JPS6157169B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in injection molding methods for thermoplastic synthetic resins.

Conventionally, for example, when applying a metallic color or pattern to the internal concave surface of the lid of a compact, which is a cosmetic container, Japanese Patent Application Laid-Open No. 56-5747 discloses the following techniques:
The decorative film plate is held in a clamping mold connected to the cavity side of a pair of molds consisting of a cavity and a core, and the core is clamped and the molten synthetic resin is injected and filled. The film plate is automatically cut and pushed into the cavity, and the decorative film plate is plastically deformed by the injection pressure and temperature to fit the mold, and is fused with the injected molten resin to form the uneven surface of the product. A method of molding is disclosed.

However, in this prior art, depending on the temperature of the molten resin and the injection pressure when the synthetic resin is injected,
Since the wide surface of the decorative film plate is plastically deformed, most of the wide surface of the film plate may become thinner due to the plastic deformation, or may break during plastic deformation. Therefore, a molded product in which most of the wide side of the film plate is left intact and injection synthetic resin is integrally fused only to the edges, such as a flexible wide side and a relatively It has been impossible to manufacture portable toothbrush cases, shaving tool cases, toiletries cases, etc. that have a hard frame.

The present invention involves sandwiching the wide side of a pre-made thin sheet made of thermoplastic synthetic resin between a pair of molds for injection molding, and in this state, aligning the outer peripheral edge of the thin sheet with the outer edge of a molding hole in the mold. The thin sheet is cut according to the shape of the molded product at the cutting section, and the outer peripheral edge of the thin sheet is exposed to the molding cavity, and the outer peripheral edge is integrally fused with the molten resin to form an injection molded part. This makes it possible to easily obtain lightweight injection molded products that have never been seen before.

Next, an embodiment of the present invention will be described. Reference numeral 1 denotes a portable toothbrush case which is a finished product. In the case 1, a thin sheet 2 of an appropriate width has semicircular plate-shaped frames 3, 3 at both left and right ends, respectively. ', 3, 3' are integrally fused at their semicircular portions. Approximately linear edge members 4, 4' are integrally fused to the front and rear ends of the thin sheet 2, extending between the semicircular frames 3, 3'.

These thin sheets 2, frames 3, 3', and edge members 4, 4' are made of the same thermoplastic synthetic resin, such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, etc.

In the toothbrush case 1, the middle part of the thin sheet 2 separated by the frames 3 and 3' becomes a hinge part 5 that can be bent in one piece, and when it is closed around these five hinge parts, it becomes a sealed cylindrical shape. becomes.

The edge members 4, 4' are integrally provided with engaging portions 6, 6' for hooking and releasable engagement.

Reference numeral 7 denotes an injection molding device for integrally molding the toothbrush case 1, which includes a pair of molds 8, 8'.
and a pair of front and rear rollers 9, 9' for drawing out the thin sheet 2 from the coil portion 2' and inserting it between a pair of molds 8, 8' (see FIG. 2).

A thin sheet 2 is inserted between the two molds 8, 8' so that the longitudinal direction of the edge members 4, 4 of the toothbrush case 1, which is the product, coincides with the width direction of the thin sheet 2. Yes, in this example, thin sheet 2
By making the width direction dimension H of the edge members 4, 4' substantially equal to or slightly shorter than the length dimension of the edge members 4, 4', only the front and rear positions in the feeding direction are cut when cutting the thin sheet 2, which will be described later. (see figure).

Both molds 8, 8' have molding holes 10, 10' for injection molding and edge members 4, 4' which correspond to the shape of the frame bodies 3, 3' of the toothbrush case 1 when these molds are put together. Molding cavity 1 corresponding to the shape of the spot
0″, 10″ are formed, and molding holes 10′ and 1
0'' communicates with each other when both molds 8 and 8' are put together. Reference numeral 13 is a gate for guiding the molten resin A to the molding cavities 10' and 10''.

Further, on the mating surface of both molds 8, 8', both molds 8, 8' are aligned with the outer periphery of molding holes 10'', 10'' corresponding to the edge members 4, 4' in plan view. Stepped cutting portions 11, 11 that cut the thin sheet 2 into a shape approximately equal to that of the product.
(See Figure 3). These upper and lower cut portions 11, 11 seal the molding cavities 10'', 10'' when both molds 8, 8' are brought together (see FIG. 4).

Furthermore, on the mating surfaces of the two molds 8, 8',
Clamping parts 12, 12 having a wide area are formed on the inner circumferential side surrounded by the molding cavities 10' and 10'', and the upper and lower clamping parts 12, 12 form a thin plate on the inner peripheral side of the molding cavities 10', 10''. Hold the wide side of sheet 2.

With the device having this configuration, the front and rear pair of rollers 9,
When the thin sheet 2 is inserted between the upper and lower molds 8, 8' through the insertion device 9' and the mating surfaces of the molds 8, 8' are brought close together, the result is shown in the dashed line in FIG. Since the thin sheet 2 is pushed down by the convex holding portion 12, the thin sheet 2 is held between the two holding portions 12, 12.

At this time, both or one of the pair of rollers 9 and 9' rotates, and the thin sheet 2 does not undergo so-called plastic deformation, but shifts and moves along the uneven surfaces of the holding parts 12 and 12.

Therefore, as in the case where the wide side of the thin sheet is plastically deformed by fitting the mold with the four circumferences of the thin sheet tightly held, the thickness of the thin sheet itself may become thinner, or in some cases. There have been no accidents where thin sheets have been torn.

When the clamping parts 12, 12 have almost completed clamping the thin sheet 2, the cutting parts 1 of both molds 8, 8'
1 and 11 cut both ends of the thin sheet 2 in the longitudinal direction.

In this state, the molding holes 10'', 1 correspond to the edge members 4, 4 of the toothbrush case 1, which is a product.
0'' is sealed by the cut portions 11, 11 on the outer periphery and the clamping portions 12, 12 on the inner periphery, and the outer edge of the cut thin sheet 2 forms the molding cavity 10''.
(See Figure 4).

The molding portions 10', 10' corresponding to the frames 3, 3 are also molded as described above. The parts following the cavities 0'' and 10'' are sealed by the cut parts 11 and 11, while the widthwise edges of the thin sheet 2 are inserted into the molding cavities 10' and 10' that will become the frame 3. Since it is sealed by the clamping parts 12, 12 (see Figs. 5 and 6), the synthetic resin injected from the gate 13 enters the molding cavity 1.
0' to 10'', forming holes 10', 1
The end of the thin sheet 2 located within 0" is injected and fused with the high temperature molten resin A to be integrated. After this,
When the two molds are separated, the toothbrush case 1 as shown in FIG. 1 can be taken out.

When manufacturing the lid 14' of the text box 14 as shown in FIG. 7, the thin sheet 2 is used as is for the thin top plate 14'' of the lid 14', and Four circumferential frames adjacent to the thin sheet 2 are integrally injection molded onto the outer peripheral edge of the thin sheet 2.

Therefore, on the mating surfaces of the upper and lower molds 8, 8',
Four mutually communicating molding cavities 10, 10, 10, 10 corresponding to the four peripheral frame parts of the lid body 14'
The coil thin sheet 2 is fed so that the longitudinal direction of the lid body 14' coincides with the width direction of the thin sheet 2, as in the first embodiment.

The molding cavity 1 is formed on the mating surfaces of both molds 8 and 8'.
0, 10, 10, 10, adjacent to the inner circumferential side thereof, the holding portions 12, 12 are formed, while the thin sheet 2
Cutting portions 11, 11 are provided on the outer periphery of the pair of forming cavities 10, 10 so as to cut the front and rear ends in the feeding direction (see FIG. 8).

If the thin sheet 2 is inserted between the upper and lower molds 8, 8' and then the two molds 8, 8' are brought together, the wide side of the thin sheet 2 will be clamped by the clamping parts 12, 12. , the outer edge of the thin sheet 2 cut at the cutting parts 11, 11 is in a free state in the molding cavities 10, 10,
For example, the molding cavity 10 in the upper mold 8 and the molding cavity 10 in the lower mold 8' enter in a rounded and contracted state.
The gate 13 for the molten resin A may normally be provided only in one of the upper or lower molds, but it can be provided in both the upper and lower molds 8. , 8' both molding holes 10, 10
A gate 13 may be provided for each.

In this way, by injecting the molten resin A with both the upper and lower molds 8, 8' aligned, the lid body 14 is formed by forming the top plate 14'' made of the thin sheet 2 and the frame portion around its four peripheries. Can be molded in one piece.

In summary, the present invention provides an injection molding method for integrally molding an injection molded part of the same material on the outer periphery of a thin sheet made of a thermoplastic synthetic resin, which is provided with a molding cavity for injection molding the thermoplastic synthetic resin. A pre-made thin sheet is inserted between a pair of molds, and the inserted thin sheet is inserted at a gripping portion formed on the inner peripheral side of the molding hole adjacent to the molding hole of the mating surface of both molds. The outer periphery of the thin sheet is cut by a cutting part that pinches the wide surface inside the outer periphery of the thin sheet and seals the outer periphery of the molding cavity provided in both molds, and the outer periphery of the thin sheet is inserted into the molding cavity. A thermoplastic synthetic resin injection molding method characterized by injecting a molten resin into the molding hole after the mold is placed in the mold, the wide inner peripheral surface of the thin sheet being held between the holding parts of both molds. Since the outer circumferential edge of the thin sheet is then cut at the cutting section, the thin sheet can be cut almost in accordance with the molded product without wrinkles on the inner wide surface of the thin sheet, and the process can be simplified.

Furthermore, since the thin sheet to be clamped is clamped by the wide inner peripheral surface without clamping the four peripheral edges as in the prior art, so-called plastic deformation does not occur, and therefore the thin sheet becomes even thinner due to plastic deformation. There will be no more accidents such as cracking or tearing. Further, the pressing force of the mold can be small.

The inner circumferential side of the molding cavity is sealed by the clamping part, and the outer circumferential side is sealed by the cutting part, and the cut edge part of the thin sheet is located inside the molding cavity. When molten resin is injected into the molding cavity, the edge of the thin sheet and the injected resin are fused together within the molding cavity and are integrally molded, forming a wide thin section and an adjacent thick wall. Since the parts can be integrally molded, the process of bonding the thin sheet part and the thick part later can be omitted.

Therefore, it is possible to extremely easily produce a product having a thin-walled, wide-area section that cannot be obtained by injection molding alone, and it is also easy to make the color and transparency of the thin sheet section different from those of the injection section. Product designs can be extremely diversified, and together with the use of thin sheets and the reduction in materials used, this has the effect of significantly reducing manufacturing costs.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a perspective view of a portable toothbrush case manufactured according to the present invention, and FIG. 2 shows an apparatus for manufacturing the product shown in FIG. 1, and FIG. Linear cross-sectional view, Figure 3 is the same as in Figure 2.
4 is an enlarged sectional view of FIG. 3, FIG. 5 is an enlarged sectional view of FIG. 3, and FIG. 6 is an enlarged sectional view of FIG. Figure 7 is a perspective view of a text box, which is a product in another embodiment;
FIG. 8 is a sectional view of a mold showing a part of the manufacturing process for the lid of the text box. 2... Thin sheet, 8, 8'... Mold, 10, 10',
10″...molding cavity, 11,11...cutting part, 12,1
2... Holding part, A... Molten resin.

Claims (1)

[Claims] 1 In an injection molding method in which an injection molded part of the same material is integrally molded around the outer periphery of a thin sheet made of a thermoplastic synthetic resin, between a pair of molds equipped with a molding cavity for injection molding the thermoplastic synthetic resin. A pre-made thin sheet is inserted into the mold, and a wide width inside the outer periphery of the inserted thin sheet is held at a clamping portion formed on the inner peripheral side adjacent to the molding cavity of the mating surfaces of the two molds. After cutting the outer periphery of the thin sheet with a cutting part that pinches the surfaces and sealing the outer periphery of the forming cavity provided in both molds, and positioning the outer periphery of the thin sheet in the forming cavity, A method for injection molding thermoplastic synthetic resin, characterized by injecting molten resin into a molding cavity.