WO2025021263A1 - Filter for filtering liquid metal - Google Patents

Abstract

The present invention relates to a filter for filtering liquid metals which has a filter housing comprising: a filter main part; a filter cover; and a tubular filter element disposed within the filter housing. The filter housing has at least one inlet and at least one outlet. The filter main part and the filter cover have connection structures which are designed such that, when the filter cover is rotated relative to the filter main part, the installation height for the filter element in the filter housing increases or decreases in order to fix the filter element between the bottom of the filter housing and the underside of the filter cover.

Description

Filter for filtering liquid metal

The present invention relates to a filter for filtering liquid metals with a filter housing comprising a filter base, a filter cover and a tubular filter element arranged within the filter housing. The filter housing has at least one inlet and at least one outlet. The filter base and the filter cover have connecting structures which are designed such that when the filter cover is rotated relative to the filter base, the installation height for the filter element in the filter housing increases or decreases in order to fix the filter element between the base of the filter housing and the underside of the filter cover.

State of the art

Filters for filtering liquid metals are known in very different designs. A simple embodiment of such filters is known from DE 3902151 A1. The hot metal is poured into a pouring sprue that is open at the top. The pouring sprue is directly connected to the mold cavity, with a sleeve made of refractory material arranged in the pouring sprue, in which a cellular ceramic filter is attached. The ceramic filter is the filter element.

From DE 4229417 C2, another geometry of a filter housing for filtering liquid metals is known, with a filter housing made of refractory material, with at least one inlet and one outlet, wherein at least one filter element is arranged between the inlet and outlet and the filter housing has an annular channel on the inlet side and an inner collecting space enclosed by the annular channel on the outlet side, wherein disk-shaped filter elements are arranged between the annular channel and the collecting space, e.g. in a circle or an oval. The filter housing is made of a refractory material.

A known problem of filters known from the state of the art is that the filtering performance is often relatively low, since the filter elements have small filter passage areas in relation to the filter volume and can quickly become clogged, which limits the casting performance of the filters. To solve this problem, "filter banks" have been proposed as filter elements, which increase the casting performance by using several flat filter disks as filter elements next to each other, e.g. in recesses in the mold parting plane. However, this requires a high level of effort in the production of these filters, increases the risk of filter breakage and leads to an uneven throughput of the liquid metal in relation to the filter discs arranged at different positions.

In order to avoid the high costs of producing and assembling filters with several flat filter discs as filter elements, filters with one-piece, tubular filter elements are known from the state of the art. The problem with these filters, however, is that the ceramic filter elements have manufacturing tolerances due to production, which has a negative effect on a precise fit in the filter housing. If the length of the filter elements deviates upwards, the filter housing can no longer be closed without a gap, and if it deviates downwards, a gap remains between the filter element and the housing parts of the filter. Such filter elements must either be discarded or the filter housing must be reworked manually.

The invention was therefore based on the object of providing a filter which enables a higher filtration performance, improved adaptability of the filter housing to the filter element, especially with regard to the manufacturing tolerances of the filter element, and easy installation in the casting system. Two outlets should also be available if required.

Summary of the Invention

These and other objects are achieved with a filter according to the subject matter of claim 1. Further advantageous embodiments are the subject matter of the subclaims or are described in more detail below.

The filter for filtering liquid metal has a filter housing and at least one filter element arranged within the filter housing. The filter housing further comprises a filter base body and a filter cover and furthermore at least one inlet for unfiltered liquid metal and at least one outlet for filtered liquid metal. Apart from the inlets and outlets, the filter base body and the filter cover form a closed filter housing which can be embedded on all sides, for example, in a mold base material to be hardened in a mold without the mold base material being able to penetrate into the filter housing. The filter element is tubular with an outer surface and an inner surface and with a filter element interior that is at least partially delimited by the inner surface. The filter element extends along a longitudinal axis and has a first end and a second end substantially opposite the first end, wherein the filter element has an opening at at least one first end, preferably at both ends. The filter element is located inside the filter housing.

The opening at the first end of the filter element is fluidly connected to an opening in the cover or an opening in the filter housing. Preferably, the filter element has an opening at the first and second ends of the filter element and

- only one of the openings corresponds to an opening in the cover or an opening in the filter housing (and the other opening is designed as a dead end, for example) or

- one opening of the filter element is fluidly connected to an opening in the cover and the other opening of the filter element is simultaneously fluidly connected to an opening in the filter housing.

The filter base body and the filter cover are connected to one another in a rotatable manner via connecting structures, whereby the connecting structures are designed in such a way that when the filter cover is rotated relative to the filter base body, the installation height of the filter element can be varied, whereby the installation height between the filter housing base and the underside of the filter cover increases or decreases. The installation height runs along the longitudinal axis of the filter element.

Inlet and outlet are assigned to the openings in the filter housing and/or the filter cover as follows:

- the filter housing has at least one first opening in the filter base body and at least one second opening in the filter cover, related to a filter element installed in the filter housing or

- the filter housing has at least one first opening in the filter base body and one second opening in the filter cover and one second opening in the filter base body per filter element, wherein the second opening(s) are in direct fluid communication with the filter element and a) either at least the first opening in the filter body is the inlet for the unfiltered liquid metal and

(only) the second opening in the filter cover outlet or

(only) the second opening in the filter base body is the outlet or both, i.e. the second opening in the filter cover and the second opening in the filter base body are the outlet for the filtered liquid metal, or b) conversely, at least the first opening in the filter base body is the outlet for the unfiltered liquid metal and

(only) the second opening in the filter cover or

(only) the second opening in the filter body or both the second opening in the filter cover and the second opening in the filter body are inlets for the filtered liquid metal.

The opening or openings of the second type are each in fluid communication with the filter element interior or the opening or openings in the tubular filter element.

A filter is thus proposed which has a filter housing and a filter element arranged within the filter housing. The filter housing has a filter base body with a base and a filter cover with a bottom (pointing towards the base) as well as at least one inlet for unfiltered liquid metal and at least one outlet for filtered liquid metal. The filter element, which is arranged within the filter housing, has an outer shell surface and an inner shell surface as well as a filter element interior for filtered liquid metal, which is at least partially delimited by the inner shell surface. The filter element extends along a longitudinal axis and has a first end and a second end substantially opposite the first end. Furthermore, the filter element has an opening at least at the first end, which is fluidically connected to the outlet or the inlet, preferably the outlet. The filter base body and the filter cover can be reversibly connected to one another and have connecting structures which are designed in such a way that when the filter cover is rotated relative to the filter base body, in particular around the longitudinal axis, the height of the filter housing increases or decreases along the longitudinal axis of the filter element in order to fix the filter element between the base of the filter base body and the underside of the filter cover. The filter element is tubular. "Reversibly connectable" means that the connection can also be removed without causing any damage, but does not rule out the possibility that after the height adjustment the connection is locked or glued, for example, or that an adhesive hardens and the connection can therefore no longer be removed "reversibly". Detailed description of the invention

The present invention relates to a filter housing that can be variably adapted to a filter element for filtering liquid metals with regard to the installation height of the filter element. The metals to be cast are primarily iron, iron and steel alloys, but also non-ferrous metals such as copper, nickel and/or aluminum or alloys containing copper, nickel, aluminum and/or magnesium.

The filter according to the invention comprises a filter housing and a filter element arranged within the filter housing. The filter housing has at least one filter base body and a filter cover. The filter element is tubular, whereby the tube can also be conical (conical filter element) or truncated pyramid-like (truncated pyramid filter element). The tubular filter element has an elongated hollow body, the length of which is preferably greater than its diameter. The filter element can have a circular cross-section. The tubular filter element is closed at one end or open at both ends.

The filter element can be made from different materials, preferably the filter material is a fired ceramic. Usually the filter element used in the filter according to the invention is a foam ceramic filter, which has a ceramic foam structure with pores that are connected to one another. Such structures can be produced by burning out organic material or by 3D printing, e.g. according to the method of EP3325428 B1. Such filter elements are known from the prior art.

The material of the housing parts, filter cover and filter base can also be of different types, as long as it has sufficient fire resistance, abrasion resistance and chemical and mechanical stability. Ceramic masses based on a wide variety of binding agents, hydraulically hardening masses, monolithic refractory bodies, stamped, cast, pressed, shot or 3D printed are possible. It is also possible to manufacture them from loose bulk materials such as refractory sands and/or other natural or artificial masses, using hardening binding agents. The housing parts can also be manufactured using 3D printing or shooting machines. To improve the thermal, chemical and other resistance, the housing part can also be provided with a coating, applied e.g. by dipping, brushing or spraying. The filter housing and the filter cover of the filter according to the invention are preferably made of fireproof materials (so-called refractory materials), in particular using binding agents. The filter element, filter housing and the filter cover are preferably fired again in order to minimize the escape of gases when filtering the liquid metals.

The filter housing has at least one inlet for unfiltered liquid metal and at least one outlet for filtered liquid metal. The inlet for unfiltered liquid metal can be arranged in the filter base body or in the filter cover or in both, and alternatively the outlet for filtered liquid metal can be arranged in the filter base body and/or in the filter cover. Preferably, the inlet for unfiltered liquid metal is located in the filter base body or is arranged on the filter base body. In a further preferred embodiment, the outlet for filtered liquid metal is arranged in the filter cover and optionally additionally in the filter base body (opposite), particularly preferably the outlet for filtered liquid metal is arranged in the filter cover. A particularly preferred filter has an inlet for unfiltered liquid metal in the filter base body and an outlet for filtered liquid metal in the filter cover and optionally a further second outlet for filtered liquid metal in the filter housing. The outlet or outlets are then each located above the longitudinal axis of the tubular filter element.

In a further preferred embodiment, the inlet or two or more inlets for unfiltered liquid metal is/are arranged completely and exclusively in the housing base body.

The filter housings known from the prior art are often designed in two parts with two housing parts that are roughly similarly dimensioned in terms of volume. In these known filter housings, the inlet for unfiltered liquid metal is usually designed centrally perpendicular to the dividing plane of the housing, so that the inlet is then located half in the first and half in the second half of the housing. The disadvantage of this design, however, is that experience has shown that when the two housing halves are put together, damage to the filter housing can occur, such as chipping and cracks in the refractory material. This can lead to further undesirable effects when the liquid metal flows through, such as erosion and flushing of the backfill material into the system, and thus to premature blocking of the filter element(s) or the escape of the liquid material from the system. This is avoided by the stable design of the inlet in one piece without separating the housing parts. Furthermore, the present invention provides a more robust and resilient connection between the inlet in the filter housing and the supply pouring system, and assembly is significantly easier. The pouring system consists of simple fireproof pipes, for example, which are pushed into the inlet and usually also into the outlet or coupled to it using plug-in connections.

The filter element is located inside the filter housing, which is formed at least by the filter base body and the filter cover. The filter element, which is formed in particular from a foam ceramic, is a tubular body and can also be conical or truncated pyramid-shaped. The filter element also comprises an outer surface and an inner surface. These designs have the advantage that the usable filter surface is considerably larger than conventional plate-shaped, flat filter elements. The filter element also has a filter element interior for liquid metal. The filter element interior for receiving liquid metal is at least partially delimited by the inner surface of the filter element. The filter element extends along a longitudinal axis and has at least a first end and a second end substantially opposite the first end. The filter element is open at one or both ends, preferably at both ends. In the region of the longitudinal axis, the filter element is hollow. However, it can also have a closed base at one end. The tubular filter element then has a cup shape. The liquid metal inside the filter element fills up or empties itself through the only open pipe end.

The filter element interior preferably contains filtered liquid metal and is emptied via an opening in the filter cover or filter base and in both, preferably in the filter cover. The opening or openings are then outlets.

The filter element thus has an opening at least at a first end, and preferably the filter element also has a second opening at the second end. The opening at the first end is preferably substantially opposite the opening at the second end. The filter element is designed in such a way that, in a metal casting process according to the application, unfiltered liquid metal passes through the inlet of the filter housing and then hits the outer surface of the filter element. The unfiltered liquid metal passes through the outer surface of the filter element into the filter element interior of the filter element, which is at least partially formed by the inner surface. Filtered liquid metal is then located inside the filter element interior. The opening of the filter element, which is located at the first end of the filter element, is fluidically connected to the outlet of the filter housing, preferably in the filter cover, so that filtered liquid metal from the filter element interior of the filter element can pass through the outlet in the filter housing, in particular in the filter cover, from the filter according to the invention into the casting mold. The flow direction of the liquid metal can also be the other way around, however.

The filter element is preferably arranged centrally in the filter housing.

The filter base body and filter cover can also be designed in such a way that the filter base body has several receptacles for filter elements and that the filter cover is also adapted accordingly. The filter base body and filter cover then have at least a number of openings or outlets that corresponds to the number of filter elements or is greater if two openings or outlets are provided for each or for individual filter elements, one in the filter cover and one in the filter base body.

According to the invention, the filter base body and the filter cover can be connected to one another and have connecting structures. According to the invention, the connecting structures are designed such that when the filter cover is rotated relative to the filter base body, in particular about the longitudinal axis of the filter element, the height of the filter housing and in particular the installation height for the filter element increases or decreases along the longitudinal axis of the filter element. This design according to the invention makes it possible to compensate for manufacturing tolerances of the filter elements, which mostly arise due to production. The filter elements used usually have manufacturing tolerances of a few millimeters.

As a result, it may happen that when these filter elements are inserted into a conventional filter housing known from the state of the art, the filtering performance of the filter is reduced because the filter element cannot be adequately or only poorly positioned within the filter housing. Likewise, liquid metal can then leak out of the filter housing or the liquid metal can pass through the filter element at one or both ends between the filter housing and the filter element or the filter housing and the filter cover without being filtered. This is undesirable because unfiltered metal can deteriorate the quality of a casting.

The connecting structures that connect the filter base body and the filter cover to one another can have different designs. According to a first design, the connecting structures are designed as at least two, preferably at least three support surfaces, wherein the support surfaces wind in a circle around the longitudinal axis of the filter element and are designed as inclined planes corresponding to the filter base body and in the filter cover, so that when the filter cover rotates relative to the filter base body, the height of the filter housing and thus the installation height for the filter element is reduced or increased.

Typically, the filter base body and filter cover each have 2 to 8 inclined planes on a circular path, preferably the same number on the filter base body and in the filter cover. The inclined planes in particular form a closed band and lie on a circular path, e.g. when viewed from above, looking at the inclined planes in the following sequence (e.g. for the filter base body and filter cover in the same direction of rotation when viewed from above): first inclined plane sloping, step up, second inclined plane sloping, step up, third inclined plane sloping, step up and then to the beginning of the first inclined plane and the same for 2 or 4 or more inclined planes.

The three inclined planes in the filter cover and on the filter base body 3 are arranged in the same way but complementarily, so that a depression in the inclined plane engages in a raised area of the opposite inclined plane and vice versa when they come to rest on top of each other, so that when the filter cover is rotated relative to the filter base body in one direction, the height of the filter housing and thus the installation height along the longitudinal axis of the filter element increases and in the other direction it decreases. When opposite steps hit each other, the inclined planes have moved into each other to the maximum and the minimum installation height is reached.

The connecting structures in the form of the inclined planes are arranged in opposite directions in the filter base body and in the filter cover, in particular at least two connecting structures in the filter base body and in the filter cover. The connecting structures are located on each of the two housing parts (filter body and filter cover) and when the housing is closed they complement each other to form pairs of inclined planes lying opposite one another, which form a circle. This means that when the two housing parts are rotated against each other, the distance between the filter body and the filter cover can be changed in relation to the installation height of the filter element when the filter housing is closed.

This makes it possible to directly compensate for the previously described disadvantage of manufacturing tolerances, particularly of the filter element, at least in the height of the filter elements and to ensure that all parts of the system, i.e. filter element and filter housing parts, fit together precisely without using new or specially selected parts or expensive reworking of the same. These tolerances of the filter element, which mostly occur in the length (height) of the filter element, can now be easily compensated without it being necessary to check the filter element and housing individually in advance and to specifically match them to one another. This is made possible by the fact that by rotating the filter cover relative to the filter base body, the height of the filter housing increases or decreases along the longitudinal axis of the filter element.

By shifting the connecting structures in the form of inclined planes against each other, the manufacturing tolerances of the filter element can be easily compensated and the filter element can be easily arranged in the filter housing. The range of displacement of the connecting structures can extend over several millimeters, so that even larger tolerances can be compensated, e.g. in height 4 to 18 mm, in particular 6 to 12 mm.

At the end of each inclined plane, a short, horizontal surface is preferably provided (end surfaces of the inclined planes) in order to achieve a defined end position when the full compensation distance is used. In principle, these inclined planes and surfaces can also have a surface structure, such as teeth or predefined locking points. This can be supported by a display or scale attached to the outside of the housing parts or incorporated into the material, for example to visualize the distance between the two housing parts in a suitable manner. Furthermore, the connecting structures between the filter base and the filter cover can be designed as threads, for example as an external thread on the filter base and an internal thread on the filter cover, or vice versa. This creates a positive connection between the two housing parts. In this case, further measures to subsequently create a positive connection between the housing parts, for example for easier handling or intermediate storage, are not necessary. This thread can be made of the same material as the housing parts, but can also be made of another suitable material or applied to the housing parts using suitable methods (e.g. by gluing). The structure, shape and appearance of the threads can be very different. It is also possible, for example, for several bolts to run in one thread.

In one embodiment, the ring-shaped area around the filter element in the filter housing, into which liquid metal flows, does not have a constant cross-section, but rather this cross-section decreases against the direction of flow back to the inlet to an area where it meets the open cross-section of the inlet on the inside of the filter body. This area is designed like a ship's bow, for example, and is intended to bring the circulating flow back together with the incoming flow with as little turbulence as possible.

The reduction of the cross-section of the channel between the filter element and the housing wall of the filter base body in the area of the inlet ensures that the pressure conditions in this channel are not too different, since as the metal flows into the channel around the filter element, a part flows directly into the filter element and thus ensures a decrease in volume in the ring channel.

In a further preferred embodiment, the filter housing of the filter according to the invention has at least two outlets for filtered liquid metal. In this embodiment, it is necessary for the filter element to have two openings, one at the first end and one at the second end, wherein the openings are substantially opposite one another (in particular diametrically opposite one another). It is further preferred that one outlet for filtered liquid metal is arranged substantially opposite one another (in particular diametrically opposite one another) to the other outlet for filtered liquid metal. It is also preferred that the opening of the filter element at the second end is (directly) fluidically connected to the further outlet. According to this embodiment, the outlet for filtered liquid metal is arranged in the filter cover and the further outlet for filtered liquid metal is arranged in the filter base body. The presence of two outlets or the alternative between two outlets means that the casting system can be used in a wider variety of ways and the structure of the casting system can be simplified.

Alternatively, one of the outlets can be closed using a plate (particularly a plate of the same shape) if the design and/or structural shape of the cast part requires it, e.g. by gluing the plate into the outlet. This allows the filter system to be adapted to the respective requirements quickly and easily. It is also possible for the filter element to have a cup shape, whereby the bottom of the cup is not permeable to the liquid metal and an opening can thus be closed, i.e. with this design, no plate needs to be glued into the outlet.

In a further preferred embodiment, the inlet for unfiltered liquid metal and the filter element are fluidically connected. Independently of this, it is also preferred that the inlet for unfiltered liquid metal and the outlet for filtered liquid metal are arranged substantially orthogonally to one another.

The inlet for unfiltered liquid metal is also preferably designed in a conical manner or has a conicity, with the diameter tapering in the direction of the filter element (regardless of whether the opening is in the filter base body or in the filter cover). According to a further embodiment, if the opening in the filter base body is an inlet, the opening is aligned so that the liquid material flows in radially. One or both of these embodiments ensure that when the unfiltered liquid metal enters the filter housing, the force when the unfiltered liquid metal hits the filter element is reduced. In particular, it can be prevented that the inflowing melt hits the wall of the filter element directly when the filter housing is filled with unfiltered liquid metal. This preferred embodiment can also prevent the filter element from being damaged or even breaking.

According to a further preferred embodiment, the filter cover is provided on the underside with one or two circumferential collars, wherein the collar is in contact with the outer surface and/or with the inner surface of the filter element. Likewise, according to a further preferred embodiment, a circumferential collar can be arranged on the bottom of the filter base body, wherein the collar is in contact with the outer surface and/or with the inner surface of the filter element. According to another embodiment, it is also possible for the filter element to be fixed with an annular recess in the filter cover and/or in the filter base body. Mixed forms between these alternatives are also possible. By using one or both of the above embodiments of the filter cover and/or the filter base body, the filter element located inside the filter housing can be arranged in a stable manner and it can be prevented that the filter element slips inside the filter housing when unfiltered liquid metal enters the filter housing through the inlet. Furthermore, this preferred embodiment can prevent liquid metal from passing through any narrow gap between the filter element and the underside of the filter cover or the filter element and the bottom of the filter base body.

In an even more preferred embodiment, elevations (also called “filter supports”) can be provided on the underside of the filter cover and/or on the bottom of the filter base body in the filter base body, which fix the filter element in the direction of the longitudinal axis and are attached to the upper and/or lower edge of the filter element.

These elevations can, for example, have circular geometries or can also be designed in geometries that deviate from circles, for example n-sided. In particular, these elevations are made of an elastic material, for example a moldable and/or elastic fireproof mass or similar. When the filter cover is rotated relative to the filter base body about the longitudinal axis of the filter element, the height of the filter housing increases or decreases along the longitudinal axis of the filter element. In this preferred embodiment, the elevations first come into contact with the filter element when the filter housing is twisted together (twisting together means that the height of the filter housing decreases along the longitudinal axis of the filter element).

This prevents the filter element from being damaged or even breaking if the filter housing is tightened too much, which is undesirable. Filter supports on the collar and/or the second collar also ensure that the filter element is positioned stably within the filter housing. The housing parts can be permanently connected to one another by using material-locking methods (e.g. by gluing with hot glue or other materials), or by using force-locking clamps, tape or, for example, locking pins inserted around the circumference of the filter cover, which lead through the overhanging cover into the filter base body.

The invention is further explained by the figures, without being limited to them. They show

Fig. 1 View of a filter according to the invention;

Fig. 2 View of the filter base body with inserted filter element of the filter according to Fig. 1; Fig. 3 Top view of the filter base body from Fig. 2;

Fig. 4 View of the filter cover of the filter according to Fig. 1;

Fig. 5 Top view of the filter cover from Fig. 4;

Fig. 6 and Fig. 7 are sectional views through a filter according to the invention as shown in Fig. 1. Fig. 8 and Fig. 9 are a filter with an external thread with which the filter cover is screwed onto the filter base body.

For figures 1 to 9 it is also possible to swap the inlet and outlet and thus enable a different flow direction of the metal.

Fig. 1 shows (partially with reference to Fig. 2) a perspective view of a filter 1 according to the invention with a filter housing 2, which has a filter cover 4 and a filter base body 3. A tubular filter element 5 (not shown) is arranged inside the filter 1. An outlet 8 is arranged in the middle of the filter cover 4. The opening 11 of the filter element 5 is located below the outlet 8. Through the outlet 8, filtered liquid metal from the filter interior 10 of the filter element 5 (not shown) can pass through the opening 11, which is fluidly connected to the outlet 8, from the filter 1 into the casting mold. An inlet 7 is arranged in the filter base body 3.

Outlet 8 and inlet 7 can also be swapped if the flow direction is opposite or can be called a neutral opening; this also applies to the patent claims (then outlet 7 and inlet 8 and 8'). Outlet 8 and inlet 7 are arranged orthogonally to one another. Inlet 7 and outlet 8 of filter housing 2 each have a circumferential groove 12, which is intended to simplify the coupling of the filter housing to the pouring pipes and ensures a quick connection. Liquid, unfiltered metal can enter the interior of filter 1 through the inlet. When unfiltered liquid metal enters the interior of filter housing 2, the unfiltered liquid metal strikes filter element 5 and flows through the walls of filter element 5 into the filter element interior 10 of filter element 5. Liquid filtered metal flows from filter element interior 10 of filter element 5 through opening 11 and outlet 8 via a connected pipe system into the casting mold.

Fig. 2 and Fig. 3 show a filter base body 3 and the filter element 5 as part of a filter 1 according to the invention with an inlet 7 and a tubular filter element 5 inserted into the filter base body 3. The filter element 5 has an outer surface, an inner surface, an opening 11 and a filter element interior 10. The filter element 5 is surrounded on the bottom surface of the filter base body 3 by a collar 6, which is in contact with the outer surface of the filter element 5. This arrangement ensures that the filter element 5 is arranged stably in the filter base body 3. At the same time, this arrangement of collar 6 and filter element 5 prevents unfiltered liquid metal from the space for unfiltered liquid metal 9 from entering the casting mold through the outlet 8 in the filter cover. This arrangement of the filter element 5 in the collar 6 ensures that only filtered liquid metal from the filter element interior 10 passes through the opening 11 and the outlet 8 into the casting mold.

The outer surface of the filter element 5 forms a closed filter surface. The filter element interior 10 of the filter element 5 is formed by the inner surface of the filter element 5. When unfiltered liquid metal enters the space for unfiltered liquid metal 9 through the opening 7, the unfiltered liquid metal strikes the outer surface of the filter element 5. The unfiltered liquid metal diffuses through the outer surface of the filter element 5 into the filter element interior 10 of the filter element 5, in which filtered liquid metal collects. The filtered liquid metal can then flow into the casting mold (not shown) through the opening 11 of the filter element 5, which is fluidly connected to the outlet 8 (not shown) of the filter cover 4 (not shown). The filter base body 3 has, as part of the connecting structure 14 of the filter base body 3, three inclined planes and three steps of equal size. Each of the three inclined planes of the filter base body 3 has an end surface 13. The end surface 13 ends where the step leads up to the beginning of the next inclined plane. The end surface is arranged orthogonally to the longitudinal axis of the filter element or, in other words, the inclined plane has a zero gradient at this point. Each step has the same height.

Fig. 4 and Fig. 5 show a filter cover 4 as part of a filter 1 according to the invention with an outlet 8 through which filtered liquid metal can flow through the opening 11 from the filter element interior 10 of the filter element 5 (not shown) (not shown) into the casting mold (not shown). Inside the collar 6, three elevations (filter supports) 15 are arranged between the collar 6 and the outlet 8 in the filter cover 4. The elevations align the filter cover and prevent the filter element from being damaged or even breaking if the filter housing is twisted too tightly. The filter cover 4 has a total of three inclined planes as part of the connecting structure 14, analogous to the filter base body 3 in Figs. 2 and 3. Each of the three inclined planes of the filter cover 4 has an end surface 13 with a gradient 0, from which a step rises to the beginning of the next inclined plane.

The three inclined planes in the filter cover and on the filter base body 3 are arranged in the same way but complementarily, so that a depression of the inclined plane engages in a raised portion of the opposite inclined plane and vice versa when they come to rest on one another, so that when the filter cover 4 is rotated relative to the filter base body 3 in one direction, the height of the filter housing 2 and thus the installation height along the longitudinal axis of the filter element 5 increases and decreases in the other direction.

Fig. 6 and Fig. 7 show a section through a filter 1 according to the invention, having a filter housing 2 comprising a filter cover 4 and a filter base body 3. The inlet 7 as well as the outlet and the second outlet 8' of the filter housing 2 each have a circumferential groove 12, which is intended to simplify the use of the filter housing with the usual under-casting systems and ensures a quick connection. A tubular filter element 5 is arranged within the filter 1. The filter element has an opening 11 and a second opening 11 *, which is arranged opposite the opening 11. The opening 11 is (directly) fluidically connected to the outlet 8, which is arranged in the filter cover 4 of the filter 1 according to the invention. The second opening 11' is (directly) fluidically connected to the second outlet 8', which is arranged in the filter base body 3 of the filter 1 according to the invention. Unfiltered liquid metal enters the space for unfiltered liquid metal 9 through the inlet 7, which is arranged in the filter base body 3 and is conical. The conical design of the inlet 7 reduces the cross section in the direction of the filter element 5, which leads to the flow rate of the incoming unfiltered metal being reduced. The unfiltered liquid metal hits the outer surface of the filter element 5 and flows through the outer surface of the filter element 5, so that filtered liquid metal collects in the filter element interior 10 of the filter element 5. This filtered liquid metal then flows through the two openings 11, 11' and the two outlets 8, 8' (openings in the filter cover or bottom of the filter base body) via a connected pipe system into the casting mold (not shown). A collar 6 is arranged around each of the two outlets 8, 8', which rests on the outer surface and in which the filter element 5 is arranged. This arrangement ensures that the filter element 5 is arranged stably in the filter housing 2. The collar 6 is in contact with the outer surface of the filter element 5. This arrangement prevents unfiltered liquid metal from the space for unfiltered liquid metal 9 from entering the casting mold through one of the outlets 8, 8'. When the filter cover 4 is rotated relative to the filter base body 3, the height of the filter housing 2 changes along the longitudinal axis of the filter element 5. The filters according to the invention shown in Figs. 6 and 7 are identical in terms of filter base body and filter cover, with the difference that Fig. 6 is a filter 1 according to the invention set to a minimum installation height with a shorter filter element 5, ie with a minimum height of the filter housing 2, whereas the filter 1 according to the invention shown in Fig. 7 is set to the maximum installation height by rotating the filter cover 4 and receives and secures a longer filter element 5 between the filter cover 4 and the filter base body 3.

Fig. 8 and Fig. 9 show a section through a filter 1 according to the invention according to a different design, which corresponds to the filter according to Figs. 1 to 7 in all details, except that the connecting structure 14 is different. The filter element 5 is not shown in Figs. 8 and 9, but is arranged in the same way. The filter cover 4 surrounds the filter base body 3, but threads of a thread are introduced all the way around the outside of the filter base body 3, which engage in a corresponding thread in the cover on the inside. The thread allows the distance to be regulated and also enables a positive connection of the housing parts filter cover 4 and filter base body 3.

Claims

Patent claims: 1. Filter (1) for filtering liquid metal, comprising: - a filter housing (2) and a filter element (5) arranged within the filter housing (2), - wherein the filter housing (2) comprises a filter base body (3) with a bottom and a filter cover (4) with a bottom, - wherein the filter housing (2) has at least one inlet (7,8) for unfiltered liquid metal and at least one outlet (7,8) for filtered liquid metal, - wherein the filter element (5) comprises an outer surface and an inner surface and has a filter element interior (10) for filtered liquid metal which is at least partially delimited by the inner surface, - wherein the filter element (5) is tubular and extends along a longitudinal axis and has a first end and a second end substantially opposite the first end, one end extending to the bottom of the filter base body (3) and one end extending to the underside in the filter cover (4), - wherein the filter element (5) has an opening (11) at at least the first end, - wherein the opening (11) is fluidly connected to the inlet (7) or outlet (8), preferably outlet (8), - wherein the filter base body (3) and the filter cover (4) are reversibly connectable to one another and have connecting structures (14), - wherein the connecting structures (14) are designed such that when the filter cover (4) is rotated relative to the filter base body (3), the height of the filter housing (2) and thus the installation height for the filter element (5) increases or decreases along the longitudinal axis of the filter element (5) in order to fix the filter element (5) between the bottom of the filter base body (3) and the underside of the filter cover (4). 2. Filter according to claim 1, wherein the inlet (7) for unfiltered liquid metal is arranged in the filter base body (3). 3. Filter according to claim 1 or 2, wherein the outlet (8) is arranged in the filter cover (4) or in the filter base body (3), preferably at least in the filter cover (4). 4. Filter according to at least one of the preceding claims, wherein the tubular filter element (5) is a truncated cone-shaped body or a truncated pyramid-shaped body, preferably a tubular body with a uniform wall thickness, wherein the filter element is preferably made of one or more refractory materials and in particular is fired. 5. Filter according to at least one of the preceding claims, wherein the filter base body (3) and/or the filter cover (4) is made of one or more refractory materials. 6. Filter according to at least one of the preceding claims, wherein the inlet (7,8), the filter element (5) and the outlet (8/8,8' or 7/7,7") are fluidically connected and/or wherein the inlet (7) and the outlet (8) or the inlet (7) and the outlets (8,8') are each arranged substantially orthogonally to one another. 7. Filter according to claim 6, wherein the inlet (8 / 8.8' or 7/ 7.7") is conical, in particular the inlet (7) in the direction of the filter element (5). 8. Filter according to at least one of the preceding claims, wherein the bottom of the filter base body (3) and/or the underside of the filter cover (4) each have at least one collar (6) or an annular recess with an edge on both sides, wherein the collar (6) or the edge of the recess are at least partially in contact with the outer circumferential surface and/or the inner circumferential surface of the filter element. 9. Filter according to at least one of the preceding claims, wherein both ends of the filter element 5 have an opening (11, 11'). 10. Filter according to at least one of the preceding claims, wherein the opening in the filter cover (4) and the possibly present opening in the filter base body (3) is/are preferably designed as an outlet (8) and are substantially opposite one another. 11. Filter according to at least one of the preceding claims, wherein one or more filter supports (15), in particular three in each case, are arranged in the form of elevations on the bottom of the filter base body (3) and/or the underside of the filter cover (4) in order to engage the end surfaces of the filter element 5 and to fix the filter element 5, wherein the elevations are preferably each arranged between the outlet (8) and the collar (6). 12. Filter according to at least one of the preceding claims, wherein the connecting structures (14) are designed as support surfaces in the form of at least two inclined planes, preferably at least three inclined planes, in the filter base body (3) and in the filter cover (4), in particular connected with the same number of steps, along a circular line, and the inclined planes on the filter base body (3) and in the filter cover (4) each lie on top of one another in a rotatable manner. 13. Filter according to at least one of the preceding claims 1 to 12, wherein the connecting structures are designed as threads on the filter base body (3) and in the filter cover (4) and the filter base body (3) and in the filter cover (4) can be screwed together by twisting. 14. Use of the filter according to at least one of the preceding claims for filtering liquid metals, in particular in a casting process. 15. Casting system comprising the filter according to at least one of the preceding claims 1 to 13 embedded in a casting mold and pipe connections connected to the filter.