JPH0260501B2 - - Google Patents

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 multilayer injection, and more specifically, to a hot runner for forming a multilayer molded structure by co-injection of multiple types of resins. ,
The present invention relates to a structure of a hot runner in which supply of one resin can be stopped and started smoothly and quickly.

(Prior art) In the field of injection blow molding of containers, gas barrier resins such as ethylene-vinyl alcohol copolymer and polyamide are interlayered between resin layers such as polyolefin or polyethylene terephthalate that constitute the inner and outer surfaces of container walls. Intervening as a layer is performed. When co-injecting these multiple types of resins, 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 highly viscous as it cools, and the next injected resin is added to the inner and outer surfaces of the cavity. Taking advantage of the properties introduced in the center,
A method has been adopted in which the resin for forming the intermediate layer is then injected. 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 is controlled by controlling the screw movement of the intermediate layer resin injection machine, or by controlling the opening and closing of an on-off valve provided in the intermediate layer resin flow path of the hot runner.

[Problems to be Solved by the Invention] However, in the method of controlling the injection of the intermediate layer resin by controlling the injection movement of the screw, there is a considerable length of hot water between the nozzle of the injection machine and the gate of the mold. There is a runner passage, for example, even after stopping the injection movement by the screw,
The molten resin in the hot runner flows into the mold as other resins are injected, making it extremely difficult to finish and start injection of the intermediate layer resin at precisely the same timing.

Especially when using a multi-cavity injection mold,
Since there is a difference in the distance of the hot runner to the gate of each cavity, there is a problem that a timing difference occurs for each cavity. The above-mentioned drawbacks also occur, although to a different degree, even when an on-off valve is provided in the resin passage of the hot runner.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a hot runner device that, when manufacturing a multilayer molded structure by co-injecting a plurality of resins, can cut off and start injection of one of the resins at precise timing and reliably. There is something to do.

Another object of the present invention is to provide a method for smoothly and quickly shutting off and starting injection without changing the injection timing for each cavity even in co-injection molding using a multi-cavity mold. To provide runner equipment.

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

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

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 resin disposed between the core member and the core member are provided. An inner cylinder member provided through a passage and an outer cylinder member having a nozzle at the tip are arranged coaxially, a movable member movable in the axial direction is provided between the inner cylinder member and the outer cylinder member, and a movable member inside the movable member is provided. A second resin passage is disposed between the circumferential surface and the outer circumferential surface of the inner cylindrical member, and the inner circumferential surface of the movable member and the portions of the outer circumferential surface of the inner cylindrical member close to the nozzle are respectively truncated conical surfaces, and the axis of the movable member is There is provided a multilayer injection hot runner characterized in that the truncated conical surface engages with the truncated conical surface and blocks the second resin passage by directional movement.

(Function) Part 1 showing the outline of the main parts of the hot runner of the present invention.
In the figure, this hot runner is roughly composed of a core member 1, an inner cylinder member 2, and an outer cylinder member 3, which are arranged coaxially. A nozzle 4 is provided at the center of the tip of the outer cylinder member 3, which is connected to a gate (none of which is shown) of an injection mold. Core member 1
A first resin passage 5 which is cylindrical and converges toward the nozzle 4 is provided on the outer surface of the inner cylinder member 2 and on 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 is generally cylindrical, and its outer surface and the inner surface of the outer cylinder member 3 are slidably provided, and there is a small space between the inner surface of the movable member 6 and the outer surface of the inner cylinder member 2. There is a 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 taper angles of both these truncated conical surfaces 8 and 9 are substantially equal.

In FIG. 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.
This can be done without timing delay and with good rise and fall characteristics. Moreover, 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 for keeping the resin in a molten state is provided in the hollow part, and the first resin passage 5 on the outer periphery of the core member 1 is connected inside and outside. A polyester resin passageway is used for forming the surface layer, and the 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.

By adopting this arrangement, the gas barrier resin, which is susceptible to thermal decomposition, can be kept in a sufficiently molten state while the polyester for the inner and outer layers, which has a high melting point (the melting point of polyester (PET) is 245°C) and a large flow rate, is kept in a sufficiently molten state. Even when the gas barrier resin remains in the runner for a relatively long time, it is possible to prevent the gas barrier resin from being excessively heated.

(Example) As shown in FIG. 1, the outer cylinder member 3 used in the present invention may have a closed end 11 on one side and a short inward projection 12 at the center of the end 11. desirable. This inward protrusion 12 and the outer cylinder 3
There is an annular cavity 13 between the movable member 6 and the annular cavity 13, into which the distal end 14 of the movable member 6 is fitted. A resin passage 15 connected to the nozzle 4 is formed in the inward protrusion 12 and the closed end 11.
In addition, it has a truncated conical surface 16 that is flush with the truncated conical surface 8 of the movable member 6 when the movable member 6 is open. In this structure, the tip 1 of the movable member 6
4 is always fitted into the annular cavity 13 of the movable member 3, the opening and closing operations are 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 with a heat insulating plate 21 and a spacer 22 in between. The 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 heater plug 24. A hot runner sprue bushing 25 is provided around the lower portion of the core member 1, and a first hot runner manifold 26 is provided around the hot runner sprue bushing 25. A sprue block 27 is provided. The first sprue 27 has a first resin injection machine (not shown).
A first sprue 28 is attached to the sprue block 27, hot runner manifold 26, and hot runner sprue bushing 25, and a first resin flow path 29 connected to the first sprue 28 is attached to the sprue block 27, hot runner manifold 26, and hot runner sprue bushing 25. is provided.

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 inner cylinder member 2, and a support ring 32 for supporting the second hot runner block is further provided on the outer periphery of the sleeve 31. ing.

Above the support ring 32 and on the outer periphery of the sleeve 31 is a second hot runner manifold 33.
and a second sprue block 34 are provided. A second sprue 35 is attached to the second sprue block 34 and is connected to a second resin injection machine (not shown), with a second sprue 35 extending through the second sprue block 34 and the manifold 33. Resin flow path 3
Connected to 6.

The movable member 6 is movable in the vertical direction between the fixed outer cylinder member 3 and the inner cylinder member 2.
A second resin passage 7 is formed between the inner peripheral surface of the inner cylinder member 2 and the outer peripheral surface of the inner cylinder member 2.
6 and is connected to the second sprue 35.

In order to move the movable member 6 up and down between the open and closed positions, a vertical elongated hole (not shown) is provided in the fixed outer cylinder member 3, and a pin 37 is provided that projects outward through this elongated hole. On the other hand, a hydraulic cylinder device 38 equipped with a piston 39 is fixed to the hot runner fixing plate 20, and a rotation shaft 42 that rotates via a link 40 and a lever 41 as the piston 39 moves up and down is fixed. An arm 44 having a long notch 43 that engages with the pin 37 described above is pivotally connected to the pivot shaft 42 .

In FIG. 2 and FIG. 3 for explaining the operation of the hydraulic cylinder, 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; In the raised position, the movable member 2 is in the lowered position, and therefore the second resin passage 7 is closed.

When manufacturing a multilayer injection molded product, the hot runner nozzle 4 is connected to a split mold gate (none of which is shown), and the first sprue 27 is connected to a first resin injection machine (not shown). , and a second resin injection machine (not shown) is connected to the second sprue 35, respectively. Further, the heater 10 is energized via the connector 23 to perform necessary heat retention. When the injection machine starts operating, the first resin passes through the first sprue 28, the first resin flow path 29, and the first resin passage 5, and is injected into the mold cavity through the nozzle 4. be done.

When a predetermined amount of the first resin has been injected, the hydraulic cylinder device 38 is activated and the piston 39
is lowered, the movable member 6 is raised accordingly, and the second resin passage 7 is opened. As a result, the second resin passes through the second sprue 35, the second resin flow path 36, and the second resin passage 7 to the nozzle 4.
It is injected into the mold cavity. In this second stage injection cycle, the first resin and the second resin may be injected simultaneously, or the injection pressure of the second resin may be set high so that the injection of the second resin takes priority. It can also be made to occur automatically.

When a predetermined amount of the second resin has been injected, the hydraulic cylinder device 38 is actuated, and the piston 3
9 is raised, the movable member is lowered accordingly, and the second resin passage 7 is closed. This stops the injection of the second resin, and 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 an intermediate layer made of a second resin is completely encapsulated in inner and outer layers made of a 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 multi-cavity mold, the opening and closing of the passage is done at a position close to the nozzle, which has the advantage that injection can be shut off and started for each cavity smoothly without any timing lag. be.

[Brief explanation of 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 one embodiment of the hot runner of the present invention, and FIG. 3 is a cross-sectional view showing the operation of the movable member of the hot runner. FIG. 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
11 is a closed end, 12 is an inward protrusion, 13 is an annular cavity, 14 is a tip, 27 is a first sprue block, 34 is a second sprue block, and 38 is a hydraulic cylinder device.

Claims (1)

[Scope of Claims] 1. A multilayer injection hot runner equipped with a nozzle at the tip and a plurality of independent resin passages converging toward the nozzle, comprising: a core member; 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 the inner circumferential surface of the movable member A hot runner for multilayer injection, characterized in that the truncated conical surfaces engage with each other by axial movement, thereby blocking 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.