; striking the products with a main stream of carrier fluid which is directed substantially horizontally and with speeds which decrease from the top of the tunnel downwards in order to convey the products and make them fall, in a differentiated manner according to the products'ratio of mass to surface of impact with said carrier fluid, into receptacles which are provided in the bottom of said tunnel and are mutually spaced in a direction which is parallel to the direction of said main stream inside the tunnel.

The method according to the invention is performed preferably by using an apparatus for separating, by using a stream of a carrier fluid, products having a different ratio of mass to surface of impact with the carrier fluid, characterized in that it comprises a tunnel which runs substantially horizontally and has, in an upward region, an inlet for introducing the products to be separated and, in a downward region, a bottom in which there is a plurality of receptacles for the separated products, means for delivering a main stream of fluid in a substantially horizontal direction along said tunnel below said inlet and means for adjusting the speed of said main stream which are adapted to provide, for said main stream, speeds which decrease from the top downwards in order to produce a differentiated fall of the products into said receptacles, which are mutually spaced in a direction which is substantially parallel to the direction of said main stream.

Brief Description of the Drawings Further characteristics and advantages of the invention will become apparent from the description of a preferred but not exclusive embodiment of the method according to the invention and of the apparatus for performing it, illustrated only by way of non-limitative example in the accompanying drawings, wherein: Figure 1 is a schematic view of the apparatus for performing the method according to the invention; Figure 2 is a schematic view of a component of the apparatus for homogenizing the products before introducing them in the tunnel; Figure 3 is an enlarged-scale view of a detail of Figure 1; Figure 4 is a schematic view of the operation of the apparatus according to the invention; Figure 5 is a schematic comparison between the operation of the apparatus according to the invention and a theoretical operation in which the main stream of the carrier fluid has a constant speed.

Ways of carrying out the Invention With reference to the above figures, the apparatus for performing the method according to the invention, generally designated by the reference numeral 1, comprises a tunnel 2 which runs substantially horizontally and has, in an upward region, an inlet 3 for introducing the products to be separated and, in a downward region, a bottom in which there is a plurality of receptacles 4 which are mutually spaced in a direction which is parallel to the longitudinal extension of the tunnel 2.

The apparatus also comprises means for delivering a main stream of carrier fluid in a substantially horizontal direction which is parallel to the longitudinal extension of the tunnel 2, below the inlet 3, and means for adjusting the speed of the main stream which are adapted to provide, for the main stream, speeds which decrease from the top downwards in order to achieve a differentiated fall of the products into the receptacles 4, which, as mentioned, are mutually spaced in a direction which is parallel to the direction of the main stream.

The receptacles 4 are constituted by hoppers which are connected, with their mouth, at holes provided for this purpose in the bottom of the tunnel 2.

Baffles 5 are arranged between the receptacles 4, proximate to their mouth, and can move on command parallel to the direction of the main stream of the fluid, i. e., parallel to the longitudinal extension of the tunnel 2.

The means for delivering the main stream of fluid comprise a main delivery duct 6, along which there are fluid movement means which, if the fluid is constituted by air, can be constituted by a fan 7. The delivery duct 6 is connected to the longitudinal end of the tunnel 2 which is proximate to the inlet 3.

The mouth of a main return duct 8 is connected at the other end of the tunnel 2 and is connected to the main delivery duct 6 so as to allow recirculation of the fluid used. A centrifugal separator 9 can also be arranged along the main return duct 8 to eliminate the dust carried by the fluid.

The means for adjusting the speed of the main stream

delivered by the main delivery duct 6 comprise, as shown in particular in Figure 3, a plurality of ports 10 which are formed in a diaphragm 11 which is arranged at the outlet of the main delivery duct 6 inside the tunnel 2.

The ports 10 can have an adjustable size, i. e., they can be formed by flaps whose position can be adjusted in order to vary the passage section of the fluid, or their size can decrease from the top downwards, as shown in particular in Figure 3, in which the ports 10, located in an upper region of the outlet of the main delivery duct 6, are larger than the ports 10 formed in the lower region.

In order to better guide the threads of fluid, it is possible to provide similar ports also at the mouth of the main return duct 8.

Advantageously, directly below the inlet 3 and above the outlet of the main delivery duct 6 there are means for delivering at least one auxiliary stream of fluid in a substantially horizontal direction which is parallel to the longitudinal extension of the tunnel 2.

More particularly, these means for delivering at least one auxiliary stream of fluid comprise first means 15 for delivering a first auxiliary stream of fluid in a substantially horizontal direction and second means 16 for delivering a second auxiliary stream of fluid in a substantially horizontal direction below the first auxiliary stream of fluid emitted by the delivery means 15.

The first delivery means 15 comprise a first auxiliary delivery duct 17, which is served by fluid movement means which are constituted by a fan 18 if the fluid used is air, and which ends at the end of the tunnel 2 that lies

proximate to the inlet 3, directly below said inlet 3.

Baffles 19a and 19b are arranged at the outlet of the first auxiliary delivery duct 17 and gradually move mutually apart in the advancement direction of the first auxiliary stream of fluid, so that the first auxiliary stream of fluid has a high speed directly below the inlet 3 and so that said speed decreases rapidly.

The mouth of a first auxiliary return duct 20 is connected in the region of the tunnel 2 that faces the outlet of the first auxiliary delivery duct 17 and is connected to the first auxiliary delivery duct 17 in order to achieve recirculation of the fluid.

The second delivery means 16 comprise a second auxiliary delivery duct 21 which is served by fluid movement means, which can be constituted by a fan 22 if the fluid used is air, and which ends at the end of the tunnel 2 that lies proximate to the inlet 3 directly below the first auxiliary delivery duct 17.

At the outlet of the second auxiliary delivery duct 21 there are means for adjusting the inlet speed of the second auxiliary stream of fluid; said means allow, for said second auxiliary stream of fluid, speeds which decrease from the top downwards.

Said adjustment means can be constituted, in a manner similar to what has been described with reference to the means for adjusting the speed of the main stream, by ports whose size decreases from the top downwards and can optionally be adjusted and which are formed in a diaphragm located at the region that connects the second auxiliary delivery duct 21 to the tunnel 2.

The mouth of a second auxiliary return duct 23 is connected in a region of the tunnel that faces the outlet of the second auxiliary delivery duct 21; said second auxiliary return duct is connected to the second auxiliary delivery duct 21 to achieve an at least partial recirculation of the fluid delivered by the second auxiliary delivery duct 21.

In order to provide uniform orientation of the fluid threads of the second auxiliary stream even at the mouth of the second auxiliary return duct 23 it is possible to provide ports in a manner similar to the ports provided at the outlet of the second auxiliary delivery duct 21.

Preferably, the distance between the outlet of the first auxiliary delivery duct 17 and the mouth of the first auxiliary return duct 20 is substantially equal to 1/3 of the length of the tunnel 2, i. e., of the distance between the outlet of the main delivery duct 6 and the mouth of the main return duct 8.

Preferably, the distance between the outlet of the second auxiliary delivery duct 21 and the mouth of the second auxiliary return duct 23 is substantially equal to 2/3 of the length of the tunnel 2, i. e., of the distance between the outlet of the main delivery duct 6 and the mouth of the main return duct 8.

Conveniently, the apparatus comprises means 30 for homogenizing the products before feeding them into the tunnel 2.

The homogenizing means 30, as shown in particular in Figure 2, can be constituted by a chamber 31 which has a substantially cylindrical shape, is arranged so that its

axis lies horizontally, is fed with the products by means of a hopper 32, and internally accommodates a coaxial shaft 33 which can be actuated with a rotary motion about its own axis and is provided with a plurality of vanes 34 which are arranged in a spiral pattern with opposite inclinations starting from the region of the hopper 32, so as to produce an agitation which breaks up any clumps of the products introduced in the hopper 32 before they are fed into the tunnel 2.

The bottom of the chamber 31 is conveniently perforated and can be constituted for example by a grid 35.

It should be noted that the vanes 34 are meant only to break up any clumps of the products, without having any shredding or cutting effect on the products.

For the sake of completeness in description, it is noted that inspection ports 37 can be provided in the walls of the tunnel 2.

The operation of the apparatus described above in performing the method according to the invention is as follows.

Before examining the operation of the apparatus in detail, it is convenient to analyze the products to be separated. Said products have mutually different dimensions and masses. More particularly, the various products have mutually different ratios of mass to surface of impact with the fluid.

Said products are fed into the hopper 32, which feeds the chamber 31, inside which, as mentioned, any clumps of product are broken up so that the products are introduced through the inlet 3 with their various components mutually

loose.

The products are then struck by the first auxiliary stream of fluid delivered by the first auxiliary delivery duct 17.

The first auxiliary stream is meant to reduce the effect of the force of gravity, which tends to make the products fall vertically. By virtue of the action of the first auxiliary stream, the products that have a lower ratio of mass to surface of impact with the fluid are propelled furthest from the outlet of the first auxiliary delivery duct 17 and therefore the various products undergo a first spacing as a function of the value of said ratio.

This spacing increases when the products, as they descend by gravity, are struck by the second auxiliary stream emitted by the second delivery duct 21, which further increases the mutual spacing of the products as a function of the value of the ratio of mass to surface of impact with the fluid.

The spacing action continues during the further descent of the products, which are struck by the main stream delivered by the main delivery duct 6.

The streams of fluid emitted horizontally substantially produce a horizontal spacing of the various products, since they produce a higher acceleration for the products that have a lower ratio of mass to surface of impact of the fluid than for those which have higher values of said ratio.

Owing to the fact that the speeds of the various streams of fluid decrease starting from the inlet 3 to the bottom of the tunnel 2, the products fall, at the bottom,

along a path which still has a vertical component which allows precise entry into the various hoppers 4.

In order to better understand this effect, Figure 5 shows a comparison between the paths, designated by the reference numerals 50 and 51, that are followed by the products struck by horizontal streams of fluid with speeds which decrease from the top downwards, as in the case of the apparatus according to the invention, and the paths 52 and 53, which would be followed by the same products if they were struck with a stream at a constant speed.

A first substantially vertical portion 52a, 53a is clearly shown to be present in the paths 52 and 53. In this portion the force of gravity is predominant, since the products, by falling from above, are not yet accelerated by the horizontal air stream.

The paths 52 and 53, which correspond to two products having mutually different ratios of mass to surface of impact with the fluid, then start to mutually separate along a curve; proximate to the bottom of the tunnel, their direction has a modest vertical component and a predominant horizontal component owing to the entrainment applied by the fluid to the products. As clearly shown, in the case of a stream with constant speed, i. e., in which the speed does not decrease from the top downwards, since the paths of the products are predominantly horizontal it would be difficult to precisely select the various products, since they would collide with the baffles 5 in their predominantly horizontal motion and their sorted fall into the various hoppers 4 would therefore be unlikely.

With the apparatus according to the invention, owing

to the fact that the speeds of the streams of fluid that strike the products decrease from the top downwards, the paths of the products, which correspond to the paths 50 and 51, are different from the paths 52 and 53, and proximate to the bottom, i. e., at the baffles 5, they have a motion whose vertical component is sufficient to ensure satisfactory precision in entering the hoppers 4 depending on the ratio of mass to surface of impact with the fluid.

The first auxiliary stream in fact reduces the vertical initial portion of the paths 50 and 51, performing a first horizontal spacing of said paths.

Then, since the speeds of the streams of fluid decrease from the top downwards, the thrust applied by the fluid gradually decreases and the force of gravity acts again, correctly conveying in a different manner the products into the various hoppers according to the horizontal spacing produced by the fluid as a consequence of the difference in the ratio of mass to surface of impact with the fluid of the various products.

It should be noted that if a less than fully satisfactory sorting of products occurs in one or more hoppers 4, the bottom of said hopper can be connected to the hopper 32 in order to subject the products of said hopper to a new sorting cycle together with other products fed into the tunnel 2.

The possibility to move the baffles 5 allows a further adjustment which increases sorting precision.

The method and the apparatus according to the invention have been conceived in particular to separate the various components of a forage for animal feeding,

preferably Medicago sativa, which as known is constituted after harvesting and optionally after drying by leaves and stalks which have mutually different dimensions and moisture contents and accordingly have mutually different ratios of mass to surface of impact with a fluid.

In practice, by introducing these products in the hopper 32, at the end of the cycle performed by the apparatus according to the invention in the hoppers 4, starting from the end of the tunnel 2 that is proximate to the inlet 3, there are provided the stalks, i. e., the products that have a higher ratio of mass to surface of impact with the fluid, and, in the following hoppers, stalks whose mass gradually decreases from hopper to hopper with respect to their surface of impact with the fluid.

The last hopper, i. e., the hopper that lies furthest from the inlet 3, contains the leaves, i. e., the parts that have a smaller ratio of mass to surface of impact with the fluid.

For an apparatus for separating the various forage products such as Medicago sativa it is possible to consider an overall length of the tunnel 2 of approximately 6 meters, a height of approximately 2 meters and a width which can be changed as a function of the intended production of the apparatus. The height of the region struck by the first auxiliary stream can be approximately 0.7 meters and the height of the region affected by the second auxiliary stream can also be approximately 0.7 meters. The length of the region struck by the first auxiliary stream is preferably 2 meters, while the length of the region struck by the second auxiliary stream is

preferably 4 meters.

The speed of the first auxiliary stream preferably varies from 10 m/s to 6 m/s, whilst the speed of the second auxiliary stream varies from the top downwards from 6 m/s to 4 m/s.

The speed of the main stream can vary from the top downwards from 4 m/s to 3 m/s.

The size values and the value of these speeds are of course given merely by way of example and can vary according to the requirements and to the type of product being separated.

In practice it has been observed that the method and the apparatus according to the invention fully achieve the intended aim, since they allow to obtain, with excellent precision, a separation of products which have different ratios of mass to surface of impact with a fluid.

Although the method and the apparatus according to the invention have been conceived in particular to separate the various components of forage such as Medicago sativa or the like, they can in any case be used to separate products which have mutually different ratios of mass to surface of impact with a fluid.

The method and the apparatus thus conceived are susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept; all the details may furthermore be replaced with other technically equivalent elements.

In practice, the materials used, as well as the dimensions, may be any according to the requirements and the state of the art.

The disclosures in Italian Patent Application No.

MI98A000300 from which this application claims priority are incorporated herein by reference.