DE10039519A1 - Feeder insert used for casting metals comprises mold elements which slide into each other along a longitudinal axis to surround a hollow space for liquid metal - Google Patents

Abstract

Feeder insert (2) used for casting metals comprises at least two mold elements (4, 6) which slide into each other along a longitudinal axis (20) to surround a hollow space for liquid metal. Independent claims are also included for: (a) a kit for manufacturing a feeder insert; and (b) a method for arranging a feeder insert in a casting mold.

Description

The present invention relates primarily to a closed one Feeder insert, also called feeder for short, for use with Pouring metals into molds, with a cavity for receiving liquid to metal.

Such feeder inserts are used in the manufacture of a mold integrated into this and form a space surrounded by molding material has a passage (passage) to the mold cavity and during casting is filled by the pouring stream with liquid metal that during the Flow solidification process back to the casting and the volume deficit to compensate for the solidification of the casting. In this way the Formation of so-called blowholes (these are shrinkage cavities caused by the Metal volume contraction during the solidification process) prevented.

In order to ensure a proper feeding process, the Metal in the feeder solidifies later than the metal of the casting pieces, d. H. the module (ratio of volume to surface) of the feeder must be larger than that of the casting. At the same time after solidification For reasons of cost, the smallest possible amount of metal in the feeder remain, and for this purpose the walls of the feeder become frequent made of an exothermic material, for example an aluminothermic Mixture, formed. Such a material is made by the liquid metal ignited, and it therefore runs in after the pouring flow such a feeder exothermic reaction, by which in the feeder  indoor metal heat is supplied. This remains through the Heat supply liquid longer than the metal in the mold cavity of the mold and is therefore better usable for feeding.

Many molds are made using a model plate, which specifies the inner contour of the mold cavity. In the places where a feeder insert is required, then a holding is often in each case direction provided for the feeder use, z. B. a mandrel to fix the Location of the feeder insert.

After placing the feeders on the model plate (with or without Thorn) then becomes the molding material (usually molding sand, in individual cases also other granular materials) so applied to the model plate that he the Covered feeder insert. In a further step, the molding material is then condensed and the feeder more or less firmly from the condensed Molded material included. In this respect, one speaks of compression molding.

In the endeavor to provide a punctiform sealing feed even for small castings Reaching rich, the space or top areas are more modern Feeder inserts are often designed to be very small. The feeder insert tapers thus considerably towards its top surface, and at Applying the molding material to the molding plate often gives rise to the subsequent problem on that the compression of the molding material in the vicinity of the esophagus insufficiently near the top surface, which is disadvantageous when casting is.

Another problem is that in particular exothermic isolating feeders with the process of molding compression associated upsetting forces often cannot withstand and therefore break. Such breakage then inevitably leads to one uncontrolled feeding of the casting.

Despite this problem, which has been known for a long time, the trend is forever higher compression pressures, what the manufacturers of feeder inserts has already forced particularly stable, thick-walled feeder inserts to offer, but due to the increased material requirements quite are expensive.  

For some years now, attempts have been made to increase the Ver sealing pressure related problems by means of so-called spring mandrels to encounter. Spring mandrels as well as fixed (rigid) mandrels are designed to to hold a feeder insert in a predetermined position. she typically include (a) a tubular member for attachment a model plate, (b) one arranged in the tubular element Spring and (c) a resting on the spring, in the longitudinal direction within the tubular element telescopically displaceable mandrel tip element. Such a spring mandrel is usually on the model plate (model upper surface) and a feeder insert is then placed on it, the lower surface of which is in the starting arrangement before the filling of the Molding material is located at a predetermined distance from the model surface. The subsequent filling of the molding material therefore also runs between model surface and feeder (bottom surface). And so there is at the subsequent compression (compression molding) no direct contact between feeder and model surface, so that destruction of the feeder is usually prevented even when applying high compression pressures. The shape of the feeder insert placed on the spring mandrel acts on it press a force towards the model plate that causes the feeder insert against the action of the spring force in the direction of the Model plate is pressed. That in the gap between feeder insert and The molded material layer on the model plate is compressed.

The use of spring mandrels does alleviate the above problems described, but again brings a number of others Problems with themselves.

This is how the so-called residual feeder (i.e. the after solidified metal remaining in the feeder insert) from the casting often not directly at the predetermined breaking point, d. H. the mental Interface between casting and feeder, but in a considerable Distance from the casting, somewhere in the range of often several centimeters wide sand gap between the casting and feeder insert.

A sensible use of crushing cores (also as constricting, ab impact or collar cores) used in the field of foundry technology otherwise be used to precisely localize separation from  Reaching the remaining feeder and casting was done using spring mandrels so far not possible. The cleaning effort is therefore usually quite high. Spring mandrels are also quite expensive and prone to wear.

Given the problems outlined above, it was the primary one Object of the present invention to provide a feeder insert that in Foundry operation also withstands high compression pressures.

The footprint of the feeder insert to be specified should be included should preferably be small without relevant stability disadvantages can.

In addition, the use of expensive and susceptible to wear Spring mandrels are at least generally not necessary.

And finally, the feeder insert to be specified should also be together can be used with a crushing core that separates the rest relieved by the casting. Such a crushing core is in the Framework of the present text as part of the use of food understood and not as a separate component.

The task is solved by specifying a closed one Feeder insert of the type mentioned, wherein the feeder insert at least two into one another along a longitudinal axis of the food (telescopically) comprises displaceable shaped elements which liquid the cavity for receiving Enclose metal on the side. A first shaped element is closer to Passage of the feeder insert arranged as an associated second Feature.

The displaceability of the first and second shaped elements into one another causes that during a normal compression process in feeder Long direction acting on the feeder insert according to the invention high Compression pressures (compression forces) do not lead to its destruction, but only to a tolerated, by the compressibility of the surrounding molding material (molding sand) limited insertion of one mold elements into the other. The footprint of the feeder insert can small and the wall of the feeder is comparatively thin.  

The shaped elements should be out of their initial arrangement, i. H. out the relative arrangement out for the shaped elements before wrapping the Feeder insert with molding material is provided, at least by 5 mm, can preferably be pushed together by 10 mm.

The feeder insert can meet the requirements of the individual case correspondingly, for example, in the manner of a compact or ball feeder designed or with an almost cylindrical feeder in the upper area be provided with a cap.

When using a feeder insert according to the invention, it only becomes in exceptional cases it may be advantageous to use a spring mandrel, because the effect described above corresponds essentially to that of the reached feeder invention.

The use of spring mandrels with the feed unit according to the invention So zen is not excluded, but usually you can rely on it to be dispensed with.

However, the use of a fixed centering mandrel is common in many Cases make sense. A preferred feeder insert according to the invention is therefore set up for use with a centering mandrel, in particular can be designed as a self-centering feeder. Such a self centering feeder has one or more wall sections that towards the upper one in operation (opposite the feeder passage Taper the end wall of the feeder so that a mandrel tip when positioning the feeder insert in these along these sections Target position is performed. In the (upper) wall part, which the Opposing feeder passage is then often a centering recess intended to accommodate the mandrel tip, cf. our DE utility models publication 93 03 392. A self-centering feeder according to the invention is especially suitable for use on fast molding lines.

First and second shaped element of a dining table according to the invention set can be glued together after their manufacture or otherwise get connected. The shaped elements can also be used as separate parts stored and combined (stacked) as needed.  

Identical first (or second) form elements can also be constructed (e.g. in size) different second (or first) form elements can be combined into respective feeder inserts according to the invention.

Feeder inserts according to the invention are particularly preferred in which one or more holding elements are arranged on the first and / or second shaped element,

• - About which the first shaped element (in the initial arrangement) the second Form element carries and
• - Which are so separable or deformable that an interlocking Ver push the two form elements (out of the starting arrangement) along the longitudinal axis of the feeder is possible.

The holding elements are preferably an integral part of the respective formula element, and they can in the manufacture of the resp form elements without an additional step. It can in particular with standing or clamping projections, rotating Stand rings, pins that can be brought into engagement with complementary recesses or act like that. It is important that the holding elements are designed to operate in the foundry when the first and second The shape element is still roughly in its initial arrangement, the shape but the substance is already filled into the molding box, through which connect the molding process of their associated molded element can be separated or at least deformed to the extent that the first and can slide one another into each other. The holding elements are therefore preferably only via small connecting surfaces with their associated one Form element connected.

As an alternative to using holding elements, the use of a Spring mandrel. One such can namely be a second one, the upper one in operation Form element in the intended starting position relative to the model upper surface and hold to the first shaped element without the inventive Feeder insert itself includes holding elements. Since spring mandrels, however, like mentioned at the beginning are quite expensive and prone to wear and tear, their use be limited to exceptional cases.  

This is preferably closer to the passage of the feeder insert or this forming the first shaped element so that it (if necessary after separation or deformation of holding elements) in the second form element can be inserted. The outer dimensions of the first, in Operation of lower form elements closer to the casting are therefore preferred smaller than the internal dimensions of the associated second, upper in operation Form element. This configuration is the reverse of that (Also according to the invention) embodiment in which the upper in operation Shaped element can be inserted into the lower shaped element, advantageous because it ensures that no disturbing quantities are present during the filling process Penetrate molding material into the first molding element.

An embodiment is particularly advantageous in which the first, in Operation lower mold element is designed so that it (telescopic) in the second shaped element can be inserted, the outer wall of the first form elements in the inner wall of the second form elements intervenes. The gap width between the outer wall of the first The form elements and the inner wall of the second form element are in the intended starting arrangement of the shaped elements, if necessary is characterized by the position of the holding elements, preferably maximum 3 mm, advantageously not more than 1.5 mm. With this Ausge during the molding process, no relevant form can be created Quantities of material penetrate into the gap between the shaped elements, so that at least not significantly impaired their relative displacement becomes.

The shaped elements should come from their intended, if necessary output arrangement defined by the holding elements into feeder Longitudinal direction by at least 5 mm, preferably by at least 10 mm allow it to slide before pushing it further together Forces occurring between the shaped elements to tear or Breaking of the first or second feature comes.

It is particularly favorable if the first and / or the second form element comprises one or more guide elements which are set up tilting or tilting of the two shaped elements relative to one another to prevent at least essentially if this (from the starting  arrangement out) shifted into each other along the longitudinal axis of the feeder become. These guide elements preferably have the shape themselves Thin strips or ridges extending along the length of the feeder, and them are advantageously located on the outer wall of that shape elements which can be inserted into the partner form element; in So in a lot of cases they are on the outside of the first Formula elements arranged.

Advantageously, the first molded element of an invention According to the feeder insert, a breaking edge is integrated, which if necessary Is part of a crushing core, which is then directly on the model plate during operation can be put on. This integration of a breaking edge (a breaking kerns) ensures a significant reduction in Cleaning effort in comparison with the known feeder inserts used for Use with spring mandrels are provided and therefore no breaking edge (no crusher core). The footprint of the feeder according to the invention can be very difficult, especially when using a breaking edge (a breaking core) be kept small.

The feeder insert according to the invention or the associated shaped elements can partially or completely from insulating or exothermic formmas be manufactured. If a crushing core is inte is then typically not exothermic, the associated second The shaped element will then often be exothermic.

The feeder inserts according to the invention comprise two or more Form elements that can be combined as required when stored separately can. The invention therefore also relates to a kit for manufacturing of a feeder insert according to the invention, comprising a first shaped element and a second mold element which can be arranged so that they are slidable into one another along a longitudinal axis of the feeder. preferred Embodiments of the form elements belonging to the kit are from above to take guides to the feeder insert according to the invention.

According to a further aspect, the invention relates to a method for arranging a feeder insert in a casting mold, with the following steps:

• - Provision of a feeder insert according to the invention in one its configurations described above,
• - Arrange the feeder insert in a molding machine (the space above a model plate, which is usually delimited by a form box attached)
  so that the first and the second shaped element assume an (initial) arrangement from which the two shaped elements can be moved into one another along a longitudinal axis of the feeder,
• - Filling molding material into the molding machine (the one on the model plate attached molding box), so that the outer walls of the dining room are contacted with the molding material,
• - Compacting the molding material (compression molding) so that the first and the second shaped element (if necessary after separation or deformation of holding elements) along the longitudinal axis of the feeder be pushed.

The molding machine usually includes a model plate (i.e. a model facility for molding machines, usually consisting of a flat plate with cast or mechanically fastened model len), and the first shaped element is preferably arranged so that it is in front the compression process in direct contact with the model plate (the Model surface). This is especially true if in the first Forming element is integrated into a crushing core.

With regard to further preferred refinements of the invention according to the preferred method is based on the above explanations Referrer inserts referenced.

Preferred embodiments of the invention are described below of the accompanying figures explained. They represent:

FIG. 1a longitudinal section through an inventive feeder insert in its initial assembly, with two intermeshing ver slidable mold members, wherein the feeder insert by means of a centering mandrel on a pattern plate is BEFE Stigt,

FIG. 1b Länsgsschnitt through the lower (first) forming element of the feeder insert according to Fig. 1a,

Fig. 1c plan view of the lower (first) forming element of the SpeI sereinsatzes according to Fig. 1a,

Fig. 2 shows a longitudinal section through an alternative feeder insert with a molded breaking edge . 3a-d Schematic representation of a method according to the invention for arranging a feeder insert according to the invention in a casting mold.

The feeder insert 2 according to the invention shown in FIG. 1a in its initial arrangement (before the filling of molding material and before the compression process) comprises a first (lower) molding element 4 and a second (upper) molding element 6 , both molding elements being essentially rotationally symmetrical. The longitudinal axis of rotation of the feeder insert 2 (feeder longitudinal axis) is indicated by a dashed line 20 .

The first mold member 4 is shown in Fig. 1b again separately in Länsgsschnitt and in Fig. 1b in plan view. It is formed from a molding compound (e.g. insulating or exothermic) and has a relatively thin wall. The footprint of the first molded element 4 with which it sits on a model plate 22 is small, the footprint diameter is only about 40 mm, the diameter of the feeder passage lying within the footprint is only about 20 mm. Starting from its footprint, the first shaped element widens conically on the outside to a maximum diameter of approximately 77 mm, and the conical section 34 defined in this way then merges into an upper section 44 , which increases very slightly up to a diameter of about 76 mm tapered.

Already in the area of the upper section 44 , but adjacent to the lower conical section 34 , a total of four holding projections 12 are molded onto the first shaped element 4 . The (imaginary) connecting surfaces between the holding projections 12 and the shaped element 4 are each quite small, so that the holding projections 12 can be mechanically separated from the shaped element with little effort.

The holding projections 12 are also assigned a total of four guide and spacer strips 14 , which jump from the Haltvor jumps in the longitudinal direction of the feeder insert 2 upwards and protrude from the outer wall of the upper portion 44 of the lower mold elements 4 each by about 2 mm.

Placed according to Fig. 1a with its lower edge 26 on the holding projections 12 of the lower mold member 4 is the second (upper) mold member 6. It is formed from an exothermic molding compound and also has a very thin wall. The outer contour of the upper molded element 6 tapers slightly upwards in the direction of an on the outside in wesentli chen flat upper wall closure 36th The inner wall of the upper molding element 4 , starting from its lower edge 26, initially runs parallel to the outer wall of the upper portion 44 of the lower molding element 4 and then merges into a conically tapering wall portion 46 , along which the tip of a centering mandrel during positioning of the feeder insert can be guided. The conical wall section 46 finally opens into a centering recess 56, which lies in the feeder axis and passes through the closure 36 , for receiving a mandrel tip.

The two molded elements 4 , 6 are designed so that the four guide strips 14 of the lower molded element 4 fit frictionally against the inner wall of the upper molded element 6 when this, as shown in Fig. 1a, in the starting arrangement on the four retaining projections of the lower molded element 4 rests. They therefore cause an interference fit and prevent undesirable lateral displacement of the two shaped elements; they also define a uniform width of the gap between the lower (here inner) and the upper (here outer) shaped element.

Finally, a centering mandrel 16 is also shown in FIG. 1 a, which is fastened to the model plate 22 and from there (always lying in the feeder axis of rotation 20 ) through the feeder passage 10 and the feeder cavity into the centering recess 56 extends.

The two shaped elements 4 , 6 of the feeder insert 2 can be telescopically pushed into one another if a force directed towards the model plate 22 (arrow F) acts on the feeder insert parallel to the axis of rotation 20 , as is the case, for example, after the molding material has been filled in during compression molding ( see Fig. 3a-d). The force need only be large enough to separate the holding projections 12 from the lower mold element 4.

The inner wall of the second (upper, outer) molded element approaches the outer (wall) continuously when pushed onto the first (lower, inner) molded element and finally, after a displacement of approx. 15 mm, comes into full contact with it. Such a displacement path is sufficient for many compaction processes. The end position of the lower edge 26 of the upper molded element 6 after covering said displacement path is indicated by a dashed line. The guide strips 14 are deformed or separated when the molded elements 4 , 6 are pushed into one another and / or they cut into the inner wall of the outer (upper) molded element 6 .

The centering recess 56 extends through the upper Abschlusswan extension of the feeder insert 2 and the tip of the centering mandrel comprises a cylindrical portion which is significantly longer than 15 mm and the diameter of which is adapted to the inner diameter of the centering recess 56 . Therefore, there is no hindrance when telescoping the upper molded element onto the lower molded element; rather, the mandrel tip emerges unhindered from the feeder insert.

The lower edge 26 of the wall of the upper molding element 6 projecting beyond the lower molding element 4 acts during a compression process like a stamp surface on the molding material to be compressed between the edge 26 and the model plate 22 . The (also) occurring during a compression process using the feeder insert 2 are explained in more detail below with reference to FIGS . 3a-d.

An alternative feeder insert 202 according to the invention is shown in longitudinal section in FIG. 2. In contrast to the feeder insert 2 from FIGS. 1a-c, the first (lower) shaped element 204 of the feeder insert 202 comprises a breaking edge 214 . The feeder insert 202 is also more compact and thick-walled than the feeder insert 2 . The centering recess 256, which is also present here, does not pass through the upper feeder end, but extends in the longitudinal direction of the feeder insert to such an extent that an associated centering mandrel can be inserted into it sufficiently far when the upper shaped element 206 telescopically on the lower shaped element 204 in the direction Model plate is moved.

In FIGS. 3a-d, an inventive method is shown for arranging a feeder insert in a casting mold according to the invention schematically. The following explanations apply to the feeder insert according to FIGS. 1a-c as well as to the feeder insert from FIG. 2.

According to Fig. 3a, a first mold member is placed on a centering pin 116 104, which is mounted on a model plate 122. The shaped element 104 is brought into direct contact with the model plate 122 .

Fig second mold member is then in accordance with. 3b placed 106 on the first mold member 104 so that it is carried by this. For this purpose, holding projections 112 are provided, for example, which correspond in shape and function to the holding projections 12 explained with reference to FIGS. 1a-c. There is now a composite feeder insert 102 in its starting arrangement, cf. Fig. 1a.

In a subsequent step shown in FIG. 3c, the feed insert 102 is coated with molding sand 150 or another molding material (coating only indicated in the lower area).

After a compression process, not shown, the arrangement according to FIG. 3d is obtained. The holding projections 112 are broken off from the first shaped element 104 , the second (upper) shaped element 106 is telescopically pushed onto the first (lower) shaped element 104 . The displacement path D of the second molding element 106 on the first molding element 104 fixed in its position is predetermined and limited by the degree of molding material compression.

Since the outer wall of the second molding element 106 projecting over the first molding element 104 acts like a stamp on the one between it and the model plate 122 during the compression process, excellent molding material compression occurs in this area (in FIG. 3d due to a comparison with FIG. 3c denser puncturing of the molding sand 150 indicated).

Claims (10)

1. feeder insert for use in the casting of metals in casting molds, with a cavity for holding liquid metal, characterized in that the feeder insert ( 2 , 102 , 202 ) has at least two molded elements ( 4 , 2 ) which can be displaced into one another along a longitudinal axis ( 20 ) of the feeder 104 , 204 ; 6 , 106 , 206 ) which laterally enclose the cavity for receiving liquid metal. 2. feeder insert according to claim 1, characterized in that it most, the passage of the feeder insert ( 2 , 102 , 202 ) closer or forming this form element ( 4 , 104 , 204 ) and / or on the second form element ( 6 , 106 , 206 ) one or more holding elements ( 12 , 112 ) are arranged,
over which the first shaped element ( 4 , 104 , 204 ) carries the second shaped element ( 6 , 106 , 206 ) and
which can be separated or deformed in such a way that the two shaped elements can be moved into one another along the longitudinal axis of the feeder ( 20 ). 3. Feeder insert according to claim 1 or 2, characterized in that the first shaped element ( 4 , 104 , 204 ) is designed such that it can be inserted into the second shaped element ( 6 , 106 , 206 ). 4. feeder insert according to claim 3, characterized in that the first molded element ( 4 , 104 , 204 ) is designed such that it can be inserted into the second molded element ( 6 , 106 , 206 ), the outer wall of the first molded element being form-fitting engages in the inner wall of the second molded element. 5. Feeder insert according to one of the preceding claims, characterized in that the first and / or the second shaped element comprises one or more guide elements ( 14 ) which are arranged to tilt or tilt the two shaped elements ( 4 , 104 , 204 ; 6 , 106 , 206 ) at least essentially to be prevented relative to one another if they are shifted into one another along the longitudinal axis ( 20 ) of the feeder. 6. Feeder insert according to one of the preceding claims, characterized in that in the first shaped element ( 4 , 104 , 204 ) a breaking edge ( 214 ) is integrated, optionally as part of a breaking core. 7. feeder insert according to one of the preceding claims, characterized in that a guide for a centering mandrel ( 16 , 116 ) is integrated in the first and / or second shaped element. 8. kit for producing a feeder insert ( 2 , 102 , 202 ) according to any one of the preceding claims, comprising a first shaped element ( 4 , 104 , 204 ) and a second shaped element ( 6 , 106 , 206 ), which can be arranged as that they can be moved into one another along a longitudinal axis of the feeder ( 20 ). 9. A method of arranging a feeder insert in a mold, comprising the following steps:

• Providing a feeder insert ( 2 , 102 , 202 ) according to one of claims 1-7,
• Arranging the feeder insert in a molding machine,
  so that the first and second shaped elements ( 4 , 104 , 204 ; 6 , 106 , 206 ) are in an arrangement from which the two shaped elements can be moved into one another along a longitudinal axis of the feeder ( 20 ),
• - Filling molding material into the molding machine, so that the outer walls of the feeder insert ( 2 , 102 , 202 ) are contacted with the molding material,
• - Compacting the molding sand so that the first and the second molding element are shifted into one another along the longitudinal axis ( 20 ) of the feeder.

10. The method of claim 9, wherein the molding machine comprises a model plate ( 22 , 122 ) and the first molding element ( 4 , 104 , 204 ) is inserted into the molding machine so that it is in direct contact with the model plate.