JP2003048244A - Vacuum molding roll for manufacturing foamed plastic sheet and method for manufacturing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roll in which it is unnecessary to drive a vacuum blank sheet for forming cavities in the roll which continuously performs vacuum molding for manufacturing a foamed plastic sheet manufactured by laminating a cap film and a back film and has a number of the cavities for molding caps on the surface of a metal cylinder and provides vacuum suction holes for vacuum suction on the bottom part of each cavity. SOLUTION: A cylinder for vacuum molding roll is constituted of inner and outer double metal cylinders being closely overlapped one over another and a number of circular cavities (3) for molding the caps are provided by a definite arrangement on the outside cylinder (1) and a number of circular air flow paths (4) are provided by a corresponding arrangement in a positional relation deviated from the cavities on the inside cylinder (2) and the circular cavities and the circular air flow paths are a little overlapped at each end to form vacuum suction holes (5).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum forming roll for producing a plastic foam sheet, and a production method thereof. In the present invention, the term plastic foam sheet (hereinafter abbreviated as “foam sheet”) is intended to include a thick product called “foam board”, and is used as a term indicating both of them.

[0002]

2. Description of the Related Art A cap film having a large number of cap-shaped protrusions is prepared by vacuum forming a plastic film, and a flat back film is attached to the bottom surface of the cap to form a large number of sealed air chambers. There is a molded product called a bubble sheet. Widely used thin products are mainly used in the field of cushion packaging, and also used as heat insulating materials for buildings. Thick products that are becoming popular nowadays are used as materials for packaging containers and building materials, and are in the process of being developed for various uses.

In the production of such an air bubble sheet, continuous vacuum forming of the cap film is performed using a roll type vacuum forming die. The vacuum forming roll is composed of a metal cylinder provided with both end faces and a rotating shaft, has a large number of cap forming cavities on the surface of the cylinder, and a vacuum in the radial direction for vacuum suction at the bottom of each cavity. The structure has suction holes, and a vacuum communication path that runs in the axial direction and that connects the vacuum suction holes to the opening of the end face. The structure of a typical vacuum forming roll is shown in FIGS. 1 to 5 of Japanese Utility Model Publication No. 62-7462.

The bottom of the cavity for molding the cap is formed by driving a small circular plate having vacuum suction holes in the form of a plurality of slits or small holes, which is called a "vacuum blanking plate". A typical example of a vacuum blank can be found in Figures 2 and 4B of Utility Model 1-23796. Since the vacuum forming rolls commonly used have a diameter of about 300 mm and a length of about 1100 mm, for example, in the case of a zigzag arrangement with a cap diameter of 7 mm and a pitch of 11 mm, the number of vacuum punched plates to be driven into one roll is , About 10,000
It is an individual.

However, in recent years, an increase in production speed has been demanded in the production of a bubble sheet, and accordingly,
It has become necessary to increase the diameter of the vacuum forming roll that constitutes the manufacturing apparatus. If you increase the line speed,
The vacuum forming roll may be incompletely cooled, resulting in deterioration of product quality. In order to avoid it, the roll diameter must be increased. In addition, the uses of the air bubble sheet are diversifying, and accordingly, wide products (2 m width) are required. These factors are overlapped with each other, and the number of vacuum blanks to be punched into one vacuum forming roll is dramatically increased. Roll diameter 500
When the width is 2 mm and the width is 2100 mm, the number of cavities to be provided in the roll, that is, the number of vacuum punched plates is about 25,000 with the same cap diameter and pitch as above.

It is complicated and inefficient to manufacture vacuum forming rolls by individually punching such a number of vacuum punched plates, and the manufacturing cost of rolls becomes unreasonably high. The problem caused by the increase in the number of vacuum blanks is not limited to the time of manufacturing, but is also related to maintenance. In that case, it is desirable that the vacuum forming roll for producing the air bubble sheet does not need to be punched with the vacuum punching plate.

[0007]

An object of the present invention is to provide a vacuum forming roll for producing an air bubble sheet as described above,
It is an object of the present invention to provide a cavity capable of forming a cap without the need for driving a vacuum blank.

[0008]

The vacuum forming roll of the present invention which achieves the above object prepares a cap film having a large number of cap-shaped projections by vacuum forming a plastic film, and a flat back is provided on the bottom surface of the cap film. A roll for performing continuous vacuum forming for producing a plastic foam sheet formed by laminating films together,
The metal cylinder is provided with both end surfaces and a rotary shaft, the surface of the cylinder has a large number of cavities for cap molding, and the bottom of each cavity has vacuum suction holes directed in the radial direction for vacuum suction, and In a roll provided with an axial vacuum passage connecting the vacuum suction holes to the end face opening, as shown in FIGS. 1 and 2, the inner and outer double cylinders in which the cylinders are closely overlapped with each other. The outer cylinder (1) has a large number of circular cavities (3) for forming the cap in a fixed arrangement, and the inner cylinder (2) has a circular air passage (4). In a positional relationship that is offset from the cavities, a large number are provided in a corresponding array, and the circular cavities and the circular air flow paths slightly overlap at each end, so that there are multiple locations on the bottom circumference of each cavity. A vacuum forming roll, characterized in that so as to form a vacuum suction hole (5).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In FIG. 1, reference numeral (6) is the axial vacuum communication path described above. FIG. 3 is an enlarged view of a part of FIG. 2, in which the vacuum suction hole (5) is replaced by the cavity (3).
Are formed at four places on the circumference of the bottom part of the car at angles of 90 degrees. The width (W) of this vacuum suction hole is usually 0.
It is suitable to be in the range of 2 to 1.0 mm. 0.2 mm
Small gaps that do not reach the above range tend to cause clogging, while large gaps exceeding 1.0 mm cause the cap sheet to come out and be strongly vacuumed, resulting in the possibility of pinholes. This risk depends, of course, on the thickness of the sheet, and for thicker sheets (in the case of making cellular boards) a relatively wide gap may be rather appropriate. In any case, the width (W) is generally 0.
The range of 3 to 0.8 mm is preferable. The diameter of the cap is 5
30 mm is practically used, and it can be arbitrarily selected to some extent centering on this range.

The arrangement of cavities shown in FIG. 2, that is, the arrangement of caps is a so-called staggered arrangement. Although FIG. 4 is usually called “inverse zigzag arrangement”, the zigzag arrangement is tilted by 90 degrees. Arrangement of the caps is arbitrary, and the caps may be arranged in a lattice shape, or in addition, a mode called “oblique arrangement” as shown in FIG. 5 is also possible. In this mode, the staggered arrangement is 15 to 45 degrees (about 40 degrees in the illustrated example).
This is a cap arrangement that is tilted, and that has the advantage that the difference in buckling strength between the longitudinal direction and the width direction of the bubble sheet becomes small.

The method for producing the vacuum forming roll for producing the plastic foam sheet of the present invention is a production method comprising the following steps. 1) a step of drilling an axial vacuum communication path (6) in the inner cylinder (2), 2) a step of attaching both end faces and a rotary shaft (both not shown), and 3) the inner cylinder (2), Perforating the circular air channels (4) in a corresponding arrangement so that each connects with the vacuum communication channel (6) and in a positional relationship offset from the cavity (3) intended to be provided in the outer cylinder. 4) a step of providing the outer cylinder (1) on the inner cylinder (2) by shrinkage fitting or shrink fitting, and 5) a step of forming a cavity (3) in the outer cylinder (1) .

In the above step 3), that is, in the inner cylinder (2),
Drilling a circular air flow path (4), and step 4)
That is, the step of boring the cavity (3) in the outer cylinder (1) can be performed accurately and efficiently by the NC machine tool. In this case, in order to prevent the deviation of the drilling position due to the accumulation of minute errors, it is necessary to always set the distance from one end of the cylinder as a starting point, which is well known to those skilled in the art.

This is also understood by those skilled in the art, but it is preferable that the outer cylinder and the inner cylinder are made of the same metal material, for example, carbon steel of the same steel type. Even if dissimilar metals are used for some reason, they should combine as much mechanical and thermal properties as possible. Superposition therefore has to be done by shrink fit or chill fit. By preparing one of the inner and outer cylinders with a softer metal than the other, it is not impossible to superimpose them by press fitting, but such superposition naturally entails the problem of corrosion, and there are double cylinders inside and outside. We do not guarantee full adhesion between them. If there is a portion where the adhesion is insufficient, heat is partially accumulated during the operation of the vacuum forming roll, and a difference in roll surface temperature occurs, resulting in impaired product quality.

[0014]

The vacuum forming roll for producing a plastic bubble sheet of the present invention, unlike the conventional one, does not need to be individually punched in a vacuum forming plate to form a cavity for forming a cap. Since the preparation and the material and labor for implanting the same are unnecessary, the period required for manufacturing can be shortened and the cost can be remarkably reduced. Therefore,
It becomes easy to manufacture a vacuum forming roll having a larger diameter and / or wider width than a conventional product.

In addition to the complexity of manufacturing and driving, the vacuum blanking plate has a problem that the temperature is likely to rise due to heat accumulation due to rapid operation. The heat storage depends on the principle that the vacuum punching plate does not come into contact with the roll body over its entire circumference. Due to If the heat storage is significant, that part will be insufficiently cooled and the product quality will deteriorate. This problem has been fundamentally solved by the present invention.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view of an example of a vacuum forming roll of the present invention.

FIG. 2 is an expanded view of a part of the vacuum forming roll of FIG. 1, showing an overlapping relationship between inner and outer double cylindrical portions.

FIG. 3 is a development view showing a state in which a vacuum suction hole is formed by further enlarging a part of FIG. 2.

FIG. 4 is a development view similar to FIG. 2, showing an embodiment different from FIG. 2 in regard to the cavity arrangement of the vacuum forming roll of the present invention.

FIG. 5 is a development view similar to FIG. 2, showing an aspect different from FIG. 4 in the cavity arrangement of the vacuum forming roll of the present invention.

[Explanation of symbols]

1 outer cylinder 2 inner cylinder 3 cavities 4 air flow paths 5 Vacuum suction hole 6 vacuum connection

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3J103 AA02 AA13 AA45 AA61 AA80                       EA03 EA05 EA11 FA15 GA24                 4F202 AC03 AG01 AG05 AG18 AJ03                       AJ09 CA17 CB02 CD01 CD21                       CP01 CP04 CP06

Claims (3)

[Claims] 1. A plastic bubble sheet comprising a cap film having a large number of cap-shaped protrusions prepared by vacuum forming of a plastic film, and a flat back film bonded to the bottom surface of the cap film.
It is a roll that performs continuous vacuum forming.It is made of a metal cylinder with both end faces and a rotating shaft. There are many cap forming cavities on the surface of the cylinder, and vacuum suction is performed at the bottom of each cavity. In a roll with vacuum suction holes extending in the radial direction, and with a vacuum communication path running in the axial direction that connects the vacuum suction holes to the opening on the end surface, the cylinders are closely overlapped inside and outside. It is composed of a double cylinder, and the outer cylinder has a large number of circular cavities for forming the cap in a fixed arrangement, and the inner cylinder has a circular air flow path connected to a vacuum communication path, which is displaced from the cavity. In relation to each other, a large number of corresponding cavities are provided, and the circular cavities and the circular air flow paths slightly overlap each other at their ends, so that a plurality of cavities are formed on the bottom circumference of each cavity. In vacuum forming roll, characterized in that so as to form a vacuum suction hole. 2. The vacuum forming roll according to claim 1, wherein the outer cylinder and the inner cylinder are made of the same metal material. 3. A method for producing a vacuum forming roll for producing a plastic foam sheet according to claim 1, comprising:
A manufacturing method comprising the following steps: 1) a step of drilling an axial vacuum communication path in the inner cylinder, 2) a step of attaching both end faces and a rotary shaft, 3) a circular air flow path in the inner cylinder, A step of providing a large number of holes by punching in a corresponding array in a positional relationship shifted from the cavity that is planned to be provided in the outer cylinder so as to be continuous with the vacuum communication path, 4) baking the outer cylinder on the inner cylinder The step of covering by fitting or cooling, and 5) the step of forming a cavity for cap molding in the outer cylinder by punching at a predetermined position.