JPH0614998Y2 - Mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a mold suitable for molding an injection molded product having an undercut such as a screw or a lateral hole therein.

(B) Problems to be solved by the conventional technology and device The injection molding method includes a cold runner method in which a solidified sprue or runner is taken out together with a molded product, and a mold block with the sprue or runner is heated by a heater to produce a metal There is a hot runner method in which the molding material in the mold is always kept molten and only the molded product is taken out.

In the cold runner method, sprues and runners must be separated and removed from the molded product, which leads to a decrease in the molding cycle, and it is customary to crush and reuse the separated sprues and runners after removal. However, the quality of the molded product may be deteriorated due to the inclusion of foreign matter during pulverization.

The hot runner method does not have the drawbacks of the cold runner method as described above and can improve the molding cycle and improve the quality, but it is necessary to incorporate a heater in the mold block.

By the way, when applying the hot runner method to injection molding of a cap or the like having a protrusion such as a screw inside thereof, a gate for resin injection is provided on the front side of the top surface of the cap or the like,
The so-called front gate method has been adopted so far.

The reason is as follows. When removing a molded product such as a cap having a protruding portion such as a screw from the inside of the mold,
Since there is a risk of damaging the protrusions such as the screws if the core is forcibly removed, the core is divided into the core and the slide core, and the slide core is slid to perform die cutting.
Other than this slide core, there is a system such as a rotating core. As shown in FIG. 5, the conventional slide cores 1 and 1 have a substantially crescent shape in which a circle is divided by parallel strings 2 and 2.
Since it is provided in a narrow area sandwiched between the strings 2 and 2, it is difficult in terms of area to incorporate the heater in the middle core 3 by the hot runner method.

However, when the front gate method is adopted as described above, the marks of the gate portion appear on the outer surface of the molded product such as the cap, which makes it unsightly.

The present invention provides a mold that enables a so-called back gate method in which a gate portion is arranged on the back side of the top surface in injection molding by a hot runner method such as a cap having a protrusion such as a screw inside. The purpose is to

(C) Means for Solving the Problems The mold of the present invention is a mold for an injection-molded product having an undercut, and has a hot runner heated by a heater in the center thereof, and its outer peripheral portion. And a slide core slidable with the middle core, which has a concave portion having a shape corresponding to the protruding portion and which has a mountain-shaped protruding portion that bulges outward in the radial direction. To do.

(D) Action and effect As described above, the die of the present invention forms a chevron-shaped projecting portion that bulges outward in the radial direction on the outer peripheral portion of the middle core, thereby making the area of the middle core relatively small. Since it can be widely used, a hot runner heated by a heater can be arranged in the center thereof.

This makes it possible to employ the so-called hot runner system, which eliminates the need for sprue and runner molding and improves the molding cycle and quality.

A so-called back gate method, in which a hot runner gate is provided on the core mold side forming the screw portion, can be adopted, and the mark of the gate portion is not formed on the outer surface of the molded product, so that the appearance is remarkably improved.

(E) Embodiment FIG. 1 shows a first embodiment of an injection molding die 4 according to the present invention. As shown in the drawing, a cap which is an injection molded product having a screw 10 which is an undercut portion is provided. Mold for molding, hot runner 5 for gate in the center
Are disposed on the outer peripheral portion of the core 7, and the inner core 7 has a mountain-shaped protruding portion 6 that bulges outward in the radial direction, and a concave portion 8 having a shape corresponding to the protruding portion 6. In the illustrated embodiment, the cores 7 and 9 are caps 11 each having a screw 10 on the inner surface thereof.
The chamber 12 is formed.

The molten resin is supplied from the nozzle 13 of the injection molding machine to the sprue bush 14 and the runner 16 in the manifold block 15.
After that, it reaches the gate runner 5 in the middle core 7, is injected into the cavity 18 from the gate 17 at the tip thereof, and is molded with the cap 11 in which the trace of the gate portion remains on the back surface thereof. Two
0 is a cavity plate.

The sprue bush 14 and the manifold block 15 are heated by a heater (not shown) so that the resin is always melted in the runner 16 of the manifold block 15. Similarly, the gate hot runner 5 is also heated by the heater 19. There is. The heater 19 for heating the gate hot runner 5 is provided inside the runner 5 so that the runner 5 can be heated from the inner peripheral surface in the example shown in the figure, but it is a bush-shaped heater that surrounds the runner 5 and surrounds it. You may heat from the surface.

The slide core 9 is slidably engaged with a slide rail 21 which is integral with the middle core 6, and after injection molding, the slide core 9 together with the support block 22 of the slide core 9 slide rail 9 as shown in FIG. Slide on 21 to release the molded cap 11.

FIG. 4 shows a second embodiment of the mold 4 of the present invention. In the mold 4 of the second embodiment, the wall surface of the recess 8 of the slide core 9 of the first embodiment has an arc shape. On the other hand, except for the trapezoidal shape, the same reference numerals as those of the first embodiment are used for the same members.

In this way, the recessed portion 8 of the slide core 9 having a shape corresponding to the chevron-shaped protruding portion 6 bulging outward in the radial direction of the middle core 7 is a semicircle if the protruding portion of the middle core 7 can be accommodated. It may have any shape such as a shape, a trapezoidal shape, and a triangular shape.

[Brief description of drawings]

FIG. 1 is a sectional view taken along the line II of FIG. 2 of the first embodiment of the injection molding die of the present invention, and FIG. 2 shows a main part of an injection molding machine incorporating the die of the present invention. Sectional view, FIG. 3 is a sectional view of the sliding core of FIG. 2 in a slid state, FIG. 4 is a sectional view of a second embodiment of the mold of the present invention, and FIG. 5 is a sectional view of a conventional mold. It is a figure. 4 ... Mold, 5 ... Hot runner for gate, 6 ... Overhang part, 7 ... Medium core, 8 ... Recessed part, 9 ... Slide core.

Claims (1)

[Scope of utility model registration request] 1. A center core having a hot runner heated by a heater in its central portion, and having a chevron-shaped protruding portion bulging outward in the radial direction on its outer peripheral portion, and a core corresponding to the protruding portion. A mold for an injection-molded product having an undercut, which has a concave portion having a shape and includes the above-mentioned middle core and a slidable slide core.