JPH06293035A - Vacuum mold - Google Patents

Abstract

PURPOSE:To obtain a vacuum mold which prevents development of leakage into vacuum and can make cast material of high reliability by providing a mold release means for the cast material in one of the divided molds and by forming a vacuum chamber which is capable of expansion and contraction around the mold release means. CONSTITUTION:Metal molds 1a and 1b that have been divided in two are respectively connected to cylinders 2a and 2b of a clamping device, and the molds 1a and 1b opens or closes by operation of the cylinders 2a and 2b. Rubber packing 3 is provided at parting lines of the molds 1a and 1b to seal vacuum from leakage when the inside of the metal molds 1a and 1b is vacuum. When molds 1a and 1b are opened after completion of the primary setting, the metal mold 1a where a cast material 4 obtained by pouring into a bung hole 4a always remains is provided with knockout pins 5, and the inside face of the metal mold 1a and the ends of the pins 5 always remain at their meeting position except the time release of the cast material 4. The space between the pins 5 and the metal mold 1a is provided with rubber packings 6, and when epoxy resin is poured into the molds 1a and 1b, leakage of the epoxy resin is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum mold applied, for example, for pressure gelation.

[0002]

2. Description of the Related Art Generally, electric equipment used at high voltage and large current is generally produced by epoxy resin casting. Such epoxy resin casting products (hereinafter referred to as casting products) generally have excellent electrical and mechanical properties, and in order to exhibit these excellent properties, it is necessary to secure a particularly electrical life. It is important to prevent partial discharge during use of the equipment.

By the way, if minute voids exist in the epoxy resin portion of the cast product, the electric field concentrates on the void portions, and partial discharge easily occurs. Therefore, the vacuum casting method is used when the epoxy resin is cast in an electric device used at a high voltage. In this case, in recent years, a pressure gelation method has been applied in which a high quality and highly reliable cast product can be manufactured and mass production is possible. In this pressure gelation method, the temperature of the mold is raised by several steps as compared with the case of the general casting method, and the epoxy resin injected into the mold is cured in a short time.

The mold used in this pressure gelation method is generally attached to a clamping device in two parts and opened and closed by the clamping device. Also, when the primary curing of the cast material is completed and the mold is opened, one mold is deeply dug so that the cast material always remains in one mold. To occupy.

On the other hand, when releasing the cast material after the primary curing is completed in the mold, the mold is opened by a clamping device, and the knockout pin provided in the die where the cast material remains is the cast material. Is pushing up. Further, a rubber packing is attached to a sliding portion between the die and the knockout pin so as not to cause a vacuum leak.

[0006]

As described above, when an electric device used at a high voltage is cast with an epoxy resin,
In order to prevent minute voids from existing in the epoxy resin portion of the cast product, it is essential to evacuate the mold when injecting the epoxy resin into the mold.

However, if an attempt is made to evacuate the pressure gelling die, vacuum leakage may occur due to wear of the rubber packing provided at the sliding portion between the die and the knockout pin. If there is this vacuum leak, minute voids will occur in the epoxy resin portion of the casting. When the minute voids are generated, electric field concentration occurs and partial discharge occurs, which may induce dielectric breakdown. An object of the present invention is to provide a vacuum mold that can prevent a vacuum leak and can obtain a highly reliable cast product.

[0008]

In order to achieve the above object, the present invention provides a mold releasing means for releasing a cast product obtained by casting a resin in one of the divided molds. Since the expandable and contractible vacuum chamber is formed around the mold releasing means, even if the sliding part of the mold releasing means is defective, the vacuum does not leak and the normal vacuum degree can be maintained. it can.

[0009]

EXAMPLE An example of the vacuum mold of the present invention will be described below. FIG. 1 is a cross-sectional view of a vacuum mold for pressure gelation showing an embodiment of the present invention, showing a state in which two molds are combined by a clamping device.

In FIG. 1, the molds 1a, 1 divided into two parts.
b is connected to cylinders 2a and 2b of the clamping device, respectively, and by moving the cylinders 2a and 2b, the halves of the molds 1a and 1b are opened and closed. Also, mold 1
A rubber packing 3 is provided at the joint between a and 1b so as not to cause a vacuum leak from the joint between the molds 1a and 1b when the inside of the molds 1a and 1b is evacuated.

Further, when the molds 1a and 1b are opened after the completion of the primary curing, the casting 1 obtained by injecting the resin from the resin injection port 4a is always left, and the mold 1a is provided with a knockout pin 5. The inner surface of the mold 1a and the tip of the knockout pin 5 are always in the same position except when the casting 4 is released. A rubber packing 6 is provided between the knockout pin 5 and the mold 1a to prevent the epoxy resin from leaking when the epoxy resin is injected into the molds 1a and 1b.

On the other hand, a vacuum chamber composed of a metal plate 7 and a bellows 8 is provided on the outer side of the die 1a of the knockout pin 5. This vacuum chamber is fixed to the knockout pin 5 and the mold 1a by welding or the like so that the vacuum does not leak. In addition, a vacuum pump (not shown) for evacuating the molds 1a, 1b through the pipe 9 and the molds 1a, 1b.
1b, which is connected to a pipe 10 that connects with 1b.
The inside and the vacuum chamber have the same degree of vacuum.

On the other hand, the mold 1b is provided with a stop valve 11 which prevents the epoxy resin from entering the vacuum pump. Further, FIG. 2 shows a state where the casting 4 is released. In the figure, the molds 1a and 1b are opened by the cylinders 2a and 2b of the clamping device, and the knockout pin 5 connected to the other cylinder 12 has the cylinder 12a.
The mold 4 is pushed by to release the casting 4 from the mold 1a. At that time, the vacuum chamber composed of the metal plate 7 and the bellows 8 is expanded and contracted by the bellows 8 in accordance with the movement of the knockout pin 5.

Therefore, even if the rubber packing 6 is worn due to the sliding of the knockout pin 5, a vacuum chamber having the same degree of vacuum as in the molds 1a and 1b is provided outside the mold 1a of the knockout pin 5. Therefore, the vacuum leak does not occur, and the cast product cast is highly reliable without voids.

[0015]

As described above, according to the present invention, the mold releasing means for releasing the cast material obtained by casting the resin is provided on one of the divided molds, and the mold releasing means is provided around the mold releasing means. Since the expandable and contractible vacuum chamber is formed, it is possible to obtain a vacuum mold in which the occurrence of vacuum leakage is prevented and a highly reliable cast product is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a vacuum mold showing an embodiment of the present invention.

FIG. 2 is a view showing a releasing state of FIG.

[Explanation of symbols]

1a, 1b ... Mold, 5 ... Knockout pin, 7 ... Metal plate, 8 ... Bellows, 9, 10 ... Piping.

Claims (2)

[Claims] 1. A mold releasing means for releasing a cast product obtained by casting a resin is provided on one of the divided molds, and an expandable vacuum chamber is formed around the mold releasing means. A vacuum mold characterized by that. 2. The vacuum mold according to claim 1, wherein the vacuum chamber is connected to a vacuum pump that evacuates the mold.