JPH0518116Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to a sprue bush, and more specifically, it constitutes a molten resin passageway for injecting molten resin from the nozzle of an injection molding machine into a cavity formed in a mold. Concerning sprue-buttoning.

(Prior Art) Conventionally, molds used for injection molding heat a molten resin passage through which molten resin is injected from a nozzle of an injection molding machine into a cavity formed in the mold, A hot runner mold is used that can carry out injection molding while keeping the resin held in a molten state at all times.

Usually, a sprue bush that contacts the nozzle tip of the injection molding machine and/or a sprue bush that includes a gate portion that connects the molten resin passage and the cavity is inserted into the molten resin passage.

In a hot runner mold having such a molten resin passage, temperature control devices such as a heater and a temperature sensor are inserted near the sprue bush and the molten resin passage (manifold), and furthermore, a temperature control device such as a temperature sensor is inserted near the cavity formed in the mold. is equipped with a cooling circuit.

Therefore, during injection molding, by maintaining the sprue bushing and manifold portion at a constant temperature, the resin in the sprue and runner portions can be kept in a molten state, and only the molded product can be cooled and solidified before being taken out.

(Problem to be solved by the invention) In injection molding using such a hot runner mold, injection molding can be performed without a runner, and only the molded product can be taken out from the injection molding machine. It is possible to achieve automation, shorten the molding cycle, improve the quality of the molded product obtained, and reduce molding costs.

By the way, the temperature of the molten resin in the sprue bush or manifold portion generally affects the amount of molten resin injected into the cavity, and also has a large effect on the quality of the molded product obtained, so fine temperature control is required.

On the other hand, in a hot runner mold, heat radiation due to heat transfer from the cooling circuit, sprue bush, and manifold provided near the cavity affects the temperature of the molten resin in the sprue bush and manifold portions.

In particular, the sprue bush is provided on the surface of the mold or near the cavity in order to make contact with the nozzle tip of the injection molding machine or to connect the molten resin path and the cavity, and a part of the sprue bush is exposed on the mold surface or in the vicinity of the cavity. Since it is adjacent to the cooling circuit that cools the cavity, the amount of heat dissipated is large, and the temperature of the molten resin in the sprue bushing is likely to fluctuate due to external factors such as outside air temperature and cooling temperature.

In order to eliminate such fluctuations in the temperature of the molten resin, conventional hot runner molds are equipped with temperature control devices such as heaters and temperature sensors inside the mold, as described above. A heat insulating material is inserted between the two to insulate them so that heat is not transferred to the cavity, etc., which is being cooled.

However, if the molten resin temperature in the sprue bush fluctuates greatly due to the influence of outside air temperature or cooling temperature, the manifold section alone cannot sufficiently absorb the molten resin temperature fluctuations.
The amount of molten resin injected into the cavity fluctuates.

In order to minimize such fluctuations in the temperature of the molten resin, it is necessary to sufficiently insulate the sprue bush or manifold and the vicinity of the cavity that is being cooled, and to use a large-capacity, high-performance heater and temperature control. By providing the sensor in the sprue bush or manifold part, it is necessary to reduce heat transfer from the sprue bush etc. to the cavity part and to be able to quickly respond to changes in the temperature of the molten resin.

However, loading a sufficient amount of heat insulating material to provide a sufficient heat insulation effect increases the thickness of the mold, making maintenance of the mold difficult, and installing a large-capacity, high-performance heater, etc. This makes the process complicated and the mold expensive. For this reason, such a mold cannot be used industrially.

Therefore, the purpose of the present invention is to provide a sprue bushing that can reduce the amount of heat radiation and heat transfer from the sprue bushing as much as possible, and that can provide a hot runner mold at low cost and easy maintenance. .

(Means for Solving the Problems) In order to achieve the above object, the inventor of the present invention, as a result of intensive studies, decided to use a sprue bush as a double pipe, and an inner cylinder (hereinafter referred to as an inner sprue bush) provided with a molten resin passage. ) and the outer cylinder containing the inner sprue bush (hereinafter referred to as the outer sprue bush), and by reducing the pressure in the space and creating a high degree of vacuum, radiation from the outer wall of the sprue bush is reduced. We discovered that the amount of heat and heat transfer can be reduced, and arrived at the present invention.

That is, the present invention provides a sprue bush and/or a molten resin passage that comes into contact with the nozzle tip of an injection molding machine and constitutes a molten resin passage through which molten resin is injected from the nozzle of the injection molding machine into a cavity formed in a mold. and a cavity, the sprue bush is constituted by an inner sprue bush having a molten resin passage and an outer sprue bush enclosing the inner sprue bush, and the sprue bush is provided between the inner and outer sprue bushes. The sprue bush is characterized in that the space in which the molten resin is located is evacuated to a high degree of vacuum, and a vacuum heat insulating layer is formed adjacent to the outer peripheral wall surface of at least a portion of the molten resin passage.

In this invention, the space is 10 ^-5 mmHg.
By reducing the pressure to below, it is possible to significantly reduce the influence of external factors such as the amount of heat radiated from the sprue bushing and the outside temperature.

(Function) According to the sprue bush of the present invention, the space provided between the inner and outer sprue bushes is reduced in pressure to a high degree of vacuum and becomes a vacuum insulation layer, thereby minimizing the amount of heat radiation and heat transfer from the sides of the sprue bush. Therefore, the molten resin inside the sprue bush is less affected by external factors such as outside air temperature, and the molten resin temperature can be maintained at a constant temperature without using heating means even if the outside temperature fluctuates. be able to.

(Example) The present invention will be explained in more detail using the drawings.

FIG. 1 is a sectional view of a sprue bush that comes into contact with the nozzle tip of an injection molding machine. Sprue bush A is composed of an inner sprue bush 3 and an outer sprue bush 4 containing the inner sprue bush 3. Passage 1
A concave nozzle touch part 8 is provided at the upper end of the molten resin passage 1, with which the nozzle of the injection molding machine body comes into contact.

Inner sprue bush 3 and outer sprue bush 4
Insulating rings 6, 7 made of a thermal insulator such as ceramic are fitted between the inner and outer sprue bushings 3, 4 and the upper and lower ends of the insulating rings 6, 7, respectively, and the joint surfaces between the insulating rings 6, 7 and the inner and outer sprue bushings 3, 4 are sufficiently sealed.

A space 2 surrounded by the inner and outer sprue bushes 3, 4 and the insulation rings 6, 7.
is maintained at a reduced pressure of 10 ^-5 mmHg or less.

In order for the space 2 to maintain such a high degree of reduced pressure, air is first removed from the space 2 through an air vent pipe 10 provided in the outer sprue bush 4 and equipped with a check valve (not shown). is discharged to obtain a predetermined degree of vacuum, and then the pipe 10 is screwed into the space 2 and the inlet portion of the pipe 10 is welded.

This sprue bush A is used as a sprue bush for a hot runner mold, as shown in FIG.

The hot runner mold shown in FIG. Side mounting plate 24
The sprue bush A is fitted so that the top surface of the sprue bush A matches the top surface of the sprue bush A, and a locate ring 16 is also attached to the top surface of the fixed side mounting plate 24.

In addition, a manifold 19 is provided on the fixed side back plate 25.
The manifold 19 is provided with a branch passage 23 of the molten resin passage 1 of the sprue bush A and a heater 18, and a portion of the lower end of the sprue bush A is fitted into the manifold 19.

A heat insulating material 17 such as ceramic is attached to the periphery of the manifold 19, and is insulated from the fixed side mounting plate 24, the fixed side mold plate 26, etc.

In the mold according to this embodiment, a cavity 21 is formed by a fixed side mold plate 24 and a movable side mold plate 22, and the secondary sprue bush 20 including a gate 28 for injecting molten resin into the cavity 21 also has a cavity 21 formed by a fixed side mold plate 24 and a movable side mold plate 22. ,
A space 27 that is evacuated to a high degree of vacuum is provided adjacent to the outer peripheral wall surface of the branch passage 23 including the gate 28 .

In addition, in the hot runner mold of this example,
A cooling circuit (not shown) through which cooling water flows is provided near the cavity 21 .

In the hot runner mold shown in FIG. 2 using the sprue bush A shown in FIG. 1, the nozzle of the injection molding machine comes into contact with the nozzle touch portion 8 of the sprue bush A to inject molten resin. The injected molten resin passes through the molten resin passage 1 and runner 23 of the sprue bush A, and is filled into the cavity 21 through the gate 28.

Next, after a predetermined amount of molten resin is injected, the nozzle of the injection molding machine leaves the nozzle touch part 8, and after the molten resin filled in the cavity 21 is cooled and solidified, it is transferred to the fixed side mold plate 26 and the movable side mold plate 26. Template 2
2 is opened and the molded product is taken out.

Thereafter, the space between the stationary mold plate 26 and the movable mold plate 22 is closed, and the nozzle of the injection molding machine comes into contact with the nozzle touch part 8 again to inject and fill the mold with molten resin.

In such an injection molding cycle, from the entrance of the molten resin passage 1 of the sprue bush A to the gate 2
8, the molten resin is kept in a molten state and the temperature is kept as constant as possible, which prevents fluctuations in the amount of molten resin filled into the cavity 21 and improves the quality of the resulting molded product. It can be kept constant.

In this respect, the sprue bush A of the hot runner mold according to this embodiment has a space 2 adjacent to the outer peripheral wall surface of the molten resin passage 1 and maintained at a high degree of vacuum.
A manifold 1 is provided with a sprue bush A, and the lower end of the sprue bush A is heated by a heating tube 18.
9, which prevents heat radiation due to heat transfer from the outer peripheral wall surface of the molten resin passage 1 of the sprue bush A, and since heat from the manifold 19 is transferred to the sprue bush A, the molten resin passage 1 is fitted into the sprue bush A. The temperature of the molten resin in the chamber 1 can be kept as constant as possible even if the outside air temperature etc. fluctuate.

In addition, the runner 23 is provided in the heated manifold 19, and the temperature of the molten resin in the sprue bush A can be stabilized as much as possible as described above, so the temperature of the molten resin in the runner 23 is further increased. Can be held stably.

Furthermore, since the high vacuum space 27 in the secondary sprue bushing 20 is provided adjacent to the outer peripheral wall surface of the runner portion including the gate 28, the gate 28
The nearby molten resin can be prevented from being affected by the cooling of the cavity 21.

In this way, the hot runner mold of this embodiment prevents heat radiation due to heat transfer between the molten resin passage entrance of the sprue bush A and the gate 28, and eliminates as much as possible the effects of outside temperature, etc. The temperature of the molten resin can be maintained as constant as possible and the cavity 21
Since it is possible to prevent variations in the amount of molten resin filled into the mold, it is possible to obtain molded products of constant quality.

In addition, there is no need for a special heater etc. to heat the sprue bush A, and there is no need to use a large capacity heater etc. installed in the manifold 19, so the mold thickness does not increase and maintenance is easy. is easy, and the manufacturing cost of the mold can be made low.

The sprue bush described so far is an example of use in a hotline mold that can mold many molded products at the same time, but an example of use in a mold that molds one molded product is shown in Figures 3 and 4. I will explain using

FIG. 4 is a cross section of a single-cavity mold using the sprue bush B shown in FIG.
3 and the movable mold plate 14 form a cavity 15, and the sprue bush B is fitted into the fixed mold plate 13.

The sprue bush B has a locate ring 11 in contact with its upper surface, and a heat insulating material 12 is inserted between the side wall surface of the sprue bush B and the stationary mold plate 13.

A sectional view of such a sprue bush B is shown in FIG.

The sprue bush B in Fig. 3 is the molten resin passage 1.
The lower end is narrowed to form a gate 9, which is connected to the cavity 15 via a sprue 5 below the gate 9.

The other parts are substantially the same as the sprue bush shown in FIG. 1, and their explanation will be omitted.

In the mold shown in FIG. 4 in which the sprue bush A shown in FIG. The cavity 15 is immediately filled from the gate 9 at the lower end of the passage 1.

In this molten resin passage 1, a space 2 provided adjacent to the outer peripheral wall surface and maintained at a high degree of vacuum (reduced pressure to 10 ^-5 mmHg or less) serves as a vacuum insulation layer, so that the molten resin is Since heat radiation due to heat transfer from the outer peripheral wall surface of the passage 1 can be prevented, the temperature of the molten resin in the molten resin passage 1 can be kept constant without the need for a special heating device such as a heater, resulting in uniform quality. molded products can be obtained.

Incidentally, the sprue bush B shown in FIG. 3 can also be used as the secondary sprue bush 20 shown in FIG. 2.

(Effects of the invention) According to the mold in which the sprue bushing of the invention is used, the temperature of the molten resin in the molten resin passage of the mold is constant, so it is possible to mold a molded product of constant quality. can.

Furthermore, since no special device is required to control the temperature of the molten resin within the mold, the mold structure can be simplified, maintenance is easy, and manufacturing costs can be reduced.

Further, since parts such as the molten resin passage and the runner which must be kept at a high temperature are sufficiently insulated, the cooling efficiency of the cavity part can be improved and the molding cycle can be shortened.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an example of the sprue bush of the present invention, Fig. 2 is a sectional view of a hot runner mold using the sprue bush shown in Fig. 1, and Fig. 3 is a sectional view showing another example of the sprue bush of the present invention. Figure, 4th
Each figure shows a sectional view of a mold using the sprue bush shown in FIG. 3. In the figure, A...Spring bushing, B...2
Next sprue bush, 1... Molten resin passage, 2...
A space reduced to a high degree of vacuum, 3...inner sprue bush, 4...outer sprue bush, 6,
7...Insulation ring, 8...Nozzle touch part.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A sprue bush that contacts the tip of the nozzle of an injection molding machine and/or constitutes a molten resin passage through which molten resin is injected from the nozzle of the injection molding machine into a cavity formed in a mold. Alternatively, in a sprue bush including a gate portion connecting a molten resin passage and a cavity, the sprue bush is constituted by an inner sprue bush having a molten resin passage and an outer sprue bush containing the inner sprue bush, and the inner and outer sprue bushes A sprue bushing characterized in that a space provided between the two is evacuated to a high degree of vacuum, and a vacuum heat insulating layer is formed adjacent to the outer peripheral wall surface of at least a portion of the molten resin passage. 2. The sprue bushing according to claim 1, wherein the space is reduced in pressure to 10 ^-5 mmHg or less.