JPS60206612A - Runnerless injection molding and hot runner - Google Patents

Abstract

PURPOSE:To open and shut a gate smoothly by heating or cooling the resin at the gate part by a hot runner provided with a cartridge heater that can take higher temperature to the point of the cartridge. CONSTITUTION:In a hot runner 12 that melts and plasticizes the resin at the runner part, heats or cools the resin at the gate part and opens or shuts the gate, the hot runner external cylinder body 13 is charged with the cartridge heater 14 with the lever projection 14a and the electric heater wire 15 whose winding density becomes higher to the point part of the cartridge, and cooled air supply pipe 19 is installed to charge the clearance part with air-permeable filler 16. The point part 12a also near the gate part can be heated sufficiently and the heater power source cut and the coolant introduced easily cool the point part 12a to enable smooth gate operation. Additionally, the gate heater which was indispensable before can be omitted.

Description

[Detailed Description of the Invention] [Technical Field] The present invention provides two-stage control of constant melting and plasticization of a thermoplastic resin material accumulated in a runner, and cooling solidification and heating melting of the resin located at a gate portion. The present invention relates to a new runnerless injection molding method and a hot runner in which switching control can be effectively performed by a single thermal control.

[Prior art]

Conventionally, the Spear System developed by the present inventor is widely known as a runnerless injection molding method and apparatus. This method and apparatus will be explained with reference to the basic configuration shown in FIGS. 1 and 2. In each figure, 1 is a pair of molds 2
, 3 for obtaining a molded product; 4 is a gate for injecting molten resin that is opened along the mold 2 leading to the cavity 1; 5 is integral with the gate 4; A portion of the runner is shown.

'By the way, the structure shown in FIG.
It has a roughly cannonball-shaped hot runner 6 arranged along the central axis of the
A controller (see Fig. (not shown) was required.

Further, the structure shown in FIG. 2 includes a cylindrical hot runner 9 such that the runner part 5 can be formed on the central axis, and the tip of the hot runner 9 is formed into a truncated shape and narrow. A small gate 4 is bored, and an intermittent heating wire 10 is embedded in the periphery of the gate 4 so as to surround it, and a runner for heating a portion of the runner 5 is provided around the outer periphery of the hot runner 9. A heating heater 11 is provided.

And an intermittent heating wire 10 and a runner heating heater 11
controller to control the temperature of each separately (
(not shown) were required as in the case of FIG.

By the way, since the conventional 7-pierce, 7"-striped and diagonal configuration is used, when injection molding a desired thermoplastic resin, one of the heaters 8 and 11 of the hot runners 6 and 9 is connected to the runner. The resin in the part 5 must be kept at a desired set temperature to plasticize and melt, but the intermittent heating element 7 and the intermittent heating wire 10 are used only when melting a small amount of solidified resin in the gate part 4. In other words, each time an injection molding operation is performed by an injection mechanism (not shown), the solidified resin is melted by heating instantaneously and the so-called gate 4 is opened to pour the molten resin in the runner part 5 into the cavity 1. In order to solidify the molten resin in the gate 4 after the injection operation is completed, the temperatures of the intermittent heating element 7 and the intermittent heating wire 10 are lowered to close the so-called gate 4, and the injected resin in the cavity 1 is can be solidified and molded, and then the mold 2.3
The molded product can be removed by opening it.

In other words, this conventional spear system locally sprays a small amount of resin in an extremely narrow area of the gate 4 by controlling the temperature of the intermittent heating element 7 and the intermittent heating wire 10 each time an injection molding operation is performed. By switching between a heated state and a non-heated state or a high-temperature heated state and a low-temperature heated state to effectively perform melting and solidification, so-called gate 4 closing operations are performed, which improves precision moldability, mass productivity, and Although it has many advantages such as low cost productivity, hot runner-6
, 9 for heating the runners 8, 11,
It is necessary to separately provide a heater for opening and closing the gate 4, that is, an intermittent heating body 7 and an intermittent heating wire 10.

Moreover, since separate temperature control is required, the configuration of the controller has to be complicated and large.

In particular, there are many problems when two or more cavities 1 are provided or when two or more gates are required for one cavity.

[Summary of the invention]

This invention was made by focusing on the diagonal point, and uses only a single electric heat source, such as a heater, to keep the molten resin in a part of the runner warm to a plasticized state, and uses the thermal energy of this heater. In addition to effectively transmitting the information to the gate section,
Assimilation of the resin in the gate area is based on the amount of heat acting on the gate area.

Opening/closing control of melting is performed by temperature control of the heater, and the spear system is completely similar to the conventional spear system using a so-called controller that performs only single temperature control, omitting the gate heater that was previously indispensable. Runnerless injection molding method and hot runner
It provides:

Furthermore, in order to obtain effective heat conduction all the way to the gate part with a single heater, the heater itself is enlarged, has a large heat capacity, and is formed to be able to generate high temperature. The present invention provides a runnerless injection molding method and a hot runner in which energy is forcibly dissipated heat so as not to adversely affect the plasticized molten resin in a part of the runner. The present invention provides a method for injection molding a part of a runner and a hot runner in which cooling can be effectively performed not only by turning off the power to the heater itself but also by locally intermittent supply of cooling fluid.

〔Example〕

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

Note that the same or equivalent parts as in the conventional example are given the same reference numerals '' and detailed explanation thereof will be omitted.

First, three embodiments shown in FIGS. 3 to 7 will be explained in detail. These embodiments have a so-called bullet-shaped shape and are arranged north of the central axis of the runner part 5.
It has a structure that can maintain a molten state by heating the plasticized resin accumulated inside from the center outward.

12 is the hot runner-113 is this hot runner-12
The outer cylindrical body 14 represents an electric heating source, ie, a cartridge heater, as a single heating element housed within the outer cylindrical body 13. Reference numeral 15 denotes a heating wire wound inside the cartridge heater 14, and as it goes toward the tip of the pot runner 12, the replacement density increases and the heat generation temperature reaches the hot runner 1.
The setting is such that the thermoplastic resin can be heated and melted at the sharp end portion 12a of No. 2.

By the way, in the embodiment shown in FIG. 3, a thin rod-like projection 14a is provided at the tip of the cartridge heater 14, and this projection 14a is formed so as to face the sharp portion 12a of the hot runner 12. As a whole, the cartridge heater 14 and the outer cylindrical body 13 are integrally joined without being brought into close contact with each other through the air-permeable filler 16. 17 is wiring for a temperature sensor having a temperature sensing element 18; 19 is a cooling air supply pipe, the tip of which is connected to the sharp part 12a of the hot runner 12;
Kt Thin rod-like projection 14 of the target cartridge heater 14
The structure is such that local cooling can be performed by facing the area a. Reference numeral 20 indicates a conducting wire of the cartridge heater 14.

Since the configuration is diagonal, in the embodiment shown in FIG. 3, the hot runner 12 is sufficiently heated by the action of the cartridge heater 14, and the winding density of the cartridge heater 14 gradually increases toward the tip of the hot runner 12. Therefore, the heat conduction to the thin rod-shaped projection 14a, which has a large amount of heat dissipation, is also reduced, so that the sharp end portion 12a of the pot runner 12 is also sufficiently heated, making it possible to thermally melt the resin at the gate portion 4. .

Incidentally, the heat generated by the cartridge heater 14 other than the amount of heat necessary for plasticizing the resin in the runner part 5 is exhausted to the outside of the hot runner 12 through the air permeable filler 16, so that the resin in the runner part 5 is exhausted. There is no risk of heating it to a higher temperature than necessary. This heat discharging means may be combined with forced suction means, cold air supply means, etc.

In this way, if the resin in the runner part 5 and the gate 4 part is in a molten state due to the action of the cartridge heater 14, the injection molding operation can be performed with the so-called gate 4 open.

Next, if the current supply to the cartridge heater 14 is stopped or the amount of current supplied is reduced, the temperature of the cartridge heater 14 decreases, and in particular, the temperature of the heat conduction to the narrow rod-like projections 14a also decreases, and the hot runner Since the heat generation temperature of the sharp end portion 12a of -12 also decreases, the heating of the resin in the gate 4 also decreases, and the resin is rapidly cooled and solidified, so that the so-called gate can be closed.

At this time, the hot runner is connected to the cooling air pipe 19.
By forcibly supplying cooling air to the sharp end portion 12a of the gate 12, the gate can be closed more quickly.

In this way, the molten resin in the gate 4 part can be locally cooled and solidified to close the gate, but the molten resin in the runner part 5 is transferred to the cartridge heater 1 in the hot runner 12.
Even if the heating action of 4 is temporarily stopped or weakened due to the stoppage of energization or a decrease in the amount of energization, the hot runner-1
By forming the internal body 2 to have a large heat capacity, there is no risk of a temperature drop to the extent that the molten resin is cooled and solidified. Gate 4 again
By heating and melting the assimilated resin in the mold, a so-called gate can be opened to allow smooth subsequent injection molding operations.

The embodiment shown in FIG. 3 shows the simplest and basic configuration of this invention.

Next, the embodiment shown in FIGS. 4 and 5 will be described.

In this embodiment, an electric heating source as a single heating element, that is, a heating element 21, which is a modification of the cartridge heater 14 in the previous embodiment, is embedded and fixed in a bullet-shaped hot runner 12, and a hollow cylinder is disposed on the central axis. The heating wire 15 is wrapped around the outer periphery of this cylindrical portion 22 in the same manner as in the embodiment described above, and a narrow tube portion 24 is further connected to the tip of this cylindrical portion 22 via a conical constriction portion 23. The thin tube portion 24 is connected to the sharp tip portion 12a of the hot 2-ner 12.
It is composed so that it faces inside. Furthermore, a baffle plate 25 for overheating prevention is interposed between the inner peripheral surface of the hot runner 12 and the heating body 21, and the baffle plate 25 is passed through the numerous small holes 26 of the baffle plate 25 to the outer cylindrical body 13 of the hot runner 12. Only the necessary amount of heat can be conducted, and a larger amount of heat than necessary can be stopped by the baffle plate 25 or can be exhausted to the outside of the pot runner 12 via a heat radiation path 27 provided on the outer periphery of the baffle plate 25. It has become. A cooling air supply pipe 19 is inserted into the heat radiation path 27, and the tip of the tube 19 is formed into a nozzle shape so that the tip of the heating element 21, that is, the narrow tube portion 24 can be locally cooled. The opening is made near the thin tube portion 24. Further, reference numeral 28 indicates a cap for reliably housing and fixing the heating element 21 within the hot runner 12.

The action will be explained based on the structure of the text.

The electric heating element 15 of the heating body 21 generates high heat by energizing the conductive wire 20, heats the hot runner 12 and at the same time heats the hollow cylinder part 22, effectively heating the air inside. When the amount of heat emitted from the heating wire 15 is higher than necessary, the outer cylinder 13 of the pot runner 12 is blocked by the baffle plate 25.
1!1-1, the heat conducted outward through the small hole 26 mainly acts on the outer cylinder 13, and further transfers the necessary thermal energy outward of the hot runner 12. It can be released to heat-melt the resin. Since the heating wire 15 is a comb with a thick winding density locally at the tip of the hot runner 12, it not only has a good effect of transmitting thermal energy to the sharp tip portion 12a, but also heats the air inside the hollow cylindrical portion 22. Since the effect works extremely effectively, the expanded heated air passes through the constriction section 23 and reaches the thin tube section 24, and furthermore, the heated air is discharged from the tip opening of the thin tube section 24 as shown by the arrow in Fig. The sharp tip portion 12a of the runner 12 can be effectively heated from the inside.

Therefore, it is possible to locally heat a small amount of the resin in the portion of the gate 4 where the sharp tip portion 12a faces to melt it into a plasticized state. In this state, the so-called gate 4 is open, so that the injection molding operation can be performed as described above.

After this injection molding operation is completed, the electricity to the heating wire 15 is stopped, but if the amount of electricity is reduced, the hollow cylindrical part 22
Since the heating effect on the thin tube section 24 is stopped or reduced, the heating effect of the heated air on the thin tube section 24 also gradually decreases, and the cooling air supply'
By supplying cooling air from i"4' 19, the thin tube section 24 is rapidly and instantaneously cooled, and the hot runner ~1
The sharp end portion 12a of the gate 4 is also cooled, and the molten resin within the gate 4 is solidified, so that the so-called gate can be closed.

Next, the supply of this cooling air is stopped and the heating wire 15 is restarted.
When the current is applied and the amount of current is increased, the thin tube part 24 is reheated by the action of the heated air in the hollow cylinder part 22 and the heat conduction by the heating wire 15, as described above, and the resin of the gate 4 is melted. The injection molding operation can be repeated by opening the gate.

Note that the temperature of the outer cylindrical body 13 of the hot runner 12 slightly changes due to the energization control operation for the heating wire 15, but the temperature change is so small that the molten resin in the runner part 5 is cooled and solidified. There is no inconvenience caused by this process, and the plasticized molten state can be maintained at all times.

Further, the temperature of the heating wire 15 can be safely controlled by a controller (not shown) based on the temperature detected by the temperature sensing element 18.

Furthermore, the embodiments shown in FIGS. 6 and 7 will be described.

In this embodiment, a cooling air supply pipe 29 corresponding to the cooling air supply pipe 19 shown in FIGS. The structure is such that cooling air is discharged toward the needle tube 31.

The heating body 30 is an electric heat source as a single heating source similar to the above embodiment, and has a replaced heating wire 15, and the heating wire 15 is further provided with a baffle plate 25 for preventing overheating. A heater core 32 is provided on the outer periphery of the air pipe 29, and a heating wire 15 is inserted between the core 32 and the baffle plate 25 with a filler 33 such as an insulating material or an anti-hardening agent interposed therebetween. It is buried. The cap 34 is provided with a drilled through hole through which the cooling air pipe 29 can be inserted. 31a indicates a gap formed between the hot runner 12 and the heating body 30.

Since the heating wire 15 is configured to be tilted upward, when the heating wire 15 is energized, the sharp tip portion 1 of the hot runner 12 is heated as described above.
2a is heated and melts the resin in the gate 4 part to open the gate, and conversely, if the amount of current supplied to the heating wire 15 is reduced, the heating temperature of the sharp tip portion 12a will decrease. At the same time, by locally cooling the air from the cooling air supply pipe 29, the temperature of the sharp tip portion 12a is effectively instantaneously lowered to solidify the resin in the gate portion, thereby effectively closing the gate. Moreover, no matter how the energization control to the heating wire 15 changes, the minimum necessary thermal energy is supplied to the resin in the runner part 5 by the hot runner 12, so there is no risk of it cooling and solidifying. The injection molding operation can be carried out extremely smoothly.

Hereinafter, three embodiments have been described, but each hot runner 12 has a cavity formed by a pair of molds 2 and 3 from a manifold 35, as shown in FIG. 1 and the runner part 5 for use.

FIG. 9 shows an embodiment in which the runner part 5 is formed on the central axis of the hot runner 36, and the structure will be explained below.

That is, the gate 4 is connected to the central axis of the cylindrical outer body 37.
A cylindrical body 38 with a runner part 5 connected thereto is disposed, and a baffle plate 25 for overheating prevention, which has a number of small holes 26 bored through an annular small space 39, is interposed on its outer periphery. In addition to replacing the heating wire 15 on the outer periphery, this replacement
The outer cylindrical body 37 is formed so that the compression density increases as it reaches the front part. Further, a large annular space 40 is formed between the outer periphery of the heating wire 15 and the outer cylindrical body 37, and a cooling air supply pipe 19 as shown in FIG. 3 is vertically split. Note that the tip portion 38a of the inner cylindrical body 38 constituting the gate 4 is
Like the tip portion 37a of the outer cylinder 37, this is formed as a thin tube structure. Reference numeral 41 indicates a cylindrical heating adapter disposed around the outer periphery of the heating wire 15, and the tip 41a of the adapter 41 is shaped into a thin tube so that the thermal energy from the heating wire 15 can be effectively transmitted to the gate 4. It is brought into contact with the tip portion 38a of the inner cylindrical body 38 forming the gate 4 by squeezing.

The hot runner 36 is connected to the manifold 35 and the cavities 1 of the pair of molds 2 and 3, as shown in FIG.
The gate 4 is arranged so that it faces the same direction as the gate 4.

Therefore, when the heating wire 15 is energized, the front part of the hot runner 36 is heated more strongly than the other parts as described above, and the tip 4 is heated through the heating adapter 41.
1a can be heated rapidly.

Of course, the heating wire 15 generates more thermal energy than necessary in the entire area of its contraction, so a part of it is blocked by the baffle plate 25, but it heats the inner cylindrical body 38 through the annular small space 39, The molten resin within the runner portion 5 formed on the central axis can be heated to maintain a plasticized state. Thermal energy of the heating wire 15 that is more than necessary is stored inside and outside the small space 39.
Heat is radiated through the large space 40, so that the runner part 5 is heated to an appropriate heating temperature, and thermal energy that can be heated and melted is exclusively supplied to the gate part 4.

Therefore, when the heating wire 15 is energized, the resin in the gate 4 is heated and melted, and the so-called gate is in an open state, so that the injection molding operation can be performed.

Next, if the power supply to the heating wire 15 is stopped or the amount of current supplied is reduced, the temperature of the gate 4 portion decreases, and at the same time, the molten resin is cooled and solidified by local cooling by the air from the cooling air pipe 19. The gate can be closed. Moreover, no matter how the energization control to the heating wire 15 changes, the hot runner 36 supplies the minimum necessary thermal energy to the resin in the runner part 5, so the heating process is extremely smooth without cooling and solidifying. can perform injection molding operations.

A number of embodiments of the present invention have been described above, but in particular, the heating wire 15 is energized, stopped or energized, the meter is lowered, and the cooling air is supplied from the cooling air pipe without being carried out simultaneously. Of course, the effect of cooling and assimilating the resin in the gate 4 can be performed by only one operation.

As described above, this invention uses an electric heat source with a crucible structure like a heater for heating a hot runner, and sufficiently heats the tip of the pot runner with this single electric heat source. Since the gate part can be locally heated and cooled, the opening and closing operations of the gate, which involves heating and melting the resin in the gate part and cooling and solidifying them, can be performed extremely smoothly, and at the same time, the gate can be opened and closed without unnecessary heat. Energy/L, can be heated and can constantly give the appropriate temperature to a part of the runner, and control of an electric heat source equivalent to a heating wire is possible by controlling a heat source of a single structure, so a controller is used. This has the effect of making it possible to downsize, making it possible to produce products in season and at low cost.

[Brief explanation of the drawing]

1 and 2 are explanatory sectional views showing a conventional example, FIG. 3 is an explanatory sectional view showing an embodiment of a hot runner used in the runnerless injection molding method according to the present invention, and FIG. 4 is an explanatory sectional view showing an embodiment of the present invention. A partially cutaway cross-sectional view of a hot runner showing another example according to the above, an enlarged cross-sectional view of the same striped area A in Figure N45, No. 6
The figure is a partially cutaway sectional view showing another embodiment of the present invention, FIG. 7 is an enlarged sectional view of the LB section, and FIG. 8 is a sectional view of essential parts when the embodiment is used in an injection molding machine. , FIG. 9 is an explanatory sectional view No. 1 showing another hot runner according to the present invention.
FIG. 0 is an explanatory sectional view of essential parts showing an embodiment of a runnerless injection molding apparatus using the same hot runner. 4......Gate 5...Runner part 6, 9, 12.・36...Hot Runner-7...-
・・・・・・Heating body 10・・・・・・Intermittent heating wire 14.21.30・・・・・・・・・・・・・・・・・・
Cliff - Cartridge heater as a heating element (electrical heating source) 17...Temperature sensor arrangement for temperature sensing element 18 19.29...Cooling air supply pipe 25...
・Baffle plate 28.34...Cap 31...Needle tube 35...-Manifold 38...Inner cylinder body 41...Heating adapter No. 6 Figure 8 Figure 2

Claims (1)

[Claims] ([) The thermoplastic resin in a part of the runner is melted and plasticized by a hot runner having an electric heating source, and the resin in the gate portion leading to the cavity is heated and melted or cooled and solidified. In a runnerless injection molding method in which the injection molding operation is performed by opening and closing, the electric heating source built into the hot runner is a single component, and the front part facing the gate side is compared to the other parts. The tip of the hot runner can be heated by heat conduction as a high temperature distribution, and the heat energy beyond the required amount can be exhausted, and the gate can be opened or closed depending on the power supply of the electric heat source or the amount of electricity supplied. Runnerless injection haze that enables injection molding by opening and closing the gate by raising and lowering the temperature of the tip of the hot runner that faces the area to heat and melt or cool and solidify the resin in the gate part] (2) In the above method, a cooling air supply pipe is provided in the hot runner, and cooling is discharged from the cooling air supply pipe without being related to or related to the opening/closing of the power source of the electric heat source or the amount of electricity supplied. A runnerless injection molding method in which air is supplied to the tip of a hot runner to rapidly cool the tip to promote cooling assimilation of resin in the gate, thereby closing the gate. (3) A single heating wire is wound inside the shell-shaped external body, increasing the winding density toward the front, and a porous structure is provided between the heating wire and the outer cylinder to prevent overheating. 8 (4) The gate and a part of the runner are passed vertically on the central axis of the cylindrical outer body, and porous holes are provided on the outer periphery of the hot runner. A hot runner 6 is constructed by interposing a structural baffle plate and having a cooling air supply pipe vertically split around the outer periphery of a single heating wire, the winding density of which increases as it goes toward the front, on the outer periphery of the baffle plate.