JPS62164515A - Hot runner for multi-layer injection - Google Patents

Abstract

PURPOSE:To intercept the supply of resin quickly and smoothly by a method wherein a movable member, provided in a hot runner, is moved in case a multi- layer forming structure is formed by the co-injection of a plurality of resins. CONSTITUTION:A movable member 6, capable of moving into an axial direction, is arranged coaxially between an inner tubular member 2 and an outer tubular member 3. The movable member is a tubular member as a whole and the outer surface thereof is provided so as to be slidable on the inner surface of the outer tubular member 3 while a small clearance is provided between the inner surface of the movable member 6 and the outer surface of the inner tubular member 2 and a second resin path 7 for controlling an injection timing is formed between them. A truncated conical surface 8 is provided at the side end of the movable member 6 while the conical surface 9 is also provided on the inner tubular member 2. Accordingly, the conical bodies 8, 9 are engaged when the movable member 6 descends, whereby the resin path 7 is intercepted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to the structure of a hot runner for multi-layer injection, and more specifically, to a multi-layer molded structure formed by co-injection of a plurality of resins. Related to the structure of a hot runner that allows the supply of one resin to be cut off and started smoothly and quickly when forming a resin. (Prior art) In the field of injection blow molding of containers, etc. A gas barrier resin such as ethylene-vinyl alcohol copolymer or polyamide is interposed as an intermediate layer between resin layers such as polyolefin or polyethylene terephthalate constituting the material. When these multiple types of resin are co-injected, a part of the resin for forming the inner and outer surfaces is injected into the injection mold, and the resin on the cavity surface becomes υ high in viscosity as it cools, and the next injected resin is A method has been adopted in which the resin for forming the intermediate layer is then injected by utilizing the property of being introduced into the center of the resin. In order to completely encapsulate the resin for the intermediate layer between the resins for the inner and outer surfaces without exposing it to the outside, it is necessary to wait a certain time lag from the start of injection of the resin for the inner and outer surfaces before injecting the intermediate layer resin. It is necessary to start the injection process and finish the injection of the intermediate layer resin a certain period of time before the injection of the inner and outer surface layer resins is finished.

The injection timing of the intermediate layer resin can be determined by controlling the screw movement of the intermediate layer resin injection machine or by controlling the hot runner.
This is done by controlling the opening and closing of an on-off valve provided in the intermediate layer resin flow path.

(Problem to be Solved by the Invention) However, in the method of controlling the advance of the intermediate layer resin by controlling the injection movement of the screw, there is a slight difference between the nozzle of the injection machine and the dirt of the mold. There is a long hot runner passage, and even if the injection movement by the screw is stopped and the diameter is fixed, the molten resin in the hot runner will flow into the mold as other resins are injected, and the injection of the intermediate layer resin will be interrupted. It is extremely difficult to finish and start injection at precisely the same timing.

Particularly when a multi-cavity injection mold is used, there is a problem in that the distance of the hot runner to the dirt of each cavity is different, resulting in a timing shift for each cavity. The above-mentioned drawbacks occur to varying degrees even when an on-off valve is provided in the hot runner's resin passage.
occurs in the same way.

Accordingly, an object of the present invention is to provide a hot runner system (1) that is capable of shutting off and starting injection of one of the resins at precise timing and reliably when manufacturing a multi-molded structure by co-injecting multiple types of resins. lt-provided.

Another object of the present invention is that even in co-injection molding using a multi-cavity mold, injection can be shut off and started smoothly and quickly without any deviation in injection timing for each cavity. To provide a hot runner device.

Still another object of the present invention is to provide a hot runner for multilayer injection that can be particularly advantageously applied to the production of preforms for blow molding.
is to provide.

(Means for Solving the Problems) The present inventors provided a movable member that is movable in the axial direction in a hot runner for multilayer injection, and set the injection timing between this movable member and the corresponding cylindrical member. The above-mentioned problems can be solved by providing a passage for the resin to be controlled, by forming truncated conical surfaces on the parts of these members near the nozzle, and by engaging the truncated conical surfaces with each other as the movable member moves. I found that it was solved all at once.

According to the present invention, in a multilayer injection hot runner equipped with a nozzle at the tip and a plurality of independent resin passages converging toward the nozzle, a core member and a first An inner cylindrical member provided through a resin passage and an outer cylindrical member having a nozzle at the tip are arranged coaxially, a movable member movable in the axial direction is provided between the inner cylindrical member and the outer cylindrical member, and the movable member A second resin passage is arranged between the inner circumferential surface and the outer circumferential surface of the inner cylinder member, and the inner circumferential surface of the movable member and the portions of the outer circumferential surface of the inner cylinder member close to the nozzle are respectively formed into truncated conical surfaces, and There is provided a hot runner for multilayer injection, characterized in that the truncated conical surface engages with the truncated conical surface and blocks the second resin passage by moving in the axial direction.

(Function) In FIG. 1, which schematically shows the main parts of the hot runner of the present invention, this hot runner roughly speaking includes a core member 1 arranged coaxially. It is composed of an inner cylinder member 2 and an outer cylinder member 3. At the center of the tip of the outer cylinder member 3 is an injection mold f-) (
A nozzle 4 is provided, which is connected to a device (not shown). A first resin passage 5 having a cylindrical shape and converging toward the nozzle 4 is provided on the outer surface of the core member 1 and the inner surface of the inner cylinder member 2.

According to the present invention, the movable member 6 that is movable in the axial direction is arranged coaxially between the inner cylinder member 2 and the outer cylinder member 3. The movable member 6 has a cylindrical shape as a whole, and the outer surface and the inner surface of the outer cylinder member 3 are slidably provided. There is a small gap, and a second resin passage 7 whose injection timing is to be controlled is formed between the two.

A truncated conical surface 8 with a tapered diameter is provided at the nozzle side end of the movable member 6, and a truncated conical surface 9 with a tapered diameter is also provided at the nozzle side end of the inner cylinder member 2. The inclination angles or chii4 angles of both these truncated conical surfaces 8 and 9 are substantially equal.

In Figure 1, the movable member 6 is in the raised position and the second resin passage 7 is open toward the nozzle 4, but when the movable member 7 is lowered, both truncated conical surfaces 8 and 9 are engaged. It will be understood that the second resin passage 7 is then blocked.

According to the present invention, by adopting the above configuration, the injection start and injection stop of the second resin can be started and stopped at the part closest to the nozzle 4, which is the final outlet of the resin, without any timing delay and in a good manner. This can be done with rising and falling characteristics. The opening/closing operation by moving the movable member 6 in the axial direction is performed by opening/closing the truncated conical surfaces 8 and 9, which also serve as the second resin, and is performed over a relatively wide opening/closing area.
The start and stop of injection of the second resin can be performed reliably and smoothly.

According to one preferred embodiment of the present invention, the core member 1 is hollow, and a heating mechanism is provided inside the core member 1 to keep the resin in a molten state, so that the first resin passage 5 on the outer periphery of the core member 1 is formed. A polyester resin passageway is used for forming the inner and outer surface layers, and a second resin passageway 7 is used as a gas barrier resin passageway for forming an intermediate layer of ethylene vinyl alcohol copolymer, polyamide resin, or the like.

If this arrangement is adopted, the melting point is high (polyester (P)
(ET) has a melting point of 245°C) and the gas barrier resin, which is susceptible to thermal decomposition, remains in the hot runner for a relatively long time while maintaining the polyester for the inner and outer layers, which has a large flow rate, in a sufficiently molten state. Also, it is possible to prevent the gas barrier resin from being excessively heated.

(Embodiment) The outer cylindrical member 3 used in the present invention has a passage shown in FIG. 1, an end 11 closed at one end, and a short inward projection 12 at the center of the end 11. is desirable. An annular cavity 13 is provided between the inward protrusion 12 and the outer cylinder 3, and the distal end 14 of the movable member 6 is fitted into the annular cavity 3.

A resin passage 15 is formed in the inward protrusion 12 and the closed end 11 and is flush with the truncated conical surface 8 of the movable member 60 when the movable member 6 is open. It has a truncated conical surface 16t. In this structure,
Since the opening/closing operation is performed with the distal end 14 of the movable member 6 always fitted into the annular cavity 13 of the outer cylinder member 3, the opening/closing operation is performed smoothly and with high precision.

In FIG. 2 showing the overall structure of the hot runner, a hollow core member 1 is provided above a hot runner fixing plate 20 via a heat insulating plate 21 and a spacer 22.

A heater 10 is inserted into the hollow part of the core member 1 and connected to a power source (not shown) via a connector 23, and its lower part is closed by a pipe 24. A hot runner sprue bushing 25 and a first hot runner manifold 26 are provided around the lower part of the core member 1. First sprue block 27
is provided. Attached to the first sprue 27 is a first sprue 28 that is connected to a first resin injection machine (not shown), and includes a sedge/l/7' lock 27, a hot runner manifold 26, and a hot runner manifold 26. The runner sprue bushing 25 is provided with a first resin flow path 29 that is connected to the first sprue 28 .

A hollow cylindrical member 2 is provided on the hot runner sprue bushing 25 coaxially with the core member 1. A first resin passage 5 is formed between the inner surface of the inner cylinder member 2 and the outer surface of the core member 1. It is connected to the flow path 29. The root portion of the inner cylindrical member 2 has an increasing diameter and has a portion 30 with an outer diameter equal to the outer diameter of the movable member 6 disposed outside the inner cylindrical member 2.

A sleeve 31 for supporting the outer cylinder member 3 is provided at the base of the cylindrical member 2, and a second hot runner is provided on the outer periphery of the sleeve 31. A support ring 32 is provided to support the lock.

vinegar? - Above the ring 32 and on the outer periphery of the sleeve 31, a second hot runner manifold 33 and a second sprue block 34 are provided. Second sprue pro, Ri3
4 is fitted with a second sprue 35 which is connected to a second resin injection machine (not shown) and which injects a second resin flow extending through the second sprue 34 and manifold 33. It is connected to the line 36.

The movable member 6 is vertically movable between the fixed outer cylinder member 3 and the inner cylinder member 2, and there is a second A resin passage 7 is formed, which is connected to the second sprue 35 via a second resin flow passage 36.

In order to move the movable member 2 up and down between open and closed positions, a vertical elongated hole (not shown) is provided in the fixed outer cylinder member 3, and a bottle protrudes outward through the entire elongated hole. 37 will be provided. On the other hand, the piston 3 is connected to the hot runner fixing plate 20.
While fixing the hydraulic cylinder device 38 equipped with 9,
A rotation shaft 42 is disposed that rotates via a link 40 and a lever 41 as the piston 39 moves up and down, and a long notch 43 engages with the pin 37 described above with respect to the rotation shaft 42. An arm 44 with a

Figure 2 and Figure 3 to explain the operation of the hydraulic cylinder.
In the figure, when the piston 39 is in the lowered position, the movable member 2 is in the raised position, so the second resin passage 7 is open.
Conversely, when the piston 39 is in the raised position, the movable member 2 is in the lowered position, and therefore the second resin passage 7 is closed.

When producing a multilayer injection molded article, the hot runner nozzle 4 is connected to a dart of a split mold (none of which is shown),
A No. 10 resin injection machine (not shown) is connected to the first sprue 27, and a second resin injection machine (not shown) is connected to the second sprue 35. Further, the heater 10 is energized via the connector 23 to perform necessary heat retention. With the start of operation of the injection machine, the first resin is transferred to the first sprue 2.
8. The first resin flow path 29 and the first resin passage 5 are energized, and the resin is injected into the mold cavity through the nozzle 4.

When a predetermined amount of the first resin has been injected, the hydraulic cylinder device 38 is activated to lower the piston 39, and accordingly, the movable member 6 is raised to open the second resin passage 7.
Open. As a result, the second resin is injected from the nozzle 4 into the mold cavity via the second sprue 35, the second resin flow path 36, and the second resin passage 7. In this second stage injection cycle, the first resin and the second resin may be injected at the same time, or the injection pressure of the second resin may be lowered to lower the injection pressure of the second resin. It can also be made to occur preferentially.

When a predetermined amount of the second resin has been injected, the hydraulic cylinder device 38 is activated to raise the piston 39;
Along with this, the movable member 6 is lowered and the second resin passage 7 is closed. This stops the injection of the second resin,
Only the injection of the first resin proceeds. The injection cycle ends when the mold cavity is filled with resin.

According to this injection method, a multilayer injection molded structure is obtained in which the intermediate layer made of the second resin is completely encapsulated in the inner and outer layers made of the first resin.

(Operations and Effects of the Invention) According to the present invention, when manufacturing a multilayer molded structure by co-injecting multiple types of resins, injection interruption and injection start of one resin are performed accurately and reliably, and Even in co-injection molding using a large number of molds,
Since the passage is opened and closed at a position close to the nozzle, there is an advantage that injection can be stopped and started for each cavity smoothly without any timing lag.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a cross-sectional view showing the main parts of the hot runner of the present invention, FIG. 2 is a cross-sectional view showing an embodiment of the hot runner of the present invention, and FIG. The figure is a perspective view showing the operation of the movable members of the hot runner. 1 is a core member, 2 is an inner cylinder member, 3 is an outer cylinder member, 4 is a nozzle, 5 is a first resin passage, 6 is a movable member, 7 is a second resin passage, 8 and 9 are truncated conical surfaces, 10 is a heater, 11 is a closed end, 12 is an inward protrusion, 13 is an annular cavity, 14
27 is a first sprue block, 34 is a second sprue block, and 38 is a hydraulic cylinder device. Patent applicant Toyo Seikan Co., Ltd. Figure 1

Claims (3)

[Claims] (1) In a multilayer injection hot runner equipped with a nozzle at the tip and a plurality of independent resin passages converging toward the nozzle, a core member and a first resin passage are interposed between the core member and the core member. An inner cylinder member provided with A second resin passage is disposed between the outer circumferential surface of the inner cylinder member, and the inner circumferential surface of the movable member and the portions of the outer circumferential surface of the inner cylinder member close to the nozzle are respectively formed into truncated conical surfaces, and the axial movement of the movable member A hot runner for multilayer injection, characterized in that the truncated conical surfaces engage with each other to block the second resin passage. (2) The hot runner according to claim 1, wherein the core member is provided with a heating mechanism for keeping the resin in a molten state. (3) The hot runner according to claim 2, wherein the first resin passage is a polyester resin passage for forming the inner and outer surface layers, and the second resin passage is a gas barrier resin passage for forming the intermediate layer. .