Patent EA-000486-B1 (EA)
Title: An extrusion method, an extruder and a product prepared with the method
Inventor: KIRJAVAINEN KARI
IPC: B29C48/06
Filed: 1997-04-04
Abstract: 1. An extrusion method wherein material to be extruded is fed into an extruder comprising at least one stator (1, 2) and at least one rotor (3), whereupon the stator (1, 2) has a conical surface at least on the side of the rotor (3), and which rotor (3) has a conical surface at least on the side of the stator, the ratio of the length of the rotor (3) to its greatest diameter being at most five-fold, and which rotor (3) is rotated, the rotor (3) resting on bearings provided in its widest point as it rotates, characterized in that as the rotor (3) rotates, it rests on at least two bearings (12a, 12b), whereupon the first bearing (12a) receives the force acting in one axial direction of the rotor (3) and the second bearing (12b) receives the forces acting in the opposite axial direction of the rotor (3), and that the bearings (12a, 12b) are positioned diagonally with respect to the axial and radial direction of the extruder, the bearings (12a, 12b) receiving together the forces acting in the radial direction. 2. A method according to Claim 1, characterized in that the elastic displacement between the rotor (3) and the stator (1, 2) is measured, and the forces acting on the extruder are determined on the basis of the measurement result. 3. A method according to Claim 1 or 2, characterized in that the extruder comprises at least two stators (1, 2), the inner stator (1) having at least an outer surface that is conical and the outer stator (2) having at least an inner surface that is conical, that between the stators (1, 2) there is at least one rotatable conical rotor (3), and that the elastic displacements between the rotor (3) and the inner stator (1) and between the rotor (3) and the outer stator (2) are measured separately, and the forces acting on the stators (1, 2) and the rotor (3) are determined on the basis of the measurements. 4. A method according to Claim 2 or 3, characterized in that a slip agent is blended with the material to be supplied between the stator (1, 2) and the rotor (3), and the amount of the slip agent is adjusted on the basis of the measurement result obtained from the elastic displacement. 5. A method according to Claim 3, characterized in that the material to be extruded is fed separately into the exterior and interior of the rotor (3), and that the amount of the slip agent in the material to be supplied to at least one side of the rotor (3) is adjusted on the basis of the information obtained from the measurements of the elastic displacements. 6. A method according to any one of the preceding Claims, characterized in that by controlling the temperature of the lubricating oil lubricating the bearings (12a, 12b) the temperature of the extruder is controlled. 7. A method according to any one of the preceding Claims, characterized in that the frame of the extruder is assembled with pretensioning that is provided by heating the fastening bolts (14) from inside before they are mounted in place and by cooling the bolts to the normal working temperature after the mounting. 8. An extruder comprising at least one stator (l, 2) and at least one rotor (3), the stator having a conical surface at least on the side of the rotor (3), and the rotor (3) having a conical surface at least on the side of the stator, the ratio of the length of the rotor (3) to its greatest diameter being at most five-fold, and which rotor (3) is mounted in bearings from its widest point to the extruder, characterized in that the rotor (3) is mounted at least with two bearings (12a, 12b), whereupon the first bearing (12a) receives the forces directed in one axial direction of the rotor (3) and the second bearing (12b) receives the forces directed in the opposite axial direction of the rotor, and that the bearings (12a, 12b) are positioned diagonally with respect to the axial and radial direction of the extruder, the bearings (12a, 12b) receiving together the forces acting in the radial direction. 9. An extruder according to Claim 8, characterized in that between the rotor (3) and the stator (1, 2) there are measuring means for measuring the elastic displacement between the rotor (3) and the stator (1, 2). 10. An extruder according to Claim 8 or 9, characterized in that the extruder comprises at least two stators (1, 2), the inner stator (1) having at least an outer surface that is conical and the outer stator (2) having at least an inner surface that is conical, and at least one rotatable conical rotor (3) being provided between the stators (1, 2), and that the extruder comprises measuring means for measuring separately the elastic displacements between the rotor (3) and the outer stator (2) and between the rotor (3) and the inner stator (1). 11. An extruder according to any one of Claims 8 to 10, characterized in that the bearings (12a, 12b) are conical bearings. 12. An extruder according to any one of Claims 8 to 11, characterized in that the extruder comprises a gearing frame (11) that constitutes together with the bearings (12a, 12b) a unit that can be detached from the rest of the extruder. 13. An extruder according to any one of Claims 8 to 12, characterized in that au least the gearing frame (11) of the extruder and the rotor (3) constitute a unit that is arranged to be moved during maintenance with a wagon (22) along a rail (23) that is parallel with the axis of the extruder. 14. A product prepared with the method according to Claim 1, characterized in that at least 0.5% of a slip agent has been blended with the material of the product, and that the product is substantially without weld lines, and that the tolerance of the wall thickness of the product is less than 2%. 15. A product according to Claim 14, characterized in that the product comprises at least two layers, the inner one of which contains 0.5 to 10% of a slip agent blended therein 16. A product according to Claim 14, characterized in that the product is a protecting tube for cables, wherein at least the inner layer is of polyolefin and the slip agent is silicone oil or fluoropolymer.