SUPPORT BEARING ELEMENT FOR AN EXTRUDER SCREW FOR A MULTI-SCREW EXTRUDER

Abstract

A support bearing element for an extruder screw for a multi-screw extruder, at least comprising a cone, a plurality of grooves, which are located on the outer periphery and are axially parallel to the axis of rotation of the support bearing element, each for receiving a satellite screw and a drive pinion connected thereto. At least one plain bearing is provided in the groove in order to support the satellite screw next to the drive pinion thereof, the plain bearing being positioned or designed in a bearing holder formed on the support bearing element.

Claims

1. A support bearing element for an extruder screw for a multi-screw extruder, the support bearing element comprising: a cone; a plurality of grooves arranged on an outer periphery and are axially parallel to the axis of rotation of the support bearing element, each for receiving a satellite screw and a drive pinion connected thereto; and at least one plain bearing provided in the groove in order to support the satellite screw next to the drive pinion thereof, the plain bearing being positioned or designed in a bearing holder formed on the support bearing element.

2. The support bearing element according to claim 1, wherein at least one plain bearing is positioned in a bearing insert element that is detachably inserted into the groove.

3. The support bearing element according to claim 2, wherein the groove is undercut and that the bearing insert element is positively retained in the groove in a plane transversely to the central axis of the extruder screw.

4. The support bearing element according to claim 1, wherein at least one bore is inserted on the outer periphery of the support bearing element for each plain bearing, which extends into the respective groove for the drive pinion of the satellite screw or into the bearing holder.

5. The support bearing element according to claim 1, wherein, between at least two adjacent grooves, a flow channel is formed in the support bearing element, which extends from an inlet opening on the cone to an outlet opening arranged in the direction of flow behind the position provided for the drive pinions.

6. An extruder screw for a multi-screw extruder, the extruder screw comprising: an intake and metering section; a rotor body enlarged in diameter as compared to the intake and metering section; a plurality of satellite screws, which have at least one screw flight and are located on the outer periphery of the rotor body exposed at least part over part of their length; a drive zone on the rotor body in which the satellite screws each have a drive pinion in order to engage in an internal toothing in or on the inner wall of an extruder housing of the multi-screw extruder; a cone formed between the intake and metering section and the drive zone on the rotor body; wherein the rotor body is connected to the support bearing element according to claim 1, on which the cone is formed and that the satellite screws are each mounted in at least one plain bearing in the support bearing element arranged next to the drive pinion.

7. The extruder screw according to claim 6, wherein the satellite screws each have an end-side bearing shoulder which is mounted in a plain bearing in a bearing holder in the support bearing element or in the rotor body in a bearing insert element inserted therein.

8. The extruder screw according to claim 7, wherein the plain bearing for the end-side bearing shoulder of the satellite screws is each arranged in a bearing holder in the support bearing element, which is arranged next to the cone.

9. The extruder screw according to claim 7, wherein the satellite screws are each mounted in at least one plain bearing which is positioned at an axial position between the drive pinion and the beginning of the screw flight.

10. The multi-screw extruder comprising: an extruder housing with an extruder bore; and an extruder screw according to claim 6, which is rotatably mounted in the extruder bore and whose drive pinion engages in an external toothing on the rotor body section of the extruder screw or in an internal toothing in a stator ring or in the inner wall of the housing.

11. The multi-screw extruder according to claim 10, further comprising a drive zone in which the drive pinions are arranged in the grooves, wherein, in the support bearing element, at least one flow channel is formed between two adjacent grooves or in a housing wall of the extruder housing, at least one flow channel is formed which, seen in the longitudinal direction, extends from an inlet opening located in front of the position of the drive pinions to an outlet opening located beyond the drive pinions.

12. The multi-screw extruder according to claim 11, wherein the flow channels are completely closed and tubular in shape.

13. The multi-screw extruder according to claim 11, wherein the flow channels are designed to be open on the outer periphery.

14. The multi-screw extruder according to claim 11, wherein the flow channels are formed in a stator ring and/or in a retaining ring inserted into the extruder bore in the drive zone.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0026] FIG. 1 is a support bearing element with further parts of an extruder screw in perspective view;

[0027] FIG. 2 is a perspective view of the support bearing element according to an example;

[0028] FIGS. 3A and 3B are case parts of the extruder screw with the support bearing element according to FIG. 2 in perspective view; and

[0029] FIG. 4 shows parts of a multi-screw extruder with the extruder screw in lateral section view;

[0030] FIG. 5 is a perspective view of a support bearing element according to an example;

[0031] FIG. 6 is a perspective view of the back of the support bearing element as shown in FIG. 5;

[0032] FIG. 7 is a perspective view of an arrangement of several satellite screws of the extruder screw; and

[0033] FIG. 8 is a perspective view of a support bearing element according to an example.

DETAILED DESCRIPTION

[0034] FIG. 1 shows a support bearing element 10 with further parts of an extruder screw 100 for a multi-screw extruder in perspective view, namely the transition area between an intake and metering section 30 with a screw flight 31 and a multi-screw section with several satellite screws 20. In between, a cone 11 is 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. In grooves inserted therein, the satellite screws 20 are each supported with their end section, which is provided with a drive pinion 21.

[0035] Between adjacent drive pinions 21, an elongated, axial section of the support bearing element 10 is provided, in which 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 ends in axial extension of the extruder screw 100 and in the direction of flow beyond the drive pinion 21.

[0036] FIG. 2 is a perspective view of the support bearing element 10. This has a groove 15 for each satellite screw, in which the drive pinion is mounted, and a bearing recess 16 in front of the head, into which a bearing shoulder of the satellite screw or the drive pinion can be inserted, so that a plain bearing is formed. The plain bearings of the satellite screws, such as the drive pinions, 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 for the lubrication of the plain bearings, each of which extends from the outer circumference to the bearing recess 16.

[0037] FIG. 2 also clearly shows a trapezoidal, almost triangular cross-section of the flow channels 13. The fact that the tip of the triangular cross-sectional surface points to the central axis and the wide base is on the outer periphery makes optimum use of the space between the drive pinions. In each case, the outlet openings 14 of the flow channels 13 are not located at the end of the support bearing element 10; rather, the flow channels 13 extend axially only about as far as the drive pinions reach.

[0038] The advantage of this arrangement is shown in FIG. 3A. There, the extruder screw 100 with its intake and metering section 30, the support bearing element 10 and the satellite screws 20 is shown in perspective. In addition, a part of a rotor body 50 is shown, which adjoins the support bearing element 10.

[0039] The grooves 15 of the support bearing element 10 continue in grooves 52 on the rotor body 50. The satellite screws 20 are guided in grooves 15, 52, wherein they are exposed with the outside. The rotor body 50 has portions of its own main screw flight 51 between the grooves 52. As a result of the fact that the outlet openings 14 of the flow channels 13 do not extend to the end of the support bearing element 10, the melt gushing out of the outlet opening 14 reaches directly laterally into the intake area of the main screw flight 51 and the flights 22 on the satellite screws 20.

[0040] A plain bearing element 70 is mounted on a rear bearing shoulder terminating in front of the area of the screw flight 22, which has a helical non-return valve on the outer periphery in order to convey melt in the direction of the treatment chamber, and thus away from the drive pinion 21.

[0041] FIG. 3B is similar to FIG. 3A. Compared to the illustration in FIG. 3A, however, the rotor body is not shown. In addition, one of the drive pinions 20 of a satellite screw 20 is removed to allow for a view of the formation of the satellite screws 20 in their end area.

[0042] The long part of the satellite screws 20 intended for polymer processing, which is provided with the screw flight 22, ends at a flange 23, the diameter of which is so large that the adjacent bearing shoulder is largely covered. This prevents excessive backflow from the degassing chamber of the extruder into the area of the drive pinion 21 during operation.

[0043] The plain bearing elements of the satellite screws 20 are each received in a bearing insert element 60, which is inserted into the groove 15 of the support bearing element 10. Behind the shoulder 24 for the plain bearing element, a bearing section 25 is formed on each of the satellite screws 20, which receives the drive pinion 21.

[0044] At the very end of the satellite screw 20, another bearing shoulder 26 is formed, which either engages directly with the bearing recess 16 in the support element 10 and forms a plain bearing with the bearing recess or which engages in a separate plain bearing element located there.

[0045] FIG. 4 shows parts of a multi-screw extruder 200 in lateral sectional view. The same section of the extruder screw shaft 100 is shown as in FIG. 3A. The extruder screw shaft 100 is rotatably mounted in an extruder housing 240 with an extruder bore 241.

[0046] The extruder housing 240 has a transition housing part 242 to receive the cone 11 and a housing part 243 with a reduced diameter to receive the intake and metering section 30 of the extruder screw 100. In the drive zone, a stator ring 244 is inserted into the extruder bore 241, which has an internal toothing into which the drive pinions 21 of the satellite screws 20 engage. In addition, a retaining ring 245 is used to adjust the annular gap between an inner wall of the extruder housing 240 and the outer periphery of the extruder screw 100 at this point.

[0047] FIG. 5 shows a further example of a support bearing element 110 with grooves 115 for accommodating the satellite screws with their drive pinions. On a rear section, which is designed as a cone 111, bearing recesses 116 are formed, in which one plain bearing element 170 with a clamping ring 171 is inserted for each satellite screw, which serves to hold the plain bearing element 170 in the support bearing element 110. Due to differences in thermal expansion, the fit between the support bearing element 110 and the plain bearing element 170 may change. The clamping ring 171 prevents the plain bearing element 170 from rotating in the support bearing element 110.

[0048] For each second bearing point, a bearing insert element 160 with a bearing recess 161 is inserted into the groove 115. What differs from the first embodiment of the support bearing element 10 according to FIGS. 3A, 3B and 4 is that in the support bearing element 110 flow channels 113 are formed, which are open at the outer periphery. A channel 118 branches off from each of them, which ends in the bearing recess 161 of the bearing insert element 160 in order to ensure lubrication there.

[0049] FIG. 6 is a perspective view of the rear of the support bearing element 110. Of particular note are the holes 117, each of which is located between two inlet openings 112 of the flow channels 113 and ends laterally in the bearing recesses 116 (see FIG. 5) in order to lubricate the plain bearings arranged there with polymer that is diverted from the production flow.

[0050] FIG. 7 shows three of the satellite screws 120, which are intended to be received in the support bearing element 110 shown in FIGS. 5 and 6.

[0051] On the left is a satellite screw 120 with a screw flight 122 without additional parts. The screw flight 122 ends at a flange 123. Behind it is a bearing section 125.

[0052] In the case of the center satellite screw 120, a drive pinion 121 is mounted on the bearing section 125. This includes not only a toothed area, but also a plain bearing element 124, 126 on each side of it with external spiral grooves that form a return thread.

[0053] In the case of the satellite screw 120 shown on the far right in FIG. 7, the following are mounted: the drive pinion 121; a bearing insert element 160 disposed in front of the drive pinion 21 in the direction of conveyance of the extruder screw and in which a plain bearing element 170 is inserted; a plain bearing element 170 into which the end-side bearing shoulder 126 of the satellite screw 120 is inserted; and a clamping ring 171 surrounding the plain bearing element 170.

[0054] FIG. 8 shows an example of a support bearing element 210, which in turn has a cone 211 at its one end and has a large number of undercut grooves 215 on the periphery, in which the drive zone of the satellite screws with their drive pinions is formed when the support bearing element is fitted as part of an extruder screw shaft. In the case of the support bearing element 210, the bearing holders 261 are provided for the two bearing points of the satellite screws on both sides of the respective drive pinion in separate bearing insert elements 260.

[0055] Flow channels 213 extend from inlet openings 212 at the cone 211 to outlet openings 214. Channels 218 branch off from the flow channel 213 and extend into bearing holders 261 of the bearing insert elements 260. In this embodiment, too, the bearing insert elements 260 are adapted with their outer contour to the inner contour of the grooves 215 in such a way that they are positively fixed in a plane transversely to the central axis, i.e., they cannot be moved radially outwards. The axial fixation of the bearing insert elements 260 is carried out by means of shoulders on the satellite screws.

[0056] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.