JPH07106583B2 - Injection mold with undercut - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding die having an undercut portion, and for example, an undercut portion suitably applied for injection molding a molded product having an inner peripheral thread portion in the undercut portion. And an injection mold having

[0002]

2. Description of the Related Art Conventionally, there has been known a technique of using an injection molding die having an open core or a slide core to injection-mold a molded product having an undercut portion. Japanese Examined Patent Publication No. 59-14333 is an example of such an injection molding die, and according to the present proposal, it is configured by providing 6 groups of 2 slide pieces engaged in a dovetail groove on the outer peripheral surface of the central core. By moving the central core in the mold opening direction when the mold is opened, each slide piece engaged in the dovetail groove can be moved inward in the diametrical direction to take out the molded product after molding. It is something to do.

Further, according to Japanese Patent Laid-Open No. 59-150715, it is proposed that a pair of dovetail groove engaging portions provided in the above-mentioned injection molding die be formed into a special shape to prevent interference between slide pieces. Has been done. On the other hand, JP-A-61-748
According to the "Undercut molding method" of Japanese Patent No. 17, a structure is proposed in which large and small slide pieces are moved by an angular pin provided on a movable mold plate.

The proposal will be outlined with reference to the drawings. FIG. 8 is an operation explanatory drawing disclosed in Japanese Patent Laid-Open No. 61-74817. This figure shows that after the molded product H is formed, the mold is opened and
It is shown that the slide piece is moved to the inner diameter side of the undercut portion. In the figure, the center pin 31 is provided through the through hole formed at the center of the taper pin 32 whose lower end is fixed to the edge plate and whose outer peripheral surface is tapered. The angular pins 18 are radially fixed in the circumferential direction of the taper pin 32 whose lower end is fixed to the movable mold plate 19, and the working ends are holes 50a and 90a provided in the large and small slide pieces 50 and 90.
The large slide piece 50 having a larger arc-shaped undercut portion has a hole 50a formed in an elongated hole shape, while the small slide piece 90 having a small arc-shaped undercut portion The hole 90a is formed in a substantially circular shape.

In the "undercut molding method" of Japanese Patent Laid-Open No. 61-74817 described above, when the mold is closed, the slide pieces 50 and 90 radially arranged are closely attached to the taper surface of the taper pin 32. By doing so, an undercut portion for forming the molded product H is formed by opening in the outer diameter direction to form the undercut portion. Thereafter, as shown in the above figure, first, the small slide piece 90 having a small arc-shaped undercut portion is moved in the inner diameter direction by the mutual movement action of the hole 90a and the angular pin 18, and the large slide piece 50 is moved. After securing a space for moving, the hole 50a of the large slide piece 50 and the angular pin 18 move in the inner diameter direction by the mutual movement action.

[0006]

However, according to the proposal of Japanese Patent Publication No. 59-14333, the one surface of the pair of slide pieces engaged with the central core in the dovetail groove is used as the slide surface of the other slide piece. As a result, the divided surface of the slide piece is always a sliding surface, and the slide piece is worn. Further, since the central core and the slide piece are positioned by the dovetail groove engaging portion, there is a problem that if the dovetail groove engaging portion wears, accurate positioning between the central core and the slide piece cannot be performed.

On the other hand, in the proposal of Japanese Patent Laid-Open No. 59-150715, when the slide piece moves in the diametrical direction when the mold is opened, the special dovetail groove engaging portion is abraded, so that the central core is eventually brought about. There is a problem that accurate positioning between the slide piece and the slide piece cannot be performed. In addition, JP-A-61-7
In Japanese Patent No. 4817, a center pin is provided in a penetrating state with respect to a taper pin and a large number of slide pieces are radially arranged, which causes a problem that a die becomes complicated. Further, since the structure depends on the mutual movement action of the hole of each slide piece and the angular pin in order to move each slide piece to the inner diameter side, a guide portion for moving each slide piece to the inner diameter side is required. However, there is a problem that the mold becomes complicated.

Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to eliminate the conventional reference plane for alignment determined by the relative relationship between the central core and each open core. As a result, the mold can be configured easily and inexpensively, and when the mold is closed, the center core and the open cores can be completely adhered to each other without any gap, and the precision of the undercut part can be secured, and the dovetail groove can be secured. The purpose of the present invention is to provide an injection molding die having an undercut portion having excellent durability by preventing wear of the engaging portion. In addition to the above purpose,
It is an object of the present invention to provide an injection molding die having an undercut portion in which a burr does not occur at a portion of a molded product formed at a seam of an open core.

[0009]

[Means for Solving the Problems] and

In order to solve the above problems and achieve the object, the present invention has the following constitutions. That is, side surfaces facing each other have a small inclination angle surface with a small inclination angle, a substantially quadrangular pyramid-shaped central core formed of a large inclination angle surface with a large inclination angle, and a longitudinal center line of the central core. An injection molding mold having an undercut portion whose outer dimensions increase and decrease with movement and an undercut portion having two pairs of open cores each having a slide surface slidably moved on each side surface,
A pair of first pair having a mating surface that is slidably moved on the small inclination angle surface and that is formed in a substantially V shape on a surface that is parallel to the center line and is orthogonal to the center line. And the mating surface that is slidably moved on the large inclination angle surface and that is formed in a substantially M shape on a surface that is parallel to the center line and is orthogonal to the center line. 1
A pair of second open cores, and a guide portion for guiding the second open cores so as to reduce the outer dimension of the molds when the mold is opened, as the central core moves. When the mold is closed, the central core and each open core can be accurately positioned, and the accuracy of the cavity is secured and the durability is improved.

Preferably, in order to form the undercut portion on the inner peripheral thread, a large arcuate thread portion is formed in the pair of first open cores, and the pair of second open cores. In, a small arcuate screw portion is formed, and the precision of the cavity in which the undercut portion has an inner peripheral screw shape at the time of mold closing is secured, and the durability is improved.

Further, preferably, the guide portion is formed into a dovetail groove engagement between a slide surface slidingly moving along the small inclination angle surface and a slide surface slidingly moving along the large inclination angle surface. Consists of working to ensure the accuracy of the cavity and improve durability.

Further, preferably, the guide portion is formed integrally with the open core, which slides with respect to the guide portion formed along the side surface of the central core, and the open core. (EN) A flange portion having a hole portion and an angular pin provided on a movable die that is inserted into the hole portion, so that an injection molding die having an undercut portion can be easily configured. Then, in the seam, a molding recessed portion toward the central core side is further formed so that burr formation after molding does not reach the threaded portion.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a three-dimensional exploded perspective view of an injection-molding die having an undercut portion according to a first embodiment, showing only a main part configuration at a molding position indicated by a two-dot chain line in the figure. Although the slide pieces 5 and 9 are assembled in a state where the undercut portions of the slide pieces 5 and 9 are located, the slide pieces 5 and 9 are shown separated from the central core 1 for the sake of explanation.

In the figure, the central core 1 is formed in a truncated pyramid shape whose side surface area gradually decreases from the mounting portion 1b to the movable die toward the upper surface 1a, as shown in the drawing, while facing each other. And the first inclined surface 2 having an inclination angle θ1 formed by the perpendicular to the plane Q perpendicular to the central axis of the central core 1 in the longitudinal direction, and the longitudinal direction of the central core 1. It has a second inclined surface 3 having an inclination angle θ2 formed by a perpendicular line to a plane Q perpendicular to the central axis of the direction.

These inclination angles θ1 are, for example, 4 degrees, θ2
By setting 8 degrees, it is possible to make a difference in the movement amount of each slide piece described later. Further, the first inclined surface 2 has slide guide surfaces 2a parallel to each other on its side surface,
It has a mating surface 6 formed in a substantially V-shape, and is in close contact with a mating surface 10 formed in a substantially M-shape of the small slide piece 9, and a slide side surface 8a of the large slide piece 5. It is configured to be able to slide and guide with respect to. Further, by fitting into the convex groove portions 7 formed on the large slide piece 5 and the small slide piece 9, respectively, approximately at the centers of the first and second inclined surfaces 2 and 3 described above, they are slidable after assembly. Although formed, dovetail grooves 4 that cannot be separated from the angled inclined surfaces 2 and 3 are machined as shown by opening the upper and lower ends, respectively.

As shown in the figure, the second inclined surface 3 has a side surface gradually narrowing from the upper surface portion 1a to the mounting portion 1b, and is formed by a flat surface intersecting with the slide guide surface 2a. Next, as shown in the figure, a pair of large slide pieces 5 assembled so as to face each other includes a slide surface 8 that slides along the first inclined surface 2 having the above-described inclination angle θ1, and a center of the slide surface 8. The convex groove portion 7, the large arcuate screw portion 5a forming a part of the above-mentioned undercut portion, and the mating surface 6 formed by a plane parallel to the central axis of the central core 1 in the longitudinal direction are formed symmetrically. ing.

Further, as shown in the figure, the pair of small slide pieces 9 assembled so as to face each other has a structure in which the above-mentioned inclination angle θ is set.
Slide surface 11 slidingly moving along the second inclined surface 3
A convex groove portion 7 at the center of the slide surface 11, a small arcuate screw portion 9a forming a part of the above-mentioned undercut portion, and a flat surface parallel to the central axis of the central core 1 in the longitudinal direction. The surface 10 is formed symmetrically while the flank 12 is formed.
Is formed.

The convex groove portion 7 is formed in the dovetail groove 4 of the central core 1 described above.
By assembling by inserting from the opening, so that the pair of small arc-shaped screw portions 9a and the pair of large arc-shaped screw portions 5a are located at the molding position 20 shown by the chain double-dashed line, Perform molding. Molding position 2 shown by the two-dot chain line
In order to make it 0, the slide surface 8 of the large slide piece 5 moves while being slid with respect to the first inclined surface 2, while the slide surface 11 of the small slide piece 9 moves to the second inclined surface 3.
It moves while sliding with respect to, but before and after this, the mating surfaces 6, 10 are moved in parallel so that they come close to each other, and finally they come into close contact with each other to reach the molding position 20 shown by the chain double-dashed line.

FIG. 2 shows how the mold is opened after the above molding.
The operation will be described with reference to the operation explanatory diagram. When the mold is opened after molding, the central core 1 is moved in the direction of arrow A in the figure, but the large slide piece 5 and the small slide piece 9 are prevented from moving in the direction of arrow A by a mold plate (not shown). Since it is restricted, it starts to move inward in the diameter of the molding position 20. That is, a component force of moving in the direction of arrow A acts on the large slide piece 5 engaged with the dovetail groove 4 of the first inclined surface 2,
Heading to the center in the direction of arrow C in the figure. The central core is A
The center core upper surface is lower than the surface positions of the upper surface 5b and the upper surface 9b of the slide piece during operation.

Further, a component force moving in the direction of arrow A also acts on the small slide piece 9 engaged with the dovetail groove 4 of the second inclined surface 3 to move it to the center in the direction of arrow B in the figure. As described above, the inclination angle θ1 of the first inclined surface 2 is set to 4 degrees and the inclination angle θ2 of the second inclined surface is doubled to 8 degrees as described above. Since the amount of movement in the direction of arrow B is twice the amount of movement of the large slide piece 5 in the direction of arrow C, the small slide piece 9 moves to the center side earlier than the large slide piece 5, thus reducing the diameter. You can move in any direction. Further, interference between the slide pieces 5 and 9 when the mold is opened is prevented.

On the other hand, when the central core 1 is moved again in the direction opposite to the arrow A for closing the mold for preparation for molding, the slide pieces 5 and 9 move upward in the direction opposite to the arrows B and C. Although it is moved and moved to the position shown by the two-dot chain line in the figure, the joints 6 and 10 of the slide pieces 5 and 9 are moved in parallel as described above to be in close contact with each other. No wear on the eyes 6, 10 will occur. Further, since the large slide piece 5 is also slidably guided by the side surface 8a of the slide surface 8, the movement in the arrow direction C can be smoothly performed.

Next, FIG. 3 is a front view of an injection molding die according to the second embodiment, in which the slide pieces 5 and 9 are placed under the molding position 20 shown by the chain double-dashed line in FIG. It shows how the cut part is located. In this figure, since the basic configuration has already been described with reference to FIGS. 1 and 2, the detailed description will be omitted by omitting the description with the same reference numerals,
The upper surface portion 1a of the central core 1 and the upper surface portions 5b, 9b of the slide pieces 5, 9 are flush with each other, and the joints 6,
10 has been moved so that they are in close contact. In this state, the undercut portion having the outer dimension D is formed by the pair of small arc-shaped screw portions 9a and the large arc-shaped screw portion 5a, and the convex mating portions 14 having the width dimension w and the height dimension h are respectively aligned. Formed in eyes 6 and 10.

With the above construction, when a gap is formed in the joints 6 and 10 after the mold has been used for a long period of time, burrs which enter the gap and are generated are generated on the molded product side. , By the above-mentioned convex mating portion 14,
Since a burr is formed on the inner diameter side of the screw part of the molded product, the effect of the burr does not affect the function of the screw part. Therefore, if the above-described height dimension h is set to 0.1 mm, the effect of the burr does not affect the function of the screw portion if the burr height is 0.1 mm or less. By the way, when the height dimension h is set to 0.1 mm, the D dimension is 5
Good results could be obtained by setting the width to 7 mm and the w dimension to 4 mm.

Next, FIG. 4 is a front view of the injection molding die according to the third embodiment, and FIG. 5 is a sectional view of the main part of the injection molding die, showing the mold closed state. First, FIG. 4 shows a state in which the undercut portions of the slide pieces 5 and 9 are located at the molding position 20 shown by the chain double-dashed line in FIG. In this figure, the basic structure has already been described with reference to FIGS. 1 and 2, and therefore the details are given the same reference numerals and the description will be omitted and the description will be limited to different parts. The upper surface of the central core 1 and the slide piece 5, Each upper surface of 9 is flush with each other, and the joints 6 and 10 are moved so as to be in close contact with each other. In this state, the undercut portion is formed by the pair of small arc-shaped screw parts and the large arc-shaped screw parts.

The dovetail grooves 4 formed on the respective inclined surfaces of the central core 1 have vertical side surfaces on both sides as shown in the drawing, and convex dovetails directly inserted into the dovetail grooves 4 are formed. Slide pieces 5 and 9 each provided with a groove portion 7 are provided so as to be movable on four side surfaces as shown in the drawing. Flange portions 5f and 9f extending radially from the central core 1 are integrally formed on the slide pieces 5 and 9, and holes 5g and 9g formed in the flange portions 5f and 9f will be described later. The angular pins 18 are put into the respective inserted states.

Next, in FIG. 5, a fixed mold 16 is provided with a runner for injection of resin, a gate and a hole 16a. In the mold closed state shown in the drawing, a cavity formed by the above-mentioned undercut portion is formed. While allowing molten resin to be injected therein, the mutual positional relationship between the fixed side mold 16 and the central core 1 is determined by guiding and inserting the bolt 15 screwed into the threaded portion of the central core 1 into the hole 16a. I am able to do it.

The fixed mold 16 includes a movable mold plate 17 having the first separating surface P1 as a separating surface and a receiving plate 19 having the second separating surface P2 as a separating surface with respect to the movable mold plate 17. The molds are provided so as to be movable so as to be in a mold closed state and a mold opened state, respectively, to form a known mold structure. In addition, the sliding guide plate 21 having the elongated hole 21b for allowing the angular pin 18 to be inserted is provided with the spacer 22 by using the bolt 15.
Is fixed to the movable-side mold plate 17 via a sliding surface 21a of the sliding guide plate 21 and the sliding surface 17a of the movable-side mold plate 17 to form a space portion. The flange portions 5f and 9f of 5 and 9 are slidable within this space portion.

On the other hand, a female part 17a is formed on the movable side mold plate 17, and a cavity is formed by a pair of small arc-shaped screw parts 9a and large arc-shaped screw parts 5a which are the undercut parts of the slide piece. ing. Further, as described above, the central core 1 fixed to the receiving plate 19 by the bolts 15 and moved in the direction of arrow A in the figure has a side surface gradually becoming smaller from the mounting portion 1b for the movable die toward the upper surface 1a. The first inclined surface 2 is formed in the shape of a quadrangular pyramid and is formed to face each other, and the inclination angle formed by the plane Q perpendicular to the central axis of the central core 1 in the longitudinal direction is θ1.
And a second inclined surface 3 which is also formed to face each other and has an inclination angle of θ2 with a plane Q perpendicular to the central axis of the central core 1 in the longitudinal direction.

These inclination angles θ1 are, for example, 4 degrees, θ2
By setting 8 degrees, the amount of movement of the large and small slide pieces 5 and 9 is made different. Further, the angular pin 18 fixed to the receiving plate 15 with the bolt 15 is used.
When the mold is closed, the tip thereof sneaks into the relief hole 17c of the movable side mold plate 17 and the slide pieces 5, 9
Of the flanges 5f and 9f of the respective holes 5g and 9g, which are slanted at inclination angles θ1 and θ2, respectively, and are slidably received in the holes 5g and 9g. It is tilted and fixed to the plate 19.

In the above structure, when the resin is injected into the cavity and curing is waited for, and the molds are opened on the separation surfaces P1 and P2, the central core 1 is moved in the direction of arrow A in the figure, The slide piece 5 and the small slide piece 9 are restricted so as not to move in the direction of arrow A as described above, and as described in FIG. Start moving. That is, due to the holes 5g and 9g that sneak into the angular pin 18 without play, a component force that moves in the direction of arrow C acts on the large slide piece 5 and moves toward the center.

An arrow A also appears on the small slide piece 9 (not shown).
The component force moving in the same direction acts toward the center of the central core in the same manner, but as described above, the inclination angle θ1 of the large slide piece 5 is set to 4 degrees, while the inclination angle of the small slide piece 9 is set. Since θ2 is doubled to 8 degrees, the amount of movement of the small slide piece 9 in the direction of arrow B is twice the amount of movement of the large slide piece 5 in the direction of arrow C, so the small slide piece 9 is larger. Since it moves to the center side earlier than 5, each piece can be moved in the direction of reducing the diameter. Further, interference between the slide pieces 5 and 9 when the mold is opened is prevented.

On the other hand, when the central core 1 is moved in the direction opposite to the arrow A and the slide cores 5 and 9 are moved in the direction opposite to the arrows B and C, the mold is closed again for the preparation for molding and the slide cores 5 and 9 are moved upward. Although the slide pieces 5 and 9 are moved to the positions shown in the drawing to be in a molding preparation state, the joints 6 and 10 of the slide pieces 5 and 9 are moved in parallel as described above to be in close contact with each other. No wear of 6, 10 will occur. Further, since the dovetail groove engaging structure may be processed into the extremely simple groove shape in which the undercut portion is not formed on the side surface as described above, the manufacture of the central core 1 and each slide piece 5, 9 becomes easy, Processing costs are greatly reduced.

Next, FIG. 6 is a front view of an injection molding die according to the fourth embodiment. In this figure, the basic configuration is shown in FIGS.
Since it has already been described, the details will be given the same reference numerals and the description will be omitted to limit the description to the different parts. In place of the dovetail groove of the central core 1, a convex guide is provided on each inclined surface of the central core 1. Part 40
Are integrally formed in a cross shape. Further, the large and small slide pieces 5, 9 are formed with guide recesses 70 which are slidable by entering the guide portions 40. According to the central core described above, the mold can be further simplified.

Finally, FIG. 7 is a front view of the central core according to the fifth embodiment, in which the central core 1 is formed by a hexagonal pyramid as shown in order to provide four or more slide pieces. , A total of 6 slide pieces can be moved radially of the central core. As described above, according to each embodiment, the positioning accuracy between the central core 1 and each slide piece 5, 9 can be realized by the mating surfaces 6, 10, so that the cavity accuracy can be ensured and the dovetail groove engaging portion can be secured. Wear can be prevented. Further, by using the Eingular pin, it is possible to provide an injection molding die having an undercut portion that can be more easily configured. In each of the above-described embodiments, only the case where the undercut portion is formed as a helicoid screw formed in the lens barrel has been described, but the present invention is not limited to this, and a precision component having an undercut portion may be used. Anything is fine.

[0035]

As described above, according to the present invention,
By eliminating the reference plane for alignment, which is determined by the relative relationship between the conventional central core and each open core, the mold can be configured easily and inexpensively, and when the mold is closed, the central core and each open core are separated from each other. Provide an injection molding die with an undercut part that has excellent durability by ensuring the accuracy of the undercut part while ensuring complete contact without gaps and by preventing wear of the dovetail groove engaging part can do. Further, it is possible to prevent burrs from being generated in the part of the molded product formed at the joint of the open core.

[Brief description of drawings]

FIG. 1 is a first injection molding die having an undercut portion.
It is a three-dimensional disassembled perspective view which concerns on an Example.

FIG. 2 is an external perspective view for explaining the operation of FIG.

FIG. 3 is a front view of an injection molding die having an undercut portion according to a second embodiment.

FIG. 4 is a front view of an injection molding die having an undercut portion according to a third embodiment.

FIG. 5 is a fragmentary cutaway view of an injection molding die using the central core and the slide piece of FIG.

FIG. 6 is a front view of an injection molding die having an undercut portion according to a fourth embodiment.

FIG. 7 is a front view of a central core according to a fifth example.

FIG. 8 is a fragmentary cutaway view of a conventional injection molding die having an undercut portion.

[Explanation of symbols]

 1 central core, 2 first inclined surface 3 second inclined surface 4 dovetail groove 5 large slide piece 6 mating surface 7 convex groove portion 8 slide surface 9 small slide piece 10 mating surface 11 slide surface 12 niger surface 18 angular pin 20 at the molding position is there.

Claims (5)

[Claims] 1. A substantially quadrangular pyramid-shaped central core whose side surfaces facing each other have a small inclination angle surface with a small inclination angle, a large inclination angle surface with a large inclination angle, and a center in the longitudinal direction of the central core. With the movement along the line,
An injection molding die having an undercut portion having an outer dimension increasing and decreasing and an undercut portion having two pairs of open cores each having a slide surface slidably moved on each side surface, wherein the small inclination angle A pair of first open cores each having a mating surface that is slidably moved on a surface and that is formed in a substantially V shape on a surface that is parallel to the center line and is orthogonal to the center line. A pair of first mating surfaces that are slidably moved on the large tilt angle surface and that have a mating surface that is parallel to the center line and that is formed in a substantially U-shape on a surface orthogonal to the center line. And a guide portion that guides the second open core so as to reduce the outer dimension first when the center core moves when the mold is opened. Injection molding with characteristic undercut Mold. 2. In order to form the undercut portion as an inner peripheral thread, a large arcuate thread portion is formed in the pair of first open cores, and a small circle is formed in the pair of second open cores. An injection molding die having an undercut portion according to claim 1, wherein an arcuate screw portion is formed. 3. The guide portion is configured such that a slide surface that slides along a small tilt angle surface and a slide surface that slides along the large tilt angle surface engage in a dovetail groove. An injection molding mold having an undercut portion according to claim 1 or 2. 4. The open core, which slides with respect to the guide portion formed along the side surface of the central core, and the hole portion formed integrally with the open core. The injection molding die having an undercut portion according to claim 1 or 2, comprising a flange portion and an angular pin provided on a movable die that is inserted into the hole portion. 5. The injection-molding die having an undercut portion according to claim 1, further comprising a molding concave portion formed at the seam toward the central core.