JPS6040221A - Vacuum device for injection molding machine - Google Patents

Abstract

PURPOSE:To enable the smooth entry of melted material into a cavity and to prevent the sticking of smear to molded articles so as to upgrade the appearance thereof, by exhausting a gas and extraneous oily substances in the cavity by suction during a period between the completion of closure of a mold and the start of injection. CONSTITUTION:When two side members 1a and 1b of a mold 1 make contact with each other, a limit switch 2 operates to open a solenoid valve 3 for 10sec, for instance, whereby the cavity of the mold 1 is made to communicate with a vacuum tank 5 through the intermediary of a vacuum hose 4. Thereby a gas and oily substances in the cavity are sucked into the vacuum tank 5, and further they are sucked by a vacuum pump 6 to be discharged outside. After the solenoid valve 3 is closed and thereby the vacuum suction is stopped, a stroke of normal injection molding proceeds, and the above-stated suction discharge is conducted after the mold is closed again. A high pressure usually required for making resin enter the corner part of the cavity in injection becomes unnecessary, and such a disadvantage as the impairment of the appearance of molded articles is eliminated, since the oily substances are exhausted completely.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum system for an injection molding machine using Glasty material.

In general, injection molding involves heating the material
In the process of converting into J, the silverized material is injected into the mold using light J.
The process of cooling, solidifying and taking out the molded product)
Restyrene, polyethylene, polyzolopyrene, etc. are often used as plastic fillers for injection molding, as well as acrylic resins, acetate resins, polyamides, polycarbanates, woven vinyl resins,
Some thermoplastic resins and thermosetting 11 resins are also used.

There are various injection molding methods such as Noranger set, pre-plasticizing method, in-line scree set, and other methods, but in general, the plasticizing ability is better, the material has less TT retention, and the work efficiency is better. Although it is widely used for certain reasons, it also has the following problems and flaws.

In other words, since each plastic pellet is plasticized to a fairly high degree, some parts decompose at that time, resulting in decomposition gas, which remains in the cavity of the mold and causes the size to decrease. However, the oily substance produced when the gas is liquefied in portions ends up on the inner wall of the cavity. As a result, there are disadvantages such as the injection pressure not being pushed to the corner of the cavity or having to increase the injection pressure unnecessarily in order to push it to the corner. In addition, the oily substance significantly contaminates the surface of the molded product, leading to frequent defective products.

The present invention has been made in view of the above circumstances.
Gas and adhering oily substances in the mold cavity are suctioned out within a predetermined time after completion of closing, and as a result, the molten material enters the cavity smoothly, and the appearance of the molded product is maintained without contamination. The object of the present invention is to provide a vacuum device including a vacuum tank that has remarkable effects such as significantly improving quality.

The present invention will be explained below based on embodiments with reference to the drawings. FIG. 1 is an explanatory diagram showing an injection molding method to which the present invention is applied.

First, the movement A of the screw has two stages, opening and closing, and the movement B of the screw has three modes: forward movement, backward movement, and stopping.Furthermore, the molding process C includes resin injection and plasticization. There are modes of repeating the process of molding, cooling the molded product, and taking it out.

The present invention starts immediately after the mold is closed, and is applied within a very short time (about 10 seconds at most) until the advancement of the scree and the accompanying injection of resin begin at the latest.

Next, FIG. 2 is a schematic explanatory diagram of the apparatus of the present invention.

For a split type mold that is separated into left and right sides when open, when both sides 1a+1b come into close contact in the closing direction as shown in the figure, the limit switch 2 is activated and the solenoid valve is activated for a predetermined period of time, for example, about 10 seconds. 3 is opened, and the cavity of the mold 1 and the vacuum tank 5 are communicated via the vacuum hose 4.
It is connected to a vacuum pump 6 so as to maintain the degree of vacuum at approximately 0 mM) Ig.

Thus, the gas and oil in the cavity are sucked into the vacuum tank via the vacuum hose while the solenoid valve is open, and are further sucked into the vacuum 4 pump, which is water-sealed and supplied with water from the outside, to remove the gas and oil. The oil is dissolved in the water and discharged to the outside. When the solenoid valve is closed, the vacuum suction stops, the normal injection molding stroke proceeds, and the above-mentioned suction and discharge is performed until the mold is closed again.

Based on the above configuration, the present invention is based on the above configuration,
) ↑ Until the injection of fat starts, a vacuum tank is provided that communicates with the cavity of the mold and maintains a nearly constant degree of vacuum to suck out the gas and oily substances in the cavity. As a result, gas etc. no longer accumulate in the corners of the mold cavity, and while conventionally, high pressure was required to force the resin into the cavity during injection, the pressure applied is reduced. In addition, the resin can flow into every nook and cranny to produce a molded product, and since the oily matter is completely discharged, there is no inconvenience such as disturbing the appearance of the molded product. It is very suitable.

In particular, in the past, the molding machine had to be stopped at 19 degrees once every few hours during work, and if the mold cavity was not carefully reworked, problems could occur one after another and the work could be delayed. Although it required a lot of time and effort and significantly reduced the overall work efficiency, the present invention completely eliminates these drawbacks.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an injection molding method to which the present invention is applied, and FIG. 2 is a schematic explanatory diagram of the apparatus of the present invention. 1... Mold, 2... Limit switch, 3... Solenoid valve, 4... Vacuum hose, 5... Vacuum tank, 6...
··Vacuum pump. Patent applicant Akio Sato! Masanori Kai, Patent Attorney, Arakawa Plastic Cork Industry Co., Ltd.

Claims (1)

[Claims] Applicable to injection molding where the molten plastic material is injected into the cavity when the mold is closed and the molded product is taken out to the outside when the mold is opened, from the time the mold closes to the start of injection. The method is characterized in that a vacuum tank maintained at a constant degree of vacuum is provided, which communicates with the cavity of the mold and can suck out the gas and oily substances in the cavity. Vacuum equipment for injection molding.