JPS611442A - Method and device for producing shell mold - Google Patents

Abstract

PURPOSE:To reduce the time for sintering and curing and to improve the efficiency of producing a shell mold in the stage of producing said mold by blowing hot wind to shell sand to calcine and cure the shell sand in combination with the temp. of preheated dies. CONSTITUTION:The upper and lower dies 2, 3 are preheated and the temps. thereof are held by a heater, etc. The shell sand is blown from a blow head 5 through a bushing 4 for blowing in such a state to start packing the shell sand into a cavity 8. A stop valve 13 is driven to open by a timer 14 to pass the air from a pessure air source 12 to the line on the down stream of the valve when the start of packing the shell sand is detected. The time for supplying the air is controlled by the timer 14. The air is heated in the course of flowing through the passages 7, 9 of the dies 2, 3 and is ejected and supplied in the hot wind state into the cavity 8 so as to arrive at the inside of the sand packed therein. An initially cured layer is thus formed to the packed shell sand by the die temp. and the inside of the surface is heated by the hot wind, by which the heating and curing are accelerated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method and apparatus for manufacturing a shell mold.

(Background Art) When obtaining a shell mold by filling a heated mold cavity with shell sand (resin sand) and sintering and hardening the shell sand, it is possible to shorten the sintering and hardening time. Manufacturing efficiency can be improved and manufacturing costs can be reduced.

In order to achieve the above, as a conventional technology,
In this method, the shell sand is preheated to the extent that the fluidity of the shell sand is not inhibited and then blown into the cavity of a heating mold.

According to this technique, the time required for sintering and hardening the shell sand in a preheated public mold is shortened, but there is a limit to the preheating of the shell sand within a range that does not impede its fluidity, so there is a limit to the time reduction. .

In all conventional techniques, the shell sand cannot receive heat only from the surface of the cavity acid, and it takes a long time to harden the shell sand, which has low thermal conductivity, to the inside. It is.

(Objective of the Invention) The present invention has been made in view of the above, and its purpose is to significantly shorten the sintering and hardening time for obtaining a shell mold, thereby improving manufacturing efficiency and reducing costs of the shell mold. The object of the present invention is to provide a method and apparatus for manufacturing a shell mold, which can accomplish the above with a simple configuration.

(Structure of the Invention) In order to achieve the above object, the present invention provides, as a first invention, a method in which heated pressurized air is fed into a cavity of a mold from an air passage provided in the mold. In addition, as a second invention, an air passage is provided in the mold so as to surround the outside of the cavity, and pressurized air is supplied from the outside to the air passage, and the pressurized air is heated in the process of passing through the long passage. The gist is:

(Example) Next, an example of the present invention will be described in detail with reference to the attached drawings.

Fig. 1 is a vertical i-plane view of the apparatus for explaining the method according to the present invention, Fig. 2 is a plan view of one of the molds constituting the apparatus, and Fig. 3 is a bottom view of the other mold. .

First, the manufacturing method of the shell mold according to the present invention will be explained. (1) is a mold manufacturing mold, which in the example is a vertically split mold, and consists of an upper mold (2) and a lower mold (3).

The upper mold (2) is formed with an upper cavity (202) that is open toward the mold mating surface (201) with the lower mold (3), and a shell sand blowing bush ( 4) is installed vertically, and the bushing (0 is the lower mold (2)
A passage (401) connected to the supply part (501) of the blow head (5) disposed above and in sliding contact with the bush (4) communicates with the inside of the blow head (5) to supply shell sand. and guide the shell sand into the cavity.

The bush (4) has a mounting hole (20) installed vertically in the upper mold (2).
3) from above, and the flange part (40
2) is engaged with the step (204) at the top of the mounting hole (203) to perform vertical positioning. 0 or more forming an air vent (8) opening to the ceiling of the cavity (202) between the outer periphery of the main body (403) that fits into the mounting hole (203) of the bush (4) and the inner diameter of the mounting hole (203) The downstream end (701) of the air passage (7) is opened perpendicularly to the axial direction in a part of the inner diameter part of the mounting hole (203) of the air passage (7).
) is bored horizontally in the upper mold (2), and the upstream end (702
) opens on the negative side of the upper mold (2).

The lower mold (3) is formed with a lower cavity (302) that is open toward the mold mating surface (301) with the upper mold (2), and the cavity (302) is connected to the upper and lower molds (2') and (3). A cavity (8) is formed by combining the molds with the lower cavity (202).

A horizontal air passage (9) with a downstream end (901) closed is provided below the lower cavity (302) in the lower mold (3), and a portion of the passage (9) directly below the cavity (302) is are spaced apart in the length direction of the passage (9) and the cavity (
302) and the passageway (8) (902)...
. is installed vertically, and an air vent member is fitted into the through hole (902) to form an air vent (10).

Passage (7) provided in the above upper and lower molds (2) and (3)
, (9) to the air supply line (11), and connect the line (
11) is connected to a pressure source (12), and an on-off valve such as an on-off valve (13) is interposed in the line (11).
) is controlled to open and close using a timer (14), for example.
) is controlled, for example, by a blow head (5).

In the above, the upper and lower molds (2) and (3) are heated in advance, or heated and then kept warm by a heater (not shown) or the like. Under such conditions, shell sand (resin sand) is blown from the blow head (5) through the blowing bush (4) to fill the cavity (8) with shell sand. An initial thin hardened layer is formed on the outside of the filled shell sand by the heat of the cavity (8) wall. The start of filling the shell sand into the cavity (8) is detected, the opening/closing (13) is driven via the timer (14) to open it, and air from the pressurized air source (12) is introduced into the line downstream of the valve. sink,
The air supply time, that is, the opening/closing time of the on-off valve (13) is controlled by a timer (14).

Line (11) has two systems (111) downstream of valve (13)
.

(+12), one line (Ill) is connected to the passage (7) of the upper mold, and the other line (112) is connected to the passage (9) of the lower mold (3), so the air is will flow into each passage (?) and (9). The inflowing air is filled into the cavity (8) through the air vent (6) of the upper mold (2) and the air vent (10) of the lower mold, forming an initial hardened shell layer on the outermost part and hardening the surface. It is spray-fed onto sand whose inside hardening is insufficient. By the way, since the air is heated in the process of flowing through the passages (7) and (9) of the upper and lower molds (2) and (3), it is heated and is ejected into the cavity (8) in the form of hot air. As a result, the hot air reaches the inside of the filled sand surface. The surface of the filled shell sand is heated to form an initial hardening layer due to the mold temperature as described above, and the inside of the surface is heated by hot air, so it is heated from the inside ψ and outside, promoting heating and hardening at an early stage. becomes.

In this way, heating and hardening can be carried out quickly, and a shell mold can be obtained by sintering and hardening in a short time.

By the way, the air supplied to the passages (7) and (9) may be outside air at room temperature, but heaters (15) and (15) are attached to the lines (111) and (112) so that the air is supplied to the mold before being introduced into the mold. The air may be preheated or heated to a predetermined temperature.

Next, specific examples of the present invention will be described.

Blow pressure of shell sand (resin sand) 3kg/c++*
After 10 seconds, 5 kg/cm2 of compressed air was supplied into the mold cavity to obtain a shell mold having a sinter hardening thickness of 2 to 3 mm in 20 seconds.

On the other hand, the same type of shell sand was blown into the mold under the same conditions using the conventional method, and after 60 seconds, a shell mold having a sinter-hardened thickness of 2 to 3 mm was obtained.

That is, as is clear from the above, the same cured thickness can be obtained in 1/3 to 172 times less time than the conventional method, and the production efficiency can be improved by more than twice.

This also means that if a shell mold is obtained in the same amount of time, it is possible to obtain a shell mold with a hardened thickness more than twice as thick.

2 and 3 show an embodiment of the apparatus including the second aspect of the present invention.

FIG. 2 shows a plan view of the lower mold, in which a lower cavity (32) with a predetermined volume is located in the center of the lower mold (30), and the upper mold matching surface (
31).

The air passage (90) is as shown in Fig. 2 and has a cavity (32).
) is spaced from one side (32a) of the cavity and forms an introduction path parallel to the first passage (32a).
91) is formed so that one end is open (91a), and the other end (91b) of one passage (81) is formed to the outside of one end (32b) of the cavity (32), and is formed in the shape of a blind hole. One end (32b) of the cavity (32) is located outwardly from one end (32b).
A second passage (82) is provided such that the passage (91) crosses the end (91b) of the passage (91), and the second passage (82)
The opening is closed with a blind plug (93).

The second passage (82) is located at one end (32) of the cavity (32).
b) It is provided so as to be spaced apart from and parallel to the outer side, and extends to the outer side of the end (32b). Cavity (32
) A third passage (90) is provided on the outside of the other side (32c) parallel to and spaced apart from the third passage (90).
4) connects one end (s4a) to the other end (θ2) of the second passage (θ2).
θ2b), and the outer end (94a) is a blind plug (
85), and the third passageway (80 is closed by the cavity (32
) to the outside of the other end (32d).

The fourth passage (96) is located at the end (3) of the cavity (32).
2d), one end (138a) of the fourth passage (86) intersects and is connected to the other end (84b) of the third passage (84), End (98a
) is closed with a blind plug (87), a fourth passageway (86) is formed in the middle part, and one end of a connecting passageway (88) formed in the widthwise middle part of the bottom (32e) of the cavity (32). The tip portion (Hb) is cross-communicated with the portion (98a), and
) is a blind plug, and the other end (98b) of the passageway (98) is closed. This passageway (88) is connected to an air vent (10
0)... through the bottom (32e) of the cavity (32)
be communicated with.

In this way, the passage (90) is formed outside and below the cavity (32) so as to surround it. This allows the passage length to be set longer.

Figure 3 is a bottom view of the upper mold (20), in which a ring-shaped air vent (60) is provided at the center of the bottom (22e) of the upper cavity (22) that is open to the mold mating surface (2I). The passage (70) has a first passage (71) that opens on the - side of the mold (20), similar to the passage (90) described above, and a second passage (72) that bends at a right angle at the end and communicates with the first passage (71). ), a third passageway (70), which is bent at right angles at the end and communicates with the first passageway (71), and is parallel to the first passageway (71); , approximately 1 of the passage (72)
It consists of a fourth passage (76) with a length of Set.

The above upper mold (20) and lower mold (30) are molded together, shell sand is filled into the cavity through the blow head, and the shell sand is sintered and hardened at the temperature of the mold. Similarly, air is sent into the cavity from above and below. The aforementioned passages (70) and (1110) are connected to the aforementioned air supply line, and the pressurized air at room temperature is used as is.

The air introduced into the passages (70) and (90) of the molds (20) and (30) flows through the passages (70) and (90) because one passage (70) and (9G) is long as described above. In the process, it is sufficiently heated by the molds (20) and (30) and becomes hot air, which blows into the air vent (80).

From (1oo), it is ejected and supplied into the cavity and explodes. In this way, there is no need for an air heating device,
The air is heated by the heat of the mold, and since the passage is long, sufficiently heated air is supplied into the cavity, promoting sintering and hardening of the shell sand, and making it possible to obtain shell castings in a short time.

(Effects of the Invention) As detailed above, according to the present invention, when manufacturing a shell mold, hot air is blown into the shell sand at the same time as the temperature of the mold to harden it by firing. The surface of the sand with poor shell and the inside of the sand are simultaneously heated by the contact between the sand and the mold and the hot air, making it possible to manufacture molds with a predetermined hardening thickness in a much shorter time than in the past. It is possible to improve production efficiency and mass productivity, and thereby reduce costs, and the above can be achieved with a simple configuration in which hot air is blown into the cavity.

Further, according to the present invention, by providing a passage in the mold so as to surround the cavity, the length of the air passage can be increased, and therefore, even if room temperature air is used, sufficient and efficient heating can be achieved at the temperature of the mold. The air can be heated using a mold without the need for a dedicated heat source, simplifying the entire system.
Rationalization and further cost reduction can be achieved.

The present invention has many advantages as described above.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is an explanatory diagram including an apparatus for carrying out the method of the present invention, FIG. 2 is a plan view of a lower mold, and FIG. 3 is a plan view of an upper mold. It is a diagram. In the drawings, (2), (3), (20), and (30) are molds, and (8). (22), (32) are cavities, (7), (11
), (70), (90) are air passages, (8),
(10), (1110), and (100) are air supply ports.

Claims (1)

[Claims] 1. Shell sand is blown into a heated mold cavity, an initial fired hardened layer is formed on the surface of the mold, and then heated compressed air is supplied into the cavity. A method for manufacturing a shell mold, characterized in that firing is accelerated by heat from air. 2. A heating mold having a cavity for blowing and filling shell sand, an air supply port opening into the cavity for supplying compressed air into the cavity of the mold, and a connection between the supply port and the air supply source. an air supply passage provided in the mold to surround the cavity;