JP2012020563A - Die high in degassing effect in injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To pursue a cross-sectional shape of a runner narrowly formed in a die and a desirable shape of the planar arrangement of the runner on the die in order to reduce gas pressure in the die to the utmost extent in injection molding.SOLUTION: This die high in degassing effect in injection molding is provided by forming the cross-sectional shape of a runner into a trapezoidal or triangular shape in order to generate a fine pressure change in the flow of gas compressed by a filler to be filled in the die, and changing a conventional linear arrangement of the runner on the die to a planarly-bent arrangement to improve degassing effect.

Description

      The present invention relates to a synthetic resin injection mold, and particularly to a mold having a high degassing effect in injection molding.

      In the past, the present inventor has developed a degassing device used for degassing a mold for injection molding or a protruding pin as shown in FIG. 15 having a degassing effect, and used these devices while repeating actual use. We have been researching how to use it more effectively. Their technical contents are disclosed in the following patent documents. Conventionally, in injection molding, it is known that degassing the inside of the mold has a great influence on the finished product, and various degassing methods have been studied, but good results have been obtained. First, a desirable degassing means was introduced to the world by the invention disclosed in the following patent. In these inventions, that is, “a cross-sectional area other than the plug relative to the cross-sectional area of the plug chamber having a cutout portion along the axis of the plug on the outer circumferential surface of the circular or polygonal plug inserted into the plug chamber continuous with the exhaust passage. Of the injection molding using the “gas venting device in injection molding” in which the narrowed portion and the gas vent groove are continuously drilled and one or more plug chambers are installed in the runner of the mold for injection molding. The concept is shown in FIGS. 10 to 14, in which P indicates a gas venting device, S indicates a filling material, M indicates a mold, and R indicates a runner. In order to help understand the problem of degassing, the movement of the material such as synthetic resin during injection molding and the outline until the completion of filling will be described. As shown in FIG. 10, the filling material S advances in the runner R. In the meantime, the gas in the runner R and the mold M is discharged to the outside from the degassing device P, and the filling material S enters the mold M from the left in the figure while slightly compressing the gas remaining in the mold M. Proceed to the right. When the compression of the residual gas by the filling material S reaches the limit as shown in FIG. 11, the residual gas flows back between the filling material S and the inner wall of the mold M as shown in FIG. When the filling material S fills the space inside the mold M from which the residual gas has escaped as shown in FIG. 13, the filling is finally completed as shown in FIG. 14, and a finished product can be obtained.

  Japanese Patent No. 4085182   Japanese Patent No. 4096327

      In order to make the inside of the mold for molding the product as low pressure as possible, preferably as close as possible to a vacuum state, the shape of the planar arrangement of the runner for feeding the filler to the mold or the internal shape of the runner is improved, Ensure more efficient operation of the venting device or venting pin.

      As a result of applying the invention described in the above-mentioned literature to on-site injection molding operations, various difficult injection moldings that could not be realized until now are possible, thereby pursuing the possibility of more advanced injection molding operations. It became necessary to do. More advanced operations include, for example, obtaining a larger finished product that far exceeds the limits of the past, obtaining a thinner finished product as well as a gas that remains in the mold that could not be avoided in the past. In addition to these, it is also required to obtain a finished product made of a material or a compounded material that has been difficult to injection mold conventionally. Conventionally, in order to solve such a difficulty, techniques for excessively increasing the injection pressure or extremely increasing the mold temperature have been carried out by hand, but none of them has obtained a desirable result.

      The inventor said that for injection molding, it is desirable that the residual gas pressure inside the mold and the runner be as low as possible, ideally the mold is evacuated prior to filling with the synthetic resin. The invention shown in the above patent document has been completed based on the technical idea of the above, but as the finished product by injection molding becomes better by implementing this patent, further quality improvement and As a result, the inventor has not only applied the invention product to the technical field, but also used an injection mold for applying the invention product. It was necessary to expand the scope of research.

      In such a situation, in order to make the two inventions work more effectively, a number of experiments are repeated, and the new facts discovered by the inventor are the following two points. The first is that if the runner has a circular cross-section, the trapezoidal shape will show a significant improvement in the degassing effect. This cross-sectional shape is a rectangle or other polygonal shape, but it can be seen that the cross-sectional shape is superior to that of the circular cross-section. The two runner cross-sectional shapes are considered to be the most economical and reasonable.

      Secondly, the improvement of the planar arrangement shape of the runners where the gas venting pins and the like are installed, that is, if the filling passage is bent rather than the conventional linear shape, a higher gas venting effect can be obtained. It is a fact. This is because a subtle change in pressure is added to the gas that moves in the runner prior to the filler that moves in the runner for each bent portion of the runner, resulting in a change in the gas venting effect at that portion. From this experimental fact, it was possible to derive a further improvement in the gas venting effect by changing the cross-sectional area of the obstacle or the runner that generates a subtle pressure change in the runner.

      According to the present invention, so-called gas remaining inside the runner and the mold can be almost removed prior to the progress of the material filled in the runner and the mold. In addition to eliminating problems such as air traps that frequently occur in molded products due to the effects of gas pressure, the finished molded product surface can maintain the most desirable aesthetic finish, and the range of materials that can be injection-molded is greatly expanded. There is an effect that can be done.

  It is a conceptual diagram of the 1st Example by this invention.   It is a conceptual diagram of a prior art example.   It is a conceptual diagram which shows the cross-sectional shape of the runner by this invention.   It is a conceptual diagram which shows the cross-sectional shape of the conventional runner.   It is a conceptual diagram of the degassing by the degassing apparatus which this invention uses.   It is a conceptual diagram of the 2nd Example of this invention.   It is a perspective view of what applied the 2nd Example of this invention to the fixed side metal mold | die.   It is the slope view which showed the movement side metal mold | die which supplements the 2nd Example of this invention.   It is the conceptual diagram which applied the cross section triangle runner to the 1st example of the present invention.   It is sectional drawing of "in filling" which shows the relationship between a degassing apparatus and filling.   It is sectional drawing of the "filling limit" state which shows the relationship between a degassing apparatus and filling.   It is sectional drawing of the "gas backflow" state which shows the relationship between a degassing apparatus and filling.   It is sectional drawing of the "backflow gas exhaustion" state which shows the relationship between a degassing apparatus and filling.   It is sectional drawing of the "filling completion" state which shows the relationship between a degassing apparatus and filling.   It is a perspective view of the protrusion pin shown by prior art literature.

      When the present invention is applied to actual injection molding, the embodiment selects only the optimum material for the injection material, the size and shape of the finished product, the temperature of the injection material, and the injection pressure. In order to generate subtle fluctuations in the gas pressure in the runner in the injection molding using the gas venting device shown in Patent Document 1 and Patent Document 2, it is difficult to summarize in the form of form. There are two specific embodiments of the present invention, namely, that the cross-sectional shape of the runner is a polygon, and that the planar name arrangement of the runner is further bent. The cross-sectional shape of the runner is preferably a trapezoid and a triangle among the polygons, and the purpose of the two forms is to give a subtle change to the gas pressure in the runner.

Several embodiments will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing a trapezoidal runner 1 and a mold product part 2, and it is difficult to display the entire space inside the mold in the drawing. The shape of the exhaust passage 3 that intersects with the runner 1 at a right angle is trapezoidal like that of the runner 1, and the lower surface of the runner 1 and the exhaust passage 3 is shown in the figure. A plurality of degassing devices 6 are installed in the runner 1 through the filling port 4 and the gas in the mold product portion 2 and the runner 1 is moved while moving in the runner 1 and the exhaust passage 3. Is finally discharged from the gate 5 at the end of the runner 1 to the mold product part 2 and injection molding is performed.
A conceptual diagram of a conventional runner R having a circular cross section is shown in FIG. 2 as an object formed by a mold in the same manner as in FIG. 1, except for the difference in cross sectional shape. Has almost the same configuration. A partially enlarged conceptual view of the runner 1 according to the present invention is as shown in FIG. 3, and a partially enlarged conceptual view of the conventional runner R is shown in FIG. When each runner is drilled between the fixed side 7 and moving side 8 molds, the conventional runner R having a circular cross section is equally drilled on the fixed side 7 and moving side 8, whereas All the trapezoidal runners 1 according to the invention are drilled in the fixed side 7 and the moving side 8 is used as a simple lid.

      In the present invention, the gas venting device shown in the above-mentioned patent document is used. The principle of the gas venting is the application of a venturi tube as shown in FIG. The gas inside the runner R and the mold M pressurized by the above is discharged from the degassing pin P to the outside while being largely depressurized. According to this degassing device, the higher the internal pressure of the runner R and the mold M, the higher the depressurization rate in the degassing device P, and the reason for filling because the gas does not escape as in the prior art. The idea of forcibly pushing the material into the mold M by increasing the filling pressure of the material S has been completely revised, and if the filling pressure required in the relationship between the filling material S and the mold M is selected, degassing can be performed. The most desirable degassing method has been established that is necessary and sufficient.

      Under such circumstances, more precise and more reliable filling is required, and it is more difficult to use materials for injection molding that were previously not used due to frequent problems with the finished product. When faced with a problem, the internal gas, which was thought to have smoothly progressed spirally inside the conventional runner with a circular cross section, was changed by changing the cross-sectional shape of the runner from a conventional circular shape to a polygon such as a trapezoid. The discovery that this new cross-sectional shape adds subtle turbulence, trying to proceed in a trapezoidal runner as well, and as a result, increases the degassing effect by increasing the discharge from the degassing pin, has created the present invention. It was.

      The second embodiment is an embodiment in which the runner provided with the vent pin is viewed in a plan view and is arranged not in a straight line but in a continuous groove state. It is comprised by the cross-sectional trapezoid similar to the Example of this. This idea focuses on the custom of the runners being arranged in a straight line so that the filling material can move quickly and smoothly in conventional injection molding. The gas venting device is used depending on how the gas pressure is reduced, and in the same situation, a gas venting device that increases the gas discharge effect when the gas pressure increases is used. It was developed based on the conclusion that a runner with a bent arrangement is effective when viewed in a plane that will cause subtle turbulence in the flow. In the field of injection molding, this idea has been very effectively embodied, and has actually produced a highly complete injection molded product.

      The specific shape of the second embodiment is as shown in FIG. 6 as a conceptual diagram. In the figure, 1 is a runner, 4 is a filling port, and 5 is a gate. And an exhaust chamber 10 for disposing a gas venting device P is installed below the runner 1. The filling material S filled in the runner 1 from the filling port 4 is changed direction while discharging the gas from the exhaust chamber 10 in the turbulent flow chamber 9, and this is repeated to finally greatly reduce the pressure from the gate 5. Molding is completed by flowing into a mold (not shown). FIG. 7 shows a second embodiment drilled in the fixed side 7 of the mold. The movable side 8 is sufficient if the upper surface of the fixed side 7 is closed to form the runner 1. It is also possible to install a projection 11 for generating further turbulent flow in the turbulent flow chamber 9, and an example of such a configuration is shown in FIG.

      FIG. 9 is a conceptual diagram similar to FIG. 1 in the case where the first embodiment shown in FIG. 1 is configured with a runner having a triangular cross-sectional shape, and the configuration other than the cross-sectional shape of the runner 1 is shown in FIG. This is exactly the same as the one embodiment.

      Currently, the technical improvements that require plastic injection molding in the field are to achieve the following three points: larger finished products, thinner finished products, and fine finishes on the surface and peripheral surfaces of those finished products. It has been narrowed down. According to the present invention, all of these requirements can be achieved, and more efficient injection molding technology can be established by pursuing more detailed behavior trends of the gas inside the runner and the mold based on this technical idea. is there.

DESCRIPTION OF SYMBOLS 1 Runner 2 Mold product part 3 Exhaust way 4 Filling port 5 Gate 6 Gas venting device 7 Fixed mold 8 Moving mold 9 Turbulence chamber 10 Exhaust chamber 11 Protrusion

  It is a conceptual diagram of the 1st Example by this invention.   It is a conceptual diagram of a prior art example.   It is a conceptual diagram which shows the cross-sectional shape of the runner by this invention.   It is a conceptual diagram which shows the cross-sectional shape of the conventional runner.   It is a conceptual diagram of the degassing by the degassing apparatus which this invention uses.   It is a conceptual diagram of the 2nd Example of this invention. It is a perspective view of what applied the 2nd Example of this invention to the movement side metal mold | die. It is the slope view which showed the stationary side metal mold | die which supplements the 2nd Example of this invention.   It is the conceptual diagram which applied the cross section triangle runner to the 1st example of the present invention.   It is sectional drawing of "in filling" which shows the relationship between a degassing apparatus and filling.   It is sectional drawing of the "filling limit" state which shows the relationship between a degassing apparatus and filling.   It is sectional drawing of the "gas backflow" state which shows the relationship between a degassing apparatus and filling.   It is sectional drawing of the "backflow gas exhaustion" state which shows the relationship between a degassing apparatus and filling.   It is sectional drawing of the "filling completion" state which shows the relationship between a degassing apparatus and filling.   It is a perspective view of the protrusion pin shown by prior art literature.

Several embodiments will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing a trapezoidal runner 1 and a mold product part 2, and it is difficult to display the entire space inside the mold in the drawing. The shape of the exhaust passage 3 that intersects with the runner 1 at a right angle is trapezoidal like that of the runner 1, and the lower surface of the runner 1 and the exhaust passage 3 is shown in the figure. A plurality of degassing devices 6 are installed in the runner 1 through the filling port 4 and the gas in the mold product portion 2 and the runner 1 is moved while moving in the runner 1 and the exhaust passage 3. Is finally discharged from the gate 5 at the end of the runner 1 to the mold product part 2 and injection molding is performed.
A conceptual diagram of a conventional runner R having a circular cross section is shown in FIG. 2 as an object formed by a mold in the same manner as in FIG. 1, except for the difference in the cross sectional shape of the runner . 1 is substantially the same configuration. A partially enlarged conceptual view of the runner 1 according to the present invention is as shown in FIG. 3, and a partially enlarged conceptual view of the conventional runner R is shown in FIG. When each runner is drilled between the molds on the moving side 7 and the fixed side 8, the conventional runner R having a circular cross section is drilled equally on the moving side 7 and the fixed side 8, whereas All the trapezoidal runners 1 according to the invention are drilled on the moving side 7 and the fixed side 8 is used as a mere lid.

The specific shape of the second embodiment is as shown in FIG. 6 as a conceptual diagram. In the figure, 1 is a runner, 4 is a filling port, and 5 is a gate. And an exhaust chamber 10 for disposing a gas venting device P is installed below the runner 1. The filling material S filled in the runner 1 from the filling port 4 is changed direction while discharging the gas from the exhaust chamber 10 in the turbulent flow chamber 9, and this is repeated to finally greatly reduce the pressure from the gate 5. Molding is completed by flowing into a mold (not shown). FIG. 7 shows a second embodiment drilled on the moving side 7 of the mold, and it is sufficient that the fixed side 8 forms the runner 1 by closing the upper surface of the moving side 7. It is also possible to install a projection 11 for generating further turbulent flow in the turbulent flow chamber 9, and an example of such a configuration is shown in FIG.

DESCRIPTION OF SYMBOLS 1 Runner 2 Mold product part 3 Exhaust way 4 Filling port 5 Gate 6 Degassing device 7 Mold on moving side 8 Mold on fixed side 9 Turbulent flow chamber 10 Exhaust chamber 11 Protrusion

Claims (3)

      On the outer peripheral surface of a circular or polygonal plug inserted into the plug chamber continuous with the exhaust passage, a notched portion along the axis of the plug, and a narrow portion where the cross-sectional area other than the plug with respect to the cross-sectional area of the plug chamber is narrowed In addition, the runner cross-sectional shape is trapezoidal in a mold using a gas venting device in injection molding, in which one or more plug vents are continuously drilled and one or more plug chambers are installed in a runner of the mold for injection molding. A mold having a high degassing effect in injection molding, characterized by       On the outer peripheral surface of a circular or polygonal plug inserted into the plug chamber continuous with the exhaust passage, a notched portion along the axis of the plug, and a narrow portion where the cross-sectional area other than the plug with respect to the cross-sectional area of the plug chamber is narrowed In the mold using the gas venting device in injection molding, in which one or more plug vents are continuously drilled and one or more plug chambers are installed in the runner of the mold for injection molding, the cross-sectional shape of the runner is triangular. A mold having a high degassing effect in injection molding, characterized by       On the outer peripheral surface of a circular or polygonal plug inserted into the plug chamber continuous with the exhaust passage, a notched portion along the axis of the plug, and a narrow portion where the cross-sectional area other than the plug with respect to the cross-sectional area of the plug chamber is narrowed In a mold using a gas venting device in injection molding, in which one or more plug vents are continuously drilled and one or more plug chambers are installed in a runner of a mold for injection molding, the mold is drilled in the mold. A mold having a high degassing effect in injection molding, characterized in that the planar arrangement of the runner is configured by a continuous groove by bending.

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