Multi-screw preparation equipment for molten plastics

Abstract

A multi-screw preparation unit (20) for molten plastics, comprising an extruder housing (24) having an enclosed treatment chamber (21) for the molten plastics therein, and at least one rotor body shaft (22) rotatably supported in the treatment chamber (21), the rotor body shaft (22) having a seal and guide body (22.3) with a plurality of receiving grooves in which one satellite screw (23) is supported, the multi-screw preparation unit (20) comprising a drive unit (30) which is connected between a drive motor (32) and the treatment chamber (21) outside the extruder housing (24). A multi-shaft preparation unit (20) is provided, characterized in that a transmission unit (31) is provided, the transmission unit (31) is connected to drive shaft sections (22.2, 23.2) of the rotor body shaft (22) and the satellite screws (23) leading out from the processing chamber (21) of the extruder housing (24), and a separating device (33) is provided between the extruder housing (24) and the transmission unit (31) for blocking the flow of fluid and / or heat leaving the processing chamber (21), and the drive shaft ends (22.2, 23.2) of the rotor body shaft (22) and the satellite screws (23) are guided through the separating device (33).

Description

[Technical field]

[0001] The invention relates to a multi-shaft preparation device for molten plastics having the features of the preamble of claim 1.

[0002] For preparing molten plastics, especially polyesters, multi-shaft preparation devices in the form of so-called multi-rotation systems (MRS), which are basically described in WO 2003033240, have proven effective. These multi-shaft preparation devices incorporate an extruder screw, which between an intake and metering zone for drawing in and melting the plastic and a delivery zone is a so-called multi-rotation unit with a rotor main shaft. The rotor main shaft has a significantly increased diameter in relation to the other zones and furthermore has several rotating satellite screws. The multi-rotation system allows a significantly increased degassing output compared to single-shaft and multiple-shaft screw systems. As a result, the residence time of the molten plastic in the multi-rotation unit can be kept extremely short. The filling factor, i.e. the proportion of the volume occupied by the molten plastic during operation to the total free volume in the treatment chamber in which the rotor main shaft with the satellite screws rotates, is set in the construction by adjusting the diameter and pitch of the screws and is optimized for a given use case. Changes in the filling rate and residence time are in any case only possible to a limited extent during ongoing operation.

[0003] Furthermore, the known drive concept provides a drive zone for the satellite screw, which is located inside the treatment chamber provided for degassing. The molten plastic transferred from the metering zone is guided through the drive zone. On the one hand, the energy supply caused by the shear occurring there can be advantageous, since it promotes homogenization of the molten plastic. On the other hand, a high drive power is required to drive the extruder screw, which is in any case very long and has several zones in succession, together with the satellite screw from its end. This limits the processing of highly viscous molten plastics in such a multi-rotation system.

[0004] In the multi-spindle preparation machine described in CN 101293397, no external transmission is provided. All gears are located directly in the medium that is transported and processed in the preparation machine. This makes it impossible to isolate the heat at all. Moreover, the molten plastic is adversely affected by the shear that is exerted on it by the teeth in the drive zone. Moreover, the treatment chamber is so open in the direction of the drive that the rotating sealing ring is exposed there to the hot molten plastic.

[0005] The multi-screw extruder according to DE 10 2006 052 610 A1 has satellite screws which are arranged in a fixed position but are not part of the rotating unit. The processing unit and the gear unit are indeed separated from one another, but this is not intended for cooling purposes. Cooling is only provided via cooling channels.

[0006] The object of the invention is therefore to develop a multi-shaft preparation device for molten plastics of the type mentioned at the beginning in such a way that molten plastics, in particular highly viscous plastics, can also be processed successfully.

[0007] The solution according to the invention consists in a multi-spindle preparation device having the features of claim 1 .

[0008] According to the invention, the molten plastic is guided into the processing chamber from a remotely located melting extruder, so that the rotor body shaft, which serves as the main rotor shaft supporting the rotor body on which the satellite screws are supported, does not have a lead-in and metering zone.

[0009] The invention provides an external drive for a multi-shaft preparation machine, in which the central rotor body shaft and each individual satellite screw have an extended rear shaft end leading out from the treatment chamber. Between the extruder housing surrounding the treatment chamber and the transmission unit arranged outside the extruder housing, a decoupling device is provided by means of or in which possible negative effects on the transmission can be reduced or even compensated: i.e. The material flow in the form of a leakage stream leaving the extruder housing is interrupted in the separating device, so that contamination of the transmission with molten plastic is prevented even in the event of a fault, in which pressure builds up in the treatment chamber. - Alignment errors between the supports of the front shaft ends of the extruder housing and the transmission can be compensated for by the coupling device arranged in the separating device, also in cases where the satellite screws have no front support in the extruder housing or on the extruder screw shaft, but rotate freely in the cutouts in the rotor body shaft. - The heat flow from the treatment chamber by heat conduction through the section of the rotor body shaft and the satellite screw extending into the transmission can be reduced, especially if the separation device is circulated by a fluid. By choosing a suitable coupling device for the shaft section extending through the separation device, the heat flow can likewise be suppressed or interrupted. By such measures, the transmission temperature can be kept below 100°C.

[0010] The rotor body shaft has a seal and guide section on the side facing the separation device. Between this seal and guide section and the extruder bore in the housing, an annular gap is formed, which, with respect to its radial gap width and axial extension, is dimensioned in such a way that some molten plastic can penetrate therein to ensure lubrication. Via the seal and guide section, the rear end of the rotor body shaft is supported in the extruder housing.

[0011] At least one sealing means is provided in the annular gap, which prevents the molten plastic from flowing into the separating device. The sealing means can be formed by a return thread and / or a heat-resistant shaft sealing ring. The seal and guide section also forms a bearing for the satellite screw shaft extending therethrough. At least one sealing means is likewise provided between each bearing bore and the satellite screw shaft, which prevents the molten plastic from flowing along the satellite screw shaft into the separating device.

[0012] The rotor body shaft is preferably provided with 5 to 8 satellite screws, so that, depending on the construction dimensions, the recesses, each housing one satellite screw, and the sections of the rotor circumferential wall with the main screw webs can be arranged in alternating succession.

[0013] The separating device and / or the end section of the multi-shaft preparation unit adjacent to the separating device may be provided with a temperature control medium passage through which a cooling medium is passed, thereby making it possible to cool the hollow space of the separating device and thus to reduce the heat flow conducted to the transmission unit via the respective shaft section by thermal conduction.

[0014] The invention will now be explained in greater detail with further advantageous configurations and with reference to an embodiment shown in the drawing. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a side view showing the multi-axis preparation unit. [Diagram 2] FIG. 2 is a rear perspective view of the multi-axis preparation unit. [Diagram 3] FIG. 1 is a cross-sectional side view of a multi-axis preparation unit; [Figure 4] FIG. 2 is an enlarged cross-sectional view showing a portion of the multi-axis preparation unit. [Diagram 5] FIG. 2 is a perspective view showing a transmission unit and a separation device. [Figure 6] FIG. 2 is a perspective view showing a portion of the multi-axis preparation unit and a transmission unit.

[0016] 1 shows a side view of a multi-screw preparation unit 20. The multi-screw preparation unit 20 comprises an extruder housing 24 which contains an enclosed processing chamber 21 for molten plastic. Molten plastic supplied from an external melting extruder is introduced at peripheral inlet openings 26 in the housing periphery of the extruder housing 24 and is discharged at outlet openings 27 which are also arranged at the periphery. The outlet openings 27 are preferably arranged at the underside of the processing chamber 21 to facilitate gravity delivery in pressure-free operating conditions.

[0017] A flange 29 at the end side of the extruder housing 24 is provided with a connection to a temperature adjustment medium passage 28, which extends into the interior of a rotor main shaft having several satellite screws that rotate within the treatment chamber 21.

[0018] As is already clear from the view shown in FIG. 1, the drive unit 30 is arranged externally, i.e. outside the extruder housing 24, in particular completely outside the flow path for the molten plastic formed between the inlet opening 26 and the outlet opening 27. A motor 32 acts on the rotor body shaft in the treatment chamber 21 via a coupling unit 34 and a transmission unit 31. Between the transmission unit 31 and the rotor body shaft 22, a separating device 33 is provided, which blocks the medium and / or heat flows leaving the treatment chamber 21. The separating device 33 is thermally insulated and sealed with respect to the treatment chamber 21 and at the same time leads the shaft ends of all shafts of the multi-shaft preparation unit 20 in the direction of the transmission 31.

[0019] 2, which is a perspective view of the rear side of the multi-shaft preparation unit 20, one can see the rotor body shaft 22 with the satellite screws 23, which rotates beside suction openings 24.1, 24.2 in the extruder housing 24. A suction line of a vacuum pump is connected to each of the suction openings 24.1, 24.2. For effective degassing of the treatment chamber, the suction housing openings 24.1, 24.2 extend together over at least 75% of the axial length of the treatment chamber 21.

[0020] In Figure 3, the multi-axis preparation unit 20 with the drive unit 30 is shown in a cross-sectional side view, in which the feed openings 26, which are actually arranged laterally and peripherally, are rotated in the cross-sectional plane for better clarity.

[0021] In the process chamber 21 of the extruder housing 24, the rotor body shaft 22 with the satellite screws 23 is rotatably supported. The front support point of the rotor body shaft 22, seen in the flow direction, is formed in the region of a flange 29. The front support point can be preheated, for example at start-up, but can also be cooled, by means of a temperature-regulating medium channel 28 which opens into the region of the flange 29. The rear support point of the rotor body shaft 22 is formed by a seal and guide shoulder 22.3.

[0022] The required cooling power of the system can be significantly reduced according to the invention, because the drives of the satellite screws 23 are not located in the treatment chamber, as is common in the prior art, in the drive zone formed by the teeth on the rotor body shaft 22, but are completely separated into the area beyond the separating device 33. Due to the completely separated drives for all shafts, the energy supply is prevented, which would otherwise be caused by the shearing of the molten plastic, which always occurs there.

[0023] According to the invention, each satellite screw 23 is extended towards the rear by a shaft step 23.2 and terminates in the transmission 31 by a pinion 23.1. The transmission 31 comprises a toothed ring 31.2 with substantially internal toothing and a transmission rotor body 31.1, which is connected in a torque-transmitting manner on the one hand to the drive end 22.1 of the rotor body shaft 22 and, on the other hand, a support point is formed in the transmission rotor body 31.1 for each satellite screw 23. The satellite screws 23 are engaged by the respective pinions 23.1 in the toothed ring 31.2 and are driven via the toothed ring 31.2 when the rotor body shaft 22 is driven to rotate.

[0024] The separating device 33 has a hollow space 33.1 through which the rotor body shaft 22 and the shaft ends of the satellite screws 23 are guided. The shaft ends 23.2 of the satellite screws 23 are each divided inside the separating device 33 in the embodiment shown, and both shaft sections are each connected to a coupling element 25 arranged inside the hollow space 33.1. This makes it possible to compensate for possible alignment errors between the respective parts of the satellite screws 23 located in the extruder housing 24 and the ends of the satellite screws 23 supported on the gear rotor body 31.1. At the same time, the heat transfer into the gear 31 can be reduced.

[0025] Figure 4 shows a part of the cross-section shown in Figure 3 on a further enlarged scale, thereby showing in detail the rear area of ​​the extruder housing 24 and the gear unit 31 extended by the separating device 33. Since the cutting plane is horizontal in this figure, the cross-section also includes part of the lateral suction opening 24.1.

[0026] On the left side of Fig. 4, a section of the rotor body shaft 22 is visible. The rotor body shaft 22 has a main screw web 22.5, the outer diameter of which corresponds approximately to the inner diameter of the cylindrical cavity in the extruder housing 24, which forms the treatment chamber 21. Distributed over the entire circumference, the rotor body shaft 22 is provided with a number of deep cuts, which each form a receiving groove 22.6 for a satellite screw 23. For the sake of better illustration, the satellite screws are not shown in Fig. 4 in the receiving groove 22.6 facing the viewer.

[0027] In the illustrated embodiment, each shaft section 23.2 of the satellite screws 23 is guided firstly through the seal and guide section 22.3 of the rotor shaft 22 at the rear end of the extruder housing 24 and then through a pressure-free cavity 33.1 in the separating device 33. The shaft sections 23.2 of the satellite screws 23 guided through the seal and guide section 22.3 are each provided with a return thread 23.4, the orientation of which is selected such that in each direction of rotation of the rotor body shaft 22 and the satellite screws 23, which is applied during operation, a conveying direction in the direction of the delivery opening towards the processing chamber 21, i.e. a conveying direction away from the gear unit 31, occurs. The seal and guide shoulder 22.3 also has at least one return thread 22.4 on its outer circumferential surface, which is also aligned in the direction of rotation of the rotor body shaft 22 during operation so that conveying takes place in the direction of the delivery opening.

[0028] In most operating conditions, the treatment chamber 21 is usually not under internal pressure, since a relatively low filling rate is set in the multi-shaft preparation unit 20 and a vacuum is applied to the suction openings. The seal and guide section 22.3 with the return thread 22.4 and the shaft shoulder 23.2 with the return thread 23.3 therefore do not need to be pressure-sealed in normal operation and serve as a safeguard against unforeseen operating conditions and at other times avoid the general dragging of molten plastic into the gear unit 31 via the separating device 33.

[0029] On the outside of the housing of the separating device 33 there is provided a temperature control medium channel 33.3 through which a cooling medium is circulated.

[0030] On the other side of the transmission unit 31 there is a coupling unit 34 with a shaft coupling 34.1, by means of which the transmission rotor body 31.1 is connected to the driven shaft 32.1 of the motor 32.

[0031] The transmission unit 31 is shown in a perspective view in Figure 5. The rotor body shaft 22 and the shaft shoulders 22.2, 23.2 of the satellite screws extend into the transmission rotor body 31.1 through a hollow space 33.1 of the separating device 33. The drive shaft end 22.1 of the rotor body shaft 22 is provided with external teeth which engage in a correspondingly toothed receiving bore in the center of the transmission rotor body 31.1.

[0032] The transmission rotor body 31.1 and the rotor body shaft 22 are thus connected in a torque-transmitting manner so as not to rotate relative to each other. The satellite screws 23 are supported at their shaft shoulders 23.2 in rolling bearings 31.5 in the transmission rotor body 31.1, on both sides of a toothed ring 31.2 which is also fixedly fixed in the transmission housing 31.4. Between the support points, the satellite screws 23 each have a pinion 23.1 which engages with the toothed ring 31.2. The satellite screws 23 are thus driven in the opposite direction to the rotor body shaft 22 by the rotation of the transmission rotor body 31.1 relative to the transmission housing 31.4. The rotation speed of the satellite screws 23 is then determined by the pitch diameter of the pinion 23.1 and the toothed ring 31.2 and is preferably approximately three times the rotation speed of the transmission rotor body 31.1. The satellite screws 23 are therefore in this embodiment only driven by the internal toothing of the toothed ring 31.2 and are not engaged with the other external toothing of the transmission rotor body 31.1, i.e. the satellite screws 23 are not driven by the sun gear and therefore the transmission unit 31 is not a planetary gear transmission.

[0033] The transmission rotor body 31.1 is provided on its outer periphery with a number of sealing rings 31.6, 31.7, by means of which the oil-filled interior space 31.8 of the transmission unit 31 can be sealed against the hollow space 33.1 of the separation unit 33. A shaft sealing ring 31.8 is provided to seal the through-hole in the transmission rotor body 31.1 for the shaft step 23.2 of the satellite screw 23 against the hollow space 33.1 of the separation unit 33.

[0034] FIG. 6 shows the rear area of ​​the rotor body shaft 22 and the gear unit 31 located behind it. The extruder housing and the housing of the separating device are not shown. On its side facing the gear unit 31, the rotor body shaft 22 has a seal and guide section 22.3, which is provided with a return thread 22.4 on its outside. Between the seal and guide section 22.3 and the extruder bores in the housing, annular gaps are formed, which, with respect to their radial gap width and axial extension, are dimensioned large and long enough that some molten plastic can penetrate therein to ensure lubrication. Via the seal and guide section 22.3, the rear end of the rotor body shaft 22 is supported in the extruder housing. The seal and guide section 22.3 forms a bearing for the satellite screw shaft steps 23.2 extending therethrough with a number of bores arranged on the pitch circle. [Explanation of symbols]

[0035] 20 Multi-axis adjustment unit 21 Processing Room 22 Rotor body shaft 22.1 Drive End 22.2 Shaft steps 22.3 Seal and guide divisions 22.4 Return thread 22.5 Main screw web 22.6 Receiving Groove 23 Satellite screw 23.1 Pinion 23.2 Shaft steps 23.4 Return thread 24 Extruder housing 24.1,24.2 Suction opening 25 Coupling elements 26 Inlet opening 27 Delivery opening 28 Temperature adjustment medium passage 29 Flange 30 Drive unit 31 Transmission unit 31.1 Transmission rotor body 31.2 Toothed ring 31.4 Transmission housing 31.5 Rolling bearings 31.6,31.7 Seal ring 31.8 Shaft seal ring 32 Motor 32.1 Driven shaft 33 Separation device 33.1 Hollow chamber 33.3 Temperature adjustment medium passage 34 Coupling unit 34.1 Shaft Couplings

Claims

1. A multi-shaft preparation unit (20) for molten plastics, comprising at least an extruder housing (24) with an enclosed treatment chamber (21) for molten plastics therein, and at least one rotor body shaft (22) rotatably supported in said treatment chamber (21), the rotor body shaft (22) having a number of receiving grooves (22.6) in each of which a satellite screw (23) is supported, the multi-shaft preparation unit (20) has a drive unit (30) in which a transmission unit (31) is arranged outside the extruder housing (24) between a drive motor (32) and the treatment chamber (21), the transmission unit (31) being connected to the rotor body shaft (22) and to the drive shaft steps (22.2, 23.2) of the satellite screws (23) which are led out of the treatment chamber (21) of the extruder housing (24); - between the extruder housing (24) and the transmission unit (31) there is provided a separating device (33) for isolating the fluid and / or heat flows emerging from the treatment chamber (21), through which the drive shaft stages (22.2, 23.2) of the rotor body shaft (22) and of the satellite screws (23) are guided, the drive shaft stages (22.2, 23.2) of the rotor body shaft (22) and of the satellite screws (23) being guided through at least one hollow space (33.1) provided in the separating device (33), the rotor shaft (22) and the drive shaft steps (22.2, 23.2) of the satellite screws (23) are guided through holes in a seal and guide body (22.3) which closes the rear part of the treatment chamber (21) on the rotor shaft (22); A multi-axis preparation unit (20).

2. 2. The multi-shaft preparation unit (20) according to claim 1, characterized in that at least one temperature-regulating medium passage (33.3), through which a temperature-regulating fluid can flow, is formed in the end of the extruder housing (24) facing the hollow chamber (33.1) and / or in the wall of the separating device (30).

3. 3. A multi-shaft preparation unit (20) according to claim 1 or 2, characterized in that the drive shaft stages (23.2) of the satellite screws (23) are each divided into two sections in the hollow space (33.1), and the two sections are each connected to each other by means of a coupling element (25).

4. 4. A multi-axis preparation unit (20) according to claim 3, characterized in that the coupling element (25) is formed as a metal bellows coupling.

5. 5. The multi-axis preparation unit (20) according to claim 1, characterized in that the drive shaft step (23.2) of the satellite screw (23) is provided with a return thread (23.4) over at least a part of the length section located in the respective bores of the seal and guide body (22.3).

6. 5. The multi-shaft preparation unit (20) according to claim 1, characterized in that the seal and guide body (22.3) on the rotor body shaft (22) is provided with a return thread (22.4) over at least a part of its length.

7. - said rotor body shaft (22) is connected to the transmission rotor body (31.1) of said transmission unit (31); the drive shaft step (23.2) of the satellite screw (23) is rotatably supported in the transmission rotor body (31.1), the satellite screws (23) each with a pinion (23.1) at their end engaging only with a fixed internal toothing (31.2) surrounding the transmission rotor body (31.1); A multi-axis preparation unit (20) according to any one of claims 1 to 6, characterised in that it is

8. 8. A multi-screw preparation unit (20) according to any one of the preceding claims, characterized in that the extruder housing (24) is provided with a downwardly facing delivery housing opening (27).

9. 9. A multi-shaft preparation unit (20) according to any one of claims 1 to 8, characterized in that the extruder housing (24) of the multi-shaft preparation unit (20) is provided with at least one suction opening (24.1, 24.2) to which a vacuum pump is connected, the suction opening or openings (24.1, 24.2) together extending over at least 75% of the axial length of the treatment chamber (21).

Images