The invention will be explained hereinafter with reference to a plurality of exemplary embodiments. In the drawing:
FIG. 1 shows a section through a cylinder arrangement of a screw extrusion press with a view of the screw; and
FIGS. 2-9 show different sectional views of embodiments of a mixing ring.
As shown in FIG. 1, a screw 1 is disposed in a cylinder 2 of a screw extrusion press, said screw comprising three mixing rings 3 and a conveying zone 7 with individual screw channels 8. The mixing rings 3 extend from the bottom of the screw, which is indicated at 10, to a shear gap 9 at the wall indicated at 20 of the cylinder 2. The width of the shear gap 9 may for example be about 1 mm in the radial dimension.
According to FIG. 2, a mixing ring 3 comprises a groove 4 that commences at the bottom 10 of the screw and extends as far as the shear gap 9. The groove on the inflow side 11 of the mixing ring 3 is thereby completely open, whilst the outflow side 12 is closed except for the shear gap 9. The flow direction of the molten mass is indicated at 13.
In the implementation shown in FIG. 3, the groove 4, which is milled in the radial direction, is completely open on the inflow side 11 and partly closed on the outflow side 12 so that here the molten mass comprises a larger outflow cross section than in the implementation according to FIG. 2, where only the shear gap 9 remains to form the outflow port.
Although the reference numeral 4 indicates a groove in the special case, it is understood to refer generally to a passage hole of any configuration.
In the embodiments shown in the FIGS. 4 through 8, one passage hole is configured to be a bore 5.
FIG. 4 shows an oblique arrangement of the bore 5 extending from the bottom 10 of the screw as far as the shear gap 9. Accordingly, this bore ends in the perimeter region of the mixing ring 3.
In the illustration shown in FIG. 5, the bore 5 ends on the outflow side 12. Here also, the bore commences at the bottom 10 of the screw on the inflow side 11. It is noted though, that the bore 5 shown in FIG. 5 constitutes an additional bore that is configured on the mixing ring 3. On same mixing ring there is also provided a passage hole (not shown), which opens out at least partially in the shear gap.
In FIG. 6, the bore ends partly on the outflow side 12 and partly in the shear gap 9, with the bore 5 again commencing at the bottom 10 of the screw on the inflow side 11.
Another variant may be achieved in that the sectioned portion shown on the top right side of FIG. 6 and which bounds the flow channel 5 toward the shear gap is advanced radially outward or is provided with a projection extending radially outward so that the shear gap 9 is configured to be very narrow toward the inflow side 11, more specifically even sealing it. This may for example be achieved in that the shear gap is so restricted there that it acts as a seal gap. In such a configuration, when viewed in the direction of the flowing molten mass, meaning from the inflow side 11 to the outflow side 12, there is first provided a seal gap (not shown) on the circumference of the mixing ring, and then, further downstream, a shear gap 9 into which the passage hole opens out.
FIG. 7 shows an inflow side comprising, in its upper part, a portion 14 extending at right angles to the screw axis and a portion 15 extending at an incline to the screw axis. The bottom of the screw is provided with a notch 16 from which the bore 5 extends at right angles to the screw axis and ends in the shear gap 9 which comprises a flaring portion 6 when viewed in the flow direction.
In the illustration shown in FIG. 8, the mixing ring 3 is inclined with respect to the screw axis, meaning that the inflow side 11 is inclined at an acute angle with respect to the axis of symmetry of the screw, whilst the outflow side 12 is inclined at an obtuse angle with respect to the axis of symmetry of the screw. In this exemplary embodiment, the bore 5 extends from the bottom 10 of the screw at an incline to the wall 20 of the cylinder, part of the bore ending in the shear gap 9 and another part of the bore ending on the outflow side 12.
FIG. 9 shows a configuration of the mixing ring according to FIG. 2 in which, on the inflow side, the shear gap, which is slightly larger than the shear gap 9 in FIG. 2, is closed with a sealing ring 21 so that the shear gap 9 remaining for the molten mass is shorter.
Patent Application
20070263479
