Extruder with sealing element and food production method

Abstract

The invention relates to an extruder, comprising an intermediate housing (13) arranged between an extruder housing (8) and a gearbox (12), and a support shaft (5) of an extruder screw arranged in the extruder (7), said support shaft (5) being provided with at least one flow choking element (1) on a section located in a processing zone (9) of the extruder (7), and a choke element (1) sealing the intermediate housing (13) with respect to the processing region (9), the choke element (1) having a pitch of 5 mm to 30 mm, preferably 10 mm to 20 mm. The invention also relates to a method for producing food or animal feed using such an extruder (7), in which the material introduced into the processing zone (9) is conveyed only in the direction of the discharge opening (11) of the extruder (7).

Description

Technical Field

[0001] The present invention relates to an extruder, in particular to an extruder for producing food or animal feed and having an improved sealing effect on the processing area. Background Art

[0002] An extruder is a machine that processes materials such as polymers, elastomers or protein-containing mixtures used in the production of various food products, including cereals, snacks, animal feed and alternative foods, under set pressure and temperature conditions. A typical extruder consists of at least one extruder screw shaft, each of which has a set of extruder screw elements mounted on a support shaft. The extruder screw shaft is housed in a cylindrical body called a barrel. An extruder usually contains several barrels connected end to end. Several barrels are required to carry out the various processes that are to be carried out in the extruder, such as conveying, kneading, mixing, degassing, metering, etc.

[0003] The processing zone of an extruder is located within one or more barrels. This is the area within which the extruder screw shaft is movably mounted, and the movement of the screw shaft allows the material fed into the processing zone to be processed. The material to be processed is introduced into the processing zone through a feed port. This feed port is typically located at one end of the processing zone on the machine side (i.e., opposite the extruder discharge port) and is typically positioned so that the material can be introduced into the processing zone from above by gravity.

[0004] DE 202010003416 U1 shows an extruder of this type. The extruder screw shaft is characterized by a splined support shaft, the external teeth of which extend parallel to the shaft axis. Internally toothed screw elements and kneading elements can be attached to the support shaft in a form-fitting manner by meshing the internal teeth with the external teeth of the support shaft.

[0005] The extruder screw shaft is connected to a motor via a gearbox, which drives the extruder screw shaft. The motor and gearbox are located on the machine side, with an intermediate housing (also known as a gearbox indicator) positioned between the processing area and the gearbox. The intermediate housing is separated from the processing area by a partition wall, which necessitates an opening through which the support shaft extends from the gearbox to the processing area.

[0006] This opening cannot be sealed because the support shaft must be able to rotate within it. Consequently, during extended extruder operation, the extruded material could enter and contaminate the intermediate housing. Besides the inevitable loss of material, this would also require disassembly of the extruder for cleaning.

[0007] This issue has not yet been satisfactorily resolved.

[0008] In conventional extruders, the support shaft typically passes through a so-called stuffing box, where it rotates with the aid of lubricating oil. However, this stuffing box fails to seal the intermediate housing from the extruder's processing area, leading to the aforementioned contamination issues during extended extruder operation. Furthermore, lubricating oil can enter the processing area, which is undesirable in extruders used to produce food or animal feed. From a hygienic perspective, this known system presents drawbacks.

[0009] Therefore, in the food or animal feed industry, solutions are preferred in which the support shaft is arranged in a sliding support that does not use lubricating oil. However, this sliding support also cannot seal the intermediate housing from the processing area of ​​the extruder, so the above-mentioned problems still occur. Summary of the Invention

[0010] The object of the present invention is to provide an extruder whose intermediate housing can be reliably sealed from the processing zone of the extruder.

[0011] This problem has been solved by the present invention.

[0012] Specifically, the present invention relates to an extruder comprising:

[0013] an electric motor having a gearbox;

[0014] An extruder housing having a processing area therein and having a feed port and a discharge port;

[0015] An intermediate housing disposed between the extruder housing and the gear box;

[0016] A support shaft disposed within the extruder;

[0017] wherein a screw element is provided on at least one section of the support shaft, the screw element and the support shaft forming an extruder screw, wherein the extruder screw is movably arranged in the extruder housing; wherein at least one flow-blocking element is provided on a section of the support shaft located in the processing zone;

[0018] It is characterized in that the intermediate housing is sealed relative to the processing area by the at least one flow-blocking element, which has a pitch of 5 mm to 30 mm, preferably 10 to 20 mm.

[0019] According to the present invention, it has been discovered that by providing a special screw element on the processing zone side of the support shaft, it is possible to reliably prevent the extruded material from escaping through the opening in the partition wall between the processing zone and the intermediate housing of the extruder. According to the present invention, this screw element is referred to as a flow-blocking element. This flow-blocking element prevents the extruded material from being transported toward the partition wall between the processing zone and the intermediate housing; instead, the extruded material accumulates and is prevented from passing through the opening in the partition wall through which the support shaft of the extruder screw is guided.

[0020] The solution according to the present invention is characterized by the ability to operate the extruder without lubricant, significantly improving the hygienic conditions of the extruder for producing food or animal feed. Since the intermediate housing is sealed from the processing area by at least one flow-blocking element, a stuffing box operated with lubricant (as used in the prior art) can be eliminated. In particular, the use of oil, water, or air for lubrication or sealing purposes is preferably eliminated, which offers advantages both in terms of equipment and process technology.

[0021] The screw element according to the present invention has a pitch of 5 mm to 30 mm, preferably 10 mm to 20 mm. The pitch of the screw element of the extruder screw refers to the degree of inclination of the threads (turns) of the screw element. These threads are spirally wound around the central section of the spiral element. The greater the pitch, the more vertically the threads at this position are aligned with the central longitudinal axis of the screw element (i.e. the axis extending longitudinally along the center of the screw element). The pitch describes the distance between two thread positions that have a maximum distance from the central longitudinal axis of the screw element. The smaller this distance, the greater the pitch of the screw element.

[0022] Due to the large pitch, the screw element has a relatively large number of threads (turns) over a relatively short axial length of the screw element. According to the invention, the screw element preferably has 2 to 10, more preferably 3 to 4, threads.

[0023] According to the present invention, it is further preferred that the obstruction element has a length of 30 mm to 90 mm, more preferably 40 mm to 80 mm.

[0024] Thus, for example, a flow-blocking element according to the present invention has a pitch of 10 mm and may have 4 threads over a length (ie, axial length) of 40 mm.

[0025] Due to the large pitch of the flow-blocking element, the flow-blocking element according to the invention does not convey the material to be extruded, thereby preventing this material from moving towards the opening in the partition wall between the processing area and the intermediate housing.

[0026] For example, DE 10-2004052055 B4 discloses such a screw element with a large pitch. This document shows a monolithic screw element in which a conveyor screw segment is arranged in tandem with a working segment having a pitch greater than that of the conveyor screw segment. A gap of approximately 1 to 3 mm in width between these segments is not present and cannot be provided for manufacturing reasons. This element is not intended for sealing the process zone. Furthermore, only one segment of the monolithic screw element has a pitch that matches the pitch of the screw element described herein.

[0027] The flow-blocking element according to the present invention can be mounted on the support shaft of the extruder screw in a known manner. Preferably, the flow-blocking element has internal teeth, and the support shaft has external teeth, with the teeth connected to each other in a form-fitting manner. For example, as disclosed in DE 202010003416 U1 or WO 2013 / 030322 A1.

[0028] The flow-blocking element according to the present invention is arranged on the section of the extruder screw support shaft located within the processing zone. This section is located between the feed inlet of the processing zone and the opening of the partition wall. The partition wall is located between the processing zone and the intermediate housing and is used to prevent the product from entering the intermediate housing from the processing zone.

[0029] According to one embodiment of the present invention, the flow-blocking element can rest against an opening in the partition wall between the intermediate housing and the processing area. According to another embodiment of the present invention, the flow-blocking element is arranged on the support shaft in such a way that a gap of 1 mm to 5 mm, preferably 1 mm to 4 mm, remains between the end of the flow-blocking element facing the opening and the opening. According to the present invention, this is preferably achieved by the flow-blocking element having unthreaded sections on both sides. In this way, when installed, a gap is formed on both sides of the flow-blocking element, which gap preferably has a width in the range of 1 mm to 5 mm. If material enters this gap during operation of the extruder, it is transported back by the rotation of the support shaft. The threads of the flow-blocking element remain completely intact.

[0030] There are no further screw elements between the flow-blocking element according to the invention and the opening in the partition wall between the intermediate housing and the processing zone.

[0031] According to one embodiment of the present invention, the flow-blocking element is arranged on the support shaft in such a manner that the end of the flow-blocking element facing the extruder feed opening is flush with the edge of the feed opening, which faces the opening in the partition wall between the intermediate housing and the processing zone. In other words, according to this embodiment, the flow-blocking element does not extend into the area of ​​the processing zone below the feed opening. However, preferably, there is also no gap between the area of ​​the processing zone below the feed opening and the location of the flow-blocking element. Therefore, the flow-blocking element is arranged downstream of the extruder feed opening.

[0032] However, according to another embodiment of the present invention, the flow-blocking element is arranged on the support shaft in such a manner that the flow-blocking element extends into the processing area below the feed inlet. The advantage of this is that no dead corners where material can be trapped are formed in the processing area. However, it is crucial that the flow-blocking element does not extend to cover the entire processing area below the feed inlet. Preferably, in this embodiment, the flow-blocking element according to the present invention extends into the processing area below the feed inlet in such a manner that the flow-blocking element occupies a maximum of 10% of the axial length of the processing area (i.e., the area into which the flow-blocking element extends), and more preferably, a maximum of 5%.

[0033] The above-described flow-blocking element can be used in any conventional extruder.

[0034] The present invention also relates to an extruder screw comprising a support shaft and at least one flow-blocking element, wherein the flow-blocking element has a pitch of 5 mm to 30 mm, preferably 10 mm to 20 mm, and the extruder screw diameter D is equal to the flow-blocking element length L. S The ratio D / L S Within the range of 1.35 to 1.6, preferably 1.45 to 1.55.

[0035] In this case, the flow-blocking element can be designed in the above-mentioned manner. As mentioned above, the flow-blocking element has a large pitch, so that the flow-blocking element has a relatively short axial length L. S According to the present invention, the flow-blocking element preferably has 2 to 10 threads, more preferably 3 to 4 threads. Therefore, according to the present invention, the extruder screw diameter D and the flow-blocking element length L S The ratio D / L S Within the range of 1.35 to 1.6, preferably 1.45 to 1.55.

[0036] According to the present invention, an extruder screw having a diameter D in a wide range of 30 mm to 180 mm, preferably 40 mm to 160 mm, particularly preferably 60 mm to 130 mm, can be used. S The obstruction element is between 20 mm and 120 mm, preferably between 25 mm and 100 mm, more preferably between 30 mm and 90 mm, and particularly preferably between 40 mm and 80 mm.

[0037] According to the present invention, the flow-blocking element is the first screw element on the support shaft of the extruder screw. The extruder screw is implemented by sequentially assembling the required screw elements onto the support shaft in a predetermined order. According to the present invention, at least one flow-blocking element is assembled as the first element onto the support shaft of the extruder screw, thereby becoming the first screw element on the support shaft of the extruder screw. Therefore, when installed in the extruder, the flow-blocking element is the screw element closest to the opening in the partition wall between the extruder intermediate housing and the processing zone.

[0038] According to the present invention, the flow-blocking element is preferably detachably arranged on the support shaft of the extruder screw.

[0039] According to one embodiment of the invention, the flow-blocking element is arranged on the support shaft of the extruder screw in such a way that, when installed in the extruder, the flow-blocking element abuts against an opening in a partition wall between the intermediate housing and the processing zone of the extruder.

[0040] According to another embodiment of the present invention, the flow-blocking element is mounted on the extruder screw support shaft in such a manner that, when installed in the extruder, a gap of 1 to 5 mm, preferably 1 to 4 mm, is left between the end of the flow-blocking element facing the opening in the partition wall between the intermediate housing and the processing zone and the opening. According to the present invention, this is preferably achieved by having a non-threaded section on each side of the flow-blocking element. Thus, when installed, a gap is formed on both sides of the flow-blocking element, the width of which is preferably in the range of 1 to 5 mm.

[0041] According to another embodiment of the invention, the flow-blocking element is arranged on the support shaft of the extruder screw in such a way that, when installed in the extruder, no further screw elements are present between the flow-blocking element according to the invention and the opening in the partition wall between the intermediate housing and the processing zone.

[0042] According to another embodiment of the present invention, the flow-blocking element is arranged on the support shaft of the extruder screw in such a manner that, when installed in the extruder, the end of the flow-blocking element facing the feed inlet of the extruder is flush with the boundary of the opening in the partition wall between the feed inlet and the intermediate housing and the processing area. In other words, in this embodiment, the flow-blocking element does not extend into the area of ​​the processing area below the feed inlet. However, preferably, there is no gap between the area of ​​the processing area below the feed inlet and the position of the flow-blocking element. Therefore, the flow-blocking element is arranged downstream of the extruder feed inlet.

[0043] According to another embodiment of the present invention, the obstruction element is arranged on the support shaft of the extruder screw in such a manner that, when installed in the extruder, the obstruction element extends into the processing zone below the feed inlet. However, it is crucial that the obstruction element does not extend to cover the entire processing zone below the feed inlet. In this embodiment, preferably, the obstruction element according to the present invention extends into the processing zone below the feed inlet so that the obstruction element occupies at most 10% of the axial length of the processing zone (i.e., the area into which the obstruction element extends), and more preferably at most 5%.

[0044] According to the present invention, at least one flow-blocking element as described above is provided. However, in a multi-shaft extruder, it is also possible and preferred to provide multiple flow-blocking elements. For example, one to three flow-blocking elements can be formed one behind the other on the support shaft and together constitute the flow-blocking element according to the present invention.

[0045] In the case of a multi-shaft extruder, as described above, the flow-blocking element according to the present invention is preferably provided on each support shaft of each extruder screw. A particularly preferred arrangement is one in which the flow-blocking elements on different support shafts intermesh. This enhances the sealing effect of the flow-blocking elements and, preferably, achieves a self-cleaning effect.

[0046] Extruders are well known. For example, see WO 2012 / 158023 A1 or extruders from Bühler, in particular twin-screw extruders. Such extruders preferably have an aspect ratio (ratio of total length to screw diameter) in the range of 12-60, preferably 20 to 40. According to the present invention, the extruder is preferably operated at 100 to 1000 rpm, particularly preferably 200 to 600 rpm, and even more preferably 250 to 350 rpm.

[0047] The extruder according to the present invention comprises a motor with a gearbox for driving the extruder screw. For this reason, the support shaft of each extruder screw is operatively connected to the gearbox. This can be achieved in a conventionally known manner.

[0048] The extruder according to the present invention further comprises an extruder housing having a processing zone therein and having a feed opening and a discharge opening. The extruder housing preferably comprises 2 to 20 barrels, more preferably 2 to 15 barrels. These barrels are preferably interconnected by end faces and together form the extruder housing.

[0049] The extruder housing (or the individual barrels forming the extruder housing) has a through hole that runs axially through the entire length of the extruder housing, and the processing zone of the extruder is located in the through hole.

[0050] The extruder housing 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. The energy input is typically 10 to 150 Wh / kg, preferably 10 to 120 Wh / kg, and particularly preferably 15 to 30 Wh / kg.

[0051] The extruder's feed port is used to feed raw materials into the first section of the extruder. This port communicates with the processing zone. The feed port is typically and preferably located on the extruder housing, allowing the material to enter the extruder housing, more specifically, the processing zone, under gravity.

[0052] The material to be extruded can be fed directly into the processing area through the feed port. Preferably, a metering device is located above the feed port, by which the material to be extruded is metered and optionally mixed before the material to be extruded is fed through the feed port. According to the present invention, the material to be extruded can preferably be pre-treated in a conventional pre-treatment machine and fed into the feed port, for example, via a conventional screw conveyor.

[0053] A discharge port is provided at the end of the processing zone away from the feed port, through which the extruded material is discharged from the extruder, and the discharge port is communicated with the processing zone.

[0054] The extruder also typically has a water supply line, an oil supply line and optionally a steam supply line.

[0055] The extruder according to the invention further comprises an intermediate housing (also referred to as a gearbox shroud) which is arranged between the extruder housing and the gearbox in a conventionally known manner. The support shaft of the extruder screw passes through the intermediate housing, but no screw elements are arranged on this section of the support shaft.

[0056] Preferably, the end of the intermediate housing facing the extruder housing forms a partition wall; however, a separate partition wall may also be provided. This partition wall separates the intermediate housing from the processing area within the extruder housing. The partition wall has openings through which the support shafts of the extruder screws are guided. In multi-screw extruders, the number of openings in the partition wall corresponds to the number of extruder screws. This is conventionally known.

[0057] The transition area between the intermediate housing and the processing zone is preferably lubricant-free to improve the hygienic conditions of the extruder during food or animal feed production. According to a preferred embodiment of the present invention, a sleeve is provided in the opening in the partition wall, through which the support shaft of the extruder screw is guided. Because the intermediate housing is sealed from the processing zone by at least one flow-blocking element, a stuffing box operated with lubricants (as used in the prior art) can be eliminated. In particular, the use of oil, water, or air for lubrication or sealing purposes can be eliminated, which offers numerous advantages in terms of both equipment and process technology.

[0058] According to another preferred embodiment of the present invention, a bearing is provided on the partition wall or the opening on the partition wall to support the support shaft and the sleeve that is optionally provided.

[0059] In addition to the aforementioned flow-blocking element, additional screw elements are provided on at least one section of the support shaft within the processing zone, forming an extruder screw with the support shaft. These additional screw elements are distinct and separate from the flow-blocking element. This separation increases flexibility when the different screw elements are arranged on the support shaft in a predetermined sequence.

[0060] Preferably, the additional screw elements are selected from conveying screw elements, mixing elements, barrier elements and kneading screw elements. Particularly preferably, screw elements with an Erdmenger-type profile are used.

[0061] These additional screw elements may be arranged on the support shaft in a predetermined sequence.

[0062] As previously mentioned with respect to the flow-blocking element according to the present invention, the additional screw element can also be arranged on the support shaft of the extruder screw in a known manner. According to the present invention, it is preferred that the additional screw element has internal teeth and the support shaft has external teeth, wherein the teeth are connected to each other in a form-fitting manner. This is disclosed, for example, in DE 202010003416 U1 or WO 2013 / 030322 A1.

[0063] According to the invention, the extruder is preferably a twin-screw extruder with two extruder screws, wherein each extruder screw has at least one flow-blocking element according to the invention. Each flow-blocking element is arranged on the support shaft of the twin-screw extruder in the manner described above.

[0064] A particularly preferred arrangement is one in which the flow-blocking elements on different support shafts mesh with the additional screw elements.

[0065] According to a preferred embodiment of the present invention, a cooling tool, such as a cooling die, can be provided at the discharge port of the extruder. Cooling tools for extruders are well known. Preferably, a known distribution unit can be arranged between the extruder and the cooling tool.

[0066] An advantage of the extruder according to the invention is that it can be operated without unnecessary material losses and can particularly preferably be operated under highly hygienic conditions, making it particularly suitable for producing food products or animal feed.

[0067] The present invention therefore also relates to a method for producing food or animal feed using an extruder according to the invention, comprising the following steps: feeding a material for producing food or animal feed into a processing zone of the extruder via an inlet of the extruder, wherein the material fed into the processing zone is conveyed exclusively in the direction of the outlet of the extruder.

[0068] As mentioned above, this is achieved by providing a flow-blocking element according to the invention, which prevents material from being conveyed in the direction of the opening in the partition wall between the intermediate housing and the processing zone.

[0069] According to the present invention, material conveyance within the processing zone is preferably performed without lubricant. This is possible because the opening in the partition wall between the intermediate housing and the processing zone is sealed by the flow-blocking element of the present invention, eliminating the need for measures such as oil-lubricated stuffing boxes. In particular, the use of oil, water, or air for lubrication or sealing purposes can be preferably eliminated, which offers numerous advantages in terms of both equipment and process technology.

[0070] The present invention therefore also relates to the use of the extruder according to the invention in the production of food or animal feed.

[0071] According to the present invention, all foods or animal feeds that are usually produced by extrusion can be prepared. For example, protein-containing mixtures can be produced for the manufacture of various foods including cereals, snacks, animal feed and alternative food products (such as alternative meat and fish products). BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The present invention will be described in more detail below by way of non-limiting examples with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals represent the same elements. The accompanying drawings are shown as follows:

[0073] Figure 1 is a schematic diagram of an embodiment of two flow-blocking elements according to the present invention;

[0074] Figure 2 It is along Figure 1 A cross-sectional view of a flow-blocking element according to the present invention is shown;

[0075] Figure 3 is a schematic diagram of an embodiment of a flow-blocking element having a fin with no threaded portion;

[0076] Figure 4 is a schematic diagram of an embodiment of a support shaft having external teeth;

[0077] Figure 5 is a schematic diagram of an embodiment of an extruder according to the present invention. DETAILED DESCRIPTION

[0078] Figure 1A schematic diagram of an embodiment of two flow-blocking elements 1 according to the present invention is shown. However, the following description is also applicable to a single flow-blocking element.

[0079] According to the present invention, the flow-blocking element 1 comprises a central section 3 and a thread (turn) 2 helically arranged thereon. In the present embodiment, each flow-blocking element 1 according to the present invention has four threads 2, which, according to the present invention, preferably have a large pitch of 10 mm. Figure 1 The length of each of the impeding elements 1 according to the invention shown is 40 mm.

[0080] Figure 1 It also shows how two flow-blocking elements 1 according to the invention can mesh with one another. This can be achieved, for example, in a twin-screw extruder in which one flow-blocking element 1 is provided on each of the two support shafts.

[0081] Figure 2 Shown Figure 1 A sectional view of a screw element 1 according to the invention is shown. It can be seen that each choke element 1 according to the invention has an internal toothing 4 which can be connected in a form-fitting manner to an external toothing of a support shaft 5 (not shown here).

[0082] Figure 3 Schematic diagram of an embodiment of a flow-blocking element 1 with a non-threaded section is shown. Figure 1 As in the embodiment shown, Figure 3 In the embodiment shown, the flow-blocking element 1 according to the present invention comprises a central section 3 and threads (turns) 2 helically arranged thereon.

[0083] In the present embodiment, each of the flow-blocking elements 1 according to the invention has four threads 2 , which according to the invention preferably have a large pitch of 10 mm. Figure 3 The length L of the obstruction element 1 according to the invention is shown s The obstruction element 1 has a non-threaded section 3a, 3b at each end. This creates a gap on either side of the obstruction element 1 during installation. The widths b and b' of these gaps are preferably between 1 and 3 mm and correspond to the widths of sections 3a and 3b. During extruder operation, if material enters this gap, it is transported back through the rotation of the support shaft. This ensures that the threads of the obstruction element remain completely intact.

[0084] Figure 4 A schematic diagram of an embodiment of a support shaft 5 with a diameter D and external teeth 5a is shown. The external teeth of the support shaft 5 can be connected in a form-fitting manner with the internal teeth 4 of the choke element 1 according to the invention or (as shown in the figure) with an additional screw element 6 with corresponding internal teeth. The pitch of the thread of the additional screw element 6 is smaller than the pitch of the thread of the choke element 1.

[0085] Figure 5 A schematic diagram of an embodiment of an extruder 7 according to the present invention is shown. The extruder 7 comprises an extruder housing 8. Figure 5 In the embodiment shown, the extruder housing 8 is composed of four barrels. Inside the extruder housing 8 is a processing zone 9, which is formed by an axial through hole on the extruder housing 8 (or each barrel constituting the housing).

[0086] The extruder 7 is provided with a feed port 10 through which the material can be fed into the processing zone 9. A discharge port 11 is provided at the other end of the processing zone 9 through which the material after extrusion or mixing can be discharged from the extruder 7.

[0087] The processing area 9 is provided with an extruder screw, which is composed of a support shaft 5 with a diameter D and a length L mounted on the support shaft 5. S The invention comprises a flow-blocking element 1 and several additional screw elements 6 mounted on a support shaft 5. The support shaft 5 extends through an intermediate housing 13 to a gearbox 12, which is in turn operatively connected to a motor 14 (not shown). The motor 14 generates rotational motion through the gearbox 12.

[0088] The intermediate housing 13 is arranged between the gearbox 12 and the extruder housing 8 or the processing area 9 located therein. The intermediate housing 13 is separated from the extruder housing 8 or the processing area 9 located therein by a partition wall 15. The partition wall 15 is provided with an opening 16, through which the support shaft 5 of the extruder screw passes.

[0089] The flow-blocking element 1 is disposed in the area between the feed port 10 and the opening 16 , wherein a gap preferably exists between the flow-blocking element 1 and the partition wall 15 . In this embodiment, the gap is approximately 4 mm in size. In this embodiment, the flow-blocking element 1 does not extend into the processing zone 9 below the feed port 10 .

[0090] According to the present invention, the gap between the blocking element and the partition wall 15 is preferably formed by adopting Figure 3 This is achieved using the obstruction element 1 shown, which has a non-threaded section on each side. This creates a gap on either side of the obstruction element 1 during installation, with the width of the gap preferably ranging from 1 mm to 4 mm. During operation of the extruder, if material enters this gap, it will be transported back due to the rotation of the support shaft. The threads of the obstruction element 1 remain completely intact.

Claims

1. An extruder comprising: a motor (14) having a gearbox (12); at least one extruder housing (8), wherein the extruder housing (8) has a processing area (9) therein and has a feed port (10) and a discharge port (11); an intermediate housing (13), the intermediate housing (13) being arranged between the extruder housing (8) and the gear box (12); a support shaft (5), the support shaft (5) being arranged in the extruder (7); wherein a screw element (6) is provided on at least one section of the support shaft (5), the screw element (6) and the support shaft (5) forming an extruder screw, wherein the extruder screw is movably arranged in the extruder housing (8); wherein at least one flow-blocking element (1) is arranged on a section of the support shaft (5) located within the processing area (9); It is characterized in that the intermediate housing (13) is sealed relative to the processing area (9) by the at least one flow-blocking element (1), which has a pitch of 5 mm to 30 mm, preferably 10 to 20 mm.

2. The extruder according to claim 1, characterized in that The flow-blocking element (1) has 2 to 10, preferably 3 to 4, threads (2).

3. The extruder according to claim 1 or 2, characterized in that The flow-blocking element (1) has internal teeth (4) and the support shaft (5) has external teeth (5a), wherein the teeth (4, 5a) are connected to each other in a form-fitting manner.

4. Extruder according to any one of the preceding claims, characterized in that The flow-blocking element (1) has a length of 30 mm to 90 mm, preferably 40 mm to 80 mm.

5. Extruder according to any one of the preceding claims, characterized in that Both ends of the flow-blocking element (1) each have a non-threaded section (3a, 3b).

6. Extruder according to any one of the preceding claims, characterized in that An additional screw element (6) is arranged on the support shaft (5) in the processing area (9), and the screw element (6) is different from and separated from the flow-blocking element (1).

7. The extruder according to claim 5, characterized in that The additional screw elements (6) are selected from the group consisting of conveying screw elements, mixing elements, barrier elements and kneading screw elements.

8. Extruder according to any one of the preceding claims, characterized in that The flow-blocking element (1) is arranged downstream of the feed port (10) of the extruder (7) and does not extend into the area of ​​the processing zone (9) below the feed port (10).

9. Extruder according to any one of the preceding claims, characterized in that The extruder ( 7 ) is a twin-screw extruder having two extruder screws, each of which has at least one flow-restricting element ( 1 ) according to any one of claims 1 to 8 .

10. Extruder according to any one of the preceding claims, characterized in that The transition region (16) between the intermediate housing (13) and the processing region (9) is free of lubricant.

11. An extruder screw comprising a support shaft (5) and at least one flow-blocking element (1), characterized in that: The obstruction element (1) has a pitch of 5 mm to 30 mm, preferably 10 mm to 20 mm, and the diameter D of the extruder screw is equal to the length L of the obstruction element. S The ratio D / L S It is 1.35 to 1.6, preferably 1.45 to 1.

55.

12. A method for producing food or animal feed using an extruder (7) according to any one of claims 1 to 10, comprising the following steps: The material for producing food or animal feed is introduced into the processing zone (9) of the extruder (7) through the feed port (10) of the extruder (7), characterized in that the material introduced into the processing zone (9) is transported only in the direction of the discharge port (11) of the extruder (7).

13. The method according to claim 12, characterized in that The material is conveyed in the processing zone (9) without lubricant.

14. The method according to claim 12 or 13, characterized in that The material is conveyed within the processing zone (9) by at least one flow-blocking element (1) and only in the direction of the discharge opening (11) of the extruder (7), wherein the flow-blocking element (1) has a pitch of 5 mm to 30 mm, preferably 10 mm to 20 mm.

15. Use of an extruder (7) according to any one of claims 1 to 10 for producing food or animal feed.

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