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(11) | EP 0 949 023 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Apparatus and method for producing a shell mould |
| (57) An apparatus (20, 50) for defining a thin, shell-like mold space (4A) in a flask
(3) is disclosed. The apparatus includes metal forms (4, 4; 26A, 26B, 26C; 46A, 46B)
that are located over both a pattern plate (2) and a pattern (1), which has stepped
parts. By fasteners (5, 6) these metal forms are attached, for example, to the inner
wall of the flask (3). These metal forms have surfaces that correspond to the surfaces
of the pattern (1) and a pattern plate (2). The surfaces of the metal forms are spaced
apart a predetermined distance from the surfaces of the pattern and pattern plate
so that they define a thin, shell-like mold space (4A) over both the pattern and pattern
plate. When self-hardening molding sand is charged into the mold space, a mold that
has a thin, uniform thickness is produced. |
Field of the Invention
[0001] This invention relates to a method and apparatus for producing a thin mold, especially a shell-like, thin mold from self-hardening molding sand, where less molding sand is used.
Description of the Prior Art
[0002] When producing a mold from self-hardening molding sand, a flask is placed on a pattern plate, and self-hardening molding sand is then charged in the flask. Such a mold has a thickness depending on the height of the flask.
[0003] Since self-hardening molding sand is made from the mixture of expensive hardening material such as a furan resin, and silica sand, a mold has been requested that uses as little self-hardening molding sand as possible.
[0004] This invention was conceived to meet that request. It aims to provide a metal form apparatus and method that can produce a thin, "shell-like" mold where less molding sand is used. The term shell-like denotes an object shaped like a shell or shaped like stepped parts so that they resembles a shell.
Summary of the Invention
[0005] The metal form apparatus of this invention for defining a thin, shell-like mold space in a flask includes a plurality of metal forms. These metal forms are located over both a pattern plate and a pattern that has stepped parts or a shell-like shape. The metal forms are secured to the inner wall of a flask or the bottom of a plate which is placed on the flask, or to both of them. These metal forms have surfaces that correspond to the surfaces of a pattern and a pattern plate. The surfaces of the metal forms are spaced apart a predetermined distance from the surfaces of the pattern and pattern plate. Thus the surfaces of the metal forms define a shell-like mold space over the surfaces of the pattern and pattern plate. When self-hardening molding sand is charged into the mold space, a shell-like mold that has a thin, uniform thickness is produced from less self-hardening molding sand than in the prior art.
Brief Description of the Drawings
[0006]
Fig. 1 is a cross-sectional view of the first embodiment of the apparatus of the present invention.
Fig. 2 is a cross-sectional view that shows two combined molds produced by the apparatus of Fig. 1.
Fig. 3 is a cross-sectional view of the second embodiment of the apparatus of the present invention.
Fig. 4 is a perspective view of a metal form used in the apparatus of Fig. 2, which metal form is in the form of a block.
Fig. 5 is a cross-sectional view that shows two combined molds produced by the apparatus of Fig. 3.
Fig. 6 is a cross-sectional view of an apparatus for carrying out the method of this invention.
Fig. 7 is cross-sectional view of two combined molds produced by the apparatus of Fig. 6.
Description of the Preferred Embodiments
[0007] In Figs. 1 and 2 a first embodiment of the invention is explained. In Fig. 1 a pattern plate which has a pattern 1 thereon is placed on a floor (not shown). A flask 3 is placed on the pattern plate 2. A metal form apparatus 20, comprised of a plurality of metal forms 4, 4, is fixedly mounted on the inner wall of the flask 3 by fasteners such as bolts 5 and nuts 6. Since the right metal form 4 is attached by the fasteners to the front and rear inner walls (not shown) of the flask 3, these fasteners are not shown in Fig. 1.
[0008] The surfaces of these metal forms that face the pattern 1 and pattern plate 2 are spaced apart a predetermined distance from the surfaces of the pattern 1 and pattern plate 2. Thus the metal forms 4, 4 define a mold space 4A over both the pattern 1 and pattern plate 2. The mold space 4A has a substantially uniform, thin thickness. A rigid metal plate 8 is sealingly placed on the top of the flask 3. The metal plate 8 has a throughbore 7 for introducing molding sand. The throughbore 7 communicates with the mold space 4A. A sand hopper 10 is placed on the metal plate 8 for supplying self-hardening molding sand S into the mold space 4A through the throughbore 7.
[0009] The sand S is introduced from the hopper 10 through its outlet 9 and charged into the mold space 4A by a known blowing mechanism, suction and charging mechanism, or evacuating and pressurizing mechanism (none shown). Fig. 1 shows the mold space 4A charged with the self-hardening molding sand. Thus a thin, shell-like mold is produced.
[0010] The pattern plate 2, the flask 3 (and metal form apparatus 20), and the mold, are then all lowered in a known way so that they are separated from the plate 8, while the mold is cured until the self-hardening molding sand hardens. When it hardens, the pattern plate 2 is removed, so that the mold held in the flask 3 and metal forms 4, 4 is produced. As in Fig. 2, this mold is combined with another mold that is produced in the same way as described above, and that is held in a flask 3 and metal forms 4, 4. This mold assembly acts as a mold to produce a cast. Before these molds are used, the flasks and the metal forms may be removed.
[0011] In Figs. 3 and 4 a second embodiment is explained. The same reference numbers are used for the same elements as in the first embodiment, shown in Figs. 1 and 2. Since in the second embodiment only a metal form apparatus 50 and a mount plate 25, to which the apparatus 50 is mounted, differ from the first embodiment, we explain only them.
[0012] The mount plate 25 is placed on the flask 3 so that it is located between the flask 3 and the rigid plate 8. The mount plate 25 has a throughbore 24 that corresponds to the throughbore 7 of the rigid plate 8. The metal form apparatus 50 includes metal forms that are in the form of columns or blocks 26A, 26B, 26C, and 27. These columns are made from an adequate combination of these three blocks 26A, 26B, and 26C such that the bottoms of the columns are stepped and spaced apart a predetermined distance from the surfaces of the pattern 1 and the pattern plate 2 (that is, such that the columns define a thin, shell-like mold space over both the pattern and pattern plate). The columns (metal forms) are attached to the bottom of the mount plate 25 by fasteners (not shown). As in Fig. 4, each block (only block 26B is shown in the drawing) has four bolt holes, two of which are holes 28, 28 for flat head bolts, and the other two 29, 29 for tap bolts. The blocks 26A, 26B, or 26C are mounted on the bottom of the mount plate 25 through the holes and bolts, and the blocks 26A, 26B, 26C are also connected to each other through the holes and bolts.
[0013] When self-hardening molding sand is charged into the mold space in the same way as described above as in the first embodiment, a thin, shell-like mold is produced. Fig. 5 shows this mold and another mold, which are combined as are those shown in Fig. 2. By using the mold assembly of Fig. 5 a cast is produced.
[0014] The flask 3 and mount plate 25 can be used for a variety of metal forms 4, 4, 26A, 26B, and 26C that have been prepared for many patterns and pattern plates. Although in the first and second embodiments the metal forms are attached to either the flask 3 or the mount plate 25, they may be attached to both of them, if so desired.
[0015] In Figs. 6 and 7 a third embodiment is explained. A thin, shell-like mold is produced by using the device shown in Fig. 6. In this embodiment the same reference numbers are used for the same elements as in the first and second embodiments.
[0016] Metal forms or blocks 46A, 46B, 46C are attached to the inner wall of a metal flask 3 such that they define a thin, shell-like mold space 4A over both a pattern 1 and a pattern plate 2. A rigid plate 8, which has a throughbore 7, is placed on the flask 3.
[0017] A means 32 for evacuating the mold space 4A and introducing ambient air into the evacuated mold space is mounted on the rigid plate 8. The means 32 includes a vertical, cylindrical chamber 33, which at one end is airtightly connected to the throughbore 7 of the rigid plate 8 and at the other end to a sand hopper 10. The means 32 also has a valve 34 and an air passage 35 leading from the valve 34 to the cylindrical chamber 33. The means 32 also includes a passage 37, a valve 37, and a vacuum pump 38. The passage 37 is airtightly connected to the cylindrical chamber 33. When the mold space 4A is closed and when the valve 37 is opened, the vacuum pump 28 can evacuate the mold space 4A.
[0018] A gate means 40 is airtightly disposed between the sand hopper 10 and means 32 for evacuating the mold space. The gate means 40 includes a cylinder 41 and a slidable gate plate 42, which is operated by the cylinder 41. The gate plate 42 stops the feed of self-hardening molding sand from the hopper 10 when it is closed, and starts the feed of the sand when it is opened.
[0019] Now the operation of the device to produce a mold is explained. An amount of self-hardening molding sand, which corresponds to the volume of the mold space 4A, is held in the hopper 10. By actuating the cylinder 41 the gate 42 is opened, so that almost all the molding sand freely drops from the hopper 10 into the mold space 4A Since the wall of the sand hopper 8 forms an acute angle with a vertical line, a small amount of the molding sand remains at the outlet of the hopper 8. The gate 42 is then closed. This state is shown in Fig. 6. Then the valve 37 is opened and the vacuum pump 38 is actuated to evacuate the mold space 4A The valve 34 is then opened to introduce ambient air into the mold space. Since an airflow hits the surface of the molding sand S in the mold space 4A, the sand is compacted. The valve 34 is then closed, and the gate 42 is then opened. Thus all or almost all of the molding sand that remains in the hopper 8 drops into the mold space 4A. The gate 42 is then closed, and the mold space 4A is again evacuated. After this, the valve 34 is opened to introduce the ambient air into the mold space to compact the molding sand S in the space.
[0020] If desired or necessary, introducing into the mold space the molding sand that remains in the hopper 8, evacuating the mold space, and introducing ambient air into the space, may be repeated one or more times.
a plurality of metal forms attachable to the inner wall of a metal flask, said metal forms having surfaces that face surfaces of a pattern and a pattern plate, said metal form surfaces being spaced apart a substantially constant distance from said surfaces of said pattern plate and said pattern when said metal forms are attached to said metal flask to define a mold space over both said pattern and said pattern plate for producing a thin, shell-like mold.
a metal flask;
a plate placed on said flask, said mount plate having a throughbore for introducing molding sand:
a plurality of metal forms attached to the bottom of said mount plate, said metal forms having surfaces that face surfaces of a pattern and a pattern plate, said metal form surfaces being spaced apart a substantially constant distance from said surfaces of said pattern plate and said pattern to define a mold space over both said pattern and said pattern plate for producing a thin, shell-like mold.
placing a pattern plate that has a pattern thereon;
placing a flask on said pattern plate;
placing a plate on said flask, said plate having a throughbore for introducing self-hardening molding sand;
attaching metal forms to at least one of said flask and said plate, said metal forms having surfaces spaced apart a substantially constant distance from said pattern and said pattern plate to define a shell-like mold space over both said pattern and said pattern plate;
introducing self-hardening molding sand into said mold space through said throughbore of said plate; and
compacting said molding sand located in said mold space.
i) closing and evacuating said mold space; and
ii) introducing ambient air from a level higher than the surface of said molding sand located in said mold space into said mold space to compact said molding sand, and that further includes the step of carrying out at least once the step of:
iii) opening said mold space and introducing molding sand into said mold space, and after this, repeating the steps i) and ii).