DE102021124034A1 - Extruder screw for a multi-screw extruder and multi-screw extruder - Google Patents

Abstract

Extruder screw (100) for a multi-screw extruder, at least comprising:
- a collection and metering section (30),
- A rotor body section (50) which is enlarged in diameter compared to the intake and metering section (30) and has a plurality of satellite screws (20) which are arranged openly at least over part of their length on the outer circumference of the rotor body section (50); A cone (11) and an adjoining drive zone are formed between the intake and metering section (30) and the rotor body section (50), in which the satellite worms (20) each have a pinion (21) in an internal toothing in or on engage the inner wall of an extruder barrel of the multi-screw extruder;
the drive zone being formed on a support bearing element which has a groove (15) for each satellite worm (20) for receiving the pinion (21) and the satellite worms (20) each in at least one plain bearing arranged next to the pinion (21) in the support bearing element is stored.

Description

The invention relates to an extruder screw for a multi-screw extruder having the features of the preamble of claim 1 and to a multi-screw extruder having the features of the preamble of claim 9.

A multi-rotation system (MRS) has proven itself for the processing of plastic melts, in particular polyester WO 2003 033 240 A1 is fundamentally described. It contains an extruder screw that includes a so-called polyrotation unit with a rotor body shaft between an entry zone for drawing in and melting the plastic and a discharge zone. The latter has a significantly larger diameter than the other zones and also has several rotating satellite snails. With the multi-rotation system, a significant increase in degassing performance is achieved compared to single and twin screw systems. Consequently, the dwell time of the melt in the polyrotation unit can be kept very short.

The known drive concept provides a drive zone for the satellite screws, which is located within the treatment space provided for the degassing. Locating the drive zone directly at the upstream end of the multi-rotation unit is necessary in most applications and cannot be moved to the downstream end in order to keep the length of that section of the extruder screw that is loaded by the drive torque short.

The melt transferred from the metering zone via the cone is guided through the drive zone of the satellite screws. In some applications, the energy input that takes place via the shearing that occurs there can be advantageous because it promotes the homogenization of the plastic melt. On the other hand, the shearing of the polymer in the drive zone can be detrimental to the product properties.

The propulsion zone of the satellite scrolls is highly stressed in various respects. The gearing, consisting of the pinions attached to the satellite worms and a gear ring with internal gearing on the housing side, can only be lubricated by the hot polymer. It is therefore necessary for the polymer to flow through the drive zone. As a result, hard plastic particles that are not completely melted in the metering zone also get into the drive zone. When recycling plastics, impurities such as metal particles or grains of sand can also be contained in the plastic melt. In addition, the melt pressure of the melt flowing on the outer circumference of the extruder screw means that the pinions of the floating satellite screws are pressed into the receiving grooves on the satellite carrier element and the tooth flanks there cause heavy wear and are also subject to heavy wear.

The object of the invention is therefore to improve an extruder screw for an MRS system or a multi-screw extruder equipped with it in such a way that the wear in the drive zone of the satellite screws is reduced.

The solution according to the present invention consists in an extruder screw having the features of claim 1 or a multi-screw extruder having the features of claim 7.

According to the invention, the satellite screws are supported in their grooves in the satellite screw carrier element at least on one side next to the pinion via a slide bearing in order to counteract the melt pressure and to prevent the pinion from scraping the bottom of the groove with its outer flanks of the teeth.

For this purpose, provision can be made for the end of the satellite worm to be in the form of a bearing shoulder which is mounted in a bearing recess on the satellite worm carrier element. In this embodiment, the bearing recess is located directly behind the cone, which represents the transition between the metering zone and the degassing zone.

In order to be able to compensate for tolerances that can occur as a result of the heating or cooling of the extruder screw during operation, the bearing shoulders are not to be used directly in the respective bearing recess, but rather to be stored in a bearing insert element additionally used there.

According to a preferred embodiment, the satellite worm is supported on both sides next to the pinion in plain bearings. In addition to the bearing at the end, another bearing shoulder is formed between the area of the worm, which has a worm web, and the area for receiving the pinion.

Particularly preferably, the bearing bores of the end bearing and of the second bearing that may be present on the other axial side of the pinion are each formed in a separate bearing insert element, which is inserted into the groove on the satellite worm carrier element. In the case of the bearing insert element, the outer contour largely corresponds to the inner contour the receiving groove. Since this is preferably deeply incised, the bearing insert element is held in the groove in a form-fitting manner without additional securing elements in the cross-sectional plane aligned transversely to the central axis and can be inserted together with the satellite worm into the satellite worm carrier element. A deep cut groove is when the cross-section of the groove covers an arc greater than 180°.

Furthermore, the bearing at the end of the satellite worm is preferably also formed by such a bearing insert element, which is inserted into the groove. This means that both bearing insert elements can be easily replaced when they are worn. A metallic material can be chosen for them, which is post-compacted by Hot Isostatic Pressing (HIP) in order to increase wear resistance. The satellite worm carrier element can thus be formed from other suitable materials, independently of the requirements for the strength of the bearing points.

According to an advantageous embodiment, a substantial proportion of the melt flow in the drive zone is not guided over the pinions but in channels within the support bearing past the pinions. The advantage of this is that the melt is not heated by shearing. When processing PET, for example, it is advantageous if the melt is not completely plasticized and is therefore relatively cool, so that excessive degradation of the melt in the entry area can be avoided. A further advantage for the extruder screw itself is that the risk of damage to it if the melt is contaminated is reduced.

For the effectiveness of the flow channels, it is important that they are large enough so that a major part of the volume flow of the polymer conveyed and treated with the extruder screw is not passed through the drive zone. Sufficient cross-section is also important to prevent incompletely plasticized feed screw material from clogging the channels and leading to high pressure drops. Both cause a high head pressure at the end of the feed and thus a significantly higher energy input and thus avoid damage to the melt.

In concrete terms, the channels should offer at least 5 mm of free cross-section in each dimension, preferably 8 mm to 10 mm.

It is also possible for the flow channels to be routed around the toothing on the outside, that is to say to be introduced into the wall of the extruder housing and/or into the stator ring.

The annular gap between the outside of the support bearing element and the inside of the extruder bore in the housing should have a radial width of preferably 1 mm to 3 mm and a maximum of 5 mm. With a diameter of 130 mm, for example, the annular gap is measured at 1.6 mm to 2.0 mm.

This ensures that only a small volume flow flows over the outer circumference, so that the polymer can act as a lubricant in the drive zone, while the larger part of the volume flow is divided between the flow channels and thus does not experience any shearing in the drive zone. It is also advantageous if the size of the annular gap is chosen to be so small, since foreign bodies are retained in the melt flow that are of such a size that they can lead to significant mechanical damage to the toothing.

• 1 Teile einer Extruderschnecke in perspektivischer Ansicht:
• 2 eine perspektivische Ansicht auf das Satellitenschneckenträgerelement nach einer ersten Ausführungsform;
• 3A, 3B jeweils Teile der Extruderschnecke mit dem Satellitenschneckenträgerelement nach 2 in perspektivischer Ansicht; und
• 4 Teile eines Mehrschneckenextruders mit der Extruderschnecke in seitlicher Schnittansicht;
• 5 eine perspektivische Ansicht auf ein Satellitenschneckenträgerelement nach einer zweiten Ausführungsform;
• 6 eine perspektivische Ansicht auf die Rückseite des Stützlagerelements nach 5;
• 7 eine perspektivische Ansicht auf eine Anordnung mehrerer Satellitenschnecken der Extruderschnecke; und
• 8 eine perspektivische Ansicht auf ein Satellitenschneckenträgerelement nach einer dritten Ausführungsform.

The invention is explained in more detail below using an exemplary embodiment and with reference to the drawings. The figures show in detail:

• 1 Perspective view of parts of an extruder screw:
• 2 a perspective view of the satellite worm carrier element according to a first embodiment;
• 3A , 3B parts of the extruder screw with the satellite screw carrier element 2 in perspective view; and
• 4 Parts of a multi-screw extruder with the extruder screw in a side sectional view;
• 5 a perspective view of a satellite worm carrier element according to a second embodiment;
• 6 a perspective view of the back of the support bearing element 5 ;
• 7 a perspective view of an arrangement of several satellite screws of the extruder screw; and
• 8th a perspective view of a satellite worm carrier element according to a third embodiment.

In 1 parts of an extruder screw 100 for a multi-screw extruder are shown in perspective, namely the transition region between a feed and metering section 30 with a screw flight 31 and a multi-screw section with a plurality of satellite screws 20 is shown there. In between is a cone 11 from formed so that the diameter of the extruder screw 100 expands in the direction of flow. The cone 11 is part of a support bearing element 10. The satellite worms are each mounted with their end, which is provided with a pinion 21, in grooves introduced therein.

An elongated, axial section of the support bearing element 10 is provided between adjacent pinions 21, in which section a tubular flow channel 13 is formed. The flow channel 13 extends from an inlet opening 12 on the cone 11 to an outlet opening 14 which is arranged beyond the pinion 21 in the axial extension of the extruder screw 100 and seen in the direction of flow.

2 is a perspective view of the support bearing element 10. This has a groove 15 for each satellite worm, in which the pinion is mounted, and a bearing recess 16 in front of the head, into which a bearing shoulder of the satellite worm or the pinion can be inserted. The bearings of the satellite screws and the pinion are lubricated by the polymer conveyed with the extruder screw. Since the bearing recesses 16 are shielded from the flow by the cone 11, radial bores 17 are provided, each of which extends from the outer circumference into the bearing recess 16.

In 2 a trapezoidal, almost triangular cross section of the flow channels 13 is also clearly visible. Because the tip of the triangular cross-sectional area points to the central axis and the wide base is on the outer circumference, the space between the sprockets is optimally used. The outlet openings 14 of the flow channels 13 are not located at the end of the support bearing element 10; on the contrary, the flow channels 13 extend axially only approximately as far as the pinions reach.

The advantage of this arrangement arises from 3A . There, the extruder screw 100 is shown in perspective with its feed and metering section 30, the support bearing element 10 and the satellite screws 20. Additionally, a portion of a rotor body portion 50 adjoining the support bearing member 10 is shown.

The grooves 15 of the support bearing element 10 each continue in grooves 52 on the rotor body section 50 . The satellite augers 20 are guided therein, being exposed to the outside. The rotor body section 50 has parts of its own main screw flight 51 between the grooves 52. Because the outlet openings 14 of the flow channels 13 do not extend to the end of the support bearing element 10, the melt escaping from the outlet opening 14 reaches the intake area of the main screw flight 51 and directly to the side the webs 22 on the satellite worms 20.

3B is similar to 3A . Compared to the representation in 3A however, the rotor body portion is not shown. In addition, one of the pinions 20 of a satellite worm 20 has been removed in order to allow a view of the formation of the satellite worm 20 in its end region. The long part of the satellite screws 20 provided for the polymer processing, which is provided with a web 22, ends at a collar 23, the diameter of which is so large that a bearing shoulder 24 lying behind it is largely covered. This prevents excessive backflow from the degassing chamber of the extruder into the area of the pinion 20 during operation.

The bearing shoulders 24 of the satellite worms 20 are each accommodated in a bearing insert element 60 which is inserted into the groove 15 of the support bearing element 10 . A bearing section 25 , which accommodates the pinion 21 , is formed on all satellite worms 20 behind the bearing point 24 . At the very end there is a bearing shoulder 26 which engages directly in the bearing recess 16 in the support element 10 or in a slide bearing element located there.

4 shows parts of a multi-screw extruder 200 in a side sectional view. Shown is the same section of the extruder screw shaft 100 as in FIG 3A , Which is rotatably mounted in an extruder housing 40 with an extruder bore 41 . The extruder housing 40 has a transition housing part 42 for accommodating the cone 11 and a housing part 43 with a reduced diameter for accommodating the feed and metering section 30 of the extruder screw 100. In the drive zone, a stator ring 44 is inserted into the extruder bore 41, which has internal teeth, in which the pinions 21 of the satellite worms 20 engage. In addition, a baffle ring 45 is used in order to be able to set the annular gap between an inner wall of the extruder housing 40 and the outer circumference of the extruder screw 100 at this point.

5 shows a further embodiment of a support bearing element 110 with grooves 115 for receiving the satellite worms with their pinions. Bearing recesses 116 are formed on a rear section, which is designed as a cone 111, in which a slide bearing element 170 with a clamping ring 171 is inserted for each satellite worm, which serves to hold the slide bearing element 170 in the support bearing element 110. Because of different thermal expansion, the Change fit between the support bearing element 110 and the plain bearing element 170. The clamping ring 171 prevents the slide bearing element 170 from rotating in the support bearing element 110 .

A bearing insert element 160 with a bearing recess 161 is inserted into the groove 115 for the respective second bearing point. Different in comparison to the first embodiment of the support bearing element according to FIGS 3A , 3B and 4 is that the support bearing element 110 flow channels 113 are formed, which are open on the outer circumference. A channel 118 branches off from each of them and opens into the bearing recess 161 of the bearing insert element 160 in order to ensure lubrication there.

6 is a perspective view of the back of the support bearing element 110. The bores 117, which are each arranged between two inlet openings 112 of the flow channels 113 and laterally in the bearing recesses 116 (see 5 ) to lubricate the plain bearings arranged there with polymer that is diverted from the production flow.

7 FIG. 13 shows three of the satellite snails 120 designed for inclusion in the FIG 5 and 6 shown support bearing element 110 are determined.

A satellite worm 120 with a worm flight 122 without additional parts is shown on the left. The screw flight 122 ends at a collar 123. A bearing section 125 is formed behind it.

A pinion 121 is placed on the bearing section 125 in the middle satellite worm 120 . This includes not only a toothed area, but also a bearing shoulder 124, 126 with spiral grooves on each side thereof to improve lubrication.

• - das Ritzel 121;
• - ein Lagereinsatzelement 160, in das der Lagerabsatz 124 des Ritzels 121 eingeführt ist;
• - ein Gleitlagerelement 170, in das der Lagerabsatz 126 eingeführt ist; und
• - einen das Gleitlagerelement 170 umgebenden Spannring 171.

At the far right in 7 satellite screw 120 shown are attached:

• - the pinion 121;
• - A bearing insert element 160 in which the bearing shoulder 124 of the pinion 121 is inserted;
• - A plain bearing element 170 into which the bearing shoulder 126 is inserted; and
• - a clamping ring 171 surrounding the plain bearing element 170.

8th shows a third embodiment of a support bearing element 210, which in turn has a cone 211 at one end and a large number of undercut grooves 215 on the circumference, in which the drive zone of the satellite worms with their pinions is formed. In the case of the support bearing element 210, the bearing mounts 261 for the two bearing points of the satellite worms are provided in separate bearing insert elements 260 on both sides of the respective pinion. Flow channels 213 extend from inlet openings 212 on the cone 211 to outlet openings 214. Channels 218 branch off from the flow channel 213 and extend into the bearing receptacles 261 of the bearing insert elements 260. The bearing insert elements 260 are also in this embodiment with their outer contour to the inner contour of the grooves 215 adjusted so that they are positively defined in a plane transverse to the central axis. The bearing insert elements 260 are axially fixed by shoulders on the satellite worms.

Reference List

200

multi-screw extruder

100

extruder screw

10; 110; 210

support bearing element

11; 111; 211

cone

12; 112

entrance opening

13; 113

flow channel

14; 214

exit port

15; 115; 215

groove

16; 116; 216

bearing recess

17; 117; 217

drilling

118; 218

channel

20; 120

satellite snail

21; 121

pinion

22; 122

snail web

23; 123

Federation

24; 124

stock sales

25; 125

Bearing section to accommodate the pinion

26; 126

stock sales

30

Feeding and metering section

31

snail web

40

extruder body

41

extruder bore

42

transition housing part

43

housing part

44

Stator ring with internal teeth

45

constriction ring

50

rotor body section

51

main screw flight

52

groove

70; 170

plain bearing element

60; 160; 260

bearing insert element

161; 261

stock shots

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2003033240 A1 [0002]

Claims (7)

Extruder screw (100) for a multi-screw extruder (200), at least comprising: - a feed and metering section (30), - a rotor body section (50) which is larger in diameter than the feed and metering section (30) and which has a plurality of satellite screws (20 ) which are arranged lying openly on the outer periphery of the rotor body section (50) over at least part of their length; wherein between the intake and metering section (30) and the rotor body section (50) a cone (11; 111; 211) and an adjoining drive zone are formed, in which the satellite worms (20) each have a pinion (21) in a Internal teeth engage in or on the inner wall of an extruder housing (40) of the multi-screw extruder (200); the drive zone being formed on a support bearing element (10; 110; 210) which has a groove (15; 115; 215) for each satellite worm (20) to accommodate the pinion (21), characterized in that the satellite worms (20) is mounted in at least one slide bearing (70 (; 170)) arranged next to the pinion (21) in the support bearing element (10; 110; 210). extruder screw (100) after claim 1 , characterized in that the satellite worms (20) each have an end bearing shoulder (26) in a slide bearing (70; 170) in a bearing mount (16; 116; 216) in the support bearing element (10; 110; 210) or in a bearing insert element (60; 160; 260) inserted therein. extruder screw (100) after claim 1 or 2 , characterized in that the satellite worms (20) are each mounted in a sliding bearing (70; 170) which is arranged at an axial position between the pinion (21) and the start of the worm flight (22). extruder screw (100) after claim 2 or 3 , characterized in that at least one bearing seat (16; 116; 216) for the sliding bearing (70; 170) is formed in a bearing insert element (60; 160; 260) which is detachably inserted into the groove (15; 115; 215). . extruder screw (100) after claim 4 , characterized in that the groove (15; 115; 215) is undercut and that the bearing insert element (60; 160; 260) is held positively in the groove (15; 115; 215) in a plane transverse to the central axis of the extruder screw (100). is. Extruder screw (100) according to one of the preceding claims, characterized in that at least one bore (17; 117; 217) is made on the outer circumference of the support bearing element (10; 110; 210) for each slide bearing (70; 170) and extends to the groove (15; 115; 215) for the pinion (21) or into the bearing mount (16; 116; 216). Multi-screw extruder (200), at least comprising an extruder housing (40) with an extruder bore (41) in which an extruder screw (100; 100'; 100") according to one of the preceding claims is rotatably mounted.

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