JPH10119090A - Injection mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection mold for manufacturing a product having extremely small thickness of flash without mechanically weak point. SOLUTION: The injection mold comprises a lower mold 2, an upper mold 3 vertically movable to the mold 2, and a core 5 having a ring-shaped cavity 16 formed between the molds 2 and 3 in the state that the molds 2, 3 are superposed. Downward movement of the core 5 is controlled by a spacer 18 in the state that the molds 2 and 3 are superposed, and gaps S1 for rubber flow communicating with the cavity 16 are formed at inner and outer radial sides of the cavity 16. The downward movement of the core 5 is allowed in the state that the control of the spacer 18 is released to reduce the gaps S1 to 0 to small amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold.

[0002]

2. Description of the Related Art Conventionally, when an O-ring or the like is molded by using an injection mold, rubber is injected into a cavity with a slight gap between upper and lower molds, and then the mold is clamped.

[0003]

However, in the above method, the rubber first flows out around the runner before the rubber is injected into the cavity. For this reason, when the cavity is filled with rubber, rubber flows out of the flow path to the outside over a wide range, and the pressurized area is widened at the time of mold clamping, so that the burr thickness cannot be reduced sufficiently. Also, if the inflow amount of rubber is reduced to reduce the burr thickness, a weld (joint) is likely to be formed at a portion where the rubber farthest from the runner joins, and this weld becomes a mechanical weak point as a product. . Accordingly, it is an object of the present invention to provide an injection molding die which does not have a weld and does not have a mechanical weak point portion and can reduce the thickness of a formed burr.

[0004]

In order to achieve the above object, an injection mold according to the present invention comprises a lower die, an upper die movable up and down with respect to the lower die, and a lower die. A core that forms a ring-shaped cavity between the lower mold and the lower mold in the overlapping state of the lower mold; A gap for rubber flow is formed, and the core is allowed to descend in a state where the regulation is released.
And a small spacer. The spacer comprises an insertion member which is inserted between the upper die and the hot plate holding the core so as to be able to be inserted and removed so as to restrict the lowering of the core.

[0005]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an injection mold according to the present invention.
The injection mold includes a lower mold 2 placed on a lower hot plate 1, an upper mold 3 that is vertically movable with respect to the lower mold 2, and a lower surface 4 b of an upper hot plate 4. Core 5 fixed to
And. The upper and lower dies 3, 2 and the core 5, and the upper and lower hot plates 4, 1 are fastened by a fastening device (not shown).

On the upper surface 2a of the lower mold 2, a core 5
Are formed with a plurality of recesses 6.
A peripheral groove 7 is formed around the recess 6. Further, the upper die 3 is formed with holes 8 each composed of a small-diameter portion 8a and a large-diameter portion 8b by the number corresponding to the number of the recesses 6, and the core 5 is inserted into the hole 8. A sprue 9 is formed at the center of the upper die 3 and connected to a runner 10 formed between the lower surface 3b of the upper die 3 and the upper surface 2a of the lower die 2. In this case, as shown in FIG.
An injection nozzle 22 is pressed against and separated from the sprue, and a molding material (rubber) is injected from the injection nozzle 22 to the sprue 9.
In FIGS. 2 and 3, rubber is indicated by dots.

As shown in FIGS. 2 and 3, the core 5 includes a main body 5a formed of a disc, an outer flange 11 formed at the upper end of the outer peripheral surface of the main body 5a, and a main body 5a. A bulge 13 is formed at the center of the lower surface 12, and a circumferential groove 14 is formed in the lower surface 12 of the main body 5a. A ring-shaped notch 15 is formed on the outer peripheral surface of the bulging portion 13. Therefore, in a state where the core 5 is superposed, the circumferential groove of the core 5 is formed.
14 and the corresponding peripheral groove 7 of the lower die 2, the cavity 16
Is formed.

[0009] In this case, the thickness dimension T ₁ of the main body 5a is larger than the thickness dimension T ₂ of the upper die 3, identical to the depth W of the thickness T ₃ is the recess 6 of the bulging portion 13 Or slightly smaller. Further, the thickness T ₄ of the outer collar portion 11 is set substantially equal to the depth W ₁ of the large diameter portion 8b of the hole 8.

However, this mold has an upper mold 3 and a hot plate 4
And a spacer 18 composed of an insertion member (rod) inserted removably between them. That is, the horizontal piston rod 20a of the cylinder 20 is attached to the spacer 18,
By the reciprocating motion of the piston rod 20a in the axial direction, the spacer 18 is removably inserted into the notch 19 formed on the upper surface 3a of the upper die 3. The thickness T of the spacer 18
₅ is set to be larger than the height dimension H of the notch 19, and as shown in FIG. 2, when the spacer 18 is inserted into the notch 19, the vertical movement of the upper die 3 is restricted, and the hot plate 4 A gap S is formed between the lower surface 4b of the upper die 3 and the upper surface 3a of the upper die 3. Also,
As shown in FIG. 3, when the spacer 18 is pulled out from the notch 19, the core 5 can be lowered and the upper die 3 slightly rises with respect to the lower die 2 with respect to the state shown in FIG. Is made possible. Reference numeral 23 denotes a circumferential groove 24 on the outer peripheral surface of the core 5.
Reference numeral 26 denotes a seal material attached to the concave groove 27 of the lower die 2.

As shown in FIG. 3, when the upper die 3 is raised (slightly) higher than the lower die 2, a gap S is formed between the upper surface 2a of the lower die 2 and the lower surface 3b of the upper die 3. ₂ is formed, the clearance S ₂ is communicatively connected to the flow of rubber for the clearance S ₁ on the outer peripheral side at the recessed groove 21 formed on the upper surface 2a of the lower die 2.

Next, a method of forming an O-ring (product) P using the mold having the above-described configuration will be described. First, as shown in FIG. 2, the spacer 18 is inserted into the notch 19 so that a gap S is formed between the hot plate 4 and the upper die 3. In this case, between the lower surface of the main body 5a of the core 5 and the corresponding upper surface 2a of the lower mold 2, specifically, the circumferential grooves 7, 14
The gaps S ₁ , S ₁ for rubber flow (the gaps S ₁ , S ₁ are respectively formed on the inner and outer diameter sides of the cavity 16 formed by
The communication is connected. ) Is formed. In this state, the molding material is injected from the injection nozzle 22 to the sprue 9. As a result, the molding material passes through the plurality of cavities 16... And the rubber flow gaps S ₁ , S
Flowing through the _primary. In this case, the material (rubber) flows freely in a relatively open space, and no weld is formed.

Thereafter, the spacer 18 is pulled out of the notch 19 to release the restriction on the lowering of the core 5, and the hot plate 4 is lowered,
As shown in FIG. 3, the gaps S ₁ , S ₁ for the inner and outer rubber flows are set to 0 to slight. That is, the spacer 18 is removed and the mold is clamped. As a result, the rubber in the rubber flow gap S ₁ on the inner diameter side escapes to the cutout portion 15 of the core 5, and the rubber in the rubber flow gap S _{1 on} the outer diameter side mixes with the upper surface 2 a of the lower mold 2 and the upper mold 3. Lower surface 3b
Escape through the grooves 21 (the slightly increased gap size becomes large and the upper die 3 with respect to the lower die 2) runner 10 gap S ₂ and is formed between the.

Thus, the inner and outer burrs formed on the product P to be formed have extremely small thickness. If the mold P is opened from this state, the product P is taken out, and the inner and outer burrs are removed, thereby completing the manufacture of the O-ring.

In this mold, the number of cores 5 can be freely increased or decreased, that is, the number of cavities 16 to be formed can be freely increased or decreased, and the diameter and cross-sectional area of the cavities 16 can also be freely adjusted. Can be changed to The means for reciprocating the spacer 18 may include a screw shaft and a nut member screwed to the screw shaft.

[0016]

Since the present invention is configured as described above, the following effects can be obtained.

According to the first aspect of the present invention, the formed product has no weld, no mechanical weakness, and a very small thickness of the formed burr. As a result, the operation of removing burrs becomes easy, and waste of material is eliminated. According to the injection molding die of the second aspect, the effects of the first aspect are obtained, and the rubber flow gaps S ₁ and S ₁ are reliably formed on the inner and outer diameter sides of the cavity 16 so that the rubber can easily flow. At the same time, the restriction on the lowering of the core 5 can be reliably released, and the thickness of the burrs can be reliably reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an injection mold according to the present invention.

FIG. 2 is a sectional view of a main part showing an injection molding state.

FIG. 3 is a sectional view of a main part showing an injection molding state.

[Explanation of symbols]

2 Lower mold 3 Upper mold 4 Hot plate 5 Core 16 Cavity 18 Spacer S ₁ Gap for rubber flow

Claims (2)

[Claims] 1. A lower mold, an upper mold movable up and down with respect to the lower mold, and a core forming a ring-shaped cavity between the lower mold and the lower mold in an overlapping state with the lower mold. When the upper and lower molds are overlapped, the lowering of the core is regulated to form a rubber flow gap communicating with and connected to the cavity on the inner and outer diameter sides of the cavity, and the core is allowed to descend when the regulation is released. And a spacer for reducing the gap for rubber flow from 0 to slight. 2. The injection device according to claim 1, wherein the spacer comprises an insertion member inserted between the upper die and the hot plate holding the core so as to be able to be inserted and removed so as to restrict the lowering of the core. Molding mold.