TRANSPORTATION SCREWS

DESCRIPTION

Technical field of the invention

The present invention regards a continuous compound mixing or conveyor plant, in particular for polymeric compounds, and a method for cleaning extrusion/transportation screws of a continuous compound mixer or of a conveyor. In particular, the present invention regards the field of testing and producing elastomeric and thermoplastic compounds used for manufacturing tyres for vehicle wheels.

State of the art

The continuous compound mixers in question are compound mixers provided with extrusion screws housed in a compound mixing chamber which extends between at least one inlet and one outlet.

Such devices are capable of processing the polymeric compounds with continuity over time, producing a continuous flow of outflowing compound, contrary to batch compound mixers which require the loading, processing and unloading of each batch.

One-screw and multi-screw, for example two-screw, continuous compound mixers are known.

Known are continuous compound mixers comprising a fixed central spindle and a plurality of lateral screws surrounding the central spindle, extending parallel to the central spindle and each rotating around an axis thereof. An example of such compound devices is illustrated in the document WO 2010/004595.

Also known are planetary continuous compound mixers, referred to in the technical jargon as‘planetary roller extruders’, wherein the lateral or planetary screws are meshed with the central spindle so that a rotation of the central spindle (by a motor of the continuous compound mixer) triggers, for each planetary spindle, a (counter)-rotating motion around an axis thereof and a translation motion along a circular trajectory coaxial to the central spindle. Examples of planetary compound mixing devices are illustrated in documents US 4,192,617 and US 8,957,119.

An extrusion screw has axial segments with different characteristics and tasks (essentially: advancing the compound, mixing the compound or both). The axial segments have different shapes with reliefs and recesses in which the compound tends to remain stuck/trapped.

The expression‘conveyor’ is used to indicate a device which continuously carries out the transportation of the elastomeric compound across the length thereof and confers to the outflowing compound a suitable shape for the subsequent handling or storage. Examples of conveyors are the batch-off devices for unloading from the batch compound mixers or extruders of semi-finished products precursor of tyre components (for example tread strips, side walls, liners etc.). The conveyors typically comprise elements that mainly facilitate the axial movement of the material, such as helical conveyor screws.

Summary

In the context of producing and testing polymeric compounds, in particular elastomeric and thermoplastic compounds for tyres, the Applicant observed that the continuous compound mixers for producing compounds and the conveyors must be disassembled and cleaned so as to subsequently test, produce and convey different compounds that must not be contaminated by the previously tested/produced/conveyed compounds.

The Applicant observed that the materials that are processed in continuous compound mixers, in particular elastomeric materials, are sticky and tend to adhere against and deposit on the internal members of the device.

In particular, the Applicant observed that, during testing, le extrusion/transportation screws must often be removed from the respective device and cleaned, for example to check the wear thereof, so as to be able to reconfigure them for a new subsequent test or simply so as to be able to use a different compound in the subsequent test without contamination between the materials.

The Applicant also observed that the extraction and maintenance of the extrusion/transportation screws is also required during the industrial production of such compounds aimed at the subsequent manufacturing of the tyres. The Applicant observed that the operations for cleaning the extrusion/transportation screws are currently carried out manually by one or more operators and require several hours of manual work.

Thus, the Applicant felt the need for facilitating and accelerating the operations for cleaning the extrusion/transportation screws of the continuous compound mixers and of the conveyors used in particular for testing and producing elastomeric compounds for vehicle wheels.

The Applicant also felt the need for carrying out such cleaning operations in a more efficient and effective manner, so as to guarantee better cleaning.

The Applicant observed that the aforementioned objectives can be obtained by means of a method and an apparatus for cleaning extrusion/transportation screws of a continuous compound mixer or conveyor for polymeric compounds, wherein the screw is supported while the cleaning is carried out by means of at least one motor-driven brush.

According to a first aspect, the present invention regards a method for cleaning extrusion/transportation screws of a continuous compound mixer or of a conveyor, said continuous compound mixer or conveyor comprising an outer body housing at least one extrusion/transportation screw, said method comprising:

positioning an extrusion screw on at least one support guide of an apparatus for cleaning extrusion/transportation screws, wherein the apparatus comprises a framework delimiting a cleaning area, at least one brush connected to the framework and having an operative portion positioned or positionable in the cleaning area, at least one motor, preferably mounted on the framework, connected to the brush;

bringing an axial portion of the extrusion/transportation screw to the cleaning area of said apparatus;

engaging an operative portion of said at least one brush of the apparatus with the axial portion of the extrusion/transportation screw and moving the operative portion of the brush with respect to the axial portion by means of said at least one motor of the apparatus for cleaning said axial portion;

displacing - at least axially - the extrusion/transportation screw with respect to the apparatus to change the axial portion of said extrusion/transportation screw arranged in the cleaning area. According to a second aspect, the present invention regards a continuous compound mixing or conveyor plant comprising a continuous compound mixer or a conveyor and an apparatus for cleaning extrusion/transportation screws of the continuous compound mixer or of the conveyor, wherein the apparatus comprises: a framework delimiting a cleaning area;

at least one support guide mounted on the framework and configured to support an extrusion/transportation screw and maintain an axial portion of the extrusion/transportation screw in the cleaning area;

at least one brush connected to the framework and having an operative portion positioned or positionable in the cleaning area;

at least one motor, preferably mounted on the framework, connected to the brush to move at least the operative portion in the cleaning area and relatively to said axial portion of the extrusion/transportation screw.

Preferably, the continuous compound mixer or conveyor for polymeric compounds comprises an outer body that is substantially cylindrical and mainly extending along a main axis; wherein the substantially cylindrical outer body delimits - therein - a compound mixing/transportation chamber mainly extending along said main axis and housing at least one extrusion/transportation screw.

The expression brush connected to the framework is used to indicate that the brush is directly or indirectly, for example by means of one or more intermediate elements carried by the framework, supported by said framework.

Preferably, the continuous compound mixer for polymeric compounds is a one- screw or multi-screw extruder, for example two-screw.

Preferably, the continuous compound mixer for polymeric compounds comprises a fixed central spindle and a plurality of lateral screws surrounding the central spindle, extending parallel to the central spindle and each rotating around an axis thereof.

Preferably, the continuous compound mixer for polymeric compounds is of the planetary roller type and it comprises a central spindle rotating around a main axis thereof, a plurality of lateral or planetary screw meshed with the central spindle, so that a rotation of the central spindle triggers, for each planetary screw, a (counter- rotating motion around an axis thereof and a translation motion along a circular trajectory coaxial to the central spindle. The Applicant observed that the present invention allows to clean the extrusion/transportation screw/s of compound residues in a precise, quick, simple and safe manner.

In particular, the Applicant observed that the present invention allows to carry out the cleaning of an extrusion/transportation screw within very quick times if compared to manual cleaning.

The Applicant also observed that the present invention allows to remove the residues effectively.

The Applicant also observed that the present invention allows an operator to carry out the cleaning of the extrusion/transportation screw effortlessly and under entirely safe conditions.

The present invention, in at least one of the aforementioned aspects may have one or more of the preferred characteristics described hereinafter.

Preferably, the method for cleaning extrusion/transportation screws according to the invention is implemented by means of an apparatus for cleaning extrusion/transportation screws according to the invention.

Preferably, two support guides are positioned on opposite sides of the cleaning area, one per each side.

Preferably, positioning the extrusion/transportation screw comprises: placing the extrusion/transportation screw on two support guides arranged on opposite sides of the cleaning area.

In this manner, the extrusion/transportation screw is stably supported while the axial portion interposed between the guides is cleaned.

Preferably, said at least one support guide has the shape of a sleeve.

Preferably, two sleeve-shaped support guides are positioned on opposite sides of the cleaning area and they are coaxial.

Preferably, an internal passage delimited by the sleeve or by each of the sleeves is configured to allow the extrusion/transportation screw to pass through.

Preferably, positioning the extrusion/transportation screw comprises: fitting the extrusion/transportation screw through at least one support guide, having the shape of a sleeve, or through both of the support guides, each having the shape of a sleeve.

The sleeve-shape of the support guide or guides allows the operator to insert the extrusion/transportation screw into the apparatus precisely and easily. Preferably, said at least one support guide has a support surface made of plastic material.

Preferably, positioning the extrusion screw comprises: sliding the extrusion/transportation screw on a plastic material support surface of said at least one support guide.

Preferably, the plastic material of the support surface is polytetrafluoroethylene. Preferably, said at least one support guide comprises an insert, wherein the support surface made of plastic material is part of said insert.

Preferably, the insert is a tubular body inside the sleeve and it at least partly delimits the internal passage of the sleeve.

The support surface made of plastic material allows an easy sliding of the screw without the risk of ruining it.

Preferably, the support guide can be interchanged with at least another different support guide.

Preferably, different support guides have different dimensions and/or different materials.

Preferably, different support guides have internal diameters of the respective internal passage that are different.

The replacement of the support guides allows to handle extrusion/transportation screws with different characteristics, for example with different diameters.

Preferably, the brush is circular-shaped.

Preferably, the brush is oval-shaped, more preferably elliptical-shaped.

Preferably, the brush has a central rotation axis.

Preferably, the central rotation axis is substantially parallel to an axis of the extrusion/transportation screw.

Preferably, the central rotation axis is substantially perpendicular to an axis of the extrusion/transportation screw.

Preferably, the central rotation axis is oriented obliquely with respect to an axis of the extrusion/transportation screw by an angle comprised between 10° and 80°. The expression axis of the extrusion/transportation screw is used to indicate the longitudinal axis around which the extrusion/transportation screw rotates during the operation thereof in the continuous extruder or in the compound mixer.

The expression central rotation axis substantially parallel or substantially perpendicular with respect to the axis of the screw is herein used to indicate that the two axes are respectively parallel or perpendicular to each other, less than an angle smaller than 10°.

Preferably, the central rotation axis can be oriented with respect to said at least one support guide and/or with respect to the axis of the extrusion/transportation screw when the extrusion/transportation screw is supported by said at least one support guide.

Preferably, changing said angles during cleaning is envisaged.

Preferably, the operative portion is a radially peripheral portion of the brush.

Preferably, engaging and moving the operative portion comprises: placing a radially peripheral portion of the brush against the axial portion of the extrusion/transportation screw and rotating the brush around a central rotation axis thereof.

Preferably, said at least one brush comprises a plurality of brushes, preferably two brushes, having operative portions mutually approached at the cleaning area.

Preferably, the two brushes are counter-rotating and have the radially peripheral portion thereof mutually approached.

Preferably, said at least one brush comprises a plurality of circular brushes, preferably two brushes, and wherein engaging and moving the operative portion comprises: placing radially peripheral portions of the brushes against the axial portion of the extrusion/transportation screw and rotating the brushes around the central axes thereof, preferably in opposite directions.

Preferably, said at least one motor comprises a motor coupled to each brush.

Preferably, said at least one motor comprises a single motor operatively coupled to both brushes, preferably by means of a transmission.

Preferably, at least one reduction gearbox is interposed between said at least one motor and the brush/brushes.

Preferably, the cleaning area is positioned beneath said at least one brush.

Preferably, the cleaning area is delimited between the plurality of mutually approached operative portions of the brushes.

Preferably, the brush comprises a plurality of bristles, preferably metallic, preferably made of brass or steel.

Preferably, brushes with different bristles, for example made of different materials and/or having different degrees of hardness are envisaged.

Preferably, the brushes are interchangeable. Preferably, the bristles of the brush extend from the radially peripheral portion of said brush.

Preferably, the bristles of the brush extend radially with respect to a central rotation axis of the brush.

Preferably, the bristles of the brush extend parallel to a central rotation axis of the brush.

Preferably, at least one robotic arm carries said at least one brush.

Preferably, the robotic arm is of the anthropomorphic type, preferably with six axes.

Preferably, an adjustment mechanism is operatively coupled to said at least one brush and/or to said at least one support guide and it is configured to vary a distance between said at least one brush and said at least one support guide.

Preferably, varying a distance between the operative portion of said at least one brush and the axial portion for adjusting a pressure exerted by the brush on the axial portion is envisaged. This allows managing the cleaning intensity.

Preferably, the adjustment mechanism allows to adapt the distance to the dimensions of the extrusion/transportation screw.

Preferably, the adjustment mechanism is operatively interposed between the framework and said at least one brush to move said at least one brush with respect to the framework.

Preferably, the robotic arm comprises the adjustment mechanism.

Preferably, the robotic arm comprises said motor.

Preferably, the apparatus comprises an electronic control unit operatively connected to the adjustment mechanism and configured to adjust a pressure exerted by the brush on the extrusion/transportation screw.

Preferably, the electronic control unit is configured to control the adjustment mechanism or the robotic arm so that the brush exerts a determined pressure on the extrusion/transportation screw.

Preferably, the electronic control unit is configured to control the adjustment mechanism or the robotic arm so that the brush copies a profile of the extrusion/transportation screw.

Preferably, the electronic control unit receives - as input - the type of the extrusion/transportation screw and controls the adjustment mechanism or the robotic arm as a function of said type. Preferably, said at least one brush is moveable vertically and/or horizontally and/or obliquely.

Preferably, the brushes are moveable mutually approaching and moving apart. Preferably, the apparatus comprises at least one brush unit comprising said at least one brush and said at least one motor.

Preferably, the apparatus comprises a plurality of brush units operating on different axial areas of the extrusion/transportation screw.

Preferably, the entire brush unit can be displaced through the adjustment mechanism.

Preferably, the adjustment mechanism comprises a worm screw coupled to an actuator, preferably a crank, and a holder nut joined to the brushes unit, in which the holder nut is coupled to the worm screw to move the brush unit through the actuator.

Preferably, a collection vat for collecting cleaning waste is arranged beneath the cleaning area.

Preferably, the collection vat is a removable drawer.

Preferably, a safety switch is combined with the removable drawer and connected to said at least one motor, to prevent the starting of the apparatus if the drawer is at least partially removed.

Preferably, the framework comprises a protection box.

Preferably, at least the cleaning area is enclosed in the protection box.

In this manner, the cleaning waste detached by the brush does not risk to hit the operator and/or dirty the area surrounding the apparatus.

Preferably, the protection box has through holes arranged at the support guides, to allow the insertion of the extrusion/transportation screw.

Preferably, the motor or motors is/are inside the protection box.

Preferably, the motor or motors is/are sealed.

Preferably, the motor or motors is/are outside the protection box.

If the motors are inside and sealed or outside, the dust and other waste does not risk to damage them.

Preferably, the robotic arm is arranged inside the protection box.

Preferably, the extrusion/transportation screw is driven along an axis thereof, preferably manually, while the operative portion of the brush moves in contact with the axial portion. Preferably, the extrusion/transportation screw is driven in rotation around itself, preferably manually, around an axis thereof while the operative portion of the brush moves in contact with the axial portion.

Preferably, said at least one motor has a maximum power comprised between 0.55 kW and 1.5 kW.

Preferably, said at least one motor has a maximum torque on the shaft comprised between 2 Kgm and 4 Kgm.

Preferably, the circular brush has a diameter comprised between 0.115 m and 0.125 m.

Preferably, during the cleaning, a rotation speed of the shaft is comprised between 2500 RPM and 3500 RPM.

The values indicated in the present description (speed, forces, torques, dimensions) shall be considered to be exemplifying and non-limiting and they may vary as a function of the dimensions and/or types of extrusion/transportation screws. Further characteristics and advantages will be more apparent from the detailed description of a preferred but non-exclusive embodiment of an apparatus and of a method for cleaning extrusion/transportation screws of a continuous compound mixer or conveyor for polymeric compounds according to the present invention.

Description of the drawings

Such description will be outlined hereinafter with reference to the attached drawings, provided solely for by way of non-limiting example, wherein:

- figure 1 schematically illustrates an apparatus for cleaning extrusion/transportation screws of a continuous compound mixer or conveyor for polymeric compounds according to the present invention associated to an extrusion/transportation screw;

- figure 2 illustrates the apparatus of figure 1 with one part removed to highlight internal elements;

- figure 3 is an enlargement of the apparatus of figure 2;

- figure 4 shows a section of the apparatus of figure 1 ;

- figure 5 shows a different section of the apparatus of figure 1.

Detailed description With reference to figure 1 , an apparatus for cleaning extrusion/transportation screws 2 of a continuous compound mixer or conveyor for polymeric compounds, per se known and not illustrated, for example used for producing compounds for manufacturing tyres for vehicle wheels was indicated in its entirety with 1.

The continuous compound mixer and the apparatus 1 are for example part of a plant for mixing elastomeric and/or thermoplastic compounds. The compound mixing plant may for example comprise several continuous compound mixers and an apparatus 1 for cleaning extrusion/transportation screws 2.

The continuous compound mixer for polymeric compounds comprises an external substantially cylindrical outer body and mainly extending along a main axis. The substantially cylindrical outer body delimits - therein - a compound mixing chamber extending mainly along the main axis and extending between at least one inlet and one outlet. The compound mixing chamber houses at least one or more extrusion/transportation screws capable of processing the polymeric compounds with time continuity, producing a continuous flow of outflowing compound.

An extrusion/transportation screw 2 comprises a central core fitted into which are different elements suitable to constitute axial segments of the screw with different characteristics and tasks (essentially: advancing the compound, mixing the compound or both). In the attached figures, the extrusion/transportation screw 2 is represented schematically. The axial segments have threads, reliefs and recesses in which the compound tends to remain stuck/trapped.

The apparatus 1 for cleaning the extrusion/transportation screws 2 comprises a framework 3 provided with legs for resting against the ground mounted on wheels. The framework 3 comprises an upper arc 4 on which a brush unit 5 is hung.

The brush unit 5 comprises a box-like structure 6. Mounted in an upper wall of the box-like structure 6, integrally joined thereto, is a holder nut 7 with vertical axis. Joined to each of two lateral walls of the box-like structure 6 is a cylindrical guide 8 with vertical axis.

A worm screw 9 is mounted vertically through the upper arc 4 in a guide cylinder 10. The worm screw 9 can rotate in the guide cylinder 10 but it is axially fixed with respect to the guide cylinder 10. The worm screw 9 projects under the arc 4 and it is engaged with the holder nut 7. Mounted at an upper end of the worm screw is a crank 11. Two guide shafts 12 extend downwards from the upper arc 4 and they are each slidably inserted into one of the cylindrical guides 8. The rotation of the crank 11 determines a vertical upward or downward movement of the entire brush unit 5. The worm screw 9, the guide cylinder 10, the crank 11 , the holder nut 7, the guide shafts 12 and the cylindrical guides 8 are part of an adjustment mechanism whose function will be described hereinafter.

A lower wall of the box-like structure 6 carries two electric motors 13 arranged adjacent to each other with the shafts thereof parallel. Mounted on each end of the two shafts is a circular brush 14. The box-like structure 6 is open on the side on which the two circular brushes 14 overlook hence the latter project from the box- like structure 6.

Each of the two electric motors 13 has a maximum power of 0.75 kW and a maximum torque at the shaft of 2.5 Kgm.

Each circular brush 14 has a radially peripheral portion 15 provided with metallic bristles, for example made of brass or steel, not illustrated, which constitutes an operative portion of the brush 14. In an embodiment, the bristles extend radially with respect to a central rotation axis of the brush 14. In a different embodiment, the bristles are inclined with respect to respective radial directions. In a further embodiment, the bristles are arranged on a face of the circular brush proximal to the radially peripheral portion 15 and extend parallel to the central rotation axis of the brush 14.

Each circular brush 14 is mounted coaxially on the respective drive shaft and it is made to rotate by the respective motor 13 around a central rotation axis“X-X” coincident with the axis of the shaft. The radially peripheral portions 15 of the two circular brushes 14 are arranged adjacent to each other and the two motors 13 are configured to make them rotate in opposite directions. Each circular brush 14 has a diameter of about 0.12 m. Preferably, the brushes 14 are interchangeable with others with bristles made of different materials and/or degrees of hardness as a function of the type of screws and/or of the compounds.

The adjustment mechanism described above allows to vertically displace the two brushes 14 and thus adjust the vertical position thereof with respect to the framework 3.

The framework 3 comprises a first bracket 16 arranged facing the circular brushes 14 and a second bracket 17 arranged on an opposite side of the brush unit 5. The first and the second bracket 16, 17 each carry a support guide 18. The support guides 18 each have the shape of a sleeve which internally delimits a cylindrical internal passage. The two support guides 18 and the two cylindrical internal passages are coaxial to each other and a main axis thereof is parallel to the drive shafts. Each of the two support guides 18 comprises an insert 19 (figure 4) defined by a tubular body inside the sleeve made of plastic material, for example made of polytetrafluoroethylene. The insert 19 at least partly delimits the internal passage of said sleeve and it has a surface for supporting the extrusion/transportation screw 2. The main axis of the two cylindrical internal passages passes between the two circular brushes 14. In particular, the main axis of the two cylindrical internal passages passes through the substantially triangular space delimited at the lower part between the two circular brushes 14. Such substantially triangular space defines a cleaning area 20 of the apparatus 1. The two sleeve-shaped support guides 18 are thus positioned on opposite sides of the cleaning area 20. The internal passages of the two support guides 18 are configured and dimensioned to allow the passage of the extrusion/transportation screw 2 which is fitted through the sleeves. The support guides 18 are also easily disassemblable so as to be able to change them with others suitable for extrusion/transportation screws 2 of different diameters.

A protection box 21 is mounted on the framework 3 and it encloses the upper arc 4, the brushes unit 5, the support guides 18 and thus the cleaning area 20 too. The crank 11 remains outside the protection box 21 instead. A window 22 with a transparent plate allows the operator to see inside the apparatus 1. Through holes 23 obtained in the protection box 21 and arranged at the support guides 18, allow the insertion of the extrusion/transportation screw 2 into the apparatus 1.

A collection vat 24 for collecting cleaning waste defined by a removable drawer is arranged beneath the cleaning area 20. A safety switch, not illustrated, is combined with the removable drawer 20 and it is connected to the motors 13, for example by means of a control panel, so as to prevent the apparatus 1 from starting if the drawer 20 is at least partially removed.

In use and according to the method of the invention, the operator initially provides for inserting the correct support guides 18 depending on the extrusion/transportation screw 2 to be cleaned. He closes the protection box 21 and inserts - through one of the two through holes 23 and one of the support guides 18 - the extrusion/transportation screw 2, after disassembling it from the continuous compound mixer, making it slide up to insert it into the other support guide 18 too.

At this point, with the screw 2 supported by the support guides 18, the operator manually adjusts, using the crank 11 , the position of the brushes unit 5 up to bring the radially peripheral portions 15 of the brushes 14 against an axial portion of the extrusion/transportation screw 2 arranged in the cleaning area 20. Such adjustment also allows to adjust a pressure exerted by the brushes on the extrusion/transportation screw 2 and thus the cleaning intensity.

The operator starts the motors 13 of the apparatus 1 and the circular brushes 14 rotate in opposite directions. The radially peripheral portions 15 exert a cleaning action brushing the screw 2. The operator moves the extrusion/transportation screw 2 in the axial direction making it slide in the support guides 18 and rotates it manually around itself to obtain the cleaning of the entire radially outer surface of said screw 2.

In the non-limiting embodiment illustrated in the attached figures, the central rotation axes 14 are parallel to an axis of the extrusion/transportation screw 2. In other embodiments, not illustrated in the attached figures, the central rotation axes of the brushes 14 can be perpendicular to the axis of the extrusion/transportation screw 2 or oriented obliquely.

Possibly, a detergent can be used to obtain an effective cleaning.

For example, during the cleaning, a rotation speed of the shaft is of about 2760 RPM and a peripheral speed of each circular brush 14 is of about 35m/s.

The waste and/or dust removed from the extrusion/transportation screw 2 fall into the collection vat 24 of the removable drawer which can be removed and emptied whenever necessary.

Should there arise the need to clean extrusion/transportation screws 2 with different diameter, the operator replaces the support guides 18 with others of appropriate dimensions. The diameter of the through holes 23 is such to allow the largest screw to be cleaned to pass through.

The motors 13 are preferably of the sealed type so as to prevent waste and/or dust from damaging them.

In variant embodiments, not illustrated, the motors 13 are separated from the cleaning area 20 and from the collection vat 24 by means of partitionings or they are positioned outside the protection box 21. In variant embodiments, not illustrated, the circular brushes 14 are connected and driven by a single motor by means of a transmission.

In variant embodiments, not illustrated, the circular brush 14 is only one or they can also be more than two, for example three of four arranged adjacent to each other and mutually delimiting the cleaning area.

In variant embodiments, not illustrated, a reduction gearbox can be interposed the motor or the motors and the brushes.

In variant embodiments, not illustrated in the attached figures, the structure of the apparatus is such that the adjustment of the position of the brushes 14 can be carried out by moving them horizontally and/or obliquely and/or mutually approaching or moving them apart.

In variant embodiments, not illustrated in the attached figures, the apparatus comprises a plurality of brush units operating on axially different areas of the extrusion/transportation screw.

In variant embodiments, not illustrated in the attached figures, the brush/brushes 14 are carried by one or more six axes anthropomorphic robotic arms, of the per se known type, for example controlled and commanded by an electronic control unit. The robotic arm or arms allows/allow to orient the brushes so as to copy a profile of the extrusion screw and so as to reach and clean even the most hidden interstices and portions. Furthermore, the robotic arm or arms thus commanded can apply a controlled pressure on the extrusion/transportation screw during the cleaning. The aforementioned robotic arms can be housed in the protection box 21 or only terminal ends thereof, carrying the brush/brushes 14, are operatively active in the protection box 21.

In variant embodiments, not illustrated in the attached figures, the brush/brushes 14 can be oval-shaped or elliptical-shaped instead of circular so as to exert - on the screw 2 - a variable pressure over time during the rotation thereof.