Extrusion system with planetary spindles and guide ring

Abstract

Extrusion layer with a planetary roller extruder or planetary roller extruder section or planetary roller extruder module with a central spindle (9, 28), planetary spindles (10, 27) and an internally toothed housing bushing or an internally toothed housing (5), wherein the planetary spindles (10, 27) slide with their end faces facing the melt flow on a thrust ring (8) and thereby rotate around the central spindle (9, 28) and in the surrounding housing (5), and wherein their toothing meshes simultaneously with the toothing of the central spindle (9, 28) and the internal toothing of the housing (5), wherein an involute toothing is used, characterized in that, depending on the size of the planetary roller extruder or planetary roller extruder section in mm and with reference to the pitch circle diameter of the internal toothing of the housing (5) or the housing bushing (24), the following tooth modules in mm are used. and tooth counts for the planetary spindles (10,27) are used Size in mm Module / new Planetary spindle / number of teeth new 150 5,5 6, preferably 5 170 3.5 or 5.5 7, preferably 5 180 5,5 7, preferably 5 200 3.5 or 5.5 7, preferably 5 250 5,5 5 300 8 5 400 8 5 500 8 5

Description

[0001] The invention relates to a planetary roller extruder according to claim 1. Planetary roller extruders are a special type of extruder. Extruders are preferably used for processing plastics. However, planetary roller extruders are also suitable for processing foodstuffs and other substances that can be converted into a molten state or are introduced into the extruder already in a molten state. The processing often includes mixing with solids.

[0002] In this process, plastic, usually in granular form, is fed into the extruder along with additives. The feed mixture is plasticized, dispersed, and homogenized within the extruder, then cooled to extrusion temperature and discharged in a molten state. This occurs through a discharge die, also known as an extruder die.

[0003] It is also possible to extrude without a die. The die is shaped to match the cross-section of the desired extruded strand. That is, the die gives the melt its form. The extruded strand is cooled in ambient air and / or with other coolants until the melt solidifies and the strand assumes a permanent shape. Until sufficient strength is achieved on the outer surfaces, the extruded strand is preferably supported on these surfaces by so-called calibrators.

[0004] There are various applications where the extrusion die is unnecessary. This is the case, for example, when extrusion is carried out in multiple stages. The extruder for the first stage is called the primary extruder, which transfers the melt produced and preferably further processed within it to the secondary extruder. Degassing of the melt is often incorporated between the two stages. For this purpose, the transfer area is enclosed. A negative pressure relative to the melt pressure in the primary extruder is created in the transfer housing, causing trapped gas to escape from the melt. The resulting gas is extracted from the transfer housing using a suitable suction device.

[0005] Extrusion processes that do not require an extrusion tool include the production of color raw materials, where the melt from the extruder is fed onto a belt for cooling, and after solidification is brought to the desired grain size in a crusher / grinder.

[0006] Extruders without extrusion dies are common, for example when the extruders are tasked with generating and, if necessary, processing melts in order to then press the melt into another extruder where the melt is mixed with other substances.

[0007] The planetary roller extruder offers significant advantages over other extruder designs in plasticizing, homogenizing, and cooling.

[0008] Therefore, the planetary roller extruder is gaining increasing importance. Combined designs are common, combining planetary roller extruder sections with single-screw extruder sections. The single-screw extruder sections are preferably used in the material feed or at the extruder discharge. Or the planetary roller extruder sections are combined with sections of a different design.

[0009] When planetary roller extruder sections are designed or manufactured modularly, they are referred to as planetary roller extruder modules, or simply planetary roller modules. Planetary roller modules simplify planning and manufacturing.

[0010] Planetary roller extruders can process mixtures with a very high solids content. In the production of WPC (wood-plastic composite) products, solids content of 70% and more is sometimes found. A wide variety of solids are used in planetary roller extruders. Most often, these solids serve as fillers. However, they can also fulfill other functions.

[0011] The higher the proportion of solids, the greater the wear on the extruder parts. There are also plastics with a high abrasive effect.

[0012] This also includes rubber.

[0013] The higher the wear resistance, the longer components can withstand wear.

[0014] Extruders with the properties described above are described, for example, in DE102007059299A1. The following is described there regarding the gearing of planetary spindles, central spindle and housing: The spindles are capable of running with the same tooth module and the same type of gearing, for example involute gearing.

[0015] For involute gearing, a specific tooth module is appropriate depending on the extruder application. More information about possible gear types can be found in DE102007050466A1. In addition to involute gearing, other gear types are also mentioned. The advantages of involute gearing are explained. Further information can be found in WO 2013 / 159 801 A1. This information pertains to commonly used tooth modules.

[0016] These printed materials contain no information on reducing wear and tear.

[0017] The invention aims to increase the wear resistance of planetary roller extruder components. It is based on the understanding that planetary spindles have thus far exhibited the lowest wear resistance. The wear resistance of the central spindle is many times higher than that of the planetary spindle. The wear resistance is highest in the internal gearing within the extruder housing or in the internally toothed bushing of the extruder housing.

[0018] Increased wear resistance is achieved with the features of the main claim. The dependent claims describe preferred embodiments.

[0019] The invention is based on the idea of ​​increasing the gear module of the involute gearing and reducing the number of teeth for the planetary spindles. Planetary roller extruders typically have involute gearing. Besides involute gearing, other types of gearing exist. Involute gearing differs from other gear types in that it exhibits less sliding and less wear on the teeth. The force to be transmitted should always be tangential to the base circle diameters at the pitch point. This is achieved when the pitch points lie on an involute.

[0020] The larger gear module results in larger teeth on the planetary spindles. Since the teeth on all meshing parts of the planetary roller extruder must be identical, the larger teeth on the planetary spindles also result in larger teeth on the central spindle and on the internal gearing of the housing or the internal gearing of the housing bushing. The larger teeth can withstand wear for a longer period than smaller teeth.

[0021] Advantageously, larger teeth can also possess greater strength than smaller teeth. However, larger teeth do not automatically result in greater strength. Rather, with an increase in the tooth module and a decreasing number of teeth, a tapered tooth neck develops when the pitch circle diameter of the gearing on the planetary spindles only contacts the pitch circle diameter of the corresponding gearing on the central spindle and simultaneously the pitch circle diameter of the corresponding internal housing gearing or internal gearing of the housing bushing at a single point. A tapered tooth neck is naturally less robust than a thicker one. According to the invention, an impermissible reduction of the tooth neck on the planetary spindles is avoided by a correction factor. The correction factor determines the degree to which the gearing of a planetary spindle is machined less deeply into a blank than gearing without a correction factor.The measurement in millimeters is obtained by multiplying the correction factor by the tooth height.

[0022] The greater tooth height and all other derived tooth dimensions and the selected number of teeth result in a larger planetary spindle diameter compared to conventional planetary spindles, even with a larger core.

[0023] Preferably, a correction factor is also applied to the central spindle and the internal gearing of the housing or housing bushing. The gearing is machined into the housing or housing bushing blank and the central spindle blank according to the correction factor. The correction factor can be the same as or different from the correction factor for the planetary spindle gearing. Preferably, the correction factor for the internal housing gearing or the internal gearing of the housing bushing has a different sign than the correction factor for the planetary spindles. In this case, the gearing is not machined to a lesser depth in the blank, as with the planetary spindles, but rather, preferably, the gearing is machined to the same depth—not less—to create the necessary space for the gear meshing of the planetary spindles and sufficient clearance for their movement.The associated reduction in tooth neck thickness on the central spindle and the internal housing teeth or the internal teeth of the housing bushing is harmless because the wear on the central spindle and the internal teeth of the housing is distributed over many more teeth and therefore puts significantly less stress on each individual tooth than on the planetary spindles.

[0024] According to the invention, the correction factor is 0.1 to 0.5, preferably 0.2 to 0.4 and even more preferably 0.3.

[0025] Surprisingly, no adverse behavior of the planetary roller components in their interaction can be observed with these correction factors.

[0026] For various sizes (based on the pitch circle diameter of the housing internal gearing or the internal gearing of the housing bushing), the following new gear modules in millimeters and numbers of teeth are provided for the planetary spindles compared to conventional gear modules and numbers of teeth: Size in mm standard module New module Planetspi. Number of teeth typical Planetspi.Number of teeth new 150 3 5,5 7 6, preferably 5 170 3 3.5 or 5.5 8 7, preferably 5 180 3,5 5,5 8 7, preferably 5 200 3 3.5 or 5.5 8 7, preferably 5 250 3,5 5,5 7 5 300 3.5 or 5.5 8 7 5 400 3.5 or 5.5 8 7 5 500 5,5 8 7 5

[0027] The drawing shows an embodiment of the invention.

[0028] Fig. Figure 1 shows an extruder with a planetary roller section 11 and an inlet screw 1. The planetary roller section consists of three planetary roller extruder modules with a common central spindle 9. Each module comprises an outer housing 5 in the form of a tube, which has flanges 6 and 7 at both ends. The modules are bolted together at the flanges 6 and 7. The housings 5 ​​are centered by centering rings. The centering rings are recessed in corresponding recesses in the housing flanges.

[0029] Each planetary roller extruder module also includes a bushing. The bushing is located inside the housing 5. It is preferably inserted before the flanges 6 and 7 are screwed together. For this purpose, the centering rings are provided with a bore that matches the bore of the housing.

[0030] A thrust ring 8 is located between each of the bushings. The thrust ring holds the planetary spindles 10 in their orbital position around the common central spindle 9. The planetary spindles slide on the thrust ring.

[0031] The tip of the central spindle is designated 12 and corresponds to a front thrust ring 11, which has the same function as the thrust rings 8 and also forms a gap through which the extruded material is pushed towards the extruder discharge.

[0032] Special centering rings, which are firmly connected to the housing 5, are provided for centering the thrust ring 11. The centering rings fill the recess in the flange 6, which is designed for the centering rings. On the front side, the centering rings form an additional centering flange.

[0033] At its right end, the central spindle 9 forms a screw for an inlet zone. A separate housing 1 with an inlet opening 2 is provided in this area. Housing 1 is constructed like housing 5. The associated flanges are designated 3 and 4. The interaction of flange 4 with the connecting flange 7 of the next housing 5 is the same as the interaction of flanges 6 and 7. The filling screw on the right side of the central spindle has a filling and plasticizing function, but no significant dispersion or homogenization function. Dispersion and homogenization take place in downstream planetary roller extruder modules.

[0034] Each housing 5 of a planetary roller extruder module is equipped with two cooling / heating sections. One section comprises spirally arranged channels running along the inner surface of the housing, which can be supplied with a cooling / heating medium via connections. The other section comprises spirally arranged channels on the inner surface of the housing, which can be supplied with a coolant / heating medium via connections.

[0035] Fig. Figure 3 shows a section through a planetary roller extruder module. The housing is labelled 25, the internally toothed housing bushing 24, the planetary spindles 27, and the central spindle 28. It can be seen that the planetary spindles 27 mesh simultaneously with the internal teeth of the bushing 24 and with the external teeth of the central spindle 28. Furthermore, it shows Fig.3 cooling channels 23 and 26 for a temperature control medium with which the temperature in the extruder is regulated by cooling or heating.

[0036] Fig. Figure 2 shows two normally toothed teeth 30 of a planetary spindle.

[0037] The planetary spindles are designed for a planetary roller extruder section with a size of 150 mm. The illustration is not to scale with regard to the number of teeth, because only five teeth are provided, which enclose a significantly larger angle between them than shown.

[0038] The gear module is 5.5 in the exemplary embodiment. In a normal gear, this results in significantly tapered tooth necks 31 on the teeth 30.

[0039] According to the invention, a correction factor of 0.3 is applied to the gear teeth. The tooth height is multiplied by this factor. The resulting value is the amount by which the gear teeth are machined less deeply into the blank for the planetary spindle. A form cutter is typically used for machining the gear teeth.

[0040] As a result of the shallower interlocking, the teeth shown in dashed lines 32 have less or no tapered necks.33

Claims

[1] Extrusion layer with a planetary roller extruder or planetary roller extruder section or planetary roller extruder module with a central spindle (9, 28), planetary spindles (10, 27) and an internally toothed housing bushing or an internally toothed housing (5), wherein the planetary spindles (10, 27) slide with their end faces facing the melt flow on a thrust ring (8) and thereby rotate around the central spindle (9, 28) and in the surrounding housing (5), and wherein their toothing simultaneously meshes with the toothing of the central spindle (9, 28) and the internal toothing of the housing (5), wherein an involute toothing is used, characterized by , that depending on the size of the planetary roller extruder or planetary roller extruder section in mm and in relation to the pitch circle diameter of the internal toothing of the housing (5) or the housing bushing (24), the following gear modules in mm and tooth counts for the planetary spindles (10, 27) are used Size in mm Module / new Planetary spindle / number of teeth new 150 5,5 6, preferably 5 170 3.5 or 5.5 7, preferably 5 180 5,5 7, preferably 5 200 3.5 or 5.5 7, preferably 5 250 5,5 5 300 8 5 400 8 5 500 8 5 [2] Extrusion plant according to claim 1, characterized by , that the toothing in the planetary spindles (10,27) is determined by a correction factor in which the toothing protrudes less deeply into the planetary spindles (10,27) than in a toothing whose pitch circle diameter only touches the pitch circle diameter of the housing internal toothing or internal toothing of the bushing (24) at one point and / or has the pitch circle diameter of an uncorrected toothing. [3] Extrusion plant according to claim 2, characterized by , that the correction factor is 0.1 to 0.5, preferably 0.2 to 0.4 and even more preferably 0.3, and multiplied by the tooth height gives the distance that the pitch circle diameter of the corrected gearing has from the pitch circle diameter of an uncorrected gearing. [4] Extrusion plant according to claim 2 or 3, characterized by, that the same or a different correction factor is applied to the gearing on the central spindle (9,28) and / or to the internal gearing of the housing (5) or the internal gearing of the housing bushing (24). [5] Extrusion plant according to claim 4, characterized by , that the toothing extends deeper into the planetary spindles (10,27) than in the case of toothing whose pitch circle diameter only touches the pitch circle diameter of the housing internal toothing or internal toothing of the bushing (24) at one point and / or only touches the pitch circle diameter of the toothing of the central spindle (9,28) at one point.

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