JPH0688292B2 - Injection mold - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a mold used for injection molding, and more particularly to a mold with improved gas release properties in a cavity during injection.

[Prior Art] In the case of injection molding, if gas such as air remains in the cavity, a gas pool is generated and the appearance of the product is impaired. Therefore, as a method for venting the gas in the cavity, conventionally, a die is provided with a gas vent hole consisting of a fine slit or a through hole of 3 to 50 μm for communicating the cavity with the outside. Specifically, a method of providing a slit in the mold split surface, a method of forming a part of the mold surface with a porous sintered alloy, and a method of providing a through hole for communicating the sintered alloy with the outside, a knock pin and a pin hole. Known methods are to provide a gap between them, or to form a nested structure having fine through holes.

[Problems to be Solved by the Invention] In the above-described conventional injection mold, the gas vent holes are fine slits or through holes through which the molding material does not pass but the gas passes. However, in such a mold, the gas vent hole is clogged, and the mold must be regularly cleaned or replaced. Further, since the diameter of the gas vent hole is very small, there is a problem that the ventilation resistance is large and the gas escape rate is slow.

The present invention has been made in view of such circumstances,
The object is to increase the diameter of the gas vent hole and prevent the molding material from entering the gas vent hole.

[Means for Solving the Problems] In the case of injection molding, the air in the cavity is pressed by the injected molding material. Therefore, there is no air in the portion of the molding material filled in the cavity, and the air exists in a compressed state on the front side of the advancing molding material. Moreover, the injected molding material has a large internal pressure.

Therefore, the inventors of the present invention have completed the present invention as a result of diligent research, remembering that the gas is released in front of the advancing molding material and the gas vent hole is closed by utilizing the internal pressure of the molding material.

That is, the injection molding die of the present invention includes a slide hole provided in one of the split molds and opening into the molding cavity, a shaft member coaxially arranged in the slide hole, and a shaft member coaxially arranged outside the shaft member in the slide hole. Has a tubular slide member that is slidably in contact with the inner peripheral surface of the slide hole and is movable in the axial direction, and a biasing means that biases the slide member in the direction of projecting into the molding cavity. Has a sealing surface on the inner peripheral surface that is in close contact with the tip of the shaft member, and at least one of the slide member and the shaft member is provided with a gas vent passage that communicates the opening with the outside, and the molding material reaches the tip of the slide member. Before the slide member, the tip of the slide member projects into the molding cavity by the biasing means, and a gap for communicating the gas vent passage and the molding cavity is formed between the sealing surface and the shaft member. When the molding material reaches the tip of the slide member, the slide member is pressed by the molding material in a direction to be retracted into the slide hole, and the sealing surface is brought into close contact with the shaft member to disconnect the communication between the molding cavity and the gas vent passage. It is characterized by that.

A general thermoplastic resin is mainly used as a molding material, but a thermosetting resin, rubber, ceramics or the like may be used depending on the case.

The greatest feature of the present invention is that the slide member and the shaft member are provided in the slide hole. This slide member is tubular and has an opening at the tip. The gas in the molding cavity is discharged to the outside through this opening. Here, it is preferable that the tip end surface of the slide member has a substantially frustoconical shape in which the opening is highest and decreases toward the peripheral edge. In this way, the molding material first reaches the lower peripheral edge portion, so that the slide member is pressed from the molding material and sinks into the slide hole before the molding material reaches the opening. Then, at the position where the slide member is immersed in the slide hole, the sealing surface is in close contact with the tip of the shaft member, so that the communication between the opening and the gas vent passage is cut off and the molding material is prevented from entering the gas vent passage. It The longer the distance between the peripheral edge of the slide member and the opening, the greater the above effect, and it is generally desirable that the distance be 20 mm or more. Further, the width and depth of the gas vent passage can be arbitrarily selected, and can be increased to, for example, 0.5 mm or more.

The urging means holds the slide member in a state of protruding into the molding cavity when the molding material is not filled, and a spring, the weight of the slide member or the like can be used.

The slide hole may be directly provided in one of the split dies, but it is preferable that the slide hole is provided and the core having the shaft member and the slide member held therein is fixed to one of the split dies. This simplifies the structure of the mold and reduces the cost required for the mold. It is also easy to replace the core. The position where the slide hole is provided is preferably the weld portion of the molding cavity, but is not particularly limited.

[Operation] In the injection molding die of the present invention, the tip of the slide member projects into the cavity by the biasing means before the injection of the molding material. When the molding material is injected into the cavity in that state, the molding material advances in the cavity and the gas in the cavity is pressed by the molding material and is in a compressed state.
At this time, the opening of the slide member is exposed in the cavity, and the sealing surface and the shaft member are separated from each other to form a gap, so that the gas in the cavity is discharged from the opening through the gap and the degassing passage. It is discharged to the outside through.

When the molding material reaches the position of the slide member, the internal pressure of the molding material is transmitted to the slide member, the force overcomes the urging force of the urging means, and the slide member immerses in the slide hole. At this time, if the opening is located at the center of the end surface of the slide member, the opening is at the farthest position from the peripheral edge of the slide member, and even if the molding material reaches the slide member from either direction, it does not reach the opening. The slide member is immersed in the slide hole. When the molding material reaches the position of the opening, the sealing surface of the slide member and the shaft member are in close contact with each other and the communication between the opening and the gas vent passage is cut off. Intrusion is prevented.

That is, gas is smoothly discharged from the opening through the gas vent passage until the molding material moves on the tip surface of the slide member and reaches the position of the opening. When the molding material reaches the position of the opening, the sealing surface is in close contact with the shaft member and seals, so that the molding material is prevented from entering the degassing passage.

[Advantages of the Invention] Therefore, according to the injection molding die of the present invention, since the molding material is prevented from entering the degassing passage, the frequency of cleaning or replacement as in the conventional case is greatly reduced. Therefore, the number of steps can be reduced. Further, the diameter of the gas vent passage can be increased to, for example, 0.5 mm or more. This reduces ventilation resistance, so that the gas in the molding cavity can be smoothly discharged and gas accumulation can be prevented more reliably, so that various obstacles to the molded body can be prevented.

[Examples] Hereinafter, specific examples will be described.

(Embodiment 1) FIGS. 1 to 4 show an injection molding die according to an embodiment of the present invention. This mold comprises a fixed mold 1 and a movable mold 2, and a molding cavity 12 filled with the molten resin 100 injected between the fixed mold 1 and the movable mold 2 is formed.

In the movable die 2, a slide hole 20 is formed in a portion where the molten resin 100 is welded, the axial direction being orthogonal to the flowing direction of the molten resin 100 and penetrating the movable die 2. After the slide hole 20 extends a predetermined depth, the diameter of the slide hole 20 is slightly expanded, and when the slide hole 20 is further extended, the diameter of the slide hole 20 is greatly expanded to form a first recess 21.
The other end of the recess 21 is further expanded in diameter to form a second recess 22,
The second recess 22 constitutes an end surface of the movable die 2. The mounting seat 3, the shaft member 4, and the slide member 5 are arranged from the second recess 22 toward the slide hole 20.

The mounting seat 3 has a substantially disc shape, is disposed in the second recess 22 and is fixed to the movable die 2 with a bolt 30. Also the mounting seat 3
Has a concentric circular ring-shaped thick portion 31 in the central part,
A holding space 32 for holding the shaft member 4 is formed inside the thick portion 31. And at the bottom of the holding space 32, the holding space 32
A through hole 33 that communicates with the outside is formed, and the thick portion 31 is inserted into the first recess 21.

The shaft member 4 includes a truncated cone-shaped head portion 40, a shaft portion 41 extending from the head portion 40, and a collar portion 42 formed at the other end of the shaft portion 41. The shaft member 4 is fixed to the mounting seat 3 by holding the collar portion 42 in the holding space 32. On the surface of the head portion 40, as shown in an enlarged view in FIG. 3, a flat surface portion 40a that is on the same plane as the mold surface of the movable mold 2 and descends at an angle of 45 degrees from the flat surface portion 40a. Tapered surface part 40 with a conical peripheral surface
has b. On the surface of the shaft portion 41, a plurality of grooves 41a opening in the tapered surface portion 40b and extending in the axial direction up to the flange portion 42 are formed. Further, the surface of the flange portion 42 also has a plurality of grooves 42a, and the groove 41a opening to the tapered surface portion 42b is configured to communicate with the outside through the holding space 32, the groove 42a, and the through hole 33. The depths of the grooves 41a and 42b are 0.5 to 1 respectively.
It is configured to be mm.

The slide member 5 has a substantially cylindrical shape, and the shaft member 4 is in sliding contact with the center hole, and the outer peripheral surface is in sliding contact with the slide hole 20 of the movable die 2. An opening 51 of φ3 mm is opened at the center of the front end surface 50 of the slide member 5 exposed in the molding cavity 12,
The tip surface 50 of 0 mm has a tapered shape that inclines downward as it goes away from the opening 51. The diameter of the opening 51 is the shaft member 4
The diameter of the flat hole 40a is the same as that of the flat hole 40a, and the diameter of the central hole at the tip of the slide member 5 gradually increases as the distance from the opening 51 increases, so that the seal surface 52 of the inverted shape of the tapered surface 40b is formed. The large diameter portion 53 is provided at the other end of the slide member 5.
And the large-diameter portion 53 is located in the first concave portion 21.
By abutting the bottom surface 21a of 21 and the thick portion 36, the movement distance of the slide member 5 is restricted.

The spring 6 is arranged between the large-diameter portion 53 of the slide member 5 and the flange portion 42 of the shaft member 4, and the slide member 5 is biased in a direction projecting from the molding cavity 12. The movement is restricted by the large-diameter portion 53 coming into contact with the bottom surface 21a of the first recess 21, and the sealing surface 52 of the slide member 5 and the shaft member 4 are prevented.
Between the tapered surface portions 40b of the and the large diameter portion 53 of the slide member 5
A predetermined gap (0.71 mm and 1 mm) is formed between and the thick portion 31 of the mounting seat 3.

The operation of the mold of this embodiment configured as described above will be described. First, before injecting the molten resin, as shown in FIG. 1 and FIG.
The tip of the is protruding into the molding cavity 12. At this time, the amount of protrusion of the opening 51 is the largest, 1 mm, and the peripheral edge of the front end surface 50 coincides with the mold surface of the movable mold 2. And molten resin 10
When 0 is injected, the air generated in the molding cavity 12 and the gas generated from the molten resin, etc., will flow from the opening 51 to the sealing surface.
It passes through the gap between 52 and the tapered surface portion 40b, and is discharged from the through hole 33 through the groove 41a, the holding space 32, and the groove 42a.

When the molten resin 100 reaches the front end surface 50 of the slide member 5, the internal pressure of the molten resin 100 overcomes the urging force of the spring 6, and the slide member 5 moves in the direction in which it is retracted into the movable die 2. The distance from the peripheral edge of the tip surface 50 of the slide member 5 to the opening 51 is 18.5 mm, and it is known from experiments that the slide member 5 moves sufficiently while the molten resin 100 moves that distance. Therefore, as shown in FIG. 4, when the slide member 5 comes into contact with the thick portion 31 and its movement is restricted, the seal surface 52 and the taper surface portion 40b of the shaft member 4 come into close contact with each other, and at the same time, the flat surface portion 40a is opened. Block part 51. After that, the molten resin 100 reaches the position of the opening 51. As a result, the gas in the molding cavity can be sufficiently discharged, and the molten resin 100 is prevented from entering the slide member 5 through the opening 51.

Therefore, according to the injection molding die of this embodiment, it is possible to surely perform degassing, and to prevent the molten resin from entering the degassing passage. Therefore, a molded product of good quality can be formed, and the frequency of cleaning and replacement of the slide member and the like is extremely low, and the number of steps is remarkably reduced as compared with the related art.

(Embodiment 2) FIG. 5 shows a mold according to a second embodiment of the present invention. In the mold of Example 1 described above, the shaft member 4 and the slide member 5 are mounted on the movable mold 2 via the mounting seat 3. Therefore, when the thickness of the movable die 2 is large, the length of the shaft member 4 and the slide member 5 becomes long, which may complicate the die structure. Further, the biasing force of the spring 6 needs to consider not only the sliding resistance between the slide member 5 and the slide hole 20 and the internal pressure of the molten resin 100, but also the self-weight of the slide member 5. Therefore, when the length of the slide member 5 becomes long, the biasing force of the spring 6 needs to be increased, which easily causes an increase in weight and a malfunction.

Therefore, in this embodiment, the mounting seat 3, the shaft member 4, and the slide member 5 are of a core type. That is, the slide member 5 is configured to be in sliding contact with the core member 7 that constitutes a part of the mold surface of the movable mold 2, and the mounting seat 3 is fixed to the core member 7 by screwing. Then, by fixing the core member 7 to the movable die 2, the same operational effect as that of the first embodiment is achieved. It is necessary to provide the movable die 2 with a through hole 22 that communicates the outside with the groove 42a.

According to the mold of this embodiment, the mounting seat 3, the shaft member 4, the slide member 5, the spring 6 and the core member 7 can be separated from the movable mold 2 as separate parts, and can be supplied as a compact degassing core. . Therefore, the structure of the movable mold becomes simple, and maintenance of the degassing core becomes extremely easy.

(Other Embodiments) Although the tip surface 50 of the slide member 5 has a tapered surface in the above embodiments, it may have a flat surface as shown in FIG. In this way, the tip surface 50 can be made flush with the mold surface of the movable mold 2 when the slide member 5 is pressed by the molten resin, so that an extra protrusion is formed on the molded body. It can be prevented. In the mold shown in FIG. 6, a sealing surface 52 is formed on the inner peripheral surface of the opening 51.

Further, as shown in FIG. 7, the tip of the slide member 5 can be enlarged in a brim shape. In this way, the area of the tip surface 50 can be increased, and the peripheral portion of the tip surface 50 and the opening
Since it is possible to increase the distance from the opening 51, it is possible to detect the pressure of the molten resin and the slide member 5 may be retracted earlier, so that the opening 51
It is possible to more reliably prevent the molten resin from entering.

[Brief description of drawings]

1 to 4 relate to a mold for injection molding according to a first embodiment of the present invention. FIG. 1 is a sectional view of an essential part showing a state before molding, and FIG. 2 is a view of a mold surface of a movable mold. 3 is a fragmentary plan view, FIG. 3 is an enlarged cross-sectional view of an essential part of FIG. 1, and FIG. 4 is an essential part cross-sectional view showing a state after molding. FIG. 5 is a sectional view of an essential part of the injection molding die of the second embodiment before molding. 6 and 7 show another mode of the embodiment, FIG. 6 is a cross-sectional view of the main part of the movable mold, and FIG. 7 is a cross-sectional view of the main part of the mold. 1 ... Fixed type, 2 ... Movable type, 3 ... Mounting seat 4 ... Shaft member, 5 ... Slide member 6 ... Spring (biasing means), 7 ... Core member 12 ... Molding cavity, 20 …… Slide holes 41a, 42a …… Groove (gas vent passage) 51 …… Opening part, 52 …… Seal surface

Claims (1)

[Claims] 1. A slide hole provided in one of the split molds and opening to a molding cavity, a shaft member coaxially arranged in the slide hole, and coaxially arranged outside the shaft member in the slide hole. An end opening of the slide member, which has a cylindrical slide member that is slidably in contact with the inner peripheral surface of the slide hole and is movable in the axial direction, and an urging unit that urges the slide member in a direction of protruding into the molding cavity. The inner peripheral surface of the portion has a sealing surface in close contact with the tip of the shaft member, and at least one of the slide member and the shaft member is provided with a gas vent passage communicating the opening and the outside. Before the molding material reaches the tip of the slide member, the tip of the slide member projects into the molding cavity by the biasing means so that the gas vent passage and the molding cavity are communicated between the sealing surface and the shaft member. When a molding material arrives at the tip of the slide member, the slide member is pressed by the molding material in a direction to be recessed into the slide hole, and the sealing surface is brought into close contact with the shaft member and the molding cavity. An injection molding die, characterized in that it is configured so as to be disconnected from the gas vent passage.