JPH07178777A - Hot nozzle for runnerless injection molding of plastic - Google Patents

Abstract

PURPOSE:To provide the hot nozzle capable of preventing the adverse effect of cold slag on a product without providing a slag well to a mold and capable of obtaining a product good in the appearance of its cut surface in a gate part. CONSTITUTION:In a hot nozzle for injection molding equipped with the nozzle part 2 inserted in the nozzle hole H formed so as to communicate with the cavity C1 of a mold M and constituted so as to allow the nozzle part 2 itself to generate heat by the supply of a current, a leading end member 7 consisting of the base part 8 positioned at the almost center part of the nozzle part 2 and branch parts 9-9 connecting the base part 8 and the inner wall of the gate part 6 is provided in the gate part 6 provided to the leading end of the nozzle part 2. The front 12 of the leading member 7 is formed into an almost planar shape to be made almost flush with the opening surface of the gate part 6 and faces to the inlet part of the cavity C1 in such a state that the nozzle part 2 is inserted in the nozzle hole H and the gate cut surface B1 of a product P1 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic runnerless structure having a nozzle portion inserted into a nozzle hole formed in communication with a cavity of a molding die, and the nozzle portion itself generating heat when energized. The present invention relates to a hot nozzle for injection molding.

[0002]

2. Description of the Related Art The applicant of the present invention previously filed a patent No. 1589967.
No. (Japanese Patent Application No. 59-124814, Japanese Patent Publication No. 1-59)
No. 895) proposed a hot nozzle for a plastic runnerless injection molding, which does not require an external heater for heating the nozzle and has an excellent structure capable of raising and lowering the temperature in a short time. There is.
A schematic structure of such a hot nozzle will be described with reference to FIG. 3. The illustrated hot nozzle 1 is a substantially hollow cylindrical nozzle inserted into a nozzle hole H formed in communication with a cavity C of a molding die M. The nozzle portion 2 has a portion 2 and a base portion 3 that guides the molten resin injected from an injection molding machine (not shown) to the nozzle portion 2.
Is provided with a split groove 4 and is separated by the split groove 4,
A voltage is applied between both ends of the base portion 3 through the conductive wires 5 and 5 to heat the nozzle portion 2 itself. The detailed structure of such a hot nozzle 1 is described in the above-mentioned Patent No. 158.
Since it is disclosed in Japanese Patent No. 9967, description thereof will be omitted.

In such a hot nozzle 1, the gate portion 6 at the tip of the nozzle portion 2 has an annular shape, and when the molten resin is injected again into the cavity C after the product is taken out, as shown in FIG. As shown in (a), the cold resin, that is, cold slug S, remaining in the tip portion of the nozzle portion 2 flows in as it is together with the molten resin. Since such cold slug S causes a flow mark in the product, it is necessary to previously provide a slug well W in the cavity C as shown in FIG.

[0004]

However, by providing such a slug well W, a protrusion Pa corresponding to the slug well W is formed in the molded product P as shown in FIG. 4B. Therefore, it is necessary to remove this by post-processing, which causes a problem of high cost.

Further, when the product is taken out from the mold, the resin in the gate portion 6 needs to be maintained in a semi-solid state rather than in a completely solidified state in order to separate it from the product. For this reason, as shown in FIG. 4B, the cut surface B of the gate portion 6 of the product becomes jagged and the appearance of the product is deteriorated. Therefore, it is necessary to smooth the cut surface B by post-processing. Therefore, there is a problem that the cost becomes higher.

[0006]

In view of the above-mentioned drawbacks of the prior art, the present invention is a product in which cold slugs can be prevented from adversely affecting products without providing slug wells and the appearance of the cut surface at the gate portion is good. For injection molding, which is provided with a nozzle part that is inserted into a nozzle hole that is formed in communication with the cavity of the molding die, and that the nozzle part itself generates heat when energized. In the hot nozzle, a tip member is provided in the gate portion at the tip of the nozzle portion, the tip member including a base portion located substantially in the center of the nozzle portion and a branch portion connecting the base portion and the inner wall of the gate portion. The front surface of the tip member is formed to be substantially flat and is substantially flush with the opening surface of the gate portion, and the front surface is in a state in which the nozzle portion is inserted into the nozzle hole. It faces the inlet of the cavity, and forming a gate cut surface in the product.

It is preferable that the base portion of the tip member is provided with a protrusion protruding from the base portion toward the upstream side.

[0008]

In the present invention, when the molten resin is injected again into the cavity after the product is taken out, the cold slag remaining in the tip portion of the nozzle portion hits the base portion of the tip member and is crushed and fragmented. Also, at this stage, the hot nozzle is generating heat due to the energization,
This heat is transferred from the base of the tip member to the cold slug, and the cold slug undergoes a heating action in addition to the above-mentioned subdivision action, so that the cold slug almost disappears before reaching the cavity. Further, the front surface of the tip member is formed to be substantially flat and is substantially flush with the opening surface of the gate portion. Since this front surface forms the gate cutting surface of the product, the gate cutting surface is smooth. In addition, by disposing the tip member in the gate portion, the tip member can serve as a reinforcing rib.

Further, in the above-mentioned subdivision action and heating action, the tip member is provided with the protrusion protruding from the base portion toward the upstream side, so that the crushing action and the heating action can be more effectively performed on the cold slug. Can be exerted.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a hot nozzle according to an embodiment of the present invention will be described with reference to FIGS. The present embodiment is different from the conventional hot nozzle 1 shown in FIGS. 3 and 4 only in the structure of the tip portion of the nozzle portion 2, and the same members are designated by the same reference numerals and the description thereof is omitted.

As shown in FIG. 1A, the hot nozzle 1
Inside the gate portion 6 at the tip, a tip member 7 made of the same material and integral with the gate portion 6, that is, the same material and integral as the nozzle portion 2, is provided. As shown in FIG. 2, the tip member 7 has a base portion 8 located in the center of the inside of the gate portion 6 and three branch portions 9 to 9 radially extending from the base portion 8, The outer ends of the branch portions 9 to 9 are connected to the inner circumference of the gate portion 6. As shown in FIG. 2, the branch portions 9 to 9 have a mutual length of 1
They are arranged at equal intervals in the circumferential direction at an angle of 20 ° and form outflow openings 10 to 10 between each other. Further, as shown in FIG. 1A, the base portion 8 is provided with a protrusion 11 that projects from the center of the back side of the base portion 8 toward the upstream side. It has a conical shape facing.

Further, as shown in FIG. 1A, the front surface 12 of the tip member 7 including the base portion 8 and the branch portions 9 to 9 is formed into a flat surface which is flush with the end surface of the gate portion 6, As shown in the figure, the boundary surface with the cavity C1 is formed in a state where the nozzle 2 is inserted into the nozzle hole H of the mold M.

The operation of the above embodiment will be described below.
When the molten resin is injected again into the cavity C1 after the product is taken out, the cold slug S remaining in the tip portion of the nozzle portion 2 is the base portion 8 of the tip member 7 immediately before the gate portion 6.
It collides with the protrusions 11 provided on the crusher and is crushed into smaller pieces. Further, at this stage, the hot nozzle 1 is heating the nozzle portion 2 itself by energization. Therefore, the tip member 7 formed of the same material as and integrally with the hot nozzle 1 is also heating. Therefore, the cold slug S is subjected to a heating action in addition to the above-described subdivision action, and is almost extinguished before it flows into the cavity C1 from the outflow openings 10 to 10.

Therefore, it is not necessary to provide the slug well W in the cavity C1 of the mold M as in the conventional example. Therefore, the projecting portion Pa is not formed in the product P1 and the work after removing it is unnecessary. Become.

Further, the front surface 12 of the tip member 7 has a gate portion 6
Since it is formed in a flat surface that is flush with the end surface of the mold and forms a boundary surface with the cavity C1, the product P1 taken out of the mold M is separated with the front surface 12 as a boundary and faces the front surface 12. The product P1 portion has a smooth surface, and only the area of the outflow openings 10 to 10 other than the front surface 12 directly faces the cavity C1, and the area directly facing the cavity C1 becomes small. The cut surface B1 has a smooth appearance as a whole as shown in FIG. Therefore, the work of smoothing the cut surface B1 by post-processing becomes unnecessary.

Furthermore, since the tip member 7 plays a role of a reinforcing rib inside the gate portion 6, the strength of the gate portion 6 is improved.

Although the tip member 7 is made of the same material as that of the nozzle portion 2 in the above embodiment, it may be made of a different material. In this case, the material of the tip member 7 has a high thermal conductivity. The material is selected. When such a material is used, the tip member 7 does not perform its own heat generating action similar to the nozzle portion 2, but the heat of the nozzle portion 2 is quickly transferred to the tip member 7, and the same action as above is performed. The effect can be obtained.

[0018]

According to the present invention, the cold slag remaining in the tip portion of the nozzle portion is heated by the base portion of the tip member in addition to the subdivision action, and is substantially eliminated before reaching the cavity. , There is no need to provide a slug well in the cavity. Along with this, the product has no protrusion corresponding to the slug well, so that a product with a good appearance can be obtained, and post-processing for removing the protrusion is not required, so that the manufacturing cost is reduced.
Further, since the gate cut surface is smoothed by the front surface of the tip member, the appearance of the product is further improved, and the post-processing for smoothing the cut surface is not required, so that the manufacturing cost is further reduced. In addition, by disposing the tip member in the gate portion, there is an advantage that the tip member serves as a reinforcing rib and the strength of the gate portion can be improved.

Further, by providing the protrusion protruding from the base portion toward the upstream side, the crushing action and the heating action can be more effectively exerted on the cold slug, so that mixing of the cold slug into the product is effective. Can be effectively prevented and the product quality is improved.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a main part of a hot nozzle according to an embodiment of the present invention, showing a mold and a product after molding, in a cross section corresponding to a cross section taken along the line I-I of FIG.

FIG. 2 is an end view of the tip of the gate portion of the hot nozzle shown in FIG.

FIG. 3 is a schematic sectional view showing a conventional hot nozzle together with a mold.

FIG. 4 is an enlarged sectional view of an essential part corresponding to FIG. 1, showing a conventional hot nozzle.

[Explanation of symbols]

 1 Hot Nozzle 2 Nozzle Part 6 Gate Part 7 Tip Member 8 Base 9 Branch 12 Front M Mold C1 Cavity P1 Product B1 Cut Surface

Claims (2)

[Claims] 1. A hot nozzle for injection molding, comprising a nozzle portion inserted into a nozzle hole formed in communication with a cavity of a molding die, and configured so that the nozzle portion itself generates heat when energized, A tip member is provided in the gate portion at the tip of the nozzle portion, the tip member including a base portion located substantially at the center of the nozzle portion and a branch portion connecting the base portion and the inner wall of the gate portion, and the front surface of the tip member. Is substantially flat and is substantially flush with the opening surface of the gate portion, and the front surface faces the inlet portion of the cavity with the nozzle portion inserted into the nozzle hole. Hot runner for plastic runnerless injection molding, characterized in that it forms a gate cut surface in. 2. The base of the tip member is provided with a protrusion protruding from the base toward the upstream side.
A hot nozzle for runnerless injection molding of plastic according to.