JPH0731329U - In-mold vacuum device - Google Patents

Abstract

(57) [Abstract] [Purpose] In mold clamping work of an injection molding machine, a closed chamber is formed around the mold before the mold is clamped, and the closed chamber is evacuated to obtain a mold in a vacuum state. Complete the tightening. [Structure] In a mold clamping device of an injection molding machine, a movable platen 2 is brought close to a stationary platen 1 in order to clamp a mold. By operating the vacuum cover 3 together with the operation of the movable platen 2, the closed chamber A is formed so as to cover the fixed mold 5 and the movable mold 4. At the time of forming the closed chamber A, since the fixed mold 5 and the movable mold 4 have not been clamped in the closed chamber A, the cavity surface is exposed. When the inside of the closed chamber A is evacuated, the fixed mold 5 and the movable mold 4 are placed under vacuum. Further, the movable platen 2 is advanced toward the fixed platen 1 to complete the mold clamping.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement of an in-mold vacuum drawing device.

[0002]

[Prior art]

 The injection molding of rubber will be described as an example. In an injection molding machine, the inside of the mold is usually tightly closed, so when the molten resin is filled in the cavity, the enclosed air is adiabatically compressed and instantly becomes hot, causing burns or gas. As a result, the molten resin is insufficiently filled and the gloss of the product is obstructed, resulting in poor appearance of the molded product. In rubber injection molding, this effect becomes noticeable, causing blistering and burning troubles.

[0003] Therefore, there has conventionally been a method of making a vacuum in a mold (referred to as vacuuming) to solve the problem of the appearance defect of a molded product caused by the air contained in the mold. It was An apparatus using this method is said to have a hole for vacuum evacuation in the mold, and after completing the mold clamping, the air in the mold cavity is evacuated from the hole provided in the mold to fill the mold with molten resin. It was a thing.

[0004]

[Issues to be solved by the device]

 With the conventional in-mold vacuuming device, vacuuming is performed after mold clamping.Therefore, if there is a complicated part in the shape of the mold cavity that is formed by mold clamping, it will be sufficiently vacuumed. However, the residual air in the mold caused a defective appearance of the molded product, and the above problems could not be completely solved.

The present invention has been made in view of the above problems, and when a movable mold of an injection molding machine is brought close to a fixed mold, a sealed chamber is formed around the mold before the mold is clamped. It is intended to provide an in-mold vacuum drawing device that completes mold clamping in a vacuum state by vacuum drawing.

[0006]

[Means for Solving the Problems]

 Means for solving the above problems is to provide an inner surface of a fixed plate of a mold clamping device in an in-mold vacuum drawing device of an injection molding machine for performing vacuum injection molding in a mold. And a movable die installed on the movable plate, which is provided on the outer peripheral surface of the fixed plate so as to be movable in the movable axis direction of the movable plate, and has a vacuum cover having an inner diameter that is in sliding contact with the outer peripheral surface of the movable plate. When clamping the fixed mold installed on the fixed plate, a closed chamber is formed by the fixed plate, the movable plate close to the fixed plate and the vacuum cover, and the closed chamber formed around the mold is closed. The feature is that the vacuum is applied before the mold clamping is completed.

[0007]

[Action]

 Since the present invention is constructed in this way, it has the following effects. That is, in order to perform mold clamping in the mold clamping device, the movable platen 2 is brought close to the fixed platen 1. By operating the movable platen and the vacuum cover 3, the fixed mold 5 and the flexible mold 5 can be moved. A closed chamber A is formed so as to cover the moving die 4. From the beginning of forming the closed chamber A to the completion of the mold clamping, the fixed mold 5 and the movable mold 4 expose the cavity surface in the closed chamber A. If the inside of the closed chamber A is evacuated during this period, the fixed mold 5 and the movable mold 4 are placed under vacuum.

[0008]

【Example】

 An embodiment of the present invention will be described below. In FIGS. 1 to 3, the movable platen 2 is guided by the tie bar 6 and moves toward and away from the fixed platen 1 by the operation of the ram 7. A fixed die 5 is installed on the fixed platen 1, and a movable die 4 is installed on the movable platen 2. The configuration is the same as the mold clamping device of a general injection molding machine. Reference numeral 3 in the figure denotes a vacuum cover, which has an inner diameter that makes sliding contact with the outer peripheral surfaces of the fixed plate 1 and the movable plate 2. The vacuum cover 3 is attached so that the outer peripheral surface of the fixed plate 1 is slidable in the movable axis direction of the movable plate 2 by the operation of the hydraulic cylinder 8. O-rings 9 and 10 are provided on the outer peripheral surfaces of the fixed plate and the movable plate. As shown in FIG. 2, the fixed platen 1 is provided with a hole 11 for evacuation and a nozzle insertion port 12 of the injection device. In FIG. 1, a portion indicated by a chain double-dashed line is an operation range diagram of the movable platen 2 and the vacuum cover 3.

The in-mold evacuation device configured as described above evacuates the mold by the following operations. Referring to FIG. 4, the operation process of the vacuuming method and the vacuuming apparatus of the present invention will be described. FIG. 4 (a) shows the mold opening state of the mold clamping device. In the mold open state, the vacuum cover 3 is at the upper limit position on the outer peripheral surface of the stationary platen 1. First, when the vacuum cover 3 is lowered in the direction of the movable platen 2 by the operation of the hydraulic cylinder 8, and at the same time the movable platen 2 is raised by the operation of the ram 7, the sky cover 3 becomes as shown in FIG. 4 (b). The stationary platen 1 and the movable platen 2, that is, the movable mold 4 and the fixed mold 5 are enclosed to form a closed chamber A. In this operation, when the movable platen 2 starts to rise, the movable platen 2 operates at high speed in order to shorten the non-molding time in the molding process. When the movable platen 2 comes close to the end of the vacuum cover, the movement of the movable platen 2 is advanced at a low speed so as to reduce the impact of the sliding contact between the vacuum cover 3 and the movable platen 2, and the movable platen 2 is brought into sliding contact with the inner wall of the vacuum cover 3. .

The joint surfaces of the fixed plate 1 and the vacuum cover 3 and the movable plate 2 and the vacuum cover 3 are sealed by the O-rings 9 and 10, so that the closed chamber A and the outside do not communicate with each other. At this point, the evacuation of the closed chamber A is started via the hole 11.

For evacuation, a general vacuum pump is used. Measure the degree of vacuum in the closed chamber A with a pressure switch (not shown), and pull the vacuum until the degree of vacuum reaches 700 mmHg or higher. The higher the degree of vacuum, the greater the effect of drawing a vacuum. Further, the movable platen 2 is advanced at a low speed, and the fixed mold 4 is clamped to the movable mold 5 as shown in FIG. 4 (c). After the formation of the closed chamber A, when the vacuum degree cannot be obtained during the continuous low speed movement of the movable platen, the movement of the movable platen 2 is stopped at a predetermined position after the evacuation is started, and after confirming the vacuum degree, It is also possible to tighten.

Next, the molten resin is injected to fill the mold cavity with the molten resin. The degree of vacuum in the closed chamber A is reduced during molten resin vulcanization, and when the atmospheric pressure is reached, the hydraulic cylinder 8 is actuated as shown in FIG. 4 (d) to raise the vacuum cover 3. After the vulcanization is completed, the movable platen 2 is lowered at a high speed, the mold is opened, and the state shown in FIG. 4 (a) is restored.

The operation of the present embodiment configured as described above is as follows. The closed chamber A is formed by first surrounding the fixed mold with the stationary platen 1 and the vacuum cover 3, and then slidingly contacting the movable platen 2 with the inner wall of the vacuum cover 3. That is, the closed chamber A is formed by the operation of the movable platen 2 approaching the fixed platen 1 for mold clamping. The cavity surface of the fixed mold 5 and the movable mold 4 is exposed in the closed chamber A from the initial formation of the closed chamber A to the completion of the mold clamping. By vacuuming the inside of the closed chamber A during this period, the fixed mold 5 and the movable mold 4 are placed under vacuum.

[0014]

[Effect of device]

 As described in detail above, according to the present invention, in the process of bringing the movable mold close to the fixed mold, a closed chamber is formed by the vacuum cover, the fixed plate, and the movable plate, and the closed chamber is closed. Since the vacuum is applied, the fixed mold and the movable mold in the closed chamber are placed in a vacuum state before clamping. That is, since the mold clamping is performed in a vacuum state, air does not remain in the mold cavity. Therefore, the defective appearance of the molded product caused by the residual air in the mold, which has been a problem, is eliminated. In addition, the closed chamber has a simple structure and operation, and is easy to maintain, because a fixed plate and a movable plate, which are essential components of the mold clamping device, are covered with a vacuum cover. Furthermore, since the closed chamber is formed when the fixed platen and the movable platen are close to each other, the volume of the closed chamber is small and the time required to reach a desired vacuum state is short. It is possible to minimize the lost time due to this.

[Brief description of drawings]

FIG. 1 is a schematic view of an in-mold vacuuming device showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line EE in FIG.

FIG. 3 is a cross-sectional view taken along the Loro line in FIG.

FIG. 4 is an operation process chart in one embodiment of the present invention.

[Explanation of symbols]

 1 Fixed plate 2 Movable plate 3 Vacuum cover 4 Movable mold 5 Fixed mold

Claims (1)

[Scope of utility model registration request] 1. An in-mold vacuum drawing apparatus of an injection molding machine for performing vacuum injection molding in a mold, and sliding on the outer peripheral surface of a fixed plate of a mold clamping unit and the outer peripheral surface of a movable plate. A vacuum cover having a contacting inner diameter is provided on the outer peripheral surface of the fixed plate so as to be movable in the movable axis direction of the movable plate, and a movable mold installed on the movable plate and a fixed mold installed on the fixed plate. When the mold is clamped, a closed chamber is formed by the fixed plate, the movable plate close to the fixed plate, and the vacuum cover, and the closed chamber formed around the mold is evacuated before completion of the mold clamping. The in-mold vacuuming device that features