Paddle type mixing device and cleaning method thereof

Abstract

The invention relates to a paddle-type mixing device (1), in particular a pre-treatment machine, comprising a cylindrical mixing unit (2) having a shaft arranged in the mixing unit, the shaft having paddles and the mixing unit having a base surface (2b), characterized in that the paddle-type mixing device (1) is arranged in the base surface (2b). A closable opening (2c) is provided in the base surface for introducing a cleaning device into the mixing unit (2). The invention also relates to an extruder (7) comprising such a paddle mixing device (1) and to a method for cleaning such a paddle mixing device (1).

Description

Technical Field

[0001] The present invention relates to a paddle-type mixing device for an extruder for producing food or animal feed, in particular a pre-treater. Background Art

[0002] An extruder is a machine that processes materials such as polymers, elastomers, or protein-containing mixtures under defined pressure and temperature conditions to produce food products, including cereals, snacks, animal feed, and alternative foods. A typical extruder consists of at least one extruder screw shaft, each with a set of extruder screw elements mounted on a support shaft. The extruder screw shaft is housed within a cylindrical body called a barrel. Extruders typically contain multiple barrels connected end-to-end. Multiple barrels are required to carry out the various processes required in an extruder, such as conveying, kneading, mixing, degassing, metering, and more.

[0003] Preconditioners are often used in conjunction with extruders or other equipment for pretreatment and mixing of food and feed. For example, one or more flours or concentrates / insulators are treated with water / steam and / or other additives to prepare them for subsequent extrusion. The material to be treated is first mixed with water in the preconditioner and then treated with steam before entering the extruder.

[0004] For example, a suitable pre-treater is known from DE 197 43 470 A1. This pre-treater comprises a mixing unit and a holding unit, wherein the mixing unit is arranged above the holding unit. Both units are provided with at least one shaft equipped with paddles to transport the material through the respective units. The separation of the mixing unit from the holding unit allows, on the one hand, optimally intensive mixing of the material at high shaft speeds, while, on the other hand, allowing the material to be retained in the holding unit under gentle conditions at low shaft speeds.

[0005] After the material passes through the two devices, it enters the material inlet of the extruder through the material outlet at the lower end of the holding device. A conveying screw can be provided to convey the material from the material outlet of the holding unit to the material inlet of the extruder.

[0006] In this known pre-treater, the mixing unit and the holding unit are equipped on both sides with doors which can be folded upwards so that the interior of both units is accessible for cleaning of dust. This is not yet optimal. Summary of the Invention

[0007] The problem underlying the present invention is to provide a paddle mixer which can be cleaned in an advantageous manner.

[0008] In particular, the present invention relates to a paddle-type mixing device, in particular a pre-treater, comprising a cylindrical mixing unit having a shaft arranged in the mixing unit, wherein the shaft has paddles and the mixing unit has a base surface, characterized in that a closable opening for introducing a cleaning device into the mixing unit is provided in the base surface.

[0009] The invention is based on the idea of ​​providing an opening at the base surface of the cylindrical unit of the paddle mixer, through which opening a cleaning device can be introduced into the interior of the unit for cleaning the unit.

[0010] In its simplest form, a paddle mixer comprises a cylindrical mixing unit. This type of mixing unit is well known and includes a material inlet through which the material can be introduced into the mixing unit. The material inlet is typically arranged so that the material can be introduced into the mixing unit by gravity. A shaft is provided in the mixing unit, extending along the entire length of the mixing unit, and the paddles are arranged on this shaft. The shaft can be set into rotational motion by means of a drive device, such as an electric motor, and the material contained in the mixing unit can be transported through the mixing unit.

[0011] The mixing unit may also have one or more additional inlets for introducing a liquid, such as water, and / or a gas, such as water vapour, into the mixing unit.

[0012] The cylindrical mixing unit further comprises a base surface facing away from the side where the drive device is located. The base surface comprises a closable opening for inserting a cleaning device into the mixing unit. It is also conceivable to provide a closable opening for inserting a cleaning device into the mixing unit on the base surface where the drive device is located.

[0013] The opening is preferably circular and has a diameter that allows for the insertion of conventional cleaning equipment, such as a spray gun (e.g., from Kärcher). Such cleaning devices are known and are not the subject of the present invention. The diameter of the opening is preferably in the range of 10 mm to 80 mm, more preferably in the range of 10 mm to 45 mm, and even more preferably in the range of 15 mm to 30 mm.

[0014] According to the present invention, the diameter of the opening is preferably selected in conjunction with the diameter of the spray gun used for cleaning, so that the ratio r(d(opening) / d(spray gun)) is in the range of 4 to >1, preferably in the range of 3 to >1, more preferably in the range of 2 to >1, and particularly preferably in the range of 1.5 to >1. For example, for a spray gun with a diameter of 16 mm, an opening diameter of 17 mm can be selected. This prevents excessive cleaning fluid from escaping from the opening during the cleaning process.

[0015] According to the invention, the opening is preferably provided with fastening means, such as a thread, in order to close the opening tightly, for example by means of a closing nut.During operation of the mixing device, the opening should be closed.

[0016] Preferably, according to the present invention, the opening can also be closed by a plug, optionally in combination with an O-ring seal. The plug and the O-ring seal are preferably made of an elastic material such as rubber.

[0017] Preferably, according to the invention, the element for closing the opening can be mounted and removed, preferably without tools, for example by using a blind plug.

[0018] According to one embodiment of the present invention, the base preferably has 2-8, more preferably 2-6, even more preferably 3-6, and particularly preferably 4, closable openings for inserting cleaning devices. In conventional shaft designs with paddles, the interior of the mixing unit is divided into four sections, each of which occupies approximately one-quarter of the cross-section of the cylindrical mixing unit. To thoroughly or optimally clean the mixing unit, the cleaning device is sequentially inserted into the four openings corresponding to each section, with each opening leading to a corresponding section.

[0019] According to one embodiment of the present invention, for safety considerations, the base surface is preferably covered by a cover. In this way, the closable opening arranged in the base surface is hidden from the outside and, for example, can not be accidentally opened during operation.

[0020] According to a preferred embodiment of the invention, the length of the opening is such that even if the relevant opening is not closed, it is not possible to reach the shaft rotating during operation (ISO 13857) through the opening. Therefore, there is no need to monitor the open opening.

[0021] According to a preferred embodiment of the present invention, the mixing unit is additionally provided with a cylindrical holding unit having an axis therein, wherein the axis has blades and the holding unit has a base surface, wherein the holding unit is preferably arranged below the mixing unit, wherein a closable opening for introducing a cleaning device into the holding unit is provided in the base surface of the cylindrical holding unit.

[0022] As mentioned above, a holding unit is known from conventional pre-processors. A shaft is provided in the holding unit, extending over the entire length of the holding unit, and paddles are arranged on the shaft. The shaft can be set into rotational motion by means of a drive device, such as an electric motor, and the material contained in the holding unit is conveyed through the holding unit.

[0023] In the above pre-treatment machine, the material is transferred to an independent holding unit after leaving the mixing unit. According to the present invention, the mixing unit and the holding unit are preferably arranged one above the other, wherein the mixing unit is above the holding unit so that the material is transferred from the mixing unit to the holding unit by gravity.

[0024] According to the present invention, the mixing unit and the holding unit are preferably connected to each other via a closed conduit, which is preferably arranged at the end of the mixing unit farthest from the material inlet. In this way, the material is first conveyed through the entire length of the mixing unit and processed therein before being transferred to the holding unit via the conduit.

[0025] The above description of the openings of the mixing unit also applies to the holding unit, ie information on the number, position, diameter, closability and blockability of the openings and covering of the openings by a cover also applies to the holding unit.

[0026] The holding unit further comprises a material outlet, which is preferably located at the bottom of the holding unit so that the material can be transferred from the holding unit to the conveying screw unit or directly to the extruder by gravity.

[0027] According to the invention, the holding unit and the conveying screw unit or extruder are preferably connected to each other via a closed line, preferably located at the end of the holding unit furthest from the connecting line to the mixing unit. In this way, the material is first conveyed through the entire length of the holding unit and processed therein before being transferred to the conveying screw unit or extruder via the line.

[0028] According to the invention, a cylindrical conveying screw unit connected to a holding unit is additionally provided, the conveying screw unit having an internally arranged shaft, wherein the shaft has paddles and the conveying screw unit has a base surface, wherein the conveying screw unit is preferably arranged below the holding unit, wherein a closable opening is provided in the base surface of the cylindrical conveying screw unit for introducing a cleaning device into the conveying screw unit.

[0029] Conveying screw units are known from conventional extruders with preconditioners. They have a shaft that extends over the entire length of the unit and on which paddles are arranged. Using a drive such as an electric motor, the shaft can be set into rotation, thereby conveying the material within the unit through it.

[0030] The above statements regarding the openings of the mixing unit also apply to the conveying screw unit, ie the information regarding the number, position, closability and pluggability of the openings and whether the openings are covered with a cover also applies to the conveying screw unit.

[0031] The conveying screw unit also has a material outlet. The material outlet is preferably located at the lower side of the conveying screw unit so that the material can be transferred from the conveying screw unit to the extruder by gravity.

[0032] According to the invention, the conveying screw unit and the extruder are preferably connected to one another via a closed line, which is preferably provided at that end of the conveying screw unit which is furthest away from the connecting line to the holding unit.

[0033] According to the present invention, a bypass pipe is preferably provided on the conveying screw unit, and the bypass pipe can be opened and closed by a flange plate coaxially arranged with a shaft in the conveying screw unit.

[0034] Bypasses are known. When a plant is started up, they are used to initially convey product out of the plant through the bypass outlet, rather than into the product stream. In this way, material formed during plant startup but not yet meeting product specifications can be removed from the plant to prevent contamination.

[0035] If a bypass pipe is provided at the conveying screw unit according to the present invention, the pretreatment of the product can continue even if a downstream extruder fails; the pretreated product is then fed into a container through the bypass pipe outlet.

[0036] In a conventional bypass pipe, the bypass outlet is sealed by a slide, which is preferably pneumatically driven and reciprocates horizontally. The slide and bypass outlet are typically located below the material inlet. However, the barrel shape of the conveying screw unit, and the consequently curved shape of the slide, creates dead corners where large amounts of material can accumulate. This is unacceptable for product safety reasons. Cleaning and sealing such bypass pipes is also difficult.

[0037] According to a preferred embodiment of the present invention, the bypass duct is opened and closed by a flange that is coaxially arranged with a shaft provided in the conveying screw unit. In other words, in this preferred embodiment, the bypass duct is opened and closed by moving the flange from a first position in the conveying screw unit to a second position in the conveying screw unit.

[0038] In the first position, the flange is located between the material inlet and the bypass outlet and divides the interior of the conveying screw unit into two separate sections, with the bypass outlet located in one section and the material inlet and the remaining interior of the conveying screw unit located in the other section. Product introduced through the material inlet cannot enter the bypass outlet because the flange divides the interior of the conveying screw unit into two separate sections that are not in fluid communication with each other.

[0039] In the second position, the flange separates the interior of the conveying screw unit into two further independent parts, with the bypass pipe outlet and at least a portion of the material inlet being located in one part. At this point, the product introduced through the material inlet can enter the bypass pipe outlet.

[0040] The flange may be moved from the first position to the second position by conventional means. Preferably, the flange is moved by one or more pneumatic cylinders.

[0041] The flange is coaxially arranged with the conveying screw shaft to prevent the formation of a dead angle.

[0042] The flange may preferably be provided with a sealing member, such as an O-ring made of an elastic material such as rubber.

[0043] When the system is started, the flange moves axially away from the material inlet to the second position described above. The conveyor screw then rotates in the reverse direction, conveying the incoming material to the bypass outlet, which can be connected. Once the product reaches the desired specifications, the flange returns to the first position, separating the inlet material from the bypass outlet. The conveyor screw then rotates forward, and the material enters the extruder.

[0044] The bypass pipe with flange according to the invention can generally be used in any paddle mixing device, in particular any pre-treater or extruder, and is not limited to this device.

[0045] The paddle mixing device according to the invention, in particular the pre-treater, can be arranged on any conventional extruder.

[0046] Therefore, the present invention also relates to an extruder comprising the above-described paddle mixing device according to the invention, in particular a pre-treater.

[0047] 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 to 60, preferably 20 to 40. According to the present invention, the extruder is preferably operated at a speed of 100 to 1000 rpm, particularly preferably 200 to 600 rpm, and most preferably 250 to 350 rpm.

[0048] The extruder according to the present invention comprises a motor with a gearbox for driving the extruder screw. For this reason, the drive shaft of each extruder screw is operatively connected to the gearbox. This can be achieved in a conventionally known manner.

[0049] 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.

[0050] The extruder housing (each barrel forming the extruder housing) has a through hole. This through hole runs axially through the entire length of the extruder housing. The processing area of ​​the extruder is located in this through hole.

[0051] The extruder housing is preferably temperature-controlled. The material to be extruded is kneaded under pressure (generally 1 to 400 bar, preferably 1 to 200 bar) to form a homogeneous mixture. This generally requires an energy input of 10 to 150 Wh / kg, preferably 10 to 120 Wh / kg, particularly preferably 15 to 30 Wh / kg.

[0052] The feed port of the extruder is used to feed the raw materials into the first section of the extruder. The feed port is usually and preferably located at the top of the extruder housing so that the material can enter the extruder housing, more precisely the processing area of ​​the extruder, under the influence of gravity.

[0053] According to the present invention, the feed port of the extruder is connected to the above-mentioned pre-treatment machine, or to the material outlet of the holding unit or to the material outlet of the conveying screw unit (if present).

[0054] 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 it 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-treater and then conveyed from the pre-treater to the feed port, for example, by a conventional conveying screw.

[0055] 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 connected to the processing zone.

[0056] The extruder also typically has a water supply line, an oil supply line and optionally a steam supply line.

[0057] 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. A known dispensing unit is preferably arranged between the extruder and the cooling tool.

[0058] The present invention also relates to a method for cleaning the paddle mixing device according to the above, comprising the following steps:

[0059] - opening a closable opening in the base surface of at least one unit selected from the group consisting of a mixing unit, a holding unit and a conveying screw unit;

[0060] - inserting the cleaning device into the opened opening (2c, 3c, 4c);

[0061] - Cleaning of at least one unit (2, 3, 4) with an inserted cleaning device.

[0062] The method can be carried out through any closable opening provided on the unit (and preferably through each opening). For example, the mixing unit, the holding unit and the conveying screw unit of the paddle mixer according to the invention can be cleaned simultaneously or sequentially, in particular through all openings provided thereon.

[0063] Optionally, before the cleaning device is introduced into one of the openings, the shaft located in the unit to be cleaned must be moved into a position that does not hinder the introduction of the cleaning device into the unit to be cleaned. If necessary, the shaft can be moved into the desired position by the motor of the unit or manually, for example with the aid of a tool that can be inserted into a hole in the shaft, such as a screwdriver.

[0064] According to the present invention, preferably, liquid at a pressure higher than normal pressure is fed into the unit to be cleaned by the cleaning device. Pressurized water is preferably used.

[0065] For cleaning, open the closable opening on one of the units (mixing unit, holding unit, conveying screw unit). In a preferred embodiment of the invention, this opening is sealed with a closed cap (nut) or knurled nut, which is loosened from the thread (manually or with the aid of a known tool) to open the opening. If there is a plug in the opening, this must also be removed.

[0066] A cleaning device, such as a commercial cleaning gun, is inserted into the opening. According to the invention, it is preferred that the cleaning device has a tube whose length corresponds to the axial extension of the unit to be cleaned. With this cleaning device, the corresponding unit can be cleaned over its entire axial extension.

[0067] After the cleaning device has been inserted, cleaning is carried out in the conventional manner by introducing a cleaning fluid.

[0068] Repeat the above process for each desired opening as needed.

[0069] In order to discharge the cleaning fluid introduced into the unit to be cleaned from the paddle mixer according to the invention, a bypass pipe is preferably opened, which, as mentioned above, is preferably arranged at the conveying screw unit. Subsequently, the cleaning fluid can be discharged from the paddle mixer through the bypass pipe outlet. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] The present invention will be described in more detail below by way of non-limiting embodiments with reference to the accompanying drawings. In the accompanying drawings, like reference numerals denote like elements. The accompanying drawings show:

[0071] Figure 1 A schematic diagram of an embodiment of an extruder having a paddle-type mixing device according to the present invention;

[0072] Figure 2 is a schematic diagram of an embodiment of a cell having an opening in a base surface according to the present invention;

[0073] Figure 3 is a schematic diagram of an embodiment of a cell having a closed opening according to the present invention;

[0074] Figure 4a is a schematic diagram of an embodiment of a bypass pipe in a closed state according to the present invention;

[0075] Figure 4b FIG. 4 is a schematic diagram of an embodiment of a bypass pipe in an open state according to the present invention. DETAILED DESCRIPTION

[0076] Figure 1 A schematic diagram of an embodiment of an extruder 7 according to the invention is shown with a paddle mixing device 1. The product flow through the device is indicated by black arrows.

[0077] The paddle type mixing device 1 comprises a cylindrical mixing unit 2 having a material inlet arranged on the mixing unit 2. The base surface 2b ( Figure 2 ) is covered by a cover 2a. A shaft (not shown) with blades is arranged in the mixing unit 2, and the shaft can be rotated by a driving device (not shown).

[0078] The cylindrical holding unit 3 is arranged below the mixing unit 2 and is connected to the mixing unit 2 via a pipeline. The pipeline is arranged at the end of the mixing unit 2 away from the material inlet so that the material flows through the entire length of the mixing unit 2 before entering the holding unit 3 through the pipeline by gravity. Figure 2 ) is covered by a cover 3a. A shaft (not shown) with blades is arranged in the holding unit 3, and the shaft can be rotated by a driving device (not shown).

[0079] A cylindrical conveying screw unit 4 is arranged below the holding unit 3, and the conveying screw unit 4 is connected to the holding unit 3 via a material outlet 5. The material outlet 5 is arranged at the end of the pipeline of the holding unit 3 away from the mixing unit 2, so that the material flows through the entire length of the holding unit 3 before entering the conveying screw unit 4 through the pipeline by gravity. Figure 2 ) is covered by the cover 4a. The shaft 4f with blades 4g (such as Figure 4a and Figure 4b As shown) is arranged in the conveying screw unit 4, the shaft 4f can be driven by the driving device 11 (as shown) Figure 4a and Figure 4b to achieve rotational motion.

[0080] The bypass pipe 6 including the bypass pipe outlet 6a is arranged at the end of the conveying screw unit 4 facing away from the base surface 4b. Figure 4a and Figure 4b A preferred embodiment of the bypass pipe 6 will be described.

[0081] The conveying screw unit 4 is fluidically connected to the inlet of the extruder 7 so that the material can enter the processing zone 9 of the extruder 7 from the conveying screw unit 4. In the processing zone 9 of the extruder 7 (shown in dotted and transparent lines), a conveying screw 9a is arranged, which can be rotated by the drive device 8 of the extruder 7 to transport the material through the processing zone 9. Further details of the extruder 7 are well known and are not described in detail. Figure 1 Shown in.

[0082] Figure 2 The following description also applies to the mixing unit 2, the retaining unit 3 and the conveying screw unit 4.

[0083] exist Figure 2 In the embodiment shown, in the base surface 2b, 3b, 4b (i.e., the bottom surface of the cylindrical units 2, 3, 4), four openings 2c, 3c, 4c are arranged so that each of the openings 2c, 3c, 4c forms an entrance into an area of ​​the unit 2, 3, 4. This area corresponds to one-quarter of the cross-sectional area of ​​the unit 2, 3, 4. If a cleaning device (not shown) is sequentially inserted into each opening 2c, 3c, 4c, the unit 2, 3, 4 can be completely cleaned.

[0084] according to Figure 2 In the preferred embodiment shown, the openings 2c, 3c, 4c protrude from the base surfaces 2b, 3b, 4b, and the protruding portions have fastening elements, such as threads. Figure 3 As shown, for example, nuts 2d, 3d, 4d can be screwed onto the thread.

[0085] Figure 3The following description also applies to the mixing unit 2, the holding unit 3 and the conveying screw unit 4 and all openings 2c, 3c, 4c arranged thereon.

[0086] exist Figure 3 In the illustrated embodiment, the openings 2c, 3c, 4c arranged on the base surfaces 2b, 3b, 4b of the units 2, 3, 4c have threads in the area protruding from the base surfaces 2b, 3b, 4b, onto which nuts 2d, 3d, 4d are fastened. Plugs 2e, 3e, 4e are also provided in the openings 2c, 3c, 4c to seal them. The plugs 2e, 3e, 4e may be equipped with O-ring seals (not shown).

[0087] Figure 4a FIG. 1 is a schematic diagram showing an embodiment in which the bypass pipe 6 a according to the present invention is in a closed state.

[0088] The material enters the conveying screw device 4 through the material outlet 5. A shaft 4f equipped with paddles 4g is rotatably provided in the conveying screw unit 4. Figure 4a The shaft 4 f with blades 4 g shown in FIG. 4 is similar in structure to the shafts with blades provided in the mixing unit 2 and the holding unit 3 .

[0089] The shaft 4 f can be rotated by a drive device 11 .

[0090] A bypass pipe 6 is arranged between the drive device 11 and the material outlet 5. The bypass pipe 6 comprises a bypass pipe outlet 6a, through which the material can be discharged from the conveying screw unit 4 as required without entering the extruder 7.

[0091] The bypass pipe 6 further comprises a flange 10 which is coaxially arranged with the shaft 4f in the conveying screw unit 4 and can be passed through ( Figure 4a and Figure 4b The two cylinders shown in FIG. 1 reciprocate to the right in the direction of the dotted double arrows.

[0092] exist Figure 4a In the embodiment shown in FIG. 1 , flange 10 is in a position blocking access to bypass outlet 6a. Shaft 4f is driven forward in the direction (indicated by the dotted arrow) toward extruder 7. Material entering conveying screw unit 4 through material outlet 5 is conveyed toward extruder 7 as indicated by the bold arrow.

[0093] exist Figure 4b In the embodiment, the flange 10 is in a position that allows access to the bypass pipe outlet 6a. The flange 10 is relative to the cylinder 12. Figure 4aThe shaft 4f is driven backward in the direction toward the bypass outlet 6a (indicated by the dotted arrow). The material entering the conveying screw unit 4 through the material outlet 5 is conveyed toward the bypass outlet 6a as shown by the thick arrow.

Claims

1. A paddle mixing device (1), in particular a pre-processor, comprising a cylindrical mixing unit (2) having a shaft arranged in the mixing unit (2), wherein the shaft has paddles, and the mixing unit has a base surface (2b), It is characterized by: A closable opening (2c) for introducing a cleaning device into the mixing unit (2) is provided in the base surface (2b).

2. The paddle type mixing device according to claim 1, characterized in that A cylindrical holding unit (3) connected to the mixing unit (2) is also provided, wherein a shaft is provided in the cylindrical holding unit (3), wherein the shaft has blades and the holding unit (3) has a base surface (3c), wherein the holding unit (3) is preferably arranged below the mixing unit (2) and wherein a closable opening (3c) for introducing a cleaning device into the interior of the holding unit (3) is provided on the base surface (3b) of the cylindrical holding unit (3).

3. The paddle type mixing device according to claim 1 or 2, characterized in that: A cylindrical conveying screw unit (4) connected to the holding unit (3) is also provided, wherein a shaft (4f) is provided in the cylindrical conveying screw unit (4), wherein the shaft (4f) has blades (4g) and the conveying screw unit (4) has a base surface (4b), wherein the conveying screw unit (4) is preferably arranged below the holding unit (3) and wherein a closable opening (4c) for introducing a cleaning device into the interior of the conveying screw unit (4) is provided in the base surface (4b) of the cylindrical conveying screw unit (4).

4. The paddle-type mixing device according to any one of claims 1 to 3, characterized in that At least one unit selected from the group consisting of a mixing unit (2), a holding unit (3) and a conveying screw unit (4) has a base surface (2b, 3b, 4b) having 2-8, preferably 2-6, more preferably 3-6 and most preferably 4 closable openings (2c, 3c, 4c) for introducing a cleaning device.

5. The paddle-type mixing device according to any one of claims 1 to 4, characterized in that The closable openings (2c, 3c, 4c) are closed by screw caps (2d, 3d, 4d).

6. The paddle-type mixing device according to any one of claims 1 to 5, characterized in that Also included is a plug (2e, 3e, 4e) disposed in the closable opening (2c, 3c, 4c).

7. The paddle-type mixing device according to any one of claims 1 to 6, characterized in that Also included is a cover (2a, 3a, 4a) disposed above the closable opening.

8. The paddle-type mixing device according to any one of claims 1 to 7, characterized in that It also includes a bypass pipe (6) arranged at the conveying screw unit (4) and capable of being opened and closed by a flange (10), wherein the flange (10) is coaxially arranged with the shaft (4f) arranged in the conveying screw unit (4).

9. An extruder (7) comprising a paddle mixing device (1) according to any one of claims 1 to 8.

10. A method for cleaning a paddle mixer (1) according to any one of claims 1 to 8, comprising the following steps: - opening a closable opening (2c, 3c, 4c) in a base surface (2b, 3b, 4b) of at least one unit selected from the group consisting of a mixing unit (2), a holding unit (3) and a conveying screw unit (4); - inserting the cleaning device into the opened opening (2c, 3c, 4c); - Cleaning of said at least one unit (2, 3, 4) with said cleaning device inserted.

11. The method according to claim 10, characterized in that The method can be implemented via each closable opening (2c, 3c, 4c) provided in the unit (2, 3, 4).

12. The method according to claim 10 or 11, characterized in that A liquid is fed through the cleaning device into the unit (2, 3, 4) to be cleaned, the liquid having a pressure exceeding the normal pressure.

13. The method according to any one of claims 10 to 12, characterized in that The cleaning device has a pipeline, the length of which corresponds to the axial extension of the unit (2, 3, 4) to be cleaned.

14. The method according to any one of claims 10 to 13, characterized in that The bypass pipe (6) is opened to allow the liquid fed into the unit (2, 3, 4) to be cleaned to be discharged from the paddle mixer (1).

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