Patent Application
20170056964
The present invention relates to a feeder in the form of a head feeder for use in a casting mold during casting of metals, having a feeder body comprised of an exothermic and/or insulating material and which surrounds an inner hollow cavity as a feeder volume, which has a feeder opening in its bottom or floor surface facing the mold cavity formed in the casting mold, the feeder opening provided for connecting the inner cavity of the feeder body with the mold cavity of the casting mold during the casting process.
In casting technology, it often is necessary to arrange an additional feeder in the casting mold, whose feeder body is filled with the liquid metal during casting of the casing piece and upon hardening of the casting piece, the feeder body compensate volume deficits that occur, in order to prevent the formation of cavitation shrink holes in the casting piece. In this connection, the feeder must be produced, such that the liquid metal that is fed into it hardens later than the casting piece, so that during the hardening process, a material transport to the casting piece can occur, which sealingly feeds the casting piece. In this regard, the feeders comprise an exothermic and/or insulating material or are formed as so-called natural feeders in the mold sand surrounding the casting model. In the frame of known methods for manufacturing casting molds that are provided with feeders, the feeders are arranged with any desired geometric form on the position to be supplied of the later casting piece on the casting model and with the formation of the casting mold by dealing of the mold sand that is applied, are solidly cast or molded. With another method, during casting of the casting model hollow spaces are produced by means of the mold sand, in which individual feeders made of an exothermic and/or insulating material are subsequently inserted and in this manner, are connected to the mold cavity produced by the demolding of the casting model in the casting mold. Thus, the feeders are arranged as so-called head feeders uniformly on the surface of the casting model or on the later=produced casting piece. A feeder with the above-noted characteristic features is described, for example, in DE 20 2013 104 863 U1.
A problem generally exists when using feeders. Specifically, after casting, hardened casting material in the form of so-called feeder residue remains in the feeder body, which must be removed after removing the casting piece from the feeder body. In order to facilitate this separation, the use of so-called breaker cores is common, which are defined on the feeder body on the underside of the feeder body facing toward the mold cavity of the casting mold. The breaker cores are made of a fire-resistant material and have a through-opening, via which the increasingly hot metal can flow out of the mold cavity of the casting mold into the inner cavity of the feeder body or from there flow further back into the mold cavity. The breaker cores, which are generally manufactured by shooting in a core shooting machine, are disk-shaped, whereby the through-opening is formed by a constriction formed in the disc-shaped breaker core body, in order to produce a predetermined breaking point for breaking off feeder residue from the surface of the casting piece. Such an arrangement of the feeder with a breaker core is described, for example, in WO 2009/103539A1.
Breaker cores now have a netlike webbing which is anchored on the breaker core and which spans the through opening formed by the constriction. These netlike webbings permit the entry of the liquid metal in the cavity of the feeder body or from it back into the mold cavity, but also form a metal layer that is penetrated by the webbing, based on the bathing of the net structure by the hot metal after hardening of the casting piece, and thereby creates a defined material weakness, whereby the existing feeder residue can be knocked off in the course of the webbing layer. Thus, the netlike webbing, with the manufacture of the breaker core, is positioned in the plane of the constriction in the shooting mold and shot with the fire resistance molding material mixture that is used to make the breaker core.
The disadvantage of using a breaker core made in this manner is that with the arrangement of the netlike webbing in the interior of the breaker core, a spacing of the webbing from the surface of the casting piece is required, so that after breaking off of the feeder residue in the predetermined breaking points formed by the netlike webbing, a part of the feeder residue still remains on the casting part, which in turn, must be still be removed by expensive cleaning processes. Thus, the breaker core represents an additional and in particular, if including a netlike webbing, an expensive component that must be made.
The present invention is therefore based on the object of improve a feeder with the above-noted features, such that a breaker core can be eliminated and nevertheless, the occurrence of material residue remaining on the casting piece after the casting process and which must be removed by cleaning process is further reduced.
The present invention contemplates a feeder with the above-noted features, in which a ring-shaped frame made of a heat-resistant material and having a netlike webbing tensioned over the frame is secured to the feeder body, the netlike webbing made of a fire-resistant material and spanning the feeder opening of the feeder body, whereby the frame is arranged on the bottom surface of the feeder body, so that the netlike webbing is positioned with the feeder formed in the casting mold directly on the surface of the casting piece to be formed by the casting process.
An important advantage is connected with the present invention. Specifically, based on the arrangement of the frame with the netlike webbing retained thereon on the bottom surface of the feeder, the plane of the netlike webbing is positioned in the lower, bottom surface of the feeder that contacts the casting model, so that the predetermined breaking point formed by the netlike webbing for the removal of the feeder residue is displaced directly onto the surface of the casting piece. Thus, any additional cleaning expense are minimal. A further advantage is that the frame with the netlike webbing is much simpler to make than a common breaker core with a net arranged thereon. In so far as a sufficient tensioning of the netlike webbing in the flow path between the mold cavity and the feeder must be ensured, so that the webbing, during the flowing of the liquid metal during pouring, is not pulled into the mold cavity and therewith, into the casting piece structure, the arrangement of the frame makes possible a corresponding tensioning and retention of the netlike webbing in the frame. The use of a frame made from a heat-resistance material for holding the tensioned netlike webbing offers the advantage that the frame is not melted by the hot metal flowing through the breaker core and thus, no combustion gasses that are damaging to the casting process are present.
According to one embodiment of the invention, it is provided that the frame comprises two frame parts which are placed against one another to hold the webbing therebetween. The two frame parts can be attached to one another after appropriate tensioning of the netlike webbing. The frame parts can be fixed together by welding, particular, at individual points using spot welding.
According to the present invention, the width of the frame may correspond to the material thickness of the feeder body on its bottom surface and the frame is disposed on the bottom surface of the feeder body and is secured to the feeder body, whereby this attachment, for example, can be created by means of a clamping connection of the frame and feeder body or through an adhesive connection.
In this regard, the frame, at least in some areas, projects outwardly over the periphery of the feeder body. The areas of the frame that projects over are bent up when the frame is positioned on the bottom surface until it contacts the outer periphery of the feeder body, so that the bent-up region of the frame fixedly clamps onto the feeder body. Therefore, it is not necessary that the frame is clamped over its entire periphery or circumference with the feeder body. In addition, it is sufficient if the frame has a plurality of tongues that can be bent upwardly distributed about its circumference which project over the feeder body for securing the frame to the feeder body.
Alternatively, it can be provided that the frame is adhered with the bottom surface of the feeder body.
With regard to the formation of the netlike webbing, according to the present invention, the netlike webbing has a through-hole with a smaller dimension that the through-opening of the breaker core in order to reduce flow resistance. According to another embodiment of the present invention, the through-hole can have a surface of 10% to 50% of the surface of the through-opening of the breaker core that is surrounded by the frame, whereby the width of the net, that is the width of the net opening, is 1 mm to 20 mm with a width of the fibers forming the net structure being 1 to 15 mm.
According to an embodiment of the invention, the frame can be made from metal as the heat-resistance material. Since the underside of the frame facing away from the feeder can come into contact with the liquid metal from the side of the casting mold or from its mold cavity, the casting part could be connected with the frame because of the heat of the liquid metal, which in turn, would make a separation of the feeder residue more difficult. Thus, if a metal is used as the material for making the frame, the underside of the frame that faces the mold cavity is provided with a heat-resistant coating. In this connection, for example, a fire-resistant die coating can be used.
Alternatively, the frame can be made from ceramic or a fire-resistant material as the heat-resistance material.
An exemplary embodiment of the present invention is shown in the drawings and will be described in greater detail below. In the figures:
The feeder 10 shown in
A frame 17 is mounted to the lower bottom surface 15 of the feeder 10, which holds a netlike webbing, which spans the feeder opening 16 of the feeder formed in the lower bottom surface 15.
The frame 17 comprises two frame parts, specifically, an upper frame part 19 facing the feeder body 11 and a lower frame part 20, facing away from the feeder body 11, whereby the two frame parts 19, 20 retain the netlike webbing 18 between them. After application of the required tensioning of the netlike webbing 18, the two frame parts 19, 20 are fixed to one another, preferably welded with one another. In this manner, a stabile component exists, which can be safely manipulated during manufacture of the feeder.
As shown in
The features of the subject matter of this invention set forth in the above description, the patent claims, the abstract and the drawings can be used individually and in any desired combination for the realization of the invention in its various embodiments.
The specification incorporates by reference the disclosure of DE 20 2015 104 554.9, filed Aug. 27, 2015.
The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202015104554.9 | Aug 2015 | DE | national |
The instant application claims the priority date of Aug. 27, 2015, the filing date of the German patent application DE 20 2015 104 554.9.
