JPH08290468A - Manufacture of sheet type molded article - Google Patents

Abstract

PURPOSE: To provide a manufacturing method for a sheet type molded article which can make the molded articles accurately without being affected by the shrinkage of a plastic sheet even when a number of the articles are made at a time from the wide plastic sheet with the use of so called an after-trim method and cooled, and then the blanks of them are cut. CONSTITUTION: A method has a molding process in which a plastic sheet 10 is heated, and more than one sheet type molded article 11 is made by a mold and a blank cutting process in which the blanks of the molded articles 11 are cut to separate the articles 11 from the plastic sheet 10. Simultaneously with the molding process or between the molding process and the blank cutting process, a notch forming process is provided in which notch lines 15-1, 15-2 for separating the articles 11 in the plastic sheet 10 are formed, with a connection part 13 left having a form in which the articles 11 are connected mutually expandably in the sheet 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sheet molded product, which is capable of producing a plurality of sheet molded products at a time by molding a plastic sheet.

[0002]

2. Description of the Related Art Conventionally, beverage containers having a structure in which a top end opening of a cylindrical container body is covered with a plastic lid and sealed have been developed and used.

In this type of lid, for example, as shown in FIG. 6, a lid body 80 is formed from a plastic sheet, and then a portion 81 of the lid body 80 which serves as a drainage residue for a drinking mouth.
It is manufactured by putting a cut line 83 around the periphery of, and then affixing an inner film 85 to the back surface of the portion 81 which becomes the scrap, and further welding a pull tab 87 to the upper surface of the portion 81 which becomes the scrap.

When the pull tab 87 is pulled up, the portion 81 which is the scraps adhered to the pull tab 87 is raised, and at the same time, the inner film 85 is torn and the drinking spout is opened.

By the way, the lid body 80 is usually manufactured by a vacuum pressure forming method. That is, a strip-shaped plastic sheet is pulled out from a roll and sequentially heated and softened, and then air pressure such as compressed air or vacuum is applied to the plastic sheet to form a female or male shape, that is, a shape of the lid body 80. Take out.

After cooling, cut lines 83 and the like are provided, and finally the outer shape of each lid body 80 is cut.

Here, as a means for increasing the productivity of the plastic sheet molding, the molding die is enlarged, that is, so-called multiple cutting is performed. That is, for example, a metal mold having 48 cavities or 60 cavities and a wide plastic sheet are prepared, and a large number of sheet molded products are manufactured by one molding.

[0008]

By the way, when a large number of lid main bodies 80 are formed on a plastic sheet that has been softened by heating and then cooled, the entire plastic sheet shrinks.

The shrinkage rate at that time varies depending on the material of the plastic sheet and the manufacturing conditions. For example, in the case of a polypropylene sheet, there is generally a shrinkage of about 1/100 to 2/100.

For this reason, when a method of inserting a cut line 83 or cutting the outer shape after cooling the molded plastic sheet (so-called after trim system) is used,
The position of the cut may be displaced by the shrinkage ratio.

This problem becomes more remarkable as the width of the plastic sheet becomes wider, so that the shrinkage dimension at the time of cooling becomes larger, and it becomes more difficult to perform alignment in the post-process after molding.

If it is desired to eliminate such problems and perform the outer shape cut-out with extremely high precision, a punch-die type cutting tool for punching is incorporated in the vacuum pressure air forming die itself. A so-called in-station trim method is used in which the outer shape of each lid main body 80 is punched out before the plastic sheet immediately after vacuum pressure molding has not cooled.

In the punch / die system, a die for a male and a die for a female are respectively incorporated in a die for vacuum / pneumatic forming, and the punch is thrust into the die immediately after the vacuum / pneumatic forming. Then, the plastic sheet is cut and pulled out at the portion where the outer periphery of the punch and the inner periphery of the die are joined.

However, according to this method, the precision with which the punch and the die are fitted must be considerably high, and the cutting edges of both must be made of special steel (tool steel), which not only increases the die cost. However, it becomes difficult to align the centers of both.

In particular, when a molded product is to be multi-faced, it is necessary to align all the centers of a plurality of punches and dies, and the precision of the adjustment is required. .

Further, in order to take out each lid body 80 punched out by the punch die system from the molding die, the molding die table is reversed, or the molding die table is moved to the take-out station. It required complicated movements, and the structure of the entire device was complicated.

Furthermore, if each lid body 80 is punched out immediately after molding, when the cut body 83 (see FIG. 6) is provided on the lid body 80, each lid body 80 is separated.
However, it is necessary to individually provide the cut lines 83, which makes the handling difficult. In particular, if the outer shape of the lid main body 80 is circular, it becomes difficult to align the rotational direction.

The present invention has been made in view of the above points, and an object thereof is to make a wide plastic at a time by using a so-called after-trim system in which a mold which is easy to multi-face and relatively inexpensive can be used. Even if a number of sheet molded products are molded into a sheet and then cooled to cut the outer diameter, each sheet molded product can be easily and accurately manufactured without adverse effects due to shrinkage of plastic sheets in various processes after molding. It is an object of the present invention to provide a method for producing a sheet molded product that can be manufactured.

[0019]

In order to solve the above problems, the present invention provides a molding step of heating a single plastic sheet to mold a plurality of sheet molded articles by a molding die, and the molded sheet. In the method of manufacturing a sheet molded product, which comprises a contour cutting process of cutting each contour of the molded product to separate each sheet molded product from the plastic sheet, the sheet molding product may be manufactured at the same time as the molding process or the molding process and the contour cutting process. In between, a notch forming step is provided to separate the sheet molded products of the plastic sheet from each other while leaving a connecting portion having a shape in which the sheet molded products are connected to each other in the plastic sheet so as to be able to expand and contract with each other.

[0020]

In the plastic sheet which has undergone the molding process and the notch forming process, a plurality of sheet molded products are connected to each other so as not to fall apart and to be able to expand and contract with each other. Therefore, when pulling out the outer shape of each sheet molded product connected to this plastic sheet from the plastic sheet, even if the size of the entire sheet shrinks due to cooling of the plastic sheet, each sheet molded product has its outer shape. The cavities of the cutting die for cutting can expand and contract vertically and horizontally, so each can be accurately aligned. In addition, in the case where a predetermined cut line is provided in the sheet molded product or another component is attached, the step of providing the cut line or attaching another component is performed after the forming process and the notch forming process. By doing so, each sheet molded product is not disjointed,
Since the positions thereof are almost fixed and they can expand and contract with each other, it is possible to easily align the cut line and the separate parts with each sheet molded product.

[0021]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is an overall schematic view showing an example of an after-trim type vacuum pressure air forming process used in the present invention.

As shown in the figure, the wide plastic sheet 10 pulled out from the roll sheet 31 is heated by the heater 33 and then introduced into the molding die 35 to form the molding die 35. The plastic sheet 10 is sandwiched between 37 and the plug 39 to form a plurality of sheet molded products 11 (molding step).

Next, the plastic sheet 10 is removed from the die 41.
Is cut into the plastic sheet 10 by cutting the outer shape of each of the sheet molded articles 11 formed into the plastic sheet 10 (outer shape cutting step). As a result, the sheet molded product 11 is completed.

By the way, in the present embodiment, the notch forming step is performed at the same time as the forming step. The cut forming step will be described below.

2 (a) and 2 (b) are schematic cross-sectional views showing a molding step and a notch forming step in which an essential part of the molding die 35 shown in FIG. 1 is enlarged.

As shown in FIG. 3A, the mold 37 is provided with a cavity 51 having the same shape as that of the sheet molded product 11, and the cavity 51 has a plurality of small holes for introducing compressed air. The piping 53 and the piping 55 for vacuuming are attached.

On the other hand, the plug 39 has a pipe 57 for introducing compressed air.
Is attached, and a cutting tool 59 for forming a notch is incorporated around it. This knife 59 is J
The punch die is used because it is a plate-shaped straight blade that is used by simply bending the saw blade for woodworking specified in ISB 4803, etc., and is easily attached by incorporating it in the plug 39. Mold cost is very low compared to the method.

First, as shown in FIG. 3A, the heated plastic sheet 10 before molding is placed on the mold 37. At this time, air is press-fitted into the cavity 51 from the pipe 53 to inflate the plastic sheet 10 as shown by the dotted line.

Next, the plug 39 is pressed against the plastic sheet 10 to remove the air in the cavity 51 from the pipe 55 and simultaneously press the air from the pipe 57 as shown in FIG. The plastic sheet 10 is brought into close contact with the inner surface of the cavity 51 by.

At the same time, the blade 59 provided on the plug 39 cuts the plastic sheet 10.

When the plug 39 is separated downward, a large number of sheet molded products 11 are formed in the plastic sheet 10 (molding process), and at the same time, the cut lines 15-1 and 15-2 are provided between the sheet molded products 11. (See FIG. 3) is provided (cutting step).

FIG. 3 is a partially enlarged plan view showing the plastic sheet 10 on which the sheet molded product 11 and the cut lines 15-1 and 15-2 are formed in this way.

As shown in the figure, the plastic sheet 1
The straight cut line 15-1 extending in the longitudinal direction and the horizontal direction to separate the sheet molded products 11 from each other and the end portion of each cut line 15-1 in the plane portion connecting the sheet molded products 11 of 0. In, a substantially square-shaped triple cut line 15-2 forming the connecting portion 13 is provided.

FIG. 4 is an enlarged plan view of the cut line 15-2. As shown in the figure, the triple cut line 15-2 is provided with a portion a in which the plastic sheet 10 is not cut, and the non-cut portion a is alternated for each cut line 15-2. Thus, the sheet-formed products 11 are connected to each other so as to be capable of expanding and contracting, thereby forming a connecting portion 13.

That is, when the sheet molded products 11 are pulled in the directions away from each other as shown by the arrows in FIG. 4,
As shown in FIG. 5, each cut line 15-2 of the connecting portion 13
Since the part of No. 15 spreads, the part of the cut line 15-1 also expands, and the interval between the sheet molded products 11 expands. That is, each sheet molded product 11 expands and contracts in any of the up, down, left, right, and diagonal directions.

Further, since the uncut portion a is provided in each score line 15-2 as described above, the plastic sheet 10 is not divided into pieces.

That is, the connecting portion 13 is formed in such a shape that the sheet-formed products 11 are not separated but are connected in a net shape and can expand and contract in the plastic sheet 10.

The cut line 15 forming the connecting portion 13
The shape of -2 may be any other shape as long as the sheet molded products are stretchably connected.

The plastic sheet 10 in which the sheet molded product 11 is formed by forming the score lines as described above is introduced into the die 41 shown in FIG. 1 so that the outer shapes of a plurality of sheet molded products 11 can be molded at once. 10 is cut (after trim system), but at this time, even if the plastic sheet 10 is shrunk in size due to cooling, each sheet molded product 11 is guided by each cavity of the die 41. Since it expands and contracts vertically and horizontally, it is possible to accurately position each.

When a predetermined cut line (such as the cut line 83 shown in FIG. 6) is provided in the sheet molded product 11, the cut line is formed after the molding step and the cut forming step. If the step of providing is provided, the sheet molded products 11 are not disjointed, their positions are almost fixed, and they can expand and contract with each other. Especially, the alignment in the rotation direction) can be easily performed. This is a separate part from the sheet molded product 11 (such as the pull tab 87 shown in FIG. 6).
The same applies when attaching.

In the above embodiment, the notch forming step is performed at the same time as the forming step, but this notch forming step may be performed between the forming step and the outer shape cutting step.

Further, it goes without saying that the sheet molded product molded from a plastic sheet using the present invention is not limited to the lid of the container, but can be applied to various other sheet molded products such as cup-shaped containers and cups. .

[0043]

As described above in detail, according to the present invention, even if a sheet molded article is subjected to multi-face cutting using a so-called after-trim system in which a relatively inexpensive die can be used, The effect of shrinking the plastic sheet can be improved, the accuracy of alignment of each sheet molded product in various steps after molding and cooling can be improved, and a highly accurate sheet molded product can be manufactured, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is an overall schematic view showing an example of an after-trim vacuum vacuum forming process used in the present invention.

2 (a) and 2 (b) are molding dies 35 shown in FIG.
FIG. 7 is a schematic cross-sectional view showing an enlarged main part of the step of forming and notch forming step.

FIG. 3 is a sheet molded product 11 and cut lines 15-1 and 15;
2 is a partially enlarged plan view showing the plastic sheet 10 on which -2 is formed. FIG.

FIG. 4 is an enlarged plan view of a connecting portion 13.

FIG. 5 is an enlarged plan view showing an operation of a connecting portion 13.

FIG. 6 is an exploded perspective view showing a lid of a beverage container.

[Explanation of symbols]

 10 Plastic Sheet 11 Sheet Molded Product 13 Connection Part 15 (15-1, 15-2) Notch Line 35 Molding Die 37 Die 39 Plug 41 Die Cutting 51 Cavity 59 Cutter

Claims (1)

[Claims] 1. A molding step of heating a single plastic sheet to mold a plurality of sheet molded products with a molding die, and cutting the outer shape of each of the molded sheet molded products to form each sheet molded product. In the method for manufacturing a sheet molded product, which comprises a contour cutting step of separating from a plastic sheet, the sheet molded articles are mutually separated within the plastic sheet at the same time as the molding step or between the molding step and the contour cutting step. A method for manufacturing a sheet molded product, comprising: a notch forming step for separating the plastic sheet from each sheet molded product while leaving a connecting portion having a shape in which the sheet is stretchably connected.