JP3359276B2 - Vacuum forming method and molded product thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deep cup-shaped container, a container having an inner cross-sectional area larger than that of an opening,
The present invention relates to a vacuum forming method of a synthetic resin particularly suitable for forming a hollow molded product having a complicated surface shape, and a hollow molded product used as a container molded by the method.

[0002]

2. Description of the Related Art As a method of molding a hollow synthetic resin molded article having a complicated surface shape, for example, a food display dummy in a restaurant or the like, or a toy imitating the shape of a character or an animal, a method of molding a powder of vinyl chloride with plastic powder is used. A molding method in which the material is mixed into a sol and poured into a mold formed in a recess to cure the surface, and then the uncured resin inside is poured out and the cured surface layer is released. Is used. Although this method is widely used to mold soft molded articles of various shapes, it has been pointed out that dioxin is emitted when discarded and incinerated, and it is desired to use a resin instead of PVC. Have been.

[0003] As a resin that can be used in place of vinyl chloride for forming a molded article of the type described above, there are polyethylene resin and ever resin (resin used for molding boots made of synthetic resin). Resin cannot be molded by the molding method such as vinyl chloride described above,
A method of forming a pre-formed sheet into a complicated surface shape by a vacuum forming method is employed.

That is, as shown in FIG. 4, a sheet mounting surface 10c and a forming recess 10a opened in the sheet mounting surface are provided.
Using a vacuum forming die 10 provided with a number of small holes for air suction on the wall surface of the forming recess, the heat-softened synthetic resin sheet 14 is placed on the sheet mounting surface 10c to form the forming recess 10a. The molding is performed by sucking the air inside, deforming the synthetic resin sheet 14 by the action of the atmospheric pressure, following the wall surface of the molding recess 10a, cooling and hardening, and then removing the mold.

[0005]

In such a vacuum forming method, when the heat-softened synthetic resin sheet is stretched along the wall surface of the forming recess, the sheet is stretched and its thickness becomes thin. In this case, as shown in FIG. 4, when the shape of the molding recess 10a is such that the cross-sectional area of the intermediate portion is larger than the cross-sectional area of the opening and the periphery of the opening is an acute-angled edge, When the depth 10a is deep, the synthetic resin sheet in the peripheral portion of the opening of the molding recess 10a is greatly stretched, so that the thickness of the molded product in that portion becomes extremely thin (shown by imaginary lines in the figure). In order to prevent the sheet from being excessively stretched and becoming thin, a thicker sheet must be used, and since the sheet is formed into a rectangular shape in advance, the opening of the formed article is required. Even though the area of the burrs remaining on the peripheral portion is large and can be reused by re-melting, the loss of material due to the need to thicken the sheet and the loss of energy for re-melting are large.

An object of the present invention is to reduce such a loss as much as possible, and it is possible to form a molded article having a uniform thickness, and therefore, the loss and strength of the material due to the uneven thickness. A vacuum forming method that does not cause a decrease and that reduces the amount of burrs separated from the molded article after molding, and therefore reduces the loss of material and thermal energy due to disposal and re-melting of burrs, and a method for use as a container manufactured by the method. The task is to obtain a molded product with a unique appearance.

[0007]

According to the vacuum forming method of the present invention, there is provided an extruder 1 for softening and extruding a resin by heating and kneading.
And a receiving device 4 having a recess 4a for receiving a predetermined amount of resin extruded from the extruder 1, a pressing machine 8 equipped with a mold having a flat plate-shaped forming surface facing the pressing device 8, and a flat sheet mounting device. A vacuum forming die 10 having a forming recess 10a having an air suction hole on the mounting surface 10c is used. A predetermined amount of the softening resin extruded from the extruder 1 is received by the receiving tool 4 and the mass of the softening resin 5 is received.
Is formed, and the lump 5 of the softening resin is pressed by a flat molding surface of a mold mounted on the press machine 8 to form a synthetic resin sheet 14 having an uneven thickness distribution.
4 is placed on the sheet mounting surface 10c in a state where the thick portion of the molding die 4 is located at the peripheral edge of the molding recess 10a of the molding die, and the air in the molding recess is sucked from the air suction port to make the synthetic resin sheet 1
4 is brought into close contact with the wall surface of the molding recess 10a and is cooled and hardened.

In the mirror-shaped container according to the second aspect, a fitting ridge is provided at one opening 11a of the two round-shaped hollow molded products 11, 12 formed by the above-mentioned method and at the periphery of the other opening 12a. 12b. Claim 3
The described bale-shaped container is formed by fitting one opening peripheral edge of one of the two cup-shaped hollow molded products 13a and 13b molded by the above-mentioned method.

[0009]

According to the method of the present invention, according to the shape of the concave portion of the vacuum forming die, the sheet is press-formed so that the thickness of the portion where the amount of stretching of the sheet is large at the time of forming is a thickness corresponding to the amount of stretching. Since the sheet is used, the thickness of the molded article after molding can be made substantially constant. Therefore, there is no partial unevenness in the strength of the molded product, and it is possible to mold the thickness of the part requiring the strength thicker than the thickness of the part not requiring the strength. There is no loss of material due to having a thickness. In addition, since the sheet before molding is formed by pressing the softening resin formed in a lump in advance, the contour shape of the sheet can be made to be a shape close to the shape of the opening of the molded product, and particularly the opening of the molded product is In the case of a circular shape or a shape close to the circular shape, the amount of burrs remaining around the molded product can be reduced, and also in this respect, the loss of materials and thermal energy can be reduced as much as possible.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view showing a vacuum forming method of the present invention in the order of steps. The extruder 1 is provided with a horizontal barrel, and the resin charged into a hopper provided at the base end of the barrel is melted and softened by the kneading action of a heater loaded in the barrel and a screw rotating in the barrel. It is pushed downward from the die 2 attached to the tip. A cutter 3 is provided immediately adjacent to the extrusion opening of the die, and when a predetermined amount of resin is extruded downward from the die, the cutter 3 operates to receive a predetermined amount of softened resin below the die. Drop into the recess 4a of the tool 4.

The massive resin 5 received by the receiving member 4 is inserted between upper and lower dies 6, 7 of a mold having a flat lower molding surface 7a and an upper molding surface 6a provided with loose irregularities. Then, the upper die 6 is pressed by a press machine 8 to form a sheet having a non-uniform thickness distribution shown in FIG. The position and thickness of the portion 9a where the thickness of the sheet is increased is determined by the shape of the forming recess 10a of the vacuum forming die 10 and the peripheral shape of the opening 10b thereof as shown in FIG. , And the upper molding surface of the mold is shaped based on the determined thickness.

The synthetic resin sheet 9 manufactured by press molding in this way is placed on the sheet placing surface 10c of the vacuum forming die 10. The vacuum forming die 10 has a flat sheet mounting surface 10c.
And a forming recess 10a formed in a recess opening in the sheet mounting surface 10c. A large number of air suction ports (not shown) are opened in the wall surface of the forming recess 10a. The port is connected to a vacuum pump (not shown).
As shown in the figure, when the synthetic resin sheet 9 formed by the press molding is mounted on the sheet mounting surface, and the vacuum pump is operated to make the inside of the molding recess a negative pressure, the synthetic resin sheet is pressed at atmospheric pressure on the back surface. And closely contact the wall surface of the molding recess 10a. At this time, if necessary, the synthetic resin sheet is heated with an infrared lamp or the like to assist the stretching of the resin.

After a predetermined time has passed after the synthetic resin sheet has been brought into close contact with the wall surface of the molding recess and the resin sheet has cooled and cured, the molded product is pulled out from the molding recess 10a. Since the resin used for molding is a soft resin and easily deformed even in a hardened state, it is possible to remove the molded product even if the inside is a recess having a larger sectional area than the opening as shown in the figure. .
After demolding, burrs on the periphery of the opening of the molded product are removed.

FIG. 2 shows an embodiment in which a mirror cake-shaped container is formed by two round cake-shaped products 11 and 12 formed as described above. One of the molded products 11 has an opening 11a on the top surface of the round rice cake shape, and the other one 12 has an opening 12a on the bottom surface of the round rice cake shape, and a fitting ridge is formed on the periphery of the opening. 12b is formed. The container shown in FIG. 2 is formed by inserting the fitting ridge 12b into the opening of the other molded article 11 and engaging the peripheral edges of the opening. This mirror rice cake-shaped container is filled with rice and used as a decorative rice cake for the New Year.

FIG. 3 shows an embodiment in which a container 13 in the shape of a rice bale is formed by two cup-shaped products 13a and 13b formed by the above-described method. Both the one container 13a and the other container 13b are molded into a shape having rice-bale-shaped irregularities on the surface, and are sealed by fitting their opening peripheral edges to each other. The rice bale-shaped container 13 can be used as a gift rice container, and a sealing tape is stuck on the outer periphery of the fitting portion so as not to be separated.

The molded article 11 below the rice cake-shaped container of FIG.
And the molded products 13a and 13b of the rice-bale-shaped container in FIG.
After taking out the rice inside, it can be reused as a flowerpot and its sink. That is, a hole is formed in the bottom of the molded product 13 of the rice-bale-shaped container, and the soil is stuffed therein to form a flowerpot, which is inserted into the opening of the mirror-mochi-shaped molded product to stand up. Use it. By such recycling, it is possible to prevent the container made of synthetic resin from becoming waste after use.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing steps of a molding method of the present invention.

FIG. 2 is a sectional view showing an embodiment of the invention of claim 2;

FIG. 3 is a sectional view showing an embodiment of the invention of claim 3;

FIG. 4 is a schematic view showing a conventional vacuum forming method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extruder 4 Receiving tool 4a Concave part 5 Bulk resin 8 Press machine 10 Vacuum forming die 10a Forming concave part 10c Sheet mounting surface 11,12 Round cake forming product 11a, 12a Opening 12b Fitting protrusion 13a, 13b Shaped products 14 Synthetic resin sheet

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 51/02 B29C 51/10 B29C 51/20

Claims (3)

(57) [Claims] An extruder for softening and extruding a resin by heating and kneading, a receiving device for receiving a predetermined amount of resin extruded from the extruder, a pressing machine having a flat molding surface opposed to the extruder, Using a vacuum forming die having a forming recess having an air suction hole on the sheet mounting surface, a predetermined amount of the softening resin extruded from the extruder is received by a receiver to form a mass of the softening resin, and this softening is performed. The lump of resin is pressed by a flat molding surface of a pressing machine to form a synthetic resin sheet having an uneven thickness distribution, and the thick portion of the synthetic resin sheet is formed on a peripheral portion of a molding recess of the molding die. The vacuum is characterized in that it is placed on the sheet placement surface in a state where it is positioned, and the air in the molding recess is sucked from the air suction port to bring the synthetic resin sheet into close contact with the wall surface of the molding recess and cool and harden, a vacuum Molding method. 2. A two-piece hollow mold product formed by the vacuum forming method according to claim 1, wherein one of the openings is fitted with a fitting ridge provided on the periphery of the other opening. Mirror rice cake-shaped container. 3. A rice-bale-shaped container, wherein two cup-shaped hollow molded articles formed by the vacuum forming method according to claim 1 are fitted with one opening peripheral edge at the other opening peripheral edge.