EXTRUDER FOR THE EXTRUSION OF FOOD OR FEED

Abstract

A single screw extruder (E) for the extrusion of food or feed, comprising in the direction of flow of a product to be extruded: i) a processing section (8); ii) a bypass outlet (B); iii) a valve plate (V); iv) a die plate (D); and iv) a cutter (6). The flow of product can be directed through the valve plate, under normal operating conditions of the extruder (E), and through the bypass outlet (B), during start-up of the extruder (E) or for maintenance purposes, downstream of the valve plate (V). The valve plate (V) is arranged on or in a mounting plate (M). The cutter (6) and the mounting plate (M) are provided with interacting guiding mechanism that prevent rotation of the cutter (6), vis--vis the mounting plate (M); and the cutter (6) and the mounting plate (M) are mechanically fastened to each other with rotational locking mechanism.

Claims

1-14. (canceled)

15. A single screw extruder for extrusion of food or feed, the single screw extruder comprising in a direction of flow of a product to be extruded: i) a processing section; ii) a bypass outlet; ii) a valve plate; iii) a die plate; iv) a cutter with (a) rotating knife(s) in a cutter housing; wherein the flow of product can be directed through the valve plate under normal operating conditions of the extruder, and through the bypass outlet, during start-up of the extruder or for maintenance purposes, downstream of the valve plate; the valve plate (V) is arranged on or in a mounting plate; the cutter housing and the mounting plate are provided with interacting guiding means that prevent rotation of the cutter housing vis--vis the mounting plate; and the cutter housing and the mounting plate are mechanically fastened to each other by rotational locking means.

16. The single screw extruder according to claim 15, wherein the interacting guiding means that prevent rotation of the cutter housing, vis--vis the mounting plate, are: pins; and holes or blind holes.

17. The single screw extruder according to claim 16, wherein the interacting guiding means are the pins, and the pins are provided on the cutter housing.

18. The single screw extruder according to claim 16, wherein the interacting guiding means are the holes or blind holes, and the holes or blind holes are provided in the mounting plate.

19. The single screw extruder according to claim 15, wherein the rotational locking means that mechanically fasten the cutter housing and the mounting plate to each other are: a rotatable locking ring, provided with a first set of mechanical fastening elements; and a second set of mechanical fastening elements that interlock with the first set of mechanical fastening elements.

20. The single screw extruder according to claim 19, wherein the second set of mechanical fastening elements is positionally fixed.

21. The single screw extruder according to claim 19, wherein the rotatable locking ring with the first set of mechanical fastening elements is provided on the cutter housing; and the second set of mechanical fastening elements is provided on the mounting plate.

22. The single screw extruder according to claim 19, wherein elements of the second set of mechanical fastening elements are angle brackets extending away from the mounting plate towards the cutter housing, which angle brackets provide undercuts that are engaged behind by elements of the first set of mechanical fastening elements.

23. The single screw extruder according to claim 19, wherein the first set of mechanical fastening elements and the second set of mechanical fastening elements have complementary tapered surfaces that are friction-locked against each other when the cutter housing and the mounting plate are mechanically fastened to each other.

24. The single screw extruder according to claim 19, wherein the first set of mechanical fastening elements is a male thread, either continuous or segmented; and the second set of mechanical fastening elements is a female thread, either continuous or segmented.

25. The single screw extruder according to claim 19, wherein the first set of mechanical fastening elements and the second set of mechanical fastening elements are complementary elements of a bayonet coupling.

26. The single screw extruder according to claim 19, wherein the locking ring with the first set of mechanical fastening elements; and/or the second set of mechanical fastening elements is/are pneumatically operated, hydraulically operated or operated by a motor.

27. The single screw extruder according to claim 15, wherein the position in which the cutter housing and the mounting plate are mechanically fastened to each other, by the rotational locking means, can be mechanically locked.

28. The single screw extruder according to claim 15, wherein the die plate is hinge-mounted so that the die plate can be swiveled out when the cutter housing is dismounted.

29. A method of mounting the extruder according to claim 15, comprising the steps of: providing the mounting plate; providing the cutter with a/the rotating knife(s) in the cutter housing; wherein the cutter housing and the mounting plate are equipped with the interacting guiding means; arranging the cutter housing and the mounting plate such that the interacting guiding means prevents rotation of the cutter housing vis--vis the mounting plate; and mechanically fastening the cutter housing at the mounting plate with the rotational locking means provided on the mounting plate and the cutter housing.

30. The method according to claim 29, wherein the interacting guiding means are pins, and holes or blind holes.

31. A method of operating the extruder according to claim 15, wherein the valve plate is closed, downstream of the valve plate, during start-up of the extruder or for maintenance purposes in order to direct the flow of product through the bypass outlet; and/or the valve plate is at least partially opened under normal operating conditions of the extruder.

32. A kit comprising a cutter for a single screw extruder, wherein the cutter comprises (a) rotating knife(s) in a cutter housing; a mounting plate for a single screw extruder; wherein the cutter housing and the mounting plate are provided with interacting guiding means that prevent rotation of the cutter housing vis--vis the mounting plate; and the cutter housing and the mounting plate are mechanically fastened to each other with rotational locking means.

Description

[0041] The invention will now be explained in further detail by means of specific embodiments and illustrative figures. It is to be understood that the invention is not limited in any way to these illustrative embodiments.

[0042] FIG. 1: Single screw extruder with cutter (prior art);

[0043] FIG. 2: Partial view from FIG. 1;

[0044] FIG. 3: Side-view of an extruder according to the invention from the end of the processing section onwards (schematically);

[0045] FIG. 4a: Cross-sectional view (schematically) of FIG. 3 from the plane Y1;

[0046] FIG. 4b: Cross-sectional view (schematically) of FIG. 3 from the plane Y2;

[0047] FIG. 5a: Side view (schematically) of a locking ring with elements of the first set of mechanical fastening elements;

[0048] FIG. 5b: Side view (schematically) of elements of the second set of mechanical fastening elements.

[0049] A typical single screw extruder E that is known in the art is shown in FIG. 1. The extruder E is powered by a main motor 1 to which a drive unit 2 and a bearing chamber 3 are associated. The processing section 8 is typically made up from several so-called barrels that are supported by a barrel support 5. Raw product is supplied to the extruder E through a side feeder 4 and is transported through the processing section 8 by a screw (not shown). Prior to entering the processing section 8, the raw product can be pretreated in a so-called conditioner or retentioner, and is then fed to the side feeder 4 via a feeder 10. The configuration of the screw can vary over the length of the processing section 8, depending on the product to be extruded. The extruder E is operated by a technician via a control panel 9. At the end of the processing section 8, there is die head comprising a die plate 7. Downstream of the die head, a cutter 6 is arranged. The cutter 6 is equipped with a rotating knife that cuts the strands exiting the die into pellet. The size of the pellets depends on both the flow rate of the product and the rotating speed of the knife of the cutter 6.

[0050] The invention specifically concerns the interface between the processing section 8 and the cutter 6; this area is marked with a dotted line in FIG. 1 and reproduced in an enlarged view in FIG. 2. Upstream of the die head is the processing section 8. After the die plate 7, the product enters the cutter 6 and the strands of product exiting the die plate 7 are cut into pellets by a rotating knife (not shown). The rotating knife is powered by a motor 12. The pellets fall into the cutter 6 and either exit the cutter 6 at the bottom or are blown upwards, depending on the product.

[0051] An extruder E according to the invention is equipped with a specifically mounted and arranged SSDS between the processing section 8 and the die plate 7, as will be further illustrated below.

[0052] FIG. 3 schematically illustrates a side-view of an extruder E according to the invention from the end of the processing section 8 and further downstream to the cutter 6. On the left side, the extruder screw is schematically represented. Further downstream of the processing zone 8, a sanitary start-up and discharge system (SSDS) is installed with a flange F. The SSDS provides for a bypass outlet B that can be opened and closed. The SSDS further comprises a mounting plate M, onto which the valve plate V is arranged (suggested in broken lines). Further downstream of the valve plate V is the die plate D. The die plate D is hinge mounted so that it can be easily swung out for maintenance purposes when the cutter 6 is dismounted. The cutter 6 is located downstream of the die plate D, and it houses a rotary knife (not shown) powered by a motor 12. The cutter 6 is mechanically fastened with rotational locking means (not shown). The general orientation of the cutter 6 vis--vis the mounting plate M is safeguarded by guiding pins P extending from the cutter 6 and reaching through complementary holes H in the mounting plate M.

[0053] FIGS. 4a and 4b schematically show cross-sectional views of FIG. 3 from the planes Y1 and Y2, respectively, as marked in FIG. 3. FIG. 4a shows the side of the cutter that faces towards the extruder E. Four pins P are located in the corners of the face of the cutter box. In the center of FIG. 4, a circular opening in the face of the cutter 6 which is the product flow channel opens the view on the rotary knife K. The complementary view in FIG. 4b is a view onto the valve plate V with slits 15 that can be fully or partially closed when the valve plate V is rotated vis--vis an underlying base plate with complementary openings (not shown). In the corners of the mounting plate M there are holes H matching with the pins depicted in FIG. 4a that extend from the cutter 6 towards the mounting plate M.

[0054] FIG. 5a shows the locking ring R with elements 13 of the first set of mechanical fastening elements. The elements 13 are elevated structures extending outwards on the circumference of the locking ring R. The elements 13 have a tapered surface 16 that matches with complementary tapered surfaces of elements 14 of a second set of mechanical fastening elements provided on the mounting plate M, as depicted in FIG. 5b. The elements 14 are angle brackets, wherein one flank of the bracket substantially extends parallel to the paper plane, and the other flank of the bracket extends downwards into the paper plane on the left side of FIG. 5b, thus forming an undercut. The undercut has a tapered surface 17 which is complementary to the tapered surface 16 on the elements 13. Upon rotation of the locking ring R vis--vis the mounting plate, the elements 13 can slide into the undercut of the angle bracket, whereby the locking ring R (and the cutter) gets mechanically fastened on the mounting plate.