JP4096327B2 - Gas venting device in injection molding - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a degassing apparatus in injection molding in which various products are manufactured by filling molten raw materials into a mold.
[0002]
[Prior art]
In an injection molding operation in which a mold is filled with heated and melted material to obtain a product, the filled material needs to spread quickly and reliably and uniformly throughout the interior space of the mold. Improvements are repeated. Since such a basic problem is described in detail in Japanese Patent Application No. 2000-182105 related to the applicant's application, the conventional general injection molding method will be described in detail in the present application. It should be noted here that only the most important problem in injection molding is to quickly discharge the gas generated during material filling in injection molding to the outside of the mold.
[0003]
In the above-mentioned Japanese Patent Application No. 2000-182105, the projecting pin for taking out the molded product has been improved, and the projecting pin that can perform degassing quickly and surely has been disclosed. The present inventor who succeeded in deriving a new degassing apparatus capable of further improving the quality of the molded product from other parts of the mold has made a new patent application here.
[0004]
[Problems to be solved by the invention]
The idea in the invention is that an exhaust notch and a gas vent groove are formed in the outer peripheral portion of the protruding pin, and a portion where the cross-sectional area of the gas passage is narrower than both provided between them, that is, a narrow portion is provided. Using this, the gas generated by filling the material is quickly discharged from the notch to the gas vent groove, and the part with a narrow cross-sectional area increases the gas pressure in the notch and simultaneously reduces the pressure toward the gas vent groove. By using this, it prevents the filled material from entering the notch and generating burrs and protrusions on the product. Generation and surface roughness were almost certainly removed.
[0005]
By using such an ejector pin, a sufficiently satisfactory effect was obtained, but further pursuing the above invention, the gas generated by the filled material was extracted from each part before reaching the ejector pin. In this case, the inventor who discovered that various problems appearing in the product can be further eliminated before the material filled in the mold from the nozzle of the molding machine finally reaches the female (core) part through the gate. I came up with the idea of venting.
[0006]
However, in the conventional molding machine, such a design has never been made because of the fixed idea that the degassing before reaching the gate attenuates the pressure for filling the material and generates a pressure loss.
[0007]
[Means for Solving the Problems]
The reason why the concept of degassing before the gate was not born is that the filling material enters the degassing structure and generates a large amount of burrs, which reduces workability and attenuates the filling pressure. However, according to the above-mentioned Japanese Patent Application No. 2000-182105 proposed by the present inventor, the generation of burrs can be suppressed to the minimum, and the conditions for degassing instantaneously and quickly are in place. Therefore, by applying this, it became possible to perform degassing from an arbitrary position. Furthermore, especially in injection molding using synthetic resin as a material, it is desirable to place a minimum amount of material in the material runner (runner) other than the product, but in the present situation the pressure required for filling is there. Depending on the gas generated, if the gas can be quickly and surely vented before reaching the pin gate, the cross-sectional area of the runway will be reduced by the amount that attenuated the gas pressure resistance. In addition, the manufacturing cost of the mold can be reduced.
[0008]
In addition, the position where the gas venting device is installed is arbitrary at any portion that is continuous with the running path of the filling material installed inside the mold, but if considering the discharge of the extracted gas outside the machine, It can be said that the end portion A of the runner R and the end portion C of the sprue S in the overall conceptual diagram relating to the travel of the material shown in FIG. In the figure, the end A of the runner R bends to reach the pin gate P, fills the product M portion, and the gas in the product M portion is extracted by the protruding pin D. Moreover, you may install a gas vent suitably on the runner R between the sprue S and the edge part A of the runner R as needed.
[0009]
The plugs for the gas venting device including the end A of the runner R and the end C of the sprue S must have different external shapes depending on the design requirements, but the cross-section is circular, square or polygonal. Japanese Patent Application No. 2000-182105 has a notch part, a narrow part in which a cross-sectional area of a passage through which gas passes is narrower than the notch part, and a gas vent part on the outer peripheral surface of the part for degassing It is exactly the same.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The embodiment of the present invention will be described with reference to the drawings. FIGS. 1 and 2 are sectional views showing the concept of a fixed mold G, a cavity movable mold F, and a runner R and a core K formed thereby. Yes, N on the right side of the figure indicates the nozzle of the molding machine. Also, the fixed mold G, the cavity movable mold F, and the core movable mold E on the stationary side of the molding machine form a filling flow path for the filling material and a cavity for the object to be molded as shown in FIG. When the material is filled, the material runs on the runner R and reaches the pin gate P, and flows from there to the core K to complete the filling.
[0011]
After completion of filling, the movable core mold E and the movable cavity mold F are separated from the fixed mold G as shown in FIG. In the runner R portion maintained on the runner plate RP by the runner lock pin RL, the runner plate RP is separated from the fixed mold G to reach the position shown in FIG. 2, and the runner plate RP further moves to the left in the figure. As a result, the engagement with the runner lock pin RL is released, and the state shifts to a state where it can be taken out.
[0012]
A portion formed by solidifying the material filled in each mold is formed between the product M, the core movable mold F, and the fixed mold G in the core K formed by the core movable mold E and the cavity movable mold F. The end material J inside the runner R is formed, but the end material J must be disposed of unless it can be reused. The smaller the value, the better the manufacturing cost. The part of product M and end material J is shown as a conceptual bevel view in FIG. 15, but in actual injection molding, the volume of the part occupied by end material J is much larger than in the case of this conceptual diagram. Usually, depending on the type of product, it is not rare that the amount of material occupied by the end material J is larger than the actual product M.
[0013]
Here, the importance of expelling the gas generated in the runner R as well as exhausting the gas generated in the core K forming the product M emerges. If the gas generated in the runner R can be quickly discharged, the filling pressure of the molten material when filling from the nozzle N can be reduced, and if the resistance to filling by the gas pressure is attenuated, the contents of the runner R Since the product can be reduced, the volume of the end material J can be reduced accordingly, and the amount of material used can be saved, thereby reducing the manufacturing cost.
[0014]
In FIG. 15, it is preferable to install a gas venting device at an appropriate position of the end portion A of the runner R, the end portion C of the sprue S, and the runner R between the end portion A of the runner R and the sprue S, respectively. However, when a specific explanation is given regarding these devices, when a gas venting device is applied to the end A of the runner R, the end A of the flow path through which the filling material of the runner R travels as shown in FIG. The plug chamber V that continuously opens the runner R to the outside is installed, and the plug 1 that is a gas venting device according to the present invention is embedded in the plug chamber V , whereby the gas generated in the runner R is shown in FIG. The notch 2 of the plug 1 shown can be led to the gas vent groove 4 through the narrow portion 3 and discharged from the gas vent groove 4 to the outside atmosphere of the fixed mold G.
[0015]
3 and 4 is a knurled portion provided on the outer peripheral surface of the plug 1, and in the case of this embodiment structure, the plug chamber V is directly opened to the outside atmosphere. Therefore, the plug 1 is manufactured by adapting the outer diameter of the plug 1 to the inner diameter of the plug chamber V, and the plug 1 is driven into the plug chamber V and fixed by providing the knurled portion 5 on the outer peripheral surface of the plug 1. The format can be adopted. FIG. 5 is an enlarged cross-sectional view of the plug 1 portion showing a part of FIG. FIG. 13 and FIG. 14 show a modification of the plug 1 shown in FIG. 4. In these examples, the cylindrical plug 1 has two sets of notches 2, narrow portions 3 and gas vent grooves 4. It is drilled at intervals of degrees.
[0016]
FIG. 6 shows a plug 1a in the case of degassing from the end C of the sprue S described above. In this case, since there is a slight structural difference from the venting of the end of the runner R, it is desirable to make a slight change to the structure of the plug 1a. The difference between the two is that it is often difficult to open the end of the sprue S directly to the outside atmosphere because of the structure of the mold. Therefore, the plug chamber Va continuing to the sprue S is opened to the exhaust passage Vb. The plug 1a is inserted into the plug chamber Va from the opening toward the sprue S portion. In this case, since the wall surface W of the exhaust passage Vb faces the opening of the plug chamber Va, the plug 1a can be fixed in the plug chamber Va using the wall surface W. Further, the plug 1a to be inserted is provided with two each of the notch part 2, the narrow part 3 and the gas vent groove 4 as shown in FIG.
[0017]
The structure of this plug 1a is that a protrusion 6 is provided at the end of the plug 1a having a circular cross section, and a notch 2, a narrow portion 3 and a gas vent groove 4 are formed in the outer peripheral surface of the plug 1a. Is the same as in the above-described embodiment. However, in this embodiment, since the plug 1a needs to slide in the plug chamber Va, the outer peripheral surface is not knurled.
[0018]
The shape of the plug 1 or the plug 1a is not limited to the two illustrated examples. As shown in FIGS. 13 and 14, a plurality of sets of cutout portions 2, narrow portions 3 and The gas vent groove 4 may be drilled and installed, or a plurality of sets of cutout portions 2 of the plug 1a may be provided as only one set.
[0019]
An embodiment in which the concepts of the two embodiments described above are summarized into a more refined form will be described with reference to FIGS. In the two embodiments, the plug 1 or the plug 1a is inserted into the plug chamber V or the plug chamber Va drilled in the molding die, and the notch 2 is formed between the inner wall of the plug chamber and the outer peripheral surface of the plug. The part 3 and the gas vent groove 4 are established, but in such a system, the design is slightly changed for each location of the mold where the gas venting device is installed, for example, the plug 1 is attached to the plug 1 and the plug As in the case of 1a, unnecessary labor and complicated number of parts are required.
[0020]
By standardizing the plug so that the same parts can be installed in any place, it is possible to save such troubles. Was devised. In the embodiment shown in FIG. The outer cylinder 7 is formed with a truncated cone-shaped lumen 9, and the top 8 inserted into the lumen 9 adopts a truncated cone shape or a cone shape. A notch 2 similar to that in the previous embodiments is formed in a portion corresponding to the bottom surface 8a such as a truncated cone shape of the top 8, and a narrow portion 3 and a gas vent groove 4 are installed from there toward the apex direction of the cone. When the piece 8 is inserted into the lumen 9 of the outer cylinder 7, the tip of the piece 8 protrudes from the opening at the end of the lumen 9 at a position where the piece 8 is accommodated in the outer cylinder 7. The relationship as shown in FIG. 8 is obtained between the cylinders 7.
[0021]
FIG. 9 is a perspective view of FIG. 8, and the truncated cone shape indicated by the lumen 9 of the outer cylinder 7 and the truncated cone shape of the top 8 are similar to each other, and the diameter of the bottom surface of the top 8 is the bottom surface of the lumen 9. When the frame 8 is inserted into the lumen 9, the gap 10 is formed near the bottom surface of the lumen 9 as shown in FIGS. 8 and 9. The shape of the top 8 is as shown in FIG. 10 and FIG. 11. The notch portion 2 is provided on the bottom surface 8a, and the narrow portion 3 and the gas vent groove 4 are subsequently formed. Note that four cutout portions 2, narrow portions 3 and gas vent grooves 4 are provided on the outer peripheral surface of the frame 8 at intervals of 90 degrees.
[0022]
For example, the plug formed in this way is installed at the end of the sprue S portion as shown in FIG. 7, and the cavity is movable so that the opening of the bottom surface of the lumen 9 of the outer cylinder 7 is continuous with the sprue S portion. The outer cylinder 7 is embedded in the mold F, and the frame 8 is inserted into the inner cavity 9 thereof. The apex portion of the truncated cone formed by the inner cavity 9 of the outer cylinder 7 is opened to the exhaust passage Vb as an opening having a smaller area than the bottom surface, and the end of the top 8 inserted into the inner cavity 9 is slightly exposed to the exhaust passage Vb. Protruding. When the material is filled from the nozzle N in the state of FIG. 7, the generated gas flows into the cutout portion 2 formed between the wall surface of the inner cavity 9 of the outer cylinder 7 and the top 8 and is narrowed by the narrow portion 3. While being depressurized, it is quickly discharged to the gas vent groove 4, and when it flows out to the exhaust flow path Vb, it is also depressurized and discharged almost instantaneously from the exhaust flow path Vb to the outside of the mold.
[0023]
The advantage of this embodiment is that if the number of shots of filling increases and wear or damage of the notch 2 or the like occurs, all can be updated by simply replacing the frame 8, and the inside of the outer cylinder 7 If the frustoconical shape that the cavity 9 exhibits and the truncated cone that the frame 8 exhibits are similar, the height of the frame 8 can be freely selected, so that it can be freely designed according to the length of the required sprue S Should. Further, in this embodiment, the frame 8 having a truncated cone shape and the inner cavity 9 of the outer cylinder 7 are described. However, these are not limited to the truncated cone shape, and any polygonal truncated pyramid shape can be used. Don't wait.
[0024]
The conceptual diagram shown in FIG. 16 to FIG. 19 is an example in which a gas venting device is installed in addition to the end portion A of the runner R and the end portion C of the sprue S described so far. An example in which two plugs 1 are further added to the runner R between the end A of the runner R is shown. 16 is a state in which filling of material is started, FIG. 17 is a state in which material is filled from the nozzle N to the entrance of the runner R, FIG. 18 is a state in which the filled material proceeds to the end A of the runner R, Reference numeral 19 denotes a state in which the filled material reaches the pin gate P and is filled in the core K. At any point in time, any of the gas venting devices operates to discharge the generated gas from the runner R. To do. Instead of the plug 1, it is optional to use a plug constituted by the outer cylinder 7 and the frame 8 described in the embodiment.
[0025]
Conventionally, when filling is started, the generated gas reaches the pin gate P from the runner R, flows into the core K and is discharged for the first time there, so the generated gas inside the runner R cannot be discharged instantaneously, In the runner R, a gas pressure that is not low is resident, and the generated gas is discharged from the core K by being pushed by the pressure of the filling material. According to the present invention, the generated gas is generated in the core K. Since the gas is quickly and surely discharged to the outside prior to the progress of the filling material, the filling material filled in the runner R runs smoothly in the runner R without being subjected to the resistance of the gas pressure, and directly from the pin gate P. It is fed into the core K.
[0026]
【The invention's effect】
According to the present invention, since degassing is performed before reaching the core K, the filling material in the runner R can proceed without losing the filling pressure. Therefore, the material uneconomical due to the generation of the end material J can be completely removed, and the amount of gas to be degassed in the core K can be greatly reduced. In addition, there is an effect that the influence of the gas on the finished product formed with the core K can be almost certainly removed.
[Brief description of the drawings]
FIG. 1 is a conceptual cross-sectional view showing a state before material filling of an injection molding machine.
FIG. 2 is a conceptual cross-sectional view showing a state of separation of the mold after the material is filled in FIG. 1;
FIG. 3 is a sectional view of a mold in which a gas venting device according to the present invention is installed at an end of a runner.
FIG. 4 is a perspective view of a pin of a first example used in the present invention.
FIG. 5 is a partially enlarged cross-sectional view of the apparatus shown in FIG.
FIG. 6 is a cross-sectional view of a mold in which a gas venting device according to the present invention is installed at the end of a sprue by using a pin of a second example.
FIG. 7 is a sectional view of a mold in which a gas venting device according to the present invention is installed at the end of a sprue by using a pin of a third example.
FIG. 8 is a cross-sectional view of a pin of a third example.
FIG. 9 is a perspective view of a pin of a third example.
FIG. 10 is a bottom view of a pin piece of a third example;
FIG. 11 is a plan view of a pin top of a third example.
FIG. 12 is a side view of a pin top of a third example.
FIG. 13 is a perspective view showing the deformation of the pin of the first example.
14 is a plan view of the pin shown in FIG.
FIG. 15 is a conceptual slope view showing a relationship between a runner and a product in injection molding.
FIG. 16 is a conceptual diagram showing a relationship between a runner and a gas venting device, and is a cross-sectional view showing a stage before material filling.
FIG. 17 is a conceptual diagram showing the relationship between a runner and a gas venting device, and is a cross-sectional view showing an initial stage of material filling.
FIG. 18 is a conceptual diagram showing the relationship between a runner and a gas venting device, and is a cross-sectional view showing a middle stage of material filling.
FIG. 19 is a conceptual diagram showing a relationship between a runner and a gas venting device, and is a cross-sectional view showing a stage of material filling completion.
[Explanation of symbols]
1 Pin 2 Notch 3 Narrow part 4 Degassing groove 5 Knurling part 6 Knurl 7 Outer cylinder 8 Top 9 Inner cylinder lumen 10 Gap R Runner S Spru J End material N Nozzle

Claims (1)

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 narrowed portion where the cross-sectional area other than the plug with respect to the cross-sectional area of the plug chamber is narrowed And a gas venting device in injection molding, in which one or more plug chambers are installed in a runner of a mold for injection molding by continuously drilling gas venting grooves .

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