EP4010128B1

EP4010128B1 - Ring to select incoherent material and corresponding selector machine

Info

Publication number: EP4010128B1
Application number: EP20771928.7A
Authority: EP
Inventors: Michele Libralato
Original assignee: Pal SRL
Current assignee: Pal SRL
Priority date: 2019-08-09
Filing date: 2020-08-04
Publication date: 2023-07-26
Anticipated expiration: 2040-08-04
Also published as: EP4010128A1; IT201900014487A1; PT4010128T; WO2021028955A1; ES2961410T3

Description

FIELD OF THE INVENTION

The present invention concerns a ring to select incoherent material and the corresponding selector machine. In particular, the incoherent material to be selected is preferably of the wood type, for example wood shavings, wood chips, crushed wood, wood residues or similar or comparable material.
In particular, the invention is used in machines designed to select incoherent material in order to then be able to use fractions with differentiated granulometry and to remove polluting materials, for example, but not only, inert materials such as stones, glass, sand, etc.

BACKGROUND OF THE INVENTION

It is known that the reuse of wood material, for example in the form of wood chip, is becoming increasingly important since, where possible, it allows to avoid cutting down new trees.
In particular, recovered wood, from which chip can be obtained, can be wood coming from various sources and therefore often having a high quantity of polluting materials.
By way of example, recovered wood can come from the processing of the wood used to obtain panels or furniture; from the recovery of packaging, pallets, bins and crates; from beams, rafters or planks; from waste treatment and separate collection.
It is quite evident that in the recovered wood there may be pebbles, stones, sand, metals, etc., which are all extraneous components that have to be separated from the flakes of wood.
It is also known that wood chips are obtained from felled trees of various sizes that have in themselves, or are associated with, sand or small stones.
These extraneous or polluting components are normally discharged during the operations to select and calibrate the chips.
In particular, screening machines have been known in the state of the art for some time, designed to separate and select chips and particles on the basis of their granulometry from an incoherent or fibrous mass, whether dry or wet, generally but not exclusively of wood-based material.
Screening machines are also known which are configured to remove polluting materials, inert and not, from this incoherent mass in order to obtain better quality wood material for subsequent processing.
These machines typically provide screens with a mesh or disc, or roll-type screens with one or more levels, or tiers, of selection elements which define a bed onto which the material to be selected is fed.
These machines generally work in cascade according to the different selection levels using respectively meshes, or discharge gaps, with progressively increasing passage section in order to discharge particles having progressively increasing grain sizes or dimensions.
Roll machines of this type are described, for example, in patent EP1007227 , in the name of the present Applicant, in which a progressive series of rolls is provided, in cascade, with zig-zag discharge gaps of different amplitudes, in order to obtain the subdivision of the material to be selected into different sizes.
However, known roll-type machines currently have limitations.
These limitations require that, below certain sizes of the chip, both the wood material and also the polluting material are discarded.
However, it has been found that this limitation in the selection of the chip gradually entails a large quantity of discarded wood material, mixed with polluting material, which is not used even with an energy function.
In fact, known types of roll machines are not able to meet the need for a more thorough cleaning of the wood material, especially of fine polluted particles such as sand, and the need to produce less wood waste.
Furthermore, known roll-type machines are generally very bulky and have a large number of components to define a cascade selection of the incoherent material for different sizes thereof.
Another disadvantage of the roll-type screens described in document EP1007227 is the inefficiency in the dimensional selection of the wood chips linked to the length of the single surface defining each of the zig-zag discharge gaps. This inefficiency means that, especially in the start and stop steps of the flow of material to be selected, that is, when the machine is most unloaded, the finer fractions can have thin and long chips inside them, which entails a substantially non-homogeneous screening.
Other devices to select incoherent material which, however, can be improved from the point of view of the selection of the material and the elimination and recovery of possible polluting materials, are variously described, for example in documents WO-A-02/062493 , US-A-2082302 , which discloses a ring in accordance with the preamble of claim 1, FR-A-1139560 , WO-A-2019/137830 and DE-C-589557 .
Applicant therefore set himself the purpose of improving the selection activity of known roll-type machines for the selection of both recycled and fresh wood material.
More particularly, the purpose of the present invention is to improve the selection of chips both by improving the elimination of possible inert polluting materials and also by allowing the recovery of such inert polluting materials, for example with an energy function.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claim.
The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.
In accordance with what described above, the present invention concerns a ring to select incoherent material in the form of chip, in particular wood-based, and to eliminate inert materials contained in the incoherent material.
According to the invention, a ring comprises a circumferential cusp and two circumferential base surfaces connected to the cusp by means of circumferential lateral surfaces.
According to the invention, the base surfaces have a smaller diameter than that of the cusp.
According to the invention, the ring is configured to rotate around an axis of rotation and the lateral surfaces have a plurality of circumferential teeth each defined respectively by a conical annular surface followed by a cylindrical annular surface, wherein the cylindrical annular surface is directed parallel to such axis of rotation.
Such circumferential development substantially defines a serrated development that follows the development of the lateral surfaces.
Advantageously, these circumferential teeth promote the drawing of the material to be selected, in accordance with the invention thanks to a shape that has a cross-section with a trapezoid shape.
In particular, the ring has a cross-section, with respect to the axis of rotation itself, which is substantially triangular, reducing the diameter toward the axis of rotation.
In addition, the ring is normally, although not necessarily, axial symmetrical with respect to the axis of rotation.
According to one embodiment, the lateral surfaces have a symmetrical development with respect to a lying plane of the cusp. In this way, the ring is balanced during the rotation and can be easily used in series.
In particular, the lying plane of the cusp is normally, but not necessarily, perpendicular to the axis of rotation.
According to one embodiment, the lateral surfaces have an asymmetrical development with respect to the lying plane of the cusp. In this way, a single ring can perform different types of selections on the two lateral surfaces.
According to one variant, the ring can be asymmetrical both in terms of position of the lying plane of the cusp, and also in terms of number and size of the circumferential teeth.
In accordance with the present invention, a machine to select incoherent material in the form of chip, in particular wood-based, and to eliminate inert materials contained in the incoherent material comprises a plurality of rolls disposed adjacent and distanced laterally in a direction of feed of the material to be selected, in order to define a selection plane thereof.
According to the invention, the rolls are each provided with a drive shaft configured to rotate around an axis of rotation and a plurality of rings as above adjacent to each other along the drive shaft to form a plurality of circumferential cusps alternated with a plurality of circumferential grooves.
The circumferential grooves of the roll are defined by two circumferential base surfaces of two respective adjacent rings alternated and located substantially on the same selection plane.
According to the invention, the rolls are adjacent so that the cusps of one roll co-penetrate into the grooves of the adjacent roll, defining a discharge gap with a substantially zig-zag development.
Advantageously, since they have circumferential teeth, the adjacent rolls produce a serrated or jagged discharge gap with a zig-zag development allowing to obtain a selection according to shape, as well as size.
Furthermore, according to one embodiment, the machine has discharge gaps with increasing amplitude in the direction of feed, generating a progressive selection of the incoherent material in terms of size and shape.
In this way, it is possible to select both fractions of small-sized inert materials, such as for example stones, pulverized glass, sand, ceramic or other, which generally have a cubic or round shape, and also small-sized wood material with a generally elongated shape.
In doing so, moreover, a fraction of wood waste is obtained, separated from the inert materials, which takes on an energy function of great value.
According to one embodiment, the machine comprises two or more groups of adjacent rolls wherein the groups of rolls are substantially the same.
According to one variant, each group of rolls has rings that have lateral surfaces with circumferential teeth different, in number and size, from the group of rolls provided in succession in the direction of feed. Furthermore, there is provided a variation of the amplitude of the discharge gap between one roll and the subsequent one in the direction of feed of the material to be selected and according to the selection provided.
Furthermore, according to one embodiment, the discharge gap has a minimum amplitude comprised between 0.5 mm and 1.5 mm and a maximum amplitude comprised between 4 mm and 16 mm, advantageously between 8 mm and 12 mm, preferably between 4 mm and 6 mm.
According to one embodiment, the minimum amplitude is, advantageously but not necessarily, correlated to the number of circumferential teeth present on each lateral surface.
In particular, the minimum amplitude is correlated to a number of circumferential teeth greater than those connected to the maximum amplitude.
Advantageously, the invention allows to obtain a continuous selection plane passing from one degree of selection to the next.
In particular, in order to pass from one type of selection to another, there can be provided only a variation of the distance between the rolls.
According to another embodiment, in addition to varying the distance between the rolls, it is possible to act on the variation of the number of circumferential teeth in order to modify the amplitude of the discharge gap.
These possible methods for varying the amplitude of the discharge gap allow to obtain a high selection capacity, reducing the number of selector machines required compared to the state of the art and improving the degree of cleaning and selection with respect thereto.
The invention therefore allows to obtain a more compact and efficient machine and a more thorough selection of the material, at the same time also recovering fine fractions which cannot be selected with current technologies.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:

fig. 1 is a lateral view of a ring to select incoherent wood-based material and to eliminate the inert materials in accordance with the present invention;
fig. 2 is a view along section line II - II of the ring of fig. 1;
fig. 3 is a front view of the ring of fig. 1;
fig. 4 is a top view of a machine to select incoherent wood-based material and to eliminate the inert materials in accordance with the present invention;
fig. 5 is a view of an enlarged detail of fig. 4;
fig. 6 is a view of another enlarged detail of fig. 4;
fig. 7 is a view of another enlarged detail of fig. 4.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can conveniently be incorporated into other embodiments without further clarifications.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

We will now refer in detail to the various embodiments of the invention, of which one or more examples are shown in the attached drawings. Each example is supplied by way of illustration of the invention and shall not be understood as a limitation thereof. For example, the characteristics shown or described insomuch as they are part of one embodiment can be adopted on, or in association with, other embodiments to produce another embodiment. It is understood that the present invention shall include all such modifications and variants.
Before describing these embodiments, we must also clarify that the present description is not limited in its application to details of the construction and disposition of the components as described in the following description using the attached drawings. The present description can provide other embodiments and can be obtained or executed in various other ways. We must also clarify that the phraseology and terminology used here is for the purposes of description only, and cannot be considered as limitative.
A ring 10 to select incoherent material in the form of chips, in particular, but not exclusively, wood-based, and to eliminate the inert materials contained in the incoherent material is shown by way of example in figs. 1-3.
With the term "incoherent material" here and hereafter in the description we generally mean a loose material with homogeneous or non-homogeneous sizes, preferably, but not necessarily, wood-based and possibly also containing polluting material, for example, but not only, inert material such as sand, stones, glass and suchlike.
With the term "chips", here and hereafter in the description we generally mean any type of recycled or fresh wood-type incoherent material suitable to be selected by means of roller screens, that is, for example wood flakes, wood fragments, forest residues, wood chips, sawdust or sawmill scraps, or suchlike.
With reference to figures 1-3, the ring 10 comprises a circumferential cusp 14 and two circumferential base surfaces 15 connected to the cusp 14 by means of circumferential lateral surfaces 17.
The base surfaces 15 have a smaller diameter than that of the cusp 14.
The base surfaces 15 can be cylindrical or sub-cylindrical.
In particular, by way of a non-limiting example, the diameter of the base surfaces 15 can be comprised between 50 mm and 80 mm, and the diameter of the cusp 14 can be comprised between 100 mm and 130 mm.
The ring 10 is configured to rotate around an axis of rotation X.
For example, but not only, the axis of rotation X can be perpendicular to a lying plane of the circumferential cusp 14.
According to the invention, the lateral surfaces 17 have a plurality of circumferential teeth 20 defined respectively by a conical annular surface 19 alternating with a cylindrical annular surface 18. This cylindrical annular surface 18 is directed parallel to the axis of rotation X of the ring 10.
Consequently, the lateral surfaces 17 have a substantially serrated development.
A ring 10 can be keyed onto a drive shaft 12 by means of connection means 25, for example of the key type.
According to a possible embodiment, the ring 10 can be made in a single body with the drive shaft 12.
In particular, the ring 10 has a substantially triangular or V-shaped cross-section with the vertex, defining the cusp 14, facing toward the outside with respect to the drive shaft 12 and the two circumferential base surfaces 15 defining the base points of the triangular section.
According to one embodiment, the ring 10 can have a section with an isosceles triangle shape with an angle at the vertex, defining the cusp 14, comprised between 45° and 75°, preferably between 60° and 70°.
According to one embodiment, shown by way of example in fig. 2, the circumferential teeth 20 have a cross-section, with respect to the axis of rotation X, with a substantially trapezoid shape.
In particular, the circumferential teeth 20 have a cross-section with a substantially rectangular trapezoid shape.
According to one embodiment, the cross-section with a trapezoid shape is defined, on the lateral surface 17, by a straight segment 21, substantially parallel to the axis of rotation X, and by an oblique segment 22 connected to the straight segment 21 and inclined with respect to the latter in the direction of the cusp 14.
According to one embodiment, the ring 10 is axial symmetrical around the axis of rotation.
In accordance with the invention, the straight segments 21 and the oblique segments 22, in an axial symmetrical development of the ring 10 around the axis X, respectively define the cylindrical annular surfaces 18 and the conical annular surfaces 19.
Furthermore, the lateral surface 17, in an axial symmetrical development of the ring 10 around the axis of rotation X, defines a cone.
Consequently, the sides of the triangular cross-section of the ring 10, defining the lateral surfaces 17 in axial symmetry, have a saw tooth-type development, in particular with trapezoidal teeth, given by the alternation of straight segments 21 and oblique segments 22.
According to one embodiment, the lateral surfaces 17 of one ring 10 have the same number of circumferential teeth 20.
According to one embodiment, the lateral surfaces 17 of one ring 10 have a symmetrical disposition of the circumferential teeth 20 with respect to the lying plane of the cusp 14.
According to one embodiment, the lateral surfaces 17 of one ring 10 have circumferential teeth 20 that have the same sizes.
The lateral surfaces 17 of one ring 10 can have circumferential teeth 20 with increasing or decreasing sizes from the base surfaces 15 to the cusp 14.
According to one variant, the straight segments 21 can have small inclinations, positive or negative, comprised between 0° and 15° with respect to the axis of rotation X.
According to one embodiment, the straight segments 21 have a width, in the direction parallel to the axis of rotation X, which varies according to the number of circumferential teeth 20 provided for each lateral surface 17.
For example, but not only, the width of the straight segments 21 can be comprised between about 0.6 mm and about 4 mm, preferably between 1 mm and 2 mm, advantageously around 1 mm.
The straight segments 21 can have a variable width, increasing or decreasing, along the lateral surface 17 of the ring 10.
According to one embodiment, the cusp 14 also has a variable width according to the type of selection to be obtained.
For example, the width of the cusp 14 can be comprised between 0.8 and 1.2 mm, advantageously around 1 mm.
The width of the oblique segment 22 can be variable according to the number of circumferential teeth 20.
For example, but not only, the width of the oblique segment 22, parallel to the axis of rotation X, can be comprised between 1 and 5 mm, preferably between 2 mm and 3 mm, advantageously around 2 mm.
The oblique segments 22 can have a variable width, increasing or decreasing, along the lateral surface 17 of the ring 10.
According to one embodiment, the oblique segment 22 is inclined by an angle α comprised between 40° and 75°, advantageously comprised between 50° and 70°, with respect to the straight segment 21 in the direction of the cusp 14. In this way, a sequence of oblique 22 and straight segments 21 can be easily obtained on the lateral surface 17, following the development of the latter starting from the base surface 15 until reaching the cusp 14.
According to one embodiment, each ring 10 can have a number of circumferential teeth 20 comprised between two and ten, preferably between four and six. This choice depends on the type of selection to be carried out.
In counting the number of circumferential teeth 20, the last circumferential tooth 20 ending in the cusp 14 is also counted. Consequently, the number of circumferential teeth 20 is equal to the number of the repetitions of conical annular surfaces 19 along a lateral surface 17 of one ring 10.
Each ring 10 can be made in a single piece.
According to a possible embodiment, shown by way of example in fig. 4, each ring 10 can be made of at least two distinct annular elements 24.
By way of a non-limiting example, the cross-section, with respect to the axis of rotation X, of such annular elements 24 can be in the shape of a right-angled triangle so as to form a substantially isosceles triangle when installed adjacent to form a ring 10.
According to one embodiment, shown in fig. 4, a roll 11 is provided with a respective drive shaft 12 rotating around the axis of rotation X.
According to one embodiment, shown in fig. 4, a roll 11 comprises a plurality of rings 10 disposed adjacent and in sequence along a drive shaft 12 in order to define a selection profile of the roll 11 given by the alternation of cusps 14 and grooves 16.
In particular, the base surface 15 of one ring 10 adjacent to the base surface 15 of the adjacent ring 10 defines the groove 16 of the roll 11.
Consequently, the plurality of rings 10 defines a selection profile of the roll 11 with respectively positive and negative V shapes which follow one another.
According to a possible embodiment, the roll 11 can be made in a single body providing a plurality of rings 10 integrally constrained to each other.
According to one embodiment in accordance with the present invention and shown in fig. 4, a machine 13 to select incoherent material in the form of chips and to eliminate inert materials comprises a plurality of rolls 11 disposed adjacent so that the cusps 14 of one roll 11 co-penetrate into the grooves 16 of the adjacent roll 11, defining a discharge gap 26 with a substantially zig-zag development.
In particular, by discharge gap 26 we mean the passage gap obtained from the distance between the lateral surfaces 17 of two adjacent rolls 11. Even more particularly, by discharge gap 26 we mean the passage gap obtained from the distance between the oblique segments 22 of the lateral surfaces 17 of two adjacent rolls 11.
According to one embodiment, the machine 13 comprises a plurality of rolls 11 rotating in the same direction and disposed adjacent to each other, in order to define a progressive succession of discharge gaps 26 of desired and adjustable value.
In particular, the discharge gap 26 has a serrated or jagged pattern given by the contrapositioning of respective conical annular surfaces 19 and cylindrical annular surfaces 18 of adjacent rolls 11.
The adjacent rolls 11, rotating in the same direction, define a selection plane on which the material to be selected is fed. The material to be selected advances on said rolls 11 in a direction of feed F.
According to one embodiment, the machine 13 comprises a plurality of adjacent drive shafts 12, or at least two adjacent drive shafts 12.
Each drive shaft 12 is configured to rotate around its own axis of rotation X coaxial to the drive shaft 12 itself.
In particular, each drive shaft 12 can be configured to rotate at different rotation speeds in a manner correlated to the subsequent drive shafts 12.
The rolls 11 of the machine 13 can be disposed adjacent horizontally so that the respective axes of rotation X are parallel and aligned with each other.
The rolls 11 of the machine 13 can be disposed adjacent horizontally so that the respective axes of rotation X are parallel and offset with respect to each other.
In particular, the discharge gap 26 can be defined by a series of discharge areas A1 with a substantially parallelogram shape provided consecutive, adjacent and offset with respect to each other.
The discharge gap 26, since it has a serrated development, can provide, in the direction of feed F of the material to be selected, at least two different amplitudes, a first amplitude G1 and a second amplitude G2. Each of these amplitudes G1 and G2 identifies a respective discharge area, indicated by way of example and respectively with A1 and A2. Such discharge areas A1 and A2 are repeated cyclically along the discharge gap 26. The discharge areas A1 and A2 therefore have different sizes, since they are defined by different amplitudes G1 and G2.
In particular, these discharge areas A1, A2 also allow a selection according to shape as well as size.
According to a possible embodiment, a first discharge area A1 can be in the shape of an elongated parallelogram defined by the contrapositioning of two oblique segments 22 facing each other and belonging respectively to two opposite rolls 11.
In particular, the distance between the two oblique segments 22, facing each other and belonging respectively to two opposite rolls 11, identifies the first amplitude G1 of the discharge gap 26.
A second selection area A2 can have a square, rectangular or parallelogram shape of smaller sizes than the first discharge area A1. The second area A2 can be defined by the contrapositioning of two oblique segments 22 facing each other and offset consecutively with respect to each other and belonging respectively to two opposite rolls 11.
In particular, the distance between the two oblique segments 22, facing each other and offset consecutively with respect to each other and belonging respectively to two opposite rolls 11, identifies the second amplitude G2 of the discharge gap 26.
The ratio between the second amplitude G2 and the first amplitude G1 can be comprised between 1.5 and 2, preferably between 1.6 and 1.8.
Advantageously, the second selection area A2 is favorable to the passage of small-sized inert polluting material with a generally round or square shape, while the parallelogram-shaped selection area A1 is more favorable to the passage of wood material with a generally elongated shape.
According to one embodiment, one or more of the conical annular surfaces 19 can be knurled so as to better direct and accompany the incoherent material to be selected toward the discharge gap 26.
In particular, the cusp 14 can have a plurality of hollows 23 disposed circumferentially to define an indentation that facilitates the drawing and removal of the material in the zone of cooperation between the grooves 16 of one roll 11 and the cusps 14 of the adjacent roll 11.
According to one embodiment, such rolls 11 can all be identical to each other or progressively differentiated continuously or in groups in the direction of feed F according to the selection level to be reached.
In particular, the machine 13 comprises two or more groups of adjacent rolls 11 wherein one group of rolls 11 comprises at least two rolls 11 adjacent and identical to each other.
The machine 13 can comprise groups of rolls 11 all identical to each other.
The machine 13 can provide groups of rolls 11 with different rotation speeds to each other.
The machine 13 can provide groups of rolls 11 each of which have rings 10 that have lateral surfaces 17 with a number of circumferential teeth 20 different from the subsequent group of adjacent rolls. In this way, it is possible to vary the amplitude G1, G2 of the discharge gap 26, as well as by possibly acting on the distance between one roll 11 and the next, also by varying the number of circumferential teeth 20 provided in the direction of feed F of the material to be selected.
In particular, the amplitude G1, G2 of the discharge gap 26 is gradually increased in the sense of the direction of feed F of the material to be selected, so as to select particles of material with gradually increasing sizes.
In the direction of feed F of the material to be selected, there can be two or more groups of rolls 11 that are, on each occasion, positioned so as to create a discharge gap 26 which is gradually increasing starting from a discharge gap with minimum amplitude G1 comprised between 0.5 and 1.5 mm up to a discharge gap with maximum amplitude G1 comprised between 4 mm and 12 mm, or as an extreme case also 16 mm.
In particular, for example but not only, the minimum amplitude G2 can be comprised between 0.75 mm and 3 mm and the maximum amplitude G2 can be comprised between about 6 mm and about 24 mm.
By way of example, in fig. 5, rings 10 are shown with six circumferential teeth 20 and, in fig. 7, rings 10 are shown with four circumferential teeth 20.
For example, the rolls 11 with lateral surfaces 17 with six circumferential teeth 20 (fig. 5) can, advantageously, select materials with sizes comprised between 0.5 mm and 1.5 mm allowing to eliminate inert materials such as pebbles and sand which, with the current technology, are difficult to identify and, at the same time, reducing the losses of wood material in an attempt to eliminate these inert materials.
The invention therefore allows to obtain a high degree of cleanliness of the incoherent wood material eliminating fractions of inert materials even below the order of a millimeter.
Furthermore, such wood material mixed with inert materials discarded in said selection can undergo another cleaning or screening, for example by means of flotation, in order to recover as much wood material as possible and/or it can be re-used with an energy function, that is, for example, it can be burned in special burners. This solution allows to make the most of the incoherent material to be selected, also re-using the discarded material so as to optimize the screening of the chips and reduce waste of energy and material.
For example, but not only, the rolls 11 with rings 10 that have lateral surfaces 17 with four circumferential teeth 20 (fig. 7) can select materials with sizes comprised between 1.6 mm and 3 mm, preferably between 1.6 mm and 2.8 mm.
By way of a non-limiting example, with reference to fig. 4, such rolls 11 with lateral surfaces 17 with four circumferential teeth 20 located in sequence, in the direction of feed F, with rolls 11 with rings 10 with lateral surfaces 17 with six circumferential teeth 20, allow to obtain a more thorough selection of the wood material.
According to a possible embodiment, the discharge gap 26 between adjacent rolls 11 can be adjusted by further acting on the distance between the rolls 11 themselves, bringing them closer or further away from each other.
Furthermore, the discharge gap 26 can be adjusted by acting on the distance between the rolls 11 in cooperation with the choice of the number and size of the circumferential teeth 20 to be provided on each lateral surface 17.
Advantageously, the zig-zag profile of the rolls 11 with a serrated or jagged surface development also allows cooperation between rolls 11 with rings 10 that have different numbers of circumferential teeth 20, allowing to obtain a continuous and gradual selection of the incoherent material in the form of chips, without adding additional components, limiting the bulk of the machine 13 and reducing the respective energy consumption.
Advantageously, compared to the state of the art the invention also allows to use fewer rolls 11 to process the same amount of incoherent material, guaranteeing high efficiency of the machine 13 and a consequent lower operating cost thereof.
By way of a non-limiting example, fig. 6 shows the cooperation between one roll 11 with rings 10 having lateral surfaces 17 with six circumferential teeth 20 and one roll 11 with rings 10 having lateral surfaces 17 with four circumferential teeth 20 in the passage, in the direction of feed F, from the selection of material with size 0.5 mm - 1.5 mm to the selection of material with size 1.6 - 3 mm.
In particular, with the rolls 11 as above it is possible to perform a plurality of different types of selections of chip continuously in the direction of feed F of the material to be selected, guaranteeing a high versatility of the machine 13.
In fact, in the machine 13 a further selection could be provided for materials comprised between 3 mm and 16-18 mm, for example by acting on the distance between the rolls 11 and/or providing rings 10 acting on the number of circumferential teeth 20 for each lateral surface 17.
Furthermore, one or more intermediate selections could be provided in the machine 13 to improve the selection of incoherent material by acting on the number of circumferential teeth 20 and on their disposition.
The choice of the number of circumferential teeth 20 on a lateral surface 17 of the rings 10 of each roll 11, and the choice of the number of different types of consecutive selections to be obtained depends on the final use of the wood. For example, in the case of MDF panels it is necessary to obtain chips with a high degree of cleanliness from inert materials, or polluting materials in general, in order to obtain a superior quality panel.
In particular, the machine 13, in accordance with some embodiments described here, can be used both to select virgin or fresh incoherent wood material and also to select recycled incoherent wood material coming from production waste and/or post-production recovered material.
Furthermore, the machine 13, in accordance with some embodiments described here, can be used downstream and/or upstream of further screening steps.
The machine 13, in accordance with some embodiments described here, can be used in combination with known screening techniques and technologies, for example with blowing devices (not shown) in order to improve the selection.
The machine 13, in accordance with some embodiments described here, can be preferentially used to select wood in its wet phase, that is, with a high percentage of moisture, for example even up to 100% moisture. However, it is not excluded that this machine 10 can also be used in the dry phase, that is, with wood with a low percentage of moisture even lower than 10%.
It is clear that modifications and/or additions of parts or steps may be made to the ring 10 to select incoherent material and to the corresponding selector machine 13 as described heretofore, without departing from the scope of the present invention as defined by the claims.
In the following claims, the sole purpose of the references in brackets is to facilitate reading: they must not be considered as restrictive factors with regard to the field of protection claimed in the specific claims.

Claims

Ring suitable to select incoherent material in the form of wood-based chip and to eliminate inert materials contained in said incoherent material, said ring (10) comprising a circumferential cusp (14) and two circumferential base surfaces (15) connected to said cusp (14) by means of circumferential lateral surfaces (17), said base surfaces (15) having a smaller diameter than that of said cusp (14), wherein
said ring (10) is configured to rotate around an axis of rotation (X) and said lateral surfaces (17) have a plurality of circumferential teeth (20) each defined respectively by a conical annular surface (19), followed by a cylindrical annular surface (18), wherein said cylindrical annular surface (18) is directed parallel to said axis of rotation (X) of the ring,

characterized in that the circumferential teeth (20) have, with respect to said axis of rotation (X), a cross-section with a trapezoid shape defined, on the lateral surface (17), by a straight segment (21), parallel to the axis of rotation (X), and by an oblique segment (22) connected to said straight segment (21) and inclined with respect thereto in the direction of the cusp (14) and wherein said straight segment (21) and said oblique segment (22), in an axial symmetrical development of the ring (10) around said axis of rotation (X), respectively define said cylindrical annular surface (18) and said conical annular surface (19).
Ring as in claim 1, characterized in that said lateral surfaces (17) have a symmetrical development with respect to a lying plane of said cusp (14).
Ring as in claim 1, characterized in that said lateral surfaces (17) have an asymmetrical development with respect to a lying plane of said cusp (14).
Ring as any claim hereinbefore, characterized in that said oblique segment (22) is inclined at an angle (α) comprised between 40° and 75° with respect to said straight segment (21) in the direction of the cusp (14).
Ring as in any claim hereinbefore, characterized in that a lateral surface (17) has a number of circumferential teeth (20) comprised between four and six.
Ring as in any claim hereinbefore, characterized in that one or more of the conical annular surfaces (19) are knurled.
Ring as in claim 6, characterized in that said cusp (14) has a plurality of hollows (23) disposed circumferentially to define an indentation.
Machine configured to select incoherent material in the form of wood-based chip and suitable to eliminate inert materials contained in said incoherent material, said machine comprising a plurality of rolls (11) disposed adjacent and distanced laterally in a direction of feed (F) of the material to be selected in order to define a selection plane thereof, said rolls (11) each being provided with a drive shaft (12) configured to rotate around an axis of rotation (X) and a plurality of rings (10) as in any claim hereinbefore, adjacent to each other along said drive shaft (12) to form a plurality of circumferential cusps (14) alternated with a plurality of circumferential grooves (16), said grooves (16) each being defined by two base surfaces (15) of two adjacent rings (10), said rolls (11) being adjacent so that the cusps (14) of one roll (11) co-penetrate into the grooves (16) of the adjacent roll (11) defining a discharge gap (26) with a zig-zag development.
Machine as in claim 8, characterized in that it comprises two or more groups of adjacent rolls (11) wherein each group of rolls (11) has rings (10) having lateral surfaces (17) with circumferential teeth (20) different, in number and size, from the group of rolls (11) provided in succession in the direction of feed (F).
Machine as in claim 8 or 9, characterized in that it has discharge gaps (26) with an amplitude (G1, G2) increasing in the direction of feed (F).
Machine as in claim 10, characterized in that each of said discharge gaps (26) has a serrated development and a discharge area (A1, A2) is identified for each amplitude (G1, G2) of the discharge gap (26).
Machine as in claim 11, characterized in that said discharge areas (A1, A2) are repeated in cyclical manner along the discharge gap (26).
Machine as in any claim from 8 to 12, characterized in that said discharge gap (26) has an amplitude (G1, G2) correlated to the number of circumferential teeth (20) present on each lateral surface (17).
Machine as in claim 10, characterized in that said discharge gap (26) has a first minimum amplitude (G1) comprised between 0.5 mm and 1.5 mm and a first maximum amplitude (G1) comprised between 4 mm and 12 mm, and a second minimum amplitude (G2) comprised between 0.75 mm and 3 mm and a second maximum amplitude (G2) comprised between 6 mm and 24 mm, said minimum amplitudes being correlated to a number of circumferential teeth (20) greater than those connected to said maximum amplitudes.