JPH0239915A - Folding method for plastic sheet - Google Patents

Abstract

PURPOSE:To provide a folding line of given depth and shape easily and accurately by placing a plastic sheet of resistance to breakage on a heating female mold forming component, pressing a heated lining mold and forming a folding line. CONSTITUTION:A flat plate mold 3 is lifted and lowered by lifting and lowering a piston rod 2. A heating and cooling means 4 consisted of fluid and a heater for cooling or heating and a lining mold 5 for processing a laminating sheet are provided in the mold 3. A female mold forming plate 6 with a female mold formed preliminarily is fixed on a surface plate 7, and a plastic sheet 8 to be folded is placed on said female mold forming plate 6. The lining mold 5 and the female mold forming plate 6 are heated up to the given temperature preliminarily and the lining mold 5 is molded and pressed to the plastic sheet 8, and then the lining mold 5 is fitted on the female mold of the female mold forming plate 6 and lifted up.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for bending plastic sheets, particularly for electrical, electronic equipment, daily necessities, tools, food, clothing, accessories, personal items, The present invention relates to a method for bending plastic sheets that is useful for packaging boxes for cosmetics, book covers that are frequently opened and closed, album covers, etc., and bars.

(Prior art 1) Problems to be solved by the invention In the past, packaging or covers for various products have been made of paper or a combination of paper and plastic, but recently plastic is often used. These sheets of plastic are punched out into a predetermined shape using an automatic box-making machine, folded lines are added, and then assembled into each container.

However, folding of this type of plastic sheet is usually done mechanically using a folding blade and a back blade, but plastic sheets are less likely to form folding lines than paper, so it is difficult to force folding lines mechanically. When folding plastic sheets, there are disadvantages such as cracks occurring on the two sides and the sheet being easily broken, so the bending process of plastic sheets is usually carried out by placing the plastic sheet on a flat plate as shown in Figure 5. This is done by pressing a heated wire-forming mold from above to form folding lines on the plastic sheet. There is a disadvantage that it easily breaks during the bending process because most of the parts are lost, and the pressing of the mold with this line tends to sometimes result in a shocking load, resulting in cracks occurring at the fold line part of the plastic sheet. Since it has the disadvantage of being easy to fold, the depth of this folding line is made uniform,
It is difficult to finely adjust this depth, and this requires the use of extremely high-precision molds.

In addition, when this folded plastic film is made into a box using an automatic backing machine, the process is carried out in the order shown in Fig. 6, for example, but this is done in the order shown in Fig. 6 (a). Folded plastic sheet 21
are sent to the next process one by one, and as shown in FIG. 6(b), they are automatically folded and the adhesive surface 22
The adhesive 23 is automatically injected into the adhesive 23, and the adhesive 23 is then pressed and deformed into a flat shape as shown in FIG. 6(c), and the adhesive surface 22 is sufficiently fixed by the adhesive 23. By pressing it from the side, it is returned to its original box shape as shown in Figure 6(d), but the folding line processing of the plastic sheet is insufficient for this purpose. If so, the automatic box lining machine may stop due to a problem, or the adhesive may peel off or partially break due to strain when forming the box body with pressing force from the side. This has the disadvantage that when inserting an item, it cannot be inserted smoothly because it returns to its old shape as soon as the pressing force becomes zero. It is necessary that the fold line is reliably formed in the plastic sheet.

(Means for Solving the Problem) The present invention relates to a method for folding a plastic sheet that solves the above-mentioned disadvantages. This method is characterized by pressing a mold (male mold) placed on the plastic sheet and heated to a predetermined temperature to form a bending line in the plastic sheet.

In other words, the present inventors believe that when folding plastic sheets to be fed into an automatic box-lining machine or the like, it is necessary to make the folding lines have a uniform depth, be easy to fold, and be difficult to break. Therefore, as a result of various studies on this bending method, we found that the bending process of plastic sheets using a male die and a female die forming member having a female die with a concave groove that matches the shape of the male die. They completed the present invention by discovering that by placing a plastic sheet on this female molding member and pressing a male mold onto it, folding lines with a predetermined depth and shape can be easily and reliably obtained. Ta.

(effect) This will be explained below based on the attached drawings.

FIG. 1 is a schematic vertical cross-sectional view of a device used to carry out the present invention, FIG. The figure is a longitudinal cross-sectional view showing the method for producing this female molded member, and FIG. 4 is an enlarged longitudinal cross-sectional view of the principal part of the folded portion of the folded laminated sheet made according to the present invention.

The apparatus for carrying out the present invention shown in FIG.
The mold 3 has a heating/cooling means 4 including a fluid or a heater for cooling or heating the mold 3, and a mold 5 with at least one wire for processing the laminated sheet. is provided. Furthermore, a female mold forming plate 6 on which a female mold has already been formed by this device is fixed on top of this surface plate 7 as described later, and a female mold forming plate 6 to be bent and processed is fixed on top of this female mold forming plate 6. A plastic sheet 8 is placed.

In this process, the wire forming mold 5 and the female mold forming plate 6 are heated to a predetermined temperature in advance, and then the wire forming mold 5 is lowered and pressed against the plastic sheet 8. After fitting it into the female mold of the female mold forming plate 6, it is sufficient to pull it up.
This may be done by performing the same operation multiple times or by continuing to press for a certain period of time, but the insertion depth of the wire forming die 5 at this time may be set by the adjustment stopper 9.

FIG. 2 shows an enlarged view of the main part when forming folding lines on a plastic sheet according to the present invention. FIG. 2(a) shows the female mold forming plate 6 placed on the surface plate 7, This is a layout diagram before processing in which the wire mold 5 is placed on the plastic sheet 8 placed on the mold forming plate 6, and the wire mold 5 is lowered during processing. When this is pressed against the female mold forming plate 6 and the wire forming mold 5 is fitted into the female mold 1o, the plastic sheet is melted and a folded line 11 is formed on the N. However, when a male mold and a female mold are mated together in this way, it is usually necessary to have a complex integrated mechanism in which multiple guide posts are used as guides to move up and down. ) and the female mold forming plate 6 are heated under temperature control, so thermal expansion caused by the rise in temperature causes the male mold and female mold to fit loosely, making it difficult to process. Although it is easy to
For this female mold processing, for example, as shown in FIG. 3(a), a plate serving as a female mold forming plate is placed on the surface plate 7, and this plate and the wire forming mold 5 are heated to a predetermined temperature. Then, by lowering the wire forming mold 5 to form a female mold on this plate, a female mold 10 that fits into the wire forming mold 5 is formed as shown in FIG. 3(b). A female mold forming plate is obtained,
In this case, the female mold is made at approximately the same temperature as when processing the plastic sheet described above, so it will not be difficult to fit the wire forming mold 5 and the female mold 1o together due to heating.
If the depth of this female mold is set to an appropriate depth by adjusting the adjustment stopper 9 shown in Fig. 1, the depth of the bending line can be adjusted by simply fitting the wire fitting 5 and the female mold 10 during plastic processing. The advantage is that it can be adjusted.

If paper is used as the material for forming the female mold forming board 6, it will cause deformation and will have poor durability, so it is necessary to use something other than paper. It may be made of thermoplastic plastics such as terephthalate, nylon, or thermosetting plastics such as Bakelite, but it may also be made of relatively hard and soft metal plates such as copper plates, aluminum plates, brass plates, etc. may be wood, etc. The thickness of this female mold forming plate 6 is 5 to 10 mm when it is made of plastic, and 10 to 10 mm when it is made of metal or wood.
The shape of the female mold formed in 2N may be any shape depending on the shape of the wire forming mold 5, such as a flat shape, a U-shape, a 7-shape, etc. However, the depth of this female mold is in the range of 4t, where t is the thickness of the plastic sheet to be bent, and the width of this female mold is 3t<width of female mold<Lot
It is recommended that the range be within the range of .

In addition, although the wire forming die and the male blade are constructed as separate members in this wire forming mold, various types of removable male blades can be easily attached thereto. The number of male blades of this wire forming mold is not limited to one, and a plurality of male blades can be attached depending on the shape of the box to be folded.

Moreover, FIG. 4(a) shows an enlarged cross-sectional view of the folding line part of the plastic sheet folded according to the present invention. It is not something that forces you to form a bend line.

This is a plastic sheet that has been subjected to so-called drawing processing by male and female processing, and at the fold line processing part, the entire plastic sheet is gradually stretched evenly and becomes thinner, and at the R part at the tip, the thickness t' of the sheet is the same as before processing. Compared to the sheet thickness t, it is stretched thinner with t'< 1/3 t, so it can be easily bent with a small pressing force P, and the sheet bent by 90'' is As shown in Figure 4(b), without breaking,
It can be folded neatly.

The present invention relates to a method for bending a plastic sheet, and since the plastic sheet to be bent by this method must have folding durability, polyvinyl chloride, polyvinylidene chloride, polyethylene, polypropylene, polycarbonate, polyacetal, polyethylene terephthalate,
It may be made of nylon, polytetrafluoroethylene, etc., but it may also be a copolymer of these or a laminate of sheets of the same or different types. This thickness is 0.1~2.0+nm because this material is mainly used as packaging material.
It should be the one of .

Since the folding line formation on the laminated sheet according to the present invention is carried out as described above, this has an industrial advantage in that it does not require particularly high-precision equipment or molds. The heating temperature, degree of pressure, and processing time may be arbitrarily set according to the depth and size of the desired folding line, and the shape of the tip of the folding line can also be adjusted by changing the shape of the tip of the wire forming mold 5. It can be changed arbitrarily by changing the cross section to a 7-shape, a U-shape, a W-shape, a flat shape, a slanted shape, etc.

Note that the folding line 10 does not necessarily have to be a straight line, and can be formed into a desired curve, an interrupted line (broken line, -dotted chain line, etc.), a double line, or a double line by appropriately selecting the line forming mold 5.
It is also possible to use three lines or a combination thereof.

(Example) Next, examples of the present invention will be given, and the degree of bending and folding durability in each example are shown as results measured by the following method.

[Degree of bending]

A load is applied to a plastic sheet having a width of 20 mm that has been processed with a folding line, using the folding line as a fulcrum, and a surface layer 30 m from the fulcrum, and the load required to bend the sheet by 90 degrees is measured.

[Folding durability]

Using the folding line of the folded sheet provided with the folding line as a fulcrum, the tension is 1 kg, and the repeated folding speed is 180 times/
A folding durability test was conducted under the condition of a bending angle of 270°, and the number of times until breakage was measured.

Example 1 Using the apparatus shown in Fig. 1, a mold with a thickness of 1rrn was formed.
, Width 3001TR1 A wire mold with a tip R of 0.5tm was attached and heated to 200℃, and this was placed on a surface plate, and 10kg/cd was placed on a 5cm thick polycarbonate plate.
When the polycarbonate plate was pressed 10 times with a pressure of
A U-shaped female mold with a groove width of 1 mm, a depth of 0.1 mm, and a length of 300 nm was formed.

Next, a polyvinyl chloride sheet with a thickness of 0.25+nm was placed on the polycarbonate plate on which the female mold was formed, and the above-mentioned wire forming mold was heated to 90°C, and this was placed on the polyvinyl chloride sheet for 5 minutes. When the polyvinyl chloride sheet was pressed for 1 second at a pressure of kg/aJ and pulled up, the polyvinyl chloride sheet had the following properties (see Figure 4).
Since a folding line as shown in a) was formed, the degree of bending and folding durability of this product were examined, and the bending degree was 10 g, and the folding durability was 200 times.

However, for comparison, the degree of bending and folding resistance of a polyvinyl chloride sheet obtained by processing in the same manner as above except that the female mold forming plate was not used and the depth of the folding line was 0.2 mm. When the properties were examined, it was found that the degree of bending was 40 g and the folding durability was 90 times, so it was confirmed that the product of this example had an excellent degree of bending and folding durability.

Example 2 Using the apparatus shown in Figure 1, a 5 nm thick copper plate was fixed on a surface plate heated to 300°C with a built-in heater, and a 1 m thick and 300 mm wide copper plate was fixed on top of the surface plate heated to 300°C. 50kg/ci of wire forming mold with tip R of 0.5mm
When pressed 20 times with this pressure, the copper plate had a depth of 1
．． 5+nm, width 1nws, length 300m, tip R is 0
．． A U-shaped female mold measuring 5 mm was formed.

Next, on the copper plate on which this female mold was formed, a layer with a thickness of 0.5
1 polyethylene sheet is placed and this copper plate is heated to 90'C.
In addition, when the above-mentioned wire forming mold was heated to 100°C and this wire forming mold was pressed against a polyethylene sheet for 2 seconds at a pressure of 5 kg/cd and then pulled out, the polyethylene sheet had the following properties as shown in Fig. 4. ) was provided, so we investigated the bending degree and folding durability of this item, and found that it had a bending degree of 20g and a folding durability of 250 times. However, for comparison, the folding line shown above was When examining the degree of bending and folding durability of a polyethylene sheet obtained by processing in the same manner as above except that the copper plate with the female mold was not used and the depth of the folding line was 0°35Wn, the degree of bending was 100g. , the folding durability is 50 times, and this Example 2
It was confirmed that the product obtained in the above method had an excellent degree of bending and folding durability.

(Effects of the Invention) As described above, in the present invention, a male wire forming mold and a female mold forming member having a groove matching the shape of the male mold as a female mold are used, and a plastic sheet is inserted into the female mold. It is placed on the forming member and a male wire forming mold is pressed against it, so it is possible to easily and reliably form folded lines with a predetermined depth and shape on the plastic sheet. Therefore, if the plastic processed in this way is fed into an automatic box-making gutter, it is advantageous in that a box can be easily and stably obtained without any trouble.

[Brief explanation of the drawing]

Figure 1 is a schematic vertical cross-sectional view of the device used to carry out the present invention, and Figures 2 (a), (b), and (c) show when this device is used to provide folding lines on a plastic sheet. FIG. 3 is a vertical cross-sectional view showing a method for producing a female mold forming plate using this method, and FIG. 4 is a vertical cross-sectional view of a folding line portion of a plastic sheet made according to the present invention. Figure 5 is an enlarged vertical cross-sectional view of the main part when forming folding lines on a plastic sheet by the conventional method.
FIG. 6 shows the factors involved in each process when manufacturing boxes using an automatic box making gutter. 1...Cylinder, 2...Piston Rondo, 3
... Flat mold, 4... Heating and cooling means. 5... Wire attachment mold, 6... Female mold forming plate. 7...Surface plate, 8...Plastic sheet. 9...Stopper for adjusting insertion depth 10...Female type, 11.21...Folding line. 22... Adhesive surface, 23... Adhesive (a) (a) A Figure Figure Figure Figure Figure (a) 7 (b) Figure

Claims (1)

[Claims] 1. A plastic sheet with fold-resistant properties is placed on a female mold forming member heated to a predetermined temperature, and a wire forming mold (male mold) heated to a predetermined temperature is pressed onto the plastic sheet. A plastic folding method characterized by forming a fold line on the plastic.