JPH0440097B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a shell type used when vertically casting an article having a flange at one end of a columnar part using backup material.

Incidentally, in the present invention, the term "column-shaped part" includes a part whose inside is substantially hollow.

As is well known (for example, as shown in Japanese Utility Model Application Publication No. 54-134725), one of the methods for forming this type of shell is to form a shell by the steps shown in FIGS. 1a to 1e. There is a dump method for molding mold Sa. In this method, as shown in figure a, dump box 1
After attaching the pattern plate P of the desired shape to the shutter 2, open the shutter 2 as shown in Figure b.
By dropping shell sand 3 such as resin sand onto the heated pattern plate P and covering it, the shell sand 3 around the pattern plate P is solidified. Thereafter, as shown in FIG. Increase the strength of the shell type Sa, and finally, as shown in the same figure e, the shell type Sa
is released from the pattern plate P. in this case,
If necessary, before demolding, the dump box 1 is turned over again as shown in FIG.

Shell type Sa manufactured by such a dumping method
The method of vertical casting using the is shown in Figure 2. That is, as is clear from the figure, when performing vertical casting, a pair of half-shell molds Sa and Sb formed by the above-mentioned dumping method are placed in the casting box 4 by gluing their split surfaces. A back-up material 5 such as iron shot, gravel, green molding sand, etc. is loaded around it to form a shell type Sa,
A method is adopted in which Sb is backed up and in this state is poured into the shells Sa and Sb from the sprue 6 at the top.

By the way, a half-split type is used when casting an article 7 having a flange 9 at one end of a columnar part 8, such as the exhaust manifold of an automobile engine shown in FIG. 3, by the above-described vertical casting. When molding the shell type Sa, a pattern plate P shown in FIGS. 4a and 4b is used. This pattern plate P has a convex split surface d ₁ at a position corresponding to the longitudinal middle part of the columnar part 8 of the article 7, and a concave split surface at a position corresponding to the joint surface of the flange 9 of the article 7. Each has a surface d ₂ , and the convex split surface d ₁ and the concave split surface d ₂ form a stepped portion d _3.
is continuous by , and the concave split surface d ₂ has
It has a columnar pattern part 8a and a flange pattern part 9a. In such a pattern plate P, since the flange portion 9a protrudes from the lower end side of the columnar pattern portion 8a, the step portion _d3 cannot be provided closer to the columnar pattern portion 8a than a certain level, and the step portion The distance between the portion _d3 and the columnar pattern portion 8a is relatively large. Therefore, when this pattern plate P is used to mold a shell type Sa by the dumping method explained in FIG. 1, the columnar pattern portion of the pattern plate P is formed as shown in FIGS. Deep depressions 10a and 10b are formed between the shell sand solidified layers formed around each of the shell sand 8a and the stepped portion _d3 .

When vertically casting the article 7 described in FIG. 3 using such a shell mold Sa, as shown in FIG. 5, the shell mold Sa and the other half shell mold Sb are
and are placed in the casting box 4 (see Figure 2) with their split surfaces aligned, and then the shell molds Sa,
Around Sb, back up material 5 (see Figure 2)
Load. At this time, the hollow portion 10b located above the shell sand consolidated layer _S1 around the columnar pattern portion 8a (see FIG. 4b) is sufficiently filled with the backup material 5, but the shell sand consolidated layer S The recessed portion _10a located below the shell sand layer S1 is not sufficiently filled with the backup material 5, and the backup force against the shell sand solidified layer _S1 is insufficient. On the other hand, the shell sand consolidated layer _S1 is applied from above to the columnar pattern portion 8a shown in FIG. 4b (see FIG. 1b).
Since the shell sand consolidated layer S ₁ is inevitably thinner near the tip of the columnar pattern portion 8a, a decrease in the strength of the shell sand consolidated layer S ₁ is unavoidable. Due to this lack of back-up force and decrease in strength, during the vertical casting shown in Figure 5, the shell sand consolidation layer _S1 deforms downward as shown by the two-dot chain line, causing bulges in the cast product. or sometimes cause a crack. In addition, in FIG. 5, 20 is a core.

By the way, as a measure to locally increase the strength of the shell-shaped shell sand solidified layer, as shown in _FIG . There is a method in which a pin 12 for auxiliary heating is placed upright close to the corner 11a of the pattern portion 11, and both the pattern plate P and the pin 12 are heated to carry out the dumping method shown in FIG. . The shell type Sa formed by this method has shell sand 3 in the portion corresponding to the side surface and corner 11a of the pattern portion 11.
is heated by both the pattern plate P and the pin 12, and the thickness of the shell sand consolidation layer in this part becomes equal to or thicker than the thickness of the shell sand consolidation layer in other parts, This results in greater strength.

Therefore, in order to strengthen the shell sand consolidation layer _S1 explained in Fig. 5 and prevent deformation during vertical casting, a sixth
It is possible to apply the method explained in the figure.

However, in the method explained in FIG. 6, it is not possible to locally thicken the shell sand solid layer and increase its strength by arranging the pin 12 close to the side surface of the pattern section 11. It is possible. However, in the pattern plate P described with reference to FIGS. 4a and 4b, since the flange pattern part 9a protrudes from the lower end side of the columnar pattern part 8a, this flange pattern part 9a becomes an obstacle. Since it is not possible to erect an auxiliary heating pin close to the side of the shell, the method explained in Fig. 6 cannot be used as a measure to prevent deformation of the shell sand solidified layer _S1 in Fig. 5. be.

This invention provides a shell molding method that can be particularly advantageously adopted in cases where the above-mentioned difficulties exist. By using the dummy plate as an auxiliary heating for the shell sand and forming shell ribs extending in the direction connecting the columnar pattern part of the pattern plate and the step part of the uneven split surface, the necessary part of the shell mold can be locally heated. It is intended to reinforce.

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIGS. 7a and 7b, a holding pin 1 is placed on the side of the flange pattern portion 9a of the concave split surface _d2 of the pattern plate P with a gap.
3 is erected, and a metal dummy plate 14 is locked to the end of this holding pin 13. As shown in FIG. 8, the holding pin 13 has a cross-shaped slit 15 formed at its end, into which the dummy plate 14 is inserted. With this, the dummy plate 14 is
Projection piece 1 divided by the slit 15
6, it is held elastically and securely locked without wobbling.

The dummy plate 14 needs to be disposed within the concave space of the pattern plate P so as to face the columnar pattern portion 8a with a gap therebetween. This is because if the dummy plate 14 is placed in contact with the columnar pattern portion 8a, the end face of the dummy plate 14 will be exposed to the cavity of the shell sand Sa, which will be described later, and casting will not be carried out smoothly.

Thereafter, the pattern plate P and the dummy plate 14 are heated, and the dumping method described in FIG. 1 is performed to form the mold. In this way, not only the shell sand along the pattern plate P but also the shell sand along the dummy plate 14 is heated and solidified, so that the molded shell mold Sa has
As clearly shown in FIGS. 7a and 7b, a shell rib 17 is formed along the dummy plate 14 and extends in a direction connecting the columnar pattern portion 8a and the stepped portion _d3 . mold
The structure is one in which the above-mentioned shell sand consolidation layer _S1 of Sa is reinforced. Therefore, when performing vertical casting with the shell type Sa in the state shown in Fig. 9, the shell sand solidified layer S ₁
Even if the above-mentioned back-up force is insufficient, this shell sand consolidated layer _S1 will not be deformed. Note that the dummy plate 14 is a shell type Sa
When it is released from the pattern plate P, it is pulled out from the slit 15 of the holding pin 13 and remains buried in the shell rib 17.

10a and 10b show the case where a shell type Sa is molded according to a modification of the above embodiment.
That is, as the holding pin 13, the gas vent pin shown in FIG.
As shown in b, the stepped portion of the pattern plate P is also engaged with the notch groove 18 formed at _d3 ,
In this state, the dumping method shown in FIG. 1 was carried out to mold a shell type Sa. in this case,
The dummy plate 14 is connected to the holding pin 13 and the notch groove 1.
8 has the advantage of being firmly held. In addition, the first
As shown in Figure 2, the shell type Sa molded using this method
It is necessary to form a groove 19 in the half shell type Sb, which is the other half, for accommodating the end of the dummy plate 14 buried in the shell rib 17 thereof. Other configurations and effects are the same as those described in FIGS. 7a and 7b and FIG. 9.

In addition, in the drawings, for convenience of explanation, the same reference numerals are given to the same or corresponding parts, and the explanation is omitted.

As detailed above, according to the present invention, within the concave space of the pattern plate, the columnar pattern portion and the stepped portion of the pattern plate are arranged along the dummy plate that faces the columnar pattern portion with a gap therebetween. Since shell ribs extending in the connecting direction are formed, a shell mold is formed that is locally reinforced by the shell ribs. Therefore,
When vertically casting an article having a flange at one end of a columnar part, even if the back-up force against the shell mold is locally insufficient, it is possible to form a shell mold with the strength to compensate for the lack of back-up force. This prevents deformation of the cast product and occurrence of cracks due to deformation of the shell mold.

[Brief explanation of drawings]

Figures 1 a to e are explanatory diagrams showing an example of a general shell mold manufacturing method, Figure 2 is an explanatory diagram showing a vertical casting method, and Figure 3 is an explanatory diagram showing an example of a flanged article. A perspective view of the manifold, FIG. 4a is a plan view showing the state of the shell mold before release from the mold in the conventional method, FIG. 4b is a cross-sectional view taken along the - line in FIG. An explanatory diagram of vertical casting using a shell mold formed by
FIG. 6 is an explanatory diagram showing another example of the conventional shell mold manufacturing method, FIG. 7 a is a plan view showing the state of the shell mold before release in the embodiment method of the present invention, and FIG. FIG. 8 is an enlarged perspective view of the holding pin, and FIG. 9 is a cross-sectional view taken along the - line in FIG. Explanatory drawings, FIG. 10a is a plan view showing the state of the shell mold before release in another embodiment of the present invention, and FIG. 10b is the - of FIG. 10a.
11 is an enlarged perspective view of a degassing pin as a holding pin, and FIG. 12 is a cross-sectional view taken along the line, FIG. It is an explanatory diagram. DESCRIPTION OF SYMBOLS 1... dump box, 3... shell sand, 7... article, 8... columnar part of article, 8a... columnar pattern part,
9... Flange of article, 9a... Flange pattern portion, 13... Holding pin, 14... Dummy plate, 1
5...Slit, 17...Shell rib, P...Pattern plate, _d1 ...Convex split surface, _d2 ...Concave split surface, _d3
...stepped part, Sa...shell type.

Claims (1)

[Scope of Claims] 1. A method for forming a half-shell mold for casting an article having a flange at one end of a columnar part, the method comprising joining the longitudinal middle part of the columnar part and the flange in the article. A pattern plate having an uneven split surface at a position corresponding to the surface and a columnar pattern section and a flange pattern section on the concave split surface is prepared, and a flange pattern of the concave split surface in this pattern plate is prepared. A holding pin is erected on the side of the pattern plate, and a metal dummy plate, which is opposed to the columnar pattern part with a gap in the concave space of the pattern plate, is locked to the end of the holding pin. By heating the pattern plate and the dummy plate and using a dump box to cover the pattern plate with shell sand, the sand is extended along the dummy plate in the direction connecting the columnar pattern part and the stepped part of the uneven split surface. A method for forming a shell mold for flanged articles that forms shell ribs. 2. The method of forming a shell mold for a flanged article according to claim 1, wherein the dummy plate is inserted into and locked into a slit formed at the end of the holding pin.