JPH1016005A - Valve gate device for injection molding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a perforated molding in a satisfactorily finished shape. SOLUTION: This valve gate device 1 is assembled into a top force B arranged opposite to a bottom force A, and consists of a center core pin 2, a ring gate 3, pistons 4, 4 which travel up and down through the ring gate 3, a cylinder 5, a nozzle 6 enclosing the ring gate 3, a heater 7 arranged on the outer periphery of the nozzle 6, a manifold 8 and a runner 9. Consequently, the ring gate 3 does not come into contact with the nozzle 6 even when a valve is closed, hence there is no possibilities of wear, and the prolongation of the life of the ring gate 3 is obtained. In addition, a molten resin is directly injected into a cavity from the nozzle 6, so that it is possible to adequately prevent a poor weld, fin and a wall of ununiform thickness from being generated, and thereby efficiently manufacture a perforated molding in a satisfactory finished shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot runner type valve gate device of an injection molding machine for a perforated molded product.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 3-48 discloses a technique for reducing the damage of a mold and a nozzle for mass production of injection molded articles.
No. 851 proposes a "needle opening type nozzle for an injection mold". However, with this technique, it is not possible to manufacture a hole-formed product (a product having holes formed at the same time as forming).

[0003] In order to manufacture a perforated molded product, the following method can be considered. 6A to 6C are schematic diagrams of a conventional pin gate forming method. 1A, a molded article 103 having a large hole 102 can be manufactured by injecting a resin from a pin gate 101 into a cavity. In (b), a weld 104 is formed at a location where the resin collides after the resin is divided into right and left, and the weld 104 is likely to become a defect. In (c), the side closer to the pin gate 101 is likely to be thicker T1, and the side farther away is likely to be thinner T2. Therefore, the pin gate molding method has a problem of weld and uneven thickness.

FIGS. 7A and 7B are schematic views of a conventional ring gate forming method. In (a), the runner section 1
11. Since resin is injected into the cavity through the ring gate 112, uniform injection is possible. However, in (b), when the runner portion 111 is removed, the burrs 113 remain and the appearance is poor, so that a step of removing the burrs 113 is required.

FIGS. 8A and 8B are schematic views of a conventional disk gate forming method. In (a), since the resin is injected into the cavity through the runner section 121 and the drain 122, uniform injection becomes possible. But (b)
When the runner part 121 is removed,
However, the appearance is poor, and a step of removing the burr 123 is required. That is, both the ring gate forming method and the disk gate forming method have a problem of burr.

Therefore, as a technique for solving the problems of weld and burr, Japanese Patent Publication No. Sho 60-23972 has proposed a "valve assembly". This technique is for making a disk having a hole in the center, and FIG. 9, the sleeve valve 130 is opened (the lower end is raised to the position indicated by the broken line), the resin is fed through the hole 55,
Then, the sleeve valve 130 is closed (the end is lowered to the position indicated by the solid line), that is, the sleeve valve 13 is connected to the dispersion head 66.
By pressing 0, the center hole of the disk 113 is cut and trimmed. The shaft 60 employs a structure in which the heater 64 always keeps the temperature so that the sealed resin does not solidify.

[0007]

However, the sleeve valve 1
Pressing the 30 against the dispersing head 66 will damage both or one of the abutting parts, shortening the service life. If the surface to be cut becomes thicker, it may not be possible to cut, and if the cutting force is increased, the life of the component parts is shortened. Further, the diameter of the shaft portion 60 is increased in order to heat the shaft portion 60. Shaft 60
The outer diameter of the sleeve valve 130 changes, while a force is applied toward the central axis of the sleeve valve 130 because the outer temperature of the sleeve valve 130 is low. That is, since the expansion force is applied to the sleeve valve 130 from the center and the contraction force is applied from the outside, the slide of the sleeve valve 130 becomes unstable, and the slide becomes extremely impossible. Thus, Japanese Patent Publication No. 60-23972
In the “valve assembly” of the publication, there is a problem that the life is shortened because the valve abuts on the head, and the smooth movement of the sleeve valve is difficult to maintain due to the arrangement of the heater.

[0008]

In order to solve the above-mentioned problems, a first aspect of the present invention is a nozzle for injecting a molten resin, and a nozzle inserted into the center of the nozzle for making a hole in a molded product and having a tip end. A more protruding center core pin, a ring gate that slides along the outer peripheral surface of the center core pin and stops the flow of resin while keeping a very small gap without contacting the nozzle, and raising and lowering the ring gate A cylinder and a piston for controlling the injection constitute a valve gate device of the injection molding machine.

A hole is formed in a molded product by interposing a center core pin in a cavity. Opening and closing of the injection port (small inner diameter part) at the tip of the nozzle is performed by raising and lowering the ring gate, but this ring gate does not contact the nozzle even when the injection port (small inner diameter part) at the nozzle tip is closed. There is no need to worry about wear and the service life is extended. Since the molten resin is directly injected into the cavity in a direction perpendicular to the radial direction of the center core pin from the injection port (small inner diameter portion) at the nozzle tip, welds, burrs, and uneven thickness can be sufficiently prevented. Can be efficiently produced.

According to a first aspect of the present invention, the nozzle has a small inner diameter portion, a middle inner diameter portion, a tapered portion, and a large inner diameter portion from the tip to the base, and the ring gate has a small diameter portion from the tip to the base on the outer periphery. It has a medium diameter part and a large diameter part, and when the injection port (small diameter part) at the nozzle tip is closed, the small diameter part faces the small diameter part and the medium diameter part faces the medium diameter part, respectively. The inclination angle of the tapered portion is α1, and α2> α1 when an angle formed by a line connecting the tip of the small diameter portion and the tip of the middle diameter with the nozzle axis is α2. Even if the ring gate is moved up and down, there is no fear that the ring gate hits the inner periphery of the nozzle, so that the life of the ring gate and the nozzle is extended.

According to a second aspect of the present invention, a good heat conducting member is provided at the tip of the center core pin, and a good heat conducting member is also provided on the mold side facing the center core pin. Before the mold assembly, the resin near the nozzle tip was kept in an appropriate molten state, and immediately after the mold assembly, heat was sufficiently transmitted from the center core pin to the low-temperature mold to warm the low-temperature mold. . When the cooling effect of the mold on the low-temperature side is large, it is possible to prevent the disadvantage that the resin of the nozzle hardens and the operation of the nozzle becomes defective, so that the injection molding can be continued more smoothly.

A third aspect is characterized in that a heater is arranged on the outer periphery of the nozzle. Heat the nozzle with the outer heater,
Since the ring gate is housed in this nozzle, the nozzle thermally expands so that the inner diameter of the nozzle is always larger than the outer diameter of the ring gate. On the other hand, since there is a center core pin at a temperature slightly lower than the temperature held by the ring gate inside the ring gate, there is a minute gap between the center core pin and the ring gate, Since the outer periphery is made only of the resin in a molten state, a smooth elevating operation of the ring gate can be secured.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is an overall sectional view of a valve gate device of an injection molding machine according to the present invention.
A center core bin 2, a ring gate 3 surrounding the center core pin 2, and pistons 4, 4 and a cylinder 5 for moving up and down the ring gate 3 are assembled into an upper die B opposed to the lower die A. A nozzle 6 surrounding the ring gate 3 and a heater 7 arranged on the outer periphery of the nozzle 6
, A manifold 8, and a resin passage 9.

The lower mold A is a movable mold and has a convex portion 11 on its upper surface.
And a small concave portion 12 above the convex portion 11. The upper die B is a fixed die, and is formed by stacking a die plate 14, an intermediate plate 15, and a mounting plate 16 for convenience of manufacture and the like. At the same time, the nozzle 6 is fitted from above,
The manifold 8.

Further, the ring gate 3 is mounted on the intermediate plate 15 via the cylinder 5 and the pistons 4, 4, and the center core pin 2 is hung on the mounting plate 16 by the stop ring 21, the clamping washers 22, 23 and the nut 24. The intermediate plate 15 and the mounting plate 16 are sequentially stacked on the template 14. At this time, as shown, the ring gate 3 is guided by the guide hole 6 a at the base of the nozzle 6.
In the figure, reference numeral 25 denotes a manifold heater.

FIG. 2 is an enlarged view of a main part of the valve gate device according to the present invention. In this figure, the shape characteristics of the ring gate 3 and the dies provided on the center core pin 2 and the lower die B will be described. The outer periphery of the ring gate 3 has a three-stage configuration of a small diameter portion 31, a middle diameter portion 32, and a large diameter portion 33 from the bottom to the top. , A middle inner diameter portion 37, a tapered portion 38, and a large inner diameter portion 39. Here, the small-diameter portion 31 has a slightly smaller diameter than the small-diameter portion 35, the middle-diameter portion 32 has a slightly smaller diameter than the middle-diameter portion 37, the tip (lower end) 31 a of the small-diameter portion 31 and the middle-diameter portion 32. A line segment connecting the tip (lower end) 32a of the nozzle with the nozzle axis (the center axis of the nozzle 6) is inclined by an angle α2,
On the other hand, when the inclination angle of the tapered portion 38 of the outer nozzle 3 is α1, α2> α1.

As a result, when only the ring gate 3 is lowered and the small diameter portion 31 faces the small inside diameter portion 35, the resin stops due to the extremely small gap and the viscosity of the resin. As a result, the ring gate 3 can be raised and lowered smoothly without touching the inner surface of the nozzle 6.

The thickness t of the small diameter portion 31 (shown in FIG. 2)
The value of the small inner diameter portion 35 and the diameter of the center core pin 2 can be appropriately set according to the shape, thickness, size, and the like of the molded product.

Next, the good heat conducting members provided on the center core pin 2 and the lower mold B will be described. The center core pin 2 is made of carbon steel for machine structure (S-C, JIS), and a copper rod 41 as a good heat conducting member is driven into the lower end of the center core pin 2. Further, a brass (seven brass) plate 42 as a good heat conducting member is embedded in the bottom of the concave portion 12 of the lower die B. The brass plate 42 is also a soft material.

The operation of the valve gate device described above will now be described. 3A and 3B are explanatory diagrams (first half) of the operation of the valve gate device according to the present invention. In FIG. 1, the ring gate 3 is lowered with the molten resin flowing in the resin passage 9 to stop the flow of the resin, and in this state, the lower die A is raised and the upper die B is overlaid on the upper die B. This indicates that a cavity 44 for a product has been formed between the upper die B and the lower die A in a state where the center core pin 2 has entered the concave portion 12 of the lower die B.

Here, although the nozzle 6 is sufficiently heated by the heater 7, the temperature of the lower die A is much lower than that of the upper die B. Therefore, when the cooling action of the cold lower mold A is large, the resin at the tip of the nozzle 6 is hardened, and there is a possibility that the opening and closing of the ring gate 3 may be supported. As a countermeasure, in this embodiment, the copper rod 41 and the brass plate 4 as good heat conducting members are used.
2 is embedded.

[0022]

[Table 1]

Table 1 shows the thermal conductivity of carbon steel for machine structural use (S-C, JIS) constituting the center core pin, a copper rod inserted into the center core pin, and a brass (733 brass) plate embedded in the bottom of the recess. Is a comparison table in which copper can transmit 7 times more heat to S-C, and brass can transmit twice as much heat. Then, the resin in the vicinity of the small inner diameter portion 35 located at the tip of the center core pin 2 can be maintained at an appropriate resin temperature, and at the same time when the copper rod 41 comes into contact with the brass plate 42, the holding of the center core pin 2 is started. Heat is transmitted to the brass plate 42 via the copper rod 41, and the temperature of the concave portion 12 of the lower die A rises within a very short time. As a result, lump of resin can be avoided.

In (b), only the ring gate 3 is raised. Then, a so-called valve open state is established, and the resin flows into the cavity 44 and is filled.

FIGS. 4A and 4B are explanatory diagrams (second half) of the operation of the valve gate device according to the present invention. In (a), only the ring gate 3 is lowered. Then, the valve is closed. In (b), the lower mold A is lowered as indicated by the white arrow. Thus, the molded article 45 can be paid out. Thereafter, FIG. 3 (a) → (b) → FIG. 4 (a) → (b) → FIG.
By repeating as (a) → (b)..., Injection molding can be performed quickly.

FIGS. 5A and 5B are views showing an example of a molded product obtained by the apparatus of the present invention. (A) shows a circular molded product 50 including a bottom 52 having a hole 51, a cylinder 53, and a wide flange 54. (B) is a bottom 62 having a hole 61 and a wall 6.
Angular shaped product 6 consisting of 3, 63 and flanges 64, 64
Indicates 0. As described above, according to the present invention, it is possible to effectively manufacture the hole-opened products 50 and 60 without welds and burrs.

The materials of the good heat conducting members 41 and 42 and
These shapes and attachment methods can be set as appropriate.

[0028]

According to the present invention, the following effects are exhibited by the above configuration. A first aspect of the present invention provides a nozzle for injecting a molten resin, a center core pin inserted into the center of the nozzle to form a hole in a molded product and having a tip protruding from the nozzle, and along an outer peripheral surface of the center core pin. A valve gate for an injection molding machine, comprising a ring gate that slides and does not contact the nozzle and keeps the flow of resin while keeping a very small gap, and a cylinder and a piston that raises and lowers the ring gate to control injection. Since the apparatus is configured, the ring gate does not come into contact with the nozzle even when the valve is closed, there is no fear of wear, and the life is extended. Since the molten resin is directly injected into the cavity in a direction perpendicular to the radial direction of the center core pin from the injection port (small inner diameter portion) at the nozzle tip, welds, burrs, and uneven thickness can be sufficiently prevented. A perforated molded product having a good shape can be manufactured efficiently.

In addition, the first aspect of the present invention is characterized in that the inclination angle of the tapered portion of the nozzle with respect to the nozzle axis is α1, and the angle formed by the line connecting the tip of the small diameter portion and the tip of the middle diameter portion with the nozzle axis is α2. Since α2> α1, even if the ring gate is moved up and down, there is no worry that the ring gate hits the inner periphery of the nozzle.
The life of the ring gate and the nozzle is prolonged.

The second aspect is characterized in that a good heat conducting member is provided at the tip of the center core pin, and a good heat conducting member is also provided on the mold side facing the center core pin. Before the mold assembly, the resin near the nozzle tip was kept in an appropriate molten state, and immediately after the mold assembly, heat was sufficiently transmitted from the center core pin to the low-temperature mold to warm the low-temperature mold. . When the cooling effect of the mold on the low-temperature side is large, it is possible to prevent the disadvantage that the resin of the nozzle hardens and the operation of the nozzle becomes defective, so that the injection molding can be continued more smoothly.

A third aspect of the present invention is characterized in that a heater is arranged on the outer periphery of the nozzle. Heat the nozzle with the outer heater,
Since the ring gate is housed in this nozzle, the nozzle thermally expands so that the inner diameter of the nozzle is always larger than the outer diameter of the ring gate. On the other hand, since there is a center core pin at a temperature slightly lower than the temperature held by the ring gate inside the ring gate, there will be a minute gap between the center core pin and the ring gate, and Since the outer periphery is made only of the resin in a molten state, a smooth elevating operation of the ring gate can be secured.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a valve gate device of an injection molding machine according to the present invention.

FIG. 2 is an enlarged view of a main part of the valve gate device according to the present invention.

FIG. 3 is an explanatory view of the operation of the valve gate device according to the present invention (first half).

FIG. 4 is a diagram illustrating the operation of the valve gate device according to the present invention (second half).

FIG. 5 is a view showing an example of a molded product obtained by the apparatus of the present invention.

FIG. 6 is a schematic view of a conventional pin gate molding method.

FIG. 7 is a schematic view of a conventional ring gate forming method.

FIG. 8 is a schematic view of a conventional disk gate molding method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Valve gate device, 2 ... Center core pin, 3 ... Ring gate, 4 ... Piston, 5 ... Cylinder, 6 ... Nozzle,
7: heater, 8: manifold, 9: resin passage, 12:
Recessed part, 31 ... small diameter part, 31a ... tip of small diameter part, 32 ... medium diameter part, 32a ... tip of medium diameter part, 33 ... large diameter part, 35 ... small inside diameter part, 37 ... medium inside diameter part, 38 ... tapered part , 39 ... large inner diameter part, 41 ... good heat conduction member (copper bar), 42 ... good heat conduction member (brass plate), 44 ... cavity, 45, 50, 60 ...
Molded products, 51, 61: holes, A: lower mold, B: upper mold.

Claims (3)

[Claims] 1. A nozzle for injecting a molten resin, a heater for heating the molten resin in the nozzle, and a nozzle inserted into the center of the nozzle to make a hole in a molded product, and a tip protruding from the nozzle. The center core pin, a ring gate that slides along the outer peripheral surface of the center core pin, stops the flow of resin while keeping a very small gap without contacting the nozzle, and raises and lowers the ring gate to perform injection. A nozzle having a small inner diameter portion, a middle inner diameter portion, a tapered portion and a large inner diameter portion from the tip to the base, and the ring gate has a small diameter from the tip to the base at the outer circumference. Part, a medium diameter part, and a large diameter part. When the nozzle is closed, the small diameter part faces the small diameter part, and the medium diameter part faces the medium diameter part. The inclination angle of the tapered part with respect to the nozzle axis is α1. The angle at which the line connecting the tip of the intermediate-diameter portion and the tip of the small diameter portion is formed between the nozzle axis when the [alpha] 2, [alpha] 2
2. The valve gate device for an injection molding machine according to claim 1, wherein the molten resin is injected from a small inner diameter portion of the nozzle in a direction perpendicular to a radial direction of the center core pin. 2. A valve gate for an injection molding machine according to claim 1, wherein a good heat conducting member is provided at a tip of said center core pin, and a good heat conducting member is also provided on a mold side facing said center core pin. apparatus. 3. The valve gate device for an injection molding machine according to claim 1, wherein the heater is arranged on an outer periphery of the nozzle.