The present invention relates to an impact mill for milling loose material, particularly for secondary and tertiary breakup.

In the field of material recycling, it is known to use milling or crushing machines, which are typically known as mills.

Mills of the known type particularly for secondary and tertiary breakup, i.e., for the breakup of materials with a fragment size respectively up to approximately 100 millimeters or up to approximately 30 millimeters, typically comprise two rotors with mutually parallel horizontal axes accommodated in two laterally adjacent and communicating chambers, in the first of which, termed feed chamber or launcher, the loose material to be milled is introduced, and in the second of which, known as milling chamber, the actual milling or breakup of the material occurs, so as to disaggregate the material introduced in the feed chamber.

In greater detail, the breakup of the material occurs by means of the impact of adapted hammers mounted eccentrically on the rotor accommodated in the milling chamber, which, by virtue of the rotation of the rotor, strike the material, partially breaking it up and propelling it against adapted impact surfaces provided at the internal perimetric surface of the milling chamber, with consequent further breakup of said material.

In the feed chamber, instead, the material is introduced by means of adapted circumferential and/or axial openings such as to make the material being milled settle in a collection region located along the trajectory of adapted launching elements which are mounted eccentrically on the rotor contained in said feed chamber.

In this manner, as a consequence of the rotation of the rotor mentioned above, the material to be milled is collected and propelled in the direction of the milling chamber through an adapted passage opening formed astride the two chambers. For the entire system to operate correctly, as a function of the number of launching elements and of the number of hammers with which the two rotors are provided, said rotors are synchronized so that the individual accumulations of material collected and propelled by the rotor of the feed chamber trace a trajectory that is incident to the trajectory of the individual hammers, with an impact speed that is determined by the sum of the rotation rate of the individual hammer and of the launching speed of the individual accumulation of material.

These impact mills of the known type are not free from drawbacks, which include the fact that the feed chambers typically used have geometries that are studied to optimize the introduction of the material but are subject to unwanted impacts of the introduced material, which is launched against the internal surface of the feed chamber as a consequence of the rotation of the rotor.

In other words, in particular as the rotation rate of the rotor of the feed chamber increases, uncontrolled and unwanted wear of the inside of the perimetric wall of the chamber, which is not designed to withstand impacts of this kind, occurs in said chamber.

The aim of the present invention is to provide an improved impact mill such as to obviate the drawbacks of the background art described above.

Within this aim, an object of the present invention is to provide an impact mill that allows to safeguard the integrity of the elements of the feed chamber.

Another object of the present invention is to provide an impact mill that allows to extend the useful life of the elements of the feed chamber, raising it to a level that is higher than that of mills of the known type, with a manufacturing cost that is comparable and economically competitive with respect to those of mills of the known type.

Another object of the invention is to provide an impact mill that is highly reliable, relatively easy to provide and at competitive costs.

This aim, as well as these and other objects which will become better apparent hereinafter, are achieved by an impact mill according to claim 1, optionally provided with one or more of the characteristics of the dependent claims.

Further characteristics and advantages of the invention will become better apparent from the description of a preferred but not exclusive embodiment of an improved impact mill, particularly for milling loose material, according to the invention, illustrated by way of non limiting example in the accompanying drawings, wherein:

Figure 1 is a sectional side view of an impact mill according to the present invention, taken along a plane that is perpendicular to the rotation axes;

Figures 2 and 3 are two side views of the impact mill shown in Figure 1, showing in sequence the operation.

With reference to the figures, an impact mill, particularly for secondary breakup, according to the invention, designated generally by the reference numeral 1, comprises a first structure 2, which forms a milling chamber 3 inside which at least one main rotor 4 is accommodated which can rotate about a first rotation axis 5 and is adapted for the milling of loose material 6, for example inert materials, metals, zorba, coal, glass. The loose material 6 has a maximum fragment size of about 100 millimeters, for example 100-150 mm.

Adjacent to the first structure 2 there is a second structure 7 which forms a feed chamber 8, which has an inlet 9 for the loose material 6 and functionally communicates with the milling chamber 3 for the passage of the loose material 6 from the feed chamber 8 to the milling chamber 3.

This feed chamber 8 accommodates at least one secondary rotor 10 which can rotate about a second rotation axis 11 in the opposite direction with respect to the main rotor 4 and is adapted to propel the loose material 6 from the feed chamber 8 to the milling chamber 3.

Conveniently, the two rotation axes 5 and 11 are substantially parallel to each other and lie along a geometric plane P that is substantially parallel or inclined with respect to the substantially horizontal plane on which the mill rests, for example inclined at an angle of less than 10° and more preferably less than 5°, so that the second rotation axis 11 is at a distance from the horizontal plane that is greater than or equal to the distance of the first rotation axis 5 from the same horizontal plane.

The rotors are actuated so as to rotate synchronously by motor means, for example by a single motor which drives one of the two rotors and a transmission mechanism that drives the other rotor by means of the rotation of the first one. The minimum rotation rate can be 250-700 rpm in the case of secondary breakup (maximum fragment size of the material 6 of 120 mm) or 850-1250 rpm in the case of tertiary breakup (maximum fragment size of the material 6 of 30 mm).

The two chambers 3 and 8 are delimited axially by at least two mutually opposite side walls which are substantially transverse to the respective rotation axis 5 or 11 and are delimited radially by respective perimetric walls 12 and 13 that connect the two side walls and are extended around the rotation axis of the respective rotor so as to surround most of it.

The milling chamber 3 preferably has a plurality of per se known impact surfaces 23, also known as plating, which are mutually inclined so as to form a plurality of protrusions and recesses, which are mutually consecutive and alternated and which the loose material 6 strikes as a consequence of the rotation of the main rotor 4.

In greater detail, the impact surfaces 23 are substantially planar and mutually inclined so as to form at least one protrusion that has an angle comprised between 80° and 110° and at least one recess having an angle comprised between 210° and 240°.

Furthermore, the first structure 2 can comprise at least one unloading hatch 24 which is hinged between the side walls of the milling chamber 3 and can move between a closed position and an open position, in which it is rotated with respect to the closed position in order to allow the unloading of the broken up loose material 6.

An inlet 9 communicates with the feed chamber 8 through one of said side walls at the feed chamber 8 so that the loose material 6 is introduced in the feed chamber 8 along a direction that is substantially parallel to the second rotation axis 11.

The chambers 3 and 8 communicate directly with each other via an opening 14 for launching the loose material 6 that is formed on the perimetric walls 12 and 13 substantially below the geometric plane P on which the rotation axes 5 and 11 lie.

The perimetric wall 13 of the feed chamber 8 forms, towards the inside of said chamber 8, a cylindrical surface having a substantially circular base which is coaxial to the second rotation axis 11. The cylindrical surface is extended all around the second rotation axis 11 with a radius that is substantially equal to the maximum radius of the secondary rotor 10 and is interrupted by the launch opening 14.

The substantial match between the radius of the cylindrical surface and the maximum radial space occupation of the secondary rotor 10 allows the latter to affect all the loose material 6 that is introduced in the feed chamber 8 and to prevent it from striking the internal walls of the feed chamber 8.

The perimetric wall 13 of the feed chamber 8 therefore has a substantially C-shaped internal profile, in which the cylindrical surface is in practice interrupted by the launch opening 14.

The cylindrical surface that is internal to the perimetric wall 13 comprises, starting from an upper edge of the launch opening 14 and in succession in the direction of rotation of the secondary rotor 10, a first portion 15 shaped substantially like a circular arc and a second portion 16 substantially shaped like a circular arc, downstream of which there is a rectilinear launch ramp 17, which ends at the base of the launch opening 14 and is extended below the geometric plane P on which the rotation axes 5 and 11 apply and substantially tangentially to the cylindrical surface that is formed inside the perimetric wall 13, in particular tangentially to the downstream end of the second arc-like portion 16.

The geometric plane of the upper surface of the ramp 17 and the geometric plane P on which the rotation axes 5 and 11 lie are preferably inclined so as to intersect on a straight line that is external to the region of the plane P that is comprised between the two rotation axes 5 and 11.

In particular, the rectilinear launch ramp 17 is preferably inclined, with respect to the horizontal resting plane of the mill 1, by an angle of less than 5°, more preferably less than 2°.

The launch opening 14 of the loose material 6 that is formed astride the chambers 3 and 8 is located at the lower portion of the chambers 3 and 8 in such a manner that the loose material 6 can be launched by the secondary rotor 10 through the launch opening 14 along a preset direction from the lower region of the feed chamber 8 toward the inside of the milling chamber 3.

Advantageously, the second structure 7 comprises an extractable portion 18, which is arranged below the inlet 9, for access to the feed chamber 8 on the part of the operator and comprises the second arc-like portion 16 and the ramp 17 of the perimetric wall 13 of the feed chamber 8.

In greater detail, said extractable portion 18 can be moved by translation substantially parallel to the side walls of the feed chamber 8 between an operating configuration, in which it is aligned with the remaining portion of the second structure 7, and an extraction configuration, in which it is spaced from the remaining portion of the second structure 7 with respect to the operating configuration.

In the described embodiment, the second structure 7 comprises at least one openable wall 19 which is hinged to the side walls of the feed chamber 8 and can be moved between a closed position and an open position, in which the openable wall 19 is rotated with respect to the closed position so as to form a resting surface for the sliding of the extractable portion 18.

As regards the rotors 4 and 10, the main rotor 4 comprises at least two breakup hammers 20 which are diametrically opposite and radially spaced from the first rotation axis 5 and the secondary rotor 10 comprises at least two launch elements 21 which are diametrically opposite and radially distant from the second rotation axis 11.

The synchronized rotation of the rotors 4 and 10 is such that the loose material 6 propelled by the two launch elements 21 strikes the two hammers 20 of the main rotor 4 substantially at right angles.

The main rotor 3 can furthermore comprise at least one connecting surface 22 which is interposed between the two consecutive breakup elements 20 and has a shape that is convex and substantially circular, with a center of curvature that is eccentric with respect to the first rotation axis 5.

The operation of the mill 1 can be easily deduced from what has just been described.

With particular reference to Figures 2 and 3, as a consequence of the insertion by gravity of the loose material 6 to be milled in the feed chamber 3 through the inlet 9 and by virtue of the rotation of the secondary rotor 10, the launch elements 21 entrain the loose material 6, making it slide against the perimetric wall 13 of the feed chamber 8 and making it acquire sufficient kinetic energy so that when it arrives at the launch opening 14 it is launched along the tangent to the trajectory of the secondary rotor 10 in the direction of the incoming hammer 20 of the primary rotor 4 in the milling chamber 3. The incoming hammer 20, which is synchronous in rotation with the elements 21 of the secondary rotor 10, strikes the loose material 6, breaking it up and making it strike several times the plating 23 until it is disaggregated.

Once milling has been performed, it is then possible to unload the milled loose material 6 from the milling chamber 3 by means of the opening of the unloading hatch 24.

Likewise, if it is necessary to access the feed chamber 8, the operator can intervene in this regard by removing the extractable portion 18.

It is appropriate to point out, in what has just been described, that in the steps for the pickup and launching of the loose material 6 from the feed chamber 8 to the milling chamber 3, this material 6 is forced by the particular internal shape of the feed chamber 8 to trace a circular trajectory without assuming accelerations in a radial direction such as to make it strike the perimetric wall 13 of the feed chamber 3.

In practice it has been found that the impact mill according to the present invention fully achieves the intended the aim and objects, since it allows to safeguard the integrity of the elements of the feed chamber, extending their useful life.

The improved impact mill thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the accompanying claims.

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

The disclosures in Italian Patent Application No. 102019000007560 from which this application claims priority are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.