EP3107708A1

EP3107708A1 - Device for filtering a plastic melt

Info

Publication number: EP3107708A1
Application number: EP15712520.4A
Authority: EP
Inventors: Harald Pohl
Original assignee: Maag Pump Systems GmbH
Current assignee: Maag Automatik GmbH
Priority date: 2014-02-21
Filing date: 2015-02-19
Publication date: 2016-12-28
Also published as: WO2015124306A1; DE202014001675U1

Abstract

The invention relates to a device for filtering a plastic melt, comprising a housing (1) which has at least one inlet channel (2) and at least one outlet channel (3) for the plastic melt. The at least one inlet channel (2) is separated from the at least one outlet channel (3) by at least one filter cavity (4) for receiving at least one filter pin (5) which can be moved axially in the cavity. The at least one filter pin (5) has at least one filter main part (6) with a filter surface (7) comprising filter openings (8) which pass through the filter main part (6) and through which the plastic melt passes into a filter cavity (9) in the filter main part (6). The filter cavity (9) is fluidically connected to the at least one outlet channel (3), the filter surface (7) of the filter main part (6) is surrounded by a pleated filter screen (12), and clamping elements (14 and 14') are provided in smoothed axial edge regions (11 and 11') of the pleated filter screen (12).

Description

Device for filtering a plastic melt

The invention relates to a device for filtering a plastic melt, in particular a thermoplastic melt. According to the preamble of claim 1, the device has a housing which has at least one inlet channel and at least one outlet channel for the plastic melt, wherein the at least one inlet channel is separated from the at least one outlet channel by at least one filter cavity for receiving at least one filter pin axially displaceable therein wherein the at least one filter pin has at least one filter base with a filter surface with filter openings passing through the filter body through which the plastic plug passes to a filtrate cavity in the filter body, and wherein the filtrate cavity is in fluid communication with the at least one outlet channel.

A device for filtering with the features according to the preamble of claim 1 is known for example from the patent DE 34 19 822 C2, wherein in this generic device, the filter surface is running around the entire circumference of the filter pin running there around and doing a distribution fabric and a mesh are provided, which encase the filter pin there and are held there for example by means of a cylindrical clamping body. Thus, the local filter assembly is relatively expensive in construction, and in the case of maintenance or replacement of the distribution fabric or the mesh there is a high manual effort and associated with a relatively long life of the overall device unavoidable.

From the document DE 202010014709 U1 a generic device for filtering plastic melts is known, which achieves a clear improvement with respect to maintenance and replacement of a flexible and elastic filter screen _that can be clamped onto the filter surface of the filter base body. However _. the maximum filter surface of the filter screen is limited to the filter surface of the filter body. Thus, it comes with increasing pollution and corresponding clogging of the filter screen to an undesirable increase in pressure. The known device achieves its maximum throughput of plastic melts per unit time relatively early, with no prospect of further increasing the throughput of plastic melts per unit time. Only by a complete redesign with a correspondingly enlarged housing, enlarged filter pin and enlarged filter body pollution or the associated increase in pressure can be slowed down and the maximum throughput of plastic melts per unit time are increased, although the dimensions of inlet channel, outlet channel, filter pin and Filtrathohlraum perfectly adequate are theoretically up to one To achieve four times the throughput of plastic melts per unit time, without an enlargement of the filter surface of the filter body or the other components.

The present invention is therefore based on the object to provide a device for filtering a plastic melt, which overcomes the disadvantages of the prior art, and in particular to provide a device for filtering a plastic melt, wherein, while maintaining the dimensions of housing, filter pin, filter body, inlet channel , Outlet channel, Filtrathohlraum and filter surface of the filter body, an increase in the filter life, a possible higher filtration fineness, a lower pressure drop and an increase in the throughput of plastic melts per unit time is ensured. A reduction of the size (the dimensions) with constant throughput can be achieved as fiction, accordingly.

This object is achieved by a device having the features of claim 1. Preferred embodiments of the invention are defined in the subclaims.

The invention fiction, a device for filtering a plastic melt, in particular a thermo-elastic plastic melt, has a housing which with at least one inlet channel and at least one outlet channel for the filtered

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Plastic melt is provided. The at least one inlet channel is separated from the at least one outlet channel by at least one filter cavity, preferably by at least one perpendicular to these channels extending, particularly preferably cylindrical: filter cavity, wherein within the at least one. Filter cavity is arranged there axially displaceable filter pin, so that thereby the at least one inlet channel is separated from the at least one outlet channel. The filter pin is preferably arranged so precisely within the preferably cylindrical filter cavity in each case that is prevented without additional sealing means even with an axial displacement of the filter pin that press through between the corresponding outer wall of the bolt and the corresponding inner wall of the cylindrical filter cavity in an undesirable manner plastic melt can.

The preferably cylindrical filter pin has at least one filter base body with a filter surface with there through the filter body passing through the filter openings, through which the Plastic melt passes to a Filtrathohlraum in the filter body, wherein the Filtrathohlraum with the at least one outlet channel in

Fluid connection is. The plastic melt to be filtered thus occurs from the outer area

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of the filter base body to the filtrate cavity in the filter body to the inside, wherein the plastic melt to be filtered is supplied via the inlet channel in the filter cavity of the housing and the fluid via the filtrate and thus in fluid communication standing outlet channel is removed in the housing from there. In contrast to the generic type known device described above, the filter surface of the filter body is covered by a pleated filter in fiction, like devices are provided in axial smoothed edge regions of the pleated filter screen (12) clamping elements.

According to the invention, therefore, despite unchanged dimensions of housing, filter pin, filter body, inlet channel, outlet channel, Filtrathohlraum and filter surface of the filter body an increase in throughput of plastic melts per unit time can be ensured because instead of known from the document DE 202010014709 Ul tight fitting and clamping stable and flexible Now, a pleated filter screen comprises the filter surface of the filter body, so that a multiplication of the filtering surface is possible due to the pleating with preferably axially aligned convolutions, which are preferably evenly distributed radially on the filter surface of the filter body, and thus a corresponding multiplication of Throughput of plastic melts per unit of time with unchanged dimensions of

Device is connected.

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In a further embodiment of the invention, it is provided that clamping strips are provided as clamping elements on the axial smoothed edge regions of the pleated filter screen, which advantageously with a limited number of Schraubverbiridungen to the corresponding axial edge regions of the filter body, the pleated filter uniformly on the axial edge regions distributed can act on a clamping voltage. For this purpose, preferably have the smoothed edge regions. Dowel holes and the filter body in the local axial edge areas corresponding to the fitting holes provided dowel pins for aligning and pre-fixing of the pleated filter screen, which supports a fast and accurate installation during maintenance and replacement of the pleated filter screen.

Furthermore, it is provided that the clamping elements have through holes, which correspond with slot openings in the radial direction of the smoothed edge regions of the pleated filter screen and with threaded holes in the axial edge regions of the filter base body. As a result, clamping screws can be introduced into the through holes under clamping of the smoothed edge regions of the pleated filter screen and be brought into engagement with the threaded holes in the axial edge regions of the filter body, especially since the slot openings in the radial direction of the smoothed edge regions, the pleated filter screen compensate for manufacturing tolerances in the radial direction. In a further embodiment of the invention, the pleated filter screen has a plurality of filter layer layers of different mesh sizes and different diameter of filtration holes adapted to the mesh mesh widths. In this case, the outermost layer in the direction of the filter cavity has the smallest diameter of the filtration holes. Furthermore, the sieve mesh sizes and the filter screen layer diameters increase toward the filtrate cavity. This has the advantage that no inner filter layers can clog before the outermost Filljersieblage and a cleaning of the multilayer pleated filter screen maintenance friendly at the outermost and thus accessible from the outside filter layer. is feasible.

In a further embodiment of the invention, it is provided that the filter screen arranged on the filter surface of the filter base body has, in addition to the pleated filter screen, a support screen which can be clamped onto the filter surface at least in sections. The support screen or its sections are arranged between the pleated filter screen and the filter surface of the filter main body. The support screen can be formed arcuate in cross section.

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In addition, a flexible-elastic design of the carrier screen preferably also so

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be stable, for example, consisting of metal material, that it is in attachment of such

Carrier according to Invention can not come to dislocations of the support screen material, as may be the case with 'to be fastened with separate fasteners mat-like screen materials according to the prior art in an unfavorable manner. According to Invention, the operation of such a filter device is thus particularly reliable and, in the case of maintenance, a carrier screen exchange can be carried out particularly simply and quickly with the pleated filter screen arranged thereon.

In order to prevent possible dead spaces in the region of the filter device according to the invention the greatest possible extent, so that the operation of such a filter device is particularly reliable, and the clamping action of the flexible elastic carrier screen in the area of the filter surface on the filter body particularly ensure follows according to a preferred A ^{'usführungsform} the invention, the contour of the clamped carrier screen of

Contour of the filter surface, seen in cross-section. A particularly secure clamping and optimal Raunausnutzung is advantageously according fiction, then given when the Filtejrfläche there aufklemmbare carrier screen in cross-section, as mentioned above, is arcuate, wherein the support screen case then particularly preferably also the corresponding arcuate contour of the filter surface or . of the filter body follows there.

In any case, it must be ensured that penetration of the unfiltered plastic melt behind the pleated filter screen, ie on the clean side of the pleated filter screen, eg on the End faces thereof, for example by appropriate adaptation of the contour of the pleated filter screen to the contour of the filter surface or, for example, by an additional cover, for example by means of correspondingly structured cover plates takes place.

The clamping effect is fiction, according to particularly preferred given when the filter surface aufklemmbare there on the filter screen, seen in cross section, an angle of at least 180 ° and a maximum of 270 ° of the local scope of the filter pin comprises, more preferably about 240 ° of the local circumference, and while covering the corresponding peripheral portion of the filter surface. Thus, due to the thus incomplete: wrap it is also ensured that the fiction, like strainer with the pleated filter screen is relatively easy to remove again from the filter surface.

The longitudinal folds of the pleated filter screen can be aligned parallel to the longitudinal axis of the filter pin on the filter surface of the filter base body of the filter pin. However, it is particularly advantageous to provide the longitudinal folds of the pleated filter screen at an angle of inclination α to the longitudinal axis with α between 0 _: -S α ^ 5 °. This can particularly reliably be possible to as wide a variety of filter openings of the filter surface of the filter body with the _by: pleating enlarged Filtersieboberfläche the pleated filter screen cover. Further ^■ . can be improved by the inclination angle α of the deformation resistance and the stability of the longitudinal folds of the pleated filter screen.

With a particularly low flow resistance, the plastic melt through the pleated Fijtersieb and through the filter openings arranged underneath the filter

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To be able to flow filter body, it is particularly preferred that the filter openings, seen in plan view of the filter body in the region of the filter surface of the filter pin, can be arranged in rows and columns, the filter openings can form a spatially offset grid arrangement so that a high density of filter openings on the filter surface can be achieved.

The pleated filter screen may preferably be aligned with its longitudinal folds in such a way that there is a division of the longitudinal folds and the filter openings in the respective transverse direction of the longitudinal folds, that exactly one longitudinal fold is respectively arranged above a filter opening of the filter base body, so that the filter surface enlargement achieved by the corresponding pleating is effective, In this embodiment of the invention, the pitch number of the filter openings in the cross section on the filter surface thus preferably corresponds to the number of: longitudinal folds. A further improvement in the stability and the deformation resistance of the pleated filter screen can preferably be achieved by inserting a carrier screen between the screen surface and the pleated filter screen, if In addition, the pleated filter screen on the support screen pointwise cohesively, for example, is fixed by spot welding.

According to an advantageous embodiment of the device according to the invention, the filter pin, at least in the region of the filter base body and in the region thereof in which the fluid connection between the Filtrathohlraum and the outlet channel is made, have a filter base part which: in cross-section in its outer contour of the local

Inner contour of the filter cavity corresponds in the housing and there has no filter surface. Thus, the dead space volume can be further reduced. In addition, thus, the axial guidance of the filter pin can be improved in the filter cavity of the housing, so that also no: to be filtered plastic melt between the filter pin there and the housing can pass. :

According to another preferred embodiment of the invention, it may also be possible for at least two locating pins to be provided in the region of the filter body, so that the carrier screen with corresponding openings can be placed therein and held in such a way, resulting in the advantages described correspondingly in the previous paragraph the additional guidance also result.

As previously described, the shape of the filter cavity or filter pin therein is preferably cylindrical. In this case, in accordance with a preferred embodiment of the invention, the filter cavity may be circular in cross section and the filter base body in cross section may have the shape of at least one or more: circle segment portion (s) of different diameter. Such. Shapes are constructive in particular

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easy to produce and for the; passing melt trom particularly favorable flow, so that the operation of a so inventively designed device can be particularly reliable possible.

The Filterbolzjen may conveniently be axially displaceable between a filtering position and a non-filtering position. The displacement can be done appropriately by a (respective) hydraulic device.

It is particularly preferred if, according to a preferred embodiment, the filter pin next to the main filter body still has a bolt portion which 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-filtration position. Thus, for example, in the case of a Auswechseins fiction, like the outer support strainer, the supply and ^■ discharge of plastic material to be filtered alone thereby be interrupted in a structurally simple manner. It should be noted that the term plastic melt used in the present specification particularly includes a polypropylene, polyethylene, high-pressure polypropylene, low-pressure polyethylene, linear low-pressure polyethylene, polystyrene, polyamide, alkyl butadiene styrene (ABS), polyester, Polyoxymethylene (PO), polyacrylate,

Polymethylmethacrylate (PMMA) - and polyvinyl chloride melt can denote. It should also be noted that ^: the cylindrical or circular designated elements of the device according to the invention may also have corresponding polygonal shapes.

The invention fiction, ate device will be explained in more detail by way of example with reference to the drawing. Show it:

1 is a schematic representation of a fiction, a device according to the invention for filtering a thermoplastic resin melt,

2 shows a partial view in section along the section line A-A in Figure 1,

3 shows a schematic cross section through a: filter pin in the region of

Filter main body with a filter surface of the filter main body comprehensive pleated filter screen,

4 is a detail of a schematic plan view of the filter screen,

5 is a detail of a schematic plan view of the filter body in the region of the filter surface,

6 is a partial view in section along the section line CC in Figure 5 _.

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Fig. 7 a; schematic cross section through a filter pin in the region of the filter body with a filter surface of the filter body comprehensive

Support screen and a pleated filter screen comprising the support screen,

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FIG. 8 is a schematic cross-section through: a portion of a multilayer pleated filter screen partially spot welded to a portion of a carrier screen. FIG.

In Fig. 1 is a device for filtering a plastic melt according to the

Invention shown. The device has a housing 1, wherein the housing 1 with two i

cylindrical filter cavities 4 is provided, wherein the filter cavities 4 are each provided with a filter pin 5 axially displaceable therein. The axial displaceability is indicated by the corresponding double arrow A at the bottom right in FIG. 1. In order to effect the axial displacement of the filter pin 5, the bolts are each associated with hydraulic elements. The filter pin 5 are arranged side by side, as also shown in Figure 2, and identical.

Here, the left filter pin 5 is shown in a filtering position and the right filter pin 5 is shown in a non-filtering position. Viewed in the flow direction of the melt to be filtered plastic, this passes through an inlet channel 2 into the housing 1, from There, via the Y-shaped dividing inlet channel 2 in each case in one of the filter cavities 4, as shown in FIG. 2, in the housing 1. There, the plastic melt is guided through the filter body 6 with a filter surface 7 there through the filter openings 8, through which the plastic melt passes to a Filtrathohlraum 9 in the filter body 6. Finally, the filtered plastic melt then passes from the filtrate cavity 9 to the at least one, thus in fluid communication outlet channel 3 and thus again from the housing 1. The exact location of the elements and channels or cavities is partially not completely visible in Fig. 1, however, will be shown in more detail in connection with FIG.

As can be seen in the illustration of FIG. 1, the filter surface 7: of the filter base body 6 is in each case made of a removable, flexible, elastic and yet stable, ie. not mat-like trained, carrier wire 10 includes, so that this support wire 10 is clamped there on the filter body 6. The support screen 10 can thereby with its axial end edges 11 by means of clamping elements, e.g. by means shown in: Fig. 2 clamping elements 14, be held. As shown, at least two fixing pins 16 are provided in the upper region of the filter base body 6, so that there the support wire 10 can be placed with corresponding openings 17 and is thus held. In this case, according to the illustration, the carrier screen 10 which can be clamped onto the filter surface 7 is arcuate in cross section and comprises approximately 240 ° of the circumference of the filter pin 5, the carrier screen 10 covering the corresponding peripheral portion of the filter surface 7.

As already indicated, in the device according to the invention shown in Fig. 1 and Fig. 2, the left filter pin 5 is in a filtration position (working position), while the right filter pin 5 is shown in the non-filtering position, in which the filter surface 7 of the filter body 6 is freely accessible from the outside, so that there in this position an exchange of. For example, with dirt particles laden pleated filter screen, which is fixed on the support wire 10, can be done according to the local double arrow B in Fig. 1 against an unloaded pleated filter.

The cylindrical filter pin 5. are so adapted to the diameter of the respective filter cavities 4 in the housing 1 ', that even with an axial displacement of the filter pin 5 in the corresponding arrow direction of FIG. 1 no leakage occurs and thus undesirable neither in the filtration position nor in the non-filtration position plastic melt can escape. For this purpose, the filter pin 5 in addition to the main filter body 6 and the filter base part 13 still a bolt portion 15 which corresponds in cross section to the cross section of the filter cavity 4 in the housing 1. The filter cavity 4 is thus filled appropriately in the non-filtration position. Fig. 2 shows the embodiment of the device according to the invention along the section of the line AA of Fig. 1. Components with the same functions as in Figure 1 are identified in the following figures including Figure 2 with the same reference numerals and not discussed separately.

As can be seen particularly clearly in FIG. 2, the inlet channel 2 in the housing 1 is divided into two partial channels, whereby in each case a partial flow of the plastic melt to be filtered is directed respectively to the left filter cavity 4 and the filter pin 5 located there Filtrierposition is supplied or the right filter cavity 4 with the there located in the non-Filtrierposition filter pin 5 is supplied. Right in Fig. 2 is particularly well seen that the filter pin 5 still has the bolt portion 15 which corresponds in cross section to the cross section of the filter cavity 4 in the housing 1 so that it fills this right filter cavity 4 in the non-filtration position. Each filter cavity 4 has, as shown, a separate outlet channel 3, wherein it would also be conceivable for the respective outlet channels 3 to be brought together again in the housing 1 and to emerge from the housing 1 in a common outlet opening (which, however, is not shown).

In the cross-section of Fig. 2 left good to see next to the filter body 6 of the filter base part l3, which corresponds in cross section in its outer contour of the local inner contour of the filter cavity 4 of the housing 1 and there has no filter surface 7. The filter body 6, the filter surface 7, through which the plastic melt passes through the filter openings 8 for Filtrathohlraum 9 in ^■ filter body 6, wherein the Filtrathohlraum 9 communicates with the outlet channel 3 in the to be seen to the left in Fig. 2 filtering position in Fluidverbiridung. The filter surface 7 of the filter base body 6 is on the one hand by the flexible-elastic support member 10 according to the Invention comprises so that -this support member 10 is removable there on the filter body 6 can be clamped. On the other hand, the pleated filter screen is on the support wire, as in the left in Fig. 2. see provided with smoothed axial end edges 11, which are clamped on both sides in each case by a clamping element 14 on the filter body 6 and secured. Contrary to the stepped arrangement of the transition from filtrate cavity 9 to the channel, which is aligned with the outlet channel 3, according to the illustration of FIG. 3, it is also possible for this area to be rounded off in a flow-wise manner in the flow direction. or frusto-conical narrowed from Filtrathohlraum 9 to the outlet channel 3 accordingly.

Fig. 3 shows a schematic cross section through a filter pin 5 in the region of the filter base 6 with a filter surface 7 of the filter main body 6 comprehensive pleated Fil ersieb 12. The filter body 6 is disposed between a filter cavity 4 and a filtrate 9. A plastic melt to be filtered first fills the

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Filter cavity 4, penetrates through the pleated filter screen 12 through filter openings 8 of the Filter main body 6 in the filtrate cavity 9 and is derived as a filtered plastic melt through the outlet opening 3 of the filter pin 5 shown here.

Can be achieved in the cross-section of Fig. 3 it can be seen that the effective area is considerably increased compared to a smooth filter by the pleating of the filter screen 12, so that an increased maximum flow rate of molten plastic material per unit of time. ^"The pleated filter 12 has axial longitudinal folds 7, which extend over the entire axial width of the screen surface 7 of the filter base body 8. The pleated filter screen 12 is in direct contact with the filter surface 7 of the filter base body 6 in the embodiment according to FIG.

With the aid of clamping elements 14 and 14 ', the pleated filter screen 12 is fixed in areas of smooth axial end edges 11 and 11' on the filter base body 6. The clamping elemerjte 14 and 14 'are formed in this embodiment of Figure 3 as terminal strips, which extend over the entire width, the smoothed axial end edges 11 and 11', wherein clamping screws 22 and 22 '^; are guided by corresponding D.urchgangsbohrungen the clamping elements 14 and .. 14 'and are screwed into a threaded hole in the end edge regions 24 and 24' of the filter body 6.

For this purpose, dowel pins (not shown here) are provided in the terminal edge regions 24 and 24 ^'of the filter base body 6, which engage with fitting bores of the terminating ducts 11 and 11', not shown here, for the clamping and clamping of the pleated filter screen. In order to compensate for manufacturing tolerances of the pleated filter screen 12 in the region of the end edges 11 and 11 ^' , areas in which clamping screws 22 and 22' are provided, radial slots through which the clamping screws 22 and 22 'in the threaded holes of the filter base 6th are introduced.

In this embodiment of the invention, a prepared pleated filter screen 12 with at least 4; Passing holes in the region of the axial end edges 11 and 11 'placed over the filter surface 7 of the filter base 6 and by bringing preferably 4 of

Fitting holes fixed in areas of the terminal edges 11 and 11 'preparatory, then i

clamped with the aid of the above-described clamping elements 14 and 14 'in the smooth Abschlusskanjien 11 and 11' on the filter base 6, wherein for changing the pleated filter screen 12 with a few simple steps, only the terminal strips must be removed. The pleated filter screen 12 consists essentially of longitudinally folded filter material, which is described in more detail in Fig. 5.

4 shows a detail of a schematic top view of the pleated filter screen 12 with longitudinal folds 25. These longitudinal folds 25 can be parallel to the longitudinal axis 26 of the filter pin

I be aligned on the filter surface of the filter body of the filter pin. However, it is particularly advantageous to provide the longitudinal folds of the pleated filter screen at an angle of inclination α to the longitudinal axis 26 with α between 0 ^ α ^ 5 °, as shown schematically in Figure 4, as possible a plurality of filter openings of the filter surface of the filter body with the pleating enlarged filter screen surface of the pleated filter screen 12 cover. Further, by the inclination angle α of the deformation resistance and the stability of the

Longitudinal folds 26 of the pleated filter screen 12 improved.

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5 shows a detail of a schematic plan view of the filter base body 6 in the region of the filter surface 7 of the filter pin. The filter openings 8 and 8 'are arranged in rows and columns. In this case, the filter openings 8 form a spatial grid, which is arranged offset relative to the spatial grid of the filter openings 8 ', so that a high density of filter openings on the filter surface 7 can be achieved with minimal flow resistance, the plastic melt through the pleated filter screen and through the arranged below filter openings 8 and 8 'of the filter body 6 to flow.

6 shows a partial view in section along the section line CC in FIG. 5, wherein the pleated filter screen 12 is aligned with its longitudinal folds 25 such that exactly one longitudinal fold 25 is arranged above a filter opening 8 of the filter base body 6, so that the filter surface enlargement is not only clearly visible, but can also be effective. In this embodiment: the invention corresponds to the number of pitches of the filter openings in cross-section on the filter surface 7 of the number of longitudinal folds 15. Further improvement of the stability and deformation resistance of the pleated filter screen 12 can be achieved by inserting a support screen between the screen surface 7 and the pleated filter screen 12 can be achieved if in addition the _: pleated filter screen 12 is fixed point-wise plug-in, for example by spot welding on the support frame.

In addition to: a fixation by means of terminal strips as in Figure 2, Fig. 7 shows a schematic cross section through a filter pin 5 in the region of the filter base body 6 with a filter surface 7 of the filter main body 6 comprehensive support screen 10 and the support screen 10 comprehensive pleated filter screen 12 Das Supporting screen 10 also has axial end edge regions 11 ^" and 11"'in the region of the axial end edges 11 and 11'. Ejiese areas can each be fixed together with the smoothed axial end edges 11 and 11 ^'of the pleated filter screen 12 on the filter base 6 by means of the clamping elements 14 and 14' and the clamping screws 22 and 22 '. However, it is also possible, the support wire 10 of a flexurally elastic prestressed material arcuate 'form, so that it self-locking on the filter surface. 7 of the

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Filter body 6 is fixed, so that the clamping elements 14 and 14 ', for example in the form of terminal strips only improve the sealing function, so no unfiltered Plastic melt can penetrate into the filtrate cavity 9. The carrier screen 10 is shown in FIG. 7 coarser mesh compared to the pleated filter screen 12.

Fig. 8 shows a schematic cross section through a portion of a multilayer pleated filter screen 12, which on a. Section of a support wire 10 is partially spot welded in welds 23. Such a carrier screen 10 may have a thickness d between 1 mm <d ^ 2 mm. Preferably, the support wire 10 has a thickness of 1, 5 mm at a Siebm ashes of w = 1, 25 mm and a filter diameter D of 0.63 mm. This filter diameter of 0.63 mm is smaller than the filter diameter of the filter openings 8 in the filter base 6, as shown in Figures 3 and 7, and significantly larger than the ¹ sieve meshes Wi8, Wi9, W20, and W21: and Filtrierdurchmesser Dig, D ₁₉ , D ₂ o and D21 of a arranged on the support 10 multi-layer filter screen 12th

For example, the pleated filter screen 12; As shown in Fig. 8, have four filter layers, wherein the outermost filter layer. 18 has the smallest Filtrierdurchmesser with Di ₈ = 0.2 mm at a Siebm ashes Wi ₈ of 0.315 mm. The next filter screen 19 may be formed from a standard Betamesh 60 filter, since the subsequent deeper filter layer 20 in turn a mesh size of w ₂ o = 0.315 mm at. a filtration diameter of D ₂ o = 0.2 ^: mm. The innermost filter layer 21 of the pleated filter screen _. Finally, 12 has a sieve mesh width of w ₂ i = 0.85: mm at a filter diameter Ό21 = 0.4 mm. With; this staggering _, the filter diameter ensures that the impurities settle on the outermost layer 18 and can not penetrate deeper into the volume of the pleated filter screen 12, and thus be removed from the outermost Filterieblage.18 when cleaning or replacing the pleated filter screen 12 can.

In the in Fig. 8 _; In the embodiment shown, the pleated filter screen 12 at weld points 23 is partially bonded by spot welding to the carrier screen 10, so that both can be exchanged together. The strength, a of the multilayer pleated

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Filter screen 12 is between 2 mm ^ a 4 mm and the enlargement of the surface shown here over a length v with respect to the surface portion u of the: support 10, which is arranged directly on the filter surface 7 of the filter body 6, v: u = 2: 1 , so

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that, for example, a doubling of the throughput of plastic melt per unit of time is possible with this embodiment. In essence, this depends on the shape of the longitudinal folds, which have a pleated design with the same filter area up to four times higher active filter area and thus up to four times higher throughput per _; Time unit can allow.

The above embodiments have been described to illustrate possible embodiments, it being understood by those skilled in the art that various alternatives to the can be used in the embodiments of the claims described herein without departing from the scope of the invention. It is expected, and is intended, that further developments of the technique discussed herein may occur, especially as the disclosed apparatus is exemplary and not limiting, so that overall the scope of protection is limited only by the subject matter of the present invention. is limited to the appended claims.

Claims

claims

1. Device for filtering a plastic melt, comprising a housing (1) which has at least one inlet channel (2) and at least one outlet channel (3) for the plastic melt, wherein the at least one inlet channel (2) of the at least one outlet channel (3) by at least one filter cavity (4) for receiving at least one axially displaceable filter pin (5) is separated, wherein the at least one filter pin (5) at least one filter base (6) with a filter surface (7) with there through the filter body (6) passing Filter openings (8) through which the plastic melt passes to a Eiltrathohlraum (9) in the filter base body (6), wherein the Filtrathohlraum (9) with the at least one outlet channel (3) is in fluid communication, characterized in that

the filter surface (7) of the filter base body (6): is surrounded by a pleated filter (12) and in axially smoothed edge regions (11 and 11 ') of the pleated filter screen (12) clamping elements (14 and 14') are provided.

2. Apparatus according to claim 1, characterized in that as clamping elements (14 and 14 ') on the axiajen smoothed edge regions (11 and 11') of the pleated filter screen (12) terminal strips; are provided.

3. Apparatus according to claim 1 or claim 2, characterized in that the smoothed edge regions (11 and 11 ') fitting holes and the filter base body (6) provided in the local axial edge regions corresponding to the fitting holes dowel pins for aligning and prefixing the pleated filter screen (12 ) exhibit.

4. device ^; according to one of claims 1 to 3, characterized in that the clamping elements (14 and 14 ') have through holes, with slot openings in the radial direction of the smoothed edge regions (11 and 11') of the pleated filter screen (12) and with threaded holes in the axial edge regions the filter base body (6) correspond, wherein clamping screws (22) in the through holes under clamping of the smooth edge regions (11 and 11 ') of the pleated filter screen (12) with the threaded holes in the axial Randtiereichen the filter base body (6) are engaged.

5. Device according to one of the preceding claims, characterized in that the pleated filter screen (12) a plurality of filter layer layers (18 to 21) of different Siebmaschenweiten (w) and different to the Siebmaschenweiten (w) adapted Diameter (D) of Filtrierbohrungen, wherein the outermost layer (18) in the direction of the filter cavity (4) has the smallest diameter (die) of the Filtrierbohrungen and the (W) as well as the diameters (D) of the filter screen layers (18 to 21) towards the Filtrathohlraum (9) towards increase.

6. Device according to one of the preceding claims, characterized dä.ss on the filter surface (7) of the filter base body (6) arranged filter screen, in addition to the pleated filter screen (12) on the filter surface (7) there clampable carrier screen (10th ), which is arranged between the pleated filter screen (12) and the filter surface (7) of the filter base body (6), wherein the support screen (10) is arcuate in cross section and an angle of at least 180 ° and a maximum of 270 ° of the circumference of the Filter pin (5), preferably comprises about 240 ° of the local circumference, and thereby covers the corresponding peripheral portion of the filter surface (7).

7. Device according to one of the preceding claims, characterized in that the filter pin (5) at least in the region of the filter base body (6) and in the region thereof in which the fluid connection of Filtrathohlraum (9) and outlet channel (3), a FilterbasisteiL (13), which corresponds in cross-section in its outer contour of the local inner contour of the filter cavity (4) in the housing (1), and there has no filter surface (7).

8. Device according to one of the preceding claims, characterized in that in the region of the filter base body (6) at least two fixing pins (16) are provided so that there the support screen (10) with corresponding openings (17) can be placed and held.

9. Device according to one of the preceding claims, characterized in that the support screen (10) at least in the region of its axial end edges (11 "and 11" ') the fitting holes and the dimensions of the radial slots of the axial end edges (11 and 11') of the pleated filter screen (12) is adjusted.

10. Device according to one of the preceding claims, characterized in that in cross section the filter cavity (4) is circular and the filter base body (6) in cross section has the shape of at least one or more circular segment portion (s) with different diameters.

11. Device according to one of the preceding claims, characterized in that the filter pin (5) is axially displaceable between a filtering position and a non-filtering position.

12. Device according to one of the preceding claims, characterized in that the filter pin (5) next to the filter base body (6) still a bolt portion (15) which in cross-section of the cross section of the filter cavity (4) in the housing (1)

i

corresponds to ^: that it fills this filter cavity (4) in the non-filtration position.