Patent Application
20240416414
The present invention relates to a riser for metal casting, with the riser having a metal riser body. Furthermore, the present invention relates to the use of the riser for metal casting using separable casting molds, in particular with horizontally separable casting molds.
Risers are generally known from prior art. Usually, moldable risers, i.e. risers that are attachable to a mold plate, are made of exothermic materials or insulating materials. For example, the type of riser material used (exothermic or insulating) depends on the casting piece to be produced or the type of metal casting.
A riser is arranged above the portion of the casting piece to be fed on so that due to the metallostatic pressure, the liquid metal can be post-fed to the casting piece. Usually, a casting mold is filled with liquid metal from the outside, for example via a suitable gating system, wherein the liquid metal runs through the casting mold into the riser. With risers arranged above the casting piece, the liquid metal only reaches the riser cavity when the casting mold or the portion of the casting to be fed on is almost completely filled up with liquid metal.
Exothermic riser materials are characterized, among other things, by the fact that an exothermic reaction takes place when the riser is filled with liquid metal, thereby heating the metal inside the riser during a specified period of time, thus remaining liquid while being supplied to the casting piece being cooled. Volume contraction of the casting piece during solidification can be compensated for by the liquid metal in the riser. Insulating riser materials slow down heat dissipation from the riser or from the liquid metal in the riser into the mold material, keeping the liquid metal liquid or flowable over a longer period of time. As a result, liquid metal is kept available to compensate for volume contraction of the casting. This is also known as post-feeding.
Natural risers are risers that are made from the same molding material as the entire casting mold and are produced or formed without the use of insulating or exothermic materials. In the simplest case, a natural riser is, for example, a recess in the molding material into which liquid metal can flow in or out. Natural risers can also be covered with exothermic covering powder to maintain their feeding capacity for a long time.
By definition, natural risers are neither made from insulating nor exothermic materials. This has the advantage that natural risers produce fewer emissions during metal casting than conventional risers made from exothermic or insulating materials. Another advantage of natural risers over conventional risers is that they leave less residue in the mold material after metal casting, for example in the form of pyrolysis products, than conventional risers made from exothermic or insulating materials.
Natural risers are usually formed in the mold material as a mold cavity using a riser model, which is firmly arranged on the mold plate (model plate). In the simplest case, the riser model matches the mold cavity. The molded material surrounds the riser model and the mold plate forming the casting mold (cast mold) following compaction and subsequent molding of the mold plate from the compacted molded material.
This means that the riser models known from the prior art are connected to the mold plate and the riser models are removed again from the compacted mold material when molding the natural riser. This has the disadvantage that natural risers can only be placed laterally next to the casting geometry on the mold plate (model plate) without undercuts, i.e. in the direction of the surface normal to the plane of the mold plate, as otherwise undercuts occur during molding, i.e. when the mold plate is removed together with the riser model from the compressed molding material, rendering the mold unusable. Moldable natural risers that allow placement above the casting are not yet known.
Moldable risers made of exothermic or insulating material are usually placed on a riser pin attached to a mold plate, i.e. they are not firmly attached to the mold plate. The molded material around the formable riser is then compacted. After compaction, the mold plate, which corresponds to the casting, is pulled out of the compacted molding material together with the riser pin, leaving the moldable riser in the molded material.
The production of castings occurs, among other things, in separable casting molds, wherein the casting molds are either vertically separable or horizontally separable. Vertically separable casting molds are described, for example, in EP 2982458 A1. Vertically separable casting molds are for example employed in molding systems of DISAMATIC Company (Denmark).
DE 202006009015 U1 discloses a one-piece, metal riser, wherein the riser body is double-walled with an inner wall and an outer wall. The cavity between the inner and outer walls is used for insulation. However, the riser cavity is not formed by two riser body parts.
The disadvantage of moldable risers according to prior art is that production of such risers from exothermic or insulating materials is costly due to expensive feedstocks and the time required for production. In addition, when exothermic and insulating materials are used, pyrolysis products thereof and components such as fluorine carriers, unburned aluminum or fibers are introduced into the molded material. This may reduce reusability of used casting sands resulting in additional costs for disposal of used casting sands (used sands). Emissions are also released during riser incineration, which significantly contribute to the overall emission load of a foundry. However, this is undesirable. In addition, it is a known problem that industrially produced risers are usually delivered to the customer ready for use, i.e. in a fully assembled state, although shipping of the risers is usually inefficient due to the empty volumes of the manufactured risers resulting in high shipping costs.
Therefore, there is still a need for risers that can be produced more cost-effectively than the risers known from prior art. It would also be desirable if such risers, when properly used, would neither contaminate the molding material nor increase the foundry emission load. Furthermore, it would be desirable if such risers could be stored and shipped in a more cost-efficient and space-saving manner, i.e. if the risers could be packed in a more space-saving manner, for example.
It is thus an object of the present invention to provide a riser which can be produced at a reasonable cost and combining the advantages of a natural riser in terms of reduced emission load and impurities during metal casting with the geometric freedom of a moldable riser. Furthermore, it would be desirable to provide a riser the transportation of which is more cost-effective because, among other things, it requires less space.
According to the invention, this object and further objects will be achieved by the subject matter of the independent patent claims. Preferred embodiments are the contents of the subclaims or will be described herein in more detail below.
Surprisingly, it was found that risers which have a metal riser body can be produced in a cost-effective manner without achieving casting results of poorer quality, for example with regard to any defects found on the casting (so-called shrinkage). Furthermore, it was surprising that the riser bodies of the risers according to the invention, which are preferably made of a metal sheet such as aluminum or steel sheet, can withstand the usual compaction pressures of high-pressure molding systems without the risers collapsing when the molding material is compressed.
The present invention relates to a riser for metal casting, which comprises a riser body made of metal. The riser body has a riser cavity for receiving liquid metal and additionally has at least one opening through which the liquid metal can flow into the riser cavity or out of the riser cavity.
Furthermore, the present invention relates to the use of a riser according to the invention in metal casting in separable casting molds, in particular in horizontally separable casting molds.
Surprisingly, the inventors have found that risers having a metal riser body can be produced and used with ease and at reasonable cost as compared to conventional insulating or exothermic risers. Furthermore, it was unexpected that the risers can withstand compression pressures, as required for molding materials to be compressed, without collapsing.
According to the invention, the risers have a metal riser body. This means that the riser body of the riser according to the invention is not made of insulating or exothermic riser materials.
The metal riser body of a riser according to the invention has a thickness of 0.1 to 1.5 mm. In particular, the metal sheet of the riser body preferably has a thickness of 0.1 mm to 1.2 mm, more preferably 0.2 mm to 1.0 mm and more preferably 0.3 mm to 0.7 mm. Surprisingly, the inventors have found that metal sheets which have a thickness of at least 0.1 mm do not collapse the riser bodies when the molding material is compressed at conventional compression pressures, which in some cases can be more than 100 bar.
The riser body is made of one or more metals. In particular, the riser body of the riser according to the invention is produced from a metal sheet by forming, wherein the metal sheet is preferably produced on a similar basis of material as the casting material used. Thus, a riser according to the invention, which has a riser body made of an aluminum sheet, is preferably used for an aluminum casting, whereas a riser body made of a steel sheet or an iron sheet is preferably used for a steel casting or an iron casting. It is also possible for the riser body to be made of different metals. The sheet metals preferably used are such that they can be deep-drawn or otherwise cold-formed. In one embodiment, the riser body is made from cold-rolled strip DIN 10130 DC01 or DC04, which is known to persons skilled in the art.
The riser body of the riser according to the invention has a riser cavity and at least one opening. The riser cavity is designed to receive liquid metal during the casting process. During the casting process or when the casting cools, liquid metal can be post-fed to the riser body via the opening or be fed to the casting to be cooled.
The riser body of the riser according to the invention can have different shapes. In particular, it is possible for the riser body to have the shape of a so-called spherical riser. This may be preferred, as spheres have the smallest surface area of all possible bodies for a given volume. The advantage of such a shape is that the heat exchange with the environment during the casting process is kept to a minimum, which means that the liquid metal in the riser is kept liquid or flowable for as long as possible during proper use.
The riser body of a riser according to the invention is formed in multiple parts. In one embodiment, the riser body of a riser according to the invention is formed in two parts and has two riser body parts which are assembled together, the two riser body parts preferably being of approximately the same size.
In another embodiment, the riser body of a riser according to the invention can have a shape which tapers at least partially towards the mold plate.
Tapering of the riser body may be preferred to create a suitable breaking edge between the riser body and the mold plate or, after molding, between the riser body and the casting after compaction, which obviates the need for post-processing the casting or at least simplifies post-processing and reduces post-processing time.
Preferably, the riser according to the invention has a connecting element that is in contact with the riser body via the opening in the riser body. The riser body is directly or indirectly connected to the casting or to the casting mold via the connecting element. The connecting element tapers towards the casting thereby helping to form a breaking edge. Connecting elements are known, for example, from DE 202012102418 U1, DE 10142357 A1, EP 1184104 A1 and DE 102005008324 A1. The connecting element is designed to create a breaking edge between the riser body and the mold plate or, after molding, between the riser body and the casting after compaction, which makes post-processing of the casting unnecessary or at least simplifies post-processing and reduces the time required for post-processing.
In one embodiment, the connecting element is a tube-like body, which can have any length, wall thickness and diameter that is suitable in each individual case. Depending on the material used, the wall thickness will generally be between 0.1 mm and 10 mm, preferably between 0.3 mm and 5 mm, particularly preferably 0.3 mm to 0.5 mm. The person skilled in the art may be able to determine the optimum dimensions based on his experience. As a rule, the tube-like body has a length of between about 15 and about 300 mm, in particular between about 35 and about 100 mm. In a preferred embodiment according to the invention, the length of the tube-like body is selected such that at least the distance between the riser body and the casting will be bridged.
Basically, the inner diameter of the tube-like body can arbitrarily be selected, the opening at the lower or upper end of the tube-like body being large enough to ensure the flow of the melt into or out of the riser during the casting and solidification procedure. The diameter of the tube-like body is generally based on the diameter of the opening provided in the riser body through which the tube-like body is passed and in which it is displaceable. As a rule, the diameter of the tube-like body is selected such that the opening in the riser body ensures sufficient guidance of the tube-like body when pushing it into the riser body during compression of the molding material or pulling it out of the riser body before attaching it to the mold plate.
The tube-like body itself can be formed from any suitable material showing appropriate strength without any interference with the casting piece to be supplied. These materials are known to persons skilled in the art and include, for example, metal, plastic, cardboard, ceramic or similar materials. Preferably, the tube-like body is made of a material that is equivalent to a material used in the casting routine, such as aluminum or steel sheet metal or iron sheet metal. Particularly preferably, the connecting element or the tube-like body is made of the same material as the riser body.
In one embodiment, the tubular body has a stop in the portion facing the riser cavity. The stop is therefore arranged in a position on the tubular body such that it is located within the riser cavity provided in the riser body. When the tubular body is pulled out of the riser body, the stop comes to rest against a surface which adjoins the opening in the cavity. Basically, the stop can be of any design as long as it is ensured that the tubular body cannot fall out of the opening. For example, the stop can be designed as a thickening on the outside of the tubular body and run around the tubular body along its circumference. However, individual projections may also be provided, with the number of projections preferably being sufficiently high to prevent the tubular riser from tilting when it is fully pulled out. It is also possible to design the stop as a separate component and subsequently attach it to the tubular body. The stop is preferably designed as an annular projection that runs around the outer circumference of the tubular body. This ensures the tubular body to be centered when it is pulled out of the riser body so that the longitudinal axis of the tubular body runs parallel to the longitudinal axis of the riser body.
In another embodiment, the connecting element is a tube-like body and has a thickening at a lower portion, which is designed to prevent the connecting element from slipping into the riser cavity of the riser body when compressing the molding material. For the purposes of the present invention, the lower end of the connecting element means the end facing the casting or the end facing the mold plate.
In another embodiment, the connecting element has a stop or a thickening at the upper end and a thickening or a stop at another lower end. This can be particularly preferable to prevent the connecting element from completely slipping into the riser cavity and also to prevent the connecting element from falling out of the riser body.
In another embodiment, the connecting element is designed to be retractable, equivalent to an accordion, as disclosed, for example, in DE 202012102418 U1. In this case, the connecting element is attached to or on the riser body such that the connecting element retractably moves in relation to the riser body of the riser according to the invention when compressing the molded material. In this embodiment, the connecting element is preferably made of plastics or metal, in particular a sheet metal, and is attached directly to the riser body. In this case, the connecting element and riser body can be integrally formed.
In a preferred embodiment, the riser body has a recess adjacent to the opening to accommodate the upper end of a centering pin and/or a spring pin. The recess is arranged opposite the opening of the riser body to allow a centering pin or a spring pin to be inserted through the opening in the riser body (and, if present, previously guided through the connecting element) and into the recess to center the riser on the mold plate. The centering pin or spring pin is used to position the riser according to the invention on the mold plate (model plate). The spring pin or the centering pin is pulled out of the final casting mold or part of the final casting mold together with the mold plate after compacting the molding material.
In a preferred embodiment, the riser body has a recess for a lid. In this embodiment, the lid also preferably has the recess described above, into which a centering pin and/or a spring pin can be inserted. The riser according to the invention is arranged on a mold plate or the riser according to the invention is placed on the mold plate using a centering pin or a spring pin. The centering pin or spring pin is guided through the opening in the riser body or through an optional connecting element arranged in the riser body through the riser cavity to the opening in the lid. In this embodiment, the lid arranged in the riser body is arranged opposite the opening of the riser body through which liquid metal enters the riser cavity or through which liquid metal can be fed to the cooling casting. In a preferred embodiment, the lid can form a William core. The lid has the shape of a conical, tapered core. The William core is inserted into the riser and serves to form a sand edge which is for delaying solidification of the liquid metal due to the sand edge effect. The lid can be made of different materials, but in particular it is made of the same materials as the riser body or the optional connecting element.
The riser body of the riser according to the invention is of a multiple part design, in particular a two-part or three-part design, particularly preferably a two-part design. This riser has at least a first and a second riser body part. Conventional risers known from prior art have one-piece riser bodies. One of the disadvantages thereof is that the risers occupy a large empty volume during shipping due to the riser cavity, making transport economically inefficient. Surprisingly, the inventors have found that risers with multiple part riser bodies, in particular two-part or three-part riser bodies, are easy to transport and can be assembled or plugged together easily by the end user or customer. It was particularly surprising that even risers with multiple part riser bodies can withstand the high compression pressures without collapsing.
In one embodiment, the riser body is formed in two parts, having a first and a second riser body part. In another embodiment, the riser body is formed in three parts having a first, a second and a third riser body part. Preferably, the riser body of a riser according to the invention is formed in two parts having a first riser body part and a second riser body part. In another preferred embodiment, the multiple part riser body part is separable horizontally into two riser body parts, for example of approximately equal size. In another preferred embodiment, the multiple part riser body part is separable vertically into two riser body parts, e.g. of approximately equal size. In a further preferred embodiment, the two riser body parts have a half-shell shape. This expressly also includes embodiments in which, for example, the riser body is horizontally separable and the first riser body part optionally has an opening, for example for a centering or riser pin or a lid, and the second riser body part has an opening through which liquid metal can flow into or out of the riser cavity. For the purposes of the present invention, half-shell shape expressly means not only those riser body parts which have an identical shape, but also those riser body parts which are of different shapes. The riser body parts are joined together essentially horizontally or essentially vertically and form the riser cavity for receiving the liquid metal. In particular, the riser body parts are joined together such that both riser body parts additively form the riser cavity. In particular, the riser body parts are preferably designed almost identically. This has the advantage that they can be produced using a single tool.
In a preferred embodiment, the riser body parts of a multiple part riser body of a riser according to the invention have connecting means used to connect or assemble and/or join the riser body parts to form the riser body. In the context of the present invention, assemblable or joinable means that the riser body parts have connecting means which are used to plug them together and/or assemble them. Thus, in a preferred embodiment of the present invention, a multiple part riser can be assembled or joined using a click fastener. According to another embodiment, the first and second riser body parts can be plugged together and/or assembled by means of a bayonet catch. According to another embodiment, the riser body parts have one or more plug connections with which the riser body parts can be plugged together. According to another embodiment, the riser body parts have tongue and groove so that these respective riser body parts can be joined to form a riser body. According to another embodiment, one of the riser body parts has clamping elements with which the riser body part can be clamped to another riser body part. According to another embodiment, the riser body parts each have a crimped edge, wherein the riser body parts can be placed against each other in such a way that the crimped edges can be placed against each other and connected to each other by crimping or riveting.
In another embodiment, the multiple part riser bodies can be welded together. In another embodiment, it is possible for the riser body parts of a riser according to the invention to be screwed together. It is also possible for the riser body parts to be glued together. In another embodiment, the riser body parts are joined together by a rivet.
In another preferred embodiment, it is possible that at least one riser body part of a multiple part riser, preferably a horizontally separable multiple part riser, is designed such that it tapers towards the model plate, equivalent to the shape of a connecting element. Tapering of the riser body may be preferred to create a suitable breaking edge between the riser body and the model plate or, after molding, between the riser body and the casting piece after compaction, which obviates the need for post-processing of the casting or at least simplifies post-processing and reduces the post-processing time or at least the simple cutting off of the riser neck. Another preferred design of a riser body part is such that it deforms like an accordion when being compressed with the molding material and can thus be retracted. In particular, the accordion-like portion assumes the function of the connecting element, but in this case will preferably be an integral component of a riser body part. In particular, the accordion-like portion tapers to form a grommet, which is for connecting it to the casting.
The present invention is further illustrated while reference is made to the following figures, wherein:
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 2021 106 147.2 | Nov 2021 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DE2022/100757 | 10/12/2022 | WO |
