JPH09277307A - Hot runner device, mold equipment for injection molding wherein the device is incorporated and usage thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hot runner device preventing a gate mark or a mark of an ejection mechanism from being left on the surface of a small molded article, dispensing with treatment for a mark of a cold runner or a cold gate and enabling execution of molding in a large amount in a runner-less manner. SOLUTION: In a hot runner device 10 of a valve gate system wherein a gate 11a of a hot nozzle 11 is opened and closed by a needle valve 13, construction is so made that the fore end of the needle valve 13 can be extruded into a cavity from the fore end of the gate of the hot nozzle 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve gate type hot runner apparatus, an injection molding die apparatus incorporating the hot runner apparatus, and a method of using the same. INDUSTRIAL APPLICABILITY The present invention can be particularly suitably used for injection molding of various machine parts, OA parts, electronic parts and the like of small articles.

[0002]

2. Description of the Related Art A hot runner device is an open gate system in which the gate of the hot nozzle is always open during the molding cycle, and the gate of the hot nozzle is opened during the injection pressure holding process to perform cooling and mold opening / closing operations. Is classified as a valve gate system that closes the gate of the hot nozzle. The present invention relates to the latter valve gate type hot runner device.

FIG. 4 shows the most general form of a conventional valve gate type hot runner device 10 '. In the figure, 11' is a hot nozzle, 11a 'is its gate, and 11b' is an inner part. A hole, 12 'is a heater, 13' is a needle valve, 14 'is an actuator, 14a' is its piston, and 14b 'is a cylinder. In such a conventional valve gate type hot runner device,
The purpose of the invention is to prevent the resin leakage from the gate 11a 'of the hot nozzle 11' by using the needle valve 13 'and to efficiently open and close the gate. As described above, in the conventional valve gate type hot runner device, since the purpose is only to efficiently open and close the gate 11a 'of the hot nozzle by the needle valve 13', the molded product is released from the cavity. In order to do so, it is necessary to equip the template on the opposite side of the template containing the hot nozzle 11 'with a projecting mechanism such as a projecting pin, a projecting sleeve, and a projecting plate.

However, when such a protruding mechanism is used, in addition to the problem that the marks of the protruding pins and the protruding sleeve are formed on the surface of the molded product, the problem that the applicable shape of the protruding plate is limited, etc. There was a point. Also, when the molded product is large, there are many places where the marks of these protruding pins and the marks of the protruding sleeve can be allowed in the product design, so there is no problem so much, but small molded products,
For example, thrust plugs, thrust plates, thrust washers that are mechanical parts that support thrust loads, retainers with sliding surfaces, face plates, rollers,
Ball bearing balls, nuts having a tightening surface, screws, caps, ferrules, and the like have restrictions such that even if a gate mark is allowed on the back side of the molded product, a protruding pin mark is not allowed on the front side. Therefore, in the molding of such small items, the semi-hot runner method is usually adopted,
The hot nozzle and protruding pin marks were formed on the runner portion of the molded product.

FIG. 5 shows a partial cross-sectional view of such a conventional semi-hot runner type injection molding die apparatus, in which 1 is a fixed side die, 2 is a movable side die, 3 is a cavity, 4 is a sprue, 5 is a manifold, 6 is a return pin, 7 is a protruding pin, 8 is a protruding plate, 9
a is a cold runner, 9b is a cold gate, and 10 '
Is a hot runner device, 11 'is its hot nozzle, 1
1a 'is a gate, 13' is a needle valve, and 14 'is an actuator. When a small-sized molded product is molded using such a semi-hot runner type injection molding die device, the cold runner 9a portion and the cold gate 9b portion need to be traced after molding, and the number of molded products is reduced. In many cases it was not practical.

[0006]

As described above, in molding a molded product of a small article, even if a trace of a gate or a protrusion mechanism is allowed on the back surface of the molded product, the surface of the molded product is not designed. Under the circumstances where these marks are not allowed, there is a demand for the development of a hot runner device or the like that can perform a large amount of molding without a runner without the need to treat the cold runner and cold gate after molding.

[0007]

As a result of intensive studies to solve the above problems, the present inventor has devised a needle valve, a hot nozzle, and an actuator in a valve gate type hot runner device using a needle valve. It was found that the molded product can be released from the mold by using the needle valve, and the present invention has been completed. That is, the present invention is characterized in that, in a valve gate type hot runner device that opens and closes the gate of the hot nozzle by a needle valve, the tip of the needle valve can be projected into the cavity from the gate tip of the hot nozzle. It is a thing. In this case, it is recommended to provide a limit mechanism for preventing the tip of the needle valve from protruding into the cavity from the gate tip of the hot nozzle during the period of cooling and solidifying the resin filled in the cavity. In order to facilitate the protruding operation of the needle valve, it is recommended to form a groove along the axial direction on the outer peripheral surface of the tip of the needle valve or the inner peripheral surface of the gate of the hot nozzle.

The present invention also provides a mold apparatus for injection molding, which is characterized by incorporating the hot runner apparatus having the above-mentioned structure. Furthermore, the present invention provides a method of using the injection molding die apparatus. That is, when performing injection molding with the injection molding die device, in the process from filling the cavity with resin to releasing the molded product, in the closed state, the tip of the needle valve of the hot runner device is inserted into the hot nozzle. Back into the cavity through the gate to fill the cavity with resin, the screw of the injection device is rotated to maintain the pressure inside the cavity, and the tip of the needle valve enters the gate and the tip of the hot nozzle. The step of advancing the needle valve until it reaches close to it, the step of cooling and solidifying the resin in the cavity, the step of separating the movable side mold from the fixed side mold and opening the mold, and further advancing the needle valve, The step of projecting the tip into the cavity from the tip of the hot nozzle, ejecting the solidified molded product, and releasing the mold, There is provided the use of the injection mold apparatus characterized by sequentially performed. By adopting such a method of use, it becomes possible to mold a molded product without a runner.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described more specifically with reference to the drawings. FIG. 1 is a sectional explanatory view showing the operation of a needle valve in an embodiment of a hot runner device according to the present invention. FIG. 2 is a partial cross-sectional view of an injection molding die apparatus according to the present invention incorporating the hot runner apparatus shown in FIG. FIG. 3 is an enlarged view showing a desirable configuration of the gate portion and the tip portion of the needle valve of the hot runner device shown in FIG. In each figure, 1 is a fixed mold, 2 is a movable mold, 3 is a cavity, 4 is a sprue, 5 is a manifold, 6 is a return pin, 10 is a hot runner device, 11 is its hot nozzle, and 11a is a gate. , 11b
Is an inner hole, 12 is a heater, 13 is a needle valve, 14 is an actuator, 14a is its piston, 14b is a cylinder chamber, 14c is a piston rod, and 15 is a limit bar.

Thus, the main mold in the embodiment shown in FIG. 2 is divided into a fixed mold 1 attached to the fixed platen of the injection molding machine and a movable mold 2 attached to the movable platen. When these are matched with each other, a cavity 3 which is a space for molding a molded product is formed. This mold is attached to a platen of a known injection molding machine (not shown) for use.

The resin melted in the cylinder of a known injection device (not shown) is injected from the sprue 4 and introduced into the inner hole 11b of the hot nozzle 11 via the manifold 5 in the hot runner device of the present invention. Gate 11a
Is injected and filled into the cavity 3. At this time, the tip of the needle valve 13 is attached to the hot nozzle 1 as shown in FIG.
Since it stays at the position a in the No. 1, the gate 11a of the hot nozzle is open, and the molten resin can easily flow into the cavity 3.

After the resin is filled in the cavity 3 in this way, in order to prevent sink marks of the molded product, the screw of a known injection device (not shown) is rotated to increase the pressure of the molten resin, A holding pressure is applied in the cavity 3. After applying a holding pressure until the sink of the molded product can be prevented,
In order to prevent the backflow of the resin in the cavity 3 and the leakage of the resin in the hot nozzle 11, the tip of the needle valve 13 is moved to a position b near the tip of the hot nozzle 11 by using an actuator 14 that operates pneumatically or hydraulically. To move forward. This timing needs to be changed depending on the type of resin, the resin temperature, the mold temperature, the diameter of the gate 11a of the hot nozzle 11, etc., but in the case of a crystalline resin, it is usually 1 to 6 seconds after the completion of filling, and the 3 seconds to 1 in case of resin
It is necessary to operate it after 2 seconds.

In the illustrated embodiment, the limit bar 15 attached to the upper end of the piston rod 14c prevents the tip of the needle valve 13 from advancing beyond the position b while the mold is closed. Blocked by the upper end of the return pin 6, the needle valve 13 is prevented from advancing (falling) any further. The limit mechanism is not limited to the illustrated embodiment, and any structure can be adopted as long as it can achieve the same operation.

In this way, the gate 11a is connected to the needle valve 13
After forcibly closing with, the cooling time for cooling the resin in the cavity 3 is set. After the elapse of a predetermined cooling time, the mold opening / closing device of the injection molding machine (not shown) is operated to move the movable side platen to separate the movable side mold 2 from the fixed side mold 1 and open the mold.

At this time, since the sufficiently cooled molded product is hard to deform and easily released from the mold, the tip of the needle valve 13 of the hot runner device of the present invention is moved from the tip of the hot nozzle 11 to the cavity 3 by using the actuator 14. The mold is advanced to the inner position c (see FIG. 1), and the molded product is ejected and released.

When the mold is opened as described above, the return pin 6 is moving downward together with the movable mold 2, so that its tip no longer blocks the limit bar 15 and the needle valve 13 Is capable of moving forward beyond the b position to the c position.

The shape of the needle valve 13 of the hot runner device of the present invention may be the shape shown in FIG. 3 in order to efficiently and surely perform the protruding operation rather than the opening and closing of the gate 11a. Recommended. In order to reliably perform the ejecting operation, the clearance p between the gate 11a of the hot nozzle and the needle valve 13 is preferably about 10 to 50 microns, and in order to ensure the escape of the resin, the needle valve 1
It is recommended to form a plurality of grooves 13 a, 13 a along the axial direction at the tip of 3. Alternatively, a similar groove may be formed on the inner peripheral surface of the gate 11a of the hot nozzle. In addition, in order to improve wear resistance and sliding characteristics, the outer peripheral surface of the tip of the needle valve 13 and the gate 11 of the hot nozzle are
It is recommended to apply TiCN or TiN coating to the inner peripheral surface of a. Needle valve 13 and hot nozzle 11
The material of the gate 11a portion is appropriately selected from those which are advantageous in mass production.

When the hot runner device 10 of the present invention is incorporated into a mold, it is incorporated into the fixed mold 1 side in the embodiment shown in FIG. 2, however, on the contrary, the movable mold 2 is incorporated.
May be installed on the side of. Further, the number of hot nozzles 11 of the hot runner device is not limited to one, but may be plural, and the number of gates 11a may be plural in one hot nozzle. Further, as the actuator 14 for operating the needle valve 13 of the hot runner device, any drive device such as pneumatic pressure, hydraulic pressure, electric drive, etc. can be used, and it may be connected to the projecting plate.

[0019]

According to the present invention, when the hot runner device of the present invention is used by incorporating it into an injection molding die, regardless of the type of resin material, a gate mark and a protrusion mechanism mark are formed on the surface. It is possible to form a large number of molded products without leaving the hot nozzle gate traces and the needle valve protrusion traces only on the back surface without runners. This includes, for example, thrust plugs, thrust plates, thrust washers that are mechanical parts that support thrust loads, retainers with sliding surfaces, face plates, rollers, balls for ball bearings, nuts with tightening surfaces, screws, caps, It is extremely effective for molding a wide range of fields such as ferrules.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing an operation of a needle valve in an embodiment of a hot runner device according to the present invention.

FIG. 2 is a partial cross-sectional view of an injection molding die device according to the present invention in which the hot runner device shown in FIG. 1 is incorporated.

FIG. 3 is an enlarged view showing a desirable configuration of a gate portion and a tip portion of a needle valve of the hot runner device shown in FIG.

FIG. 4 is a partial cross-sectional view of a valve gate type hot nozzle using a conventional needle valve.

FIG. 5 is a partial cross-sectional view of a conventional semi-hot runner type injection molding die device.

[Explanation of symbols]

 1 Fixed Side Mold 2 Movable Side Mold 3 Cavity 4 Sprue 5 Manifold 6 Return Pin 10 Hot Runner Device 11 Hot Nozzle 11a Gate 12 Heater 13 Needle Valve 14 Actuator 15 Limit Bar

Claims (7)

[Claims] 1. A gate (11a) for a hot nozzle (11)
In a valve gate type hot runner device (10) that opens and closes by means of a needle valve (13), the tip of the needle valve (13) can be projected into the cavity (3) from the gate tip of the hot nozzle (11). A hot runner device characterized by that. 2. A limit mechanism for preventing the tip of the needle valve (13) from protruding into the cavity from the gate tip of the hot nozzle (11) during the cooling and solidifying period of the resin filled in the cavity (3). Claim 1 provided with (15)
Hot runner device described in. 3. The hot runner device according to claim 1, wherein a groove (13a) extending along the axial direction is formed on the outer peripheral surface of the tip of the needle valve (13). 4. A gate (11a) of a hot nozzle (11)
The hot runner device according to claim 1, wherein a groove along the axial direction is formed on the inner peripheral surface of the. 5. A mold apparatus for injection molding, comprising the hot runner device (10) according to any one of claims 1 to 4. 6. When performing injection molding with the injection molding die apparatus according to claim 5, in the process from filling the cavity with the resin to releasing the molded article, the hot runner apparatus is used in a closed state. The step of fully retracting the tip of the needle valve (13) into the hot nozzle (11) and filling the resin into the cavity (3) through the gate (11a), and rotating the screw of the injection device to make the cavity (3) A step of applying a holding pressure to the inside of the cavity, and a step of advancing the needle valve until the tip of the needle valve (13) enters the gate (11a) and reaches near the tip of the hot nozzle (11); Step of cooling and solidifying the resin, step of separating the movable side mold (2) from the fixed side mold (1) and opening the mold, and further advancing the needle valve (13) 6. The step of projecting the tip of the solidified molded product by releasing the tip of the hot nozzle (11) into the cavity (3) from the tip of the hot nozzle (11) and releasing the molded article from the mold is sequentially performed. Of using the injection molding die device described above. 7. The use method according to claim 6, wherein the molded product is molded without runners.