Housing segment, and method for producing same

Abstract

The invention relates to a housing segment (7) to be assembled as part of a housing of an extruder, and to a method for producing the housing segment, wherein a hardened bushing (11) is inserted into an external body (10) of the housing segment (7), which bushing: has a length (8) of the external body (10) in a longitudinal direction (3) of the extruder; is undivided in a peripheral direction (15) of the extruder; and surrounds a working chamber (4) of the housing, in which working chamber at least one extruder screw is mounted so as to be rotatable about the longitudinal direction (3). In order to simplify the production of the bushing (11), according to the invention the bushing (11) is assembled, inside the housing segment (7), from a plurality of segments (12) each having a length (14) in the longitudinal direction (3) of at most 60 mm.

Description

[0001] Housing segment and method for producing the same

[0002] The invention relates to a housing segment for assembling as part of a housing of an extruder and a method for producing the same, wherein a wear-resistant bushing is inserted into an outer body of the housing segment, which bushing has a length of the outer body in a longitudinal direction of the extruder, is undivided in a circumferential direction of the extruder and encloses a working space of the housing in which at least one extruder screw is mounted so as to be rotatable about the longitudinal direction.

[0003] Such housing segments are known from DE 10 2010 003 154 A1, DE 43 28 159 A1, and EP 0 144 192 A1. The known housing segments have a length several times the extruder shaft diameter. The bushing of the known housing segments is sintered and hardened, and the inner surface is remachined after hardening by milling or wire EDM.

[0004] In milling, the cutting insert deviates increasingly from the specified path with the length of the spindle; in wire EDM, the machining time increases disproportionately with the length. Both processes require precise monitoring and control of the manufacturing process to avoid dimensional deviations. Simpler machining processes are not suitable for producing the inner surface due to the machining length.

[0005] In the background of the invention, DE 37 80 996 T2 discloses an extruder with a bushing divided longitudinally into segments, each of which is circumferentially divided into two half-shells for pinning to the outer body from the inside. Housing segments without a wear-resistant bushing are known from DE 92 00 047 U1.

[0006] Task

[0007] The invention is based on the object of simplifying the manufacture of the bushing. Solution

[0008] Based on the known housing segment, the invention proposes that the bushing within the housing segment be composed of several segments, each with a maximum length of 60 mm in the longitudinal direction. In each of the segments, the inner surface can be manufactured cost-effectively with the required dimensional accuracy using simple machining processes.

[0009] In a housing segment according to the invention, the outer body is preferably made of a cold-work steel. Cold-work steels, such as ST37, are particularly cost-effective materials that are easy to machine with standard tools.

[0010] Preferably, in a housing segment according to the invention, at least two of the segments have different outer contours. The different outer contours and a corresponding inner contour of the housing segment prevent displacement of the segments in the longitudinal direction. In particular, one or both end segments can have a larger outer cross-section than the others.

[0011] Preferably, in a housing segment according to the invention, at least two of the segments have different inner contours. The different inner contours support the mixing and kneading action of the extruder. In particular, in one of the segments, the cross-section of one or more of the bores assigned to a respective extruder screw can be larger than in an adjacent segment. Alternatively or additionally, the inner surface of one or more of the segments can have one or more grooves spiraled parallel or counter-rotating around the longitudinal direction.

[0012] Preferably, at least one barrel segment according to the invention is combined with other barrel segments in the extruder to form the barrel. The barrel and screw shafts form the process section of the extruder. Such an extruder according to the invention is equally characterized by the aforementioned advantages of the barrel segments according to the invention.

[0013] Such an extruder according to the invention preferably has two intermeshing extruder screws mounted for rotation within the working chamber. Alternatively, such an extruder has a single extruder screw. Preferably, the extruder screws in such an extruder according to the invention are co-rotatable. Alternatively, the extruder screws are counter-rotatable. The aforementioned types of extruders are well known and proven in practice.

[0014] Based on the known method, the invention proposes that the bushing be assembled from segments each with a maximum length of 60 mm in the longitudinal direction. The method according to the invention results in a housing segment according to the invention and is therefore equally characterized by the aforementioned advantages.

[0015] In a method according to the invention, the outer body is preferably produced using a primary or forming process, in particular powder metallurgy or by casting, pressing, or forging. The housing segment and the segments can thus be manufactured particularly cost-effectively.

[0016] In a method according to the invention, the segments are preferably wear-protected, in particular hardened, nitrided, or coated. This increases the service life of the segments.

[0017] Preferably, an inner surface of the segments is milled in a method according to the invention. This allows the inner surface to be produced particularly cost-effectively.

[0018] Preferably, in a method according to the invention, contact surfaces where the segments are in contact with each other are ground flat. The segments then lie seamlessly against each other after assembly in the housing segment. Alternatively, the segments can be formed with longitudinally interlocking structures, for example, with grooves. The segments can then not rotate relative to each other in the longitudinal direction during operation. Alternatively or additionally, the segments can be pinned or wedged together for this purpose.

[0019] Example

[0020] The invention is explained below using an exemplary embodiment.

[0021] Fig. 1 shows an extruder according to the invention and

[0022] Fig. 2 shows a housing segment according to the invention.

[0023] The extruder 1 shown in Figure 1 - here: a twin-screw extruder - has a housing 2. The housing 2 has a working chamber 4 extending in the longitudinal direction 3 with a cross-section in the shape of a horizontal figure eight, in which two extruder screws 5 with a diameter D of 6 cm and a process length 6 of 240 cm, i.e. 40 D, are mounted so as to rotate in the same direction.

[0024] The housing segment 7 according to the invention shown in Figure 2 has a length 8 of 24 cm in the longitudinal direction 3 and two flange surfaces 9 extending transversely to the longitudinal direction 3. An outer body 10 with the length 8 of the housing segment 7 is manufactured from ST37 using the malleable cast iron process; the flange surfaces 9 are ground flat.

[0025] The housing segment 7 has a bushing 11 radially enclosing the working chamber 4 in the outer body 10. The bushing 11 has a length 8 of the housing segment 7 and the outer body 10. The bushing 11 is made of a high-alloy tool steel with volume fractions of 2.6% carbon, 0.6% silicon, 0.4% manganese, 26% chromium, 3.7% vanadium, and 1.1% molybdenum. The bushing 11 consists of five identical segments 12.

[0026] The segments 12 are sintered by isostatic pressing and then hardened. The inner surface 13 of the segments 12 is milled after hardening. The outer body 10 is shrunk onto the bushing 11, which is loosely assembled from the segments 12, and is wedged to them in a manner not shown. The segments 12 each have a length 14 of 4.8 cm and are undivided in a circumferential direction 15 of the extruder 1, thus each consisting of a single, uniform element. The housing 2 essentially consists of ten identical housing segments 7 bolted together at the flange surfaces 9.

[0027] Other housing segments according to the invention differ from the aforementioned only in that the segments 12 have interlocking grooves and tongues in the longitudinal direction 3 and / or are pinned to one another.

[0028] In the figures are

[0029] 1 extruder

[0030] 2 housings

[0031] 3 Longitudinal direction

[0032] 4 Workspace

[0033] 5 extruder screw

[0034] D Diameter

[0035] 6 Process length

[0036] 7 Housing segment

[0037] 8 Length of the housing segment

[0038] 9 Flange surface

[0039] 10 outer bodies

[0040] 11 socket

[0041] 12 segments

[0042] 13 Surface

[0043] 14 Length of the segment

[0044] 15 Circumferential direction

Claims

Patent claims 1. Housing segment (7) for assembling as part of a housing (2) of an extruder (1), wherein in the housing segment (7) an outer body (10) with a hardened bushing (11), which has a length (8) of the outer body (10) in a longitudinal direction (3) of the extruder (1), is undivided in a circumferential direction (15) of the extruder (1) and encloses a working space (4) of the housing (2), in which at least one extruder screw (5) of the extruder (1) can be mounted so as to rotate about the longitudinal direction (3), characterized in that the bushing (11) within the housing segment (7) is composed of a plurality of segments (12) each with a length (14) in the longitudinal direction (3) of at most 60 mm.

2. Housing segment (7) according to the preceding claim, characterized in that the outer body (10) consists of a cold-work steel.

3. Housing segment (7) according to one of the preceding claims, characterized in that at least two of the segments (12) have different outer contours.

4. Housing segment (7) according to one of the preceding claims, characterized in that at least two of the segments (12) have different inner contours.

5. Extruder (1) with a housing (2) which is composed of several housing segments (7) according to one of the preceding claims.

6. Extruder (1) according to the preceding claim, characterized in that exactly two extruder screws (5) are rotatably mounted in the working chamber (4).

7. A method for producing a housing segment (7) for assembly as part of a housing (2) of an extruder (1), wherein a hardened bushing (11) is inserted into an outer body (10) of the housing segment (7), which bushing has a length (8) of the outer body (10) in a longitudinal direction (3) of the extruder (1), is undivided in a circumferential direction (15) of the extruder (1) and encloses a working space (4) of the housing (2), in which at least one extruder screw (5) is mounted so as to be rotatable about the longitudinal direction (3), characterized in that the bushing (11) is assembled within the housing segment (7) from a plurality of segments (12) each with a length (14) in the longitudinal direction (3) of at most 60 mm.

8. Method according to one of the preceding claims, characterized in that the outer body (10) is produced in a primary forming process.

9. Method according to one of the preceding claims, characterized in that the segments (12) consist of a powder metallurgical material.

10. Method according to one of the preceding claims, characterized in that the segments (12) are protected against wear.

11. Method according to one of the preceding claims, characterized in that an inner surface (13) of the segments (12) is milled.

12. Method according to one of the preceding claims, characterized in that contact surfaces in which the segments (12) are in contact with each other are ground flat.

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