DEVICE AND METHOD FOR CLEANING AN EXTRUDER FOR ELASTOMER MIXTURES

Abstract

Device for cleaning an extruder intended to operate with elastomeric mixtures comprising a frame (11) supporting a screw (2) and a barrel (1), the screw (2) being made to rotate about the longitudinal axis (X-X) of the barrel (2) when it is rotationally driven by drive means, the barrel comprising an elastomeric-mixture feed inlet (3) and an outlet (4) opening directly into an extrusion die (21) mounted on a support (20).

According to the invention, the frame (11) is mounted with the ability to move translationally with respect to the die (21) support (20) in a direction parallel to the longitudinal axis X-X between a first position in which the barrel (1) and the die (21) are in sealed contact to allow the elastomeric mixture to pass through the die (21) and a second position in which the barrel (1) is moved away from the die (21) in order to perform cleaning, the parting line between the barrel (1) and the die being substantially axisymmetric with respect to the axis X-X and in that the said device comprises an automatic coupling mechanism (40) for quickly locking and unlocking the barrel (1) and the die (21) and allowing the frame (11) to move between the two positions.

Claims

1-14. (canceled)

15: A device for cleaning an extruder of elastomeric mixtures, the device comprising: a frame; a barrel supported by the frame, the barrel having a longitudinal axis X-X and including an elastomeric-mixture feed inlet and an outlet that opens directly into an extrusion die mounted on a support; a screw supported by the frame, the screw being rotatable about the axis X-X when the screw is rotationally driven by a driver; and an automatic coupling mechanism, wherein the frame is movably mounted such that the frame is translationally movable with respect to the die and the support in a direction parallel to the axis X-X between a first position, in which the barrel and the die are in sealed contact with each other in order to allow the elastomeric mixture to pass through the die, and a second position, in which the barrel is moved away from the die in order to allow cleaning to be performed, wherein a parting line between the barrel and the die is axisymmetric with respect to the axis X-X, and wherein the automatic coupling mechanism enables a quick locking and a quick unlocking of the barrel and the die, to allow the frame to move between the first and second positions when the barrel and the die are unlocked.

16: The device according to claim 15, wherein the automatic coupling mechanism includes a lock structured to produce locking forces that are distributed uniformly over a circumference of the barrel.

17: The device according to claim 15, wherein the automatic coupling mechanism is a screw-nut system that includes: a first ring surrounding the barrel, a second ring secured to the support and surrounding the die, the second ring being structured to collaborate with the first ring, and a rotational driver for causing relative rotational turning between the first and second rings.

18: The device according to claim 17, wherein: the first and second rings are coaxial, the first ring includes inclined ramps, the second ring is secured to an outlet end of the barrel, and the second ring includes inclined ramps that are structured to collaborate with the inclined ramps of the first ring.

19: The device according to claim 18, wherein: the inclined ramps of the first ring are first tenons that are uniformly distributed along a circumference of the first ring, the inclined ramps of the second ring are second tenons that are uniformly distributed along a circumference of the second ring, and the first tenons of the first ring are structured to be axially slidable in spaces between the second tenons of the second ring.

20: The device according to claim 17, wherein the rotational driver includes a latch-lock lever device that connects one of the first and second rings in an articulated manner to a rod of a translational-actuation actuating cylinder.

21: The device according to claim 15, further comprising a central control unit that controls opening and closing actions of the automatic coupling mechanism.

22: A method for cleaning an elastomeric-mixture extruder that includes a frame supporting a screw and a barrel, the screw being rotatable in the barrel when rotationally driven about a longitudinal axis X-X of the barrel by a driver, the barrel including an elastomer-mixture feed inlet and an outlet that opens into an extrusion die mounted on a support, the method comprising steps of: using an automatic coupling mechanism to unlock the barrel from the die, the automatic coupling mechanism enabling the barrel and the die to be locked and unlocked quickly along a parting line that is substantially axisymmetric with respect to the axis X-X; moving the frame translationally with respect to the support of the die in a direction parallel to the axis X-X from a first position, in which the barrel and the die are in sealed contact with each other in order to allow an elastomeric mixture to pass through the die, to a second position, in which the barrel is moved away from the die in order to allow cleaning to be performed; and rotating the screw in order to empty the extruder.

23: The method according to claim 22, wherein rotation of the screw when the frame is in the second position during the rotating step is performed in a same direction as rotation of the screw when the frame is in the first position.

24: The method according to claim 22, wherein the translational movement of the frame during the moving step is over a distance at least equal to a distance between a downstream end of the screw and a downstream end of the die when the frame is in the first position.

25: The method according to claim 22, wherein the die has a convergent shape.

26: The method according to claim 22, wherein the barrel includes claws that interact with the elastomeric mixture.

27: The method according to claim 22, wherein the die outputs into a nip formed between a first calendering roller and a second calendering roller.

28: The method according to claim 27, wherein, when the frame is in the second position, the first and second calendering rollers are turned in order to remove a remaining mixture.

Description

[0032] The invention will be understood better from studying the attached FIGS. 1 to 5 which are provided by way of examples and are in no way limiting, in which:

[0033] FIG. 1 depicts a schematic overview in axial section of a device for cleaning an extruder according to the invention,

[0034] FIGS. 2a to 2d depict, in schematic views in cross section, the various steps in the method for cleaning an extruder according to the invention,

[0035] FIG. 3 is a view in cross section on the plane A-A of FIG. 2d of the device of the invention when the locking device is in the unlocked position,

[0036] FIG. 4 is a view in cross section on the plane A-A of FIG. 2d of the device of the invention when the locking device is in the locked position,

[0037] FIG. 5 is a perspective view of part of the automatic coupling mechanism of the device of the invention, the extruder and the die support being situated distant from one another.

[0038] The device for cleaning an extruder intended to operate with elastomeric mixtures is depicted in FIG. 1 and comprises a bed 30 on which there are mounted an assembly forming an extruder 10 and a support 20 for a die 21. The assembly forming an extruder 10 comprises a cylindrical screw 2 which rotates inside a barrel 1 and the means (not visible in the drawing) for driving the screw, such as an electric motor and reduction gearbox arranged at the upstream end thereof. The screw 2 rotates inside the barrel 1 about the longitudinal axis X-X thereof. The barrel 1 has a cylindrical overall shape and comprises, upstream, an elastomeric-material feed inlet 3 and, downstream, an outlet 4 towards a die through which the elastomeric mixture propelled by the screw 2 passes. It will be recalled that upstream and downstream mean as seen in the direction of flow of the material between the feed inlet to the barrel and the outlet via the die 21.

[0039] The support 20 is secured to the bed 30 and comprises a through-orifice 24 the axis of symmetry of which is aligned with the longitudinal axis X-X of the barrel 1, in the continuation thereof. The die 21 is mounted using fixing screws in the through-orifice 24 of the support 20 so that it is centred on the axis of the latter. The die 21 has a flattened overall shape (the cross section being of elliptical overall shape) and is convergent, as seen in axial section, between an upstream end 22 situated facing the outlet 4 of the barrel 1 and a downstream end 23 via which a profiled element exits. In operation, the mixture propelled by the screw 2 exits in the form of a profiled element through the die 21 and is transferred for example via a conveyor to a storage reel onto which it is wound.

[0040] In an alternative form of the invention, the die 21 delivers into the nip formed between a first calendering roller and a second calendering roller the horizontal axes of which are mutually parallel and perpendicular to the longitudinal axis X-X, the two rollers (not depicted in the drawings) being rotationally driven in opposite directions about their respective axes. The rollers are mounted with their respective drive systems on the support 20 at the exit from the die 21. The two rollers form a roller-die system the purpose of which is to profile the elastomeric mixture exiting via the die 21 into the form of a strip. The profiled element thus obtained is then wound onto a storage reel or may be laid directly onto a building drum adjacent to one of the rollers.

[0041] According to the invention, the assembly forming an extruder 10 is mounted on a mobile frame 11, the frame being able to move translationally in a direction parallel to the longitudinal axis X-X of the barrel 1 as indicated by the double arrow in FIG. 1. The frame 11 for this purpose comprises guide tabs 12 which are made to slide along a fixed rail (not visible in the drawings) belonging to the bed 30. The frame 11 is able to move under the action of the rod 13 of an electric actuating cylinder 14 mounted on the bed 30. The extruder 10 is thus moved axially with respect to an extrusion die 21 mounted fixedly on a support 20 so as to separate and then bring together the two parts along a parting line that is axisymmetric with respect to the axis X-X. The frontal part of the barrel 1 of the extruder is thus pressed firmly without play against the facing frontal part of the die 21 and held in position by an automatic coupling mechanism.

[0042] The device for cleaning the extruder according to the invention for this purpose comprises an automatic coupling mechanism 40 allowing the barrel 1 to be locked and unlocked quickly with respect to the die 21 so that these can be brought into sealed communication and then separated easily. The automatic coupling mechanism 40 comprises two rings 5, 25 each provided with fixing tenons 6, 26 and a latch lock lever rotational drive mechanism 41 for driving one ring with respect to the other. More particularly, a first ring 5 is fixedly mounted on the barrel 1 and arranged in such a way as to surround the outlet end 4 thereof, and a second ring 25 is mounted with the ability to rotate on the side of the support 20 that faces the barrel 1, the two rings 5, 25 are coaxial being arranged along the axis X-X. The ring 25 is held by an annular support 27 inside which it is made to turn, the annular support 27 being secured to the support 20. The first ring 5 comprises tenons 6 which at their upstream end exhibit inclined ramps 7 which are made to collaborate with the inclined ramps 27 situated at the downstream end of the tenons 26 of the second ring. The inclined ramps 7 and 27 follow a helical curve which, in one preferred embodiment of the invention has an angle of inclination of around 10 so as to be reversible and to leave the friction cone of the friction between the two components. The tenons 5, 25 thus represent the threads of the automatic coupling mechanism 40 of the screw-nut type.

[0043] The number of tenons needs to be at least two in order to distribute the closure force over the circumference of the ring, the number of tenons increasing with the diameter of the ring and the axial force reacted by the tenons. Moreover, it is found that the lower the number of tenons, the higher the angle through which the ring 25 has to rotate in order to unlock/lock, the longer the latch lock lever links need to be and, therefore, the longer the travel of the actuating cylinder needs also to be. The solution of the invention makes it possible to take all of these considerations into account and to provide an automatic coupling mechanism that is small in bulk but at the same time allows for effective closure, without the risk of the mixture leaking from the interface between the two components. In the example illustrated, the ring 25 comprises eight tenons, which corresponds to the number of threads of the automatic coupling mechanism 40, for a ring diameter of around 180 mm.

[0044] The tenons 6 and 26 are uniformly distributed on the circumference of each ring 5 and 25 and are produced in such a way that the tenons 6 of one ring 5 can slide axially in the spaces between the tenons 26 of the other ring 25 opposite when the barrel 1 and the die 21 are in the unlocking position.

[0045] The mechanism 41 for rotationally driving the ring 25 comprises a latch lock lever device 42 with a pushrod which is the rod 43 of an electric actuating cylinder 44 as can best be seen in FIGS. 3 and 4. More particularly, the latch lock lever device 42 comprises two links 45 and 46 which are mounted in such a way as to pivot at a common articulation 49 the axis of which is parallel to the axis X-X. A first link 45 is mounted via a pivot 50 and a flange 47 on the frontal face of the ring 25, while the second link 46 is mounted via a pivot 51 and an upright 48 on the support 20, the axes of the pivots 50, 51 also being parallel to the axis X-X. During operation, when the actuating cylinder is commanded for closure, its rod 43 lengthens and applies pressure to the articulation 49 of the latch lock lever device 42 which makes the ring 26 rotate with respect to the ring 5 which is fixed and causes the locking device of the automatic coupling mechanism 40 to pass from the open position illustrated in FIG. 3 to the closed one illustrated in FIG. 4. When the actuating cylinder 44 is actuated in the opposite direction, the rod 43 thereof applies a pulling force to the articulation 49 and this unlocks the two rings 5 and 25 from one another, the ramps of the tenons 26 of the ring 25 then finding themselves beside the ramps of the tenons 6 of the ring 5. The body of the actuating cylinder 44 is mounted with the ability to pivot about a hinge 52 of an upright 53 fixed to the support 20. The use of a latch lock lever device offers the advantage that the force applied to the link 45 by the actuating cylinder 44 is low by comparison with the clamping force ultimately applied to the ring 25.

[0046] The operation of the cleaning device according to the invention will be explained hereinafter with reference to FIGS. 2a to 2d and to the steps of the method of the invention.

[0047] FIG. 2a illustrates the extruder cleaning device of the invention at the end of the extrusion operation when the screw of the extruder has stopped so that the extruder can be emptied. The actuating cylinder 44 of the automatic coupling mechanism 40 receives a command (coming from a central control unit or from a command and control controller) to unlock the rings 25 and 5 when the tenons 6 come to face the spaces provided between the tenons 26 so as to be able to release the barrel 1. The command is then given to the actuating cylinder 14 to move the mobile frame 11 in the direction of the arrow illustrated in FIG. 2a.

[0048] FIG. 2b illustrates the extruder 10 in its position away from the support 20 and therefore from the die 21. The residual mixture 60 that was initially between the downstream end of the screw 2 and the die 21 remains caught on the screw and a distance away from the die. In an alternative form, claws for catching on the mixture are provided to make sure that it remains completely attached to the screw. The claws 61 are placed on the ring 5 at the exit from the barrel 1. One or several claws are provided these remaining permanently attached to the barrel 1 and passing through the thickness thereof in order to penetrate the residual mixture 60. In one alternative form of the invention, the claws 61 act as an insert in which to house a mixture pressure or temperature sensor. The claws are dimensioned in such a way as to be long enough that they do not release the residual mixture 60 as the latter deforms as a result of the movement of the extruder. In an alternative form, the shape of the outlet orifice of the barrel 1, or that of the ring 5, is non-circular; it is produced in such a way as to act as a claw in order to hold back the residual mixture when the shape of the die includes an undercut.

[0049] Starting from the position illustrated in FIG. 2b, the screw begins to be turned in order to completely remove the mixture remaining inside the extruder, which mixture then drops under gravity (in the direction of the arrow in FIG. 2c) and is collected in a container (not illustrated) underneath. When rollers are provided at the downstream exit of the die, these are also turned in rotation in this step in order to remove the mixture remaining between the rollers and the die.

[0050] FIG. 2d illustrates the step that completes the cleaning operation, the extruder 10 being completely emptied and the automatic coupling mechanism 40 being in the locking position. The extruder 10 is operational again and ready to receive a new mixture of elastomers, because the barrel 1 is in sealed contact with the support 20 and therefore the die 21.

[0051] Other alternative forms and embodiments of the invention may be envisaged without departing from the scope of these claims. Thus it is possible to envisage replacing the tenons with a continuous screw thread produced in each of the rings.