JPH08323823A - Injection molding method and mold used therefor - Google Patents

Abstract

PURPOSE: To easily and highly accurately form continuous undercut part along the peripheral edge of the opening part of a box-like molded article. CONSTITUTION: A projecting part 14C, which fits to a dovetail provided on the inclined plane of a vertically moving movable core block 8, is provided on a side slide core 14. Further, in inclined through hole 27A, into which an angular pin 25 slantly fixed to a movable retainer plate 4 interlocking with the movable core block 8, is provided on a corner slide core 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method for a box-shaped resin molded product having a rectangular or elliptical shape having a continuous undercut portion on the periphery of an opening, and an injection molding die used therefor. .

[0002]

2. Description of the Related Art For example, when a door of an electric refrigerator is made of synthetic resin, a resin molded product 101 for forming a door body.
Has a box shape having an opening for providing the heat insulating material layer 102, and in order to fix the decorative plate 103 holding the heat insulating material layer 102, it is necessary to provide a continuous rib 104 at the periphery of the opening. (See Figure 1a). As a result, a continuous undercut portion 105 is formed around the opening of the resin molded product 101.

Conventionally, a box-shaped resin molded product 10 having an undercut portion 105 which is continuous at the periphery of the opening portion as described above.
1 is injection-molded (see FIG. 1), the portion corresponding to the undercut portion 105 is forcibly punched out by using an injection-molding die in which the portion corresponding to the undercut portion 105 is made fine, or the undercut portion at the periphery of the opening is formed. The mold part corresponding to 105 is notched at a plurality of positions, and the notched part is used to form a mold by using an inclined pin, a slide core, or the like.

[0004]

When a box-shaped resin molded product having a continuous undercut portion at the peripheral edge of the opening is molded by a conventional injection molding die, a molded product having a desired shape is accurately obtained. It is difficult to obtain the molded product, and it is difficult to avoid deformation and burrs of the resulting molded product, so that a molded product having a commercial value cannot be efficiently obtained.

Further, there is a problem that the depth of the undercut portion cannot be increased and it is difficult to obtain a resin molded product having high strength.

According to the present invention, the box-shaped molded article has
An object of the present invention is to provide an injection molding method capable of easily forming a continuous undercut portion with high accuracy and a mold used for the injection molding.

[0007]

In order to achieve the above object, in the injection molding method of the present invention, a fixed side portion,
In the cavity formed by the side portion corresponding to the linear portion of the molded product by providing the protruding piece on the outer peripheral portion and the movable side portion having the bent portion of the molded product by providing the protruding piece on the outer peripheral portion and the corresponding corner core. After injecting and injecting a molten resin and cooling and solidifying the molten resin, the side cores are moved inward, and then the corner cores are displaced in the vertical direction and moved inwardly to release the resin molded product. .

In order to achieve the above object, in the injection molding die of the present invention, a fixed side portion and a protruding strip forming an undercut portion are provided, and a side core and an underlayer corresponding to a straight portion of the molded product are provided. A movable side portion that forms a cavity portion with the fixed side portion by providing a corner piece corresponding to the bent portion of the molded product while providing a protruding piece that forms a cut portion, and injection for injecting and injecting molten resin into this cavity portion Means, moving means for moving the side core and the corner core inward, and displacement means for vertically displacing the corner core.

The moving means mounts a core block having an inclined surface that abuts on the inner peripheral portions of the side core and the corner core so as to be movable in the vertical direction, and either the inner peripheral portion of the side core or an inclined surface that abuts on the inner peripheral portion. It is also possible to form the groove by providing a groove on one side and a convex line on the other side.

Further, the moving means tilts the angular pin on the movable side mold plate which moves up and down in conjunction with the up and down movement of the core block having the inclined surfaces which come into contact with the inner peripheral portions of the side cores and the corner cores. Then, the angular pin and the corner core may be connected and fixed.

Further, the displacement means can be formed by supporting the corner core on a stripper plate connected to the fixed side portion.

[0012]

According to the injection molding method configured as described above, after the molten resin injected and injected into the cavity is cooled and solidified, the side core is first moved inward,
The ridge strip is released from the undercut portion of the straight part formed by the ridge strip of the side core, and then the corner core is displaced in the vertical direction, so that the corner core is on a surface different from the surface on which the side core is located. Then, the corner core can be easily moved inward, and this movement allows the protruding strip of the corner core to be released from the undercut portion of the bent portion.

Further, according to the injection molding die configured as described above, the side core provided with the protruding strip forming the undercut portion on the straight portion of the molded product and the undercut portion on the bent portion of the molded product. The corner cores provided with the protruding strips forming the can be moved inward by the moving means, and at that time, the corner cores are moved inward by the moving means to a surface different from the surface on which the side cores are located. Since it moves, the side core does not hinder the movement.

If the side cores are made to be slidable along the inclined surface of the vertically moving core block, the side cores move smoothly inward, and the corner cores are interlocked with the vertical movement of the core block. The corner core can be smoothly moved inward along the angular pin by connecting to the angular pin that is inclined and fixed to the movable side mold plate that moves vertically.

Further, when the corner core is supported by the stripper plate connected to the fixed side portion, the corner core can be smoothly displaced in conjunction with the movement of the stripper plate.

[0016]

EXAMPLE An example of the present invention will be described with reference to FIGS. 2 to 5 in the case of forming a resin molded product 101 having an undercut portion 105 having a shape as shown in FIG. 1a.

In the figure, 1 is a fixed-side mounting plate for fixing the fixed-side mold plate 2, 3 is a ring-shaped stripper plate,
4 is a ring-shaped movable side template, 5 is a spacer block, 6
Is a ring-shaped movable side auxiliary template plate interposed between the spacer block 5 and the movable side mounting plate 7, and 8 is a columnar movable side core block whose lower part is fixed to the movable side mounting plate 7, and which is the lower portion 8
D is a quadrangular prism shape, and the upper portion 8E is formed in an octagonal truncated pyramid shape, and a stepped core block type plate receiving portion 8A is provided on the side wall of the joint portion between the lower portion 8D and the upper portion 8E.

In this movable side core block 8, the side wall surface between the core block die plate receiving portion 8A and the top surface, that is, the side wall surface of the octagonal frustum-shaped upper portion 8E is formed from eight inclined side wall surfaces. 4 facing the side slide core 14
A smooth surface 8B and a dovetail groove 8C are provided on the side wall surface of the surface.
9 is a rocket ring provided on the fixed side mounting plate 1, 10 is a sprue runner portion provided on the fixed side template 2, 11 is a pin 2A provided on the fixed side template 2 and a pin 3A provided on the stripper plate 3 A pulling link with a long hole to
Reference numeral 12 denotes a cavity portion communicating with the sprue runner portion 10 via the fan gate portion 10A.
By injecting and injecting the molten resin into the resin molding product 12A having the undercut portion 12B is molded.

Reference numeral 13 denotes a movable side mold plate inserter which is housed in the central portion of the stripper plate 3 and is supported and fixed to the movable side mold plate 4, and 14 denotes a side slide core corresponding to the linear side portion of the resin molded product 12A. The outer peripheral portion has a protruding strip 14A forming an undercut portion 12B, and the inner peripheral portion has a smooth surface 1 that abuts on a smooth surface 8B of the movable core block 8.
4B and a projecting portion 14C that engages with the dovetail groove 8C of the movable side core block 8 and is fitted and supported on the movable side template insert 13 so as to be movable inward and outward.

Reference numeral 14D is a support portion for supporting the side slide core 14 on the movable side core block 8 and is formed by extending the protrusion 14C in relation to the stroke of movement of the side slide core 14. Reference numeral 15 is a ring-shaped lower protruding plate that is housed in the central portion of the spacer block 5, and 16 is a ring-shaped upper protruding plate that is housed in the central portion of the spacer block 5, and these ring-shaped movable side mold plates 4, The movable core block 8 is housed in a space formed in the center of the lower protrusion plate 15 and the upper protrusion plate 16.

Reference numeral 17 denotes a movable side support guide pin whose lower portion is fixed to the movable side mounting plate 7, and upper portion is a guide bush 18 in a through hole provided in the movable side template 4, spacer block 5 and movable side auxiliary template 6. Has been inserted through. Reference numeral 19 is a runner ejecting pin whose lower portion is fixed to the upper ejecting plate 16 and whose upper portion is opposed to the fan gate portion 10A, and 20 is an ejector pin whose lower portion is fixed to the upper ejecting plate 16 and whose upper portion is opposed to the resin molded product 12A. , 21 are stop bolts for locking the upper part to the spacer block 5 and the lower part to the movable side mounting plate 7, respectively, and 22 are the spacer blocks 5
And a movable side mounting plate 7, and a compression coil spring that urges them in a direction to separate them, and 23 is a return pin that is fixed to the stripper plate 3 at the upper portion and to the upper protruding plate 16 at the lower portion, and is movable. It penetrates the side template 4.

Reference numeral 24 denotes a plate return coil spring which is stretched between the movable side mold plate 4 and the upper protruding plate 16 and urges them in a direction to separate them, and 25 fixes the lower part to the movable side mold plate 4 and the upper part. Is an angular pin that is tilted inward,
Reference numeral 26 denotes a corner slide core corresponding to the bent corner portion of the resin molded product 12A, and the undercut portion 12 is provided at the outer peripheral edge portion.
It has a protruding strip 26A that forms B, contacts the inclined side wall surface of the upper portion 8E of the movable side core block 8 at the inner peripheral edge, and can move inward and outward on the stripper plate 3. It is supported. Reference numeral 27 denotes a corner slide core drive unit connected to the corner slide core 26 by a connecting shaft 28, which is supported by the stripper plate 3 and has an inclined through hole 27 into which an upper portion of the angular pin 25 is fitted.
Have A. 29 is a stripper plate nesting, 30
Is a main guide pin whose lower part is fixed to the movable side mold plate 4 and whose upper part is inserted into a through hole formed in the stripper plate 3 via a stripper plate guide bush 31.
32 is an outer peripheral line of the resin molded product 12A, 33 is an inner rising line of the resin molded product 12A, and 34 is a resin molded product 1.
2A undercut line.

Next, the operation of injection molding the resin molded product 12A will be described. When the mold clamping process is completed and the resin can be injection-molded, the fixed side mold plate 2 and the stripper plate 3 are joined together, and the stripper plate 3 and the movable side mold plate 4 form the plate return coil spring 2
The movable side mold plate 4 is supported by the core block mold plate receiving portion 8A of the movable side core block 8. Further, the sliding surface 14B of the side slide core 14 contacts the sliding surface 8B formed on the four inclined side wall surfaces of the upper portion 8E of the movable core block 8, and the dovetail groove 8
The protrusion 14C is engaged with C, and further, the inner peripheral edge portion of the corner slide core 26 comes into contact with the other four inclined side wall surfaces of the upper portion 8E of the movable core block 8 and the side slide core 14 Being held by. As a result, the fixed-side template 2 and the movable-side core block 8, the side slide core 14, and the corner slide core 26 form the cavity portion 12 (see FIGS. 2A and 3).

Since the movable mold plate 4 is supported by the core block mold plate receiving portion 8A of the movable core block 8, another reinforcing support block is used even if the central portion is cut out in a ring shape. Can fully withstand the injection pressure of resin injection.

After this mold clamping step, a molten resin injection / injection step is started, and the molten resin is transferred to the sprue runner portion 10.
Is injected into the cavity 12 through the fan gate portion 10A, and the molded product 12 is formed by cooling and solidifying the molten resin.
A is molded, and the process moves to the next mold opening step. The mold opening process is mainly performed by the first stage side slide core 14 opening process and the second stage corner slide core 26.
And the process of opening. In the resin molded product 12A, an undercut portion 12B is formed by the protruding strip 14A of the side slide core 14 and the protruding strip 26A of the corner slide core 26.

The step of opening the side slide core 14 will be described (see FIGS. 2b and 4). Compression coil spring 22
When the elastic force of the movable side mounting plate 7 is operated, the movable side mounting plate 7 is retracted by being guided by the movable side support guide pin 17 for a limited stroke until the upper portion and the lower portion of the stop bolt 21 are locked. The movable core block 8 fixed to the back also retreats. The four side slide cores 14 having the protrusions 14C that engage with the dovetail grooves 8C of the movable core block 8 when the movable core block 8 retracts
Slides along the sliding surfaces 8B and 14B and moves inward in the front-rear direction or the left-right direction on the movable mold plate insert 13 as shown by the arrow in FIG. 2b. The inward movement of the side slide core 14 separates the protruding strip 14A from the undercut portion 12B.

When the mold opening process is further advanced to open the parting line and the movable mold is retracted, the fixed mold plate 2 is opened.
With the pulling link 11 in which the pin 2A of
The stripper plate 3 is guided by the main guide pin 30 via the pin 3A and floats above the movable mold plate 4, and the process proceeds to the step of operating the corner slide core 26.

Next, a process of operating the corner slide core 26 will be described (see FIGS. 2c and 5).

As the stripper plate 3 floats above the movable side mold plate 4, the lower protruding plate 15 and the upper protruding plate 16 also float, and the movement of the stripper plate 3 also lifts the corner slide core 26 and the resin molded product 12A. To do. In this case, since the lower protruding plate 15 and the upper protruding plate 16 are respectively floated up, the protruding pins 20 are also floated up, so that the protruding strip 14A of the side slide core 14 is separated from the undercut portion 12B. Resin molded product 12A
The undercut portion 12B is released from the movable side mold plate insert 13 by the operation of the protruding pin 20. When the stripper plate 3 floats, this movable side mold plate 4
The corner slide core drive portion 27 fitted in the inclined through hole 27A slides inward by the angular pin 25 that is inclined and fixed inward.

By the sliding of the corner slide core driving portion 27, the corner slide core 26 connected by the connecting shaft 28 also moves inward on the stripper plate 3 as shown by the arrow in FIG. 26A separates from the undercut portion 12B. Although the corner slide core 26 moves inward at an angle of 45 degrees with respect to the moving direction of the side slide core 14, it differs from the side slide core 14 because it moves together due to the movement of the stripper plate 3. Therefore, the side slide core 14 does not hinder the movement.

Further, the protruding strip 1 of the side slide core 14
4A and the protruding strip 26A of the corner slide core 26,
When the resin molded product 12A is separated from the undercut portion 12B by the movable mold plate insert 13 and the stripper plate insert 29, the resin molded product 12A is supported from the mold release resistance, so that the resin mold product 12A can be removed smoothly without applying an external force. it can. Then, after the protruding strip 26A of the corner slide core 26 is separated from the undercut portion 12B, it is built into the stripper plate nest 29 and the resin molded product 12A is separated by the protrusion pin driven by the corner slide core drive portion 27. The step of molding and releasing is completed.

In the above description, since the shape of the resin molded product 12A is a square shape, four side slide cores 14 and four corner slide cores 26 are used, but if the shape is circular or polygonal. Can be similarly molded using a plurality of slide cores.

[0033]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it is possible to easily form a continuous undercut portion at the periphery of the opening of a box-shaped resin molded article with high accuracy. The molded product obtained is of high commercial value without any deformation or burrs.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a resin molded product having an undercut portion.

FIG. 2 is an operation explanatory view of a mold in the injection molding method of the present invention.

FIG. 3 is an AO in FIG. 2 of the injection molding die of the present invention.
It is a side sectional view taken along the line -A.

FIG. 4 is a side sectional view of the injection molding die taken along the line AA in FIG.

FIG. 5 is a view of the same injection molding die taken along the line A-O-B- in FIG.
It is a sectional side view in the C line.

[Explanation of symbols]

 2 Fixed-side mold plate 4 Movable-side mold plate 8 Movable-side core block 8B, 14B Smooth surface 8C Dovetail groove 10 Sprue runner part 12 Cavity part 12A Resin molded product 12B Undercut part 14 Side slide core 14A, 26A Projection strip 14C Projection Part 25 Angular pin 26 Corner slide core

Claims (5)

[Claims] 1. A molten resin is injected and injected into a cavity portion formed by a fixed side portion, a movable side portion having a side core having a ridge piece provided on an outer peripheral portion and a corner core having a ridge piece provided on an outer peripheral portion. An injection molding method in which, after the molten resin is cooled and solidified, the side cores are moved inwardly, and then the corner cores are vertically displaced and moved inwardly to release the resin molded product. 2. A fixed-side portion, a side core provided with a protruding strip for forming an undercut portion in a straight portion of a molded product, and a corner core provided with a projected strip for forming an undercut portion in a bent portion of a molded product. A movable side portion that forms a cavity portion with the fixed side portion, an injection means that injects and injects a molten resin into the cavity portion, a moving means that moves the side core and the corner core inward, and a corner core that moves up and down. A mold for injection molding having a displacement means for displacing in the direction. 3. A core block having slanted surfaces that come into contact with the inner peripheral portions of the side cores and corner cores is movably mounted in the vertical direction, and the inner block of the side cores or the slanted surface that comes into contact with the core blocks is provided with a strip. The mold for injection molding according to claim 2, further comprising a groove and a moving means having a ridge formed on the other side to fit with the groove. 4. An angular pin is tilted and fixed to a movable side mold plate that moves up and down in conjunction with the up and down movement of a core block having inclined surfaces that come into contact with the inner peripheral portions of the side core and the corner core. The mold for injection molding according to claim 2, further comprising a moving means in which a corner core is connected to the angular pin. 5. The mold for injection molding according to claim 2, wherein the stripper plate connected to the fixed side portion has displacement means for supporting the corner core.