Venting pin and molding method using venting pin

Abstract

To provide a venting pin with suppressed failure occurrence in a molding, and a resin molding method with suppressed failure occurrence in a molding using the venting pin.SOLUTION: A venting pin for discharging a gas generated in a mold cavity on injection molding to the outside includes a sleeve arranged in a manner that an opening is inserted in the mold cavity to become a passage to release the gas and a pin body arranged energized to the opening in the sleeve and constituted so as to block the opening by being pushed into the sleeve, wherein the pin body is provided with a head arranged in the mold cavity in the open state and having an outer peripheral side tilted to an axis direction center of the pin body at a marginal part of the exposed part to the mold cavity of the pin body.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a gas vent pin in injection molding for manufacturing a product by filling a molten resin member into a mold, and a molding method using the gas vent pin.

Background Art

[0002] In injection molding, when a multi-point gate is provided, air is trapped at the junction where the molten resin injected into the cavity of the mold from each gate merges within the cavity. Since the trapped air is formed as bubbles as it is, defects occur in the molded product. In addition, since molten resins such as polycarbonate have low fluidity, when heated to a high temperature to improve the filling property of a thin-walled cavity, the heated molten resin generates gas within the cavity. The gas in the cavity causes problems such as cloudiness and deformation in the molded product. Since such gas and air cause defects in the molded product, they are discharged outside the mold during injection molding.

[0003] For example, Patent Document 1 discloses a molding apparatus that provides an air passage in the cavity that can be opened and closed by an air cylinder to release gas to the outside, and closes the air passage before the molten resin reaches the air passage.

[0004] Also, sometimes a gas vent pin is used without using power such as an air cylinder. As a conventional gas vent pin, there is one having a sleeve and a pin body disposed within the sleeve, and the gap between the sleeve and the pin body serves as a ventilation passage for releasing gas. The pin body is disposed biased by an elastic member toward the cavity, and when the molten resin flows through the cavity and pushes the pin, the pin is pushed into the sleeve and the air passage is closed. Therefore, an operation for opening and closing the ventilation passage is unnecessary, and there is no need to match the timing of opening and closing.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, in the gas vent pin having the above structure, molten resin enters the vent passage from the cavity during gas discharge, and there is a problem that the gas venting performance deteriorates due to the resin member adhering to and solidifying in the vent passage. When the gas venting performance deteriorates, gas burns and burrs occur in the resin molded product, resulting in defective products.

[0007] The present invention has been made in view of the above problems, and provides a gas vent pin that suppresses the occurrence of defects in a molded product, and a resin molding method that suppresses the occurrence of defects in a molded product using the gas vent pin. MEANS FOR SOLVING THE PROBLEMS

[0008] In one aspect of the present invention, in a gas vent pin for discharging gas generated in a cavity during injection molding to the outside, a sleeve that is disposed by inserting an opening into the cavity and serves as a passage for releasing the gas, and the sleeve is biased toward the opening and disposed therein, and is configured to close the opening by being pushed into the sleeve. A pin body for opening and closing the opening is provided, and the pin body is disposed in the cavity in an open state, and a head having an outer peripheral side surface inclined toward the axial center of the pin body is provided at an edge of the exposed portion of the pin body in the cavity. A gas vent pin configured as described above is provided.

[0009] According to the above aspect, when the molten resin reaches the gas vent pin, it first contacts the outer peripheral side surface and pushes the pin body downward into the sleeve. As a result, the opening is closed by the pin body, and the vent passage through which the gas escapes is blocked. Before the molten resin enters the vent passage, the air passage is closed by the molten resin. Therefore, it is possible to suppress the molten resin from entering the passage and solidifying, and the deterioration of the gas venting performance.

[0010] Also, in certain embodiments, a second sleeve is further provided which has a through-hole formed therein and in which the sleeve is inserted through the through-hole. At least one microgroove is formed along the extending direction of the sleeve on the outer peripheral side surface of the second sleeve or the outer peripheral side surface of the sleeve to form a passage for releasing the gas, thereby constituting a gas vent pin. According to this embodiment, the passage for releasing the gas is increased, and the gas discharge capacity of the gas vent pin is improved.

[0011] Also, in certain embodiments, a plurality of the microgrooves are formed in the circumferential direction on at least one of the outer peripheral side surface of the second sleeve or the outer peripheral side surface of the sleeve. According to this embodiment, the passage for releasing the gas is increased, and the gas discharge capacity of the gas vent pin is further improved.

[0012] Also, according to certain embodiments, the radial width of the microgroove with respect to the through-hole is configured to be more than 0 mm and 0.04 mm or less. The molten resin cannot pass through, only the gas can pass through, and there is no need to provide an opening / closing mechanism at the opening.

[0013] Also, in certain embodiments of the present invention, a mold is provided which includes a sleeve that is disposed by inserting an opening into a cavity and serves as a passage for releasing gas, and a pin body that is disposed in the sleeve and biased toward the opening and is configured to close the opening by being pushed into the sleeve. The pin body is disposed in the cavity in an open state, and a head having a circumferential side surface that inclines toward the axial center is provided at an edge of the exposed portion of the pin body in the cavity. When molten resin is poured into the cavity, the molten resin pushes the head of the pin body into the sleeve when passing through the opening of the sleeve, thereby closing the opening, and a molding method is provided.

[0014] When the molten resin reaches the gas vent pin and abuts against the outer peripheral side surface, the pin body is pushed downward into the sleeve. As a result, the opening is closed by the pin body, and the vent passage through which the gas escapes is blocked. Before the molten resin enters the vent passage, the air passage is closed by the molten resin, suppressing the occurrence of defects.

[0015] Also, in one aspect, the gas vent pin is provided with a through hole on the inside, and further includes a second sleeve disposed by inserting the sleeve into the through hole. The second sleeve has at least one fine groove formed along the extending direction of the sleeve on the outer peripheral side surface or the inner peripheral side surface of the through hole, serving as a passage for releasing the gas. When the molten resin is poured into the cavity, the molding method is configured such that only the gas in the cavity passes through the fine groove. According to this aspect, the passages for releasing the gas increase, and the gas discharge capacity of the gas vent pin is further improved.

[0016] Also, in one aspect, at least one of the fine grooves is arranged to be on the downstream side of the flow of the molten resin from the opening, and is configured such that at least one of the fine grooves allows the gas in the cavity to pass even after the pin body closes the opening. According to this aspect, since the gas can pass through the fine groove even after the opening is closed by the pin body, the gas in the cavity can be more discharged outside the mold.

Advantages of the Invention

[0017] As is clear from the above description, it is possible to provide a gas vent pin that suppresses the occurrence of defects in a molded product, and a resin molding method that uses the gas vent pin and suppresses the occurrence of defects in a molded product.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0019] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The embodiments are illustrative and not restrictive, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention. Also, in the following descriptions of the embodiments and modified examples, the same components are denoted by the same reference numerals, and redundant descriptions are omitted as appropriate.

[0020] (Extension member) As a molded product using the mold according to a preferred embodiment of the present invention, the extension member 20 will be described. Fig. 1 is a schematic front view of the vehicle lamp 10 including the extension member 20. Fig. 2 is a front perspective view (perspective view showing the front side) and a rear perspective view (perspective view showing the back side) of the extension member 20. Fig. 3 is a front view and a rear view of the extension member 20.

[0021] The vehicle lamp 10 is a combination lamp having two lamps. As shown in FIG. 1, the vehicle lamp 10 includes a lamp body 12 and a lamp cover 14. The lamp body 12 is formed in a box shape with an open front. The lamp cover 14 is formed of a resin or glass having translucency, and is attached to the front opening of the lamp body 12 to form a lamp chamber. Inside the lamp chamber, two lamp units LU1, LU2 for forming a predetermined light distribution, and an extension member 20 are accommodated.

[0022] The extension member 20 has two large molded product openings 28, 29 formed on the inside. The lamp units LU1, LU2 are arranged on the back surface of the extension member 20 with optical members such as reflectors and projection lenses for irradiating light forward exposed to the molded product openings 28, 29. The extension member 20 is arranged in front of the lamp units LU1, LU2, and is a light shielding material that covers the gaps between the lamp units LU1, LU2 and the lamp body 12, and the gaps between the adjacent lamp units LU1, LU2 so that the internal structures of the lamp units LU1, LU2 are not visible from the outside.

[0023] As shown in FIGS. 2 and 3, the extension member 20 has an outer shape that is pentagonal in front view, and is formed by connecting five sides and a bridge 26 having a certain predetermined width. Specifically, the extension member 20 includes an upper side 21 which is the longest side, a lower side 22 having a length about half of that of the upper side 21 and configured in parallel with the upper side 21, a right side 23 which is a hypotenuse connecting the right end of the upper side 21 and the right end of the lower side 22, a left side 24 extending vertically downward from the left end of the upper side 21, and a lower left side 25 which is a hypotenuse connecting the lower end of the left side 24 and the left end of the lower side 22. The extension member 20 further includes a bridge 26 that vertically connects the connection portion between the lower side 22 and the right side 23 and the upper side 21.

[0024] The extension member 20 is a thin-walled injection molded product, and is composed of PBT (polybutylene terephthalate) resin, polypropylene resin, polyester resin, colored polycarbonate resin, and the like.

[0025] As shown in FIG. 3, on the wall surfaces at approximately the central positions of the upper side 21 and the lower side 22 of the extension member 20, gate marks GM are formed. That is, gates are provided in the mold of the extension member 20 corresponding to the above positions.

[0026] Two large molded product openings 28 and 29 are formed in the extension member 20, and the cavity of the mold for molding the extension member 20 has two large ring shapes that share a part. During injection molding, the molten resin circulates in the ring-shaped cavity and merges at a certain location. Air is trapped at this merging location and is molded as bubbles as it is, so problems such as weld lines may occur.

[0027] Also, for example, a colored polycarbonate resin is used as a component of the extension member 20. Since molten resins such as polycarbonate have low fluidity, when heated to a high temperature to improve the filling property of the thin-walled cavity, the heated molten resin generates gas in the cavity. Especially in recent years, due to the demand for weight reduction of resin molded products, the resin molded products are made thinner and the multi-point gate method is adopted in the mold to increase the fluidity of the molten resin, and gas is likely to be generated from the molten resin into the cavity. The gas in the cavity remains and adheres to the molded product, causing problems such as cloudiness and deformation. Hereinafter, the gas that should be discharged from the cavity to the outside in this way is referred to as gas. Since gas is a cause of defects in the molded product, it is necessary to provide a gas vent pin in the mold to discharge the gas outside the mold.

[0028] Gas vent pin marks PM are formed on the back sides at approximately the central positions of the right side 23, the left side 24, and the bridge 26 of the extension member 20, respectively. That is, gas vent pins are provided at the corresponding positions in the mold of the extension member 20. By providing gas vent pins in the mold of the extension member 20, the gas in the cavity is discharged from the gas vent pins outside the mold during molding, and the occurrence of defects such as gas burns and weld lines is suppressed.

[0029] (Mold of the extension member) Figure 4 shows the mold 80 of the extension member 20. Figure 4 is a cross-sectional view of the mold cut at a position corresponding to the line IV-IV in Figure 3. The cutting line passes through the gate mark GM and the vent pin mark PM.

[0030] The mold 80 has a fixed-side mold 81 and a movable-side mold 82. The fixed-side mold 81 and the movable-side mold 82 are arranged facing each other and clamped together, and are configured to form a cavity C corresponding to the extension member 20 therebetween.

[0031] The movable-side mold 82 is provided with a gate G. The fixed-side mold 81 is provided with a vent pin 1 as a nested structure.

[0032] As shown in Figure 4, in order to stably arrange the gate during injection molding, the cavity C includes an additional portion CC, and the gate G is arranged with the injection port Ga opening into the additional portion CC. The molten resin is injected from the gate G into the cavity C, fills the cavity C, solidifies by cooling, and when removed from the mold 80, the resin formed in the additional portion CC is cut off. The mark of this cutting becomes the gate mark GM.

[0033] (Vent pin) Figure 5 shows the vent pin 1. Figure 5(A) is a longitudinal sectional view of the vent pin 1. Figures 5(B) and 5(C) are enlarged views of part B in Figure 5(A). Figure 5(B) shows the open state of the vent pin. Figure 5(C) shows the closed state of the vent pin.

[0034] As shown in Figure 5, the vent pin 1 has a substantially cylindrical sleeve 50, a pin body 60 inserted through the inner hole 51 of the sleeve 50, and a spring 70 that biases the pin body 60.

[0035] The sleeve 50 is a path for the gas to escape to the outside. Therefore, the gas vent pin 1 is disposed in the mold 80 by connecting one opening 54 of the sleeve 50 to the cavity C of the mold and the other opening 55 to the outside air, thereby connecting the cavity C and the outside air and discharging the gas generated in the cavity C to the outside of the mold 80.

[0036] The pin body 60 is a valve for opening and closing the opening 54 of the sleeve 50. It is inserted into the inner hole 51 of the sleeve 50 and moves forward and backward in the extending direction of the inner hole 51 to open and close the opening 54.

[0037] The pin body 60 has a cylindrical shaft body 61, a head 69 provided at the tip of the shaft body 61, a lid portion 62, and a pressing portion 63 provided above the lid portion 62. The head 69 has a larger diameter than the shaft body 61 and is disposed in the opening 54 communicating with the cavity C. The lid portion 62 has an inverted frustum shape with a diameter increasing toward the tip. The lid portion 62 has a larger diameter than the shaft body 61 even at the base end side with the smallest diameter. The pressing portion 63 has a frustum shape with a diameter decreasing toward the tip. That is, the outer peripheral side surface of the lid portion 62 is inclined in a direction away from the axial center of the pin body 60 (i.e., outward), and the outer peripheral side surface of the pressing portion 63 is inclined in the opposite direction, toward the axial center of the pin body 60 (i.e., inward). The maximum diameters of the lid portion 62 and the pressing portion 63 are the same, the upper and lower edges of the lid portion 62 coincide, there is no step in the cross section of both, and in the longitudinal section, it is in a mode of bending at the joint portion. For this reason, the head 69 has a double frustum shape that becomes thicker toward the tip but then becomes thinner further toward the tip.

[0038] The shaft body 61 has a smaller diameter than the inner hole 51 of the sleeve 50. When the pin body 60 is inserted into the sleeve 50, a gap is formed between the outer peripheral side surface of the pin body 60 and the inner peripheral surface of the sleeve 50. This gap is the ventilation path through which the gas actually passes.

[0039] In the vicinity of the opening 54 communicating with the cavity C, the inner hole 51 of the sleeve 50 has a funnel shape in which the inner wall is shaved and gradually thinned, so that the diameter increases toward the outlet portion. The inclination angle of the funnel portion 52 of the inner hole 51 is the same as the inclination angle of the outer peripheral surface of the lid portion 62. When the pin body 60 moves forward and backward, the lid portion 62 comes into contact with and adheres to the funnel portion 52, and the opening 54 is closed.

[0040] On the side of the opening 55 communicating with the outside air of the sleeve 50, there is an enlarged diameter portion 53 whose diameter increases, and a spring 70 is disposed in this enlarged diameter portion 53. The spring 70 is attached near the tip end portion on the side opposite to the head portion 69. When the gas vent pin 1 is disposed in the mold 80, the opening 55 of the enlarged diameter portion 53 is covered by the receiving plate 83 (see FIG. 4). Since the receiving plate 83 closes the opening 55 while compressing the spring 70, the spring 70 biases the pin body 60 toward the opening 54. Note that the opening 55 is not completely sealed by the receiving plate 83, and a part thereof is open and communicates with the outside air.

[0041] The pin body 60 opens and closes the opening 54. As shown in FIG. 5(B), in the normal state, due to the biasing force F1 of the spring 70, the pin body 60 is pushed up, and the head portion 69 is disposed apart from the opening 54. Specifically, the lid portion 62 is disposed apart from the funnel portion 52. A gap is formed between the pin body 60 and the sleeve 50, and the opening 54 is in an open state.

[0042] In a state where the opening 54 is open, the pressing portion 63 is configured to protrude from the opening 54. The lid portion 62 does not protrude from the opening 54 and remains in the inner hole 51. That is, when the opening 54 is in an open state, not the entire pressing portion 63 protrudes from the opening 54, but a part of the tip end side becomes an exposed portion exposed to the cavity C.

[0043] As shown in FIG. 5(C), when a force F2 equal to or greater than the biasing force F1 of the spring 70 is applied to the pin body 60 in a direction opposite to the biasing force F1 of the spring 70, the pin body 60 is pushed down, the gap between the lid portion 62 and the funnel portion 52 gradually becomes smaller, and finally the lid portion 62 abuts against the funnel portion 52. The outer peripheral surface of the lid portion 62 is in close contact with the inner peripheral surface of the funnel portion 52, and the opening portion 54 is in a closed state.

[0044] With the opening portion 54 closed, the pressing portion 63 slightly protrudes from the opening portion 54, but the pressing portion 63 may also be held within the inner hole 51.

[0045] (Molding process) An injection molding method using the gas vent pin 1 configured as described above will be described. FIG. 6 is a partial view of FIG. 4 and shows the molding process using the gas vent pin 1. In FIG. 6, the resin is shown colored in light ink.

[0046] When the gas vent pin 1 is incorporated into the mold 80, it is disposed in the mold 80 as an insert, and the end of the gas vent pin 1 is configured as a part of the molding surface that partitions the cavity C (see FIG. 4).

[0047] FIG. 6(A) shows the state before the molten resin is injected into the cavity C. The pin body 60 is biased by the spring 70, the opening portion 54 is open, and is in communication with the cavity C. At least a part of the pressing portion 63 is disposed so as to protrude from the opening portion 54 into the cavity C.

[0048] As shown in FIG. 6(B), when the molten resin is injected into the cavity C from the gate G, the molten resin flows in the cavity C. The molten resin heated to a high temperature generates gas GAS in the cavity. Downstream of the molten resin flowing in the cavity C, the gas GAS is discharged to the outside through the air passage of the gas vent pin 1.

[0049] As shown in Fig. 6(C), the flowing molten resin reaches the vent pin 1 and contacts the pressing portion 63 protruding into the cavity C. The outer peripheral side surface of the pressing portion 63 is inclined inward. In other words, the outer peripheral side surface of the pressing portion 63 is inclined from the orthogonal direction to the flowing direction with respect to the flowing direction of the molten resin. Therefore, the force pressing the pressing portion 63 acts obliquely downward in the front direction rather than in the flowing direction. When the flowing molten resin contacts the pressing portion 63, it flows straight forward and pushes down the pressing portion 63.

[0050] As shown in Fig. 6(D), the pin body 60 is pushed down against the biasing force of the spring 70 applied to the pin body 60 by the flowing molten resin, the lid portion 62 is in close contact with the funnel portion 52, and the opening 54 is closed. When the molten resin contacts the pressing portion 63, it directly pushes down the pin body 60, so that the opening 54 is immediately closed, and the inflow of the molten resin into the air passage of the gas is suppressed. Thereby, the generation of burrs on the molded product and the adhesion of the resin to the inner peripheral surface of the sleeve 50, which cause problems in opening and closing, are suppressed.

[0051] As shown in Fig. 6(E), since the opening 54 is closed by the pin body 60, the molten resin does not enter the vent passage through which the gas escapes, and the molten resin flows as it is and is filled into the cavity C. In the state where the opening 54 is closed, the molten resin is cooled.

[0052] As shown in Fig. 6(F), when the molten resin is completely cooled and solidified and the extension member 20 is molded, the mold 80 is opened and the extension member 20 is taken out of the mold 80. When the extension member 20 is removed, the force pressing the pin body 60 disappears, so that the pin body 60 is pushed up by the biasing force of the spring 70 and the opening 54 returns to the open state.

[0053] (Function and Effect) To explain the function and effect of the gas vent pin 1, first, the molding process using the conventional gas vent pin 901 will be described. FIG. 7 is a comparison diagram showing the conventional molding process and shows the injection molding process using the conventional gas vent pin 901. FIG. 7 corresponds to FIG. 6. In FIG. 7, the resin is shown in color.

[0054] As shown in FIG. 7(A), the conventional gas vent pin 901 is provided in a mold 980 having a fixed-side mold 981 and a moving-side mold 982, and is inserted into the cavity C2 with an opening 954 communicated therewith. The conventional gas vent pin 901 has the same configuration as the gas vent pin 1 except that it has a hanging portion 964 instead of the pressing portion 63. Specifically, the conventional gas vent pin 901 includes a sleeve 950, a shaft body 961, and a lid portion 962, which are equivalent to the sleeve 50, the shaft body 61, and the lid portion 62. The opening 954 communicating with the cavity C2 is opened and closed by the forward and backward movement of the pin body 960 biased by a spring (not shown).

[0055] The hanging portion 964 is thinner and smaller than the pressing portion 63, has the shape of a flat inverted frustum of a cone, and is provided at the center of the upper surface of the lid portion 962 having the shape of an inverted frustum of a cone.

[0056] As shown in FIG. 7(B), when the molten resin is injected into the cavity C2 from the gate G, the molten resin flows in the cavity C2. The molten resin heated to a high temperature generates gas GAS in the cavity. The gas GAS generated in the cavity C2 is discharged to the outside through the air passage of the conventional gas vent pin 901 (the gap between the inner hole 951 of the sleeve 950 and the pin body 960).

[0057] As shown in FIG. 7(C), the molten resin reaches the pin body 960. The upper surface of the lid portion 962 is flush with the upper surface of the sleeve 950 or is disposed below the upper surface of the sleeve 950. The force by which the molten resin moves is applied in the direction of flowing through the cavity C2 and does not act much on the lid portion 962 whose upper surface is arranged in parallel in the flowing direction. The force that attempts to push down the pin body 960 is not large enough to counteract the biasing force of a spring (not shown). Therefore, even if the molten resin reaches the lid portion 62 and contacts the upper surface of the lid portion 62, the pin body 960 does not move.

[0058] As shown in FIG. 7(D), when the molten resin reaches the engaging portion 964, the force for the molten resin to advance forward is applied to the circumferential side surface of the engaging portion 964, and the pin body 960 starts to be pushed down. During this time, the opening 954 remains open, and the molten resin may enter the gap (vent passage) between the pin body 960 and the inner hole 951. When the cavity C2 is filled, an internal pressure is also applied inside the cavity C2, and the pin body 960 is pushed down and the opening 954 is closed. However, until it is completely closed, the resin may further enter the vent passage.

[0059] As shown in FIG. 7(E), with the molten resin filled in the cavity C2 and the opening 954 of the inner hole 951 closed by the lid portion 962, the molten resin is cooled.

[0060] As shown in FIG. 7(F), when the resin is completely cooled and the extension member 920 is formed, the mold 980 is opened, and the extension member 920 is taken out from the mold 980. The step between the sleeve 950 and the pin body 960 with the opening 954 closed by the lid portion 962 is formed on the extension member 920 as a vent pin mark 921.

[0061] The molten resin that enters the vent passage before the pin body 960 is pushed down is formed as burr 922 on the molded extension member 920, or adheres to and remains on the inner hole 951 or the pin body 960 as residual resin 923. The burr 922 causes molding defects, and the residual resin 923 cannot seal the air passage, reducing the gas venting performance.

[0062] In this way, the molten resin that enters the vent passage becomes burr 922 or residual resin 923, causing defects in the extension member 920, which is a molded product, and the mold 980.

[0063] On the other hand, in the present embodiment, the pressing portion 63 has a frustum shape, the bottom surface has the same shape as and is shared with the upper surface of the lid portion 62, and since it protrudes most in the outer peripheral direction with the pin body 60 and protrudes from the opening 54 into the cavity C, when the molten resin flowing in the cavity C reaches the gas vent pin 1, it first contacts the pressing portion 63. For this reason, the force F2 for pushing down the pin body 60 is applied when the molten resin reaches the pin body 60, and the opening 54 is closed earlier than in the case of the conventional pin body 960. By providing the pressing portion 63, the timing at which the pin body 60 is pushed down can be made earlier than before, and the entry of the molten resin into the air passage can be suppressed. Thereby, the occurrence of defects in the molded product is suppressed.

[0064] Also, the pressing portion 63 has a larger volume than the engaging portion 964 and protrudes more greatly into the cavity C. When the molten resin passes through the gas vent pin 1, the passage becomes narrower by the amount of the pressing portion 63, so the pressure increases, and the force for pressing the molding surface defining the cavity C also increases. Specifically, since the force with which the molten resin presses the outer surface of the pressing portion 63 and the cavity surface of the movable mold 82 facing the pressing portion 63 becomes larger than before, the pin body 60 is pushed down earlier.

[0065] If the outer peripheral side surface of the pressing portion 63 is a vertical surface, since it is orthogonal to the flow direction of the molten resin, it becomes a wall surface for retaining the molten resin, and the force pushing the pin body 60 does not act downward. Instead, it guides the molten resin to the ventilation path. For this reason, it is preferable that the outer peripheral side surface of the pressing portion 63 is inclined inward. The height and inclination angle of the pressing portion 63 are not limited as long as the outer peripheral side surface is inclined inward. Also, if the pin body 60 moves and the opening portion 54 is closed when the molten resin abuts against the inclined outer peripheral side surface, the shape of the lid portion 62 is not limited.

[0066] The shape of the lid portion 62 and the inner hole 51 (funnel portion 52) that abuts against the lid portion 62 is not limited to this embodiment either. The pin body 60 inserted into the sleeve 50 is arranged in an open state such that the head portion 69 that closes the opening portion 54 protrudes into the cavity, and it is sufficient that the head portion 69 having an outer peripheral side surface inclined toward the axial center of the pin body 60 is provided at the outermost edge of the exposed portion exposed to the cavity C. For example, the pressing portion 63 may have a conical shape or a frustum of a pyramid shape.

[0067] (Second Embodiment) Another embodiment will be described with reference to the drawings. Those having the same configuration are denoted by the same reference numerals and detailed description thereof will be omitted. FIG. 8 shows a gas vent pin 101 according to the second embodiment. FIG. 8 shows a state in which the gas vent pin 101 is assembled to the fixed-side mold 81 of the mold 80, and the fixed-side mold 81 is also shown. FIG. 8(A) shows a top view of the gas vent pin 101. FIG. 8(B) shows a longitudinal sectional view of the gas vent pin 101. Note that the fixed-side mold 81 in FIG. 8(A) is shown by hatching to clarify the boundary with the gas vent pin 101.

[0068] As shown in FIG. 8, the gas vent pin 101 includes a first sleeve 150, a second sleeve 130, a pin body 60, and a spring 70.

[0069] The first sleeve 150 corresponds to the sleeve 50 of the gas vent pin 1, and in this embodiment, it is referred to as the first sleeve 150 in order to distinguish it from the second sleeve 130.

[0070] The gas vent pin 101 has the same configuration as the gas vent pin 1, except that it includes a second sleeve 130. The second sleeve 130 is configured in a substantially cylindrical shape, similar to the first sleeve 150, and the first sleeve 150 is inserted and disposed in the through-hole 131, which is an inner hole. Therefore, as shown in Fig. 8(A), when the gas vent pin 101 is viewed from above, the first sleeve 150 is disposed on the outer periphery of the pin body 60, and further, the second sleeve 130 is disposed on the outer periphery of the first sleeve 150, resulting in a double structure in the circumferential direction. In addition, since the second sleeve 130 is assembled into the mold hole 81b for assembly formed in the fixed-side mold 81, the fixed-side mold 81 is disposed on the outer periphery of the second sleeve 130. In this way, the pin body 60, the first sleeve 150, the second sleeve 130, and the fixed-side mold 81 are sequentially arranged in the circumferential direction.

[0071] Similar to the gas vent pin 1, the gas vent pin 101 is disposed in the mold 80 in communication with the cavity C and the outside air outside the mold. Specifically, in the gas vent pin 101, one opening 54 of the inner hole 51 of the first sleeve 150 communicates with the cavity C of the mold 80, and the other opening 55 communicates with the outside air and is disposed in the fixed-side mold 81. When the gas vent pin 101 is assembled into the mold 80, the inner hole 51 of the first sleeve 150 becomes a gas vent passage through which the gas escapes to the outside air.

[0072] The pin body 60 is a valve that opens and closes the opening 54 of the first sleeve 150. It is inserted and disposed in the inner hole 51 of the first sleeve 150 and moves forward and backward in the extending direction of the inner hole 51 to open and close the opening 54. The spring 70 biases the pin body 60 to push up the pin body 60 so that a gap is generated between the pin body 60 and the first sleeve 150. Due to the biasing force of the spring 70, the opening 54 is normally in an open state.

[0073] On the side surface of the outer periphery of the first sleeve 150 (hereinafter referred to as the first outer peripheral side surface 158), along the extending direction of the first sleeve 150, a first fine groove 159 with a very small depth D (the radial width when viewing the gas vent pin 101 from above, which is the radial width of the through hole 131) is formed. Similarly, on the side surface of the outer periphery of the second sleeve 130 (hereinafter referred to as the second outer peripheral side surface 138), a second fine groove 139 is formed along the extending direction of the second sleeve 130.

[0074] The first fine groove 159 is formed on the surface of the first outer peripheral side surface 158 with a depth D of about 0.04 mm. When the first sleeve 150 is inserted into the through hole 131 of the second sleeve 130, the first fine groove 159 is covered by the second inner peripheral side surface 136 which is the peripheral side surface of the through hole 131 of the second sleeve 130, and becomes a very small and elongated hole. One opening of the first fine groove 159 communicates with the cavity C, and the other opening communicates with the outside air outside the mold. The first fine groove 159 becomes a gap formed between the first outer peripheral side surface 158 of the first sleeve 150 and the second inner peripheral side surface 136 of the second sleeve 130.

[0075] During injection molding using the mold 80 provided with the gas vent pin 101, the gas generated in the cavity C is discharged to the outside of the mold through the first fine groove 159. Since the size of the cross-section of the first fine groove 159, particularly the depth D, is very fine, during injection molding, the molten resin does not enter the first fine groove 159, and only the gas, which is a gas, passes through the first fine groove 159. Thus, similar to the inner hole 51 of the first sleeve 150, the first fine groove 159 becomes a gas vent passage for discharging gas from the cavity C.

[0076] The second fine groove 139 is configured in the same manner as the first fine groove 159. The gas vent pin 101 is fitted and installed in the mold hole 81b of the mold 80 in the same manner as the gas vent pin 1. When the gas vent pin 101 is assembled to the mold 80, the open surface of the second fine groove 139 is covered by the inner peripheral side surface 81a of the mold hole of the mold hole 81b. One opening of the second fine groove 139 communicates with the cavity C, and the other opening communicates with the outside air outside the mold. The second fine groove 139 becomes a gap formed between the second outer peripheral side surface 138 of the second sleeve 130 and the inner peripheral side surface 81a of the mold hole of the fixed-side mold 81.

[0077] During injection molding using the mold 80 provided with the gas vent pin 101, the gas generated in the cavity C is discharged outside the mold through the second fine groove 139. The second fine groove 139, together with the inner hole 51 of the first sleeve 150 and the first fine groove 159, serves as a gas vent passage for discharging gas from the cavity C.

[0078] Similar to the first fine groove 159, the second fine groove 139 is formed on the surface of the second outer peripheral side surface 138 of the second sleeve 130 with a depth D of about 0.04 mm.

[0079] In the gas vent pin 101 assembled to the mold 80, since the depth D is very small, the first fine groove 159 and the second fine groove 139 are very narrow gaps. During injection molding, the molten resin does not enter the first fine groove 159 and the second fine groove 139, and only the gas, which is a gas, passes through the first fine groove 159 and the second fine groove 139. Since the molten resin does not enter the first fine groove 159 and the second fine groove 139 during injection molding either, an opening and closing mechanism is not provided at the communication portion with the cavity C in the first fine groove 159 and the second fine groove 139.

[0080] Fig. 9(A) shows the open state of the gas vent pin 101 assembled to the fixed-side mold 81. Fig. 9(B) shows the closed state of the gas vent pin 101 assembled to the fixed-side mold 81.

[0081] Similar to the gas vent pin 1, in the gas vent pin 101 as well, the pin body 60 opens and closes the opening 54. As shown in Fig. 9(A), in the normal state, due to the biasing force F1 of the spring 70, the pin body 60 is pushed upward, and the opening 54 is in an open state. At this time, the first microgroove 159 and the second microgroove 139 also communicate the cavity C with the outside air.

[0082] As shown in Fig. 9(B), when a force F2 greater than or equal to the biasing force F1 of the spring 70 is applied to the pin body 60 in a direction opposite to the biasing force F1 of the spring 70, the pin body 60 is pushed downward, the outer peripheral surface of the lid portion 62 is in close contact with the inner peripheral surface of the funnel portion 52, and the opening 54 is in a closed state. Even in this state, the first microgroove 159 and the second microgroove 139 are in a state where both openings communicate with the outside air.

[0083] Whether the opening 54 is in the open state or the closed state, the first microgroove 159 and the second microgroove 139 do not automatically open and close the openings and maintain the same state.

[0084] (Molding process using the gas vent pin 101) An injection molding method using a mold equipped with the gas vent pin 101 configured as described above will be described. Figs. 10 and 11 show the molding process using the gas vent pin 101. Figs. 10 and 11 correspond to Fig. 6. In Figs. 10 and 11, the resin is shown colored in light ink.

[0085] Similar to the gas vent pin 1, when the gas vent pin 101 is incorporated into the mold 80, it is arranged in the mold 80 as a nested structure, and the end portion of the gas vent pin 1 is configured as a part of the molding surface that partitions the cavity C.

[0086] Step (1) of FIG. 10 shows the state before the molten resin P is injected into the cavity C. The pin body 60 is biased by the spring 70, the opening 54 is open, and is in communication with the cavity C. At least a part of the pressing portion 63 protrudes from the opening 54 into the cavity C. The inner hole 51, the first fine groove 159, and the second fine groove 139 of the first sleeve 150 communicate with the outside air. At this time, the gas vent pin 101 is assembled such that in the flow direction of the molten resin, the first fine groove 159 and the second fine groove 139 are on the downstream side of the opening 54.

[0087] As shown in FIG. 10 (Step (2)), when the molten resin P is injected into the cavity C from the gate G, the molten resin P flows in the cavity C. The molten resin P heated to a high temperature generates gas GAS in the cavity. Downstream of the molten resin P flowing in the cavity C, the gas GAS is discharged to the outside through the inner hole 51, the first fine groove 159, and the second fine groove 139 as the air passage of the gas vent pin 101.

[0088] As shown in FIG. 10 (Step (3)), the flowing molten resin P reaches the gas vent pin 101 and contacts the pressing portion 63 protruding into the cavity C. The outer peripheral side surface of the pressing portion 63 is inclined inward. In other words, the outer peripheral side surface of the pressing portion 63 is inclined from the orthogonal direction to the flow direction of the molten resin P toward the flow direction. Therefore, the force pressing the pressing portion 63 acts obliquely downward forward instead of in the flow direction. When the flowing molten resin P contacts the pressing portion 63, it flows straight forward and pushes down the pressing portion 63.

[0089] As shown in Fig. 11 (Process 4), the pin body 60 is pushed down against the biasing force of the spring 70 applied by the flowing molten resin P, the lid portion 62 comes into close contact with the funnel portion 52, and the opening 54 is closed. When the molten resin P abuts against the pressing portion 63, since the pin body 60 is pushed down as it is, the opening 54 is immediately closed, and the inflow of the molten resin P into the inner hole 51 which is the air passage of the gas is suppressed. Even when the opening 54 is closed, the first fine groove 159 and the second fine groove 139 arranged downstream of the opening 54 communicate the cavity C with the outside air. The gas GAS is discharged to the outside through the first fine groove 159 and the second fine groove 139.

[0090] As shown in Fig. 11 (Process 5), the molten resin P flows as it is and is filled into the cavity C. Since the opening 54 is closed by the pin body 60, the molten resin P does not enter the inner hole 51 which is the ventilation passage for the gas to escape. The openings of the first fine groove 159 and the second fine groove 139 are very narrow, and the molten resin P does not enter, and the openings on the cavity C side are closed by the molten resin P. When the cavity C is filled with the molten resin P, the opening 54 is closed, and the first fine groove 159 and the second fine groove 139 are in a state where the openings with the cavity C are blocked by the molten resin P, and the molten resin P is cooled.

[0091] As shown in Fig. 11 (Process 6), when the molten resin P is completely cooled and solidified and the extension member 20 is formed, the mold 80 is opened, and the extension member 20 is taken out from the mold 80. When the extension member 20 is removed, the force pressing the pin body 60 disappears, so the pin body 60 is pushed up by the biasing force of the spring 70, and the opening 54 returns to the open state. In the first fine groove 159 and the second fine groove 139, the molten resin P (extension member 20) that blocked the opening with the cavity C is removed, and the cavity C communicates with the outside again.

[0092] (Function and Effect) The gas vent pin 101 is provided with a second sleeve 130, and the formation of the first microgroove 159 and the second microgroove 139 enables both of them to function as gas vent passages during injection molding, increasing the passages for discharging the gas during injection molding. As a result, the gas vent pin 101 has improved gas discharge capacity.

[0093] The depth D, which is the width of the cross-section, of the first microgroove 159 and the second microgroove 139 is extremely narrow, being 0.04 mm or less. Both of them function as gas vent passages, allowing gas to pass through and preventing the molten resin from passing through. The first microgroove 159 and the second microgroove 139 do not require an opening and closing mechanism, and the mechanism is simple.

[0094] As shown in FIGS. 10 and 11, when at least one of the first microgroove 159 and the second microgroove 139 is arranged on the downstream side of the flow of the molten resin P rather than the opening 54, even after the pin body 60 closes the opening 54, at least one of the microgrooves continues to allow the gas GAS in the cavity C to escape to the outside air. By using the gas vent pin 101, the gas trapped in the cavity C can be further reduced, and the occurrence of defective products during resin molding can be further reduced.

[0095] Since the first sleeve 150 is inserted into the through hole 131, which is the inner hole of the second sleeve 130, the outer diameter of the first sleeve 150 is configured to be slightly smaller than the diameter of the inner hole of the second sleeve 130. In this embodiment, the first sleeve 150 is configured to be slightly smaller as a whole so that the gap between the second inner peripheral surface 136 of the second sleeve 130 and the first outer peripheral surface 158 of the first sleeve 150 is uniformly 0.03 mm. Therefore, when the first sleeve 150 is inserted into the through hole 131 of the second sleeve 130, a gap is formed between them in the circumferential direction over the entire circumference and in the entire length in the extending direction. This gap also serves as a passage for the gas to escape during injection molding.

[0096] A first microgroove 159 is formed at a depth of 0.04 mm from the first outer peripheral surface 158 of the first sleeve 150. In the present embodiment, the clearance for inserting the second sleeve 130 is configured to be 0.03 mm, but the depth D of the first microgroove 159 does not include the clearance for fitting. Therefore, the size of the gap between the first sleeve 150 and the second sleeve 130 is at most 0.07 mm at the position of the first microgroove 159, which is the sum of 0.03 mm of the clearance and the depth D = 0.04 mm of the first microgroove 159. Even when the size of the gap between the first sleeve 150 and the second sleeve 130 is at the maximum value of 0.07 mm, only gas can pass through from the first microgroove 159 during injection molding, and the value is small enough that the molten resin does not enter. The above description is not limited to the first microgroove 159, and the same applies to the second microgroove 139.

[0097] Thus, it is preferable that the insertion clearance and the depth D of the microgroove are set in consideration of the molten resin not entering and the assembly tolerance.

[0098] In the present embodiment, the circumferential length L of the first microgroove 159 and the second microgroove 139 is formed to be 0.3 mm. Not limited to this value, the length L can also be increased by configuring the depth D to be small enough so that the molten resin does not enter.

[0099] (Modification example) FIG. 12 shows a modification example of the gas vent pin 101. On the first outer peripheral surface 158 of the first sleeve 150 of the gas vent pin 201 shown in FIG. 12(A), first microgrooves 159A, 159B, 159C, and 159D having the same configuration as the first microgroove 159 are formed at equal intervals in the circumferential direction.

[0100] Similarly, on the second outer peripheral surface 138 of the second sleeve 130 of the gas vent pin 201, second microgrooves 139A, 139B, 139C, and 139D having the same configuration as the second microgroove 139 are formed at equal intervals in the circumferential direction.

[0101] Thus, a plurality of fine grooves may be provided in the circumferential direction on at least one of the first outer peripheral surface 158 of the first sleeve 150 and the second outer peripheral surface 138 of the second sleeve. By increasing the number of fine grooves, the gas discharge capacity of the gas vent pin 201 can be further improved.

[0102] In the gas vent pin 301 shown in FIG. 12(B), a first fine groove 159 is formed on the first outer peripheral surface 158 of the first sleeve 150, but no fine groove is formed on the second outer peripheral surface 138 of the second sleeve 130.

[0103] Similarly, in the gas vent pin 401 shown in FIG. 12(C), a second fine groove 139 is formed on the second outer peripheral surface 138 of the second sleeve 130, but no fine groove is formed on the first outer peripheral surface 158 of the first sleeve 150.

[0104] Thus, it is sufficient that fine grooves are formed on at least one of the first outer peripheral surface 158 of the first sleeve 150 and the second outer peripheral surface 138 of the second sleeve 130.

[0105] In the gas vent pin 101, even after the opening 54 is closed during injection molding, the gas GAS in the cavity C can be discharged to the outside of the mold. By providing fine grooves as gas vent passages, the gas GAS can be more effectively discharged from the cavity C, and the advantage is that the timing at which the gas GAS cannot escape from the cavity C can be delayed. This solves the problem of the timing at which the gas venting of the gas vent pin ends and can be effective even for a gas vent pin without a pressing portion 63.

[0106] As described above, the preferred embodiments of the present invention have been described. However, the above embodiments are examples of the present invention, and it is possible to combine them based on the knowledge of those skilled in the art, and such forms are also included in the scope of the present invention.

Explanation of Reference Numerals

[0107] 1: Gas vent pin 50: Sleeve 54: Opening 60: Pin body 62: Cover part 63: Pressing part 69: Head 80: Mold 101: Vent pin 130: Second sleeve 131: Through hole 138: Second outer peripheral surface (outer peripheral surface of the second sleeve) 139: Second fine groove (fine groove) 150: First sleeve (sleeve) 158: First outer peripheral surface (outer peripheral surface of the first sleeve) 159: First fine groove (fine groove) C: Cavity D: Depth (radial width)

Claims

1. In a gas vent pin for discharging gas generated in a cavity to the outside during injection molding, a sleeve that is disposed by inserting an opening into the cavity and serves as a passage for discharging the gas, and a pin body that is disposed in the sleeve so as to be biased toward the opening and is configured to close the opening by being pushed into the sleeve. The pin body is disposed in the cavity in an open state, and a head having an outer peripheral side surface that inclines toward the axial center of the pin body is provided at an edge of an exposed portion of the pin body in the cavity. A gas vent pin characterized by the above.

2. Further comprising a second sleeve having a through hole provided therein, and the sleeve is disposed by inserting the sleeve into the through hole. At least one fine groove that is provided along the extending direction of the sleeve and serves as a passage for discharging the gas is formed on an outer peripheral side surface of the second sleeve or an outer peripheral side surface of the sleeve. The gas vent pin according to claim 1, characterized by the above.

3. A plurality of the fine grooves are formed in the circumferential direction on at least one of the outer peripheral side surface of the second sleeve or the outer peripheral side surface of the sleeve. The gas vent pin according to claim 2, characterized by the above.

4. The width in the radial direction of the through hole of the fine groove is more than 0 mm and 0.04 mm or less. The gas vent pin according to claim 2 or claim 3, characterized by the above.

5. A mold is provided with a gas vent pin including a sleeve that is disposed by inserting an opening into a cavity and serves as a passage for discharging gas, and a pin body that is disposed in the sleeve so as to be biased toward the opening and is configured to close the opening by being pushed into the sleeve. The pin body is disposed in the cavity in an open state, and a head having a circumferential side surface that inclines toward the axial center is provided at an edge of an exposed portion of the pin body in the cavity. When molten resin is poured into the cavity, the molten resin pushes the head of the pin body into the sleeve when passing through the opening of the sleeve, thereby closing the opening. A molding method characterized by the above.

6. The gas vent pin further includes a second sleeve having a through hole provided therein, and the sleeve is disposed by inserting the sleeve into the through hole. ​ ​ The second sleeve is provided with at least one fine groove serving as a passage for releasing the gas along the extending direction of the sleeve on the outer peripheral side surface or the inner peripheral side surface of the through hole. When the molten resin is poured into the cavity, only the gas in the cavity passes through the fine groove. The molding method according to claim 5, characterized in that.

7. At least one of the fine grooves is arranged to be on the downstream side of the flow of the molten resin rather than the opening. Even after the pin body closes the opening, at least one of the fine grooves allows the gas in the cavity to pass through. The molding method according to claim 6, characterized in that.

Images