JP3816249B2 - Nozzle for injection molding machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nozzle for an injection molding machine in which a nozzle chip having nozzle holes for discharging molten resin from a resin passage in a hot runner is attached to an outlet portion of the hot runner.
[0002]
[Prior art]
Conventionally, as this type of nozzle, according to JP-A-5-278074, a nozzle tip, a bottomed cylindrical outer tip having a nozzle hole formed at the bottom, and a bottomed cylindrical shape fitted into the outer tip are used. The inner chip has an inner / outer dual structure composed of an inner chip, and the inner circumferential space of the inner chip is configured as a communication path communicating with the resin path in the hot runner, and a nozzle is provided between the bottom outer surface of the inner chip and the bottom inner surface of the outer chip. A gap communicating with the hole is formed, and further, a communicating hole communicating with the gap through the communicating path is formed in a portion not facing the nozzle hole at the bottom of the inner chip. There is known a phenomenon in which melted resin is drawn out from the inside in a thread-like manner, so-called stringing can be prevented.
[0003]
[Problems to be solved by the invention]
In the above conventional example, there is a problem that the processing of the outer chip and the inner chip takes time and costs are increased.
[0004]
In view of the above points, an object of the present invention is to provide a low-cost nozzle for an injection molding machine that can prevent stringing.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a nozzle for an injection molding machine in which a nozzle tip in which a nozzle hole for discharging molten resin from a resin passage in a hot runner is attached to an outlet portion of the hot runner. A portion of the inner end surface of the nozzle tip facing the resin passage is formed as a recessed surface, the nozzle hole is opened in the recessed surface, and the rising portion of the outer periphery of the recessed surface of the inner end surface of the nozzle chip A disc-shaped piece member that is overlapped at the outer peripheral edge portion, and an opening portion that communicates with the resin passage is formed in a portion of the piece member that does not face the nozzle hole, and the molten resin from the opening portion is formed. The nozzle hole is guided through a gap formed between the recessed surface and the piece member.
[0006]
A portion of the piece member that faces the nozzle hole serves as a shielding portion that shields the nozzle hole from the resin passage in the hot runner, and stringing of the molten resin in the resin passage during demolding is suppressed.
[0007]
In the present invention, it is only necessary to superimpose a disk-shaped piece member on the inner end face of the nozzle tip, and the processing is easier and the cost is lower than that of the conventional example in which the inner tip is fitted to the outer tip.
[0008]
In addition, when the width of the gap becomes narrow, the flow resistance of the welding resin increases, and when the width of the gap becomes wide, stringing is likely to occur. In order to prevent the flow resistance from becoming excessive and to effectively prevent stringing, the width of the gap is set to 10% to 50% of the diameter of the open end of the nozzle hole with respect to the recessed surface. It is desirable.
[0009]
Further, if the wall surface around the opening is formed on an inclined surface that is inclined inward of the opening toward the nozzle tip, the molten resin can easily flow at the time of injection. An edge that cuts stringing is formed by the inclination of the wall surface, and stringing is more effectively prevented.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, reference numeral 1 denotes a molding die of an injection molding machine, 2 denotes a hot runner heated by a heater (not shown), and a nozzle tip 3 is attached to an outlet portion of the hot runner 2. The end surface is brought into close contact with the outer surface of the mold 1 and molding is performed through the nozzle hole 3a in which the molten resin from the resin passage 2a in the hot runner 2 is formed in the nozzle chip 3 and the spool portion 1a formed in the mold 1. It is injected into a cavity (not shown) in the mold 1.
[0011]
A screw hole 2b having a diameter larger than that of the resin passage 2a is formed at the outlet of the hot runner 2, and the nozzle tip 3 is screwed into the screw hole 2b. Further, a portion of the inner end surface of the nozzle chip 3 facing the resin passage 2a is formed in the recessed surface 3b, and the nozzle hole 3a is opened in the recessed surface 3b. Furthermore, a disc-shaped piece member 4 is provided that is superimposed on the outer peripheral edge of the rising edge 3c on the outer periphery of the recessed surface 3b on the inner end face of the nozzle tip 3,
When the nozzle chip 3 is screwed into the screw hole 2b, the piece member 4 is clamped and fixed between the shoulder surface 2c at the bottom of the screw hole 2b and the rising portion 3c at the outer peripheral edge thereof.
[0012]
A plurality of fan-shaped openings 4a (three in the illustrated example) as shown in FIG. 2 communicating with the resin passage 2a are formed in a portion of the piece member 4 not facing the nozzle hole 3a. A portion facing 3a is configured as a shielding portion 4b that shields the nozzle hole 3a from the resin passage 2a.
[0013]
According to the above configuration, the molten resin that has flowed into the opening 4a from the resin passage 2a flows into the nozzle hole 3a via the gap between the shielding portion 4b and the recessed surface 3b, and the spool portion from this nozzle hole 3a. Molten resin is injected into the cavity through 1a. After injection, the mold 1 is cooled to solidify the resin. At this time, the nozzle tip 3 that is in close contact with the mold 1 is also cooled, and the resin in the nozzle hole 3a is also solidified. The resin in the gap between the entrance surface 3b is also semi-solidified. Then, when the molded product is extracted from the mold 1 (at the time of demolding), as shown in FIG. 3, the semi-solidified resin a in the gap serves as a plug, and the solidified resin b in the nozzle hole 3a is melted. Demold without resin stringing.
[0014]
When the width L of the gap is less than 10% of the diameter D of the opening end of the nozzle hole 3a with respect to the recessed surface 3b, the flow resistance of the molten resin at the time of injection becomes excessive, and the width L is equal to the diameter D. If it exceeds 50%, the molten resin is drawn into the nozzle hole 3a through the gap, and stringing is likely to occur. Therefore, the width L is desirably 10% or more and 50% or less of the diameter D.
[0015]
Further, in the present embodiment, the wall surface around the opening 4 a is formed on the inclined surface 4 c that is inclined inward of the opening 4 a toward the nozzle chip 3. According to this, the molten resin easily flows at the time of injection, and the inclined surface 4c on the side of the shielding portion 4b functions as an edge for cutting the molten resin that is likely to be drawn into the nozzle hole 3a at the time of demolding. More effectively prevented.
[0016]
【The invention's effect】
As is apparent from the above description, according to the present invention, stringing can be prevented with a simple structure in which a disk-shaped piece member is superposed on the inner end face of the nozzle tip, and the cost can be reduced.
[Brief description of the drawings]
1 is a vertical cross-sectional view of an example of the nozzle of the present invention. FIG. 2 is a perspective view of a piece member. FIG. 3 is an enlarged vertical cross-sectional view of a main part during demolding.
2 Hot runner 2a Resin passage 3 Nozzle tip 3a Nozzle hole 3b Recessed surface 3c Rising part 4 Piece member 4a Opening

Claims (3)

In the nozzle for an injection molding machine, in which a nozzle tip is formed with a nozzle hole for discharging molten resin from the resin passage in the hot runner at the outlet of the hot runner.
Forming a portion of the inner end surface of the nozzle tip facing the resin passage into a recessed surface, and opening the nozzle hole in the recessed surface;
A disk-shaped piece member is provided at the outer peripheral edge of the rising edge of the outer periphery of the recessed surface of the inner end surface of the nozzle tip, and the resin passage is formed in a portion of the piece member that does not face the nozzle hole. Forming a communicating opening,
An injection molding machine nozzle, wherein the molten resin from the opening is guided to the nozzle hole through a gap formed between the recessed surface and the piece member. 2. The nozzle for an injection molding machine according to claim 1, wherein a width of the gap is 10% to 50% of a diameter of an opening end of the nozzle hole with respect to the recessed surface. The nozzle for an injection molding machine according to claim 1 or 2, wherein a wall surface around the opening is formed on an inclined surface inclined inward of the opening toward the nozzle chip.

Images