JPH09253793A - Method for molding sand mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the pressure of hardening gas in a gassing head and to eliminate unhardening of molding sand. SOLUTION: A molding method for a sand mold is constituted so as to harden the molding sand 40 in a metallic mold 10 by supplying the hardening gas into the inner part of the metallic mold 10 through the gassing head 20. In this case, the gas pressure supplied in the gassing head 20 is detected and the pressure in a supplying source of the hardening gas is controlled so that the gas pressure in the gassing head 20 always becomes a prescribed value based on this detected value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sand molding method of a type in which a molding gas blown in a mold is cured by passing a hardening gas such as triethylamine.

[0002]

2. Description of the Related Art A technique relating to this type of molding method is disclosed in, for example, Japanese Patent Publication No. Sho 63-22900. According to the technique disclosed in this publication, after molding sand is filled in the mold of the core molding machine for cold boxes, the curing gas generated by the gas generator is blown into the mold through the gassing head to cure the molding sand. I am letting you. Then, in order to keep the pressure of the curing gas supplied into the gassing head constant, generally, the compressed air pressure for forcibly sending the gas generated in the gas generator, that is, the pressure of the source of the curing gas is set to It is set constant with a pressure reducing valve.

[0003]

However, even if the pressure of the supply source is kept constant, the pressure of the hardening gas in the gassing head immediately before being supplied into the mold is often greatly reduced. The cause thereof is, for example, a pressure drop at the supply source due to consumption of a large amount of compressed air, or a flow resistance in the supply path from the pressure reducing valve to the gassing head.

Therefore, it is also practiced to set the pressure of the supply source to a high value in anticipation of a decrease in the gas pressure in the gassing head. However, in this case, if the gas pressure in the gassing head becomes higher than the expected value due to clogging of the mold vent (the part that extracts gas from the molding sand in the mold), the seal between the gassing head and the mold Gas leakage from the parts easily occurs, and eventually the gas pressure in the gassing head decreases. As described above, in any of these phenomena, the supply pressure of the hardening gas to the molding sand becomes insufficient due to the decrease of the gas pressure supplied into the mold, which causes a problem that the molding sand is not hardened.

An object of the present invention is to stabilize the pressure of the hardening gas in the gassing head and eliminate the uncured molding sand. Another object of the present invention is to be able to deal with a situation that cannot be dealt with only by controlling the pressure of the supply source, such as gas leakage in the curing gas supply path or clogging of the vent in the mold. Is.

[0006]

A first aspect of the present invention is a sand molding method for curing molding sand in a mold by supplying a hardening gas into the mold through a gassing head.
Detecting the gas pressure of the curing gas supplied into the gassing head, and controlling the pressure of the source of the curing gas so that the gas pressure in the gassing head is always a predetermined value based on the detected value. Is characterized by. Therefore, the pressure of the hardening gas in the gassing head immediately before being supplied into the mold is stabilized, and as a result, the amount of the hardening gas supplied to the molding sand is stabilized and uncured molding sand is eliminated. It

A second aspect of the present invention is a sand mold making method for hardening a molding sand in a mold by supplying a hardening gas into the mold through a gassing head, wherein the hardening gas is supplied in the gassing head. Obtain the detected value that becomes the element and the detected value that becomes the supply element at the source of the curing gas, and supply the curing gas into the mold when the difference between these detected values deviates from the specified range. It is characterized by treating as an abnormal amount. Due to this, gas leakage in the supply path from the supply source of the curing gas to the gassing head,
Alternatively, an abnormality that cannot be dealt with only by controlling the pressure of the supply source such as clogging of the mold vent can be promptly detected. By promptly detecting gas leaks and coping with them, the amount of curing gas used can be reduced, and the cycle time of molding work can be shortened.

A third invention is characterized in that, in the sand molding method of the second invention, the detection values serving as the respective supply elements in the gassing head and at the supply source of the hardening gas are pressure values. In this way, determining whether or not the supply amount is normal by the pressure difference of the curing gas in the gassing head and the supply source is easy to obtain the determination accuracy,
Moreover, the detection means is also easy.

A fourth invention is characterized in that, in the sand molding method of the second invention, the detection values serving as respective supply elements in the gassing head and at the supply source of the hardening gas are flow velocity values. The flow velocity value can be easily detected by general means.

[0010]

Embodiments of the present invention will be described below. Embodiment 1 FIG. 1 is an explanatory diagram showing an outline of a sand molding system using a cold box method. In this drawing, a mold 10 including an upper mold 10A and a lower mold 10B is provided on the upper surface of the surface plate 12.
Has been posted. Inside of this mold 10 (cavity)
The molding sand 40 filled in the mold is blown into the mold 10 through the inlets 14 of the upper mold 10A by the blow head (not shown) in the previous step. Lower mold 10
B is provided with a plurality of vents 16, and these vents 16 communicate with the pipes 19 of the surface plate 12 through the outlets 18 of the lower mold 10B.

On the upper surface of the die 10 (upper die 10A),
The gassing head 20 is attached so as to cover each of the inlets 14 described above. The joint surface between the die 10 and the gassing head 20 is kept airtight by a seal 22. A curing gas (triethylamine gas or the like) that causes a curing reaction with respect to the molding sand 40 is supplied to the inside of the gassing head 20 as described below. Is equipped with a pressure sensor 24 capable of detecting the gas pressure.

Compressed air is fed into the gassing head 20 from the air supply pipe 30 to the gas generator 34, so that the hardening gas generated in the gas generator 34 is changed by the pressure of the compressed air. Gas supply pipe 36
Will be supplied through. A pressure reducing valve 32 is provided in the air supply pipe 30, and the pressure reducing valve 32 is controlled based on a control signal from a control device 26 to adjust the pressure of the compressed air, that is, the pressure of the curing gas supply source. You can do it.

When molding the sand mold, the gassing head 20 is passed from the gas generator 34 through the gas supply pipe 36.
The curing gas supplied to the inside of the mold flows into the inside of the mold 10 through the respective inlets of the upper mold 10A. This curing gas is used for the mold 10.
By passing through the molding sand 40 inside, the molding sand 40 obtained by coating silica sand with a phenol resin or the like undergoes a curing reaction to mold a sand mold such as a core. The hardening gas that has passed through the molding sand 40 flows out of the pipe 19 through the vent 16 of the lower mold 10B.

To prevent the molding sand 40 from being uncured,
It is required that the hardening gas be uniformly passed through the molding sand 40 and the hardening speed be uniform. Therefore, it is important to stabilize the amount of the hardening gas supplied to the molding sand 40.
Therefore, the pressure of the curing gas in the gassing head 20 immediately before being supplied into the mold 10 is detected by the pressure sensor 24, and the detection signal is transmitted to the control device 26. A control signal corresponding to this detection signal is sent from the control device 26 to the control circuit of the pressure reducing valve 32, and the pressure of the supply source of the curing gas is controlled by the control of the pressure reducing valve 32 based on this signal. Therefore, the pressure of the hardening gas in the gassing head 20 is always stable, and as a result, the supply amount of the hardening gas to the molding sand 40 is stable.

Embodiment 2 FIG. 2 is an explanatory view showing a sand molding system according to Embodiment 2. In this embodiment, the pressure sensor 24 detects the pressure of the curing gas in the gassing head 20, and the pressure sensor 52 also detects the pressure of the air supply pipe 30, which is the supply source of the curing gas. The detection signals of the two pressure sensors 24 and 52 are respectively sent to the control device 50, and the control device 50 determines the difference between the individual detection values and determines whether or not the difference is within a predetermined range. To do. When the difference between the detected values is out of the predetermined range, it is warned that there is an abnormality, or the molding operation is stopped.

When gas leak occurs from the inside of the gassing head 20 which is the supply path of the hardening gas due to the damage of the seal 22 or the like, the gassing head 2 is thereby leaked.
Although the pressure in 0 decreases, the pressure in the air supply pipe 30 is kept substantially constant. Therefore, the difference between the detection values based on the detection signals of both the pressure sensors 24 and 52 becomes abnormally large. When the vent 16 of the mold 10 is clogged, the hardening speed of the molding sand 40 is remarkably slowed and the molding sand 40 is likely to be uncured. And in this case, contrary to the above case, both pressure sensors 24,
The difference in the detected value by 52 becomes abnormally small. When such a situation occurs, for example, by stopping the work, it becomes possible to deal with an abnormality that cannot be dealt with in the first embodiment.

When the pressure inside the gassing head 20 rises abnormally, the balance between the internal pressure and the tightening force of the clamp (not shown) that presses the gassing head 20 against the mold 10 is lost. Gas leakage from the gassing head 20 may occur. The gas leakage from the gassing head 20 causes not only insufficient supply of the hardening gas to the molding sand 40, but also hardening of the sand in the blow head for blowing the molding sand 40 into the mold 10 or work. It causes the environment to deteriorate. The second embodiment can easily deal with such a situation.

In the second embodiment, the difference between the pressure in the gassing head 20 and the pressure in the air supply pipe 30 is obtained. In other words, this is the pressure in the gas generator 34 and the gas supply pipe 36. The loss is being measured.
Since this pressure loss is generally in proportion to the flow rate of the supply gas, the gas flow velocity can be predicted by obtaining the pressure difference. Further, as shown in FIG. 3, in place of the pressure sensors 24 and 52, the flow velocity measuring device 6 is provided in the gas supply pipe 36 and the air supply pipe 30, respectively.
By providing 0 and 62, it is also possible to directly detect the gas flow velocity in the gassing head 20 and the air supply pipe 30.

[0019]

Industrial Applicability According to the present invention, the pressure of the hardening gas supplied into the mold can be stabilized to eliminate the uncured molding sand.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an outline of a sand molding system using a cold box method.

FIG. 2 is an explanatory diagram showing a sand molding system according to a second embodiment.

FIG. 3 is an explanatory view of a sand molding system showing a modified example of FIG. 2.

[Explanation of symbols]

 10 Mold 20 Gassing Head 40 Mold Sand

Claims (4)

[Claims] 1. In a sand mold molding method for hardening molding sand in a mold by supplying a hardening gas into the mold through a gassing head, a gas of a hardening gas supplied into the gassing head. A sand molding method characterized by detecting a pressure and controlling a pressure of a supply source of a hardening gas so that a gas pressure in a gassing head always becomes a predetermined value based on the detected value. 2. A sand mold molding method for hardening a molding sand in a mold by supplying a hardening gas into the mold through a gassing head, and a hardening gas supply element in the gassing head. And the detection value which is also a supply element at the source of the curing gas, and when the difference between these detection values deviates from the predetermined range, the supply amount of the curing gas into the mold is A sand molding method characterized by treating as abnormal. 3. The sand molding method according to claim 2, wherein
A sand molding method, wherein the detection values serving as respective supply elements in the gassing head and at the supply source of the curing gas are pressure values. 4. The sand molding method according to claim 2, wherein
A sand molding method, wherein the detection values serving as the respective supply elements in the gassing head and the supply source of the curing gas are flow velocity values.