Device for filtering a plastic melt
A device for filtering a plastic melt, having a housing that has at least one inlet passage and at least one outlet passage for the plastic melt. The at least one inlet passage is separated from the at least one outlet passage by at least one filter cavity for accommodating at least one filter piston that is axially displaceable therein. The at least one filter piston has at least one filter base body with a filter surface with filter openings passing through the filter base body there, through which openings the plastic melt passes into a filtrate cavity in the filter base body. The filtrate cavity is fluidically connected to the at least one outlet passage, and the filter surface of the filter base body is enclosed by a flexible, elastic filter screen in such a manner that this filter screen can be clamped onto the filter base body there.
1. A device for filtering a plastic melt, wherein the device comprises:
a. a housing, wherein the housing has at least one inlet passage and at least one outlet passage for the plastic melt;
b. at least one filter cavity separating the at least one inlet passage from the at least one outlet passage;
c. at least one filter piston disposed within the filter cavity, wherein the at least one filter piston is axially displaceable therein, wherein the at least one filter piston comprises:
(i) at least one filter base body with a filter surface; wherein the filter surface has filter openings passing through the filter base body; and
(ii) a filtrate cavity formed in the filter base body, wherein the plastic melt passing through the filter openings pass into the filtrate cavity, and wherein the filtrate cavity is fluidically connected to the at least one outlet passage; and
(iii) a flexible, elastic filter screen enclosing the filter surface, wherein the flexible, elastic filter screen self-clamps onto the filter base body.
2. The device of claim 1 , wherein the flexible, elastic filter screen has a contour that follows the contour of the filter surface.
3. The device of claim 2 , wherein the flexible, elastic filter screen has a curved cross-section.
4. The device of claim 1 , wherein the flexible, elastic filter screen has a curved cross-section.
5. The device of claim 1 , wherein flexible, elastic filter screen encloses an angle viewed in cross-section of a minimum of 180° and a maximum of 270° of the circumference of the filter piston and covers the corresponding circumferential portion of the filter surface there.
6. The device of claim 2 , wherein flexible, elastic filter screen encloses an angle viewed in cross-section of a minimum of 180° and a maximum of 270° of the circumference of the filter piston and covers the corresponding circumferential portion of the filter surface there.
7. The device of claim 3 , wherein flexible, elastic filter screen encloses an angle viewed in cross-section of a minimum of 180° and a maximum of 270° of the circumference of the filter piston and covers the corresponding circumferential portion of the filter surface there.
8. The device of claim 4 , wherein flexible, elastic filter screen encloses an angle viewed in cross-section of a minimum of 180° and a maximum of 270° of the circumference of the filter piston and covers the corresponding circumferential portion of the filter surface there.
9. The device of claim 8 , wherein the filter piston has, at least in the region of the filter base body and in the region where the fluidic connection exists between the filtrate cavity and the outlet passage, a filter base part that has an outer contour corresponding in cross-section to the inner contour there of the filter cavity in the housing and that has no filter surface there.
10. The device of claim 1 , wherein the filter piston has, at least in the region of the filter base body and in the region where the fluidic connection exists between the filtrate cavity and the outlet passage, a filter base part that has an outer contour corresponding in cross-section to the inner contour there of the filter cavity in the housing and that has no filter surface there.
11. The device of claim 10 , wherein the flexible, elastic filter screen is held by axial terminating edges on both sides in respective axial grooves in the filter base part.
12. The device of claim 1 , wherein the flexible, elastic filter screen is held by axial terminating edges on both sides in respective axial grooves in the filter base part.
13. The device of claim 12 , wherein at least two positioning pins are provided in the region of the filter base body so that the flexible, elastic filter screen can be placed thereon with corresponding filter openings, and is thus held.
14. The device of claim 1 , wherein at least two positioning pins are provided in the region of the filter base body so that the flexible, elastic filter screen can be placed thereon with corresponding filter openings, and is thus held.
15. The device of claim 14 , wherein the flexible, elastic filter screen has, at least in the region of each of its axial terminating edges, one or more handling eyes so that a handling tool can be applied there to spread the flexible, elastic filter screen.
16. The device of claim 15 , wherein the filter cavity is circular in cross-section and the filter base body has the shape in cross-section of at least one or more section(s) of a circular segment with different diameters.
17. The device of claim 1 , wherein the filter cavity is circular in cross-section and the filter base body has the shape in cross-section of at least one or more section(s) of a circular segment with different diameters.
18. The device of claim 17 , wherein the filter piston is axially displaceable between a filtering position and a non-filtering position.
19. The device of claim 1 , wherein the filter piston is axially displaceable between a filtering position and a non-filtering position.
20. The device of claim 1 , wherein the filter piston has, in addition to the filter base body, a piston section that corresponds in cross-section to the cross-section of the filter cavity in the housing so that it fills this filter cavity in the non-filtering position.