EP2191912A1

EP2191912A1 - Method and mould for stratified moulding with metalostatic pressure compensation

Info

Publication number: EP2191912A1
Application number: EP07834482A
Authority: EP
Inventors: Enrique Alvarado Murillo
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-07-25
Filing date: 2007-08-29
Publication date: 2010-06-02
Also published as: US20100193151A1; MX2007008956A; WO2009014412A1; BRPI0721865A2

Abstract

A mould for stratified moulding with metalostatic pressure compensation formed by one or more stackable moulds formed by a tapping cavity of a generally rhomboidal truncated cone shape and one or more moulding cavities connected to the tapping cavity by one or more supply conduits; in such a way that each tapping cavity of each stackable mould interconnects to form a central filling collector, and each tapping cavity compensates for the metalostatic pressure of the molten metal as it is drained by the central filling collector to achieve generally uniform filling of each of the moulding cavities of each of the stackable moulds. In addition, the generally rhomboidal double truncated cone shape serves to keep a temperature distribution in the mould during the pouring of molten metal.

Description

TECHNICAL FIELD OF THE INVENTION

This invention relates to the casting of molten metal, and in particular relates to a method and mould for stratified moulding of multiple parts by stackable moulds that have a tapping cavity in a generally rhomboidal truncated cone shape that allows compensating the metalostatic pressure and achieve a temperature distribution in the mould during casting of the molten metal.

BACKGROUND OF THE INVENTION

Currently, the normal mode for simultaneous casting in a plurality of stackable sand moulds and similar to fill a plurality of similar or identical parts, is that the stackable moulds are placed on each other (in what is known as stratified moulding or moulding stacking), and arranged in such form that the core or central filling collector that interconnects the stackable moulds in a vertical way and, therefore, arranging the moulding cavities of each stackable mould on top of one another. Pouring the molten metal into an entrance opening into the top stackable mould or into the central filling collector, the moulding cavities of the lower stackable moulds are filled first and the upper cavities are filled later, but control is minimal as to the way in which the cast metal fills each moulding cavity.
The inevitable turbulence introduced into the molten metal stream that descends through the central filling collector and enters a moulding cavity practically in a right angle with respect to the direction of the flow of molten metal filling the central filling collector, has resulted in a production of deficient quality parts. Also, the stackable moulds being arranged vertically, the molten metal when drained, induces a high static pressure (known as metalostatic pressure) on the lower stackable moulds, which often produces the effect of the molten metal passing through the metal of the stackable moulds (known as interior fusion), thus forming shrinkage during solidification of the molten metal and a complete crack in the mould wall, and finally this may produce leaks in the joints between adjacent moulds, causing the formation of burr or the complete break of a joint. Another disadvantage is that the central filling collector is usually straight which leads to an inadequate temperature distribution throughout the mould when pouring the molten metal, thus it does not allow the formation of hot spots along the mould.
Given the complex structure of the parts to be moulded and due to the lack of metalostatic pressure control during stratified moulding, the use of feed heads with enough metal left over to allow the location of the shrinkage cavity that forms the end of the solidification of the part, allowing to obtain non-defective parts.
One current solution to prevent formation of shrinkage in stratified moulding is described by Jose Lopez Almendros, in European patent EP-0640418 , which shows a mould for stratified moulding where each of its stackable moulds includes an appendix in its end corresponding to the moulding cavity to control shrinkage that remains in the interior of the part, in the remote zone of the exterior surface of said part, therefore achieving the complete filling of the moulding cavity without the use of feed heads.
Given the above, and the ongoing need for price reduction of parts, along with obtaining a high quality of said parts, it is necessary in the industry to provide a method and a mould for stratified moulding that through the control of the metalostatic pressure, and an adequate distribution of the temperature in the mould when pouring the molten metal allows an optimal use of the cast metal used, which means an elevated coeficient of use of said metal mass and allowing simultaneously obtaining a major number of parts of high quality for a certain number of stackable moulds, in order to increase productivity.

SUMMARY OF THE INVENTION

Referring to the aforementioned and in order to offer a solution for the limitations encountered, the object of this invention is to provide a mould for stratified moulding with metalostatic pressure compensation formed by one or more stackable moulds, consisting of a tapping cavity of a generally rhomboidal truncated cone shape and one or more moulding cavities connected to the tapping cavity by one or more supply conduits; in such a way that each tapping cavity of each stackable mould interconnects to form a central filling collector, and each tapping cavity compensates the metalostatic pressure of the molten metal as it is drained by the central filling collector to achieve generally uniform filling of each of the moulding cavities of each of the stackable moulds.
Another object of the invention is to provide a stackable mould that includes a tapping cavity of a generally rhomboidal double truncated cone shape and one or more moulding cavities connected to said tapping cavity by one or more supply conduits, so that the tapping allows for compensation of the metalostatic pressure of the molten metal as it is drained to achieve generally uniform filling of each of the moulding cavities.
Finally, it is also the object of the invention to provide a method for stratified moulding with metalostatic pressure compensation, the method includes the steps of: (a) forming a mould for stratified moulding from a plurality of stackable moulds arranged one on top of the other in a vertical column, each stackable mould includes a tapping cavity of a generally rhomboid shaped double truncated cone shape, and one or more moulding cavities connected to the tapping cavity by one or more supply conduits; where the stackable moulds are arranged in such way that their corresponding tapping cavities are arranged one on top of the other to form a central filling collector; and (b) pouring the molten metal in the central filling collector so that the molten metal flows through each tapping cavity and fills the moulding cavities from the lower stackable mould up to the upper stackable mould, where each tapping cavity allows metalostatic pressure compensation of the molten metal during its draining to achieve a generally uniform filling of each of the moulding cavities of each stackable mould.

BRIEF DESCRIPTION OF THE FIGURES

The characteristic details of the present invention are described in the following paragraphs, together with the figures related to it, in order to define the invention, but not limiting the scope of it.

Figure 1 illustrates a schematic perspective view of a mould for stratified moulding according to the invention.
Figure 2 illustrates a schematic view in cross section by the cutting plane 2-2' shown in Figure 1 of a mould for stratified moulding according to the invention.
Figure 3 illustrates a schematic view in longitudinal section by the cutting plane 3-3' shown in Figure 1 of a mould for stratified moulding according to the invention.
Figure 4 illustrates a detailed schematic view in longitudinal section of an embodiment of a tapping cavity of a mould according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The term "mould for stratified moulding" in the context of this description, means a mould formed by one or more stackable moulds arranged one on top of the other in a vertical column.
The term "stackable mould" in the context of this description, means each of the mould blocks forming the mould for stratified moulding, including the mould cavities, tapping cavities and supply conduits.
The term "moulding" in the context of this description, means the manufacturing process of parts based on pouring the molten metal into the moulding cavity of a mould, to obtain for the solidification and cooling of a part that is a reproduction of the moulding cavity.
The term "moulding cavity" in the context of this description, means a hollow space inside a mould which represents the shape of the part to be moulded.
The term "tapping cavity" in the context of this description, means hollow space inside a mould used to distribute and feed through the supply conduit the molten metal into the moulding cavity.
The term "supply conduit" in the context of this description, means the passage for the molten metal that connects the tapping cavity with a moulding cavity.
The term "metalostatic pressure" in the context of this description, means the static pressure exerted by the molten metal on the inner walls of the mould for stratified casting and its stackable moulds.
With reference to Figures 1, 2, 3 and 4 a mould is illustrated for stratified moulding according to the invention. The mould for stratified moulding 10 is formed by one or more stackable moulds 20 which in turn each one is formed by a casting cavity 30 and one or more moulding cavities 40 connected one to another by one or more supply conduits 50. Each stackable mould 20 can be a sand mould, a permanent mould, or a ceramic mould.
The tapping cavity 30 and moulding cavities 40 of each stackable mould 20 is formed from the assembly of an upper mould part 60 with a lower mould part 70 by a mechanism generally of the male-female-type.
Each of the tapping cavities 30 have a generally rhomboidal double truncated cone shape and are vertically interconnected to form a central filling collector 80, through which a flow of molten metal passes, as it is poured into the mould for stratified moulding 10, the tapping cavities 30 of the stackable moulds 20 are successively filled, starting with the lower ones and then up to the upper ones. As the molten metal fills each tapping cavity 30, the moulding cavities 40 connected to them are filled.
The generally rhomboidal double truncated cone shape form of each of the tapping cavities 30 allows metalostatic pressure compensating of molten metal during its casting by the central filling collector 80, so that a generally uniform filling is accomplished by each of the moulding cavities 40 of each of the stackable moulds 20.
The rhomboidal form of the double truncated cone shape of each of the tapping cavities 30 is formed by an upper cavity 110 in the upper mould part 60 in the form of a truncated cone with a smaller base and a larger base, and a lower mould part 70 also in the form of a truncated cone with a smaller base and a larger base; in such way that when assemblying the upper mould part 60 with the lower mould part 70, to make a stackable mould 20, the upper cavity 110 and the lower cavity 120 remain opposite to each other and interconnected by their respective larger base. The upper cavity 110 or lower cavity 120 may have a bell-shaped form of a truncated pyramid shape, a spherical segment of two bases, or the combinations thereof.
During pouring of molten metal through the central filling collector 80 and as it fills the lower cavity 120 of each stackable mould 20, the metalostatic pressure decreases according to the increase of the cross-sectional area of this cavity, and in the counterpart as the upper cavity 110 is being filled of each stackable mould 20, the metalostatic pressure increases as the cross-sectional area of this cavity decreases. This metalostatic pressure compensation of the molten metal by its passage through the tapping cavities 30 allows filling uniformly and without any contractions in any of the moulding cavities 40, thereby eliminating shrinkage without the use of feed heads.
In each tapping cavity 30, the smaller base of the upper cavity 110 is smaller than the smaller base of the lower cavity 120, while the larger base of the upper cavity 110 is smaller than the larger base of said lower cavity 120. This arrangement allows forming a central filling collector 80 that varies (from top to bottom) in a stepped form in its diameter. This irregularly shaped central filling collector 80 allows the formation of hot spots in the junction points of the casting cavities 30, when pouring the molten metal and therefore achieves a temperature distribution in the mould for stratified moulding 10.
In an alternative embodiment, the mould for stratified moulding 10 includes a pouring cup 90 through which molten metal is poured and which is located in the upper part of mould 10 and connected to the central filling collector 80 by its upper part. The draining cup 90 is defined by a mould cavity with a bell-shaped form, a truncated pyramid shape, a spherical segment of two bases, or the combinations thereof.
In another alternative embodiment, the mould for stratified moulding 10 includes a flow stabilizer 100 located at the bottom of the mould 10 and connected to the central filling collector 80 at its bottom part. The flow stabilizer 100 is defined by a mould cavity with a bell-shaped form, a truncated pyramid shape, a spherical segment of a base, a spherical segment with two bases, and the combinations thereof.
The shape of the pouring cup 90 and the flow stabilizer 100 allows no bubbles to be formed when pouring the molten metal, because it counteracts or dampens the turbulence of the flow.
In accordance with Figures 1, 2, 3 and 4 described above, a method is shown for stratified moulding with metalostatic pressure compensation, the method starts by forming a mould for stratified moulding 10 starting from a plurality of stackable moulds 20 (as described above) arranged one on top of the other in a vertical column. Alternatively, a pouring cup 90 is located at the upper part of the mould for stratified moulding 10 and at the bottom a flow stabilizer 100, both connected to the central filling collector 80; and then draining the molten metal in the central filling collector 80 so that the molten metal flows through the tapping cavity 30 and fills the moulding cavities 40 from the lower stackable mould 20 up to the upper stackable mould 20; so that each tapping cavity 30 allows compensating the metalostatic pressure of the molten metal when it is drained to achieve a generally uniform filling of each of the moulding cavities 40 of each stackable mould 20. In addition, each tapping cavity allows the formation of hot spots during the draining of the molten metal by the central filling collector 80 to achieve a distribution of the temperature along the mould for stratified moulding 10.
Based on the embodiments described above, provided that the modifications to the described implementation environments, as well as alternative embodiment environments will be considered obvious to a person skilled in the art of the technique under the present description. Therefore, it is considered that the claims cover those modifications and alternatives that are within the scope of the present invention or its equivalents.

Claims

A mould for stratified moulding with metalostatic pressure compensation consisting of one or more stackable moulds, characterized in that each stackable mould includes:
a tapping cavity of a generally rhomboidal double truncated cone shape; and

one or more moulding cavities connected to said tapping cavity by one or more supply conduits;
wherein each tapping cavity of each stackable mould is interconnected to form a central filling collector and wherein each tapping cavity allows metalostatic pressure compensation of the molten metal during its draining by said central filling collector, so that a generally uniform filling is accomplished of each said moulding cavities of each said stackable moulds.
The mould for stratified moulding of claim 1, characterized in that each stackable mould is formed by a portion of upper mould and a portion of lower mould assembled to define said tapping cavity and said moulding cavities.
The mould for stratified moulding of claim 1, characterized in that said tapping cavity includes:
an upper cavity in the form of a truncated cone with a smaller base and a larger base; and

a lower cavity in the form of a truncated cone with a smaller base and a larger base; and
wherein said upper cavity and said lower cavity are opposite between each other and are joined at their respective larger base.
The mould for stratified moulding of claim 3, characterized in that the lower base of said upper cavity is smaller than the smaller base of said lower cavity.
The mould for stratified moulding of claim 3, characterized in that the larger base of said upper cavity is smaller than the larger base of said lower cavity.
The mould for stratified moulding of claim 3, characterized in that said lower cavity allows decreasing the metalostatic pressure during the draining of molten metal through said central filling collector by feeding the contractions that may be formed in said moulding cavities and thus eliminate mould shrinkage.
The mould for stratified moulding of claim 3, characterized in that said upper cavity allows increasing the metalostatic pressure during the draining of molten metal through said central filling collector, by feeding the contractions that may be formed in said moulding cavities and thus eliminate mould shrinkage.
The mould for stratified moulding of claim 3, characterized in that said upper cavity has a shape selected from a group consisting of a bell-shaped form, a truncated pyramid shape, a spherical segment with two bases, or combinations thereof.
The mould for stratified moulding of claim 3, characterized in that said lower cavity has a shape selected from a group consisting of a bell-shaped form, a truncated pyramid shape, a spherical segment with two bases, or combinations thereof.
The mould for stratified moulding of claim 1, characterized in that further includes a draining cup located at the upper portion of said mould and connected to said central filling collector.
The mould for stratified moulding of claim 10, characterized in that said draining cup has a shape selected from a group consisting of a bell-shaped form, a truncated pyramid shape, a spherical segment with two bases, or combinations thereof.
The mould for stratified moulding of claim 1, characterized in that further includes a flow stabilizer located at the lower portion of said mould and connected to said central filling collector.
The mould for stratified moulding of claim 12, characterized in that said flow stabilizer has a shape selected from a group consisting of a bell-shaped form, a truncated pyramid shape, a spherical segment with one base, a spherical segment with two bases, or combinations thereof.
The mould for stratified moulding of claim 1, characterized in that said tapping cavity allows the formation of hot spots during the draining of molten metal through said central filling collector to achieve a temperature distribution in said mould.
A stackable mould characterized by comprising:
a tapping cavity of a generally rhomboidal double truncated cone shape; and

one or more moulding cavities connected to said tapping cavity by one or more supply conduits;
wherein each tapping cavity allows metalostatic pressure compensation of the molten metal during its draining in order to achieve a generally uniform filling is accomplished of each of said moulding cavities.
The stackable mould of claim 15, characterized in that it is formed by a portion of upper mould and a portion of lower mould assembled to define said tapping cavity and said moulding cavities.
The stackable mould of claim 15, characterized in that said tapping cavity includes:
an upper cavity in the form of a truncated cone with a smaller base and a larger base; and

a lower cavity in the form of a truncated cone with a smaller base and a larger base; and
wherein said upper cavity and said lower cavity are opposite between each other and are joined at their respective larger base.
The stackable mould of claim 17, characterized in that the lower base of said upper cavity is smaller than the smaller base of said lower cavity.
The stackable mould of claim 17, characterized in that the larger base of said upper cavity is smaller than the larger base of said lower cavity.
The stackable mould of claim 17, characterized in that said lower cavity allows decreasing the metalostatic pressure during the draining of molten metal through said central filling collector by feeding the contractions that may be formed in said moulding cavities and thus eliminate mould shrinkage.
The stackable mould of claim 17, characterized in that said upper cavity allows increasing the metalostatic pressure during the draining of molten metal through said central filling collector, by feeding the contractions that may be formed in said moulding cavities and thus eliminate mould shrinkage.
The stackable mould of claim 17, characterized in that said upper cavity has a shape selected from a group consisting of a bell-shaped form, a truncated pyramid shape, a spherical segment with two bases, or combinations thereof.
The stackable mould of claim 17, characterized in that said lower cavity has a shape selected from a group consisting of a bell-shaped form, a truncated pyramid shape, a spherical segment with two bases, or combinations thereof.
The stackable mould of claim 15, characterized in that said tapping cavity allows the formation of hot spots during the draining of molten metal to achieve a temperature distribution in said mould.
A method for stratified moulding with metalostatic pressure compensation, said method is characterized by comprising the steps of:
(a) forming a mould for stratified moulding from a plurality of stackable moulds arranged one on top of the other in a vertical column, wherein each stackable mould includes:
a tapping cavity of a generally rhomboidal double truncated cone shape; and

one or more moulding cavities connected to said tapping cavity by one or more supply conduits;
wherein the stackable moulds are arranged so that their respective tapping cavities are located one on top of the other to form a central filling collector; and

(b) pouring the molten metal in said central filling collector so that the molten metal flows through each tapping cavity and starts filling the moulding cavities from the lower stackable mould up to the upper stackable mould;
wherein each tapping cavity allows compensating the metalostatic pressure of the molten metal when it is drained to achieve a generally uniform filling of each of said moulding cavity of each stackable mould.
The method of claim 25, characterized in that each stackable mould is formed by a portion of upper mould and a portion of lower mould assembled to define said tapping cavity and said moulding cavities.
The method of claim 25, characterized in that said tapping cavity includes:
an upper cavity in the form of a truncated cone with a smaller base and a larger base; and

a lower cavity in the form of a truncated cone with a smaller base and a larger base; and
wherein said upper cavity and said lower cavity are opposite between each other and are joined at their respective larger base.
The method of claim 27, characterized in that the lower base of said upper cavity is smaller than the smaller base of said lower cavity.
The method of claim 27, characterized in that the larger base of said upper cavity is smaller than the larger base of said lower cavity.
The method of claim 27, characterized in that said lower cavity allows decreasing the metalostatic pressure during the draining of molten metal through said central filling collector by feeding the contractions that may be formed in said moulding cavities and thus eliminate mould shrinkage.
The method of claim 27, characterized in that said upper cavity allows increasing the metalostatic pressure during the draining of molten metal through said central filling collector, by feeding the contractions that may be formed in said moulding cavities and thus eliminate mould shrinkage.
The method of claim 27, characterized in that said upper cavity has a shape selected from a group consisting of a bell-shaped form, a truncated pyramid shape, a spherical segment with two bases, or combinations thereof.
The method of claim 27, characterized in that said lower cavity has a shape selected from a group consisting of a bell-shaped form, a truncated pyramid shape, a spherical segment with two bases, or combinations thereof.
The method of claim 25, characterized in that said step of forming a mould for stratified moulding from a plurality of stackable moulds including the steps of:
locating a draining cup in the upper portion of said mould for stratified moulding and connected to said central filling collector; and

locating a flow stabilizer in the lower portion of said mould for stratified moulding and connected to said central filling collector.
The method of claim 34, characterized in that said draining cup has a shape selected from a group consisting of a bell-shaped form, a truncated pyramid shape, a spherical segment with two bases, or combinations thereof.
The method of claim of claim 34, characterized in that said flow stabilizer has a shape selected from a group consisting of a bell-shaped form, a truncated pyramid shape, a spherical segment with one base, a spherical segment with two bases, or combinations thereof.
The method of claim of claim 25, characterized in that said tapping cavity allows the formation of hot spots during the draining of molten metal through said central filling collector to achieve a temperature distribution in said mould.