CN113320097A

CN113320097A - Mold for injection molding

Info

Publication number: CN113320097A
Application number: CN202110216719.9A
Authority: CN
Inventors: 下楠园涉; 铃木忠雄; 藤谷贵之
Original assignee: FUTABA ELECTRONICS CO LTD
Current assignee: FUTABA ELECTRONICS CO LTD; Futaba Corp
Priority date: 2020-02-28
Filing date: 2021-02-26
Publication date: 2021-08-31
Also published as: JP7141609B2; JP2021133661A

Abstract

A mold for injection molding, which has a fixed mold and a movable mold, wherein a cavity filled with a molten resin is formed by abutting the fixed mold and the movable mold, a movable pin movable in an axial direction is provided inside and outside the cavity, a tip end portion of the movable pin is positioned in the cavity filled with the molten resin, and the movable pin is provided as a hole forming portion for forming a molding hole in a molded product. In this way, since the hole forming portion of the movable pin is positioned in the cavity in a state where the cavity is filled with the molten resin, and the molded hole is formed in the molded article by pulling out the hole forming portion from the solidified molten resin, it is difficult to apply a pressure in a direction in which the movable pin is tilted from the molten resin to the movable pin, and the molding accuracy of the molded article can be improved.

Description

Mold for injection molding

Technical Field

The present invention relates to a technical field of a mold for injection molding, which molds a molded product in a structure having a fixed mold, a movable mold, and a movable pin.

Background

There is a mold for injection molding, which has a fixed mold and a movable mold, and a cavity, which is a space formed by abutting the fixed mold and the movable mold, is filled with a molten resin to mold a molded product. Such a mold for injection molding is incorporated in an injection molding machine as a part of the structure of the injection molding machine.

In such an injection molding die, a cavity is filled with a molten resin, and the solidified molten resin is taken out from the cavity by an ejector pin to form a molded article. There are various types and shapes of molded articles formed by a mold for injection molding, and for example, a molded article having a molding hole can be formed by a mold for injection molding (for example, refer to patent document 1). Patent document 1 discloses that a gear having a through hole in the center is formed as a molded article, and the gear is formed using a plurality of gates that are equally spaced around the through hole.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2005-22368

Disclosure of Invention

Problems to be solved by the invention

However, in the injection molding die described in patent document 1, when the molten resin is filled, a molding pin called a core pin is provided in the cavity, and a portion where the core pin exists is formed as a through hole in the molded article.

However, in such injection molding, since the core pin is located in the cavity, when the cavity is filled with the molten resin, the molten resin applies pressure to the core pin, and the core pin may be inclined due to the magnitude of the applied pressure and the direction of the applied pressure to the core pin, thereby lowering the molding accuracy of the molded product.

In particular, as described in patent document 1, when a plurality of gates are present around the core pin, pressure is applied to the core pin from a plurality of directions on the outer peripheral side, and the core pin is easily toppled.

In order to suppress such falling of the core pin, there is also a mold for injection molding in which a small injection speed or a small injection pressure is provided for the molten resin injected into the cavity, however, in this case, a void is likely to be generated in the molten resin, and there is a possibility that the molding accuracy of the molded product is lowered.

Therefore, an object of the injection molding die of the present invention is to improve the molding accuracy of a molded product.

Technical scheme for solving problems

First, the present invention provides an injection molding die comprising a fixed die and a movable die, wherein a cavity filled with a molten resin is formed by abutting the fixed die and the movable die, wherein movable pins movable in an axial direction are provided inside and outside the cavity, tip portions of the movable pins are located in the cavity filled with the molten resin, and a hole forming portion for forming a molding hole in a molded product is provided.

Thus, in a state where the cavity is filled with the molten resin, the hole forming portion of the movable pin is positioned in the cavity, and the hole forming portion is pulled out from the solidified molten resin, thereby forming the molding hole in the molded article.

Second, in the injection molding die according to the present invention, it is preferable that one gate is formed at a position corresponding to a central portion of the cavity.

Thus, since the molten resin is filled into the cavity from one gate formed at a position corresponding to the central portion of the cavity, the weld line is not easily formed on the molded product, and the molten resin is easily and uniformly flowed to each portion of the cavity.

Third, in the injection molding die according to the present invention, it is preferable that: a nozzle having an ejection port for ejecting the molten resin toward the cavity; and a valve pin that opens and closes the ejection port, the valve pin being used as the movable pin.

Thus, the valve pin has two functions: a function of opening and closing the ejection port and the gate; and a function of forming a molding hole.

Fourth, in the injection mold according to the present invention, it is preferable that an ejector pin for taking out the molded article from the cavity is used as the movable pin.

Thus, the ejector pin has two functions: a function of taking out the molded product from the cavity; and a function of forming a molding hole.

Fifth, in the injection molding die according to the present invention, it is preferable that the tip end surface of the movable pin is located at a position away from a wall surface of the movable die or a wall surface of the fixed die forming the cavity in a state where the hole forming portion is located in the cavity.

Thus, the depth of the molding hole can be freely set by adjusting the position of the tip end surface of the hole forming portion in the cavity.

Sixthly, in the injection molding die according to the present invention, it is preferable that a tip end surface of the movable pin is in contact with a wall surface of the movable die or a wall surface of the fixed die forming the cavity in a state where the hole forming portion is located in the cavity.

Thus, the hole forming portion forms a molding hole penetrating the shape of the molded article.

Seventh, in the injection molding die according to the present invention, the hole forming portion is preferably formed in a shape having a smaller diameter toward the tip.

Thus, the hole forming portion is easily pressed into the molten resin filled in the cavity, and easily pulled out from the molten resin which is filled in the cavity and solidified.

Eighth, in the injection mold according to the present invention, it is preferable that the movable pin is rotatable around an axis, and a thread groove is formed on an outer peripheral surface of the hole forming portion.

Thus, the formation of the molding hole and the formation of the thread groove do not need to be separately performed.

Effects of the invention

According to the present invention, since the hole forming portion of the movable pin is positioned in the cavity in a state where the cavity is filled with the molten resin, and the molding hole is formed in the molded article by pulling out the hole forming portion from the solidified molten resin, the molten resin does not easily apply a pressure to the movable pin in a direction in which the movable pin is tilted, and the molding accuracy of the molded article can be improved.

Drawings

Fig. 1 is a sectional view of an injection molding die showing a state before a movable die and a fixed die are butted and a molten resin is filled in a cavity, showing a first embodiment of the present invention together with fig. 2 to 9.

Fig. 2 is a sectional view of the injection mold showing a state in which the cavity is filled with the molten resin, following fig. 1.

Fig. 3 is a sectional view of the injection molding die showing a state in which the hole forming portion of the valve pin is pressed into the molten resin, following fig. 2.

Fig. 4 is a sectional view of the injection molding die showing a state where the movable die is separated from the fixed die, following fig. 3.

Fig. 5 is a sectional view of the injection mold showing a state where the molded product is ejected by the ejection pin, following fig. 4.

Fig. 6 is an enlarged sectional view showing an example in which the molding hole is formed as a screw hole.

Fig. 7 is a cross-sectional view showing an example of a structure in which the molten resin flows in a flow path formed on the side of the valve pin and is discharged toward the cavity.

Fig. 8 is an enlarged sectional view showing a state before the valve pin is pressed into the molten resin, together with fig. 9, showing an example in which the molding hole is formed as a through hole.

Fig. 9 is an enlarged sectional view showing a state where the valve pin is pressed into the molten resin and the molding hole is formed as a through hole.

Fig. 10 is a sectional view of an injection molding die showing a state in which a movable die and a fixed die are butted against each other and a cavity is filled with a molten resin, showing a second embodiment of the present invention together with fig. 11 and 12.

Fig. 11 is a sectional view of the injection molding die showing a state in which the hole forming portion of the valve pin is pressed into the molten resin, following fig. 10.

Fig. 12 is a sectional view of the injection molding die showing a state where the movable die is separated from the fixed die and the molded product is ejected by the ejector pin, following fig. 11.

Fig. 13 is a sectional view of an injection molding die showing a state in which a movable die and a fixed die are butted against each other and a cavity is filled with a molten resin, showing a third embodiment of the present invention together with fig. 14 and 15.

Fig. 14 is a sectional view of the injection molding die showing a state in which the hole forming portion of the valve pin is pressed into the molten resin, following fig. 13.

Fig. 15 is a sectional view of the injection molding die showing a state where the movable die is separated from the fixed die and the molded product is ejected by the ejector pin, following fig. 14.

Reference numerals

1: a mold for injection molding;

2: a movable mould;

2 b: a wall surface;

3: a fixed mold;

5: a mold cavity;

6: ejecting a pin;

8 b: a gate;

15: a valve pin;

16: a hole forming part;

16 a: a front end surface;

16 b: a thread groove;

20: a nozzle;

23 a: an ejection port;

300: melting the resin;

400: a molded article;

401: forming holes;

20X: a nozzle;

1A: a mold for injection molding;

6 a: a hole forming part;

6 b: a front end surface;

15A: a valve pin;

1B: a mold for injection molding;

52: a movable mould;

53: a fixed mold;

53 c: a wall surface;

55: a mold cavity;

56: ejecting a pin;

56 a: a hole forming part;

56 b: a front end surface;

67 a: and a gate.

Detailed Description

Next, a mode of implementing the injection molding die of the present invention will be described with reference to the drawings.

In the following description, the direction in which the fixed mold and the movable mold of the injection molding mold are butted and separated is referred to as the vertical direction, and the vertical, front, rear, and left directions are shown. The directions of the upper, lower, front, rear, left and right are shown below for convenience of explanation, and the present invention is not limited to these directions. The number, shape, arrangement, and the like of the respective members are not limited to those illustrated in the drawings, within a range not departing from the scope of the present invention.

< Structure of injection molding die of first embodiment >

First, the structure of the injection mold 1 according to the first embodiment will be described (see fig. 1). The injection mold 1 functions as a hot runner.

The mold 1 for injection molding is incorporated into an injection molding machine as a part of the structure of the injection molding machine, and has a movable mold 2 and a fixed mold 3 which are butted against and separated from each other in the vertical direction. An internal space is formed in the fixed die 3, and this internal space is defined as an arrangement space 4. The lower end of the fixed die 3 is formed with

recesses

3a, 3a, … … opened downward. The

recesses

3a, 3a, … … are formed separately in the horizontal direction.

The movable mold 2 is moved in the up-down direction with respect to the fixed mold 3 to be butted and separated. The movable mold 2 is formed in a substantially flat plate shape with the thickness direction being the vertical direction, and when the upper surface side is butted against the fixed mold 3, the movable mold is combined with the

concave portions

3a, 3a, … … formed in the fixed mold 3, and has a plurality of

concave portions

2a, 2a, … … formed as

cavities

5, 5, … …, respectively. The

concave portions

2a, 2a, … … are opened upward and formed separately in the horizontal direction.

In the movable mold 2, the ejector pins 6, 6, … … are supported so as to be movable in the up-down direction. At least two of the ejector pins 6, 6, … … are located at positions corresponding to the

recesses

2a, 2a, … …, respectively. Therefore, the upper end portions of the plurality of ejector pins 6, 6, … … can be inserted into one recess 2 a. In a state before the

cavity

5, 5, … … is filled with a molten resin described later, the upper surface of the ejector pin 6 is fitted to the outer peripheral portion of the bottom surface forming the recess 2 a.

The fixed mold 3 has: a flat plate-like mounting plate 7 having a thickness direction directed in the vertical direction; a cavity plate 8 located below the mounting plate 7; and a connecting plate 9 for connecting the outer periphery of the mounting plate 7 and the outer periphery of the cavity plate 8. The installation plate 7, the connecting plate 9, and the cavity plate 8 form an arrangement space 4 inside the fixed die 3.

An annular positioning ring 10 is attached to an upper surface of a central portion of the attachment plate 7, and the positioning ring 10 has a function of positioning with respect to the injection molding machine when incorporated into the injection molding machine.

A supply nozzle 100 serving as a resin supply portion for supplying molten resin is inserted and attached to a central portion of the mounting plate 7. The supply nozzle 100 is partially inserted into the mounting plate 7 in a state of being inserted through the positioning ring 10.

On the mounting plate 7, drive

rods

11, 11 are supported on the outer peripheral side of the positioning ring 10 so as to be freely movable in the up-down direction. The drive levers 11, 11 are driven by the

drive sources

200, 200 to move in the up-down direction with respect to the mounting plate 7.

The driving source 200 may be, for example, a cylinder, a piston, or a motor.

The cavity plate 8 has vertically penetrating

arrangement holes

8a, 8a, … … formed therein. The opening at the lower side of the arrangement hole 8a is smaller than the opening at the upper side. The lower end portion of the arrangement hole 8a in the cavity plate 8 is formed as a gate 8 b. One gate 8b is formed at a position corresponding to a central portion (central portion) of one cavity 5.

Guide shafts

12, 12 are disposed in the disposition space 4 of the fixed mold 3. The upper and lower ends of the

guide shafts

12, 12 are coupled to the mounting plate 7 and the cavity plate 8, respectively.

A drive plate 13 is supported on the

guide shafts

12, 12 so as to be movable in the vertical direction. The drive plate 13 is supported on the upper end sides of the

guide shafts

12, 12 by inserting the

guide shafts

12, 12 into the outer peripheral portion, respectively. On the guide shafts 12, compression coil springs 14, 14 are supported on the lower side of the drive plate 13, respectively. Therefore, in a state where the compression coil springs 14, 14 are biased upward and are not biased downward, the drive plate 13 is pressed against the attachment plate 7 from below by the elastic force of the compression coil springs 14, 14. The driving force of the drive levers 11, 11 is transmitted to the drive plate 13.

The valve pins 15, 15, … … functioning as movable pins movable in the up-down direction are coupled to the drive plate 13 in a state of being separated in the horizontal direction. The valve pin 15 has an upper end coupled to the drive plate 13 and a lower end (tip end) serving as a hole forming portion 16. A portion of the valve pin 15 near the lower end is a gate opening/closing portion 17, and the gate opening/closing portion 17 and the hole forming portion 16 are continuously connected in the vertical direction.

The hole forming portion 16 is formed in a tapered shape, and the diameter of the lower end side portion thereof is smaller than the diameter of the upper end side portion. The hole forming portion 16 may be formed in a shape in which the diameter gradually decreases as it approaches the front end surface 16a, or may be formed in a shape in which the diameter gradually decreases as it approaches the front end surface 16 a. The diameter of the gate opening/closing portion 17 is larger than the diameter of the hole forming portion 16 and smaller than the diameter of the upper portion of the gate opening/closing portion 17.

The manifold 18, the runner 19, and the

nozzles

20, 20, and … … are disposed in the disposition space 4 of the fixed mold 3.

The manifold 18 is formed into a flat shape having a small thickness in the vertical direction, and is positioned between the

guide shafts

12, 12. A flow path 21 through which the molten resin flows is formed inside the manifold 18, and the flow path 21 is composed of an intermediate portion 21a located at the center in the vertical direction, an inflow portion 21b located above the intermediate portion 21a, and

branch portions

21c, 21c, … … located below the intermediate portion 21 a.

The intermediate portion 21a is formed as a space having a width in the horizontal direction larger than a width in the vertical direction.

The inflow portion 21b is formed in the central portion of the manifold 18, and has an upper opening opened in the upper surface of the manifold 18 and a lower opening communicating with the central portion of the intermediate portion 21 a.

The

branch portions

21c, 21c, … … are formed to be separated in the horizontal direction, and are formed in the same number as the valve pins 15, 15, … …. The diameter of the

branch

21c, 21c, … … is slightly larger than the diameter of the

valve pin

15, 15, … …. The upper opening of the branch portion 21c communicates with the intermediate portion 21a, and the lower opening opens on the lower surface of the manifold 18.

The manifold 18 is mounted on the upper surface of the cavity plate 8, for example via an annular gasket 22.

The runner 19 is formed in a cylindrical shape extending vertically, and has a lower surface joined to an upper surface of the central portion of the manifold 18, and an internal space communicating with the inflow portion 21b of the manifold 18. The upper end of the runner 19 is inserted into the mounting plate 7 while passing through the drive plate 13, and the upper surface is coupled to the supply nozzle 100.

The

nozzles

20, 20, … … are arranged horizontally apart and are provided in the same number as the valve pins 15, 15, … …. The nozzle 20 is formed in a cylindrical shape, and portions other than the upper end portion are inserted into the arrangement hole 8a of the cavity plate 8.

The nozzle 20 has a vertically penetrating flow path 23 formed therein. The lower end of the flow path 23 has a smaller diameter than the other portions, and the lower opening is formed as a discharge port 23 a. The ejection port 23a communicates with the gate 8b of the cavity plate 8. The diameter of the flow path 23 is slightly larger than the diameter of the valve pin 15 except for the lower end portion.

The upper surface of the nozzle 20 is coupled to the lower surface of the manifold 18, and the flow path 23 communicates with the branch portion 21c of the manifold 18.

A heater 24 is disposed around the nozzle 20, and the heater 24 is disposed in the disposition hole 8 of the cavity plate 8. The nozzle 20 is heated by the heater 24, and the molten resin flowing through the flow path 23 is prevented from being cooled and solidified.

The manifold 18 and the runner 19 are also heated by a heater not shown, and solidification caused by cooling of the molten resin flowing through the manifold 18 and the runner 19 is prevented.

The valve pins 15, 15, … … are inserted through the manifold 18, respectively, and are supported on the manifold 18 so as to be freely movable in the up-down direction. Valve pin 15 is inserted into flow path 23 of manifold 18 and nozzle 20. Since the diameter of the valve pin 15 is smaller than the diameter of the flow channel 23, a space through which the molten resin flows is formed on the outer peripheral side of the valve pin 15 in the flow channel 23.

< operation in the mold for injection molding of the first embodiment >

Next, an operation of forming a molded article, for example, a gear, in the injection molding die 1 will be described (see fig. 1 to 5).

In the injection molding die 1, when the movable die 2 is moved upward relative to the fixed die 3 and the movable die 2 and the fixed die 3 are butted against each other, the

cavities

5, 5, … … are formed by the

recesses

2a, 2a, … … formed in the movable die 2 and the

recesses

3a, 3a, … … formed in the fixed die 3, respectively (see fig. 1). At this time, the drive plate 13 is pressed against the mounting plate 7 from below by the compression coil springs 14, the valve pin 15 is positioned at the upper moving end, and the gate opening/closing portion 17 is positioned above the ejection port 23a and the gate 8 b. Thus, the gate 8b is opened.

When the movable mold 2 and the fixed mold 3 are butted against each other to form the

cavity

5, 5, … …, the molten resin 300 is supplied from the supply nozzle 100 to the runner 19, and the molten resin 300 flows through the flow path 21 of the manifold 18, is branched by the branching

portions

21c, 21c, … …, and flows through the

flow paths

23, 23, … … of the

nozzles

20, 20, … … (see fig. 2). At this time, the runner 19, the manifold 18, and the nozzle 20 are heated by the heater 24, and solidification due to cooling of the molten resin 300 is prevented.

The molten resin 300 flows from the gate 8b to the cavity 5, and is filled in the cavity 5. At this time, the filling state of the molten resin 300 into the cavity 5 may be a filling state slightly smaller than the filling state, instead of the filling state.

When the molten resin 300 is filled in the cavity 5, the

drive rods

11, 11 are moved downward by the drive sources 200, respectively, and the drive plate 13 is pressed by the

drive rods

11, 11 and moved downward against the elastic force of the compression coil springs 14, 14 (see fig. 3). The timing when the driving plate 13 moves downward is in an uncured state before the molten resin 300 filled in the cavity 5 is solidified.

When the drive plate 13 moves downward, the valve pin 15 moves downward along with the movement of the drive plate 13, and the gate 8b is closed by the gate opening/closing portion 17. Accordingly, the ejection of the molten resin 300 from the nozzle 20 to the cavity 5 is stopped.

At this time, the hole forming portions 16 of the valve pin 15 are simultaneously pressed into the molten resin 300, and the hole forming portions 16 are located in the cavity 5 inside the molten resin 300. In a state where the hole forming portion 16 is located in the cavity 300, the front end surface 16a of the hole forming portion 16 is located at a position apart from the wall surface (bottom surface) 2b of the movable mold 2 forming the cavity 5, and the front end surface 16a is located above the wall surface 2 b.

As described above, when the ejection of the molten resin 300 into the cavity 5 is stopped, the molten resin 300 filled in the cavity 5 is cooled and solidified after a predetermined time has elapsed, and the molded article 400 is formed.

When the molten resin 300 filled in the cavity 5 is cooled and solidified, the movable mold 2 moves downward and is separated from the fixed mold 3 together with the molded article 400 (see fig. 4). Therefore, the molded article 400 moves downward relative to the valve pin 15, the hole forming portion 16 of the valve pin 15 is pulled out from the molded article 400, and the molded article 400 forms the molding hole 401. The molding hole 401 is, for example, a hole having a bottomed shape.

As described above, in the mold 1 for injection molding, in a state in which the hole forming portion 16 is located in the cavity 5, the tip end surface 16a of the hole forming portion 16 is located at a position apart from the wall surface 2b of the movable mold 2 forming the cavity 5, and therefore, the molding hole 401 having a bottom surface is formed in the molded product 400 through the hole forming portion 16.

Therefore, by adjusting the position of the front end surface 16a of the hole forming portion 16 in the cavity 5, the depth of the molding hole 401 can be freely set, and the degree of freedom in design regarding the shape of the molded article 400 can be improved.

When the movable mold 2 moves downward together with the molded article 400, the ejector pins 6, 6, … … move upward relative to the movable mold 2, and the molded article 400 is ejected by the ejector pins 6, 6, … … and taken out from the cavity 5 (see fig. 5).

As described above, in the mold 1 for injection molding, one gate 8b is formed at a position corresponding to the central portion (central portion) of one cavity 5.

Therefore, since the molten resin 300 is filled into the cavity 5 from the one gate 8b formed at the position corresponding to the central portion of the cavity 5, it is difficult to form a weld line on the molded article 400, and the molten resin 300 easily flows uniformly to each portion of the cavity 5, thereby improving the molding accuracy of the molded article 400.

In particular, in the structure in which the molten resin is filled into the cavity from each of the plurality of gates separated in the circumferential direction, for example, in the case of forming a molded article in point symmetry such as a gear, the circularity may be reduced, but since the gate 8b is formed in the center portion of the point symmetry shape, a molded article having high circularity can be formed.

Further, in the case where there are a plurality of gates, a plurality of gate marks are formed on the molded product, and the amount of solidified molten resin remaining in the gate portion tends to increase, and the manufacturing cost may increase due to the wasted material, and by providing a structure in which the molten resin 300 is filled from one gate 8b, the number of gate marks and the manufacturing cost can be reduced.

Further, the valve pin 15 is used as a movable pin for forming the molding hole 401 in the molded article 400.

Therefore, since the molding hole 401 is formed in the molded article 400 by opening and closing the valve pin 15 of the ejection port 23a and the gate 8b of the nozzle 20, the valve pin 15 has two functions: the function of opening and closing the ejection port 23a and the gate 8b and the function of forming the molding hole 401 can achieve not only reduction in the number of components but also high functionality of the mold 1 for injection molding by using the conventional structure.

Further, the hole forming portion 16 is formed in a shape having a smaller diameter as it is closer to the front end.

Therefore, the hole forming portion 16 can be easily press-fitted into the molten resin 300 filled in the cavity 5, and can be easily pulled out from the molten resin 300 which is filled in the cavity 5 and solidified, and the molding accuracy of the molded article 400 can be improved.

In the above-described example of the injection mold 1 having the plurality of

nozzles

20, 20, … …, at least one nozzle 20 may be provided in the injection mold 1.

In addition, in the above description, the valve pin 15 is moved in the vertical direction to form the molding hole 401 in the molded article 400, and the valve pin 15 may be rotated in the axial direction when moved in the vertical direction. In this case, by forming the screw groove 16b on the outer peripheral surface of the hole forming portion 16, the molding hole 401 of the molded product 400 can be formed as a screw hole having the screw groove (see fig. 6).

In this way, by forming the screw hole as the molding hole 401 in the molded article 400 through the screw groove 16b of the hole forming portion 16, it is not necessary to separately form the molding hole 401 and the screw groove, and it is possible to improve the degree of freedom in designing the molded article 400 in addition to shortening the molding time of the molded article 400.

Further, while the above description shows an example in which the nozzle 20 is used to cause the molten resin 300 to flow around the valve pin 15 and to be ejected from the ejection port 23a toward the cavity 5, the nozzle 20X may be used instead of the nozzle 20 to cause the molten resin 300 to flow through a flow path 23X formed on the side of the valve pin 15 and to be ejected from the ejection port 23a toward the cavity 5 (see fig. 7).

Further, the above shows an example in which the tip end surface 16a of the hole forming portion 16 is located at a position apart from the wall surface 2b of the movable mold 2 when the hole forming portion 16 of the valve pin 15 is press-fitted into the molten resin 300, and the tip end surface 16a may be brought into contact with the wall surface 2b when the hole forming portion 16 of the valve pin 15 is press-fitted into the molten resin 300 (see fig. 8 and 9).

In this case, at the time of an uncured state before the molten resin 300 is solidified, the hole forming portion 16 of the valve pin 15 is pressed into the molten resin 300, and the tip end surface 16a is brought into contact with the wall surface 2 b.

Therefore, when the molded article 400 is moved downward relative to the valve pin 15 and the hole forming portion 16 is pulled out of the molded article 400, the molding hole 401 is formed to penetrate the shape of the molded article 400.

In this way, by forming the leading end surface 16a of the hole forming portion 16 in a state of being in contact with the wall surface 2b in a state where the hole forming portion 16 is located in the cavity 5, the molding hole 401 penetrating the shape of the molded article 400 is formed through the hole forming portion 16, and therefore, the molding hole 401 can be easily formed as a through hole.

< mold for injection molding of second embodiment >

Next, a mold 1A for injection molding according to a second embodiment will be described (see fig. 10 to 12). The injection mold 1A functions as a hot runner.

Further, the injection molding die 1A shown below is different from the injection molding die 1 only in the shape of the valve pin and the formation of the molding hole by the ejector pin. Therefore, only the portions of the injection mold 1A different from the injection mold 1 will be described in detail, and the portions of the other portions that are the same as those of the injection mold 1 will be given the same reference numerals and will not be described again.

In the injection molding die 1A, for example,

cavities

5, 5, … … are formed by the

concave portions

2a, 2a, … … formed in the movable die 2 and the

convex portions

2c, 2c, … … formed in the fixed die 3, respectively (see fig. 10). However, in the injection mold 1A, the cavity 5 may be formed by a recess formed in the movable mold 2 and a recess formed in the fixed mold 3, similarly to the injection mold 1.

In the injection mold 1A, the ejector pins 6, 6, … … are supported on the movable mold 2 so as to be movable in the vertical direction. Ejector pins 6, 6, … … are positioned one after the other in positions corresponding to mold

cavities

5, 5, … …, respectively. The ejector pin 6 is located at a position corresponding to the center of the cavity 5, and the upper end of the ejector pin 6 is a hole forming portion 6 a.

The valve pins 15A, … … serving as movable pins movable in the vertical direction are coupled to the drive plate 13 in a state separated in the horizontal direction. The valve pin 15A has an upper end coupled to the drive plate 13, a lower end (tip end) serving as a gate opening/closing portion 17, and a hole forming portion 16 not provided in the valve pin 15A.

In the injection mold 1A configured as described above, when the movable mold 2 and the fixed mold 3 are butted against each other, the

cavities

5, 5, … … are formed (see fig. 10). When the cavity 5 is formed, the molten resin 300 flows from the gate 8b to the cavity 5, and the cavity 5 is filled with the molten resin 300. At this time, the filling state of the molten resin 300 into the cavity 5 may be a filling state slightly smaller than the filling state, instead of the filling state.

When the cavity 5 is filled with the molten resin 300, the drive plate 13 moves downward, the valve pin 15A moves downward along with the movement of the drive plate 13, and the gate 8b is closed by the gate opening/closing portion 17A (see fig. 11). Accordingly, the ejection of the molten resin 300 from the nozzle 20 to the cavity 5 is stopped. The timing at which the driving plate 13 moves downward is the timing at which the molten resin 300 is in an uncured state before solidification.

At this time, simultaneously with or after the ejection of the molten resin 300 into the cavity 5 is stopped, the ejector pin 6 is moved upward by a predetermined amount, the hole forming portion 6a of the ejector pin 6 is pushed into the molten resin 300, and the hole forming portion 6a is positioned in the cavity 5 inside the molten resin 300. In a state where the hole forming portion 6a is located in the cavity 300, a front end surface (upper end surface) 6b of the hole forming portion 6a is located at a position apart from a lower end surface of the valve pin 15A.

As described above, after the ejection of the molten resin 300 into the cavity 5 is stopped and a predetermined time has elapsed, the molten resin 300 filled in the cavity 5 is cooled and solidified to form the molded article 400.

When the molten resin 300 filled in the cavity 5 is cooled and solidified, the movable mold 2 moves downward and is separated from the fixed mold 3 together with the molded article 400 (see fig. 12). When the movable mold 2 moves downward together with the molded article 400, the ejector pins 6 move upward relative to the movable mold 2, and the molded article 400 is ejected by the ejector pins 6 and taken out from the cavity 5.

In the molded article 400, the hole forming portion 6a of the ejector pin 6 is press-fitted into the molded article 400, thereby forming a molding hole 401. The molding hole 401 is a hole having a bottomed shape.

As described above, in the mold 1A for injection molding, one gate 8b is formed in the central portion (central portion) of one cavity 5.

Therefore, since the molten resin 300 is filled into the cavity 5 from one gate 8b formed in the central portion of the cavity 5, it is difficult to form a weld line on the molded article 400, and the molten resin 300 uniformly flows to each portion of the cavity 5, thereby improving the molding accuracy of the molded article 400.

Further, in the case of forming the molded article 400 having a point-symmetric shape, the molded article 400 having a high roundness can be formed, similarly to the mold 1 for injection molding, and the number of gate marks and the manufacturing cost can be reduced.

Further, as the movable pin for forming the molding hole 401 in the molded article 400, an ejector pin 6 that takes out the molded article 400 from the cavity 5 is used.

Therefore, since the molding hole 401 is formed in the molded article 400 using the ejector pin 6 that takes out the molded article 400 from the cavity 5, the ejector pin 6 has two functions: by using the conventional structure, the function of taking out the molded article 400 from the cavity 5 and the function of forming the molding hole 401 can be achieved, and high functionality of the mold for injection molding 1A can be achieved in addition to reduction in the number of parts.

Further, in the injection mold 1A, as in the injection mold 1, one nozzle 20 may be provided, or the ejector pin 6 may be rotated in the axial direction to form the molding hole 401 of the molded product 400 as a screw hole, or the molten resin 300 may be caused to flow through the flow path 23X formed on the side of the valve pin 15A using the nozzle 20X instead of the nozzle 20.

< third embodiment of the injection molding die >

Next, a mold 1B for injection molding according to a third embodiment will be described (see fig. 13 to 15). The injection mold 1B functions as a cold runner.

The mold 1B for injection molding is incorporated into an injection molding machine as a part of the structure of the injection molding machine, and has a movable mold 52 and a fixed mold 53 which are butted and separated in the up-down direction. An internal space is formed in the movable die 52, and this internal space is set as an arrangement space 54. At the lower end of the fixed die 53, a recess 53a opening downward and a recess 53b for a flow path are formed continuously in the left-right direction.

The movable die 52 is moved in the up-down direction relative to the fixed die 53 to be butted and separated. The movable die 52 has a convex portion 52a which is formed as a cavity 55 in combination with a concave portion 53a formed in the fixed die 53 when the upper surface side is butted against the fixed die 53. The movable mold 52 is formed with a flow path concave portion 52b that is continuous with the side of the convex portion 52a and opens upward.

The movable mold 52 has: a vertically oriented flat plate-like mounting plate 57; a cavity plate 58 located above the mounting plate 57; and a coupling plate 59 that couples the outer peripheral portion of the mounting plate 57 and the outer peripheral portion of the cavity plate 58. The mounting plate 57, the connecting plate 59, and the cavity plate 58 form the arrangement space 54 inside the movable mold 52.

An annular positioning ring 60 is attached to the upper surface of the center portion of the fixed mold 53, and the positioning ring 60 has a function of positioning with respect to the injection molding machine when assembled into the injection molding machine.

A supply nozzle 100 serving as a resin supply unit for supplying molten resin is inserted into the fixed die 53. The supply nozzle 100 is inserted partially into the fixed mold 53 in a state of being inserted through the positioning ring 60.

Drive levers 61, 61 are supported on the mounting plate 57 so as to be movable in the vertical direction. The drive levers 61, 61 are driven by the

drive sources

200, 200 to move in the up-down direction with respect to the mounting plate 57.

Guide shafts

62, 62 are disposed in the disposition space 54 of the movable mold 52. The upper and lower end portions of the

guide shafts

62, 62 are coupled to the cavity plate 58 and the mounting plate 57, respectively.

A drive plate 63 is supported on the

guide shafts

62, 62 so as to be movable in the vertical direction. The drive plate 63 is supported by the

guide shafts

62, 62 by inserting the

guide shafts

62, 62 into the outer peripheral portion, respectively. On the guide shafts 62, compression coil springs 64, 64 are supported on the upper side of the drive plate 63, respectively. Therefore, in a state where the compression coil springs 64, 64 are biased downward and no upward force is applied, the drive plate 63 is pressed against the attachment plate 57 from above by the elastic force of the compression coil springs 64, 64. The driving force of the drive levers 61, 61 is transmitted to the drive plate 63.

Lower end portions of the ejector pins 56, 56, … … functioning as movable pins movable in the up-down direction are coupled to the drive plate 63. The upper surface of the ejector pin 56 is fitted to the upper surface of the convex portion 52a in a state before the cavity 55 is filled with a molten resin described later. The runner ejector pin 65 movable in the up-down direction is coupled to the drive plate 63 at the side of the ejector pins 56, 56, … …. The ejector pins 56, 56, … … and the runner ejector pin 65 move in the up-down direction simultaneously with the movement of the drive plate 63 in the up-down direction. The upper end of the ejector pin 56 is a hole forming portion 56 a.

A runner 66 is provided in the center of the fixed die 53. The runner 66 is disposed in a state of being inserted into the central portion of the fixed die 53, and is formed in a substantially cylindrical shape extending vertically. The runner 66 is inserted with its upper end fitted to the positioning ring 60, and the internal space communicates with the flow path recess 53 b. The upper surface of the runner 66 is joined to a supply nozzle 100.

A heater, not shown, is disposed around the runner 66, and the runner 66 is heated by the heater to prevent solidification caused by cooling of the molten resin flowing through the runner 66.

In the injection molding die 1B configured as described above, the movable die 52 moves upward relative to the fixed die 53, the movable die 52 abuts against the fixed die 53, and the cavity 55 is formed by the convex portion 52a formed in the movable die 52 and the concave portion 53a formed in the fixed die 53 (see fig. 13). Further, when the movable mold 52 is butted against the fixed mold 53, the flow path 67 is formed by the flow path concave portion 52b formed in the movable mold 52 and the flow path concave portion 53b formed in the fixed mold 53. The runner 67 communicates with the cavity 55, and an opening of the runner 67 on the cavity 55 side is set as a gate 67 a.

At this time, the drive plate 63 is pressed against the mounting plate 57 from above by the compression coil springs 64, 64.

When the movable mold 52 abuts against the fixed mold 53 to form the cavity 55, the molten resin 300 is supplied from the supply nozzle 100 to the runner 66. At this time, the runner 66 is heated by the heater, thereby preventing solidification due to cooling of the molten resin 300.

Molten resin 300 flows from gate 67a to cavity 55, and molten resin 300 is filled in cavity 55. At this time, the filling state of the molten resin 300 into the cavity 55 may be a filling state slightly smaller than the filling state, instead of the filling state.

After the cavity 55 is filled with the molten resin 300, the

drive rods

61, 61 are moved upward by the drive sources 200, respectively, and the drive plate 63 is pressed by the

drive rods

61, 61 and moved upward against the elastic forces of the compression coil springs 64, 64 (see fig. 14). The timing at which the driving plate 63 moves upward is the timing in an uncured state before the molten resin 300 solidifies.

When the drive plate 63 moves upward, the supply nozzle 100 is closed by, for example, an unillustrated opening/closing pin, and the discharge of the molten resin 300 from the supply nozzle 100 into the cavity 55 is stopped.

At this time, as the drive plate 63 moves upward, the ejector pin 56 and the runner ejector pin 65 move upward by a predetermined amount, the hole forming portion 56a of the ejector pin 56 is pushed into the molten resin 300, and the hole forming portion 56a is positioned in the cavity 55 inside the molten resin 300. In the state where the ejector pin 56 is located in the cavity 300, the front end surface (upper end surface) 56b of the ejector pin 56 is located at a position apart from the wall surface (bottom surface) 53c of the fixed mold 53 forming the cavity 55, and the front end surface 56b is located below the wall surface 53 c.

As described above, after the ejection of the molten resin 300 into the cavity 55 is stopped and a predetermined time has elapsed, the molten resin 300 filled in the cavity 55 is cooled and solidified to form the molded article 400.

After the molten resin 300 filled in the cavity 55 is cooled and solidified, the movable mold 52 moves downward, and is separated from the fixed mold 53 together with the molded article 400 (see fig. 15). When the movable mold 52 moves downward together with the molded product 400, the ejector pins 56 and the runner ejector pins 65 move upward relative to the movable mold 52, and the molded product 400 is ejected by the ejector pins 56, 56, … … and taken out from the cavity 55. At this time, the molded product 400 is ejected from the movable mold 52 together with the runner molding portion 500 formed by solidifying the molten resin 300 filled in the runner 66. The runner molding portion 500 is a portion cut out from the molded article 400.

The hole forming portion 56a of the ejector pin 56 is press-fitted into the molded article 400, and a molding hole 401 is formed in the molded article 400. The molding hole 401 is a hole having a bottomed shape.

As described above, in the mold for injection molding 1B, in the state where the upper end portion of the ejector pin 56 is located in the cavity 55, the front end surface 56B of the ejector pin 56 is located at a position apart from the wall surface 53c of the fixed mold 53 forming the cavity 55, and therefore, the molding hole 401 having the bottom surface is formed in the molded product 400 by the ejector pin 56.

Therefore, by adjusting the position of the front end surface 56b of the ejector pin 56 in the cavity 55, the depth of the molding hole 401 can be freely set, and the degree of freedom in design regarding the shape of the molded article 400 can be improved.

In the injection mold 1B, the ejector pins 56 for taking out the molded article 400 from the cavity 55 are used as movable pins for forming the molding holes 401 in the molded article 400.

Therefore, since the molding hole 401 is formed in the molded article 400 using the ejector pin 56 that takes out the molded article 400 from the cavity 55, the ejector pin 56 has two functions: the function of taking out the molded article 400 from the cavity 55 and the function of forming the molding hole 401 can reduce the number of parts and achieve high functionality of the injection molding die 1B.

< review >)

As described above, in the injection molding dies 1, 1A, 1B, the tip portions of the valve pin 15 or the

ejector pin

6, 56 functioning as movable pins are located in the

cavities

5, 55 filled with the molten resin 300, and are provided as the

hole forming portions

16, 6a, 56a for forming the molding hole 401 in the molded article 400.

Therefore, in a state where the

cavity

5, 55 is filled with the molten resin 300, the

hole forming portions

16, 6a, 56a are located in the

cavity

5, 55, and the molding hole 401 is formed in the molded article 400 by pulling out the

hole forming portions

16, 6a, 56a from the solidified molten resin 300. This makes it difficult to apply pressure from the molten resin 300 to the valve pin 15 and the ejector pins 6, 56 in the direction in which the valve pin 15 and the ejector pins 6, 56 tilt, and thus improves the molding accuracy of the molded article 400.

Further, since the molding hole 401 can be formed in the molded article 400 without using a dedicated member, the molding hole 401 can be formed in the molded article 400 without increasing the manufacturing cost.

Further, it is not necessary to set a low injection speed or a low injection pressure to the molten resin 300 injected into the cavity 5 as in the case of forming the molding hole 401 using a core pin, and thus a void is less likely to be generated in the molten resin 300, and the molding accuracy of the molded article 400 can be improved.

Further, since the molding hole 401 is formed by pressing a part of the valve pin 15 or a part of the ejector pins 6, 56 into the molten resin 300 in a state where the cavity 5 is filled with the molten resin 300 and the

gates

8b, 67a are closed, problems such as sink marks and dimensional defects are less likely to occur when the molten resin 300 is cooled, and high molding accuracy of the molded article 400 can be ensured.

Claims

1. A mold for injection molding comprising a fixed mold and a movable mold, wherein a cavity filled with a molten resin is formed by abutting the fixed mold and the movable mold,

a movable pin capable of moving in the axial direction is provided inside and outside the cavity,

the tip end portion of the movable pin is positioned in the cavity filled with the molten resin, and is provided as a hole forming portion for forming a molding hole in a molded article.

2. The mold for injection molding according to claim 1, wherein one gate is formed at a position corresponding to a central portion of the cavity.

3. The mold for injection molding according to claim 1 or 2,

is provided with: a nozzle having an ejection port for ejecting the molten resin toward the cavity; and

a valve pin that opens and closes the ejection port,

using the valve pin as the movable pin.

4. The mold for injection molding according to claim 1 or 2, wherein an ejector pin that takes out the molded article from the cavity is used as the movable pin.

5. The mold for injection molding according to claim 1 or 2, wherein a front end surface of the movable pin is located at a position away from a wall surface of the movable mold or a wall surface of the fixed mold forming the cavity in a state where the hole forming part is located in the cavity.

6. The mold for injection molding according to claim 1 or 2, wherein a front end surface of the movable pin is in a state of being in contact with a wall surface of the movable mold forming the cavity or a wall surface of the fixed mold in a state where the hole forming part is located in the cavity.

7. The mold for injection molding according to claim 1 or 2, wherein the hole forming portion is formed in a shape having a smaller diameter toward the front end.

8. The mold for injection molding according to claim 1 or 2, wherein the movable pin is rotatable around an axis, and a thread groove is formed on an outer peripheral surface of the hole forming portion.