JPH04262833A - Method and device for producing shell mold - Google Patents

Abstract

PURPOSE: To enable a uniform temp. distribution and to enable uniform and perfect curing by spraying a resin to the surface of a shell mold formed with highly hot air for perfect curing by melting the resin. CONSTITUTION: A sand-resin mixture is first placed on a heated pattern plate 3. A heat hood 11 is then lowered onto this pattern plate 3 and is put on the resin-sand layer, i.e., sand shell, existing on the pattern plate 3 concurrently therewith. In such a case, rails 12 connected with the heat hood 11 are lowered along rollers 15 until a hand-over port 18 and a receiving port 19 are aligned to each other and form a continuous highly hot air route. A highly hot air generator 16 is thus operated to blow the highly hot air via pipelines 17, 18, 19, 13 into the heat hood 11. The highly hot air is distributed to the entire part of the hood chamber by a baffle plate 14 at the time of blowing the same and, therefore, the highly hot air is evenly blown to the sand shell surface on the pattern plate 3. As a result, the uniform melting of the resin and the curing to the hard and infusible rigid state are induced.

Description

[Detailed description of the invention]

0001

[Industrial Technical Field] The present invention involves placing a mixture of sand and resin on a hot model board, melting the resin to form a shell mold of a desired thickness, and then removing excess sand. The present invention relates to a shell mold manufacturing method and a shell mold manufacturing apparatus having a high-heat model plate.

0002

2. Description of the Related Art In the shell method (cloning method), a mixture of powdered dry sand and resin is placed on a hot model board. When the sand-resin mixture comes into contact with the hot model board, the resin melts and transitions from the resol state (A stage) to the resitor state (B stage). Heating of the sand progresses outward from the model plate. After a period of time corresponding to the desired shell thickness, the unused sand-resin mixture is removed, so that the sand shell (sand mask) in the resitor state remains on the model board with the desired thickness. Following this, the sand shell is post-cured, which transfers the resin to a hard, infusible resit state (C-stage), which is then demolded from the model board. Post-curing is performed by heating the model board by gas heating using a gas heating element or an electric heating element such as a spiral wire placed above the sand shell, which radiates heat to the sand shell, or by thermal radiation. This is done by applying heat to the side of the sand shell that is away from the sand shell. In this case, depending on the distance between the heating device and the sand shell area, completely non-uniform heating occurs in different areas of the sand shell. A surface to be treated that is arranged at a relatively strong inclination with respect to the heating plane also suffers from heating defects. This is because the incident heat per unit area is smaller than in a sand shell area arranged parallel to the heating plane.

0003

SUMMARY OF THE INVENTION It is an object of the present invention to avoid the above-mentioned drawbacks of the prior art and to load the sand shell evenly with heat, thereby achieving uniform and complete hardening.

0004

[Means for Solving the Problems] The constituent means of the present invention for solving the above-mentioned problems is to blow high-temperature air onto the formed shell-shaped surface to melt the resin and completely cure it, so that the temperature is uniform. The point is to enable distribution.

According to the invention, the sand shell is heated not by thermal irradiation of the sand shell, but by heat transfer to the sand shell via air supplied to the sand shell, in short by convection, particularly preferably by forced convection. By transferring heat to the shell, a uniform heating of the sand shell is obtained, independent of the level of the individual shell sections or independent of the orientation of the individual shell sections with respect to a reference plane.

[0006] In an advantageous method of the invention, a sufficiently closed space is created above the shell mold before blowing with hot air.

The device for producing shell molds according to the invention is particularly advantageously constructed in such a way that the hot air generator is or can be connected via a conduit to a heat hood which is brought above the model board. ing. If the heat hood for heating is to be placed as directly above the model board as possible, the heat hood must be moved away from the model board in order to charge the sand-resin mixture. In such cases the conduit may be a flexible hose, such as a corrugated hose. However, the prerequisite in this case is that the hose has a temperature of 220° to 4°C, which is required for processing depending on the resin used.
It is made of material that can withstand temperatures of 00°C. In an advantageous embodiment, the connection between the hot air generator and the heat hood has separable, insulated tube sections, which are arranged in the lower part of the heat hood onto the model board. to form a consistently continuous connection for the sometimes hot air. Moreover, the end surfaces of the tube section are configured to be inclined with respect to a perpendicular line drawn on the axis of the tube section, so that the end surfaces can be moved into contact with each other until the tube sections are connected airtightly. It is particularly advantageous to do so.

[0008]

Embodiments Next, embodiments of the present invention will be explained in detail based on the drawings.

The device according to the invention has a frame 1 in a known manner, which supports a support 2 for a model board 3 (FIG. 2) as well as a sand hood 4. The support body 2
and the sand hood 4 are pivotally connected to each other by a shaft 6, so that both can be used for charging the mixture of sand and resin onto the model board 3 and for shaking out excess sand into the sand hood 4. They can be closed by mutually pivoting around axis 6 to return them. The support 2 has a lower heater for heating the model plate 3. Further, a charging sand hopper 7 is arranged on the frame 1, and since the charging sand hopper is located above the opening of the sand hood 4 in the open position, the sand-resin mixture is released from the charging sand hopper 7. It can be loaded into the sand hood 4.

Furthermore, two rails 8 are laid on the frame 1 and extend parallel to each other at approximately the height of the charging sand hopper 7, and a carriage 9 for the heat hood 11 runs horizontally on the rails. It is possible to travel in the direction. The carriage 9 has a plurality of rollers 15 along which a heat hood 11 can be raised and lowered by a vertical rail 12 connected to the heat hood. heat hood 1
A supply air connection pipe 13 is attached to the upper side of 1. A baffle plate 14a is arranged below the opening 14 of the supply air connection pipe 13, and the baffle plate allows the supply air connection pipe 1
The hot air supplied through the heat hood 11 is distributed over the entire surface of the heat hood 11.

A high-temperature air generator 16 is installed on the side of the frame 1.
The high-temperature air generator has a discharge pipe 17, and the discharge pipe is guided to the running space side of the heat hood 11 and has a delivery port 18 therein, and the delivery port is provided with a heat transfer port 18. When the hood 11 is lowered onto the model board 3, it cooperates with the receiving opening 19 of the supply air connection pipe 13. For this purpose, the end face of the delivery port 18 and the end face of the receiving port 19 are similarly inclined, and the upper range of the delivery port 18 is set back from the lower range of the delivery port, in other words, it is shortened. The lowering of the heat hood 11 and the associated lowering of the supply air connecting pipe 13 and its receiving port 19 causes the receiving port 19 to slide along the delivery port 18, and the periphery of the receiving port comes into close contact with the periphery of the delivery port 18. Thus, a continuous high-temperature air path is created from the high-temperature air generator 16 to the interior of the heat hood 11 via the discharge pipe 17, the delivery port 18, the receiving port 19, and the supply air connection pipe 13.

First, a sand-resin mixture is placed on a heated model board 3 in a known manner. For this purpose, sand is loaded into the sand hood 4 from a charging sand hopper 7 . The support 2 for the model board 3 and the sand hood 4 are closed by pivoting around an axis 6. A further swirl transfers the sand-resin mixture onto the model board 3. The resin softens and binds a certain layer of sand on the model board 3. Following this, the support 2 and the sand hood 4 are opened, and excess sand and resin remain in the sand hood 4. Next, heat hood 11
is lowered onto the model plate 3 and thereby overlies the resin-sand layer or sand shell located on the model plate 3. In this case, the rail 12 coupled to the heat hood 11 is operated until the delivery port 18 and the receiving port 19 are aligned with each other to form the continuous high-temperature air path.
It is lowered along rollers 15. In this way, the high-temperature air generator 16 is activated, and the high-temperature air is supplied to the pipes 17, 18, 1.
The air is blown into the heat hood 11 via the air filters 9 and 13. Since the high-temperature air is distributed throughout the hood chamber by the baffle plate 14 during blowing, the high-temperature air is evenly blown onto the sand shell surface on the model board 3. This results in extremely uniform melting of the resin and a hard, infusible resin state (C
hardening occurs.

After the desired curing time, the heat hood 1
1 is lifted again and then the sand shell or sand mask is lifted from the model plate 3 and combined with other shell mold parts as a shell mold part to form a complete shell mold for casting the desired part. Can be done.

[Brief explanation of the drawing]

1 shows a first side view of an apparatus for carrying out the method of the invention; FIG.

FIG. 2 is a second side view shown shifted by 90 degrees with respect to FIG. 1;

[Explanation of symbols]

Claims (7)

[Claims] Claim 1: A shell mold in which a mixture of sand and resin is placed on a hot model plate, the resin is melted to form a shell mold of a desired thickness, and excess sand is removed. In the manufacturing method, high-temperature air is blown onto the formed shell-shaped surface in order to melt and completely cure the resin.
Shell-shaped manufacturing method, characterized by allowing uniform temperature distribution. 2. The manufacturing method according to claim 1, wherein a sufficiently closed space is formed above the shell mold before blowing the hot air. 3. A shell mold manufacturing apparatus having a high-temperature model plate, characterized in that the apparatus is equipped with a high-temperature air generator. 4. A heat hood (
4. The shell mold manufacturing apparatus according to claim 3, wherein the shell mold manufacturing apparatus is connected to or can be connected to 11). [Claim 5] The heat hood (11) is a model plate (3).
5. The shell mold manufacturing apparatus according to claim 4, wherein the shell mold manufacturing apparatus is capable of being lowered onto. 6. The connection between the hot air generator (16) and the heat hood (11) has a plurality of separable tube sections (17, 18; 19, 13), and the plurality of tube sections (17, 18; 19, 13) 6. Apparatus for making shell molds according to claim 4, wherein the sections form a continuous connection for hot air during lowering of the heat hood (11) onto the model plate (3). 7. An end surface (18;
19) is formed obliquely with respect to a perpendicular line drawn on the axis of the tube section, and the two end surfaces move into contact with each other until the tube sections (17; 13) are connected airtightly. The shell mold manufacturing apparatus according to claim 6, which is possible.