JPS60212308A - Vacuum casting method - Google Patents

Abstract

PURPOSE:To prevent resin from flowing out of a casting mold in time of vacuum casting by a method wherein a decompression container of flexible material is brought in contact with a casting mold by the use of the deformation of the decompression container of flexible material in time of decompression. CONSTITUTION:A casting mold 15 is located in a decompression container 11, vacuumized through exhaust holes 13, 14 and the decompression container of flexible material like sheet is deformed and compressed by atmospheric pressure and stuck closely so as to surround the circumference of the casting mold. The outer and the inner part of the casting mold are reduced in pressure and the circumference of the casting mold becomes nearly free from spaces and enables vacuum casting. Then, thermosetting resin is injected through the injecting inlet 12 and vacuum-cast.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a support insulator, a bushing, and a spacer.

The present invention relates to a method of vacuum casting a thermosetting resin using a mold in order to manufacture or insulate parts used mainly in electrical and electronic equipment, such as transformer coils, transformer coils, rotating machine coils, and semiconductor parts lists.

[Prior art and its problems]

In order to manufacture or insulate the above-mentioned support insulators or semiconductor parts (hereinafter referred to as resin cast products), a mold for resin cast products is installed in a vacuum container, and an oil rotary vacuum pump or other pump is used to evacuate the product. The method of driving a device to reduce the pressure inside a vacuum container and then vacuum-casting a thermosetting resin is well known as one of the important manufacturing methods for resin castings.

The reduced pressure containers conventionally used for vacuum casting are generally cylindrical or box-shaped metal containers, and their construction will be schematically explained with reference to FIGS. 3 and 4. FIG. 3 shows a box-shaped vacuum container, and FIG. 4 shows a cylindrical vacuum container. It is generally composed of a container 1, a resin injection hole 2, a vacuum exhaust hole 3, a peephole 4, etc., and 5 is a casting mold installed inside the reduced pressure container. In the conventional vacuum casting method using these vacuum containers, the casting mold 5 is first placed in the vacuum container, and then an exhaust device such as an oil rotary vacuum pump is driven to evacuate the inside of the container from the vacuum exhaust hole 3. Then, at the same time as K, the inside of the open casting mold was also evacuated, and! A fixed amount of thermosetting resin is injected from the resin injection hole 2 depending on the size of the casting mold, and the remaining gas in the injected thermosetting resin is used to create air bubbles in a part of the resin casting. In order to prevent this from occurring, the general procedure is to perform sufficient vacuum defoaming, then break the vacuum in the reduced pressure container and return to normal pressure to complete the process.

However, in the vacuum casting method using such a reduced pressure container, during the vacuum casting process, for example, during the assembly process of the casting mold, foreign matter such as Paris may be accidentally caught in the seam of the mold. If an assembled casting mold is used, or a casting mold that has been assembled as it is with a part of the backing such as an O-ring used to prevent resin leakage being damaged or missing, In the step of vacuum injecting or vacuum defoaming the thermosetting resin, a problem arises in that the resin flows out from the seam of the casting mold.

In this case, even if resin leakage is discovered through the observation window 4, no proactive measures can be taken than to break the vacuum in the depressurized container each time and take out the casting mold that caused the resin leakage. If the leak is on the back side of the casting mold that can be seen through the peephole, the discovery of the resin leak may be delayed.
It also has a major drawback in that a large amount of resin leaks into the vacuum container, and the reality is that this often causes delays in processes, internal disturbances, and losses due to defects.

[Purpose of the invention]

In view of the above-mentioned drawbacks of the prior art, the present invention aims to provide an extremely meaningful vacuum casting method that allows vacuum casting to be performed effectively and without waste even if there is a defect in the resin leakage prevention mechanism of the casting mold. It is.

[Key points of the invention]

That is, 1. The present invention does not consist of a rigid body that does not generally deform the decompressed container itself when the inside is evacuated as in the past, but the container is constructed of a rigid body such as a sheet material or an elastic body when the inside is evacuated. At least a part of the vacuum container is made of a flexible material that can be easily deformed inward and reduced in volume due to external pressure, and the vacuum container can be made into a cast mold due to the deformation when the pressure is reduced. By bringing the resin into contact with the mold, it is possible to prevent the resin from flowing out of the mold during vacuum casting.

[Embodiments of the invention]

The vacuum casting method according to the present invention will be explained below with reference to the drawings.

1(a) to 1(C) show a first embodiment of the present invention, in which 11 is a vacuum container made of a sheet-like flexible material, and 15 is installed inside the vacuum container. It is a cast mold. 16 is a resin pot attached to the casting mold; 17
18 is a flange, and 14 is an exhaust hole of the vacuum container.

To explain the vacuum casting procedure in this embodiment, first, the casting mold 15 is installed in the reduced pressure container 11, and then an exhaust device such as an oil rotary vacuum pump is driven, and the injection is performed through the exhaust holes 13 and 14. Vacuum the mold and vacuum container. By this operation, the reduced pressure container made of a sheet-like flexible material is deformed and compressed by the atmospheric pressure, and as shown in FIG. 1(b), it tightly covers the periphery of the casting mold with almost no gaps. At this time, the parts that cannot be tightly attached to the periphery of the casting mold are caused by the containers themselves coming into close contact with each other, so that the parts of the casting mold as a whole are
While the outside pressure remains reduced, a state is created in which vacuum casting is possible with almost no space around the casting mold.

Next, a thermosetting resin is injected through the injection hole 12, and sufficient defoaming is performed to complete the vacuum casting.

In this embodiment, the vacuum container does not necessarily have to be made entirely of a sheet-like flexible material, but it is possible to use such material as long as the part of this material comes into contact with the seam of the casting mold. In a casting mold where the resin leakage prevention function of the part is activated, the purpose may not be achieved and the injected resin may leak out due to particles or other foreign objects being caught in the mold or a malfunction of the backing such as an O-ring. This method also has the advantage that by evacuating the inside of the container, the sheet-like flexible material is firmly adhered to the periphery of the relevant part of the casting mold, thereby preventing resin from flowing out.

FIGS. 2(a) to 2(C) show a second embodiment of the present invention, in which 21 is a vacuum container made of an elastic material.

22 is an injection hole, 23.24 is an exhaust hole, 25 is a casting mold, 2
6 is a resin pot.

To explain the vacuum casting procedure in this example, first, the casting mold 25 is installed inside the vacuum container 21 so that the seam part of the casting mold faces the thin part of the vacuum container, and then An exhaust device such as a vacuum pump is driven to evacuate the inside of the casting mold 25 and the reduced pressure container 21 through the exhaust holes 23 and 24 . As a result, the decompression container made of an elastic material is compressed and deformed by atmospheric pressure, and in particular, the parts that are thinner than other parts are deformed more greatly, and the seam part of the casting mold is strongly compressed.

Therefore, while resin is injected into the casting mold and vacuum degassing is performed, resin is prevented from flowing out from the seam part of the casting mold, even if the mold has a defective resin outflow prevention mechanism. It has the same advantages as the first embodiment.

The sheet-like flexible material and elastic body used in the reduced pressure container according to the present invention are plastic sheets.

Rubber sheets, rubber elastic bodies, etc. are used, but it goes without saying that any material may be used as long as it meets the purpose.

〔Effect of the invention〕

In the present invention, not only the great effect of preventing the resin from flowing out as described above can be obtained, but also various advantages can be enjoyed.

For example, if a transparent material is used as the sheet-like flexible material or elastic material used in the vacuum container of the present invention, it will be possible to cover the entire circumference of the casting mold without a special viewing window as in the vacuum container of the prior art. Not only does it allow you to observe the situation, but it also has the great advantage of not being restricted in your field of view like a peephole.

In addition, if the material used for the vacuum container is a material that does not adhere to the thermosetting resin to be injected, such as polyethylene, tetrafluoroethylene, silicone rubber, etc., the resin attached to the vacuum container can be easily removed. This makes it possible to simplify maintenance.

Furthermore, the vacuum container according to the present invention can be easily manufactured to match the size of the casting mold, etc., compared to the vacuum container of the prior art, and therefore it is possible to reduce wasted space of the vacuum container. As a result, the evacuation time and return time to the atmosphere can be shortened, a large-capacity vacuum evacuation device is not required, and the decompression vessel itself can be manufactured at low cost. The economic effects on manufacturing processes and equipment are significant.

[Brief explanation of drawings]

FIG. 1(a), FIG. 1(b), and FIG. 1(C) are a longitudinal cross-sectional view before evacuation, a longitudinal cross-sectional view after evacuation, and a transverse cross-sectional view, respectively, in one embodiment of the present invention. Adashi,
FIG. 2(a), FIG. 2(b), and FIG. 2(C) are a longitudinal cross-sectional view before evacuation, a longitudinal cross-sectional view after evacuation, and a cross-sectional view, respectively, in other embodiments of the present invention. FIG. 3 and FIG. 4 are cross-sectional views of the conventional device. 11.21...Reduced pressure container, 12.22...Injection hole,
13.14;23,24...Exhaust hole, 15,25...
・° Casting mold, 16.26...Resin pot. Age 1 (2) (Figure 1 (b) Age 10 (S)

Claims (1)

[Claims] 1) Vacuum the inside of m, and after 9 days, W! In the method of injecting resin into the container, if the inside is depressurized as a vacuum container, the K
A vacuum casting method characterized by using a container made of a flexible or elastic material, at least a portion of which can be easily deformed. 2. In the casting method described in claim 1. A vacuum casting method characterized in that the vacuum container is made of a flexible material or an elastic material that can be easily deformed at least at the seam portion of the mold.