JPH0441045A - Method and press for producing core from molding sand - Google Patents

Abstract

PURPOSE: To facilitate the production of a core of an intricate shape having high hardness by putting green sand into a pressure die and precompressing the green sand in the pressure die by using a liquid pressure press, then subjecting the green sand to finish compressing. CONSTITUTION: An upper die tool 8 of a liquid pressure press 1 has an intricate die cavity 9 and a groove hole 11 communicating with the die cavity 9. The die cavity 9 is arranged at the peripheral edge of the die tool 8. At the time of production of the core, the liquid pressure press 1 allows the use of the green sand 12 as molding sand. The green sand 12 is first precompressed by the pressure die 6 and is then subjected to finish compression after the precompression. The green sand 12 can, then, be completely packed into the intricate die cavity 9 in such a manner. At this time, the green sand 12 is sucked through the groove hole 11 before the precompression in the intricate die cavity 9, by which a packing effect is maximized. Pressure air is fed into the groove hole 11 after the pressurizing step to assist the parting of the pressed articles or the core.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to the production of cores or similar molded articles from foundry mold sand using a mold tool having complex mold recesses on the tool surface and capable of entering a pressurized mold. Relating to a method of manufacturing.

TECHNICAL BACKGROUND Various methods for producing cores from molding sand for casting are known, in particular with respect to the molding sand used and the production of the mold tools. Typically, mechanically operated presses are used when using conventional molding sand and uncomplicated mold tooling. On the other hand, when using complex mold tools with mold recesses or hollow spaces on the tool surface, the use of silica sand mixed with resinous adhesives or similar bonding agents is recommended on the one hand, and vibration or Requires the use of machinery. However, silica sand is expensive and the use of vibration or ejection machines is expensive from a mechanical engineering point of view. The present invention provides a countermeasure against this.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a method and a press for mechanically, completely and economically producing cores with complex, fine surface shapes from green sand.

(Structure and effect of the invention) In order to achieve the above object, the present invention puts green sand as molding sand into a pressure mold, pre-compresses the green sand in the pressure mold using a hydraulic press, and finishes after this pre-compression. It is characterized by compression. In the present invention, green sand is first pre-compressed in a pressure mold,
If you continue with final compaction, the complex mold recesses on the surface of the mold tool will be fully filled with sand during the pre-compression process, so green sand, the most affordable molding sand, and hydraulic presses and complex and fine molds can be used. This is based on the knowledge that it can be used to manufacture cores with a surface shape. By the method described above, the green sand itself is sufficiently hardened within the complex mold recesses, and the hydraulic press allows precise control for pre-compaction and subsequent final compaction.

As a result, a core with high hardness and a complex surface shape is produced. Therefore, according to the method of the present invention, cores for complex casting articles can be manufactured simply and inexpensively from affordable green sand. The present invention has such effects.

The present invention has various embodiments as described below. 1 of the present invention
In an embodiment, the green sand is sucked into the mold recess of the mold tool before pre-compaction. According to this, the filling of green sand into the complicated mold recesses is optimal. In other embodiments, a lower mold tool with a raised tool surface or mold recess is raised toward an upper mold tool with a mold recess or raised tool surface to precompact the green sand, and then To compress, both mold tools are simultaneously pressed towards each other. Furthermore, although in principle the lower mold tool can also have a mold recess, if the upper mold tool has a complex mold recess, the pressed product can be easily released from the green sand. , The suction and pre-compression of green sand can also be carried out from the bottom to the top. The ejecting of the pressed parts takes place with or with the aid of pressurized air in the area of complex mold recesses. Since the pressed product can be easily released from the green sand, damage to complex and fine surface shapes is prevented.

The invention furthermore relates to a press having a mold recess and a mold tool and a mold plate capable of entering the pressurized mold. This press is suitable for carrying out the method of the present invention, and consists of a hydraulic press, in which a mold tool having a mold recess communicates with the mold recess, and grooves to which negative pressure and positive pressure are alternately applied. It is characterized by having holes.

Said slots serve, on the one hand, as suction conduits for sucking the green sand into the complex mold recesses and, on the other hand, in the area of the complex mold recesses for ejecting the associated pressed workpieces with the aid of pressurized air. Acts as a pressurized air conduit. In one embodiment, the upper mold tool has a complex mold recess and slot, the slot communicating with the mold recess. It is also within the scope of the invention for the lower mold tool to have mold recesses and slots. The suction of the green sand into the complex mold recesses directly at the tool periphery and its precompaction are carried out in a particularly controlled manner, in order to subsequently give the pressed parts or cores exact dimensional stability - and on both sides. In order to carry out the finishing compaction from the mold, the mold recess is preferably arranged at the periphery of the associated mold tool. Therefore, −
The resulting variable porosity ensures sufficient degassing during the casting process, thus ensuring a smooth surface on the cast article.

The invention will now be described with reference to illustrated embodiments.

(Embodiment) FIG. 1 shows a lower transverse member 2, an upper transverse member 3, a cylinder-piston device 4 and a mold recess 9, and a guide piece 5 for a mold tool 7.8 which enters the pressurizing mold 6. A hydraulic press 1 is shown. The pressure mold 6 is in the area of the mold plate 10. A mold tool 8 having a complex mold recess 9 on the tool surface has a slot 11 communicating with the mold recess 9 and to which negative and positive pressures are applied alternately. 1
As an example, the upper mold tool 8 has a complex mold recess 9 and a sliding slot 11 communicating with this mold recess. The mold recess 9 is arranged around the mold tool 80 . When implementing the method of the present invention, the hydraulic press 1 can use green sand 12 as molding sand. First, the green sand is preliminarily compressed in a pressurizing mold 6, and after this preliminarily compressed, it is finished compressed. In this way it is ensured that the complex mold recesses 9 are completely filled with green sand 12. This effect can be maximized by sucking the green sand 12 through the slots 11 before precompacting it in the complex mold recesses 9. This slot can also be blown with pressurized air after the pressurization step to assist in demolding the pressed product or core.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a hydraulic press implementing the method of the invention; FIG. 2 is an enlarged sectional view of a portion of FIG. 1 showing the peripheral area of the mold tool. 1... Hydraulic press 2... Lower horizontal member 3...
・Upper horizontal member 4...Cylinder/piston device 5...Guide piece 6...Pressure type 7.8...
・Mold tool 9...Mold recess 10...Mold plate
11...Slot hole 12...Green sand patent applicant Georg Fischer Akchengesellschaft

Claims (1)

[Scope of Claims] 1. A method for manufacturing a core or similar molded article from foundry molding sand using a molding tool having a molding recess on the tool surface and capable of entering a pressurized mold, in which the molding sand is used as molding sand. A method characterized by placing green sand in a pressure mold, pre-compressing the green sand in the pressure mold using a hydraulic press, and performing final compression after this pre-compression. 2. Suck the green sand into the mold cavity of the mold tool before pre-compression.
The method according to claim 1. 3. To pre-compact the green sand, the lower die tool with the raised tool surface is raised towards the upper die tool with the die recess, or conversely the former is lowered towards the latter, and then final compaction is carried out. 3. The method according to claim 1, wherein both mold tools are simultaneously pressed towards each other. 4. The method according to claim 1, wherein the pressed product is discharged using or with the aid of pressurized air. 5. In a press equipped with a mold tool that has a mold recess and can enter the pressurized mold, and a mold plate, the mold tool (8) is composed of a hydraulic press (1) and has a mold recess (9). Mold recess (9
) A press characterized in that it is equipped with a slot (11) that communicates with the air pressure and that negative pressure and positive pressure are alternately applied thereto. 6. Press according to claim 5, wherein the upper or lower mold tool (8) has a mold recess (9) and a slot (11), said slot communicating with the mold recess. 7. Press according to claim 5 or 6, wherein the mold recess (9) is arranged at the periphery of the associated mold tool (8).