MELT FILTER

Abstract

The invention relates to a melt filter (1) for filtering plastic melts, comprising a screen rotor (3) which is arranged such that it can be rotationally driven between two housing plates (2) and which has recesses (5) along a circular path (4) for receiving exchangeable filter elements (6), and comprising a melt channel (7) which penetrates the housing plates (2) in the region of the circular path (4) and is associated with the screen rotor (3). In order to create advantageous conditions, it is proposed that the screen rotor (3) comprises two axially spaced rotor cheeks (9) which are provided opposite one another with filter elements (6) through which the plastic melt can flow and towards which the melt channels (7) of the two housing plates (2) open out, wherein at least one collecting chamber (10) for plastic melt filtered by the filter elements (6) is provided in the screen rotor (3) between opposing filter elements (6), and wherein a flow channel (11) opening out of the screen rotor (2) in the region of the rotor axis (8) is provided for discharging filtered plastic melt from the collecting chamber (10).

Claims

1. A melt filter for filtering a plastic melt, said melt filter comprising: a screen rotor arranged between two housing plates such that said screen rotor rotates about a screen rotor axis; wherein said screen rotor has recesses along a circular path accommodating exchangeable filter elements and said screen rotor has a melt channel penetrating the housing plates in a region of the circular path receiving the plastic melt that is filtered; wherein the screen rotor forms a transport structure for the filter elements by which the filter elements are displaced about the screen rotor axis at least between a first filter position and a further filter position; wherein the screen rotor has two axially spaced rotor cheeks opposite one another with the filter elements through which the plastic melt flows and towards which the melt channels of the two housing plates open out; wherein the screen rotor has at least one collecting chamber receiving the plastic melt filtered by the filter elements in the screen rotor between opposing filter elements; and wherein the screen rotor has a flow channel opening out of the screen rotor in the region of the rotor axis discharging the filtered plastic melt from the collecting chamber.

2. The melt filter according to claim 1, wherein one of the housing plates in a bearing region of a screen rotor shaft has, next to one of the rotor cheeks, an annular channel groove into which the flow channel opens out and to which a discharge channel for the filtered plastic melt adjoins.

3. The melt filter according to claim 1, wherein a rotor shaft that is fixed with respect to the housing plates and on which the screen rotor is mounted rotatably about the screen rotor axis forms the flow channel which is adjoined by a discharge channel guiding the filtered plastic melt through one of the housing plates.

4. The melt filter according to claim 3, wherein the fixed rotor shaft has, between the two housing plates, at least one backwashing line that passes radially through the rotor shaft and that, at one end, adjoins the flow channel and, at the other end, opens out at a backwashing position backwashing the filter elements, wherein a slide valve is arranged in the backwashing line, said slide valve selectively releasing or blocking the backwashing line.

5. The melt filter according to claim 1, wherein the screen rotor has two collecting chambers, separated by a web receiving the plastic melt filtered by the filter elements between each two of the filter elements opposing each other.

6. The melt filter according to claim 1, wherein the screen rotor comprises at least three opposing pairs of the filter elements, one, two or more of which are associated with a filter position, one, two or more of which are associated with a backwash position, and one, two or more of which are associated with an alternate or waiting position.

7. The melt filter according to claim 2, wherein the annular channel groove connects the flow channels of two pairs of the filter elements.

8. The melt filter according to claim 2, wherein a valve element is provided in the annular channel groove between the flow channels of two pairs of the filter elements.

9. The melt filter according to claim 6, wherein the housing plates have, in a region of an exchange position of the filter element pairs, maintenance openings that can be closed and that penetrate the housing plates.

10. The melt filter according to claim 1, wherein the screen rotor is rotatably mounted between the two housing plates, and the two housing plates are connected to one another with tie rods arranged circumferentially radially outside the rotor and pressing the housing plates against spacer elements arranged therebetween.

11. The melt filter according to claim 1, wherein the screen rotor comprises four or more opposing pairs of the filter elements, one, two or more of which are associated with a filter position, one, two or more of which are associated with a backwash position, and one, two or more of which are associated with an alternate or waiting position.

12. The melt filter according to claim 11, wherein the housing plates have, in the region of an exchange position of the filter element pairs, maintenance openings that can be closed, in particular with covers, and that penetrate the housing plates.

13. The melt filter according to claim 12, wherein the maintenance openings are closed with covers.

14. The melt filter according to claim 9, wherein the maintenance openings are closed with covers.

Description

BRIEF DESCRIPTION OF THE INVENTION

[0021] In the drawing, the subject matter of the invention is shown by way of example, wherein:

[0022] FIG. 1 shows a side view of a melt filter with a pair of filter elements in filter position,

[0023] FIG. 2 shows the melt filter from FIG. 1 in section according to line II-II,

[0024] FIG. 3 shows a side view of the melt filter with two pairs of filter elements in filter position and one pair of filter elements in backwash position,

[0025] FIG. 4 shows the melt filter from FIG. 3 in section according to line IV-IV,

[0026] FIG. 5 shows the melt filter in side view with a pair of filter elements in filter position and a pair of filter elements in filter change position,

[0027] FIG. 6 shows the melt filter from FIG. 5 in section according to line VI-VI,

[0028] FIG. 7 shows the melt filter from FIG. 6 in section according to line VII-VII,

[0029] FIG. 8 shows a design variant of a melt filter in side view with three filter element pairs in filter position and one filter element pair in backwash position,

[0030] FIG. 9 shows the melt filter from FIG. 8 in section according to lines IX-IX and

[0031] FIG. 10 shows the melt filter from FIG. 8 in section according to the line X-X.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The invention relates to a melt filter 1 for the purification of plastic melts, in particular those discharged by extruders, having a screen rotor 3 which is arranged in a rotatably drivable manner between two housing plates 2 and comprises recesses 5 along a circular path 4 for accommodating exchangeable filter elements 6, and having a melt channel 7 which penetrates the housing plates 2 in the region of the circular path 4 and is assigned to the screen rotor 3 in the region of the filter position of the filter elements 6, the screen rotor 3 in the region of the filter position of the filter elements 6, wherein the screen rotor 3 forms a transport means for the filter elements 6, with which the filter elements 6 can be displaced about the screen rotor axis 8 at least between a filter position F, a backwashing position R and an exchange or waiting position W. In the present exemplary embodiment, the melt channels 7 of the two housing plates 2 are connected to each other via a melt channel 15 formed by a sleeve 20 inserted between the two housing plates 2. However, both melt channels could also be supplied with melt to be filtered from the outside via a separate connection.

[0033] The screen rotor 3 comprises two axially spaced rotor cheeks 9, which are equipped opposite one another with filter elements 6 through which the plastic melt can flow and towards which the melt channels 7 of the two housing plates open out in the filter position. Between opposing filter elements 6, i.e. a pair of filter elements, a collecting chamber 10 for filtered plastic melt through which the filter elements 6 flow is provided in the rotational body of the screen rotor 3. The discharge of filtered plastic melt from the collecting chamber 10 takes place via a flow channel 11 in the region of the rotor axis 8.

[0034] According to the exemplary embodiment as shown in FIGS. 1 to 7, the screen rotor 3 is rotationally driven by two stub axles 12 between the two housing plates 2 and has on both sides, in the rotor cheeks 9 facing away from each other, several screen nests equipped with filter elements 6. The two directly opposite filter elements 6 of a pair of filter elements, through which the plastic melt can flow, are simultaneously acted upon by the likewise opposite melt channels 7 of the two housing plates 2 with plastic melt to be filtered, whereby the forces acting on the screen rotor 3 in the axial direction practically cancel each other out. Between the opposing filter elements 6 of at least one pair of filter elements, the collecting chamber 10 for filtered plastic melt pressed through the filter elements 6 is provided in the screen rotor 3. This collecting chamber 10 opens out of the screen rotor 3 via the flow channel 11 in the area of the rotor axis 8.

[0035] A housing plate 2 has, in the bearing region of the rotor axis 8, in addition to a rotor cheek 9, an annular channel groove 13, into which the flow channel 11 opens out and to which annular channel groove 13 a discharge channel 14 for filtered molten plastic adjoins. The screen rotor 3 comprises four opposing pairs of filter elements, one or two of which are assigned to a filter position, one to a backwash position and one to an alternating or waiting position. In addition, a valve element 16, in particular a throttle, is provided in the annular channel groove 13 between the flow channels 11 of two pairs of filter elements and is radially adjustably arranged in a radial bore of the of the housing plate 2. In the region of the exchange position W of the filter element pairs, the housing plates 2 have maintenance openings which can be closed, in particular with covers 17, and which penetrate the housing plates 2 axially, via which the filter elements can be exchanged. In addition, the screen rotor 3 is provided on its outer circumference with a toothing 18 in which an adjusting drive 19 engages as a rotary drive for the screen rotor 3. The screen rotor 3 is rotatably mounted in the two housing plates 2. In addition, the two housing plates 2 are connected to one another via tie rods arranged circumferentially radially outside the screen rotor 3, in particular along a further circular path, and pressing the housing plates 2 against spacer elements arranged therebetween. The melt channels 7 of the two housing plates 2 are connected to one another via a connecting channel 21.

[0036] In the exemplary embodiment according to FIGS. 1 to 7, the screen rotor 3 is rotatably mounted with axle stubs in the two housing plates 2. In the exemplary embodiment according to FIGS. 8 to 10, the screen rotor 3 is rotatably mounted on a rotor axis 28 held in a rotationally fixed manner in the two housing plates 2.

[0037] In this case, a rotor shaft 28, which is fixed with respect to the housing plates 2 and on which the screen rotor 3 is mounted so as to be rotatable about the screen rotor axis 8, forms the flow channel 11, which is adjoined by a discharge channel 14, guided through a housing plate 2, for filtered molten plastic.

[0038] The fixed rotor shaft 28 has, between the two housing plates 2, at least one backwashing line 29 which passes radially through the rotor shaft 28 and, at one end, adjoins the flow channel 11 and, at the other end, opens out at a backwashing position for the backwashing of filter elements, wherein a slide valve 30 is arranged in the backwashing line 29, by means of which valve the backwashing line 29 is optionally released or blocked. The slide valve 30 is mounted coaxially to the screen rotor axis 8 in the rotor shaft 28 in such a way that it is displaceable along the screen rotor axis 8. The slide valve 30 also has a bore radially extending through the slide valve 30, which bore can be brought into overlap with the respective backwashing line in order to release the flow through this backwashing line. The bore radially extending through the slide valve 30 may also be replaced by an annular groove on the periphery of the slide valve. Two collecting chambers 10, separated by a web 32, for plastic melts filtered by the filter elements 6 are provided in the screen rotor 3 between each two opposing filter elements 6, so that each filter element 6 can be backwashed separately in the corresponding slide valve position (FIG. 10 below). For this purpose, in the backwash position, the web 32 lies sealingly against the rotor shaft 28. Material cleaned by the respective filter element 6 is discharged from the device via a channel 33.