Bushing for extruder

Abstract

The invention relates to a bushing (1) for an extruder (13), comprising an inner part (2) having a machining zone (3) extending axially through the inner part (2), and a sealing sleeve (4) completely surrounding the inner part (2), characterized in that the inner part (2) has at least one cooling channel (8). The invention also relates to a cylinder (9) for an extruder (13), comprising an outer housing (9a) and a through-hole (12), characterized in that a bushing (1) according to the invention is arranged in the through-hole (12), and to an extruder (13) comprising at least one such cylinder (9).

Description

Technical Field

[0001] The invention relates to a bushing for an extruder, wherein the bushing is replaceable and has at least one cooling channel. Background Art

[0002] An extruder is a machine in which materials such as polymers, elastomers, or protein-containing mixtures can be processed under desired pressure and temperature conditions to produce food products, including cereals, snacks, animal feed, and alternative foods. A typical extruder includes at least one extruder screw shaft, each of which has a set of extruder screw elements mounted on the shaft. The extruder screw shaft is housed in a cylindrical body called a barrel. An extruder typically includes multiple barrels that are connected to each other at the ends. Multiple barrels are required to perform the different processes to be performed in the extruder, such as conveying, kneading, mixing, degassing, dosing, etc.

[0003] Each cylinder includes an insert element, called a bushing, which is pressed into the cylinder housing. Channels for the medium are also provided in the cylinder housing to regulate the temperature in the cylinder within the desired range. The medium guided in the channels can be brought to the desired temperature by means of a temperature control device, such as a heat exchanger.

[0004] The bushing comprises a working region in the form of an axial bore, in which at least one extruder screw shaft is arranged and in which the desired processing of the material to be extruded takes place. Since the extruder screw shaft rotates in the working region during extrusion and, in the process, comes into contact with the surface of the working region of the bushing, the bushing wears over time.

[0005] To ensure the proper functioning of the extrusion process, the bushing must be replaced after a certain period of time. Since the bushing is typically pressed into the barrel housing, as mentioned above, replacing the bushing in conventional barrels is a laborious process. Typically, the bushing is pressed into the barrel housing by shrinking it, which results in the bushing being fixedly positioned in the barrel housing. Consequently, the entire bushing and barrel housing system must be replaced in the event of wear. This is clearly disadvantageous.

[0006] For example, US 2011 / 0063939 A1 proposes to provide an extruder in which a bushing is arranged in a replaceable manner in a barrel. The proposed solution comprises a barrel consisting of two parts that can be separated from each other in order to be able to replace the bushing arranged in the barrel.

[0007] This solution is still not optimal. For one thing, a special two-part barrel is required. For another, temperature control within the barrel is suboptimal. During extrusion, heat is generated in the processing zone of the liner, which must be dissipated. Cooling channels in the barrel are spaced apart from the replaceable liner and only indirectly cool the processing zone.

[0008] The object of the present invention is to provide a bushing for an extruder which overcomes the disadvantages of the prior art and which, in particular, improves the efficiency of the temperature control, in addition to being easier to replace.

[0009] This object is achieved by the bushing according to the invention. Summary of the Invention

[0010] In particular, the invention relates to a bushing for an extruder, comprising an inner part having a processing zone extending axially through the inner part and a sealing sleeve completely circumferentially surrounding the inner part, the bushing being characterized in that the inner part has at least one cooling channel.

[0011] The bushing according to the present invention adopts a modular design. The bushing according to the present invention comprises a sealing sleeve and an internal component arranged in the sealing sleeve.

[0012] The sealing sleeve preferably has an outer cylindrical shape and is designed so that it can be placed in the preferably cylindrical through-hole of the barrel of the extruder and can be removed therefrom again. This can be achieved in that the outer diameter of the sealing sleeve is slightly smaller than the diameter of the through-hole of the barrel (preferably 0.01% to 0.5% smaller) and the sealing sleeve therefore has a certain "play" in the through-hole of the barrel.

[0013] The sealing sleeve is made of a material commonly used for bushings of extruders. The sealing sleeve is preferably made of a metal or a metal alloy. For example, iron, steel or alloys containing aluminum, chromium, molybdenum or a combination of these metals can be mentioned.

[0014] The sealing sleeve completely circumferentially surrounds the preferably cylindrical inner part of the bushing according to the invention, so that the inner part does not come into contact with the housing of the cylinder.

[0015] According to a preferred embodiment of the present invention, the sealing sleeve is fixedly applied to the inner component. In this embodiment, the inner component and the sealing sleeve cannot be replaced separately from each other, but form an inseparable whole.

[0016] The internal components are also made of materials commonly used for bushings of extruders. The internal components are preferably made of metal or metal alloys. For example, iron, steel or alloys containing aluminum, chromium, molybdenum or combinations of these metals can be mentioned.

[0017] The connection between the sealing sleeve and the inner component can be produced in a conventional manner.According to a preferred embodiment, the sealing sleeve and the inner component are cast components, and the sealing sleeve is shrunk onto the inner component and optionally brazed or welded.

[0018] The inner component comprises a processing zone extending axially therethrough, the processing zone being in the form of a continuous bore in which at least one extruder screw is arranged. According to a preferred embodiment, the processing zone is selected from the group consisting of a cylindrical processing zone and two partially overlapping cylindrical processing zones. This corresponds to the design of a single-shaft extruder or a twin-shaft extruder. However, the present invention is not limited to these variants and can also be used in multi-shaft extruders having more than two extruder screws.

[0019] Embodiments of the bushing according to the invention make it possible to arrange at least one cooling channel in the inner component of the bushing according to the invention in a simple manner. Since the inner component is preferably manufactured separately from the sealing sleeve, the at least one cooling channel can be provided in the inner component before the sealing sleeve is applied to the inner component. According to a preferred embodiment, more than one cooling channel, for example 2 to 10 cooling channels, can be provided in the inner component. These cooling channels can be connected to one another or overlap. According to the invention, each cooling channel preferably has a diameter in the range of 5 mm to 20 mm, more preferably 8 mm to 12 mm.

[0020] Compared to the prior art, the at least one cooling channel is arranged closer to the processing area of ​​the bushing because, as described above, it is directly provided in the inner part of the bushing (rather than in the cylindrical shell as in the prior art). This significantly improves the temperature control efficiency.

[0021] The at least one cooling channel can be a hole or a groove which extends axially through the inner component or on the outer side of the inner component and is arranged parallel to the machining zone.

[0022] According to a preferred embodiment of the present invention, at least one cooling channel is arranged in or on the surface of the internal component. Particularly preferably, the at least one cooling channel is arranged in the surface of the internal component in the form of a cooling coil. This embodiment is particularly advantageous during manufacturing. Preferably, the at least one cooling channel is provided in the surface of the internal component as a cooling channel component, particularly preferably as an outwardly open channel. During the manufacture of the internal component, the at least one cooling channel component is produced, for example, by casting the internal component in a casting mold, which produces a corresponding cooling channel component in the surface of the internal component. Subsequently, by applying the sealing sleeve to the internal component as described above, the at least one cooling channel component in the surface of the internal component is sealed outwardly, forming a complete cooling channel.

[0023] The bushing according to the invention preferably has elements with which the bushings according to the invention can be connected to one another at their end faces. To this end, for example, positioning holes can be provided at the inner component and / or the sealing sleeve, preferably at both ends of the inner component, into which fixing elements such as screws or pins can be arranged. The inner component of the bushing according to the invention preferably has 2 to 10, particularly preferably 2 to 6, positioning holes on each end face.

[0024] According to another preferred embodiment of the invention, the bushing has at least one radial hole extending through the sealing sleeve and the inner component into the processing area. In this way, at least one radial through-channel is formed, which can be a material inlet or can be used to arrange a measuring device.

[0025] For example, water or gas can be introduced into the material to be extruded located in the processing zone via through-channels designed in this manner in order, for example, to adjust the moisture content of the material to be extruded or to produce pore formation in the material to be extruded.

[0026] The number and position of the radial holes in the bushing according to the present invention are not particularly limited. For example, 2 to 10, preferably 3 to 6, radial holes may be provided, parallel to or staggered with one another. The diameter of the radial holes is preferably in the range of 1 mm to 5 cm.

[0027] As described above, the bushing according to the invention is arranged in a barrel. Therefore, the present invention also relates to a barrel for an extruder, comprising an outer shell and a through-hole, characterized in that the bushing according to the invention is replaceably arranged in the through-hole.

[0028] According to the present invention, a cylinder commonly used in extruders can be used. The cylinder can have a square or cylindrical shape, wherein a cylindrical shape is preferred. The cylinder is made of a material conventionally used for extruder cylinders. The cylinder is preferably made of a metal or a metal alloy. For example, iron, steel or an alloy containing aluminum, chromium, molybdenum or a combination of these metals can be mentioned.

[0029] Components such as flanges can be arranged at the ends of the cylinder; these components are preferably used for end-face connection of the cylinder. For this purpose, for example, positioning holes can be provided in these components, preferably flanges, in which fastening elements such as screws or pins can be arranged. Preferably, each component of the cylinder according to the present invention, preferably each flange, has 2 to 20, particularly preferably 2 to 16, positioning holes.

[0030] According to the invention, both the bushing (preferably via its inner part) and the cylinder are therefore preferably connected to each other (via a part such as a flange).

[0031] The cylinder has a through-hole. This through-hole extends axially through the entire length of the cylinder. A bushing according to the present invention is replaceably positioned in this through-hole. As described above, this is achieved by having the outer diameter of the bushing's sealing sleeve slightly smaller than the diameter of the cylinder's through-hole (preferably 0.01% to 0.5% smaller), so that the sealing sleeve has a certain amount of "play" in the cylinder's through-hole.

[0032] The cylinder preferably has a length corresponding to the length of the bushing according to the present invention. In other words, when the bushing is arranged in the cylinder, the end of the bushing is flush with the end of the cylinder. However, according to another preferred embodiment of the present invention, the axial length of the cylinder can also be lower than the axial length of the bushing, so that only the bushings are subsequently connected to each other without an intermediate space between them, while a small gap of preferably 0.1 mm to 6 mm is formed between two consecutive cylinders.

[0033] According to another preferred embodiment of the present invention, the cylinder has at least one radial hole, which forms a radial through-channel with the radial hole of the bushing.

[0034] In this way, at least one radial through-channel is formed, which can be a material inlet or can be used for the arrangement of a measuring device.

[0035] For example, water or gas can be introduced into the material to be extruded located in the processing zone via through-channels designed in this manner in order, for example, to adjust the moisture content of the material to be extruded or to produce pore formation in the material to be extruded.

[0036] Alternatively, a measuring device can be arranged in a through-channel designed in this manner, for example, to determine the pressure or temperature in the machining area of ​​the bushing. Such measuring devices are known and do not need to be explained in greater detail.

[0037] The cylinder according to the present invention is not particularly limited in terms of the number and position of these radial holes. For example, 2 to 10, preferably 3 to 6, radial holes may be provided, parallel to or staggered with one another. The diameter of the radial holes is preferably in the range of 1 mm to 5 cm.

[0038] The barrel described above can be used in any conventional extruder. Therefore, the present invention also relates to an extruder comprising at least one barrel described above.

[0039] According to the present invention, the extruder comprises 2 to 20 cylinders, preferably 2 to 15 cylinders. As mentioned above, the cylinders are preferably connected to each other at the end face. According to a preferred embodiment of the present invention, the bushings arranged in the cylinders are additionally connected to each other at the end face, as mentioned above.

[0040] Extruders are well known. For example, see WO 2012 / 158023 A1 or Bühler extruders, in particular twin-screw extruders. Such extruders preferably have an L / D ratio (ratio of total length to screw diameter) in the range of 12 to 60, preferably 20 to 40. According to the present invention, the extruder is preferably operated at 100 to 1000 rpm, particularly preferably 200 to 800 rpm, and particularly preferably 20 to 400 rpm.

[0041] Suitable extruders include at least one unit for introducing the raw materials into the first section of the extruder. If different raw materials are to be introduced into the extruder, a plurality of such units may also be provided. The extruder typically also has a water supply line, an oil supply line and optionally a steam supply line.

[0042] The housing of the extruder is preferably temperature-controlled. The material to be extruded is kneaded under pressure (typically 1 to 400 bar, preferably 1 to 200 bar) to form a homogeneous mixture. This typically requires an energy input of 10 to 160 Wh / kg, preferably 10 to 130 Wh / kg.

[0043] According to a preferred embodiment of the present invention, a cooling tool, such as a cooling nozzle, can be provided at the outlet of the extruder. The cooling tool for the extruder is well known. Known distributor unit can preferably be arranged between the extruder and the cooling tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will now be described in detail based on non-limiting exemplary embodiments with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals denote the same elements. In the accompanying drawings:

[0045] Figure 1 shows a schematic diagram of an embodiment of an extruder according to the present invention;

[0046] Figure 2 A schematic diagram showing the individual components of an embodiment of a bushing according to the invention;

[0047] Figure 3 shows a schematic diagram of an embodiment of a cylinder according to the present invention;

[0048] Figure 4 A schematic diagram of an embodiment of an extruder according to the invention is shown. DETAILED DESCRIPTION

[0049] Figure 1is a schematic diagram of an embodiment of an extruder 1 according to the present invention. The bushing 1 comprises an inner part 2 having a processing zone 3 extending axially through the inner part and a sealing sleeve 4 which completely circumferentially surrounds the inner part 2. In this embodiment, the inner part 2 and the sealing sleeve 4 are cylindrical and made of metal or a metal alloy. In this embodiment, the processing zone 3 extending axially through the entire length of the bushing 1 is also cylindrical and is intended for use in a single-shaft extruder. However, as mentioned above, other processing zones can also be provided. Positioning holes 6 are provided on the end face 5 of the inner part 2 in order to connect multiple bushings 1 to each other. The bushing 1 also has radial holes 7 leading to the processing zone 3.

[0050] The inner component 2 and the sealing sleeve 4 are cast parts. The sealing sleeve 4 is shrunk onto the inner component 2. It can be seen that a channel-like cooling channel 8 (shown in dashed lines) is arranged in the surface of the inner component 2 below the sealing sleeve 4. This cooling channel spirals through the surface of the inner component 2 and is closed off to the outside by the sealing sleeve 4.

[0051] Figure 2 A schematic diagram of the individual components of an embodiment of a bushing 1 according to the invention is shown.

[0052] It can be seen that channel-shaped cooling channels 8 are arranged in the surface of the inner component 2, spirally passing through the surface of the inner component 2 and opening outward. When the sealing sleeve 4 is applied to the inner component 2, the cooling channels 8 are closed by the sealing sleeve 4.

[0053] Radial bores 7 are present both in the inner component 2 and in the sealing sleeve 4 and open into the processing region 3 .

[0054] Figure 3 The diagram shows an embodiment of a cylinder 9 according to the present invention. The cylinder 9 has an outer shell 9a and has a flange 10 at each end, in which positioning holes 11 are provided for connecting a plurality of cylinders 9 to each other at the end faces.

[0055] In this embodiment, the barrel 9 is cylindrical and made of metal or a metal alloy.

[0056] according to Figure 1 The inner bushing 1 is arranged in the through hole 12 of the cylinder 9 .

[0057] Radial holes 7 are also provided in the cylinder 9 , extending through the inner component 2 and the sealing sleeve 4 and leading to the processing zone 3 .

[0058] Figure 4is a schematic diagram of an embodiment of an extruder 13 according to the present invention. The extruder 13 comprises a plurality of barrels 9. The raw material R can be supplied via a dosing unit 14. Water or steam can be introduced into the extruder 13 via a supply line 15, preferably through a radial through-channel formed by radial holes 7 in the barrels 9. Figure 1 In the embodiment of the present invention, the cooling means 16 is arranged at the end of the extruder 13. Of course, other conventional components can also be arranged at the end of the extruder. As an example, a cutting device or an end plate with a subsequent cutting device can be mentioned. The cooling medium is preferably supplied from a tank 17 on the downstream side of the cooling means 16 and discharged on the upstream side of the cooling means 16. The flow direction of the cooling medium is therefore opposite to the flow direction of the extrudate.

[0059] Reference Signs List

[0060] 1 Bushing

[0061] 2 Internal components

[0062] 3 Processing Area

[0063] 4 Sealing sleeve

[0064] 5 End face

[0065] 6 Positioning holes

[0066] 7 Radial holes

[0067] 8 cooling channels

[0068] 9 Cylinder

[0069] 9a External housing

[0070] 10 flange

[0071] 11 Positioning holes

[0072] 12 through holes

[0073] 13 Extruder

[0074] 14 batching unit

[0075] 15 Supply lines

[0076] 16 Cooling tools

[0077] 17 cans.

Claims

1. A bushing (1) for an extruder (13), comprising an inner part (2) and a sealing sleeve (4), wherein the inner part has a processing zone (3) extending axially through the inner part (2), and the sealing sleeve completely circumferentially surrounds the inner part (2), the bushing being characterized in that the inner part (2) has at least one cooling channel (8).

2. The bushing (1) according to claim 1, characterized in that The at least one cooling channel (8) is arranged in a surface of the inner component (2).

3. The bushing (1) according to claim 2, characterized in that The at least one cooling channel (8) is arranged in the form of a cooling coil in the surface of the inner component (2).

4. The bushing (1) according to any one of claims 1 to 3, characterized in that The inner component (2) is a casting made of metal.

5. The bushing (1) according to any one of claims 1 to 4, characterized in that The sealing sleeve (4) is fixedly applied to the inner component (2).

6. The bushing (1) according to claim 5, characterized in that The sealing sleeve (4) is shrunk onto the inner component (2) and optionally brazed or welded.

7. The bushing (1) according to any one of claims 1 to 6, characterized in that The processing area (3) is selected from the group consisting of a cylindrical processing area and two partially overlapping cylindrical processing areas.

8. The bushing (1) according to any one of claims 1 to 7, characterized in that The bushing (1) has at least one radial hole (7) extending through the sealing sleeve (4) and the inner component (2) into the machining area (3).

9. A barrel (9) for an extruder (13), comprising an outer shell (9a) and a through-hole (12), characterized in that an inner bushing (1) according to any one of claims 1 to 8 is replaceably arranged in the through-hole (12).

10. The cylinder (9) according to claim 9, characterized in that The cylinder (9) has at least one radial hole (7), which forms a radial through-channel with the radial hole (9) of the bushing (1).

11. Cylinder (9) according to claim 10, characterized in that The at least one radial through-channel is a material inlet, or a measuring device is arranged in the radial through-channel.

12. An extruder (13) comprising at least one barrel (9) according to any one of claims 9 to 11.

13. The extruder (13) according to claim 12, characterized in that The extruder (13) comprises 2 to 20 cylinders (9), wherein the cylinders (9) are connected to each other at the end faces.

14. The extruder (13) according to claim 13, characterized in that The bushings (1) arranged in the cylinder (9) are additionally connected to one another at the end faces.

15. The extruder (13) according to any one of claims 12 to 14, characterized in that The extruder (13) is selected from the group consisting of a single-screw extruder and a twin-screw extruder, wherein the extruder screw is arranged in the processing zone (3) of the bushing (1).

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