JPH0466169B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a runnerless injection method in which high-precision molding is performed using a heat source provided in a mold to heat a gate portion leading to a cavity. Regarding molding equipment.

[Conventional technology]

BACKGROUND ART Conventionally, this kind of runnerless injection molding apparatus called a hot runner method has been known as the trademark Spear System developed by the present inventor as an apparatus that heats a gate portion. This spear system is
By locally heating the gate part with a heater from inside or outside, the molten resin in the gate part can be solidified, and precision molding can be performed by switching between melting and eliminating sprue runners that waste raw material resin. This system is highly praised both in Japan and overseas as a system that can perform high-precision molding similar to the runner method.

[Problem that the invention seeks to solve]

Using a conventional heater as a means of heating the gate part requires high-precision processing and high costs, and furthermore, it is difficult to control the temperature of the heater in connection with the injection molding operation. When doing so, it is essential to install a controller, and it has been extremely difficult to provide a highly accurate runnerless injection molding machine except for economical reasons.

[Means for solving problems]

This invention was made by paying attention to the points mentioned above, and includes a material plasticizing means commonly used in the past,
A heating method that utilizes the injection molding means, mold structure, etc. as is, stores the thermal energy held by the mold heated by a heating means such as a cartridge heater installed in the mold in a heat storage part, and forms the gate part. The above problem was solved by locally heating the gate portion by supplying heat to the space via a heat flow path using a pressurizing means such as a piston.

As a result, an expensive controller and a highly accurate and expensive heating means for the gate portion can be omitted, and an inexpensive runnerless injection molding apparatus can be provided with an extremely simple configuration.

[Effect]

The hot melted raw material obtained by the raw material plasticizing means and supplied to the runner section is molded by injection molding means by filling a necessary amount of molten resin into the cavity through the gate section.

By the way, a thermal space is formed in the gate section, and the thermal energy held by the mold is instantly and efficiently supplied from the heat storage section through the heat flow path by pressurizing means, so that the raw resin in the gate section is It exhibits a phase change of solidification, semi-solidification, and melting depending on the temperature state of the part, and can be sensitively operated to open and close the so-called gate.

Therefore, the temperature of the raw resin inside the gate part can be effectively controlled each time an injection molding operation is performed by appropriately controlling the pressurizing means, thereby ensuring that the raw resin is injected into the cavity. Moreover, it is possible to perform highly accurate injection molding by preventing the unnatural nose dripping phenomenon from the gate part.

Furthermore, the fluid heat exchanged in the heating space of the gate part passes through the air gap between the molds and is discharged to the outside without any problem.

〔Example〕

Examples of the present invention will be described below with reference to the drawings.

1 is a means for thermoplasticizing raw materials, 2 is an injection molding means for molten resin, 3 is a mold, especially a runner formed in a fixed mold 4, and 5 is a manifold forming two or more injection channels. , a necessary number of heating means 6 such as cartridge heaters are provided at necessary locations.

A runner heating means 7 is disposed between the manifold 5 and the intermediate mold 9 communicating with the cavity 8, and is housed in an annular support holder 10.

Incidentally, the runner heating means 7 does not need to be particularly specified, but it is possible to select and use a self-heating type such as a heater or a high-frequency electromagnetic induction coil, or a heat-dependent type such as a heat pipe filled with a heat transfer fluid. be able to. Self-heating types may require a controller, but heat-dependent types do not require a controller at all. 8a is a movable mold.

In this example, a heat-dependent heat pipe is used, and the whole is formed into a pipe ring shape of a double pipe.
A runner portion 11 corresponding to a straight hole with a desired diameter R ₁ is formed as a part of the so-called runner 3 .

Reference numeral 12 denotes a gate section connected to the runner heating means 7 and communicating with the cavity 8. A heating space H is formed around the outer periphery of this gate section, and an annular collar 13 is provided at the base of the gate section, and the tip of the heat pipe is connected to the gate section 12. It is engaged with the step part 14, and passes from the narrow taper part 15 through the gate hole 16 having a diameter _R2 smaller than the diameter _R1 , and further through the taper part 17 to the cavity 8.
The gate 16a is opened. The runner section 11 and the gate section 12 are arranged on the same axis, that is, on the same straight line. It is preferable that the gate portion 12 be formed of copper, a metal such as copper, beryum, or other material having good thermal conductivity.

18 is the runner heating means 7 and the gate part 1
It is an outer peripheral fixing body that is disposed on the outer periphery of the support holder 10 that supports the mold 2 and can also form the heating space H, and is firmly supported by the positioning ring 19 of the intermediate mold 9.

20 are the positioning ring 19 and the outer peripheral fixing body 1.
8 and the intermediate mold 9 are shown.

Reference numeral 21 denotes a heat storage section provided in the mold, particularly the manifold 5, which has a hollow cylinder structure, has a piston 22 slidably disposed thereon, and is pressurized with heated air by means of a control means 23 such as an air cylinder. 24
is formed. Reference numeral 25 denotes a passage for heated air, that is, a heat flow passage, leading from the heat storage section 21 to the heating space H of the gate section 12, and is a passage 25a of the manifold 5.
A passage 26 on the discharge side of the heating space H communicates with the air gap 20 via the outer fixed body 18. 27 is a movable mold.

The action will be explained based on the above structure.

First, the raw material to be used is melted by the raw material thermoplasticization means 1 to enable injection molding, and the thermal energy of a large number of heaters 6 disposed in the manifold 5 of the fixed mold 4 is applied to the mold. The heat is transmitted to the support holder 10 that collides with the heat, and the runner heating means 7 constituted by a heat pipe is heated to a required temperature by receiving heat conduction from the support holder 10.

At the same time, the necessary thermal energy is also supplied to the gate portion 12, which is a separate member and is in contact with the runner heating means 7.

On the other hand, since the heat storage part 21 is formed in the manifold 5 and a cylindrical hollow chamber is formed,
The air in this section 21 is heated by the heater 6 of the manifold 5, and its temperature is rising.

In such a state, when the molten raw material resin is injected by the injection molding means 2, the molten resin in the runner 3 in the mold 4 passes through the runner part 11 and the gate part 12, and a desired amount of molten resin is released. The cavity 8 is filled.

During this injection molding operation, the pressure means 24 works,
When the piston 22 exhibits a stroke motion of the heated air in the heat storage section 21 by the control means 23 such as an air cylinder, the heated air according to the stroke amount passes through the heat flow path 25 and enters the heating space H of the gate section 12. The air H is heated to heat and melt the raw resin in the gate portion 12.

The thermal influence acting on the gate portion 12 can be variably adjusted by adjusting the flow rate of heated air, heating time, heating temperature, etc., and phase changes such as solidification, semi-solidification, and melting can be freely performed.

Then, when the pressurizing means 24 is activated, the heated air is circulated through the heating space H of the gate section 12 while exchanging heat, becomes low-temperature air, passes through the flow path 26 on the discharge side, and leaves the mold 4 from the air gap 20. is exhausted to the outside.

Although this pressurizing means 24 itself cannot be supported even if it is provided with a heat generating function such as a heater, the heat retention energy of the manifold 5 is usually sufficient. Once the heated air is discharged,
It is possible to repeat the operation by once making a backward movement and then making the same stroke forward movement again in conjunction with the injection molding operation.

At that time, it goes without saying that a mold opening/closing operation is performed to take out the molded product in the cavity 8.

By leaving the gate portion 12 without heating during this mold opening operation, the raw resin in the gate hole 16a portion can be solidified and the so-called gate can be kept in a closed state, thereby preventing the nasal drip phenomenon.

In addition, the runner part 11 and gate part 12 of the runner 3 are formed in a straight line, and there is no resistance part, so the injection pressure can be significantly reduced. Furthermore, since the air gap 20 is formed, the temperature can be dissipated easily. Energy loss is prevented.

Moreover, since the runner part 11 and the gate part 12 are separate members and are connected to each other so as to maintain effective heat conduction, the thermal energy acting on the heating space H of the gate part 12 needs to be larger than necessary. It also has the advantage that the remaining heat of the heater 6 of the mold 4 can be used.

〔Effect of the invention〕

According to this invention, the heat of the heating means of the mold is used as the heating means of a very small part called the gate part, and the thermal energy of the heat storage part provided in the mold part is used by the pressurizing means. Since the heat is pumped into the heating space of the gate through a heat flow path to locally heat it, the heating operation of the gate can be performed with good response, and the raw resin in the gate can be heated by pressurizing means. By changing the phase to various states such as solidified, semi-solidified, and molten depending on the pumping state of the heated air, highly accurate runnerless injection molding with no waste can be performed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional plan view of essential parts showing an embodiment of a runnerless injection molding apparatus according to the present invention, and FIG. 2 is an explanatory view of the same as seen from the front. 1... Means for thermoplasticizing raw materials, 2... Means for injection molding, 3... Runway, 4... Mold, 5... Manifold, 6... Heating means such as a heater, 7... Runner heating means, DESCRIPTION OF SYMBOLS 10... Support holder, 11... Runner part, 12... Gate part, 20... Air gap, 21... Heat storage part, 24... Pressurizing means, 25
...Heat flow path, H...Heating space.

Claims (1)

[Scope of Claims] 1. Runnerless injection in which thermoplasticized raw material can be injected into a desired cavity via a runner section and a gate section through a runner provided in a mold using an injection means such as a piston. In the molding apparatus, a heating space is formed in the gate part, and thermal energy obtained by a heating means provided in the mold is transferred from a heat storage part through a heat flow path using a pressurizing means such as a piston. A runnerless injection molding apparatus characterized in that the runnerless injection molding apparatus is configured such that the gate portion can be locally heated by transferring the runner to the heating space. 2 The heat storage part for thermal energy in the mold is bored into a cylindrical shape, and a piston that moves back and forth intermittently is installed in this heat storage part as a pressurizing means, and the heat flow path communicating with the heating space of the gate part is connected to the runner part. The runnerless injection molding apparatus according to claim 1, wherein the runnerless injection molding apparatus is formed by being bored in a support holder disposed on the outer periphery of the runner.