* * * * * DESCRIPTION The present invention relates to equipment for the separation of material of various kinds in small pieces or leaves, treated in a plant which uses water or another appropriate liquid as conveying fluid. This is the case which occurs, for example, in plants for the recycling of plastic ^' material.

Equipment for the separation of material of various kinds in small pieces is already known, such as for example that described in the U.S.A. patent no. 4,483,768. This patent relates to equipment consisting of a separation tank filled up to a predetermined level with a certain liquid, and of extremely simple devices for feeding into the tank material to be separated with a horizontal jet of material and conveying liquid at a pressure higher than that existing in the inlet area due to the weight of the mass of liquid contained in the tank. The jet having these features is divided almost immediately into two vertical flows: an ascending flow for the material with lower specific weight than that of the mass of liquid contained in the tank and a descending flow for the material with higher specific weight respectively. In similar equipment the position of the feed device varies according to the different possible specific weights of the components of the material.

The equipment comprises, finally, a first and second means for removing the material separated from the mass of liquid contained in the tank. The two means are positioned at said

predetermined Level and at the bottom of the tank respectively for the ejection of the components having Lower and higher specific weight respectively than that of the mass of liquid contained in the tank. It may occur, in some cases, that the separation between the various components of the material in the mass of liquid contained in the tank is not complete and that the ascending flow entrains not only the conveying liquid and the material of Lower specific weight, for example plastic material in small sheets, but also part of the material with higher specific weight, for example pollutants.

The main object of the following invention is therefore the improvement to the equipment described above in respect of efficiency of separation of the components of material with different specific weight.

In accordance with the invention this object is accomplished by means of equipment comprising a tank containing a certain Liquid up to a predetermined Level, a device for feeding the material to be separated together with a conveying Liquid of the same kind as that contained in the tank with a horizontal jet at a pressure higher than that of the liquid contained in the tank in the inlet area due to the weight of the mass of Liquid and means pLaced at the top and at the bottom of the tank for removing from the mass of Liquid the components of the material with Lower and higher specific weight respectively, characterised in that the device for feeding material and conveying Liquid into the separation tank is a hydraulic cyclone provided with a tangential inlet conduit.

The use of a hydraulic cyclone as a feed device is justified by the fact that, as is known, said hydraulic cyclone is a

device suitable for imparting a rotary motion to material in a liquid medium. Said rotary motion, in a manner likewise known, can facilitate, through a centrifugal action, the separation of material into its various components. In this particular case, the action of the hydraulic cyclone continues even when the material has already been discharged from the cyclone itself since the rotary motion is maintained in the mass of liquid contained in the tank with a consequent lengthening of the path of the material in the mass of liquid and a Lengthening of the separation phase, outside of the hydraulic cyclone, in the mass of liquid contained in the tank.

In this way the separation of material can be made more efficient and the resolution power of the separation increased, as is necessary for example in the case of plastic material with an extremely Low specific weight.

In order to improve further the performances and flexibility of the equipment, the abovementioned hydrauLic cyclone can be placed at a variable height inside the tank according to the physical properties of the material treated. The features of the present invention will be made clearer by the following detailed description of its possible embodiments, shown by way of a non-limitative example in the accompanying drawings, in which: fig. 1 shows in axial section equipment according to the invention with a device for feeding material consisting of a first type of hydraulic cyclone; fig. 2 shows said equipment Sectioned transversely along line II-II of fig. 1; fig. 3 shows in axial section other equipment according to the invention with a device for feeding material consisting of

a second type of hydraulic cyclone; fig. 4 shows said equipment sectioned transversely along line IV-IV of fig. 3.

The separation equipment illustrated in figs. 1 and 2 comprises a separation tank 1 designed to be filled with a Liquid 2 up to a predetermined Level L.

The tank 1 is related to a device 3 for feeding the material to be separated and a conveying liquid, which consists of a hydraulic cyclone 4 with vertical axis formed by an external lateral wall 5, whose upper part 6 is cylindrical and whose Lower part 7 is a truncated cone. The hydraulic cyclone 4, internally, has a cylindrical sleeve 8 with vertical axis; said cylindrical sleeve 8 is open at the two bases, apertures 9 and 10, and is connected above to the lateral wall 5 of the cyclone 4 by means of an annular plate 11. The hydraulic cyclone 4 is connected in its lower part to the internal space of the tank 1 via an aperture 12.

An inlet conduit 13 for the material and the conveying Liquid flows into the upper cylindrical part 6 of the external wall 5, and which in this case also has the function of supporting the cyclone 4; said conduit 13 is inserted tangentially in an annular space 14 defined by the upper part 6 of the Lateral wall 5 of the cyclone 4 and by said cylindrical sleeve 8. A system 15 is positioned at the clear surface of the mass of liquid 2, Level L, for the removal of the material with lower specific weight, which comprises rollers 16 provided with blades 17 and rotatably supported by the external walls of the tank 2. The rollers 16 are made to rotate by an electric motor 18. As shown by fig. 1, the rollers 16 are bLaded in such a way

that their blades 17 dip into the liquid 2 to a Limited extent.

Again at the Level L, there is the Lower edge 19 of a discharge aperture 20, which is in turn connected to a discharge conduit 21 for the material and through a grating 22 with a discharge conduit 23 for any liquid remaining together with the material of lower specific weight.

The system for ejecting heavy material consists of a variable flow rate pump 24 placed below the bottom of the tank 1. As described previously, the material and the conveying liquid (C) are fed into the separation tank 1 at a selected pressure which is higher than that of the mass of Liquid 2 by means of the feed device 3 consisting of the hydraulic cyclone 4 and the tangential conduit 13. The material and the conveying liquid forced into the upper part of the hydraulic cyclone 4 are imparted, by means of the structure of the upper part of the cyclone (upper part 6 of the Lateral wall 5 and cylindrical sleeve 8), with a rotary motion for the purposes of separating the material. At the end part of the cylindrical wall 6 and the lower aperture 10 of the sleeve 8 two different flows of material are formed: this corresponds to the separation of the material according to the different specific weights of its components. There is therefore an ascending flow (A ¹ ) of the components of the material with lower specific weight and of the conveying Liquid which, through the upper aperture 9 of the sleeve, passes into the mass of Liquid 2 in the tank 1 and moves towards the clear surface of the mass of Liquid, level L, and a descending flow (A") of the components of material with higher specific weight and of the conveying liquid which, having flowed into the mass of liquid 2, flows down towards the

removal device 24 placed at the bottom of the tank 1.

The blades 17 of the rollers 16 of the system for removing lighter material 15 push the material out of the tank 1 towards the discharge conduit 21 together with a small quantity of Liquid, which is in turn discharged via the conduit 23 after having passed through the small apertures of the grating 22.

The variable flow rate pump 24 serves to increase the efficiency of the separation equipment and allows, if necessary, the discriminating power of the separation equipment to be defined in terms such that only extremely light materials are allowed to float at the level L of the Liquid 2 in the tank 1.

The separation equipment shown in figs. 3 and 4 differs from that shown in figs. 1 and 2 only by the internal structure of the hydraulic cyclone 4.

The hydraulic cyclone 4 in this case has, internally, instead of a cylindrical sleeve, a vertical axis rotary body 25 with an upper cylindrical part 26 and a Lower truncated cone part 27 with radial blades 28. The rotary body 25 is inserted on a shaft 29 supported by a motor 20. The lateral wall 5, as moreover in the previous case, is supported by the tangential inlet conduit 13. The annular space 31 defined by the lateral wall 5 and by the rotary body 25 is connected to the internal space of the tank 1 both above and below to enable the formation of the two vertical flows (A ¹ and A") previously mentioned.

The presence of the rotary body 25, set in motion via the shaft 29, by the motor 30, intensifies the rotary motion of the material to be separated and of the conveying Liquid along the whole of the hydraulic cyLone 4 and then also in the tank 1 and

further accentuates the phenomenon of separation of the material.