JPH0657424B2 - Method for producing hollow double-wall molded product - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a hollow double-wall molded product having a complicated uneven portion.

[Conventional technology]

In the conventional method for manufacturing a hollow double-wall molded product, a molten tubular parison is extruded between a pair of split molds that have been opened, and the protrusions provided on one split mold by closing the molds There is one in which a part is compressed to form a hinge and is confined in a split mold cavity, and a pressurized fluid is supplied into the confined tubular parison to expand it (see Japanese Patent Publication No. 49-44112).

The above-mentioned conventional technique is to manufacture a hollow double-wall molded product having few irregularities and good mold release, and a hollow double-wall having complicated irregularities as shown in FIGS. 1 and 2. In the case of producing a molded product, there is a problem that the mold release is bad and the product is deformed if the mold is forcibly released.

[Problems to be Solved by the Invention]

In view of the above problems of the prior art, the method shown in FIGS. 12 to 16 was tried in order to manufacture a hollow double-wall molded product having complicated uneven portions as shown in FIGS. 1 and 2. It was

First, a set of split molds 22 and 23 used based on FIG.
The protruding pin 24 is arranged such that its tip end surface is flush with the tip end surface of the protruding portion 22a of the split mold 22. The other structures of the split molds 22 and 23 are the same as those of the present invention described later, and thus the description thereof will be omitted.

Next, the molding process will be described with reference to FIGS. 12 to 16. The molten cylindrical parison is extruded between the pair of split molds 22 and 23 that are opened to form a pair of split molds 22 and 2.
The mold 3 is closed, the cylindrical projection 23a of the other split mold 23 is curved and deformed, and it is pressed against the projection 22b of one split mold 22 to weld the part. Then, the hinge 21 is compression-molded by completely closing the mold,
At the same time, the cylindrical parison is clamped by the peripheral portions of the split molds 22 and 23, and this portion is welded. By closing the mold, the cylindrical parison is transformed into two hermetically sealed hollow bodies. Therefore, when the blow needle 25 is pierced into each hollow body and a pressurized fluid such as air or an inert gas is supplied, each hollow body is closed. As shown in FIG. 12, it expands along the cavity formed by the split molds 22 and 23, and a hollow double-wall molded product 20 having a complex uneven portion on the inner shell is formed. Next, as shown in FIG. 13, the mold halves 22 and 23 are opened, and then the projecting pin 24 is projected as shown in FIG.
Since the inner shell of 0 deforms and abuts the outer shell, and the pressing force of the projecting pin 24 is supported by both the inner shell and the outer shell, good mold release is performed as shown in FIG. However, when the mold is released, the inner shell momentarily elastically deforms toward the tip end surface of the protruding pin 24 and returns to its original shape, and as shown in FIG. A so-called "bound phenomenon" that is hit is generated. As a result, the part or the periphery of the inner shell that is strongly struck on the tip surface of the protruding pin is deformed, and the inner shell surface is scratched with irregular asperities, resulting in poor appearance and high precision. There was a problem that it became unusable.

The present invention has been made in view of the above problems, and a method for producing a hollow double-wall molded article having good appearance without scratches by preventing the occurrence of the above-mentioned bounce phenomenon during the protruding step. The purpose is to provide.

[Means for Solving the Problems]

In order to achieve the above object, in the method for producing a hollow double-wall molded product of the present invention, at least one split mold of a set of split molds has a plurality of projections, and at least one projection is Using a pair of split molds provided with a projecting pin with the tip protruding slightly from the tip surface of the projecting part, introducing a molten cylindrical parison between the pair of split molds opened, After sealing the cylindrical parison by closing the split mold, supply pressurized fluid to the inside and expand it to form a hollow double-wall molded product with complicated uneven parts, and then divide both split molds. The mold is opened and the hollow double-wall molded product is projected by the projecting pin.

[Work]

Introducing a molten cylindrical parison between the two molds opened.
After sealing the cylindrical parison by closing the mold,
When pressurized fluid is supplied to the inside, it expands along the cavity formed by the split mold and is molded so as to wrap around the tip of the protruding pin that slightly protrudes from the tip surface of the protruding portion. One of the shells of the wall molded product is in close contact, and it does not always separate from the tip of the protruding pin until the completion of the projecting step due to contraction or the like, so the above-mentioned bounce phenomenon does not occur, and the tip of the protruding pin A hollow double-wall molded product having a complicated concave-convex portion formed on the shell on the side of the hollow double-wall molded product that abuts the protruding pin of the hollow double-wall molded product is molded.

〔Example〕

 An embodiment will be described with reference to the drawings.

The hollow double-walled molded product 1 having complicated uneven portions shown in FIGS. 1 and 2 is composed of two hollow double-walled main body parts joined by a hinge 3 and intersects each main body part. Each of the compartments 2 is divided into four small chambers 4, and four storage spaces are formed when the hinge 3 is closed.

3 to 10 show respective steps of one embodiment for forming the hollow double-walled molded product 1 described above.

First, a pair of split molds 12 and 13 used in this embodiment will be described with reference to FIG.

One split mold 12 is provided with a low-height projection 12b for molding the hinge 3 of the hollow double-wall molded product 1 in the center thereof, and a hollow formed symmetrically with the projection 12b sandwiched therebetween. It has two main body molding portions for molding the main body portion of the double wall molded product 1. Each body forming part has four protrusions 12a.
And the projection pin 1 driven by the fluid pressure cylinder 14a or the like is provided on the two projections 12a at the diagonal positions.
4 are provided, and a groove 12c for molding the partition wall 4 of the hollow double-wall molded product 1 shown in FIG. 2 is provided at the boundary between the protrusions 12a. The protruding pin 14 has a tip portion 14a slightly protruding from the tip surface of the protruding portion 12a to prevent a bouncing phenomenon and to easily take out a molded product after protruding by the protruding pin 14. The protruding length of the tip portion 14a is preferably about 0.2 to 2 times the wall thickness of the shell of the hollow double-wall molded product, specifically 0.4 to 4 mm. In addition, the protrusion 1
Blowing holes 16 are formed in appropriate portions near 2b and the peripheral portion 12d, respectively.

On the other hand, the other split mold 13 has a recess for molding the outer shell of the hollow double-walled molded product 1, and the center of the recess has a high height at a portion facing the protrusion 12b. Central protrusion 13a
Is provided, and the central projection 13a and the projection 12b of the split mold 12 on one side press the molten cylindrical parison 11 when the mold is closed to compression-mold the hinge 3 (see FIGS. 4 and 5). Is configured.

The split molds 12 and 13 are attached to a known mold opening / closing mechanism (not shown) to open and close, and when the molds are closed, a cavity for forming a hollow double-wall molded product is formed.

Next, the molding process will be described.

As shown in FIG. 3, the molten cylindrical parison 11 is extruded from the extrusion die 10 of an extruder (not shown) between the two mold halves 12 and 13 which are opened. When the extruded cylindrical parison 11 reaches a length slightly protruding from the split molds 12 and 13, the split molds 12 and 13 are closed and the central projection of the other split mold 13 is shown in FIG. The cylindrical parison 11 is formed by the portion 13a.
Is bent and deformed, and it is pressed against the protrusion 12b of one split mold 12 to weld that portion. Then, as shown in FIG. 5, the hinge 3 is compression-molded by completely closing the mold, and at the same time, the cylindrical parison 11 is divided into two molds 12, 13.
It is sandwiched by the peripheral edge portions 12d and 13b (see FIG. 3), and this portion is welded. By closing the mold, the cylindrical parison 11
Is transformed into two hermetically sealed hollow bodies with the hinge 3 as a boundary, and is also transformed so as to wrap around the tip portion 14a of the projecting pin 14. Then, when each of the sealed hollow bodies is pierced with a blowing needle 15 and a pressurized fluid such as air or an inert gas is supplied, each hollow body expands along the cavity formed by the split molds 12 and 13, A hollow double-wall molded product 1 having a complicated uneven portion is molded.

When the molded hollow double-wall molded product 1 is cooled to a temperature at which it can be taken out, the mold is opened as shown in FIG. Due to this mold opening, the hollow double-wall molded product 1 is brought into a state of being in close contact with one split mold 12 having a more complicated uneven portion than the other split mold 13 by shrinkage or the like. Then, when the projecting pin 14 is projected, the inner shell of the hollow double-wall molded product 1 is deformed by the tip portion 14a of the projecting pin 14 for a moment and abuts against the outer shell, and the pressing force of the projecting pin 14 is Since it is supported by both outer shells, the hollow double-walled molded product is not further deformed, and good mold release is performed as shown in FIG. Further, as shown in FIG. 9, when the protruding pin 14 is projected, at this time, the hollow double-wall molded product 1 that has been molded is further cooled, so that the inner shell is only slightly deformed. Then, as shown in FIG. 10, the projecting pin is completely projected to project the hollow double-wall molded product 1.

In the present embodiment, since the inner shell of the hollow double-wall molded product 1 is always stuck during the projecting step so as to wrap around the tip portion 14a of the projecting pin 14, the projecting phenomenon occurs as described above. Instead, the inner shell of the hollow double-walled molded product 1 is provided with a highly accurate concave portion along the shape of the tip portion 14a of the protruding pin 14.

FIG. 11 shows a step of another embodiment of the present invention,
The tip surface of the tip portion 14a 'of the projecting pin 14' is formed in a curved shape so as not to be damaged when the molded product is taken out after projecting the projecting pin 14 '. Other than the above, It is similar to that of the first embodiment. This embodiment is also the first
The pound phenomenon does not occur in the same manner as in the above embodiment.

Needless to say, the present invention can be applied to the case where there is no hinge portion, and the number and shape of the protruding portions 12a of the split mold 12 on one side are not limited to those in the above-mentioned respective embodiments, and complicated unevenness to be formed. It can be arbitrarily changed according to the structure of the hollow double-walled molded product 1 having a portion. In this case, it is desirable to select the protruding portion 12a on which the protruding pin 14 is to be provided, in such a manner that the portion and the number of the molds can be uniformly removed when the hollow double-wall molded product 1 is projected.

Further, when manufacturing a hollow double-wall molded product having a complex uneven portion on the outer shell, it is preferable to provide a plurality of projecting portions on the other split mold 13 and dispose projecting pins on the projecting portions.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY Since the present invention is configured as described above, when the molded hollow double-wall molded product is projected, the mold release is good, and the bouncing phenomenon does not occur during the projecting step, so it is irregular. It is possible to manufacture a hollow double-wall molded product having a complex uneven portion that is good in appearance and is free from scratches on the unevenness.

[Brief description of drawings]

FIG. 1 is a front view of a hollow double-wall molded product manufactured according to the present invention, FIG. 2 is a plan view showing the opened state, and FIGS. 3 to 10 are moldings of one embodiment of the present invention. Fig. 3 shows the process, and Fig. 3 is a sectional view of the split mold taken along the line AA in Fig. 2.
4 to 10 are sectional views of the main part of the split mold taken along line BB in FIG. 2, and FIG. 11 is a line BB in FIG. 2 showing one step of another embodiment of the present invention. 12 to 16 are sectional views of the main part of the split mold according to the drawings. Each of the manufacturing methods of the hollow double-wall molded product is shown in which the tip surface of the projecting pin is the same as the tip surface of the projecting part of the split mold. It is an important section sectional view of a split mold showing a molding process. 1 …… Hollow double wall molded product, 2 …… Partition wall, 3 …… Hinge, 4 …… Small chamber, 10 …… Extrusion die, 11 …… Cylindrical parison, 12,13 …… Split mold, 12a …… Projection, 12b ... Projection, 12c ... Groove, 12d, 13b ... Peripheral area, 13a ... Central projection, 14,14 '... Projection pin, 15 ... Blowing needle, 16 ... Blowing hole.

Claims (1)

[Claims] 1. At least one split mold (12) of a set of split molds (12, 13) has a plurality of protrusions (12a), and at least one protrusion (12a) has the protrusions (12a). 1
2a) has a tip (14a, 14)
a ') a pair of split molds (12, 13) provided with projecting pins (14, 14'), and melted between the set of split molds (12, 13) opened. Tubular parison 11
The cylindrical parison (11) is hermetically closed by closing the two molds (12, 13), and then a pressurized fluid is supplied to the inside of the cylindrical parison (11) to expand the hollow parison (11). A heavy wall molded product (1) is molded, and then a split mold (12,
13) The mold is opened, and the hollow double-wall molded product (1) is projected by the projecting pins (14, 14 ').