JPH0450171B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flow control device in a synthetic resin injection molding system known as a hot runner type runnerless system.

[Conventional technology]

In general, this type of hot runner synthetic resin injection molding method and its equipment are structurally as follows:
A plasticizing barrel that plasticizes raw resin and discharges the molten raw resin from a nozzle part via an injection mechanism using a piston, torpedo, etc., and a mold part that is connected to the plasticizing barrel by a nozzle touch;
It has a manifold part, a runner part, a gate, and a cavity necessary for forming a dividing path communicating with the nozzle part, and the runner from the nozzle part to the gate has complicated parts with various cross-sectional areas and routes. has been done.

From the point of view of the injection molding machine manufacturer, the runner may be thinned by an unspecified mold maker using their own experience and technology without paying particular attention to the size of the injection molding machine or the size of the cavity. The current situation is to create thick and incomprehensible channel configurations.

By the way, as a means to prevent resin leaking from the gate during non-molding operations and to improve moldability in the cavity, for example, it is possible to directly cool and solidify the resin in the narrow cross-sectional area of the gate, or to This was dealt with by providing an opening/closing piston inside the runner that reciprocated in accordance with the flow direction, or by installing a hot runner chip inside the runner, which indirectly affected the injection mechanism. Currently, this is handled by incorporating a back-back device.

In addition, if the cross-sectional area of the runner has a relatively small change, this problem is not a problem, but if a hot runner chip is installed in the runner, the cross-sectional area and route of the runner may vary in a complex way. Dripping, or the runner parts near the runner gates partially solidify and adhere to non-circulating resin, which can cause the flow rate of the molten resin, a highly viscous fluid, to decrease in each part of the runner. Changes in water and flow rate act unbalancedly and are extremely harmful to formation.

In order to eliminate such harmful effects, we use expensive accessories and computers for electronic control.
The current situation is that we have purchased partial solutions that target individual problems.

This means that manufacturers of synthetic resin injection molding machines are not necessarily consistently involved in manufacturing, and even if injection molding machine manufacturers manufacture other mechanical structures other than the mold part, they The mold section forming the cavity is manufactured by another unspecified mold manufacturer.

Originally, a runner manufactured by an injection molding machine manufacturer that runs from the tip of the plasticizing barrel to the nozzle, and a runner that leads to the cavity in the mold that is connected by a nozzle touch, are made of a single molten resin. I cannot help but say that the fundamental technical issue that must be taken into account as a flow path was overlooked.

Moreover, the historical development of synthetic resin injection molding methods and equipment in two directions, namely hot runner methods that do not produce sprue runners and cold runner methods that produce sprue runners, has made it difficult to provide consistency in the formation of runners. It can also be considered as something that

[Problem that the invention seeks to solve]

This type of hot runner synthetic resin injection method and its equipment, which is runnerless and highly economical, generally requires a large volume of molten resin in the runner leading to the plasticizing barrel and gate during non-molding operations. As the resin accumulates, the residual pressure becomes extremely high, and leakage of resin from the gate (runny nose phenomenon) is unavoidable.

Therefore, as mentioned above, various measures have been taken to prevent resin leakage from the gate, but directly they rely exclusively on solutions that target the gate, and indirectly they rely on solutions that target the injection mechanism. This problem is solved by backflow suction of the molten resin that is about to leak from the gate on the side using a suction device.Moreover, the leakage prevention means, which is equipped with a movable structure, is configured to operate in the same direction as the direction in which the resin flows out. We are prepared.

Moreover, in the case of an opening/closing piston for a gate, the opening/closing operation of the gate in a small space called the gate and high precision are required, making the configuration extremely complicated, and the piston is constantly moving inside the runner. Since the piston comes into contact with the molten resin, there are many disadvantages such as resin adhering to the piston when the gate is closed, such as the resin adhering to the piston being inadvertently abutted against the gate and being forced into it, and the stroke action being eccentric. In addition, since the suction device is attached to the injection mechanism, it will not function properly if the distance from the gate is long, and if the suction action is too strong, too much molten resin will flow back and cannot be used for the next molding operation. There were many problems that hindered this.

In addition, the conventional structure in which the cross-sectional area of the runner leading to the nozzle part and the mold part of the resin level changes in various stages is generally made thicker without any particular basis as mentioned above. There is usually one.

Therefore, although the cross-sectional area has been made large from the beginning of manufacture, injection operation of molten resin, a unique fluid with high viscoelasticity, is carried out regardless of the wall thickness or size of the molded cavity. Conventional molding methods and devices are clearly unreasonable and have fundamental problems that should be improved.

In addition, as mentioned above, each part of the runner is formed in multiple stages in several places with poorly grounded changes in cross-sectional area, so in order to obtain the necessary injection pressure of molten resin, Another disadvantage was that a very high source pressure had to be supplied from a hydraulic pump and column.

Next, the measurement of the raw material supplied to the plasticizing barrel is generally calculated by weight or volume, and the amount is commensurate with the cavity volume, but it is inaccurate and has extremely large variations, and the tip of the plasticizing barrel Although it is measured based on the resin volume of the resin reservoir part communicating with the nozzle part, a considerable amount of variation is unavoidable.

Therefore, there is a problem in that for precision molding, the measurement must be corrected by electronic control such as an expensive computer. Moreover, if the amount of molten resin injected is larger than the volume of the cavity due to a calculation error, the problem of burrs occurring around the cavity cannot be avoided.

Furthermore, small molded products require a large mold clamping force of several tons per effective area, and in particular, large mold clamping forces are often required for precision molding and prevention of burrs. There was a problem that it was an absolute condition for molding that could not be done.

A general problem with precision molding is that the injection mechanism requires an expensive back pressure device such as a holding pressure device or a suction device.

[Means for solving problems]

This invention was made by focusing on the numerous problems mentioned above, and basically focuses on the flow of molten resin between the nozzle part of the plasticizing barrel having an injection mechanism and the gate leading to the mold cavity. A flow rate control mechanism that can open and close the runner or open and close the runner and change the cross-sectional area is installed in the middle of the runner, so that the flow rate of the molten resin can be appropriately reduced according to the volume of the cavity. The flow rate control mechanism includes a valve rod section that adjusts the opening and closing of the runner, a drive section that drives the valve rod section, and an adjustment section that freely controls the flow rate of the valve rod section. The valve rod section is equipped with a heat retention mechanism for melting and retaining the molten resin stored in the valve hole where the resin is stored in the valve rod section, and a heat cutoff mechanism such as a heat dissipation mechanism that prevents heat from propagating to the drive section. and perform flow rate correction using an expensive computer with simple control.
Flow control in a new synthetic resin injection molding system that enables high-precision molding while preventing burr generation by constantly applying a mold clamping force that matches the size of the molded product instead of using an unnecessarily large mold clamping force. We are in the process of providing equipment.

Further, in the present invention, in the above structure, the flow rate control mechanism provided in the middle of the runner has a valve function for opening and closing the runner and a control function for changing and adjusting the cross-sectional area of the runner as much as possible. Flow rate control in a synthetic resin injection molding system that solves the conventional problems at once by incorporating each as an independent structure and simultaneously opening and closing the runners and adjusting the flow rate of the molten resin flowing through the runners. We are in the process of providing equipment.

[Effect]

The resin melted with the raw material in the plasticizing barrel is injected in a predetermined amount by the action of an injection mechanism. The required amount of the injected molten resin is injected into the cavity through a runner from the nozzle of the plasticizing barrel to the gate.

By the way, the runner is equipped with a flow rate control mechanism that has a valve function of the runner and a flow rate control function that adjusts the valve function and flow rate. The runner is opened by the action of the runner to allow the molten resin to flow therethrough, but the runner is closed by the action of the valve when the injection molding operation is completed.

By instantaneously interlocking the closing operation of the next valve function with respect to this injection molding operation, unnecessary intrusion of molten resin can be prevented, and transmission of excess pressure can also be completely blocked. Furthermore, burrs do not occur because the amount of resin that causes burrs is not supplied in an accurately controlled manner from the beginning. Also, there is no need for a mold clamping force or a large pressure of several tons per unit projected area of the cavity.

In this way, the opening and closing of the mold are interlocked by this valve function, and the molten resin filled in the cavity is solidified and molded to obtain a desired molded product.

In addition, when the runner is blocked by a flow control mechanism with a valve function installed in the middle of the runner, the molten resin in the runner between this mechanism and the gate is cooled and solidified in the cavity and becomes a molded product. Until it is taken out, it remains in a molten or softened state without being cooled and solidified, and is kept on standby until the next injection molding operation.

Furthermore, since the influence of the injection mechanism on the plasticizing barrel side is completely blocked, there is no back pressure effect.

Moreover, the resin in the waiting runner runner mentioned above remains with a small residual pressure depending on its volume, and exhibits a kind of pressure retention effect, and the narrow gate becomes semi-solidified and semi-molten while the molded product is cooling. Since the gate can be temporarily closed, there is no sinkage of the filled resin in the cavity, and there is no leakage of molten resin from the gate when releasing the molded product.

The above is the entire process of one injection molding, but the next injection molding operation begins when the mold is closed, a cavity is formed, and the flow control mechanism with a valve function operates to open the runner, as described above. The same operation is repeated.

Next, a flow rate control mechanism installed in the middle of the runner that performs variable flow rate adjustment adjusts the flow rate that passes through the runner depending on the volume of the cavity, so that the flow rate is always approximately equal to the absolute calculated value. The calculated value of is given.

Moreover, depending on the size of the cavity, the cross-sectional area of the runner can be changed as much as possible, focusing on either flow velocity or pressure, so as a result, the optimum cross-sectional area, optimum flow rate, and optimum pressure can be applied to the molten resin. It can be selectively given, allowing precision molding.

When the above-mentioned valve function is added to this flow rate control mechanism and the injection molding operation is carried out by installing it integrally or separately in the middle of the runner, the ideal hot runner method is achieved by the functions of both mechanisms. Injection molding is performed to enable high precision molding.

Moreover, the flow rate control mechanism includes a valve rod portion,
It is equipped with a driving part and an adjusting part, and the valve rod part has a heat insulation mechanism as well as a heat isolation mechanism that prevents heat from propagating to the driving part, so that a small amount of deviation in the valve hole of the rod part can be avoided. This prevents the solidification of the resin and the transfer of heat to the driving part, making subsequent injection molding operations smooth, and allowing the driving part and adjustment part to operate and operate without being affected by heat. Optimal flow control and opening/closing of hot water can be performed.

〔Example〕

Two embodiments of the invention will be described below with reference to the drawings.

In each figure, A is a plasticizing barrel for raw resin, which can plasticize the raw resin and discharge the molten raw resin from the nozzle part 1 via an injection mechanism using a piston, torpedo, etc. . B is a mold part connected to this plasticizing barrel A by a nozzle touch, and has a manifold part 2, a runner part 3, a gate 4, and a cavity 5 necessary for forming a dividing path communicating with the nozzle part 1. A runner P is formed from the gate 3 to the gate 4.

Next, the embodiment shown in FIGS. 1 to 3 will be described.

F indicates a flow rate control mechanism, which is attached to the nozzle portion 1 with a plurality of upright support rods 6 forming a heat dissipation interval portion 7. Reference numeral 8 designates a valve rod portion disposed in a direction transverse to the nozzle portion 1, and is provided with a valve hole 9 that can be opened in line with this runner P and can store resin in a molten state. Adjacently mounted along the free end of the valve rod portion 8 is a heat retention mechanism 10 made of a highly thermally conductive material such as copper or copper-beryllium. The heat retention mechanism 10 functions to absorb heat from the band heater 11 of the nozzle portion 1 to prevent the molten resin stored in the valve hole 9 from cooling and solidifying. Moreover, in order to equalize the heat distance from this heat retention mechanism 10, the valve hole 9
The hole shape is preferably formed into a prismatic shape as shown in FIG. Reference numeral 12 designates a hollow heat radiation hole bored toward the other side of the valve rod portion 8, that is, toward the heat radiation spacing portion 7, and a thermocouple 13 is provided in the hole so that the internal temperature of the valve rod portion 8 can be measured. Reference numeral 14 denotes an air vent hole of the hollow heat radiating section 12, which opens into the heat radiating interval section 7. Reference numeral 15 denotes a driving section of the valve rod section 8, which is composed of a piston 16 and a cylinder 17, and is capable of linear stroke movement using fluid pressure such as hydraulic pressure or air pressure. Reference numeral 18 denotes a heat insulating plate disposed along the heat radiation interval section 7 in the drive section 15, and forms a heat shielding mechanism 19 together with the hollow heat radiation hole 12. Reference numeral 20 indicates an adjustment section connected to the drive section 15, and a handle 21
, a nut 22 and a stroke adjustment stopper 23, and is configured to be able to adjust the flow rate of the valve rod portion 8. The adjustment screw 24, which moves up and down with the rotation of the handle 21, is connected to the rod 25 of the drive section 15 through a bearing 26 with a coupling 27, and a stopper for preventing rotation of the rod 25 and a circumferential stop around the rod 25 are connected. Stop 28
A guide portion 29 is disposed within a casing 30 provided on the cylinder 17 to form the entire body.

Prior to the injection molding operation, the handle 21 of the adjustment part 20 is adjusted in advance according to the volume of the cavity 5.
is operated to set the size of the communication state between the fluid P and the valve hole 9 of the valve rod portion 8 which can be opened and closed.

That is, when the amount of adjustment of the handle 21 is large, the communication state becomes small, the flow rate is narrowed down,
In addition, if the adjustment amount of the handle 21 is small, the communication state becomes large and the flow rate can be set large.

Next, the molding operation will be explained.

When the melting process of the raw resin in the plasticizing barrel A is completed and the preparation for the molding operation is completed, the molten resin can be injected into the cavity 5 by the function of the injection mechanism, but before the start of the injection molding operation, the flow rate control mechanism F is The valve rod part 8 is operated by the driving part 15, and the valve hole 9 of the mechanism F is made to match the diameter of the water movement P to a necessary throttling amount (set amount).

Immediately upon receiving the signal to open the valve of this mechanism F, the injection mechanism operates, and the necessary amount of molten resin is injected from the nozzle part 1 of the plasticizing barrel A through the liquid P and into the cavity 5 from the gate 4, and the injection operation is carried out. Complete.

Upon receiving this completion signal, the drive section 15 slides the activated valve hole 9 in the opposite direction again, and the flow path of the molten metal P moves into a valve-closed state, so that the pressure from the injection mechanism can be instantly shut off.

By closing the valve of the flow rate control mechanism F, the residual pressure in the runner P becomes small, so the pressure acting on the cavity 5 is also reduced, and as a result, cooling and solidification are rapidly promoted, and the product is released by releasing the mold part B. Removal is performed efficiently.

Furthermore, the phenomenon of dripping of the molten resin from the gate portion 4 during demolding can be prevented since the residual pressure of the molten resin in the runner P is small.

After taking out the released product, when the mold clamping operation is performed and preparations for the next injection molding operation are completed, the signal is transmitted to the flow rate control mechanism F, and the drive unit 15 is activated to open the valve in the same manner as described above. An injection molding operation is performed.

Thereafter, runnerless injection molding is performed by repeating the same operation.

By the way, when the valve is opened after injection molding is completed, the molten resin stored in the valve hole 9 is constantly exposed to heat from the band heater 11 by the heat retention mechanism 10 provided nearby, so that the molten resin is not cooled and solidified. Then, when the valve is opened, the resin in the valve hole 9 remains molten, so it mixes with the molten resin in the runner and the molding operation can be performed without any trouble.

Further, the valve rod portion 8 is provided with a hollow heat radiation portion 12 for heat radiation, and a heat radiation gap portion 7 having a heat insulating plate 18 is formed between the valve rod portion 8 and the drive portion 15 for stroking the valve rod portion 8. The inconvenience of heat being transmitted to the drive unit is completely prevented, and the molding operation can be repeated and continued completely and efficiently.

Although the case where the flow rate control mechanism F is provided in the nozzle part 1 has been shown above, it can be installed in any other runner P at any desired location.

Next, other embodiments will be shown with reference to FIGS. 4 to 6. Note that the same reference numerals are given to the same or corresponding parts as in the above embodiment, and detailed explanation thereof will be omitted.

This embodiment is substantially the same as the first embodiment except for the driving method of the valve rod portion 8.

That is, in this embodiment, the valve rod section 8 is rotated to close the valve, open the valve, and control the flow rate, and the above operations are performed using a drive motor 31 and a pair of bevel gears 32 and 33. It was designed to allow

Therefore, the valve rod 8 exhibits a stroke motion in the embodiment described above, and the positional relationship between the valve hole 9 and the runner P is as shown in FIG. Thus, the positional relationship between the valve hole 9 and the runner as shown in FIG. 6 is maintained.

The state of alignment between the valve hole 9 and the runner P can be regulated by the amount of rotation of the motor 31.

Note that the molding operation is exactly the same as in the first embodiment.

This flow rate control mechanism F can also be installed not only in the nozzle section 1 but also at any desired location in the runner P.

As mentioned above, two embodiments of this invention have been described, but both flow rate control mechanisms F control the flow rate of the molten resin injected from the plasticizing barrel A by the injection mechanism, depending on the size of the mold section B such as the capacity of the cavity 5. Since the cross-sectional area of the runner P can be easily adjusted depending on the flow rate, etc., and the flow rate can be controlled to the optimum flow rate, high-precision molding can be performed by maintaining an appropriate relationship with the injection pressure.

Specifically, when molding a large wall thickness, it is sufficient to greatly adjust the cross-sectional area of the runner P to reduce the flow velocity and increase the pressure.This method is particularly effective for molding precision processed products such as lenses. At the same time, for molding small pieces of meat such as small pieces, the flow rate can be increased by reducing the cross-sectional area of the runner P, and the pressure can be reduced to easily achieve the optimum flow rate according to the size and thickness of the molded product. , the optimum pressure can be easily selected.

In addition, the optimum pressure is the setting amount of the flow rate control mechanism F,
Of course, it is possible to set the conditions such as the volume of the cavity 5 by simple calculation.

Further, in the above embodiments, the flow control mechanism F having a valve function has been described, but it goes without saying that the flow control mechanism F can be implemented even when both functions are configured independently.

By the way, if the runner P and the valve hole 9 have a circular shape,
If the flow rate control image deviates by the radius r of the circle, that is, in the state shown in Figure 7 a, the flow rate will be 39.1%, and if it deviates by 3/2 of the radius, that is, in the state shown in Figure 7 b, the flow rate will be 39.1%. can be easily calculated to be controlled to 15.4%.

In addition, if the device is equipped with a flow rate adjustment function as a valve function as in the above embodiment, both the valve opening/closing operation and the flow rate control operation work synergistically in relation to the injection molding operation, so high-speed molding is possible. As a result, precision molding is performed using an appropriate mold clamping force, and there is no dripping phenomenon or burr generation at the gate 5. There is no need for a mechanism or controller for opening and closing the passage, and the configuration can be simplified and provided at low cost.

Although the embodiments of the present invention have been listed above, it goes without saying that the configuration of the mold section B includes a heater, a sensor, and other components necessary for the mold.

Furthermore, it goes without saying that the operation of the valve function and the flow control function can be controlled in conjunction with the operating conditions of the injection mechanism.

〔Effect of the invention〕

According to this invention, a flow control mechanism having a valve function or a valve function and a flow rate adjustment function is disposed in the middle of the runner through which the molten resin flows, so that the valve function is activated to open the valve properly. When the injection operation of the molten resin function into the cavity is completed under proper flow rate control, the valve function instantly closes the valve, so the injection pressure to the filled resin in the cavity is completely cut off, and the flow rate control mechanism and Only the residual pressure of the molten resin remaining in the runner between the gates acts, allowing rapid cooling and solidification to occur, significantly shortening the time from solidification to removal of the molded product, and reducing the amount of molten resin from the gate. The nasal drip phenomenon is also prevented, and the next injection molding operation can be carried out immediately.

Therefore, the time required for one molding operation can be shortened as a whole, so that the molding cycle can be significantly improved and high-precision molding can be performed.

Moreover, since there is no leakage of molten resin from the gate portion, it is possible to eliminate the need for molten resin leakage prevention means that have conventionally been required in various forms, and the back pressure device can also be removed.

Further, according to the present invention, since a flow rate control mechanism is provided that can control the flow rate by freely changing the size of the flow path in the runner, an appropriate flow rate is constantly given to the cavity. Without the need for an unnecessarily large mold clamping force, the injection pressure and the flow rate set by the variable flow rate adjustment mechanism allow for extremely high precision and reasonable molding without the occurrence of burrs.

In particular, variations in the metering of raw materials provided in the plasticizing barrel can be easily and precisely controlled by this simple variable flow rate adjustment mechanism.

Furthermore, according to the present invention, without providing a step in the runner that causes an unnecessarily large change in cross-sectional area,
A simple and straight configuration is sufficient, and the flow rate control mechanism is composed of a valve rod part, a driving part, and an adjustment part, and has a heat retention function for the valve hole of the valve rod part,
The structure of the mechanism that cuts off heat to the drive section allows the molten resin in the valve hole to cool and solidify during repeated injection molding operations, allowing it to function smoothly and completely blocking heat transfer to the drive section. This has the effect of making it possible.

Next, although the flow rate control mechanism disclosed in the embodiment is perpendicular to the runner, there is no problem with forming it in an oblique direction, and the raw material used may be a synthetic resin alone or a composite material such as glass fiber. be able to.

[Brief explanation of the drawing]

1 to 3 show an embodiment of a flow control device in a synthetic resin injection molding system according to the present invention, and FIG. 1 is an overall explanatory diagram showing a main part partially cut away in cross section. , Figure 2 is a front view of the main parts,
Figures 3a, b, and c are explanatory diagrams showing three relative positional relationships between the runner and the valve hole, Figures 4 to 6 show other embodiments, and Figure 4 shows the main parts. Figure 5 is a front view; Figures 6a, b, and c are cross-sectional explanatory diagrams showing the three relative positional relationships between the runner and the valve hole; Figure 7a , b are explanatory diagrams showing two examples in which the runner and the valve hole coincide and are in a controlled state. A... Plasticizing barrel, B... Mold part, 1... Nozzle part, 3... Runner part, 4... Gate, 5...
... Cavity, P... Runway, F... Flow rate control mechanism, 8... Valve rod section, 9... Valve hole, 10... Heat retention mechanism, 15... Drive section.

Claims (1)

[Scope of Claims] 1. According to the injection molding operation, the molten resin is injected into the cavity from the nozzle part of the plasticizing barrel through the runner leading to the gate of the mold part, and the opening and closing of the runner or opening and closing of the runner and the flow rate are controlled. A synthetic resin injection molding system is provided with a flow rate control mechanism to adjust the flow rate and injection pressure to perform the molding operation at an appropriate flow rate and injection pressure suitable for the size of the cavity. It consists of a valve rod section that adjusts opening and closing, a drive section that drives this valve rod section, and an adjustment section that controls the flow rate of the valve rod section, and the valve rod section has a valve hole in the valve rod section. a heat retention mechanism for melting and retaining the molten resin stored therein;
A flow control device characterized in that the drive section is provided with a heat cutoff mechanism such as heat radiation that does not propagate heat. 2. The heat retaining mechanism is made of a material with good thermal conductivity and is embedded in the valve rod part, and the heat retention mechanism is formed with equal thermal spacing with respect to the valve hole in the valve rod part. A flow rate control device in the synthetic resin injection molding system according to item 1. 3. The heat cutoff mechanism is characterized by comprising a hollow heat radiation hole extending vertically through the valve rod portion and a heat radiation interval portion having a heat insulating plate provided at the boundary with the drive portion. Flow control device for synthetic resin injection molding systems.