The present invention relates to a hammer mill for milling refuse.

The invention relates to the recycling sector and it is adapted for milling refuse of various types, constituted by materials such as plastic, rubber, ferrous and non-ferrous metals, glass, rubble, wood, etc.

In the recycling sector, hammer mills are known for refining apparatuses, and are used to mill refuse with a sizing of approximately 30 mm, which may optionally originate from a previous processing stage for breaking up the refuse, in order to obtain a sizing of maximum 2 mm at the end of the processing. Such reduced sizing serves mainly to select the material with gravimetric boards. Secondly, it has been observed that during the processing and in the various stages of passing through the recycling stations, stainless steel takes on a magnetic charge and the sizing reduction enables separation with special magnets.

Interest in the sector in taking maximum advantage of the potential of hammer mills for milling refuse is therefore evident.

Nowadays hammer mills are known which comprise a casing which defines a receptacle for a roller-type rotor which is provided with milling hammers. In particular, fixed hammer mills and movable hammer mills are known, the latter being movable because they are installed so that they can tilt.

The casing is provided with an entry channel for the material to be milled and with an exit channel for discharging the milled material. The transit of material occurs by pneumatic conveyance, via aspiration at the exit of the casing.

The casing is provided, on the inner walls, with lining armor plates which have channels that make it possible to channel and conduct the material being processed toward the exit channel.

In these mills, the entry and exit channels are positioned radially with respect to the rotor and this implies that the material is milled substantially only in the central part of the rotor. As a consequence, the greatest wear is supported by the hammers located in the central part of the rotor and the performance of the mill is only partially exploited.

Furthermore, the greatest wear of the hammers in the central part requires numerous replacement interventions which require the disassembly and reassembly substantially of all of the rotor.

The aim of the present invention is to provide a hammer mill for milling refuse which is capable of improving the known art in one or more of the above mentioned aspects.

Within this aim, an object of the invention is to increase the milling ratio of the hammer mills.

Another object of the invention is to facilitate a uniform wear of the hammer mills for the milling and to reduce and simplify the maintenance interventions on the rotor.

Another object of the invention is to provide a hammer mill that is highly reliable, easy to implement and of low cost.

This aim and these and other objects which will become better apparent hereinafter are achieved by a hammer mill for milling refuse, which comprises a substantially cylindrical casing with two heads, which defines a receptacle for a roller-type rotor with peripheral milling hammers and which has an entry channel for the material to be milled and an exit channel for the milled material, said mill being characterized in that said entry channel and said exit channel have inlets for connection to said casing which are arranged on respective said heads and along directions that are parallel to the direction of the rotation axis of said rotor.

Further characteristics and advantages of the invention will become better apparent from the detailed description that follows of a preferred, but not exclusive, embodiment of the hammer mill according to the invention, which is illustrated by way of non-limiting example in the accompanying drawings wherein: - Figure 1 is a perspective view of the hammer mill according to the invention with the casing open in order to show the rotor inside;

- Figure 2 is a cross-sectional front elevation view of the hammer mill according to the invention, taken along a vertical plane that passes through the axis of the rotor.

With reference to the figures, the mill according to the invention, generally designated by the reference numeral 10, comprises a supporting chassis 11 on which are installed an electric motor 12 and a cylindrical casing 13 with two heads, which defines a receptacle for a roller- type rotor 14 with peripheral milling hammers 15. The motor 12 and the rotor 14 are conveniently connected by way of transmission belts 16 and in a conventional manner.

The casing 13 is provided with an entry channel 17 for the material to be milled and with an exit channel 18 for the milled material.

As can be seen in Figure 2, such entry channel 17 and exit channel 18 have inlets for connection to the casing 13 which are arranged on respective heads 17a, 18a and along directions that are parallel to the direction of the rotation axis 19 of the rotor 14. In particular, the entry channel 17 is on one side, the right-hand side in the illustration, in the upper part of the casing 13, which acts as a lid to be closed over the rotor 14, while the exit channel 18 is on the opposite side to the previous one, on the side where the processed material exits, in the lower part.

The conveyance is pneumatic and it is provided by creating an aspiration at the exit.

The mill illustrated is a movable hammer mill 15, in that the hammers oscillate, but the same inventive concept described can also be applied to fixed hammer mills.

As can be seen in Figure 1, the rotor 14 has a pack of coaxial disks 20, mounted on the same rotation axis 19 as the rotor 14, which are spaced apart and which define between them stages 21 of milling hammers 15, from which the hammers protrude radially.

At each stage a predefined number of hammers 15 is present, six in the case shown.

The rotor 14 also has a first disk 20a, substantially definable as "entry disk" because it is located first in line on the side where the material enters the casing 13, which is arranged in front of the other coaxial disks 20, has a smaller diameter than those disks, and defines with the subsequent second disk 20b (the first disk of the pack of disks) a first stage 21a which is adapted to intercept the material to be milled entering from the entry channel 17 by way of oscillating first milling hammers 15a.

These hammers 15a are oscillating hammers even if the mill 10 is of the type with fixed hammers, installed between the other, following disks.

The first milling hammers 15a protrude radially from the first disk 20a, but not past the perimeter of the second disk 20b, and they define the first stage 21a of hammers. Substantially, during the rotation of the rotor 14, the first milling hammers 15a trace a circumference having a diameter smaller than the diameter of a circumference traced by the other milling hammers 15.

The rotor 14 is assembled in a manner that is known per se. In the case shown, there are eleven disks 20, ten of which have the same dimensions and the first disk 20a has a smaller diameter.

The disks 20 are separated by spacers 22 and locked between a loading flange (on the side where the material enters the casing), which is the first disk 20a, and an offloading flange (on the opposite side), which is the last disk of the pack 20.

The second disk 20b is covered with an annular metal plate 23 on the side directed toward the first disk 20a.

The annular metal plate 23 is installed on the second disk 20b by way of pins 24 for fixing the first milling hammers 15a, the plate being interposed between the hammers and the second disk 20b. Second fixing pins 25 join the hammers 15 to the pack of disks 20.

The casing 13 has, on its inner walls, lining armor plates 26 which have parallel series of recesses 27 which extend along a same longitudinal direction and are alternated with regions without recesses.

The recesses 27 can be seen in Figure 1, on the innermost side of the upper part of the casing 13 and partially on the innermost side of the lower part.

The interspace between the hammers and the lining armor plates 26 is at most 5 mm.

Operation of the mill, according to the invention, is the following.

The material to be milled is introduced through the entry channel 17 and conveyed with air into the casing 13.

The material initially encounters the first stage 21a of the first milling hammers 15a, which substantially constitutes a pre-mill, and which is useful, in particular, for the larger-sized pieces of material, which may exceed 30 mm, preventing these from impacting directly on the other hammers 15.

The inward material comes directly into contact with these first hammers 15, which as a consequence are the hammers that are subjected to the greatest wear. The metal plate 23 arranged in the entry region protects the rotor 14 from wear.

Substitution of these hammers 15a is simple and easy, since they are fixed to the second disk 20b by way of the first pins 24.

The arrangement of the channels 17 and 18, with inlets parallel to the rotation axis 19 of the rotor 14, force the material to come into contact with the hammers 15, thus preventing them from going through the mill 10 by passing through the interspace, i.e. without being subjected to milling.

During rotation of the rotor 14, the material being processed is pushed outward, against the lining armor plates 26. Here the recesses 27, because they have a longitudinal extension and are aligned, are adapted to convey the material being processed toward the region for exiting from the casing 13, and at the same time they force its return toward the hammers 15.

The efficiency of the machine is appreciably increased, raising the ratio of reducing the material being recycled from 3: 1 to 5.5: 1.

In practice it has been found that the invention fully achieves the intended aim and objects by providing a hammer mill for milling refuse with a milling ratio that exceeds the ratio of the mills known today and which enables simpler and more immediate maintenance of the rotor.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. Moreover, all the details may be substituted by other, technically equivalent elements.

In practice the materials employed, provided they are compatible with the specific use, and the contingent dimensions and shapes, may be any according to requirements and to the state of the art.

The disclosures in Italian Patent Application No. 102018000009339 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.