Filter system for viscous or highly viscous liquids, in particular plastic melts and method for filtering viscous or highly viscous liquids

Abstract

A device and a method for filtering viscous or highly viscous liquids, in particular plastics melts, includes use of an oscillating filter plate.

Claims

1. A filtration system for the continuous filtration of viscous liquids comprising: a filter chamber defining an active filter area in a filter zone; a groove between an unfiltered chamber and a filtered chamber; a filter sieve at least twice as wide as the active filter area; a filter sieve support plate, said filter sieve being supported by said support plate and both being slidably disposed in said groove; a cleaning chamber arranged on each side of the filter zone; a blocking slider on each side of the filter zone; and a slider element situated on each side of the filter sieve support plate for reciprocatingly moving said filter sieve and said support plate back and forth so that one portion of the filter sieve can be filtering by flowing unfiltered liquid from said unfiltered chamber through said active filter area to said filtered chamber, while the other portion is being back-flushed by passing a portion of filtered liquid back through said filter sieve in a cleaning area.

2. The filtration system of claim 1, wherein the filter sieve is selected from the group consisting of a belt, a sheet, a plate or a mat.

3. The filtration system of claim 1, wherein the blocking sliders include an integral valve.

4. The filtration system of claim 3, wherein the blocking sliders define a fluid passage capable of permitting any back-flushed liquid to flow to a discharge duct in said cleaning chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1 to 9 show embodiments according to the invention. In particular:

(2) FIGS. 1a-1c show a method for cleaning the filter;

(3) FIGS. 2a-2c show a method for cleaning the filter with free back-flushing;

(4) FIGS. 3a-3c show a filtration method with forced back-flushing;

(5) FIG. 4 shows an embodiment of the filter;

(6) FIG. 5 shows an embodiment of the filter in which only the filter plate is oscillated;

(7) FIG. 6 shows an embodiment for conveying away the filter cake;

(8) FIG. 7 shows an embodiment in which the filter cake is conveyed away in a controlled manner by a conveying screw;

(9) FIG. 8 shows cooling ducts in the cleaning chamber for conveying away the filter cake; and

(10) FIG. 9 shows an embodiment according to FIG. 7, in which the pressure is reduced by active cooling by cooling ducts.

DETAILED DESCRIPTION OF THE INVENTION

(11) In the description below, the following reference numbers are used: 1 the filter chamber 2 the filter plate 3 the filter support plate 4 the contaminants (filter cake) 5, 5a a cleaning chamber 6, 6a a blocking slider with integral valve 7 the discharge duct in the cleaning chamber 8 plain bearings 9 a conveying screw for conveying away the filter cake 10 the viscous or highly viscous liquid to be filtered, for example the plastics melt to be filtered 11 the filtrate of the viscous or highly viscous liquid 12 a blocking element 13 an insulating layer 14 heating or cooling ducts 15 the melt chamber for back-flushing 15a the back-flushed melt 16 the slider for moving the filter or the filter support plate 17 the melt inlet 18 the melt outlet 19 a shut-off element for forced back-flushing 20 solidified contaminant material 21 the cleaning zone 22 the filter zone.

(12) FIGS. 1a-1c show a method for cleaning the filter in which the filter is cleaned without back-flushing.

(13) The device consists in this respect of a filter chamber 1 and a filter plate 2, which is supported by a filter support plate 3.

(14) As shown in FIG. 1a, the contaminants settle on the filter plate 2 as filter cake 4 during the course of the process of filtering a viscous or highly viscous liquid 10.

(15) To clean the filter plate 2 of the filter cake 4, the valve 6, which in this case takes the form of a piston, is actuated and the filter cake 4 is passed into the cleaning chamber 5 and removed from the cleaning chamber through the duct 7. Removal of the filter cake 4 proceeds by displacing the filter plate 2 optionally together with the filter support plate 3 in the direction of the arrows, wherein the filter plate 2 is transported to a second cleaning chamber 5a and the process for complete cleaning of the filter plate is carried out.

(16) FIGS. 2a-2c show a method for cleaning the filter with free back-flushing.

(17) Here, the pressure difference up- and downstream of the filter plate 2 which arises during cleaning of the filter ensures that some of the filtrate 11 from the melt chamber is forced back for back-flushing 15 through the filter support plate 3 and the filter plate 2 in the back-flushing zone 21 below the filter cake 4 (FIG. 2b). The filter cake 4 is lifted up by the back-flushed melt 15a and in this way forced more readily into the duct 7 of the cleaning chamber 5.

(18) Removal of the filter cake 4 proceeds by displacing the filter plate 2 optionally together with the filter support plate 3 in the direction of the arrows, wherein the filter plate 2 is transported to a second cleaning chamber 5a and the process for further cleaning of the filter plate is carried out.

(19) FIGS. 3a-3c show a filtration method with forced back-flushing. Here the back-flushing process is initiated by sealing the back-flushing zone 15 by the slider motion. The filter system here comprises an additional shut-off element 19. The material is forced through the filter from below with elevated pressure and the filter plate cleaning process is carried out as in the procedure shown in FIG. 2.

(20) FIG. 4 shows an embodiment of the filter, in which filter plate 2 and filter support plate 3 oscillate together, i.e. are pushed to and fro. The filter support plate 3 is here mounted in the filter chamber 1 on plain bearings 8.

(21) FIG. 5 shows an embodiment of the filter in which only the filter plate 2 is oscillated. In this case, the filter plate 2 is mounted on plain bearings 8 which are situated on the filter support plate 3.

(22) FIG. 6 shows an embodiment for conveying away the filter cake 4 out of the cleaning chamber. In this case, in duct 7 modification of the cross-section reduces the pressure from a pressure level P1 to a pressure level P0, the filter cake 4 thereby being conveyed out of the duct

(23) In FIG. 7, filter cake 4 is conveyed away in a controlled manner by means of a conveying screw 9.

(24) In FIG. 8, cooling ducts 14 are provided in the cleaning chamber for conveying away the filter cake 4, such that the pressure in the cleaning chamber is reduced by cooling. The insulating layer 13 serves to decouple the temperature of the discharge duct 7, and thus the temperature of the material to be discharged may be reduced and the viscosity increased by a lower temperature than in the filter.

(25) FIG. 9 shows an embodiment according to FIG. 7, in which the pressure is however reduced by active cooling by cooling ducts 14. Solidified material thereby exits from the end of the discharge duct 2.