DE2315344A1 - Extruder filter - with collars to hold mounting to plate and inner layers - Google Patents

Abstract

The mounting plate holds >=2 filter units of 20-40 mm dia. for the extrusion of thermoplastic materials, each comprising an outer filter basket of perforated metal sheeting held in place by a collar, allowing it to be withdrawn by hand. The inner layers of a grid, a supported wire mesh, and a fine-woven filters are held by a common collar to allow extraction, separation and reassembly after cleaning. Filter does not generate high pressure, and can be changed while the extruder is in operation.

Description

Filter device for plastics processing machines, in particular for extruders The invention relates to a filter device for plastics processing machines, especially for extruders, with a direction transverse to the direction of flow to be filtered Plastic melt arranged holding plate, which distributed over the flow cross-section and with elongated, cylinder-like, arranged parallel to the direction of flow Has screen elements provided holes.

These are filter devices from the field of plastics processing machines known in the form of quick-change screen slides, for example in an extruder are arranged between the screw end and the outlet-side perforated plate and which have two circular sieve areas, - which alternate in the flow channel can be introduced. The sieve elements consist of several on top of one another Disks made of sieve mesh, which are placed on a thick, slotted holding plate support (U.S. Patent 2,661,497).

A disadvantage of this and similar known devices is that that with increasing diameter of the flow cross-section the retaining plate for reasons of strength always has to get thicker. But this also increases the pressure build-up in the plastic melt very strongly at the filter device. In the case of large diameters, the stir predominant part of the pressure build-up from the carrier plate. Apart from this, that too high a pressure build-up puts excessive stress on some types of plastic, it also has a very detrimental effect on the life of the axial bearings of the extruder the end.

In plastics processing, the development is clearly heading in the right direction to larger machines and throughputs that alone ensure competitive production to back up. The filter devices described are, however, for the reasons mentioned limited in their dimensions upwards.

It is also a filter device for spinning heads for fiber production known, in which cylindrical filter candles to enlarge the filter surface, as they are known for filtering thin media, on a perpendicular to Direction of flow arranged and holding plate provided with holes are attached. The filter candles are made of sintered material, preferably made of made of stainless steel. This device is presumably used to filter low-viscosity Well suited fiber raw materials, but not suitable for filtering high molecular weight, particularly viscous plastic melts, such as those found primarily in screw extruders prepared and processed. The sintered material must have the necessary strength to achieve a large wall thickness compared to the dimensions of the filter candle exhibit. This wall thickness in turn leads to an increased flow resistance and thus strong pressure build-up, which makes the filter cartridges unsuitable for use in Preparation extruders. This is also due to the ratio of the flow cross-section in the filter area of the known spinning head to the flow cross-section in the feed line clear. Such a relationship is found in the machining of viscous and thermally sensitive plastics made of fluidic and thermal Reasons not allowed.

The invention is based on the object while avoiding the described Disadvantages of a filter device to create the one for viscous ones Melt plastic and a sufficient filter surface even with arbitrarily high throughputs without causing an unacceptably high pressure build-up.

This object is achieved according to the invention in that the sieve elements consist of a support basket made of perforated sheet metal, which at its open end with is provided with a collar for inclusion in the holding plate, as well as a strainer basket, which in turn consists of a layer of supporting wire mesh and a layer of fine There is screen mesh and has a common 3und for inclusion in the support basket.

When the melt to be filtered has a higher proportion of impurities contains and the filter device must therefore be cleaned more often, are after a further embodiment of the invention two or more retaining plates with sieve elements inserted into a screen change slide that can be moved transversely to the direction of flow. This means that the filter can be changed practically without interrupting operation will.

Further advantageous for special fields of application training Invention are in further subclaims and in the descriptive of the exemplary embodiments disclosed.

The advantages achieved with the invention are, in particular, that the filter device can be cleaned particularly quickly. The sieve elements are only inserted into the retaining plate and are held in place by a collar. They can be removed with one handle. The same applies to the bracket of the sieve basket in the support basket of the sieve element.

Furthermore, the screen elements are not so narrowly limited in their dimensions like the filter cartridges made of sintered materials, which require thick walls for reasons of strength.

Some embodiments of the invention will now be made with reference to the drawings described. In a somewhat simplified representation, FIG. 1 shows a parallel section to the direction of flow through two inserted into a rectangular screen change slide Filter devices, FIG. 2 shows a view in the direction of flow onto the slide Fig. 1, partly in section along the line 11-11, Fig. 3 a Longitudinal section through an outer support basket of a sieve element, on a larger scale, " FIG. 4 shows a longitudinal section through an inner, two-layer screen basket; FIG. 5 shows a Section from a holding plate with two inserted sieve elements, the upper one in section, the lower in view, FIG. 6 shows another embodiment of a retaining plate with screen elements, inserted into a screen change slide similar to that in Fig. 1, with indicated drive device, FIG. 7 various other exemplary embodiments from to sieve elements for a filter device Fig.ll according to Fig. 6 and Fig.12 a Section through an inserted into a screen change slide with a circular cross-section Filter device.

In Fig. 1 several are parallel to the flow direction (by arrow A indicated) to recognize the sieve elements 1 arranged in the medium to be filtered, which are inserted into a holding plate 2. The holding plate 2 is perpendicular to the direction of flow arranged and has uniform, over the flow cross-section distributed bores to accommodate the sieve elements 1. the Distribution of the holes The flow cross section can be seen in FIG. 2. In the exemplary embodiment of Figures 1 and 2, the holding plate 2 is in one with two through bores 3 slider 4 provided with paragraphs 3a is used. The slide 4 is rectangular Cross-section and can be moved back and forth perpendicular to the direction of flow (through Arrow B indicated), so that in each case one of the retaining plates 2 alternately in the flow channel is introduced, while the second holding plate for cleaning or replacing the Siebelemente can be removed.

The medium to be filtered is, for example, melted thermoplastic Plastic, which is indicated by an extruder with housing 5 and screw shaft 6 and after flowing through the filter device through a perforated plate 7 is pressed. This is usually followed by a granulating device (not shown) at. The filter device according to the invention can, however, also be used for other purposes can be used.

The reference symbols in Fig. 2 have the same meaning as in Fig. 1. The through holes 3 in the screen change slide 4 have in about the same diameter as the housing bore of the extruder. So changed the flow cross-section in the filter device is practically impossible, which is fluid is very cheap It is thus avoided the formation of dead zones; in which Plastic residues could stick.

Fig. 3 shows on an enlarged scale an outer support basket la one Sieve element. The support basket is made of perforated sheet metal and at its open The end is provided with a collar lb with which it is received in the holding plate 2 can. In exceptional cases, this outer support cage can also consist of a very strong one Wire mesh must be made.

Fig. 4 shows an inner screen basket lc of a screen element that consists of an outer layer of supporting wire mesh ld, from an inner layer of fine Screen mesh le and from a common bundle lf with which the screen basket in the support basket la can be held exists. As a rule, when the screen is changed, the outer Support basket reused, if necessary after cleaning, while the inner strainer basket is also cleaned or replaced by a new one.

Should the filter device be; Extruding plastic first Line to improve the mixing effect and to build up a certain back pressure (11Strainereffekt11) are used, it is often sufficient to use outer support baskets la without inner Insert the strainer baskets into the holes in the retaining plate 2.

Fig. 5 shows a section from a holding plate 2 according to Fig. 1, on an enlarged scale, with two inserted sieve elements 1. The upper sieve element is cut open and leaves the outer support basket la with collar lb and the inner one Recognize the sieve basket lc with the two layers ld and le as well as the collar lf. Insecurities can be seen how the outer support basket la through its collar lb in the retaining plate 2 is held and also the inner, two-layer strainer basket lc by its collar lf in the outer support basket la.

Fig. 6 shows another embodiment of one according to the invention Filter device. The sieve elements 1 inserted into an Ilalteplatte 2a are here flows through from the outside to the inside. This can happen in the case of heavily soiled melts be beneficial. Similar to the embodiment of FIG. 1, the holding plate is in a Screen change slide that can be moved perpendicular to the direction of flow 4th used. The filter device is in the upper position in the flow channel while the lower one is removed for cleaning or replacement. Of the In Fig. 1 not shown drive of the screen change slide 4 is here schematically shown. An anchor lo transmits the movement from a hydraulic or compressed air cylinder 11 on the screen change slide 4. The cylinder 11 is by means of rods 12 and plate 13 attached to the extruder housing 5.

An arrow C indicates the movement of the screen change slide. The access and lines for the pressure medium to the cylinder 11 are not shown.

Another embodiment of a sieve element (Fig. 7) has an inner support basket 14 made of perforated sheet metal with a collar 15 for receiving in a holding plate 2a according to FIG. 6. At the opposite end, that in this case is flowed against, the support basket of the sieve element is through a double> cone-shaped Displacer 16 completed. A cylindrical screen sleeve 17, consisting of an inner layer 17a made of wire mesh and an outer layer 17b made of fine mesh, is pushed onto the support cage 14 on the outside.

The sieve element according to FIG. 8 has a support basket 14a and a two-layer one Sieve sleeve 17c, both of which taper in the shape of a truncated cone.

In Fig. 9 a section of a screen element is shown, the outer screen sleeve 17d made of a wound single or multi-layer filter tape consists.

Fig. Lo shows a section of a sieve element with an outer sieve shell 17e made of coiled wire triangular or trapezoidal profile, as is commercially available is available under the name ~ metal edge filter ".

The sieve element shown in detail in FIG. 11 has a outer sieve sleeve 17f made of ceramic or metallic sintered material. Through this that this sleeve is seated on the inner support basket 14, the sintered layer can do a lot be chosen thinner than with the known filter cartridges and thus their disadvantages largely avoid.

In the embodiment of FIG. 12, the holding plate 2 is with Sieve elements 1 inserted into a screen change slide 19 of circular cross-section. This slide, just like the screen change slide 4 after Fig. 1, moved perpendicular to the direction of flow, i.e. H. here perpendicular to the plane of the drawing. It can accommodate two or more filter devices next to each other. The view in the direction of flow corresponds approximately to the view according to FIG. 2. The screen change slide 19 is guided in a housing 2o, the bores 21 for the passage of a temperature control medium having.

The valve version with a circular cross-section is simpler and easier to seal than those with rectangular. Cross-section. aside from that it is thermally advantageous. The drive takes place as described in FIG. 6.

The sieve elements according to the invention have a diameter of approximately lo to 50 mm, but preferably from 20 to 40 mm. Advantageously, only A standardized size of screen elements is kept in stock, adapting to the flow cross-sections Plastic processing machines of different sizes are then carried out by changing the number of screen elements inserted in the flow channel.

-Patent claims-

Claims (5)

Patent claims filter device for plastics processing machines, especially for extruders, with a direction transverse to the direction of flow to be filtered Plastic melt arranged holding plate, which over the flow cross-section distributed and with elongated, cylinder-like, arranged parallel to the direction of flow Has bores provided with sieve elements, characterized in that the sieve elements (1) consist of a support basket (la) made of perforated sheet metal, which at its open The end is provided with a collar (lb) for inclusion in the retaining plate (2), as well from a sieve basket (lc), which in turn consists of a layer (ld) of supporting wire mesh and a layer (le) made of fine mesh and a common collar (lf) for inclusion in the support cage (la). 2. Filter device according to claim 1, characterized in that two or more retaining plates (2) with Sieve elements (1) in a cross The screen change slide (4), which can be moved to the direction of flow, is used. 3. Filter device according to claim 1 or 2-, characterized by Sieve elements with an inner support basket (14) made of perforated sheet metal, which is attached to a End with a displacer (16) closed and at its other, open The end is provided with a collar (15) for inclusion in the holding plate (2), as well as with an outer screen cover (17), which in turn consists of an inner layer (17a) supporting wire mesh and an outer layer (17b) made of fine mesh. 4. Filter device according to one of claims 1 to 3, characterized by a conical tapering of the sieve elements (14a, 17c). 5. Filter device according to claim 3 or 4, characterized by an outer screen cover (17d) made of a single or multi-layer filter tape.