JPH0767717B2 - Hot runner mold - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot runner mold, and more particularly to a hot runner mold suitable for preform injection molding in a blow molding machine.

[0002]

2. Description of the Related Art In a hot runner mold for guiding a molding resin material to an injection cavity mold, it is necessary to control the temperature of the molding resin material to its own molding temperature. As the temperature control of this hot runner mold, there is one disclosed in the following publication.

FIG. 1 of Japanese Utility Model Publication No. 60-4742 discloses a mold in which four nozzle bodies are fixed to a hot runner block, and a band heater is wound around the hot runner block having a circular cross section. ing.

On the other hand, the first in US Pat. No. 4,500,279
FIG. 2 and FIG. 2 disclose a mold in which a heat pipe is arranged along the longitudinal direction of a hot runner block, and a heater is built in one end of the heat pipe in the longitudinal direction. Further, in U.S. Patent Publication No. 6, column 39, et seq., It is disclosed that the torpedo is arranged at the center of the resin supply port of the nozzle body, and the heat pipe is arranged over the entire axial area of the torpedo. There is. The heat pipe in this torpedo is
It is described as an alternative to conventional built-in heaters.

[0005]

With the technology disclosed in Japanese Utility Model Publication No. 60-4742, it is not possible to effectively control the temperature of the resin in the runner that extends substantially along the center of the hot runner block. It must consume a large amount of heat energy. Moreover, even if a large amount of heat energy is supplied, it is impossible to ensure temperature uniformity in the entire block. Further, the temperature control of the nozzle main body which is in contact with the injection cavity type that serves as a cooling source requires only the solid heat conduction of the nozzle main body to use the heat of the hot runner block, and precise temperature control is impossible at all. In particular, the longer the nozzle body, the more difficult it becomes to control the temperature of the nozzle body, and the temperature of the nozzle body becomes lower than that of the hot runner block.

On the other hand, in the technique disclosed in US Pat. No. 4,500,279, a heat pipe is arranged along the longitudinal axis direction of the hot runner block, and the heat of a heater provided at one end of the heat pipe is efficiently transferred in the longitudinal direction of the block. Heat can be transferred over the entire area.

However, even in the above-mentioned US patent,
The temperature control of the nozzle body is similar to the technique of Japanese Utility Model Publication No. 60-4742 in that it depends entirely on the heat of the hot runner block. In the above-mentioned US patent, the heat transfer efficiency between the hot runner block and the nozzle body can be increased by disposing the heat pipes throughout the torpedo. However, even if a heat pipe is used, the nozzle mouth side (injection cavity mold side) of the nozzle body is always greatly affected by the cooling part in the injection cavity mold, so it is not possible to rely only on the temperature of the hot runner block. However, it is difficult to raise the temperature of the nozzle body to the required temperature, and the temperature of the nozzle body is inevitably lower than the temperature of the hot runner block. Further, if the temperature of the nozzle body is to be raised to the required temperature, the temperature of the hot runner block must be raised to a considerably high temperature, which may deteriorate the resin in the runner. In particular, since heat is exchanged at the tip of the nozzle, it is necessary to supply heat, and in addition, precise temperature control is required for resin entry, sealing, and the like.

Further, in the above-mentioned US patent, a heater is provided at one end of the heat pipe as the temperature control means of the hot runner block, but in particular, the number of simultaneous molded pieces is increased and the length of the longitudinal axis of the block is increased. In this case, even if a heat pipe is provided, the temperature at the other end without the heater decreases, and a uniform temperature cannot be achieved along the longitudinal axis.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems, and to maintain the temperature uniformity of the entire hot runner block having a large heat capacity, while exchanging heat between the nozzle body and the injection cavity type. It is to provide a hot runner mold that can perform temperature control while maintaining a good balance.

Another object of the present invention is to provide a hot runner mold which can achieve uniform temperature control of the block over the entire length even if the total length of the hot runner block is increased.

[0011]

According to a first aspect of the present invention, a plurality of nozzle main bodies having a nozzle opening communicating with an injection cavity type gate and a runner communicating with the nozzle opening, and a plurality of nozzle main bodies fixed to each other are fixed. And, in a hot runner mold having a hot runner block having a runner for introducing a resin material into the runner of the nozzle body from a sprue, the hot runner block is
A first temperature control unit for controlling the temperature of the hot runner block, and one or a plurality of first heat pipes arranged inside the hot runner block along the longitudinal axis direction of the block. , a plurality of the nozzle body, the
Embedded solid that is embedded and fixed in the hot runner block
And Teitan portion is disposed on at least the nozzle opening side, and second temperature control means for temperature control of the nozzle opening side, the hotline
Exposed from the inner block and the embedded solid
One or a plurality of second heat pipes that are disposed inside the nozzle main body over both parts of the fixed end portion and that extend along the runners inside the nozzle main body, respectively. .

According to a second aspect of the present invention, a plurality of nozzle main bodies having a nozzle opening communicating with an injection cavity type gate and a runner communicating with the nozzle opening, a plurality of the nozzle main bodies are fixed, and the sprue comprises In a hot runner die having a hot runner block having a runner for introducing a resin material into the runner of the nozzle body, the hot runner block is arranged inside the hot runner block along the longitudinal axis direction of the block. And a built-in heater disposed inside the hot runner block in parallel with the first heat pipe and across the disposition range of the first heat pipe. Characterize.

[0013]

According to the first aspect of the present invention, the hot runner block having a large heat capacity is provided with one or a plurality of first heat pipes along the longitudinal axis thereof, so that the heat from the first temperature control means can be reduced. Can be efficiently transmitted to the entire area, and the constant temperature of the resin in the runner arranged in the block can be maintained with relatively little power consumption.

Temperature control on the nozzle body side is performed by two methods.
First, the temperature control on the fixed end side of the nozzle body is realized by utilizing the second heat pipe and efficiently transferring the heat of the hot runner block. The fixed end side of the nozzle body has a first heat pipe to maintain a substantially uniform temperature.
It is embedded and fixed in a temperature-controlled hot runner block . Therefore, this embedded fixed end is
It can be considered as almost one, and embedding multiple nozzle bodies
Each runner in the fixed end is almost identical to the block
Temperature controlled to temperature. Runner formed on the nozzle body
-In addition to this embedded fixed end, the hot runner
It is also installed on the exposed part exposed to the outside of the block.
It A second heat is applied to the embedded fixed end and the exposed portion.
Since the pipe is provided, the embedded fixed end and dew
Heat conduction is actively performed between the outlets, and multiple nozzle bodies
Each runner in the exposed part of the hot runner
The temperature can be set to be almost uniform with that of the block. Next, on the nozzle mouth side of the nozzle body, since this region abuts the injection cavity mold serving as the cooling source, the temperature of the nozzle body cannot be controlled only by transferring the heat of the block. In the present invention, the second temperature adjusting means is provided on the nozzle mouth side of the nozzle body, thereby performing temperature control independent of the block. Moreover, since the fixed end side of the nozzle body is maintained at substantially the same temperature as the block due to the heat of the block side, local temperature control on the nozzle mouth side of the nozzle body becomes easy. Further, as compared with the case where the temperature of the entire nozzle body is controlled by the built-in heater, the temperature control is easy because the temperature control region is narrow and the power consumption is reduced.

The second aspect of the invention is to improve the uniform temperature maintenance of the hot runner block. According to the present invention, the heat pipe and the built-in heater are arranged in parallel along the longitudinal direction of the block and over substantially the same length. Usually, the heat pipe is used so as to have a heating source at one end and a heat radiation source at the other end, but the configuration of the second invention can achieve more uniform temperature maintenance along the longitudinal axis. In this case, the heat pipe rarely circulates the gas and the liquid in the entire axial direction from one end of the longitudinal axis to the other end, and the circulation of the gas and the liquid is repeated locally in the axial direction.
The heat transfer function is realized.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an injection molding station of a blow molding apparatus for blow molding a hollow container will be specifically described with reference to the drawings.

As shown in FIG. 5, the apparatus of this embodiment has an injection molding station 10, a temperature control station 12, a blow molding station 14 and an ejection station 16 and is capable of supporting a preform or a bottle (see FIG. 5). (Not shown) is rotatably conveyed to each of the stations 10 to 16.

The injection molding station 10 is roughly divided into an injection cavity mold 20, an injection core mold 26 and a hot runner mold 30. After the injection cavity mold 20, the injection core mold 26 and a neck mold (not shown) are clamped, , Injection molding of the preform is performed. The injection cavity mold 20 has a cavity 20a along the outer shape of a preform to be injection-molded, and in this embodiment, for example, four preforms can be simultaneously molded into four cavities 20a.
a. Around the cavity 20a is provided a cold water passage 22 through which a coolant such as cold water can circulate. Further, at the bottom of each cavity 20a, there is a gate 24 that can be filled with a preform molding resin, for example, poly ethylene terephthalate (hereinafter abbreviated as PET).

Next, the hot runner die 30 having the characteristic construction of this embodiment will be explained.

The hot runner die 30 has a base 32, the lower end of a pressure receiving rod 34 is fixed to the four corners of the base 32, and the upper end is fixed to the injection cavity 20. Further, pressure receiving plates 36 are provided at a plurality of positions on the upper surface of the base 32.
Are arranged, and the hot runner block 40 is supported thereon. The pressure receiving rod 38 is also provided between the block 40 and the injection cavity mold 20. The hot runner block 40 has one sprue 42 as shown in FIG.
It has a first runner 44 for introducing resin. further,
A horizontal flow path 46a that communicates with the first runner 44 and is arranged in the horizontal direction, and a vertical flow path 4 that branches in the vertical direction toward the four cavities 20a and introduces the PET resin.
And a second runner 46 having 6b is formed. Although a so-called comb-shaped hot runner is formed in this embodiment, a tournament-type hot runner called a pressure balance type may be used.

Inside the hot runner block 40, the longitudinal direction of the block 40, that is, the second runner 4 is provided.
There are four built-in heaters 48 extending in parallel along the six horizontal flow paths 46a. Furthermore, this heater 48
Six heat pipes 50, for example, are arranged in parallel with and inside the heater 48. Various modifications can be made to the positions of the heat pipe 50 and the heater 48. As the heat pipe 50 is known,
For example, a pipe made of aluminum, stainless steel, copper or the like is covered with a wick core made of glass fiber or fine mesh copper wire, and a heat medium such as Freon or ammonia is filled to remove air. When the pipe becomes hot, the heat medium evaporates and moves, returning to the original liquid by heat dissipation, and then refluxing through the wick core material. This process is repeated for efficient heat transfer. A temperature detecting element is arranged at an appropriate position, for example, in the block 40, the temperature of the heater 48 is controlled, and the block 40 is kept at a constant temperature.

On the upper surface of the hot runner block 40, four nozzle bodies 60 corresponding to the four cavities 20a are fixed via screw portions 62. Each of the nozzle bodies 60 has a vertical flow path 46 of the second runner 46.
It has a third runner 64 communicating with b. Then, inside each nozzle body 60, for example, two heat pipes 66 are arranged in parallel with the third runner 64 from the lower end position of the screw portion 62 to almost the intermediate position of the nozzle body 60. . Further, a band heater 68 is wound around the side wall of each nozzle body 60 above the upper end position of the heat pipe 66 so as to surround the side wall. Although not shown, a temperature detecting element such as a thermocouple is arranged in each nozzle body, and the temperature of each band heater 68 can be controlled independently based on the detected temperature.

At the upper end of each nozzle body 60, a detachable tip piece 70 is fixed by a screw. The tip piece 70 has a fourth runner 72 that communicates with the third runner 64 of the nozzle body 60. further,
A circular recess 74 having an area larger than the diameter of the fourth runner 72 is formed at the position contacting the upper surface of the tip piece 70, that is, the lower surface of the injection cavity mold 20.
Further, the fourth runner 7 communicates with the circular recess 74.
A ring-shaped slit 76 is formed so as to surround the circumference of 2. The circular recess 74 and the ring-shaped slit 76
The PET resin wraps around and is cooled and solidified to form a resin heat insulating layer for the injection cavity mold 20. Further, a metal O-ring 78 is fitted along the outer edge of the circular recess 74, and the metal O-ring 78 has a sealing function of preventing resin leakage.

Next, the preform injection molding process in the injection molding station 10 will be described.

The sprue 42 of the hot runner die 30 is nozzle-touched at the tip of the injection device, and the PET resin of 4 shots corresponding to the number of simultaneous moldings is filled at a predetermined pressure. This newly filled PE
The T resin presses the resin remaining on each runner of the hot runner block 40, and passes through the runner of the nozzle body 60 and the gate 24 to the P of the four cavities 20a.
The ET resin will be filled.

Here, the PET resin used for injection molding of the preform has an inherent molding temperature, for example, 275.
It is necessary to control the temperature to ℃. Above this temperature, PET
The resin is thermally decomposed and deteriorates. On the contrary, when the temperature is lower than the intrinsic molding temperature, the resin flow is deteriorated, and particularly in the nozzle body 60, the resin is clogged by the runner, which causes molding defects such as short-circuiting of the molded product. Furthermore, the nozzle body 60
In this case, since the PET resin is filled in the injection cavity mold 20 or has a function of stopping the filling, the resin entering from each nozzle body 60 is not constant unless the temperature is controlled. Therefore, the PET resin remaining on the hot runner block 40 and the nozzle body 60 is
The temperature must be adjusted to around 275 ° C., which is the above-mentioned inherent molding temperature.

There are two reasons why such temperature control is difficult.

One of them is the hot runner block 40.
Has a considerable heat capacity. This becomes more remarkable as the number of simultaneously molded pieces increases. A large amount of energy is required to maintain the hot runner block 40 having a large heat capacity at a constant temperature. The other one is that the nozzle body 60 requires highly accurate temperature control. This is because the nozzle body 60 comes into contact with the injection cavity mold 20, which serves as a cooling source, so that the temperature changes significantly. Moreover, unless a large amount of heat energy is supplied to the block, the temperature at the tip of the nozzle does not rise to the required temperature.

The apparatus of this embodiment solves these two problems with a characteristic structure. First, the temperature control of the hot runner block 40 will be described. The horizontal flow path 46a of the second runner 46 is used as a central axis, and four heaters 48 and six heat pipes 50 are arranged in parallel with the horizontal flow path 46a. ing. Since the heater 48 and the heat pipe 50 are arranged along the longitudinal axis direction of the hot runner block 40, the constant temperature of the entire block 40 can be effectively achieved. In particular, by disposing the heater 48 on the outer wall side of the block 40 having a large heat radiation amount, the heat amount supplementing the heat radiation amount can be supplied by the heater 48, and the heat fluctuation inside the heater 48 can be reduced. Since the heat pipe 50 is further arranged inside the heater 48, a local heat transfer action is repeated in the axial direction of the heat pipe 50. Therefore, inside the heat pipe 50, uniform temperature is achieved in the axial direction, and the heat fluctuation inside the heat pipe 50 is further reduced. This effect can be similarly ensured even when the number of simultaneous moldings increases and the length of the longitudinal axis of the block 40 increases. As is well known, the heat pipe 50 has a very high heat exchange rate. Therefore, even if the hot runner block 40 has a large heat capacity, the hot runner block 40 has a relatively small heat energy supply.
It is possible to effectively achieve the constant temperature control, that is, the heat retention. In other words, the heat energy supplied to the hot runner block 40 can be reduced.

Next, the temperature control of the nozzle body 60 will be described. Two types of temperature control are adopted as the temperature control method of the nozzle body.

One of them is the hot runner block 40.
It is to utilize the temperature control energy of. That is, on the lower end side of the nozzle body 60 having the threaded portion 62, a plurality of heat pipes 66 are arranged from the lower end portion to an intermediate position of the nozzle body 60. Therefore, the heat on the hot runner block 40 side can be supplied from the lower end side of the nozzle main body 60 fitted in the hot runner block 40 to the heat radiating portion at the intermediate position of the nozzle main body 60 exposed to the outside air. Therefore, the temperature control from the lower end of the third runner 64 of the nozzle body 60 to the intermediate position can be realized by utilizing the heat of the hot runner block 40, and the power consumption can be reduced.

The other one is that the upper end side of the nozzle body 60 is
That is, the temperature is independently controlled by the band heater 68. The upper end side of the nozzle body 60 is
It has an injection cavity mold 20 as a cooling source, and requires more accurate temperature control than the hot runner block 40. Further, the resin injection port 72a of the fourth runner 72 of the tip piece 70 provided at the tip of the nozzle body 60.
Has a taper in a taper shape, and at a temperature lower than the intrinsic molding temperature, clogging causes resin filling failure. For this reason as well, highly accurate temperature control of the nozzle body 60 is required. Therefore, each nozzle body 6
A temperature detection element such as a thermocouple is provided for each zero, and the band heater 68 is feedback-controlled based on the detection result, whereby the temperature of each nozzle body 60 can be adjusted to the peculiar molding temperature of the PET resin. Becomes Moreover, when performing this temperature control, the band heater 68 only needs to locally control the temperature of only the nozzle opening 72a side of the nozzle body 60, so that the temperature control region is narrower than that of the temperature control of the entire nozzle body 60. Therefore, highly accurate temperature control is realized. Further, the thermal influence from the side of the hot runner block 40 having a large heat capacity is sufficiently reduced, so that more accurate temperature control is realized.

In order to control the temperature of the nozzle body 60 with higher accuracy, it is desirable to form the nozzle body 60 with a material having high thermal conductivity. As a particularly preferable material of this type, beryllium copper can be cited, or it is desirable to silver-plat the outer wall side of the nozzle body 60.

The present invention is not limited to the above embodiment, but various modifications can be made within the scope of the gist of the present invention.

FIG. 3 is a schematic sectional view showing a modified example of the independent temperature control of the nozzle body 60. In this embodiment, instead of the band heater 68 in the above embodiment, a built-in heater 80 is arranged on the upper end side of the nozzle body 60. That is, in carrying out the first invention, the independent temperature control of the nozzle body 60 is not limited to the one in which heat is supplied from the outside like the band heater 68, but an internal heating type as in the embodiment of FIG. May be It should be noted that the nozzle main body 60 needs to be replaced with one suitable for the distance because the distance from the hot runner block 40 to the injection cavity mold 20 changes when the preform length to be molded changes. In this case, since it is not necessary to change the band heater 68 or the built-in heater 80 even if the length of the nozzle body 60 changes, there is an effect that the band heater 68 or the built-in heater 80 can be standardized.

Further, in carrying out the first invention,
The first temperature adjusting means for adjusting the temperature of the block 40 is not necessarily limited to one in which the built-in heater 48 is arranged along the heat pipe 50. For example, as shown in FIG. 4, at both ends of a plurality of heat pipes 90 arranged along the longitudinal axis,
A built-in heater 92 may be provided orthogonally to this. In this case, the heat pipe 90 is connected to the block 4 as shown in FIG.
The two heat pipes 90a,
It may be 90b. In addition to this, various other modifications can be implemented as long as the heat pipe is arranged along the longitudinal axis of the block 40.

In carrying out the second invention,
The temperature of the nozzle body 60 can be adjusted arbitrarily.

Further, the present invention is not necessarily applied to the injection molding station 10 in the stretch blow molding apparatus, but can be similarly applied to a general injection molding apparatus. However, in the case of a general injection molding apparatus, since the injection molded product is simply cooled and taken out after molding, temperature control sufficient to fill the resin through the gate is sufficient. However, in the injection molding station 10 in the blow molding apparatus of the hot parison type as in the above embodiment,
Not only the smooth filling of the resin is ensured, but also the variation in the temperature of each resin passing through each gate 24 must be reduced. That is, unless uniform control is performed by each nozzle body 60, it becomes difficult to obtain a suitable stretching temperature for stretch-blow molding of each preform by utilizing the retained heat during injection molding. Therefore, when the present invention is applied to an injection molding station in a hot parison blow molding apparatus, it can greatly contribute to the improvement of the yield and the quality of the hollow container which is the final molded product.

[0039]

As described above, according to the first aspect of the invention, the heat pipes arranged along the longitudinal axis can maintain the uniform temperature of the hot runner lock while reducing the power consumption, and the plurality of nozzles can be realized. The temperature of the main body is controlled by using the heat of the block with a heat pipe on the fixed end side and the local area on the nozzle mouth side by means of independent temperature control, so that each of the multiple nozzle bodies is molded with resin. The molding temperature can be adjusted to a specific molding temperature, and the yield and quality of injection molded products can be improved.

According to the second aspect of the present invention, the heat pipe and the built-in heater are arranged along the longitudinal axis of the hot runner block, so that the block having a large heat capacity is more uniform with a small temperature gradient in the longitudinal direction. The temperature can be maintained, and a uniform temperature can be maintained even if the number of simultaneous moldings increases.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment in which the present invention is applied to an injection molding station in a stretch blow molding device.

2 is a cross-sectional view of the injection molding apparatus shown in FIG.

FIG. 3 is a schematic cross-sectional view showing a modified example of the independent temperature control system of the nozzle body.

FIG. 4 is a schematic cross-sectional view showing a modified example of temperature control of a hot runner block.

FIG. 5 is a schematic plan view for explaining each station of the blow molding device to which the present invention is applied.

[Explanation of symbols]

20 injection cavity 26 injection core type 30 hot runner die 40 hot runner block 42 sprue 44, 46, 64, 72 runner 48 heater 50 heat pipe 60 nozzle body 66 heat pipe 68 band heater 80 built-in heater 90, 90a, 90b heat pipe 92 heater
NS010601

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Claims (2)

[Claims] 1. A plurality of nozzle bodies having a nozzle port communicating with an injection cavity type gate and a runner communicating with the nozzle port; a plurality of nozzle bodies being fixed; A hot runner block having a runner for introducing a resin material into the runner, and a hot runner mold having the hot runner block, wherein the hot runner block has a first temperature control means for controlling the temperature of the hot runner block, and the inside of the hot runner block. And one or a plurality of first heat pipes arranged along the longitudinal axis direction of the block, wherein the plurality of nozzle bodies are embedded and fixed in the hot runner block.
A fixed end portion, a second temperature adjusting means arranged at least on the nozzle opening side and adjusting the temperature of the nozzle opening side, an exposed portion exposed from the hot runner block and the front.
One or a plurality of second heat pipes arranged inside the nozzle main body over both portions of the embedded fixed end portion and arranged along the runner in the nozzle main body; A hot runner mold featuring. 2. A plurality of nozzle bodies having a nozzle opening communicating with an injection cavity type gate and a runner communicating with the nozzle opening, and a plurality of nozzle bodies fixing the nozzle body, and a runner of the nozzle body with a sprue. In a hot runner mold having a hot runner block having a runner for introducing a resin material into the hot runner block, the hot runner block is disposed inside the hot runner block along the longitudinal axis direction of the block, or A hot runner, comprising: a plurality of first heat pipes; and a built-in heater that is arranged inside the hot runner block in parallel with the first heat pipes and over an area where the first heat pipes are arranged. Mold.