TWIN-SCREW MIXING AND EXTRUSION MACHINE WITH MOBILE ELEMENTS
20220152874 · 2022-05-19
Inventors
Cpc classification
B29B7/484
PERFORMING OPERATIONS; TRANSPORTING
B29C48/402
PERFORMING OPERATIONS; TRANSPORTING
B29B7/488
PERFORMING OPERATIONS; TRANSPORTING
B29B7/52
PERFORMING OPERATIONS; TRANSPORTING
B29B7/183
PERFORMING OPERATIONS; TRANSPORTING
B29B7/802
PERFORMING OPERATIONS; TRANSPORTING
B29B7/728
PERFORMING OPERATIONS; TRANSPORTING
B29B7/726
PERFORMING OPERATIONS; TRANSPORTING
B29C48/395
PERFORMING OPERATIONS; TRANSPORTING
International classification
B29B7/20
PERFORMING OPERATIONS; TRANSPORTING
B29B7/74
PERFORMING OPERATIONS; TRANSPORTING
B29B7/80
PERFORMING OPERATIONS; TRANSPORTING
B29C48/40
PERFORMING OPERATIONS; TRANSPORTING
Abstract
A mixing and extrusion machine (10) has a converging conical twin-screw mixer (12) with a fixed frame (14) that supports sleeves (16) in which two screws (18) are mounted at an angle between an opening (22) arranged upstream of the sleeves, where an introduction hopper (24) of the machine (10) feeds the screws, and an outlet (25) arranged downstream of the sleeves, where the mixer discharges the mixture at the end of a mixing cycle. At least one mobile sleeve (34) is disposed towards the outlet, each mobile sleeve with a support surface (34a) of a predetermined surface area (34a) according to an elasticity of the mixture, and each mobile sleeve having one or more mobile elements that move by a linear movement with respect to the outlet in order to adjust a predetermined space between the sleeves and the screws.
Claims
1. A mixing and extrusion machine (10) for the production of rubber mixtures, the machine (10) comprising: a converging conical twin-screw mixer (12) with a fixed frame (14) that supports sleeves (16) in which two screws (18) are mounted at an angle between an opening (22) disposed upstream of the sleeves, where an introduction hopper (24) of the machine (10) feeds the screws, and an outlet (25) disposed downstream of the sleeves, where the mixer (12) discharges the mixture at the end of a mixing cycle, one or more motors (20) that rotate the two screws in the sleeves during the mixing cycle, and one or more movable doors (28) provided at the outlet (25) that allow, during the mixing cycle, the discharge and shaping of a rubber mixture, wherein at least one mobile sleeve (34) is disposed towards the outlet (25), each mobile sleeve with a support surface (34a) of a predetermined surface area depending on an elasticity of the mixture, and each mobile sleeve comprising one or more mobile elements that move by a linear movement with respect to the outlet (25) in order to adjust a predetermined space between the sleeves (16) and the screws (18), and the linear motion being defined between a closed position of a mobile sleeve to facilitate mixing of the mixture, and an open position of a mobile sleeve to facilitate the flow of the mixture inside the mixer.
2. The machine (10) of claim 1, in which at least two mobile sleeves (34) are arranged towards the outlet.
3. The machine (10) of claim 2, in which the mobile sleeves (34) are arranged top-down towards the outlet.
4. The machine (10) of claim 3, wherein the linear movement of the mobile sleeves (34) is selected from simultaneous movement, reciprocating movement and random movement of the mobile elements.
5. The machine (10) of claim 2, further comprising a ram (30) with an inner surface (30a) having a shape that is complementary to an outer contour of the two screws (18), the ram moving inside the introduction hopper (24) between a raised position, where the two screws remain accessible for introducing the mixture, and a lowered position, where the inner surface (30a) of the ram forms an upper part of the mixer (12).
6. The machine (10) of claim 5, further comprising a roller nose system comprising two counter-rotating rollers (32) arranged just downstream of the outlet (25) to form a sheet of the mixture discharged from the mixer (12).
7. The machine (10) of claim 1, wherein the screws (18) are mounted in the mixer (12) so that the threads of each screw contact tangentially the surfaces of the opposite screw so that the screws remain substantially in contact with each other when rotating the screws at an angle and at a center distance that facilitates self-cleaning.
8. The machine (10) of claim 7, wherein the screws (18) are selected from interpenetrated and conjugated profiles, including interpenetrated co-rotative profiles with conjugated profiles.
9. A mixing process of the type comprising a step of mixing and extruding a mixture from a machine (10) of claim 1, the process comprising the following steps: a step of rotating the screws (18) forward with the movable door (28) closed; a step of introducing the mixture to the machine (10), during which the screws (18) continue to rotate and the movable door (28) remains closed; and a step of emptying the machine (10), during which the movable door opens to let the mixture out of the machine outlet (25) toward a downstream process, and during which the screws continue to rotate until the mixer is empty.
10. The process of claim 9, in which the step of introducing the mixture to the machine (10) comprises introducing the raw materials to form the mixture.
11. The process of claim 9, in which the step of introducing the mixture to the machine (10) includes the introduction of one or more masterbatches.
12. The process of claim 9, in which: the movable door (28) is in the closed position at the beginning of the mixing cycle and in the open position at the end of the mixing cycle; and each mobile sleeve (34) is in the open position at the beginning of the mixing cycle and in the closed position at the end of the mixing cycle.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The nature and various advantages of the invention will become more obvious when reading the following detailed description, in conjunction with the attached drawings, in which the same reference numbers refer everywhere to identical elements, and in which:
[0023]
[0024]
[0025]
[0026]
[0027]
[0028]
[0029]
[0030]
[0031]
DETAILED DESCRIPTION
[0032] Referring now to the figures, in which the same numbers identify identical elements,
[0033] Referring further to
[0034] The machine 10 can include an optional conveyor known to the skilled person (for example, the belt 26 shown in
[0035] Referring further to
[0036] The mobile door 28 is installed with respect to the mixer outlet 25 so that, in a closed position, it prevents the mixture from exiting the mixer 12 (for example, to promote mixing when the mixture has a lower viscosity). At the end of the mixing cycle, the mobile door 28 is opened so that the rubber mixture can be evacuated and shaped. The machine 10 can allow partial or complete opening of the mobile door so as to allow part or all of the mixture to be extruded.
[0037] Referring again to
[0038] The mobile sleeve 34 adjusts the space between the sleeves and screws to facilitate the flow of the mixture inside the mixer 12, thus allowing the duration and degree of mixing of the mixture to be adjusted. In
[0039] The two screws 18 circulate the mixture from an upstream side (next to the introduction hopper 24) to a downstream side where the sleeves 16 of the machine 10 are installed. The mobile sleeve 34 is installed in relation to the outlet 25 of the mixer 12 so that, in an open position, it allows the mixture to circulate. The mobile sleeve can move continuously or intermittently to reduce the space between the screws and the bearing surface in a corresponding manner, thus creating downstream-to-upstream mixing flows. For example, in a manner of using the machine 10, the mobile sleeve 34 is mostly in the open position at the beginning of the mixing cycle when the mixture has a high viscosity (to promote the mixing flow) (see
[0040] In addition, with reference to
[0041] In the embodiments of the machine 10 including the mobile sleeves 34, the linear movement of the mobile sleeves 34 is selected from simultaneous movement, reciprocating movement and random movement of the mobile elements. The mobile sleeves 34 can move in an alternative or random manner to reduce the space between the screws 18 and the bearing surfaces 34a in a random manner, thus creating downstream-to-upstream mixing flows and preferably above or below. For example, in a manner of using the machine 10, the two mobile sleeves 34 are mostly in the open position at the beginning of the mixing cycle when the mixture has a high viscosity (to promote the mixing flow) (see
[0042] The design shown in
[0043] The use of one or more mobile sleeves allows, from the beginning of the mixing cycle, to have a large air gap and therefore a low pressure drop despite a high viscosity. The product to be extruded or mixed passes through the spaces left by the difference in volume between the screw and its sleeves. These spaces, and more particularly the clearance left between the top of the screw threads and the top of the sleeve threads (if the sleeve has no threads, the smallest inside diameter is considered), are important for working the product, for its forward speed and for any pressure inside the machine. The product that is subjected to a very high pressure at the end of the screw will seek to move to areas where the pressure is lower. When the product moves through the machine, it will undergo significant shearing, which will promote the work and homogenization of the product. The product can be worked as from the beginning of the cycle.
[0044] Referring also to
[0045] The ram 30 is similar to rams used during mixing processes such as those performed by Banbury type internal mixers (disclosed, for example, by patents U.S. Pat. Nos. 1,370,398 and 7,404,664). As with internal mixers, the ram 30 is used to press the mixture and exert pressure on the mixture during production. Thus, the ram 30 allows the transmission of more energy and shear to the mixture and thus improves the working of the rubber.
[0046] An inner surface 30a of the ram 30 has a shape that is complementary to an outer contour of the two screws 18. The guidance of the ram 30 is realized between a raised position (represented by
[0047] Referring again to
[0048] Referring again to
[0049] A roller nose system of an embodiment of the invention includes two counter-rotating rollers 32 arranged just downstream of the outlet 25 to form a sheet of the mixture emerging from the mixer 12. The roller nose system may also include an optional control means (not shown) to control the feeding speed of the mixture to the rollers. The rotation of the rollers 32 is managed by the amount of the mixture discharged by the mixer 12 (detected, for example, by a proximity sensor, by a pressure sensor or by an equivalent device).
[0050] For all embodiments of the machine 10, the screws are chosen from known profiles, including Archimedes screw type screws and profiles known for their self-cleaning nature. Self-cleaning profiles include interpenetrated and conjugated profiles (and particularly interpenetrated co-rotative profiles with conjugated profiles). In other words, for self-cleaning profiles, the screws can be in substantial contact with each other at an angle and at a center distance that will allow self-cleaning. Screws are said to be “substantially in contact” when the screws can be cleaned by friction, or when the two screws face each other with such a small gap between them that an extruded material cannot remain attached to the surfaces of the screws. Screws are said to rub against each other, or to be “self-cleaning”, when the materials transported in the channel of one of the screws cannot remain in that channel for more than one revolution of the screw. As a result, the material undergoes much more movement in the downstream direction, parallel to the screw axis, than in a lateral direction, perpendicular to the axis. Examples of self-cleaning screws are disclosed by patents EP0160124B1, EP0002131B1, U.S. Pat. Nos. 4,300,839, 4,131,371, and 6,022,133 and by publication WO2016/107527.
[0051] With reference to
[0052] By initiating a cycle of the mixing process of the invention, the mixing process includes a step of rotating the screws 18 forward with the removable door 28 closed. During this step, the rotating screws cause the product to move downstream of the mixer as soon as the mixture (or raw materials) is introduced into the machine 10. In all embodiments of the machine 10, the rotational speed can be variable during the cycle. When the screws 18 are interpenetrated, the rotational speed of the two screws is synchronized.
[0053] The mixing process includes a step of introducing a mixture M into the machine 10 (shown being transported by belt 26 as designated by arrow A in
[0054] The step of introducing a mixture into the machine 10 can be executed by introducing into the empty machine the different raw materials necessary for the production of the product, including, without limitation, an elastomeric material (for example, natural rubber, synthetic elastomer and combinations and equivalents thereof) and one or more ingredients, such as one or more processing agents, protective agents and reinforcing charges. Raw materials may also include one or more other ingredients such as carbon black, silica, oils, resins and cross-linking or vulcanization agents. All ingredients are introduced in varying quantities depending on the desired performance of the products obtained from the mixing processes (for example, tires).
[0055] The step of introducing a mixture into the machine 10 can also be done by starting the cycle with a product that has already been mixed but does not contain all the ingredients of the recipe (called “masterbatch”). For example, resins and curing agents are not present in the masterbatch. These ingredients, which make mixing difficult, can be added to the mixer 12 to complete mixing. In this case, either the masterbatch is recovered hot from an upstream mixer (such as an internal mixer or an external mixer), or the masterbatch is cold because it has been manufactured and packaged several hours or even several days in advance.
[0056] During the mixing cycle, the machine 10 (or a system that incorporates the machine 10) can be trained to recognize values representative of the mixture discharged from the mixer 12 (for example, temperature and viscosity values) and to make a comparison with target values. This machine training includes the recognition of non-equivalences between the compared values. Each step of the training can include a classification generated by self-learning means. This classification may include, without limitation, the parameters of the raw materials and masterbatches of the chosen mixing recipe, the screw configurations (either Archimedes or self-cleaning screws), the process cycle times and the predicted values at the end of a cycle in progress (for example, the value of the space between the sleeves and screws during the current mixing cycle, etc.).
[0057] During the step of introducing the mixture into the machine 10, the belt 26 (or another equivalent means) is used to successively introduce the necessary raw materials and other ingredients according to a predetermined recipe. In one embodiment, elastomeric material is introduced into the machine 10, followed by the introduction of reinforcing fillers such as carbon black or silica, oils, resins and vulcanizing agents.
[0058] In the embodiments of the machine 10 having a ram 30, the mixing process includes a step of lowering the ram after the step of introducing the mixture M into the machine 10 (see arrow B in
[0059] The mixing process includes a step of partial closure of the mobile sleeve(s) 34. In the embodiments of the mixer with two or more mobile sleeves, the partial closure of the mobile sleeves may refer to their reciprocating movement or to their simultaneous movement. In the embodiments of the machine 10 with a ram 30, the ram remains lowered. During this step, the screws 18 continue to turn.
[0060] In embodiments of the machine 10 including a ram 30, the mixing process includes a step of raising the ram. During this step, the mobile sleeve(s) are in a partially closed position. For each embodiment of the machine 10, the screws continue to rotate during this step. In embodiments of the machine 10 including the rollers 32, both rollers remain on standby during this step.
[0061] The mixing process includes a step of reversing the screws 10 with the removable door 28 closed. During this step, the screws rotate in a direction opposite to the direction rotation realized during the step of rotating the screws forward. The entire mixture located in machine 10 has a downstream to upstream movement that will cause an additional distribution of raw materials. The mobile sleeve(s) 34 remain partially closed during this step. In embodiments of the machine 10 including a ram 30, the ram remains raised during this step. In the embodiments of the machine 10 including the rollers 32, both rollers remain on standby during this step.
[0062] The mixing process includes a step of reversing the screws 10 with the removable door 28 closed. During this step, the screws rotate in the direction opposite to the direction of rotation taken during the step of turning the screws forward. The entire mixture located in the machine 10 has a downstream-upstream movement of the machine that will cause an additional distribution of raw materials. The mobile sleeve(s) 34 remain partially closed during this step. In embodiments of the machine 10 including a ram 30, the ram remains raised during this step. In embodiments of the machine 10 including the rollers 32, both rollers remain on standby during this step.
[0063] The mixing process also includes an additional step of rotating the screws 18 forward with the removable door 28 closed. During this step, the screws rotate in the direction opposite to the direction of rotation taken during the step of turning the screws in reverse. The mobile sleeve(s) 34 remain partially closed during this step. In embodiments of the machine 10 including a ram 30, the ram remains raised during this step. In embodiments of the machine 10 including the rollers 32, both rollers remain on standby during this step.
[0064] In embodiments of the machine 10 including the ram 30, the mixing process includes a step of lowering the ram that is realized after the preceding step of rotating the screws 18 in reverse. During this step, the screws continue to turn and the mobile sleeve(s) remains partially closed. In embodiments of the machine 10 also having the rollers 32, the rollers remain on standby during this step.
[0065] The mixing process includes a step of completely closing the mobile sleeve(s) 34, thus eliminating the gap between the sleeve(s) 34 and the screws 18 (see
[0066] The mixing process includes a final step of emptying the machine 10. During this step, the movable door 28 opens in order to discharge the mixture from the outlet 25 of the machine toward a downstream process. In embodiments of the machine 10 where the movable door has two or more mobile elements, this step includes either simultaneous opening or alternative opening of the mobile elements. The mobile sleeve(s) 34 remain completely closed, but they can be adjusted according to a volume of the mixture discharged from the mixer. In embodiments of the machine 10 having a ram 30, the ram is lowered during this step. In embodiments of the machine 10 that also include the rollers 32, this step also includes the step of rotating the rollers in order to allow the mixture to be discharged in the form of sheets. In each embodiment of the machine 10, the screws 18 continue to rotate during this step in order to completely empty the machine 10.
[0067] At the end of the mixing cycle, the product can be used in a downstream process (which may be, for example, a palletizing process, a shaping process, and/or another mixing process such as an extrusion process). After the end of the step of emptying the machine 10, the mixing process cycle can be restarted.
[0068] It is understood that some steps of a mixing cycle, as well as the cycle itself, can be carried out in an iterative manner depending on the selected mixture recipe.
[0069] It is also understood that the machine 10 can operate independently or that it may be part of a system or systems that constitute a production plant.
[0070] It is envisaged that the machine 10 can carry out one or more processes concerning the plasticization of natural elastomers.
[0071] A process cycle can be performed by PLC control and may include pre-programming of control information. For example, a process setting can be associated with the mixture that is supplied to the mixer 12, including the properties of the screws 18, the properties of the mixture entering the introduction hopper 24 and the properties of the mixture exiting the mixer. An adjustment can be, for example, the opening (either partial or total) and closing (partial or total) of the mobile sleeve(s) 34.
[0072] For all embodiments of the machine 10, a monitoring system may be put in place. At least part of the monitoring system may be provided in a portable device such as a mobile network device (for example, a mobile phone, a portable computer, a portable device or devices connected to the network, including augmented reality and/or virtual reality devices, portable clothing connected to the network and/or any combinations and/or equivalents).
[0073] In some embodiments of the invention, the machine 10 (and/or a system that incorporates the machine 10) may receive voice commands or other audio data representing, for example, a step or stop in the rotation of the screws 18. The request may include a request for the current status of a mixing process cycle. A generated response can be represented in an audible, visual, tactile (for example, using a haptic interface) and/or virtual or augmented manner.
[0074] In order to obtain mixtures with the desired properties, the invention preserves all the advantages of a mixer equipped with a converging conical twin-screw mixer. At the same time, the invention combines mobile sleeve solutions to provide a single machine that is capable of processing a variety of mixtures without changing equipment in a mixing facility.
[0075] The terms “at least one” and “one or more” are used interchangeably. The ranges that are presented as “between a and b” include the values “a” and “b”.
[0076] Although specific embodiments of the disclosed apparatus have been illustrated and described, it is understood that various changes, additions and modifications can be made without departing from the spirit and scope of this disclosure. Therefore, no limitation should be imposed on the scope of the described invention with the exception of those set out in the annexed claims.