JP2015214057A - Injection mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable stable filling of a group of difficult-to-pack cavities with a rubber material, increase the number of rubber products ejected and also enable efficient ejection of rubber products by mechanical ejection means, e.g. an automatic ejection robot.SOLUTION: In an injection mold, a rubber material 5 is injected from a sprue in the center in the plane view into a large number of cavities 3 formed by superposition of an upper mold and a lower mold 2: the rubber material 5 flows radially from the central sprue toward outer edges through the runner central region part 7 and is packed, in order, into the cavities 3. The geometrical shape of the runner central region part 7 has protrusions 9 in the direction toward the group Z of difficult-to-pack cavities hard for the rubber material 5 to be packed, among the cavities 3 arranged on the outer edges.

Description

  The present invention relates to an injection mold for rubber products.

  Conventionally, in injection molding, a large number of molding cavities are formed between an upper mold and a lower mold, rubber materials are sequentially filled into the cavities from a sprue for injection injection through a runner, and a large number of rubber products are taken. An injection mold has been used (see Patent Document 1).

Japanese Patent Laid-Open No. 62-178314

  However, the injection mold disclosed in Patent Document 1 requires a very complicated branch-shaped runner, or has a complicated configuration composed of an upper flat circular film-shaped runner and a large number of vertical sub-runners. It was. Therefore, there is a problem that it is difficult to manufacture the mold, the cost is high, and the amount of the discarded material of the rubber material is large due to the complicated runner.

  Therefore, the above-described runner is a simple sheet-like (film-like) planar runner, and all the cavities are connected with the single planar runner to form a single (sheet-like) rubber molded product. The inventor has conducted experiments and research on an injection molding method and a mold that can be taken out from the mold.

  By the way, in order to take out a small rubber product (seal etc.) molded by many cavities from a sheet-like rubber molded product with high efficiency using an automatic take-out robot, etc. Ideally, they should be arranged in a grid and with a square outer edge. In other words, if a plurality of horizontal take-outs are simultaneously taken out by the automatic take-out robot, the vertical feed and the horizontal feed can be performed quickly and efficiently.

  However, as shown in FIG. 7, the rubber material injected and injected into the mold from the central sprue position 29 flows radially from the circular center region 30 of the runner while drawing a substantially circular shape that gradually increases in diameter. In FIG. 7, the outer peripheral edge of the planar runner becomes a circle C as indicated by a dotted line.

  Thus, in the planar runner whose outer peripheral edge is a circle C, the outer edge of the cavity 33 arranged in a lattice shape is far from the ideal described above. As a second best measure, the octagonal outer edge shape shown in FIG. 7 can be considered as the outer edge shape between the circle and the square. However, it was also found that the four cavities Z indicated by the dots shown in FIG. 7 protrude to the outside of the circle C, so that it is difficult to stably fill the 12 cavities Z with the rubber material. In other words, Z can be referred to as a difficult-to-fill cavity group.

  Therefore, the present invention is capable of stably filling a rubber material into the difficult-to-fill cavities group, increasing the number of rubber products, and improving the efficiency of rubber products by mechanical take-out means such as an automatic take-out robot. The purpose is to enable easy removal.

  The injection mold according to the present invention is a method in which a rubber material is injected and injected from a sprue at the center in a plan view, and into a large number of cavities formed by overlapping an upper die and a lower die, In the injection mold that sequentially fills the rubber material that flows radially toward the outer edge through the inner shape of the runner central region, the geometry of the runner center region is within the cavity disposed on the outer edge. The rubber material has a shape having a protrusion in a direction facing the difficult-to-fill cavity group in which the rubber material hardly flows.

In addition, a large number of the cavities are arranged in a lattice pattern, and the runner center region protrudes in an oblique direction toward the hard-filling cavities arranged in the four corners of the outermost cavities of the lattice array. It has a part.
The runner center region is formed in a square shape in plan view.
In addition, the runner center region has the protrusion from the circular base toward the radial outer side.
Moreover, the said runner center area | region part is formed in planar view X shape.

  According to the injection mold of the present invention, the rubber material flows radially from the runner center region having the protrusion toward the outer edge, and the rubber material is also passed through the protrusions in the difficult-to-fill cavities. Can be filled reliably. Rubber products can be stably molded in the difficult-to-fill cavities, and the number of products can be increased.

It is one Embodiment of this invention, and is a top view of a lower mold | type. It is the top view which showed the rubber molded product obtained by the injection mold of this invention. It is a top view of other runner center region. It is a top view of another runner center region part. It is sectional drawing of a low-pressure clamping state, (A) is sectional drawing, (B) is a principal part expanded sectional view. It is sectional drawing of an injection injection state, (A) is sectional drawing, (B) is a principal part expanded sectional view. It is a figure for demonstrating the problem of the conventional injection molding metal mold | die, Comprising: It is a top view of a lower mold | type.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments.
As shown in FIG. 5, in a state where the upper mold 1 and the lower mold 2 are overlapped, a large number of cavities 3 are formed by the unevenness of the upper surface 2 </ b> A of the lower mold 2 and the lower surface 1 </ b> A of the upper mold 1. The upper mold 1 is provided with a sprue 6 in the center in plan view, and a rubber material (raw rubber) 5 is injected and injected from the sprue 6. The rubber material 5 is caused to flow radially toward the outer edge via the planar thin-walled runner center region 7 that is orthogonal to the central sprue 6 and sequentially filled into the cavities 3.

As shown in FIG. 1, a large number of cavities 3 are arranged in a lattice pattern, and among the outermost cavities 3 of the lattice array, several cavities Z arranged at four corners are outside the circular C. It is arranged. In the present invention, the several cavities Z arranged at the four corners where the rubber material 5 is difficult to flow in are referred to as difficult filling cavity groups Z. The runner center region 7 has a geometrical shape having the protrusions 9 in the direction facing the difficult-to-fill cavity group Z.
In FIG. 1, the runner center region 7 is formed in a square shape in plan view and has four corners. In other words, the protrusion 9 is provided in an oblique direction, and the distance between the difficult-to-fill cavity group Z and the runner center region 7 is shortened by the protrusion 9.

As shown in FIG. 5, the runner center region 7 is formed by a shallow countersunk recess 20 formed on the upper surface 2 </ b> A of the lower mold 2 and the lower surface 1 </ b> A of the upper mold 1, and is connected to the sprue 6. Yes. The outer peripheral edge of the recess 20 has a sloped surface 21 that gradually approaches the lower surface 1A of the upper mold 1. In FIG. 5, the upper mold 1 and the lower mold 2 are clamped with a predetermined low clamping force F ₀ and held in a low-pressure mold clamping state. In this low-pressure mold clamping state, the thickness dimension T ₀ of the gap between the recess 20 and the lower surface 1A of the upper mold 1 is set to 1.0 mm to 1.3 mm. In the region outside the runner central region portion 7, the upper surface 2A of the lower surface 1A of the upper mold 1 and lower mold 2 are close, the thickness _{T 1} of the the small gap is set to 0.1mm~0.3mm Has been. In the low-pressure mold clamping state, the upper mold 1 and the lower mold 2 are always trying to press-contact each other with a low clamping force F ₀ , but in a direction to separate (isolate) the upper mold 1 and the lower mold 2 ( when the internal pressure, etc.) the force of the inflow to come rubber material 5 is applied, while maintaining the attached low clamping force F _0, it is separable (quarantine). In other words, a constant low tightening force F _{0 is applied} to the upper mold 1 and the lower mold 2 while being kept pressed by a clamping means (not shown) such as a fluid pressure cylinder. When an internal pressure is generated on the mating surface of the lower mold 2, one or both of the upper mold 1 and the lower mold 2 are movable in the mutual separation direction. Note that arc-shaped concave grooves 11 and 12 for excess rubber relief are formed around the outer peripheral edges of the upper mold 1 and the lower mold 2.

  The planar shape of the runner center region portion 7 may be a geometric shape having a protruding portion 9 in a direction facing the difficult-to-fill cavity group Z (see FIG. 1) in which the rubber material 5 hardly flows. For example, as shown in FIG. 3, the runner center region portion 7 is preferably a geometric shape having a protruding portion 9 from the circular base portion 10 toward the radially outer side. Alternatively, as shown in FIG. 4, the geometric shape of the runner center region portion 7 may be formed in an X shape with a rounded plan view.

The use method (action) of the injection mold of the present invention described above will be described.
As shown in FIGS. 5 to 6, and the low-pressure mold clamping state upper mold 1 and lower mold 2 and the mold clamping at a predetermined force F ₀ with a low tightening from above and below, the rubber material 5 from the plan view center of the sprue 6 Injection injection is performed in the direction of arrow Y. At this time, the upper die 1 or the lower die 2 are mutually the separating direction, keep moving freely while holding the urging low clamping force F _0. It is desirable that the cavity 3 is in a vacuum state.

As shown in FIG. 6, the injected and injected rubber material 5 first flows from the sprue 6 into the runner center region 7 and then flows in a 360 ° radial direction R (radially) from there toward the outer edge. Since the runner center region portion 7 has a quadrangular shape in plan view having the protruding portion 9 in the oblique direction, the rubber material 5 has a slightly rounded shape (substantially quadrangular shape with rounded corners) and radially expands toward the outer edge, The planar area is increased, and it flows to the outside of the circle C to be filled in the difficult-to-fill cavities Z at the four corners (see FIG. 1). At this time, the upper mold 1 and the lower mold 2 maintain the same low clamping force F ₀ in both the low-pressure mold clamping state before injection injection (FIG. 5) and the injection injection state (FIG. 6). When the rubber material 5 is supplied from the runner center region 7 toward the outer edge, the gap is expanded by the injection pressure of the rubber material 5. Due to the mechanical balance between the internal pressure when the rubber material 5 flows in the 360 ° radial direction R and the low tightening force F ₀ in the direction in which the upper die 1 and the lower die 2 are relatively close to each other, A planar runner 13 that connects a large number of cavities 3 arranged in a grid is formed thinly and uniformly while automatically securing gaps necessary for flow. At a outside of the runner the central region 7, the thickness T ₂ of the planar runner 13, a size for the rubber material 5 flows is thus automatically ensured.

  After all the cavities 3 are filled with the rubber material 5 through the planar runner 13, the upper mold 1 and the lower mold 2 are clamped with a predetermined high clamping force to be in a high-pressure mold clamping state, and vulcanized by heating and pressing. I do. Thereafter, the upper mold 1 and the lower mold 2 are loosened, and a sheet-like rubber molded product 15 having a large number of rubber product portions 16 is taken out.

  As shown in FIG. 2, the rubber molded product 15 includes a large number of rubber product parts 16 formed in the cavity 3 around the thick central base part 17 formed in the sprue 6 and the runner center region part 7. Are arranged in a grid pattern. In FIG. 2, rubber product portions 16 are also formed at the four corners of the grid-like arrangement. Many rubber product parts 16 are integrally connected by a thin planar runner part 18. The planar runner portion 18 is formed by a minute gap between the upper mold 1 and the lower mold 2 and has a very small thickness (for example, 0.1 mm to 0.3 mm). The rubber molded product 15 may have a complicated shape with an outer peripheral edge having an uneven shape or a broken portion, or a surplus rubber material 5 flows into the concave grooves 11 and 12 to slightly surround the wall. A thick burr edge may be formed.

  That is, the injection mold according to the present invention can be molded in the difficult-to-fill cavity group Z at the four corners as compared with the conventional injection mold shown in FIG. More) increase by 12. Since the rubber product parts 16 are arranged in a lattice shape, the rubber product parts 16 can be easily removed by mechanical take-out means, and the rubber product parts 16 can be quickly removed by sequentially taking out the rubber product parts 16 along the rows. And the planar runner portion 18 can be separated.

  The design of the present invention can be changed. For example, a gap is left between the upper mold 1 and the lower mold 2, and after the rubber material 5 is injected and injected into the sprue 6, the upper mold 1 and the lower mold 2. The mold may be clamped (not shown).

  As described above, the injection mold according to the present invention is formed by injecting and injecting the rubber material 5 from the sprue 6 at the center in a plan view, into a large number of cavities 3 formed by superposing the upper mold 1 and the lower mold 2. In the injection mold in which the rubber material 5 that flows radially from the central sprue 6 to the outer edge through the runner center region 7 is sequentially filled, the geometric shape of the runner center region 7 is formed on the outer edge. Since the rubber material 5 has a shape having the protruding portion 9 in the direction facing the difficult-to-fill cavity group Z in which the rubber material 5 hardly flows in the arranged cavity 3, the rubber material 5 has a runner center region having the protruding portion 9. The rubber material 5 flows preferentially from the portion 7 toward the outer edge, and the rubber material 5 can be preferentially filled into the difficult-to-fill cavity group Z via the protruding portion 9. Rubber products can be stably molded in the difficult-to-fill cavity group Z, and the number of products can be increased.

  In addition, a large number of cavities 3 are arranged in a lattice pattern, and the runner center region 7 is obliquely directed toward the difficult-to-fill cavity groups Z disposed at the four corners of the outermost cavities 3 in the lattice array. Therefore, it is possible to reliably fill the rubber material 5 in the difficult-to-fill cavity group Z, and to stably form the rubber product in the difficult-to-fill cavity group Z, and to increase the number of parts. it can. The rubber product can be easily and quickly removed by the mechanical removal means.

  Moreover, since the runner center region portion 7 is formed in a square shape in plan view, the rubber material 5 can be reliably filled into the difficult-to-fill cavity group Z.

  Moreover, since the runner center region portion 7 has the protruding portion 9 from the circular base portion 10 outward in the radial direction, the hardly filled cavity group Z can be reliably filled with the rubber material 5.

  Moreover, since the runner center region 7 is formed in an X shape in plan view, the rubber material 5 can be reliably filled into the difficult-to-fill cavity group Z.

DESCRIPTION OF SYMBOLS 1 Upper mold | type 2 Lower mold | type 3 Cavity 5 Rubber material 6 Sprue 7 Runner center area | region 9 Protrusion part 10 Circular base Z Z difficult filling cavity group

Claims (5)

The rubber material (5) is injected and injected from the sprue (6) at the center in plan view, and the sprue at the center is formed in a large number of cavities (3) formed by overlapping the upper mold (1) and the lower mold (2). In the injection mold in which the rubber material (5) that flows radially from the runner center region (7) to the outer edge is sequentially filled from (6),
The geometric shape of the runner center region (7) is such that the rubber material (5) is less likely to flow into the cavity group (Z) in the cavity (3) disposed on the outer edge. An injection mold characterized by having a shape having a protrusion (9).   A large number of the cavities (3) are arranged in a lattice shape, and the center of the runner is directed toward the difficult-to-fill cavities (Z) disposed at the four corners of the outermost cavities (3) of the lattice-like arrangement. The injection mold according to claim 1, wherein the region (7) has an oblique protrusion (9).   The injection mold according to claim 1 or 2, wherein the runner center region (7) is formed in a square shape in plan view.   The injection mold according to claim 1 or 2, wherein the runner center region (7) has the protrusion (9) radially outward from a circular base (10).   The injection mold according to claim 1 or 2, wherein the runner center region (7) is formed in an X shape in a plan view.

Images