Patent EA-003547-B1 (EA)
Title: Buffer store for polymer melts, especially cellulose solutions
Inventor: ZIKELI STEFAN
IPC: B29C48/475
Filed: 2000-11-20
Abstract: 1. A buffer tank for supplying an extrusion device, in particular a spinning machine, with a polymer melt, in particular a cellulose solution, in a substantially constant manner, comprising at least one polymer melt entry opening, at least one polymer melt exit opening and at least one compensation chamber of variable volume that is arranged between polymer melt entry opening and polymer melt exit opening and has the polymer melt flowing there through, characterized in that the compensation chamber (5) between the polymer melt entry opening (3) and the polymer melt exit opening (4) is divided into at least two partial chambers (5a, 5b) extending in the direction of flow. 2. The buffer tank according to claim 1, characterized in that in a normal operative state of the buffer tank (1) the flow cross-section of each partial chamber (5a, 5b) corresponds substantially to the flow cross-section of the polymer melt entry opening (3) and/or the polymer melt exit opening (4). 3. The buffer tank according to claim 1 or 2, characterized in that the partial chambers (5a, 5b) have substantially identical flow cross-sections. 4. The buffer tank according to any one of the aforementioned claims, characterized in that the partial chambers (5a, 5b) extend essentially from the polymer melt entry opening (3) substantially up to the polymer melt exit opening (4). 5. The buffer tank according to any one of the aforementioned claims, characterized in that a wall of the compensation chamber (5) is formed at least section wise by a piston (8) being movable in the buffer tank (1). 6. The buffer tank according to claim 5, characterized in that at the side of the piston (8) facing away from the compensation chamber (5), a fluid-filled piston chamber (9) is provided with a fluid supply line (10) and a fluid discharge line (11), the piston chamber (9) being actuable with an adjustable pressure. 7. The buffer tank according to claim 5 or 6, characterized in that the piston is connected to a displacement sensor (12) by which a signal can be output for calculating the volume of the compensation chamber (5). 8. The buffer tank according to claim 5, characterized in that the piston (8) is acted upon with a spring force produced by a mechanical spring element. 9. The buffer tank according to any one of the aforementioned claims, characterized in that-the compensation chamber (5) is designed as an annular chamber. 10. The buffer tank according to claim 9, characterized in that the piston (8) is designed as an annular piston. 11. The buffer tank according to claim 9 or 10, characterized in that the polymer melt entry opening (3) and the polymer melt exit opening (4) are arranged on diametrically opposite regions of the annular chamber. 12. The buffer tank according to any one of the aforementioned claims, characterized in that the polymer melt is guided through the polymer melt entry opening (3) and/or the polymer melt exit opening (4) substantially in the direction of an axis of symmetry (2) of the compensation chamber (5) into the compensation chamber (5). 13. The buffer tank according to any one of the aforementioned claims, characterized in that the polymer melt entry opening (3) and/or the polymer melt exit opening (4) is/are arranged in the compensation chamber (5) to be opposite to the piston (8). 14. The buffer tank according to any one of the aforementioned claims, characterized in that the polymer melt entry opening (3) and the polymer melt exit opening (4) are arranged at the same side of the compensation chamber (5). 15. The buffer tank, in particular according to claim 1, characterized in that for flow optimization the compensation chamber (5) is provided with at least one flow guiding element (14, 15, 21 a-d) projecting into the flow of the polymer melt, which is smaller than the flow cross-section of the compensation chamber (5) and by which the velocity profile in the direction of flow through the compensation chamber (5) is made uniform at least in sections in that the flow guiding element (14, 15, 21 a-d) is arranged in a region of the compensation chamber (5) in which in the absence of a flow guiding element (14, 15, 21 a-d) a drop in velocity occurs relative to the core flow of the compensation chamber. 16. The buffer tank according to claim 15, characterized in that the fast core flow of the flow through the compensation chamber (5) is guided by the flow guiding element (14, 15, 21 a-d) towards a region in which in the absence of a flow guiding element (14, 15, 21 a-d) a flow is observed that is slowed down in comparison with the core flow. 17. The buffer tank according to claim 15 or 16, characterized in that the flow guiding element (4, 15, 21 a-d) is arranged in a region of the compensation chamber (5) in which the flow through the compensation chamber (5) has a strong curvature. 18. The buffer tank according to any one of the aforementioned claims, characterized in that the compensation chamber (5) has a flow cross-section, which forms at least one corner. 19. The buffer tank according to claim 18, characterized in that the flow guiding element (14, 15, 21 a-d) is arranged in the region of the corner, and the corner flow formed during flow through the compensation chamber (5) is made uniform by the flow guiding element (14, 15, 21 a-d). 20. The buffer tank according to any one of the aforementioned claims, characterized in that the flow-guiding element (14, 15, 21 a-d) is arranged on the wall of the compensation chamber (5), which is opposite to the polymer melt entry opening (3) and/or the polymer melt exit opening (4). 21. The buffer tank according to claim 20, characterized in that the flow guiding element (14, 15) has substantially the form of a preferably radially symmetrical nose oriented towards the flow entry opening (3). 22. The buffer tank according to claim 20 or 21, characterized in that the nose is arranged on the piston (8). 23. The buffer tank according to any one of claims from 1 to 22, characterized in that the flow-guiding element is substantially designed in the form of a blade or wing. 24. A kit consisting of an extrusion machine for extruding a polymer melt, at least one pump means for conveying the polymer melt to the extrusion machine, and a buffer tank, characterized in that the buffer tank is designed according to one of claims from 1 to 23.