JP2002200650A - Hot runner unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a molding fault such as burning or the like of a molding by preventing a backflow of a gas and a molten resin into a hot runner unit and sufficiently precisely controlling its temperature. SOLUTION: The hot runner unit 61 comprises a backflow preventive valve for preventing an invasion of the gas and the molten resin into the unit 61 at a nozzle 65 section, and a cooling means 100 for precisely controlling the temperature of the unit 61. According to such a constitution, the backflow of the gas or the once injected molten resin into the unit 61 can be prevented, and the temperature of the molten resin in the unit 61 can be held in a suitable range. As a result, the molding fault such as burning of the molding due to the invasion of the gas or the molten resin, a short mold, a silver streak or the like can be prevented. The molding fault due to burning, deforming, stringing or the like of the resin due to overheating of the molten resin can be reduced, and the fault can be almost eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot runner unit in a mold used for an injection molding method (particularly, a gas assist molding method and an injection press molding method) as a molding method of a thermoplastic resin.

[0002]

2. Description of the Related Art In an injection molding method using a thermoplastic resin as a raw material, various structures have been proposed for a hot runner unit which is used for the purpose of shortening a molding cycle and reducing material costs, and is commercially available from various manufacturers. Have been. Particularly, hot runner units having a needle valve structure include a hot runner unit manufactured by Mold Masters of Canada and a hot runner unit manufactured by Husky Corporation.

[0003] In these hot runner units, when the molten resin is injected into the mold cavity,
The needle valve provided in the gate portion is opened by retreating the rod of the cylinder provided by the hydraulic pressure or pneumatic provided in the rear portion, and the molten resin is filled into the mold cavity through the gap. Then, after filling is completed (after using a holding pressure, the holding pressure is completed), the rod of the cylinder provided at the rear of the hot runner unit moves forward, the needle valve mechanism provided at the gate is closed, and the hot runner is closed. This prevents the molten resin from flowing back into the unit. That is, the resin pressure of the molten resin is supported by hydraulic pressure or pneumatic pressure for operating a cylinder provided at the rear of the hot runner unit.

Here, a gas assist molding method and an injection press molding method, which are one type of injection molding method, will be described. The gas-assist molding method is a method in which the molten resin in the mold cavity starts to be cooled and solidified during the injection of the molten resin into the mold cavity, immediately after the injection is completed, and after the injection is completed (during the cooling and solidification). High-pressure compressed gas (mainly an inert gas such as nitrogen) directly to the nozzle, runner, product, or from the hot runner unit to the inside or outside of the molten resin in the mold (between the mold surface and the molten resin). Gas). According to this molding method, a hollow injection molded product can be easily obtained.

[0005] Injection press molding is a technique in which the upper and lower dies are opened slightly before injection molding (of course, the molten resin does not leak out even if it is opened). ), And perform injection molding. Thereafter, at a stage where the resin is cooled and solidified, the mold is completely closed by hydraulic pressure to apply a press pressure to the injection-molded molded product to make it more dense and strong.

[0006]

However, in the gas assist molding method, when a high-pressure gas is injected into the molten resin injected into the mold cavity, the high-pressure gas has a low pressure in the mold cavity and low viscosity of the molten resin. A part is selected to form a hollow part. At this time, the area around the gate of the hot runner unit is heated by a heater provided in the hot runner unit, and since this portion has been completely injected, the pressure is reduced.

When the high-pressure gas reaches the vicinity of the gate of the hot runner unit in such a state, the gas pressure pushes up the needle valve of the hot runner unit to form a gap. Further, an accident may occur in which the resin enters the molding machine heating cylinder, pushes up the molding machine screw to the last position, and in some cases, blows the molten resin inside the heating cylinder through the molding machine hopper.

[0008] When the injection molding process is continuously performed in a state where the high-pressure gas injected into the mold cavity flows back into the hot runner unit or the heating cylinder of the molding machine as described above, burning of the molded product and short molding are performed. And molding defects such as silver streaks.

Further, in the injection press molding method or the gas press injection molding method, the needle valve is pushed up by the pressure of the molten resin in the same manner as in the gas assist molding method, so that a gap is generated. There is a problem that the resin flows back into the hot runner unit, which also causes molding failure.

Further, an electric heater is generally used for controlling the temperature of the hot runner unit (controlling the temperature of the molten resin). In this case, the temperature is controlled by a thermocouple, and when the temperature rises above a set temperature, the electric heater is used. It is a mechanism to cut off the electric current flowing through. However, the temperature drop is caused by natural cooling. Generally, since the hot runner unit is deeply embedded in the mold, the temperature drop by natural cooling is extremely slow. In particular, the tip of the hot runner unit is in direct contact with the resin melted and heated at every shot, so that it is more difficult to lower the temperature. Therefore, the temperature of the hot runner unit does not drop immediately, but rises further for some time due to residual heat. For this reason, the temperature of the molten resin in the hot runner unit greatly exceeds the set temperature.

In addition, when the molten resin heated and melted by the electric heater provided in the molding machine heating cylinder or the hot runner unit through the gap of the needle valve structure is injected into the mold cavity, shearing heat is generated. Further, heat is further generated by the frictional force, and as a result, the temperature of the tip portion of the hot runner unit becomes too high, and the molded product shows molding defects such as deformation and burning failure around the gate.

If the temperature of the gate of the hot runner unit is not sufficiently controlled, the molded product is released from the mold without cooling and solidifying the gate, and the molded product is released. In some cases, phenomena such as poor stringing occurred in the product.

Therefore, in the present invention, in the gas assist molding method and the injection press molding method, the intrusion of gas and molten resin into the hot runner unit and the molding machine heating cylinder is prevented, so that the molded product is burnt, An object of the present invention is to prevent molding defects such as short molds and silver streaks, and to enable safe molding operations.

[0014] In addition, by performing the temperature control in the hot runner unit with sufficient precision, it is possible to prevent burning of the resin.
Another object is to reduce molding defects due to deformation, stringing, and the like, and to improve the yield of molded products.

[0015]

According to a first aspect of the present invention, there is provided a hot runner unit which closes a nozzle portion by gas pressure in a gas assist molding method or pressure of a molten resin in an injection press molding method. It is equipped with a check valve for preventing intrusion.

Accordingly, during normal molding, the molten resin in the hot runner unit passes through the nozzle portion and is injected into the mold cavity. Thereafter, gas pressure by gas assist molding or injection of molten resin by injection press molding is used. When gas or molten resin tries to enter the hot runner unit through the nozzle portion under pressure, the check valve closes to prevent gas and molten resin from entering.

As a result, the high-pressure gas enters from the inside of the hot runner unit to the inside of the heating cylinder of the molding machine, pushes the molding machine screw down to the end, and blows up the molten resin inside the heating cylinder via the molding machine hopper. Can be prevented beforehand, and the molding operation can be performed safely. Further, since no gas or molten resin injected once enters the hot runner unit, molding defects such as burning of molded products, short molding, and silver streaks can be prevented.

By providing the check valve in the nozzle in this manner, gas and molten resin can be prevented from entering the hot runner unit and the heating cylinder of the molding machine in the gas assist molding method and the injection press molding method. It is possible to prevent molding defects such as burning of a molded product, short mold, silver streak, and the like, and to perform a molding operation safely.

A hot runner unit according to a second aspect of the present invention is the hot runner unit according to the first aspect, wherein one or two or more annular grooves are provided in a seal portion of the check ring. As a result, the molten resin in the hot runner enters the annular groove, and when the gas pressure or the molten resin pressure is applied and the check valve operates, the molten resin in the annular groove serves as an O-ring to complete the operation. Is sealed.

Therefore, backflow of gas and molten resin into the hot runner unit and the molding machine heating cylinder can be more reliably prevented, and molding defects such as burning of a molded product, short molding, and silver streaks can be more reliably achieved. And the molding operation can be performed safely.

According to a third aspect of the present invention, in the hot runner unit according to the first or second aspect, the check valve is configured such that a movable ball is provided at an entrance of a cavity provided in the middle of the nozzle portion by a movable ball. It is a plug. As described above, since the ball valve structure is employed as the check valve, there is no need to provide a structure for supporting and sliding the valve, and the structure can be simplified.

In the case where a groove is provided in the ball valve structure, if a groove is provided in the seal portion on the ball receiving portion side when the ball closes the entrance of the cavity, the sealing effect by the molten resin can be reliably obtained. it can.

According to a fourth aspect of the present invention, in the hot runner unit according to the first or second aspect, the check valve is a gas injection for injecting a gas from the hot runner unit into a mold cavity. It has holes. Therefore, the check valve can be cooled by injecting a small amount of gas into the gas injection hole every shot or every several shots during injection molding. For this reason, it is possible to prevent the molten resin in the hot runner unit, particularly at the nozzle portion, from being overheated, and to maintain the temperature within an appropriate temperature range. As a result, it is possible to reduce molding defects such as deformation, burning, and stringing at the time of releasing the molded product. Further, when performing the gas assist molding method, it is also possible to inject a high-pressure gas from this gas injection hole.

According to a fifth aspect of the present invention, in the hot runner unit according to any one of the first to fourth aspects, when the hot runner unit is no longer in a heated state, a part of the hot runner unit or It is provided with cooling means for cooling the whole. That is,
The hot runner unit according to the fifth aspect includes a check valve that prevents gas or molten resin from entering the hot runner unit in the gas assist molding method or the injection press molding method, and precisely controls the temperature of the hot runner unit. And cooling means for cooling.

According to this configuration, it is possible to prevent the gas or the molten resin once injected from flowing back into the hot runner unit, and to maintain the temperature of the molten resin in the hot runner unit within an appropriate range. As a result, it is possible to prevent molding defects such as burning of molded products due to intrusion of gas or molten resin, short molding, silver streaks, etc., and to reduce molding defects due to resin burning, deformation, stringing, etc. due to overheating of molten resin Can be
Molding defects can be almost eliminated. As a result, the yield of molded products can be significantly improved.

A hot runner unit according to a sixth aspect of the present invention is provided with a cooling means for cooling a part or the whole of the hot runner unit when the hot runner unit is not in a heated state. As described above, the electric heater for heating the hot runner unit cuts off the current when the temperature measured by the thermocouple exceeds the set temperature, but the temperature of the molten resin further rises due to residual heat for a while thereafter. Therefore, when the heater is turned off, that is, when the heating state is stopped, the cooling means immediately cools a part or all of the hot runner unit (a part which is likely to be overheated), thereby forcibly reducing the temperature of the hot runner unit. And the temperature of the molten resin inside is returned to the set temperature in a short time. As a result, the temperature of the molten resin during injection molding is maintained in an appropriate range, and molding defects such as deformation around the gate, burning, and stringing do not appear in the molded product.

By performing the temperature control in the hot runner unit with sufficient precision in this manner, molding defects due to burning, deformation, stringing, etc. of the resin can be reduced, and the yield of molded products can be improved.

According to a seventh aspect of the present invention, in the hot runner unit according to the sixth aspect of the present invention, the cooling means includes:
The compressed gas is blown to part or all of the hot runner unit. According to this configuration, since the cooling means can be provided separately from the hot runner unit, the degree of freedom of the arrangement of the cooling means is increased, and the portion of the hot runner unit which is easily overheated can be mainly cooled.
Further, the blowing of the compressed gas causes adiabatic expansion of the gas to lower the temperature, so that the cooling effect is further enhanced. Here, the compressed gas is compressed air, compressed nitrogen,
It is desirable from the viewpoint of safety to use an inert gas such as compressed argon.

The hot runner unit according to an eighth aspect of the present invention is the hot runner unit according to the sixth aspect, wherein the cooling means comprises:
A pipe for flowing a refrigerant is wound around a part or all of the hot runner unit. Here, as the refrigerant, water and other liquids, cooling gas including cooling air,
Further, a liquefied gas such as liquid nitrogen or liquid ammonia can be used. According to such a configuration, the part to be cooled can be reliably and more strongly cooled.

According to a ninth aspect of the present invention, in the hot runner unit according to the sixth aspect of the present invention, the cooling means includes:
A pipe is wound around a part or the entirety of the hot runner unit, a liquid is caused to flow and vaporized, and cooled by the heat of vaporization. Since the heat of vaporization of the liquid is large, a more powerful cooling effect can be obtained than simply flowing the refrigerant through the wrapped pipe. Here, the liquid to be vaporized is desirably a liquid having a boiling point of about 100 ° C. or less and easily vaporized.
For example, alcohols such as methanol, ethanol, and isopropyl alcohol, water, hydrocarbons such as n-hexane, halides such as chlorofluorocarbon and halon, and liquefied gases such as liquid nitrogen and liquid ammonia can be used. Some of these substances are easily flammable, and some of them can cause environmental pollution if released to the atmosphere.Therefore, guide the end of the pipe to a safe place, cool the vaporized substance, Careful handling is necessary, such as returning to a wastewater for reuse or burning safely in a boiler or the like. According to such a configuration, the portion to be cooled can be more strongly and effectively cooled.

[0031]

Embodiments of the present invention will be described below.

First Embodiment First, a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1A is a longitudinal sectional view showing a nozzle portion of the hot runner unit according to the first embodiment of the present invention, and FIG. 1B is a longitudinal sectional view showing a state where the nozzle portion is closed. FIG. 2 is a vertical cross-sectional view illustrating an example in which the angle of the nozzle portion of the hot runner unit according to the first embodiment of the present invention is changed. FIG. 3 is a vertical cross-sectional view showing an example in which the height of the check ring in the nozzle portion of the hot runner unit according to the first embodiment of the present invention is changed.

The molten resin in the heating cylinder of the injection molding machine is injected into the mold cavity 7 from the manifold of the hot runner unit 1 through the center cast (generally called a nozzle) 2. As shown in FIG. 1, the check valve 3 of the first embodiment has a substantially conical tip, and a valve seat 5 for receiving the check valve 3 is provided on the nozzle 2 side. That is, the check ring 3 has a larger area on the mold cavity side than the inside of the hot runner unit 1 so that the gas pressure by the gas assist molding method or the resin pressure by the injection press molding method is in the opposite direction to the check ring 3. The pressure applied is set to be large. Around the vicinity of the tip of the check ring 3, there are provided two annular grooves 4 for storing the molten resin in the nozzle 2 and improving the sealing performance. The check valve 3 is supported by a cylinder and a spring (not shown) so as to be vertically slidable above the rod portion 3a.

Now, the screw of the injection molding machine advances, and the molten resin in the heating cylinder of the molding machine is removed from the hot runner unit 1.
When the check valve 3 is pushed out, the check ring 3 slides downward to form a clearance 6 which serves as a path for the molten resin. The molten resin is filled into the mold cavity 7 through the clearance 6. Thereafter, when the gas pressure by the gas assist molding method or the resin pressure by the injection press molding method is applied to the check valve 3 from the mold cavity 7, the check valve 3 slides upward due to the gas pressure or the resin pressure. It closely adheres to the seat 5 to prevent gas or molten resin from entering. Here, the molten resin accumulated in the two grooves 4 serves as an O-ring, and the sealing by the check ring 3 is more reliable.

As described above, by providing the check valve 3 in the nozzle 2, the gas and the molten resin can be introduced into the hot runner unit 1 and the molding machine heating cylinder in the gas assist molding method and the injection press molding method. Intrusion can be prevented, molding defects such as burning of the molded product, short molding, and silver streaks can be prevented, and the molding operation can be performed safely.

Next, the relationship between the angle of the valve seat 5 and the angle of the check ring 3 will be described with reference to FIGS. 1 (b), 2 and 3. In a normal injection molded product, ∠A + ∠B = 1
Preferably, it is 80 degrees, ΔB must be less than 90 degrees, and preferably in the range of 60 degrees to 30 degrees. As shown in FIG. 2, when ∠A + ∠B <180 degrees, the molded product shape of the gate portion becomes concave,
∠B must also be less than 90 degrees, 60 degrees to 3 degrees
It is preferable that it is within the range of 0 degrees. As shown in FIG. 3, when ∠A + ∠B = 180 degrees, the check valve 3
Above, the shape of the molded product of the gate portion is convex. Even in this case, ΔB must be less than 90 degrees, and is preferably in the range of 60 degrees to 30 degrees. In any case, there is no problem in the injection molding process.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4A is a longitudinal sectional view showing a nozzle portion of the hot runner unit according to the second embodiment of the present invention.
(B) is a transverse sectional view showing an AA section of (a).

As shown in FIG. 4, for the nozzle portions 12 and 13 of the hot runner unit 11 according to the second embodiment, a check valve having a spherical ball 15 as a valve is used. The nozzle body 12 and the nozzle tip 13 are detachable by a screw. A ball valve 15 is inserted into a cavity 14 provided therein, and then the nozzle body 12 and the nozzle tip 13 are screwed together. The cavity 14 has an inner diameter that is substantially the same as the outer diameter of the ball valve 15 as shown by the imaginary line.
Is closed and there is no way for the molten resin to pass through, so the four resin passages 17 are engraved in the nozzle body 12 and the nozzle tip 13. The upper end of the cavity 14 is a valve seat 16 which is an annular 2 for storing the molten resin and improving the sealing property.
The groove 16a of the book is carved.

When the screw of the injection molding machine advances and the molten resin in the molding machine heating cylinder is pushed out into the hot runner unit 11, the ball valve 15 slides downward, and the cavity 14 and the four resin passages 17 are formed. The molten resin is filled into the mold cavity 19 along the path of the molten resin.
Thereafter, the hollow portion 20 is formed by the gas pressure by the gas assist molding method, and this gas pressure is applied to the mold cavity 19.
When the ball valve 15 is applied to the ball valve 15 through or through the molten resin, the gas pressure causes the ball valve 15 to break.
Slides upward and comes into close contact with the valve seat 16 to prevent gas from entering. Here, the molten resin accumulated in the two grooves 16a serves as an O-ring, and the sealing by the ball valve 15 is more reliable.

In the case of the injection press molding method, the pressure of the molten resin in the mold cavity 19 causes the ball valve 15 to slide upward and adhere to the valve seat 16 to prevent the molten resin from flowing backward.

As described above, by providing the check valve 15 in the nozzles 12 and 13, the gas and molten resin in the hot runner unit and the heating cylinder of the molding machine in the gas assist molding method and the injection press molding method are provided. Infiltration can be prevented, molding defects such as burning of a molded product, short molding, and silver streaks can be prevented, and the molding operation can be performed safely.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a longitudinal sectional view illustrating a nozzle portion of the hot runner unit according to the third embodiment of the present invention. FIG. 6 is a longitudinal sectional view illustrating a nozzle portion of a hot runner unit according to a modification of the third embodiment of the present invention.

As shown in FIG. 5, the check valve 23 of the hot runner unit 21 according to the third embodiment is obtained by changing the tip of the check valve 3 of the first embodiment from a conical shape to a spherical shape. . A valve seat 24 for receiving the check valve 23 is provided on the nozzle 22 side. The valve seat 24 is provided with two annular grooves 25 for storing the molten resin in the nozzle 22 and improving the sealing property. is there. The check valve 23 is supported above the rod portion 23a by a cylinder and a spring (not shown) so as to be slidable in the vertical direction.

When the screw of the injection molding machine advances and the molten resin in the molding machine heating cylinder is pushed out into the hot runner unit 21, the check ring 23 slides downward, and the clearance 26 which serves as a path for the molten resin is formed. Occurs. The molten resin is filled into the mold cavity 27 through the clearance 26. Thereafter, a hollow portion 28 is formed by the gas pressure by the gas assist molding method. When the gas pressure is applied to the check valve 23 via the molten resin in the mold cavity 27 or through the molten resin, the hollow portion 28 is formed by the gas pressure. The check ring 23 slides upward and closely contacts the valve seat 24 to prevent gas from entering. Here, the molten resin accumulated in the two grooves 25 serves as an O-ring, and the sealing by the check ring 23 is more reliable.

In the case of the injection press molding method, the check valve 23 slides upward due to the pressure of the molten resin in the mold cavity 27 and comes into close contact with the valve seat 24.
Prevent backflow of molten resin.

As described above, the check valve 2 is provided in the nozzle 22.
3, the gas and the molten resin can be prevented from entering the hot runner unit and the molding machine heating cylinder in the gas assist molding method and the injection press molding method. In addition, it is possible to prevent molding defects such as silver streaks and the like, and to perform molding operations safely.

In the third embodiment, the check valve 2
Since the tip of 3 is spherical, the tip enters the mold cavity 27, and this portion of the molded product becomes thin. In order to prevent this, as a modification of the third embodiment, it is preferable to use a check valve 29 having a hemispherical tip as shown in FIG. The other parts of the modification shown in FIG. 6 are the same as those in the third embodiment shown in FIG. According to this modification, it is possible to reliably prevent a part of the molded product from becoming thin.

As described above, the check valve 2 of the hot runner unit 21 according to the third embodiment shown in FIG.
No. 3 has a problem in that a part of the molded product is made thinner, but also has an advantage that the tip of the check ring 23 enters the mold cavity 27. That is, the tip of the check ring 23 is heated by the thermal energy of the molten resin injected into the mold cavity 27, and the temperature of the check ring 23 as a whole increases, so that the flow of the molten resin during injection molding is not hindered. The operation and effect are obtained.

Fourth Embodiment Next, a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a longitudinal sectional view illustrating a nozzle portion of the hot runner unit according to the fourth embodiment of the present invention. FIG. 8 is a longitudinal sectional view illustrating a nozzle portion of a hot runner unit according to a modification of the fourth embodiment of the present invention.

Based on the concept described in the third embodiment, the hot runner unit 1 of the first embodiment shown in FIG. 1 in which the shape of the check valve 3 is improved is the fourth embodiment shown in FIG. 3 is the check valve 8 of the hot runner unit 31 according to FIG. The check valve 8 has a substantially conical check valve 3 with a conical protruding part added to the tip of the check valve 3. As a result, the tip of the check ring 8 enters the mold cavity 7 and the molded product in this portion becomes thin.
The molten resin injected into the inside is heated by the thermal energy of the molten resin, and the temperature of the entire check valve 8 is increased, so that the effect of not obstructing the flow of the molten resin during injection molding is obtained. The other parts of the configuration of the hot runner unit 31 according to the fourth embodiment are the same as those of the hot runner unit 1 according to the first embodiment shown in FIG.

In the case of the shape of the check ring 8, this part of the molded product becomes too thin, and therefore, in the fourth embodiment,
A non-return valve 9 shown in FIG. The check ring 9 has a shape in which a frusto-conical protrusion is added to the tip of the substantially conical check valve 3. As a result, the tip of the check ring 9 does not enter the mold cavity 7 too deeply, the molded product in this portion does not become too thin, and the tip of the check ring 9 is injected into the mold cavity 7. Since the molten resin is heated by the thermal energy of the molten resin and the temperature of the entire check valve 9 increases, the effect of not obstructing the flow of the molten resin during injection molding can be obtained. Since the configuration of other parts in FIG. 8 is the same as that of hot runner unit 1 of the first embodiment shown in FIG. 1, the same reference numerals are given and the description is omitted.

Fifth Embodiment Next, a fifth embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 9 is a longitudinal sectional view illustrating a nozzle portion of a hot runner unit according to Embodiment 5 of the present invention. FIG. 10 is a longitudinal sectional view showing a nozzle portion of a hot runner unit according to a modification of the fifth embodiment of the present invention.

As shown in FIG. 9, the hot runner unit 41 according to the fifth embodiment is not a check valve which automatically closes by gas pressure or resin pressure as described in the first to fourth embodiments. The rod portion 44a is lowered by a hydraulic cylinder provided above the rod portion 44a,
The spherical check valve 44 is brought into close contact with the valve seat 45 to prevent gas and molten resin from entering. The gate 46 at the tip of the nozzle 42 is a thin pin gate. Therefore, since the area receiving the gas pressure and the resin pressure is very small, it can withstand the gas pressure in the gas assist molding method and the resin pressure in the injection press molding method even by the hydraulic pressure of the hydraulic cylinder, and the gas or molten resin is Intrusion into the hot runner unit 41 can be reliably prevented.

Since the molten resin is injected into the mold cavity from the narrow pin gate 46 through the cavity 43 in the nozzle 42, the gate trace remaining on the molded product is minimized, and the appearance of the product is improved. Another advantage is that the gate of the molded product is hardly deformed. Further, since the tip of the heated check valve 44 does not touch the molded product, the cooling time of the molded product can be reduced.

Check valve 4 according to the fifth embodiment.
The hot runner unit 51 of the modified example shown in FIG. The needle valve 54 of the hot runner unit 51 also lowers the rod portion 54a by a hydraulic cylinder provided above the rod portion 54a, and makes the needle valve 54 adhere to the valve seat 55 to prevent gas and molten resin from entering. Things. The gate 56 at the tip of the nozzle 52 is a thin pin gate. Therefore, since the area receiving the gas pressure and the resin pressure is very small, it can withstand the gas pressure in the gas assist molding method and the resin pressure in the injection press molding method even by the hydraulic pressure of the hydraulic cylinder, and the gas or molten resin is Intrusion into the hot runner unit 51 can be reliably prevented.

Since the molten resin is injected into the mold cavity from the narrow pin gate 56 through the cavity 53 in the nozzle 52, the gate trace remaining on the molded product is minimized, and the appearance of the product is improved. Another advantage is that the gate of the molded product is hardly deformed. Further, since the tip of the heated needle valve 54 does not touch the molded product, the cooling time of the molded product can be reduced. further,
By causing a part of the needle valve 54 to enter into the tip of the nozzle 52 of the hot runner unit 51, it is possible to reduce threading defects at the time of mold release.

In the fifth embodiment, the check valve 4
The hydraulic cylinder is used as an actuator for generating pressure to prevent gas and molten resin from entering, by moving the needle 4 and the needle valve 54 forward (downward) so as to be in close contact with the valve seat 45 and the valve seat 55. Also, a pneumatic cylinder, a hydraulic motor, an electric motor, an electromagnetic actuator or the like can be used.

Sixth Embodiment Next, a sixth embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 11 is an explanatory diagram illustrating the hot runner unit according to the sixth embodiment of the present invention. FIG. 12 is a partially cutaway perspective view showing a structure and a gate position of a molded product used in a molding test using the hot runner unit according to the sixth embodiment of the present invention. As shown in FIG. 11, the hot runner unit 61 according to the sixth embodiment includes a cooling unit 10 for precisely controlling the temperature.
0 is provided.

A mold sprue bush 63 is located immediately below the heating cylinder 62 of the injection molding machine. The manifold 64 of the hot runner unit 61 is connected to the sprue bush 63.
Is connected to The nozzle 65 is provided with two electric band heaters 66 for heating the hot runner unit 61. The temperature control of the heating is performed by a thermocouple (not shown) attached to the nozzle 65. When the temperature measured by the thermocouple exceeds the set temperature, the current flowing to the band heater 66 is cut off, and the heating is stopped. When the temperature measured by the thermocouple becomes equal to or lower than the set temperature, a current flows through the band heater 66 and heating is resumed.

Cooling means 100 in the sixth embodiment
Is for cooling by blowing compressed air to the hot runner unit 61. That is, the air compressed by the air compressor 101 is supplied to the air tank 102.
When the solenoid valve 103 is opened.
Compressed air flows toward the nozzle 65 from the plurality of air blowing nozzles 106 of the stainless steel tube 105 provided near the nozzle 65 of the hot runner unit 61, and the nozzle 65 is cooled.

The solenoid valve 103 is linked with the thermocouple, and while the temperature measured by the thermocouple is equal to or lower than the set temperature, that is, while current is flowing through the band heater 66 and heating is performed, the solenoid valve 103 is operated. 103 is closed and cooling with compressed air is not performed. When the temperature measured by the thermocouple exceeds the set temperature (that is, when the heating state stops), the timer 104 counts for a predetermined time, and then the solenoid valve 103
Is opened and the compressed air flows from the stainless steel pipe 105 to the nozzle 6
5 and is cooled. When the temperature measured by the thermocouple by the cooling with the compressed air becomes equal to or lower than the set temperature, a current flows through the band heater 66, and the heating is restarted.

By alternately repeating the heating and the cooling as described above, the temperature of the nozzle 65 is maintained near the set temperature, and the temperature of the molten resin in the hot runner unit 61 is also appropriately maintained. As described above, by performing the temperature control in the hot runner unit 61 with sufficient precision, molding defects due to resin burning, deformation, stringing, and the like can be reduced, and the yield of molded products can be improved.

In the sixth embodiment, the stainless steel tube 105 is disposed near the nozzle 65 in the hot runner unit 61 to cool only the nozzle 65. However, depending on the type of resin used and the molding conditions, the stainless steel tube 105 is cooled. The stainless steel tube 105 may be arranged near the manifold 64 to cool the manifold 64 as well.

In order to test the actual cooling effect, an injection molding test of the molded product 120 shown in FIG. 12 was performed using the hot runner unit 61. The size of the molded article 120 is a box shape with a length of 300 mm, a width of 380 mm, a height of 50 mm, and an average thickness of 3 mm, and two vertical and two horizontal ribs 124 are provided inside. Each corner has a C3 chamfer to support the flow of molten resin.
The number of gates 122 is one at the center.

As the molding resin, AGI manufactured by Asahi Kasei Kogyo Co., Ltd., which is a HIPS resin developed for gas assist, is used.
02 (trade name), and was molded at a molten resin temperature of 215 ° C. using a 350-ton injection molding machine. As the hot runner unit 61, a stainless steel pipe 105 is arranged around a valve gate type hot runner unit made by Mold Masters, so that not only the nozzle 65 but also the manifold 64 is cooled. While current is flowing through the band heater 66 and heating is being performed, the solenoid valve 103 is closed, and cooling with compressed air is not performed. When the temperature measured by the thermocouple exceeds the set temperature, the solenoid valve 103
Is opened, and compressed air of 0.8 MPa
The hot runner unit 61 was cooled by blowing air from the air blowing nozzle 106 of No. 5.

The results of the molding test show that when not cooled,
Burns of about 20 mm in diameter occurred around the gate, but when cooling was performed, the occurrence of the burn failure was not confirmed. As described above, it was found that molding failure can be prevented by cooling the hot runner unit 61 using the cooling means 100 and keeping the temperature of the molten resin inside the proper range.

Seventh Embodiment Next, a seventh embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 13 is an explanatory diagram illustrating the hot runner unit according to the seventh embodiment of the present invention. As shown in FIG. 13, the hot runner unit 71 according to the seventh embodiment also includes a cooling unit 110 for precisely controlling the temperature. The same parts as those in the sixth embodiment shown in FIG. 11 are denoted by the same reference numerals, and description thereof will be omitted.

The seventh embodiment is different from the sixth embodiment in that a copper pipe (hereinafter referred to as “copper pipe”) 107 is connected to the solenoid valve 103 and the copper pipe 107 is connected to the hot runner unit 71. Is wound around the nozzle 65.
That is, the cooling means 110 according to the seventh embodiment performs cooling by flowing compressed air as a refrigerant through the copper tube 107 wound around the hot runner unit 61. When the solenoid valve 103 is opened, compressed air flows through the copper pipe 107, and compressed air as a refrigerant flows through the copper pipe 107 wound around the nozzle 65 of the hot runner unit 61, thereby cooling the nozzle 65. The tip 108 of the copper tube 107 is open, and compressed air is supplied from the nozzle 6
5 is sprayed on the tip.

In the seventh embodiment, the copper pipe 107 is wound around the nozzle 65 of the hot runner unit 71 to cool only the nozzle 65. However, depending on the type of resin used and the molding conditions, the manifold 64 may be used. Alternatively, the copper tube 107 may be wound to cool the manifold 64.

In order to test the actual cooling effect, an injection molding test of the molded article 120 shown in FIG. 12 was performed using the hot runner unit 71. A copper tube 107 having an inner diameter of 6 mm (wall thickness: 0.5 mm) was wound around a valve gate type hot runner unit manufactured by Mold Masters of Canada, and compressed air of 0.8 MPa was supplied from the air compressor 101 to confirm a cooling effect. Resin used (A
GI02), the injection molding machine, the mold, and the molding conditions are the same as in the sixth embodiment.

While current is flowing through the band heater 66 and heating is being performed, the solenoid valve 103 is closed, and cooling with compressed air is not performed. When the temperature measured by the thermocouple exceeds the set temperature, the solenoid valve 103 opens and the
The compressed air of Pa flowed in the copper tube 107 as a refrigerant to cool the hot runner unit 71.

The results of the molding test show that when not cooled,
20 mm diameter around the gate as in the case of the sixth embodiment.
Although some degree of burning occurred, when cooling was performed, the occurrence of the burning failure was not confirmed. As described above, it was found that molding failure can be prevented by cooling the hot runner unit 71 using the cooling means 110 and keeping the temperature of the molten resin inside the proper range.

In the seventh embodiment, compressed air is used as the refrigerant. However, other refrigerants such as water and other liquids, cooling gas such as cooling air, and the like may be used as the refrigerant.
Further, a liquefied gas such as liquid nitrogen or liquid ammonia can be used.

Eighth Embodiment Next, an eighth embodiment of the present invention will be described with reference to FIG. 1, FIG. 11, and FIG. The hot runner unit according to the eighth embodiment has a structure in which the tip of the nozzle 65 of the hot runner unit 61 shown in FIG. 11 has the check ring 3 shown in FIG. That is, the hot runner unit of the eighth embodiment includes the check valve 3 for preventing gas or molten resin from entering the hot runner unit in the gas assist molding method or the injection press molding method. It also has a cooling means 100 for performing control precisely. According to such a configuration,
Backflow of the gas or the molten resin once injected into the hot runner unit can also be prevented, and the temperature of the molten resin in the hot runner unit can be maintained in an appropriate range.

As a result, molding defects such as burning of the molded product due to intrusion of gas or molten resin, short molding, silver streaks, etc. can be prevented, and molding due to burning, deformation, stringing, etc. of the resin due to overheating of the molten resin. Defects can also be reduced, and molding defects can be almost eliminated. As a result, the yield of molded products can be significantly improved.

In order to actually confirm the effect of preventing molding defects, a molding test of the molded article 120 shown in FIG. 12 by the gas assist molding method was performed. The resin used for the molding was ABS resin Sebian 500 (trade name) manufactured by Daicel Chemical Industries, Ltd.
It is. The injection molding machine, the mold, and the molding conditions are the same as those in the sixth embodiment.
Is the same as As shown in FIG.
Needle pin 126 for gas injection at one end of cavity
The injection gas pressure was increased to 42 MPa (gas was nitrogen gas), and injection was performed for 20 seconds immediately after the filling of the molten resin into the mold cavity was completed. However, the high-pressure gas did not enter the hot runner unit 61 and the heating tube of the molding machine through the gate of the hot runner unit 61, and a non-defective product could be formed continuously for 100 shots.

For comparison, the mold gates hot runner unit of the valve gate type was not modified at all and was molded at a gas pressure of 20 MPa as it was. Gas enters the short mold
Many silver streaks occurred and continuous production was not possible. When the gas pressure was reduced to 15 MPa, there was no gas intrusion, but the hollow ratio was reduced, and some sink marks were generated at the corners and the ribs. Further, the gas pressure is reduced in the eighth embodiment.
At the same pressure as 42 MPa, the gas enters through the gate of the hot runner unit, passes through the hot runner unit, enters the molding machine heating cylinder, and pushes up the screw in the molding machine heating cylinder to the end. Was.

As described above, the hollow ratio (the ratio of the weight of the gas-assisted molded product to the weight of the solid molded product (solid internal molded product)) of the molded product 120 molded using the hot runner unit of the eighth embodiment. Is the gas-assisted molded product weight /
In contrast to the solid molded product weight = 90/100, when the gas pressure of injection was 15 MPa using the valve runner type hot runner unit manufactured by Mold Masters, the gas assisted product weight / solid molded product weight = The economical effect (reduction of the amount of material used) by the gas assist molding method was larger when the hot runner unit according to the eighth embodiment was used.

Ninth Embodiment Next, a ninth embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 14 is a longitudinal sectional view illustrating a nozzle portion of a hot runner unit according to Embodiment 9 of the present invention. FIG. 15 is a longitudinal sectional view illustrating a nozzle portion of a hot runner unit according to a modification of the ninth embodiment of the present invention.

As shown in FIG. 14, the ninth embodiment
The hot runner unit 81 has a structure in which an annular through hole for gas injection is provided in the check valve 8 of the fourth embodiment shown in FIG. Figure 7 for other parts
Therefore, the same reference numerals are given and the description is omitted. That is, the non-return valve 82 of the hot runner unit 81 according to the ninth embodiment has an annular gas injection hole 83 penetrating along the axial direction inside.

Therefore, the gas injection holes 83 are formed every shot or every several shots during injection molding.
The check valve 82 can be cooled by injecting a small amount of gas (such as nitrogen gas) into the air. by this,
The cooling means 100 according to the sixth and seventh embodiments,
The same effect as 110 can be obtained, and molding defects such as deformation, burning, and stringing at the time of mold release can be reduced. In performing the gas assist molding method, a high-pressure gas can be injected from the gas injection hole 83.

As a modification of the ninth embodiment, a hot runner 91 shown in FIG. 15 is provided with a similar gas injection hole, and is provided in the check valve 29 of the third embodiment shown in FIG. It has a structure in which an annular through hole for gas injection is provided. The other parts are the same as those shown in FIG. That is, the check valve 92 of the hot runner unit 91 of the modification of the ninth embodiment has an annular gas injection hole 93 penetrating in the axial direction inside.

Therefore, the gas injection holes 93 are formed every shot or every several shots during injection molding.
The check valve 92 can be cooled by injecting a small amount of gas (such as nitrogen gas) into the air. by this,
The cooling means 100 according to the sixth and seventh embodiments,
The same effect as 110 can be obtained, and molding defects such as deformation, burning, and stringing at the time of mold release can be reduced. In addition, GP which is a kind of gas assist molding method
In carrying out the I molding method, it is also possible to inject a high-pressure gas from the gas injection hole 93.

The GPI molding method is a kind of gas assist molding method, in which a gas is not injected into a molded product to make the molded product hollow, but a gas is formed between the molded product and a mold inner wall. Is a molding method for adjusting the shape of a molded article by injecting the same.

The injection molding method that can be performed in the present invention includes:
Injection of the molten resin heated and melted in the injection molding machine heating cylinder into the mold cavity, applying a holding pressure as necessary, cooling and solidifying in the mold cavity, and then taking out other than a known molding method, For example, a foam molding method using a foaming agent (NSF method,
GCP method), two-color molding method, two-layer molding method, sandwich molding method, injection blow molding method, injection press molding method, in-mold molding method, etc.
These molding methods can be performed not only alone but also in combination with the above-described gas assist molding method.

As the resin for injection molding used in the present invention, any resin composition containing a resin exhibiting thermoplasticity as a main component can be used. Typical examples are styrene resins represented by ABS resin, HIPS resin and modified PPE resin, olefin resins represented by polypropylene resin and polyethylene resin, ester resins represented by PET resin and PBT resin, Amide resins represented by nylon-6, nylon-66, etc., other polycarbonate resins, vinyl chloride resins, polymer blends of these resins, polymer alloys, and resin reinforcing materials such as glass fiber (GF) are added. Composite material.

Further, as the check valve, the check valve 3 of the first embodiment has a substantially conical tip, the ball valve 15 of the second embodiment, and the check valve of the third and fifth embodiments has a spherical tip. The valves 23 and 44 and the hemispherical check valve 29, the check valves 8 and 82 in which the conical protrusions are added to the substantially conical tips of the fourth and ninth embodiments, and the truncated cone protrusions are provided. The added check valves 9 and 92 and the needle valve 54 of the fifth embodiment have been described. However, the shape of the check valve is not limited to these, and various other shapes are possible. The structure, material, shape, size, quantity, connection relationship, and the like of other portions of the hot runner unit according to the present invention are not limited to the above embodiments.

[0089]

As described above, in the hot runner unit according to the first aspect of the present invention, the nozzle is closed by the gas pressure in the gas assist molding method or the pressure of the molten resin in the injection press molding method. It is provided with a check valve for preventing intrusion of resin.

Therefore, during normal injection molding, the molten resin in the hot runner unit passes through the nozzle portion and is injected into the mold cavity. Thereafter, the molten resin in the gas assist molding method or the molten resin in the injection press molding method is used. When the gas or the molten resin tries to flow back into the hot runner unit through the nozzle portion under the pressure, the check valve closes to prevent the gas and the molten resin from entering.

As a result, the high-pressure gas enters from the inside of the hot runner unit to the inside of the molding machine heating cylinder, pushes up the molding machine screw to the end, and blows up the molten resin inside the heating cylinder through the molding machine hopper. Can be prevented beforehand, and the molding operation can be performed safely. Also, since no gas or molten resin injected once enters the hot runner unit, molding defects such as burning of molded products, short molding, and silver streaks can be prevented.

By providing the check valve in the nozzle as described above, the back flow of the gas and the molten resin into the hot runner unit and the heating cylinder of the molding machine in the gas assist molding method and the injection press molding method can be prevented. It is possible to prevent molding defects such as burning of a molded product, short mold, silver streak, and the like, and to perform molding work safely.

A hot runner unit according to a second aspect of the present invention is the hot runner unit according to the first aspect, wherein one or two or more annular grooves are provided in the seal portion of the check ring. Thereby, in addition to the effect of claim 1,
The molten resin in the hot runner enters the annular groove, and when the gas pressure or the molten resin pressure is applied and the check valve operates, the molten resin in the annular groove acts as an O-ring and is more completely sealed. You. Therefore, it is possible to more reliably prevent the backflow of the gas and the molten resin into the hot runner unit and the inside of the molding machine heating cylinder, and to more reliably prevent molding defects such as burning of the molded product, short molding, and silver streak. In addition, the molding operation can be performed safely.

According to a third aspect of the present invention, in the hot runner unit according to the first or second aspect, the check valve is configured such that a movable ball forms an entrance of a cavity provided in the middle of the nozzle portion. It is a plug. As described above, since the ball valve structure is employed as the check valve, in addition to the effects described in the first and second aspects, there is no need to provide a mechanism for supporting and sliding the valve. can do.

According to a fourth aspect of the present invention, in the hot runner unit according to the first or second aspect, the check valve is provided for injecting gas into the mold cavity from the hot runner unit. It has holes. Therefore, in addition to the effects described in claim 1 and claim 2, the check valve is cooled by injecting a small amount of gas into this gas injection hole every shot or every several shots during injection molding. be able to. This prevents the molten resin in the hot runner unit, especially at the nozzle, from becoming overheated,
An appropriate temperature range can be maintained. As a result, it is possible to reduce molding defects such as deformation, burning, and stringing at the time of releasing the molded product. Further, when performing the gas assist molding method, it is also possible to inject a high-pressure gas from this gas injection hole.

According to a fifth aspect of the present invention, in the hot runner unit according to any one of the first to fourth aspects, when the hot runner unit is not in the heating state, a part of the hot runner unit or It is provided with cooling means for cooling the whole. That is,
The hot runner unit according to the fifth aspect includes a check valve that prevents gas or molten resin from entering the hot runner unit in the gas assist molding method or the injection press molding method, and precisely controls the temperature of the hot runner unit. And cooling means for cooling.

According to this configuration, in addition to the effects described in any one of claims 1 to 4, backflow of the gas or the molten resin once injected into the hot runner unit can be prevented. The temperature of the molten resin in the hot runner unit can also be kept in an appropriate range. As a result, it is possible to prevent molding defects such as burning of molded products due to intrusion of gas or molten resin, short molding, silver streaks, etc., and to reduce molding defects due to resin burning, deformation, stringing, etc. due to overheating of molten resin. And molding defects can be almost eliminated. As a result, the yield of molded products can be significantly improved.

The hot runner unit according to the invention of claim 6 is provided with a cooling means for cooling a part or all of the hot runner unit when the hot runner unit is no longer in a heated state. As described above, the electric heater for heating the hot runner unit cuts off the current when the temperature measured by the thermocouple exceeds the set temperature, but the temperature of the molten resin further rises due to residual heat for a while thereafter. Therefore, when the heater is turned off, that is, when the heating state is stopped, the temperature of the hot runner unit is forcibly reduced by cooling part or all of the hot runner unit (portion that is likely to be overheated) immediately by the cooling means. And the temperature of the molten resin inside is returned to the set temperature in a short time. As a result, the temperature of the molten resin during injection molding is maintained in an appropriate range, and molding defects such as deformation around the gate, burning, and stringing do not appear in the molded product.

By performing the temperature control in the hot runner unit with sufficient precision in this way, molding defects due to resin burning, deformation, stringing, etc. can be reduced, and the yield of molded products can be improved.

The hot runner unit according to a seventh aspect of the present invention is the hot runner unit according to the sixth aspect, wherein the cooling means comprises:
The compressed gas is blown to part or all of the hot runner unit. According to this configuration, in addition to the effect described in claim 6, since the cooling means can be provided separately from the hot runner unit, the degree of freedom of arrangement of the cooling means is increased, and the hot runner unit is likely to be overheated. Can be intensively cooled. Further, the blowing of the compressed gas causes adiabatic expansion of the gas to lower the temperature, so that the cooling effect is further enhanced.

The hot runner unit according to the eighth aspect of the present invention is the hot runner unit according to the sixth aspect, wherein the cooling means comprises:
A pipe for flowing a refrigerant is wound around a part or all of the hot runner unit. According to such a configuration, in addition to the effect described in claim 6, it is possible to surely and more strongly cool the portion to be cooled.

The hot runner unit according to a ninth aspect of the present invention is the hot runner unit according to the sixth aspect, wherein the cooling means comprises:
A pipe is wound around a part or the entirety of the hot runner unit, a liquid is caused to flow and vaporized, and the hot runner unit is cooled by the heat of vaporization. Therefore, in addition to the effect described in claim 6, since the heat of vaporization of the liquid is large, it is possible to obtain a stronger cooling effect than simply flowing the refrigerant through the wound pipe. According to such a configuration, the part to be cooled can be more strongly and effectively cooled.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view showing a nozzle portion of a hot runner unit according to a first embodiment of the present invention, and FIG. 1B is a longitudinal sectional view showing a state where the nozzle portion is closed. .

FIG. 2 is a longitudinal sectional view showing an example in which the angle of a nozzle portion of the hot runner unit according to the first embodiment of the present invention is changed.

FIG. 3 is a vertical cross-sectional view showing an example in which the height of a check ring in a nozzle portion of the hot runner unit according to the first embodiment of the present invention is changed.

FIG. 4A is a longitudinal sectional view showing a nozzle portion of a hot runner unit according to a second embodiment of the present invention;
(B) is a transverse sectional view showing an AA section of (a).

FIG. 5 is a longitudinal sectional view illustrating a nozzle portion of a hot runner unit according to a third embodiment of the present invention.

FIG. 6 is a vertical sectional view showing a nozzle portion of a hot runner unit according to a modification of the third embodiment of the present invention.

FIG. 7 is a longitudinal sectional view illustrating a nozzle portion of a hot runner unit according to a fourth embodiment of the present invention.

FIG. 8 is a longitudinal sectional view showing a nozzle portion of a hot runner unit according to a modification of the fourth embodiment of the present invention.

FIG. 9 is a longitudinal sectional view showing a nozzle portion of a hot runner unit according to a fifth embodiment of the present invention.

FIG. 10 is a longitudinal sectional view showing a nozzle portion of a hot runner unit according to a modification of the fifth embodiment of the present invention.

FIG. 11 is an explanatory diagram illustrating a hot runner unit according to a sixth embodiment of the present invention.

FIG. 12 is a partially broken perspective view showing a structure and a gate position of a molded product used in a molding test using a hot runner unit according to a sixth embodiment of the present invention.

FIG. 13 is an explanatory diagram illustrating a hot runner unit according to a seventh embodiment of the present invention.

FIG. 14 is a longitudinal sectional view showing a nozzle portion of a hot runner unit according to a ninth embodiment of the present invention.

FIG. 15 is a longitudinal sectional view showing a nozzle portion of a hot runner unit according to a modification of the ninth embodiment of the present invention.

[Explanation of symbols]

1,11,21,31,41,51,61,71,8
1,91 Hot runner unit 2,12,13,22,42,52,65 Nozzle part 3,8,9,15,23,29,44,54,82,9
2 check valve 4, 16a, 25 annular groove 14 cavity 15 ball 100, 110 cooling means 107 piping

Claims (9)

[Claims] In a hot runner unit of a mold used for injection molding of a thermoplastic resin, a nozzle portion is closed by gas pressure in a gas assist molding method or pressure of a molten resin in an injection press molding method. A hot runner unit comprising a check valve for preventing intrusion of air. 2. The hot runner unit according to claim 1, wherein one or two or more annular grooves are provided in a seal portion of the check ring. 3. The hot runner according to claim 1, wherein the check valve closes an entrance of a cavity provided in the middle of the nozzle portion by a movable ball. unit. 4. The check valve according to claim 1, wherein the check valve has a gas injection hole for injecting a gas from the hot runner unit into a mold cavity. Hot runner unit. 5. A cooling means for cooling a part or all of the hot runner unit when the hot runner unit is no longer in a heated state.
The hot runner unit according to claim 1. 6. A hot runner unit of a mold used for injection molding of a thermoplastic resin, comprising cooling means for cooling a part or all of the hot runner unit when the hot runner unit is no longer in a heated state. A hot runner unit characterized by: 7. The hot runner unit according to claim 6, wherein said cooling means blows a compressed gas to a part or all of said hot runner unit. 8. The hot runner unit according to claim 6, wherein said cooling means is formed by winding a pipe for flowing a refrigerant around a part or all of said hot runner unit. 9. The cooling means according to claim 6, wherein a pipe is wound around a part or the entirety of the hot runner unit, the liquid is caused to flow and vaporized, and the vaporized heat is cooled. Hot runner unit.