JPH0582287B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention relates to a method for thermoforming a thermoplastic resin sheet, and more specifically, a method for forming a thermoplastic resin sheet into a predetermined shape by partially heating and softening a veneer. The present invention relates to a thermoforming method.

<Problems to be solved by conventional technology and invention> Conventionally, thermoplastic resin sheets have been used as materials.
When manufacturing containers, etc., the sheet material is unrolled one after another, and the thermoplastic resin sheet is heated to a predetermined length by heating means such as radiant heating using an infrared heater, heat transfer or radiant heating using a heating plate, or hot air heating. A method is adopted in which the entire surface is simultaneously heated and then molded into a predetermined shape using a mold.

However, when the above-described front heating method is employed, the heated thermoplastic resin sheet tends to sag, resulting in uneven heating, catching in the mold, and the like. In particular, in alignment molding, there is a problem that pattern deviation becomes large during heating, and in the case of strongly stretched sheets, uneven thickness tends to occur during heating. Furthermore, since the entire surface is heated simultaneously, it is susceptible to external disturbances, making it difficult to control the heating temperature for the thermoplastic resin sheet.

In order to solve these problems, a method has been proposed in which only the molded part of the thermoplastic resin sheet is partially heated and softened (for example, Japanese Patent Application Laid-Open No. 59-199206
(see publication). However, the above-mentioned partial heating method is applicable only to cases in which the thermoplastic resin sheet is unrolled from a roll and continuously fed by running, and the thermoplastic resin sheet is cut into predetermined dimensions or injection molded. It is difficult to heat-form the veneer obtained by this process due to transport problems.

<Purpose> This invention was made in view of the above problems, and it is a thermoplastic resin sheet that can be partially heated and softened to form a veneer into a predetermined shape with a simple structure. The purpose of this invention is to provide a method for thermoforming a resin sheet.

<Means for Solving the Problems> In order to achieve the above object, the thermoplastic resin sheet thermoforming method of the present invention includes supporting the outside of the molded portion of the veneer made of the thermoplastic resin sheet, and A veneer is sandwiched between the protruding pins or sunk into the stepped portions of the index table, which is equipped with a number of frame-shaped receiving molds each having protruding pins or stepped portions for positioning. The method is characterized in that the following steps 1 to 2 are performed by fixing the index table in place and sequentially moving the receiving mold to a predetermined position by rotating the index table. With the veneer clamped by a brushing plate and a receiving mold that contact the veneer before the heating element and separate from the veneer later than the heating element, the molded part is sandwiched between the pair of heating elements, and the veneer is A heating process that heats and softens the board. The ejector, which contacts the veneer before the mold and separates from the molded product later than the mold, clamps the heat-softened veneer with the receiving mold, and then molds the veneer with the mold. A forming process of forming the part into a predetermined shape. Unloading process in which the molded product is removed from the receiving mold.

<Example> Hereinafter, an example will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing each step of the method of thermoforming a thermoplastic resin sheet according to the present invention.
is a foamed sheet of thermoplastic resin as a material,
This is a loading process in which a veneer 1 made of a non-foamed sheet, a combination sheet of a foamed sheet and a non-foamed sheet, etc. is set in a receiving mold 2.
Molded part 1a of veneer 1 set in (see Fig. 5)
C is a molding process in which the heated and softened molded part 1a is molded into a predetermined shape, and D is an unloading process in which the molded product after molding of the molded part 1a is taken out from the receiving mold 2. The steps A to D above are, for example, the second
As shown in the figure, by rotating the four receiving molds 2, which are equally distributed on the index table 3, at equal intervals, it is possible to simultaneously and repeatedly perform the process. In FIG. 2, the zone where loading step A is performed is designated by 10, the zone where heating step B is performed is designated by 20, the zone where molding step C is performed is designated by 30, and the zone where unloading step D is performed is designated by 40. are shown respectively.

The above-mentioned veneer 1 is formed into a contour shape that matches or approximates the planar shape of the finished product, such as a round shape or a square shape, and is formed by cutting a thermoplastic resin sheet or by injection molding a thermoplastic resin. This can be obtained by

The receiving mold 2 is a frame-shaped one in which at least a portion of the veneer 1 corresponding to the molding part 1a is hollowed out, and a predetermined part outside the molding part 1a of the veneer 1, the peripheral edge in the case of the figure, is hollowed out. It is designed to be supported. Further, on the upper surface of the receiving mold 2, a means for positioning the veneer 1 using a protruding pin 2a is formed. It can also be configured with a step portion 2b formed in the step portion 2b. (See Figure 4). Note that the receiving die 2 device portion of the index table 3 is hollowed out to a wider area than the hollowing range of the receiving die 2.

To explain in more detail the above-mentioned loading process A, heating process B, molding process C, and unloading process D, first, the loading process A corresponds to the loading zone 10 as shown in FIG. The veneers 1 stacked at a predetermined position are horizontally moved one by one to a position directly above the receiving mold 2 using vacuum suction or the like, and are pushed down using a drive mechanism such as a cylinder 11.
The veneer 1 is set in the portion of the receiving mold 2 surrounded by the protruding pins 2a. When moving the veneer 1 downward as described above, the support plate 12 that is waiting below the index table 3 is advanced to the upper part of the receiving mold 2 using a cylinder 13 or the like, and the veneer 1 is held in the state. By moving the veneer 1 downward, the veneer 1 can be set more reliably. and,
After the above loading step A is completed, the index table 3 is rotated 1/4 turn and the veneer 1 is transferred together with the receiving mold 2 to the adjacent heating zone 20.

In the heating zone 20, as shown in FIG.
1 and 21, and only the molded part 1a is heated and softened. As the heating bodies 21, 21, a single plate 1
molding temperature (e.g. polystyrene foam sheet,
By pressurizing and heating the veneer 1 at a predetermined pressure for a predetermined time, the molded part 1a of the veneer 1 can be formed in a short time and at a temperature 20 to 30°C higher than It can be softened uniformly. The heating bodies 21, 21 are, for example, heating plates 2 made of aluminum or the like having a built-in nichrome sheathed heater 22.
It can be heated and kept warm by heat conduction from 3. Further, the advancing of the heating bodies 21, 21 can be performed by a drive mechanism including cylinders 24, 24, etc., configured behind the heating bodies 21, 21. The heat softening range of the veneer 1 is as follows:
The range may be slightly wider (usually 2 to 5 mm) than the outer dimension of the .

When heating and softening of the molded part 1a is completed,
In order to transfer the veneer 1 to the next forming zone 30,
Although the heating bodies 21, 21 are separated from the veneer 1 by the cylinders 24, 24, there is a risk that the veneer 1 may adhere to the upper heating body 21 and detach from the receiving mold 2. Reference numeral 25 denotes a brushing plate provided on the heating body 21 side in the upper part to avoid the above-mentioned inconvenience, and is attached to be slidable along the guide rods 26, 26, and is fitted into the guide rods 26, 26. It is elastically biased downward by coil springs 27, 27, and when the heating body 21 advances, it comes into contact with the veneer 1 before the heating body 21, and when the heating body 21 advances further, the coil springs 27, 27 can be elastically compressed. In other words, when the upper heating body 21 retreats, it is configured so that it separates from the veneer 1 later than the heating body 21 and can brush off the veneer 1.

When the heating step B described above is completed, the index table 3 is further rotated by 1/4 turn,
The veneer 1 is transferred to the forming zone 30 while being set in the receiving mold 2.

In the molding zone 30, as shown in FIG.
is advanced toward the veneer 1 side by a drive mechanism such as the cylinder 32, and the peripheral edge of the veneer 1 is pressed against the receiving mold 2 and clamped, and the heated and softened molded part 1 is
Vacuum form a. At this time, since the peripheral edge of the veneer 1 has not been softened, the concave mold 31 and the receiving mold 2
Vacuum forming can be carried out simply by clamping the material between the two. Further, depending on the processing conditions described above, an auxiliary convex mold 34 that moves forward and backward by a drive mechanism such as a cylinder 33 is used. Note that 35 is an ejector having the same structure as the brushing plate 25 in the heating zone 20, and is used to move the molded product 1' into the concave mold 3.
It acts to release the mold from 1.

Next, after the above molding step C is completed, the index table 3 is further rotated by 1/4 turn to form the molded product 1'.
The molded product 1' is transferred to the subsequent unloading zone 40, and is removed from the receiving mold 2 by pushing up the molded product 1' with a cylinder, for example, and stored therein (not shown).

In addition, each process of the above-mentioned loading process A, heating process B, molding process C, and unloading process D is carried out in each corresponding zone 10, 20, 30, 40.
Both processes are carried out at the same time, so there is little idle time, and the process can be carried out very efficiently and at low cost. The timing for moving the index table 3 is set to coincide with the completion of the heating process B, which takes the longest time.

The method of thermoforming a thermoplastic resin sheet according to the present invention is not limited to the above-described embodiments. For example, as shown in FIG.
It is also possible to set two or more locations, and in this case, a receiving mold 2 having a partition 2c facing the non-molded part may be used. According to the above embodiment, it is possible to manufacture a molded product 1' having two or more concave portions, and also to produce two or more molded products by cutting off or trimming the non-molded portion afterwards. 1' can be produced simultaneously.

Regarding the veneer 1 made of a thin sheet,
As shown in FIG. 9, on a predetermined part of the upper surface of the receiving mold 2,
By forming the needle-like protrusion 14 that can penetrate the veneer 1, the veneer 1 can be removed from the receiving mold 2 during transfer.
can be reliably prevented from leaving. In this case, loading zone 1
By forming a pressure member 15 having the same structure as the brushing plate 25 in the heating zone 20 at the heating zone 20, the veneer 1 can be reliably penetrated by the needle-like projections 14.

In addition, as the molding process C, a molding method other than the above-mentioned vacuum forming, such as pressure molding, matuti molding, etc., may be adopted, and the loading process A
Various changes can be made without changing the gist of the invention, such as performing the heating step B and heating step B in the same zone, or adding a heating zone 20 to heat the molded part 1a in stages.

<Example 1> A cut polypropylene foam sheet (with filler) was used as a veneer, and the heat forming method of the present invention was carried out under the following conditions.
Good molded products could be manufactured efficiently.
However, the heat softening range of the veneer 1 was set to be within 2 mm (within 1 mm on one side) from the outer dimension of the molded portion 1a.

Implementation conditions Single plate Dimensions 240mm x 130mm x 750μm Expansion ratio 1.5x Molded product External dimensions 120mm x 230mm Depth 15mm Heating element temperature 180℃ Heating time 4 seconds Molding method Vacuum forming Heating element pressure 0.6-0.8Kg/cm ³ <Test Example 2〉 An injection molded product made of non-foamed high impact polystyrene resin was used as a veneer, and under the following conditions:
When the thermoforming method of this invention was carried out, it was possible to efficiently produce a good molded product. However, the heat softening range of the veneer 1 was set to be within 2 mm (within 1 mm on one side) from the outer dimension of the molded portion 1a.

Implementation conditions Single plate Dimensions φ 120 mm x 2.5 mm Molded product External dimensions φ 90 mm Depth 25 mm Heating body temperature 180°C Heating time 8 seconds Molding means Vacuum forming Heating body pressing force 0.6 to 0.8 Kg/cm ² <Effects of the invention> As described above According to the thermoplastic resin sheet thermoforming method of the present invention, a veneer made of a thermoplastic resin sheet is partially heated and softened, and a veneer positioning means is provided. The veneer is set in a frame-shaped receiving mold that supports the outside of the molded part of the veneer, and during the heating process, the veneer is brought into contact with the veneer before the heating element, and the veneer is brought into contact with the veneer later than the heating element. Since the sheet is softened while the veneer is separated from the veneer and the veneer set above is clamped by the receiving mold, when the heating element is separated from the veneer, the veneer may stick to the heating element. The inconvenience of detachment from the receiving mold can be easily avoided, and the veneer softened by the heating element can be smoothly moved to the molding process. In addition, during the molding process, the heat-softened veneer is clamped between the ejector and the receiving mold, which contact the veneer before the mold and separate from the molded product later than the mold. Since the veneer is formed into a predetermined shape, it is possible to avoid the inconvenience of the molded product adhering to the mold and detaching from the receiving mold, and the molded product is transported to the next unloading process while being securely set in the receiving mold. Become what you can. As described above, according to the present invention, it is possible not only to prevent the veneer from sagging, uneven heating, and getting caught in the mold, but also to perform molding with reliable alignment. .

Further, since the veneer is transferred while being set in the receiving mold, the loading process, heating process, molding process, and unloading process can be carried out efficiently and at low cost even though the veneer is a veneer. Furthermore, since the index table is rotated to move the receiving molds to predetermined positions one after another, the installation space for the equipment can be reduced, and direct connection to the packaging line is also possible. Furthermore, since the receiving mold is used as one of the molding molds, the structure of the molding device can also be simplified. Further, the receiving mold itself includes a veneer positioning means consisting of a protruding pin or a stepped portion, a sweeper plate for clamping the veneer during heating, and an ejector for clamping the veneer during molding. Therefore, there is no need to specifically configure a means for clamping the veneer in the receiving mold itself, and the method allows heat-forming of the veneer using equipment with a simpler structure. Moreover, injection molded products can also be used as veneers, so it is possible to secure the advantages of both injection molding and thermoforming, and it is possible to achieve thinner walls with good stretchability, as well as increase strength. can also be achieved.

Therefore, it has the unique effect of being able to perform reliable molding efficiently and at low cost using simple equipment.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a schematic plan view of an apparatus used to carry out the invention, Fig. 3 is a cross-sectional view of a receiving mold portion, and Fig. 4 is a diagram showing another receiving mold. 5 is a sectional view showing the loading process; FIG. 6 is a sectional view showing the heating process; FIG. 7 is a sectional view showing the molding process; and FIG. 8 is the molding process showing another example. FIG. 9 is a sectional view of a main part showing another receiving mold. 1... Single plate, 1a... Molded part, 1'... Molded product,
14...Acicular projection, 2...Reception mold, 2a...Protruding pin as positioning means, 21, 21...Heating body, 3...Index table, 31...Recess, A...Loading process, B ...Heating process,
C... Molding process, D... Unloading process.

Claims (1)

[Scope of Claims] 1. An index table that supports the outside of a molded portion of a single plate made of a thermoplastic resin sheet and is provided with a number of frame-shaped receiving molds each having protruding pins or step portions for positioning. The veneer is fixed in position on the receiving mold by being sandwiched between the protruding pins or sunk into the stepped part, and the indexing table is rotated to move the receiving mold to a predetermined position one after another. A method for thermoforming a thermoplastic resin sheet, characterized by performing the steps of . With the veneer clamped by a brushing plate and a receiving mold that contact the veneer before the heating element and separate from the veneer later than the heating element, the molded part is sandwiched between a pair of heating elements, and the veneer is separated. A heating process that heats and softens the board. The ejector, which contacts the veneer before the mold and separates from the molded product later than the mold, clamps the heat-softened veneer with the receiving mold, and then molds the veneer with the mold. A molding process in which parts are molded into a predetermined shape. Unloading process in which the molded product is removed from the receiving mold. 2. The method for thermoforming a thermoplastic resin sheet according to claim 1, wherein a receiving mold having needle-like projections penetrating the veneer is used.