JPH0742680Y2 - Thread pull prevention pad for resin molding die - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention is used by being installed in a nozzle touch portion of a resin molding die, and is used for pulling a sprue product between a sprue product and a nozzle. The present invention relates to a thread-pulling prevention pad suitable for preventing this.

[Conventional technology]

Generally, in injection molding, the mold is forcibly cooled with a coolant such as water in order to shorten the molding cycle. On the other hand, the resin in the nozzle is always kept in a molten state by heating means such as a heater so that continuous injection is possible. The molded product and the sprue product are taken out in a slashed state.

However, if the molded product is taken out,
As shown in the drawing, the so-called stringing 38 in which the molten resin in the nozzle is dragged and the tail is drawn easily occurs on the end surface 8 ′ of the sprue product 8 taken out together with the passage component 36. When stringing occurs, even if the sprue product 8 is taken out, the stringing portion 38 enters the parting surface or cavity of the mold, causing damage to the parting surface, deterioration of dimensional accuracy, or uneven surface texture. It was

For this reason, for example, Japanese Utility Model Publication No. 63-50102 proposes a technique for dissipating heat from the nozzle portion by providing a metal thin plate having a high thermal conductivity having a hole communicating with the sprue between the sprue bush and the nozzle. Has been done. It is intended to cool the thread of the molten resin by the heat dissipation effect of the thin plate to make it difficult to stretch and to easily cut the thread.

Further, Japanese Utility Model Application Laid-Open No. 1-116619 discloses a technique in which a partition is provided to divide a molten resin into a plurality of pieces, and a stringing is prevented by improving a cooling and solidifying action by increasing a surface area.

[Problems to be solved by the device]

By the way, to consider the cause of stringing, the nozzle directly touches the nozzle touch surface of the mold and direct thermal coupling is made.
Further, since the cooling of the mold by the refrigerant is mainly performed around the cavity, the end surface 8'of the sprue product 8 is maintained in a high temperature state and becomes a semi-solidified state, and due to the approximation of the state, it is coupled with the molten resin on the nozzle side. Is expected to be strong. That is, in this type of resin molding, the nozzle is constantly heated by the heater to a temperature higher than the mold temperature so that continuous molding can be performed, and the contact causes a gentle temperature gradient between the nozzle and the nozzle touch surface, resulting in sprue. It seems that the ends are semi-solidified.

Taking ABS resin as an example, the nozzle temperature is about 200 ℃,
Even if molding is performed under the condition that the temperature of the mold is about 60 ° C, stringing actually occurs even though the temperature of the mold is sufficiently lower than the curing temperature of the ABS resin (about 120 ° C). It is considered that this is because the temperature gradient between the nozzle and the nozzle touch surface becomes gentle due to the heat transfer from the nozzle side to the mold, and the sprue end is maintained at the curing temperature of the ABS resin or higher.

Therefore, it is expected that the stringing can be prevented by suppressing the relaxation of the temperature gradient between the nozzle and the mold.

However, in the stringing prevention tool disclosed in Japanese Utility Model Publication No. 63-50102, although a thin plate having a high thermal conductivity provides a heat radiation effect to some extent, it has a small effect on a nozzle which is constantly heated to a high temperature. Further, since the thermal conductivity is high, the heat is smoothly transferred between the nozzle, the preventive tool and the nozzle touch surface which are in close contact with each other, and it is not possible to sufficiently suppress the relaxation of the temperature gradient. For this reason, the threading prevention function is uneven.

Further, the yarn pulling prevention tool disclosed in Japanese Utility Model Laid-Open No. 1-116619 has a problem that the flow resistance at the time of filling the resin increases because the partition is provided.

Further, in these conventional techniques, there is also a problem that handling is inconvenient because the stringing prevention tool is manufactured only from the viewpoint of the shape corresponding to the nozzle touch surface.

Therefore, the present invention can suppress the relaxation of the temperature gradient between the nozzle and the mold, and thus can reliably prevent the stringing without increasing the flow resistance, and can easily handle the stringing prevention pad with excellent usability. The purpose is to provide.

[Means for Solving the Problems]

This invention was created to achieve the above-mentioned purpose,
The characteristic is a pad member of a thin-walled metal plate that has a convex portion that abuts against the nozzle touch surface and is sandwiched between the nozzle and the nozzle portion, and that has a flange portion that integrally extends from the convex portion and that abuts against the end surface of the sprue bush. The pad member is provided with a resin passage hole that is formed substantially at the center thereof and communicates with the resin introduction port, and the pad member has a heat insulating portion formed in layers at least on the convex portion and is overlaid on the heat insulating portion. The adhesive layer is formed.

[Action]

According to this invention, the convex portion of the pad member is aligned with the nozzle touch surface of the mold and temporarily fixed by the adhesive layer. In this case, the pad member is handled with its flange portion, whereby the convex portion is easily associated with the nozzle touch surface.
The convex portion is temporarily fixed to the nozzle touch surface and is sandwiched between the nozzle and the nozzle. When the molten resin is injected, the resin passes through the resin passage hole, enters the resin introduction port of the mold, and is sent to the sprue.

The mutual heat insulating function of the heat insulating portion and the adhesive layer hinders heat transfer from the nozzle to the nozzle touch surface, and suppresses the relaxation of the temperature gradient between the nozzle and the mold. When injection is completed and cooling and solidification is performed, the end surface of the sprue product is also in a solidified state, and when the sprue product is taken out, the end surface of the sprue product and the molten resin on the nozzle side are separated by a weak bonding force.

〔Example〕

 1 to 6 show an embodiment of the present invention.

A sprue bush 6 is installed in the resin molding die 2 at a setting position of a nozzle 4 of the molding machine, and a sprue 8 is formed in the sprue bush 6. The end of the sprue 8 serves as a resin introduction port 10. A nozzle touch surface 12 forming a curved surface is formed on the end surface of the sprue bush 6,
A stringing prevention pad 14 is installed between the nozzle touch surface 12 and the nozzle 4.

The molten resin P injected from the injection port 16 of the nozzle 4 passes through the resin passage hole 20 of the stringing prevention pad 14 and is sent to the sprue 8. After this, although not shown, it is sent to the cavity through a runner and a gate. To be After the injection is completed, the mold 2 is opened through the cooling and solidifying process, and the sprue product 8 and the like are taken out.

As shown in FIGS. 2 and 3, the stringing prevention pad 14 is formed of a thin metal plate and is in contact with the nozzle touch surface 12 and is sandwiched between the pad member 18 and the nozzle 4. A resin passage hole 20 communicating with the mouth 10 is provided, and heat insulating portions 21 are formed in layers on the front and back surfaces of the pad member 18. Further, in this example, an expanding piece 22 that can expand in the radial direction of the sprue 8 inside the resin introducing port 10 is provided on the periphery of the resin passage hole 20.
Are formed.

The pad member 18 has a convex portion 24 corresponding to the nozzle touch surface 12.
And a collar portion 28 that comes into contact with the end surface 26 of the sprue bushing 6. Further, an adhesive material layer 30 is provided on the surface of the pad member 18 so as to overlap with the heat insulating portion 21 to obtain a temporary stop prior to the sandwiching. A double-sided tape or the like can be used as the adhesive layer 30. The adhesive material layer 30 may be attached only on the surface of the convex portion 24.

In this example, TAFRON No. 3 (trade name; manufactured by Bellwood Junka Co., Ltd.) was used as the material of the heat insulating portion 21. For example, the heat insulating portion 21 can be formed by immersing the pad member 18 in a solution of Taflon. The thickness of the heat insulating section 21 is preferably about 0.03 mm.

The heat insulating portion 21 prevents heat transfer from the nozzle 4 to the nozzle touch surface 12, and suppresses the relaxation of the temperature gradient between the nozzle 4 and the nozzle touch surface 12. Therefore, in the cooling and solidifying process, the end surface 8'of the sprue product 8 is also solidified as shown in FIG. 6, and the end face 8'is removed when the sprue product 8 is taken out due to the weak bonding force between the solidified material and the molten material. ′ To molten resin P
Are separated well and stringing is prevented. The nozzle temperature is
As a result of injection molding of ABS resin under the same conditions of 200 ° C. and mold temperature of 60 ° C., as a result, when the stringing prevention pad 14 of this example was not installed, stringing occurred, but when it was installed, Did not happen.

The heat insulating portion 21 may be only the area corresponding to the nozzle touch surface 12, that is, the portion of the convex portion 24, or only one of the front and back surfaces. However, the production cost can be reduced by the above-mentioned whole immersion. Further, in this example, in addition to the heat insulating action of the heat insulating portion 21, the heat insulating action by the adhesive material 30 can be obtained.

Since the pad member 18 has the flange portion 28, there is the convenience that the nozzle 4 can be set and pinched while the flange portion 28 is pressed with a finger.

Further, in this example, on the back surface side of the convex portion 24, a notch 32 is formed which extends radially from the central portion and the depth of which gradually decreases outward. The notch 32 is formed to such an extent that it bursts from the center portion under the flow pressure of the molten resin P, and the molten resin P is injected by this, so that the notch 32 in the convex portion 24 is formed as shown in FIG. The formed portion is opened inward of the resin introducing port 10, and the resin passage hole 20 and the expanding piece 22 are simultaneously formed.

When the injection is finished, the fluid pressure of the molten resin P disappears, and as shown in FIG. 5, the expanding piece 22 has a valve action of slightly contracting in the radial direction of the sprue 8 due to elasticity. After the process of cooling and solidifying the resin in the mold 2 is completed, the mold 2 is opened and the sprue product 8
6, the molten resin P in the nozzle 4 is dragged along with the movement of the sprue product 8 as shown in FIG. The flow resistance increases due to the characteristics of the Newtonian fluid, that is, viscoelasticity, and the close contact with the sprue product 8 is cut off. This promotes the stringing prevention function.

Next, FIG. 7 shows another example.
Is a surface of the pad member 18 coated with a ceramic layer 38 with a thickness of about 0.03 mm. In this example as well, the same stringing prevention function as that of the above-described example can be obtained by the heat insulating function.

[Effect of device]

According to this invention, since the thermal insulation can suppress the relaxation of the temperature gradient between the nozzle and the nozzle touch surface, it is possible to obtain the solidified state of the sprue end face during the cooling and solidification process, and thus, when the sprue product is taken out, the sprue is removed. It is possible to reliably prevent stringing between the end surface and the molten resin on the nozzle side.

Also, by having a collar part, it is possible to easily align the nozzle touch surface, and to easily perform temporary fixing with the adhesive layer, and to obtain the heat insulating function of the adhesive layer in addition to the heat insulating part. You can

Furthermore, since the pad member can be easily formed by pressing and the layered heat insulating portion can be easily formed by partially or wholly immersing the pad member,
The manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a usage state of a stringing prevention pad according to an embodiment of the present invention, FIG. 2 is an overall perspective view, and FIG.
The figure is an enlarged cross-sectional view taken along the line III-III in FIG. 2, FIG. 4 is a schematic cross-sectional view showing the state at the time of injection, and FIG. 5 is a schematic cross-sectional view showing the state at the time when the injection is finished. FIG. 7 is a schematic cross-sectional view showing a state when a molded product is extruded, FIG. 7 is a schematic cross-sectional view showing another example, and FIG. 8 is a perspective view showing an example of a stringing product. 2 ... Mold for resin molding, 4 ... Nozzle 8 ... Sprue, 10 ... Resin introduction port 12 ... Nozzle touch surface 14,36 ... Thread pull prevention pad 18 ... Pad member 20 ... Resin passage port , 21 …… Insulation part 24 …… Convex part 26 …… End face of sprue bush 28 …… Collar part

Claims (1)

[Scope of utility model registration request] 1. A threading prevention tool installed in a resin molding die including a nozzle touch surface with which a nozzle of a molding machine abuts and a resin introduction port to a sprue. A pad member of a thin metal plate having a convex portion that is sandwiched between the pad member and a flange portion that integrally extends from the convex portion and abuts on the end surface of the sprue bush, and the resin introduction member formed at substantially the center of the pad member. A resin passage hole communicating with the mouth, wherein the pad member has a heat insulating portion formed in a layer on at least the convex portion, and an adhesive layer formed on the heat insulating portion. A stringing prevention pad for resin molding dies.