Feeding means and process for feeding pellet material and ground material into a plastics extruder

Abstract

The invention relates to a process for feeding pellet material and ground material, especially fluff, into a plastics extruder, comprising the steps of: supplying the pellet material and the ground material to an inlet opening of the plastics extruder using a supplying apparatus, wherein the ground material and / or the pellet material is compressed using a compressing means during the supplying; and controlling the compressing means according to at least one first parameter which characterizes a compression of the pellet material and / or of the ground material in the supplying apparatus.

Description

[0001] Feeding device and method for feeding granules and ground material into a plastics extruder

[0002] The invention relates to a feeding device and a method for feeding granules and ground material into a plastics extruder, wherein the granules and / or the ground material are fed to an inlet opening of the plastics extruder by means of a feeding device and the ground material and / or the granules are compressed during feeding by means of a compression device.

[0003] Many devices for producing film webs, particularly those involving cast-roll extrusion lines, produce strips that are created by cutting the film web longitudinally. The film web is, in particular, a plastic film web. Such strips are primarily edge strips, which represent waste due to the process. Such strips are first shredded in a shredder to form ground material, in particular small flakes, generally called fluff, before being fed into an extruder. A feeding device is provided for feeding the strips into the extruder. Preferably, fresh granulate is fed in at the same time so that the fluff and granulate are melted together in the extruder and fed to the extrusion line as plastic melt. Alternatively, however, it can also be provided that only waste that arises during the production of plastic films, e.g. edge strips, scrap rolls, etc., is fed into the extruder., or even used film can be shredded and fed into an extruder. This ground film waste can be returned to the extruder alone or in combination with fresh granulate. Such a process can be part of a regranulation plant.

[0004] The plastic extruder must be continuously supplied with sufficient plastic material by the feed device during the extrusion process, i.e. an amount of plastic material that is necessary for the extrusion process.The document WO 2021 / 074184 A1 relates to a feed device for feeding fluff and granules into an extruder with a feed device with an outlet-side pipe section for the granules, with which the granules can be fed to form a granule column, wherein the pipe section is connected to an inlet opening of the extruder and to a hopper with a hopper outlet for feeding fluff, wherein a conveyor screw for conveying fluff is provided within the hopper, which projects through the hopper outlet and into the pipe section, wherein the fluff can be conveyed within the granule column, wherein the conveyor screw is designed to also convey parts of the granules and / or to compress the fluff with a compacting device.

[0005] The document WO 2019 / 224261 A1 relates to a system for suctioning and shredding at least one strip, which is produced by at least one longitudinal cut of a film web, opposite a conveyor line through which the strip can be removed from the film web, with a shredder for shredding the strip and with a device for providing a volume flow for conveying the strip from the film web to the shredder, wherein the device for providing a volume flow comprises a first suction device which - viewed in the transport direction of the strip - is connected to the conveyor line upstream of the shredder.

[0006] It is an object of the present invention to provide an improved method for feeding granulate and / or ground material into a plastics extruder, as well as an improved feeding device. In particular, it is an object of the invention to ensure a sufficient supply of plastics material to the plastics extruder.

[0007] This problem is solved by the independent claims. Advantageous embodiments are claimed in the dependent claims.

[0008] A first aspect of the invention is a method for feeding granulate and / or ground material, in particular fluff, into a plastic extruder, comprising the following steps:

[0009] Feeding the granulate and / or the ground material to an inlet opening of the plastic extruder by means of a feeding device, wherein the ground material and / or the granulate is compacted during feeding by means of a compacting device; and

[0010] • Controlling the compaction device as a function of at least one first parameter which characterises a compaction of the granulate and / or the ground material in the feed device.

[0011] A second aspect of the invention relates to a feed device for a plastic extruder, comprising:

[0012] • a feeding device for feeding granulate and / or ground material, in particular fluff, to an inlet opening of the plastic extruder;

[0013] • a compaction device for compacting the ground material and / or granules during feeding; and

[0014] • a control device with means for regulating the compaction device as a function of at least one parameter which characterizes a compaction of the ground material and / or the granulate in the feed device.

[0015] A third aspect of the invention relates to a feed device for a plastic extruder, comprising:

[0016] • a feed device for feeding granulate and ground material, in particular fluff, to an inlet opening of the plastic extruder, wherein the granulate can form a granulate column in the region of the outlet in the feed device;

[0017] • a hopper for receiving ground material, especially fluff; and

[0018] • a screw conveyor as a compaction device, which is arranged within the hopper and projects through its neck into the feed device in such a way that the ground material can be conveyed within the granulate column as the screw conveyor rotates. A pipe section is arranged at the outlet, in the area of ​​which the screw conveyor has a diameter that ensures that both ground material and granulate are conveyed to the inlet opening. The invention is based on the idea of ​​operating and designing the feed device in such a way as to improve the supply of the extruder with plastic material comprising a mixture of granulate and ground material.

[0019] In a device for producing film webs, film strips, after being separated from the used film, and any other plastic waste, are ground into regrind, particularly fluff, in a recirculation system in a mill. This regrind is conveyed to the feed device. The feed device returns the regrind to the plastic extruder using a compaction device, which is generally a screw conveyor. Devices for processing film waste and used film for regranulation systems operate in a similar manner.

[0020] The inventors have discovered that the operating speed of the compaction device, generally the speed of a conveyor screw of the compaction device, has a significant influence on the operation of the plastics extruder. If the operating speed of the compaction device is too low, the feed zone of the extruder screw is not sufficiently filled with material due to the low bulk density of the ground material. This leads to a decrease in the feed rate of the plastics extruder compared to granules, and the extruder begins to pump. Pumping in this context means that the output of the plastics extruder fluctuates at a constant speed of the extruder screw.

[0021] This leads to thickness variations and / or profile variations of the extruded product as well as to unstable system operation.

[0022] This is where the invention comes in: The compaction device compacts the plastic material in the feed device in such a way that sufficient plastic material is fed to the plastic extruder. For this purpose, the compaction device is controlled depending on at least one first parameter that characterizes the compaction of the granulate and / or the ground material, i.e., the plastic material fed to the plastic extruder.

[0023] By making the control of the compression device dependent on the compression of the plastic material, it can be ensured that a provided volume of plastic material contains sufficient mass of plastic material to ensure stable operation of the extruder.

[0024] In particular, the better controlled compaction of the ground material in a feed zone of the plastics extruder increases the feed rate of the plastics extruder and reduces output fluctuations. Reducing output fluctuations, in turn, reduces thickness fluctuations in the extruded plastic product, especially in a film, and thus increases the operational stability of the entire system. In particular, output fluctuations lead to unstable edge strips on the film, for example. The melt quality in the plastics extruder is also improved due to its more stable operation. Furthermore, the invention can reduce the time until good production during start-up.

[0025] The regrind content of the plastic material supplied to the plastic extruder can also be generally increased. This makes it possible to feed additional regrind from other plastic waste, such as scrap rolls, edge strips from a rewinder, etc., into the plastic extruder, in addition to the film strips generated during the production of the plastic product, especially the film.

[0026] Preferably, a so-called PID controller is used to control the compression device. Further preferably, the compression device comprises or is a conveyor screw. This conveyor screw is further preferably driven by a motor, the speed of which is further preferably controlled at the output shaft in accordance with the invention. Further preferably, this output shaft is connected to a shaft of the compression device, in particular the conveyor screw. Preferably, the speed of the shaft of the compression device is controlled as an absolute value or as a change in a factor that specifies the ratio of the shaft of the compression device to the extruder screw speed.

[0027] According to the invention, sufficient compaction of the plastic material in the area of ​​the inlet opening of the plastic extruder or in the area of ​​the extruder screw's feed zone is also ensured by a conveyor screw of the compaction device having a sufficiently large diameter relative to the inner diameter of a pipe section at the outlet of the feed device, which ensures that both the ground material and the granulate are conveyed to the inlet opening of the plastic extruder. A suitable plastic screw geometry is advantageous for sufficiently high compaction at the inlet opening or in the feed zone.

[0028] In an advantageous embodiment of the method, the at least one first parameter which characterises a compaction of the ground material and / or the granulate is selected from the group of the following parameters:

[0029] • Torque applied to the compression device;

[0030] • Motor parameters, in particular speed and / or motor current and / or motor load of a motor of the compression device;

[0031] • Forces on the compaction device, in particular on the conveyor screw;

[0032] • Pressure in the compacted plastic material.

[0033] These parameters are particularly easy to determine.

[0034] In a further advantageous embodiment of the method, the compression device is further controlled as a function of at least one second parameter which characterizes an operation of the plastic extruder and is selected from the group of the following parameters:

[0035] • Feed rate of the plastic extruder;

[0036] • Throughput or gravimetric parameters of the plastic extruder;

[0037] • Melt pressure in the plastic extruder, in particular a constancy of the melt pressure;

[0038] • Melting temperature in the plastic extruder;

[0039] • Motor parameters, in particular speed and / or motor current and / or motor load of the motor of the plastic extruder;

[0040] Temperature in the plastic extruder;

[0041] Heating power of the plastic extruder; torque applied to a shaft of the plastic extruder, in particular an extruder screw;

[0042] • Forces on the shaft of the plastic extruder, in particular on the extruder screw;

[0043] • Speed ​​of the plastic extruder shaft, especially the extruder screw.

[0044] In particular, taking into account the speed of the shaft or the extruder screw of the plastic extruder offers the advantage that the compression remains essentially constant even when the speed of the shaft of the plastic extruder changes.

[0045] In a further advantageous embodiment of the method, the compression device is further controlled as a function of a rotational speed of a shaft of the plastics extruder, in particular of the extruder screw, and the at least one first parameter changes a factor between a rotational speed of the compression device and the rotational speed of the shaft of the plastics extruder.

[0046] This allows for particularly stable operation of the plastics extruder, as the speed of the compression device reacts without any time delay to a change in the speed of the plastics extruder's shaft. Controlling solely via a PID control loop, however, results in time delays in the compression device's response, which can lead to system overdrive.

[0047] In a further advantageous embodiment, the method further comprises the following work step:

[0048] • Selecting the at least one first parameter depending on an operating mode of the plastic extruder; and / or

[0049] • Changing at least one control parameter of a control loop which controls the compression device, depending on an operating mode of the plastic extruder.

[0050] Such a selection of the first parameter and the variation of a control parameter depending on the operating mode take into account the different operating characteristics of the respective operating modes. This can also lead to more stable operation of the plastics extruder.

[0051] In a further advantageous embodiment of the method, a distinction is made at least between a production mode and a start-up mode, wherein a lower reaction speed is provided in the production mode and a higher reaction speed is provided in the start-up mode.

[0052] A start-up mode in the sense of the invention is in particular a process of starting up a plant to the production mode and / or a process of switching an operation from a first production mode to a second production mode.

[0053] The slower response speed of the control loop in production mode ensures that large control steps, which would otherwise result in a high response speed, do not lead to stable operation due to constant fluctuations in the extruder's operating parameters. Fast control, i.e., with a higher response speed in start-up mode, is necessary to respond to the comparatively large changes in operation that occur there. Other examples of a start-up mode include switching a regrind feed on and off and changing the extruder speed.

[0054] Preferably, the reaction speed can be achieved via control parameters of the PID controller and / or via the smoothing of the at least one input signal, in particular the at least one first parameter and / or the at least one second parameter.

[0055] In a further advantageous embodiment of the method, the granulate forms a granulate column in the feed device, and the ground material is received in a hopper. The compaction device is a conveyor screw arranged within the hopper and extending through its neck into the feed device in such a way that, when the conveyor screw rotates, the ground material is conveyed within the granulate column, with the speed of the conveyor screw being controlled. This embodiment is particularly suitable for feeding and compacting plastic material to a plastic extruder.

[0056] In an advantageous embodiment of the feed device, the diameter of the conveyor screw in the region of the pipe section is at most 30%, preferably at most 25%, more preferably at most 10%, and most preferably at most 5% smaller than the inner diameter of the pipe section.

[0057] This allows for particularly effective conveying of the plastic material through the screw conveyor. In particular, this allows not only ground material but also granules to be conveyed.

[0058] In a further advantageous embodiment of the feed device, the diameter of the conveyor screw increases in the area of ​​the funnel, following the shape of the funnel.

[0059] This can improve the drawing of ground material from the hopper into the feed device. Preferably, those sections of the conveyor screw that enlarge it to follow the shape of the hopper are designed as an attached plastic wiper.

[0060] In a further advantageous embodiment of the feed device, at least one, in particular two, obstacles are arranged on an inner side of the hopper, which are aligned at least substantially perpendicular to the wings of the conveyor screw.

[0061] This also improves the drawing of the ground material into the conveyor screw by preventing the ground material in the hopper from rotating with the conveyor screw. The feed device is preferably further equipped with a deionization tube through which the ground material passes before it is collected in the hopper. This can reduce any electrostatic charge on the ground material. Furthermore, the hopper is preferably provided with air nozzles which prevent the ground material from sticking to the walls. In a further advantageous embodiment, the blades of the conveyor screw are each spaced one to thirty millimeters from the at least one obstacle. This prevents an area of ​​ground material from forming between the obstacles and the conveyor screw, which area rotates with the conveyor screw.

[0062] The features and advantages described above with respect to the first aspect of the invention also apply accordingly to the second and third aspects of the invention and vice versa.

[0063] Further features and advantages are evident from the following description with reference to the figures. They show:

[0064] Figure 1 is a cross-sectional view of a first embodiment of a feed device arranged on a plastic extruder;

[0065] Figure 2 is a cross-sectional view of part of a second embodiment of a feed device;

[0066] Figure 3a shows a detailed view corresponding to section A of Figure 1 with a first embodiment of a conveyor screw;

[0067] Figure 3b is a detailed view corresponding to section A of Figure 1 with a second embodiment of a conveyor screw;

[0068] Figure 4 is an enlarged view of the screw conveyor and the pipe section in section A of Figure 1;

[0069] Figure 5 is a block diagram of an embodiment of a method for feeding granulate and ground material into a plastic extruder; and

[0070] Figure 6 is a circuit diagram of an embodiment of a control circuit for controlling the compression device.

[0071] Figure 1 shows an embodiment of a feed device 11, which is arranged on a plastics extruder 1 in such a way as to feed plastics material into an inlet opening 2 of the plastics extruder 1. The feed device 11 has a hopper 9, which tapers toward the plastics extruder 1 and continues into a neck 10. Extending within the hopper 9 and through its neck 10 is a conveyor screw 4, which, together with a motor 18 driving the conveyor screw 4, forms a compacting device. During operation, the conveyor screw 4 rotates in the direction of arrow 17.

[0072] The conveyor screw 4 comprises a helix 16, of which individual elements are visible due to the sectional view, which form wings that extend from the shaft of the conveyor screw 4 outwards to the hopper 9 and its neck 10.

[0073] In Figure 1, ground material (not shown), particularly so-called fluff, can be fed into the hopper 9 from above. During operation, this ground material is conveyed through the neck 2 by a rotation of the conveyor screw 4.

[0074] Furthermore, the feed device 1 comprises a feed device 3, which extends from a pipe section 14 to an inlet opening 2 of the extruder 1. Granules are fed through the upper part of the feed device 3 in Figure 1, which, as indicated by the arrows, flows into a likewise funnel-shaped part of the feed device 3. In the lower part of the feed device 3 above the outlet 13, the granules preferably form a granulate column.

[0075] The ground material is conveyed from the hopper 9 via its neck 10 and through the granulate column by means of the conveyor screw 4 towards an outlet 13 of the feed device 3. The ground material flows through the outlet 13 together with the granulate via the pipe section 14 to the inlet opening 2 of the plastics extruder 1 into a feed zone (no reference symbol) of the extruder screw 8. Here, the plastics material, in particular the ground material and / or the granules, is compacted in the pipe section 14 by means of the conveyor screw 4. In the extruder 1, the plastics material is conveyed from the feed zone to the right in Figure 1, where the plastics material is gradually melted and mixed.

[0076] Preferably, the conveyor screw 4 has an agitator 19 in the area of ​​the hopper 9, which assists in transporting the material to be ground. Further preferably, air nozzles are provided in the area of ​​the hopper 9 to prevent the material to be ground from accumulating on the walls of the hopper 9. Furthermore, a deionization device can be provided to reduce electrostatic charging of the material to be ground. Figure 2 shows a second embodiment of the upper part of a feed device 3 for a feed device 11.

[0077] The spirals 16 of the conveyor screw 4 have widened portions in the area of ​​the funnel 9, which follow the shape of the funnel 9. These widened portions are preferably formed as steel or plastic extensions of the spirals 16.

[0078] Furthermore, at least one obstacle 15, in particular in the form of a rod, is preferably arranged on the inner wall of the hopper 9, which prevents or at least reduces rotation of the ground material in the hopper 9 with the rotation of the conveyor screw 4.

[0079] In Figure 2, the spirals 16 of the conveyor screw 4 reach to the inner wall of the neck 10 of the funnel 9.

[0080] Figures 3a and 3b show two embodiments of the conveyor screw 4 corresponding to section A of Figure 1.

[0081] In Figure 3a, the helix 16 has a relatively small diameter D compared to the inner diameter I of the pipe section 14. This primarily conveys the ground material 6 through the granulate column. In the lower region of Figure 3a, the ground material 6 is even pushed outward by the rotation of the conveyor screw 4 in the pipe section 14, forming a widened portion 7, thus preventing any further flow of granulate 5 through the inlet opening (not shown) of the extruder.

[0082] In Figure 3b, however, the conveyor screw 4 has a larger diameter D in relation to the inner diameter I of the pipe section 14. This ensures that not only the ground material 6, but also granulate 5 are conveyed by means of the conveyor screw 4 in the direction of the inlet opening (not shown) through the outlet 13 of the feed device 3. In addition, the conveyor screw 4 of the embodiment according to Figure 3b has a double helix 16. This allows transverse forces on the conveyor screw 4 to be reduced and also the compaction by the rotating conveyor screw 4 can be improved. In Figure 4, the diameter D of the conveyor screw 4 is shown, which is predetermined by the helices 16. Furthermore, the inner diameter i of the pipe section 14 is shown in the area A of Figure 1.

[0083] The ratio of the diameter D of the conveyor screw 4 to the inner diameter i of the pipe section 14 can influence the conveying and also the compression of the plastic material to the inlet opening (not shown) of the plastic extruder 1.

[0084] Figure 5 shows a block diagram of an embodiment of a method 100 for feeding granules with ground material 6 into a plastic extruder 1. Preferably, the method 100 is carried out with a feed device 11, as explained with reference to the embodiments of Figures 1 to 4.

[0085] In a first step 101 of the method 100, the granulate s and the ground material 6 are fed to the inlet opening 2 of the plastics extruder 1 by means of the feed device 3. The granulate 5, driven in particular by gravity, flows through the upper part of the feed device 3 into the lower funnel-shaped section of the feed device 3, where it forms a granulate column.

[0086] The ground material 6, which is preferably in the form of so-called fluff, flows, in particular through a deionization device, into the hopper 9. From there, the granules are conveyed by means of the conveyor screw 4 through the neck 10 of the hopper 9 into the funnel-shaped region of the feed device 3 and there, likewise by means of the conveyor screw 4, through the granule column. From there, the granules 5 and the ground material 6 pass through the outlet 13 of the feed device 3 and the pipe section 14 to the inlet opening 2 of the plastics extruder 1 and thus into the feed zone (no reference symbol) of the extruder screw 8. Here, the granules 5 and the ground material 6 are also driven by gravity. They are additionally conveyed by the rotation of the conveyor screw 4, which also extends into the pipe section 14.

[0087] Depending on the ratio of the diameter of the conveyor screw 4 to the inner diameter i of the pipe section 14, essentially only the ground material 6 or the ground material 6 and the granulate 5 are conveyed. Depending on the rotation speed of the conveyor screw 4, the granulate 5 and the ground material 6 are compacted to varying degrees in the area of ​​the pipe section 14 and the intake zone of the extruder screw 8. The conveyor screw 4, optionally in conjunction with a motor 18 that drives it, acts as a compaction device.

[0088] In a second work step 102, a first parameter M is preferably selected depending on the operating mode of the plastic extruder 1.

[0089] Alternatively or additionally, in a third work step 103, a value of at least one control parameter N4 of a control loop which controls the compression device 4 is changed depending on an operating mode of the plastic extruder 1.

[0090] Finally, in a fourth work step 104, the rotational speed N4 of the conveyor screw 4 is controlled as a function of the at least one first parameter M, which characterizes a compaction of the granulate 5 and / or the ground material 6 in the feed device 3. The first parameter M is preferably the torque applied to the conveyor screw 4. This torque is preferably determined either by means of a torque sensor in the region of the shaft of the conveyor screw 4 or in the region of the motor 18. Further preferably, this torque is determined indirectly by means of motor parameters, in particular a speed and / or a motor current and / or a motor load of the motor 18, forces on the conveyor screw 4, or a determination of the pressure of the compacted plastic material.

[0091] Preferably, a PID controller is used to control the speed of the conveyor screw 4. Depending on the operating mode, the reaction speed of the PID controller is then adjusted in the third work step 103. Preferably, a distinction is made here, in particular, between a production mode and a start-up mode, with a lower reaction speed being set in the production mode and a higher reaction speed being set in the start-up mode.

[0092] The reaction speed can also be adjusted by smoothing the controller's input signal, in particular the torque M as the first parameter. Preferably, the speed N4 of the conveyor screw 4 is further controlled as a function of a second parameter N8 in a work step 104, which characterizes the operation of the plastic extruder 1 and is selected from the group of the following parameters:

[0093] • Feed rate of the plastic extruder 1 ;

[0094] • Throughput or gravimetric parameters of the plastic extruder 1 ;

[0095] • Melt pressure in the plastic extruder 1 ;

[0096] • Melt temperature in the plastic extruder 1 ;

[0097] • Motor parameters, in particular speed and / or motor current and / or motor load of the motor of the plastic extruder 1 ;

[0098] • Temperature in the plastic extruder 1 ;

[0099] • Heating power of the plastic extruder 1 ;

[0100] • Torque which is applied to a shaft 8 of the plastic extruder 1, in particular an extruder screw;

[0101] • Forces on the shaft 8 of the plastic extruder 1 , in particular on the extruder screw;

[0102] • Speed ​​of the shaft 8 of the plastic extruder 1 , in particular the

[0103] Extruder screw.

[0104] If the speed N4 of the conveyor screw 4 is controlled as a function of the speed N8 of the extruder screw 8, the respective value of the torque M on the conveyor screw 4 preferably changes a factor N4:N8 between the speed of the conveyor screw 4 and the speed of the extruder screw 8. This ensures that the speed N4 of the conveyor screw 4 reacts immediately, without delay, to a change in the speed of the extruder screw 8. At a higher feed rate of the extruder screw 8, the speed N4 of the conveyor screw 4 is therefore increased proportionally in addition to the torque-dependent control. Preferably, the speed N4 of the conveyor screw 4 is controlled in such a way that the throughput through the plastic extruder 1 only fluctuates by one to two percent. At the same time, the speed N8 of the extruder screw 8 should also only fluctuate by a maximum of + / - one revolution per minute.

[0105] Figure 6 shows an embodiment of a control diagram for controlling the speed N4 of the conveyor screw 4 as a function of the first input parameter M.

[0106] For this purpose, the feed device 11 preferably has a control device 12 with means for regulating the compression device 4. A means within the meaning of the invention can be designed in hardware and software and in particular can have a processing unit, in particular a microprocessor unit (CPU), which is preferably connected to a memory and bus system for data or signals, and / or one or more programs or program modules. The CPU can be designed to process instructions implemented as a program stored in a memory system, to detect input signals from a data bus and / or to output output signals to a data bus. A memory system can have one or more, in particular different, storage media, in particular optical, magnetic solid-state devices and / or other non-volatile media. The program can be designed in such a way that it embodies the methods described here orcapable of executing such methods, so that the CPU can execute the steps of such methods. Preferably, the control device is computer-implemented.

[0107] The torque M applied to the conveyor screw 4 is input into the control system as the first input parameter of the control device 12. Further preferably, the speed N8 of the extruder screw 8 of the extruder 1 is input into the control system in the control device 12 as the second input parameter. There, a target speed N4 of the conveyor screw 4 is determined using a factor N4:N8, which, on the one hand, specifies a speed ratio between the conveyor screw 4 and the extruder screw 8 and, at the same time, depends on the torque M applied to the conveyor screw 4.

[0108] It should be noted that the embodiments are merely examples and are not intended to limit the scope of protection, application, or structure in any way. Rather, the preceding description provides the skilled person with a guide for implementing at least one embodiment. Various modifications, particularly with regard to the function and arrangement of the described components, may be made without departing from the scope of protection as defined by the claims and equivalent combinations of features.

[0109] List of reference symbols

[0110] 1 plastic extruder

[0111] 2 inlet opening

[0112] 3 Feeding device

[0113] 4 Compaction device / conveyor screw

[0114] 5 granules

[0115] 6 Ground material

[0116] 7 Widening

[0117] 8 extruder screw

[0118] 9 T funnel

[0119] 10 neck

[0120] 11 Feed device

[0121] 12 tax resources

[0122] 13 Outlet

[0123] 14 Pipe section

[0124] 15 Obstacle

[0125] 16 spirals

[0126] 17 Direction of rotation

[0127] 18 Engine

[0128] 19 stirrers

Claims

Claims 1. Method (100) for feeding granulate (5) and / or ground material (6), in particular fluff, into a plastic extruder (1), comprising the following steps: Feeding (101) the granulate (5) and / or the ground material (6) to an inlet opening (2) of the plastics extruder (1) by means of a feeding device (3), wherein the ground material (6) and / or the granulate (5) is compressed during feeding by means of a compression device (4); and Controlling (104) the compaction device (4) as a function of at least one first parameter (M) which characterises a compaction of the granulate (5) and / or the ground material (6) in the feed device (3).

2. Method (100) according to claim 1, wherein the at least one first parameter (M) which characterizes a compaction of the ground material (5) and / or the granulate (6) is selected from the group of the following parameters: • Torque applied to the compression device (4), in particular to the conveyor screw; • Motor parameters, in particular speed and / or motor current and / or motor load, of a motor of the compression device (4); • Forces on the compaction device (4), in particular on the conveyor screw; • Pressure in the compacted plastic material.

3. Method (100) according to claim 1 or 2, wherein the compression device (4) is further controlled as a function of at least one second parameter (N8) which characterizes an operation of the plastic extruder (1) and is selected from the group of the following parameters: • Feed rate of the plastic extruder (1); • Throughput or gravimetric parameters of the plastic extruder (1 ); • Melt pressure in the plastic extruder (1); • Melt temperature in the plastic extruder (1); • Motor parameters, in particular speed and / or motor current and / or motor load, of the motor of the plastic extruder (1); • T emperature in the plastic extruder (1 ); • Heating power of the plastic extruder (1); • Torque which is applied to a shaft (8) of the plastic extruder (1), in particular to an extruder screw; • Forces on the shaft (8) of the plastic extruder (1), in particular on the extruder screw; • Speed of the shaft (8) of the plastic extruder (1), in particular the extruder screw.

4. Method (100) according to one of the preceding claims, wherein the compression device (4) is further controlled as a function of a rotational speed of a shaft (8), in particular of the extruder screw, of the plastic extruder (1) and the at least one first parameter (M) changes a factor (N4:N8) between a rotational speed (N4) of the compression device (4) and the rotational speed (N8) of the shaft (8) of the plastic extruder (1).

5. The method (100) according to any one of the preceding claims, further comprising the step of: Selecting (102) the at least one first parameter (M) depending on an operating mode of the plastic extruder (1); and / or Changing (103) a value of at least one control parameter (N4) of a control loop which controls the compression device (4), depending on an operating mode of the plastic extruder (1).

6. The method (100) according to claim 5, wherein a distinction is made at least between a production mode and a start-up mode, wherein a lower reaction rate is provided in the production mode and a higher reaction rate is provided in the start-up mode.

7. Method (100) according to one of the preceding claims, wherein the granulate (5) forms a granulate column in the feed device and the ground material (6) is received in a hopper (9), wherein the compression device (3) has a conveyor screw (4) which is arranged inside the hopper (9) and projects through the neck (10) of the hopper into the feed device (3) in such a way that when the conveyor screw (4) rotates, the ground material is conveyed within the granulate column, wherein a speed of the conveyor screw (4) is regulated.

8. Feed device (11) for a plastic extruder (1), comprising: a feed device (3) for feeding granulate (5) and / or ground material (6), in particular fluff, to an inlet opening (2) of the plastic extruder (1); a compacting device (4) for compacting the ground material (5) and / or the granulate (6) during feeding; and a control device (12) with means for regulating the compacting device (4) as a function of at least one first parameter (M) which characterizes a compaction of the ground material (4) and / or the granulate (5) in the feeding device (3).

9. Feed device (11) according to claim 8, further comprising: a hopper (9) for receiving the ground material (5); wherein the granules (6) can form a granule column in the feed device (3), and wherein the compacting device (4) is a conveyor screw which is arranged within the hopper (9) and projects through its neck (10) into the feed device (4) in such a way that, upon rotation of the conveyor screw (4), the ground material (6) can be conveyed within the granule column (5).

10. Feed device (11) for a plastic extruder (1), in particular according to claim 8, comprising: a feed device (4) for feeding granulate (5) and ground material (6), in particular fluff, to an inlet opening (2) of the plastic extruder (1), wherein the granulate (5) can form a granulate column in the region of the outlet (13) in the feed device (3); a hopper (9) for receiving ground material (6); and a conveyor screw (4) which is arranged inside the hopper (9) and projects through the neck (10) of which into the feed device (3) in such a way that the ground material (5) can be conveyed inside the granulate column when the conveyor screw (4) rotates, wherein a pipe section (14) is arranged at the outlet (13), in the region of which the conveyor screw (4) has a diameter (D) which ensures that both the ground material (6) and the granulate (5) are conveyed to the inlet opening (2) and compacted.

11. Feed device (11) according to claim 10, wherein the diameter (D) of the conveyor screw in the region of the pipe section (14) is at most 30%, preferably at most 25%, more preferably at most 10% and most preferably at most 5% smaller than the inner diameter (I) of the pipe section (14).

12. Feed device (11) according to one of claims 7 to 11, wherein at least one single, in particular two, obstacles (15) are arranged on an inner side of the hopper (9), which are aligned at least substantially perpendicular to wings (16) of the conveyor screw (4).

13. Feed device (11) according to claim 12, wherein the wings (16) of the conveyor screw (4) are each spaced 3 to 6 mm from the at least one obstacle (15).

14. Plastic extruder (1) with a feed device (11) according to one of claims 8 to 13.

15. Cast roll extrusion line or blown film extrusion line with a feed device (11) according to one of claims 8 to 13 or an extruder (1) according to claim 14.

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