JPS5890347A - Molding method for master mold - Google Patents

Abstract

PURPOSE:To obtain a master mold like a shell with safe stages at a low cost by charging molding sand contg. a gas hardenable additive into the spacing between a pattern plate and a molding flask and subjecting the same to compression molding and gushing treatments. CONSTITUTION:Molding sand 8 including a gas hardenable additive is charged into the delineating space between a pattern plate and a molding flask 7. A flexible film is put on the sand 8, and the inside of the sand 8 is evacuated to negative pressure by starting a vacuum pump 23 to mold the sand 8 by compression. Thereafter, the film is removed, and a cover member 24 communicating with a producing device 29 for a hardening gas is fitted airtightly to the upper part of the flask 7. The pump 23 is operated to conduct the hardening gas from the device 29 to the inside of the flask 7 and the inside of the sand 8 is sucked by the pump 23 to deodorize mold. The sucked gas is released into the atmosphere. In this stage the sand 8 is hardened by the hardening gas by which the master mold is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves supplying molding sand containing a gas-curing additive to a space defined by a pattern plate and a molding flask, compressing the molding sand, and then molding the molding sand. The present invention relates to a method suitable for implementing the so-called cold box method or 802 method, in which foundry sand is hardened by passing a hardening gas through the sand.

When molding a main mold by the above-mentioned method i, compression molding of foundry sand and gutting of hardened gas have conventionally been carried out using compressed air, but this has had various problems.
- For example, the amine gas and So2 gas used for gutting in the above molding method are harmful to the human body, but if these gases are blown into the foundry sand using compressed air, the gases will leak from the gaps in the flask, etc., so some kind of protective measures should be taken. A mechanism must be provided to prevent the flask and pattern plate from separating due to the blowing pressure, the flask must be strong enough to withstand the blowing pressure, and The additives for the molding sand used in these molding methods are much more expensive than ordinary ones.

The present invention has been made in view of the above circumstances, and the point is to provide a method for implementing the cold box method or the SOz method at low cost using a safe and compact device.

Hereinafter, the present invention will be explained with reference to the drawings. In Fig. 1, (i) is equipped with a decompression chamber (2) inside, and has a plurality of parts connected to the decompression chamber (2) at appropriate locations on the top surface. A suction box (5) equipped with a plurality of ventilation holes (3) and a plurality of push-out pin holes (4) passing through the upper and lower surfaces, and a pattern (
A casting flask (7) is placed on the upper surface of the pattern plate (1), positioned by a fitting pin (not shown). Note that the ventilation hole (3)
A vent plug (not shown) is embedded in the hole to prevent the molding sand (8) from being discharged. (9) is a frame for supporting and fixing the pattern plate (1);
An air cylinder (11) is attached upward to the horizontal member (10) of the frame (9) via a flange (12), and a piston rod (13) of the cylinder (11) is attached to the tip of the air cylinder (11). An extrusion plate (15) is fixed at its center via a bracket (14). The extrusion plate (1
5) On the top surface, there is an extrusion pin (16>) extending vertically upward.
A plurality of them are implanted in correspondence with the positional relationship of the push-out pin holes (4) provided through the upper and lower surfaces of the suction box (5).

And when the rod (13) of the cylinder (11) is extended,
The ejector pin (16) passes through the ejector pin hole (4) and projects from the upper surface of the suction box (5). It should be noted that a gasket (1
A bushing (18) containing a suction box (7) is attached, and the bushing (17) has a hole through which an ejector pin (16) can slide, keeping the bottom surface of the suction box (5) airtight. ing.

In Figure 2, (9) is a flexible film sheet that is airtightly placed over the foundry sand (8), and (2)
0) is a suction hole, which communicates with a vacuum pump (23) via a conduit (21) and an on-off valve (22).

In Figure 3, (24) has a packing (25) around its entire circumference.
) is attached to the cover member, and is airtightly fitted inside the upper part of the flask (7). A gas supply hole (26) is bored in the center of the cover member (24), and the supply hole (26) is connected to the curing gas generator (26) through a conduit (27) and an on-off valve (28). 29). “In the apparatus configured as described above, first, molding sand (8) containing a gas-hardening additive is placed in the space defined by the pattern plate (1) and the molding flask (7). 1) (7) Add so that the top surface is coated with an almost even thickness (see Figure 1).

Next, a flexible film sheet (19) is airtightly covered over the foundry sand (8), and when the vacuum pump (23) is started and the on-off valve (22) is opened, the conduit (21) is opened. ,
Negative pressure is created inside the molding sand (8) through the suction hole (20), decompression chamber (2), and ventilation hole (3), and the atmosphere presses the film sheet (19) covering the molding sand (8). The foundry sand (8) is then tightly compression molded onto the surface of the pattern plate (1) (see FIG. 2).

After that, the operation of the vacuum pump (23) is stopped, and the on-off valve (23) is stopped.
2) and close the film sheet covering the molding sand (8).
) Remove (19). Then fit the cover member (24) with the airtight number inside the upper part of the flask (7), and connect the gas supply hole (26) of the cover member (24) to the conduit (27) and the on-off valve (28). ), then the vacuum pump (23) is started again and both on-off valves <m (28) are opened, and the curing gas generator (29)
The hardening gas stored inside is guided into the flask (7) through the conduit (27) and the gas supply hole (26) by the suction action of the vacuum pump (23), and is poured into the molding sand (8). Through the vent hole (3), vacuum chamber (2), suction hole (20), conduit (
21) and an on-off valve (22), is sucked into a vacuum pump (23), and is discharged into the atmosphere through a deodorizing device (not shown) (see FIG. 3). In this process, the foundry sand (8) containing the gas hardening additive is hardened by the hardening gas to form a mold.

After passing the hardening gas into the foundry sand (8) for a predetermined time in this way, the on-off valve (2) of the hardening gas generator (29)
8), the cover member (24) is removed, and the operation of the vacuum pump (23) is further continued to completely remove the hardening gas remaining in the molding sand (8).

After the above process is completed, remove the flask (7) and cylinder (1).
1) to cause the push-out pin (16) to protrude from the upper surface of the suction box (5), thereby peeling off the molding sand (8) hardened and adhered to the surface of the pattern plate (1). As a result, a shell-shaped main mold undergarment is obtained.

As is clear from the above description, the present invention applies molding sand containing a gas-hardening additive to the space defined by the pattern plate and the casting flask in a substantially uniform thickness along the upper surface of the pattern plate. The present invention provides a method for obtaining a shell-shaped main mold by putting the molding sand into a mold, and subjecting the molding sand to compression molding and gutting by the suction action of a vacuum pump. Therefore, according to this method, there is no need for a gas leak prevention mechanism or a clamping mechanism between the flask and pattern plate, which are essential in the blowing method, and the equipment becomes compact. A frame or a pattern plate may be used, which is advantageous in terms of cost and handling. Furthermore, since this method produces a shell-shaped mold, the amount of molding sand used, that is, the amount of additives used, is reduced, making it possible to significantly reduce costs.

The method of the present invention, which has many advantages as described above, will promote the spread of this type of molding method8.

[Brief explanation of drawings]

The drawings show the carrying out apparatus and molding process according to the present invention; FIG. 1 is a cross-sectional view when molding sand is introduced, FIG. 2 is a cross-sectional view during compression molding, and FIG. 3 is a cross-sectional view during gutting. (1): Pattern plate (5): Suction box (6): Pattern (7): Casting flask (8t) +:
Foundry sand (11): Air cylinder (15)
: Extrusion plate (16) : Extrusion pin (19)
: Film sheet (23) Dual vacuum pump (24)
: Cover part (29) : Hardened gas generator leak 1 section

Claims (1)

[Claims] Molding sand (8) containing a gas-hardening additive is introduced into the space defined by the pattern plate (1) and the flask (7), and the molding sand (8) is compression-molded. In a method for manufacturing a main mold in which compression-molded foundry sand (8) is hardened by applying a hardening gas, the pattern plate (8) is
1) and the molding flask (7) to a substantially uniform thickness along the upper surface of the pattern plate (1). The upper surface of (8) is airtightly covered with a film sheet (19),
A step of connecting the space and a vacuum source (23) to create a negative pressure in the space and compression molding the foundry sand (8) via a film sheet (19); and compressing the foundry sand (8). After molding, the film sheet (19) is removed and the flask (7) is removed.
A cover member (24) with a gas supply hole (26) is engaged in the upper position, a hardening gas generation source (29) is connected to the space via the cover member (24), and then the molding sand (
8) is compressed and molded, and the hardening gas from the hardening gas generation source (29) is sucked into the space and passed through the compression molded molding sand (8). A method for molding a main mold, comprising the step of hardening foundry sand (8).