JP3011247B2 - Injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is 2, such as sandwich molding
The present invention relates to an injection molding machine for performing color molding, and particularly to a switching mechanism for a nozzle between a first injection unit for injecting a resin for a skin layer material and a second injection unit for injecting a resin for a core layer material.

[0002]

2. Description of the Related Art Sandwich molding for molding a composite molded product (sandwich molded product) formed of a skin layer (outer layer) and a core layer (inner layer) using two different resins in an injection molding machine. There is an injection molding machine. As a product (composite molded product) formed by this sandwich molding, a polyacetal resin having good abrasion characteristics and good self-lubricating properties is used for the skin layer, and a resin containing glass fibers and the like without sink marks is used for the core layer. Used precision parts such as gears. Soft-touch sensation molded products for automobiles and furniture, etc., using a thermoplastic elastomer for the skin layer and a rigid resin for the core layer, with a soft touch feel on the outside. Electromagnetic wave shielding parts for computers and the like using an ABS resin with good appearance for the skin layer and a resin containing a conductive material for the core layer. A large molded product that uses foamed resin for the core layer to prevent sink marks and reduce costs. A molded product with a change in pattern, such as a container, using a transparent resin for the skin layer and a colored resin for the core layer. These are widely used in various fields in recent years.

FIG. 4 is a view showing the operating principle of such an injection molding machine for sandwich molding. In FIG. 4, reference numeral 101 denotes a first injection unit for injecting a resin for a skin layer material,
Reference numeral 02 denotes a second injection unit for injecting the core layer material resin, and reference numeral 103 denotes a cavity formed by the fixed mold 104 and the movable mold 105. Although not shown in FIG. 4, a nozzle is pressed against a resin injection port (sprue bush) of the fixed mold 104, and the first and second injection units 101 are moved into a nozzle passage at the tip of the nozzle. , 102 can be alternatively communicated. Then, the nozzle and the first injection unit 1
01 in communication with the first injection unit 101
Of the skin layer material resin 10
8 is injected into the cavity 103 by a predetermined amount, and then, with the nozzle and the second injection unit 102 in communication, the screw 107 of the second injection unit 102 is advanced to Into the uncured skin layer material resin 108 in the cavity 103.
By filling, a composite molded article in which the core layer is clogged in the skin layer is obtained.

FIG. 5 is a plan view showing a conventional injection molding machine for sandwich molding. In FIG. 5, parts equivalent to those in FIG. 4 are denoted by the same reference numerals. In FIG. 5, reference numeral 110 denotes a mold opening / closing mechanism, which includes a fixed die plate 111 to which the fixed mold 104 is attached, a movable die plate 112 to which the movable mold 105 is attached, and which is moved back and forth by a mold clamping cylinder. Have been. Numeral 113 denotes a resin passage switching means provided with a nozzle 114 at the tip.
3, the first injection unit 101 and the nozzle 11
A first resin passage communicating with the nozzle passage of No. 4;
A first opening / closing valve member for controlling the opening and closing of the resin passage, a second resin passage for communicating the second injection unit 102 with the nozzle passage of the nozzle 114, and a second opening and closing control for the second resin passage. An open / close valve member is provided, and the first open / close valve member and the second open / close valve member are
It has a double structure, and is independently controlled to open and close by opening and closing cylinders (hydraulic cylinders) 115 and 116 for valve control.

[0005] FIG. 5 shows a state in which the nozzle is backed.
01, 102, resin passage switching means 113, open / close cylinders 115, 116, etc., the entire injection mechanism is advanced by a nozzle touch cylinder (not shown), and the nozzle 114 is pressed against the resin injection port of the fixed mold 104. Is maintained. Then, at the time of injection by the first injection unit 101, the first opening / closing valve member is moved by the opening / closing cylinder 115 to the retracted position (open position).
And the first injection unit 101 and the nozzle 114
And the second opening / closing valve member is set in the forward position (closed position) by the opening / closing cylinder 116, and the second injection unit 102 and the nozzle 114 The second resin passage communicating with the nozzle passage is closed. On the other hand, at the time of injection by the second injection unit 102, the second opening / closing valve member is set to the retracted position (open position) by the opening / closing cylinder 116, and the second injection unit 102 and the nozzle passage of the nozzle 114 are connected to each other. Second
And the opening and closing cylinder 115
The first opening / closing valve member is moved to the forward position (closed position) by the first injection unit 101 and the nozzle 1
The first resin passage communicating with the fourteen nozzle passages is in a closed state. As a conventional injection molding machine for sandwich molding having the above configuration, for example, Japanese Patent Application No. Hei.
No. -298988.

[0006]

As described above, in the conventional injection molding machine for sandwich molding, two dedicated driving sources are used for switching the nozzles of the first injection unit and the second injection unit. (The first and second opening / closing cylinders, etc.), and the structure of the resin passage switching means is relatively complicated, resulting in an increase in cost. In addition, since the open / close valve member is moved back and forth by a separate drive source such as a hydraulic cylinder, resin leaks easily from a gap between the open / close valve member and its holding member, and further, a gap between the open / close valve member and its holding member. As a result, a structure in which a contact portion between the resin and the atmosphere is inevitably generated is caused. Furthermore, if the two dedicated driving sources are not accurately synchronized and controlled (when the switching timing is shifted), the skin layer and the core layer may be mixed due to the backflow of the resin. Occasionally, when the core layer is mixed, the quality of the molded article is significantly deteriorated.

Accordingly, a technical problem to be solved by the present invention is to solve the above-mentioned problems of the prior art.
The purpose is to switch between the first and second injection units (switching between the skin layer injection and the core layer injection) without requiring a separate drive source, with a simple mechanism, high operation reliability, and resin. An object of the present invention is to provide an injection molding machine for two-color molding , which has an injection unit switching mechanism without the risk of burning or resin leakage.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to provide a two-color molding injection molding machine, comprising:
This is achieved by providing a switching valve means having a hollow needle-shaped valve actuator, for example, which is switched and controlled by the injection resin pressure between the second injection unit and the second injection unit.

[0009]

During injection of the first injection unit, the hollow needle-shaped valve actuator is moved to the retracted position, for example, by the resin pressure pushed out from the first injection unit, and the nozzle passage at the tip of the first injection unit and the tip of the nozzle. And the valve actuator closes the space between the tip of the second injection unit and the nozzle passage at the tip of the nozzle. Further, at the time of injection of the second injection unit, the hollow needle-shaped valve actuator is moved between the front end of the first injection unit and the nozzle passage at the front end of the nozzle by the resin pressure extruded from the second injection unit. And the internal resin passage of the hollow needle-shaped valve actuator is communicated with the nozzle passage at the tip of the nozzle, thereby communicating the tip of the second injection unit with the nozzle passage at the tip of the nozzle.

As described above, the switching position of the hollow needle-shaped valve actuator is directly controlled by the injection resin pressure, so that a separate drive source for the switching valve is not required unlike the related art, and the structure is simple. And greatly contribute to cost reduction. Further, since the switching valve is controlled by the injection resin pressure, the operation reliability is high, and the possibility that the skin layer and the core layer are mixed is reduced as much as possible. Further, since the switching valve portion can have a structure in which there is no contact portion between the resin and the atmosphere (the switching valve portion has an airtight structure), there is no risk of resin burning or resin leakage.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in FIGS. 1 and 2 relate to a first embodiment of the present invention. FIG. 1 is a plan view showing an injection mechanism part of an injection molding machine according to the present embodiment. FIG. 2 is an enlarged sectional view of a main part of FIG. In FIG. 1, 1 is a first injection unit for injecting a resin for a skin layer material, 2 is a second injection unit for injecting a resin for a core layer material, and 3 is a machine located on the tip side of the first injection unit. The switching valve mechanism 4, which is temporarily held, is a nozzle attached to the tip of the switching valve mechanism 3. Although the two injection units 1 and 2 do not show detailed internal cross sections, they employ a well-known in-line screw type mechanism, and kneading plasticizing and injection screws 11 and 21, respectively (see FIG. 2). Heating cylinder 1 built so that it can rotate and move forward and backward
Hoppers 13 and 23 for supplying raw resin to the rear ends of the heating cylinders 12 and 22, and hydraulic motors 14 and 2 for rotating screws during a charge stroke.
4. Injection cylinders (hydraulic cylinders) 15, 25 for moving the screw forward during the injection stroke. Further, the front end of the heating cylinder 12 of the first injection unit 1 is connected to the rear end of the switching valve mechanism 3 (the injection resin passage on the first injection unit 1 side), and the intermediate valve side surface of the switching valve mechanism 3 is connected. Through a connecting member 26 attached to the tip of the heating cylinder 22 of the second injection unit 2 and a resin passage tube 27 connected to the connecting member 26.
The injection resin passage on the second injection unit 2 side is connected. Although not shown, the entire injection mechanism can be moved back and forth by a nozzle touch cylinder (hydraulic cylinder), and during the molding operation, the entire injection mechanism is placed at the forward position by the nozzle touch cylinder, thereby providing a switching valve mechanism. Nozzle 4 attached to 3
Is pressed against a resin injection port (sprue bush) of a molding die (not shown).

FIG. 2 shows a structure around the switching valve mechanism 3. In the figure, reference numeral 31 denotes a hollow valve base which is screwed and fixed to the distal end of the heating cylinder 12 of the first injection unit 1. The base end side of the nozzle 4 is screwed and fixed to the distal end side of the valve base 31. Have been. Reference numeral 32 denotes a sleeve body disposed in the valve base 31, which is fixed and positioned at a predetermined position by attaching the nozzle 4 to the valve base 31. 33 is a poppet fitted and fixed to the bottom of a bottomed center resin passage (bottomed center hole along the axial direction) 32a of the sleeve body 32;
2 is a hollow needle-shaped valve actuator arranged so as to be able to move back and forth in the center resin passage 32a.

The resin passage 12a at the tip of the heating cylinder 12 of the first injection unit 1 penetrates axially through the resin passage 31a on the base end side of the valve base 31 and the position outside the sleeve 32. Resin passage 32 drilled
b, and a resin passage 4b formed between the inner wall of the nozzle 4 and the outer periphery of the sleeve body 32 and the valve operator 34
Can be connected to the nozzle passage 4a at the tip of the nozzle 4 via the. The resin passage 22a at the tip of the heating cylinder 22 of the second injection unit 2 is connected to the connecting body 2
6, the resin passage 26a, the resin passage 27a of the resin passage tube 27, the resin passage 31b formed on the side of the valve base 31, the resin passage 32c formed on the side of the sleeve 32, and the like. The nozzle 4 can be connected to the nozzle passage 4a at the tip of the nozzle 4 via the central resin passage 32a thus formed and the central resin passage 34a in the hollow needle valve actuator 34. As apparent from the drawing, the inside of the switching valve mechanism 3 has an airtight structure,
It is configured such that there is no portion in which the resin contacts the atmosphere.

In the above-described configuration, during the injection process of the skin layer material resin by the first injection unit 1, the hollow needle-shaped valve actuator 34 is provided at its tip side with the molten metal injected from the first injection unit 1 side. In response to the resin pressure of the resin, it takes a state of retreating to the right-hand limit position.
The molten resin from the first injection unit 1 is injected into the cavity of the molding die (not shown) from the nozzle passage 4a at the tip of the nozzle 4 via the resin passage described above. When the valve actuator 34 is at the right-hand limit position, the rear end face of the valve operator 34 is pressed into the tapered portion of the poppet 33 by the resin pressure of the molten resin injected from the first injection unit 1 side. The resin path for the second injection unit 2 is closed at the poppet 33 at the portion of the poppet 33 so as to prevent the backflow of the skin layer material resin.

On the other hand, during the injection process of the core layer material resin by the second injection unit 2, the hollow needle-shaped valve actuator 34 is provided with the resin of the molten resin injected from the second injection unit 2 side at the rear end side. In response to the pressure, the vehicle moves forward to the leftmost position shown in FIG.
The outer surface of the tip of the nozzle 4 is the inner surface of the nozzle 4 (nozzle passage 4a).
(The inner surface in the vicinity) by the resin pressure injected from the second injection unit 2 side, so that the space between the resin passage 4b and the nozzle passage 4a for the first injection unit 1 is closed. Further, the rear end face of the valve actuator 34 is separated from the tapered portion of the poppet 33, and the molten resin from the second injection unit 2 passes through the above-described resin passage from the nozzle passage 4a at the tip of the nozzle 4 as shown in FIG. It is injected into the cavity of a molding die not shown.

As is apparent from the above description, the operation of this embodiment will be described below. From the state of FIG. 2, when the timing of starting the injection of the skin layer material resin by the first injection unit 1 is reached, the screw 11 of the first injection unit 1 is driven forward, whereby the injection from the first injection unit 1 is performed. The valve actuator 34 is retracted by the resin pressure of the melted resin, the resin passage for the first injection unit 1 in the switching valve mechanism 3 is opened, and the resin for the second injection unit 2 is opened. The passage is closed. Then, in this state, a predetermined amount of the skin layer material resin is injected into the cavity by the first injection unit 1. Strictly speaking, in the initial stage of the injection of the skin layer material resin, a very small amount of the core layer material resin remaining in the nozzle passage 4a of the nozzle 4 is mixed, but this amount is very small and can be completely ignored in practical use. . Next, after the injection by the first injection unit 1 is completed, when the injection start timing of the core layer material resin by the second injection unit 2 is reached, the screw 21 of the second injection unit 2 is driven forward, whereby The valve actuator 34 advances by the resin pressure of the molten resin injected from the second injection unit 2 (in this case, the first injection unit 1
, The resin passage for the second injection unit 2 in the switching valve mechanism 3 is opened, and the resin passage for the first injection unit 1 is closed. I will put it. Then, in this state, the core layer material resin is injected and filled into the uncured skin layer material resin in the cavity by the second injection unit 2. At the initial stage of the injection of the core layer material resin, a small amount of the skin layer material resin that has flowed back into the hollow needle-shaped valve actuator 34 is mixed, but this amount is also very small. Even if the resin for the skin layer is mixed to some extent, there is usually no problem in quality. Then, after the resin in the cavity is cured, the mold is opened and the molded product is taken out, whereby a sandwich molded product is obtained.

In this embodiment having such a configuration, the switching position of the hollow needle-shaped valve actuator 34 is directly controlled by the injection resin pressure, so that a separate drive source for the switching valve is required as in the prior art. In addition, the structure is simplified, which greatly contributes to cost reduction. Further, since the switching valve is controlled by the injection resin pressure, the operation reliability is high, and the possibility that the skin layer and the core layer are mixed is reduced as much as possible. Further, the valve actuator 3 is driven by the injection resin pressure.
Since the switching valve mechanism 4 is controlled, the switching valve mechanism 3 can have an airtight structure, and since there is no contact portion between the resin and the atmosphere in the switching valve mechanism 3, there is no risk of resin burning or resin leakage.

FIG. 3 relates to a second embodiment of the present invention, in which the heating cylinder 1 of the first injection unit 1 is used.
The distance between the heating cylinder 22 and the heating cylinder 22 of the second injection unit 2 is reduced, and the resin passage 22 a at the tip of the heating cylinder 22 of the second injection unit 2 is switched by the resin passage 28 a of the single connection block 28. It is connected to the valve mechanism 3. With such a configuration, the connection structure is simplified, and the resin path from the second injection unit 2 is shortened, which is convenient.

Although the present invention has been described with reference to the illustrated embodiment, it is needless to say that various modifications can be made by those skilled in the art without departing from the spirit of the present invention. Can be changed.

[0020]

As described above, according to the present invention, a separate drive source is not required for switching the first and second injection units (switching between the skin layer injection and the core layer injection), and the operation is simplified with a simple mechanism. High reliability and no risk of resin burning or resin leakage,
It is possible to provide an injection molding machine for two-color molding such as sandwich molding having an injection unit switching mechanism, and its value is great.

[Brief description of the drawings]

FIG. 1 is a plan view showing an injection mechanism portion of an injection molding machine for sandwich molding according to a first embodiment of the present invention.

FIG. 2 is a fragmentary plan view showing a configuration around a switching valve mechanism of the injection molding machine for sandwich molding according to the first embodiment of the present invention.

FIG. 3 is a fragmentary plan view showing a configuration around a switching valve mechanism of an injection molding machine for sandwich molding according to a second embodiment of the present invention.

FIG. 4 is an explanatory view showing the operation principle of an injection molding machine for sandwich molding.

FIG. 5 is a plan view of a conventional injection molding machine for sandwich molding.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st injection unit 2 2nd injection unit 3 Switching valve mechanism 4 Nozzle 11 Screw 12 Heating cylinder 21 Screw 22 Heating cylinder 31 Valve base 32 Sleeve body 33 Poppet 34 Hollow needle valve actuator

Continuation of front page (56) References JP-A-51-119063 (JP, A) JP-A-4-71813 (JP, A) JP-A-58-179632 (JP, A) JP-A-61-297116 (JP) JP-A-5-104578 (JP, A) JP-A-5-169493 (JP, A) JP-A-5-131495 (JP, A) JP-A-4-316818 (JP, A) 49-47268 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/00-45/24

Claims (1)

(57) [Claims] 1. A first nozzle capable of injecting a molten resin into a cavity of a molding die through one nozzle whose tip is pressed against a resin injection port of the molding die. Injection molding that includes a unit and a second injection unit, in which a first injection unit injects a skin layer material resin to be a skin layer, and then a second injection unit injects a core layer material resin to be a core layer. When a hollow valve base is attached to the rear of the nozzle,
A valve actuator holder is provided in the valve base, and the valve
A hollow needle-shaped valve actuator is enclosed by a child holder
Held so as to be slidable in the axial direction in the inner, the valve operating element holding body, from the first injection unit
For guiding the resin of the above to the nozzle passage at the nozzle tip
The passage and the resin from the second injection unit into the hollow
Via the inside of the needle-shaped valve actuator, the nozzle tip
Forming a resin passage for leading to an end nozzle passage, and when the first injection unit performs injection, the first injection
Hollow needle shape by injection resin pressure from unit
The tip of the valve actuator is separated from the inner surface of the tip of the nozzle.
The first injection unit tip
And communicate with the nozzle passage at the tip of the nozzle,
A member for closing the rear end opening of the hollow needle valve actuator
By pressing the second injection unit
Close the space between the end and the nozzle passage at the tip of the nozzle.
Come, wherein at the time of injection of the second injection unit, the second injection
Hollow needle shape by injection resin pressure from unit
The valve operator is advanced, and the tip of the valve operator is
Press against the inner surface of the tip of the chisel and open the rear end of the valve actuator.
With the mouth part separated from the closing member, the second injection unit is opened.
The knit tip and the nozzle passage at the nozzle tip are
Communicating with the inside through the empty needle valve actuator
The first injection is performed by the tip of the valve actuator.
Close between the unit tip and the nozzle passage at the nozzle tip
An injection molding machine characterized by being kept in a closed state .