JPS6268715A - Molding mold - Google Patents

Abstract

PURPOSE:To eliminate to cause damage on a mold and a molded product by a method wherein a fixed pin is positioned at a place, not contacted with a gate, under a condition that a slide core is being elevated while the tip end of the fixed pin is positioned at a place in the same level as the surface of the slide core under a condition that the slide core is descended. CONSTITUTION:The upper surface of a slide core 20 closes a cavity and is contacted with a fixed side mold. A fixed pin 21 is separated from the outlet part of a gate 18 by a distance corresponding to the thickness of the cavity, therefore, there is no possibility that the gate is broken even when there is the dropping of a resin on the gate 18. The resin is poured into the cavity 25 for primary injection through the gate under this condition. When the resin in the cavity 25 is set, the slide core 20 is pulled up. The upper surface of a fixed pin 21 becomes the same level as the upper surface of the slide core 20. According to this constitution, a part, molded by second injection, becomes flat and protuberances will never be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION 1) Industrial Application Field The present invention is a method of molding using a hot runner molding method using multiple colors or a variety of raw materials, that is, a molding method that uses a part of a molding die. Two-color or two or more types of integrated molding is possible by using a mold that increases the number of secondary and subsequent molding cavities that are connected to the molding cavity during the primary injection, and separate injection devices for the primary and secondary injection molding cavities. In the injection molding method (hereinafter referred to as the stepwise molding method) for obtaining a desired product, the purpose of this method is to eliminate damage to the mold or molded product caused by gate residue. do.

2) Conventional examples and their problems First, before explaining the present invention, the upper case (black resin) and see-through window (transparent resin) of a private VTR tape cassette will be explained.
A conventional example of a step-by-step molding method using a hot runner molding method in manufacturing will be explained.

FIG. 1 shows a diagram of the completed tape cassette. 1 is an upper case, 2 is a transparent window, 3 is a guard panel, and 4 is a lower case. i, 3.4 is made of black resin, and 2 is made of transparent resin.

2 to 4 show the stepwise molding process of the upper case 1 and the transparent window 2 using the hot runner molding method, as seen from the cross section AA' in FIG. Fig. 2 is a sectional view of the mold configuration during the first injection, that is, molding the upper case 1, in which 5 is the fixed side mold, 6 is the movable side mold, 7 is the slide core, 8 is the second injection gate, 9 is the secondary injection gate. The molten black resin forming the upper case 1 passes through the gate 8 and is filled into the mold and solidified. FIG. 3 is a sectional view of the mold structure during the second injection, that is, molding of the transparent window 2. When the molding of the upper case 1 is completed, the slide core moves in the direction of the arrow by a distance equal to the thickness t of the transparent window 2. The molten transparent resin that forms the see-through window 2 enters the second cavity created there.
It becomes more filled and solidified. At this time, due to the heat and injection pressure of the newly inflowing transparent resin, the parts of the already solidified black resin that come into contact with the transparent resin are in a semi-molten state, and when the black resin is cooled and solidified again, the upper case 1 and the transparent window 2 is glued. FIG. 4 is a sectional view of the stationary mold after removing the molded product. When the completed upper case with see-through window is removed from the mold, the transparent resin solidified at the tip of the gate 9 may remain as a protrusion. This is called the gate remainder (A in Fig. 4).

In the conventional case, when the slide core 7 returns to its original state and enters the primary injection state, it crushes the solidified resin protrusion. By repeating this phenomenon, the crushed resin adheres to the gate 9 due to work hardening, which not only causes damage to the mold, but also has the disadvantage of having a large effect on the molded product. . Furthermore, in the molding die of this method, the position of the gate is severely restricted, so the above-mentioned drawbacks were considered to be unavoidable due to the mold structure.

In order to improve these drawbacks, Japanese Patent Publication Sho dO-29335 has been proposed.

Since the slide core adhesion surface is a concave part, the product in that part will look convex, so when used as a see-through window of a gate cassette as shown in this example, the thickness of this part is standardized. It is limited and cannot be made thicker. If it becomes too thick, running problems will occur.1. I'm done.

3) Structure of the Invention The present invention attempts to improve the above-mentioned problems. A hole for a fixed bottle is provided in the slide core opposite to the gate date of the fixed mold, and the fixed bottle is set there. During the first injection when the slide core is up, the fixed bottle is placed in a place where it does not touch the gate. When the slide core is lowered during the second injection, the tip of the fixing bottle will be flush with the surface of the slide core, and the molded product will have a convexity.

4) Embodiment FIGS. 5 and 6 are sectional views of essential parts of a molding die according to an embodiment of the present invention. The basic construction of the mold is similar to that of FIGS. 2-3, except that the secondary injection cavity and related parts have been modified in accordance with the present invention. FIG. 5 shows the raised position of the slide core (the position shown during the first injection), and FIG. 6 shows the lowered position of the slide core (the position occupied during the second injection). In the figure, 17 is a fixed side mold, 19 is a movable side mold, and 20 is a contact surface facing the second injection gate part 18 (
The slide core 2o has a top surface).

A through hole is formed in the center of the slide core 20, into which a fixing pin 21 is inserted, and its lower end is fixed to a mounting plate 22. The upper surface of the fixed bin is a horizontal plane, and is spaced downward by the cavity dimension from the earth wall surface of the secondary molding cavity.

Now, the primary injection is performed in the state shown in FIG.

At this time, the upper surface of the slide core 20 closes the cavity and is in close contact with the stationary mold. However, since the fixed bottle 21 is separated by the cavity thickness at the exit portion of the gate portion 1B, there is no risk that the gate portion will be damaged due to closing of the slide core even if resin drips on the gate portion 1B.

In this state, resin is injected into the primary injection cavity 25 from a gate (not shown).

Next, when the resin in the cavity 25 is solidified [7], the slide core 20 is pulled down as shown in FIG. As a result, the upper surface of the fixed bin 21 and the upper surface of the slide core 20 become one plane. With this structure, the portion formed by the secondary injection (for example, the see-through window portion) becomes a flat surface, and no convex portion is formed, thereby solving the above-mentioned problem.

[Effect]

As described above, according to the present invention, even if particles of solidified resin adhere to the gate part, there is no risk of damaging the gate part during primary molding, and during secondary molding, there is no risk of damaging the gate part. The bottom surface of the molding cavity can be formed flat so that the molded product does not become convex.

[Brief explanation of drawings]

Figure 1 is a perspective view of a completed VTR tape cassette, Figure 2 is a sectional view of the finished product during the first injection (when molding the upper case), and Figure 3 is a cross-sectional view of the finished product during the second injection (when molding the transparent window). Mold configuration sectional view,
@ Figure 4 is a sectional view of the stationary side mold after taking out the molded product, and Figures 5 and 6 are sectional views of the mold structure at the time of primary injection and secondary injection, respectively, in an embodiment of the present invention. . 2nd concave Fig. 5 Fig. 6

Claims (1)

[Claims] 1 A fixed side mold and a movable side mold each having a molding surface of the first cavity, and a surface that is in close contact with the molding surface including the gate opening used for the secondary injection of the fixed side mold, and other than this surface. The first cavity is configured by the surface and the molding surfaces of the fixed and movable molds, and has a slide core disposed so as to be separable from the fixed mold. The contact surface of the slide core comes into close contact with the surface including the gate port used for secondary injection to form the first cavity, and during the secondary injection, the contact surface moves away from the surface including the gate port. In a stepwise molding mold configured to move in a direction to form a second cavity, a through hole for sliding a fixing pin is provided on the contact surface of the slide core facing the gate opening, and a fixing pin is inserted into the die. The molding metal is characterized in that during the first injection, the fixing pin is located away from the gate part, and during the second injection when the slide core is lowered, the tip of the fixing pin is flush with the slide core contact surface. Type.