JPS59163052A - Molding method of green sand core - Google Patents

Abstract

PURPOSE:To provide substantial strength to a green sand core and to prevent the collapsion of the core in molding said core by inserting a rammer into the green sand to compress and harden the sand to a specific extent and removing the core from a core box in the state of leaving the rammer in the inside. CONSTITUTION:A vertically split core box 4 provided with a cavity 3 formed with apertures 1, 2 at the top and bottom ends is placed on a bottom plate 5 and green sand is blown and packed in the cavity 3. A rammer 8 of which the bottom end part is formed into a circular conical shape and the top end is connected to a lifting device is inserted into the green sand to compress the green sand at 10-50% to harden. After the rammer 8 is inserted to a prescribed depth into the cavity 3, the rammer is detached from the lifting device and when the box 4 is opened while the rammer 8 is left in the green sand, the core S having the prescribed hardness is obtd.

Description

[Detailed description of the invention] The present invention relates to a method of molding a core using green sand.

The present inventors first developed a method of molding a core using green sand, that is, inserting a protruding flat rod into the cavity of a core box filled with green sand to compress and harden the green sand, and then using the piercing rod. He invented a method of extracting the above-mentioned hardened green sand and opening the above-mentioned core box to obtain a core.
No. 55).

By the way, the core molded by the above molding method has a hollow shape, so there are problems with its strength, and when the upper and lower molds are put together, the core set in the mold collapses, and when pouring into the mold. There were three cases of breakage due to the buoyancy of the molten metal. The present invention has been made in view of the above circumstances, and provides a method for molding a green sand core that has sufficient strength.

The present invention will be explained in detail based on examples below.
FIG. 1 shows an embodiment of the present invention, in which a vertically split core box (4) equipped with a cavity (3) in which openings (1) and (2) are formed at the upper and lower ends of the bottom plate ( 5) After placing the green sand on top of the core box, fill the cavity (3) with green sand by blowing compressed air, letting it fall naturally, or adding it while applying vibration to the core box. When a piercing rod (8) whose lower end has an inverted conical shape and whose upper end is connected to a lifting device (not shown) is inserted into the transfer cavity (3), the green sand will move between the piercing rod (8) and the It is compressed and hardened in the horizontal direction by the core box (4). The transfer piercing rod (8) with the piercing rod (8) inserted into the cavity (3) to a predetermined depth was separated from the lifting device, and the piercing rod (8) was left in the hardened green sand. If the core box (4) is opened as it is, a core (S) having a predetermined hardness will be obtained. Note that the upper end of the piercing rod (8), that is, the connecting portion with the lifting device protrudes from the core, but this may be left as it is, or it may be pushed into the core depending on the situation. It can be crowded.

FIGS. 2 and 3 show another embodiment of the present invention, in which a cavity (3) is formed with openings (1) and (2) at the upper and lower ends.
) is placed on the bottom plate (5) of the soil, and a vertically split core box (4) with the same diameter as the opening (1) is placed on the top opening (1) of the core box (4). Auxiliary member (
7) was placed with the openings (1) and (6) aligned, and green sand was poured into the cavity (3) and the opening (6) of the auxiliary member (7) as in the first embodiment. Filled in the same manner, the piercing rod (8) passes through the transfer opening (6) into the cavity (3) and has a lower end shaped like an inverted cone and an upper end connected to a lifting device (not shown). ), the green sand is compressed and hardened in the horizontal direction by the stabbing rod (8) and the core box (4). The piercing rod (8) is inserted into the cavity (
3) After inserting the elevating device to a predetermined depth, the elevating device is separated from the stabbing rod (8) and raised, and the auxiliary member (7)
A suppressing member (9) having an outer shape that can be loosely fitted into the opening (6) of the opening (6), or a suppressing member (9) having an outer shape that can be loosely fitted into the opening (6) and having the When the pressing member (12) having a through hole (, 11) through which the piercing rod (8) can slide is inserted, the green sand in the opening (6) will be removed from the pressing member (9) ( 12) is vertically compressed. After inserting the pressing members (9) (12) to a predetermined level, the pressing members (9) (12) and the auxiliary member (7) are separated, and the piercing rod (8) is inserted into the hardened green sand. When the core box (4) is opened with the core left inside, a core (S) is obtained which is strongly hardened, especially at the upper end.

In this embodiment, the piercing rod (8) is inserted from only one direction in the cavity of the core box, but depending on the shape of the cavity, it may be inserted from two or more directions at the same time.

Regarding the shape of the piercing rod used in the molding method according to the present invention, in addition to the straight piercing rod (8) whose lower end has an appropriate inverted conical shape as shown in FIGS. 1 to 3, As shown in Fig. 4, the lower end is in the shape of an inverted cone, and the diameter gradually increases from the lower part with appropriate dimensions corresponding to the shape of the cavity of the core box (13). ), as shown in Figure 5, a tapered piercing rod (14) whose diameter gradually increases upward, or as shown in Figure 6, the lower end forms an inverted conical shape and the upper part is a core box. A stepped pin (1) with a large diameter that can be loosely fitted into the upper end opening (1) of the cavity (3).
5) etc. are possible. In addition, the piercing rod (8) (13
) (14) (15) The volume of the part inserted into the core box cavity (3) is equal to (3) It is desirable to be constructed so that it occupies 10 to 30% of the volume, and when using the sieving natural fall method, it is desirable to be constructed so that it occupies 25 to 50%.

Furthermore, the piercing rod (&) (13
) (14) and (15) all have smooth outer circumferential surfaces, but if the outer circumferential surfaces are provided with irregularities such as threaded portions, the piercing rods left inside the cores during handling of the cores can be easily removed. There is no need to worry about it falling off unexpectedly.

As is clear from the above description, the present invention involves inserting a piercing rod into the cavity of a core box filled with green sand, compressing and hardening the green sand, and thereby molding a green sand core. At this time, the molded core is taken out from the core box with the piercing rod remaining in the hardened green sand. Therefore, the molded core maintains sufficient strength and will not collapse when the upper and lower molds are fitted together, or break due to the buoyancy of the molten metal when pouring into the mold.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view of a main part of one embodiment of the present invention, FIGS. 2 and 3 are longitudinal sectional front views of main parts of another embodiment of the invention,
Figures 4-6 illustrate various types of piercing rods that may be used in the present invention. (3): Hollow part (4): Core box (5): Bottom plate (7): Auxiliary member (8) Nistrade piercing rod (9) (12): Pressing member (13) (15)
: Stepped pierced rod (14) : Theno (shaped pierced rod 2 causes Figure 4)

Claims (1)

[Claims] 1. Insert a piercing rod whose tip is approximately in the shape of an inverted cone into the cavity of the core box filled with green sand to
% compression and hardening to mold the core, and then taking out the core from the core box with the piercing rod remaining inside. 2. Insert into the cavity of the core box filled with green sand a piercing rod whose tip is approximately in the shape of an inverted cone and with irregularities formed at appropriate locations on the outer circumferential surface, and then pour the green sand into the core box for 10~ 50% compression/
A method for molding a green sand core, comprising: curing and molding the core, and then removing the core from the core box with the piercing rod remaining inside.