COEXTRUDING EXTRUDER ESPECIALLY FOR FOODSTUFFS SUCH AS PASTE AND STUFFING

Abstract: The extruder comprises a mantle (1) surrounding a number of flights (8, 9) corresponding to the number of materials to be coextruded, and an extruder head (15), in which extruder the flights (8, 9) are coaxial and placed in extension of each other in the common transport direction of the materials. The front end of a flight which is behind (9) is connected to a duct (22) which within the flight/flights ahead (8) extends to the front end of the front flight (8). Several flights (8, 9) for different materials are provided in a single worm member (7) and within the mantle (1) at a flight (8, 9) an axially displaceable reversal member (17, 23) for controlled rerouting of extruded material is provided.

Description: COEXTRUDING EXTRUDER ESPECIALLY FOR FOODSTUFFS SUCH AS PASTE AND STUFFING The present invention relates to a coextruding ex- truder especially for foodstuffs like paste and stuffing, said extruder comprising a mantle surrounding a number of flights corresponding to the number of materials to be co- extruded, and an extruder head, in which extruder the flights are coaxial and placed in extension of each other in the common transport direction of the materials, and the front end of a flight which is behind is connected to a duct which within the flight/flights ahead extends to the front end of the front flight. Coextrusion is a generally known process which is used when it is desired to extrude an object which over its cross section comprises various materials. From the plastic industry it is thus known to coextrude profiles, in which various parts of the profile for instance have different hardnesses. From the food industry it is for instance known to coextrude paste like canelloni, i.e. paste tubes with stuffing. In some of the known machines for coextrusion sepa¬ rate extruders are used for extrusion of the individual materials, which from each their extruder are conveyed to a common extruder head, in which the desired profile with the desired distribution of material is provided. Extruders are known, in which the two flights are mounted one within the other, see for instance US Patents Nos. 1 647 683, 2 764 780 and 2 769 201. Furthermore, an apparatus is known from US Patent No. 1265853, which apparatus consists of two extruders placed in extension of each other, where the outlet from the rear extruder is passed coaxially through the worm member in the front extruder to the outlet of the latter. The two ex- truders are driven by a gear transmission by means of a single crank handle. There are no means for direct control of the ratio between the amount of material delivered from the two extruders. The object of the invention is to provide an extruder for coextrusion, in which the need for use of separate ex¬ truders for the individual materials is eliminated, and where there is a possibility of adjusting the ratio between the extruded amount of the individual materials. This is attained according to the invention by means of an extruder of the type mentioned by way of introduct¬ ion, which extruder is characterstic in that several flights for different materials are provided in a single worm member and that within the mantle at a flight an axi¬ ally displaceable reversal member for controlled rerouting of extruded material is provided. In an embodiment the duct extends backwards from the point for connection with the front end of the flight behind to the inlet of the flight behind, where the duct is also connected with the flight, and an axially displaceable mem-ber in the duct comprises a wall adapted by axial displace-ment to connect the front end of the flight with the for-wards facing and/or backwards facing part of the duct. Hereby it becomes possible to rerout the material conveyed by the flight behind back to the inlet of the flight, the possibility of controlling the amount of material conveyed by the flight behind being thus provided. In a second embodiment a flight is conically tapering and a corresponding conical, surrounding mantle portion is axially displaceable relative to the flight. Hereby it be¬ comes possible to adjust the gap between the windings of the flight and the surrounding mantle, whereby it becomes possible to reroute part of the material conveyed and to consequently adjust the amount of material discharged from the flight. In a further embodiment the conical mantle portion is fixed against rotation relative to the housing of the ex- truder and adapted to be axially displaced by means of an internally threaded union which is axially movable relative to either the extruder housing or the conical mantle por- tion and axially fixed relative to the other one of these two. Extruded articles like paste is normally cut up in pieces of a predetermined length, for which reason at the outlet of the extruder head a rotating knife rotating around an axis parallel with the flights is provided for the cutting of an extruded string. This knife is according to an embodiment of the invention sickle-shaped to get the best possible cut. An extruder which in an embodiment of the invention is intended for the manufacture of ravioli is at the outlet of the extruder head provided with a driven pair of rol¬ lers, in which preferably one roller is circular-cylindric¬ al and the second roller comprises recesses in the roller surface. According to this embodiment of the invention the pair of rollers is mounted displaceably towards and away from the outlet from the extruder head, the pair of rollers is biased towards a resting position, sensing means are provided for sensing the position of the pair of rollers in relation to the resting position, and the drive of the pair of rollers is adapted to be controlled depending on said sensing. The invention will be explained in the following by means of embodiments with reference to the drawing, in which Fig. 1 shows a broken sectional view through an extruder according to the invention, Fig. 2 a sectional view along the line II-II in Fig. 1, Fig. 3 a sectional view along the line III-III in Fig. 1, Fig. 4 a second embodiment of a conical mantle por¬ tion, Fig. 5 a rotating knife for the cutting of extruded paste, and Fig. 6 equipment for the manufacture of ravioli. Fig. 1 shows an extruder intended for the manufacture of filled paste. The extruder comprises a housing 1 con¬ sisting of two coaxial tubes la,lb, where a peripheral helical recess 2 has been established in the tube lb to provide a cooling water duct with an inlet spigot 3 and an outlet spigot 4. At the front of the extruder a second cooling water duct 5 with an inlet spigot 6 has been provided. A worm member 7 extends through the major part of the length of the housing 1. This worm member 7 comprises two flights 8 and 9. In the wall of the housing 1 inlets 10 and 11 are provided for the flights 8 and 9, respectively. These inlets 10 and 11 are provided in the bottom of each their inlet reservoir 12 and 13 for the materials to be extruded. The inlet reservoirs 12 and 13 are schematically indicated by mans of partition walls 14. The extruder is provided with an extruder head 15 comprising the front part of the housing 1. The extruder head comprises several ex¬ changeable parts and will be described in detail below. The front flight 8 has a conical pressure-building part 16 which is surrounded by a corresponding conical mantle portion 17 which is axially displaceable relative to the housing 1 and the worm member 7. Axial displacement of the mantle portion is achieved by the turning of an intern¬ ally threaded union 18. The union is provided with an in- ternal peripheral groove 19 receiving three pins 20, said pins extending through longitudinal slits through the housing 1 to fixedly engage the mantle portion 17. The housing is provided with an external thread corresponding to the internal thread of the union 18, whereby the union when rotating moves forwards or backwards relative to the housing 1, and due to the fact that the pins 20 are received in the groove 19, the mantle portion 17 will follow the axial movement of the union 18. A central duct 22 extends through the major part of the length of the worm member 1 , said duct discharging at the front end of the worm member at the exctruder head 15. The duct 22 holds a tube 23, which is closed at the ends by walls 24 and 25. The tube 23 is axially displaceable, but fixed against rotation relative to the worm member 7 and comprises at the ends openings 26 and 27 facing the wall of the duct 22, said openings being mutually positioned in the same way as openings 29 and 30 between the rearmost flight 9 and the duct 22. The tube 23 is axially displaceable in the worm member 7 by means of a rod 31. The housing 1 is closed at the end by means of a cover 32, through which a transmission member 33 and the rod 31 extend. The extruder functions in such a way that paste dough to be extruded to an outer layer in the finished product is placed in the inlet reservoir 12, from where it, through the inlet 10 to the front flight 8, penetrates into this flight and is conveyed forwards towards the extruder head 15. On its way the dough passes the pressure building part 16, where on the one hand a pressure is built up in the dough and on the second hand a rerouting of a part of the dough may be performed by displacement of the mantle portion 17 forwards, a clearance being provided between the flanges of the flight 8 and the mantle portion 17, through which clearance part of the dough can move back. Filling, for instance stuffing, which is to constitute the interior part of the finished product, is filled in a similar way into the inlet reservoir 13 and penetrates through the inlet 11 down into the flight 9 and is conveyed forwards by the rotation of the worm member 7. The filling is led to the opening 29 from the flight to the duct 22 and from there through the duct 22 towards the extruder head 15. By means of the tube 23 and axial displacement thereof, a major or a smaller part of the conveyed filling may be led through the opening 26 through the tube 23 to the open-ings 27 and 30 and out into the flight 9 at the inlet opening 11 from the inlet reservoir 13. In this way the conveyed amount of stuffing is controlled. In the extruder head, which is shown partly in Fig. 1, partly in Figs. 2 and 3, which are cross sectional views in relation to Fig. 1, a receiving tube 34 is provided for the material coming from the duct 22, and in the receiving tube 34 an alignment cross 35 is provided for the alignment of the flow of the material coming from the duct 22. The receiving tube 34 is held by means of a member 36 having a screw flange with openings for the distribution and the passage of the material coming from the front flight 8. Having passed the openings 37 in the flange of the member 36, the material coming from the front flight 8 is led out through an annular nozzle 38. The material coming from the rearmost flight 9 is led out through a central opening 39 within the annular nozzle 38. The extruder head 15 is sealed and closed by means of a sealing 40, an annular cover 41, and a union 42. The individual members of the extruder head 15 may be replaced by other members known from machines for the extrusion of paste. In Fig. 4 an alternative embodiment of the front part of the housing 1 is shown with another mechanism for the displacement of the mantle portion 17. The mantle portion 17 comprises a longitudinal recess 43 engaging a screw 44 mounted in the housing 1. The front part of the housing is constituted by a tube part 45 with an internal thread. The union 42 and the cover 41 are mounted on the tube part 45. The remaining members of the extruder head 15 are not shown. The tube part 45 is fixed to the housing 1 by means of a ring 47 which is screwed onto the tube part 45 and engages a rim 48 at the end of the housing 1. In this way the tube part 45 becomes axially fixed, but rotatable rela¬ tive to the housing 1. By rotation of the tube part 45, the mantle portion 17, which is provided with an external thread engaging the internal thread 46 of the tube part 45, is moved axially relative to the housing 1, as it is pre¬ vented from rotating by the screw 44. Fig. 5 shows the outlet from the extruder head 15 with the union 42, the cover 41, the annular nozzle 38, and the opening 39. Next to the extruder head 15 a rotating knife 49 is provided, the rotational axis 50 of which is parallel with the rotational axis of the worm member 7. The blade 51 of the knife 49 has the shape of a sickle and moves in the direction of the arrow 52. By the rotation of the knife 49 an extruded article will be cut into lengths by means of a cut, during which the cutting edge of the blade 51 is moved obliquely through the extruded article relative to its longitudinal direction, which results in a good cut. In Fig. 6 the extruder head 15 is shown, which in this case is provided with equipment for the manufacture of ravioli. This equipment comprises a protruding tube 53 in extension of the duct 22. Moreover, a pair of rollers 54, 55 are provided, the roller 54 being circular-cylindrical while the roller 55 is provided with recesses 56 in its roller surface. The annular nozzle 38 is in this case di¬ vided in two in an upper and a lower half 38a and 38b, an upper and a lower band of paste dough being thus extruded. These two bands are rolled together by means of the rollers 54, 55, and the tube 53 feeds stuffing between the bands, where on account of the recesses 56 in the roller 55 the stuffing is embedded in pockets between the two paste dough bands. To make this ravioli equipment function properly it is of importance that the speed of the rollers 54 and 55 is adjusted in relation to the speed of extrusion. Therefore, the pair of rollers 54, 55 is mounted displaceably on a threaded rod 57, and to springs 58 are biasing the pair of rollers 54, 55 towards an equilibrium position relative to the extruder head 15. The equilibrium position may be ad- justed by means of nuts 59 on the threaded rod 57. An arm 60 which is fixed in relation to the pair of rollers is adapted to influence two switches 61 and 62. When ravioli is manufactured, the pair of rollers 54, 55 moves towards the extruder head 15 on account of the combined power of the springs 58 and thereby establish a certain tension in the paste dough bands. If the pair of rollers 54, 55 rotates too quickly, the arm 60 will be drawn towards the switch 61 which is thereby activated and causes a reduction of the rotational speed of the pair of rollers. If the pair of rollers runs too slowly, the arm 60 will on account of the force of the springs 58 be taken back to the switch 62, which is activated and causes an increase of the rotational speed of the pair of rollers. Thus, the rotational speed of the pair of rollers and the tension in the paste dough bands are controlled.

Claims: C L A I M S 1. A coextruding extruder, especially for foodstuffs such as paste and stuffing, comprising a mantle (1) sur- rounding a number of flights (8, 9) corresponding to the number of materials to be coextruded, and an extruder head (15), in which extruder the flights (8, 9) are coaxial and placed in extension of each other in the common transport direction of the materials, and the front end of a flight which is behind (9) is connected to a duct (22) which with¬ in the flight/flights ahead extends to the front end of the front flight (8), c h a r a c t e r i z e d in that several flights (8, 9) for different materials are provided in a single worm member (7) and that within the mantle (1) at a flight (8, 9) an axially displaceable reversal member (17, 23) for controlled rerouting of extruded material is provided. 2. An extruder according to claim 1, c h a r a c t e r i z e d in that the duct (22) extends backwards from the point (29) for connection with the front end of the flight (9) behind to the inlet (11) of the flight (9) behind, where the duct (22) is also connected with the flight (9) , and in that the reversal member com¬ prises a member (23) in the duct (22) with a wall (24) adapted by axial displacement to connect the front end of the flight (9) with the forwards facing and/or backwards facing part of the duct (22) . 3. An extruder according to claims l or 2, c h a r a c t e r i z e d in that a flight (8) is conic- ally tapering and that the reversal member comprises a corresponding conical, surrounding mantle portion (17) which is axially displaceable relative to the flight (8) . 4. An extruder according to claim 3, c h a r a c t e r i z e d in that the conical mantle portion (17) is fixed against rotation relative to the housing (1) of the extruder and is adapted to be axially displaced by means of an internally threaded union (18) which is axially movable relative to either the extruder housing (1) or the conical mantle portion (17) and axially fixed relative to the other one of these two. 5. An extruder according to claims 1-4, in which at the outlet from the extruder head (15) a rotating knife (49) rotating around an axis (50) parallel with the flights is provided for the cutting of an extruded string, c h a r a c t e r i z e d in that the blade (51) of the knife (49) is sickle-shaped. 6. An extruder according to claims 1-4, in which at the outlet from the extruder head (15) a driven pair of rollers (54, 55) is provided, in which preferably one roller (54) is circular-cylindrical and the second roller (55) com¬ prises recesses (56) in the roller surface, c h a r a c t e r i z e d in that the pair of rollers (54, 55) is mounted displaceably towards and away from the outlet from the extruder head (15) , that the pair of rol¬ lers (54, 55) is biased towards a resting position, that sensing means (60, 61, 62) are provided for sensing the position of the pair of rollers (54, 55) in relation to the resting position, and that the drive of the pair of rollers is adapted to be controlled depending on said sensing.

Inventors: SVENDSEN TORBEN JOERGEN, SVENDSEN, TORBEN, JOERGEN
Applicants: MEGABITE APS, SVENDSEN TORBEN JOERGEN, SVENDSEN, TORBEN, JOERGEN
Application year: 1993
Main classification: A21C11
IPC codes: A21C11