JPS6026691B2 - Spherical injection mold with multilayer structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection mold for efficiently manufacturing a sphere having a multilayer structure with high quality by an injection molding method.

Traditionally, the method for producing spheres with a multilayer structure has been to punch out material for the outer covering (e.g., thermoplastic resin, thermosetting resin, or rubber composition) from a flat plate and preform it into a hemispherical shape, or by injection molding. The coating material (hereinafter referred to as a cell) formed into a hemispherical shape by the method is inserted into a desired cavity, the central sphere is placed inside the hemispherical cell,
It is common to compression mold from the top and bottom.

However, these compression molding methods for hemispherical cells have drawbacks such as being extremely inefficient, producing a lot of burrs, and taking a long time to buff after molding. Patterns and methods were devised.

However, with conventional injection molding molds and methods, it is difficult to remove the injection molded sphere (hereinafter referred to as the molded sphere), and especially in the case of soft cell materials, when pushing up the molded sphere with the ejector pin, it is difficult to remove the molded sphere. Local scratches and dents were likely to occur on the surface, and satisfactory quality could not be obtained.

Another method for demolding the sphere is to mirror the mold, but with this method only the injected molded sphere can be demolded by rotating on the dividing surface of the cavity, but the spool and runner parts does not rotate at all and does not come off the mold. Therefore, the gate part for injecting the cells into the cavity is torn off due to the misalignment between the molded sphere and the runner part, and scratches occur on the surface of the molded sphere, which is not a method that is satisfactory in terms of quality. The mold of the present invention is a mold for injection molding of molded spheres having a multilayer structure, which solves the drawbacks of efficiency and quality that could not be satisfied with conventional molding molds and molding methods, and also enables automatic molding operation. This is what we are trying to provide.

First, in a spherical injection mold, the face angle B formed between the dividing surface 3 of the mold and A with respect to the mold opening direction A of the injection molding machine is set to an angle of 800 to 750. and provide cavities 5 on the upper and lower sides of this dividing surface 3, respectively.
A pin 6 that holds the core sphere 1 in this cavity 5
Three or more are provided, and the structure is such that they move in a direction perpendicular to the dividing surface 3 or in a vertical direction and act as ejector pins after the mold is opened. The present invention is characterized in that air is released onto the surface of the injection-molded sphere, and the resin or rubber composition 2 coated on the core sphere 1 is cooled and the injection-molded sphere is modeled at the same time.

Furthermore, the present invention is characterized in that, in addition to this, an ejector pin 12 for ejecting the Z pin hole 11 is provided, and the injection molded sphere is operated at the same time as the pin 6 holding the core sphere 1 is ejected as an ejector pin. shall be.

To explain the mold of the present invention more specifically, it is made to be able to move in and out from the inner wall surface of the cavity 5 in a direction perpendicular to the dividing surface 3 of the mold or in a vertical direction. At least three central sphere holding pins 6 that can be freely moved in and out and have tips that are integrated with the surface of the cavity 5 so as not to leave scratches or special unevenness marks on the surface of the injection molded sphere, and that also serve as ejector pins. When performing injection molding, the core sphere holding pin 6 is inserted toward the inside of the cavity 5 to hold the core sphere 1 at the center of the cavity 5.

While holding the core sphere 1, insert the cell 2 from the injection molding machine 17.
Perform the injection. Immediately before the injection of the cell 2 is completed, the core spherical holding pin 6 is retracted until the tip of the core spherical holding pin 6 matches the surface of the cavity 5, and the material of the cell 2 is completely filled into the cavity 5. to obtain a molded sphere with a two-layer structure. After injection is completed, the central sphere holding pin 6 functions as an ejector pin to push out the molded sphere after the mold is opened.

Since pressure tends to be locally concentrated on the surface of the molded sphere when the core sphere holding pin 6 pushes it out, the portion pressed by the core sphere holding pin 6 needs to have great strength. Therefore, in order to improve this damage, we invented a method of cooling and hardening the surface of the molded sphere with cooling air, and then extruding it by opening the mold so that it could be easily taken out.

At the same time as the injection of the molded sphere is completed, the cooling air is distributed from the outside through the cooling air conduit 7 in the cooling air distribution chamber 8 so that it can be blown out from each of the core sphere holding pin slide holes 9 provided in the cavity 5, and the core sphere is held. This cooling air is discharged into the cavity 5 through the gap between the pin 6 and the core sphere holding pin slide hole 9 to promote hardening of the surface of the molded sphere, thereby increasing the strength to withstand the extrusion pressure of the ejector pin. obtain.

Furthermore, it was found that the release of cooling air had a peeling effect on the adhesion surface of the molded sphere.

The cooling air released from the center sphere holding slide hole 9 is
It was found that a thin air layer entered the contact surface between the inner wall surface of the cavity 5 and the molded sphere, peeled off this contact part, and escaped to the dividing surface 3, and the demolding of the molded sphere was more effective. The cooling air is released from the gap between the core sphere holding pin 6 and the core sphere holding pin slide hole 9, and the distance between this gap is preferably 0.03 feet to 0.1 feet.
If the interval is too small, the amount of cooling air discharged will be small, resulting in poor cooling effect and frequent occurrence of scratches.

On the other hand, if the distance is too large, the injection material will easily enter the molded sphere, resulting in the formation of burrs on the surface of the molded sphere. Therefore, the most desirable gap is 0.04 to 0.06 ribs. In this case, it is of course possible to use a configuration in which cooled compressed air is blown out from a small pinhole-shaped hole (not shown) drilled in the tip surface of the central sphere holding pin 6 itself, and the same result will be obtained. is obtained. To make demolding easier,
The dividing surface 3 of the mold is the same as the mold opening direction A of the injection molding machine and the dividing surface 3.
The face angle B formed by the angle B is oriented at an angle of 80o to 75o. When the mold is opened, the molded sphere is rotated at the end of the dividing surface 3 of the cavity 5, and the positions of the mold and the molded sphere are moved to promote demolding. If this is done alone, the spool 14 and runner 15 will not come off, and the gate 6 attached to the surface of the molded sphere will be torn and scratched, so a Z pin ejector 12 is provided to remove the spool 14 and runner 15.

In order to pull out the subur 14 when the mold is opened,
A Z pin hole 11 is provided in the mold on the opposite side of the spool hole, and at the same time that the holding pin 6 of the core sphere 1 operates as an ejector pin, the Z pin ejector 12 is operated and the spool 1
4. Remove the runner 15 to prevent the gate from being cut due to the rotation of the molded sphere.

If this Z pin ejector operates too early, the spool will not come out and demolding will not be possible.

On the other hand, if it is slow, the gate will break due to the rotation of the molded sphere, causing scratches on the surface of the molded sphere, resulting in a defect. Therefore, the timing of the ejecting operation of the Z pin ejector 12 is preferably such that it operates at the same time as the center sphere holding pin 6 ejects the formed sphere. Examples will be further described below.

Example 1 This is an example in which the pressure of the cooling air released from the core sphere holding pin slide hole in the mold of the present invention and the cooling time were changed, and the molded sphere was coated with a polyethylene thermoplastic resin. The surface temperature and the number of defects were measured and evaluated.

Experiments Nos. 1 to 3 were conducted in which the cooling time was kept constant and the pressure of the cooling air was varied in the range of 2k9' to 6k9/m. Experiments Nos. 4 to 6 were conducted in which the pressure of the cooling air was kept constant and the cooling time was varied.

The comparative example shows the values obtained when cooling air is not released from the mold of the present invention.

Table-1 Injection conditions Injection time: 5 seconds, injection temperature: 230°C (indicated temperature on the nozzle roller), mold temperature: 50°C, Note 1: After the molded sphere has been demolded, the K surface is measured with a digital thermometer, Note 2:
Number of defective products per 100 experimental samples.

As shown in Table 1, it was found that by using the mold of the present invention, molded spheres of high quality, which could not be obtained by conventional methods, could be obtained.

By using the mold of the present invention, injection products such as molded spheres, spools, and runners can be completely demolded, work efficiency is improved, and above all, high-quality and defect-free products can be obtained. If a robot takes out the injection product and supplies the core sphere, automatic molding operation will be possible.

Furthermore, the molded sphere injected using the mold of the present invention is finished, and the core sphere is charged as a core sphere into a mold having the same structure as the present invention, which has a larger diameter than the cavity of the mold in which injection molding was previously performed. Perform molding.

By repeating this operation, it is possible to mold a shaped sphere having a desired multilayer structure of two or more layers. Note that the pin 6
However, other embodiments of the invention which are movable in a direction perpendicular to the mold parting plane 3 are similarly shown in FIGS. 4-6.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional front view showing the state when the mold into which the core sphere 1 is inserted is closed in an embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view showing the state when injection is completed. The front view and FIG. 3 are vertical sectional front views showing a state in which the mold is opened and the injection product is removed from the mold using the center sphere holding pin 6 and the Z pin ejector pin 12. Furthermore, FIGS. 4 to 6 are vertical cross-sectional front views of a mold in which the center sphere holding pin 6 operates perpendicularly to the mold dividing surface 3 in another embodiment of the present invention. The figure is a sectional view showing the state in which the core sphere holding pin 6 moves forward and holds the core sphere when the core sphere 1 is inserted and the mold is closed. Figure 5 shows the state immediately after injection molding. FIG. 6 is a sectional view showing the state in which the center sphere holding pin 6 has retreated to the mold spherical surface, and FIG. It is a sectional view showing a state where the injection molded product is demolded. 1... Core sphere, 2... Outer covering material (cell), 3... Mold dividing surface, 4...
... Guide pin and guide pin hole, 5 ... Cavity, 6 ... Central sphere holding pin (also serves as ejector pin), 7 ... Cooling air conduit, 8 ...・・・
・Cooling air distribution chamber, 9... Central sphere holding pin slide hole, 10... Hydraulic or air cylinder, 1
1... Z pin hole, 12... Z pin ejector, 13... Hydraulic pressure or air cylinder for Z pin ejector, 14... Spool and spool hole, 15
...Runner and runner list, 16...
・Gate and gate groove, 17... Injection molding machine,
A: Mold opening direction, B: Surface angle formed by the mold opening direction and the dividing plane. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. In a spherical injection mold, the surface angle B formed between the dividing surface 3 of the mold and the mold opening direction A of the injection molding machine is 80° to 75°. A cavity 5 is provided on each of the upper and lower sides of the dividing surface 3, and three or more pins 6 are provided to hold the core sphere 1 in the cavity 5, and the direction perpendicular to the dividing surface 3 or It has a structure that moves in the vertical direction and acts as an ejector pin after the mold is opened. Cooling air is released to the surface of the injection molded sphere from the core sphere holding pin slide hole 9 in the cavity 5, and the core sphere is A mold for injection molding a sphere having a multilayer structure, characterized in that the injection molded sphere is released from the mold at the same time as the resin or rubber composition 2 coated on the resin or rubber composition 2 is cooled. 2. Claim 1 characterized in that an ejector pin 12 for ejecting the Z pin hole 11 is provided, and the injection molded sphere is operated at the same time as the pin 6 holding the core sphere 1 is extruded as an ejector pin. A spherical injection mold having a multilayer structure as described in 1.