JPS6168212A - Vacuum reactive injection molding machine - Google Patents

Abstract

PURPOSE:To prevent molding defects from occurring by a method wherein relief parts for molding material are provided on the split surfaces adjacent to the end part of a cavity and the air between the forces is prevented from remaining in the relief parts through an exhaust passage. CONSTITUTION:The bottom force 1 and the top force 2 are clamped to each other and the relief parts 8a-8c for molding material are shut out from the open air. Then, the cavity 3 is communicated to a vacuum tank to absorb the air in the cavity 3 into the vacuum tank in a vacuum state and to remove the air completely from the cavity 3. After the molding material is injected into the cavity 3, the material is hardened in any one of the 1st to the 3rd relief parts 8a, 8b and 8c. The molded piece made in this manner is free from molding defects such as foams, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vacuum reaction injection molding apparatus.

[Conventional technology]

In reaction injection molding (RIM) for molding urethane bumpers and the like that are installed in automobiles, when the shape of the molded product is complex or the size of the molded product increases, molding defects tend to occur, resulting in a decrease in productivity.

The most common molding defects are, for example, when the flow of the molding raw material in the cavity is disrupted, creating areas where air in the mold stagnates, and this mold air is trapped in the molding raw material in the cavity, causing air to flow into the molded product. There are things that form pools.

As a measure to eliminate the occurrence of air pockets, there is Japanese Patent Application No. 113947/1983 filed by the present applicant entitled "Injection Molding Apparatus" (unpublished).

As shown in FIG. 4, this invention provides a sealing member 4 on the dividing surface 5 of the injection mold 1.2 to shut off the cavity 3 from the outside air in the mold closed state.
．． The opening/closing valve 1 is provided in a recess formed on the inner surface of the opening/closing valve 1.
This injection molding apparatus is characterized in that a vacuum device 14 connected to the injection mold 1.2 through an exhaust passage 13 is disposed outside the injection mold 1.2, and the inside of the cavity 3 is evacuated. It is designed to be reaction injection molded.

C Problems to be Solved by the Invention] However, in this injection molding apparatus, after the air in the cavity 3 is sucked into the vacuum device 14 and completely removed, and the on-off valve 12 is closed, The disadvantage is that it is difficult to maintain a complete vacuum at the end of the cavity 3 until the end of the cavity 3 is filled with the molding material.

As a means to eliminate this drawback, the closing timing of the on-off valve 12 is controlled by a timer so that it is closed after an optimum time has elapsed after the start of injection of the molding material, that is, it is opened and closed at the time when the molding material reaches the end of the cavity 3. Although there is a proposal to close the valve 12, there is a problem that if the molding material enters the opening/closing valve I2 due to an error in the closing timing of the opening/closing valve 12, the opening/closing valve 12 becomes unusable.

The present invention has been made in view of these drawbacks, and it eliminates the on-off valve and maintains a high degree of vacuum at the end of the cavity until the end of the cavity is filled with molding raw material. The purpose is to

[Means for solving problems]

To this end, the present invention provides a sealing member on the dividing surface of the injection mold to isolate the cavity from the outside air when the mold is closed.
A parting surface that is shut off from the outside air together with the cavity by this sealing member, and which is adjacent to the end of the cavity, is connected to the cavity to form a release part for the molding raw material, and further, in this part, A vacuum device disposed outside the injection mold is connected through an exhaust passage.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

Reaction injection molding involves mixing two or more types of highly reactive molding raw materials (liquids) using a high-pressure impingement mixing injection molding machine (not shown) and injecting the mixture into a mold to perform a rapid polymerization reaction. The reaction injection mold shown in FIG. 1 has a lower mold 1 which is a fixed mold, and a concave molding surface that opens upward in the center of the upper surface of the lower mold 1. is formed, and dividing surfaces 5a and 5b from the upper mold 2 are formed on the outer peripheral edge of the molding surface.

FIG. 2 shows the mold closed state in which the movable upper mold 2 is mounted on the lower mold 1, and the molding surface of the front filling lower mold 1 and the upper mold 2
A cavity 3 is formed by the molding surface.

Seal members 4 are provided on the dividing surfaces 5a and 5b of the lower mold 1 to isolate the cavity 3 from outside air in the mold closed state.

This sealing member 4 is made of an elastic material such as rubber or soft synthetic resin, and is fitted into dovetail-shaped grooves provided on the dividing surfaces 5a and 5b of the lower mold 1. When the mold is closed, this sealing member 4 The dividing surface 5C of the upper die is pressed against the upper die to form a seal.

Reference numeral 6 indicates an inlet (hereinafter referred to as a gate) for injecting the molding raw material into the cavity 3, and the dividing surface 5b adjacent to the end of the cavity 3 furthest from the gate 6 is different from the other dividing surface 5a. The enlarged dividing surface 5b is surrounded by the sealing member 4 together with the cavity 3, and the cavity 3 and the cavity 3 are isolated from the outside air.

A first relief part 8a for the molding raw material communicated with the cavity 3 through the communication groove 7 is formed on this dividing surface 5b,
A second relief portion 8b and a third relief portion 8C are continuously formed in a zigzag shape in the first relief portion 8a via throttle grooves 9a and 9b.

The third relief portion 8C is designed to increase the volume by recessing the dividing surface 5C of the upper mold 2, thereby increasing the capacity for receiving the molding raw material.

Furthermore, a through hole 1O is formed in the dividing surfaces 5b and 5C of the lower mold 1 and the upper mold 2 from this third relief part 8C toward the outside of the mold, and a vacuum device ( (not shown) is connected to the third
It is connected to the relief part 8C.

This piping 11 constitutes an exhaust passage.

Although not shown, the vacuum evacuation device is composed of a vacuum pump and a vacuum tank, and the vacuum tank is always maintained at a predetermined vacuum state by the vacuum pump.

Next, the operation of the reaction injection molding apparatus having the above configuration will be described.

First, the upper mold 2 is molded into the lower mold l and the mold is clamped, and the cavity 3 and the first to third molding raw material escape portions 8a, 3b, 3c are isolated from the outside air by the sealing member 4.

Thereafter, the cavity 3 and the vacuum tank are brought into communication, and the air in the cavity 3 is sucked into the vacuum tank in a vacuum state and completely removed.

In a state where cavity 3 and the vacuum tank are in communication,
Injection of the molding raw material into the cavity 3 is started.

A high degree of vacuum is maintained in the cavity 3 until the molding raw material reaches the end of the cavity 3 and flows into the first relief part 8a.

The molding raw material that has flowed into the first relief part 8a becomes thicker due to the progress of the polymerization reaction, and the flow resistance increases.1. The flow is weakened by the flow resistance in the throttle grooves 9a and 9b,
It hardens inside any one of the first to third relief parts 8a, 8b, and 8C.

The molded product molded in this manner does not suffer from molding defects such as air pockets.

〔Effect of the invention〕

According to the present invention, a relief part for the molding material is formed in the dividing surface adjacent to the end of the cavity, and a vacuum device is connected to this relief part through an exhaust passage, so that an on-off valve can be eliminated. At the same time, it is possible to maintain a high degree of vacuum at the end of the cavity until the molding material is filled into the end of the cavity, completely preventing air from stagnation in the mold at the end of the cavity. It is possible to obtain molded products without molding defects due to air pockets.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing an embodiment of the vacuum reaction injection molding apparatus according to the present invention, and FIG.
FIG. 3 is a cross-sectional view of a portion corresponding to the m-line in FIG. It is a diagram. 1.----Lower mold 2-1111 Upper mold 3----Cavity 4---Seal member 5a---Divided surface 5b of lower mold.--1111 Dividing surface of lower mold (dividing surface adjacent to the end of the cavity) 5c --- Dividing surface 6 of upper mold --- Gate 7 --- Communication groove 8a --- First relief part 8b...-Second relief portion 8c.--1---Third relief portion 9a, 9b.--11--Aperture groove Fig. 1 Solo, 9D-J Shihib station 4 Fig. 2 Fig. 3 Figure 4

Claims (1)

[Claims] (1) A sealing member is provided on the dividing surface of the injection mold to isolate the cavity from the outside air when the mold is closed, and the dividing surface is shut off from the outside air together with the cavity by this sealing member, and the end portion of the cavity is A molding raw material relief part is formed in the divided surface adjacent to the mold by communicating with the cavity, and further, a vacuum pulling device disposed outside the injection mold is connected to this relief part via an exhaust passage. Vacuum reaction injection molding equipment featuring: