Plasticating screw

Abstract

A plasticating screw is proposed, with a screw channel, which runs spirally around a screw core, is laterally delimited by a flight (1), (2) and has flow elements (3), (4) that are distributed over its longitudinal direction, extend transversely over the screw channel and comprise a deep section (5) and a compression section (6), rising radially in the longitudinal direction. In order to design a plasticating screw of the type mentioned at the beginning in such a way that its length is reduced and good melting characteristics can be achieved even with little energy input, it is proposed that the compression section (6) forms at least one run-up surface (7), which is inclined towards the flight (1), (2) and is adjoined in the longitudinal direction by a plateau (8) for forming the flow.

Claims

1. A plasticating screw comprising: a screw channel that runs spirally around a screw core and is laterally delimited by a flight, said screw channel comprising flow elements that are distributed over its longitudinal direction and extend transversely over the screw channel, the flow elements extending across a breadth of the flight, each flow element comprising: a deep section extending in the longitudinal direction of the screw channel; and a compression section radially rising in the longitudinal direction such that a flow of material enters the deep section and further enters the compression section, the compression section comprising: a first run-up surface inclined towards the flight and a plateau for flow formation, the first run-up surface connected to the plateau such that the flow of material flows over the first run-up surface toward the plateau; and a second run-up surface inclined towards another flight opposite the flight such that the first run-up surface and the second run-up surface form a wedge, wherein the flow elements are provided at least in a melting zone of the plasticizing screw.

2. The plasticating screw according to claim 1, wherein the first run-up surface and the second run-up surface of the compression section are concavely or convexly curved in the longitudinal direction of the screw channel.

3. The plasticating screw according to claim 1, wherein the plateau for flow formation is designed in a wave-like manner in the longitudinal direction of the screw channel.

4. The plasticating screw according to claim 1, wherein the plasticating screw forms at least two screw channels that are separated from one another by a common flight, in which screw channel flow elements are arranged that are offset and spaced apart from one another.

5. The plasticating screw according to claim 4, wherein the common flight is broken through in an area that is upstream from the respective flow elements in the flow direction.

Description

BRIEF DESCRIPTION OF THE INVENTION

(1) An example of the object of the invention is shown in the drawing. The following are shown:

(2) FIG. 1 a schematic view of two screw channels of a plasticating screw according to the invention,

(3) FIG. 2 a cut along line II-II of FIG. 1 on a larger scale,

(4) FIG. 3 a cut along line of FIG. 1 on a larger scale,

(5) FIG. 4 a cut according to FIG. 2 of an alternative embodiment of the flow element according to the invention, having convex run-up surfaces,

(6) FIG. 5 a cut according to FIG. 2 of an alternative embodiment of the flow element according to the invention, having concave run-up surfaces,

(7) FIG. 6 a view according to FIG. 1 of two screw channels of a plasticating screw according to the invention in an alternative embodiment.

MANNERS OF EXECUTING THE INVENTION

(8) A plasticating screw according to the invention has a screw channel running spirally around a screw core and laterally delimited by a flight 1, 2. Flow elements 3, 4 extending in a transverse direction over the screw channel are distributed over the longitudinal direction of the screw channel.

(9) As can be seen in particular in FIGS. 2-5, these flow elements 3, 4 have a deep section 5 and a compression section 6 rising along the screw channel in a radial direction, which forms at least one run-up surface 7 inclined towards the flight 1, 2. Subsequent to the compression section 6, there is a plateau 8 parallel to the screw core surface, to which plateau a deep section 5 is connected for decompression. The expansion in the radial direction of the flow elements 3, 4 is smaller than the height of the screw channel.

(10) A flow of a solid material melt mixture or a melt transported in the longitudinal direction of the screw channel is first conveyed over the deep section 5 of a flow element 3, 4 and subsequently meets the run-up surfaces 7 of the compression section 6. Then, the flow continues over the plateau 8 until it finally flows into a deep section 5 for decompression.

(11) In order to split up and break up a solid material bed, the compression section 6 can comprise at least two run-up surfaces 7 inclined towards opposing flight sections 1, 2, respectively, which form a wedge 9 pointed against the flow direction of the solid material melt mixture and the melt. According to the invention, multiple such wedges 9, 10 can also be provided, which are spread evenly over the breadth of a screw channel and form a main wedge 9 having multiple side wedges 10. Such an embodiment is shown in the drawing, for example in the flow elements 3.

(12) As already described above, the run-up surfaces 7 can be designed either convexly, as shown in FIG. 4, or concavely, as shown in FIG. 5, in order to positively influence the flow profiles, which are set according to the invention, as needed.

(13) While not shown separately in the drawing, the plateau 8 can have a wave-like design or, in principle, comprise wave elements known from the prior art in order to increase the shearing and stretching forces occurring in the melt.

(14) According to a further embodiment, the plasticating screw according to the invention can form at least two screw channels that are parallel to each other in the longitudinal direction, said screw channels being separated from one another by a common flight 2. This is illustrated in FIG. 1, in particular, where the flow elements 3 of the one screw channel are offset and spaced apart from the flow elements 4 of the other screw channel.

(15) In an alternative embodiment shown in FIG. 6 with respect to the screw channels shown in FIG. 1, the common flight 2 of the screw channels can have breakthroughs 11 in an area that is upstream from the respective flow elements 3, 4 in the flow direction.