EP3687694B1

EP3687694B1 - Impact mill for grinding loose material

Info

Publication number: EP3687694B1
Application number: EP18792477.4A
Authority: EP
Inventors: Stefano Marchetti; Giuseppe Pisani
Original assignee: Individual
Current assignee: MARCHETTI, STEFANO; PISANI, GIUSEPPE
Priority date: 2017-09-27
Filing date: 2018-09-27
Publication date: 2021-08-25
Anticipated expiration: 2038-09-27
Also published as: IT201700107927A1; ES2901513T3; PL3687694T3; RU2020114194A; RU2764991C2; WO2019064210A1; RU2020114194A3; EP3687694A1

Description

Technical Field

The present invention relates to an impact mill for grinding loose material.

Background Art

Impact mills for grinding loose material generally comprise a main rotor moveable in rotation around a relative axis and provided with one or more hammers designed to crush the incoming material. Known impact mills also have a secondary rotor provided with a number of blades adapted to convey the material to be ground towards the main rotor. The main rotor and the secondary rotor are placed inside a grinding chamber and an inlet chamber respectively, in communication with each other.
Each chamber is delimited by a pair of side walls arranged orthogonally to the relative axis of rotation and by a connecting wall, placed between the side walls to substantially surround the relative rotor.
The main rotor has a central core with a cylindrical conformation which extends around the axis of rotation and with which the crushing hammers are associated in an integral manner. More specifically, the crushing hammers have a portion which comes out of the central core and which is adapted to impact the material to be ground and a portion which, on the other hand, is contained inside the base core to allow fixing to same.
The known types of mills can be classified as horizontal axis mills or vertical axis mills, depending on the spatial arrangement of the axis of rotation of the main rotor.
The present invention relates in particular to horizontal axis mills. A horizontal axis impact mill according to the preamble of claim 1 is disclosed in EP-2908954-A1 .
This mill envisages that the inlet chamber be arranged laterally to the grinding chamber and that the two chambers be placed in communication with each other through a connecting opening. In particular, the secondary rotor and the main rotor rotate in the same direction and the secondary rotor is adapted to convey the material to be ground into the grinding chamber from top to bottom so that it meets the crushing hammers of the main rotor during their rotation.
The mill described by EP2908954 , however, has a number of limitations.
In particular, the material to be ground is introduced into the inlet chamber at its bottom, so that the blades of the secondary rotor have to drag it substantially along the entire extension of the corresponding connecting wall before conveying it to the grinding chamber. During the rotation of the secondary rotor, the material to be ground interposes itself between the corresponding blades and the connecting wall of the inlet chamber, causing wear on the parts subject to rubbing.
Conveying the material to be ground into the grinding chamber therefore entails high expenditure of energy, due to the effort the secondary rotor has to make to drag the material, and of materials, due to the wear of the parts subject to rubbing.
This drawback affects not only the need to replace worn parts, but also the launching efficiency of the material to be ground and, therefore, the grinding efficiency. In fact, the wear of the secondary rotor blades can lead to the material being conveyed to the grinding chamber at an angle which is not optimal for fully exploiting the action of the crushing hammers and, in any case, is totally independent of the physical properties (specific weight and humidity) of the material to be ground.

Description of the Invention

The main aim of the present invention is to devise an impact mill which overcomes the drawbacks of the prior art.
In particular, the present invention proposes to increase the grinding efficiency while reducing energy consumption with respect to known mills.
Within this aim, one object of the present invention is to reduce the wear of the moving parts, and in particular of the secondary rotor blades.
Another object is to optimize the launching phase of the material to be ground inside the grinding chamber according to the state of wear of the parts involved and of the properties of the material itself.
Another object of the present invention is to devise an impact mill for grinding loose material, which allows overcoming the aforementioned drawbacks of the prior art within the scope of a simple, rational, easy, efficient to use and cost-effective solution.
The aforementioned objects are achieved by the present impact mill for grinding loose material according to claim 1.

Brief Description of the Drawings

Other characteristics and advantages of the present invention will become more evident from the description of a preferred, but not exclusive embodiment of an impact mill for grinding loose material, illustrated by way of an indicative, but non-limiting example, in the attached drawings in which:

Figure 1 is a side elevation view of a mill according to the invention in a first operating configuration;
Figure 2 is a side elevation view of the mill of Figure 1 in a second operating configuration;
Figure 3 is a side elevation view of the mill of Figure 1 in a third operating configuration.

Embodiments of the Invention

With particular reference to these illustrations, reference numeral 1 globally indicates an impact mill for grinding loose material.
The mill 1 comprises a first body 2 defining a grinding chamber 3 inside which is housed at least one main rotor 4 moveable in rotation around a first axis X.
More in detail, the grinding chamber 3 is delimited by two side walls 5, arranged transversally with respect to the first axis X on opposite sides with respect to the main rotor 4, and by at least one connecting wall 6 interposed between the side walls 5 and configured so as to surround the main rotor itself, at least in part. The connecting wall 6 therefore extends around the first axis X. The main rotor 4 comprises at least two crushing elements 7 adapted to impact the material to be ground. Alternative embodiments cannot however be ruled out wherein the main rotor comprises a larger number of crushing elements 7. Each crushing element 7 is composed in practice of a corresponding plate made of wear-resistant material and locked together, e.g. by means of threaded means, with a base core 8.
More specifically, each crushing element 7 has a front face facing outwards and intended to impact the material and a rear face associated with the base core 8. The base core 8 is in turn locked together with a motion transmission shaft, not shown in detail in the illustrations, which can be operated in rotation around the first axis X according to procedures known to the expert in the sector.
Preferably, the base core 8 has at least a curvilinear and convex joining surface 8a interposed between two consecutive crushing elements 7. In particular, the joining surface 8a corresponds to the portion of a cylindrical surface offset with respect to the first axis X. More in detail, in the embodiment shown in the illustrations, wherein the main rotor comprises two crushing elements 7 arranged on opposite sides with respect to the first axis X, the base core 8 has two joining surfaces 8a. Each of these joining surfaces 8a has one extremity arranged at the front face of a crushing element 7 and the opposite extremity arranged at the rear face of the other crushing element 7. This conformation of the main rotor 4 is not, however, restrictive, so alternative embodiments cannot be ruled out which do not provide for the presence of the joining surfaces 8a or which provide joining surfaces having only some of the above-mentioned characteristics.
In the preferred embodiments shown in the illustrations, the connecting wall 6 has, at least at the upper portion of the grinding chamber 3, a plurality of impact surfaces 9 inclined the one to the other and facing the inside of the grinding chamber itself.
Such impact surfaces 9 are inclined in such a way as to define a plurality of consecutive and alternating projections and recesses.
Preferably, at least one recess consisting of two consecutive impact surfaces 9 defines an angle α between 80° and 110°, preferably between 90° and 110°. This is particularly the case for the impact surfaces 9 which are affected by the crushing process, i.e. those located at the upper portion of the grinding chamber 3.
At least one projection consisting of two consecutive impact surfaces 9 defines an angle β between 210° and 240°.
More in detail, the inclination angle of the impact surfaces 9 and the rotation speed of the main rotor 4 are such that the material hit by one of the crushing elements 7 is thrown against one of these impact surfaces 9 following the impact with which it is rejected and hit again by the other crushing element 7 which directs it towards another impact surface 9. This way, the material to be ground is in practice "bounced" between the impact surfaces 9 and the crushing elements 7, resulting in particularly effective crushing.
The mill 1 also comprises a second body 10, associated with the first body 2, defining an inlet chamber 11 communicating with the grinding chamber 3 and inside which is housed a secondary rotor 12 moveable in rotation around a second axis Y.
The inlet chamber 11 is also delimited by two side walls 13 arranged transversely to the second axis Y on opposite sides with respect to the secondary rotor 12 and by at least one connecting wall 14 interposed between the side walls 13 to surround at least partly the secondary rotor itself. Preferably, the connecting wall 14 surrounding the secondary rotor 12 at least partly has a substantially circular extension.
The secondary rotor 12 has one or more launch elements 15 adapted to contact the material to be ground arranged inside the inlet chamber 11 and to push it towards the grinding chamber 3. In the embodiment shown in the illustrations, the secondary rotor 12 comprises two launch elements 15 arranged on sides diametrically opposite to the second axis of rotation Y. The number of launch elements 15 is generally equal to the number of crushing elements 7.
The first and the second axis X and Y are substantially horizontal and are arranged substantially parallel to each other.
The inlet chamber 11 is arranged laterally with respect to the grinding chamber 3. More in detail, the inlet chamber 11 is arranged outside the vertical projection of the grinding chamber 3. This arrangement allows optimizing the grinding efficiency as it maximizes the working stroke of the main rotor 4, i.e. the stroke during which the rotor itself is active in the crushing process of the material. Conveniently, the first and the second body 2 and 10 are locked together with each other.
The grinding chamber 3 and the inlet chamber 11 are communicating with each other by means of a connecting opening 16 defined on the respective connecting walls 6, 14.
The inlet chamber 11 has in turn an inlet opening 17 for the introduction of the material to be ground inside.
Preferably, the inlet opening 17 is arranged at at least one of the side walls 13. More in detail, the inlet opening 17 is arranged along the second axis Y. In the preferred, but not exclusive, embodiments shown in the illustrations, the inlet chamber 11 has only one inlet opening 17 defined on one of the side walls 13, the other side wall 13 being connected to the motion transmission shaft of the secondary rotor 12.
According to the invention, the connecting opening 16 is arranged at the lower portion of the inlet chamber 11, so that the material sent from the secondary rotor 12 is directed from the bottom of the inlet chamber 11 towards the inside of the grinding chamber 3.
The material to be ground is then sent from the bottom of the inlet chamber 11 towards the upper portion of the grinding chamber 3 or at most in a horizontal direction.
Still according to the invention, the connecting wall 14 of the inlet chamber 11 comprises at least one adjustable portion 14a which is moveable, during use, around an axis of adjustment Z to vary the inlet direction of the material to be ground inside the grinding chamber 3.
In other words, by adjusting the adjustable portion 14a, e.g., depending on the state of wear of the launch elements 15 and the type of material to be ground, or depending on its specific weight and its degree of humidity, it is possible to change the angle at which the material to be ground is introduced into the grinding chamber 3.
The remaining portion of the connecting wall 14, identified in the illustrations by the reference numeral 14b, may be fixed or, preferably, shift along a compensation direction, identified by the reference numeral 29 in the illustrations, to allow it to move close to the adjustable portion 14a after its displacement, so as to maintain the surface continuity of the connecting wall 14. Advantageously, the axis of adjustment Z coincides with the second axis Y. Preferably, the main rotor 4 and the secondary rotor 12 are counter-rotating to each other. This causes the material to be ground introduced from below inside the grinding chamber 3 to be impacted by the crushing elements 7 and pushed therefrom towards the upper portion of the grinding chamber itself, thus causing an increase in the number of impacts that the material undergoes.
Suitably, the adjustable portion 14a is defined at the lower portion of the connecting wall 14.
More particularly, the adjustable portion 14a is arranged lower than the inlet opening 17, in such a way that the material to be ground which is introduced into the inlet chamber 11 falls directly onto the adjustable portion 14a.
The direction of rotation of the secondary rotor 12, the arrangement of the adjustable portion 14a and of the connecting opening 16 are such that the stroke completed by the launch elements 15 to bring the material to be ground from the adjustable portion 14a to the connecting opening 16 is greater than the stroke completed by the secondary rotor itself to return from the latter again to the adjustable portion 14a.
The working stroke completed by the secondary rotor 12, meaning by this term the stroke length that begins when the launch elements 15 come into contact with the material to be ground introduced into the inlet chamber 11 and which ends when they release it to send it to the grinding chamber 3, is therefore minimum.
Preferably, the adjustable portion 14a has at least one curvilinear section 18 and at least one rectilinear section 19 which are contiguous to each other. More particularly, the rectilinear section 19 is arranged downstream of the curvilinear section 18 with respect to the direction of rotation of the secondary rotor 12. The rectilinear section 19 thus delimits the lower extremity of the connecting opening 16.
In other words, the launch elements 15, during the rotation of the secondary rotor 12 around the second axis Y, approaching the connecting opening 16, run in succession along the curvilinear section 18 and the rectilinear section 19. The inlet chamber 11 therefore has a conveying channel 20 for conveying the material to be ground, which comprises the connecting opening 16 and is delimited by the rectilinear section 19. The inclination of the rectilinear section 19 with respect to a horizontal direction substantially defines the direction in which the material is conveyed into the grinding chamber 3.
Advantageously, the second body 10 comprises at least one base element 21 supporting the adjustable portion 14a in rotation around the axis of adjustment Z.
More particularly, regulating means 22 are provided for regulating the rotation of the adjustable portion 14a around the axis of adjustment Z.
In the embodiment shown in the illustrations, the regulating means 22 are of the mechanical type and comprise one or more slots 23 having a curvilinear extension defined on the base element 21 and one or more pins 24, locked together with the adjustable portion 14a, each of which is housed in a sliding manner into a corresponding slot 23.
Appropriately, each slot 23 extends along a circumferential arc having its center at the axis of adjustment Z.
In this embodiment, the adjustable portion 14a is displaced around the axis of adjustment Z manually by an operator.
In an alternative embodiment not shown in the illustrations, the regulating means 22 comprise at least one sensor means adapted to detect the angular position of the adjustable portion 14a with respect to the axis of adjustment Z, e.g. of the type of a position sensor or the like, movement means for moving the adjustable portion itself and at least one electronic control unit. The electronic control unit comprises at least one memory settable with at least one value of the angular position of the adjustable portion 14a, and comprises a microprocessor programmed to receive a signal from the sensor means relating to the detected angular position, to compare the set position to the detected position and to activate the movement means in the event of the detected position being different from the set position.
In this alternative embodiment, therefore, the adjustment of the angular position of the adjustable portion 14a is substantially automatic. Preferably, the adjustable portion 14a is moveable in translation with respect to the side walls 13 of the inlet chamber 11 between at least an operating configuration, in which it is substantially aligned with the remaining portion 14b in such a way that the connecting wall 14 is substantially without interruption, and an extraction configuration in which it is misaligned with respect to the remaining portion 14b.
More in detail, the base element 21 is associated moveable in translation with the side walls 13 along an extraction direction 25 and the adjustable portion 14a is locked together in translation with the base element 21.
Appropriately, the base element 21 comprises rolling means 26, e.g., of the type of one or more wheels, arranged on a holding surface 27 and adapted to allow the movement of the base element itself along the extraction direction 25. Advantageously, the second body 10 comprises at least one openable wall 28, hinged to the side walls 13 of the inlet chamber 11 and moveable between at least one closed position and one open position. More particularly, in the open position, the openable wall 28 is rotated with respect to the closed position and defines the extension of the holding surface 27. As a result of the movement of the openable wall 28 to the open position, the base element 21 and the adjustable portion 14a can be shifted from the operating configuration to the extraction configuration.
The operation of the mill according to the invention is as follows.
The material to be ground which is introduced into the inlet chamber 11 through the inlet opening 17 falls by gravity and deposits at the adjustable portion 14a. By effect of the rotation of the secondary rotor 12 the launch elements 15 therefore contact the material to be ground and drag it towards the connecting opening 16.
In case it is found that the launch direction of the material to be ground is not optimal, for reasons that may be due to wear on the mechanical parts involved or to the type of material, the position of the adjustable portion 14a will have to be changed by means of the regulating means 22. This operation can be carried out either by keeping the openable wall 28 in the closed position or by moving it to the open position.
In the first case, the regulation is carried out by opening a door that makes the pins 24 accessible from the outside.
In the second case, instead, once the openable wall 28 has been brought into the open position, the base element 21 is extracted by sliding it on the holding surface 27 in the extraction direction 25. Once the base element 21 has been extracted and, therefore, the adjustable portion 14a has been brought from the operating configuration to the extraction configuration, it is possible to access the regulating means 22 and thus vary the position of the adjustable portion itself. In detail, the operator adjusts the pins 24, making them slide inside the corresponding slots 23, so as to change the position of the adjustable portion 14a with respect to the remaining portion 14b and, consequently, the inclination of the rectilinear section 19. Once the adjustable portion 14a has been fixed in the desired position, it is returned to the operating configuration by sliding the base element 21 in the opposite direction to the previous one.
The material to be ground entering the grinding chamber 3 is then hit by the crushing elements 7 which, in addition to causing an initial decrease in size, project it against the impact surfaces 9.
It has, in practice, been ascertained that the described invention achieves the intended objects and, in particular, the fact is underlined that the launching of the material from the bottom of the inlet chamber towards the inside of the grinding chamber and the possibility of regulating the launch direction make it possible to optimize the effectiveness of the action of the crushing elements.
In particular, by rotating the adjustable portion around the regulating axis, it is possible to vary the trajectory covered by the material to be ground according to its physical properties, such as specific weight, humidity and size, as well as to the wear of the parts involved in the launch phase.
The working stroke completed by the secondary rotor to convey the material to be ground into the grinding chamber is therefore minimal, thus making it possible to reduce energy costs and wear on the parts involved in the launch phase.
Furthermore, the possibility of extracting the adjustable portion makes it easy and practical to carry out both regulation and maintenance operations.

Claims

Impact mill (1) for grinding loose material, comprising:
- a first body (2) defining a grinding chamber (3) inside which is housed at least one main rotor (4) moveable in rotation around a first axis (X);

- a second body (10) defining an inlet chamber (11) of the material to be ground communicating with said grinding chamber (3) and inside which is housed at least one secondary rotor (12) moveable in rotation around a second axis (Y), said secondary rotor (12) being adapted to send the material to be ground inside said grinding chamber (3);

- said inlet chamber (11) and said grinding chamber (3) being delimited by at least two side walls (5, 13) arranged substantially transversely to said first and second axis (X, Y) respectively, and by at least one connecting wall (6, 14) interposed between the respective side walls (5, 13) to surround at least partly the relevant rotor (4, 12), said first and second axis (X, Y) being arranged substantially horizontal and parallel to each other;
wherein said inlet chamber (11) is arranged laterally to said grinding chamber (3) and they communicate to each other by means of a connecting opening (16) defined on the respective connecting walls (6, 14); characterized in that said connecting opening (16) is arranged at the lower portion of said inlet chamber, so that the material sent from said secondary rotor (12) is directed from the bottom of said inlet chamber towards said grinding chamber (3) and wherein the connecting wall (14) of said inlet chamber (11) has at least one adjustable portion (14a) moveable in rotation, during use, around an axis of adjustment (Z) to vary the inlet direction of the material to be ground inside said grinding chamber (3).
Mill (1) according to claim 1, wherein said axis of adjustment (Z) coincides with said second axis (Y).
Mill (1) according to claim 1 or 2, wherein said adjustable portion (14a) is defined at the lower portion of the connecting wall (14) of said inlet chamber (11).
Mill (1) according to one or more of the preceding claims, wherein said adjustable portion (14a) has at least one curvilinear section (18) and at least one rectilinear section (19) which are contiguous to each other.
Mill (1) according to claim 4, wherein said rectilinear section (19) is arranged downstream of said curvilinear section (18) with respect to the direction of rotation of said secondary rotor (12), said rectilinear section (19) delimiting said connecting opening (16).
Mill (1) according to one or more of the preceding claims, wherein said second body (10) comprises at least one base element (21) supporting said adjustable portion (14a) in rotation.
Mill (1) according to one or more of the preceding claims, wherein it comprises regulating means (22) for regulating the rotation of said adjustable portion (14a) around said axis of adjustment (Z).
Mill (1) according to claim 7, wherein said regulating means (22) comprise at least one curvilinear slot (23) defined on said base element (21) inside which at least one relevant pin (24) is housed sliding which is locked together with said at least one adjustable portion (14a).
Mill (1) according to claim 8, wherein said slot (23) extends substantially along a circumferential arc having its center at said axis of adjustment (Z).
Mill (1) according to one or more of the preceding claims, wherein said adjustable portion (14a) is moveable in translation with respect to the side walls (13) of said inlet chamber (11) between at least an operating configuration, in which it is substantially aligned with the remaining portion (14b) of the connecting wall (14) of said inlet chamber (11), and an extraction configuration in which it is misaligned from said remaining portion (14b) with respect to the operating configuration.
Mill (1) according to one or more of claims 6 to 10, wherein said base element (21) is associated in a sliding manner in translation with the side walls (13) of said inlet chamber (11), said adjustable portion (14a) being integral in translation with said base element (21).
Mill (1) according to claim 11, wherein said second body (10) comprises at least one openable wall (28) hinged to the side walls (13) of said inlet chamber (11) and moveable between at least one closed position and at least one open position, in which it is rotated with respect to the closed position and defines a holding surface (27) for the sliding of said base element (21).
Mill (1) according to one or more of the preceding claims, wherein said main rotor (4) and said secondary rotor (12) are counter-rotating to each other.
Mill (1) according to one or more of the preceding claims, wherein said inlet chamber (11) has an inlet opening (17) of the material to be ground arranged at one of said side walls (13).
Mill (1) according to claim 14, wherein said adjustable portion (14a) is arranged at the bottom of said inlet opening (17).