KR100324218B1 - Metal mold for a injection molding - Google Patents

Abstract

The present invention relates to an injection molding die for molding a plurality of small cages made of synthetic resin such as plastic in one molding operation by an injection molding method. According to the present invention, the two-point gates 51 and 52 and the overflow gates 53 are formed in the movable lower core 20, and the first and second gates 51 and 52 of the two-point gate are cavities. The cage C formed in 30 is set at a position corresponding to the left and right wall surfaces C2 with respect to the arbitrary ball pocket C1, and the overflow gate 53 is formed in the first gate. It is set on the opposite side relative to the virtual intermediate point formed by the 51 and the second gate 52. In the present invention, the entire lower core 20 forming the cavity 30 is integrally assembled on the movable side of the mold, and a disc shape is formed at the lower center of the two cores 23 on which the plurality of ball cores 24 are arranged. At the same time to combine the anti-rotation core 25, to form a circular arc surface (24a) having the same center of curvature on the lower end side of the ball cores 24 to be in close contact with the outer peripheral surface of the anti-rotation core 25, After assembling the ball cores 24 into the second core 23, they are curved to have the same center of curvature on the inner and outer surfaces of the pocket forming portions 24b, which are upper ends.

Description

Metal mold for a injection molding

The present invention relates to an injection molding die used for molding a bearing cage made of synthetic resin such as plastic by an injection molding method, and more particularly, an injection for molding a plurality of small cages in one molding operation. It relates to a molding die.

In general, a mold used in an injection molding machine constitutes a mold body having a splittable upper core and a lower core in pairs.

The mold body is formed in a shape corresponding to the shape of the molded article and filled with molten resin, a runner for flowing the molten resin toward the cavity, and a gate connecting the molten resin having passed through the runner into the cavity. Is formed.

The lower core is in contact with the upper core and is displaced in the direction perpendicular to the divided surface so as to open and close the mold body.

1 is a cross-sectional view of a mold body provided in a conventional injection molding die.

In FIG. 1, the upper core 1 and the lower core 2 are interviewed so that they can be displaced at the position of the split surface PL. In the drawing, the cavity 3 is formed over the upper core 1 and the lower core 2, and the runner 4 and the gate 5 are formed on the side surface of the cavity 3 along the divided surface PL. To make it flow. Thus, the gate which is installed to inject the resin into the cavity 3 along the dividing surface PL is hogged into a submarine gate or tunnel gate, and although not shown in the figure, the molten resin is injected into the upper portion of the cavity in a direction perpendicular to the dividing surface. The gate to be installed is called a pinpoint gate.

The mold body is fastened by injection molding and injection molded, and a plurality of cavities are formed in order to obtain a plurality of molded products at the same time, and these cavities are connected to a sprue at the top center of the mold through a runner.

When molding using such a mold, the molten resin is injected into the mold body and injected into the cavity 3 through the runner 4 and the gate 5, and the injected molten resin a is the runner 4. And filled into the cavity 3 through the gate 5 to form a resin molded body. The resin molded product is cured in a state in which the cured resin molded product a is hardened in the gate 5, the runner 4, and the sprue (not shown) together with the molded product b cured in the cavity 3.

Thereafter, the lower core 2 is displaced downward on the drawing in a state in which the resin b in the runner 4 is restrained to the upper support plate not shown in the drawing of the mold body.

Accordingly, the molded article (a) and the resin molded article (b) are released from the upper core (1), and then the molded article (a) is separated from the lower core (2) by extraction pins (not shown).

However, when molding a small cage into a mold for injection molding, there have been the following problems.

First, in general, the mold for forming a small cage is made of a small size of the cavity, so the flow of resin in the cavity is not smooth and the gas generated from the molten resin in the cavity is not completely removed. It resulted in molding failure.

Second, the conventional mold has a structure in which the core forming the cavity is arranged on the fixed side of the mold and the core is slid with the movable side core during the molding operation, thereby causing continuous wear of both cores. There was a lung bud.

Thirdly, in the case of a mold for molding a small cage, a plurality of ball pins having a general pin shape are formed to form ball pockets at a predetermined interval in the cage, and then assembled into a circular hole formed in the mold. There is a problem in that the shape of the ball pocket of the cage is bad because the ball core is rotated after assembly. In addition, conventionally, since a plurality of ball pockets provided in one set are pre-processed and then assembled in a mold, the size of a series of ball pockets formed in one cage is not uniformly formed due to processing errors between the pocket forming portions. There was also.

An object of the present invention for solving such a conventional problem is as follows.

First, the present invention forms the core of the two-point gate while setting the position of the two-point gate and the position of the overflow-side gate appropriately to facilitate the flow of resin in the cavity and to generate the melted resin in the cavity. This ensures that the gas is removed completely and minimizes the center distance dimension distribution with respect to the ball pocket.

Second, the present invention is to prevent the wear of the core and the occurrence of burrs in the molded article by placing the entire core forming the cavity on the movable side of the mold and excluding sliding with the fixed side core. .

Thirdly, the present invention generally includes a plurality of ball pins having a general pin shape in order to form ball pockets at a predetermined interval in a small cage, and to assemble them into a circular hole formed at the lower core side. Assemble the structure to prevent rotation when assembling, and after assembling a plurality of ball cores provided in a set in a mold to be able to precisely form the pocket forming portion by integrally curved inside and outside of the pocket forming portions have.

1 is a cross-sectional view of a mold body provided in a conventional general injection mold.

Figure 2 is a cross-sectional view of the mold body provided in the injection molding mold of the present invention for injection molding the plastic cage for bearings.

3 is a plan view of the first core shown in FIG. 2;

FIG. 4 is a cross-sectional view taken along the line A-A of FIG. 3, and FIG. 5 is an exploded view of the mold body cut along the cavity in FIG.

Figure 6 is a bottom view of the anti-rotation core and the ball core coupled to the second core in Figure 2;

7 is a cross-sectional view of a state in which a mold body according to the present invention is installed in a mold for injection molding.

8 is a view showing a molded article (cage) injection molded by a mold according to the present invention.

* Description of the symbols for the main parts of the drawings *

10; Phase core 20; Harcore 21; First core 22; Core

23; Second core 24; Ballcore 24a; Circular arc surface 24b; Pocket forming part

25; Anti-rotation core 30; Cavity 40; Runner 50; Kate

51; First gate 52; Second gate 53; Overflow gate

a; Molded article b; Resin molded C; Cage C1; Ball pocket

C2; Wall surface S; Sprue bush S1; Sprue P1; First extraction pin

P2; 2nd extraction pin

A mold body having a fixed side upper core 10 and a movable side lower core 20 that are installed in a partitionable manner is provided, and the upper core 10 and the lower core 20 have a shape corresponding to a shape of a molded article. The compact bearing is provided with a cavity 30 formed in the form of a mold and a runner 40 for flowing molten resin injected into the cavity 30, and a submarine gate connecting the runner 40 and the cavity 30 in communication with each other. In a conventional injection mold for molding a cage for

A first feature of the present invention is to form a two-point gate (51, 52) and an overflow gate 53 on the movable side lower core 20, the first gate 51 and the second gate of the two-point gate 52 are respectively set at positions corresponding to the left and right wall surfaces C2 with respect to the cage C formed in the cavity 30 based on an arbitrary ball pocket C1, and the overflow gate 53 Is set on the opposite side of the virtual intermediate point formed by the first gate 51 and the second gate 52.

The second feature of the present invention is that the entire lower core 20 forming the cavity 30 is integrally assembled on the movable side of the mold, and the lower core 20 has two-point gates 51 and 52 and overflows. A first core 21 having a gate 53 formed therein, a central core 22 integrally coupled to a center of the first core 21 to form a wall surface of the cavity 30, and the first core 21. A second core 23 integrally coupled to the central core 22 and a lower portion of the cavity 30 at a predetermined interval so as to be positioned at a bottom of the cavity 30. A plurality of ball cores 24 forming the ball pocket C1 of the cage C are included.

The third aspect of the present invention is to combine the disk-shaped anti-rotation core 25 in the lower center of the second core 23 is disposed a plurality of ball cores 24, the ball cores 24 of It is to be in close contact with the outer circumferential surface of the anti-rotation core 25 by forming a circular arc surface (24a) having the same center of curvature on the lower side.

The fourth feature of the present invention is that the ball cores 24 are assembled to the second core 23, and then the inner and outer surfaces of the pocket forming portions 24b, which are upper ends thereof, are curved to have the same center of curvature.

Hereinafter, the preferred embodiment of the present invention will be described in detail.

Figure 2 is a cross-sectional view of the mold body provided in the injection molding die of the present invention for injection molding the plastic cage for bearings, Figure 3 is a plan view of the first core shown in Figure 2, Figure 4 is AA of Figure 3 5 is an exploded view of the mold body cut along the cavity in FIG. 2, and FIG. 6 is a bottom view of the rotating bicore and the ball core coupled to the second core in FIG. 2, and FIG. It is sectional drawing of the state which the mold main body which concerns on this invention was installed in the injection molding die. 8 is a view showing a molded article (cage) injection molded by a mold according to the present invention.

As shown in FIG. 2, the injection molding die according to the present invention includes a mold main body having an upper core 10 and a lower core 20 that are provided in a partitionable manner.

The upper core 10 contacts the mating surface of the lower core 20 to form an upper wall surface of the cavity 30, and the cavity 30 along the split surface PL of the upper core 10 and the lower core 20. The runner 40 which flows the molten resin injected into and the submarine gate 50 which connects the runner 40 and the cavity 30 in communication are formed.

As shown in FIG. 2, the present invention includes a first core 21 having two-point gates 51 and 52 and an overflow gate 53 formed on the movable lower core 20. As shown in FIG.

3 and 4, in the present invention, the first gate 51 and the second gate 52 formed in the first core 21 are formed with respect to the cage C formed in the cavity 30. As shown in FIG. The ball gate C1 is set at a position corresponding to the left and right wall surfaces C2 based on an arbitrary ball pocket C1, and the overflow gate 53 is an imaginary structure formed by the first gate 51 and the second gate 52. It is set opposite to the midpoint of. As illustrated, seven ball pockets C1 are formed in one cage C, and the first and second gates 51 and 52 are formed based on the center point of the first core 21. The angle is about 36 °, and as shown in FIG. 5, each of the first gate 51 and the second gate 52 is a ball pocket C1 with respect to the cage C, which is a molded product formed in the cavity 30. While not shown, the overflow gate 53 also faces the wall surface C2 between the ball pockets C1. As such, the position where the molten resin enters through the first gate 51 and the second gate 52 avoids the fat part of the cage C and faces the thick part of the body, thereby smoothing the flow of the molten resin and forming the molded article. The strength characteristic of can also be secured. In addition, the position of the overflow gate 53 corresponds to the point where the molten resin meets in the cavity 30, thereby reliably removing impurities and residual gas, thereby eliminating fatal product defects that may occur in a compact injection molded product. You can prevent it.

According to the present invention, as shown in FIG. 2, the entire lower core 20 forming the cavity 30 is integrally assembled on the movable side of the mold, and the lower core 20 is a two-point gate 51. 52 and a first core 21 having an overflow gate 53 formed therein, a central core 22 integrally coupled to the center of the first core 21 to form a wall surface of the cavity 30, A second core 23 positioned below the first core 21 and integrally coupled with the central core 22, and a circumference of the second core 23 to be located at a bottom surface of the cavity 30; It includes a plurality of ball cores 24 are inserted at regular intervals to form the ball pocket (C1) of the cage (C).

As such, the entire lower core 20 forming the cavity 30 is integrally assembled to the movable side of the mold so that the upper core 10 and the lower core 20 do not slide during molding and wear occurs. It doesn't work.

According to the present invention, as illustrated in FIG. 6, as illustrated, a disk-shaped anti-rotation core 25 in a lower center of the second core 23 in which seven ball cores 24 are arranged at regular intervals. To form a circular arc surface 24a having the same center of curvature on one side of the lower end of the ball cores 24 so as to be in close contact with the outer circumferential surface of the anti-rotation core 25, thereby rotating the ball core 24 (rotating the ) Is being prevented.

On the other hand, the ball cores 24 are assembled to the second core 23, and then grinding the inner and outer surfaces of the pocket forming portion 24b to a curved surface to eliminate the machining error. The inner and outer surfaces of the curved pocket forming parts 24b have the same center of curvature and the center of curvature coincides with the center point of the second core 23.

The mold body of the present invention having such a structure is installed in the injection molding mold as shown in FIG. 7 to perform molding.

When molding, the injection nozzle of the injection machine not shown in the figure is advanced to inject molten resin through the sprue S1 of the sprue bush S. FIG. Accordingly, the injected molten resin is filled into the cavity 30 through the runner 40 and the gate 50. After the resin is injected, the pressure is maintained until the resin in the cavity 30 is cured, and then the lower core 20 is moved downward in the drawing to be spaced apart from the upper core 10. At this time, the lower core 20 is moved on the basis of the split surface PL, and the resin cured in the runner 40 and the gate 50 is moved to the state attached to the lower core 20 side. The resin cured in S1) is also released in the sprue bush S. FIG. In addition, the molded article cured in the cavity 30 in the mold body is also moved together with the lower core 20.

Thereafter, the molded article attached to the cavity 30 and the resin in the runner 40 and the gate 50 are released by the operation of the first extraction pin P1 and the second extraction pin P2. At this time, the molded product cured in the cavity 30 and the resin cured in the runner 40 are separated by the gate 50 as a split point, and the product normally released falls automatically and the resin cured in the sprue and runner. Is drawn from the mold by a robot or the like not shown.

In this way, a plurality of molded articles can be molded by one injection molding operation, and as shown in FIG. 8, a molded article having a ball pocket C1 at a predetermined interval on the ring-shaped wall surface, that is, a ball bearing cage C Can be produced in large quantities.

As described above, the present invention forms the core of the two-point gate, and properly set the position of the two-point gate and the position of the overflow gate to facilitate the flow of the resin in the cavity and generated in the molten resin in the cavity. The gas is completely removed to prevent molding defects due to impurities, stress, and residual gas in the molded product.

In the present invention, the entire core forming the cavity is disposed on the movable side of the mold to eliminate sliding with the fixed core, thereby preventing the core from abrasion and preventing burrs from forming in the molded article.

The present invention provides an anti-rotation core, and a series of ball cores are interviewed on the outer circumferential surface of the anti-rotation core to prevent the rotation of the ball core. Therefore, the ball pockets of the cage formed by the pocket forming portion of the ball core are uniform. There is an advantage to having.

In addition, the present invention has the effect of preventing the molding failure of the molded article due to the processing error by integrally curved the inner and outer surfaces of the pocket forming parts in the state in which the ball core is inserted into the second core provided in the lower core.

Claims (4)

A mold body having a fixed side upper core 10 and a movable side lower core 20 that are installed in a partitionable manner is provided, and the upper core 10 and the lower core 20 have a shape corresponding to a shape of a molded article. And a runner 40 for flowing molten resin injected into the cavity 30 and a submarine-type gate 50 in communication with the runner 40 and the cavity 30. In a conventional injection molding die for molding a small bearing cage (C), Two-point gates 51 and 52 and an overflow gate 53 are formed in the movable lower core 20, and the first gate 51 and the second gate 52 of the two-point gate are cavity 30. ) Is set at positions corresponding to the left and right wall surfaces C2 on the basis of the arbitrary ball pockets C1 with respect to the cage C to be molded in the cavity, and the overflow gate 53 is the first gate 51. Injection molding die, characterized in that it is set on the opposite side relative to the virtual intermediate point formed by the second gate (52). A mold body having a fixed side upper core 10 and a movable side lower core 20 that are installed in a partitionable manner is provided, and the upper core 10 and the lower core 20 have a shape corresponding to a shape of a molded article. And a runner 40 for flowing molten resin injected into the cavity 30 and a submarine-type gate 50 in communication with the runner 40 and the cavity 30. In a conventional injection molding die for molding a small bearing cage (C), The entire lower core 20 forming the cavity 30 is integrally assembled on the movable side of the mold, and the lower core 20 is formed of two-point gates 51 and 52 and an overflow gate 53. One core 21, a central core 22 integrally coupled to the center of the first core 21 to form a wall surface of the cavity 30, and located below the first core 21 to the The second core 23 integrally coupled to the central core 22 and the ball pocket of the cage C are inserted at regular intervals around the second core 23 so as to be located on the bottom surface of the cavity 30. An injection molding mold comprising a plurality of ball cores 24 forming (C1). The method of claim 2, While combining the disk-shaped anti-rotation core 25 to the lower center of the second core 23 in which the plurality of ball cores 24 are disposed, the same curvature on the lower ends of the ball cores 24 Injection molding mold, characterized in that to form a circular arc having a center (24a) in close contact with the outer peripheral surface of the anti-rotation core (25). The method of claim 2, After inserting the ball cores (24) into the second core (24), the injection molding mold, characterized in that the inner and outer surfaces of the upper and lower pocket forming portion (24b) to be curved to have the same center of curvature.